Cystic echinococcosis in slaughtered domestic ruminants from Tunisia

A total of 10,818 domestic ruminants (3913 cattle, 2722 sheep, 3779 goats, 404 dromedaries) slaughtered in various abattoirs in Tunisia between 2003 and 2010 were examined for the presence of Echinococcus granulosus hydatid cysts. The prevalence of cystic echinococcosis (CE) was 16.42% in sheep, 8.56% in cattle, 5.94% in dromedaries and 2.88% in goats. CE prevalence increased with age according to an asymptotic model and there was evidence of variation in infection pressure depending on the region of Tunisia where the animals were slaughtered. Cattle appeared to have the highest infection pressure of the species examined. The mean intensity of hepatic cysts was higher than that of pulmonary cysts in all species. The highest mean intensity of infection with E. granulosus larvae was observed in cattle (18.14) followed by sheep (9.58), goats (2.31) and dromedaries (2.12). The abundance of infection increased in a linear fashion with age in all animal species. Cyst abundance varied with species of animal and district of Tunisia. Cysts from dromedaries were more fertile (44.44%) than those from sheep (30.25%), goats (30.32%) and cattle (0.95%). The viability of the protoscoleces from fertile cysts from cattle (78.45%) was higher than those from sheep (70.71%) and camels (69.57%). The lowest protoscolex viability was recorded for hydatid cysts from goats (20.21%). This epidemiological study confirms the importance of CE in all domestic ruminant species, particularly in sheep, throughout Tunisia and emphasizes the need to interrupt parasite transmission by preventive integrated approaches in a CE control programm

Defining the importance of landscape metrics for large branchiopod biodiversity and conservation: the case of the Iberian Peninsula and Balearic Islands

The deficiency in the distributional data of invertebrate taxa is one of the major impediments acting on the bias towards the low awareness of its conservation status. The present study sets a basic framework to understand the large branchiopods distribution in the Iberian Peninsula and Balearic Islands. Since the extensive surveys performed in the late 1980s, no more studies existed updating the information for the whole studied area. The present study fills the gap, gathering together all available information on large branchiopods distribution since 1995, and analysing the effect of human population density and several landscape characteristics on their distribution, taking into consideration different spatial scales (100 m, 1 km and 10 km). In overall, 28 large branchiopod taxa (17 anostracans, 7 notostracans and 4 spinicaudatans) are known to occur in the area. Approximately 30% of the sites hosted multiple species, with a maximum of 6 species. Significant positive co-occurring species pairs were found clustered together, forming 4 different associations of large branchiopod species. In general, species clustered in the same group showed similar responses to analysed landscape characteristics, usually showing a better fit at higher spatial scales.Brazilian Conselho Nacional de Desenvolvimento Cientifico e Tecnologico-CNPq [401045/2014-5]Spanish Ministry of Education, Culture and Sport [FPU014/06783]info:eu-repo/semantics/publishedVersio

Multiaxial high-cycle fatigue criteria and life prediction : Application to gas turbine blade

International audienceA recent work conducted by the authors (Maktouf and Saï, 2015) demonstrated that the root cause of the premature blade failure was caused by high-cycle fatigue (HCF) mechanism initiated at a localized carbon-rich area inducing grain boundary brittleness. The blade was subject to multiaxial cyclic loadings during its service life and any attempt to assess component fatigue strength leads to the question of choosing an appropriate fatigue design criterion. In this paper several multiaxial fatigue models are applied as post-processing step of the Finite Element Analysis (FEA) output results and the estimated fatigue lifetimes were assessed under different loading conditions. The material fatigue parameters, required as an input to the selected fatigue models were determined through a series of bending and torsion tests on specimens made of aged Inconel 718. A numerical post-processing algorithm was developed for Fatemi-Socie fatigue criterion and included as additional post-computation model in the used computer aided fatigue damage evaluation tool. The authors point out that the majority of the multiaxial fatigue studies available in the literature are conducted mainly for correlating the experimental laboratory results on specimens while they have been used in the frame of this study to investigate their application to an industrial case

Micromechanical modeling of the ratcheting behavior of 304 stainless steel

International audienceNumerical simulations of 304 austenitic stainless steel (SS304) cyclic and ratcheting responses are performed using polycrystalline plasticity models. On the basis of the polycrystalline model of Cailletaud and Pilvin (1994, “Utilisation de modèles polycristallins pour le calcul par éléments finis,” Rev. Eur. Élém. Finis, 3, pp. 515–541), a modification of the β rule that operates the transition between the macroscopic level and the grain level is proposed. The improvement of the transition rule is obtained by introducing a “memory variable” at the grain level, so that a better description of the local stress–strain behavior is provided. This new feature is calibrated by means of previous simulations using finite element (FE) aggregate models. The results of the updated polycrystalline plasticity model are in good agreement with the macroscopic responses

A new polycrystalline plasticity model to improve ratchetting strain prediction

International audienceIn this work, a polycrystalline plasticity model is proposed with a new scale transition rule from the macroscopic level to the grain level. The proposed constitutive model intended to improve ratchetting behavior is presented within a thermodynamic framework. Material parameter estimates are obtained through an identification study, where the error is minimized by simultaneous comparison with (i) an aggregate model computed by the FE (finite element) technique and (ii) experimental data taken from the literature. Noticeable improvements for describing experimental ratchetting tests are obtained compared to the β-rule of the Pilvin Cailletaud model [Cailletaud, G., Pilvin, P., 1994. Utilisation de modèles polycristallins pour le calcul par éléments finis. Rev. Eur. Eléments Finis 3, 515–541]

Multi-mechanism damage-plasticity model for semi-crystalline polymer: Creep damage of notched specimen of PA6

International audienceThe multi-mechanism model devoted to the semi-crystalline polymers proposed in the recent study (Regrain et al. [1]) is generalized in this work to account for mechanical damage behaviour. To assess model reliability, finite element simulations of notched specimens subjected to creep behaviour were performed and compared successfully to experiments in terms of creep notch opening displacement. The model is able to reproduce the location of the maximum damage in a structure. This is a key information for the lifetime prediction of engineering components made of semi-crystalline polymers such as pressure vessel or pipes subjected to creep loading