The correction for the counting yield in nuclear spectroscopy

Pulser and live timer are alternate tools. Dead time effects can be expressed in terms of a pulse rate dependent factor of the counting yield. The task of their correction should be shifted from the live timer of the ADC to a central timing unit. A new method is proposed, combining the advantages of the pulser and the live timer, where by each selected and accepted event is adjoined to a clock time interval and each selected but not accepted event to a dead time interval. The length of each interval is determined by the arrival of the next selected event.     

Gravimetrische Halogenbestimmung in organischen Verbindungen nach dem Hydrierverfahren

Zusammenfassung Es wurde eine gravimetrische Halogenbestimmung zur Analyse organischer Substanzen ausgearbeitet. Die Pyrolyse und Hydrierung wird in ammoniakhaltigem Wasserstoffstrom ausgeführt, die gebildeten Ammoniumhalogenide werden in einem nach dem Hydrierrohr geschalteten Absorptionsrohr gesammelt. Die Analyse läßt sich durch Wägung des Absorptionsrohres ausführen. Gleichzeitige Gegenwart von Schwefel stört die Analyse nicht.

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Summary A gravimetric method has been worked out for determining the halogens in organic materials. The pyrolysis and hydrogenation are conducted in a current of hydrogen containing ammonia, and the ammonium halides formed are collected in an absorption tube attached to the hydrogenation tube. The analysis can be done by weighing the absorption tube. The presence of sulfur does not interfere with the analysis.

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Résumé On a élaboré un dosage gravimétrique des halogènes dans l'analyse des substances organiques. On réalise la pyrolyse et l'hydrogénation dans un courant d'hydrogène contenant de l'ammoniac et l'on recueille les halogénures d'ammonium formés dans un tube à absorption disposé après le tube à hydrogénation. On peut effectuer l'analyse en pesant le tube à absorption. La présence simultanée du soufre ne gêne pas l'analyse.

     

Correlation between transport and equilibrium properties through the ternary interaction parameter for cosolvent and cononsolvent polymeric systems

A study of the ternary polymer systems dimethyl formamide-ethyl acetate-polystyrene, chloroform-1,4 dioxane-polystyrene and tetrahydrofuran-chloroform-polystyrene was carried out by viscosity and light scattering at 298 K. A good correlation has been found between the excess intrinsic viscosity, unperturbed polymer dimensions, second virial coefficient and the excess Gibbs free energy by using a ternary interaction parameter, dependent on molecular weight. This modification enables the conversion between transport and equilibrium properties.     

Nucleophilic additions of lithiated allylphenylsulfone to nitrones: experimental and theoretical investigations

The nucleophilic addition of lithiated allylphenylsulfone to nitrones at −80 °C proceeds exclusively α to the phenylsulfonyl group affording anti adducts in high yield. At 0 °C isoxazolidines are obtained with complete all-trans selectivity. The formation of these compounds involves isomerization of the allylsulphonyl moiety to give a transient vinylsulfone that then undergoes a subsequent intramolecular Michael addition. The addition to several nitrones has been studied and theoretical calculations have been refined to accurately explain the selectivity of the allylation reaction.     

Effect of macromolecules and Triton X-100 on the triplet of aggregated chlorophyll in aqueous solution

Chlorophyll a (Chla) in aqueous solution (2-6% acetone) is present as mono- and dihydrated aggregated forms which are characterized by specific ground state absorption spectra. The amount of dihydrated form is larger in the presence of macromolecules, such as bovine serum albumin (BSA), lysozime and polyvinyl alcohol (PVA), increasing from BSA to lysozime and PVA. Chla in aqueous acetone with and without macromolecules is characterized by low fluorescence and the absence of triplet-triplet (T-T) absorption. The ratio of dihydrated to monohydrated forms is significantly influenced by triton X-100. For lower triton X-100 concentrations, i.e. smaller than the critical micelle concentration of 0.26 mM (cmc), dihydrated forms are converted into monohydrated in both aqueous acetone and the presence of BSA or lysozime. In the presence of PVA dihydrated forms appeared to be resistant to triton X-100 action. Moreover, for triton X-100 concentrations of 2-3 times higher than cmc the amount of these forms is increased with time. T-T absorption of both mono- and dihydrated Chla aggregates was not detected in the presence of [triton X-100] < cmc. The lack of T-T absorption in aqueous acetone solution as well as in the presence of macromolecules implies that the triplet lifetime of the chlorophyll aggregates is short (tauT<10 ns) and/or the quantum yield of intersystem crossing is small (<5 x 10(-3)). The Chla monomers start to be formed as solubilized in the micelle for [triton X-100] larger than cmc, showing substantial fluorescence and T-T absorption.     

Synthesis and spectral properties of 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodi-azepine-2-thiones

A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr and ms.     

Thermal decomposition of lanthanum selenate pentahydrate in air and nitrogen

Thermogravimetric studies, supported by IR and X-ray diffraction measurements, were carried out for La₂(SeO₄)₃ · 5H₂O in order to establish its decomposition scheme under various experimental conditions. Several analytical methods were tested for the simultaneous determination of (Se(IV) and Se(VI) in the quenched samples. TG weight losses and analyses of the solid intermediates indicated that after dehydration La₂(SeO₄)₃ decomposes in nitrogen mainly to oxyselenite(IV) compoundsvia the normal selenite(IV) but in air the oxyselenate La₂O₂SeO₄ was detected as one of the intermediates. The final product of the thermal degradation is La₂O₃. TG curves of La₂(SeO₄)₃ · 5H₂O were also compared with those obtained for the isostructural neodymium compound.     

Racematspaltung von chiralen Ferrocenderivaten durch Gegenstromverteilung

Optical resolution by counter-current distribution has been demonstrated on a preparative scale for two chiral ferrocene derivatives, e.g. 1.2-(α-oxotetramethylene)ferrocene (1), and 1.2-(α-butenylene)ferrocene (2), resp., in the system cyclohexane—(+)-diethyltartrate. The optical yields were 12 and 1%, resp., and are in good agreement with the values calculated from the partition coefficients of the enantiomers. The optical purity of1 could be increased to 40% by crystallization from cyclohexane. A resolution of1 with an optical yield of 14% was also possible by thin layer partition chromatography on silica gel using the same solvents.     

Studies of the silica reduction process by carbon

The reduction of amorphous silica by carbon black was studied in argon atmosphere by use of MOM Derivatograph C. The apparent kinetic parameters of the process were determined. The possible mechanism of reaction was proposed.

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Zusammenfassung Unter Verwendung eines MOM Derivatograph C wurde in Argonatmosphäre die Reduktion von Siliziumdioxid mit Ruß untersucht. Es wurden die scheinbaren kinetischen Größen des Prozesses bestimmt und ein möglicher Reaktionsmechanismus vorgeschlagen.