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141.
Donghui Jo Gi Tae Park Dr. Jiho Shin Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2018,57(8):2199-2203
From a technological point of view, the synthesis of new high‐silica zeolites is of prime importance owing to their high potential as industrial catalysts and catalyst supports. Two such materials have been synthesized which are made up of the 1,3‐stellated cubic unit (hexahedral ([4254]) bre unit) as a secondary building unit, with the aid of existing imidazolium‐based structure‐directing agents under “excess fluoride” conditions. One of them, denoted PST‐21, is the first aluminosilicate zeolite consisting of 9‐ring apertures solely; it displays exceptional activity towards steering the skeletal isomerization of 1‐butene to isobutene and bridges the gap between small‐ and medium‐pore structures. A series of hypothetical structures are also described that are nonjointly built from the bre unit; all of these structures are chemically feasible and will thus be helpful in designing the synthesis of novel zeolites containing 9‐ring and/or 10‐ring channels. 相似文献
142.
Modification of aqueous polyurethanes by forming latex interpenetrating polymer networks with polystyrene 总被引:15,自引:0,他引:15
A series of latex particles with interpenetrating polymer network structure have been synthesized from waterborne polyurethane
(PU) and polystyrene (PS). The effect of PU/PS composition, cross-linking density in the PS domain as well as in PU have been
studied in terms of dispersion size, transmission electron microscopy morphology, mechanical and dynamic mechanical properties
in addition to swellability in water and toluene of the dispersion cast film. It was found that inverted core (PS)–shell (PU)
morphology was well defined and that the domain size as well as the film properties were well controlled by the latex composition
and cross-linking density of both phases.
Received: 15 March 2000 Accepted: 21 February 2001 相似文献
143.
Nam DH Song SY Park K Kim MH Suh YL Lee JI Kim JS Hong SC Shin HJ Park K Eoh W Kim JH 《Experimental & molecular medicine》2001,33(3):111-116
Several molecular and genetic changes have been found in pituitary adenomas. We looked for correlations between these changes and the degree of invasiveness of the tumors. The invasiveness of 11 pituitary adenomas was graded by Hardy classification. We examined the retinoblastoma gene (RB1.20 on chromosome 13q) and the region around the MEN1 locus (chromosome 11q13.1-5) for loss of heterozygosity. Also examined are p53 mutations using single strain conformation polymorphism, p53 protein overexpression using immuno cytochemistry, homozygous deletions of p15 and p16 by polymerase chain reaction, and cellular proliferative activity using MIB-1 antibody. Six tumors (54.5%) had an LOH at either RB1.20 or the MEN1 locus. LOHs were found more frequently in Grade 4 and stage E tumors (72% and 67%) than in Grade 3 and stage D tumors (25% and 40%). However, no mutation or overexpression of p53 was found. No homozygous deletions of p15 or p16 were identified. The cell proliferative index ranged from 0 to 3%. LOH at 11q13 and 13q may be valuable in predicting the invasiveness of pituitary adenomas. 相似文献
144.
Taisei Ueda Naoyoshi Yatsuzuka Shin‐Ichi Nagai Kumiko Okada Emi Takeichi Hiromi Segi Jinsaku Sakakibara 《Journal of heterocyclic chemistry》2001,38(1):141-145
Oxidation of 7,8‐diaminotheophylline (1) with lead tetraacetate in refluxing toluene gave a mixture of 3‐amino‐5,7‐dimethylpyrimido[4,5‐e][1,2,4]triazine‐6,8‐dione ( 2 ) and 6‐cyanoimino‐5‐diazo‐1,3‐dimethylpyrimidine‐2,4‐dione ( 4 ). The latter was transformed to 2 by the reaction with 1‐propanethiol in quantitative yield. The reaction of 4 with methanol, ethanol and 1‐propanol in the presence of rhodium ( II ) acetate gave 5‐alkoxy‐6‐(2‐alkyl‐3‐isoureido)‐1,3‐dimethylpyrimidine‐2,4‐diones ( 7a‐c ). A similar reaction of 4 with alkylamines such as n‐propylamine, n‐butylamine, isobutylamine and n‐hexylamine gave a mixture of 7‐alkyl‐8‐aminotheophyllines ( 8a‐d ) and (5‐alkylamino‐1,3‐dimethyl‐2,4‐dioxopyrimidin‐6‐yl)cyanamides ( 9a‐d ). 相似文献
145.
Shinji Sugihara Shin‐Ichiro Matsuzono Hideki Sakai Masahiko Abe Sadahito Aoshima 《Journal of polymer science. Part A, Polymer chemistry》2001,39(18):3190-3197
Amphiphilic diblock copolymers were prepared by the living cationic polymerization of vinyl ethers in the presence of added bases, and their selective solvent‐induced physical gelation behavior was investigated. The block copolymerization of 2‐phenoxyethyl vinyl ether (PhOVE) and 2‐methoxyethyl vinyl ether (MOVE) was carried out in the presence of ethyl acetate with Et1.5AlCl1.5 in toluene at 0 °C. Despite the rate difference, diblock copolymers with a very narrow molecular weight distribution were obtained, quantitatively. By adding the selective solvent, water, to the acetone solution of the diblock copolymer, PhOVE200‐b‐MOVE400, physical gelation occurred suddenly and the system ceased to flow, maintaining transparency. Viscoelastic measurements and transmission electron microscopic observations were performed to examine the characteristic gelation behavior and structure of the obtained gels. Various gelation conditions and physical gelation by other amphiphilic block copolymers were also designed on the basis of the solubility of each block segment. Further, new forms of physical gelation, accompanied by the solubilization of immiscible organic compounds, were achieved using similar diblock copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3190–3197, 2001 相似文献
146.
Shin Hattori 《Journal of Number Theory》2008,128(5):1091-1108
In this paper, for a complete discrete valuation field K of mixed characteristic (0,p) and a finite flat group scheme G of p-power order over OK, we determine the tame characters appearing in the Galois representation in terms of the ramification theory of Abbes and Saito, without any restriction on the absolute ramification index of K or the embedding dimension of G. 相似文献
147.
148.
Most of previous research on tolerance optimization seeks the optimal tolerance allocation with process parameters such as fixed process mean and variance. This research, however, differs from the previous studies in two ways. First, an integrated optimization scheme is proposed to determine both the optimal settings of those process parameters and the optimal tolerance simultaneously which is called a parametric tolerance optimization problem in this paper. Second, most tolerance optimization models require rigorous optimization processes using numerical methods, since closed-form solutions are rarely found. This paper shows how the Lambert W function, which is often used in physics, can be applied efficiently to this parametric tolerance optimization problem. By using the Lambert W function, one can express the optimal solutions to the parametric tolerance optimization problem in a closed-form without resorting to numerical methods. For verification purposes, numerical examples for three cases are conducted and sensitivity analyses are performed. 相似文献
149.
150.
In this work, a projection algorithm is considered for treating strongly continuous semigroups of demicontinuous pseudocontractions. Theorems of strong convergence of fixed points are established in the framework of real Hilbert spaces. 相似文献