Flux decline during cross flow membrane filtration of electrolytic solution in presence of charged nano-colloids: a simple electrokinetic model

An electrokinetic transport based approach for quantification of reversible flux decline due to the concentration polarization of an electrolyte solution in presence of charged colloids is presented. The model envisions the electrolyte transport across a charged cake or gel layer as transport of ions through charged cylindrical capillaries. This model is coupled with the standard theory of concentration polarization during cross flow membrane filtration. The analysis is carried out entirely in terms of generalized, non-dimensional variables. A dimensionless group termed as the scaled gel layer resistance evolves from the analysis, which accounts for the electrical properties of the charged nano-colloids and the electrolyte solution. A parametric study is performed to elucidate the coupled influence of mass transfer, membrane resistance, gel resistance, and electrical properties of the gel-electrolyte polarized layer. The effects of these parameters are examined on the filtration performance through the model equations.     

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)～5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.     

Formation of nanoscale aggregates of a coumarin derivative in Langmuir–Blodgett film

In the present communication, we report the formation of organized nanoscale aggregates of a coumarin derivative 7 Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) at the air–water interface and in Langmuir–Blodgett (LB) films in the presence and absence of stearic acid (SA). A pressure-area isotherm reveals that the 7HNO3C form stable monolayer at the air–water interface. However, the stability can be improved by mixing it with a fatty acid stearic acid (SA). The miscibility study shows that the nature of interaction is strongly dependent on the mixing ratio and surface pressure. At a mole fraction of 0.4 of 7HNO3C in SA, the attractive and repulsive interaction between these two molecules balance each other forming a stable film with nanoscale aggregates. UV-Vis absorption spectroscopic studies reveal the nature of the aggregates in LB films. Scanning electron microscopy gives compelling visual evidence of formation of nanoscale aggregates in the mixed LB films.     

Scaling laws for plasma transport due toη i-driven turbulence

The scale invariance technique has been employed to discuss theη _i-driven turbulent transport under a new fluid model developed by Kimet al [1]. Our analysis reveals that the finite Larmour radius effect plays a decisive role to determine the scaling behaviour of the energy transport under the new fluid model. However, the overall scaling of the transport coefficient remains unchanged as compared to that derived by Connor [2] under the traditional fluid model. The approximations considered by Connor [2] are qualified with additional requirements within the new fluid approach. In the dissipative case, which has not been discussed earlier, additional constraints on the power scaling laws of the transport properties are imposed due to the dissipative mechanisms in the basic governing equations.     

Amplification without population inversion in molecules

We have studied the feasibility of amplification without population inversion (AWI) in LiH molecule for three-level ladder, V, and Λ schemes. We have shown the salient features of AWI in a molecular system in comparison to that in an atomic system, viz. the dependence of gain profile on the choice of different rotational and vibrational transitions. Under different three-level schemes, the effect of homogeneous and inhomogeneous broadening on the gain profile has been studied. We have also studied the dependence of gain on different external parameters. The temporal evolution of gain has been analyzed and it was found that AWI is achievable in both the transient and the steady state regime. For all the three-level schemes and in particular for the ladder scheme, amplification of the weak probe was obtained using a coupling laser of smaller frequency.     

Oxidation of naphthalene and phenanthrene by pyridinium fluorochromate (PFC)—a kinetic and mechanistic study

The kinetics of the oxidation of naphthalene and phenanthrene by pyridinium fluorochromate, C₅H₅NHCrO₃F, PFC, has been studied. The main product of the oxidation is the corresponding quinone. While each oxidation, studied in aqueous acetic acid (80–95%, v/v) medium, is first order with respect to the oxidant, the rate is almost independent of the substrate concentration. The reactions are catalyzed by acid, the acid-catalyzed reactions being very fast, which precluded determination of their order in acid medium. The kinetic isotope effect, k_H/k_D is 5.50 at 303 K for naphthalene. The reaction does not induce polymerization of acrylonitrile. The effects of temperature and solvent compositions were studied and activation parameters evaluated. Probable mechanisms are discussed.     

General dynamic scaling theory of critical ultrasonic attenuation and dispersion

Because of the critical slowing down of the order parameter fluctuations, they do not follow the temperature oscillations produced adiabatically by a pressure wave. The resulting hysteresis leads to the observed dispersion and attenuation of ultrasound. The effect depends entirely upon the frequency dependent specific heat. We discuss here the mathematical features of this function, including it dynamic scaling properties.     

Large deflections of rhombic plates—a new approach

Non-linear static behaviour of rhombic plates has been analysed following Banerjee's hypothesis (B. Banerjee, Large deflections of polygonal plates under non-stationary temperature. J. Thermal Stresses 7, 285–292 (1984)). Calculations have been carried out for different skew angles. To test the accuracy of the theoretical results so obtained, experiments were carried out on copper and steel rhombic plates. The theoretical results were found to be in excellent agreement with those obtained from an analysis of the experimental data.     

A parallel search algorithm for directed acyclic graphs

A parallel algorithm for depth-first searching of a directed acyclic graph (DAG) on a shared memory model of a SIMD computer is proposed. The algorithm uses two parallel tree traversal algorithms, one for the preorder traversal and the other for therpostorder traversal of an ordered tree. Each of these traversal algorithms has a time complexity ofO(logn) whenO(n) processors are used,n being the number of vertices in the tree. The parallel depth-first search algorithm for a directed acyclic graphG withn vertices has a time complexity ofO((logn)²) whenO(n ^2.81/logn) processors are used.     

THE PHOTODYNAMIC EFFECTS ONV–79 CHINESE HAMSTER CELLS

Abstract— Holding of acriflavine sensitizedV–79 cells in growth medium before visible light exposure decreases inactivation by visible light. The decrease depended upon the period of holding, indicating that there was release of cellular dye during this period. Exposures to visible light were done in two conditions: (a) with no dye in the medium during visible light exposure (washed) and (b) with dye in the medium during exposure (unwashed). Caffeine was found to slightly increase the sensitivity of the cells to visible light in the washed condition, whereas, in the unwashed condition no such effect was observed. Interaction studies with far UV did not reveal any correlation between photodynamic damage and UV damage. Visible light exposure of acriflavine sensitized cells was found to be mutagenic, as studied from the induction of 8-azaguanine resistant mutants. Inhibition of singlet oxygen production by sodium azide suppressed the induction of mutants. All these, taken together, have been discussed with respect to the relative importance of DNA and non-DNA damage in the photodynamic action of acriflavine.