Events at Physics |
Events During the Week of February 17th through February 24th, 2008
Monday, February 18th, 2008
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Validation in Fusion Research: Toward Guidelines and Best Practices
- Time: 12:05 pm
- Place: 2241 Chamberlin Hall
- Speaker: Terry, Department of Physics/Plasma, University of Wisconsin
- Medical Physics Seminar
- Brachytherapy Facility Shielding
- Time: 4:00 pm
- Place: 1345 Health Science Learning Center (refreshments will be served)
- Speaker: Glenn P. Glasgow, M.S. Ph.D., F.A.A.P.M., F.A.C.R Professor Emeritus, Department of Radiation Oncology Loyola University Chicago Stritch School of Medicine
- Abstract: Neither NCRP Report 147, Structural Shielding Design for Medical X-Ray Imaging Facilities nor NCRP Report 151, Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities addresses brachytherapy facility shielding. This presentation reviews new shielding data (TVLs) for 103Pd, 131Cs, 169Yb, 170Tm (Thulium), and 192Ir, reviews typical workloads for high-dose-rate (HDR) facilities, compares textbook recommended HDR vault shielding designs to those recently reported in the literature, and investigates HDR maze scatter using the methodology described in NCRP 151 for linear accelerators. The data and subsequent representative calculations represent the current state-of-the-art of brachytherapy facility shielding.
Tuesday, February 19th, 2008
- Chaos & Complex Systems Seminar
- Acceleration of human evolution: interactions of genes with culture and geography
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: John Hawks, Anthropology
- Abstract: Recent surveys of the human genome have shown that thousands of recent mutations have strong advantages and have increased greatly in frequency since their origins during the last 40,000 years. The rate of such changes appears to have increased by a factor of 100 times over the rate that characterized most of human evolution. Natural selection, as Darwin recognized, is fundamentally a demographic phenomenon: individuals with one allele have a higher intrinsic rate of growth than those having alternative alleles, resulting in the replacement of such alleles over time. When this process occurs across a population spread over geographic space, a wave of population growth and migration tends to disperse a selected allele outward from its source. This process is well understood when modeled for a single gene. However, the introduction of many (perhaps thousands) of simultaneously selected alleles may lead interactions between genes to outweigh the fitness consequences of individual genes.
- Astronomy Colloquium
- Illuminating the Glowing Magnetospheres of Massive, Luminous Stars
- Time: 3:45 pm
- Place: 6515 Sterling Hall (coffee at 3:30 pm in 6521 Sterling)
- Speaker: Richard Townsend, University of Delaware- Bartol Research Institute
- Abstract: Massive, luminous stars are not expected to harbor magnetic fields, owing to their lack of envelope convection zones and associated field-generating dynamos. Puzzlingly, however, it has been known since the 1970s that a small yet growing subset of massive stars possess strong, global-scale fields. These fields channel and confine the stars' supersonic, radioactively driven winds, leading to the formation of glowing, co-rotating magnetospheres that can be observed across the electromagnetic spectrum, from X-rays through to radio.My interest in massive-star magnetospheres stems from the challenge of understanding the rich variety of phenomena they manifest, at a detailed, quantitative level. In my presentation, I aim to illuminate the basic physical processes responsible for the existence of these magnetospheres. Then, with the aid of extensive animations, I willintroduce the new 'Rigidly Rotating Magnetosphere' and 'Rigid Field Hydrodynamics' models that I have developed for understanding magnetospheric signatures at optical, UV and X-ray wavelengths.
Wednesday, February 20th, 2008
- No events scheduled
Thursday, February 21st, 2008
- R. G. Herb Condensed Matter Seminar
- Anderson localization transitions, multifractal wave functions, and conformal invariance
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Ilya Gruzberg, Physics Dept. University of Chicago
- Abstract: Anderson metal-insulator transitions (MIT) caused by disorder in electronic systems exhibit many fascinating features making them quite special. In particular, electronic wave functions that are extended in the metal and localized in the insulator, appear to have intricate self-similar structure right at the transition. This structure leads to an infinite number of scaling multifractal exponents that describe the moments of the wave functions. We have recently developed the concept of multifractality of wave functions for finite samples with boundaries and corners. It appears that the critical behavior of various observables related to wave functions near a boundary at a MIT is different from that in the bulk. In two dimensions (2D), the multifractal exponents at a corner are found to be directly related to those at a straight boundary through a relation arising from conformal invariance. This provides direct evidence for conformal invariance at a 2D MIT. Moreover, the presence of boundaries modifies the multifractal spectrum of the whole sample even in the thermodynamic limit. I will illustrate all these ideas and developments with several examples of MIT's that we have studied.
- Host: Vavilov
Friday, February 22nd, 2008
- Special Atomic Physics Seminar
- Engineering a Quantum Information Processor
- Time: 10:00 am
- Place: 5280 Chamberlin Hall
- Speaker: Professor Jungsang Kim, Duke University
- Abstract: Fundamental advantage of utilizing quantum resources for computation and communication has been discovered in the last two decades. Experimental demonstration of representing and manipulating quantum bits in physical systems and simple quantum algorithms followed. While the experimental research in this field has progressed at a rapid pace, the notion of a practical information processor based on quantum physics still faces tremendous amount of challenges. Construction of a scalable quantum information processor is a system design challenge that requires cutting-edge technology guided by engineering principles. The task requires expertise in quantum physics, computer architectures and integrated microsystems technology, and lots of exciting research is still to be done. In this talk, I will discuss the multidisciplinary challenge of designing a quantum information processor, and some of the technology progress made to date. I will present micro electromechanical systems (MEMS) technology applied to creating a beam control system that can address quantum bits represented by atoms trapped in a ultra-high vacuum chamber.
- Phenomenology Seminar
- Matching NLO Calculations with Parton Shower: the POsitive-Weight Hardest Emission Generator
- Time: 2:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Carlo Oleari, Univ. di Milano-Bicocca
- Physics Department Colloquium
- Visualizing Pair Formation and the Riddle of High-Temperature Superconductivity
- Time: 4:00 pm
- Place: 2241 Chamberlin Hall (coffee at 3:30 pm)
- Speaker: Ali Yazdani, Princeton University
- Abstract: The pairing of electrons underlies the formation of a superconducting state with zero electrical resistance. After twenty years of work, the mechanism of pairing and the temperature at which pairs first form in high-temperature copper-oxide superconductors are still hotly debated. Do pairs form at the critical temperature like conventional superconductors? Is pairing mediated by a bosonic excitation, as in conventional BCS superconductors, or is pairing with d-wave symmetry an unavoidable consequence of strong Coulomb repulsion in these compounds? In search of experimental answers to these important questions, we have develop several new techniques, based on the scanning tunneling microscope (STM), to visualize the process of pair formation on the atomic scale and to probe what controls the strength of pairing in these compounds with high precision. We show that pairing in the cuprates is strongly local, with pairs forming in nanoscale regions of samples over a range of temperatures above the critical temperature. I will discuss these experiments and other high resolution studies of electronic states in search of clues as to what controls the strength of the pairing interaction in the cuprates.
- Host: Chubukov