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871.
I. Sedat Gunes Feina Cao Sadhan C. Jana 《Journal of Polymer Science.Polymer Physics》2008,46(14):1437-1449
The effects of thermal expansion on shape memory performance of shape memory polyurethanes and their nanocomposites with organoclay, carbon nanofiber (CNF), silicon carbide (SiC), and carbon black (CB) were evaluated. The shape memory test cycle involved tensile deformation at above the trigger temperature to initiate shape memory function, cooling to room temperature to fix the shape, and shape recovery induced by heating to above the trigger temperature. Phenomenological models were used to interpret the experimental data on coefficient of thermal expansion (CTE). It was found that Kerner model showed good fit for composites of SiC and CB, and Halpin model gave better fit for composites of organoclay and CNF. It was observed that thermal expansion exerts negative effect on recovered strain, the extent of which depends on the magnitude of temperature gradient, CTE, and the level of tensile strain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1437–1449, 2008 相似文献
872.
We examine project scheduling with net present value objective and exponential activity durations, using a continuous-time Markov decision chain. On the basis of a judicious partitioning of the state space, we achieve a significant performance improvement as compared to the existing algorithms. 相似文献
873.
Ji?í Hetflejš Ji?í Podešva Jana Ková?ová Miloš Netopilík Jan Sýkora 《Polymer Degradation and Stability》2010,95(4):579-586
Three new low-molecular-weight stabilisers, bearing in their molecules a tri(dimethylsiloxane) chain, end-capped with primary OH groups, have been synthesised and characterised. One is based on a sterically hindered phenolic antioxidant, the others on sterically hindered piperidines (HALS-type). When added to the reaction mixture for the preparation of model soluble elastomeric polyurethanes (containing a polybutadiene α,ω-diol, a diisocyanate and a catalyst), each of these stabilisers, due to the presence of the OH group, is joined by a covalent bond at one or both chain ends of the polyurethane formed, and acts simultaneously as a molecular-weight regulator. Thermoanalytical methods revealed that the stabilising efficiency of these polymer-bound structures is comparable with that of their low-molecular-weight analogues, physically admixed with the polyurethane. The advantage of these chemically fixed stabilisers lies in the fact that they remain in the matrix and cannot be evaporated nor washed out. 相似文献
874.
875.
876.
Jana Björn 《manuscripta mathematica》2008,125(3):369-381
We obtain pointwise estimates for solutions of obstacle problems on metric measure spaces and prove that p-superharmonic functions are p-finely continuous. Consequently, we show that p-quasicontinuous functions are p-finely continuous at p-quasievery point. As a byproduct, we obtain the sufficiency part of the Wiener criterion in metric spaces without the assumption
of linear local connectedness.
The author was supported by the Swedish Research Council. 相似文献
877.
Adriana Czímerová Lubos Jankovič Jana Madejová Alexander Čeklovský 《Journal of Polymer Science.Polymer Physics》2013,51(23):1672-1679
An organo‐montmorillonite (MMT) complex [poly‐diallyldimethyl(PDDA)‐Kunipia F] with various loadings of polycation was modified with a laser dye Rhodamine 6G (R6G) to obtain a photofunctional hybrid materials for monitoring of dye‐polymer‐MMT nanocomposite interactions. The polymer‐MMTs were prepared in a colloidal state via ion‐exchange reaction. The content of polycation (PDDA) in suspensions varied from 20 mg to 1000 mg per 1 g of Kunipia F (KF) MMT. Dramatic changes was observed in the structure of PPDA‐MMT containing 200–300 mg of polymer per 1 g of KF, which was the saturation point of the polycation for this system. The PDDA molecules were able to suppress the formation of nonluminescent H‐aggregates and to enhance the overall luminescence properties. The PDDA/MMT nanocomposite systems are the novel ones that have not been studied before in order to prepare highly fluorescence hybrid systems. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2013 , 51, 1672–1679 相似文献
878.
Olga Novakova Dr. Jaroslav Malina Dr. Tereza Suchankova Jana Kasparkova Dr. Tijana Bugarcic Dr. Peter J. Sadler Prof. Dr. Viktor Brabec Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(19):5744-5754
We studied the thermodynamic properties, conformation, and recognition of DNA duplexes site‐specifically modified by monofunctional adducts of RuII complexes of the type [RuII(η6‐arene)(Cl)(en)]+, in which arene=para‐, meta‐, or ortho‐terphenyl (complexes 1 , 2 , and 3 , respectively) and en=1,2‐diaminoethane. It has been shown (J. Med. Chem. 2008 , 51, 5310) that 1 exhibits promising cytotoxic effects in human tumor cells, whereas 2 and 3 are much less cytotoxic; concomitantly with the high cytotoxicity of 1 , its DNA binding mode involves combined intercalative and monofunctional (coordination) binding modes, whereas less cytotoxic compounds 2 and 3 bind to DNA only through a monofunctional coordination to DNA bases. An analysis of conformational distortions induced in DNA by adducts of 1 and 2 revealed more extensive and stronger distortion and concomitantly greater thermodynamic destabilization of DNA by the adducts of nonintercalating 2 . Moreover, affinity of replication protein A to the DNA duplex containing adduct of 1 was pronouncedly lower than to the adduct of 2 . On the other hand, another damaged‐DNA‐binding protein, xeroderma pigmentosum protein A, did not recognize the DNA adduct of 1 or 2 . Importantly, the adducts of 1 induced a considerably lower level of repair synthesis than the adducts of 2 , which suggests enhanced persistence of the adducts of the more potent and intercalating 1 in comparison with the adducts of the less potent and nonintercalating 2 . Also interestingly, the adducts of 1 inhibited DNA polymerization more efficiently than the adducts of 2 , and they could also be bypassed by DNA polymerases with greater difficulty. Results of the present work along with those previously published support the view that monodentate RuII arene complexes belong to a class of anticancer agents for which structure–pharmacological relationships might be correlated with their DNA‐binding modes. 相似文献
879.
Zuzana Bujdo?ová Katarína Gy?ryová Milan Melník Marian Koman Jana Ková?ová 《Journal of chemical crystallography》2011,41(4):443-448
Abstract
Two ligand isomers [Zn{4-ClC6H3-2-(OH)COO}2(Menia)2(H2O)2] (I) and [Zn{5-ClC6H3-2-(OH)COO}2(Menia)2(H2O)2] (II) (Menia = N-methylnicotinamide) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The X-ray crystal structures of complexes (I) and (II) were determined. Compound (I) crystallizes in the triclinic space group P[`1] P\bar{1} with a = 8.105(1) ?, b = 10.036(2) ?, c = 10.545(2) ?, α = 109.088(9)°, β = 91.416(8)°, γ = 102.757(9)°, V = 786.2(2) ?3, Z = 1. Compound (II) crystallizes in the triclinic space group P[`1] P\bar{1} . Its cell parameters are: a = 8.133(1) ?, b = 10.119(2) ?, c = 10.428(1) ?, α = 66.44(1)°, β = 74.32(1)°, γ = 80.16(1)°, V = 755.5(2) ?3, Z = 1. The molecular structure of both isomers is monomeric. Each Zn(II) atom is hexacoordinated by three pairs of unidentate ligands in trans-positions (ZnO4N2). The 5-Clsal complex is somewhat less distorted than 4-Clsal complex (Cl-sal = chlorosalicylate). The structural data are compared with those found in similar [Zn(RCOO)2(NL)2(H2O)2]. 相似文献880.
Tomas Cajka Chris Sandy Veronika Bachanova Lucie Drabova Kamila Kalachova Jana Pulkrabova Jana Hajslova 《Analytica chimica acta》2012
In this work, a new rapid method for the determination of 135 pesticide residues in green and black dry tea leaves and stalks employing gas chromatography coupled to tandem mass spectrometry (GC–MS/MS) with a triple quadrupole was developed and validated. A substantial simplification of sample processing prior to the quantification step was achieved: after addition of water to a homogenised sample, transfer of analytes into an acetonitrile layer was aided by the addition of inorganic salts. Bulk co-extracts, contained in the crude organic extract obtained by partition, were subsequently removed by liquid–liquid extraction using hexane with the assistance of added 20% (w/w) aqueous NaCl solution. The importance of matrix hydration prior to the extraction for achieving good recoveries was demonstrated on tea samples with incurred pesticide residues. For most of the analytes, recoveries in the acceptable range of 70–120% and repeatabilities (relative standard deviations, RSDs) ≤20% were achieved for both matrices at spiking levels of 0.01, 0.1 and 1 mg kg−1. Under optimised GC–MS/MS conditions, most of the analytes gave lowest calibration level ≤0.01 mg kg−1, permitting the control at the maximum residue levels (MRLs) laid down in Regulation (EC) No 396/2005. The developed method was successfully applied to the determination of pesticide residues in real tea samples. 相似文献