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101.
V. Balsamo N. Calzadilla G. Mora A. J. Müller 《Journal of Polymer Science.Polymer Physics》2001,39(7):771-785
In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(ϵ‐caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass‐transition temperature (Tg) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the Tg was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T) by the Hoffman–Weeks extrapolation method. A T depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60–70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 771–785, 2001 相似文献
102.
Jose R. Rojas Marcos Loroño Jose R. Mora Rosa M. Dominguez Tania Cordova Gabriel Chuchani 《国际化学动力学杂志》2009,41(3):168-175
The gas‐phase elimination of several ω‐bromonitriles (ZCH2CH2Br, Z = NC, NCCH2, NCCH2CH2) has been examined at the MP2/6‐31G(d,p), MP2/6‐31G(2d,2p), B3PW91/6‐31G(2d,2p), and MPW91PW91/6‐31(2p,2d) levels of theory. The bromonitriles yield the corresponding cyano‐olefin and HBr gas in a rate‐determining step. The MPW91PW91/6‐31G(2p,2d) results suggest a concerted mechanism, with a polar, four‐membered transition state. The calculated kinetic and thermodynamic parameters were found to be within reasonable agreement with the experimental determinations. Substituent effects are discussed in terms of electronic structure. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 168–175, 2009 相似文献
103.
Attempting to model the processes resulting in complex pattern formation and small-scale roughness of surfaces and to compare
with experimental measurements calls for numerical methods which allow a quantitative characterization being as complete as
possible. New methods incorporating wavelets and stochastic approaches based on the theory of Markov processes allow a stepwise
characterization of increasing completeness and unambiguousness. In this paper we demonstrate the underlying numerical approaches
taking electropolished and laser-jet etched surfaces for demonstration. 相似文献
104.
105.
High-Q microwave photonic filter with a tuned modulator 总被引:1,自引:0,他引:1
We propose the use of tuned electro-optic or electroabsorption external modulators to implement high-quality (high-Q) factor, single-bandpass photonic filters for microwave signals. Using this approach, we experimentally demonstrate a transversal finite impulse response with a Q factor of 237. This is to our knowledge the highest value ever reported for a passive finite impulse-response microwave photonic filter. 相似文献
106.
In this note we show that a diffeomorphism which has a Hopf's bifurcation point, can be perturbed around the bifurcation point in order to get a diffeomorphism which exhibits homoclinic tangencies. In the case this is not possible because of the typical unfolding of a Hopf's bifurcation point.
107.
DC magnetic field generation in resonance absorption is studied, in a non-linear regime, when it becomes of sufficient order of magnitude to affect wave propagation, as well as electron-ion collisions or thermal dispersion do. It is shown that a simple expression obtained in the linear regime is still valid in the non-linear theory. Scaling laws are set up. 相似文献
108.
Ohne Zusammenfassung 相似文献
109.
Cristoni S Cuccato D Sciannamblo M Bernardi LR Biunno I Gerthoux P Russo G Weber G Mora S 《Rapid communications in mass spectrometry : RCM》2004,18(1):77-82
Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder mainly caused by 21-hydroxylase deficit (21-OHD). Deletions or mutations of the CYP21 gene induce the impairment of glucocorticoid and mineralcorticoid synthesis. 17-Hydroxyprogesterone (17-OHP) is the hormonal marker in patients, but not in the heterozygous subjects. Excess 17-OHP is hydroxylated into 21-deoxycortisol (21-DF), and therefore 21-DF can be used as a specific marker for diagnosis of heterozygous individuals. We report an analytical method for analysis of 21-DF in blood samples using electrospray (ESI) and atmospheric pressure chemical ionization (APCI), showing that ESI is very sensitive for the analysis of this marker molecule. The multiple reaction monitoring (MRM) approach was used to increase the specificity and the sensitivity of the method. 相似文献
110.
Martinez-Montero ME Mora N Quiñones J González-Arnao MT Engelmann F Lorenzo JC 《Cryo letters》2002,23(4):237-244
In this paper, we investigated if the differences consistently noted in survival and plantlet production between cryopreserved and non-cryopreserved, control sugarcane embryogenic calluses were related to modifications induced during cryopreservation in the structural and functional integrity of cell membranes. For this, the evolution of electrolyte leakage, lipid peroxidation products and cell membrane protein contents was measured during 5 d after cryopreservation. Differences between control and frozen calluses were observed only during the first 2 (electrolyte leakage) or 3 d (lipid peroxidation products and membrane protein content) after freezing. It was not possible to link these differences with the differences noted in survival and plant production between control and cryopreserved calluses. Additional studies are thus needed to elucidate which biochemical factors, linked to survival and plantlet regeneration, are affected by cryopreservation. 相似文献