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Click here for:Date: | Thursday |
Time: | 1:30-3:00 PM |
Place: | 106 B Studio Room, Classroom Building, OSU |
& Nielsen Hall, Room 103, OU | |
Inquiries: | kaladi.babu@okstate.edu or kao@nhn.ou.edu |
Date: | Thursday |
Time: | 3:30-4:30 PM |
Place: | PS 110 |
Inquiries: | s.nandi@okstate.edu or perk@okstate.edu |
Date: | Friday (bi)weekly |
Time: | 2:00 PM |
Place: | PS 147 |
Inquiries: | perk@okstate.edu or girish.agarwal@okstate.edu |
No talks scheduled
No talks scheduled: Prelim Exams
No talks scheduled: First Week of Classes
Martin Luther King Day, Monday, January 20, 2014
Second Week of Classes
Speaker: | Dr. Pierre Darancet |
Applied Physics & Applied Mathematics Department | |
Fu Foundation School of Engineering & Applied Science | |
Columbia University, New York, NY | |
Date: | Thursday, January 23, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Understanding Non-Equilibrium Charge Transport and Rectification at Nanoscale Interfaces |
Understanding and controlling non-equilibrium charge transport across nanoscale interfaces and in supramolecular assemblies is central to developing an intuitive picture of fundamental processes in nanoelectronics, photovoltaics, and other energy conversion applications. In this talk, I will discuss our theoretical studies of finite-bias transport at prototypical organic/metal interfaces, single-molecule junctions, small organic molecules trapped between gold electrodes. I will show how many-body effects influence energy level alignment in these systems, and that a simple model of non-local correlations on the top of density functional theory leads to quantitative agreement with experiments [1-6]. Finally, I will discuss the implications of this theory in the context of transport in molecular diodes [7]; in particular, how to systematically optimize rectification by tuning the competing energy scales in single-molecule junctions via molecular conformation [8].
References: [1] J.B. Neaton et al. Phys. Rev. Lett. 97, 216405 (2006); [2] I. Tamblyn,, et al. Phys. Rev. B, 84, 201402(R) (2011); [3] J. Widawsky, et al. NanoLett. 12, 354 (2012); [4] P. Darancet, et al. NanoLett 12, 6250 (2012); [5] T. Kim, et al. submitted (2013); [6] B. Capozzi, et al. submitted (2013); [7] A. Aviram and M. A. Ratner, Chem. Phys. Lett. 29, 277 (1974); [8] A. Batra, et al. NanoLett. 13, 6233 (2013).
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Mario F. Borunda |
Department of Physics | |
Oklahoma State University | |
Date: | Friday, January 31, 2014 |
Time: | 12:30 PM |
Place: | PS 147 |
Title: | Introduction to Graphene and Dirac Fermions |
Join us for an informal talk discussing graphene. I will show how a plane layer of C atoms bonded together in a honeycomb lattice has become the most interesting two-dimensional system available. After an overview of its physical properties, I will use the last part of the talk to concentrate on the outstanding transport properties of graphene (some of which can be attributed to charges behaving as massless Dirac fermions). The purpose of this presentation is to introduce undergraduate and graduate students to this fascinating research subject but experts are also invited.
This week's colloquium is postponed till next week because of the weather situation.
Speaker: | Prof. Jihn E. Kim |
Department of Physics | |
Seoul National University, Seoul, South Korea | |
Date: | Thursday, February 13, 2014 |
Time: | 1:30 PM |
Place: | 106 B Studio Room, Classroom Building, OSU |
& Nielsen Hall, Room 103, OU | |
Title: | Dark Energy from Approximate U(1)de and U(1)PQ |
Speaker: | Dr. Howard A. Baer |
Homer L. Dodge Professor of High Energy Physics | |
Homer L. Dodge Department of Physics & Astronomy | |
University of Oklahoma | |
Date: | Thursday, February 13, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Supersymmetry and Dark Matter in the Post Higgs Discovery Era |
The recent discovery of the Higgs boson at the CERN Large Hadron Collider seemingly completes the discovery of all matter states predicted by the Standard Model of particle physics. But from the theory side, it is hard to understand how the Higgs can be so light without a protective symmetry known as supersymmetry. Yet, also, no superparticles have been discovered. The Higgs mass itself provides deep clues as to where the superparticles are lurking. Current theory and experiment also point to dark matter as being comprised of an axion-higgsino mixture (two dark matter particles) and thus we might expect ultimately detection of both an axion and a weakly-interacting massive particle, or WIMP!
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
For details see researchweek.okstate.edu.
Cancelled and replaced by faculty meeting.
APS March Meeting
No talks scheduled this week.
Spring Break
Speaker: | Dr. Xin Chen |
Department of Radiation Oncology | |
School of Medicine | |
Stanford University | |
Date: | Wednesday, March 26, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Monte-Carlo Based Verification of Dose Distribution and Monitor Units for Volumetric-Modulated Arc Therapy (VMAT) |
Patient-specific verification for volumetric-modulated arc therapy (VMAT) is incapable of providing full 3D dosimetric information and is labor intensive in the case of severe heterogeneities or small-aperture beams. In this work, a cloud-based Monte Carlo (MC) dose calculation method is developed to perform the evaluation in entire 3D space and reveals the source of discrepancies between measured and planned dose. Another outstanding problem in VMAT is how to independently validate the monitor units (MUs) of the treatment plan for a patient generated by the treatment planning system (TPS). A novel MC-based framework for independent MU verification of VMAT is established. As an example of the applications, the dosimetric impact of real-time prostate motion during VMAT is assessed using this Monte Carlo dose calculation method by incorporating the interplay effect between aperture modulation and target motion.
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Seodong Shin |
Department of Physics | |
Indiana University, Bloomington, IN | |
Date: | Thursday, March 27, 2014 |
Time: | 1:30 PM |
Place: | 106 B Studio Room, Classroom Building, OSU |
& Nielsen Hall, Room 103, OU | |
Title: | A Probe of the Charged Higgs from a SM Higgs to WW Search at the LHC |
Speaker: | Dr. Tianye Niu |
Zhejiang University School of Medicine, Hangzhou, Zhejiang, China | |
and George W. Woodruff School | |
Nuclear & Radiological Engineering and Medical Physics Program | |
Georgia Institute of Technology, Atlanta, GA | |
Date: | Monday, March 31, 2014 |
Time: | 3:30 PM |
Place: | PS 141 |
Title: | Advanced Conebeam CT Imaging for Image-guided Radiation Therapy |
X-ray cone-beam CT (CBCT) system is becoming an indispensable modality in the image guidance for radiation therapy and other clinical procedures. Major components of a CBCT scanner include x-ray tube and large-area flat panel detector. The system is designed as open-gantry geometry to facilitate its incorporation into treatment process. The hardware configuration of CBCT enables its on-board capability to detect the two-dimensional x-ray projections passing through a large illuminated volume of an object, and then to reconstruct three-dimensional volumetric images. Thus CBCT system acquires accurate patient geometry during treatment and is applied in routine clinical procedures, such as the patient setup. Advanced clinical applications of CBCT imaging, however, are hindered by several major bottlenecks due to physical and mechanical constraints in the current system design, including the inferior image quality, high accumulated dose in repeated scans, and limited movement flexibility. The inferior image quality is mainly caused by the physical and engineering non-ideals, such as scatter photon contamination, beam hardening, mechanical and patient motion and etc. The CT number error of CBCT image is as high as 300 HU for a middle-size human torso. The high-accumulated imaging dose from the daily use of CBCT can go up to 2 Gy after a standard radiation treatment. The circular scanning geometry of CBCT on Linac restricts the coplanar imaging scheme and limited longitudinal coverage. A quantitative, safe and flexible CBCT imaging is in urgent demand for its advanced applications. In my present work, effective scatter correction method is proposed to suppress the severe shading artifacts in the CBCT images, and the CT number error is reduced to around 20 HU. Based on the compressed sensing theory, a low-dose iterative algorithm is developed to reconstruct CBCT images of high quality using no more than 30% of projections in a conventional scan. On-going work will combine the above two schemes and achieve the simultaneous image quality improvement and imaging dose reduction. More flexible scanning trajectories will be investigated to increase the longitudinal coverage and achieve the scan mode in a volume of interest. These new techniques have the potential to facilitate the advanced use of CBCT and promote the clinical outcomes.
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Aihua Xie |
Department of Physics | |
Oklahoma State University | |
Date: | Thursday, April 3, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Principles and Dynamics of Proton Transfer in Proteins |
Proton transfer is broadly employed in protein functions, not only in energy transformation but also in biological signaling and enzymatic catalysis. Unlike electron transfer which has been well understood for nearly two decades, some key questions regarding the physical mechanism of proton transfer remains elusive after extensive studies. We will report a proof of concept study on principles and dynamics of proton transfer and its applications in proteins. In addition, we will discuss how to apply time-resolved infrared structural biology to probe and explore proton transfer during protein functions.
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Jeremy Schmit |
Department of Physics | |
Kansas State University | |
Date: | Thursday, April 3, 2014 |
Time: | 3:30 PM |
Place: | PS 103 |
Title: | Many-body Protein Systems: Challenges of Timescale and Resolution |
The properties distinguishing one protein from another are all determined by perturbations in the sequence of amino acid side chains. This complicates many problems in protein physics, like protein folding, because there is a wide range of relevant length scales. This problem is even worse with questions involving many-body protein interactions where the system sizes are much bigger and the timescale are often much longer. In this seminar I will discuss two cases where we have used simple analytic models to reduce many-body protein systems to smaller problems that are tractable by modern computer hardware. First, pharmaceutical companies need to be able to predict the viscosity of antibody solutions in order to avoid wasting resources on molecules that will be too difficult to manufacture and deliver. We show that antibody solutions behave much like semi-dilute polymer solutions in that the viscosity is determined by molecular entanglements. These entanglements depend strongly on interactions between the antigen binding domains, which cause the antibodies to polymerize into longer structures. Secondly, there is a great need to understand the mechanism by which proteins self-assemble into disease-related aggregates called “amyloids.” We show that the long timescale characterizing amyloid assembly is caused by the exhaustive sampling required to find the ordered structure of the final aggregate. By identifying the reaction coordinate characterizing this sampling process, we can use a series of small computer simulations to probe the effects of amino acid sequence on aggregation kinetics.
Refreshments will be served at 3:00 pm in PS 117.
Speaker: | Dr. Chuanwei Zhang |
Department of Physics | |
University of Texas at Dallas | |
Date: | Thursday, April 10, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Search for Majorana Fermions in Spin-Orbit Coupled Superfluids and Superconductors |
Topological quantum matter has been an active research field in physics in the past three decades with numerous celebrated examples, including quantum Hall effect, chiral superconductor, topological insulator, etc. In topological materials, Majorana fermions, first envisioned by E. Majorana in 1935 to describe neutrinos, often emerge as topological quasiparticle excitations of the systems. Majorana fermions are intriguing because they are their own anti-particles and follow non-Abelian anyonic statistics. Although the emergence of Majorana fermions in any condensed matter or atomic system is by itself an extraordinary phenomenon, they have also come under a great deal of recent attention due to their potential use in fault tolerant quantum computation. In this talk, I will discuss recent theoretical and experimental progress on the search for Majorana fermions in two spin-orbit coupled systems: spin-orbit coupled degenerate Fermi gases and semiconductor/superconductor nanostructures. I will discuss the contribution of my group in this rapidly developing field.
References
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Jessica Adam |
Senior Research and Development Engineer | |
MicroLink Devices, Inc., Niles, IL | |
Date: | Friday, April 11, 2014 |
Time: | 9:30 AM |
Place: | Videoconference Room, PS 148 |
& Nielsen Hall, Room 103, OU | |
Title: | The Physics and Applications of High-Efficiency, Ultra-Thin Solar Cells |
High-efficiency III-V material solar cells have a venerable fifty-year history powering space satellites. Further applications are now opening up in terrestrial power generation, portable power and unmanned aerial vehicle sectors as innovative manufacturing processes lead to large reductions in cell cost. An overview of the physics of today’s highest-efficiency solar cell technology—the multi-junction structure—will be presented. An enabling technology to significantly reduce cell cost and increase specific power, the epitaxial lift-off and substrate reuse process, will be discussed. The manufacture of such cells will be described, from growth through fabrication and characterization. Current and potential applications will be highlighted.
For more information, contact Dr. Mario Borunda (OSU) or Dr. Kieran Mullen (OU).
Speaker: | Dr. Jorge A. López |
Department of Physics | |
University of Texas at El Paso | |
Date: | Thursday, April 17, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Neutron-Rich Nuclear Physics |
Modern nuclear facilities are producing neutron-rich nuclei and using them in collisions to study reactions with neutron-rich nuclei. In this talk the study of neutron-rich systems with molecular dynamics will be presented. In particular, neutron star crusts have been studied and found to form non-uniform nuclear structures known as “nuclear pasta” due to their shapes like “meat-pie”, “lasagna-like” layers, “spaghetti-like” rods, and “meatball-like” clumps.
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Jorge A. López |
Department of Physics | |
University of Texas at El Paso | |
Date: | Friday, April 18, 2014 |
Time: | 11:30 AM |
Place: | PS 147 |
Title: | Phase Changes in Nuclear Matter |
Low temperature systems composed of neutrons and protons exhibit crystalline phases around saturation densities that go from FCC to SC. At sub-saturation densities molecular dynamics simulations indicate that a phase transition occurs from the crystalline phase to a mixture of liquid-gas phases. These changes, however, depend strongly on the ratio of protons to neutrons.
Speaker: | Dr. Bruce J. Ackerson |
Department of Physics | |
Oklahoma State University | |
Date: | Thursday, April 24, 2014 |
Time: | 3:30 PM |
Place: | PS 110 |
Title: | Cream Patterns in Empty Coffee Cups |
One day I noticed by chance a strange symmetric pattern of cream in the bottom of an empty coffee cup. With awareness aroused, I found that similar patterns occurred quite often. Why do such patterns form from the well-mixed coffee and cream left at the bottom of the cup?
This talk examines possible causes for the pattern formation: evaporation, Rayleigh–Bénard convection, Maragoni convection, Soret diffusion, Rayleigh–Taylor instability, etc. These mechanisms describe non-equilibrium phenomena capable of spontaneous pattern formation. Analysis of related dimensionless numbers, still photos, and time lapsed movies provides answers.
Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 PM. All students are welcome! Refreshments will be served.
Speaker: | Dr. Yong P. Chen |
Department of Physics and Astronomy | |
Purdue University | |
Date: | Friday, April 25, 2014 |
Time: | 9:30 AM |
Place: | Videoconference Room, PS 148 |
& Nielsen Hall, Room 103, OU | |
Title: | Taming Topological Insulators |
Topological insulators (TI) are gapped band insulators in the bulk, but have nontrivial, “topologically protected”, spin-helical conducting states with gapless Dirac fermion dispersion on the surface. Such novel “topological surface states” are considered promising platforms to explore various novel physics ranging from new types of quantum Hall effects, Majorana fermions to excitonic condensation. A major experimental challenge is that real TI materials often contain competing conduction channels such as the bulk that can mask the topological surface states. In this talk, I will discuss our recent experimental progress in reducing and eliminating the bulk conduction, ultimately realizing a truly intrinsic topological insulator with surface dominated transport. Along this journey, we have found many interesting electronic transport phenomena in TI materials, learned how to distinguish the bulk versus surface conduction, and revealed the signatures of the spin-helical, Dirac fermion topological surface states in magneto and spin transport measurements.
For more information, contact Dr. Mario Borunda (OSU) or Dr. Kieran Mullen (OU).
Prefinals Week
Speaker: | Dr. Yong Huang |
Department of Physics and Astronomy | |
University of Oklahoma | |
formerly at Georgia Institute of Technology | |
Date: | Friday, May 2, 2014 |
Time: | 9:30 AM |
Place: | Videoconference Room, PS 148 |
& Nielsen Hall, Room 103, OU | |
Title: | Development of Long Wavelength V/III Optoelectronic Devices |
V/III compound semiconductor infrared (IR) optoelectronic devices have always been an active research area with wide civilian and military applications such as optical communication, gas sensing, and thermal imaging. Material technology and band gap engineering play a vital role in realizing infrared optical emission and detection, utilizing for example, type-II space indirect transition or intersubband transition. In this talk, I will give a brief introduction to the current status of V/III research program at Georgia Institute of Technology focusing on the advanced IR devices. Research and development on the novel InP/InAlGaAs light emitting transistors (LETs) and transistor lasers (TLs) operating at 1.55μm for fiber optics communication, InGaAs/InAlAs quantum cascade lasers (QCLs)working at 6–10 μm, and MOCVD-grown InAs/GaSb type-II superlattice (T2SL) photodetectors with cut-off wavelength of ∼8 μm will be presented.
For more information, contact Dr. Mario Borunda (OSU) or Dr. Kieran Mullen (OU).
Finals Week
No talks scheduled.
No talks scheduled.
No talks scheduled.
No talks scheduled.
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This page was prepared by Helen Au-Yang and Jacques H.H. Perk.
jhhp@jperk.phy.okstate.edu