TcSUH EventS
Distinguished Lecture Series
Atoms and Ions Near Carbon Nanostructures
by: Prof. Jene Golovchenko
Date: Thursday April 29, 2010
Time: 4:00 pm – 6:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
I will present recent results revealing new aspects of the interaction of atoms and ions with carbon nano-structures. Two examples of new research directions are discussed. In the first, laser cooled neutral atoms are launched towards the sidewalls of a highly charged, freestanding, carbon nanotube. A long range interaction causes the atoms to spiral towards the nanotube, as if attracted to an atomic scale "black hole". As an atom approaches the surface of the nanotube an outer electron tunnels into the tube leaving an ion behind that can be readily detected. Experimental results reveal many nano-scale and atomic scale processes at work. Application include high spatial resolution and extremely sensitive detectors of neutral atoms. The second topic involves the use of an atomically thin graphene layer as a "trans-electrode" for ions in aqueous solution. I will show electrical properties of a graphene sheet that is mounted in a fluidic cell so one side of the sheet serves as an electrochemical anode and the other a cathode. The structure shows a very low trans-ionic conductivity at low voltage bias. Embedding a small nanopore in a membrane dramatically increases the trans-ionic conductivity and allows the insulating thickness of the graphene to be determined. Sub nanometer insulating thicknesses are observed which remarkably withstand hundred of millivolts of applied voltage bias. Applications to molecular and chemical sensing are discussed.
Back to TcSUH News & Events
Bi-Weekly Seminar
An Overview on Ion Beam Channeling in Single Crystal: Discovery, Understanding, Applications, Current Status and Future
Date: Friday April 23, 2010
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
When an energetic Ion projectile enters a single crystal along a major crystalline axial or planar direction, the collective Coulomb potential from a crystal steers the ion away from the lattice. Ion channeling in a crystalline solid can be observed as great reduction of close encounter process such as elastic Rutherford scattering, ion induced x-ray emission, and nuclear reactions, due to the steering of ions away from the nuclei array. Channeling phenomenon was first discovered at Oak Ridge National Lab from a Monte Carlo simulation back in the earlier 1960's. It was quickly verified by several experiments, and Lindhard provided a theoretical treatment on channeling. The phenomenon is well adopted as a powerful real-space analytical tool which can be used for studies on lattice dynamics, depth resolved crystalline defect analysis, strain analysis and ion-beam crystallography.Potential applications include the use of channeling in particle beam guiding and beam splitting in high energy accelerators. Resonant Coherent Excitation (RCE) which is the radiation produced by channeling ions are considered in applications in tunable polarized X-Ray sources. This talk will give an overview on channeling, historical remarks, present status of channeling, our present efforts, contribution and future plan on channeling.
Back to TcSUH News & Events
Special Seminar
Spin Fluctuation and Unconventional Pairing in Iron-Based Superconductors
by: Prof. Jian-Xin Li
Date: Thursday April 08, 2010
Time: 1:00 pm – 2:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Recently, the discovery of high-temperature superconductivity in iron pnictides has added a new class of materials to the family of high-Tc superconductors. In this talk, I will give a brief review of the progress of the theoretical understanding on their superconductivity and the related experiments, and report our theoretical works on the relation between the spin fluctuation and the pairing symmetry as well as the interplay between spin density wave and superconductivity in the vortex state in iron-pnictides.
Back to TcSUH News & Events
Distinguished Lecture Series
Past, Present and Future of the ICTP Trieste
by: Dr. Fernando Quevedo
Date: Friday April 02, 2010
Time: 4:00 pm – 6:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
The Abdus Salam International Center for Theoretical Physics is the pre-eminent center for scientifc collaboration and training between developed and developing countries. For more four decades the ICTP has trained thousands of students and scientists from developing countries, promoting the development of science and technology in their countries of origin and establishing long-lasting connections among scientists from different parts of the world. Dr. Quevedo will give an overview of the ICTP and some of its plans for the future, including possible ICTP-USA Centers.
Back to TcSUH News & Events
Distinguished Lecture Series
“Why Our Proteins Have to Die So We Shall Live”
by: Dr. Aaron Ciechanover
Date: Thursday February 11, 2010
Time: 4:00 pm – 6:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Between the sixties and eighties, most life scientists focused their attention on studies of nucleic acids and the translation of the information coded by DNA. Protein degradation was a neglected area, considered to be a non-specific, dead-end process. While it was known that proteins do turn over, the large extent and high specificity of the process - whereby distinct proteins have half-lives that range from a few minutes to several days - was not appreciated. The discovery of the lysosome by Christian de Duve did not significantly change this view, as it was clear that this organelle is involved mostly in the degradation of extracellular proteins, and their proteases cannot be substrate-specific. The discovery of the complex cascade of the ubiquitin pathway revolutionized the field. It is clear now that degradation of cellular proteins is a highly complex, temporally controlled, and tightly regulated process that plays major roles in a variety of basic pathways during cell life and death, and in health and disease. With the multitude of substrates targeted, and the myriad processes involved, it is not surprising that aberrations in the pathway are implicated in the pathogenesis of many diseases, certain malignancies and neurodegeneration among them. Degradation of a protein via the ubiquitin/proteasome pathway involves two successive steps: (a) conjugation of multiple ubiquitin moieties to the substrate, and (b) degradation of the tagged protein by the downstream 26S proteasome complex. Despite intensive research, the unknown still exceeds what we currently know on intracellular protein degradation, and major key questions remain unsolved. Among these are the modes of specific and timed recognition for the degradation of the many substrates, and the mechanisms that underlie aberrations in the system that lead to pathogenesis of diseases.
Back to TcSUH News & Events