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The Broadcast side of the Physics Colloquium.

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Colloquiums that were recorded in 2001:

Mar. 2nd
Speaker:
Katie Freese, University of Michigan

Title:
"Dark Matter and Dark Energy in Cosmology"

Abstract:
The quest in cosmology is to understand the origin and evolution of the universe. Experiments at the turn of the millennium have answered some questions almost a century old and have raised some new ones. Balloon experiments at the South Pole have settled questions about the geometry of space-time and the mass density of the universe. But what and where is this mass? From comparison with element abundances from Big Bang nucleosynthesis, we know it cannot be baryonic. Some of it is the dark matter in galaxies. I will argue that this dark matter cannot be in the form of stars or substellar objects, and discuss recent experiments that claim a detection of supersymmetric dark matter. Remarkably, the bulk of the universe may be in the form of "dark energy," as evidenced by studies of distant supernovae. While still uncertain, these results imply a shift in the paradigm of cosmology. Implications for the fate of the universe will be discussed.

Mar. 23rd
Speaker:
Gelsomina De Stasio, University of Wisconsin-Madison

Title:
"Physics and Medicine Get Together to Cure Brain Cancer"

Abstract:
Glioblastoma, the most common brain cancer in the US, has incidence and mortality of approximately 12,000 cases per year; incidence and mortality are the same because this malignancy is resistant to currently available therapies, and patients succumb within 1 year of diagnosis. This stimulates the search for new therapeutic strategies, such as neutron capture or radiotherapy, enhanced by a locally accumulated sensitizer. Gadolinium is a candidate radiosensitizer and neutron capture agent. Gadolinium Neutron Capture Therapy (GdNCT) for brain cancer is so far only a hypothetical therapy, since it has never been tested on human or animal cases. We must find a Gd compound that targets all and only cancer cells, and accumulates in cell nuclei, before it can be suggested for clinical trials. At the UW-Synchrotron Radiation Center we are using X-ray PhotoElectron Emission spectro Microscopes (X-PEEMs) to investigate the micro-localization of Gd in glioblastoma cells and tissues, to identify the right Gd-compound for the therapy. The MEPHISTO X-PEEM, after reaching a resolution of 20 nm, has been extensively used for the last five years. The recently acquired Elmitec PEEM III, has reached a resolution of 5.5 nm, during the first 3 weeks of operation. Among the most recent results of both instruments, we will the micro-localization of gadolinium in glioblastoma cells in culture and tissue sections. The results obtained with the first Gd-compound prove that gadolinium is uptaken in the cancer cell nuclei, as necessary for GdNCT, in the in vitro case, while in vivo only 28% of the tumor exhibits Gd. Therefore new Gd-compounds must be tested, in collaboration with UW-Human Oncology, before GdNCT can become a real therapy. These experiments demonstrate the need for close interaction of physicists and medical doctors to address the elusive goal of curing brain cancers. A brief overview of other experiments will include the microchemistry of bacteria, rocks, colossal magnetoresistive materials, superconductors, tribology and archaeology specimens, demonstrating the of our approach.

Mar. 30th
Speaker:
Dr. Bob Bowman, Institute for Space & Security Studies

Title:
"Dissecting Trajectories: The Key to Ballistic Missile Defense"

Abstract:
Physics Special Lecture
Dr. Bowman earned the Ph.D. at CalTech in aeronautics and nuclear engineering. He is currently president of the Institute for Space and Security Studies. He has had extensive experience in the US Air Force (101 missions, Air Medal with 5 oak leaf clusters) and, in addition, was director of Advanced Space Programs for the Air Force. He has had substantial experience in the aerospace industry with General Dynamics

Spring 01
Speaker:
Keath Simon, From the Univerity of Wisconsin-Madison

Title:
"Non-Linesr Dynamic Study on the Aladdin Electron Storage Ring at SRC by Jianyang Lin"

Abstract:

Apr. 13th
Speaker:
George Srajer, Argonne National Laboratory

Title:
"Measurements of Magnetic Properties Using X-rays"

Abstract:
X-ray scattering and spectroscopy techniques can be used to determine magnetic properties of matter. First, a general introduction will be given on how x-rays interact with atoms with specific emphasis on electrons that give rise to magnetism. The introduction will be followed by a brief description of the Advanced Photon Source, a national facility for the application of synchrotron radiation. In the main part of the talk, reflectivity data from a Fe/Gd multilayer will be presented. The interplay between structural and magnetic roughness will be discussed, as well as its implication on the performance of new magnetic storage devices. In the second example, imaging of magnetic domains with a micron-sized beam will be presented. The experiment was performed on a SmCo/Fe sample, which belongs to an important class of nanocomposite materials called "spring magnets." For the first time, information on the size, orientation, and distribution of Sm moments were revealed. Finally, the future application of microfocused beam to the study of magnetic nanoarrays will be discussed.

May 4th
Speaker:
F. Barry Dunning, Rice University

Title:
"Rydberg Atoms: A Novel Probe of Non-Linear Dynamics and of Atom/Surface Interaction"

Abstract:
Studies of atoms in which one electron is excited to a state of are principal quantum number n are described. Such atoms possess unusual physical characteristics. At high n, the classical electron orbital period Tn is very large (Tn ~ 10 ns at n ~ 400) allowing application of unidirectional electric field pulses, termed half-cycle pulses (HCPs), whose duration is <<Tn. In this limit, the HCP simply delivers an impulsive momentum transfer or "kick" to the excited electron. This opens up new opportunities for the control and manipulation of atomic wavefunctions and for testing classical-quantum correspondence. In addition, the "kicked" atom provides a new paradigm for the study of nonlinear dynamics in Hamiltonian systems and many interesting effects such as dynamical stabilization and quantum localization are evident. Rydberg atoms are strongly perturbed by the presence of a nearby metal surface. Image charge effects lead to formation of hybridized states similar to Start states that can be oriented towards, parallel to, or away from the surface. Ionization can occur through tunneling of the excited electron into vacant levels in the metal. Rydberg atom measurements can thus provide new insights into charge transfer and electron tunneling during atom/surface interactions and into surface-induced atomic perturbations.

Sept. 21st
Speaker:
Eric G. Adelberger, University of Washington

Title:
"Sub-millimeter Tests of the Gravitational Inverse Square Law: Searching for 'Large' Extra Dimensions"

Abstract:
It is remarkable that questions about gravitation, the oldest known interaction in physics, are again at the center of physics and that small-scale experiments can address important open issues. Modern string theory ideas (new scalar particles and extra dimensions) hint that Einstein's Equivalence Principle and Newton's Inverse-Square Law may be exact.I will discuss motivations (large-extra dimensions, a small cosmological constant), techniques (torsion and beam balances), and results of such tests, emphasizing the Eot-Wash group's recent tests of the Inverse-Square Law for length scales down to 100 micrometers.

Sept. 27th
Speaker:
Herrison H. Schmitt, From the Univerity of Wisconsin-Madison

Title:
"Origin & Evolution of the Moon: A Contrary View"

Abstract:
Physics Special Lecture

Oct. 19th
Speaker:
Ali Yazdani, University of Illinois at Urbana-Champaign

Title:
"Nanoscale Investigations of Superconductors with a Cooled Scanning Tunneling Microscope"

Abstract:
The scanning tunneling microscope (STM) is a powerful tool to study electronic phenomena on solid surfaces with atomic scale precision. My goal in this talk is to show you how this technique can provide a new local perspective of the superconducting state. I will begin by discussing experiments on conventional superconductors, which provide important background on how to interpret STM experiments in general. For example, these experiments show what happens when we change just one atom in a superconductor. I will then turn to the application of STM to the high-Tc cuprate superconductors, in which planes consisting of Cu and O atoms are believed to be responsible for a more exotic form of superconductivity. I will show the first STM image of this famous CuO2 plane which up to now has remained hidden, buried underneath the surface in all STM measurements performed to date. The STM measurements on this CuO2 plane turns out to be surprising making us think hard about what we probe with the STM and how to interpret surface experiments on high-Tc superconductors in general.

Nov. 9th Speaker: Richard Henry, From johns Hopkins University

Title: "The Search for the Intergalactic Medium"

Abstract:

Nov. 16th Speaker: D.N.Basov, Dept. of Physics, Univ. of California, San Diego

Title: "High-Tc Superconductivity: Summing Up"

Abstract: Discovered nearly 15 years ago, high-Tc superconductors have consolidated a large fraction of the condensed matter community in the search for the mechanism leading to the transition temperatures as high as 160 K. In this talk I will overview recent developments in the experimental studies of high-Tc cuprates using several spectroscopic probes, including infrared spectroscopy. The crucial advantage of the latter technique is that one can get insights into the key characteristics of the superconducting state through a variety of model-independent sum rules. Specifically, our group at UCSD has employed a new analysis based on sum rules to examine the energy scales associated with the superconducting condensate and with the so-called pseudogap state. We believe that the sum rule results may be instrumental in narrowing down the field of plausible microscopic scenarios of high-Tc superconductivity.

Mar. 2nd	Speaker:	Katie Freese, University of Michigan
	Title:	"Dark Matter and Dark Energy in Cosmology"
	Abstract:	The quest in cosmology is to understand the origin and evolution of the universe. Experiments at the turn of the millennium have answered some questions almost a century old and have raised some new ones. Balloon experiments at the South Pole have settled questions about the geometry of space-time and the mass density of the universe. But what and where is this mass? From comparison with element abundances from Big Bang nucleosynthesis, we know it cannot be baryonic. Some of it is the dark matter in galaxies. I will argue that this dark matter cannot be in the form of stars or substellar objects, and discuss recent experiments that claim a detection of supersymmetric dark matter. Remarkably, the bulk of the universe may be in the form of "dark energy," as evidenced by studies of distant supernovae. While still uncertain, these results imply a shift in the paradigm of cosmology. Implications for the fate of the universe will be discussed.

Mar. 23rd	Speaker:	Gelsomina De Stasio, University of Wisconsin-Madison
	Title:	"Physics and Medicine Get Together to Cure Brain Cancer"
	Abstract:	Glioblastoma, the most common brain cancer in the US, has incidence and mortality of approximately 12,000 cases per year; incidence and mortality are the same because this malignancy is resistant to currently available therapies, and patients succumb within 1 year of diagnosis. This stimulates the search for new therapeutic strategies, such as neutron capture or radiotherapy, enhanced by a locally accumulated sensitizer. Gadolinium is a candidate radiosensitizer and neutron capture agent. Gadolinium Neutron Capture Therapy (GdNCT) for brain cancer is so far only a hypothetical therapy, since it has never been tested on human or animal cases. We must find a Gd compound that targets all and only cancer cells, and accumulates in cell nuclei, before it can be suggested for clinical trials. At the UW-Synchrotron Radiation Center we are using X-ray PhotoElectron Emission spectro Microscopes (X-PEEMs) to investigate the micro-localization of Gd in glioblastoma cells and tissues, to identify the right Gd-compound for the therapy. The MEPHISTO X-PEEM, after reaching a resolution of 20 nm, has been extensively used for the last five years. The recently acquired Elmitec PEEM III, has reached a resolution of 5.5 nm, during the first 3 weeks of operation. Among the most recent results of both instruments, we will the micro-localization of gadolinium in glioblastoma cells in culture and tissue sections. The results obtained with the first Gd-compound prove that gadolinium is uptaken in the cancer cell nuclei, as necessary for GdNCT, in the in vitro case, while in vivo only 28% of the tumor exhibits Gd. Therefore new Gd-compounds must be tested, in collaboration with UW-Human Oncology, before GdNCT can become a real therapy. These experiments demonstrate the need for close interaction of physicists and medical doctors to address the elusive goal of curing brain cancers. A brief overview of other experiments will include the microchemistry of bacteria, rocks, colossal magnetoresistive materials, superconductors, tribology and archaeology specimens, demonstrating the of our approach.

Mar. 30th	Speaker:	Dr. Bob Bowman, Institute for Space & Security Studies
	Title:	"Dissecting Trajectories: The Key to Ballistic Missile Defense"
	Abstract:	Physics Special Lecture Dr. Bowman earned the Ph.D. at CalTech in aeronautics and nuclear engineering. He is currently president of the Institute for Space and Security Studies. He has had extensive experience in the US Air Force (101 missions, Air Medal with 5 oak leaf clusters) and, in addition, was director of Advanced Space Programs for the Air Force. He has had substantial experience in the aerospace industry with General Dynamics

Spring 01	Speaker:	Keath Simon, From the Univerity of Wisconsin-Madison
	Title:	"Non-Linesr Dynamic Study on the Aladdin Electron Storage Ring at SRC by Jianyang Lin"
	Abstract:

Apr. 13th	Speaker:	George Srajer, Argonne National Laboratory
	Title:	"Measurements of Magnetic Properties Using X-rays"
	Abstract:	X-ray scattering and spectroscopy techniques can be used to determine magnetic properties of matter. First, a general introduction will be given on how x-rays interact with atoms with specific emphasis on electrons that give rise to magnetism. The introduction will be followed by a brief description of the Advanced Photon Source, a national facility for the application of synchrotron radiation. In the main part of the talk, reflectivity data from a Fe/Gd multilayer will be presented. The interplay between structural and magnetic roughness will be discussed, as well as its implication on the performance of new magnetic storage devices. In the second example, imaging of magnetic domains with a micron-sized beam will be presented. The experiment was performed on a SmCo/Fe sample, which belongs to an important class of nanocomposite materials called "spring magnets." For the first time, information on the size, orientation, and distribution of Sm moments were revealed. Finally, the future application of microfocused beam to the study of magnetic nanoarrays will be discussed.

May 4th	Speaker:	F. Barry Dunning, Rice University
	Title:	"Rydberg Atoms: A Novel Probe of Non-Linear Dynamics and of Atom/Surface Interaction"
	Abstract:	Studies of atoms in which one electron is excited to a state of are principal quantum number n are described. Such atoms possess unusual physical characteristics. At high n, the classical electron orbital period Tn is very large (Tn ~ 10 ns at n ~ 400) allowing application of unidirectional electric field pulses, termed half-cycle pulses (HCPs), whose duration is <<Tn. In this limit, the HCP simply delivers an impulsive momentum transfer or "kick" to the excited electron. This opens up new opportunities for the control and manipulation of atomic wavefunctions and for testing classical-quantum correspondence. In addition, the "kicked" atom provides a new paradigm for the study of nonlinear dynamics in Hamiltonian systems and many interesting effects such as dynamical stabilization and quantum localization are evident. Rydberg atoms are strongly perturbed by the presence of a nearby metal surface. Image charge effects lead to formation of hybridized states similar to Start states that can be oriented towards, parallel to, or away from the surface. Ionization can occur through tunneling of the excited electron into vacant levels in the metal. Rydberg atom measurements can thus provide new insights into charge transfer and electron tunneling during atom/surface interactions and into surface-induced atomic perturbations.

Sept. 21st	Speaker:	Eric G. Adelberger, University of Washington
	Title:	"Sub-millimeter Tests of the Gravitational Inverse Square Law: Searching for 'Large' Extra Dimensions"
	Abstract:	It is remarkable that questions about gravitation, the oldest known interaction in physics, are again at the center of physics and that small-scale experiments can address important open issues. Modern string theory ideas (new scalar particles and extra dimensions) hint that Einstein's Equivalence Principle and Newton's Inverse-Square Law may be exact.I will discuss motivations (large-extra dimensions, a small cosmological constant), techniques (torsion and beam balances), and results of such tests, emphasizing the Eot-Wash group's recent tests of the Inverse-Square Law for length scales down to 100 micrometers.

Sept. 27th	Speaker:	Herrison H. Schmitt, From the Univerity of Wisconsin-Madison
	Title:	"Origin & Evolution of the Moon: A Contrary View"
	Abstract:	Physics Special Lecture

Oct. 19th	Speaker:	Ali Yazdani, University of Illinois at Urbana-Champaign
	Title:	"Nanoscale Investigations of Superconductors with a Cooled Scanning Tunneling Microscope"
	Abstract:	The scanning tunneling microscope (STM) is a powerful tool to study electronic phenomena on solid surfaces with atomic scale precision. My goal in this talk is to show you how this technique can provide a new local perspective of the superconducting state. I will begin by discussing experiments on conventional superconductors, which provide important background on how to interpret STM experiments in general. For example, these experiments show what happens when we change just one atom in a superconductor. I will then turn to the application of STM to the high-Tc cuprate superconductors, in which planes consisting of Cu and O atoms are believed to be responsible for a more exotic form of superconductivity. I will show the first STM image of this famous CuO2 plane which up to now has remained hidden, buried underneath the surface in all STM measurements performed to date. The STM measurements on this CuO2 plane turns out to be surprising making us think hard about what we probe with the STM and how to interpret surface experiments on high-Tc superconductors in general.

Nov. 9th	Speaker:	Richard Henry, From johns Hopkins University
	Title:	"The Search for the Intergalactic Medium"
	Abstract:

Nov. 16th	Speaker:	D.N.Basov, Dept. of Physics, Univ. of California, San Diego
	Title:	"High-Tc Superconductivity: Summing Up"
	Abstract:	Discovered nearly 15 years ago, high-Tc superconductors have consolidated a large fraction of the condensed matter community in the search for the mechanism leading to the transition temperatures as high as 160 K. In this talk I will overview recent developments in the experimental studies of high-Tc cuprates using several spectroscopic probes, including infrared spectroscopy. The crucial advantage of the latter technique is that one can get insights into the key characteristics of the superconducting state through a variety of model-independent sum rules. Specifically, our group at UCSD has employed a new analysis based on sum rules to examine the energy scales associated with the superconducting condensate and with the so-called pseudogap state. We believe that the sum rule results may be instrumental in narrowing down the field of plausible microscopic scenarios of high-Tc superconductivity.