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  • 1
    Language: English
    In: Chemosphere, 1999, Vol.38(14), pp.3237-3245
    Description: The use of probabilistic neural networks (PNN) to model the acute toxicity (96 h LC50) to the fathead minnow (Pimephales promelas), based on 865 chemical data sets, is described. The octanol/water partition co-efficient was not used as an input parameter and the information fed into the PNN was solely based on simple molecular descriptors that could be derived from the chemical structure. An extensive list of functional group descriptors is provided and the development of a model and cross validation procedures is explained. Predictions resulted from procedures involved in 5 subsets, each containing 20 per cent of the data, and compared to measured (expected) output data. High values of the correlations between the measured and predicted values strongly suggested the use of linear correlation to improve the model. The excellent statistics obtained with the PNN model indicate its applicability to a great variety of compounds.
    Keywords: Fathead Minnow ; Acute Toxicity ; Neural Network ; Model ; Prediction ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 2
    Language: English
    In: Chemosphere, 1983, Vol.12(9), pp.1159-1167
    Description: An investigation is described of the effects of increasing halogen substitution on octanol/water partition coefficients of a variety of aromatic and heterocyclic parent molecules. It is suggested that the increasing chlorine substitution of compounds such as benzene, aniline, pyridine and diphenyl results in declining increases of the octanol/water partition coefficients. Two equations are derived which allow the quick estimation of the partition coefficient of any congener from the known value of another. These equations are of particular value for compounds the partition coefficients of which are difficult to determine experimentally, for the prediction of their environmental fates and bioaccumulation potentials and for their toxicities, which often correlate with their partition coefficients.
    Keywords: Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 3
    Language: English
    In: Chemosphere, 1993, Vol.27(7), pp.1159-1169
    Description: In comparison to traditional “index-card-type” databases, spreadsheets can hold much the same information, but allow much more manipulation and use of the data contents. Until recently, spreadsheets were limited by computer power, i.e. speed, memory and programs of the budget priced available hardware and software. With the availability of new, more effective spreadsheet software, such as Quattro ® Pro for Windows ™ , and much faster “386” and “486” desktop computers at a much reduced cost, the potential of spreadsheets to hold and manipulate scientific databases has developed into a new powerful research tool. We have now compiled a toxicity database in spreadsheet format, which contains acute and sub-chronic toxicity data on approximately 1500 chemicals for aquatic and terrestrial species, together with various physico-chemical and topological data. This paper provides an overview of the spreadsheet-type database structure and capabilities using the COMPUTOX ™ toxicity database as an example to show the development of qualitative and quantitative relationships of acute toxicities of organic chemicals between various species and/or endpoints, with emphasis on the Microtox ™ ( Photobacterium phosphoreum ) toxicity test.
    Keywords: Desktop Computer ; Spreadsheet ; Research Tools ; Acute Toxicity ; Correlations ; Plotting ; Microtox ; Photobacterium Phosphoreum ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 4
    Language: English
    In: Chemosphere, 1983, Vol.12(11), pp.1421-1442
    Description: Tests with the Microtox technique using twenty chlorphenols, twelve chlorobenzenes and thirteen para-substituted phenols indicate that a correlation exists with the acute effects of these chemicals on fish, bacteria and shrimp. The Microtox toxicity test, which measures the reduction of the light emitted by Photobacterium phosphoreum when exposed to a toxic sample from which the toxicity value is calculated, is considered to afford good estimates of the toxicities to various biota, as shown by linear correlations. The test may also be useful for calculating structure-activity correlations with physico-chemical parameters such as the octanol-water partition coefficient.
    Keywords: Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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