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31.
32.
Particle clustering in photocurable nanocomposites: Dependence of curing kinetics and viscoelastic properties 下载免费PDF全文
Piotr Ziobrowski Ewa Andrzejewska Miroslaw Szybowicz Ariadna Nowicka Mariola Sadej‐Bajerlein Hubert Gojzewski Miroslaw Drozdowski 《应用聚合物科学杂志》2014,131(4)
The aim of this article is to investigate the effect of nanoparticle clustering on the mobility of nanoparticles in nanocomposites, using spectroscopic methods (Brillouin and Raman). Special attention is paid to the effect of particle clustering on photocuring kinetics. The model system was poly(2‐hydroxyethyl acrylate) filled with fumed nanosilica in concentration range encompassing the percolation threshold. Results obtained from Brillouin spectroscopy show substantial changes in the sound velocity and the attenuation coefficient with increasing filler content. The damping of acoustic waves reaches the maximum at the percolation threshold (~15 wt %), which is related to changes in the mechanism of acoustic wave propagation. The formation of the cocontinuous silica phase strongly affects the curing kinetics of the monomer/silica system: the polymerization rate is the highest at a silica content corresponding to the percolation threshold. These results correlate well with the results of AFM surface roughness analysis. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39895. 相似文献
33.
Identification of a novel structure in heparin generated by sequential oxidative-reductive treatment
Beccati D Roy S Lech M Ozug J Schaeck J Gunay NS Zouaoui R Capila I Kaundinya GV 《Analytical chemistry》2012,84(11):5091-5096
Unfractionated heparin is isolated from animal organs, predominantly porcine intestinal mucosa, and goes through an extensive process of purification before it can be used for pharmaceutical purposes. While the structural microheterogeneity of heparin is predominantly biosynthetically imprinted in the Golgi, subsequent steps involved in the purification and manufacture of commercial heparin can lead to the introduction of additional modifications. Postheparin crisis of 2008, it has become increasingly important to identify what additional structural diversity is introduced as a function of the purification process and thus can be determined as being heparin-related, as opposed to being an adulterant or contaminant, e.g., oversulfated chondroitin sulfate. Our study focuses on the identification of a previously unreported structure in heparin that arises due to specific steps used in the manufacturing process. This structure was initially observed as a disaccharide peak in a complete enzymatic digest of heparin, but its presence was later identified in the NMR spectra of intact heparin as well. Structural elucidation experiments involved isolation of this structure and analysis based on multidimensional NMR and liquid chromatography coupled with mass spectrometry (LC-MS). Heparin was also subjected to specific chemical reactions to determine which steps in the manufacturing process are responsible for this novel structure. Our results allowed for the definitive assignment of the structure of this novel process-related modification and enabled an identification of the putative steps in the process that give rise to the structure. 相似文献
34.
Marcin Lukasiewicz Anna Ptaszek Lidia Koziel Bohdan Achremowicz Miroslaw Grzesik 《Polymer Bulletin》2007,58(1):281-288
Summary Polyaniline (PANI) as one of the conducting polymers focuses intensive research on both scientific and practical field. There
are quite a lot of known hybrid materials of PANI and other polymer systems with various synthetic polymers, which results
in blends with various properties. The presented research covers the blends of polyaniline with semisynthetic (carboxymethyl)
cellulose (CMC). The system could lead to a new antielectrostatic material with interesting properties and seems to be applicable
as an additive for packaging in both food and non-food industry. The final material was obtained using both protonated (HCl)
and deprotonated form of polyaniline in its semi-oxidized form of leucoemeraldine. Blending consisted in obtaining of thin
layer by slow evaporation of the solvent from a mixture of PANI and CMC. For the main investigation atomic force microscopy
(AFM) in non-contact mode was used, which gave the topological information about the surface and also some structural information
about the material.
The described process seems to be very interesting as a route for obtaining a new hybrid natural/synthetic material with very
interesting properties and a potential for application. 相似文献
35.
Miroslaw Staron Wilhelm Meding Bo Söderqvist 《Information and Software Technology》2010,52(10):1069-1079
ContextPredicting a number of defects to be resolved in large software projects (defect backlog) usually requires complex statistical methods and thus is hard to use on a daily basis by practitioners in industry. Making predictions in simpler and more robust way is often required by practitioners in software engineering industry.ObjectiveThe objective of this paper is to present a simple and reliable method for forecasting the level of defect backlog in large, lean-based software development projects.MethodThe new method was created as part of an action research project conducted at Ericsson. In order to create the method we have evaluated multivariate linear regression, expert estimations and analogy-based predictions w.r.t. their accuracy and ease-of-use in industry. We have also evaluated the new method in a life project at one of the units of Ericsson during a period of 21 weeks (from the beginning of the project until the release of the product).ResultsThe method for forecasting the level of defect backlog uses an indicator of the trend (an arrow) as a basis to forecast the level of defect backlog. Forecasts are based on moving average which combined with the current level of defect backlog was found to be the best prediction method (Mean Magnitude of Relative Error of 16%) for the level of future defect backlog.ConclusionWe have found that ease-of-use and accuracy are the main aspects for practitioners who use predictions in their work. In this paper it is concluded that using the simple moving average provides a sufficiently-good accuracy (much appreciated by practitioners involved in the study). We also conclude that using the indicator (forecasting the trend) instead of the absolute number of defects in the backlog increases the confidence in our method compared to our previous attempts (regression, analogy-based, and expert estimates). 相似文献
36.
Lengning Liu Enrico Pontelli Tran Cao Son Miroslaw Truszczyński 《Artificial Intelligence》2010,174(3-4):295-315
We provide a new perspective on the semantics of logic programs with arbitrary abstract constraints. To this end, we introduce several notions of computation. We use the results of computations to specify answer sets of programs with constraints. We present the rationale behind the classes of computations we consider, and discuss the relationships among them. We also discuss the relationships among the corresponding concepts of answer sets. One of those concepts has several compelling characterizations and properties, and we propose it as the correct generalization of the answer-set semantics to the case of programs with arbitrary constraints. We show that several other notions of an answer set proposed in the literature for programs with constraints can be obtained within our framework as the results of appropriately selected classes of computations. 相似文献
37.
38.
The {alpha}/{beta} hydrolase fold 总被引:1,自引:0,他引:1
Ollis David L.; Cheah Eong; Cygler Miroslaw; Dijkstra Bauke; Frolow Felix; Franken Sybille M.; Harel Michal; Remington S. Jamse; Silman Israel; Schrag Joseph; Sussman Joel L.; Verschueren Koen H.G.; Goldman Adrian 《Protein engineering, design & selection : PEDS》1992,5(3):197-211
We have identified a new protein foldthe /ßhydrolase foldthat is common to several hydrolytic enzymesof widely differing phylogenetic origin and catalytic function.The core of each enzyme is similar: an /ß sheet, notbarrel, of eight ß-sheets connected by -helices. Theseenzymes have diverged from a common ancestor so as to preservethe arrangement of the catalytic residues, not the binding site.They all have a catalytic triad, the elements of which are borneon loops which are the best-conserved structural features inthe fold. Only the histidine in the nucleophile-histidine-acidcatalytic triad is completely conserved, with the nucleophileand acid loops accommodating more than one type of amino acid.The unique topological and sequence arrangement of the triadresidues produces a catalytic triad which is, in a sense, amirror-image of the serine protease catalytic triad. There arenow four groups of enzymes which contain catalytic triads andwhich are related by convergent evolution towards a stable,useful active site: the eukaryotic serine proteases, the cysteineproteases, subtilisins and the /ß hydrolase fold enzymes. 相似文献
39.
Wioletta Kuncewicz-Kupczyk Dietmar Kobertz Miroslaw Miller Christian Chatillon Lorenz Singheiser Klaus Hilpert 《Journal of the American Ceramic Society》2002,85(9):2299-2305
The vaporization of the samples of the compositions Ga2 O3 + LaGaO3 , LaGaO3 + La4 Ga2 O9 , and La4 Ga2 O9 + La2 O3 was investigated using Knudsen effusion mass spectrometry in the temperature range 1494–1937 K. The partial pressures of the gaseous species O2 , Ga, GaO, Ga2 O, and LaO were determined over the samples investigated. The equilibrium partial pressures were used for the calculation of the thermodynamic activities of the components at 1700 K. Gibbs energies of formation of LaGaO3 ( s ) and La4 Ga2 O9 ( s ) at 1700 K from the component oxides were derived from the thermodynamic activities as −46.4 ± 4.7 and −99.2 ± 7.9 kJ·mol−1 , respectively. The results were compared with the literature data obtained using other methods. 相似文献
40.
Wang HQ Batentschuk M Osvet A Pinna L Brabec CJ 《Advanced materials (Deerfield Beach, Fla.)》2011,23(22-23):2675-2680
With the aim of utilizing the infrared region of solar radiation to improve solar cell performance, significant progress, including theoretical analysis and experimental achievement, has been made in the field of up-conversion for photovoltaic applications. This Research News article reviews recent progress in the development of rear-earth (RE) ion doped up-conversion materials for solar cell applications. In addition, new trends for RE-ion-doped phosphors are briefly discussed, among them trivalent RE-ion-doped up-conversion materials for organic solar cell applications. 相似文献