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971.
meso-Alkylporphyrinogen-like cyclic oligomers containing furans and pyrroles have been synthesized by "3 + 2" and "4 + 2" approaches. Condensation of 5,5,10,10,15,15-hexaethyl-21, 22-dioxatetrapyrromethane with 2,5-bis[(alpha-hydroxy-alpha, alpha-dimethyl)furan] resulted in the formation of cyclic hexamer and cyclic dodcamer. Effects of catalysts, temperature, inorganic additives, solvent, and reaction concentration were examined. 相似文献
972.
D. Lee S. Lee H. Kim D.-J. Jang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):303-306
DNA-connected strings of gold nanoparticles are arranged
to form very uniformly annular arrays having various diameters
of a few micrometers by adjusting evaporation conditions as well
as the concentrations of gold nanoparticles and
phosphorothioate-modified oligonucleotides. The circles are
formed by the dry hole-opening mechanism rather than by the
Marangoni effect. However, their sizes are very diverse and
their circumferences are approaching to show single-particle
thinness instead of close-packed particle cluster thickness
owing to DNA-linked gold nanoparticle strands. 相似文献
973.
Seung Uk Son Do Han Kim Il Gu Jung Young Keung Chung Sueg‐Geun Lee Sung‐Ho Chun 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):76-83
New norbornene derivatives synthesized from Pauson–Khand reaction products were homopolymerized and copolymerized with norbornene with an allyl–palladium complex as a catalyst. The ketone group was tolerated by the polymerization reaction. Monomers bearing protected alcohols were easily homopolymerized. Most of the homopolymers were soluble in tetrahydrofuran, CH2Cl2, toluene, and cyclohexane. As the steric bulkiness of the substituent increased, the chain length of the homopolymer decreased. Copolymers with a molecular weight of up to 153,800 were formed and were soluble in tetrahydrofuran, CH2Cl2, toluene, and diethyl ether. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 76–83, 2003 相似文献
974.
Ki‐Suk Lee Yun‐Hi Kim Yongkyun Lee Jin Jang Soon‐Ki Kwon 《Journal of polymer science. Part A, Polymer chemistry》2005,43(11):2316-2324
Polymers containing alkoxy‐substituted spirobifluorene have been prepared from nickel(0)‐mediated coupling or palladium‐catalyzed Suzuki coupling. The polymers were characterized using various spectroscopies, such as 1H‐NMR, FT‐IR, and elemental analysis. The high glass transition temperature and high decomposition temperature suggested that the resulting polymers possessed a high thermal stability. The obtained polymers possessed weight average molecular weight of 4500–33,000 with polydispersity index of 1.1–1.9 and good solubility. The low onsets of the oxidation potential suggested that the polymers containing alkoxy substituted spirobifluorene possessed a good hole injection property. The photoluminescence and electroluminescence of the polymers containing alkoxy substituted spirobifluorene showed stable blue color by suppressing the excimer formation due to intermolecular interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2316–2324, 2005 相似文献
975.
A. S. Argon R. E. Cohen B. Z. Jang J. B. Vander Sande 《Journal of Polymer Science.Polymer Physics》1981,19(2):253-272
Crazing was investigated in two commercial polystyrene/polybutadiene block copolymers made by the Phillips Petroleum Co. and marketed under the trade names of KRO-1 and KRO-3 resins. The two block copolymers each with 23% polybutadiene (PB), have radically different microstructure and radically different crazing behavior, leading to strains to fracture of 0.1 and 1.0, respectively. Of these, the KRO-1 Resin has a phase microstructure that consists of randomly wavy and often interconnected rods of PB of 20 nm diameter surrounded by polystyrene (PS). The microstructure of KRO-3 Resin consists of lamellae of PB with 20 nm thickness and large aspect ratio which range in packing from regular aligned lamellar domains with randomly varying misorientation in the annealed material, to randomly corrugated and wavy sheets in the as-received material. Crazes in KRO-1 Resin have well delineated planar shapes with a conventional, tufty craze matter structure which suggests growth by the now well-established meniscus instability mechanism proposed by one of us. In KRO-3 Resin, on the other hand, crazing involves profuse cavitation if the PB lamellae, giving rise to less well delineated zones of cavitational growth dispersed over the volume and suggests a mechanism of craze growth by stable, interfacial cavitational degradation in a process zone ahead of the craze tip. The measured stress and temperature dependences of craze velocities in these two polymers is in partial support of the suggested mechanisms which are also developed in outline. 相似文献
976.
977.
Core/shell nanomaterials composed of only polypyrroles (PPys) were fabricated by microemulsion polymerization using two oxidants with different chemical oxidation potentials, and used as a precursor for the fabrication of PPy and carbon nanocapsules. 相似文献
978.
Kim SM Chung KW Choi BO Yoon ES Choi JY Park KD Sunwoo IN 《Experimental & molecular medicine》2004,36(1):28-35
Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant inherited disorder characterized by recurrent pressure palsies. Most HNPP patients have a 1.5 mb deletion in chromosome 17p11.2-p12. The present study aimed at evaluating the deletion of the 17p11.2-p12 region in Korean subjects with families exhibiting HNPP phenotype, and to determine the clinical, electrophysiological and morphological aspects specifically associated with this deletion in HNPP patients. By genotyping six microsatellite markers (D17S921, D17S955, D17S1358, D17S839, D17S122 and D17S261), HNPP with the deletion was observed in 79% (19 of 24) of HNPP families. Nerve conduction studies were performed in 35 HNPP patients from these 19 families. The observed HNPP deletion frequency in Koreans is consistent with findings in other populations. Disease onset occurred at a significantly earlier age in patients with recurrent pressure palsies than in those with a single attack (P < 0.01). Nerve conduction studies demonstrated diffuse mild to moderate slowing of nerve conduction velocities that were worse over the common entrapment sites, regardless of the clinical manifestations. A long duration of compound muscle action potentials without a conduction block or a temporal dispersion is a characteristic of this disease. A sural nerve biopsy with teasing was performed in four patients, and tomacula of the myelin sheath was found in 56.4%. Our findings appear to support the existence of a phenotype/genotype correlation in HNPP patients of Korean ancestry with the deletion, and suggest that HNPP patients with earlier symptom onset face an increased chance of having recurrent attacks. 相似文献
979.
We have demonstrated that site-selective patterning of organic monolayers can be accomplished simply by inducing Ag nanoparticle-mediated catalytic reduction to occur on the desired regions of those monolayers. 相似文献
980.