Pressure induced phase transformation in U2O(PO4)2

The high pressure behavior of U₂O(PO₄)₂ has been investigated with the help of Raman scattering and X-ray diffraction measurements up to ∼14 and 6.5 GPa, respectively. The observed changes in the Raman spectra as well as the X-ray diffraction patterns suggest that U₂O(PO₄)₂ undergoes a phase transition at ∼6 GPa to a mixture of a disordered ambient pressure phase and a new high pressure phase. The new phase resembles the triclinic mixed-valence phase of uranium orthophosphate (U(UO₂)(PO₄)₂). On release of pressure the initial phase is not retrieved.     

Regiospecific, enantiospecific total synthesis of C-19 methyl substituted sarpagine alkaloids dihydroperaksine-17-al and dihydroperaksine

The optically active tetracyclic ketone 8 was converted into the pentacylic core 14 of the C-19 methyl substituted N(a)-H sarpagine and ajmaline alkaloids via a critical haloboration reaction. The ketone 14 was then employed in the total synthesis of 19(S),20(R)-dihydroperaksine-17-al (1) and 19(S),20(R)-dihydroperaksine (2). The key regioselective hydroboration and controlled oxidation-epimerization sequence developed in this approach should provide a general method to functionalize the C(20)-C(21) double bond in the ajmaline-related indole alkaloids.     

Entanglement Concentration Protocols for GHZ-type Entangled Coherent State Based on Linear Optics

International Journal of Theoretical Physics - We proposed two entanglement concentration protocols (ECPs) to obtain maximally entangled Greenberger-Horne-Zeilinger (GHZ)-type entangled coherent...     

Seasonal variation of uranium and physico-chemical parameters in spring water sources of Pithoragarh city,Uttarakhand, India

Journal of Radioanalytical and Nuclear Chemistry - The paper deals with the seasonal variation of physico-chemical parameters in natural spring water sources collected from Pithoragarh city,...     

High pressure studies on α-cristobalite form of Al0.5Ga0.5PO4: hydrostatic versus non-hydrostatic conditions

High pressure angle-dispersive X-ray diffraction investigations have been carried out on α-cristobalite form of Al_0.5Ga_0.5PO₄. Our investigations show that the structural stability of this phase under high pressure depends on the nature of pressure conditions in the diamond anvil cell. Under hydrostatic pressure conditions using neon as a pressure transmitting medium, ambient orthorhombic C222₁ phase transforms to orthorhombic Cmcm phase at 4.9?GPa. The high pressure Cmcm phase remains stable up to the highest pressure in the experiment, i.e. 19?GPa. The values of bulk modulus for C222₁ and Cmcm phases are 19(2) and 126(4)?GPa, respectively. In contrast to this, under non-hydrostatic pressure conditions, transformation of ambient C222₁ phase to Cmcm phase has not observed up to 17.4?GPa. Instead, a new monoclinic phase P2₁ is observed which contains layers of six coordinated Al/Ga ions separated by less dense five coordinated Al/Ga ions.     

Selective Reductions with Sodium Borohydride in Dimethyl Sulphoxide with Added Metal Salts

Sodium borohydride in Dimethyl Sulphoxide in the presence of added metal salts selectively reduces aldehydes in the presence of ketones and converts α,β -unsaturated ketones to the corresponding unsaturated alcohols.     

C-O bond fragmentation of 4-picolyl- and N-methyl-4-picolinium esters triggered by photochemical electron transfer

Photochemical reduction of several 4-picolyl- and N-methyl-4-picolinium esters was examined using product analysis, laser flash photolysis, and fluorescence quenching. It is demonstrated that the radical (anions) formed in these reactions readily fragment to yield a carboxylic acid and a 4-pyridylmethyl radical intermediate. The high chemical and quantum yields observed for these photoreactions suggests that these esters can be used as photolabile protecting groups.     

Conformational and dielectric analysis of hydrogen bonded polar binary mixtures of propan-1-ol with propionaldehyde

The dielectric behaviour of polar liquids such as propan-1-ol, propionaldehyde and their equimolar binary mixture in non-polar solvent benzene is studied in the microwave frequency range using the cavity perturbation technique at 6.218 GHz (J band), 9.880 GHz (X band), 16.331 GHz (P band) and 24.951 GHz (K band). Ab initio geometry optimization is performed in the 6-31G (d) basis set using the Gaussian 94W program for both pure and binary systems of propan-1-ol and propionaldehyde. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the ab initio results. Conformational analysis of the formation of hydrogen bond between the propan-1-ol and propionaldehyde is supported by the FT-IR spectra. The average relaxation times are calculated from their respective Cole–Cole plots.     

Mononuclear boron(III) complexes of neo bidentate thioimines derived from hydrazinecarbodithioic acid

Boron chemistry has been intensively studied in the recent past. Although the study of the interactions between transition‐metal ions and the phenyl methylene ester derivatives of hydrazine carbodithioic acids has been carried out on a long period, particularly via the formation of adducts, their interaction of Main Group metal ions and the formation of their coordination complexes are subjects of current interest. We have synthesized and isolated a variety of complexes of phenyl dihydroxyborane with substituted dithiocarbazates. The benzene‐soluble, high‐molecular‐weight complexes have been characterized using a wide range of analytical and spectroscopic techniques. The pathogenicity of microbial infections associated with the complexes have been subjected to a variety of biointeraction studies and the results are discussed. Copyright © 1999 John Wiley & Sons, Ltd.