New anisotropic models from isotropic solutions

We establish an algorithm that produces a new solution to the Einstein field equations, with an anisotropic matter distribution, from a given seed isotropic solution. The new solution is expressed in terms of integrals of known functions, and the integration can be completed in principle. The applicability of this technique is demonstrated by generating anisotropic isothermal spheres and anisotropic constant density Schwarzschild spheres. Both of these solutions are expressed in closed form in terms of elementary functions, and this facilitates physical analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

A Cousin problem for systems of PDE

This article formulates an additive Cousin type problem for systems of partial differential equations. The obstruction to the solution of this problem, like the obstruction in the classical Cousin problem, lies in a first cohomology module, viz. in an Ext¹ module associated to the problem. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic molecularly imprinted polymer nanoparticles for dispersive micro solid-phase extraction and determination of buprenorphine in human urine samples by HPLC-FL

A simple, sensitive and accessible while reliable method was developed and validated for quantitation of buprenorphine (Bup) as a highly lipophilic drug in human urine samples. The proposed method is based on a rapid and easy dispersive micro solid-phase extraction procedure using magnetic molecularly imprinted polymer nanoparticles (MMIPNPs), magnetite (Fe₃O₄) cores surrounded by polyamidoamine and Bup as template, followed by high-performance liquid chromatographic analysis with fluorescence detector (HPLC-FL). The prepared MMIPNP adsorbent was characterized by different techniques. Transmission electron microscopy images show that the Fe₃O₄ core nanoparticles are well enwrapped by MIP layers. In determination process, Bup could be quantitatively extracted using MMIPNPs and then can be easily desorbed by mixture of sodium hydroxide (0.1 mol/L) and methanol (1:9, v/v) solution before injection to HPLC. The relative recoveries of Bup were found to be 97.4–100.3%, and the linear dynamic range was within the ranges of 1–1000 ng/mL with R² of 0.9998. Remarkably high quality of 0.21 and 0.71 ng/mL was obtained as the limit of detection and limit of quantification, respectively. The developed method was successfully applied for determination of Bup in infected human urine samples.     

Electrochemical preparation of orthophenylenediamine on different cathodes in sulfuric acid

The electrochemical reduction of nitro group of orthonitroaniline (ONA) is carried out on Pb, Cu, and Sn electrodes. The effect of current density, temperature, and acid concentration on product yield is studied. The polarization curve for ONA in acidic condition is recorded. Under preparative electrolysis, ONA gives a mixture of hydroxylamine and phenylenediamine, the proportion of phenylenediamine increasing with the electrolysis time. The product formation is confirmed by thin-layer chromatography, melting-point test, UV-visible, IR, and NMR methods. The operating conditions are optimized for a good yield of orthophenylenediamine. The catalytic activity of different metals for the reduction of nitro group is discussed. The percent yield of orthophenylenediamine is found to be high on the lead electrode. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 215–221. The text was submitted by the authors in English.     

A fiber-optic transmission system based on differential polarization-shift keying

A differential polarization-shift keying (DPolSK) scheme in which information is encoded as a differential polarization state with respect to the previous symbol is considered. A novel DPolSK demodulator consisting of optical delay interferometer and a pair of birefringence plates that do polarization rotation are proposed. Numerical simulations of the long haul fiber-optic systems based on differential phase-shift keying (DPSK) and DPolSK are carried out and it is found that DPolSK has a higher nonlinear tolerance than DPSK. This is because the ghost pulse generation due to intra-channel four-wave mixing (IFWM) is less efficient for DPolSK signals as compared to DPSK.     

Stability of nonthermodynamic equilibrium cation distribution frozen during pulsed laser deposition of Co-ferrite thin films

Co-ferrite thin films were prepared by pulsed laser deposition technique at room temperature, and magnetization was studied as a function of annealing temperature (T _A ) and annealing time. One set of films was quenched immediately after annealing while the other set was furnace cooled. Spontaneous magnetization value, 4π M _S , of the quenched films was observed to be higher than the furnace cooled films in all the cases. Magnetization increases monotonically up to T _A =650°C and then became nearly constant with the increase in T _A . Magnetization values even higher than the Co-ferrite bulk value of 5300 G was observed in the quenched films annealed at and above 650°C. In the case of furnace cooled films, magnetization decreased with the increase in annealing time, while it remained nearly constant in quenched films. Coercivity values of the quenched films were always found to be lower than those of the furnace cooled films. The observed magnetic properties in the films were attributed to the cation distribution and the grain sizes.     

Synthesis and biological evaluation of aromatic analogues of conduritol F, L-chiro-inositol, and dihydroconduritol F structurally related to the amaryllidaceae anticancer constituents

Pancratistatin is a potent anticancer natural product, whose clinical evaluation is hampered by the limited natural abundance and the stereochemically complex structure undermining practical chemical preparation. Fifteen aromatic analogues of conduritol F, l-chiro-inositol, and dihydroconduritol F that possess four of the six pancratistatin stereocenters have been synthesized and evaluated for anticancer activity. These compounds serve as truncated pancratistatin analogues lacking the lactam ring B, but retaining the crucial C10a-C10b bond with the correct stereochemistry. The lack of activity of these compounds provides further insight into pancratistatin's minimum structural requirements for cytotoxicity, particularly the criticality of the intact phenanthridone skeleton. Significantly, these series provide rare examples of simple aromatic conduritol and inositol analogues and, therefore, this study expands the chemistry and biology of these important classes of compounds.     

Microindentation Hardness of Nanostructured Thermoplastic Materials

Summary: The micromechanical behaviour of various thermoplastics based nanocomposites was investigated with the aid of the microindentation technique. The materials studied were microphase separated styrene-butadiene block copolymer systems and several thermoplastics reinforced with nano-sized fillers having variable dimensionality. It was found that the microhardness behaviour of the nanocomposites studied was strongly influenced by the dimensionalities of the filler. Due to large surface to volume-ratio one- and two-dimensional fillers exhibit a far better reinforcing behaviour than the three dimensional ones. In case of nanostructured block copolymers, the microhardness is not determined by the total polystyrene (PS)/polybutadiene (PB) composition alone but diminishes gradually in presence of freely standing dangling polybutadiene chains even if the morphology of the systems remains unaltered.     

The reductive etherification of carbonyl compounds using polymethylhydrosiloxane activated by molecular iodine

Aldehydes and ketones undergo a smooth reductive etherification by polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding symmetrical ethers in excellent yields. This new reagent system (PMHS/I₂) provides a simple and convenient route for the preparation of symmetrical ethers from carbonyl compounds.