POLAR is space-borne detector designed for a precise measurement of gamma-ray polarization of the prompt emissions of Gamma-Ray Bursts in the energy range 50 keV - 500 keV. POLAR is a compact Compton ...polarimeter consisting of 40\(\times\) 40 plastic scintillator bars read out by 25 multi-anode PMTs. In May 2015, we performed a series of tests of the POLAR flight model with 100\% polarized x-rays beams at the European Synchrotron Radiation Facility beam-line ID11 aming to study thresholds, crosstalk between channels and responses of POLAR flight model to polarized X-ray beams. In this paper we present the data analysis method and some analysis results. According the results, POLAR FM has good polarimetric capabilities.
As a space-borne detector POLAR is designed to conduct hard X-ray polarization measurements of gamma-ray bursts on the statistically significant sample of events and with an unprecedented accuracy. ...During its development phase a number of tests, calibrations runs and verification measurements were carried out in order to validate instrument functionality and optimize operational parameters. In this article we present results on gain optimization togeter with verification data obtained in the course of broad laboratory and environmental tests. In particular we focus on exposures to the \(^{137}\)Cs radioactive source and determination of the gain dependence on the high voltage for all 1600 detection channels of the polarimeter. Performance of the instrument is described in detail with respect to the dynamic range, energy resolution and temperature dependence. Gain optimization algorithms and response non-uniformity studies are also broadly discussed. Results presented below constitute important parts for development of the POLAR calibration and operation database.
Gamma-ray polarimetry is a new powerful tool to study the processes responsible for the emission from astrophysical sources and the environments in which this emission takes place. Few successful ...polarimetric measurements have however been performed thus far in the gamma-ray energy band due to the difficulties involved. POLAR is a dedicated polarimeter designed to perform high precision measurements of the polarization of the emission from gamma-ray burst in the 50-500 keV energy range. This new polarimeter is expected to detect approximately 50 gamma-ray bursts per year while performing high precision polarization measurements on approximately 10 bursts per year. The instrument was launched into lower earth orbit as part of the second Chinese space lab, the Tiangong-2, on September 15th 2016 and has been taking data successfully since being switched on one week after. The instrument uses a segmented scintillator array consisting of 1600 plastic scintillator bars, read out by 25 flat-panel multi-anode photomultipliers, to measure the Compton scattering angles of incoming photons. The small segmentation and relatively large uniform effective area allow the instrument to measure the polarization of a large number of transient events, such as gamma-ray bursts, with an unprecedented precision during its two year life-time. The final flight model underwent detailed calibration prior to launch as well as intensive space qualification tests, a summary of which will be presented in this paper. The instrument design will be discussed first followed by an overview of the on-ground tests, finally the in-orbit behavior as measured during the first weeks of the mission will be presented.
Gamma Ray Bursts (GRBs) are the strongest explosions in the universe which might be associated with creation of black holes. Magnetic field structure and burst dynamics may influence polarization of ...the emitted gamma-rays. Precise polarization detection can be an ultimate tool to unveil the true GRB mechanism. POLAR is a space-borne Compton scattering detector for precise measurements of the GRB polarization. It consists of a 40\(\times\)40 array of plastic scintillator bars read out by 25 multi-anode PMTs (MaPMTs). It is scheduled to be launched into space in 2016 onboard of the Chinese space laboratory TG2. We present a dedicated methodology for POLAR calibration and some calibration results based on the combined use of the laboratory radioactive sources and polarized X-ray beams from the European Synchrotron Radiation Facility. They include calibration of the energy response, computation of the energy conversion factor vs. high voltage as well as determination of the threshold values, crosstalk contributions and polarization modulation factors.
Sorbitol from Common Plantain Galkowski, T. T; Gauvin, P. N; Santurri, P. R
Journal of agricultural and food chemistry,
05/1966, Letnik:
14, Številka:
3
Journal Article
Mitochondria are dynamic organelles, undergoing both fission and fusion regularly in interphase cells. Mitochondrial fission is thought to be part of a quality-control mechanism whereby damaged ...mitochondrial components are segregated from healthy components in an individual mitochondrion, followed by mitochondrial fission and degradation of the damaged daughter mitochondrion 1. Fission also plays a role in apoptosis 2. Defects in mitochondrial dynamics can lead to neurodegenerative diseases such as Alzheimer’s disease 3. Mitochondrial fission requires the dynamin GTPase Drp1, which assembles in a ring around the mitochondrion and appears to constrict both outer and inner mitochondrial membranes 4. However, mechanisms controlling Drp1 assembly on mammalian mitochondria are unclear. Recent results show that actin polymerization, driven by the endoplasmic reticulum-bound formin protein INF2, stimulates Drp1 assembly at fission sites 5. Here, we show that myosin II also plays a role in fission. Chemical inhibition by blebbistatin or small interfering RNA (siRNA)-mediated suppression of myosin IIA or myosin IIB causes an increase in mitochondrial length in both control cells and cells expressing constitutively active INF2. Active myosin II accumulates in puncta on mitochondria in an actin- and INF2-dependent manner. In addition, myosin II inhibition decreases Drp1 association with mitochondria. Based on these results, we propose a mechanistic model in which INF2-mediated actin polymerization leads to myosin II recruitment and constriction at the fission site, enhancing subsequent Drp1 accumulation and fission.
•Myosin II inhibition by blebbistatin or siRNA increases mitochondrial length•Myosin II acts in the same fission pathway as INF2 and Drp1•Myosin II accumulation on mitochondria depends on INF2-mediated actin polymerization•Short-term Arp2/3 complex inhibition does not affect mitochondrial size
Korobova et al. find that myosin II participates in mitochondrial fission through a pathway involving the ER-bound formin INF2. Myosin II is recruited to fission sites through INF2-mediated actin assembly. Myosin II inhibition causes a decrease in Drp1 accumulation on mitochondria, suggesting that myosin II enhances Drp1 recruitment during fission.
The Large Hadron Collider beauty (LHCb) experiment at CERN (Conseil Européen pour la Recherche Nucléaire) is designed to perform precision measurements of b quark decays. The LHCb Silicon Tracker ...consists of two sub-detectors, the Tracker Turicensis and the Inner Tracker, which are built from silicon micro-strip technology. First performance results of both detectors using data from Large Hadron Collider synchronization tests are presented.
Flexible nasopharyngoscopy is the instrument of choice for evaluating velopharyngeal function. The authors propose to do this evaluation by percentage of closure for each of the phonems during the ...re-education and before a surgical treatment.
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