02
SJ S
Swarthmore Journal of Science
BEYOND THE
ATO M
Letter from the Editor Dear Readers, For those of us who are seniors , the end of the Spring semester also means the end of our Swarthmore education. Reminders of graduation poke at our memories and we are forced to stop and think about the ways we have grown since arriving to campus as freshman.
Claudia Lujรกn
Ariel Parker and Randall Burson
My time at Swarthmore was difficult. As a biology major on the pre-med track, my time was arguably spent more in Cornell than in my room. Between problem sets and the Science Center coffee bar, it was sometimes difficult to appreciate the relevance of the work I was doing. At times, I felt my interest (like my caffeine sensitivity) waning amid its rigor. I found my conversations with peers , however, to be the perfect antidote and hoped to recreate that sense of community with SJS. I am happy to say that my time as SJS has been as much a learning experience as a space of support, I hope it will do the same for others. After a rocky start and a steep learning curve, I am happy to present the second issue of SJS. We have been working hard to bring you the best of Swattie science talent into your hands and hope you will enjoy. . Before I sign-off, I would like to thank my partnerin-crime Randy and Ariel for their foundational role in establishing the journal. I would also like to thank the editors and contributors for the time and effort they have dedicated to each article. Lastly, I would like to thank all the professors who have served as mentors and guided us through our time here. Most of all, I hope SJS will continue to have a place within Swarthmore. I hope it will build community as much as it increases science literacy. Enjoy the read!
Math and Statistics: Meghana Ranganathan Chemistry: JeeHae Kang Biology: Justin Sui and Madeleine Booth Engineering: Chrissy McGinn Physics: Samer Nashed Copy Editor: Phoebe Cook Graphic Design/Layout: Claudia Lujan
Chemistry: Alice Herneisen Biology: Talia Borofsky, David Tian Physics: Peter Weck
Aaron Holmes Shenstone Huang Mike McVerry
swatjournalscience@gmail.com Connect with us on:
Keeping it Proton,
http://issuu.com/swarthmorejournalofscience
Claudia
www.facebook.com/SwatJournalScience http://www.pinterest.com/sciencejournal/
2
Black Holes
4 6 9 14
Diamonds: More than a Girl’s Best Friend
SENIOR SPREAD
M2 Protein: Killing Bird Flus with 1 stone Agriculture + the City: Not a Dichotomy
18
Senior Spread!
Contents Zebrafish Tends and Human Development
20 22 26
Whats Math Got to Do With It?
Fritz Haber: A Life
BEYOND THE ATOM 3
30 32
34 36
Faculty Spotlight: Tristan Smith
Finding Velocities of Young M Stars
Mass, Energy, and E= Mc2 Human Health and Ecosystems
Diamonds
more than a girl’s best friend
by Chrissy McGinn
Sorry, Marilyn, but diamonds are quickly becoming al-
most as important to science as they are to girls everywhere because of their utility in quantum computing. These diamonds are synthetic, however, so don’t think there will be a shortage of diamond necklaces anytime soon. Quantum computing uses the spin of quantum particles, such as electrons and atoms, as the most basic unit of computation instead of the 1's and 0's used in traditional digital computing. When the spin is used in computing, it is called a “qubit.” Spin is a physical quantity of the quantum particle, and for a given spin value, the particle is described as being in a spin state associated with that value. Manipulating the spin allows data processing to be done in the same ways as traditional computing. What makes diamond so useful for quantum computing is its nitrogen-vacancy centers. The nitrogen vacancy (NV center) is considered the qubit for the diamond system. An NV center is a defect in the diamond’s lattice of carbon atoms consisting of a nitrogen atom and an empty space in place of two adjacent carbons. The possibilities of NV centers and the other potential choices for quantum information systems (crystalline defects, doped semiconductors, electrons, and others) are vast. All of these systems can operate faster and more efficiently than any in traditional computing. NV centers have several properties that make them ideal for quantum computing. Probably NV centers’ biggest advantage is that they are able to operate in ambient temperatures, while most other systems must be ultra cold to exhibit the necessary qualities for quantum computing. For quantum computing systems to be mass-produced, operation in ambient temperatures is an obvious objective, and makes further experiments on this system available. In addition, NV centers can maintain their spin state after being set for a significantly longer time than most other quantum computing candidates, with coherence times between one and ten milliseconds. The spin of the NV centers can be set and manipulated with microwaves, meaning that the state of the qubit can be excited with a rate on the order of 1 GHz. A fast rate of change with spin states being held for long times means that a million operations can be accomplished with the qubit in one second. 4
“
It is clear that diamon promising option for computations, but both difficulties must
The final advantage of the NV center is that its state can be read with light at optical frequencies. NV Centers are photoluminescent with red light. This means that when red light is shown on the NV center, another light color is emitted, which indicated the spin of the NV center. In the case of the NV center, green light is emitted. The typical sources of error in quantum computing systems are minimal for the NV center. Common sources of error are spin orbit coupling and magnetic coupling, issues that stem from the quantum mechanics of the system. Complications when large electric fields are applied to the system can frequently be observed. Diamond’s material properties, such as low conductivity and high dielectric strength, allow it to avoid such problems with large electric fields. Despite diamond’s many advantages in quantum computing, there is a high cost both in time and money to fabricate samples of diamond for testing. The samples themselves are expensive because they must be fabricated. Also, diamond has a very large index of refraction, which makes it difficult to make sure that the light used to control the NV center actually reaches the defect. Overcoming this problem requires extensive sample preparation. This is one of diamond’s foremost challenges as a candidate for quantum computing. It is clear that diamond’s NV centers are a very promising option for the future of quantum computations, but both monetary and technical difficulties must be conquered first. There are several solutions to the technical problems, so hopefully one day diamonds truly will be a girl’s best friend—if that girl is a scientist with a new, diamond-based computer that works better and faster than anything before.
nd’s NV centers are a very r the future of quantum h monetary and technical t be conquered first.
”
Literature Cited 1.Acosta, Victor, and Philip Hemmer. "Nitrogen-vacancy Centers: Physics and Applications." MRS Bulletin 38.02 (2013): 127-30. Web. 2.Awschalom, D. D., L. C. Bassett, A. S. Dzurak, E. L. Hu, and J. R. Petta. "Quantum Spintronics: Engineering and Manipulating AtomLike Spins in Semiconductors." Science 339.6124 (2013): 1174179.b. 3.Childress, Lilian, and Ronald Hanson. "Diamond NV Centers for Quantum Computing and Quantum Networks." MRS Bulletin 38.02 (2013): 134-38. Web. 4.Lonar, Marko, and Andrei Faraon. "Quantum Photonic Networks in Diamond." MRS Bulletin 38.02 (2013): 144-48. Web. 5.Toyli, David M., Lee C. Bassett, Bob B. Buckley, Greg Calusine, and David D. 6. Awschalom. "Engineering and Quantum Control of Single Spins in Semiconductors." MRS Bulletin 38.02 (2013): 139-43. Web.
5
Senior Sprea
This summer Phoebe will be doing summer fieldwork in Hawai’i, as part of a Masters in biology at James Madison University.
As of right now, Ariel is hoping for a research position for the next one to two years, before starting a PhD program in biology.
6
After graduation, Justi work as a lab technician DiNardo lab at the Unive Pennsylvania Perelman of Medicine. He plans on ing an M.D. after conduc velopmental biology re for two years.
ad
tin will n in the ersity of n School n pursucting deesearch
what’s next for the SJS seniors?
Claudia has been named a 2015 fellow for Venture for America, a non-profit program that mobilizes recent graduates as entrepreneurs to revitalize American cities. After training camp at Brown University this summer, Claudia will be working at an up-and-coming startup.
Randy will be Clinical Research Coordinator with Dr. Lee Fleisher at University of Pennsylvania before going to his Fulbright in Chile where he will be doing research on depression in the Mapuche people.
7
Samer plans to continue his computer science education at the University of Massachusetts Amherst, where he will be working towards a PhD. His research will focus on problems at the intersection of artificial intelligence and robotics, in the Laboratory for Perceptual Robotics.
This summer Peter will be working on the Appalachian Trail in Vermont doing trail maintenance and outreach. He was also recently accepted to a Philosophy of Physics Masters program at Oxford, so come October he might be headed to England.
Maddy will travel around China this summer and then will take a year or two trying out life before pursuing a PhD in Linguistics.
CONGRATS Y’all! 8
M2 PROTEIN As Swarthmore students sifted through their
Hitting Several BirdFlus With One Stone by Shenstone Huang
replication processes are complete, the viral proteins are exported out of the nucleus and congregate together near the cell surface. Influenza then uses the host cell’s plasma membrane to form new viral particles. These particles bud from the host cell’s membrane and infect neighboring cells.3 Three proteins form the viral coat for all influenza subtypes: hemagglutinin (HA), neurominidase (NA), and M2 (Fig 1). Of these three, scientists have identified the larger HA and NA as early as the 1940s. Hence, the influenza subtypes are usually identified by which HA and NA proteins the virus carries (H1N1, for example). HA plays a vital role in the beginning of the viral replication cycle by anchoring the virus particles to the host cell. NA allows for the release of newly formed virus particles by cleaving the viral buds from the host cell’s plasma membrane towards the end of the cycle. This ensure that these new virus particles do not aggregate at the cell surface but are released.4 Scientists have committed significant resources to combat both seasonal and pandemic outbreaks by finding antiviral drugs, such as Zanamivir and Oseltamivir, that target these proteins. Even so, Influenza A stubbornly develops drug resistance through mutations. However, new studies have shown that previously unexplored Figure 2. The M2 protein is a homotetramer. A truncated construct with functions of M2 only the proton channel and amphimay, when Proton Channel
Swatmail last semester, they may have come across a semi-urgent yet friendly reminder to receive flu vaccinations at the Worth Health Center. Fall ushers in new students, new trends, and new strains of the flu, or influenza A virus. Every year, more than 200,000 hospitalizations and an average of 36,000 deaths in the United States are a direct result of this powerful self-replicating machine.1 This virus is an international public health concern as new, deadlier strains have developed the ability to transmit from birds and swine to humans. Whether the flu is just a nuisance or a pandemic like that of 1918, where 500 million people were infected and 3050 million of those infected died,2 influenza A is everpresent in the daily lives of all people. Figure 1. Influenza A virus capsule. The membrane proteins consists of HA, NA, and M2.
The flu has dodged repeated efforts to control it since the beginning of modern healthcare. Influenza A is a highly mutable virus, and every year, the Center for Disease Control and Prevention releases a new flu vaccine that combats the “trending” strain. People must collect an arsenal of vaccines to prepare their immune system’s defenses against multiple strains, but strains mutate faster than vaccine production. Influenza self-replicates by hijacking the human body’s respiratory cells and introducing its RNA into the host cell’s DNA. This forced implantation of viral genes directs human cell machinery to start producing the viral proteins and viral RNA. Once these
pathic helix is shown here. Residues 50 -60 highlight the amphipathic helix region of interest. 9
amantadine block the channel and can shorten the duration or moderate the severity of influenza (Figure 4).8 Unfortunately, M2 has found ways to mutate so that most currently circulating viruses are resistant to these drugs. Thus, current research has shifted to M2’s role in viral budding, which involves the amphipathic helix from residues 50-60. If the budding can be controlled, the scientists could significantly reduce the spread of the virus to other cells in the respiratory system. An amphipathic alpha helix, typically found at the membrane solvent interface, is a stable protein structure characterized by one side of the helix containing hydrophobic (water fearing) amino acids buried in the memFigure 3. M2 aggregates around the scission location to help budding occur towards the end of the replication cycle. The newly budded viral particles go on to infect other cells.
inhibited, provide additional pathways towards mitigating virulence. M2 has two known important functions. First, it forms a channel that shuttles protons into the virus core to create the acidic necessary conditions for replication.5 Second, M2 serves as an agent that helps membrane curvature and scission during viral budding at the end of the replication cycle. The amphipathic region, amino acid residues 50-60, aggregates around the scission location and help create the curvature necessary for budding (Fig 3).6, 7 Given the significant role M2 plays in virus influenza propagation, a vaccine that targets M2 has promise in the quest of controlling influenza.
Figure 5. Cross section of the M2 amphipathic helical wheel showing hydophilic and hydrophobic residues 45-62.
brane and the opposite side containing hydrophilic amino acids (water loving) exposed to the water (Fig 5). Recent research has found that the relationship between cholesterol and the fourteen-residue Spin Label long amphipathic alpha helix is necessary for the formation of viral buds. Researchers found that mutating the amphipathic Alpha helix helix and removing cholesterol from the region significantly lowered viral growth and mortality.9 A promising aspect of Figure 6. Alpha helix with spin this amphipathic helix is that it label attached. Information is not subject to frequent mu- on the environment of the tations like the NA and HA pro- protein can be gleaned by teins.6 This information quickly examining the behavior of the spin label. caught the eyes of researchers. The amphipathic helix may serve as a universal anti-viral target because of its consistency and importance amongst all influenza strains.
By plugging the M2 channel, the acidic environment in the virus core is made impossible because protons cannot be shuttled through the channel. Exploitation of the proton channel activity of M2 has been intensively explored; antiviral drugs like rimantadine and
Figure 4. Rimantadine plugging the M2 proton channel.
In the Howard Lab, students have studied this amphipathic helix on various shortened versions and the 10
tified the importance of M2 throughout the influenza life cycle, and scientists believe vaccines targeting M2, particularly the conservative amphipathic region, might help stop the spread of influenza. Therefore, structural studies on the M2 protein are currently an important re-
Literature Cited: 1.Thompson, W. W.; Shay, D. K.; Weintraub, E.; Brammer, L.; Cox, N.; Anderson, L. J.; Fukuda, K., Mortality associated with influenza and respiratory syncytial virus in the United States. Jama-Journal of the American Medical Association 2003, 289 (2), 179-186. 2.Taubenberger, J. K.; Morens, D. M., 1918 influenza: the mother of all pandemics. Emerging Infectious Diseases 2006, 12 (1), 15-22. 3.Samji, T., Influenza A: understanding the viral life cycle. The Yale journal of biology and medicine 2009, 82 (4), 153-9. 4.Gamblin, S. J.; Skehel, J. J., Influenza Hemagglutinin and Neuraminidase Membrane Glycoproteins. Journal of Biological Chemistry 2010, 285 (37), 28403-28409. 5.Goto, H.; Kawaoka, Y., A novel mechanism for the acquisition of virulence by a human influenza A virus. Proceedings of the National Academy of Sciences of the United States of America 1998, 95 (17), 10224-10228. 6.Schmidt, N. W.; Mishra, A.; Wang, J.; DeGrado, W. F.; Wong, G. C. L., Influenza Virus A M2 Protein Generates Negative Gaussian Membrane Curvature Necessary for Budding and Scission. Journal of the American Chemical Society 2013, 135 (37), 13710-13719. 7.Nguyen, P. A.; Soto, C. S.; Polishchuk, A.; Caputo, G. A.; Tatko, C. D.; Ma, C. L.; Ohigashi, Y.; Pinto, L. H.; DeGrado, W. F.; Howard, K. P., pH-induced conformatioal change of the influenza M2 protein C-terminal domain. Biochemistry 2008, 47 (38), 9934-9936. 8.Pinto, L. H.; Lamb, R. A., The M2 proton channels of influenza A and B viruses. Journal of Biological Chemistry 2006, 281 (14), 8997-9000. 9.Thaa, B.; Tielesch, C.; Moller, L.; Schmitt, A. O.; Wolff, T.; Bannert, N.; Herrmann, A.; Veit, M., Growth of influenza A virus is not impeded by simultaneous removal of the cholesterol-binding and acylation sites in the M2 protein. Journal of General Virology 2012, 93, 282-292; Stewart, S. M.; Wu, W. H.; Lalime, E. N.; Pekosz, A., The cholesterol recognition/interaction amino acid consensus motif of the influenza A virus M2 protein is not required for virus replication but contributes to virulence. Virology 2010, 405 (2), 530-538. 10.Klug, C. S.; Feix, J. B., Methods and applications of sitedirected spin Labeling EPR Spectroscopy. Biophysical Tools for Biologists: Vol 1 in Vitro Techniques 2008, 84, 617-658. 11. Thomaston, J. L.; Nguyen, P. A.; Brown, E. C.; Upshur, M. A.; Wang, J.; DeGrado, W. F.; Howard, K. P., Detection of drug-induced conformational change of a transmembrane protein in lipid bilayers using site-directed spin labeling. Protein Science 2013, 22 (1), 65-73.
Figure 7. A. The amphipathic helix lies on the membrane surface in the full -length protein. B. The transmembrane domain and the amphipathic helix in a lipid environment.
full-length protein by using site directed spin labeling – electron paramagnetic resonance (SDSL-EPR) structural studies to understand the role of the amphipathic helix in the viral budding mechanism.10 Unlike other methods that require detergents and crystallization, SDSL-EPR is exquisitely suited to study membrane proteins reconstituted into lipid bilayers in physiologically relevant environments.11 SDSL-EPR attaches a spin label to sites of interest to glean information regarding the environment of the probe by measuring the relative mobility of the probe, accessibility of oxygen to the probe (high oxygen accessibility means the probe is inside the membrane, low oxygen accessibility indicates that the probe is outside the membrane), and the distances between two spin labels (Fig 6). These studies provide valuable new structural and membrane topology data for the fulllength M2 protein, which has yet to be extensively characterized. Results from the Howard lab show that this region forms an amphipathic helix that lies on the surface of the membrane in the full-length protein (Fig 7). Additionally, Howard Lab experiments confirm that cooperation between cholesterol and the amphipathic helix does cause conformational changes in the M2 protein. This research project is significant because it provides valuable new structural and membrane topology data for the full-length M2 protein. Therefore, this biophysical evaluation has useful implications for potential drug development that targets the release phase of the viral life cycle. Antiviral drug researchers’ exhaustive efforts have failed to curb the spread of influenza in the recent decades. In 2009, the swine flu scare reminded the scientific community and the public of the agility of influenza in developing resistance to vaccines. This year the vaccines distributed were not a good match for one of the influenza strains (H3N2). With the recent scientific developments, researchers have iden11
Untitled by Anonymous Between the still of day you can find us in the hazy deep. Waters browned with summer rust and we hold our breathe thinking only of the next time, the next tide. Quiet now, you’ll miss the drift.
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Photography by Michael McVerry 13
Urban gardens grow on almost every block of Philadelphia. Sometimes, as is the case with Preston’s Paradise (See Figure 1), they consist of fruit trees and vegetable patches nestled in side yards. At other times, they are full farms (See Figure 2) or community gardens. Urban gardening in the city began with the victory gardens of the 1950s and flourished during the 70s and 80s when Philly’s industrial economy disintegrated, leaving unemployed workers with hungry families and time to reclaim vacant lots (Vitiello and Nairn 2009). In recent years, perhaps due to job loss during the recession, urban gardening has increased in cities around the country. Gardens offer fresh produce in neighborhoods where food comes exclusively from fast food restaurants and convenience stores. Alongside Philadelphia’s diverse urban gardening and agriculture scene, there are multiple organizations that create networks of gardens and farms. The most important of these is the Pennsylvania Horticulture Society (PHS) (Vitiello and Nairn 2009), which distributes gardening materials, such as soil and seeds, 14
through its Grower’s Alliance; preserves community gardens through the Neighborhood Gardens Trust; and distributes produce to food cupboards through City Harvest. While gardening in the city has been growing, it faces major roadblocks, two of which are obtaining ownership of vacant lands and dealing with contaminated soil. Vacant lots and ownership During the 1970s, local industry declined, and as a result Philadelphia lost 13% of its population (Weigly et al. 1982). When residents moved out, they left vacant space behind (Vitiello and Nairn 2009). Many of these vacant spaces remain arable. As of 2011, grass or bare soil covered 7,600 out of Philadelphia’s 91,237 in residential neighborhoods, leaving an astounding 8% of the city unused. If only 5% of this land were gardened, then the city could locally produce 9.9 million pounds of fresh produce per year, according to a conservative estimate by researchers at the University of Delaware (Kremer and Deliberty 2011). Connecting people with these lots remains a formidable challenge. As of 2008, gardens only occupied 1.87% of the vacant space in the city (Vitiello and Nairn 2009). The problem with settling a patch of bare soil, a process called guerrilla gardening, is legal ownership. The idea of spontaneously starting a garden on a bare piece of land might be enchanting, but it is not a sustainable practice. Many guerilla gardeners have seen their plots razed after the city government or a private owner reclaimed the vacant space (Vitiello and Nairn 2009). Amy Laura Cahn is a lawyer at the Garden Justice Legal Initiative who works to provide legal resources to gardeners. In an interview, Cahn described meetings where she repeatedly heard complaints about legally accessing land in Philadelphia. She explained that until 2008, when Mayor Nutter signed the Philadelphia Food Charter, the city had a history of failing to provide sufficient legal programs to help people get ownership of the land. Even now, policy legislation regulating urban gardening is not being fully implemented. In 2012, the Garden Justice Legal Initiative (GJLI) started Grounded in Philly to facilitate “the transitioning of vacant land into communitycontrolled green spaces, gardens, and gathering places.” Grounded in Philly is a website that aggregates Philadelphia’s transparent, albeit scattered, land data into one interactive map. The program also organizes people in neighborhoods across the city to report gardens and empty land. Each entry offers information on the legal status of the land, including land zoning, plot size, ownership, known use, and ways to legally use the land, and information is added every day.
Image 1a. Preston’s paradise consists of small gardens in side yards along North Preston Street, in West Philadelphia. Here, Kale, herbs, and scallions grow next to a neighbor’s doorstep (Ryan Kuck Interview 2014). Photo by Talia.
Grounded in Philly only provides online resources, but often gardeners need in-person support to navigate Philadelphia convoluted bureaucracy and land-code. Cahn wishes Grounded in Philly could offer more in-person support, but resources and funding are limited. Furthermore, not all empty plots are truly suited for gardening, as will be described in the next section. Information is needed on whether land is fit for gardening purposes. Contaminated Soil Cities alter soil chemistry—industries leave dangerous toxins such as lead in the soil, and as old homes deteriorate, lead from the paint falls into nearby soil reservoirs (Craul 1985). According to the EPA, lead above 400 ppm is a well-known health hazard, which most acutely affects children and pregnant women. However, lead is not the only toxin present in urban soils. Soil contaminants can be heavy metals (lead, mercury, cadmium, and arsenic), petrochemicals (from fuels), and biohazards (human waste). Few urban gardeners know if their soil is toxic. Gardeners can send samples of their plot’s soil to get tested by a local county extension. However, soil tests only check for a limited set of chemicals. They will not indicate whether or not such toxins as petrochemicals are present in the soil. The other option for gardeners is to check land history; for instance, if there used to be a gas station on the plot, the soil could be contaminated. Exposure to contaminants from the garden can be prevented. Plants effectively filter out unwanted contaminants when they absorb water from the soil, and of the contaminants they don’t remove, few move to the plant’s shoots. In conditions of high contamination, chemicals can accumulate in root tissue, so root vegetables pose a danger. However, the main 15
Conclusion An aging population of gardeners contributed to the disappearance of many gardens between 1990 and 2008 (Vitiello and Nairn 2009). However, since 2008, I suspect that this trend has changed in Philadelphia. When I researched new gardens, such as Preston’s Paradise and Germantown Kitchen Garden, I often interviewed gardeners in their 20s or 30s. I noticed that many programs had gone through recent bursts of change or had started after 2008, when the recession hit and when Mayor Nutter signed the Food Charter. The question is whether this trend is long-lasting or a fad. Urban agriculture brings tangible benefits to Philadelphia’s neighborhoods. In food deserts, neighborhoods with little or no access to supermarkets and farm markets, community gardens can provide fresh produce. They beautify neighborhoods where vacant lots would otherwise contribute to an aura of decrepitude. However, urban agriculture is rarely covered in highly respected science magazines, such as Nature, Science, or Proceedings of the National Academy of Sciences. In order for the increase in urban agriculture in Philadelphia and across the world to be more than a temporary change, investments are needed not only in policy reform, but also in scientific research.
Image 2. A picture taken from the outside of Germantown Kitchen Garden, a 1.5 acre for-profit farm on E. Penn Street. The farm sells its produce to a restaurant and in market stands to neighbors and accepts both SNAP benefits and FMNP coupons (Amanda Staples Interview, May 2014).
method by which people get lead poisoning is by ingesting the soil itself. Children play outside and then put their hands in their mouths, people inhale dust, and gardeners forget to wash their vegetables. The first line of prevention is to wash hands before eating. After that, gardeners should incorporate organic matter into the soil. This reduces the bioavailability, or ability to be dissolved in an animal’s bloodstream, of heavy metals (Alkort et al 2004). The next step is to cover bare soil with vegetation, which prevents erosion.
Literature Cited 1. Brown, S., Chaney, R., Hallfrisch, J., Ryan, J. A., & Berti, W. R. (2004). In situ soil treatments to reduce the phyto-and bioavailability of lead, zinc, and cadmium. Journal of Environmental Quality, 33(2), 522-531. 2. Cahn, Amy L. Phone Interview. June 2014. 3. Craul, Phillip J. "A description of urban soils and their desired characteristics." Journal of arboriculture (USA) (1985). 4. "Grounded in Philly." About. Web. 10 Mar. 2015. <http://www.groundedinphilly.org/about/>. 5. Kremer, Peleg, and Tracy L. DeLiberty. "Local food practices and growing potential: Mapping the case of Philadelphia." Applied Geography 31.4 (2011): 1252-1261. 6. Kuck, Ryan. Personal Interview. May 2014. 7. “Soil Safety Resource Guide for Urban Food Growers.” The John Hopkins Center for a Livable Future. Feb. 2014. 8. Staples, Amanda. Email Interview. May 2014. 9. Singh, Maanvi. "Newbie Urban Gardeners May Not Be Aware Of Soil's Dirty Legacy." NPR. NPR, 5 Apr. 2014. Web. 13 Mar. 2015. 10. "US Environmental Protection Agency." US Environmental Protection Agency. N.p., n.d. Web. 08 Mar. 2015. <http://www2.epa.gov/>. 11. Vitiello, Domenic, Michael Nairn, and Penn Planning. "Community gardening in Philadelphia: 2008 harvest report." Penn Planning and Urban Studies, University of Pennsylvania 68 (2009). 12. Weigley, Russell Frank., Nicholas B. Wainwright, and Edwin Wolf. Philadelphia: A 300 Year History. New York: W.W. Norton, 1982. Print.
Image 3. This map depicts Philly’s food system and household incomes (Image credits: Kremer and Deliberty 2011). 16
R
e p i ec
How to Make a Scientist
Take 1 inquisitive child and mix in a healthy amount of skepticism. Slowly blend in awe and excitement about learning. Add a large dash of compassion. Finally whisk in some understanding of statistics and probability. Let loose on world.
Passionate, curious, driven, resilient, constantly fascinated, skeptical. -Max Krackow â&#x20AC;&#x2122;15
-Professor Vince Formica
(1) a little sleep (2) critical thinking (3) some math (4) a fair amount of masochism -Anonymous
17
Zebraf At the age of three, Cameron Mott suffered persistent seizures as her immune system began attacking the right side of her brain. Surgeons successfully removed the right half (hemisphere) of her brain, and Cameron did not experience partial paralysis, which would happen if you or I had such a procedure. Children have neurons in the brain that can take on a variety of different roles, and, as in Cameron’s case, can even allow one hemisphere to take over the other’s function. (1) The flexibility, or “plasticity,” of children’s neurons shows an underlying theme in biology: premature cells can take on a variety of fates. This summer, I studied the growth of cells in a developmental biology lab, where I examined embryos. While I did not learn all the secrets of an extremely daring surgical procedure, I received a greater appreciation for spines through researching somites, patterned structures on the backside of embryos. How are these somites related to the spine, and what even is developmental biology, you may ask? Developmental biology analyzes the complex chain of events on the molecular level as a zygote, a single cell, matures into an embryo. One important concept in this field is developmental potential, also known as potency. A zygote has maximum potential, as it can lead to forming any cell in an organism. You probably have heard of stem cells before; these are cells formed by the zygote dividing, and possess very high potency, but gradually lose their potential as they divide into more speFigure 1: Zebrafish at the 12-somite cialized cell types. A stage. Each somite pair appears as a great way to visualize unit from the side. (Photo by Aaron) the loss of potency is reading a “choose your own adventure” book. The very beginning of the book, when you have the choice of all possible fates for your character, represents the zygote that can become any cell. Plot choices are similar to a stem cell dividing and thus forming specialized cells. The eventual storyline that you determine is much like the development of one stem cell into a specialized cell, including a red blood cell. To be clear, a cell cannot “choose” its fate, and the process is not random. Proteins greatly affect the devel-
opment of different cells, but explaining their full role is for another entry. A good thing to remember is that this great process, the growth of a cell into specialized cells, is known as differentiation. Amazingly, you can appreciate differentiation on the microscopic level with somites, which resemble a spine (Fig1). A somite, in more specific terms, is a paired block of specialized cells in the mesoderm, a layer of an early embryo that forms bone, muscle, blood, and a small amount of skin. While the majority of cells in one somite do go on to form the spine, as well as the ribcage, the top end leads to skeletal muscle and skin formation. Early in somite growth, all the cells that end up becoming the spine and ribcage congregate near the base of the somite, in an area known as the sclerotome. In early somitic growth, the cells that will become skeletal muscle or skin cells are not fully specialized. Since the muscle-forming portion is called the myotome, and the skin-forming section is the dermatome, these unspecialized cells in newly developed somites are part of a joint unit called the dermomyotome. (2) Differentiation in the dermomyotome was the lab’s focus, and my role was to find patterns in somite development among zebrafish, a vertebrate that develops quickly and is easily visible in a microscope. Before I go into the details of my findings, it is important to gain perspective from the effects of somite growth. If distinct somites combine, the somites can lead to an abnormally curved spine, causing a condition known as Scoliosis. Fused somites can also lead to defects in the ribcage, and missing somites can lead to embryonic death. (3) Unpaired somites are characterized with Spina bifida myeloschisis, a disorder involving the spinal cord (spinal nerves) protruding outward through gaps in the back (Fig 2). This severe case of Spina bifida involves neurological defects. (4) Wonder why nerves relate to somites? In humans, somite pairing occurs after the gradual closing of folds along an embryo’s backside. These folds, referred to as neural folds, must close to form the neural tube, which leads to forming 18
ish Trends: The Building Blocks of our Development By Aaron Holmes
two days! Somites, with their fascinating symmetry and aesthetics, let us visualize the complex nature of development, the forming of our uniquely distinct selves.
the brain and spinal cord. This process, known as neurulation, allows somite pairing to detect the closing of neural folds. After forming its first somite pair, the zebrafish embryo develops new pairs every thirty minutes. The embryos maintain this rapid rate of development until about 15 somite pairs are formed, about halfway through complete somite formation. (5) This sequential formation of somites allows them to be used as a marker of an organismâ&#x20AC;&#x2122;s development. Conventionally, a somite pair is defined as â&#x20AC;&#x153;one somiteâ&#x20AC;? when counting somite stages. I recorded the patterns seen in the 8-to-15 somite stages, as this is the period during prominent somite formation and differentiation. I saw patterns recorded extensively in zebrafish literature, including a Figure 2: A drawing of an early huthickening of the eye man embryo forming somites and clos- socket (orbit) and an ing neural folds. The gap within the elongation of the emsomite region of the 28-day embryo bryo as the head and will lead to Spina bifida myeloschisis. tail curl around the Note the unpaired somites across this yolk (Fig 3). In lessgap (6). documented trends, my results also suggested that the future cornea (tissue around eye) faces progressively downward, and the tail protrudes outward. These developmental trends, which are increasingly characterized until the 15-somite stage, correspond with neurulation, the somite differentiating, and the embryo progressing in developmental time. Once 15 somites are formed, the tail branches off from the yolk, the embryo eventually hatches from its chorion (egg), and the zebrafish begins swimming. This entire process in a zebrafish, which began from a single cell, occurs in about
Figure 3: From left to right, the development of a zygote into a 7-somite embryo, an 18-somite embryo, and a zebrafish 24 hours post-fertilization. Notice the eye socket formation and tail elongation (7). Literature Cited 1. "Rasmussen's Syndrome & Hemispherectomy." Neuroscience Fundamentals. Sept. 2012. Web. Jan. 2015. <http:// www.mayoclinic.org/diseases-conditions/spina-bifida/ multimedia/spina-bifida/img-20006705>. 2. "Musculoskeletal System Development." Embryology. Web. Jan. 2015. <https://embryology.med.unsw.edu.au/ embryology/index.php/ Musculoskeletal_System_Development>. 3. White, P. H. "Defective Somite Patterning in Mouse Embryos with Reduced Levels of Tbx6." Development 130 (2003): 1681690. Print. 4. "Spina Bifida." Embryology. Web. Jan. 2015. <http:// www.embryology.ch/anglais/hdisqueembry/ patholdisque03.html>. 5. "ZFIN Zebrafish Developmental Stages."ZFIN: The Zebrafish Model Organism Database. 1995. Web. Jan. 2015. <http:// zfin.org/zf_info/zfbook/stages> 6. "Diseases and Conditions-Spina Bifida."Mayo Clinic. Web. Jan. 2015. <http://www.mayoclinic.org/diseases-conditions/spinabifida/multimedia/spina-bifida/img-20006705>. 7. Lapedriza, Alberto. "My Research: Understanding Melanocyte Development." Sciplexity. Jan. 2013. Web. Jan. 2015. <https:// sciplexity.wordpress.com/2013/01/24/melanocytedevelopment>. 19
Whats math got to do with it? By Meghana Ranganathan
While going through the traditional high
presidents borrowed a combined $1.01 trillion from foreign governments and financial institutions according to the U.S. Treasury Department. In the past four years alone (2001-2005), the Bush Administration has borrowed a staggering $1.05 trillion,” ignoring the inflation that has occurred over those 228 years). This information would be very important for any student in high school, even those who go into non-math related fields or those who don’t pursue higher education at all.
school sequence of algebra, geometry, pre-calculus, and calculus, many students end up asking themselves a very common question: “Why do I need to know this?” And for those who don’t plan on going into very quantitative fields, it’s a fairly legitimate question. Most people will never need to know the fundamental theorem of calculus, but that definitely does not mean that those who decide not to pursue math-related fields don’t need to learn mathematics. However, the necessary mathematics knowledge is very rarely emphasized in high school. I have put together a list of important mathematical concepts that everyone should learn at some point:
Error Every measurement has some error associated with it. Error is a measure of the uncertainty inherent in a measurement. Think about looking at a ruler. You can measure 4.3 inches, but you can’t be sure whether it is 4.32 inches or 4.33 inches because the ruler does not have tick marks to indicate that. That is the uncertainty in that measurement.
Understanding how to compare and interpret numbers Numbers can be very powerful, and many people and companies attempt to use them to advance an agenda, anywhere from a simple ad (Maybelline trying to advertise that their mascara gives 65% more lift to eyelashes – how does one measure lift to eyelashes?) to a criticism of a president (the Blue Dog Coalition criticizing the Bush Administration: “Throughout the first 224 years (1776-2000) of our nation’s history, 42 U.S.
An example from Leonard Mlodinow’s book The Drunkard’s Walk demonstrates why an understanding of error is so important: a few years ago it was announced that we had an unemployment rate in the United States of 4.7%, and then a few months later it had changed to 4.8%. News sources declared that unemployment is slowly rising. However, this is not 20
necessarily true; these measurements are subject to error, and therefore there is no way to tell whether that 0.1% was due to a true rise in unemployment or just due to error. Mlodinow points out that if the unemployment rate was measured at noon and then remeasured at 1 PM, the number would probably be different by a little bit due to error, but that does not mean that unemployment actually rose in an hour.
A Pineapple at a Cocktail Party by Claudia Lujan
conditional Probability Conditional probability describes the probability that some event will occur given that another event has already occurred. One commonly cited example is the Sally Clark case. Sally Clark had one son in 1996 who died fairly quickly after his birth. Again, she had a second son and he died quickly after his birth. She claimed that they both died of SIDS (Sudden Infant Death Syndrome), but she was arrested for killing her two sons. During her trial, a statistician declared that the probability of a child dying of SIDS is 1 in 8500, and therefore the probability of two children dying of SIDS is 1 in 73 million ((1/8500)^2). This seems fairly persuasive, and in fact the jury thought so too and convicted her. But the statistician ignored conditional probability: it turns out, the probability that a second child will die of SIDS given that the first one has already died of SIDS increases substantially. Additionally, the probability of a child dying of SIDS if the child is male is also much higher. Secondly, the jury should have weighed the two possibilities: that of both children dying of SIDS and that of Sally Clark killing both her sons. It turns out that the probability that Sally Clark killed both her sons is much, much lower than the probability that they both died of SIDS. The jury, the lawyer, and the statistician did not consider these when arguing the case.
I am of the prickly variety. Sweetest in my slumber but the early morn finds me sour. I have prepped for your greed and hope to find you stunned. I am no easy apple, no plain sugar cane, no seducing plum. Exotic might come to mind but Iâ&#x20AC;&#x2122;ll remind you this juice ainâ&#x20AC;&#x2122;t a squeeze. Gold is mined.
Hint: Pineapples are CAM plants
This list provides three examples of why mathematics is important for everyone, but it is definitely not exhaustive. Many applications of mathematics are incredibly useful, but they are commonly overlooked in traditional math classes. I think there should be some addition to mathematics courses in high school to account for the population of people who may never use calculus, but who will be making decisions for the rest of their life and need the information to make those decisions educated. Work Referenced 1.
2. 3.
Democratic Underground, "Bush Borrows More than 42 Previous Presidents Combined, http:// www.democraticunderground.com/ discuss/duboard.php? az=view_all&address=132x3162826 Leonard Mlodinow, The Drunkardâ&#x20AC;&#x2122;s Walk: How Randomness Rules Our Lives, 2009 Charles Seife, Proofiness, 2010 21
Fritz Haber A LIFE by ALIce Herneisen
T
vent what was then seen as an impending, widespread famine. The limiting factor in crop growth is often nitrogen. Frustratingly, plants cannot employ the most abundant source of nitrogen, air, for their needs. Instead, they rely on microorganisms to convert, or “fix,” this atomic nitrogen (N2) into its biologically relevant form, ammonia (NH3). During the nineteenth century, agriculturalists depended upon natural sources of fertilizer – primarily guano and saltpeter from South America – to replenish nutrients in the emaciated farmlands. Were these finite stocks of brown gold to run out, scientists believed that Europe, Germany in particular, would not be able to feed its burgeoning population (1).
wo years ago I sat in a history classroom in
Germany and listened to secondary school students debate the namesake of the renowned Fritz Haber Institute, a research facility in Berlin associated with over half a dozen Nobel laureates. No general chemistry textbook is complete without mention of the Haber-Bosch process for the conversion of hydrogen and nitrogen gas into ammonia. The textbook will note that this process is used to synthesize fertilizer. It may confess that the reverse operation has been used for explosives. Most likely, it will not mention the tragically ironic life of Fritz Haber - grandfather of the Green Revolution, father of chemical warfare, and loyal son to an abusive country.
Early attempts to create an inorganic alternative to natural nitrogen fixation resulted in disaster for the scientists involved. Microorganisms have had billions of years to develop enzymes that delicately fit molecular pieces together; industrial processes can only succeed with hellishly high temperatures and crushing pressures, offering slim benefits at high costs, such as the loss of a hand. Haber, however, pushed forward where others, notably French chemist Henry Louis Le Châtelier, were retreating. By 1909, Haber successfully fixed nitrogen and hydrogen gas into ammonia using an osmium and uranium catalyst at 550°C and 175 atm. Five years later, Carl Bosch and Alwin Mittasch, working under the German company BASF, overcame the considerable challenge of converting the Haber process into a commercial enterprise (2).
The paradox of Haber’s life began with his boyhood in Breslau, then a part of Prussia. He was born in 1868 to a Jewish merchant family and excelled under the tenets of a standard Prussian upbringing: discipline, respect, and patriotism for the newly united Germany. With the disastrous aggression of the new Kaiser Wilhelm II came a new threefold creed: “God, Science, and Nation.” The dedicated Haber aspired to this trinity of Deutschtum, or “German-ness”; after earning his doctorate in chemistry, he abandoned his father’s occupation, converted to Protestantism, and moved 500 miles away to join the teaching and research staff at the University of Karlsruhe (1). At this time the scientific community was scrambling against the Malthusian countdown to pre-
Haber, for his part, was hailed as an alchemist for 22
is something paradoxical about this evil scientist; Haber died a victim. His Jewish background negated his life’s work, despite his proven ardor for his country and conversion to Christianity. Haber resigned his post after the 1933 ascension of the National Socialist party in an effort, it seemed, to stall the mandatory dismissal of Jewish scientists from the Institute. He had no choice but to flee Germany for the countries that reviled him. He died shortly later, in early 1934. The epilogue of this tragic irony came some years after Haber’s death. Under Haber’s reign at the Institute, one of his daughter companies developed an insecticide known as Zyklon. Years later it would be used to kill Haber’s relatives in the gas chambers of Nazi extermination camps (1).
the common man; he had given Germany Brot aus der Luft, “bread out of air”(1). Haber found himself rubbing shoulders with his national heroes, not the least of whom included Kaiser Wilhelm II. In 1911 Haber was named director of the newly formed Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry. Forty-two years later it would be renamed in his honor (3). Sixty years after that, its appellation would be debated by pupils in a history classroom in North-Rhine Westphalia, Germany.
What lesson might one learn from the life of Fritz Haber, and why is it missing from textbooks? He does not entirely fit the motif of the Promethean scientist, whose well-meaning discovery is expropriated by some governmental organization and used for evil. Haber undeniably took part in the killing of soldiers; yet one has the nagging feeling he would have refused to expose civilians to the same fate. Perhaps the warning to be garnered from Haber’s life is as follows: a scientist, and science, is only as good as the society in which they work. Even the seemingly greatest of discoveries – bread out of air – will inflict great pain, if that is what society demands.
Under the directorship of Haber (1911-1933), the institute made great strides in industrial chemistry, potentially at the cost of other global markets (3). Whole international industries, such as the dye cultivation of Southern France and indigo trade of British India, went barren as German chemical engineering came into fruition, providing cheaper alternatives. As international relations fell apart in the prewar years, so too did relationships in the scientific community. Research was increasingly published in English rather than German; French laureates decried La science allemande as “a degenerate form of French science” (1). When the First World War broke out, Haber switched his allegiance from humanity to the Vaterland. Without his work, Germany may have lost the war in 1915. Instead, the Haber process more than replaced the fertilizer and nitrogen-based explosives lost due to the British-led blockade of Germany. Haber wished to do more, however, and ardently advocated the use of poisonous gas despite initial government opposition to such a “cowardly” weapon. On April 25, 1915, the man known for his “bread out of air” prevailed. Haber orchestrated the release of a wall of chlorine gas over the trenches of Ypres. For the unsuspecting Allied soldiers, the poison was “death out of air.” This was the beginning of the era of chemical warfare (1).
Our classroom discussion took place after the hundred-year commemoration of the industrialization of the Haber process. This April marks the hundred-year memorial of the first mass gas attack. What conclusion, you might ask, did we reach? Some students, of course, believed it was the responsibility of the Institute to disassociate itself from its namesake, both the shadow of the man, and his brilliance. That same choice has been made in every general chemistry textbook I have seen.
Haber’s willingness to descend to such depths in the name of victory made him unpopular in the scientific community, even in Germany. The Nobel Committee’s decision to award Haber the 1918 Nobel Prize in Chemistry for the Haber process was met with outrage and boycotts. Haber, however, appeared unfazed. After an unsuccessful attempt to extract gold from seawater to repay Germany’s war debts (“gold out of water,” it seems, was beyond even this alchemist), Haber settled down into administrative life (1).
Literature Cited 1. Dunikowska, Magda, and Ludwik Turko. "Fritz Haber - Ein Verfemter Gelehrter." Angewandte Chemie 123.43 (2011): 10226-0240. Web.
Most of us, however, agreed that there is a great deal to be learned from the name Fritz Haber. The responsibility falls on us, as students of science and the liberal arts, to make sure that the full story is known.
2. Flavell-While, Claudia. "Feed the World." Chemical Engineer Mar. 2010: 54-55. Web. 3. James, Jeremiah, and Dieter Hoffmann, and Thomas Steinhauser. "’under My Protection and Name...’ - Origins and Founding of the Institute." One Hundred Years at the Intersection of Chemistry and Physics : The Fritz Haber Institute of the Max Planck Society, 1911-2011. Berlin: Walter De Gruyter, 2011. 1-34. Web.
Were Haber’s story to end here, he might have succumbed to the cliché of the evil scientist. Yet there 23
BLACK HOLES.
Fact or Fiction?
By Peter Weck
{ 1
The galaxy eating, time warping, black holes of science fiction have become well-established features of modern astrophysics. While some of the popular folklore reflects real science, other common ideas about black holes are simply nonsense. Take a look and see how many black hole facts you had right.
Black Holes Suck Fiction – Black holes do not suck things toward them selves any more than other matter does. If the sun suddenly collapsed to form a black hole of the same mass, the earth’s orbit would not budge. What makes this myth so compelling is that the black holes we can detect are often very, very massive, formed during the collapse of stars many times heavier than our own sun. For example, there is a supermassive black hole at the center of our galaxy with a mass and gravitational pull 4.3 million times greater than the sun’s. Another version of this myth is that the Universe will end with everything getting sucked up into one giant black hole. Actually, there is strong evidence that the universe is expanding at an ever increasing rate. Instead of everything getting sucked up, matter is spreading out as space itself expands. If that expansion keeps up, even black holes will one day die out, evaporated into the vast, cosmic void (see 3.).
24
}
Black holes are time machines
2
Fact – Black holes are time machines, but only the boring, one-way kind that take you into the future. Time passes more slowly for someone near a massive object relative to someone further away. So if you were to go spend your summer vacation in a spaceship orbiting very close to a black hole and then come back to earth, anywhere from months to thousands of years could have passed on earth. How far earth time gets ahead of you depends on the mass of the black hole, how close your orbit was, and even how fast the black hole is rotating.
3
Black holes are black
Sort of – The gravity at the edge of a black hole, called the event horizon, is so strong that any matter or light which goes in never comes out. In this sense black holes really are black. However, as material falls into a black hole it jostles together and gets very, very hot. This material collects into a disk known as an accretion disk, and would appear very bright to the naked eye. If the accretion disk gets big enough, some superheated material can actually get blasted out into space in jets which are so powerful they can be observed from earth. Even a black hole without an accretion disk is not totally black. Stephen Hawking discovered that black holes actually radiate a very small amount, thanks to quantum mechanics. If left alone long enough a black hole would lose so much mass to this so-called Hawking radiation that it would disappear entirely!
4 Black holes are infinitely dense Unknown – Black holes form when lots of matter gets very close together, forming an object with mind-bogglingly high density. How dense? Once the matter becomes concentrated enough for a black hole to form, we cannot see what is going on past its event horizon, and are forced to rely on mathematical predictions. Unfortunately Einstein’s theory of General Relativity, which is usually great for handling really massive objects, breaks down when you squish matter together on such a small scale. The density diverges, which means that according to the math it approaches infinity. Many physicists take that to mean we need a new theory with new mathematics to talk about what is going on inside a black hole, instead of actually implying that black holes are infinitely dense. Since you cannot see past the event horizon of a black hole, we may never know for sure.
Black holes are tunnels to other parts of the universe
5
Fiction - There is no evidence indicating that black holes are tunnels to other parts of the universe. That would be a wormhole, an entity which some argue is a theoretical possibility. Wormholes would act as bridges connecting far away regions of space. However, General Relativity predicts that matter with negative energy density would be required to create a wormhole, and normal matter has positive energy densities.
Black holes give birth to new universes
6
Unknown – Some theories suggest that black holes give birth to new universes. The only other thing as dense as a black hole that we know about in the history of the universe is the universe itself, right at the moment of the big bang. At the center of each black hole a miniature big bang might occur. The baby universe would grow in a new region of space-time, connected to our own universe only at the center of the parent black hole. 25
BEYOND THE ATOM Quantum Field Theory and the Nature of Matter by Samer Nashed
26
M
odern physics can tell us the chemical composition of stars 1,000,000,000,000,000 miles away, or the temperature of the universe 0.000001 seconds after the big bang. However, answers to seemingly simple questions like “What are we made of?” have eluded us for thousands of years and have lead us on journeys full of twists and turns. As nature and the scientific method take us from one strange picture of the universe to the next, we have continually redefined the fundamental constituents of matter as we probe the Russian nesting doll that is the atom. Large objects made of smaller particles, which are in turn made of yet smaller particles; it seemed in the mid-1900s as though this cycle was doomed to continue. However, in the last few decades, there has been a dramatic fork in the road. Our current theory of matter no longer works in terms of particles, but rather we see matter as made of vibrating fields. How did we end up at such a wild idea, and why should we take it seriously? The strange answer to the question of material existence begins in the minds of ancient philosophers and ultimately finds resolution under the Swiss-French border, in the subterranean tunnels and computer banks of the Large Hadron Collider.
From Particles to Fields The idea that matter is composed of atoms was hypothesized around 400 BCE by the Greek philosopher Leucippus and later reached a wider audience through his more well-known disciple Democritus, who used atomic theory to explain a variety of questions including mixtures, human senses, and the existence of the human soul via “soul atoms.” Eventually, many aspects of Democritus’ natural philosophy were supported by more rigorous scientific experiment, and in the late 1800s the 27
existence of atoms was widely accepted as a fact of nature. However, this model would undergo two major revisions. First, around 1900, subatomic particles like electrons and protons were found, and thus replaced the atom as the fundamental building blocks for all matter. This model was further complicated in the 1960s, when the existence of particles called quarks was discovered. These quarks, of which there are many different types, come together in groups of three to form protons and neutrons. Our theory about what we were made of had changed again, but was still centered on the idea of particles. This and other discoveries had placed physicists at a crossroads. They had working theories for a number of particle phenomena, but needed to extend their mathematical theories to problems beyond particle physics. During much of the early 20th century, physicists were also investigating the properties and behavior of light and waves. Hundreds of years ago, Sir Isaac Newton and Christiaan Huygens championed seemingly incompatible views on the nature of light. Newton preferred to think of light as made of particles, and Huygens thought of light as waves. In the end, they were both right. We now know that light is made of photons, which sometimes behave like particles and sometimes behave like waves. The enormous scientific effort spent in studying the wave-particle duality of the photon would turn out to have profound implications. As physicists extended experiments initially used to study photons to other particles, like electrons, a new physical intuition was adopted wherein quantum mechanical objects, such as photons, electrons, protons, etc., behave at times like particles and at times like waves. This intuition would form the basis for much of the work done in the 1970s by physicists Michael Fisher and Leo Kadanoff, as they put the finishing touches on a theory that would become one of the most rigorously tested and successful theories in all of physics: Quantum Field Theory (QFT). In fact, according to physicist Sean Carroll, “Quantum Field Theory is the most important thing we know.” In addition to being spectacularly successful, QFT also helps us contextualize the discovery of the Higgs Boson and entertain our philosophical musings about the nature of the universe. If QFT is such a superstar, why don’t we hear more about it in popular science news? The answer is twofold. One, it is possibly the most difficult theory in terms of both mathematics and conceptualization, and therefore difficult to explain. Two, the consequences of QFT are often counterintuitive, and serve only to muddle most non-physicists’ physical conception. To understand how QFT relates to other areas of
image from http://www.britannica.com/EBchecked/topic/462888/Max-Planck
this force field, where the force on the magnet depends on its proximity to the fridge. Electromagnetic radiation, including visible light, is a manifestation of waves or vibrations in this same electromagnetic field. It turns out that photons are actually groups of electromagnetic waves that travel together through the electromagnetic field, and it is this grouping that gives them some properties one would normally associate with particles. Although QFT certainly incorporates the electromagnetic and gravitational fields, most fields in QFT are not force fields, rather they are fields associated with what we think of as particles, like electrons and quarks. These fields permeate all of space just like all other fields, but their values have a different interpretation. The values of these fields correspond to the probability that a ‘particle’ exists at that point. The field is what is real, and the imposition of the existence of a particle is why we experience probabilistic behavior in quantum mechanics. Every type of particle has an associated field, and vibrations in these fields can interact with each other and with vibrations in other fields. This view of the world, as a collection of fields, begs the question: If everything is made of fields, why consider particles at all? To answer this, we look at the “Quantum” part of QFT. The word “quantum” is derived from “quantized,” which perfectly describes our observa-
physics and philosophy, we need to understand the implications of the theory itself.
What is Quantum Field Theory? According to QFT, all the matter in the entire universe is just a manifestation of vibrations in fields. You, me, and this publication are all made of vibrating fields. That’s a pretty bizarre and abstract idea, and it is a lot easier to illustrate physics concepts using diagrams of ball-like particles bouncing off each other. However, we believe that by keeping QFT out of the public arena, physicists are losing out on the opportunity to tell people about one of the coolest and most successful ideas in physics. So sit back and relax—it’s time we took QFT for a walk. First, what are fields? Fields are entities which permeate all of space-time and at each point have a value. Temperature is a field, since you can put a thermometer anywhere in the universe and get a temperature reading. The first fields introduced in physics were force fields, the most common example being gravity. At every point in space, all objects with mass feel a force with a certain magnitude and direction, depending on the gravitational field in their vicinity. The value of the field depends on the distribution of mass nearby. Another example of a force field is the electromagnetic field. Your fridge and fridge magnets interact via 28
tions about the amount of energy fields can possess at any one point. Since we only observe energy in quantized amounts, we call these discrete, observable features “particles.” It is worth emphasizing that we do not have a good theoretical reason for this discrete nature. Rather, it is an artifact of the way we gather information about our world. The real world and the world we observe are different in this respect; we can only observe quantized amounts of energy, but the actual fields may contain continuous energy values.
Are Fields Real?
with the electron and positron annihilating each other to generate a photon. It’s not that any of these particles are made of any of the others—all three have no known smaller parts. So what’s going on? In quantum field theory, the photon is just a vibration in the electromagnetic field. When the electromagnetic field vibrates, it can transfer its energy into the electron and positron fields, like strings on a violin. One vibrating violin string may transfer its energy through the wood of the instrument to another string, causing the second one to vibrate noticeably. The resulting vibrations in the electron and positron fields show up as particles when a measurement is taken. Before quantum field theory, there was no coherent account of how this creation and destruction of particles was possible.
“
Whichever side of the philosophical debate you fall on, quantum field theory is our Why Particles have Mass You probably heard somebest explanation of thing over the last few years about the discovery of the Higgs boson the physics we at the Large Hadron particle Collider. The discovery made quite observe.
If we see particles when we measure fields, then why bother with the fields at all? Is this just some hokey interpretation? In the mathematics of quantum field theory, the behavior of matter and energy is always represented as interactions between fields. If the fields aren’t there then the theory doesn’t make a whole lot of sense. Modern philosophers of science might frame the argument this way: we have good evidence to believe the world is made of fields because that is the best explanation for the unparalleled experimental and theoretical success of quantum field theory. Other philosophers of science argue that we should not necessarily expect nature to make sense, and therefore we should not believe everything is made of fields just because our fundamental theory of matter says so. Whichever side of the philosophical debate you fall on, quantum field theory is our best explanation of the physics we observe. However, because it is such a difficult theory, physicists prefer to avoid it when talking to a general audience. As a result, they end up waving their hands when asked why the Higgs Boson is so important, or how it is that particles can be created, destroyed, or decay into other particles.
”
the stir in the physics community, and a lot of non-scientists wanted to know why. Most physicists just mumbled something about the Higgs boson being responsible for giving other particles mass. This made little sense to most of us, and the title “God Particle” did little to clarify. It is not the Higgs particle which gives other particles mass, but the Higgs field. Vibrations in fields associated with massive particles excite the Higgs field. This interaction between the Higgs field and the fields of other particles causes all the effects we associate with mass. The more strongly a field couples to the Higgs field, the more massive the particle corresponding to that field. To verify the existence of a Higgs field, physicists searched for a particle with the right energy to be a manifestation of a vibration in the Higgs field. The search for the Higgs boson was really a search for vibrations in the Higgs field. We have come a long way from the atoms of Democritus, reducing and refining our understanding of matter again and again. Quantum Field Theory is the culmination of this journey—our fundamental theory of matter and its interactions. If we take the mathematics of the theory seriously, then our world is made entirely of vibrating fields, transferring energy back and forth and resolving into the particles we know and love only when meddled with. It is a bizarre picture of the world, but it is also our best yet.
Something from Nothing If you were to look very, very closely at an empty chunk of space, you would actually see particles popping in and out of existence. For example, a photon can spontaneously turn into an electron and its anti-matter partner, the positron, so long as the energy and momentum of the electron/positron pair match the energy and momentum of the photon. The same process can also happen in reverse, 29
Tristan Smith
Theoretical Cosmologist on Staff: A conversation
with Peter Weck The Department of Physics & Astronomy recently hired
basic questions. Where did we come from? How did we get here? Where are we going? Cosmologists do this by observing and theorizing about the physics of the universe, all the way from the first moments of the big bang to today. For example, our current understanding of the very early universe links the formation of galaxies, stars, and planets, to microscopic quantum processes which occurred just after the big bang. Cosmology has unveiled a story which connects our physical existence to processes that have occurred throughout the universe; in this way it humanizes the universe, makes it less foreign and cold. I also think that although very technical, the answers provided by cosmology weave a story that is meaningful, and even poetic, in a way which is unique to scientific investigation.
Tristan Smith as a tenure-track professor. He is a theoretical cosmologist by trade, and has been at Swarthmore since 2013 as a Visiting Assistant Professor. On the first day of the semester, I sat down with Tristan to talk about his life, about Swarthmore, and about the beginning of the universe.
Q: What is theoretical cosmology? In particular, why is it something non-scientists should care about?
A: Cosmology attempts to answer some of our most 30
Q: How did you get into science?
more Physics Department is really on the same level as most of the research done at larger institutions.
A: Well, both my parents are artists. I think that is one
Q: Do you think science can answer questions about why
important reason why I got into science, cosmology in particular. Theoretical cosmology incorporates so many different ideas that you have to be creative much in the same way that an artist has to bring together various different components to make a painting or sculpture. Another important motivation came from my grandmother, who was a biology teacher. She would come over to our house once or twice a week with a copy of the Science Times and quiz me on it. I would get a quarter if I got things right. She wanted me to be a biologist, but I was attracted to physics because it asks such fundamental questions. I have this memory of seeing an integral symbol in a book, and knowing that it was part of a mathematical language describing all these deep ideas without having any clue what it really meant. I wanted to learn that language, and am still learning, so that I can say for myself that we know what the universe was doing 10-34 seconds after the big bang. That was a journey I needed to go on.
the big bang happened or why our universe looks the way it does?
A: The real sticking point here is that when you go far
from your first year and a half here?
enough back in time, things get hotter and hotter, until all of our current laws of physics have to break down. As people learn more about string theory, we might develop a theoretical framework to describe the laws of physics in those first few moments after the birth of the universe. However, right now we do not have the theoretical tools to understand what exactly happened at the big bang. There are also some serious arguments out there trying to explain why the fundamental constants of nature take on the values that they do. For example, the anthropic principle plays a fairly active role in cosmology. Basically, proponents of this principle argue there could be multiple universes where the fundamental constants take on a range of values, and only a subset of those are properly setup for life. However, a lot of people are not satisfied with that kind of explanation, since it starts with our existence and argues from there.
A: The most striking thing that I have experienced is the
Q: What are some classes that you have taught or would
interest and encouragement that I have received to explore the scientific aspects of my work alongside a wide range of other ways to ask questions. That has come from our conversations about the philosophy of science, from conversations I have had with music professor Mark Lomanno when we co-taught a class about the physics and experience of time, and just from talking with students and faculty on a day to day basis. It is what I thought my college experience might be like, this pure desire to ask awesome questions.
like to teach which would give someone who is interested in these topics but does not necessarily have a background in science the chance to learn more?
Q: Do you have any striking impressions of Swarthmore
A: Last year I offered a cosmology class for non-majors, and I would like to teach another class like it soon. For me the most amazing thing about cosmology is not necessarily the answers that it comes up with, but the fact that as we learn more we are able to ask questions which were once unaskable. For example, we talked about how in the late 1700s William Herschel and his sister Caroline were the first people to map out the shape of the Milky Way galaxy. Now, he got it wrong, but it is an interesting example because at the time that was a crazy question! To even think that the Milky Way is the sort of thing that could have a shape, like this table or the recorder, is awesome. This is the sort of message I wanted to convey in the class- that cosmology is about these very heady, non-human things, but that our human experiences inform the concepts we use to describe the universe as a whole. Looking to the future, religion professor Mark Wallace and I have talked about co-teaching a class that would tease out the profound implications of the way in which cosmology addresses our physical origins, and the intersection between this approach and more theological perspectives.
Q: How much can we learn about the history and the fate of the whole universe with the resources of a small liberal arts college like Swarthmore?
A: One big advantage is that I am a theorist. That means that the tools that I use to do my research are mainly my own ideas, pen and paper, and of course all the colleagues that I have formed collaborations with at universities across the country. Another important tool I use is computing resources. Swarthmore actually has access to a large national supercomputer facility, and in that sense, the resources available to me are on par with those available to my colleagues at other institutions. Overall the level of research being done in the Swarth31
Motivation
their angular momentum, so in a sample of mostly older stars we would expect to see a decline in the total fraction of rapid rotators. The youngest of the Reiners sample are of a similar age to our stars and comprise most of the Reiners sample’s rapid rotators. Most of their remaining, slower rotating stars are older, in the neighborhood of a Gyr.
With the launch of the Kepler Spacecraft in 2009, efforts to identify Earth-like exoplanets within the habitable zones of stars have increased dramatically. For some, the search has concentrated on lowmass M-type stars, which constitute roughly 75% of the stars in the nearby galactic neighborhood [1], because their smaller size allows easier detection of Earth-sized planets.
Rotational Velocity: How it Works To understand work done on rotational velocity, the first step is to understand how we use the light from a star to measure how it is spinning. The light spectrum of a star consists of dips and peaks in a continuum, known as spectral features, created by interactions of that light with molecules. When a star is rotating, half of the star is moving toward us and half is moving away from us, which causes the light from one side to be redshifted and the light from the other side to be blueshifted. Hence, when we study the spectrum of a rotating star we see a ‘broadening’ in the spectral features. The total area of the feature will be the same because the same amount of light is leaving the star, but the feature will be shallower and wider as some of the wavelengths will be slightly longer and some will be slightly shorter. We can use a slowly rotating star as a “template” spectrum and artificially broaden its spectral features to match those of an “object” star to figure out the rotational velocity of that object star. Figures 1 and 2 illustrate how we used the rotational broadening of a spectrum to find rotational velocity. The term “rotational velocity” is slightly misleading, since we can only measure the full rotational velocity, v, if the star has a rotational axis perpendicular to our line of sight. The orientations of the rotational axes, i, are assumed to be distributed randomly. To acknowledge the dependence of rotational velocity on the inclination of the rotational axis, we call the measured rotational velocity “v sin i.”
The physical properties of a star change depending on its mass and temperature, yet not everything about these low-mass stars is understood. Within the M-type classification, a star is further identified by its spectral subtype, which is an indication of its temperature. The normal range of subtypes in a spectral class is 0 to 9.0 where subtype 0.0 is hotter than 9.0. The temperature of a star changes the types of atoms a star fuses and how those atoms interact with photons within the star, which can affect its magnetic fields and light activity (e.g. strength of flares). Both parameters can affect nearby planets. The better we understand the magnetic fields, surface activity, and rotational velocities associated with a star, the more likely we are to know when we have found a potentially lifesupporting planet, called a Goldilocks planet.
Finding the Rotational Velocities of Young M Stars By Catherine Martlin
Last year I measured the rotational velocities – or spinning rates – of a subset of 140 previously documented young M stars (most younger than 300 Myrs) [2;3] while working in collaboration with Professor Eric L.N. Jensen of Swarthmore College and Dr. Evgenya Shkolnik of Lowell Observatory. Previous research, such as that led by Professor Ansgar Reiners at the Institut für Astrophysik Göttingen, has indicated an increase in the total fraction of rapid rotators within certain spectral types [4;5], where rapid rotators are stars that rotate faster than 5 km s -1 . However, in our young sample I found no increase across the spectral types. Our sample’s average age is less than half that of the Reiners sample. As stars age, they lose 32
Figure 1: Left: An object star and template star before the object has been corrected for its radial velocity. Right: The object star has been correlated and shifted.
Comparing Ages
correlation in the Reiners sample. As a second test, we found the probability of whether the rotational velocity distribution of the early spectral subtypes (0.0M - 2.9M) and the rotational velocity distribution of the later spectral subtypes (3.0 - 4.5 in Reiners et al.; 3.0 - 6.4 in our data) were drawn from the same parent distribution using Kolmogorov–Smirnov statistics [7]. A probability close to 1 indicates that our distributions are not different while a low probability means that the two distributions are different. We found the older sample from Reiners to have a K-S value of 0.00012 while our data had a K-S value of 0.964208. There is a difference between the early and late spectral subtypes in the Reiners sample, but no difference in our sample. This suggests that the mechanisms that drive the correlation between early and late
Previous research found a correlation in M stars between spectral subtype and fraction of rapid rotators [4] as well as spectral subtype and fraction of active stars [6]. When we applied a lower limit for “rapid rotation” of 5 km s-1, 83% of our sample was rapidly rotating – while only 11% of the Reiners sample were. (As a comparison, our Sun is not a rapidly rotating star as its equator spins at about 1.87 km s-1.) The fraction of rapid rotators per spectral subtype for both our data and the Reiners sample can be seen in Figure 3.
Figure 2: This is the fit of the template spectrum to the object spectrum. Black line – the object spectrum. Red line – the adjusted template spectrum. Blue dots – points of the target spectrum used for weighting. Black dots – the residuals.
Figure 3: Comparison of fractions of rapid rotators using a cutoff of 5 km s-1. Blue – Our sample. Green – Reiners sample.
spectral subtype and rotation need more than 300 Myrs to cause a difference in rapid rotation fractions. M star populations as young as 300 Myrs appear to be too young for angular momentum-stealing mechanisms that have acted upon older populations to take effect.
To test whether there is a linear dependence between the rotational velocity and the spectral subtype of the data, we calculated their correlation coefficient. While our data has a small coefficient of -0.082214 the Reiners data has a coefficient of 0.242645, indicating there is no linear dependence for our data but a positive 33
Mass and energy are perhaps the most fundamental concepts in all of physics. Everything we know to exist in the universe has either mass or energy – most have both. Einstein’s famous equation E=mc2 relates the two, where c is the constant speed of light. The deeper physical implication of this equation is that changing the energy of an object can actually increases or decrease its mass. The m in the equation E=mc2 is called relativistic mass.
Figure 1: Amy and Carl both observe a proton. Amy’s frame is at rest relative to the proton, while the proton moves with velocity v in Carl’s frame.
However, Einstein introduced this equation to a world which was already comfortable with the current definition of mass. Namely, that mass was a characteristic of an object that was invariant in time and space. It is intuitively satisfying that a particle should have the same mass regardless of its velocity. Additionally, problems in particle physics become easier mathematically if we define a different type of mass called invariant mass. This mass is given by the equation E² – (pc)² = (mc²)², where p is the momentum of the object.
Figure 2: Relativistic mass is always greater than or equal to invariant mass.
Though they seem diametrically opposed, these two definitions actually coexist happily, and it all has to do with the mathematics of what physicists call reference frames. A reference frame is a mathematical object representing someone’s perspective. In Figure 1, we see Carl and Amy, each of whom are associated with a reference frame. We know how Carl perceives events in the world be analyzing them in the context of his frame, frame A.
Similarly, Amy has her own interpretation of events based on her frame, frame B. Amy is moving with the same velocity as the proton and Carl is standing still. If Amy and Carl both try to measure the invariant mass of the proton, they will get the same 34
answer. However, if they both measure the relativistic mass, Carl will measure a higher value than he did when measuring the invariant mass and Amy will measure the exact same mass as before. This is because Amy is not moving relative to the proton, so in the first measurement she measures p=0. This means her equation for the invariant mass becomes E² = (mc²)², which is the same as the equation used to measure relativistic mass. Carl on the other hand,
of the box, Carl says it has a relativistic mass greater than the invariant mass and Amy says that they are equal. Things get even weirder when we consider the phenomenon of matter-antimatter annihilation. When an electron meets its antimatter partner, the positron, they destroy each other, generating a pair of photons. Although they possess energy, photons have no invariant mass. What happened to the mass of the electron and the positron? It’s tempting to say that it was converted into the energy of the photons and leave it at that. But although neither photon has any invariant mass, the system consisting of both photons does have mass, the exact same invariant mass possessed by the electron-positron system before the collision. In a system which is not interacting with its surroundings, both total energy and momentum are conserved. The equation E² – (pc)² = (mc²)² tells us that the invariant mass of a closed system must therefore be conserved as well.
Figure 3: Amy and Carl both observe a box of gas. Amy’s frame is at rest relative to the box, while the box moves with velocity v in Carl’s frame.
measures a momentum p>0, since the proton is moving relative to his reference frame. Therefore, Carl measures the proton’s relativistic mass to be greater than its invariant mass. In general, the relativistic mass is always greater than or equal to the invariant mass, as shown in Figure 2.
Is mass just another word for energy? Or perhaps they are different but can still be converted into one another? While answers to these questions can be logically supported, they are not yet distinguishable experimentally. So instead of scientific theories, they are known as philosophical interpretations of mass-energy equivalence. There are a variety of arguments, but one thing philosophers definitely don’t claim is that E=mc² means that matter can be converted into energy. There is no universally agreed upon definition, but in physics matter is a kind of stuff, whereas mass and energy are properties that stuff can have. Therefore, talking about converting between matter and energy would be like suggesting someone convert their textbook into the color orange.
In practice, most physicists use invariant mass because it does not depend on who makes the measurement, which makes conducting experiments much easier. Invariant mass may be relatively well-behaved, but it can still exhibit some surprising behavior due its intimate connection with energy. Imagine a box filled with gas. If the box is at rest, p=0 and we can just use E=mc2 to calculate its invariant mass from its total energy. However, this means the invariant mass of the box of gas will change depending on the energy of the gas. For example, if the gas is heated, its molecules will, on average, gain kinetic energy, thereby increasing the invariant mass of the whole system. This isn’t just definitional- the box really would feel heavier if you tried picking it up. This is the essence of massenergy equivalence.
Whichever definition of mass and matter you choose to use, adding energy to a system can sometimes increase its mass. Similarly, just by virtue of their mass objects have an associated energy. Does this mean that the distinction between mass and energy is artificial? Unless physics uncovers still deeper connections between mass and energy in the future, this will remain a question for philosophy. 1
Some people consider all particles to be matter, including massless particles like photons. Others use more restrictive definitions, but either way, matter and energy are not comparable concepts.
What about the relativistic mass of the box? Well, if the box is at rest the relativistic mass is equal to the invariant mass. The two definitions only diverge if the box is moving relative to the observer, as for Carl in Figure 3. Like the proton example earlier, while Amy and Carl agree on the invariant mass 35
{
Unraveling the Link Between Ecosystems and Human Health
}
By David Tian
diseases may point to underlying and predictable ecological relationshipsâ&#x20AC;? (Dybas, 2015).
nterestingly, the study of human disease and medicine does not tend to take into account the influence animals have on the field. Perhaps human exceptionalism clouds our views from the fact that we are organisms within a large web of biodiversity. As Homo sapiens, we are simply primates that are characterized by bipedal locomotion and larger brain sizes, and some have even gone as far as to characterize modern humans as a sub species; Homo sapiens sapiens, indicating that we are twice as wise. Ecosystems are incredibly complex and our current roles in environmental degradation have far greater effects than global warming and pollution. Diseases do not randomly pop up once in a blue moon. As recent examples in the past few decades have indicated, their emergence is inextricably tied to humans and our adverse effects on the environment. As Sam Scheiner, the director of the Ecology and Evolution of Infectious Diseases program at the NSF said, â&#x20AC;&#x153;Virtually all the world's terrestrial and aquatic communities have undergone dramatic changes in biodiversity due primarily to habitat transformations such as deforestation and agricultural intensification, invasions of exotic species, chemical contamination and climate-change events. The coincidence of broad-scale environmental changes with the emergence of infectious
Disease Origins Believe it or not, the origin of disease is mostly environmental. Nearly 60% of infectious diseases are zoonotic, meaning they are transferred from animals (Smith et al. 2014). These diseases are not only rare ones that affect rural villages in the developing world, but also include Lyme disease and Salmonella. Diseases such as West Nile, Ebola, and even HIV/AIDS are all products of zoonosis. The fear is that one such disease will jump from animals to humans, and then evolve to be transferable by human contact and spread as a disease that nobody has ever encountered (Robbins, 2015). Emerging diseases tend to be caused by novel pathogens or ones that mutate rapidly, such as the flu. Although infectious diseases have always originated from the environment, scientists indicate that in recent decades human encroachment in tropical regions has dramatically increased the number of emerging infectious diseases (Robbins, 2015). These potentially disastrous effects are further compounded by the fact that within the technologically advanced world of today, an infected individual can fly across the world in less than a day. Disease scares, which in recent years have included SARS, swine flu, and Ebola, are likely to increase. A recent study
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to the West Coast of the United States within three years (Sejvar, 2003). The reason? Mosquitos act as vectors for WNV, and the American robin, a common sight on lawns all across America, serves as the amplifier host for the mosquitos. Once the bird is bitten, it serves as a reservoir for WNV, and other mosquitos that bite the bird can carry the virus to humans when they bite them (Stephens, 2015).
at Brown University found that zoonotic disease outbreaks are increasing in total number and richness, but not in diversity or per capita cases, after analyzing 12,012 outbreaks of 215 infectious diseases over a 33-year period (1980-2013) (Smith et al. 2014).
What’s Being Done About It?
Another disease that has zoonotic regions and is specific to the East Coast area is Lyme disease. The cause of this disease is the human destruction of large contiguous forests. As human development expanded, predator populations of wolves, foxes, and hawks decreased, which resulted in an incredible five-fold increase in white-footed mice. The mice are the reservoirs for Lyme bacteria, likely due to the fact that they are unhygienic and do not have strong immune systems. According to Richard Ostfeld, the mice tend to produce huge numbers of impacted nymphs, which are immature forms of insects. Mice only remove about half of the larval ticks that spread Lyme disease during self-grooming, as opposed to nearly ninety percent for other animals such as gray squirrels. Indirect consequences of human expansion and development can result in zoonotic diseases in the most unimaginable ways.
Many governments are recognizing the necessity of addressing the role of ecology and the environment in public health, and have factored them into models. Key to these efforts includes public health awareness, public sanitation efforts, and infrastructure enhancement to improve health care responses. An example of an organization that tackles such issues is EcoHealth Alliance, based in New York City. It has pioneered the field of “conservation medicine,” a field that addresses the links between the ecological disruption of wildlife, domesticated livestock, and human health (EcoHealth Alliance, 2015). One of EcoHealth Alliance’s most exciting programs is the PREDICT program, which focuses on identifying and responding to new zoonotic diseases before they spread to humans. Scientists within this program test the wildlife that are most likely to be vectors, namely rodents, bats, and nonhuman primates, in countries across the world such as China, Brazil, and Indonesia. These countries have incredible swaths of biodiversity and are also in the midst of economic growth and expansion, leading to environmental issues. Blood is collected from a specimen, analyzed for disease, and the data is then added to a database that uses mathematical models to predict areas of potential zoonotic disease outbreak. Other ongoing EcoHealth Alliance initiatives include stopping the illegal wildlife trade; bat conservation and health; and the economics of treatment cost, reduction of labor supply, and losses in trade and tourism in areas of disease (EcoHealth Alliance, 2015).
Ultimately, the efforts of the people that work in disease ecology and organizations such as EcoHealth Alliance are not intended to rope off the environment to further human intrusion. The goal is rather to understand what drives the emergence of infectious diseases ecologically, so we can learn how to modify and utilize our environments effectively and sustainably. In the future, the increasing prevalence of infectious diseases from zoonotic origins will require a multipronged approach involving biologists, doctors and veterinarians, economists, sociologists and anthropologists, and others to tackle a constantly evolving problem. Perhaps the key to understanding zoonotic diseases is the acknowledgement that human health depends on biodiversity health, and that ignorance of the effects that our own environmental degradation has caused may come back to haunt us.
A Pressing U.S Domestic Concern It is important to realize that this issue is not just relegated to foreign countries in tropical regions. The threat of zoonotic diseases is very serious right here at home in the States. An example is West Nile Virus (WNV), a zoonotic disease that was first characterized in Uganda in 1937. In the years after its discovery, outbreaks were mainly contained in Northern Africa and the Mediterranean area (Sejvar, 2003). In 1999, cases of WNV in New York City were the first documented cases of the virus making an appearance in North America, and it spread all the way
Literature Cited 1. Dybas, Cheryl. "Research Areas." Ecology of Infectious Diseases: Overview: Infectious Diseases Spreading. NSF, n.d. Web. 14 Mar. 2015. 2. "EcoHealth Alliance." Home - EcoHealth Alliance. N.p., n.d. Web. 14 Mar. 2015. 3. Ostfeld, Richard. "The Ecology of Lyme-Disease Risk." American Scientist. N.p., 1997. Web. 14 Mar. 2015. 4. Robbins, Jim. "The Ecology of Disease." The New York Times. The New York Times, 14 July 2012. Web. 12 Mar. 2015. 5. Sejvar JJ. West Nile Virus: An Historical Overview. The Ochsner Journal. 2003;5(3):6-10. 37
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