883 research outputs found

    De moeder het kind van de rekening

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    Quasi dynamical symmetry in an interacting boson model phase transition

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    The oft-observed persistence of symmetry properties in the face of strong symmetry-breaking interactions is examined in the SO(5)-invariant interacting boson model. This model exhibits a transition between two phases associated with U(5) and O(6) symmetries, respectively, as the value of a control parameter progresses from 0 to 1. The remarkable fact is that, for intermediate values of the control parameter, the model states exhibit the characteristics of its closest symmetry limit for all but a relatively narrow transition region that becomes progressively narrower as the particle number of the model increases. This phenomenon is explained in terms of quasi-dynamical symmetry.Comment: 4 figure

    De Doelen Declaration

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    Perinatale sterfte: een N=1 studie.

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    Relapsing fever, a disappearing cause of fever and maternal death in Sengerema, Tanzania, east Africa

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    Objective: To study the incidence of tick borne relapsing fever (TBRF) during the last 50 years, once like malaria an endemic disease in Sengerema, Tanzania.Design: By analyzing the annual reports, focusing on the number of admissions, maternal deaths, blood smears of patients with fever for Borrelia.Setting: Sengerema district, Tanzania.Subject: Admissions in Sengerema Hospital due to TBRF.Main Outcome Measures: From 1960 to 2010, we analyzed the incidence of TBRF.Result: Forty annual admissions in the sixties/seventies, 200 in the eighties (range from 37 in 1964 to 455 in 1988), dropping to 30 in the nineties. For the last nine years no Borrelia spirochetes were found in blood smears at the laboratory anymore and no admissions for TBRF were  registered. The number of maternal deaths due to relapsing fever  decreased simultaneously; the last one recorded was in 2002.Conclusion: During the last century, we have witnessed the disappearing of tick borne relapsing fever in Sengerema. Increase of gold mining,  improved local economy, housing and standards of living after the nineties resulted in an almost complete eradication of the incidence of TBRF

    Measurement of the local Jahn-Teller distortion in LaMnO_3.006

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    The atomic pair distribution function (PDF) of stoichiometric LaMnO_3 has been measured. This has been fit with a structural model to extract the local Jahn-Teller distortion for an ideal Mn(3+)O_6 octahedron. These results are compared to Rietveld refinements of the same data which give the average structure. Since the local structure is being measured in the PDF there is no assumption of long-range orbital order and the real, local, Jahn-Teller distortion is measured directly. We find good agreement both with published crystallographic results and our own Rietveld refinements suggesting that in an accurately stoichiometric material there is long range orbital order as expected. The local Jahn-Teller distortion has 2 short, 2 medium and 2 long bonds.Comment: 5 pages, 3 postscript figures, minor change
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