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991.
Chiral and C2-symmetric seven-membered cycloalkanones 2--6 bearing 1,2-diphenylethane-1,2-diamine and cyclohexane-1,2-diamine backbones were synthesized and evaluated their asymmetry inductive behaviours in an asymmetric epoxidation of stilbene with oxone. Although the reaction of the ketones 2 and 3 of a 1,2-diphenylethane-1,2-diamine backbone gave stilbene oxide in trace to 31% yield, those of the ketones 4-6 of a cyclohexane-1,2-diamine backbone gave the epoxide in satisfactorily high yield up to 98%. It is noteworthy that both reactions with use of stoichiometric and substoichiometric amounts of a ketone 4 gave the epoxide in the essentially same enantioselectivity, 17 and 18%. Eleven-membered cyclic ketones 7 and 8 bearing a binaphthalene backbone were also synthesized and examined their behaviours, while the enantioselectivity turned out to be marginal. 相似文献
992.
Nobutoshi Kiba Ayumi Koga Masaki Tachibana Kazue Tani Hitoshi Koizumi Tetsuo Koyama Akira Yamamura Kunio Matsumoto Tohru Okuda Koki Yokotsuka 《Analytical sciences》2006,22(1):95-98
A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel. 相似文献
993.
994.
This paper shows an important exception to the common perception that three-dimensional meshes are more powerful than two-dimensional ones. Let N be the total number of processors. Then permutation routing over three-dimensional mesh computers needs Θ(N2/3) steps while it takes Θ(N1/2) steps over two-dimensional ones under the following conditions: (1) The path of each packet must be determined solely by its initial position and destination, i.e., the algorithm must be oblivious. (2) Each path must be “elementary,” i.e., it must be shortest and as straight as possible. Thus the conditions, under which, somewhat surprisingly, three-dimensional meshes are significantly less powerful than two-dimensional ones for the fundamental network operation, are quite reasonable in practice. 相似文献
995.
996.
Gi-Chol Cho Kaoru Hagiwara Seiji Matsumoto 《The European Physical Journal C - Particles and Fields》1998,5(1):155-165
We investigate the constraints on four-Fermi contact interactions from low-energy lepton-quark and lepton-lepton scattering
experiments – polarization asymmetries in electron (muon)-nucleon scattering experiments, cesium and thallium atom parity
violation measurements, neutrino-nuclei and neutrino-electron scattering experiments. These constraints are then combined
by assuming the lepton and quark universalities and gauge invariance of the contact interaction, which leave independent six lepton-quark and three pure-leptonic interactions.
Impacts of these constraints on models with an additional -boson are briefly discussed. We also present updates of the low-energy constraints on the and parameters.
Received: 28 November 1997 / Published online: 26 February 1998 相似文献
997.
Matsuta K. Fukuda M. Tanigaki M. Minamisono T. Nojiri Y. Akai H. Izumikawa T. Nakazato M. Mihara M. Yamaguchi T. Harada A. Sasaki M. Miyake T. Onishi T. Minamisono K. Fukao T. Sato K. Matsumoto Y. Ohtsubo T. Fukuda S. Yoshida K. Ozawa A. Momota S. Kobayashi T. Tanihata I. Alonso J. R. Krebs G. F. Symons T. J. M. 《Hyperfine Interactions》1996,97(1):501-508
The spin relaxation timeT
1 for short-lived beta emitters13O and23Mg implanted in Pt have been measured for the first time;T
1T13O) = 2.90 ±0.65 Ks andT
1
T(23Mg) = 1665 ±140 Ks. The Knight shift for13O in Pt was measured at 300 K to beK(13O) = +(4.23 ±0.14) × 10–3. In the case of13O, the Knight shift is unusually large and the relaxation time is unusually fast compared with other interstitial impurities in Pt. A KKR band-structure calculation reproduces the present large Knight shift fairly well. 相似文献
998.
Kazuya Matsumoto Tomoya Higashihara Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》2009,47(13):3444-3453
Novel locally sulfonated poly(ether sulfone)s with highly sulfonated units were successfully synthesized for fuel cell applications. Poly(ether sulfone)s were prepared by the nucleophilic substitution of bis(4‐fluorophenyl) sulfone with 1,2,4,5‐tetrakis([1,1′‐biphenyl]‐2‐oxy)‐3,6‐bis(4‐hydroxyphenoxy)benzene and bis(4‐hydroxyphenyl) sulfide, followed by oxidation using m‐chloroperoxybenzoic acid. The desired highly sulfonated units were easily introduced by postsulfonation and each one had ten sulfonic acid groups. The sulfonated polymers gave tough, flexible, and transparent membranes by solvent casting. The high contrast in polarity between highly sulfonated units and hydrophobic poly(ether sulfone) units enabled the formation of defined phase‐separated structures and well‐connected proton paths. The sulfonated polymers exhibited excellent proton conductivity over a wide range of relative humidities. The proton conductivity of the sulfonated polymer with an ion exchange capacity value of 2.38 mequiv/g was comparable to that of Nafion 117 even at 30% relative humidity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3444–3453, 2009 相似文献
999.
In order to convert a color image into a monochrome one, the lightness components of pixels have to date been used as gray-levels
for the representation of the monochrome image. However, saliencies of an image embedded only in the chrominance components
are eliminated in such conversion. To cope with this problem, “Color2Gray” algorithm, which excels in the color removal of
digital images, has been proposed by Gooch et al. [ACM Trans. Graphics 24 (2005) 634]. In this paper, the algorithm is first analyzed and its mathematical property is revealed. Then a fast Color2Gray
algorithm is proposed by using the mathematical property. Finally, the validity and the effectiveness of the proposed algorithm
are proven by some experiments. 相似文献
1000.
Akikazu Matsumoto Keiichi Shimizu Keiichiro Mizuta Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1994,32(10):1957-1968
Radical polymerization of several alkyl crotonates (RCr) was carried out in bulk or in benzene in the presence of radical initiators. Homopolymerization of RCr bearing bulky ester alkyl groups, e.g. tert-butyl (tBCr), 1-adamantyl (AdCr), and 3,5-dimethyl-1-adamantyl crotonate (DMAdCr) proceeded to give a polymer with molecular weight of several thousands despite of the steric hindrance and chain transfer by the presence of the β-methyl group, while the methyl and ethyl esters gave no polymer. The kinetics of the polymerization was examined in detail and absolute rate constants were evaluated by means of electron spin resonance spectroscopy. The propagation rate constants of RCr were 0.41–1.0 L/mol s, being much smaller than those of the corresponding methacrylates (530–570 L/mol s). The termination rate constants were also determined from the analyses of steady state and non-steady state polymerizations. Radical copolymerizations of AdCr (M2) with several vinyl monomers (M1) were carried out in bulk at 60°C and the rate constants for cross propagations were calculated to examine reactivities of the monomer and its polymer radical. The structure and thermal properties of the resulting poly (AdCr) were also investigated. Onset temperature of decomposition and glass transition temperature of poly(AdCr) were revealed to be much high as 302 and 234°C, respectively. © 1994 John Wiley & Sons, Inc. 相似文献