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  • 1
    Electronic Resource
    Electronic Resource
    Chemical State of Radio-iodine in Neutron-irradiated Periodate after Thermal Treatment (1957)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 79 (1957), S. 63-66 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01558a015
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  • 2
    Electronic Resource
    Electronic Resource
    Cannibalism as a life boat mechanism (1988)
    Springer
    Journal of mathematical biology 26 (1988), S. 619-633 
    Details
    ISSN: 1432-1416
    Keywords: Structured population model ; McKendrick equation ; Subcritical bifurcation ; Solver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Under certain conditions a cannibalistic population can survive when food for the adults is too scarce to support a non-cannibalistic population. Cannibalism can have this lifeboat effect if (i) the juveniles feed on a resource inaccessible to the adults; and (ii) the adults are cannibalistic and thus incorporate indirectly the inaccessible resource. Using a simple model we conclude that the mechanism works when, at low population densities, the average yield, in terms of new offspring, due to the energy provided by one cannibalized juvenile is larger than one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00276144
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  • 3
    Electronic Resource
    Electronic Resource
    A size dependent predator-prey interaction: who pursues whom? (1990)
    Springer
    Journal of mathematical biology 28 (1990), S. 609-643 
    Details
    ISSN: 1432-1416
    Keywords: Predator-prey interaction ; Size-structured population dynamics ; Behavioural mechanisms ; Dynamical phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We investigate the properties of an (age, size) -structured model for a population of Daphnia that feeds on a dynamical algal food source. The stability of the internal equilibrium is studied in detail and combined with numerical studies on the dynamics of the model to obtain insight in the relation between individual behaviour and population dynamical phenomena. Particularly the change in the (age, size)-relation with a change in the food availability seems to be an important behavioural mechanism that strongly influences the dynamics. This influence is partly stabilizing and partly destabilizing and leads to the coexistence of a stable equilibrium and a stable limit cycle or even coexistence of two stable limit cycles for the same parameter values. The oscillations in this case are characterized by drastic changes in the size-structure of the population during a cycle. In addition the model exhibits the usual predator-prey oscillations that characterize Lotka-Volterra models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160229
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cadmium kinetics in freshwater clams. III. Effects of zinc on uptake and distribution of cadmium inAnodonta cygnea (1987)
    Springer
    Archives of environmental contamination and toxicology 16 (1987), S. 95-101 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Freshwater clams (Anodonta cygnea) were exposed to Cd2+ (25 μg/L) or to Cd2+ (25 μg/L) plus Zn2+ (2.5 mg/L). In the presence of zinc, uptake of cadmium in whole clam was halved. In organs such as the gills, mantle, and labial palps a still larger reduction of Cd accumulation occurred. By contrast, accumulation in midgut gland and kidney was hardly affected by the presence of zinc. It is shown that in the gills zinc competes with cadmium for metal binding sites both within the particulate fraction and the high-molecular weight fraction of the cytosol. Zinc probably did not induce an enlarged synthesis of specific metal-binding, metallothionein-like, proteins. In conclusion, zinc exerts antagonistic effects on uptake of cadmium by gills, and accelerates Cd transport from the gills towards the internal organs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01055364
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of dimensionality on Lotka-Volterra predator-prey dynamics: Individual based simulation results (1995)
    Springer
    Bulletin of mathematical biology 57 (1995), S. 507-526 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The effect of varying habitat dimensionality on the dynamics of a model predator-prey system is examined using an individual-based simulation. The general results are that in one dimension fluctuations in abundance of prey and predators occur over a large range of spatial scales (extinctions occur over many spatial scales). In two dimensions (and low mobilities of prey and predators) the dynamics become more predictably periodic at local scales and constant at larger scales due to statistical stabilization. In three dimensions, the model can become “phase-locked” with prey and predators displaying oscillations in abundance over large spatial scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460780
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  • 6
    Electronic Resource
    Electronic Resource
    What individual life histories can (and cannot) tell about population dynamics (1997)
    Springer
    Aquatic ecology 31 (1997), S. 37-45 
    Details
    ISSN: 1573-5125
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an overview of a long-term research programme that is aimed at revealing the relations between individual feeding, growth, reproduction and mortality in Daphnia pulex and the state and dynamics of the population. We analyse a physiologically structured population model, in which individual performance is described using an energy budget model that incorporates a food dependence. The model predictions are shown to be at odds with experimental observations on populations of Daphnia. We argue that these discrepancies are primarily due to insufficient knowledge about the precise size-scaling of the food ingestion rate, which plays a central role in the competitive interaction among individuals. To a lesser extent, the discrepancies arise because details about the energy budget of individual Daphnia are not sufficiently known for the food conditions prevailing in population experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009995420368
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical methods for structured population models: The Escalator Boxcar Train (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Numerical Methods for Partial Differential Equations 4 (1988), S. 173-195 
    Details
    ISSN: 0749-159X
    Keywords: Mathematics and Statistics ; Numerical Methods
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A numerical integration method is introduced for the class of hyperbolic partial differential equations that occur in physiologically structured population models. These equations describe the time evolution of the population density-function over the individual state-space Ω. Exploiting the biological interpretation of the equation, this density-function is represented by a set of moments over a collection of subdomains in Ω, moving along the characteristics of the partial differential equation (PDE). These moments are readily interpreted as numbers of individuals in a cohort, mean individual state in a cohort, etc. The numerical method consists of approximating the differential equations.The method appears to be very efficient for this special type of PDE. It combines such desirable properties as as lack of dispersion and dissipation and a preservation of monotonicity of the density function along the characteristics with a strong relation to the biological background of the equations for these moments to arrive at a closed system of ordinary differential equations. The method also allows one to incorporate the usual type of nonlinearities that occur in physiologically structured population models. A numerical example is presented as an illustration of the application of the method.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/num.1690040303
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