Tuesday, January 16, 2007
Yufeng Zhao
National Renewable Energy Laboratory, Golden, CO
"Theory for hydrogen storage:
the organometallic approaches"
Our recent work at National Renewable Energy Laboratory is leading to design
principles for hydrogen storage in carbon-based materials. In this presentation,
a common theory for all hydrogen storage techniques will first be addressed
on the basis of thermodynamics and quantum chemistry. From this theory, we extract
a few principles guiding rational design of nanoscale hydrogen adsorbents and
their macroscopic assemblies. Our study demonstrated that organometallic adsorbents
hold the promise for reversible, high capacity hydrogen storage at near ambient
conditions. A few key technical challenges will also be addressed.
Tuesday, January 23, 2007
Kevin L. Moore
G.A. Dobelman Distinguished Chair and Professor of Engineering
Division of Engineering, Colorado School of Mines
"Towards Autonomous Systems: From Control Systems to Intelligent Control
to Intelligent Behavior Generation to Cooperative Autonomy"
Today a number of enabling technologies have matured to the point that it is
possible to build robots and intelligent machines that are physically capable
of autonomous behavior. However, to achieve the promise of autonomy, we also
need equivalently-mature information-processing and decision systems to exploit
these physical capabilities. In this talk we discuss the problem of devising
truly autonomous systems in three parts, describing several threads of research
from the speaker’s experience. In Part 1, we begin with a discussion of intelligent
control, including its promise and reality, introducing specifically the paradigm
of iterative learning control (ILC). From this motivator, in Part 2 we consider
how to move beyond conventional intelligent control to develop intelligent behavior
generators for single-system autonomy, focusing on mobile robots operating in
semi-structured environments. Part 3 of the talk looks to the next frontier
of autonomy: cooperative behavior of multiple autonomous entities. We discuss
this notion from the idea of what we call a dynamic resource network, in which
mobile, autonomous actuators and sensors cooperate to accomplish a global objective
in a spatial-temporal domain.
Tuesday, January 30, 2007
Dane Gillaspie
National Renewable Energy Laboratory, Golden CO
"Magnetism and Transport in Manganite Thin Films"
Research into strongly correlated
electron materials, such as the CMR (colossal magnetoresistance) perovskite
manganites, is one of the major topics in modern materials physics. In the case
of the manganites, this is due to the inherent richness of the underlying physics
as well as the tantalizing possibilities for future device applications. In
my talk, I will give an overview of the history of the field, and then describe
some of the most recent results of our group at Oak Ridge National Laboratory.
Finally, if time permits, I would also like to describe some of the major new
user facilities at ORNL, which are available for outside users.
Tuesday, February 6, 2007
Joe Redish
University of Maryland
" Problem Solving and the Use of Math in Physics Courses"
Mathematics is an essential element of physics problem solving, but as professionals, we often fail to appreciate exactly what we are doing with it. Math may be the language of science, but math-in-physics is a distinct dialect of that language that requires both more subtlety and more skills than are typically taught in math courses. Research with students in classes ranging from algebra-based physics to graduate quantum mechanics indicates that (1) we sometimes don't appreciate the skills students need to solve the problems we assign, and (2) students problems are sometimes with their expectations about what they are supposed to be doing rather than with their math skills. Implications for instruction will be discussed.
Monday, February 12, 2007,
Meyer Hall 375, 4-5pm (Note special date and location)
Lawrence Wiencke
University of Utah
"The Mystery of High Energy Cosmic Rays"
The existence of astrophysical subatomic particles with macroscopic energies presents an intriguing puzzle. Theoretical models to explain their existence range from the real to the conceptual: active galactic nuclei, gamma ray bursts, cosmic relics or other exotic objects, and even violation of Lorentz invariance. Whatever their origin, these high-energy messengers are produced by the most energetic processes in the universe. A few of the observed events even exceed the energy loss threshold expected from photo-pion production with the cosmic microwave background (predicted by Greisen, Zatsepin, and Kuzmin shortly after the 1965 discovery of this radiation). These extreme particles, even if charged, may point back to their source(s), which because of this effect should be relatively nearby, rather than at cosmological distances. That the flux falls to roughly one particle/km^2/century at the intriguing energy scale of 10^20 eV, hints at the experimental challenges. This talk will discuss experimental progress in this area and focus on the first results and future plans of the Pierre Auger Observatory.
Tuesday, February 20,
2007
Fat Tuesday Faculty/Staff/Grad Student Mixer
It's nearly midterms and time take a break from the grind, exchange tales with your colleagues, and spend an hour unwinding. We will meet at the Blue Canyon on 13th Street at 4:00pm.
Monday, February 26, 2007,
Meyer Hall 375, 4-5pm (Note special date and location)
Richard Schnee
Case Western Reserve University
"What's the Matter in the Universe? Looking for WIMPs with the Cryogenic
Dark Matter Search"
The stuff that makes up us (and everything else on the Earth) appears to be quite unusual in the universe. Astrophysical observations indicate that at least 90% of the mass of any galaxy -- and as much as 98% of the mass of the universe -- is in the form of matter that cannot be seen. Furthermore, most of this matter isn't even made from protons and neutrons -- or any other known particles. What could this matter be and how can we find out? Perhaps the best motivated possibility is weakly interacting massive particles (WIMPs) left over from the Big Bang; these particles naturally arise, for example, under supersymmetry. Detection of these particles requires sophisticated detectors such as the CDMS experiment's crystals of silicon or germanium cryogenically cooled to 40 milliKelvin. Operation of these detectors and the prospects for discovering what's the matter in the universe will be discussed.
Wednesday, February 28,
2007, Meyer Hall 363, 4-5pm (Note special date and location)
Dan Melconian
University of Washington
"Probing fundamental properties of the weak interaction: What haven't we
seen yet?"
The culmination of our scientic endeavours to understand the basic constituents of matter and the interactions between them has been formally embodied in the Standard Model of particle physics. This is, by far, the most thoroughly tested theory ever conceived; the recent discovery that neutrinos have a finite mass is the only observation that requires a revision of the model as originally developed in the late 1970's. Even though the Standard Model provides us with a comprehensive and elegant understanding of the basic laws of physics, there are many unanswered questions, such as why is the weak force the only one which violates parity-symmetry? Nuclear decay has played a crucial role throughout the development of our understanding of the fundamental symmetries of electroweak interactions. This tradition continues by using ever more precise measurements of decay observables to test Standard Model predictions. An observed discrepancy would signify an important discovery that would help guide theorists toward a more complete model.
This talk will present the outlook for a research program that is searching for physics beyond the Standard Model. I will describe three experiments which each probe the weak interaction in different ways: I will show how delayed proton emitters and ultra-cold neutrons can both be used to test whether the quark mass-mixing matrix is unitary or not, and how a polarized sample of laser-cooled atoms investigates the chiral structure of the weak interaction.
Tuesday, March 6, 2007
No Colloquium, Week of the March Meeting of the APS to be held in Denver
Tuesday, March 13, 2007
Spring Break
Tuesday, March 20, 2007
Christoph Boehme
University of Utah
"Control of electric currents with coherent spin states"
In recent years, a number of studies have shown that spin-dependent charge carrier transport and recombination processes in semiconductors work as very sensitive spin probes not only for the mere detection of the presence of spins but also for a spin readout which is the spin measurement of distinct eigenstates or even their coherent superpositions. These discoveries open up the possibility of a coherent electrical spin spectroscopy with extraordinary sensitivity, even single spin sensitivity, on spin systems which have not been accessible before with optically detected or conventional radiofrequency detected magnetic resonance spectroscopy. Examples for such spin systems can be found in low dimensional materials and devices such as thin film semiconductors, quantum-dots, quantum-wires or quantum-wells. The ability to read spins states electrically may also benefit technical applications such as spintronics devices or spin based quantum information techniques.
In this talk, I will briefly review some of the qualitatively different spin-dependent mechanisms known in semiconductors and the methods to observe and investigate these processes, foremost the pulsed electrically detected magnetic resonance (pEDMR) experiments. I will discuss the potential, the limitations as well as some applications of pEDMR for the investigation of organic and inorganic semiconductors.
Monday, March 26, 2007
at 3:00pm in Meyer Hall 375 (note special date, time, and location)
Azriel Genack
Queens College of the City University of New York
"Photon localization and mesoscopic fluctuations: coupling to underlying
electromagnetic modes"
This talk will illustrate the way in which the dramatic change is the nature
of electromagnetic transport in the Anderson transition from extended to localized
waves is controlled by the coupling of the incident wave to the underlying electromagnetic
modes of the medium. This will be illustrated in observations of the spatial
and frequency variation of the microwave field inside a random waveguide as
two localized modes coalesce to form quasi-extended quasimodes as the sample
is perturbed. In amplifying random layered media, coupling to long-lived modes
is the basis of a low-threshold photon localization laser. The increasing role
of long-lived modes with delay time from an exciting pulse is associated with
the increasing impact of weak localization. This leads to suppression of the
decay rate of transmission and enhancement of the degree of intensity correlation
with increasing time delay, even in nominally diffusive samples. The degree
of intensity correlation is shown to be precisely the variance of relative transmission
and to provide a reliable indicator of localization in both static and dynamic
experiments. Finally, the evolution of the transmitted speckle pattern and the
motion of phase singularities with frequency shift is shown to reflect the coupling
to modes of the medium.
Tuesday, April 3, 2007
No Colloquium - Advising Week
Tuesday, April 10, 2007
Mike Seibert
National Renewable Energy Laboratory
"Algal BioHydrogen Production from Water-A Future Renewable Energy Option"
Several years ago we discovered that the application of a nutrient stress (removal of sulfate) with the green alga, Chlamydomonas reinhardtii, resulted in the direct coupling of photosynthetic water oxidation to hydrogenase-linked H2 production for a period of 4 days. The mechanism involves the co-occurrence of oxygenic photosynthesis, anaerobic fermentation, and respiration when photosystem II O2-evolution activity is significantly down-regulated in the absence of sulfate. Hydrogen photoproduction was first demonstrated as an anaerobic batch process, but process improvements have included (a) optimization of the culture and light conditions, (b) conversion to a continuous process with H2 production maintained for up to 6 months, (c) improvement in continuity as well as efficiency by immobilizing the algae on glass fibers, and (d) development of a new immobilization technique using low cost materials, suitable for scale-up.While helpful in learning how to produce H2 in different types of photobioreactor systems, only a fraction of the photosynthetic potential of the alga can be used when sulfate is missing. In order to utilize the maximum photosynthetic potential of the algae, we must eliminate the sulfur stress, address the O2-sensitivity of the [FeFe]-hydrogenase enzyme, and operate the organism under aerobic conditions.
To this end we have developed Molecular Dynamics computational methods for simulating H2 and O2 gas diffusion in [FeFe]-hydrogenases. These studies have identified two well-defined pathways by which O2 can access and inactivate the catalytic site, and many more pathways for molecular H2 to diffuse to the surface of the protein once it is released at the catalytic site. One strategy to protect the catalytic site from O2 is to employ site-directed mutagenesis in a rational approach to physically restrict access of O2 along the two pathways. To identify candidate amino acid residues for mutagenesis, we generated Potential Mean Force maps, which plot the free energy for O2 placed at positions along the two pathways. These show regions of low (cavities) and high (barriers) energy, and provide us with the identity of potential specific amino acid residues to mutate. Site-directed mutants have been generated, the mutated proteins expressed in E. coli using an [FeFe]-hydrogenase expression system developed our lab, and the initial results are encouraging.
Finally, we have started to develop a better understanding of the factors that promote H2 production in algae by global transcript profiling and real time PCR methods. These demonstrate significant changes in the transcript levels of many genes associated with photosynthesis, electron transport, proton transport, metabolism, fermentation, translational regulation, post translational modification, transcriptional regulation, stress response, signal transduction, as well as a variety of other physiological processes when H2 is produced. The work is elucidating pathways used by C. reinhardtii during anaerobiosis and will provide insights into how mutants, altered in normal H2 metabolism, acclimate to H2-production conditions. More detailed knowledge of the metabolic and regulatory context that facilitates H2 production will be necessary to understand and also ultimately eliminate current limitations in H2-production yields.
Tuesday, April 17, 2007
Graduate student presentations
CSM Physics Department
This is an opportunity to learn about some of the research projects of graduate students in the physics program. Students will give a ten-minute, APS-style presentation on their thesis research.
Tuesday, April 24, 2007
Brian T. Saam
University of Utah
"Hyperpolarized Gases: From Atomic Physics to Imaging Lungs"
Despite the constraints of the Boltzmann factor, nuclear magnetic resonance (NMR) has been enormously successful using tiny (ppm) thermal polarizations to generate the signal. By comparison, enormous non-equilibrium nuclear-spin polarizations (of order 10%) can be achieved in 3He and 129Xe via spin-exchange optical pumping, greatly enhancing the NMR sensitivity of these nuclei. These hyperpolarized (HP) gases are now applied to a broad range of problems in physics, chemistry, biology, and even medicine. Perhaps the most dramatic example is magnetic resonance imaging (MRI) of the air spaces of the lung, a notoriously difficult organ to image conventionally. The lecture will broadly address the physics of optical pumping and spin exchange, the study of nuclear relaxation mechanisms that constrain the achievable polarization and storage time of HP gases, and a few of the applications with which our group is involved.
Tuesday, May 1, 2007
P. Craig Taylor
CSM Physics Department
"Hydrogen, the Economy, and Solar Energy"
The movement toward an energy system that does not rely on fossil fuels will be a long and tortuous path requiring breakthroughs in many areas science, including condensed matter physics, materials science, and various engineering disciplines. One possibility is the development of a “hydrogen economy” where oxygen is combined with hydrogen to produce only water as a by-product. I will start with the general motivation for moving to a hydrogen economy, discuss some of the currently intractable problems associated with this movement, and speculate concerning the role of photovoltaic panels in such an economy. I will conclude with a short discussion of a very different role for hydrogen, namely its use in passivating electronic materials, such as those used for thin-film solar panels.
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Last updated:
April 23, 2007