Diode-end-pumped Tm:GdVO4 laser operating at 1818 and?1915?nm

High power operation at 1818 and 1915 nm has been demonstrated from a Tm:GdVO₄ laser operating in quasi-continuous-wave mode with a maximum measured power of 8.7 W and a laser output energy of 175 mJ was observed in a 20 ms pulse at 1.9 μm. The operation at 1818 nm is the shortest wavelength achieved at multi-watt power levels for a Tm-doped solid-state laser without intra-cavity tuning elements. It has been shown that by careful analysis of the emission spectra, the Tm:GdVO₄ laser can be tuned over a 100 nm wavelength range simply by appropriate selection of the reflectivity of the output coupler.     

Interpolation formula for the electrical conductivity of nonideal plasmas

On the basis of a quantum‐statistical approach to the electrical conductivity of nonideal plasmas we derive analytical results in the classical low‐density regime, in the degenerate Born limit, and for the contribution of the Debye‐Onsager relaxation effect. These explicit results are used to construct an improved interpolation formula of the electrical conductivity valid in a wide range of temperature and density which allows to compare with available experimental data of nonideal plasmas.     

Determination of selenium with solid sampling and direct Zeeman-AAS

Summary It is demonstrated by analysis of four standard reference materials (NBS 1632 a coal, NBS 1633 a coal fly ash, NBS 1648 urban particulate matter and BCR 176 city waste incineration ash) that the selenium determination by Solid Sampling ZAAS works well, if fine grained elemental nickel is used as matrix modifier. Optimum nickel-to-sample ratios are in the range of 21 to 81. Admixture of graphite powder is necessary in some cases in addition. The detection limit is about 0.1 g/g. If the matrix is well-known, the described method is a convenient and fast alternative to conventional trace analytical techniques.

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Selenbestimmung aus festen Proben mit direkter Zeeman-AASTeil 1

Zusammenfassung Durch die Analyse von vier Standardreferenzmaterialien (NBS 1632 a Kohle, NBS 1633 a Kohleflugasche, NBS 1648 Stadtstaub und BCR 176 Stadtmüllverbrennungsasche) wird gezeigt, daß die Selenbestimmung mittels Feststoff-ZAAS zu guten Ergebnissen führt, wenn feinkörniges elementares Nickelpulver als Matrixmodifizierer eingesetzt wird. In der Regel ist ein zwei- bis achtfacher Nickelüberschuß erforderlich, ggf. auch eine Beimischung von Graphitpulver. Die Nachweisgrenze des Verfahrens liegt bei etwa 0,1 g/g. Bei gut bekannter Matrix ist die beschriebene Methode eine bequeme und schnelle Alternative zu konventionellen spurenanalytischen Techniken.

     

Effect of Molecular Structure on Mesomorphism: 5. Comparison of Methyl and Trifluoromethyl as Lateral Substituents in the Solid and Nematic Phases.1

Two laterally-substituted nematogenic liquid crystals, methyl-p-phenylene-di-p-butoxybenzoate and trifluoromethyl-p-phenylene-di-p-butoxybenzoate, have been studied by differential scanning calorimetry, powder x-ray diffraction, and polarized light microscopy (hot stage microscopy and hot-wire stage microscopy). Comparison of thermodynamic data for the nematicisotropic transitions of these two compounds suggests a strongly repulsive electronic interaction between molecules in the nematic phase of the trifluoromethyl compound. Detailed molecular structural augments are presented to rationalize the thermodynamic data. The room temperature solid phases of the two compounds were found to have different crystal structures. However, the high temperature solid phases were found, by a novel application of hot-wire stage microscopy, to be isomorphous.