TcSUH
Special Seminar
Nanoscale Torque Measurements of F1 ATP-Synthase
Date: Monday January 07, 2008
Time: 3:00 pm – 4:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
What is the efficiency of a biological molecular motor? The enzyme F1 ATP-synthase is a rotary motor/ generator found in a huge variety of organisms (plants, animals, and bacteria). Being a major player in cellular respiration, F1 has evolved to optimize efficiency. However, a thermodynamic measurement of F1?s efficiency has been difficult to obtain due to the 10 nanometer size of F1. To address this, we have constructed a new type of magnetic torque manipulator, involving the binding of specially designed nanoscale magnetic rods to glass surface anchored F1. By controlling the external magnetic field and observing the rod?s rotation via optical microscopy, kBT scale torque can be both applied and measured. Attaining this required overcoming non-trivial obstacles such as reducing thermal fluctuations of the rod magnetization, non-specific surface interactions, focus drift, and background magnetic field effects. Both mechanical energy production (ATP hydrolysis) and consumption (ATP synthesis) will be discussed.
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Special Seminar
Exploring Exotic Superfluidity of Polarized Ultracold Fermions in Optical Lattices
by: Prof. Yan Chen
Date: Friday January 04, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Enormous interest has been paid to ultracold Fermi gases due to the interplay between Cooper pairing and strong correlations. Beautiful experiments on the superfluidity have been performed in these systems with unequal spin populations. Arrestingly, it was found that the superfluid paired core is surrounded by a shell of normal unpaired fermions while the density distribution of the difference of the two components becomes bimodal. Here we explore theoretically the novel superfluidity of harmonically- trapped polarized ultracold fermionic atoms in a two-dimensional optical lattice by solving the Bogoliubov-de Gennes equations. The pairing amplitude is found to oscillate along the radial direction at low particle density and along the angular direction at high density. The former is able to account for the existing experimental observations, while the latter predicts a new kind of Fulde-Ferrell-Larkin- Ovchinnikov states, which can be tested in experiments.
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Special Seminar
Enhanced ferroelectricity in doped niobium clusters
by: Prof. Ramiro Moro
Date: Friday January 04, 2008
Time: 3:00 pm – 4:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
In September of 2002 we observed a surprising effect in free niobium clusters: some of them acquired an electric dipole moment at low temperature. It is a surprising phenomenon because metallic particles are supposed to screen electric fields and because electronic transitions in small particles usually have very high transition temperatures, but the most surprising characteristic of the effect is that it seems to be related with superconductivity: It happens in the same metals, with similar transition temperatures, it is affected by magnetic dopants and it is enhanced for particles with even number of electrons (suggesting pairing).
It was already suggested in 1992 [Friedel, 1992] that a weakly interacting lattice of superconducting nanoparticles or clusters could yield a very high temperature superconductor. That work was prompted by the superconductivity seen in doped fullerenes, but the idea can be extended further. Recently there has been a discovery of superconductivity in a gallium cluster compound [Bakharev, 2006] which could be the first realization of Friedel?s proposal. Moreover there is recent theoretical work done by V.Z. Kresin and Ovchinnikov [Ovchinnikov, 2005] that suggest that small particles of certain metals could have an enhanced Tc due to shell effects.
Barring an incredible coincidence, Nb clusters are indeed superconducting, but its superconductivity is manifested as ferroelectricity. And some alloys, like gold-doped niobium have transition temperatures at more than 300K!
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Special Seminar
Technology Needs for Future Human Space Missions
by: Dr. Kumar Krishen
Date: Wednesday November 07, 2007
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
A discussion of the need for technology development for the human exploration and development of space will be presented. Human exploration and development of space is aimed at opening the space frontier by exploring, using, and enabling the development of space and expanding the human experience into the far reaches of space. This includes increasing human knowledge of nature's processes using the space environment, exploring and settling the solar system, achieving routine space travel, and enriching life on Earth through people living and working in space. NASA's Mars Pathfinder and the International Space Station provide extensive experience, research and technology (R&T), and infrastructure for other envisioned programs in support of human exploration and development of space.
In the past decade, the Clementine and the Lunar Prospector missions have provided valuable remotely sensed data of the Moon. In addition, NASA has studied the development of a lunar habitat and human mission to Mars as possible missions. These missions face common challenges of travel to these planets and for survival of humans on the surface of planets. With the human Mars mission being the first to such a distant planet, advanced technologies will be required to enable the mission and to provide cost effective and safer approaches.
The R&T areas considered important for a human mission to Mars include advanced human support, renewable resources and utilization of planetary resources, space transportation, automation and robotics, space power, information processing and communications systems, sensors, and instruments. NASA is actively providing the technology developed for the space applications to industry, universities, and other organizations for research, education and commercialization purposes. Strategies for this technology transfer will also be presented.
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Special Seminar
Superconducting Magnets in Space
by: Dr. Stephen M. Harrison
Date: Tuesday October 23, 2007
Time: 11:00 am – 12:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
A brief introduction to Scientific Cryomagnetics Company will be given, followed by a review of some of the earlier attempts to use superconducting magnets in space. Our present and past projects will be shown emphasizing design, construction and cryogenics of some of the superconducting magnets built (or still under fabrication) by our company for space applications: Alpha Magnetic Spectrometer (AMS), Variable Specific Impulse Magnetoplasma Rocket (VASIMR), and X-Ray Evolving Universe Spectroscopy (XEUS). Future possibilities for applied superconductivity in space will be presented, with project overviews and possibility to discuss details during and after the seminar.
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