An efficient reusable silver-exchanged tungstophosphoric acid heterogeneous catalyst for solvent-free intermolecular hydroamination of alkynes

Hydroamination of alkynes with both aromatic and aliphatic amines proceeds efficiently in the presence of silver-exchanged tungstophosphoric acid (AgTPA) catalyst under solvent-free conditions to afford ketimines in excellent yields.     

Development and Validation of a New Analytical Method for the Determination of Related Components in Tolterodine Tartarate Using LC

A novel liquid chromatographic method has been developed, and validated for the determination of tolterodine tartarate, for its potential three impurities in drug substances and drug products. Efficient chromatographic separation was achieved on a C8 stationary phase (150 × 4.6 mm, 3.5 μm particles) with a simple mobile phase combination delivered in an isocratic mode at a flow rate of 0.8 mL min^?1 and quantitation was carried out using ultraviolet detection. Microwave assisted degradation procedure was employed for stress testing studies in addition to the conventional way of a refluxing method. The results of both studies were compared. In the developed LC method, the resolution between tolterodine and its three potential impurities was found to be greater than 2.0. Regression analysis shows an r value (correlation coefficient) greater than 0.999 for tolterodine and for its three impurities. This method was capable to detect all three impurities of tolterodine at a level below 0.0038% with respect to a test concentration of 0.5 mg mL^?1 for a 10 μL injection volume. The inter- and intra-day precisions for all three impurities and for tolterodine were found to be within 1.1% RSD at its specification level. The method has shown good, consistent recoveries for tolterodine (98.9–101.6%) and for its three impurities (94.5–103.0%). The test solution was found to be stable in the diluent for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation, as prescribed by ICH. Degradation was found to occur in alkaline stress condition, while the drug was stable to water hydrolysis, acid hydrolysis, oxidative stress, photolytic and thermal stress. The assay of stressed samples was calculated against a qualified reference standard and the mass balance was found close to 99.5%. Microwave degradations were very fast and comparable to the conventional way of the refluxing method. Robustness studies were carried out and suggested that system suitability parameters were unaffected by small changes in critical factors. The validated method was successfully applied for the determination of tolterodine tartarate in drug substances and drug products.     

Photo-neutron cross-section measurement in the 8 and 10 MeV bremsstrahlung induced reaction of 238U

The ²³⁸U(γ, n)²³⁷U reaction cross-section at the end point bremsstrahlung energies of 8 and 10 MeV was measured by using an activation technique. Induced gamma ray activities were measured by high resolution gamma-ray spectrometer with high-purity germanium detector. The photo neutron cross section on ²³⁸U is also calculated theoretically using TALYS 1.2 computer code. The experimentally obtained reaction cross sections were compared with the flux weighted average values from the literature data based on mono-energetic photon as well as the value from TALYS. It was found that the cross section of ²³⁸U(γ, n)²³⁷U reaction increases with increase of bremsstrahlung energy and were closer to the flux-weighted experimental data from literature and the values from TALYS based on mono-energetic photons.     

Measurements of 60Ni(p,n)60Cu reaction cross-sections and covariance analysis of the uncertainty

The cross sections of the ⁶⁰Ni(p,n)⁶⁰Cu reaction from threshold energy to?~?20 MeV have been measured by employing stack foil activation technique and off-line γ-ray spectrometry. The uncertainties for the reaction cross sections have been estimated by applying covariance analysis and least square method. The measured cross-sections are found to be in agreement with most of the literature data available in EXFOR database. The excitation function of the ⁶⁰Ni(p,n)⁶⁰Cu reaction was also theoretically calculated by using the TALYS-1.9 code. The excitation functions of ⁶⁰Ni(p,n)⁶⁰Cu reaction from TALYS-1.9 and TENDL-2017 follow a similar trend as of the experimental data of present work and literature but are little higher around the peak cross-section region.

     

Measurement of 56Fe(n, p)56Mn reaction cross-section at E n = 5.9, 9.85, 14.8 and 15.5 MeV

The ⁵⁶Fe(n, p)⁵⁶Mn reaction cross-section at neutron energies of 5.9 ± 0.6, 9.85 ± 0.38, 14.8 ± 0.1 and 15.5 ± 0.7 MeV from the ⁷Li(p, n) as well as ³H(d, n) reactions has been experimentally measured using activation and off-line γ-ray spectrometric technique. The experimentally determined ⁵⁶Fe(n, p)⁵⁶Mn reaction cross-sections from the present work were compared with the latest available evaluated nuclear data libraries of ENDF/B-VII.1, JENDL-4.0 and JEFF-3.1/A. The present data along with the literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels. The measured cross-sections were also estimated theoretically using TALYS-1.4 and EMPIRE-2.19 computer codes over neutron energies from near threshold to 20 MeV to compare with the experimental data.     

Dielectric Properties of Diphasic Composites of BaTiO3 and LiFe5O8

A composite material has been prepared by sintering a mixture of a piezoelectric BaTiO₃ and a piezomagnetic ferrite phase. The two-phase nature of the composite has been characterised by X-ray analysis. The electrical resistivity and dielectric properties of the composite material are studied as a function of the volume fraction of the components. The effect of poling on the dielectric constant is also discussed.     

Effect of Lithium Doping in the Bi-2212 Superconducting System

Samples with the nominal composition Bi₂Sr₂Ca_1–xLi_xCu₂O_y (x = 0.2,0.4, and 0.6) and Bi₂Sr₂CaCu_2−x L1_xO_z (x = 0.4, 0.6, and 1.0) were prepared by the solid state reaction method. The role of L1 at both Ca and Cu sites in the Bi-2212 composition were studied. From the X-ray diffraction data it was found that the L1-doped at the Ca site increases the c-axis and that doped at the Cu site decreases the c-axis. From the D.C. four-probe resistivity data it was found that Li-doped at the Ca site reduces the T_c and the L1-doped at the Cu site gives T_c(0) above the liquid nitrogen temperature. It was observed that the L1 doping reduces the melting point of Bi-2212 composition. The presence of Lithium was confirmed by inductive the coupled plasma method.     

Debye characteristic temperature of some silver-base binary alloys

The Debye characteristic temperature (θ) of eight silver base binary alloys in the cubic phase having various compositions have been calculated making use of four different averaging methods from the data on elastic constants. The values of θ are also evaluated from series expansion method. The results obtained were examined in terms of solute concentration, reciprocal of the lattice parameter, mass, electron to atom ratio, and elastic anisotropy. Important conclusions are made.