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91.
Zhirong Xin Yongtao Ding Jinghua Yin Zhuo Ke Xiaodong Xu Ying Gao Giovanna Costa 《Journal of Polymer Science.Polymer Physics》2005,43(3):314-322
Three nonionic surfactants, S1, S2, and S3 and their acrylates, AS1, AS2, and AS3, were synthesized with poly(ethylene oxide) and diols such as glycol, 1,6‐hexanediol, and 1,10‐decanediol as the main starting materials. Their chemical structures were characterized by means of Fourier transform infrared (FTIR) spectroscopy and 1H NMR. The surface activity and surface tension (γ) of S1, S2, and S3 were evaluated by a drop weight method. The surface tension was found to decrease with the length of the lipophilic spacer in the molecular chains (γS1 < γS2 < γS3). AS1, AS2, and AS3 were adopted as functionalizing monomers and grafted onto linear low density polyethylene (LLDPE) with a melt reactive extrusion procedure. The graft degrees of LLDPE were determined by FTIR. Three grafted LLDPE samples with grafting degrees of 1.16% (AS1), 0.82% (AS2), and 0.71% (AS3) were prepared. Thermal and rheological properties of grafted LLDPE samples were studied with differential scanning calorimetry and a rotational rheometer. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at a given crystallization temperature because graft chains could act as nucleating agents. The isothermal crystallization behavior of grafted LLDPE was in accordance with the Avrami model only in the first stage, and deviated from the model with an increase in the crystallization time. Shear thinning at high shear rates and shear thickening at low shear rates were observed for the grafted LLDPE. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 314–322, 2005 相似文献
92.
Marco Luigi Bernardi Giovanna Bonfanti Fabio Luterotti 《Annali di Matematica Pura ed Applicata》1998,174(1):209-239
The Cauchy problem is studied for a class of linear abstract differential equations of hyperbolic type with variable domain. Existence and uniqueness results are proved for (suitably defined) weak solutions. Some applications to P.D.E. are also given: they concern linear hyperbolic equations either in non-cylindrical regions or with mixed variable lateral conditions.This work was supported in part by the M.U.R.S.T. (Italy), through 60% and 40% research funds, and by the «G.N.AF.A. of the C.N.R.» (Italy). 相似文献
93.
The B-spline density-functional method has been applied to the conformers of the (1R, 2R)-1,2-dibromo-1,2-dichloro-1,2-difluoroethane molecule. The cross section, asymmetry, and dichroic parameters relative to core and valence orbitals, which do not change their nature along the conformational curve, have been systematically studied. While the cross section and the asymmetry parameter are weakly affected, the dichroic parameter appears to be rather sensitive to the particular conformer of the molecule, suggesting that this dynamical property could be a useful tool for conformational analysis. The computational method has also been applied to methyl rotation in methyloxirane. Unexpected and dramatic sensitivity of the dichroic-parameter profile to the methyl rotation, both in the core and valence states, has been found. Boltzmann averaging over the conformers reproduces quite closely the profiles previously obtained for the minimum-energy conformation, which is in good agreement with the experimental results. 相似文献
94.
Ugo Azzena Giovanna DettoriMaria Vittoria Idini Luisa PisanoGrazia Sechi 《Tetrahedron》2003,59(40):7961-7966
Selective removal of the 4-methoxy group of 3,4,5-trimethoxystilbenes was performed under electron transfer conditions from Na metal in THF. Careful control of reaction conditions and quenching procedure allowed the synthesis of either (E)-3,5-dimethoxystilbenes or 3,5-dimethoxybibenzyls. 相似文献
95.
96.
Giovanna Carnovale 《Acta Appl Math》1998,53(2):187-228
This paper answers a few questions about algebraic aspects of bialgebras, associated with the family of solutions of the quantum Yang–Baxter equation in Acta Appl. Math. 41 (1995), pp. 57–98. We describe the relations of the bialgebras associated with these solutions and the standard deformations of GLn and of the supergroup GL(m|n). We also show how the existence of zero divisors in some of these algebras are related to the combinatorics of their related matrix, providing a necessary and sufficient condition for the bialgebras to be a domain. We consider their Poincaré series, and we provide a Hopf algebra structure to quotients of these bialgebras in an explicit way. We discuss the problems involved with the lift of the Hopf algebra structure, working only by localization. 相似文献
97.
Riassunto Si dimostrano teoremi di esistenza, di unicità e di regolarizzazione per la soluzione del problema di Cauchy-Dirichlet per
una classe di sistemi parabolici a coefficienti misurabili.
Lavoro eseguito nell'ambito del gruppo G.N.A.F.A. del C.N.R. 相似文献
Summary We show that the Cauchy-Dirichlet problem for a class of parabolic systems with measurable coefficients admits a unique solution. We show, also, regularity's properties for the solution.
Lavoro eseguito nell'ambito del gruppo G.N.A.F.A. del C.N.R. 相似文献
98.
We study bilateral problems for a second order parabolic operator with principal part not of divergence form. We prove existence, uniqueness, Holder-continuity and approximation results for both strong and generalized solutions. 相似文献
99.
Giovanna Pizzirani Pierluigi Magagnini Paolo Giusti 《Journal of Polymer Science.Polymer Physics》1971,9(6):1133-1145
The glass transition temperatures of a number of poly(vinyl phenyl ketones), poly-(vinyl benzoates), and poly(phenyl acrylates) have been measured by a refractometric method. The effects exerted on Tg by the nature and position of the ring substituents and by the different groups binding the pendant phenyl rings to the polyvinyl chain are discussed. The importance of knowledge of the side-group motions in the glassy state for the interpretation of glass temperature data is emphasized. 相似文献
100.