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171.
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
172.
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
173.
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
174.
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
175.
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
176.
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
177.
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
178.
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
179.
180.
Convex Transitive Norms on Spaces of Continuous Functions 总被引:1,自引:0,他引:1
A norm on a Banach space X is called maximal when no equivalentnorm has a larger group of isometries. If, besides this, thereis no equivalent norm with the same isometries (apart from itsscalar multiples), the norm is said to be uniquely maximal,which is equivalent to the convex-transitivity of X: the convexhull of the orbits under the action of the isometry group onthe unit sphere is dense in the unit ball of X. The main resultof the paper is that the complex C0() is convex-transitive inits natural supremum norm if is a connected manifold (withoutboundary). As a complement, it is shown that if is a connectedmanifold of dimension at least two, then the diameter norm isconvex transitive on the corresponding space of real functions.2000 Mathematics Subject Classification 46B15, 47B99 相似文献