Steric structure and thermodynamic aspects of the complexes of dysprosium(iii) with aminobenzoic acids in aqueous solutions

Steric structures of dysprosium(III) aminobenzoate complexes with the 11 and 12 molar ratio in aqueous solutions were determined on the basis of pH-metric and paramagnetic birefringence data. An increase in conjugation observed for the series of the acids,viz., benzoic,meta-, ortho-, andpara-aminobenzoic acids, results in the increased stability of the complexes with the 11 and 12 composition. In the case ofpara-aminobenzoic acid, the polyhedra [DyL(H₂O)₆]²⁺ and [DyL₂(H₂O)₄]⁺ are cubes with the ligands coordinated to one and two edges, respectively. In the case ofmeta-aminobenzoic acid, the polyhedra [DyL(H₂O)₆]²⁺ and [DyL₂(H₂O)₄]⁺ are a dodecahedron with the ligand coordinated to one edge and a square anti-prism with the ligands coordinated to two edges, respectively. In the case ofortho-aminobenzoic acid, both the 11 and 12 complexes have structures that are intermediate between the structures ofmeta- andpara-aminobenzoic acids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1767–1770, October, 1994.     

Experimental study of the induced flow birefringence of a suspension of rigid particles at the transition from Couette flow to Taylor vortex flow

The flow birefringence induced in solutions of rigid particles is studied experimentally in the region of the axisymmetrical Taylor vortex flow which arises once the velocity gradient G in the annular gap of a conventional Couette cell reaches a critical value G _c .The measurements are performed for several values of G > G _c and for 10 radial observation points in the annular gap. Solutions of two types of rigid particles are investigated: the first is a suspension of flattened clay particles like bentonite, while the second contains rod-like particles of tobacco mosaic virus (TMV). The variations of the birefringence intensity n and of the extinction angle measured in the domain of the axisymmetrical flow show a different behavior according to the shape of the particle in solution. This fact is confirmed theoretically with a good agreement for the measurements performed with solutions of flat particles.     

Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization

The copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]₀:[I]₀ ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (M_w/M_n < 1.4) even at high conversion. Decreasing the [CuBr]₀:[I]₀ ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by ¹H and ¹³C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from ¹³C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002     

Microgravimetric Investigations of High-Temperature Superconductors

It has been confirmed that, in oxide superconductors, the superconducting transition temperature T_c depends strongly on the oxygen content and oxygen ordering. The microgravimetric method is very useful in the analysis of oxide superconductors, because it allows investigations in vacuum and controlled environments in classical applications: thermogravimetric analysis, kinetics and thermodynamics of reaction, determination of oxygen contents in redox reactions, investigations of the correlation of the deviation from stoichiometry and carrier concentration and also the combined measurement of mass and additional parameters, e.g. evolved gas analysis, etc. Selected papers are reviewed. This revised version was published online in July 2006 with corrections to the Cover Date.     

双旋转附属圆柱对主圆柱尾流控制的影响

基于Fluent软件平台,采用数值模拟方法对非稳态圆柱体结构尾流流动特性进行了研究。对在Re=50～200范围内,双旋转附属圆柱的转速对主圆柱体尾流流动特性的影响进行了分析。研究结果表明:随着附属圆柱旋转速率的增加,主圆柱体表面所受阻力系数平均值与均方根值、升力系数均方根值均会减小。同时,旋转速率的变化对柱体结构表面压力分布的影响显著,压力系数在附属圆柱的位置产生了跳跃性变化。另外,当附属圆柱转速达到临界值时,尾流涡街变窄,涡脱落现象消失,并且系统的能量效率到达最佳状态。     

Preparation of Co-Processed Excipients for Controlled-Release of Drugs Assembled with Solid Lipid Nanoparticles and Direct Compression Materials

The purpose of the study was to develop a novel, directly compressible, co-processed excipient capable of providing a controlled-release drug system for the pharmaceutical industry. A co-processed powder was formed by adsorption of solid lipid nanoparticles (SLN) as a controlled-release film onto a functional excipient, in this case, dicalcium phosphate dihydrate (DPD), for direct compression (Di-Tab^®). The co-processed excipient has advantages: easy to implement; solvent-free; industrial scaling-up; good rheological and compressibility properties; and the capability to form an inert platform. Six different batches of Di-Tab^®:SLN weight ratios were prepared (4:0.6, 3:0.6, 2:0.6, 1:0.6, 0.5:0.6, and 0.25:0.6). BCS class III ranitidine hydrochloride was selected as a drug model to evaluate the mixture’s controlled-release capabilities. The co-processed excipients were characterized in terms of powder rheology and dissolution rate. The best Di-Tab^®:SLN ratio proved to be 2:0.6, as it showed high functionality with good flow and compressibility properties (Carr Index = 16 ± 1, Hausner Index = 1.19 ± 0.04). This ratio could control release for up to 8 h, so it fits the ideal profile calculated based on biopharmaceutical data. The compressed systems obtained using this powder mixture behave as a matrix platform in which Fickian diffusion governs the release. The Higuchi model can explain their behavior.     

大口径非球面元件可控气囊抛光系统

根据大口径非球面光学元件的实际加工需要,设计并制造可控气囊抛光系统,并对机构进行运动学仿真,仿真结果表明,气囊自转轴的运动空间可以满足大口径非球面光学元件的连续进动加工要求。为了证明所设计系统的可加工性,以直径320 mm的圆形平面光学元件进行加工实验。经过该气囊抛光工具24 h的抛光后,工件达到较好的面型精度,光学元件的表面粗糙度由0.272减小到0.068(＝632.8 nm), PV值从1.671降低到0.905。对光学元件的实际加工实验结果表明：可控气囊抛光系统在加工过程中结构稳定性好,符合设计要求,可有效提高加工工件面型精度。     

宽动态范围的双正交磁光电流传感器技术

提出了一种新的双正交磁光电流传感器技术,该技术可解决传统磁光电流传感器测量大电流脉冲时仅根据正弦或余弦信号无法唯一确定法拉第偏转角的技术难题。在该传感器中,起偏器的透光轴与两个偏振分束器的S分量偏振方向有0与45的夹角,四路输出信号两两之间有/2的相位差。针对该传感器,提出了大电流脉冲的一种反正切函数数据处理方法,该数据处理方法具有可避开正弦函数的不灵敏区间,从而提高数据处理精度的优点。采用双正交磁光电流传感器与罗果夫斯基线圈对比测量了FP-1装置的短路电流脉冲,两种测试技术的实验结果能很好地吻合,证实该光学电流传感器可有效地测量大电流脉冲。

     

Studies on the thermotropic liquid crystalline polycarbonates. III. Synthesis and properties of fully aromatic liquid crystalline polycarbonates

Four series of fully aromatic thermotropic liquid crystalline polycarbonates were prepared by melt polycondensation from various novel phenylene diphenyl dicarbonates with monomers, such as hydroquinone, methylhydroquinone, chlorohydroquinone, resorcinol, bisphenol A, 4,4′-dihydroxydiphenylsulfone, or phenylhydroquinone, respectively. The thermotropic liquid crystalline properties were studied by polarizing microscope with a heating stage, differential scanning calorimeter (DSC), and wide-angle x-ray diffraction (WAXD). It was found that the nonlinearity of the carbonate group was compensated by resorcinol (1,3-phenylene unit), a bent shape unit. Nematic melts were found for the resulting polycarbonates. © 1993 John Wiley & Sons, Inc.     

Controlled Variable Oxidative Doping of Individual Organometallic Nanoparticles

The charging and controlled oxidative doping of single organometallic ferrocene nanoparticles is reported in aqueous sodium tetrafluoroborate using the nano‐impacts method. It is shown that ferrocene nanoparticles of approximately 105 nm diameter are essentially quantitatively oxidatively doped with the uptake of one tetrafluoroborate anion per ferrocene molecule at suitably high overpotentials. By using lower potentials, it is possible to achieve low doping levels of single nanoparticles in a controlled manner.