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81.
The fluorescence lifetime of coronene and the rate of dipole-dipole energy transfer from coronene to rhodamine 6G in PMMA matrices were found to be temperature dependent. For both these photophysical processes an activation energy of about 500 cm?1 is obtained. The energy transfer results can be analyzed in terms of a model involving thermally activated energy transfer from excited states of coronene. 相似文献
82.
Reuven R. Rottenberg 《Israel Journal of Mathematics》1971,10(2):160-171
Given a finite set of points Γ0 which span a projective spaceP
3, we show here that a plane spanned by points of Γ0 can be a neighbour of at most eight points of Γ0, these being the vertices of a projective cube; the common neighbour plane is then elementary with the three only points
of Γ0 in it being diagonal points of the cube. This extends toP
3 some results of L. M. Kelly and W. O. J. Moser in the planeP
2. 相似文献
83.
Ray theory plays an important role in determining the propagation properties of high-frequency fields and their statistical measures in complicated random environments. According to the ray approach, the field at the observer can be synthesized from a variety of field species arriving along multiple ray trajectories resulting from refraction and scattering from boundaries and from scattering centers embedded in the random medium. For computations of the statistical measures, it is desirable therefore to possess a solution for the high-frequency field propagating along an isolated ray trajectory. For this reason, a new reference-wave method was developed to provide an analytic solution of the parabolic-wave equation. 相似文献
84.
Scale-free networks on lattices 总被引:1,自引:0,他引:1
We suggest a method for embedding scale-free networks, with degree distribution Pk approximately k(-lambda), in regular Euclidean lattices accounting for geographical properties. The embedding is driven by a natural constraint of minimization of the total length of the links in the system. We find that all networks with lambda>2 can be successfully embedded up to a (Euclidean) distance xi which can be made as large as desired upon the changing of an external parameter. Clusters of successive chemical shells are found to be compact (the fractal dimension is df=d), while the dimension of the shortest path between any two sites is smaller than 1: dmin=(lambda-2)/(lambda-1-1/d), contrary to all other known examples of fractals and disordered lattices. 相似文献
85.
Surface plasmon sensor based on the enhanced light transmission through arrays of nanoholes in gold films 总被引:5,自引:0,他引:5
Brolo AG Gordon R Leathem B Kavanagh KL 《Langmuir : the ACS journal of surfaces and colloids》2004,20(12):4813-4815
Arrays of nanoholes in a gold film were used to monitor the binding of organic and biological molecules to the metallic surface. This technique is particularly sensitive to surface binding events because it is based upon the resonant surface plasmon enhanced transmission through the array of nanoholes. The sensitivity was found to be 400 nm per refractive index unit, which is comparable to other grating-based surface plasmon resonance (SPR) devices. The array of nanoholes is well suited for dense integration in a sensor chip. Furthermore, the optical geometry is collinear, which simplifies the alignment with respect to the traditional Kretschmann (reflection) arrangement for SPR sensing. 相似文献
86.
Amatzya Y. Meyer Reuven Pasternak Jeffrey Sterling Naftali Lander Raphael Mechoulam 《Tetrahedron》1976,32(22):2805-2810
The bathochromic-hypochromic spectral shifts, observed in bicyclic enones that contain a 4- or a 3-membered ring, are discussed in molecular-mechanical and molecular-orbital terms. It is proposed that the effect, not only by the cyclopropane but also by the cyclobutane ring, is due to extension of the CCCO chromophore, and not to its mere distortion from “normal” geometry. The high-energy absorption of umbellulone (3), 220 nm in ethanol, is characterized as a second π-π*. 2-Methylbicyclo[3.2.1]oct-2-en-4-one (7) has been synthesized, and its preparation and spectrum are described. 相似文献
87.
A LCHO SCF-CI semiempirical scheme is formulated for compounds of carbon and hydrogen, and far-UV transition energies computed for a number of acyclic alkanes. The type of spectral bands (CH CH*, etc.) and symmetries of subbands are assigned, and their dependence on conformation and branching discussed. It is argued that, for pentanes and higher alkanes, spectral quantities can be estimated from data on the lower alkanes.Multi-Conformational Compounds, part X. For part IX, see Ref. [1]. 相似文献
88.
Reuven R. Rottenberg 《Journal of Geometry》1981,16(1):19-29
It is shown that if is a finite set of points in an ordered d-dimensional projective space, d2 and if all the hyperplanes spanned by points of are considered, then every such a hyperplane is visible from at most 2d distinct points of ; if a hyperplane bounds 2d distinct residences, then it contains exactly d points of . These results have been proved previously for d=2 and d=3.This paper is a revised version of results presented at the Conference on Geometry held at the University of Haifa (Israel), March. 10–13 (1975), [6]. 相似文献
89.
Derrida Bernard Jacobsen Jesper Lykke Zeitak Reuven 《Journal of statistical physics》2000,98(1-2):31-55
We calculate, using numerical methods, the Lyapunov exponent (E) and the density of states (E) at energy E of a one-dimensional non-Hermitian Schrödinger equation with off-diagonal disorder. For the particular case we consider, both (E) and (E) depend only on the modulus of E. We find a pronounced maximum of (|E|) at energy E=2/
, which seems to be linked to the fixed point structure of an associated random map. We show how the density of states (E) can be expanded in powers of E. We find (|E|)=(1/
2)+(4/3
3) |E|2+. This expansion, which seems to be asymptotic, can be carried out to an arbitrarily high order. 相似文献
90.
In microwaves, a TE-polarized rectangular-waveguide resonator with an inserted thin ferrite disk gives an example of a nonintegrable system. The interplay of reflection and transmission at the disk interfaces together with the material gyrotropy effect gives rise to whirlpool-like electromagnetic vortices in the proximity of the ferromagnetic resonance. Based on numerical simulation, we show that a character of microwave vortices in a cavity can be analyzed by means of consideration of equivalent magnetic currents. Maxwell equations allows introduction of a magnetic current as a source of the electromagnetic field. Specifically, we found that in such nonintegrable structures, magnetic gyrotropy and geometrical factors leads to the effect of symmetry breaking resulting in effective chiral magnetic currents and topological magnetic charges. As an intriguing fact, one can observe precessing behavior of the electric-dipole polarization inside a ferrite disk. 相似文献