Seminars and Colloquia, January through June, 1999

• This Week's schedule.
• Earlier Semesters.
• Typical Week's schedule.
• January 4-8, 1999's schedule.
• January 11-15, 1999's schedule.
• January 18-22, 1999's schedule.
• January 25-29, 1999's schedule.
• February 1-5, 1999's schedule.
• February 8-12, 1999's schedule.
• February 15-19, 1999's schedule.
• February 22-26, 1999's schedule.
• March 1-5, 1999's schedule.
• March 8-12, 1999's schedule.
• March 15-19, 1999's schedule.
• March 22-26, 1999's schedule.
• March 29-April 2, 1999's schedule.
• April 5-9, 1999's schedule.
• April 12-16, 1999's schedule.
• April 19-23, 1999's schedule.
• April 26-30, 1999's schedule.
• May 3-7, 1999's schedule.
• May 10-14, 1999's schedule.
• May 17-21, 1999's schedule.
• May 24-28, 1999's schedule.
• May 31-June 4, 1999's schedule.
• June 7-11, 1999's schedule.
• June 14-18, 1999's schedule.
• June 21-25, 1999's schedule.
• June 28-July 2, 1999's schedule.

Seminars and Colloquia, Typical Week:

Laser and Photonics Research Seminar:

Physics Undergraduate Journal Club:

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Journal Club on Biophysics:

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

Oklahoma State Physics Department

Seminars and Colloquia, January 4-8, 1999

No Seminars: Preliminary Exams

Oklahoma State Physics Department

Seminars and Colloquia, January 11-15, 1999

Oklahoma State Physics Department

Seminars and Colloquia, January 18-22, 1999

Physics Colloquium:

Abstract:

Optical physics is an area in which it is still possible for an individual to do both theoretical and experimental work. In this talk, I will describe some of my recent research. Theoretical results in high-field suppression of photoionization, carrier heating in semiconductors, and multimode instability of nonlinear resonators will be described. Also to be discussed is experimental work on whispering-gallery modes of dielectric microspheres, including coupling, nonlinear optics, and evanescent-wave detection of atmospheric and biogenic trace gases.

Note:

The colloquium starts at a special time for this week only.

OSU Biophysics Journal Club:

Abstract:

A confocal Raman spectroscopy system has been developed in order to noninvasively characterize ocular tissue with both an in vitro and in vivo capability. The system consists of a long working distance optical probe, which focuses the incident laser light onto the tissue and collects the backscattered Raman signal, a single grating spectrometer with CCD camera, and an optical fiber which couples the optical probe to the spectrometer. Essential to the confocal design is that the sample volume is limited, preventing detection of interference signals and fluorescence from adjacent ocular tissues. Potential applications of this technique such as assessing corneal and lens hydration, detecting biological molecules in the aqueous humor, and quantifying pharmacokinetic drug transport across the cornea will be discussed.

Oklahoma State Physics Department

Seminars and Colloquia, January 25-29, 1999

Physics Colloquium:

Abstract:

Investigations of singly doped laser materials have shown the feasibility of efficient energy extraction when pumped in schemes where the pump and lasing wavelengths are comparable. When compared to multiply doped material, lasing of singly doped material is not reliant on energy transfer processes and fewer channels for radiation and non-radiative losses are present. Efficient lasing of Ho: LuAG is demonstrated by simulated diode pumping at 1.87 mm. The results show this material to be more efficient than Ho: YAG and has prospects for a broad range of applications.

Note:

The colloquium is on Tuesday for this week only. Refreshments will be served at 3:00 pm in Room 147 PS II.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, February 1-5, 1999

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

Oklahoma State Physics Department

Seminars and Colloquia, February 8-12, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Postponed due to scheduling conflict at OU.

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

Oklahoma State Physics Department

Seminars and Colloquia, February 15-19, 1999

Laser and Photonics Research Seminar:

Abstract:

The effects of structural properties on electrical and optical properties of GaN layers grown on (0001) sapphire substrates by metalorganic chemical vapor deposition have been investigated by high resolution x-ray diffraction (HRXRD), atomic force microscopy (AFM), Hall, transmission electron microscopy, deep level transient spectroscopy (DLTS), cathodoluminescence (CL), photocurrent (PC) and photolumines-cence (PL) measurements. It was observed that edge dislocations among the several threading dislocation components play a critical role in the reduction of electron Hall mobility and optical luminescence efficiency. Also the dependence of yellow band emission on deep level defects had been investigated by deep level optical spectroscopy (DLOS) , CL and PL in undoped GaN samples with different growth conditions. The relationship between them will be discussed.

Note:

Refreshments will be served following the seminar. If you have any questions, you may contact Heath K. Hignight (X46404).

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, February 22-26, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

The coherent emission of light associated with band-to-band transitions in bulk semiconductors and multiple quantum wells is directly determined by the nonequilibrium carrier and excitonic dynamics. In this talk, we will describe sensitive techniques that allow one to measure the amplitude, phase and polarization state of extremely weak, ultrafast coherent emission from semiconductor multiple quantum wells. We will show that the vectorial dynamics contain useful information about exciton-exciton interactions, quantum interference effects and material anisotropies that would be difficult to obtain in any other way.

Note:

Refreshments will be served at 3:00 pm in Room 147 PS II.

OSU Biophysics Journal Club:

Abstract:

I will discuss the theoretical and experimental approaches used to determine the free energy of unfolding of proteins.

Center for Sensors & Sensor Technologies Seminar:

Abstract:

Recent evidence of sharp increases in the number and severity of deformations in many amphibian species worldwide resulting from increased ultraviolet-B (UVB) exposure has prompted the development of a new integrating UVB dosimeter. This dosimeter can be readout by either thermoluminescence (TL) or optically stimulated luminescence (OSL) techniques. The detection method takes advantage of the phototransferred properties of Al₂O₃:C in the UVB region (280-320 nm). These UVB dosimeters have a linear dynamic range of several orders of magnitude and no significant temperature dependence.

The inherent angular dependence of the interference filter has been flattened through the use of diffusers and by the increased phototransfer efficiency of Al₂O₃:C at shorter UVB wavelengths. The new UVB dosimeters can be used in air or in water and, unlike their electronic-based counterparts, require no external power source. Their small, lightweight and watertight design makes them ideally suited for measuring the UVB exposure of egg sacks in situ. These dosimeters have been field tested in Argentina, Belize, Chile, Mexico and the United States.

Oklahoma State Physics Department

Seminars and Colloquia, March 1-5, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Muon colliders, while technically quite challenging to build, offer the prospect of experimentally reaching several TeV in energy. This novel form of high energy collider offers a wide range of opportunities for studying particle physics within and beyond the Standard Model of particle interations. I will address the possibilities that a muon collider provides: from Higgs boson and supersymmetric particle production to intense neutrino beams.

Note:

Refreshments will be served at 3:00 pm, Room PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, March 8-12, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Abstract:

The vacuum polarization of the electromagnetic field is considered in the presence of a dielectric medium with dispersion (position dependent e(x)). The quantization procedure is (re-)considered and the renormalization prescription is discussed in detail using the heat kernel expansion. The relevant heat kernel coefficient a₂ is calculated both for a generic e(x) and for a spherically symmetric step like e(r) (i.e., for a dielectric sphere). In the latter case an additionally cancellation occurs which makes the vacuum energy of a dielectric sphere in the dilute approximation physically meaningful.

Physics Colloquium:

Abstract:

Not available

Note:

Refreshments will be served at 3:00 pm in Room 147 PS II.

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

Oklahoma State Physics Department

Seminars and Colloquia, March 15-19, 1999

Spring Break

Oklahoma State Physics Department

Seminars and Colloquia, March 22-26, 1999

APS Centennial Meeting, Atlanta, Georgia

Oklahoma State Physics Department

Seminars and Colloquia, March 29-April 2, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Two-dimensional turbulence has been a domain of computational physics for many years. It is only recently, with the development of new experimental techniques, that laboratory experiment becomes possible. Using particle imaging velocimetry and laser Doppler velocimetry, we have measured velocity fluctuations in rapidly moving soap films that were rendered turbulent by mechanical and electromagnetic means. The measurements show marked differences in the energy spectra depending on whether turbulence is continuously forced or freely decaying. Such differences are expected base on Kraichnan and Saffman's theory of 2D turbulence, and illustrate the importance of conservation laws and spatial dimensions for this fascinating hydrodynamic phenomenon.

Note:

Refreshments will be served at 3:00 pm in Room 147 PS II.
Dinner will be at Stillwater Bay at 6:00 pm (sign up sheet is in 145 PS II).
Reception will be held at 8:00 pm at Dr. Tong's, 1112 Greystone.

OSU Biophysics Journal Club:

Abstract:

Time resolved Fourier-transformed infrared spectroscopy (TRS-FTIR) is one of the most powerful methods to follow the structural changes of a protein during its function. The most advanced FTIR instruments can produce infrared spectra series with up to 5 ns temporal resolution. At the beginning of the talk two methods of TRS FTIR will be introduced briefly, one providing nanosecond tme resolution and the other providing millisecond time resolution.

During the function of a protein changes may take place in its secondary structure (backbone movements, folding-unfolding, etc) that can be followed in the Amide regions and in the environment and/or ionic state of the amino acid side chain appearing in various regions of the IR spectrum. TRS FTIR using a polarized infrared probe beam may give direct steric/angular information on these movements inside the protein.

Application of polarized TRS FTIR measurements to the membrane protein bacteriorhodopsin to obtain data for angular changes in the molecule's active groups will be discussed at the end of the talk.

Oklahoma State Physics Department

Seminars and Colloquia, April 5-9, 1999

Oklahoma State Physics Department

Seminars and Colloquia, April 12-16, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Center for Sensors & Sensor Technologies Seminar:

Abstract:

A discussion of the design and implementation of surface acoustic wave (SAW) and fluorescence quenching based sensors and instrumentation. These devices are targeted at detecting extremely low concentrations of environmental analytes as well as explosive materials.

Oklahoma State Physics Department

Seminars and Colloquia, April 19-23, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Abstract:

In the bound state approach the heavy baryons are constructed by binding the heavy meson multiplet (with any orbital angular momentum) to the nucleon which emerges as a soliton in an effective meson theory. We investigate the hyperfine splitting of the heavy baryons in the bound-state approach. We start with an ordinary relativistic Lagrangian which has been extensively used to discuss finite mass corrections to the heavy limit predictions. We observe that the dominant contribution arises from terms which do not manifestly break the heavy spin symmetry. The actual heavy spin violating terms are uncovered by carefully performing a 1/M expansion of this Lagrangian. A reasonable description of the spectrum of both the light and heavy baryons can only be achieved when vector mesons are added to the Skyrme model. In the vector meson model we then predict the following mass differences for the heavy baryons: M(\Sigma_C)-M(\Lambda_C)=178 MeV, M(\Lambda_C)-M(N)=1.321 GeV and M(\Lambda_B)-M(N)=4.495 GeV. These compare reasonably well with the empirical values 165 MeV, 1.345 GeV and (4.70±0.05) GeV, respectively.

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

Note: The starting time is earlier due to a scheduling conflict with the Photonics Seminar.

Laser and Photonics Research Seminar:

Abstract:

Lasing/amplification without inversion can be obtained in three-level systems due to destructive quantum interference between two different absorption pathways. Such interference relies on the coherence between appropriate atomic states. Previous work on lasing without inversion neglected the effect of any stochastic perturbation, collisions in particular.

While, usually, atomic coherence is destroyed by stochastic perturbations, we have found that elastic (dephasing) collisions cause important contribution to the atomic coherence. (This counter-intuitive mechanism is analogous to the, so called Pressure-Induced Extra Resonances, seen e.g. in four-wave mixing.) Such coherence reduces reabsorption of the amplified radiation and allows amplification (or lasing) without inversion in three-level systems.

I will also discuss the question of a possible frequency up-conversion in Lasing without Inversion.

Note:

Refreshments served at 1:30 PM.
Refreshments will be served following the seminar. If you have any questions, you may contact Dr. Jerzy Krasinski (x47543).

Center for Sensors & Sensor Technologies Seminar:

Abstract:

Sensors that incorporate inkjet bioprinting and molecular biotechnology can provide new vistas in biosensor technology. Emerging areas that have been pursued include the concept of "tissue engineered" sensors.

"Biojet" printing can produce three-dimensional growth matrices that can be "seeded" with young cells from different sources. With up to one-hundred separate fluid channels per inch, biojet printing heads can be used to build 3-dimensional structures of composites that include local micro-zones of collagen, growth factors, attachment proteins, anti-growth factors, gene transfection factors, and other genetic materials. These seeded-matrices can promote and guide growth for custom-engineered "tissue" with almost unlimited potential as biosensor "chips" or "brains". For example, immature olfactory receptor cells can potentially be harvested from an animal tissue such as a bovine species and seeded into a growth matrix that have had trails of growth factor "printed" into the matrix. These biojet printed matrices can guide axon outgrowth over embedded electrodes, also microjet printed into the composite matrix. "Patches" of gene-transfection vectors with the attendant genetic material can also be printed into the matrix composite. The end result will be a hybrid-tissue "nose" that fires individual axons when an individual aromatic molecule arrives.

Oklahoma State Physics Department

Seminars and Colloquia, April 26-30, 1999

Prefinals Week

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

The status of the Standard Model of particle physics and the role of symmetry in its development are reviewed. Searches for the breakdown of these symmetries motivate all new particle accelerators and point the way to new physics which will be uncovered in the coming years.

Note:

The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3:00 p.m. Refreshments will be served.

Dinner at Stillwater Bay, 6:00 p.m. (Sign-up sheet in main office.)

OSU Biophysics Journal Club:

Abstract:

Oxygenic photosynthesis depends upon a cluster of four manganese atoms associated H₂O-oxidation enzyme of the photosystem II (PSII) complex. Although the mechanism for the O₂-yielding H₂O-oxidation reaction remains under debate, it is clear that the Mn cluster (Mn)₄ is a catalytic component of the reaction. During H₂O-oxidation, light-induced charge separation in the reaction center results in the production of electron holes (=oxidizing equivalents) which are accumulated in the H₂O-oxidation enzyme and used to oxidize two substrate H₂O molecules to molecular oxygen. The Mn cluster (Mn)₄ appears to be sequestered within a region of the membrane-bound PSII complex formed by intrinsic and extrinsic proteins near the lumenal surface of the thylakoid membrane. Most, if not all, ligands appear to be provided by the intrinsic portion of the PSII complex. Extrinsic proteins serve to kinetically optimize reaction and to isolate strong oxidizing equivalents associated with the H₂O-oxidation reaction.

Current evidence is consistent with the steric isolation of active site (Mn)₂ by the extrinsic proteins, which may form an active site crevice just large enough to give substrate H₂O molecules access to the strong, and otherwise destructive, oxidizing equivalents accumulated in the active site. The research problems addressed by our group are essentially two-fold: the first part concerns the process of photoactivation: the light-driven ligation of Mn⁺² into the H₂O- oxidation complex of photosystem II culminating in the formation of an enzymatically active complex containing Ca⁺² and four Mn^?+3. The second part concerns the functioning of the fully assembled H₂O-oxidation complex. The seminar will introduce these aspects of the overall problem, and, if time permits, describe our efforts to determine the role of the intrinsic and extrinsic polypeptides in mediating these processes.

Laser and Photonics Research Seminar:

Abstract:

The demonstrated applications for freely propagating and guided pulses in the THz regime are becoming wide spread. Pulses of radiated THz electromagnetic waves are generated by utilizing femtosecond laser pulses to close an ultrafast optoelectronic switch. For this THz transmitter the switch generally consists of biased coplanar microstrip lines. Along with this freely propagating THz pulse, guided ultrashort electrical pulses are also generated which propagate along the coplanar stripline. The optoelectronic generation and detection of THz pulses will be reviewed as well as several applications of these picosecond THz pulses will be discussed. For example, in our table top THz impulse radar range, unprecedented agreement between theory and experiment is obtained for both the time domain scattering signature and the frequency domain radar cross section of a dielectric cylinder. Also, the first experimental determination of the surface wave coupling efficiency is extracted. Investigations of ultrafast electrical pulse propagation on quadrupole transmission lines, near field surface wave cross-talk, on chip communication of THz pulses, and THz waveguides will also be discussed.

Note:

Refreshments will be served. If you have any questions, you may contact Heath Hignight (x46404).

Oklahoma State Physics Department

Seminars and Colloquia, May 3-7, 1999

Finals Week

Oklahoma State Physics Department

Seminars and Colloquia, May 10-14, 1999

Special Physics Seminar:

Abstract:

The development of solvable lattice models in statistical mechanics will be reviewed, with particular attention to the role of the star-triangle or "Yang-Baxter" relation.

Oklahoma State Physics Department

Seminars and Colloquia, May 17-21, 1999

Laser and Photonics Research Seminar:

Abstract:

Placing the active or passive device structure inside a Fabry-Perot resonant microcavity can enhance the performance of optoelectronic devices. Such resonant cavity enhanced (RCE) device benefit from the wavelength selectivity and large increase of the resonant optical field introduced by the cavity. Semiconductor/IIa fluoride distributed Bragg reflector (DBR) has a very broad bandwidth and high reflectivity and thus is advantageous for such RCE devices. Mid-infrared vertical cavity surface emitting lasers (VCSELs) with such mirror will reach high operation temperature in CW mode and improve the mode behavior. RCE UV solar blind detector can be fabricated on Si with high quantum efficiency and high speed. One major limitation for ultrafast mode-locking solid state lasers is the bandwidth of the saturable absorber mirror (SAM). Broadband semiconductor saturable absorber mirrors (SESAM) shows promising results of record-fast mode-locking solid-state lasers. Some results of above mentioned devices will be discussed.

Note:

Refreshments will be served at 1:00 p.m. If you have any questions, you may contact Heath Hignight (x46404).

Oklahoma State Physics Department

Seminars and Colloquia, May 24-28, 1999

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 31-June 4, 1999

Laser and Photonics Research Seminar:

Abstract:

In this talk I shall outline a systematic approach to nonperturbative many-body theory that is both elegant and nearly universally-applicable, Using this technique we have computed the single-particle Green function of an interacting Fermi system in arbitrary dimensions. Recent applications include extension of the formalism to regimes where the random phase approximation breaks down, generalisation to spin systems and more pertinent to the present audience, a generalisation to charge-conserving electron-hole systems. I shall demonstrate how the exciton and biexciton Green functions may be evaluated taking into account exciton-exciton collisions. I will conclude by relating these calculations to the pump-probe experiments.

Note:

Refreshments will be served at 1:00 p.m. If you have any questions, you may contact Heath Hignight (x46404).

Oklahoma State Physics Department

Seminars and Colloquia, June 7-11, 1999

Laser and Photonics Research Seminar:

Abstract:

This presentation includes a back-illuminated GaN/AlGaN ultraviolet (UV) heterojunction photodiode with improved quantum efficiencies, high dark impedance, and large visible rejection ratio. Also included is a GaN/AlGaN heterojunction bipolar phototransistor with gain in excess of 105 and extremely high visible-rejection ratio: 8 orders of magnitude from 360 nm to 400 nm. The phototransistor features a rapid electrical quenching of persistent photoconductivity, and exhibits high dark impedance. These results represent an internal gain UV detector with significantly improved performance over GaN based photoconductors. The potential applications and further improvements of these devices will be discussed.

Note:

Refreshments will be served at 1:00 p.m. If you have any questions, you may contact Heath Hignight (x46404).

Oklahoma State Physics Department

Seminars and Colloquia, June 14-18, 1999

Research Experience for Undergraduates Colloquium:

Research Experience for Undergraduates Colloquium:

Oklahoma State Physics Department

Seminars and Colloquia, June 21-25, 1999

Research Experience for Undergraduates Colloquium:

Research Experience for Undergraduates Colloquium:

Oklahoma State Physics Department

Seminars and Colloquia, June 28-July 2, 1999

Research Experience for Undergraduates Colloquium:

Research Experience for Undergraduates Colloquium:

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