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Sökning: LAR1:gu > Tidskriftsartikel > Chalmers tekniska högskola > 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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2.
  • 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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7.
  • 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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8.
  • 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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9.
  • Jagers, Peter, 1941- (författare)
  • Extinction
  • 2009
  • Ingår i: Math. Pop Studies. - 0889-8490. ; 16:3, s. 175-176
  • Tidskriftsartikel (refereegranskat)
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10.
  • Jagers, Peter, 1941-, et al. (författare)
  • General branching processes in discrete time as random trees.
  • 2008
  • Ingår i: Bernoulli. - 1350-7265. ; 14:4, s. 949-962
  • Tidskriftsartikel (refereegranskat)abstract
    • The simple Galton-Watson process describes populations where individuals live one season and are then replaced by a random number of children. It can also be viewed as a way of generating random trees, each vertex being an individual of the family tree. This viewpoint has led to new insights and a revival of classical theory. We show how a similar reinterpretation can shed new light on the more interesting forms of branching processes that allow repeated bearings and, thus, overlapping generations. In particular, we use the stable pedigree law to give a transparent description of a size-biased version of general branching processes in discrete time. This allows us to analyse the xlog x condition for exponential growth of supercritical general processes, and also the relation between simple Galton-Watson and more general branching processes.
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