357 research outputs found
Novel bio-based materials from cellulose and chitin
Chitin and cellulose are the most abundant natural polymers. They have unique properties suitable for the design of new bio-sourced and biodegradable materials for various applications such as textile fibers, food packaging, and biomedical products. Unfortunately, these biopolymers suffer from a lack of solubility in regular solvents. But, due to their intractable bulk structure, the dissolution of such polymers is a crucial step for their processing. In this context, the solubility of non-modified cellulose and chitin in different solution media such as ionic liquids, deep eutectic solvents, and other conventional solvent systems was first studied in this work. It was found that the ionic liquid, 1-butyl-3-methylimidazolium acetate (BmimOAc), was the most efficient solvent for the dissolution of both polymers. Despite its good solubilizing capacity, BmimOAc is neither biodegradable nor bio-renewable. As the aim of this thesis was to provide an easy and environmentally friendly method to process cellulose and chitin, a second solvent was added in the dissolution process to reduce the necessary amount of BmimOAc. The biodegradable and bio-based co-solvent, Îł-valerolactone (GVL), was an ideal candidate for this purpose. In order to assess its potential, the influence of GVL in the cellulose proceeding was also evaluated according to the industrial Lyocell process. N-methylmorpholine N-oxide monohydrate (NMMO) was used for this procedure. Besides increasing the sustainability of the studied systems, GVL was observed to enhance polymer dissolution and to facilitate manufacturing of the regenerated polymers. To understand these positive effects, physicochemical properties of binary mixtures (GVL/BmimOAc or NMMO) were characterized by viscosity, ionic conductivity, and thermal analysis measurements. The properties of the polymer solutions were also investigated by thermal and rheological studies. In a third step, materials such as cellulose fibers and new cellulose/chitin composite materials were successfully prepared from these solutions. All produced materials were characterized in detail by means of spectroscopical, morphological, and mechanical analysis methods. Wetting and permeability studies were additionally performed to demonstrate the advantages of a chitin coat on the properties of cellulose-based textiles. The results showed that the presence of chitin decreases the water wettability of the textiles on the coated site. Furthermore, the chitin layer acts as a promising water and oxygen barrier, which makes these novel materials potential candidates for various applications such as impermeable textiles for hygiene products
Importance de l'environnement des primates en parc zoologique ; application Ă l'Ă©tude d'un type d'enclos : l'Ăźle
La plupart des espĂšces de primates sont aujourd'hui menacĂ©es par la destruction de leur habitat. Les parcs zoologiques ont pour missions la conservation des animaux et l'Ă©ducation du public, mais cela n'est justifiĂ© que si le bien-ĂȘtre animal est respectĂ©. AprĂšs avoir exposĂ© les contraintes de l'hĂ©bergement en captivitĂ© des primates, l'auteur prĂ©cise les recommandations actuelles concernant le logement et le regroupement social de ces animaux en captivitĂ© ; les principes de l'enrichissement environnemental chez les primates sont Ă©galement expliquĂ©s, et un exemple d'Ă©tude qui en Ă©value les effets est proposĂ©. Les rĂ©sultats d'une enquĂȘte sur les Ăźles aux primates, menĂ©e auprĂšs des zoos europĂ©ens, sont ensuite rapportĂ©s : ce type d'enclos apparaĂźt bien adaptĂ© Ă la majoritĂ© des espĂšces, et semble apprĂ©ciĂ© aussi bien des visiteurs que des zoos, qui y voient un intĂ©rĂȘt Ă la fois pour leur image et pour les animaux grĂące aux nouvelles possibilitĂ©s d'amĂ©nagement que ces Ăźles procurent
Approximation mit verallgemeinerten Splines
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Contribution diffĂ©rentielle de Neuroligineâ1 et dâEphA4 Ă la rĂ©gulation du sommeil
Le sommeil est un besoin vital et le bon fonctionnement de lâorganisme dĂ©pend de la quantitĂ©
et de la qualité du sommeil. Le sommeil est régulé par deux processus : un processus circadien
qui dĂ©pend de lâactivitĂ© des noyaux suprachiasmatiques de lâhypothalamus et qui rĂ©gule le
moment durant lequel nous allons dormir, et un processus homéostatique qui dépend de
lâactivitĂ© neuronale et se reflĂšte dans lâintensitĂ© du sommeil. En effet, le sommeil dĂ©pend de
lâĂ©veil qui le prĂ©cĂšde et plus lâĂ©veil dure longtemps, plus le sommeil est profond tel que mesurĂ©
par des marqueurs électroencéphalographiques (EEG). Des études ont montré que le bon
fonctionnement de ces deux processus régulateurs du sommeil dépend de la plasticité
synaptique. Ainsi, les éléments synaptiques régulant la communication et la force synaptique
sont dâimportants candidats pour agir sur la physiologie de la rĂ©gulation du sommeil. Les
molĂ©cules dâadhĂ©sion cellulaire sont des acteurs clĂ©s dans les mĂ©canismes de plasticitĂ©
synaptique. Elles rĂ©gulent lâactivitĂ© et la maturation des synapses. Des Ă©tudes ont montrĂ© que
leur absence engendre des conséquences similaires au manque de sommeil. Le but de ce projet
de thĂšse est dâexplorer lâeffet de lâabsence de deux familles de molĂ©cule dâadhĂ©sion cellulaire,
les neuroligines et la famille des récepteur Eph et leur ligand les éphrines dans les processus
rĂ©gulateurs du sommeil. Notre hypothĂšse est que lâabsence dâun des membres de ces deux
familles de molécule affecte les mécanismes impliqués dans le processus homéostatique de
rĂ©gulation du sommeil. Afin de rĂ©pondre Ă notre hypothĂšse, nous avons Ă©tudiĂ© dâune part
lâactivitĂ© EEG chez des souris mutantes nâexprimant pas Neuroligineâ1 (Nlgn1) ou le rĂ©cepteur
EphA4 en condition normale et aprĂšs une privation de sommeil. Dâautre part, nous avons
mesuré les changements moléculaires ayant lieu dans ces deux modÚles aprÚs privation de
sommeil. Au niveau de lâactivitĂ© EEG, nos rĂ©sultats montrent que lâabsence de Nlgn1 augmente
la densitĂ© des ondes lentes en condition normale et augment lâamplitude et la pente des ondes
lentes aprÚs privation de sommeil. Nlgn1 est nécessaire au fonctionnement normal de la
synchronie corticale, notamment aprÚs une privation de sommeil, lui attribuant ainsi un rÎle clé
dans lâhomĂ©ostasie du sommeil. Concernant le rĂ©cepteur EphA4, son absence affecte la durĂ©e
du sommeil paradoxal ainsi que lâactivitĂ© sigma qui dĂ©pendent du processus circadien. Nos rĂ©sultats suggĂšrent donc que ce rĂ©cepteur est un Ă©lĂ©ment important dans la rĂ©gulation circadienne du sommeil. Les changements transcriptionnels en rĂ©ponse Ă la privation de
sommeil des souris nâexprimant pas Nlgn1 et EphA4 ne sont pas diffĂ©rents des souris sauvages.
Toutefois, nous avons montré que la privation de sommeil affectait la distribution des marques
Ă©pigĂ©nĂ©tiques sur le gĂ©nome, tels que la mĂ©thylation et lâhydroxymĂ©thylation, et que
lâexpression des molĂ©cules rĂ©gulant ces changements est modifiĂ©e chez les souris mutantes
pour le récepteur EphA4.
Nos observations mettent en Ă©vidence que les molĂ©cules dâadhĂ©sion cellulaire, Nlgn1 et le
récepteur EphA4, possÚdent un rÎle important dans les processus homéostatique et circadien
du sommeil et contribuent de maniÚre différente à la régulation du sommeil.Sleep is a vital need and the proper functioning of the body depends on the amount and quality
of sleep. Sleep is regulated by two processes: a circadian process that depends on the activity of
suprachiasmatic nuclei of the hypothalamus and regulates the time of day during which we are
going to sleep, and a homeostatic process that seems to depend on neuronal activity and that
reflects sleep intensity. The homeostatic process controls a pressure for sleep as a function of
the amount of time spent awake. Indeed, sleep quality depends on the duration of preceding
wakefulness, the more one is awake, deeper the sleep afterwards as measured by
electroencephalographic markers (EEG). Studies have shown that the proper functioning of
these two sleep regulatory processes depends on synaptic plasticity. Thus, elements that
regulate synaptic communication and synaptic strength are important candidates to act upon
the physiology of sleep regulation. Cell adhesion molecules are key elements regulating synaptic
plasticity. They control synapse activities and maturation. Studies have shown that their
absence leads to consequences similar to sleep deprivation. The aim of this study is to explore
the effect of the absence of two different cellular adhesion molecule, Neuroliginâ1 and EphA4
receptor in sleep regulatory processes. Our hypothesis is that the absence of either of these
molecules will affect sleep regulation and more specifically sleep homeostasis. To address our
hypothesis, we first studied EEG activity in mice which do not express Nlgn1 and EphA4 in
normal condition or after sleep deprivation. Secondly, we measured the molecular changes that
occur in these two models after sleep deprivation. At the level of EEG activity, our results show
that the absence of Nlgn1 increases the density of slow waves under baseline condition, and
that the amplitude and slope of slow waves are increased after sleep deprivation. We concluded
that Nlgn1 is required for normal functioning of cortical synchrony especially after sleep
deprivation, thereby giving it a key role in sleep homeostasis. Regarding the EphA4 receptor, its
absence affects the duration of paradoxal sleep and sigma activity which are known to depend
on the circadian process. These results suggest that the EphA4 receptor is an important element
in the circadian regulation of sleep. The transcriptional response after sleep deprivation in mice
not expressing Nlgn1 or EphA4 is not different from that in wildâtype mice. However, we found that sleep deprivation affects the distribution of specific epigenetic markers like methylation and hydroxymethylation and the expression of molecules regulating these changes is altered in EphA4 null mice.
Our observations show that two cell adhesion molecules, Nlgn1 and EphA4 receptor, have an
important role in the homeostatic and circadian sleep process and contribute differentially to
sleep regulation
Histoire et autobiographie dans lâĆuvre de Dion Cassius
Il y a dans lâHistoire romaine de Dion Cassius une partie annalistique dont la technique sâapparente Ă la mĂ©thode livienne, et une partie biographique quelque peu analogue aux Vies de SuĂ©tone. Il convient en outre de distinguer du point de vue mĂ©thodologique lâhistoire du passĂ© et lâhistoire du prĂ©sent puisque les derniers livres sont contemporains de leur auteur, nĂ© vers 165 et mort aprĂšs 229. Or il apparaĂźt nettement que Dion Cassius passe insensiblement de lâhistoire annalistique Ă lâhistoire biographique. Lâarticle Ă©tudie donc lâintervention auctoriale de Dion-historien puis les aspects autobiographiques qui se rencontrent dans son Ćuvre pour montrer comment Dion passe dans son Ćuvre du JE auctorial le plus traditionnel au JE autobiographique (en passant par le NOUS des sĂ©nateurs), qui devient une persona, un personnage fictif, mis en scĂšne de façon grandiose, Ă mi-chemin entre le hĂ©ros tragique et le hĂ©ros Ă©pique, dans une construction originale
Le « Patrimoine humaniste du Rhin Supérieur
Pour recenser et communiquer autour des éditions humanistes régionales, un partenariat productif entre conservateurs de bibliothÚques et universitaires a été apprécié tant des collectivités que du grand public
Commande linéarisée et mesure intégrée de la température dans un composite actif
Les travaux présentés dans cette publication concernent le développement du contrÎle du composite intelligent M3C (composite qui se déforme grùce à une variation de température obtenue par effet joule via des fibres de carbone intégrées). Nous présentons plus particuliÚrement la linéarisation de la commande et la mesure de température. La linéarisation est obtenue par une alimentation en tension modulée en largeur d'impulsion. La mesure de température découle de la mesure de variation de résistance électrique du composite (loi de Matthiessen)
Aetiology of canine infectious respiratory disease complex and prevalence of its pathogens in Europe
The canine infectious respiratory disease complex (CIRDC) is an endemic worldwide syndrome involving multiple viral and bacterial pathogens. Traditionally, Bordetella bronchiseptica (Bb), canine adenovirus type 2 (CAV-2), canine distemper virus (CDV), canine herpesvirus (CHV) and canine parainfluenza virus (CPiV) were considered the major causative agents. Lately, new pathogens have been implicated in the development of CIRDC, namely canine influenza virus (CIV), canine respiratory coronavirus (CRCoV), canine pneumovirus (CnPnV), Mycoplasma cynos and Streptococcus equi subspecies zooepidemicus. To better understand the role of the different pathogens in the development of CIRDC and their epidemiological relevance in Europe, prevalence data were collected from peer-reviewed publications and summarized. Evidence of exposure to Bb is frequently found in healthy and diseased dogs and client-owned dogs are as likely to be infected as kennelled dogs. Co-infections with viral pathogens are common. The findings confirm that Bb is an important cause of CIRDC in Europe. CAV-2 and CDV recovery rates from healthy and diseased dogs are low and the most likely explanation for this is control through vaccination. Seroconversion to CHV can be demonstrated following CIRDC outbreaks and CHV has been detected in the lower respiratory tract of diseased dogs. There is some evidence that CHV is not a primary cause of CIRDC, but opportunistically re-activates at the time of infection and exacerbates the disease. The currently available data suggest that CIV is, at present, neither a prevalent nor a significant pathogen in Europe. CPiV remains an important pathogen in CIRDC and facilitates co-infection with other viral and bacterial pathogens. CnPnV and CRCoV are important new elements in the aetiology of CIRDC and spread particularly well in multi-dog establishments. M. cynos is common in Europe and is more likely to occur in younger and kennelled dogs. This organism is frequently found together with other CIRDC pathogens and is significantly associated with more severe respiratory signs. S. zooepidemicus infection is not common and appears to be a particular problem in kennels. Protective immunity against respiratory diseases is rarely complete, and generally only a reduction in clinical signs and excretion of pathogen can be achieved through vaccination. However, even vaccines that only reduce and do not prevent infection carry epidemiological advantages. They reduce spread, increase herd immunity and decrease usage of antimicrobials. Recommending vaccination of dogs against pathogens of CIRDC will directly provide epidemiological advantages to the population and the individual dog
Cardiovascular actions of the hypotensive agent, N, N-diallylmelamine (U-7720)
Diallylmelamine is an effective hypotensive agent in hypertensive dogs and rats, having a duration of action exceeding twenty-four hours from a single oral dose. It has limited efficacy in normotensive rats. Hypotensive activity of gradual onset is preceded by a latent period of up to two hours and becomes maximal six hours or more after dosing. This agent does not depress cardiac output or sympathetic vasoconstrictor activity. It is suggested that its hypotensive activity results from a direct effect upon vascular smooth muscle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46303/1/210_2004_Article_BF00245728.pd
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