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  • 11
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 48 (1983), S. 1471-1474 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 444 (2006), S. 1003-1004 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Although quantifying the quality of individual scientists is difficult, the general view is that it is better to publish more than less and that the citation count of a paper (relative to citation habits in its field) is a useful measure of its quality. How citation counts are weighed and analysed ...
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 444 (2006), S. 56-60 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It has been proposed that the efficacy of neuronal connections is strengthened when there is a persistent causal relationship between presynaptic and postsynaptic activity. Such activity-dependent plasticity may underlie the reorganization of cortical representations during learning, although ...
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] After the completion of a draft human genome sequence, the International Human Genome Sequencing Consortium has proceeded to finish and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human ...
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Human chromosome 12 contains more than 1,400 coding genes and 487 loci that have been directly implicated in human disease. The q arm of chromosome 12 contains one of the largest blocks of linkage disequilibrium found in the human genome. Here we present the finished sequence of human ...
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 402 (1999), S. 457-457 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sir Monsanto's decision to abandon ‘terminator’ technology has been welcomed by those concerned about the genetic modification of food crops. The public perception is that this technology would force farmers in the developing world to purchase expensive seed year ...
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 424 (2003), S. 760-763 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A large number of high-accuracy vector measurements of the Earth's magnetic field have recently become available from the satellite Oersted, complementing previous vector data from the satellite Magsat, which operated in 1979/80. These data can be used to infer the morphology of the ...
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 103 (1990), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Remanent and induced magnetization occurs in crustal materials when they are below their Curie temperature, and we consider the problem of determining the magnetic field originating in the earth's core in the presence of such magnetization. Simple physical models of induced magnetization which have been proposed and which lead to deterministic effects account for only a small proportion of the high-degree internal field found using Magsat data, and thus a stochastic description appears more useful. We investigate the effect of remanent magnetization in the crust on satellite measurements of the core magnetic field by posing the question: if the crustal magnetization is correlated only on the shortest possible length-scale, and different components are uncorrelated everywhere, what is the correlation lengthscale at a radius above the earth's surface? Using an idea due to Parker (1988), we model the crust as a zero-mean, stationary, Gaussian random process. We show that the matrix of second-order statistics is proportional to the Gram matrix, which depends only on the inner-products of the appropriate Green's functions, and that at a typical satellite altitude of 400 km the data are correlated out to an angular separation of approximately 15°. Accurate and efficient means of calculating the matrix elements are given. This theory leads to a more conservative form for the correlation in the data than that previously given by Langel, Estes & Sabaka (1989), whilst not being incommensurate with the imprecisely known high-degree power spectrum. Previous studies examining the core field have treated satellite data as independent, and have given different orthogonal components equal weight. Both these assumptions are incorrect, and we show that the variance of measurements of the radial component of magnetic field due to the crust is expected to be approximately twice that in horizontal components. However, the size of the crustal effect is small compared to the random noise in the data, and may not lead to radically different results from those already published.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 119 (1994), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We present a general statistical theory for relating magnetic fields to the magnetization of their source region, when the geometry of the source is spherical and the magnetization is a realization of a stationary, isotropic random process. For the case of Gaussian statistics, considered here, the second-order statistics are sufficient to determine the process uniquely. Observed high-degree coefficients from a spherical-harmonic expansion of the field appear to be consistent with this model. We find simple models of crustal magnetization that are compatible with observational constraints, namely the values of the magnetic power spectra believed to be derived from the crust, and the total crustal power. Any statistical model of the crust can be used to ‘pre-whiten’ observations prior to modelling the core field in a way described previously by Jackson.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 105 (1991), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We examine the problem of determining the fluid flow and the shear (the radial derivative of the flow) at the core surface given a model of the temporal variation of the magnetic field. Whereas most previous work has focused on determining only the flow, which requires only the use of the radial component of the magnetic field, here, in addition, we determine the shear for which we must use the horizontal component of the magnetic field. Estimates of the jump in the value of the horizontal magnetic field Bh across the boundary layer between the top of the free stream and the base of the mantle are small, and suggest that to a high level of accuracy the mantle values of Bh can be used at the top of the core. Except in the special case of an insulating mantle, only the horizontal poloidal field is known at the core-mantle boundary and supplies one extra equation for the determination of velocity and shear. We show how the matrix elements relating the coefficients of the spectral expansion of the flow and shear are related to the geomagnetic secular variation coefficients in closed form. We examine the uniqueness of the resulting inverse problem, and show that one part of the non-uniqueness from which the shear suffers is particularly easy to describe: it takes the same form as that which affects the flow, namely a toroidal ambiguity in the field u′Br. However, certain uniqueness theorems can be derived: we extend the steady motions theorem of Voorhies & Backus (1985) and the geostrophic motions theorem of Hills (1979) and Backus & LeMouël (1986) to the determination of the flow and shear, and derive closely analogous results. Uniqueness in the steady case depends on the value of the same discriminant as the velocity, and in the geostrophic case the shear can be determined uniquely in the same areas as can the velocity (i.e. outside certain ambiguous patches). For the geostrophic regime, the lateral density (or temperature) variations at the top of the core can be found in a self-consistent manner. We apply our method to the temporal evolution of the field over the period 1960–1980, and produce solutions for each of the assumptions of unconstrained steady motions, geostrophic motions, and purely toroidal motions. We find that the form of the flow changes very little from solutions based only on the radial induction equation, and that the shear is weak and aligned with the flow, with a sense such that the strength of the flow decreases with depth with a length-scale for linear decay of half the core radius. This suggests that the flow near the core surface is indicative of whole core flow, rather than a flow confined to a layer near the core surface.
    Type of Medium: Electronic Resource
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