分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: The KM2A(one kilometer square extensive air shower array) is the largest detector array in the LHAA- SO(Large High Altitude Air Shower Observatory) project. The KM2A consists of 5635 EDs(Electromagnetic particle Detectors) and 1221 MDs(Muon Detectors). The EDs are distributed and exposed in the wild. Two channels, Anode and Dynode, are employed for the PMT(photomultiplier tube) signal readout. The readout electronics proposed in this paper aims at the accurate charge and arrival time measurement of the PMT signals, which cover a large amplitude range from 20P.E(photoelectrons) to 2?x10^5P.E. By using the Trigger-less architecture, we digitize signals close to the PMTs. All digitized data is transmitted to DAQ(Data Acquisition) via the simplified WR(White Rabbit) protocol. Compared with traditional high energy experiments, high-precision of time measurement in such a large area and suppression of temperature effects in the wild become the key techniques. Experiments show that the design has fulfilled the requirements in this project.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-15
摘要: Multicellular organisms have multiple homologs of the yeast ATG8 gene, but the differential roles of these homologs in autophagy during development remain largely unknown. Here we investigated structure/function relationships in the two C. elegans Atg8 homologs, LGG-1 and LGG-2. lgg-1 is essential for degradation of protein aggregates, while lgg-2 has cargo-specific and developmental-stage-specific roles in aggregate degradation. Crystallography revealed that the N-terminal tails of LGG-1 and LGG-2 adopt the closed and open form, respectively. LGG-1 and LGG-2 interact differentially with autophagy substrates and Atg proteins, many of which carry a LIR motif. LGG-1 and LGG-2 have structurally distinct substrate binding pockets that prefer different residues in the interacting LIR motif, thus influencing binding specificity. Lipidated LGG-1 and LGG-2 possess distinct membrane tethering and fusion activities, which may result from the N-terminal differences. Our study reveals the differential function of two ATG8 homologs in autophagy during C. elegans development.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: The neutrino detector of the Jiangmen Underground Neutrino Observatory (JUNO) is designed to use 20 kilotons of liquid scintillator and approximately 16,000 20-inch photomultipliers (PMTs).One of the options is to use the 20-inch R12860 PMT with high quantum efficiency which has recently been developed by Hamamatsu Photonics. The performance of the newly developed PMT preproduction samples is evaluated. The results show that its quantum efficiency is�0%燼t�00nm. Its Peak/Valley (P/V) ratio for the single photoelectron is 4.75 and the dark count rate is�7kHz燼t the threshold of 3 mV while the gain is at��07. The transit time spread of a single photoelectron is2.86ns. Generally the performances of this new 20-inch PMT are improved over the old one of R3600.