Connections between neutron monitor count rate and solar modulation strength

We suggest a new approach to the normalisation of neutron monitor response to galactic cosmic rays. The reference normalisation count rate is the neutron monitor response to the model unmodulated flux of galactic cosmic rays. A comparison of the actually recorded neutron monitor count rate with the calculated normalisation count rate can provide one with an observationally obtained true-of-date integral measure of the current level of solar modulation of galactic cosmic rays. The Slovak VEGA grant agency is acknowledged for the grant 2-5137.     

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.     

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.     

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。      

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.     

冷冻干燥中升华界面移动的微CT实验研究

采用微CT扫描仪的扫描成像,图像重构及灰度值分析技术对不同厚度苹果片冷冻干燥的升华过程进行实验观察,分析了界面的移动特性.结果表明,对于单面传导加热的升华干燥过程,物料升华不仅在顶面进行,与搁板接触的底面以及侧面也会有水蒸气逸出.厚物料在升华过程中有一个明显的球形冻结区,升华界面呈三维模式逐渐向物料几何中心收缩.无论物料厚薄,刚开始升华干燥速率比较快,随着干燥层的增厚,升华过程的热质阻力增大,升华速率减慢.     

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-raydiffraction single crystal structure analysis. The title complex crystallizes in monoelinic 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 therepeated eight-membered ring units (Cd-O-C-O)2. The crystal structure is stabilized by intra- and interchainhydrogen bonds interactions.     

High-performance liquid chromatographic analysis of norepinephrine and alpha-methylnorepinephrine in microdissected noradrenergic cell groups of the rabbit brain

A high-performance liquid chromatographic method with electrochemical detection has been developed to measure norepinephrine (NE) and alpha-methylnorepinephrine (alpha-MeNE) in microdissected noradrenergic cell groups of the rabbit brain stem. The method is shown to be specific, accurate and precise and has a sensitivity of 0.5 pmol per sample. The method has been applied to the measurement of NE and alpha-MeNE levels in the A1, A2, A5, A6 and A7 noradrenergic cell groups after administration of the antihypertensive drug alpha-methyldopa (alpha-MD), so that the sites of action of alpha-MD within the central nervous system may be localised.     

Molecular species in liquid carboxylic acids

Measurements of dielectric permittivity and electric conductance are presented for mixtures of carboxylic acids — formic, trifluoroacetic, acetic and propionic — and non-polar liquids. For the dielectric and associative behavior of carboxylic acids a knowledge of the cis—trans conformational equilibria of the monomeric acid molecules seems to be essential. Therefore the cis and trans conformations of these molecules have been calculated by the CNDO/2 and PCILO methods. Appreciable rotational barriers for their interconversion have been obtained.