Convergence of invariant measures for singular stochastic diffusion equations

It is proved that the solutions to the singular stochastic $p$-Laplace equation, $p\in (1,2)$ and the solutions to the stochastic fast diffusion equation with nonlinearity parameter $r\in (0,1)$ on a bounded open domain $\Lambda\subset\R^d$ with Dirichlet boundary conditions are continuous in mean, uniformly in time, with respect to the parameters $p$ and $r$ respectively (in the Hilbert spaces $L^2(\Lambda)$, $H^{-1}(\Lambda)$ respectively). The highly singular limit case $p=1$ is treated with the help of stochastic evolution variational inequalities, where \mathbbm{P}-a.s. convergence, uniformly in time, is established. It is shown that the associated unique invariant measures of the ergodic semigroups converge in the weak sense (of probability measures).Comment: to appear in Stoch. Proc. Appl. (in press), 18 p

Endogenous protein and peptide analysis with LC-MS/(MS) : A feasibility study for authentication of raw-milk farmer's cheese

When consumers buy Dutch ‘Boerenkaas’ (farmer's cheese), a cheese made from raw milk protected under the European traditional specialties guaranteed (TSG) label, they expect this product to be authentic. Because of the difference in production costs and risks, it is tempting to sell cheeses made from heat-treated milk as ‘Boerenkaas’. It is therefore essential that there are methods that can verify the heat-treatment status of the milk in cheese. Here, for the first time a proof of principle method for analysis of endogenous cheese proteins/peptides with liquid chromatography-mass spectrometry (LC-MS) in combination with multivariate analysis to detect discriminatory protein/peptide biomarkers between ‘Boerenkaas’ and heat-treated milk cheese is described. A top-down MS method was developed for biomarker identification. The identified biomarkers were confirmed with the well-established bottom-up approach. Overall, there was good agreement between the outcome of the developed methods based on the known thermal treatment of the used sample set.</p

Nonlinear stochastic partial differential equations with singular diffusivity and gradient Stratonovich noise

International audienc

Development and application of criteria for classification of hydrolysed proteins in the framework of feed safety

In the view of a circular economy, there is an increasing need for (re-)using animal by-products that have a wide range of applications and sufficient safety. Hydrolysates of animal proteins (HPs) are frequently used as feed ingredients. Nevertheless, clear criteria for legal use and methods for monitoring feed applications are not available. Here, a range of methods have been used and evaluated for characterizing a set of 26 samples of hydrolysed proteins, ‘hydrolysed’ feather meals and processed animal proteins (PAPs), with verification based on an additional set of eight samples. Methods included determination of ash content, sediment (mineral fraction) content, protein content, species identity, solubility, protein solubility, size exclusion chromatography and polyacrylamide gel electrophoresis (SDS-PAGE). After a comparison of results obtained with water and SDS, water was chosen as the solvent for environmental and occupational reasons. Typical HP samples have a protein content higher than 60%, a solubility exceeding 50% and a virtual absence of a mineral fraction. The first discrimination between HPs and PAPs could be based on the absence or presence, respectively, of a mineral fraction. An approach for HP characterization is designed using a Hydrolysation Index (HI) based on the fraction of peptides smaller than 10 kDa, the solubility of the sample and the fraction of soluble proteins. A simplified version (HIs), exclusively based on the fraction of peptides smaller than 10 kDa and the solubility of the sample, shows a trend among the samples highly comparable to HI. Values for HI and HIs exceeding 60% would characterise HPs. Feather meals, which are heat treated instead of treatment by a chemical process of hydrolysation, range among the PAPs and should not be indicated as “hydrolysed.” The HIs can be used as an easy parameter for classifying HPs and for legal enforcement

Native Tandem and Ion Mobility Mass Spectrometry Highlight Structural and Modular Similarities in Clustered-Regularly-Interspaced Shot-Palindromic-Repeats (CRISPR)-associated Protein Complexes From Escherichia coli and Pseudomonas aeruginosa *

The CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated genes) immune system of bacteria and archaea provides acquired resistance against viruses and plasmids, by a strategy analogous to RNA-interference. Key components of the defense system are ribonucleoprotein complexes, the composition of which appears highly variable in different CRISPR/Cas subtypes. Previous studies combined mass spectrometry, electron microscopy, and small angle x-ray scattering to demonstrate that the E. coli Cascade complex (405 kDa) and the P. aeruginosa Csy-complex (350 kDa) are similar in that they share a central spiral-shaped hexameric structure, flanked by associating proteins and one CRISPR RNA. Recently, a cryo-electron microscopy structure of Cascade revealed that the CRISPR RNA molecule resides in a groove of the hexameric backbone. For both complexes we here describe the use of native mass spectrometry in combination with ion mobility mass spectrometry to assign a stable core surrounded by more loosely associated modules. Via computational modeling subcomplex structures were proposed that relate to the experimental IMMS data. Despite the absence of obvious sequence homology between several subunits, detailed analysis of sub-complexes strongly suggests analogy between subunits of the two complexes. Probing the specific association of E. coli Cascade/crRNA to its complementary DNA target reveals a conformational change. All together these findings provide relevant new information about the potential assembly process of the two CRISPR-associated complexes

Rapport final du projet TRACKYLEAKS - Développement d'une méthode d'identification et de quantification des émissions fugitives de biogaz - Application aux installations de méthanisation

The French government encourages the development of biogas plants, fulfilling a dual purpose to produce renewable energy and recycle organic residues. This commitment resulted in a reassessment of the price of electricity produced from biogas plants. French government also authorized the Injection of biogas in the natural gas network in 2011. In particular, the agricultural sector is expected to benefit from a strong increase in the coming years. Indeed, a recent Energy Plan (PMAA) carried by the French government schedules a total of 1000 biogas plants in the farms in 2020 whereas only 130 units are present in 2013 . Targeted benefits of anaerobic digestion through this plan are (1) the reduction of methane emissions inherent to conventional manure management, (2) the recycling of organic waste, (3) the contribution to renewable energy (4) the substitution of mineral nitrogen by the digestate. The IPCC estimates biogas leakage between 0 and 10 % (IPCC06), and recommends a default value of 5% in the absence of specific data. According Börjesson and Berglund (2007), these leaks are normally less than 2 %, but can vary between 0.2 % and 13 %. To face this situation on the environmental issue of biogas leakage, data compatible with the life cycle assessment tools are needed, obtained through measurements aiming to identify and quantify the leaks. The ultimate challenge is to prove or move towards an environmental relevance of biogas plants currently and soon implemented in France. The French literature on the subject does not establish specific emission factors to the national context. The international literature shows a range of values which in extreme cases can compromise the environmental benefits foreseen. The proposed project aims at providing new knowledge on the detection and quantification of biogas leaks. An important part of the project will be devoted to experimental work. A validation of a novel method is expected, based on the analysis of optical flow from infrared video imaging.Les pouvoirs publics français incitent au développement d'installations de méthanisation, répondant ainsi à un double objectif de production d'énergie renouvelable et de valorisation des résidus organiques. Cet engagement de l'Etat s'est traduit en 2011 par une réévaluation du tarif de rachat d'électricité produite à partir de biogaz et par l'autorisation d'injection du biogaz dans le réseau de gaz naturel. Le secteur agricole notamment devrait subir un fort accroissement dans les prochaines années puisque le récent Plan Energie Méthanisation Autonomie Azote (EMAA) porté par le gouvernement français ambitionne un total de 1000 unités de méthanisation à la ferme en 2020 contre un parc de 130 unités en 2012. Les avantages ciblés de la méthanisation à travers ce plan sont (i) la réduction des émissions de méthane inhérentes à la gestion conventionnelle des effluents, (ii) la valorisation matière de résidus organiques, (iii) la contribution à la production d'énergie renouvelable, (iv) le moindre recours à l'azote minéral par substitution de celui-ci par le digestat. Le GIEC estime les fuites de biogaz entre 0 et 10% (IPCC06) au niveau du digesteur, et préconise une valeur par défaut de 5% en l'absence de données spécifiques. D'après Börjesson et Berglund (2007), ces fuites sont normalement inférieures à 2%, mais peuvent varier entre 0,2% et 13%. Face à ce constat sur l'enjeu environnemental des fuites de biogaz et le besoin de données compatibles avec les outils d'évaluation environnementale, l'identification et la quantification des fuites de biogaz se révèlent être un défi majeur, dans le but de conforter la pertinence environnementale des unités de méthanisation actuellement installées et à venir en France. La bibliographie française sur le sujet ne permet pas d'établir de facteurs d'émissions caractéristiques du contexte national et la bibliographie internationale montre une amplitude de valeurs allant dans les cas extrêmes jusqu'à compromettre le bénéfice environnemental pressenti. Aussi, TrackyLeaks ambitionne un travail de recherche en connaissances nouvelles sur l'identification et la quantification des fuites de biogaz sur les sites de méthanisation. Une part importante du projet sera consacrée à des travaux expérimentaux qui permettront de valider une méthode originale d'analyse du flot optique à partir d'imagerie vidéo infrarouge