A high spin isomer in 153Eu

A search for new isomers of nanosecond lifetimes were carried out in ¹⁵³Eu via the ¹⁵⁰Nd(⁷Li,xnγ) reaction. The single particle angular momentum alignment and dynamical moment of inertia estimated from the experimental data indicate a configuration change at rotational energy ħω∼ 0.30 MeV. A decrease of B(E2) values is also observed at the same frequency. An isomeric level is identified at an excitation energy of 3100 keV (J^π=35/2⁻) which corresponds to this frequency. The lifetime of the level is found to be 8.6 ± 1.3 nanosecond. Received: 22 April 1997 / Revised version: 26 September 1997     

Etching and annealing studies of nuclear tracks in glasses

A series of etching and annealing experiments are designed to evaluate the characteristics of fission tracks in a number of glasses of varying silica content. A comparative study has been made by comparing the calculated value of bulk etch rate, optimum etch time and annealing rate for each glass. The present investigation suggests that both bulk etch rate (V_G) and annealing rate (V_a) increases with the decrease in silica content of glasses. A minimum value of these parameters is observed for pure silica glass.     

Hybrid systems through natural product leads: an approach towards new molecular entities

Hybrid systems are constructs of different molecular entities, natural or unnatural, to generate functional molecules in which the characteristics of various components are modulated, amplified or give rise to entirely new properties. These hybrids can be designed from carefully selected components either through domain integration of key structural/functional features or via straightforward covalent linkages. Some of the recently reported hybrid systems based on steroid, carbohydrate, C60-fullerene platforms, amongst others, mainly crafted with the object of enhancement of the therapeutical spectrum, will be discussed.     

Enhanced coherent emission aided by an incoherent process

Enhanced emission of a coherent signal generated by the nonlinear process omega(f)+omega(b)-omega(p) has been found in an incoherently pumped four-level system. It is shown that finite (large) atomic coherence can be generated by (incoherent) pumping of the intermediate states, which removes the destructive interference effects that otherwise inhibit coherent emission of signals.     

Simultaneous determination of bergenin and gallic acid in Bergenia ligulata wall by high-performance thin-layer chromatography

A simple and reproducible high-performance thin-layer chromatographic method was developed for the simultaneous determination of bergenin and gallic acid in Bergenia ligulata. Water and methanol were used as the extracting solvents. The concentrations of bergenin and gallic acid in both of these solvents were found to be almost the same. The method involves separation of the components by thin-layer chromatography on a precoated Silica Gel 60 F254 plate with a solvent system of ethyl acetate-formic acid-acetic acid-water (100 + 11 + 11 + 27). The sensitivity of the method for bergenin was 0.30 microg, whereas for gallic acid it was 0.25 microg. The proposed method is precise and sensitive and can be used for the detection, monitoring, and simultaneous quantification of bergenin and gallic acid in B. ligulata.     

Electronic structure of non-magnetic impurities in dilute alloys of Al

The electronic structure of substitutional non-magnetic impurities Cu, Ag, Cd, Mg, Zn, Ga, In, Ge, Si and Sn in Al is studied using density functional theory. A simple physical model is proposed to calculate the effective charges on impurities in trivalent metal Al. A linear relation is found between the effective charges on impurities and impurity vacancy capture radii. The spherical solid model (SSM) is used to account for discrete nature of the host. The impurity-induced change in charge density, scattering phase shifts, host-impurity potential, residual resistivity and impurity self-energy are calculated. Higher order scattering phase shifts are found significant and the host-impurity potential is found proportional to effective charge on impurity in its vicinity. The self-consistently calculated potential is used to calculate the electric field gradients (EFGs) at the first and second nearest neighbours (1NNs, 2NNs) of impurity. The calculated values are in agreement with the experimental results.     

Molar excess free energy of mixing of 1-propanol or 2-propanol with cyclohexane at 298.15 and 308.15 K in terms of association model with a Flory contribution term

Excess molar Gibbs free energies of mixing for 1-propanol or 2-propanol + cyclohexane over the whole composition range at 298.15 and 308.15 K have been calculated from vapour pressure data measured by static method. The data have been analysed in terms of a Mecke-Kempter association model with a Flory contribution term.     

Ru(III) catalysis in N-bromoacetamide oxidation of ethylene glycol and glycerol: A kinetic and mechanistic study

Kinetics of oxidation of ethylene glycol and glycerol by acidic solution of N-bromoacetamide (NBA) in the presence of ruthenium (III) chloride as a homogeneous catalyst and mercuric acetate as scavenger in the temperature range of 30–50°C have been reported. The reactions follow identical kinetics, being zero-order in substrate and first-order in Ru(III). First order dependence of the reaction on NBA at its low concentrations tends to zero order in the higher concentration range. Positive effect of [H^?] and [Cl^?] has been observed. A negative effect of acetamide and ionic strength of the medium is observed while D₂O and mercuric acetate show zero effect on the reaction velocity. Various activation parameters have been computed. The main product of the oxidation is corresponding acid. (H₂OBr)⁺ has been postulated as the oxidizing species. A suitable mechanism in conformity with the kinetic data has been proposed.