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排序方式: 共有317条查询结果,搜索用时 377 毫秒
1.
2.
Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献
3.
The action of ultra violet rays of 260 nm on aqueous solutions of bases, nucleosides and nucleotides of DNA at 77°K is studied by electron spin resonance. It is shown that the free radicals observed are similar, with a few noteworthy exceptions to those induced by X-rays, under the same conditions of temperature, in the solid state. Contrary to what might be excepted on the basis of the results obtained by X-rays, the variation in the yield in paramagnetic centres in each sequence studied does not seem to be important. 相似文献
4.
ALBERT VAN DE VORST 《Photochemistry and photobiology》1971,13(4):321-336
Abstract— –The photosensitization of amino acids by proflavine is studied using the technique of electron spin resonance spectroscopy. The analysis of the line shape as a function of the incident microwave power (both in the presence and absence of oxygen) and the dependence of the numbers of free radicals on the intensity of the incident light allow one to suggest that two types of radicals are formed. One is formed by a biphotonic process, the nature of the radicals being the same as in the case of ionising radiation, while the other is probably the RO2 radical formed as a result of photodynamic action. 相似文献
5.
We attained tunable UV laser radiation between 195 and 198 nm by sum-frequency mixing two synchronized flashlamp-pumped solid-state Q-switch lasers, a Nd:YAG laser frequency quadrupled to 266 nm and a tunable (730–770 nm) alexandrite laser. UV pulse energies of 0.12 mJ with repetition rates of 10 Hz were attained in collinear, as well as non-collinear sum-frequency interaction in a-Barium Borate (BBO) crystal with a conversion efficiency of 2.5%. Theoretical models for the non-collinear phase-matching interaction were investigated at UV wavelengths below 200 nm. 相似文献
6.
BARB FLORIN DAN; IONESCU VLAD; KONING WILLEM DE 《IMA Journal of Mathematical Control and Information》1994,11(4):277-309
In this paper, we deal with the digital output-measurement-feedbackH control problem for Pritchard-Salamon infinite-dimensionalsystems with unbounded input and output operators. A discretePopov-theory-based solution is given in terms of the solvabilityof Kalman-Szegö-Popov-Yakubovitch systems associated withthe equivalent discrete-time time-invariant system obtainedby lifting the T-periodic continuous-time system. 相似文献
7.
M. Vogler 《Zeitschrift für Physik A Hadrons and Nuclei》1978,288(1):7-10
The velocity distributions of H-H fragment pairs arising from dissociative collisions of 10keV H 2 + ions incident on H2, He, and Ar were measured using a flight-time-difference method. The H 2 + ions were produced in an electron impact ion source at two different electron energies, at 100eV and 18eV. The influence of the electron energy on the fragment velocity distributions is studied. Conclusions are drawn on the processes which lead to the formation of neutral fragment pairs. Electron capture into the repulsive b3 Σ u + state of H2 plays a dominant role. 相似文献
8.
A new phenolic glucoside gallate, vanillic acid 4-O-beta-D-(6'-O-galloyl) glucopyranoside (1) was isolated from the bark of Terminalia macroptera Guill.et Perr., together with 3,3',4'-tri-O-methylellagic acid (2) and two triterpene glucopyranosyl esters, 24-deoxysericoside (3) and chebuloside II (4). Compounds 2-4, not described previously for this plant, showed antimicrobial activities against Bacillus subtilis, while 3 and 4 possessed haemolytic properties. In both assays 1 was found to be inactive. 相似文献
9.
The intermolecular cyclotrimerisation of terminal and internal alkynes can be catalysed by simple cobalt complexes such as a CoBr2(diimine) under mild reaction conditions when treated with zinc and zinc iodide with high regioselectivity in excellent yields. 相似文献
10.
Zusammenfassung Mit Hilfe von Berechnungen der Polansky-Charakterordnungen, der magnetischen Suszeptibilitäten und der chemischen Verschiebungen (1H-NMR) im Rahmen der HMO-Theorie wird gezeigt, daß Corannulene nicht als makrocyclische Annulensysteme aufgefaßt werden können.
Teilweise vorgetragen auf dem VII. Symposium für Theoretische Chemie vom 29. 3. bis 2. 4. 1971 in Göttingen.
Wir danken den Herren Prof. O. E. Polansky und Prof. G. Derflinger für hilfreiche Diskussionen, der Deutschen Forschungsgemeinschaft für die Unterstützung dieser Arbeit und dem Rechenzentrum der Universität Heidelberg für die Gewährung von Rechenzeit auf der IBM 360/44. 相似文献
Conjugation in macrocyclic bonding systems XX. Order of character, magnetic susceptibility and chemical shifts of corannulenes
By means of calculations of the Polansky character order, ring current contributions to the magnetic susceptibilities and to the chemical shift in the Hückel approximation, it is shown, that corannulenes cannot be treated as macrocyclic annulenes.
Résumé Des calculs des caractères annulènoides, des contributions du courant cyclique à la susceptibilité magnétique et aux déplacements chimiques dans la méthode de HMO montrent, que les corannulènes ne peuvent pas considérer comme des annulènes macrocycliques.
Teilweise vorgetragen auf dem VII. Symposium für Theoretische Chemie vom 29. 3. bis 2. 4. 1971 in Göttingen.
Wir danken den Herren Prof. O. E. Polansky und Prof. G. Derflinger für hilfreiche Diskussionen, der Deutschen Forschungsgemeinschaft für die Unterstützung dieser Arbeit und dem Rechenzentrum der Universität Heidelberg für die Gewährung von Rechenzeit auf der IBM 360/44. 相似文献