Search Results - (Author, Cooperation:R. Schuetz)

2012-05-05

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Adaptation, Physiological ; Adenosine Triphosphate/metabolism ; Aerobiosis ; Algorithms ; Bacteria/growth & development/*metabolism ; *Biological Evolution ; Biomass ; Computer Simulation ; Escherichia coli/genetics/growth & development/*metabolism ; Glucose/metabolism ; *Metabolic Networks and Pathways ; Models, Biological

article

1985

Gesundheitserziehung ; Weiterbildung ; Alter Mensch

Seniorenstudium - eine neue Aufgabe fuer Hochschulen., Dortmund: Sanduhr (1985), S. 262-270

German

0030-5383

Linguistics and Literary Studies

Ethnic Sciences

History

Besprechungen

1432-1912

Springer Online Journal Archives 1860-2000

Medicine

Summary The chemical nature of the „slow reacting substance“ (SRS) which appears in perfusates or extracts of guinea pig lung after injection of cobra venom has been investigated. The solubility pattern of SRS, its behaviour in liquid-liquid distribution and in chromatography as well as its actions on smooth muscle indicate that SRS consists of pharmacologically active unsaturated fatty acids. These acids apparently derive from tissue phosphatides from which they are cleaved by the action of phospholipase A contained in cobra venom. This conclusion is confirmed by the finding that purified phospholipase A obtained from bee venom also liberates SRS.

Zusammenfassung Es wurden Untersuchungen zur chemischen Natur der „slow reacting substance“ (SRS), die sich in der Durchströmungsflüssigkeit isolierter Meerschweinchenlungen und in Lungenextrakten nach Cobragifteinwirkung nachweisen läßt, angestellt. Auf Grund der Löslichkeit, des Verhaltens bei Verteilung und Chromatographie und pharmakologischer Eigenschaften wird geschlossen, daß es sich bei der SRS um ungesättigte Fettsäuren handelt, die aus Gewebsphosphatiden durch die Cobragift-Phospholipase A abgespalten werden. Dieser Schluß wird dadurch bestätigt, daß gereinigte Bienengift-Phospholipase A ebenfalls SRS freisetzt.

Electronic Resource

1432-1912

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1432-1440

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Es wird eine eingehende Beschreibung der Kälteverdünnungsmethode zur Herzzeitvolumenbestimmung gegeben. Als Injektionsflüssigkeit wird isotonische Lösung von +1° C bzw. Zimmertemperatur verwandt. Die Messung der Temperaturdifferenz erfolgt mit Thermoelementen im arteriellen und venösen System. Die Vergleichslötstelle liegt im Rectum. Die theoretischen und praktischen Grundlagen der Methode werden beschrieben. Die Anwendungsmöglichkeiten in der Klinik nach Untersuchungen an 70 Patienten mit angeborenen und erworbenen Herzfehlern sowie an einigen Patienten ohne nachweisbares Vitium werden dargestellt. Durch entsprechende Wahl des Injektionsortes und der Meßstelle gelingt der Nachweis und die Lokalisation selbst kleiner, gasanalytisch nicht faßbarer, Shuntverbindungen in beiden Richtungen, sowie von Klappeninsuffizienzen. Auf die Bedeutung der Methode zur Differenzierung von richtig- und fehlmündenden Pulmonalvenen wird hingewiesen. Weiterhin ist eine quantitative Berechnung der Shunt- bzw. Regurgitationsvolumina möglich. Abschließend wird die von uns angewandte Kälteverdünnungsmethode einem kritischen Vergleich mit anderen Indicatormethoden und Meßprinzipien unterzogen.

Electronic Resource

1432-1912

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1434-6036

Springer Online Journal Archives 1860-2000

Physics

Abstract We calculate the spin fluctuation spectra of VN and NbN in the relevant frequency- and wave vector regime. Significant quantitative differences between the dynamical spin susceptibilities of both substances are found. While in the case of VN their amplitudes are large, especially towards the Brillouin zone boundary and for frequencies below 1 eV, enhancement effects in NbN are of minor importance.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Rate constants and efficiencies of the oxidative bleaching of triplet-excited methylene blue by different arene diazonium salts are determined by flash photolysis and stationary experiments.In the same way the rate constants of methylene blue photoreductions by diazabicylo[2,2,2]-octane (DABCO), sodium tetraphenyl borate (TPB), sodium ethylenediamine tetraacetate (EDTA), and allyl thiourea (ATU) are determined.According to these results TPB reduces methylene blue photochemically not exceedingly fast (ke = 1.5 × 107M-1s-1) but with a high efficiency (η = 0.8).At high diazonium salt concentrations (10-1 - 10-2 M), the oxidation and the reduction mechanisms of the triplet-methylene-blue sensitized dediazoniation of arene diazonium salts have similar efficiencies at high as well as at low light intensities.At low diazonium salt concentrations and with diazonium salts of low reactivity, the reduction mechanism is favoured over the oxidation mechanism.

6 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Configuration and Thermochromic Properties of Benzoine Hydrazone DerivativesZ-Benzoine aroylhydrazones (2a-d), E-benzoinephenylether phenylhydrazone (4) and E-benzoinephenylether p-chlorobenzoylhydrazone (5), respectively, are produced by acid-catalyzed reaction of benzoine and corresponding hydrazone derivatives. The configuration of these new compounds are proved by their u.v.-spectra and n.m.r.-spectra data. In comparison to the Z-isomers, the E-isomers possess a hypsochromically shifted electron transition. In the n.m.r.-spectra the Z-isomers can be detected by a downfield N-H-signal. Only the aroylhydrazones 2 have thermochromic properties in methanolic solutions, based on a geometrical E/Z-isomerization. The kinetic and thermodynamic data of this reaction agree with an inversion mechanism.

2 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Photo-excited zinc phthalocyanine tetra(sulfomorpholide) (ZnPcTSM) sensitizes the dediazoniation of arene diazonium salts via electron transfer. 1ZnPcTSM* reacts with p-methyl-, p-methoxy-, and p-diethylamino benzenediazonium tetrafluoroborate, respectively, diffusion-controlled, 3ZnPcTSM* with rate constants 3.3 × 107, 8.5 × 107, and 1.1 × 108 M-1 s-1.Quantum yields of the dye bleaching by p-methoxy benzenediazonium tetrafluoroborate show that the singlet reaction proceeds due to symmetry-allowed back electron transfer with very low efficiency, whereas the triplet reaction reaches the ISC quantum yield at [ArN2⊕] ≍ 10-3 M.In the triplet reaction an exciplex is formed as proved by the temperature dependence of the quenching rate constants and direct spectroscopic determination (τexciplex = 157 μs). From ΔG≠ of the quenching reaction the solvation reorganization parameter λ0 and the reaction distance (r = 0.37 nm) are calculated.

8 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Quenching of Fluorescence of Aromatic Compounds by Diazonium Cations in Aqueous Solutions of PolyelectrolytesThe absorption and fluorescence spectra, and lifetimes of sodiumpyrene-3-sulfonate, N-phenylacridone and acridizinium perchlorate have been measured in the absence and in the presence of sodiumpolyvinylsulfate. A study is made of the quenching by diazonium ions of the fluorescence of the aromatic compounds. The results of Stern-Volmer plots are discussed by a micro-heterogeneous model and compared with results in homogeneous solutions. It is suggested that contributions of quencher and aromatic compound in both polyelectrolyte and aqueous phases are important.

4 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Photoexcited zink tetraphenylporphyrin (ZnTPP) reacts with arene diazonium salts via electron transfer according to the oxidation mechanism. This is proved by ESR spectroscopy of ZnTPP+ formed and the fact that N2 and ZnTPP+ are formed in a molar ratio.Due to very different life-times of1(ZnTPP)* and 3(ZnTPP)* it is possible to differentiate between singlet and triplet electron transfer reactions using different diazonium salt concentrations. In this way, the respective quenching constants are determined by means of flash spectroscopy.Due to electron back transfer the singlet reaction at high concentrations of diazonium salts (0.1M) is inefficient (quantum yield 0.1), whereas back electron transfer is symmetry-forbidden in the triplet reaction which, therefore, proceeds with high quantum yields, mearly reaching the ISC quantum yield.From differences between the triplet quenching constants determined by flash spectroscopy and from product quantum yields, respectively, and from corresponding kinetic models it is concluded that the triplet reaction proceeds via a reversibly formed triplet exciplex.Complexes of meso tetraphenyl porphyrin containing Pb(II), Sn(IV), Mn(II), Ni(II), Cu(II) and Fe(III), respectively, have lower sensitization activities decreasing in the order, given in the text.

5 Ill.

Electronic Resource

0941-1216

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The Influence of Sodium Polyvinylsulfate on the Photodimerization of Acridizinium PerchlorateDuring the irradiation of aqueous solutions of acridizinium perchlorate (λexc = 405 nm) a photodimer of this compound is formed. The quantum yield of the reaction depends on the concentration of the acridizinium ion. In 10-4 m solutions the quantum yield of dimerization is π = 0.0054 ± 0.0005. Addition of the anionic polyelectrolyte sodium polyvinylsulfate leads to a considerable increase of the quantum yield (up to π = 0.6) in dependence on the concentration of the polyion. A kinetic model is developed, including the electrostatic interaction of the acridizinium cation and the polyanion.The influence of diazonium cations as competitive agent is investigated and dicussed.

6 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Quenching of Fluorescence and Excimer Formation of Sodiumpyren-3-sulfonate in Aqueous Solutions of Polydimethyldiallylammonium ChlorideThe fluorescence spectra and lifetimes of sodium-pyren-3-sulfonate have been measured in the presence of polydimethyldiallylammonium chloride. It is shown, that the excimer formation by static self-quenching of fluorescence of the pyren-3-sulfonate is based on the cooperative effect of the macroion. The association constants of interaction between the aromatic compound and the polycation are determined. Presence of diazoniumcations leads to quenching of fluorescence of pyren-3-sulfonate in both the polyelectrolyte and aqueous phases. The quenching constants are discussed.

8 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The kinetics of azocoupling between 1-benzyl-4-phenyl-, 1,3,4-triphenyl-, 4-benzyl-1-methyl-, 1,4-dimethyl-, 1,4-diphenyl-3-methylmercapto- and 3-benzyl-mercapto-1,4-diphenyl-1,2,4-triazolium salts, and p-N,N-dimethylamino benzenediazonium tetrafluoroborate are studied spectroscopically in methanol/water 1:1 (v/v) at various pH values following up the growing-in of the respective azodyes.The competing reactions of the diazonium salt with the solvent and the buffer (NH3/NH4Cl), and of some bleaching of the azodye formed were studied separately and accounted for in the kinetic treatment.From the pH dependence of the coupling rate constants and by application of kinetic models it turned out that not the widely accepted one-step deprotonation mechanism of the quaternary triazolium salts applied but a two-step mechanism comprising of pseudobase formation and their subsequent deprotonation is valid.Using the pertinent kinetic model the pK values of pseudo-base formation (pKR+) and their deprotonation (pKA) were determined by non-linear regression.

3 Ill.

Electronic Resource

0021-8383

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The Mechanism of Photoreactions of 2-Chloro Quinoline with NucleophilesThe photochemical reactions of 2-chloro quinoline with various nucleophiles in water or methanol are studied.The main products are: 1,4-dihydro quinolines (1,4-addition of the respective nucleophile) 1, quinoline 2, and quinolines substituted in 2-position by the nucleophile 3. There is good evidence that the elementary step of the photochemical reactions is an electron transfer reaction from the nucleophile to the singlet or triplet excited 2-chloro quinoline. The results are discussed with regard to free enthalpie differences of the electron transfer and the character of radical pairs formed.

4 Ill.

Electronic Resource