Events

Jake Bennett
Department of Physics
Carnegie Mellon University

Amplitude Analysis: A Powerful Tool for Hadron Spectroscopy

Extracting useful information from experimental data is often far from straightforward. This is particularly true for studies in hadron spectroscopy that seek to determine the properties of constituent quark states. The presence of multiple, often broad, states leads to potentially intricate interference patterns that make the extraction of meaningful information challenging. Amplitude analysis is a powerful tool to disentangle the effects of interference and extract useful properties of hadronic states. This information is vital for a deeper understanding of the fundamental laws of nature. In this talk, I will review the experimental challenges that are associated with amplitude analysis, as well as its potential as a tool for hadron spectroscopy at Belle II.

Brian Anderson
Department of Physics and Astronomy
Brigham Young University

Listening For Cracks Using Resonance And Time Reversal Techniques To Prevent Radiation Leakage From Nuclear Storage Containers

Spent nuclear fuel is often stored in stainless steel canisters in the United States. Stainless steel is susceptible to Stress Corrosion Cracking (SCC). This presentation will discuss progress on the use of the Time Reversed Elastic Nonlinearity Diagnostic (TREND) and Nonlinear Resonant Ultrasound Spectroscopy (NRUS) to determine whether SCC is present and attempt to quantify the depth of the cracking. NRUS is the measurement of the amplitude dependence of a sample's resonance frequency, which occurs because of a softening of the elastic modulus in damaged media. NRUS provides a global indication of damage in a sample. TREND employs time reversal acoustics, which focuses wave energy at various points of interest to excite localized high amplitude. The amplitude dependence of this localized energy allows pointwise inspection of a sample.

Aaron Zimmerman
Canadian Institute for Theoretical Astrophysics
University of Toronto

Black Holes, Alone and in Pairs

The recent detections of gravitational waves have revealed an invisible side of the universe: black holes in binaries. These observations test our understanding of black holes, their violent mergers, and the theory of general relativity. A combination of analytic approximations and full numerical simulations is required to understand black hole binaries and predict the gravitational waves they emit. I will take us on a tour of these systems, discuss the “ringdown” of the final merged black hole, and present the most recent results from the Advanced LIGO and Virgo detectors.

Jessica McIver
Division of Physics, Mathematics and Astronomy
California Institute of Technology

Gravitational Wave Astrophysics: A New Era of Discovery

Large-scale interferometric detectors including LIGO and Virgo sense gravitational waves; minuscule fluctuations in space-time from the most extreme phenomena in the Universe. The recent detection of gravitational waves by LIGO and Virgo in concert with an associated electromagnetic counterpart was a breakthrough in multi-messenger astronomy that confirmed the association between neutron star collisions and short gamma-ray bursts (GRBs) and yielded new insight into the physical engine driving GRBs. Future gravitational wave observations have the potential to provide critical insight into key open questions in astrophysics, including the distribution of compact objects in the Universe, the evolution of compact binary systems, galaxy formation, and the explosion mechanism of core-collapse supernovae.

I will present the major outstanding challenges in gravitational wave astrophysics, including searching for transient signals in noisy data that contains a high rate of transient noise artifacts. I will discuss future prospects for how this quickly growing field will shape our understanding of the Universe.

Dan Cherdack
Department of Physics
Colorado State University

Searching for CP-Violation with the DUNE Experiment

Of the four known fundamental forces the weak force has many unique properties. It is the only standard model force that couples to all known fermions, that has massive exchange bosons, and that induces particle flavor changes. Even more surprising is that the weak force maximally violates parity symmetry, and has even been demonstrated to break charge-parity (CP) symmetry, meaning the weak force interacts differently with matter and anti-matter. This last property may hold the key to understanding several fundamental mysteries of the universe from the three-generation structure of matter, to the missing link between the big bang and the observed universe.

Neutrinos only interact via the weak force which means they are hard to detect, but provide a unique test bed for studying the weak interaction. Over the past few decades it was discovered that neutrinos have mass and change flavors. Studying the way neutrinos change flavors, termed neutrino oscillations, allows us to search for a new source of CP-violation. The next-generation Deep Underground Neutrino Experiment (DUNE) will usher in an era of high precision neutrino physics with the worlds most intense neutrino beam and high resolution Liquid Argon (LAr) Time Projection Chamber (TPCs) detectors. The Fermilab Short-Baseline Neutrino (SBN) Program will employ three LAr TPCs, which will provide and excellent test bed for LAr TPC R&D, and allow for many important measurements crucial to DUNE. I will discuss the theoretical framework we use to describe neutrino oscillations, and the exciting opportunities and new challenges afforded us by these experiments.

Tony Jun Huang
Pratt School of Engineering
Duke University

Acoustofluidics: Merging Acoustics and Microfluidics for Biomedical Applications

The past two decades have witnessed an explosion in lab-on-a-chip research with applications in biology, chemistry, and medicine. The continuous fusion of novel properties of physics into microfluidic environments has enabled the rapid development of this field. Recently, a new lab-on-a-chip frontier has emerged, joining acoustics with microfluidics, termed acoustofluidics. Here we summarize our recent progress in this exciting field and show the depth and breadth of acoustofluidic tools for biomedical applications through many unique examples, from exosome separation to cell-cell communications to 3D bioprinting, from circulating tumor cell isolation and detection to ultra-high-throughput blood cell separation for therapeutics, from high-precision micro-flow cytometry to portable yet powerful fluid manipulation systems. These acoustofluidic technologies are capable of delivering high-precision, high-throughput, and high-efficiency cell/particle/fluid manipulation in a simple, inexpensive, cell-phone-sized device. More importantly, the acoustic power intensity and frequency used in these acoustofluidic devices are in a similar range as those used in ultrasonic imaging, which has proven to be extremely safe for health monitoring during various stages of pregnancy. As a result, these methods are extremely biocompatible; i.e., cells and other biospecimen can maintain their natural states without any adverse effects from the acoustic manipulation process. With these unique advantages, acoustofluidic technologies meet a crucial need for highly accurate and amenable disease diagnosis (e.g., early cancer detection and prenatal health) as well as effective therapy (e.g., transfusion and immunotherapy).

Harry Swinney
Center for Nonlinear Dynamics
University of Texas — Austin

Universality in Nature

In the seventeenth century Newton thought about the gravitational force between the earth and an apple falling from a tree, and he said “I began to think of gravity extending to the orb of the Moon.” This led him to postulate that his gravitational force law is a universal law of nature, applying to any two masses in the universe. We now know that there are three other fundamental universal forces in nature, the electromagnetic and the strong and weak nuclear forces. Systems of many atoms or molecules can similarly exhibit universal behavior. For example, studies of phase transitions in the 20th century culminated with Kenneth Wilson's theory of universality in phase transitions of systems as different as fluids and magnets. The present talk examines spatial patterns that emerge in systems driven away from thermodynamic equilibrium by imposed gradients in pressure, temperature, or nutrient concentration. Experiments and mathematical models provide insights into the formation of patterns in physical, chemical, and biological systems, as will be illustrated through examples that reveal mathematical similarity in phenomena such as in the fractal wrinkling of flower petals and plastic sheets.

Tyrone Porter
Department of Mechanical Engineering and Biomedical Engineering
Boston University

Tensionless Bubbles and Exploding Droplets

Fluid-filled particles play a pivotal role in biomedical applications of ultrasound. This talk will cover two examples, lipid-coated microbubbles and vaporizable nanoemulsions, highlighting their interesting nonlinear dynamics and utility. Due to their compressibility, microbubbles are more echogenic than tissue, making them ideal ultrasound contrast agents. The microbubble surface must be coated with surface-active molecules such as lipids in order to reduce the interfacial tension and stabilize the microbubble against dissolution. The interfacial tension is a function of lipid surface density, which varies from zero upon deep compression to that of an uncoated bubble upon expansion. The forces acting on the microbubble wall vary as the interfacial tension changes, resulting in a nonlinear response to acoustic excitation. Using monodisperse lipid-coated microbubbles, we have studied this nonlinear behavior, including pressure-dependent resonance frequency and subharmonic emissions at ultralow excitation pressures. In contrast to microbubbles, liquid perfluorocarbon nanoemulsions are incompressible and thus poorly echogenic. The nanoemulsions can be vaporized with high pressure acoustic pulses. The phase conversion is immediate and highly energetic and thus resembles an explosion on a microscale. The resultant bubbles can be used to transiently permeabilize cell membranes, thus enabling drug delivery to intracellular targets, or can be used to enhance tissue absorption of ultrasound, making ultrasound-mediated ablation more efficient. These studies provide insight into the unique nonlinear behavior of these fluid-filled particles and how they may be leveraged for exciting biomedical applications.

David Meyer
Department of Mathematics
University of California — San Diego

Data Science and Quantum Gravity

Data, even “big data”, is finite, and thus discrete. A common goal is to describe them as the outcome of a random process specified by a small number of parameters; doing so at least compresses the data, and at best explicates the process by which they were generated. Some important approaches include low-rank matrix factorization and multi-dimensional scaling, both of which reveal a geometry behind the data. Such interplay between the discrete and the continuous is familiar in theoretical and computational physics, from the definition and regularization of path integrals to numerical methods for fluid dynamics. In this talk I'll explain how recent data science results in non-metric multidimensional scaling provide a new perspective on the Hawking-Malament theorem that is the foundation of the causal set program for quantum gravity. I'll describe a new algorithm for embedding causal sets in Lorentzian manifolds motivated by this perspective. And I'll end with some speculations about possible quantum dynamics for causal sets. Familiarity with the causal set program for quantum gravity will not be assumed.

Mir Emad Aghili, Vishal Baibhav, and Shrobana Ghosh
Department of Physics and Astronomy
University of Mississippi

Presentations by Graduate Students

"Manifoldlikeness of Causal Sets" by Mir Emad Aghili
Abstract: We study the distribution of maximal-chain lengths between two elements of a causal set, and its relationship with the embeddability of the causal set in a region of flat spacetime. We start with causal sets obtained from uniformly distributed points in Minkowski space. After some general considerations we focus on the 2-dimensional case and derive expressions for the expected number nk of maximal chains as a function of their length k, the most probable maximal-chain length k₀, and the width Δ of the length distribution, as functions of the number N of causal set elements in the interval between the two points. These results, together with the results of numerical simulations of causal sets embedded in Minkowski space of various dimensionalities, show that for a given N the values of k₀ and Δ can be used to estimate the dimensionality of a causal set embeddable in Minkowski space. Other dimension estimators are known for manifoldlike causal sets, but the length distribution also gives us a way to evaluate the embeddability of a causal set. We provide a first test of manifoldlikeness based on k₀ and Δ, and end with a few simple examples of nk distributions for non-manifoldlike causal sets.

"Systematic Errors and Energy Estimates in Binary Black Hole Ringdown" by Vishal Baibhav
Abstract: High signal-to-noise ratio gravitational wave observations will enable us to measure the quasinormal frequencies of binary black hole merger remnants. In general relativity, these frequencies depend only on the remnant's mass and spin, so they can be used to test general relativity and the Kerr nature of the remnant. To carry out these tests, systematic errors must be subdominant with respect to statistical errors. I'll talk about how accurately ringdown frequencies can be extracted from state-of-the-art numerical simulations from the Simulating eXtreme Spacetimes (SXS) catalog. I'll also present some results on the relative excitation of different quasinormal modes. To quantify these excitations, one must define a suitable “starting time“, e.g. by maximizing the energy content “parallel” to a quasinormal mode (as suggested by Nollert). We used Nollert's method to quantify the energy radiated in quasinormal modes for aligned-spin binaries, and we produced post-Newtonian inspired fits of the resulting energy estimates.

"Detectability of Gravitational Radiation from Superradiant Instabilities" by Shrobana Ghosh
Abstract: An incident wave, when scattered off a black hole may get amplified, at the expense of the rotational energy of the black hole. This process is known as superradiance and due to this rotating black holes can serve as particle detectors. For a massive field, the mass of the field helps in confining the field. Therefore, even an ultralight bosonic field can form a non-axisymmetric cloud around the black hole due to repeated amplification from the black hole. This leads to emission of gravitational radiation that can be detected by ground-based or space-based gravitational wave detectors, depending on the mass of the boson. Based on astrophysical models we show that adLIGO should see 10⁴ events in a 4 year mission for a scalar field mass of 3×10^-12 eV, while LISA will see about 10³ events in a 4 year mission for a scalar field mass of 10^-17 eV. In the absence of detection at a particular detector, we can rule out the corresponding mass range of the scalar field. We also look at the detectability of such events from the remnants of the merger events already seen by adLIGO at the present and future ground-based detectors.

Bruno Uchoa
Department of Physics and Astronomy
University of Oklahoma

Topology and Quantum Phenomena in Nodal Matter

Nodal matter describes a new metallic form where the Fermi surface collapses into sets of points or lines, and is not stabilized by Fermi pressure but by symmetries. The non-trivial quantum phenomena of those systems are described by topology, a field of mathematics that studies properties that remain invariant under continuous deformations of shapes and surfaces. In the first part of the talk I will give a general overview of the field. In the second one, I will describe a particular class of nodal materials where the Fermi surface has the shape of closed lines. I will show that interactions can drive this system into an exotic topological phase in three dimensions (3D) known as the 3D anomalous quantum Hall effect, where the system has spontaneous and topologically protected surface currents.

Mukunda Acharya, Khagendra Adhikari, and Xudong Fan
Department of Physics and Astronomy
University of Mississippi

Presentations by Graduate Students

"Sound Speed Profiles of the Global Ocean calculated from Physical Oceanographic Data" by Mukunda Acharya
Abstract: Sound speed profiles in the global ocean are useful for modeling of sound propagation over the global oceans. This talk presents the sound speed profiles calculated from physical oceanographic data that were collected in the world ocean circulation experiment. They are data of conductivity, temperature, and pressure, taken from multiple cruises with a typical spacing of 60 km along the route of each cruise and consisting of an elaborate series of zonal (east-west) and meridional (north-south) coast-to-coast cruises across the global oceans. Nearly 8000 sound speed profiles were mapped out that were then used to determine the dependence of sound speed minimum and depth for those minima on the longitude and latitude. Based on the characterization, practical formulas of the dependence were given.

"Deforming the Fredkin Spin Chain Away from its Frustration-free Point" by Khagendra Adhikari
Abstract: The Fredkin model describes a spin-half chain segment subject to three-body, correlated-exchange interactions and twisted boundary conditions. The model is frustration-free, and its ground state wave function is known exactly. Its low-energy physics is that of a strong xy ferromagnet with gapless excitations and an unusually large dynamical exponent. We study a generalized spin chain model that includes the Fredkin model as a special tuning point and otherwise interpolates between the conventional ferromagnetic and antiferromagnetic quantum Heisenberg models. We solve for the low-lying states, using exact diagonalization and density-matrix renormalization group calculations, in order to track the properties of the system as it is tuned away from the Fredkin point. We identify a zero-temperature phase diagram with multiple transitions and unexpected ordered phases. The Fredkin ground state turns out to be particularly brittle, unstable to even infinitesimal antiferromagnetic frustration. We remark on the existence of an “anti-Fredkin” point at which all the contributing spin configurations have a spin structure exactly opposite to those in the Fredkin ground state.

"Enhancing Sound Emission by Using Subwavelength Metacavities" by Xudong Fan
Abstract: Efficient directional emission of sound waves is critical in imaging and communication, yet is held back by the inefficient emission of a small source. A change in the surrounding environment of an acoustic source can lead to enhanced emission and mode conversion. This talk will present frames of enclosing small sound sources in subwavelength meta-cavities to achieve sound enhancement and conversion with high efficiency. The enhancement is an analog of modifying spontaneous emission rate of a quantum source in a resonant cavity. The enhancement by a subwavelength meta-cavity offers a practical path toward miniaturization in applications that demand efficient emission, such as sonar, loudspeakers, or ultrasound transducers.

S.T.E.M. Fest 2018 at the University of Mississippi

The physics department will participate in the 2018 S.T.E.M. Fest.

Friday, April 20, 2018

• Physics Open House. Learn why a curve ball curves or how to hit the perfect home run from the Society of Physics Students.
  Lewis Hall & Swayze Field 3 - 5 PM.
• National Center for Physical Acoustics Tours. Discover cutting-edge research on a variety of acoustic phenomena, from ultrasonic to infrasonic. NCPA, 3 PM & 4 PM.
• Hidden Figures: The movie. The 2016 blockbuster presented by the Women in Physics and the Office of Diversity and Community Engagement. Overby, 5 - 7:15 PM.
• Astronomy Open House: Viewings of the moon and Jupiter with the historic 1893 Grubb telescope, weather permitting.
  Kennon Observatory, 8 - 10 PM.

Saturday, April 21, 2018

• Lightning Research at UM Field Station. Lecture on lightning and atmospheric physics by Professor Tom Marshall.
  Field Station, 10:40-11am.
• Fun Demos at UM Field Station. Explore the physics of sound, a fire tornado, liquid nitrogen, and what happens when you lay down on a bed of nails. Field Station, 2:30-3:30pm.

Deidre Shoemaker
School of Physics
Georgia Institute of Technology

Numerical Relativity in the Age of Gravitational Wave Observations

The advent of gravitational wave astronomy has created opportunities to probe strong-field gravity as we measure the merger of black holes. Numerical relativity provides the means to confront the measurements with theoretical prediction. In this talk, I'll discuss the role numerical relativity played in the observed black hole binaries by LIGO and Virgo and the future potential for unveiling strong-field gravity in both future ground and space based detectors.

Emanuele Berti
Department of Physics and Astronomy
University of Mississippi

Strong Gravity and Astrophysics with Compact Binaries at the Dawn of Gravitational-wave Astronomy

Einstein's general relativity has passed all experimental verifications with flying colors, but cosmological observations and difficulties in quantizing gravity suggest that general relativity should be modified at some level. Strong-field modifications of general relativity (if they occur in nature) will in general affect the dynamics of black holes and neutron stars, with potentially observable signatures. Therefore compact objects - whether in isolation or in binary systems - are excellent astrophysical laboratories for high-energy physics and strong-field gravity. Furthermore, the gravitational radiation emitted during the inspiral and merger of compact binaries encodes important information on their astrophysical formation mechanism. I will discuss potential smoking guns of modified gravity in gravitational-wave detectors, and the theoretical and observational challenges associated with their search. I will also discuss the potential of Earth- and space-based detectors to further our understanding of the formation and evolution of compact binaries.

Zheguang Zou
National Center for Physical Acoustics
University of Mississippi

Underwater Sound Propagation in Estuarine Environments

Estuaries are shallow-water regions that are highly dynamic due to a variety of environmental variability, such as tidal flow, water mixing,
wind-driven water surface waves, etc. The environmental variability has significant effect on underwater sound propagation and acoustic
communication. This talk will present some of these effects in the Delaware bay. The examinations include water-column variations due to tidal
dynamics, and surface variations due to wind-wave dynamics. The results gain insight into the link between physical environments and underwater
acoustic fields, suggesting the demanding of next-generation underwater acoustic communication systems for dynamic oceans.

Robert J. Doerksen
Department of BioMolecular Sciences
University of Mississippi

Laws of Physics Applied to Molecules: Accurate Electronic Structure Calculations and Molecular Dynamics Simulations

Quantum mechanics, classical mechanics (so-called “molecular mechanics”) and molecular dynamics (which could be classical- or quantum-based) methods can be used to study molecules and molecular systems to provide accurate fundamental properties, to compare to experimental results or to provide insight. In this seminar I will give a brief explanation of a variety of fundamental calculation approaches. I will illustrate the use of the methods for solving practical problems with calculations of optical rotations, NMR chemical shifts and electronic circular dichroism spectra that assist in assigning the absolute configuration of newly discovered natural product molecules and molecular dynamics simulations used to study the role of allosteric modulators of cannabinoid receptors.

Parsa Bakhtiari Rad
National Center for Physical Acoustics
University of Mississippi

3D Seismic Oceanography: The New Frontier in Ocean Water-Column Exploration

Seismic oceanography is a newly-introduced technique that links exploration seismology and physical oceanography. It consists of the application of the multi-channel seismic reflection method, commonly used in the oil and gas industry to image the subsurface geological structure, to the investigation of the fine structure of the ocean interior. Seismic reflection sections provide high quality images of the oceans fine structures with higher vertical and horizontal resolution and complement conventional physical oceanography measurements and logs. These images consist of seismic reflections that occur and are recorded whenever a seismic wave traveling in a heterogeneous media encounters interfaces between different water layers and is reflected back to the surface and recorded by special receivers. This talk will report the implement of a three dimensional (3-D) seismic study to better image the ocean interior. A very large seismic data set collected from the Mississippi canyon in the Gulf of Mexico is used to produce the 3-D seismic images of the ocean interior. The initial images obtained using massive hardware/software efforts exhibit promising results for further studies.

Eyal Schwartz
Department of Physics and Astronomy
University of Mississippi

Single Atoms Dynamics in Tight Optical Tweezers

One of the enduring ambitions in atomic physics is to build an understanding of interacting macroscopic systems completely from knowledge of the underlying microscopic dynamics. In recent years, experimental advancements in the near-deterministic isolation and control of single atoms, paved the way for this connection of the few-body and many-body regimes. As experimental techniques in engineering atom-atom interactions become more reliable and widespread, further opportunities for direct observations of quantum phenomena come to light.

In this talk I will give an overview of our past and present work. From laser cooling and trapping of a single atom in optical tweezers, through different manipulations to study few body dynamics in an atomic level. I will detail our latest works of “Thermally-robust spin correlations between two atoms” and “Direct measurements of collisional dynamics in ultra-cold atom triads”.

Our facility gives a push button mechanism for future quantum chemistry, quantum computers and cool fundamental quantum experiments to explore the relations between the micro and macro worlds.

Stefanos Kourtis
Physics Department
Boston University

Quantum-inspired Approaches to Hard Computational Problems

Many classes of complex computational problems admit no efficient solution or even approximation, yet have a vast reach in applications across science and industry. From a physics perspective, computational complexity originates from strong correlations between bits of information. It is reasonable to ask whether computational approaches to quantum many-body problems can be practically useful in this context. In this talk, I will present newly found cases where the answer is affirmative. I will introduce constraint satisfaction problems (CSPs) and reformulate them as interacting models whose ground states represent the solution manifold. A procedure that reaches the ground states of these models implements a protocol of computation. In some protocols, the complexity that arises during computation can be viewed as quantum entanglement, and efficiency is achieved by controlling its growth. Using this reasoning, I will introduce practical methods for solving CSPs based on tensor network contraction and demonstrate that they outperform state-of-the-art solvers for some of these problems by a significant margin. I will conclude with an outline of ongoing work on extensions and applications to problems of current interest, such as the simulation of existing and near-term quantum circuits.

Surajit Sen
Department of Physics
State University of New York at Buffalo

A New Look at Nonlinear Dynamics - Fundamental Physics, Shocks and Metamaterials

Nonlinear dynamics as a subject began in the late 1600s and matured into a broad based area in the late 20^th century. The talk will shed light on the breadth of the subject, the characters that seem to inhabit the nonlinear world, how they interact, and the newly introduced quasi-equilibrium phase. What nonlinear dynamics gives us in terms of making novel metamaterials and technologies will be highlighted.

Ryan C. Fortenberry
Department of Chemistry
University of Mississippi

Quantum Chemistry and Spectroscopy: A Match Made in the Heavens

The chemistry of the Earth is tied to only a small set of conditions while most of the rest of the Universe is often grossly different from terrestrial circumstances. Consequently, astrochemical experiments can be quite difficult to perform, but quantum chemistry does not suffer the same difficulties. Here, quantum chemistry is applied to the prediction of gas-phase spectroscopy and molecular formation of various “unstable” molecular systems including radicals, cations, and anions. The spectra of seemingly strange species including proton-bound complexes (i.e. OC—H⁺—CO), noble gas molecules (i.e. ArCH₂⁺, NeON⁺, & ArOH⁺), premineral molecules (i.e. Mg₂O₂ & MgF₂), and odd bonding in chalcogen hydrides (H₂S—S⁺) have been produced and even linked with laboratory and astrophysical detections. The applications of these findings stretch from the esoteric of cool and novel chemistry to indicators of early stages of planet formation even to abiotic molecular oxygen synthesis in comets, atmospheres, and the early Earth.

Karim Sabra
George W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology

Ocean Remote Sensing Using Passive Acoustics

Acoustic waves carry information about their environment as they propagate, especially in the ocean which can conduct sound very efficiently over significant distances. Hence underwater acoustic waves can be exploited for a wide variety of ocean remote sensing activities. Modern acoustic remote sensing involves receiver arrays and array signal processing to recover multidimensional results, for instance the characterization of medium inhomogeneities due to sound speed fluctuations or discrete sound scatters. On one hand receiver arrays are becoming increasingly autonomous, miniaturized and capable of long term deployment thus enabling the practical use of acoustics for ocean remote sensing applications. However, on the other hand, conventional acoustic remote sensing techniques still typically rely on controlled active sources which can be problematic to deploy and operate over the long term, especially if multiple sources are required to fully illuminate the ocean region of interest. To address this crucial limitation, totally passive versions-i.e. using only receiver arrays- of existing remote sensing techniques can be developed by taking advantage of uncooperative sources of opportunity (e.g. shipping noise) or the ubiquitous ocean ambient noise which have not typically been used in traditional ocean sensing applications due to their apparent complex nature. This fully passive approach can also be advantageous when regulations forbid the use of active sound sources to prevent the disruption of natural animal activities or when no active sources are readily available-e.g. at very low frequencies (~10Hz) or during covert operations. This presentation will discuss recent development of ocean remote sensing using passive acoustics notably 1) Passive acoustic thermometry to estimate deep ocean temperatures variations using coherent processing of low-frequency ambient noise, 2) Localization of drifting sensor networks using ambient noise to enable random volumetric ad-hoc receiver array for tracking underwater targets; and 3) Monitoring of shallow water sound channel using shipping sources of opportunity. Additionally the extension of these passive remote sensing techniques to seismic and structural health monitoring applications will also be presented.

Baharak Sajjadi
Department of Chemical Engineering
University of Mississippi

Efficient Carbon Modification for Sustainable Food/Energy/Water Nexus

Climate change mitigation is arguably the leading grand challenge facing mankind. Our critical reviews of physical modifications (Reviews in Chemical Engineering, 2018. in press, doi.org/10.1515/revce-2017-0113) and chemical modifications (Reviews in Chemical
Engineering, 2018. in press, doi.org/10.1515/revce-2018-0003) of biochar in addition to our experimental results suggest that acoustic, photochemical and plasma treatments, in selected reaction environments and conditions; are capable of inducing either structural or functional group changes on carbonaceous materials. These tunable, low energy treatments have potential to mitigate climate change through a number of transformative tracks.

The pioneering work of our transdisciplinary team revealed that single-staged ultrasound and photochemical treatments of
biochar in H₂O with dissolved CO₂ results in fixation of C from CO₂ on biochar, fixation of H from water on biochar, mineral leaching by water including minerals detrimental to gasification, increase in biochar's heating value (due to the 3 processes stated above), and increase in biochar's internal surface area (AIChE Journal, 2014. 60 (3):1054-1065). These synergisms seem to be tunable by feedstock, reactants stoichiometry and reaction conditions in pyrolysis, and treatments (Fuel, 2019. 235:1131-1145). Carbon and hydrogen fixations seem to be connected to the formation of H₂, CO, formic acid, formaldehyde, and associated radicals during sonolysis of aqueous CO₂. Similar to ultrasound waves, non-thermal plasma  can split water vapor and CO₂ to excited chemicals and fuels including methanol, H₂ and CO (Current Opinion in Green & Sustainable Chemistry, 2017. 3:45-49). The presence of carbon in the plasma system has not been explored. However, treatment of biochar in non-thermal chlorine plasma yields a high adsorption capacity of elemental mercury in flue gas due to the creation of Cl-active sites (Chemical Engineering Journal, 2018. 331C:536-544).

In this seminar, we will discuss the potential routes of the observed synergisms in mitigation of climate change through CO₂
capture/recycle, energy production through advanced gasification, Remediation of global carbon cycle (Fuel, 2018. 225
:287-298) & water resource (Ultrasonics Sonochemistry, 2018, in press). These treatments can also open new routes for tackling challenges such as water desalination through functionalized defected graphene membrane.

Andrea Welsh
School of Physics
Georgia Institute of Technology

Coming Together: Individuals at Different Scales Working for A Common Goal

Patterns in time and space are ubiquitous in everyday life, from the formation of structure by cell morphogenesis, to the coloration of animal's skin and fur, to the construction of large sand dunes from the driving and dissipation of the environment. My thesis can be classified into two threads: investigating the formations of patterns by the collective motion of systems — such as swarms of brine shrimp and human spiral waves — and the exploration of “chimera states,” a spatio-temporal pattern with more than one distinct behavior, both of which occur in biologically-relevant models of excitable tissue. I use a combination of computer simulation, mathematical methods, and table-top experiments to study these instances of pattern formation and learn how they are formed in biological systems, as well as the relevant physical parameters that control what sort of patterns are formed. Investigation of these systems have important consequences in how we understand our world, quantify and predict their dynamics and gain insights on why some patterns are physically chosen over others, and how to control them for our benefit.