The nearby Magellanic Cloud galaxies are tidally interacting with each other, displacing over 2 billion times the mass of the Sun in gas. A tidal feature called the Leading Arm is spearheading these galaxies on their trajectory to the Milky Way. Its fragmented morphology suggests that it is already interacting with our galaxy and supplying it with star-forming material in the form of gas. We present new optical observations of the Leading Arm with which we derive a heliocentric distance to the structure.
Located inside the Large Magellanic Cloud, fierce explosions called supernovae have thrown out massive amounts of gas in every direction. A portion of this gas is aimed toward the Milky Way and is on a crash course with our galaxy. We are observing this gas with the Wisconsin H-Alpha Mapper, which provides a window into how the gas is distributed. These observations show two periods of supernovae explosions that created two distinct gas winds. One of these winds is currently active while the other was produced roughly 300 Million years old. Studying these gas clouds will provide information on how massive these winds are and the rate at which they are produced. The ejected gas is headed toward the Milky Way could supply our galaxy with additional gas to form stars in the future.
Studying something as large as the Milky Way can be a daunting task, and studying the galaxy in its entirety is impossible, so astronomers use small pieces, such as star clusters, to “trace" the behavior and make-up of the galaxy. With the advent of large-scale surveys covering 70%-100% of the sky, more of these tracer components are available than ever before. But they aren’t trivial to pick out of the massive datasets. We have developed a program that integrates data from multiple large scale surveys to identify star clusters and determine fundamental parameters that trace the galaxy in that location (3D velocity and location, chemical make-up, age). We also present initial work using these clusters to study the distribution of chemicals in the Milky Way.
Author(s): Md Tanvir Hasan Physics & Astronomy Roberto Gonzalez-Rodriguez Chemistry & Biochemistry Anton Naumov Physics & Astronomy Conor Ryan Physics & Astronomy Brian Senger Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy
Location: Session: 2; 3rd Floor; Table Number: 1
(Poster is private)
Graphene oxide (GO) inherits high transparency, substantial conductivity, high tensile strength from its parent materials graphene. Apart from these properties, it emits fluorescence which makes it a potential material to use in optoelectronics and bio-sensing applications. In this work, we have utilized systematic ozone treatment to alter the optical band gap of single-layered graphene oxide in aqueous suspensions. Due to controlled ozonation, additional functionalization takes place in GO graphitic sheet which changes GO electronic structure. This is confirmed by the increase in vibrational transitions of a number of oxygen-containing functional groups with treatment and the appearance of the prominent carboxylic group feature at c.a. 1700 1/cm. Albeit, timed ozone induction introduces only slight change in color and absorption spectra of GO samples, the emission spectra show a gradual increase in intensity with a significant blue shift up to 100 nm from deep red to green. This large blue shift suggests an increase in optical band gap with additional functionalization introduced by ozone treatment. We utilize a semi-empirical theoretical approach to describe the effects of functionalization-induced changes. This model attributes the origins of fluorescence emission to the quantum confined sp² carbon islands in GO encircled by the functional groups. As we decrease the graphitic carbon cluster size on the GO sheet, the optical bandgap calculated via HyperChem molecular modeling increases, which supports the experimentally observed blue shifts in emission. This theoretical result is further supported by the TEM measurement of ozone-treated samples, which shows a decreasing trend of average ordered graphitic carbon cluster size on GO sheets with treatment time. Theoretical modeling, as well as the experimental results, indicate that the optical bandgap and emission intensity of GO are alterable with controlled ozone treatment, which allows tailoring the optical properties of GO for specific applications in optoelectronics and bio-sensing.
Two small galaxies outside the Milky Way, called the Magellanic Clouds, are violently interacting with each other. As they interact, gas is stripped out of them, which leaves a huge gaseous tail as they orbit the Milky Way. This tidal debris covers a quarter the sky from earths perspective. The goal of this to project determine the properties of the gas that is trailing behind the Magellanic Clouds by creating maps of the neutral and ionized gas. We trace the neutral hydrogen with radio observations taken with the Arecibo Observatory and the ionized hydrogen using optical observations taken with the Wisconsin H-alpha Mapper telescope. This gaseous stream will one day fall onto the Milky Way and provide our galaxy with material to create new stars.
A massive gas cloud, known as Complex A, is headed towards our Galaxy. This high-velocity cloud is made up of 2 million times the mass of the Sun of neutral and ionized hydrogen. This cloud is traveling towards the Milky Way's disk, through the Galactic halo. This halo is made up of low density gas at a million degrees Kelvin that acts as a headwind that damages the cloud. Light escaping the Milky Way’s disk also hits the cloud and ionizes it. Using 21-cm radio observations from the Green Bank Telescope, we studied the motions of the gas. We found that diffuse gas is lagging behind the denser parts of the cloud. These motions suggest that gas is being stripped off the cloud and that it is dissolving into the Galactic halo. This disruptive process means that less gas will safely reach the disk of Milky Way and therefore the cloud will provide less gas for making future stars.
Resonances occurring in quantum mechanical cross-sections can be attributed to the existence of complex eigenvalues of the associated Schrödinger equation. For sufficiently narrow resonances the real part of such eigenvalues corresponds to the energy of the resonance and the imaginary part is directly related to its width.
Recently, mathematicians settled a more than 30-year-old controversy regarding the distribution of such resonance eigenvalues for a specific model scattering potential. The controversy arose due to the fact that two different numerical approaches applied to solving the non-relativistic Schrödinger equation gave rise to two different results. In addition to providing a mathematical proof as to which of the two methods was correct, the recent study predicted the approximate location of additional resonance eigenvalues in the complex energy plane.
The present study seeks to revisit this problem in an attempt to provide more accurate eigenvalues for these additional resonances. The complex rotation method was applied to the Riccati equation corresponding to the one-dimensional Schrödinger equation and a Python code was written to numerically integrate the logarithmic derivative of the wave function and search for energy eigenvalues in the complex plane.
We use 3D plots and short videos to illustrate our technique, the original controversy, as well as the reason for the difficulty in locating the new resonances. Much improved numerical values for these resonances are also presented.
Author(s): Hana Jaafari Physics & Astronomy Hung Doan Physics & Astronomy Sangram Raut Physics & Astronomy
Advisor(s): Zygmunt Gryczynski Physics & Astronomy
Location: Session: 1; 2nd Floor; Table Number: 3
Medical therapeutics is an ever-growing field seeking to improve patients’ livelihoods through means including efficient drug delivery, which ensures that the medication reaches its maximum efficacy. The micro-viscosities within a cell may affect the diffusion of medication, and can be measured through molecular viscometers in order to potentially increase the quality of future therapeutic research. The BODIPY dye is utilized as a molecular viscometer and past spectroscopic and lifetime studies have characterized BODIPY monomers, as well as rotor and non-rotor BODIPY dimers. Triazine-based rotor and non-rotor BODIPY trimers were synthesized for this study, and then the dyes’ photophysical properties and behavior within cells were measured. The results of this study indicated that the BODIPY trimer is a fluorophore with a high molar extinction coefficient, and may successfully be employed as a molecular viscometer within cells.
Author(s): Matthew Melendez Physics & Astronomy John Donor Physics & Astronomy Peter Frinchaboy Physics & Astronomy Julia O'Connell Physics & Astronomy
Advisor(s): Peter Frinchaboy Physics & Astronomy
Location: Session: 1; B0; Table Number: 6
The Open Cluster Chemical Abundances and Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. However, neutron capture elements are limited in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we are conducting a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. As part of this effort, we present Ba II, La II, Ce II and Eu II results for a few open clusters without previous abundance measurements using data obtained at McDonald Observatory with the 2.1 m Otto Struve telescope and Sandiford Echelle Spectrograph.
Author(s): Hope Murphy Physics & Astronomy Elizabeth Sizemore Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy Anton Naumov Physics & Astronomy
Location: Session: 2; B0; Table Number: 8
Three million women have breast cancer in US, causing breast cancer to be the second most common cause of death from cancer for women. Doxorubicin is a commonly used drug for cancer treatment. The focus of my research is characterizing the drug efficacy for doxorubicin in the human breast cancer cell line MCF-7. There are two quantities that characterize the effect of a drug: E_max is the maximum possible effect from a drug and IC_50 is the drug concentration where the effect diminishes by half. We are using mathematical modeling to extract E_max and IC_50 for Doxorubicin in MCF-7 cells. 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 for patients.
Graphene is thought to be revolutionary material due to its vast inherent properties. It can give us thinner, faster, and cheaper electronics. Graphene oxide (GO) inherits its properties from graphene and as opposed to graphene, can be conveniently mass- produced using chemical synthesis. We seek to classify new derivatives of graphene with specific optical properties for applications in optoelectronics. The properties of graphene can be tailored through chemical modifications, such as hydrogenation and halogenation.
In this work we present various methods for the synthesis of graphene derivatives by utilizing different functional groups and study their optical properties. The successfully functionalized graphitic derivatives include diazonium functionalized graphene; lightly oxidized graphene; nitro-graphene; and bromo-graphene. The presence of functional groups is confirmed by FTIR spectra showing characteristic vibrational frequencies. All of functionalized graphitic derivatives exhibit fluorescence regarding their functionalization. This leads us to understand that the fluorescence in GO appears not to be dependent on specific functional groups but rather on the confinement of the graphitic regions produced by those.
Such functional derivatives of graphene may expand its applications in optoelectronics and make it a more versatile material for a variety of applications.
Thus we also look into the behavior of graphene oxide in applications related to microelectronics studying the fluorescence of GO in the electric fields.
Emission quenching was observed using GO films under electric fields of the order of 10^6 V/m. A dried GO/PVP film was subject up to 1500V in between transparent conductive ITO electrodes. As high voltage was applied to the slides, a fluorescence signal decreased by 35.9%.
A capability of such electric-field controlled emission is highly applicable in optoelectronic transistors and can advance modern microelectronics.
Respiratory viral infections are a leading cause of mortality worldwide. As many as 40% of patients hospitalized with influenza-like illness are reported to be infected with more than one type of viruses. Mathematical models can be used to help us understand the dynamics of respiratory viral coinfections and their impact on the severity of the illness. We develop a mathematical model which allows for respiratory cells to be infected simultaneously with two types of viruses. A mathematical analysis is performed to assess the full behavioral dynamics of the model. We find that chronic coinfection does not occur in this model; infection grows due to only one viral species. Some other mechanism must be responsible for the long-lasting coinfections in humans.
The goal of this study was to conduct a survey of 913 M-dwarf stars from the Lepine and Shara Proper Motion(LSPM) catalog within 33 parsecs. This research was conducted to improve upon the statistics of nearby multiple M-dwarf star systems. Identifying and confirming multiple systems at both wide and small separations will expand understanding of M-dwarf formation by comparing these results to existing star formation models. Data for these targets was collected with the Robo-AO camera on the Palomar 60in telescope. Separation and position angles were determined and compared for two epochs of the images containing multiple stars, one taken in 2012 and the other taken in 2014, to look for changes in these values. Stars with little change in position with respect to one another suggest they are common proper motion pairs. The Washington Double Star(WDS) catalog and other resources were used to further determine binarity. There were 50 multiple star system candidates found with a multiplicity fraction of 28.6±3.0 and a companion star fraction of 34.7±2.1.
Author(s): Hannah Richstein Physics & Astronomy Kat Barger Physics & Astronomy Jing Sun Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy
Location: Session: 1; 3rd Floor; Table Number: 3
Our universe contains billions of galaxies, made up of stars, gas, and interstellar dust. We can examine the light emitted from these galaxies to learn about the different energetic events occurring within them. These include supernova explosions in the disk and active black holes at the center, which are both enhanced by galaxy interactions. Before the light from the stellar activity and the warm gas reaches us, it scatters off dust along its path. This causes the light to appear redder than it originally was. If we do not correct for this reddening effect, we could misinterpret the processes occurring within the galaxies. This project examines the properties of two galaxies interacting over a large distance and illustrates the importance of reddening correction for better understanding galaxy evolution.
Many influenza experiments are done in vitro, however, not all cell lines used in these experiments possess the proteins necessary to cleave hemagglutinin, an important step in cell infection. Trypsin is a protein used to facilitate in vitro influenza infections. Trypsin cleaves the viral surface protein hemagglutinin, allowing it to fuse with the cell membrane and enter the cell. We use data from in vitro influenza infections in the presence and absence of trypsin to parameterize a within-host mathematical model of influenza infection. This allows us to quantify the dynamical changes caused by the presence of trypsin.
Author(s): Elizabeth Sizemore Physics & Astronomy Marais Culp Physics & Astronomy Md. Tanvir Hasan Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy
Location: Session: 2; 1st Floor; Table Number: 4
Graphene and its derivatives are novel materials with a number of unique properties that can be applied in electronics, sensing and biotechnology. Particularly, graphene oxide (GO) is an exceptional system that, unlike graphene, can be chemically mass-produced at low cost and possesses physical properties that are critical for biomedical applications. GO exhibits pH-dependent fluorescence emission in the visible/near-infrared, providing a possibility of molecular imaging and pH-sensing. It is also water soluble and has a substantial platform for functionalization, which allows for the delivery of multiple therapeutics, or the attachment of different sensing moieties. Some of these properties can be adjusted by the means of chemical/physical processing to fit the desired therapeutic delivery or sensing approaches. We utilize and modify these properties to yield a multifunctional delivery/imaging/sensing platform geared toward the analysis of cancer therapeutics delivery in vitro. In our work GO serves as a drug transport agent when paired with cancer therapeutic drugs and as a molecular marker for imaging the delivery pathways. The optimal emission and excitation of the graphene oxide flakes are selected to maximize the imaging modality in the spectrally-confined region and reduce the effects of biological autofluorescence. We also modify GO physical properties via controlled oxidation to maximize the emission and reduce the cytotoxicity to low/negligible levels: we report over 90% cell viability with GO concentration levels of 15 ug/mL based on the MTT assay in HEK-293 cells. GO emission in healthy (HEK-293) and cancer (HeLa) cells is quantified for a variety of pH environments, as well as flake sizes, to identify the ideal conditions for cellular internalization and pH-sensing of acidic cancerous environments. In addition, in-vitro fluorescence microscopy analysis provide quantitative assessment of the drug delivery and preferential targeting for cancer versus healthy cells. The results of this work suggest GO as an innovative and effective multifunctional platform for cancer therapeutics.
A galaxy environment influences its internal properties. All galaxies start out small and grow bigger after merging with other galaxies. We are conducting a statistical study on isolated and interacting galaxies to determine how their environment impacts on their star-formation ability. We are using observations from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which has already observed more than 3000 galaxies. We are examining the differences and similarities of the gas and stars in isolated and interacting galaxies to explore their past and current star formation activity. From these comparisons, we will identify which conditions promote and hinder star formation to learn how different types of galaxies evolved. An example of an isolated galaxy is shown here.
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 S1-S2 restitution properties of action potential duration of ventricular cells by using a human ventricular cell model. The restitution hypothesis suggests that the slope of the restitution curve governs the transition to alternans. Our study examines the slope of these curves for three classes of drug to determine whether they are proarrhythmic or antiarrhythmic.