Mouillage de polymères solubles

The wetting of a soluble substrate is a situation commonly encountered in day-to-day life. For instance, the practical motivation of this study concerns the preparation of beverages using dehydrated powders, consisting of water-soluble substances such as carbohydrates. Hydrodynamical theories describing wetting onto insoluble substrates cannot account for experimental observations in the case of a liquid spreading onto a soluble substrate. Tay et al.(1) made the hypothesis that the water content at the contact line controls the contact angle value and they showed the importance of the evaporation/condensation of the solvent during wetting. In this study, we demonstrate that other mass transfers have to be considered to improve the understanding on wetting dynamics on soluble surfaces; thus diffusion within the polymer of the condensed water or directly from the droplet are processes that contribute to the hydration of the substrate and the modification of the contact angle of the drop. Therefore, we use the following approach to carry out this study: (i) finite elements simulations are performed in order to take into account diffusion effects in the layer and validate our theoretical arguments, (ii) spreading experiments of water onto maltodextrin thin layers are performed in order to study the wetting and the hydration ahead the contact line. This work allows us to highlight the influence of the diffusion in the polymer that makes the hydration profiles ahead the contact line more complex with a diffusion region where evaporation occurs. A wetting diagram thickness-velocity (e−U) with different regimes is established. Those regimes are validated with the experimental data. In particular, we evidence a regime where the contact angle is a function of the quantity eU. Furthermore, we evidence the effect of glass transition in the polymer on the contact angle and the hydration of the substrate. Finally, a preliminary study is performed to understand the influence of another transfer at stake in the wetting process: the dissolution of the polymer in the solvent.Le mouillage d'un substrat soluble est une situation couramment rencontrée dans la vie de tous les jours les jours. Par exemple, les motivations pratiques de cette étude concernent la préparation de boissons à partir de poudres déshydratées, constituées de substances solubles dans l'eau telles que les glucides. Les modèles hydrodynamiques décrivant le mouillage sur un substrat non soluble ne peuvent pas expliquer les observations expérimentales dans le cas d'un liquide s'étalant sur un substrat soluble. Tay et al.(1) ont émis l'hypothèse que la fraction d'eau à la ligne de contact contrôle la valeur de l'angle de contact et ils ont montré l'importance du processus d'évaporation/condensation du solvant lors du mouillage. Dans cette étude, nous montrons que d'autres transferts de matière doivent être considérés pour améliorer la compréhension du processus de mouillage d'une couche soluble; ainsi la diffusion dans le polymère de l'eau condensée, ou directement depuis la goutte sont des processus qui contribuent à hydrater le substrat et modifier l'angle de contact de la goutte. Nous avons utilisé l'approche suivante pour réaliser cette étude: (i) pour prendre en compte la diffusion dans le substrat, nous avons réalisé des simulations en éléments finis qui permettent de valider nos arguments théoriques, (ii) des expériences d'étalement de goutte sur des couches minces de maltodextrine ont été réalisées afin d'étudier le mouillage et l'hydratation en avant de la ligne de contact. Ce travail nous permet de mettre en avant l'influence de la diffusion dans la couche qui complexifie les profils d'hydratation en avant de la ligne de contact, avec notamment l'apparition d'une région de diffusion où de l'évaporation est observée. Un diagramme de mouillage épaisseur-vitesse (e − U) avec différents régimes est établi. Nous validons ces régimes expérimentalement et plus particulièrement un régime où l'angle de contact est une fonction du produit eU. Par ailleurs, nous montrons l'influence de la transition vitreuse du polymère sur l'angle de contact et l'hydratation. Enfin, une étude préliminaire est réalisée pour comprendre l'influence de la dissolution du polymère lors du mouillage

Wetting of soluble polymers

The wetting of a soluble substrate is a situation commonly encountered in day-to-day life, life. Hydrodynamical theories describing wetting onto insoluble substrates cannot account for experimental observations in the case of a liquid spreading onto a soluble substrate. Tay et al. made the hypothesis that the water content at the contact line controls the contact angle value and they showed the importance of the evaporation/condensation of the solvent during wetting. In this study, we demonstrate that other mass transfers have to be considered to improve the understanding on wetting dynamics on soluble surfaces; thus diffusion within the polymer of the condensed water or directly from the droplet are processes that contribute to the hydration of the substrate and the modification of the contact angle of the drop. Therefore, we use the following approach to carry out this study: (i) finite elements simulations are performed in order to take into account diffusion effects in the layer and validate our theoretical arguments, (ii) spreading experiments of water onto maltodextrin thin layers are performed in order to study the wetting and the hydration ahead the contact line. A wetting diagram thickness-velocity (e-U) with different regimes is established and validated experimentally. In particular, we evidence a regime where the contact angle is a function of the quantity eU. Furthermore, we evidence the effect of glass transition in the polymer on the contact angle and the hydration of the substrate. Finally, a preliminary study is performed to understand the influence of another transfer at stake in the wetting process: the dissolution of the polymer in the solventLe mouillage d'un substrat soluble est une situation couramment rencontrée dans la vie de tous les jours les jours. Les modèles hydrodynamiques décrivant le mouillage sur un substrat non soluble ne peuvent pas expliquer les observations expérimentales dans le cas d un liquide s étalant sur un substrat soluble. Tay et al. ont émis l'hypothèse que la fraction d'eau à la ligne de contact contrôle la valeur de l'angle de contact et ils ont montré l'importance du processus d'évaporation/condensation du solvant lors du mouillage. Dans cette étude, nous montrons que d'autres transferts de matière doivent être considérés pour améliorer la compréhension du processus de mouillage d'une couche soluble; ainsi la diffusion dans le polymère de l eau condensée, ou directement depuis la goutte sont des processus qui contribuent à hydrater le substrat et modifier l angle de contact de la goutte. Nous avons utilisé l'approche suivante pour réaliser cette étude: (i) pour prendre en compte la diffusion dans le substrat, nous avons réalisé des simulations en éléments finis qui permettent de valider nos arguments théoriques, (ii) des expériences d'étalement de goutte sur des couches minces de maltodextrine ont été réalisées afin d'étudier le mouillage et l'hydratation en avant de la ligne de contact. Un diagramme de mouillage épaisseur-vitesse (e-U) avec différents régimes est établi et validé expérimentalement. Par ailleurs, nous montrons l'influence de la transition vitreuse du polymère sur l'angle de contact et l hydratation. Enfin, une étude préliminaire est réalisée pour comprendre l'influence de la dissolution du polymère lors du mouillagePARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Diagnostic de l'état pulpaire (état des lieux de l'enseignement en France)

La classification de Baume est enseignée à la faculté de chirurgie dentaire de Nantes. Est-ce obsolète ? Qu'en est-il dans les autres UFR de France ? C'est la connaissance de la pathologie pulpaire et de la sémiologie dentaire qui permet d'établir un diagnostic. Ce dernier est cependant un procédé d'intégration de données subjectives et objectives. Il s'agit de la synthèse d'un savoir scientifique et d'une expérience clinique. Pour établir ce diagnostic, nombres d'auteurs ont établi des classifications de pulpopathies afin d'en tirer, ou non, les directives thérapeutiques pour réaliser le traitement adéquat. Après avoir passé en revue les différentes classifications connues, nous les analyserons et les comparerons à celle de Baume afin de voir si elle reste toujours d'actualité. Enfin un tour d'horizon de l'enseignement sur ces classifications des pulpopathies dans les autres facultés françaises nous montrera la grande disparité qui existe entre tous les UFR . Ne serait-il pas possible de trouver une classification capable de satisfaire tout le monde et ainsi d'uniformiser cet enseignement sur le plan national ?NANTES-BU Médecine pharmacie (441092101) / SudocNANTES-Bib.Odontologie (441092219) / SudocSudocFranceF

Use Cases of Pervasive Artificial Intelligence for Smart Cities Challenges

International audienceSoftware engineering has been historically topdown. From a fully specified problem, a software engineer needs to detail each step of the resolution to get a solution. The resulting program will be functionally adequate as long as its execution environment complies with the original specifications. With their large amount of data and their ever changing multi-level dynamics, smart cities are too complex for a topdown approach. They prompt the need for a paradigm shift in computer science. Programs should be able to self-adapt on the fly, to handle unspecified events, and to efficiently deal with tremendous amount of data. To this end, bottom-up approach should become the norm. Machine learning is a first step, and distributed computing helps. Multi-Agent Systems (MAS) can combine machine learning and distributed computing and may be easily designed with a bottom-up approach. This paper explores how MASs can answer challenges at various levels of smart cities, from sensors networks to ambient intelligence

: Sam68 and neuronal mRNA translation

International audienceIn cultured hippocampal neurons and in adult brain, the splicing regulatory protein Sam68 is partially relocated to the somatodendritic domain and associates with dendritic polysomes. Transfer to the dendrites is activity-dependent. We have investigated the repertoire of neuronal mRNAs to which Sam68 binds in vivo. By using coimmunoprecipitation and microarray screening techniques, Sam68 was found to associate with a number of plasticity-related mRNA species, including Eef1a1, an activity-responsive mRNA coding for translation elongation factor eEF1A. In cortical neuronal cultures, translation of the Eef1a1 mRNA was strongly induced by neuronal depolarisation and correlated with enhanced association of Sam68 with polysomal mRNAs. The possible function of Sam68 in Eef1a1 mRNA utilization was studied by expressing a dominant-negative, cytoplasmic Sam68 mutant (GFP-Sam68DeltaC) in cultured hippocampal neurons. The level of eEF1A was lower in neurons expressing GFP-Sam68DeltaC than in control neurons, supporting the proposal that endogenous Sam68 may contribute to the translational efficiency of the Eef1a1 mRNA. These findings are discussed in the light of the complex, potentially crucial regulation of eEF1A biosynthesis during long-term synaptic change

Dynamic Wetting on a Thin Film of Soluble Polymer: Effects of Nonlinearities in the Sorption Isotherm

International audienceThe wetting dynamics of a solvent on a soluble substrate interestingly results from the rates of the solvent transfers into the substrate. When a supported film of a hydrosoluble polymer with thickness e is wet by a spreading droplet of water with instantaneous velocity U, the contact angle is measured to be inversely proportionate to the product of thickness and velocity, eU, over two decades. As for many hydrosoluble polymers, the polymer we used (a polysaccharide) has a strongly nonlinear sorption isotherm phi(a(w)), where phi is the volume fraction of water in the polymer and a(w) is the activity of water. For the first time, this nonlinearity is accounted for in the dynamics of water uptake by the substrate. Indeed, by measuring the water content in the polymer around the droplet phi at distances as small as 5 mu m, we find that the hydration profile exhibits (i) a strongly distorted shape that results directly from the nonlinearities of the sorption isotherm and (ii) a cutoff length xi below which the water content in the substrate varies very slowly. The nonlinearities in the sorption isotherm and the hydration at small distances from the line were not accounted for by Tay et al., Soft Matter 2011, 7, 6953. Here, we develop a comprehensive description of the hydration of the substrate ahead of the contact line that encompasses the two water transfers at stake: (i) the evaporation condensation process by which water transfers into the substrate through the atmosphere by the condensation of the vapor phase, which is fed by the evaporation from the droplet itself, and (ii) the diffusion of liquid water along the polymer film. We find that the eU rescaling of the contact angle arises from the evaporation condensation process at small distances. We demonstrate why it is not modified by the second proces

A DFT study of the formation of xanthydrol motifs during electrophilic poly(aryl ether ketone) synthesis

International audienceThe reaction pathway of the cyclization of 2-phenoxybenzophenone into 9-phenyl-9H-xanthen-9-ol in the presence of acid and an excess of AlCl33 was studied using density functional theory. This type of reaction is known to occur during the Friedel–Crafts polycondensation of poly(aryl ether ketones) following the undesired benzoylation of nucleophilic positions ortho- to the growing polymer’s ether groups. The formed defect acts as an undesired terminator of the polymer chain, causing severe problems in the polymer’s melt state. A branched, multistep mechanism reminiscent of the Friedel–Crafts acylation reaction is discovered; the reaction starts with the protonation of the carbonyl oxygen, followed by intramolecular electrophilic attack on the carbonyl carbon that determines the turnover frequency of the catalytic cycle and ends by deprotonation of the Wheland intermediate

A DFT study of the Al₂Cl₆-catalyzed Friedel-Crafts acylation of phenyl aromatic compounds

International audienceThe reaction pathways of several Friedel–Crafts acylations involving phenyl aromatic compounds were studied using density functional theory. The reactions were related to the Friedel–Crafts polycondensation of polyaryletherketones. In particular, the acylation of benzene with benzoyl chloride to form benzophenone and variations on this reaction were investigated. The acylation of benzene by one molecule of terephthaloyl chloride or isophthaloyl chloride as well as acylations at the m-, o-, and p-positions of diphenyl ether with one molecule of benzoyl chloride were studied. Adding an additional acyl chloride group to the electrophile appeared to have little influence on the reaction pathway, although the activation energy for the C–C bond-forming steps that occurred when isophthaloyl choride was used was different to the activation energy observed when terephthaloyl chloride was used. Upon changing the nucleophile to diphenyl ether, the reactivity changed according to the trend predicted on based on the o-, p-directing effects of the ether group. The deprotonation step that restored aromaticity varied widely according to the reaction. The rate-determining step in all of the studied reactions was the formation of the acylium ion, followed in importance by either the formation of the Wheland intermediate or the abstraction of hydrogen, depending on the reactivity of the nucleophile

A chromatographic procedure for semi-quantitative evaluation of caseinphosphopeptides in cheese

Caseinphosphopeptides (CPPs) are phosphorylated fragments of caseins, which arefound in dairy products. One of their unique features is their ability to bind calcium. There are several published methods to extract CPPs from cheese, but none allows their quantitative evaluation. A chromatographic procedure allowing a semi-quantitative evaluation of cheese CPPs was adapted from a previously published method and tested on Beaufort cheese. Water-soluble peptides were extracted from cheese and purified using cation-exchange chromatography followed by immobilised metal-ion affinity chromatography (IMAC). CPPs were identified using mass spectrometry (LC-ESI-MS/MS). Fifty-five peptides, including 48 CPPs carrying one to three phosphorylations, were identified in Beaufort cheese. It can thus be considered that the selectivity of the chromatographic procedure proposed is sufficient for a semi-quantification of CPPs with a molecular mass ranging from 600 to 10 000 g·mol−1 in cheese. As IMAC fractions contain molecules with a molecular mass < 600 g·mol−1 (such as phosphoserine), a gel filtration step was performed in order to remove these compounds. The semi-quantification based on an estimation of the extinction molar coefficient of CPPs at 215 nm allowed to estimate that the CPPs content of the fresh Beaufort cheese sample analysed was around 1.9 g·100 g−1