Performance optimization of scintillator neutron detectors for EMD in CSNS

Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

The key environmental factors driving the succession of phytoplankton functional groups in Hongfeng Reservoir, southwest China

Reservoirs are an important water source in many densely populated areas in southwest China.Phytoplankton play an essential role in maintaining the structure and function of reservoir ecosystems.Understanding the succession in phytoplankton communities and the factors driving it are essential for eff ective water quality management in drinking water reservoirs.In this study,water samples were collected monthly at the surface layers from March 2016 to December 2019 in Hongfeng Reservoir,southwest China.The relationship between functional group succession was analyzed based on nonmetric multidimensional scaling analysis(NMDS),redundancy analysis(RDA),succession rate,and other analysis methods.The results showed distinct shifts in the community structure of phytoplankton functional groups within study period.The Cyclotella sp.was dominant in 2016 and 2017,and Pseudanabaena limnetica was the dominant group in 2018 and 2019.It appears that the phytoplankton composition and biomass are closely related to the water temperature and nutrient status in this reservoir.The results clearly showed that the permanganate index(COD_(Mn))was the key factor of dramatic phytoplankton functional group succession,and the change in succession rates was closely caused by total nitrogen concentration(TN).Therefore,the succession pattern and key factors of Hongfeng Reservoir revealed in this study were important guidance for the management of drinking water reservoirs in southwest China.A reasonable limit on exogenous nutrient input should be a priority,especially in high water temperature period.

Molecular Cloning,Bioinformatics Analysis and Transcriptional Expression of Virulence-related Gene(exsA)of Vibrio alginolyticus

[Objectives]The purpose was to investigate the function and mechanism of exsA gene in type III secretion system of Vibrio alginolyticus.[Methods]The full length of exsA was cloned using molecular biology techniques to analyze its biological information.Fluorescence quantitative PCR technology was used to analyze the expression of exsA after different media stress.[Results]The exsA gene contains an open reading frame(ORF)of 861 bp,encoding 286 amino acids.The physico-chemical analysis shows that the molecular structural formula is C1442H2267N393O441S12,the theoretical molecular weight is 32.549 kD,the theoretical pI value is 6.0,and the protein is non-hydrophilic and unstable.The gene does not contain a transmembrane region,and there is no obvious signal peptide.The prediction result of protein subcellular localization shows that the protein is inside the cell.The deduced amino acid sequence and constructed phylogenetic tree show that V.alginolyticus has a close relationship with Vibrio antiquarius.The qPCR results show that the expression level of exsA in different media is different,highest in TSB medium containing bile salts,followed by DMEM medium,and lowest in ordinary TSB medium.[Conclusions]The gene sequence,molecular structure and isoelectric point of exsA,as well as its expression in three different media were obtained.

Neuroprotective effect of Eleutheroside B on 1-methyl-4-phenylpyridinium ion-induced apoptosis in PC12 cells

Apoptosis and viability of PC12 cells following 1-methyl-4-phenylpyridinium ion （MPP＋）-induced injury were monitored by flow cytometry, following Annexin V-propidium iodide double labeling, and 3-（4,5-Dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide assay, respectively. The release of lactate dehydrogenase, superoxide dismutase activity and levels of malondialdehyde were determined by UV spectrophotometry. The changes in mitochondrial membrane potential and the intracellular concentration of calcium were determined by flow cytometry, and the activity of caspase-3 was monitored by western blot. According to cell viability and apoptosis studies, MPP＋-induced apoptosis in PC12 cells was inhibited in the presence of 10 tJg/mL of Eleutheroside B Our results indicate that the neuroprotective effect of Eleutheroside B, following MPP＋-induced apoptosis in PC12 cells, involves increasing the anti-oxidative stress capacity of cells, maintaining the high-energy state of mitochondrial membrane potential, reducing intracellular calcium concentration and inhibiting caspase-3 activity.

Cloning and Bioinformatics Analysis of tye A Gene of Vibrio alginolyticus

[Objectives]This study aimed to clone the tye A gene of Vibrio alginolyticus HY9901 strain and analyze its sequence by bioinformatics.[Methods] By referring to the entire genome sequence of Ⅴ.alginolyticus on Gen Bank,specific primers were designed.According to the principle of PCR amplification,the target gene tye A was amplified.By means of bioinformatics,the sequence of tye A was further analyzed,and the phylogenetic tree of tye A genes of Vibrio spp.and the corresponding subunit three-dimensional structure models were constructed.[Results] The length of the tye A gene of Ⅴ.alginolyticus strain HY9901 is 285 bp,and its theoretical molecular weight is 10.98 kD.According to prediction,there is no signal peptide or transmembrane region at the N-terminus of the sequence,and the amino acid sequence contains two casein kinase Ⅱ phosphorylation sites.The results of protein subcellular localization prediction show that the Tye A protein is located in the cell membrane.The protein is unstable and non-hydrophilic.The tertiary structure of Tye A protein of Ⅴ.alginolyticus is similar to that of Yersinia sp.According to prediction,Tye A has a major functional domain Pfam.In terms of secondary structure,alpha helix,random coil,extended strand and beta turn account for 85.11%,7.45%,4.26% and 3.19%,respectively.The homology of Tye A between Ⅴ.alginolyticus and Vibrio parahaemolyticus is up to 83%,so they are classified into one cluster.[Conclusions]This study will help to further understand the regulation mechanism of type Ⅲ secretion system in Ⅴ.alginolyticus.

Molecular Cloning and Bioinformatics Analysis of araC Gene of Vibrio alginolyticus

[Objective]To clone araC gene of Vibrio alginolyticus HY9901 strain,and analyze bioinformatics.[Methods]the whole genome sequence of Vibrio alginolyticus on GenBank was used to design specific primers.According to the principle of PCR amplification sequence,the target gene araC was amplified,and then the sequence was further analyzed by bioinformatics method to establish the phylogenetic tree of araC gene and its corresponding subunit three-dimensional structure model.[Results]Sequence analysis revealed araC gene is 711 bp and encodes a putative protein of 236 amino acids.The predicted molecular mass of AraC was 26.92 ku.Using Signal P 4.0 and TMHMM Server 2.0 software for analysis,it was predicted that the AraC protein did not contain a signal peptide or a transmembranous region.The AraC protein had two cAMP and cGMP dependent protein kinase phosphorylation site,five protein kinase C phosphorylation sites,three casein kinase II phosphorylation sites,one prenyl group binding site(CAAX box)and five microbodies C-terminal targeting signal.The predicted results of protein subcellular localization showed that AraC was located in the mitochondria,nucleus and cytoplasm.Its protein is unstable and hydrophilic.The AraC protein is a transcriptional regulatory protein which belongs to HTH_18 superfamily.According to the prediction,secondary structure:a-helix(Alpha helix)accounted for 52.12%,random coil(31.78%),extended strand(11.02%),b-fold(Beta turn)accounted for 5.08%.V.alginolyticus,Vibrio parahaemolyticus and Vibrio palustris were clustered together,which implies that the genetic relationship between these three species was the closest.

Cloning and Bioinformatics Analysis of pepck Gene in Vibrio alginolyticus

[Objectives]To clone the pepck gene of Vibrio alginolyticus strain HY9901 and analyze its sequence by bioinformatics.[Methods]According to the complete gene sequence of V.alginolyticus on GenBank,specific primers were designed to amplify the target gene pepck by PCR.The sequence of the pepck gene was analyzed using bioinformatics.The phylogenic tree of pepck gene and the corresponding single-subunit three-dimensional structure were constructed.[Results]The pepck gene of V.alginolyticus strain HY9901 has a full length of 1629 bp,with theoretical molecular weight of 60.12 kD.The prediction results show that there is no signal peptide or transmembrane region at the N-terminus of the sequence,the amino acid sequence contains 11 phosphorylation sites of casein kinase II.The prediction results of protein subcellular localization indicate that PEPEK protein is localized in the cytoplasm.The protein is stable and hydrophobic.The tertiary structure of the PEPCK protein of V.alginolyticus is similar to that of Vibrio parahaemolyticus.It is predicted that PEPCK has a major functional domain PEPCK_ATP.In the secondary structure,alpha helix,random coil,and extended strand accounted for 21.96%,52.03%and 26.01%,respectively.The PEPCK homology between V.alginolyticus and Vibrio diabolicus is as high as 99%.[Conclusions]This study lays the foundation for further understanding the function of pepck gene in V.alginolyticus.

Analysis of Biological Activity and Immunogenicity of Extracellular Products from Streptococcus iniae

[Objectives] This study aimed to analyze the biological activity and immunogenicity of extracellular products from Streptococcus iniae .[Methods] S. iniae was incubated with brain heart infusion agar medium （BHIA ＋ 4% calf serum） for 60 h. The bacterial liquid was rinsed with PBS, centrifuged, and filtered through microporous filtering film to collect extracellular products （ECPs）.[Results] Extracellular proteinase （ECPase） of S. iniae exhibited amylase, protease, lecitinase, gelatinase, lipase activities and hemolytic activity but had no urease activity. EDTA, DTT and PMSF could reduce ECPase activity to 72.4%, 77.6% and 72.4%, respectively. Cu^2＋ , Ca 2＋ , K^＋ and Mg^2＋ exhibited an inhibitory effect on ECPase activity, whereas Fe^3＋ , Co^2＋ and Mn^2＋ could activate ECPase activity. ECPs had good heat stability and exhibited relatively high activities under alkaline conditions. The optimal temperature for ECPs was 55 ℃. Two-dimensional electrophoresis was performed to analyze the main protein of ECPs. The results indicated that there are 12 main bands of ECPs, and the molecular weights mainly ranged between 28-68 kDa. About 120 protein spots were detected, and the molecular weights mainly ranged between 26-95 kDa. The mouse anti- S. iniae was used for Western-blot analysis of ECPs, and the results showed that there were four proteins, with molecular weights of 26, 37, 95, and 97 kDa, respectively. The pathogenicity assay indicated that ECPs of S. iniae were highly pathogenic to tilapia. The mortality rate of tilapia was enhanced as the concentration of ECPs increased.[Conclusions] This study provided a certain theoretical basis for revealing the pathogenic mechanism of Streptococcus iniae .

用于中子位置灵敏探测器的SiPM性能研究

为满足中国散裂中子源(China Spallation Neutron Source,CSNS)工程材料衍射谱仪的探测器需求,CSNS探测器组设计并研制了基于硅光电倍增管(Silicon Photomultiplier,SiPM)读出的闪烁体探测器。本工作针对该探测器,选取了Sensl MicroFJ-30035-TSV和Hamamatsu S13363-3050NE-16两种型号的SiPM,开展了其击穿电压、增益、温度特性、暗计数率等关键性能的测试。测试结果显示,两者单光子分辨能力,增益、暗计数率等性能均可满足当前闪烁体探测器需求,相同过偏压下,前者增益高于后者,且Hamamatsu SiPM增益对温度更敏感。测试了两SiPM的温度补偿系数分别为22.0 mV/ºC(Sensl)和53.6 mV/℃(Hamamatsu),为后续SiPM温度补偿电路设计奠定了基础。利用研制的探测器工程样机,在CSNS BL09下测试了两种SiPM读出的探测器对2.8Å中子探测效率分别为76%和68%,为目标探测器及同类型探测器的SiPM选型提供了参考。

Bionic Stepping Motors Driven by Piezoelectric Materials

By imitating the behavioral characteristics of some typical animals, researchers develop bionic stepping motors to extend the working range of piezoelectric materials and utilize their high accuracy advantage as well. A comprehensive review of the bionic stepping motors driven by piezoelectric materials is presented in this work. The main parts of stepping piezoelectric motors, including the feeding module, clamping module, and other critical components, are introduced elaborately. We classify the bionic stepping piezoelectric motors into inchworm motors, seal motors, and inertia motors depending on their main structure modules, and present the mutual transformation relationships among the three types. In terms of the relative position relationships among the main structure modules, each of the inchworm motors, seal motors, and inertia motors can further be divided into walker type, pusher type, and hybrid type. The configurations and working principles of all bionic stepping piezoelectric motors are reported, followed by a discussion of the advantages and disadvantages of the performance for each type. This work provides theoretical support and thoughtful insights for the understanding, analysis, design, and application of the bionic stepping piezoelectric motors.