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K. J. Siemsen A. A. Madej G. R. Hanes J. Reid 《Applied physics. B, Lasers and optics》1992,55(2):126-131
A sodium-filled Fabry-Perot resonator shows many different types of irregular behavior. A sophisticated experimental apparatus allows reproducible measurements of oscillation scenarios leading to chaos and thus permits a detailed classification of the different phenomena. A quantitative explanation — featuring a new mechanism — for the best reproducible class of chaotic oscillations is given. 相似文献
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F. Evers R. D. L. Hanes C. Zunke R. F. Capellmann J. Bewerunge C. Dalle-Ferrier M. C. Jenkins I. Ladadwa A. Heuer R. Castañeda-Priego S. U. Egelhaaf 《The European physical journal. Special topics》2013,222(11):2995-3009
The dynamics of colloidal particles in potential energy landscapes have mainly been investigated theoretically. In contrast, here we discuss the experimental realization of potential energy landscapes with the help of laser light fields and the observation of the particle dynamics by video microscopy. The experimentally observed dynamics in periodic and random potentials are compared to simulation and theoretical results in terms of, e.g. the mean-squared displacement, the time-dependent diffusion coefficient or the non-Gaussian parameter. The dynamics are initially diffusive followed by intermediate subdiffusive behaviour which again becomes diffusive at long times. How pronounced and extended the different regimes are, depends on the specific conditions, in particular the shape of the potential as well as its roughness or amplitude but also the particle concentration. Here we focus on dilute systems, but the dynamics of interacting systems in external potentials, and thus the interplay between particle-particle and particle-potential interactions, are also mentioned briefly. Furthermore, the observed dynamics of dilute systems resemble the dynamics of concentrated systems close to their glass transition, with which it is compared. The effect of certain potential energy landscapes on the dynamics of individual particles appears similar to the effect of interparticle interactions in the absence of an external potential. 相似文献
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The effects of nuclear spin-spin coupling are included in the analysis of the nuclear hyperfine structure of the R(127) line of the 11-5 band in the B-X electronic band system of I2. The fit to the experimental data is improved over earlier fits in which only the effects of nuclear spin-rotation interaction and nuclear electric quadrupole coupling were considered. The electron-coupled contribution to the spin-spin constant of the upper state is determined to be dE = ?36.3 ± 8.5 kHz. However, the fit (standard deviation = 59.8 kHz) is still not at the level of the experimental precision (40 kHz) and further measurements are in progress to test the model used for the hfs hamiltonian. 相似文献
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For l, an -triangulation F of a planar domain is such that,for every T F, there holds 1 RT/2rT , where RT (resp. rT)denotes the radius of the circumscribed (resp. inscribed) circleof the triangle T. When T is varying in F the centre of itsinscribed circle is varying in a compact interior to T and itsorthogonal projections on the sides are varying in compact intervalsinterior to these sides. Precise results are given about thesizes of these compacts and are used for the computation oferror constants in the problem of Hermite interpolation by Powell-Sabinquadratic finite elements, bringing to the fore their dependenceon the parameter . 相似文献
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Zhong Z Postnikova BJ Hanes RE Lynch VM Anslyn EV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(8):2385-2394
A series of synthetic receptors (4-6) incorporating metal ions, specifically copper(II), were examined for their ability to enhance the acidity of active methylene compounds. The copper(II) complexes were observed to reduce the pKa of 1,3-diketone carbon acids in acetonitrile by as much as 12 pKa units. The relatively large pKa reduction achieved by the complex is attributed to the electrostatic interaction between the anionic pi system of the enolate and the copper(II) ions. The cage structure and hydrogen bonding sites in receptors 4 and 5 lead to a very modest further enhancement of the acidity relative to that with 6. This study provides insight into the way in which metalloenzymes stabilize an enolate intermediate. 相似文献
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