niversite Nantes Angers Le Mans

Angers, France

niversite Nantes Angers Le Mans

Angers, France
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Ranaivomanana H.,University of Nantes | Razakamanantsoa A.,niversite Nantes Angers Le Mans | Amiri O.,University of Nantes
International Journal of Geomechanics | Year: 2017

The present paper deals with the proposition of an original analytical permeability model of compacted soils. The model involves the microstructure of the material through the porosity and the pore-size distribution obtained by mercury intrusion porosimetry (MIP), as well as the degree of compaction. Their effects on the morphological parameters of the porous network (tortuosity and interconnection of pore network) are studied. The model was developed and tested on various types of soil: a loamy sand, a gravelous sand, a clay, and an alterite. Samples were compacted with various degrees of compaction: 85, 95, 100, and 105% of the optimum dry density as determined by a standard compaction method. The experimental results obtained for both loamy and gravelous sands and for clay were well reproduced by the model, except for the alterite. Such results might be explained by the high brittleness of the alterite, leading to a crumbling phenomenon rather than to its densification during the compaction process. © 2016 American Society of Civil Engineers.

Gourdain P.,French Institute of Health and Medical Research | Gourdain P.,University Pierre and Marie Curie | Ballerini C.,University of Florence | Nicot A.B.,French Institute of Health and Medical Research | And 4 more authors.
Journal of Neuroinflammation | Year: 2012

Background: The cellular prion protein (PrPc) is a host-encoded glycoprotein whose transconformation into PrP scrapie (PrPSc) initiates prion diseases. The role of PrPc in health is still obscure, but many candidate functions have been attributed to the protein, both in the immune and the nervous systems. Recent data show that experimental autoimmune encephalomyelitis (EAE) is worsened in mice lacking PrPc. Disease exacerbation has been attributed to T cells that would differentiate into more aggressive effectors when deprived of PrPc. However, alternative interpretations such as reduced resistance of neurons to autoimmune insult and exacerbated gliosis leading to neuronal deficits were not considered.Method: To better discriminate the contribution of immune cells versus neural cells, reciprocal bone marrow chimeras with differential expression of PrPc in the lymphoid or in the central nervous system (CNS) were generated. Mice were subsequently challenged with MOG 35-55peptide and clinical disease as well as histopathology were compared in both groups. Furthermore, to test directly the T cell hypothesis, we compared the encephalitogenicity of adoptively transferred PrPc-deficient versus PrPc-sufficient, anti-MOG T cells.Results: First, EAE exacerbation in PrPc-deficient mice was confirmed. Irradiation exacerbated EAE in all the chimeras and controls, but disease was more severe in mice with a PrPc-deleted CNS and a normal immune system than in the reciprocal construction. Moreover, there was no indication that anti-MOG responses were different in PrPc-sufficient and PrPc-deficient mice. Paradoxically, PrPc-deficient anti-MOG 2D2 T cells were less pathogenic than PrPc-expressing 2D2 T cells.Conclusions: In view of the present data, it can be concluded that the origin of EAE exacerbation in PrPc-ablated mice resides in the absence of the prion protein in the CNS. Furthermore, the absence of PrPc on both neural and immune cells does not synergize for disease worsening. These conclusions highlight the critical role of PrPc in maintaining the integrity of the CNS in situations of stress, especially during a neuroinflammatory insult. © 2012 Gourdain et al; BioMed Central Ltd.

Membre J.-M.,French National Institute for Agricultural Research | Membre J.-M.,niversite Nantes Angers Le Mans | Laroche M.,French National Institute for Agricultural Research | Laroche M.,niversite Nantes Angers Le Mans | And 2 more authors.
Food Microbiology | Year: 2011

The variations in prevalence and levels of pathogens and fecal contamination indicators in large wild game meat were studied to assess their potential impact on consumers. This analysis was based on hazard analysis, data generation and statistical analysis. A total of 2919 meat samples from three species (red deer, roe deer, wild boar) were collected at French game meat traders' facilities using two sampling protocols. Information was gathered on the types of meat cuts (forequarter or haunch; first sampling protocol) or type of retail-ready meat (stewing meat or roasting meat; second protocol), and also on the meat storage conditions (frozen or chilled), country of origin (eight countries) and shooting season (autumn, winter, spring). The samples were analyzed in both protocols for detection and enumeration of Escherichia coli, coagulase. +. staphylococci and Clostridium perfringens. In addition, detection and enumeration of thermotolerant coliforms and Listeria monocytogenes were performed for samples collected in the first and second protocols, respectively. The levels of bacterial contamination of the raw meat were determined by performing statistical analysis involving probabilistic techniques and Bayesian inference. C. perfringens was found in the highest numbers for the three indicators of microbial quality, hygiene and good handling, and L. monocytogenes in the lowest. Differences in contamination levels between game species and between meats distributed as chilled or frozen products were not significant. These results might be included in quantitative exposure assessments. © 2011 Elsevier Ltd.

Dagnas S.,niversite Nantes Angers Le Mans | Onno B.,niversite Nantes Angers Le Mans | Membre J.-M.,niversite Nantes Angers Le Mans | Membre J.-M.,French National Institute for Agricultural Research
International Journal of Food Microbiology | Year: 2014

The objective of this study was to quantify the effect of water activity, pH and storage temperature on the growth of Eurotium repens, Aspergillus niger and Penicillium corylophilum, isolated from spoiled bakery products. Moreover, the behaviors of these three mold species were compared to assess whether a general modeling framework may be set and re-used in future research on bakery spoilage molds. The mold growth was modeled by building two distinct Gamma-type secondary models: one on the lag time for growth and another one on the radial growth rate. A set of 428 experimental growth curves was generated. The effect of temperature (15-35. °C), water activity (0.80-0.98) and pH (3-7) was assessed. Results showed that it was not possible to apply the same set of secondary model equations to the three mold species given that the growth rate varied significantly with the factors pH and water activity. In contrast, the temperature effect on both growth rate and lag time of the three mold species was described by the same equation. The equation structure and model parameter values of the Gamma models were also compared per mold species to assess whether a relationship between lag time and growth rate existed. There was no correlation between the two growth responses for E. repens, but a slight one for A. niger and P. corylophilum. These findings will help in determining bakery product shelf-life and guiding future work in the predictive mycology field. © 2014 Elsevier B.V.

Vittecoq M.,IRD Montpellier | Vittecoq M.,Center for Ecological and Evolutionary Cancer Research | Roche B.,Center for Ecological and Evolutionary Cancer Research | Roche B.,University Pierre and Marie Curie | And 10 more authors.
Trends in Ecology and Evolution | Year: 2013

Cancer is a disease that affects the majority of metazoan species and, before directly causing host death, is likely to influence the competitive abilities of individuals, their susceptibility to pathogens, their vulnerability to predators, and their ability to disperse. Despite the potential importance of these ecological impacts, cancer is rarely incorporated into model ecosystems. We describe here the diversity of ways in which oncogenic phenomena, from precancerous lesions to generalized metastatic cancers, may affect ecological processes that govern biotic interactions. We argue that oncogenic phenomena, despite their complexity, can have significant and sometimes predictable ecological consequences. Our aim is to provide a new perspective on the ecological and evolutionary significance of cancer in wildlife, and to stimulate research on this topic. © 2013 Elsevier Ltd.

Dagnas S.P.,niversite Nantes Angers le Mans | Membre J.-M.,niversite Nantes Angers le Mans | Membre J.-M.,French National Institute for Agricultural Research
Journal of Food Protection | Year: 2013

This article is a review of how to quantify mold spoilage and consequently shelf life of a food product. Mold spoilage results from having a product contaminated with fungal spores that germinate and form a visible mycelium before the end of the shelf life. The spoilage can be then expressed as the combination of the probability of having a product contaminated and the probability of mold growth (germination and proliferation) up to a visible mycelium before the end of the shelf life. For products packed before being distributed to the retailers, the probability of having a product contaminated is a function of factors strictly linked to the factory design, process, and environment. The in-factory fungal contamination of a product might be controlled by good manufacturing hygiene practices and reduced by particular processing practices such as an adequate air-renewal system. To determine the probability of mold growth, both germination and mycelium proliferation can be mathematically described by primary models. When mold contamination on the product is scarce, the spores are spread on the product and more than a few spores are unlikely to be found at the same spot. In such a case, models applicable for a single spore should be used. Secondary models can be used to describe the effect of intrinsic and extrinsic factors on either the germination or proliferation of molds. Several polynomial models and gamma-type models quantifying the effect of water activity and temperature on mold growth are available. To a lesser extent, the effect of pH, ethanol, heat treatment, addition of preservatives, and modified atmospheres on mold growth also have been quantified. However, mold species variability has not yet been properly addressed, and only a few secondary models have been validated for food products. Once the probability of having mold spoilage is calculated for various shelf lives and product formulations, the model can be implemented as part of a risk management decision tool. Copyright ©, International Association for Food Protection.

PubMed | niversite Nantes Angers Le Mans and French National Institute for Agricultural Research
Type: Journal Article | Journal: Journal of food protection | Year: 2015

The combined effect of undissociated lactic acid (0 to 180 mmol/liter), acetic acid (0 to 60 mmol/liter), and propionic acid (0 to 12 mmol/liter) on growth of the molds Aspergillus niger, Penicillium corylophilum, and Eurotium repens was quantified at pH 3.8 and 25C on malt extract agar acid medium. The impact of these acids on lag time for growth () was quantified through a gamma model based on the MIC. The impact of these acids on radial growth rate () was analyzed statistically through polynomial regression. Concerning , propionic acid exhibited a stronger inhibitory effect (MIC of 8 to 20 mmol/liter depending on the mold species) than did acetic acid (MIC of 23 to 72 mmol/liter). The lactic acid effect was null on E. repens and inhibitory on A. niger and P. corylophilum. These results were validated using independent sets of data for the three acids at pH 3.8 but for only acetic and propionic acids at pH 4.5. Concerning , the effect of acetic and propionic acids was slightly inhibitory for A. niger and P. corylophilum but was not significant for E. repens. In contrast, lactic acid promoted radial growth of all three molds. The gamma terms developed here for these acids will be incorporated in a predictive model for temperature, water activity, and acid. More generally, results for and will be used to identify and evaluate solutions for controlling bakery product spoilage.

PubMed | niversite Nantes Angers Le Mans, Aristotle University of Thessaloniki and French National Institute for Agricultural Research
Type: | Journal: International journal of food microbiology | Year: 2016

The inhibitory effect of water activity (a

Thorel L.,niversite Nantes Angers Le Mans | Ferber V.,niversite Nantes Angers Le Mans | Caicedo B.,University of Los Andes, Colombia | Khokhar I.M.,niversite Nantes Angers Le Mans
Geotechnique | Year: 2011

The relevance of the oedometer tests used for the prediction of wetting-induced deformations in embankments is examined. Single and double oedometer tests are carried out. A comparison is made between laboratory tests and geotechnical centrifuge modelling at 100g conducted to examine an inundated embankment made of a sand-clay mixture. A 20 cm high embankment model is built and instrumented. The material is compacted on the 'dry side' of the optimum Proctor curve at a low compaction rate in order to emphasise settlement phenomena. The inundation simulation is conducted in two successive sequences during centrifuge flight up to a water table of 5 cm. The results prove that the prediction of the dry density after settlement due to inundation is good.

Nasser H.,niversite Nantes Angers Le Mans | Chabot A.,niversite Nantes Angers Le Mans
Civil-Comp Proceedings | Year: 2015

This paper presents an engineering tool for the rapid analysis of the mechanical fields in cracked pavements. The pavement structure is reduced to three elastic and homogeneous equivalent layers resting on a soil. The soil is modelled by one layer, named the shear layer, connected to Winkler's springs in order to ensure the transfer of shear stresses between the pavement structure and the springs. The whole fourlayer system (three pavement layers connected to the shear layer) is modelled using a simplified model (M4-5n) developed for the analysis of delamination in composite materials. For the case of two-dimensional plane strain, a system of twelve equations is written analytically. These second order differential equations are solved by a finite difference method (Newmark). In the case of a pavement containing a vertical cracking through one layer, the half-analytical solutions are obtained in less than one second of CPU. This tool, called M4-5nW, thus allows parametric studies such as the distribution of mechanical fields (especially interface stresses) as a function of the load position more or less distant from the vertical crack. This new modelling shows its effectiveness compared to the use of a conventional finite element code. © Civil-Comp Press, 2015.

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