1,054 research outputs found

    The Cancer Transition in Japan since 1951

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    The overall trend of cancer mortality in Japan has been decreasing since the 1960s (age-standardized death rates for ages 30-69), though trends differ enormously among various forms of the disease. Cancer mortality was heavily influenced by Japanese postwar economic recovery, which led to improved living conditions and better control of infectious agents known to cause some common forms of cancer (stomach, cervical). However, Japanese wealth and development have also been associated with risky personal behaviors (smoking, drinking) and other conditions, leading to increases in cancers with no known or else very weak links to infection. This shift away from infectious and toward non-infectious causes of prevalent forms of cancers is called the "cancer transition," by analogy to Omran's "epidemiologic transition." We suggest that the cancer transition described here in the case of Japan must be a part of efforts to revise and update the epidemiologic transition, which should incorporate new knowledge about the role of infection in chronic disease morbidity and mortality.cancer, cancer transition, epidemiologic transition, health, health and development, infectious diseases, Japan, mortality, non-infectious disease

    On the algorithmic construction of classifying spaces and the isomorphism problem for biautomatic groups

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    We show that the isomorphism problem is solvable in the class of central extensions of word-hyperbolic groups, and that the isomorphism problem for biautomatic groups reduces to that for biautomatic groups with finite centre. We describe an algorithm that, given an arbitrary finite presentation of an automatic group Γ\Gamma, will construct explicit finite models for the skeleta of K(Γ,1)K(\Gamma,1) and hence compute the integral homology and cohomology of Γ\Gamma.Comment: 21 pages, 4 figure

    Soft-core meson-baryon interactions. I. One-hadron-exchange potentials

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    The Nijmegen soft-core model for the pseudoscalar-meson baryon interaction is derived, analogous to the Nijmegen NN and YN models. The interaction Hamiltonians are defined and the resulting amplitudes for one-meson-exchange and one-baryon-exchange in momentum space are given for the general mass case. The partial wave projection is carried through and explicit expressions for the momentum space partial wave meson-baryon potentials are presented.Comment: 25 pages, 2 PostScript figures, revtex4, submitted to Phys. Rev.

    SOME DUALITY CONJECTURES FOR FINITE GRAPHS AND THEIR GROUP THEORETIC CONSEQUENCES

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    Primitive Words, Free Factors and Measure Preservation

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    Let F_k be the free group on k generators. A word w \in F_k is called primitive if it belongs to some basis of F_k. We investigate two criteria for primitivity, and consider more generally, subgroups of F_k which are free factors. The first criterion is graph-theoretic and uses Stallings core graphs: given subgroups of finite rank H \le J \le F_k we present a simple procedure to determine whether H is a free factor of J. This yields, in particular, a procedure to determine whether a given element in F_k is primitive. Again let w \in F_k and consider the word map w:G x G x ... x G \to G (from the direct product of k copies of G to G), where G is an arbitrary finite group. We call w measure preserving if given uniform measure on G x G x ... x G, w induces uniform measure on G (for every finite G). This is the second criterion we investigate: it is not hard to see that primitivity implies measure preservation and it was conjectured that the two properties are equivalent. Our combinatorial approach to primitivity allows us to make progress on this problem and in particular prove the conjecture for k=2. It was asked whether the primitive elements of F_k form a closed set in the profinite topology of free groups. Our results provide a positive answer for F_2.Comment: This is a unified version of two manuscripts: "On Primitive words I: A New Algorithm", and "On Primitive Words II: Measure Preservation". 42 pages, 14 figures. Some parts of the paper reorganized towards publication in the Israel J. of Mat

    Abelian subgroups of Garside groups

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    In this paper, we show that for every abelian subgroup HH of a Garside group, some conjugate g1Hgg^{-1}Hg consists of ultra summit elements and the centralizer of HH is a finite index subgroup of the normalizer of HH. Combining with the results on translation numbers in Garside groups, we obtain an easy proof of the algebraic flat torus theorem for Garside groups and solve several algorithmic problems concerning abelian subgroups of Garside groups.Comment: This article replaces our earlier preprint "Stable super summit sets in Garside groups", arXiv:math.GT/060258

    Beat-wave generation of plasmons in semiconductor plasmas

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    It is shown that in semiconductor plasmas, it is possible to generate large amplitude plasma waves by the beating of two laser beams with frequency difference close to the plasma frequency. For narrow gap semiconductors (for example n-type InSb), the system can simulate the physics underlying beat wave generation in relativistic gaseous plasmas.Comment: 11 pages, LaTex, no figures, no macro

    Anomalous spectral scaling of light emission rates in low dimensional metallic nanostructures

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    The strength of light emission near metallic nanostructures can scale anomalously with frequency and dimensionality. We find that light-matter interactions in plasmonic systems confined in two dimensions (e.g., near metal nanowires) strengthen with decreasing frequency owing to strong mode confinement away from the surface plasmon frequency. The anomalous scaling also applies to the modulation speed of plasmonic light sources, including lasers, with modulation bandwidths growing at lower carrier frequencies. This allows developing optical devices that exhibit simultaneously femto-second response times at the nano-meter scale, even at longer wavelengths into the mid IR, limited only by non-local effects and reversible light-matter coupling
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