The dielectric constant associated with direct interband transitions in germanium

An expression for the complex dielectric constant associated with direct interband transitions in germanium has been obtained using a simple model. The model consists of four damped oscillators, and a fit to experimental results for the complex dielectric constant is made to obtain the model parameters, i.e., the oscillator frequencies and damping constants. The results show good agreement with experimental data over a broad range of frequencies.     

Accuracy and precision of natural gas analysis

Summary Calculations of natural gas properties from chromatographic analysis is increasingly popular. An application of the significance of the various sources of error allows the overall uncertainty of the analytical procedure to be evaluated. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Theory of the effect of a DC magnetic field on surface space-charge-wave/optical phonon instabilities in semiconductor media

A theoretical investigation has been carried out on the effect of a DC magnetic field on surface space-charge-wave instabilities caused by a drift current parallel to the surface of a doped polar semiconductor. The magnetic field is taken as perpendicular to the semiconductor surface. The dispersion relation is obtained using a generalization of the Kliewer-Fuchs specular-reflection boundary conditions. Calculated results are obtained in the non-retarded limit for two cases: (1) where a current-carrying, nonpolar semiconductor interfaces a polar insulator half-space and (2) where a current-carrying, polar semiconductor interfaces a nonpolar insulator half-space. Convective or amplifying instabilities arise because of the presence of optical phonons. Numerical results are presented for the gain as a function of frequency and magnetic field.     

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are reported, including a 4:1 salt with the meso stereoisomer of the dinuclear [Fe₂(oxalate)₅]⁴⁻ anion in which both cation and anion have chiral components linked together by hydrogen bonding, and a semiconducting salt with triiodide.     

Tristaenone A: A New Anti-Inflammatory Compound Isolated from the Australian Indigenous Plant Tristaniopsis laurina

Inspired by ethnopharmacological knowledge, we conducted a bioassay-guided fractionation of the leaves of Tristaniopsis laurina which led to the discovery of a new anti-inflammatory compound, tristaenone A (1). The structure was elucidated by detailed spectroscopic data analysis, and the absolute configuration was established using X-ray crystallography analysis. Tristaenone A (1) suppressed LPS and IFN-γ-induced NO, TNF-α and IL-6 production in RAW 264.7 cells with IC₅₀ values of 37.58 ± 2.45 μM, 80.6 ± 5.82 μM and 125.65 ± 0.34 μM, respectively. It also inhibited NF-κB nuclear translocation by 52.93 ± 14.14% at a concentration of 31.85 μM.