UM Department of Physicsw

Colloquia/Seminars - Spring 2008

Date		Room	Time	Speaker	Title
2/8/2008	Colloquium	Wilder	4:30 pm	Dr. Taotao Fang, University of California, Irvine	Cosmic Structure and Evolution as Revealed by the Intergalactic Medium
2/15/2008	Colloquium	Wilder	4:30 pm	Dr. Brad Johnson, University of Oxford	Measuring the Beginning of the Universe
2/18/2008	Colloquium	Wilder	4:30 pm	Dr. Elena Gallo, University of California, Santa Barbara	Accretion modes and jet production in stellar and super-massive black holes
2/22/2008	Colloquium	Wilder	4:30 pm	Dr. Thushara Perera, University of Chicago	Discovering Galaxies and Galaxy Clusters at Millimeter Wavelengths
2/25/2008	Colloquium	Wilder	4:30 pm	Dr. Scott Porter, NASA/GSFC	Advanced x-ray spectrometers on the ground, with rockets, and with large observatories
2/29/2008	Colloquium	Wilder	4:30 pm	Dr. Kevin Huffenberger, Caltech / Jet Propulsion Lab	Cosmic Microwave Background: from measurements to cosmology
3/17/2008	Colloquium	Wilder	4:30 pm	Dr. Martin Forstner, University of California, Berkeley	Bio-Membranes: Structured, Adaptive and Dynamic - New Insights from in vivo and in vitro Experiments
3/19/2008	Colloquium	Wilder	5:00 pm	Dr. Denis Karaiskaj, JILA, University of Colorado & NIST	Two-dimensional optical spectroscopy on biomolecules
3/24/2008	Colloquium	Wilder	5:00 pm	Dr. Christopher V. Gabel, Harvard University	The Study of Neurocircuitry and Neural Regeneration in C. elegans Using Femtosecond Laser Surgery
4/4/2008	Colloquium	Wilder	4:30 pm	Prof. Greg Gbur, UNC Charlotte	From Nonradiating Sources to Optical Cloaks: A Short History of the Physics of Invisibility
4/7/2008	Colloquium	Wilder	4:30 pm	Prof. Steve Eikenberry, University of Florida	Black Hole Astrophysics & the FLAMINGOS-2 Galactic Center Survey

Unless otherwise notified, Colloquia start at 4:30 pm in the Wilder Auditorium (refreshments are in the Physics Library starting at 4:00 pm). Seminars are organized on an individual basis (see seminar link for details).

Colloquia organized by Dr. Massimiliano Galeazzi

Department of Physics
University of Miami

February 8th, 2008
Dr. Taotao Fang, University of California, Irvine
Title: Cosmic Structure and Evolution as Revealed by the Intergalactic Medium
Abstract: The intergalactic space is a fascinating place to study cosmic structure formation and evolution. Multi-wavelength studies of the intergalactic medium (IGM), the main repository of baryonic matter in the universe, have revealed the complex history of the IGM and its critical role in galaxy formation and evolution. In this talk, I will begin with a brief review of our current understanding of the IGM, and what the IGM study can tell us about the cosmic structure and evolution.
Details of the IGM study are presented through our research of the warm-hot IGM (WHIM) and the gaseous galactic halo, which is the interface between galaxies and the IGM. I will also discuss future prospects of the IGM study, including instrumental development.

February 15th, 2008
Dr. Brad Johnson, University of Oxford
Title: Measuring the Beginning of the Universe
Abstract: I will discuss the ongoing effort to experimentally understand how the universe began and how it has evolved. This effort is driven largely by measurements of the cosmic microwave background radiation (CMB), and these measurements will be the focus of my talk. The CMB is an image of the universe as it was 380,000 years after the Big Bang, and this image, which only appears in the millimeter-wave band of the electromagnetic spectrum, spans the entire sky. Angular intensity and polarization variations in the CMB (also commonly called CMB anisotropies) encode information about physical processes that operated in the universe when the CMB formed. At the University of Oxford, I am currently collaborating on two, world-class experiments called CLOVER and EBEX. Both of these experiments are designed to precisely characterize one of the faintest and therefore most challenging CMB anisotropies: the primordial "B-mode" polarization pattern, which is predicted by the prevailing cosmological model to have been produced by gravity waves emanating from the epoch of inflation. Inflation is an explosive burst of rapid expansion that is thought to have occurred during the first fraction of a second after the Big Bang. An experimental characterization of inflation would be a breakthrough for both astrophysics and particle physics, for currently there is no way to create inflation-like conditions in a laboratory or particle accelerator and therefore no way to experimentally constrain the various theories of inflation. The majority of my talk will focus on the details of CLOVER and EBEX. Though these two experiments have similar astrophysical goals, they each take a very different observational approach. EBEX will observe the CMB from a stratospheric balloon-borne platform above Antarctica, while CLOVER will make ground-based observations from Atacama, Chile. I will conclude my talk by discussing the future of CMB observations.

February 18th, 2008
Dr. Elena Gallo, University of California, Santa Barbara
Title: Accretion modes and jet production in stellar and super-massive black holes
Abstract: Relativistic jets are amongst the most spectacular, and yet poorly-understood consequences of accretion onto super-massive black holes at the center of galaxies, and onto stellar-mass black holes and neutron stars in X-ray binaries. They extract a large, possibly dominant, fraction of the total available accretion energy, and may even tap the power of the black hole spin. After reviewing the phenomenological properties of relativistic jets powered from stellar-mass black holes, I will focus on their importance both for the overall energetics of the accretion process and as a source of energy input into the interstellar medium. Along this path, I will also present recent results from a multi-wavelength survey of super-massive black holes in the nuclei of nearby galaxies. This campaign is designed to quantify the impact of outflows powered by weakly accreting super-massive black holes on the host galaxies.

February 22nd, 2008
Dr. Thushara Perera, University of Chicago
Title: Discovering Galaxies and Galaxy Clusters at Millimeter Wavelengths
Abstract: Galaxies with the highest star formation rates are often enshrouded in dust, making them optically faint but easily detectable at mm wavelengths. Recent surveys show that the number density of these objects evolves rapidly with time/redshift to reach the very low numbers observed in today's universe. Detailed studies of these dusty galaxies promise to yield a wealth of information about the evolution of massive galaxies, galaxy clusters, the star formation rate of the universe, and large scale structure. Such a comprehensive study is the main aim of several upcoming projects in observational cosmology. I will present results from a new survey that represents a first step towards this goal, conducted with a mm-wave bolometer array named AzTEC. I will also discuss the potential and future of this research, especially in the context of targeted searches for dusty galaxies around mass over-densities at various stages of becoming a present-day galaxy cluster. I will also describe "frequency selective bolometers," a new detector technology that will enable the efficient spectral profiling of many such galaxies as well as high-efficiency multi-color imaging of the Sunyaev-Zel'dovich effect in galaxy clusters. I will highlight instrumental and analysis techniques that facilitate robust measurements at these wavelengths.

February 25th, 2008
Dr. Scott Porter, NASA/GSFC
Title: Advanced x-ray spectrometers on the ground, with rockets, and with large observatories
Abstract: X-ray spectroscopy directly probes some of the most violent processes in the universe including accretion around supermassive black holes, nuclear burning on neutron stars, mergers of clusters of galaxies, and the shock-heated interstellar medium in young supernova remnants. With the high-resolution x-ray spectrometers on the Chandra and XMM-Newton x-ray observatories, we are just starting to use high resolution spectroscopy to probe and understand some of these phenomena. New instruments based on cryogenically cooled x-ray detectors will revolutionize this field and provide an unprecedented view of cosmic x-ray generation and the underlying physical processes in a wide range of astrophysical objects. We are already using these instruments to great effect on the ground and on suborbital sounding rockets as an important adjunct to orbital observatories. In the next decade, four important large scale x-ray observatories are planned, all of which are centered around cryogenic x-ray spectrometers. Here I will discuss the great progress that we have made in developing, building, and flying cryogenic x-ray spectrometers and the great wealth of scientific results we have already achieved with these novel, new instruments. In addition, I will discuss developments for future observatories, and research into truly large scale imaging x-ray spectrometers.

February 29th, 2008
Dr. Kevin Huffenberger, Caltech / Jet Propulsion Lab
Title: Cosmic Microwave Background: from measurements to cosmology
Abstract: The Cosmic Microwave Background (CMB) probes physics inaccessible to terrestrial laboratories, providing unique constraints on the unknown interaction mechanisms, and mysterious forms of matter and energy, which persist in our picture of the universe. The achievement of the recent tabulation of a rough matter-energy budget for the universe (the Wilkinson Microwave Anisotropy Probe (WMAP) measures roughly 5% baryons, 20% dark matter, 75% dark energy) serves to highlight how much work remains: we know little about roughly ninety-five percent of the universe. Nor have we positively identified, from a wide variety of inflationary scenarios, the precise mechanism for quantum fluctuations to generate inhomogeneities in the universe in the first place. The next generation of CMB observatories will address these questions from the ground, from balloons, and from space--- highlighted by the launch this year of the Planck satellite---and are becoming so precise that the universe itself is a significant source of noise, in the form of contaminating radiation and spectral distortions from other galaxies and galaxy clusters.

March 17th, 2008
Dr. Martin Forstner, University of California, Berkeley
Title: Bio-Membranes: Structured, Adaptive and Dynamic - New Insights from in vivo and in vitro Experiments
Abstract: Lipid membranes are an essential building block of all cellular life, separating the inside of a cell from the outside and compartmentalizing the cell interior. Once thought of as passive and featureless environments for membrane proteins, a new picture of bio-membranes has begun to emerge that paints them as structured, complex fluids that are organized on many time and length scales. Recent advances in optical microscopy and spectroscopy techniques have facilitated the study, on a single molecule level, of membrane structure, membrane interactions with proteins and their underlying physics. New results on both bio-mimetic model membranes and live cell membranes not only gives credence to the new membrane model, but also point towards a much more active role for membranes in the fascinating physicochemical machinery of cellular life.

March 19th, 2008
Dr. Denis Karaiskaj, JILA, University of Colorado & NIST
Title: Two-dimensional optical spectroscopy on biomolecules
Abstract: The development and applications of methods that can determine the time dependence of structural changes in complex molecular assemblies offer exciting challenges to physics, biology, and chemistry. The new optical multidimensional spectroscopy, which has essentially unlimited time resolution on the scale of large molecular motions, is expected to contribute significantly to this goal (PNAS September 4, 2007). Such advances will complement the vast knowledge of average structures being obtained by the established methods in biology. The most widely successful example of multidimensional spectroscopy is 2D NMR, which has revolutionized structural biology. Results on femtosecond 2D spectroscopy in the mid infrared spectral range used to study the conformations of a model dipeptide will be presented. Different pulse sequences and polarizations in combination with simulations have been used in order to further enhance the ability of 2D optical spectroscopy to obtain structural information. Recent applications of this new method on different peptide structures, such as α-helices, β-sheets and turns, and the future implications of this technique in understanding protein folding and aggregation will be discussed.
Furthermore, developing nanoscale biosensors is an important task in the objective of detecting conformation changes of biomolecules. Carbon nanotubes have a tunable near-infrared emission leading to greater tissue penetration and reduced auto-fluorescent background in thick tissue and whole-blood media. The emission energies respond to changes in the local dielectric function and/or microscopic external strain, but remain stable to permanent photobleaching. In the mean time they also respond to temperature fluctuations, and therefore, to separate the intrinsic temperature effects from extrinsic effects, which originate from the surrounding environment, is a very important task in the effort of developing reliable biosensors.

March 24th, 2008
Dr. Christopher Gabel, Harvard University
Title: The Study of Neurocircuitry and Neural Regeneration in C. elegans Using Femtosecond Laser Surgery
Abstract: Using tightly-focused pulses from an ultrafast laser, we can ablate regions of biological tissue with submicron precision. It is thus possible to snip individual nerve fibers with minimal collateral damage. The C. elegans hermaphrodite, a simple nematode (roundworm), has 302 neurons, the morphology and connectivity of which have been completely mapped. The application of femtosecond laser surgery to this model organism allows the precise dissection of simple behavioral circuits as well as the study of neural regeneration in vivo. Combined with optical neurophysiology, quantitative behavioral analysis and the powerful genetic methods of C. elegans these biophysical techniques are creating new opportunities in the study of neural function and regeneration at the molecular, cellular and circuits level.

April 4th, 2008
Prof. Greg Gbur, UNC Charlotte
Title: From Nonradiating Sources to Optical Cloaks: A Short History of the Physics of Invisibility
Abstract: In recent years, much attention has been given to the development of 'optical cloaking devices', metamaterial shells which guide light around an interior region and render the device and its contents invisible. However, the study of invisible and radiationless systems stretches back at least a century, to early questions involving quantum mechanics. In this talk we will discuss the physics and history of a number of these invisibility schemes.

April 7th, 2008
Prof. Steve Eikenberry, University of Florida
Title: Black Hole Astrophysics & the FLAMINGOS-2 Galactic Center Survey
Abstract: I will review the relatively young field of black hole studies using multi-wavelength (particularly combined X-ray and infrared) observational techniques. I will place special emphasis on the insights this is providing into the physics of "microquasars" -- stellar-mass black hole binaries exhibiting relativistic jet outflows. I will also discuss our plans for the immediate future of this field using the upcoming FLAMINGOS-2 near-infrared multi-object spectrograph on the 8-meter Gemini South telescope in combination with the Chandra X-ray Observatory to conduct a large-scale survey of the Galactic Center region.