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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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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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Zijie Yan, PhD,
Chemical & Biomolecular Engineering, Clarkson University
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, February 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

The ability to reconfigure nanoscale building blocks into different architectures, as if they were Lego pieces, has enormous potential for nanoscience. The development of colloidal synthesis has largely increased the availability of nanocrystals with well-controlled sizes and shapes. Bottom-up assembly of these nanoscale building blocks opens the prospect of creating novel artificial materials and systems with unusual properties and functionalities. However, it is still a great challenge to achieve precise, controlled, and reconfigurable assembly of nanomaterials. This seminar will introduce an optical approach to address this fundamental challenge in nanoscience. My research group exploits light-driven self-organization to create artificial nanomaterials. Shaped optical fields are created by modulating the intensity, phase, and polarization of laser beams in space and time. Self-organization arises from electrodynamic interactions among strongly scattering plasmonic nanoparticles, leading to a new type of material: reconfigurable optical matter with nanoparticle superlattices. New science has emerged in these artificial materials, for example, negative optical torque in optical matter arrays, and the developed optical methods will lead to more research opportunities and applications in microfluidics, microrheology, optical physics, and cell biology.

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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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Dr. Ajay Ram Srimath Kandada,
Marie Sklodowska Curie Fellow (Global)
Georgia Institute of Technology,
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, January 16, 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

Excitonic interactions in 2D semiconductors garner considerable attention, both due to their relevance in quantum opto-electronics and to the richness of their physics. Quantum-well like derivatives of organic-inorganic perovskites are emerging material systems where strongly bound two-dimensional excitons have been observed even at room temperature.1 These hybrid semiconductors feature complex lattice dynamics due to the ‘softness’ arising from non-covalent bonds between molecular moieties and the inorganic network and due to the ionic character of the crystal.2 I will discuss the profound and unique consequences of such dynamic structural complexity on the fundamental character of primary photo-excitations. I will present evidences of polaronic effects3 and multi-body correlations,2 both of which are strongly affected by the lattice dynamics, based on various ultrafast optical spectroscopies. Going beyond the conventional ultrafast optical tools, I will also discuss a new proposal to use entangled photon-pairs as probe of correlations in matter.

 

(1)       Neutzner, S.; Thouin, F.; Cortecchia, D.; Petrozza, A.; Silva, C.; Kandada, A. R. S. Exciton-Polaron Spectral Structures in Two Dimensional Hybrid Lead-Halide Perovskites. Phys. Rev. Mater. 2018, 2, 064605.

(2)       Thouin, F.; Neutzner, S.; Cortecchia, D.; Dragomir, V. A.; Soci, C.; Salim, T.; Lam, Y. M.; Leonelli, R.; Petrozza, A.; Kandada, A. R. S.; et al. Stable Biexcitons in Two-Dimensional Metal-Halide Perovskites with Strong Dynamic Lattice Disorder. Phys. Rev. Mater. 2018, 2, 034001.

(3)       Thouin, F.; Chávez, D. A. V.; Quarti, C.; Cortecchia, D.; Bargigia, I.; Beljonne, D.; Petrozza, A.; Silva, C.; Kandada, A. R. S. Phonon Coherences Reveal the Polaronic Character of Excitons in Two-Dimensional Lead-Halide Perovskites. Nat. Mater. 2018, in press.

 

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Dr. Ilaria Bargigia,
Georgia Institute of Technology
George P. Williams, Jr. Lecture Hall, (Olin 101)
Thursday, January 17, 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

Conjugated polymers are widely used as bio-electronic interfaces thanks to their inherent softness, biocompatibility, electronic properties, and unparalleled versatility. In particular, thin films of poly(3-exylthiophene) have demonstrated the capability to restore light sensitivity in animal models and are now being proposed as artificial retinal implants. However, there is no clear understanding of the mechanism behind light-induced activation of cellular activity mediated by the photophysical characteristics of the conjugated polymers. In particular, there is a need to address how structural properties control the various functionalities and the role played by the interface between the polymer and biological media. In this talk, I will present our recent efforts made towards the understanding of how photo-physical properties transform in the presence of relevant biological media and what these transformations entail in the context of in-vivo biological applications.

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Dr. K. Maria Mills,
Laboratory of Molecular Biophysics, NIH
George P. Williams, Jr. Lecture Hall, (Olin 101)
Wednesday, December 5, 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

Type IA topoisomerases cleave single-stranded DNA and relieve topological strain by passing an intact DNA strand through the broken strand. Although it is assumed that these enzymes accomplish this strand passage via a protein-mediated DNA gate, opening of this gate has never been observed. We developed a single-molecule magnetic tweezers assay to directly measure gate opening of the E. coli type IA topoisomerases, topo I and topo III. Following cleavage of single-stranded DNA, the protein gate opens by as much as 6.6 nm and can close against forces in excess of 16 pN. The force-dependent kinetics reveal that the gate dynamics of these enzymes are remarkably fast. Key differences in the cleavage, ligation, and gate dynamics of these two enzymes provide insights into their different cellular functions. The single-molecule results are broadly consistent with conformational changes associated with gate-opening obtained from molecular dynamics simulations. These results allow us to develop a complete mechanistic model of type IA topoisomerase-ssDNA interactions.