Wide-aperture muon detector for diagnostics of the Earth’s atmosphere and magnetosphere

A wide-aperture large-area multilayered muon hodoscope is being constructed above the water Cherenkov calorimeter NEVOD (Moscow Engineering Physics Institute). This hodoscope is aimed at studying the processes in the Earth’s atmosphere and magnetosphere that lead to variations in the muon flux at the ground level. The structure of the detector and its data acquisition and triggering systems are described. Some preliminary results of the analysis of the data obtained using the first two supermodules of the system in the continuous series of measurements during 2005–2006 are discussed.     

充粘液管材中超声纵向轴对称导波的频散特性分析

模拟分析充粘液管内径-壁厚比和超声纵向轴对称导波波包宽度的关系。考虑了衰减的情况下,在各传播距离、频厚积和激发脉冲周数上,采用脉冲回波法,分析了导波的频散特性。结果表明:对于特定的材料,当频厚积一定时,充粘液管材中传播的导波特性只与内径-壁厚比有关;各高阶模式的截止频厚积随内径-壁厚比的增大而减小。用L(0,1)模式检测内径-壁厚比在4附近的充粘液管时灵敏度较低;而用L(0,2)模式检测内径-壁厚比在9.2附近的管时灵敏度较低。对于不同内径-壁厚比的充粘液管,检测中应当用不同的纵向轴对称导波模式,所用的激发脉冲周数和频厚积也应当不同。     

Cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of several members of the 1,ω-bis(4-cyanobiphenyl-4′-yl) alkane (CBnCB) and the 1-(4-cyanobiphenyl-4′-yloxy)-ω-(4-cyanobiphenyl-4′-yl) alkane (CBnOCB) homologous series are reported. The new odd members described CB5CB, CB13CB, CB4OCB, CB8OCB and CB10OCB all exhibit twist-bend nematic and nematic phases. The members of these series already reported in literature, CB7CB, CB9CB, CB11CB and CB6OCB, were also prepared in order to allow for a direct comparison of their transitional properties. The properties of these dimers are also compared to those of the corresponding members of the 1,ω-bis(4-cyanobiphenyl-4,-yloxy) alkanes (CBOnOCB). For any given total spacer length, for odd members of these series, the nematic–isotropic transition temperatures and associated entropy changes are greatest for the CBOnOCB dimer and lowest for the CBnCB dimer. These trends are understood in terms of molecular shape. For short spacer lengths, the twist-bend nematic–nematic transition temperature (T_NTBN) is higher for the CBnOCB series than for the CBnCB series but this is reversed as the spacer length increases. Of the CBOnOCB dimers, a virtual value of T_NTBN was estimated for CBO3OCB and T_NTBN was measured for CBO5OCB. These values are considerably lower than those observed for the corresponding members of the CBnCB or CBnOCB series. The dependence of T_NTBN on molecular structure is discussed not only in terms of the molecular curvature but also in the ability of the molecules to pack efficiently. As the temperature range of the preceding nematic phase increases, so the twist-bend nematic–nematic transition entropy change decreases and the transition approaches second order for the longer spacers. For comparative purposes, the transitional behaviour of the even-membered dimers CB6CB, CB5OCB and CBO4OCB is reported and differences accounted for in terms of molecular shape.     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

HYDRA hydroacoustic antenna in the NEVOD experimental complex

The main characteristics of the HYDRA hydroacoustic antenna intended for the detection of signals generated by cores of extensive air showers in a water Cherenkov detector involved in the NEVOD experimental complex are considered. Primary attention is focused on the calibration of antenna sensors and on the selection of an optimum trigger that ensures an effective detection of acoustic signals generated by cores of extensive air showers in the water volume of the Cherenkov detector.     

Investigation of cosmic rays above the knee by means of muon bundles detected in a wide range of zenith angles

The results of investigation of muon bundles at the Earth’s surface in a wide range of zenith angles on the basis of the new phenomenological characteristic of extensive air showers—spectra of local muon density—have been investigated. Features of the local-density spectra are considered within a simple analytical model. The expected distributions of muon density in a wide range of zenith angles and primary energies, calculated on the basis of the CORSIKA code, are compared with the experimental data.     

Solvothermal Synthesis and Characterization of Sheet Structure Containing Adamantane [Hg2Sn2S10]8– Anions

Sheet Rb2HgSnS4 was synthesized solvothermally and characterized by X-ray single crystal diffraction. The compound is comprised of sheets with admantane-like [Hg2Sn2S10]8– units. The crystals belong to the space group C2/c, with the unit cell parameters a=1.1063(2) nm, b=1.1071(2) nm, c=1.5741(3) nm, a=90°, β=100.13(3)°, γ=90°. A reflectance spectroscopy study reveals the nature of the semiconductor with an energy of 2.1 eV for the compound.     

骨小梁材料特性对超声背散射信号的影响

基于时域有限差分法(FDTD)建立了松质骨的超声背散射仿真系统,研究了骨小梁材料特性对超声背散射信号的影响。首次得到松质骨中的超声背散射系数(BSC)和积分背散射系数(IBC)随骨小梁材料参数(密度、拉梅常数、黏度系数及声阻抗系数)的变化关系。研究结果表明,IBC随骨小梁密度的增加而增加;BSC和IBC随拉梅常数的增加而增加、随第一黏度系数的增加而近似线性地减小,第二黏度的变化对背散射信号的影响很小;背散射参数随阻抗系数的增加而减小。说明松质骨中的超声背散射特性不仅受骨矿密度(BMD)和骨微结构的影响,还与骨小梁的材料参数密切相关。研究结果有利于理解松质骨中超声的背散射特性,对松质骨骨质状况的评价有一定帮助。      

一维链状配位聚合物[Cd{5-(NO2)sal}2(2,2′-bipy)]n的合成与晶体结构

A coordination polymer of [Cd{5-(NO₂)sal}₂(2,2′-bipy)]_n(5-(NO₂)sal=5-nitrosalicylate, 2,2′-bipy=2,2′-bipyridine) was synthesized by hydrothermal reaction and characterized by elemental analysis, IR and X-ray diffraction single crystal structure analysis. The title complex crystallizes in monoclinic with space group C2/c, a=2.730 8(16) nm, b=1.272 3(5) nm, c=0.674 5(3) nm, β=96.73(2)°, V=2.327(2) nm³, Z=4, R=0.022 2, wR=0.057. The 5-nitrosalicylate anions doubly bridge the Cd(Ⅱ) atoms to form one-dimensional polymeric chain with the repeated eight-membered ring units (Cd-O-C-O)₂. The crystal structure is stabilized by intra- and interchain hydrogen bonds interactions. CCDC: 694568.     

基于催化应用调控氧化铈纳米材料的形貌

催化剂的设计、合成和结构调控是获得优异性能的关键.传统的策略主要是尽量减小催化剂颗粒尺寸以增加活性中心的数目,即尺寸效应.近年来,材料科学的快速发展使得在纳米尺度上调变催化剂的尺寸和形貌成为可能,特别是通过形貌调控可暴露更多的高活性晶面,大幅度提高催化性能,即纳米催化中的形貌效应.因此,调节催化剂的尺寸与形貌可以单独或协同优化材料的性能.氧化铈作为催化剂的重要组分与结构、电子促进剂被广泛应用于多相催化剂体系.本文总结了近期氧化铈材料形貌可控合成的进展,包括主要的合成策略和表征方法; 进而分析了氧化铈和金-氧化铈催化材料的形貌效应,指出金-氧化铈之间独特的相互作用与载体形貌密切相关; 阐述了氧化铈纳米材料因暴露晶面的差异而获得不同催化性能的化学机制.