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11.
12.
Asymmetric Horner-Wadsworth-Emmons reactions of selected meso-α-dicarbonyl compounds with chiral phosphonate reagents, which possessed axially dissymmetric 1,1′-bi-2- or 8-naphthol at the carboxylate moiety as a chiral auxiliary, were examined. The reactions proceeded smoothly with good chemical yields as well as with high diastereoselectivities. Z-olefins were preferentially formed, and it was found that the free hydroxy group at the 2′- or 8′-position on the naphthalene ring plays a crucial role in the high diastereoselectivity, probably due to a complex-induced proximity effect. Mechanistic considerations are also described. 相似文献
13.
The propulsion methods of the aquatic lives are the results of optimization by evolution and are useful for the design of
swimming-robot, etc. Among them, loach has unique propulsion technique both bending its long body and shaking caudal fin.
Our purpose of the research is to clarify its swimming mechanism through flow field analysis. Two dimensional motion and flow
around it have been experimentally visualized by particle image velocimetry (PIV). Vortices around a loach and the interactions
between the loach body and surrounding water are analyzed. Generating and growing vortices by bending its body, it pushes
water backward to gain repulsing force, and it seems that moves through vortices reducing the resistance force at the same
time. When a vortex reaches to the caudal fin, it accelerates both sides of the vortex pushing water backward and seems gaining
propulsion utilizing the caudal fin. After moving forward, loach leaves a vortex street like reverse Karman vortices, which
means that loach gains propulsion. 相似文献
14.
15.
XPS measurement revealed that the original state of TiO2 was changed to Ti2O3 and TiO by ion bombardment. TiO2 decreased and Ti2O3 increased at the initial stage. TiO increased at a later stage than Ti2O3. Each of them saturated after enough sputtering time.A formulation was proposed in order to explain the change of XPS spectra for oxides as a function of ion sputtering time. This formulation was based on reaction equations that contain two reduction processes (from TiO2 to Ti2O3 and from Ti2O3 to TiO), and sputtering effects. Using four fitting parameters (two reduction coefficients, sputtering yield and information depth), the present formula was fitted to the experimental results. The fitting results agree satisfactorily with the experimental results. The calculation shows that the reduction coefficient from TiO2 to Ti2O3 is about ten times larger than that from Ti2O3 to TiO. This calculation predicts that surface composition of an oxide that is changed by ion bombardment will reach a different value depending on its bulk composition. Moreover, the present formulation can determine the chemical states of compounds changed by ion bombardment. 相似文献
16.
Satoru Ibaraki Masao Fukushima Toshihide Ibaraki 《Computational Optimization and Applications》1992,1(2):207-226
A primal-dual version of the proximal point algorithm is developed for linearly constrained convex programming problems. The algorithm is an iterative method to find a saddle point of the Lagrangian of the problem. At each iteration of the algorithm, we compute an approximate saddle point of the Lagrangian function augmented by quadratic proximal terms of both primal and dual variables. Specifically, we first minimize the function with respect to the primal variables and then approximately maximize the resulting function of the dual variables. The merit of this approach exists in the fact that the latter function is differentiable and the maximization of this function is subject to no constraints. We discuss convergence properties of the algorithm and report some numerical results for network flow problems with separable quadratic costs. 相似文献
17.
Kazunori Tanaka Kaoru Okuno Tomoyuki Hattori Kiyoaki Moriuchi Hiroshi Hayami Wataru Katsurashima Yoshikyo Tamekuni 《光学学报》2003,23(Z1)
A non-halogen highly flame-retardant 0.9mm optical fiber and 2.0mm simplex optical cord, which are harmonized with the ecosystem, have been developed. The characteristics of them are presented in this paper. 相似文献
18.
19.
Kenji Hara Keiji Iwahashi Satoru Takakusagi Kohei Uosaki Masaya Sawamura 《Surface science》2007,601(22):5127-5132
Functionalization of self-assembled monolayer (SAM) of alkanethiolate with metal containing unit is one of the versatile methods to obtain functional surfaces such as heterogeneous catalysts. However, organic molecules that strongly bind to transition metals at SAM terminal are limited. Recently N-heterocyclic carbenes (NHCs) such as cyclic diaminocarbenes have emerged as strongly σ-donating ligands forming a robust bond with broad spectrum of transition metals. In the present study, for the purpose of establishment of a new robust basement for heterogeneous metal catalysts, a SAM of the alkanethiolate terminated with NHC-rhodium(I) complex moiety was prepared by utilizing a newly designed disulfide molecule bearing NHC-metal complex terminals. X-ray photoelectron spectroscopy (XPS) analysis and angle resolved XPS measurement revealed successful formation of the Rh-complex-terminated SAM on a gold substrate. Infrared reflection absorption spectroscopy (IRRAS) analysis suggested that the linker methylene chains connecting the rhodium complex moiety and the gold surface are in a loosely packed structure. This unique chemical species, NHC, would be a promising candidate as a basement for the construction of functional surface. 相似文献
20.
Syun-ichi Kiyooka Yushi Takeshita Yoshinori Tanaka Takafumi Higaki Yosuke Wada 《Tetrahedron letters》2006,47(26):4453-4456
A dicationic ((−)-sparteine)palladium complex underwent a superior catalytic enantioselective aldol reaction of aldehydes with 1-phenyl-1-trimethylsilyloxyethene performing satisfactorily, starting with ((−)-sparteine)PdCl2 and AgSbF6 as catalyst precursors (1 mol % loading) in the presence of 3 Å molecular sieves over the reaction. 相似文献