Department of Physics and Astronomy

Seminars/Colloquia, Fall 2020

Unless noted otherwise, Tuesday Colloquia are at 4:00 PM
Scheduling for additional seminars will vary.

For the Online colloquia, please join Zoom Meeting:
https://olemiss.zoom.us/j/213798950
Meeting ID: 213 798 950

Date/Place	Speaker	Title (and link to abstract)
Tue, Aug 25 Online	Stewart Prager Program of Science & Global Security Princeton University	The Increasing Peril from Nuclear Arms: And How Physicists Can Help Reduce the Threat
Tue, Sep 1 Online	Nobuchika Okada Department of Physics and Astronomy University of Alabama	Solving Big Mysteries in Particle Physics with a New Force
Tue, Sep 8 Online	Guancong Ma Department of Physics Hong Kong Baptist University	Geometric Phases in Acoustics
Tue, Sep 15 Online	Charles F. Caskey Institute of Imaging Science Vanderbilt University	Transcranial MR-guided Focused Ultrasound Neuromodulation
Tue, Sep 22 Online	Kimberly Boddy Department of Physics University of Texas at Austin	Searching for Dark Matter Interactions in Cosmology
Tue, Sep 29 Online	Nathan E. Murray National Center for Physical Acoustics University of Mississippi	Two Examples of Turbulence Interactions
Tue, Oct 6 Online	Mukunda Acharya Stewart Acoustical Consultants Raleigh, North Carolina; Benjamin "B.B." Pilgrim and Anil Panta Department of Physics and Astronomy University of Mississippi	Benjamin "B.B." Pilgrim: The Chain Action and a Variational Principle for Two Dimensional Causal Sets Anil Panta: Developing Tools for Analysis on the Open Science Grid Mukunda Acharya: From a MS Degree to Industry Career in Acoustics
Tue, Oct 13 Online	Louis E. Strigari Department of Physics and Astronomy; Texas A&M University	Terrestrial and Astrophysical Applications of Coherent Neutrino Scattering
Tue, Oct 20 Online	Feng Guo Intelligent Systems Engineering Indiana University — Bloomington	Development of Acoustofluidics for Cancer Research
Tue, Oct 27 Online	David G. Grier Department of Physics and the Center for Soft Matter Research New York University	Holography and the Pandemic: Using Holographic Video Microscopy to Detect Viruses and Antibodies
Tue, Nov 3 Online	Darin Van Pelt School of Engineering University of Mississippi	Rocket Physics and Experience with SpaceX
Tue, Nov 10 Online	Joshua B. Bostwick Department of Mechanical Engineering Clemson University	Elastocapillary Dynamics in Soft Gels
Tue, Nov 17 Online	Anuradha Gupta (Host) Department of Physics and Astronomy University of Mississippi	A Lecture Exploring Supermassive Black Holes
Tue, Nov 24 Lewis 101	Final Exam Week
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Abstracts of Talks

Stewart Prager Program of Science & Global Security Princeton University The Increasing Peril from Nuclear Arms: And How Physicists Can Help Reduce the Threat With geopolitical and technological changes mostly driven by the nuclear weapons states, we are slipping towards a new arms race and deterioration of the multi-decade arms control regime. This talk will describe the current situation, feasible steps to reduce the nuclear threat, and a new project sponsored by the American Physical Society to engage physical scientists in advocacy for nuclear threat reduction. A short meeting will be held immediately after the colloquium for those interested in learning about, or joining, the APS Coalition.

Nobuchika Okada Department of Physics and Astronomy University of Alabama Solving Big Mysteries in Particle Physics with a New Force For the last decades, the Standard Model of particle physics has been the best theory for describing elementary particle phenomena observed in nature. However, there still are big mysteries that the Standard Model fails to explain: (1) Why are neutrino masses so tiny? (2) What is the nature of the dark matter in our universe? (3) What drives the Cosmological Inflation before Big Bang? (4) Where does ordinary matter come from, and what happened to antimatter? (5) Why is the CP-violation so small in the strong interaction? In this colloquium, I will first review the Standard Model, its success and fails, and then discuss our recent proposal of a simple extension of the Standard Model with a new force that offers a solution to the above 5 mysteries.

Guancong Ma Department of Physics Hong Kong Baptist University Geometric Phases in Acoustics Geometric phase is a universal concept associated with the adiabatic evolution of states. It manifests in a wide diversity of physical systems, ranging from solid-state electronics to classical mechanics. Its profound implication makes it the cornerstone of numerous cutting-edge research, in particular, topological phases. The universality of the geometric phase means that it can be investigated using acoustic wave systems. The advancement of phononic crystals and the advent of acoustic metamaterials, in particular, laid the foundation for such endeavors. In this talk, I will discuss some of our recent attempts to study geometric phases and related phenomena in acoustic systems. Topics include: geometric phase mediated transport of sound vortex in a spiral waveguide, the realization of quantized Zak phase in a one-dimensional phononic crystal, topological acoustic pumping, and hybrid winding around an exceptional point.

Charles F. Caskey> Institute of Imaging Science Vanderbilt University Transcranial MR-guided Focused Ultrasound Neuromodulation Ultrasound has the ability to focus energy to a small point beyond the skull and is being widely explored by researchers as a tool for non-invasive neuromodulation. When combined with magnetic resonance imaging (MRI), focused ultrasound (FUS) can be precisely guided while the effects of FUS can be visualized at the network level using fMRI. In this talk, I will discuss our ongoing work in developing systems to apply image-guided FUS neuromodulation in the MRI environment while imaging functional activity. Specifically, I will cover the development of optical tracking as a method to guide FUS neuromodulation, the creation of transducer arrays for steerable FUS neuromodulation, and the development of MR acoustic radiation force imaging methods to visualize the acoustic focus. We have used these methods to modulate the somatosensory network in non-human primates, demonstrating that MRI-guided FUS is capable of exciting precise targets in somatosensory areas 3a/3b, causing downstream activations in off-target brain regions within the circuit which we can simultaneously detect with fMRI. Our observations are consistent with others’ work in the field of FUS neuromodulation; however, questions remain about mechanisms underlying FUS neuromodulation and potential confounds. The talk will conclude by reporting on recent work at the cellular level where we are measuring calcium signaling in mouse brain slices with optical markers during FUS neuromodulation.

Kimberly Boddy Department of Physics University of Texas at Austin Searching for Dark Matter Interactions in Cosmology There is overwhelming evidence for the existence of dark matter. It plays a crucial role in the formation of structure in the Universe, yet little is known about its properties beyond gravitational effects. In this talk, I will discuss the current and future prospects of understanding the fundamental nature of dark matter using observations in cosmology and astrophysics. These observations offer glimpses into different cosmic eras that may shed light on the mystery of dark matter.

Nathan E. Murray National Center for Physical Acoustics University of Mississippi Two Examples of Turbulence Interactions A brief introduction to turbulence, it’s characteristics and mechanisms, is presented. A conceptual model for turbulence is discussed. This is followed by two specific examples. First, the action of turbulence on the dispersion of solid particulate in a high-shear scenario in a gas-solid flow is explored. Second, the characteristics of turbulence in a transient, shock-driven acceleration are explored. In both examples, the “fingerprints” of turbulence are highlighted as they appear in statistical analyses of the data.

Benjamin "B.B." Pilgrim Department of Physics and Astronomy University of Mississippi The Chain Action and a Variational Principle for Two Dimensional Causal Sets I will present the chain action for causal sets and evaluate its accuracy for causal sets embeddable in two dimensional manifolds. I will also propose a discrete variational principle, and the results of manifoldlike causal sets will be compared to Kleitman-Rothschild causal sets.

Anil Panta Department of Physics and Astronomy University of Mississippi Developing Tools for Analysis on the Open Science Grid The Belle II dataset searcher is a tool to get the location of files that are stored on the open science grid for analysis use. I will report on my efforts to expand the usefulness of this tool by implementing a NoSQL database, called Elasticsearch, rather than the usual SQL database. With this change, it will be possible to make full text searches on dataset metadata, enabling a more efficient way for analysts to find the samples of interest.

Mukunda Acharya Stewart Acoustical Consultants Raleigh, North Carolina From a MS Degree to Industry Career in Acoustics The talk will be an overview of how I develop my career from a master degree in physics focusing on physical acoustics to my current job as an acoustical consultant in industry. Most of the talk would be focused on giving you a general idea of my career as an acoustical consultant. Acoustical consultants use a combination of scientific theory, analytical modeling tools, experimental data, experience, and judgment to analyze problems and provide advices for clients on acoustics related problems. Answers to some of the common problems can be immediate, but many problems require analysis, measurements, or both. I am going to share my experience about the knowledge and skills that are vital to becoming a professional acoustical consultant. I believe the talk will be helpful to graduate students who are planning to pursue their research in physical acoustics and continue in the future as a professional.

Louis E. Strigari Department of Physics and Astronomy; Texas A&M University Terrestrial and Astrophysical Applications of Coherent Neutrino Scattering Coherent elastic neutrino-nucleus scattering (CEνNS) is a long-standing theoretical prediction of the Standard Model (SM), and the COHERENT experiment has recently achieved the first detection of it. CEνNS provides an important probe of physics beyond the SM. In addition, it can open up a new window into neutrino astrophysics, through studies of low energy neutrinos from the Sun, atmosphere, and supernovae. CEνNS is also vital for understanding and interpreting future particle dark matter searches. In this talk, I will discuss the prospects for learning about the nature of neutrinos and astrophysical sources from CEνNS detection, highlighting how astrophysical and terrestrial-based detections play important and complementary roles.

Feng Guo Intelligent Systems Engineering Indiana University — Bloomington Development of Acoustofluidics for Cancer Research The acoustofluidics technology harnesses sound waves and microfluidics for the manipulation of cells and liquids. This technique has many unique advantages. Firstly, this technique handles cells and/or liquids using gentle mechanical vibrations. These vibrations create a pressure gradient in the medium to move suspended micro-objects yielding a contamination-free, contactless, and label-free manipulation. Secondly, acoustofluidics has minimal impact on cell integrity and function. Thirdly, this technology can operate in a single, inexpensive micro-device without complicated setups, which offer additional advantages in ease of use, versatility, and portability. Here, we report a series of acoustofluidic devices and systems for the manipulation of cells and liquids in the microfluidic environment to address the problems in the field of cancer biology and translational cancer medicine.

David G. Grier Department of Physics and the Center for Soft Matter Research New York University Holography and the Pandemic: Using Holographic Video Microscopy to Detect Viruses and Antibodies The hologram of a microscopic object encodes information about that object's size, shape, composition and three-dimensional position. Often, that information is retrieved by computing a three-dimensional reconstruction of the complex medium and then analyzing the result. The three-dimensional reconstruction, however, contains no more information than the original two-dimensional hologram (and usually less). In special cases, the recorded hologram instead can be fit, pixel-by-pixel, to the exact Lorenz-Mie theory of light scattering. For a micrometer-scale colloidal sphere, this analysis yields the position to within a few nanometers over a range extending to hundreds of micrometers. More importantly, it yields the sphere's diameter to within a couple of nanometers. This is fine enough to monitor molecules and viruses binding to the surfaces of functionalized beads simply by watching the beads grow larger in real time. The same analysis yields the bead's refractive index with part-per-thousand resolution, which elegantly solves the barcoding problem for multiplexed binding assays. This talk will explain how to use holographic microscopy for precision particle characterization. It then will showcase a few practical and scientific applications that illustrate the power of the technique before diving into the emergency application for COVID-19 testing.

Darin Van Pelt School of Engineering University of Mississippi Rocket Physics and Experience with SpaceX A discussion of my nearly 20yrs in the aerospace industry is presented. Those included nearly a decade at SpaceX and time as co-founder of ABL Space Systems, a launch vehicle company currently developing a vehicle capable of 1000kg to orbit. One interesting experience is leading the propulsion team in creating the Falcon 9 booster you see launching and routinely landing while delivering payloads to orbit and starlink satellites for the future of the internet. Efficiently and accurately landing a 150ft tall pencil is a special challenge and some of the physics involved will be discussed.

Joshua B. Bostwick Department of Mechanical Engineering Clemson University Elastocapillary Dynamics in Soft Gels Soft gels are utilized in emerging applications, e.g. bioprinting, and are distinguished in that the forces of capillarity (surface tension) and elasticity are comparable in magnitude leading to elastocapillary phenomena including the observation of new analogous hydrodynamic instabilities in soft materials. This talk will provide a survey of our recent work in this area including gel drop oscillations in ultrasonic levitation, soft fracture, splash suppression, and droplet durotaxis. In each example, we highlight the multiphysics through the elastocapillary number and viscoelastic relaxation time scale. Of particular note is that our results can be used as novel diagnostic techniques to measure the surface tension and fracture energy of soft gels.

Anuradha Gupta (Host) Department of Physics and Astronomy University of Mississippi A Lecture Exploring Supermassive Black Holes In this colloquium, we will watch a lecture exploring supermassive black holes, for which Andrea Ghez shared the 2020 Nobel Prize in Physics. THe link to the talk can be found here.