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51.
52.
Hayashi Y Tsuboi W Shoji M Suzuki N 《Journal of the American Chemical Society》2003,125(37):11208-11209
High pressure induced by water-freezing has been successfully applied to the direct catalytic asymmetric-three component List-Barbas-Mannich reaction, in which higher yield and better enantioselectivity can be realized than those from the reaction at room temperature under 0.1 MPa. 相似文献
53.
54.
In this paper, we shall establish a fixed point property on Fréchet spaces for left reversible semitopological semigroups generalizing some classical results. 相似文献
55.
Hiroshi Onizuka Masaki Kato Tetsuo Shimura Wataru Sakamoto Toshinobu Yogo 《Journal of Sol-Gel Science and Technology》2008,46(1):107-115
Proton conductive inorganic–organic hybrid membranes were synthesized from dimethylethoxyvinylsilane (DMEVS), vinylphosphonic
acid (VPA) and 3-glycidoxypropyltrimethoxysilane (GPTMS) through copolymerization followed by sol–gel process. The ratio of
phosphorus to silicon in the copolymer almost corresponded to the charged molar ratio of VPA to DMEVS when the ratio of VPA
to DMEVS was below 1/2. Self-standing, homogeneous, highly transparent membranes were synthesized from DMEVS–VPA copolymer
and GPTMS via sol–gel condensation. Differential thermal analysis-thermogravimetry analyses indicated that these membranes
were thermally stable up to 200 °C. The results of Fourier transform infrared and 13C NMR revealed that phosphonic acid groups of VPA were chemically bound to organosiloxane network. The copolymerization and
condensation of (DMEVS–VPA)/GPTMS were confirmed by 31P and 29Si NMR spectra. The proton conductivity of the hybrid membranes increased with phosphonic acid content. The membrane of (DMEVS–VPA)/GPTMS
showed a remarkable conductivity of 6.3 × 10−2 S cm−1 at 130 °C and 100% relative humidity. 相似文献
56.
Thomas RM Widger PC Ahmed SM Jeske RC Hirahata W Lobkovsky EB Coates GW 《Journal of the American Chemical Society》2010,132(46):16520-16525
A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (k(fast)/k(slow)) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T(m) values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides. 相似文献
57.
Combined DFT calculations and UV-vis-NIR, ESR, and SQUID measurements revealed that the ground-state electronic structure of a linear π-conjugated oligomer dication composed of two pyrrole and six or seven thiophene rings and methylthio end-capping units is dominated by a singlet biradical character. 相似文献
58.
We report on the fabrication and characterization of nanoscale solid immersion lenses (nano-SILs) with sizes down to a subwavelength range. Submicrometer-scale cylinders fabricated by electron-beam lithography are thermally reflowed to form a spherical shape. Subsequent soft lithography leads to nano-SILs on transparent substrates for optical characterization. The optical characterization is performed using a high-resolution interference microscope with illumination at 642 nm wavelength. The focal spots produced by the nano-SILs show both spot-size reduction and enhanced optical intensity, which are consistent with the immersion effect. 相似文献
59.
Wataru Sakamoto 《Computational Statistics》2007,22(4):583-597
An empirical Bayes method to select basis functions and knots in multivariate adaptive regression spline (MARS) is proposed,
which takes both advantages of frequentist model selection approaches and Bayesian approaches. A penalized likelihood is maximized
to estimate regression coefficients for selected basis functions, and an approximated marginal likelihood is maximized to
select knots and variables involved in basis functions. Moreover, the Akaike Bayes information criterion (ABIC) is used to
determine the number of basis functions. It is shown that the proposed method gives estimation of regression structure that
is relatively parsimonious and more stable for some example data sets. 相似文献
60.
In this paper, we study the problem of existence of zero points for set-valued operators in Banach spaces. We present a simple
condition which can be used to verify that under some conditions, set-valued operators have zero points. Furthermore, we derive
the surjectivity result and the Kakutani fixed point theorem by using this condition.
相似文献