5,873 research outputs found
On the Sensitivity of a Hollow Sphere as a Multi-modal Resonant Gravitational Wave Detector
We present a numerical analysis to simulate the response of a spherical
resonant gravitational wave detector and to compute its sensitivity. Under the
assump- tion of optimal filtering, we work out the sensitivity curve for a
sphere first taking into account only a single transducer, and then using a
coherent analysis of the whole set of transducers.Comment: 24 pages, 11 figures, published versio
Deconvolving the information from an imperfect spherical gravitational wave antenna
We have studied the effects of imperfections in spherical gravitational wave
antenna on our ability to properly interpret the data it will produce. The
results of a numerical simulation are reported that quantitatively describe the
systematic errors resulting from imperfections in various components of the
antenna. In addition, the results of measurements on a room-temperature
prototype are presented that verify it is possible to accurately deconvolve the
data in practice.Comment: 5 pages, 2 figures, to be published in Europhysics Letter
An anti-Schwarzshild solution: wormholes and scalar-tensor solutions
We investigate a static solution with an hyperbolic nature, characterised by
a pseudo-spherical foliation of space. This space-time metric can be perceived
as an anti-Schwarzschild solution, and exhibits repulsive features. It belongs
to the class of static vacuum solutions termed "a degenerate static solution of
class A". In the present work we review its fundamental features, discuss the
existence of generalised wormholes, and derive its extension to scalar-tensor
gravity theories in general.Comment: 3 pages, contribution to the proceedings of the Spanish Relativity
Meeting-ERE200
Thermal diagnostic of the Optical Window on board LISA Pathfinder
Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra
The Effect of Bond-Slip in the Numerical Assessment of RC Frames Under Cyclic Loading
Bond-slip may have significant influence on the assessment, with numerical models, of reinforced concrete structures
subjected to cyclic loadings, whether static or dynamic. Its influence is discussed with the correlation of experimental and
analytical results, where two numerical models are considered, including a perfect bond fiber-section finite element
formulation and a force-based fiber-section model including bond-slip in the vicinity of the frame joints, both exterior and
interior. In this case, the model implemented makes it possible to consider the coupling effect of the response of the beams
adjacent to the joint, and the models are constructed from the geometrical and material characteristics of the structure,
without any calibration procedures. The experimental results are from a reinforced concrete column and a beam-column
subassemblage, both subjected to static cyclic loadings, with predefined displacements sequences for the element-ends, and
from a shaking table test of a one bay two-story reinforced concrete frame structure.
The comparisons show that the considered bond-slip based model makes it possible to satisfactorily predict the response of
reinforced concrete frames under both static and dynamic cyclic loadings. The influence of reinforcement slippage was
evaluated by comparison of the previous results with those obtained with the perfect bond-based model. This made it
possible to conclude that the accuracy of the model considering bond-slip is significantly superior to that of the perfect bond
model. Furthermore, responses obtained with the previous model show the pinching effect, which is characteristic of
reinforced concrete structures and significantly changes the hysteretic dissipated energy, not delivered by the latter model.
This can also be seen in the effect of bond-slip in the response of the fibers which model the reinforcing rebars.info:eu-repo/semantics/publishedVersio
On-ground tests of LISA PathFinder thermal diagnostics system
Thermal conditions in the LTP, the LISA Technology Package, are required to
be very stable, and in such environment precision temperature measurements are
also required for various diagnostics objectives. A sensitive temperature
gauging system for the LTP is being developed at IEEC, which includes a set of
thermistors and associated electronics. In this paper we discuss the derived
requirements applying to the temperature sensing system, and address the
problem of how to create in the laboratory a thermally quiet environment,
suitable to perform meaningful on-ground tests of the system. The concept is a
two layer spherical body, with a central aluminium core for sensor implantation
surrounded by a layer of polyurethane. We construct the insulator transfer
function, which relates the temperature at the core with the laboratory ambient
temperature, and evaluate the losses caused by heat leakage through connecting
wires. The results of the analysis indicate that, in spite of the very
demanding stability conditions, a sphere of outer diameter of the order one
metre is sufficient. We provide experimental evidence confirming the model
predictions.Comment: 18 pages, 5 figures, LaTeX2e (compile with pdflatex), sumbitted to
CQG. This paper is a significant extension of gr-qc/060109
Wideband dual sphere detector of gravitational waves
We present the concept of a sensitive AND broadband resonant mass
gravitational wave detector. A massive sphere is suspended inside a second
hollow one. Short, high-finesse Fabry-Perot optical cavities read out the
differential displacements of the two spheres as their quadrupole modes are
excited. At cryogenic temperatures one approaches the Standard Quantum Limit
for broadband operation with reasonable choices for the cavity finesses and the
intracavity light power. A molybdenum detector of overall size of 2 m, would
reach spectral strain sensitivities of 2x10^-23/Sqrt{Hz} between 1000 Hz and
3000 Hz.Comment: 4 pages, 3 figures. Changed content. To appear in Phys. Rev. Let
Risk factors for symptomatic retears after arthroscopic repair of full-thickness rotator cuff tears
Background: Factors affecting a rotator cuff symptomatic retear after arthroscopic repair have yet to be clearly identified, since they usually influence the surgical decisions.
Methods: Consecutive patients with full-thickness tear of the supraspinatus who underwent arthroscopic repair were retrospectively analyzed. Cases of symptomatic retear, defined as Sugaya type IV and V on magnetic resonance imaging, associated with intensive pain and/or functional impairment were identified at follow-up. The patients with no symptomatic retear were selected as the control group. Information from potential risk factors of symptomatic retear, including depression and subacromial corticosteroid injections, was extracted from the medical records. The statistical analysis included multivariant logistic regression.
Results: The symptomatic retear rate was 9.5% in 158 patients. Patients in the symptomatic retear group were more likely to be smoking, to have massive tears, a short acromiohumeral distance, and moderate to severe fatty infiltration. They also had had more frequently subacromial corticosteroid injections and depression. However, following the multiple logistic regression analysis, only massive tears and moderate to severe fatty infiltration remained significantly associated. Similarly, in relation to the study hypothesis, both corticosteroid injections (odds ratio [OR] 6.66, 95% confidence interval [CI] 1.49, 29.81; P =.013) and depression (OR 8.26, IC 1.04, 65.62; P =.046) were significantly associated with symptomatic retear risk.
Conclusions: This study found support for the hypothesis that both depression and corticosteroid infiltration before surgery are independent risk factors for symptomatic retear after arthroscopic repair of rotator cuff
Sub-nanosecond, time-resolved, broadband infrared spectroscopy using synchrotron radiation
A facility for sub-nanosecond time-resolved (pump-probe) infrared
spectroscopy has been developed at the National Synchrotron Light Source of
Brookhaven National Laboratory. A mode-locked Ti:sapphire laser produces 2 ps
duration, tunable near-IR pump pulses synchronized to probe pulses from a
synchrotron storage ring. The facility is unique on account of the broadband
infrared from the synchrotron, which allows the entire spectral range from 2
cm-1 (0.25 meV) to 20,000 cm-1 (2.5 eV) to be probed. A temporal resolution of
200 ps, limited by the infrared synchrotron-pulse duration, is achieved. A
maximum time delay of 170 ns is available without gating the infrared detector.
To illustrate the performance of the facility, a measurement of electron-hole
recombination dynamics for an HgCdTe semiconductor film in the far- and mid
infrared range is presented.Comment: 11 pages with 9 figures include
The LISA PathFinder DMU and Radiation Monitor
The LISA PathFinder DMU (Data Management Unit) flight model was formally
accepted by ESA and ASD on 11 February 2010, after all hardware and software
tests had been successfully completed. The diagnostics items are scheduled to
be delivered by the end of 2010. In this paper we review the requirements and
performance of this instrumentation, specially focusing on the Radiation
Monitor and the DMU, as well as the status of their programmed use during
mission operations, on which work is ongoing at the time of writing.Comment: 11 pages, 7 figures, prepared for the Proceedings of the 8th
International LISA Symposium, Classical and Quantum Gravit
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