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Sökning: LAR1:gu > Jagers Peter 1941

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1.
  • Grandin, Karl, et al. (författare)
  • Nuclear Energy
  • 2010
  • Ingår i: AMBIO. - 0044-7447. ; 39:Suppl. 1, s. 26-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Nuclear energy can play a role in carbon free production of electrical energy, thus making it interesting for tomorrow’s energy mix. However, several issues have to be addressed. In fission technology, the design of so-called fourth generation reactors show great promise, in particular in addressing materials efficiency and safety issues. If successfully developed, such reactors may have an important and sustainable part in future energy production. Working fusion reactors may be even more materials efficient and environmental friendly, but also need more development and research. The roadmap for development of fourth generation fission and fusion reactors, therefore, asks for attention and research in these fields must be strengthened.
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  • Hamza, K., et al. (författare)
  • On the establishment, persistence, and inevitable extinction of populations
  • 2016
  • Ingår i: Journal of Mathematical Biology. - 0303-6812. ; 72:4, s. 797-820
  • Tidskriftsartikel (refereegranskat)abstract
    • Comprehensive models of stochastic, clonally reproducing populations are defined in terms of general branching processes, allowing birth during maternal life, as for higher organisms, or by splitting, as in cell division. The populations are assumed to start small, by mutation or immigration, reproduce supercritically while smaller than the habitat carrying capacity but subcritically above it. Such populations establish themselves with a probability wellknown from branching process theory. Once established, they grow up to a band around the carrying capacity in a time that is logarithmic in the latter, assumed large. There they prevail during a time period whose duration is exponential in the carrying capacity. Even populations whose life style is sustainble in the sense that the habitat carrying capacity is not eroded but remains the same, ultimately enter an extinction phase, which again lasts for a time logarithmic in the carrying capacity. However, if the habitat can carry a population which is large, say millions of individuals, and it manages to avoid early extinction, time in generations to extinction will be exorbitantly long, and during it, population composition over ages, types, lineage etc. will have time to stabilise. This paper aims at an exhaustive description of the life cycle of such populations, from inception to extinction, extending and overviewing earlier results. We shall also say some words on persistence times of populations with smaller carrying capacities and short life cycles, where the population may indeed be in danger in spite of not eroding its environment.
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  • Jagers, Peter, 1941-, et al. (författare)
  • Branching processes with deteriorating random environments
  • 2002
  • Ingår i: Journal of Applied Probability. - 0021-9002. ; 39, s. 395-401
  • Tidskriftsartikel (refereegranskat)abstract
    • We introduce Galton-Watson style branching processes in random environments which are deteriorating rather than stationary or independent. Some primary results on process growth and extinction probability are shown. Two simple examples are given.
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9.
  • Jagers, Peter, 1941-, et al. (författare)
  • Convergence to the coalescent in populations of substantially varying size.
  • 2004
  • Ingår i: J. Appl. Probab.. - 0021-9002. ; 41:2, s. 368-378
  • Tidskriftsartikel (refereegranskat)abstract
    • Kingman's classical coalescent uncovers the basic pattern of genealogical trees of random samples of individuals in large but time-constant populations. Time is viewed as discrete and identified with non-overlapping generations. Reproduction can be very generally taken as exchangeable (meaning that the labelling of individuals in each generation carries no significance). Recent generalisations have dealt with population sizes exhibiting given deterministic or (minor) random fluctuations. We consider population sizes which constitute a stationary Markov chain, explicitly allowing large fluctuations in short times. Convergence of the genealogical tree, as population size tends to infinity, towards the (time-scaled) coalescent is simply proved under minimal conditions. As a result, a formula for effective population size obtains, generalising the well-knownharmonic mean expression for effective size.
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10.
  • Jagers, Peter, 1941-, et al. (författare)
  • Dependence and interaction in branching processes
  • 2013
  • Ingår i: Springer Proceedings in Mathematics and Statistics. - 2194-1009. - 9783642335488 ; 33, s. 325-333
  • Konferensbidrag (refereegranskat)abstract
    • Independence of reproducing individuals can be viewed as the very defining property of branching processes. It is crucial for the most famous results of the theory, the determination of the extinction probability and the dichotomy between extinction and exponential increase. In general processes, stabilisation of the age-distribution under growth follows, and indeed of the over-all population composition, and so do the many fine results of the area, like conditional stabilisation of the size of non-extinct subcritical processes. The last two decades have witnessed repeated attempts at treating branching processes with various kinds of dependence between individuals, ranging from local dependence between close relatives only to population size dependence. Of particular interest are very recent findings on processes that change from being supercritical to subcriticality at some threshold size, the carrying capacity of the habitat. We overview the development with an emphasis on these recent results. © Springer-Verlag Berlin Heidelberg 2013.
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