Origines et fondements philosophiques de la relativité : les conceptions de Mach, Galilée et Einstein

L'article qui suit se propose de montrer que le concept de « relativité » trouve, dans les conceptions de Mach, de Galilée et d'Einstein, une origine et un fondement philosophiques différents. En mettant ainsi en évidence les différences fondamentales qui séparent ces conceptions, il s'oppose en particulier à toute interprétation visant à faire de la théorie de la relativité d'Einstein, un « prolongement » de la philosophie positiviste de Mach et du principe galiléen de relativité.The following paper analyses relativity's philosophical origin and fundament through the conceptions of Mach, Galileo and Einstein. It emphasizes the fundamental differences that lie between these conceptions thus opposing all interpretations suggesting that Einstein's theory of relativity can he properly described as being a mere "extension" of Mach's positivism and Galileo's principle of relativity

L'esprit, le pouvoir et les femmes. Polygraphie d'un mouvement culturel québécois

L'intérêt porté au Renouveau charismatique catholique québécois est né d'une double constatation : la baisse très marquée de la pratique religieuse d'une part, la survivance des institutions religieuses et la croissance exponentielle des mouvements religieux dans la société postindustrielle d'autre part. De cette situation un peu contradictoire, le Renouveau charismatique offre un exemple privilégié.Influencé dans sa naissance par les groupes pentecôtistes américains, l'essor québécois de ce mouvement ne doit toutefois pas être réduit à la reproduction dépendante d'une identité importée. Une acculturation québécoise dynamique met en branle un mouvement endogène, produit localement par des acteurs relativement autonomes, en marge des hiérarchies institutionnelles, attestant des conduites et des valeurs différentielles prônées par les nouvelles idéologies dominantes au sein de l'intelligentsia québécoise.Divisée en quatre sections : l'historiographie, la démographie, l'ethnographie et la thanatographie, l'étude de ce mouvement nous montre que, même s'il est de culture pré-moderne et capable d'opérer des transactions avec son environnement — par exemple fusion de la joie, de la spontanéité et de la rationalité moderne —, il peut ainsi attirer dans ses rangs des adeptes appartenant soit aux cadres, soit, plus largement, à la classe moyenne

Coarse limestone particles limit the formation of Ca-phytate complexes in laying hens

Session 60, Theatre 10International audienceReducing phosphorus (P) excretion in laying hen production is a challenge. In the digestive tract, calcium (Ca) can form de novo unavailable complexes with phytate, impairing phytase efficiency to release non-phytic P (NPP) from phytate. In broilers, it has been shown that coarse limestone particles (CL) limit the formation of Ca−phytate complexes. Thus, the effect of CL and microbial phytase was investigated in laying hens between 31 and 35 wk of age to study the potential beneficial effect of CL incorporation on P utilization. Seventy-two Lohmann Tradition laying hens were randomly assigned to one of the four experimental diets. A 2×2 factorial arrangement was used with two levels of phytase and basal available P (aP); 0 FTU/kg with 0.30% aP or 300 FTU/kg with 0.15% aP and two limestone particle sizes (LmPS); fine particles (FL, <0.5 mm) or a mix (MIX) of 75% CL (2-4 mm) and 25% FL. Diets contained equivalent levels of Ca (3.5%), phytic P (PP, 0.18%) and, considering the phytase P equivalency, equivalent levels of aP (0.30%). Egg production and average daily feed intake (ADFI) were measured weekly throughout the experimentation. Tibia ash (%), apparent pre-caecal digestibility (APCD) of P and Ca (%) and PP disappearance at the ileal level (%) were measured. No differences were observed between treatments in ADFI, FCR and tibia ash. Phytase and CL together increased the APCD of Ca by 7.3 percentage points (Phytase × LmPS, P<0.001). Hens fed with FL and phytase exhibited a lower APCD of P compared with hens fed FL without phytase, while no differences were observed in hens fed with CL (Phytase × LmPS, P<0.001). Additionally, hens fed with FL and phytase showed a lower PP disappearance at the ileal level than hens fed with CL and phytase (Phytase × LmPS, P=0.005). These results may be explained by a lower formation of Ca-phytate complexes when limestone was provided as CL, and thus a higher availability of minerals for the animal. This strategy may therefore help improving the utilization of P and Ca and reducing P excretion in laying hens

Effect of phytase and limestone particle size on performance, eggshell quality, bone mineralization and mineral digestibility in laying hens

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Impact of dietary phosphorus and calcium feeding strategies on intestinal gene expression of broilers

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Effect of phytase and limestone particle size on mineral digestibility, performance, eggshell quality, and bone mineralization in laying hens

International audienceThe effect of microbial phytase and limestone particle size (LmPS) was assessed in Lohmann Tradition laying hens from 31 to 35 wk of age. Seventytwo hens were used in a completely randomized trial according to a 2 £ 2 factorial arrangement with 2 levels of phytase/basal available P (aP); 0 FTU/kg with 0.30% aP or 300 FTU/kg with 0.15% aP, and 2 limestone particle sizes; fine particles (FL, <0.5 mm) or a mix (MIX) of 75% coarse limestone (CL, 2−4 mm) and 25% FL. Diets contained equivalent levels of Ca (3.5%), phytic P (PP; 0.18%), and aP (0.30%) considering the P equivalency of phytase. Thus, dietary treatments were FL0 and MIX0 without phytase, and FL300 and MIX300 with 300 FTU/kg phytase. Performance were recorded daily and eggshell quality (eggshell weight proportion, weight, thickness, and breaking strength) was measured weekly. At the end of the trial, bone parameters (tibia breaking strength, elasticity, and ash) and th

Effects of dietary calcium and phosphorus deficiency and subsequent recovery on broiler chicken growth performance and bone characteristics

International audienceThe ability of birds to modify dietary phosphorus utilisation when fed with low-phosphorus and calcium (Ca) diets was studied using different sequences of dietary phosphorus and Ca restriction (depletion) and recovery (repletion) during the grower and the finisher phases. A total of 3600 Ross 708 broilers were randomly divided into 10 replicate pens per treatment (60 per pen, six pens per block). Chicks were fed a common starter diet from days 0 to 10, then a grower control diet (C: 0.90% Ca, 0.39% non-phytate phosphorus, nPP), mid-level diet (M: 0.71% Ca, 0.35% nPP) or low Ca and nPP diet (L: 0.60% Ca, 0.30% nPP) from days 11 to 21, followed by a finisher diet C, M or L containing, respectively, 0.85%, 0.57% or 0.48% Ca and 0.35%, 0.29% or 0.24% nPP from days 22 to 37. Six treatment sequences were tested: CC, MM, LL, ML, LC and LM. Bone mineral content by dual-energy X-ray, tibia ash, toe ash weight and tibia breaking strength were measured on days 21 and 37. No significant effect was observed on growth performance throughout the experiment. Diet L reduced bone mineral content, breaking strength, tibia and toe ash by 9%, 13%, 11% and 10%, respectively, on day 21 (compared with diet C, for linear effect, P<0.05). On day 37, bone mineral content, breaking strength, tibia and toe ash remained lower compared with control values (CC v. MM v. LL, P<0.05 for linear and quadratic effects). Mineral depletion duration (ML v. LL) did not affect bone mineral status. Replenishing with the C diet during the finisher phase (LC) restored bone mineral content, tibia ash and toe ash weight better than the M diet did, but not to control levels (CC v. LC v. LM, for linear effect, P<0.05). These results confirm that dietary Ca and nPP may be reduced in the grower phase without affecting final growth performance or breaking strength as long as the finisher diet contains sufficient Ca and nPP. The practical applications of this strategy require further study in order to optimise the depletion and repletion steps

Early-life conditioning strategies to reduce dietary phosphorus in broilers: underlying mechanisms

International audienceChickens adapt to P and Ca restriction during the very first days of life by improving P utilisation efficiency. The present study was built to identify the mechanisms underlying this adaptive capacity, and to identify the optimal window of application of the restriction (depletion). A total of 1600 Cobb 500TM male broilers were used. During each phase (from age 0 to 4 d, 5 to 8 d, 9 to 18 d and 19 to 33 d), the animals received either a control diet (H) or a restricted diet (L) with reduced levels of non-phytate P (nPP) and Ca (between −14 and −25 % for both) with four dietary sequences: HHHH, HLHL, LHHL and LLHL. None of the feeding strategies affected growth. Tibia ash content at day 4 and 8 was impaired when the L diet was fed from 0 to 4 and 5 to 8 d, respectively (P = 0⋅038 and P = 0⋅005). Whatever the early restriction period or length between 0 and 8 d of age, the mineralisation delay was compensated by day 18. This was accompanied by an increased mRNA expression of the Ca transporter, CALB1, and an increased apparent ileal digestibility of Ca at day 8 (P < 0⋅001). This adaptation was limited to the starter phase in restricted birds. No effect was seen on P transporters mRNA or protein expression. In conclusion, birds adapted to mineral restriction by increasing Ca and nPP utilisation efficiencies. Depletion−repletion strategies are promising in improving the sustainability of broiler production but need to be validated in phytase-supplemented diets