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1.
Dr. Takeshi Nanjo Natsuki Kato Xuan Zhang Prof. Yoshiji Takemoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(68):15504-15507
Strategies for the formation of amide bonds, that is, one of the most basic and important transformations in organic synthesis, have so far focused predominantly on dehydration reactions. Herein, we report and demonstrate the practical utility of a novel decarboxylative amidation of α-ketoacids by using inexpensive tert-butyl hydroperoxide (TBHP), which is characterized by high yields, a broad substrate scope, mild reaction conditions, and a unique chemoselectivity. These features enable the synthesis of peptides from amino acid derived α-ketoacids under preservation of the stereochemical information. 相似文献
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Surface texturing has been recognized as an effective means to improve the tribological performances of sliding surfaces. Usually, generation additional hydrodynamic pressure to increase the load carrying capacity is regarded as the most significant effect of surface texture. In the case of silicon carbide sliding against identical material in water, the experimental results indicate that surface texture is also helpful to improve the running-in progress to smooth the contact surfaces, showing another reason to result in low friction. Based on the consideration of enhancing the generation of hydrodynamic pressure and improving running-in progress, a surface texture pattern, which was combined with large (circle, 350 μm in diameter) and small (rectangular, 40 μm in length) dimples, was designed to maximize the texture effect on the load carrying capacity of SiC surfaces sliding in water. The friction coefficient of such textured surface was evaluated and compared with that of untextured and those only with large or small dimples only. The friction reduction mechanisms of the patterns with different dimples in size are discussed. 相似文献
3.
Katsunari Inoue Kazuaki Kato Norimitsu Tohnai Mikiji Miyata 《Journal of polymer science. Part A, Polymer chemistry》2004,42(18):4648-4655
We studied simulations by computer graphics to estimate the steric mechanism of the asymmetric polymerization of prochiral diene monomers in channels of inclusion compounds of steroidal bile acids, such as deoxycholic acid (DCA) and cholic acid. We applied a hierarchization method to interpret the crystal structures of bile acids, clarifying that the chiral host molecules associated to form characteristic 21-helical assemblies with uneven surfaces. A detailed analysis of the uneven channels in a close-packing state indicated that there were many possible arrangements of the monomers in the channels. The plausible arrangements in the channel could explain a previous study, which showed that the polymerization in the DCA channel yielded chiral polymers with a predominant configuration from prochiral diene monomers, such as 2-methyl-trans-1,3-pentadiene. On the basis of such simulation studies of the arrangements of guest monomers in the channel, we examined a plausible steric mechanism for asymmetric inclusion polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4648–4655, 2004 相似文献
4.
Seiichi Nishizawa Tomoyuki Kamaishi Tomoyuki Yokobori Ryo Kato Ying-Yu Cui Takeshi Shioya Norio Teramae 《Analytical sciences》2004,20(11):1559-1565
Facilitated SO4(2-) transfers by hydrogen bond-forming ionophores are investigated across the nitrobenzene (NB)-water interface by using polarography with a dropping electrolyte electrode. Bis-thiourea 1, alpha,alpha'-bis(N'-p-nitrophenylthioureylene)-m-xylene, is found to significantly facilitate the transfer of the highly hydrophilic SO4(2-) whereas its counterpart, N-(p-nitrophenyl)-N'-propylthiourea (ionophore 2), cannot. In contrast to the predominant formation of a 1:1 complex with SO4(2-) in the bulk NB phase, the SO4(2-) transfer assisted by 1 is indeed based on the formation of a 1:2 complex between SO4(2-) and ionophore, even under the condition of [SO4(2-)]aq > [1]org. Such an exclusive formation of the 1:2 (SO4(2-) to ionophore) complex at the NB-water interface is not observed with structurally similar bis-thiourea 3, alpha,alpha'-bis(N'-phenylthioureylene)-m-xylene, where p-nitrophenyl moietes of bis-thiourea 1 are simply replaced by phenyl groups. The facilitated transfer of SO4(2-) with bis-thiourea 1 is further compared to that of HPO4(2-) and H2PO4- across the NB-water interface, which was previously shown to be assisted by 1 through the formation of the 1:1 and 2:1 (anion to ionophore) complexes, respectively. On the basis of these examinations, unique binding behaviors of hydrogen bond-forming ionophores at the NB-water interface are discussed, with a view towards development of ionophore-based anion-selective chemical sensors. 相似文献
5.
Nobuyuki Hanaki 《Complexity》2004,9(5):41-50
This article seeks to ascertain whether the strategy‐learning model of Hanaki, Sethi, Erev, and Peterhansl (2003) better accounts for observed behavior than do the various action‐learning models. It does so by measuring the goodness‐of‐fit of the models' predictions against published experimental results for such games as Coordination, Prisoner's Dilemma, and Chicken. The fit is measured via the mean squared deviation (MSD) between the observed behavior and the one predicted by the model. The results show that, for Chicken, the strategy‐learning model fits the observed data much better than do the action‐learning models. The best action‐learning model, on the other hand, fits the observed data well in Coordination. Overall, the strength of the strategy‐learning model is best shown in games where alternations between the two stage‐game Nash equilibria are often observed in the laboratory experiments. © 2004 Wiley Periodicals, Inc. Complexity 9: 41–50, 2004 相似文献
6.
Endoscopic Observation of Tissue by Narrowband Illumination 总被引:6,自引:0,他引:6
Kazuhiro Gono Kenji Yamazaki Nobuyuki Doguchi Tetsuo Nonami Takashi Obi Masahiro Yamaguchi Nagaaki Ohyama Hirohisa Machida Yasushi Sano Shigeaki Yoshida Yasuo Hamamoto Takao Endo 《Optical Review》2003,10(4):211-215
We propose a new illumination method for a medical endoscope: narrow band imaging (NBI), in which the spectral bandwidth of the filtered light is narrowed. To confirm how the spectral specifications of the filtered light influence a reproduced image, an experiment was conducted observing the endoscopic images of the back mucosa of a human tongue. In addition, the effect of NBI on endoscopic images was investigated through preliminary clinical tests in colonoscopy and upper gastrointestinal endoscopy. It has been shown that NBI can enhance the capillary pattern and the crypt pattern on the mucosa. These patterns are useful features for diagnosing an early cancer. 相似文献
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9.
Yasuhiko Iwasaki Keiko Shimakata Nobuyuki Morimoto Kimio Kurita 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):68-75
To obtain a hydrogel‐like elastic membrane, we prepared semi‐interpenetrating polymer networks (IPNs) by the radical polymerization of methacrylates such as 2‐methacryloyloxyethyl phosphorylcholine (MPC), 2‐hydroxyethylmethacrylate, and triethyleneglycol dimethacrylate diffused into segmented polyurethane (SPU) membranes swollen with a monomer mixture. The values of Young's modulus for the hydrated semi‐IPN membranes were less than that for an SPU membrane because of higher hydration, but they were much higher than that for a hydrated MPC polymer gel (non‐SPU). According to a thermal analysis, the MPC polymer influenced the segment association of SPU. The diffusion coefficient of 8‐anilino‐1‐naphthalenesulfonic acid sodium salt from the semi‐IPN membrane could be controlled with different MPC unit concentrations in the membrane, and it was about 7 × 102 times higher than that of the SPU membrane. Fibroblast cell adhesion on the semi‐IPN membrane was effectively reduced by the MPC units. We concluded that semi‐IPNs composed of the MPC polymer and SPU may be novel polymer materials possessing attractive mechanical, diffusive‐release, and nonbiofouling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 68–75, 2003 相似文献
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