Effect of solvent environment on the Photophysics of a newly synthesized bioactive 7-oxy(5-selenocyanato-pentyl)-2H-1-benzopyran-2-one

The synthesis and solvatochromic behavior of the compound, 7-oxy(5-selenocyanato-pentyl)-2H-1-benzopyran-2-one (PCM), a pervasive, bioactive coumarin derivative, which is expected to possess antioxidative properties and other important therapeutic activities of significant potency with low systematic toxicity, have been reported employing steady state and time resolved fluorescence techniques. Spectroscopic studies reveal that the solvatochromic behavior of the probe depends not only on the polarity of the medium but also on the hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction of PCM in polar solvents modulated the order of the two close-lying lowest singlet states. The photophysical response of PCM in different solvents has been explained considering solute-solvent interactions. To corroborate these results, we performed the ground-state geometry, lowest energy transition and the UV–vis spectrum of PCM using the density functional theory (DFT) and the time-dependent density functional theory (TD–DFT) at B3LYP/6-31G^? level. We found excellent correlation between the predicted and experimental spectral data, providing a useful tool in the design of new fluorogenic probes having potential therapeutic activity.     

A new approach to modified gravity models

We investigate f (R)-gravity models performing the ADM-slicing of standard General Relativity. We extract the static, spherically-symmetric vacuum solutions in the general case, which correspond to either Schwarzschild de-Sitter or Schwarzschild anti-de-Sitter ones. Additionally, we study the cosmological evolution of a homogeneous and isotropic universe, which is governed by an algebraic and not a differential equation. We show that the universe admits solutions corresponding to acceleration at late cosmological epochs, without the need of fine-tuning the model-parameters or the initial conditions.     

Influence of the nanofiller type and content on permeation characteristics of multifunctional NR nanocomposites and their modeling

Along with other properties, superior gas permeation behavior would impart an extra dimension to multifunctional natural rubber (NR) nanocomposites used in various applications, like tires. For the first time, the impact on thermodynamics and kinetics of oxygen transport has been evaluated for nano, micro, and dual filler based multifunctional NR nanocomposites through oxygen permeation studies at three different temperatures. It is seen that, the kinetics is less affected by platelet like nanofillers, while the thermodynamics and eventual permeability are not altered much by fibrous nanofillers. The permeability of the nanocomposites decreased in the presence of nanofillers due to high aspect ratio and exquisite dispersion, as ascertained from morphological studies, which caused increment in tortuosity and the reduction in free volume. Relative permeabilities were compared to predictions of existent permeation models and a novel function was successfully introduced to address deviations in a model. Finally, nearly 60% decrement in permeability of dual filler based nanocomposites explained by the formation of zeta potential driven filler associations indicate potency in development of thinner, but stronger and more durable multifunctional materials with longer air retention capabilities. These could be applied in tire research to reduce material, energy costs and increase fuel efficiencies. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of the molecular weight of polyacrylamide fractions by osmometry

The polymerization of acrylamide, initiated with permanganate/oxalic acid, has been studied at 35 ± 0.2 in an aqueous medium under nitrogen. Samples of polyacrylamide were fractionated by the triangular fractionation method using methanol as non-solvent. Molecular weights of the fractions have been determined by viscometry and osmometry. Integral and differential distribution curves were plotted using the fractionation data. The narrow molecular weight distribution for high conversion polymers has been discussed. For fractionated samples of polyacrylamide in water at 30°, the equation $\text{[η]}{}_{\mathrm{ml/g}}\text{= 6.5 × 10}{}^{\mathrm{?3}}\text{M}{}_{\mathrm{n}}{}^{0.82}$ is applicable for the molecular weight range 4 × 10⁴ to 127 × 10⁴. This equation is very similar to the equation $\text{[η]}{}_{\mathrm{ml/g}}\text{= 6.31 × 10}{}^{\mathrm{?3}}\text{M}{}_{\mathrm{/}}{}^{0.80}$ of Scholtan. Other parameters (osmotic second virial coefficient and unperturbed dimension) have also been evaluated.     

Kinetics and mechanism of the reactions ofcis-tetraaminediaqua-cobalt(III) with nitrite,azide and salicylate ions in aqueous acidic media

Summary Kinetic studies of the anation of the title complex by NO ₂ ^– show that it occurs in a stepwise manner leading to thecis-dinitro-complex both steps having a common rate equation:-d[complex]/dt = a[NO ₂ ^– ]/{[NO ₂ ^– ] + b}. The variation ofpseudo-first-order rate constant (k_obs) with [NO ₂ ^– ] indicates that the reaction proceeds through ion-pair interchange path. Activation parameters calculated by the Eyring equation are: H ₁ = (65±7) kJ mol^–1 and S ₁ = (–82±11) JK^–1 mol^–1 for the formation of [Co(NH₃)₄(NO₂)(H₂O)]²⁺, and H ₂ = (97±1) kJ mol^–1 and S ₂ = (6±2) JK^–1 mol^–1 for the formation of [Co(NH₃)₄(NO₂)₂]⁺. Anation of the title complex by N ₃ ^– at pH 4.1 also occurs in a stepwise manner ultimately producing thecis-diazido species. At a fixed pH the reaction shows a first-order dependence on [N ₃ ^– ] for each step. pH-variation studies at a fixed [N ₃ ^– ] show that the hydroxoaqua-form of the complex reactsca. 16 times faster than the diaqua form. Evidence is presented for an ion-pair preequilibrium at high ionic strength (I = 2.0 mol dm^–3). Activation parameters obtained from temperature variation studies are: H ₁ = (121±1) kJ mol^–1 and S ₁ = (104±3) JK^–1 mol^–1 (for the first step anation), and H ₂ = (111±2) kJ mol^–1 and S ₂ = (74±9) JK^–1 mol^–1 (for the second step anation). The reaction ofcis-tetraaminediaquacobalt(III) ion with salicylate (HSal^–) has been studied in aqueous acidic medium in the temperature range 39.8–58.2°C. The reaction is biphasic corresponding to the anation of two salicylate ions. The kinetic results for the first phase reaction are compatible with the equation: k_obs = k_IPQ[HSal^–]/(1 + Q[HSal^–]) where Q denotes ion-pair formation constant and k_IP is the first-order rate constant for the interchange reaction. The activation parameters obtained from the temperature dependence of rate are: H = (138±3) kJ mol^–1 and S = (135±4) JK^–1 mol^–1. The reaction seems to take place by a dissociative interchange mechanism.     

Charge carriers dynamics in PEO + NaSCN polymer electrolytes

Sodium-ion-conducting poly(ethylene oxide) (PEO)-based solid polymer electrolyte films mixed with salt sodium thiocyanate (NaSCN) have been prepared by solution-cast method. Films were characterized in detail using optical microscopy, differential scanning calorimetry, and impedance spectroscopy. The drop in ionic conductivity with increasing salt concentration is supported by a decrease in number of charge carriers. Dielectric constant is supported by decreases in numbers of charge carriers and increase in mobility. The maximum ionic conductivity and number of charge carriers for material are found 9.86 × 10^?6 S/m and 1.21 × 10²⁰, respectively, for weight % ratio (95:05) of PEO:NaSCN polymer salt complex. The maximum mobility of material is found 2.58 × 10^?6 m²/Vs for weight % ratio (80:20) of PEO:NaSCN polymer salt complex.     

Assessment of the metabolic profile in Type 2 diabetes mellitus and hypothyroidism through proton MR spectroscopy

The metabolic changes in the brain of patients affected with Type 2 diabetes mellitus (DM) alone, both Type 2 DM and hypothyroidism and hypothyroidism only were investigated using proton magnetic resonance spectroscopy ((1)H MRS). Single-voxel spectroscopy was carried out in right and left frontal lobe white matter, left parietal white matter and left occipital gray matter. Choline (Cho)/creatine (Cr) value was found to be increased in the left occipital gray matter of the subjects affected with Type 2 DM and both Type 2 DM and hypothyroidism as compared to controls. No significant change in the Cho/Cr value in the occipital gray matter was observed in hypothyroid subjects as compared to controls. However, they showed an increased level of Cho/Cr in the frontal white matter. High Cho is associated with altered membrane phospholipid metabolism. The high Cho in frontal white matter in hypothyroids and occipital gray matter in diabetic patients suggests that, though both the diseases are endocrine disorders, they differ from each other in terms of regional brain metabolite changes.