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51.
Conclusions 1. In their deformation properties the polyolefins studied are substances of a single class even under creep conditions. The principal factor which distinguishes the behavior of one polyolefin from another is the critical values of the specific volume Vo. At an identical value of V-Vo (at corresponding temperatures) the creep process is identical in polyolefins of different density.2. Change in the specific volume of polyolefins takes place upon the action, not only of temperature, but also of stress, and also as a result of thermooxidative processes, which exert a strong effect on the creep of these substances.A report presented at the Third All-Union Conference on Polymer Mechanics, Riga, 1976.M. I. Kalinin Leningrad Polytechnic Institute. Translated from Mekhanika Polymerov, No. 1, pp. 22–26, January–February, 1978. 相似文献
52.
53.
For a large class of metric spaces with nice local structure, which includes Banach–Finsler manifolds and geodesic spaces
of curvature bounded above, we give sufficient conditions for a local homeomorphism to be a covering projection. We first
obtain a general condition in terms of a path continuation property. As a consequence, we deduce several conditions in terms
of path- liftings involving a generalized derivative, and in particular we obtain an extension of Hadamard global inversion
theorem in this context. Next we prove that, in the case of quasi-isometric mappings, some of these sufficient conditions
are also necessary. Finally, we give an application to the existence of global implicit functions.
O. Gutú and J. A. Jaramillo were supported in part by D.G.E.S. (Spain) Grant BFM2003-06420. 相似文献
54.
An experimental study on rotating detonation is presented in this paper. The study was focused on the possibility of using
rotating detonation in a rocket engine. The research was divided into two parts: the first part was devoted to obtaining the
initiation of rotating detonation in fuel–oxygen mixture; the second was aimed at determination of the range of propagation
stability as a function of chamber pressure, composition, and geometry. Additionally, thrust and specific impulse were determined
in the latter stage. In the paper, only rich mixture is described, because using such a composition in rocket combustion chambers
maximizes the specific impulse and thrust. In the experiments, two kinds of geometry were examined: cylindrical and cylindrical-conic,
the latter can be simulated by a simple aerospike nozzle. Methane, ethane, and propane were used as fuel. The pressure–time
courses in the manifolds and in the chamber are presented. The thrust–time profile and detonation velocity calculated from
measured pressure peaks are shown. To confirm the performance of a rocket engine with rotating detonation as a high energy
gas generator, a model of a simple engine was designed, built, and tested. In the tests, the model of the engine was connected
to the dump tank. This solution enables different environmental conditions from a range of flight from 16 km altitude to sea
level to be simulated. The obtained specific impulse for pressure in the chamber of max. 1.2 bar and a small nozzle expansion
ratio of about 3.5 was close to 1,500 m/s. 相似文献
55.
Shah F Mukherjee P Gut J Legac J Rosenthal PJ Tekwani BL Avery MA 《Journal of chemical information and modeling》2011,51(4):852-864
Malaria, in particular that caused by Plasmodium falciparum , is prevalent across the tropics, and its medicinal control is limited by widespread drug resistance. Cysteine proteases of P. falciparum , falcipain-2 (FP-2) and falcipain-3 (FP-3), are major hemoglobinases, validated as potential antimalarial drug targets. Structure-based virtual screening of a focused cysteine protease inhibitor library built with soft rather than hard electrophiles was performed against an X-ray crystal structure of FP-2 using the Glide docking program. An enrichment study was performed to select a suitable scoring function and to retrieve potential candidates against FP-2 from a large chemical database. Biological evaluation of 50 selected compounds identified 21 diverse nonpeptidic inhibitors of FP-2 with a hit rate of 42%. Atomic Fukui indices were used to predict the most electrophilic center and its electrophilicity in the identified hits. Comparison of predicted electrophilicity of electrophiles in identified hits with those in known irreversible inhibitors suggested the soft-nature of electrophiles in the selected target compounds. The present study highlights the importance of focused libraries and enrichment studies in structure-based virtual screening. In addition, few compounds were screened against homologous human cysteine proteases for selectivity analysis. Further evaluation of structure-activity relationships around these nonpeptidic scaffolds could help in the development of selective leads for antimalarial chemotherapy. 相似文献
56.
57.
Zirconium(IV) selenoiodates have been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0.1 mol L–1 potassium iodate and 0.1 mol L–1 sodium selenite to aqueous solution of 0.1 mol L–1 zirconium(IV) oxychloride. Its ion-exchange capacity for K+ and Pb2+ was found to be 3.20 and 2.35 meq g–1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has also been studied. The analytical importance of the material has been established by quantitative separation of Pb2+ from other metal ions. 相似文献
58.
Oxonium pentafluorotitanate was prepared by the reaction of H2O with TiF4 in HF. Single crystal x-ray diffraction studies on H3O+TiF5- show that the compound crystallizes in monoclinic form. The space group is C2/c and the unit cell dimensions are a = 14.528(5), b = 4.839(1), c = 13.798(5)Ao α = 115.59(5)o with 8 formula units per unit cell. 相似文献
59.
Allan Gut 《Statistics & probability letters》2011,81(8):1292-1299
We prove some analogs of results from renewal theory for random walks in the case when there is a drift, more precisely when the mean of the kth summand equals kγμ, k≥1, for some μ>0 and 0<γ≤1. 相似文献
60.
The analysis of deoxyribose nucleic acid (DNA) by mass spectrometry (MS) has evolved to where it can be used to analyze most known types of DNA and ribose nucleic acid (RNA) situations. It can efficiently deal with the analysis of DNA polymorphisms, sequences, haplotypes, human leukocyte antigen (HLA) typing, DNA methylation and RNA expression. Implementations of MS for these forms of DNA analyses are reviewed. The use of DNA analysis by MS is compared with competing technologies. Finally, an overview is given of worthwhile applications where the know-how gained so far could be used for future developments. 相似文献