Über Glasbildung und Eigenschaften von Chalkogenidsystemen. XXVIII. Zur Bindungsenergie der Si?Si- und Ge?Ge-Bindung in den Verbindungen Na6Si2X6 und Na6Ge2X6 (X = S,Se)

About Glas Formation and Properties of Chalcogenide Systems. XXVIII. On Bonding Energies of Si? Si and Ge? Ge Bonds in Na₆Si₂X₆ and Na₆Ge₂X₆ (X = S, Se) Potentiometric titration of 0.01 molar solutions of Na₆Si₂S₆, Na₆Si₂Se₆, Na₆Ge₂S₆, and Na₆Ge₂Se₆ in methanol with bromine yields the thermodynamic data of the reactions which take place under scission of the Si—Si or Ge—Ge bonds, respectively. The bonding energies of these homonuclear bonds are estimated and compared with data from the literature.     

Test of a rich-prototype detector with solid photocathode for hades

The development of a Ring Imaging CHerenkov (RICH) detector working in an environment of strong hadronic background is needed for the High Acceptance Di-Electron Spectrometer (HADES). To get information about the charged particle background situation, a CERN RICH prototype with solid (CsI) photocathode was tested in a 1×A GeV U+Pb reaction at GSI. Also the quantum efficiency of the CsI photocathode was determined to be 10% at 175 nm.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994.For the HADES Collaboration (IOP Bratislava, Univ. Clermont-Ferrand, GSI Darmstadt, Univ. Frankfurt, Univ. Gießen, Univ. Kraków, Univ. Milano, ITEP Moscow, LPI Moscow, MEPI Moscow, TU München, Univ. Nikosia, NPI e, Univ. Valencia).We would like to thank F. Piuz for providing the detector and A. Braem for the production of the CsI photocathode. We are also grateful to the accelerator crew at GSI for the stable beam and the Gießen crew W. Döring, A. Rühl and J. Schneider for support.This work was supported in part by BMFT under contract No. 06 GI 475 I(3) and by GSI.     

Über Glasbildung und Eigenschaften von Chalkogenidsystemen. XIII. Über die Verbindungen Na6Ge2S6 · 4 CH3OH und Na6Ge2Se6 · 4 CH3OH

Glass Formation and Properties of Chalcogenide Systems. XIII. On the Compounds Na₆Ge₂S₆ · 4 CH₃OH and Na₆Ge₂Se₆ · 4 CH₃OH The glasses Ge₂S₃ and Ge₂Se₃ are soluble in solutions of Na₂S or Na₂Se in CH₃OH forming Na₆Ge₂S₆ · 4 CH₃OH and Na₆Ge₂Se₆ · 4 CH₃OH. On heating the CH₃OH-free substances are formed. From the i.r. and Raman spectra can de seen that the structure of the ions Ge₂S, Ge₂Se, P₂S₆^4?, and of Si₂Cl₆ is of the same type. The formation of the compounds can be regarded as a chemical proof for the existence of [Ge₂S₆] and [Ge₂Se₆] units as structural groups in the glasses Ge₂S₃ and Ge₂Se₃.     

Gewöhnliche lineare Differentialgleichungen zweiter Ordnung mit Distributionskoeffizient

Zusammenfassung Läßt man in der gew. lin. Dgl. zweiter Ordnung einen Distributionskoeffizient zu, der Ableitung einerL _loc ² -Funktion ist, so existieren eindeutig festlegbare, stetige Lösungen derart, daß die in der Dgl. auftretenden Produkte definiert werden können. Mit einer Regularisierung des Distr.-Koeffizienten können die Lösungen durchC -Funktionen approximiert werden. Es wird der Sturmsche Vergleichssatz verallgemeinert. Hieraus und aus den Eigenschaften der mit zwei Basislösungen gebildeten Lösungskurve folgt die Gültigkeit des Ljapunovschen Satzes über die Eigenwertverteilung der verallgemeinerten Hillschen Dgl. mit positivem Distr.-Koeffizient, falls eine zusätzliche Bedingung erfüllt ist. Die vorliegende Arbeit enthält einige Ergebnisse meiner Dissertation [6] (weitere Resultate und Details finden sich dort).     

Development of a manual method for the determination of mineral oil in foods and paperboard

So far the majority of the measurements of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) were obtained from on-line high performance liquid chromatography–gas chromatography–flame ionization detection (on-line HPLC–GC–FID). Since this technique is not available in many laboratories, an alternative method with more easily available tools has been developed. Preseparation on a small conventional liquid chromatographic column was optimized to achieve robust separation between the MOSH and the MOAH, but also to keep out the wax esters from the MOAH fraction. This was achieved by mixing a small portion of silica gel with silver nitrate into highly activated silica gel and by adding toluene into the eluent for the MOAH. Toluene was also added to the MOSH fraction to facilitate reconcentration and to serve as a keeper preventing loss of volatiles during solvent evaporation. A 50 μl volume was injected on-column into GC–FID to achieve a detection limit for MOSH and MOAH below 1 mg/kg in most foods.     

Rho(0) meson production in the pp-->pppi(+)pi(-) reaction at 3.67 GeV/c

Total and differential cross sections for the exclusive reaction pp-->pp rho observed via the pi(+)pi(-) decay channel have been measured at p(beam)=3.67 GeV/c. The observed total meson production cross section is determined to be (23.4+/-0.8+/-8) mu b and is significantly lower than typical cross sections used in model calculations for heavy-ion collisions. The differential cross sections measured indicate a strong anisotropy (approximately cos(theta(CM)(rho)) in the rho(0) meson production.     

Comparison of surface coverage values of tungsten-alumina catalysts determined by different methods

Apparent surface coverage (ASC) of a series of tungsten-alumina catalysts was determined by the electrophoretic migration method (EM). A linear increase in W coverage with increasing W loading (up to 13.1 wt.% W) was observed. The results were in close agreement with those obtained previously by ion scattering spectroscopy (ISS) and low temperature CO adsorption.