Calibration and characterization of the IceCube photomultiplier tube Abdou, Y.; Baker, M.; Bay, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2010, Letnik:
618, Številka:
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Journal Article
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Over 5000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy ...neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-in. diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.
We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-2008 with 22 strings of the IceCube detector (approximately one-fourth of the planned ...total) and 275.7 days of live time. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2 sigma after accounting for all trials. The average upper limit over the northern sky for point sources of muon-neutrinos with E -2 spectrum is , in the energy range from 3 TeV to 3 PeV, improving the previous best average upper limit by the AMANDA-II detector by a factor of 2.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted) We present the results of a search for high-energy muon neutrinos with the IceCube detector in coincidence with the Crab Nebula flare ...reported on 2010 September by various experiments. Due to the unusual flaring state of the otherwise steady source we performed a prompt analysis of the 79-string configuration data to search for neutrinos that might be emitted along with the observed gamma -rays. We performed two different and complementary data selections of neutrino events in the time window of 10 days around the flare. One event selection is optimized for discovery of ... neutrino spectrum typical of first-order Fermi acceleration. A similar event selection has also been applied to the 40-string data to derive the time-integrated limits to the neutrino emission from the Crab. The other event selection was optimized for discovery of neutrino spectra with softer spectral index and TeV energy cutoffs as observed for various Galactic sources in gamma -rays. The 90% confidence level (CL) best upper limits on the Crab flux during the 10 day flare are 4.73 x 10 super(-11) cm super(-2) s super(-1) TeV super(-1) for an ... neutrino spectrum and 2.50 x 10 super(-10) cm super(-2) s super(-1) TeV super(-1) for a softer neutrino spectra of ..., as indicated by Fermi measurements during the flare. In this paper, we also illustrate the impact of the time-integrated limit on the Crab neutrino steady emission. The limit obtained using 375.5 days of the 40-string configuration is compared to existing models of neutrino production from the Crab and its impact on astrophysical parameters is discussed. The most optimistic predictions of some models are already rejected by the IceCube neutrino telescope with more than 90% CL.
Chondroblastoma is a rare, cartilaginous primary bone tumor, which presents predominantly in children and young adults. These tumors represent 1% of all primary bone tumors. Patients tend to complain ...of progressive joint pain which usually aids in early diagnosis. However, early diagnosis has made the understanding of the untreated, progressive course of chondroblastoma quite difficult. This case report highlights a patient who was first encountered with locally advanced chondroblastoma and discusses the challenges of diagnosis and treatment with a focus on the natural progression of this disease.
We report the case of a 16-year-old male encountered during relief efforts after the 2010 Haiti earthquake, who was found to have a massive, expansile, and destructive mass of the proximal left tibia and fibula. Radiographic appearance was concerning for a malignant bone forming process. However, biopsy revealed features most consistent with chondroblastoma with secondary aneurysmal bone cyst formation. Marginal resection was considered, but the degree of soft tissue and neurovascular invasion made it impossible to salvage the leg and thus an above-the-knee amputation was performed.
This report reviews the challenging diagnosis of a massive chondroblastoma with locally aggressive features which required ablative surgery. This may provide insight into the untreated, natural course of this pathology.
INTRODUCTIONChondroblastoma is a rare, cartilaginous primary bone tumor, which presents predominantly in children and young adults. These tumors represent 1% of all primary bone tumors. Patients tend ...to complain of progressive joint pain which usually aids in early diagnosis. However, early diagnosis has made the understanding of the untreated, progressive course of chondroblastoma quite difficult. This case report highlights a patient who was first encountered with locally advanced chondroblastoma and discusses the challenges of diagnosis and treatment with a focus on the natural progression of this disease. CASE REPORTWe report the case of a 16-year-old male encountered during relief efforts after the 2010 Haiti earthquake, who was found to have a massive, expansile, and destructive mass of the proximal left tibia and fibula. Radiographic appearance was concerning for a malignant bone forming process. However, biopsy revealed features most consistent with chondroblastoma with secondary aneurysmal bone cyst formation. Marginal resection was considered, but the degree of soft tissue and neurovascular invasion made it impossible to salvage the leg and thus an above-the-knee amputation was performed. CONCLUSIONThis report reviews the challenging diagnosis of a massive chondroblastoma with locally aggressive features which required ablative surgery. This may provide insight into the untreated, natural course of this pathology.
A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillation models, ...derivable from extensions to the standard model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. A discrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Because of the unique high energy reach of IceCube, it was possible to improve constraints on certain Lorentz-violating oscillations by 3 orders of magnitude with respect to limits set by other experiments.
En este artículo examino los sentidos sobre la violencia que distintas disidencias grupales de Montoneros desplegaron durante la década del setenta. ¿Fue desestimada por los grupos que rompieron con ...la organización? ¿Qué enunciaron sobre la violencia revolucionaria y sus posibilidades en la coyuntura? ¿Cuáles fueron sus similitudes y distancias? Para dar respuesta a estos interrogantes, analizo un conjunto de documentos y publicaciones que los Montoneros Columna José Sabino Navarro de 1972, la Juventud Peronista Lealtad de 1974, el Peronismo Montonero Auténtico de 1979, y los Montoneros 17 de Octubre de 1980 publicaron en Argentina y en el exilio. Además, si bien no constituyó una disidencia grupal, tomaré las críticas de Rodolfo Walsh. Con ello, pretendo realizar tres aportes: a) contribuir a un área todavía vacante en la bibliografía académica, que es la de los grupos disidentes que Montoneros tuvo en distintos momentos de su derrotero; b) brindar elementos para restituir la diversidad de la militancia en los años setenta; y c) problematizar, desde una perspectiva teórico-política, el vínculo conceptual entre violencia y política en las identidades insurgentes de la época.
In this article, I analyze the debates, declarations, and silences surrounding the issue of violence during the final years of the Argentine insurgent group Montoneros (1979–1983). I examine the ...official documents and bulletins written while the group was in exile, as well as the statements and publications of dissident groups (the Peronismo Montonero Auténtico of 1979 and the Montoneros 17 de Octubre of 1980) and other critical groups (the Agrupación Eva Perón of 1980). From a political theory perspective, I will focus on the specificity of this space of belonging, its symbols, its representations, and its actions. In this study, I intend to (a) shed light on the final stage of the Montoneros organization, which, with few exceptions, has not been subjected to historiographical or sociological analysis, or studied by political science and (b) contribute to a deeper understanding of the dissolution processes undergone by armed insurgent groups in Latin America in the 1960s and 1970s.
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