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951.
Time evolution of second-order nonlinear profiles induced within thermally poled silica samples 总被引:1,自引:0,他引:1
The second-order nonlinear profile induced within thermally poled Infrasil silica samples is characterized as a function of the duration of the poling process. For poling durations shorter than 5 min the spatial distribution of the chi(2) susceptibility exhibits a triangular shape. This observation, as well as the maximum value of the electric field recorded during poling (1.9 x 10(9) V/m), is in excellent agreement with charge migration models that involve a single charge carrier. It is shown that for higher poling durations the nonlinear profiles tend to flatten; in that case the charge injection mechanisms cannot be neglected. For another point of view, the experimental method introduced herein has allowed us to determine the mobility of the rapid charge carrier involved in the poling process: micro = 1.5 x 10(-15) m2 V(-1) s(-1) at 250 degrees C. 相似文献
952.
We analyze the influence of heat generation caused by nonradiative transitions in a high-power 1.55 microm double-clad erbium-ytterbium fiber laser on the Stark level population. At strong pumping rates, 1 microm lasing can start as a result of parasitic reflections. We present a model that allows us to simulate the effect of self-generated heat on the Stark level population by using the MacCumber relation. Heat generation plays a significant role and improves the 1.5 microm laser's efficiency by increasing the 1 microm lasing threshold. 相似文献
953.
Yves Colin de Verdiere 《Mathematische Zeitschrift》1980,171(1):51-73
Sans résumé 相似文献
954.
955.
Addition of a trivalent phosphorus compound to dimethyl acetylenedicarboxylate gives a carbanionic species which can be trapped by dimethyl acetylenedicarboxylate; a trialkoxy-1,1,1 phospholev is obtained. 相似文献
956.
Photo-stimulated field emission of electrons is shown using a barium covered tungsten tip illuminated by a focused laser beam. The laser is a low power (1 mW) HeNe type emitting a 6328 Å (1.96 eV) radiation. The pattern given by photoelectrons shows that high work function planes such as (011), (121), (211) which are dark in field emission pattern become bright in photo-stimulated field emission pattern. 相似文献
957.
958.
Julie Schobing Valérie Tschamber Jean-François Brilhac Aglaé Auclaire Yves Hohl 《Comptes Rendus Chimie》2018,21(3-4):221-231
Simultaneous NOx reduction and soot combustion over a commercial vanadia-based selective catalytic reduction (SCR) catalyst were investigated. Carbon black was used as model soot. The impact of the contact intensity between carbon and catalyst was studied. The experiments appeared as promising results for the utilization of vanadia-based SCR catalysts in SCR on filter system as, in the SCR operating temperature range (250–400 °C), no significant impact of the presence of carbon black on NOx reduction was observed. However, a decrease in the specific carbon oxidation rate was highlighted. This latter increases with the contact between carbon and catalyst and is attributed to a lack of NO2, consumed by the fast SCR reaction. At temperatures greater than 400 °C, the contact between carbon particles and the SCR catalyst partially inhibits the NOx reduction, whereas it exhibits a catalytic effect on the carbon oxidation rate. The tighter the contact between the two materials, the more significant is this behavior. A redox mechanism, which competes with the redox cycle of the SCR mechanism, was proposed. The impregnation of a V-based SCR catalyst with 2 wt % of calcium was also performed. A drastic loss of DeNOx activity was observed, whereas the effect of the contact between carbon and catalyst was reduced. 相似文献
959.
Taking Photochromism beyond Visible: Direct One‐Photon NIR Photoswitches Operating in the Biological Window
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Kristin Klaue Yves Garmshausen Prof. Stefan Hecht 《Angewandte Chemie (International ed. in English)》2018,57(5):1414-1417
The success of photopharmacology is inevitably tied to the availability of photoswitches, which can be operated within the biological window (λ=650–1450 nm) to maximize penetration in tissue. A general design strategy has been devised and a dihydropyrene derivative is described here that displays negative T‐type photochromism, allowing for efficient and nearly quantitative (95 %) switching induced by NIR light λ>800 nm. The thermal half‐life of the decolored ring‐open meta‐cyclophanediene isomer ranges from minutes to hours, depending on the solvent polarity and hence serves as a probe of the local environment. Due to the rather subtle geometrical differences between the two isomers, suitably modified NIR photoswitches are potential candidates for switching when bound in the pocket of the biological target, in principle allowing for reversible light‐induced inhibitor deactivation as an alternative approach to externally regulate biological functions. 相似文献
960.
Yves Fé lix Aniceto Murillo 《Proceedings of the American Mathematical Society》1998,126(2):625-627
Let be the group of homotopy classes of self-homotopy equivalences of such that . We prove that is a nilpotent group and that .