Search results for "Absolute"
showing 10 items of 518 documents
Über die Elementarreaktionen der radikalischen Polymerisation von Benzylmethacrylat
1973
Durch Kombination stationarer und instationarer Methodik (rotierender Sektor) werden die Absolutwerte der Geschwindigkeitskonstanten von Kettenwachstum und Kettenabbruch von Benzylmethacrylat unter dem Einflus verschieden viskoser Losungsmittel bestimmt. Die Radikalausbeute f hangt von der Viskositat des Losungssystems und der Art der Monomeren, dagegen nicht (oder fast nicht) von der Konzentration des Monomeren und der Geschwindigkeit der Radikalerzeugung ab. Daraus wird geschlossen, das ein merklicher Anteil von Zwillingsrekombinationen auserhalb des primaren Losungsmittelkafigs stattfindet. Die Geschwindigkeitskonstante kw des Kettenwachstums stimmt praktisch uberein mit der des Methylme…
Power-law relaxation in a complex system: Omori law after a financial market crash
2003
We study the relaxation dynamics of a financial market just after the occurrence of a crash by investigating the number of times the absolute value of an index return is exceeding a given threshold value. We show that the empirical observation of a power law evolution of the number of events exceeding the selected threshold (a behavior known as the Omori law in geophysics) is consistent with the simultaneous occurrence of (i) a return probability density function characterized by a power law asymptotic behavior and (ii) a power law relaxation decay of its typical scale. Our empirical observation cannot be explained within the framework of simple and widespread stochastic volatility models.
Applications de type Lasota–Yorke à trou : mesure de probabilité conditionellement invariante et mesure de probabilité invariante sur l'ensemble des …
2003
Abstract Let T :I→I be a Lasota–Yorke map on the interval I, let Y be a nontrivial sub-interval of I and g 0 :I→ R + , be a strictly positive potential which belongs to BV and admits a conformal measure m. We give constructive conditions on Y ensuring the existence of absolutely continuous (w.r.t. m) conditionally invariant probability measures to nonabsorption in Y. These conditions imply also existence of an invariant probability measure on the set X∞ of points which never fall into Y. Our conditions allow rather “large” holes.
Absolute Risk and Loss-of-Lifetime Estimates for Quantitative Risk Assessment
1998
Quantitative risk assessments in public health settings intend to describe the hazard of a specific exposure in a given population on the basis of epidemiological and/or experimental results. Two different risk quantities, the absolute lifetime excess risk and the loss-of-lifetime, which differ in their definition of hazard, are discussed and compared. For both measures estimation procedures are derived and the relationship between the various estimates which are currently in use are investigated. It is shown that the two most common estimators can be written as special cases of a more general concept. This leads to conclusions about the assumptions on which different estimation procedures …
Residuenanalyse des Unabhängigkeitsmodells Zweier Kategorialer Variablen
1985
For the ‘cellwise’ analysis of independence of two categorial variables, Haberman (1973) proposes the method of ‘adjusted residuals’. Fuchs and Kenett (1980) use (the absolute value of) the maximal adjusted residual as a measure for the deviation from the null hypothesis.
Individual stereoisomers of phosphinic dipeptide inhibitor of leucine aminopeptidase
2008
Abstract Individual stereoisomers of the phosphinic pseudodipeptide hPheψ[P(O)(OH)CH2]Phe were obtained by stereoselective liquid chromatographic separation as N- and C-terminally protected derivative on quinidine carbamate modified silica stationary phase. The stereoisomeric purity, exceeding 95% for each fraction, was determined before and after deprotection using two independent methods. The absolute configuration was rationally assigned by application of enantiomerically pure phosphinic acid substrates in the synthetic procedure and correlation with biological activity of the products. Substantial differences in inhibition of leucine aminopeptidase by the individual isomers revealed nov…
Synthesis of all 7αH-guaia-4,11-dien-3-one diastereomers from (+)-dihydrocarvone
2005
Abstract All four 7α H -guaia-4,11-dien-3-one diastereomers have been synthesized from the common intermediate 1α H ,10α-acetoxy-7α H -guaia-4,11-dien-3-one obtained from (+)-dihydrocarvone. The spectral features of the four diasteromers have been correlated and the structure and absolute configuration of 1β H ,10β H ,7α H -guaia-4,11-dien-3-one isolated from Pleocarphus revolutus has been confirmed.
Synthesis of (−)-auricularic acid and its C-4 epimer the absolute configuration of auricularic acid
1991
Abstract A synthesis of (−)-auricularic acid (2a) starting from methyl (+)-13-oxo- podocarp-8(14)-en-19-oate (3a) and a synthesis of its C-4 epimer (2b) starting from methyl (+)-13-oxopodocarp-8(14)-en-18-oate (3b) are described. The absolute configuration of natural auricularic acid is stablished as (4R, 5S, 8S, 9R, 10S, 14S).
Assignment of the Absolute Configuration and Total Synthesis of (+)-Caripyrin
2014
The antifungal secondary metabolite (+)-caripyrin was studied by vibrational circular dichroism spectroscopy. Analysis of the recorded data, with the Boltzmann weighted-average of the spectra calculated at the B3LYP/6-311G(d,p) level of theory for all relevant conformers, unequivocally proved the (R,R)-configuration for the dextrorotatory natural product. Based on this finding, a short enantioselective synthesis of (+)-caripyrin was developed.
Crystal structures and absolute configurations of dexmedetomidine and its tosyl derivative
1993
Abstract X-ray diffraction data were used to determine the absolute configuration of dexmedetomidine, a new member of a class of drugs with 4-arylalkyl-1H-imidazole structure. When the anomalous effect of the parent compound proved to be too small for determination of the absolute configuration the tosyl derivative, with the same configuration, was synthesised and used as a reference. Stability of the stereogenic center was verified by HPLC technique. The absolute configuration of the compounds is S. Complete crystal structures are reported for both compounds. Co radiation was used for measurements.