SCIENCE SCIENCE FOR FOR SOUTH SOUTH AFRICA AFRICA
ISSN 1729-830X ISSN 1729-830X
50 years of laser technology: from light shows to Petrie dishes
VOLUME 6 • NUMBER 3 • 2010 VOLUME 3 • NUMBER 2 • 2007 R29.95 R20
Laser processing: changing the face of materials science Shaping light: laser beams made to order
Lasers in the sky: understanding the atmosphere Optical tweezers: lasers and disease A C AACDAEDMEYM YO FO FS C I EI ENNCCEE OOFF SS O U TT HH AAFFRRI C I CA A SC OU
Laser processing: the world of advanced manufacturing technologies Charl Smal and Herman Burger Lasers have changed the the way we use materials and so the face of manufacturing, providing impetus for a new generation of engineers and technologists. 10
Shaping light Andrew Forbes, Craig Long and Philip Loveday Modern optics and adaptive mirrors use the physics of diffraction to shape the light inside a laser.
Lasers in the sky: LIDAR and atmospheric particulate measurement QUEST found out how lasers are measuring, and so helping us to understand the effects of, pollution across southern Africa.
Contents VOLUME 6 • NUMBER 3 • 2010
How lasers can help us understand HIV and other illnesses
Pumping iron and climate control Mike Lucas
Highly focused light provided by lasers forms ‘optical tweezers’ that can tease out the secrets of disease by manipulating single cells.
The continuing story of phytoplankton, iron fertilisation and climate control.
First images from the KAT antennas Anja Schröder and Ian Stewart
The KAT radiotelescope array is starting to show its worth to the global scientific community.
Bringing science to the people Gillian Armstrong How students from the University of Stellenbosch Laser Physics unit are making sure that no-one is left out of the celebration of 50 years of lasers.
Richest of the rich: South Africa’s biodiversity treasure trove Ronell R. Klopper, Michelle Mamer, Yolande Steenkamp, Gideon Smith and Neil R. Crouch South Africa has an enormous range of species, both plant and animal; all are of vital importance to the nation. Biodiversity conservation: a new way of looking at our heritage
Regulars Career focus 9
A career in laser technology Patience Mthunzi How to be a laser physicist.
Biodiversity research and conservation Eureta Rosenberg You can make a real difference to the world around us.
Reyhana Mahomed Sustainable living is impossible without maintaining biodiversity.
Fact file The atom – p. 13 • Photosynthesis – p. 39 • www.questinteractive.co.za – p. 39
Crop damage Juan Vorster, Dominique Michaud, Andrew Kiggundu and Karl Kunert
Diary of events
Crop damage by insects is a major threat to food security in Africa. Molecular technology may provide some of the answers.
Back page science • Mathematical puzzle
CSIR biennial conference: science real and relevant QUEST finds out just how close to the cutting edge CSIR are.
Quest 6(3) 2010 1
SCIENCE SCIENCE FOR FOR SOUTH SOUTH AFRICA AFRICA
ISSN 1729-830X ISSN 1729-830X
50 years of laser technology: from light shows to Petrie dishes
VOLUME 6 • NUMBER 3 • 2010 VOLUME 3 • NUMBER 2 • 2007 R29.95 R20
Laser processing: changing the face of materials science Shaping light: laser beams made to order
Lasers in the sky: understanding the atmosphere Optical tweezers: lasers and disease A C AACDAEDMEYM YO FO FS C I EI ENNCCEE OOFF SS O U TT HH AAFFRRI C I CA A SC OU
SCIENCE FOR SOUTH AFRICA
Editor Dr Bridget Farham Editorial Board Roseanne Diab (University of KwaZulu-Natal) (Chair) Michael Cherry (South African Journal of Science) Phil Charles (SAAO) Anusuya Chinsamy-Turan (University of Cape Town) George Ellis (University of Cape Town) Jonathan Jansen (University of Free State) Penny Vinjevold (Western Cape Department of Education) Correspondence and The Editor enquiries PO Box 663, Noordhoek 7979 Tel.: (021) 789 2331 Fax: (021) 789 2233 e-mail: firstname.lastname@example.org (For more information visit www.questinteractive.co.za) Advertising enquiries Barbara Spence Avenue Advertising PO Box 71308 Bryanston 2021 Tel.: (011) 463 7940 Fax: (011) 463 7939 Cell: 082 881 3454 e-mail: email@example.com Subscription enquiries Patrick Nemushungwa and back issues Tel.: (012) 349 6624 e-mail: Patrick@assaf.org.za Copyright © 2010 Academy of Science of South Africa
Published by the Academy of Science of South Africa (ASSAf) PO Box 72135, Lynnwood Ridge 0040, South Africa (021) 789 2233 Permissions Fax: e-mail: firstname.lastname@example.org Subscription rates (4 issues and postage) (For subscription form, other countries, see p. 56.)
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Design and layout Creating Ripples Graphic Design Illustrations James Whitelaw Printing Paradigm
2 Quest 6(3) 2010
From Dr No to cell biology
hen I was a child I spent a lot of time living with my grandparents near Bulawayo. In those days a visit to the cinema was a big occasion and I remember my grandmother putting on very smart clothes to go all the way into town to watch a film. My earliest exposure to the concept of laser beams came from one of those trips. The film was Dr. No, starring Sean Connery as James Bond. I vividly remember a scene in which Bond was shackled to a metal table by the villain of the hour – Dr. No himself – watching a laser beam slicing through the thick metal of the table as though it were butter – heading towards a very tender part of Bond’s anatomy. The word LASER – to give it its original upper-case acronym – stands for light amplification by stimulated emission of radiation. When lasers were first invented in 1960 they were called a ‘solution looking for a problem’. And for many years, the James Bond image remained my idea of what lasers were all about – fascinating ‘beams of light’ with the power to cut through thick metal. Now, 50 years of development mean that lasers have become ubiquitous. They are found in every section of modern society – consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment and the military. The first common use of lasers in general society was in the humble bar code scanner, now used in shops all over the world – which was invented in 1974. Then in 1978 the laserdisc player was the first successful consumer product to include a laser, although it wasn’t until the development of the compact disc (and now DVD) player that laser-equipped devices became common. The laser printer followed in 1982. It is now almost impossible to imagine a world without these devices – at least among those of us fortunate enough to live in a world in which electronics are part of our lives. However, as this edition of QUEST shows, we have come a long way even from these widely-known technologies. Now lasers are being used in ways their inventors could hardly have imagined – to move individual cells in a sample, for example; to break protein bonds in viral capsules – the list goes on. The concept of a ‘solution looking for a problem’ is often used as an argument against blue-sky research – pure research – where applications are not necessarily immediately apparent. And this argument is used particularly in countries such as South Africa, where research budgets are limited. But it is a dangerous attitude. Without the ‘blue sky’ there will be no applications because there will be no ‘solution’ in the first place. Lasers are an excellent example of why we must not concentrate entirely on research that has immediate and potentially lucrative applications. We will, in the end, be poorer. For more on lasers go to www.questinteractive.co.za.
Bridget Farham Editor – QUEST: Science for South Africa Join QUEST’s knowledge-sharing activities Write letters for our regular Letters column – e-mail or fax your letter to The Editor. (Write QUEST LETTER in the subject line.) ■ Ask science and technology (S&T) questions for specialist members of the Academy of Science to answer in our regular Questions and Answers column – e-mail or fax your questions to The Editor. (Write QUEST QUESTION in the subject line.) ■ Inform readers in our regular Diary of Events column about science and technology events that you may be organising. (Write QUEST DIARY clearly on your e-mail or fax and provide full and accurate details.) ■ Contribute if you are a specialist with research to report. Ask the Editor for a copy of QUEST’s Call for Contributions (or find it at www.questsciencemagazine.co.za), and make arrangements to tell us your story. To contact the Editor, send an e-mail to: email@example.com or fax your communication to (021) 789 2233. Please give your full name and contact details. ■
All material is strictly copyright and all rights are reserved. Reproduction without permission is forbidden. Every care is taken in compiling the contents of this publication, but we assume no responsibility for effects arising therefrom. The views expressed in this magazine are not necessarily those of the publisher.
Laser processing: the world of advanced manufacturing technologies Charl Smal and Herman Burger describe a world of possibilities when applying laser processing to materials.
ifty years after the discovery of the laser, the manufacturing community sees the laser as an indispensible part of advanced manufacturing technologies that are at the disposal of the new-generation engineers and technologists. To meet the stringent demands of increased quality and precision while simultaneously reducing cost and improving production rates, laserbased manufacturing has proven its value. Because the laser beam can transport considerable amounts of energy it can be applied to: ■ Heat material for hardening or soldering. ■ Melt material for cutting or welding operations. ■ Vaporise material for drilling or surface structuring. ■ Ionise material to form a plasma that will allow deep penetration welding. Modern-day laser operators are able to focus or defocus laser beams using optical components such as lenses, mirrors and collimators. In combination with the capability to vary the interaction time between laser beam and material surface, a variety of processing mechanisms become possible. A collimator is a device that narrows a beam of particles or waves.
minimal difficulty. Manufacturing engineers have also become used to the attractive benefits of laser-based manufacturing: ■ Contactless machining removes the costly tool wear and replacement burden. ■ The ability to focus down to a few microns and the inherent automation of the processes ensure high precision results. ■ Focusing energy to high intensities means the total heat input is considerably less than that in more traditional methods. ■ Unwanted side-effects caused by heating of adjacent material can be eliminated. ■ A moving light beam ensures flexibility in movement and access to difficult areas that is simply not possible with mechanical tooling. ■ Lasers are also fast. Processing speeds are normally faster than conventional machining or welding methods. Laser cutting Lasers are extremely versatile cutters (see Figure 2). Lasers can cut a wide range of thicknesses, from
wafer-thin semiconductor chips for the electronics industry to steel plate material 30 mm thick for the construction industry. Nitrogen, argon or helium gas is used to shield components from oxygen, to prevent fires and oxidation because these gases are inert.
The different strategies developed by laser engineers include: ■ Fusion cutting, which uses a laser to liquefy the metal substrate and then an assist gas (normally nitrogen or argon) is used to blow the molten droplets out of the groove. ■ Plasma-assisted cutting, which is done with CO2 lasers set up to concentrate enough energy in the cutting area to ionise part of the material. This results in more effective energy transfer from the laser. During this high-speed plasma cutting, process speeds of 40 m per minute are not uncommon. ■ Sublimation cutting, which adds enough energy onto the substrate to allow gas formation on the surface. Nitrogen, argon or helium
This is illustrated in Figure 1, which shows that low-power densities at interaction times of about one second will introduce hardening effects on carbon steels. High-power densities introduced at reaction times shorter than one millisecond, on the other hand, will result in ablation (evaporation) of material, giving a micro machining effect. This application is not limited to metals or polymers. Ceramic materials can be treated in the same way with
Figure 1. Laser processing domains.
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Figure 2. The laser cutting process illustrated diagramatically.
Figure 3. Three-dimensional laser cutting of catalytic converter shell.
Figure 4. Cross section of laser-drilled hole: 1 mm diameter and 12 mm deep. Image: CSIR
gas is employed to shield oxygen and prevent spontaneous burning. The process is common for cutting plastics, textiles and non-melting materials like wood, cardboard or foam. ■ Microjet cutting, which is an option when the use of shielding gas is not favoured. The laser energy is transferred to the substrate in exactly the same way that light is transported along an optic fibre. The laser beam is contained inside a water jet of 20 to 150 micrometer diameter. The water not only carries the laser energy, it also washes away any debris at the cutting surface and cools the surface. Excess water forms a film around the work area, preventing the formation of spatter (molten metal droplets that re-attach to the surface). The final result is a smoothly cut, high-quality surface. Laser drilling Drilling small holes into tough or brittle materials used to be a cumbersome experience that often ruined the part – laser drilling now provides the solution. The process does not depend on the hardness of the material. Paper, polymers, metals,
4 Quest 6(3) 2010
Figure 5. Laser-drilled cooling channels in turbine blades.
ceramics and even precious stones have become regular candidates for laser drilling. An added advantage is the fact that no mechanical stresses are introduced into the material. The laser doesn’t blunt and all holes can be finished to the same quality and dimensional accuracy. Along with this, the relative ease of moving light beams around the work area has enabled considerable improvements in production speeds. Laser drilling requires intensely focused laser beams that allow instant melting and gas formation. The high intensities are created by setting up lasers to deliver radiation in short, intermittent pulses of high energy. Four machining strategies are used: ■ Single shot drilling exposes the work area to a single high energy laser pulse of short duration. This approach is suited to drilling small holes in thin materials. A large number of holes can be created in an extremely short time. A popular application is the creation of micropores in paper layers for filter applications. ■ Percussion drilling employs a series of successive low-energy pulses at the same positon to produce
deeper, more precise holes. Smaller diameters are possible with this strategy. The process is well suited for drilling deep holes in small nozzle components. ■ Trepanning drilling starts off with a single percussion drilled hole which is then enlarged by the application of repetitive pulses delivered in circular patterns that gradually move outwards from the centre. Relatively large holes are machined that can typically serve as lubrication holes in mechanical transmission systems. ■ Helical drilling does not remove all material. Percussion drilling in a helical spiral configuration is done to move gradually from the top to the bottom of the material. The unaffected core is then removed to expose the hole. High-quality holes that are relatively large and deep can be created. Cooling channels in aerospace turbine blades is a popular application for this technique. Laser structuring and ablation Laser ablation is similar to mechanical milling where parts are produced by removing material layer by layer from a workpiece. The cutting tool is replaced in this case by a finely
welds are possible, which require less finishing work afterwards or even completely eliminate this process. ■ Laser welding produces welds of comparable or higher strength than conventional techniques in most applications. ■ Lasers only need to access the component from one side because full penetration of the component is possible in most cases. Conventional arc welding processes normally require access from both sides. ■ Welding speeds up to about 10 m per minute are possible for most applications, which is much faster than typical conventional welding processes. ■ Laser welding is well suited to automation. ■ Inherent in laser processes is good process control, which will deliver components of good quality. ■ Laser welding is a contactless process. No mechanical forces are applied to the component. In order to exploit the deep penetration capabilities of the laser beam, it is focused to obtain power densities of 1 MW/cm2. This results in melting as well as partial vaporisation of the exposed material. The vapour exerts pressure on the molten metal and partially displaces it. The result is a narrow, deep vapour-filled hole (also called a keyhole), which is surrounded by molten metal. As the welding beam is traversed along the welding joint, the keyhole moves with it through the workpiece. The molten metal flows around the keyhole and solidifies at the trailing end. High aspect ratios are characteristic of laser welds. Penetration depth can be up to ten times greater than the width of the molten material. A typical laser weld in cross-section is illustrated in Figure 7 and the keyhole concept in Figure 8. Laser surface treatment It is possible to selectively modify the surface properties of metals by radiating relative small amounts of energy in very high concentration onto a surface. Heating steel surfaces close to the melting temperature where it transforms to a phase called austenite. When the laser has passed the area the underlying material (that was not affected by the laser radiation) acts as a heat sink, resulting in self-quenching and rapid
Figure 6. Micro mould produced by means of laser ablation.
Figure 7. Cross-section of a typical deep penetration laser weld.
Figure 8. Diagram illustrating the concept of keyhole welding.
cooling of the heated surface. This results in a layer of surface material that transforms to a martensite phase, which is considerably harder than the original surface while the toughness of the bulk material underneath is retained. Martensite phase: this is a hard steel crystalline structure that is formed by the rapid cooling (quenching) of the austenite phase, which traps carbon atoms that do not have time to diffuse out of the crystalline structure.
Distortion is also minimal because the total amount of heat applied is very small. This treatment prolongs the service life of tools. The same beneficial effect occurs when bearing and bushing surfaces of moving machine parts are hardened. Laser remelting of surfaces can improve the wear and corrosion resistance of components. During ▲ ▲
focused laser of high intensity that vaporises the material layer by layer. Since the active area is typically only 20 microns in diameter and the layer thickness removed is typically only 2 microns of material, removal rates are much slower. However, intricate detail and superior surface finish are possible with this process. Hard and brittle materials pose no problem either. This technology finds application in the manufacture of tools and moulds, as well as in electronics and semiconductor technology where intricate details with very smooth surfaces are required. An example of a micro mould that was manufactured with laser ablation is shown in Figure 6. Laser joining Laser joining technology has been around for the last 40 years and has gained wide commercial acceptance in the automotive industry because it makes extremely fast production rates possible and simultaneously guarantees good quality and consistency. Applications are found mainly in polymers and metals, but there are a few examples of ceramic welding. Welding requires melting of the work piece. To obtain sufficient energy densities it is necessary to focus the laser beam to produce a spot size of about 0.25 mm on the work piece surface. This implies that the fit between components needs to be good. If there are gaps between adjoining plates laser welding will not be possible because the laser beam will pass through the gap and no melting will take place. Some polymers are transparent to laser light, which means that the energy from the beam will not be absorbed and no welding will take place. The neat solution to this problem is to either add an absorbing pigment to the polymer to enable absorption of the energy or to introduce an absorbing powder between the mating surfaces that will absorb the energy and transfer the heat to the polymer parts. Welding engineers turn to laser technology for the following reasons: ■ Small heat inputs are used, which ensure lower thermal stresses in components (resulting in less distortion) and also less material around the weld area that is adversely affected by the heat from the welding process. ■ Smooth surfaces and narrow seam
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Figure 9. An example of laser marking.
Figure 10. Diagram illustrating the principles of laser metal deposition.
resolidification a finer structure appears that is normally also more homogeneous and free from internal defects. This technique is applied with great success to automobile camshafts, which regulate the movement of engine valves. During processing of the cast iron surface, an extremely hard phase called ledeburite is created that can withstand the sliding wear conditions experienced in operation. Laser marking Laser marking is definitely the most versatile and flexible marking method available today. The laser does not make physical contact, it does not wear out and its movement is fast and easy to program. The laser produces a high-quality durable mark. These qualities make the laser ideal for marking surfaces of all shapes and even areas that are difficult to access. Three techniques are used for marking: ■ Engraving involves the removal of material through ablation to create grooves or recessed areas. A colour can easily be added. Surfaces are covered by a material of different colour and this top layer is then selectively removed to expose the bottom layer. Black substrate
6 Quest 6(3) 2010
material with a white coating on top is used with good effect for lettering and bar codes. ■ Annealing can be used on materials that change colour on exposure to heat. It is usually applied to create various colours of oxide layers on metal surfaces. ■ Organic materials undergo colour changes when laser radiation changes the surface composition of the material. Depending on the combination of laser type and substrate material, both lighter and darker lettering are possible. Where do we find laser markings? ■ Functional signs and symbols such as lines and numbers. Think about speedometers, gauges and washing machines. ■ Logos and names on parts and products. ■ Expiry and sell-by dates on products. ■ Material specification information on raw materials. ■ Serial numbers and tracing codes on parts and packaging material. ■ Marker indications for downstream processing on the manufacturing line. ■ Decorative sculpturing inside transparent solid objects such as glass or perspex. Laser refurbishment Maintenance of equipment in the manufacturing sector is absolute essential in order to deliver orders on time and keep the factories profitable. The vast majority of equipment used in production is still imported from overseas suppliers. This means that both the cost of replacement and the waiting times for delivery will increase. Companies are forced to buy additional stock of critical components to ensure that equipment will remain operational at all times. This would not be necessary if repair technologies were available for damaged or worn components that could restore it to the ‘as new’ specification. Laser refurbishment is such a technology. It does not only allow refurbishment of components; in many instances it can produce components with improved performance and extended life times when compared to the original ones. Refurbishment is done by a laser metal deposition process. A focused laser beam of high intensity produces a very shallow melt pool on the surface. Metallic powder or wire is fed into the melt pool where it is fused
onto the surface of the component. When the melt pool is moved along the surface of the component, a weld bead is produced. By creating overlap between successive weld beads a layer is produced. The thickness of a single layer is typically in the range of 0.5-2 mm. Thicker layers can be produced by applying successive layers until the required thickness is achieved. The composition of this added layer can be the same as that of the component or the layer can consist of a different alloy. In the latter case, materials engineers will take great care to ensure that brittle intermetallic compounds do not form in order to guarantee optimum mechanical properties. Laser refurbishment is used to rebuild worn-out surfaces and to improve the abrasive wear, corrosion resistance and oxidation resistance of components. Layers of high performance alloys such as stainless steels, nickel base alloys and cobalt base alloys are applied in the critical areas. The advantage of this approach is that components can be manufactured from inexpensive alloys and a thin layer of the expensive alloy can be applied only to those areas where it is really required. The advantages of the laser refurbishment process in comparison to conventional techniques are: ■ The much lower heat input results in minimal distortion and much smaller heat-affected zones in the underlying component material. ■ A solid metal bond is created at the interface. This differs from the mechanical keying and partial metal bonding present in thermal spraying processes. The impact and fatigue resistance are therefore superior. ■ The dilution of the substrate material into the deposited layer is much lower than with conventional welding processes. Thinner layers are needed to ensure a surface that is free from contamination by the elements from the underlying material. ■ The low heat input causes rapid solidification, which results in fine microstructures. The result is higher strength properties and better corrosion resistance. ■ The excellent surface quality of the deposited layer reduces the amount of post machining. This is a significant benefit, as the overlay
Figure 12. Diagram illustrating the scanning process used in SLM (left) and the SLM process in action (right).
Figure 11. Laser refurbishment of a shaft.
Figure 13. LMD-based laser additive manufacturing.
materials are invariably hard and difficult to machine. Laser refurbishment has proven to be a very versatile process. It is particularly attractive where high-value components are concerned. These include: ■ Moulds and dies for sheet metal processing ■ Turbine blades and housings of jet engines ■ Turbine blades and couplings found in power generation equipment ■ Large compressor screws used in the petrochemical industry ■ Shafts and valves found in pumps for the mining industry ■ Repair of casting defects and correction of machining errors on high value components.
Laser additive manufacturing Conventional machining is widely used in the manufacturing industry. In this approach a mechanical cutting tool is used to remove material from a solid block. This process is referred to as subtractive manufacturing and has proven to be cost effective for a wide range of components. Apart from the normal problems like tool wear and the need for rigid clamping it also has limitations in terms of the geometries that can be produced. It is difficult to produce very thin webs and near
impossible to make hollow components. In the aerospace industry, typically up to 90% of the raw material is wasted as scrap in the production of aerodynamic components. When large components have to be produced from expensive materials like titanium alloys, nickelbased super alloys or aircraft-grade aluminium alloys the raw material cost becomes the main cost driver. In this case laser additive manufacturing is the most attractive alternative. In laser additive manufacturing a CAD (computer-aided design) model of the component is ‘sliced’ into layers by software and transformed into machine instructions for the laser system. The component is then manufactured layer by layer. Each layer is produced by a laser beam that melts and consolidates the raw material, which is in the form of a fine powder. The laser power supplied is sufficient to fuse the new layer completely into the previous layer. Two approaches to laser additive manufacturing have been developed. In selective laser melting, a uniform layer of powder, 50-200 micrometer thick, is placed across the working area by a hopper and scraper system. The computerised data that describe the particular layer of the component are converted into a robotic instruction for
the laser system, which is then used to scan and selectively melt the area on the powder layer which corresponds to the component. Once the layer has been consolidated, a new layer of powder is applied and the process is repeated until the entire part has been produced. The powder that is not melted can be re-used and is not wasted. The second approach is based on the laser metal deposition process, which is described in the section on laser refurbishment. Instead of using a laser beam to consolidate a layer of preplaced powder, powder nozzles move in harmony with the laser beam to deliver powder only to the areas where welding takes place. Each layer is produced by converting the CAD data for the particular layer into a series of overlapping tracks. The laser beam is then moved along these tracks where it generates a melt pool of base material and molten powder droplets. A layer is formed which is fused to the preceding layer. Repeating this process for all the layers in the computer model builds up the total component. Apart from tremendous savings in raw material costs, the laser additive manufacturing process offers additional advantages over traditional production techniques. These include: ■ Freedom of design. In the selective laser melting process the unused powder supports the part in space during production. This allows for practically any geometry to be produced, especially overhang structures that are only attached to their support structures when welding is done later on layers higher up.
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Laser materials processing at the National Laser Centre The National Laser Centre (NLC) at the CSIR aims to enhance the global competitiveness of the South African manufacturing industry through the introduction and implementation of appropriate advanced laser-based manufacturing technologies. In order to achieve this goal the NLC conducts research and development in aspects of laser-based manufacturing which are of special interest to South Africa. In addition NLC also offers specialised laser-based manufacturing services to industry, which are not available form other local companies. These include laser refurbishment, laser joining, laser ablation and laser cutting. In order to ensure that laser-based manufacturing assumes it rightful place in industry the NLC also strives to increase the local awareness of the advantages of laser based manufacturing. Of primary importance is that the engineers of tomorrow are introduced to the benefits of this exciting technology. One of the mechanisms through which this is achieved is the PULSE (Public Understanding of Laser Technology) initiative, which primarily targets schools and higher education institutions. The PULSE activities include demonstrations at the educational institutions as well as visits to the NLC’s facilities in Pretoria. The CSIR also offers bursaries to science and engineering students who whish to pursue a career in laser technology.
Figure 15. Scanning electron microscope photograph of a fly wearing laser-cut spectacles! Images courtesy of Trumpf GmbH.
Figure 14. SLM produced part (right) and CAD model (left).
■ Flexibility. Design changes can be implemented by changing the CAD model and do not require modifications of moulds and tooling as would be necessary in a casting process. ■ Excellent mechanical properties. The rapid solidification associated with this process produces mechanical properties which are comparable to those of the wrought alloys. ■ Quick turnaround time. The fact that no geometry-specific tooling is required shortens the time for developing first prototypes considerably. Laser additive manufacturing is a comparatively new manufacturing technique, which shows great promise. It is expected to gain even more applications in future as manufacturing engineers optimise processes even further and drive unit costs down. Conclusion Over the past 50 years laser-based manufacturing has emerged as a key technology for global competitiveness. When it was first invented the laser was seen as a solution in search of a problem. This situation has changed dramatically. Today engineers and
scientists turn to laser technology in search of solutions to problems which can’t be solved by conventional means. The laser has proven itself not only to perform faster and better, but also to do the seemingly impossible – see Figure 15! ■ Charl Smal is a certified professional engineer who started off as a metallurgical engineering graduate. He specialised in welding technology and the management of technology projects. He has managed various development projects in the nuclear industry, defense and laser-based manufacturing. Herman Burger studied physics at the University of Pretoria before joining the Laser Section at the National Physics Research Laboratory in 1982. He was involved in the development of laser sources until 1987, when the Laser Section was incorporated into the newly constituted Division for Production Technology. He was responsible for the development of laser sources and laser-based production systems for industrial applications. In 2000 he joined the National Laser Centre at the CSIR, where he is currently the research Group Leader in the Laser Materials Processing competence area. Research and development projects are conducted to enhance the competitiveness of the South African manufacturing industry through the implementation of laser-based manufacturing processes.
CSIR – Our future through science The Council for Scientific and Industrial Research (CSIR) is a leading scientific and technology research, development and implementation organisation in Africa. It undertakes directed and multidisciplinary research and technological innovation to improve the quality of life of South Africans. To ensure that it achieves maximum impact, the CSIR focuses its research and development to impact in the following portfolio areas: Built Environment; Health; Industry; Natural Environment; Energy; Defence; and security. Contact: Tel: 012 841 2911 e-mail: firstname.lastname@example.org www.csir.co.za
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A career in laser technology P
atience Mthunzi is a remarkable young woman. Growing up in a middle-class family in Soweto, she has travelled the long road to academic and personal success in science. After matriculating in 1994, an interest in the human mind led her to a degree in psychology through UNISA. However, this was not enough and she enrolled at the then Rand Afrikaans University (now the University of Johannesburg) to study for a BSc in biochemistry, followed by an MSc in medical biochemistry, which focused on the study of HIV. Her first position was as a contract scientist at the National Institute for Communicable Disease (NICD) in their HIV vaccine unit. Although the work was stimulating enough for Patience’s inquiring mind, the constant ‘renewable contract’ was worrying and she moved to a permanent position at the Council for Scientific and Industrial Research (CSIR), which is everything she has wanted as a young scientist. As far as Patience is concerned, everything in life revolves around science,
Life in St Andrews, Scotland.
engineering and technology (SET). As she says, ‘science teaches us how things work, engineering allows us to construct and design the objects that scientists and others use to harness our knowledge of the world around us and technology – well, where would we be without technology!’ Patience has taken her career further by completing a PhD in laser physics, specifically biophysics. This research area is a true mixture of physics, medicine, chemistry, biochemistry and biology. She describes this as ‘turning science into science
fiction’! Her PhD involved the study of the manipulation of nanoscale and/or microscale biological material with laser light tweezers in medical applications. She builds and uses optical tweezers designed using lasers of different wavelengths and regimes. These vary between continuous wave versus pulsing waves for various different applications. She is the first person in South Africa to hold a PhD in this field and her expertise is valued across the national scientific community. Patience was lucky enough to be able to study for her PhD in Scotland – at the
oldest University in Scotland, St Andrews, which is also the second oldest university in Britain. She worked under two of the big names in laser physics Wilson Sibbett (the father of femtosecond lasers) and Kishan Dholakia (a guru in optical tweezers). After this experience simply nothing is impossible! Patience already has an impressive list of publications in journals such as the Journal of Selected Topics in Quantum Electronics, Optics Express and the Journal of Biomedical Optics and hopes to eventually publish in prestigious journals such as Nature and Science.
Q News The future belongs to electric cars Engineers have been working on electric cars for a surprisingly long time. In fact, the first trials stretch back well into the 19th century. There were some 30 000 electric vehicles on the road in the USA alone in 1912. Climate change, particulate pollution and oil prices have prompted renewed interest in electric cars. By 2020, a million electric cars should be on the roads in Germany according to plans tabled by the federal government. Thirty three Fraunhofer institutes are cooperating closely to promote the development of electric vehicles, focusing not just on the drive concepts, but also on the specification for solar-powered charging stations, and the kind of challenges that lie ahead in terms of power supply and urban planning. Source: Fraunhofer-Gesellschaft
The Fraunhofer-Gesellschaft electric car.
Quest 6(3) 2010 9
Shaping light Modern micro-optical elements and adaptive mirrors exploit diffraction to shape light inside a laser. By Andrew Forbes, Craig Long, Philip Loveday and Igor Litvin.
When the laser operates in rectangular symmetry, the output light patterns (called modes) form 2D patterns of light following what are called Hermite–Gaussian functions. The number of null lines between the ‘spots’ of light correspond to the order of the functions – more spots, higher order.
The bell curve – or normal distribution
Back to basics LASER (Light Amplification by the Stimulated Emission of Radiation) light can easily be distinguished from other light sources (such as torches) by its brightness and directionality. This can be demonstrated at home by holding a laser pointer in one hand and a torch in the other, and shining both towards a wall at the opposite end of a room: the laser light will be concentrated in a small bright spot, whereas the torch light will be far more diffuse. This property is as a result of what is known as coherence, a measure of how ‘in-step’ the emitted photons of light are. Coherent light can be made to interfere with itself, in a way that is similar to the way in which ripples on a pond interact. As a result, it is possible to take some light, add some more light to it, and the result will be no light! This never happens with torch light (unless you pass it through a very small pin-hole) but it does happen with laser light, since laser light is coherent while torch light is not. So, how is laser light produced? When a material is supplied with energy the atoms in the material become excited, resulting in electrons jumping to higher, unstable, energy levels. When an excited electron returns to its original energy level a light particle, or photon, is emitted. You encounter this phenomenon every day; this is the process that causes a heater element in a toaster, or a torch light bulb filament, to glow when supplied with electrical energy. This
does not, however, mean that your toaster is a laser! In a toaster or a light bulb, photons are released randomly, while in a laser the photons are released coherently through a process known as stimulated emission. An atom with excited electrons encountering a photon with certain properties, such as direction and frequency, tends to release photons with similar properties. These two similar photons will then interact with other high-energy atoms releasing even more ‘in-step’ photons, and so on. To make a laser one therefore requires only three basic ingredients. First, we need a transparent or semitransparent substance capable of amplifying light. That is to say, if we put some light in, we would like to get even more light out. We call this the gain medium. Unfortunately no medium exists that will amplify light without some form of excitation, so our second requirement is an excitation system. In many lasers this is simply an electrical current, but in some more exotic lasers in the former Soviet Union the excitation was a nuclear bomb, so it really only depends on what you want to do, and how crazy the scientists are!
Dark blue is less than one standard deviation from the mean. For the normal distribution, this accounts for about 68% of the set (dark blue), while two standard deviations from the mean (medium and dark blue) account for about 95%, and three standard deviations (light, medium, and dark blue) account for about 99.7%. The normal distribution, or bell curve, is a curve that describes any data that tend to cluster about a mean (average) figure, for example, the heights of men or women in a specific population. The standard deviation is a measure of variation from this mean. The curve describes the probability of a particular data point occuring in a specific population. In lasers, the intensity of light across a beam will form a bell curve.
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A schematic of a laser, showing the three core components: the resonator bound by the two end mirrors, a gain medium, and a means to excite the gain medium.
Left: The rainbow colours on the readable surface of a compact disc (CD). Image: Wikimedia commons
Diffraction is most pronounced when features are comparable in size to the wavelength of the light passing through (or reflected off) them, and the resulting field is an interference pattern. The distinguishing property of DOEs is therefore the feature sizes on the optical element. If the DOE is designed carefully, this interference pattern can take on almost any shape – customised light! This shaping of laser beams can be done external to the laser, but there are advantages in doing it inside the resonator: no additional optics and fewer optical alignment problems. We routinely create such patterns digitally in our laboratory for the creation of vortex beams and non-diffracting beams for the optical trapping and tweezing of miniature particles and biological specimens. ▲ ▲
The excited gain medium has what is called a population inversion (it contains more atoms in an excited state than at a lower energy state). Laser light requires stimulated emission, and Einstein showed that this benefits from a strong field of photons. Thus, the third requirement is a box that keeps the light bouncing back and forth inside the gain medium, so that more stimulated emission takes place. This ‘box’, or resonator, is usually made of two mirrors, one of which is partially transmitting so that on each pass a little of the light is let out of the box. While the gain medium determines the wavelength (and therefore the colour) of the laser light, the resonator determines the shape of the light. Laser beams usually have a Gaussian intensity distribution with a smooth profile following the well-known Bell curve function – they have a high peak intensity at the centre which slowly drops to zero at the edges of the beam. If the optical elements inside the resonator are custom designed however, it is possible to create laser beams with very complicated cross-sectional patterns. We refer to this as shaping the light inside the laser, and typically we do this with diffractive optical elements (DOEs). Shaping light with DOEs When encountering an obstacle, travelling waves such as light, may be reflected, refracted and/or diffracted. For pure reflection or refraction, obstacles such as mirrors or lenses are much larger (mm to cm range) than the wavelength of light (400-700 nm for visible light). Although diffraction may not be as well known, it is just as common as reflection and refraction. Diffraction is what gives the bottom of a CD that rainbow effect, caused by light interacting with the spiral pattern of tiny, closely spaced, alternating flat and raised lines on the bottom of a CD.
Top and above: Light can be shaped outside a laser by using spatial light modulators – liquid crystal devices for creating digital holograms to mimic DOEs. Light diffracts off these devices into a wide range of diffraction orders, as shown by these long exposure pictures. Image: CSIR
A Gaussian profile laser beam, with a characteristic peak at the centre and slow decay at the edges.
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The resonator concept, as shown here, comprises two transparent DOEs (like lenses) at either end as well as the usual bounding mirrors to complete the box.
A technician evaluates the interaction of multiple lasers that will be used aboard the Airborne Laser. Image: Wikimedia commmons
Keeping light in shape with adaptive optics In practice, it is not possible to create a perfect optical component or system, and there are always small errors due to manufacture, assembly, and so on. Furthermore, as the laser works it heats up and components may expand slightly or experience other temperature- or time-dependent changes. It is possible to measure this error continuously at the point where the beam exits the resonator using a special piece of equipment called a wavefront sensor. Using this information, we can calculate how the laser beam should be modified in such a way that the best beam quality is maintained, and all we then need is to appropriately adjust an optical element to correct the wavefront. This is known as adaptive optics. Similar techniques are used to eliminate the effects of atmospheric turbulence in large telescopes, such as the Southern African Large Telescope (SALT) in Sutherland. Using small actuators located behind a mirror it is indeed possible to manipulate the beam slightly to compensate for these errors, and thereby ensure that the laser is functioning optimally. This way, if we wanted a Gaussian beam from the laser for example, we get a Gaussian beam.
A fat-top profile laser beam; such beams have a constant energy density in the central part of the beam, that sharply falls to zero at the edges.
Laser beams made to order Gaussian laser beams are popular because they propagate with a very small rate of spreading, and so are ideal for long-distance communication and military applications. Unfortunately they fill a very small region of the gain medium inside the laser, so there’s a lot of the gain material not being used. As a result, there is always a choice between having a good laser beam (Gaussian) or a laser with lots of energy but which is not Gaussian. For example, in recent experiments the Gaussian beam could be produced from a laser using standard techniques, but then the energy was 25 times less than the
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maximum without a Gaussian shape! In a ground-breaking development, we have designed DOEs to create a very special laser beam – one that changes (metamorphosis) from one shape to another when travelling inside the laser resonator, so that we can have different shapes at the two resonator mirrors: a smooth ‘Gaussian’ beam at one end, and a ‘flat’ beam at the other. This metamorphosis obeys the wave equation, which predicts how these fields propagate, but the custom phase of the light ensures a more complex propagation across the resonator than would usually be observed. By designing our resonator to have the flat beam at the one end, we can extract high energy, while the metamorphosis ensures that all this energy goes into the ideal Gaussian laser beam – the best of both worlds! By selecting the Gaussian beam by a DOE we are ensuring that no energy is lost in the process. It was previously thought that such beams cannot be selected by phase because they share the same phase function as many other types of beams, so distinguishing them would be difficult. We have now shown that the metamorphosis idea circumvents this problem, thus demonstrating a key technology that will revolutionise laser design in the future. At the moment high-energy lasers with good laser beams require very large and expensive systems. For example, the USA Air Force Airborne Laser, a highpower laser to shoot down missiles, fills an entire Boeing 747! By customising the laser resonator it is possible to design light to order. Laser technology has been around for 50 years, yet new research and ideas are ensuring that it will remain an active area of investigation for years to come. ■ Professor Andrew Forbes is Chief Researcher and Research Group Leader at the CSIR National Laser Centre, and holds honorary positions in the Schools of Physics at both the University of Stellenbosch and the University of KwaZulu-Natal. Dr Craig Long is a Senior Researcher at CSIR Material Science and Manufacturing. Dr Philip Loveday is a Principal Researcher and Research Group Leader at the CSIR Material Science and Manufacturing division. Dr Igor Litvin has recently graduated with his PhD and has joined the CSIR National Laser Centre as a Senior Researcher.
Q Fact File
The atom T
he atom is a basic unit of matter. It is made up of a dense (heavy) central nucleus, surrounded by a cloud of negatively charged particles that are called electrons. An electron is a sub-atomic (smaller than an atom) particle that carries a negative electrical charge. A proton is a sub-atomic particle that carries an electrical charge of +1. Protons can also exist on their own â€“ the hydrogen ion (H+) is a proton. The number of protons in a nucleus is the atomic number and this defines the type of element (pure chemical substance) that the atom forms. A neutron is a sub-atomic particle with no electrical charge. Its mass is slightly larger than that of a proton. The nucleus of an atom is a mixture of positively charged protons and electrically neutral neutrons. The electrons of an atom are bound to the nucleus by the electromagnetic force that is generated by the electrical charges they carry. More than 99.9% of an atomâ€™s mass is concentrated in the nucleus. Electrons that are bound to atoms have a stable set of energy levels, which are also called orbitals, and these electrons can move between these energy levels by absorbing or emitting photons (light particles) that match the energy difference between these levels. Electrons determine the chemical properties of an element and
also its magnetic properties. Bohr referes to the atomic physicist, Neils Bohr, who was one of the first people to describe the energy levels of the electrons in an atom.
Atoms and elements A chemical element is a pure chemical substance that is made up of one type of atom. Each element has a specific atomic number, which is the number of protons in its nucleus. Common examples of elements are iron, copper, silver, gold and oxygen. At the time of writing 118 elements have been observed, 92 of which occur naturally on the Earth. The rest are synthetic elements that have been produced artificially in particle accelerators. Oxygen is the most abundant element in the Earthâ€™s crust. The number at the top of each element is its atomic number.
Top right: A depiction of the atomic structure of the helium atom. The magnified nucleus is schematic, showing protons in pink and neutrons in purple. Image: Wikimedia commons
Right: A simple diagram to show the orbitals of an atom according to the Bohr model. The red line depicts an electron jumping between these levels. Image: Wikimedia commmons
Below: The periodic table of the elements.
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Sunset in Mumbai, India. The high levels of particulate matter make for a spectacular scene, but not for good health! Image: Wikimedia commons
L aser s i n t he s k y : LIDA R and a tmospher ic par ticula t e measur ement QUEST takes a look at the way in which laser research is contributing to our understanding of pollution across the country and into the rest of Africa.
ow can laser technology help us to understand the atmosphere â€“ and more importantly â€“ the effects of particulate matter in the atmosphere? Letâ€™s start by looking at what particulate matter is and why it is important. Particulate matter plays a key role in physical and chemical atmospheric processes, locally and on a global scale. Particulates Particulate matter is composed of fine particles, also called soot. These are tiny subdivisions of solid or liquid matter that are suspened in a gas or a liquid. The term aerosol, which you will also come across, is given to particles and gas together. Particulate matter can come from man-made sources, or it may come from natural sources, such as volcanoes, dust storms and forest and grassland fires, living vegetation and sea spray. However, human activities lead to what are called anthropogenic sources of particulates. This includes burning fossil fuels, power plants and various industrial processes that also generate significant amounts of aerosols.
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The map illustrates just how much warmer temperatures were in the decade (2000-2009) compared to average temperatures recorded between 1951 and 1980 (a common reference period for climate studies). The most extreme warming, shown in red, was in the Arctic. Very few areas saw cooler than average temperatures, shown in blue. Grey areas over parts of the Southern Ocean are places where temperatures were not recorded. The analysis, conducted by the Goddard Institute for Space Studies (GISS) in New York City, is based on temperatures recorded at meteorological (weather) stations around the world and satellite data over the oceans. Image: Wikimedia commons
On average, across the world, anthropogenic sources of particulates account for about 10% of aerosols in our atmosphere. Increased levels of fine particules in the environment are linked to health problems such as
respiratory diseases, heart disease and even lung cancer. Particulates and climate change One of the main effects of increasing levels of atmospheric particulates is the concentration of these particles
You can see the laser beam coming out of the roof of the LIDAR vehicle. Image: CSIR
Figure 1 The LIDAR system.
The laser beam easily passes through clouds. Image: CSIR Geographical locations of the LIDAR sites in Pretoria and Durban, with other operational systems elsewhere shown as well (stars).
in the atmosphere, which has been implicated in global warming. This is generally thought to be as a result of increasing concentrations of greenhouse gases and particulates, that are produced by burning fossil fuels and deforestation. Global dimming, which results from aerosols blocking sunlight from reaching the Earth, may counter this to some extent but the jury is out just how much effect this is having, while it appears that the Earth is, in fact, generally getting warmer in all regions. Tracking particulates As in all scientific processes, we need to be able to measure particulates and track their behaviour in the atmosphere so that we can understand the effect of pollution on other atmospheric systems. Enter the laser! LIDAR, standing for light detection and ranging, is known to be a reliable tool for active atmospheric remote sensing, essentially laser radar. Many developed countries already have ground-based LIDAR systems in place, but this technique is still relatively new in South Africa and other African countries. LIDAR measurements have made a huge contribution to our understanding of the role of atmosphere dynamics and particle microphysics. The measurements are made on a predetermined spatial scale
– from site to region – it is possible to work out where the particulates have come from; for example, burning forests or grasslands. It is also possible to classify the particulates into source regions, such as industrial, biological and anthropogenic. The LIDAR system A mobile LIDSAR system has been developed at the CSIR National Laser Centre. The diagram above (Figure 1) explains how the LIDAR system works. The three main sections, namely the transmission, receiver and data acquisition sections, are shown. The transmission section shows the laser system with turning mirrors and beam expander. The receiver section shows the receiver telescope with the primary mirror as well as the motorised translation stage and photo-multiplier tube (PMT). The data acquisition section shows the personal computer as well as the transient recorder. The laser beam comes through the roof of the mobile LIDAR and can propagate through any clouds. Measurements can be made from the ground to 40 km into the atmosphere. With a mobile system, measurements can be made all over South Africa, significantly improving our understanding of what contributes to pollution in our atmosphere, which will allow far better control in the future. ■
A laser beam propagating through the Pretoria night sky. Image: CSIR
This article was compiled using material provided by Professor Venkataraman Sivakumar, who is is a principal researcher at the CSIR/National Laser Centre. He leads the LIDAR team’s efforts to integrate and develop a new mobile system for detection and characterisation of atmospheric particulate matter and pollutants.
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How lasers can help us understand Patience Mthunzi explains how the highly focused light provided by lasers can help us to understand how disease cells behave in the body. Coherence: in physics coherence describes the relationship between all the properties of a wave. In lasers, coherence means that the laser emits light in waves that are of identical frequency, phase and polarisation.
Figure 1. (A) profile of CW laser output with respect to time while (B) denotes the output profile of a pulsed laser relative to time.
Figure 2. Newton’s Third Law illustrated. Molecular motor: a motor is a device that consumes energy and converts it into motion or mechanical work. On the molecular level an example is the way in which proteins in a single cell use the chemical energy released by adenosine triphosphate (ATP) to do mechanical work – a molecular motor.
asers are highly coherent, monochromatic (single colour) light beams that may be focused into an extremely small spot size (micrometer size range). Lasers can produce either a continuous wave (CW) of light or pulses of light in high peaks (see Figure 1). Recently, scientists have found that both CW and pulsed laser light sources are an essential tool in biomedical research. Classic applications include manipulating single cells and their subcellular organelles, measuring the elasticity and structure of DNA or that of red blood cells, creating molecular motors, studying the interaction of infectious agents, chromosome cutting, stimulating neuronal growth, sorting cells and delivering both genetic and non-genetic matter of varying sizes into the cytoplasm of mammal cells. Optical tweezers Optical tweezers are the tool that laser physicists use for this targeted, specific and single-molecule analysis. What are optical tweezers? Light can behave as particles, so it can be governed by the same rules as other particles; by Newton’s Laws,
Organelles are the specialised sub-units within a cell that have specific functions.
A typical animal cell. Within the cytoplasm, the major organelles and cellular structures include: (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (6) Golgi apparatus (7) cytoskeleton (8) smooth endoplasmic reticulum (9) mitochondria (10) vacuole (11) cytosol (12) lysosome (13) centriole. Image: Wikimedia Commons
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for example. Let’s look at light as a photon entity. The photons in light possess momentum, a property that is used for the operation of optical tweezers. When light interacts with a micro-particle, it can exchange both energy and momentum with the particle. The force exerted on the particle is equal to the momentum transferred per unit time. As stated by Newton’s Third Law of motion, ‘every action force has an equal and opposite reaction force’ (see Figure 2). Because the force exerted by the photons in the laser beam is met by an equal and opposite force from any micro-particles (e.g. a single cell) the laser light traps or ‘tweezes’ the micro-particle and can move it about without any actual physical contact. This concept was first introduced by Arthur Ashkin and co-workers in the late 1980s when they showed that a laser beam can be used to create an ‘optical trap’ for manipulating microscopic particles. Once trapped, the particle can then be manoeuvred by controlling the laser beam; this is referred to as optical tweezing. Up to the mid 1980s biological studies were performed on whole tissues. But now optical tweezers allow us to examine single cells or even molecules. Optical tweezers exert such tiny forces (pico-Newton - 10-12 N) that they can manipulate tiny objects such as whole mammalian cells and their intracellular structures such as DNA, chromosomes and protein motors. Indeed this revolutionary technology paves the way to novel biomedical and biotechnological experiments at micro and/or nano scale levels. The relative refractive index (n) of the particle to be micro-manipulated determines whether they are attracted to the high or low intensity region of the laser beam (see Figure 3). The refractive index of a substance is the speed of light in that substance. The value of refractive index is expressed as a ratio of the speed of light in a vacuum relative to the speed of light in the substance being examined.
HIV and other illnesses That is, when light passes through a micro-particle (e.g. colloid, mammalian cell or any other micro-particle), there is a change in its propagation (spread) direction that is caused by refraction. In addition, because light carries momentum, this change in direction also corresponds to a change in momentum, which results in a force acting on the micro-particle that moves it away from its original position (see Figure 4). During lightâ€“particle interaction, the optical force that arises is said to be divided into two important components, called the gradient force (Fgrad) (in the direction of the spatial light gradient) and the scattering force (Fscat) (in the direction of light propagation). The latter can be thought of as a photon exerting a force on the particle in the direction of light propagation, while the gradient force tends to draw the particle towards the centre of the focal region. During optical tweezing, it is the scattering force that causes the microparticle to always move towards the most intense region of the beam; this is the way that the micro-particle is trapped. This trapped micro-particle can now be manipulated by moving the laser focal spot. Imagine grabbing micro-particles in three dimensions using only a very tightly focused laser beam spot with a diameter of less than one micrometer! Another important factor is that the biological specimens are not harmed by the light because most optical tweezers use near infrared continuous wave and pulsed laser sources, which will not penetrate the cells or micro-particles. Optical tweezers as tools Since their discovery, optical tweezers have contributed to a wealth of biomedical investigations. Optical tweezers have allowed scientists to indentify, characterise and isolate individual cells and cell subpopulations from a complex mixture of different cell types. Recently, the author used optical tweezers to separate two populations of Chinese hamster ovary cells (CHO) â€“ with (green spots in the illustration right) and without ingested polymer microspheres. This allowed the two cell populations to be cultured separately (see Figure 5). This technique can be applied to any class of cell types. For example, we can separate cancer cells from healthy cells, or stem cells from ordinary cells for cell
Figure 3. Particles of high refractive index (n>1) are amenable to optical tweezing.
Figure 4. Here the particle is held transversely by the gradient force and longitudinally by the focusing of the light beam.
transplants. The technique is expected to become an important technology in the future in the study of cancer and related biomedical research fields. Optical tweezing and HIV HIV-1 infection destroys the immune system by lowering levels of vital immune cells such as helper T cells (CD4+ T cells), macrophages and dendritic cells. As the disease progresses there is a critical decline in numbers of CD4+ T cells in particular, which leads to a decrease in cell-mediated immunity and allows opportunistic infections to take hold. HIV-1 has high genetic variability because it replicates so fast. This leads to massive rates of genetic mutation, which produces many variants of HIV1 within a single infected patient. This seriously complicates HIV-1 vaccine development. However, by using optical tweezing, HIV-1 cells can be analysed, and then sorted from small samples of human blood. Traditional cell sorting methods require large volumes of cells. Optical tweezing techniques, however, can be used on minute sample volumes and low cell concentrations. This is highly cost effective, patricularly in investigations that involve taking samples from infected people or that use precious cell lines that are difficult to culture and expand into large populations. This revolutionary technology has the potential to provide insight into the biochemistry of diseased cells and help develop valuable treatment regimes for a whole host of diseases. â–
Figure 5. Cell sorting by a laser light beam.
Dr Patience Mthunzi is a senior scientist in the Biophotonics: National Laser Centre at the Council for Scientific and Industrial Research (CSIR).
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Bringing science to the people Stellenbosch Laser Physics students tour through South Africa and Namibia with ‘Colourful Optics’ Roadshow. By Gillian Armstrong.
n a country where resources are scarce and education is a privilege, science sometimes needs to be brought to the people. In June this year (2010), a group of eight postgraduate students from the University of Stellenbosch embarked on such a science outreach expedition in celebration of the 50th Anniversary of the Laser. The students are from the physics department of the University of Stellenbosch, under the banner of the Laser Research Institute. In 2008 they founded a student chapter of the Optical Society of America (OSA), named the Stellenbosch Laser Student Chapter, through which they obtained funding to facilitate these outreach activities. The outreach initiative aims to provide exposure to the study of laser
Learners investigating the rainbow peephole, a diffraction grating that splits up white light into its colour components. Image: Laser Research Institute
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physics research and optics in general to students, learners and communities who would otherwise not have such an opportunity. This particular journey would lead them all the way to the north of Namibia, close to the Angolan border. The itinerary took them through Wellington, Springbok, Keetmanshoop, Stampriet, Windhoek and the Rundu area in northern Namibia. It spanned some 5 500 km and provided exposure to over 600 school learners from 10 different schools from diverse economic, social and cultural backgrounds. The highlight of the trip, and indeed its primary focus, was in the Rundu area, at the start of the Caprivi strip. There the group were able to visit four very remote schools and present their show to some 300 students between grades 10 and 12. Colourful optics The show presented to all the students was entitled ‘Colourful optics’, a multimedia presentation, sprinkled with interactive optics demonstrations. This allowed the group not only to provide information about the theoretical side of optics, but also to use entertaining and impressive practical displays to bring that information to light. One experiment used a powerful green laser pointer to light a match (which had been dipped in boracic acid before the show). The students were always amazed at the resultant green flame! On the more serious side, the application and relevance of lasers
and optics in the modern world was discussed and illustrated. One fascinating experiment showed that white light is not exactly what we perceive it to be, but rather a full spectrum of all colours. A second experiment uses the light from a small laser pointer to send music across the room to illustrate how lasers are used in modern telecommunication. If the light from the laser is blocked, the music stops. Those who had never heard of lasers were convinced that the group were magicians – and even insisted that the group leave the room so they could investigate the trickery. But in the end they were satisfied that this was science and that science is often just as mysterious as magic. Glowing in the dark, 3D cinema and LCD displays! Phosphorescence and fluorescence were demonstrated to learners using a board painted with phosphorescent powder, on which the learners were able to write their names using a blue laser pointer. Where the laser meets the phosphorescent powder, it glows bright green. The Stellenbosch students also showed how 3D technology in a modern cinema works, explaining how polarised light is used to create the illusion of 3-dimensional images. This demo uses a simplified technique with colour filter glasses to trick the mind into perceiving 3D images. Learners were then introduced to the theory behind liquid crystals and how these are used in liquid crystal displays
Opposite page (above left): The setup used to demonstrate the additive mixing of colours with lasers. Image: Laser Research Institute Opposite page (above right): David van der Westhuizen explains to learners at Ndiyona School how a red, green and blue laser can be combined to a white beam of light. Image: Laser Research Institute
Above: Colour filter glasses help to trick the mind into perceiving 3D images shown in the presentation. Image: Laser Research Institute Above right: Dancers at the Laser Evening held at Kayova River Lodge.
Image: Laser Research Institute
Magic with the plasma ball and fluorescent light bulb – the bulb lights up without being connected to a power plug, just by the touch of a hand. Image: Laser Research Institute
The roadshow team at the Kayova River Lodge. From left to right: David van der Westhuizen, Charles Rigby, Gurthwin Bosman, Alexander Heidt, our lodge host Paulyn, Nicolas Erasmus, Günther Kassier, Wilfred Ndebeka, Egmont Rohwer. Image: Laser Research Institute
(LCD) – their cell phone screens were a perfect example and small patches of liquid crystals were handed out to show exactly how the screens work. Laser evening Laser evening provided both learners and the Stellenbosch students with the opportunity to entertain each other. The laser group were treated to a ‘celebration dance’, which was performed by local children in traditional costumes, using traditional instruments. The laser group, in turn, used technology to entertain, pumping out the music of the Waka Waka as a background to a spectacular laser light show on the banks of the Okavango river. Thanks to the sponsors of the trip, without whom none of which would have been possible:
■ Laserfest.org (for providing the bulk of the funding) ■ Optical Society of America (OSA) Foundation, both for financial and structural support ■ National Laser Centre at the CSIR ■ Faculty of Natural Sciences, University of Stellenbosch ■ International Office, University of Stellenbosch ■ Kayova River Lodge and Father Denner Foundation for accommodation. The students who took part are Nicolas Erasmus; Alexander Heidt; Gurthwin Bosman; Günther Kassier; Egmont Rohwer; Charles Rigby; Wilfred Ndebeka and David van der Westhuizen. ■ Please visit our facebook page www.facebook.com/ LaserChapter for contact information.
A learner explores phosphorescence, induced with a powerful blue laser. Image: Laser Research Institute
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Richest of the rich: South Africa’s biodiversity treasure trove Ronell R. Klopper and her colleagues explain what exactly is meant by biodiversity in South Africa.
Encephalartos transvenosus, the Modjadji palm, is an endemic cycad. Image: Ronell Klopper
Aloe succotrina on the Cape Peninsula is one of the many succulent plants found in South Africa. Image: Arrie Klopper
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ver the past years there has been an increasing global awareness of the importance of biodiversity. Humans are finally recognising that they are part of nature and that the conservation of species diversity and ecosystems is essential to sustaining their lives. However, biodiversity is being lost at an alarming rate, mainly as a result of human activities. It is in the light of this that 2010 was declared the International Year of Biodiversity by the United Nations. South Africans are privileged to live in an exceptionally biodiverse region. The country harbours a remarkably rich, diverse and unique vascular flora and has one of the highest species densities in the world. This botanical diversity also supports an immensely rich fauna (animal) diversity. South Africa is recognised as one of 17 megadiverse countries that collectively harbour more than two-thirds of the world’s biodiversity. The exceptional diversity of South Africa is, however, under severe threat due to habitat loss. The sites where biodiversity occurred naturally are being transformed as a result of overpopulation, unsustainable or large-scale agricultural and medicinal harvesting practices, infrastructure development, mining activities, the spread of invasive species and climate change. Therefore, many species are lost before they are even discovered or named. These losses cannot be reversed and systematically and permanently deteriorate the lifesupport systems on which we depend. Extinctions in South Africa are not just ‘plodding on’ – they are proceeding at an accelerating rate, highlighting the urgent need for nature conservation in its broadest sense. To adequately conserve the biotic riches of the world a proper knowledge of species, their relationships, and their functions within ecosystems is essential. Fundamental questions for conserving biodiversity are ‘what have we got?’,
‘where does it occur?’ and ‘how much is left?’. Our knowledge and understanding of the biodiversity in South Africa is, in many respects, still inadequate to completely answer these questions and therefore to guarantee proper conservation support. This is where the biodiversity sciences and especially taxonomy plays a fundamental role. Further scientific research is needed where we accurately document the country’s biodiversity and improve the possibilities for its optimal conservation. At the end of the day it is not knowledge, though, that will save the South African biodiversity treasure trove – it is action. Whether the information generated by scientists is used wisely and effectively depends on the capacity of the country’s conservation agencies to deliver. Such agencies (e.g. National Parks Board) need adequate resources to do so, which means that unless politicians act on the seriousness of our current situation and support biodiversity conservation adequately, we will continue to witness an accelerating erosion of our natural heritage. Facts and figures about the rich biodiversity of South Africa Plant diversity
Species richness: ■ South Africa has the richest temperate flora in the world with two floristic kingdoms within its borders, the Palaeotropical and the Cape Floristic Kingdoms, with a large diversity of landscapes including seven biomes. ■ Around 50% of all the vascular plant species found in Africa, as well as almost 50% of all continental endemics, occur in southern Africa, which is less than 10% of the total land area of the continent. ■ South Africa contains around 20 500 vascular plant taxa or ± 6% of the world’s plant diversity and includes the whole of one of the world’s six floristic kingdoms, the Cape Floristic Kingdom.
Q Biodiversity Definitions Endemic: An endemic species is only found in a given country or otherwise specified geographic region and nowhere else in the world. Flora of southern Africa-region: The Flora of southern Africa – or FSA-region – includes South Africa, Namibia, Botswana, Lesotho and Swaziland. Hotspot: A hotspot is an area characterised by high species richness and endemism, and which is experiencing high rates of habitat modification or loss. Threatened: A threatened species is any species (animals, plants, fungi, etc.) that is at risk of extinction in the near future. In the World Conservation Union (IUCN) list of threatened species (also known as the Red Data List), threatened species fall within one of three categories (namely Vulnerable, Endangered and Critically Endangered) depending on the degree to which they are threatened.
plant species, which is 79% of the country’s endemic flora in 47% of the area. This figure further translates to 4% of the world’s flora on 0.4% of the earth’s surface. ■ This exceptionally high species:area ratio indicates that the hotspots in southern Africa should be counted among the world’s most important areas for conservation. Conservation: ■ Unfortunately, many plant species in southern Africa are threatened with extinction, mainly through agricultural, mining, industrial and urban activities. ■ The most recent Red Data List for South Africa lists 2 577 plant taxa or 13% of the country’s indigenous flora as being in danger of extinction. A further 2 232 taxa are listed in other categories of conservation concern, which brings the total proportion of South African plants that are of conservation concern to 24%. ■ Both in terms of area and in an absolute sense, southern Africa has the highest concentration of threatened plant taxa in the world. Medicinal plants: ■ South Africa has just over 2 000 plant species used for traditional medicine or muthi (about 10% of the flora). ■ Around 3% of the country’s flora are regularly traded in large traditional medicine markets in urban areas. ■ A total of 80 plant species in South Africa are threatened with extinction as a result of exploitation for the extensive, commercial trade in muthi, with many more listed as being of conservation concern. Animal diversity
■ In terms of the number of endemic mammals, birds, reptiles and amphibians, South Africa is the fifth richest country in Africa and the 24th richest in the world.
Southern Africa harbours 858 bird species of which 4% are endemic to the region. Image: Japie Kruger.
■ For some animal groups the level of endemism is as high as 80–90%, and many species of invertebrate are confined to a small area. An estimated 50% of invertebrate species are endemic to South Africa. Mammals: ■ South Africa is home to an estimated 5% of the global total of mammal species (299 species). ■ Around 12% of South Africa’s mammals are endemic to the country. ■ A total of 27 (9%) of South African mammals are threatened (critically endangered, endangered or vulnerable) with a further 38 (12.8%) near-threatened. Birds: ■ South Africa harbours around 9% of the world’s bird species (± 858 species) (BirdLife South Africa, 2010) of which 600 breed in the country (African Bird Club, 2008). ■ Around 31 (4%) birds are endemic to South Africa, with a further 50 (6%) being near-endemic (BirdLife South Africa, 2010). ■ A total of 58 (7%) bird species in South Africa are threatened and 61 (7%) are near-threatened. This is the second largest number of bird species of global conservation concern in an African country, after Tanzania. ▲ ▲
■ Southern Africa is host to nearly 50% of the known succulent plants of the world. ■ The flora of specifically the Flora of southern Africa (FSA) region is extremely species-rich in terms of species:area ratios, with a value of 0.0081 species/km2. This is almost double the values recorded for humid tropical floras such as Brazil (0.0044) and Asia (0.0041). ■ Much of the species richness of the FSA-region lies in South Africa’s Cape Floristic Kingdom, with ± 9 000 species of which 69% are endemic in an area of only 90 000 km2. In terms of number of species per unit area, the Cape Floristic Kingdom is the world’s richest plant area. Endemism: ■ The level of endemism in southern Africa is more akin to those of oceanic islands than a portion of a continent. ■ Southern Africa is host to three Regions and 15 Centres of plant endemism. ■ Around 13 300 taxa or 65% of South Africa’s plants are endemic. Biodiversity hotspots: ■ Three globally recognised biodiversity hotspots occur within the boundaries of South Africa, namely: ■ the Cape Floristic Kingdom, the richest of the world’s hotspots of plant diversity. ■ the Succulent Karoo biome, the most speciose arid zone in the world, and one of only two arid zone hotspots recognised globally. ■ the Maputaland-Pondoland-Albany Region, which contains around 1 900 endemic plant species, 39 endemic vascular plant genera, 4 endemic or near-endemic birds, 36 endemic reptiles and 5 endemic mammals. ■ Biodiversity hotspots in South Africa contain around 10 730 endemic
Quest 6(3) 2010 21
If you look at these graphs you can see that, when you place both South Africa and Australia in a global context, South Africa is by far the more important of the two areas – in terms of biodiversity. This is particularly the case given the substantial difference in land surface areas of the two countries. South Africa and Australia harbour equal numbers of taxa in certain groups, even though Australia is more than six times the size of South Africa. When considered in terms of species per unit area, the resultant ratios for the South African fauna and flora are much higher than those of Australia.
South Africa is home to over 50 000 insect species. Not surprisingly they come in all shapes, sizes, and colours of the rainbow. Image: Arrie Klopper
Knysna dwarf chameleon (Bradypodion damaranum); around 95% of South Africa’s chameleons are endemic. Image: Arrie Klopper
Amphibians: ■ A total of ±120 frog species have been recorded for South Africa. ■ Around 55 (49%) species of frog are endemic to South Africa, with a further ±17 being near-endemic. ■ No less than 23 (17%) frog species in South Africa, Lesotho and Swaziland are threatened, with a further five species near threatened. Reptiles: ■ South Africa has an extremely rich diversity of reptiles and is home to 5% of the global total of reptile species (363 species). ■ After Australia (a much larger area) and Mexico, South Africa has the third richest lizard fauna in the world, with at least 165 species, of which 86 species are endemic or near-endemic. ■ Around 95% of South Africa’s chamaeleons are endemic. ■ Approximately 103 snake species are found in South Africa, with 21 being endemic or near-endemic. ■ Southern African has more endemic reptiles than other vertebrates. Aquatic species: ■ Over 10 000 animal species are found in South African coastal
22 Quest 6(3) 2010
waters. This is almost 15% of global marine species. ■ A total of 13% of marine species are endemic to South Africa. ■ Southern African coastal waters are home to 270 marine fish families out of a world total of 325. ■ Over 2 500 marine fish species, of which 13% are endemic, are known or likely to occur in the seas off southern Africa. This is 15% of the world total for coastal marine fish species. ■ South Africa’s estuaries harbour 8 globally threatened estuarine fish species. ■ Approximately 355 species of freshwater fish occur in the continental waters of southern Africa. ■ At least 40 freshwater fish species occurring in South Africa are considered to be globally threatened. ■ The conservation status of marine fish in South Africa is in urgent need of re-assessment. ■ A total of 122 species of freshwater mollusc have been recorded in southern Africa, and 10 of these are threatened.
South Africa’s biodiversity in a global context Key: ~ = estimate only. Only the main groups have been listed. (Global totals taken from Chapman, 2009; marine animal figures taken from Gibbons et al., 1999; threatened species figures for animals from the IUCN Red List 2010.1) World described
SA described SA % of world SA endemic described
281 621 ~268 600 1 021 ~12 000 ~16 236 64 788 5 487 9 990 8 734 6 515 31 153 ~1 359 365 7 400 8 428
~368 050 ~352 000 ~1 050 ~15 000 ~22 750 ~80 500 ~5 500 >10 000 ~10 000 ~15 000 ~40 000 ~6 755 830 ~18 000 unknown
21 700 21 380 45 275 820 ~4 838 299 858 363 138 ~3 000 68 859 289 842
7% 8% 4% 2% 5% 7% 5% 9% 5% 2% 10% 14% 4% 10%
~13 584 (63%) ~13 314 (62%) 33 (73%) 32 (12%) ~205 (25%) ~605 (13%) ~35 (12%) 31 (4%) ~130 (36%) ~77 (56%) ~330 (11%) ~41 310 (60%) ~11 (4%) ~235 (28%)
8 366 (3%) 7 904 (3%) 323 (32%) 139 (1%) 82 (0.4%) 5 966 (9%) 1 221 (22%) 1 360 (14%) 488 (6%) 1 934 (30%) 1 518 (5%) 2 524 (0.2%) not assessed 236 (3%)
SA threatened SA threatened % of world threatened 2 577 (12%) 31% 2 535 (13%) 32% 28 (62%) 9% 10 (4%) 7% not assessed ? ~211 (4%) 4% 27 (9%) 2% 58 (7%) 5% 21 (6%) 4% 21 (15%) 1% 84 (3%) 6% unknown ? not assessed ? 9 (1%) 4%
~1 000 000
~5 000 000
~102 248 ~13 000
~600 000 ~100 000
4 638 ~580
96 (0.2%) (most not assessed) not assessed 14 (2%) (most not assessed) not assessed
~25 000 (50%) 801 (most not assessed) ~3 245 (70%) 18 (0.02%) ~435 (75%) 14 (most not assessed) 30% marine 614 (1.2%) 51% freshwater 84% terrestrial unknown 6 (most not assessed)
52% marine 1 346 8% freshwater 83% terrestrial
Vascular plants Flowering plants Gymnosperms Ferns & lycophytes Bryophytes Vertebrates Mammals Birds Reptiles Amphibians Fish Invertebrates Porifera (sponges) Cnidaria (sea anemones, corals, jelly fish)
Echinodermata (star fish, sea cucumbers, sea urchins, brittle stars, feather stars)
(millipedes & centipedes)
Crustacea (crabs, crayfish, shrimps, barnacles)
Annelida (earthworms, leeches,
fan worms and tube worms)
octopus, squid mussels, chitons)
Terrestrial invertebrates: ■ Even though invertebrates are the biggest group of animals in South Africa and globally, it is also the group with the least amount of data available. The insects are probably the most-studied group of invertebrates. ■ Among the animals, most of the invertebrates have not yet been assessed according to the Red List criteria for threat status. ■ South Africa is home to around 6% of all known insect species (50 000+ species). This is estimated to be half the real number of species in South Africa; the other half remain undiscovered and unnamed. ■ There are ± 664 butterfly species in South Africa of which two are extinct and 63 species are considered to be globally threatened. ■ There are 293 species of dragonfly in southern Africa of which 15 are globally threatened.
■ South Africa harbours thousands of endemic non-insect, terrestrial invertebrates including, but not limited to: 370 species of land snails (83% endemic), 458 millipede species (87% endemic), 105 species of acanthodrilline earthworms, two genera of giant earthworm, two genera of velvet worms (11 species known but probably at least double this many after DNA study, all endemic), and 149 species of isopods (woodlice), of which 85% are endemic. ■ Ronell R. Klopper, Michelle Hamer, Yolande Steenkamp, Gideon Smith are scientists at the Biosystematics Research and Biodiversity Collections Division, Head Office, South African National Biodiversity Institute. Neil R. Crouch is a scientist at the Biosystematics Research and Biodiversity Collections Division, Ethnobotany Unit, South African National Biodiversity Institute.
Recommended reading African Bird Club. 2008. http://www.africanbirdclub.org/countries/ SouthAfrica/species.html – Accessed May 2010. BirdLife South Africa. 2010. Checklist of birds in South Africa. BirdLife South Africa, Cape Town. Branch B. 1998. Field guide to snakes and other reptiles of southern Africa. Struik, Cape Town. Branch B. 2005. Introduction to southern Africa’s reptile fauna. http://sarca.adu.org.za/intro.php –– Accessed 25 May 2010. Carruthers V. 2001. Frogs and frogging in southern Africa. Struik, Cape Town. Chapman AD. 2009. Numbers of living species in Australia and the world (2nd edn). Australian Biological Resources Study, Canberra. Gibbons M., et al. The taxonomic richness of South Africa’s marine fauna: a crisis at hand. South African Journal of Science 1999. 95: 8–12. Henning GA, Terblanche RF, Ball JB. 2009. South African Red Data Book: butterflies. SANBI Biodiversity Series 13. IUCN. 2010. IUCN Red List of Threatened Species. Version 2010.1. http://www.iucnredlist.org –– Accessed 25 May 2010. Klopper RR, Smith GF, Van Rooy J. The biodiversity of Africa. In: H Baijnath and Y Singh (eds), Rebirth of science in Africa: a shared vision for life and environmental sciences. 2002. Umdaus Press, Hatfield. pp. 60–86.
Quest 6(3) 2010 23
a new way of looking at our heritage Reyhana Mahomed shows us how important biodiversity is to sustainable living.
Fynbos in the Western Cape. Indigenous forest.
Image: Wikimedia commons
An example of an unspoilt wilderness area, Dassiesboskloof River, above Wupperthal in the Cape. Image: SAIAB
24 Quest 6(3) 2010
iodiversity is a broad concept used to refer to all life on Earth as well as the ecosystems in which it occurs. Issues concerning the natural world and the conservation of our natural heritage are at the fore this year as 2010 is the International Year of Biodiversity. South Africa is a signatory to the United Nations’ Convention on Biological Diversity (CBD) which focuses on the conservation of biodiversity. The 22nd May saw the celebration of International Day for Biological Diversity under the theme: ‘Biodiversity and Poverty Alleviation – Challenges for Sustainable Development’. This calls for a new way of looking at biodiversity conservation. Biodiversity is not only about greenness and plants and animals, it is also about the economy and the lives of people at community level. This falls in line with current debates in South Africa where matters of biodiversity have shifted beyond the sphere of conservation to include wider issues such as politics, economics and culture. Our biodiverse world South Africa boasts the third highest
level of biodiversity in the world and an impressive increase in domestic and foreign tourists each year - the New York Times named South Africa as a place to visit in 2009. South Africa is home to the ‘living fossil’, the coelacanth, long thought to be extinct along with dinosaurs at the end of the Cretaceous period until one was found off the east coast of South Africa in 1938. One of the world’s six floristic kingdoms, the Cape Floral or Fynbos Kingdom is found only in the southwestern region of South Africa. It is the smallest, yet richest floral kingdom in the world – with a concentration of 1 300 species per 10 000 km². The Cape Floral Kingdom’s nearest competitor is the South American rain forest with a concentration of only 400 species per 10 000 km². Many South African fish are endemic to the region. It is therefore safe to conclude that our biodiversity is one of our greatest assets and a heritage to be proud of. Can we afford to lose our biodiversity? ‘Absolutely not,’ proclaimed SAIAB Chief Scientist, Prof Alan Whitfield,
A day’s takings.
Dr Olaf Weyl.
‘The northern hemisphere doesn’t have a rich biodiversity, and tourists from America and Europe come specifically to see the biodiversity we have here in South Africa’. ‘Everything has its role in an ecosystem and all aspects of the ecosystem are held together by a web of interactions between animal and plant life on all levels,’ said SAIAB Aquatic Biologist, Dr Nikki James. ‘Freshwater fisheries are often based on alien invasive fishes, which in some cases have resulted in severe impacts on aquatic ecosystems,’ says Dr Olaf Weyl Senior Aquatic Biologist. Because ecosystem functioning is dependent on the interactions between all components, losing key components of these ecosystems and reducing biodiversity could result in unforeseeable and irreversible consequences, warns Weyl.
estuaries in particular provide for the livelihoods of many people and South Africa has a wide variety of these ecosystems, including Lake St Lucia, a World Heritage Site. For aquatic animals, estuaries provide nursery areas for juvenile fish, and a number of commercially important fish species depend on these systems for their growth and development. Some of the other economic benefits drawn from estuaries include tourism and recreational opportunities, with protected coastal waters supporting public infrastructure such as harbours and ports that are central to shipping activities. Wetlands are another type of aquatic ecosystem that adds to the biodiversity of a country. Wetlands filter the water upon which we all depend for life explains Weyl, thus benefiting both people and aquatic organisms. Some of the threats to our biodiversity While all scientists on the panel agree that freshwater biodiversity is most under threat due to excessive water abstraction and pollution, Rhodes University PhD candidate, Albert Chakona, emphasises the continuous destruction of natural habitats. ‘Increased human development and demand on the environment destroy critical biodiversity habitats,’ said Chakona, who is working on a thesis entitled Comparative phylogeography of freshwater fishes of the Breede and associated river systems. SAIAB Senior Aquatic Biologist, Dr Monica Mwale, adds: ‘There needs to be a balance between human demands and the importance of conserving the natural environment.’ Biodiversity as an economic strategy Economic development demands an increase in the growth rate of national income and an equitable distribution of income. These can, however,
The coelacanth, showing its colours in life. Image: Wikimedia commons
Dr Monica Mwale.
only be achieved with an increase in the production of commodities and increasing output would logically involve an increase in the consumption of natural resources such as land, forests, water, etc. With these in limited supply, irresponsible use of natural resources would lead to their exhaustion and degradation, rendering a stunted economic growth. In this context, James emphasised that there is a need for sustainable development. Considering the economic benefits
Biodiversity conservation and economic development: the dilemma With latest estimates showing that more than 50% of South Africans are living below the poverty line, economic development at all costs often preside over biodiversity issues that, if left unattended, could be detrimental to the country, said South African National Biodiversity Institute (SANBI) Research Taxonomist, Daksha Naran. ‘If you are a bird, you can fly away and find another tree to make your home, but with aquatic systems it is different,’ said Weyl. Aquatic systems are little islands that are surrounded by a sea of land – plants and animals that live there are trapped in them, explained Weyl. Water obstruction is our biggest concern, cautioned Weyl. ‘If some poisonous chemical enters a pond taking out the oxygen, there is nowhere else for the fish to go.’ Aquatic animals are very diverse and important to our heritage,
Quest 6(3) 2010 25
Weighing and measuring.
drawn from resource conservation, Weyl emphasised the need for conservation in terms of tourism benefits. ‘Look at tourism’s contribution to GDP [5% per year]. The wildlife experience is driven by biodiversity, which will be lost if we carry on destroying our ecosystems’ warned Weyl. Natural ecosystems also perform important life-support services, without which humans cannot survive. Ecosystems play an important role in purifying the air and water, regulating the climate, regenerating soil fertility and detoxifying and decomposing wastes. ‘The value of these services to a society is infinite’, said Weyl, ‘but because these are not traded in economic markets, they have no tangible price and therefore do not alert society when there is a change in supply’. ‘Apart from the tourism economic benefits that biodiversity brings to a country, our basic livelihoods are very dependent upon healthy ecosystems’ added Chakona. Can biodiversity conservation alleviate poverty? In contrast to South Africa’s rich biodiversity, we also have large numbers of poor people, saddled with problems of unemployment, housing backlogs and inadequate sanitation. With biodiversity conservation now part of development planning, ecosystems are counted as an asset capable of enhancing access to economic opportunities. Tourism, with ecotourism as the fastest growing segment, makes an annual contribution of 5% to the national economy, with the international norm being between 7-8%. In 2010, total tourism is expected to contribute 12% to total GDP which could see over 1.5 million jobs created. Thus, for the sake of our economy, it remains important that the country’s natural heritage remains protected. South African ecotourism depends, to a large extent upon our biodiversity. Put bluntly, ‘the prettiness of our biodiversity is important for tourism’, says Weyl. As the fastest growing part of our economy, tourism has the potential to alleviate poverty. Those people living in the areas being visited by tourists need to be educated about the importance of protecting their immediate environments. In this way they will feel a certain sense of responsibility to their environment. In turn, these communities will benefit from the economic growth generated by the tourism industry. Some conclusions All the SAIAB scientists agree that focus needs to be placed on sustainable development – this can be achieved through education and an improved awareness of the value of our natural environment to present and future generations. However, Naran believes that there is not enough ‘effective education’ out there. ‘The truth is,’ said Weyl, ‘people will only care about things that they can associate with’. He suggests, therefore, that national parks and other conservation areas be made accessible to everyone at least once in their lifetime. He adds, ‘Conservation is a privilege rather than a right and access to seeing and experiencing our natural heritage is as important as education’. People also need to appreciate the economic and ecological benefits of biodiversity conservation. With policies already in place and penalties for contraventions of the laws accompanied by fines of up to R10 million or 10 years, imprisonment in some instances, Chakona believes that South Africa has good management policies and is ‘committed to preventing further loss of biodiversity—provided the laws are properly enforced.’ Hence, to pull South Africa out of the pool of some of the poorest nations in the world, it is imperative that we start to appreciate our assets and realise their value on a large-scale. ■ Stats: www.nationsencyclopedia.com Reyhana Mahomed is the DST/NRT Intern in Science Communication and Media Liaison at SAIAB.
26 Quest 6(3) 2010
Biodiversity research and conservation Dr Eureta Rosenberg tells QUEST how you can make a difference to the environment around us.
A bird’s eye view of the field and the careers it offers At the heart of the concept of biodiversity is the vast array of plants, animals and ecosystems that make up our natural world. Biodiversity careers involve studying this natural world, taking care of it, and learning and teaching about the fact that biodiversity is – or should be – a fundamental part of our social world. Gone are the days when a career in this field simply meant donning a khaki uniform or trudging off into the bush, not to be seen again for months! Today’s biodiversity specialists are found on stages around the world informing their audiences about the role and requirements of biodiversity, or behind a desk writing policy briefs for ministers. When they do walk into the bush, they might be accompanied by a group of industry leaders, journalists, farmers or sangomas! Biodiversity is increasingly being recognised as not just the concern of a nature conservator, but as everybody’s business. Forestry companies are learning that by protecting the wetlands on their land, they can help off-set the vast amounts of water timber plantations need, and market the paper they produce as ecofriendly. But where exactly are the wetlands? A soil scientist can help the forestry company. Local authorities are learning that by protecting the grasslands or fynbos in the mountains, they can secure water for the communities downstream. Botanists help the conservation planners to look after fynbos and other indigenous biomes. Town planners are finding out that protecting nature in urban areas can
reduce flood damage, reduce the cost of water purification and attract tourists. But they are under pressure to develop the same areas. What to do? Ecologists help environmental assessment practitioners to inform planning decisions. There is also a great need for resource economists, to estimate in rands and cents what these natural assets are worth (see Box 1). Society at large is starting to appreciate the immense contribution nature makes to our economy and well-being, but the lessons are only slowly sinking in. A citizen concerned about the poaching of South Africa’s marine resources noted that if our gold and diamonds were being plundered by foreigners, we would be up in arms. Why then, he asks, is so little being done to stop the illegal taking of our ‘red gold’, in the form of kreef and abalone? The answer has much to do with our capacity to monitor, prosecute and enforce the law. We need more people to do the job, from marine guards who will pursue poachers in the dead of night, to managers who can supply the necessary back-up and resources, marine scientists who can determine the size of a sustainable catch, and prosecutors to argue a case in court. In reality we have too few people with the necessary skills, and too few posts, to appoint the people with the skills. This situation is likely to change, as the recognition of the importance of biodiversity management and conservation grows. A changing field that might surprise! Research shows that most teachers and university guidance counsellors know little about environmental careers. And among the general public there are some misconceptions. This has much to do with the history of the field, with its early roots in nature conservation and narrow scientific interests, pursued as if people did not really matter. But since the days when the only career in this field might have been as a poorly paid conservation officer, much has changed. Let’s examine some of these misconceptions.
You won’t find a job
There is a demand for scientists with research skills and managers with biodiversity-related qualifications. It is true that some government departments are not appointing large numbers of specialists, but this is not because they do not need them. Many biodiversity professionals are based in universities, research institutes or in private firms, from ▲ ▲
t is the International Year of Biodiversity, and if you are interested in a career in biodiversity, there are many options from which to choose. This article introduces the dynamic and growing field of biodiversity management, research and conservation. It gives a taste of the varied careers that would suit different interests and talents and invites you to look with fresh eyes at the field and its possibilities.
The practical side of conservation.Image: Eureta Rosenberg
Cape Point in the Table Mountain National Park. Image: Wikimedia commons
Box 1: Cape Point Nature Reserve In the 1800s Cape Point, south of Cape Town, was described as ‘a worthless wasteland’. Having given up trying to farm this windswept tip of the peninsula jutting into the Atlantic Ocean, the authorities declared it ‘too barren to sustain even a locust’. Today, Cape Point is one of the top tourist attractions in the world, bringing in more than a R1 million per year in gate fees. The marine resources and other natural assets of the Western Cape contribute a conservatively estimated R10 billion each year, nearly 10% of the Regional Gross Domestic Product.
Quest 6(3) 2010 27
A plan to boost careers in biodiversity
A job assisting the fishing industry
In 2009 SANBI (the South African National Biodiversity Institute) took the lead in the development of a national Human Capital Development Strategy. This is a plan to ensure that there are more people with the necessary qualifications, representative of all South Africans, to fill professional positions in the biodiversity sector. The strategy will look at greater promotion of the sector, career guidance, more bursaries and suitable courses, and better conditions in the workplace – among other focus areas. SANBI’s funding partner in the strategy is the Lewis Foundation, a private conservation fund. For more information, visit www.skillsforbiodiversity.org.za .
Imagine this problem: The population of anchovies – yes , those salty bits on your pizza – has for some reason shifted east along the coast of South Africa. The anchovy fishing companies have traditionally been based on the west coast; now they have to send their boats to the Southern Cape coast, and then bring their catches back by truck to their factories on the west coast. Should they now move their factories? Or will the anchovies move back? This is an important question to the industry, and one which requires scientific knowledge of marine species, as well as mathematical modeling skills. You’ll get paid next to nothing
It is true that one is not particularly well paid in some organisations. However, this is not the case in all organisations, and the level at which one is appointed makes a difference. Senior managers and scientists are often well paid, and you can make a good living by running your own environmental consulting business. Biodiversity skills are also becoming increasingly relevant in careers that are traditionally well paid, such as engineering, law and accounting. You have to be from a certain kind of background
Teaching about nature.
Image: City of Cape Town
Image: Ellen Elmendorp
where they consult to government. Environmental science graduates in some university departments are being offered positions while they are still studying. That is how sought after they are! Today biodiversity specialists and practitioners find work in organisations like SANBI, SAIAB and SANParks, various municipal departments, provincial and private conservation agencies, national government departments like Environment Affairs and Oceans and Coasts, industries like Forestry and Mining, research institutions like the CSIR and the Agricultural Research Council, NGOs like Traffic, Birdlife, WWF and WESSA, in private practice and in numerous university departments.
28 Quest 6(3) 2010
People drawn to biodiversity careers have tended to come from middleclass families who spend recreational time in nature, visiting game reserves and picking up an interest in nature from their parents. Twenty years ago the majority of South Africans were excluded from visiting game parks, could not afford nature-based holidays, and knew nature only as either a threat to survival, or a source of livelihoods. As a result, the senior staff in conservation and research agencies have been mostly South Africans of European descent, and it is only in recent times that this has started to change. South Africa needs researchers and conservationists who represent the population as a whole, and people who understand nature from a ‘use’, rather than a ‘hobby’, perspective, to contribute to research questions and conservation planning. So, be the first in your family to join the green pioneers! Studies are expensive
If you want to be a scientist or highlevel manager in biodiversity, you need a first degree and usually also a further (post-graduate) degree (masters or doctorate). While there are posts for those with degrees, diplomas and certificates, most senior posts require a degree or a further degree. A university education is expensive. The good news is that there are bursaries available. Information on where to find out about such bursaries is provided at the end of the article. Some career examples The next section takes a look at just some of the work opportunities in this field. The focus is on the higher level careers, where the core is a biodiversityrelated post-matric qualification.
However, it is important to note that biodiversity management also creates significant employment for people with entry-level skills and qualifications. These may range from wetland rehabilitation workers, beach cleaners and alien clearing contractors, to field rangers, game guides, sea fisheries monitors and indigenous gardeners. This is an important observation for two reasons: first, the biodiversity sector in its full scope is by no means an elitist field. Second, researchers and managers are needed to guide the work of biodiversity workers to ensure that it succeeds, both in terms of restoring ecosystems and conserving biodiversity, and in terms of creating jobs, reducing poverty and developing rural areas. These are key priorities for government – and biodiversity jobs are centrally involved. Do you dream of working with nature? Many people would love to live and work in a tranquil natural setting surrounded by little more than the call of birds and jackals! South Africa has some of the most special protected areas (parks and nature reserves) in the world, and with a qualification in nature conservation or wildlife management, among others, you can climb the career ladder and become the manager of a conservation area (terrestrial or marine). You could also work in the national parks as a researcher or veterinarian. If your core skills and subjects are not science, wildlife management or conservation planning, however, you could be employed in a conservation area for tourism, education or human resource management, or visit the parks as a wildlife documentary maker or professional photographer. Could you be a research boffin? If you have analytical skills and the ability to obtain an honours, masters or doctoral degree, you can become a biodiversity researcher. Depending on your area of specialisation, you can study insects (perhaps in the interesting area of bio-control of invasive alien plant species); sea birds and the impact of fisheries’ practices on their survival; soil organisms; taxonomy; genetics; climate change; freshwater ecology; or the ways in which rural communities use firewood and wild plants …
You may find work in universities, research institutes, national parks, or a government department. Research could be mainly laboratory based, or mainly field based, or a combination of the two. South Africa is a soughtafter research destination because of its world-renowned biodiversity, excellent facilities, and challenging social issues, which are a microcosm of inequalities around the globe. As a result there is a good chance that you may work with some of the best brains internationally if you choose a biodiversity-related topic as a research focus. And yes, research in the social sciences is relevant too! So even a BA and MA could lead to a research career in the biodiversity arena, as explained in the next section. Do you have a ‘social’ side? The social side of managing biodiversity is a new but increasingly important area of study. Environmental economics, sociology, indigenous languages, politics and education are important areas of investigation in relation to the understanding, use, valuing, protection and governance of biodiversity. Combining subjects from the natural sciences (such as conservation biology) with subjects from the social sciences (such as anthropology) is now possible at many universities, and puts one in a good position to do such pioneering research. Social skills are sought after in many organisations that work with biodiversity. There is a great need for educators, interpretation staff and those with the ability to advocate for a good cause, to educate the public, children, businesses, politicians and other decision-makers about the role and the value of biodiversity, and how we can incorporate biodiversity considerations in our lifestyle and development decisions. We need journalists who can write the stories of the amazing biodiversity of this country, and marketing and communication specialists who understand the conservation message, to help organisations promote the cause. We need social scientists to contribute to environmental impact assessments, and to inform and facilitate public participation. Do you have a head for figures and computers? One of the areas where South Africa has a great scarcity of skills is biodiversity informatics, which
includes data management, software development, modelling and prediction. People who have studied in both information and computer technology, and the environmental sciences, are highly sought after in organisations like SANBI. This is because conservation planning uses increasingly sophisticated mathematics and technologies. Researchers collect data in the field and produce geographic information system (GIS)based maps; data are manipulated; models are developed and applied; and we are able to indicate where development can or should not take place, and to predict what might happen to a certain species or habitat. GIS specialists, statistical biologists, ecological modellers and systems analysts are among the professionals involved in these processes. This work is used to lobby government, for example to argue for green tax incentives to help farmers to protect pockets of threatened biodiversity on their land. None of it is possible without the staff who set up and maintain electronic databases of species, and the database manager is another important member of the biodiversity team.
For more information The PACE Careers Centre is a South African site endorsed by the Department of Education. It provides information on careers in conservation and the sciences (among others); details on the applicable courses and the universities that offer them; and the contact details for those universities. Visit this one-stop-shop at www. gostudy.com, or ask your school for a copy of the CD. To find out what marks and subjects you need to qualify for a particular course, contact the universities in which you are interested, directly. Many universities have this information on their websites, while others will provide you with a prospectus (brochure) if you contact the student advisory bureau or admissions office. The university is also a good port of call for information about bursaries and study loans, particularly for first year studies. For those who have already completed their first degree, there is a wider range of bursaries for post-graduate studies available from a range of organisations. Some of them also offer internships, which give you work experience. These include SANBI, SANParks, the CSIR, Department of Environment Affairs, Oceans and Coasts, and some large municipalities. For more information about careers in SANBI, as well as bursaries, studentships and internships offered by this organisation, visit www.sanbi.org.za or contact the Training Coordinator.
More to choose from! There are many more careers in this field! Let your interests, personality and aptitude guide you. Curators are the behind-the-scenes people who look after precious collections of plants and animals in museums and herbariums. Information specialists interact more with the public. Environmental lawyers must have the gift of the gab! Environmental engineers are guaranteed lots of time in the outdoors, as they advise farmers and local authorities on stabilising river banks and restoring wetlands. For each of these occupations, you can put together a package of courses to obtain a suitable qualification. In some cases, a number of different study paths could all take you to a particular career.
■ I want to make a difference. ■ It’s exciting to contribute to new knowledge. ■ I feel I contribute to the development of South Africa and its communities. ■ My job got me to travel the world and see special places, many of which are not accessible to the public. ■ I love being part of a community of people who are passionate about what they do! ■
What’s in it for you? You may not be the best-paid member of your family if you take up a career in this field – but do not rule out that possibility! There are also more than one way to be successful and happy in a career. These are just some of the things people have said about their work: ■ I like the fact that I’m doing something really worthwhile.
Dr Eureta Rosenberg is an independent consultant in environmental education and training, with an academic and developmental background in environmental education. She supported clients such as SANParks, local government, Department of Education, WESSA and others in developing, implementing and evaluating environmental education and training programmes and resources materials.
Quest 6(3) 2010 29
Thorns on an acacia species. Image: Wikimedia commons
Crop damage E
The Colarado potato beetle feeding on a potato plant. Image: Karl Kunert
The bark of the Cinchona or Quina tree is the only natural source of quinine. Image: Wikimedia commons
30 Quest 6(3) 2010
ver wondered what plants are doing to defend themselves from insects? Or what type of work scientists are doing around the world to help protect important crops against insects? Because plants canâ€™t run or hide they are continuously under threat from insects or pathogens. Insect pests cause severe damage to the worldâ€™s commercially important agricultural crops, despite the large-scale use of insecticides. Most strategies aimed at reducing crop losses rely primarily on chemical pesticides, biological control and plant breeding to increase host plant resistance. According to CropLife International, the global market for insecticides had risen by 15% from 2003 to 2004 to reach US$7.7 billion and is second only to herbicides among the pesticides in the agrochemical market. In South Africa, the insecticide market grew by 12% in 2007 to reach a total of R612 million per year. Unfortunately, the exclusive use of chemicals not only results in rapid build-up of resistance to such compounds, but their non-selectivity affects the balance between insects and natural predators. In the rest of Africa pesticide use is the lowest among all world regions for economic reasons. African farmers rely mainly on the use of low-cost indigenous pest management approaches, such as intercropping with plants that either repel insects or attract the natural enemies of crop pests, using microbial control agents or conventional breeding for host plant resistance.
Juan Vorster, Dominique Michaud, Andrew Kiggundu and Karl Kunert tell us how molecular biotechnology is used to combat the insect threat in Africa. Plants defend themselves Plants have different mechanisms to combat the insect threat. All of them possess natural systems to combat insect or any other herbivore threat. Some plants have evolved physical defences, such as thorns, spines, and prickles. Thorns can also harbour pathogenic bacteria that produce dangerous toxins for the attacker. While some defences are always present in plants, others are induced in response to mechanical damage during insect attack or to chemicals present in insect egg depositions on leaves or stems. The plantâ€™s recognition device, usually a protein, eventually activates the genetic machinery to produce defensive proteins or chemicals in the plant. These chemical defences, often called secondary compounds because they are not necessary for primary plant functions such as growth or development, can be quite widespread and occur in many plants, while others occur only in a few species. Well-known secondary compounds include alkaloids, such as caffeine and nicotine, affecting the nervous system; terpenoids, that are often volatile, which give their characteristic smell to conifers and mints; and phenolics, the most common group of secondary compounds, which include the famous tannins of tea or red wine. Volatile compounds, which are often produced when the plant is attacked by an insect, may be recognised by natural insect predators, guiding them to the plant and the insects they prey
Above: This diagram shows how the protease inhibitors act in the insect gut. Left: Foxgloves produce several deadly chemicals, namely cardiac and steroidal glycosides. Ingestion can cause nausea, vomiting, hallucinations, convulsions, or death. Image: Wikimedia commons
on, such as ladybirds feeding on plant lice. Many extremely bitter compounds, such as quinine, which is also used to treat malaria and gives tonic water its distinctively bitter taste, are terpenoids combating Lepidopteran (moths and butterflies) larvae. Finally, various phenolic compounds can be produced that are distasteful and toxic, inhibit digestion and discourage insect feeding. Plants also use proteins in their defence against insects. Some of these proteins, such as the so-called protease inhibitors, act as antinutritional compounds that interfere with the digestive functions of insects. These proteins prevent the insect midgut proteases from breaking down the proteins that the insect needs for development and growth. Such antidigestive proteins, however, can not only affect insect proteases, but also proteases in the human digestive tract. Proteases are enzymes. Enzymes are proteins that increase the rate of chemical reactions and remain unchanged themselves during the reaction.
acid interference (RNAi) technology is also currently being investigated. If these RNAi compounds are fed to insects they prevent the formation of specific vital proteins and the application of this technology opens new avenues for insect-resistant crops. Strategies that work Production of toxic insecticidal proteins, originally derived from the microbe Bacillus thuringiensis, the so-called Bt-toxins, was the first successful biotechnology-based strategy to combat the insect threat in crop plants. This technology has been shown to be very safe, and until now there is no scientific evidence that humans and animals are affected by the Bt-toxin. Several modified crop plants including cotton, maize and soybean have now been commercially grown for over ten years to control potentially devastating insects such as the maize stalk borer or the cotton boll worm. Currently, over 114 million hectares of plants producing a Bt-toxin, particularly maize and cotton lines, are grown in 23 countries worldwide, including South Africa. When a Bt-toxin is ingested by an insect, it is dissolved in the midgut, where it binds to areas of the cells that line the gut, eventually causing the cell to break down and die. However, because not all pests are susceptible to Bt-toxins, other strategies have to be developed. Strategies that might work Protease inhibitors might be useful. In 1987 it was shown that tobacco plants over-producing an anti-nutritional protease inhibitor were toxic to the tobacco budworm moth, reducing feeding damage in insect bioassays by
Beans, for example, contain large amounts of protease inhibitors active against the digestive protease trypsin, which can cause severe indigestion when beans are eaten in large amounts or not cooked properly. Substances called oligo-galacturonides are released from wounded plant cell walls when the plant is damaged by hervivores, which are then damaged by these compounds. No plant is perfectly protected in nature, even if it is deadly to insects. The ability to produce defences is controlled
by the plantâ€™s genetic makeup as well as by the environment it is growing in. If the plant lacks the genetic machinery necessary for the development of certain defences, then that defence is not a viable option. Furthermore, insects have evolved mechanisms to tolerate or detoxify some plant defences. Many plant pests can attack only a few plant species, to which they are adapted, but no plant species is totally protected. Producing defences may also be costly because the production uses energy and resources for defence at the expense of growth or reproduction. The production of some defences may also be hampered by certain environmental conditions, such as low soil nitrogen, which limits alkaloid production, and low light, which limits the production of phenolic compounds. Biotechnology can help Crop biotechnologists can help plants to fight insects. These biotechnologists use and develop new biotechnologybased tools to combat the insect threat. Application of these new tools can help plants to produce specific compounds or proteins that are toxic to insects. Biotechnologists have developed, or are currently trying to develop, promising strategies for insect control but any success may, in the end, be hampered by the fact that some of these compounds are toxic to humans. For instance, naturally occurring plant lectins are toxic to insects because they can bind with carbohydrates, but some of them can also be toxic to mammals, making it unlikely that they could ever be used commercially. Other strategies aim to interfere with insect moulting. Preventing the production of vital proteins in insects through ribonucleic
Quest 6(3) 2010 31
The structure of cysteine protease and its inhibition by cystatin.
Weevil larvae, showing larvae that have been reacted with protease inhibitors and control larvae that are untouched. Image: Juan Vorster
about 50%. Protease inhibitors of the cystatin protein superfamily, which targets the cysteine proteases in the midgut of several herbivorous insects, such as the Colorado potato beetle, do not affect mammalian guts, including humans. Several protease inhibitors have been developed and inserted into a variety of crop species, such as potato, to improve insect resistance. But, although the crops were more insect-resistant than varieties without the protease inhibitors, the protection was not as great as it is with chemical pesticides. This is because, as we develop new technologies, so insects evolve ways of combating these technologies. This means that we need to engineer our technology in a way that overcomes the insect’s ability to compensate for it. Africa’s contribution A small number of African crop biotechnologists are already contributing to improving the crop breeding process and to developing basic knowledge allowing the future design of new insect-resistant crops. The protease inhibitor technology, for example, is currently the focus of a long-standing collaboration between South African, Ugandan and Canadian scientists, all aiming to combat Coleopteran insect infestations. The Coleoptera family includes beetles and weevils. It is the largest order of insects.
The banana weevil and its eggs.
Image: Andrew Kiggundu
A diagram showing where the banana weevil lays its eggs.
32 Quest 6(3) 2010
This multidisciplinary group has recently shown that inhibiting digestive cysteine proteases in banana weevils significantly and negatively affected the growth of larvae eating banana corm loaded with a cysteine protease inhibitor, also called cystatin. The adult banana weevil lays eggs on the banana plant just above the soil surface. When the eggs hatch, the emerging larvae burrow through the underground stem causing fewer bananas per plant and weakness in the stem, which can result in the plant falling over. The African-Canadian group is currently involved in modifying the sequence of the inhibitors to significantly improve their inhibitor potency against this banana pest. Scientists in South Africa are part of an integrated pest management programme that is investigating the application of the Bt-toxin technology against Eldana saccharina, a very
damaging stalk-boring pyralid moth, which affects the sugarcane industry. The economic impact of this pest may be in the order of R60 million annually. They found that several sugarcane lines had substantially less larval survival and stalk damage than sugarcane plants not producing the toxin. The development of DNA-based markers for insect resistance also shows great promise in crop breeding. Scientists in South Africa, together with US scientists, have recently focused on developing DNA-based markers for a marker-assisted selection process. Such markers will, for instance, assist South African wheat breeders with a biotechnology-based tool to more easily select Russian aphid-resistant wheat lines. This aphid is responsible for significant crop losses in wheat-producing countries around the world. In East Africa, scientists are also currently investigating the genetic basis for resistance to bean weevils which is an important bean storage pest in Tanzania. The weevil contributes to the destruction of seeds, resulting in significant reduction in seed quality and quantity or even complete loss of seeds when they are stored for a long time. Without doubt, insects pose a significant threat to plant survival in Africa and worldwide. A stronger interest in this research area would, in the future, allow for the testing of new hypotheses and the development of novel strategies and tools for efficient control of herbivorous pests and improved agricultural output in Africa. ■ Juan Vorster is Lecturer in the Plant Production and Soil Science Department of the University of Pretoria. His research focuses on computational biology investigating protease-protease inhibitor interaction. Dominique Michaud is Professor of Plant Biochemistry in the Département de Phytologie of Laval University, Québec City, Canada. His research focuses on the elucidation of protease-inhibitor interactions in plant systems and the proteomic characterisation of genetically modified crops. Andrew Kiggundu is Research Scientist at NARO’s National Agricultural Biotechnology Centre, Kawanda, Uganda. His research focuses on identifying banana weevil control mechanisms. Karl Kunert is Professor in the Plant Science Department of the University of Pretoria. His research focuses on studying systems for protection of plants against environmental stresses.
Junfeng Gou receiving his award.
South Africa’s top science learners rewarded
he National Science Olympiad awards ceremony was held on the evening of 30 September, 2010 at the Gallagher Convention Centre in Midrand. In March this year, 20 833 learners from around South Africa and SADC countries sat down to write the Science Olympiad test and 100 of the best achievers arrived in Pretoria on Monday for a week of edutainment and exposure to careers in Science and Technology (SET). The National Science Week Olympiad is a flagship programme of the South African Agency for Science and Technology Advancement (SAASTA). SAASTA is a business unit of the National Research Foundation (NRF) and is committed to steering young minds towards careers in science, technology and innovation. This commitment ties in with one of the main aims of the National Science Olympiad: ‘to identify talent in SET and nurture it into excellence,’ said SAASTA’s Science Education Unit Manager, Dr Jabulani Nukeri. The Olympiad test consists of a number of curriculum-based and general science and technology questions for grades 11-12 learners. There are two Olympiad papers that candidates can select from: Physical and Life Sciences. Several prizes are awarded to the top five national winners per section, the top learner and girl learner from disadvantaged schools per section,
the top girl learner per section, the top learner per grade per section, the top three schools with the most participants, the top three best performing schools and the top three best performing disadvantaged schools. The project is sponsored by Harmony Gold Mining Company, the fifth largest gold producer in the world. Prizes include laptop and desktop computers, iPods, laboratory equipment and book vouchers, invitations to attend a Science Focus Week in Pretoria, and a trip to the UK to attend the London International Youth Science Forum for the top five learners. The top 100 learners participated in the National Science Olympiad Focus Week which ran from Monday, 27 September till Friday, 1 October. The focus week is aimed at enhancing and cultivating learners’ interest in careers in SET. According to Nukeri, the science focus week events include lectures, excursions and industry visits to Harmony Gold Mining, the National Zoological Gardens, and Forensic Laboratories. ‘We want to expose learners to science and let them see for themselves where the science is happening,’ said Nukeri. The top five learners are: Physical Science in Grade 12: Junfeng Guo from York High School, George, Western Cape Life Science in Grade 12:
Sam Tolmay from Voortrekker Hoër, Bethlehem, Free State Physical Science in Grade 11: Sean Wentzel from Westerford High School, Rondebosch, Cape Town Life Science in Grade 11: Fatima Haq from Sama High School, Johannesburg, Gauteng Disadvantage School Physical Science Grade 12: Sibongukuhle Gladness Masango from Bantfwabetfu High School, Mashishila, Mpumalanga. These five learners had already been awarded the opportunity to attend the London International Youth Science Forum in England, which ran from 28 July – 11 August. The Forum brought together over 300 students of the sciences from almost 60 countries on the five continents. The participants joined in a programme of lectures and demonstrations from leading scientists, visits to industrial sites and research facilities. The coordinator of this project at SAASTA, James Thlabane, accompanied the top five learners for the Youth Science Forum this year and found it ‘informative and a great opportunity for some of South Africa’s top science learners to interact with other young scientists and exchange ideas on solving issues in their home countries.’ Registration for the 2011 National Science Olympiad will open in October this year. Please visit www.saasta.ac.za for more information. ■
Sibongukuhle Gladness Masango
Quest 6(3) 2010 33
Science real and relevant The CSIR held their third biennial conference in Pretoria recently. QUEST was there.
his year, 2010, marks 50 years since the invention of the laser and the CSIR conference opening showcased lasers in a riot of colour and sound. Naledi Pandor, Minister of Science and Technology opened the conference, with a discussion of the place of science in society and the importance of nurturing young scientists in South Africa. The number of speakers and topics made it necessary to run parallel sessions each day, covering health, natural environment, defence and security, built environment, energy, ICT, industry and built environment.
An entertaining use of lasers.
Naledi Pandor, Minister of Science and Technology.
At the face – a dangerous, noisy environment.
34 Quest 6(3) 2010
Image: Anita Edwards
The hidden cost of mining Noise-induced hearing loss is an unfortunate consequence of working in mining. This has major negative effects on miner’s lives and costs the industry millions of rands in compensation claims. Anita Edwards, a senior researcher in the human factors research group of the CSIR’s Centre for Mining Innovation, presented a paper on a novel method for evaluating miners who are at risk of noise-induced hearing loss. The aim of the research is to find ways of detecting hearing loss early in order to prevent progression, and ways that can be used routinely in annual medical testing. The testing used is distortion product otoacoustic emissions (DPOAE), which uses two tones as input into the ear and measures the ‘echo’ that returns from the interacting waves that are set up in the hair cells of the cochlea and the fluids in the inner ear. This form of testing appears to be a feasible way of assessing the part of the ear that is damaged by noise exposure. It has several advantages: no active response is needed from the person being tested, the test reliably identifies early cochlear damage caused by noise, the test is speedy and cost-effective and does not need to be conducted in a sound-proof booth. However, there are possible problems with the test if it is to be used in annual medical testing. The research so far has shown the validity of the test when administered by a skilled audiologist, in a relatively quiet environment. Researchers are also
not sure if the test is useful in people who already have a certain level of hearing loss or how easily it will identify people with early cochlear damage in a mining environment. So far, the research has been in a military situation. The pilot study focused specifically on the relationship between conventional screening audiology tests and DPOAE results in annual medical testing, which is often carried out in a much noisier environment. The results were encouraging, suggesting that, as long as the testing environment is not too noisy, the test can be carried out by a technician. The study also showed that DPOAE can identify early hearing loss before pure tone audiometry can, in 73% of miners tested. Tuberculosis drugs from local plants Tuberculosis (TB) is an all-too common infection in South Africa and, although research into novel drug therapies is in process, the drugs currently used have not been updated for decades and are difficult to take and fraught with side effects. The biodiversity research group at CSIR biosciences is carrying out research that taps into South Africa’s plant biodiversity with the aim of finding products that can be used to develop new medicines effective against TB. To do this, the group is using the 96 well plate fractionation technique. Fractionation is a separation process in which a certain quantity of a mixture (solid or liquid) is divided up into a number of smaller quantities. Fractions are collected based in the difference in a specific property of individual components of the mixture. The advantage of the 96 well plate fractionation approach is that the team were able to speed up the identification of active ingredients and groups of molecules that can be used to formulate medical products. The group were able to use the technique to isolate and identify the compound pellitorine, which is found in the tree, Zanthoxylum capense which grows across southern Africa. This compound is known to have anti-TB properties and will now be the subject of further research.
Cell phone use has expanded at an unprecendented rate across Africa.
Image: Anita Edwards
E. coli bacteria enlarged using an electron microscope. Image: Wikimedia commons
The structure of the M13 bacteriophage. Image: Wikimedia commons
The mobile phone in Africa: providing services to the masses The story of mobile telecommunications in Africa and the developing world is a remarkable one. Africa’s mobile cellular growth rate has been the highest of any region over the past five years, averaging close to 60% year on year. Large cellular infrastructure investments, which have enabled millions of people to communicate better, have been made. Adele Botha, who is a senior researcher in the mobile technologies research group of the CSIR, and her colleagues, have looked at the various technical and operational considerations associated with creating a middleware platform for mobile services. The platform should be able to support different mobile paradigms (voice, text, multimedia, mobile web, applications) using a variety of communications protocols (SMS, USSD, MMS, Bluetooth, WAP data via GPRS/3G/HSDPA). This will enable components to be reused, ensure scalability, support multiple access devices (from basic phones to more powerful smart phones, including traditional PCs), provide interoperability via different modes of access and also ensure faster development time. The new millennium is witness to a telecommunications world that differs vastly from even the recent past, with developments in the mobile sector having dramatically changed the Information and Communication Technology (ICT) landscape. Mobile cellular technology has proliferated faster than any previous technology
Vinesh Maharaj, one of the lead researchers in the TB project, examining fractions. Image: CSIR
and is now the most ubiquitous technology in the world. It enables more than 4.7 billion people worldwide to communicate and share information. By the end of 2009, about one in every two people in the world owned a mobile phone, while the International Telecommunications Union (ITU) reports that Africa’s mobile cellular growth rate has been the highest of any region over the past five years, averaging close to 60% year on year. Researchers at the CSIR are developing the Mobi4D platform initiative. This will make use of as many different mobile technologies as possible, in order to provide mobile services in areas such as health, education, disability and rural development. Using lasers to deactivate viruses Viruses are microscopic particles that can only replicate within a living cell – a host cell. In these cells they make specialised elements, called virions, which carry the virus’s genetic material from cell to cell within the host. Many viruses are harmful and antiviral drugs are difficult to develop and often have unwanted side effects. However, laser scientists have been experimenting with using lasers to deactivate viruses without harming the host cell, by targeting the weak bonds in the protein shells of the virus. CSIR researchers at the CSIR National Laser Centre, Femtosecond Science Group looked at a specific virus, the M13 bacteriophage (a virus that only infects bacteria) and its host
Leaves of the tree Zanthoxylum capense.
Image: Wikimedia commons
Makobetsa Khati, one of the researchers on the bacteriophage project. Image: CSIR
bacterium Escherichia coli or E. coli. The group used this bacteriophage/ host complex to examine the use of femtosecond (very, very short) laser pulses to determine the deactivation intensity threshold and compare this with the damage threshold for the host cell. They are hoping to gain a better understanding of the mechanism of virus deactivation using this type of laser pulse. Once the mechanism of the physical phenomenon is understood this will lead to a wide variety of applications for the technique. ■
Quest 6(3) 2010 35
Pumping iron and climate control Mike Lucas continues the story of phytoplankton, iron fertilisation and climate control.
RSS Discovery and a map of the study area in the NE Atlantic affected by the ash cloud in the spring of 2010.
The Eyjafjallajökull volcano erupted violently in April 2010.
Eucampia antarctica A Scanning Electron Microscope image of a chain-forming diatom characteristic of Southern Ocean ecosystems. False colours identify structural differences. Image: Alex Poulton and Daria Hinz (NOC, UK)
Figure 1 A simplified planktonic food web showing three size-classes of phytoplankton, which ‘fix’ atmospheric CO2. The vertical green arrow represents the downward sinking of particulate organic carbon and nitrogen (POC, PON) after the cells die; the basis of the biological carbon pump. Rice grain sized mesozooplankton feed on large phytoplankton cells (often diatoms). Their faeces (F) add to the downward export of POC/N. Some of this sinking material is decomposed by bacteria (red cells) that respire much of the ingested carbon (R.CO2) and convert dissolved organic carbon (DOC; mostly from phytoplankton) into dissolved inorganic carbon (DIC). The smallest phytoplankton are eaten by full-stop sized microzooplankton, which remineralise (excrete) NH4 and urea that is used by all phytoplankton. The upward flux of nutrients (black arrows) from the deep ocean nourishes phytoplankton growth.
36 Quest 6(3) 2010
he eruption of Iceland’s Eyjafjallajökull volcano beneath a glacier in April 2010 introduced vast quantities of iron-rich volcanic ash into the North Atlantic Ocean to the south and west of Iceland. This infrequent event provided a unique opportunity to study the effect of natural iron fertilisation on phytoplankton growth rates and on their potential to control climate during two research cruises (2010) to the region aboard RRS Discovery in spring (April/May) and again in summer (July/August). See Beyond the ash cloud, QUEST 6(2), 2010. The biological carbon pump Phytoplankton are microscopic single-celled plants that float in the surface of the ocean and ‘fix’ carbon dioxide (CO2) into their cells as organic carbon during the process of photosynthesis. While phytoplankton support oceanic food webs, including the fish that we eat, phytoplankton also play a central role in the control of global warming, which is due to the accumulation of greenhouse gases in the atmosphere. The most important of these is CO2, which is produced from fossil fuel combustion. However, as a result of phytoplankton photosynthesis, some of the CO2 derived from fossil fuel is ‘exported’ into the deep ocean as particulate organic carbon (POC) when
Image: Mike Lucas
phytoplankton cells die and sink. As the POC slowly sinks, taking as long as two to three months to get from the surface to the sea floor at about 3-5 km depth, bacteria decompose this organic ‘rain’ of ‘marine snow’ into dissolved inorganic carbon (DIC). This will stay in the deep ocean for hundreds to thousands of years. This effectively removes CO2 and its warming influence from the atmosphere. In fact, typically less than 1% of the sinking POC ultimately becomes buried in the sediments, because most of the POC is decomposed during its long downwards journey. This entire process is called the ‘biological carbon pump’ (see Figure 1), which climate change scientists believe may hold the key to removing some of the unwanted atmospheric CO2. The strength of the biological carbon pump depends on the scale of phytoplankton productivity, as well as on the size structure of phytoplankton communities. Since large cells of 20200 µm diameter, such as diatoms, typically sink faster than small cells of only 2-20 µm in size, large-celled phytoplankton such as diatoms are responsible for most of the carbon export in the world’s oceans. But what controls productivity and community size structure? The essentials are sufficient light and an abundance of nutrients. In the oceans, it is just the top 100-200 m that receives sufficient
light for photosynthesis, while the nutrients required in significant quantities are inorganic nitrogen (often as nitrate, NO3), phosphate and silicate for diatoms. But in the 1980s, scientists such as John Martin (USA) observed that the Southern Ocean contained a vast reservoir of unused nitrate and silicate (Figure 2), yet phytoplankton biomass and growth rates remained much lower than expected. At first, many scientists believed that in the forbidding and cold Southern Ocean, there was insufficient light in these high polar latitudes to drive photosynthesis. However, Southern Ocean phytoplankton evolved over millions of years in this low-light environment, so they are adapted to these conditions. Light is not the overriding problem.
Where does iron in the oceans come from? One way or another, dFe in the oceans originates from terrestrial or marine sediment sources. Most is delivered by atmospheric dust, volcanic ash, industrial air pollution, riverine inputs, diffusion from sediments, melting icebergs, glacial erosion and from hydrothermal vents. Of these, atmospheric iron-rich dust
The role of dissolved iron Instead, Martin proposed that phytoplankton growth rates were limited by a lack of dissolved iron (dFe), which he called the ‘iron hypothesis’. Since the early 1980s, marine scientists have verified his hypothesis and confirmed that, in many of the world’s oceans, the lack of sufficient dFe severely limits phytoplankton growth rates, and by extension, the efficiency of the biological carbon pump; particularly in the Southern Ocean. Since then, biological oceanographers have been unravelling the reasons why dFe is so important, and at the same time finding out in which oceans dFe limits productivity. So, how does a lack of dFe in the oceans negatively affect phytoplankton growth rates? First, light captured by the photosynthetic pigments (often chlorophyll-a) and light-harvesting reaction centres (photosystems I and II) of all plant cells needs to be converted into chemical energy (ATP) that is then used to convert CO2 into organic carbon. This process requires substantial amounts of dFe, which helps to ‘switch on’ the multitude of photo-chemical reactions that collectively we know as photosynthesis. Second, cells that assimilate nitrate (NO3) as an inorganic source of nitrogen must reduce this within the cell to nitrite
(NO2) and then to ammonium (NH4), which is then used as the building blocks for amino acid and protein synthesis. The two enzymes involved in reducing NO3 to NH4 are nitrate reductase and nitrite reductase respectively; both require dFe to function. There is another group of very specialised phytoplankton, called nitrogen fixers or diazotrophs (e.g. Trichodesmium), that make use of atmospheric nitrogen (N2) to satisfy their nitrogen demands in the absence of dissolved NO3 in surface waters. Such conditions occur in the warm sub-tropical gyres of the Pacific and Atlantic Oceans because these oceans are so strongly stratified, where warm 25-30 °C water overlies much colder water (4 °C). In such oceans, upward nutrient flux into surface waters is prevented because these two water layers do not readily mix. Atmospheric N2 fixation depends, however, on the iron-hungry enzyme nitrogenase, so that N2 fixation is limited to oceans where dissolved NO3 is mostly absent, but where there is a substantial source of atmospheric iron inputs. This occurs when Saharan dust storms extend into the North Atlantic subtropical gyre, depositing dust and iron into the ocean. All of these Fe-dependent processes in phytoplankton cells are illustrated schematically in Figure 3. This diagram illustrates why phytoplankton photosynthesis and biomass is reduced in iron deficient oceans, while also explaining why high concentrations of unused NO3 exist in the Southern Ocean, and elsewhere, as in the seas around Iceland. Such regions are considered to be high-nutrient-low-chlorophyll (HNLC) oceans, and all are ironlimited.
Figure 2 Nitrate levels in the world’s oceans.
The cyanobacterium, Trichodesmium, a member of the phytoplankton that is a specialised nitrogen fixer. Image: http://www.tweed.nsw.gov.au/
Global distribution of dust fluxes into the atmosphere. Note the importance of the Saharan contribution and the lack of dust in the southern hemisphere.
Figure 3 Diagram of a phytoplankton cell showing the importance of iron in photosynthesis (PS I, PSII) and for nitrate assimilation and reduction to ammonium.
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CO2 removal by phytoplankton, and whether this resulted in increased carbon export to depths of 4-5 km. Iron-enrichment did indeed increase phytoplankton productivity and carbon export by about four- to five-fold relative to the unfertilised surrounding ocean. However, considerably less carbon was exported to the deep ocean per unit of iron added than we expected, meaning that iron-fertilisation was less efficient than anticipated. Although this efficiency term needs further testing, the result has profound consequences for proposals by some entrepreneurs and scientists to artificially fertilise the Southern Ocean with iron to remove excess atmospheric CO2 – one of the many geo-engineering options being considered to mitigate climate change. A satellite image showing the dust from a storm in the Sahara.
A satellite image of an extensive phytoplankton bloom (red) immediately to the North and East of the sub-Antarctic Crozet Island (west of M3) in Dec 2004. The bloom occurs because of natural iron-fertilisation from the island. M10, M1, M3, M2 and M6 were sampling stations.
transport and deposition from the world’s major deserts is the most important; particularly from the Sahara Desert. Dust clouds from the Sahara can easily be seen from space as they extend westwards across the tropical and sub-tropical North Atlantic. Note that most of the atmospheric dust fertilisation occurs in the northern hemisphere, particularly in the North Atlantic sub-tropical gyre. This is due to atmospheric and oceanic circulation patterns that rotate to the right in the northern hemisphere, due to the Coriolis effect, but rotate to the left in the southern hemisphere. This means that dust introduced into the northern hemisphere tends to remain in that hemisphere. Furthermore, as most land-masses are in the northern rather than southern hemisphere, this explains why the Southern Ocean is so iron deficient. With global warming, there is considerable focus on desert and atmospheric sources of iron because the Sahara and many other deserts are likely to become drier and
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more extensive, therefore increasing the potential for enhanced ocean fertilisation by atmospheric dust. In southern Africa, iron is introduced into the Benguela upwelling system from the Namib Desert, while there is good circumstantial evidence that outflow from the Orange River introduces considerable quantities of iron into the ocean to the west and south of the continent, but the scale of this remains to be established. However, atmospheric and climate scientists from Wits University have found that a significant source of iron is delivered to the iron-limited sub-Antarctic region south of the continent (e.g. to the Crozet islands) by air streams flowing southwards from the industrial interior near Pretoria and Johannesburg. Iron fertilisation of the Southern Ocean I began this article by referring to the eruption of Iceland’s Eyjafjallajökull volcano as a good example of how the oceans can be naturally fertilised with iron. Another example of this can be found in the Southern Ocean. All the sub-Antarctic Islands stimulate phytoplankton blooms around them due to iron leached from surface runoff, or from iron that diffuses upwards from shallow sediments, while iron from atmospheric inputs may also be significant. A UK funded cruise (CROZEX) on RRS Discovery to the sub-Antarctic Crozet Islands (due south of Durban) in 2004/5 had the goal of measuring phytoplankton growth rates and carbon export to the deep ocean in response to natural iron fertilisation from the islands. The key question we asked was whether iron-enrichment of the seas around Crozet increased atmospheric
Geo-engineering climate by Iron fertilisation of the Southern ocean Humans are currently emitting about 9 Gt y-1 (= 9 billion tons per year) of CO2 into the atmosphere from fossil fuel burning and from land-use changes. The Southern Ocean alone currently removes about 50% of the total global ocean uptake of CO2 (about 2.2 Gt y-1), but this could potentially be improved if the Southern Ocean is fertilised with iron, notwithstanding our results from CROZEX. Apart from complicated legal issues associated with adding iron to the ocean (which could be considered as a pollutant), not all of the effects are positive. Tinkering with ecosystems may have severe negative effects, and the record of human interference is dismal in many instances. But in the event that there is no political will to curb fossil fuel CO2 emissions, the scientific community needs to be in a position to offer sound scientific advice on all geo-engineering options, including iron fertilisation. Studies on oceans that are naturally fertilised by iron offer us the opportunity to improve our understanding of the impact of iron on ocean systems, from controls on photosynthesis and nitrogen metabolism at the cellular level, to projections at ocean basin scales of what benefits and problems large-scale iron fertilisation might bring. ■ Associate Professor Mike Lucas is employed within the University of Cape Town’s Zoology Department. He is also an Honorary Research Associate at the National Oceanography Centre (NOC) in Southampton, UK. He conducts much of his research in the North and South Atlantic, as well as in the Southern Ocean and in the Benguela upwelling system. He is a member of the southern African SOLAS Network, which forms part of the International SOLAS Project, which research described in this article contributed to.
Plant cells with visible chloroplasts.
Image: Wikimedia commons
lant photosynthesis is the ‘engine’ that makes the Earth habitable. Plants, including trees, grasses and phytoplankton in the seas do this by converting atmospheric carbon dioxide (CO2) into organic compounds, particularly plant sugars and carbohydrates. These plants then support almost the entire food web of planet Earth, including us. Photosynthesis also largely controls the amount of CO2 and oxygen (O2) in the atmosphere, so plants can be regarded as the Earth’s ‘lungs’. Photosynthesis can be summarised as: photosynthesis --> 6CO2 + 6H20 <--------> C6H12O6 + 6O2 <-- respiration Note that phytoplankton cells not only fix CO2 during photosynthesis, but they also use oxygen and release CO2 during respiration. Photosynthesis is of course light dependent, but respiration is not. Photosynthesis takes place in two linked steps, the light reactions,
and the dark reactions. 1. Light reactions: 2H2O + light (48 photons) --> 4[H+] + ATP + O2 The light-dependent reactions convert sunlight into chemical energy. First, light in the photosynthetically available radiation (PAR) wavelengths (~400-700 nanometres) is captured by pigments such as chlorophyll-a in photosystems I and II (PS-I and PSII), contained within the chloroplasts (see Figure 3 in the main article). This raises electrons in the pigment molecules to a higher energy state. This higher energy is in turn transferred by electron transfer systems through a series of reactions, mediated by plastoquinones (PQ) and cytochromes (Cyt. B6/f), which convert adenosine diphosphate (ADP) to the higher energy level adenosine triphosphate (ATP). The reductant, nicotinamide adenine di-nucleotide phosphate (NADPH) is also produced.
A false ocean colour satellite (SeaWiFS) image of global phytoplankton biomass in the ocean surface. Red colours, high biomass; blue colours, low biomass. Image from Christo Whittle, Marine Remote Sensing Unit, Dept. Oceanography, University of Cape Town. 2. Dark reactions: 4[H+] + (ATP --> ADP + energy) + CO2 --> [CH2O] + H2O In these light-independent reactions, inorganic CO2 is ‘fixed’ within the Calvin Cycle and transformed into carbohydrate. The dark reactions of photosynthesis involve the reduction of CO2 by NADPH and the subsequent synthesis of carbohydrate (and amino acids from NH4) using the energy liberated from ATP. The first step of CO2 reduction is catalysed by the important enzyme, ribulose biphosphate carboxylase/oxygenase, or RUBISCO for short. RUBISCO comprises 50% of a cell’s protein and is the most abundant protein on the planet; amounting to about 40 million tonnes of RUBISCO at any one time, with each gram fixing 2500 g C yr-1! This equates to about 100 terawatts, or about six times as much power as used by the entire human population. ■
Q UEST interactive – the place to be QUEST magazine is now complemented by www.questinteractive.co.za. Take a look!
ver wanted to know what is happening in science right now? Simply log into www. questinteractive.co.za and take a trip to all the sciences – what’s new right now. www.questinteractive.co.za provides you with regularly updated news across all science topics, including ‘Science in society’ so that you can keep abreast of the most interesting and important news stories as they break. The site is easy to navigate with sections covering health, physics and maths, space, life, environment
and science in society. Each story is carefully picked from the literature by a dedicated science news writer to ensure that not only is breaking news covered, but that there is a broad range of news stories, covering each of the web site topics areas each week. The print issue of QUEST is also featured and can be read online in full – open access – in line with the ASSAf open access policy. Summaries of the current QUEST articles are also available for a brief overview of the
contents of each issue. Science videos, online polls and a list of suggested links to other science sites, complete this exciting new web site. Don’t be left out – go there now. ■
Quest 6(3) 2010 39
One of the anntenas.
Anja Schröder and Ian Stewart take us through the KAT-7 radiotelescope array.
First images from the KAT antennas
outh Africa is building the Karoo Array Telescope (MeerKAT), which will be one of the largest and most powerful radio telescopes in the world, using state-of-the-art technologies. As South Africa is one of the two candidates for the location of the Square Kilometer Array (SKA), which will be a hundred times larger than MeerKAT, the Department of Science and Technology and the National Research Foundation decided to build a Interferometry Radio waves are just like light waves, only the wavelength is longer. Our eyes can’t see them, but one can make photographs with radio waves with the right equipment. A clever technique called interferometry allows one to combine the signals from several radio detectors to simulate a ‘camera lens’ equal in size to the separation between the detectors. For MeerKAT, the maximum separation will be 50 km. This will be like having a satellite dish 50 km across! Such a telescope will be extremely sensitive and will be able to make pictures, in radio waves, of the most distant objects in the universe. ‘Interferometry’ makes use of the the fact that any sort of waves may interfere – that is, if you add two waves, how strong the result is depends on whether the waves are in step or out of step. If in step, the result is twice as strong as the inputs; out of step, and they will cancel to nothing. This is the same effect that makes the coloured patterns in soap bubbles. Scientists call such patterns ‘interference fringes’. From measurements of such fringes, mathematics can reconstruct an accurate picture of how the sky looks in radio waves.
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South-African precursor array next to the site proposed for the SKA. This site is near the small town of Carnarvon in the Northern Cape Province. The Astronomy Geographic Advantage Act of 2007 declares an area of 12.5 million hectares with the proposed SKA site at its centre as an astronomy advantage area. This means, that the area where MeerKAT will be built is protected as a radio astronomy reserve where strict regulations control the generation and transmission of interfering radio signals. As a consequence, images obtained with MeerKAT will be among the ‘purest’ of the world, revealing even the faintest traces of radio signals. To gather experiences in building a world-class instrument, the MeerKAT project decided to build a prototype consisting of seven 12-m diameter antennas in the same area in the Karoo. This array is called the MeerKAT Precursor Array or KAT-7 for short. The construction of the dishes was finished earlier this year. Currently the engineering, software and science teams of the project are testing four of the seven antennas which have so-called uncooled receivers installed. First fringes In the meantime, KAT-7 has already achieved some of the major milestones
in the building of a radio telescope. In December 2009, the first combined signals (commonly called ‘fringes’) were obtained from a few astronomical radio sources with the first two antennas. Figure 1 shows the two antennas tracking the moon low at the horizon. Interference fringes are formed by correlating the signal which is simultaneously received by two antennas from a radio source. Since the Earth rotates, the antennas have to follow the source as it moves across the sky as, for example, does the Moon. As a consequence, the interference pattern of the two radio rays changes with time, very similar to the way the optical Michelson-Morley interferometer works when changing the path length of one of the light rays. Figure 2 shows time on the vertical axis and (radio) frequency on the horizontal axis. The frequency bandwidth displayed is 400 MHz with a centre frequency of 1.8 GHz (frequency increasing to the right). The various colourful strips are interference patterns for different celestial sources as indicated. In some cases, a coarse delay was applied to the data, and in some cases none. This delay is introduced in the correlator and is meant to compensate the difference in signal path length between the two
The array during the building process.
The precursor array in the Karoo.
Michelson interferometer The Michelson interferometer is the most common way of placing mirrors to produce an interference pattern, which is produced by splitting a beam of light into two paths, bouncing the beams back and recombining them. The different light paths may be of different lengths or may be made up of different materials to create alternating interference fringes on a back detector. The Michelson interferometer was used by Michelson and Morely in 1887 for a famous experiment in which the interferometer was used to show that the speed of light is constant.
object, in this case the Centaurus A radio galaxy, in a raster pattern. We could do this with each of the two antennas that were already used to produce the fringes. Later in July, after the next two antennas had their receivers installed, the same observation was done with these two. Since all four antennas observed the same object, a direct comparison of the images would show if there were a problem with the signal (that is, through the hardware) coming from one of the antennas. Figure 3 shows the image obtained with Antenna 1. The image shows a contour map of radio continuum emission of the brightest radio galaxy in the sky, called Centaurus A or, as the astronomers say, Cen A. This interesting object is too far south to be seen from northern▲ ▲
antennas. With no delay, the pattern moves fast both with time and frequency (that is, wavelength), while adding an exact delay will stop the movement with time and remove the frequency dependence. Our correlator was only set up to do a coarse estimate of the delay correction once (in time), which explains why the pattern labelled ‘with coarse delay’ are almost horizontal (that is, frequency independent), but they still vary with time. To form a proper image of the sky from the data, one needs to constantly recalculate the exact delay as the Earth rotates. The astronomers call this fringe-stopping. Single-dish raster scans of Centaurus A As a next step, in March this year the first raster scan images were produced. For this, an antenna moves across an
A Michelson interferometer for use on an optical table. Image: Wikimedia commons
Figure 1 Two of the KAT-7 antenae tracking the moon low at the horizon. Image: SAAO
Figure 2 A multisource fringe showing interference patterns for different celestial sources.
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Figure 3 A contour map of radio continuum emission of one of the brightest radio galaxy in the sky, Centaurus A.
Figure 4 The interferometric image of Cen A.
Figure 5 A false colour image of Cen A made with the 26-m hartRAO antenna.
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hemisphere telescopes. Cen A has a central ‘engine’, seen here as the bright, compact centre of the image. This engine squirts out narrow jets of material to either side, which extend completely outside the rest of the galaxy, and which end in vast balloons of hot, radio-bright plasma. These balloons, the so-called radio lobes of Cen A, form the broad extensions above and below the centre of the image. At lower left, faint emission from our own Galaxy is also visible. The entire structure extends across 9° of the sky, about the size of the palm of your outstretched hand against the sky. The data were obtained via a raster scan, with 89 scans covering a square area of ~11 degrees. The image shows a slightly smaller cut out region. The central radio frequency is 1836 MHz and the bandwidth is 223 MHz. The size of the beam of the antenna (~ 1 degree in diameter, twice as large as the moon) is shown by the circle in the upper left corner. The contours on the image are lines of equal radio brightness, in terms of percentage of the maximum value. For comparison, an image from the South African Rhodes/HartRAO 2326 MHz survey in false colours is shown in Figure 5, which has a higher resolution and shows more details. It should be noted that while such an image is easily surpassed by observations with larger (single-dish) radiotelescope, it is a very important end-to-end test of antenna hardware, system stability, pointing accuracy and software. A comparison with existing images of this galaxy at a similar spatial resolution as well as the comparison between the four antennas proves that KAT-7 is fulfilling the requirements relevant to this kind of observation. In fact, ‘commissioning’ means (a) to show that all requirements in building this instrument are met, and (b) to test and characterise the integrated system so that we know how to set up and calibrate our future science observations. First interferometric image Finally, in April this year, KAT-7 achieved its most important milestone by linking together the four antennas as an integrated system to produce the first interferometric image of an astronomical object. The correlator used to process these signals is a state-of-the-art South African built correlator which is the product of an international project called CASPER (Collaboration for Astronomy Signal Processing and Electronics Research) in which our team has taken a leading role. The image (Figure 5) was created from a six-hour observation and shows the radio emission from the central ‘engine’ in the galaxy which is the same
as in the raster scan image but zoomed to a higher resolution: the beam size is now only about a tenth of a degree in diameter. And while in the raster scan image we can see the plumes of gas created by the jet, this image shows part of the jet itself close to the core, visible as the fainter blob to the lower right of the centre. This image can also be compared with images obtained at other radio telescopes using a similar spatial resolution, and in fact it compares well. This not only means that the hardware is in good shape, but that the team who developed all the software for the purpose of initial exploration and commissioning of the array, is doing an excellent job. Later this year, the first final, cryogenically cooled receiver will be installed in one of the antennas and thoroughly tested. Once all seven dishes have the cooled receivers and are made to work together, deeper and more detailed images will be possible. The full MeerKAT array will be more powerful again by a factor of 10, and will be able to explore previously uncharted regions of the radio universe. Outlook: the MeerKAT All the experiences gathered with KAT-7 will be used when building the MeerKAT array which will consist of 64 13.5-meter offset antennas where the receivers are at the Gregorian focus. This will be different to the KAT-7 antennas where the receivers are located at the prime focus and the diameter of the dishes is 12 m. The change in the dish design provides higher image quality. The first MeerKAT dish will be built approximately in 2013. It will then be extensively tested in conjunction with the existing KAT-7 array to investigate all aspects of a design that is still largely unexplored in radio astronomy but maybe used as well for the grand SKA itself. ■ Dr Anja Schröder is an Operations Scientist for the MeerKAT project (SKA-SA) and has worked around the world before coming to Cape Town. Her research field is looking for galaxies that lie behind the obscuring layers of our Milky Way. Tracing how they form clusters and filaments helps us to understand how the Local Group (a group of galaxies in which our own Galaxy resides) moves with respect to the cosmic microwave background. Dr Ian Stewart trained as a physicist but these days mostly likes thinking up neat computer programs - an activity which feels something like half-way between clock making and solving crosswords. He has been interested in all kinds of things, from the way new species arise in nature, through artificial intelligence, to the best way to find stars in pictures of the sky. He has worked in Australia and England and is now a Research Associate with the Department of Astronomy at the University of Cape Town.
Q Diary of events Shows and exhibitions Iziko Planetarium, Cape Town Between now and December Especially for children Silly Solly and the Shooting Stars Solly Snail wants to be chosen for his garden's soccer team and thinks up ways to become a speedier snail, so that he will be chosen. He decides to ask a shooting star to help him, but does his plan work and will he be chosen for his garden's soccer team? Join him on his quest and find out for yourself! 11 December – 18 January Monday to Friday – 11:00 and 12:00 • Saturday – 12:00 (excluding 25 December) • Sunday – 12:00 PLUS 22, 23, 29 and 30 January – 12:00 Especially for children aged 5-12
For teenagers and adults Living Inside the Cosmic Egg On a clear night you cannot see forever, even with the most powerful telescope imaginable. The observable universe ends abruptly at an opaque wall, created by the conditions that followed the big bang beginning. That wall appears to surround us – forming the shell of a hollow sphere, with us at the centre – a Cosmic Egg that contains everything of our universe. Generally dark inside – at least to normal eyesight – it is populated with billions of galaxies, each a gigantic city of stars in itself, each star probably having its own solar system. Starts 11 December Monday to Friday – 14:00 • Tuesday evening – 20:00 (and sky talk) • Saturday – 14:30 (excluding 25 December) • Sunday – 14:30 Suitable for teenagers and adults
A Basic Guide to Stargazing This presentation will give you a basic understanding of the night sky and how it changes through the year. We introduce some easily recognisable constellations, explain the nature of stars and the galaxy in which we live and give basic information in using binoculars and small telescopes. 13 December – 18 January Monday to Friday – 13:00 Suitable for teenagers and adults Planetarium entrance fees Adults: R20.00; Children: R6.00; Adults (children’s show only): R10.00; SA Pensioners and Students (with cards): R8.00 The Planetarium reserves the right to change or cancel advertised shows without prior notice. The Iziko Planetarium is closed for maintenance on the first Monday of the month, excluding school holidays.
Talks, outings and courses Botanical Society of South Africa, Kirstenbosch: Birds of Kirstenbosch Otto Schmidt will talk about the birds of Kirstenbosch. (27 October 2010)
Autumn in France Sue Hillyard will talk about autumn in France. (10 November 2010) Biodiversity showcase – Green Point common Marijke Honig will talk about Green Point common as a biodiversity showcase. (8 December) Common gardens in Britain and Europe Yvonne le Roux will talk about gardens in Britain and Europe. (8 Decemver 2010) All talks between 10.30 and 11.30. • Venue: Kirstenbosh NBG. • Contact Cathy Abbott: Tel: 0121 465 6440, email: email@example.com
Witwatersrand Bird Club Evening meeting/Andrè Marx Birding Northern Finland and Arctic Norway André has been involved in various aspects of birding in the Gauteng region for 26 years and is currently the rarities coordinator for the Gauteng region. He arranged his visit to Finland and Norway for early June in order to find as many of the breeding migratory species as possible. Habitats visited included the lakes and taiga forest of northern Finland as well as the tundra and coastal areas of the Varanger peninsula of northern Norway, an area widely regarded as one of the hotspots for 'specials' found in the Western Palaearctic region as a number of species reach the western edge of their distribution here. 19:15 Delta Environmental Centre. • Email: firstname.lastname@example.org • (21 October 2010) Sunday outing/Zaagkuildrift road Route: Take N1 North Pretoria then N1 Pietersburg/ Pretoria. Approx 63 km from N1/N4 junction in Pretoria take Pienaarsrivier/Rust Der Winter off ramp (exit no 205). Turn left (R25 Pienaarsrivier) and drive ±700m to stop sign. Turn right (R101 Bela-Bela/ Warmbaths) and 1km later turn left on to dirt road at Zaagkuildrift sign. Drive 300m (crossing railway line) and turn right at Zaagkuildrift sign. Meet: 07:00 for 07:15 at the Zaagkuildrift sign Leader: Ernst Retief (072 223 2160) (31 October 2010) Sunday outing/Korsman Bird Sanctuary and possible visit to Bullfrog Pan SABAP2 Pentad: 2610_2815 Declared a natural reserve in 1967, the sanctuary covers an area of around 44 ha, at the centre is a natural pan about 1.5 metres deep. It is inhabited by about 170 bird species and includes several active heronries. The reedbeds could yield Little Bittern or Black Crake while the shore edges should be scanned for migrant waders and the surrounding grassland for displaying LBJs. A spotting scope is recommended. Route: Take the Atlas Road/Benoni turnoff from the N12 to Witbank. Turn right into Atlas road and proceed to the Total garage (meeting point) on the corner of Atlas and Racecourse Road. The sanctuary is located within a closed off suburb. Facilities available: There are several hides which are accessible to the public. Please bring a picnic lunch. Peter may include a visit to another local pan: Bullfrog pan (this will however depend on the conditions of the pan and if the rains have started) Meet: 07:00 at the Total Garage on corner of Atlas and Racecourse Road, Westdene, Benoni. Leader: Peter Huggins (082 783 3142). (7 November 2010)
Diarise Saturday 27 November 2010/Birding Big Day Are you a casual or enthusiastic birder, a twitter or a twitcher? Then join SAPPI in the fun of
Birdlife South Africa’s birding big day on 27th November 2010 and win great prizes! The categories are garden bird (urban), sabap2 and traditional birding big day. Teams may enter the garden bird and sabap2 categories the week preceding and on the official day. The traditional Birding Big Day category may only be entered on the 27th November 2010 and observations should be done over a 24 hour period (midnight to midnight). Only free-flying birds may be recorded (no caged birds). Remember, your participation will help bird research and bird conservation. For more information visit www. birdlife.org.za or call (011) 789-1122. Good luck!
World AIDS Day 2010 Universal access and human rights The theme for World AIDS Day 2010 is 'Universal Access and Human Rights'. Global leaders have pledged to work towards universal access to HIV and AIDS treatment, prevention and care, recognising these as fundamental human rights. Valuable progress has been made in increasing access to HIV and AIDS services, yet greater commitment is needed around the world if the goal of universal access is to be achieved. Millions of people continue to be infected with HIV every year. In low- and middle-income countries, less than half of those in need of antiretroviral therapy are receiving it, and too many do not have access to adequate care services. The protection of human rights is fundamental to combating the global HIV and AIDS epidemic. Violations against human rights fuel the spread of HIV, putting marginalised groups, such as injecting drug users and sex workers, at a higher risk of HIV infection. By promoting individual human rights, new infections can be prevented and people who have HIV can live free from discrimination. World AIDS Day provides an opportunity for all of us – individuals, communities and political leaders – to take action and ensure that human rights are protected and global targets for HIV/ AIDS prevention, treatment and care are met.
International year of chemistry The International Year of Chemistry 2011 (IYC 2011) is a worldwide celebration of the achievements of chemistry and its contributions to the well-being of humankind. Under the unifying theme ‘Chemistry—our life, our future,’ IYC 2011 will offer a range of interactive, entertaining, and educational activities for all ages. The Year of Chemistry is intended to reach across the globe, with opportunities for public participation at the local, regional, and national level.
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Indigenous knowledge Great South African inventions. By Mike Bruton. (Cape Town. Cambridge University Press. 2010). This title is in Cambridge University Press’s Library of Indigenous Knowledge. The author, Mike Bruton, says that his initial interest in South African inventions was sparked by his involvement in an exhibition at the MTN Sciencecentre in Cape Town in 2004 – ‘Great South African inventions’, which was part of the celebrations around the ten year anniversary of democracy in South Africa. And there are a remarkable number of inventions that have come out of South Africa over the years. The introduction clears up any misunderstandings about the differences between an invention, an innovation and a discovery. An invention is something that is ‘created’ – something new and developed for a specific purpose by an inventor. An innovation is an improvement on someone else’s invention. A discovery involves ‘revealing a truth that was always there’ – finding out something about the natural and physical world that is new. South African inventions include the use of natural materials, such as the stone, bone and wood tools first made by prehistoric peoples, and the medicinal uses of traditional plants such as buchu. Other South African inventions range from wind up, self charging radios to pool cleaners such as the Kreepy Krauly. The book is written in an accessible style and in a way that makes it easy to use in the classroom, perfectly complementing the curriculum requirement for teaching of indigenous knowledge systems. It has a comprehensive glossary and a good index.
The prehistoric roots of modern mining in Africa Indiginous mining and metallurgy in Africa. By Shadrak Chirikure. (Cape Town. Cambridge University Press. 2010). Another title in the Cambridge University Press Library of Indigenous Knowledge, this book
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makes it clear that mining and metallurgy were not technologies that were introduced to Africa from elsewhere, but that they were part of the daily lives of indigenous peoples in Africa from prehistoric times. Some of the earliest evidence of mining in the world comes from Africa, where archaeological evidence shows that Late Stone Age populations (around 40 000 years ago) in Swaziland quarried and collected iron ores from the Earth’s surface to use as pigments. As far as metallurgy is concerned, West and East African metal workings began with iron and copper around 900 BCE, while bronze work appeared around 900 years later. The book covers all aspects of mining and metallurgy, from the smelting process that is essential to extracting metals such as copper and iron from their deposits, to the importance of mining in the development of various African populations, including our own in South Africa. The chemistry of the reactions in smelting are covered and the book includes a periodic table of the elements, as well as maps of Africa showing archaeological sites, the distribution of smelting techniques and the trade routes that grew up as a result of these technologies. Again, the structure of the book makes it perfect for use within the curriculum and it contains a comprehensive glossary and an index.
Art in the Karoo San Rock Engravings: Marking the Karoo Landscape. By Neil Rusch and John Parkington. (Cape Town. Struik Travel and Heritage. 2010). This small, beautifully produced book is a wonderful showcase for the ‘visual legacy’ of the San hunter-gatherers who roamed the Karoo in pre-colonial times. In the author’s words, ‘… tangible signs of the presence of people who hunted and gathered in this region for uncounted millennia.’ About 2 000 years ago, this part of Africa was colonised by farming people
from further north and about 200 years ago the first European settlers arrived. Before these two waves of colonisation, all the people in the region were hunter-gatherers. Engravings – seen on rocks and in caves – are images that are made by pecking, scraping or incising into rock surfaces. The shape or form is then visible as a lighter area against the dark rock. Some images were painted rather than engraved, although engraving is generally thought to be more effective in this environment. Engraving is characteristic of huntergatherer societies and is found across the world. In this book, the authors show that this imagery is deeply rooted in what it means to be a hunter-gatherer and that these images remain as powerful symbols for future generations. It is no longer believed that the images were simply decoration. The book is set out in sections in which the authors explore the role engravings in a hunting society. First, they look at the places that are engraved and ask ‘why there?’. They then examine the images selected as subjects and ask the same question. They describe the techniques of engraving and place these in context. Using these clues, they speculate on the motivations of engraving – when, by whom and why? Finally, they offer a summary of the meaning of the San engraving of the landscape. Anyone who is interested in this crucial part of our heritage in southern Africa will enjoy this book. It neatly combines archaeology and anthropology, as well as an understanding of what shaped the environment and the way in which this influenced the inhabitants of the Karoo for around 20 000 years before their way of life was destroyed. Truly science and society.
Rock hopping Rocks and Minerals of Southern Africa. A Pocket Guide. By Bruce Cairncross. (Cape Town. Struik Nature. 2010). As with all the Struik Pocket Guides, this one is truly pocket-sized and perfect for that hike just about anywhere in southern Africa – a particularly rich region for interesting geology. The introduction
takes you through the difference between minerals and gem stones – interesting to know that gemstones are defined by their beauty, durability and rarity – and all are naturally occuring minerals apart from pearls and coral. Southern Africa’s geological history spans a huge time period, with some of the rocks over 3 000 million years old. All the three important rock types – igneous, metamorphic and sedimentary – occur here. The book is divided into two parts – mineral and rocks (with rocks being split into the three rock types). The introduction goes through the information that you require before you can start to indentify minerals and rocks and explains the terminology used in describing them, as well as the icons used in the book. The photographs are clear and large enough to use to compare your sample with a named example. There is also a glossary and an index – always a mark of a good book – and a useful bibliography for those who would like to delve further into this fascinating subject.
Indigenous forest Pooley’s Trees of Eastern South Africa: A Complete Guide. By Richard Boon. (Durban. Flora and Fauna Publications Trust. 2010). This wonderful book is a revision of the 1993 book by Elsa Pooley, The Complete Field Guide to Trees of Natal, Zululand and Transkei. The field guide describes over 1 000 species, representing almost all the indigenous trees and naturalised alien species in the area between East London in the Eastern Cape in the south and Swaziland in the north. Vegetation types are introduced before the species accounts, providing a potentially excellent teaching tool for those in the areas covered. This is followed by instructions
on how to use the book and a word and picture glossary. The comprehensive key will help the experienced botanist (amateur or otherwise) with identification – and is also an excellent resource for those parts of the Life Sciences curriculum that ask for an understanding of keys. The species accounts are provided by family and follow the classification system. Each species has a distribution map, a diagram of a leaf and a colour photograph to go with the description and explanation of the origin of the name. There are two indexes – a detailed one and a quick one. A useful addition in this revision is information on gardening, traditional and other uses of the trees listed. Altogether, this book is an excellent resource for the public, teachers and gardeners in the area covered.
is particularly detailed and will be an excellent reference for environmentalists and provide material for activites for Life Science teachers, as will the section entitled ‘Significance of the bush’. Survival in the bush includes a historical account of humankind’s interactions with this environment, inlcuding the prehistory of the region. Food of the veld should probably be read along with the section on poisonous plants earlier in the book!
Conserving the bush Bushveld Ecology and Management. Editor: PT van der Walt. (Pretoria. Briza Publications. 2010). South Africa’s bushveld biome covers a large area and is arguably the landscape that foreigners, in particular, associate most with the region. It is also where many locals go to rest and recover from the rigours of urban life, which makes its conservation important – not that conservation of such an important biome should not be an end in itself. This book covers such a wide range of topics that it is suitable for those in the conservation and environmental management industry and will also make an excellent resource for teachers, since our Life Sciences curriculum covers Environmental Science in depth. The biome is described in depth, including the geology and the climate. The characteristic plant patterns are covered in detail, illustrated by photographs of the different species. The section on bush management
Birds from your armchair Remarkable Birds of South Africa. By Peter le Sueur Milstein. (Pretoria. Briza Publications. 2010). This is not a field guide. It is a book about South Africa’s birds that you can sit down and read and enjoy. The author has drawn information from many different sources and does far more than simply describe the species and their habitats. For example, I had no idea that the Egyptians marketed quail in their millions, causing the extinction of the species in the region. This in contrast to the Japanese who selectively bred quail as poultry. The book is lavishly illustrated with photographs provided by most of the well-known bird photographers and bird watchers in South Africa. Sit down and enjoy it.
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Q ASSAf News
Genetically modified wheat. Image: ecollo.com
Genetically modified crops can help alleviate African food shortage Agricultural biotechnology, specifically genetic modification (GM) technology, can be one of the most vital tools for addressing the chronic food shortages in sub-Saharan Africa maintains a new report released by the Academy of Science of South Africa (ASSAf). This report has been published as a result of a forum study in which ASSAf convened a series of expert workshops aimed at engaging African scientists in assessing the current challenges, opportunities and risks associated with the use of GMOs. Africa is the only continent where food production per capita is decreasing and where hunger and malnutrition affect at least one in three people. Crop yields in sub-Saharan Africa have hardly changed over the past 40 years and cereal production has been steadily declining over the past four years. The report suggests that GM technology can contribute to the resolution of the African food shortage, provided it is carried out within a framework of appropriate biotechnology policy with sufficient financing for human capital development, the construction and equipping of the necessary laboratories, and the use of rigorously planned, results-orientated GM food research. Research results have shown the possibility of increasing crop yields, improving the storage potential of harvested crops, improving the protein content of starchy foods, biofortification of local foods, and improving the functional potential of local foods. Despite widespread scepticism surrounding the value of GM crops, this application of biotechnology is gradually finding its niche across the globe. A decade after GM crops were introduced into the world, their production has grown to approximately 125 million hectares globally. The use of GM technology and its products is still in its infancy in Africa, and while South Africa remains the continent’s leader in the field, other African countries have begun to produce biotechnology products for commercial use. South Africa is one of three countries on the continent (along with Egypt and Burkina Faso)
producing commercial GM crops. Despite most African countries having ratified the Cartagena Protocol on Biosafety (CPB), only a few African countries have functioning biosafety legislation that allows field trials of GM products (South Africa, Zimbabwe, Malawi, Kenya, Uganda, Tanzania, Burkina Faso, Ghana, Nigeria, Egypt, Tunisia, Morocco and Mauritania). To allow developing countries to derive the full potential benefits of biotechnology crops, technology developers should also consider factors such as the relevance and accessibility of a particular technology to ensure sustainability, not only in their post-release safety but also in terms of their potential socioeconomic impacts within developing countries, which to date have usually only been considered at a very late stage of product development. Ongoing biotechnology research in Africa focuses largely on attempting to solve local problems associated with food production, health and the environment. Locally focused biotechnology can play a role in increased global crop productivity to improve food, feed and fibre security in sustainable crop production systems that also conserve biodiversity. It can contribute to the alleviation of poverty and hunger, and the augmentation of traditional plant breeding, and can reduce the environmental footprint of agriculture, mitigate climate change, reduce greenhouse gas emissions and contribute to the cost effective production of biofuel. The study was undertaken in collaboration with the Union of German Academies of Sciences and Humanities, the Network of African Science Academies (NASAC) and the Uganda National Academy of Sciences (UNAS). The full report is available at www.assaf.org.za.
Delegates at the TWOS conference. Image: TWOS
Women under-represented in science and technology: is consensus at TWOWS Conference Women are still under-represented in in science and technology. This was highlighted by South African Minister of Science and Technology, Ms Naledi Pandor, at the Fourth General Assembly and International Conference of the Third World Organisation for Women in Science (TWOWS). The conference focused on ‘Women Scientists in a Changing World’. Representatives from the South African chapter of the TWOWS attended the conference in Beijing, China from 27-30 June 2010.
The conference was opened by Xi Jinping, Vice-President of the People’s Republic of China. In a keynote address Pandor, highlighted the under-representation of women in the field of science and technology as a whole, as well as their under-representation in research management positions and policy-making. ‘The involvement of women in STI activities,’ said Pandor, “is critical in ensuring that the full diversity of a nation is utilised in providing expertise and in contributing to the development of nations.” She further commended the role of TWOWS in promoting greater participation of women scientists and technologists in the development process of their countries and in the international community, and called on its members to take a lead in service to their countries and regions to continually make a difference in this area. Leading scientists from developing countries presented keynote papers, followed by workshops with papers and discussions on the scientific contribution of women to these critical areas. Eminent women scientists from the South presented their research work, stressing policy issues pertaining to the participation of women in science and technology in their countries. At the conference, the name of the organisation was changed to the Organisation for Women in Science for the Developing World (OWSDW), to better reflect its focus on promoting both the greater participation of women in science, technology and innovation, as well as the use of science, technology and innovation to better the lives of both women and men in the developing world. Additionally, a revised set of statutes was presented to and approved by the General Assembly. The Beijing Statement was approved by the conference and released on 29 June, 2010. In view of the commitments in the Platform for Action of 1995 Fourth United Nations World Conference on Women, and the recommendations in Para 90 of the Framework for Action of the World Conference on Science held in Budapest in 1999, the participants called on governments and the international community to recognise, document and highlight the contributions made by women to science, technology, engineering and innovation, and to take steps in policy and programming to ensure the full participation of women and girls in all aspects of science and technology. OWSDW is an international organisation whose central role is to promote women’s access to science and technology , enhancing their greater involvement in the decision-making processes for the development of their countries and in the international scientific community. Created in 1989, the former TWOWS’ overall goal was formulated as to work towards bridging the gender gap in S&T. OWSDW uses its forum for intellectual discussions to assist in the development of national capabilities to evolve, explore, and improve strategies for increasing female participation in science. The South African national chapter is hosted by ASSAf, who provide a secretariat for the implementation of its activities.
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