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An artificial neural network (ANN) includes nonlinear computational elements called neurons, which are linked by weighted connections. Typically, a neuron receives an input information and performs a weighted summation, which is propagated by an activation function to other neurons through the ANN. Numerous ANN paradigms have been proposed for pattern classification, clustering, function approximation,...
Assessment of genotoxicity of chemicals is one of the utmost priorities of a regulatory agency since it is indicative of its potential carcinogenic properties. A major challenge to the regulatory agencies today is how to assess the genotoxicity of the large proportion of existing and new substances that have otherwise very little or no information on their genotoxicity potential given the high costs...
Skin sensitization is a significant environmental and occupational health concern. The possibility of workers and consumers becoming sensitized is a major problem for individuals, employers and marketing certain products. Consequently, there exists an important need to accurately identify chemicals that have the potential to cause skin sensitization. Under Registration, Evaluation, Authorization and...
LD50 tests on rat and mouse are commonly used to express the relative hazard associated with the acute toxicity of new and existing substances. These tests are expensive, time consuming, and actively fought by Animal Rightists. Consequently, there is a need to find alternative methods. If the design of QSAR models can be used as surrogate, the search for interspecies correlations also represents a...
It is now well admitted that a battery of ecotoxicity tests should be designed by accounting for the requirements of a specific scenario such as classification of wastes or remediation efficiency of contaminated soils. The development of a single battery of tests for all applications is thereafter recognized not to be relevant. The selection of tests for constituting a battery may be established according...
Physiologically based toxicokinetic [(PBTK), or alternatively referred to as physiologically based pharmacokinetic (PBPK)] models are quantitative descriptions of absorption, distribution, metabolism, and excretion of chemicals in biota. PBTK models are increasingly being used as an effective tool for designing toxicology experiments and for conducting extrapolations essential for risk assessments...
A healthy terrestrial food web is essential for the sustainable use of soils. Earthworms are key species within terrestrial food webs and perform a number of essential functionalities like decomposition of organic litter, tillage and aeration of the soil, and enhancement of microbial activity. Chemicals may impact the functions of the soil by directly affecting one or more of these processes or by...
This chapter introduces ABMs, their construction, and the pros and cons of their use. Although relatively new, agent-based models (ABMs) have great potential for use in ecotoxicological research – their primary advantage being the realistic simulations that can be constructed and particularly their explicit handling of space and time in simulations. Examples are provided of their use in ecotoxicology...
The dynamic energy budget (DEB) theory for metabolic organisation specifies quantitatively the processes of uptake of substrate by organisms and its use for the purpose of maintenance, growth, maturation and reproduction. It applies to all organisms. Animals are special because they typically feed on other organisms. This couples the uptake of the different required substrates, and their energetics...
Nowadays, one of the big challenge in ecotoxicology is to understand how individually measured effects can be used as predictive indices at the population level. A particular interesting aspect is to evaluate how individual measures of fitness and survival under various toxic conditions can be used to estimate the asymptotic population growth rate known as one of the most robust endpoint in population...
The uptake of neutral and ionizable organic compounds from soil into plants is studied using mathematical models. The phase equilibrium between soil and plant cells of neutral compounds is calculated from partition coefficients, while for ionizable compounds, the steady state of the Fick–Nernst–Planck flux equation is applied. The calculations indicate biomagnification of neutral, polar, and nonvolatile...
In this chapter we first review the concept of fugacity as a thermodynamic equilibrium criterion applied to chemical fate in environmental systems. We then discuss the evolution of fugacity-based models applied to the multimedia environmental distribution of chemicals and more specifically to bioaccumulation and food web models. It is shown that the combination of multimedia and bioaccumulation models...
Structurally dynamic models (SDMs) are models that account for the changes in the model parameters due to the adaptation or the shift in species composition resulting from current changes in the forcing functions. The parameter changes are found by introduction of eco-exergy as goal function in the model. The set of parameters that give the highest eco-exergy by the prevailing conditions are currently...
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