155 research outputs found

    Limit distributions for the maxima of stationary Gaussian processes

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    AbstractLet {Xn} be a stationary Gaussian sequence with E{X0} = 0, {X20} = 1 and E{X0Xn} = rn n Let cn = (2ln n)built12, bn = cn− 12c-1n ln(4π ln n), and set Mn = max0 â©œkâ©œnXk. A classical result for independent normal random variables is that P[cn(Mn−bn)â©œx]→exp[-e-x] as n → ∞ for all x. Berman has shown that (1) applies as well to dependent sequences provided rnlnn = o(1). Suppose now that {rn} is a convex correlation sequence satisfying rn = o(1), (rnlnn)-1 is monotone for large n and o(1). Then P[rn-12(Mn − (1−rn)12bn)â©œx] → Đ€(x) for all x, where Đ€ is the normal distribution function. While the normal can thus be viewed as a second natural limit distribution for {Mn}, there are others. In particular, the limit distribution is given below when rn is (sufficiently close to) Îł/ln n. We further exhibit a collection of limit distributions which can arise when rn decays to zero in a nonsmooth manner. Continuous parameter Gaussian processes are also considered. A modified version of (1) has been given by Pickands for some continuous processes which possess sufficient asymptotic independence properties. Under a weaker form of asymptotic independence, we obtain a version of (2)

    Electronic Structure Calculation by First Principles for Strongly Correlated Electron Systems

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    Recent trends of ab initio studies and progress in methodologies for electronic structure calculations of strongly correlated electron systems are discussed. The interest for developing efficient methods is motivated by recent discoveries and characterizations of strongly correlated electron materials and by requirements for understanding mechanisms of intriguing phenomena beyond a single-particle picture. A three-stage scheme is developed as renormalized multi-scale solvers (RMS) utilizing the hierarchical electronic structure in the energy space. It provides us with an ab initio downfolding of the global band structure into low-energy effective models followed by low-energy solvers for the models. The RMS method is illustrated with examples of several materials. In particular, we overview cases such as dynamics of semiconductors, transition metals and its compounds including iron-based superconductors and perovskite oxides, as well as organic conductors of kappa-ET type.Comment: 44 pages including 38 figures, to appear in J. Phys. Soc. Jpn. as an invited review pape

    "They brought you back to the fact you're not the same": Sense of self after traumatic brain injury

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    This paper considers contexts following traumatic brain injury, exploring what may be at stake when dominant expectations predict a ‘lost’ or ‘broken’ self. I explore stories co-constructed with one young man and his mother to illustrate their personal and intersubjective understandings of identity, at times conflicting, within family interactions and when encountering normative practices of neurorehabilitation clinicians. The ower relations portrayed confront this man’s narrative attempts to align his present and pre-injury self, including standard assessments delineating change, administered by healthcare professionals. I consider a need for greater attention to interaction-generated disruption to sense of self, wthin contemporary conceptualisations of ‘person-centred care’

    Cognitieve revalidatie voor kinderen en jongeren met niet-aangeboren hersenletsel:wat zijn de effectieve componenten?

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    Veel kinderen en jongeren met niet-aangeboren hersenletsel (nah) ervaren problemen met cognitief functioneren, zoals een verminderd geheugen of slechtere concentratie. Dit artikel is gebaseerd op bevindingen en inzichten uit het proefschrift ‘executive functions of children and adolescents: novel perspectives on assessment and intervention’. Een belangrijk doel van het promotietraject was beter inzicht te krijgen in hoe we cognitieve functies en bijbehorende problemen bij kinderen en jongeren met nah kunnen verbeteren. Cognitieve problemen bij kinderen en jongeren kunnen mogelijk worden behandeld met cognitieve revalidatie. Interventies voor cognitieve revalidatie kunnen worden gecategoriseerd op basis van hun hoofdcomponenten: 1) strategiegebruik en/of metacognitie, 2) herhaald oefenen, en 3) externe hulpmiddelen. Resultaten van een literatuurstudie naar cognitieve revalidatie laten zien dat door interventies die zijn gebaseerd op metacognitie en/of strategiegebruik vooral adaptief gedrag en sociaal functioneren verbeteren. Interventies op basis van herhaald oefenen verbeterden de prestaties op taken die vergelijkbaar zijn met de geoefende taken. Multi-componenten-interventies die deze twee componenten combineren, leken te leiden tot verbeteringen in zowel cognitief als adaptief gedrag en sociaal functioneren. Externe hulpmiddelen verbeterden het functioneren in het specifieke gebied waarop het hulpmiddel was gericht, bijvoorbeeld het geheugen. De beschikbare gegevens suggereren dat interventies bestaande uit meerdere componenten, zoals een combinatie van metacognitie- en/of strategiegebruik en herhaald oefenen, veelbelovend zijn, omdat deze kunnen leiden tot verbeteringen in zowel het cognitieve als psychosociale functioneren van kinderen en adolescenten met nah
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