Bulletin of the American Physical Society
Far West Section Fall 2022 Meeting
Volume 67, Number 10
Friday–Saturday, October 7–8, 2022; University of Hawaiʻi at Mānoa, Honolulu, HI
Session P02: Materials Science and Biophysics |
Hide Abstracts |
Chair: Alexander Weber-Bargioni, Lawrence Berkeley National Laboratory Room: University of Hawai'i at Manoa, East-West Center Asia |
Saturday, October 8, 2022 10:30AM - 10:54AM |
P02.00001: Ferroelectric Perovskites Investigated by Synchrotron X-ray Scanning Tunneling Microscopy and First-principles Simulations Pedram Abbasi, David P Fenning, Tod A Pascal Ferroelectrics can add an extensive array of functionalities to various electronic devices, such as field effect transistors, non-volatile memories, and micro electromechanical system (MEMSs), where interfacial properties play a critical role. Despite this, understanding the role of polarization on the surface structure and chemistry has remained a longstanding challenge, mainly because this ideally requires a combination of both atomic scale imaging and chemical spectroscopy. Here we investigate the role polarization switching on the morphology, chemical composition, and surface reactivity of well-defined MBE-grown ferroelectric thin films using a combination of synchrotron X-ray scanning tunneling microscopy (SX-STM), ab-initio DFT+U electronic state calculations and simulated X-ray adsorption spectroscopy (XAS). SX-STM is a new tool that combines the chemical fingerprinting of XAS with signal collection via an STM tip, enabling chemical specificity at high lateral resolution and the possibility of in-situ electric biasing and gas dosing on the surface. We complement these measurements, and elucidate the effect of polarization switching on the core-hole excitations, using simulated, many-body XAS, calculated with the Bethe-Salpeter equation (BSE). This approach captures the interplay between polarization and lattice distortion at the atomic scale, including the complex physics at the surface seen in the experimental measurements. We find that polarization switching from downward to upward in (001) single crystalline BaTiO3 thin films increases the number of excitations to unoccupied states and consequently the intensity of X-ray absorption across Ba M, Ti L and O K edges as well as a stronger binding strength with molecular O2 as a model reactant. Harnessing the ability of investigating and ultimately control of ferroelectric interfaces down to atomic level can aid strategies in the design of heterostructures with tailored properties. |
Saturday, October 8, 2022 10:54AM - 11:06AM |
P02.00002: A Low-Cost Shutter Driver and Arbitrary Waveform Generator Using a Programmable System-on-Chip (PSoC) Device Justin M Craven, Gabe Delich, Elliott Meeks, Eric Ayars, Hyewon K Pechkis, Joseph A Pechkis We have developed a low-cost mechanical shutter driver with integrated arbitrary waveform generation using a programmable system-on-chip (PSoC) device. This microcontroller-based device with configurable digital and analog blocks is readily reprogrammed using free software, allowing for easy customization for a variety of applications. Additional digital and analog outputs with arbitrary timings can be used to control a variety of devices, such as acousto-optical modulators, additional shutters, or camera trigger pulses, for complete control of optical switching and imaging of laser light. Utilizing TTL-level control signals, this device can be readily integrated into existing computer control and data acquisition systems for expanded hardware capabilities. We report on the performance of this device and its integration into cold atom experiments. |
Saturday, October 8, 2022 11:06AM - 11:18AM |
P02.00003: Coherent light emission from teleost iridophores Nathan J Dawson Iridescence is observed in both plants and animals. The iridescent color of fish iridophores is caused by guanine platelets separated by layers of cytoplasm, where the color depends on several factors including the size, shape, orientation, and ordering of the guanine platelets found in iridophores. Many silvery fish use their iridophores with aperiodic photonic structures as camouflage, while other species of fish have developed periodic photonic crystal structures for communication. Some passive, linear, optical techniques have been developed to investigate the visual appearance of animals with structural color including spectrophotometry, coherent back scatter, imaging scatterometry, determination of total reflected light with an integrating sphere, and methods that study the photonic structures after changing the refractive index of the fluid/void region. A sensitive nonlinear method to quantify the aperiodic photonic structures in silvery fish iridophores is presented, where the amplified spontaneous emission threshold is used to determine a single figure-of-merit. Preliminary observations of one-dimensional, distributed-feedback, laser emission from periodic photonic crystal structures found in the iridophores of a freshwater fish will also be presented. |
Saturday, October 8, 2022 11:18AM - 11:30AM |
P02.00004: Physical Properties of Topologically Linked Polymers Alexander R Klotz, Maria Maalouf, Sierra Rheaume, Henry S Sundland There is interest in the soft materials community about the relationship between the molecular topology of polymer chains and the physical properties of polymeric materials. Kinetoplast DNA is a naturally occurring network of topologically linked (catenated) circular molecules, akin to molecular chainmail. Complete kinetoplasts form curved sheets that have been studied in the context of two-dimensional soft materials. Kinetoplasts can be broken into smaller catenated molecular structures using either restriction enzyme digestion or photodisintegration, leaving a population of large and small structures. Here, we report on recent work examining the properties of these smaller topologically linked structures, using fluorescence microscopy, nanopore sensing, and atomic force microscopy. |
Saturday, October 8, 2022 11:30AM - 11:42AM |
P02.00005: Probing the Architecture of the Cell: Relating Intracellular Forces to Cell Geometry with High-Resolution Mechanical Imaging Techniques Nicola Mandriota, Claudia Friedsam, John A Jones-Molina, Kathleen V Tatem, Donald E Ingber, Ozgur Sahin Our novel mechanical imaging tool based on atomic force microscopy (AFM) is capable of probing nanoscale structures in living cells to produce high spatial resolution mechanical images. Prior studies of cell stiffness could not produce enough mechanical contrast to study the mechanics of cell physiology at this length scale. Experimental results indicate that intracellular forces are responsible for the stiffness patterns we observe. While prior studies of cell stiffness provide qualitative insights into the relationship between intracellular forces and material properties of cells, we produce a mechanical model that quantitatively includes intracellular forces in the local nanomechanical response at the molecular level, which we also relate to cell shape. From our model, we can predict cell geometry and determine tension in intracellular structures, such as actin fiber bundles and the cell membrane. Parameters relevant to cell physiology can be obtained directly from mechanical AFM images using our model, which expands existing cell mechanical models into the molecular level. |
Saturday, October 8, 2022 11:42AM - 11:54AM |
P02.00006: Production and uptake of bacterial extracellular vesicles James Q Boedicker Bacteria naturally produce extracellular vesicles. Vesicles are approximately 100 nm in diameter and are involved in many cellular processes including infection and the exchange of genetic material. Vesicle production and uptake involves large amounts of energy associated with deforming and merging cellular membranes. In eukaryotic systems, such as human cells, many specialized proteins have evolved to create and traffic vesicles, however bacterial vesicles are not known to involve any specialized molecular machinery. Our work has examined how bacteria are able to overcome these energetic barriers. For example, membrane deformation can be assisted by the presence of molecules that bind to and restructure membranes. We have shown several such molecules produced by bacteria, including several antibiotics, increase the rate of the both vesicle production and uptake. In another study, we examine how the detachment of the bacterial outer membrane from the bacterial cell wall is another key step in vesicle production. This talk will discuss how such aspects of membrane mechanics influence the exchange of vesicles within bacterial populations. |
Saturday, October 8, 2022 11:54AM - 12:06PM |
P02.00007: Quantum Neuroscience and Neural Signaling Melanie Swan Mathematical models in quantum information science enable the study of neural signaling. Approaches first interpret wavefunctions from imaging modalities such as EEG and fMRI scans. Methods then target neural field theories to model collective neuron behavior, and treat single-neuron models (Hodgkin-Huxley, integrate-and-fire, theta neurons). Advanced applications are in neuroscience physics, the interpretation of physics findings in the neuroscience context. Areas of study include AdS/Brain multiscalar modeling, Chern-Simons biology, neuronal gauge theories, network neuroscience, chaotic dynamics of bifurcation and bistability explaining epileptic and resting states, molecular knotting, and genome physics. These models are used to investigate neural signaling, a problem of integrating thousands of inputs and pursuing not only axonal and calcium spike-based signaling but also the dendritic spike train as it accelerates and tempers to signal the receiving neuron’s axon. The potential benefit of this work is an improved understanding of disease and pathology resolution in humans. |
Saturday, October 8, 2022 12:06PM - 12:18PM |
P02.00008: Understanding musical cognition and its emotional responses in humans by developing machine learning pattern tools Quinn Picard Music is arguably the artform which humans most naturally react to. Most humans display an emotional response to music, irrespective of their understanding of music theory. This unique ability to experience complex music is a defining feature of human cognition, begging the question: can it be replicated using machine learning? We aim to develop an algorithm able to process and analyze music and correlate the musical patterns with human emotions that they spark, mimicking the human cognitive process. First, through digital signal analysis by neural networks, we have created an algorithm to separate music into individual components (tracks), analyzing and categorizing patterns in music of different styles and tonalities. In parallel, we are constructing a deep neural network to correlate musical patterns and tonalities to the human emotions they usually induce. Shedding light on how to evoke specific emotions could have applications in music composition, medical therapeutics, and neuroscience. This research will allow us to gain insight into how our brains process musical information and to mimic that with neural networks which replicate human emergent cognition. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700