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991.
A. Aleškevičienė 《Lithuanian Mathematical Journal》2010,50(1):1-12
In this paper, we consider the Sparre Andersen insurance risk model with initial surplus x > 0. Let Ax denote the deficit at the time of ruin. Assuming that the tail probabilities of claim size are regularly varying, the second-order
asymptotic of the deficit distribution and its moments at the time of ruin are derived. 相似文献
992.
In this paper, we prove that all manifolds with affine or projective connection are globally projectively equivalent to some
manifolds with equiaffine connection (equiaffine manifold). 相似文献
993.
Ahmed Al‐Harrasi Dr. Fabian Pfrengle Dipl.‐Chem. Vladimir Prisyazhnyuk Dr. Shahla Yekta Dr. Peter Koóš Dr. Hans‐Ulrich Reissig Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11632-11641
1,3‐Dioxolanyl‐substituted 1,2‐oxazines, such as syn‐ 1 and anti‐ 1 , rearrange under Lewis acidic conditions to provide bicyclic products 2 – 5 . Subsequent reductive transformations afforded enantiopure 3‐aminopyran derivatives such as 7 and 9 or their protected diastereomers 16 and 18 , which can be regarded as carbohydrate mimetics. An alternative sequence of transformations including selective oxidation of the primary hydroxyl groups in 21 and 24 led to two protected β‐amino acid derivatives with carbohydrate‐like backbone (sugar amino acids). Treatment of bicyclic ester 23 with samarium diiodide cleaved the N? O bond and furnished the unusual β‐lactam 27 in excellent yield. Alternatively, γ‐amino acid derivative 29 was efficiently prepared in a few steps. Fairly simple transformations gave azides 32 and 35 or alkyne 30 which are suitable substrates for the construction of oligosaccharide mimetics such as 34 by copper iodide catalyzed cycloadditions. With this report we demonstrate that enantiopure rearrangement products 2 – 5 are protected precursors of a variety of polyfunctionalized pyran derivatives with great potential for chemical biology. 相似文献
994.
Copper electrodeposition processes in the hydrogen co-deposition range by the pulsating current (PC) regime were examined by the determination of the average current efficiency of hydrogen evolution and by the scanning electron microscopic (SEM) analysis of the morphology of the formed deposits. The two sets of the square-wave PC of the same pause to pulse ratios, but with different duration of deposition pulses and pauses were analyzed. The one set of square-wave PC was with the constant pause duration and different deposition pulses. In the other set, the deposition pulse was constant while the pause duration was varied. The obtained results were compared with those obtained by electrodeposition at the constant overpotential from solutions of different CuSO4 and H2SO4 concentrations. It was found that the effect of the increasing deposition pulse was equivalent to the decreasing CuSO4 concentration, while the effect of the decreasing pause duration was equivalent to the increasing H2SO4 concentration. It is shown that it is possible to achieve a substitution of more solutions of different CuSO4 and H2SO4 concentartions by the use of the only one solution if the appropriate PC parameters were applied, what can be of high technological significance. 相似文献
995.
996.
Optical absorption of vitreous GeSb2Se4 was studied in spectral region 0.7–25 μm. At low absorption levels near the edge the absorption coefficient K depends exponentially on energy. At high absorption levels the quadratical energy dependence of K is observed. In the present work we determined the optical energy gap Eoptg = 1.29 eV and discussed the temperature dependence of the absorption coefficient. Measured reflectivity curves were used to estimate the value of the refractive index of GeSb2Se4 (). Vitreous GeSb2Se4 is also transparent in the spectral interval 2–15.7 μm. 相似文献
997.
O. Habuštová L'. Weismann M. Harangozó A. Bumbálová 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):825-826
The influence of copper on adults of the Colorado potato beetle (Leptinotarsa decemlineata Say) was studied. The adults were treated by the contact fungicide Kuprikol 50, which is used to control down powder mildew (Phytophtora infestans de Bary). Copper content was determined by radio-nuclide X-ray fluorescence analysis using a 238Pu exciting source. The obtained results contribute to the control measures against the Colorado potato beetle and to the question of the resistance of Colorado potato beetle towards pyrethroide insecticides. 相似文献
998.
Ivo Petráš 《Nonlinear dynamics》2009,57(1-2):157-170
This paper deals with a new fractional-order chaotic system. It is based on the concept of Volta’s system, where the mathematical model of Volta’s system contains fractional-order derivatives. This system has simple structure and can display a double-scroll attractor. The behavior of the integer-order and the fractional-order Volta’s system with total order less than three which exhibits chaos is presented as well. Computer simulations are cross-verified by the numerical calculation and the Matlab/Simulink models. 相似文献
999.
The copolyamides consisting of ε-caprolactam and 6.1–24.5 wt.% of nylon salt prepared from adipic acid and 1-(2-aminoethyl)
piperazine were synthesized. Physical and thermal characteristics of polyamide 6 and the copolyamides were compared. Nylon
salt does not influence the polyreaction equilibrium so it is possible to prepare the copolyamides with high molecular weight
and with the content of low-molecular compounds comparable with that of pure PA 6. Melting temperatures of the copolyamides
are lower in comparison with PA 6 and decrease proportionally to the amount of the nylon salt. The thermal stability of the
copolyamides is good and equal to that of PA 6. The melting enthalpies indicate that the process of crystallization of the
copolyamides is influenced by the time of crystallization and the amount of comonomer present. Longer time of the crystallization
assures higher degree of crystallization. The kinetics and the level of crystallization are positively influenced by the mobility
of copolyamide segments mainly up to 10 wt.% of comonomer. 相似文献
1000.
Rud Wegscheider Leo Ritter Kuśy v. Dúbrav 《Monatshefte für Chemie / Chemical Monthly》1903,24(10):805-831
Ohne Zusammenfassung 相似文献