866 research outputs found

    Distribution et détection du Sirococcus clavigignenti-juglandacearum au Québec

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    La maladie du chancre du noyer cendré, causée par le Sirococcus clavigignenti-juglandacearum, affecte principalement le noyer cendré, Juglans cinerea, bien que le noyer noir, Juglans nigra, et les noyers hybrides puissent en être atteints. La maladie est présente dans plusieurs États américains ainsi qu'en Ontario et au Québec. Au Québec, elle a été rapportée pour la première fois en 1990, dans la région de Fort-Coulonge, en Outaouais. Depuis, de nouveaux foyers d'infection ont été notés en forêt naturelle ainsi que dans une plantation. En 1995, elle a été observée pour la première fois sur des semis de noyer dans deux pépinières forestières québécoises. Cette détection constitue le premier cas documenté de la maladie sur des semis de noyer cendré et de noyer noir dans des pépinières forestières.Although the Sirococcus canker of butternut, caused by Sirococcus clavigignenti-juglandacearum, has caused damage only to butternut, Juglans cinerea, black walnut, Juglans nigra, and hybrids of walnut are also susceptible to a certain degree. The disease is present in the United States, in Ontario and in Quebec. In Quebec, the disease was first reported in 1990 near Fort-Coulonge, in the Outaouais region. Since then, new infection sites have been observed in natural stands and in one plantation. In 1995, this disease was isolated for the first time from seedlings in two forest nurseries in Quebec. This constitutes the first report of the disease on butternut and black walnut seedlings in forest nurseries

    Multiple cyclical fractional structures in financial time series

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    This paper analyses multiple cyclical structures in financial time series. In particular, we focus on the monthly structure of the Nasdaq, the Dow Jones and the Standard&Poor stock market indices. The three series are modelled as long-memory processes with poles in the spectrum at multiple frequencies, including the long-run or zero frequency

    A probabilistic approach to some results by Nieto and Truax

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    In this paper, we reconsider some results by Nieto and Truax about generating functions for arbitrary order coherent and squeezed states. These results were obtained using the exponential of the Laplacian operator; more elaborated operational identities were used by Dattoli et al. \cite{Dattoli} to extend these results. In this note, we show that the operational approach can be replaced by a purely probabilistic approach, in the sense that the exponential of derivatives operators can be identified with equivalent expectation operators. This approach brings new insight about the kinks between operational and probabilistic calculus.Comment: 2nd versio

    Explicit representations of biorthogonal polynomials

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    Given a parametrised weight function ω(x,μ)\omega(x,\mu) such that the quotients of its consecutive moments are M\"obius maps, it is possible to express the underlying biorthogonal polynomials in a closed form \cite{IN2}. In the present paper we address ourselves to two related issues. Firstly, we demonstrate that, subject to additional assumptions, every such ω\omega obeys (in xx) a linear differential equation whose solution is a generalized hypergeometric function. Secondly, using a generalization of standard divided differences, we present a new explicit representation of the underlying orthogonal polynomials

    The role of color and attention-to-color in mirror-symmetry perception

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    The role of color in the visual perception of mirror-symmetry is controversial. Some reports support the existence of color-selective mirror-symmetry channels, others that mirror-symmetry perception is merely sensitive to color-correlations across the symmetry axis. Here we test between the two ideas. Stimuli consisted of colored Gaussian-blobs arranged either mirror-symmetrically or quasi-randomly. We used four arrangements: (1)‘segregated’ – symmetric blobs were of one color, random blobs of the other color(s); (2)‘random-segregated’ – as above but with the symmetric color randomly selected on each trial; (3)‘non-segregated’ – symmetric blobs were of all colors in equal proportions, as were the random blobs; (4)‘anti-symmetric’ – symmetric blobs were of opposite-color across the symmetry axis. We found: (a) near-chance levels for the anti-symmetric condition, suggesting that symmetry perception is sensitive to color-correlations across the symmetry axis; (b) similar performance for random-segregated and non-segregated conditions, giving no support to the idea that mirror-symmetry is color selective; (c) highest performance for the color-segregated condition, but only when the observer knew beforehand the symmetry color, suggesting that symmetry detection benefits from color-based attention. We conclude that mirror-symmetry detection mechanisms, while sensitive to color-correlations across the symmetry axis and subject to the benefits of attention-to-color, are not color selectiv

    Scalar Casimir Effect on a D-dimensional Einstein Static Universe

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    We compute the renormalised energy momentum tensor of a free scalar field coupled to gravity on an (n+1)-dimensional Einstein Static Universe (ESU), RxS^n, with arbitrary low energy effective operators (up to mass dimension n+1). A generic class of regulators is used, together with the Abel-Plana formula, leading to a manifestly regulator independent result. The general structure of the divergences is analysed to show that all the gravitational couplings (not just the cosmological constant) are renormalised for an arbitrary regulator. Various commonly used methods (damping function, point-splitting, momentum cut-off and zeta function) are shown to, effectively, belong to the given class. The final results depend strongly on the parity of n. A detailed analytical and numerical analysis is performed for the behaviours of the renormalised energy density and a quantity `sigma' which determines if the strong energy condition holds for the `quantum fluid'. We briefly discuss the quantum fluid back-reaction problem, via the higher dimensional Friedmann and Raychaudhuri equations, observe that equilibrium radii exist and unveil the possibility of a `Casimir stabilisation of Einstein Static Universes'.Comment: 37 pages, 15 figures, v2: minor changes in sections 1, 2.5, 3 and 4; version published in CQ

    A new class of coherent states with Meixner-Pollaczek polynomials for the Gol'dman-Krivchenkov Hamiltonian

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    A class of generalized coherent states with a new type of the identity resolution are constructed by replacing the labeling parameter zn/n! of the canonical coherent states by Meixner-Pollaczek polynomials with specific parameters. The constructed coherent states belong to the state Hilbert space of the Gol'dman-Krivchenkov Hamiltonian.Comment: 10 pages, Submitte

    Use of inverse PCR to amplify and sequence breakpoints of HPRT deletion and translocation mutations

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    Deletion and translocation mutations have been shown to play a significant role in the genesis of many cancers. The hprt gene located at Xq26 is a frequently used marker gene in human mutational studies. In an attempt to better understand potential mutational mechanisms involved in deletions and translocations, inverse PCR (IPCR) methods to amplify and sequence the breakpoints of hprt mutants classified as translocations and large deletions were developed. IPCR involves the digestion of DNA with a restriction enzyme, circularization of the fragments produced, and PCR amplification around the circle with primers oriented in a direction opposite to that of conventional PCR. The use of this technique allows amplification into an unknown region, in this case through the hprt breakpoint into the unknown joined sequence. Through the use of this procedure, two translocation, one inversion, and two external deletion hprt breakpoint sequences were isolated and sequenced. The isolated IPCR products range in size from 0.4 to 1.8 kb, and were amplified from circles ranging in size from 0.6 to 7.7 kb. We have shown that inverse PCR is useful to sequence translocation and large deletion mutant breakpoints in the hprt gene. Environ. Mol. Mutagen. 39:22–32, 2002 © 2002 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35019/1/10040_ftp.pd
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