A new fast method for ceramic foam impregnation: Application to the CCVD synthesis of carbon nanotubes

A new process that allows preparing, in a single step, good washcoats of catalytic materials for the catalytic chemical vapour deposition (CCVD) synthesis of carbon nanotubes (CNTs) in reticulated ceramic foams is reported. It is shown that the washcoats, obtained by impregnation using viscous slurries made of finely divided powders dispersed in different media, cover the total surface of foams with good adhesions. The catalytic activity with regards to the CNT synthesis is finally verified, showing that our new fast impregnation process makes possible to get materials with final architectures suitable for heterogeneous catalysis applications

Simulation numérique de la propagation d'une source laser incohérente dans une fibre optique

International audienceLe présent travail concerne les lasers à fibre impulsionnels de puissance de type MOPFA (oscillateur laser maître suivi d'un amplificateur à fibre). Un travail expérimental a permis d'établir que les non-linéarités observées (effet Kerr, mélange à quatre ondes, effet Raman) pouvaient être de nature très différentes selon les caractéristiques de la source issue du laser maître sans toutefois permettre de déterminer si la statistique des photons est seule responsable des différents scénarios non-linéaires observés. Nous avons développé un code de simulation numérique afin de pouvoir valider l'hypothèse selon laquelle les propriétés du laser maître en termes de cohérence jouent un rôle prépondérant dans la manifestation des non-linéarités

Petite fabrique de la connaissance : aborder le savoir scientifique en se racontant des histoires

L’article évalue les effets d’un dispositif expérimenté depuis deux ans dans le cadre du cours de « Pratexte » à l’Université Stendhal, visant l’appropriation de savoirs théoriques par le biais de l’activité scripturale (atelier de lecture/écriture). Le travail proposé amène les étudiants à construire des connaissances théoriques dans leur domaine disciplinaire (Sciences du langage) dans et par l’écrit, la finalisation du travail prenant la forme originale d’une fiction scientifique, réalisée dans le cadre d’un atelier d’écriture. Cette démarche se fonde sur l’hypothèse suivante : pour s’approprier un savoir il faut l’apprivoiser, et pour cela le faire entrer en résonance avec sa propre histoire. On considère que la pensée scientifique (abstraction, distanciation), l’imagination (pensée métaphorique, rêverie, fiction) et l’expérience (versant matériel de l’activité d’écriture, expérience individuelle de la réalité) ne sont jamais séparées, mais fonctionnent au contraire en interaction permanente dans le processus d’élaboration des connaissances. L’écrit produit dans le cadre du dispositif est par conséquent susceptible de favoriser cette articulation entre « singulier » (pôle de la subjectivité) et « générique » (pôle de l’objectivité scientifique), en reliant des espaces habituellement coupés de façon hermétique dans le cadre des apprentissages scolaires. L’évaluation de la démarche permet d’explorer des pistes didactiques inédites, de révéler et de mettre en valeur des compétences scripturales souvent ignorée

Plasma biomarkers of small intestine adaptations in obesity-related metabolic alterations

Background: Evidence suggests that pathophysiological conditions such as obesity and type 2 diabetes (T2D) are associated with morphologic and metabolic alterations in the small intestinal mucosa. Exploring these alterations generally requires invasive methods, limiting data acquisition to subjects with enteropathies or undergoing bariatric surgery. We aimed to evaluate small intestine epithelial cell homeostasis in a cohort of men covering a wide range of adiposity and glucose homoeostasis statuses. Methods: Plasma levels of citrulline, a biomarker of enterocyte mass, and I-FABP, a biomarker of enterocyte death, were measured by UHPLC‑MS and ELISA in 154 nondiabetic men and 67 men with a T2D diagnosis. Results: Plasma citrulline was signifcantly reduced in men with insulin resistance and T2D compared to insulin sensi‑ tive men. Decreased citrulline levels were, however, not observed in men with uncontrolled metabolic parameters during T2D. Plasma I-FABP was signifcantly higher in men with T2D, especially in presence of uncontrolled glycemic and lipid profle parameters. Integration of both parameters, which estimate enterocyte turnover, was associated with glucose homeostasis as well as with T2D diagnosis. Diferences in biomarkers levels were independent of age and BMI and glucose fltration rates. Conclusions: Our study supports a decreased functional enterocyte mass and an increased enterocyte death rate in presence of metabolic alterations but emphasizes that epithelial cell homeostasis is especially altered in presence of severe insulin resistance and T2D. The marked changes in small intestine cellularity observed in obesity and diabe‑ tes are thus suggested to be part of gut dysfunctions, mainly at an advanced stage of the disease

Procédé de correction auditive utilisant un modèle paramétrique du signal de parole

Cet article présente un nouveau procédé de correction auditive utilisant un modèle paramétrique du signal de parole. Ce procédé permet, en plus des opérations classiques de compression et d'amplification, d'effectuer des transformations élaborées (modification du rythme temporel, modification de l'enveloppe spectrale, etc.) tout en conservant la structure naturelle du signal de parole. Les premiers résultats d'une série de tests cliniques montrent que ce procédé est bien accueilli par les personnes atteintes de surdités intermédiaires (moyennes ou sévères) et pour lesquelles il n'existe pas véritablement de traitement prothétique adapté

Suckling Dairy Calves/Nurse Cows System And Risk Of Gastrointestinal Nematodes Infection During The First Grazing Season In Organic Farms

In dairy farms, new rearing practices of calves with nurse cows have been developed by farmers but still remain poorly documented. The objective was to assess the impact of rearing suckling calves with nurse cows on the same pastures on the risk of gastrointestinal nematode (GIN) infection in calves. The grazing management has been recorded for each group. Serum pepsinogen level and GIN egg excretion per gram of faeces (epg) were determined in 438 calves belonging to 38 groups from 30 farms in the western part of France at housing (October 2018 to January 2019). The maximum number of infective larval generations met by the animals (LG) in each pasture plot was modelled by Parasit’Sim expert system. The data were analyzed using logistic regression (univariate and multivariate). Mean parasiticological parameters per group were low. On average, the serum pepsinogen level was 1.1 units of tyrosine (U Tyr) and the GIN egg output was 130 epg. Pasture infectivity was above LG4 for 2/3 of the groups. These results suggest that rearing suckling dairy calves with nurse cows decreases the level of GIN infection in calves at the end of the 1st grazing season compared with putting out to pasture weaned heifers alone. This can be explained by i) the fact that cows were immune and have a cleansing effect on the pastures when eating a lot of larvae while excreting few eggs and ii) Because not weaned calves had a slow larval intake when drinking milk from nurse cows

Performance and health status of dairy calves reared with nurse cows, a 2-year study involving 3 cohorts

The agro-ecological transition is based on “bottom up” innovation processes developed by agricultural stakeholders. The role of researchers is now to accompany this process by working closely with them. Since the 90s, groups of dairy farmers have been set up in many developed countries to exchange information about intensive grazing management. Within these groups, organic dairy breeders have experimented new cow-calf rearing practices, in which a specific batch of lactating cows is constituted in order to nurse and raise 2-4 calves each (usually replacement heifers) for several months on pasture. The objective of our study was to assess effects of this innovative rearing system on growth and health of the calves, with a focus on the risk of grazing parasite (gastrointestinal nematodes). On an experimental organic farm located in East of France, we designed a cow-calf rearing system in collaboration with farmers experienced on this practice. A 2-year study of 3 cohorts of 9, 16 and 23 calves was conducted from 2016 to 2019. We weighed, recorded all health events and measured different parasitic indicators at key times of the grazing season. Calves showed a fast and steady growth during the 2 years of follow-up, allowing a calving at 24 months old. Parasitic risks were low, with nurse cows playing a protective role towards infection. In addition, early immunity against gastrointestinal nematodes was developed in calves. Throughout the study, the calves did not receive any antibiotic nor anti-parasitic treatments. Only one calf died due to ruminal tympany. Rearing calves with nurse cows seems to be of real interest for their growth and health, and in particular the management of parasitic risks. Further studies in other farms are needed to validate these results