1,721,060 research outputs found
A General Bioaccumulation DEB Model for Mussels
Get PDFA bioaccumulation model to predict, based on the concentration of contaminants in the water column, the concentration in mussels (Mytillus galloprovinciales) has been implemented and calibrated using experimental data from Thau lagoon (France). The model uses input data from a 3D biogeochemical model that provides biomasses in the different compartments, i.e. phytoplankton, zooplankton and
bacteria; and from a 3D fate model that provides the concentrations in the water column as well as in the sediments. The bioaccumulation model is based on the Dynamic Energy Budget approach (DEB). The model predicts correctly the concentrations of several POPs families: PCDD/Fs and PCBs. This is the first step for developing a general screening tool able to predict the bioaccumulation of new chemicals in mussels based on its physico-chemical properties that will contribute to the B(bioaccumulative) and vB assessment. In addition, the model could be use by MS to convert measured concentrations in mussels to water concentrations for WFD (Water Framework Directive) compliance checking.JRC.I.3 - Consumer products safety and qualit
Application of Recurrent Neural Networks in Batch Reactors. Part II. Non-linear Inverse and Predictive Control of the Heat Transfer Fluid Temperature.
No full textAltough nonlinear inverse and predictive control techniques based on artificial neural netwotks have been extensively applied to nonlinear systems, their use in real time applications is generally limeted. In this paper neural inverse and predictive control systems have been applied to the real- time control of the heat transfer fluid temperature in a pilot chemical reactor. The training of the inverse control system is carried out using both, generalised and specialised learning. This allows the preparation of weights of the controller acting in real-time and appropriate performances of inverse neural controller can be achieved, The predictive control system makes use of a neural network to calculate the control action . Thus, the problems related to the high computational effort involved in nonlinear model-predictive control systems are reduced. The performance of the neural controllers is compared against the PID conntroller currently installed in the plant. The results show that neural-based controllers improve the performance of the real plant.JRC.(ISIS) - Institute For Systems, Informatics And Safet
Analysis of Toxicity Effects from Molecular to Population Level: Circadian Oscillator Case Study
Get PDFTo analyze how toxic effects propagate from molecular to population level, a simple model of a circadian oscillator has been coupled with a cyanobacteria growth model. It has been assumed that the circadian oscillator synchronizes with light-dark environmental conditions and toxicants affect this synchronization reducing the population growth. Then dose-response curves have been developed. The results evidence that to understand toxic effects we have to focus our study on the interactions that a certain compound may have with proteins, and/or DNA, since the result of these interactions will determine the final mode of action at macroscopic level. Therefore an intermediate step for assessing toxic effects has been proposed.JRC.I.6 - Systems toxicolog
Towards the definition of Environmental Quality Standards for biota: The influence of food web structure and dynamics on bioaccumulation and biomagnification
Get PDFWith the implementation of the Water Framework Directive and the daughter directive on Environmental Quality Standards (EQS), the development of EQS values for biota has become an important issue. However, for certain hydrophobic compounds, bioaccumulation and biomagnification in the food chain may occur. In this case, it is important to analyze, if depending on the food web and diet preferences, bioaccumulation values could be different for the same species in different ecosystems. To analyze this effect, we have studied four terrestrial and aquatic trophic network models generated previously for three similar lakes and a costal lagoon. In addition a simple ecological plus bioaccumulation model has been developed for analyzing diet preferences which could not be assessed using the developed trophic food webs. The objective was to assess if the similarities and differences between calculated trophic level could have consequences on the bioaccumulation and biomagnification potential of contaminants. The results indicate that differences of around two orders of magnitude can be expected for similar ecosystems. These results are important since they indicate that the ecosystem structure should be first assessed for the development of EQS for biota and that without this information intercomparison exercises between EU ecosystems are not possible.JRC.I.6 - Systems toxicolog
Analysis of toxicity effects from molecular to population level: Circadian oscillator case study
No full textTo analyze how toxic effects propagate from molecular to population level, a simple model of a circadian oscillator has been coupled with a cyanobacteria growth model. It has been assumed that the circadian oscillator synchronizes with light-dark environmental conditions and toxicants affect this synchronization reducing the population growth. Then dose-response curves have been developed. The results evidence that to understand toxic effects we have to focus our study on the interactions that a certain compound may have with proteins, and/or DNA, since the result of these interactions will determine the final mode of action at macroscopic level. Therefore an intermediate step for assessing toxic effects has been proposed.JRC.DG.I.6 - Systems toxicolog
Non-linear Trading Strategy for Financial Time Series
No full textA new trading strategy based on state space reconstruction techniques is proposed. The technique uses the state space volume evolution and its rate of change as indicators. This methodology has been tested off-line using eighteen high-frequency foreign exchange time series with and without transaction costs. In our analysis an optimum mean value of approximately 25% gain may be obtained in those series without transaction costs and an optimum mean value of approximately 11% gain assuming 0.2% of costs in each transaction.JRC.H.5 - Rural, water and ecosystem resource
Analysis and simulation of metabolic networks: Application to HEPG2
Get PDFChemical toxicity in most of the cases has a metabolic component and metabolic pathways are the most studied biochemical reactions. For these reasons we have started to analyze modelling approaches for studying toxicity at molecular level using the metabolism and focusing in HepG2 cell lines. Two approaches have been investigated. The first consists on the analysis of metabolic fluxes in HepG2 under different toxicants concentrations by complex network analysis tools. This is important when a correlation between dose-response curves and metabolomic data has to be established. The second approach is based on the development and application of a simplified dynamic model of metabolism. This approach requires the specification of the biochemical reactions as well as their kinetic parameters and, therefore, at the moment, the degree of detail in the description of HepG2 metabolism is reduced. The results suggest that a combined approach starting from metabolic fluxes and then solving the kinetic equations as our experimental data and knowledge of metabolic pathways increases is the most promising avenue to develop a quantitative approach of toxicity at molecular level. In addition, there is the necessity to link the molecular level approach with the cell growth and mortality with an intermediate level that translates metabolism changes into measurable parameters in cell-based assays.JRC.DG.I.6 - Systems toxicolog
Time-Step Volume-Preserving Control of Chemical Reactors
No full textWe present a general control and optimization strategy based on time-step state space volume preservation. This is performed by maintaining the divergence of the system close to zero. The on-line implementation is shown for batch chemical reactors. The divergence of these systems is reconstructed on-line using only reactor temperature measurements by applying state space reconstruction techniques. The simulated results are compared with a traditional control scheme. This kind of control allows to operate in safety conditions and to optimize the performance of the process by accelerating the slow reactions and reducing batch times.JRC.H.5 - Rural, water and ecosystem resource
Phase-Space Volume Based Control of Semibatch Reactors
No full textWe present and apply a control methodology using the divergence of the system as a goal function to control semibatch chemical reactors and show how the process operation may be optimized by only measuring the reactor and jacket temperatures. The implementation of the approach is also demonstrated using phase space reconstruction techniques. This new control methodology offers a complementary approach to more traditional techniques and it can be easily extended to other industrial installations and processes.JRC.I.5 - Systems Toxicolog
New Trading Methodology for Financial Time Series
No full textIn this work, we have applied state space reconstruction techniques to estimate state space volume and its variation. These values have allowed us to define a trading methodology by considering a sort of acceleration in a high-dimensional state space system as a kind of momentum indicator similar to those used in financial technical analysis. Our interest was to develop a general trading strategy to determine and quantify the amount of predictability in these time series. This trading methodology has been applied to high-frequency currency exchange time series data from the HFDF96 data set provided by Olsen & Associates. The time series studied are the exchange rates between the US Dollar and 18 other foreign currencies from the Euro zone; i.e. Belgium Franc (BEF), Finnish Markka (FIM), German Mark (DEM), Spanish peseta (ESP), French Frank (FRF), Italian Lira (ITL), Dutch Guilder (NLG),
and finally ECU (XEU); and from outside the Euro zone: Australian Dollar (AUD), Canadian Dollar (CAD), Swiss Frank (CHF), Danish Krone (DKK), British Pound (GBP), Malaysian Ringgit (MYR), Japanese Yen (JPY), Swedish Krona (SEK), Singapore Dollar (SGD), and South African Rand (ZAR)JRC.H.5 - Rural, water and ecosystem resource
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