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131.
J.-Ph. Bouchaud P. Doussineau T. de Lacerda-Arôso A. Levelut 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(3):335-340
We characterize in details the aging properties of the ferroelectric phase of KTa1-xNbx O3 (KTN), where both rejuvenation and (partial) memory are observed. In particular, we carefully examine the frequency dependence
of several quantities that characterize aging, rejuvenation and memory. We find a marked subaging behaviour, with an a.c.
dielectric susceptiblity scaling as ω, where t
w is the waiting time. We suggest an interpretation in terms of pinned domain walls, much along the lines proposed for aging
in a disordered ferromagnet, where both domain wall reconformations and overall (cumulative) domain growth are needed to rationalize the experimental findings.
Received 10 November 2000 and Received in final form 20 February 2001 相似文献
132.
133.
Roberto Castillo Maurus Biedermann Anne-Marie Riquet Koni Grob 《Polymer Degradation and Stability》2013
High performance liquid chromatography (HPLC) was used for the fractionation of extracts from polypropylene (PP) films and coupled on-line to gas chromatography (GC) with automated transfer of the complete HPLC fractions (comprehensive on-line HPLC-GC, i.e. HPLCxGC). Flame ionization detection (FID) was used for the estimation of concentrations, mass spectrometry (MS) for identification work. This method was applied to investigate whether pulsed light (PL) treatment for the microbiological decontamination of polypropylene packaging materials produces reaction products requiring an evaluation to meet regulatory requirements. To demonstrate the safety of PL treatments with regard to the formation of reaction products, i.e. that no component is formed that could endanger human health, basically comprehensive analysis of components potentially migrating into food is required, but comprehensiveness cannot be proven and remains an approximation. The threshold concentration in the film was estimated either from the conventional European non-detection limit of 0.01 mg/kg food or the concept of the threshold of toxicological concern (TTC) for an unknown substance, i.e. an exposure to 0.15 μg per person and day. PL treatment of the films containing Irgafos 168 produced several new components exceeding these limits, i.e. a toxicological safety assessment would probably be required. No such peaks were detected for Tinuvin 326, Irganox 1076 and Chimassorb 81. No degradation of the polymer was detected. 相似文献
134.
Sébastien Gottis Lara-Isabel Rodriguez Régis Laurent Inmaculada Angurell Miquel Seco Oriol Rossell Jean-Pierre Majoral Anne-Marie Caminade 《Tetrahedron letters》2013
The first association of carbosilane dendrons (having a phosphine at the focal point) with phosphorhydrazone dendrons (having a thiophosphoryl azide at the focal point) has been successfully carried out by ‘Staudinger click’ reaction. The corresponding Janus dendrimers possess the characteristics of both components; they are oily as the carbosilane dendrons, and they can be easily functionalized as the phosphorhydrazone dendrons. 相似文献
135.
G. Scherowsky U. Müller J. Springer W. Trapp A. M. Levelut P. Davidson 《Liquid crystals》2013,40(4):1297-1306
The synthesis and mesomorphic properties of two liquid-crystalline side chain polymers with a chiral centre in the α or β position of the α-hydroxy acid representing the spacer unit are described. The chiral α branching leads to a dramatic decrease in the transition temperatures and a strong narrowing of the smectic mesophase (compared with the unbranched model compound I). The chiral β branching results in a chiral smectic phase, a pronounced contraction of the Sc phase, and the loss of the higher ordered Sf phase. The S*c phase was confirmed by X-ray investigations of oriented samples. Depending on the polymerization conditions samples were obtained which were oriented in melt drawn fibres either with their smectic layers or their mesogenic units in the direction of stress. 相似文献
136.
X-ray measurements on hexakis(4-(4'-alkyloxy)biphenoxy)cyclotriphosphazenes [PN-(OC6H4C6H4OCnH2n + 1)2]3 (HACP, n = 7-9), confirm the previous mesophase identification. The apparent molecular length measured in the mesophase compares to twice the length of an alkyloxybiphenyl side group. Specific features are added to the usual features of the nematic and smectic diffraction patterns which show that the molecular arrays in directions parallel and perpendicular to the director both reflect the peculiar shape of the cyclotriphosphazenes. 相似文献
137.
138.
Yves L. Janin Anne-Marie Aubertin Angéle Chiaroni Claude Riche Claude Monneret Emile Bisagni David S. Grierson 《Tetrahedron》1996,52(48):5109-15170
The imidazo[1,5-g][1,4]diazepine derivatives 7a and 7b, analogues of TIBO lacking the aromatic ring, were prepared as part of a research program to find compounds displaying antiviral activity against HIV-2 and resistant strains of HIV-1. Condensation of N-trityl and N-tosyl 4-(2-chloroethyl)-imidazole with the appropriate amino alcohols gave compounds 10a-c and 16a-e. The hydroxyl group in these intermediates was activated toward closure of the [1,4]diazepine ring by either conversion to the corresponding chloro derivative, or by N → O transfer of the tosyl group. However, only cyclization to compounds 13a and 13b proved efficient. These products were converted to the target molecules 7 by reaction of their C-2 anion with S8. In vitro evaluation of compounds 7a,b and 13,a,b in cell culture (CEM SS/HIV-1-LAI and CEM SS/HIV 1 nevirapine resistant cells) revealed that only 13b displayed minimal activity. 相似文献
139.
In this paper, we examine the problem of finding minimum-cost production schedules that satisfy known demands over a finite planning horizon. A dynamic programming algorithm is developed to find these schedules for cases in which production in each period is constrained by a time-dependent capacity bound. The costs considered are production and inventory holding costs, and all cost functions are assumed to be nondecreasing and concave. The algorithm is an extension of Florian and Klein's method developed for problems in which capacity bounds are the same in all periods. Although the problem with time-dependent bounds is NP-complete, the algorithm is shown to be efficient when the capacity bounds are integer multiples of a common divisor and the largest multiplier is small. Hence, it is useful in applications in which production capacity is periodically increased by adding facilities of the same size. 相似文献
140.
Bengt Karlsson Anne-Marie Pilotti Anne-Charlotte Söderholm Torbjörn Norin Stefen Sundin Masashi Sumimoto 《Tetrahedron》1978,34(15):2349-2354
The structure of verticillol diepoxide 4 has been established by direct single crystal X-ray analysis. The structure of verticillol 5 follows from the chemical correlation to the diepoxide 4 as well as from NMR-LIS studies on verticillol which also provide evidence for the conformation of this alcohol. The absolute configuration of verticillol 5 has been assigned on the basis of CD data for the verticillol norketodiepoxide 6a. 相似文献