824 research outputs found
Thermal noise study of a radiation pressure noise limited optical cavity with fused silica mirror suspensions
No full textIn this work we study the thermal noise of two monolithically suspended mirrors in a tabletop high-finesse optical cavity. We show that, given suitable seismic filters, such a cavity can be designed to be sensitive to quantum radiation pressure fluctuations in the audio band of gravitational wave interferometric detectors below 1 kHz. Indeed, the thermal noise of the suspensions and of the coatings constitutes the main limit to the observation of quantum radiation pressure fluctuations. This limit can be overcome with an adequate choice of mirror suspension and coating parameters. Finally, we propose to combine two optical cavities, like those modeled in this work, to obtain a tabletop quantum radiation pressure-limited interferometer
Monolithic fused silica suspension for the Virgo gravitational waves detector
No full textThermal noise in mirror suspension wires is the most severe limit to the low frequency sensitivity of interferometric gravitational wave detectors presently under construction. The pendulum mode mechanical quality factor of the suspension last stage significantly affects the noise level of the detector output. The monolithic design for this suspension stage, using a low dissipation material, is proposed for Virgo. High mechanical Q(s) and high breaking strengths have been obtained for monolithic fused silica fibers. A low dissipation and high strength bonding technique using potassium silicate bonding is proposed. (C) 2002 American Institute of Physics
A parallel Beowulf-based system for the detection of gravitational waves in interferometric detectors
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Mechanical quality factor of large mirror substrates for gravitational waves detectors
No full textThermal noise in the mirror substrates sets a most severe limit to the low-frequency sensitivity of the interferometric gravitational wave detectors presently under construction. The mechanical quality of the mirror substrates and the geometry of their suspension are shown to affect markedly the noise level of the detector output. High mechanical Q have been obtained for different large fused silica substrates under Virgo suspension conditions. Moreover, calcium fluoride substrates are shown to provide a more promising option for the design of future cryogenic, low thermal noise interferometers. (C) 2002 American Institute of Physics
The thermal noise limit to the Virgo sensitivity
No full textThe expected current limit to the Virgo sensitivity is presented. New materials to realize a low thermal noise suspension for the Virgo optics are investigated. A promising fused silica suspension for the Virgo mirrors is presented
Relationship between global end-diastolic volume and cardiac output in critically ill infants and children.
No full textOBJECTIVE: The objective of this study was to investigate possible correlations between the preload index global end-diastolic volume (GEDV) and the indexes of cardiac function, cardiac index, and stroke volume index in critically ill pediatric patients. The aim was to evaluate whether GEDV may help in the decision-making process concerning volume loading. DESIGN: Prospective clinical study. SETTING: Pediatric intensive care unit of the Bambino Gesù Children's Research Hospital. PATIENTS: Seventy patients, 40 male and 30 female, mean age 62 +/- 41 months (range 5-156 months), divided into six groups: group A, hemorrhagic shock, ten cases; group B, head injury, 21 cases; group C, septic shock, ten cases; group D, encephalitis, ten cases; group E, respiratory failure, nine cases; group F, cardiogenic shock, ten cases. INTERVENTIONS: All patients received volumetric hemodynamic monitoring following initial resuscitation and every 4 hrs thereafter or whenever a hemodynamic deterioration was suspected. During the cumulative in-hospital stay, a total 1,184 sets of measurements were done. MEASUREMENTS AND MAIN RESULTS: Findings are consistent with a statistically significant linear correlation of GEDV with cardiac index and stroke volume index in hemorrhagic shock (group A) (R2 = .647, p .0001; R2 = .738, p .0001) and cardiogenic shock (group F) (R2 = .645, p .0001; R2 = .841, p .0001). CONCLUSIONS: GEDV may potentially be a useful guide to treatment in preload-dependent conditions, such as hemorrhagic and cardiogenic shock. In the other groups where there is little relationship between preload and cardiac function indexes, the influence of non-preload-dependent mechanisms on cardiac output is certainly more significant
Monocrystalline fibres for low thermal noise suspension in advanced gravitational wave detectors
No full textThermal noise in mirror suspension will be the most severe fundamental limit to the low-frequency sensitivity of future interferometric gravitational wave detectors. We propose a new type of materials to realize low thermal noise suspension in such detectors. Monocrystalline suspension fibres are good candidates both for cryogenic and for ambient temperature interferometers. Material characteristics and a production facility are described in this paper
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