Volume VII Issue I FALL 2021 by JUST Journal

Journal of Undergraduate Science & Technology

JUST VOL VII // ISSUE I // FALL 2021

Journal of Undergraduate Science & Technology

UW-Madison's only undergraduate STEM research & communication journal

is RECRUITING for SPRING 2022! editors | staff writers | designers and accepting submissions for: research reports | editorials | photographs

LETTER FROM THE EDITOR-IN-CHIEF Dear Reader, I am elated to present to you with Volume VII, Issue I of the Journal of Undergraduate Science and Technology (JUST). JUST is truly a campus wide effort and a celebration of not only the extraordinary research that takes place on this campus, but the work conducted by undergraduates specifically. I would like to extend my sincerest thanks to the undergraduate researchers who submitted their work along with the faculty and staff who supported them. I would also like to express my gratitude for the JUST staff that have chosen to make JUST a part of their undergraduate experience and worked diligently to bring you this publication. Additionally, without the generous support of the Wisconsin Institute for Discovery, the Holtz Center for Science and Technology Studies, the College of Agriculture and Life Sciences, and Associated Students of Madison, the publication of this journal would not have been possible. JUST’s mission has always been to support undergraduate researchers and make science accessible to broader audiences. At UW-Madison, we have been uniquely able to provide the opportunity for undergraduates to publish their work in a peer-reviewed journal and give students a glimpse into the publication process of an academic journal. On the other hand, our staff gain exceptional skills and experience the publication process from the perspective of a producer in a scholarly journal. We believe that these experiences are an invaluable supplement to a traditional undergraduate education, especially for those students who wish to continue research. As for the second part of our mission, I believe that scientific literacy is more important than ever in today’s advancing society. STEM topics have immersed themselves in all aspects of daily life, and all of our lives can only be enriched by a solid understanding of scientific thought. Effective communication of research and science is key to this. We are honored to be a small part in a much larger effort to make research and scientific achievement more accessible to non-expert communities beyond academia. In many ways, the space we occupy on campus mirrors the tenets of the Wisconsin Idea: that the influence of the university should better people’s lives outside of the classroom and across the state. We believe that by helping to train the next generation of researchers and assisting in the dissemination of scientific knowledge, JUST is helping to realize and advance the Wisconsin Idea. JUST has brought me incredible opportunities to work with and support talented peers. It has truly been an honor to be a part of this organization and continue to forward its mission. In this issue of JUST, you will find a wide range of scientific disciplines represented both by our peer reviewed reports and our shorter editorials as well as the visual pleasure of scientific imagery. Please join us in making it a tradition to recognize the incredible research and thoughtful written pieces presented by UW-Madison undergraduates, and in our larger pursuit to support science literacy.

Sincerely,

www.justjournal.org | contact@justjournal.org Aadhishre Kasat JUST Editor-in-Chief JUST VOL VII // ISSUE I // FALL 2021

TABLE OF CONTENTS

SPONSORS & PARTNERS

EDITORIALS EDITOR-IN-CHIEF Aadhishre Kasat MANAGING EDITOR Jaitri Joshi DIRECTOR OF MARKETING Hannah Landsly

We would like to sincerely thank the Integrated Studies in Science, Engineering, and Society Undergraduate Certificate Program [ISSuES] at UW-Madison; The College of Agriculture and Life Sciences [CALS]; The Wisconsin Institute for Discovery; the Associated Students of Madison (ASM) and Wisconsin Alumni Research Foundation for financially supporting the production of JUST’s Spring 2021 issue. Thank you!

6. A Remarkable Experience: Psychedelics as a Treatment for Mental Illness Britta Wellenstein

10. Can “poop transplants” make you lose weight? Mahak Kathpalia

14. Enlightening the Brain: How Optogenetics has Shaped Neuroscience Carter Wood

DIRECTOR OF DESIGN Ashley Harris

18. Healthy Forests Help Prevent Pandemics

WEBMASTER Louis Griffin

21. Slothful Slowness as a Strategy

EDITORS OF CONTENT Adina Shaikh Catherine Nguyen Dima Hamdan Lucas Chini Manasi Simhan Naba Rao

26. The Human Genome is Fully Mapped... Again?

Lydia Larsen

Leta Landucci

Natalie Martinson

29. The Truth About Blue Light Sarah Kamal

PIXELS

STAFF WRITERS Myra Mohammad, Head Staff Writer Tala Shaibi, Head Staff Writer Leta Landucci Britta Wellenstein Carter Wood Lydia Larsen Mahak Kathpalia Natalie Martinson Sarah Kamal

32. Catherine Nguyen

REPORTS The Journal of Undergraduate Science and Technology (JUST) is an interdisciplinary journal for the publication and dissemination of undergraduate research conducted at the University of Wisconsin-Madison. Encompassing all areas of research in science and technology, JUST aims to provide an open-access platform for undergraduates to share their research with the university and the Madison community at large.

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36. Current State of Air-Breathing Rocket Engine Reserach and Development Garrett Cobb

SCIENCE + SOCIETY: How to be creative and effective in a rapidly changing environment

JUST VOL VII // ISSUE I // FALL 2021

J demic, with a 20% increase in prescribed anti-depression and anxiety medication. Although these medications are beneficial, they often only work for two-thirds of patients (Ly et al.). As a result, scientists have resumed their investigations on how psychedelics can be used to treat mental illnesses.

PSYCHOLOGY

The Benefits of Psychedelics

A Remarkable Experience: Psychedelics as a Treatment for Mental Illness By Britta Wellenstein

"The full potential of psychedelics is still being actualized. Some studies suggest LSD could be used as a pain reliever and an alternative to opioid medication."

EDITORIAL

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magic, psychedelic chemicals. Many scientists saw them as a tool to combat mental illness at a time when other mental health treatments were not available. However, rising recreational use and increasing-anti-drug policies in the 1960s caused the United States Drug Enforcement Administration to make psychedelics a Schedule 1 drug, the harshest label a drug can have. This not only made the recreational use of the drug illegal but also halted all associated research. Today, we face an increasingly worse mental health crisis, especially amplified since the COVID-19 pan-

Therapeutic Practices

Figure 1. The image on the left is a placebo, while the image on the right is psilocybin. The lines represent links between certain neural communities in the brain. The connectivity in the psilocybin group (the right) has a significantly higher number of and stronger connections than those in the placebo group (the left). Source: Petri et al., 2014.

These cognitive changes that occur during a “trip” have convinced scientists to further investigate how psychedelics can be used therapeutically. One of the ways it can be harnessed is through psychedelic-assisted therapy. Patients are given a higher dose and assisted as they experience a “trip” with visual hallucinations. Medical professionals guide the patient through the hallucinations to ensure that the patient doesn’t experience a “bad trip.” One psychedelic fronting this research is psilocybin. A 2020 study at the Center for Psychedelic and Conscious-

EDITORIAL

In 1943, Albert Hofmann lived through what he called “a remarkable experience—both in its sudden onset and its extraordinary course.” Hofmann, a chemist, was working in his lab when he started to experience “an uninterrupted stream of fantastic pictures, extraordinary shapes with the intense, kaleidoscopic play of colors,” as he recorded in his journal. These images were brought on by accidentally ingesting lysergic acid diethylamide, better known as LSD, which he had been synthesizing in his lab. Put more simply; he was tripping on acid. This accidental discovery brought on a surge of interest and research into

Before Hofmann’s accidental trip, LSD was deemed an “unremarkable drug,” not useful as a medicine because of its lack of physical side effects. After the mental effects were discovered, over 1,000 studies investigating classical psychedelics pre-prohibition were conducted. Even in tests with high doses, LSD was continually seen to produce no adverse physical, toxic, or addictive effects, which has been validated by multiple studies today. Furthermore, in a systematic review of pre-prohibition psychedelic studies treating the mentally ill, almost 80% of patients’ health was seen to improve (Rucker, J., Iliff, J., & Nutt, D. 2018.). However, both the ban in 1967 and the stigma that followed caused many to overlook the benefits, seeing psychedelic use as a relic of the 1970s counterculture movement. Today, increased research into psychedelics has allowed these benefits to be realized. Other than LSD, there are many other forms of psychedelics that can potentially be used as therapeutics, such as MDMA (3,4-Methylenedioxymethamphetamine, or better known as molly and ecstasy), psilocybin (magic mushrooms), DMT, and ketamine. The basis for using psychedelics as a treatment for mental illness comes from how it affects one’s consciousness. Besides the hallucinations and sensory distortion that come during a “trip,” there are other cognitive impacts as well. Psychedelics can increase awareness of memories, traumas and create a feeling of connection to those around you. They can create

ego-dissolution, allowing one to look at life without their ego and subjective self. Such dissolution allows people to see past their problems, among other conscious changes. These cognitive changes can be physically seen in the brain too. Figure 1, from the Journal of Royal Society, shows the new connections formed after using psilocybin. This demonstrates how these drugs promote neural plasticity, which is the rearrangement and growth of neural networks in the brain. These changes and growth in neural connections can explain the visual hallucination experienced when on psilocybin and the shift in thinking that occurs after its consumption. These new connections can help mental health patients better understand their emotions and trauma. The neural changes and new connections create a “reset” of the initial, possibly problematic patterns of thinking, creating a different outlook even after the drug wears off. It’s almost like “rebooting a computer,” as put by Dr. Jerrold Rosenbaum, direct of the Center for the Neuroscience of Psychedelics at Massachusetts General Hospital (Grinspoon, 2021). These findings are especially important when looking at mental disorders’ impact on the brain. Take depression, for example. One of the biggest physical markers of depression is decreased neuron size in the pre-frontal cortex and retraction of dendritic spines (Ly et al., 2018). However, psychedelics are seen to reverse these effects, increasing dendrite spines. Medically combating depression, PTSD, and other mental illnesses involves finding chemicals that can reverse these deteriorations and promote neuroplasticity, which psychedelics do. In comparison to the anti-depressants on the market right now, psychedelics work differently and possibly more effectively. Current anti-depressants, most of which are selective serotonin reuptake inhibitors, work to alleviate and mask the effects of depression and can take months to have any measurable impact. Psychedelics, on the other hand, can eradicate the source of the problem by promoting the rearrangement and growth of neural networks, which can nip unhealthy patterns of thinking in the bud (Kim, 2021).

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J ness Research in Baltimore, Maryland, utilized psilocybin as therapeutic support in people with major depressive disorder (MDD). During the psilocybin sessions, patients were taken to a comfortable environment, asked to lay on a couch, and describe what they were experiencing to medical professionals. After two sessions, this intervention produced profound results, with lasting and rapid anti-depressive effects. These effects are 2.5 times greater when compared to psychotherapy. Psilocybin is also non-addictive and presents a few negative sides effects, like small headaches. Typical anti-depressants can have much more severe side effects, like increased suicidal ideation, and take much longer to positively impact the patient (Davis et al., 2021). MDMA also shows promising results as a therapeutic for post-traumatic stress disorder (PTSD). Currently, there are no substantial treatments on the market for PTSD. Selective serotonin reuptake inhibitors anti-depressants can be used but are seen to be resistant with 40-60% of people. A 2021 study gave subjects three MDMA-assisted therapy sessions over 18 weeks and found significant decreases in depressed moods and overall PTSD symptoms. MDMA can create a “window of tolerance,” where patients can look at past traumatic events without as much anxiety or fear as before. After three sessions, patients saw significantly fewer symptoms. Some even went into remission, meaning they lost their diagnosis and had a low CAPS-5 score, a measurement for PTSD severity, as Figure 2 shows. Considering the limited treatment options for those with PTSD and the hundreds of millions that suffer from it annually, MDMA-assisted therapy is a glimmer of hope (Mitchell et al., 2021). University of Wisconsin-Madison’s new Transdisciplinary Center for Research in Psychoactive Substances in

the School of Pharmacy and the Usona Institute in Madison deals directly with these drugs, aiming to get their therapeutic use approved by the FDA. Currently, they have a Phase 2 clinical trial for using psilocybin to treat MDD, in which patients are given 25mcg of psilocybin under the supervision of trained professionals. This clinical trial is scheduled to end in 2022(Kim 2021). University of Wisconsin-Madison’s MDMA and PTSD trial is currently in Phase 3 and is scheduled to finish in 2023 (Kim, 2021). This isn’t to say these drugs don’t have their risk. For starters, although many studies studying the use of psychedelics as therapeutics are underway, we don’t know all their impacts on the body. Although they are generally non-addictive and safe, they still are strong hallucinogens and could produce adverse, negative experiences under certain conditions. Therefore, taking high doses of MDMA or psilocybin must be done under medical and psychiatric supervision to ensure it says a positive experience. However, considering the increasingly worse mental health crisis in this country and on the University of Wisconsin-Madison’s campus, finding new ways to combat mental heathy is essential.

EDITORIAL

Davis, A. K., Barrett, F. S., May, D. G., Cosimano, M. P., Sepeda, N. D., Johnson, M. W., ... & Griffiths, R. R. (2021). Effects of psilocybin-assisted therapy on major depressive disorder: a randomized clinical trial. JAMA Psychiatry, 78(5), 481-489 Mitchell, J. M., Bogenschutz, M., Lilienstein, A., Harrison, C., Kleiman, S., Parker-Guilbert, K., ... & Doblin, R. (2021). MDMA-assisted therapy for severe PTSD: a randomized, double-blind, placebo-controlled phase 3 study. Nature Medicine, 27(6), 1025-1033. Ly, C., Greb, A. C., Cameron, L. P., Wong, J. M., Barragan, E. V., Wilson, P. C., ... & Olson, D. E. (2018). Psychedelics promote structural and functional neural plasticity. Cell reports, 23(11), 3170-3182.

Grinspoon, P. (2021, June 22). Back to the future: Psychedelic drugs in psychiatry. Harvard Health. Petri, G., Expert, P., Turkheimer, F., Carhart-Harris, R., Nutt, D., Hellyer, P. J., & Vaccarino, F. (2014). Homological scaffolds of brain functional networks. Journal of The Royal Society Interface, 11(101), 20140873. Kim, A. (2021, August 16). New UW Center to study emerging field of psychedelic compounds for medical treatments. University of Wisconsin-Madison School of Pharmacy.

The full potential of psychedelics is still being actualized. Some studies suggest LSD could be used as a pain reliever and an alternative to opioid medication. It also could be used to treat addiction, especially alcoholism. The future of this field is vast and exciting. The University of Wisconsin-Madison’s new Transdisciplinary Center for Research in Psychoactive Substances demonstrates these substances' therapeutic potential, which is a call for triumph.

EDITORIAL

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Carhart-Harris, R. (2020, June 8th). “We can no longer ignore the potential of psychedelic drugs to treat depression.” The Guardian.

Rucker, James J.H., Iliff, Jonathan, and Nutt, David J. 2018. “Psychiatry & the psychedelic drugs. Past, present & future,” Neuropharmacology, Volume 142, Pages 200-218, ISSN 0028-3908,

Figure 3: University of Wisconsin-Madison’s School of Pharmacy room used for testing these treatments. It is designed to be a comfortable and “safe place for patients.” Source: Kim, 2021.

Figure 2: There is a decrease in symptoms after patients are treated with MDMA-assisted therapy, as compared to the placebo patient group. Source: Mitchell et al., 2021.

References:

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J HEALTH

Figure 1. Changes in the Firmicutes/Bacteroidetes (F/B) ratio can cause obesity. Source: Stojanov et at., 2020

What do we know about these “life-saving bacteria”?

What does ongoing research show?

The human microbiome is composed of bacteria, archaea, viruses, and many other microbes that live in and on our bodies. These “good” microorganisms assist in various metabolic functions, protect the body against patho-

The effect of the gut microbiome’s composition on the likelihood of suffering from obesity sparked researchers’ interest in the concept of outsourcing an “enhanced” microbiome to reverse the effects of a poor mi-

Can “Poop Transplants” Make You Lose Weight? By Mahak Kathpalia

"To answer this question, you might just have to trust your gut!"

EDITORIAL

Around one in every three individuals across the globe are either obese or overweight. According to the Centers for Disease Control and Prevention, the United States comprises the highest proportion of this population, with an all-time high obesity rate of 42.4% (Galvin, 2020). There is no denying that the country’s healthcare has been struggling to combat this rising epidemic for the past two decades now. So, how do we move forward? Aside from recommending a healthier lifestyle, medical professionals and researchers believe that innovating more effective pharmacological therapies to treat obesity is the need of the hour. One such fascinating and novel option is 10 JUST VOL VII // ISSUE I // FALL 2021

crobe composition and potentially prevent diseases like obesity. In 2014, a study extracted gut bacteria from a pair of twins – one obese and one lean - and monitored its effects on a group of recipient mice once they got the respective human fecal matter transplanted (Ridaura et al., 2013). It was observed that mice that received the transplant from the obese twin’s microbiota displayed increased body weight and mass. In another study, the transfer of gut bacteria from mice who have undergone bariatric surgery (gastric bypass and other weight-loss surgeries) to germ-free mice led to decreased body fat (Basulto, 2016). These studies show the association between body mass and the constitution of the gut microbiome and how it can be altered artificially. This concept is actually not as new as it may seem; people have been using gut bacteria to induce weight gain in farm animals for a very long time (Tennant, 2016). Lately, scientists have been attempting to understand how this research in model organisms could be extended to humans. In fact, fecal transplants via colonoscopies are already being performed to treat C. difficile colitis (inflammation of the inner lining of the colon). However, its prospects regarding obesity are still being studied. Fecal transplants in humans were first performed in 2012 by Dutch researchers that showed moving a lean donor’s microbiota to the guts of obese men improved their suppressed sensitivity to insulin and influenced body mass. Even more recently, another small study at the Brigham and Women’s Hospital led by Dr. Jessica R. Allegretti, a professor at the Harvard Medical School, found that administering fecal transplants orally via cap-

EDITORIAL

conducting “fecal transplants.” Yes, you read it right! Many ongoing and past studies show that transplanting gut bacteria from the stool sample of a healthy, lean individual may be an extremely efficient remedy, despite how absurd it may sound.

gens by helping the immune system distinguish between the self and non-self, and directly or indirectly impact the health of several different parts of the body. The largest component of this unique organ system is located in the cecum, a “pocket” in the large intestine, called the gut microbiome (Robertson, 2017). The gut microbiota’s diversity and composition are found to be correlated to the individual’s susceptibility to obesity (Davis, 2016). A favorable ratio of two types of bacteria, in particular, Bacteroidetes and Firmicutes, are known to help maintain internal homeostasis, a state of steady physical and chemical conditions (Stojanov et al., 2020). Research suggests that people with obesity contain tinier amounts of Bacteroidetes and larger amounts of Firmicutes, disrupting the ratio of compounds produced by these two bacterial families required to maintain the intestine at equilibrium for digestion (Tseng & Wu, 2019). The imbalance of Firmicutes and Bacteroidetes can dysregulate appetite and fat storage by negatively affecting processes that harvest energy from consumed food sources. Moreover, in overweight/obese people, the gut microbiota is also more likely to produce compounds that, when absorbed and circulated in the body, contribute to complications like inflammation and insulin resistance (a hormone that regulates blood sugar concentration) which causes diabetes (Tseng & Wu, 2019).

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J other infections or medical risks in the recipient. Moreover, there has been quite some debate on the status of such treatment in terms of whether it should be treated as a “drug” or a “tissue,” which would affect national and international regulations. Lastly, no matter how sophisticated the manufacturing of such medication is, the thought of getting someone’s fecal matter infused into your body sounds nasty and repulsive to most people (Lagier, 2014). Changing this preconceived narrative would also require effective and systematic communication with patients. So, can “poop transplants” actually be used as a weight-loss strategy in the near future? To answer this question, you might just have to trust your gut! References: Basulto, D. (2016, January 14). Eating poop pills could make you thin. seriously. The Washington Post. Cassella, C. (2021, July 7). Poop transplants have been linked to improved COVID-19 in two patients in Poland. ScienceAlert. Davis C. D. (2016). The Gut Microbiome and Its Role in Obesity. Nutrition today, 51(4), 167–174. Galvin, G. (2020, February 27). U.S. obesity rate passes 40 percent. U.S. News. Lagier, J. C. (2014). Faecal microbiota transplantation: From practice to legislation before considering industrialization. Clinical Microbiology and Infection, 20(11), 1112–1118. O’Connor, A. (2019, September 27). Researchers turn to ‘poop pill’ in search of cure for obesity. The Irish Times.

Figure 2: Fecal transplant therapy: taking healthy stool from a donor and processing and delivering it to a sick recipient. Source: Shutterstock

EDITORIAL

What could this mean in the future? Fecal transplant techniques have come a long way, even though the research is still in its infancy stage. Currently, the only accepted routes for delivering bacteria are into your gut by a colonoscopy or through a plastic tube nasally. New techniques are constantly evolving, tested, and expanded for use in multiple gastrointestinal issues 12 JUST VOL VII // ISSUE I // FALL 2021

like obesity. “I can imagine a universe in the not-too-distant future where a microbial treatment can complement diet and exercise to deeply impact the obesity epidemic,” says Zain Kassam, chief medical officer at OpenBiome, a non-profit organization that supports such research and operates a public stool bank (Basulto, 2016). However, even if fecal microbiota transplantation gets widely approved and accepted as a form of therapy, numerous factors need to be considered before it can be implemented industrially on a large scale. There are concerns regarding the holistic clinical examinations and biological screening of stool samples from donors to prevent

Robertson, R. (2017, June 27). Why the gut microbiome is crucial for your health. Healthline.

EDITORIAL

sules led to positive changes in the production of bile acids and other liver digestive aids that help break down fat molecules in obese patients (O’Connor, 2019).

Ridaura, V. K., Faith, J. J., Rey, F. E., Cheng, J., Duncan, A. E., Kau, A. L., Griffin, N. W., Lombard, V., Henrissat, B., Bain, J. R., Muehlbauer, M. J., Ilkayeva, O., Semenkovich, C. F., Funai, K., Hayashi, D. K., Lyle, B. J., Martini, M. C., Ursell, L. K., Clemente, J. C., … Gordon, J. I. (2013). Gut microbiota from twins discordant for obesity modulate metabolism in mice. Science, 341(6150).

Stojanov, S., Berlec, A., & Štrukelj, B. (2020). The influence of probiotics on the Firmicutes/bacteroidetes ratio in the treatment of obesity and inflammatory bowel disease. Microorganisms, 8(11), 1715. Tennant, M. (2016, December 1). Fecal microbiota transplantation: The future of feces. Yale Global Health Review. Tseng, C.H., & Wu, C. Y. (2019). The gut microbiome in obesity. Journal of the Formosan Medical Association, 118. JUST VOL VII // ISSUE I // FALL 2021 13

J brain cells (Barth, 2019; Adams, 2014). All of this needed to be accomplished without triggering any immunological response from the test subject, which would potentially shut down this novel invader (Barth, 2019). To achieve this, Deisseroth turned to a specialized protein called opsin. Opsins are proteins unique to single-celled organisms and function similarly to human neurons. When opsins are activated, a cellular channel that is present within their interiors opens, and the movement of chemical ions through the channel can occur. Consequently, this allows for neural functioning to commence. Found in green algae, the most important attribute of opsin proteins is their activation trigger: light (Adams, 2014).

NEUROLOGY

Figure 1. Francis Crick, world-renowned scientist, and co-founder of the structure of DNA. Source: CC BY-SA 2.5.

Enlightening the Brain: How Optogenetics has Shaped Neuroscience By Carter Wood

"This groundbreaking scientific advancement could potentially be used to help treat and possibly someday cure mental illnesses that devastate lives."

EDITORIAL

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Crick’s idea remained just that for decades: an idea. Science and technology were not advanced enough to undertake such a prospect. That is, however, until the arrival of Dr. Karl Deisseroth, MD, Ph.D. (Adams, 2014). In 1998, Deisseroth was in his third year at Stanford Medical School completing his psychiatry rotation, when he witnessed something that would change his career path forever. In the hospital beds lay several patients awaiting their turn to undergo electroconvulsive therapy. Electroconvulsive therapy (ECT) is used as a treatment for depression in which electrodes are stuck onto

Figure 2. Dr. Karl Deisseroth, MD, Ph.D. Source: AP images for Howard Hughes Medical Institute. Opsin science is not new. Natural examples of the opsin protein have been known since 1971 when Stoeckenius and Oesterhelt discovered an opsin protein, bacteriorhodopsin, which can act as an ion channel when stimulated by green light. Since then, several other opsin proteins have been found that work analogously, such as halorhodopsin (activated by yellow light) and channelrhodopsin (activated by blue light) (Deisseroth, 2010). The latter of these two would become the solution to Deisseroth’s light sensitivity problem. Produced by the microbe Chlamydomonas reinhardtii, the opsin protein channelrhodopsin-2 (ChR2) became the basis for Deisseroth’s optogenetic research. The thought was that ChR2 would be placed inside neurons, opening and closing ionic channels in a manner that the neurons cannot. This would allow scientists to activate and deactivate the neuron, using light, at will (Adams, 2014). To integrate the opsin protein into specific neurons, Deisseroth’s team manipulated HIV, removing all

EDITORIAL

Francis Crick, a world-renowned scientist, received the 1962 Nobel Prize in Physiology and Medicine. In 1979, he proposed that the biggest hurdle in neuroscience is a lack of tools that can control cranial neurons and manipulate their function (Barth, 2019; Deisseroth, 2010). Neurons are cells located in the brain responsible for conducting electrical impulses that control the human nervous system. Crick believed in order to influence these cells; scientists need to harness a tool with impeccable speed and precision. This tool, Crick alleged, was light (Barth, 2019).

the patient’s temples, and small electrical shocks are sent through the brain, seizing it and “resetting” the patient’s neurons. If done correctly, this treatment can temporarily cure depression for up to months at a time (Barth, 2019). As a neuroscience expert in brain physiology and neural communication, Deisseroth was perplexed by how someone could intentionally inflict such catastrophic damage on a patient’s wellbeing. He began thinking about how other less painful treatments could be developed, which led him to a psychiatric residency. In 2004, he decided to further explore this question as a Principal Investigator of a research laboratory at Stanford University (Barth, 2019). He dove deep into what he believed to be the answer to his long-asked question regarding the complexity of mental health: optogenetics (Barth, 2019). According to Lim and Ledue (2017), optogenetics is defined as “A method for controlling a neuron’s activity using light and genetic engineering.” Simply speaking, Deisseroth hoped to engineer a method that could switch neurons on and off using light, as first proposed by Crick. This task was not straightforward; Deisseroth needed to overcome several arduous challenges. To begin, he needed to find a light-sensitive organism that can couple with non-light-sensitive neurons and elicit desired control responses. Before Deisseroth could find a safe way to shine a light on such an organism without destroying brain matter, he needed to find a transportation method to insert the light-sensitive organism within

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J increasingly brave, less anxious, and more likely to engage in riskier behavior compared to mice without any optogenetic interference. This experiment indicates potential future treatments for anxiety and depression using optogenetics. This groundbreaking scientific advancement could potentially be used to help treat and possibly someday cure mental illnesses that devastate lives. Optogenetics has already been used to study neurological pathways associated with diseases such as Parkinson’s, addiction, anxiety, depression, and a wide range of other mental illnesses and is recognized as one of the most important neurological discoveries ever (Adams, 2014). According to Rob Malenka, optogenetics has “Revolutionized science…[and] has allowed neuroscientists to manipulate neural activity in a rigorous and sophisticated way and in a manner that was unimaginable 15-20 years ago.” (Adams, 2014), and is undoubtedly a tool that will help shape the future of neurological medicine.

References: Barth, A. (2019, October 18). Controlling Brains With a Flick of a Light Switch. Discover Magazine. Deisseroth, K. (2010, December 20). Optogenetics. Nature Methods. Howard Hughes Medical Institute. (n.d.). Dr. Karl Deisserth, MD, Ph.D. [Photograph]. Howard Hughes Medical Institute. Lim, D. H., & LeDue, J. (2017, September 20). What Is Optogenetics and How Can We Use It to Discover More About the Brain? Frontiers for Young Minds. Pittalwala, I. (2020, July 24). Neurons [Illustration]. Neurons Are Genetically Programmed to Have Long Lives. Saper, C. B. (2001, December 24). The sleep switch: hypothalamic control of sleep and wakefulness. PubMed. Adams, A. A. (2014). Stanford’s Karl Deisseroth wins Keio Prize in Medicine. Stanford News.

Figure 3. Neural pathways in the brain. Source: Shutterstock.

EDITORIAL

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became immune to the high and were completely unaffected by the drug, indicating a potentially groundbreaking method in the treatment of addiction (Barth, 2019). In another experiment, the optics cable was implanted into the amygdala of the mouse, part of the brain associated with fear and anxiety responses. When the neural pathway involved with these fear responses was deactivated using optogenetics, the mouse became

Figure 4. Common functionality of opsin proteins. Source: Henry Yin

EDITORIAL

dangerous genes of the virus and replacing them with ChR2. This modified HIV was then used to shuttle the ChR2 protein into the neuron, where it was replicated by the neuron itself, completely avoiding immunological detection (Barth, 2019). As a result, neurons were genetically engineered to produce the opsin protein (Adams, 2014). Once the opsin was integrated within the neuron, the true experiment began. Deisseroth’s team surgically implanted a fiber optics cable into the test mouse’s brain, connecting it to a mini laser attached to the mouse’s head and a computer to measure neural activity. The cable was embedded deep into the mouse’s hypothalamus, part of the brain filled with neurons that produce a neuropeptide called hypocretin, a signaling molecule involved in wakefulness (Saper, 2001). Amazingly, the researchers found that they were able to activate and deactivate hypocretin production on command with light. When the light was turned on, the mouse began to stir and wake up, showing that the neurons embedded with ChR2 were activated when exposed to light. Due to the extraordinary success of the initial trial, Diesseroth’s team soon set their sights on using this science to investigate Deisseroth’s initial driving goal: mental illness (Barth, 2019). Since the initial experiment with the sleeping mouse, optogenetics has been used in a variety of successful endeavors by Diesseroth. In one such study, Diesseroth exposed mice to cocaine, but with targeted optogenetic yellow light, he was able to deactivate the neural pathway associated with addiction. As a result, the mice

Yin, H. (2015). Schematic Illustration of Common Opsins. Figure 1 [Illustration]. Research Gate.

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J ENVIRONMENT

Figure 1: Bats are associated with several emerging infectious diseases, including SARS, COVID-19, and MERS. Source: NC State University.

Healthy Forests Help Prevent Pandemics By Lydia Larsen

"Finding better ways to address all aspects of emerging infectious diseases will require a multifaceted approach; connecting the dots between biodiversity loss & EIDs is a worthy starting point." If you look at the front page of any newspaper within the last year and a half, you will likely see some headline on COVID-19. With COVID-19 being so ubiquitous, it’s hard to remember a time without masks, social distancing, and wall-to-wall COVID-19 coverage. But have you ever wondered where novel viruses come from? Do these contagions come from people, research labs, or nature? We usually only hear about emerging infectious diseases when they appear in humans. Where was the SARS-CoV-2 virus that causes COVID-19 before it started spreading within human 18 JUST VOL VII // ISSUE I // FALL 2021

communities? A deeper dive revealed that many emerging infectious diseases (EIDs) are linked to the health of our planet and deforestation. Deforestation has long been part of discussions on global warming, biodiversity loss, and endangered species. However, research highlighting its role as a catalyst in the spread of viral infections has only recently made headlines. Meanwhile, epidemiologists have long acknowledged the relationship between infectious disease transmission from animals to humans and the rise in deforestation. Such re-

Deforestation and Disease Spillover Confrontations between animals and humans increase when humans encroach on previously undisturbed wild habitats, often to build roads or clear land for farming. As humans move into previously undisturbed habitats, there is an increase in human and wildlife contact in an area epidemiologists call the edge. The edge (Figure 2), the area where human and wild populations meet, is where disease spillover occurs. As humans have been moving into these habitats at increasing rates, there has been an increase in pathogen spillover from wild animals to human communities. Such human interference has also fragmented and eliminated an increasing number of habitats (Daszak et al., 2021). These concurrent phenomena impact the rate of pathogen transmission. The frequency of these spillover events is dependent on the pathogen and the size of the surrounding human population, but mathematical models created by epidemiologists show some general trends. The highest probability of outbreak occurs at intermediate levels of human land conversion, this is when there is a relatively high human population residing by a significant edge. Trends show that the possibility of spillover declines as the edge between disease-carrying wildlife and humans becomes smaller. However, while the spillover rate is low, any diseases that make it into the human population are the most devastating due to the high-density human population residing in the area (Faust, 2018). Furthermore, displaced wild animals often move into new habitats when theirs are destroyed. An outbreak of the Nipah virus in Malaysia in (1997-1998) was caused by the

EDITORIAL

Origin of Emerging Infectious Diseases

search has finally gained traction during the rise of the COVID-19 pandemic. EIDs often only make the news after circulating among humans, but most actually come from other animals. According to a study in Nature, 60% of total emerging infectious diseases from 1940 to 2004 originate in animals, 71% of which come from wildlife. Even when considering mitigating factors, data indicates that the number of EIDs coming from wildlife has increased over time with a peak in the 1980s, possibly due to the AIDs epidemic (Jones et al., 2008). It may seem as though diseases attack humans spontaneously, but the jump from wildlife to humans is not instantaneous. Pathogens that originate in animals need to evolve before they can subsist solely in a human host (Wolf et al., 2007). For example, hantavirus pulmonary syndrome (HPS) is caused by a type of virus that coevolved in rodents. People only become sick from this virus when they encounter rat droppings. However, once they become sick, an infected person can’t pass the virus to another human (Morens et al., 2004). On the other hand, diseases such as HIV, since emerging from chimpanzees, have evolved such that now they can only be transmitted through humans. (Morens et al., 2004). These viral links from animals to humans can and do have catastrophic effects and are deserving of more study. EIDs starting in animals can be the deadliest and most disruptive among humans. Sars-CoV-2 is hypothesized to have originated from bats (Figure 1), transmitted through other animal species, and passed onto the human population (Burki, 2020). A recent preprint, a paper that has not been peer-reviewed, found a virus remarkably similar to Sars-Cov-2 in a population of bats in Laos. This virus could attach to human cells as effectively as the earlier variants (Malapaty, 2021).

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J may result in better world health outcomes. If we have learned anything from COVID-19, it is that being subject to the whims of a devastating and prolific virus is not feasible in the long term. Finding better ways to address all aspects of emerging infectious diseases will require a multifaceted approach; connecting the dots between biodiversity loss and EIDs is a worthy starting point.

ECOLOGY

References: Burki, T. (2020). The origin of SARS-CoV-2. The Lancet Infectious Diseases, 20(9), 1018-1019.

Figure 2: Deforestation creates an edge where wildlife to human disease transmission can occur. Source: Greenpeace. clearing of a rainforest containing high levels of biodiversity. As a result, the bat species in the forest moved into fruit orchards near industrial factory farms. The bats spread the Nipah virus to pigs in the large farms, which then spread the disease further into the residing human population. Through cross-species transmission, researchers predict the virus had a 40% mortality rate among humans (McNeely, 2021). As in many EID cases, there is often an intermediate species between the original pathogen-host and humans. In the context of COVID-19, the virus likely originated in bats, spread through frequently occurring illegal wildlife trade to humans (McNeely, 2021). What Next?

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Faust, C. L., McCallum, H. I., Bloomfield, L. S., Gottdenker, N. L., Gillespie, T. R., Torney, C. J., ... & Plowright, R. K. (2018). Pathogen spillover during land conversion. Ecology letters, 21(4), 471-483. Jones, K. E., Patel, N. G., Levy, M. A., Storeygard, A., Balk, D., Gittleman, J. L., & Daszak, P. (2008). Global trends in emerging infectious diseases. Nature, 451(7181), 990-993. Mallapaty, S. (2021). Closest known relatives of virus behind COVID-19 found in Laos. Nature, 597(7878), 603-603. McNeely, J. A. (2021). Nature and COVID-19: The pandemic, the environment, and the way ahead. Ambio, 1-15. Morens, D. M., Folkers, G. K., & Fauci, A. S. (2004). The challenge of emerging and re-emerging infectious diseases. Nature, 430(6996), 242-249. Wolfe, N. D., Dunavan, C. P., & Diamond, J. (2007). Origins of major human infectious diseases. Nature, 447(7142), 279-283

Slothful Slowness as a Strategy Assembling Evolution’s Cryptic Clues By Leta Landucci

"Being marvelously slow has allowed the sloth to settle into an evolutionarily strategic, energy-saving arboreal life. The sloth it seems, simply has no need for speed." Sloths are marvelously bizarre and fascinating creatures. There are two different types: the two-toed sloth (Figure 1) and the three-toed sloth. Within these two genera are six species, which all live in the warm and tropical environments of Central and South America (Kaup et al., 2021). Even if you know very little about sloths, you’ve likely learned that they are incredibly slow, so slow that their lives seem to occur in slow-motion. This characteristic has confounded many: how and why are sloths so incredibly slow? The answer comes down to the peculiar workings of evolution and its creative solutions to confront challenge and change. As described by Lucy Cooke, the founder of the Sloth Appreciation Society, sloths are “one of natural selection’s quirkiest creations, and fabulously successful

to boot” (Cooke, 2018). Sloths have settled into a lethargic and lackadaisical pace of life because somehow, being slow has lent itself to survival. Scientists have begun to piece together evolutionary clues to understand why being slow is advantageous and how this may help to explain other sloth behaviors, their unique physiology, and ecological interactions. Slothful slowness as a strategy - metabolic constraints: The sloth is, indeed, remarkably slow. Sloths average a leisurely cruising speed of about 0.2 miles per hour, a pace “unlikely to challenge even a tortoise” (Cooke, 2018). Scientists have attributed this pacing to slot’s unique JUST VOL VII // ISSUE I // FALL 2021 21

EDITORIAL

Current pandemic preparedness policies advocate for testing, personal protective equipment stockpiling, and vaccine and therapeutic development. Unfortunately, these approaches address pandemics only after they emerge and infect large swaths of people. At the same time, the development of therapeutic drugs relies heavily on organisms and molecules found in a healthy and biodiverse environment. Therefore, the destruction of varied habitats could ultimately destroy a potential therapeutic medicine. Coupled with the fact that these therapeutics rely on indigenous medicine, and indigenous populations are often most affected by deforestation and biodiversity loss, the impetus for protecting our forests has become more important than ever. Concurrently, certain practices in the wildlife trade require better monitoring and enforcement to reduce disease emergence in human populations. Deforestation and biodiversity loss can be mitigated by investing in sustainable farming and more responsible meat consumption globally (Daszak et al., 2021). We can better develop EID monitoring and prevention practices using the knowledge we have gathered on the effects of environmental changes and biodiversity loss. Developing an integrated approach to monitoring potential EID reservoirs can help streamline the process and provide efficient updates on disease outbreaks that

Daszak, P., das Neves, C., Amuasi, J., Haymen, D., Kuiken, T., Roche, B., ... & Ngo, H. T. (2020). Workshop Report on Biodiversity and Pandemics of the Intergovernmental Platform on Biodiversity and Ecosystem Services.

Figure 1: A two-toed sloth in Costa Rica. Source: Marika, licensed under CC BY-NC 2.0 metabolism. Around 12,000 years ago, giant ground sloths, distant relatives of modern-day sloths, roamed much of South and North America (Bradford, 2016). These giant ground sloths were massive, often weighing over two tons. These gigantic creatures galumphed around, foraging leaves and fruit from trees by standing on their hind legs, and may have also eaten scavenged meat (Tajada et al., 2021). Researchers think their diet changed dramatically as sloth ancestors transitioned from a life on the ground to an arboreal habitat (living in the trees). A diet of leaves - a Snickers bar of energy to spend:

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of invisibility” that allows the sloth to easily vanish from sight in the rainforest canopy, evading potential predators (Cooke, 2018; Kaup, 2021; Cliffe, 2016). It is also possible that the algae growing prolifically in sloth fur provide a food source for some of the insects in this coat ecosystem, which in turn may return nutrients like nitrogen with their fecal excrement and decomposition (Kaup, 2021; Cooke, 2018). In other words, researchers speculate that insects may effectively “farm” slothfur algae (Kaup, 2021). Meanwhile, sloths may act as slowmoving vectors of dispersal for microbes, insects, fungus, and algae through different layers of the forest, connecting and transporting organisms between different ecological niches, serving as a genetic and biotic “taxicab” (Kaup, 2021). The organization of these sloth-fur communities is thought to be partially dependent upon the slowness of sloths and temperature regulation, another strategy used by sloths to conserve energy. Sun basking sloths - strategies of thermoregulation:

Sloths are miniature mobile ecosystems: Recent research has begun to explore how sloths act as mobile, miniature ecosystems by carrying entire microcosmic worlds within their fur. It’s almost like the strands of their fur make a prairie or forest, inhabiting countless organisms, all organized in layers, and contributing to a complex food web of predators, prey, and detritivores (organisms that feed on dead organic material) (Kaup et al., 2021). Sloth fur is teeming with a slew of insects, including moths, beetles, mites, and ticks, making up a largely selfcontained community (Kaup 2021). Sloth moths of the genus Cryptoses are completely dependent on sloths, forming a tight life-cycle association (Figure 2) (Kaup, 2021; Cooke, 2018). When sloths descend to the forest floor to defecate, female moths lay their eggs in

Figure 2: The sloth, moth, algae lifecycle. Sloths descend the tree to defecate. Sloth moths lay eggs in the dung pile. After the eggs hatch, the moths fly up to live in sloth fur where they defecate and provide vital nutrients to algae growing on hair. Source: Wildreturn, licensed under CC BY 2.0

Figure 3: The Sloth Moth (Cryptoses choloepi), well camouflaged in the grey-brown fur of a three toed sloth (Bradypus variegatus). Source: Kaup et al., 2021 the feces, upon which hatched larvae proceed to feed (Kaup, 2021). After maturing, these moths fly from the dung pile into the forest canopy in search of a new sloth host (Figure 3) (Kaup, 2021). Sloths are considered a crawling, climbing, mobile island of biodiversity (Cooke, 2018). One study reported a single sloth harboring within its coat “nine species of moth, six species of tick, seven species of mite and four species of beetle, including 980 individuals from just one of those beetle species”, which is absolutely mind-boggling! (Cooke, 2018). Additionally, strands of sloth fur possess specialized grooves (Figure 4) that are thought to help collect and retain water to act as hydroponic gardens for dozens of different

Figure 4: Scanning electron micrographs of sloth hairs. (A) Bradypus variegatus (brown-throated three-fingered sloth). (B) Choleopus hoffmanni (Hoffmann's two-fingered sloth) hair. Algae grow within the deep horizontal cracks and long lengthwise grooves. Source: Kaup et al., 2021 species of algae and fungi (Figure 4). These species grow along hair surfaces, giving sloths a distinct green hue (Figure 5). This has been suggested to provide a camouflaged “cloak

Figure 5: Sloth hair tinted with green algae and cyanobacteria. Source: SqueakyMarmot, licensed under CC BY-SA 2.0 Cold-blooded creatures like reptiles and amphibians cannot regulate their temperature independently from the environment, so they resort to absorbing solar energy or retreating to the shade (Cliffe, 2016 & 2018). Meanwhile, most mammals are considered homeotherms, which means that they can maintain a constant body temperature by producing heat via metabolism (Cliffe, 2016 & 2018). However, this type of thermoregulation is energetically expensive – especially for a sloth that has only a Snickers bar worth of energy to spend per day (Cliffe, 2014, 2016 & 2018). Therefore, because of their extremely slow metabolic rate, sloths seem to have adopted a hybrid approach, operating at a lower body temperature than most other mammals and moving between different layers of the forest canopy, either to warm up in the sun or cool off in the shade (Cliffe, 2018). Researchers suggest that the multitude of organisms inhabiting the “grasslands” of sloth hair are “organized JUST VOL VII // ISSUE I // FALL 2021 23

EDITORIAL

Modern-day sloths primarily eat tree leaves, which are poor in nutrients. This means that the caloric intake of sloths is minimal, averaging around 160 calories per day, which is equivalent to a single Snickers bar (Dowling, 2019; Cliffe et al., 2018; Cooke, 2018). Additionally, the leaves that sloths consume contain toxic secondary plant metabolites, which require extensive digestion (Cliffe et al., 2018). The sloth is equipped with a large multichambered fermentative stomach which allows it to digest and tolerate the strong chemicals of the foliage they eat (Mesquita, 2020; Dowling, 2019). However, digestion by fermentation takes a very long time, especially to process plant materials, roughly estimated to be between 7 to 50 days. This translates to a very low metabolic rate; as a result, sloths have one of the lowest metabolic rates of non-hibernating animals (Cliffe et al., 2018 & 2015; Kaup et al., 2021; Cooke, 2018). Having a diet strictly of leaves imposes “severe energetic constraints” because the sloth’s slow rate of digestion limits its “rate of energy acquisition” (Cliffe et al., 2018). Since sloths cannot produce usable energy quickly, they need to be very careful in how they expend it. This principle of energy conservation forms a founding argument to rationalize why sloths move so slowly (Kaup et al., 2021). The slower a sloth moves and the fewer unnecessary movements it makes, the less energy it expends (Cliffe et al., 2018; Dowling, 2019). Essentially, sloths have evolved to waste as little energy as possible, “assiduously

avoiding unnecessary exertion” (Cooke, 2018). Given their arboreal lifestyle high up in the canopies of trees, sloths are far less likely to encounter forest floor predators. They, therefore, have less need for speedy reflexes for escape, an extremely energy-costly process (Dowling, 2019). Furthermore, the sloth’s predators (mainly jaguars, ocelots, and harpy eagles) are visual hunters, so the sloth’s slow pace and sluggish movements may help it remain undetected (Cliffe, 2016; Cooke, 2018). Additionally, because sloths take such a long time to digest their food, they use the bathroom very infrequently. This lends itself to energy conservation by avoiding unnecessary travel because, bizarrely, sloths only defecate about once per week. Coupled with this strangeness is that sloths make a long, arduous climb down from the canopy to the forest floor just to defecate (Cliffe et al., 2015; Cooke, 2018). Interestingly, this bizarre ritual is one leg of a symbiotic journey that connects sloths to the moths and algae that live in their fur, a network of organisms made possible by the slowness of the sloth.

J based on gradients in temperature,” which is influenced by the thermoregulation behavior of sloths (Kaup et al., 2021). The environment near the base of hair stalks and close to the skin is “warmer, dimmer, and more stable” in conditions compared to the ends of hair tips, which are much “more exposed to the elements” (Kaup et al., 2021). In this way, despite being constrained metabolically, the slow-moving sloth adjusts its temperature through thermoregulatory behavior, which in turn fosters reservoirs with conditions ideal for specific symbiotic organisms living on its coat (Kaup et al., 2021; Cooke, 2018).

story of the sloth. Sloths are slow and for a good reason. The slowness of sloths has promoted its survival and enabled it to maintain a balance between its energy production and

A brief history of slothful misunderstandings:

Cliffe, R. N., Haupt, R. J., Avey-Arroyo, J. A., & Wilson, R. P. (2015). Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus). PeerJ, 3, 1–14.

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Cliffe, R. N., Scantlebury, D. M., Kennedy, S. J., Avey-Arroyo, J., Mindich, D., & Wilson, R. P. (2018). The metabolic response of the Bradypus sloth to temperature. PeerJ, 6, 1–15. Cooke, L. (2018). Introduction, Chapter 3: Sloth, Suborder Folivora. In The Unexpected Truth About Animals - Stoned Sloths, Lovelorn Hippos, and Other Wild Tales (pp. 1–107). essay, Transworld Publishers Ltd.

Kaup, M., Trull, S., & Hom, E. F. Y. (2021). On the move: sloths and their epibionts as model mobile ecosystems. Biological Reviews. Mesquita, E. Y. E., Soares, P. C., Mello, L. R., Freire, E. C. B., Lima, A. R., Giese, E. G., & Branco, R. (2020). Sloths (Bradypus variegatus) as a polygastric mammal. Microscopy Research and Technique, 84(1), 79–88. Tejada, J. V., Flynn, J. J., MacPhee, R., O’Connell, T. C., Cerling, T. E., Bermudez, L., Capuñay, C., Wallsgrove, N., & Popp, B. N. (2021). Isotope data from amino acids indicate Darwin’s ground sloth was not an herbivore. Scientific Reports, 11(1), 1–10. Turner, D. (1985). Forgotten Treasure from the Indies: The Illustrations and Drawings of Fernández de Oviedo. Huntington Library Quarterly, 48(1), 1–46.

Dowling, S. (2019, August 29). Why do sloths move so slowly? BBC Future. Figure 6: Sloth illustration ("periquito ligero") drawn by Oviedo that was included in his book on General History. Source: Turner, 1985. expenditure. Being marvelously slow has allowed the sloth to settle into an evolutionarily strategic, energy-saving arboreal life. The sloth simply has no need for speed.

EDITORIAL

The origins can be traced to the 16th-century ventures of the Spanish knight Gonzalo Fernández de Oviedo y Valdés, who spent several years exploring the Americas. Upon encountering the sloth, he commented that it was the “stupidest animal that [could] be found in the world” and was “so awkward and slow in movement that it would require a whole day to go fifty paces” (Cooke, 2018). A French naturalist Georges Buffon had similar opinions of the sloth, and in 1749 described in his encyclopedia of life sciences that “slowness, habitual pain, and stupidity are the results of this strange and bungled conformation. One more defect would have made their lives impossible” (Cliffe, 2016). These descriptions, coupled with Oviedo’s drawings (Figure 6) of a sloth, indicate that both naturalists likely observed sloths that had been pulled from the trees and placed on the ground. Sloths’ limbs are adapted for suspending their hanging bodies and not for lifting themselves against gravity. As a result, sloths are forced to drag themselves across the ground ungracefully and laboriously (Dowling, 2019; Cooke, 2018). Oviedo and Buffon may never have seen sloths maneuver aptly in their optimal canopy environment, instead only “observed the animal the wrong way up” (Cooke, 2018). Clearly, these depictions of the sloth and its slowness paint a portrait of evolutionary failure. Evolution has the tendency to fashion some of the world’s most bizarre and seemingly implausible creatures, which means that in “seeking to understand animals, context is key” (Cooke, 2018). Understanding why an organism is a certain way requires a careful assembly of clues to trace a circuitous natural history. Contemporary scientists have painstakingly presented the evidence, constructing a complex

Bradford, A. (2016, November 5). Facts About the Giant Ground Sloth. Livescience. Cliffe, B. (2016, August 19). Sloths aren’t lazy – their slowness is a survival skill. The Conversation.

Assembling evolution’s cryptic clues - slowness for survival:

Evolution has endowed the sloth with slowness as a creative solution to adapt to an arboreal environment. Being slow has allowed sloths to live in trees and survive on a diet of nutrient-poor leaves. Slowness is the sloth’s strategy to cope with an incredibly low metabolic rate. Moving sluggishly through the canopy assists the sloth in going undetected by predators and harbors an entire microcosmic world of symbiotic organisms. However, the slowness of the sloth has not always been understood as advantageous but rather was seen as a culprit characteristic for many years. When did such slothful slander begin?

References:

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J GENETICS

The Human Genome is Fully Mapped... Again? By Natalie Martinson

"Is full human genome map, many of the world’s seemingly impossible questions may be answered very soon, prompting the generation of other questions and research avenues."

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researchers found 3.05 billion new DNA base pairs, 200 million more than the advancement made to the genome map in 2013 (Nurk et al., 2021). Although their work has not yet been peer-reviewed or published, it is a huge step forward in medicine, technology, and genetics. This complete image of the human genome can fast track the development of personalized healthcare and hereditary disease research. The genes responsible for most genetic disorders are unknown (Nurk et al., 2021). However, now that the Human Genome Project is complete, identifying these

genes is possible. This is the first step towards gaining a deeper understanding of genetic disorders. In fact, gene markers, biological warning signs for developing genetic disorders, have been discovered for cystic fibrosis, muscular dystrophy, and sickle-cell anemia (Chial, 2008). The complete genome map can advance research conducted on genetic markers and the protein structures of different diseases. The information gathered from these studies will greatly benefit preventative medicine. While it is not likely that all unidentified genetic disorders reside in the initial 8% of the genome that was missing, this added chunk will help answer some questions that can deepen our understanding of diseases such as Alzheimer’s, diabetes, and schizophrenia and potentially allow for early-stage diagnoses (National Research Council, 1988). The benefits reaped by the complete mapping of the genome do not stop there. Many impressive advances in the field of cancer have been made. Cancer is the abnormal growth of cells caused by genetic mutations. The genes and genetic mutations that put people at risk for developing certain types of cancer have not all been identified. A fully mapped genome can help discover these genes, the associated mutations and predict an in-

dividual’s risk of developing a certain type of cancer by comparing DNA sequences (National Research Council, 1988). With this new prognostic tool, medical personnel can treat those at a high risk of developing cancer earlier, leading to higher survival rates. DNA sequencing can also be used to personalize cancer treatments, as shown in Figure 2 (Nurk et al., 2021). Personalized cancer treatments are preferable over standardized treatments because they better target cancerous cells, leaving the healthy cells and tissue unharmed and decreasing adverse side effects (Van’t Veer et al., 2008). Furthermore, the fully mapped genome can guide the study of non-genetic factors such as stress levels and drug use on the cause and spread of diseases (Logsdon et al., 2020). Identifying how genetic and environmental factors interact with each other is truly the next step forward in medicine and epidemiology. In addition to medicine, the discovery of the remaining 8% of the human genome is pushing the field of technology. The new genome was mapped with a different approach. DNA samples used to map the genome were taken from a tissue that forms in humans when a sperm fertilizes an egg with no nucleus. This tissue only has the father’s chromosomes, making the mapping of

EDITORIAL

In 2000, The Human Genome Project was completed, and the entirety of the human genetic makeup – the biological reasoning behind what makes someone their own person - had been mapped out, or so is the common misperception. The truth is that the genome was only 92% mapped at the time when the Human Genome Project was announced successfully complete. What is hidden within that missing 8%? That information was released this summer when a team of researchers from 30 institutions worldwide collaborated and completed the entire map. As seen in Figure 1, the

Figure 1: A graphical analysis of the mapping of the genome. Source: Reardon, S (2021).

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Figure 2: A demonstration of personalized cancer treatments being created. Source: CC BY-SA-4.0.

Figure 3: The Human Genome Project has several ethical, political and legal implications. Source: National Human Genome Research Institute

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side this goal is decreasing the 0.3% possible error in mapping the human genome because the smaller the margin of error, the more accurate the predictions in medicine and technology will be (Reardon, 2021). Researchers are also interested in mapping the complete genomes of multiple individuals and comparing them. This can lead to a better understanding of genetic disorders. As the technology to map full genomes is now faster and more accurate than ever before. With the full human genome map, many of the world’s seemingly impossible questions may be answered very soon, prompting the generation of other questions and research avenues.

Chial, H. (2008). Rare genetic disorders: learning about genetic disease through gene mapping, SNPs, and microarray data. Nature education, 1(1), 192. Logsdon, G. A., Vollger, M. R., & Eichler, E. E. (2020). Long-read human genome sequencing and its applications. Nature Reviews Genetics, 21(10), 597-614. National Research Council. (1988). Mapping and sequencing the human genome. National Academies Press. Nurk et al. (2021). The Complete Sequence of a Human Genome. bioRxiv Reardon, S. (2021). A complete human genome sequence is close: how scientists filled in the gaps. Nature. Van’t Veer, L. J., & Bernards, R. (2008). Enabling personalized cancer medicine through analysis of gene-expression patterns. Nature, 452(7187), 564-570.

References:

EDITORIAL

the genome easier because researchers don’t have to distinguish chromosomes based on which parent they come from. It was later discovered that the sperm from which the genome was mapped carried only an X chromosome. Generally, sperms have one X and one Y chromosome (Nurk et al., 2021). Since only the X chromosome was mapped, the Y chromosome is still a mystery. The sequencer used for mapping the genome utilizes lasers that scan up to 20,000 base pairs of chromosomes at a time, whereas traditional sequencers typically only scan around 100 (Logsdon et al., 2021). This helps make the next step of mapping the genome easier. Researchers have to match all the base pair chunks from the sequencers into a perfect puzzle. Much like how a nine-piece puzzle is much easier to solve than a 1000-piece puzzle, the base pair chunks are far easier to match up when they come in the larger chunks of 20,000 than smaller chunks of 100. However, the technology is not perfect, and although there are no gaps in the full genome, there could be up to a 0.3% error (Reardon, 2021). Of course, medicine and technology are not the only fields that have benefitted from the discovery of the complete human genome; the field of genetics is also significantly impacted. The question of what was hidden in that missing 8% of the genome that has been asked by geneticists for two decades has finally been answered. So, what’s next? Mapping the Y chromosome and decreasing error. The Y chromosome is a crucial part of the human genome for males, and many questions will remain unanswered until the Y chromosome is mapped. Along-

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HEALTH

The Truth About Blue Light

light intensity, which explains the relationship between a dark room and sleepiness (Mayo Clinic, 2021). Blue light interferes with melatonin secretion by activating light receptors in the eye and tricking the brain into thinking that it is still daytime. As a consequence, melatonin secretion is suppressed, which affects the continuity and quality of sleep. A study conducted at the University of Houston revealed that individuals who wore blue light glasses a few hours before bedtime displayed a 58% increase in nighttime melatonin levels (Ostrin, et. al., 2017). Thus, limiting exposure to blue light during night hours could improve sleep by maintaining the body’s natural light cycle. It is important to address that adopting healthy screen time habits may be more valuable and less expensive than investing in blue light glasses. These healthy habits include remembering to take breaks after prolonged screen time, holding devices at arm’s length, and avoiding electronics a few hours before bedtime (Cleveland Clinic, 2021). A popular practice is the 20/20/20 rule: every 20 minutes, refocus the eyes on something 20 feet away for 20 seconds. People tend to blink less often when staring at a screen, which dries out the eyes and causes strain (Mayo Clinic, 2020), so taking time to rest the eyes after prolonged screen time can greatly improve the bothersome symptoms associated with eye strain. It is not quite time to throw away your blue light glasses, but there is no need to overnight ship them either. Limiting blue light exposure will improve sleep quality, but blue light glasses do not act as a replacement for healthy habits when it comes to device usage.

References: Cleveland Clinic. (2021, September 23). Do blue light glasses work? HealthEssentials. Guarana, C. L., Barnes, C. M., & Ong, W. J. (2020). The effects of blue-light filtration on sleep and work outcomes. Journal of Applied Psychology. Mayo Clinic. (2020, August 28). Eyestrain. Mayo Foundation for Medical Education and Research. Mayo Clinic. (2021, March 3). Melatonin. Mayo Foundation for Medical Education and Research. NPR. (2021, February 21). Do blue light blocking glasses really work? NPR. Ostrin, L. A., Abbott, K. S., & Queener, H. M. (2017). Attenuation of short wavelengths alters sleep and the IP RGC pupil response. Ophthalmic and Physiological Optics, 37(4), 440-450. Safronova, V. (2021, February 18). When did everyone get blue-light glasses? The New York Times. Wahl, S., Engelhardt, M., Schaupp, P., Lappe, C., & Ivanov, I. V. (2019, December). The inner clock- blue light sets the human rhythm. Journal of biophotonics.

By Sarah Kamal

"It is not quite time to throw away your blue light glasses, but there is no need to overnight ship them either."

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are from harmful habits such as holding devices too close to the face or forgetting to take breaks from the screens (National Public Radio, 2021). While limiting nighttime blue light exposure may help improve sleep quality, blue light glasses are not a long-term solution against excessive screen time and device dependence. Although blue light doesn’t cause digital eye strain, it may contribute to sleep dysfunction. The production of melatonin, a hormone that plays an important role in sleep, is inhibited by blue light. It does so by interfering with the circadian rhythm, the body’s internal clock that regulates the sleep-wake cycle (Guarana, et. al., 2020). As seen in Figure 1, Melatonin is secreted by the brain in response to a decrease in

Figure 1. Melatonin levels peak in the middle of the night since it is secreted in response to decreased light intensity. Blue light exposure interferes with melatonin production by mimicking the daytime. Source: Wikkicommons.

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EDITORIAL

Blue light glasses first skyrocketed in popularity during the COVID-19 pandemic. At a time when engaging in everyday activities was difficult, most people began relying heavily on technology to keep themselves entertained. With a dramatic increase in screen time, it is no surprise that many jumped at the opportunity to save their vision and relieve their eyes from the ‘dangers’ of blue light. Unfortunately, the harsh reality is that blue light glasses show no evidence of actually reducing digital eye strain; although the strain itself is certainly real, the culprit was never specifically blue light. The blue light that digital devices emit is not enough to cause damage to the eyes (Safronova, 2021). Rather, it is likely that eye strain and discomfort

PIXELS

Prothonotary Warbler Nesting Swamp Site

(Protonotaria citrea)

where science and art collide

Giant Leopard Moth (Hypercompe scribonia)

Found on the outskirts of a forested swamp in Shawnee National Forest, located in Southern Illinois. Their caterpillar form looks like a wooly bear with a thick coat of black bristles that are non-venomous and don’t cause irritation when touched.

A gorgeous, forested swamp in Cache River State Natural Area, located in Southern Illinois. At the time this photograph was taken, a research project studying the nesting of prothonotary warblers at this swamp was being conducted. Prothonotary warblers breed in hardwood swamps in the Eastern United States and then migrate to Central and Southern United States in the winter.

Green Tree Frog (Hyla cinerea)

Box Turtle

(Terrapene)

Found trudging through the mud of a swamp in Shawnee National Forest, located in Southern Illinois. The orange coloration on this one was quite astounding in contrast with the brown colors typically seen in Box Turtles in this area.

Found in a forested swamp in Shawnee National Forest, located in Southern Illinois. They commonly inhabit areas surrounding freshwater bodies, such as ponds, lakes, marshes, and streams, spanning anywhere from Central to the Southeastern United States. They are found in higher abundance in open forest canopies.

PHOTO SUBMISSIONS

Catherine Nguyen 32 JUST VOL VII // ISSUE I // FALL 2021

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Current State of Air-Breathing Rocket Engine Research and Development...................................................................36 Several studies have examined the feasibility of a combined rocket and jet engine cycle—also known as an air-breathing rocket engine. This review paper investigates the current state of research of air-breathing rocket engines and specifically examines two engines currently in development. Preliminary results indicate both of the engines, the Synergetic Air-Breathing Rocket Engine (SABRE) and the Fenris Engine, have the potential to realize high gains in efficiency (specific impulse). However, some researchers question the performance will carry over to operating environments in which they have not yet been tested. Air-breathing rocket engines would be drastically more efficient than current rocket engines as they would not have to carry as much oxidizer to reach orbit. This would significantly decrease the onboard mass and the associated launch costs.

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Current State of Air-Breathing Rocket Engine Research and Development Garrett Cobb 1. INTRODUCTION: Making access to space more economical is one of NASA’s next Grand Challenges in order to promote “robust and frequent space research, exploration and commercialization” [1]. Launch costs have declined since governments began sending rockets into orbit in the 1950s [2], but it still costs around $10,000 per pound to send something into space [1]. However, reusable technologies could make orbital launches less expensive and less wasteful. Currently, rockets need multiple engines to reach orbit. Each engine is housed in a stage - the surrounding components and structure needed to operate. After using up their fuel, each stage detaches from the rocket to remove the extra weight, as shown in Figure 1. In this way the rocket gets smaller and lighter until it reaches orbit [3]. However, this generally lacks the reusability and efficiency of a modern airliners.

Rockets and jets both operate on the same principle: they burn fuel and expel mass in one direction to accelerate themselves in the opposite direction [4]. Just as a candle needs oxygen to burn, so do jets and rockets need an oxidizing agent in order to burn their fuel. Rockets must carry this oxygen source or other reactant (oxidizer) to facilitate combustion because there is no oxygen in space. In contrast, jets use the oxygen in the atmosphere which allows them to generate the same amount of thrust (propulsive power) using less onboard weight. Like a jet, an air-breathing rocket engine would use oxygen in the atmosphere to burn fuel and switch to the onboard oxygen supply once the air becomes too thin [5]. In this way, an air-breathing engine would combine the efficiency of a jet with the orbital reach of a rocket. Vehicle weight would be reduced by using less onboard oxidizer, less fuel, and a single integrated propulsion system [5]. While air-breathing engines have theoretically higher efficiency, hurdles exist in their technological development. They will likely not be a mature technology for years to come until their shortcoming are addressed by independent verification. One issue is the heat exchanger technology necessary to cool the high-speed air entering

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2. BACKGROUND: 2.1.

Types of Rocket and Jet Propulsion Systems

While less efficient by weight, rockets outperform jet engines in the following ways: their thrust increases with altitude and is not dependent on flight speed because they do not take in air [8]. Jets behave in the opposite manner: their thrust increases with flight speed, but decreases with altitude, which puts an upper limit on their vertical range [8]. Similar to how a fan uses rotating blades to move air, jets require a compressor at the intake to draw in air and pressurize it prior to combustion [4], as shown in the diagram in Figure 2. This pressurization is required for a more efficient chemical reaction, but the compressor needs additional power to operate. Figure 2. Diagram of a jet engine [9] However, two other types of jet, ramjets and scramjets (supersonic ramjets) compress air by “ramming” it into the inlet using their own forward momentum [4], as shown in the diagram in Figure 3. The primary advantage of a ramjet is there are very few moving parts compared to a conventional jet engine. Since ramjets and scramjets do not have compressors, no extra power is required [4]. Figure 3. Diagram of a ramjet [10] Ramjets slow down the incoming air to subsonic levels before initiating combustion, while scramjets combust while the airflow is still supersonic [4], and each method is more efficient at different velocities. However, they cannot attain the necessary forward velocity on their own; they need to be brought up to their operating speed using a traditional jet engine or rocket, making them good candidates for forms of combined cycle propulsion [11].

Proposed

Combined

Propulsion

Systems

An article by University of Queensland researchers states that traditional rockets have been in development for decades and are now in a state of well matured technology; they are close to their theoretical performance limits, and efficiency can only be improved marginally [11]. In order to improve upon these limits, future launch vehicles could use combined rocket and airbreathing propulsion systems in conjunction with a winged vehicle. Such a system would be able to both takeoff and land on a runway like a conventional airliner. Benefits would include increased launch window flexibility and shorter times to reach the intended destination. The benefits would be obtained by lift generated by the wings in addition to the thrust provided by the air-breathing engine [11]. In the following section a proposed form of airbreathing propulsion using a combined turbojetramjet-rocket system, the Rocket Based Combined Cycle (RBCC), will be examined, and a more novel form of air-augmented propulsion will be explored. 3.

Analysis of Air-breathing Rocket Engines

3.1.

Performance Metrics

The significance of the metrics that will be used to analyze the engines are listed in Table 1. These metrics are explained in further detail in Appendix A. 3.2.

Rocket Based Combined Cycle

The first concept for air-breathing propulsion is Rocket Combined Cycle Propulsion (RBCC). According to research funded by the University of Sheffield and the China Scholarship Council, it is the ideal propulsion system for reusable round trip space missions [12] because RBCC engines operate as a jet, ramjet, or rocket depending on which mode is most efficient at the current altitude. The foremost issue with RBCC engines is cooling the high-speed incoming air. Because the incoming air has high kinetic energy, slowing it down releases the energy in the form of heat, which can damage the engine and its components [5,7]. Unlike a ramjet or scramjet, there are many more internal components that are susceptible to damage from the heat transfer from the air [5]. The only RBCC engine currently in development is the Synergetic Air Breathing Rocket Engine (SABRE), as seen in Figure 4. It is being developed by Reaction Engines Limited for their Skylon Space Plane — a single stage to orbit vehicle. The idea for SABRE and Skylon began in the early 1980s, when two British engineers were convinced that there must be a better way to make space more accessible and commercialized [13]. Figure 4. SABRE cutaway diagram [13] Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc.

According to a 2016 NASA paper, SABRE has superior performance due to its ultra-light heat exchanger [6]. Most high performance heat exchangers are heavy and bulky which is not ideal for integration in a rocket engine. The SABRE heat exchanger shown in Figure 4 represents a breakthrough and heat exchanger technology and can cool the incoming air within hundredths of a second [6,7]. However, the hot exhaust plumes from the engine could damage the body of the spacecraft itself, especially once the vehicle reaches Mach 8.5. The temperatures in these regions could be 8-16 times too high according to the computational models. If this is the case, new materials or a significant redesign of Skylon may be required [6]. Skylon has a proposed payload percentage of 21 percent [13], which is 9 percent higher than a conventional rocket [13], while still lower than a normal jet. As shown in Figure 5, SABRE consistently has the highest thrust to weight ratio of all of engine types across the range of operating velocities (Mach Numbers). While it is not the most efficient engine at any one velocity, it is consistent across the range of velocities required to reach orbit, making it the highest performing and most efficient choice overall. Figure 5. SABRE thrust to weight ratio (left) and specific impulse (right) compared to other engine types [13] Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc. While SABRE’s goal is to power Skylon as a reusable single-stage vehicle, two studies authored by the University of Paris and the Air Force Research Laboratory stated that, under the current assumptions about the projected performance,a two-stage vehicle is far more likely [14,15].The SABRE engine would be used only in the first stage [14,15]. Additionally, switching the SABRE fuel with “methane or other high endothermic (energy releasing) hydrocarbon fuel” [15], could reduce the engine size and lower the fuel weight compared to the liquid hydrogen currently used by SABRE. However, this would require changes to SABRE that would need to be further modeled and verified [15]. A 2019 update presented at the 8th European Conference for Aeronautics and Space Sciences put SABRE at a Technology Readiness Level around 5, meaning that the components in the SABRE technology were ready to be tested in a relevant environment outside of the laboratory [16,17]. 3.3.

Air-augmented propulsion

An alternative air-augmented solution has been proposed by the Montana startup Mountain Aerospace Research Solutions (MARS). Instead of the combined cycle approach, MARS used air augmentation for their Fenris engine. Fenris is intended to be the first stage engine of a vertical launch vehicle, as opposed to SABRE, which would take off and land horizontally like an airliner. The following information comes from an interview conducted on February 23, 2021, with Aaron Davis, founder and CEO of MARS. The combustion chamber of Fenris, shown in red in Figure 6, operates for the entire duration on a fuel and oxidizer combination. The difference, however,

REPORTS

Figure 1. Illustration of Rocket Staging [3]

the engine [6,7]. To evaluate the current state of research this paper will: 1. Review the current technological readiness level of air-breathing engines currently in development 2. Discuss the obstacles in the technological development of air-breathing rocket engines. 3. Review the state of the research into proposed airbreathing rocket engine designs

2.2.

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J is that the combustion occurs in the toroidal combustion chamber (shown in red). The combustion occurs and flows through the hot gas expansion zone. As the exhaust gases speed up, they lose pressure, and the low-pressure region pulls in higher pressure air through the central nozzle (shown in blue). This increases the total mass flowing through the system, and therefore the thrust. This would theoretically increase performance at all altitudes. The faster the engine travels, the more air is forced through the nozzle, further increasing the thrust at higher speeds. Figure 6. Fenris engine diagram [18] According to Davis, conservative estimates based on experimental testing data show Fenris has the potential to increase the payload percentage to 20 percent (standard rockets are ~5 percent). Fenris would have a thrust-toweight ratio of 300:1. For comparison the state-of-the-art SpaceX Raptor engine has a thrust-to-weight ratio of 200:1 at sea level conditions. This is achieved by the low weight of the Fenris engine compared to conventional rocket engines. Fenris has skeptics however, such as University of Southern California Professor Dan Erwin. Erwin is concerned about the air intake; because air is 78 percent nitrogen (which does not contribute to combustion) it could have a dampening effect on the hot rocket exhaust. This would reduce the reaction temperature and therefore the thrust. This could be especially problematic at high velocities where Fenris has not yet been tested [19]. The Fenris technology has only been in development since 2018 and has not yet been verified by independent investigation

There are several potential methods that could enable air-breathing propulsion systems to become reality. Two such methods are combined cycle and air augmented propulsion systems. While the rocket based combined cycle has been more extensively researched, both methods have yet to prove themselves in practice. The current performance metrics for each engine are shown in Table 2 and compared to the SpaceX Merlin engine currently in use.' Ultimately, several questions must be answered before these technologies can reach a flight-proven technological readiness level. SABRE must show that its novel heat exchanger can perform as modeled and that the engine exhaust does not pose a threat to the airframe. Fenris needs to prove that it can remain efficient at high air speeds. More research and independent verification must be carried out on both engines before these technologies can revolutionize the way we access space.

5. APPENDIX A: PERFORMANCE METRICS 5.1.

Thrust

The thrust, or propulsive power, of jet and rocket is mainly determined by the velocity and the rate at which 38 JUST VOL VII // ISSUE I // FALL 2021

5.2.

Mach Number

The speed of aircraft and rockets are often measured by the Mach number, which is defined as the air speed divided by the speed of sound (~761 mph at sea level) [4]. 5.3.

Thrust to Weight Ratio (TWR)

One measure of engine performance is the thrust that an engine provides divided by its mass, also known as the thrust-to-weight ratio [8]. Rockets have a higher thrust to weight ratio than jet engines, but at the cost of fuel efficiency. Rockets have a higher thrust to weight ratio by necessity as they need to directly overcome gravity to escape orbit. In contrast, jet engines generate thrust, but the wings also generate an upward force, so less thrust is needed to leave the ground. 5.4.

Specific Impulse (Isp)

Another measure of rocket and jet engine efficiency is specific impulse, which has units of seconds. This represents the length of time that 1 kg of fuel can be burned while exerting 1 N of thrust. Lighter, less dense fuels like hydrogen have a higher theoretical specific impulse because they are easier to speed up, and they therefore provide greater thrust per mass but have the tradeoff of needing larger fuel tanks because they occupy a greater volume [4]. Because jets do not carry an oxidizing agent, they burn less onboard fuel while exerting an equivalent amount of thrust, giving them have significantly higher specific impulse values [4]. 5.5.

Payload Percentage

Ultimately, the goal of orbital vehicles is to deliver a payload to space. The more efficient they can be, the more payload they can deliver for a given amount of fuel. The payload percentage is the payload mass divided by the total vehicle weight [4]. The higher the payload percentage, the lower the relative costs.

6. ACKNOWLEDGMENTS: The author would like to give a special thanks to Mike Shapiro, who helped guide the structure of this research remotely during the Spring 2021 semester, and who put together a fantastic Engineering Communication curriculum in the process. The author would also like to thank Aaron Davis, who was generous enough to meet for a couple of hours to go over the inner workings of Fenris, and Scott Stegman for providing the Fenris diagram.

AUTHOR INFORMATION: Garrett Cobb, Undergraduate Student, Department of Engineering Physics, University of Wisconsin-Madison.

REFERENCES: 1. Office of the Chief Technologist. Space Technology Grand Challenges. In: NASA.gov [Internet]. 2010. 2. Jones HW. The Recent Large Reduction in Space Launch Cost. 48th International Conference on Environmental Systems. Albuquerque, New Mexico; 2018. p. 10. 3. Lopez DR. Rocket Staging. In: NASA Glenn Research Center [Internet]. 13 May 2021.

14. Brevault L, Balesdent M, Wuilbercq R, Subra N, Oriol S, Bonnal C, et al. Conceptual design of a TwoStage-To-Orbit vehicle using SABRE engines. The 8th European Conference for Aerospace Sciences. Madrid: European Research Council; 2019. p. 19. doi:10.13009/ EUCASS2019-454 15. Hellman BM. Two Stage to Orbit Conceptual Vehicle Designs using the SABRE Engine. 2016 AIAA Space Forum. Long Beach: American Institute of Aeronautics and Astronautics; 2016. p. 16. doi:10.2514/6.2016-5320

4. Hill P, Peterson C. Mechanics and Thermodynamics of Propulsion. 2nd ed. New York: Pearson Education; 1992.

16. Varvill R, Duran I, Kirk A, Langridge S, Nailard O, Payne R, et al. SABRE Technology Development: Status and Update. 8th Eur Conf Aeronaut Space Sci. 2019. doi:10.13009

5. Nailard O. Air-breathing rocket engines: the future of space flight. In: Physics World [Internet]. 15 Oct 2020.

17. Tzinis I. Technology Readiness Level. In: NASA.gov [Internet]. 1 Apr 2021.

6. Mehta U, Aftosmis M, Bowles J, Pandya S. Skylon Aerospace Plane and Its Aerodynamics and Plumes. J Spacecr Rockets. 2016;53: 340–353. doi:10.2514/1.A33408

18. Stegman S. MARS Engine Diagram. 2021. 19. Oberhaus D. The Rocket Motor of the Future Breathes Air Like a Jet Engine. Wired. 26 Jun 2020.

7. Lee H, Ma S, Chen Y, Zou Z, Liu H. Experimental study on compact heat exchanger for hypersonic aeroengine. 21st AIAA International Space Planes and Hypersonics Technologies Conference. Xiamen, China: American Institute of Aeronautics and Astronautics; doi:10.2514/6.2017-2333 8. Sutton GP, Biblarz O. Rocket propulsion elements. 7th ed. New York: John Wiley & Sons; 2001. 9. Dahl J. Jet Engine. 2007. Available: https://commons. wikimedia.org/wiki/File:Jet_engine.svg 10. Hall N. Ramjet Parts. In: NASA Glenn Research Center [Internet]. 13 May 2021 [cited 7 Oct 2021]. Available: https://www.grc.nasa.gov/www/k-12/airplane/ rampart.html 11. Jazra T, Preller D, Smart MK. Design of an Airbreathing second stage for a rocket-scramjet-rocket launch vehicle. J Spacecr Rockets. 2013;50: 411–422. doi:10.2514/1.A32381 12. Zhang T, Wang Z, Huang W, Ingham D, Ma L, Porkashanian M. An Analysis Tool of the Rocket-Based Combined Cycle Engine and its Application in the TwoStage-to-Orbit Mission. Energy Int J. 2020;193: 116709. doi:10.1016/j.energy.2019.116709

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4. CONCLUSION

the mass is ejected from the end of the nozzle [4].

13. Longstaff R, Bond A. The SKYLON Project. 17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2011. San Francisco: American Institute of Aeronautics and Astronautics; 2011. p. 10. doi:10.2514/6.2011-2244 JUST VOL VII // ISSUE I // FALL 2021

J FIGURES AND TABLES

Table 1. Explanation of Performance Metrics. Table by author [4]

FIGURES AND TABLES

Table 2. Performance metrics based on experimental and simulation data. Table created by author.

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J FIGURES AND TABLES

FIGURES AND TABLES

Figure 1. Illustration of Rocket Staging [3]

Figure 4. SABRE cutaway diagram [13] Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc.

Figure 2. Diagram of a jet engine [9]

Figure 5. SABRE thrust to weight ratio (left) and specific impulse (right) compared to other engine types [13]

Figure 3. Diagram of a ramjet [10]

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Reprinted by permission of the American Institute of Aeronautics and Astronautics, Inc.

Figure 6. Fenris engine diagram [18] JUST VOL VII // ISSUE I // FALL 2021

The Journal of Undergraduate Science and Technology (JUST) is an interdisciplinary journal for the publication and dissemination of undergraduate research conducted at the University of Wisconsin-Madison. Encompassing all areas of research in science and technology, JUST aims to provide an open-access platform for undergraduates to share their research with the university and the Madison community at large.