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排序方式: 共有70条查询结果,搜索用时 15 毫秒
1.
N. M. Agababyan I. V. Ajinenko Yu. A. Belokopytov K. S. Belous H. Boettcher F. Botterweck M. M. Chapkin P. V. Chliapnikov F. Crijns A. De Roeck E. A. De Wolf K. Dziunikowska A. M. F. Endler A. Eskreys Z. C. Garutchava P. van Hal T. Haupt A. I. Katargin W. Kittel S. S. Megrabyan F. Meijers A. B. Micha?owska V. I. Nikolaenko K. Olkiewicz V. M. Ronjin R. Rosmalen H. M. T. Saarikko L. Scholten E. K. Shabalina J. Stepaniak O. G. Tchikilev V. A. Uvarov F. Verbeure R. Wischnewski S. A. Zotkin Y. V. Yarba EHS-NA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,46(3):387-395
We report on a study of ρ0, ρ+, ω, \(\bar K^{*0} (892)\) andK *0 (892) inclusive production in π+ p interactions at 250 GeV/c, for ρ+, \(\bar K^{*0} (892)\) for the first time in a π+ p experiment. The data are compared withK + p data in the same experiment, with results of other experiments and with quark-parton models. Interesting differences are found between ρ+,0 and ω production. 相似文献
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F. P. Boettcher 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-7):665-678
Application of anionic polymerization and group transfer polymerization to the synthesis of methacrylate polymers with one or two functional endgroups and with functional groups in the side chain is described. Success in the preparation of end-functional polymers depends largely on the absence of chain transfer and chain termination reactions. The higher stability of living chains in group transfer polymerization at temperatures as high as 100°C makes it the preferred route to functional polymers. 相似文献
6.
Lead Structures for New Antibacterials: Stereocontrolled Synthesis of a Bioactive Muraymycin Analogue
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Daniel Wiegmann Dr. Stefan Boettcher Agnes Mihalyi Prof. Timothy D. H. Bugg Prof. Christian Ducho 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15292-15297
Naturally occurring muraymycin nucleoside antibiotics represent a promising class of novel antibacterial agents. The structural complexity suggests the investigation of simplified analogues as potential lead structures, which can then be further optimized towards highly potent antimicrobials. Herein we report studies on muraymycin‐derived potential lead structures lacking an aminoribose motif found in most naturally occurring muraymycins. We have identified a 5′‐defunctionalized motif to be ideal in terms of stability and chemical accessibility and have synthesized a full‐length muraymycin analogue based on this structure using a novel fully stereocontrolled route. The obtained 5′‐deoxy analogue of the natural product muraymycin C4 showed good inhibitory properties towards the bacterial target protein MraY, sufficient pharmacokinetic stability and no cytotoxicity against human cells, thus making it a promising lead for antibacterial drug development. 相似文献
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L-Lactide was polymerized in toluene with various alkoxide initiators. These initiators were prepared in situ from potassium t.-butoxide and primary or secondary alcohols such as tetradecanol, diethylene glycol butyl ether, menthol or testosteron. All these alcohols were incorporated as ester endgroups into the polylactide chain. However 1H-NMR spectroscopy proves the existence of more OH-endgroup than ester endgroups. This finding and 10–20% racemization observed for all anionic polymerizations suggest that chain-transfer reactions with the monomer via deprotonation take place. When poly(ethylene glycol) monomethyl ether in combination with KOtBu was used as initiator, twoblock copolymers were obtained. With poly(ethylene glycol) A-B-A-triblock copolymers could be synthesized. The quantitative reaction of the poly(ethylene glycol)s with L-lactide could be proven by both 1H NMR spectroscopy and gelpermeation chromatography. DSC-measurements show that depending on their lengths either the polylactide or the poly(ethylene oxide)blocks can crystallize. Due to partial racemization the melting temperatures (Tm) of the poly(L-lactide) blocks did not exceed 155°C. 相似文献
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Susceptibility to acoustic trauma in young and aged gerbils 总被引:2,自引:0,他引:2
Boettcher FA 《The Journal of the Acoustical Society of America》2002,112(6):2948-2955
The effect of age on susceptibility to noise-induced hearing loss (NIHL), the effect of gender on the interaction of age-related hearing loss (ARHL) and NIHL, and the relative contributions of ARHL and NIHL to total hearing loss are poorly understood. The issues are difficult to resolve empirically in human subjects because of lack of control over extrinsic variables and for ethical reasons. Accordingly, these issues were examined in a well-studied animal model of both ARHL and NIHL, the Mongolian gerbil. Animals were exposed to an intense tone (3.5 kHz, 113 dB SPL, 1 h) either as young adults (6-8 months) or near the end of the average lifespan of the species (34-38 months). Hearing thresholds were determined with the auditory brainstem response (ABR). ARHL was approximately 5-10 dB, with slightly more observed in males at 16 kHz (p<0.05). NIHL of approximately 15-20 dB was similar for the young and old groups, suggesting no differences in susceptibility as a function of age. There were no gender differences in NIHL. The relative contributions of ARHL and NIHL to total hearing loss in aged, noise-exposed gerbils were predicted by an addition of ARHL and NIHL in dB, similar to an international standard on hearing loss allocation, ISO-1999 [Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment (1990)]. Previous evaluations of ISO-1999 using the gerbil animal model concluded that addition of ARHL and NIHL in dB overpredicts total hearing loss. However, in these studies, ARHL was large and nearly equal to NIHL. In the current study, where ARHL was much less than NIHL, addition of the two factors in dB, as recommended by ISO-1999, results in fairly accurate predictions of total hearing loss. 相似文献
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Cheng CH Boettcher SW Johnston DH Lonergan MC 《Journal of the American Chemical Society》2004,126(28):8666-8667
Unidirectional electronic current is reported for a device based on the interface between an anionically functionalized and a cationically functionalized polyacetylene. The unidirectional current in this mixed ionically/electronically conducting system is electronic but is regulated by asymmetry in the ionic processes. 相似文献
10.
Optimization with extremal dynamics 总被引:6,自引:0,他引:6
We explore a new general-purpose heuristic for finding high-quality solutions to hard discrete optimization problems. The method, called extremal optimization, is inspired by self-organized criticality, a concept introduced to describe emergent complexity in physical systems. Extremal optimization successively updates extremely undesirable variables of a single suboptimal solution, assigning them new, random values. Large fluctuations ensue, efficiently exploring many local optima. We use extremal optimization to elucidate the phase transition in the 3-coloring problem, and we provide independent confirmation of previously reported extrapolations for the ground-state energy of +/-J spin glasses in d = 3 and 4. 相似文献