Physicochemical Characterization of Acidiphilium sp. Biofilms

The biofilm formation of a strain of the extremophile bacterium Acidiphilium sp., capable of donating electrons directly to electrodes, was studied by different surface characterization techniques. We develop a method that allows the simultaneous study of bacterial biofilms by means of fluorescence microscopy and atomic force microscopy (AFM), in which transparent graphitic flakes deposited on a glass substrate are used as a support for the biofilm. The majority of the cells present on the surface were viable, and the growth of the biofilms over time showed a critical increase of the extracellular polymeric substances (EPS) as well as the formation of nanosized particles inside the biofilm. Also, the presence of Fe in Acidiphilium biofilms was determined by X‐ray photoelectron spectroscopy (XPS), whereas surface‐enhanced infrared absorption spectroscopy indicated the presence of redox‐active proteins.     

Inverse gas chromatographic characterization of Porapak Q as an extractant of pollutants from aqueous media

The surface of Porapak Q was characterized by inverse gas chromatography (IGC) carried out by the determination of dispersive and specific adsorption components of Porapak Q surface, calculating γ_s^d and -ΔH _a^s parameters, respectively. An interpretation was given based on the chemical structure of Porapak Q. The obtained results were confirmed through the surface Lewis acidity and basicity constants, K _a and K _b, respectively, correlating well with the determined thermodynamic parameters.     

Fabrication and characterization of 1.55 μm single transverse mode large diameter electrically pumped VECSEL

We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-μm diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L–I) curves are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the maximum CW output power of 50-μm diameter VECSELs, rather than current injection inhomogeneity.     

Three dimensional tris[triorganotin(IV)]hexacyanoiron(III) polymeric complexes as oxidising agents

The oxidation of N₂H₄ by tris[triorganotin(IV)]hexacyanoiron(III) polymer complexes has been studied spectrophotometrically. The oxidation rate is first order in both complex and N₂H₄ and the rate constant increases with increasing pH. Experiments over the temperature range (15–30 °C) allowed calculation of the activation parameters. An outer-sphere mechanism involving a rate-determining one-electron transfer is proposed. In addition, the products of the solid reactions between the iron(III) polymeric complexes and N₂H₄ were investigated by i.r., u.v. reflectance, X-ray powder diffraction, e.p.r. spectra and magnetic measurements.     

A route to dicyanomethylene pyridines and substituted benzonitriles utilizing malononitrile dimer as a precursor

The conditions of the reaction of malononitrile dimer with enaminones and arylidenemalononitrile could be adapted to yield either pyridines or benzene derivatives. A new synthesis of pyrido[1,2-a]pyrimidines from the reaction of malononitrile dimer 1 and 2-phenyl-3-piperidin-1-yl-acrylonitrile (11) is described. Compound 1 condensed with DMFDMA to yield an enaminonitrile that reacted with hydrazine hydrate to yield N',4,6-triamino-2H-pyrazolo[3,4-b]pyridine-5-carboxamidine (17).     

Fundamentals of designing cylindrical high-order transformation optics invisibility cloaks using silver–silica metamaterials

Metamaterials have effective properties that are distinct from their composites as they consist of engineered-designed properties that are not in nature. In order to be able to design a metamaterial, we should establish sufficient understanding of the properties of the constituents. This will enable us to engineer new effective parameters of the metamaterial. We shall perform a detailed analytical study for the effective parameters and the constituents’ parameters of silver–silica metamaterial. This will define the optical response of the mixture at different sizes of the inclusions’ and different volume fractions of the silver and silica. Also an optimum value of the volume fraction is proposed to achieve a broadened resonance optical response. Finally, we propose the design technique and constraints of a non-magnetic optical cloaking device, based on high-order transformation optics with different volume fractions of silver and silica.     

Effect of Cd content on the structural characteristic and some physical properties of Zn1−x Cd x Se

The present work focuses on the structural, optical, and electrical properties of Zn_1?x Cd _x Se (0.1≤x≤0.25) compounds. The compounds were synthesized by solid state reaction. X-ray diffraction (XRD) patterns confirm that the samples have cubic single phase (zinc-blende) crystal structure with space group F-43m. The crystal structural parameters were refined by the Rietveld method using the FullProf program. It was found that the lattice parameters increase linearly with increasing the Cd content and obeys Vegard’s law. The refined values of the crystallite size and the bond lengths increase with increasing the Cd content. The energy band gap of the samples has been calculated and it was found that it decreased as Cd increased. The conductivity of the samples increases with increasing both of composition parameter x and temperature, and showing semiconducting behavior.     

Synthesis,Structural Characterization,Thermogravimetric, and Molecular Modelling of Novel Mn(II), Co(II), and Ni(II) Metal Complexes Derived from New Synthesized 4,6-Diaryl-2-oxonicotinonitrile Ligand

Russian Journal of General Chemistry - Novel coordination compounds of Mn(II), Co(II), and Ni(II) with a new 4-(4-chlorocyclohexyl)-2-oxo-6-(thien-2-yl)-1,2-dihydropyridine-3-carbonitrile ligand...     

Recent progress on coumarin scaffold-based anti-microbial agents (Part III)

The biological, therapeutic, and medicinal properties of coumarins (chromen-2-ones), and its analogs have triggered enormous studies aimed toward growing synthetic routes to these heterocyclic compounds. This review presents a systematic and comprehensive survey of the method of preparation, the chemical reactivity, and the anti-microbial properties associated with this system.     

Two-dimensional q-differential transformation and its application

The one-dimensional q-differential transformation was introduced in [8] for solving the ordinary q-differential equations. Here, we present the definition and operation of the two-dimensional q-differential transform. A distinctive feature of the q-differential transform is its ability to solve linear and nonlinear partial q-differential equations.