Jennie Traschen, PhD
Department of Physics
University of Massachusetts Amherst
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, April 10, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

The Laws of Thermodynamcis, and the properties of Black Holes, are two topics that have long engaged both our imagination and calculational stamina. The formal identification of the area and surface gravity of a black hole horizon as an entropy and a temperature respectively, was made into a physics connection by Hawking’s 1975 calculation that classical black holes radiate quantum mechanical particles. Subsequently the field of black hole thermodynamics has expanded to study black holes in different environments, including black holes with a cosmological constant Λ. Here we will focus on that case of a positive Λ, which plays important roles in cosmology– whether as a GUT (Grand Unified Theory) scale Λ that drives the rapid expansion of the universe during an inflationary epoch, or the milli-eV scale Λ that models the observed dark energy in our universe today. Black holes with Λ > 0 have fascinating properties that are distinct from the asymptotically flat Λ = 0 case, starting with the fact that there are two horizons in the spacetime, one black hole and one cosmological. Hence there are two (generally unequal) temperatures, and two horizon areas that contribute to the total gravitational entropy. Both the mass M and entropy S are bounded between minimum and maximum values. There is a peak in the heat capacity ∂M/∂T as well as in the curve ∂S/∂T, which resemble the Schottky anomaly of a two level system in statistical mechanics. This talk will start with an introduction to black hole thermodynamics and particle production, and then discuss classical and quantum mechanical features of the cosmological black hole system that resemble the physics of a paramagnet.

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Randall D. Ledford, PhD
Wake Forest Alumni
Retired CTO of Emerson Electric Company
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, April 3, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

Dr. Ledford is this year’s winner of the Distinguished Alumni award. He recently retired as Chief Technology Officer of Emerson Electric Company, one of the world’s leading electronics companies. After graduating from Duke, Dr. Ledford joined Bell Telephone Labs in New Jersey where he worked on microwave communication leading to today’s cell phone communication. Before joining Emerson Electric Dr. Ledford was president and general manager of several divisions of Texas Instruments Inc. including software, digital imaging, enterprise solutions and process automation. Dr. Ledford also generously sponsors scholarships for physics undergraduate majors here at Wake Forest University. He will be speaking about …Emerson Corporation, a global manufacturer of industrial and residential products focusing on the technical and engineering challenges on business in today’s economic climate. Dr. Ledford graduated from WFU with honors in physics (with the assistance of a very young Bill Kerr) and received his Ph.D. in nuclear physics from Duke University.

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WFU Physics Career Advising Event

SPEAKER:  Dr. Heather Bedle, Assistant Professor, Conoco Philips School of Geology and Geophysics, University of Oklahoma

TIME: Wednesday, March 27, 2019, from 12:00 – 1:00 PM

PLACE: Olin Physical Laboratory, Lounge


Lunch will be provided. All interested persons are cordially invited to attend.


Dr. Bedle received her BS in Physics from WFU in 1999.  She initially worked in the defense industry, focusing on signal analysis physics for the development of various antenna and radar systems.  After a few years working as an engineer, Dr. Bedle then decided to go to graduate school for a degree in geophysics, studying earthquakes and velocity structure of the Earth.  After being granted her PhD in 2008 from Northwestern University, she went to work in the petroleum industry, where she further developed her seismic analysis and rock physics skills – all based on physics which she initially learned at WFU.  In 2016, Dr. Bedle left her industry job to instruct graduate-level applied geophysics courses at the University of Houston, and recently started a tenure-track position at the University of Oklahoma.

Dr. Bedle’s research interests focus primarily on combining a range of techniques across the disciplines of geophysics, petrophysics, and geology to further improve our understanding of the subsurface through seismic interpretation.  Her research works to refine and employ a wide range of interpretation tools and workflows from multiattribute seismic analysis, geostatistics, and seismic geomorphology to rock physics modeling.

Dr. Bedle is currently working on a variety of projects including improving the seismic identification of gas hydrate zones in the subsurface, as well as techniques to improve reservoir characterization and prediction on the sub-seismic scale, and seismic tomography.

For this Career Advising Event, Dr. Bedle will discuss her non-linear career path and will close the event with an interactive Q&A session.

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Heather Bedle, PhD
School of Geology and Geophyics
University of Oklahoma
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, March 27, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

Methane gas hydrates buried in the shallow crust of the Earth are often difficult to image with current geophysical techniques.  Understanding their extent in the crustal subsurface is important as they play a role as a future energy source.  In addition, if the clathrates are destabilized from their solid form to a gas, they can enter the atmosphere and affect the climate as methane is a greenhouse gas.  To improve subsurface mapping techniques of gas hydrates, Dr. Bedle and her research group have been approaching the imaging and detection problem by combining rock physics and geophysical seismic techniques.  These methods are additionally enhanced by incorporating new approaches including the use of seismic attributes and machine learning algorithms.  Initial results focused on gas hydrate accumulations in New Zealand will be presented.

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Tevian Dray, PhD
Department of Mathematics
Oregon State University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, March 20, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

Calculus as taught by mathematicians typically involves a large toolbox of algebraic manipulations. Almost all computations are done using rectangular coordinates and, later, the associated standard basis of unit vectors. Vector calculus as used by physicists, on the other hand, typically involves geometric reasoning, and the frequent use of coordinates and basis vectors adapted to the symmetries that are present. Thermodynamics goes even further, fundamentally altering the notion of “standard coordinates.” These treatments are sufficiently different from each other that they constitute different languages; students are often unable to translate.

Our research group at Oregon State University has been working to bridge this gap between mathematics and physics for more than two decades, primarily by restructuring upper-division physics courses, but also by developing materials for second-year calculus that emphasize geometric reasoning. The Paradigms in Physics project, continuously supported since 1997 by the NSF, has evolved from “merely” designing novel curricula to studying student learning of mathematical concepts such as partial derivatives.

This talk describes several examples of these language differences, the curricular materials we have developed to help students bridge this gap (including an online textbook and a website featuring more than 300 classroom activities), and some of the education research in which our materials are grounded.

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Steven Erwin, PhD,
Head of the Center for Materials Physics and Technology at The Naval Research Laboratory
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, February 27, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

The mechanisms which control the growth of nanocrystals are difficult to investigate because nanocrystals occupy a position awkwardly intermediate between molecules and solids. Two case studies highlight these difficulties and their solution.

(1) Cation exchange is a chemical reaction in which all the cations of a material are replaced by different cations, thus creating a new material. In semiconductor nanocrystals, cation exchange happens extremely fast – many orders of magnitude faster than for macroscopic crystals and far faster than simple size-scaling would suggest. I propose a theoretical mechanism for cation exchange in nanocrystals that reveals a surprising consequence of Coulomb interactions acting at nanometer length scales.

(2) Semiconductor nanostructures take a wide variety of physical forms. One of the most active areas of this research focuses on semiconductor “nanoplatelets,” the name given to nanostructures that are very thin and very wide. An early question asked by researchers was, what causes materials to form these very thin shapes in the first place? The question is even more puzzling when you learn that even materials with an underlying isotropic crystal structure form these extremely asymmetrical shapes. I will propose an explanation of this “kinetic instability” in the growth and show how this theory can be be used by researchers to create new families of nanoplatelet materials.

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Thomas Anthopoulos, PhD,
Professor of Material Science and Engineering at King Abdullah University of Science and Technology
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, February 20, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

In traditional optoelectronics the ability to downscale critical device dimensions has proven extremely successful over the past sixty years in increasing their functionality and performance. These extraordinary developments have been achieved through a virtuous circle of scientific and engineering breakthroughs which have led to the proliferation of information & communication technologies with an extraordinary impact on our daily life and society. However, adopting established manufacturing methods to emerging technologies such as printed optoelectronics, has proven challenging both in terms of technology and economics. This talk will focus on progress being made downscaling emerging forms of large-area optoelectronics through a new fabrication paradigm and their application in a variety of functional devices including, light-emitting nanogap diodes, photo-detectors and rectifying diodes.

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Peijun Guo, PhD,
Named Fellowship-Enrico Fermi, Argonne National Laboratory
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, February 13, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

The need for exquisite control of light is ubiquitous in energy-relevant applications, optoelectronics, and information science. In this talk, I will discuss how hybrid materials consisting of distinct sub-lattices and periodically nanostructured materials allow for dramatically enhanced light absorption, emission, and charge carrier generation at various time- and length-scales. I will first focus on hybrid organic-inorganic perovskites. These solution-processed, scalable materials exhibit remarkable optoelectronic properties such as strong light absorption, defect tolerance, and long carrier lifetimes. I will describe how electronic excitations in these materials are coupled to and influenced by the vibrational degrees of freedom of the organic and inorganic sublattices, investigated using an array of optical spectroscopic techniques. The unique soft nature of the lead-halide octahedral framework gives rise to dynamic fluctuations in the electronic bandgap, which distinguishes hybrid perovskites from traditional inorganic semiconductors. Furthermore, strong quantum confinement can be easily imparted to hybrid perovskites with the use of organic spacer-cations, leading to hyperbolic dispersion relation and enhanced light-emitting properties. Beyond solution-processed semiconductors, I will demonstrate how widely-used materials, such as indium-tin-oxide (ITO), can be grown in ordered, nanoscale array form by chemical vapor phase epitaxy to exhibit well-defined localized surface plasmon resonances in the infrared spectral range. The unique band structure and carrier concentration of ITO result in an unusual type of optical nonlinearity that is significantly larger and faster than the noble metal counterparts. I will conclude by discussing how such material platforms open new avenues for infrared molecular sensing, ultrafast optical switching and active photonic devices.

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WFU Physics Career Advising Event

SPEAKER:  Dr. Charles W. Miller, Consultant in Nuclear and Radiological Environmental Health

TIME: Wednesday, March 6, 2019, from 12:00 – 1:00 PM

PLACE: Olin Physical Laboratory, Lounge


Lunch will be provided. All interested persons are cordially invited to attend.


Dr. Miller is retired from the Centers for Disease Control (CDC) where he was the Chief of the Radiation Studies Branch, Division of Environmental Hazards and Health Effects, National Center for Environmental Health.  He also worked for the Office of Environmental Safety, Illinois Department of Nuclear Safety and the Health and Safety Research Division, Oak Ridge National Laboratory (ORNL), to name a few.

Dr. Miller’s primary area of expertise is centered on the transport and dose assessment of radionuclides released to the atmosphere, as well as other facets of environmental radiological dose assessment.

Dr. Miller will be happy to answer questions regarding his career path, and what let him to it.

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Charles W. Miller, PhD,
Consultant in Nuclear and Radiological Environmental Health
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, March 6, 2019, at 4:00 PM


There will be a reception with refreshments at 3:30 PM in the lounge. All interested persons are cordially invited to attend.


ABSTRACT

Many people believe that the detonation of an Improvised Nuclear Device (IND) will automatically result in massive death and destruction.  Such an event will almost certainly result in many deaths, but many other people will survive IF they know what to do to protect themselves.  The key message is to “Go in, stay in, and tune in” (see https://emergency.cdc.gov/radiation/). The purpose of this presentation is to explain what an IND is, how it works, what its impact will be, and how, because some of the effects of an IND decreases with time, people can survive the initial impact if they act quickly and appropriately.  This presentation will also discuss the role that scientifically literate citizens can have in helping to educate their family members, friends, and neighbors on these important concepts.

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