Seminars and Colloquia, January through June, 2001

• This Week's schedule.
• Earlier Semesters.
• Typical Week's schedule.
• January 1-5, 2001's schedule.
• January 8-12, 2001's schedule.
• January 15-19, 2001's schedule.
• January 22-26, 2001's schedule.
• January 29-February 2, 2001's schedule.
• February 5-9, 2001's schedule.
• February 12-16, 2001's schedule.
• February 19-23, 2001's schedule.
• February 26-March 3, 2001's schedule.
• March 5-9, 2001's schedule.
• March 12-16, 2001's schedule.
• March 19-23, 2001's schedule.
• March 26-30, 2001's schedule.
• April 2-6, 2001's schedule.
• April 9-13, 2001's schedule.
• April 16-20, 2001's schedule.
• April 23-27, 2001's schedule.
• April 30-May 4, 2001's schedule.
• May 7-11, 2001's schedule.
• May 14-18, 2001's schedule.
• May 21-25, 2001's schedule.
• May 28-June 1, 2001's schedule.
• June 4-8, 2001's schedule.
• June 11-15, 2001's schedule.
• June 18-22, 2001's schedule.
• June 25-29, 2001's schedule.

Seminars and Colloquia, Typical Week:

Center for Laser and Photonics Research Seminar:

Center for Sensors & Sensor Technologies Seminar:

Physics Undergraduate Journal Club:

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Journal Club on Statistical Mechanics and Condensed Matter Physics (Informal):

Oklahoma State Physics Department

Seminars and Colloquia, January 1-5, 2001

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, January 8-12, 2001

No talks scheduled: Prelim Exams

Oklahoma State Physics Department

Seminars and Colloquia, January 15-19, 2001

No talks scheduled: First Week of Classes

Oklahoma State Physics Department

Seminars and Colloquia, January 22-26, 2001

Joint Physics-Mechanical Engineering Colloquium:

Abstract:

The flow mixing processes in diffusion flames on Earth are complicated by non-linear coupling of buoyancy with convection and diffusion. In this study, experiments were conducted in microgravity to isolate gravitational effects on gas-jet diffusion flames. Fast reacting hydrogen was used to eliminate soot and associated radiative heat loss and chemical kinetics effects. The objectives were (1) to obtain non-intrusive measurements in the whole field of view, and (2) to quantify temporal evolution of flames in the 2.2-second drop tower used to simulate microgravity. Measurements were obtained using quantitative Rainbow Schlieren Deflectometry (RSD), a line-of-sight optical diagnostics technique. Results show significant effects of buoyancy even in momentum-dominated gas-jets. The presentation will include an overview of the RSD technique and challenges involved in performing microgravity experiments in the drop tower.

Note the unusual date.

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.

Oklahoma State Physics Department

Seminars and Colloquia, January 29-February 2, 2001

Week of memorial services for plane crash victims.

Colloquium is postponed in view of urgent faculty meeting.

Oklahoma State Physics Department

Seminars and Colloquia, February 5-9, 2001

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Joint Physics Department-Sensor Center Colloquium:

Abstract:

Nanoscale state of matter imparts new optical, electronic and magnetic properties to the conventional materials. 1-100 nm clusters, typically associated with it, can be prepared from a variety of compounds.

In order to utilize the unique properties of nanoparticles (NPs) a thin film technique called, layer-by-layer assembly had been developed. It may be universally applied to any type of water-soluble NPs, which makes it applicable to a wide spectrum of advanced materials. As well, it affords the preparation of highly organized multilayers. Several examples of the structural control over magnetic, optical, electrical, and mechanical properties in thin film materials will be presented. The focus of the seminar will be made on the utilization of the NP multilayers in biomedical sensing and new possibilities opening by NPs for these technologies.

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.

Oklahoma State Physics Department

Seminars and Colloquia, February 12-16, 2001

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

According to the scaling theory of localization, all quantum electronic states are localized in two-dimensional (2D) systems. One consequence of the theory is that there is no quantum percolation transition in 2D. However, in a real system at a finite temperature, electron phase coherent length is finite and the system is between quantum and classical. We find, in such a 2D system, a metal-insulator transition (MIT) caused by a novel type of semi-classical percolation. The relevance to recently observed 2D MIT will also be discussed.

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.

Mathematics Colloquium:

Abstract:

Turbulent thermal convection is an intriguing problem in nonlinear physics and has attracted much attention in recent years. Despite its special way of generating turbulence at large length scales and its relatively low Reynolds number (Re), turbulent convection shares many common features that are usually associated with high-Re turbulent flows. These features include coherent structures, intermittent fluctuations and anomalous scaling. In this talk I will briefly review the recent development in the study of turbulent thermal convection and report our recent velocity and temperature measurements in the convection cells with smooth and rough upper and lower surfaces. Using laser Doppler velocimetry, we measure the velocity profiles in the smooth cell with different aspect ratios. Despite the large velocity fluctuations in the turbulent bulk region, the mean flow field maintains a large-scale structure, which rotates and oscillates in a coherent manner. The experiment provides an interesting example to show how otherwise random unstable modes in a closed system are organized in both space and time to generate a large-scale coherent structure in a turbulent environment. The novel convection experiment carried out in the rough cell shows that the heat transport in the rough cell is increased by more than 76% when compared with the smooth cell. Flow visualization and near-wall temperature measurements reveal new dynamics for the emission of thermal plumes. It is found that the interaction between the large-scale circulation and the rough surface creates a secondary flow (eddies) in the groove region. This secondary flow together with the large-scale circulation enhances the detachment of the thermal boundary layer from the tip of the rough elements. The extra thermal plumes are responsible for the enhanced heat transport in the rough cell. The discovery of the enhanced heat transport has important applications in engineering for more efficient heat transfer.

Note: There will be a reception in the department lounge (MS 423) at 3.30 PM. (Contact persons: Amit Ghosh or Jiahong Wu, Department of Mathematics. Phone: 405-744-5688.)

Oklahoma State Physics Department

Seminars and Colloquia, February 19-23, 2001

No talks scheduled. Colloquium is postponed.

Oklahoma State Physics Department

Seminars and Colloquia, February 26-March 2, 2001

Physics Colloquium:

Abstract:

When a layer of granular media is oscillated vertically, a variety of patterns can form. These patterns are similar to surface waves on a fluid. Depending on the conditions, patterns of stripes, squares, hexagons, or localized structures can be observed. I will discuss the behavior of stripe and spiral patterns, and show that the dynamics of these patterns is very similar to that of convection rolls in Rayleigh-Benard convection. This suggests that, despite the unusual characteristics of the granular system, a description of its dynamics in terms of continuum equations is possible.

Note:

The traditional student-speaker chat will begin in Physical Sciences Room 147 at 2:30 PM. Refreshments will be served.

Note the special date and place.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Journal Club on Statistical Mechanics and Condensed Matter Physics:

Oklahoma State Physics Department

Seminars and Colloquia, March 5-9, 2001

Physics Colloquium:

Abstract:

Discrete Event Simulations (DES) are used in a large number of engineering, scientific, military, and manufacturing applications. My application is to use a type of DES known as kinetic Monte Carlo to study dynamics of nanoscale ferromagnets. I will introduce DES, and the idea of 'virtual time' which is used in parallel DES (PDES). The importance of avoiding causality violations in PDES will be described, and both the conservative and optimistic approaches to causality violations introduced. One important question to be addressed is the scalability of PDES algorithms, i.e. the computer simulation time required as the number of processing elements and the problem size grow. A recent connection [1] between non-equilibrium surface science and the PDES 'virtual time' allows questions of scalability to be addressed. For example, we have recently proven in 1-dimension that ALL conservative short-ranged PDES are scalable for the computation portion of the algorithm [1]. This is independent of the specific PDES problem. I will present numerical evidence that this is also true for PDES in higher dimensions [2]. Methods [3] to make both the computation and the measurement portions of ALL short-ranged PDES scalable will be described.

1. G. Korniss, Z. Toroczkai, M.A. Novotny, and P.A. Rikvold, Physical Review Letters, vol. 84, p. 1351 (2000).
2. G. Korniss, M.A. Novotny, Z. Toroczkai, and P.A. Rikvold, in 'Computer Simulation Studies in Condensed Matter Physics XIII', edited by D.P. Landau, S.P. Lewis, and H.-B. Schuttler, preprint: http://xxx.lanl.gov/abs/cond-mat/0002469, in press.
3. M.A. Novotny and G. Korniss, unpublished.

Note:

The traditional student-speaker chat will begin in Physical Sciences Room 147 at 2:30 PM. Refreshments will be served.

Note the special date and place.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Journal Club on Statistical Mechanics and Condensed Matter Physics:

Preview of talks to be presented at the APS March Meeting

Oklahoma State Physics Department

Seminars and Colloquia, March 12-16, 2001

Analysis Seminar:

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Photonics Colloquium:

Sponsored by: Center for Laser and Photonics Research, Center for Sensors and Sensor Technologies, Department of Physics, and School of Electrical and Computer Engineering

Abstract:

The perovskite oxide family encompasses a wide variety of epitaxially compatible materials with interesting properties including ferroelectric effect, piezoelectric effect, colossal magnetoresistance (CMR), high dielectric constant, and large electro-optic effect. The major missing ingredient for many integrated applications is an efficient field effect switch. At IBM we have designed, fabricated and tested perovskite oxide channel FET's which operate at room temperature. These devices use a channel capable of undergoing the Mott metal-insulator transition. Specifically, we have chosen to use normal-state cuprates such as YBCO and LCO for the channel. We have achieved large modulations in current and high on-off ratios. However, careful measurements of these devices show limitations due to contact resistance, polycrystalline channels, and inadequate surface charge density induced by the gate voltage. We will review progress made on these issues and outline our roadmap for future research.

Note:

Host: Daniel R. Grischkowsky [Phone (405)-744-6622, FAX (405)-744-9198,
email: grischd@ceat.okstate.edu, danielg@thzsun.ecen.okstate.edu].

Oklahoma State Physics Department

Seminars and Colloquia, March 19-23, 2001

Spring Break.

Photonics Seminar:

Postponed till next week.

Oklahoma State Physics Department

Seminars and Colloquia, March 26-30, 2001

Physics Colloquium:

Abstract:

We shall discuss two unsettled issues in the integer quantum Hall (QH) effect, namely how QH systems jump from one plateau to another, and the nature of such a transition. Using the edge-state approach, we suggest that the direct transition occurs because, in certain parameter regime, the edge states of different Landau levels are strongly coupled and behave as a single edge state. It is indicated under what conditions successive transitions may be seen. The inter-Landau-band mixing is studied within the network model. We show that mixing of localized states with opposite chirality can delocalize electronic states. Based on numerical results, we propose the existence of a metallic phase between two quantum Hall phases. This result is consistent with non-scaling behaviors observed in recent experiments on quantum-Hall-liquid-to-insulator transition.

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.

* Note special date.

Photonics Seminar:

Abstract:

Following the pioneering work of Esaki and coworkers, there has been a great deal of experimental and theoretical research on transport in double barrier quantum well structures and superlattices. Such structures often have current-voltage characteristics with regions of negative differential resistance (NDR) responsible for many interesting phenomena such as domain wall formation and current self-oscillations. Here we presented a general theory of instabilities oscillations of sequential tunneling transport in superlattices. Temporal current self-oscillations are attributed to the generation of a limit cycle around an unstable point of steady state solution. General conditions are established for the stability of regions of DC current-voltage characteristic of the superlattice, and for the existence of instabilities leading to current self-oscillations. Dynamic DC-bias band is predicted and is confirmed.

Refreshments will be provided.

Oklahoma State Physics Department

Seminars and Colloquia, April 2-6, 2001

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

The Ising model is one of the classic models of phase transitions and, in particular, of the effects of randomness on phase transitions. Despite its importance in our general understanding of random systems, the characterization of the d=3 random-field Ising model (RFIM) phase transition has remained incomplete, despite much experimental and theoretical effort over more than 20 years. In the experimental realizations of the RFIM, dilute antiferromagnets in an applied field, metastable domain formation has obscured the transition. Recently, such nonequilibrium behavior has been circumvented by studying samples with high magnetic concentration. The new equilibrium critical exponents do not agree with Monte Carlo simulations that utilize finite scaling. New simulations on large lattices appear to agree with the new experiments. After introducing the models, the recent equilibrium experiments and the large lattice simulations will be discussed, as well as prospects for a complete characterization of the model in the near future.

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.

Journal Club on Statistical Mechanics and Condensed Matter Physics:

Abstract:

Below the magnetic percolation threshold concentration, long-range magnetic order cannot occur because spins are not geometrically connected. The static correlations from neutron scattering experiments and the specific heat have been studied as the percolation threshold is approached from above. The system's behavior is very sensitive to tiny frustrating interactions and extremely slow dynamics. The excitations are also being studied as the magnetic percolation threshold is approached using neutron scattering and electron spin resonance techniques. Very recently, novel effects have been observed in neutron scattering studies at much higher magnetic concentrations where magnetic vacancies percolate. Scattering from the lattice of percolating vacancies has been observed away from the Bragg scattering point at very low temperatures, something that is not observed at slightly higher or lower magnetic concentrations. This vacancy percolation threshold is also the concentration which separates equilibrium random field behavior at higher concentrations from the nonequilibrium domain behavior at lower concentrations.

Oklahoma State Physics Department

Seminars and Colloquia, April 9-13, 2001

Physics Colloquium:

Abstract:

Our research group at the Naval Research Laboratory has been active in theoretical studies of the electronic and structural properties of carbon nanotubes over most of the past decade. Single-wall carbon nanotubes---which can be visualized as constructed from rolled-up graphitic sheets---exhibit helical symmetries that can be used to reduce the computational effort needed for electronic band structure calculations of these materials. We have carried out extensive first-principles calculations on these materials using a local-density functional approach developed at NRL for helical chain polymers. We will review the history of carbon nanotubes, highlighting both our early work that predicted all armchair nanotubes should be conducting and more recent work showing the universal nature of the density of states near the Fermi level in these novel materials. A brief discussion will also be presented of our current areas of research on carbon nanotubes involving their potential applications in nanotechnology.

This work was supported by the U. S. Office of Naval Research, both directly and through the Naval Research Laboratory.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 2.30 PM. All students are welcome! Refreshments will be served.

* Note special date.

College of Engineering, Architecture & Technology

The Melvin R. Lohmann Distinguished Lecture 2001:

Open to the Public

Physics Colloquium:

Abstract:

The grail of protein science is the connection between structure and function. In myoglobin, the goal is close. Described as only a passive dioxygen storage protein in texts, myoglobin is actually an allosteric enzyme that can catalyze reactions among small molecules. Studies of the structural, spectroscopic, and kinetic properties of myoglobin lead to a model that relates structure, energy landscape, dynamics, and function. Myoglobin functions as a miniature chemical reactor, concentrating and orienting diatomic molecules in highly conserved internal cavities. Reactions can be controlled because myoglobin exists in distinct taxonomic substates with different catalytic properties and connectivities of internal cavities, and with population ratios governed by the environment. This allostery may allow control of important molecules such as NO, CO, O₂, and H₂O₂ during normal muscle activity, as well as periods of anaerobic stress. The allostery may also help understand proteomics.

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.

Oklahoma State Physics Department

Seminars and Colloquia, April 16-20, 2001

Special High Energy Seminar:

Physics Colloquium:

Abstract:

Gyroscopes are an essential tool for navigation, platform stabilization, and geophysical studies (and may eventually be accurate enough for tests of general relativity!). Our atom interferometer gyroscope operates on the same principles as a laser gyro, but takes advantage of the extremely short de Broglie wavelength of thermal atoms. Our interferometer has many advantages over mechanical and laser gyros, and has the highest reported sensitivity of any gyroscope.

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.

* Note special date.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Photonics Colloquium:

Abstract:

Diode lasers have already ushered in the fiber optic communication revolution through the Internet. It also has the potential to bring in the desktop manufacturing revolution. We will present results of generating high peak power pico second pulses generated directly from diode lasers that could open up the pico second ablative machining. We are finding that novel GCSEL (grating coupled surface emitting laser) has the potential to be scaled to very high power, while lending itself to very broad, continuous tunability for dense WDM and spectral sensing applications. However, pico second pulses also require careful study as they propagate through spectrometric devices (like Fabry-Perot and Grating) because they generate a train of partially overlapped beams due to time delays between the replicated pulses. We will present our time domain analysis to understand the so-called spectral response to short pulses from a different point of view.

Physics Colloquium:

Abstract:

A preponderance of astrophysical data strongly suggest that the universe is now undergoing acceleration. This flies in the face of decades of theoretical prejudice, but that is because such a universe is extremely difficult to construct from first principles. I will review the data, what the data means, and how one might try to account for the acceleration in terms of new physics, including quintessence and/or a cosmological constant. This talk will provide far more questions than 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.

Oklahoma State Physics Department

Seminars and Colloquia, April 23-27, 2001

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

The ability to control the momentum and position of cold atoms through optical means has generated much interest throughout the world in the last ten years. In this talk I will examine some of the schemes used for atom manipulation, with particular emphasis on how they have been applied to the construction of devices such as atom interferometers. I will describe a new approach which we have developed at Oxford which allows atoms to be coherently accelerated to velocities more than one hundred times greater than has been available with previous methods. In our technique, atoms are accelerated by a pulsed standing light wave in a process which is roughly analogous to pushing a child on a swing. If the pushes are timed correctly the child can gain momentum with each push. I will present some of the recent results from our experiments on these "accelerator modes" and will show that they offer exciting possibilities for experiments ranging from atom interferometry to quantum chaos.

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.

Oklahoma State Physics Department

Seminars and Colloquia, April 30-May 4, 2001

Prefinals Week

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, May 7-11, 2001

Finals Week

Oklahoma State Physics Department

Seminars and Colloquia, May 14-18, 2001

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 21-25, 2001

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 28-June 1, 2001

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, June 4-8, 2001

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, June 11-15, 2001

Special Physics Seminar:

Coffee and cookies will be served in PS 147 immediately preceding the seminar.

Physics Colloquium:

Abstract:

Every physics major knows that studying the dropped ball (or apple) produced profound evolution in our conceptual understanding the universe from Aristotle, Galileo, and Newton to Einstein. What more can possibly be learned by dropping balls in this age of super-strings, photonics, and quantum encryption? However, the settling of balls in a fluid still proves vexing. When a ball settles in a fluid of infinite extent, the magnitude of the (theoretical) fluid velocity field decays as 1/r to leading order, where r is the distance from the center of the ball. This velocity field or "wake" produces a force on another ball placed a the distance r. The magnitude of the force being proportional to the solvent velocity also decays as 1/r to leading order. This hydrodynamic force decays with distance more slowly than the gravitational or Coulomb forces (which decays as 1/r² and are said to have "infinite" range!) As a result the collective motion of balls at a large distance produces stronger forces on a given ball than the motion of nearby balls. This turns physical intuition inside out! My talk will explore the effect of these long range interactions and give some examples of interesting settling phenomena including recent measurements of subtle "ordering" in mixed "random" suspensions.

Work done in collaboration with Professor Penger Tong and Dr. Xinya Lei. Supported by NASA

Oklahoma State Physics Department

Seminars and Colloquia, June 18-22, 2001

REU/Physics Colloquium:

Physics Colloquium:

Abstract:

A rainbow at the end of the day seen in a retreating storm is what most people think of when asked about colors in the clouds. Yet there are other colors associated with clouds, which can be as spectacular as a rainbow, and can all be understood in terms of sunlight interacting with drops of water. In my talk I will show examples of each of the types of colors that water drops can display: primary and secondary rainbows, supernumary bows, fogbows, coronae, glories, iridescent clouds, and blue clouds. I will then show how the size of the water drop determines the colors that are seen at a given angular distance from the sun, and finally provide a novel way in which all of these colors can be seen at once.

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.

Oklahoma State Physics Department

Seminars and Colloquia, June 25-29, 2001

REU/Physics Colloquium:

REU/Physics Colloquium:

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This page was prepared by Helen Au-Yang and Jacques H.H. Perk.