Complexometric determination of thorium using p-nitrobenzene-azo-chromotropic acid (chromotrope 2-B) as indicator

Summary p-Nitrobenzene-azochromotropic acid (chromotrope 2 B) has been found useful as metal indicator in the titration of thorium ions against ethylenediaminetetraacetic acid. Titrations are best carried out with concentrations of thorium upto 0.001 M, within the p_H range 1.5 and 2.9. Temperature has no effect on the end point. Many of the common ions interfere in the titration excepting lithium, sodium, potassium, gold, alkaline earths, zinc, mercury, aluminium, lead, nickel, and acetate. Iron(III) if present may be masked by the addition of ascorbic acid.

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Zusammenfassung p-Nitrobenzol-azochromotropsäure (Chromotrope 2 B) wird als Metallindicator bei der komplexometrischen Titration von Thorium verwendet. Die besten Ergebnisse erhält man bei Konzentrationen bis 0,001 m im p_H-Bereich von 1,5–2,9. Die Temperatur hat keinen Einfluß auf die Erkennung des Endpunkts. Lithium, Natrium, Kalium, Gold, Erdalkalien, Zink, Quecksilber, Aluminium, Blei, Nickel und Acetat stören nicht, während viele andere Ionen Störungen verursachen. Eisen(III) kann mit Ascorbinsäure maskiert werden.

     

A perturbation analysis for modes in diffused waveguides with a gaussian profile

We have developed a first order perturbation approach to obtain the propagation constants for a gaussian index profile by considering it as a perturbation on an appropriately matched secant hyperbolic profile. The secant hyperbolic profile itself well approximates the gaussian profile and hence the perturbation approach yields very accurate results. We have also compared our results with those obtained by the WKB or ray technique and earlier perturbation approaches.     

Self-consistent mode-coupling theory for the viscosity of rodlike polyelectrolyte solutions

A self-consistent mode-coupling theory is presented for the viscosity of solutions of charged rodlike polymers. The static structure factor used in the theory is obtained from polymer integral equation theory; the Debye-Huckel approximation is inadequate even at low concentrations. The theory predicts a nonmonotonic dependence of the reduced excess viscosity eta(R) on concentration from the behavior of the static structure factor in polyelectrolyte solutions. The theory predicts that the peak in eta(R) occurs at concentrations slightly lower than the overlap threshold concentration, c*. The peak height increases dramatically with increasing molecular weight and decreases with increased concentrations of added salt. The position of the peak, as a function of concentration divided by c*, is independent of salt concentration or molecular weight. The predictions can be tested experimentally.     

Adaptive, Restart, Randomized Greedy Heuristics for Maximum Clique

This paper presents some adaptive restart randomized greedy heuristics for MAXIMUM CLIQUE. The algorithms are based on improvements and variations of previously-studied algorithms by the authors. Three kinds of adaptation are studied: adaptation of the initial state (AI) given to the greedy heuristic, adaptation of vertex weights (AW) on the graph, and no adaptation (NA). Two kinds of initialization of the vertex-weights are investigated: unweighted initialization (w _i := 1) and degree-based initialization (w _i := d _i where d _i is the degree of vertex i in the graph). Experiments are conducted on several kinds of graphs (random, structured) with six combinations: {NA, AI, and AW} × {unweighted initialization, degree-based initialization. A seventh state of the art semi-greedy algorithm, DMclique, is evaluated as a benchmark algorithm. We concentrate on the problem of finding large cliques in large, dense graphs in a relatively short amount of time. We find that the different strategies produce different effects, and that different algorithms work best on different kinds of graphs.     

Nonlinear Phase Shift by Parametric Amplification in Leaky Waveguides

In this article, the cascaded second-order nonlinear phase shifts induced in the signal wave are studied using the three-wave parametric interaction in a four-layered QPM leaky waveguide configuration in Z-cut LiNbO 3 . In this interaction, the pump-andsignal waves are guided modes and the idler is radiated into the substrate. We have analyzed the nonlinear phase shifts induced in the signal wave due to cascaded second-order effects, as a function of different waveguide parameters. These studies should find application in realizing practical all-optical signal processing devices.     

Improvements in titer,productivity, and yield using solka-floc for cellulase production

Researchers studying cellulase enzymes for the economical production of fuel ethanol envision cellulose as the carbon source. However, submerged Trichoderma reesei cultures grown on cellulose exhibit high run-to-run variability. Thus, an investigation of 30 batch cellulase production experiments was instrumental in determining fermentation conditions that improved enzyme titers, yields, and productivities. Eighteen of the 30 batch experiments experienced minimal process upsets and were classified into eight groups based on agitation rate, gas sparge rate, and the use of oxygen supplementation. Comparing corn steep liquor with yeast extract/peptone also tested the effect of different sources of nitrogen in the media. Average 7-d enzyme titers were doubled from 4 to 8 FPU/mL primarily by increasing aeration.     

Hypolipidaemic Effects of Methanol Extract of Holoptelea integrifolia (Roxb.) Planchon Bark in Diet-Induced Obese Rats

The leaf and bark paste of Holoptelea integrifolia is traditionally used for the treatment of obesity in Asian countries. However, no scientific studies have been undertaken to reveal the actual mechanism of action. The present study aimed to investigate the hypolipidaemic effect of H. integrifolia and its mechanism in diet-induced obese rat model. After 4 weeks of oral administration, blood samples were collected for the estimation of serum lipids, lecithin: cholesterolacyltransferase (LCAT) apolipoproteins (apo) and liver for HMG-CoA reductase (HMGR) assay. The faecal samples were also collected to estimate the faecal fat content. The H. integrifolia treatment markedly lowered body weight, serum lipids and apo B and increase high-density lipoprotein-cholesterol and apo A1 concentrations. In this study, HMGR activity was enormously reduced, which helps to reduce cholesterol biosynthesis and an increase in LCAT activity was also observed. The detailed faecal analysis showed a remarkable increase in faecal lipids, which indicates the ability to inhibit intestinal fat absorption. The methanol fraction of H. integrifolia on LC-MS and tandem mass spectrometry analysis shows the presence of a compound, 3-(7-ethoxy-4-methyl-2-oxo-2H-chromen-3-yl)propanoate (C1). The result showed that the significant hypolipidaemic effect of H. integrifolia may be linked to its ability to inhibit HMGR activity and block intestinal fat absorption.     

Stereoselective total synthesis of Jaspine B (Pachastrissamine) utilizing iodocyclization and an investigation of its cytotoxic activity

The stereoselective synthesis of Jaspine B has been achieved from easily available (S)-Garner’s aldehyde. The trisubstituted tetrahydrofuran core of Jaspine B was constructed by utilizing a diastereoselective iodocyclization as the key step. Deiodination and debenzylation were performed in a single step by using n-Bu₃SnH and ABCN as a conjugate catalyst system. The in vitro cytotoxicity of compounds 1 and 1a against 3 human cancer cell lines-A549 (lung), MCF7 (breast), and KB (oral); and a non-cancer cell line (NIH3T3) was determined by sulphorhodamine B based assay.