Mechanical spectroscopy gives information on the structure of solids and their relaxation mechanisms through the measurements of the elastic constants and the mechanical loss angle of materials. One ...common way to estimate these quantities is the resonant method where the frequency and the characteristic decay time of oscillations are measured. Since many solid materials can be easily found in the shape of thin disc we have investigated the mechanical loss of these resonators and we have found experimentally that the loss angle dependence on the mode is not trivial but rather follow a distribution of modes into families. We give a model that is able to justify the existence of these families and to predict the level of losses in silicon, silica and brass discs. The model considers the thermoelastic effect and the excess damping caused by the condition of the disc edge. The results of this research are relevant to the research on thin films that are deposited on thin discs like the optical coatings used on the mirrors for the gravitational wave detectors.
•It provides the first experimental evidence and justification of mode families in loss measurements in discs.•A simple and reliable model of thermoelastic loss in thin discs is provided.•A method of calculation of thermoelastic loss in thick cylinder and non-isotropic materials is provided.•Total loss expression is provided in the most general case of heterogeneous systems with multiple loss mechanisms.
In this work We report on the extensive characterization of amorphous silicon carbide (a-SiC) coatings prepared by physical deposition methods. We compare the results obtained on two different ...sputtering systems (a standard RF magnetron sputtering and a ion-beam assisted sputtering) to seize the impact of two different setups on the repeatably of the results. After a thorough characterization of structural, morphological, and compositional characteristics of the prepared samples, we focus on a detailed study of the optical and mechanical losses in those materials. Mechanical losses are further investigated from a microscopic point of view by comparing our experimental results with molecular dynamic simulations of the amorphous SiC structure: first we define a protocol to generate a numerical model of the amorphous film, capturing the main features of the real system; then we simulate its dynamical behaviour upon deformation in order to obtain its mechanical response. Our results are discussed within the perspective application of a-SiC as an optical material for high-precision optical experiments and in particular in gravitational wave interferometry.
We perform a statistical standard siren analysis of GW170817. Our analysis does not utilize knowledge of NGC 4993 as the unique host galaxy of the optical counterpart to GW170817. Instead, we ...consider each galaxy within the GW170817 localization region as a potential host; combining the redshift from each galaxy with the distance estimate from GW170817 provides an estimate of the Hubble constant, \(H_0\). We then combine the \(H_0\) values from all the galaxies to provide a final measurement of \(H_0\). We explore the dependence of our results on the thresholds by which galaxies are included in our sample, as well as the impact of weighting the galaxies by stellar mass and star-formation rate. Considering all galaxies brighter than \(0.01 L^\star_B\) as equally likely to host a BNS merger, we find \(H_0= 76^{+48}_{-23}\) km s\(^{-1}\) Mpc\(^{-1}\) (maximum a posteriori and 68.3% highest density posterior interval; assuming a flat \(H_0\) prior in the range \(\left 10, 220 \right\) km s\(^{-1}\) Mpc\(^{-1}\)). Restricting only to galaxies brighter than \(0.626 L^\star_B\) tightens the measurement to \(H_0= 77^{+37}_{-18}\) km s\(^{-1}\) Mpc\(^{-1}\). We show that weighting the host galaxies by stellar mass or star-formation rate provides entirely consistent results with potentially tighter constraints. While these statistical estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, \(H_0=76^{+19}_{-13}\) km s\(^{-1}\) Mpc\(^{-1}\) (determined from the same publicly available data), our analysis is a proof-of-principle demonstration of the statistical approach first proposed by Bernard Schutz over 30 years ago.
In August 2017, Advanced Virgo joined Advanced LIGO for the end of the O2 run, leading to the first gravitational waves detections with the three-detector network. This paper describes the Advanced ...Virgo calibration and the gravitational wave strain h(t) reconstruction during O2. The methods are the same as the ones developed for the initial Virgo detector and have already been described in previous publications, this paper summarizes the differences and emphasis is put on estimating systematic uncertainties. Three versions of the h(t) signal have been computed for the Virgo O2 run, an online version and two post-run reprocessed versions with improved detector calibration and reconstruction algorithm. A photon calibrator has been used to establish the sign of h(t) and to make an independent partial cross-check of the systematic uncertainties. The uncertainties reached for the latest h(t) version are 5.1% in amplitude, 40 mrad in phase and 20 microseconds in timing.
Mast cells are abundant in the heart, among myocardial fibers, around coronary arteries, within arterial intima and intramural vessels, and in atherosclerotic plaques. Their mediators can be released ...during anaphylaxis and be responsible for acute coronary syndrome. This condition has been described as Kounis syndrome (KS). We report three cases of acute myocardial ischemia, which fulfill the definition for KS. In Cases 1 and 2, the association of intense chest pain with acute urticaria after an allergenic contact (wasp sting and betalactam antibiotic administration, respectively) was suspected to be an attack of angina related to an allergic reaction. No signs of an allergic reaction were observed in Case 3, but only the history of a wasp sting suggested its relationship to loss of consciousness and heart ischemia when hypersensitivity to venom was ascertained. These cases strongly recommend measurement of anaphylactic biomarkers, such as tryptase, during acute coronary syndromes to detect the possible involvement of an allergic reaction. Conversely, measurement of cardiac biomarkers during anaphylaxis, even without obvious signs of myocardial ischemia, might identify patients at risk of myocardial injury.
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