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  • Agroinfection  (1)
  • Approximate aggregation of variables  (1)
  • 2020-2023
  • 1995-1999  (2)
  • 1970-1974
  • 1995  (2)
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Publisher
Years
  • 2020-2023
  • 1995-1999  (2)
  • 1970-1974
Year
  • 1995  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 43 (1995), S. 465-476 
    ISSN: 1572-8358
    Keywords: Approximate aggregation of variables ; population dynamics ; perturbations ; time scales ; eigenvalues and eigenvectors analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aggregation of variables allows to approximate a large scale dynamical system (the micro-system) involving many variables into a reduced system (the macro-system) described by a few number of global variables. Approximate aggregation can be performed when different time scales are involved in the dynamics of the micro-system. Perturbation methods enable to approximate the large micro-system by a macro-system going on at a slow time scale. Aggregation has been performed for systems of ordinary differential equations in which time is a continuous variable. In this contribution, we extend aggregation methods to time-discrete models of population dynamics. Time discrete micro-models with two time scales are presented. We use perturbation methods to obtain a slow macro-model. The asymptotic behaviours of the micro and macro-systems are characterized by the main eigenvalues and the associated eigenvectors. We compare the asymptotic behaviours of both systems which are shown to be similar to a certain order.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Ds1 excision ; Maize Streak Virus ; Zea mays plants ; Agroinfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A reverse genetic system for studying excision of the transposable elementDs1 in maize plants has been established previously. In this system, theDs1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence of theAc element, excision ofDs1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA sequences requiredin cis for excision ofDs1. TheDs1 element contains theAc transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5′ subterminal region). We showed that mutation of these motifs abolished completely the excision capacity ofDs1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with oligonucleotide insertions in the other (3′) subterminal region resulted in elements with either a reduced or an increased excision efficiency, indicating that this subterminal region also has an important function.
    Type of Medium: Electronic Resource
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