Parametrische 4-Photonenfluoreszenz in Rutil

Tunable four-photon parametric fluorescence due to the third-order optical nonlinearity has been observed in a rutile (TiO₂)-crystal. AQ-switched ruby-laser was used as a pump. The produced idler wave could be tuned from 5900 to 6550 Å by rotation of the crystal.     

15N Distribution in Wheat and Chemical Fractionation of Root-Borne 15N in the Soil

Abstract

Spring wheat plants were grown in split-root containers and labelled with ¹⁵N by fertilizing one compartment of the container with ¹⁵NH₄ ¹⁵NO₃ (95 at.-% ¹⁵N exc.). After the harvest, approx. 90% of the ¹⁵N incorporated by the plants were found in the shoots and 3% in the roots; approx. 7% had been released into the soil of the unlabelled compartment. The ¹⁵N in the soil of the unlabelled compartment was extracted with KCl and hydrolysed with HCl. Approx. 60% of the ¹⁵N was found in the hydrolysable organic N pool of the soil and 9% in the fraction of the soluble and exchangeable inorganic nitrogen.     

The reaction of ethyl chromone-2-carboxylates with 1,2-diaminobenzene

Ethyl chromone-2-carboxylate and all its benzoanalogs were prepared and caused to react with 1,2-diami-nobenzene to give 2-(2-hydroxybenzoyl)methinyl-3-oxo-1,2,3,4-tetrahydroquinoxaline and its benzo analogs. The condensation products of diethyl oxalate and methyl hydroxyaryl ketones which were required for the preparation of the starting esters, were found to be subject to ring chain tautomerism.     

Zur Synthese von Human-Big-Gastrin I und seinem 32-Leucin-Analogon

The preparation of the pure tetratriacontapeptide amide 2 (human big gastrin I) and the analogue Leu³²-human big gastrin I from the crude synthetic materials obtained after deblocking of the overall protected tetratriacontapeptide amide derivatives by means of trifluoroacetic acid is described. The criteria for homogeneity obtained by chromatographic, electrophoretic, enzymatic and spectroscopic methods are reported.

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Abkürzungen HBG-I Human-Big-Gastrin I - LHBG-I 32-Leucin-Human-Big-Gastrin I - HBG-[1-20] N-terminale Teilsequenz [1–20] des Human-Big-Gastrins I - HG-17-I Human-Gastrin I - LHG-17-I 15-Leucin-Human-Gastrin I - HG-13-I Human-Minigastrin I - LHG-13-I 11-Leucin-Human-Minigastrin I Es werden hier die von der IUPAC-IUB Commission on Biochemical Nomenclature empfohlenen Abkürzungen für Aminosäuren und Schutzgruppen verwendet.Andere Abkürzungen.Anm.: Auf Grund der kürzlich erfolgten Strukturkorrektur (R. A. Gregory, H. J. Tracy, J. I. Harris, M. J. Runswick, S. Moore, G. W. Kenner undR. Ramage, Hoppe-Seylers Z. physiol. Chem.360, 73, 1979) sind HG-13-I und LHG-13-I neuderdings richtiger als Des-1-Tryptophan-Human-Minigastrin I bzw. [Des-1-Tryptophan]-11-Leucin-Human-Minigastrin I zu bezeichnen].Vorläufige Mitt.:E. Wünsch, G. Wendlberger, A. Hallett, E. Jaeger, S. Knof, L. Moroder, R. Scharf, I. Schmidt, P. Thamm undL. Wilschowitz, Z. Naturforsch.32c, 495 (1977).3. Mitt.:G. Wendlberger, L. Moroder, A. Hallett undE. Wünsch, Mh. Chem.110, 1407 (1979).     

Estimation of quantum efficiencies and Arrhenius parameters of organic laser dyes by measuring fluorescence decay times down to T = 115 K

The fluorescence decay times of several organic dyes in alcoholic solution in the temperature range between 300 K and 115 K are measured. These measurements offer the possibility to determine Arrhenius parameters and to estimate quantum efficiencies.     

An assessment of the mobility of squalene in part-aqueous solutions from carbon magnetic resonance spin-lattice relaxation times : Comparison with squalene and 2,3-dihydroxy-2,3-dihydrosqualene

The ¹³C NMR of squalene in tetrahydrofuran-d₈ is sufficiently resolved for T₁ measurements (by the inversion-recovery method) to permit the derivation of relative mobilities along the chain On addition of water, no detectable changes occur to the point of saturation, consistent with the absence of conformational changes (coiling) with change in solvent polarity. On the basis of silver-ion induced carbon chemical shifts, complexation occurs unselectively at all three double bonds in THF, but with some preference for the terminal double-bond in part-aqueous solutions. Squalane shows similar mobility to the unsaturated compound but complications from line overlap are apparent. In squalene-2,3-glycol, the polar end of the molecule is of lower mobility, and this difference is accentuated on addition of water consistent with specific association of water at the OH terminus.     

Determination of mercury in seawater by cold vapour atomic absorption spectrophotometry

Summary To avoid systematic errors in the sampling and determination of mercury in seawater an integrated sampling-analyzing system has been developed. A 500 ml PTFE-bottle attached to a sampling gear is used as sampling vessel for the cold vapour atomic absorption Spectrophotometry, using nitrogen aeration, SnCl₂ reduction, and preenrichment/ purification by amalgamation on finely dispersed gold. The detection limit of this procedure was found to be 0.5 ng·l^–1 and the coefficient of variation 4% for 1.5 ng·l^–1.

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Bestimmung von Quecksilber im Meerwasser durch Kaltdampf-Atomabsorptionsspektralphotometrie

Zusammenfassung Zur Vermeidung von systematischen Fehlern bei der Ultraspurenanalyse von Quecksilber im Meerwasser wurde ein integriertes Probenahme-Analysensystem entwickelt. Eine 500 ml PTFE-Flasche dient in Verbindung mit einem Greifarm als Probenahmegefäß für Oberflächenwasser und wird anschließend als Reaktionsgefäß in die Analysenapparatur gesetzt. Die Bestimmung erfolgt mit der Kaltdampf-Atomabsorptionsspektralphotometrie nach Reduktion des Quecksilbers durch SnCl₂ und Anreicherung sowie Reinigung mittels Amalgamierung an feinverteiltem Gold. Die Nachweisgrenze dieses Verfahrens beträgt 0,5 ng·l^–1, der Variationskoeffizient 4% bei 1,5 ng·l^–1.

     

A comparison of negative and positive ion mass spectrometry

Negative ion mass spectrometry using a conventional mass spectrometer with a special ion source and a sample pressure of approximately 2 × 10^?5 Torr is shown to be an excellent method for the qualitative analysis of lower mass alcohols, mercaptans, ketones, aldehydes, aliphatic carboxylic acids and esters, the spectra of which are characterized by intense [M – H] ^? ions. The method may be termed a ‘selective’ low energy ionization technique, being suitable for the above organic compounds, but not for nitriles, nitro compounds, hydrocarbons, ethers, amines, amides, nitrogen heterocycles and chlorinated compounds. This method can be looked upon as a complementary method, to positive ion mass spectrometry.