This site will look much better in a browser that supports web standards, but it is accessible to any browser or Internet device.
Skip Navigation skip menu and banner
University of Wyoming

University of Wyoming Physics & Astronomy Colloquium Series

Fridays -- 4:10 PM -- Prowse Room 234

Pre-Colloquium tea served at 3:45 in the Cinnamon Room, PS 237

Fall 2005 Schedule

Sep 16 Tom Cherewic (Medical Physicist) and Margaret Barnes (Doctor) from Radiation Oncology, Gillette, Wyoming
Careers in Medical Physics

This colloquium will feature Medical Physics as an applied subdiscipline for professionals with training in physics, math, or engineering. A medical physicist is the preemptive, proactive insurance policy to ensure timely and competent patient care when radiation is involved. We build, maintain and protect medical infrastructure. Medical Physics is a challenging, technologically advancing and secure career with branches to radiation therapy, nuclear medicine, diagnostic radiology (CT, PET, MRI, US, image manipulation and fusion), computer networking, RSO, DICOM EMR and PACS. Research, clinical, teaching, sales, administration (private sector and government) and combinations of these areas are options for employment.

Oct 14 Karl Gordon (U. Arizona)
Dust in Galaxies: Aromatic Features in M101/Starbursts and M31's Disturbed Spiral Structure

I will talk about two projects on dust in galaxies based on new Spitzer Space Telescope data. The first is the study of the behavior of dust emission as a function of metallicity for HII regions in M101 and starburst galaxies. M101 is unique in that it is face-on and has a large metallicity gradient ranging from log(O/H) of ~9.2 in the nucleus to 7.5 at its edge. The sample of 44 starburst galaxies was picked to have metallicities ranging from the lowest known (i.e., I Zw 18) to super solar (7.2 < log(0/H) < 9.3). Spitzer spectroscopy and imaging is used to probe the behavior of the Aromatic Infrared Features (AIFs, also commonly called the PAH features) as a function of HII region diagnostics. The AIFs are seen to decrease in strength with decreasing metallicity in both M101 HII regions and starburst galaxies. The second is the study of the structure of the nearest spiral galaxy Andromeda (M31). Mid- and far-infrared imaging of the optical disk of M31 has revealed the structure of M31's interstellar medium at a much improved resolution and sensitivity. For the first time, spiral arms are traced from the nuclear region to well beyond the prominent star forming ring. This ring is seen to be quite circular, offset from the nucleus, and split in two near the position of M32, a satellite galaxy of M31. Detailed numerical simulations of the M31-M32 interaction give evidence that M32 may will have recently punched directly through M31's disk creating the split in the ring and causing the offset of the ring.

Oct 17 Abraham Nitzan (Tel Aviv University)
How Molecules Conduct

An overview of molecular electronics with an emphasis on recent experimental and theoretical results will be given.

Oct 20 Jon Gardner (NASA Goddard)
Studying Galaxy Formation with the Hubble and James Webb Space Telescopes

The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z~6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble Space Telescope. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth-Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 27 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

Oct 21 Guy Worthey (Washington State University)
The Space Interferometry Mission (SIM)

Space Interferometry Mission (SIM) is an astrometry mission scheduled for launch in 2011. It will obtain parallaxes and proper motions for stars halfway across the Galaxy, measure the proper motion of local group galaxies, and dissolve any remaining uncertainty in the distance scale. In addition, it will intensively survey the nearest stars to discover rocky planets, measuring their masses and obtaining complete orbital information. Other questions in planetary, stellar, Galactic, and extragalactic astronomy will also be tackled. This talk is an overview of the mission, its science, and its technical status.

Wed Oct 26 - 2:00 p.m. Lifan Wang (Lawrence Berkeley National Lab)
Supernovae and the Dark Energy of the Universe

Abstract: I will review recent progresses on the studies of Type Ia supernovae and discuss the impact of these studies on the measurement of the expansion history of the universe. To beat down systematic errors to levels around 1-2% level as required by NASA's JDEM mission, observations of a large number of nearby SNe are required; this can be best achieved by dedicated transient survey telescope with very large field of view.

Nov 4 Web Cash (University of Colorado)
Extinguishing Poisson's Spot: Direct Observation of Exo-planets with the New Worlds Observer

A new approach to apodization of occulters in the Fresnel regime has enabled the suppression of diffraction and the creation of very deep shadows in an optimal way. We present the concept of the New Worlds Observer, a mission that is based on an occulting disk to extinguish the light from a central star and reveal the very faint planets in orbit around it. We show how, by using this technology, we are poised to discover the first Earth-like planets and search for evidence of life.

Nov 11 Dan Tyson (University of Wyoming)

Nov 18 Constantine Deliyannis (Indiana University)
Lithium Tests of Big Bang Cosmology and Stellar Evolution

Testing big bang nucleosynthesis remains a key path to improve our understanding of cosmology. I will focus on estimating the big bang Li abundance from halo dwarf observations and considerations of surface Li depletion over time. Solving this problem will require an improved understanding of physical processes occuring in the stellar interior. I will discuss steps being taken towards such an improved understanding using data of the light element tracers, including Li data at WIYN using the Hydra multi-object spectrograph.

Nov 29 V.G. Zakrzewski (Kansas State U.)
Electron Propagator Studies of Molecular Wires

Development in computer technologies drastically changed the world during the last 50 years. It is very likely, however, that conventional semiconductor based technologies will reach saturation soon. Development of alternative approaches is necessary. The question is: is it possible to make individual molecules work as elements of electronic circuits? Experimental data are positive about it. It is necessary, however, to find a theoretical explanation for the dependence of current (I) on voltage (V), and how IV characteristics depend upon structure of perspective molecular wires. Preliminary results will be discussed.

Dec 1 Ramesh Mani (Harvard U.)
Radiation-induced zero-resistance states in the GaAs/AlGaAs two-dimensional electron system

We report the experimental observation of novel photo-excited zero-resistance states in the two-dimensional electron system at low temperatures, in a small magnetic field, large filling factor limit. Briefly, GaAs/AlGaAs 2DES specimens exhibit vanishing diagonal resistance, without Hall resistance quantization, about B = 4/5 Bf and B = 4/9 Bf, where Bf = 2p f m*/e, m* is the electron mass, e is electron charge, and f is the EM-wave frequency, as the resistance-minima follow B = [4/(4j+1)] Bf with j=1,2,3... Here, we illustrate the basic characteristics, in light of recent theory for this remarkable effect.

Dec 6 Yi Ji (Argonne National Lab)
Spin-dependent transport in nanoscale systems

Spintronics is an emerging area of science and technology, where electron spins are utilized to realize new effects and process information. Very rich spintronic phenomena can be generated in nanoscale metallic heterostructures involving ferromagnetic metals (FM) and non-magnetic metals (NM). In this talk, I will describe two examples: non-local spin valve and spin-transfer torque effects. In a non-local spin valve, a pure spin current without charge flow can be obtained, and the spin diffusion length and the spin injection polarization can be determined. In spin-transfer torque effect, a nanoscale magnetic domain can be manipulated by a spin polarized current.

Dec 8 Filip Ronning (Los Alamos National Lab)
Strongly Correlated Electrons: Emergence of New Physics

In this talk I will try to convey the excitement in strongly correlated electron systems, with particular emphasis on quantum critical points, heavy fermions, and high temperature superconductors. Our conventional wisdom of solid state physics fails completely in these cases. I will also explain the concepts of emergent behavior and quantum criticality, and why our current research at Los Alamos National Lab on these issues suggests promising avenues toward understanding strongly correlated systems.

Previous colloquia series: Fall 2002 Spring 2003 Fall 2003
Spring 2004 Fall 2004
Spring 2005
Contact for program information: Daniel Dale (ddale @