Coherent versus coincidence detection of gravitational wave signals from compact inspiraling binaries

We compare two multi-detector detection strategies, namely, the coincidence and the coherent, for the detection of spinless inspiraling compact binary gravitational wave signals. The coincident strategy treats the detectors as if they are isolated - compares individual detector statistics with their respective thresholds while the coherent strategy combines the detector network data {\it phase coherently} to obtain a single detection statistic which is then compared with a single threshold. In the case of geographically separated detectors, we also consider an {\it enhanced} coincidence strategy because the usual (naive) coincidence strategy yields poor results for misaligned detectors. For simplicity, we consider detector pairs having the same power spectral density of noise, as that of initial LIGO and also assume the noise to be stationary and Gaussian. We compare the performances of the methods by plotting the \emph{receiver operating characteristic} (ROC) for the two strategies. A single astrophysical source as well as a distribution of sources is considered. We find that the coherent strategy performs better than the two coincident strategies under the assumptions of stationary Gaussian detector noise.Comment: Based on the presentation at the 1st Galileo Xu Guangqi conference, Shanghai

Role of proton irradiation and relative air humidity on iron corrosion

This paper presents a study of the effects of proton irradiation on iron corrosion. Since it is known that in humid atmospheres, iron corrosion is enhanced by the double influence of air and humidity, we studied the iron corrosion under irradiation with a 45% relative humidity. Three proton beam intensities (5, 10 and 20 nA) were used. To characterise the corrosion layer, we used ion beam methods (Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA)) and X-ray Diffraction (XRD) analysis. The corrosion kinetics are plotted for each proton flux. A diffusion model of the oxidant species is proposed, taking into account the fact that the flux through the surface is dependent on the kinetic factor K. This model provides evidence for the dependence of the diffusion coefficient, D, and the kinetic factor, K, on the proton beam intensity. Comparison of the values for D with the diffusion coefficients for thermal oxygen diffusion in iron at 300 K suggests an enhancement due to irradiation of 6 orders of magnitude

Fibroblast spheroids: a useful assay for drug screening in idiopathic pulmonary fibrosis?

Introduction: Idiopathic pulmonary fibrosis (IPF) is characterised by excessive deposition of extracellular matrix proteins and destruction of the lung architecture. The aetiology of this disorder is unknown and few effective therapies are available. Several models have been established to identify key pathological cells and mediators that may be important in IPF, however these models lack the classical histopathological features seen in IPF, such as fibrotic foci. The aim of this project was to develop a novel 3-D in vitro assay system which more closely mimics a fibrotic focus, for pre-clinical drug evaluation. Methods: Primary human lung fibroblasts were isolated as outgrowths from small (<1 mm3) lung explants (non-IPF and IPF patients). Non-IPF (n = 10) and IPF (n = 10) fibroblasts were cultured in non- adherent 96-well plates to generate fibroblastic spheroids. Spheroid formation and phenotypic features were characterised using time-lapse videomicroscopy, histological analysis, (including TUNEL assay) and, electron microscopy. RNA was extracted from the spheroids and microarray analysis and qRT-PCR were used to analyse mRNA levels. Total collagen was measured using HPLC analysis of hydroxyproline levels while active TGFβ within the spheroid homogenates and supernatants were measured using the transformed mink lung epithelial cell bioassay. A medium-throughput screen of potential anti-fibrotic compounds (using a focused GSK compound library known as the fibrosis toolbox) was also performed, using hydroxyproline levels as the endpoint measure. Results: Non-IPF and IPF fibroblasts were able to form non-proliferating spheroids within 24 hours of incubation, with clear organisation and orientation of cells within the spheroid. IPF spheroids had a myofibroblastic phenotype with increase expression of αSMA. TUNEL assay identified increased numbers of apoptotic cells in non-IPF spheroids in comparison to IPF spheroids, which may be due, in part, to autocrine/paracrine COX1-mediated PGE2 generation. The mink lung cell assay demonstrated that non-IPF and IPF spheroids spontaneously produced high levels of active TGFβ, which was partially dependent on β3 and β8 integrins. Antagonising TGFβ signalling did not however affect spheroid collagen production. Microarray data analysis illustrated a limited number of differentially expressed genes, with the majority involved in encoding proteins that play a key role in metabolic pathways. The fibrosis toolbox identified potential target molecules that impact on collagen biosynthesis including EP2/4 compounds, an integrin αv inhibitor, Smo antagonists, MCP-1 inhibitor, and mTORC 1/2 inhibitors. Conclusions: Fibrotic fibroblast spheroids mimic some of the key characteristics of fibroblasts in fibrotic foci of IPF lungs (i.e. increased collagen production, elevated levels of active TGFβ and resistance to apoptosis). In addition, microarray and medium-throughput screening identified several potential targets. Therefore, fibrotic fibroblast spheroids may represent a novel assay system for pre-clinical drug evaluation, and warrant further investigation

A systematical veto by all monitor signals in a gravitational-wave detector

We present the current state of veto studies in TAMA300 by monitor signals of the interferometer and its environment. In GW data analysis, fake GW events may bury real GW events or worse upper limits on the event rate. Thus, fake-event rejection is an important issue. In general, we can reject these fake events by the monitor signals, since these fake events are induced due to detector instabilities. However, using all monitor signals for the fake-event rejection would increase the accidental rejection probability and dead time without improving veto efficiency, since all monitor signals do not have correlations to the detector instabilities. Here, we analyze coincidences between the main and selected monitor signals with the optimal parameters for the fake-event rejection. Then, coincident events are rejected as the fake events. For the signal selection and parameter optimization, we systematically investigate the correlations with the detector instabilities. As a result, we achieved 30–99% veto efficiency using ten selected monitor signals with the 3.2% accidental rejection probability and 0.2% dead time

Role of dynamic Jahn-Teller distortions in Na2C60 and Na2CsC60 studied by NMR

Through 13C NMR spin lattice relaxation (T1) measurements in cubic Na2C60, we detect a gap in its electronic excitations, similar to that observed in tetragonal A4C60. This establishes that Jahn-Teller distortions (JTD) and strong electronic correlations must be considered to understand the behaviour of even electron systems, regardless of the structure. Furthermore, in metallic Na2CsC60, a similar contribution to T1 is also detected for 13C and 133Cs NMR, implying the occurence of excitations typical of JT distorted C60^{2-} (or equivalently C60^{4-}). This supports the idea that dynamic JTD can induce attractive electronic interactions in odd electron systems.Comment: 3 figure

Stochastic backgrounds of gravitational waves from extragalactic sources

Astrophysical sources emit gravitational waves in a large variety of processes occurred since the beginning of star and galaxy formation. These waves permeate our high redshift Universe, and form a background which is the result of the superposition of different components, each associated to a specific astrophysical process. Each component has different spectral properties and features that it is important to investigate in view of a possible, future detection. In this contribution, we will review recent theoretical predictions for backgrounds produced by extragalactic sources and discuss their detectability with current and future gravitational wave observatories.Comment: 10 pages, 9 figures, proceedings of the GWDAW 10 Conference, submitted to Class. & Quantum Gra

Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper. Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix. Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior. The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study. It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand. The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands. It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands