Development and validation of a liquid chromatographic method for the analysis of capreomycin sulfate and its related substances

A gradient LC method for the analysis of capreomycin sulfate and its related substances was developed. The chromatographic conditions include the use of a Hypersil base deactivated C₁₈ (250 mm × 4.6 mm, 5 μm) column maintained at 25 °C, a mobile phase containing acetonitrile, phosphate buffer pH 2.3 and 0.025 M hexanesulfonate at a flow rate of 1.0 mL/min and UV detection performed at 268 nm. Good separation of the four active components of capreomycin and eleven unknown impurities was achieved. A system suitability test to check the quality of the separation is specified. The method shows good repeatability, linearity and robustness.     

Low-threshold current, high-efficiency 1.3-μm wavelengthaluminum-free InGaAsN-based quantum-well lasers

We demonstrate high-performance Al-free InGaAsN-GaAs-InGaP-based long-wavelength quantum-well (QW) lasers grown on GaAs substrates by gas-source molecular beam epitaxy using a RF plasma nitrogen source. Continuous wave (CW) operation of InGaAsN-GaAs QW lasers is demonstrated at λ=1.3 μm at a threshold current density of only J_TH =1.32 kA/cm². These narrow ridge (W=8.5 μm) lasers also exhibit an internal loss of only 3.1 cm^-1 and an internal efficiency of 60%. Also, a characteristic temperature of T₀=150 K from 10°C to 60°C was measured, representing a significant improvement over conventional λ=1.3 μm InGaAsP-InP lasers. Under pulsed operation, a record high maximum operating temperature of 125°C and output powers greater than 300 mW (pulsed) and 120 mW (CW) were also achieved     

Probing interface electronic structure with overlayer quantum-well resonances: Al/Si(111)

The dispersion of quantum-well resonances in ultrathin epitaxial Al films on Si(111) reveals energy- and wave vector-dependent reflection properties at the Al/Si interface. The substrate electronic structure strongly influences the phase shift of the electron waves upon reflection at the interface. Thus the details of the substrate electronic structure need to be taken into account for a complete analysis of metallic quantum-well resonances. Furthermore, the assumption of loss of parallel wave vector information upon reflection or transmission through a lattice-mismatched interface is challenged. The changes induced in the electronic structure of the overlayer can be used to probe the ground-state substrate band edges.     

A note on resolutions mod i

In this note we give new examples of Golod pairs, extending results of Shamash, Avramov, Gover and Salmon. We also prove a result, relating Betti numbers of ideals I and I + (x) in a local ring R where the ideal I has a linear protective resolution and x is a non zero divisor in R.     

Variational approach to the Hamiltonian structure of a new hierarchy of nonlinear equations

We determine the symplectic Hamiltonian structure associated with the nonlinear evolution equations obtained from two new isospectral problems. We follow the method of variation with respect to the field variables. An explicit example is given to demonstrate the new class of equations that are generated.     

Kinetics and mechanism of the oxidation of d-mannose with pyridinium chlorochromate

The kinetics of oxidation of D-mannose with pyridinium chlorochromate, C₅H₅NHCrO₃Cl, was investigated in aqueous perchloric acid medium. The ionic strength of the medium was maintained constant by adding sodium perchlorate solution. The oxidation process exhibits unit dependence in each of the reactants, namely D-mannose and pyridinium chlorochromate. The reaction is acid catalyzed. A 32 stoichiometry is observed in the oxidation and the reaction did not induce polymerization of acrylonitrile. Activation parameters have been computed by measuring the rates at different temperatures. A reaction mechanism consistent with the experimental observation is proposed.     

High-power high-efficiency 0.98-μm wavelengthInGaAs-(In)GaAs(P)-InGaP broadened waveguide lasers grown by gas-sourcemolecular beam epitaxy

We describe the design and experimental results for high-power, high-efficiency, low threshold current, 0.98-μm wavelength, broadened waveguide (BW) aluminum-free InGaAs-(In)GaAs(P)-InGaP lasers. The decrease in the internal losses with an increase in the width of the waveguide layer for a separate-confinement heterostructure multiple-quantum-well (SCW-MQW) structure is attributed to lower free-carrier absorption due to the reduced overlap of the optical mode with the highly doped cladding regions. The BW lasers grown with both InGaAsP and GaAs waveguides show lower internal losses and similar threshold currents than those designed for an optimum optical confinement factor within the QW region. We report a record-low internal loss of 1.8±0.2 cm^-2 for (In)GaAs(P)-InGaP lasers grown by gas-source molecular beam epitaxy (GSMBE). The temperature dependence of internal loss suggests that optical loss from free-carrier absorption in the waveguide dominates at T>40°C, while near room temperature, the residual loss is attributed to scattering and free-carrier absorption in the QW's. The relative insensitivity of internal loss near room temperature has enabled the use of a simplified InGaAs-GaAs-InGaP BW structure to achieve very high CW and quasi-CW (QCW) power operation. We report the highest CW output power of 6.8 W for a GaAs-InGaP laser, and the highest quasi-continuous output power of 13.3 W measured for a single 100-μm-wide aperture, 0.8-0.98-μm wavelength Al-free laser diode grown by GSMBE     

Effect of plant extracts on book deteriorated fungal species

Abstract

The aim of the study was to evaluate the effect of leaf extracts of four plants against some isolated fungal species from deteriorated books. Aqueous, methanol and chloroform extracts of selected plant species were screened in vitro for their antifungal activity against some book deteriorating fungal species. Fifteen species belonging to 09 genera were isolated and identified from infested books in library. Aqueous and solvent extracts of leaves of Azadiracta indica, Callistemon citrinus, Eucalyptus lanceolatus and Pongamia pinnata were tested against some dominant fungal species viz. Chaetomium spiralis, Alternaria alternata, Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus and Rhizopus stolonifer. Solvent extracts exhibited potent inhibitory activity than aqueous extracts. However, these plant extracts exhibited moderate activity against A. flavus, C. spiralis, R. stolonifer and A. alternata.