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排序方式: 共有253条查询结果,搜索用时 15 毫秒
191.
Reaction-diffusion systems with zero-flux Neumann boundariesare widely used to model various kinds of interaction in, forexample, the scientific fields of ecology, biology, chemistry,medicine and industry. The physical systems within these fieldsare often known to be (conditionally or unconditionally) resilientwith respect to shocks, disturbances or catastrophies in theimmediate environment. In order to be good mathematical modelsof such situations the reaction-diffusion systems must havethe same resilient or asymptotic behaviour as that of the physicalsituation. Three fundamentally different kinds of reaction termsare usually distinguished according to the entry signs of thereaction Jacobian: mutualism, mixed (predator-prey) interactionand competition. The asymptotic stability (in the Poincarésense) of mutualistic systems has already been studied extensively,but the results cannot be generalized (globally) to the othertwo fundamental types, which are not order-preserving. A partial(local) generalization is, however given here for these twotypes, involving simple Jacobian inequalities and knowledge(often prompted by the underlying physical situation) of invariantsets in solution space. The return time of resilient systemsand the approach rate of asymptotically stable solutions arealso estimated. 相似文献
192.
Schroeter TS Schwaighofer A Mika S Ter Laak A Suelzle D Ganzer U Heinrich N Müller KR 《Journal of computer-aided molecular design》2007,21(9):485-498
We investigate the use of different Machine Learning methods to construct models for aqueous solubility. Models are based on about 4000 compounds, including an in-house set of 632 drug discovery molecules of Bayer Schering Pharma. For each method, we also consider an appropriate method to obtain error bars, in order to estimate the domain of applicability (DOA) for each model. Here, we investigate error bars from a Bayesian model (Gaussian Process (GP)), an ensemble based approach (Random Forest), and approaches based on the Mahalanobis distance to training data (for Support Vector Machine and Ridge Regression models). We evaluate all approaches in terms of their prediction accuracy (in cross-validation, and on an external validation set of 536 molecules) and in how far the individual error bars can faithfully represent the actual prediction error. 相似文献
193.
固相萃取-高效液相色谱法同时测定水中的16种苯脲除草剂(英文) 总被引:12,自引:1,他引:12
建立了固相萃取 高效液相色谱 (SPE HPLC)同时测定水中 16种苯脲除草剂的方法。HPLC采用Lichrospher 10 0RP 18e柱 ,紫外检测波长为 2 40nm ,流动相为乙腈水溶液 ,流速为 1mL/min ,采用梯度洗脱方式。HPLC分析时间少于 2 0min。水中的除草剂用C18柱固相萃取富集 10 0 0倍。在优化的条件下 ,各成分的添加回收率为 87 8%~ 10 3 7%。 相似文献
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Massoud S. Stephan Antonius J. J. M. Teunissen Gerard K. M. Verzijl Johannes G. de Vries 《Angewandte Chemie (International ed. in English)》1998,37(5):662-664
Environmentally benign and economical production of arylated olefins can be achieved by a new variant of the Heck reaction in which no halogen salts are formed. The trick is the use of aromatic carboxylic anhydrides 1 as arylating agents. With halide-activated palladium chloride as catalyst, which requires no phosphane ligands, the olefins 2 can be prepared according to Equation (a) in good yields. 相似文献
197.
Endar Puspawiningtiyas Oki Muraza Hary Devianto Meiti Pratiwi Subagjo Tirto Prakoso Krisnawan Usamah Zaki Lidya Elizabeth Tatang H. Soerawidjaja Yohanes Andre Situmorang Antonius Indarto 《Molecules (Basel, Switzerland)》2022,27(3)
The production of sustainable diesel without hydrogen addition remains a challenge for low-cost fuel production. In this work, the pyrolysis of unsaturated fatty acid (UFA) basic soaps was studied for the production sustainable diesel (bio-hydrocarbons). UFAs were obtained from palm fatty acids distillate (PFAD), which was purified by the fractional crystallization method. Metal hydroxides were used to make basic soap composed of a Ca, Mg, and Zn mixture with particular composition. The pyrolysis reactions were carried out in a batch reactor at atmospheric pressure and various temperatures from 375 to 475 °C. The liquid products were obtained with the best yield (58.35%) at 425 °C and yield of diesel fraction 53.4%. The fatty acids were not detected in the pyrolysis liquid product. The gas product consisted of carbon dioxide and methane. The liquid products were a mixture of hydrocarbon with carbon chains in the range of C7 and C20 containing n-alkane, alkene, and iso-alkane. 相似文献
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D–π–A Triarylboron Compounds with Tunable Push–Pull Character Achieved by Modification of Both the Donor and Acceptor Moieties 下载免费PDF全文
Dr. Zuolun Zhang Dr. Robert M. Edkins Jörn Nitsch Dr. Katharina Fucke Antonius Eichhorn Dr. Andreas Steffen Prof. Dr. Yue Wang Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):177-190
The push–pull character of a series of donor–bithienyl–acceptor compounds has been tuned by adopting triphenylamine or 1,1,7,7‐tetramethyljulolidine as a donor and B(2,6‐Me2‐4‐RC6H2)2 (R=Me, C6F5 or 3,5‐(CF3)2C6H3) or B[2,4,6‐(CF3)3C6H2]2 as an acceptor. Ir‐catalyzed C?H borylation was utilized in the derivatization of the boryl acceptors and the tetramethyljulolidine donor. The donor and acceptor strengths were evaluated by electrochemical and photophysical measurements. In solution, the compound with the strongest acceptor, B[2,4,6‐(CF3)3C6H2]2 ((FMes)2B), has strongly quenched emission, while all other compounds show efficient green to red (ΦF=0.80–1.00) or near‐IR (NIR; ΦF=0.27–0.48) emission, depending on solvent. Notably, this study presents the first examples of efficient NIR emission from three‐coordinate boron compounds. Efficient solid‐state red emission was observed for some derivatives, and interesting aggregation‐induced emission of the (FMes)2B‐containing compound was studied. Moreover, each compound showed a strong and clearly visible response to fluoride addition, with either a large emission‐color change or turn‐on fluorescence. 相似文献
200.