分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间: 2024-01-17
摘要: A 20-kiloton liquid scintillator detector is designed in the Jiangmen Underground Neutrino Observatory (JUNO) for multiple physics purposes, including the determination of the neutrino mass ordering through reactor neutrinos, as well as measuring supernova neutrinos, solar neutrinos, and atmosphere neutrinos to explore different physics topics. Efficient reconstruction algorithms are needed to achieve these physics goals in a wide energy range from MeV to GeV. In this paper, we present a novel method for reconstructing the energy of events using hit information from 3-inch photomultiplier tubes (PMTs) and the OCCUPANCY method. Our algorithm exhibits good performance in accurate energy reconstruction, validated with electron Monte Carlo samples spanning kinetic energies from 10~MeV to 1~GeV.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: In the past few years, Chinese astronomical community is actively testing astronomical sites for several new optical/infrared ground-based telescopes. These site testing campaigns conducted were mainly focused on fundamental performances of the site, such as cloud coverage, seeing, temperature, etc. With increasing interests in sodium laser guide star adaptive optics for these new telescopes in the Chinese astronomical community, it is interesting to investigate the performance of the laser guide star at these sites, especially considering that the sodium laser guide star's on-sky performance is significantly influenced by sites' local performances, such as geomagnetic field, sodium layer dynamics, density of air molecule, etc. In this paper, we studied sodium laser guide star's performance of a 20W class Quasi-CW pulsed laser developed by TIPC with numerical simulation for five selected sites in China.
分类: 天文学 >> 天文学 提交时间: 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Dwarf irregular galaxies (dIrrs), as rotationally supported systems, have more reliable J-factor measurements than dwarf spheroidal galaxies and have received attention as targets for dark matter detection in recent years. In this paper, we use 10 yr of IceCube muon-track data and an unbinned maximum-likelihood-ratio method to search for neutrino signals beyond the background from the directions of seven dIrrs, aiming to detect neutrinos produced by heavy annihilation dark matter. We do not detect any significant signal. Based on such null results, we calculate the upper limits on the velocity-averaged annihilation cross section for 1 TeV–10 PeV dark matter. Our limits, although weaker than the strictest constraints in the literature in this mass range, are also a good complement to the existing results considering the more reliable J-factor measurements of dIrrs.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The application of sodium laser guide star is the key difference between modern adaptive optics system and traditional adaptive optics system. Especially in system like multi-conjugate adaptive optics, sodium laser guide star asterism which is formed by several laser guide stars in certain pattern is required to probe more atmospheric turbulence in different directions. To achieve this, a sodium laser guide star asterism launching platform is required. In this paper, we will introduce the sodium laser guide star asterism launching platform built and tested on the 1.8m telescope of the Gaomeigu Observatory. The platform has two functions: one is to compare the performance of sodium laser guide stars generated by different lasers at the same place; the other is to generate sodium laser guide star asterism with adjustable shape. The field test results at the beginning of 2021 verify the important role of the platform, which is also the first time to realize sodium laser guide star asterism in China.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-12
摘要: The participation of large-conductance Ca2+ activated K+ channels (BKs) in chloroquine (chloro)-induced relaxation of precontracted airway smooth muscle (ASM) is currently undefined. In this study we found that iberiotoxin (IbTx, a selective inhibitor of BKs) and chloro both completely blocked spontaneous transient outward currents (STOCs) in single mouse tracheal smooth muscle cells, which suggests that chloro might block BKs. We further found that chloro inhibited Ca2+ sparks and caffeine-induced global Ca2+ increases. Moreover, chloro can directly block single BK currents completely from the intracellular side and partially from the extracellular side. All these data indicate that the chloro-induced inhibition of STOCs is due to the blockade of chloro on both BKs and ryanodine receptors (RyRs). We also found that low concentrations of chloro resulted in additional contractions in tracheal rings that were precontracted by acetylcholine (ACH). Increases in chloro concentration reversed the contractile actions to relaxations. In the presence of IbTx or paxilline (pax), BK blockers, chloro-induced contractions were inhibited, although the high concentrations of chloro-induced relaxations were not affected. Taken together, our results indicate that chloro blocks BKs and RyRs, resulting in abolishment of STOCs and occurrence of contraction, the latter will counteract the relaxations induced by high concentrations of chloro.
分类: 物理学 >> 核物理学 提交时间: 2016-08-31
摘要: The quality of PMT signal is one of the key items for a large and high precision neutrino experiment, like Daya Bay, JUNO, while most of the experiments are affected by the PMT signal overshoot from its positive HV-single cable scheme. For JUNO prototype detector, we have a detailed study on the PMT overshoot and successfully reduced the ratio of overshoot amplitude to signal to ~1% from previous typical ~10%, with no affection to PMT other parameters. Furthermore, we calculated that the overshoot is a result of discharging of capacitors in the HV-signal splitter and the PMT voltage divider. The study result is extremely important for JUNO and other similar experiments.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The application of sodium laser guide star is the key difference between modern adaptive optics system and traditional adaptive optics system. Especially in system like multi-conjugate adaptive optics, sodium laser guide star asterism which is formed by several laser guide stars in certain pattern is required to probe more atmospheric turbulence in different directions. To achieve this, a sodium laser guide star asterism launching platform is required. In this paper, we will introduce the sodium laser guide star asterism launching platform built and tested on the 1.8m telescope of the Gaomeigu Observatory. The platform has two functions: one is to compare the performance of sodium laser guide stars generated by different lasers at the same place; the other is to generate sodium laser guide star asterism with adjustable shape. The field test results at the beginning of 2021 verify the important role of the platform, which is also the first time to realize sodium laser guide star asterism in China.