Inhaltsverzeichnis
Auswahl der wissenschaftlichen Literatur zum Thema „Gels et hydrogels“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Gels et hydrogels" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Zeitschriftenartikel zum Thema "Gels et hydrogels"
1
Chen, Miao, Weimin Lin, Le Hong, Ning Ji und Hang Zhao. „The Development and Lifetime Stability Improvement of Guanosine-Based Supramolecular Hydrogels through Optimized Structure“. BioMed Research International 2019 (13.06.2019): 1–18. http://dx.doi.org/10.1155/2019/6258248.
Der volle Inhalt der QuelleAnnotation:
Guanosine is an important building block for supramolecular gels owing to the unique self-assembly property that results from the unique hydrogen bond acceptors and donor groups. Guanosine-derived supramolecular hydrogels have promise in the fields of drug delivery, targeted release, tissue engineering applications,etc.However, the property of poor longevity and the need for excess cations hinder the widespread applications of guanosine hydrogels. Although guanosine-derived supramolecular hydrogels have been reviewed previously by Dash et al., the structural framework of this review is different, as the modification of guanosine is described at the molecular level. In this review, we summarize the development and lifetime stability improvement of guanosine-based supramolecular hydrogels through optimized structure and elaborate on three aspects: sugar modification, base modification, and binary gels. Additionally, we introduce the concept and recent research progress of self-healing gels, providing inspiration for the development of guanosine-derived supramolecular hydrogels with longer lifespans, unique physicochemical properties, and biological activities.
2
Wang, Zi, Xujun Zheng, Tetsu Ouchi, Tatiana B. Kouznetsova, Haley K. Beech, Sarah Av-Ron, Takahiro Matsuda et al. „Toughening hydrogels through force-triggered chemical reactions that lengthen polymer strands“. Science 374, Nr. 6564 (08.10.2021): 193–96. http://dx.doi.org/10.1126/science.abg2689.
Der volle Inhalt der QuelleAnnotation:
Longer and stronger; stiff but not brittle Hydrogels are highly water-swollen, cross-linked polymers. Although they can be highly deformed, they tend to be weak, and methods to strengthen or toughen them tend to reduce stretchability. Two papers now report strategies to create tough but deformable hydrogels (see the Perspective by Bosnjak and Silberstein). Wang et al . introduced a toughening mechanism by storing releasable extra chain length in the stiff part of a double-network hydrogel. A high applied force triggered the opening of cycling strands that were only activated at high chain extension. Kim et al . synthesized acrylamide gels in which dense entanglements could be achieved by using unusually low amounts of water, cross-linker, and initiator during the synthesis. This approach improves the mechanical strength in solid form while also improving the wear resistance once swollen as a hydrogel. —MSL
3
Kim, Junsoo, Guogao Zhang, Meixuanzi Shi und Zhigang Suo. „Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links“. Science 374, Nr. 6564 (08.10.2021): 212–16. http://dx.doi.org/10.1126/science.abg6320.
Der volle Inhalt der QuelleAnnotation:
Longer and stronger; stiff but not brittle Hydrogels are highly water-swollen, cross-linked polymers. Although they can be highly deformed, they tend to be weak, and methods to strengthen or toughen them tend to reduce stretchability. Two papers now report strategies to create tough but deformable hydrogels (see the Perspective by Bosnjak and Silberstein). Wang et al . introduced a toughening mechanism by storing releasable extra chain length in the stiff part of a double-network hydrogel. A high applied force triggered the opening of cycling strands that were only activated at high chain extension. Kim et al . synthesized acrylamide gels in which dense entanglements could be achieved by using unusually low amounts of water, cross-linker, and initiator during the synthesis. This approach improves the mechanical strength in solid form while also improving the wear resistance once swollen as a hydrogel. —MSL
4
Aldakheel, Fahad M., Dalia Mohsen, Marwa M. El Sayed, Mohammed H. Fagir und Dalia K. El Dein. „RETRACTED: Aldakheel et al. Employing of Curcumin–Silver Nanoparticle-Incorporated Sodium Alginate-Co-Acacia Gum Film Hydrogels for Wound Dressing. Gels 2023, 9, 780“. Gels 10, Nr. 6 (05.06.2024): 383. http://dx.doi.org/10.3390/gels10060383.
Der volle Inhalt der Quelle
5
Surowiecka, Agnieszka, Jerzy Strużyna, Aleksandra Winiarska und Tomasz Korzeniowski. „Correction: Surowiecka et al. Hydrogels in Burn Wound Management—A Review. Gels 2022, 8, 122“. Gels 9, Nr. 1 (31.12.2022): 37. http://dx.doi.org/10.3390/gels9010037.
Der volle Inhalt der Quelle
6
Sheng, Chengju, Xuemei Tan, Qing Huang, Kewen Li, Chao Zhou und Mingming Guo. „Correction: Sheng et al. Antibacterial and Angiogenic Poly(ionic liquid) Hydrogels. Gels 2022, 8, 476“. Gels 9, Nr. 6 (08.06.2023): 472. http://dx.doi.org/10.3390/gels9060472.
Der volle Inhalt der Quelle
7
Jaik, Thorben G., Assegid M. Flatae, Navid Soltani, Philipp Reuschel, Mario Agio, Emiliano Descrovi und Ulrich Jonas. „Correction: Jaik et al. Photomotion of Hydrogels with Covalently Attached Azo Dye Moieties—Thermoresponsive and Non-Thermoresponsive Gels. Gels 2022, 8, 541“. Gels 9, Nr. 5 (15.05.2023): 411. http://dx.doi.org/10.3390/gels9050411.
Der volle Inhalt der Quelle
8
Myers, David R., Ashley C. Brown, Yongzhi Qiu, Yumiko Sakurai, Reginald Tran, Byungwook Ahn, Robert Mannino et al. „High-Throughput Nanomechanical Platelet Contraction Measurements Using Patterned Hydrogels.“ Blood 120, Nr. 21 (16.11.2012): 2172. http://dx.doi.org/10.1182/blood.v120.21.2172.2172.
Der volle Inhalt der QuelleAnnotation:
Abstract Abstract 2172 Background: Previous studies on clot formation have shown that the mechanical properties of clots have direct effects on hemostasis and thrombosis, and alterations of those clot mechanics are associated with disease(Collet, et al. 2006) (Hvas, et al. 2007). As such, understanding the mechanical properties of clots is vital to understand hemostasis and thrombosis. As platelets drive this contraction phenomenon, single platelet measurements are required to obtain a mechanistic understanding of the retraction process and to identify specific therapeutic targets for disease states in which platelet/clot retraction is pathologically altered. In addition, as fibrin has recently been shown to have extremely complex material and mechanical properties (Brown, et al. 2009), single platelet studies would decouple the effects of fibrin from platelets when examining clot mechanics. However, few studies have focused on the biomechanical role of platelets in clot formation and clot mechanics, especially at the single cell level. Our group has recently published measurements of single platelet contraction (Lam, et al, Nature Mat, 2011), showing that platelets are capable of applying large forces and are quite varied in their response. However, the key barrier which has prevented the study of single platelets has been the lack of a technology with the sufficient precision and sensitivity to both manipulate and measure individual platelets in a high throughput manner. To that end, we have extended a technique (Polio, et al. 2012) that is capable of measuring the contraction of individual platelets in a high throughput manner. Results: Here we precisely pattern FITC conjugated fibrinogen dots in a geometrical array (Fig 1A) on polyacrylamide (PAA) gels. Thrombin activated platelets are incubated on the gel and contract upon contact with the micropatterned fibrinogen “dots”. When the platelet comes into contact with two dots and contracts, the distance in which the platelet moves the dots from their original position is used to determine the force. Conceptually, this is similar to the idea of a linear spring, in which a certain spring displacement corresponds to a known force. Using this technique, we measured 71 platelets which were attached to two fibrinogen dots each, and found that on low stiffness gels, that the average contractile force was approximately 4nN (Fig 2A). Platelets may attach to a maximum of four dots, but do so with a much lower frequency as compared to two dots (Fig 2B). Preliminary results indicate that as platelet area increases, as indicated by contact with additional protein “dots”, the total force exerted by the platelet increases, with a maximum contractile force achieved when touching three protein dots (Fig 2C). Based on this data, there may be an optimum platelet spread area that maximizes contractile force. Conclusions and Ongoing Efforts: We will determine how the biophysical parameters, such as micro-environmental stiffness and shear flow, quantitatively affect platelet contractility. As our current understanding of the underlying biological mechanisms of platelet contraction is solely qualitative, we will also quantitatively investigate the biological signaling pathways of platelet contraction using pharmacological agents and platelet agonists using our system. Pharmacologic agents including glycoprotein IIb/IIIa (integrin αIIbβ3) antagonists, Rho kinase inhibitors, calcium inhibitors, and myosin inhibitors, will be used to measure the quantitative effect each biological component has on platelet contraction. In addition, soluble agonists known to activate platelets including thrombin, ADP, thromboxane A2, and epinephrine will be investigated quantitatively and systematically to measure their interactive and synergistic effects on platelet contraction. Furthermore, this device represents a new platform which could be used in drug discovery and to test for changes in platelet contraction with differing pharmacological doses. Disclosures: No relevant conflicts of interest to declare.
9
Bermudez-Lekerika, Paola, Katherine B. Crump, Karin Wuertz-Kozak, Christine L. Le Maitre und Benjamin Gantenbein. „Correction: Bermudez-Lekerika et al. Sulfated Hydrogels as Primary Intervertebral Disc Cell Culture Systems. Gels 2024, 10, 330“. Gels 10, Nr. 10 (24.09.2024): 612. http://dx.doi.org/10.3390/gels10100612.
Der volle Inhalt der Quelle
10
Horkay, Ferenc, und Jack F. Douglas. „Evidence of Many-Body Interactions in the Virial Coefficients of Polyelectrolyte Gels“. Gels 8, Nr. 2 (04.02.2022): 96. http://dx.doi.org/10.3390/gels8020096.
Der volle Inhalt der QuelleAnnotation:
Simulation studies of aqueous polymer solutions, and heuristic arguments by De Gennes for aqueous polyethylene oxide polymer solutions, have suggested that many-body interactions can give rise to the ‘anomalous’ situation in which the second osmotic virial coefficient is positive, while the third virial coefficient is negative. This phenomenon was later confirmed in analytic calculations of the phase behavior and the osmotic pressure of complex fluids exhibiting cooperative self-assembly into extended dynamic polymeric structures by Dudowicz et al. In the present study, we experimentally confirm the occurrence of this osmotic virial sign inversion phenomenon for several highly charged model polyelectrolyte gels (poly(acrylic acid), poly(styrene sulfonate), DNA, hyaluronic acid), where the virial coefficients are deduced from osmotic pressure measurements. Our observations qualitatively accord with experimental and simulation studies indicating that polyelectrolyte materials exhibit supramolecular assembly in solution, another symptomatic property of fluids exhibiting many-body interactions. We also find that the inversion in the variation of the second (A2) and third (A2) virial coefficients upon approach to phase separation does not occur in uncharged poly(vinyl acetate) gels. Finally, we briefly discuss the estimation of the osmotic compressibility of swollen polyelectrolyte gels from neutron scattering measurements as an alternative to direct, time-consuming and meticulous osmotic pressure measurements. We conclude by summarizing some general trends and suggesting future research directions of natural and synthetic polyelectrolyte hydrogels.
Dissertationen zum Thema "Gels et hydrogels"
1
Roux, Rémi. „Élaboration d'assemblages colloïdaux à partir de nanoparticules de poly(acide lactique) et de chitosane“. Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10088/document.
Der volle Inhalt der QuelleAnnotation:
Les assemblages colloïdaux représentent une nouvelle piste très prometteuse dans le domaine de l'ingénierie tissulaire. Idéalement, ce type d'assemblage permet l'obtention de matériaux injectables et gélifiants sur le site lésionnel, favorisant par la suite le développement de néo-tissus viables. Ce travail porte sur la formation de tels assemblages à base de chitosane et de poly(acide lactique) (PLA). Deux types d'assemblages ont été conçus et étudiés dans ce travail. Dans une première approche, le mélange de particules anioniques de poly (acide lactique) (PLA) avec du chitosane en solution faiblement acide conduit à la formation de « gels composites », résultant des interactions colloïde-polymère. Des analyses rhéologiques et de diffusion des rayons X aux petits angles ont permit de mettre en évidence le mode de formation et l'influence de plusieurs paramètres sur les propriétés finales de ces gels. Notamment, ils présentent des propriétés rhéofluidifiantes et un caractère réversible, c'est-à-dire que le gel peut se reformer après déstructuration mécanique. Le second type d'assemblage résulte du mélange de particules anioniques de PLA et de nanogels cationiques de chitosane, conduisant à la formation de « gels colloïdaux », par interactions colloïde-colloïde. L'influence de plusieurs facteurs sur la formation et les propriétés de ces gels a également été étudiée par mesures rhéologiques. Notre étude s'est notamment orientée sur la caractérisation et la stabilité des hydrogels physiques de chitosane sous forme colloïdale, ainsi que sur l'optimisation de leur cohésionColloidal assemblies may be a promising pathway to obtain injectable scaffolds favoring the development of neo-tissue in regenerative medicine. This work investigates the formation of such assemblies composed of chitosan, soluble or in suspension (nano-hydrogel), and poly(lactic acid) (PLA) nanoparticles. Two types of assemblies are studied. As a first approach, mixing negatively charged PLA particles and chitosan solution leads to the formation of “composite gels”, based on colloidpolymer interactions. Rheological and Small Angle X-Ray Scattering measurements highlighted the formation process and the influence of various parameters on final properties of these gels, which features shear-thinning and reversibility behavior, that is, the capacity to gel again after yielding. PLA nanoparticles could also be mixed with cationic chitosan nanoparticles, which are crosslinker free nano-hydrogels, leading to the formation of “colloidal gels”, based on colloid-colloid interactions. Influence of various parameters on gel synthesis and properties are investigated through rheological measurements. The study also focuses on the characterization and control of the morphological and cohesion properties of chitosan nanogel
2
Daou, Dania. „Intégration de moteurs moléculaires photoactivables dans des gels supramoléculaires“. Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAF021.
Der volle Inhalt der QuelleAnnotation:
Cette thèse a exploré l'intégration de moteurs moléculaires synthétiques photoactivables dans des réseaux de gels supramoléculaires. L'objectif principal était d'obtenir un mouvement macroscopique réversible en exploitant à la fois la rotation unidirectionnelle des moteurs moléculaires et la nature réversible des interactions supramoléculaires. Des moteurs moléculaires hautement fonctionnalisés ont été synthétisés et intégrés comme unités de réticulation dans des réseaux de gel supramoléculaire de peptides de diphénylalanine et de poly(γ-benzyl-L-glutamate) et d'oligonucléotides d'ADN. L'activation de la rotation unidirectionnelle des moteurs moléculaires par la lumière a permis de produire un travail nanomécanique suffisant pour perturber les interactions supramoléculaires dans les réseaux de gel à base de peptides, ce qui entraîne la contraction ou la fonte du gel à l'échelle macroscopique. Grâce aux interactions supramoléculaires réversibles, le matériau gélifié initial a pu être récupéré dans l'obscurité, soit spontanément, soit par l'application d'un stimulus thermique. Les systèmes étudiés dans cette thèse représentent une nouvelle classe de matériaux fonctionnant dans des conditions dissipatives hors équilibre, promettant des applications dans divers domaines tels que la biologie, la médecine et la science des matériauxThis thesis explored the integration of light-driven synthetic molecular motors in supramolecular gel networks. The main goal was to achieve reversible macroscopic motion by exploiting both the unidirectional rotation of molecular motors and the reversible nature of supramolecular interactions. Highly functionalized molecular motors have been synthesized and integrated as crosslinking units in supramolecular gel networks of diphenylalanine and poly(γ- benzyl-L-glutamate) peptides, as well as DNA oligonucleotides. Activation of the unidirectional rotation of molecular motors by light, allowed the production of nanomechanical work which is sufficient to disrupt supramolecular interactions in peptide-based gel networks leading to contraction or melting of the gel material at the macroscopic scale. Thanks to the reversible supramolecular interactions, the initial gel material was recovered in the dark, either spontaneously or by applying a thermal stimulus. The systems studied in this thesis represent a novel class of materials operating in dissipative out-of-equilibrium conditions, holding promise of applications in various fields such as biology, medicine and material science
3
Ribeiro, Cédric. „Assemblages (macro) moléculaires à base de complexe intra et/ou intermoléculaire de CBPQT4+, X-“. Electronic Thesis or Diss., Centrale Lille Institut, 2023. http://www.theses.fr/2023CLIL0018.
Der volle Inhalt der QuelleAnnotation:
L’association de la science des polymères et de la chimie supramoléculaire a conduit au développement de matériaux polymères supramoléculaires dotés de propriétés structurelles, mécaniques et fonctionnelles atypiques. Ces matériaux sont d’ores et déjà exploités dans divers domaines d’applications, tels que les matériaux auto réparants,l’ingénieur tissulaire ou encore la libération contrôlée de principes actifs. Ainsi, la chimie supramoléculaire s’est avérée être un outil puissant pour moduler les propriétés des matériaux en contrôlant le caractère dynamique des interactions supramoléculaires via l’application de stimuli adaptés. Les travaux réalisés dans le cadre de cette thèse s’inscrivent dans ce contexte et avaient pour principal objectif de développer de nouveaux assemblages (macro)moléculaires à base de complexes intra- et inter-moléculaires de CBPQT4+. Pour ce faire, un nouveau dérivé CBPQT4+-Fu intégrant une unité furane connectée de manière covalente à la partie hôte CBPQT4+ a été développé.Ce dérivé se présente en milieu aqueux sous une conformation auto-incluse dans laquelle l’unité furane au sein de la cavité témoigne d’une extrêmement faible réactivité(Diels-Alder) vis-à-vis de diènophiles. Néanmoins, celle-ci peut être libérée en ajoutant une molécule invitée (Naphtalène) présentant une forte affinité pour le macrocycle.Cette synergie, mise en évidence à l’échelle moléculaire, permettant de déclencher la réaction de Diels-Alder par la formation d’un complexe intramoléculaire a ensuite été exploitée pour concevoir divers hydrogels physiques ou réticulés physiquement et chimiquementThe combination of polymer science and supramolecular chemistry has led to thedevelopment of supramolecular polymer materials with unusual structural, mechanical,and functional properties. These materials have already been exploited in manyapplications, including self-repairing materials, tissue engineering, and the controlledrelease of active ingredients. Supramolecular chemistry has proved to be a powerful toolfor modulating the properties of materials by controlling the dynamic nature ofsupramolecular interactions using appropriate stimuli. The work carried out within theframework of this thesis falls within this context, and its main objective was to developnew (macro)molecular assemblies based on intra- and inter-molecular CBPQT4+complexes. To this end, a new CBPQT4+-Fu derivative was developed, integrating a furanunit covalently connected to the CBPQT4+ host moiety. This derivative presents itself inaqueous media a self-included conformation in which the furan unit within the cavityexhibits extremely low reactivity (Diels-Alder) towards dienophiles. However, this can bereleased by adding a guest molecule (naphthalene) with a strong affinity for themacrocycle. This synergy, demonstrated at the molecular scale, enabling the Diels-Alderreaction to be triggered by forming an intramolecular complex, was then exploited to design various physical and chemically cross-linked hydrogels
4
Hellio, Serughetti Dominique. „Les gels physiques et chimiques de gelatine : structure et rhéologie“. Paris 6, 2004. http://www.theses.fr/2004PA066461.
Der volle Inhalt der Quelle
5
Chalal, Mohand. „Structure multi-échelle et propriétés physico-chimiques des gels de polymères thermosensibles“. Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00680076.
Der volle Inhalt der QuelleAnnotation:
La "cryopolymérisation" permet d'obtenir des gels de polymère macroporeux ou "cryogels". Cette méthode a été utilisée pour la synthèse d'hydrogels thermosensibles à base de pNIPA. La température critique TC correspondant à la transition de volume a été déterminée par des mesures de taux de gonflement et par DSC. La macroporosité (distribution de la taille des pores et épaisseur des parois) et son évolution en fonction de T ont été étudiées par la microscopie biphotonique donnant des informations à l'échelle du µm à plusieurs dizaines de µm. La diffusion de rayons X (SAXS et WAXS) a été utilisée pour caractériser la structure multi-échelle (de quelques dixièmes à quelques dizaines de nm) du gel constituant les parois des macropores. Les courbes de diffusion ont été décrites analytiquement. L'évolution des dix paramètres contenus dans l'équation a été étudiée en fonction de T et discutée. Enfin, des expériences utilisant les phonons hyperfréquences générés par la technique des réseaux transitoires avec détection hétérodyne (HD-TG) ont été réalisées. Ces mesures ont permis de déterminer la vitesse de propagation de l'onde ultra-sonore (à 340 MHz), son atténuation, et la constante de diffusion thermique à différentes températures.
6
Gasmi, Sarah Nawel. „Action d'une hydrolase dans des hydrogels à base d'alginate et d'alginate fonctionnalisé“. Rouen, 2015. http://www.theses.fr/2015ROUES049.
Der volle Inhalt der QuelleAnnotation:
L'objectif de ce travail a été d'étudier l'activité hydrolytique d'une enzyme, la pullulanase, vis à vis du pullulane dans des hydrogels fonctionnalisés ou non à base d'alginate de calcium. L'alginate a été modifié chimiquement par une polyéther amine de la famille Jeffamine® qui présente un caractère LCST "Low Critical Solubility Temperature". L'enzyme immobilisée à hauteur de 30% dans des billes d'alginate de calcium hydrolyse lentement le pullulane en raison de la pénétration de celui ci dans les billes et libère du maltotriose et ses premiers multiples alors que l'enzyme libre donne un mélange d'oligosaccharides très polydispersé. La proximité entre enzyme et substrat au sein de l'hydrogel explique ce comportement. L'activité de l'enzyme au sein des hydrogels est très peu affectée par le pH. L'enzyme est même active à pH 4 contrairement à l'enzyme libre ce qui montre la protection de l'enzyme dans ceshydrogels. Avec l'alginate fonctionnalisé, le taux d'immobilisation de l'enzyme est de 100% en raison d'interactions préférentielles entre la pullulanase et les greffons Jeffamine®. L'enzyme immobilisée dans ces matrices ne présente pas une activité enzymatique différenteThe aim of this project has been to study the hydrolytic activity of the enzyme, pullulanase, toward its substrate pullulan into functionalized or non-functionalized hydrogels based on calcium alginate. Alginate has been chemically modified with a polyether amine, Jeffamine®, with LCST "Low Critical Solubility Temperature" property. The immobilized enzyme amounted to 30% within calcium alginate beads hydrolyses pullulan slowly owing to its penetration into beads and releases maltotriose and its multiples compared to free enzyme which a large distribution of pullulan fragments is observed during the treatment. The close relationship between enzyme and its substrate into these hydrolgels is only marginally affected by pH. The enzyme is even active at pH 4 contrary to the free enzyme indicating an enzyme protection within these hydrogels. In the case of functionalized alginate, the enzyme immobilisation amount is about 100% because of the preferential interactions between pullulanase and Jeffamines-grafted. The immobilized enzyme does not show a different enzyme activity
7
Miquelard-Garnier, Guillaume. „Synthèse et propriétés mécaniques d'hydrogels polyélectrolytes modifiés par des groupements hydrophobes“. Paris 6, 2007. https://pastel.archives-ouvertes.fr/tel-00343871.
Der volle Inhalt der Quelle
8
Servant, Nathalie. „Mise au point et propriétés rhéologiques d'un hydrogel mucoadhésif à usage ophtalmique en vue de l'amélioration de la biodisponibilité d'un principe actif hydrosoluble“. Montpellier 1, 1996. http://www.theses.fr/1996MON13525.
Der volle Inhalt der Quelle
9
Desprez, Valérie. „Caractérisations, applications et modélisation d'électrodes modifiées par des hydrogels : laponite-oligosilsesquioxanes(-enzyme)“. Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10108.
Der volle Inhalt der QuelleAnnotation:
Ce memoire est consacre a la caracterisation, aux applications et a la modelisation cinetique d'electrodes modifiees par des hydrogels de laponite expansee par des oligosilsesquioxanes et fonctionnalisee par des especes electrocatalytiques (microparticules de metaux nobles, mediateurs redox, enzymes). Les etudes physico-chimiques et electrochimiques de ce nouveau materiau hybride d'electrode ont mis en evidence l'intercalation des oligosilsesquioxanes et l'existence d'une micro-porosite induite susceptible d'etre conservee en milieu organique. La stabilite des films obtenus ainsi que leur propriete d'echange d'ions offrent de larges potentialites d'application qui ont ete demontrees par plusieurs exemples en electrocatalyse (hydrogenation electrocatalytique) et en electroanalyse (biocapteurs amperometriques). En particulier, l'immobilisation de la polyphenol oxydase (ppox) permet l'elaboration d'un capteur sensible aux composes phenoliques aussi bien en milieux aqueux qu'en milieu organique. Les performances analytiques de ce capteur, tant en sensibilite, temps de reponse qu'en seuil de detection, comptent parmi les meilleures jusqu'ici decrites pour de tels systemes. Enfin, la modelisation cinetique du systeme electroenzymatique catechol/ppox qui met en jeu dans son fonctionnement une regeneration electrochimique du substrat de l'enzyme, a permis de rationaliser le processus d'amplification electroenzymatique responsable des limites de detection extremement basses de ce type de capteur. L'ensemble de ces etudes nous a ainsi permis de proposer une structure mesoporeuse de l'hydrogel enzyme-laponite expansee et de quantifier les modes de transport et d'amplification electroenzymatique.
10
Gerard, Eric-Jack. „Synthese, caracterisation et comportement de polyurethannes hydrophiles : etude du mecanisme de la polycondensation reticulante“. Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13192.
Der volle Inhalt der QuelleAnnotation:
Synthese d'hygrogels, constitues de chaines elastiques de polydioxolanne. Les reticulats sont synthetises en milieu organique par couplages multiples des extremites hydroxylees, du polydioxolanne precurseur avec un compose isocyanate plurifonctionnel. Apres reaction, un echange progressif du solvant organique par l'eau permet d'obtenir les hydrogels
Konferenzberichte zum Thema "Gels et hydrogels"
1
Chippada, Uday, Xue Jiang, Michelle Previtera, Rene Schloss, Bernard Yurke, Bonnie L. Firestein und Noshir A. Langrana. „Alteration of Fibroblast Cell Behavior due to Contraction of Substrate“. In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19507.
Der volle Inhalt der QuelleAnnotation:
Many researchers have utilized hydrogels as substrates for cell attachment. The stiffness of these substrates has been found to influence the cellular behavior such as morphology, proliferation, growth and differentiation. Lo et al. deformed polyacrylamide substrates with a blunted microneedle and observed the movement of NIH 3T3 fibroblasts. In both pulling and pushing, the cells reversed their direction and moved away from the needle. This shows that cellular behavior is also affected by stretching the underlying substrates. In a previous study, Lin et al. have demonstrated the ability to contract DNA-crosslinked polyacrylamide hydrogels (‘DNA gels’ in short) by addition of crosslinks. Jiang et al. have utilized these DNA gels as substrates to observe the cellular responses of L929 and GFP fibroblasts to both static and dynamic substrate compliances.
2
Li, Bojun, und Erdong Yao. „High-Temperature Resistant, Low-Concentration Polyacrylamide Gel System“. In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-2042.
Der volle Inhalt der QuelleAnnotation:
ABSTRACT: After tertiary oil recovery in old oilfields, problems such as high-water output and low recovery efficiency have generally appeared, which is urgently need to be solved by water blocking and profile control measures. However, the current water blocking gel has low strength and poor-temperature resistance and cannot meet the site requirements, and the organic concentration of most polyacrylamide hydrogels is 0.6 wt% ~ 3.0 wt%, which further increases the economic cost of oil exploitation. In this work, organic zirconium is used to cross-link anionic polyacrylamide with large molecular weight and low concentration to form gel. It can not only meet the strength requirements of the water blocking gel, but also reduce the amount of polyacrylamide and save costs. The gel formation quality, the temperature resistance of the gel and the blocking effect were evaluated experimentally. The cross-linking mechanism of the gels was analysed by SEM observation of the microscopic morphology. This paper selects the best formula of organic zirconium cross-linked polyacrylamide, which can meet the requirements of the strength and temperature resistance of the water-blocking gel even at low polymer concentrations, and provides a reference for water-blocking to improve oil recovery. 1. INTERDUCTION As crude oil reservoirs have strong non-homogeneous characteristics, and most oil fields have entered the high water content development period, polymer gel water blocking technology is gradually becoming one of the effective measures to improve the recovery of crude oil can effectively solve the common problems of high water content and low recovery efficiency after three oil recovery in old oil fields (Yang, H. et al, 2012). At present, it is widely recognized that polyacrylamide and other polymers are cross-linked to form a gel system to seal the high-permeability layer, thereby expanding the swept area of injected water, improving mobility ratio, and enhancing oil recovery (Jia, H. et al, 2011; Zhu, D. et al, 2017).
3
Horikoshi, Satoshi. „IN-LIQUID PLASMA USING MICROWAVE POWER FOR APPLICATIONS“. In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9815.
Der volle Inhalt der QuelleAnnotation:
More than 30 years have passed since Clements, et. al. succeeded in generating plasma in liquid (in-Liquid plasma: LP). Meanwhile, then plasma generation experiments using AC and DC power sources have been performed in electrolyte solutions. On the other hand, in 2000, by Nomura, et. al., they succeeded in generating plasma in aqueous solution by using microwave as a power source. When the microwave is used as a power source, there is a problem that the electrode is deteriorated and melted by the heat of plasma, and there is a problem that the device cannot be used continuously. We solved this problem using a semiconductor (solid-state) microwave generator. In order to investigate the possibility of using this new plasma, we have applied to wastewater treatment (e.g. degradation of 1,4-dioxane, rhodamine B dye and hypochlorous) and gel synthesis (polyvinylpyrrolidone (PVP) gel and silicone hydrogel gel). The photograph of the LP apparatus is illustrated in Figures 1. The MW generator was constructed using an Ampleon M2A-R semiconductor generator (2.45-GHz; maximal power, 1300 W) coupled to an isolator (air cooling device), a power monitor, a three-stub tuner and a short-circuit plunger. Microwaves continuously irradiated the liquid through the tungsten antenna (dia.: 10 mm; length: 200 mm). The tungsten antenna was isolated from the reactor and the waveguide using a ceramic spacer to irradiate MW in the solution. In the application of LP for wastewater treatment, the model wastewater of rhodamine B dye (RhB) were decomposed by LP irradiation, and degradation efficency of LP method was compared with conventional methods (UV photodegradation, NaClO chemical treatment, UV/NaClO chemical/photodegradation and the UV/TiO2 photocatalytic degradation method). The degradationon rate of LP method was remarkably fastest to conventional methods (Figure 2). In the application of LP for gel-synthesis, synthesizing the polymer-gel (PVP-gel and HySi-gel) was tried by the LP method. This feature of the method can significantly reduce (or eliminate) the initiator and crosslinking agent needed for conventional synthesis. Because these chemicals are very toxic, the LP approach is effective in green chemistry. In addition, it will further extend the application of these gels to the medical field.More than 30 years have passed since Clements, et. al. succeeded in generating plasma in liquid (in-Liquid plasma: LP) [1]. Meanwhile, then plasma generation experiments using AC and DC power sources have been performed in electrolyte solutions. On the other hand, in 2000, by Nomura, et. al., [1], they succeeded in generating plasma in aqueous solution by using microwave as a power source. When the microwave is used as a power source, there is a problem that the electrode is deteriorated and melted by the heat of plasma, and there is a problem that the device cannot be used continuously. We solved this problem using a semiconductor (solid-state) microwave generator [2]. In order to investigate the possibility of using this new plasma, we have applied to wastewater treatment (e.g. degradation of 1,4-dioxane, rhodamine B dye and hypochlorous) and gel synthesis (polyvinylpyrrolidone (PVP) gel and silicone hydrogel gel).More than 30 years have passed since Clements, et. al. succeeded in generating plasma in liquid (in-Liquid plasma: LP) [1]. Meanwhile, then plasma generation experiments using AC and DC power sources have been performed in electrolyte solutions. On the other hand, in 2000, by Nomura, et. al., [1], they succeeded in generating plasma in aqueous solution by using microwave as a power source. When the microwave is used as a power source, there is a problem that the electrode is deteriorated and melted by the heat of plasma, and there is a problem that the device cannot be used continuously. We solved this problem using a semiconductor (solid-state) microwave generator [2]. In order to investigate the possibility of using this new plasma, we have applied to wastewater treatment (e.g. degradation of 1,4-dioxane, rhodamine B dye and hypochlorous) and gel synthesis (polyvinylpyrrolidone (PVP) gel and silicone hydrogel gel).
4
Chippada, Uday, Bernard Yurke, David I. Shreiber, Rene Schloss, Xue Jiang, Lulu Li und Noshir A. Langrana. „Force/Torque Field Generation to Obtain Local Properties within Soft Hydrogels“. In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176081.
Der volle Inhalt der QuelleAnnotation:
Soft media like hydrogels are used as substrates for cellular engineering of different cell types and the stiffness of these media plays an important role in the cellular behavior like adhesion, proliferation, matrix deposition and differentiation. The global mechanical properties of such substrates were previously calculated using spherical beads embedded in micro-liter samples and then deflecting them by a magnetic manipulator [1]. Knowing the force and the displacement the elastic modulus was evaluated using closed form solutions. However in the context of our studies for biological applications there are circumstances where the local elastic properties of the hydrogel play an important role. For example in the vicinity of a cell, the cell will distort the gel and the modulus of elasticity of the surface may get altered, particularly if the gel is non-linear and if the distortions are substantial. In order to measure these local properties a four magnet manipulator based on Amblard, et al [2] was built, which is capable of applying large forces on micron sized particles embedded in the media.
5
Suciu, Claudiu Valentin. „Thermal Effects on Nano-Energy Absorption Systems (Nano-EAS)“. In 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70039.
Der volle Inhalt der QuelleAnnotation:
Development of intelligent and ecological energy absorption systems (EAS) is important to various fields such as automotive (vehicle suspensions, bumpers, engine mounts), construction (protections against seismic and wind-induced vibrations), and defense (parachuted objects, armors). Usual EAS use composites, shape-memory alloys and foams. Recently, liquid adsorption/desorption in/from nanoporous solids was employed to develop high-performance nano-EAS. Energy loss is based on the well-known capillary phenomenon: external work must be done to spread a non-wetting liquid on a solid surface. Nano-EAS provide considerably higher dissipated energies, about 1–10J/g at deformability of 30–70%, compared with the energy absorption of Ti-Ni alloys, about 0.01–0.05J/g at deformability of 5–8%. For water against hydrophobic nanoporous silica gel (artificial sand), the nano-EAS become ecological; they can be also made intelligent by thermo-electrical control. Relative to thermal effects, Qiao et al. have investigated, for nanoporous silica gel with insufficient coverage of the alkyl-based hydrophobic coating, the problem of hysteresis recovery by increasing the temperature in the range 20∼80°C. Energy loss capacity reduced severely after the first loading-unloading cycle, so, the hysteresis was found as irreversible. Shape of the first hysteresis, the accessible specific pore volume and the desorption pressure were almost unaffected by the temperature change. At temperature augmentation the second hysteresis was partially recovered and when the temperature exceeded 50°C the system became almost fully reusable. Water inflow was found as governed by Laplace-Washburn equation but the outflow process was perceived as thermally aided. On the other hand, Eroshenko et al. have contradictorily obtained for nanoporous silica gel with full coverage of the alkyl-based hydrophobic coating, a stable hysteresis at repeated working cycles. Adsorption pressure decreased and desorption pressure increased at temperature augmentation, this producing a reduction of the hysteresis area and damping. However, the accessible specific pore volume was found as thermally unaffected. Oppositely, both the in- and out-flows were found as governed by Laplace-Washburn equation. In this work, for nanoporous silica gels with partial and full coverage of the alkyl and fluorocarbon based hydrophobic coatings, the thermal effects on the hysteresis and damping performances are studied. Test rig used is a compression-decompression chamber introduced inside of an incubator that allows temperature adjustment in the range of −10∼50°C. Results reveal that, depending on the hydrophobic coating coverage, findings reported by Qiao et al. and Eroshenko et al. are in fact not contradictory but complementary. However, as expected, the accessible specific pore volume was found to decrease at temperature reduction. In order to explain all these apparently opposite experimental findings, a model based on the water cluster size distribution versus temperature, the pore size distribution of silica gel and the ability of water molecules to form hydrogen bonds with the uncovered hydroxyl groups on the solid surface is proposed.
6
Wunch, Kenneth, und Veronica Silva. „Protecting the Reservoir from Diminishing Productivity Caused by Downhole Biofilm Growth in Shale Plays“. In SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213852-ms.
Der volle Inhalt der QuelleAnnotation:
Abstract Hydraulic fracturing of shale in unconventional oil & gas recovery is accomplished through the addition of large volumes of water and biodegradable additives to reservoirs, creating environments conducive for microbial contamination. Contamination of reservoirs by sulfate reducing organisms often leads to biogenic souring, the biological production of hydrogen sulfide (H2S), which devalues crude, corrodes metallic assets via microbially influenced corrosion (MIC), and creates dangerous health and safety conditions for field personnel (Ferrar et al. 2021). Often overlooked is the impact of this downhole contamination on formation damage and hydrocarbon recovery. Microbes introduced into a hydraulically fracked reservoir form biofilms by attaching to the rock or proppant surfaces and secreting a lipopolysaccharide "gel" that protects the microbial colony. These biopolymers are dynamic and have the potential to effect reservoir permeability and conductivity in tight shales. Furthermore, biofouling can impact the reservoir pore mineral cementation via biomineralization and the production of iron sulfide scale. Bottero et al. (2010) modelled formation damage and the impact on gas flow caused by biofilms growing within proppant packs of hydraulically fractured reservoirs. They concluded that in the presence of 10% biofilm volume, the gas production flow rates were reduced by half and that the biofilm growth on proppants affected the gas flow rate due to the differential change in the medium tortuosity and flow patterns.