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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

Research 6RFLDOLQĂ XHQFHVRQUHSURGXFWLYHVXFFHVVLQEURZQ KHDGHGFRZELUGVPRORWKUXVDWHU

14

Lane  Robinson

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20

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

PennScience 11  |  5


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.

6

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 6PDUWSKRQHVMHWLQMHFWRUVWUDQVODWRUVDQGKDQGKHOGELRORJLFDOVFDQQHUV:KDWGRDOOWKHVHGH-­ YLFHVKDYHLQFRPPRQ"7KH\DOODSSHDUHGLQWKHXQLYHUVHRI6WDU7UHNORQJEHIRUHWKH\DSSHDUHG LQWKHUHDOZRUOGDOEHLWZLWKPRUHREVFXUHQDPHVOLNHWKH´7ULFRUGHU¾DQGWKH´+\SRVSUD\¾ ,QGHHGPDQ\RIRXUJDGJHWVKDYHKDGWKHLUEHJLQQLQJVDERDUGWKH866(QWHUSULVH7KHPRVW VSHFWDFXODUIHDWXUHVRI6WDU7UHNKRZHYHUUHPDLQPHUHO\GUHDPVWRGD\2XUJUHDWVXFFHVVLQ UHSOLFDWLQJFHUWDLQHOHPHQWVRI6WDU7UHNGRHVSURYLGHKRSHWKDWVRPHGD\GHYLFHVVXFKDVWKH 7UDQVSRUWHUDQGWKH:DUS'ULYHZLOOEHLQYHQWHG+RZHYHUWKHUHLVRQO\VRPXFKWKDWWKH/DZVRI 3K\VLFVDOORZ6KRXOGZHJLYHXSRQWKHVHWHFKQRORJLHVRUDUHWKH\VWLOOZRUWKGUHDPLQJDERXW"

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

,QDQ\FDVHLWZLOOEHORQJEHIRUHZHVHHVXFKWHFKQRORJLHVIURP6WDU7UHNLQRXUHYHU\GD\OLYHVLI HYHU6RPHVXFKDVWKH7UDQVSRUWHUVHHPVRLPSUDFWLFDODVWREHLPSRVVLEOHZKLOHRWKHUVVXFKDV WKH:DUS'ULYHVKRZFRQFUHWHSURPLVHIRUWKHIXWXUH,WGRHVEHDUPHQWLRQWKDWQHZEUHDNWKURXJKV LQSK\VLFVKDYHSURYHGXVZURQJEHIRUHIRUFLQJVFLHQWLVWVWRUHWKLQNWKHLPSRVVLEOHDQGHQGRZLQJ XVZLWKKRSHWKDWWKHQH[WEUHDNWKURXJKPLJKWMXVWEHDURXQGWKHFRUQHU8QWLOWKHQZHQHHGRQO\ ZDWFKVRPH6WDU7UHNDQGOHWRXULPDJLQDWLRQVOHDGWKHZD\ PennScience  11  |  11


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  

16

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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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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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.

REFERENCES

D. M.  F.,  Barbisan,  L.  F.,  &  Costa,  M.  “Cholesterol  reduction   and  lack  of  genotoxic  or  toxic  effects  in  mice  after  repeated   21-day  oral  intake  of  lemongrass  (Cymbopogon  citratus)  essential  oil.”  Food  and  Chemical  Toxicology,  49,  9  (2011):   2268-2272. Devi,  R.C,  R  Ismail,  and  S.M  Sim.  “Spasmolytic  Effect  of   Citral  and  Extracts  of  Cymbopogon  Citratus  on  Isolated  Rabbit  Ileum.”  Journal  of  Smooth  Muscle  Research.  47.5  (2011):   143-156. Farnsworth,  N  .R.  (1966).  Biological  and  Phytochemical   screening  of  plants.  J.  Pharm  Sci.  55(3):  225-276. Di  Flumeri,  C.,  A.  Miller  and  E.  Schurr,  (Jan.  2000).  In  vitro   Antimarial  properties  of  extracts  of  Malarex  against  Plasmodium  falciparum,  McGill  University  Malarex  letter,  www.milleniahope.com/malarex Houghton,  P.  J:  1995.The  Role  of  Plants  in  Traditional  Medicine  and  Current  Therapy.  The  Journal  of  Alternative  and   Complementary  Medicine.  June  1995,  Vol.  1,  No.  2:  131-143

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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