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941.
Takashi Shimizu Tsuneki Ichikawa 《Journal of polymer science. Part A, Polymer chemistry》2005,43(5):1068-1075
Polystyrene with a benzyl ester of carboxylic acid at the center of a polymer skeleton was synthesized by living radical polymerization. The initiator used had two functional groups for 2,2,6,6‐tetramethylpiperidinoxyl (TEMPO)‐mediated living radical polymerization on the benzyl and the carboxylic sides of the benzyl ester. Introduction of the benzyl ester changed the polystyrene from a crosslink type to a scission type polymer on γ‐irradiation. Irradiation of the polymer resulted in a binary change of the molecular weight because of the dissociative capture of secondary electrons by the benzyl ester, as: The binary change of the molecular weight suggests that the polymer can be used as a new type of radiation resist with high sensitivity and spatial resolution to ionizing and high resistivity to plasma etching. The number of scissions per 100 eV radiation energy absorbed was 0.29, which was about one fourth of the yield of secondary electrons. The low efficiency was because of the recombination of polymer radicals generated by the dissociative electron attachment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1068–1075, 2005 相似文献
942.
Yasuo Wakatsuki Hiroshi Yamazaki Yooichiroh Maruyama Isao Shimizu 《Journal of organometallic chemistry》1992,430(3):C60-C63
The butadienyl complexes formed by the reaction of trans-(R1)CH=CHCCR2 (R1, R2 = SiMe3, tBu, Me, Et) with RuCl(CO)H(PPh3)3 exhibit unique structures: instead of taking the 18-electron configuration of the metal by conventional η3-coordination of the butadienyl ligand, they shift significantly to the 16-electron η1-coordination state. 相似文献
943.
Takaaki Horaguchi Chikara Tsukada Eietsu Hasegawa Takahachi Shimizu Tsuneo Suzuki Kiyoshi Tanemura 《Journal of heterocyclic chemistry》1991,28(5):1273-1280
Photocyclization reactions were carried out on ethyl 2-formylphenoxyacetates 1a-e and ethyl 2-acetylphenoxyacetates 2a-e in acetonitrile. Irradiation of 1a-e gave dihydrobenzofuranols 3 in 20–46% yields. Similarly, irradiation of 2a-e afforded dihydrobenzofuranols 6 and their derivatives 7, 8 in 40–86% yields. Substituent effects on photocyclization and reaction pathways are discussed. 相似文献
944.
945.
Nanostructured poly(vinylidene fluoride) (PVDF)/polyamide 11 (PA 11) blends of various compositions were prepared using a high-shear extruder. The lamellar morphology of the nanoblends consisting of two crystalline constituents was investigated by transmission electron microscopy (TEM) and temperature-variable small-angle X-ray scattering (SAXS). The average lamellar long period and the thickness of the amorphous part for the high-shear-processed blends were larger than those for the low-shear-processed sample, indicating the molecular incorporations between PVDF and PA 11 upon high-shear processing. A novel scattering peak, corresponding to the long period of 25.2 nm, is observed when the SAXS measurements were carried out at a temperature between the melting points of PVDF and PA 11. The structural change with time at high temperature was investigated in situ by SAXS. It was found that the intensity of the new peak increased with time at high temperature and the peak position slowly shifted in the low-angle direction, indicating a gradual increase of the long period for PA 11 crystals upon annealing. The novel scattering peak originates from the enlarged PA 11 lamellar long period in the nanodomain because the peak cannot be observed for the same blends prepared by low-shear-processing. It is considered that the melt PVDF chains are gradually diffused into the galleries of PA 11 lamellae in the PA11 nanodomain, which enlarged the long period of PA 11 because of the more favorable interaction at high temperature. The chain diffusion can only occur from the interface between the PVDF and PA 11 phases, and therefore, almost no change was observed for the long period of bulk PA 11 crystals in the nanoblend. 相似文献
946.
K Torizumi Y Taniguchi H Aibata S Kiji A Ueyoshi E Shimizu Y Okamoto T Tuda K Ota 《Radioisotopes》1987,36(9):469-472
This study was focussed our attention on the measurement within the upper physiological level of human serum parathyroid hormone (PTH), using kits of human PTH 53-84. This assay kit was able to detect serum PTH in sera with subtle changes of serum calcium concentrations before and after short term exercise. These serum PTH levels before and after exercise seemed to be changed within the upper physiological levels of PTH. Thus, this study suggested that the assay kit was likely to become a useful tool of the measurement of the physiological level of serum PTH in humans. 相似文献
947.
Phosphoglucomutase and glucose-6-phosphate dehydrogenase were immobilized to s-triazine trichloride activated cellulose. The optimal conditions for binding the immobilized enzymes were determined and the kinetic and physical properties were investigated.The final ratio of the two enzymes immobilized to the surface was determined by the physical properties of the enzymes as well as by the ratio of the enzymes present in the attachment solution. The immobilized enzymes were found to retain at least 60% of the original activity for at least 40 days when stored at 4°C and in the presence of substrates and cofactors. Immobilized phosphoglucomutase and glucose-6-phosphate dehydrogenase also were much more stable at 58°C, retaining 28 and 13% of the original activity, respectively, after 75 min. The apparentK m’s were 5.4 to 1.5 times higher for immobilized phosphoglucomutase and glucose-6-phosphate dehydrogenase, respectively than for the soluble enzymes. 相似文献
948.
Huang J Ogihara Y Zhang H Shimizu N Takeda T 《Chemical & pharmaceutical bulletin》2000,48(10):1413-1417
Four new triterpenoid saponins, ardisimamilloside C (1), 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->4)-[beta -D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl]-3beta,16al pha,28,30-tetrahydroxy-olean-12-en, ardisimamilloside D (2), 3-O-?alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->4)-[beta -D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl]-3beta,15al pha,28,30-tetrahydroxy-olean-12-en, ardisimamilloside E (3), 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->4)-[beta -D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosl]-13beta,2 8-epoxy-3beta,16alpha,29-oleananetriol, and ardisimamilloside F (4), 3-O-[alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->4)-[beta -D-glucopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl]-3beta,16al pha-dihydroxy-13beta,28-epoxy-oleanan-30-oic acid were isolated from the roots of Ardisia mamillata Hance. Structure assignments were established on the basis of highresolution (HR)-FAB-MS, 1H-, 13C-, and two-dimensional (2D)-NMR spectra, and on the chemical evidence. 相似文献
949.
Kitov PI Shimizu H Homans SW Bundle DR 《Journal of the American Chemical Society》2003,125(11):3284-3294
A series of bivalent ligands for a Shiga-like toxin have been synthesized, their experimentally determined inhibitory activities were compared with a simplified thermodynamic model, and computer simulations were used to predict the optimal tether length in bivalent ligands. The design of the inhibitors exploits the proximity of the C-2' hydroxyl groups of two P(k)-trisaccharides when bound to two different, neighboring carbohydrate recognizing binding sites located on the surface of Shiga-like toxin. NMR studies of the complex between the toxin and bivalent ligands show that site 2 and site 1 of a single B subunit are simultaneously occupied by a tethered P(k)-trisaccharide dimer. A simplified thermodynamic treatment provides the intrinsic affinities and binding energies for the intermolecular and intramolecular association events and permits the deconvolution of the contributions to the relative binding energies for the set of bivalent ligands. Conformational analysis based on MD simulations for bivalent galabioside dimers containing different tethers demonstrated that the calculated local concentrations of the pendant ligand at the second binding site correlate with the experimentally determined relative affinity values of the respective bivalent ligands, thereby providing a predictive method to optimize tether length. 相似文献
950.
[reaction: see text] Catalytic asymmetric hydroxymethylation of silicon enolates with an aqueous formaldehyde solution has been developed using a chiral bismuth complex. This is the first example of highly enantioselective reactions using a chiral bismuth catalyst in aqueous media. In this paper, we have added Bi(OTf)(3)-1 complex as a "water-compatible Lewis acid". Bi(OTf)3 is unstable in the presence of water but is stabilized by the basic ligand. 相似文献