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September 2, 2005 |
| Theodora Leventouri (FAU), "Nanoscale Magnetic Biomaterials" |
| The potential to advance the design and development of new biomaterials for medical applications has been made possible by progress on two fronts. One is the recent development of new technologies such as microscale, nanoscale, and biologically inspired fabrication including surface modification methods. The other is the increase in fundamental understanding of cell and molecular biology, tissue engineering, targeted drug delivery and other biomedical processes at the cellular level. The properties of nanoscale materials are not, in general, predictable from those of bulk materials. This arises from a number of factors, including the emergence of quantum phenomena at the nanoscale and the fact that a high proportion of the atoms or molecules find themselves at surfaces and interfaces with different environments from those they encounter in bulk materials. Magnetic nanoparticles are ideal for construction of nanostructured materials with adjustable physical and chemical properties that are not characteristic of the atom or the bulk compound. Vertically-aligned carbon nanofibers (VACNFs) are a promising way to get more interesting nanoscale-size magnetic elements in a biocompatible system. We' ll discuss processing and properties of new nanoscale magnetic biomaterials and carbon nanofibers. |
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September 9, 2005 |
| Warner Miller (FAU), "State of the Department Address" |
| Free pizza will be served at this special colloquium session to students, faculty and staff in the Department of Physics. The chair, Warner Miller, will introduce new members of the Department and describe recent developments. Members of the curriculum committee will be present to eat free pizza and to outline a planned overhaul of both the undergraduate and graduate physics curricula. This presentation will offer students and other interested parties an opportunity to make comments as the committee heads into the second and final year of its work. All are encouraged to attend. Did I mention there would be free pizza? |
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September 16, 2005 |
| Silke Dodel (FAU/Center for Complex Systems), "Team Dynamics - From Psychology to Manifolds" |
| What is specific about team interaction and how can it be measured? Such question addresses the essential nature of human social interactions, but despite being a presence in daily life, it has not been answered satisfactorily. A team consisting of one excellent and several poor members may score reasonably well by conventional standards, but may not in terms of team interaction. Our aim is to develop a metric by which the quality of team interaction can be assessed without the knowledge of an outcome (such as a score in a basketball match). This requires a quantitative analysis of team interaction for which we use a dynamical systems approach. In this approach at every point in time each team can be described by a set of variables (location of the team members, head orientations, etc.) and their temporal derivatives. Taken together, these variables form a team vector, that, across time, passes through a trajectory in a high-dimensional phase space. Multiple trajectories from the team performing the same task over and over again, lie in some manifold in phase space. The conceptual idea is that the properties of the manifold inform us about the quality of team interaction. For instance we expect the manifold to be low-dimensional due to constraints imposed by team interaction. In our presentation we will introduce our approach using data from teams of soldiers performing a room clearing task. |
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September 23, 2005 |
| Ruslan Vaulin (FAU), "Do you have a Hamiltonian? Then, what is the Problem? Towards the Problem of Time in Canonical Quantum Gravity" |
| Canonical quantum gravity is one of the most direct approaches to quantizing Einstein's theory of general relativity. Here the configuration variable represents the state of the universe in an instant of "time" i.e. the 3-dimensional spacelike geometry of the universe. One faces the challenge of choosing the correct form of the operator of time translation which is responsible for the evolution of 3-geometries. The property of general covariance (the independence of the choice of coordinates) of the theory impose severe restrictions on the possible candidates for the generator of the quantum evolution. It is been a long standing challenge to find such operator and complete the canonical quantization program of gravity. This amounts to overcoming both conceptual and technical difficulties and is often referred as "problem of time". In this talk we will review the traditional ADM (Arnowitt, Misner and Deser) and Wheeler-DeWitt quantization schemes. We do this to critically examine the recent candidate theory of canonical quantum gravity due to W.A. Miller and A. Kheyfets, and test them on the analytically tractable Bianchi IX cosmological model. This cosmologically relevant model is a special case of a highly symmetrical spacetime which allows one to demonstrate the relative successes and failures of each approach together with possible testable predictions. |
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September 30, 2005 |
| David Cai (New York University/Courant Institute), "Spatiotemporal Dynamics of Primary Visual Cortex" |
| It has been shown experimentally that spontaneous cortical activity in the absence of sensory inputs modulates stimulus-evoked activity and is correlated with behavior. In the primary visual cortex (V1), there is a close relationship between ongoing spontaneous activity and the spontaneous firing of a single neuron. There are dynamic switchings amongst spontaneous cortical states. To study theoretically these spatially coherent patterns of spontaneous activity, which emerge in a fluctuation-dominated neuronal network, we have developed a coarse-grained representation of neuronal network dynamics in terms of (1+1)-D kinetic equations, which are derived via a novel moment closure, directly from the original large-scale integrate-and-fire neuronal network without any free parameters. This powerful kinetic theory captures the full dynamic range of neuronal networks. We have applied this kinetic theory to investigate the spatiotemporal cortical activity in V1 under the line-motion illusion stimulus paradigm. |
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October 7, 2005 |
| Aurelian Rusanu (FAU), "First-principles band structure calculations in metallic alloys" |
| Designing materials, particularly at the nano-scale, is an important scientific research area. It includes a large spectrum of basic science and technological developments. In order to provide results that are relevant to real materials, quantum mechanical simulations involving thousands to millions of atoms must be carried out. The locally self-consistent multiple scattering (LSMS) method is the method of choice for such calculations because it has a technical feature called order-N scaling. We describe an implementation of the LSMS for massively parallel supercomputers using k-space and real-space methods. For magnetic materials, the constrained local moment approach and the exchange interaction method are used. We demonstrate our approach by calculating the electronic and magnetic structure of an iron nano-particle embedded in iron aluminide crystal matrix. |
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October 14, 2005 |
| Spyros Magliveras (FAU-Mathematics), "Cryptography Today" |
| A brief historical introduction of cryptology will be given of cryptology for the years up to 1950. The transition to modern day cryptologic problems and solutions will be presented. Symmetric vs asymmetric cryptography will be explored with particular emphasis on asymmetric (public-key) cryptography. One-way functions, trap-door one-way functions, current robust and failed systems and attacks. System failures if quantum computers become practical. Elliptic curve cryptography, and group-theoretic cryptography will be discussed. |
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October 21, 2005 |
| Pablo Laguna (Penn State University), "Black Hole Simulations: A Tool in a Multi-messenger Astronomy" |
| A new era in astronomy will begin once gravitational wave interferometers such as LIGO detect first light. These detectors will give us a revolutionary view of the Universe, complementary to the electromagnetic perspective. In this new astronomy, the messengers are gravitational waves, waves such as those produced by binary systems consisting of black holes and/or neutron stars. The detection of gravitational waves is a formidable undertaking, requiring innovative engineering, powerful data analysis tools and careful theoretical modeling. In support of this theoretical modeling, there is an urgent need to develop generic numerical codes capable of assisting us in exploring where and how gravitational wave observations can constrain or inform our understanding of astronomical phenomena and gravity. This talk focuses on the latest developments in the effort to simulate compact object binaries involving black holes and the potential role of these simulations as tools in a multi-messenger astronomy. |
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November 18, 2005 |
| Marc Herant, "Mechanics of Motile Cells" |
| Although there exists a wealth of data on the mechanical characteristics of cells, attempts to arrive at quantitative models of their behavior have been few, especially in the case of active phenomena such as protrusion or crawling. Instead, emphasis has been placed on the identification of the myriad of cellular proteins, signals, and pathways made possible by the tremendous advances of molecular biology. To fill these lacunae, we develop a rigorous, deterministic, continuum-mechanical description of ameboid cells that includes proper treatment of the membrane, cytosol, and cytoskeleton components. As an example, I will present an application of this paradigm to the important process of phagocytosis and describe what can be learned by a close comparison with experimental observations of the ingestion of beads by white blood cells. |
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December 2, 2005 |
| Daniel Britt, "The Dark Side of Asteroids" |
| Our knowledge about asteroids has rapidly progressed since the Galileo spacecraft delivered our first up-close view of an asteroid on October 29, 1991. Asteroids have turned out to be far more complex then the cold lumps of rock we originally expected. These objects have complex collisional histories, varied structures, and a surprising range of bulk densities/porosities. New observations of comets and Kuiper belt objects have added to our picture of the evolution of small bodies. I will review what is known about the structure of the small bodies of the solar system and the implications for future research and exploration. |
