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Department of Physics and Astronomy

University of Mississippi

SPRING 2019 Colloquium Schedule

Tuesdays from 4 – 5 pm in Lewis 101 unless otherwise indicated.

01/29/19Targeted therapies at the interface of nanotechnology and cancer biology.
Thomas Werfel
Assistant Professor of Chemical Engineering
University of Mississippi

In the Interdisciplinary NanoBioSciences (iNBS) Lab, we work largely at the interface of nanotechnology and cancer biology. The complexity of cancer necessitates creative, multi-faceted solutions that nanotechnologies have the potential to offer. However, the successful application of nanotechnologies is currently stymied by oversimplified biological models and a dearth of data from advanced biological studies that faithfully recapitulate human disease. Ultimately, our scientific goals are to better understand nanomaterial-biological system interactions to improve the performance of nanotechnologies in humans, discover new cancer molecular targets ideal for nanotechnology-based therapies, and identify cellular and molecular processes that impact drug delivery efficiency, cancer metastasis, and resistance to therapy. In this colloquium, I will highlight three research thrusts in the iNBS Lab that span nanotechnology and targeted cancer therapy: 1) Drugging previously ‘undruggable’ cancer-causing genes with siRNA nanomedicines, 2) Combating the immunosuppressive impact of efferocytosis in the tumor microenvironment, and 3) Targeting the platelet-tumor cell interaction to prevent breast cancer metastasis.
(Biomedical Engineering)
02/05/19Simulating relativistic jets from microphysics to global dynamics.
Kyle Parfrey
Senior Fellow, NASA Postdoctoral Program
NASA Goddard Space Flight Center

The most extreme and surprising behaviors of black holes and neutron stars are driven by their surrounding plasmas and magnetic fields. Numerical simulations which capture basic physical processes like particle acceleration, magnetic reconnection, and magneto-rotational turbulence can yield insight into such disparate phenomena as black-hole jets and X-ray coronae, magnetar giant gamma-ray flares, and the spin limit of millisecond pulsars. I will focus on what simulations can teach us about the launching of relativistic jets in compact binary mergers, and will describe how a new technique for general-relativistic plasma kinetics will aid in understanding black holes' jets and particle acceleration, and in interpreting future observations with the Earth-spanning Event Horizon Telescope.
02/07/19 (Thursday)Astrophysics with synergy of electromagnetic and gravitational wave observations.
Shaon Ghosh
Postdoctoral Research Associate
University of Wisconsin

About three and a half years ago, the direct detection and measurement of gravitational waves from a pair of coalescing black holes by the LIGO interferometers opened a new window for astrophysicists to look into the universe. Almost two years later, the discovery of gravitational wave from a binary neutron star system marked the beginning of the era of joint electromagnetic and gravitational wave astronomy. In this talk, I will present a brief history of this discovery and its importance in that context. I will then focus on the rich scientific results of the multi-messenger observation and finally, discuss how such joint observations can help us extract astrophysical information from some of the most extreme objects in the universe. Specifically, I will highlight how observations of neutron stars can help us understand how matter behaves in conditions that cannot be replicated in earth-based laboratories. The required information for such studies comes to us from various avenues of astrophysical observations. I will delineate the methods that we will be employing in combining these information to make robust inferences on the neutron star equation of state.
02/12/19Frontiers of multi-messenger black-hole physics.
Stephen Taylor
NANOGrav PFC Senior Postdoctoral Scholar
Caltech Senior Postdoctoral Scholar
California Institute of Technology

The bounty of gravitational-wave observations from LIGO and Virgo has opened up a new window onto the warped Universe, as well as a pathway to addressing many of the contemporary challenges of fundamental physics. I will discuss how catalogs of stellar-mass compact object mergers can probe the unknown physical processes of binary stellar evolution, and how these systems can be harnessed as standard distance markers (calibrated entirely by fundamental physics) to map the expansion history of the cosmos. The next gravitational-wave frontier will be opened within 3-6 years by pulsar-timing arrays, which have unique access to black-holes at the billion to ten-billion solar mass scale. The accretionary dynamics of supermassive black-hole binaries should yield several tell-tale signatures observable in upcoming synoptic time-domain surveys, as well as gravitational-wave signatures measurable by pulsar timing. Additionally, pulsar-timing arrays are currently placing compelling constraints on modified gravity theories, cosmic strings, and ultralight scalar-field dark matter. I will review my work on these challenges, as well as in the exciting broader arena of gravitational-wave astrophysics, and describe my vision for the next decade of discovery.
02/14/19 (Thursday)Gravitational waves and fundamental properties of matter and spacetime.
David Nichols
Senior Postdoctoral Researcher
University of Amsterdam

Gravitational waves from the mergers of ten binary black holes and one binary neutron star were detected in the first two observing runs by the Advanced LIGO and Virgo detectors. In this talk, I will discuss the eleven gravitational-wave detections and the electromagnetic observations that accompanied the neutron-star merger. These detections confirmed many of the predictions of general relativity, and they initiated the observational study of strongly curved, dynamical spacetimes and their highly luminous gravitational waves. One aspect of these high gravitational-wave luminosities that LIGO and Virgo will be able to measure is the gravitational-wave memory effect: a lasting change in the gravitational-wave strain produced by energy radiated in gravitational waves. I will describe how this effect is related to symmetries and conserved quantities of spacetime, how the memory effect can be measured with LIGO and Virgo, and how new types of memory effects have been recently predicted. I will conclude by discussing the plans for the next generation of gravitational-wave detectors after LIGO and Virgo and the scientific capabilities of these new detectors. These facilities could detect millions of black-hole and neutron-star mergers per year, and they can provide insights on a range of topics from the population of short gamma-ray bursts to the presence of dark matter around black holes.
02/19/19Probing Massive and Supermassive Black Holes with Gravitational Waves.
Sarah Vigeland
NSF Physics Frontier Center Postdoctoral Fellow
University of Wisconsin - Milwaukee

Observations have shown that nearly all galaxies harbor massive or supermassive black holes at their centers. Gravitational wave (GW) observations of these black holes will shed light on their growth and evolution, and the merger histories of galaxies. Massive and supermassive black holes are also ideal laboratories for studying strong-field gravity. Pulsar timing arrays (PTAs) are sensitive to GWs with frequencies ~1-100 nHz, and can detect GWs emitted by supermassive black hole binaries, which form when two galaxies merge. The Laser Interferometer Space Antenna (LISA) is a planned space-based GW detector that will be sensitive to GWs ~1-100 mHz, and it will see a variety of sources, including merging massive black hole binaries and extreme mass-ratio inspires (EMRIs), which consist of a small compact object falling into a massive black hole. I will discuss source modeling and detection techniques for LISA and PTAs, as well as present limits on nanohertz GWs from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration.
02/21/19 (Thursday)Physics and astrophysics with gravitational waves from compact binary coalescences.
Anuradha Gupta
Postdoctoral Fellow
Institute for Gravitation and Cosmos
Pennsylvania State University

The recent detections of gravitational waves from several binary black holes and binary neutron star mergers have opened up new avenues for gravitational wave astronomy and astrophysics. These detections provide us with great opportunities to study astrophysical sources in both weak and strong gravity regimes. In this presentation, I'll tell you how one does physics and astrophysics with gravitational waves emitted from compact binary coalescences. In particular, how to constrain binary formation mechanisms from their observed properties, how to test general relativity and other theories of gravity and lastly how to do precision cosmology with gravitational waves. I'll also touch upon the future prospects of these efforts.
02/28/19 (Thursday)MicroBooNE - Using Neutrinos to Probe Nuclear Physics for the Future
Libo Jiang
Postdoctoral Fellow
University of Pittsburgh

MicroBooNE is a large 170-ton liquid-argon-Time Projection Chamber Neutrino experiment located on the Booster neutrino beamline at Fermilab. The detector serves as a next step in a phased program towards the construction of massive kiloton scale LArTPC detectors for future long-baseline neutrino physics (DUNE) and is the first detector in the short-baseline neutrino program at Fermilab. A major physics goals of the experiment is to probe the source of the anomalous excess of electron-like events in MiniBooNE/LSND with improved detection capabilities. In addition, MicroBooNE has an extensive cross section physics program that will improve current models on neutrino-nucleus interactions, especially nuclear effects in argon, and decrease systematic errors in the oscillation program. This colloquium introduces the detector & performance of MicroBooNE and summarizes the status of MicroBooNE's neutrino cross section analyses.
(Particle Physics)
03/04/19 (Monday NCPA)Reviving the Poltergeist: Bringing water-based neutrino experiments into the precision era with efficient neutron detection.
Jonathan Eisch
Assistant Scientist
Iowa State University

Advances in water-based neutrino-detection technology are setting the stage for a new generation of detectors to answer questions about the nature of matter in the universe and to make our world a safer place. Leading the way in these new technologies is the Accelerator Neutrino Neutron Interaction Experiment (ANNIE) at Fermilab. ANNIE will revisit the use of neutron capturing salts, pioneered in the first experiment to detect the neutrino, to detect the number of neutrons produced in GeV-scale neutrino interactions. This measurement, the first on a neutrino beam, will help push future neutrino-oscillation experiments into the precision era by separating quasi-elastic charged-current interactions from more complicated many-body neutrino interactions and thus improving the models of neutron production in neutrino interactions. The WATCHMAN experiment, under construction in the UK, will use the same technology at a much larger scale to demonstrate the ability to remotely monitor nuclear reactors from tens of kilometers away. This demonstration will enable remote reactor monitoring to be a part of future nuclear nonproliferation treaties. In this talk, I will describe the ANNIE and WATCHMAN experiments along with their impacts on detector technology development toward future large multipurpose neutrino detectors like Theia.
(Particle Physics)
03/05/19The wonderful world of neutrino oscillations
Gavin Davies
Postdoctoral fellow
Indiana University

In 1998 it was discovered that neutrinos oscillate and have mass which led to the award of the 2015 Nobel Prize in Physics. That discovery generated a global campaign to better understand neutrino properties using oscillations of neutrinos produced in the Sun, in the atmosphere, at reactors, and by accelerators. The community has learned much but several important questions remain such as: Which neutrino is heaviest? Do neutrinos break the symmetry between matter and antimatter? Are there more than three neutrino types? In my talk, I will introduce neutrinos and the questions surrounding them, their chameleon-like flavor-changing behavior, and the experiments that hunt for them including the leading-edge, international Deep Underground Neutrino Experiment.
(Particle Physics)
03/07/19 (Thursday)Exploring the neutrino physics with the Deep Underground Neutrino Experiment
Jingbo Wang
University of California, Davis

One of the biggest surprises in particle physics is that the neutrinos have mass, which was discovered by the neutrino oscillation experiments. This fundamental property of neutrinos leads to some new questions. What is the ordering of the neutrino mass states? Do the neutrinos violate the matter/antimatter symmetry? What characteristics does the neutrino mixing matrix have? The Deep Underground Neutrino Experiment (DUNE) will address these questions with the high-precision Liquid Argon Time Projection Chamber (LArTPC) technology. In this talk, I will give a brief overview of neutrino oscillations, then describe DUNE and its physics programs. I will also talk about the Pulsed Neutron Source as a newly proposed calibration technique for liquid argon TPCs. The precision measurements of the neutrinos will open a window to new physics beyond the standard model. The future and prospects will be discussed.
(Particle Physics)
03/19/19Three Dimensional Numerical Modeling of Temperature Distribution in a High Dam Reservoir with the Effect of Channel Curvature on Mekong River
Xiaobo Chao
Senior Research Scientist
National Center for Computational Hydroscience and Engineering
University of Mississippi

A three dimensional numerical model has been developed to simulate the flow circulation as well as temperature distribution in a high dam reservoir with the effect of channel curvature. In the model, the density induced buoyant force on the turbulent flow is considered. This “ buoyancy-extended version of k- model” is used for turbulence closure, and the flow velocity and temperature distribution are simulated simultaneously. The model was first validated using a laboratory case of turbulent buoyant flow in a curved open channel. The secondary flow circulation in the curved channel was simulated and the temperature distribution in the channel was validated using experimental data. The model was then applied to simulate the flow and temperature distribution in Xiaowan Reservoir, a high dam reservoir on Mekong River, with deep water depth and curvature affect. The numerical results are generally in good agreement with field observations. The thermal stratification, temperature distribution in the reservoir and the effect of channel curvature on the temperature distribution are discussed.
(Computational Hydroscience and Engineering)

04/02/19Precision Fundamental Symmetry Measurements With Cold Neutrons
Jason Fry
The neutron can be used as a powerful tool to study a wide range of phenomena through many disciplines of physics. In particular, cold neutrons are utilized in condensed matter, nuclear, and particle physics with deep connections to cosmology. The free neutron has a slightly larger mass than the proton leading to far reaching implications. How long a free neutron lives determines how the light elements formed in the early universe. The kinematics of neutron decay give us insight into how quarks mix in the weak interaction. Additionally, as a neutral particle, neutrons can penetrate deeply into nucleons to further our understanding of how the strong and weak interaction mix at the smallest scales. In this talk, I will discuss the neutron physics experiments carried out and planned on the Fundamental Neutron Physics Beamline (FNPB) at the Spallation Neutron Source at Oak Ridge National Lab. The NPDGamma experiment, the first experiment on the FNPB, studied the most fundamental process in the Hadronic Weak Interaction (HWI) and the results set the best constraint for future investigation of the HWI. Currently we are commissioning the Nab experiment on FNPB which will make precise measurements of the electron neutrino correlation parameter "a" and the Fierz interference term "b" in unpolarized neutron beta decay. These results will lead to a new, precise, independent determination of the ratio λ = GA/GV that will sensitively test CKM unitarity.
(Particle Physics)
04/09/19Microfluidics: Thinking small to improve biological research
Glenn M. Walker
Associate Professor of Electrical Engineering
University of Mississippi

Microfluidics is the study of fluid behavior at micrometer length scales and the development of devices that leverage microscale fluid phenomena. A major focus of the field has been on solving problems in biology since biological cells typically range in size from 1–20 micrometers and are difficult to manipulate with traditional instruments. Researchers have been able to exploit the manipulation of fluid volumes down to the picoliter to enable biological experiments that were previously impossible. This talk will cover some of the microscale phenomena that become dominant at micrometer lengths and also show examples of enabling biological experiments. Research from our lab on high throughput screening and cancer cell hypoxia will also be presented.
(Biomedical Engineering)
04/16/19New physics in inclusive $B \to X_c \tau \nu_\tau$ decays in light of $R(D^{(*)})$ measurements
Saeed Kamali
Department of Physics and Astronomy
University of Mississippi

There has been persistent deviations from Standard Model predictions of the lepton universality observables $R(D)$ and $R(D^*)$ defined as $R(D^{(*)})=\frac{BR(B \to D^{(*)} \tau \nu_{\tau})}{BR(B \to D^{(*)} \mu \nu_{\mu})}$. I present a study of the new physics operators in the inclusive decay $B \to X_c \tau \nu_{\tau}$ where $X_c$ is any hadron containing a charm quark. This decay mode is relevant to the $R(D^{(*)})$ anomalies since it has the same quark level transition, $b \to c \tau \nu_{\tau}$. I will also talk about some leptoquark models that can potentially explain these anomalies."

Development of vibrational metrics for internal damage scenarios of a scaled Transnuclear-32 dry storage cask for spent nuclear fuel
Kevin Lin
Department of Physics and Astronomy
University of Mississippi

The assessment of the internal structural integrity of dry storage casks for used high burnup nuclear fuel assemblies is of critical importance before transporting these to permanent repositories. The large size and structural complexity of the Transnuclear-32 (TN-32) cask as well as the inability to access its interior make this a challenging task. To address these difficulties, we use an active acoustics approach to develop metrics that are sensitive to the internal configuration of these casks. A 6:1 scaled model of the TN-32 cask was constructed in order to study internal configuration of the fuel assemblies including various damage scenarios. The vibration modes were verified in Finite Element simulations. Each mock-up fuel assembly consists of bundled steel rods, and their structural failure is mimicked by steel shot of equal weight. This talk will report the amplitude- and phase-based active acoustics metrics we developed to characterize different levels of internal damage. Our studies indicate that vibrometric signatures of various internal conditions can be measured using sources and sensors mounted on the exterior shell. Our current methodology is sensitive enough to detect structural failures at the single fuel assembly level.

Droplet extraction and manipulation at a fluid interface using fraxicon modified ultrasound
Robert Lirette
Department of Physics and Astronomy
University of Mississippi

Ultrasound focused at a fluid-fluid boundary creates an acoustic radiation pressure on the boundary that is dependent on the incident energy density and the relative density and sound speed of each fluid. For different fluid combinations this radiation pressure can either be positive or negative. For this study ultrasound propagating from water to carbon tetrachloride was used to create a negative radiation pressure at the interface. This fluid combination is impedance matched eliminating reflections and heating effects at the boundary. A fraxicon phase plate lens is a low profile analog of an axicon and generates an approximate Bessel beam in the far field. The near field exhibits a complex diffraction pattern including shadow zones capable of acoustic trapping. Starting with a planar interface, we demonstrate the extraction, capture, and manipulation of a carbon tetrachloride droplet. The negative radiation pressure draws the carbon tetrachloride surface up into the water, eventually breaking a droplet free. The trapped droplet is then transported through the water by moving the transducer.

(Particle Physics, Acoustics)
04/30/19Infrasound Generation and Propagation in the Earth's Atmosphere
Roger Waxler
Principal Scientist and Research Associate Professor of Physics and Astronomy
University of Mississippi

The term infrasound is applied to low frequency sound in the atmosphere, generally below the limit of human hearing. The frequencies of interest in our research range from 10 Hz down to as low as 0.001 Hz, corresponding to periods of 0.1 to 1000 seconds. Such signals tend to be geophysical in nature, propagating globally and generated by large, violent events such as hurricanes, tornadoes, earthquakes and large detonations. Their propagation depends critically on large scale temperature and wind velocity gradients. These produce a variety of acoustic ducts in the atmosphere. These are asymmetric with respect to azimuth and interact with each other. They are also spatially and temporally varying, with small scale fluctuations on top of diurnal and seasonal cycles. An overview of sources, generation and propagation of infrasound in the atmosphere will be presented.