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Viktoriia Babicheva, PhD,
College of Optical Sciences, University of Arizona
George P. Williams, Jr. Lecture Hall, (Olin 101)
Tuesday, February 5, 2019, at 2:00 PM

There will be a reception with refreshments at 1:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Optical metamaterials are three-dimensional structures with rationally designed building blocks that enable devices with distinct optical responses not attainable with naturally available materials. Comprising a class of metamaterials with reduced dimensionality, optical metasurfaces allow the miniaturization of conventional refractive optics into planar structures, and a novel planar technology is expected to provide enhanced functionality for photonic devices being distinctly different from those observed in the three-dimensional case. In this talk, I will show that nanostructures made of high-index materials, such as silicon, transition metal dichalcogenides, or hexagonal boron nitride, support optically induced both electric and magnetic resonances in the visible and infrared spectral ranges. I will present the results on antireflective properties of metasurfaces based on high-index nanoparticle arrays and explain how zero backward scattering from the highly reflective substrate can be achieved [1]. Scattering-type scanning near-field optical microscope (s-SNOM) provides optical, chemical, and structural information of metasurfaces and enables their imaging with nanoscale resolution. I will show an approach to analyze layered of materials with different permittivities and demonstrate a technique to identify material type based on near fields at sample edges [2]. The recent discovery of high-index materials that offer low loss and tunability in their optical properties as well as complementary metal-oxide-semiconductor (CMOS) compatibility can enable a breakthrough in the field of nanophotonics, optical metamaterials, and their applications.

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Jun Chen, PhD,
Postdoctoral Research Fellow, Department of Materials Science and Engineering, Stanford University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, January 24, 2018, at 2:00 PM

There will be a reception with refreshments at 1:30 PM in the lounge. All interested persons are cordially invited to attend.

ABSTRACT

Energy crises and global warming severely limit the ability of human civilization to develop along a sustainable path. By using remotely deployed sensors, the Internet of Things (IoT) has already changed our daily life in fundamental and meaningful ways. On the one hand, batteries may not be the best solution for the IoT, owing to their limited lifetime of batteries, size and environmental problems. Additionally, wide distribution of the sensors and high maintenance costs make batteries an insufficient solution, especially for remote or inaccessible areas. Powering the IoT would be impossible without making the sensors self-powered by harvesting energy from the working environment to ensure long-term operation. On the other hand, the power required for each sensor is small, but the sheer number of sensors in the world can be on the order of billons to trillions. Developing self-powered sensors can save considerable energy.

 

In this talk, I will introduce my research that contributed to sustainability via energy saving and harvesting by using novel materials and energy technologies. I will firstly introduce a nanophotonic structure textile with tailored infrared property for passive radiative cooling using nanoporous polyethylene fabric, saving more than 20% of the indoor cooling energy. Then, I will present a large-scale woven smart textile for simultaneously harvesting energy from solar radiation and human body biomechanical motion.  In addition, I will introduce various self-powered/low-power sensors /systems, especially the machine learning assisted fully integrated stretchable sensor arrays for wearable and low-power sign language translation to voice.

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Jessica McIver, PhD,
Senior Postdoctoral Scholar in Physics, Caltech
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, January 23, 2018, 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

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 first detection of gravitational waves from a binary black hole merger by LIGO in 2015 was recently awarded a Nobel Prize, and the 2017 detection of gravitational waves by LIGO and Virgo in concert with an associated electromagnetic counterpart was a breakthrough in multi-messenger astronomy. Future gravitational wave observations will provide exciting new insight into key open questions in astrophysics, including the distribution of stellar remnants in the Universe, the evolution of compact binary systems, galaxy formation, the expansion of the Universe, and the explosion mechanism of core-collapse supernovae.
I will summarize the major outstanding challenges in gravitational wave astrophysics, including extracting transient signals from noisy interferometer data that contains a high rate of transient noise artifacts. I will present transformative new data science and machine learning techniques to address these challenges and enable future multi-messenger discoveries. I will discuss how the rapidly developing field of gravitational wave astrophysics will shape our understanding of the Universe, including the growing global interferometer network, the next generation of terrestrial interferometers, and the Laser Interferometer Space Antenna (LISA).
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Terra Dwayne Colvin, Jr., Masters Candidate,
Public Presentation in Olin Physical Laboratory, Room #107
Friday, November 30, 2018, at 2:30 PM
Fred Salsbury, PhD, Advisor

The defense will follow.

ABSTRACT

Molecular dynamics (MD) simulations permit the probing of biomolecular systems in both high spatial and temporal resolution. Advances in computing power and techniques combined with the proliferation of online bioinformatics resources enable highly detailed in silico experimental analysis of molecular events. Using the GPU-optimized ACEMD software package, we simulate disease-associated mutants of a zinc finger domain in IKK-gamma known to bind with ubiquitin and analyze the results using a variety of statistical and computational methods.

An overview of the essential physics for MD simulations and the biochemistry of proteins is presented followed by a discussion of the critical role that IKK-gamma plays in the regulation of inflammatory response. Finally, a series of computational experiments to assess the impact of point mutations on the conformational ensemble and dynamics of the NEMO zinc finger domain are detailed and compared to known experimental results.

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Professor Divine Kumah,
Department of Physics, North Carolina State University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, November 28, 2018, 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

Complex oxide materials provide a wide range of unique electronic, orbital and magnetic properties which are intimately linked to their atomic scale structure. The ability to form heterostructures comprising of atomic layers of different oxide materials with differing properties has led to the realization of emergent phenomena including multiferroicity, high mobility two dimensional electron gases and superconductivity which are not found in the constituent materials. A key research question relates to understanding the origin of these interface-induced phenomena. Using high-resolution synchrotron diffraction to image the interfacial structures of oxide heterostructures, we show that structural distortions driven by interfacial polar distortions significantly affect their electronic, orbital and magnetic properties.

This talk will focus on rare-earth nickelate and manganite thin films where observed structural distortions affecting the transition metal-oxygen bond lead to metal-insulator and magnetic transitions. Novel approaches will be presented to control atomic distortions and engineer the electronic, orbital and magnetic properties of these systems.

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Lauren Nelson, Masters Candidate,
Public Presentation in ZSR Library, Auditorium
Tuesday, November 20, 2018, at 10:00 AM
Dany Kim-Shapiro, PhD, and Sam Cho, PhD, Advisors

The defense will follow.

ABSTRACT

Neuroglobin (Ngb) is a hexacoordinated heme protein closely related to hemoglobin (Hb) and myoglobin (Mb) and normally found in the brain and nervous systems. To protect the brain tissue from hypoxic or ischemic conditions, Ngb increases O2 availability and acts as an O2 sensor. Ngb is believed to play roles in: sustaining ATP production under anaerobic conditions, detoxifying reactive species (O2 and NO), cellular oxygen homeostasis, and reversible binding of O2 with a higher binding affinity than hemoglobin. Tejero et al. previously showed that a mutant form of Ngb reduces nitrite to nitric oxide 50x faster than myoglobin and 500x faster than hemoglobin. Ngb also tightly binds to carbon monoxide (CO) with an association rate that is 500x faster than hemoglobin. Computational simulations and physical investigations were utilized to analyze the structure and kinetics of neuroglobin and the characteristics causing these phenomena. Molecular dynamics simulations of Mb were used as a control to analyze wild-type oxidized human Ngb and mutants for a total of eighteen 1µs trajectories. Time-resolved absorption spectroscopy and flash photolysis experiments were accomplished with Mb and two Ngb mutants. These studies will help identify treatments for diseases involving low nitric oxide availability and carbon monoxide poisoning.

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Professor Xifan Wu,
Temple University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, November 7, 2018, 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

Proton transfer via hydronium and hydroxide ions in water is ubiquitous. It underlies acid-base chemistry, certain enzyme reactions, and even infection by the flu. Despite two-centuries of investigation, the mechanism underlying why hydronium diffuses faster than hydroxide in water is still not understood. Herein, we employ state of the art Density Functional Theory based molecular dynamics, with corrections for nonlocal van der Waals interactions, and self-interaction in the electronic ground state, to model water and the hydrated water ions.

At this level of theory, structural diffusion of hydronium preserves the previously recognized concerted behavior. However, by contrast, proton transfer via hydroxide is dominated by stepwise events, arising from a stabilized hyper-coordination solvation structure that discourages proton transfer. Specifically, the latter exhibits non-planar geometry, which agrees with neutron scattering results. Asymmetry in the temporal correlation of proton transfer enables hydronium to diffuse faster than hydroxide and may underlie observed isotope anomalies.

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Dr. Peter G. Wolynes, Bullard-Welch Foundation Professor of Science; Professor of Chemistry, MSNE, and Physics and Astronomy at Rice University,
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, October 31, 2018, at 4:00 PM
(Colloquium sponsored jointly with WFU Dept. of Chemistry)

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

DR. WOLYNES WILL ALSO HOLD A CLASS WITH DR. SAM CHO ON TUESDAY, OCTOBER 30, FROM 4-5PM IN OLIN PHYSICAL LABORATORY, ROOM 101, THAT WILL GIVE A CLIFF NOTES VERSION OF THIS TOPIC.

ABSTRACT

Protein folding can be understood as a biased search on a funneled but rugged energy landscape.  This picture of the folding mechanism can be made quantitative using the statistical mechanics of glasses and first order transitions in mesoscopic systems.  The funneled nature of the protein energy landscape is a consequence of natural selection, a connection that can also be made quantitative.

I will discuss recent advances using energy landscape ideas to create algorithms capable of predicting protein tertiary structure from sequence.  I will discuss how energy landscape theory also can be used to study the mechanisms of protein aggregation that underlie neurodegenerative diseases such as Alzheimer’s disease and Huntington’s disease.

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Professor Martin Guthold, Department of Physics, Wake Forest University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, October 17, 2018, 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

Blood coagulation leads to the formation of a blood clot. Blood clots are beneficial in hemostasis as they prevent life-threating blood loss in the event of injury. However, blood clots can also be harmful when they block healthy blood flow (thrombosis); they are the underlying cause of such diseases as heart attacks, stroke and venous thromboembolism, with the first two diseases accounting for 25% of deaths worldwide.

Blood clots perform the mechanical task of stemming the flow of blood. To improve our understanding of blood clots it is, therefore, important to understand their structure and mechanical behavior. The main structural and mechanical component of a blood clot is a mesh of microscopic fibrin fibres.

We have developed an AFM/inverted optical microscope-based technique to study the mechanical behavior of single, microscopic fibers, including fibrin fibres. I will present this technique and the results we have obtained on fibrin fiber mechanical properties, and discuss them in the context of blood clotting, clot lysis, and the properties of other microscopic fibers.

 

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Professor Gordon Brittan, Montana State University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, October 10, 2018, 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 Dreams of a Final Theory, Steven Weinberg writes that “Today’s scientists” should not expect philosophy “to provide [them] with useful guidance about how to go about their work or about what they are likely to find.” Philosophers don’t have much guidance to offer. What they do instead, indeed what Weinberg himself does in his popular books, is to offer aids to understanding. They do this by examining concepts that don’t belong, e.g., to physics, but which come into play when assessing the credibility of scientific claims. Weinberg’s three favorites in this regard are “reality,” “objectivity,” and “truth.” The first and the third are problematic. A case can, however, be made for objectivity on the basis of an Evidential (as against a Bayesian) paradigm of statistical inference.

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