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991.
Antoine Michel Ghanem Roger S. Porter 《Journal of Polymer Science.Polymer Physics》1989,27(13):2587-2603
Solid-state coextrusion has been used to prepare uniaxially drawn films from isotropic poly(ethylene 2,6-naphthalate) (PEN) of a minimum degree of crystallinity (ca. 5%) both below and above its glass transition temperature Tg. The onset of cold crystallization (Tc) of the drawn films has been studied as a function of the extrusion temperature (ET) and the draw ratio (EDR). It has been shown that Tc decreases markedly on draw, as much as 95°C, and, at constant draw ratio Tc goes through a minimum in the Tg region. For undrawn PEN, annealing below 153°C has no significant effect on Tc. To evaluate the crystallization rate constant (k) and the activation energy (Ea) of the drawn specimens, a nonisothermal DSC procedure has been used. With increasing EDR, k increases markedly and Ea goes down over threefold compared with the undrawn polymer. At high ET, strain-induced crystallization has also been shown to play an important role in lowering Ea for cold crystallization. Thermal shrinkage above Tm indicates a high elastic recovery, underlining the efficiency of deformation, ca. 93%, achieved by solid-state coextrusion. 相似文献
992.
Roger B. Nelsen José Antonio Rodríguez-Lallena 《Insurance: Mathematics and Economics》2008,42(2):473-483
We study a method, which we call a copula (or quasi-copula) diagonal splice, for creating new functions by joining portions of two copulas (or quasi-copulas) with a common diagonal section. The diagonal splice of two quasi-copulas is always a quasi-copula, and we find a necessary and sufficient condition for the diagonal splice of two copulas to be a copula. Applications of this method include the construction of absolutely continuous asymmetric copulas with a prescribed diagonal section, and determining the best-possible upper bound on the set of copulas with a particular type of diagonal section. Several examples illustrate our results. 相似文献
993.
We present an axiomatic characterization of price measures that are superadditive and comonotonic additive for normally distributed random variables. The price representation derived involves a probability measure transform that is closely related to the Esscher transform, and we call it the Esscher-Girsanov transform. In a financial market in which the primary asset price is represented by a stochastic differential equation with respect to Brownian motion, the price mechanism based on the Esscher-Girsanov transform can generate approximate-arbitrage-free financial derivative prices. 相似文献
994.
Roger M. Hill Robert W. K. Odoni 《The Journal of the Operational Research Society》1988,39(10):969-972
The asymptotic behaviour of the time to sell a given quantity of stock depleted by a discrete demand process is derived for discrete time and continuous time (block depletion and continuous depletion). 相似文献
995.
A sandwich technique based on the very affinity between avidin and biotin is used. Antibodies are covalently bound to glass-fibre on which the antigen is captured. The discs are then treated in sequence with monoclonal antibodies of high selectivity, species-specific anti-IgG (biotin-linked), streptavidin and β-galactosidase, (biotin-linked). The discs are then incubated with the substrate, 4-methylumbelliferyl-β-d-galactopyranoside and the fluorescence is measured in an automatic immunoassay system. 相似文献
996.
Speculations about the role of consciousness in physical systems are frequently observed in the literature concerned with the interpretation of quantum mechanics. While only three experimental investigations can be found on this topic in physics journals, more than 800 relevant experiments have been reported in the literature of parapsychology. A well-defined body of empirical evidence from this domain was reviewed using meta-analytic techniques to assess methodological quality and overall effect size. Results showed effects conforming to chance expectation in control conditions and unequivocal non-chance effects in experimental conditions. This quantitative literature review agrees with the findings of two earlier reviews, suggesting the existence of some form of consciousness-related anomaly in random physical systems. 相似文献
997.
Products of the reaction of OH radicals with 1-butene have been investigated in the presence of NO in one atmosphere of air at room temperature using gas chromatography and in situ long pathlength Fourier transform infrared absorption spectroscopy. The major product observed was propionaldehyde, with a formation yield (after allowing for its subsequent loss processes) of 0.94 ± 0.12. Minor yields of organic nitrates (RONO2) and of peroxypropionyl nitrate, a secondary product arising from propionaldehyde, were also observed. However, none of the products expected from the reactions subsequent to H-atom abstraction from 1-butene by OH radicals were observed, allowing an upper limit of 10% for this process to be derived. These data are compared with the available literature results and the implications are discussed. 相似文献
998.
A fast, sensitive sandwich fluorimmunoassay for hepatitis B surface antigen (HBs-ag) is described. Rabbit antibodies to HBs-ag are covalently bound to the centre of a glass-fiber filter disk. The second antibody is a swine anti-human HBs-ag conjugated with β-d-galactosidase from E. coli. The substrate is 4-methylumbelliferyl-β-d-galactopyrano-side. The technique is applied with the Stratus system which does the entire test in 8 min. the detection limit is 1 ng ml?1, and the results correlate well with a radioimmunoassay technique. 相似文献
999.
Experimental and theoretical results on the helix-coil transition of DNA are reviewed. The theoretical model of the transition is described, and the influence of heterogeneous base pair stacking, and strand dissociation on the predicted melting transition is examined. New experimental transition data on seven DNAs, 154–587 base pairs (bp) long, are reported and compared with theoretical calculations. We review and evaluate previous studies on long DNAs (≥1000 bp) as well as previous and recent results on short DNAs. The comparison of theory with equilibrium melting curves of short DNAs indicates that base pair sequence has a relatively small influence on the stacking free energy. Excellent agreement is obtained between theory and equilibrium transitions of 14 out of 15 fragments 80–587 pb. The deviation between theory and experiment for a 516 bp DNA can be attributed to the formation of stem-loop structures. This may provide the explanation for inconsistent results observed with long DNAs. The effect of single base pair changes on DNA transitions is discussed. Current views on fluctuational opening of base pairs at temperatures below the transition are described. 相似文献
1000.
Roger L. Jones 《Proceedings of the American Mathematical Society》2004,132(4):1087-1090
We give a new (shorter) proof of a result of L. Ephremidze showing that if two functions have the same ergodic maximal function, then they are equal a.e.