Incoherent harmonic emission from strong electromagnetic waves inplasmas

The work of E.S. Sarachik and G.T. Schappert (Phys. Rev. D, vol.1, pp.2738-2753, 1970) on higher-order or harmonic Thomson/Compton scattering is reexamined, with a view to its evaluation as a useful diagnostic for the interaction of weakly relativistic laser light with low-density plasma. Some consideration is given to plasma effects not mentioned in the original single-electron model (electron plasma oscillation and electron filamentation effects). While relative power scattering measurement can still be made, these plasma effects will seriously complicate or compromise any attempts to use the Doppler shift content of the single-electron harmonic scattering, although plasma oscillations of some sort may well be inferred     

The retrieval of profile and chemical information from ground-based UV-visible spectroscopic measurements

An algorithm has been developed to retrieve altitude information at different diurnal stages for trace gas species by combining direct-sun and zenith-sky UV-visible differential slant column density (DSCD) measurements. DSCDs are derived here using differential optical absorption spectroscopy. Combining the complementary zenith-sky measurements (sensitive to the stratosphere) with direct-sun measurements (sensitive to the troposphere) allows this vertical distinction. Trace gas species such as BrO and NO₂ have vertical profiles with strong diurnal dependence. Information about the diurnal variation is simultaneously retrieved with the altitude distribution of the trace gas. The retrieval is a formal optimal estimation profile retrieval, allowing a complete assessment of information content and errors.     

Discount Weighted Regression

A recursive procedure for discounted multiple linear regression is described, together with a discounted estimator for the residual variance. The method is simple to program and involves no matrix inversion. Two examples are given.     

Superconductivity in a new ternary structure class of boride compounds

The occurrence of superconductivity at temperatures up to 9.6 K is reported for the system M(Rh_0.85Ru_0.15)₄B₄, where M can be Y or a rare earth element. In contrast, most members of the isostructural series MRu₄B₄ are either not superconducting or order magnetically instead. These materials were found to crystallize in a body-centered-tetragonal structure, with space group I⁴₁/acd and 8 formula units per unit cell. The atomic positions were determined through a structural study of the LuRu₄B₄ compound. These results are discussed with reference to the previously reported primitive tetragonal MRh₄B₄ system of superconducting or ferromagnetic compounds.     

A short formal synthesis of squalamine from a microbial metabolite

A short formal synthesis of squalamine is described, utilizing the biotransformation product 2, which is available in one step from commercially available 3-keto-23,24-bisnorchol-4-en-22-ol (1). Regioselective C-22 oxidation and C-24 sulfation of the corresponding alcohols in the presence of a free C-7 alcohol make for an efficient preparation of squalamine intermediate 11.