Colloquia held Fall Semester, 2008

November 25, 2008
Professor Carlos Bertulani
Department of Physics
Texas A&M - Commerce
CommeDepartment of Physics
Texas A&M - Commerce
Commerce, Texas, Texas
"Tunneling of Composite Objects"
 Quantum tunneling is a subject of renewed interest, both experimentally and theoretically.  As a rule, chemical and nuclear sub-barrier reactions, especially in astrophysical conditions, involve complex objects with their intrinsic degrees of freedom. Although a number of theoretical works have studied tunneling phenomena in various situations, quantum tunneling of a composite particle, in which the particle itself has an internal structure, has yet to be clarified. I will discuss new effects, usually ignored, that are important for nuclear fusion and fission, nucleosynthesis in stars, molecular processes, transport phenomena in semiconductors and superconductors, in both quasi-one-dimensional and three-dimensional systems.
Dr. Bertulani's Presentation

November 18, 2008
Dr. Narayan Sahoo
Department of Radiation Physics
UT MD Anderson Cancer Center
Houston, Texas
"Proton Beam Therapy for Cancer: Benefits and Obstacles"
Technological advances have made it possible to deliver highly conformal proton radiation therapy to the target with a dramatic reduction of the dose delivered to surrounding normal tissue as compared to techniques employing photons and electrons.  Relative to other modalities, proton therapy can thus lead to a greater complication-free tumor control.  Despite superior dose distributions in proton therapy, its full potential has not been utilized due to physical and technical limitations. This talk will provide a comprehensive review of the current status of proton therapy and outline some of the future  developments that may help in utilizing its full potential to achieve substantial therapeutic gain. 

November 11, 2008
Professor Jim Roberts
Department of Physics
University of North Texas
Denton, Texas
"Utility of Microwaves to Explore Properties of Matter"
I will discuss some history of the development and applications of microwaves over the past 70 years.  Microwaves can be used to understand molecular structures. They can be used to produce "smart skins" to shield devices and reduce target cross sections for RADAR imaging. Microwaves can also be used to produce plasmas and high temperature plasma products. Microwave probing can be used to obtain the dielectric response of materials. I will also discuss a cavity sensor for "sniffing" selected gases.

November 4, 2008
Dr. Bibhudutta Rout
Ion Beam Modification and Analysis Laboratory
Department of Physics
University of North Texas
Denton, Texas
"High Energy Ion Beam Microscopy for Multi-disciplinary Research"
High Energy Focused Ion Beam Systems, traditionally known as Nuclear Microprobes, are extremely powerful tools that utilize ion beam analytical techniques as microcopies with spot sizes in the micro-nano meter range. It is now possible to carryout multi-dimensional materials analysis with high spatial resolution in a wide range of fields involving semiconductors, micro-electronics, geology and biological systems. We will discuss the capabilities of ion microprobes in materials analysis as well as micro-fabrications.

October 28, 2008
Mr. Michael Buser
Institut für Quantenphysik
Universität Ulm
Ulm, Germany
"Visit the Gödel Universe!"
An intriguing solution of Einstein's field equations was found by Kurt Gödel in 1949. The Göodel universe describes a homogeneous rotating space time in which closed time-like wordlines exist. Traveling along such a worldline allows an observer the paradoxical  journey into his own past. This talk addresses some fundamentals in computer graphics and how they can be applied to Gödel's space time. In my talk I present a few scenarios and illustrate how an observer, who is located in the Gödel Universe, would perceive these scenarios. In order to grasp the nature of the pictures shown I also discuss the propagation of light in conjunction with the existence of an optical horizon.
Mr. Buser Presentation 1
Mr. Buser Presentation 2
Mr. Buser Presentation 3
Mr. Buser Presentation 4
Mr. Buser Presentation 5

October 21, 2008
Dr. Lin Shao
Texas A&M University,
Department of Nuclear Engineering
College Station, Texas
"Techniques of Vacancy and Strain Engineering in Microelectronics Fabrication"
This talk gives a brief overview of the status and perspective of a few ion beam-assisted techniques in overcoming technology barriers in microelectronics processing. For the technique of vacancy engineering, in which high energy co-implantations are used to introduce excessive vacancies near a Si surface region to suppress boron diffusion and enhance boron activation, we discuss its mechanisms and integrability issues in device processing. For the technique of strain-facilitated ion cutting, in which a nanometer thick strained layer is buried in monocrystalline Si to provide H trapping and to initialize a smooth cracking for ultrathin layer transfer (<20 nm), we discuss the underlying physics and its application in fabrication of 3-D electronics and detectors. Finally, we discuss the progress in building a new Center of Ions & Materials at Texas A&M University for ion beam-related materials science, and particularly for development of nuclear materials in advanced nuclear energy systems.

October 14, 2008
Professor Stephen Buckman
Australian Research Council Centre for Antimatter-Matter Studies
Australian National University
Canberra, Australia
“Positron Interactions with Atoms, Molecules and Materials”
Positrons are becoming more widely used in a variety of areas, for example as a diagnostic tool in medical and bioscience and for characterising nanoscale open space and voids in materials.  The ARC Centre for Antimatter-Matter Studies has been funded to enable leading-edge positron research to be carried out in Australia.  At the heart of the Centre are two, state-of-the-art positron beamlines, one for low energy studies of atoms and molecules and the other for materials science research. This presentation will outline the new facilities and the experimental techniques involved in generating both high resolution, low energy positron beams for atomic and molecular studies, and high energy, fast-pulsed beams for materials science studies.  The first results from the new facilities will be discussed.

October 7, 2008
Dr. Simone Bianco
Department of Applied Science
College of William and Mary
Williamsburg, Virginia
"Chaos in Spreading of Epidemics: Cross Immunity & Antibody-Dependent Enhancement"
The study of multistrain diseases, diseases with several coexisting strains, is a major challenge for today's science. Example of such diseases are influenza, AIDS, dengue and ebola. The inclusion of mechanisms of interactions between the strains represents a further step in the implementation of a realistic model for this type of disease, which is paramount towards the assessment of disease control, as well as the study of vaccination strategies. In this talk I will present a mathematical model for multistrain disease with nonlinear interactions among the strains. I will focus my attention on dengue fever, a 4-strains subtropical disease which is responsible for the infection of over 50 million people worldwide every year, because of the interesting interaction among the strains. Once an individual is infected with one strain, after a period of temporary cross immunity, his antibodies will increase his infectiousness in the case of secondary infection with a different strain. This mechanism is called antibody dependent enhancement (ADE). While the presence of ADE alone is known to trigger chaotic outbreaks and desynchronization among the strains, the inclusion of weak cross immunity in the model is proved to have a stabilizing effect on the dynamics. Strong cross immunity leads instead to instability and chaos. Finally, I will present new results about the emergence of chaos in coupled communities with migration terms. These results may help to give important insight for new mechanisms of disease control.
Dr. Bianco's Presentation

September 30, 2008
Dr. Mauro Bologna
Department of Physics
University of North Texas
Denton, Texas
"Collapse of Civilizations:  A Mathematical Model"
In this talk I consider a mathematical model for the evolution and collapse of the Easter Island society. Based on historical reports, the available primary sources consisted almost exclusively on the trees. I describe the inhabitants and the resources as an isolated dynamical system. A mathematical and numerical analysis of the collapse of the Easter Island community is performed. In particular, we analyze the critical values of the fundamental parameters and a demographic curve is presented. The technological parameter, quantifying the exploitation of the resources, is calculated. I apply it to the case of  another extinguished civilization (Copan Maya) confirming the consistency of the adopted model.
*Previously at Universidad de Tarapaca, Arica, Chile.
Dr. Bologna's Presentation

September 23, 2008
Professor Maurizio Benfatto
Istituto Nazionale Fisica Nucleare, Frascati, Italy
and
Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford California
"X-Ray Absorption Spectroscopy: State of Art and New Applications in Material Science"
X-Ray Absorption spectroscopy (XAS) is a powerful tool to investigate both the electronic and geometrical structure around a well defined absorbing atom that belongs to any type of material, from biological samples to condensed matter. In this talk I will present a general theoretical scheme to analyze the experimental data from a low energy edge to a very high energy. This scheme, based on Multiple Scattering (MS) theory, allows a complete recovery of experimental data. In particular, I will discuss a new method to obtain quantitative information about structure using the low energy part of the spectrum, starting from the low energy edge. This procedure allows a complete three-dimensional determination of the local geometry around the photo-absorber for many different systems.  Some chemical and biological applications will be presented in detail.

September 16, 2008
Dr. Daniel Day
Centre for Micro-Photonics
Swinburne University of Technology
Victoria, Australia
"Femtosecond Biophotonics"
The use of the femtosecond pulse laser for microfabrication is demonstrated with an emphasis on the design and fabrication of devices for biological applications.  The fabrication of microscopic landscapes or microgrids is a technological advancement which is enabling live cell studies of biological applications previously not possible.The femtosecond pulse laser has added many new dimensions to biophotonics research beyond the traditional imaging applications.  Indeed, femtosecond biophotonics has now achieved the ability to be utilised as a dynamic tool for imaging, manipulation and fabrication to create the next generation of technology for biological and biomedical applications.

September 9, 2008
Dr. Chris Littler
Department of Physics
University of North Texas
Denton, Texas
"Research in Physics at the University of North Texas"
Dr. Littler will welcome new students to the Physics Department and tell about the department. Then faculty members will introduce themselves and make some comments about  their research interests and group.