An expeditious,solvent-free synthesis of some 5-aryl-2-(2-hydroxyphenyl)-1,3,4-oxadiazoles

An efficient, rapid, microwave-accelerated one-step synthesis of some 5-aryl-2-(2-hydroxy-phenyl)-1,3,4-oxadiazoles by reaction of salicylic hydrazide with carboxylic acids in the presence of thionyl chloride under neat conditions is described. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1264–1267, August, 2007.     

Analysis of organomercury compounds in sediments by capillary GC with atomic fluorescence detection

Analysis of methyl- and ethylmercury (MM and EM) halides in biological and environmental samples is generally performed by gas chromatography with electron capture detection. Tedious sample work-up protocols and poor chromatographic response (using packed columns) have, however, shown the need for the development of new methods in this field. This paper reports a sensitive method, free from these deficiencies, for the determination of methyl- and ethylmercury. The organomercury compounds (MM and EM) are first released from the sample matrix, by the combined action of acidic potassium bromide and cupric ions, and then extracted into dichloromethane. The initial extracts are subjected to thiosulfate clean-up and the organomercury species are isolated as their chloride derivatives by addition of cupric chloride, and subsequent extraction into a small volume of organic solvent. Capillary GC coupled with atomic fluorescence detection provided excellent separation efficiencies for methyl- and ethylmercury and proved to be a very selective and sensitive technique. The absolute detection limit for both MM and EM was found to be 0.2 pg.     

The polymerization of 1,4-pentadiene to [3.3.1]bicyclo-linked chains

1, 4-Pentadiene has been polymerized by Ziegler-Natta catalysts to give amorphous polymers which are up to 64 wt.-% soluble. The polymers all have residual unsaturation which is substantially less than one double bond per mer, some as low as 0.1 double bond per mer. The polymerizations proceed by an unusual double inter-, double intramolecular cyclopolymerization mechanism leading to the formation of [3.3.1] bicyclic repeat units. Some main-chain (internal) unsaturation as well as pendant-group (external) unsaturation is observed. The latter results from incompletely cyclized 1,4-pentadiene units. The former is due to some concurrent isomerization of 1,4- to 1,3 pentadiene, which then copolymerizes with the 1,4 diene. The extent of isomerization varied with the catalyst system used. The soluble polymer fractions were brittle for internal unsaturations of less than about 0.05 double bond per mer and were viscous for higher values. The insoluble fractions were brittle and are believed to be lightly crosslinked.     

Relativistic calculations on the ground and excited states of AgH and AuH in cylindrical harmonic confinement

The relativistic ground and low-lying excited state potential energy curves of AgH and AuH in the presence of a cylindrical harmonic confining potential were calculated using the multi-state multi-reference perturbation theory with the spin-free no-pair Hamiltonian obtained via the third-order Douglas–Kroll transformation, incorporated with the full two-electron Breit–Pauli spin–orbit operator. The spectroscopic parameters were obtained for both the scalar- and quasi-relativistic potentials. The spin–orbit coupling constants were calculated for several strengths of the confining potential, and the effects of the applied potential on the coupling constants were analyzed using configuration interaction. This paper is dedicated to Serafín Fraga—colleague, mentor, and friend.     

Drag on two nonuniformly structured flocs moving along the axis of a cylindrical tube

The boundary effect on the drag on two identical, nonuniformly structured flocs moving along the axis of a cylindrical tube filled with a Newtonian fluid is investigated at a small to medium larger Reynolds number. A two-layer model is adopted to simulate various possible structures of a floc, and the flow field inside is described by Darcy–Brinkman model. The results of numerical simulation reveal that a convective flow is present in the rear region of a floc when Reynolds number is on the order of 40. The presence of the tube wall and/or the porous structure of a floc has the effect of reducing that convective flow. For a fixed level of the volume-average permeability of a floc, the influence of the tube wall on the drag depends upon floc structure; the influence on a nonuniformly structured floc is more significant than that on a uniformly structured floc. The more nonuniform the floc structure, the more appreciable the deviation of the drag coefficient–Reynolds number curve from a Stokes’-law-like relation becomes. The smaller the volume-average permeability of a floc and/or the smaller the separation distance between the two flocs, the greater is the deviation, but the presence of the tube wall has the effect of reducing that deviation.     

Effects of wavelength, pulse duration and power density on laser activation of glassy carbon electrodes

The hypothesis that laser activation of glassy carbon (GC) electrodes is thermally driven was investigated by comparing simulated surface temperatures for several lasers and experimental conditions. Assuming no phase changes, the surface temperature vs. time profile for a laser pulse striking a GC electrode was predicted by finite difference simulation. It was predicted that peak surface temperature depends on power density, wavelength, pulse duration and the optical properties of the carbon. Experimentally, laser activation is weakly wavelength dependent for ascorbic acid and Fe . The surface temperatures required for activation were consistent for different lasers, supporting the conclusion that laser activation is thermally driven. Furthermore, predicted surface temperatures during activation were below the melting point of carbon but well above the boiling point of water. The results should be useful for predicting the effectiveness of different laser conditions on electron transfer activation.     

Electrochemical monitoring of indigo preparation using Maya’s ancient procedures

The preparation of indigo from Indigofera suffruticosa following the procedures attributed to ancient Mayas was electrochemically monitored using the voltammetry-of-microparticles approach. The mechanism formation of indigotin and indirubin from its precursors, indican and isatan, is discussed. Comparison of voltammetric profiles for differently prepared and commercial indigos and genuine Maya Blue samples suggests that the preparation procedure of indigo changed during the Late Classical Maya period. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Use of an automated image processing program to quantify recombinant adenovirus particles.

Electron microscopy has a pivotal role as an analytical tool in pharmaceutical research. However, digital image data have proven to be too large for efficient quantitative analysis. We describe here the development and application of an automated image processing (AIP) program that rapidly quantifies shape measurements of recombinant adenovirus (rAd) obtained from digitized field emission scanning electron microscope (FESEM) images. The program was written using the macro-recording features within Image-Pro Plus software. The macro program, which is linked to a Microsoft Excel spreadsheet, consists of a series of subroutines designed to automatically measure rAd vector objects from the FESEM images. The application and utility of this macro program has enabled us to rapidly and efficiently analyze very large data sets of rAd samples while minimizing operator time.     

Elemental analysis of Korean women’s blood serums using instrumental neutron activation analysis

Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization. Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated. NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46, 0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the reported values.     

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.