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  • Numerical Methods and Modeling  (2)
  • Scenedesmus quadricauda  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Metal interactions in algal toxicology: conventional versus in vivo tests (1981)
    Springer
    Hydrobiologia 85 (1981), S. 67-71 
    Details
    ISSN: 1573-5117
    Keywords: metal interactions ; toxicity ; algal assays ; bottle test ; algae ; Scenedesmus quadricauda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Different studies on the toxicity of the same metals to algae have often shown divergent and sometimes contradictory results. The inconsistency of these findings was often attributed to environmental factors such as the degree of chelation, complexation and precipitation of metals. Conventionally, toxicity tests of metal mixtures were conducted by adding metals to algae growing in synthetic media. In our study, we examined the ‘in vivo’ toxic effects of metals by pretreating the algal cells with one metal, resuspendeding them in fresh medium, then exposing them to a second metal. The algal response showed marked differences between the conventional and the new approach. The conventional approach shows that the toxicity depends upon the complexes formed externally, whereas the in vivo approach shows that the toxicity probably depends upon the molecular transformation of the metals internally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011346
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  • 2
    Electronic Resource
    Electronic Resource
    Algal bioassays to determine toxicity of metal mixtures (1980)
    Springer
    Hydrobiologia 74 (1980), S. 199-208 
    Details
    ISSN: 1573-5117
    Keywords: metals ; toxicity ; algal assay ; bottle test ; algae ; Chlorella fusca ; Ankistrodesmus bibraianum ; Scenedesmus quadricauda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shortcomings of many established toxicity criteria for metals have resulted from a simplification of bioassays performed with single metals. A more comprehensive approach was needed to diagnose the effects of metal mixtures on aquatic organisms. Using Chlorella, Ankistrodesmus and Scenedesmus as test organisms, we experimented on a number of factors which affected metal toxicity bioassays. These included metal interactions, algal competitions, species sensitivities, the ratio of an excess metal to other metals and nutrient levels. An alternative technique was finally established which involved an evaluation of individual assays of Chlorella and Ankistrodesmus in separate media and a tissue-metal analysis on Chlorella. Chlorella fusca, commonly found in lakes with high metal concentrations, showed high tolerance to mixed-metal solutions, while Ankistrodesmus proved to be very sensitive. By determining the maximum yield ratio between Ankistrodesmus and Chlorella (i.e. the A/Ch ratio) it was possible to compare the toxic strength of harmful metals according to an established standard curve of A/Ch ratio versus mixed-metal concentrations. The levels of tissue-metal analysed in Chlorella also gave some indication as to which metals were responsible for the toxicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008753
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  • 3
    Electronic Resource
    Electronic Resource
    Finite element solution for the continuum traffic equilibrium problems (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 43 (1998), S. 1253-1273 
    Details
    ISSN: 0029-5981
    Keywords: finite element method ; continuum modelling ; traffic equilibrium ; user-optimal pattern ; fixed demand ; variable demand ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, we consider a city with a highly compact Central Business District (CBD), and the commuters’ destinations from the CBD are dispersed over the whole city. The street network is approximated as a continuum and commuters’ movements in the city are measured by the flow intensity, and the local travel cost depends on the location and the traffic flow intensity. We extend the continuum user equilibrium problem to deal with the case of variable demand, in which the traffic demand from any destination in the city to the CBD is assumed to be a function of both the destination location and the total travel cost to the CBD. An equivalent mathematical model is formulated and proved to satisfy the user equilibrium conditions, which is then solved by a finite element solution algorithm. Numerical examples are given to illustrate the effectiveness of the proposed method. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of Jordan chains by extended matrices (1998)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 14 (1998), S. 879-893 
    Details
    ISSN: 1069-8299
    Keywords: derogatory eigenproblems ; Jordan blocks ; Jordan chains ; Segre characteristic ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The major obstacle to determination of the Jordan chains for a highly degenerated eigenproblem is that the triangular combinations of the principal vectors in a Jordan chain are also principal vectors and the linear combinations of the eigenvectors of all Jordan blocks associated with the same eigenvalue are also eigenvectors. These indeterminate constants will hide the Jordan block structure and make the analysis very difficult. We propose an extended matrix method to find the Jordan chains and eliminate the indeterminate constants so that the Jordan block structure can be computed sequentially. An example with the Segre characteristic [(321)11] is given. © 1998 John Wiley & Sons, Ltd.
    Type of Medium: Electronic Resource
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