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1.
V. Badescu M. Radu M. Zaharescu A. Vasilescu 《Journal of Sol-Gel Science and Technology》1994,2(1-3):43-49
Gas-chromatography coupled with mass spectrometry was used to investigate the hydrolysis and condensation of tetra-ethoxysilane (TEOS) in nonparental solvents (MeOH and nPrOH). In the presence of nonparental solvents, the reaction that advanced at highest rate is alkoxy group scrambling, that changes the precursor at the molecular level. Subsequent stages of hydrolysis-polycondensation process are essentially determined by the reactivity of the new molecular species formed. 相似文献
2.
Weil's well-known converse theorem shows that modular forms are characterized by the functional equation for twists of Lf(s). Conrey–Farmer had partial success at replacing the assumption on twists by the assumption of Lf(s) having an Euler product of the appropriate form. In this Note we obtain a hybrid version of Weil's and Conrey–Farmer's results, by proving a converse theorem for all q?1 under the assumption of the Euler product and, moreover, of the functional equation for the twists to a single modulus. To cite this article: A. Diaconu et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 621–624. 相似文献
3.
Vanadium Doped Sol-Gel TiO2 Coatings 总被引:1,自引:0,他引:1
Maria Crisan Maria Zaharescu D. Crisan Rodica Ion Mihaela Manolache 《Journal of Sol-Gel Science and Technology》1998,13(1-3):775-778
A study of the experimental conditions required to obtain vanadium doped sol-gel TiO2 coatings is presented. Tetraethyl orthotitanate was employed as the TiO2 source and VCl3, VOSO4 · H2O and VOSO4 dissolved H2SO4 where employed as vanadium sources.Dip coating has been used to produce coatings on silicon wafers, spectral carbon electrodes and titanium electrodes. Both supported and unsupported films have been studied by UV-Vis spectra, IR spectroscopy and X-ray diffraction (XRD). The measurements have been made on samples as prepared and treated thermally at temperatures between 100°C and 300°C. The thermal treatment temperatures have been established from DTA/TGA measurements.The vanadium doped sol-gel TiO2 coatings have been tested as sensors for redox potential measurements in electrochemical processes. The influence of both the thickness of films and the nature of substrate has been investigated. 相似文献
4.
We investigate the distribution of the numbers x∈[1,p] for which all lie in a subset of the set of multiplicative inverses modulo a prime p. Here the ai are integers coprime to p and the numbers are distinct . 相似文献
5.
In this paper we continue to study the spectral norms and their completions ([4]) in the case of the algebraic closure $ \overline {\mathbb Q} $ of ? in ?. Let $ \widetilde{\overline{\mathbb{Q}}} $ be the completion of $ \overline {\mathbb Q} $ relative to the spectral norm. We prove that $ \widetilde{\overline{\mathbb{Q}}} $ can be identified with the R‐subalgebra of all symmetric functions of C(G), where C(G) denotes the ?‐Banach algebra of all continuous functions defined on the absolute Galois group G = Gal$ {\overline {\mathbb Q}} / {\mathbb Q} $. We prove that any compact, closed to conjugation subset of ? is the pseudo‐orbit of a suitable element of $ \widetilde{\overline{\mathbb{Q}}} $. We also prove that the topological closure of any algebraic number field in $ \widetilde{\overline{\mathbb{Q}}} $ is of the form $\widetilde{\mathbb{Q}[x]}$ with x in $ \widetilde{\overline{\mathbb{Q}}} $. 相似文献
6.
Maria Crisan Mariuca Gartner Luminita Predoana Rares Scurtu Maria Zaharescu Raluca Gavrila 《Journal of Sol-Gel Science and Technology》2004,32(1-3):167-172
SiO2-ZrO2 based nanostructured multilayers films have been prepared by sol–gel processing from metallorganic precursors by low temperature inorganic polymerization reactions. Simultaneous gelation of both precursors was realized. Homogeneous and transparent films were obtained at room temperature by dip- and spin-coating on glass and silicon wafer substrates. Samples with successively deposited layers (1–3 layers) and successive thermal treatments have been also studied. Each deposited layer was thermally treated for 1 h at 300°C. The coatings were characterized by XRD, spectroellipsometry (SE), UV-VIS spectroscopy and AFM methods. The influence of substrates, number of coatings and number of thermal treatments on the optical and structural properties of the films was established. The thickness of three deposited SiO2-ZrO2 layers is about 496 nm on glass substrates and 413 nm on the silicon wafer substrate. The films deposited on glass are more porous than those deposited on silicon. The properties of optical waveguide prepared from SiO2-ZrO2 layers on silicon substrates will be discussed. 相似文献
7.
Petre Ionita Vasile Dinoiu Cornel Munteanu Ioana Maria Turcu Victorita Tecuceanu Traian Zaharescu Eliza Oprea Cornelia Ilie Dan Anghel Gabriela Ionita 《Chemical Papers》2015,69(6):872-880
The rosemary extract was encapsulated in polyethylene or in covalently-based network gels. The covalent gels were obtained by the reaction of isocyanate end-capped polyethylene glycol (PEG) with β-cyclodextrin or glycerol. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to evaluate the antioxidant activity (AA) of rosemary extract entrapped in polymeric structures and in ethanol or water solutions. The AA of the rosemary extract was determined using a DPPH radical for samples prepared in ethanol, and a water-soluble derivative, the sulphonated DPPH radical (DPPH-SO3Na), for the rosemary extract in water. Formulation of the rosemary extract in polymeric gels ensures a rapid release which determines the AA values similar to those in solution. 相似文献
8.
Zaharescu M. Jitianu A. Brăileanu A. Madarász J. Novák CS. Pokol G. 《Journal of Thermal Analysis and Calorimetry》2003,71(2):421-428
Hybrid materials with different amounts of organics permanently bound on the inorganic network obtained in the TEOS-MTEOS
(tetraethoxysilan-methyltriethoxysilan) system are used for obtaining coatings with different optical and mechanical properties.
To study the thermal stability of the mentioned materials, compositions with different molar ratios of the precursors were
prepared. The influence of the solvent and water amounts on the gelation process was also investigated. The gels obtained
were characterised by IR spectrometry and their decomposition temperatures were determined by DTA/TG. Thermal stability of
the gels is rather influenced by their composition than the conditions of the gelation process.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Marian Vâ jâ itu Alexandru Zaharescu 《Proceedings of the American Mathematical Society》1999,127(8):2225-2232
For given elements and belonging to the ring of integers of a number field we consider the set of all tuples in for which divides for any and prove under some reasonable assumptions that the set of solutions is finite.
10.
Florin P. Boca Radu N. Gologan Alexandru Zaharescu 《Communications in Mathematical Physics》2003,240(1-2):53-73
We consider a billiard in the punctured torus obtained by removing a small disk of radius >0 from the flat torus 2, with trajectory starting from the center of the puncture. In this case the phase space is given by the range of the velocity only. Let (), and respectively R(), denote the first exit time (length of the trajectory), and respectively the number of collisions with the side cushions when 2 is being identified with [0,1)2. We prove that the probability measures on [0, ) associated with the random variables and R are weakly convergent as 0+ and explicitly compute the densities of the limits.
Research partially supported by ANSTI grant C6189/2000. 相似文献