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181.
After the intraperitoneal administration of high doses of 14C- and 3H-labelled retinoic acid ( 1 ) to rats three major urinary metabolites have been isolated in microgram amounts by use of column, thin-layer and high-pressure liquid chromatography. Their structures were elucidated by mass spectroscopy and Fourier transform 1H-NMR. spectroscopy as 2 (5-methyl-5-[2-(2,6,6-trimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-2-tetrahydrofuranone), 3 (5-[2-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)vinyl]-5-methyl-2-tetrahydrofuranone) and 4 (6-(6-hydroxymethyl-2,6-dimethyl-3-oxo-1-cyclohexen-1-yl)-4-methyl-4-hexenoic acid). In these metabolites the tetraene side chain of 1 is shortened and the cyclohexene ring oxidized. The radioactivity of 2 and 3 accounted for about 10% (0.9% of the dose) each, metabolite 4 for about 6% (0.5% of the dose) of the total urinary radioactivity. 相似文献
182.
Annette Marchand Monique Riviere-Baudet Jacques Satge 《Journal of organometallic chemistry》1976,107(1):33-48
We have examined in the 3600–100 cm?1 region the IR and Raman spectra of three bis(trialkylgermyl)amines (R3Ge)2NR′ (R = Me, Et; R′ = H, C6H5), of three dialkyl(trialkylgermyl)amines R3GeNR′2 (R = Me, Et; R′ = Me, n-Bu) and of two triethylgermylpyrazoles: Assignments are discussed for the characteristic vibrations of these derivatives. 相似文献
183.
Dr. G. Meister 《Mathematical Methods of Operations Research》1987,31(5):A189-A209
Summary In the sequel we will derive sufficient and necessary conditions for the existence of certain numeric representations of simple games. In § 2 the above mentioned representation is given by a so called, coalitionally ordered function, i.e. a numeric function representing the desirability of each coalition in the class of all coalitions. Simple games which possess a c.o.f are called coalitionally ordered games. Sufficient and necessary criteria are given for a simple game to be a c.o.g. Analogously weighted majority games are characterized in § 3. The criteria to be presented are linked by properties of the desirability relation of a simple game. The concept of a desirability relation was introduced by Peleg 1978.
Zusammenfassung Im folgenden werden wir hinreichende und notwendige Bedingungen zur Existenz von gewissen numerischen Darstellungen einfacher Spiele (simple games) herleiten. Diese oben genannte Darstellung wird in § 2 durch eine sogenannte coalitionally ordered function, gegeben, wobei wir darunter eine numerische Funktion verstehen, die die Desirability, jeder Koalition innerhalb der Klasse aller Koalitionen beschreibt. Einfache Spiele, die eine c.o.f besitzen, werden coalitionally ordered games genannt. Es werden hinreichende und notwendige Bedingungen dafür genannt, daß ein einfaches Spiel ein c.o.g ist. Analog werden gewichtete Abstimmungsspiele (weighted majority games) in § 3 charakterisiert. Die angegebenen Kriterien werden mit Eigenschaften der sogenannten desirability relation eines einfachen Spieles in Verbindung gebracht. Das Konzept einer desirability relation wurde von Peleg 1978 verwendet.相似文献
184.
J. Meister 《Fresenius' Journal of Analytical Chemistry》1886,25(1):373
Ohne Zusammenfassung 相似文献
185.
The derivatization reaction of the mycotoxin moniliformin with 1,2-diamino-4,5-dichlorobenzene was previously introduced to improve distinctly the sensitivity of an assay applying high-performance liquid chromatography prior to fluorescence detection. In the course of the implementation of this derivatization approach into a liquid chromatographic/mass spectrometric method, an unexpected derivatization product has now been discovered by mass spectrometry. In order to elucidate its structure, detailed investigations with liquid chromatography/tandem mass spectrometry and liquid chromatography coupled on-line with NMR spectroscopy were performed. These studies give evidence for a heterocyclic structure that has been formed by the loss of one water and one carbon monoxide molecule. A reasonable mechanism for this derivatization reaction is proposed. 相似文献
186.
Ladizhansky V Jaroniec CP Diehl A Oschkinat H Griffin RG 《Journal of the American Chemical Society》2003,125(22):6827-6833
We demonstrate the simultaneous measurement of several backbone torsion angles psi in the uniformly (13)C,(15)N-labeled alpha-Spectrin SH3 domain using two different 3D 15N-13C-13C-15N dipolar-chemical shift magic-angle spinning (MAS) NMR experiments. The first NCCN experiment utilizes double quantum (DQ) spectroscopy combined with the INADEQUATE type 13C-13C chemical shift correlation. The decay of the DQ coherences formed between 13C'(i) and 13C(alphai) spin pairs is determined by the "correlated" dipolar field due to 15N(i)-13C(alphai) and 13C'(i)-15N(i+1) dipolar couplings and is particularly sensitive to variations of the torsion angle in the regime |psi| > 140 degrees. However, the ability of this experiment to constrain multiple psi-torsion angles is limited by the resolution of the 13C(alpha)-(13)CO correlation spectrum. This problem is partially addressed in the second approach described here, which is an NCOCA NCCN experiment. In this case the resolution is enhanced by the superior spectral dispersion of the 15N resonances present in the 15N(i+1)-13C(alphai) part of the NCOCA chemical shift correlation spectrum. For the case of the 62-residue alpha-spectrin SH3 domain, we determined 13 psi angle constraints with the INADEQUATE NCCN experiment and 22 psi constraints were measured in the NCOCA NCCN experiment. 相似文献
187.
Reetz MT Torre C Eipper A Lohmer R Hermes M Brunner B Maichele A Bocola M Arand M Cronin A Genzel Y Archelas A Furstoss R 《Organic letters》2004,6(2):177-180
[reaction: see text] The epoxide hydrolase (EH) from Aspergillus niger, which shows a selectivity factor of only E = 4.6 in the hydrolytic kinetic resolution of glycidyl phenyl ether, has been subjected to directed evolution for the purpose of enhancing enantioselectivity. After only one round of error-prone polymerase chain reaction (epPCR), enantioselectivity was more than doubled (E = 10.8). The improved mutant enzyme contains three amino acid exchanges, two of which are spatially far from the catalytically active center. 相似文献
188.
The metallo-phosphaalkenes (η5-C5Me5)(CO)2FeP=C(R)(SiMe3) (Ia: R = SiMe3, Ib: R = Ph) and MeO2C---CC---CO2Me undergo a dipolar [3+2]-cycloaddition to afford the metallo-heterocycles [(η5-C5Me5)(CO)
=C(R)SiMe3] (IIIa,b) with exocyclic P=C double bonds. 相似文献
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189.
Konkin A Wendler F Roth HK Schroedner M Bauer RU Meister F Heinze T Aganov A Garipov R 《Magnetic resonance in chemistry : MRC》2006,44(6):594-605
The processes of radical formation in N-methylmorpholine-N-oxide monohydrate (NMMO) and cellulose/NMMO solutions were studied by ESR at 77 K under high-power UV (lambda = 248 nm) excimer laser flash photolysis. Radicals mainly generated were attributed to the nitroxide type radicals -CH2-NO*-CH2- and -CH2-NO*-CH3 at the first step and methyl *CH3 and formyl *CHO radicals at the second step of the photoreaction. Kinetic studies of these radicals revealed that formation and recombination rates of the radicals depend on the cellulose concentration in cellulose/NMMO solutions and the concentration of additional ingredients, e.g. Fe(II) and propyl gallate. Even at frozen state temperature, acceleration or quenching of radical reaction processes was found. The proposed scheme of UV light-induced NMMO degradation during irradiation based on ESR data correlates well with independently obtained results based on high-performance liquid chromatography (HPLC). The analysis of degradation products by HPLC, e.g. aminoethanol and acetaldehyde, supports the assumption concerning a radical-initiated ring opening of NMMO. 相似文献
190.
Sabine Amberg-Schwab Ulrike Weber Annette Burger Somchith Nique Rainer Xalter 《Monatshefte für Chemie / Chemical Monthly》2006,137(5):657-666
Summary. With a new kind of barrier coating material, namely inorganic–organic polymers, it is possible to obtain excellent barrier
properties against oxygen, water vapor, and flavor permeation. These hybrid polymers can be synthesized by the sol–gel technique.
If extremely low permeation values are needed, the combination of hybrid polymer coatings with thin inorganic oxidic layers
(SiOx, AlOx) is very effective and leads to permeation values for oxygen and water vapor below 10−3 cm3/m2 · d · bar or g/m2 · d. These passive barrier layers can be further improved by the combination with active oxygen barrier layers which have
been developed for the food packaging industry. This approach makes these multilayer laminates promising candidates for special
applications in the food packaging industry as well as for sophisticated applications in technical areas: the encapsulation
of sensitive organic devices like solar cells, organic light emitting diodes, or polymer electronic systems. 相似文献