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201.
Gaëtan R. P. Henry Xavier Drooghaag Dimitri D. J. Rousseaux Michel Sclavons Jacques Devaux Jacqueline Marchand‐Brynaert Véronique Carlier 《Journal of polymer science. Part A, Polymer chemistry》2008,46(9):2936-2947
This study reports a reactive extrusion process leading to very high levels of anhydride grafting (2.5–3 wt %) along polypropylene backbone without recovering grafted PP waxes at the die exit. Such high graftings are attainable without excessive degradation of the PP chain by using a brominated reagent. Simultaneously, this brominated reagent allows the tuning of the grafted PP crystallinity via epimerization of the PP backbone. Indeed, the synthesis of a mainly isotactic/atactic stereoblock polymer containing high levels of grafted succinic anhydride moieties is demonstrated by NMR and melting enthalpies recorded by DSC are definitely observed depressed and broadened. Grafting levels of around 3 wt % have been achieved and ascertained by both chemical titration and NMR spectroscopy. In addition, FTIR spectroscopy reveals an unusual observation: for the first time, only one single pair of symmetric and asymmetric carbonyl stretching bands are observed on those grafted PP, while, in other processes of anhydride grafting, those symmetric and asymmetric bands were both split in at least two bands. This suggests, for the here reported process, the absence of interacting grafted anhydride rings, i.e., absence of closely grafted anhydride moieties and absence of poly(maleic anhydride). All those observations support that this “bromine route” brings a really new grafting process for PP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2936–2947, 2008 相似文献
202.
Gaëtan R. P. Henry Xavier Drooghaag Mikhaël Vandeuren Michel Sclavons André Schanck Jacques Devaux Véronique Carlier Jacqueline Marchand‐Brynaert 《Journal of polymer science. Part A, Polymer chemistry》2009,47(18):4505-4518
Amorphous and low crystallinity polypropylenes were produced by reactive processing of commercial isotactic polypropylenes in the presence of a peroxide (2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane) and N‐bromosuccinimide. Characterization of the modified polypropylene microstructures using 13C NMR spectroscopy revealed that crystallinity loss is correlated with the epimerization of numerous methynes randomly along the polymer backbone, leading to decreasing isotacticities ([mmmm]) and average isotactic block lengths. Moreover, degradation usually induced by peroxide was shown to be comparatively limited in additional presence of N‐bromosuccinimide. This fast and easy process therefore allows the production of polypropylene plastomers and elastomers with controlled and homogeneous crystallinities and isotacticities, and relatively low molecular weight distributions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4505–4518, 2009 相似文献
203.
204.
This paper describes the computation of fusion protons detection efficiency, which has been carried out by means of the known GOURDON code. For this purpose an analytical model of the tokamak magnetic field has been used. Computer simulations of different trajectories of charged particle, on the basis of the motion equations, have been performed with the GOURDON code. Detection efficiency, defined as the ratio of the number of detected particles to that of particles emitted from plasma, has been calculated. The transparency function of the detector system has been derived for given geometry of the ion-pinhole camera. Calculations have been carried out for the detector position used in recent experiments. The poloidal-and toroidal-symmetry of plasma and standard fusion-product source profile have been assumed. The computed detection efficiency is presented as a function of the main radius and particle pitch-angle for different spatial orientations of the detector head. 相似文献
205.
Jan Ga?uszka 《Discrete Mathematics》2008,308(24):6414-6425
Connections of some groupoid identities with the quasigroup and Latin square properties are investigated using combinatorial methods. 相似文献
206.
Given a number field K, it is well-known that the height of a subspace in KN and of its orthogonal complement coincide. We prove the analogous fact when K is replaced by a positive definite rational quaternion algebra with respect to the heights recently introduced by the first author. Since quaternion algebras are non-commutative, we cannot just follow the classical proof but have to work with localizations and certain finite rings. 相似文献
207.
Alt C Anticic T Baatar B Barna D Bartke J Betev L Białkowska H Billmeier A Blume C Boimska B Botje M Bracinik J Bramm R Brun R Buncić P Cerny V Christakoglou P Chvala O Cramer JG Csató P Darmenov N Dimitrov A Dinkelaker P Eckardt V Farantatos G Flierl D Fodor Z Foka P Freund P Friese V Gál J Gaździcki M Georgopoulos G Gładysz E Grebieszkow K Hegyi S Höhne C Kadija K Karev A Kliemant M Kniege S Kolesnikov VI Kollegger T Kornas E Korus R Kowalski M Kraus I Kreps M van Leeuwen M Lévai P Litov L 《Physical review letters》2005,94(5):052301
Emission of pi+/-, K+/-, phi, and Lambda was measured in near-central C+C and Si+Si collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S, and Pb+Pb, the system-size dependence of relative strangeness production in nucleus-nucleus collisions is obtained. Its fast rise and the saturation observed at about 60 participating nucleons can be understood as the onset of the formation of coherent systems of increasing size. 相似文献
208.
The aim of this paper is a study of the quasilinear transport equation, for instance the stationary heat equation. For periodically microheterogeneous media asymptotic homogenization has been performed with the local problem formulated as a minimization problem. The Golden–Papanicolaou integral representation theorem and some bounds developed for the linear equation have been extended. Two-point Padé approximants have been used to calculate bounds. Examples are also provided. 相似文献
209.
Given a number field K, it is well-known that the height of a subspace in KN and of its orthogonal complement coincide. We prove the analogous fact when K is replaced by a positive definite rational quaternion algebra with respect to the heights recently introduced by the first author. Since quaternion algebras are non-commutative, we cannot just follow the classical proof but have to work with localizations and certain finite rings. 相似文献
210.
In this paper there are briefly summarized the results of our experimental measurements of the fluorescence spectra, originating in levels of the4 F 3/2 term and terminating on the first two terms of the4I multipet, and the results of the absorption spectra at room temperature (RT) and at liquid-nitrogen temperature (NT) from which Nd3+: Y3Al5O12 energy-level diagram was determined. Further, using the splitting of the4F3/2,4F5/2 and4F7/2 terms the crystal-field parameters were calculated. 相似文献