212 research outputs found
PMT Test Facility at MPIK Heidelberg and Double Chooz Super Vertical Slice
Proceedings supplement for conference poster at Neutrino 2010, Athens,
Greece
Transit Time and Charge Correlations of Single Photoelectron Events in R7081 PMTs
During the calibration phase of the photomultiplier tubes (PMT) for the
Double Chooz experiment the PMT response to light with single photoelectron
(SPE) intensity was analysed. With our setup we were able to measure the
combined transit time and charge response of the PMT and therefore we could
deconstruct and analyse all physical effects having an influence on the PMT
signal. Based on this analysis charge and time correlated probability density
functions were developed to include the PMT response in a Monte Carlo
simulation.Comment: minor changes by referee reques
Transit Time and Charge Correlations of Single Photoelectron Events in R7081 PMTs
During the calibration phase of the photomultiplier tubes (PMT) for the
Double Chooz experiment the PMT response to light with single photoelectron
(SPE) intensity was analysed. With our setup we were able to measure the
combined transit time and charge response of the PMT and therefore we could
deconstruct and analyse all physical effects having an influence on the PMT
signal. Based on this analysis charge and time correlated probability density
functions were developed to include the PMT response in a Monte Carlo
simulation.Comment: minor changes by referee reques
Qualification Tests of 474 Photomultiplier Tubes for the Inner Detector of the Double Chooz Experiment
The hemispherical 10" photomultiplier tube (PMT) R7081 from Hamamatsu
Photonics K.K. (HPK) is used in various experiments in particle and
astroparticle physics. We describe the test and calibration of 474 PMTs for the
reactor antineutrino experiment Double Chooz. The unique test setup at
Max-Planck-Institut f\"ur Kernphysik Heidelberg (MPIK) allows one to calibrate
30 PMTs simultaneously and to characterize the single photo electron response,
transit time spread, linear behaviour and saturation effects, photon detection
efficiency and high voltage calibration
Qualification Tests of 474 Photomultiplier Tubes for the Inner Detector of the Double Chooz Experiment
The hemispherical 10" photomultiplier tube (PMT) R7081 from Hamamatsu
Photonics K.K. (HPK) is used in various experiments in particle and
astroparticle physics. We describe the test and calibration of 474 PMTs for the
reactor antineutrino experiment Double Chooz. The unique test setup at
Max-Planck-Institut f\"ur Kernphysik Heidelberg (MPIK) allows one to calibrate
30 PMTs simultaneously and to characterize the single photo electron response,
transit time spread, linear behaviour and saturation effects, photon detection
efficiency and high voltage calibration
Qualification Tests of 474 Photomultiplier Tubes for the Inner Detector of the Double Chooz Experiment
The hemispherical 10" photomultiplier tube (PMT) R7081 from Hamamatsu
Photonics K.K. (HPK) is used in various experiments in particle and
astroparticle physics. We describe the test and calibration of 474 PMTs for the
reactor antineutrino experiment Double Chooz. The unique test setup at
Max-Planck-Institut f\"ur Kernphysik Heidelberg (MPIK) allows one to calibrate
30 PMTs simultaneously and to characterize the single photo electron response,
transit time spread, linear behaviour and saturation effects, photon detection
efficiency and high voltage calibration
Modulation of Mutant Huntingtin N-Terminal Cleavage and Its Effect on Aggregation and Cell Death
Huntington’s disease (HD) is a neurodegenerative disorder caused by a polyglutamine expansion near the N-terminus of huntingtin. A neuropathological hallmark of Huntington’s disease is the presence of intracellular aggregates composed of mutant huntingtin N-terminal fragments in human postmortem brain, animal models, and cell culture models. It has been found that N-terminal fragments of the mutant huntingtin protein are more toxic than the full-length protein. Therefore, proteolytic processing of mutant huntingtin may play a key event in the pathogenesis of HD. Here, we present evidence that the region in huntingtin covering amino acids 116 to 125 is critical for N-terminal proteolytic processing. Within this region, we have identified mutations that either strongly reduce or enhance N-terminal cleavage. We took advantage of this effect and demonstrate that the mutation Δ121–122 within the putative cleavage region enhances N-terminal cleavage of huntingtin and the aggregation of N-terminal fragments. Furthermore, this particular deletion increased the activation of apoptotic processes and decreased neuronal cell viability. Our data indicate that the N-terminal proteolytic processing of mutant huntingtin can be modulated with an effect on aggregation and cell death rate
Qualification Tests of the R11410-21 Photomultiplier Tubes for the XENON1T Detector
The Hamamatsu R11410-21 photomultiplier tube is the photodetector of choice
for the XENON1T dual-phase time projection chamber. The device has been
optimized for a very low intrinsic radioactivity, a high quantum efficiency and
a high sensitivity to single photon detection. A total of 248 tubes are
currently operated in XENON1T, selected out of 321 tested units. In this
article the procedures implemented to evaluate the large number of tubes prior
to their installation in XENON1T are described. The parameter distributions for
all tested tubes are shown, with an emphasis on those selected for XENON1T, of
which the impact on the detector performance is discussed. All photomultipliers
have been tested in a nitrogen atmosphere at cryogenic temperatures, with a
subset of the tubes being tested in gaseous and liquid xenon, simulating their
operating conditions in the dark matter detector. The performance and
evaluation of the tubes in the different environments is reported and the
criteria for rejection of PMTs are outlined and quantified.Comment: 24 pages, 16 figure
Reanalysis of the GALLEX solar neutrino flux and source experiments
After the completion of the gallium solar neutrino experiments at the
Laboratori Nazionali del Gran Sasso (GALLEX}: 1991-1997; GNO: 1998-2003) we
have retrospectively updated the GALLEX results with the help of new technical
data that were impossible to acquire for principle reasons before the
completion of the low rate measurement phase (that is, before the end of the
GNO solar runs). Subsequent high rate experiments have allowed the calibration
of absolute internal counter efficiencies and of an advanced pulse shape
analysis for counter background discrimination. The updated overall result for
GALLEX (only) is (73.4 +7.1 -7.3) SNU. This is 5.3% below the old value of
(77.5 + 7.5 -7.8) SNU (PLB 447 (1999) 127-133) with a substantially reduced
error. A similar reduction is obtained from the reanalysis of the 51Cr neutrino
source experiments of 1994/1995.Comment: Accepted by Physics Letters B January 13, 201
Fusion of green fluorescent protein to the C-terminus of granulysin alters its intracellular localization in comparison to the native molecule
The engineering of green fluorescent protein (GFP) fusion constructs in order to visibly tag a protein of interest has become a commonly used cell biology technique. Although caveats to this approach are obvious, literature reports in which the chimeric molecule behaves differently than the native molecule are scant. This brief report describes one such case. Granulysin, a small lytic and antimicrobial protein produced by cytotoxic lymphocytes, traffics to the regulated secretory system and is subsequently released from cells upon proper stimulus. In an attempt to elucidate mechanisms by which it accumulates in and is released from cytolytic granules, GFP was fused to the C-terminus of granulysin and expressed in an NK cell line. A control construct expressing the native protein was similarly expressed. The data demonstrate that, while the fusion protein is expressed and secreted, its subcellular localization is altered in comparison to native granulysin. Thus, the addition of GFP to the C-terminus of granulysin obscures the signal(s) that cytotoxic lymphocytes use to sort it to the regulated secretory pathway despite its normal biosynthesis and secretion. This example is offered as a cautionary account for other researchers who contemplate using this technology
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