The barrel DIRC detector for the P¯ ANDA experiment at FAIR Schwiening, J.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Volume:
639, Issue:
1
Journal Article
Peer reviewed
The
P
¯
ANDA
experiment at FAIR will perform high precision experiments in the charmed quark sector using cooled antiproton beams of unprecedented intensities of
L=2×10
32
cm
−2
s
−1 in the momentum ...range of 1–15
GeV/
c. The charged particle identification in the barrel region needs a thin detector operating in a strong magnetic field. A ring imaging Cherenkov detector using the DIRC principle is an excellent match to those requirements. This article describes aspects of the design and R&D for the
P
¯
ANDA
barrel DIRC detector. The availability of highly pixelated fast photon detectors allows several key improvements compared to the successful BaBar-DIRC detector, some of which were tested in a proton beam at GSI. The optical properties of the radiator bars, made from synthetic fused silica, are critical to the success of the DIRC. Measurements of the attenuation length and reflection coefficient allow the determination of the surface roughness of prototype radiator bars.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Tools that allow acute and selective silencing of synaptic transmission in vivo would be invaluable for understanding the synaptic basis of specific behaviors. Here, we show that presynaptic ...expression of the proton pump archaerhodopsin enables robust, selective, and reversible optogenetic synaptic silencing with rapid onset and offset. Two-photon fluorescence imaging revealed that this effect is accompanied by a transient increase in pH restricted to archaerhodopsin-expressing boutons. Crucially, clamping intracellular pH abolished synaptic silencing without affecting the archaerhodopsin-mediated hyperpolarizing current, indicating that changes in pH mediate the synaptic silencing effect. To verify the utility of this technique, we used trial-limited, archaerhodopsin-mediated silencing to uncover a requirement for CA3-CA1 synapses whose afferents originate from the left CA3, but not those from the right CA3, for performance on a long-term memory task. These results highlight optogenetic, pH-mediated silencing of synaptic transmission as a spatiotemporally selective approach to dissecting synaptic function in behaving animals.
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•Archaerhodopsin selectively and reversibly silences synaptic transmission•Archaerhodopsin silences synaptic transmission without blocking action potentials•Archaerhodopsin mediates synaptic silencing through changes in pH•Synaptic silencing reveals distinctions among CA3-CA1 synapses during learning
El-Gaby et al. demonstrate that archaerhodopsin can acutely and selectively silence synaptic transmission through changes in pH rather than hyperpolarization. Application of this tool in behaving animals reveals a necessity for synapses from the left CA3 onto CA1 neurons, but not from the right CA3, in long-term memory performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aims/hypothesis
We set out to test the hypothesis that insulin secretion from beta cells is targeted towards the vasculature.
Methods
The spatial location of granule fusion was identified by ...live-cell two-photon imaging of mouse pancreatic beta cells within intact islets, using sulforhodamine B labelling. Three-dimensional (3D) immunofluorescence of pancreatic slices was used to identify the location of proteins associated with neuronal synapses.
Results
We demonstrated an asymmetric, non-random, distribution of sites of insulin granule fusion in response to glucose and focal targeting of insulin granule secretion to the beta cell membrane facing the vasculature. 3D immunofluorescence of islets showed that structural proteins, such as liprin, piccolo and Rab2-interacting molecule, normally associated with neuronal presynaptic targeting, were present in beta cells and enriched at the vascular face. In contrast, we found that syntaxin 1A and synaptosomal-associated protein 25 kDa (SNAP25) were relatively evenly distributed across the beta cells.
Conclusions/interpretation
Our results show that beta cells in situ, within intact islets, are polarised and target insulin secretion. This evidence for an ‘endocrine synapse’ has wide implications for our understanding of stimulus–secretion coupling in healthy islets and in disease.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Phototransduction in microvillar photoreceptors is mediated via G protein-coupled phospholipase C (PLC), but how PLC activation leads to the opening of the light-sensitive TRPC channels (TRP and ...TRPL) remains unresolved. In
Drosophila, InsP
3 appears not to be involved, and recent studies have implicated lipid products of PLC activity, e.g., diacylglycerol, its metabolites, or the reduction in PIP
2. The fact that hydrolysis of the phosphodiester bond in PIP
2 by PLC also releases a proton is seldom recognized and has neither been measured in vivo nor implicated previously in a signaling context.
Following depletion of PIP
2 and other phosphoinositides by a variety of experimental manipulations, the light-sensitive channels in
Drosophila photoreceptors become remarkably sensitive to rapid and reversible activation by the lipophilic protonophore 2-4 dinitrophenol in a pH-dependent manner. We further show that light induces a rapid (<10 ms) acidification originating in the microvilli, which is eliminated in mutants of PLC, and that heterologously expressed TRPL channels are activated by acidification of the cytosolic surface of inside-out patches.
Our results indicate that a combination of phosphoinositide depletion and acidification of the membrane/boundary layer is sufficient to activate the light-sensitive channels. Together with the demonstration of light-induced, PLC-dependent acidification, this suggests that excitation in
Drosophila photoreceptors may be mediated by PLC's dual action of phosphoinositide depletion and proton release.
► Light induces rapid phospholipase C-mediated acidification in
Drosophila photoreceptors ► The light-sensitive channels (TRP/TRPL) can be rapidly activated by protonophores ► But only after PIP
2 and other phosphoinositides (PI) have been depleted by PLC ► Combinatorial activation of TRP channels by PI depletion and proton release
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Significantly improved lifetime of micro-channel plate PMTs Lehmann, A.; Britting, A.; Eyrich, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Volume:
718
Journal Article
Peer reviewed
Open access
The lifetime of the most recent generation micro-channel plate (MCP) PMTs of BINP, Hamamatsu (R10754X) and PHOTONIS (XP85112) is being studied in a simultaneous measurement. We find that the new ...techniques applied to reduce the aging of the photocathode of the MCP-PMTs has significantly increased the lifetime. Dark count rate, gain and quantum efficiency of the tubes are given as a function of the integrated anode charge. Several times the quantum efficiency was also measured across the surface of the photocathode. At this point of the ongoing measurements the best MCP-PMT turns out to be the XP85112 with its MCP surfaces coated by an atomic layer to reduce the outgassing of the lead glass. This tube shows no aging after an integrated anode charge of 2.1C/cm2 which is more than an order of magnitude better than that of previous generation MCP-PMTs.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The GlueX experiment at Jefferson Laboratory aims to perform quantitative tests of non-perturbative QCD by studying the spectrum of light-quark mesons and baryons. A Detector of Internally Reflected ...Cherenkov light (DIRC) was installed to enhance the particle identification (PID) capability of the GlueX experiment by providing clean
π
/K separation up to 3.7 GeV/
c
momentum in the forward region (
θ
< 11°), which will allow the study of hybrid mesons decaying into kaon final states with significantly higher efficiency and purity. The new PID system is constructed with radiators from the decommissioned BaBar DIRC counter, combined with new compact photon cameras based on the SuperB FDIRC concept. The full system was successfully installed and commissioned with beam during 2019/2020. The initial PID performance of the system was evaluated and compared to one from Geant4 simulation.
This paper discusses the most recent advances with 2-inch MCP-PMTs. The status in terms of lifetime, detection efficiency, rate capability, time resolution, and gain behavior in magnetic fields are ...summarized. Significant progress in collection (CE) and quantum efficiency (QE) led to an excellent detection efficiency DQE = QE*CE of ∼30%. With a new DAQ setup up to several hundred anode pixels can be read out simultaneously in 3D allowing a glance “inside the PMT”. Parameters like dark count rates and ion afterpulsing are measurable as a function of the incident photon position as well as the temporal and spacial spread of recoil electrons and electronic and charge-sharing crosstalk even inside a magnetic field.
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