Status of Virgo Amico, P; Antonucci, F; Aoudia, S ...
Classical and Quantum Gravity,
06/2008, Letnik:
25, Številka:
11
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved. ...Commissioning breaks were organized during the run which permitted improvement of the sensitivity and the robustness of the interferometer against environmental perturbations like bad weather and earthquakes. The post-run commissioning phase has now started, with the goal of preparing the next upgrade step of the detector, Virgo+.
Abstract Purpose To compare radiation dose and image quality between a slot-scanning system (SSS) and a dynamic flat-panel detector (DFD) in assessing scoliosis in children. Methods An experimental ...study was first performed with a phantom to assess the quality of each device. The clinical part included a prospective observational dosimetric and qualitative comparative study with acquisition of whole-spine X-ray: SSS (31 children), DFD (26 children). Institutional review board approval and informed consent were obtained. Dosimetric statistical analysis was performed from dose area product (DAP) and entrance skin dose measured by thermo-luminescent dosimeters localized in the cervical, thoracic and sacral areas. Assessment of the diagnostic quality (phantom and clinical) was realized by independent evaluation by 3 observers, using statistical analysis of quality score and inter-observer reproducibility. Results DAP was equivalent with the 2 systems. Entrance skin dose was significantly higher with DFD in thoracic and pelvic regions ( P < 0.05). Image quality scores of the SSS were significantly better than DFD for a majority of criteria, in both phantom and clinical evaluations. Conclusion For scoliosis evaluation, the SSS, compared to the DFD system, offers enhanced image quality while reducing the entrance skin dose in the most radiosensitive areas.
The detection of gravitational waves by Advanced LIGO and Advanced Virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations ...and laboratory tests. We present four tests of the consistency of the data with binary black hole gravitational waveforms predicted by general relativity. One test subtracts the best-fit waveform from the data and checks the consistency of the residual with detector noise. The second test checks the consistency of the low- and high-frequency parts of the observed signals. The third test checks that phenomenological deviations introduced in the waveform model (including in the post-Newtonian coefficients) are consistent with 0. The fourth test constrains modifications to the propagation of gravitational waves due to a modified dispersion relation, including that from a massive graviton. We present results both for individual events and also results obtained by combining together particularly strong events from the first and second observing runs of Advanced LIGO and Advanced Virgo, as collected in the catalog GWTC-1. We do not find any inconsistency of the data with the predictions of general relativity and improve our previously presented combined constraints by factors of 1.1 to 2.5. In particular, we bound the mass of the graviton to be mg≤4.7×10−23 eV/c2 (90% credible level), an improvement of a factor of 1.6 over our previously presented results. Additionally, we check that the four gravitational-wave events published for the first time in GWTC-1 do not lead to stronger constraints on alternative polarizations than those published previously.
Présentation neurologique d’un ostéome ostéoïde du col fémoral Cabasson, S.; Yvert, M.; Pillet, P. ...
Archives de pédiatrie : organe officiel de la Société française de pédiatrie,
November 2012, 2012-11-00, Letnik:
19, Številka:
11
Journal Article
Recenzirano
L’ostéome ostéoïde est une tumeur osseuse bénigne fréquente de l’enfant. La présentation clinique comprend des douleurs articulaires sensibles à l’aspirine. Cependant des formes à présentation ...neurologique peuvent exister, et rendre le diagnostic difficile. Nous rapportons le cas d’un enfant de 8ans qui présentait une boiterie aux dépens de la jambe gauche évoluant depuis plusieurs mois, associée à une amyotrophie du quadriceps et des gastrocnémiens. L’enfant souffrait de douleurs d’allure neurogène à l’aine gauche, avec un horaire de type inflammatoire. Les réflexes ostéotendineux achilléens et rotuliens étaient diminués du même côté. Il n’y avait pas d’anomalie sur la jambe et la cuisse droites. L’imagerie par résonance magnétique (IRM) et la tomodensitométrie ont mis en évidence un ostéome ostéoïde du col fémoral gauche. Ce cas illustre également l’efficacité de la prise en charge en radiologie interventionnelle par radiofréquence percutanée, qui permet une récupération rapide.
We report the case of an 8-year-old boy, suffering from nocturnal pain localized on the left groin and presenting as a limp over several months. Examination revealed diminished strength of the left leg, atrophy of the thigh and calf, and a diminished deep tendon reflex. The pain could be intense and the patient had found an analgesic position by pushing on his groin or by flexing his thigh on the pelvis. He could no longer run. He was unsuccessfully treated with carbamazepine and gabapentin. His evaluation included a negative abdominal ultrasound study and a normal spine and cerebral MRI. Electromyography was unremarkable. He finally underwent an MRI of the pelvis that revealed a hyperintense T2 signal of the left femoral neck; CT confirmed the diagnosis of osteoid osteoma. Radiofrequency ablation of the lesion was performed. His clinical state dramatically improved after the procedure. His walk is normal, without any limping. Deep tendon reflexes are normal, and he only presents residual pain. Physicians should be aware that osteoid osteoma may take the form of a slowly evolving neuropathy. We review the literature on this underestimated condition.
The status of VIRGO Amico, P; Al-Shourbagy, M; Avino, S ...
Classical and Quantum Gravity,
04/2006, Letnik:
23, Številka:
8
Journal Article, Conference Proceeding
Recenzirano
VIRGO interferometer commissioning started in September 2003. The complete lock of the interferometer was achieved in October 2004 via several steps. The main commissioning activity deals with ...improvements in the interferometer stability and sensitivity. The status of the advancement of VIRGO and the short-term plans are discussed here
Tests of General Relativity with GW150914 Aguiar, O D; Arceneaux, C C; Arnaud, N ...
Physical review letters,
2016-Jun-03, Letnik:
116, Številka:
22
Journal Article, Web Resource
Recenzirano
Odprti dostop
The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final ...merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 10^{13} km. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.
Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves, with the aim of increasing the number of observable galaxies (and thus the detection rate) by three ...orders of magnitude. The project is now in an advanced construction phase and the assembly and integration will be completed by the end of 2015. Advanced Virgo will be part of a network, alongside the two Advanced LIGO detectors in the US and GEO HF in Germany, with the goal of contributing to the early detection of gravitational waves and to opening a new window of observation on the universe. In this paper we describe the main features of the Advanced Virgo detector and outline the status of the construction.
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