Gromov-Thurston manifolds and anti-de Sitter geometry

We consider hyperbolic and anti-de Sitter (AdS) structures on $M\times (0,1)$, where $M$ is a $d$-dimensional Gromov-Thurston manifold. If $M$ has cone angles greater than $2\pi$, we show that there exists a "quasifuchsian" (globally hyperbolic maximal) AdS manifold such that the future boundary of the convex core is isometric to $M$. When $M$ has cone angles less than $2\pi$, there exists a hyperbolic end with boundary a concave pleated surface isometric to $M$. Moreover, in both cases, if $M$ is a Gromov-Thurston manifold with $2k$ pieces (as defined below), the moduli space of quasifuchsian AdS structures (resp. hyperbolic ends) satisfying this condition contains a submanifold of dimension $2k-3$. When $d=3$, the moduli space of quasifuchsian AdS (resp. hyperbolic) manifolds diffeomorphic to $M\times (0,1)$ contains a submanifold of dimension $2k-2$, and extends up to a "Fuchsian" manifold, that is, an AdS (resp. hyperbolic) warped product of a closed hyperbolic manifold by~$\R$. We use this construction of quasifuchsian AdS manifolds to obtain new compact quotients of \O(2d,2)/\U(d,1). The construction uses an explicit correspondence between quasifuchsian $2d+1$-dimensional AdS manifolds and compact quotients of \O(2d,2)/\U(d,1) which we interpret as the space of timelike geodesic Killing fields of \AdS^{2d+1}.Comment: 48 page

Metabolisme des acides gras volatils dans les ecosystemes methanogenes : application de la RMN du carbone 13

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Gromov-Thurston manifolds and anti-de Sitter geometry

We consider hyperbolic and anti-de Sitter (AdS) structures on $M\times (0,1)$, where $M$ is a $d$-dimensional Gromov-Thurston manifold. If $M$ has cone angles greater than $2\pi$, we show that there exists a "quasifuchsian" (globally hyperbolic maximal) AdS manifold such that the future boundary of the convex core is isometric to $M$. When $M$ has cone angles less than $2\pi$, there exists a hyperbolic end with boundary a concave pleated surface isometric to $M$. Moreover, in both cases, if $M$ is a Gromov-Thurston manifold with $2k$ pieces (as defined below), the moduli space of quasifuchsian AdS structures (resp. hyperbolic ends) satisfying this condition contains a submanifold of dimension $2k-3$. When $d=3$, the moduli space of quasifuchsian AdS (resp. hyperbolic) manifolds diffeomorphic to $M\times (0,1)$ contains a submanifold of dimension $2k-2$, and extends up to a "Fuchsian" manifold, that is, an AdS (resp. hyperbolic) warped product of a closed hyperbolic manifold by~$\R$. We use this construction of quasifuchsian AdS manifolds to obtain new compact quotients of \O(2d,2)/\U(d,1). The construction uses an explicit correspondence between quasifuchsian $2d+1$-dimensional AdS manifolds and compact quotients of \O(2d,2)/\U(d,1) which we interpret as the space of timelike geodesic Killing fields of \AdS^{2d+1}

Hydroxytyrosol from tyrosol using hydroxyphenylacetic acid-induced bacterial cultures and evidence of the role of 4-HPA 3-hydroxylase

International audienc

Characterization of clostridial species and sulfite-reducing anaerobes isolated from foie gras with respect to microbial quality and safety

International audienceAnaerobic sulfite-reducing bacteria are generally considered as indicators of clostridial contamination in meat products. We reconsidered the relevance of this indicator for crude and pasteurized foie gras. A three-year study was conducted to recover anaerobic sulfite-reducing bacteria from foie gras manufactures. Under anaerobic culture at 37 °C, 98 isolates were obtained from crude or pasteurized foie gras, surfaces and pepper used in the recipe and further identified. Heat-treated products lead to the exclusive isolation of Clostridium strains, but other samples demonstrated a high diversity of non-spore forming bacterial species. The diversity in the Clostridium group was also high, with 14 different species represented from the 49 clostridial isolates, including Clostridium perfringens and psychrotolerant species. All the 12 C. perfringens isolates belonged to type A, but none carried the enterotoxin gene. In addition, none of them was able to grow in foie gras at 8 °C over a 130-days period. Other species were also tested for their ability to grow in these conditions: only three isolates, identified as Clostridium sordellii, Clostridium tertium and Clostridium algidicarnis/putrefaciens, grew at 8 °C, exhibiting 5 to 6 log of population increase in 70 days. Consequently, regarding the risk of product spoilage, we recommend anaerobes enumeration at 37 °C for pasteurized foie gras products, or after a thermal treatment aiming at spore selection, for crude foie gras

Réponses physiologiques de Listeria monocytogenes aux stress (applications particulières aux stress froid, salin et matriciel)

L. monocytogenes est un problème majeur de sécurité des aliments, au cœur des préoccupations des acteurs en charge de la santé publique. L'étude des réponses physiologiques de diverses souches de L. monocytogenes à des stress technologiques a constitué le sujet principal de cette thèse. Ainsi, pour cette bactérie nous avons (i) déterminé les paramètres de croissance dans différentes conditions de culture, (ii) établi les profils d'acides gras membranaires. Puis, par référence à la fabrication du saumon fumé, nous avons abordé le comportement de L. monocytogenes, en termes de cultivabilité, viabilité et modulation du pouvoir pathogène in vivo (modèle souris). Enfin, l'étude de la réponse au stress oxydant a été initiée. Les résultats obtenus mettent en évidence une grande diversité des réponses de L. monocytogenes. Ce travail met en lumière l'approche expérimentale qui doit être utilisée dans la démarche d'appréciation quantitative des risques microbiologiques dans les aliments.L. monocytogenes is a major problem of food safety. Indeed, it is of major concern for the public health professionals. The main subject of this thesis was the study of the physiological adaptation to technological stress of several strains of L. monocytogenes. Therefore, we established for this bacterium (i) the growth parameters under different culturing conditions, (ii) the membrane fatty acids profiles. Afterwards, in relation to the cold smoked salmon process, we studied the behaviour of L. monocytogenes, in terms of culturability, viability and modulation of the in vivo pathogenicity (mouse model). Finally, we started the study of the adaptation to oxidative stress. Our data show that the responses of this microorganisme are extremely diverse. This work highlights the experimental approach that should be used in the microbiological quantitative risk assessment in foods.NANTES-BU Sciences (441092104) / SudocSudocFranceF

First evidence of aerobic biodegradation of BTEX compounds by pure cultures of Marinobacter

Marinobacter vinifirmus was shown to degrade toluene as sole carbon and energy source under aerobiosis and at NaCl concentrations in the range 30-150 g/L. Maximum toluene consumption rate, total CO2, and biomass productions were measured in the presence of 60 g/L of NaCl. Under these conditions, 90% of the carbon from toluene was recovered as CO2 and biomass. Maximum specific toluene consumption rate was about 0.12 mgC toluene mgC biomass(-1) h(-1) at NaCl concentrations between 30 and 60 g/L. It decreased to 0.03 mgC toluene mgC biomass(-1) h(-1) at 150 g/L. Besides toluene, M. vinifirmus degraded benzene, ethylbenzene, and p-xylene. Benzene and toluene were utilized to a lesser extent by another Marinobacter sp., Marinobacter hydrocarbonoclasticus