Probing the electric field alignment of a thermotropic liquid crystalline polymer by synchrotron radiation

The orientation of a cyclic side-chain thermotropic liquid crystalline material in an AC field was monitored in real-time using synchrotron radiation. Monitoring the realignment processes in the millisecond-to-minute time-scale was made possible by the high X-ray flux. Orientation parameters and response times were calculated as a function of temperature and frequency. Response times decreased exponentially with temperature due to a decrease in the viscosity. Very little dependence of the response time on frequency was observed, except at low temperatures, where a switch from homeotropic to planar alignment of the molecules was detected. This reorientation of the director was studied in real-time and the resulting complex diffraction patterns were due to equal but opposite director rotations from an alignment parallel to the applied electric field to an alignment perpendicular to the applied electric field. The orientation parameters were highest in the central portion of the mesophase temperature range. At temperatures near clearing, the net degree of orientation diminished. Cooling through the mesophase with an applied electric field resulted in much larger orientation parameters than could be obtained by aligning at a fixed temperature in the mesophase.     

Construction of fully symmetric numerical integration formulas of fully symmetric numerical integration formulas

The paper develops a construction for finding fully symmetric integration formulas of arbitrary degree 2k+1 inn-space such that the number of evaluation points isO((2n)^k)/k!),n . Formulas of degrees 3, 5, 7, 9, are relatively simple and are presented in detail. The method has been tested by obtaining some special formulas of degrees 7, 9 and 11 but these are not presented here.     

Syntheses of substituted 3-methyleneisoindolin-1-ones by a palladium-catalyzed Sonogashira coupling-carbonylation-hydroamination sequence in phosphonium salt-based ionic liquids

Two efficient approaches for the synthesis of isoindolin-1-one derivatives in phosphonium salt ionic liquids are described. The palladium-catalyzed carbonylation-hydroamination reaction of 1-halo-2-alkynylbenzene with amines afforded the substituted 3-methyleneisoindolin-1-ones in good yields and high selectivities in favor of the Z-isomers. The target molecules could also be synthesized by the Sonogashira coupling-carbonylation-hydroamination one-pot reaction of dihalides, alkynes, and amines. Both processes can be conducted under mild conditions and tolerate a wide array of functionalized substrates.     

Fracture of thick laminated composites

The fracture of thick laminated graphite/epoxy composites has been the subject of an extensive research program. The program was divided into three major areas of investigation which included laminate thickness, laminate stacking sequence, and part-through surface flaws. The results from this program are reviewed with emphasis placed on their applicability to the design of thick laminated composite structures. Paper was presented at 1985 SEM Spring Conference on Experimental Mechanics held in Las Vegas on June 9–14, 1985.     

Physicochemical characterization of an anatase TiO2 surface and the adsorption of a nonionic surfactant: an atomic force microscopy study

Atomic force microscopy was used to characterize an anatase TiO2 surface, prepared by the helical vapor preparation method. The forces between two bare TiO2 surfaces were measured in the presence of water at various pH values. This TiO2 isoelectric point (iep) was characterized by the presence of only a van der Waals attraction and was measured at pH 5.8; this value is similar to that for a rutile TiO2 surface. The adsorption mechanism of a nonionic surfactant molecule to this anatase TiO2 surface was investigated by measuring the forces between two such TiO2 surfaces at their iep pH in the presence of linear dodecanol tetraethoxylate (C12E4), a poly(ethoxylene oxide) n-alkyl ether. C12E4 was seen by the presence of steric forces to adsorb to the uncharged TiO2 surface. For low surfactant concentrations, C12E4 adsorbed with its hydrophobic tail facing the TiO2 substrate, to reduce its entropically unfavorable contacts with water. Additional surfactant adsorption occurred at higher surfactant concentrations by the hydrophobic and hydrophilic interactions between the surfactant tails and heads, respectively, and gave sub-bilayers. A two-step adsorption isotherm was subsequently proposed with four regions: (1) submonolayer, (2) complete monolayer, (3) sub-bilayer, and (4) bilayer. The absence of a long-range repulsive force between the two TiO2 surfaces in the presence of the C12E4 surface aggregates indicated that a C12E4 nonionic surfactant aggregate did not possess charge.     

C64H6的结构和光谱的理论研究

本文用INDO系列方法研究了C64H6的结构与光谱, 表明C64H6有C2v和Cs两种稳定构型, 其中C2v构型能量较低, 讨论其加成及环加成产物对称性的规律并与13C NMR谱的实验结果相结合。计算了两种构型的电子光谱, 对电子跃迁进行了理论指认,并讨论了C64H6谱带红移的原因, 理论计算结果与实验事实基本吻合。     

氢原子在Ru(0001)和Ru(1010)面上吸附扩散势能面的结构

本文构造了H-Ru相互作用的五参数Morse势,用经典的对势方法研究了氢原子在Ru(0001)和Ru(1010)面上的吸附和扩散,得到了氢原子在两个表面上的吸附位、吸附几何、结合能及本征振动等数据与实验结果符合得很好;同时研究了两个体系的吸附扩散势能面结构。     

二氧化硅悬浮体和水解聚丙烯酰胺体系的流变性

研究了二氧化硅悬浮体的流变性。在固体含量较少的情况下, 体系呈Newton型;固体含量达到一定程度以后, 产生三维结构, 为假塑性体系。三维结构的固体含量与pH值有关。实验证实, 在等电点(i,e, p)附近三维结构最为疏松。还研究了水解聚丙烯酰胺(HPAM)对悬浮体流变性能的影响。HPAM破坏了二氧化硅粒子聚集体结构, 呈絮凝体结构, 并出现触变性。当高聚物在固体表面覆盖一半时, 具有最大触变性和动剪切力。HPAM的水解度达到一定程度, 由于对固体粒子由“强”吸附转变为“弱”吸附, 固体粒子“屏蔽”了高分子间的相互作用, 出现了负触变性现象。在流动时粒子会脱附, 静止以后又产生吸附, 这种吸附与脱附是产生负触变性的主要原因。HPAM水解过度或用量过多, 均会减弱负触变性现象。     

旋转回归分析在提高作物产量中的应用

本文根据旋转回归正交试验,深入研究探讨了不同肥量、密度条件下对小麦产量的影响。创建了小麦产量与种植密度、施肥量之间的回归模型。通过检验,肯定了模型的可靠性和应用的有效性。为农业生产起到了很好的指导作用。     

Evolving to the optoelectronic mouse for phycotoxin analysis in shellfish

Despite ethical and technical concerns, the in vivo method, or more commonly referred to mouse bioassay (MBA), is employed globally as a reference method for phycotoxin analysis in shellfish. This is particularly the case for paralytic shellfish poisoning (PSP) and emerging toxin monitoring. A high-performance liquid chromatography method (HPLC-FLD) has been developed for PSP toxin analysis, but due to difficulties and limitations in the method, this procedure has not been fully implemented as a replacement. Detection of the diarrhetic shellfish poisoning (DSP) toxins has moved towards LC-mass spectrometry (MS) analysis, whereas the analysis of the amnesic shellfish poisoning (ASP) toxin domoic acid is performed by HPLC. Although alternative methods of detection to the MBA have been described, each procedure is specific for a particular toxin and its analogues, with each group of toxins requiring separate analysis utilising different extraction procedures and analytical equipment. In addition, consideration towards the detection of unregulated and emerging toxins on the replacement of the MBA must be given. The ideal scenario for the monitoring of phycotoxins in shellfish and seafood would be to evolve to multiple toxin detection on a single bioanalytical sensing platform, i.e. ‘an artificial mouse’. Immunologically based techniques and in particular surface plasmon resonance technology have been shown as a highly promising bioanalytical tool offering rapid, real-time detection requiring minimal quantities of toxin standards. A Biacore Q and a prototype multiplex SPR biosensor have been evaluated for their ability to be fit for purpose for the simultaneous detection of key regulated phycotoxin groups and the emerging toxin palytoxin. Deemed more applicable due to the separate flow channels, the prototype performance for domoic acid, okadaic acid, saxitoxin, and palytoxin calibration curves in shellfish achieved detection limits (IC₂₀) of 4,000, 36, 144 and 46 μg/kg of mussel, respectively. A one-step extraction procedure demonstrated recoveries greater than 80 % for all toxins. For validation of the method at the 95 % confidence limit, the decision limits (CCα) determined from an extracted matrix curve were calculated to be 450, 36 and 24 μg/kg, and the detection capability (CCβ) as a screening method is ≤10 mg/kg, ≤160 μg/kg and ≤400 μg/kg for domoic acid, okadaic acid and saxitoxin, respectively.