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- Ahadi, Aylin, et al.
(författare)
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Implementation and evaluation of a binary mixture model and three-dimensional FE-analysis of water saturated soil
- 2006
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Ingår i: ECCOMAS CFD 2006: Proceedings of the European Conference on Computational Fluid Dynamics. - 9090209700
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Konferensbidrag (refereegranskat)abstract
- A binary mixture model for soils has been formulated and analyzed. In the model one of the constituents is soil and the other constituent an incompressible liquid. The effects of water are included by formulating a mixture model is formulated as an extension of an existing non-associated elasto-plastic material model for granular materials. This paper is focused on the balance of momentum equations of the mixture model, primarily to avoid the difficulties arising when the interaction terms between the constituents needs to be formulated and constituted. Considering the momentum balance of the mixture as an extension of the balance equation of the soil constituent, it is supplemented with body forces, stresses and flow effects from the water constituent. These supplemented terms are evaluated and analyzed. An alternative way of deriving equation of motion for the fluid is also presented. The computer algorithm for integrating the constitutive relation of dry sand is supplemented and numerical simulations with a finite element code are carried out. It is shown that although the mixture model consists of two constituents, it is possible to include the existence of voids and a system with three constituents, i.e. water unsaturated soil, can be analyzed. Results from single element tests and simulations of a flexible footing resting on a surface of water saturated sand are presented.
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| 3. |
- Monge, Patricia, et al.
(författare)
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Parental occupational exposure to pesticides and the risk of childhood leukemia in Costa Rica
- 2007
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Ingår i: Scandinavian Journal of Work, Environment and Health. - : Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 33:4, s. 293-303
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Parental exposure to pesticides and the risk of leukemia in offspring were examined in a population-based case-control study in Costa Rica. METHODS: All cases of childhood leukemia (N=334), in 1995-2000, were identified at the Cancer Registry and the Children's Hospital. Population controls (N=579) were drawn from the National Birth Registry. Interviews of parents were conducted using conventional and icon-based calendar forms. An exposure model was constructed for 25 pesticides in five time periods. RESULTS: Mothers' exposures to any pesticides during the year before conception and during the first and second trimesters were associated with the risk [odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0-5.9; OR 22, 95% CI 2.8-171.5; OR 4.5, 95% CI 1.4-14.7, respectively] and during anytime (OR 2.2, 95% CI 1.0-4.8). An association was found for fathers' exposures to any pesticides during the second trimester (OR 1.5, 95% CI 1.0-2.3). An increased risk with respect to organophosphates was found for mothers during the first trimester (OR 3.5, 95% CI 1.0-12.2) and for fathers during the year before conception and the first trimester (OR 1.5, 95% CI 1.0-2.2 and OR 1.6, 95% CI 1.0-2.6, respectively), and benzimidazoles during the first, second, and third trimesters of pregnancy (OR 2.2, 95% CI 1.0-4.4; OR 2.2, 95% CI 1.0-5.0; OR 2.2, 95% CI 1.0-5.2, respectively). There was a suggestion of an exposure-response gradient for fathers as regards picloram, benomyl, and paraquat. Age at diagnosis was positively associated with fathers' exposures and inversely associated with mothers' exposures. CONCLUSIONS: The results suggest that parental exposure to certain pesticides may increase the risk of leukemia in offspring.
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