163 research outputs found
Anderson Localization in a String of Microwave Cavities
The field distributions and eigenfrequencies of a microwave resonator which
is composed of 20 identical cells have been measured. With external screws the
periodicity of the cavity can be perturbed arbitrarily. If the perturbation is
increased a transition from extended to localized field distributions is
observed. For very large perturbations the field distributions show signatures
of Anderson localization, while for smaller perturbations the field
distribution is extended or weakly localized. The localization length of a
strongly localized field distribution can be varied by adjusting the
penetration depth of the screws. Shifts in the frequency spectrum of the
resonator provide further evidence for Anderson localization.Comment: 7 pages RevTex, to be published in Phys. Rev.
THE IMPACT OF FEDERALISM ON EDUCATION FINANCE: A COMPARATIVE ANALYSIS *
Drawing on the implications suggested by several recent studies in comparative public policy, this article examines the impact of the structure of intergovernmental relations on the patterns of distribution of educational funds. The fundamental hypothesis underlying this analysis is that differences in this structure, and in particular the distinction between federal and unitary systems of government, are systematically related to differences in distribution across and within nations. The variations in total educational allocations among eighteen nations in Europe and North America are considered in order to discover whether the aggregate funding of education, relative to a nation's wealth, is related to the structure of intergovernmental relations. Then, in a more intensive analysis, the intranational patterns of distribution are compared in four federal and four unitary systems. This analysis suggests that there is a significant difference between the two types of system in the degree to which educational policy outputs equalize the territorial disparities in wealth and effect a redistribution of funds within the nation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74630/1/j.1475-6765.1974.tb00752.x.pd
Wave Dynamical Chaos in a Superconducting Three-Dimensional Sinai Billiard
Based on very accurate measurements performed on a superconducting microwave
resonator shaped like a desymmetrized three-dimensional (3D) Sinai billiard, we
investigate for the first time spectral properties of the vectorial Helmholtz,
i.e. non-quantum wave equation for a classically totally chaotic and
theoretically precisely studied system. We are thereby able to generalize some
aspects of quantum chaos and present some results which are consequences of the
polarization features of the electromagnetic waves.Comment: 4 pages RevTex; 4 postscript figures; to be published in Phys. Rev.
Lett.; Info: [email protected]
Experimental vs. Numerical Eigenvalues of a Bunimovich Stadium Billiard -- A Comparison
We compare the statistical properties of eigenvalue sequences for a gamma=1
Bunimovich stadium billiard. The eigenvalues have been obtained by two ways:
one set results from a measurement of the eigenfrequencies of a superconducting
microwave resonator (real system) and the other set is calculated numerically
(ideal system). The influence of the mechanical imperfections of the real
system in the analysis of the spectral fluctuations and in the length spectra
compared to the exact data of the ideal system are shown. We also discuss the
influence of a family of marginally stable orbits, the bouncing ball orbits, in
two microwave stadium billiards with different geometrical dimensions.Comment: RevTex, 8 pages, 8 figures (postscript), to be published in Phys.
Rev.
Mode Fluctuation Distribution for Spectra of Superconducting Microwave Billiards
High resolution eigenvalue spectra of several two- and three-dimensional
superconducting microwave cavities have been measured in the frequency range
below 20 GHz and analyzed using a statistical measure which is given by the
distribution of the normalized mode fluctuations. For chaotic systems the limit
distribution is conjectured to show a universal Gaussian, whereas integrable
systems should exhibit a non-Gaussian limit distribution. For the investigated
Bunimovich stadium and the 3D-Sinai billiard we find that the distribution is
in good agreement with this prediction. We study members of the family of
limacon billiards, having mixed dynamics. It turns out that in this case the
number of approximately 1000 eigenvalues for each billiard does not allow to
observe significant deviations from a Gaussian, whereas an also measured
circular billiard with regular dynamics shows the expected difference from a
Gaussian.Comment: 7 pages, RevTex, 5 postscript figure, to be published in Phys. Rev.
E. In case of any problems contact A. Baecker ([email protected]) or H.
Rehfeld ([email protected]
Coupled Microwave Billiards as a Model for Symmetry Breaking
Two superconducting microwave billiards have been electromagnetically coupled
in a variable way. The spectrum of the entire system has been measured and the
spectral statistics analyzed as a function of the coupling strength. It is
shown that the results can be understood in terms of a random matrix model of
quantum mechanical symmetry breaking -- as e.g. the violation of parity or
isospin in nuclear physics.Comment: 4 pages, 5 figure
Genomic architecture of potato resistance to Synchytrium endobioticum disentangled using SSR markers and the 8.3k SolCAP SNP genotyping array
BACKGROUND: The soil borne, obligate biotrophic fungus Synchytrium endobioticum causes tumor-like tissue proliferation (wart) in potato tubers and thereby considerable crop damage. Chemical control is not effective and unfriendly to the environment. S. endobioticum is therefore a quarantined pathogen. The emergence of new pathotypes of the fungus aggravate this agricultural problem. The best control of wart disease is the cultivation of resistant varieties. Phenotypic screening for resistant cultivars is however time, labor and material intensive. Breeding for resistance would therefore greatly benefit from diagnostic DNA markers that can be applied early in the breeding cycle. The prerequisite for the development of diagnostic DNA markers is the genetic dissection of the factors that control resistance to S. endobioticum in various genetic backgrounds of potato. RESULTS: Progeny of a cross between a wart resistant and a susceptible tetraploid breeding clone was evaluated for resistance to S. endobioticum pathotypes 1, 2, 6 and 18 most relevant in Europe. The same progeny was genotyped with 195 microsatellite and 8303 single nucleotide polymorphism (SNP) markers. Linkage analysis identified the multi-allelic locus Sen1/RSe-XIa on potato chromosome XI as major factor for resistance to all four S. endobioticum pathotypes. Six additional, independent modifier loci had smaller effects on wart resistance. Combinations of markers linked to Sen1/RSe-XIa resistance alleles with one to two additional markers were sufficient for obtaining high levels of resistance to S. endobioticum pathotypes 1, 2, 6 and 18 in the analyzed genetic background. CONCLUSIONS: Potato resistance to S. endobioticum is oligogenic with one major and several minor resistance loci. It is composed of multiple alleles for resistance and susceptibility that originate from multiple sources. The genetics of resistance to S. endobioticum varies therefore between different genetic backgrounds. The DNA markers described in this paper are the starting point for pedigree based selection of cultivars with high levels of resistance to S. endobioticum pathotypes 1, 2, 6 and 18. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12863-015-0195-y) contains supplementary material, which is available to authorized users
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