Alkene‐Directed N‐Attack Chemoselectivity in the Gold‐Catalyzed [2+2+1]‐Annulations of 1,6‐Enynes with N‐Hydroxyanilines

Kinetically unstable nitrones are generated from gold‐catalyzed reactions of 1,6‐enynes with N‐hydroxyanilines, and subsequently trapped by tethered alkenes to furnish [2+2+1]‐annulations. Our experimental data reveal that such nitrones arise from atypical N‐attack chemoselectivity that is triggered by tethered alkenes to facilitate the key protodeauration reaction.     

Effect of maleic anhydride content on the rheology and phase behavior of poly(styrene-co -maleic anhydride)/ poly(methyl methacrylate) blends

 We investigated the thermo- rheological behavior of high glass transition, high molecular weight and small dynamic asymmetry blends of poly(styrene-co-maleic anhydride) (SMA) and poly (methyl methacrylate) (PMMA) with varying amounts of maleic anhydride (MA) content, namely 8 wt%, 14 wt% and 32 wt%, in the SMA component. The phase separation (binodal) temperature of each blend was determined rheologically using a combination of dynamic frequency and temperature sweeps in parallel plate geometry; it was marked by a change in slope of the elastic modulus and the occurrence of a peak in tan δ in temperature sweeps. Failure of the time-temperature superposition principle and observation of two peaks in the Cole-Cole plots corroborated these findings. The blends displayed lower critical solution temperature (LCST) behavior with the critical temperatures exhibiting a non-monotonic dependence on the MA content. From rheological and thermal measurements it was concluded that SMA/PMMA blends containing 14% MA were more miscible than those containing 8% or 32% MA, a finding attributed to the compositional dependence of the interplay between SMA-SMA and SMA-PMMA interactions in the different samples. MA also influenced the dynamic asymmetry and pretransitional concentration fluctuations. The phase diagrams corresponding to each blend were modeled using a two-parameter temperature dependent interaction parameter, based on the concept of generalized Gibbs free energy of mixing. The fitted values of interaction parameter were in good agreement with values calculated explicitly using the Flory-Huggins theory. Received: 16 February 2001 Accepted: 11 July 2001     

Poly(acrylonitrile) ultrafiltration membranes. I. Polymer‐salt‐solvent interactions

Fourier transform infrared spectroscopy was used to study the interactions among LiCl, ZnCl₂, and AlCl₃ with N,N‐dimethylformamide (DMF) and poly(acrylonitrile) (PAN). It was observed that all three salts complex with DMF as well as PAN. The strength of the cation interaction with the >C?O oxygen of DMF was found to be higher than that with the ? CN group of PAN. The >C?O stretching frequency of DMF with ZnCl₂ was red shifted, indicating stronger complex formation compared with other two cations. With the addition of salt, the salt–DMF pseudo solvent was found to become a θ solvent for PAN compared with neat DMF. This change in PAN solvation power was primarily the result of DMF–salt complexation. As a result of the complexation, Mark‐Houwink constant a, was found to reduce from 0.75 (for pure DMF) to ～0.6 for DMF–salt solvents, indicating decreased PAN chain expansion. Comparison of intrinsic viscosity [η] values indicated that addition of salts to PAN–DMF solutions resulted in: (i) decrease in the DMF solvation power, which causes less expanded polymer coils, and (ii) increased interpolymer chain entanglements via salt‐promoted chain association. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2061–2073, 2005     

TLC Supplemented by UV Spectrophotometry Compared with HPLC for Separation and Determination of Some Antidiabetic Drugs in Pharmaceutical Preparations

JPC – Journal of Planar Chromatography – Modern TLC - A simple and sensitive method for separation and quantitative determination of antidiabetic drugs in pharmaceutical preparations...     

Polarization mode dispersion in single mode optical fibers due to core-ellipticity

The variation of polarization mode dispersion (PMD) with V-parameter in single mode optical fibers due to core-ellipticity is studied by performing numerical simulations taking into account both geometrical and thermal-stress-induced birefringences as well as the variation of fiber refractive indices with wavelength. Simple empirical relations are given for calculating the mean PMD for any value of core-ellipticity and V-parameter of a standard single mode fiber. It is observed that the mean PMD saturates for V ? 1.8 leading to very small second order PMD.     

Ligand-Exchange TLC Resolution of Some Racemic β-Adrenergic Blocking Agents

JPC – Journal of Planar Chromatography – Modern TLC -     

MoO3-TiO2纳米晶体复合材料光降解糖蜜（英文）

A MoO3-TiO2 nanocrystalline composite material was prepared by a simple solgel method.The synthesized material was charac-terized by X-ray diffraction,scanning electron microscopy with an electron dispersion spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water.This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water,soil,and air pollution.The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation.Analysis of treated and untreated molasses was carried out by measuring its color,chemical oxygen demand,biological oxygen demand,pH,and total dissolved solid.Results from these analyses indicate the effective photodegradation of the molasses.This methodology has several advantages such as high photocatalytic activity,non-toxicity,cleanliness,and reusability of the catalytic material.     

$(p,q)$-Analogue of Mittag-Leffler Function with $(p,q)$-Laplace Transform

The aim of this paper is to define $(p, q)$-analogue of Mittag-Leffler Function, by using $(p, q)$-Gamma function. Some transformation formulae are also derived by using the $(p, q)$-derivative. The $(p, q)$-analogue for this function provides elegant generalization of $q$-analogue of Mittag-Leffler function in connection with $q$-calculus. Moreover, the $(p, q)$-Laplace Transform of the Mittag-Leffler function has been obtained. Some special cases have also been discussed.