PennScience Spring 2013 Space Exploration

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About Pennscience

PennScience is a peer reviewed journal of undergraduate research published by the Science and Technology Wing at the University of Pennsylvania. PennScience is an undergraduate journal that is advised by a board of faculty members. PennScience presents relevant science features, interviews, and research articles from many disciplines including biological sciences, chemistry, physics, mathematics, geo-­ logical sciences, and computer sciences. PennScience is a SAC funded organization. For additional information about the journal including submission guidelines, visit www.pennscience.org or email us at pennscience@gmail.com.


Table  of  Contents Features 5

The Potential of Curiosity

7

The Physics of Star Trek

10

Andy  Guo

Donald  Zhang

The Search for Earth-­Like Planets Natalie  Neale

12

Interview with Larry Gladney

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14

Lane  Robinson

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Ghislain  B.  Tchomobe,  Sr.

PennScience  11  |  3


Dear Readers,

We are proud to introduce you to the double issue of the 11th volume of PennScience, commemorating our tenth anniversary as the premier journal for undergraduate research at Penn. The theme of this issue, space exploration, was inspired by the recent landing of the new Mars Rover “Curiosity,” a breakthrough that has significant implications on science, on fiction, and on our collective futures. Our writers explore the science behind “Star Trek,” the day-today of a Mars rover, and the potential of finding more inhabitable planets. We also interviewed Larry Gladney from the Astrophysics department here at Penn to better understand the path of research in this burgeoning field. In additon, we are pleased to showcase two stellar pieces of research. Lane Robinson presents her investigations on the social influences of reproduction in brown-headed cowbirds. Ghislain Tchomobe presents his work on the diverse properties associated with pharmacological plants in the Dominican Republic. We would like to thank the groups and individuals that have made PennScience possible. First and foremost is our staff and their dedication to the journal. We owe our funding to the Student Activities Council and the Science and Technology Wing, without which we could not publish a such high-quality magazine. We would also like to thank our faculty advisors for their constant support and insight. Finally, we would like to thank the Penn faculty who took the time to meet with us to discuss their research. Finally, we would like to introduce our two new Editors-in-Chief for next year, Sarah Murray and Vihang Nakhate. They both served as Editing Managers for the journal last year and have proven to be indispensible in the production of this magazine. Thank you for reading PennScience and we hope you enjoy our latest issue! Sincerely, Lucy Shi, Editor-in-Chief Sally Chu, Editor-in-Chief

Editors in Chief

Layout Managers

Writing Managers

Assistant Business Manager

Sally Chu Lucy Shi

Vinayak Kumar Natalie Neale

Editing Managers Sarah Murray Vihang Nakhate

Business Manager Lisa Pang 4

Editorial Staff Alan He Jenny Yan

Claudia Cheung

Faculty Advisors Dr. M. Krimo Bokreta Dr. Jorge Santiago-Aviles

Writers

Andy Guo Coby Basal Donald Zhang Rami Ezzibdeh

Editors

Leora Apfelbaum Claudia Cheung Kurt Koehler Maria Lee Vivek Nimgaonkar


in commemoration of our tenth anniversary A decade ago, on the eve of the new millennium, while in parts of the world some didn’t know how to apprehend the incoming decade, in others places, all kinds of fantastic forecasts were made. Here at Penn, a group of students, from the Science and Technology Wing at Kings Court English College House, sat around and had a discussion about how they would contribute to such a momentous occasion. Many ideas were raised but their thoughts galvanized around the start-up of a journal for undergraduate research. They felt that students needed their voices to be heard in this field, especially during their formative years at College. They immediately refashioned a revolutionary motto for the mission of their new endeavor: “by the students and for the students”. It was a new voice on the block to be heard. It was unique. It was smart. A flurry of activities ensued. They researched and studied existing models; they organized and created a governing structure; they lobbied and obtained funds for the publication; they solicited their peers and obtained paper submissions. PennScience was born. It took them 2 years to complete the project. They created a journal for undergraduate research that would be published biannually. The students realized that they had learned a craft by themselves. A multifaceted craft that a single discipline would not have taught them: entrepreneurship, management, leadership, innovation, public relations, collaboration, and communication - all must-have skills in today’s world. For an administrator and faculty, the formula is simple. It contains two key ingredients: empowering the students, and trusting them to be able to use all tools at their disposal, to successfully accomplish the task and the mission at hand. Ten years after the first issue, the spirit of innovation, of taking part in transforming their world and having a channel for communicating their own research and voice, is still alive. What makes PennScience such a novel media for undergraduate students expressing their research results is the breadth of the publication. The editorial board has always focused on excellence, and to help the students articulate their thoughts in the clearest and most explicit form as to demonstrate their capacity for a quality article. This estimable spirit has permeated PennScience throughout their decade long presence at Penn, and has also clearly enhanced its visibility in neighboring colleges and universities. Kudos to the vision of the founders and to the continuing brilliance of the editors and contributors of PennScience! M’hamed Krimo Bokreta Jorge Santiago-Aviles

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FEATURES

The potential of Andy Guo

Curiosity

The origins of space exploration in the United States are rooted in competition with the Soviet Union during the Cold War Era. The two countries pitted themselves against each other in attempts to attain world power status by traveling to space. As two global leaders, the race was on to determine which nation could successfully attain the next great achievement in science and technology. As space exploration increased, one aspect of outer space that scientists became particularly interested in was Mars, in our own solar system. As scientists began focusing their attention toward Mars, this unknown Red mystery quickly captured the imagination of the whole world. Since the Cold War Era, our knowledge about this planet has steadily increased. Recently, NASA has landed the Curiosity rover on Mars, which will study the planet and bring back unprecedented knowledge about its habitability. The Curiosity rover is currently the newest vehicle on the Red Planet. Launched from Cape Canaveral on November 26, 2011, Curiosity landed on Mars after an 8 month journey on August 6, 2012 (1). The mission was originally supposed to be two years long, but in December 2012, it was extended indefinitely. NASA hopes to achieve several goals with Curiosity as the rover continues to explore the Gale Crater on Mars’s surface (2). Since previous rovers Spirit and Opportunity discovered evidence of water on Mars, scientists hope to discover more elements on the surface of the planet that could potentially sustain life, allowing us to determine if life ever arose on the planet. Mars Science Laboratory will use the rover to look for the presence building blocks of life that are necessary to support life on Earth on the surface of Mars. These include the elements oxygen, hydrogen, nitrogen, carbon and phosphorus (3). In addition to finding elements, the Curiosity mission hopes to study the carbon and water cycles on Mars. To find more clues of life, Curiosity will search for evidence of a stable environment where organisms can thrive with protection from natural disasters (3). The information that Curiosity brings back will be invaluable to understanding the development of life in the universe.

Another related goal that NASA has for the mission is to document the climate and the geology of the Martian surface (1). It is believed that in the past Mars had a warm atmosphere that could have supported a wetter surface and potentially life. However, it is now thin and cold with no signs of water. Much of the water could be trapped under the surface either as ice in the poles or hot thermal vents. The discovery of large magnetic materials on Mars by the Mars Global Surveyor also indicates that there once was a magnetic field on the planet similar to the one on Earth. This field is believed to have once been a shield to cosmic radiation and climate change (3). The Curiosity rover will search for water molecules and provide further insight about Mars’s geographic history. The Mars Science Laboratory will also use Curiosity to continue to study the weather patterns on Mars and measure radiation from the Sun. Additionally, one integral aspect of the climate on Mars is the dust storms that evolve during the spring and the summer (4). These storms can grow to envelop the whole planet, and understanding

Thisisjustoneofmanyfuturecluesthatwill allowustouncoverthemysteriesofMars.

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their formation will be crucial to future climatic studies. Curiosity will attempt to study these storms as well as look into the past of Mars by examining layered deposits of dust and rock. Curiosity hopes to determine the age and composition of different types of rocks on the Martian surface to paint a picture of what happened in the past on the surface of the planet. In order to achieve these lofty goals, the $2.5 billion Curiosity rover carries several instruments to aid scientific discovery (5). Perhaps the most important tool is the imaging device that captures high-resolution videos of the Martian landscape, which has already transmitted many images back to Earth. There is also a high-powered magnifying glass used to take a closer look at the rocks and soil. An instrument called the ChemCam will complement this study of rocks on the surface by firing a laser to determine the composition of


FEATURES vaporized bits (6). To further explore the surface, Curiosity is equipped with SAM-Sample Analysis at Mars. SAM is the heart of Curiosity and it consists of three instruments: a gas chromatograph, a mass spectrophotometer, and a tunable laser spectrometer (7). All three of these tools will measure abundance of hydrogen, carbon, oxygen and nitrogen on the surface of Mars. They will also measure the isotopic composition of the atmosphere. As mentioned previously, in addition to studying the composition of the surface and atmosphere, another important goal of the rover is to search for water molecules. To accomplish this, Curiosity is equipped with DAN, the Dynamic Albedo of Neutrons. This tool fires neutrons into the ground and can determine water concentrations as low as 0.1 percent (8). To achieve another major goal of the mission, studying the climate on Mars, the rover has a Rover Environmental Monitoring System (REMS) designed to measure atmospheric pressure, humidity and wind speed on Mars. Finally, an instrument called radiation assessment detector (RAD) is designed to gauge the amount of high-energy radiation on Mars. This machine can determine how suitable the surface would be for humans and for other life forms to persist, allowing us to assess the habitability of Mars (5). With all these high-tech tools that can determine the composition, climate, and geography of Mars, Curiosity is likely to make exciting discoveries about the Red Planet. In fact, some discoveries have already been underway. On December 3, 2012, it was reported that SAM had found possibly found chlorinated compounds on the surface of Mars. Scientists were not sure if the compounds were actually from the surface of Mars or if they had hitched a ride from Earth through the rover itself (9). Nonetheless, these findings offer hope that scientists are one step closer to finding lifesupporting elements on the surface of the planet, and further investigation will provide more clarity. Scientists are working on deciphering the chemical reactions these molecules have been involved in order to determine if there is, or once was, microbial life. This is just one of many future clues that will allow us to uncover the mysteries of Mars. As these discoveries are uncovered, the mission is capturing widespread interest in the public through the media. Preceding the big announcement on December 3, the media had already begun assuming that the discovery would be a very large step forward for Curiosity. Chief scientist John Grotzinger of Caltech told NPR that the data was “gonna be one for the history books” (10). As a result, the small discovery came somewhat as a disappointment to the public. The public had expected something awe-inspiring, but what they heard was just another small clue of life on the Red Planet. Nonetheless, the hype surrounding the announcement indicates that Curiosity coverage through social networking and the media has captured the interest and imagination of many. There has been a lot of craze about Curiosity, as its landing and images have received millions of views on Youtube (11). The mission has really tried to connect with the rest of the scientific community as well as the entire public by announcing discoveries through Facebook and Twitter. With 1.2 million followers, Curiosity has quickly become a

huge hit on Twitter, where it tweets images of findings. The gallery of images is continuing to inspire young scientists and connects with the world with the mission (12). In a world where communication is vitally important, the mission has tried to relay as much information as possible to the public. The coverage that it has received in the news, especially surrounding the discovery of the chlorinated species, indicates that it has become part of our culture. Curiosity has had a large impact not only on the public but also on the field of space exploration. As Curiosity continues to strive for its goals, it has already laid the framework for another unmanned rover to Mars in 2020 (13). The European Space Agency is also in the process of working on a Mars rover that is scheduled to launch in 2018 through its ExoMars program (14). Scientists suggest that the future of Mars exploration could involve humans, and tools such as RAD help scientists prepare for possible human exploration on Mars (5). While scientists have yet to determine whether or not the surface can be safe for human health and operation, landing humans on Mars may certainly be a possibility in future space exploration. Curiosity has paved the way for the future of space travel, and it will continue to inspire with its groundbreaking findings. The information that it brings back will help shape our understanding of the universe and may have many practical implications for the future of the human race. 1) Jet Propulsion Laboratory. Curiosity 8) Jet Propulsion Laboratory. Dyamanic Rover. http://mars.jpl.nasa.gov/msl/ (acAlbedo of Neutrons (DAN) http://mslcessed January 7, 2013). scicorner.jpl.nasa.gov/Instruments/DAN/ 2) Associated Press, NASA Launches Sophis- (accessed January 7, 2013). ticated Rover on Journey to Mars. The New 9) Chang, K. Mars Rover Discovery York Times [Online], Nov. 26, 2011 http:// Revealed. The New York Times [Online], www.nytimes.com/2011/11/27/science/ Dec. 3, 2012 http://thelede.blogs.nytimes. space/nasas-curiosity-rover-sets-off-forcom/2012/12/03/mars-rover-discoverymars-mission.html?_r=0 (accessed January revealed/ (accessed January 7, 2013). 7, 2013). 10) Space. Mars Rover Discovery Hype a 3) Jet Propulsion Laboratory. Mars Science Big Misunderstanding. http://www.space. Laboratory Contribution to Mars Explora- com/18758-mars-rover-curiosity-discoverytion Program Science Goals. http://mars.jpl. hype-misunderstanding.html (accessed nasa.gov/msl/mission/science/goals/ (accessedJanuary 7, 2013). January 7, 2013). 11) Youtube. Mars Curiosity Descent – Ultra 4) Jet Propulsion Laboratory. Mars Science HD 30 fps Smooth-Motion. http://www. Laboratory Contribution to Mars Explora- youtube.com/watch?v=Esj5juUzhpU (action Program Science Goals. http://mars.jpl. cessed February 19, 2013). nasa.gov/msl/mission/science/goals/ (accessed12) Twitter. MarsCuriosity. https://twitter. January 7, 2013). com/MarsCuriosity (accessed January 7, 5) Space. NASA’s Huge Mars Rover Curios- 2013). ity: 11 Amazing Facts. http://www.space. 13) The Planetary Society. The 2020 Rover com/13699-nasa-mars-rover-curiosityin Context. http://www.planetary.org/blogs/ 11-facts.html (accessed January 7, 2013). casey-dreier/20121204-the-2020-rover-in6) Mars Science Laboratory. ChemCam on context.html (accessed February 18, 2013). Mars. http://www.msl-chemcam.com/ (ac- 14) European Space Agency. Robotic Explocessed January 7, 2013). ration of Mars. http://exploration.esa.int/ 7) NASA. SAM Curiosity. http://ssed.gsfc. science-e/www/area/index.cfm?fareaid=118 nasa.gov/sam/curiosity.html (accessed Janu- (accessed January 7, 2013). ary 7, 2013).

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FEATURES

THE SEARCH FOR EARTH-LIKE PLANE

O

Natalie Neale

ne of the major reasons humans are fascinated by outer space is the possibility of discovering planets similar to our own. Groundbreaking discoveries have already been made, and many more explorations are underway. The implications of finding earth-like planets are profound, and the information we gain from studying these planets will shape our understanding of the universe. Recently, there have been some important breakthroughs, and this new information is leading us closer to finding planets with the potential to sustain life. For a planet to be considered “Earthlike,” there are specific criteria that it must meet. First, like Earth, its composition must be rocky rather than gas based (1). To determine this, scientists can use highly advanced instruments to see if dust is present in the planetary system of interest. For example, the Hubble Space Telescope launched into space by NASA in 1990 has allowed scientists to detect dust in other planetary systems and analyze the composition of the dust through spectroscopy (2). If dust is present, it is probable that there are rocky planets in the system because it is likely that the planetary system was formed by asteroid collisions, leaving dust as a byproduct (3). These collisions are one major theory of how rocky planets form. Another important criterion for an Earth-like planet is that it has a size and mass similar to that of Earth’s (4). Planets with a diameter and mass too 8

close to Earth’s have a similar density to Earth, indicating that they probably have similar composition. Size is also an important factor because it determines the surface gravity, and only planets with a surface gravity similar to Earth’s are likely to sustain life (5). Finally, a crucial criterion that makes a planet Earth-like is having an appropriate climate to sustain life (6). This means it is in the habitable zone of its star, close enough to not be frozen but

ExoPlanetSat (15)

far enough to have liquid water and a sustainable climate. Planets that can meet this set of stringent criteria are of great interest to astronomers. Recently, many important steps have been taken in discovering planets similar to our own. Scientists at MIT have developed a nanosatellite with the sole purpose of finding earth-like planets, called the ExoPlanetSat (7). This nanosatellite, which is only the size of a loaf of bread, is set to launch this year. It will utilize a technique

called transit observation. This method measures the dimming of a star as a planet passes in front of it, and the star’s decrease in brightness allows for the size of the planet to be calculated. Additionally, by measuring the time it takes the planet to orbit the star, scientists can determine its distance from the star. Previously, this technique has only been used among larger satellites, such as NASA’s Kepler. ExoPlanetSat will complement these larger satellites, as the larger satellites will identify stars of interest for the nanosatellite to focus on more specifically. ExoPlanetSat is just one of many nanosatellites that MIT hopes to launch in upcoming years to achieve the goal of finding earth-like planets. The discoveries that it makes will build on those that have already been made. For example, NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside of our solar system, and many of these planets are candidates for being earth-like and potentially containing life (8). One of these planets, Kepler 22b, was the first planet with a size similar to Earth’s to be found in a habitable zone of a star similar to the sun. This planet could possibly contain life forms, and further investigation, possibly through the use of nanosatellites, will provide more information. Internationally, there are also important missions underway. The European Space Agency is currently funding a project to specifically find Earth-like planets (9). They are launching a satel-


FEATURES

ETS lite called the Characterizing ExoPlanet Satellite (CHEOPS), which will start to intensively research planets outside our solar system in 2017. This satellite will also use the transit method, along with the radial velocity method to determine the density of potential earth-like planets. The radial velocity method analyzes the effect of a planet upon the velocity of the star it is orbiting and measures the movement of the star to help determine the planet’s mass (10). Essentially, this technique, also called the “wobble method,” measures the gravitational effect of the planet upon its star (11). Using the transit method and radial velocity method in conjunction, astronomers can estimate the density of the planet of interest, which provides clues to its composition. The CHEOPS satellite will collect data for over 500 stars, and this mission will hopefully bring back exciting new discoveries of earth-like planets. Despite these developments, there are still many challenges to discovering a planet with a particular size, climate, and composition. One of the major issues is that the stars that these planets orbit often are so bright that it can be difficult to observe the planets. However, a new tool called the “nulling interferometer” works to capture the starlight from four different telescopes and arrange it in a way so that the light waves cancel each other out (12). This new technology should greatly advance the search for earth-like planets. Additionally, a new tool called a “laser comb” may increase accuracy of

telescopes used to find these planets tenfold (13). This tool helps calibrate telescopes that are using the wobble technique. The HARPS (High Accuracy Radial Velocity Planet Searcher) spectrograph is also a new invention that allows more precise measurements and aids in the wobble technique (14). The combination of these new technologies is already proving useful, and will continue to be a great aid for future missions in overcoming the challenges of finding earth-like planets. Many earth-like planet candidates have been discovered, and scientists are confident that some of these could sustain life. Discovering more planets similar to our own could open up a window of opportunities. They could allow us to gain insight into the formation of life and they can help us better understand the formation of our own solar system and rocky planet. Although there is still controversy over whether funds should be put into finding earth-like planets and what should be done once we find them, there is no denying that better understanding these planets could help us greatly advance planetary science.

1) Earth Like Planets. http://www.universetoday. com/53074/earth-like-planets/ (accessed Oct 5, 2012). 2) HubbleSite- The Telescope. http://hubblesite.org/ the_telescope/ (accessed Dec 12, 2012). 3) Britt, R. How Planets Form: “It’s a Mess Out There.” Space.com. 2004, http://www.space.com/450-planets-form-mess.html (accessed Dec 12, 2012). 4) Earth Like Planets. http://www.universetoday. com/53074/earth-like-planets/ (accessed Oct 5, 2012). 5) Scientists Find Potentially Habitable Planet Near Earth. Phys.org. 2010, http://phys.org/ news204999128.html (accessed Oct 5, 2012). 6) Earth Like Planets. http://www.universetoday. com/53074/earth-like-planets/ (accessed Oct 5, 2012). 7) Sauser, B. Nanosatellite Will Look For Alien Worlds. MIT Technology Review. 2011 http://www.technologyreview.com/news/424006/nanosatellite-will-look-foralien-worlds/ (accessed Oct 5, 2012). 8) NASA- Kepler: A Search for Habitable Planets http://kepler.nasa.gov/ (accessed Dec 12, 2012). 9) Woollacott, E. ESA Steps Up Search for Earth-like Planets. TG Daily. 2012, http://www.tgdaily.com/ space-features/66998-esa-steps-up-search-for-earth-likeplanets (accessed Oct 5, 2012). 10) Kepler: Planet Detection Methods http://kepler. nasa.gov/Science/about/RelatedScience/capabilitiesOfVariousPlanetDetectionMethods/ (accessed Dec 12, 2012). 11) Redd, N. “Laser Comb” May Aid Search for Earthlike Planets. Space.com. 2012 http://www.space. com/15927-earth-alien-planets-laser-comb.html (accessed Dec 12, 2012). 12) Earth-Like Planets May Be Ready for Their Closeup http://kepler.nasa.gov/news/newsaboutplanetfinding/index.cfm?FuseAction=ShowNews&NewsID=46 (accessed Oct 5, 2012). 13) Redd, N. “Laser Comb” May Aid Search for Earthlike Planets. Space.com. 2012 http://www.space. com/15927-earth-alien-planets-laser-comb.html (accessed Dec 12, 2012). 14) Fifty New Exoplanets Discovered by HARPS. ESO. 2011 http://www.eso.org/public/news/eso1134/ (accessed Dec 12, 2012). 15) Sauser, B. Nanosatellite Will Look For Alien Worlds. MIT Technology Review. 2011 http://www. technologyreview.com/news/424006/nanosatellite-willlook-for-alien-worlds/ (accessed Oct 5, 2012).

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THE PHYSICS OF STAR TREK 6PDUW SKRQHV MHW LQMHFWRUV WUDQVODWRUV DQG KDQGKHOG ELRORJLFDO VFDQQHUV :KDW GR DOO WKHVH GH-­ YLFHV KDYH LQ FRPPRQ" 7KH\ DOO DSSHDUHG LQ WKH XQLYHUVH RI 6WDU 7UHN ORQJ EHIRUH WKH\ DSSHDUHG LQ WKH UHDO ZRUOG DOEHLW ZLWK PRUH REVFXUH QDPHV OLNH WKH ´7ULFRUGHU¾ DQG WKH ´+\SRVSUD\ ¾ ,QGHHG PDQ\ RI RXU JDGJHWV KDYH KDG WKHLU EHJLQQLQJV DERDUG WKH 866 (QWHUSULVH 7KH PRVW VSHFWDFXODU IHDWXUHV RI 6WDU 7UHN KRZHYHU UHPDLQ PHUHO\ GUHDPV WRGD\ 2XU JUHDW VXFFHVV LQ UHSOLFDWLQJ FHUWDLQ HOHPHQWV RI 6WDU 7UHN GRHV SURYLGH KRSH WKDW VRPHGD\ GHYLFHV VXFK DV WKH 7UDQVSRUWHU DQG WKH :DUS 'ULYH ZLOO EH LQYHQWHG +RZHYHU WKHUH LV RQO\ VR PXFK WKDW WKH /DZV RI 3K\VLFV DOORZ 6KRXOG ZH JLYH XS RQ WKHVH WHFKQRORJLHV RU DUH WKH\ VWLOO ZRUWK GUHDPLQJ DERXW"

Donald Zhang

The Transporter [

] n.

One of the most desirable technologies in the Star Trek universe is the Transporter, which can instantly teleport a person to any destination within 40,000 kilometers. It works by converting an object into an energy pattern. The energy is then “beamed� to the target location, and reconverted into matter. This process seems simple enough, but is it actually possible? The first issue to deal with is how to keep track of the object being teleported. As it turns out, humans are a gigantic data entry problem. The “Bekenstein Bound� is the maximum entropy, or information, that is contained in a system with a given amount of space and energy.(1) For a human, the Bekenstein Bound is 1045 bits; that is, it takes 1045 bits to perfectly recreate a human. To put that in perspective, you could fit more than a septillion (1024) centuries of HD video in 1045 bits.(2) A Transporter would need to be able to equipped to store all this data, as well as access all of it within the (almost instantaneous) time it takes to teleport the person. However, Moore’s law is still in full swing, so perhaps in the future this enormous amount of computing power will not be a problem.

step of the transportation process is to make the vanished item reappear in the desired location. Unfortunately, this is where we encounter the biggest obstacle of all: the Heisenberg Uncertainty Principle. Essentially, it is impossible to accurately determine both the position and momentum of small and subatomic particles such as electrons.(4) To replicate a person, both of these parameters must be known for every single particle in their body. Clearly, an object as complicated as a human cannot be reassembled when the information needed to do so cannot be obtained. Even if one could bypass the Laws of Physics and invent a “Heisenberg compensator,� as was used in the show, to be able to successfully teleport people, ethical dilemmas arise. Some might find the idea of a person being destroyed and resurrected in another location upsetting. Is the transported person really the same person? Can the information obtained during transportation be used to create copies of people? Such ethical problems may prove even more troublesome than those presented by science today.

The next issue: how exactly does one go about transforming something into energy? This is where the recent Higgs boson excitement comes into play. The existence of the Higgs boson would imply the existence of the Higgs field, a theoretical entity that is responsible for giving particles their masses. Thus, if the Higgs field could be manipulated, objects could be reversibly turned into energy.(3) However, the only theoretical way to do this is to inject astronomical levels of energy into the system, probably by applying extreme amounts of heat, which would likely destroy the object before converting it to energy. Another problem is the amount of energy this process would produce; according to Einstein’s famous equation E = mc2, the mass of a typical 60 kg human would be converted into the energy equivalent of more than 61,000 Fat Man atomic bombs. Let us assume that researchers eventually develop the capability to harness all this energy and transport it to the desired location. Arguably the most important and impressive 10

Source: http://www.slschofield.com/star_trek/Transporter.jpg


FEATURES The Warp Drive [

] n.

Human space travel is still taking its baby steps. We still have not managed to send people beyond our own moon, let alone to another planet or star. The fastest ever man-made objects, the Helios probes launched in the 1970s, achieved speeds of 150,000 miles per hour.(5) That may sound fast, but at that speed, it would still take more than 18,000 years to reach the nearest star outside our solar system.(6) There is still much progress to be made before we can boldly go where no man has gone before. Even light photons, the fastest known moving objects, are too slow for these purposes. It takes light 25,000 years to reach the closest galaxy to Earth. (7) Suddenly intergalactic travel seems to be completely beyond the realm of reality. Faster-than-light speeds seem to be the solution, but are these possible? Traditionally, the math tells us that they are not. When Albert Einstein developed his theory of Special Relativity, mass was found to be relative: The mass of an object changes based on how fast the object is moving, as shown by the following equation: (8)

As the velocity v increases, the relative mass of the object increases. Energy is required to increase the speed of objects, and the heavier the object is, the more energy needed. Therefore at high speeds, where the object is massive, enormous amounts of energy are required to increase its speed further, even by a small portion. In fact, according to the equation, infinite energy is required to accelerate an object to the speed of light. This demonstrates the fundamental law of relativistic motion: light-speed is the maximum speed attainable in the Universe.

This might sound like a bunch of hocus pocus, but the idea is actually theoretically possible. In 1994, a physicist named Miguel Alcubierre proposed the “Alcubierre Drive.�(9) A large ring around a spaceship would cause the spacetime in front of the ship to contract and the spacetime behind the ship to expand. If this contraction and expansion occurs fast enough, the ship is carried along at a very fast speed. NASA uses the analogy of a moving sidewalk in an airport. (10) A person can only walk so fast, but can move faster if he/she walks on a moving sidewalk. This is analogous to a spaceship using the Alcubierre Drive, as it is limited by the speed of light in spacetime, but can move faster than light if the spacetime itself is also moving. Thus, in the context of its local spacetime bubble, the ship can be moving very slowly, but relative to the surrounding spacetime, the ship can ride this wave of warped space faster than the speed of light. Potential problems with this hypothetical invention are the colossal amount of energy required for its function and its requirement for “exotic matter,� matter with unusual properties such as negative mass.(11) Whether or not this exotic matter exists is unknown, but as of now there are no physical laws that would prohibit the Alcubierre drive from working. Furthermore, in September 2012, NASA scientist Harold White revealed his work on modifying the original Alcubierre drive designs, claiming that the energy requirements were much lower than originally thought. He has since been at work in the lab to attempt to put these theories into practice.

It would seem that traveling faster than light is another piece of technology that has been deemed impossible. So how does the Warp Drive of Star Trek accelerate starships to many times the speed of light? The Warp Drive mechanism exploits a physical loophole: The rules of spacetime cannot be broken, but spacetime itself can be manipulated. According to Star Trek lore, the Warp Drive creates a “warp field� that distorts the spacetime surrounding the ship. This distortion of spacetime allows the ship to travel faster than light.

Source: http://en.memory-alpha.org/wiki/Warp_drive

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FEATURES 1) Bekenstein, J. D. Universal upper bound perg.phys.ksu.edu/classes/conckirsten/modu- http://heasarc.nasa.gov/docs/cosmic/nearwarp drive. on the entropy-to-energy ratio for bounded lee/uncertainty/startrek.html (accessed Jan 3, est_galaxy_info.html http://io9.com/5963263/how-nasa-willsystems. Physical Review D 1981, 23. 2012). 8) Einstein, A. On the Electrodynamics of build-its-very-first-warp-drive (accessed Jan 2) At a bitrate of 40 Mbits/s, typical of a Blu 5) Aerospaceweb. Aircraft Speed Records. Moving Bodies. Annalen der Physik 1905, 17. 3, 2012). Ray Disc. http://www.aerospaceweb.org/question/perfor- 9) Alcubierre, M. The warp drive: hyper-fast 3) Science on NBC News. http://www.msnbc. mance/q0023.shtml (accessed Jan 3, 2012). travel within general relativity. Classical and msn.com/id/48087875/ns/technology_and_ 6) Space. The Nearest Stars to Earth. Quantum Gravity 1994, 11. science-science/t/higgs-boson-first-step-star- http://www.space.com/18964-the-nearest10) NASA. Status of “Warp Drive”. http:// trek-transporter/#.UO5umYnjnlE (accessed stars-to-earth-infographic.html (accessed Jan www.nasa.gov/centers/glenn/technology/warp/ Jan 3, 2012). 14, 2012). warpstat_prt.htm (accessed Jan 3, 2012). 4) Kansas State University. Star Trek. http:// 7) NASA. The Nearest Galaxies. 11) Io9. How NASA might build its very first

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FEATURES processes taking place in the universe now (most likely). In the very early universe however, things were much more energetic. The Higgs field may have played a role in what we call “inflation”, a period of extremely rapid expansion h t i of a patch of the Universe to w view r e become what we now see as t y n e I ladn G our universe. If that’s the y r Lar case, then the Higgs is all but literally the “God particle” in that it has an essential role in causing our universe to exist.

i H e h T

n o s o B s g g

We have all likely heard of the Higgs Boson or the Higgs Field today, after a recent discovery electrified the global scientific community perhaps as much as it bewildered the casual observer. So what did the discovery really tell us, and how does it affect our understanding of the physical world? In order to shed some light on these questions, we conducted an interview with Penn’s Larry Gladney, Professor of Physics and Astronomy. Larry Gladney, Edmund J. and Louise W. Kahn Professor for Faculty Excellence and Department Chair, is an expert in the fields of high-energy physics and cosmology. He is one of Penn’s representatives on the LSST project (Large Synoptic Survey Telescope), which is a proposed ground-based observatory aimed at measuring the expansion of the universe and understanding the nature of dark energy that is accelerating this expansion. With the recent experimental verification of the Higgs field and Higgs boson at the LHC, what are some of the consequences to the field of astrophysics? My collider colleagues would not say that the Higgs boson is experimentally verified as yet. The new boson (which simply means the particle spin is a whole number rather than 1/2 like the electron or the quarks) discovered last summer is likely to be the Higgs predicted by the Standard Model, but this requires lots more data to actually be confirmed. It turns out that lots of extensions to the Standard Model predict more than one kind of Higgs particle (the Standard Model can only accommodate one), so it is important to be sure that the one discovered actually matches the Standard Model Higgs in detail - if it’s not a match then the experimenters have discovered really new physics! It’s hopeful that enough data will have been taken by this spring to do the comparisons to Standard Model expectations well enough to say “Yes, this is the Standard Model Higgs” or “No, we don’t have a match but that’s even more exciting because it means we’ve seen the first member of what is likely to be a family of particles from some even deeper, more fundamental theory”. As for the consequences for astrophysics, I would say they are indirect. The energies at which Higgs physics becomes consequential is much higher than in any of the physical

Since dark matter is not composed of the same matter that constitutes us and our physical reality, and since it does not interact with EM radiations, is it possible for usto understand its nature, and if so, how would we go about doing that? We are attacking this in 3 ways: create and study dark matter in the laboratory (at the LHC), confirm the existence of dark matter in its native habitat (the halos of galaxies), and identify the dark matter streaming through the earth right now. If we “see” a dark matter candidate particle that appears to match the characteristics for all three kinds of experiment, then we can be pretty confident that nature is showing us what dark matter “is”. We’d still have to discover its origin but the hope is that if you can make it in the laboratory, then you’ll have other clues as to what dark matter particles “connect” to, i.e. what underlying physics is responsible for it and how that new physics relates to the already understood physics. So, yes, I think the chances are good that we will understand the nature of dark matter in the next decade or two. The existence of dark matter was postulated because there is less observable matter than there are gravitational sources. Is there a possibility, however, that our laws of gravity are inaccurate and dark matter/energy would disappear if we improve our theory of gravity? Physicists and astrophysicists take the possibility that our understanding of gravity is incomplete (or just plain wrong for large distances) very seriously. All of the proposed experiments that look at the consequences of dark matter for the universe as a whole also have the capability to distinguish between the existence of dark matter and the possibility that general relativity (Einstein’s theory of gravity) is just wrong. Luckily, dark energy, another mystery, PennScience 11 | 13


FEATURES

gives us another handle in the predictions due to general relativity that allows a “degree of freedom” to cleanly distinguish things. The general relativity predictions are pretty tight if we look at the universe over long time scales, i.e. the universe’s development from earlier times to now depend critically on dark matter and dark energy behavior according to general relativity. If either of these doesn’t exist and its just that a new theory of gravity is needed, we should be able to tell that with some degree of confidence with the next generation of astrophysical instruments (so on the timescale of 20 years). On the other hand, if we don’t discover any dark matter candidates in the laboratory that fit the properties necessary to explain the dynamics of gravity and fit with our notion of how the universe developed at early times, we’ll also know that dark matter is not the explanation that we needed dark matter for in the first place. Science is expanding at an accelerating rate. How do we overcome the challenge of keeping society up to date with the latest theoretical and experimental findings in a form that is understandable to the general public? Great question! I wish I knew the answer. Somehow I think the new media tools can play a role, but physicists as a whole are not using them for this role. There are notable exceptions of course, including my colleagues here at Penn, Mark Trodden, but for the most part we scientists have not taken this on as a serious responsibility. What are some examples of scientific advancements from Penn’s departments in the field of astrophysics? We are world leaders in getting results on the development of the early universe using the cosmic microwave background (examined through balloon-borne observatories), weak gravitational lensing, and the theory of black holes 14

through their connection to particle physics. We also made fundamental contributions to our understanding of supernovae through the discovery of neutrinos from Supernova 1987A. The prime driver of getting the design of the electronics to make that discovery died on Sunday. Al Mann was a giant in the field of neutrino physics and his legacy is a group that still carries on this work in neutrino astrophysics. On left: Penn Physics & Astronomy. http://www.physics.upenn.edu/people/ standing-faculty/larry-gladney (accessed 4/2/2013). On top, from left to right: 1) Compact Muon Solenoid. “About the Higgs Boson.” http://cms.web.cern. ch/news/about-higgs-boson (accessed 4/2/2013). 2) National Optical Astronomy Observa-

tory. http://www.noao.edu/icarchives/all. php (accessed 4/2/2013). 3) NASA. “The Mysterious Rings of Supernova 1987A.” http://apod.nasa. gov/apod/ap070107.html (accessed 4/2/2013). 4) Night sky tree. http://www. widescreen-wallpaper.eu/view-night_sky_ tree_universe-1280x800.html (accessed 4/2/2013).


RESEARCH

Social Influences on Reproductive Success in Brown-­headed Cowbirds, Molothrus ater Lane Robinson University of Pennsylvania, Philadelphia, PA

ABSTRACT All individuals vary in reproductive output, and there are multiple reasons for why this is the case. The present study investigated the influences on reproductive output in brown-headed cowbirds. a relationship between the attractiveness of a male’s song and his mating success has previously been found. This study aims to identify if frequency of singing to females affects reproductive output and to see what other influences may be present. To further test song quality’s effect on reproductive output, an HVC lesion was made in half of the females to affect their song preferences. Video recordings were taken of interactions between male and female pairs. The videos were used to observe the frequency of several different behaviors relating to pair bonding and mating, time spent together, and consistency of pair interactions. The eggs from each pair were collected, and then correlations between different behaviors and number of eggs laid were determined in order to identify what influences reproductive output in cowbirds. A relationship was found between the frequency of female rattling and high reproductive output. No relationship was found between the frequency of other behaviors and reproductive output. These results suggest that rattling may be somehow related to reproductive output and can be used as a predictor of reproductive success. For other behaviors observed in the study, frequency is not likely to be as important as other factors in determining reproductive success. Within all animal species, individuals vary in reproductive output. There are numerous possibilities for why. For sexually reproducing species, causes for variation in reproductive output could lie with the male partner, the female partner, or an interaction between the two. For example, the male may be particularly fecund or have some characteristics that cause the female partner to produce high numbers of offspring. Alternatively, it may be that the female is particularly fecund or possesses some characteristics that enable her to produce high numbers of offspring. Or, it may be that both the male and female partner are compatible in some way that enables them to have a high reproductive output. For example, genetic compatibility may be necessary to have viable offspring, causing selection to favor those who choose mates genetically distinct from themselves to avoid inbreeding and to gain other genetic benefits such as a different MHC complex (Puurtinen et al. 2005). Alternatively, behavioral compatibility may be needed in order to stimulate the hormones required for reproduction, as is seen in ring doves; the male must court the female for hours in order for her to ovulate (Silver 1978). There are multiple reasons for why a male or female may be overly fecund. It could be a result of genetics. Certain genes may cause the individual to have a longer lifespan, enabling

one to have a higher reproductive output. It may also be that certain genes are associated with better health, as suggested by Hamilton and Zuk (1982). Then reproductive success may be dependent upon an individual’s ability to express this quality to a mate. Birds who express their quality, or fitness, to a mate through behavior or sexually attractive physical characteristics may cause the mate to invest more in reproduction and raising offspring, as this passes the mate’s genes on to the offspring (rock doves, Clayton 1990). Alternatively, a male or female may be overly fecund as a result of social learning during his or her lifespan that enables him or her to make informed mate choices (Westneat et al. 2000, White 2004) and develop successful courting techniques (Smith et al. 2000). In songbirds, the male song has been considered a characteristic that may indicate fitness, potentially making it a trait females use to influence their reproductive output decisions. A song that is very attractive to a female may indicate to a female that she should invest heavily in reproduction. In brownheaded cowbirds (Molothrus ater), previous studies have been able to identify that some male songs are better able to elicit copulation postures in females than others (King and West 1977). Triggering a posture with a song is the only way a male can copulate and reproduce with a female, so there is a

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RESEARCH strong relationship between song quality, meaning the attractiveness of a song for females, and mating success (West et al. 1981). Other than as an indicator of quality, song can be used to coordinate behavior between pairs. Non-singing cowbird females are able to communicate with males about their song quality through the use of a wing stroke (West and King 1988). Wing strokes may actually be used to stimulate song learning in males by providing feedback (Smith et al. 2000). Additionally, females can use non-singing vocalizations, such as rattling, as a form of feedback (Freed-Brown and White 2009). In both cases, an action by the female results in the male editing his song to develop a more potent one. If song quality influences female’s reproductive output decisions, then those females paired with males singing the highest quality songs should lay the most eggs. One possible measure of song quality is the frequency of singing (blackcapped chickadees, Otter et al 1996; snow buntings, Hofstad et al. 2002). Another is the variability of song, as female cowbirds have been shown to prefer larger song repertoires (Hosoi et al. 2005). In the present study, the interactions between male and female cowbird pairs will be observed in order to determine what influences reproductive output. The frequency of singing will be recorded, with the expectation that a higher singing rate will correlate with a higher number of eggs laid. In order to further test the effect that the female preference for song has on reproductive output, half of the females in the study had lesions in the HVC region of their brain. This center is located in the caudal nucleus of the ventral hyperstriatum. Lesions to this area have been shown to increase the rate of copulation solicitation displays in response to weakly stimulating conspecific and heterospecific song in female canaries, songs that do not generally elicit copulation displays from healthy females (Brenowitz 1991; Del Negro et al. 1998). These findings indicate that the HVC is critical for the control of sexual preferences to conspecific songs. Therefore, in this study, females with an HVC lesion would be expected to respond with a higher frequency of copulation displays, leading to higher numbers of eggs laid, regardless of singing rate. However, if reproductive output is determined by other means, such as a female characteristic or pair compatibility, then other outcomes are possible. For example, if female quality relates to egg production, we may find behaviors of females that are indicators of quality. A behavior specific to cowbird females that may influence reproductive output includes rattling. A rattle, sometimes referred to as chatter, is the only loud vocalization given by female cowbirds. The function of chatter is not entirely clear, and there are many possibilities. These possible functions include an aggressive response to other females (Burnell and Rothstein 1994), species recognition (Hauber et al. 2001), a response to a successful courtship with a male (Freed-Brown and White 2009), as well as a means of indicating to other females the quality of a male (Freed-Brown and White 2009). If rattling is used in response

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to a successful courtship, then it may be that females who rattle more often are in more reproductively successful pairs. Female cowbirds may also influence reproductive output by being in control of the proximity of the male (Freeberg 1998). Females can either lunge toward the male, not move (therefore remaining by the male), or they can fly away. It may be that females who consistently fly away, thus prohibiting their partner from singing to them, will have a lower reproductive output, whereas females that move toward the male by lunging or remaining still will have a higher reproductive output. If behavior compatibility relates to reproductive output, then we may find that pairs that consistently exhibit a certain behavior will lay higher numbers of eggs. Social learning and cultural transmission play a significant role in cowbird mating preferences (Freeberg et al. 1999), suggesting that social interactions between pairs may be a significant influence on reproductive output. It may be that pairs that spend greater amounts of time together have a higher reproductive output because the male would have a greater chance of learning how to sexually stimulate the female. It also may be that males who consistently make efforts to remain with their mate by approaching and following them after the female moves or flies away will have a higher reproductive output because the pair will spend more time together. In order to test for multiple possible influences on reproductive output, the frequency of several behaviors will be observed between cowbird mating pairs. The amount of time spent together and the consistency of behavior between pairs will also be recorded. By then determining the correlations between different behaviors and the number of eggs laid, we can shed light on what influences reproductive output in cowbirds.

METHODS Subjects

Experimental subjects were adult male and female brownheaded cowbirds (Molothrus ater). Birds wore unique combinations of colored leg bands to permit individual identification. Twenty wild-caught adult females and twenty wild-caught adult males were used in the aviary study. All subjects were trapped in Montgomery County, PA, USA. Subjects were at least one year of age and had experienced at least one breeding season at time of capture. Prior to experiment, all subjects were living in mixed age and sex flock in large, outdoor aviaries. Aviaries measure 18.3x6.1x4m and contained trees, shrubs, grass and shelters. Subjects were used for experiment on song data and a playback study prior to video study. A mix of millet and canary seed plus a modified Bronx zoo diet for omnivorous birds and fresh water were provided.

Procedure

Subject females were removed from aviaries into outdoor flight cages measuring 4.26x1.67x2.13m. Females were taken from the University of Pennsylvania avian field station (Chestnut Hill, PA) to the Schmidt neuroscience lab on University of Pennsylvania campus (Philadelphia, PA) to receive HVC and sham chemical lesion surgeries. After recovering, females


RESEARCH were returned to field station and either returned to large, outdoor aviaries or returned to flight cages for a playback study.

Surgical and anatomical methods for HVC surgery

Previously used methods were followed for performing surgeries (Del Negro et al., 1998). Briefly, birds were first given an intramuscular injection of 5 mg/Kg diazepam followed 20 minutes later by an injection of ketamine/xylazine (35/7 mg/ Kg). Birds were then placed in a stereotaxic apparatus that allowed their heads to be tilted to a 45° angle. A portion of the outer skull layer overlaying the right and left HVC was removed and HVC was targeted using stereotaxic coordinates relative to the bifurcation of the central sinus. Spontaneous bursting patterns that are characteristic of HVC were also used to confirm the location of HVC. With the aid of a surgical microscope, glass pipettes were filled with either the neurotoxin Ibotenic acid (Sigma; 0.66% ibotenic acid; 10 mg in 1.52 ml in 0.4 M phosphate buffer) or the buffer alone, mounted on a nanoject and lowered into HVC. Birds assigned to the HVC group received up to 0.4µμL in each HVC of ibotenic acid dissolved in phosphate buffer saline (final pH 7.6). Lesions were made by slowly injecting the acid into each HVC. Sham birds underwent the same surgical procedure except that the microelectrode only contained phosphate buffered saline. After each injection, the electrode was left in place for at least 5 minutes to prevent spreading up the electrode track. Birds were then allowed to recover for at least four days after the surgery.

Egg Collection

To track egg laying, artificial egg stimuli made from plaster of paris was placed into nests. All activity on the nests was recorded using small, low-light cameras attached to a central computer. Surveillance software (Geovision 1480 v. 8, USA Vision Systems Inc., http://www.geovision.com.tw) recorded any movement on the nest. During the 33 day breeding season 16 females laying eggs were identified. Eggs were collected every morning between 6.00-8.00hrs.

Video Study

The two replicate outdoor aviaries used for data collection were located at the Morris Arboretum of the University of Pennsylvania. Each of the two aviaries housed 20 birds in total, which comprised of ten males, five sham females, and five HVC females. Video data of birds was collected for approximately 5 hours each day, weather dependent, Monday-Friday between the hours of 6 a.m.-12 p.m. from May 25th to June 17th 2011 using a Canon GL3. Videotaping of pairs was done opportunistically in a survey manner, so pairs were videotaped as they were interacting rather than focusing on any one pair. Videos were then transferred to DVD and watched to identify sequences of behaviors seen between mating pairs. Frequencies of specific behaviors for each pair were scored. Behaviors scored for each pair included direct song (DS), male approach (MA), male follow (MF), female move (FM), female leave (FL), male leave (ML), female lunge (FLUNGE),

female rattle (FRTL), and female no response (FNR). The definitions for each behavior were as follows. DS: male facing a female, unobstructed by other birds, and directing his song toward her. MA: a male directly walking toward female when they had not been previously interacting. MF: male pursuing female if she moves or flies away after he sings or approaches. FL (or ML): female (or male) terminating interaction by flying away. FLUNGE: female lunging toward male in response to a song or approach. FRTL: female making rattle noise in response to male song or approach. FNR: female not making any visible action in immediate response to male’s song or approach. The average time for each interaction was also scored, as well as how consistent the pair was in their behaviors. If a pair performed a specific behavior more than 75% percent of the time in all of their interactions, it was considered a consistent behavior. Additionally, if the pair did not perform a specific behavior consistently, less than 25%, this was also considered consistent behavior. Consistency for each behavior was averaged for each pair and they were assigned a consistency score. Two separate categories for comparison were made. In one category, the frequency of every behavior type was compared for the females that laid high numbers of eggs versus the females that laid low numbers of eggs. In the second category, the frequency of every behavior type was compared for the females with HVC lesions versus the sham females. The high vs. low counts were based on the average amount of eggs laid for all females in the study. Behaviors, interaction length, and consistency of interactions were collected for eighteen pairs.

RESULTS The average number of eggs laid for all females in the study was 6.35; egg counts above this average were considered high and egg counts below this average were considered low. There were seven pairs in the high reproductive output category (egg output range: 7-25) and eleven in the low reproductive output category (egg output range: 0-5). When comparing pairs with a high reproductive output to pairs with a low reproductive output, there was a significant behavior difference. Females in high egg laying pairs were observed to rattle significantly more than females in low egg laying pairs (t test, P<.05, see figure 1). There were no other significant behavior differences found between the high reproductive output pairs compared to the low reproductive output pairs (see appendix, table 1). Interaction length and consistency of interaction were also not found to be significant between the two groups. There were no significant differences between the pair behavior, interaction length, or consistency of interaction for birds with lesions in the HVC when compared to birds without lesions (see appendix, table 2). However, there was a significant difference in egg production difference between birds with HVC lesions and birds without lesions (t test, P<.025, see figure 2).

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RESEARCH DISCUSSION Pairs containing a female that rattled more had a significantly higher reproductive output. Therefore, the female behavior of rattling can be used as a predictor for reproductive success, and it may even directly influence reproductive success. The other behaviors that were measured were not shown to significantly correlate with egg production. One possible reason for this is that these behaviors do not influence or play a role in reproductive success. Interestingly, the frequency of singing did not relate to reproductive success, nor did the time spent together as a pair, which may mean that it is not frequency that is important, but instead only other aspects of the song quality such as size of the repertoire. Rattling was the only behavior that varied in frequency in relation to reproductive output. As of yet, the function of the rattle is not understood, and the findings of this study can be used to elucidate its purpose.

Figure 1 Rattling frequency vs. reproductive output. Females with a high egg count had a high reproductive output and were found to rattle with greater frequency than birds with a low egg count.

It may be that the rattle is induced by a male action that leads to reproductive success. Previous studies have found that females rattle in response to male singing, particularly after a male has begun to court them consistently (Burnell and Rothstein 1994, Freed-Brown and White 2009). Perhaps, then, a rattle is an indicator that a male is successfully courting a female. If this is the case, then the increase in reproductive success may be a result of the consistent courtship. The underlying reason for why a male is more successful at courting a female may relate to the male’s genes. Males with enhanced genetic quality may court females better, causing females to be more sexually attracted to these males, yet we could not detect any behaviors that could account Figure 2 Amount of eggs laid vs. HVC lesion or sham females. Females with for this variation in courtship skill. The female may then an HVC lesion had a significantly higher reproductive output than females indicate her preference for these males by rattling more without a lesion. often. This would be supported by previous findings that males who rattle more because they know they are conspesexual selection in cowbirds is based on female prefercifics. Alternatively, perhaps the rattle indicates more than ence (White et al. 2006), and that rattling indicates quality of species recognition, and it is actually sexually attractive to a male to other females (Freed-Brown and White 2009). If a a male. If this were the case, then females who rattle more rattle is an indicator of female preference for males with good would get more attention from their pair mate, and partake in genes, then future studies should find that females rattle in more copulations. The rattle may indicate something desirable response to males with high quality male song. about the female, such as health or genetic quality. Future It is also possible that the rattle is attractive to the male, experiments could further investigate this by examining male which would result in increased reproductive success for those preferences for females, and by investigating any correlation females who rattled more often. Cowbirds have been shown between health quality of a female and rattling behavior. to exhibit female preference for males (White et al. 2006), Furthermore, it may be that the rattle is used to coordinate the though the opposite has not been a focus of investigation. In behavior between the male and female, leading to an increase the present study, it was found that a female trait is associin reproductive success. Rattling has been shown to serve ated with higher reproductive success, suggesting the possibilas a signal to other females (Freed-Brown and White 2009), ity that males are attracted to this trait. This suggests it would and it may be that it could also provide a signal for the male. be interesting to study male mate choice in this species. Adult If the rattle provides feedback to the male, then females who and fledgling cowbirds approached playbacks of rattle more rattle more are providing more feedback, which better enables often than control sounds (Snyder-Mackler and White 2011, the male to alter his courtship strategy and be more sexually Hauber et al. 2001), and these studies suggested that the attractive to the female. Similarly, the theory of coordinatrattle was being used in species-specific recognition. If this ing behavior is still compatible if the rattle is sexually attracis the case, then perhaps males are more attracted to fe-

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RESEARCH tive. Males may induce rattling by singing a potent song, and then the female rattling may further attract the male to her. This coordination of behavior would mean that the pressure of sexual selection would occur on both sexes, as is seen in ring doves (Silver 1978). Future studies could investigate this by searching for any changes in song quality in response to rattle. Alternatively, it is possible that the rattle does not indicate or play any direct role in determining reproductive success. It is possible that the rattle correlates with a variable that was not measured in this study, such as hormone levels, which may be the actual critical effectors of egg production. Even so, the frequency of rattling may still be able to be used as a predictor of egg production. whether or not females that rattle more often are physiologically different than those who rattle less often should be investigated. Significant differences were not observed in the behaviors of HVC females and females without a lesion (sham females), though HVC females had a significantly higher reproductive output. These findings suggest that the ability to control sexual preferences to conspecific song is a major determinant of reproductive output, and that other behavioral factors are less influential. Interestingly, HVC females did not have increased rates of copulation displays, which suggests that reproductive output may be somewhat independent of the frequency of copulation displays. However, low HVC egg layers did not rattle at all whereas high HVC egg layers did rattle. Given that the HVC lesion has an effect on song preferences, we would not expect to see the same correlation between high reproductive output and rattling behavior in HVC females as we do in sham females if rattling behavior was only induced by potent song. Since we do actually see that both sham high egg layers and HVC high egg layers rattle more than their counterparts, this suggests that rattling is associated with a higher reproductive output in general and is not only as a result of potent song. This study has identified important aspects of pair behavior. The rattle’s precise role must be investigated further in future studies, to identify if it is used as a signal, a method of feedback, to attract a mate, in some other way, or if it actually correlates with another variable not measured in this study. This will then elucidate how sexual selection works in relation to rattling. In any case, the female rattle may be used as a predictor of reproductive success. This study has also served to highlight that time spent together as a pair and behaviors besides rattling do not correlate with reproductive output. This suggests that males must be able to demonstrate their quality to a female using their song no matter how long the interaction lasts, so frequency is not likely to be as important as other factors in determining reproductive success. The results of this study suggest that, with the exception of rattling, quality is more influential than quantity on cowbird mating success.

ACKNOWLEDGEMENTS Special thanks to David J. White and Grace Freed-Brown who assisted with the development of the project. David J. White provided the facilities for the experiment and provided com-

ments on previous drafts of the manuscript. All work was done under the University of Pennsylvania’s Institutional Animal Use and Care protocol # 800439.

REFERENCES Brenowitz, E. A. (1991). Altered perception of species-specific song by female birds after lesions of a forebrain nucleus. Science, 251, 303-305. Burnell, K. & Rothstein, S. I. (1994). Variation in the structure of female brown-headed cowbird vocalizations and its relation to vocal function and development. Condor, 96, 703–715. Clayton, D. H. (1990). Mate choice in experimentally parasitized rock doves: lousy males lose. American Zoologist, 30, 251-262. Del Negro, C., Gahr, M., Leboucher, G., & Kreutzer, M. (1998). The selectivity of sexual responses to song displays: effects of partial chemical lesion of the HVC in female canaries. Behav Brain Res, 96, 151–159. Freeberg, T. M. (1998). The cultural transmission of courtship patterns in cowbirds (Molothrus ater). Animal Behaviour, 56, 1063-1073. Freeberg, T. M., Duncan, S. D., Kast, T.L., & Enstrom, D. A. (1999). Cultural influences on female mate choice: an experimental test in cowbirds, Molothrus ater. Animal Behaviour, 57, 421-426. Freed-Brown, G. & White, D. J. (2009). Acoustic mate copying: female cowbirds attend to other female’s vocalizations to modify their song preferences. Proc. R. Soc. Lond. B, 276, 3319-3325. Hamilton, W. D. & Zuk, M. (1982). Heritable true fitness and bright birds: A role for parasites? Science, 218, 384-387. Hauber, M. E., Russo, S. A. & Sherman, P. W. (2001). A password for species recognition in a brood-parasitic bird. Proc. R. Soc. Lond. B, 268, 1041–1048. Hofstad, E., Espmark, Y., Moksnes, A., Haugan, T., & Ingebrigsten, M. (2002). The relationship between song performance and male quality in snow buntings. Canadian Journal of Zoology, 80, 524-531. Hosoi, S.A., Rothstein, S.I., & O’Loghlen, A.L. (2005). Sexual preferences of female brown-headed cowbirds (Molothrus ater) for perched song repertoires. The Auk, 122, 82-93. King, A. P. & West, M. J. (1977). Species identification in the North American cowbird: appropriate responses to abnormal song. Science, 195, 1002–1004. Otter, K., Chruszcz, B. & Ratcliffe, L. (1996). Honest advertisement and song output during the dawn chorus of blackcapped chickadees. Behavioral Ecology, 8, 167-173. Puurtinen, M., Ketola, T., & Kotiaho, J. S. (2005). Genetic compatibility and sexual selection. Trends in Ecology and Evolution, 20, 157–158. Silver, R. (1978). The Parental Behavior of Ring Doves: The intricately coordinated behavior of the male and female is based on distinct physiological mechanisms in the sexes. American Scientist, 66, 209-215. Smith, V. A., King, A. P. & West, M. J. (2000). A role of her own: female cowbirds, Molothrus ater, influence the devel-

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RESEARCH opment and outcome of song learning. Animal Behav., 60, 599–609. Snyder-Mackler, N. & White, D. J. (2011). The developmental ecology of acoustic sensitivities: reactions to song playbacks by male cowbirds change across their first year of life. Behaviour, 7, 747-764. West, M. J., King, A P., & Eastzer, D. H. (1981). Validating the female bioassay of cowbird song: relating differences in song potency to mating success. Animal Behav., 29, 490501. West, M. J. & King, A. P. (1988). Female visual displays

affect the development of male song in the cowbird. Nature, 334, 244–246. Westneat, D. F., Walters, A., McCarthy, T. M., Hatch, M. I. & Hein, W. K. (2000). Alternative mechanisms of nonindependent mate choice. Animal Behav., 59, 467–476. White, D. J. (2004). Influences of social learning on mate choice decisions. Learn. Behav., 32, 105–113. White, D. J., Gros-Louis, J., King, A. P. &West, M. J. (2006). A method to measure the development of song preferences in female cowbirds, Molothrus ater. Animal Behav., 72, 181–188.

APPENDIX

Appendix 1 Behavioral frequencies, interaction length, and consistency score when comparing high egg layers to low egg layers

Appendix 2 Behavioral frequences, interaction length, and consistency score when comparing HVC females to sham females

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RESEARCH

In-­Vivo Cytotoxicity, Allelopathic, Antimitotic, and Antibiotic Properties of Ethno Pharmacologically Selected Medicinal Plants from the Dominican Republic Ghislain B. Tchomobe, Sr.,1 Anne Osano,1 Maria T. Laux,2 and Manuel A. Aregullin2 1 Bowie State University, Bowie, MD 2 Cornell University, Ithaca, NY

ABSTRACT In the Caribbean, the use of plants for medicinal purposes is extensive. Five Dominican Republic medicinal plant species were collected and their organic extracts prepared for study. The plants were selected based on their ethno botany claims of being able to repel mosquitoes, treat asthma, cancer and many other diseases. The extracts were screened for their allelophathic, anti-mitotic, antibiotic, as well as their cytotoxic properties. Allelopathic studies using a seed germination assay showed that the isopropanol extract of Cymbopogon citratus, Rauwolfia nitida and Chiococca alba had a 100% growth inhibition activity at the concentration tested and the methanol extract of Chiococca alba was also active and possessed 100% growth inhibition at the concentration tested. The brine shrimp assay, the test for cytotoxicity exhibited increasing mortality rates at increasing dosages of a Chiococca alba methanol crude extract. Rauwolfia nitida methanol plant extract showed weak to moderate antibiotic/antifungal inhibition activity against the gram-positive bacteria Escherichia coli and Pseudomonas aeruginosa; and against the gram-negative bacteria Listeria monocytogenes and Staphylococcus aureus. The Cymbopogon citratus methanol extract displayed weak inhibition against Staphylococcus aureus. This study suggests that Chiococca alba has a high potential as a cancer treatment as well as an herbicide. Furthermore, Cymbopogon citratus and Rauwolfia nitida have a high potential as herbicides.

Keywords: Antibiotic, Cytotoxicity, Allelopathy, Antimitotic, In-vivo, Capsicum frutescens, Cymbopogon citratus, Rauwolfia nitida, Theobroma cacao, Chiococca alba.

INTRODUCTION Ethno-botany and ethno-medical studies are today recognized as the most viable methods of identifying new medicinal plants or refocusing on those earlier reported for bioactive constituents (Adjanahoun et al., 1991; Farnsworth, 1966). The clinical success of quinine and quinidine isolated from the Cinchona tree bark and artemisinin from Artemisia annua in the treatment of malaria have rekindled interest in medicinal plants as potential sources of novel drugs (Di Flumeri et al.,2000). Plants which are observed to be efficacious and frequently prescribed may contain compounds that are potential drug candidates and could rightly be recommended for further examination. Investigations of medicinal plants have been initiated in many countries because of their contributions to health care. The continual search for and the interest in natural plant products for use in medicine has acted as the catalyst for exploring methodologies involved in obtaining the required plant materials and thence probing their constituents.

The Dominican Republic is a country in the West Indies that occupies the eastern two-thirds of the Hispaniola Island. The biodiversity in terms of plant in the Dominican Republic consist of more than 600 plant species. This diversity, along with its widespread local use for medicinal purposes, makes the island an excellent site to study, assess and probably confirm part of the ethno botany use of medicinal properties in plants and maybe uncover new uses related to medicinal plants.

OBJECTIVES The objectives of this research were to study the Dominican Republic flora; understand the relationship between population and ethno botany; examine the efficiency of selected plants traditionally used in the Dominican Republic in order to support reported claims; and use bioassays to find new bioactivities among the selected plants.

MATERIALS AND METHODS Plant Collection, Processing and Extraction:

Five plant materials from Dominican Republic medicinal species were collected in the Punta Cana, Kheel Garden and

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RESEARCH filter paper. Each filter paper was slightly moistened throughout the test. The germination of the seed was monitored over 3 days and was compared to the control.

Antibacterial and Antifungal Assay: (antibiotic)

To determine the antibiotic effect of the plant extracts, BauerKirby disk diffusion method was used. For each plant extract, six filter disks were placed into the liquid extract. Two control groups were set up with the media used for dilutions (Isopropyl Alcohol and Methanol). After drying the filter disks the first time, they were dipped into the plant extract vial a second time to increase the concentration of plant extract onto each disk. The filter disks were then placed into nutrient agar plates containing each different microorganism (Escherichia Coli; Pseudomonas aeruginosa; Listeria monocytogenes; Staphylococcus aureus; and Saccharomyces cerevisiae). The plates were incubated overnight before inhibition areas were analyzed. Bonao de Higuey areas. The plant species collected include Capsicum frutescens, Cymbopogon citratus, Rauwolfia nitida, Theobroma cacao, and Chioccoca alba. The plant part used in traditional preparations was isolated from the collected plant material and laid flat on a laboratory bench top and allowed to air dry for a period of days. After four days, the dried plant material was ground in a blender to yield small particulates. One gram of ground plant material from each species was transferred to a scintillation vial and 7.5 ml of an organic solvent were added and allowed to stand overnight before use. Two extracts were prepared for each plant species, one with isopropyl alcohol [(CH3)2CHOH] and one with methanol (CH3OH). After 24 hours of extraction the extracts were ready for bioassays.

Sea Urchin Assay: (antimitotic)

To determine the antimitotic effect of the plant extracts, adult sea urchins were collected from Punta Cana Hotel reserve boat dock and kept in an aerated seawater bucket. Gametes were obtained by injection of about 1.0 mL of a 0.5 M KCl through soft tissue of oral surface. Eggs were washed with A

Brine Shrimp Assay: (cytotoxicity)

To determine toxicity of the plant extracts, brine shrimp eggs were incubated in a hatching chamber with artificial salt water at temperatures from 20 to 30°C. The eggs were sprinkled into 48 hours after the eggs were incubated; the larvae were extracted and counted using a pipette. For every plant extract, three concentrations (in triplicate) were tested in order to determine dose-response relationship, and a control group was set with the vehicle used for dilutions. Tested concentrations were 1 drop, 2 drops, and 3 drops. Each well was filled with 1mL of brine shrimp-seawater mixture, then 3mL of the brine. Each well was checked using a microscope Leica MZ7Z at low magnification to ensure that there were about 15-25 shrimps per well. The plants extract were added to each well and the mixture was allowed to rest for 24 hours. Every well with sample contained 15-25 larvae of brine shrimp, including the control group, and was filled to 4 ml total volume with artificial salt water. After 24 hours, live larvae versus death larvae were counted.

Seed Germination Inhibition Assay: (allelopathy)

B

To determine the allelopathic effect of the plant extracts, 1mL Figure 1 of each plant extract was deposited on the filter disk and alA Brine Shrimps vs. Methanol Plant Extracts lowed to thoroughly dry before been introduced in the petri B Brine Shrimps vs. Isopropyl Alcohol Plant Extracts dish. 10 test seeds (cucumber) were deposited on top of each

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RESEARCH

B

A

Figure 2 A Plants Allelopathy in Methanol B Plants Allelopathy in Isopropyl alcohol

filtered sea water and fertilized by adding drops of diluted sperm. Embryos were cultured at room temperature. The embryos were observed with a Nikon microscope model TMS number 211261 and electronic images were obtained using a Samsung ST700–16MP, 5x zoom. A Twenty plate wells were cleaned and prepared to receive the embryos. Each well received 2mL of sea water and 10 drops (200µμL) of embryos. For every plant extract, two concentrations were tested (1drop or 25µμL and 4drops or 100µμL) in order to determine doseresponse relationship, and a control group was set with the vehicle used for dilutions (Isopropyl Alcohol and Methanol). 8 hours after the plates were set up; the eggs were counted in order to determine the ratio of divided versus undivided eggs.

RESULTS

seeds did not geminate. All the seeds in the control plate germinated. The experiment was done only once. Fig.2.1 below shows the seed germination results obtained for methanol crude extracts. Capsicum frutescens had 40% germination and 60% growth inhibition; Cymbopogon citratus had 70% germination and 30% growth inhibition; Rauwolfia nitida had 40% germination and 60% growth inhibition; Theobroma cacao had 70% germination and 30% growth inhibition and Chiococca alba had 0% germination and 100% growth inhibition. Fig 2.2 below shows the seed germination results obtained for isopropyl alcohol crude extracts. Capsicum frutescens had 30% germination and 70% growth inhibition; Cymbopogon

Brine Shrimp Assay: (cytotoxicity)

The Brine shrimp assay tested the A cytotoxicity of each plant extract on shrimps. The results were observed at different dosage (25 µμL, 50 µμL and 75µμL) of each, methanol and isopropanol plant extracts. The dose-response relationship revealed that, if the plant extract is toxic to the brine shrimps, the higher the dosage, the greater the mortality percentage in the shrimps. Fig 1.1 B and Fig 1.2 show the results of the experiment. The Y-axes represent the survival rate of shrimps in the each well. And the X-axes represent the plant extracts in the well.

Seed Germination Inhibition Assay: (allelopathy) The seed germination of cucumber seeds show in Fig 2.1 and Fig 2.2 the percentages of how many seeds germinated and how many

Figure 3 In the above figures, (0) denotes no inhibition and (+) denotes weak inhibition. A Methanol plant extract tested over different bacteria and fungus B Isopropyl alcohol plant extract tested over different bacteria and fungus

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RESEARCH A

B

Figure 4 A Antimitotic Effect of Methanol Plant extracts B Antimitotic Effect of Isopropyl Alcohol Plant extracts

citratus had 0% germination and 100% growth inhibition; Rauwolfia nitida had 0% germination and 100% growth inhibition; Theobroma cacao had 60% germination and 40% growth inhibition and Chiococca alba had 0% germination and 100% growth inhibition.

Antibacterial and Antifungal Assay: (antibiotic)

Table 3.1 below shows the methanol plant extract results of the experiment. In the table, Cymbopogon citratus methanol extract shows very little inhibition against Staphylococcus aureus. Rauwolfia nitida shows very little inhibition against the gram positive bacteria Escherichia coli and Pseudomonas aeruginosa; also against the gram negative bacteria Listeria monocytogenes and Staphylococcus aureus. The other extracts did not show any inhibition on any of the bacteria or fungus. The experiment was repeated three times for relevance and accuracy. Table 3.2 below shows the isopropyl alcohol extract result of all the five selected plants. None of the extracts in isopropyl alcohol exhibited antibiotic or antifungal properties. The experiment was also repeated three times for better accuracy

Sea Urchin Assay: (antimitotic)

The Sea Urchin assay tested the antimitotic effect of the five plants extract (methanol and isopropanol) at two different concentrations for each extract (25µμL and 100µμL). The tables 4.1 and 4.2 below shows the percentage of dividing cells. Many of the wells had no eggs at the beginning of the experiment represented by (N/A) in the table below. It was thus difficult to draw a relevant conclusion.

DISCUSSION AND CONCLUSION The objective of the brine shrimp assay was to observe and assess the toxicity of the plant extract on brine shrimps. The plant extracts that exhibited significant results at the concentration tested were Chiococca alba in isopropyl alcohol and especially in methanol extract. As the concentration of the plant extract containing brine shrimps increased, the mortality rate in brine shrimps increased as well. In the well containing 1 drop of Chiococca alba methanol extract and the brine shrimps, 57% mortality was observed. In the well containing 2 drops of Chiococca alba methanol extract and brine shrimps, 72% mortality, and in the well containing 3 drops of Chiococca alba methanol extract and brine shrimps, 90% mortality were observed. These results show that Chiococca alba can

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be further studied as a potential candidate for cancer treatment. Since we were unable to relate the research on this specific plant to other studies done before, we concluded that this might be the first time the plant Chiococca alba is reported as having anti cancerous properties. Further studies will focus on the use of different organic solvents. The seed germination assay tested the allelopathic effect of the five plants extract (methanol and isopropanol). Allelochemical interaction is an important mechanism of interference that can influence the pattern of vegetation, weed growth and crop productivity (Dakshini et al. 1999, Weir et al. 2004). Even though all the plant extracts in both methanol and isopropyl alcohol showed low to high growth inhibition in the cucumber seeds, the most relevant ones were: Chiococca alba in methanol and in isopropyl alcohol exhibited 100% growth inhibition; Cymbopogon citratus in isopropyl alcohol displayed 100% growth inhibition; and Rauwolfia nitida in isopropyl alcohol revealed 100% growth inhibition. These results imply that isopropyl alcohol is a better solvent for this particular bioassay. In sum, Chiococca alba, Rauwolfia nitida and Capsicum frutescens have a high and strong potential in their utilization as herbicide. Chiococca alba appears to have a lot of bioactivities because it is very active in the brine shrimp assay and also very active in the seed germination assay in both methanol and isopropyl alcohol. Other studies of Chiococca alba found that one of the constituents of Chiococca alba plant is iridoid glucoside compound (1) (Carbonezi, et al., 1999). The plant is reported to be used in traditional medicine as a tonic for ganglionic inflammation. This plant is also used as a diuretic. Additionally, this plant has antiviral, antieodema as well as aphrodisiac properties. According to Tundis, et al. (2008), iridoids represent a large group of monoterpenoids that occur widely in nature, mainly in dicotyledonous plant family like Rubiaceae. Iridoids exhibit a wide range of bioactivity, such as neuroprotective, antinflammatory and immunomodulator, hepatoprotective and cardioprotective effects. It is also reported to have anticancer, antioxidant, antimicrobic, hypoglycaemic, hypolipidemic, choleretic, antispasmodic and purgative properties. The objective of the antibiotic assay was to determine if the plant extracts in methanol and isopropyl alcohol could inhibit the growth of bacteria and fungus (Table 3.1 & Table 3.2). The zone of inhibition for each disk was visually observed. The experiment was done in three replicates. Crude Capsicum frutescens juice and Capsicum frutescens in ether have been reported to inhibit the growth of Escherichia coli (Abdou-Zeid & Shehata, 1969). The results of Capsicum frutescens in both methanol and isopropyl did not show inhibition on any of bacteria used including Escherichia coli. This suggests that the organic solvents used for the dilution of the plants may not have been the best extraction medium. Cymbopogon citratus


RESEARCH oil has been reported to have activity against Staphylococcus aureus and Escherichia coli (Mohd, 2010). Cymbopogon citratus for this research displayed some antibiotic activity against the gram positive bacteria Staphylococcus aureus (Table 3.1 & Table 3.2). Theobroma cacao and Chiococca alba did not show any antibiotic nor antifungal activities. Rauwolfia nitida in methanol extract showed some inhibition against the gram positive bacteria (Staphylococcus aureus and Listeria monocytogenes) and against the gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Further studies will focus on the utilization of Capsicum frutescens with different organic solvents. The Sea Urchin assay tested the antimitotic effect of the five plant extracts (methanol and isopropanol) at two different concentrations for each extract (25µμL and 100µμL). Although the sea urchin assay was expected to be an essential part of this research, little information was acquired from it (Table 4.1 & Table 4.2). The reason for this was that the sea urchin collected by the dock in Punta Cana, Dominican Republic did not release enough eggs after injection of KCl. This resulted in a shortage of fertilized eggs. Nevertheless, the experiment was completed with whatever fertilized eggs were available. The control group was set up with the vehicle used for the plant extraction. That is, a control with methanol and Isopropyl alcohol. The fertilized eggs in the wells containing those two controls had a 100% eggs division. Repeating this bioassay two to three times would be ideal for a better comparative result and to draw a relevant conclusion. In summary, our study has provided evidence that Chiococca alba is a promising alternative source for anticancer compounds. It is also particularly valuable as a potential herbicide source, and further studies will focus on isolation of the active compounds therein. Furthermore, we found that methanol is a better extraction medium than isopropyl alcohol for the plant Chiococca alba. Lastly, the activities of Cymbopogon citratus and Rauwolfia nitida provide a rationale for their potential use as herbicides.

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Jacqueline C, Bede and Stephen S. (2000). Activity of insect juvenile hormone III: seed germination and seedling growth studies. JOURNAL OF CHEMOECOLOGY, 10, 89-97 Salkin R, Hosansky N, Jaret R. (1961). Leaf alkaloids of Rauwolfia nitida. J. Pharm Sci. 50:1038-41. Sanda, K, Raynaud, C, Mandin, D, Millet, J,Chaumont, JP. (2003). Antimicrobial activity of essential oils of cymbopogon citratus L. (DC) stapf., C-nardus L. rendle and C-schoenanthus L. spreng. JOURNAL DE MYCOLOGIE MEDICALE, 13(4), 175-180. Shah G, Shri R, Panchal V, Sharma N, Singh B, Mann AS. (2011). Scientific basis for the therapeutic use of Cymbopogon citratus, stapf (Lemon grass). J Adv Pharm Technol Res. 2(1):3-8. Tchoumbougnang F, Zolsolo PH, Dagne E, Mekonnen Y. (2005). In vivo antimalarial activity of essential oils from Cymbopogon citratus and Ocimum gratissimum on mice infected with Plasmodium berghei. Planta Med. 71(1):20-3. Yundis R. Loizzo M.R.Menichini F. Statti Ga,MenichiniF, 2008. Biological and pharmacological activities of iridoids: recent developments. (PMID:18473930)

Adjanahoun, E., Ahyi, M. R. A., Ake-Assi, L., Elewude, J. A., Dramane, K., Fadoju, S.O., Gbile, Z. O., Goudole, E.,. Johnson, C. L .A , Keita, A., Morakinyo, O. , Ojewole, J. A. O. , Olatunji, A. O. and Sofowora, E. A. (1991). Traditional medicine and pharmacopoeia. Contribution to ethnobotanical floristic studies in Western Nigeria, Pub. Organization of African Unity, Scientific Technical and Research Commission Lagos, Nigeria. 420p. Bassole, I.H.N, A Lamien-Meda, B Bayala, L.C Obame, A.J Ilboudo, C Franz, J Novak, R.C Nebie, and M.H Dicko. “Chemical Composition and Antimicrobial Activity of Cymbopogon Citratus and Cymbopogon Giganteus Essential Oils Alone and in Combination.” Phytomedicine. 18.12 (2011): 1070-1074. Carbonezi CA, Martins D, Young MC, Lopes MN, Furlan M, Rodriguez Filho E, Bolzani Vda S. (1999). Iridoid and secoiridoid glucosides from Chioccoca alba (Rubiaceae). Phytochemistry. 51(6):781-5 Costa, C. A. R. A., Bidinotto, L. T., Takahira, R. K., Salvadori,

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