Seminars and Colloquia, July through December, 1999

• This Week's schedule.
• Earlier Semesters.
• Typical Week's schedule.
• July 5-9, 1999's schedule.
• July 12-16, 1999's schedule.
• July 19-23, 1999's schedule.
• July 26-30, 1999's schedule.
• August 2-6, 1999's schedule.
• August 9-13, 1999's schedule.
• August 16-20, 1999's schedule.
• August 23-27, 1999's schedule.
• August 30-September 3, 1999's schedule.
• September 6-10, 1999's schedule.
• September 13-17, 1999's schedule.
• September 20-24, 1999's schedule.
• September 27-October 1, 1999's schedule.
• October 4-8, 1999's schedule.
• October 11-15, 1999's schedule.
• October 18-22, 1999's schedule.
• October 25-29, 1999's schedule.
• November 2-6, 1999's schedule.
• November 9-13, 1999's schedule.
• November 16-20, 1999's schedule.
• November 23-27, 1999's schedule.
• November 30-December 4, 1999's schedule.
• December 7-11, 1999's schedule.
• December 14-18, 1999's schedule.
• December 21-25, 1999's schedule.
• December 28-31, 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, July 5-9, 1999

Research Experience for Undergraduates Colloquium:

Research Experience for Undergraduates Colloquium:

Oklahoma State Physics Department

Seminars and Colloquia, July 12-16, 1999

Laser and Photonics Research Seminar:

Abstract:

Metal nanoshells are nanoparticles consisting of a dielectric core coated with a thin metal shell. The optical resonances of these nanoparticles are a sensitive function of the core and shell thickness, and can be shifted across a wavelength range of hundreds of nanometers. For the case of silica core-gold shell nanoshells, the resonance can be shifted from nominally 600 nm in the visible region of the spectrum to beyond 2 microns in the infrared. These highly controllable characteristics result in a variety of unique light scattering and dynamical properties. In this talk, the fabrication method of gold nanoshells will be discussed. A survey of metal nanoshell optical properties, including multipole angular light scattering, surface enhanced Raman scattering at the metal nanoshell surface, and time-resolved electron thermalization, will also be presented.

Note:

Refreshments will be served at 1:00 p.m.

Oklahoma State Physics Department

Seminars and Colloquia, July 19-23, 1999

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, July 26-30, 1999

Research Experience for Undergraduates Presentations:

Wednesday, July 28, 1999, Room PS 110

Research Experience for Undergraduates Presentations:

Thursday, July 29, 1999, Room PS 110

Oklahoma State Physics Department

Seminars and Colloquia, August 2-6, 1999

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, August 9-13, 1999

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, August 16-20, 1999

First week of classes: No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, August 23-27, 1999

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

Abstract:

The interaction between particles with polarization induced by electric field causes special behaviors either in the suspension or in granular flow. This talk presents some experimental results obtained in our group. The content is as follows:

1. Measured attractive force between two spherical particles under electric field.
2. Electric field induced fractal aggregation in a metal particle/oil system.
3. Electric field induced orientation of the particles.
4. Structure induced nonlinear dielectric properties in particle/oil suspension.
5. Permittivity dependence of the shear stress in ER fluid.
6. The granular flow controlled by electric field.

Note: Please note unusual date and starting time.

Oklahoma State Physics Department

Seminars and Colloquia, August 30-September 3, 1999

Physics Undergraduate Journal Club:

Dr. Larry Scott will speak on "The Protein Folding Problem" by Hue Sun Chan and Ken A. Dill, which appeared in Physics Today of February 1993, pp, 24-32.

Abstract: Understanding and predicting the three-dimensional structures of proteins from their sequences of amino acids requires both basic knowledge of molecular forces and sophisticated computer programs that search for the correct configurations.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

The Physics Undergraduate Journal Club welcomes all who wish to expand their interests in science through reading and discussing articles in semi-popular journals such as Scientific American. Topics range from cosmology to biophysics. Each discussion will be led by a Physics faculty member. The meetings are held every other Monday at 4:30 pm in PS 147 beginning August 31. The discussions are anticipated to last approximately one hour, but some participants may wish to stay longer. Reading materials for the up-coming discussions will be available in PS 145. One hour academic credit may be obtained by signing up for PHYSC 4010.1. However, you need not be registered to participate. Watch for the announcements of articles to be discussed.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Note: Please note the change of location from Spring, 1999.

Oklahoma State Physics Department

Seminars and Colloquia, September 6-10, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

OSU Biophysics Journal Club:

Abstract:

Cholesterol is present in all animal cell membranes, in concentrations as high as 50 %. In spite of its structural simplicity, the biological role or roles of cholesterol are not known. The properties of cholesterol in lipid bilayer model membranes have been under intense study since the late 1960s, and much is known about mechanical and thermodynamic changes to bilayers brought on by cholesterol. Still, the deeper one looks, the more mysterious things get. Recently it has been proposed that cholesterol forms "superlattices" in bilayers, and these nano-structures may be biologically important. Other strange and rather sudden changes in bilayers occur at certain "magic" lipid:cholesterol ratios. Yet there is at this time no known mechanism which can explain any of these observations. In this talk I will review the data, discuss the mysteries, and show some preliminary results from simulations which provide an atomic-level look at cholesterol in a bilayer at different concentrations.

Oklahoma State Physics Department

Seminars and Colloquia, September 13-17, 1999

Physics Undergraduate Journal Club:

Dr. Bruce Ackerson will discuss "Why National Missile Defense Won't Work" by G. Lewis, T. Postol and J. Pike, which appeared in Scientific American, August 1999.

Abstract: The current plan for defending the U.S. against ballistic-missile attack faces many of the problems that plagued a similar plan three decades ago.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, September 20-24, 1999

Laser and Photonics Research Seminar:

Abstract:

A pulsed all-solid-state diode-pumped Nd:YAG laser was realized by means of a seeded regenerative amplifier which delivers 1 mJ of energy at 1.5 kHz repetition rate, a pulse duration of 25 ps, and repetition rates up to 5 kHz. This system was used as a pump for an intracavity OPO. With LiNbO₃ as a nonlinear crystal the generated signal wave was angle tunable from 1420 nm to 1650 nm.

Furthermore, the tunability and conversion efficiency of a double OPO using LiNbO₃ and AgGaSe₂ was investigated. The first OPO was pumped with a Q-switched Nd:YAG laser to generate the idler wave at 1.5 µm which pumped the second OPO. Changing the phase matching angle by about 3.5 degrees continuously tunable radiation from 3 µm to 5 µm was obtained. Finally, for monitoring the water vapor concentrations in the higher troposphere and lower stratosphere at 935 nm and 942 nm wavelength a Ti:sapphire ring laser and an OPO ring cavity were constructed. Both systems used a diode-pumped Q-switched frequency doubled Nd:YAG pump laser with 100 Hz repetition rate.

Note:

Refreshments served at 3:00 pm.

Oklahoma State Physics Department

Seminars and Colloquia, September 27-October 1, 1999

Physics Undergraduate Journal Club:

Dr. Xincheng Xie will discuss "Electrons in Flatland" by S. Kivelson, D. Lee, and S. Zhang, which appeared in Scientific American, March 1996.

Abstract: Trapped in a two-dimensional plane, electrons can exhibit the quantum Hall effect, a startling phenomenon now thought to be intimately connected to superconductivity.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, October 4-8, 1999

Physics Colloquium:

Abstract:

The physics of spatial solitons in nonlinear optical materials will be discussed. An optical spatial soliton is simply a light beam that propagates without divergence in a medium due to nonlinear effects that tend to counteract diffraction. This phenomenon is also known as "self-guiding". Of particular interest are photorefractive spatial solitons because (i) they can be formed using very low optical intensities and (ii) they exhibit self-guiding in both transverse dimensions. The potential applications of spatial solitons in the field of optical communications will also be discussed.

Note: Refreshments at 3:00 PM in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, October 11-15, 1999

Frontiers in Physics (Physics Undergraduate Journal Club):

Dr. Penger Tong will discuss "Tackling Turbulence with Supercomputers" by Parviz Moin and John Kim, which appeared in Scientific American, January 1997.

Abstract: Computers only recently became powerful enough to illuminate simple examples of this great classical problem. In some cases, they will let engineers control it.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

OSU Biophysics Journal Club:

Abstract:

The interaction of porphyrin with bovine serum albumin (BSA) is being investigated by measuring the fluorescence and absorbance spectra at different BSA/porphyrin ratios in media of diffrent pH values. Literature wishes you to believe that a single porphyrin binding site exists on the surface of BSA and that BSA induces aggregation of the porphyrin. Neither statement seems totally consistent with our data. In particular, the pH-dependency of the spectral changes suggests multiple sites of interaction on the protein surface that are protonatable.

Oklahoma State Physics Department

Seminars and Colloquia, October 18-22, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

An example of defect physics or how I've managed to stay busy, funded, and frustrated for 22 years.

This is the first in a series of faculty talks intended to describe our research activities and opportunities.

Note room change.

Note: Meeting with the students: 2:45 PM in PS 147. Coffee and Cookies: 3:00 PM in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, October 25-29, 1999

Laser and Photonics Research Seminar:

Abstract:

In this talk, I shall summarize the MOCVD growth and characterization of high quality GaN-based nitrides and related quantum wells on Si substrates. Recently, we have developed special composite intermediate layers (CILs) which are consisting of an ultra-thin amorphous silicon film and a GaN/AlGaN multilayered buffer (MLB). Photoluminescence (PL) measurement reveals that the full width at half maximum (FWHM) of the dominant GaN band-edge-related emission peak is 40 meV. This value is approximately 38% narrower than the best value reported so far, 65 meV (Appl. Phys. Lett. 74, 1984 (1999).

More recently, we have successfully grown InGaN/GaN multiple quantum wells (MQWs) over further developed CILs with double MLBs. The PL spectra show that the double excitonic peak around 2.75 eV (corresponding to an In composition as high as 0.3 in InGaN alloy) from the InGaN/GaN MQWs grown over the CILs with double MLBs, is much stronger than that from identical MQWs grown over the conventional CILs with single MLB. Moreover, the FWHM of the dominant exciton-related emission peak was found to be reduced greatly (more than 40%) with the introduction of the second MLB. It was noted as well that the defect-related "yellow-band" emissions centered at 2.35 eV are much weaker than the dominant exciton-related emission for all our samples.

These facts indicate that the crystal quality of GaN-based nitrides and related MQWs grown on silicon substrate can be significantly improved by using the proposed CILs technology.

Note:

Refreshments served at 1:30 pm.

Frontiers in Physics (Physics Undergraduate Journal Club):

Dr. Bruce Ackerson will discuss "The Fate of Life in the Universe" by Lawrence M. Krauss and Glenn D. Starkman, which appeared in Scientific American, November 1999.

Abstract: Billions of years ago the universe was too hot for life to exist. Countless eons hence, it will become so cold and empty that life, no matter how ingenious, will perish.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

Center for Sensors and Sensor Technologies Seminar:

Abstract:

The use of breath for noninvasive diagnostics has significant potential as well as many technical challenges. The surface area of the human lung is roughly the size of a tennis court, but many exhaled compounds are only present in trace levels. The dynamics of breathing and interferences by water and other contaminants have complicated the development of breath diagnostic applications. Here, we present our efforts to develop real-time breath testing in order to monitor oxidative stress conditions. The monitoring is based on the use of a highly sensitive, long path mid-infrared tunable diode laser (TDL) system. A background on the biochemical pathology and an overview of the instrumentation and preliminary results will be presented.

Oklahoma State Physics Department

Seminars and Colloquia, November 1-5, 1999

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Note room change.

Note: The traditional student-speaker chat will begin in Physical Sciences 147 at 2:45 PM. All students are welcome! Refreshments will be served at 3:00 PM in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, November 8-12, 1999

Frontiers in Physics (Physics Undergraduate Journal Club):

Postponed until next week, because of Faculty Meeting with new Dean.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Laser and Photonics Research Seminar:

Abstract:

Semiconductor nanocrystals (also called quantum dots) whose optical properties are determined largely by the quantum confinement effect are currently being extensively studied in both physics and chemistry research. There are two possible routes to semiconductor quantum dots: they may be grown by molecular beam techniques making use of island-like growth of semiconductor materials on certain substrates (top down approach); or they may be formed by colloidal particle growth in a solvent medium.

The latter is the growth technique that we have used to synthesize CdSe, CdTe, CdHgTe and HgTe nanocrystals capped on the surface with different thiols (mercaptoalcohols, mercaptoacids, dithiols). They were characterized by UV-Vis absorption and photoluminescence spectroscopy, X-ray diffractometry and high resolution transmission electron microscopy. Nanocrystals belong to the cubic phase with a size from 2.5 to 4 nm being tunable on the preparative and post-preparative stages. The size-quantiziation effect together with the surface chemistry determine the optical properties of the nanocrystals. Room-temperature photoluminescence with a maximum depending on the nanocrystal size and composition was observed in the visible (CdTe; quantum efficiency 3-6%, at appropriate conditions up to 18%) and near-IR (CdHgTe, HgTe; quantum efficiency up to 50%) spectral ranges. Perspectives of the applications of the luminescent nanocrystals incorporated in light-emitting structures, optical amplifiers and photonics crystals will be discussed.

Note:

Refreshments will be served following the seminar. If you have any questions, you may contact Heath Hignight (405-744-6404).

Physics Colloquium:

Abstract:

This talk is directed to new graduate students to inform them of my research in chemical physics, both past and present. Then I will discuss a current research problem concerning the settling of hard spheres. While settling is an old problem, it is a difficult problem which is not fully understood. The spheres interact via long range hydrodynamic interactions. To leading order these interactions decay as 1/r, giving a much longer range interaction than that of gravity or static charge interactions. Intuitively physics is turned inside out, because (collective) effects of distant particles have stronger influence on a given particle than those of nearby neighboring particles.

Note room change.

Note: The traditional student-speaker chat will begin in Physical Sciences 147 at 2:45 PM. All students are welcome! Refreshments will be served at 3:00 PM in PS 147.

OSU Biophysics Journal Club:

Abstract:

Apolipophorin-III, apoLp-III, is an exchangeable apolipoprotein whose structure is represented as a bundle of five amphipathic a-helices. In order to study the properties of the helical domains of apolipophorin-III, we designed and obtained five single-tryptophan mutants of Locusta migratoria apoLp-III. Based on the crystal structure of the protein, the tryptophan residues were located in the nonpolar domains of the amphipathic a-helices. The proteins were studied by UV absorption spectroscopy, time-resolved and steady-state fluorescence spectroscopy and circular dichroism. This study allowed us to estimate the relative strength of the five interhelical interactions of apoLp-III. These interactions can be ordered according to their apparent stabilizing strengths as: helix3-helix4>helix2-helix3>helix4-helix5>helix1-helix2>helix1-helix5. Based on these interactions, a new model for the conformational change that is expected to occur upon binding of the apolipoprotein to lipid is proposed. This model is significantly different to the currently accepted model, which was introduced by Breiter et al., 1991. It is inferred that helix#1 and #5 would play an important role in allowing the formation of the final lipid-bound state. The conformational flexibility of helices #1 and #5 could provide the transient exposure of their hydrophobic domains as well as those of other helices. This exposure could ultimately lead to the final lipid-bound state.

Oklahoma State Physics Department

Seminars and Colloquia, November 15-19, 1999

Frontiers in Physics (Physics Undergraduate Journal Club):

Dr. Larry Scott will discuss "The Hidden Ocean of Europa" by Robert T. Pappalardo, James W. Head, and Ronald Greeley, which appeared in Scientific American, October 1999.

Abstract: Doodles and freckles, creamy plains and crypto-icebergs -- the amazing surface of Jupiter's brightest icy moon hints at a global sea underneath.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

Center for Sensors and Sensor Technologies Seminar:

Abstract:

This presentation will contain two parts. The first part is an overview of piezolectric sensors and their use in detection of organic vapors (specificallly, small aromatics and chlorinated hydrocarbons) in air. The advantages and disadvantages of a clathrate-forming nickel complex as the chemically sensitive coating will be discussed. The second part will focus on the strategies for designing an integrated chemical sensor that will work in real environments, with a low incidence of false positive and false negative responses.

Please note time change due to scheduling conflict with general faculty meeting.

Note: Refreshments will be served.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

For decades it has been known that certain nuclei are more stable than others and certain atoms are inert while others are active. In the 1980s, physicists discovered that, when atoms form clusters, certain clusters are also more stable than others. These systems are particularly stable when they each contain a "magic number" of elemental building blocks: protons and neutrons for the nuclei, electrons for the atoms, and atoms for the clusters. In this talk, we will show that, when a metal is added to a semiconductor substrate layer by layer, something magic can also take place. Specifically, we show that the competitions between the effects of quantum confinement, charge spilling, and interface-induced Friedel oscillations can make the metal film magically, critically, or marginally stable, or totally unstable against roughening. Also discussed are the novel transport properties of such ultrathin metal films, and connections of our unique predictions with recent experiments.

Note room change.

Note: The traditional student-speaker chat will begin in Physical Sciences 147 at 2:45 PM. All students are welcome! Refreshments will be served at 3:00 PM in PS 147.

Laser and Photonics Research Seminar:

Abstract:

Ultrafast nonlinear spectroscopy provides unique and powerful tools for studying the dynamics of Coulomb correlation effects. Indeed, the time resolution can be much smaller than the scattering times or periods of oscillation of the elementary excitations. Very recently, femtosecond pump-probe and four-wave-mixing experiments have begun to demonstrate the important role of many-body correlations in both coherent and dissipative optical processes in modulation-doped quantum wells and large metal clusters. In this talk, recent theoretical advances that have enabled us to describe and predict a number of dynamical features in the subpicosecond nonlinear optical response of such confined Fermi seas that are due to strong electron-electron and electron-hole correlations will be discussed.

Note: Refreshments served at 1:00 p.m.

Oklahoma State Physics Department

Seminars and Colloquia, November 22-26, 1999

Thanksgiving

Oklahoma State Physics Department

Seminars and Colloquia, November 29-December 3, 1999

Frontiers in Physics (Physics Undergraduate Journal Club):

Dr. Al Rosenberger will discuss "The Single-Atom Laser" by Michael S. Feld and Kyungwon An, which appeared in Scientific American, July 1998.

Abstract: A new type of laser that harnesses the energy of individual atoms reveals how light interacts with matter.

Copies of the articles may be picked up (free of charge) in PS 145, the General Physics office, anytime prior to the discussion.

Everyone is welcome.

Center for Sensors and Sensor Technologies Seminar:

Abstract:

Quartz crystals are normally utilized as frequency control devices as a sealed unit. The excellent stability of the device can also be utilized unsealed, with modifications, to attract material and act as a Microbalance. This allows the resultant frequency changes to determine mass changes. They can be used in both a gaseous or liquid environment. They can be used with a Potentiostat to perform Electrochemical experiments. By monitoring various frequency changes as well as impedance changes, one can determine density/viscosity changes in liquids or surface materials. In recent years, powerful leverage has resulted from combining additonal measurements that are made simultaneously or in parallel with the mass determination.

Thin film growth, condensation, adsorption, desorption, absorption, oxidation, reduction, decomposition, hydration, dehydration, solubility, surface area, surface tension, surface pressure and catalysis are the most common areas of topical interest.

Note: Refreshments will be served.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Neutrinos have been much in the news recently. This talk surveys what is old, what is new and what the next few years may hold. Understanding neutrino properties -- mass, magnetic moment, flavor (electron, muon, taon and possibly other types) -- and neutrino dynamics is crucial to progress in particle physics and astrophysics. I will comment on ideas about the origins and interactions of ultra-high-energy neutrinos from cosmic sources to highlight some of the issues in neutrino physics.

Note room change.

Note: The traditional student-speaker chat will begin in Physical Sciences 147 at 2:45 PM. All students are welcome! Refreshments will be served at 3:00 PM in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, December 6-10, 1999

Finals Week

Oklahoma State Physics Department

Seminars and Colloquia, December 13-17, 1999

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, December 20-24, 1999

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, December 27-31, 1999

No talks scheduled.

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