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MATH2018SMITH34045 MATH

Indices of Algebraic Integers in Cubic Fields

Type: Graduate
Author(s): Jeremy Smith Mathematics
Advisor(s): George Gilbert Mathematics

An algebraic integer is a complex number that is a root of a polynomial with integer coefficients and a leading coefficient of 1. This includes numbers like the square root of 2 and the cube root of 10, for example. A field is a set in which we can add, subtract, multiply, and divide (among other details). Consider the set of all algebraic integers in any given field containing the rational numbers. The index of an algebraic integer in this set is a natural number that measures how close the algebraic integer is to generating the set. For instance, the imaginary number i (the square root of -1) is an algebraic integer which generates the set of all complex numbers of the form a + bi where a and b are integers, and so has index 1. The closer the index is to 1, the closer the algebraic integer is to generating the set. We investigate these indices in cubic fields, determining not only which numbers occur as indices in given families, but also that the minimal index is unbounded as one traverses the set of all cubic fields in those families.

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NTDT2018BENEDICT28698 NTDT

SENSORY ACCEPTABILITY OF VEGAN INGREDIENT SUBSTITUTIONS IN ICE CREAM

Type: Undergraduate
Author(s): Nicholle Benedict Nutritional Sciences Chandler Bourff Nutritional Sciences Maria Martinez Nutritional Sciences
Advisor(s): Anne VanBeber Nutritional Sciences Lyn Dart Nutritional Sciences

Background: To replace milk fats and eggs commonly found in ice cream, vegan varieties substitute with vegetable fats and/or pureed fruits. Vegan ingredient substitutions for ice cream must contain similar structural components to milk fat to preserve the expected texture/mouthfeel of the product. The purposes of this study were 1) to measure university students’ preferences and sensory ratings of vegan ice cream substitutions and 2) to identify which ingredients act as the best replacements.

Methods: 54 students enrolled in one of two TCU Nutritional Sciences (NTDT) courses participated in this single-blind, cross-sectional study. Subjects completed sensory evaluation of three homemade vegan ice creams containing different structural/flavor components. Sample A included coffee, cashews, and coconut cream; B used coconut cream and dates, and C contained coconut milk. Evaluations took place on two separate occasions in the NTDT Laboratory Kitchens. Flavor, sweetness, texture, mouthfeel, eye appeal, color, and overall rating of vegan ingredient substitutions for ice cream recipes were assessed. Sensory criteria responses were analyzed using SPSS XIX. Frequency distributions, ANOVAs, correlations, and descriptive statistics were determined to meet study objectives (p≤0.05). Protocol was approved by the TCU IRB.

Results: 53% of participants preferred the flavor of sample A, 42% of participants reported that sample B was the preferred flavor, and sample C received the lowest overall acceptability rating, with 73% of the participants disliking the flavor. More than 50% of participants stated sample A was most similar to traditionally-prepared non-vegan ice cream, and 78% of participants stated that they would consume these ice creams outside of the study.

Conclusions: Acceptable vegan ice cream fat substitutes are available. Cashew, coconut cream, dates, and coffee contributed to the rich flavors, creamy textures, and overall desirable sensory qualities in samples A and B. Coconut milk, utilized in sample C, contributed to an undesirable and unacceptable crystallized texture.

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NTDT2018BOUNLUTAY27968 NTDT

The Transformation of Views and Knowledge of Plant-Based Diets of University Students Throughout the Course of Education and Exposure

Type: Undergraduate
Author(s): Alby Bounlutay Nutritional Sciences Jane Speaker Nutritional Sciences
Advisor(s): Anne VanBeber Nutritional Sciences

Background: Research indicates individuals who follow plant-based diets make healthier food choices and have less chronic disease than those consuming the Standard American Diet. It is hypothesized that Texas Christian University (TCU) students have limited knowledge and/or exposure to vegan/plant-based lifestyles and diets. The purpose of this study was to determine whether knowledge level and attitudes/beliefs of vegan/plant-based diets/lifestyle changed with exposure and newly-gained knowledge in a semester-long three-hour course.

Methods: Subjects included 23 junior/senior multidisciplinary TCU students (56%/female; 44%/male) enrolled in a course about plant-based diets and lifestyles. Students completed a pre-assessment questionnaire on the first day of class before exposure to any content regarding vegan/plant-based diets and lifestyles. Students completed a post-assessment questionnaire at semester end to ascertain if changes in attitudes/knowledge/beliefs regarding vegan/plant-based diets and lifestyles changed over time with exposure and newly-gained subject knowledge in the course. Data was analyzed using SPSS (p<0.05).

Results: Prior to starting the course, 13% of students reported they were vegetarians, and 83% typically consumed animal protein in their diets (p=0.01); more students in health-related disciplines noted having friends/family members who followed vegan diets (p=0.01). Pre-assessment results showed that female students were more knowledgeable than male students about plant-based diets/veganism (p=0.01); whereas, post-assessment knowledge scores showed no differences among gender. Overall, post-assessment scores improved for all students in the following categories: reasons why people choose veganism, acceptable foods for vegans, nutrients at risk for vegans, availability of vegan ready-to-eat foods/grocery store and restaurant meals, and risk for chronic disease of vegans vs. people who consume animal products (p=0.01).

Conclusions: Students majoring in the sciences and nursing/health sciences possessed greater knowledge about vegan/plant-based diets/lifestyles than their counterparts majoring in other subjects. Although level of prior knowledge varied among all students, exposure to the topic through a vegan/plant-based studies course increased knowledge of participants.

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NTDT2018CARR1825 NTDT

Nutrition Education and Sensory Evaluation Influence Preferences for Peanut and Alternative Nut/Seed Butters

Type: Undergraduate
Author(s): Greg Carr Nutritional Sciences Colton Galbreaith Nutritional Sciences
Advisor(s): Lyn Dart Nutritional Sciences

Background:
Peanut butter is an all-American staple in nine out of 10 households. It’s estimated that each U.S. youth consumes an average of 1,500 peanut butter sandwiches by the time he/she graduates from high school. Although, the popularity of peanut butter alternatives such as tree nuts/seed butters has grown in recent years due to their rich source of nutrients, peanut butter continues to be the “nut butter” of choice for most people. This may be due to lack of knowledge about the health benefits of different nut/seed butters and/or lack of exposure to these products.

Methods:
The purpose of this study was to examine if taste-testing and increased awareness about the health benefits of tree nut/seed butters would influence their consumption among university students. 52 students enrolled in a multi-disciplinary introductory nutrition course participated in this single-blind, cross-sectional study. Participants completed a pre-study questionnaire identifying key nutritional benefits of peanut and alternative tree nuts/seeds butters and typical consumption of each. Following education about the nutrient content of peanuts compared to cashews, almonds, and sunflower seeds, participants taste-tested and evaluated a sample butter of each and completed a post-study questionnaire. Study procedures were approved by university IRB, and participants responses and sensory rankings were analyzed to meet study objectives (SPSS; p<0.05).

Results:
Significant improvement in pre and post-study knowledge of nutrient content in nut/seed butters was noted (p=0.01). Sensory evaluation showed that preferences for peanut butter were highest among participants, followed by almond butter and cashew butter. Sunflower seed butter was least preferred (p=0.01). Taste, color, and texture/mouthfeel sensory rankings correlated with overall acceptability for each sample (p=0.05). Following sensory evaluation, preferences for consuming almond butter increased by 38% compared to pre-tasting responses (p=0.01).

Conclusions:
Education and sensory evaluation are both important strategies for enhancing awareness of health benefits and acceptability of peanut butter alternatives.

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NTDT2018COFFEY32837 NTDT

The Relationship Between Probiotic Comsumption and Immunity in College Students Ages 18-24

Type: Undergraduate
Author(s): Colleen Coffey Nutritional Sciences Claire Sorrels Nutritional Sciences Grace Williams Nutritional Sciences
Advisor(s): Rebecca Dority Nutritional Sciences

Background: Among the many benefits associated with the consumption of probiotics, modulation of the immune system has recently received the most attention. Previously, researchers and scientists thought that the use of probiotics only improved the gastrointestinal tract, thereby aiding digestion. However, there is now evidence to support that intake of probiotics is effective in the prevention and/or management of many gastrointestinal diseases plus modulating immune functions in a person with normal immunological status and microbiota.
Methods: An online survey regarding knowledge of foods containing probiotics, consumption of these foods, frequency of probiotic supplementation, and recent illness was developed to determine the relationship between probiotic intake and immune health among college students. Researchers recruited Texas Christian University students through e-mail and social media. Once the target number of participants (>150) responded to the survey, data was analyzed using SPSS.
Results: Upon surveying participants (N=157), 58% (n=91) of respondents reported that they did not take a probiotic supplement, while 19.8% (n=31) reported taking a supplement every day or ≥3-4 times/week. There was a strong correlation between those who reported frequent probiotic supplementation and lower incidence of strep throat (p<0.01), lower incidence of nausea and vomiting (p<0.01), and lower incidence of constipation (p<0.05). There was also a correlation between the consumption of certain foods containing probiotics, yogurt specifically, and illness frequency, notably, lower incidence of fever (p<0.01) and cold (p<0.05).
Conclusions: There is a significant correlation between the consumption of probiotic supplements and positive effects with certain illnesses, but some foods containing probiotics show opposite or negligible results. For more conclusive results, further research should be conducted with controlled variables to determine the relationship between illness and intake of probiotic supplements versus probiotic-containing foods.

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NTDT2018MATTSON63358 NTDT

Fad Diet or Exercise? Maintaining Weight among Millennials

Type: Undergraduate
Author(s): Leigh Mattson Nutritional Sciences Katie Shamoon Nutritional Sciences
Advisor(s): Anne VanBeber Nutritional Sciences Lyn Dart Nutritional Sciences

Background: Research indicates Millennials are more concerned about having healthy eating habits than following fad diets, and they exercise more than their Baby Boomer counterparts. The purposes of this study were 1) to determine reasons university students follow fad diets, and 2) to determine other methods students utilize for weight management.
Methods: In this un-blinded, randomized trial approved by TCU IRB, participants completed an online research questionnaire after providing informed consent. Population included 236 TCU male and female students, 18-22 years old. Analyses assessed students’ history of fad dieting and outcomes, perceived health status based on body weight and image, eating and exercise habits, and incidence of lifestyle practices such as smoking and alcohol use. Data was analyzed using SPSS (p<0.05). Frequency distributions and correlations were analyzed for trends in health maintenance behaviors.
Results: Participants self-identified as 76% females, 85% white, 6% Hispanic, and 4% other ethnicity. Only 32% of participants had followed a fad diet (p=0.01). Participants who followed fad diets included 30% Paleolithic®, 23% Gluten-Free®, 20% Weight Watchers®, and 14% Atkins®. Of those who followed the respective diets, 58% did not achieve desired results and reported feeling tired, had no change in health status, experienced temporary weight loss, and always felt hungry, and 56% of participants answered “no” when asked if fad diets work. Of those who followed a fad diet, 40% would not follow one again. Results also show a strong relationship between females and healthy eating habits, pressure to be a certain weight, and perceiving themselves to be a normal weight (p=0.01). Finally, weight loss behavior results show that 97% of participants exercise, while only 57% consciously eat less, and 55% count calories (p=0.01).
Conclusions: University students who followed fad diets experienced temporary or adverse results. Exercise was preferred rather than dieting to maintain weight.

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NTDT2018RACK5068 NTDT

CONTRIBUTORS TO RESTAURANT FOOD WASTE AND BARRIERS TO RESTAURANT FOOD DONATIONS AND SHELTER ACCEPTANCE

Type: Undergraduate
Author(s): Petra Rack Nutritional Sciences Hannah Post Nutritional Sciences Abby Read Nutritional Sciences
Advisor(s): Gina Hill Nutritional Sciences

Background: Up to 40% of food produced in America is wasted each year. Meanwhile over 42 million Americans are food insecure. The purposes of this study were to 1) identify contributing factors to local restaurant food waste, 2) describe barriers to restaurant food donations, and 3) describe barriers to donation acceptance by shelter employees.
Methods: Two electronic surveys were distributed to either local restaurant managers/owners or to employees involved in food donation acceptance in local shelters/kitchens following phone calls and/or personal visits by researchers to facilities. Data were coded into and analyzed using SPSS.
Results: There was a 17% (N=12/72) and 100% (N=14/14) response rate for restaurants and shelters requested to participate, respectively. While only 16% (N=2) of restaurant survey respondents (RSR) were concerned about food waste in their establishments, all RSR (N=12) agreed that reducing food waste in their facilities was important. Over 83% (N=10) reported having successful food waste prevention measures in their restaurants. There was a positive correlation with report of presence of prevention measures and knowledge of the Good Samaritan Act (r=.67, p<0.05). Approximately 42% (N=5) of RSR reported they would be interested in connecting with local shelters to donate food and also agreed that liability is a barrier to safe food donations.  Among shelter respondents, 81% (N=9) agreed that their facilities would benefit from excess restaurant food donations.
Conclusion: Although all RSR agreed that food waste prevention measures were important, the majority were not concerned about food waste in their facilities. Due to the overall poor response rates among restaurant owners/managers, the RSR in this survey may represent a segment that were more interested in food waste and more likely to respond to the survey.  The majority of respondents of both surveys agreed that partnering with restaurants and shelters for safe excess food donation was desirable.
Word count: 297

Funding Source: None

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PHYS2018BARTH2896 PHYS

A Stochastic Differential Equation Model of Virus Replication

Type: Undergraduate
Author(s): Dylan Barth Physics & Astronomy Hana Dobrovolny Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

In this experiment we take the differential equation model from Heldt 2012 for the viral life cycle and apply a stochastic algorithm in order to simulate random events on a molecular level. We then introduce a known mechanism by which to mutate the produced virus particles and attempt to understand the relationship between surface proteins and these random mutations. This work will shed light on the efficacy of particular antiviral drugs that act on the binding of surface proteins to the cell membrane.

(Presentation is private)

PHYS2018CIAMPA9117 PHYS

Massive Winds Triggered by Supernovae in the Large Magellanic Cloud

Type: Graduate
Author(s): Drew Ciampa Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy

Nearby, the Large Magellanic Cloud galaxy (LMC), has ejected massive amounts of gaseous material, some of which is headed toward the Milky Way. The material consists of ionized hydrogen gas which is a consequence of significantly energetic events that have occurred in the LMC. Such events are not only the cause of the ionized material, but also the immense amount of material being thrown out. This ejected wind holds a substantial amount of information regarding both galaxies in general and the LMC’s physical processes. Studying this ionized outflow will reveal new details concerning the internal processes that produce such massive ejections, the potential for galactic outflows to replenish gas reservoirs for future star formation, and the environments surrounding galaxies. The latter will influence our view of a galaxy’s environment and how it may interact with nearby neighbors such as our Milky Way galaxy.

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PHYS2018DOAN3019 PHYS

Novel Techniques of Estimating the Spectro-Photometer Correcting G-Factor

Type: Graduate
Author(s): Hung Doan Physics & Astronomy Luca Ceresa Physics & Astronomy Jose Chavez Physics & Astronomy Harris To Physics & Astronomy
Advisor(s): Karol Gryczynski Physics & Astronomy

Fluorescence anisotropy is a common measurement that helps provides important information on molecular mobility, solvent (environment) viscosity, or/and molecular size. Fluorescence anisotropy involves measurement of two orthogonally polarized light emission intensities. One of the common issues of fluorescence anisotropy measurements is that most optical detection systems respond differently to the parallel and perpendicular polarization of light. The challenging task is to estimate the calibration curve, often called as the instrumental G-factor (grating factor), a parameter indicates the contributions and/or distortion of the optical detection system to the parallel and/or perpendicular light polarization, so that one can correct their polarized emission intensity and obtain a proper fluorescence anisotropy result. Here we present novel techniques that we have been developed in our laboratory that help achieve the G-Factor curves for different instruments.

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PHYS2018DONOR57222 PHYS

A Uniform Measurement of the Galactic Abundance Gradient

Type: Graduate
Author(s): John Donor Physics & Astronomy Matthew Melendez Physics & Astronomy Julia O'Connell Physics & Astronomy
Advisor(s): Peter Frinchaboy Physics & Astronomy

Despite living inside the Milky Way, we do not know well basic quantities such as its detailed chemical makeup at the level needed to fundamentally tie the Milky Way to studies of evolution in other galaxies. One key observable is the radial chemical abundance gradient. Open star clusters provide an age datable sample by which to measure this gradient. This measurement has previously been made using a diverse and regularly conflicting compilation of clusters from various literature studies. We present the first measurement using a large (462 stars in 28 open clusters), uniform sample of open clusters abundances. Our measurements show a general agreement with recent studies of the overall metallicity gradient, with a measured ∆ [Fe/H]/∆ RGC of -0.050 ± 0.004 dex/kpc. We also explore trends with distance from the galactic plane and cluster age, and finally investigate the existence of a "knee" in the overall abundance gradient, between 12-14 kpc, within the range suggested by previous work. We show strong evidence for this phenomenon.

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PHYS2018HASAN12433 PHYS

Multi-Color Bioimaging With Graphene Quantum Dots

Type: Graduate
Author(s): Md Tanvir Hasan Physics & Astronomy Giridhar Akkaraju Biology Roberto Gonzalez-Rodriguez Physics & Astronomy Anton Naumov Physics & Astronomy Elizabeth Sizemore Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy

Since a number of medical conditions require simultaneous treatment and diagnostics, the field of molecular therapeutics has recently turned to multifunctional approaches allowing for both therapy and biomedical imaging. A number of such molecular and nanoformulations are combined with fluorophores that allow for imaging of the delivery pathways of the drug in the visible. This is optimal for in-vitro or ex-vivo work, however, cannot be utilized well in-vivo. Thus, there is a need in nanoformulations optimized for both in-vitro and in-vivo studies. Graphene quantum dots, possessing intrinsic stable fluorescence in the visible and near-IR stand out as candidates for such complex application.

In this work, we for the first time produce biocompatible graphene quantum dots (GQDs) that exhibit multi-color emission both in visible and NIR possess a capability for biological pH sensing. These GQDs show the crystalline graphitic structure in TEM and average sizes of c.a. 5 nm beneficial for cellular internalization. They show no cytotoxicity even at high doses of 1 mg/mL that are used for imaging. As opposed to related structures such as graphene oxide and other graphene derivatives GQDs show high quantum yield in green (~500 nm) of ~50%. Near-IR emission at ~860 nm is located in the water window with reduced absorption and lower autofluorescence backgrounds providing a promising potential route for in-vivo studies. Emission of GQDs also depends on pH of the surrounding medium. The change in pH of as-prepared GQDs from 2.70 to 8.0 yields an increase of fluorescence intensity up to ~60%. Additionally, pH-dependent shifts of the spectral features allow differentiating between acidic cancerous and neutral healthy exocellular environments allowing to use GQDs for cancer detection. Therefore, our results indicate that GQDs have a significant potential in bio-applications because of their capacity for multi-color green/near-IR imaging for in-vitro/in-vivo studies, pH sensitivity, water solubility, low cytotoxicity and high capacity for cellular internalization.

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PHYS2018KHAN44160 PHYS

Comparing Infection Parameters for Respiratory Syncytial Virus in Different Aged Cotton Rats

Type: Undergraduate
Author(s): Shaheer Khan Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

Respiratory syncytial virus (RSV) is an extremely common viral respiratory infection that currently has no vaccine or treatment. One of the issues in developing a treatment has been that immune system responses in both humans and rats vary in their susceptibility to RSV across different age groups. In this study, we use a mathematical model to quantify the viral kinetics of RSV and analyze its relationship to age. After fitting the model to experimental data, six parameter values were determined and used to calculate the eclipse phase length, infection phase length, basic reproductive number, and infecting time. These values were compared by age and collection site. After running several statistical tests, there was no major trend with the parameter values in relation to either age or collection site. This result provides the foundations for further studies to explore how viral models can better represent RSV and understand the immune response in general.

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PHYS2018MELENDEZ55573 PHYS

Using Machine Learning to study the chemistry of the Sagittarius dwarf galaxy

Type: Graduate
Author(s): Matthew Melendez Physics & Astronomy John Donor Physics & Astronomy Amy Ray Physics & Astronomy
Advisor(s): Peter Frinchaboy Physics & Astronomy

Sagittarius (Sgr), a dwarf galaxy and satellite to the Milky Way, is currently being tidally torn apart. To study the chemistry of
Sgr, we have taken thousands of stellar spectra across the galaxy. We have analyzed the stellar component of Sgr member
stars by using The Cannon, a machine learning algorithm for determining stellar parameters (temperature, surface gravity, chemical
abundances) from stellar spectra. A subset of our stars have previously been observed as part of SDSS/APOGEE survey, at higher
quality, which allows us to use these spectra to train The Cannon so that we can obtain accurate abundances for the ~1,100 Sgr
member stars. This will allow us to confidently study the formation history and stellar evolution of Sgr, and place it within the
context of other dwarf galaxies.

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PHYS2018MURPHY6938 PHYS

Characterizing the Efficiency of Anticancer Drug Treatement Using Mathematical Models

Type: Graduate
Author(s): Hope Murphy Physics & Astronomy Giridhar Akkaraju Biology Hana Dobrovolny Physics & Astronomy Anton Naumov Physics & Astronomy Elizabeth Sizemore Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

In order to determine correct dosage of chemotherapy drugs, the effect of the drug must be properly quantified. There are two important values that characterize the effect of the drug: Emax is the maximum possible effect from a drug, and IC50 is the drug concentration where the effect diminishes by half. Currently, the technique used to measure these quantities gives estimates of the values that depend on the time at which the measurement is made. We use mathematical modeling to test a new method for measuring Emax and IC50 that gives estimates independent of measurement time. We fit treatment data from the literature to determine values for Emax and IC50 using mathematical models under two assumptions: that the drug reduces growth rate, or maximum number of cells. Our method produced IC50 estimates similar to estimates derived using current techniques. This work is intended to characterize the efficacy of anticancer drug treatments and determine the correct doses before trying those in patients to get the most effective therapeutic treatment.

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PHYS2018NUREKEYEV48671 PHYS

Multi-pulse based approach on superresolution microscopy

Type: Graduate
Author(s): Zhangatay Nurekeyev Physics & Astronomy Julian Borejdo Biology Luca Ceresa Physics & Astronomy Jose Chavez Physics & Astronomy Sergey Dzyuba Chemistry & Biochemistry Rafal Fudala Biology Ignacy Gryczynski Physics & Astronomy Sangram Raut Biology
Advisor(s): Zygmunt Gryczynski Physics & Astronomy

Since the invention of on optical microscope various biological structures have been observed. Today we have a need to study subcellular structures and their dynamics. Here we encounter diffraction limit – two objects located closer than the half of the wavelength cannot be resolved as two distinct objects. Superresolution techniques have been developed to overcome this limit. They can be divided into two types: stochastic and deterministic. Stochastic ones (STORM, PALM) utilize natural ability of fluorescent molecules to blink. These methods require sparse labeling and significant amount of some time to acquire image. Deterministic ones (STED) utilize an additional pulsed light source to de-excite populated state. These methods require advanced technology. Our method is similar to deterministic superresolution techniques. We utilize long-living fluorescent dyes whose excited state population can be significantly enhanced by bursts of pulses. Enhancement occurs only when time delay between pulses within burst is shorter than the lifetime of the dye. By varying bursts and single pulses one may observe varying intensity of a dye, hence, achieve superresolution. Regular labeling methods become an advantage in this case, and such an experimental setup is not very different from conventional microscopy methods.

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PHYS2018PINKY10563 PHYS

Modeling of Viral Coinfection in Human Respiratory Tract Using Stochastic Method

Type: Graduate
Author(s): Lubna Pinky Physics & Astronomy Hana Dobrovolny Physics & Astronomy Gilberto Gonzalez-Parra Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

Respiratory coinfections are commonly found in patients hospitalized with influenza-like illness, but it is not clear whether these infections are more severe than single infections. Mathematical models can be used to help understand the dynamics of respiratory viral coinfections and their impact on the severity of the illness. Most models of viral infections use ordinary differential equations (ODEs) which reproduce the average behavior of the infection, however, they might not be accurate in predicting certain events because of the stochastic nature of the viral replication cycle. Stochastic simulations of single virus infections have shown that there is an extinction probability that depends on the size of the initial viral inoculum and parameters that describe virus-cell interactions. Thus the coexistence of viruses predicted by the ODEs might be difficult to observe in reality. In this work we develop a stochastic numerical implementation of the deterministic coinfection model using the Gillespie algorithm. Stochastic extinction probabilities for each viruses are calculated analytically and will be verified by stochastic simulations. Preliminary analyses of the model have showed that even if the two viruses are given the same initial growth rates, one virus can have higher probability of extinction than the other, namely competitive exclusion, opposing the coexistence cases predicted by the deterministic model.

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PHYS2018RAY7452 PHYS

Shooting for Star Cluster Chemical Abundances with The Cannon

Type: Graduate
Author(s): Amy Ray Physics & Astronomy
Advisor(s): Peter Frinchaboy Physics & Astronomy

Star clusters are key chemical and age tracers of Milky Way evolution. The use of star clusters to provide significant constraints on galaxy evolution, however, has been limited due to discrepancies between different studies. This work seeks to add additional open clusters into an existing large, uniform chemical abundance system. We analyze spectra of giant stars in 31 open clusters and, using a machine learning method called The Cannon, determine iron abundances. This uniform analysis is compared with previous results, and we present new chemical abundances of 12 star clusters.

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PHYS2018REEKS5125 PHYS

Nanoscale ZnO with Controllable Crystal Morphology as a Platform to Investigate Mechanisms of Antibacterial Action

Type: Graduate
Author(s): John Reeks Physics & Astronomy Bao Thach Engineering
Advisor(s): Yuri Strzhemechny Physics & Astronomy

Nanoscale zinc oxide (ZnO) is an inexpensive, widely accessible material used in numerous well-established and emerging applications due to the unique optoelectronic, structural and chemical properties as well as the variety of synthesis methods. One of these emerging applications of ZnO nanostructures is in the field of antibacterial tools. The antibacterial nature of this material is being actively investigated, yet the mechanisms behind remain largely unknown. Some studies indicate that there is an influence of the polarity of exposed ZnO surfaces on their antibacterial action. Crystalline ZnO forms hexagonal prisms due to an anisotropic hexagonal lattice, which in turn produces three primary surface types: Zn-polar, O-polar and nonpolar. The hexagonal faces of these prism-shaped crystals are polar while the rectangular surfaces are nonpolar. In this study we employ a hydrothermal chemical method for growing ZnO nanocrystals having tunable morphology with the aim of obtaining a reliable control of the predominant polarity of the exposed nanocrystalline surfaces. This in turn can serve as a platform to investigate mechanisms of antibacterial action. Using Scanning Electron Microscopy as a probe of the microcystal morphology we demonstrate that the predominant ZnO surface polarity can be affected through the variations in the chemical precursors of the hydrothermal process. The ability to control the morphology and prominent surface polarity of ZnO nanocrystals would allow us to investigate fundamental phenomena governing antibacterial characteristics of nanoscale ZnO.

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PHYS2018RICHSTEIN7035 PHYS

The effects of dwarf-galaxy tug-of-wars

Type: Undergraduate
Author(s): Hannah Richstein Physics & Astronomy Jing Sun Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy

Galaxies are not alone in space; often, they have neighboring galaxies with which they gravitationally interact. These interactions foster diverse characteristics, such as size, morphology, and color. This project studies the properties of galaxies in the context of their neighbors and environment. More specifically, I examine how the proximity between galaxies affects their evolution. I do this by exploring two samples: 1) galaxy pairs within a few galactic diameters of each other and 2) isolated galaxies separated from the next nearest galaxy by more than ~450,000 light years. Using existing Mapping Nearby Galaxies at Apache Point Observatory observations, part of the Sloan Digital Sky Survey IV, I determine the various types of ionization conditions present at different radii throughout each galaxy. Through these efforts, I explore which processes promote and hinder star formation within galaxies.

(Presentation is private)

PHYS2018RODRIGUEZ18820 PHYS

Impact of trypsin in dynamics infection.

Type: Graduate
Author(s): Thalia Rodriguez Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

In vitro experiments are necessary to understand the processes driving viral infections and to develop antivirals and vaccines. However, experiments do not completely replicate the in vivo environment, and not all cell lines used in these experiments have the components necessary to support viral replication. In these cases, the missing elements are added to the medium to facilitate viral infections. Trypsin is an enzyme usually added to facilitate influenza infections in cell cultures. We use data from infections of influenza in different cell lines in the presence and absence of trypsin to parameterize a within-host mathematical model of influenza infection, and in this way understand the impact of trypsin in the dynamics of the infection.

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PHYS2018RYAN16053 PHYS

Modifying the Optical Properties of Graphene Oxide via an Electric Field

Type: Undergraduate
Author(s): Conor Ryan Physics & Astronomy Fabian Grote Physics & Astronomy Anton Naumov Physics & Astronomy Thomas Paz Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy

Graphene is a promising material, due to its various inherent properties that will lead to better, smaller, faster, or flexible electronics. Graphene doesn’t exhibit optical emission, limiting its potential use in optoelectronics. However, graphene’s functional derivative Graphene Oxide (GO) maintains many of graphene’s properties and exhibits optical fluorescence emission in the visible/near-infrared, which makes it a candidate for novel applications such as optoelectronic transistors, light emitting diodes (LEDs), and solar cells. Therefore, finding a way to alter optical and electronic properties of GO will lead to more versatility and control among the aforementioned applications.
In this work, we studied the potential use of GO for microelectronic applications by observing the fluorescence of this material under the electric field. A dried GO/PVP film was subject up to 1.6 V/µm in between transparent conductive ITO electrodes resulting in observable quenching of fluorescence emission as the field was applied. The emission was further partially restored at 0 field. Additionally, microscopic flakes of graphene oxide deposited onto interdigitated 10 µm electrodes were subject to 100V/µm with no breakdown current detected. The fluorescence of individual flakes, observed via visible fluorescence microscopy, experienced substantial field-dependent quenching. In aqueous suspensions GO flakes exhibited electrophoretic migration signifying of charge separation. As a result of this work we suggest the potential of varying electronic and optical properties of graphene oxide via the electric field for the advancement and control over its optoelectronic device applications.

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PHYS2018SENGER4580 PHYS

Observing Massive Gas Outflow from Supernovae Explosions around the Large Magellanic Cloud Galaxy

Type: Undergraduate
Author(s): Brian Senger Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy

Within the Large Magellanic Cloud (LMC) galaxy, there are huge gaseous outflows that originated from violent supernovae explosions within this galaxy. Observing this outflow that is being kicked out from the LMC reveals that there is ionized gas present, which can be trace by using Ha emission. Using observations from the Wisconsin Ha Mapper (WHAM) in Chile, we are mapping out the Ha emission that is being kicked out of the LMC. In this project, I am removing the imprint of the Earth’s atmosphere in order to isolate the gas cloud. This will be used to determine how much gas is being thrown out of the galaxy. The more gas the galaxy loses, the more it would not be able to make stars in the future.

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PHYS2018SUN34899 PHYS

Star-formation activity in isolating and interacting low-mass galaxies

Type: Graduate
Author(s): Jing Sun Physics & Astronomy Hannah Richstein Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy

Interaction between galaxies is of critical importance to the formation and evolution of galaxies. We are conducting a study on both isolated and interacting low-mass galaxies to determine how their environment impacts their star-formation ability. We compare the features of gas and stars in isolated and interacting galaxies to examine the differences and similarities. The interaction-triggered star-formation activity will be further discussed to analyse how the internal properties of galaxies are influenced by the outer environment. This investigation is based on data from the fourth-generation Sloan Digital Sky Survey (SDSS-IV) / Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), and is part of the project No.0285 in SDSS-IV.

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PHYS2018TULADHAR48357 PHYS

Studying the effects of antiarrhythmic drugs on restitution properties of action potential duration of canine ventricular cells.

Type: Graduate
Author(s): Binaya Tuladhar Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy

Restitution describes a functional relationship between the action potential duration (APD) and the preceding diastolic interval (DI). It plays an important role in the function of the heart and is believed to determine the stability of heart rhythms. We investigate the effects of various antiarrhythmic drugs on dynamic and standard (S1-S2) restitution properties of APD of ventricular cells by using a canine ventricular cell model. The restitution hypothesis suggests that the slope of the restitution curve governs the transition to alternans, believed to be a precursor to the development of ventricular arrhythmias, particularly ventricular fibrillation (VF). Our study examines the slope of these restitution curves for three classes of drug to determine whether they are proarrhythmic or antiarrhythmic and to test the hypothesis for the prediction of alternans.

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