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Fall 2008

Schedule Fall 2008

September 16, 2008
3:00 pm (Tuesday)

Dr. Stepan Stepanyan
Jefferson Lab

Hadron Spectroscopy with CLAS

The most fundamental question of hadron physics is that of understanding the mechanism of confinement. It has been more than thirty years since QCD was postulated as the theory of strong interactions. While much progress has been made in understanding perturbative phenomena, the non-perturbative regime, the regime of hadrons, their excitations, and their couplings, has remained largely impervious to our varied assaults. Spectroscopy of hadrons (mesons and baryons) is one of the key tools for studying the QCD in the non-perturbative regime (i.e., confinement). Hadron spectroscopy has been an essential component of the physics program with CLAS at Jefferson Lab. To date, a large amount of experimental data on electromagnetic production of mesons and baryons has been collected by CLAS. Important results have been obtained on ordinary nucleon and meson resonances, as well as on exotic states. In this talk we will discuss some of key results from CLAS on hadron spectroscopy and will present plans for future experiments.


September 23, 2008
3:00 pm (Tuesday)

Dr. Larry Weinstein
Old Dominion University

Guesstimation: Solving the world's problems on the back of a cocktail

This talk will show how to estimate almost anything, including such serious real-world questions as 'paper or plastic', how much landfill space we need for the next century, the energy transfer rate at a gas station, or the total length of pickles consumed yearly in the US.


October 21, 2008
3:00 pm (Tuesday)

Dr. Li-Shi Luo
Old Dominion University

Why Should Fluid Motion be Interesting to Physicists?

Fluid motion is perhaps the most ubiquitous physical phenomena around us which can be observed almost everywhere, any time: How insects and birds fly, how fishes swim, how water flows, how a human lung works, and how blood flows in veins. Hydrodynamic problems are not only important for practical engineering applications (e.g., aerodynamic design of airplanes and space shuttles and vehicles), they also present a grand challenge in science because, turbulence remains as the grand challenge in classical physics.

Study of hydrodynamics and fluid mechanics has been very active in the recent two decades due to the interest in bio and nano science and technology. In dealing with devices in very small sizes, we encounter several challenges. First of all, certain physical phenomena, which are unimportant or even irrelevant in larger devices (or larger scales), become dominant ones in small scales (e.g., various surface effects). Secondly, the macroscopic or continuum theory which has been very successful in the past maybe invalid. In this presentation, we will use two examples to illustrate these points. The first example is gaseous flows in micro-electro-mechanical-systems (MEMS), and the second is rarefied flows subject to high temperature and severe shocks. We will discuss what are the interesting physics in these problems and how one can use computer simulations to understand them.


October 28, 2008
3:00 pm (Tuesday)

Dr. Alex Bogacz
Jefferson Lab

Towards Neutrino Factory and Future Muon Colliders

Muon Colliders and Neutrino Factories based on muon storage rings are attractive options for future facilities aimed at achieving the highest lepton-antilepton collision energies (e.g. to produce Higgs bosons) and precision measurements of parameters of the neutrino mixing matrix using intense, small divergence neutrino beams with well-understood systematics. Their performance and feasibility depend strongly on how well one can produce the muons, cool and 'shape' them into a beam and finally to rapidly accelerate them to multi-GeV and TeV energies. Recent progress in muon cooling and novel acceleration schemes (design studies and prototype tests) encourages the hope that such facilities can be built during the next decade. The current state of the concepts and required technologies will be reviewed. In particular, recent advances in 6-D muon cooling and innovative multi-pass linac acceleration schemes will be summarized.


November 4, 2008
3:00 pm (Tuesday)

Dr. Arne Freyberger
Jefferson Lab

CEBAF Accelerator and the symbiotic relationship with Nuclear Physics

The CEBAF accelerator at Jefferson Lab provides a unique probe for nuclear physics. After a brief overview of the CEBAF accelerator, the talk will focus on what makes the CEBAF accelerator unique and its impact on the nuclear physics experimental program. Emphasis will be placed on new and novel accelerator physics and beam diagnostics at CEBAF. The role of user requirements as drivers for improvements to the CEBAF accelerator and some future plans will also be presented.


November 11, 2008
3:00 pm (Tuesday)

Dr. Ali Beskok
Old Dominion University

AC Electrokinetic Manipulation of Colloids in Microfluidic Systems

We present experimental and theoretical research on manipulation of colloids and biological particles in microfluidic systems using AC electric fields. Navigating the AC frequency-amplitude phase space, we effectively and reversibly tune colloidal interactions to yield various steady-state configurations. The colloidal system response can be predicted using a scaling analysis based on the relative importance of dielectrophoresis, electrophoresis, AC-electroosmosis, gravity and Brownian motion. Particularly we present the following applications:

1. Colloidal Microfluidic Circuits: Electric field-directed assembly of gold nano-particles in a microfluidic system enables modulation of the electrical properties within the circuit. Specifically, regulating the colloidal structures enables a single circuit element to act as a variable resistor, capacitor, or inductor in a reversible and switchable fashion. The colloidal microfluidic circuit has the potential for adaptive control of electromagnetic properties across a surface.

2. Bacterial Spore Concentration Using Dielectrophoresis: We present experimental results for concentration of Clostridium sporogenes spores from various conductivity media, spanning from DI water (0.05 mS/cm) to milk (5247 mS/cm). Positive DEP diminishes quickly with increased conductivity, and one needs to design electrodes that amplify the negative DEP effects. We present bacterial spore capture in a wide spectrum of media that exhibit 5-orders of magnitudes variation in conductivity, and discuss utilization of the device for water and food safety applications.


Bio:
Prof. Ali Beskok received his B.S. in Mechanical Engineering from Middle East Technical University, Ankara, Turkiye in 1988. He received an MS degree in Mechanical Engineering from Indiana University Purdue University in Indianapolis in 1991, and M.S. and Ph.D. degrees from Princeton University, Mechanical and Aerospace Engineering in 1994 and 1996, respectively. Dr. Beskok was a Visiting Scholar at Brown University, Center for Fluid Mechanics from 1994 to 1996, and a Post Doctoral Research Associate at Massachusetts Institute of Technology, Research Laboratory of Electronics from 1996-1998. He joined Texas A&M University Mechanical Engineering Department as an Assistant Professor in 1998, and became an Associate Professor in 2004. Currently, he is the Batten Professor of Computational Engineering, and a professor at Old Dominion University, Aerospace Engineering Department.


November 18, 2008
3:00 pm (Tuesday)

Dr. Frank Close
Oxford University

Nothing

What is the void? What remains when you take all the matter away? Can empty Space--nothing--exist? To answer these questions, Frank Close takes us on a journey that ranges from ancient ideas and cultural superstitions to the frontiers of current research, illuminating the story of how scientists have explored the void and the rich discoveries they have made there.


December 11, 2008
12:30 pm (Thursday)

Dr. Peter Barker
University College London

Cold molecules with strong optical fields

There is currently considerable interest in creating ultra cold molecular gases below the milliKelvin regime for applications in high resolution spectroscopy, the study of strong dipolar interactions and even for testing physics beyond the standard model. At the same time, the ability to precisely control both the centre of mass motion of molecules as well as their internal degrees of freedom has opened up new vistas in chemical physics and ultra cold chemistry. In this presentation I will summarize recent progress in the creation of cold molecules, focusing in particular on our work which utilizes strong optical fields (10^12 Wcm^-2) to control the centre of mass motion of molecules and atoms. I will describe the rapid deceleration of a molecular beam using pulsed optical lattices to create cold stationary molecular gases and how the familiar optical dipole force can be tailored in a molecular system by preferential alignment of the molecules using field polarization. Finally, I will describe current progress towards the development of sympathetic cooling of Stark decelerated molecules for the production of essentially any molecular species at submillikelvin temperatures.