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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Orthopäde 26 (1997), S. 955-960 
    ISSN: 1433-0431
    Keywords: Key words Amenorrhoea • Oestrogens • Bone mineral density • Stress fracture • Exercise ; Schlüsselwörter Amenorrhö• Oestrogene • Knochendichte • Streßfraktur • Körperliche Aktivität
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Zahlreiche Studien belegen, daß Leistungssport in allen Lebensphasen die Ovarialfunktion durch Störung der Hormonausschüttung auf Hypothalamus-Hypophysen-Ebene einschränken kann. Vor der Pubertät resultiert daraus eine Verzögerung der sexuellen Reifung, in der adulten Phase sind Zyklusstörungen in Form einer Oligo-/Amenorrhö die klinischen Zeichen. Diese werden vor allem in Ausdauersportarten, in welchen ein niedriges Körpergewicht von Vorteil ist, beobachtet. Nicht nur die ausgewählte Sportart begünstigt das Auftreten solcher Störungen, sondern auch die Trainingsart, der Zeitpunkt des Trainingsbeginns und eine unausgeglichene, hypokalorische Ernährung. Die Zyklusstörungen sind reversibel, hingegen kann das chronische Östrogendefizit zu einer Abnahme der Knochendichte führen und die Prävalenz von Streßfrakturen erhöhen. Somit benötigen Leistungssportlerinnen nebst einer medizinischen Beratung über Trainingsgestaltung und Ernährung auch eine individuell angepaßte Information und Führung im Falle einer langfristig indizierten Hormonsubstitution.
    Notes: Summary Numerous studies show that (high) performance sport may reduce the ovarian function by disturbing the distribution of the hormones at the level of the hypothalamic-pituitary axis. Before puberty a delay in sexual maturity (in particular delayed menarche) and after menarche oligomenorrhoea or secondary amenorrhoea may result, most frequently in aerobic-type activities associated with lower body weight such as running, aerobics and gymnastics. Body composition and specificity of sport, intensity of training, previous menstrual history and eating disorders are all important factors. After stopping with performance sport, the regular menstrual cycle will return, but the chronic lack of oestrogen may reduce bone density and increase the prevalence of stress fractures. In conclusion, female performance athletes require medical facts about training and nutrition and individual information and guiding if a long-term hormone substitution is needed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 71 (1993), S. 471-505 
    ISSN: 1572-9613
    Keywords: Asymmetric exclusion process ; Bethe ansatz ; steady state ; boundary-induced phase transitions ; correlation functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a model for a one-dimensional anisotropic exclusion process describing particles moving deterministically on a ring of lengthL with a single defect, across which they move with probability 0 ⩽p ⩽ 1. This model is equivalent to a two-dimensional, six-vertex model in an extreme anisotropic limit with a defect line interpolating between open and periodic boundary conditions. We solve this model with a Bethe ansatz generalized to this kind of boundary condition. We discuss in detail the steady state and derive exact expressions for the currentj, the density profilen(x), and the two-point density correlation function. In the thermodynamic limitL → ∞ the phase diagram shows three phases, a low-density phase, a coexistence phase, and a high-density phase related to the low-density phase by a particle-hole symmetry. In the low-density phase the density profile decays exponentially with the distance from the boundary to its bulk value on a length scale ξ. On the phase transition line ξ diverges and the currentj approaches its critical valuej c = p as a power law,j c − j ∞ ξ−1/2. In the coexistence phase the widthδ of the interface between the high-density region and the low-density region is proportional toL 1/2 if the densityρ f 1/2 andδ=0 independent ofL ifρ = 1/2. The (connected) two-point correlation function turns out to be of a scaling form with a space-dependent amplitude n(x1, x2) =A(x2)A Ke−r/ξ withr = x 2 −x 1 and a critical exponent κ = 0.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 72 (1993), S. 277-296 
    ISSN: 1572-9613
    Keywords: Asymmetric exclusion process ; steady state ; boundaryinduced phase transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider an exclusion process with particles injected with rate α at the origin and removed with rate β at the right boundary of a one-dimensional chain of sites. The particles are allowed to hop onto unoccupied sites, to the right only. For the special case of α =β = 1 the model was solved previously by Derridaet al. Here we extend the solution to general α, β. The phase diagram obtained from our exact solution differs from the one predicted by the mean-field approximation.
    Type of Medium: Electronic Resource
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