189 research outputs found
Okada Saito and Oshiyama Reply:
No full textOriginal: Susumu Okada Susumu Saito and Atsushi Oshiyama New Metallic Crystalline Carbon: Three Dimensionally Polymerized C60 Fullerite Phys. Rev. Lett. 83 1986 (1999)
Comment: V. V. Brazhkin and A. G. Lyapin Comment on “New Metallic Crystalline Carbon: Three Dimensionally Polymerized C60 Fullerite” Phys. Rev. Lett. 85 5671 (2000)journal articl
E' Centers in alpha Quartz in the Absence of Oxygen Vacancies: A First-Principles Molecular-Dynamics Study
No full textThe displacement of an oxygen atom in pure alpha quartz is studied via first-principles molecular dynamics. The simulations show that when an O atom in a Si-O-Si bridge is moved away from its original equilibrium position, a new stable energy minimum can be reached. Depending on the spin state and charge Q of the system, this minimum can give rise to either a threefold oxygen (singlet ground state and Q=+1) or to an unsaturated Si atom carrying a dangling bond (triplet state). In the latter case, the hyperfine parameters associated with the Si-29 dangling bond are in rather good agreement with electron paramagnetic resonance/electron nuclear double resonance experiments
E' Centers in Silicon Dioxide: First-Principles Molecular Dynamics Studies
No full textThe point-like defects known as E' centers are the most abundant natural defects in silicon dioxide (SiO2) and have been identified as unpaired sp(3) dangling bonds. Their importance stems from the fact that they deeply affect the quality of electronic and optical devices. For this reason, particular attention has been paid in their characterization since the early 1960s. In this work, we review theoretical and experimental results concerning these kinds of defects, focusing on the related charge and spin states. In particular, the defect known as E' in crystalline quartz and its analogous E'gamma, in amorphous SiO2, detected by electron spin resonance, are shown to be due to the Si dangling bonds that arise either upon removal or displacement of an oxygen atom in a SiO2 network, accompanied by an asymmetric relaxation of the network
Free energy molecular dynamics simulations of pulsed-laser-irradiated SiO2: Si-Si bond formation in a matrix of SiO2
No full textRecent experiments have shown that pure Si structures in a matrix of SiO2 can be formed by electron excitation techniques, with appealing applications in nanotechnology. Our ab initio simulations provide an insight into the underlying mechanism, showing that electron excitations weaken Si-O bonds in SiO2, dislodge O atoms and allow Si dangling bonds to reconstruct in stable Si-Si structures below the melting temperature. Differences in diffusivity of O (fast) and Si (slow) are shown to play a decisive role in the process
First-principle molecular dynamics study of bond disruption and formation in SiO2 upon irradiation
No full textRecent experiments have shown that Si nanostructures can be formed in a matrix Of SiO2 by laser-pulse irradiation, with appealing applications in nanotechnology. We hereby present first principles simulations that provide a microscopic insight into the underlying mechanism, showing how electron excitations weaken Si-O bonds in SiO2, dislodging O atoms and allowing the formation of stable Si-Si structures below the melting temperature. (c) 2006 Elsevier B.V. All rights reserved
A STUDY OF QUANTUM ISOTOPIC SIEVING THORUGH CARBON NANOTUBES
No full textThe theory of molecular sieving has long been a subject of importance because of its widespread technological applications .Classical molecular sieving mainly de- pends on the size and shape of the guest molecules and the size of the host solid. However,isotope seperation is usually very difficult to achieve through classical sieving, as the isotopes generally have the same shape and size and differ only in mass.One way to resolve such an issue is through the applications of quantum effects which are prominent inside nanotubes and nanopores of diameters that are comparable with the De-broglie wavelength λ of the molecules. In the recent past, various authors have calculated the selectivity of isotopes (mainly hydrogen-deuterium) diffusing through nanotubes where they predict the preferable selectivity of the heavier species over the lighter species based on the difference in their zero point energies. The effects are more pronounced at low temperature regimes where quantum effects are dominant. However, this kind of sieving, though showing appreciable preference to the heavier isotope, is far from being "perfect" and also technologically expensive as very low temperature range is required. In our work, we try to search for a technologically inexpensive method for realising isotope sieving by introducing two nanotubes of different radii that are coupled together. Through a mathemetical model that best describes the situation, we try to search for a "perfect" sieving of the hydrogen-deuterium isotopes over a wide temeperature range, not restricting ourselves to very low temperatures. As we have found out and will be described in the following work,the two nanotube sys- tem does indeed go a long way towards a technologically efficient way of realising "perfect" sieving. We also employ MD simulations to investigate kinetic sieving of isotopes through nanotubes. The quantum effects are introduced into the system via a modified FH potential, and ring polymer MD simulation is used to model the system. Though the selectivity values we found in our results are lower in comparison to those already predicted using equilibrium sieving, our results show similar qualitative behaviour to the same approach adopted by others previously using different sieving materia
Developmental differences in myocardial transmembrane Na+ transport:
No full textLittle is currently known about possible developmental changes in myocardial Na+ handling, which may have impact on cell excitability and Ca2+ content. Resting intracellular Na+ concentration ([Na+]i), measured in freshly isolated rat ventricular myocytes with CoroNa green, was not significantly different in neonates (3–5 days old) and adults, but electrical stimulation caused marked [Na+]i rise only in neonates. Inhibition of L-type Ca2+ current by CdCl2 abolished not only systolic Ca2+ transients, but also activity-dependent intracellular Na+ accumulation in immature cells. This indicates that the main Na+ influx pathway during activity is the Na+/Ca2+ exchanger, rather than voltage-dependent Na+ current (INa), which was not affected by CdCl2. In immature myocytes, INa density was two-fold greater, inactivation was faster, and the current peak occurred at less negative transmembrane potential (Em) than in adults. Na+ channel steady-state activation and inactivation curves in neonates showed a rightward shift, which should increase channel availability at diastolic Em, but also require greater depolarization for excitation, which was observed experimentally and reproduced in computer simulations. Ventricular mRNA levels of Nav1.1, Nav1.4 and Nav1.5 pore-forming isoforms were greater in neonate ventricles, while a decrease was seen for the β1 subunit. Both molecular and biophysical changes in the channel profile may contribute to the differences in INa density and voltage-dependence, and also to the less negative threshold Em, in neonates compared to adults. The apparently lower excitability in immature ventricle may confer protection against the development of spontaneous activity in this tissue
Oshiyama, Miwako
No full textPassport photo of older woman and young woman. Negative scan.In 1922, Kinso Ninomiya opened the Ninomiya Studio in Little Tokyo, Los Angeles. Due to Executive Order 9066 in 1942, the studio was forced to close but was reopened by Kinso and his son, Elwin Ichiro, in 1949. The studio operated in Little Tokyo until its final closing in 1986. The Ninomiya Studio Collection captures slices of Japanese American life in Los Angeles from the 1950s through the 1980s. The collection contains formal portraiture and candid photography in black and white and color as well as commercial photography for local businesses and reproductions of older photographs. The negatives come in a variety of sizes, including 8 x 10 inch negatives and panoramic negatives on Cirkut film. Each negative scanned has been selected out of multiple negatives and prints from a set. The title of the negative scan reflects the purchaser's name
Oshiyama, Joann
No full textPortrait of young girl in kimono. Negative scan.In 1922, Kinso Ninomiya opened the Ninomiya Studio in Little Tokyo, Los Angeles. Due to Executive Order 9066 in 1942, the studio was forced to close but was reopened by Kinso and his son, Elwin Ichiro, in 1949. The studio operated in Little Tokyo until its final closing in 1986. The Ninomiya Studio Collection captures slices of Japanese American life in Los Angeles from the 1950s through the 1980s. The collection contains formal portraiture and candid photography in black and white and color as well as commercial photography for local businesses and reproductions of older photographs. The negatives come in a variety of sizes, including 8 x 10 inch negatives and panoramic negatives on Cirkut film. Each negative scanned has been selected out of multiple negatives and prints from a set. The title of the negative scan reflects the purchaser's name
Oshiyama, K
No full textPortraits of couple and family. Negative scan.In 1922, Kinso Ninomiya opened the Ninomiya Studio in Little Tokyo, Los Angeles. Due to Executive Order 9066 in 1942, the studio was forced to close but was reopened by Kinso and his son, Elwin Ichiro, in 1949. The studio operated in Little Tokyo until its final closing in 1986. The Ninomiya Studio Collection captures slices of Japanese American life in Los Angeles from the 1950s through the 1980s. The collection contains formal portraiture and candid photography in black and white and color as well as commercial photography for local businesses and reproductions of older photographs. The negatives come in a variety of sizes, including 8 x 10 inch negatives and panoramic negatives on Cirkut film. Each negative scanned has been selected out of multiple negatives and prints from a set. The title of the negative scan reflects the purchaser’s name
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