L-shell ionization in Au by O5+-and Ni5+-ion impact

TheL X-ray production cross sections in gold by 60 to 72 MeV O⁵⁺ ions and 58 to 87 MeV Ni⁵⁺-ions have been measured. TheL-subshell ionization cross sections derived from these experimental results have been compared with the direct ionization theories viz. plane wave Born approximation (PWBA) theory and modified perturbed-stationary-state theory with energy loss, Coulomb deflection and relativistic effects (MECPSSR). A new procedure has been described to account for the change in the yield ratioLβ₁/Lβ_{2, 15} with energy, for Ni⁵⁺-ion impact on gold. TheL sub-shell ionization cross sections have been derived fromLβ₁,Lβ₄ andLβ_{2, 15} lines of theLβ group in addition to those calculated by the conventional Datz TRY3 technique usingLα,Lγ₁ andLγ_{2, 3} X-ray lines. From the shift in the energies of variousL X-ray lines and changes in their intensities, 3 and 5 spectator vacancies in theM- andN-shells in gold have been estimated with O⁵⁺-ion impact while 7, 20 and 4 to 6 spectator vacancies have been inferred in theM-,N-andO-shells respectively with Ni⁵⁺-ion impact in the energy range of the projectiles undertaken in the present studies.     

Potentiometric studies of the complexes of chromium(VI), molybdenum(VI) and tungsten(VI) with some Azoxine S dyes

The equilibrium constants of the complexation reactions of Cr(VI), Mo(VI) and W(VI) with 8-hydroxyquinoline-5-sulphonic acid (OXS), 7-phenylazo-8-hydroxyquinoline-5-sulphonic acid (PAZOXS), 7-(4-sulphophenylazo)-8-hydroxyquinoline-5-sulphonic acid (SPAZOXS) and 7-(4-sulphonaphthylazo)-8-hydroxyquinoline-5-sulphonic acid (SNAZOXS) have been determined by potentiometric pH titration. The values in the case of chromate are different from those for molybdate and tungstate. The order of stabilities is OXS > PAZOXS > SPAZOXS > SNAZOXS.     

Temperature dependence of apparent molar volumes and viscosity B-coefficients of amino acids in aqueous potassium thiocyanate solutions from 15 to 35°C

Precise density and viscosity data at 15, 25 and 35°C for solutions of glycine, DL-alanine, L-threonine, -alanine, -aminobutyric acid and -aminocaproic acid in water and in (1m, 3m, 5m) aqueous potassium thiocyanate were measured and the limiting apparent molar volumes V ^o and the B-coefficients calculated. The V ^o and B values were split into the contributions from the NH ₃ ⁺ ,COO^– and CH₂ groups. These data are rationalized on the basis of hydrophillic and hydrophobic interactions between the various groups present in these solutions.Abstracted from the Ph.D Thesis of R. K. Goyal, University of Delhi, 1990.     

Anisotropic linear thermal expansivity of poly(ether-ether-ketone)

This paper deals with anisotropic behavior of thermal expansivity (α) of poly(ether-ether-ketone) (PEEK) sample prepared by compression molding above the melting point of polymer. The α was determined using thermo mechanical analyzer (TMA) for the temperature interval 50-250 °C in expansion mode. It is found that out-of-plane thermal expansivity (α_z) is 3.8-fold of the in-plane thermal expansivity (α_xy) below the glass transition temperature (T_g) of PEEK while α_z is decreased to 1.8-fold of the α_xy above the T_g. Moreover, the average α_z over the range studied is about 2.2-fold of the α_xy. This anisotropic behavior may be attributed to the alignment of polymer spherulites and chains along in-plane direction due to compressive forces under hot compression molding.     

Electrochemical and peroxidase-catalyzed redox chemistry of 9-Methyl uric acid

The electrochemical and peroxidase/H₂O₂ oxidation of 9-methyl uric acid has been studied over a wide pH range. Electrochemical, spectral, kinetic and analytical results support the view that the electrochemical and enzymic oxidations proceed by virtually identical mechanisms.     

A highly efficient stereoselective synthesis of β-lactams

An efficient strategy for a one-pot, single step synthesis of β-lactams employing an imidazolidinone based chiral auxiliary with various aldimines via asymmetric Mannich-type reaction has been described.     

Small angle neutron scattering from micellar solutions

Small angle neutron scattering (SANS) is an ideal tool for studying structures of macromolecules and colloidal solutions. A number of micellar solutions have been studied in our laboratory using a home built SANS spectrometer. This paper gives an introduction to the technique of SANS and gives a brief survey of the results obtained at Trombay.     

Effect of enhancement of selenium content in zirconium sulphoselenide on its photoelectrochemical behaviour

In this paper, we have attempted to fabricate PEC solar cells with mixed crystals of Zirconium sulphoselenide. Energy band location and redox analysis of the material have been made using Mott-Schottky plots. These studies justify the selection of an appropriate electrolyte for PEC work. Various solar cells fabricated with single crystals of selenium rich and selenium deficient zirconium sulphoselenide have been prepared. The solar cell parameters e.g. the fill factor (FF), open circuit voltage (V_oc), short circuit current (I_sc) and efficiency (η) for all the different cells have been determined. In order to see the effect of enhancement of selenium in ZrS_xSe_2−x on photoresponse, the electrolyte and intensity of illumination were kept constant and all the electrodes were prepared from crystals showing absolutely plane faces obtained through the act of cleavage with the help of an adhesive tape. The results have been thoroughly analysed and the implications have been discussed.     

Integration of zeolite@metal–organic framework: a composite catalyst for isopropyl alcohol conversion to aromatics

In this study, a Zn-based metal-organic framework (MOF)-zeolite composite ZSM-5@IRMOF-1 was synthesized for the alternative production of BTX from isopropyl alcohol (IPA). Incorporation ensured the capacity to tune the Lewis acidity at a framework level and design accessible pore structures, making composites highly attractive to be used as catalysts. The combination of monodispersed HZSM-5 zeolites on and within acidic IRMOF-1 provided the highly selective production of lower aromatics from IPA. The interaction of IPA with catalysts was investigated at different temperatures in a fixed-bed continuous flow reactor. The obtained product was analyzed using a standard test method ASTM D6730 through gas chromatography-detail hydrocarbon analyser. The results indicated that the reaction between IPA and MOF-supported zeolite occurred without substantial participation of MOFs. The maximum aromatic (BTEX) selectivity of 38.2% was achieved among all hydrocarbons at 92.3% carbon conversion. In addition, the gas yield was <20% for this catalyst system. The appropriate density of Brønsted and Lewis acidic sites and hierarchical pore structures provided the composite catalyst with outstanding aromatic selectivity yield and high stability.