On the breakdown of acceleration waves in dissociating gas flows

The present paper is devoted to the study of characteristic solution in the neighbourhood of the leading frozen characteristics in dissociating gas flows. It is found that at the cusp of the envelope of intersecting forward characteristics there occurs a breakdown of the wave after a finite critical timet _o. It is observed that there exists a critical value of the initial amplitude of the wave such that all compressive waves with an initial amplitude greater than the critical one will terminate into a shock wave due to non-linear steepening while an initial amplitude less than the critical one will result in a continuous decay. It is also concluded that the breakdown point moves forward along the leading characteristics due to dissociation effects.     

Competitive adsorption isotherm modelling of heterocyclic nitrogenous compounds,pyridine and quinoline,onto granular activated carbon and bagasse fly ash

In the present study, simultaneous adsorption of quinoline and pyridine onto adsorbents such as granular activated carbon (GAC) and bagasse fly ash (BFA) from pyridine–quinoline binary aqueous solution was studied at various temperatures (288–318 K). Gathered equilibrium adsorption data were further analysed using various multicomponent competitive isotherm models such as non-modified and modified competitive Langmuir isotherms, extended-Langmuir isotherm, extended-Freundlich model, Sheindorf–Rebuhn–Sheintuch (SRS) model, and non-modified and modified competitive Redlich–Peterson isotherm model. It was observed that increase in pyridine concentration decreased the total adsorption yield and the individual adsorption yield for both the quinoline and pyridine for both the adsorbents GAC and BFA at all the temperatures studied. Identical trend was observed during the equilibrium uptake of pyridine on to GAC and BFA with an increase in quinoline concentration. The extended-Freundlich model satisfactorily represented the binary adsorption equilibrium data of quinoline and pyridine onto GAC and BFA.     

Boosting Electrochemical Water Oxidation with Metal Hydroxide Carbonate Templated Prussian Blue Analogues

The development of efficient and stable catalyst systems with low‐cost, abundant, and non‐toxic materials is the primary demand for electrochemical water oxidation. A unique method is reported for the syntheses of metal hydroxide carbonate templated Prussian blue analogues (PBAs) on carbon cloth and their outstanding water oxidation activities in alkaline medium. The best water oxidation activity is obtained with cobalt hydroxide carbonate templated t‐Co^II‐Co^III with an overpotential as low as 240 mV to reach a current density of 10 mA cm^?2. It produces constant current over 50 h in chronoamperometric measurements. Moreover, the catalysts outperform the activities of the PBAs prepared without any template and even the noble metal catalyst RuO₂. Spectroscopic and microscopic studies show that the PBAs are transformed into layered hydroxide–oxyhydroxide structures during electrochemical process and provide the active sites for the water oxidation.     

Simultaneous determination of metformin in combination with rosiglitazone by reversed-phase liquid chromatography

A simple, rapid, and precise reversed-phase liquid chromatographic method is developed for the simultaneous determination of metformin in combination with rosiglitazone. This method uses a Zorbax XDB C(18) 15-cm analytical column, a mobile phase of acetonitrile and buffer containing 10mM disodium hydrogen phsosphate, and 5mM sodium dodecyl sulphate in the ratio of 34:66 (v/v), and pH is adjusted to 7.1 with orthophosphoric acid. The instrumental settings are a flow rate of 1 mL/min, column temperature at 40 degrees C, and detector wavelength of 226 nm. The internal standard method is used for the quantitation of metformin and rosiglitazone. Methylparaben is used as an internal standard. The method is validated and shown to be linear. The correlation coefficients for metformin and rosiglitazone are 0.9996 and 0.9997, respectively. The relative standard deviation for six replicate measurements in two sets of each drug in the tablets is always less than 2%.     

Chain length effects in the second virial coefficient of linear polymer molecules

A generalized perturbation theory is presented for the second virial coefficient of linear and branched polymer systems. Results have been computed for linear chains having two to five hundred statistical segments. These are found to differ significantly from the long-chain asymptotic results of Zimm. A semi-empirical modification of the Flory--Orofino theory is also suggested.     

Tris(2,2,2-trichloroethoxy)iron(III) complexes

Summary The preparation, magnetic moments, i.r., reflectance and⁵⁷Fe Mössbauer spectra of adducts of tris(2,2,2-trichloroethoxy)iron (III) complexes are reported. An alkoxybridged structure is supported by i.r. spectra.⁵⁷Fe Mössbauer spectra are explained in terms of two inequivalent sites in highspin iron(III) octahedral symmetry.Abbreviations Pic-O -picolineN-oxide - Ur urea - DMU N,N-dimethylurea - Suc succinimide - Diox dioxan - Bipy 2,2-bipyridine - Phen 1,10-phenanthroline     

Copolymers of 2-hydroxyethyl methacrylate and alkyl methacrylates. I. Synthesis and characterization

Copolymerization of 2-hydroxyethyl methacrylate (HEMA) with ethyl methacrylate (EMA) and n-butyl methacrylate (BMA) was carried out in bulk at 70°C ± 1°C using 0.2% benzoyl peroxide as initiator in nitrogen atmosphere. Number average molecular weight (M _n) of the copolymers was determined by dynamic osmometry. Intrinsic viscosity [η] of HEMA-BMA copolymers was evaluated at 35°C in dimethyl formamide. These copolymers were also characterized by infrared spectroscopy and density measurements. Cohesive energy densities (CED) of these polymers were determined by observing their swelling behavior in different solvents. It was found that a decrease in alkyl methacrylate content resulted in an increase in the CED values of the copolymers.     

Bioluminescence resonance energy transfer from aequorin to a fluorophore: an artificial jellyfish for applications in multianalyte detection

In nature, the green light emission observed in the jellyfish Aequorea victoria is a result of a non-radiative energy transfer from the excited-state aequorin to the green fluorescent protein. In this work, we have modified the photoprotein aequorin by attaching selected fluorophores at a unique site on the protein. This will allow for in vitro transfer of bioluminescent energy from aequorin to the fluorophore thus creating an artificial jellyfish. The fluorophores are selected such that the excitation spectrum of the fluorophore overlaps with the emission spectrum of aequorin. By modifying aequorin with different fluorophores, bioluminescent labels with different emission maxima are produced, which will allow for the simultaneous detection of multiple analytes. By examining the X-ray crystal structure of the protein, four different sites for introduction of the unique cysteine residue were evaluated. Two fluorophores with differing emission maxima were attached individually to the mutants through the sulfhydryl group of the cysteine molecule. Two of the fluorophore-labeled mutants showed a peak corresponding to fluorophore emission thus indicating resonance energy transfer from aequorin to the fluorophore.