Tesis: "Interface hydrogel"

1

Han, Ning. "Hydrogel-Electrospun Fiber Mat Composite Materials for the Neuroprosthetic Interface". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1292881087.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Edgerton, Alexander James. "Design and Testing of a Hydrogel-Based Droplet Interface Lipid Bilayer Array System". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56894.

Texto completo

Resumen

The research presented in this thesis includes the development of designs, materials, and fabrication processes and the results of characterization experiments for a meso-scale hydrogel-based lipid bilayer array system. Two design concepts are investigated as methods for forming Droplet Interface Bilayer (DIB) arrays. Both concepts use a base of patterned silver with Ag/AgCl electrodes patterned onto a flat polymer substrate. In one technique, photopolymerizable hydrogel is cured through a mask to form an array of individual hydrogels on top of the patterned electrodes. The other technique introduces a second type of polymer substrate that physically supports an array of hydrogels using a set of microchannels. This second substrate is fitted onto the first to contact the hydrogels to the electrodes. The hydrogels are used to support and shape droplets of water containing phospholipids, which self-assemble at the surface of the droplet when submerged in oil. Two opposing substrates can then be pushed together, and a bilayer will form at the point where each pair of monolayers come into contact. The photopatterning technique is used to produce small arrays of hydrogels on top of a simple electrode pattern. Systems utilizing the microchannel substrate are used to create mesoscale hydrogel arrays of up to 3x3 that maintained a low resistance (~50-150 kΩ) connection to the substrate. Up to three bilayers are formed simultaneously and verified through visual observation and by recording the current response behavior. Arrays of varying sizes and dimensions and with different electrode patterns can be produced quickly and inexpensively using basic laboratory techniques. The designs and fabrication processes for both types of arrays are created with an eye toward future development of similar systems at the microscale.
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Augustine, Anusree. "Swelling induced debonding of thin hydrogel films grafted on silicon substrate : the role of interface physical-chemistry". Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS040.

Texto completo

Resumen

Les revêtements d'hydrogel sont des réseaux de polymères transparents et hydrophiles capables d’abosrber plusieurs fois leur épaisseur en eau. Cependant, les contraintes induites par le gonflement du film peuvent entraîner un décollement préjudiciable de l'hydrogel ce qui peut limiter l’utilisation pratique des ces revêtements. Dans cette étude, nous proposons de décrire les mécanismes de décollement de films minces d’hydrogel en fonction de leur densité de greffage à l'interface film/substrat. Le but est de pouvoir contrôler et prédire la dégradation des revêtements hydrogel pendant le gonflement ou sous des contraintes de contact. Dans ce but, nous avons développé une méthodologie permettant de mesurer l'initiation et la propagation de la délamination induite par le gonflement de films minces d’hydrogel à partir de défauts d'interface préexistants bien contrôlés.Des films minces d'hydrogel de poly(diméthylacrylamide) (PDMA) attachés à la surface sont préparés sur des plaquettes de silicium à partir de la réticulation et du greffage simultanés (CLAG) de chaînes polymères fonctionnalisées par la chimie click thiol-ène. Cette stratégie permet de faire varier l'épaisseur du film (0.1 - 2 µm) et de contrôler le taux de gonflement du réseau, ici fixé à 2, tout en assurant une densité de réticulation homogène. Afin de faire varier la résistance de l'interface film/substrat, le substrat en silicium est greffé avec des mélanges de mercaptosilane (réactif) et de propylsilane (inerte) dans différentes proportions avant le dépôt du film mince. Alors que le mercaptosilane est capable de former des liaisons covalentes avec le réseau PDMA, le propylsilane ne réagit pas, ce qui permet de contrôler le taux de greffage du film mince d’hydrogel sur le substrat. Nous caractérisons la fraction de surface de mercaptosilane ainsi obtenue par des analyses XPS et TOF-SIMS. Par ailleurs, toujours à l’interface subtrat/film, des défauts linéaires bien contrôlés ayant une faible adhérence (largeur entre 10 et 100 µm) sont créés sur le substrat en passivant de façon localisée les groupes thiol réactifs par microlithographie. Ces défauts nucléent le décollement des films de façon bien localisée, ce qui permet ensuite de suivre la propagation de la décohésion à partir de ces défauts.Le décollement du film induit par le gonflement est réalisé sous un flux de vapeur constant assurant la saturation du film en eau. En observant le décollement progressif du film à partir des défauts linéaires préexistants, nous retrouvons un motif d’instabilité classique dit de fil de téléphone et nous montrons que le décollement résulte de contraintes de gonflement localisées proche de la ligne de décollement. Nous mesurons la vitesse de propagation du décollement dans la zone où le film est greffé sur le substrat et nous observons qu’elle augmente de deux ordres de grandeur lorsque la quantité de propylsilane dans le mélange de silanes réactifs passe de 0 à 90 %, c’est-à-dire lorsque le taux de greffage du film décroit. Un seuil d'épaisseur pour le décollement est également observé, les films pouvant se décoller étant d’autant plus minces que le taux de greffage du film ets faible. Les mesures de ce seuil sont discutées à partir d'un argument simple de mécanique de la rupture qui permet de rendre compte semi quantitativement de nos mesures
Hydrogel coatings are transparent and hydrophilic polymer networks that absorb a lot of water and can be suitable candidates for anti-mist coatings. However, swelling-induced stresses within the film can result in detrimental debonding of hydrogel and may fail. In this study, these debonding processes are investigated in the relation to the grafting density at the film/substrate interface, so as to control and predict the failure of the coatings during swelling or under contact stresses. For that purpose, we have developed a methodology consisting in monitoring the initiation and the propagation of swelling-induced delamination from well-controlled preexisting interface defects.Surface-attached poly(dimethylacrylamide) (PDMA) hydrogel thin films are prepared on silicon wafers from the simultaneous Cross-Linking And Grafting (CLAG) of functionalized polymer chains by thiol-ene click chemistry. This strategy allows to tune the film thickness (0.1-2 µm) while ensuring a homogeneous crosslinking density. In order to vary the strength of the film/substrate interface, the silicon wafer is grafted by mixing reactive mercaptosilane and unreactive propylsilane in various proportions prior to the formation of the hydrogel film. We characterize the mercaptosilane surface fraction thus obtained by XPS and TOF-SIMS analyses. Well-controlled line defects (width between 2 and 100 µm) are also created to nucleate delamination of the hydrogel from the substrate.Swelling-induced debonding of the film is achieved under a constant vapor flow ensuring water saturation. Optical observations show the progressive debonding of the film from the pre-existing line defects under the action of localized swelling stresses. We obtain a delamination pattern of typical so-called telephone cord instability. We measure the debonding propagation velocity where the hydrogel is grafted to the substrate. The debonding rate is found to decrease over two orders of magnitude when the amount of mercaptosilane in the reactive silane mixture is increased from 10% to 100% while increasing the covalent bonds between hydrogel and substrate. A threshold thickness for debonding is also observed. This threshold thickness increases with the amount of mercaptosilane used to graft the substrate. We derived quantitative values of the interface fracture energy from the measured thickness threshold with a simple fracture mechanics model

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Baxani, Kamal Divesh. "Hydrogel encapsulated droplet interface bilayer networks as a chassis for artificial cells and a platform for membrane studies". Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/112707/.

Texto completo

Resumen

There has been increasing interest in droplet interface bilayers (DIBs) as novel devices for the study of lipid membranes and the development of artificial cell systems. Although DIBs have demonstrated to be useful in a number of laboratory applications, their wider use is hampered by a limited ability to exist untethered and remain mechanically stable beyond controlled laboratory environments. In this thesis, a microfluidic system is developed which enables the facile generation of hydrogel-encapsulated DIB networks which are freestanding and can exist in air, water and oil environments, without compromise to their ability to interface with the surrounding environment. Electrophysiology is employed in order to demonstrate the formation of bilayers between the encapsulated DIBs (eDIBs) and their external environment, achieved via the incorporation of the transmembrane pore α-Hemolysin. The eDIBs produced here are able to form higher-order structures akin to tissues via their assembly and adherence to one another, further demonstrating their potential to act as a chassis for artificial cells. Furthermore, the potential of eDIBs to be used as a platform for membrane studies is demonstrated via their use as a high-throughput array for membrane disruption fluorescence measurements using a plate reader, which makes use of the ability of eDIBs to be generated in large numbers as well as to be mechanically handled and placed in the wells of a 96-well plate. Fluorescence measurements were taken on up to 47 eDIBs simultaneously, and were able to detect bilayer leakage through pores as well as bilayer failure. The above experiments comprise the design, manufacture and use of a novel kind of DIB construct as a chassis for artificial cells and a platform for high-throughput membrane studies. It is proposed that eDIBs may help in realising the unfulfilled potential of DIB networks in applications in healthcare and beyond.

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Berts, Ida. "Relating the Bulk and Interface Structure of Hyaluronan to Physical Properties of Future Biomaterials". Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198357.

Texto completo

Resumen

This dissertation describes a structural investigation of hyaluronan (HA) with neutron scattering techniques. HA is a natural biopolymer and one of the major components of the extracellular matrix, synovial fluid, and vitreous humor. It is used in several biomedical applications like tissue engineering, drug delivery, and treatment of osteoarthritis. Although HA is extensively studied, very little is known about its three-dimensional conformation and how it interacts with ions and other molecules. The study aims to understand the bulk structure of a cross-linked HA hydrogel, as well as the conformational arrangement of HA at solid-liquid interfaces. In addition, the structural changes of HA are investigated by simulation of physiological environments, such as changes in ions, interactions with nanoparticles, and proteins etc. Small-angle neutron scattering and neutron reflectivity are the two main techniques applied to investigate the nanostructure of hyaluronan in its original, hydrated state. The present study on hydrogels shows that they possess inhomogeneous structures best described with two correlation lengths, one of the order of a few nanometers and the other in the order of few hundred nanometers. These gels are made up of dense polymer-rich clusters linked to each other. The polymer concentration and mixing governs the connectivity between these clusters, which in turn determines the viscoelastic properties of the gels. Surface-tethered HA at a solid-liquid interface is best described with a smooth varying density profile. The shape of this profile depends on the immobilization chemistry, the deposition protocol, and the ionic interactions. HA could be suitably modified to enhance adherence to metal surfaces, as well as incorporation of proteins like growth factors with tunable release properties. This could be exploited for surface coating of implants with bioactive molecules. The knowledge gained from this work would significantly help to develop future biomaterials and surface coatings of implants and biomedical devices.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Vanderwerker, Zachary Thomas. "Using Lipid Bilayers in an Artificial Axon System". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/24449.

Texto completo

Resumen

Since the rise of multicellular organisms, nature has created a wide range of solutions for life on Earth. This diverse set of solutions presents a broad design space for a number of bio-inspired technologies in many different fields. Of particular interest for this work is the computational and processing power of neurons in the brain. Neuronal networks for transmitting and processing signals have advantages to their electronic counterparts in terms of power efficiency and the ability to handle component failure. In this thesis, an artificial axon system using droplet on hydrogel bilayers (DHBs) in conjunction with alamethicin channels was developed to show properties of action potential signal propagation that occur in myelinated nerve cells. The research demonstrates that the artificial axon system is capable of modifying signals that travel perpendicular to a lipid bilayer interface due to the voltage-gating properties of alamethicin within the connected bilayer. The system was used to show a signal boosting behavior similar to what occurs in the nodes of Ranvier of a myelinated axon. In addition, the artificial axon system was used to show that alamethicin channels within a lipid bilayer behave similarly to slow-acting potassium channels in a real axon in that they follow a sigmoid activation curve in response to a step potential change.
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Yang, Xianpeng. "Strong Cellulose Nanofiber Composite Hydrogels via Interface Tailoring". Kyoto University, 2020. http://hdl.handle.net/2433/253333.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Ciapa, Lola. "Frottement de films minces d'hydrogel : poroélasticité et interface". Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS006.

Texto completo

Resumen

Les films minces d’hydrogel sont des systèmes prometteurs pour des applications en ingénierie biomédicale (cartilage articulaire synthétique, lentilles de contact) ou optique (revêtements anti-buée) grâce à leur biocompatibilité, leur transparence et leurs propriétés lubrifiantes. Les propriétés frictionnelles de ces systèmes dans l’eau, cruciales pour leur utilisation, sont complexes car elles mettent en jeu plusieurs mécanismes physiques souvent couplés. La lubrification par un film d’eau, les écoulements poroélastiques dans le gel sous l’effet de gradients de pression et les interactions moléculaires à l’interface entre le gel et la surface glissante sont évoqués pour expliquer le frottement des gels.Dans ce travail de thèse, nous avons mesuré puis décrit le rôle des interactions moléculaires interfaciales dans le frottement des hydrogels dans l’eau. Pour cela, nous avons développé un dispositif expérimental permettant de supprimer à la fois les contributions poroélastiques et de lubrification par un film d’eau. En faisant glisser une lentille sphérique de silice en rotation sur un film de gel de polydiméthylacrylamide d’épaisseur micrométrique immergé dans l’eau, sous force normale et vitesse imposées, nous mesurons les forces de frottement et nous observons le contact gel/silice par interférométrie. En fonctionnalisant la silice par des silanes variés, nous mettons en évidence un effet important de la chimie de surface de la lentille de silice sur les forces de frottement mesurées et leur dépendance en vitesse de glissement, laquelle est variée sur trois ordres de grandeur. En régime transitoire, nous mettons en évidence un phénomène de vieillissement de l’interface lorsque la lentille est maintenue en contact avec le gel sur des temps longs avant d’initier le glissement. Pour discuter ces observations, nous proposons un modèle de frottement en régime stationnaire basé sur l’adsorption/désorption thermodynamique des chaînes polymères sur la surface glissante. Ce modèle rend compte des observations expérimentales à partir de paramètres moléculaires en accord avec la physicochimie des silices silanisées
Thin hydrogel films find applications in biomedical engineering (synthetic articular cartilage, contact lenses) or optics (anti-fog coatings) thanks to their biocompatibility, transparency, and lubricating properties. The frictional properties of these systems in water, which are crucial for their use, arise from the complex coupling of several physical mechanisms. Fluid film lubrication, poroelastic flows in the gel due to pressure gradients, and molecular interactions at the interface between the gel and the sliding surface are all involved in gel friction.In the present work, we provide a description of the role played by interfacial molecular interactions on friction of hydrogels in water. To this end, we built an experimental set up in which both poroelastic flows and water film lubrication are suppressed. By sliding a spherical silica lens with a rotative trajectory over a micrometer-thick polydimethylacrylamide gel film immersed in water, under imposed normal force and velocity, we measure the frictional forces and observe the gel/silica contact by interferometry. By functionalizing the silica with various silanes, we show an effect of surface chemistry of the silica lens on the measured friction forces and their dependence on sliding speed, over three decades in velocity. In transient regime, we demonstrate an ageing phenomenon of the interface when the lens is maintained in contact with the gel over long times before sliding initiation. We derive a model for steady state friction based on the thermodynamic adsorption/desorption of polymer chains on the sliding surface. This model successfully accounts for our experimental observations with a set of molecular parameters which agree with the physico-chemistry of our silanated systems

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Feng, Shi. "Elucidation of hydrogen oxidation kinetics on metal/proton conductor interface". Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48941.

Texto completo

Resumen

High temperature proton conducting perovskite oxides are very attractive materials for applications in electrochemical devices, such as solid oxide fuel cells (SOFCs) and hydrogen permeation membranes. A better understanding of the hydrogen oxidation mechanism over the metal/proton conductor interface, is critical for rational design to further enhance the performances of the applications. However, kinetic studies focused on the metal/proton system are limited, compared with the intensively studied metal/oxygen ion conductor system, e.g., Ni/YSZ (yttrium stabilized zirconia, Zr₁-ₓYₓO₂-δ). This work presents an elementary kinetic model developed to assess reaction pathway of hydrogen oxidation/reduction on metal/proton conductor interface. Individual rate expressions and overall hydrogen partial pressure dependencies of current density and polarization resistance were derived in different rate limiting cases. The model is testified by tailored experiments on Pt/BaZr₀.₁Ce₀.₇Y₀.₁Yb₀.₁O₃-δ (BZCYYb) interface using pattern electrodes. Comparison of electrochemical testing and the theoretical predictions indicates the dissociation of hydrogen is the rate-limiting step (RLS), instead of charge transfer, displaying behavior different from metal/oxygen ion conductor interfaces. The kinetic model presented in this thesis is validated by high quantitative agreement with experiments under various conditions. The discovery not only contributes to the fundamental understanding of the hydrogen oxidation kinetics over metal/proton conductors, but provides insights for rational design of hydrogen oxidation catalysts in a variety of electrochemical systems.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Matsumoto, Mitsuhiro. "Molecular Orientation near Liquid-vapor Interface of Hydrogen-bonding Systems". 京都大学 (Kyoto University), 1988. http://hdl.handle.net/2433/86403.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Lemon, Christopher P. "Neutron Compton scattering from hydrogen and perovskite oxide interfaces". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/593/.

Texto completo

Resumen

In this thesis we investigate two independent topics: neutron Compton scattering from hydrogen and perovskite oxide interfaces. Part one is an investigation of the scattering of high energy neutrons from hydrogen compounds. The motivation for this investigation stems from neutron Compton scattering experiments, performed with the VESUVIO neutron spectrometer at the ISIS pulsed neutron source, which report an anomalously reduced cross section for hydrogen. We explore the possibility that electronic excitation is responsible for the discrepancy between conventional theory and experiment. We conclude that the effect of electronic excitation on the scattering is small, at the energies relevant to the experiments, and therefore cannot account for the anomalies. Part two is an investigation of two perovskite oxide interfaces: a cuprate-manganite interface, and the interface between SrTiO\(_3\) and LaAlO\(_3\). Both interfaces are investigated using the techniques of impurity theory. Firstly, a simple model of a cuprate-manganite interface is proposed to explain several recent experiments. By applying the idea that the metallicity of the manganite spills out into the cuprate, we provide a theoretical interpretation of the unusual electronic and magnetic properties observed at the interface. Finally, a simple model of the SrTiO\(_3\)-LaAlO\(_3\) interface is investigated. Two ingredients are contained within this model: the orbital physics of the titanates, and the long range coulomb interactions produced by the polar discontinuity at the interface. From this model, we predict a two dimensional layer of charge confined to the interface, which is consistent with experimental observations.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Raymond, Elizabeth A. "Vibrational sum-frequency spectroscopic investigations of hydrogen-bonding interactions at the vapor/water interface /". view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3113024//.

Texto completo

Resumen

Thesis (Ph. D.)--University of Oregon, 2003.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 140-147). Also available for download via the World Wide Web; free to University of Oregon users.

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Sitsanidis, Efstratios D. "Controlling the interfaces of supramolecular hydrogels for tissue culture application". Thesis, University of Kent, 2018. https://kar.kent.ac.uk/69466/.

Texto completo

Resumen

The research work undertaken focused on the preparation and characterization of novel low molecular weight (LMW) hydrogels as functional biomaterials for tissue culture applications. To achieve this objective, new LMW compounds (as potential hydrogelators) were synthesized bearing a galactosamine or glucosamine moiety. The incorporation of carbohydrates was anticipated to confer molecular recognition of certain biomolecules upon the formed supramolecular gels and therefore act as potential anchor sites for cell-binding. The synthesis was based on short synthetic routes and low-cost starting materials were used as supplied. The target compounds were not confined only to those containing carbohydrates. A cinnamoyl-protected diphenylalanine hydrogelator was prepared and the properties of its corresponding hydrogel were investigated. Understanding the self-assembly mechanisms of supramolecular hydrogels is fundamental for the preparation and application of these novel materials. Therefore, a variety of techniques were employed for assessing and characterisation of gelation and to determine the configurational alignment of the formed fibres within the three-dimensional network of the gels. Specifically, the preparation and handling of hydrogels were optimized leading to robust gelation protocols. TEM and SEM microscopy revealed the size, shape and perplexing patterns of the fibres. XRD measurements verified polymorphism whereas rheology studies confirmed the viscoelastic properties of the gels. Non-covalent intermolecular interactions are the driving forces of the molecular packing, leading to higher order architectures. The combined spectroscopic analysis of the prepared hydrogels (by NMR, IR, UV-vis, CD) was advantageous to explore the nature of such interactions and allow the identification of key functional groups which actively participated in the self-assembly process. As a result of the CD work undertaken, utilisation of a synchrotron facility led to the establishment of a protocol for the evaluation of LMW hydrogels by SRCD spectroscopy, which was recently published. Finally, a preliminary biocompatibility study was undertaken to assess the toxicity of the hydrogels upon brain cancer cells. This project therefore required an interdisciplinary approach which involved the synthesis of a number of LMW compounds where some were found to be hydrogelators. This led to the preparation of their corresponding hydrogels and the study of their microscopic/macroscopic properties for the development of novel biocompatible materials suitable for tissue culture applications.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Wiener, Clinton G. Wiener. "PHYSICALLY CROSSLINKED HYDROGELS: IMPACT OF INTERFACES AND STRESS ON STRUCTURE AND PROPERTIES". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498033274841434.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Hendrickson, Grant R. "Harnessing microgel softness for biointerfacing". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50252.

Texto completo

Resumen

Hydrogel materials have become a heavily studied as materials for interfacing with biology both for laboratory investigations and the development of devices for biomedical applications. These polymers are water swellable and can be made responsive to many different stimuli by choice of monomers, co-monomers, and cross-linkers or functionalization with pendent ligands, substrates, or charged groups. The high water content, low moduli and potential responsively of these polymers make good candidates for biomaterials. A specific type of hydrogel called a microgel or a hydrogel micro/nanoparticle has similar properties to bulk hydrogel materials. Many of the interesting results and utility of the microgels in bioapplications are due to their inherent softness of the material. Here, the softness, flexibility, and conformability of these water swollen particles is used to create an interesting sensor platform, studied in the context of a microgel passing through a pore, and used as an emulsifier to create a drug delivery platform. The unifying theme of this dissertation is the softness of microgels which is critical for all of these experiments. However, the study of individual microgel softness is challenging and complex, since the softness is composed of two different components. The first is that the microgel is a swollen polymer which can be deswollen by an external stimuli or force. The second is that the microgel is a volume conserving elastic colloid which can deform without deswelling under the certain conditions. Throughout, this dissertation will discuss the ramifications of the complex softness of microgels in each experimental result and potential application.

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Eguchi, Daichi. "High Functionalization of Nanomaterials by Controlling Organic-Inorganic Interface". Kyoto University, 2017. http://hdl.handle.net/2433/227580.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Marpu, Sreekar B. "Biocompatible Hybrid Nanomaterials Involving Polymers and Hydrogels Interfaced with Phosphorescent Complexes and Toxin-Free Metallic Nanoparticles for Biomedical Applications". Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc84243/.

Texto completo

Resumen

The major topics discussed are all relevant to interfacing brightly phosphorescent and non-luminescent coinage metal complexes of [Ag(I) and Au(I)] with biopolymers and thermoresponsive gels for making hybrid nanomaterials with an explanation on syntheses, characterization and their significance in biomedical fields. Experimental results and ongoing work on determining outreaching consequences of these hybrid nanomaterials for various biomedical applications like cancer therapy, bio-imaging and antibacterial abilities are described. In vitro and in vivo studies have been performed on majority of the discussed hybrid nanomaterials and determined that the cytotoxicity or antibacterial activity are comparatively superior when compared to analogues in literature. Consequential differences are noticed in photoluminescence enhancement from hybrid phosphorescent hydrogels, phosphorescent complex ability to physically crosslink, Au(I) sulfides tendency to form NIR (near-infrared) absorbing AuNPs compared to any similar work in literature. Syntheses of these hybrid nanomaterials has been thoroughly investigated and it is determined that either metallic nanoparticles syntheses or syntheses of phosphorescent hydrogels can be carried in single step without involving any hazardous reducing agents or crosslinkers or stabilizers that are commonly employed during multiple step syntheses protocols for syntheses of similar materials in literature. These astounding results that have been discovered within studies of hybrid nanomaterials are an asset to applications ranging from materials development to health science and will have striking effect on environmental and green chemistry approaches.

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

McFearin, Cathryn LeAn 1979. "Investigations of the molecular structure and bonding of water at the liquid-liquid interface utilizing vibrational sum-frequency spectroscopy". Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10069.

Texto completo

Resumen

xvi, 120 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
The interface between water and an organic liquid is present in a variety of biological, environmental, and chemical processes throughout science and nature. Issues such as environmental remediation and ion transport are governed by the properties of these interfaces, thus the importance of understanding them at the molecular level is apparent. The research in this dissertation shows how the structure and bonding of the liquid-liquid interface changes as the interfacial environment is altered. Vibrational sum-frequency spectroscopy (VSFS), a surface specific, non-linear optical technique, is employed for these interfacial studies. The interfacial OH stretching modes are examined using VSFS under different conditions including organic liquids of varying polarity, as well as addition of acid, base, and salts to the aqueous phase. The effects of these different conditions on the water molecules' interactions both with each other and with the non-aqueous liquid are studied in order to better characterize and understand this important system. The effect of polarity of the non-aqueous phase is presented first through investigations of different mixed halocarbon liquid-water interfaces and the neat chloroform-water interface. These studies show that as the overall polarity of the organic phase increases, the water molecules exhibit less overall orientation and undergo some weak bonding interactions with the non-aqueous liquid. Next, the influence of different salts on the water structure at the interface is studied. Examining this system shows that the dissolved ions, specifically the anions, are present within the interface and significantly alter the orientation and bonding of the interfacial water molecules. The charge, size, and polarizability of the anions all play a role in determining how the water orientation is changed within the interface. Finally, the water-like ions H 3 O + and OH - are examined at the liquid-liquid interface by changing the pH of the aqueous phase through addition of HCl or NaOH. At the extremes of the pH scale, the acid and base have ordering or disordering effects, respectively, on the water structure within the interfacial region.
Adviser: Geraldine Richmond

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Pouvreau, Maxime. "Amélioration d'un champ de force pour la description des bordures de particules argileuses". Thesis, Nantes, Ecole des Mines, 2016. http://www.theses.fr/2016EMNA0291/document.

Texto completo

Resumen

Le champ de force CLAYFF est largement employé pour modéliser les interfaces de minéraux argileux – et minéraux apparentés – avec une phase aqueuse. Dans les simulations, les particules d’argile sont typiquement représentées par des feuillets semi-infinis, ainsi seules les surfaces parallèles au plan du feuillet (surfaces basales) sont considérées. Cette simplification est valable dans la mesure où ces surfaces sont majoritaires, mais les feuillets d’argile sont en réalité de taille nanométrique et terminés par des surfaces latérales, ou bordures. Ces surfaces peuvent non seulement adsorber les espèces en solution mais sont aussi sujettes aux transferts de proton, et tous les processus physico-chimiques liés à l’acidité de la phase aqueuse se produisent de façon prédominante au niveau des bordures. En ajoutant au champ de force CLAYFF un terme angulaire métal-O‑H dont les paramètres ont été correctement ajustés, les simulations réalistes des interfaces de bordure deviennent possibles.Les paramètres des termes Al-O‑H et Mg-O‑H ont été obtenus à partir de calculs DFT sur des modèles structuraux du bulk, de la surface basale et de la bordure de la gibbsite Al(OH)3 et de la brucite Mg(OH)2, dont les feuillets peuvent être considérés comme le squelette des minéraux argileux et apparentés. De plus, le terme Si-O‑H a été paramétré à partir d’un modèle de bordure de la kaolinite Al2Si2O5(OH)4. Les propriétés structurales et dynamiques issues de simulations de dynamique moléculaire DFT et classiques basées sur CLAYFF avec et sans terme métal-O‑H ont été comparées. Le champ de force modifié améliore nettement la description des surfaces hydroxylées : l'orientation et la dynamique librationnelle des groupes hydroxyles, les liaisons hydrogène dans lesquelles ils sont impliqués, et la coordination des atomes de métal appartenant aux bordures sont tous plus proches de la réalité
The CLAYFF force field is widely used to model the interfaces of clay minerals – and related layered materials – with an aqueous phase. In the simulations, clay particles are typically represented by semi-infinite layers, i.e. only surfaces parallel to the layer plane (basal surfaces) are considered. This simplification is acceptable to a certain extent, but clay layers are really nanosized and terminated by lateral surfaces or edges. These surfaces can not only adsorb solvated species but are also subject to proton transfers, and all physico-chemical processes related to the aqueous phase acidity predominantly occur at the edges. By adding to the CLAYFF force field a Metal-O‑H angle bending term whose parameters are correctly adjusted, the simulations of edge interfaces become possible.The parameters of Al-O‑H and Mg-O‑H terms were obtained from DFT calculations on bulk, basal surface and edge structural models of gibbsite Al(OH)3 and brucite Mg(OH)2, whose layers can be considered as the backbones of clay minerals and related materials. In addition, the Si-O‑H term was parametrized from an edge model of kaolinite Al2Si2O5(OH)4 . Molecular dynamics simulations based on DFT and on CLAYFF with and without Metal-O‑H term were performed. The modified force field clearly improves the description of hydroxylated surfaces : the orientation and the librational dynamics of the hydroxyl groups, the hydrogen bonding, and the coordination of metal atoms belonging to the edge are all closer to reality

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Edwards, Angela Celeste. "Probing the Hydrogen Bonding Interaction at the Gas-Surface Interface using Dispersion Corrected Density Functional Theory". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/71784.

Texto completo

Resumen

he interactions of the chemical warfare agent sulfur mustard with amorphous silica were investigated using electronic structure calculations. In this thesis, the binding energies of sulfur mustard and mimic species used in the laboratory were calculated using density functional theory and fully ab initio calculations. The wB97XD and B97D functionals, which include functions to account for long-range dispersion interactions, were compared to experimental trends. The hydroxylated amorphous silica surface was approximated using a gas-phase silanol molecule and clusters containing a single hydroxyl moiety. Recent temperature programmed desorption experiments performed in UHV concluded that sulfur mustard and its less toxic mimics undergo molecular adsorption to amorphous silica. Hydrogen bonding can occur between surface silanol groups and either the sulfur or chlorine atom of the adsorbates, and the calculations indicate that the binding energies for the two hydrogen bond acceptors are similar. The adsorption of sulfur mustard and its mimics on silica also exhibits the presence of significant van der Waals interactions between alkyl of the adsorbates and the surface. These interactions, in combination with the formation of a hydrogen bond between a surface silanol group and the Cl or S atoms of the adsorbates, provide remarkably large binding energies.
Master of Science

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Ester, Guy R. "An atomic force microscopy study of the crystal growth interface of solution grown potassium hydrogen phthalate". Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299809.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Schenck, Daniel Michael. "Submersion and lateral transport behavior of microparticles at a lung surfactant interface on model mucus hydrogels". Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2009.

Texto completo

Resumen

Barriers to effective pulmonary drug delivery are inherent to the lung physiology and present a challenge when attempting to bypass the natural defenses against inhaled particles. Inhaled particulate aerosols that deposit in the conducting airways of the lungs can become trapped in the respiratory mucus layer where they are then subjected to rapid clearance by the mucociliary escalator. The details of particle behavior after deposition and before this clearance are not well understood, however. Several physical processes may influence particle behavior on the mucus, including a penetration of particles into the mucus layer or a lateral transport of particles across the lung surface. Particles which deposit onto the respiratory mucus are subject to a number of forces which dictate these behaviors in the lung and may influence the retention of particles in the lungs and the efficacy of pulmonary drug delivery. The goal of this thesis was to investigate the behavior of microparticles deposited on a synthetic mucus model designed to mimic the bulk viscoelastic and surface tension properties of conducting airway mucus. Studies were conducted to determine the effects of mucus surface properties and particle physicochemical properties on the submersion and lateral mobility of single particles and the spreadability of particle-laden droplets at the air-liquid interface. Synthetic mucus gels were developed with viscoelastic properties that mimicked those of non-diseased tracheobronchial mucus. Infasurf, a calf lung surfactant extract, was spread onto the gel surfaces and compressed in a Langmuir trough to attain physiologically relevant surface tensions (~30-34 mN/m) and to analyze surfactant behavior on viscoelastic subphases. Microparticles were aerosolized onto the model mucus surface and imaged by brightfield microscopy at varying surface tensions on gels of varying viscoelastic properties to determine the extent of capillary submersion, in the fluid interface. Lateral transport of microparticles across the surfactant interface was quantified using particle tracking techniques. Finally, the spreading patterns of surfactant-laden droplets containing model drugs or particles were monitored by time-course imaging. Studies revealed that key physicochemical properties, including particle size and hydrophobicity, influenced particle submersion and mobility on the mimetic surfaces. Submersion, transport, and droplet spreadability were all inhibited with increasing gel viscoelastic properties, suggesting that such inhibition would be expected by healthy or disease tracheobronchial mucus. While low surface tensions promoted microparticle submersion into the subphase, the lateral transport and droplet spreadability were inhibited on gels with pre-existing surfactant films. The extent of droplet spreading could be enhanced by adding surfactant to the droplets. Overall, these studies aid our understanding of particle behavior and their fate at lung-like fluid surfaces, which has implications for both pulmonary drug delivery and pulmonary toxicity. Particulate aerosols which are designed to be smaller and more hydrophilic would experience improved mobility in the lungs and potentially gain the ability to submerge through the thick and highly viscous mucus barriers of diseased lungs. In healthy lungs, improved submersion could lead to greater particle retention, reduced mucociliary clearance, and a more effective delivery of drug to the epithelium. Lastly, by adding surfactant to drug containing liquid aerosol droplets, the deposition and distribution of drug could be improved in the peripheral regions of the obstructed lungs of cystic fibrosis patients. Results from these studies provide new knowledge that can be used to predict the behavior of aerosols deposited in the lungs and can aid the design of aerosols for drug delivery applications.

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Scatena, Lawrence Francis. "Vibrational sum frequency spectroscopic investigations of the structure, hydrogen bonding, and orientation of water molecules at the liquid/liquid interface /". view abstract or download file of text, 2001. http://wwwlib.umi.com/cr/uoregon/fullcit?p3045094.

Texto completo

Resumen

Thesis (Ph. D.)--University of Oregon, 2001.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 146-152). Also available for download via the World Wide Web; free to University of Oregon users.

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Diawara, Moussa. "Modélisation DFT des propriétés catalytiques de la Cérine utilisée comme matériaux d’interface dans les Piles à Combustible à Oxyde Solide (SOFC)". Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEC029.

Texto completo

Resumen

Le développement de nouveaux matériaux pour les piles à combustible à oxyde solide (SOFCs) est un challenge afin de répondre aux enjeux actuels: abaissement de la température de fonctionnement, utilisation de métaux non précieux, flexibilité d’utilisation du carburant ou encore résistance à la dégradation. A ces fins, une double approche théorique et expérimentale est développée depuis de nombreuses années au sein de l’équipe I2E, afin de mettre au point des matériaux à base de Cérine dopée en tant que matériaux d’interface permettant d’améliorer les propriétés catalytiques des anodes des SOFC. L’approche expérimentale a été mise en œuvre pour synthétiser des nanoparticules d’oxyde de cérium pure (baguette, cube ou octaèdre) exposant respectivement les surfaces (110), (100) et (111). Les résultats obtenus ont montré que l’orientation (100) était la plus réactive, suivie de la (110), puis de la (111) la moins réactive. Sur la base de ces résultats expérimentaux, cette thèse vise à développer une approche DFT pour étudier la première étape de l’activation de l’hydrogène sur une surface pure de CeO2, à savoir pour chaque orientation cristallographique, l’adsorption de la molécule sur la surface puis sa dissociation pour former des groupes hydroxyles : géométrie et énergie d’adsorption des états moléculaires et dissociés, chemin réactionnel conduisant de l’adsorption à la dissociation et les énergies d’activation correspondantes. Ensuite des calculs seront effectués pour évaluer l’effet d’une série de dopants (yttrium, gadolinium, samarium) sur le mécanisme de l’activation de l’hydrogène et les énergies d’activation correspondantes Mots clés : SOFC, Cérine, hydrogène, DFT
The development of new materials for solid oxide fuel cells (SOFCs) is a challenge to meet current challenges: lowering operating temperature, use of non-precious metals, flexibility of fuel use or resistance to degradation. For these purposes, a dual theoretical and experimental approach has been developed for many years within the I2E team, in order to develop doped cerine-based materials as interface materials to improve the catalytic properties of SOFC. anodes. The experimental approach was implemented to synthesize nanoparticles of pure cerium oxide (rod, cube or octahedron) respectively exposing the surfaces (110), (100) and (111). The results obtained showed that the orientation (100) was the most reactive, followed by the (110), then the (111) least reactive. On the basis of these experimental results, this thesis aims at developing a DFT approach to study the first step of the activation of hydrogen on a pure CeO2 surface, ie for each crystallographic orientation, the adsorption of the molecule on the surface then its dissociation to form hydroxyl groups: geometry and adsorption energy of the molecular and dissociated states, reaction path leading from the adsorption to the dissociation and the corresponding energies of activation. Then calculations will be made to evaluate the effect of a series of dopants (yttrium, gadolinium, samarium) on the mechanism of hydrogen activation and the corresponding activation energies Key words: SOFC, Ceria, hydrogen, DFT

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Sorrell, Courtney Davis. "Fundamental studies of responsive microgel thin films at interfaces". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24679.

Texto completo

Resumen

Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Lyon, L. Andrew; Committee Member: Beckham, Haskell; Committee Member: Janata, Jiri; Committee Member: Pielak, Gary; Committee Member: Ragauskas, Arthur

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Egidio, Fernanda do Carmo. "O uso de RMN para estudar a estrutura da água em interfaces e sistemas coloidais". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250164.

Texto completo

Resumen

Orientador: Edvaldo Sabadini, Fred Yukio Fujiwara
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-19T09:00:39Z (GMT). No. of bitstreams: 1 Egidio_FernandadoCarmo_D.pdf: 2263055 bytes, checksum: 940b47bd50de20f4597683b091bd3faf (MD5) Previous issue date: 2011
Resumo: O modelo de dois sítios, utilizado nos estudos de relaxação do solvente em soluções de carboidratos, pode ser transposto de forma satisfatória para soluções de polímeros hidrofílicos. Polímeros que possuem hidrogênios lábeis, isto é, que possuem hidrogênios disponíveis para troca química com os hidrogênios da água, causam aumento da taxa de relaxação spin-spin do solvente, R2, em relação ao valor obtido para a água pura O efeito torna-se mais intenso na medida em que a concentração dos polímeros aumenta. Polímeros que não possuem hidrogênios lábeis não alteram significativamente o R2 do solvente, pois o mecanismo de troca química não é estabelecido. A relaxação do solvente pode ser usada para estudar o processo de transição sol-gel em sistemas poliméricos. Conforme o gel e formado, as moléculas de água começam a ser confinadas e a taxa de relaxação do solvente aumenta significativamente. A estrutura de hidrogéis supramoleculares formados entre PEG e a-CD, a qual possui uma cavidade hidrofóbica em relação ao seu exterior hidrofílico, dependem das concentrações de seus constituintes e da massa molar do polímero. Quanto maior a massa molar do polímero, menor o numero de pontos de reticulação e mais frágil será o hidrogel. A partir da entrada de 2 moléculas de a-CD em uma cadeia de PEG linear 1.470 Da, a complexação torna-se mais intensa, levando ao recobrimento de toda a cadeia polimérica. A cinética de gelação entre a-CD e PEG, estudada por medidas do tempo de relaxação spin-spin (T2 = 1/R2) do solvente, fornece um perfil de curva que pode explicar o processo de complexação e formação do gel como um todo. A liberação e o confinamento de moléculas de água são refletidos no tempo de relaxação spin-spin destas. Ao liberar moléculas de água, observa-se uma diminuição nos valores de R2 da água até um ponto mínimo, a partir do qual os valores começam a aumentar devido ao confinamento destas moléculas
Abstract: The two sites model used in the studies of solvent relaxation in carbohydrate solutions was also applied for hydrophilic polymer solutions. Polymers with labile hydrogen atoms, meaning they have hydrogen available for chemical exchange with the hydrogen atoms of water, increase the solvent spin-spin relaxation rate, R2, relative to the pure water. The effect becomes more intense as the polymer concentration increases. Polymers without labile hydrogen do not affect significantly R2 of the solvent, because the chemical exchange mechanism is not established in this case. The solvent relaxation can be used to study the process of sol-gel transition in polymer systems. When the gel is formed, the water molecules become confined and the solvent relaxation rate increases significantly. The structure of supramolecular hydrogels formed from PEG and a-CD, which has a hydrophobic cavity and exterior hydrophilic, depends on the concentration of the constituents and the molar mass of the polymer. The higher is the molar mass of the polymer, the fewer is the crosslinking points and more the fragile is hydrogel. Since the inclusion of two a-CD molecules in a chain of linear PEG 1470 Da, the complexation becomes more intense, leading to the full inclusion complex. The kinetics of hydrogel formation between a-CD and PEG was studied by relaxation time measurements of the spin-spin (T2 = 1/R2) of the solvent, provides a curve, whose shape can used to explain the process of complexation and the gelation process at all. The release and confinement of water molecules of the gel are affect spin-spin relaxation the time of the water molecules. The releasing of the water molecules, results in the decreasing of R2 up to a minimum value, and beyond this point the values increases again, due to confinement of these molecules
Doutorado
Físico-Química
Doutor em Ciências

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Pillar-Little, Elizabeth A. "MECHANISMS OF HETEROGENEOUS OXIDATIONS AT MODEL AEROSOL INTERFACES BY OZONE AND HYDROXYL RADICALS". UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/80.

Texto completo

Resumen

Atmospheric aerosols play an important role in climate by scattering and absorbing radiation and by serving as cloud condensation nuclei. An aerosol’s optical or nucleation properties are driven by its chemical composition. Chemical aging of aerosols by atmospheric oxidants, such as ozone, alters the physiochemical properties of aerosol to become more hygroscopic, light absorbing, and viscous during transport. However the mechanism of these transformations is poorly understood. While ozone is a protective and beneficial atmospheric gas in the stratosphere, it is a potent greenhouse gas in the troposphere that traps heat near the Earth’s surface. It also impacts human heath by irritating the respiratory tract and exacerbating cardiovascular diseases. Additionally, ozone can alter the ecosystem through oxidizing plant foliage which can lead to deforestation and crop losses as well. Both gases and aerosols in the troposphere can react with ozone directly and indirectly with hydroxyl radicals. While daytime aging is thought to be primarily driven by photochemical processes and hydroxyl radicals, ozone is thought to be a key player in nighttime or dark aging processes that can alter the physicochemical properties of aerosols. Measured concentrations of trace gases and aged aerosol components in the field are higher than values predicted based on laboratory studies and computer simulations. Consequently, new experimental approaches are needed to narrow the gaps between observations and mechanistic understandings. In this dissertation, a plume of microdroplets was generated by pneumatically assisted aerosolization and then exposed to a flow of ozone before entering a mass spectrometer. This surface-specific technique allowed for the real-time analysis of reaction products and intermediates at the air-water interface. This work explores the in situ oxidation of iodide, a component of sea spray aerosols, by 0.05 – 13.00 ppmv ozone to explore how heterogeneous oxidation could enhance the production of reactive iodide species. Methods to study the reaction channels and intermediates were also established to not only determine a mechanism of iodide oxidation by ozone, but to enable the study of more complex systems. The developed approach was then applied to examine the oxidation of catechol and its substituted cousins, a family of compounds selected to model biomass burning and combustion emissions, at the air-water interface. While literature suggested that the primary mechanism of catechol oxidation by ozone would be the cleavage of the C1-C2 bond, it was determined that this was only a minor pathway. An indirect oxidation channel dominated heterogeneous processes at the air-water interface, giving rise to hydroxyl and semiquinone radicals that recombine to produce polyhydroxylated aromatics and quinones. This new mechanism of aging represents an overlooked channel by which brown, light-absorbing carbon aerosols are produced in the atmosphere. In addition, the work investigates how reactions on solid particulate aerosols proceed under variable relative humidity. Thin films were developed alongside a novel flow-through reactor to study of how aerosols are transformed by ozone and hydroxyl radicals when exposed to 50 ppbv - 800 ppmv of ozone. This system was employed to probe how catechol reacts with ozone under variable relative humidity. Further work was undertaken to model the adsorption process at the air-solid interface under variable humidity, permitting the estimation of the reactive uptake of ozone by the film at concentrations (50-200 ppbv) seen in rural and urban areas. Together, these results provide an increased understanding of how heterogeneous oxidation of aerosols contributes to aerosol aging processes as well as free radical production in the troposphere.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Bianco, Valentino. "Statistical Physics of Water in Hydrophobic Nano-Confinement and at Proteins Interfaces". Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/120095.

Texto completo

Resumen

Water is commonly associated with life. This substance affects the living beings in countless aspects and length scales, ranging from molecular biology to climatology. Water exhibits a long series of anomalous behaviors. These anomalies can be rationalized as a consequence of a second critical point in the supercooled region of the liquid phase. Nevertheless, the large part of the phase diagram of supercooled water is to date experimentally inaccessible for the inevitable crystallization of the bulk liquid. Confinement of water in nano-structures is a possible way to prevent the crystallization of molecules. In this thesis we present a coarse-grain model to describe the physical behavior of water at hydrophobic interfaces. The essential feature of the model is the description of water-water interaction via directional and cooperative components of the hydrogen bond (HB). We explore the phase diagram of supercooled water nano-confined between hydrophobic walls. Our results, grounded in statistical physics methods and Monte Carlo simulations, show the presence of a line of first order phase transition in the temperature-pressure plane separating two liquid phases and ending in a liquid-liquid critical point (LLCP). The LLCP universality class approaches the one of the Ising model in two dimensions in the thermodynamic limit, while large deviations are observed for strong confinement. Below the LLCP we find the locus of maxima of correlation length (the Widom line) of the system. Near the LLCP we find a large increase of the thermodynamic response functions consistent with the anomalous behaviors of water. These predictions are confirmed by a percolation description of water molecules based on the definition of cluster of correlated degrees of freedom. Along the phase transition line and the Widom line we recover a power law cluster distribution. At the LLCP the scaling of the percolation quantities agree with the Ising critical exponents. The density, energy and entropy fluctuations that are at the base of the anomalies of water and the existence of its LLCP have also consequences in the context of protein stability. General thermodynamic prediction asserts the existence of a close stability region (SR) in temperature-pressure plane for the native folded state of a protein. Experimental evidences support this theory showing hot-, cold- and pressure-denaturation. Water behavior at the protein interface is expected to be the driving force for the folding-unfolding process. To shed light on this mechanism we study the SR of a folded hydrophobic polymer solvated in the coarse-grain water. Tuning the water-water interaction at the interface and the density of the hydration shell we find an elliptic protein SR in the temperature-pressure plane, qualitatively consistent with available experimental data. Our work contributes to the ongoing debate about the role of hydration water in stabilizing the native protein state. We show here that the physics of water, and in particular its energy, density and entropy fluctuations are sufficient to rationalize the existence of a protein SR with respect to temperature and pressure.
El agua es, probablemente, el líquido más importante para la vida. Afecta el clima y la morfología de la Tierra, es fundamental en muchas tecnologías y desarrolla un papel fundamental en los procesos biológicos. A pesar de su importancia y abundancia su comportamiento sigue siendo difícil de entender respecto a los fluidos simples, del tipo argón (el agua tiene más de sesenta anomalías). En esta tesis proponemos un modelo de grano-grueso capaz de captar algunas características microscópicas de la interacción agua-agua en una interfaz hidrofóbica. Hemos analizado el diagrama de fases por baja temperatura de una mono-capa de agua confinada entre paredes paralelas hidrófobas encontrando un punto crítico líquido-líquido en la región sobre-enfriada, al final de una línea de transición de primer orden entre dos fases líquidas. El punto critico pertenece a la clase de universalidad Ising en dos dimensiones sólo por tamaño de las paredes muy grandes. Sorprendentemente, aumentando el confinamiento, la clase de universalidad desvía hacia la de Ising en tres dimensiones. Presentamos una descripción geométrica de la región de moléculas correladas en la monocapa sobreenfriada. Nuestros resultados enseñan que la línea de transición líquido-líquido y la línea Widom (su continuación analítica) se caracterizan por una línea de percolación, donde la distribución de los clúster decae según ley de potencia. Esta línea marca la región donde las fluctuaciones de puentes de hidrógeno se extienden por toda la red. Finalmente hemos estudiado cómo la red de puentes de hidrógeno puede estabilizar el estado nativo de una proteína, en función de la variación de la interacción agua-agua en la interfaz hidrofóbica y del aumento de densidad del agua interfacial al aumentar la presión. El modelo muestra que la proteína se desnaturaliza a alta y baja temperatura, y a alta y a baja presión, reproduciendo las características de desnaturalización observadas en los experimentos. La región de estabilidad de la proteína, tiene una forma elíptica de acuerdo con la teoría.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Bridges, Amanda Walls. "Host responses to microgel-based biomaterial interfaces". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31701.

Texto completo

Resumen

Thesis (Ph.D)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Garcia, Andres; Committee Member: Babensee, Julia; Committee Member: Bellamkonda, Ravi; Committee Member: Lyon, Andrew; Committee Member: Temenoff, Johnna. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Wilson, Christopher Brant. "Measurement of chemical composition and pH profiles near the liquid-vapor interface of aqueous solutions using a unique confocal microscope system /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9840.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Pálsson, Gunnar Karl. "Influence of Self-trapping, Clamping and Confinement on Hydrogen Absorption". Doctoral thesis, Uppsala universitet, Materialfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-140329.

Texto completo

Resumen

The dissociation of hydrogen molecules at surfaces is the first step in the absorption process. If the absorbing material is covered by an oxide, this layer will determine the effective uptake rate of an underlying absorbing material. This effect is illustrated when determining the rate of transport of hydrogen through amorphous aluminium oxide layers. The transport rate was determined to be strongly thickness dependent. Hydrogen absorbed in a transition metal causes a volume expansion generated by a strain field around the absorbed hydrogen. This strain field causes a self-trapping of the hydrogen and a temperature dependent distribution in the atomic distances. The local strain field generated by the self-trapping process is found to be crucial for understanding both the hydrogen induced volume expansion as well as the diffusion of hydrogen. Ab-initio molecular dynamics simulations were used to reveal the temperature dependence of the unbinding of the hydrogen and the local strain field and its influence on the diffusion rate. The symmetry of the local strain field is also important for phase formation in metallic films and superlattices which are clamped to a substrate. As the thicknesses reduced from 50 to 10 nm thick vanadium films, substantial finite size effects become apparent in the phase diagrams. The volume change associated with the strain field cannot be accurately measured using x-ray diffraction because of its sensitivity to local arrangements of atoms. X-ray and neutron reflectivity were found to be more reliable probes of global effects of the sumof the local strainfields. Finite size effects in extremely thin V layers were also explored in metallic superlattices composed of iron and vanadium. The co-existence region, composed of a hydrogen gas and a solid-like phase, was found to be suppressed by at least 100 K to below 300 K. The hydrogen-hydrogen interaction can also be influenced by the electronic states in the non hydrogen absorbing layers, as demonstrated when comparing hydrogen absorption in Fe/V and Cr/V superlattices.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 728

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Tchakalov, Rossen. "Engineering and optimization of electrode/electrolyte interfaces to increase solid oxide fuel cell (SOFC) performances". Thesis, Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLM001.

Texto completo

Resumen

Dans ce travail, nous avons établi un protocole de fabrication industrielle pour réaliser des cellules de piles à combustible avec interfaces électrode/électrolyte architecturées, ou planes. Nous avons démontré que pour deux types d'échantillons, différents par les matériaux, la microstructure, le nombre de couches et l'emplacement de l'architecture, l'architecture de l'interface électrode/électrolyte entraîne une augmentation très significative des performances. Les mesures de polarisation et l'EIS sont utilisées pour étudier les performances électrochimiques des cellules, ainsi que pour comparer les cellules architecturées et les cellules planes. Nous isolons l'influence de l'architecture sur les spectres d'impédance globaux en utilisant une méthode de comparaison innovante basée sur l'étude des écarts relatifs des parties de résistance dépendantes de la fréquence. Ainsi, l'architecture a une influence favorable sur les performances électrochimiques en améliorant les capacités catalytiques des électrodes ainsi que le transfert de charges (et en particulier le transfert d'ions) dans la cellule. L'architecture induit une augmentation de 60 % de la densité de puissance maximale pour les cellules de Type I et de 75 % pour les cellules de Type II
In this work, we have established an industrial fabrication protocol for single fuel cells with either architectured or planar electrode/electrolyte interfaces. We have demonstrated that in two types of samples, differing in materials, microstructure, number of layers, and architecture location, the architecturation of the electrode/electrolyte interface results in a highly significant performance increase. Polarization measurements and EIS are used to study the electrochemical performances of the cells, to compare the architectured and planar ones. We isolate the influence of the architecturation on global impedance spectra by using an innovative comparison method based on the study of the relative gaps of the frequency-dependent resistance parts. Thus, the architecturation has a strongly favorable influence on the electrochemical performances by enhancing the catalytic capabilities of the electrodes as well as the charge transfer (and in particular the ion transfer) within the cell. The architecturation induces a 60 % increase of the maximum power density for the Type I cells and 75% for the Type II cells

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Dalla, bernardina Simona. "Structure and connectivity of water molecules at the interfaces of nanoconfined systems". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS103/document.

Texto completo

Resumen

La compréhension des mécanismes d’absorption de l’eau, ainsi que l’arrangement moléculaire adopté par le réseau de molécules d’eau lors du confinement à l’échelle nanométrique, est crucial que ce soit pour l’optimisation de plusieurs applications, telles que la production d’énergie propre, la purification et le dessalement de l’eau, ou pour élucider certains processus complexes qui ont lieu dans les systèmes biologiques. Dans le cadre de cette thèse, l’hydratation contrôlée de trois systèmes poreux modèles suivie par spectroscopie infrarouge montre les effets de la nature des surfaces et des limitations stériques qui, en altérant les liaisons hydrogène établies entre les molécules d’eau, déclenche la formation de réseaux atypiques. La brillance de la source de rayonnement synchrotron infrarouge, exploitée par la ligne de lumière AILES au sein du synchrotron SOLEIL, a permis l’étude d’échantillons très absorbants en permettant de mettre en évidence la faible contribution de monocouches de molécules d’eau voire même de chaînes linéaires. L'effet d'une surface hydrophile sur la structure, la densité et la dynamique des molécules d'eau à l'interface a été étudié en mesurant l’absorbance d’une lamelle de Vycor poreux (pores d’environ 5 nm) à l’équilibre avec une pression de vapeur d'eau donnant lieu à la formation d’un réseau d’eau bi-dimensionnel. Les interactions fortes entre l’eau interfaciale et la surface hydrophile provoquent plusieurs transitions structurales du réseau d’eau expliquant ainsi les observations par d’autres techniques. Des similitudes et des différences surprenantes ont été observés entre l’hydratation d’une surface hydrophile et celle d’un système hydrophobe dans des conditions de confinement extrême : les nanotubes de carbone à paroi unique (SWCNTs) ayant un diamètre de quelques Angstrom. Nos mesures ont montré que l’établissement d’un réseau de molécules d’eau unique peut être à l’origine du déplacement rapide des molécules d’eau à l’intérieur des nanotubes de carbone. Enfin, l’étude des mécanismes d’adsorption de la membrane Nafion, membrane modèle dans les piles à combustible à membrane échangeuse de protons (PEMFCs), a permis de clarifier les processus en jeu lors de l’ionisation et la formation d’espèces protonique responsable de la remarquable conductivité ionique propre à cette famille de membranes.Cette méthodologie pourra être étendue à des systèmes plus complexes, tels que les réseaux de molécules d’eau dans les systèmes biologiques
Understanding the water absorption mechanisms, and the molecular arrangement adopted by the water molecules upon confinement at the nanoscale is crucial both for technological applications, such as clean energy production, purification and desalination of water, and to unveil some of the complex processes occurring in biological systems.In this thesis, the controlled hydration of three porous model systems monitored by infrared spectroscopy shows the effects of surfaces forces and steric limitations that triggers the formation atypical networks by altering the hydrogen bonds established between water molecules. The brightness of the infrared synchrotron radiation source on the AILES beamline at synchrotron SOLEIL allowed to highlight the low contribution coming from water molecules arranged as monolayer or linear chains in highly infrared absorbent matrices. The effect of a hydrophilic surface on structure, density and dynamic of water molecules at interfaces was examined by measuring the absorbance of a porous Vycor slab (pores of about 5 nm) at equilibrium with the water vapor pressure needed to obtain a two-dimensional water network. The strong interfacial interactions between water and the hydrophilic surface cause several structural transitions on the water network elucidating the observations made by other techniques. Surprising similarities and differences are observed between the hydration of a hydrophilic surface and that of a hydrophobic system under extreme confinement: single-wall carbon nanotubes (SWCNTs) having a diameter of several Angstroms. Our measurements have shown that the arrangement of a peculiar water network may be the origin of the enhanced water flux in carbon nanotubes. Finally, the study of the adsorption mechanisms of the Nafion membrane, the benchmark electrolyte in proton exchange membrane fuel cells (PEMFCs), has shed new light on the processes involved in the ionization and the formation of protonic species, accountable for the remarkable ionic conductivity typical of these membranes.This approach may be also extended to more complex systems, such as water molecules networks in biological systems

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Rerzki-Vérité, Cécile. "Nouveaux hydrogels physiques ultra-déformables dopés de cubosomes décorés par des argiles". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS632.

Texto completo

Resumen

De par leurs fortes teneur en eau et déformabilité, les hydrogels constituent un outil de choix pour concevoir des systèmes biocompatibles stimulables aux applications dans le domaine de la santé. Dans ce contexte, l’objectif de la thèse est de développer de nouveaux hydrogels permettant une délivrance contrôlée de molécules induite par sollicitation mécanique externe. Pour ce faire, ces travaux proposent une nouvelle approche de formulation d’hydrogels basée sur l’utilisation de cubosomes, i.e. de phases cristallines cubiques de lipides. Elles sont stabilisées dans l’eau par des nanoplaquettes d’argile, sur lesquelles s’adsorbent les chaînes polymériques dans la phase aqueuse. Les nano-gouttelettes forment ainsi les nœuds permettant la réticulation physique de l’hydrogel, sans introduction d’aucun liant chimique covalent. Le travail comporte en deux grandes parties : (i) la caractérisation fine des mécanismes de stabilisation de l’émulsion de cubosomes par l’argile afin d’optimiser la synthèse de l’hydrogel et (ii) la formulation de l’hydrogel et la caractérisation de ses propriétés structurales et mécaniques. Les émulsions sont obtenues par ultrasonication de phytantriol (PT) pour le lipide, de nanoparticules discotiques de laponite (d’épaisseur 1 nm et de rayon 25 nm) et d’eau. Le diagramme de phase a été établi et tous les points ont été caractérisés de façon exhaustive par une approche multi techniques. Elle combine observations visuelles, conductivité, diffusion dynamique de la lumière (DLS), diffusion des rayons X aux petits angles (SAXS) et diffusion de neutrons aux petits angles (SANS) avec variation de contraste. Un seuil de dispersion du PT a été déterminé macroscopiquement en fonction des concentrations de laponite et de PT, au-delà duquel une fraction du PT n’est pas stabilisée. La conductimétrie a quant à elle mis en évidence l’existence étonnante d’un second seuil de dispersion dans le système: la laponite s’adsorbe sur les gouttes de PT jusqu’à une concentration seuil indépendante de la concentration de lipide à disperser dans le milieu. Les données de DLS ont été analysées par un modèle qui distingue les contributions respectives des gouttes et de la laponite libre. Elles révèlent que la taille des gouttes de PT est constante sur tout le diagramme de phase, en accord avec le choix d’une énergie fixe donnée au système lors de l’étape d’ultrasonication. La détermination de la position des pics de Bragg associés à la phase cubique de symétrie Pn3m du PT par SAXS montre qu’elle est indépendante des concentrations en PT et en Laponite. Cela prouve que les laponites ne pénètrent pas les gouttes. La structure fine des émulsions a été obtenue par des expériences de de SANS, en éteignant successivement le signal du PT et celui des laponites. Un modèle de boules décorées de disques a été développé pour ajuster le signal de la laponite. La fraction déterminée de laponites adsorbées ou libres dans la solution est en très bon accord avec les mesures conductimétriques. Des hydrogels de polyacrylamide ont été synthétisés in situ à partir de ces émulsions avec une concentration élevée finale de polymère, autour de 10% en masse. Le protocole de polymérisation a été optimisé, en particulier l’ordre d’incorporation des initiateurs, et choisi de sorte à ce que les chaînes de polymère ne traversent pas les gouttes. Leur structure a été examinée au repos et sous étirement uniaxial par SANS. Ces gels purement physiques sont étirables au moins jusqu’à 1000% sans casse. La structure interne des gouttes est conservée lors de la synthèse ou de l’étirement. Sous étirement, sans se déformer, les gouttes se réorganisent au sein d’un réseau tridimensionnel très dense de chaînes à la taille de maille de quelques angströms. Enfin, les propriétés mécaniques des hydrogels dopés ont été évaluées par des expériences de rhéologie oscillatoire qui montrent que le module est relativement stable dans les gammes de concentration étudiées
Because of their high content in water and deformability, hydrogels are especially sought after in the health field to conceive stimulable biocompatible systems. In this context, the goal of this thesis is to develop new hydrogels able to perform controlled-delivery of molecules when an external mechanical stimulus is applied. To this end, a new approach in hydrogel formulation is suggested. It involves the use of cubosomes, i.e. cubic liquid crystalline lipid phases. They are stabilized in water by clay nanoplatelets, on which are adsorbed polymer chains in the aqueous phase. The nano-droplets are thus acting as nodes for the network and allow physical crosslinking of the hydrogel without any use of a chemical crosslinker. This work is organized in two parts: (i) fine characterization of the stabilization mechanisms of the cubosome emulsion stabilized by clay in order to optimize the hydrogel synthesis and (ii) hydrogel formulation and characterization of its structural and mechanical properties. Emulsions are produced by ultrasonication of a system formed of phytantriol (PT) which is a lipid, and disk-shaped nanoparticles of laponite (with a 1 nm thickness and 25 nm radius). The phase diagram was established and all points of it were comprehensively characterized with a multi-technical approach. It combines visual observations, conductivity, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) with contrast variation. A dispersion threshold for PT was macroscopically identified depending on the concentrations of laponite and PT. Above it, a fraction of the PT in the sample is not stabilized. Moreover, conductimetry surprisingly highlighted the existence of a second dispersion threshold in the system. Indeed, laponite adsorbs onto the PT droplets up to a specific concentration which is independent of the lipid concentration that is to be dispersed in the aqueous medium. DLS was used to illustrate the consistency of the size of the PT droplets across the phase diagram. The data was analyzed with a model that differentiates the contributions of the droplets from the ones of free laponite. This is coherent with the constant energy given to the system during the ultrasonication step. SAXS measurements of the position of the Bragg peaks related to the cubic PT phase of Pn3m symmetry shows independence from the concentrations of PT and of laponite. This demonstrates that the laponites do not enter the droplets. The fine structure of the emulsions was obtained with SANS experiments, in which the signals of PT and laponite were successively put out. A model of spheres decorated with disks was developed to fit the signal of laponite. It led to the fraction of adsorbed or free laponites in solution, matching the conductimetry results very well. Polyacrylamide hydrogels were synthesized from these emulsions with a high final concentration of polymer, around 10 wt%. The synthesis protocol was optimized, especially the order of addition of the polymerization initiators. It was chosen so that the polymer chains would not go through the drops. The structure of the hydrogels was investigated at rest and under uniaxial stretching with SANS. These purely physical hydrogels are stretchable to at least 1000% without breaking. The internal liquid crystalline structure of the lipid drops is unmodified by the synthesis and stretching. The drops do not deform but are reorganized under stretching in a very dense tridimensional network of chains with a mesh size of a few angströms. Lastly, the mechanical properties of these reinforced hydrogels were assessed with oscillatory rheology measurements. The modulus is rather unchanged across the range of explored concentrations

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Nishitani, Nobuhiko. "Design and Control of Cooperative Self-Assembly Processes at Liquid/Solid Interfaces by Tuning Supramolecular Interactions". Kyoto University, 2019. http://hdl.handle.net/2433/242536.

Texto completo

Resumen

付記する学位プログラム名: 充実した健康長寿社会を築く総合医療開発リーダー育成プログラム
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第21798号
工博第4615号
新制||工||1719(附属図書館)
京都大学大学院工学研究科合成・生物化学専攻
(主査)教授松田建児, 教授杉野目道紀, 教授浜地格
学位規則第4条第1項該当

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Nick, Thomas Udo. "Hydrogen Bonds and Electrostatic Environment of Radical Intermediates in Ribonucleotide Reductase Ia". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-877F-7.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Lacombe, Jérémie. "Organisation multi-échelle de matériaux polymères contrôlée par la chimie aux interfaces". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET012.

Texto completo

Resumen

Les propriétés des matériaux découlent en partie de leur organisation à l’échelle nano ou microscopique. Dans cette thèse, on montre qu’en contrôlant la chimie aux interfaces, des organisations très régulières peuvent être obtenus spontanément dans divers matériaux polymères.Dans une première, la chimie supramoléculaire a été utilisée pour contrôler l’organisation en masse de polymères greffés à une ou deux de leurs extrémités par la thymine (Thy) ou la 2,6-diamino-1,3,5-triazine (DAT), deux unités supramoléculaires complémentaires s’associant par liaisons hydrogène. Quelque soit la nature de la chaine polymère (PE, PDMS, PPG), les matériaux présentent des organisations lamellaires nanoscopiques très régulières lorsque l’unité terminale (Thy) et/ou la chaine (PE) cristallisent. Les contributions respectives à ces organisations de la ségrégation de phase, de la cristallisation, des liaisons supramoléculaires et des interactions secondaires ont été déterminées. Il a été montré que le confinement des chaines polymères dans les lamelles empêche la formation de chaines de grandes masses molaires. Cependant, les interactions supramoléculaires Thy/DAT permettent de former des copolymères à blocs supramoléculaires en mélangeant des chaines incompatibles fonctionnalisées par ces unités.Dans une seconde partie, nous avons montré que la texturation spontanée de films acrylates photopolymérisés à l’air est gouvernée à l’interface formulation/air par l’équilibre des cinétiques de polymérisation et d’inhibition par l’oxygène. Des morphologies microscopiques très régulières, hexagonales, lamellaires ou cacahuètes, sont obtenues en contrôlant différents paramètres expérimentaux et ce pour une large gamme d’épaisseur de film (6 µm – 2 mm). L’auto-texturation confère aux films des propriétés optiques singulières (flou, clarté) qui peuvent être modulées en ajustant les caractéristiques de la morphologie
Materials properties very often derive from their nano or micro-scale organization. In this thesis, we evidence that controlling the chemistry at the interfaces allows obtaining spontaneously very regular organizations in various polymer materials.In the first part, supramolecular chemistry has been used to control the organization in the bulk of polymer grafted at one or both extremities by thymine (Thy) or 2,6-diamino-1,3,5-triazine (DAT), two self-complementary supramolecular units interacting via hydrogen bonds. Whatever the polymer nature (PE, PDMS, PPG), materials present very regular nanoscale long-range ordered lamellar organizations if the end group crystallize (Thy) and/or the chain crystallize (PE). Respective contributions to these organizations of phase segregation, crystallization, supramolecular interactions and secondary interactions have been determined. It was shown that the confinement of chains in lamellae prevent the formation of high molecular weight chains, resulting in poor mechanical properties. However, Thy/DAT interactions allow creating supramolecular block copolymers by mixing incompatible chains functionalized with these units.In the second part, we have studied the spontaneous formation of patterns at the film surface of acrylate film during their photopolymerization under air. This phenomenon occurs if there is a balance at the film surface between the polymerization and the oxygen inhibition rates. Very regular microscale patterns (hexagons, lamellae, peanuts) have been generated by controlling some experimental parameters (UV intensity, initiator concentration) for a wide range of film thicknesses (6 µm – 2 mm). Self-patterning gives interesting optical properties to the films (haze, clarity) which can be modulated by adjusting the patterns wavelength and amplitude

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Lacombe, Jérémie. "Organisation multi-échelle de matériaux polymères contrôlée par la chimie aux interfaces". Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLET012.

Texto completo

Resumen

Les propriétés des matériaux découlent en partie de leur organisation à l’échelle nano ou microscopique. Dans cette thèse, on montre qu’en contrôlant la chimie aux interfaces, des organisations très régulières peuvent être obtenus spontanément dans divers matériaux polymères.Dans une première, la chimie supramoléculaire a été utilisée pour contrôler l’organisation en masse de polymères greffés à une ou deux de leurs extrémités par la thymine (Thy) ou la 2,6-diamino-1,3,5-triazine (DAT), deux unités supramoléculaires complémentaires s’associant par liaisons hydrogène. Quelque soit la nature de la chaine polymère (PE, PDMS, PPG), les matériaux présentent des organisations lamellaires nanoscopiques très régulières lorsque l’unité terminale (Thy) et/ou la chaine (PE) cristallisent. Les contributions respectives à ces organisations de la ségrégation de phase, de la cristallisation, des liaisons supramoléculaires et des interactions secondaires ont été déterminées. Il a été montré que le confinement des chaines polymères dans les lamelles empêche la formation de chaines de grandes masses molaires. Cependant, les interactions supramoléculaires Thy/DAT permettent de former des copolymères à blocs supramoléculaires en mélangeant des chaines incompatibles fonctionnalisées par ces unités.Dans une seconde partie, nous avons montré que la texturation spontanée de films acrylates photopolymérisés à l’air est gouvernée à l’interface formulation/air par l’équilibre des cinétiques de polymérisation et d’inhibition par l’oxygène. Des morphologies microscopiques très régulières, hexagonales, lamellaires ou cacahuètes, sont obtenues en contrôlant différents paramètres expérimentaux et ce pour une large gamme d’épaisseur de film (6 µm – 2 mm). L’auto-texturation confère aux films des propriétés optiques singulières (flou, clarté) qui peuvent être modulées en ajustant les caractéristiques de la morphologie
Materials properties very often derive from their nano or micro-scale organization. In this thesis, we evidence that controlling the chemistry at the interfaces allows obtaining spontaneously very regular organizations in various polymer materials.In the first part, supramolecular chemistry has been used to control the organization in the bulk of polymer grafted at one or both extremities by thymine (Thy) or 2,6-diamino-1,3,5-triazine (DAT), two self-complementary supramolecular units interacting via hydrogen bonds. Whatever the polymer nature (PE, PDMS, PPG), materials present very regular nanoscale long-range ordered lamellar organizations if the end group crystallize (Thy) and/or the chain crystallize (PE). Respective contributions to these organizations of phase segregation, crystallization, supramolecular interactions and secondary interactions have been determined. It was shown that the confinement of chains in lamellae prevent the formation of high molecular weight chains, resulting in poor mechanical properties. However, Thy/DAT interactions allow creating supramolecular block copolymers by mixing incompatible chains functionalized with these units.In the second part, we have studied the spontaneous formation of patterns at the film surface of acrylate film during their photopolymerization under air. This phenomenon occurs if there is a balance at the film surface between the polymerization and the oxygen inhibition rates. Very regular microscale patterns (hexagons, lamellae, peanuts) have been generated by controlling some experimental parameters (UV intensity, initiator concentration) for a wide range of film thicknesses (6 µm – 2 mm). Self-patterning gives interesting optical properties to the films (haze, clarity) which can be modulated by adjusting the patterns wavelength and amplitude

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Jerkiewicz, Grzegorz (Gregory). "Electrochemical surface processes at well defined platinum interfaces: Hydrogen underpotential deposition, and quasi-two-dimensional and three-dimensional oxide film formation". Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7875.

Texto completo

Resumen

The main body of research reported in this thesis was concerned with studies of H, and OH or O, chemisorption on polycrystalline and single-crystal Pt surfaces, including studies of the anodic growth of thick oxide films and distinction between the several states in which they are formed. In the work reported in the first part of this thesis, a standard procedure has been worked out for preparing polycrystalline Pt electrodes. Such electrodes reveal and sustain the same physical and electrochemical properties over long periods of time; this is probably the result of the discovery and use of the "electrochemical annealing" phenomenon. Thus, polycrystalline Pt electrodes can be well characterized in a reproducible way after selected controlled thermal and/or electrochemical pretreatments and are found to become reconverted to the same, stable and final state (the "electrochemically annealed" state) after prolonged cycling between 0.05 and 1.40 V, RHE, regardless of their initial pretreatment. At Pt anodes subjected to regimes of anodization at high controlled potentials for various periods of time, it was found that at least five states of the oxide film can be distinguished, in reduction, using the cyclic-voltammetry technique. The extent of growth of the oxide film at Pt proceeds according to a direct logarithmic law in time of growth for polarization potentials between 1.80 and 2.30 V, RHE. Upon further increase of the polarization time, the oxide growth rate increases some 400 times due to the onset of the high-field oxide growth mechanism of Mott and Cabreta. Upon increase of the polarization potential and time, it has been shown that multilayer phase oxide is generated on top of the quasi-2-d oxide. It is found that the quasi-2-d oxide can be reduced independently from the bulk-type oxide, leading to a situation where the thick-oxide film resides on bare Pt. It is also demonstrated that the quasi-2-d oxide resides between Pt and the thick oxide film. The oxide growth rate depends on the crystallographic orientation of the underlying metal surface. Cycling of "quenched" Pt(111) and Pt(100) into the oxide region results in surface restructuring (probably enhanced by the stress from quenching). Such pretreated Pt(111) and Pt(100) surfaces exhibit the same electrochemical behaviours as those of annealed Pt(111) and Pt(100). (Abstract shortened by UMI.)

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Yang, Peter J. "Incorporation of protease-sensitive biomaterial degradation and tensile strain for applications in ligament-bone interface tissue engineering". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42840.

Texto completo

Resumen

The interface between tendon/ligament and bone tissue is a complex transition of biochemical, cellular, and mechanical properties. Investigating computational and tissue engineering models that imitate aspects of this interface may supply critical design parameters for designing future tissue replacements to promote increased biochemical and mechanical integration between tendon/ligament and bone. Strategies for modeling this tissue have typically focused on the development of heterogeneous structures to create gradients or multiphasic materials that mimic aspects of the transition. However, further work is required to elucidate the role of specific mechanical and material stimuli in recapitulating features of the tendon/ligament-bone insertion. In particular, in constructs that exhibit variation in both mechanical and biochemical properties, the interplay of mechanical, material, and chemical signals can complicate understanding of the particular factors at work in interface formation. Thus, the overall goal of this dissertation was to provide insight into the role of mechanical strain and scaffold degradability on cell behavior within heterogeneous biomaterials. Specifically, a method for determining cell vertical position within a degradable gel through a laminated interface was developed. A computational model was created to examine possible variation in local mechanical strain due to heterogeneity in mechanical properties and different interface geometries. Finally, the influence of biomaterial degradability on changes in encapsulated human mesenchymal stem cell morphology under response to cyclic mechanical strain was explored. Together, these studies provide insight into mechanical and material design considerations when devising tissue engineering strategies to regenerate the tendon/ligament-bone interface.

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Ma, Mingming. "Promotion and Inhibition of Molecular Recognition at Interfaces in Aqueous Solution". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291136621.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Albaricci, Maria Carolina da Costa. "Efeitos da solução de alfatocoferol na resistência à fratura, resistência de união e na interface adesiva na dentina de dentes tratados endodonticamente submetidos ao clareamento dental com peróxido de hidrogênio /". Araraquara, 2019. http://hdl.handle.net/11449/181401.

Texto completo

Resumen

Orientador: Andréa Abi Rached Dantas
Resumo: Após o clareamento dental, radicais livres permanecem na estrutura dental interferindo negativamente na adesão, além disso também geram redução da resistência dental à fratura. Sugere-se que substâncias antioxidantes podem ser capazes de reverter tais efeitos. Assim, esse estudo buscou avaliar os efeitos da solução de alfatocoferol em diferentes concentrações sobre a resistência à fratura, formação de camada híbrida e resistência de união adesiva de dentes tratados endodonticamente e clareados. Foram realizados 3 experimentos. Experimento 1: 60 incisivos bovinos receberam tratamento endodôntico e foram distribuídos em 6 grupos (n=10): G1 - coroas apenas restauradas; G2 - coroas clareadas e restauradas; G3 - coroas clareadas e aplicação de solução de ascorbato de sódio 10%; G4 ao G6: coroas clareadas e aplicação das soluções de alfatocoferol nas concentrações de 15%, 20% e 25%, respectivamente. Os espécimes foram submetidos ao teste de resistência à fratura em máquina de ensaios mecânicos (EMIC). Experimento 2: 60 incisivos bovinos foram tratados endodonticamente, distribuídos e tratados, de acordo com o grupo, de forma idêntica ao experimento 1. Os espécimes foram seccionados na junção cemento-esmalte e no sentido vestíbulo-lingual, lixados e polidos, passaram por processo de desproteinização com ácido clorídrico 18% e hipoclorito de sódio 5%. Em seguida, foram moldados com silicona de adição e vasados com resina epóxi. Os modelos obtidos foram analisados em microscópio eletr... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: After dental bleaching, free radicals remain at the dentin, which causes reduces at adhesive and fracture resistance. To minimize these undesirable effects, the use of antioxidants to neutralize free radicals before the final restoration is recommended. This study evaluated the effects of alphatocopherol solution at different concentrations on the fracture resistance, hybrid layer and shear bond strength of endodontically treated teeth subjected to tooth bleaching. Three experiments were done. Experiment 1: 60 bovine incisors were endodontically treated and then divided into 6 groups (n=10): G1 - the teeth immediately restored with composite resin; G2 - the teeth were bleached and immediately restored; G3 - the teeth received treatment similar to that used for G2, but with 10% sodium ascorbate gel applied after the bleaching protocol; G4 to G6: the teeth received treatment similar to that used for G3, rather than sodium ascorbate, it was applied alphatocopherol at concentrations of 15%, 20% and 25%, respectively. Teeth were subjected to a fracture resistance test in an electromechanical testing machine (EMIC). Experiment 2: 60 bovine incisors were endodontically treated, distributed and treated identically to experiment 1. The specimens were sectioned at the cementum-enamel junction and in the vestibular-lingual direction, sanded and polished, and then it was made the deproteinization with 18% hydrochloric acid and 5% sodium hypochlorite. Then, they were molded with addition
Mestre

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Jin, Yining. "Water dynamics at the MHCI-peptide binding interface studied by Hydrogen-deuterium exchange and structural studies of Apo A-I mimetic peptide-lipid binding". University of Toledo Health Science Campus / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=mco1404706445.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Abe, Andréa Tami. "Efeito dos agentes clareadores sobre o esmalte dental, a resina composta e a interface dente/restauração". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/23/23134/tde-11072014-151523/.

Texto completo

Resumen

Este estudo in vitro teve como objetivo avaliar a dureza do esmalte dental, da resina composta, do adesivo e da camada híbrida em esmalte expostos a agentes clareadores à base de peróxido de hidrogênio a 35%, e analisar a interface dente/restauração com microscopia eletrônica de varredura (MEV). Foram utilizadas 40 coroas dentais de incisivos bovinos, que foram incluídas em resina epóxi. Uma cavidade de 2x2x2mm foi confeccionada no terço médio da face vestibular planificada de cada dente. As cavidades foram restauradas com o adesivo Adper Single Bond 2 e a resina nanoparticulada Filtek Z350 XT, e o polimento foi realizado após uma semana da confecção das restaurações. Os corpos de prova foram divididos em quatro grupos (n=10), correspondente a cada agente clareador à base de peróxido de hidrogênio a 35% utilizado (TB: Total Blanc Office; HPB: Whiteness HP Blue; HP: Whiteness HP; PO: Pola Office). A aplicação dos clareadores foi realizada 24 horas após o polimento, de acordo com as recomendações dos respectivos fabricantes. O valor do pH dos agentes clareadores foi medido no início e no final do procedimento clareador. A dureza dos substratos foi mensurada antes (inicial), imediatamente após o clareamento e após 7 dias de armazenamento em saliva artificial com o equipamento ultramicrodurômetro DUH-211S (Shimadzu). As cargas utilizadas foram de 100mN para o esmalte dental e para a resina composta, e de 10mN para o adesivo e para a camada híbrida em esmalte. Para a análise com MEV, foi confeccionado mais um corpo de prova para cada agente clareador, que foi replicado em resina epóxi a cada tempo de análise. Os testes estatísticos empregados foram a ANOVA de 2 fatores sendo 1 com vinculação (p<0,05) e o teste de Tukey. Quanto à dureza do esmalte e da camada híbrida, os corpos de prova expostos aos agentes TB, HPB e HP não apresentaram alteração da dureza nos três tempos de mensuração. O agente PO foi o clareador que apresentou o valor de pH mais baixo e o único que promoveu uma diminuição da dureza desses substratos imediatamente após sua aplicação, porém após 7 dias de armazenamento em saliva artificial a dureza retornou ao valor inicial. Nenhuma alteração foi observada quanto à dureza da resina composta e do adesivo expostos aos agentes clareadores utilizados. A análise em MEV revelou fendas entre o esmalte dental e o adesivo imediatamente após exposição à maioria dos clareadores. Pode-se concluir que o agente PO foi o único que diminuiu a dureza dos substratos dentais e o que promoveu a maior fenda na interface dente/restauração logo após sua aplicação. Nenhum clareador promoveu alteração da dureza da resina composta e do adesivo.
The aim of this in vitro study was to evaluate the hardness of the dental enamel, the composite resin, the dental adhesive and the enamel hybrid layer exposed to 35% hydrogen peroxide bleaching agents, and to analyze the tooth/restoration interface with scanning electron microscopy (SEM). Forty bovine incisor crowns were embedded in epoxy resin and then the labial surface of the teeth was flatted. One 2x2x2mm cavity was prepared on the middle third of each tooth labial surface. The cavities were restored with the adhesive Adper Single Bond 2 and the nanocomposite resin Filtek Z350 XT. After one week of storage, the restorations were polished. The specimens were divided into four groups (n=10), in correspondence to each 35% hydrogen peroxide bleaching agents used (TB: Total Blanc Office; HPB: Whiteness HP Blue; HP: Whiteness HP; PO: Pola Office). The bleaching procedure was performed 24 hours after polish, according to each manufacturer`s recommendation. The pH value of the bleaching agents was measured before and at the end of the bleaching procedure. Hardness test was performed before, immediately after bleaching and after storage in artificial saliva for 7 days, with the ultramicrohardness tester DUH-211S (Shimadzu). Indentations were performed using 100mN load for dental enamel and composite resin, and 10mN load for adhesive layer and enamel hybrid layer. For SEM analysis, one more specimen was made for each bleaching agent, which was replicated in epoxy resin at each measurement time. The statistical tests used were 2-way ANOVA and Tukey test (p<0,05). Regarding to dental enamel and enamel hybrid layer hardness, the specimens exposed to TB, HPB and HP agents did not present hardness alterations at any measurement time. The PO agent presented the lowest pH value and was the only that promoted hardness decrease on these dental surfaces immediately after application, however, after storage in artificial saliva for 7 days the hardness returned to initial value. No alteration was observed regarding to hardness of composite resin and adhesive exposed to bleaching agents. The SEM analysis revealed gaps between the dental enamel and the adhesive immediately after exposure to majority bleaching agents. In conclusion, the PO agent was the only that promoted hardness decrease on dental surfaces, and the major gap formation in tooth/restoration interface after application. No bleaching agents caused any alteration on composite resin and adhesive hardness.

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Dziubla, Thomas D. Lowman Anthony M. "Macroporous hydrogels as vascularizable soft tissue-implant interfaces : materials characterization, in vitro evaluation, computer simulations, and applications in implantable drug delivery devices /". Philadelphia : Drexel University, 2002. http://dspace.library.drexel.edu/handle/1721.1/36.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Törnblom, Pontus. "Ethyl 2,2-difluoroacetate as Possible Additive for Hydrogen-Evolution-Suppressing SEI in Aqueous Lithium-Ion Batteries". Thesis, Uppsala universitet, Strukturkemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448596.

Texto completo

Resumen

The performance and lifetime of lithium-ion batteries are strongly influenced by their composition. One category of critical components are electrolyte additives, which are included primarily to stabilize electrode/electrolyte interfaces in the battery cells by forming passivation layers. The presented study aimed to identify and study such an additive that could form a hydrogen-evolution-suppressing solid electrolyte interphase (SEI) in lithium-ion batteries based on aqueous electrolytes. A promising molecular additive, ethyl 2,2-difluoroacetate (EDFA), was found to hold the qualities required for an SEI former and was herein further analyzed electrochemically. Analysis of the battery cells were performed with linear sweep voltammetry and cyclic voltammetry with varying scan rate and EDFA concentrations. Results show that both 1 and 10 w-% EDFA in the electrolyte produced hydrogen-evolution-suppressing SEI:s, although the higher concentration provided no apparent benefit. Lithium-ion full-cells based on LiMn2O4 vs. Li4Ti5O12 active materials displayed poor, though partly reversible, dis-/charge cycling despite the operation of the electrode far outside the electrochemical stability window of the electrolyte. Inclusion of reference electrodes in the lithium-ion cells proved to be immensely challenging with unpredictable drifts in their electrode potentials during operation. To summarize, HER-suppressing electrolyte additives are demonstrated to be a promising approach to stabilize high-voltage operation of aqueous lithium-ion cells although further studies are necessary before any practical application thereof can be realized. Electrochemical evaluation of the reaction mechanism and efficiency of the electrolyte additives relies however heavily on the use of reference electrodes and further development thereof is necessary.

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

TEIXEIRA, LUIZ F. L. "Determinação dos radionuclídeos naturais urânio e tório nos sedimentos superficiais do sistema Cananéia - Iguape". reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28049.

Texto completo

Resumen

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-23T11:02:37Z No. of bitstreams: 0
Made available in DSpace on 2017-11-23T11:02:37Z (GMT). No. of bitstreams: 0
O sistema Cananéia-Iguape é um grande complexo de canais lagunares e estuarinos, localizado no sul do estado de São Paulo. Este sistema passou a receber as águas do rio Ribeira de Iguape após a abertura do canal do Valo Grande, finalizado no ano de 1852. Este canal tornou-se a principal rota de transporte das produções da região do Vale do Ribeira, e nas décadas de 1940 a 1990 as atividades de mineração da região contaminaram o rio Riberia de Iguape, causando alterações nas características originais do sistema Cananéia-Iguape. Este estudo avaliou os níveis de urânio e tório nas amostras de sedimentos superficiais deste sistema. Esta avaliação foi feita através de um método espectrofotométrico utilizando Arsenazo III. As amostras foram digeridas em um forno micro-ondas com aplicação de HNO3, HF e H2O2. As concentrações de urânio variam de 1,3 mg·kg-1 a 5,8 mg·kg-1 e as de tório de 0,82 mg·kg-1 a 12,1 mg·kg-1. Estes resultados foram comparados com os dados da região, e observou-se que as concentrações determinadas são similares. O índice de geoacumulação foi calculado, classificando a região como \"Não contaminada a moderadamente contaminada\" para urânio e \"Não contaminada\" para tório, indicando que não há contaminação por estes metais. Estes resultados podem ser considerados como a concentração basal da região. As avaliações estatísticas identificaram uma maior afinidade do urânio e do tório com a fração de argila e silte. As concentrações de U e Th não apresentaram um comportamento homogêneo ao longo do sistema estudado.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

ANTOINE, ANNE-MARIE. "Mecanismes de croissance et de constitution d'interfaces dans les couches minces de semiconducteurs amorphes hydrogenes etudies par ellipsometrie spectroscopique in situ". Paris 7, 1987. http://www.theses.fr/1987PA077179.

Texto completo

Resumen

Etude de la croissance de couches minces de silicium, germanium et d'alliages silicium-germanium amorphes hydrogenes deposees par decomposition radiofrequence de silane, germane et d'hydrogene. Etude des mecanismes d'initiation de la couche en fonction des conditions de preparation. Analyse de l'influence de la nature du support sur le depot des premieres couches monomoleculaires

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Costard, Rene. "Ultrafast dynamics of phospholipid-water interfaces studied by nonlinear time-resolved vibrational spectroscopy". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16955.

Texto completo

Resumen

Geladene Phosphatgruppen sind von wesentlicher Bedeutung für die Hydratisierung von Phospholipiden und DNS. Hydratisierungshüllen spielen eine wichtige Rolle für die Ausbildung und Stabilisierung von Zellmembranen und der DNS-Doppelhelixstruktur. In dieser Arbeit werden elementare Phosphat-Wasser-Wechselwirkungen in einem Phospholidmodellsystem – sogenannten inversen Mizellen - mit variablen Wassergehalt zwischen einem und 16 Wassermolekülen pro Phospholipid untersucht. Die schnellsten Prozesse an den Grenzflächen wie z.B. Phosphat-Wasser-Wasserstoffbrückendynamik und Schwingungsenergieumverteilung finden auf einer Femto- bis Pikosekundenzeitskala statt. Molekulare Schwingungen sind sensitive lokale Sonden für die Struktur und Dynamik. Deshalb ermöglicht Femtosekunden-Schwingungsspektroskope, insbesondere zweidimensionale Infrarotspektroskopie (2D IR) und Pump-Probe-Spektroskopie in einem breiten Spektralbereich, die Dynamik mikroskopischer Phosphat-Wasser-Wechselwirkungen in Echtzeit zu beobachten. Wir zeigen die ersten zweidimensionalen Infrarotspektren von Phosphat-Streckschwingungen, die unabhängig vom Wassergehalt grenzflächensensitive Sonden darstellen. Solche Spektren belegen, dass die schnellsten strukturellen Fluktuationen der Phospholipid-Kopfgruppen auf einer 300-fs Zeitskala ablaufen, wohingegen die Phosphat-Wasser-Wasserstoffbrücken länger als 10 ps bestehen bleiben. Die Schwingungsdynamik intramolekularer Wasserschwingungen, d.h. der OH-Streck- und Biegeschwingung, zeigen, dass sich kleine Wasserpools um die Phosphatgruppen bilden, sobald drei oder mehr Wassermoleküle pro Phospholipid vorliegen. Solche Wasserpools dienen als effiziente Wärmesenken für intramolekulare Schwingungen des Wassers und der Phosphatgruppen.
Charged phosphate groups are the major hydration sites of biomolecules such as phospholipids and DNA. Hydration shells play a key role in the formation and stabilization of cell membranes and the DNA double helix structure. Here, we introduce phospholipid reverse micelles with variable water content (between one and sixteen water molecules per phospholipid) as a model system to study elementary phosphate-water interactions. The fastest processes at phosphate-water interfaces , e.g. hydrogen-bond dynamics and vibrational energy transfer occur on a femto- to picosecond time scale. Since molecular vibrations are sensitive local probes of the structure and dynamics, the use of femtosecond vibrational spectroscopy, in particular two-dimensional infrared spectroscopy (2D IR) and pump-probe spectroscopy in a broad spectral range, allow for the observation of microscopic phosphate-water interactions in real time. We present the first two-dimensional infrared spectra of phosphate stretching vibrations that represent true interfacial probes independent of the hydration level. Such spectra reveal that the fastest structural fluctuations of phospholipid headgroups occur on a 300-fs timescale whereas phosphate-water hydrogen bonds are preserved for >10 ps. Vibrational dynamics of intramolecular water vibrations, i.e., the OH stretching and bending modes show that small water pools around the phosphate groups form when three or more water molecules per phospholipid are present. Such water pools act as efficient heat sinks of excess energy deposited in intramolecular vibrations of water or the phosphate groups.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Dickheuer, Sven Oliver [Verfasser], Oleksandr [Gutachter] Marchuk y Uwe [Gutachter] Czarnetzki. "The Balmer lines emission of fast hydrogen atoms at the plasma-solid interface in a low density plasma / Sven Oliver Dickheuer ; Gutachter: Oleksandr Marchuk, Uwe Czarnetzki ; Fakultät für Physik und Astronomie". Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1204258244/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "Interface hydrogel"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros