Nutrients

The gut microbiome is involved in nutrient metabolism and produces metabolites that, via the gut-brain axis, signal to the brain and influence cognition. Human studies have so far had limited success in identifying early metabolic alterations linked to cognitive aging, likely due to limitations in metabolite coverage or follow-ups. Older persons from the Three-City population-based cohort who had not been diagnosed with dementia at the time of blood sampling were included, and repeated measures of cognition over 12 subsequent years were collected. Using a targeted metabolomics platform, we identified 72 circulating gut-derived metabolites in a case-control study on cognitive decline, nested within the cohort (discovery n = 418; validation n = 420). Higher serum levels of propionic acid, a short-chain fatty acid, were associated with increased odds of cognitive decline (OR for 1 SD = 1.40 (95% CI 1.11, 1.75) for discovery and 1.26 (1.02, 1.55) for validation). Additional analyses suggested mediation by hypercholesterolemia and diabetes. Propionic acid strongly correlated with blood glucose (r = 0.79) and with intakes of meat and cheese (r > 0.15), but not fiber (r = 0.04), suggesting a minor role of prebiotic foods per se, but a possible link to processed foods, in which propionic acid is a common preservative. The adverse impact of propionic acid on metabolism and cognition deserves further investigation.COGINUT : Cognition, anti-oxydants, acides gras: approche interdisciplinaire du rôle de la nutrition dans le vieillissement du cerveauHistoire naturelle du déclin cognitif et du besoin de soins chez le sujet âg

A mathematical model for the SO_2 aggression to calcium carbonate stones: numerical approximation and asymptotic analysis

We introduce a degenerate nonlinear parabolic system which describes the chemical aggression of Calcium Carbonate stones under the attack of SO_2. For this system, we present some finite elements and finite differences schemes to approximate its solutions. Numerical stability is given under suitable CFL conditions. Finally, by means of a formal scaling, the qualitative behavior of the solutions for large times is investigated and a numerical verification of this asymptotics is given. Our results are in perfect agreement with the experimental behavior observed in the chemical literature

A MATHEMATICAL MODEL FOR THE SULPHUR DIOXIDE AGGRESSION TO CALCIUM CARBONATE STONES: NUMERICAL APPROXIMATION AND ASYMPTOTIC ANALYSIS ∗

Abstract. We introduce a degenerate nonlinear parabolic system that describes the chemical aggression of calcium carbonate stones under the attack of sulphur dioxide. For this system, we present some finite element and finite difference schemes to approximate its solutions. Numerical stability is given under suitable CFL conditions. Finally, by means of a formal scaling, the qualitative behavior of the solutions for large times is investigated, and a numerical verification of this asymptotics is given. Our results are in qualitative agreement with the experimental behavior observed in the chemical literature

Convergence of relaxation schemes for conservation laws

Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Time Asymptotic High Order Schemes for Dissipative BGK Hyperbolic Systems

We introduce a new class of finite differences schemes to approximate one dimensional dissipative semilinear hyperbolic systems with a BGK structure. Using precise analytical time-decay estimates of the local truncation error, it is possible to design schemes, based on the standard upwind approximation, which are increasingly accurate for large times when approximating small perturbations of constant asymptotic states. Numerical tests show their better performances with respect to those of other schemes

Diffusive kinetic explicit schemes for nonlinear degenerate parabolic systems

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal