A facile stereoselective synthesis of julolidine hybrid analogs via domino knoevenagel intramolecular hetero Diels–Alder reaction

We have reported here a facile stereoselective synthesis of julolidine hybrid analogs by employing domino Knoevenagel intramolecular hetero Diels–Alder reaction on symmetrical 1,3-diones and unsymmetrical 1,3-diones It was found that the cycloaddition proceeded efficiently under microwave irradiation to afford highly stereoselective cycloadducts in good yields     

Photoinduced effects in nematic liquid crystals

Temperature, concentration of the solvent and pressure are the parameters that are well known to bring about phase transitions in liquid-crystalline systems. In recent years a new parameter has been added to this list: light. The principle behind these photoinduced transitions is the light-driven shape transformation of certain photoactive materials like, e.g., azobenzene. In this article, we present results of various aspects of our recent investigations on such photoinduced transitions in the nematic phase and highlight the feature that light is a new tool to study phase transitions and the associated critical phenomena.     

Intrinsic equations for a generalized relaxed elastic line on an oriented surface in the galilean space

In this article, we derive the intrinsic equations for a generalized relaxed elastic line on an oriented surface in the Galilean 3-dimensional space G₃. These equations will give direct and more geometric approach to questions concerning about generalized relaxed elastic lines on an oriented surface in G₃.     

Studies on third-order nonlinear optical properties and reverse saturable absorption in polythiophene/poly (methylmethacrylate) composites

We report here the studies on third-order nonlinear optical properties of two novel polythiophene composite films investigated using the Z-scan technique. The measurements were carried out using a Q-switched, frequency doubled Nd:YAG laser producing 7 nanosecond laser pulses at 532 nm. Z-scan results reveal that the composite films exhibit self-defocusing nonlinearity. The real and imaginary parts of the third-order nonlinear optical susceptibility were of the order 10⁻¹² esu. The effective excited-state absorption cross section was found to be larger than the ground state absorption cross section, indicating that the operating nonlinear mechanism is reverse saturable absorption (RSA). The polythiophene composite films also exhibit good optical power limiting of the nanosecond laser pulses. The nonlinear optical parameters are found to increase on increasing the strength of the electron-donor group, indicating the dependence of χ ⁽³⁾ on the electron-donor/acceptor units of polythiophenes.     

Strongly indexable graphs and applications

In 1990, Acharya and Hegde introduced the concept of strongly k-indexable graphs: A (p,q)-graph G=(V,E) is said to be strongly k-indexable if its vertices can be assigned distinct numbers 0,1,2,…,p−1 so that the values of the edges, obtained as the sums of the numbers assigned to their end vertices form an arithmetic progression k,k+1,k+2,…,k+(q−1). When k=1, a strongly k-indexable graph is simply called a strongly indexable graph. In this paper, we report some results on strongly k-indexable graphs and give an application of strongly k-indexable graphs to plane geometry, viz; construction of polygons of same internal angles and sides of distinct lengths.     

Mechanistic aspects of oxidation on L-tyrosine by diperiodatocuprate(III) complex in alkali media: a kinetic model

Oxidation of an amino acid, L-tyrosine (L-Tyr) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.1 mol dm⁻³ was studied spectrophotometrically at different temperatures (288.1–313.1 K). The reaction between DPC and L-Tyr in alkaline medium exhibits 1:4 stoichiometry (L-Tyr:DPC). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidence, a mechanism involving monoperiodatocuprate(III) (MPC) as the reactive oxidant species has been proposed. A suitable mechanism is proposed through the formation of a complex and free radical intermediate. The products were identified by spot test and characterized by spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and are discussed. The thermodynamic quantities were determined for different equilibrium steps. Isokinetic temperature was also calculated and found to be 252.3 K.      

Electro-oxidation and determination of trazodone at multi-walled carbon nanotube-modified glassy carbon electrode

A simple and rapid electrochemical method was developed for the determination of trace-level trazodone, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNT-modified glassy carbon electrode was constructed and the electrochemical behavior of trazodone was investigated in detail. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of trazodone in neutral solutions. It leads to a considerable improvement of the anodic peak current for trazodone, and allows the development of a highly sensitive voltammetric sensor for the determination of trazodone. Trazodone could effectively accumulate at this electrode and produce two anodic peaks at about 0.73 V and 1.00 V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the trazodone determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 0.2-10 μM and 24 nM, respectively for trazodone. The proposed method was successfully applied to trazodone determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in urine as a real sample.     

Embedded silicon nanocrystal interface structure and strain

The structure of nanocrystal-matrix interface and strain in embedded nanocrystals are studied using large-scale atomistic simulations, with the examples of Si nanocrystal embedded in amorphous matrix of SiO₂. Photoluminescence from silicon nanocrystals embedded in a dielectric matrix like SiO₂ and Si₃N₄ are promising for Si-based optical devices. The nanocrystal-matrix interface plays a crucial role in understanding its optical and electrical properties. Nanocrystals with diameters varying from 2.17 to 4.56 nm are studied. A detailed quantitative analysis of the variation of Si/SiO₂ interface structure and strain distribution with nanocrystal diameter is reported. A linear variation of the interface width with nanocrystal diameter is observed with thinner interfaces for larger nanocrystals. Local deformation analysis reveals that the smaller nanocrystals are highly strained, whereas the strain in the larger ones shifts to the interface. This is in accordance with observed increase in total percentage of defect states in the interface from 39 to 70% for diameter increasing from 2.17 to 4.56 nm. Moreover, based on the atomic arrangements at the interface, optically active defects like Pb centres, E centres and non-bridging oxygen centres are identified and a dominance of Pb centres is observed for all the nanocrystals. The detailed structural characterization-related investigations using the proposed simulation approach will find useful application in designing system-level response of embedded nanocrystals and also to correlate various experimental observations.     

Lentivirus-mediated transgene delivery to the hippocampus reveals sub-field specific differences in expression

Background  

In the adult hippocampus, the granule cell layer of the dentate gyrus is a heterogeneous structure formed by neurons of different ages, morphologies and electrophysiological properties. Retroviral vectors have been extensively used to transduce cells of the granule cell layer and study their inherent properties in an intact brain environment. In addition, lentivirus-based vectors have been used to deliver transgenes to replicative and non-replicative cells as well, such as post mitotic neurons of the CNS. However, only few studies have been dedicated to address the applicability of these widespread used vectors to hippocampal cells in vivo. Therefore, the aim of this study was to extensively characterize the cell types that are effectively transduced in vivo by VSVg-pseudotyped lentivirus-based vectors in the hippocampus dentate gyrus.     

基于在线购买历史聚合的B2C电子商务差异化折扣模型

众多B2C网站已建立起会员等级制度,并据此向买家提供价格折扣。但会员等级制模型仅考虑买家交易金额,无法全面反映买家在线购买历史(online purchase history),故不能准确提供差异化折扣。针对上述问题,提出了一种面向B2C电子商务的差异化折扣模型,该模型包含能体现买家在线购买历史的交易、退单、推荐购买、晒单等四个指标,将买家在线购买历史聚合为一个综合值,进而通过min-max标准化方法进行线性转换,将转换后的聚合值与会员等级基准折扣结合得到最终的差异化折扣,从而使得B2C网站可向同级别会员实施更精准的一对一营销和价格歧视策略。以京东商城为背景的仿真实验结果证明了本文新模型的有效性。