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  • Enantioselective catalysis  (2)
  • 15N-tracer techniques  (1)
  • 45L10  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Continuous Volterra-Runge-Kutta methods for integral equations with pure delay (1993)
    Springer
    Computing 50 (1993), S. 213-227 
    Details
    ISSN: 1436-5057
    Keywords: 65R20 ; 65L06 ; 45L10 ; Volterra integral equations with delay ; collocation ; continuous Runge-Kutta methods ; superconvergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Diese Arbeit befaßt sich mit Fragen der (lokalen) Superkonvergenz bei Kollokationsverfahren und stetigen impliziten Runge-Kutta-Methoden für Volterrasche Integralgleichungen mit retardiertem Argument. Es wird insbesondere gezeigt, daß (im Gegensatz zu retardierten Differentialgleichungen) Kollokation an den Gauss-Punkten nicht zu einer höheren Konvergenzordnung führt and daß deshalbm-stufige Gauss-Runge-Kutta-Methoden nicht die Ordnungp=2m besitzen.
    Notes: Abstract In the following we give an analysis of the local superconvergence properties of piecewise polynomial collocation methods and related continuous Runge-Kutta-type methods for Volterra integral equations with constant delay. We show in particular that (in contrast to delay differential equations) collocation at the Gauss points does not lead to higher-order convergence and thusm-stage Gauss-Runge-Kutta methods for delay Volterra equations do not possess the orderp=2m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02243812
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  • 2
    Electronic Resource
    Electronic Resource
    Asymmetric catalysis, part 91: Enantioselective monophenylation ofcis-1,2-cyclopentanediol with triphenylbismuth diacetate and chiral copper(II) complexes as catalysts (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 1293-1300 
    Details
    ISSN: 1434-4475
    Keywords: Enantioselective catalysis ; Chiral Cu(II) complexes ; Monophenylation ; Triphenylbismuth diacetate ; cis-1,2-Cyclopentanediol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Monophenylierung voncis-1,2-Cyclopentandiol mit Triphenylwismutdiacetat in Gegenwart chiraler Cu(II)-Komplexe als Katalysatoren ergabcis-2-Hydroxy-1-phenoxy-cyclopentan mit Enantiomerenüberschüssen von bis zu 38%. Die eingesetzten optisch aktiven Liganden waren Triamin-Derivate von 2,6-bis(Aminomethyl)pyridin und Diamin-Derivate von 2-(Aminomethyl)pyridin. Selektivität bei der Monophenylierung war nur in Gegenwart letzterer als Auxiliar-Liganden zu beobachten.
    Notes: Summary The monophenylation ofcis-1,2-cyclopentanediol with triphenylbismuth diacetate in the presence of chiral Cu(II) complexes as catalysts gavecis-2-hydroxy-1-phenoxy-cyclopentane with enantiomeric excesses up to 38%. The optically active ligands used were triamine derivatives of 2,6-bis(aminomethyl)pyridine and diamine derivatives of 2-(aminomethyl)pyridine. Selectivity in the monophenylation occurred only in the presence of the latter as auxiliary ligands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811078
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Asymmetric catalysis, CIII: EnantioselectiveMichael addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 1063-1072 
    Details
    ISSN: 1434-4475
    Keywords: Enantioselective catalysis ; EnantioselectiveMichael addition ; Nitroalkenes ; Chiral HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Optisch aktiveMichael-Addukte werden durch die Addition von 1,3-Dicarbonylverbindungen an konjugierte Nitroalkene synthetisiert. Gute chemische Ausbeuten werden für durch aromatische Substituenten stabilisierte Nitroalkene ohne weitere Substituenten an der Doppelbindung erreicht. Acetylaceton und 2,3-Dihydro-1-oxo-1H-inden-2-carbonsäuremethylester werden alsMichael-Donoren und vier Cinchona-Alkaloide als chirale basische Katalysatoren verwendet. Die Bestimmung des Enantiomerenüberschusses wird mittels1H-NMR-Spektroskopie in Gegenwart vonPirkle-Alkohol und HPLC an chiralen stationären Phasen durchgeführt. Eine Korrelation zwischen der relativen Konfiguration der Vorzugsisomeren derMichael-Addukte und den Katalysatoren wurde hergestellt.
    Notes: Summary Optically activeMichael adducts were synthesized by addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes. Good chemical yields were obtained for nitroalkenes stabilized by an aromatic substituent without any further substituents at the double bond. Acetylacetone and methyl-2,3-dihydro-1-oxo-1H-indene-2-carboxylate were used asMichael donors and four cinchona alkaloids as chiral base catalysts. Enantiomeric excess determinations were performed by1H NMR spectroscopy in the presence of thePirkle alcohol and by HPLC on chiral stationary phases. A correlation between the relative configuration of the prevailing isomer of theMichael adduct and the catalysts was established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807579
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative assessment of symbiotic nitrogen fixation in diverse mutant lines of field bean (Vicia faba minor) (1984)
    Springer
    Plant and soil 82 (1984), S. 407-413 
    Details
    ISSN: 1573-5036
    Keywords: Carbon partitioning ; Field bean ; Mutant lines ; Nitrogen partitioning ; 15N-tracer techniques ; Symbiotic nitrogen fixation ; Vicia faba minor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Homozygous mutant lines of field bean selected for (a) improved yielding potential and (b) altered plant architecture and/or physiological response were tested for symbiotic nitrogen fixing ability under field conditions in comparison with their parent cultivar.15N-tracer techniques were applied to determine %N derived from atmosphere. Data were collected on assimilate and nitrogen accumulation and distribution among various plant parts during two stages of reproductive growth. Symbiotic nitrogen fixation was closely correlated with total plant top biomass and nitrogen yield. A similar close association was found between crop yield and nitrogen harvest index. Both harvest indices tended to be negatively correlated with stage of maturity and with the amount of N derived from air per unit of area. The generally high %N derived from symbiotic N2 fixation and its comparatively small variability implies that this parameter may be difficult to improve inVicia faba under field conditions. It is concluded, that the main genetic potential for improving the amount of biological nitrogen fixation in this crop depends upon factors that promote high photosynthetic productivity and efficient N-use under appropriate agronomic conditions and with effective rhizobial associations. The establishment of rational ideotypes with a possitive impact on yield appears to be of practical significance for increasing the amount of symbiotically fixed nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184278
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    Paper (German National Licenses)
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