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91.
DSC measurements indicate that poly(vinyl bromide) (PVB) is miscible with several polyesters [poly(caprolactone), poly(valerolactone), poly(butylene adipate) and poly(hexamethylene sebacate)] but immiscible with others [poly(α-methyl-α-n-propyl-β-propiolactone), poly(α-methyl-α-ethyl-β-propiolactone) and poly(ethylene adipate (PEA)]. However, it is known that poly(vinylchloride) (PVC) is miscible with all these polyesters but PEA. The more limited degree of miscibility of PVB with polyesters, as compared with the case of PVC, is surprising in view of the similar properties of the bromine and chlorine atoms. 相似文献
92.
The reactivity of some derivatives of perfluorooctenyl-tin, perfluorooctenyl-mercury and perfluorooctyl-mercury towards protic acids, especially hydrogen chloride, is studied.
The easy cleavage of the tin - sp2 carbon bond is painted out, and used to study possibilities of transferring the perfluorooctenyl radical on mercury, upon reaction with mercuric salts.
The mercury-perfluoroalkyl radical bond is shown to be, on the contrary, very resistant to an electrophilic attack.
These results are compared to those concerning the hydrocarbon analogs, and an interpretation, relied to the electronic density on the carbon atom bound to the metallic atom, is given. 相似文献
93.
John D. Buynak M.Narayana Rao Ramalakshmi Yegna Chandrasekaran Elizabeth Haley Patrice de Meester Shirley C. Chu 《Tetrahedron letters》1985,26(41):5001-5004
Synthetically valuable α-alkylidene-β-lactams are produced from the addition of chlorosulfonyl isocyanate to allenyl sulfides. 相似文献
94.
Colette Lacabanne Patrice Goyaud Raymond F. Boyer 《Journal of Polymer Science.Polymer Physics》1980,18(2):277-284
The thermally stimulated current (TSC) technique has been used to investigate three anionic polystyrenes of M?n 17,000, 71,700, and 1.55 × 106, i.e., M < Mc, M > Mc, and M ? Mc, where Mc is the entanglement molecular weight. A current maximum near Tg designated TMg, has relaxation times which follow an Arrhenius equation. A second current maximum at T > Tg appears to be the Tll process and is designated TMll. Relaxation times for it follow a Vogel equation. TMg and TMll vary with molecular weight, increasing below Mc and leveling off above Mc at a temperature of about 170°C. Values of TMg and TMll are compared with values of Tg and Tll obtained from torsional braid analysis, which involves melt flow; and with differential-scanning-calorimetric values on fused films, where there is no transport of polymer. It is concluded from such cross-comparisons that TSC, at least for polystyrene, is a quasistatic test which may involve microscopic viscosity. Macroscopic viscosity does not play a role. The ratio TMll/TMg is in the range 1.10–1.16, similar to Tll/Tg values by other methods. A few comments about Tll in atactic poly(methyl methacrylate) by the TSC method are given. 相似文献
95.
Wittig and Wittig-Horner reactions with α-phenylselenoaldehydes lead to allylic selenides. The corresponding selenoxides undergo 2,3-sigmatropic rearrangement providing a route to α-hydroxy β,γ-ethylenic esters and ketones in good yields. In a same way, we prepare, also enals with an additionnal carbon. 相似文献
96.
Katarzyna Raulin Odile Cristini-Robbe Patrice Baldeck Olivier Stéphan Christophe Kinowski Sylvia Turrell Bruno Capoen Mohamed Bouazaoui 《Journal of nanoparticle research》2010,12(4):1459-1467
A novel method for direct laser writing of two-dimensional cadmium sulfide (CdS) semiconductor nanoparticle microstructures
is reported. A two photon or a higher-order multiphoton absorption process, originating from femtosecond laser pulses, was
used to decompose CdS precursors dispersed in a zirconia thin film previously dip-coated on a glass substrate. The kinetics
of nanoparticle formation as a function of laser power were monitored in situ by photoluminescence spectroscopy. Raman spectroscopy
was also performed to characterize the structural changes of the zirconia matrix under irradiation and to verify the formation
of CdS nanoparticles. Results show that CdS nanoparticles were formed by two-photon absorption (TPA) with or without the help
of an additional carbazole photoinitiator. 相似文献
97.
We developed a rapid and non-toxic method for the preparation of colloidal gold nanoparticles (GNPs) by using tryptophan (Trp) as reducing/stabilizing agent. We show that the temperature has a major influence on the kinetics of gold ion reduction and the crystal growth, higher temperatures favoring the synthesis of anisotropic nanoparticles (triangles and hexagons). The as-synthesized nanostructures were characterized by UV–Vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), fluorescence, and surface-enhanced Raman scattering (SERS) spectroscopy. The UV–Vis measurements confirmed that temperature is a critical factor in the synthesis process, having a major effect on the shape of the synthesized GNPs. Moreover, fluorescence spectroscopy was able to monitor the quenching of the Trp fluorescence during the in situ synthesis of GNPs. Using Trp as molecular analyte to evaluate the SERS efficiency of as-prepared GNPs at different temperatures, we demonstrated that the Raman enhancement of the synthesized gold nanoplates is higher than that of the gold spherical nanoparticles. 相似文献
98.
Design of the spatial filter window for digital holographic convolution reconstruction of object beam field 总被引:1,自引:0,他引:1
In the convolution reconstruction process of digital holographic object beam field, the object beam fields with different magnifications can be obtained when the reconstructing beams are spherical waves with different wave curvature radii. This paper presents a theoretical and experimental discussion on the useful spatial frequency spectrum of the hologram numerically illuminated by the spherical wave. The result shows that there would be an image in the spatial frequency spectrum of digital hologram, which is completely the same as the object, if the wave surface radius of the spherical wave is equal to the distance from the object to the CCD sensor. Taking this image as a reference and designing a filter, the position of the reconstructed images with different magnifications can be predicted correctly in the reconstructed plane. Additionally, since the spectrum distribution of zero-order diffraction can be forecasted accurately in theory, its contribution can be effectively eliminated through changing the spatial filter shape; then a reconstructed object field containing more high-frequency information can be obtained. 相似文献
99.
The Ramanujan Journal - In this article we study an abelian analogue of Schanuel’s conjecture. This conjecture falls in the realm of the generalised period conjecture of André. As shown... 相似文献
100.
Issa Sanni Jérôme Fortin Patrice Coorevits 《Journal of Computational and Applied Mathematics》2010,234(4):1161-1171
We present in this paper an improved non-smooth Discrete Element Method (DEM) in 3D based on the Non-Smooth Contact Dynamics (NSCD) method. We consider a three-dimensional collection of rigid particles (spheres) during the motion of which contacts can occur or break. The dry friction is modeled by Coulomb’s law which is typically non-associated. The non-associativity of the constitutive law poses numerical challenges. By adopting the use of the bi-potential concept in the framework of the NSCD DEM, a faster and more robust time stepping algorithm with only one predictor-corrector step where the contact and the friction are coupled can be devised. This contrasts with the classical method where contact and friction are treated separately leading to a time stepping algorithm that involves two predictor-corrector steps. The algorithm has been introduced in a 3D version of the NSCD DEM software MULTICOR. Numerical applications will show the robustness of the algorithm and the possibilities of the MULTICOR software for solving three-dimensional problems. 相似文献