(NH4)2.5H0.5PW12O40-catalyzed rapid and efficient one-pot synthesis of dihydropyridines via the Hantzsch reaction under solvent-free conditions

A heterogeneous reaction with the ammonium salt of 12-tungstophosphoric acid as catalyst has been designed for synthesis of 1,4-dihydropyridine and polyhydroquinoline via the Hantzsch condensation. Molten tetrabutylammonium bromide ionic liquid was used as reaction medium.     

On fermion mass hirerachies in MSSM-like quiver models with stringy corrections

Using instanton effects, we discuss the problem of fermion mass hierarchies in an MSSM-like Type IIA orientifolded model with U(3) × Sp(1) × U(1) × U(1) gauge symmetry obtained from intersecting D6-branes. In the corresponding four-stack quiver, the different scales of the generated superpotential couplings offer a partial solution to fermion mass hierarchies. Using the known data with neutrino masses m_vt <~2 eVm_{v_\tau } \lesssim 2 eV, we give the magnitudes of the relevant scales.     

RéDUCTION CHIMIQUE ET éLECTROCHIMIQUE DE LA PHéNYL-4 DITHIOLE-1,2 THIONE-3

Abstract

4-phenyl 1.2-dithiole 3-thione gives, after reduction with sodium sulfide or electrochemical reduction at a mercury cathode followed by a methylation, the methyl 3-methylthio 2-phenyl 2-propenedithioate of E configuration. The reduction of the dithiolethione at a platinum cathode gives after methylation a dimer according to a monoelectronic process.

La réduction par le sulfure de sodium ou sur électrode de mercure de la phényl-4 dithiole-1,2 thione-3 conduit, après méthylation, au méthylthio-3 phènyl-2 propène-2 dithioate de méthyle de configuration E. Sur cathode de platine, la dithiolethione étudiée se réduit selon un processus à un électron conduisant après méthylation a un dimère.     

Crystal structure,NMR spectroscopy,electrical properties of catena-poly[(bis-glycinium-k 2 O:O)-di-μ-thiocyanate- k 2 N:S; k 2 S:N -cadmium (II)]

The crystal structure, the ¹¹¹Cd and ¹³C NMR spectroscopy, and the complex impedance have been carried out on a new polymeric hybrid compound: [Cd(NH₃CH₂COO)₂(SCN)₂] _n . Crystal structure shows that in the title compound the cadmium atoms have a 2N2S2O-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1D polymeric chains. ¹¹¹Cd and ¹³C MAS NMR spectroscopy show multiplets that result from ¹¹¹Cd, ¹⁴N and ¹³C, ¹⁴N spin–spin coupling, respectively. The AC impedance measurements were performed as a function of both frequency and temperature. The AC and DC electrical conduction have been studied. The activation energy associated with the bulk resistance determined from equivalent circuit was found close to that of the activation energy obtained from DC conductivity. The conduction mechanisms are attributed to the correlated barrier hopping model.     

A 3D modeling of static and forward smoldering combustion in a packed bed of materials

A three-dimensional (3D) model based on the first principles of mass, momentum and energy was developed that numerically simulates the processes of static and forward smoldering in a porous packed bed of plant materials. The packed bed contains cellulose material or tobacco (cigarette) wrapped in a porous paper and surrounded by an ambient air. Other major characteristics of the model are including the effects of buoyancy forces in the flow field, separate treatment of solid and gas in a thermally non-equilibrium environment, and use of multi-precursor kinetic models for the pyrolysis of staring material and oxidation of char. The changes in porosity due to pyrolysis and char oxidation and the effect of porosity on the bed permeability and gas diffusivity are included. The mass, momentum, energy, and species transport equations are solved in a discretized computational domain using a commercially available computational fluid dynamics (CFD) code. The simulation results show that the model reasonably reproduces the major features of a burning cigarette during smoldering and puffing and are in a good agreement with the existing experimental results for cigarettes. Results include the velocity profiles, gas and solid temperatures, coal shape, burn rates, profile and transport of gas and vapor species throughout the packed bed, dilution through the wrapper paper and ventilation in the filter section, and the mass fraction of some pyrolysis and oxidation products in the mainstream and sidestream flows.     

A mild and simple regioselective iodination of activated aromatics with iodine and catalytic ceric ammonium nitrate

Molecular iodine in the presence of a catalytic amount of CAN has been utilized efficiently for regioselective iodination of activated aromatic compounds under mild reaction conditions.     

Characterisation of Ni and Ni/Ti contact on n-type 4H-SiC

In this work, we report on the structural characterisation of Ni and Ni/Ti bilayer contacts on n-type 4H-SiC. The redistribution of carbon, after annealing, in the Ni/SiC and the Ni/Ti/SiC contacts is particularly studied by RBS at 3.2 MeV, XRD and AES techniques.