Dielectric Properties of Colossal-Dielectric-Constant Na1/2La1/2Cu3Ti4O12 Ceramics Prepared by Spark Plasma Sintering

In the current study, we report on the dielectric behavior of colossal-dielectric-constant Na_1/2La_1/2Cu₃Ti₄O₁₂ (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma sintering (SPS) at 850 °C, 900 °C, and 925 °C for 10 min. X-ray powder diffraction analysis showed that all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS NLCTO ceramics showed a room-temperature colossal dielectric constant (>10³) and a comparatively high dielectric loss (>0.1) over most of the studied frequency range (1 Hz–40 MHz). Two relaxation peaks were observed in the spectra of the electrical modulus and attributed to the response of grain and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance (IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary of SPS NLCTO.     

Alfvén waves in temperature anisotropic Cairns distributed plasma

The dispersion relations and Landau damping of Alfven waves in kinetic and inertial limits are studied in temperature anisotropic Cairns distributed plasma.In the case of kinetic Alfven waves(KAWs),it is found that the real frequency is enhanced when either the electron perpendicular temperature or the non-thermal parameter A increases.For inertial Alfven waves(IAWs),the real frequency is slightly affected by the electron temperature anisotropy and A.Besides the real frequency,the damping rate of KAWs is reduced when the electron perpendicular temperature or A increases.In the case of IAWs,the temperature anisotropy and A either enhance or reduce the damping rate depending upon the perpendicular wavelength.These results may be helpful to understand the dynamics of KAWs and IAWs in space plasmas where the non-Maxwellian distribution of particles are routinely observed.     

Magnetic,Electrical and Thermal Studies of Polypyrrole-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanocomposites

This research paper comprises of the synthesis of polypyrrole (PPy)-Fe₂O₃ nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H _c ), saturation magnetization (M _s ) and remanence (M _r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites.     

生物催化进展:从计算到代谢工程（英文）

经过数次技术研究和超常创新战略的大发展,生物催化逐渐达到工业化水平,从而受到人们特别的关注.基于酶值,通过生物途径生产高附加值化合物和精细工业化学品成为人们最感兴趣的领域之一.更广泛的众多生物化学路线可由酶催化来实现,其中还有一些酶尚未被人们发现.另一方面,由于非同源底物和某些化学过程所必需的苛刻条件,导致酶催化过程的效率低、稳定性差,因而限制了生物催化的应用.因此,开发具有多催化特征、更高效率和稳定性的绿色催化剂,成为生物催化的重中之重.计算科学、代谢工程、合成生物,以及机器学习路线的运用为新催化剂的工程化提供了新方法.本文重点介绍了合成生物学和代谢工程在催化中的作用,讨论了用于催化的机器学习算法和如何选择一种预测蛋白质-配体相互作用的算法;为了预测键合和催化功能,综述了分子对接的重要性;最后给出了结束语、未来挑战和前景展望.     

Development of Yttrium and Iron Oxide Thin Films via AACVD Method for Photooxidation of Water

Russian Journal of Applied Chemistry - Owing to high stability, metal oxide-based ceramic thin films are of great interest for photocatalytic oxidation of water. Therefore, the current research is...     

Sodium Bromide Catalysed Regioselective Cleavage of Oxitanes with Chlorotrimethylsilane

Sodium bromide efficiently catalyses the regioselective cleavage of oxiranes with chlorotrimethylsilane to the corresponding O-silylated chlorohydrins in excellent yields.     

Application of parameter differentiation for flow of a third grade fluid past an infinite porous plate

This article investigates the analytic solution for the flow of a third grade fluid past an infinite porous plate. The method of parameter differentiation is used to linearized the governing flow equation. The solution of the obtained linear equation is developed by differential transform method in combination with the method of superposition. The obtained results are compared with existing results in the literature and an excellent agreement is found. This shows that the parameter differentiation is a powerful technique for solving nonlinear problems. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010     

Isoflavonoid glycosides from the rhizomes of Iris germanica

Four isoflavone glycosides were isolated from the rhizomes of Iris germanica. Compounds 1 and 2 are new, while compounds 3 and 4 are known isoflavone glycosides. These compounds were identified as iriskashmirianin 4'-O-beta-D-glucoside (1), nigricin 4'-O-beta-D-glucoside (2), irilone 4'-O-beta-D-glucoside (3) and iridin (4). Their structures were determined with the help of spectroscopic methods.     

Stereoselective synthesis of beta-substituted phenylalanine-beta-phenylisoserine-derived tripeptides using N-cinnamoyl-L-proline as template: synthesis of structural analogues of HIV protease inhibitors

N-Cinnamoyl-L-proline can be used as a template on which beta-substituted phenylalanine and beta-phenylisoserine residues can be synthesized leading to tripeptide derivatives as structural analogues of HIV protease inhibitors.     

Synthesis of small cyclic peptides via reverse turn induced ring closing metathesis of tripeptides

A reverse turn induced (gamma/beta-turn) cyclization of tripeptides 1 can be performed in a ring closing metathesis reaction with Grubbs' catalyst to the corresponding cyclic peptides 2. These cyclic peptides may be useful probes as a conformationally constrained mimic of the bioactive conformation of structurally related HIV protease inhibitors.