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141.
C. Gonzalez Perez L. Polo Diez A. Sanchez Perez F. Lucena Conde 《Mikrochimica acta》1977,67(1-2):29-35
Summary A simple and direct method for the spectrophotometric determination of chloride, based on the formation of chromyl chloride and its extraction into carbon tetrachloride has been developed. The absorption spectrum of the organic extract shows two bands at 300 and 415 nm; Beer's law is obeyed at both wavelengths over the range 20–320g of chloride. The best conditions for the spectrophotometric determination of chloride are determined and a procedure is recommended. Interferences from some of the most common anions are studied.
Zusammenfassung Eine neue Methode für die Bestimmung von Chloridionen wurde angegeben. Sie beruht auf der Bildung von Chromylchlorid und dessen Extraktion mit Tetrachlorkohlenstoff. Der Extrakt hat spektrale Maxima bei 300 und 415 nm. Das Beersche Gesetz ist zwischen 20 und 320g Chlorid erfüllt. Die besten Bedingungen für die spektrophotometrische Bestimmung wurden ermittelt und ein Verfahren empfohlen. Störungsmöglichkeiten einiger üblicher Anionen wurden untersucht.相似文献
142.
D. Grosso F. Babonneau C. Sanchez G.J. de A.A. Soler-Illia E.L. Crepaldi P.A. Albouy H. Amenitsch A.R. Balkenende A. Brunet-Bruneau 《Journal of Sol-Gel Science and Technology》2003,26(1-3):561-565
Since mesoporous materials can be prepared by combining the sol-gel chemistry and the structuring effect of surfactants, they have attracted attention for application in various high technology fields. The present work deals with the analyses of the mechanisms involved in the formation of SiO2 and TiO2 highly organised 2D-hexagonal meso-structured films using Brij 58 as surfactant. The preparation of such films by dip-coating involves rapid evaporation which makes the different steps difficult to control. Simultaneous in-situ SAXS (synchrotron) and interferometry analyses have been performed to get a first understanding of the self-assembly process. SiO2 and TiO2 materials have a different chemical reactivity (kinetics and coordination aspects). However, we show that the mechanisms involved during dip-coating are quite similar : the self-assembly leading to the organised phase takes place at a final stage of the drying process, involves the formation of a disorganised intermediate phase and depends also on the presence of micellar interfaces in addition to film/air and film/substrate interfaces. 相似文献
143.
R. Klett D. Fink M. Mü ller H. Omichi F. Hosoi V. Hnatowicz J. Vacik G. Sanchez 《Radiation measurements》1997,28(1-6):51-53
Usually ion tracks are studies ex-situ, i.e. after removal of the ion-irradiated sample from the evacuated irradiation vessel. The exposure to ambient air leads to degradation effects which are frequently neglected and consequently have been studied rarely. They have never been explained consistently. In this work we compile and discuss them in the frame of today's general understanding of ion tracks in polymers. It appears that some pristine polymers such as polyethylene are covered by a surface layer which is badly permeable for gaseous contaminants. Ion irradiation leads to destruction of this protective layer so that oxygen and moisture from the ambient air can easily penetrate through the ion tracks, and eventually even into the surrounding pristine material. Moisture absorption along the tracks gives rise to some faint conductivity. Oxygen uptake adds new trapping centers to the existing ones along the tracks, so that on one hand an increased dopant uptake capability is recorded, and on the other hand oxygen-sensitive mobile dopants are immobilized along the ion tracks. Photooxidation processes contribute to the fading of the optical blackening of irradiated polymers. 相似文献
144.
Bifurcations in a forced softening duffing oscillator 总被引:1,自引:0,他引:1
The response of a damped Duffing oscillator of the softening type to a harmonic excitation is analyzed in a two-parameter space consisting of the frequency and amplitude of the excitation. An approximate procedure is developed for the generation of the bifurcation diagram in the parameter space of interest. It is a combination of second-order perturbation solutions of the system in the neighborhood of its non-linear resonances and Floquet analysis. The results show that the proposed scheme is capable of predicting symmetry-breaking and period-doubling bifurcations as well as Jumps to either bounded or unbounded motions. The results obtained are validated using analogand digital-computer simulations, which show chaos and unbounded motions, among other behaviors. 相似文献
145.
Summary The absorption spectrum near the fundamental absorption edge of an-type CuInSe2 single crystal grown by the Bridgman method has been studied at 100 and 300 K. An absorption edge corresponding to the direct-band-gap
transition is observed at about 1 eV. An additional absorption is observed at lower energies ((0.93÷0.95) eV) and is attributed
to direct transitions assisted by long-wave-length optical phonons.
Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982. 相似文献
Riassunto Lo spettro di assorbimento vicino al bordo di assorbimento fondamentale di un cristallo singolo di tipon di CuInSe2, cresciuto col metodo di Bridgman, è stato studiato a 100 e 300 K. Si osserva un bordo di assorbimento in corrispondenza della transizione del gap di banda diretta a circa 1 eV. Un ulteriore assorbimento è osservato a energie inferiori ((0.93÷0.95) eV) ed è attribuito a transizioni dirette alla presenza di fononi ottici a grande lunghezza d'onda.
Резюме При 100 К и 300 К исследуется спектр поглощения вблизи основного края поглощения монокристалла CuInSe2 n-типа, выращенного по методу Ъридгмана, Вблизи 1 эВ обнаружен край поглощения, соответствующий прямому переходу. Дополнительное поглощение наблюдается при меньших энергиях ((0.93÷0.95) эВ) и приписывается прямым переходом, связанным с длинноволновыми оптическими фононами.
Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16, 1982. 相似文献
146.
R. Castell D. Mandelbaum A. Mendez A. Sanchez 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,30(4):345-349
Experimental profiles of the hydrogen Paschen-beta line have been measured in a helium plasma with 0.85% hydrogen. Electron densities were deduced from profiles of the He(I) line (λ = 4471.5 Å) and are in the range 1014–1015 cm-3. Our measurements are compared with theoretical calculations. 相似文献
147.
Nuclear orientation experiments on 137mCe impurities in Al2La show directly at almost 0 K that these alloys correspond to the magnetic conditions assumed by Müller-Hartmann and Zittartz. 相似文献
148.
Salvatori Mdel R Abou-Jneid R Ghoulami S Martin MT Zaparucha A Al-Mourabit A 《The Journal of organic chemistry》2005,70(20):8208-8211
[Chemical reaction: see text] Various substituted 2-aminotetrahydroazolopyridines and 2-aminohexahydroazolopyridines have been prepared by bromine-mediated addition of protected guanidine or urea to hydropyridine derivatives. The pH-dependent regioselective cleavage of the resulting aminal function led to the 2-aminoazole products III. The yields of the bicycles of type II, and their conversion into azoles III depends on the electronic properties of the substituents on the nitrogen of the tetrahydopyridine. 相似文献
149.
Etienne M Grosso D Boissière C Sanchez C Walcarius A 《Chemical communications (Cambridge, England)》2005,(36):4566-4568
We provide the first electrochemical evidence of permeability changes in continuous mesoporous TiO2 thin film electrodes induced by nanocrystallisation. 相似文献
150.
Díez D Sanchez JM Rodilla JM Rocha PM Mendes RS Paulino C Marcos IS Basabe P Urones JG 《Molecules (Basel, Switzerland)》2005,10(8):1005-1009
Incubation of sclareol with Rhizopus stolonifer affords in high yield a mixture of triols with 18-hydroxy-sclareol as the main component. 相似文献