293 research outputs found
H(II) centers in natural silica under repeated UV laser irradiations
We investigated the kinetics of H(II) centers (=Ge'-H) in natural silica
under repeated 266nm UV irradiations performed by a Nd:YAG pulsed laser. UV
photons temporarily destroy these paramagnetic defects, their reduction being
complete within 250 pulses. After re-irradiation, H(II) centers grow again, and
the observed recovery kinetics depends on the irradiation dose; multiple 2000
pulses re-irradiations induce the same post-irradiation kinetics of H(II)
centers after each exposure cycle. The analysis of these effects allows us to
achieve a deeper understanding of the dynamics of the centers during and after
laser irradiation.Comment: Submitted to Journal of Non Crystalline Solid
Development of Prototype Low-cost and High-strength Fault Current Interrupting Arcing Horns for 77 kV Overhead Transmission Lines
Fault Current Interrupting Arcing Horns (FCIAH) are newly designed arcing horns installed on transmis-sion line towers as a countermeasure against lightning damage that greatly contribute to reducing power interruption by interrupting fault current independently within an AC cycle. This paper describes the de-velopment of two new prototype FCIAH for further cost reduction and strength enhancement, using computational fluid dynamics and short-circuit tests
Segregation and Phase Inversion in a Simple Granular System
The segregation and the phase inversion are investigated through a simple
granular system which consists of only two inelastic hard spheres in a square
box with an energy source. With the variation of the coefficient of
restitution, the mass ratio between two spheres or the box size, we show that
two types of segregated states and crossover between them are realized in such
a small simple system.Comment: 7 pages, 3 figure
Difference in the behavior of oxygen deficient defects in Ge-doped silica optical fiber preforms under ArF and KrF excimer laser irradiation
Photobleaching of optical absorption bands in the 5 eV region and the creation of others at higher and lower energy have been examined in the case of ArF (6.4 eV) and KrF (5 eV) excimer laserirradiation of 3GeO2:97SiO2glasses. We report a difference in the transformation process of the neutral oxygen monovacancy and also of the germanium lone pair center (GLPC) into electron trap centers associated with fourfold coordinated Ge ions and Ge-E′ centers when we use one or the other laser. Correlations between absorption bands and electron spin resonance signals were made after different steps of laser irradiation. It was found that the KrF laser generates twice as many Ge-E′ centers as the ArF laser for the same dose of energy delivered. The main reason for this difference is found to be the more efficient bleaching of the GLPC (5.14 eV) by the KrF laser compared to that by the ArF laser
Ion implantation induced photosensitivity in Ge-doped silica : E ect of induced defects on refractive index changes
Planar germanosilicate thin film glasses grown by flame hydrolysis technique on silica substrate have been implanted at 5 MeV with silicon ions to a dose of 1014 ions/cm2. Samples were subsequently exposed to a series of KrF (5 eV) and ArF (6.4 eV) excimer laser irradiation. Optical absorption and electron spin resonance were measured before and after each series of irradiation. We report an important refractive index change that can be correlated with the photobleaching of the ion implantation induced absorption bands
Size Segregation and Convection of Granular Mixtures Almost Completely Packed in the Rotating Thin Box
Size segregation of granular mixtures which are almost completely packed in a
rotating drum is discussed with an effective simulation and a brief analysis.
Instead of a 3D drum, we simulate 2D rotating thin box which is almost
completely packed with granular mixtures. The phase inversion of radially
segregated pattern which was found in a 3D experiment are qualitatively
reproduced with this simulation, and a brief analysis is followed. Moreover in
our simulation, a global convection appears after radial segregation pattern is
formed, and this convection induces axially segregated pattern.Comment: 9 pages, 5 figures, PACS number(s): 45.70.-n, 45.70.M
Liquid-Solid Phase Transition of the System with Two particles in a Rectangular Box
We study the statistical properties of two hard spheres in a two dimensional
rectangular box. In this system, the relation like Van der Waals equation loop
is obtained between the width of the box and the pressure working on side
walls. The auto-correlation function of each particle's position is calculated
numerically. By this calculation near the critical width, the time at which the
correlation become zero gets longer according to the increase of the height of
the box. Moreover, fast and slow relaxation processes like and
relaxations observed in supper cooled liquid are observed when the height of
the box is sufficiently large. These relaxation processes are discussed with
the probability distribution of relative position of two particles.Comment: 6 figure
Influences of Excluded Volume of Molecules on Signaling Processes on Biomembrane
We investigate the influences of the excluded volume of molecules on
biochemical reaction processes on 2-dimensional surfaces using a model of
signal transduction processes on biomembranes. We perform simulations of the
2-dimensional cell-based model, which describes the reactions and diffusion of
the receptors, signaling proteins, target proteins, and crowders on the cell
membrane. The signaling proteins are activated by receptors, and these
activated signaling proteins activate target proteins that bind autonomously
from the cytoplasm to the membrane, and unbind from the membrane if activated.
If the target proteins bind frequently, the volume fraction of molecules on the
membrane becomes so large that the excluded volume of the molecules for the
reaction and diffusion dynamics cannot be negligible. We find that such
excluded volume effects of the molecules induce non-trivial variations of the
signal flow, defined as the activation frequency of target proteins, as
follows. With an increase in the binding rate of target proteins, the signal
flow varies by i) monotonically increasing; ii) increasing then decreasing in a
bell-shaped curve; or iii) increasing, decreasing, then increasing in an
S-shaped curve. We further demonstrate that the excluded volume of molecules
influences the hierarchical molecular distributions throughout the reaction
processes. In particular, when the system exhibits a large signal flow, the
signaling proteins tend to surround the receptors to form receptor-signaling
protein clusters, and the target proteins tend to become distributed around
such clusters. To explain these phenomena, we analyze the stochastic model of
the local motions of molecules around the receptor.Comment: 31 pages, 10 figure
Silica-based monolithic sensing plates for waveguide-mode sensors
We developed a monolithic sensing plate for a waveguide-mode sensor. The plate consists of a SiO2 glass substrate and a thin silicon layer the surface of which is thermally oxidized to form a SiO2 glass waveguide. We confirmed that the sensing plate is suitable for high-sensitivity detection of molecular adsorption at the waveguide surface. In addition, a significant enhancement of the sensitivity of the sensor was achieved by perforating the waveguide with holes with diameters of a few tens of nanometers by selective etching of latent tracks created by swift heavy-ion irradiation. Possible strategies for optimizing the plate are discussed
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