Synthesis and characterization of multifunctional polymers via atom transfer radical polymerization of N‐(ω′‐alkylcarbazolyl) methacrylates initiated by Ru(II) polypyridyl chromophores

A series of poly(N‐(ω′‐alkylcarbazoly) methacrylates) tris(bipyridine) Ru‐centered bifunctional polymers with good filming, thermal, and solubility properties were synthesized and characterized. Atom transfer radical polymerization (ATRP) of N‐(ω′‐alkylcarbazoly) methacrylates in solution was used, where Ru complexes with one and three initiating sites acted as metalloinitiators with NiBr₂(PPh₃)₂ as a catalyst. ATRP reaction conditions with respect to polymer molecular weights and polydispersity indices (PDI) of the target bifunctional polymers were examined. Electronic absorption and emission spectra of the resultant functional polymers provided evidence of chromophore presence within a single polymeric chain. The thermal properties of all polymers were also investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and these analyses have indicated that these polymers possess higher thermal stabilities than poly(methyl methacrylate) (PMMA) obtained via free radical polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6057–6072, 2005     

Spectrometric study of solute–solvent interactions for the solvolysis of chloropentaamine cobalt(III) complex in binary aqueous mixtures

Kinetic studies of solvent structure effects and solute–solvent interactions on the solvolysis of [Co(NH₃)₅Cl]²⁺ complex ion have been investigated spectrophotometrically in binary aqueous mixtures. Three cosolvents were used (acetonitrile, dimethylsulfoxide, and urea) over a wide range of temperatures. Nonlinear plots were found for log(rate constant) against the reciprocal of the relative permitivity of the medium. The enthalpy and entropy of activation (ΔH^# and ΔS^#) exhibited extrema in the same composition region where the physical properties indicate sharp changes in the structure of the solvent, confirming that the solvent structure is an important factor in determining the solvolytic reactivity. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 416–422, 2008     

Distributional analysis for discontinuous fields

The jump conditions that hold across singular surfaces for the fields having step function discontinuities do not, in general, apply if these surfaces themselves carry concentrated fields. In this note, the general situation when the surfaces of discontinuity carry multilayers and deform as they propagate is discussed. Formulas are presented for the first and second derivatives for these multilayers.     

Optimization of the separation of flavonoids using solvent-modified micellar electrokinetic chromatography

In this work the separation of eighteen flavonoids was attempted using reduced-flow micellar elektrokinetic chromatography (RF-MEKC) electrolytes modified by selected solvents with differing properties: methanol (MeOH), acetonitrile (ACN) and tetrahydrofuran (THF). Structural aspects such as unsaturation of the C ring, number and position of OH groups, methylation and glycosylation as well as solvent effects and their impact on the electrophoretic behavior of flavonoids were addressed. By evaluating the electropherograms obtained from mixture-designed electrolytes and searching for changes in the critical pairs, a favorable separation condition was achieved using 20 mmol/L phosphate buffer at pH 2.5 containing 50 mmol/L sodium dodecyl sulfate (SDS), 15% ACN and 5% THF (one critical pair) in less than 12 min with 1.5% coefficient of variation (CV) for retention factor and 3% CV for peak area (n = 5). The applicability of the proposed separation condition was demonstrated by the inspection of flavonoids in herbal extracts of Neem.     

Predicting hydration free energies of neutral compounds by a parametrization of the polarizable continuum model

A parametrization of the polarizable continuum model (PCM) is presented having the experimental hydration free energies of 215 neutral molecules as target. The cavitation and dispersion contributions were based on the Tu?on-Silla-Pascual-Ahuir (Tu?on; et al. Chem. Phys. Lett. 1993, 203, 289) and Floris-Tomasi (Floris, F.; Tomasi, J. J. Comput. Chem. 1989, 10, 616) expressions, respectively. Both the polar and nonpolar contributions were evaluated on the same solvent-excluding molecular surface that used unscaled Bondi atomic radii. The parametrization was provided for the HF, Xalpha, LSDA, B3LYP, and mPW1PW91 methods at the 6-31G(d) basis set, and the results are in fair agreement with the experimental data. For the sake of comparison, the PCM(UAHF) and our parametrization (PCM2), both at HF level, have produced DeltaG(PCM(UAHF)) = aDeltaGexp (a = 1.02 +/- 0.02, r = 0.945, sd = 0.987, Ftest = 1778) and DeltaG(PCM2) = aDeltaGexp (a = 0.95 +/- 0.02, r = 0.952, sd = 0.843, Ftest = 2070), respectively. The mean absolute deviations from experimental data were 0.67 and 0.68 kcal/mol for PCM(UAHF) and PCM2, respectively.     

Propagation of LF/VLF radio waves below a nonuniform ionosphere

Summary A simple approach to LF/VLF field calculations for a nonuniform, isotropic ionosphere is developed. The theory introduces two modifications to the standard wave hop theory: namely the use of local reflection coefficients and the use of an average reflection height for the path integrals. Sample calculations, including a comparison with measured results, are presented.

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Riassunto Si sviluppa un semplice approccio di calcoli di campo LF/VLF per una ionosfera isotropica non uniforme. La teoria introduce due modifiche alla teoria standard del balzo delle onde: cioè l'uso di coefficienti locali di riflessione e l'uso di un'altezza media di riflessione per gli integrali di percorso. Si presentano calcoli campione, compreso un confronto con i valori risultati.

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Резюме Развивается простой подход для вычислений LF/VLF поля в неоднородиой изотропниой ионосфере. В этом подходе вводится две модификации в стандартную теорию рассеяния волн. Приводятся простые вычисления, включая сравнение с экспериментальными результатами.

     

Trivalent molybdenum as volumetric reducing agent

Summary The purpose of the present investigation is to introduce trivalent molybdenum as a new analytical reducing agent, in hydrochloric as well as sulphuric acid media.The solution is prepared in 9N acid by electrolytic or mercuryreduction of the hexavalent form. It is preferentially stocked and used in high acid concentrations, whereby its stability in air is optimal, falling to half its titer after nearly two months. It has been tested with success as reductant for ceric, dichromate, ferric and vanadate. It has the advantage of being used in ordinary opened burettes. Titrations were followed potentiometrically in general, and alternately visually in decinormal media, whereby molybdenum blue appears at the end-point. The percentage error in fifteen discussed experiments never surpassed ±1%. Some oxidation titrations were also undertaken using iodate and bromate, with the same degree of accuracy, provided they were conducted in 6N acid. In weaker acid concentrations, equilibria were more slowly attained, with a more or less pronounced deviation, due to some oxidisability that necessitates controlled inert atmosphere.     

Band selection of hyperspectral-image based weighted indipendent component analysis

Huge amounts of data in hyperspectral images have been caused to represent approaches for the band selection of these images. In this paper, a new approach based on independent component analysis (ICA) is proposed. The idea of projection pursuit is used to order the bands on the basis of a non-gaussianity distribution. Applying a negentropy function to weight bands is a novel idea that leads to the selection of bands with minimum mutual information (MI) and besides maximum entropy, with respected to the bands selected using other methods.