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J Devillers

Publications and source records attributed to J Devillers.

29 records · Page 2Linked to original sources
PubMed1993

Nonlinear dependence of fish bioconcentration on n-octanol/water partition coefficient.

The log-log relationship between the bioconcentration tendency of organic chemicals in fish and the n -octanol/water partition coefficients breaks down for very hydrophobic compounds. The use of parabolic and bilinear models allows this problem to be overcome. The QSAR equation log BCF = 0.910 log P - 1.975 log (6.8 10(-7) P + 1) - 0.786 (n = 154; r = 0.950; s = 0.347; F = 463.51) was found to be a good predictor of bioconcentration in fish.

1-Octanol↗
PubMed1993

Neural modelling of the biodegradability of benzene derivatives.

The aim of this paper was to explore the usefulness of a backpropagation neural network (BNN) to estimate the biodegradability of benzene derivatives. 127 chemicals selected from the BIODEG data bank (Syracuse Research Corporation, 1992) were described by means of 20 structural descriptors taking into account the nature and position of the substituents on the benzene ring. Three classes of biodegradability were selected and modelled from the BNN. A 20/5/3 BNN (alpha = 0.8 and eta = 0.5) correctly classified 92% (104/113) of the training and 86% (12/14) of the testing sets. The results were compared to those produced by the BIODEG probability program (Syracuse Research Corporation, Version 2.13).

Algorithms↗
PubMed1993

Estimating pesticide field half-lives from a backpropagation neural network.

The field half-lives of 110 pesticides were modelled using a backpropagation neural network (NN). The molecules were described by means of the frequency of 17 structural fragments. Before training the NN, different scaling transformations were assayed. Best results were obtained with correspondence factor analysis which also allowed a reduction of dimensionality. The training and testing sets of the NN analysis gave 95.5% and 84.6% of good classifications, respectively. Comparison with discriminant factor analysis showed that a backpropagation NN was more appropriate to model the field half-lives of pesticides.

Discriminant Analysis↗
PubMed1990

Environmental and health risks of hydroquinone.

Hazard assessment of hydroquinone has been evaluated from bibliographical and original data on the physicochemical properties, the environmental behavior, and the biological effects of this aromatic compound. Hydroquinone, which is produced in large amounts and widely used, must be considered as an environmental contaminant. However, it is not persistent. The ecotoxicity of this molecule, which must be linked to its physicochemical properties, varies from species to species. Its acute and chronic toxicity toward higher terrestrial organisms is moderate. Hydroquinone is estimated to be nonmutagenic by the Ames test but induces chromosome aberrations or karyotypic effects in eucaryotic cells. Carcinogenic and teratogenic potentials have been at present inadequately studied. The study underlines the complementarity of QSAR models and experimental approaches when an attempt is made to obtain ecotoxicological profiles of pollutants.

Animals↗
PubMed1989

Heuristic potency of the minimum spanning tree (MST) method in toxicology.

A rapid and manual mathematical method for comparing ecotoxicologic data has been investigated. It uses a classification procedure based on the calculation of chi 2 distances between the different elements of a data matrix. The classification is carried out using a simple graph-theoretical procedure (Kruskal's algorithm), allowing the construction of minimum spanning tree (MST). From an ecotoxicologic data base of 18 bacterial tests carried out on eight heavy metals the construction of the MST is explained in detail. Even if the results obtained are directly dependent on the data set chosen, they illustrate the heuristic potency of the minimum spanning tree method in comparing and estimating the dependence between environmental data.

Bacteria↗
PubMed1989

The stochastic regression analysis as a tool in ecotoxicological QSAR studies.

Correspondence factor analysis (CFA) was used in conjunction with linear regression analysis to examine the structure-activity relationships of 50 benzene derivatives tested on Pimephales promelas. From nine molecular descriptions (numbers of C, H, O, N, Br, Cl, NO2, OH, and NH2 included in the molecules), CFA made it possible to define five new independent variables which were introduced in a stepwise regression analysis procedure to describe the acute toxicity (96-h LC50) of the aromatic compounds. The model log 1/C = -0.727F1 + 1.248F3 + 4.052 (r = 0.918; s = 0.270) is more relevant to describe the ecotoxicological behavior of the studied compounds on the fathead minnow than that obtained with principal components (log 1/C = 0.151 PC1 -0.271 PC2 + 4.124; r = 0.737; s = 0.460). The heuristic potency of this particular statistical analysis, which is called stochastic regression analysis, is discussed in detail.

Animals↗
PubMed1988

Acute toxicity of cresols, xylenols, and trimethylphenols to Daphnia magna Straus 1820.

Twenty-four-hour IC50 values (50% immobilization concentration) for phenol, o-cresol, m-cresol, p-cresol, six xylenols, and three trimethylphenols were determined for Daphnia magna under static conditions. Our results show that cresols are more toxic than phenol, that xylenols do not exhibit significantly higher toxicity than cresols, and that trimethylphenols are less toxic than cresols. Thus, no direct relationship can be found between the number and position of methyl groups on the phenol nucleus and their acute toxicity to the water flea.

Animals↗
PubMedDate not supplied

Designing molecules with specific properties from intercommunicating hybrid systems.

The concept that computers can be creative in designing new molecules is now being actively explored. Our work has been aimed at developing an intercommunicating hybrid system using a genetic algorithm and a backpropagation neural network model for solving the general problem of designing molecules with specific properties. A case study dealing with biodegradation modeling is presented. The usefulness of the intercommunicating hybrid systems in QSAR and drug design is emphasized.

Algorithms↗
PubMedDate not supplied

e-statistics for deriving QSAR models.

This paper presents some freeware, shareware, and commercial statistical tools available via the Internet and which could be used in QSAR for deriving models. Programming environments useful in Statistics, newsgroups and FAQs are also introduced due to their interest for the discipline.

Internet↗