Structure Elucidation and Biological Screening of Bis(4-{[(E)-(2-Hydroxybenzylidene)amino]methyl}-cyclohexane-carboxylato-O)-triaqua-cadmium

Using a bidentate ligand, a Schiff base 4-({[(Z)-(2-hydroxyphenyl)methyldene]amino}methyl)cyclohexanecarboxylic acid, complex I(ML2, where M = Cd(Ⅱ)) was synthesized and characterized by IR spectroscopy and X-ray crystallography. It crystallizes in monoclinic system, space group C2/c, M_r = 685.04, 0.34 mm × 0.26 mm × 0.14 mm, a = 54.050(3), b = 6.1220(3), c = 9.5081(5) ?, β = 90.229(2)°, Z = 4, C_(30) H_(40) CdN_2 O_9 and V = 3146.2(3) ?~3. Complex I was screened for its bactericidal activity against four bacterial strains Chromohalobactersalexigens, Chromohalobacterisraelensis, Halomonashalofila and Halomonassalina and fungicidal activity against Aspergillusnigerand Aspergillusflavus. Antimicrobial activity results showed that the synthesized complex displayed good anti-fungal activity against two fungal strains. It was found to be inactive against four different bacterial strains analyzed and was negative for bactericidal effect.     

A structural investigation of heteroleptic pentavalent antimonials and their leishmanicidal activity

In the quest for new drug candidates for the safe treatment of parasitic diseases like leishmaniasis, a series of heteroleptic pentavalent antimonials of the type [SbR₃(OOCR′)₂] were synthesized and characterized using elemental analysis, Fourier transform infrared spectroscopy and multinuclear (¹H and ¹³C) NMR spectroscopy. The carboxylate moieties are predominantly substituted benzoates with some complexes that fit in acetato or nicotinato ligands. The crystal structures of [Sb(p‐Tol)₃(p‐CH₃C₆H₄COO)₂], [Sb(p‐Tol)₃(3,5‐Cl₂C₆H₃COO)₂] and [Sb(p‐Tol)₃(3‐nicotinato)₂] were determined crystallographically and shown to adopt geometries intermediate between trigonal bipyramidal and square pyramidal, and essentially monomeric with a five‐coordinated Sb center. The leishmanicidal activity was assessed against the Leishmania tropica KWH23 parasite, and the cytotoxicity level was also measured on human macrophage blood cells. It was observed that IC₅₀ of the antimonials was 100‐fold superior as compared with the standard antimonial drug used. Cytotoxicity results showed that these antimonials are highly active even at low concentrations and are biocompatible with human macrophages, making them highly promising drug candidates for further investigation. Copyright © 2016 John Wiley & Sons, Ltd.     

Melting heat transfer in an axisymmetric stagnation-point flow of the Jeffrey fluid

This investigation explores the characteristics of melting heat transfer in a boundary layer flow of the Jeffrey fluid near the stagnation point on a stretching sheet subject to an applied magnetic field. The governing boundary layer equations are transformed to ordinary differential equations by similarity transformations. Resulting nonlinear problems are solved analytically by the homotopy analysis method. It is noticed that an increase in the melting parameter decreases the dimensionless velocity and temperature, while an increase in the Deborah number increases the velocity and momentum boundary layer thickness.     

Dufour and Soret effects on MHD flow of viscous fluid between radially stretching sheets in porous medium

The aim of this paper is to examine the Dufour and Soret effects on the two-dimensional magnetohydrodynamic (MHD) steady flow of an electrically conducting viscous fluid bounded by infinite sheets. An incompressible viscous fluid fills the porous space. The mathematical analysis is performed in the presence of viscous dissipation, Joule heating, and a first-order chemical reaction. With suitable transformations, the governing partial differential equations through momentum, energy, and concentration laws are transformed into ordinary differential equations. The resulting equations are solved by the homotopy analysis method (HAM). The convergence of the series solutions is ensured. The effects of the emerging parameters, the skin friction coefficient, the Nusselt number, and the Sherwood number are analyzed on the dimensionless velocities, temperature, and concentration fields.     

An exact and asymptotic analysis of a diffraction problem

The present analysis deals with diffraction of acoustic waves by an oscillating strip focusing on the exact and concise formulation of a series solution in the complex domain. The complete solution is represented by a series, the eigenfunctions of which are generalized gamma functions. An exact expression of this special function, with argument being ‘integer +1/2’, is derived. The convergence analysis of the series solution in transformed domain is discussed graphically. Finally, the scattered and total acoustic fields are obtained by exact and asymptotic evaluations of inverse Fourier transforms. The significance of the present investigation is the derivation of a high order accurate solution in a convenient form.     

Electron flux distributions in photodetachment of HF~- near an interface: Theoretical imaging method study

The electron flux distributions in the photodetachment of HF- near an interface are studied using a two-center model and the theoretical imaging method. An analytical expression for electron flux distributions is derived, which displays oscillations on an observation plane similar to the recent results published by Wang but in the presence of a static electric field. We also discuss the expressions for soft and hard wall cases in detail. A comparison is made with the previous work. The expression is a more general result, and we can deduce from it the electron flux distributions for the photodetachment of H2- near an interface. Finally, we show that the expression reveals similar results as those in [Chin. Phys. B 19 020306 (2010)] when the wall effect is neglected.     

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

This article presents the use of composite resonant metamaterials for the design of highly directive subwavelength cavity antennas. These metamaterials, composed of planar metallic patterns periodically organized on dielectric substrates, exhibit frequency dispersive phase characteristics. Different models of metamaterial-based surfaces (metasurfaces), introducing a zero degree reflection phase shift to incident waves, are firstly studied where the bandwidth and operation frequency are predicted. These surfaces are then applied in a resonant Fabry–Perot type cavity and a ray optics analysis is used to design different models of ultra-compact high-gain microstrip printed antennas. Another surface presenting a variable reflection phase by the use of a non-periodic metamaterial-based metallic strips array is designed for a passive low-profile steering beam antenna application. Finally, the incorporation of active electronic components on the metasurfaces, allowing an electronic control of the phase responses, is applied to an operation frequency reconfigurable cavity and a beam steering cavity. All these cavity antennas operate on subwavelength modes, the smallest cavity thickness being of the order of λ/60. To cite this article: A. Ourir et al., C. R. Physique 10 (2009).     

Electromagnetic Time Reversal Algorithms and Source Localization in Lossy Dielectric Media

The problem of reconstructing the spatial support of an extended radiating electric current source density in a lossy dielectric medium from transient boundary measurements of the electric fields is studied. A time reversal algorithm is proposed to localize a source density from loss-less wave-field measurements. Further, in order to recover source densities in a lossy medium, we first build attenuation operators thereby relating loss-less waves with lossy ones. Then based on asymptotic expansions of attenuation operators with respect to attenuation parameter, we propose two time reversal strategies for localization. The losses in electromagnetic wave propagation are incorporated using the Debye's complex permittivity, which is well-adopted for low frequencies (radio and microwave) associated with polarization in dielectrics.     

Enzyme‐Mediated Deposition of a TiO2 Coating onto Biofunctionalized WS2 Chalcogenide Nanotubes

A chemically specific and facile method for the biofunctionalization of WS₂ nanotubes (NT‐WS₂) is reported. The covalent modification strategy is based on the affinity of the nitrilotriacetic acid (NTA) side chain, which serves as a ligand for the surface binding to NT‐WS₂ and simultaneously as an anchor group for the binding of His‐tagged proteins to the polymer backbone. The polymer functionalized WS₂ nanotubes can be solubilized either in water or organic solvents; they are stable for at least one week. The probes were characterized by FT‐IR and UV‐vis spectroscopy. The immobilization of silicatein, a hydrolytic protein encountered in marine sponges, was visualized by scanning force microscopy (SFM) and confocal laser scanning microscopy (CLSM). The formation of the biotitania coating mediated by the immobilized silicatein onto the surface was characterized by scanning electron microscopy (SEM), and transmission electron microscopy (TEM).