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221.
Mathias Mertens 《Czechoslovak Journal of Physics》2000,50(1):151-156
This paper uses the formulation of renormalization theory in a pure algebraic way providing the notion of Hopf algebras as introduced by A. Connes and D. Kreimer [Commun. Math. Phys. 199 (1998) 203]. First an introduction to the Hopf algebra of rooted trees will be given. The second section explores how renormalization is achieved using the Hopf algebra of rooted trees. So far the paper reviews the results of D. Kreimer as published in the paper cited above. The review will end with a sketch of a category-theoretical interpretation which is under thorough investigation at the time of writing. 相似文献
222.
We consider a new class of estimators for volatility functionals in the setting of frequently observed Itō diffusions which are disturbed by i.i.d. noise. These statistics extend the approach of pre-averaging as a general method for the estimation of the integrated volatility in the presence of microstructure noise and are closely related to the original concept of bipower variation in the no-noise case. We show that this approach provides efficient estimators for a large class of integrated powers of volatility and prove the associated (stable) central limit theorems. In a more general Itō semimartingale framework this method can be used to define both estimators for the entire quadratic variation of the underlying process and jump-robust estimators which are consistent for various functionals of volatility. As a by-product we obtain a simple test for the presence of jumps in the underlying semimartingale. 相似文献
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The acid catalyzed rearrangement of two cyclohexanols of spiroannelated four-membered rings has been studied. In accordance with molecular mechanics calculations, far-reaching reorganizations with formation of unsaturated hexacyclic systems, including a fully cycloalkylated cyclohexene with a bispropellane partial structure, were observed. Attempts to convert this bispropellane to a trispropellane failed. 相似文献
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Lon J. Mathias Peter D. Livant Sharf U. Ahmed 《Journal of polymer science. Part A, Polymer chemistry》1987,25(10):2711-2716
Several new copolymers have been synthesized. Initial polycondensation of mixtures of aryl and arylalkyl carboxylic acids containing aromatic hydroxyl and amine substituents led to random copolyamides. Thermal cyclization of these prepolymers (inherent viscosities of about 0.2 dL/g) gave copolybenzoxazoles with inherent viscosities of about 1.4 dL/g. Thermal stability as measured by TGA was similar for the 1:1 copolymers and the homopolymers containing hydrocinnamic units; i.e., catastrophic decomposition occurred at 450°C. Copolymers with lower ratios of the hydrocinnamic units displayed greatly improved thermal stability while maintaining good molecular weight. 相似文献