Steady rotatory flow of Bingham material between two concentric spheres

Summary Steady flow of Bingham material between two concentric rotating spheres has been investigated taking into account the constitutive equations given by Oldroyd. Motions in the elastic as well as in the flow region have been discussed. A critical value of the Bingham number has been found below which the flow takes place in the whole region and above which the elastic and flow regions occur side by side.Nomenclature r, , space co-ordinates - u _r ,u ,u velocity components - density - modulus of rigidity (constant) - bulk modulus - e _ii , the dilatation - ₁ coefficient of viscosity (constant) - e _ik strain tensor - d _ik rate of strain tensor - p _ik stress tensor primes denote deviatoric components of tensors, e.g. - p _ik p _ik +p _k ⁱ , p=–1/3p _ii - yield value (constant) - D/Dt materiaal derivative with regard to time following the particle - R ₁ radius of the inner sphere - R ₂ radius of the outer sphere - R radius of the yield surface (spherical) - ₁ velocity of the inner sphere - B Bingham number     

Rearrangements in the electron-impact induced fragmentation reactions of 5-alkylthio-1,3,4-thiadiazolyl-2-amines

The low resolution mass spectra of a number of homologous 5-alkylthio-1,3,4-thiadiazolyl-2-amines have been determined. With the methylthio compound the only significant loss from the molecular ion is the sulphydryl radical. As the homologous series is ascended this reaction becomes less important and is insignificant with the butylthio isomers. The ethylthio compound suffers extensive loss of ethylene and when the alkyl group contains three or more carbon atoms the main reaction is always loss of the olefin coresponding to the alkyl group.All of the n-alkylthio compounds showed in addition loss of methylthio radical from the molecular ion. A mechanism is proposed and comparisons made with alkyl phenyl thioethers and alkylthio substituted heterocycles.     

Quantitative Estimation of Ruthenium(III) Using Morpholine-4-Carbodithioate as a New Analytical Reagent

Ruthenium(III) has been precipitated gravimetrically in the pH range 7.0-8.5 with morpholine-4-carbodithioate and determined by weighing as a black complex (C₅H₆ONS₂)₃ Ru after drying at l00–110°C. The interference of the various metal ions has been avoided by using an ammonical mixture of EDTA and tartrate (1:1 molar ratio). The complex is thermally stable up to l60°C.     

Optimum stratification with ratio and regression methods of estimation

Summary The paper considers the problem of optimum stratification on an auxiliary variablex when the information on the auxiliary variablex is also used to estimate the population mean using ratio or regression methods of estimation. Assuming the form of the regression of the estimation variabley on the auxiliary variablex as also the form of the conditional variance function V(y/x), the problem of determining optimum strata boundaries (OSB) is shown to be a particular case of optimum stratification on the auxiliary variable for stratified simple random sampling estimate. A numerical investigation has also been made to study the amount of gain in efficiency that can be brough about by stratifying the population.     

Structural modifications of plumieride isolated from Plumeria bicolor and the effect of these modifications on in vitro anticancer activity

Plumieride was isolated as one of the major components from the biologically active methanolic extract of the bark of Plumeria bicolor (family Apocynaceae). For investigating the effect of substituents on cytotoxic activity it was modified into a series of compounds. Replacing the methyl ester functionality of plumieride with alkyl amides of variable carbon units improved the cytotoxic activity, and a correlation between overall lipophilicity and cytotoxic activity was observed. In plumieride, the glucose moiety was converted into a di- and trisaccharide by following the protection and deprotection approach, and the resulting compounds produced enhanced cytotoxicity. However, these compounds were found to be less effective than plumeiride containing a dodecyl (12 carbon units) amide group. Among all of the derivatives, the naturally occurring plumieride showed the least cytotoxicity (50% cell kill = 49.5 microg/mL), and the dodecyl amide analogue of plumieridepentaacetate produced the best efficacy (50% cell kill = 11.8 microg/mL). The di- and trisaccharide analogues were found to be slightly less effective than the dodecyl derivative (50% cell kill = 15-17 microg/mL). The in vitro cytotoxicity of the plumieride analogues was determined in radiation-induced fibrosarcoma (RIF) tumor cells.     

Fast chromatographic determination of polycyclic aromatic hydrocarbons in aerosol samples from sugar cane burning

The influence of the pH on the complexation equilibria between (S)- or (R)-alprenolol and the cellulase Cel7A was investigated by isothermal titration calorimetry. The results obtained agree with those of previous, similar studies of the same equilibria in which the protein was immobilized on silica particles, packed in a chromatographic column. The association constant and the complexation enthalpy and entropy of the (S)-enantiomer increase with increasing pH. For (R)-alprenolol, the binding is endothermic at all pH values. Thus, for both enantiomers in the pH range 5.5-6.8, the binding is an entropically driven process.     

3/4‐phenylene bisheterocycles from ring transformation reaction of sydnone derivatives: Synthesis of 3‐[3/4‐heterocyclyl]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones from 3/4‐acetylphenylsydnones and their biological properties

The bifunctional 3/4‐[acetyl]phenylsydnones 1a, 1b were subjected to a one‐pot ring conversion to 3‐[3/4‐acetyl]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 2a, 2b , which on further bromination yielded the 3‐[3/4‐bromoacyl]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 3a, 3b . Reaction of these compounds with thiourea yielded the 3‐[3/4‐(2‐aminothiazol‐4‐yl)]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 4a, 4b . The other thiazole derivatives 5a, 5b–7a, 7b were prepared by using thiosemicarbazide, thioacetamide, and thiobenzamide, respectively. In another reaction of the bromoacetyl compounds ( 3a, 3b ) with 2‐aminopyridine and 2‐aminothiazole, the fused biheterocyclic compounds 3‐[3/4‐imidazo‐[1,2‐a]pyridine‐2‐yl]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 8a, 8b and 3‐[3/4‐imidazo‐[2,1‐b]‐thiazol‐6‐yl]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 9a, 9b were obtained. The 3‐[3/4‐(benzofuran‐2‐carbonyl)]phenyl‐5‐methyl‐3H‐[1,3,4]‐oxadiazol‐2‐ones 10a, 10b were obtained by treatment of compounds 3a, 3b with o‐hydroxy benzaldehyde. Most of these compounds exhibited antifungal activity greater than the reference drugs used. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:50–54, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20255     

Synthesis of coumarin analogous of decursivine derivatives

The first synthesis of decursivine derivatives of coumarins is described via intramolecular Friedel–Craft aromatic alkylation. The Lewis acid (LA)–catalyzed reaction facilitated the rapid construction of the desired product. The targeted molecule obtained has been confirmed by spectral analysis.     

Development and validation of GC/MS method for determination of pramipexole in rat plasma

A simple, rapid and sensitive method has been developed and validated for the determination of pramipexole in rat plasma by using gas chromatography mass spectrometry. The lower limit of quantification (LLOQ) is superior to the other reported LC‐MS/MS methods. After being made alkaline with NaOH, plasma samples (0.1 mL) were subjected to liquid–liquid exteraction using methyl‐t‐butyl ether. Analytes were determined using electron impact ionization in a single quadrupole mass spectrometer. GC/MS was performed in the selected ion monitoring mode using target ions at m/z 211, 212 and 152 for pramipexole and m/z 194 and 165 for caffeine as internal standard. A linear calibration curve was plotted over the range of 20–1000 pg/mL for pramipexole (r² > 0.996). The LLOQ was 20.0 pg/mL, respectively, which offered high sensitivity and selectivity enough for bioanalytical investigation. Inter‐ and intraday precisions ranged from 0.3 to 8.8% and from 0.9 to 11.33%, respectively. The recovery of pramipexole from plasma ranged from 82.4 ± 7.1 to 87.8 ± 5.7%. The method fulfills all standards required for bioanalytical methods and can be successfully applied to a pharmacokinetic study of pramipexole in rats. Copyright © 2010 John Wiley & Sons, Ltd.