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Physics students presenting at 2020 Undergraduate Research Symposium

We are thrilled to see so many of our Physics students presenting at this year’s Undergraduate Research Symposium.

Mark your calendars: The Symposium YouTube channel will host live-streaming oral and poster presentations beginning at 10 a.m. on May 21.

https://undergradsymposium.uoregon.edu/

https://around.uoregon.edu/content/students-prep-virtual-undergrad-research-symposium

 

Time-SPIDER: Characterizing the Electric Field of Pulsed LASERs: Jeremy Guenza-Marcus—Physics and MathFaculty Mentor(s): Brian Smith Session 1: It’s a Science ThingQuantifying precise measurements is critical in any field . Our research focuses on advancing quantum optical methods in the study of metrology . SPIDER is an interferometric approach to characterizing (mathematically describing) ultrashort laser pulses in the frequency domain . Our research aims to develop a sister method to the accepted SPIDER approach, dubbed Time-SPIDER . Its purpose is to use the same approach as SPIDER, but rather in the temporal domain . The procedure is to first develop the theoretical framework, and then set up the experiment . At the moment, our work approaches the issue from a purely theoretical perspective . We find that the Time-SPIDER method is useful as a direct measurement technique for non-ultrashort pulses . Many industry-standard interferometers require an iterative approach to pulse characterization, which may not be well-calibrated if the pulse is not ultrashort . Time-SPIDER solves both of these issues . If we are able to move past the theory and create a working Time-SPIDER, it would be possible to continue with other projects in the lab that may require such set-up . In the grand scheme, Time-SPIDER is a step towards continuing the study of metrology, along with quantum optics itself

 

Simulation of Bacterial Motion in Sterically Complex Environments: Matthew Kafker—Physics, MathematicsFaculty Mentor(s): Tristan Ursell Session: Prerecorded Poster PresentationMany species of bacteria navigate complex and heterogeneous environments to search for metabolic resources and avoid toxins . Common among such complexities is steric structure—solid objects whose surface curvature alters bacterial trajectories upon impact . In previous experiments, we characterized scattering of bacteria from vertical pillars of different radii, which provides the basis for understanding how impact with a solid, curved object alters bacterial motion . However, it remains poorly understood how multiple interactions affect bacterial trajectories and whether distinct object curvatures or length-scales of separation between steric objects have qualitatively distinct effects on bacterial motion . We address this question using agent-based computer simulations of cells moving within 2D environments . Each environment presents simulated cells with steric objects (i .e .circular pillars) of radius 8 .3μm and a controlled separation between pillars of L μm, where L is a parameter of the simulation . Cells then diffuse through this environment, scattering with pillars they encounter . By measuring the mean squared displacement (MSD) of the ensemble of trajectories in time for different values of L, we are able to quantify precisely how the length-scales of separation between steric structures affect bacterial trajectories . These MSD measurements will also allow us to compare our results with future experimental work . Ultimately, we hope that our results may contribute to a more realistic model of the behavior of motile cells in natural environments such as soils or a mammalian gut.

 

Visualizing Topocluster Algorithms for the Global Trigger: Sylvia Mason—PhysicsFaculty Mentor(s): Stephanie Majewski Session 5: To the Moon and Back—Relativity MattersThere is a Standard Model of particles and forces that explain the fundamental components of matter . However, this model is incomplete, seeing as we currently understand only about 5% of our universe . The Large Hadron Collider (LHC) is a particle accelerator that collides protons in the hopes of discovering new particles or forces, so that we can learn more about the other 95% of the universe . The LHC will undergo an upgrade in 2026 that will increase its luminosity, meaning there will be an increased number of collisions per second (up to 200 collisions every 25 nanoseconds) .After this upgrade, the ATLAS trigger system will need to reduce the data by a factor of 40 within 10 microseconds, so we will need to sort out the interesting events very fast . Our group is designing an algorithm for implementation in firmware in the “Global Trigger” system for ATLAS to help select these interesting events . My research focuses on creating accurate 3-D visualizations of potential algorithms that cluster energies from particle showers in the ATLAS Calorimeters, and investigation splitting criteria for these clusters . These visualizations will help us understand the details of the performance of these algorithms, which can significantly help us reject background .

 

Supersymmetric Long Lived Particle Search Using Proton-Proton Collision Data and Simulations from the ATLAS Experiment: Laura Nosler—PhysicsFaculty Mentor(s): Laura Jeanty Session 5: To the Moon and Back—Relativity MattersDespite the wealth of information gained by high energy physics over the past few decades, there are still several fundamental gaps in our understanding of the universe . One theory that may provide answers to some of these questions is supersymmetry, which predicts the existence of new particles .In many variations of supersymmetry, some of these particles are expected to have comparatively longer lifetimes . Our research attempts to optimize searches for long lived particles by studying the properties of their signatures and comparing two different methods of reconstructing the energy missing after a collision, with the goal of understanding how the reconstruction algorithms behave for these new particles . To do this, we compare simulated data from proton-proton collisions detected by the ATLAS experiment at the Large Hadron Collider at CERN reconstructed with these two different algorithms and perform analyses that reveal their differences . The results we have found so far have displayed the differences in the efficiencies of these reconstruction methods in our search, revealing the impact these algorithms will have on our final results and allowing us to improve our sensitivity by tuning our selection routines . The final goal of our experiment is to gain a more comprehensive understanding of how to accurately identify these particles in real data, at which point we will extend our experiment to include non-simulated collision data from the ATLAS experiment.

 

Characterizing the relationship between bacterial motility and range expansion: Noah Pettinari—PhysicsFaculty Mentor(s): Raghuveer Parthasarathy Session 5: To the Moon and Back—Relativity MattersSelf-propelled organisms were first observed under the microscope over 300 years ago . Since then, great strides have been made in characterizing the mechanisms behind motile behavior in bacteria, but current models relating cellular motility to bulk range expansion have not been rigorously tested . To better characterize the relationship between these micro- and macroscale patterns, our research is focused on the analysis of images collected via light sheet fluorescence microscopy of bacterial cells and macroscopic imaging of range expansion . Preliminary results have suggested disagreements between predicted rates of range expansion and cellular motility . Further data and analysis is needed to confirm these results . These findings may highlight the need for the consideration of spatial structure or the possibility of unknown mechanisms in current models .

 

Quantifying the spatial morphology of organic films through polarization-dependent imaging: Madelyn Scott—Chemistry, PhysicsFaculty Mentor(s): Kelly Wilson, Cathy WongSession 2: Cells R UsOrganic semiconducting materials are appealing, green alternatives to conventional semiconductors because they can be solution-processed into flexible films . However, solution-processing fabrication methods can be prone to morphological disorder, meaning that crystalline structures in the film exhibit a variety of sizes and shapes . A large degree of morphological disorder inhibits the electronic functionality of a film for use in technological devices . Examining how film morphology varies with different deposition conditions allows us to connect the physical properties of organic semiconducting films to macroscopic perturbations in their formation environments . In this work, we used a homebuilt microscope to image the polarization-dependent absorption of organic films, and developed an image analysis software package to characterize their spatial morphology . A series of pictures are collected of the sample, rotating the polarizer between each image . For every pixel in the image, the absorption signal as a function of polarization angle is fit to a sinusoidal curve . These fits are employed to assign pixels in the image to discrete aggregate domains within the film . Quantitative domain metrics are computed to describe the morphology of the film . Several organic films are produced under different deposition conditions and their resulting morphologies are compared . By better understanding the relationship between deposition conditions and film formation, existing solution-processing techniques can be further controlled and refined to achieve target physical properties in organic semiconducting materials.

 

Equilibrium Solutions for 2-Dimensional Nonaxisymmetric Disks: Daniel Sellers—PhysicsFaculty Mentor(s): James Imamura Session 5: To the Moon and Back—Relativity MattersIn this study we seek equilibrium solutions for compressible, self-gravitating, 2-dimensional nonaxisymmetric disks . Such structures arise in binary star systems and other systems where tidal forces arise such as in the Earth-moon system . These disks are governed by a Scalar Momentum Equation (SME) and a partial differential equation describing hydrodynamic flow within the disk (Stream Function Equation) . We solve these equations using a self-consistent field approach . At each iterative step, the Stream Function and gravitational potential are approximated at all grid points using Guass-Seidel iteration . These quantities, taken with the SME and appropriate boundary conditions are used to find an updated guess for the density distribution .Guass-Seidel algorithms are applied to the relevant partial differential equations which have been discretized using a finite central-differencing technique . These solvers are implemented in python and verified using analytical solutions for simple cases, such as axisymmetric disks with uniform density . We find that our solvers converge to the analytical solutions over many iterations .Parameters for the overall equilibrium solutions are taken from Andalib’s 1998 Dissertation focused on 2-D self-gravitating systems . Present work is focused on reproducing some of the presented solutions as both a check on our equilibrium solutions and as a starting point for further research .

 

Vacuum Airship Design With Finite Element Analysis: Daniel Sellers—PhysicsFaculty Mentor(s): Ben McMorran Session: Prerecorded Poster PresentationThe ultimate expression of Archimedes’ principle of buoyancy would be to enclose a vacuum with some structure of less mass than the air displaced by that structure . So far such a craft has never been realized in prototype due to the daunting material and engineering challenges . We propose a novel design for such an airship, using inflatable supports and an Aramid fabric shell, and examine the physical constraints and material requirements using both SolidWorks (SW) Simulation Finite Element Analysis and principles of structural statics .We develop a dynamic simulator (in python) to approximate the shapes formed by thin fabric shell sections under unbalanced pressure loads . The resulting geometries are converted to thin shell SolidWorks models and analyzed . Attempts are made to verify the results, including mesh independence and comparison to empirical stress/strain results performed on similar materials and configurations .Deflection of thin shell sections using material properties of Kevlar Aramid fiber are found to agree qualitatively with the theoretical results of Timeshemko, though actual deflection predicted by SW is marginally smaller than predicted by theory, which in turn only very roughly agrees with the experimental results considered . The tensile stress within the shell models is found to be well within acceptable limits for typical Aramid fibers . Some models for the inflatable support structure currently under development are presented, without results . The advantages and challenges of the Finite Element Method for novel design concepts are briefly discussed .

 

The SETI Scouts Project: Developing Scientifically Literate Young Women through an Astronomy Destination Camp at Pine Mountain Observatory: Maggie Thompson—PhysicsFaculty Mentor(s): Scott Fisher Session 5: To the Moon and Back—Relativity MattersPine Mountain Observatory (PMO) and the University of Oregon are partnered with the SETI Institute and the Girl Scouts to provide a week-long summer destination camp where 10 Girl Scouts from the US come together to engage in cohort building, outdoor adventuring, and an immersion in STEM programming related to astronomy . This program combines several of the main goals of PMO: undergraduate astronomical research, scientific outreach to public and educational partners, and the development of science literacy in STEM interested groups . The Destination Camp welcomes high-school age Girl Scouts from across the United States to the Observatory, where they learn about astronomy and astronomical research through interactive lessons and close peer mentoring from University of Oregon students . This program has not only educated and inspires the Girl Scouts to continue their interest in STEM careers, but it also provides an opportunity for undergraduate physics students to develop science communication skills through mentoring . Over the two years of the program, PMO has proven to be a great resource for astronomy outreach and research with many of the smaller projects introduced during the camp being replicated by the scout alumni of the program back with their home troops . Additionally, many of these programs can be adapted to other observatories to instill a greater passion for science in the general public.

 

Confirming the 3-dimensional shape of Asteroid 283 Emma from Observations at Pine Mountain Observatory: Maggie Thompson—PhysicsFaculty Mentor(s): Scott Fisher Session: Prerecorded Poster Presentation To determine the shape of asteroid 283 Emma, we obtained time-resolved photometry of the asteroid on August 28, 2019 from 07:44:24 to 09:27:39 UTC at Pine Mountain Observatory (PMO) . The observations were carried out using the 0 .35m Robbins telescope and a large format CCD camera with a Sloan g filter . The brightness of 283 Emma was calibrated using three standard stars removing the influence of airmass . We found that the brightness changed from mag(g) = 12 .5 to 12 .8 . The light curve (time variation of the brightness) we obtained was consistent with the previous research which determined that the shape of 283 Emma is an ellipsoid . Through the process of data analysis, information on the atmospheric extinction coefficient in the Sloan g-band at the PMO was also obtained, which is useful for other observations at the observatory . The results of our observations give us confidence that we can obtain research-grade data with PMO and that this data can be analyzed by undergraduate students.

 

Quantification of Point Defects in Perovskite Solar Cells: Nicole Wales—Chemistry and Physics Faculty Mentor(s): Mark Lonergan, Zack CrawfordSession 5: The Bonds that Make UsIn order to improve perovskite solar cell efficiency, it is necessary to minimize defects within the perovskite absorber layer, which may include crystallographic point defects . By understanding how these defects form and contribute to the material’s electronic structure, we will gain insight into routes of Shockley-Read-Hall recombination and associated efficiency loss . Theoretical studies have credited some point defects with the production of energy trap states within the bandgap .As such, we aim to measure and describe the nature and formation of traps in real materials .External quantum efficiency measurements are used to describe a gaussian distribution of traps .Additionally, capacitance techniques are applied with the added advantage of increased sensitivity to the absorber layer . However, capacitance techniques are complicated by the hysteretic perovskite system, which is discussed . The samples used in this study include methylenediammonium dichloride-stabilized alpha-formamidinium lead triiodide, a perovskite with interstitially incorporated chloride .External quantum efficiency measurements showed lower defect densities compared to devices of different compositions, however, one sample did show a small signal with a defect transition energy of 1 .08 ± 0 .01 eV . Findings may point to material suppression of sub-gap defects associated with methylenediammonium dichloride-stabilization compared to alternative compositions . It will be interesting to determine if methylenediammonium dichloride is the source of defect suppression in these samples . To understand how the composition might affect defect states, it will also be necessary to take measurements of other stabilizing agents with different compositions .