Fluctuation quench and hydrophobic collapse of polymers and biopolymers in water-DMSO binary mixture at low DMSO concentration

Binary mixtures have strong influence on activities of polymers and biopolymers even at low cosolvent concentration. Among the several aqueous binary mixtures studied, water-DMSO especially stands out for its unusual behavior at certain specific concentrations of DMSO. In the present work, we study the effect of water-DMSO binary mixture on polymers and biopolymers by taking a simple linear hydrocarbon chain of intermediate length (n = 30) and the protein lysozyme, respectively. We find that at a mole fraction of 0.05 of DMSO (x(DMSO) = 0.05) in aqueous solution, the hydrocarbon chain adopts the collapsed conformation as the most stable and rigid state. In this case of 0.05 mole fraction of DMSO in bulk, the DMSO concentration in the first hydration layer around the polymer is found to be as large as 17%. Formation of such hydrophobic environment around the polymer is the reason for the collapsed state gaining so much stability. Interestingly, similar quench of conformational fluctuation is also observed for the protein investigated. It is observed that in the case of alkane polymer chains, long wavelength fluctuation gets easily quenched, the polymer being purely hydrophobic. However, in case of the protein, quench of fluctuation is prominent only at the hydrophobic surface, and quench of long wavelength fluctuation becomes insignificant for the full protein. As protein contains both hydrophobic and hydrophilic moieties, the extent of quench of conformational fluctuation with respect to that in pure water is almost half for the biopolymer complex (16.83%) than the same for pure hydrophobic polymer chain (32.43%).

Effect of convection and viscoelasticity on spinodal decomposition in fluids

Current analytical work on the effect of convection and viscoelasticity on the early and late stages of spinodal decomposition is briefly described. In the early stages, the effect of viscoelastic stresses was analysed using a simple Maxwell model for the stress, which was incorporated in the Langevin equation for the momentum field. The viscoelastic stresses are found to enhance the rate of decomposition. In the late stages, the pattern formed depends on the relative composition of the two species. Droplet spinodal decomposition occurs when the concentration of one of the species is small. Convective transport does not have a significant effect on the growth of a single droplet, but it does result in an attractive interaction between non - Brownian droplets which could lead to coalescence. The effect of convective transport for the growth of random interfaces in a near symmetric quench was analysed using an 'area distribution function', which gives the distribution of surface area of the interface in curvature space. It was found that the curvature of the interface decreases proportional to t in the late stages of spinodal decomposition, and the surface area also decreases proportional to t.

Influence of the Methane-Zeolite A Interaction Potential on the Concentration Dependence of Self-diffusivity

Studies on the diffusion of methane in a zeolite structure type LTA (as per IZA nomenclature) have indicated that different types of methane zeolite potentials exist in the literature in which methane is treated within the united-atom model. One set of potentials, referred to as model A, has a methane oxygen diameter of 3.14 angstrom, while another set of potential parameters, model B, employs a larger value of 3.46 angstrom. Fritzsche and co-workers (1993) have shown that these two potentials lead to two distinctly different energetic barriers for the passage of methane through the eight-ring window in the cation-free form of zeolite A. Here, we compute the variation of the self-diffusivity (D) with loading (c) for these two types of potentials and show that this slight variation in the diameter changes the concentration dependence qualitatively: thus, D decreases monotonically with c for model A, while D increases and goes through a maximum before finally decreasing for model B. This effect and the surprising congruence of the diffusion coefficients for both models at high loadings is examined in detail at the molecular level. Simulations for different temperatures reveal the Arrhenius behaviour of the self-diffusion coefficient. The apparent activation energy is found to vary with the loading. We conclude that beside the cage-to-cage jumps, which are essential for the migration of the guest molecules, at high concentrations migration within the cage and guest guest interactions with other molecules become increasingly dominant influences on the diffusion coefficient and make the guest zeolite interaction less important for both model A and model B.

Effect of Pt on interdiffusion and mechanical properties of the gamma and gamma ` phases in the Ni-Pt-Al system

The effect of Pt on the growth kinetics of the gamma'-Ni(Pt)](3)Al ordered intermetallic phase and the gamma- Ni(Pt, Al) solid solution diffusion rates of the species, hardness and elastic modulus was examined by employing the diffusion couple experimental technique. Experiments were conducted by using the beta-Ni(Pt)Al phase and Ni(Pt) alloy couples, each of which had a fixed amount of Pt (5, 10 and 15 at. %) in both the end members so that the Pt content is more or less constant throughout the interdiffusion zone. The results suggest that the growth kinetics of both phases and the average effective interdiffusion coefficients of Ni and Al increase with the increase in Pt content. Nanoindentation studies across the compositional gradients show that the mechanical properties of the intermetallic phase in the superalloy are relatively insensitive to the presence of Pt but are more sensitive to the Ni/Al ratio. In contrast, the marked variation in the hardness of the gamma phase were noted, increasing markedly with Al concentration in a given couple and also increasing with increasing Pt content. Possible causes for the observed variations are discussed.

Theoretical estimation of electromigration in metallic carbon nanotubes considering self-heating effect

In this paper, we estimate the solution of the electromigration diffusion equation (EMDE) in isotopically pure and impure metallic single-walled carbon nanotubes (CNTs) (SWCNTs) by considering self-heating. The EMDE for SWCNT has been solved not only by invoking the dependence of the electromigration flux on the usual applied static electric field across its two ends but also by considering a temperature-dependent thermal conductivity (κ) which results in a variable temperature distribution (T) along its length due to self-heating. By changing its length and isotopic impurity, we demonstrate that there occurs a significant deviation in the SWCNT electromigration performance. However, if κ is assumed to be temperature independent, the solution may lead to serious errors in performance estimation. We further exhibit a tradeoff between length and impurity effect on the performance toward electromigration. It is suggested that, to reduce the vacancy concentration in longer interconnects of few micrometers, one should opt for an isotopically impure SWCNT at the cost of lower κ, whereas for comparatively short interconnects, pure SWCNT should be used. This tradeoff presented here can be treated as a way for obtaining a fairly well estimation of the vacancy concentration and mean time to failure in the bundles of CNT-based interconnects. © 2012 IEEE.

Effect of Interfacial Microstructure of Adsorbed Poly(ethylene glycol) Monooleate on Steel Substrate on Sliding Friction in Oil in Water Emulsion

The concentration of a nonionic surfactant and water pH were varied in an oil-in-water emulsion to minimize the friction coefficient between a steel ball sliding on a steel flat. At a surfactant concentration near the CMC (critical micelle concentration) the oil droplet size was found to be minimum. In this paper we study the microstructure of the surfactant molecules self-assembled on the steel substrate in water to comment on the ability of the surfactant aggregate to attract and retain oil. We find that a near semicylindrical hemimiceller microstructure with hydrocarbon tails projecting into bulk water as obtained at CMC in near neutral water is best able to capture and retain oil in yielding a low coefficient of friction.

Effect of high gold salt concentrations on the size and polydispersity of gold nanoparticles prepared by an extended Turkevich-Frens method

The Turkevich-Frens synthesis starting conditions are expanded, ranging the gold salt concentrations up to 2 mM and citrate/gold(III) molar ratios up to 18:1. For each concentration of the initial gold salt solution, the citrate/gold(III) molar ratios are systematically varied from 2:1 to 18:1 and both the size and size distribution of the resulting gold nanoparticles are compared. This study reveals a different nanoparticle size evolution for gold salt solutions ranging below 0.8 mM compared to the case of gold salt solutions above 0.8 mM. In the case of Au3+]<0.8 mM, both the size and size distribution vary substantially with the citrate/gold(III) ratio, both displaying plateaux that evolve inversely to Au3+] at larger ratios. Conversely, for Au3+]>= 0.8 mM, the size and size distribution of the synthesized gold nanoparticles continuously rise as the citrate/gold(III) ratio is increased. A starting gold salt concentration of 0.6 mM leads to the formation of the most monodisperse gold nanoparticles (polydispersity index<0.1) for a wide range of citrate/gold(III) molar ratios (from 4:1 to 18:1). Via a model for the formation of gold nanoparticles by the citrate method, the experimental trends in size could be qualitatively predicted:the simulations showed that the destabilizing effect of increased electrolyte concentration at high initial Au3+] is compensated by a slight increase in zeta potential of gold nanoparticles to produce concentrated dispersion of gold nanoparticles of small sizes.

Effect of lipopolysaccharide on alteration of phospholipids and their fatty acid composition in spleen and thymus by in vitro metabolic labeling

Lipopolysaccharide (LPS) is an endotoxin, a potent stimulator of immune response and induction of LPS leads to acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). ARDS is a life-threatening disease worldwide with a high mortality rate. The immunological effect of LPS with spleen and thymus is well documented; however the impact on membrane phospholipid during endotoxemia has not yet been studied. Hence we aimed to investigate the influence of LPS on spleen and thymus phospholipid and fatty acid composition by 32P]orthophosphate labeling in rats. The in vitro labeling was carried out with phosphate-free medium (saline). Time course, LPS concentration-dependent, pre- and post-labeling with LPS and fatty acid analysis of phospholipid were performed. Labeling studies showed that 50 mu g LPS specifically altered the major phospholipids, phosphatidylcholine and phosphatidylglycerol in spleen and phosphatidylcholine in thymus. Fatty acid analysis showed a marked alteration of unsaturated fatty acids/saturated fatty acids in spleen and thymus leading to immune impairment via the fatty acid remodeling pathway. Our present in vitro lipid metabolic labeling study could open up new vistas for exploring LPS-induced immune impairment in spleen and thymus, as well as the underlying mechanism.

The effect of minor addition of Ni on the microstructural evolution and mechanical properties of suction cast Al-0.14 at. pct Sc binary alloy

Aluminum scandium binary alloys represent a promising precipitation-hardening alloy system. However, the hardness of the binary alloys decreases with the rapid coarsening of Al3Sc precipitate during high-temperature aging. In the current study, we report a new approach to compensate for the loss of mechanical properties by combining rapid solidification with very small ternary addition of transition metal Ni. This addition yields dispersion, and at a critical concentration improves the mechanical properties. We explore additions of a maximum of 0.06 at. pct of Nickel to a binary Al-0.14 at. pct Sc alloy, which yield nickel-rich dispersions. We report two kinds of biphasic dispersions containing AlNi2Sc/Al9Ni2 and alpha-Al/Al9Ni2 phase combinations. The maximum improvement in mechanical properties occurs with the addition of 0.045 at. pct Ni with a yield strength of 239 +/- A 7 MPa for an aging treatment at 583 K (310 A degrees C) for 15 hours. DOI: 10.1007/s11661-013-1624-z (C) The Minerals, Metals & Materials Society and ASM International 2013

Influence of steric effect on the structural aspects of N,N `,N `'-triarylguanidine derived six-membered C,N] palladacycles

Guanidine derived six-membered C,N] palladacycles of the types (C,N)Pd(mu-OC(O)R)](2) (1a-d), (C,N)Pd(mu-Br)](2) (2a,b), cis-(C,N)PdBr(L)] (3a-d, 4, and 5), and ring contracted guanidine derived five-membered C,N] palladacycle, (C,N)PdBr(C NXy)] (6) were prepared in high yield following the established methods with a view aimed at understanding the influence of the substituents on the aryl rings of the guanidine upon the solid state structure and solution behaviour of palladacycles. Palladacycles were characterised by microanalytical, IR, NMR and mass spectral data. The molecular structures of 1a, 1c, 2a, 2b, 3a, 3c, 3d, and 4-6 were determined by single crystal X-ray diffraction data. Palladacycles 1a and 1c were shown to exist as a dimer in transoid in-in conformation in the solid state but as a mixture of a dimer in major proportion and a monomer (kappa(2)-O,O'-OAc) in solution as deduced from H-1 NMR data. Palladacycles 2a and 2b were shown to exist as a dimer in transoid conformation in the solid state but the former was shown to exist as a mixture of a dimer and presumably a trimer in solution as revealed by a variable temperature H-1 NMR data in conjunction with ESI-MS data. The cis configuration around the palladium atom in 3a, 3c, and 3d was ascribed to steric influence of the aryl moiety of =NAr unit and that in 4-6 was ascribed to antisymbiosis. The solution behaviour of 3d was studied by a variable concentration (VC) H-1 NMR data.

Analysis of size quantization and temperature effects on the threshold voltage of thin silicon film double-gate metal-oxide-semiconductor field-effect transistor (MOSFET)

In this paper, we analyze the combined effects of size quantization and device temperature variations (T = 50K to 400 K) on the intrinsic carrier concentration (n(i)), electron concentration (n) and thereby on the threshold voltage (V-th) for thin silicon film (t(si) = 1 nm to 10 nm) based fully-depleted Double-Gate Silicon-on-Insulator MOSFETs. The threshold voltage (V-th) is defined as the gate voltage (V-g) at which the potential at the center of the channel (Phi(c)) begins to saturate (Phi(c) = Phi(c(sat))). It is shown that in the strong quantum confinement regime (t(si) <= 3nm), the effects of size quantization far over-ride the effects of temperature variations on the total change in band-gap (Delta E-g(eff)), intrinsic carrier concentration (n(i)), electron concentration (n), Phi(c(sat)) and the threshold voltage (V-th). On the other hand, for t(si) >= 4 nm, it is shown that size quantization effects recede with increasing t(si), while the effects of temperature variations become increasingly significant. Through detailed analysis, a physical model for the threshold voltage is presented both for the undoped and doped cases valid over a wide-range of device temperatures, silicon film thicknesses and substrate doping densities. Both in the undoped and doped cases, it is shown that the threshold voltage strongly depends on the channel charge density and that it is independent of incomplete ionization effects, at lower device temperatures. The results are compared with the published work available in literature, and it is shown that the present approach incorporates quantization and temperature effects over the entire temperature range. We also present an analytical model for V-th as a function of device temperature (T). (C) 2013 AIP Publishing LLC.

The effect of Sb on the electrical and magnetic properties of Ni-Zn ferrites prepared by sol-gel autocombustion method

Polycrystalline Ni-Zn ferrites with a well-defined composition of Ni0.4Zn0.6Fe2-xSbxO4 synthesized using sol-gel method. Morphological characterizations on the prepared samples were performed by high resolution transmission electron and field emission scanning electron microscopy. The powders were densified using microwave sintering method. The room temperature complex permittivity (epsilon' and epsilon aEuro(3)) and permeability (mu' and mu aEuro(3)) were measured over a wide frequency range from 1 MHz-1.8 GHz. The real part of permittivity varies as `x' concentration increases and the resonance frequency was observed at much higher frequencies and there is a significant decrease in the loss factor (tan delta). The electrical resistivity and permeability of NiZn ferrites increased with an increase of Sb content. As the concentration of `x' increases from 0 to 0.08 the saturation magnetisation decreases. The saturation magnetization (M-s) a parts per thousand aEuro parts per thousand 52.211 A.m(2)/Kg for x = 0 at room temperature. The room temperature electro paramagnetic resonance (EPR) were studied.

Effect of Gd3+ on dielectric and magnetic properties of Y3Fe5O12

The Gd3+ doped Y3-xGdxFe5O12 (x=0.0, 0.05, 0.15, and 0.25) nanopowders were prepared using modified sol-gel route. The structural characterizations such as X-ray diffraction, transmission electron microscopy has been carried out. The nanopowders were sintered at 700 degrees C/3 h. The lattice parameters and density of the samples were increased with an increase of Gd3+ concentration. The microstructure was analyzed using atomic force microscopy. The room temperature dielectric (epsilon' and epsilon `') and magnetic (mu' and mu `') properties were measured in the frequency range 5-50 GHz. with Gd3+ the dielectric properties were enhanced, but there is a decrease in the magnetic properties. The room temperature magnetization studies were carried out up to 1.5 T. the saturation and remnant magnetization were decreased with an increase of gadolinium concentration. These garnets have low permeability, low losses and a broad distribution of FMR line width which makes them a promising material for microwave devices can be used in the high frequency range i.e. up to 50 GHz. (C) 2013 Elsevier BM. All rights reserved.

The effect of Se doping on spectroscopic and electrical properties of GeTe

Selenium doped thin films of GeTe alloys were investigated for their structural modifications by X-ray Diffraction, Fourier Transform Infrared Spectroscopy, X-ray photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The band gap increase from 0.69 to 1.10 eV with increasing Se addition signifies the possibility of band gap tuning in the material. Disorder decreases, band widens and conductivity saturates about 0.20 at.% of Se addition. Structural changes are explained by the bond theory of solids. The as-deposited films are amorphous and 0.50 at.% Se alloy forms a homogeneous amorphous phase with a mixture of Ge-Se and Te-Se bonds. The XPS core level spectra and Raman spectra investigation clearly indicate the formation of Ge-Se, GeTe2 and Te-Se bonds with Se addition. Crystallization temperature is found to be increasing with Se and the 0.10 at.% Se alloy is found to have a higher resistance contrast compared to other Se concentration alloys. Up to 0.10 at.% of Se addition can enhance GeTe phase change memory properties. (C) 2013 Elsevier B.V. All rights reserved.

Analysis of 20alpha-hydroxysteroid dehydrogenase expression in the corpus luteum of the buffalo cow: effect of prostaglandin F2-alpha treatment on circulating 20alpha-hydroxyprogesterone levels

Background: During female reproductive cycles, a rapid fall in circulating progesterone (P4) levels is one of the earliest events that occur during induced luteolysis in mammals. In rodents, it is well recognized that during luteolysis, P4 is catabolized to its inactive metabolite, 20alpha-hydroxyprogesterone (20alpha-OHP) by the action of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) enzyme and involves transcription factor, Nur77. Studies have been carried out to examine expression of 20alpha-HSD and its activity in the corpus luteum (CL) of buffalo cow. Methods: The expression of 20alpha-HSD across different bovine tissues along with CL was examined by qPCR analysis. Circulating P4 levels were monitored before and during PGF2alpha treatment. Expression of 20alpha-HSD and Nur77 mRNA was determined in CL at different time points post PGF2alpha treatment in buffalo cows. The chromatographic separation of P4 and its metabolite, 20alpha-OHP, in rat and buffalo cow serum samples were performed on reverse phase HPLC system. To further support the findings, 20alpha-HSD enzyme activity was quantitated in cytosolic fraction of CL of both rat and buffalo cow. Results: Circulating P4 concentration declined rapidly in response to PGF2alpha treatment. HPLC analysis of serum samples did not reveal changes in circulating 20alpha-OHP levels in buffalo cows but serum from pseudo pregnant rats receiving PGF2alpha treatment showed an increased 20alpha-OHP level at 24 h post treatment with accompanying decrease in P4 concentration. qPCR expression of 20alpha-HSD in CL from control and PGF2alpha-treated buffalo cows showed higher expression at 3 and 18 h post treatment, but its specific activity was not altered at different time points post PGF2alpha treatment. The Nur77 expression increased several fold 3 h post PGF2alpha treatment similar to the increased expression observed in the PGF2alpha-treated pseudo pregnant rats which perhaps suggest initiation of activation of apoptotic pathways in response to PGF2alpha treatment. Conclusions: The results taken together suggest that synthesis of P4 appears to be primarily affected by PGF2alpha treatment in buffalo cows in contrast to increased metabolism of P4 in rodents.