Synthesis,characterization and fungicidal activity of zinc diethyldithiocarbamate and phosphate

Monolayers of amphiphilic di-block copolymer, PEO₄₀-b-PMA(Az)₁₉ on water surface and solid surfaces, such as silicon wafer and quartz glass, were analyzed by surface pressure — molecular area (π-A) isotherm, UV-Vis spectroscopy, atomic force microscopy (AFM) and total X-ray reflectivity (TXR). The monolayer prepared at 22 mN m-1 consisted of H aggregated azobezene (Az) moieties, which orientated perpendicular to the solid surface. The monolayer structure, including H aggregated Az and orientation of Az, was stable after annealing at 98°C, at which temperature the hydrophilic PEO domain was the liquid phase and the hydrophobic PMA(Az) was in the smectic A phase.     

测量大口径光学元件反射率用精密扫描系统误差分析

为测量高能激光传输系统中大口径高反射率光学元件的反射率,设计了一种大口径光学元件二维扫描的精密测量系统。介绍了该系统的结构及其工作原理,分析了影响系统测量精度的因素,从理论上分析了扫描系统的系统误差对测量精度的影响,结果表明在垂直于光束传播方向上,水平偏差在0.29 mm时,测量误差在10-6量级;腔长的变化量较小时,可通过对衰荡腔腔镜的调节,实现对旋转轴偏差的补偿及对系统的精细调节。通过拟合处理光强与时间的数据得到对应的一次指数函数拟合曲线,并通过计算得到衰荡时间和反射率,经过对比分析可知,该误差分析方法能比较有效地测量腔镜的反射率,并能减小实验数据本身带来的误差。     

Transitions between P21, , and P6322 modifications of SrAl2O4 by in situ high-temperature X-ray and neutron diffraction

The results of in situ high-temperature X-ray and neutron powder diffraction experiments reconcile inconsistencies in previous reports on the symmetry of high-temperature phases of SrAl₂O₄. The material undergoes two reversible phase transitions and at 680 and 860 °C, respectively, and the latter one is experimentally observed and characterized for the first time. The higher symmetry above the transition is gained by disordering off-center split site of oxygen atoms around trigonal axis rather than by unbending Al–O–Al angle to the ideal value 180°. The analysis of the literature suggests that it is a common feature of the P6₃22 phases of stuffed tridymites.     

Crystal structure and magnetic properties of complex oxides Mg4−xNixNb2O9, 0?x?4

In the Mg_4−xNi_xNb₂O₉ (0?x?4) system two ranges of solid solution have been found. One of the solid solutions has a corundum-related structure type (space group ); the second one adopts the II-Ni₄Nb₂O₉ structure type (space group Pbcn). The unit cell constants and atomic positions have been determined and refined using neutron powder diffraction data. Electron diffraction and high-resolution transmission electron microscopy (HRTEM) from MgNi₃Nb₂O₉ crystals identify the presence of planar defects and the intergrowth of several (structurally related) phases. The magnetic susceptibility of Mg₃NiNb₂O₉, measured in the temperature range T=2-300 K, shows no indications of magnetic ordering at low temperatures, while for MgNi₃Nb₂O₉ there is a magnetic ordering at temperatures below 45.5 K.     

Structural observations on La2(Ni,Co)O4±δ phases determined from in situ neutron powder diffraction

In situ neutron powder diffraction data have been analysed for a number of compositions in the solid solution series La₂Ni_1−xCo_xO_4±δ over the temperature range 150-650 °C. High-quality Rietveld refinements indicate no major structural transitions have occurred in any of the compositions, although close examination of the Ni/CoO bond distances highlight changes in the coordination environment with increasing temperature. Further, the changes in the coordination can be correlated to changes in both the oxide ion and electronic conductivity indicating a direct link between transport properties, bonding and transition metal valence state in these Co containing layered perovskites.     

Rheometry of an androstanol steroid derivative paramagnetic organogel. Methodology for a comparison with a fatty acid organogel

This paper compares and contrasts the behavior of two different gelators using rheological and neutron scattering methods. The flow properties of a steroid-made paramagnetic organogel in cyclohexane are presented. The original gelator STNO is important in the class of organogels as being one of the most documented and as such is a good candidate for comparisons with another reference system, the 12-hydroxy stearic acid (HSA) gel. The linear viscoelastic regime of deformations of STNO gels is identified and analyzed in the context of self-assembled fibrillar networks. The linear elasticity scales with the concentration as G′ α C² similarly with HSA organogels, and both systems can be considered as cellular materials. Rheological and neutron scattering experiments show that the kinetics of gel formation exhibits long equilibration times corresponding to the elaboration of entangled fibrillar aggregates. Comparison of the linear elasticities between STNO and HSA gels demonstrates that HSA gels are much more stiffer (G′_HSA/G′_STNO∼2700). Contributions from the cross-sectional sizes, the mesh size of the networks, the solubility concentrations, and the Young's modulus of the materials are discussed. Non-linear flow properties are also compared using thixotropic loops. They indicate that the transduction of the chirality from the molecular to the supramolecular stages is more efficient with STNO gels having strong chiral junction zones. Simplified scattering and optical protocols are proposed to facilitate comparisons between different organogels.     

Colloid Stabilization by an Oppositely Charged Polysaccharide: Mechanism of Interaction and Interface Studied with Synchrotron X-Rays

The liposome surface is modeled by a 2-D lipid monolayer made of behenic acid forming a negatively charged interface. The properties at the air/liquid interface were examined by pressure-area isotherms in a Langmuir trough introducing diluted chitosan solution in the subphase. X-ray reflectivity of the interface was measured in the same conditions in order to determine the layer thickness of the chitosan adsorbed on the behenic acid monolayer formed on water. Influence of pH of the subphase and molecular weight of adsorbed chitosan was investigated. All these results allow confirming that the charge and the stability of the lipid layer are controlled by the nature of the polyelectrolyte and the nature of the medium. In particular, the use of biocompatible charged polysaccharides is of interest for biomedical applications.     

采用中子衍射实验解析PbS的原子间力常数

使用日本原子能研究开发机构里设置的高分解能粉末中子衍射装置,在15 K和294 K温度下对Pb S进行了中子衍射实验.在15 K和294 K温度里观察到了明显的振动形状的热漫散射.所观察到的漫散射强度可由原子间热振动相关效应的影响来解释.在294 K下从原子间相关效应和德拜-劳厄因子的温度参数中获得了Pb S相邻原子间的力常数.     

Spin fluctuation spectrum of electron-doped high-Tc superconductors

The magnetic excitation spectrum of electron-doped copper oxide superconductors is calculated using the Hubbard model on a square lattice. First, the on-site repulsion is treated with the random phase approximation. The spectrum of electron-doped systems in the superconducting state is compared with that of hole-doped systems, and the relationship between the frequency at which a peak grows in the spectrum and the superconducting energy gap at a hot spot (an intersection of the Fermi surface and the magnetic Brillouin zone boundary) is investigated. As compared with the hole-doped systems, the resonance condition is difficult to be satisfied in the electron-doped systems because of the small density of states around the hot spot. Moreover, the correlation effect in the Hubbard model is treated by the fluctuation-exchange approximation (FLEX), and the spin fluctuation spectra in the superconducting state in a wide region of the wave vector and frequency are calculated. We have found that the intensity of the magnetic spectrum at incommensurate wave vectors obtained with the FLEX is considerably weaker than that obtained with the RPA. The validity of the Fermi-liquid approach is also discussed.     

Corelli: Efficient single crystal diffraction with elastic discrimination

Single crystal diffuse scattering provides one of the most powerful probes of short-range correlations on the 1–100 nm scale, which often are responsible for the extreme field response of many emerging phenomena of great interest. Accurate modeling of such complex disorder from diffuse scattering data however puts stringent experimental demands, requiring measurements over large volumes of reciprocal space with sufficient momentum and energy resolution. Here, we discuss the potential of the cross-correlation technique for efficient measurement of single crystal diffuse scattering with energy discrimination, as will be implemented in a novel instrument, Corelli. Utilizing full experiment simulations, we show that this technique readily leads up to a fifty-fold gain in efficiency, as compared to traditional methods, for measuring single crystal diffuse scattering over volumes of reciprocal space with elastic discrimination.