608 research outputs found
The linear variable differential transformer (LVDT) position sensor for gravitational wave interferometer low-frequency controls
Low-power, ultra-high-vacuum compatible, non-contacting position sensors with nanometer resolution and centimeter dynamic range have been developed, built and tested. They have been designed at Virgo as the sensors for low-frequency modal damping of Seismic Attenuation System chains in Gravitational Wave interferometers and sub-micron absolute mirror positioning. One type of these linear variable differential transformers (LVDTs) has been designed to be also insensitive to transversal displacement thus allowing 3D movement of the sensor head while still precisely reading its position along the sensitivity axis. A second LVDT geometry has been designed to measure the displacement of the vertical seismic attenuation filters from their nominal position. Unlike the commercial LVDTs, mostly based on magnetic cores, the LVDTs described here exert no force on the measured structure
High Sensitivity Accelerometers for High Performance Seismic Attenuators
We present concepts and features of a new horizontal accelerometer whose mechanical design and machining process aim to improve the sensitivity in the frequency region between 10 mHz and 1 Hz. The expected sensitivity, less than 10^(–11) m/s^2/√Hz around 100 mHz, is a couple of orders of magnitude below the state of art limits. This accelerometer could be integrated in the active control of the LIGO II mirror seismic isolators
Using a combination of MLPA kits to detect chromosomal imbalances in patients with multiple congenital anomalies and mental retardation is a valuable choice for developing countries
Conventional karyotyping detects anomalies in 3-15% of patients with multiple congenital anomalies and mental retardation (MCA/MR). Whole-genome array screening (WGAS) has been consistently suggested as the first choice diagnostic test for this group of patients, but it is very costly for large-scale use in developing countries. We evaluated the use of a combination of Multiplex Ligation-dependent Probe Amplification (MLPA) kits to increase the detection rate of chromosomal abnormalities in MCA/MR patients. We screened 261 MCA/MR patients with two subtelomeric and one microdeletion kits. This would theoretically detect up to 70% of all submicroscopic abnormalities. Additionally we scored the de Vries score for 209 patients in an effort to find a suitable cut-off for MLPA screening. Our results reveal that chromosomal abnormalities were present in 87 (33.3%) patients, but only 57 (21.8%) were considered causative. Karyotyping detected 15 abnormalities (6.9%), while MLPA identified 54 (20.7%). Our combined MLPA screening raised the total detection number of pathogenic imbalances more than three times when compared to conventional karyotyping. We also show that using the de Vries score as a cutoff for this screening would only be suitable under financial restrictions. A decision analytic model was constructed with three possible strategies: karyotype, karyotype + MLPA and karyotype + WGAS. Karyotype + MLPA strategy detected anomalies in 19.8% of cases which account for 76.45% of the expected yield for karyotype + WGAS. Incremental Cost Effectiveness Ratio (ICER) of MLPA is three times lower than that of WGAS, which means that, for the same costs, we have three additional diagnoses with MLPA but only one with WGAS. We list all causative alterations found, including rare findings, such as reciprocal duplications of regions deleted in Sotos and Williams-Beuren syndromes. We also describe imbalances that were considered polymorphisms or rare variants, such as the new SNP that confounded the analysis of the 22q13.3 deletion syndrome. (C) 2011 Elsevier Masson SAS. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CEPID (Centro de Pesquisa, Inovacao e Difusao)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Univ São Paulo, Inst Biociencias, Dept Genet & Biol Evolut, Ctr Estudos Genoma Humano, BR-05508900 São Paulo, BrazilUniv São Paulo, Fac Med, Dept Oncol, BR-05508 São Paulo, BrazilUniv Fed Campina Grande, Campina Grande, PB, BrazilUniversidade Federal de São Paulo, Dept Ginecol, Lab Ginecol Mol, São Paulo, BrazilAssoc Beneficente Coleta Sangue, São Paulo, BrazilUniv São Paulo, Fac Med, Inst Crianca, BR-05508 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Ginecol, Lab Ginecol Mol, São Paulo, BrazilWeb of Scienc
Current status of the CLIO project
CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational
wave detector project. One of the main purposes of CLIO is to demonstrate
thermal-noise suppression by cooling mirrors for a future Japanese project,
LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in
Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and
cryogenic-temperature experiments) is introduced in this article. In a
room-temperature experiment, we made efforts to improve the sensitivity. The
current best sensitivity at 300 K is about
around 400 Hz. Below 20 Hz, the strain (not displacement) sensitivity is
comparable to that of LIGO, although the baselines of CLIO are 40-times shorter
(CLIO: 100m, LIGO: 4km). This is because seismic noise is extremely small in
Kamioka mine. We operated the interferometer at room temperature for
gravitational wave observations. We obtained 86 hours of data. In the cryogenic
experiment, it was confirmed that the mirrors were sufficiently cooled (14 K).
However, we found that the radiation shield ducts transferred 300K radiation
into the cryostat more effectively than we had expected. We observed that noise
caused by pure aluminum wires to suspend a mirror was suppressed by cooling the
mirror.Comment: 8 pages, 9 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
Investigation of mechanical losses of thin silicon flexures at low temperatures
The investigation of the mechanical loss of different silicon flexures in a
temperature region from 5 to 300 K is presented. The flexures have been
prepared by different fabrication techniques. A lowest mechanical loss of
was observed for a 130 m thick flexure at around 10 K.
While the mechanical loss follows the thermoelastic predictions down to 50 K a
difference can be observed at lower temperatures for different surface
treatments. This surface loss will be limiting for all applications using
silicon based oscillators at low temperatures. The extraction of a surface loss
parameter using different results from our measurements and other references is
presented. We focused on structures that are relevant for gravitational wave
detectors. The surface loss parameter = 0.5 pm was obtained. This
reveals that the surface loss of silicon is significantly lower than the
surface loss of fused silica.Comment: 16 pages, 7 figure
Entropic Tension in Crowded Membranes
Unlike their model membrane counterparts, biological membranes are richly
decorated with a heterogeneous assembly of membrane proteins. These proteins
are so tightly packed that their excluded area interactions can alter the free
energy landscape controlling the conformational transitions suffered by such
proteins. For membrane channels, this effect can alter the critical membrane
tension at which they undergo a transition from a closed to an open state, and
therefore influence protein function \emph{in vivo}. Despite their obvious
importance, crowding phenomena in membranes are much less well studied than in
the cytoplasm.
Using statistical mechanics results for hard disk liquids, we show that
crowding induces an entropic tension in the membrane, which influences
transitions that alter the projected area and circumference of a membrane
protein. As a specific case study in this effect, we consider the impact of
crowding on the gating properties of bacterial mechanosensitive membrane
channels, which are thought to confer osmoprotection when these cells are
subjected to osmotic shock. We find that crowding can alter the gating energies
by more than in physiological conditions, a substantial fraction of
the total gating energies in some cases.
Given the ubiquity of membrane crowding, the nonspecific nature of excluded
volume interactions, and the fact that the function of many membrane proteins
involve significant conformational changes, this specific case study highlights
a general aspect in the function of membrane proteins.Comment: 20 pages (inclduing supporting information), 4 figures, to appear in
PLoS Comp. Bio
Observables in a lattice Universe
We explore observables in a lattice Universe described by a recently found
solution to Einstein field equations. This solution models a regular lattice of
evenly distributed objects of equal masses. This inhomogeneous solution is
perturbative, and, up to second order in a small parameter, it expands at a
rate exactly equal to the one expected in a dust dominated
Friedmann-Lema\^itre-Robertson-Walker (FLRW) model with the equivalent,
smoothed, energy density. Therefore, the kinematics of both cosmologies are
identical up to the order of perturbation studied. Looking at the behaviour of
the redshift and angular distance, we find a condition on the compactness of
the objects at the centre of each cell under which corrections to the FLRW
observables remain small, i.e. of order of a few percents at most.
Nevertheless, we show that, if this condition is violated, i.e. if the objects
are too compact, our perturbative scheme breaks down as far as the calculations
of observables are concerned, even though the kinematics of the lattice remains
identical to its FLRW counter-part (at the perturbative order considered). This
may be an indication of an actual fitting problem, i.e. a situation in which
the FLRW model obtained from lightcone observables does not correspond to the
FLRW model obtained by smoothing the spatial distribution of matter. Fully
non-perturbative treatments of the observables will be necessary to answer that
question.Comment: 23 pages, 4 figures. Replaced to matched version accepted in Class.
Quantum Grav. Results unchanged but interpretation clarifie
- …