On electromagnetic wave propagation in fractional space

The vector Helmholtz equation in fractional space can describe the complex phenomenon of wave propagation in fractal media. With this view, a generalized Helmholtz equation for wave propagation in fractional space is established and its analytical solution is obtained. The special case for integer space is recovered and the results are in exact agreement with those obtained in the literature.     

Model for Conformational Relaxation of Flexible Conjugated Polymers: Application to p‐Phenylenevinylene Trimers in Nonpolar Solvents

Photoexcitation of flexible conjugated polymers is invariably followed by a fast conformational/torsional relaxation towards a configuration favouring coplanarity of the conjugated segments. In general, the experimental relaxation rate constant (k_CR) depends on the solvent viscosity (η) and temperature (T), and is not proportional to T/η. A theory capable of explaining the observed dependence of k_CR on T and η over a wide range of these variables is not available. This gap is filled here by presenting a stochastic model that includes the participation of the oligomer side chain in storing and dissipating the stresses induced by photoexcitation. The model is able to account for the softening of solute–solvent interactions and its predictions are found to be in excellent agreement with the observed relaxation rate constants of a series of substituted p‐phenylenevinylene trimers [ChemPhysChem 2009 , 10, 448–454] on T, η and the size of the side‐chains.     

Micellar properties of a phenothiazine drug in presence of additives

In this study micellar properties of a phenothiazine drug, promazine hydrochloride, at different concentrations of NaCl and cationic surfactants (conventional as well as gemini surfactants) are presented. The parameters studied are cmc (critical micelle concentration), X ₁ (mole fraction of surfactant in micelles), f ₁, f ₂ (activity coefficients) and ΔG _ex (excess free energy). Cl⁻ ions (from NaCl) get adsorbed on the micellar head groups and, by decreasing the repulsion among them, lower the cmc. Surfactants form mixed micelles with the drug and the values of X ₁, X ₁^id (mole fraction of the surfactant in micelles in ideal state), interaction parameter β, f ₁ and f ₂ all suggest non-ideal but synergistic nature. The ΔG _ex values are negative indicating that the mixed state is more stable than the pure micelle state. The article is published in the original.     

Small polaron hopping conduction mechanism in Fe doped LaMnO3

The structural and electrical transport properties of LaMn(1-x)Fe(x)O(3) (0.1 ≤ x ≤ 0.6) bulk samples have been investigated. The powder x-ray diffraction patterns at room temperature show that all samples are formed in single phase. The temperature dependent resistivity data have been fitted with the Mott's variable-range hopping (VRH) model for an entire studied range of the temperature (77-300 K) to calculate the hopping distance (R(h)) and the density of states at Fermi level (N(E(F))). It is found that all parameters vary systematically with the increase in Fe concentration. Moreover, the resistivity data were also fitted in the small polaron hopping (SPH) model. The non-adiabatic SPH conduction mechanism is followed by all samples. This type conduction mechanism is far accompanied by subtle electronically induced structural changes involving in Fe-O-Fe and Fe-O-Mn bond angles and bond lengths. Thus we suggest that the transport properties can be explained according to the additional localization of charge carriers induced by Fe doping.     

Antimycobacterial and antioxidant activities of reserpine and its derivatives

In view of the attributed medicinal properties of reserpine, a number of acyl reserpine derivatives were prepared and tested for antimycobacterial activity against Mycobacterium tuberculosis, strain H(37)Rv and antioxidant activities. The results indicated that in the case of antimycobacterial activity, 10 out of 18 derivatives caused more inhibition than that caused by reserpine itself. The results of antioxidant activity revealed that acylation in benzene ring of reserpine decreases the percentage inhibition of DPPH in all the derivatives compared to the parent compound (1).     

Estimation of diffusive boundary layer thickness in studies involving diffusive gradients in thin films (DGT)

Recent laboratory experiments and field investigations involving diffusive gradients in thin films (DGT) have shown that the thickness (delta) of the diffusive boundary layer (DBL), which can affect the accuracy of the technique, is generally not negligible. Accordingly, the determination of delta has become a matter of considerable practical importance. Though the problem has been addressed in the recent literature, there is room for some improvement. An expression for estimation of delta is presented here, and a practical procedure for determining delta and the concentration of DGT-labile species from sparse experimental data is proposed and illustrated by analyzing data from four experiments with DGT samplers of different diffusive gel thicknesses.     

Mixed Micellization and Interfacial Properties of Nonionic Surfactants with the Phenothiazine Drug Promazine Hydrochloride at 30 °C

In the present work, the micellization and adsorption behaviors of mixed systems containing an amphiphilic phenothiazine drug, promazine hydrochloride (PMZ) and nonionic surfactants in aqueous media at different mole fractions of nonionic surfactants (?? ₁) were investigated at 30?°C by surface tension measurements. The critical micelle concentrations of the mixtures fall between the values of the individual components, which indicates nonideal mixing. With Tritons the interactions are repulsive at low mole fractions. At high ?? ₁ the mixing becomes almost ideal. On the basis of regular solution theory, the micellar mole fractions of surfactants ( $X_{1}^{m}$ ) and interaction parameter (?? ^m ) were evaluated, while their interfacial mole fractions ( $X_{1}^{\sigma} $ ) and interaction parameters at the interface (?? ^?? ) were calculated using Rosen??s model. The results indicate that the surfactant??s contribution is greater than that of the drug both at the interface and in micelles. The short and rigid hydrophobic structure of the drug resists its participation in micelle formation more than in the monolayer, leading to $X_{1}^{m}<X_{1}^{\sigma}$ . Values of the surface excess (?? _max) and minimum area per head group (A _min) indicate attractive interactions. ?? _max increases and A _min decreases as the surfactant mole fraction increases.     

Stochastic comparison of residual lifetime mixture models

In this paper, we consider stochastic comparisons of mixtures ($F^1$ and $G^1$) of residual life distributions ($F_{\theta }$ and $G_{\theta }$, $\theta >0$) arising out of different baseline distributions ($F$ and $G$) and different mixing distributions ($H_1$ and $H_2$). Under certain conditions on $F$, $G$, $H_1$ and $H_2$, we establish that the distributions $F^1$ and $G^1$ are stochastically ordered. Further, we make stochastic comparison of mixture distribution $F^1$ with the distribution of residual lifetime at random time ${\Theta }_1$.     

Narrow 3-photon autoionizing resonances in Tl and Yb

Narrow autoionizing resonances have been observed in Yb and Tl using direct 3-photon excitation of ground state atoms. The linewidth is 0.9 cm^-1 in Yb and 0.4 cm^-1 in Tl. Autoionizing levels in both atoms correspond to doubly excited electronic states. This is the first observation of such states in Tl.