220 research outputs found
Effect of heat treatment and aging on the mechanical loss and strength of hydroxide catalysis bonds between fused silica samples
Hydroxide catalysis bonds are used in the aLIGO gravitational wave detectors and are an essential technology within the mirror suspensions which allowed for detector sensitivities to be reached that enabled the first direct detections of gravitational waves. Methods aimed at further improving hydroxide catalysis bonds for future upgrades to these detectors, in order to increase detection rates and the number of detectable sources, are explored. Also, the effect on the bonds of an aLIGO suspension construction procedure involving heat, the fibre welding process, is investigated. Here we show that thermal treatments can be beneficial to improving some of the bond properties important to the mirror suspensions in interferometric gravitational wave detectors. It was found that heat treating bonds at 150\,^\circC increases bond strength by a factor of approximately 1.5 and a combination of bond ageing and heat treatment of the optics at 150\,\circC reduces the mechanical loss of a bond from 0.10 to 0.05. It is also shown that current construction procedures do not reduce bond strength
Perspective on Quark Mass and Mixing Relations
Recent data indicate that , while
seems to be GeV. The relations and suggest that %a plausible clean separation of
the %origin of the quark mixing matrix: the down type sector is responsible for
and , while comes from the up
type sector. Five to six parameters might suffice to account for the ten quark
mass and mixing parameters, resulting in specific power series representations
for the mass matrices. In this picture, seems to be the more sensible
expansion parameter, while is
tied empirically to .Comment: 10 pages, ReVtex, no figure
Cryogenic and room temperature strength of sapphire jointed by hydroxide-catalysis bonding
Hydroxide-catalysis bonding is a precision technique used for jointing components in opto-mechanical systems and has been implemented in the construction of quasi-monolithic silica suspensions in gravitational wave detectors. Future detectors are likely to operate at cryogenic temperatures which will lead to a change in test mass and suspension material. One candidate material is mono-crystalline sapphire. Here results are presented showing the influence of various bonding solutions on the strength of the hydroxide-catalysis bonds formed between sapphire samples, measured both at room temperature and at 77 K, and it is demonstrated that sodium silicate solution is the most promising in terms of strength, producing bonds with a mean strength of 63 MPa. In addition the results show that the strengths of bonds were undiminished when tested at cryogenic temperatures
The Glueball Spectrum from a Potential Model
The spectrum of two-gluon glueballs below 3 GeV is investigated in a
potential model with dynamical gluon mass using variational method. The short
distance potential is approximated by one-gluon exchange, while the long
distance part is taken as a breakable string. The mass and size of the radial
as well as orbital excitations up to principle quantum number n=3 are
evaluated. The predicted mass ratios are compared with experimental and lattice
results.Comment: Revtex, 6 pages with 1 eps figur
Electronic and structural properties of vacancies on and below the GaP(110) surface
We have performed total-energy density-functional calculations using
first-principles pseudopotentials to determine the atomic and electronic
structure of neutral surface and subsurface vacancies at the GaP(110) surface.
The cation as well as the anion surface vacancy show a pronounced inward
relaxation of the three nearest neighbor atoms towards the vacancy while the
surface point-group symmetry is maintained. For both types of vacancies we find
a singly occupied level at mid gap. Subsurface vacancies below the second layer
display essentially the same properties as bulk defects. Our results for
vacancies in the second layer show features not observed for either surface or
bulk vacancies: Large relaxations occur and both defects are unstable against
the formation of antisite vacancy complexes. Simulating scanning tunneling
microscope pictures of the different vacancies we find excellent agreement with
experimental data for the surface vacancies and predict the signatures of
subsurface vacancies.Comment: 10 pages, 6 figures, Submitted to Phys. Rev. B, Other related
publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm
A Characterization of Scale Invariant Responses in Enzymatic Networks
An ubiquitous property of biological sensory systems is adaptation: a step
increase in stimulus triggers an initial change in a biochemical or
physiological response, followed by a more gradual relaxation toward a basal,
pre-stimulus level. Adaptation helps maintain essential variables within
acceptable bounds and allows organisms to readjust themselves to an optimum and
non-saturating sensitivity range when faced with a prolonged change in their
environment. Recently, it was shown theoretically and experimentally that many
adapting systems, both at the organism and single-cell level, enjoy a
remarkable additional feature: scale invariance, meaning that the initial,
transient behavior remains (approximately) the same even when the background
signal level is scaled. In this work, we set out to investigate under what
conditions a broadly used model of biochemical enzymatic networks will exhibit
scale-invariant behavior. An exhaustive computational study led us to discover
a new property of surprising simplicity and generality, uniform linearizations
with fast output (ULFO), whose validity we show is both necessary and
sufficient for scale invariance of enzymatic networks. Based on this study, we
go on to develop a mathematical explanation of how ULFO results in scale
invariance. Our work provides a surprisingly consistent, simple, and general
framework for understanding this phenomenon, and results in concrete
experimental predictions
A Multicriteria Analysis on the Strategies to Open Taiwan's Mobile Virtual Network Operators Services
[[abstract]]This study investigates the trends followed by MVNOs (Mobile Virtual Network Operators) in the last three years and analyzes the strategies that can contribute to the success of Taiwan's telecommunications industry and marketing. We apply the method and concept of PATTERN (Planning Assistance Through Technical Evaluation of Relevance Number) to establish relevant systems for searching out the key successful factors of strategies to attract MVNOs. We also use the fuzzy Multi-Criteria Decision Making (MCDM) method for analyzing the different preference of a decision group in the criteria weights and for ranking the alternatives in a fuzzy environment in order to provide a strategy scheme. These results provide a reference to assist telecommunications operators, 3G license owners, potential MVNOs, and equipment manufacturers when working out business plans.[[incitationindex]]SCI[[booktype]]紙
Thermal noise in interferometric gravitational wave detectors due to dielectric optical coatings
We report on thermal noise from the internal friction of dielectric coatings
made from alternating layers of Ta2O5 and SiO2 deposited on fused silica
substrates. We present calculations of the thermal noise in gravitational wave
interferometers due to optical coatings, when the material properties of the
coating are different from those of the substrate and the mechanical loss angle
in the coating is anisotropic. The loss angle in the coatings for strains
parallel to the substrate surface was determined from ringdown experiments. We
measured the mechanical quality factor of three fused silica samples with
coatings deposited on them. The loss angle of the coating material for strains
parallel to the coated surface was found to be (4.2 +- 0.3)*10^(-4) for
coatings deposited on commercially polished slides and (1.0 +- 0.3)*10^{-4} for
a coating deposited on a superpolished disk. Using these numbers, we estimate
the effect of coatings on thermal noise in the initial LIGO and advanced LIGO
interferometers. We also find that the corresponding prediction for thermal
noise in the 40 m LIGO prototype at Caltech is consistent with the noise data.
These results are complemented by results for a different type of coating,
presented in a companion paper.Comment: Submitted to LSC (internal) review Sept. 20, 2001. To be submitted to
Phys. Lett.
Human induced pluripotent stem cell-derived endothelial cells in thrombosis-on-a-chip devices
A microfluidic thrombosis-on-a-chip platform was developed to compare the pro-thrombotic response of healthy and inflamed monolayers of human umbilical vein endothelial cells (HUVECs) and human induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs). Inflammation was induced by exposing the endothelial cells (ECs) to an inflammatory cytokine Tumor Necrosis Factor-α (TNF-α). After human whole blood perfusion at an arterial shear rate, the platelet coverage and average clot size were determined. Healthy endothelium showed a lower platelet coverage than inflamed endothelium. A minor difference was measured for both platelet coverage and average clot sizes on inflamed HUVECs versus hiPSC-ECs
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