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71.
Karla A. Barrera‐Rivera Ángel Marcos‐Fernández Ricardo Vera‐Graziano Antonio Martínez‐Richa 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5792-5805
Yarrowia lipolytica (YLL), Candida rugosa (CRL), and porcine pancreatic lipase (PPL) were employed successfully as catalysts in the enzymatic ring‐opening polymerization (ROP) of ε‐caprolactone in the presence of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1‐butylpyridinium tetrafluoroborate ([BuPy][BF4]), 1‐butylpyridinium trifluoroacetate ([BuPy][CF3COO]), 1‐ethyl‐3‐methylimidazolium nitrate ([EMIM][NO3]) ionic liquids. Poly(ε‐caprolactone)s (PCLs) with molecular weights (Mn) in the range of 300–9000 Da were obtained. 1H‐ and 13C‐NMR analyses on PCLs formed by YLL, CRL, and PPL showed asymmetric telechelic α‐hydroxy‐ω‐carboxylic acid end groups. Differences between CP‐MAS and MAS spectra are observed and discussed in terms of morphology. MALDI‐TOF spectra show the formation of at least seven species. Differential scanning calorimetry (DSC) and Wide Angle X‐Ray Scattering (WAXS) results demonstrate the high degree of crystallinity present in all the polyesters. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5792–5805, 2009 相似文献
72.
73.
Ulisse Stefanelli 《Journal of Differential Equations》2006,229(1):204-228
This note addresses a class of abstract quasivariational evolution equations taking into account nonlocality with respect to time. We present an existence result for suitably weak solutions to such problems, which extend previous contributions. The existence argument relies on some order technique and exploits a fixed point result for multivalued applications in ordered spaces. Moreover, we discuss the application of our results to classes of ODE and parabolic PDE problems. 相似文献
74.
75.
This paper deals with the complete characterization of solutions to an elliptic system of variational inequalities. The latter model arises in the study of the long-time behavior of shape memory materials and is suitable of describing a variety of experimentally observed phenomena. 相似文献
76.
Ribière P Bravo-Altamirano K Antczak MI Hawkins JD Montchamp JL 《The Journal of organic chemistry》2005,70(10):4064-4072
[reaction: see text] A new nickel-based catalytic system has been developed for phosphorus-carbon bond formation. The addition of alkyl phosphinates to alkynes is catalyzed by nickel chloride in the absence of added ligand. The reaction generally proceeds in high yields, even with internal alkynes, which were poor substrates in our previously reported palladium-catalyzed hydrophosphinylation of alkyl phosphinates. The method is useful for the preparation of H-phosphinate esters and their derivatives. The one-pot synthesis of various important organophosphorus compounds is also demonstrated. The reaction can be conducted with microwave heating. 相似文献
77.
Ulisse Stefanelli. 《Mathematics of Computation》2002,71(240):1431-1453
This paper deals with a semi-implicit time discretization with variable step of a three-dimensional Frémond model for shape memory alloys. Global existence and uniqueness of a solution is discussed. Moreover, an a priori estimate for the discretization error is recovered. The latter depends solely on data, imposes no constraints between consecutive time steps, and shows an optimal order of convergence when referred to a simplified model.
78.
Riassunto E stato applicato il metodo di titolazione potenziometrica con metilato sodico a composti fenolici aventi formula simile come l'1–8 diossiantrachinone, l'1–8 diossi-3-metilantrachinone e l'1–8 diossi-3-metil antrone, di notevole importanza farmaceutica.Come solvente si è usata la piridina e come rivelatori del punto di equivalenza una coppia di elettrodi vetro-antimonio non essendo possibile usare indicatori data la forte colorazione delle soluzioni.
Summary Potentiometric titration with sodium methylate was used ton determine derivatives whose constitution is similar to that of 1,8-dihydroxyanthraquinone, 1,8-dihydroxy-3-methylanthraquinone and l,8-dihydroxy-3-methylanthrone.The solvent is pyridine. The change point was determined by means of an electrode pair: glass electrode-antimony electrode, since the intense self-color of the solutions excludes the use of indicators.
Zusammenfassung Die potentiometrische Titration mit Natriummethylat wurde zur Bestimmung von Derivaten herangezogen, deren Zusammensetzung dem 1,8-Dihydroxyanthrachinon, dem 1,8-Dihidroxy-3-methylanthrachinon und dem 1,8-Dihidroxy-3-methylanthron ähnlich ist.Als Lösungsmittel wird Pyridin verwendet. Der Umschlagspunkt wird mit Hilfe eines Elektrodenpaares Glaselektrode-Antimonelektrode festgestellt, da die starke Eigenfärbung der Lösungen den Gebrauch von Indikatoren ausschließt.
Résumé Le titrage potentiométrique par le méthylate de sodium a été appliqué au dosage de dérivés dont la composition est semblable à celles de la 1, 8-dihydroxyanthraquinone, de la 1,8-dihydroxy-3-méthylanthraquinone et de la l,8-dihydroxy-3-méthylanthrone. On utilise la pyridine comme solvant.Le point final de titrage est déterminé à l'aide d'un système électrode de verre: électrode d'antimoine car la forte coloration des solutions interdit l'emploi d'indicateurs.相似文献
79.
80.
This note is concerned with the initial value problem for the abstract
nonlocal equation
where A is a
maximal monotone operator from a reflexive Banach space E to its
dual E*, while B is a
nonlocal maximal monotone operator from
.
Under proper boundedness and coercivity assumptions on the operators, a solution is achieved by means of a discretization
argument. Uniqueness and continuous dependence are also discussed and we prove some estimates for the discretization
error. Finally, we deal with the approximation of linear Volterra integrodifferential operators. 相似文献