Effect of chlorine substitution on triplet state structure of thioxanthone: A time‐resolved resonance Raman study

Substitution plays an important role in determining the triplet state reactivity. In this paper, we have studied the effect of chlorine substitution on the triplet state structure and the reactivity of thioxanthone (TX). We have employed time‐resolved resonance Raman technique to understand the structure of the lowest triplet excited state of 2‐chlorothioxanthone (CTX). The experimental findings have been corroborated with the computational results using density functional theory. Akin to the parent compound (TX), coexistence of two lowest triplet states has been observed in case of CTX, which has been substantiated using resonant probe wavelength dependence study. The relative contribution of ³n–π* to ³π–π* to the equilibrated triplet state has been found to be more for CTX compared to TX suggesting increase in the triplet state reactivity after the substitution. The above observation has been further supported by the flash photolysis experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Optical absorption near infrared and EPR studies of mottramite

Mottramite mineral from Tsumeb Corporation Mine, Tsumeb, Otavi, Namibia, is investigated in this present work. The mineral contains vanadium and copper contents of 22.73% and 16.84% by weight, respectively, as V₂O₅ and CuO. An electron paramagnetic resonance (EPR) study confirmed the presence of Cu(II) with g = 2.2. The optical absorption spectrum of mottramite indicates that Cu(II) is present in a rhombic environment. Near infrared results are due to water fundamentals.     

Complete NMR assignments of tubulosine

This article reports the structural elucidation of the Alangium alkaloid, tubulosine (1) on the basis of systematic 2D-NMR analyses (DEPT, COSY, TOCSY, NOESY, ROESY, HMQC and HMBC). The data obtained allowed the unambiguous assignment of all proton and carbon signals in 1 for the first time.     

Solvatochromic Effect on the Photophysical Properties of Two Coumarins

The absorption and emission spectra of two coumarins namely 7, 8 benzo-4-azidomethyl coumarin (C₁) and 6-methoxy-4-azidomethyl coumarin (C₂) have been recorded at room temperature in solvents of different polarities. The ground state dipole moments (μ _g ) of two coumarins were determined experimentally by Guggenheim method. The exited state (μ _e ) dipole moments were estimated from Lippert’s, Bakhshievs and Chamma-Viallet’s equations by using the variation of Stoke’s shift with the solvent dielectric constant and refractive index. The ground and excited state dipole moments were calculated by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was observed that dipole moments of excited state were higher than those of the ground state, indicating a substantial redistribution of the π-electron densities in a more polar excited state for two coumarins.     

An adjoint method for the calculation of remote sensitivities in supersonic flow

This paper presents an adjoint method for the calculation of remote sensitivities in supersonic flow. The goal is to develop a set of discrete adjoint equations and their corresponding boundary conditions in order to quantify the influence of geometry modifications on the pressure distribution at an arbitrary location within the domain of interest. First, this paper presents the complete formulation and discretization of the discrete adjoint equations. The special treatment of the adjoint boundary condition to obtain remote sensitivities or sensitivities of pressure distributions at points remotely located from the wing surface are discussed. Secondly, we present results that demonstrate the application of the theory to a three-dimensional remote inverse design problem using a low sweep biconvex wing and a highly swept blunt leading edge wing. Lastly, we present results that establish the added benefit of using an objective function that contains the sum of the remote inverse and drag minimization cost functions.     

Subdiffusivity of a Random Walk Among a Poisson System of Moving Traps on $\mathbb {Z}$

We consider a random walk among a Poisson system of moving traps on \(\mathbb {Z}\). In earlier work (Drewitz et al. Springer Proc. Math. 11, 119-158 2012), the quenched and annealed survival probabilities of this random walk have been investigated. Here we study the path of the random walk conditioned on survival up to time t in the annealed case and show that it is subdiffusive. As a by-product, we obtain an upper bound on the number of so-called thin points of a one-dimensional random walk, as well as a bound on the total volume of the holes in the random walk’s range.     

Study of electrical properties in mixed oxide sandwich structures

I—V characteristics of sandwiched Al—(SnO₂ + Sb₂O₃)—Al mixed films have been studied for different thicknesses. The current-voltage curves in general exhibit three regions, ohmie, non-ohmic and breakdown regions. The breakdown voltage increases and the dielectric strength decreases with increase of film thickness. The de breakdown studies have been done and optical photomicrographs of breakdown patterns during different stages of de voltage have been taken and the results are discussed.     

I–V characteristics and break down studies of Sb2O3 structures

I–V characteristics of sandwiched Al–Sb₂O₃–Al structures have been studied for different thicknesses. The current-voltage curves in general exhibit three regions, ohmic, non ohmic and breakdown regions. The breakdown voltage increases whereas the dielectric strength decreases with increase in Sb₂O₃ film thickness. The electrical breakdown studies have been done for dc and ac voltages and optical photomicrographs of breakdown patterns during different stages of voltage have been taken and the results are explained.     

Assay of Vancomycin and Dobutamine Using Sodium Metaperiodate

 Three simple and sensitive visible spectrophotometric methods (A–C) are described for the assay of vancomycin (VCM) and dobutamine (DB) (in pure form and in pharmaceutical formulations). These methods are based on the oxidation of vancomycin or dobutamine with excess sodium metaperiodate. Either the products formed (liberated aldehyde with 3-methyl-2-benzothiazolinone hydrazone (MBTH), method A; iodate with p-methylaminophenol sulphate (PMAP), sulphanilamide, in the presence of Mo (VI), method B) or the amount of periodate consumed (celestine blue in the presence of tellurium (IV), method C) are estimated. In this paper the reaction mechanism is presented and all the variables are optimized. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2.5–30, 0.6–6.0; 2–24, 0.8–9.6 and 2–24, 0.76–6.0 μg ml⁻¹ for methods A, B and C of VCM and DB respectively. The validity of the proposed methods was tested by analyzing pharmaceutical formulations containing drug (VCM, DB) and the relative standard deviations were within 1.0%. Recoveries are 99.55–99.94%. Received November 12, 2001; accepted March 20, 2002; published online July 22, 2002     

Titrimetric and Spectrophotometric Methods for the Determination of Glyoxal and Analysis of Ternary Mixtures of Its Oxidation Products

Using thallium(III) as an oxidant, we developed titrimetric and spectrophotometric methods for the estimation of glyoxal at mmole and µmole levels, respectively. In the titrimetric method, thallium(I) formed is determined oxidimetrically with potassium bromate. In the spectrophotometric method, the absorbance of thallium(III) at 260 nm in the presence of 0.1 mol/L sodium chloride and 1.0 mol/L perchloric acid is measured. A plausible mechanism for the oxidation of glyoxal is proposed. Based on the selective oxidation of the probable oxidation products of glyoxal (namely, glyoxylic acid, formic acid, and oxalic acid), a convenient titrimetric method is described for analyzing ternary mixtures of these products.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 8, 2005, pp. 806–810.Original English Text Copyright © 2005 by Siva Rao, Prasada Rao.The text was submitted by the authors in English.