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.     

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.     

Pt-Cu / ZSM-5 for removal of nitrates from drinking water

Removal of nitrates from drinking water by catalytic hydrogenation over ZSM-5 supported Pt-Cu catalysts was studied. Bimetallics Pt-Cu were prepared by ion exchange of copper on a parent monometallic platinum catalyst. Monometallic platinum catalysts are inactive for nitrate reduction, while Pt-Cu bimetallic catalysts are active for nitrate removal. In the bimetallic catalyst, the role of copper is probably to reduce nitrate according to a redox reaction. The addition of copper to Pt catalysts decreases the production of ammonium ions     

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).     

Target isotope effect in high energy photon production atE/A=10 MeV

A comparison has been made between the production of high energy (E _γ≧30 MeV)γ rays from the bombardment of¹²⁴Sn and¹¹²Sn targets withE/A= 10 MeV¹²C ions. The results are well explained by then-p bremsstrahlung model and do not indicate the need for any new processes.     

Novel processing tools for automated doppler picture veocimetry (DPV) evaluation

A unique technique, the Doppler Picture Velocimetry (DPV), for measuring and visualizing velocities especially in hypersonic gas flows is presented. By means of a Michelson interferometer (MI) the Doppler shifted light scattered by tracers is transformed into an image showing Fizeau fringes. The image fringe distribution provides information on the Doppler frequency shift which is related to the velocity of the particles crossing a light sheet plane. To overcome former disadvantages of DPV, the optical set-up as well as the processing scheme have been improved significantly. Two schemes have been tested in recent times for fringe processing: 1) an alternative process, the Least Square Estimators (LES) and 2) an algorithm based on a technique using Fast Fourier Transformations (FFT) to examine the DPV images in the frequency domain. The new DPV algorithms now allow an automated calculation of the velocity profiles from the Doppler pictures without manual fringe tracing as it had to be done in the past. Both methods are compared by means of Mach 6 flows around a wedge and a sphere produced in the ISL high energy shock tunnel STA. TiO₂ particles are illuminated by a laser light sheet which was perpendicularly arranged to the main flow direction. Light observation via the MI from the side (90° to illumination) informs on the vertically oriented velocity through the DPV images.     

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.     

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.