Seminars and Colloquia, January through June, 2005

• This Week's schedule.
• Earlier Semesters.
• Typical Week's schedule.
• January 3-7, 2005's schedule.
• January 10-14, 2005's schedule.
• January 17-21, 2005's schedule.
• January 24-28, 2005's schedule.
• January 31-February 4, 2005's schedule.
• February 7-11, 2005's schedule.
• February 14-18, 2005's schedule.
• February 21-25, 2005's schedule.
• February 28-March 4, 2005's schedule.
• March 7-11, 2005's schedule.
• March 14-18, 2005's schedule.
• March 21-25, 2005's schedule.
• March 28-April 1, 2005's schedule.
• April 4-8, 2005's schedule.
• April 11-15, 2005's schedule.
• April 18-22, 2005's schedule.
• April 25-29, 2005's schedule.
• May 2-6, 2005's schedule.
• May 9-13, 2005's schedule.
• May 16-20, 2005's schedule.
• May 23-27, 2005's schedule.
• May 30-June 3, 2005's schedule.
• June 6-10, 2005's schedule.
• June 13-17, 2005's schedule.
• June 20-24, 2005's schedule.
• June 27-July 1, 2005'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, January 3-7, 2005

No talks scheduled: Prelim Exams

Oklahoma State Physics Department

Seminars and Colloquia, January 10-14, 2005

First Week of Classes

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Modern theory of particle physics, the Standard Model, offers a remarkably successful description of phenomena at subatomic scales. A key ingredient of the model is the postulated existence of a Higgs field which is believed to permeate the universe. Fundamental particles acquire mass through their interactions with the quanta of this field, the Higgs boson. This picture, and consequently the Standard Model, will ruin, or triumph, depending on the outcome of experimental searches. Since Higgs boson can be produced at high energy accelerators, the primary goal of research there is to find it.

This talk will discuss the modern particle physics experiments that are specifically designed to maximize potential for the Higgs boson discovery. The status of searches at the Tevatron (Fermi National Laboratory), the world's highest energy accelerator in operation, as well as prospects at future, even more powerful accelerator under construction at CERN (European Organization for Nuclear Research) will be summarized.

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

Oklahoma State Physics Department

Seminars and Colloquia, January 17-21, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Special Physics Colloquium:

Abstract:

The “Standard Model” (SM) of particle physics has been spectacularly successful at describing matter under all conditions from seconds after the Big Bang until the present. The SM unifies two of the canonical four forces of nature (Electromagnetism and the weak force). The so called Electroweak force is of particular interest. Study of this force is a high priority in the Tevatrons experimental program. This talk will describe our knowledge of the Electroweak force, it’s history, our present efforts and the future prospects.

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:

Abstract:

We discuss recent (B physics) results from the D0 experiment at Fermilab. The results presented here correspond to an integrated luminosity of ≈ 200-440 pb⁻¹ of data collected at the Tevatron, between April 2002 and August 2004, at a center of mass energy (of pp collisions) of 1.96 TeV.

Physics Colloquium:

Abstract:

One of the more interesting topics in B physics is the phenomenon of Particle-Antiparticle oscillations, where a particle, e.g., B⁰ changes into a B⁰ (and back into a B⁰) as it propagates. I will briefly review this topic and explain how such measurements can be used to extract fundamental parameters relating to interactions between quarks. I will also discuss the status of these measurements using the D0 detector operating at the (world's highest energy) Proton-Antiproton Collider at the Fermi National Accelerator Laboratory.

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

Oklahoma State Physics Department

Seminars and Colloquia, January 24-28, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Special Physics Colloquium:

Abstract:

The Standard Model (SM) of particle physics suggested by theorists in the late sixties to combine strong and electroweak forces has been found to be extremely successful. The SM states that the matter consists of six types of leptons and six types of quarks. The last quark—top quark—was discovered at the Tevatron in 1995. Only a few dozens of events with top quarks were produced in Run I, so it was difficult to study top quark properties with a good precision. Now at the Tevatron the second round of studies started, and we have large sample of top quark events to do precision measurements. The main questions are: “how frequently it is produced?” and “how does it decay?”. Any deviations from the SM predictions in both production rate of top quarks and its decay channels would indicate a presence of new physics, like supersymmetry. I will discuss the place of top quark in high energy physics, and how to identify and study top quarks. I will present results on measured cross section and decay properties of top quark obtained in D0 experiment.

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.

Physics Colloquium:

Abstract:

Just-in-Time Teaching (JiTT) is a pedagogical strategy that leverages the power and convenience of the web technology to improve student learning, understanding, and attitudes. JiTT courses build feedback loops between pre-class preparations by students and faculty and in-class sessions that meet the students where they are to help them move forward. The basic idea is this: Before class, students complete short but carefully constructed web-based assignments related to the upcoming class topics. These assignments, often called “WarmUps” or “Preflights,” generally have the students read relevant textbook sections and reflect and draw on prior knowledge to answer the questions. The students submit their answers electronically, often just hours before class. Before class, the faculty member reads the student submissions, looking for students’ levels of understanding, troublesome areas, common approaches, and probing for any required underlying skills and/or background. Armed with these insights, the faculty member tailors the classroom session activities “just-in-time” to make the best use of the classroom face-to-face time.

The talk will first describe JiTT in some detail, relying on numerous examples from physics and other disciplines to illustrate how it works and its flexibility. Use of JiTT in introductory, upper division, and even graduate courses will be discussed. The talk will also provide background and grounding from extensive cognitive science and education research that suggests reasons why JiTT should be effective in helping students (and faculty!) learn.

JiTT has garnered considerable attention and recognition in various pedagogical circles and communities, and attracted considerable funding from NSF and other agencies. As of mid 2004, JiTT had been adopted by a few hundred faculty from over 100 institutions and spanning some two dozen different disciplines, so while this talk will focus on JiTT in physics, the topic has broad applicability. This talk is intended to be relevant to essentially any faculty member interested in having students come to class better prepared and motivated and in trying to help students learn more deeply and substantively.

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 Seminar:

Abstract:

A new sol-gello method was developed for the synthesis of spinel (MgAl₂O₄) and calcium phosphate. Spinel can be formed directly by combining Al₂O₃ and MgO, but this method is expensive and demands temperatures of 1450-1600°C. In our approach, magnesium and aluminum salts are added to gelatin, ensuring that the metal ions are trapped in a homogeneous distribution. The gelatin content controls the particle size, product reactivity, and microstructure. Ammonia is subsequently used to hydrolyze the gels creating amorphous solids. The amorphous solids are then converted to spinel nanocrystalline phases at relatively low temperature. Preliminary results have shown that the spinel phase appears in the low and high-gelatin content amorphous solids at a temperature as low as 420°C. Calcium phosphate, a bioceramic material, is formed when a calcium salt and phosphoric acid are added to the gelatin. The same method of ammonia hydrolysis and heating used in spinel synthesis is implemented in the calcium phosphate preparation. Preliminary results show the calcium phosphate nanocrystalline phases form within the gelatin matrix. The synthesis of spinel and calcium phosphate with this method will be discussed.

Oklahoma State Physics Department

Seminars and Colloquia, January 31-February 4, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

“It is not sufficiently realized that Einstein's thesis is one of his most fundamental papers . . . It had more widespread application than any other paper Einstein ever wrote. Of the eleven scientific articles published by any author before 1912, and cited most frequently between 1961 and 1975, four are by Einstein. Among these four, the thesis …… ranks first.”
—Abraham Pais

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

Oklahoma State Physics Department

Seminars and Colloquia, February 7-11, 2005

Southwest Mechanics Lecture Series:

Abstract:

The Moody Diagram has been used to estimate frictional losses in smooth and rough pipes since it was first proposed in 1944. Recent experiments at Princeton in fully-developed turbulent pipe flow have shown that many of the assumptions made in deriving this engineering guide are not correct. In particular, a detailed study of the velocity profile in a smooth pipe at very high Reynolds numbers has led to an improved correlation for the smooth pipe friction factor, and a careful examination of the behavior for rough surfaces demonstrates the shortcomings of the friction factor correlation used by Moody for traditionally rough surfaces.

This should be a very interesting presentation based upon experiments conducted in the Superpipe facility at Princeton. His web site is at: http://mae.princeton.edu/index.php?app=people&id=5.

Refreshments at 2:15 PM. Further information: (405) 744-5900.

Joint Physics, Chemistry, ECEN & Nanonet Colloquium:

Abstract:

Femtosecond optical excitation of semiconductors leads to the creation of coherent phonon and (for energies greater than the bandgap) carrier populations. Depending on the details of the material’s band structure, such excitations can give rise to a time varying polarisation and the coherent emission of few cycle electromagnetic transients. Typically the frequency of this radiation, which is analagous to Bremsstrahlung, spans the far and mid infrared spectral regions, say 0.3-30 THz, 10 μm – 1 mm. Extremely sensitive coherent detection techniques based on photoconductive or electro-optic detection allow the study of such radiation with a time resolution in the range 10 fs – 1 ps. From this it is possible to obtain information about the transient transport, population decay, wavepacket evolution, and the way in which optically excited carriers and photons couple to phonons and extrinsic carriers. In this talk I shall give an overview of some of the experiments that we have performed in the far infrared, where the experimental techniques are well developed, to illustrate the techniques and what can be learned from them and discuss recent developments on photoconductive time domain detection at up to 50 THz which provides the technology for experiments in the mid infrared.

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

Oklahoma NanoNet Seminar:

Abstract:

Atomic force microscopy (AFM) was employed to characterize the surface chemistry distribution on individual polystyrene latex particles. The particles were obtained by surfactant free emulsion polymerization and contained hydrophilic quaternary ammonium chloride, sodium sulfonate, or hydroxyethyl groups. The phase shift in dynamic force mode AFM is sensitive to charge/chemical interactions between an oscillating AFM tip and a sample surface. In this work, the phase imaging technique distinguished phase domains of 50 – 100 nm dimensions on the surfaces of dried latex particles in ambient air. The domains are attributed to separation of ion-rich and ion-poor components of the polymer on the particle surface.

Oklahoma State Physics Department

Seminars and Colloquia, February 14-18, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

No colloquium this week. Instead special presentation of Department Head.

Journal Club on Statistical Mechanics and Condensed Matter Physics:

Oklahoma State Physics Department

Seminars and Colloquia, February 21-25, 2005

Public Lecture:

Abstract:

How has the most celebrated scientific theory of the 20th century held up under the exacting scrutiny of planetary probes, radio telescopes, and atomic clocks? After 100 years, was Einstein right? In this lecture, celebrating the 100th anniversary of Einstein’s “miracle year” and the World Year of Physics, we relate the story of testing relativity, from the 1919 measurements of the bending of light to the 1980s measurements of a decaying double-neutron-star system that reveal the action of gravity waves, to a 2004 space experiment to test whether spacetime “does the twist”. We will show how a revolution in astronomy and technology led to a renaissance of general relativity in the 1960s, and to a systematic program to try to verify its predictions. We will also demonstrate how relativity plays an important role in daily life.

Special Physics Seminar:

Physics Colloquium:

Abstract:

For the last decade atomic interference phenomena such as electromagnetically induced transparency, lasing without inversion, and slow light have formed fast developing field of research in quantum optics and atomic physics. I will give an introduction into this field of research and overview the major results.

The central part of my talk will be focused on the possibility to realize the similar phenomena in gamma-rays at the nuclear transitions. I will show how the resonant driving of the electronic transitions in atoms can indirectly influence gamma-ray nuclear transitions through the different types of hyperfine interaction leading to drastic modifications of the Mössbauer spectra: vanishing and appearance of the new lines as well as broadening or narrowing, shifts or splittings of the original lines.

I will desribe the preliminary results of our first experiments demonstrating modification of the Mössbauer spectra in Eu³⁺:Ca2F and Fe²⁺:MgS under the action of laser radiation. Finally, I will discuss our further experimental program and possible applications of the novel effects, including the laser-Mössbauer spectroscopy of the nuclear transitions, quantum information storage and resolution of the gamma-ray laser dilemma.

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 Seminar:

Abstract:

The nitro organic herbicide 2,4-Dinitro-o-Cresol (DNOC), the targeted herbicide for this project, has been reported to be highly mobile in soil and is only subject to slow microbial degradation. Large quantities of DNOC along with other herbicides and pesticides are introduced into aquifers by agricultural run-off and can profoundly impact wildlife and drinking water quality. The materials used in the past for the adsorption of dinitrophenol herbicides from water such as activated carbon and clay minerals can be time consuming due to slowness of separation of the clays. Therefore, the main goal of this project is to use novel magnetic-nano materials in the adsorption of (DNOC) that allow fast separations via magnetic filtration. A new family of fine magnetic nanoparticles was prepared using iron(III) hydroxide caprylate, iron(III)-Ni(II) hydroxide caprylate, iron(II) stearate and iron(II)-Ni(II) stearate precursors. Suspending the precursors in tetralin and heating the mixture at 210°C under helium atmosphere for 12 hours yielded α-Fe₂O₃ and nickel ferrite nanoparticles capped with caprylate and stearate groups. The resulting nanoparticles have proven effective in the rapid and easy extraction of DNOC from water. Thus, they can be used in the separation of other dinitrophenols and organic compounds by the same technique.

Oklahoma State Physics Department

Seminars and Colloquia, February 28-March 4, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Postponed

Oklahoma State Physics Department

Seminars and Colloquia, March 7-11, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Our whispering-gallery quantum-dot microlasers have a number of unconventional properties. These atypical properties make the interpretation of our experimental results rather challenging. Furthermore, they are requiring us to develop an understanding of precisely what conditions must apply in order for the process of light emission (from an excited medium within an optical resonator) to be called lasing. In this talk, I will present a summary of the various characteristics of lasing that we are being led to consider. I will review some of our experimental results, with an emphasis on unusual properties such as ultralow threshold pump power (less than 200 nW). Then I will discuss how the basic characteristics of laser emission relate to our whispering-gallery-mode system and to our observations of its behavior. Finally, I will comment on what we might learn from further investigation of our microlasers.

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 and Oklahoma Nanonet Seminar:

Abstract:

The ordering and purity of the interfaces produced in modern deposition processes becomes more and more important for the design of contemporary and future devices. Here, a spectroscopic approach based on a combination of multiple internal reflection Fourier-transform infrared spectroscopy (MIR FT-IR) with other surface characterization and depth-profiling techniques will be utilized to understand the ordering processes on Si(100)-2x1 surfaces and the effects of the monolayer chemistry on the nucleation and growth of thin films. The driving forces for ordering of the stoichiometric amounts of H and I on Si(100)-2x1 surface will be discussed first. A possibility to utilize adsorption at cryogenic temperatures to selectively order bifunctional molecules on this surface and to influence the properties of the surface itself will be presented next. Finally, interaction of atomic hydrogen with TiCN films produced by CVD schemes and hydrogen diffusion towards the TiCN/Si interface will be addressed.

Note: Refreshments at 3:00 PM, in room PS 117.

Oklahoma State Physics Department

Seminars and Colloquia, March 14-18, 2005

Spring Break

Oklahoma State Physics Department

Seminars and Colloquia, March 21-25, 2005

APS March Meeting

Physics Colloquium:

Abstract:

The “particle in a box” is at the heart of quantum mechanics and is a paradigm for many problems in physics. In this talk, I will describe recent experiments conducted by my group which confine a Bose–Einstein condensate to a one-dimensional optical box. These conditions should enable the experimental realization of a “quantum tweezer” for atoms and allow preparation of atomic number states. More generally, we have demonstrated the capability to measure atom statistics by single-atom counting, paving the way for the new field of quantum atom optics.

The concept of a “particle in a box” is also widely used in thermodynamics. The historic paradox of Maxwell’s demon suggested a way to cause particles to accumulate in one side of the box, in an apparent violation of the Second Law. Motivated by these ideas we have developed a method to form an optical “one-way” barrier for atoms. This device would allow atoms coming from one side of the barrier to pass through, but those coming from the other side to be reflected. I will show how this idea can be used for phase space compression and cooling, as an optical realization of Maxwell’s demon.

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 and Oklahoma Nanonet Seminar:

Abstract:

Protein-surface interactions are important in a number of areas including the biocompatibility of implants, biosensor development, and affinity chromatography. An understanding of the influence of the substrate surface chemistry on orientation and conformation (and therefore activity) is crucial for making improvements in materials for any of these applications by rational design. We have therefore begun a series of studies aimed at developing a detailed understanding of the influence of the chemistry and structure of the substrate on protein adsorption.

The interactions of the plasma protein fibrinogen with surfaces have been studied using atomic force microscopy (AFM). Specifically, well-characterized model substrates have been used to investigate the effect of surface chemistry and structure on the adsorption of fibrinogen. Dramatic differences in the average size and shape of fibrinogen molecules adsorbed to hydrophobic and hydrophilic substrates have been observed.[1] These changes can be readily seen in AFM images of individual molecules with sub-molecular resolution. The differences have been quantified and correlated with the surface chemistry. The influence of the structure of the substrate is also investigated. We have observed clustering of molecules at steps on graphite substrates and a clearing of molecules near the step edges while on a chemically similar self-assembled monolayer surface, the distribution of molecules on the surface appears quite uniform.

In addition to investigating the influence of atomic level steps, new methods for patterning nanostructured substrates for use in these experiments have been investigated on a variety of substrates including silicon and mica.[2] Using these patterning techniques, the surface chemistry and topography can be varied in a controlled way on the nanometer length scale. Methods for chemically functionalizing AFM probe tips in order to obtain information beyond topography are also being explored.[3] This will allow the orientation and conformation of surface adsorbed protein to be probed in an even more detailed manner.

1. K. L. Marchin and C. L. Berrie; Langmuir, 19 (2003) 9883-9888.
2. J. E. Headrick, M. Armstrong, J. Cratty, S. A. Hammond, B. A. Sheriff and C. L. Berrie; accepted Langmuir (2005).
3. J. E. Headrick and C. L. Berrie; Langmuir, 20 (2004) 4124-4131.

Note: Refreshments at 3:00 PM, in room PS 117.

Oklahoma Nanonet Seminar:

Oklahoma State Physics Department

Seminars and Colloquia, March 28-April 1, 2005

Physics Colloquium:

Abstract:

Superheated emulsions are suspensions of micron-size overexpanded halocarbon droplets in an inert compliant matrix, typically an aqueous or polymeric gel. This fluid isolates the metastable drops from vibrations, while the smooth liquid-liquid interface prevents bubble nucleation on surface impurities that are inevitably present even in the cleanest solid containers. Thus, emulsions are kept in a steady superheated state and the lifetime of the droplets is extended to the point that a variety of practical applications are possible. Initially developed at Yale for studies on the metastability of liquids and cavitation effects, superheated emulsions have proven a powerful tool for ionizing radiation measurements. Halocarbons with a moderate degree of superheat can be used for high energy particle physics, while highly superheated halocarbons are suitable for three-dimensional studies of the radiation fields surrounding radiotherapy sources, which can be imaged using magnetic resonance techniques. More recently, intravenously injectable emulsions of superheated droplets have been used for occlusion therapy, whereby ultrasound is used to induce and image the evaporation of the droplets in the bloodstream in order to restrict the oxygen supply to certain tissues. Similar compositions are being investigated at Yale for targeted drug delivery purposes. In this case, drug-laden emulsions are developed which can be vaporized by exposure to diagnostic levels of ultrasound to achieve a spatially and temporally controlled release of their drug content into a target region.

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 Physics and Chemistry Colloquium:

Abstract:

We seek to devise improved methods for defense against and therapy for exposure to CWAs (chemical warfare agents) and TICs (Toxic Industrial Chemicals) for protection of military and civilian personnel.

While much information has been obtained on the function of organophosphorus (OP) compounds and one of their primary targets, the enzyme acetylcholinesterase (AChE), substantial questions remain on the mechanism of their interaction, as well as the mechanism of related compounds used for therapy and prophylaxis. Experimental studies on these systems are by their very nature dangerous and expensive, making this an ideal target for theoretical investigation. In this study, we attempt to understand the key molecular features leading to reversible and irreversible binding in the active site of AChE, and related reactions. QM and other theoretical methods are used to analyze structural effects and mechanistic details of the interactions of OP compounds, oximes, and carbamates with the enzyme active site and other key residues.

Other chemical systems are also of interest. Here we focus on the issue of collective and individual protection from cyanide and other compounds by adsorption and filtration. QM techniques are used to probe proposed reactions of CWAs and TICs with the components of filtration media to understand issues which may lead to design of advanced adsorbents with improved efficacy, increased lifetime, and decreased dependence on environmental factors.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 2:30 PM. All students are welcome! Refreshments will be served.

Oklahoma NanoNet, Chemistry Department & Phi Lambda Upsilon Seminar:

Abstract:

Chemists are exceptionally skilled at designing and constructing individual molecules with the goal of imbuing them with defined chemical and physical properties. However, the task of rationally assembling them into organized, functional supramolecular structures with precise, nanometer-level control is a daunting challenge. In this lecture, approaches to addressing this problem are described in which the ultimate goal is the fabrication of organic electronic circuit by printing techniques. Issues here concern not only the rational design of high-mobility p- and n-type organic semiconductors, but also dielectrics with ultra-high capacitance, low leakage, and high breakdown fields.

Note: Refreshments served at 3:00 PM in room PS 117.

Oklahoma State Physics Department

Seminars and Colloquia, April 4-8, 2005

Physics Colloquium:

Abstract:

Solar flares are the largest explosions in the solar system, and one of the most important contributors to the production of space weather. Despite many decades of flare observations, much of the underlying physics is not well understood. Recently, we were fortunate to observe many large flares with coverage over a large wavelength region. These data are providing much needed constraints to flare models. I will talk about using these data to produce new computational simulations of impulsive solar flares. The simulations model the radiative hydrodynamic response of the solar atmosphere to a beam of high energy electrons, and reproduce many of the signatures observed during flares. I will also discuss what can be learned about solar flares by studying flaring M dwarf stars, and how my simulations are being applied to model M dwarf stellar flares.

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.

Physics Colloquium:

Abstract:

Pictures from Mars Express, Viking, and Mariner show that the surface of Mars has been subject to aeolian and fluvial processes. To understand the planet’s geologic and climatic history, we need information about the age of these structures. Until now chronologies have been based upon relative crater densities, which leads to errors comparable to the ages themselves in the case of recent processes (~ 1 Myr). A better chronologic resolution can be obtained by optically stimulated luminescence (OSL) dating, a method widely used to obtain the depositional age of terrestrial surface sediments. In luminescence dating, the time elapsed since deposition of a sediment layer is determined from the radiation dose accumulated in minerals since the last bleaching event, and the dose rate due to naturally occurring radioactive nuclides and cosmic radiation.

The goal of our NASA-funded project is to develop a miniature instrument for in-situ dating of the deposition of Martian surface sediments. Before the actual instrument can be developed, however, it is necessary to adapt the luminescence method to the challenges on Mars. On Mars, not only do we encounter other minerals, but also another radiation environment, lower temperatures and a different solar irradiance at the surface.

In my presentation I will discuss the challenges of in-situ luminescence dating on the surface of Mars. I will present the results of our experiments and address our progress towards adapting the OSL technique for Mars.

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.

Physics Colloquium:

Abstract:

In this talk, we will discuss two different kinds of interaction with phospholipids, the first in the context of a triblock copolymer as a membrane sealant, and the second on how cholesterol complexes with phospholipids. Victims of electrical trauma suffer extensive loss of structural integrity of cell membranes. Poloxamer 188, a triblock copolymer, is known to help seal electroporated cell membranes, arresting the leakage of intracellular materials of the damaged cell.

We have examined the interaction between the poloxamer and zwitterionic and anionic phospholipid monolayers. With synchrotron x-ray reflectivity and grazing-incidence x-ray diffraction, both the out-of-plane and in-plane structures of mixed phospholipid-poloxamer 188 monolayers were investigated at the air-water interface. P188 selectively inserts into low lipid-density regions of the membrane and “corrals” lipid molecules to pack tightly, leading to unexpected Bragg peaks at low nominal lipid density and inducing the film to separate into P188-rich and -poor phases. At tighter lipid packing, the once inserted P188 is squeezed out, providing a route for the poloxamer to gracefully exit when the membrane integrity is restored.

Cryo-electron microscopy shows that the poloxamer can associate with the lipid in a reversible two-state fashion, depending on the physical state of the lipid. As for the cholesterol/phospholipids interaction, one of the models for the interaction of cholesterol with phospholipids predicts the existence of stoichiometric complexes. The phase diagrams of these cholesterol-lipid mixtures exhibit two distinct humps along with a sharp cusp, pointing to a particular stoichiometry for possible lipid/cholesterol complex formation.

It has been hypothesized that mixtures with cholesterol content greater than that at the cusp leads to the presence of reactive cholesterol monomers. To test this cholesterol monomer hypothesis, we have examined how the presence of alcohol alters the lipid/cholesterol phase diagram. Although binary mixtures of lipid and alcohol do not exhibit any mixing/demixing line like lipid/cholesterol mixtures, lipid/cholesterol/alcohol systems in which various mole fractions of cholesterol are replaced by alcohol reproduce the identical phase diagram as the lipid/cholesterol system, with the cusp position unaltered.

We have also examined the uptake of cholesterol by beta-cyclodextrin in both binary and termary systems. Our results indicate that the uptake of cholesterol is large in the ternary system as long as the total mole fraction of cholesterol and alcohol exceed that given by the cusp. This suggests that alcohol interacts more strongly with lipids and displaces cholesterol in the process. By so doing, the presence of alcohol results in the production of free cholesterol monomers even when the actual cholesterol content is low. X-ray data on these binary and ternary mixtures and have observed the presence of a broad Bragg peak, indicative of the existence of crystalline order, with coherence length of several molecular dimensions, in mixed lipid/cholesterol systems.

Note: The traditional student-speaker chat will begin in Physical Sciences Room 147 at 2:30 PM. All students are welcome! Refreshments will be served.

Oklahoma NanoNet Seminar:

Abstract:

The dielectrophoretic manipulation of nanoscopic materials is a promising approach to the large scale fabrication of electronic devices. Here we use dielectrophoresis to form individual submicron wires from nanoparticulate populations and to interface them with macroscopic electrodes at targeted locations, all in one step. We delineate key experimental parameters that must be precisely controlled in order to assemble interconnects with reproducible structural properties. These parameters include electrode design, field strength, and particle size. This control enables investigation into the particle properties that underlie and, therefore, provide control over charge transport through the interconnects. Understanding these structure-function relationships is a necessary step towards the dielectrophoretic fabrication of electronic devices of reduced size, such as photoconductive switches and field effect transistors.

Oklahoma State Physics Department

Seminars and Colloquia, April 11-15, 2005

Public Lecture:

Abstract:

What is time? This question intrigued Einstein, and in 2005 as the World Year of Physics recalls Einstein’s “miraculous year” of 1905, which changed forever our understanding of Nature, we continue to be excited by time and its measurement. Atomic clocks are the most accurate timepieces ever made, and are essential for modern life. For example, the Global Positioning System (GPS), which guides aircraft, cars, boats and backcountry hikers to their destinations, depends on atomic clocks and on Einstein’s theories. The limitations of atomic clocks come from the thermal motion of the atoms: hot atoms move rapidly and suffer from time shifts, which are also predicted by Einstein’s Theory of Relativity.

Contrary to intuition, we can cool things by shining laser light on them. With laser cooling, applying ideas that originated with Einstein, we cool gases to less than one millionth of a degree above Absolute Zero. The slowly moving atoms in such a gas allow us to make even more accurate clocks, already so good that they would gain or lose only a second in 40 million years. Laser cooling has also made possible the observation of a long-standing prediction of Einstein: Bose–Einstein condensation, hailed as one of the most important recent scientific developments.

This talk is for a general audience of non-scientists, but discusses some of the most compelling recent developments in physics. The multi-media presentation includes exciting live demonstrations.

Note: Reception following the presentation.

For more information on Dr. Phillips’s group at NIST see his group’s homepage.

Physics Colloquium:

Abstract:

An atomic-gas Bose–Einstein Condensate, placed in the periodic light-shift potential of an optical standing wave, exhibits many features that are similar to the familiar problem of electrons moving in the periodic potential of a solid-state crystal lattice. Differences include the distance scale of the lattice (100s of nanometers compared to a few Ångstroms) and the fact that the BEC represents a wavefunction whose coherence extends over the entire lattice, with what is essentially a single quasi momentum. Recent experiments at NIST–Gaithersburg explore the behavior of a BEC in an optical lattice and interpret the sometimes surprising results using traditional band theory.

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.

Informal Physics Discussion:

Oklahoma State Physics Department

Seminars and Colloquia, April 18-22, 2005

Oklahoma High Energy Physics Seminar on Talk-Back Television:

Physics Colloquium:

Abstract:

Surface and interfacial chemistry plays a critical role in many material systems. The speaker will focus upon work in his laboratory that concerns corrosion and oxidation of metal and composite systems. A variety of experimental approaches will be discussed, with emphasis placed upon the role of valence band photoemission and the use of experimental approaches specially adapted to material systems. An apparatus will be described that allows studies to be made of the solid-liquid interface. The apparatus is linked to an X-ray photoelectron spectrometer (XPS), equipped with monochromatized X-rays, an ultra-violet photon source for UPS, a scanning Auger system and a SIMS system, so allowing an investigation of the changes in surface chemistry at this interface. The use of this approach to investigate the direct reaction of liquids with surfaces to give surface films with a novel composition and considerable practical potential will be discussed. The value of using valence band XPS interpreted by calculation models will be demonstrated for these systems, and the use of core and valence band XPS for the study of buried interfaces will be demonstrated. Examples discussed will include the formation and study of thin (less than 100Å) oxide-free phosphate films and the identification of different oxide films (including aluminum oxides) with similar chemical composition.

Click here for a biographical sketch.

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 Seminar:

Special Physics Seminar:

Abstract:

A brief review will be provided of radiation cell damage processes that are predecessors to carcinogenic disease and radiotherapeutic cell killing. DNA damage and subsequent chromosome aberrations will be detailed. Only in the last 10 years has experimental data shown that DNA double strand breaks (dsBs) are readily repairable at very low dose rates. With a recent author’s dsB model, it is shown that the premise that some fraction of damage is non-repairable may be false suggesting that very low dose rates received by nuclear workers and the general public are not harmful. There are four repair processes now being studied in a DOE-funded 10-year, $20 million low dose rate research program, i.e., adaptive response (AR) inverse dose rate effect (IDRE), high radiosensitivity and induced radioresistance (HR/IRR), and apoptosis (A). These will be discussed. AR is perhaps the most applicable to reduced human risks. A separate AR model reveals that single or two radiation induced charged particle tracks through the cell nucleus induces cellular radioprotective mechanisms by activating enzymes that increase the recognition of the DNA damage sites and increase the repair rates of this damage. Most significant is that the model explicitly shows that a very small amount of radiation—at the nuclear workers or medical radiation diagnostics level—can reduce the occurrence of both natural spontaneous and radiation induced carcinogenic chromosome aberrations, the protection which may sustain itself to aged mortality. Data is also shown and discussed implying that, due to dose rate effects and cellular repair capabilities, the current concern of cosmic ray radiation health risks for the manned Mars mission may be unfounded. Finally, implications to radiation risks (or lack thereof) at low dose rates for nuclear workers and medical radiation diagnostics, i.e., mammograms, x-rays, CAT scans, pet scans will be assessed.

Oklahoma State Physics Department

Seminars and Colloquia, April 25-29, 2005

Prefinals Week

Physics Colloquium:

Abstract:

Over the past 20 years bright sources of entangled photons have lead to a renaissance in quantum optical interferometry. These photon sources have been used to test the foundations of quantum mechanics and implement some of the spooky ideas associated with quantum entanglement such as quantum teleportation, quantum cryptography, quantum lithography, quantum computing logicgates, and sub-shot-noise optical interferometers. I will discuss some of these advances and the unification of optical quantum imaging, metrology, and information processing.

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:

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

Oklahoma State Physics Department

Seminars and Colloquia, May 2-6, 2005

Finals Week

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 9-13, 2005

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 16-20, 2005

No talks scheduled.

Oklahoma State Physics Department

Seminars and Colloquia, May 23-27, 2005

Physics Colloquium:

Abstract:

In this talk, I will present some of our work on the development of computational methods for treating many-atom systems. Our main focus is on studying dynamical behavior, especially reaction dynamics, of large systems, and the main tool we use is molecular dynamics (MD) simulations. I will describe the basic idea of our work on three topics:

1. Incorporating tunneling calculations into MD simulations.
2. Combining MD calculations and statistical theories to compute reaction rates.
3. Constructing potential energy functions for dynamical studies.

Note: Refreshments will be served in Physical Sciences Room 147 at 2:00 PM. All students are welcome!

Oklahoma State Physics Department

Seminars and Colloquia, May 30-June 3, 2005

Special Physics Seminar:

Abstract:

As electronic devices become smaller, they cross over from classical physics to quantum physics. Many classical quantities such as resistance must be re-interpreted when they are examined on the nano-scale. It is very important to understand these devices theoretically as this will help us to understand existing observations and to engineer new devices. I will discuss how the I-V characteristics depend on the scattering of electrons in a quantum mechanical device through the Landauer formula. In order to calculate the scattering coefficients, we use a technique called R-matrix theory that has been very popular in Nuclear, Atomic and Molecular physics. In this talk, I will also discuss nanoscale semiconductor research at University of Oklahoma. After giving a basic introduction to the Landauer formula and R-matrix theory, I will discuss two applications of this technique, first a proposed electron cooling device and second, the modeling of experimental observations of negative bend resistance in InSb devices.

Oklahoma State Physics Department

Seminars and Colloquia, June 6-10, 2005

2005 REU Faculty Talks:

2005 REU Faculty Talks:

Mandatory Safety Meeting:

Abstract:

Warren Grider will be covering all materials regarding Oklahoma Summer Health Hazards. This includes heat stroke, heat exhaustion, etc. The guidelines covered in this meeting will help insure that we have a safe and productive summer while on the workforce. All are expected to attend and the Department will be providing refreshments for your enjoyment.

Oklahoma State Physics Department

Seminars and Colloquia, June 13-17, 2005

2005 REU Faculty Talks:

2005 REU Faculty Talks:

Oklahoma State Physics Department

Seminars and Colloquia, June 20-24, 2005

2005 REU Faculty Talks:

2005 REU Faculty Talks:

Physics Colloquium:

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

Oklahoma State Physics Department

Seminars and Colloquia, June 27-July 1, 2005

2005 REU Faculty Talks:

2005 REU Faculty Talks:

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