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861.
862.
Olivier Monasson Maryon Ginisty Janez Mravljak Gildas Bertho Christine Gravier-Pelletier Yves Le Merrer 《Tetrahedron: Asymmetry》2009,20(20):2320-2330
The synthesis of new enantiopure polyfunctionalised diazepanone scaffolds is described. The key steps involve the opening of an azido-epoxide C4 building block derived from l-ascorbic or d-isoascorbic acid by a l-serine derivative followed by a lactonisation–lactamisation two-step sequence. 相似文献
863.
864.
The absorption of the secondary hadrons in nuclear matter is studied as a function of their flavour dependent inelastic cross section on nucleons. In particular the ratiosK +/π+ andK ?/π? of particles produced in the proton-nucleus high energy interactions are examined and described in the very simple phenomenological model. The enhanced production ofK + mesons is explained by their relatively small interaction. The presence of the initial particle absorption is clearly demonstrated forx F>0.5. 相似文献
865.
Maude Le Hellaye Catherine Lefay Thomas P. Davis Martina H. Stenzel Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2008,46(9):3058-3067
The simultaneous ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and 2‐hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ε‐CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2‐ethylhexanoate (Sn(Oct)2) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA‐g‐PCL. Graft copolymer formation is evidenced by a combination of size‐exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000–10,000 g mol?1) the copolymer grafting density is higher than 90%. The ratio of free HEMA‐PCL homopolymer produced during the “one‐step” process was found to depend on the HEMA concentration, as well as the half‐life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058–3067, 2008 相似文献
866.
This paper presents a nonlinear, multi-phase and stochastic dynamical system according to engineering background. We show that the stochastic dynamical system exists a unique solution for every initial state. A stochastic optimal control model is constructed and the sufficient and necessary conditions for optimality are proved via dynamic programming principle. This model can be converted into a parametric nonlinear stochastic programming by integrating the state equation. It is discussed here that the local optimal solution depends in a continuous way on the parameters. A revised Hooke–Jeeves algorithm based on this property has been developed. Computer simulation is used for this paper, and the numerical results illustrate the validity and efficiency of the algorithm. 相似文献
867.
868.
The global formulation of the higher-order Poincaré-Cartan form for Lagrangian field theories in the calculus of variations is re-examined in terms of the theory of lifts of tensor fields on a manifold to its higher-order prolongated jet bundles.Partially supported by CNPq, Brazil, Proc. MA 30.1115/79. 相似文献
869.
870.
Zheng Wu WANG Gan Zuo LI* Da Ren GUAN Xi Zhang YI An Jing LOU Key Lab of Colloid Interface Chemistry for State Education Ministry Shandong University Ji''''nan Institute of Theoretical Chemistry Shandong University Ji''''n 《中国化学快报》2001,(7)
The electrical double layer theory is the base of the colloid stability theory (DLVO theory), and the PB eq. is a key to the study of the layer1,2. For a spherical particle, the PB eq. is (1) where and are the dielectric constant of the medium, the valence of ions, the elementary charge, the concentration of ions far away from the particle, the Boltzmann's constant and the temperature of the system, respectively. Since this eq. is a second order nonlinear differential one, only the anal… 相似文献