Reported are: determination of imperfections on a laser spatial-filter lens; oxidation of U in O/sub 2/--N/sub 2/ mixtures; use of polarized x-rays to improve detection limits in energy-dispersive x-ray fluorescence analysis; detection of less than 1 ppT of organic compounds by laser-induced molecular fluorescence; a Stark-shift laser spectrometer; photoionization thresholds of Nd, Sm, Eu, Dy, and Er; response tests of chloride ion-selective electrodes; chemical analyses of explosive composites; solid formation and corrosion in geothermal brine; analysis of carbonates in oil shales; models of methane combustion; and biofuel production from algae. (DLC)