2019 APS CUWiP at UC Davis

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Student Poster Session

A student poster session will run Saturday afternoon. Student presenters will stand by their posters to answer any questions for 30 minutes but will also have time to get coffee and look at the other posters. If you've done research, please consider presenting your progress or results. Preparing a poster can help you organize your thoughts about your project, and it's a great chance to talk to other physicists about what you've been doing. Your conversations may even give you some good ideas on how to proceed.

When you register you'll be asked whether you plan to present a poster. If so, you should submit a title, author list with their institutions, and an abstract (summary of the research) of no more than 250 words.

Poster presentations will be in the Physics Building. The assigned locations will be distributed in the welcome packet you receive at check-in. You can set up the poster before the Saturday morning announcements or during the Saturday morning coffee break.

Characterizing X-ray Emission of Supernova Remnants in the SMC
Nicole Man, Katie Auchetll, Laura Lopez, and Enrico Ramirez-Ruiz
Room 186, 4-4:30pm

Supernovae (SNe) play an important role in modern day astrophysics. Optical surveys and spectroscopic studies of these events reveal two distinct classes of explosions which result from either the core-collapse (CC) of a massive star or the thermonuclear explosion of a carbon-oxygen white dwarf in a binary system (Type Ia). However, due to these extreme events being relatively rare, supernova remnants (SNRs), which are the structures that result from a SNe that occurred up to ~1000s years of ago, provide us with a unique opportunity to probe the nature of these explosions. As the shock fronts of SNRs heat up expanding ejecta to X-ray emitting temperatures, X-ray spectroscopy allows us to constrain the nucleosynthesis properties of its progenitor, which can be used to determine the explosive nature of these events. Here we present a systematic study of three SNRs (IKT4, IKT5 and DEMS128) found in the nearby, low metallicity galaxy the Small Magellanic Cloud, which have been suggested to arise from a Type Ia based on abundance estimates derived from their X-ray spectra. However, using archival Chandra and XMM-Newton observations of these three sources, we find that IKT5 and DEMS128 have properties more consistent with that of a CC, while deeper observations of IKT4 is needed to further quantify the SN origin of this remnant.

Overcoming the Meter-Size Barrier in Planet Formation Models
Elizabeth Yunerman, Diana Powell, Ruth Murray-Clay
Room 185, 4-4:30pm

The meter-size barrier is a persistent problem in current planet formation models, where particles on the order of a meter in size fail to grow because they either fragment or drift into the star. Planetesimal formation at this size can be summarized in three characteristic timescales: growth, drift, and fragmentation. Accurate models of these timescales that resolve the meter-size barrier will improve our understanding of how planets form in a protoplanetary disk. Recent observations of protoplanetary disks indicate that they may be more massive than previously assumed. Decreasing the dust-to-gas ratio from typically assumed ISM values, and increasing the total disk mass, causes the growth timescale to be longer. According to our analytical model, the drift timescale is initially shorter than the growth timescale, allowing a particle to drift past the fragmentation limit of the meter-size barrier. Once beyond the barrier, the growth timescale becomes faster which permits the particle to grow quickly such that it is less susceptible to radial drift into the star. These preliminary results show that through increasing the total disk mass, the particle can potentially grow beyond the meter-size barrier. We adapt the two-population dust evolution numerical model from Birnstiel et al. (ApJ) 2012, 2015 to verify that, with a smaller dust-to-gas ratio and a smaller turbulence parameter, particles can survive the meter-size drift and fragmentation barrier and continue to grow.

Data Quality Monitoring Display for the FLIC Board in the ATLAS Fast Tracker Trigger at CERN
Kenia Y Medina, Dr. Bingxuan Liu, and Dr. Joshua Moss
Room 186, 4:30-5pm

The Data Quality Monitoring Display for the FLIC board was designed in order to provide the shifter at the ATLAS control room a visual representation of the physical health of the board. It provides detail descriptions and troubleshooting of each of the histograms that shifters can understand even without having prior knowledge of the FastTracKer (FTK).

Analysis of X-ray Nano-Diffraction Data of Thin Films of PbZr0.2Ti0.8O3
Joyce Christiansen-Salameh, Ian Rippy, Zhonghou Cai, Sylvia Matzen, Martin Holt, and Roopali Kukreja
Room 185, 4:30-5pm

PbZr0.2Ti0.8O3 (PZT) is a material with ferroelectric properties with potential applications in sensor and actuator devices. We have performed X-ray nano-diffraction experiments on PZT thin films to investigate structural inhomogeneities at nanoscale. In the x-ray nanodiffraction setup, a focused beam (25 nm) is used to raster scan the sample and a 2D detector captures the diffraction patterns. One of the samples that was imaged with this technique, is divided into two regions: half of the film is polarized up (+5 V), while the other half is polarized down (-5 V). MATLAB was used to analyze each detector image of the resulting nano-diffraction measurement over a sample region. Code was developed to account for experimental noise and mosaicity of the sample, and to analyze Bragg diffraction peaks. By compiling and comparing this information from each CCD image, real space sample maps of intensity and strain were produced to quantify lattice parameter inhomogeneities with nanometer lengthscale.

Manipulating Metal-Insulator Transition Temperatures in NdNiO3
Nadia Albayati, Kenneth Ainslie, and Roopali Kukreja
Room 186, 4-4:30pm

The rare-earth nickelate NdNiO3 (NNO) belongs to a class of perovskites that have tunable electronic and magnetic properties, which are of interest for reducing energy consumption and increase switching speeds in electronics. NNO has a sharp first-order metal-insulator phase transition (MIT), at 200K. In thin films this MIT can be tuned using stoichiometry and epitaxial strain. We have grown NNO on the single crystal perovskite substrates SrTiO3 (STO), NdGaO3 (NGO), and LaAlO3 (LAO) to achieve different values of epitaxial strain. We utilized off axis RF magnetron sputtering for thin film growth using a stoichiometric NNO target. Electrical and X-ray diffraction characterization shows promising results.

Identifying and Characterizing Radio-Mode Active Galactic Nuclei (AGN)
Lark Wang, Emil Noordeh, Ashley King, Rebecca Canning, and Steven Allen
Room 185, 4:30-5pm

Supermassive black holes which sit at the centers of galaxies can launch jets of highly relativistic particles which we observe primarily in the radio wavelengths. These jets can carry enough energy to prevent further growth of their host galaxy and even affect the larger-scale environment of galaxies. Key questions remain about how these jets can dissipate energy and under what conditions they are launched. We are studying such jets in the most massive galaxies which reside in galaxy clusters. I will present results from preliminary attempts to identify and characterize radio-bright supermassive black holes using traditional detection techniques and a convolutional neural network.

Wind Proofing LIGO
Elyssa Hofgard, Edgard Bonilla, and Brian Lantz
Room 185, 4-4:30pm

To reduce problematic wind that contributes to ground tilt, LIGO has proposed building a 50% porous fence around End Station X. We employed experimental and computational methods to evaluate the proposed fence. First, we measured different fence materials with a fan and a wind tunnel. Both the Tenax Wind Screen material and the Belton Industries material reduced wind speed by about 50%, so the main differences will arise from cost and material strength. Next, we employed Computational Fluid Dynamics (CFD) modeling to evaluate the wind load on End Station X with and without a porous fence. We found that the porous fence is quite effective in reducing the load on the building. Models show that with a fence, problematic wind speeds could be above 20 m/s, which only occur 1.54% of the time. We then evaluated data from the test fence at LIGO Hanford and compared these data to steady-state and transient CFD models. The Tenax test fence was found to reduce wind speed by 57%, while the steady-state CFD model showed 60% reduction. However, the transient model appears to show more variability than the real data in some areas, suggesting that the fence may smooth wind flow. A 50% porous fence is a well motivated wind proofing measure for End Station X, yet more robust model verification should be completed.

Characterizing the onset of fast flow at Institute Ice Stream, West Antarctica
Marnie Bryant, Elisa Mantelli, Jenny Suckale, Davide Castelletti, Martin Siegert, and Dustin Schroeder
Room 186, 4:30-5pm

Institute Ice stream is one of the major Ice Streams draining into the Weddell Sea in West Antarctica. Observational evidence suggests there have been changes in flow speed and direction over time. The mechanisms driving these changes are not well understood, which limits our ability to anticipate the future stability of the region. Fast flow onset in Institute does not appear to be controlled by either topography or bed geology. One possible mechanism is the onset of temperature dependent sliding at the bed. Theoretical work by Mantelli and Schoof (2019) suggests that an abrupt sliding onset is not feasible, and propose an extended transition region of sub-temperate sliding. In order to characterize the transition behavior at Institute Ice Stream, we use data from the BAS-PASIN 2010/2011 radar survey to look at englacial layer architecture along the direction of flow. We use a new SAR processing technique developed by Castelleti et al (2019) that automatically calculates layer slopes, and compare these slopes to modeled streamline slopes. Results so far support the hypothesis of an extended region of sub-temperate sliding.

Spatial Distributions of Excited Atoms in Argon Plasma
Chelsy Gonzalez and Milka Nikolic
Room 185, 4:30-5pm

Plasma describes the property of ionized gas that follows the shape of the object where it was created. When a gas which consists of mainly neutral particles is heated, the electrons and atoms are able to gain energy and break the atomic bonds becoming free, which is called ionization. Then there is a process of excitation, which is when the electron doesn't gain enough energy to break the atomic bond and may jump into an empty orbital or higher energy level. Electrons, however, cannot stay in the excited state and will decay back to the ground state through radioactive decay, and metastable levels decay back to the ground state through non-radioactive collisional quenching processes, so we try to observe and understand fundamentally plasma characteristics. The experiment was conducted in a radio-frequency cavity discharge, using a commercial RF generator operating at a frequency of 13.56 MHz, at powers of 30-100 W, and the working pressure in the quartz chamber was made to 15-50 mTorr. We have used an optical emission spectroscopy (OES) to detect the various excited energy levels higher than ground and metastable states. We are using the OES as our primary measurement tool to observe the spectra of the argon excited states by measuring photons emitted from the plasma. Through our measurement methods, we are able to collect the light of various wavelengths emitted from the plasma, through this we are able to determine plasma intensities, the population densities, graph robust two angle tomography, electron configurations, and more.

Do Smaller Galaxies Preferentially Live in Older Dark Matter Halos?
Sahar Ahmadi*, Norhan Osman*, Leah George, Joy Velasquez, Grecco Oyarzun and Viraj Pandya
Room 185, 4-5pm

It is not well understood why galaxies of the same mass show a range of sizes, and what dark matter halo properties might systematically correlate with this scatter. Using a semi-analytic model (SAM) of galaxy formation at z=0, we explore an empirical connection between the ages of dark matter halos and sizes of galaxies in narrow bins of stellar mass (from 109 to 1012). We find a weak trend where galaxies in older dark matter halos are smaller on average by ≈0.3 dex. This trend itself correlates strongly with both dark matter (DM) halo mass (despite controlling the stellar mass) and the mass fraction of stars that were acquired via mergers. We continue to explore further relationships between dark matter halo properties and their corresponding galaxies to formulate the cause of scattering in our results.

*Joint first authors and joint presenters

The Population Densities of Argon Metastable Levels
Nada Khogeer, Chelsy Gonzalez, Milka Nikolic, and Ivan Sepulveda
Room 185, 4-4:30pm

This experiment was performed to develop models to understand the most attractive properties for plasma etching and cleaning using Argon plasma generated using radio frequency powers. To understand the surface modification processes, a kinetic model for all plasma particles is developed. Electrons cannot stay long in the excited state and will decay back to the ground state by two possible processes of radiative decay and collisional quenching process. The resonant levels and the metastable levels are examined using different methods. In this study, the optical emission spectroscopy (OES) method is used to obtain the main properties of argon plasma. OES is useful only when detecting species that are excited energy levels higher than ground metastable states. For the metastable levels, the Extended Corona Model was used to define the etching process. Monte-Carlo Simulation was used to get the results of the Electron Energy Distribution Function (EEDF) by propagating electron in argon plasma with the same conditions as the experiment with 10,000 electrons (E/N = 50 Td).

How To Kill a Tardigrade -- Without Even Trying
Sonali Verma, Aimee Johnson, Harena Haile, and Dr. Sigrid Reinsch
Room 186, 4:30-5pm

Tardigrades are small aquatic animals that are known for their ability to tolerate extreme desiccation as well as ionizing radiation. The extent to which different tardigrade species are able to survive extreme doses of radiation has been previously defined, yet the molecular mechanisms underlying such radiation resistance have not been fully characterized. In Ramazzottius varieornatus, high dose radiation resistance has been attributed to the presence of a tardigrade-unique DNA-associated protein Dsup, a protein that facilitates in the reduction of DNA fragmentation immediately after radiation exposure. This suggests that tardigrades possess a unique set of proteins that confer enhanced DNA protection as opposed to enhanced DNA repair. Previous studies have suggested that tolerance to radiation resistance in the tardigrade Hypsibius dujardini is inversely correlated with cellular division and mitotic activity, yet the molecular mechanisms of such radiation resistance are poorly understood. In the current study, we plan to examine DNA damage by X-ray irradiation of metabolically active Hypsibius dujardini at three different developmental stages (egg, juvenile and adult) to quantify the relative amount of DNA damage per unit DNA. These values will be compared to measurements using Deinococcus radiodurans and Saccharomyces cerevisiae, at similar X-ray doses. X-ray exposure of D. radiodurans induces many double-stranded DNA breaks from which recovers by efficient repair. S. cerevisiae is not inherently radiation tolerant. Protection of DNA would be evidenced by reduced DNA damage in H. dujardini per unit DNA relative to the other two species. Understanding the molecular basis behind such radiotolerance is critical for space travel beyond the Van Allen Belt, where radiation levels are beyond that which humans can feasibly survive in.

If you've never designed a research poster before, check out these tips.