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991.
Hossein Tavana Dietmar Appelhans Rong-Chuan Zhuang Stefan Zschoche Karina Grundke Michael L. Hair A. Wilhelm Neumann 《Colloid and polymer science》2006,284(5):497-505
Surface energetics of two fluorinated maleimide copolymers containing fluorinated side chain, i.e., poly(ethene-alt-N-(4-(perfluoroheptylcarbonyl)aminobutyl)maleimide) (ETMF) and poly(octadecene-alt-N-(4-(perfluoroheptylcarbonyl)aminobutyl)maleimide) (ODMF), are studied by contact angle measurements with 10 liquids consisting
of fairly bulky molecules. Because of the inertness of octamethylcyclotetrasiloxane (OMCTS) and decamethylcyclopentasiloxane
(DMCPS) molecules, their contact angles are used to determine the surface tension of the two polymers. It is found that other
liquids show specific interactions with the ETMF films, and their contact angles deviate from a smooth curve that represents
the surface tension of ETMF, i.e., 11.00 mJ/m2. On ODMF surfaces, only OMCTS and DMCPS yield useful contact angles. Other liquids either dissolve the polymer film or show
a slip-stick pattern. This finding is discussed in terms of interactions between segments of the polymer chains and the test
liquids. OMCTS and DMCPS are suggested as the appropriate probe liquids, meeting specific criteria necessary for the determination
of accurate surface tension of fluoropolymers. 相似文献
992.
中国股市大公司股票与小公司股票收益关系的实证研究 总被引:1,自引:1,他引:0
对中国股市的大公司股票与小公司股票的价格与收益关系进行了实证研究,结果表明大公司股票与小公司股票的收益无论在牛市阶段还是熊市阶段都存在较高的相关性;熊市阶段大公司股票收益的自相关程度最高,存在一定趋势性.大公司股票与小公司股票的价格序列是单位根的,但不是协整的,二者的收益序列是稳定的,在牛市阶段和熊市阶段大公司股票与小公司股票收益之间存在双向的领先—滞后后关系. 相似文献
993.
994.
Bayesian semiparametric customer base segmentation of mobile phone users based on longitudinal traffic data 下载免费PDF全文
Bruno Scarpa 《商业与工业应用随机模型》2015,31(5):721-731
Customer segmentation is one of the most important purposes of customer base analysis for telecommunication companies. Because companies accumulate very large amounts of data on customer behavior, segmentation is typically achieved by profiling and clustering traffic behavior jointly with demographic data and contracts characteristics. Unfortunately, most algorithms and models used for segmentation do not take into account the longitudinal characteristics of data. In particular, in telecommunication traffic analysis, the importance of decreasing patterns of traffic in customers' lives is well known, and it is relevant to aggregate all clients with such a pattern, while other unknown clusters may be of interest for the marketing manager. Our approach to address this problem is based on specifying the distribution of functions as a mixture of a parametric hierarchical model describing the decreasing pattern segment and a nonparametric contamination that allows unanticipated curve shapes in subjects' traffic. The parametric component is chosen based on prior knowledge, while the contamination is characterized as a functional Dirichlet process. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
995.
The effects and regulatory actions of the polychlorinated biphenyls (PCBs) substituent characteristics on their relative retention times (RRTs) during gas chromatography were analyzed based on known experimental RRTs of 209 PCB congeners and biphenyl; the substituent characteristics used for this analysis included the total amount of substituents, the similarity between two phenyl rings in a single PCB congener, the substituents distribution in single phenyl ring, the main/second‐order interactions effects at each position, and the combined effect of two phenyl rings. At last, the universality of regulation was validated on other experimental conditions. Among them, the full factorial experimental design included 10 factors correlated with each substituent position and two levels (0, 1) were initially applied to the domains of the substituent characteristics. The obtained results have revealed that increasing the total amount of substituents can increase the RRTs of PCBs linearly, but similarities between the two rings cannot control the RRTs effectively. Meanwhile, the more compact the substituent distributions on a single phenyl ring are, the bigger the RRTs of PCBs are. Based on a full factorial experimental design, the overall important trend for each position is as follows: para > meta > ortho and the main regulatory substituents for the second‐order interaction effects are distributed in the same phenyl ring in the following sequence: No > Nm > Np. The congener with two perpendicular phenyl rings exhibits a milder combined effect on RRTs and smaller RRT relatively. The regulation has a good universality among different experimental conditions, revealing the dominant effect of substituent characteristics on RRTs of PCBs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
996.
Shuang Xia Jiagao Cheng Yue Feng Xusheng Shao Haibin Luo Zhiping Xu Xiaoyong Xu Zhong Li 《中国化学》2014,32(4):324-334
Molecular aggregation state of bioactive compounds plays a key role in bio‐interactive procedure. Diverse aggregation states of bioactive compounds contribute to different biological or chemical properties. Water‐bridge, as the simple hetero‐molecular aggregation, has been found bridging the binding between many bioactive compounds and their targets through hydrogen bonding network, e.g. in the recognition of neonicotinoids with insect nAChRs. To better understanding the roles of water‐bridge on bioactivities of compounds, an approach of hetero‐dimeric aggregation with water was proposed. Quantitative structure‐activity relationship (QSAR) and pharmacophore modeling investigations were applied on 19 neonicotinoids, as well as their aggregates with water. The aggregate‐based CoMSIA, PHASE and linear QSAR models presented better statistical significance and predictabilities than the monomer ones, which indicated that the bioactivities correlated with the aggregate properties and water bridged hydrogen bond of the active site. All results revealed the essential roles of water‐bridge in ligand recognition, which should be considered in future ligand design and optimization. 相似文献
997.
C.A. Carrasquer K. Batey S. Qamar S.L. Cunningham 《SAR and QSAR in environmental research》2014,25(6):489-506
We previously demonstrated that fragment based cat-SAR carcinogenesis models consisting solely of mutagenic or non-mutagenic carcinogens varied greatly in terms of their predictive accuracy. This led us to investigate how well the rat cancer cat-SAR model predicted mutagens and non-mutagens in their learning set. Four rat cancer cat-SAR models were developed: Complete Rat, Transgender Rat, Male Rat and Female Rat, with leave-one-out (LOO) validation concordance values of 69%, 74%, 67% and 73%, respectively. The mutagenic carcinogens produced concordance values in the range 69–76% compared with only 47–53% for non-mutagenic carcinogens. As a surrogate for mutagenicity, comparisons between single site and multiple site carcinogen SAR models were analysed. The LOO concordance values for models consisting of 1-site, 2-site and 4+-site carcinogens were 66%, 71% and 79%, respectively. As expected, the proportion of mutagens to non-mutagens also increased, rising from 54% for 1-site to 80% for 4+-site carcinogens. This study demonstrates that mutagenic chemicals, in both SAR learning sets and test sets, are influential in assessing model accuracy. This suggests that SAR models for carcinogens may require a two-step process in which mutagenicity is first determined before carcinogenicity can be accurately predicted. 相似文献
998.
999.
Pritesh Kumar Carl A. Carrasquer Arren Carter 《SAR and QSAR in environmental research》2014,25(11):891-903
The categorical structure–activity relationship (cat-SAR) expert system has been successfully used in the analysis of chemical compounds that cause toxicity. Herein we describe the use of this fragment-based approach to model ligands for the G protein-coupled receptor 119 (GPR119). Using compounds that are known GPR119 agonists and compounds that we have confirmed experimentally that are not GPR119 agonists, four distinct cat-SAR models were developed. Using a leave-one-out validation routine, the best GPR119 model had an overall concordance of 99%, a sensitivity of 99%, and a specificity of 100%. Our findings from the in-depth fragment analysis of several known GPR119 agonists were consistent with previously reported GPR119 structure–activity relationship (SAR) analyses. Overall, while our results indicate that we have developed a highly predictive cat-SAR model that can be potentially used to rapidly screen for prospective GPR119 ligands, the applicability domain must be taken into consideration. Moreover, our study demonstrates for the first time that the cat-SAR expert system can be used to model G protein-coupled receptor ligands, many of which are important therapeutic agents. 相似文献
1000.
Trapping of Organophosphorus Chemical Nerve Agents in Water with Amino Acid Functionalized Baskets 下载免费PDF全文
Yian Ruan Erdin Dalkiliç Paul W. Peterson Aroh Pandit Prof. Arif Dastan Jason D. Brown Shane M. Polen Prof. Christopher M. Hadad Prof. Jovica D. Badjić 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4251-4256
We prepared eleven amino‐acid functionalized baskets and used 1H NMR spectroscopy to quantify their affinity for entrapping dimethyl methylphosphonate (DMMP, 118 Å3) in aqueous phosphate buffer at pH=7.0±0.1; note that DMMP guest is akin in size to chemical nerve agent sarin (132 Å3). The binding interaction (Ka) was found to vary with the size of substituent groups at the basket′s rim. In particular, the degree of branching at the first carbon of each substituent had the greatest effect on the host‐guest interaction, as described with the Verloop′s B1 steric parameter. The branching at the remote carbons, however, did not perturb the encapsulation, which is important for guiding the design of more effective hosts and catalysts in future. 相似文献