16 research outputs found
Bulk micromegas detectors for large TPC applications
A large volume TPC will be used in the near future in a variety of experiments including T2K. The bulk Micromegas detector for this TPC is built using a novel production technique particularly suited for compact and robust low mass detectors. The capability to pave a large surface with a simple mounting solution and small dead space between modules is of particular interest for these applications. We have built several large bulk Micromegas detectors (27 x 26 cm2) and we have tested them in the former HARP field cage setup with a magnetic field. Cosmic ray data have been acquired in a variety of experimental conditions. Good detector performances and space point resolution have been achieved
Lamin A Rod Domain Mutants Target Heterochromatin Protein 1α and β for Proteasomal Degradation by Activation of F-Box Protein, FBXW10
Lamins are major structural proteins of the nucleus and contribute to the organization of various nuclear functions. Mutations in the human lamin A gene cause a number of highly degenerative diseases, collectively termed as laminopathies. Cells expressing lamin mutations exhibit abnormal nuclear morphology and altered heterochromatin organization; however, the mechanisms responsible for these defects are not well understood.The lamin A rod domain mutants G232E, Q294P and R386K are either diffusely distributed or form large aggregates in the nucleoplasm, resulting in aberrant nuclear morphology in various cell types. We examined the effects of these lamin mutants on the distribution of heterochromatin protein 1 (HP1) isoforms. HeLa cells expressing these mutants showed a heterogeneous pattern of HP1alpha and beta depletion but without altering HP1gamma levels. Changes in HP1alpha and beta were not observed in cells expressing wild-type lamin A or mutant R482L, which assembled normally at the nuclear rim. Treatment with proteasomal inhibitors led to restoration of levels of HP1 isoforms and also resulted in stable association of lamin mutants with the nuclear periphery, rim localization of the inner nuclear membrane lamin-binding protein emerin and partial improvement of nuclear morphology. A comparison of the stability of HP1 isoforms indicated that HP1alpha and beta displayed increased turnover and higher basal levels of ubiquitination than HP1gamma. Transcript analysis of components of the ubiquitination pathway showed that a specific F-box protein, FBXW10 was induced several-fold in cells expressing lamin mutants. Importantly, ectopic expression of FBXW10 in HeLa cells led to depletion of HP1alpha and beta without alteration of HP1gamma levels.Mislocalized lamins can induce ubiquitin-mediated proteasomal degradation of certain HP1 isoforms by activation of FBXW10, a member of the F-box family of proteins that is involved in E3 ubiquitin ligase activity
Time projection chambers for the T2K near detectors
The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector located 295 km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator-bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker is used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/Nomad dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system
Nanostructured Surfaces in Concentrator Photovoltaic Modules: Temperature Dependent Performance Improvements
International audienc
CPV Module to Rate Antireflective and Encapsulant Coating in Outdoor Conditions
International audienceReflections are the most important channel losses in CPV modules. Since high efficiency solar cells need a protection against moisture and oxidation, we study an antireflective coating which also encapsulates the solar cells. It is based on a monolayer of microbeads partially submerged into PDMS. In this work, a CPV module is designed to compare the electrical performance of encapsulated and bare solar cells. A preliminary study demonstrates an increase in short-circuit current by 3.8% with EQE measurements and simulations. Outdoor measurements in Sherbrooke, Quebec, Canada gave a 6.4% increase in current for a 280X module on a clear cold day in September, after rejecting aberrant measurements, which confirms the interest of using microbeads as an antireflective coating for CPV applications
CPV Module to Rate Antireflective and Encapsulant Coating in Outdoor Conditions
International audienceReflections are the most important channel losses in CPV modules. Since high efficiency solar cells need a protection against moisture and oxidation, we study an antireflective coating which also encapsulates the solar cells. It is based on a monolayer of microbeads partially submerged into PDMS. In this work, a CPV module is designed to compare the electrical performance of encapsulated and bare solar cells. A preliminary study demonstrates an increase in short-circuit current by 3.8% with EQE measurements and simulations. Outdoor measurements in Sherbrooke, Quebec, Canada gave a 6.4% increase in current for a 280X module on a clear cold day in September, after rejecting aberrant measurements, which confirms the interest of using microbeads as an antireflective coating for CPV applications
ApoA-I mimetics favorably impact cyclooxygenase 2 and bioactive lipids that may contribute to cardiometabolic syndrome in chronic treated HIV.
ObjectiveWe investigated whether apolipoprotein A-I (apoA-I) mimetic peptides 4F and 6F can be a novel therapeutic strategy to reduce blood and gut bioactive lipids, proinflammatory effects of endotoxin (LPS) and aberrant activation of cyclooxygenase 2 (COX-2) as instigators of increased risk for cardiometabolic disease in chronic treated HIV.MethodsWe used two humanized murine models of chronic treated HIV infection (n = 109 mice) and gut explants from HIV infected (n = 10) persons to determine whether Tg6F and 4F attenuate in vivo and ex vivo increased blood and gut bioactive lipids (measured by mass spectrometry) and intestinal protein levels of COX-2 (measured by immunoassays) in chronic treated HIV.ResultsIn these models of HIV, when compared to HIV-1 infected mice on antiretroviral therapy (ART) alone, oral Tg6F in combination with ART attenuated increases in plasma and gut bioactive lipids (and particularly COX lipids) and intestinal COX-2. 4F and Tg6F also reduced ex vivo production of COX-2 protein and associated secretion of bioactive lipids in gut explants from HIV-1 infected persons treated with LPS.ConclusionApoA-I mimetics favorably impact the proinflammatory effects of LPS, COX-2 and production of bioactive lipids that collectively drive gut and systemic inflammation in chronic treated HIV. Given prior experimental evidence that the proinflammatory effects of LPS, COX-2 and gut dysfunction contribute to cardiometabolic syndrome in chronic HIV, apoA-I mimetic peptides may be a novel therapy to treat cardiometabolic syndrome in chronic HIV
The T2K experiment
The T2K experiment is a long baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ13 by observing νe appearance in a νμ beam. It also aims to make a precision measurement of the known oscillation parameters, and sin22θ23, via νμ disappearance studies. Other goals of the experiment include various neutrino cross-section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem
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Mfn2 deletion in brown adipose tissue protects from insulin resistance and impairs thermogenesis.
BAT-controlled thermogenic activity is thought to be required for its capacity to prevent the development of insulin resistance. This hypothesis predicts that mediators of thermogenesis may help prevent diet-induced insulin resistance. We report that the mitochondrial fusion protein Mitofusin 2 (Mfn2) in BAT is essential for cold-stimulated thermogenesis, but promotes insulin resistance in obese mice. Mfn2 deletion in mice through Ucp1-cre (BAT-Mfn2-KO) causes BAT lipohypertrophy and cold intolerance. Surprisingly however, deletion of Mfn2 in mice fed a high fat diet (HFD) results in improved insulin sensitivity and resistance to obesity, while impaired cold-stimulated thermogenesis is maintained. Improvement in insulin sensitivity is associated with a gender-specific remodeling of BAT mitochondrial function. In females, BAT mitochondria increase their efficiency for ATP-synthesizing fat oxidation, whereas in BAT from males, complex I-driven respiration is decreased and glycolytic capacity is increased. Thus, BAT adaptation to obesity is regulated by Mfn2 and with BAT-Mfn2 absent, BAT contribution to prevention of insulin resistance is independent and inversely correlated to whole-body cold-stimulated thermogenesis