Seminars and Colloquia, July through December, 2004

• This Week's schedule.
• Earlier Semesters.
• Typical Week's schedule.
• July 5-9, 2004's schedule.
• July 12-16, 2004's schedule.
• July 19-23, 2004's schedule.
• July 26-30, 2004's schedule.
• August 2-6, 2004's schedule.
• August 9-13, 2004's schedule.
• August 16-20, 2004's schedule.
• August 23-27, 2004's schedule.
• August 30-September 3, 2004's schedule.
• September 6-10, 2004's schedule.
• September 13-17, 2004's schedule.
• September 20-24, 2004's schedule.
• September 27-October 1, 2004's schedule.
• October 4-8, 2004's schedule.
• October 11-15, 2004's schedule.
• October 18-22, 2004's schedule.
• October 25-29, 2004's schedule.
• November 1-5, 2004's schedule.
• November 8-12, 2004's schedule.
• November 15-19, 2004's schedule.
• November 22-26, 2004's schedule.
• November 29-December 3, 2004's schedule.
• December 6-10, 2004's schedule.
• December 13-17, 2004's schedule.
• December 20-24, 2004's schedule.
• December 27-31, 2004's schedule.

Seminars and Colloquia, Typical Week:

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 NanoNet Informal Seminar:

Oklahoma State Physics Department

Seminars and Colloquia, July 5-9, 2004

Physics Colloquium:

Abstract:

Ultrafast pulsed laser techniques is a key to exploring the dynamics of molecules in a real time scale. The feasibility of investigation using femtosecond and subfemtosecond pulses relies on a concept of coherence. Ultrafast spectroscopy tools make possible the observation of the dynamics in core-excited atoms and molecules. Time evolution of dynamical symmetry breaking in highly symmetrical molecules is discussed in this perspective.

Advances in laser technology stimulate the development of methods for the control of molecular motion. Coherent control of vibrational degrees of freedom is achieved using ultrafast pulse shaping in stimulated Raman spectroscopy. A semiclassical model is used to theoretically investigate the possibility of selectively exciting closed space, coupled Raman transitions. Pulse shapes are found that provide either enhancement or suppression of particular vibrational excitations [1]. The role of coupling between vibrational modes via an external field is analyzed in mode selective excitation with shaped pulses. It is shown that control of molecular vibrations using coupling mechanism of interaction with external field may be achieved by preparing molecules with particularly chosen relative phase between initially populated states [2].

References

1. S. A. Malinovskaya, P. H. Bucksbaum, and P. R. Berman, Phys. Rev. A 69, 013801 (2004).
2. S. A. Malinovskaya, P. H. Bucksbaum, and P. R. Berman, accepted for publication in J. Chem. Phys.

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 NanoNet Informal Seminar:

Abstract:

A new multiscale simulation approach will be presented that couples atomistic scale simulations using molecular dynamics (MD) with the continuum scale simulations using the recently developed material point method (MPM). In MPM, material continuum is represented by a collection of material points carrying all relevant physical characteristics, such as mass, acceleration, and velocity. The use of material points at the continuum level provides a natural connection with the atoms in the lattice at the atomistic scale. A hierarchical mesh refinement technique in MPM will be presented to scale down the continuum level to the atomistic level, so that material points at the fine level in MPM are allowed to directly couple with the atoms in the MD. A one-to-one correspondence of MD atoms and MPM points was used in the transition region, and non-local elastic theory was used to assure compatibility between MD and MPM regions, so that seamless coupling between MD and MPM can be accomplished. A single crystal silicon work material under uniaxial tension is used to demonstrate the viability of the technique. A Tersoff-type, three-body potential was used in the MD simulations. The coupled MD/MPM simulations show that the silicon under nanometric tension experiences elastic deformation, dislocation generation and slip leading to plastic deformation, necking, and final failure. Results will be presented in terms of stress–strain relationships at several strain rates, as well as the rate dependence of uniaxial properties. This new computational method has potential for use in cases where a detailed atomistic-level analysis is necessary in localized spatially separated regions whereas continuum mechanics is adequate in rest of the material.

Note: Coffee and cookies available at 3:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, July 12-16, 2004

Oklahoma State Physics Department

Seminars and Colloquia, July 19-23, 2004

Physics Colloquium:

Abstract:

Civilian and military aircrews receive some of the highest exposure to ionizing radiation of any occupationally-exposed profession. While dose rates are low, exposure is chronic and cannot be mitigated by shielding or other artificial means. We have performed dosimetric measurements of ionizing radiation exposure aboard NASA’s two ER-2 high altitude (∼20 km) research aircraft and aboard commercial jetliners (∼10 km) using both passive (CR-39 PNTD and TLD) and active (portable Si spectrometers and TEPC) detectors. Measurements are compared to model calculations made using three different computer codes. Exposure to radiation at aircraft altitudes is route dependent, with flight paths passing through latitudes >±50° receiving substantially greater exposure than more equatorial flight paths. Dose rate is also highly dependent on altitude. At high altitudes, dose rate can be roughly two times greater and dose equivalent rate can be roughly three times greater than at commercial jetliner altitudes.

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, July 26-30, 2004

Research Experience for Undergraduates Presentations:

Thursday, July 29, 2004, Room PS 147

Note: For more detail see the REU 2004 Presentations webpage.

Research Experience for Undergraduates Presentations:

Friday, July 30, 2004, Room PS 147

Note: For more detail see the REU 2004 Presentations webpage.

Oklahoma State Physics Department

Seminars and Colloquia, August 2-6, 2004

Oklahoma Nanonet Informal Seminar:

Abstract:

The surface functionalization of group IV semiconductors, in particular Si(100), with organic molecules promises the opportunity to create devices that exploit the combined properties of organic materials with conventional semiconductors. The adsorption and chemical bonding of organic molecules to fine-tune the chemical and physical properties of the surface has applications in chemical sensors, biological recognition, and molecular and optical electronics. To realize these applications, a fundamental understanding of reactivity of the Si(100) surface towards various organic compounds is required. Our investigations have focused on the reactivity of the carbon nitrogen triple-bond with these Si-dimers employing cyanogen halides (ClCN, BrCN and ICN) as models for the CN triple bond functionality. At 100K some fraction of XCN adsorbs molecularly, whereas at the room temperature all X-CN bonds dissociate producing X and CN species on the surface. UPS spectrum of XCN adsorbed at low temperature contains two peaks, resulting from the interaction of the p-electrons of the halogen atom with the CN π-bond. Consistent with the XPS results, the UPS spectra show only one peak due to dissociation of the X-C bond at room temperature. The experimental conclusions are also consistent with the results of quantum computations, in which Si(100) is represented by a single-dimer (Si₉H₁₂), double-dimer (Si₁₅H₁₆) and triple-dimer (Si₂₁H₂₀) clusters. Calculations of different XCN structures on Si clusters show that adsorption occurs via Si-N dative bond in an end-on configuration. All decomposition pathways lead to the dissociated structure with the CN triple bond intact.

Note: Coffee and cookies available at 3:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, August 9-13, 2004

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, August 16-20, 2004

Oklahoma Nanonet Informal Seminar:

Abstract:

Metal-functionalized dendrimers have been investigated primarily as potential catalytic materials; other potential applications include exploitation of photophysical properties of these dendrimer complexes. Such applications require metal complexes that are attached to the dendrimer via strong covalent bonds, and herein we describe efforts toward this goal utilizing robust metal-carbene bonds as linkers. Platinum (II) and Palladium (II) isocyanide complexes with 6-phenyl-2,2’-bipyridine as a tridentate ligand with isocyanides [CH₃NC, ^tBuNC, and 2,6-Me₂C₆H₃NC] have been prepared and characterized. Procedures for attachment of these precursors to polypropyleneimine (PPI) dendrimers have been developed. The mode of attachment of the complexes is via nucleophilic attack of the primary amine end groups of the dendrimer at the isocyanide ligand of the metal complexes, forming a new carbene ligand which tethers the complex to the dendrimer. These new, unusual polymer supported metal-carbene complexes could act as catalyst precursors or could possess useful luminescent properties, potentially leading to useful new materials.

Note: Coffee and cookies available at 3:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, August 23-27, 2004

First Week of Classes

Oklahoma State Physics Department

Seminars and Colloquia, August 30-September 3, 2004

Second Week of Classes

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma NanoNet Informal Seminar:

Abstract:

Dye-sensitized solar cells based on nanocrystalline TiO₂ films have attracted enormous interest because of their high photo-current conversion efficiencies. Dye sensitized solar cells made of porous network of TiO₂ nanoparticles have already been demonstrated with high solar to electrical conversion efficiency (10.5%). TiO₂ based solar cell is comparatively easy to construct and cheaper than that made of silicon. The transient photoconductivity of sintered TiO₂ nanoparticles has been characterized at liquid nitrogen temperature with a relative thick nanoparticle layer (∼ 3 μm). However, the operation of a solar cell usually is at room temperature or higher. Here, using continuous wave white light as the photoexcitation source, we have studied the photoconductivity of vertically aligned TiO₂ nanorod array at room temperature by THz Differential Time-domain Spectroscopy (DTDS). Frequency dependent conductivity, power absorption and optical dispersion are measured over the frequency range of 0.4–2.5 THz. The measured complex conductivity is deviate significantly from simple drude model but well fit by Smith model.

Note: Coffee and cookies available at 2:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, September 6-10, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

The detection of improvised explosive devices (IEDs), and chemical and biological agents is one of the biggest challenges in defense and homeland security. The terahertz (THz) spectral region offers much promise for detection, imaging, and security. The THz spectral region has high spatial resolution compared to microwaves, good transmission through loose fitting clothing, is non-ionizing radiation, and allows short-range atmospheric transmission. Rotational and vibrational resonances of explosive, chemical and biological threat molecules fall in the THz spectral region, enabling applications such as security screening and detection of hidden explosives, weapons, and chemical and biological agents. The talk will cover recent research that lays the groundwork for developing integrated THz photonic devices and sensors for trace molecular detection of toxic, explosive and dangerous chemical and biological agents.

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, September 13-17, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

I will review the status of Ion Trap Quantum Computing and describe the latest experiments in which deterministic teleportation of the quantum state of a qubit was demonstrated for the first time.

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 NanoNet Informal Seminar:

Abstract:

An individual single-walled nanotube is remarkably like an individual polymer molecule. Both can have dimensions on the order of 1 nanometer or less, and both have extremely high aspect ratios. This talk will focus on how the introduction of carbon nanotubes can alter the crystallization kinetics of a polymer, and speculate how morphologically nanotubes might interact with polymer crystals. Specifically, nanotubes have been shown to nucleate crystallinity in a number of different polymers. Some other nanotubes can have on certain polymers, such as substantial rheology changes and degradation enhancement will also be discussed. We will also discuss some seemingly anomalous results regarding the interaction of nanotubes with polypropylene, specifically that the qualitative effect of adding nanotubes on mechanical properties depends on the molecular weight of the host matrix.

Note: Coffee and cookies available at 2:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, September 20-24, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

We present an overview of the proposals to produce two and multiparticle quantum entanglement. We note that the quantum entanglement, besides shading light on many fundamental issues in quantum theory, is finding newer and newer applications such as in imaging, lithography and information processing. We show how various quantum optical ideas can be used to produce quantum logic operations. We describe the implementation of these ideas in the context of cavity QED with neutral atoms and ion traps.

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, September 27-October 1, 2004

Quantum Optics Seminar:

Abstract:

Recently, in a series of elegant experiments, two different groups have observed that a sequential Raman emission process generates highly correlated pair of Stokes and anti-Stokes photons^1,2. We will present a calculation on the quantum correlation between such a pair using master equation—that includes all realistic radiative and non-radiative decays. The correlation function shows photon-antibunching, and a damped sinusoidal behavior with respect to the time delay between the measurements of the two photons. This method yields the photon correlation between the pair for arbitrarily strong excitation fields and detunings. We will briefly discuss its applications to quantum microscopy and lithography.

1. A. Kuzmich et al., Nature 423, 731 (2003);
   C. W. Chou et al., Phys. Rev. Lett. 92, 213601 (2004).
    
2. C. H. van der Wal et al., Science 301, 196 (2003).

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 3.30 PM. All students are welcome! Refreshments will be served.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Although we've been measuring the structure of the proton for decades, the strange content of the proton (until recently) had large uncertainties. Recent data from charged current DIS charm production provide new information on the strange-quark PDF, as well as the difference between the strange quark and anti-quark distributions. We review the various data sets which are included in the global analysis, and examine the influence on the strange PDF. We also review some of the recent theoretical advances implemented to deal with heavy quark production, which is crucial to the proper theoretical treatment of this data. We also note that these results have a direct impact on the QCD corrections to the Paschos-Wolfenstein relation which is used in the precision determination of the Weinberg angle.

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 NanoNet Informal Seminar:

Abstract:

Control of the position and orientation of ensembles of nanowires is important for engineering working devices from nanometer sized materials. Gold islands, vapor deposited with microsphere lithography patterning, are used to nucleate arrays of ZnO nanorods during chemical vapor deposition. Gold films are vapor-deposited on ordered polystyrene microsphere lithographic masks and the microspheres are removed, producing arrays of gold nanoparticles. ZnO is grown on the resulting substrates by carbothermal reduction in a tube furnace, using a carrier gas that has passed through a water bubbler. Clusters of ∼30 nm diameter ZnO nanorods nucleate from the Au nanoparticles and grow around the nucleation sites by the vapor-liquid-solid (VLS) mechanism. Growth on nonepitaxial silicon and the epitaxial a-plane of sapphire is compared, and indicate that the growth direction is influenced by the substrate lattice and the presence of nearby neighbors.

Note: Coffee and cookies available at 2:15 in PS 147.

Oklahoma State Physics Department

Seminars and Colloquia, October 4-8, 2004

Seminar Series on Control and Related Techniques:

Abstract:

The talk will present a brief overview of the projects developed by the Radiation Dosimetry Laboratory (Physics Department) in the area of detection of radiation and radioactive sources using the Optically Stimulated Luminescence technique. Typical data and the problems associated with real-time or “near“ real-time detection will be discussed. Integration of the sensors in a network is a desirable feature in most of the potential applications, but there are still technical challenges to be overcomed.

Physics Colloquium:

Abstract:

Bose–Einstein condensation (BEC) is a quantum state of matter predicted in the 1920s and first realized in a dilute atomic gas by Cornell and Wieman in 1995. In a BEC the atoms lose their individual identities and behave as a single wavefunction. In effect they become a “superatom”. BEC is important because it allows the investigation of quantum mechanics on a macroscopic scale. With a BEC it is possible to create situations which were previously just theoretical concepts. In this talk I will describe what a Bose–Einstein condensate is, why there is so much interest in creating it, and how we go about making BEC at OSU.

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.

Southwest Mechanics Lecture Series Presentation:

Abstract:

The higher transistor densities and switching speeds accompanying the rapid migration of microelectronics into nanoelectronics have led to steep increases in heat flux and power dissipation. Without more aggressive thermal management techniques, nanoelectronic chips will have rising average temperatures and more local hot spots with sharp temperature gradients. These changes may result in accelerated failure rates and overall losses in IC reliability and performance. This lecture will begin with an overview of the industry roadmap for IC technology and a discussion of the primary thermally-driven failure mechanisms and future thermal management needs for nano-scaled semiconductor devices. Attention then will be turned to the “thermal frontier” associated with state-of-the-art electronic cooling techniques and the research required to address the challenges implicit in the commercialization of nanoelectronics. Examples from research underway at the University of Maryland will be used to illustrate these points. Solid-state refrigeration, dielectric liquid pool boiling and spray cooling, two-phase microchannel coolers, and high performance heat sinks are among the techniques that will be discussed.

Note: Refreshments at 11:15.

Note: Avram BarCohen is Professor and Chair of Mechanical Engineering at the University of Maryland. He earned his Ph.D. at MIT and began his career in industry at Raytheon and then Control Data. He has held academic positions at Ben Gurion University, MIT, the Naval Postgraduate School, and the University of Minnesota, and now continues his research in the thermal management of Micro/Nano systems at Maryland. He is the co-author of two important books on heat sinks and thermal control of electronics. He has co-edited 13 books in this field, has authored and co-authored some 250 refereed papers and book chapters, and has delivered nearly 50 invited lectures He currently is Editor-in-Chief of the IEEE Transactions on Components and Packaging Technologies. Prof. Bar-Cohen received the 2001 IEEE CPT Society Outstanding Sustained Technical Contributions Award and the 2000 ASME Worcester Reed Warner Medal. He also has been recognized with the ASME Heat Transfer Memorial Award, the ASME Curriculum Innovation Award, the ASME/IEEE ITHERM Achievement Award, the ASME Edwin F. Church Medal, and the THERMI Award from the IEEE/Semi-Therm Conference. He is a Fellow of ASME and IEEE.

Journal Club on Statistical Mechanics and Condensed Matter Physics:

Special Lecture:

Abstract:

The varied interests of Leonardo da Vinci in the arts and sciences were knots of a magnificent tapestry. Uncovering the internal dynamics of each of these interests and establishing the connections between them were Leonardo’s quest, and systematic experimentation his method. Ultimately, in every aspect of his life, he was operating as the consummate scientist. And it was the cross-fertilization of ideas and their seamless integration that led to many of his astonishing achievements. See the author’s web site, http://users.mwc.edu/~batalay/SITE/, for more information. The author will sign copies of his book immediately following the lecture.

Remarks: Sponsored by Departments of Art, Mathematics and Physics, and by the da Vinci Institute.
Contact: Dr. Bruce Ackerson, Department of Physics, Phone: 405-744-5819.

Oklahoma State Physics Department

Seminars and Colloquia, October 11-15, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Moved to Tuesday, October 19, due to conflict with Fall Convocation.

No talks on Friday as we have a retirement reception for Dr. Smith Holt, former Dean of Arts & Sciences.

Oklahoma State Physics Department

Seminars and Colloquia, October 18-22, 2004

Microbiology & Molecular Genetics Colloquium:

Refreshments will be served at 3:30 by Dr. Kim Burnham’s lab. Please bring your own cup.

High Energy Physics Seminar:

Physics Colloquium:

Abstract:

Proteins are the main functional molecules in biology, and consist of linear chains of amino acids. The principles that govern the conversion of genetic material into amino acid sequences are well known. In contrast, the principles that underlie (i) the spontaneous folding of these sequences into their native three-dimensional shape and (ii) the activity of the folded proteins remain largely unknown. We use the bacterial blue-light receptor photoactive yellow protein (PYP) as a model system to identify principles on aspects of protein function: (1) We found that partially unfolded states of PYP exhibit functional properties. This challenges the central notions that only fully folded proteins are functionally active. (2) Many proteins undergo conformational changes during their function. We propose that proton transfer resulting in a destabilizing buried charge in the protein interior is a general mechanism for triggering structural changes in proteins. (3) Proteins that interact with visible light, such as the rhodopsins in our eyes, bind light-absorbing cofactors and modulate the absorption spectrum of these cofactors. It is generally believed that the main contribution to this spectral tuning effect is a change in the energy gap between the electronic ground and excited states. We show that proteins can also perform spectral tuning by altering the shape of the excited state energy surface without changing the energy gap. (4) We performed single molecule atomic force microscopy experiments on the mechanical unfolding of long chains of PYP molecules in the presence and absence of illumination. By pulling across different segments of PYP, we derive a section of the anisotropic, structure-based energy landscape for its stability and function. Future prospects of using PYP to identify general principles in the biophysics of protein function will 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.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Some recent developments has endowed theoretical scenarios with extra spatial dimensions with observable consequences that can be tested in high-energy accelerator experiments. This talk will provide a review of such developments at a non-technical level, describing the motivations and basic structure of such theories, and emphasizing how some seemingly abstract theorization can culminate in predictions that we shall be ready to test 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.

Joint Chemistry, Physics & OSU NanoNet Seminar:

Abstract:

It is demonstrated that the nonlinear optical phenomenon, Second Harmonic Generation, in combination with ultrahigh vacuum surface science techniques, can be used to probe the growth mechanism and structure within thin films of nanometer thickness made of organic molecules. A study of prototypical systems such as pyridine and aniline films provides fundamental understanding of the relationship between intermolecular interactions and the growth, structure and properties of the ultra-thin molecular films. It has been demonstrated that the orientation and alignment of molecules in the interfacial layer between the film and the solid surface can be determined and that the structure of this interfacial layer affects the growth of the film. The nucleation process, with the critical-size molecular cluster depicted by temperature and intermolecular interaction, is shown to be deterministic for the deposition and growth of the molecular film on surface. The size of the critical nuclei (molecular clusters) can be determined by the SHG technique. And the classical nucleation theory is shown to be effective for quantitative description of the nucleation process of weakly bound molecular systems.

Note: Refreshments at 2:00 PM in PS 117.

Oklahoma State Physics Department

Seminars and Colloquia, October 25-29, 2004

Fall Break Monday-Tuesday

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Joint Physics & Chemistry Colloquium:

Abstract:

Proteins contain acidic and basic residues which would be ionized in aqueous solution. The Born solvation energy stabilizes charges in water. By having charged groups on their surface helps proteins remain soluable. A small, but significant number of ionizable residues are buried in the protein. I will describe how electrostatic analysis can be used to calculate the equilibrium ionization state of these residues by computing the interactions amongst charges and dipoles in the protein. In addition, I will describe how these buried acidic and basic groups function in pumping protons (H⁺) across cell membranes in proteins such as bacteriorhodopsin.

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 NanoNet Informal Seminar:

Abstract:

Metal sulfide thin films and nanoparticles are prepared from the low temperature (<150°C) thermal decomposition of metal alkyldithiocarbonates. For instance, decomposing nickel ethyldithiocarbonate (xanthate) powder that is pressed between two glass plates yields a mirror-like thin film of metallic nickel sulfide. When the decomposition of a metal xanthate precursor is carried out in dimethyl sulfoxide (DMSO), the result is a capping of the metal sulfide particles with a metal-DMSO complex. A high degree of sulfide size tunability is achieved by varying the heating time and precursor concentration. For example, fluorescent ZnS-DMSO particles were prepared in the range of approximately two to 60 nm. Infrared spectra recorded for the capped metal sulfides yielded peaks that are indicative of a metal-DMSO complex. The mechanism of thermal decomposition and the use of alkylxanthate precursors to produce a variety of useful metal sulfide materials, such as photovoltaic cells or light emitting diodes will be discussed. Particle size analyses were performed using dynamic light scattering, X-Ray powder diffraction, scanning electron microscopy, and transmission electron microscopy.

Oklahoma State Physics Department

Seminars and Colloquia, November 1-5, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Prolonged exposure to ionizing radiation is one of the most significant obstacles to the establishment of a permanent base on the moon or a human mission to Mars. Space crews traveling aboard interplanetary spacecraft or living and working on the moon will be exposed to a constant flux of galactic cosmic rays (GCR) and to rare, but intense fluxes of charged particles during solar particle events (SPEs). In order to keep mission costs at acceptable levels, while simultaneously minimizing the risk from radiation to astronaut health and safety, a judicious use of optimized shielding materials will be required. Three linked research projects are currently underway to characterize the space radiation shielding properties of different materials and to develop and test new materials with shielding properties superior to Al currently used in spacecraft.

The objective of the first project, BEAMS: Benchmark Evaluations and Analysis of Materials for Shielding, is to provide a comprehensive set of thick target “benchmark” measurements for use in testing, validation, and assessing the accuracy of space radiation transport codes currently under development by NASA. The measurements are made behind targets including high density polyethylene (HDPE), Al and Cu, ranging in thickness from 0.5 to >30 g/cm², during heavy ion and proton exposures at the BNL NASA Space Radiation Laboratory, the Japanese HIMAC heavy ion accelerator and the proton therapy synchrotron at Loma Linda University Medical Center.

In the second project, MMARSS: Multifunctional Materials Analysis of Radiation Shielding for Spacecraft, novel materials with low average atomic mass, high hydrogen content, and mechanical and thermal properties conducive toward their use in spacecraft are being developed and tested. The shielding properties of the novel materials, as well as novel materials currently being developed by other laboratories, are characterized during heavy ion and proton exposures, and compared to results from similar thicknesses of HDPE and Al.

The third project, Space Radiation Shielding Testing Using the NASA Deep Space Test Bed, will involve the characterization of standard and novel radiation shielding materials exposed to the deep space radiation environment during flights of an Antarctic circumpolar balloon. An important feature of the current effort is that the radiation detectors used in making the measurements—CR-39 plastic nuclear track detector (PNTD), tissue equivalent proportional counter (TEPC), thermoluminescent detector (TLD) and the Liulin-4 portable Si spectrometer—are the same detectors used for space crew dosimetry aboard ISS, the NASA Space Shuttles and potentially aboard future interplanetary spacecraft.

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, November 8-12, 2004

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Abstract:

It is well known that some of the most stringent constraints on extra dimensional theories comes from the effects overproduction of massive Kaluza-Klein gravitons can have on the evolution of the universe (and the cosmological parameters as measured today). We review these constraints, and point out that in certain situations the decays of these heavy KK gravitons can be quite important, allowing a larger portion of the parameter space of the theory to be consistent with today's universe.

Physics Colloquium:

Abstract:

The goal of the presentation is to describe the latest advances of Landauer/Stillwater R&D group in engineering of luminescent crystal and to attract prospective graduate students to work in crystal research and development of new applications.

Deep understanding of the crystal growth process, point and aggregate defect formation allowed us to develop new highly efficient Al₂O₃ luminescent crystals for solid state radiation dosimetry and high capacity volumetric optical data storage. The presentation will describe a completely new technique of 3D optical, non-destructive imaging of tracks produced by individual high energy ions in fluorescent crystals. It provides a new way to detect and assess doses from heavy charged particles and neutrons. The technique combines confocal fluorescent microscopy with a new radiation-sensitive, luminescent material based on aluminum oxide single crystals doped with carbon, magnesium and having aggregate oxygen vacancy defects (Al₂O₃:C,Mg).

The single crystal disks and confocal fluorescent detection scheme were used to demonstrate volumetric optical data storage with expected data capacity of 1 to 5 TB per standard 120 mm disk. The latest results obtained from our static and dynamic test stands will be presented.

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.

Chemistry Department Seminar:

Abstract:

Nanoscale manipulation of components has the potential to increase the performance of complex macroscale systems. For instance, we have shown in our laboratory that confinement of polymer electrolyte materials in nanoscale pores can greatly enhance ion conduction, which is necessary for these materials to find wide technological application in such systems as batteries and fuel cells. Understanding properties such as ion conduction at the micro or nanoscale, such as in nanosize channels, is very important from a fundamental science point of view and can be of great importance in comprehending similar properties at the macroscale. Recently we have used scanning probe a.c. impedance spectroscopy, which allows direct impedance measurements at localized sites the size of an AFM cantilever tip, to examine nanoscale conduction behavior in polymer electrolytes. The surface of electrolytes and the interface created with electrolyte/electrode contact is of considerable importance in understanding power system behavior. By using this AFM technique we are able to sequentially image the surface and then measure the resistance across various regions of the solid electrolyte surface. The localized nature of this technique allows clear differentiation between highly conductive amorphous regions and less conductive crystalline regions of the film. The combined AFM-impedance technique also makes it possible to monitor events such as water adsorption and absorption at the nanoscale and to distinguish the impedance behavior between bulk and surface water. Enhanced ion conduction on polymer electrolytes in nanosize channels and the use of scanning probe a.c. impedance spectroscopy to better understand the mechanism of ion conduction will be discussed in more detail.

Note: Refreshments at 3:00 p.m., PS 117.

Oklahoma NanoNet Informal Seminar:

Cancelled.

Oklahoma State Physics Department

Seminars and Colloquia, November 15-19, 2004

Quantum Optics Seminar:

Abstract:

Group velocity manipulations have become an interesting area of research recently. Both subliminal and superluminal group velocities have been achieved in a variety of systems ranging from Bose-Einstein Condensates, hot atomic gases, and both cooled and room-temperature solids. Sub and superluminality require different physical conditions, thus they have been demonstrated in different physical systems and conditions. Nevertheless, there have been theoretical proposals to achieve a tunable control of the group velocity by the groups of Agarwal [Phys. Rev. A 65, 053809 (2001)] and Friedman [Phys. Rev. A 63, 043818 (2001)] in a single physical system. We recently proposed [Phys. Rev. A 70, 023813 (2004)] a strategy to use phase of a control field in an extended lambda type system to tune the group velocity of a weak probe pulse over a wide range. This allows us to switch from subluminality to superluminality and back in a single essentially Doppler-free system.

(No speaker chat will take place at this seminar.)

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Biological systems are daunting in their complexity. Frequently, however, collective coordinates can be found which exhibit simple bi-stability. Combining detailed calculations with comparative (evolutionary) analysis over hundreds or thousands of naturally occuring examples allows detailed mechanistic understanding and functional differences to emerge in parallel. We examine in detail the importance of quantum chemistry, explicit-solvent molecular dynamics simulations, and native-state bias molecular dynamics simulations to the functions of protein kinases, heme proteins, and PAS domain proteins, respectively. We close with an examination of the general host-pathogen relationship and how comparative modeling of proteins can contribute to this understanding, illustrating the discussion with models of gp41 / gp120 and the HIV vaccine design problem.

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 (Informal):

Oklahoma State Physics Department

Seminars and Colloquia, November 22-26, 2004

Thanksgiving

Oklahoma State Physics Department

Seminars and Colloquia, November 29-December 3, 2004

Physics Seminar:

Abstract:

Galaxy clusters are the largest gravitational structures of the universe, featuring hundreds of galaxies and an X-ray emitting diffuse (~10^-3 cm^-3) intergalactic medium. Nearly ten years ago a puzzling new discovery revealed that galaxy clusters emit substantially more soft X-ray radiation (~0.1-1 keV) than expected from the hot intra-cluster medium at T~10⁷-10⁸ K. Possible interpretations for the “soft excess” emission are diffuse warm gas (T~10⁶ K) and non-thermal inverse-Compton radiation. Recent X-ray observations with XMM-Newton reveal that the emission is likely thermal in nature, and indicative that galaxy clusters host a significant reservoir of previously undetected “warm” baryons.

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Abstract:

The source of the UHE cosmic rays is expected to be changing from galactic to extragalactic sources in the energy decade above 10¹⁷eV, an energy range known as the Second Knee. This change in the source of the cosmic rays should manifest itself in a change in the composition of the cosmic ray primaries, changing from heavy (iron) to light (protons). I will present a preliminary new analysis from the High Resolution Fly's Eye Experiment which attempts to observe the change in composition in this region.

Joint Chemistry, Physics and NanoNet Seminar:

Refreshments are served at 3:00 p.m., in room PS 117

Dr. Inga Musselman is Associate Professor of Chemistry at the University of Texas at Dallas. Her major research interests are in surface analysis, particularly scanning tunneling microscopy and atomic force microscopy with applications to polymers and composite microstructures.

Oklahoma State Physics Department

Seminars and Colloquia, December 6-10, 2004

Prefinals Week

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Oklahoma State Physics Department

Seminars and Colloquia, December 13-17, 2004

Finals Week

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, December 20-24, 2004

No talks scheduled

Oklahoma State Physics Department

Seminars and Colloquia, December 27-31, 2004

No talks scheduled

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