Comparative computational appraisal of supercritical CO2-based natural circulation loop: effect of heat-exchanger and isothermal wall

Journal of Thermal Analysis and Calorimetry - Natural circulation loop (NCL) is a geometrically simple heat transfer device in which fluid flow occurs due to density gradient of loop fluid, induced...     

Studies on testing and evaluation of platinum plated titanium electrode for production of uranous nitrate

Partitioning of plutonium from uranium is an important step in the reprocessing of spent fuel by PUREX process of solvent extraction using 30% TBP-dodecane. This is achieved by selectively reducing the Pu in solution to least extractable trivalent state by uranous nitrate as the reductant. The latter is conventionally produced by electrolytic reduction of uranyl ion in presence of hydrazine nitrate as uranous nitrate stabilizer using Pt-coated titanium as the anode. The anode plating wears out after period of operation thus affecting the process efficiency and hence the quality control testing of platinum plated electrode becomes important. This article describes the use of Beta backscattering method with strontium-90 radioisotope as non-destructive testing tool for measuring the coating thickness of the sample Ti electrode. The surface characteristics and coating morphology were also examined by scanning electron microscope and the micrographs are presented.     

Imidazole derivatives as the organic precursor of ZnO nano particle

N₁-Hydroxy-2,4,5-trisubstituted imidazoles were synthesized starting from 1,2-diketones. The crystal structure of 4,5-dimethyl-2-(3-nitrophenyl)-1H-imidazol-1-ol has been determined. An unusual intermolecular hydrogen bonding through the association of water molecule has been reported. These imidazole derivatives can be thought of as the organic precursor for the synthesis of zinc oxide nano particles.     

Density of states in the conduction band of some rare earth oxides

The results of a systematic investigation of the intensity distribution near the short wavelength limit of the continuous X-ray spectrum for the most common rare earth oxides are reported. Anomalies in the band structure of some oxides have been observed and are discussed in terms of localized energy levels in the forbidden band due to the existence of colour centres. This implies that the physical properties of pure compounds strongly depend on the precise experimental conditions of preparation.     

Polarity switching and transient responses in single nanotube nanofluidic transistors

We report the integration of inorganic nanotubes into metal-oxide-solution field effect transistors (FETs) which exhibit rapid field effect modulation of ionic conductance. Surface functionalization, analogous to doping in semiconductors, can switch the nanofluidic transistors from p-type to ambipolar and n-type field effect transistors. Transient study reveals the kinetics of field effect modulation is controlled by ion-exchange step. Nanofluidic FETs have potential implications in subfemtoliter analytical technology and large-scale nanofluidic integration.     

Phosphine-mediated [4 + 2] annulation of bis(enones): a Lewis base catalyzed "mock Diels-Alder" reaction

Lewis-base-catalyzed cycloisomerization of bis(enones) to decalins has been demonstrated as an alternative to the traditional Lewis acid catalyzed Diels-Alder cycloaddition. In this process, a trialkylphosphine mediates both bond formation steps in two distinct catalytic cycles. The single-pot operation generates two carbon-carbon bonds and up to five contiguous stereocenters in one step, starting from achiral, aliphatic substrates; eight examples are provided. [reaction: see text]     

1-(2-Iodophenyl)-1H-tetrazole as a ligand for Pd(II) catalyzed Heck reaction

1-(2-Iodophenyl)-1H-tetrazole 2 was synthesized by the reaction of 2-iodoaniline, sodium azide and triethyl orthoformate in acetic acid. The newly synthesized ligand 2 was successfully used in Heck reaction to give the cross-coupled products in excellent yields.     

Resonant tunneling of ultracold atoms through vacuum induced potentials

We demonstrate resonant tunneling of ultracold atoms through potentials produced by the interaction of atoms with the vacuum field of a system of cavities. We show the close connection of the transmission characteristics to the resonant states in vacuum induced potentials. Transmission of cold atoms, though sharing some features with tunneling in finite semiconductor superlattices, is strongly dependent on the coherent addition of amplitudes from various wells and barriers.