VCU Department of Physics Colloquia: Spring 2020

 

Review of “A non-precious metal hydrogen catalyst in a commercial polymer electrolyte membrane electrolyser”

John Yates

Department of Physics,

Virginia Commonwealth University

Friday, May 1 at 4:00 pm via Zoom: https://vcu.zoom.us/j/92371806383

The future of efficient, cost-effective green energy solutions rely on the ability to find a substitute for platinum group metals in the electrolysis of water. The potential of hydrogen fuel cell use can be fully realized if the capital costs are significantly reduced through the substitution of platinum. The author investigates the ability of transition-metal compounds as substitutes for platinum catalysts in the hydrogen oxidation reaction. Through the scale up to tabletop setups, the author shows the results are promising when compared to the performance offered by platinum.

 

Biography

John Yates is a Ph.D. student in the Nanoscience Program, and is presenting his Literature Seminar

 

Review of “Plasmon-induced selective carbon dioxide conversion on earth-abundant aluminum-cuprous oxide antenna-reactor nanoparticles

Dinesh Bista

Department of Physics,

Virginia Commonwealth University

Friday, April 17 at 4:00 pm via Zoom: https://vcu.zoom.us/j/860717726  

The improvement in the efficiency and the cost of photocatalysis rely in utilizing the visible light spectrum.  Such enhancement can be achieved by combining plasmonic nanoparticle and semiconductor as an antenna-reactor system for the photocatalysis. The cost can be further reduced by using inexpensive and abundant elements rather than using expensive transition metals for the catalysis. In this article, authors have used an inexpensive element “Al” as plasmonic nanoparticle while Cu2O is preferred as the semiconductor. This combination is found to enhance the reaction- rate of reverse water gas shift reaction and showing the excellent result in the product selectivity as well. The authors have successfully explained why the composite system works better to catalyze CO2 conversion reaction providing the possible reaction mechanism.

 

Biography

Dinesh is a Ph.D. student in the Nanoscience Program, and is presenting his Literature Seminar

 

Friday, March 13 2020

There is no Colloquium Today

 

Controllable Functionalization of Biomaterial Surfaces and
Antibacterial Materials

Prof. Shun Duan

College of Materials Science and Engineering
Beijing University of Chemical Technology

Friday, March 6 at 4:00 pm in 701 W. Grace St., Room 2310

Biomedical device-associated infections (BAIs) are threating the health of people. One of the most important prerequisites of BAIs is the attachment and reproduction of bacteria on surfaces of biomedical devices. Therefore, it is essential to develop high-performance antibacterial coatings for medical devices. Based on surface-initiated living polymerization and polymer post-modification technologies, we are working on surface modification of nanoparticles and biomedical devices for antibacterial applications. By controlling the surface properties, we have developed a series of antibacterial surfaces to promote the biological performances of traditional medical devices. Part of our research findings have been applied in various fields, such as medical catheters, antibacterial containers, personal protective equipment and disease treatment of cultural relics.

Biography

Dr. Shun Duan is an associate professor in the College of Materials Science and Engineering of Beijing University of Chemical Technology (BUCT), and is currently a visiting scholar in the Department of Mechanical and Nuclear Engineering at Virginia Commonwealth University (VCU). He received his Ph.D. degree and worked in BUCT since 2013. His research interests are focused on biomedical materials, including surface functionalization of biomedical device, antibacterial materials, 3D printing materials and drug/gene delivery systems. Dr. Duan has authored and co- authored 33 peer-reviewed publications in Advanced Materials, Advanced Functional Materials,
ACS Nano, etc. He has issued and applied 10 patents for industrialization. Dr. Duan’s research projects have been supported by National Science Foundation of China and Ministry of Science and Technology of China.

 

Automatic Analysis Methods for Dynamic Nanomaterial Data

Prof. Alexander “Sasha” Klibanov

Department of Medicine, Cardiovascular Medicine,
Department of Biomedical Engineering, and
Department of Radiology and Medical Imaging
University of Virginia

Friday, February 28 at 4:00 pm in 701 W. Grace St., Room 2310

Gas microbubbles are unique materials that are highly efficient scatterers of ultrasound; they compress and expand in the ultrasound field, so they can be detected by ultrasound medical imaging, with high sensitivity, and high spatial resolution. They can also serve as focal sites for localized energy deposition, for thermal and mechanical therapeutic interventions.

Our tasks are to prepare and stabilize such bubbles, and make them useful beyond simple perfusion imaging as blood pool agents. By using simple tools such as a monolayer phospholipid membrane, we can prepare particles that microbubbles that are fully biocompatible, and have very small material mass (20 million lipid molecules in one bubble imply under a picogram mass - which can be detected by medical ultrasound imaging deep in the body, centimeters away from the imaging probe). This detection sensitivity implies the ability to perform targeted/molecular imaging of the vascular biomarkers of disease, such as in case of inflammation, ischemic injury, or tumor neovasculature. We can attach targeting ligands onto the surface of the microbubble shell (antibodies, peptides, carbohydrates, or small molecules) and achieve selective accumulation of these particles onto the areas with high density of the target biomarker receptor; it is beneficial to have high ligand surface density to achieve effective targeting and retention of microbubbles on the target surface in the presence of fast flow. Conversely, in the presence of slow-flow conditions (such as irregular tortuous tumor vasculature) rather low surface density of targeting ligand is sufficient to achieve selective retention of ultrasound contrast material in the tumor vasculature, and tumor mass delineation.

For the ultrasound-triggered therapeutic interventions, the easiest is to get the bubbles in the bloodstream, and vibrate them by (focused) ultrasound: as they compress and expand in the vascular bed of interest, they can open up endothelial lining barrier, for instance blood-brain barrier, so the drugs and drug carriers (liposomes etc) can penetrate. The barrier will stay open for up to several hours. For micro- and nanoparticle constructs, ultrasound triggering and drug delivery is also feasible: drugs (including nucleic acids) can be attached to the bubble shell. and upon insonation they can be deposited in the insonated area of the body. Also, drug can be sequestered in the carrier, and triggered release by ultrasound can be achieved, for instance, from drug-liposome-microbubble complexes, and RBCs that carry perfluorocarbon nanodroplents.

Biography

Alexander “Sasha” Klibanov is an Associate Professor in the Department of Medicine, Cardiovascular Medicine, and also a faculty member in Biomedical Engineering and Radiology and Medical Imaging. He was born and raised and educated (all the way past Ph.D.) in Moscow, then USSR, what is now Russia. In 1991, he moved to USA and worked in academic research (University of Tennessee and University of Pittsburgh) and industrial positions (Mallinckrodt Inc). Research interests are in the area of chemistry applications in biomedical research. He has been a faculty member of the University of Virginia from 2001.

 

Heterogeneous Integration: From materials and devices to systems toward AIoT applications

Prof. Kyusang Lee

Department of Electrical and Computer Engineering
Department of Materials Science and Engineering
University of Virginia

Friday, February 21 at 4:00 pm in 701 W. Grace St., Room 2310

Heterostructures composed of dissimilar materials have generated great interest because of the unique functionalities that cannot be offered by homogeneous structures owing to their unique properties. Interfacing mixed-dimensional materials, with band alignment strongly influenced by the unique nature of each material system, enables drastic changes in the electrical, magnetic, optical, and thermal properties beyond its individual counterpart. Thus, appropriate selection of dissimilar materials can allow significant modification of their physical structures resulting in intriguing properties and unprecedented device architectures. Here, I will introduce unique techniques to produce single crystalline thin-film semiconductors via epitaxy and exfoliation from graphene-coated crystalline substrates, termed remote epitaxy and 2-dimensional layer based transfer process. This technology enables heterogeneous integration of various materials on a single platform. Furthermore, I will present promising applications of hetero-integration for light detection and ranging by integrating GaN-based HEMT and GaAs VCSEL. Furthermore, integration of sensors with AI hardware platform for edge computing applications will be discussed.


Biography
Kyusang Lee is currently an Assistant Professor of Electrical and Computer Engineering and Materials Science and Engineering departments at University of Virginia. He received his B.S. degree from Korea University in 2005, M.S. degree from Johns Hopkins University in 2009, and Ph.D. degree from University of Michigan in 2014, all in Electrical Engineering. He was a postdoctoral fellow in the Department of Electrical Engineering and Computer Science at the University of Michigan, and a postdoctoral associate in the Department of Mechanical Engineering at Massachusetts Institute of Technology (MIT). His research interests highlight the use of thin-film compound semiconductors in optoelectronic devices, with a particular emphasis on applications for imaging and artificial intelligence. He is the recipient of the NSF faculty early career award, best student presentation award at the IEEE 38th Photovoltaic Specialist Conference and the UMEI postdoctoral fellowship. His works have been published in Nature, Science, Nature materials, Nature Nanotechnology, Nature electronics, Science Advances, PNAS and Nature communications etc.

 

Automatic Analysis Methods for Dynamic Nanomaterial Data

Prof. Yanjun Qian

Department of Statistical Sciences and Operations Research,
Virginia Commonwealth University

Friday, February 14 at 4:00 pm in 701 W. Grace St., Room 2310

In situ transmission electron microscope (TEM) adds a promising instrument to the exploration of the nanoscale world, allowing
motion pictures to be taken while nano objects are initiating, crystallizing and morphing in the nano-manufacturing. It is
essential to develop reliable and efficient data analysis for the captured image/video in order to make the in-process control feasible for the nanomaterial production process. My research entails a robust processing of snapshot TEM images and both offline/online analyses for in situ TEM videos, leading to identification of underlying nanocrystal’s growth mechanism and tracking the growth trajectory in real time. The fundamental statistical learning challenge to be addressed is how best to do nonparametric modeling of a time-varying probability density distribution that reflects the evolution of the nanocrystal growth process. I will also discuss my other works for nanomaterial images.

Biography

Yanjun Qian is an Assistant Professor in the Department of Statistical Sciences and Operations Research at Virginia Commonwealth University. Yanjun received his Ph.D. (2018) in Industrial Engineering from Texas A&M University, M.S. (2012) and B.S. (2009) in Automation from Tsinghua University, China. His research interests include data and quality science, statistical learning, and optimization with industrial and medical applications. His current research is to develop analysis methods for handling high-dimensional and dynamic data captured by electron microscopes in nanomanufacturing. Yanjun is a member of IISE, INFORMS, and SIAM. For more
information please visit https://sites.google.com/view/yjqian.

 

Patterning and Self-Assembly of Nanoparticles through Additive Printing Processes

Prof. Hong Zhao

Research Fellow
Department of Mechanical and Nuclear Engineering,
National Institutes of Health

Friday, February 7 at 4:00 pm in 701 W. Grace St., Room 2310

Printing, as a scalable manufacturing platform, has attracted growing attention in many areas, e.g. printed electronics, energy storage,
bioprinting, and additive manufacturing. The challenges lie in the material interactions during printing process, assembly of the functional materials to form patterns, and high resolution of critical features. In this talk, I will present our recent research work on the self-assembly of colloidal nanoparticles in a dual-droplet inkjet printing process to produce a nearly monolayer, closely-packed deposition of nanoparticles that exhibits a colorful reflection. The well-ordered deposition is achieved by tuning the solvent composition of the wetting droplets and functionalization of the nanoparticles to encourage a network formation among the colloidal particles at the air-droplet interface. pH manipulation of the supporting droplet also affects the multibody interactions among the nanoparticles in addition to particle-interface and particle-substrate interactions, leading to a spectrum of deposition morphology ranging from ring-like patterns to uniform monolayer depositions. This study suggests a new printing strategy to pattern and control the colloidal particle deposition with ordered monolayer structures. In addition, I will briefly introduce our research work on fabrication of functional devices using various printing processes, e.g. mask-assisted electrospraying process, extrusion-based printing process, etc.


Biography
Dr. Hong Zhao is currently an assistant professor in the Department of Mechanical and Nuclear Engineering at Virginia Commonwealth University (VCU). She received her Ph.D. in Mechanical and Aerospace Engineering from Rutgers University. Before joining VCU in 2014, she has worked at Xerox Research Center Webster for about 8 years. Zhao’s research areas are highly interdisciplinary, including surface science and surface engineering, transport and self-assembly of colloidal nanoparticles, development of printing processes (e.g., inkjet printing, electrohydrodynamic printing, direct extrusion printing, etc.), and printed functional devices. Dr. Zhao has authored and co-authored 33 journal and proceeding publications, 34 issued patents and patent applications, 1 book and 1 book chapter. Dr. Zhao’s research projects have been supported by National Science Foundation, Jeffress Memorial Trust, Higher Education Equipment Trust Fund, Virginia Microelectronics Consortium, and VCU Presidential Research Quest Fund.

 

Signal-enhanced Time-resolved Solid-state NMR Spectroscopy for Monitoring Biomolecules in Action

Dr. Jaekyun Jeon

Research Fellow
National Institute of Diabetes and Digestive and Kidney Diseases,
National Institutes of Health

Friday, January 31 at 4:00 pm in 701 W. Grace St., Room 2310

Proteins undergo structural transitions and dynamically interact with one another to play important physiological roles in living organisms. Understanding how these molecular machines work in detail is key to promote our understanding of biology at molecular levels. However, the complexity of their structures and rapid molecular motions make the experimental investigation with proper spatial and temporal resolutions very challenging. In this recent decade, Cryogenic Electron Microscopy (CryoEM) and single molecular techniques made breakthroughs in the achievement of spatial and temporal resolutions, respectively. But approaches that can simultaneously achieve both resolutions are still lacking. In this seminar, I will introduce a novel time-resolved solid-state NMR (ssNMR) technique that can characterize the conformational transition of such biomolecules in action. Freeze-quenching the molecular action in the millisecond time scale was enabled by developing a rapid mixer/freezer device, and distributions of intermediate ensembles were detected by a signal-enhancement technique via cross-relaxation between electron and nuclear spins, Dynamic Nuclear Polarization (DNP). As the proof of concept, folding and self-assembly processes of a short bee venom peptide, melittin, were investigated [1]. The conformational transition of melittin upon a rapid pH jump (pH 3 to pH 7), from an unstructured monomeric state at pH 3 to a helical tetrameric state at pH 7, was monitored at 2.2, 4.6, 9 and 30 millisecond time points. A series of 2D ssNMR spectra at those time points revealed that helix formation and antiparallel dimer formation occur on the same timescale (6-9 ms) and evidenced the presence of an intermediate state. In addition, I will present that the rapid freezer device can be implemented to other magnetic resonance techniques ─ i.e., Double Electron-Electron Resonance Electron Paramagnetic Resonance (DEER EPR) spectroscopy. Our rapid freeze quenching method has enabled the glycerol-free sample preparation for the DEER EPR spectroscopy, which benefits in sampling native conformational states of biomolecules.


[1] J. Jeon, K.R. Thurber, R. Ghirlando, W-.M. Yau, R. Tycko, Proceedings of the National Academy of
Sciences, 116 (34), 16717-16722 (2019)

Biography : Dr. Jeon is a research fellow in the Laboratory of Chemical Physics (LCP), National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda,
Maryland. He earned his academic degrees in Physics: B.S. and M.S. from Hanyang University, Seoul, South
Korea and Ph.D. from University of Central Florida. His Ph.D. work focused on the structural modeling on
the self-assembly of Rous Sarcoma Virus capsid protein by using solid-state NMR, CryoEM and molecular
dynamic simulations.

 

Transcranial Magnetic Stimulation to Improve Upper Limb Function after Spinal Cord Injury 

Prof. Carrie Peterson

Department of Biomedical Engineering 

Virginia Commonwealth University

Friday, January 24 at 4:00 pm in 701 W. Grace St., Room 2310

The Rehabilitation Engineering to Advance Ability Lab (REALab) develops and evaluates interventions to improve sensorimotor function for individuals with neurologic deficits. Our expertise is in neuromodulation, and modeling and simulation of human movement. Currently, we focus on improving upper limb function for individuals with tetraplegia after spinal cord injury (SCI). In this talk, I will describe two of our ongoing projects involving transcranial magnetic stimulation: (1) measuring cortical voluntary activation in individuals with SCI and (2) evaluation of the effects of a repetitive, non-invasive brain stimulation protocol called intermittent theta burst stimulation, on the excitability of corticomotor pathways projecting to the biceps. Cortical voluntary activation can indicate deficits in cortical drive to muscle, including the effects of fatigue, although it is difficult to assess in individuals with SCI. We take a new approach to measure cortical voluntary activation based on identifying optimal experimental conditions to evoke a large motor evoked potential in the target muscle relative to its antagonist. In the long term, cortical voluntary activation may guide neuromodulation therapies. Intermittent theta burst stimulation (iTBS) is a neuromodulation therapy we currently assess due to its potential to increase corticomotor excitability. iTBS paired with physical training may improve outcomes of upper limb rehabilitation in individuals with SCI.

Biography
Carrie L Peterson is an Assistant Professor in the Department of Biomedical Engineering at Virginia Commonwealth University. She earned her academic degrees in mechanical engineering: B.S.E. from the University of Michigan, and M.S.E. and Ph.D. from The University of Texas at Austin. Her graduate work focused on post-stroke walking biomechanics and rehabilitation. During her postdoctoral training at Northwestern University, her work focused on neural adaptation. 

Friday, January 17 2020

There is no Colloquium Today

 

VCU Department of Physics Colloquia: Fall 2019

DNA for Data Storage: A Literature Review

Graeme Murray 

Virginia Commonwealth University

Friday, December 6 at 4:00 pm in 701 W. Grace St., Room 2310

Digital data production is exponential increasing and outpacing the growth of mainstream storage devices such as hard disks. This demand has led to major investments in data centers on the order of billions of dollars in the Richmond area alone. As production of data is only set to increase there is demand for better storage devices. DNA has some promising properties when it comes for digital data storage owing to its extreme density, evolutionarily optimized replication machinery, and high durability. While synthesis and sequencing are still expensive, improvements have exceeded Moore’s law and continued demand for decreased costs is driven by the medical industry. In this talk, I will discuss topics from basic principles of DNA replication to the latest techniques for storing data in DNA which utilize techniques developed for mobile broadcasting to optimize storage density.   

3D Printed Neural Regeneration Devices

Prof. Daeha Joung

Department of Physics 

Virginia Commonwealth University

Friday, November 22 at 4:00 pm in 701 W. Grace St., Room 2310

Biological structures ranging in size from molecules to organelles, cells, organs, tissues, and the human body are exquisitely structured in three-dimensions (3D). In order to mimic, sense, or to interface functional devices with biological ones, there is a need to create 3D, artificially structured materials or 3D, heterogeneously integrated, functional devices (from nano- to macro- scales). Existing conventional fabrication/assembly technologies have facilitated the representation of 2D networks of interface-active devices or platforms with biology, but the technology is impeded in its application to complex 3D geometries that require hierarchical precision and multi-material heterogeneity. The solutions generally require fundamental, conceptual advances in materials science and engineering. Our approach is to use 3D printing, which is an additive manufacturing technology that permits the manufacturing of complex multi-(bio)material, multi-scale, and/or multi-functional 3D devices. In this talk, we will discuss the application of 3D printing to neural regeneration devices and how this approach benefits nervous system tissue engineering.

References:
[1] D. Joung et al., “3D Printed Neural Regeneration Devices.” Adv. Funct. Mater. 29, 1906237 (2019).
[2] D. Joung et al., “3D Printed Stem-Cell Derived Neural Progenitors Generate Spinal Cord Scaffolds.”
Adv. Funct. Mater. 28, 1801850 (2018).

No Physics Colloquium for Friday Nov. 15.

 

 

Molecular Magnets for Spectroscopic Sensing of Chemical Reactions and Qubits

Prof. Mark R. Pederson,

Department of Physics 

University of Texas – El Paso

Friday, November 8 at 4:00 pm in 701 W. Grace St., Room 2310

 Early experimental investigations on spin-carrying metal centers, initially aimed at understanding how nature converts water to hydrogen and fixes nitrogen, formed the basis for the field of molecular magnetism 25 years ago. Shortly thereafter such molecules were postulated to be potentially realistic physical manifestations of spin-based qubits for quantum computers [1]. In this talk I will discuss computational and theoretical challenges associated with the accurate quantum-mechanical computational description of these systems and discuss two recent computer experiments that respectively: (A) show how a low-energy quantum-sensing technique can be used to deduce the chemical splitting of water into hydroxyl and hydrogen molecules [2] and (B) demonstrate how computational density-functional-based methods can be used to accurately determine the properties and complexities of putative molecular magnetic qubits that are composed of a perfect triangle of half-integer spin metal ions[3,4]. Connections to recent experimental publications will be made.

   The Mn 12 O 12 (COOR) 16 (HOH) 4 molecule, with S 4 symmetry, has four of everything. Our recent calculations find that this system readily accepts four excess electrons at the cost of only 0.32 eV in vacuum. This molecule exhibits a macro-spin with S=10. It has received significant past interest due to the experimental  observations and theoretically confirmed process of quantum tunneling of magnetization (QTM). Here, we show that the spectroscopic signatures associates with QTM are extremely sensitive to the presence of the four HOH terminators (e.g. 4 waters vs. 2H 2 and 2OH) and to the number of added electrons (0 vs. 4). Our calculations suggest that QTM can be used as an ultra-low-energy non-destructive observation of water decomposition in a molecule with a core Mn 4 O 4 unit that bears a striking similarity to the reaction center in the oxygen evolving complex. See Ref. 1.   Recently, Boudalis et al have experimentally observed the magneto-electric effect in a chiral Fe 3 O(NC 5 H 5 ) 3 (O 2 CC 6 H 5 ) 6 molecule [5] and have noted further that this is the first possible spin-electric system based upon spin 5/2 metal centers. Our results [3], using standard density-functional methods, show that the spin-electric behavior of this molecule could be even more interesting as there are energetically competitive reference states with high and low local spins (S=5/2 vs. S=1/2) on the Fe 3+ ions. We provide predictions of magnetic and x-ray spectroscopies to deduce the presence of both states. Possible uses for low-temperature quantum sensing of fields and pressure variations are suggested. Recent efforts at improving standard approximations of density-functional theory using a new version of self-interaction-corrected DFT will be discussed within the context of this work [2,6].

[1] B. Georgeot and F. Mila, Chirality of triangular antiferromagnetic clusters as a qubit, Phys. Rev. Lett. 104, 200502 (2010).

[2] J. Batool, T. Hahn and M.R. Pederson, Magnetic Signatures of Hydroxyl and Water Terminated
Neutral and Tetra-anionic Mn 12 -Acetate, J. Comput. Chem. 25, 2301-2308 (2019).

[3]M. F. Islam, J. F. Nossa, C. M. Canali and M. Pederson, First-principles study of spin-electric coupling
in a Cu 3 single molecular magnet, Phys. Rev. B 82 155446 (2010).

[4]A. I. Johnson, M. F. Islam, C. M. Canali and M. R. Pederson, A Multiferroic molecular magnetic qubit,
Submitted to J. Chem. Phys. (https://arxiv.org/abs/1909.08803).

[5]A. K. Boudalis, J. Robert & P. Turek, 1 st demonstration of magnetoelectric coupling in a polynuclear
molecular nanomagnet via EPR studies Fe 3 O(O 2 CPh) 6 (Py) 3 ClO 4 , Chem. Eur. J 24 14896-14900 (2018).

[6] M.R. Pederson, A Ruzsinszky and J. P. Perdew, Communication: Self-Interaction Correction with
Unitary Invariance in Density Functional Theory, J. of Chem. Phys., 140, 121103 (2014).

 

Computational research of materials for nanoscale semiconductors and Li-ion battery applications

Prof. Xihong Peng

Department of Physics 

Arizona State University

Friday, November 1 at 4:00 pm in 701 W. Grace St., Room 2310

 First-principles electronic structure calculations are applicable to solve problems across multi-fields and play an essential role in modern scientific research. In this talk, I will outline the computational work in our group in two areas, nanoscale semiconductors and new materials as anode in Li-ion batteries. Semiconductor nanostructures have attracted extensive research efforts in the past decades due to potential applications in nanotechnology. We have studied how size,
surface/edge passivation and mechanical strain affect the properties of nano-semiconductors and obtained a picture on the interplay of size, passivation and strain on their electronic properties. Li-ion batteries are widely used as power devices and current typical anode is graphite. Other group IV elements such as Si has been considered as an alternative anode due to its higher energy capacity. However, bulk Si undergoes large volume change during lithiation. New materials such as clathrates - open framework structures attract research interests. We studied the clathrates as potential anode in Li-ion batteries via close collaborations with experimentalists.

 

 

Comparison of the structure function F2 as measured by charged
lepton and neutrino scattering from iron targets

Prof. Narbe Kalantarians

Jefferson Laboratory and Virginia Union University

Friday, October 25 at 4:00 pm in 701 W. Grace St., Room 2310

 The F2 structure function characterizes the quark composition of nucleons and nuclei. This information is obtained by deeply inelastic scattering. In this analysis, world data for the structure function F2 for Iron from charged lepton and neutrino scattering experiments are compared. The observations cleanly underscore previously observed hints of a difference in the behavior of the data between charged lepton and neutrino scattering, notably in the anti-shadowing region where the Bjorken scaling variable x is below 0.15. The charged lepton data appear to undergo shadowing/anti-shadowing whereas the neutrino data seem to exhibit no nuclear effects. Moreover, we find very good agreement between the different types of probes in the x region above 0.15. Details and results of the data comparison will be shown in this talk.

 

Gene Clustering Drives Transcriptional Coherence of Disparate biological Pathways

Prof. Richard Joh

Department of Physics 

Virginia Commonwealth University

Friday, October 11 at 4:00 pm in 701 W. Grace St., Room 2310

 The establishment of distinct transcriptional states in response to developmental or environmental cues is critical for survival. This involves the concordant or discordant transcriptional regulation of several distinct biological pathways, often involving thousands of genes, which together enhance survival. How these system-level changes to transcriptomes are coordinated is an understudied problem in eukaryotic biology. Here, using computational approaches in eukaryotes ranging from yeast to human, we report that this transcriptional coordination is in part achieved by the genic proximity of the regulatory nodes of disparate biological pathways whose co-regulation drives the transcriptional coherence of their respective pathways. Overall, our data identify conserved and species-specific transcriptional co-regulation of hundreds of different biological pathway pairs and suggest that genomic clustering of regulatory nodes such as transcription factors coordinate the expression of thousands of genes, creating tunable regulons in eukaryotes. 

 

 

The Past, Present, and Future of Quantum Chemistry

Prof. Ka Un Lao

Department of Chemistry

Virginia Commonwealth University

Friday, October 4 at 4:00 pm in 701 W. Grace St., Room 2310

 The Lao group is a computational/theoretical group that focuses on developing and applying new electronic structure models and algorithms based on quantum mechanics, combining concepts and techniques from chemistry, physics, mathematics, and computer science, to study molecules, clusters, and condensed phase systems, ranging from chemistry to biochemistry and materials science. 

One particular area of emphasis is the accurate and efficient calculation of intermolecular interactions, which is a challenging problem for electronic structure theory. Our research goal is to develop fast and accurate approaches for gaining a
fundamental understanding of the factors governing the drug binding and molecular materials packing in order to provide a basis for the development of new drug binding molecules and functionalized molecular materials. 

 Furthermore, adapting the methodology we are going to develop to the rapid evolution of machine-learning techniques offers a unique opportunity to generate new noncovalent molecular electronics and drug molecules through large-scale computational screening and design since the combination of different strategies to functionalize molecules is seemingly infinite.

 

 

 Perspectives on processing magnetocaloric transition-metal borides for solid state cooling applications

Prof. Radhika Barua 

College of Engineering,

Virginia Commonwealth University

Friday, September 27 at 4:00 pm in 701 W. Grace St., Room 2310

 

In the United States, residential and commercial buildings currently account for 72% of the nation's electricity use and 40% of carbon dioxide (CO2) emissions annually, 15% of which originates from air conditioning and refrigeration systems. Novel cooling technologies are required to minimize global energy consumption and environmental impact. To this end, solid state magnetic cooling devices enabled with the “magnetocaloric” class of functional materials are attractive as they allow complete elimination of conventional high-global warming potential (GWP) refrigerants and have the potential for efficiency improvements of up to 25% over conventional vapor compression systems, which is equivalent to 60% of Carnot efficiency

 Within this context, this talk will address the major principles guiding the development of magnetocaloric transition-metal borides for active magnetic regenerator (AMR) magnetic cooling devices.  Specific attention will be given to current research efforts for processing AlFe2B2 – a rare-earth-free intermetallic alloy that exhibits an appreciable magnetocaloric response corresponding to an adiabatic temperature change of 2.2 K and magnetic entropy change of 4.4 J/kgK at an applied magnetic field of 2 T. Computational and experimental results will be presented to demonstrate that spin-orbit coupling in the layered orthorhombic AlFe2B2 crystal structure results in an anisotropic magnetocrystalline energy, thus producing an associated anisotropic magnetofunctional response. Further, the influence of compositional variation on the magnetic properties of AlFe2B2 will be discussed.



 

Prof. John Hackett

Department of Physiology and Biophysics and

The Massey Cancer Center

Virginia Commonwealth University

Friday, September 20 at 4:00 pm in 701 W. Grace St., Room 2310

  Cytochrome P450 19A1 (CYP19A1, aromatase) required for the synthesis of estrogens from androgens, is among the key targets for treatment of estrogen-dependent cancers. It is representative of other steroidogenic CYPs (i.e. 11A1 ,11B2, 17A1, 51) insofar as it also catalyzes a sequential oxidation and shares structural features at the putative substrate recognition interface. It is one of the few enzymes known to construct an aromatic ring with a controversial mechanism. How steroidogenic CYPs, including CYP19A1, recognize, and in some cases discriminate between very similar substrates remain salient unanswered questions in the field. Little effort has been made to elucidate substrate recognition and discrimination mechanisms of the highly-selective endobiotic-metabolizing CYPs. This colloquium will provide an update on the current state of knowledge of the CYP19A1 catalytic mechanism and summarize our recent efforts to integrate experimental and computational approaches to glean novel insight into the functional dynamics of CYP19A1 in a native-like membrane.

 

Pool and Flow Boiling Heat Transfer in Variable Gravity Environments

Dr Jungho Kim

Department of Mechanical Engineering

University of Maryland

Friday, September 13 at 4:00 pm in 701 W. Grace St., Room 2310

Knowledge of how gravity affects two-phase heat transfer is critical to the design of equipment (e.g., heat exchangers and nuclear reactors) that will be operated in variable gravity environments (high-g, low-g, lunar, and Martian-g). Relatively little is known about boiling mechanisms in these environments since data from long duration microgravity environments are limited due to high cost and limited flight opportunities. Although a few studies have been performed under high quality microgravity environments on board orbital platforms, most low gravity boiling research has been obtained using drop towers, aircraft, and sounding rockets. The relatively large g-jitter and/or the short periods of microgravity duration of these studies has resulted in confusion about the heat transfer mechanisms. The results of a recent International Space Station experiment the clarifies gravity effects on pool boiling mechanisms will be presented along with a model that can be used to scale boiling data. Recent investigations into flow boiling using temperature sensitive paints will also be discussed.

 

The September 6 Colloquia Has been Cancelled!

From Fundamental Nuclear Physics to Cancer Instrumentation: Science at Jefferson Lab

Dr. Cynthia Keppel,

Hall Leader

Jefferson Lab

Friday, September 6 at 4:00 pm in 701 W. Grace St., Room 2310

The Thomas Jefferson National Accelerator Facility (Jefferson Lab) underwent a major upgrade, doubling the beam energy to 12 GeV and substantially upgrading the associated experimental equipment. Experiments leveraging this upgrade have been underway for almost two years now, with many new results recently becoming available. An overview of the laboratory and some first data will be presented. In addition, focus will be given to applications of detector technology from the fundamental nuclear physics program to medical instrumentation.  

 

 

Meeting the Faculty

Friday, August 30 at 4:00 pm in 701 W. Grace St., Room 2310