| 1/14 |
Dr. Tiglet Besara |
Introduction to research at PAMS |
| 1/21 |
Dr. Jason Jackiewicz
New Mexico State University
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Seismology of Sun and Stars |
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Abstract: For over 100 years, Earth seismologists have been compiling a detailed understanding of our planet’s interior from earthquake data and theoretical modeling. When oscillations in the Sun were first observed about 50 years ago, solar seismologists were in the fortunate position to “adopt” the tools geoseismologists had developed to peer inside our nearest star. Only within the past 10 years, seismology of distant pulsating stars has become possible, and very powerful. The coming decade holds promise for exploiting oscillations of giant planets to probe their (currently unknown) internal structure.
Seismology of these distinct objects is in principle equivalent: it comprises a set of tools to measure and interpret oscillation data with the aim of making inferences of sub-surface structure and dynamics at the highest spatial and temporal resolution possible. This talk will discuss the techniques (measurements, modeling, inversions, etc.) that seismologists employ, and present some exciting results in the context of solar/stellar structure and evolution that make this an era of precision astrophysics.
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| 1/28 |
Dr. Michael Gordon
Æsir Technologies |
Nickel-Zinc Battery Research Opportunities |
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Abstract: Æsir Technologies, a company that has developed a Nickel Zinc (NiZn) battery chemistry to address a broad range of industries including defense, data center, and automotive.
The NiZn chemistry has a variety of advantages over lead acid and Li-ion batteries. Æsir’s production G31 battery has 1.5 times the capacity, 3 times the cycle-life, and two-thirds the mass of the top-of-the-line G31 lead acid AGM battery. Additionally, the NiZn chemistry is aqueous making it inherently safer and less expensive than Li-ion.
NiZn chemistry was first patented by Thomas Edison in 1901, but the technology remained mostly idle for 100 years due to low cycle life. Æsir has made significant progress over the past 10 years and is now scaling up production of its 140 Ah G31 battery capable of over 800 cycles at 100% DOD. However, there is still ample room for improving the performance for the NiZn chemistry. The amount of research resources put into the NiZn chemistry is miniscule compared that of lead-acid and li-ion chemistries.
This presentation will review the history of nickel-zinc batteries, recent advances made by Æsir, and areas of future research.
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| 2/4 |
Kwabena Asante Boahen (PAMS) |
Modeling of Argon Bombardment and Densification of Low-temperature Organic Precursors using Reactive Molecular Dynamics Simulations and Machine Learning |
| 2/11 |
Dr. Oliver C. Grant
Complex Carbohydrate Research Center, University of Georgia |
Virus-Receptor Interactions of Glycosylated SARS-CoV-2 Spike and Human ACE2 Receptor |
| Note! This seminar will be at 12:00 pm (noon), a so-called brown bag seminar. |
Abstract: Cellular infection by the 2019 severe acute respiratory syndrome coronavirus (SARS-CoV-2) is initiated by binding of the viral spike glycoprotein (S) to its receptor, the angiotensin-converting enzyme 2 (ACE2), which is present on the cellular membrane of human tissues and organs including the lung, intestine and kidney. The SARS-CoV-2 S trimer contains 66 N-linked glycosylation sites, which have been implicated in immune evasion and modulating receptor binding affinity. All sites are occupied by glycans when the spike protein is produced recombinantly in HEK-293 cells, or isolated from virus-derived trimers, or from trimers derived from a viral vectored SARS-CoV-2 vaccine candidate. The human ACE2 (hACE2) receptor contains 6 potential N-linked glycosylation sites that were also found to be occupied under equivalent expression conditions. Recently, we combined a glycoproteomic analysis of the S glycoprotein and hACE2 with molecular dynamics (MD) simulations to generate 3D models of glycosylated hACE2 bound to the S glycoprotein trimer. An analysis of the MD simulations of these 3D structures led to the prediction that ACE2 glycans directly with the S glycoprotein. Thus differences in the occupancy or composition of glycans at these positions may modulate the strength of the S protein - ACE2 interaction, which may in turn impact infectivity, disease severity and transmissibility.
Our results highlight roles for glycans in sterically masking polypeptide epitopes and directly modulating Spike-ACE2 interactions. Furthermore, our results illustrate the impact of viral evolution and divergence on Spike glycosylation, as well as the influence of natural variants on ACE2 receptor glycosylation that, taken together, can facilitate immunogen design to achieve antibody neutralization and inform therapeutic strategies to inhibit viral infection. |
| 3/2 |
Bikash Timalsina (PAMS) |
Development of EAM and RF-MEAM Potential to Study Thermal Properties of Zirconium Diboride |
| Bishwajite Karmakar (PAMS) |
Tuning Physical Properties of ZnO for Optoelectronics Applications |
| 2/25 |
Dr. Cathy Wong
University of Oregon |
In Situ Transient Absorption Spectroscopy During Materials Formation |
| Abstract: Molecules, polymers, and nanocrystals can form the active layer in electronic devices such as photovoltaics and light-emitting diodes. Their electronic structure and excited state dynamics dictate their function and suitability for these applications. Transient absorption (TA) spectroscopy is used to measure these properties, and has provided remarkable insights into the behavior and function of electronic materials. However, multiple minutes-to-hours are typically required to perform these measurements, making it difficult to accurately measure the excited state dynamics of unstable and evolving materials systems such as electronic materials during their synthesis or deposition into a thin film. In this seminar, I will introduce a novel implementation of TA spectroscopy that can measure transient spectra in 8 ms, with good signal-to-noise achieved in ~30 s. This new technique is applied to the study of organic molecules during their aggregation into a thin film, as well as lead-halide perovskite nanocrystals during their synthesis. These examples demonstrate that in addition to providing an understanding of how excited state dynamics change during materials formation, TA signals measured in situ can reveal new insights into the mechanisms of complex materials formation processes. |
| 3/4 |
Dr. Robert Baker
National eXtreme Ultrafast Science (NeXUS), Ohio State University |
Watching Electrons Move at Interfaces: Visualizing Charge and Spin Dynamics Using Ultrafast XUV Spectroscopy |
| Abstract: Directly observing electron dynamics at surfaces is required to understand and control the material properties that determine efficiency of many applications including efficient energy conversion as well as ultrafast information processing. Toward this goal, we have developed extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy as a surface-specific analog of XUV transient absorption. This method combines the benefits of traditional X-ray absorption spectroscopy, such as element, oxidation, and spin state resolution, with surface sensitivity and ultrafast time resolution. Using this technique, we investigate charge and spin dynamics in materials with applications ranging from photocatalysis to optical control of magnetic switching. In one example, we describe a systematic comparison of surface and bulk electron polaron formation in hematite showing that surface self-trapping dynamics differ significantly from bulk and that these dynamics can be systematically tuned by surface molecular functionalization offering the possibility for design of photocatalytic interfaces with enhanced carrier transport based on earth abundant materials. In a second example, we highlight evolving applications of XUV-RA spectroscopy to study spin dynamics at surfaces. Applications include understanding ultrafast spin crossover in magnetic semiconductors as well as control of spin polarized electron dynamics at chiral photochemical interfaces. Last, I will describe capabilities that will soon become available at the NSF National eXtreme Ultrafast Science Facility (NeXUS) that is currently under development at Ohio State University. |
| 3/11 |
Alin Niraula (PAMS)
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Transport Properties of Binary and Doped Diborides |
| Abiodun Odusanya (PAMS) |
A Study of Laser-assisted Chemical Vapor Deposition (CVD) Technique to Grow Carbon-based Materials |
| 3/18 |
Spring break: no seminar |
| 3/25 |
Shannon Dulz
University of Notre Dame |
Cold Exoplanets: Ground-based Direct Imaging and Population Studies Planning for Future Space Missions |
| Abstract: Planned and proposed space-based missions with direct imaging mission components, like the Roman Space Telescope, HabEx, and LUVOIR, are expected to revolutionize our ability to measure planetary atmospheres. Optimal survey strategies are dependent, however, on our understanding of exoplanet statistics and observations in the years preceding launch. This talk will discuss the demographics of exoplanets and efforts to extend inner planet occurrence rates to less constrained cold planets. I will also discuss ground-based direct imaging with the NIRC2 instrument at Keck Observatory searching for cold giant planets around astrometrically accelerating stars. |
| 4/1 |
Spring holiday: no seminar |
| 4/8 |
Dr. Vashti Sawtelle
Michigan State University, Lyman Briggs College |
Research on Inclusive Practices: Supporting Two-Year College Transfer Students in the Physics Community |
| Abstract: Two-year colleges enroll almost half of the nation’s undergraduate students (AACC, 2014). While nearly 40% enroll in STEM or health science degree programs (Van Noy & Zeidenber, 2014), only 29% of those who plan to earn a bachelor’s degree will do so within 6-years (Horn & Skomsvold, 2011). Two-year college students are also more likely to come from underrepresented groups, low-income households, or first-generation backgrounds than students at four-year colleges (AACC, 2014). Considerable research has shown a connection between students’ confidence in their ability to perform well (also known as self-efficacy) and persistence in science fields. In this presentation I will describe what we know about supporting community college students in pursuing physics and STEM pathways. I will also outline research on a successful program that provides transitional support to community college students pursuing a bachelor’s degree in STEM. |
| 4/15 |
Dr. Ryan Behunin
Northern Arizona University |
Noise in Integrated Photonic Brillouin Lasers |
| Abstract: Owing to their highly coherent emission and compact form factor, stimulated Brillouin scattering (SBS) lasers have been recognized as an attractive solution for applications such as portable atomic clocks, precision sensors, coherent microwave synthesis and energy-efficient approaches to coherent communications. While the SBS emission can be very narrow band, noise inherent within dielectric materials leads to drift in the Brillouin laser frequency posing vexing challenges for high-end applications requiring ultra-stable emission. In this talk, I’ll discuss our efforts to develop unified models to understand Brillouin laser physics that incorporate the dominant sources of noise. The physics and applications of Brillouin scattering will be introduced, and our modeling approach will be discussed. Our predictions will be compared with data from an integrated photonic SBS laser, showing that the thermorefractive effect plays a critical role in the laser’s frequency stability. |
| 4/22 |
Dr. Marilu Perez Garcia
Ames National Laboratory, Critical Materials Institute |
Designing Ligands with Predetermined Metal Ion Selectivity using Electronic Structure Theory, Machine Learning, and Molecular Mechanics |
| Abstract: Purifying critical materials needed for high-tech equipment and machinery from raw or recycled sources often requires a solvent extraction step. Tailoring a solvent extractant for specific systems could save significant time and resources. However, tailoring extractants for different feed compositions is prohibitively expensive. Focusing on the ligand metal ion binding site, our team uses machine learning (ML) and access to large amounts of empirical data to predict absolute aqueous stability constants for a given ligand. To train the ML algorithm, we combine data related to the ligands, the metal ions, and data obtained from ab initio and molecular mechanics calculations. The prediction software is coupled with HostDesigner to quickly generate and rank theoretical ligands by selectivity between ions of interest. This software, currently under development, will enable rapid down selection of promising targets, guide empirical research, and help drive innovation in solvent extraction science. |
| 4/29 |
Joshua Kern
Clemson University |
Using ro-vibrational Emission from Protoplanetary Disks in Order to Observe Accretion and Planet Formation in Action |
| Abstract: Stars and planets form from collapsing clouds of gas. The detailed story of how that material moves from the gas cloud and eventually onto the star or forming planets is intimately tied to the physics of protoplanetary disks. In the past 30 years, advances in ground-based radio and infrared telescope facilities (as well as theoretical models) have allowed astronomers to probe the chemistry and dynamics of these disks on scales that are important for observing accretion and planet formation in action. This talk will highlight aspects of protoplanetary disk physics, their connection with observations, and some exciting preliminary results from the spectroscopic analysis of ro-vibrational emission observed using iSHELL at the NASA Infrared Telescope Facility in Mauna Kea, Hawaii. |
| 5/6 |
Finals week: No seminar |
