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

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

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

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