TcSUH
Special Seminar
The Synthesis, Properties and Chemistry of Layered Solids
by: Prof. Simon J. Clarke
Date: Friday March 30, 2007
Time: 11:00 am – 12:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
New solid state compounds will be described which are composed of alternating transition metal oxide layers and metal sulfide or selenide layers. These compounds show a wide range of electronic, magnetic and structural features which can often be tuned by making substitutions of the cations or anions in the structures.
The lecture will focus firstly on the crystal structures and electronic and magnetic properties of compounds containing titanium, manganese, cobalt or nickel oxide layers separated by copper sulfide or selenide layers. The second part of the lecture will describe the chemical reactivity of these compounds, in particular the reversible room-temperature lithiation of many of these compounds.
A wide range of investigations will be described including diffraction, magnetometry and NMR studies. The properties will be related to the general chemistry of the elements.
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Special Seminar
Materials Science and Technology at the Naval Research Laboratory
by: Dr. Donald Gubser
Date: Wednesday March 28, 2007
Time: 11:00 am – 12:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
A brief introduction to the Naval Research Laboratory will be given, followed by an overview of materials research topics under investigation at NRL. Topics included will be Superconductivity, Acoustic Transduction Materials, Quantum Spin Electronics, Nanocrystals, 3D Materials Visualization, Fracture Simulations, Materials Integration, and Thoracic Surrogate Materials.
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Special Seminar
{Non-linear Tunnelling Characteristics into the Bulk and BoundStates of {\it p}-wave Superconductors}
by: C. J. Bolech
Date: Friday March 23, 2007
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
We reconsidered the problem of point-contact tunnel junctions involving low-dimensional superconductors and introduced a simple scheme for computing the full current-voltage characteristics within the framework of non-equilibrium Keldysh-Schwinger Green functions. We extended the formalism from s-wave to p-wave symmetry and proposeed ways of determining, by looking at the Zeeman response, when the superconducting states correspond to spin-triplet pairing. Next, we directed our attention to the zero-energy bound states at the edges or vortex cores of p-wave superconductors; these are predicted to be Majorana fermions. We introduced a model Hamiltonian that describes the tunnelling processes when electrons are injected into such states and we found exact analytic expressions for the tunnelling current and noise. We identified experimental signatures that would confirm the Majorana nature of the bound states.
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Special Seminar
How the bc1 Complex Works: Killing you Softly with a Dance
by: Antony R. Crofts
Date: Monday February 12, 2007
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Redox enzymes of the bc1 complex family form the central components of all the major energy conversion processes that fuel the biosphere. Oxidation of a membrane-bound quinol (QH2, - ubihydroquinone in mitochondria and a-proteobacteria) by a higher potential acceptor (cyt c or c2) is linked to transport of protons across the membrane through a modified Q-cycle. The reaction in which QH2 is oxidized suffers from a defect. Evolution designed the mechanism before the atmosphere became aerobic, and the intermediate semiquinone (SQ) has a potential suitable for rapid reduction of O2 to superoxide (SO). As a consequence, the catalytic site (the Qo-site) is a potential source of SO, which is a precursor of a variety of reactive oxygen species (ROS) that cause damage to DNA and proteins. A substantial literature suggests that the bc1 complex is the main culprit in ROS-generated damage under a variety of pathological conditions. Under conditions in which the intermediate SQ might be expected to accumulate, a significant rate of SO production can be measured. However, under normal operation, the isolated complex does not generate detectable amounts of SO. I will review the modified Q-cycle, and discuss the mechanism of the Qo-site of the bc1 complex, with an emphasis on the molecular ballet at the site through which SO production and other bypass reactions are minimized.
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Special Seminar
III-Nitrides Materials Grown by Plasma-Assisted Molecular Beam Epitaxy
by: Prof. Li-Wei Tu
Date: Monday February 05, 2007
Time: 1:00 pm – 1:45 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
GaN, InN, AlN, and their alloys have tremendous usages in many different areas of electronics and optoelectronics. Light-emitting diodes for lighting, decoration, displays, traffic signals, and laser diodes for pointers, DVD players and recorders, sensors in detectors, solar cells for energy conversion, field-emission transistors in power devices, etc. are but some examples. In this talk, I would like to discuss some contemporary issues faced by the community and then present some interesting topics in which our laboratory has engaged. After an introductive overview of the III-nitride family, I will discuss an unusual controversy on the fundamental band gap of InN. The debates, which started in 2002 and continued unabated even up to this day, are mainly on whether the material’s energy band gap is ~1.9 eV or ~0.7 eV. I will present the current status also on the non-polar nitrides’ growth and their advantages over the traditional polar ones, which is a relevant issue challenging the viability of the III-nitride technology. I will conclude with the nanostructures of III-nitrides and their potential applications in modern technology, which include the use of some basic forms such as nanorods and nanotips.
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