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Sonia Milln Victor Snchez Luz Alicia Fucugauchi Yasuo Ito Yoneho Tabata 《Journal of Polymer Science.Polymer Physics》1992,30(1):1-9
The positron lifetime measurement technique was applied to analyze the structural changes occurring in solid-state polymerization of acrylamide and trioxane. Positronium (Ps) parameters, τ2 and I2, which show a marked change as a function of the γ-ray irradiation dose, signaled the presence of three clearly defined stages in the polymerization process: initiation, propagation, and saturation. The initial increase in τ2, may very well be the result of efficient trapping of Ps in vacancies created around the polymer nuclei. The complicated behavior of I2 may be explained as a chemical reaction between Ps precursors and the radiolysis products of this polymerization process. 相似文献
995.
Synthesis of a new catechin-pyrylium derived pigment 总被引:1,自引:0,他引:1
A new catechin-pyrylium derived pigment compound was synthesised from the reaction of catechin with sinapaldehyde in acidic conditions and its structure has been characterised by UV-vis, MS and NMR spectroscopy. Similar compounds could be expected to be formed in wines and contribute to changes in colour and astringency during ageing. 相似文献
996.
Thanks to recent technical developments (optics and detection systems), at several synchrotron radiation facilities in the world, it is possible to perform photoemission spectroscopy studies with very high resolution. In the present report, we will review the new insights gained from high-resolution core-level spectroscopy on the structural and electronic properties of different semiconductor surfaces, such as InAs(110), Si and Ge (100) and (111), as well as clean and adsorbate covered Si and Ge(111) surfaces. 相似文献
997.
998.
The cathodic reduction of oxygen in 1 mol dm−3 sodium hydroxide solutions has been investigated at several types of titanium oxide cathodes. Layers of TiO2 were prepared on titanium by spraying and thermal decomposition of solutions of titanium n-butoxide in 2-propanol and titanium tetrachloride in methanol+water and also by anodization; the reduction was also studied at Ebonex®, a conducting ceramic consisting mainly of Ti5O9. In all cases, the reduction of oxygen occurs largely by a 4e− reaction to water and the reaction occurs at potentials close to −1.0 V vs. SCE. Cyclic voltammetry in the absence of oxygen shows that, at these potentials, the surfaces undergo reduction and the electrochemistry of the Fe(CN)64− /Fe(CN)63− couple has been used to probe further the properties of the TiO2 surfaces. 相似文献
999.
Victor Pambuccian 《Indagationes Mathematicae》2004,15(3):413-417
Dimension-free Euclidean geometry over Euclidean ordered fields can be axiomatized in a two-sortedfirst-order language, with points and regular n-gons (with n = 3 or 4) as variables, and with a binary predicate standing for the incidence of a point and a regular n-gon as the only primitive notions. 相似文献
1000.
Among normed linear spacesX of dimension ≧3, finite-dimensional Hilbert spaces are characterized by the condition that for each convex bodyC inX and each ballB of maximum radius contained inC,B’s center is a convex combination of points ofB ∩ (boundary ofC). Among reflexive Banach spaces of dimension ≧3, general Hilbert spaces are characterized by a related but weaker condition
on inscribed balls.
Research of the first author was partially supported by the U.S. National Science Foundation. Research of the second and third
authors was supported by the Consiglio Nazionale delle Ricerche and the Ministero della Pubblica Istruzione of Italy, while
they were visiting the University of Washington, Seattle, USA. 相似文献