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991.
Hajime Yasuda Hitoshi Yamamoto Yasunori Takemoto Masahiro Yamashita Kiyohiko Yokota Shigenobu Miyake Akira Nakamura 《Macromolecular Symposia》1993,67(1):187-201
Organolanthanide(III) complexes such as |(C5Me55)2SmH|2 and (C5Me5)2SmMe(THF) were found to initiate the living polymerizations of methyl methacrylate (MMA) to give high molecular weight polymers (M n > 500 × 103) with extremely low polydispersity (M w/Mn = 1.04). The syndiotacticity increased up to 95.2% by lowering the temperature to −95°C. The molecular structure of the 1:2 adduct of (C5Me5)2SmH with MMA determined by X-ray method indicates that this intermediate assumes the 8 membered ring conformation where the Sm atom is bound to MMA in an enolate form and the ester of penultimate MMA is coordinated to the metal. Based upon these results, an anionic coordination mechanism has been proposed for the present reaction. Organolanthanide(II) complexes also exhibit high activity and proceed the living polymerizations. Organolanthanide(III) complexes also initiate the living polymerizations of lactones such as ϵ-caprolactone and δ-valerolactone. The stoichiometric reactions indicate that real active species assumes the alkoxylanthanide(III) form. 相似文献
992.
Tomohiro Miyatake Hitoshi Tamiaki Alfred R. Holzwarth Kurt Schaffner 《Photochemistry and photobiology》1999,69(4):448-456
Abstract— Zinc chlorins possessing 31 -hydroxyl and 131 -carbonyl groups self-assemble in nonpolar solvents, such as hexane, in a manner similar to bacteriochlorophyll c in the chlorosomes of green photosynthetic bacteria. Visible absorption and steady-state fluorescence measurements of zinc chlorin aggregates containing a small amount of the bacteriochlorin-zinc chlorin dyad molecules showed that singlet excitation energy transfer from the zinc chlorin aggregate to the bacteriochlorin moiety of the coaggre-gated dyad occurs in the homogeneous solution. In the coaggregated dyad, the bacteriochlorin moiety plays the role of an efficient energy trap and the chlorin moiety the role of an anchor to the donor aggregate. The artificial assembly thus mimics the structure and function of natural chlorosomes and can be considered as the first in vitro supramolecular light-harvesting antenna. 相似文献
993.
994.
K. Hashi T. Shimizu A. Goto H. Kitazawa G. Kido T. Suzuki 《Applied Physics A: Materials Science & Processing》2000,70(3):359-360
An NMR quantum computer based on an integrated device with CeP has been proposed by Yamaguchi and Yamamoto [Appl. Phys. A 68 1 (1999)]. We point out two problems in their scheme. We also investigate experimentally the 31P NMR spectra for our CeP. From the line width, we find that improvement of the sample quality is necessary to satisfy the experimental conditions for a quantum computer. 相似文献
995.
We discuss the concept of multiple recurrence, considering an ergodic version of a conjecture of Erdős. This conjecture applies
to infinite measure preserving transformations. We prove a result stronger than the ergodic conjecture for the class of Markov
shifts and show by example that our stronger result is not true for all measure preserving transformations. 相似文献
996.
Norio Tsubokawa Toshiya Satoh Masamichi Murota Shimpei Sato Hiroshi Shimizu 《先进技术聚合物》2001,12(10):596-602
To modify carbon black surface, the surface grafting of hyperbranched poly(amidoamine) onto the surface by using dendrimer synthesis methodology was investigated. Carbon black having amino groups (initiator sites) was prepared by the reduction of surface nitro groups introduced by nitration of aromatic rings. It was found that hyperbranched poly(amidoamine) was propagated from carbon black surface by repeating two processes: (1) Michael addition of methyl acrylate (MA) to surface amino groups and (2) amidation of the resulting esters with ethylenediamine: the percentage of poly(amidoamine) grafting reached to 96.2% after 10th‐generation. The grafting of hyperbranched poly(amidoamine) onto polystyrene‐bead as a model compound of carbon black was also achieved by the above procedures. However, the theoretical propagation of poly(amidoamine) dendrimer was not achieved, because of steric hindrance of grafted polymer. Hyperbranched poly(amidoamine)‐grafted carbon black gave a stable dispersion in a good solvent for poly(amidoamine). Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
997.
Hitoshi Furuhata 《Journal of Geometry》1999,65(1-2):111-116
We give an intrinsic characterization of isometric pluriharmonic immersions of Kähler manifolds into semi-Euclidean spaces with real codimension one, which is a generalization of the Ricci-Curbastro theorem.Research partly supported by the Grants-in-Aid for Encouragement of Young Scientists, The Ministry of Education, Science and Culture, Japan. 相似文献
998.
Seiji Yamaguchi Keiko Orito Noriko Shimizu Katsunori Taniguchi Hideo Saitoh Masahide Kurosaki Hajime Yokoyama Yoshiro Hirai Shunsaku Shiotani 《Journal of heterocyclic chemistry》1999,36(1):81-94
Furo[2,3-b:4,5-c‘]- 1a , -[3,2-b:4,5-c’]- 1b , -[2,3-c:4,5-c‘]- 1c and -[3,2-c:4,5-c’]dipyridine 1d were derived to the N-oxides 2a-d , N‘-oxides 2′b , 2′c or N,N’-dioxide 3b-d by N-oxidation with m-chloroperbenzoic acid. Chlorination of these N-oxides, N′-oxide and N,N′-dioxides with phosphorus oxychloride afforded compounds chlorinated at the α-position(s) to the ring nitrogen 4a-d , 4′c , 14b-d and 14′b . Acetoxylation of N-oxides 2a-d and 2′c with acetic anhydride gave the corresponding pyridone compounds 6a-d and 6′c in good yields, while the acetoxylation of N,N′-dioxides gave a complex mixture from which no compound could be isolated. Cyanation of 2a-d, 2′c and 3b-d with trimethylsilyl cyanide yielded the cyano compounds 7a-d , 7′c , cyano-N-oxides 15b-d and dicyano compounds 15′c and 15′d . Monocyano compounds 7a-d and 7′c were converted to the imino esters 8a-d and 8′c by treatment with sodium ethoxide. Imino esters were derived to the carboxylic esters 9a-d and 9′c , from which the corresponding alde hydes 10a-d and 10′c were obtained by reduction with diisobutylaluminum hydride. Dicyanide 15′c was converted to dialdehyde 19 by the treatment with sodium ethoxide, and the subsequent hydrolysis of the imino ester and reduction of the carboxylic ester with diisobutylaluminum hydride. 相似文献
999.
Shuki Araki Hiromi Hattori Noriyuki Shimizu Koji Ogawa Hatsuo Yamamura Masao Kawai 《Journal of heterocyclic chemistry》1999,36(4):863-867
A new type of tetrazolium-5-amide mesoions 2 with a tricyclic tetrazolo[1,5-a]benzimidazole skeleton has been synthesized via photolysis of 5-azido-1,3-diaryltetrazolium salts 1 . 相似文献
1000.