Mixed saturated-unsaturated alkyl-chain assemblies: Solid solutions of zinc stearate and zinc oleate

The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions.

A novel fibre-coated sorbent for rapid removal of heavy metals from wastewater. Sorption of Zinc(II) from dilute aqueous solutions in the presence of high concentrations of common salts

The commercial acrylic fibre "Cashmilon" was partially hydrolyzed to convert a fraction of its nitrile (-CN) groups to carboxylic acid (-COOH) groups and then coated with polyethylenimine (PEI) resin and cross-linked with glutaraldehyde to produce a novel gel-coated fibrous sorbent with multiple functionalities of cationic, anionic and chelating types, and significantly faster sorption kinetics than bead-form sorbents. The sorption properties of the fibrous sorbent were measured using Zn(II) in aqueous solution as the sorbate to determine the effects of pH and the presence of common ions in the solution on the sorption capacity. The rate of sorption on the gel-coated fibre was measured in comparison with that on Amberlite IRA-68 weak-base resin beads, to demonstrate the marked difference between fibre and bead-form sorbents in their kinetic behaviour.

Scanning Tunneling Spectroscopy on Pr0.68Pb0.32MnO3 single crystals

Scanning tunneling microscopy/spectroscopy studies were carried out on single crystals of colossal magnetoresistive manganite Pr0. 68Pb0.32MnO3 at different temperatures in order to probe their spatial homogeneity across the metal-insulator transition temperature TM-I(similar to 255 K). A metallic behavior of the local conductance was observed for temperatures T < TM-I. Zero bias conductance (dI/dV)v=(0), which is directly proportional to the local surface density of states at the Fermi level, shows a single distribution at temperatures T < 200 K suggesting a homogeneous electronic phase at low temperatures. In a narrow temperature window of 200 K < T < TM-I, however, an inhomogeneous distribution of (dI/dV)v=(0) has been observed. This result gives evidence for phase separation in the transition region in this compound.

Structural studies of decaying fluid turbulence: Effect of initial conditions

We present results from a systematic numerical study of structural properties of an unforced, incompressible, homogeneous, and isotropic three-dimensional turbulent fluid with an initial energy spectrum that develops a cascade of kinetic energy to large wave numbers. The results are compared with those from a recently studied set of power-law initial energy spectra [C. Kalelkar and R. Pandit, Phys. Rev. E 69, 046304 (2004)] which do not exhibit such a cascade. Differences are exhibited in plots of vorticity isosurfaces, the temporal evolution of the kinetic energy-dissipation rate, and the rates of production of the mean enstrophy along the principal axes of the strain-rate tensor. A crossover between "non-cascade-type" and "cascade-type" behavior is shown numerically for a specific set of initial energy spectra.

A novel fibre-coated sorbent for rapid removal of heavy metals from wastewater. Sorption of Zinc(II) from dilute aqueous solutions in the presence of high concentrations of common salts

The commercial acrylic fibre "Cashmilon" was partially hydrolyzed to convert a fraction of its nitrile (-CN) groups to carboxylic acid (-COOH) groups and then coated with polyethylenimine (PEI) resin and cross-linked with glutaraldehyde to produce a novel gel-coated fibrous sorbent with multiple functionalities of cationic, anionic and chelating types, and significantly faster sorption kinetics than bead-form sorbents. The sorption properties of the fibrous sorbent were measured using Zn(II) in aqueous solution as the sorbate to determine the effects of pH and the presence of common ions in the solution on the sorption capacity. The rate of sorption on the gel-coated fibre was measured in comparison with that on Amberlite IRA-68 weak-base resin beads, to demonstrate the marked difference between fibre and bead-form sorbents in their kinetic behaviour.

Biosynthesis of isoleucine and valine in mycobacterium tuberculosis H37Rv*1: II. Purification and properties of acetohydroxy acid isomerase

Acetohydroxy acid isomerase (AHA isomerase) was purified about 110-fold and separated from reductase and acetohydroxy acid isomeroreductase. The AHA isomerase was found to be homogeneous by agar and polyacrylamide gel electrophoreses at different pHs. The properties of AHA isomerase have been studied. The purified enzyme showed requirement for Image -ascorbic acid and sulfate ions for its activity. Synthetic ascorbic acid sulfate could replace Image -ascorbic acid and sulfate. α-Methyllactate and α-ketoisovalerate were found to inhibit AHA isomerase activity competitively whereas Image -valine and Image -isoleucine had no significant inhibitory effect. p-Hydroxymercuribenzoate inhibited AHA isomerase activity and the inhibition was reversed by β-mercaptoethanol.

Reactions with disulphur monoxide solutions obtained by the reduction of cupric oxide by elemental sulphur

When the products of reaction between elemental sulphur and copper oxide at elevated temperature in vacuum are bubbled through chilled inert organic solvents like carbontetrachloride, orange-yellow solutions were obtained indicating the presence of lower oxide of sulphur. This lower oxide has been found to be disulphur monoxide as shown by three different types of reactions; (1) Mercury decomposition, (2) Reaction with hydrogen iodide and hydrolytic reaction in an alkaline homogeneous medium.

Biosynthesis of isoleucine and valine in mycobacterium tuberculosis H37Rv. II. Purification and properties of acetohydroxy acid isomeras

Acetohydroxy acid isomerase (AHA isomerase) was purified about 110-fold and separated from reductase and acetohydroxy acid isomeroreductase. The AHA isomerase was found to be homogeneous by agar and polyacrylamide gel electrophoreses at different pHs. The properties of AHA isomerase have been studied. The purified enzyme showed requirement for l-ascorbic acid and sulfate ions for its activity. Synthetic ascorbic acid sulfate could replace l-ascorbic acid and sulfate. α-Methyllactate and α-ketoisovalerate were found to inhibit AHA isomerase activity competitively whereas l-valine and l-isoleucine had no significant inhibitory effect. p-Hydroxymercuribenzoate inhibited AHA isomerase activity and the inhibition was reversed by β-mercaptoethanol.

Numerical procedure for second order non-linear ordinary differential equations and application to heat transfer problem

In this paper, we have first given a numerical procedure for the solution of second order non-linear ordinary differential equations of the type y″ = f (x;y, y′) with given initial conditions. The method is based on geometrical interpretation of the equation, which suggests a simple geometrical construction of the integral curve. We then translate this geometrical method to the numerical procedure adaptable to desk calculators and digital computers. We have studied the efficacy of this method with the help of an illustrative example with known exact solution. We have also compared it with Runge-Kutta method. We have then applied this method to a physical problem, namely, the study of the temperature distribution in a semi-infinite solid homogeneous medium for temperature-dependent conductivity coefficient.

Reversible polyelectrolyte capsules as carriers for protein delivery

A reversible drug delivery system based on spontaneous deposition of a model protein into preformed microcapsules has been demonstrated for protein delivery applications. Layer-by-Layer assembly of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) onto polystyrene sulfonate (PSS) doped CaCO3 particles, followed by core removal yielded intact hollow microcapsules having a unique property to induce spontaneous deposition of bovine serum albumin (BSA) at pH below its isoelectric point of 4.8, where it was positively charged. These capsules showed reversible pH dependent open and closed states to fluorescence labeled dextran (FITC-Dextran) and BSA (FITC-BSA). The loading capacity of BSA increased from 9.1 x 10(7) to 2.03 x 10(8) molecules per capsule with decrease in pH from 4.5 to 3.The loading of BSA-FITC was observed by confocal laser scanning microscopy (CLSM), which showed homogeneous distribution of protein inside the capsule. Efficient loading of BSA was further confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM).The interior capsule concentration was as high as 209 times the feeding concentration when the feeding concentration was increased from 1 to 10 mg/ml. The deposition was initially controlled by spontaneous loading mechanism at lower BSA concentration followed by diffusion controlled loading at higher concentration; which decreased the loading efficiency from 35% to 7%. Circular dichroism (CD) measurements and Fourier transform infrared spectroscopy (FTIR) confirmed that there was no significant change in conformation of released BSA in comparison with native BSA. The release was initially burst in the first 0.5 h and sustained up to 5 h. The hollow capsules were found to be biocompatible with mouse embryonic fibroblast (MEF) cells during in vitro cell culture studies. Thus these pH sensitive polyelectrolyte microcapsules may offer a promising delivery system for water soluble proteins and peptides. (C) 2010 Elsevier B.V. All rights reserved.

Isolation and partial characterization of sheep plasma α1-mucoprotein

1. 1. Sheep plasma α1-mucoprotein was isolated in an electrophoretically homogeneous state by a combination of ammonium sulphate saturation, isoelectric precipitation and preparative agar electrophoresis in a yield of approx. 150 mg/l of plasma. 2. 2. The mucoprotein was water-soluble, non-coagulable on heating at 100°, not precipitable by 1.8 M perchloric acid, 10% trichloroacetic acid but precipitable by saturated ammonium sulphate solution, 0.6 M sulfosalicylic acid and 5% phosphotungstic acid in 2 N HCl. It had E1 cm1 % value of 9.57 at 278 mμ in water, refractive-index index increment 1.9·10-4 (g/l) in water, isoelectric point at pH 4.45 (sodium acetate-acetic acid buffer) and was homogeneous in pH range 4.0-11.5 but at pH values 2.6 and 3.5 showed some dissociation. 3. 3. The mucoprotein had the following chemical composition: Nitrogen, 12.4%; polypeptide, 77.4%; total hexose (only mannose and galactose), 7.1%; fucose, 1.0%; glucosamine, 4.9% and sialic acid, 4.8%. It had no N-terminal amino acid.

A three-dimensional solution for plates and laminates

A general three-dimensional solution is presented for statics and dynamics of plates, homogeneous or laminated, of orthotropic materials. The solution is in series form. Using parts of the general solution a variety of problems, especially of rectangular configurations, can be solved. As Mindlin's approximate analysis for vibration of thick plates is often adequate for specific practical purposes, a general solution for Mindlin's analysis is also given.

Endo-polygalacturonate lyase of Cytophaga johnsonii

An extracellular endopolygalacturonate lyase of Cytophaga johnsonii was purified from the culture filtrate. It appeared to be homogeneous as judged by polyacrylamide gel electrophoresis at pH 8.6 as well as pH 4.3. The purified enzyme had a pH optimum around 9.0 and required Ca++ ions for its maximum activity. The apparent Kmfor polygalacturonic acid was found to be 0.22%. Both paper and column chromatography indicated formation and accumulation of an unsaturated monomer along with unsaturated di-, tri-, tetra- and pentamers from polygalacturonic acid by the enzyme action, indicating that the enzyme cleaved the substrate randomly in a non-hydrolytic manner. The glycosidic linkage next to the non-reducing end of polygalacturonic acid was not resistant to attack by this enzyme unlike in other known polygalacturonate lyases.

Generalization of Dynkin's Identity and Some Applications

Let X(t) be a right continuous temporally homogeneous Markov pro- cess, Tt the corresponding semigroup and A the weak infinitesimal genera- tor. Let g(t) be absolutely continuous and r a stopping time satisfying E.( S f I g(t) I dt) < oo and E.( f " I g'(t) I dt) < oo Then for f e 9iJ(A) with f(X(t)) right continuous the identity Exg(r)f(X(z)) - g(O)f(x) = E( 5 " g'(s)f(X(s)) ds) + E.( 5 " g(s)Af(X(s)) ds) is a simple generalization of Dynkin's identity (g(t) 1). With further restrictions on f and r the following identity is obtained as a corollary: Ex(f(X(z))) = f(x) + k! Ex~rkAkf(X(z))) + n-1E + (n ) )!.E,(so un-1Anf(X(u)) du). These identities are applied to processes with stationary independent increments to obtain a number of new and known results relating the moments of stopping times to the moments of the stopped processes.

Investigations of a two-stage pulse tube cryocooler operating down to 2.5K

A two-stage pulse tube cryocooler (PTC) which produces a no-load temperature of similar to 2.5 K in its second stage at an operating frequency of 1.6 Hz has been designed and fabricated. The second stage of the system provides a refrigeration power of similar to 250 mW at 5.0 K. The system uses stainless steel meshes (mesh size 200) along with lead (Pb) granules and combinations of Pb, Er3Ni, and HoCu2 as the first and second stage regenerator materials, respectively. Experimental studies have been carried out on different pulse tube configurations by varying the dimensions of the pulse tubes and regenerators to arrive at the best one, which leads to the lowest no-load second stage cold head temperature. Using this configuration, detailed experimental studies have been conducted by varying the volume percentage ratios of the second stage regenerator materials such as HoCu2, Er3Ni, and Pb (with an average grain size of similar to 250 mu m). This article presents the results of our experimental studies on cryocoolers with the regenerator material arranged in layered structures. Comparative studies have also been presented for specific cases where the regenerator materials are arranged as a homogeneous mixture in the second stage. The experimental results clearly indicate that the design of PTCs should use only layered structures of regenerator materials and not homogenous mixtures.