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Van, Delinder Kurt William. "The investigation of the molecular mechanism of rhodopsin activation by small angle neutron scattering and small angle x-ray scattering techniques." Thesis, Wayne State University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1604674.
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Rhodopsin is a visual pigment found within the rod photoreceptor cells of the retina. It is a visual protein found within human beings and commonly shared amongst other vertebrate species. The major pigment protein is responsible for converting photons into chemical signals, which stimulates biological processes in the nervous system, and this allows the ability to then sense light.
The process of how rhodopsin is activated is believed to be understood with the introduction of a time ordered sequence of intermediate states. However, there are still major gaps and inconsistencies regarding the large-scale conformational changes that follow photoactivation.
The purpose of our experimental research is to use small angle neutron and x-ray scattering techniques to illuminate the structural changes and dynamics of rhodopsin that lead to the activation of the photoreceptor, and thus triggering of the amplified visual response.
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Rai, Durgesh K. "Quantification of Fractal Systems using Small Angle Scattering." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377870724.
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Ku, Chwen-Yuan. "Small-angle X-ray and neutron scattering studies of 3-component microemulsion and micellar solution of semifluorinated copolymers." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38846.
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Kulkarni, Amit S. "Nature of Branching in Disordered Materials." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1190655419.
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Ivanov, Ivan Yavorov. "Etude biophysique et structurale du complexe de réplication des virus à ARN négatif." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENV083/document.
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Les rhabdovirus, dont les virus de la stomatite vésiculaire (VSV) et de la rage (RAV) constituent des prototypes, sont des virus enveloppés dont le génome est constitué d'une seule molécule d'ARN simple brin de polarité négative qui font partie de l'ordre des Mononegavirales (MNV). La machinerie de transcription/réplication de ces virus est constituée de l'ARN génomique et de trois protéines qui sont communes à tous les virus de l'ordre des MNV, la (N) qui encapside le génome viral, la grande sous-unité de l'ARN polymérase ARN dépendante (L) et la phosphoprotéine (P) qui est un cofacteur non-catalytique de la L et sert de chaperonne à la N. Le premier objectif de mon travail de thèse consistait à déterminer la structure cristallographique du domaine de dimérisation de la phosphoprotéine du virus de la rage. La P des rhabdovirus est une protéine modulaire qui contient deux régions intrinsèquement désordonnée, un domaine central responsable la dimérisation et un domaine C-terminal responsable de la fixation sur la matrice N-ARN. Le modèle atomique obtenu à une résolution de 1.5A montre que la structure est très différente de celle du domaine correspondant chez VSV. Le second objectif de mon travail était la caractérisation structurale de la grande sous-unité L de la polymérase du virus de la stomatite vésiculaire. Cette enzyme de 2109,aa, possède six régions conservées. Le domaine conservé III comprend les régions impliquées dans l'activité de polymérisation et les domaines V et VI sont responsables de la formation de la coiffe des ARNm. Plusieurs stratégies ont été envisagées successivement. (1) Sur la base de prédictions de structures secondaires et de prédictions de désordre, nous avons essayé d'exprimer différents fragments en système d'expression bactérien. Les constructions testées se sont avérées insolubles et certaines d'entre elles fixaient GroEL, indiquant un problème de repliement. (2) Nous avons alors essayé d'exprimer la L seule ou en complexe avec la P en système d'expression eucaryote. La purification s'est avérée impossible, la protéine L restant toujours associées à des protéines cellulaires visibles par coloration au bleu de Coommassie. (3) Finalement nous avons réussi à purifier la polymérase à partir de virus entier. La préparation de la polymérase était très homogène et a permis d'entreprendre une caractérisation par microscopie électronique. Une classification d'images a permis de construire un premier modèle à basse résolution. Le modèle révèle la présence d'un domaine annulaire avec plusieurs domaines structurés attachés au coeur de la polymérase. La cryo-microscopie électronique et la tomographie permettront d'obtenir plus de détails sur cette protéineRhabdoviruses, including vesicular stomatitis virus (VSV) and rabies virus (RAV), are enveloped viruses which genome is made of a single molecule of negative-sense RNA and are classified in the order Mononegavirales (MNV). The transcription/replication machinery of these viruses consists of the genomic RNA and of three proteins, which are common to all other viruses of the order MNV, a nucleoprotein (N) that encapsidates the viral genome, a large subunit of the RNA-dependent RNA polymerase (L) and a phosphoprotein (P) that acts as a non-catalytic cofactor of L and a chaperone of N. The first goal of my research project was to determine the crystallographic structure of the dimerization domain of the rabies virus phosphoprotein. The P protein of the rhabdoviruses is a modular protein, which contains two intrinsically disordered regions, a central dimerization domain and a C-terminal domain involved in binding to the N-RNA template. The atomic model obtained at a resolution of 1.5 A showed that the structure is different from that of the corresponding domain of VSV. The second goal was the structural characterization of the large subunit L of VSV polymerase. The enzyme of 2109 aa has six conserved regions. Conserved region III includes the residues involved in the RNA synthesis activity, whereas domains V and VI are involved in mRNA capping formation. Three strategies were successively developed: (1) On the basis of secondary structure and disorder predictions, we tried to express different fragments in bacterial expression systems. These constructions appeared to be insoluble and some of them bound GroEL suggesting a folding problem; (2) We tried to express L alone or co-express it with P in eukaryotic expression system. The purification appeared to be impossible, the L protein always remaining associated with host-cell proteins in amounts detectable by Coommassie staining; (3) We succeeded in purifying the L protein from the virus. The L samples were homogenous and allowed a characterization by electron microscopy. Image classes allowed the reconstruction of a first low-resolution model. This model revealed the presence of a large ring-like domain and several globular domains. Cryo-electron microscopy and tomography should lead to a more detailed description of this protein
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Kinder, S. H. "Small angle neutron scattering and #gamma#-ray scattering for the study of second phase precipitation in semiconductor silicon and the Nimonic superalloy PE16." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378199.
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Liu, Yun 1973. "Studies of structure and dynamics of biological macro-molecular assemblies by low angle neutron diffraction and inelastic X-ray scattering." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34438.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.Includes bibliographical references (leaves 141-148).
This thesis is organized into two parts which focus on the studies of the dynamic structure factor and static inter-particle structure factor respectively. In the first part, we have measured and analyzed the dynamic structure factors of aligned 40 wt% calfthymus Na-DNA molecules with the inelastic X-ray scattering (IXS). In the second part, we have developed a new efficient method to calculate the inter-particle structure factor in a simple fluid interacting with a two-Yukawa term potential and apply it to study the kinetic phase diagram and analyze the small angle neutron scattering (SANS) intensity distribution of colloidal systems. By analyzing the dynamic structure factor measured with IXS, the phonon dispersion relations of 40 wt% calf-thymus Na-DNA with different counterion atmosphere are constructed. It is found that the addition of extra counterions will increase phonon damping at small scattering wave vector, Q. At the intermediate Q range (12.5 nm- < Q < 22.5 nm-l), it may even overdamp the phonon so that the phonon feature can not be extracted from the IXS spectra. The measured sound speed is 3100m/s, which is much higher than the sound speed, - 1800m/s, obtained by Brillouin light scattering. This difference shows that the atoms of DNA molecules are closely coupled to the surrounding water molecules.
(cont.) Therefore, the different dynamic response of water molecules in different Q range affects the overall dynamic response of the hydrated DNA molecules. By analyzing the IXS spectra, the intermediate scattering function is extracted and shows a clear two step relaxation with the fast relaxation time ranging from 0.1 to 4 ps and the slow relaxation time ranging from 2 to 800 ps. In order to understand the phase behavior and the interactive potential of a colloidal system, we have developed a new and efficient method to calculate the inter-particle structure factor of a simple fluid interacting with a two-Yukawa term potential. We have applied this method to study the kinetic phase diagram of a system interacting with a short-range attraction and a long-range repulsion. A new glass phase, cluster glass, is determined through the theoretical analysis by the mode coupling theory (MCT). The SANS intensity distribution of cytochrome C protein molecules in solutions is measured and analyzed with our method. A sharp rising intensity at very low Q value has been consistently observed, which is named zero-Q peak. The existence of the zero-Q peak implies that a weak long-range attraction between protein molecules in solutions exists and has a even longer range than the electrostatic repulsion.
by Yun Liu.
Ph.D.
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Ouali, Chakib. "Caractérisation multi-échelle de l’écoulement de mousses en milieux poreux en contexte EOR." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS001/document.
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L’utilisation de la mousse en récupération assistée du pétrole (Enhanced Oil Recovery, EOR) présente un avantage indéniable par rapport à l’injection du gaz seul pour pallier les problèmes de ségrégation gravitaire et de digitations visqueuses. Son utilisation systématique en ingénierie du réservoir nécessite des connaissances plus approfondies sur son comportement en milieu poreux. La littérature montre deux types d’approches expérimentales basées soit sur des études pétrophysiques effectuées sur des systèmes poreux 3D et basées sur des mesures de pressions intégrées sur l’ensemble du milieu poreux, soit sur des études micro-fluidiques qui permettent une visualisation directe de l’écoulement mais qui sont limitées à des systèmes modèles dans des géométries à 1 ou 2 dimensions. L’objectif de cette thèse est de faire le pont entre ces deux approches. La stratégie proposée consiste à caractériser in situ l’écoulement de la mousse dans des milieux poreux 3D à différentes échelles, en utilisant des techniques complémentaires permettant d’accéder à une large gamme de résolutions spatiale et temporelle. Un environnement instrumenté donnant accès aux mesures pétro-physiques classiques a été développé puis couplé à différentes cellules d’observation conçues spécifiquement pour chaque instrument de caractérisation. Dans un premier temps, un scanner X a été utilisé pour décrire et visualiser les écoulements de la mousse à l’échelle de la carotte. La rhéologie de la mousse à cette échelle a pu être étudiée en fonction des conditions d’injections comme la vitesse interstitielle du gaz et la qualité de mousse. Dans un deuxième temps, la technique de diffusion des neutrons aux petits angles (SANS) a permis de sonder la texture de la mousse en écoulement sur trois ordres de grandeurs en taille. Des informations in situ sur la texture de la mousse en écoulement (taille et densité des bulles et des lamelles) ont pu être mesurées pour différentes qualités de mousse puis en fonction de la distance au point d’injection. Une comparaison avec les caractéristiques géométriques du milieu poreux a également été effectuée. Dans un troisième temps, la micro-tomographie X rapide haute résolution sur Synchrotron a été utilisée pour visualiser la mousse en écoulement à l’échelle du pore. Cette technique a permis de confirmer de visu certaines caractéristiques de la mousse mesurées par SANS et de décrire en sus les effets d’intermittence du piégeage de la mousse. Cette étude constitue une étape importante de la caractérisation multi-échelle de l’écoulement des mousses en milieux poreux 3D et apporte des éléments de réponse à certaines hypothèses admisesFoam has long been used as a mobility control agent in Enhanced Oil Recovery (EOR) processes to enhance sweep efficiency and overcome gravity segregation, viscous fingering and gas channeling, which are gas-related problems when the latter is injected alone in the reservoir. However, the systematic use of foam in reservoir engineering requires more in-depth knowledge of its dynamics in porous media. The literature shows two types of experimental approaches based either on petrophysical studies carried out on 3D porous systems and based on pressure measurements, or on microfluidic studies that allow direct visualization of foam flow but are limited to 1D or 2D model systems. The research investigated in this thesis aims to bridge the gap between these two approaches. The proposed strategy is to characterize in situ the foam flow in 3D porous media with techniques providing a wide range of temporal and spatial resolutions. A coreflood setup giving access to classical petro-physical measurements was developed and then coupled to different observation cells designed specifically for each characterization instrument. First, an X-ray CT scanner was used to describe and visualize the foam flow at the core scale. The rheological behavior of foam on this scale was studied as a function of the injection conditions such as gas velocity and foam quality. Secondly, Small Angle Neutron Scattering (SANS) was used to probe the foam structure in situ during the flow, on a wide length scale, up to three orders of magnitude in size. In situ foam texture (size and density of bubbles and lamellae) was measured for different foam qualities and at different propagation distances from the injection point. A comparison to the geometric characteristics of the porous medium was also realized. Thirdly, High Resolution Fast X-ray Micro-tomography on a Synchrotron was used to visualize the foam flow at the pore scale. This allowed to confirm visually some foam characteristics measured with SANS and to investigate on local intermittent gas trapping and mobilization. This study is an important step in the multi-scale characterization of foam flow in 3D porous media and provides some answers to certain generally accepted assumptions
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Konko, Iuliia. "Aqueous solutions of complexes formed by model polyelectrolytes of opposite charges." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE049/document.
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Cette thèse présente une étude des solutions aqueuses de trois complexes de polyélectrolytes (PECs) modèles. Les PECs résultent de la complexation de deux polyélectrolytes linéaires de charge opposée: un polycation (le PDADMA) et trois polyanions de longueur de persistance non électrostatique distinctes: le polystyrene sulfoné (PSS), le poly(α-méthyl styrène sulfoné) (PαMSS) et l’acide hyaluronique (HA). En plus de l’influence de la rigidité intrinsèque des polyanions sur la formation et la structure des PECs, les effets de la force ionique et de la méthode de préparation des solutions aqueuses de PECs ainsi que l’influence de la concentration des solutions binaires de polyélectrolytes initiales ont également été abordés. Nous suggérons que le processus de complexation entre polycations et polyanions en régimes semidilué et concentré est analogue à une gélification. Il y a toutefois une différence entre les deux complexes qui est reliée à la différence de rigidité intrinsèqueThis PhD thesis presents a study of the aqueous solutions of three model polyelectrolyte complexes (PECs). PECs were formed between hydrophilic and highly charged linear macrocations of poly(diallyldimethyl ammonium) (PDADMA) and linear macroanions of distinct intrinsic persistence lengths: sulfonated polystyrene (PSS), sulfonated poly(α-methyl styrene) (PαMSS) and hyaluronate (HA). In addition to the effect of the macroion stiffness on the PEC formation and structure, those of the ionic strength and the way of preparing the PEC aqueous solutions as well as that of the concentration regimes of the initial PE aqueous solutions were also tackled. We suggest the complexation between macrocations and macroanions in the semidilute and concentrated regimes can be described as a universal gelation process. A difference between PDADMA-PSS and PDADMA-HA complexes is related to the primary self-assembling process and is associated with the distinct structural models for PECs
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Jalal, Noureddine. "Etude des agregats formes par neutralisation des chaines monocarboxylees par : diffusion aux petits angles des neutrons et des rayons x." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13137.
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Etude de polymeres possedant un seule fonction acide terminale neutralisee par des cations metalliques. Influence du cation, de la masse du precurseur et de la concentration sur l'association de chaines et de l'existence d'une concentration d'agregation critique
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Pouxviel, Jean-Claude. "Mecanisme de croissance et polymerisation sol-gel." Paris 6, 1987. http://www.theses.fr/1987PA066587.
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Etude de la polymerisation sol gel d'alcoolate((obu)::(2) al-o-si(oet)::(3)). L'analyse des spectres de rmn du silicium, relayee par des simulations numeriques mettent en evidence les effets de concentration des reactifs(eau, precurseur, alcool, acide) sur les cinetiques d'hydrolyse-condensation du tetraethoxysilane
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Pasquier, Coralie. "Interactions et structures dans les solutions hautement concentrées de protéines globulaires : étude du lysosyme et de l'ovalbumine." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S172/document.
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Les phases concentrées de protéines sont au centre de nombreuses études visant à identifier et caractériser les interactions et transitions de phases mises en jeu, en utilisant le large corpus de connaissances acquis sur les phases concentrées de colloïdes. Ces phases concentrées de protéines possèdent en outre une grande importance dans des domaines aussi variés que l’industrie agroalimentaire, l’industrie pharmaceutique et la médecine. L’établissement d’équations d’état présentant la pression osmotique (Π) en fonction de la fraction volumique (Φ) est une méthode efficace de caractérisation des interactions entre les composants d’un système. Nous l’avons appliquée à des solutions de deux protéines globulaires, le lysozyme et l’ovalbumine, en balayant une gamme de fractions volumiques allant d’une phase diluée (Φ < 0,01) à une phase concentrée, solide (Φ > 0,62). Les équations d’état obtenues, couplées à d’autres techniques (SAXS, simulations numériques), ont permis de mettre en évidence un comportement très différent des deux protéines lors de la concentration et ont montré leur complexité en comparaison avec des colloïdes modèles. La mise en relation des équations d’état et du comportement interfacial de ces deux protéines a montré des points de convergence et permis de formuler une nouvelle hypothèse expliquant certaines observations portant sur l’adsorption des protéines à l’interface air-eauConcentrated phases of proteins are the subject of numerous studies aiming at identifying and characterizing the interactions and phase transitions at play, using the large corpus of knowledge in the field of concentrated colloids. Those concentrated phases of proteins have, in addition, a great importance in various fields, such as food industry, pharmaceutical industry and medicine. The establishment of equations of state relating osmotic pressure (Ð) and volume fraction (Φ) is an efficient way of characterization of the interactions between the components of a system. We applied this method to solutions of two globular proteins, lysozyme and ovalbumin, spanning volume fractions ranging from a dilute phase ( Φ < 0,01) to a concentrated, solid phase ( Φ > 0,62). The equations of state, coupled to other methods (SAXS, numerical simulations), enabled us to show that the two proteins carry a very different behavior when submitted to concentration and that their complexity is beyond that of colloids. Relating equations of state and interfacial behavior of these two proteins also showed points of convergence and enabled us to formulate a new hypothesis which explains some of the results obtained in the study of adsorption of proteins at the air-water interface
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Feldkamp, Jan Moritz. "Scanning Small-Angle X-Ray Scattering Tomography." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-24925.
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The techniques of small-angle x-ray scattering (SAXS) and grazing-incidence small-angle x-ray scattering (GISAXS) have successfully been used for many years in the analysis of nanostructures in non-crystalline samples, e.g., polymers, metallic alloys, ceramics, and glasses. In many specimens, however, the nanostructure is not distributed homogeneously, but instead varies as a function of position in the sample. Conventional SAXS or GISAXS measurements on such heterogeneous samples merely yield an averaged scattering pattern of all the different structures present along the x-ray beam path. In this thesis, scanning tomography is combined with SAXS and GISAXS, revealing the individual local scattering cross section at each position on a virtual section through the sample. The technique thereby offers unique analytical possibilities in heterogeneous specimens. A brief review of the physics of x rays and x-ray scattering is given, before the methods of tomographic SAXS and GISAXS are introduced. Experimental requirements and limitations of both methods are discussed, including aspects of sampling, local rotational invariance and x-ray beam coherence. Experiments performed at the beamline BW4 at HASYLAB at DESY, Hamburg, Germany are described, illustrating the capabilities of the method. Finally, an outlook on possible future developments in tomographic small-angle x-ray scattering is givenDie Methoden der Röntgenkleinwinkelstreuung (SAXS) und Röntgenkleinwinkelstreuung unter streifendem Einfall (GISAXS) werden seit vielen Jahren erfolgreich eingesetzt zur Analyse von Nanostrukturen in nicht-kristallinen Proben, z.B. Polymeren, metallischen Legierungen, Keramiken und Gläsern. In vielen Proben ist die Nanostruktur allerdings nicht homogen verteilt, sondern variiert als Funktion des Ortes in der Probe. Konventionelle SAXS- oder GISAXS-Messungen an solch heterogenen Proben liefern lediglich ein über alle unterschiedlichen Strukturen entlang des Röntgenstrahls gemitteltes Streubild. In dieser Arbeit wird Rastertomographie mit SAXS und GISAXS kombiniert und so der lokale Streuquerschnitt an jedem Ort auf einem virtuellen Schnitt durch die Probe gewonnen. Diese Technik bietet so einzigartige Analysemöglichkeiten von heterogenen Proben. Es wird zunächst ein kurzer Überblick über die Physik der Röntgenstrahlung und Röntgenstreuung gegeben, bevor die Methoden der SAXS- und GISAXS-Tomographie eingeführt werden. Die experimentellen Anforderungen und Grenzen beider Methoden werden besprochen, wobei Aspekte der Abtastung, der lokalen Rotationsinvarianz und der Kohärenz im Röntgenstrahl eine Rolle spielen. Experimente, die an der Messstrecke BW4 am HASYLAB bei DESY, Hamburg, durchgeführt wurden, werden beschrieben, um die Möglichkeiten der Methode zu illustrieren. Schließlich wird ein Ausblick auf mögliche zukünftige Entwicklungen der Kleinwinkelstreutomographie gegeben
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Perché, Thierry. "Etude des phases lyotropes et de la micellisation dans des systèmes binaires tensioactif/solvant polaire non aqueux." Rouen, 1994. http://www.theses.fr/1994ROUES018.
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Cette thèse présente une étude de la formation des phases lyotropes et des micelles dans des systèmes binaires de tensioactifs ioniques en solvants polaires non aqueux. Phases lyotropes: après une étude bibliographique des phases lyotropes et de la théorie de la frustration géométrique, les systèmes binaires étudiés sont présentés et la méthode originale d'étude des phases lyotropes ordonnées par diffraction des rayons X aux petits angles est décrite. L'existence de phases lyotropes est clairement mise en évidence en milieu polaire non aqueux même si l'effet solvophobe est beaucoup plus faible que dans l'eau et le solvant aprotique. La structure des phases cristal-liquide et leur séquence en fonction de la concentration sont celles prévues par la théorie géométrique, même lorsque dans l'eau le polymorphisme des phases ordonnées est plus complexe. La densité d'énergie de cohésion du solvant joue un rôle important sur le domaine d'existence des phases et sur la valeur de leurs paramètres toujours plus petits que dans l'eau. L'influence du détail chimique, longueur de la chaine aliphatique, tête polaire et contre-ion, est discutée. Micellisation : après une étude bibliographique concernant le modèle micellaire, l'approche thermodynamique d'auto-association de molécules de tensioactif et la détermination de la structure micellaire par diffusion centrale des neutrons, les systèmes étudiés et la méthode employée sont présentés. La micellisation est abordée uniquement dans le formamide avec divers surfactants. Les résultats de la micellisation sont présentés et analysés pour montrer l'influence de la longueur de la chaîne, de la tête polaire et du contre-ion. Les micelles sont toujours trouvées plus petites que dans l'eau et plus chargées. Un fort étalement en taille des micelles est mis en évidence par modélisation des courbes expérimentales et est confirmé par l'approche thermodynamique. La faible valeur de l'énergie interfaciale cur/solvant et les densités surfaciques de charges en sont responsables
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Paglia, Gianluca. "Determination of the structure of y-alumina using empirical and first principle calculations combined with supporting experiments." Thesis, Curtin University, 2004. http://hdl.handle.net/20.500.11937/2341.
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Aluminas have had some form of chemical and industrial use throughout history. For little over a century corundum (α-Al2O3) has been the most widely used and known of the aluminas. The emerging metastable aluminas, including the γ, δ, η, θ, κ, β, and χ polymorphs, have been growing in importance. In particular, γ-Al2O3 has received wide attention, with established use as a catalyst and catalyst support, and growing application in wear abrasives, structural composites, and as part of burner systems in miniature power supplies. It is also growing in importance as part of the feedstock for aluminium production in order to affect both the adsorption of hydrogen fluoride and the feedstock solubility in the electrolytic solution. However, much ambiguity surrounds the precise structure of γ-Al2O3. Without proper knowledge of the structure, understanding the properties, dynamics and applications will always be less than optimal. The aim of this research was to contribute towards settling this ambiguity. This work was achieved through extensive computer simulations of the structure, based on interatomic potentials with refinements of promising structures using density functional theory (DFT), and a wide range of supporting experiments. In addition to providing a more realistic representation of the structure, this research has also served to advance knowledge of the evolution of the structure with changing temperature and make new insights regarding the location of hydrogen in γ-Al2O3.Both the molecular modelling and Rietveld refinements of neutron diffraction data showed that the traditional cubic spinel-based structure models, based on m Fd3 space group symmetry, do not accurately describe the defect structure of γ-Al2O3. A more accurate description of the structure was provided using supercells of the cubic and tetragonal unit cells with a significant number of cations on c symmetry positions. These c symmetry based structures exhibited diffraction patterns that were characteristic of γ-Al2O3. The first three chapters of this Thesis provide a review of the literature. Chapter One provides a general introduction, describing the uses and importance of the aluminas and the problems associated with determining the structure of γ-Al2O3. Chapter Two details the research that has been conducted on the structure of vi γ-Al2O3 historically. Chapter Three describes the major principles behind the computational methods employed in this research. In Chapter Four, the specific experimental and computational techniques used to investigate the structure of γ-Al2O3 are described. All preparation conditions and parameters used are provided. Chapter Five describes the methodology employed in computational and experimental research. The examination of the ~ 1.47 billion spinel-based structural possibilities of γ-Al2O3, described using supercells, and the selection of ~ 122,000 candidates for computer simulation, is detailed. This chapter also contains a case study of the structure of κ-Al2O3, used to investigate the applicability of applying interatomic potentials to solving complex structures, where many possibilities are involved, and to develop a systematic procedure of computational investigation that could be applied to γ-Al2O3. Chapters Six to Nine present and discuss the results from the experimental studies.Preliminary heating trials, performed to determine the appropriate preparation conditions for obtaining a highly crystalline boehmite precursor and an appropriate calcination procedure for the systematic study of γ-Al2O3, were presented in Chapter Six. Chapter Seven details the investigation of the structure from a singletemperature case. Several known structural models were investigated, including the possibility of a dual-phase model and the inclusion of hydrogen in the structure. It was demonstrated that an accurate structural model cannot be achieved for γ-Al2O3 if the cations are restricted to spinel positions. It was also found that electron diffraction patterns, typical for γ-Al2O3, could be indexed according to the I41/amd space group, which is a maximal subgroup of m Fd3 . Two models were presented which describe the structure more accurately; Cubic-16c, which describes cubic γ-Al2O3 and Tetragonal-8c, which describes tetragonal γ-Al2O3. The latter model was found to be a better description for the γ-Al2O3 samples studied. Chapter Eight describes the evolution of the structure with changing calcination temperature. Tetragonal γ-Al2O3 was found to be present between 450 and 750 °C. The structure showed a reduction in the tetragonal distortion with increasing temperature but at no stage was cubic γ-Al2O3 obtained. Examination of the progress of cation migration indicates the reduction in the tetragonal nature is due to ordering within inter-skeletal oxygen layers of the unit cell, left over from the breakdown of the hydroxide layers of boehmite when the transformation to γ-Al2O3 occurred. Above 750 °C, δ-Al2O3 was not observed, but a new phase was identified and designated γ.-Al2O3.The structure of this phase was determined to be a triple cell of γ-Al2O3 and is herein described using the 2 4m P space group. Chapter Nine investigates the presence of hydrogen in the structure of γ-Al2O3. It was concluded that γ-Al2O3 derived from highly crystalline boehmite has a relatively well ordered bulk crystalline structure which contains no interstitial hydrogen and that hydrogen-containing species are located at the surface and within amorphous regions, which are located in the vicinity of pores. Expectedly, the specific surface area was found to decrease with increasing calcination temperature. This trend occurred concurrently with an increase in the mean pore and crystallite size and a reduction in the amount of hydrogen-containing species within the structure. It was also demonstrated that γ-Al2O3 derived from highly crystalline boehmite has a significantly higher surface area than expected, attributed to the presence of nano-pores and closed porosity. The results from the computational study are presented and discussed in Chapter Ten. Optimisation of the spinel-based structural models showed that structures with some non-spinel site occupancy were more energetically favourable. However, none of the structural models exhibited a configuration close to those determined from the experimental studies. Nor did any of the theoretical structures yield a diffraction pattern that was characteristic of γ-Al2O3. This discrepancy between the simulated and real structures means that the spinel-based starting structure models are not close enough to the true structure of γ-Al2O3 to facilitate the derivation of its representative configuration.Large numbers of structures demonstrate migration of cations to c symmetry positions, providing strong evidence that c symmetry positions are inherent in the structure. This supports the Cubic-16c and Tetragonal-8c structure models presented in Chapter Seven and suggests that these models are universal for crystalline γ-Al2O3. Optimisation of c symmetry based structures, with starting configurations based on the experimental findings, resulted in simulated diffraction patterns that were characteristic of γ-Al2O3.
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Pizzey, Claire Louise. "Small angle X-ray scattering from liquid crystal clay suspensions." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414194.
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Paglia, Gianluca. "Determination of the structure of y-alumina using empirical and first principle calculations combined with supporting experiments." Curtin University of Technology, Department of Applied Physics & Department of Applied Chemistry, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14992.
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Aluminas have had some form of chemical and industrial use throughout history. For little over a century corundum (α-Al2O3) has been the most widely used and known of the aluminas. The emerging metastable aluminas, including the γ, δ, η, θ, κ, β, and χ polymorphs, have been growing in importance. In particular, γ-Al2O3 has received wide attention, with established use as a catalyst and catalyst support, and growing application in wear abrasives, structural composites, and as part of burner systems in miniature power supplies. It is also growing in importance as part of the feedstock for aluminium production in order to affect both the adsorption of hydrogen fluoride and the feedstock solubility in the electrolytic solution. However, much ambiguity surrounds the precise structure of γ-Al2O3. Without proper knowledge of the structure, understanding the properties, dynamics and applications will always be less than optimal. The aim of this research was to contribute towards settling this ambiguity. This work was achieved through extensive computer simulations of the structure, based on interatomic potentials with refinements of promising structures using density functional theory (DFT), and a wide range of supporting experiments. In addition to providing a more realistic representation of the structure, this research has also served to advance knowledge of the evolution of the structure with changing temperature and make new insights regarding the location of hydrogen in γ-Al2O3.Both the molecular modelling and Rietveld refinements of neutron diffraction data showed that the traditional cubic spinel-based structure models, based on m Fd3 space group symmetry, do not accurately describe the defect structure of γ-Al2O3. A more accurate description of the structure was provided using supercells of the cubic and tetragonal unit cells with a significant number of cations on c symmetry positions. These c symmetry based structures exhibited diffraction patterns that were characteristic of γ-Al2O3. The first three chapters of this Thesis provide a review of the literature. Chapter One provides a general introduction, describing the uses and importance of the aluminas and the problems associated with determining the structure of γ-Al2O3. Chapter Two details the research that has been conducted on the structure of vi γ-Al2O3 historically. Chapter Three describes the major principles behind the computational methods employed in this research. In Chapter Four, the specific experimental and computational techniques used to investigate the structure of γ-Al2O3 are described. All preparation conditions and parameters used are provided. Chapter Five describes the methodology employed in computational and experimental research. The examination of the ~ 1.47 billion spinel-based structural possibilities of γ-Al2O3, described using supercells, and the selection of ~ 122,000 candidates for computer simulation, is detailed. This chapter also contains a case study of the structure of κ-Al2O3, used to investigate the applicability of applying interatomic potentials to solving complex structures, where many possibilities are involved, and to develop a systematic procedure of computational investigation that could be applied to γ-Al2O3. Chapters Six to Nine present and discuss the results from the experimental studies.
Preliminary heating trials, performed to determine the appropriate preparation conditions for obtaining a highly crystalline boehmite precursor and an appropriate calcination procedure for the systematic study of γ-Al2O3, were presented in Chapter Six. Chapter Seven details the investigation of the structure from a singletemperature case. Several known structural models were investigated, including the possibility of a dual-phase model and the inclusion of hydrogen in the structure. It was demonstrated that an accurate structural model cannot be achieved for γ-Al2O3 if the cations are restricted to spinel positions. It was also found that electron diffraction patterns, typical for γ-Al2O3, could be indexed according to the I41/amd space group, which is a maximal subgroup of m Fd3 . Two models were presented which describe the structure more accurately; Cubic-16c, which describes cubic γ-Al2O3 and Tetragonal-8c, which describes tetragonal γ-Al2O3. The latter model was found to be a better description for the γ-Al2O3 samples studied. Chapter Eight describes the evolution of the structure with changing calcination temperature. Tetragonal γ-Al2O3 was found to be present between 450 and 750 °C. The structure showed a reduction in the tetragonal distortion with increasing temperature but at no stage was cubic γ-Al2O3 obtained. Examination of the progress of cation migration indicates the reduction in the tetragonal nature is due to ordering within inter-skeletal oxygen layers of the unit cell, left over from the breakdown of the hydroxide layers of boehmite when the transformation to γ-Al2O3 occurred. Above 750 °C, δ-Al2O3 was not observed, but a new phase was identified and designated γ.-Al2O3.
The structure of this phase was determined to be a triple cell of γ-Al2O3 and is herein described using the 2 4m P space group. Chapter Nine investigates the presence of hydrogen in the structure of γ-Al2O3. It was concluded that γ-Al2O3 derived from highly crystalline boehmite has a relatively well ordered bulk crystalline structure which contains no interstitial hydrogen and that hydrogen-containing species are located at the surface and within amorphous regions, which are located in the vicinity of pores. Expectedly, the specific surface area was found to decrease with increasing calcination temperature. This trend occurred concurrently with an increase in the mean pore and crystallite size and a reduction in the amount of hydrogen-containing species within the structure. It was also demonstrated that γ-Al2O3 derived from highly crystalline boehmite has a significantly higher surface area than expected, attributed to the presence of nano-pores and closed porosity. The results from the computational study are presented and discussed in Chapter Ten. Optimisation of the spinel-based structural models showed that structures with some non-spinel site occupancy were more energetically favourable. However, none of the structural models exhibited a configuration close to those determined from the experimental studies. Nor did any of the theoretical structures yield a diffraction pattern that was characteristic of γ-Al2O3. This discrepancy between the simulated and real structures means that the spinel-based starting structure models are not close enough to the true structure of γ-Al2O3 to facilitate the derivation of its representative configuration.
Large numbers of structures demonstrate migration of cations to c symmetry positions, providing strong evidence that c symmetry positions are inherent in the structure. This supports the Cubic-16c and Tetragonal-8c structure models presented in Chapter Seven and suggests that these models are universal for crystalline γ-Al2O3. Optimisation of c symmetry based structures, with starting configurations based on the experimental findings, resulted in simulated diffraction patterns that were characteristic of γ-Al2O3.
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Liu, Yazhao. "Photo-responsive systems in aqueous solution : from model polyelectrolytes to polyelectrolyte-surfactant complexes." Thesis, Strasbourg, 2021. http://www.theses.fr/2021STRAE007.
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Cette thèse vise à concevoir, synthétiser et étudier des systèmes photo-stimulables modèles en solution aqueuse formés à partir de polyélectrolytes (PEs) et de tensioactifs. La photosensibilité est liée à la présence de chromophores azobenzène (Azo) qui subissent une isomérisation trans → cis sous irradiation UV. Nous avons considéré dans un premier temps un PE hydrophile sur lequel nous avons greffé des groupements Azo. Ce système forme de agrégats globulaires en solution en raison du collapse des chaînes et des associations intermoléculaires. La taille des agrégats varie sous irradiation UV. Elle dépend également de la masse molaire des PEs et du taux de greffage des groupements Azo. Nous avons considéré dans un second temps des tensioactifs dans lesquels des groupements Azo ont été introduits (Azo-tensioactifs). Nous avons étudié leur complexation avec des PEs de charge opposée. Ces systèmes s’organisent en colliers de perles. Les polyions décorent les micelles et pénètrent à l’intérieur de celles-ci (co-micellisation). Sous irradiation UV, la taille des perles diminue sans vraiment modifier l’organisation des complexes. Nous nous sommes enfin intéressés à l’auto-assemblage d’Azo-tensioactifs et de co-tensioactifs. Ce mélange conduit à la formation des micelles allongées et à la création d’un gel. Sous irradiation UV, on observe une transition gel - fluide. L’origine ce phénomène est lié à un changement morphologique des agrégats micellaires (micelles allongées - micelles globulaires)This thesis aims at designing, synthesizing and characterizing model photo-responsive systems in aqueous solution. These systems are based on polyelectrolytes (PEs) and surfactants. The photo-sensitivity arises from the presence of azobenzene (Azo) groups that undergo a transition from a trans to a cis isomer. We first considered a hydrophilic PE on which we grafted Azo groups. This system forms globular aggregates in solution due to chains collapse and intermolecular associations. The size of the aggregates varies under UV irradiation. It also depends on the molar mass of the PEs and the Azo content. We then considered surfactants in which Azo groups have been introduced (Azo-surfactants). We studied their complexation with oppositely charged PEs. These systems show a pearl necklace organization. The PEs decorate the micelles and penetrate inside (co-micellisation). Under UV irradiation, the size of the pearls decreases without really modifying the general organization of the complexes. Finally, we were interested in the self-assembly of Azo-surfactants and co-surfactants. This mixture leads to the formation of wormlike micelles and the creation of a gel. Under UV irradiation, a gel - fluid transition is observed. The origin of this phenomenon is linked to a morphological transition of the micellar aggregates (wormlike micelles - globular micelles)
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Li, Li. "Structural analysis of cylindrical particles by small angle X-ray scattering." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975319612.
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Leu, Leon Dominik. "Small- and wide-angle X-ray scattering microscopy applied to mudrocks." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/54754.
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Geologic mudrock formations can be used for different industrial applications such as natural gas production, CO2 sequestration, and radioactive waste storage. In natural gas production the rock is the source for gas, mainly methane, that is exploited as an energy source. In CO2 sequestration and radioactive waste storage the rock acts as a flow barrier preventing the release of CO2 or radionuclides into the environment. The release or retention of fluids and gases is controlled by a variety of flow and transport processes in the mudrock reservoirs. Pore scale flow processes play a crucial role determining fluid supply through pore arrangement, porosity, diffusion, adsorption/desorption of oil, gas and water. That is why prediction of flow and transport at the pore scale is relevant for productivity and long-term integrity estimations of reservoirs. Therefore, the detailed characterization of the mudrock microstructure is crucial. The microstructure however, is heterogeneous and mineralogy varies from a sub-μm to mm scale, and pore-sizes range from sub-nm to several μm. It is challenging to resolve this heterogeneity on all relevant scales with analytical methods. Imaging techniques provide the most detailed and localized insight into pore arrangement but fail to investigate statistically relevant sample volumes including pores < 50 nm in size. Fluid invasion and radiation measurement methods measure volume averaged bulk properties, and hence do not resolve local features. This results in a situation where experimental methods cannot be used to simultaneously study the local characteristics on all scales, and probe statistically relevant sample sizes. As a consequence, little is known about the systematic variation of features on the pore scale, over which scales it extends, and how this affects flow and transport mechanisms at larger scales. In this thesis small- and wide-angle X-ray scattering microscopy (SAXS-WAXS) is used as a novel method to overcome these current experimental limitations in the pore scale characterization of mudrocks. In the first experimental results section we demonstrate that a volume averaged but local characterization is achieved by focusing the X-ray beam to microscopic dimensions measuring 10 × 25 µm2. By applying the method on specially prepared mudrock thin sections of 10 – 30 µm thickness, microscopic rock volumes are probed below the scale of the rock’s structural heterogeneity. Operated in a scanning microscopy mode, thousands of consecutive measurements are collected at an effective scanning resolution of 10 × 10 µm2 over 2 × 2 mm2 sized sample areas. Then the measurable parameter space is investigated on rock samples oriented parallel and perpendicular to the bedding plane. We measure pore orientation, porosity and pore size distribution for pores 4 – 130 nm, and mineral features on a separate WAXS detector. We find that pores are aligned parallel to the bedding in rocks cut perpendicular to the bedding plane, while pores do not have a preferential alignment in rocks cut parallel to bedding. Local porosity values in selected matrix volumes in Opalinus Clay show considerable variation which could be related to differences in local mineralogy. In a multi-scale characterization effort, aiming at a full description of the entire pore spectrum, the method is combined with other high resolution imaging techniques including FIB-SEM, SEM and µ-CT. For a validation of the method measured pore size distributions from Opalinus Clay are compared to SANS, N2 physisorption and FIB-SEM data, showing a good agreement between all measurements. In the second experimental results section, several improvements are made to the experimental protocol achieving a higher scanning resolution of 5 × 5 µm2. By performing two separate SAXS and WAXS experiments at different sample detector configurations, a wide q-range is measured to resolve pore features from approximately 6 – 202 nm and mineral reflections in the angular 2θ-range of 4 – 24°. The investigated sample set includes two Posidonia, one Opalinus Clay and, two heterogeneous Eagle Ford mudrock samples, potentially yielding a variety of structural features. Samples were mounted perpendicular to the bedding plane and polished using an ion beam surface polish. Respective SAXS parameter maps show the pore orientation and scattering intensity for sample areas measuring 1 × 1.75 mm2. The measured degree of orientation – indicating the tendency of pore alignment – varies from 0.3 to 0.7 between the Eagle Ford and Opalinus Clay. These results indicate a much stronger preferential pore alignment in Opalinus Clay, which could be related to the high clay content in it. We also find that the degree of orientation changes as a function of pore size, which cannot be explained with the experimental data. From the intensity distributions I(q) in the SAXS patterns porosity is calculated using the Porod invariant, and the distribution is plotted over the entire sample areas. The maps reveal that local porosity variation in fine grained samples is determined by the distribution of large minerals in the matrix. In the more heterogeneous Eagle Ford sample more features are visible and the porosity distribution map is characterized through two different porosity domains in the matrix. Representative elementary volumes (REV) for the porosity for all samples are at volumes < 300 pixels (< 7.5 × 〖10〗^(-14) m3). Further local mineralogy was quantified from the WAXS data in microscopic sample volumes in the oriented of the Eagle Ford sample using Rietveld refinement. Corresponding mineral distribution maps mainly show the heterogeneous distribution of calcite, quartz, kaolinite, mica, bassanite, in a sub-area of 60 × 405 µm2 containing 927 patterns. The porosity and calcite distribution correlate, suggesting that the porosity in the matrix in that sample is largely controlled by the calcite content, but must also be influenced by other effects, e.g. clay minerals or microscopic grains. Thus, the results show that quantitative SAXS and WAXS measurement can be effectively combined to investigate characteristic relationships between mineral composition and pore distribution. These characteristic relationships may play as important role for upscaling scenarios, where flow properties can be predicted based on porosity and mineral composition.
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Gryko, Piotr. "Peptide mediated nanoparticle assembly investigated using small angle X-ray scattering." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9621.
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Nanoparticle systems arranged through bio-chemical self-assembly mechanisms display novel electronic and optical characteristics applicable to biosensing, tissue engineering, therapeutics and drug delivery. Metallic Nanoparticles such as those composed of gold or CdSe are expected to replace standard chemical fluorophore due to their high optical scattering cross-section. The colloidal nature of nanoparticles necessitates the engineering of NPs surface chemistry to control particle stability and assembly order. The high intensity of modern synchrotron sources, combined with the high electron density contrast of metallic NPs, allows for fast, sensitive, in-situ synchrotron measurements. Here Small Angle X-ray scattering is used to observe nanoscale structural changes and relate them to changes in polypeptide mediated interaction potential, particle surface charge and mobility within aggregates. These results enable strategies for optimising the structure and the optical characteristics of NP assemblies, which are vital for their performance as colourimetric sensors. Here three NP systems are investigated and characterised: (1) Gold nanoparticles assembled using de novo designed polypeptides developed by D. Aili (Chapter 3). The assembly is achieved by the folding dependent bridging of the particles induced by the heteroassociation of immobilised helix-loop-helix polypeptides and a complementary non-linear polypeptide found in solution. Changes in the optical properties of the assembly as a function of particle size and linker concentration are observed, with SAXS used to obtain in-situ structural information on the aggregates. The particles are found to assemble into highly ordered close packed structures with an interparticle spacing of 4.8±0.4nm, corresponding to the length of a folded polypeptide. Changes in particle ordering, aggregation dynamics and mass fractal dimension are observed as a function of linker concentration and particle size. These transitions are related to changes in linker mediated interaction potential, particle surface charge and mobility within the aggregates. (2) Interaction of BSA with AuNP aggregates (Chapter 4). Bovine serum albumin (BSA) is a vital component of standard immunological assays and it is often extended for use in de-novo assays based on peptide modified metallic nanoparticles. Whilst a wide range of plasma proteins such as BSA and HSA have been shown to associate with nanoparticles, there is little work done on the effect of BSA on NP assemblies, which are highly dependent on particle stability. Here the effect of BSA on AuNP aggregates is characterised, using stability assays, DLS, UV-VIS and SAXS. Far from being an inert component, the introduction of BSA directly alters the structure and interaction of AuNP aggregates. Temperature is observed to be a factor in these interactions with a specific affinity for hydrophobic systems. (3) A Quantum Dot - Gold Nanoparticle conjugate assay for the detection of urokinase plasminogen activator (uPA) (Chapter 5). Proteolytic enzymes are used as disease biomarkers for several forms of cancer. The surface assembly of gold nanoparticles onto the surface of quantum dots is demonstrated, with the growth in conjugate size characterised using in-situ SAXS. Complete conjugate disassembly is observed upon the addition of the enzyme uPA, however QDs luminescence does not fully recover. This indicates that other effects may result in the permanent quenching of quantum dots. The work presented here is designed to guide in the synthesis of general principles for assembly of NPs by biomolecular mediated bridging, whilst contributing to the fundamental understanding of the assembly process.
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Ogawa, Tetsuya. "Small-Angle X-Ray Scattering from the Surfaces of Polymer Crystals." 京都大学 (Kyoto University), 1991. http://hdl.handle.net/2433/86428.
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Bonnevide, Marine. "Nanocomposites élastomère-nanoparticules de silice greffées : de la synthèse aux mécanismes de dispersion." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0354.
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L’ajout de charges nanométriques dans une matrice polymère permet d’améliorer les propriétés d’usage des matériaux. L’optimisation du renforcement des nanocomposites est liée à l’état de dispersion des charges dans la matrice ainsi qu’aux interactions charge/charge et charge/polymère. Dans l’industrie du pneu, ces paramètres ont fait l’objet de nombreuses recherches dans le but de maîtriser le renforcement de matrices élastomères par des particules de silice. Ainsi à l’échelle industrielle, on utilise des agents de couplage, comme le bis(triéthoxysilyl)propyl tétrasulfide ou des polymères fonctionnels qui permettent d’améliorer la dispersion des particules de silice dans des élastomères. Cependant il est difficile de moduler certains paramètres susceptibles d’influencer l’état de dispersion et les interactions, comme la densité de greffage, la nature et la longueur des chaînes de polymère greffées à la surface des particules. Afin de remédier à ces limites nous proposons, dans ce travail de thèse, de synthétiser des nanoparticules de silices greffées de polyisoprène, polybutadiène et copolymère poly(butadiène-co-styrène) par la méthode de « grafting from » associée à une polymérisation contrôlée par les nitroxydes. Pour cela une alcoxyamine est greffée sur la surface en deux étapes en maintenant la stabilité colloïdale des particules. Après l’optimisation des conditions de greffage et la polymérisation des monomères à partir de l’alcoxyamine greffée, les nanoparticules greffées ainsi obtenues sont caractérisées et leur état de dispersion est étudié en solution et dans des matrices de masses molaires et de compositions différentes après l’élaboration de nanocompositesThe addition of nanometric fillers into a polymer matrix significantly improves its use properties. Optimization of nanocomposite reinforcement is related to the filler dispersion state in the matrix as well as to the filler/filler and filler/matrix interactions. In the tire industry, numerous studies have been devoted to these parameters in order to understand and control the reinforcement of elastomeric matrices such as Styrene Butadiene Rubber by silica nanoparticles. On an industrial scale, functional polymer or coupling agents such as bis(triethoxysilyl)propyl tetrasulfide are used to improve the dispersion of silica particles in elastomers and strengthen the matrix. However, it is difficult to control the grafting density and to modulate some parameters that may influence the dispersion state and interactions e.g. the nature and molar mass of the polymer chains covalently attached to the surface. To address these limitations, in this project we propose to synthesize silica nanoparticles grafted with polyisoprene, polybutadiene and statistical poly(butadiene-co-styrene) chains using the “grafting from” method associated to nitroxide mediated polymerization. In this aim, an alkoxyamine is grafted onto the nanoparticle surface in two steps by keeping the colloidal stability of the particles. After optimizing grafting parameters and polymerize the different monomers, the obtained grafted nanoparticles are characterized in terms of molar mass, microstructure, grafting density and gyration radius of the grafted chains. Their dispersion state is evaluated in solution as well as in matrices of various molecular weight and composition after the elaboration of nanocomposites
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Sidhu, Sabeena. "Small angle x-ray scattering as a diagnostic tool for breast cancer." Monash University. Faculty of Science. Monash Centre for Synchrotron Science, 2009. http://arrow.monash.edu.au/hdl/1959.1/73839.
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Breast cancer is the most common cause of cancer death in Australian women. Current pathological analysis examines a small section of tissue for cellular and plasma abnormalities using a light microscope. However, this method of diagnosis, despite being the current gold standard, has its limitations, where human error and professional experience can influence a patient’s diagnosis. A potential alternative or adjunct to conventional histopathology for classifying tissue disease status is offered by Small Angle X-ray Scattering (SAXS). At the time of commencement of this work, there had been several small scale studies which examined the potential of SAXS to classify the disease status of breast tissue. These tended to focus on the supramolecular structure of collagen fibrils found in the breast, where it is known that the degradation of these fibres is related to the spread of disease. Most previous studies also used a synchrotron as an X-ray source, due to the intense and highly collimated flux available. This study used a synchrotron source, but also evaluated the use of a laboratory X-ray source, as a more convenient and relatively inexpensive alternative that could one day find application in the clinic. The work presented in this thesis analyses the largest cohort of patients and breast tissue samples studied to date using SAXS: 130 patients with 543 tissue samples. Tissues were sourced from surgical waste and classified into four groups: invasive carcinoma, benign, normal, and mammoplasty. Mammoplasty tissue samples were harvested from patients undergoing breast reduction and/or reconstruction, where no history or presence of disease was indicated. Normal tissue was sampled from patients with known disease, but pathological analysis of the tissue core diagnosed it as normal. A comprehensive analysis of the scattering patterns was carried out, analysing features arising from the collagen structure and orientation, the total scattered intensity, and adipose tissue in the breast. Features related to the axial D-spacing of the collagen fibrils within the breast tissue as well as the integrated scattering intensity (called amorphous scatter) demonstrated the highest ability to discriminate tissue types, in SAXS images acquired from both the synchrotron source and the laboratory X-ray source. The amorphous scatter intensities obtained using a synchrotron source showed highly significant differences (p < 0.01) for almost all of the tissue pair comparisons: invasive carcinoma vs. benign, invasive carcinoma vs. normal, invasive carcinoma vs. mammoplasty, benign vs. mammoplasty, and normal vs. mammoplasty. However, no significant difference was seen in the amorphous scatter between benign versus normal tissues (p = 0.30). The amorphous scatter values increased with severity of disease, i.e. it was the highest for invaded tissues and decreased progressively from benign to normal to mammoplasty. There was a significant difference between normal and mammoplasty tissue types using the amorphous scatter as a discriminator (p = 0.0025). Pathological assessment cannot differentiate between these two tissue types, which suggests that there may be changes occurring in these tissue structures at the supramolecular level that can be characterised using SAXS. The ability of SAXS to reveal structural differences between normal and mammoplasty tissue types is highly significant, for both disease diagnosis and treatment, as well as for understanding disease progression. For example, these differences might aid in determining surgical margin clearance of excised breast lesions as well as potentially provide a means of pre-screening or perhaps improve false-negative rates of diagnosis. The potential of SAXS to reveal macroscopic extent and directional spread of disease was explored using two-dimensional mapping of the amorphous scatter. These maps showed broad agreement with histopathological diagnosis, but further investigation regarding their reliability and interpretation for clinical utility is still needed. Changes in both the amorphous scatter and the axial D- spacing were seen in tissue samples up to 6 cm away from the primary site of disease. In particular, a significant decrease in both parameters was seen between the centre of the tumour (at 0 cm) and 2 cm away, suggesting that closer examination of the tissue structures over the disease/healthy tissue border may provide information regarding the mechanisms of metastasis and growth of cancerous tumours. The combination of the amorphous scattering results from the two X-ray sources indicates that the size of the scatterers may be the key in classifying tissue types. The synchrotron source was able to access a lower q-range (q = 0.1-0.6 nm-1) and the laboratory source covered a larger q-range (q = 0.25-2.3 nm-1). Mammoplasty tissues appear to be characterised by large scattering components (d > 25.13 nm), whereas normal tissues are characterised by slightly smaller scattering components (10.47 nm < d < 25.13 nm) and benign tissues by even smaller scattering components (4.83 < d < 10.47 nm). It appears that the size of the scatterers contributing to the total scattering intensity decreases with severity of disease, which was seen independently with both X-ray sources. Further investigation is warranted to determine the biological origin of these differences. These results also suggest that the optimum SAXS instrument may need to cover a scattering vector range of q < 0.25 nm-1 to identify differences in healthy tissue types, and q > 2.3 nm-1 to possibly investigate invasive carcinoma tissue types. A SAXS apparatus that can examine a large q-range may provide all of the necessary information from the amorphous scatter to differentiate between tissue groups. The periodic structure of collagen fibrils along their longitudinal axis can be characterised by the axial D-spacing, where this spacing was found to change with the presence of disease. The axial D-spacing for healthy breast tissues was found to be significantly lower in normal and mammoplasty tissues compared to invaded tissues (p = 0.0050 and p = 0.0093, respectively). However, no significant differences between the other tissue group pairs were seen (p > 0.05). These differences were evident in classification modelling of the four tissue groups, where the amorphous scatter and the amplitude of a collagen axial peak were used to build a probability model for disease status. The model showed high sensitivities (> 70%) and widely variable specificities (ranged from 18-97%) for the data examined with the synchrotron source. This means that the model was a good indicator of disease, but poor at indentifying healthy tissue types. The work presented in this thesis shows that SAXS is capable of distinguishing breast tissue types with high sensitivity and has the potential to become a significant tool for the investigation of cancer progression or even diagnosis. Further investigation into the amorphous scatter and axial D-spacing in particular may provide insight into the biological mechanisms related to tissue degradation associated with invasive disease.
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Salomons, Gregory John. "Small-angle x-ray scattering study of crazing in bulk thermoplastic polymers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0001/NQ27854.pdf.
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Matsuoka, Hideki. "Small-angle X-ray scattering studies on ordered structure of polyelectrolyte solutions." Kyoto University, 1987. http://hdl.handle.net/2433/74699.
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Hattori, Kaori. "μ-PIC gaseous area detector for small-angle X-ray scattering experiments." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124416.
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Delzenne, Pascale. "Piézoélectricité et microstructure dans des polymères ferroélectriques : PVF2 et P(VF2-F3E)." Grenoble 1, 1986. http://www.theses.fr/1986GRE10033.
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Etude de la microstructure polyfluorure de vinylidene (pvf::(2)) en phase beta orientee par diffusion rx centrale. L'organisation, la forme et les dimensions des cristallites sont caracterisees. Analyse de la transition ferro-para electrique du copolymere p(vf::(2)-f::(3)e). Mise en evidence du desordre dynamique de la phase paraelectrique qui induit une reorganisation de la microstructure du polymere oriente par laminage
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Rigden, Jane Sarah. "Development of ultra small-angle X-ray scattering for studies of heterogeneous systems." Thesis, University of Kent, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334680.
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Barnardo, Twilight. "Time resolved anomalous small angle X-ray scattering of the sol-gel process." Thesis, Aberystwyth University, 2010. http://hdl.handle.net/2160/17191ae6-e038-4c50-b380-8f4d227791a8.
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This investigation employs Anomalous Small Angle X-ray Scattering (ASAXS), and further expands the technique for conducting time resolved experiments within synchrotron facilities. ASAXS utilises the absorption effects of a given element as photon energies approach an absorption edge, and is used to extract partial scattering functions of the individual species within a composite material. In situ ASAXS is used to explore and understand the complex reactions in sol gel processing. The gelation process for zirconia, yttria stabilised zirconia (YSZ), YSZ and zirconia in silica, and zinc-silica systems are observed using in situ ASAXS across the zirconia and zinc absorption edges respectively. A new technique of high temperature time resolved double ASAXS, which explores two absorption edges in a single experiment, has also been employed to investigate phase changes during the sintering of YSZ and YSZ in silica. A computational model for ASAXS is also proposed, which can be used as a tool for data analysis. It is shown that monochromator resolution induces an uncertainty into the correct values of the coefficients - used to extract scattering information from individual species within a composite material. The model suggests methods to reduce this uncertainty in order to converge on the correct solution. New techniques for future time resolved ASAXS experiments are also presented. Time resolved ASAXS of the gelation process reveals contrast in the resonant term for sol-gels containing zirconia. The profile of which is independent of the relative concentrations of yttria and silica. It is proposed that the zirconia is being fully integrated into the gel network to form zirconia-silica chains. In comparison, the zinc systems did not reveal this effect, and instead display contrast in both the resonant and cross terms, implying a gel network is forming at the exclusion of zinc. High temperature in situ double ASAXS of the YSZ materials reveals the nucleation of nano zirconia at temperatures close to 400ºC. The nano crystals grow to eventually incorporate yttria, preserving the zirconia in the cubic and tetragonal phases. Inhomogeneities are revealed during crystal growth; caused by the mixed phase states of zirconia and YSZ present in the material. It is also shown that the presence of a silica matrix delays the growth of these crystals until a temperature of 780 ºC is reached. Samples with high concentrations of yttria also reveal an additional feature beyond 900ºC indicating a saturation point for cubic YSZ formation.
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Schmidt, Molly A. "Weighting protein ensembles with Bayesian statistics and small-angle X-ray scattering data." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119574.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 52-54).
Intrinsically Disordered Proteins (IDPs) are involved in a number of neurodegenerative disorders such as Parkinson's and Alzheimer's diseases. Their disordered nature allows them to sample many different conformations, so their structures must be represented as ensembles. Typically, structural ensembles for IDPs are constructed by generating a set of conformations that yield ensemble averages that agree with pre-existing experimental data. However, as the number of experimental constraints is usually much smaller than the degrees of freedom in the protein, the ensemble construction process is under-determined, meaning there are many different ensembles that agree with a given set of experimental observables. The Variational Bayesian Weighting program uses Bayesian statistics to fit conformational ensembles, and in doing so also quantifies the uncertainty in the underlying ensemble. The present work sought to introduce new functionality to this program, allowing it to use data obtained from Small-Angle X-ray Scattering.
by Molly A. Schmidt.
M. Eng.
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Howell, Steven C. "Dynamic Conformations of Nucleosome Arrays in Solution from Small-Angle X-ray Scattering." Thesis, The George Washington University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3738561.
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Chromatin conformation and dynamics remains unsolved despite the critical role of the chromatin in fundamental genetic functions such as transcription, replication, and repair. At the molecular level, chromatin can be viewed as a linear array of nucleosomes, each consisting of 147 base pairs (bp) of double-stranded DNA (dsDNA) wrapped around a protein core and connected by 10 to 90 bp of linker dsDNA.
Using small-angle X-ray scattering (SAXS), we investigated how the conformations of model nucleosome arrays in solution are modulated by ionic condition as well as the effect of linker histone proteins. To facilitate ensemble modeling of these SAXS measurements, we developed a simulation method that treats coarse-grained DNA as a Markov chain, then explores possible DNA conformations using Metropolis Monte Carlo (MC) sampling. This algorithm extends the functionality of SASSIE, a program used to model intrinsically disordered biological molecules, adding to the previous methods for simulating protein, carbohydrates, and single-stranded DNA. Our SAXS measurements of various nucleosome arrays together with the MC generated models provide valuable solution structure information identifying specific differences from the structure of crystallized arrays.
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Swann, Joshua Michael George. "Characterising pH response in phase separated hydrogels using small angle X-ray scattering." Thesis, University of Sheffield, 2010. http://etheses.whiterose.ac.uk/14968/.
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A range of (methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)block- poly(methyl methacrylate) [PMMA-block-PDEA-block-PMMA] and poly(methyl methacrylate )-block-poly(methacrylic acid)-block-poly(methyl methacrylate) [PMMA-blockPMAA- block-PMMA] triblock copolymers have been prepared via group transfer and anionic polymerisation respectively. These hydrophilic-hydrophobic block copolymers were characterized with respect to their chemical composition and molecular weights by 1 H and by gel permeation chromatography respectively. Morphological development in solvent cast films were followed using SAXS by monitoring changes in the structure peak. [PM MA-block-PMAA-block-PM MA] triblocks were found to be mechanically weak and therefore not suitable as chemical actuators. Using SAXS the "static" equilibrium molecular response of phase separated films of [PMMA-block-PDEA-block-PMMA] triblock copolymers to changes in pH, ionic strength and salt identity was evaluated. Changes in pH were effected using a controlled set of buffers, namely citric acid, sodium phosphate and ethanol amine. The ionic strength of the buffers was fixed using a series of salts from the Hofmeister series, namely NaAce, NaCl, NaBr, Nal, NaN03 and NaSCN. At a fixed pH and ionic strength the equilibrium expansion ratio of the polymer was found to be highly dependent on the identity of the salt. The extent of swelling was correlated with the surface charge density of the anionic component of the salt. Hydrogels swollen in solution containing more polar anions were found to have a larger expansion ratio. This was explained in terms of the water perturbing effect of the ion. The swelling of the polymer was also monitored as a function of pH. A drastic collapse of the polymer was observed at a specific pH corresponding to the apparent pKa of the PDEA block. The apparent pKa of [PMMA-block-PDEA-block-PMMA] copolymers was found to be dependent on the overall molecular weight, where higher molecular weight material had a lower apparent pKa. Below the apparent pKa the extent of swelling in solutions prepared at 0.1 M ionic strength was found to be dependent on the pH. This has been attributed to the . complex interplay of citrate species in the buffer. The effect of ionic strength on the "swelling was also investigated at fixed pH and salt identity using buffer and simple mineral acid. A modified Donnan theory has been used to interpret the results. SAXS was found to be a highly sensitive technique for measuring the "static response" of the hydrogels. The use of SAXS was also investigated as a technique for measuring the swelling "kinetics" of [PMMA-block-PDEA-block-PMMA] hydrogels. Thin annealed films of hydrogel were swollen in a range of control buffered solutions. The in-situ nature of the technique afforded high resolution data. The kinetics of swelling was monitored by following the change in the structure peak position and its half height peak width, which gave the expansion ratio and diffusive behavior respectively. Swelling stresses induced in the samples made measuring the kinetics problematic and this limited the technique. Finally, to avoid the expense and limited availability of SAXS beam lines a new technique was used to monitor the response of the hydrogels. A diffraction grating was imprinted onto the surface of the hydrogel, and "static" and "kinetic" response was measured by monitoring the change in the diffraction pattern. This technique was found to offer similar accuracy as SAXS, at a Significantly reduced cost.
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Loppinet, Benoit. "Etude de la structure de solutions d'ionomères en solvants polaires par diffusion aux petits angles." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10208.
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Ce travail presente l'etude, principalement par diffusion aux petits angles (dpa) de neutrons et de rayons-x, de solutions d'ionomeres. Les differentes analyses de l'intensite dpa (variation de contraste, analyse du comportement asymptotique, positions du pic d'interferences), appliquees aux solutions d'ionomeres perfluores (ipf), menent a la conclusion de la presence de particules colloidales de symetrie cylindrique. Cette geometrie est obtenue pour des solutions de trois ipf dans des solvants varies couvrant une gamme importante de constante dielectrique. La valeur du rayon depend de l'ipf et du solvant. En particulier les solutions dans l'eau se trouvent avoir les particules aux rayons les plus importants. Les etudes complementaires de solutions d'ipf par viscosimetrie font apparaitre des comportements dependant fortement du solvant (presence ou non d'effet polyelectrolyte suivant le solvant). Quelques mesures rmn mettent en evidence le comportement atypique des solutions aqueuses. L'etude par dpa de solutions aqueuses d'autres ionomeres, copolymeres d'ethylene et d'acide methacrylique, met la encore en evidence l'existence de particules colloidales, de geometrie ellipsoidale, dont la taille depend du taux de neutralisation
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Lerche, Michael. "Elucidating the activation mechanism of the transcription factor DntR using X-ray crystallography and small angle X- ray scattering." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENV013/document.
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Les protéines régulatrices de la transcription de type LysR (LTTR) appartient à la plus grande famille de facteur de transcription chez les procaryotes. Malgré l'importance de cette famille, les informations structurelles sur les protéines pleine-longueur sont très limitées car elles sont souvent insolubles et très difficiles à cristalliser. Les quelques structures existantes, couplés à d'autres analyses biophysiques ont pu montrer que ces protéines s'associent principalement sous forme d'homotétramère comprenant un dimère de dimères. Les dimères s'associent par un large domaine C-terminal dans une position " tête-bêche " et sont reliés en " tête-à-tête " par leurs domaines N-terminal et sont activées par la liaison de molécules inductrices. Le domaine dimèrique C-terminal qui contient la poche de liaison inductrice (Inducer Binding Cavity : IBC) est appelé domaine de liaison inductrice (Inducer Binding Domain : IBD), tandis que les dimères N-terminaux se lient chacun à une région de l'ADN par un motif hélice-tour-hélice ‘winged' (wHTH). Contrairement à d'autres facteurs de transcription, les protéines LTTR ne régulent pas l'expression par association/dissociation avec l'ADN. Ils se lient à l'ADN dans leur état actif et inactif. Le consensus actuel est qu'elles régulent l'expression des gènes par d'importants changements conformationnels qui relâchent la liaison avec l'ADN. À ce jour, aucune structure de LTTR pleine longueur homotétramérique dans une conformation active ou inactive n'a été résolu par cristallographie, et leur mécanisme d'action sur le gène reste structurellement non caractérisé.Le travail décrit dans cette thèse a utilisé DntR de la famille des LTTR. La première structure cristalline de l'apo-DntRis est présentée ici, ainsi que la structure du mutant H169TDntR, qui présente une activité en l'absence d'inducteur. L'analyse par fluorimétrie de différentiel thermique (TSA) montre que la température de dénaturation du mutant H169TDntR est similaire à DntR IBDs lié à une molécule inductrice. La comparaison de ces deux structures avec celle de DntR lié au salicylate révèle que la protéine dans son état apo adopte une conformation compacte de l'IBC, ce qui empêche la liaison d'une molécule inductrice. Dans l'IBC, les mouvements des résidus H169 et H206 permettent la liaison à l'inducteur. Pour éviter les limitations dues à l'empaquetage du cristal nous avons étudié la structure DntR en solution par diffusion des rayons X aux petits angles (SAXS).L'étude SAXS de DntR révèle que dans son état inactif, la conformation apo adopte un repliement plus compact par rapport à celle de la structure cristalline. Tout en maintenant un noyau compact de C-terminal, le repliement du dimère de wHTH est beaucoup plus fermé que dans la structure cristalline et adopte une conformation qui entrainerait une flexion beaucoup plus importante de l'ADN lié que postulé précédemment. Les études du mutant H169TDntR constitué actif ont confirmé comme l'analyse par TSA l'a suggéré que, la structure de cette protéine est nettement différente en solution que sous forme cristalline.En effet, la structure en solution de H169TDntR est très semblable à la forme ouverte de l'homotétramères observés dans la structure cristalline de TsaR. L'hypothèse de départ était que, lors de l'activation de LTTR, cet homotétramère subirait un changement de conformation d'une forme compact vers une forme ouverte, qui se traduirait par un relâchement de l'ADN lié. Cette hypothèse a été confirmée par des études de diffusion en solution de DntR activée par un inducteur.Le travail présenté dans cette thèse valide l'hypothèse précédemment, que lors de l'activation de DntR, et probablement tous les LTTRs homotétramériques, entraine un changement de conformation d'une forme compacte vers une forme beaucoup plus ouverte et permet l'accès aux régions promotrices par l'ARN polymerase et ainsi initier la transcriptionLysR type transcriptional regulatory (LTTR) proteins are the largest family of transcription factors amongst prokaryotes. In spite of the size of the family, structural information on full-length constructs of these proteins is very limited as they are often insoluble and very difficult to crystallize. From the few existing crystal structures, coupled with other biophysical evidence, it is known that the proteins mainly associate as homotetramers comprising a dimer of dimers. The dimers associate through large C-terminal domains in a “head-to-tail” fashion and are connected “head-to-head” through their N-terminal domains and the resulting homotetramers are activated by the binding of inducer molecules. Each C-terminal domain contain an inducer binding cavity (IBC) and is denoted an inducer binding domain (IBD), while the N-terminal dimers each bind a region of DNA via a winged helix-turn-helix (wHTH) motif.Unlike other transcription factors, LTTR proteins do not regulate expression by associating or disassociating with DNA. They bind to DNA in both their active and inactive states and the current consensus is that they regulate gene expression through large conformational changes that relax the bending of bound DNA. However, to this date, no crystal structures of a full length homotetrameric LTTR in both an active and inactive conformation exists, and thus their mechanism of transcriptional regulation remains structurally uncharacterized.The work described in this thesis has used the LTTR DntR as a model protein to futher structurally characterizes the activation mechanism of LTTR proteins. The first crystal structure of apo-DntR is presented as is the crystal structure of H169TDntR, a mutant which shows activity in the absence of an inducer molecule. Thermofluor assays performed on this mutant, show that it has a melting temperature similar to that of inducer bound DntR. Comparison of these crystal structures with the crystal structure of salicylate-bound DntR reveals that the protein in its apo-state adopts a compact IBC, which precludes the binding of an inducer molecule. Despite the evidence of thermofluor assays, the crystal structure of H169TDntR is very similar to that of apo-DntR suggesting that crystal packing effects impose strong limitations on the use of crystallography to elucidate the active and inactive conformations of DntR. Small Angle X-ray Scattering (SAXS) was thus used to study the structure of DntR in solution.SAXS study reveals that in solution DntR in its inactive apo-state is found in a slightly different conformation compared to that seen in its crystal structure. While maintaining a compact tetrameric C-terminal core the DNA binding wHTH dimers pack much closer to this than seen in the crystal structure and adopt a conformation that would result in much higher bending of bound DNA than previously postulated.SAXS studies of the constitutively active H169TDntR mutant confirm, as thermofluor assays had suggested, that in solution the structure of this protein is markedly different from its crystal structure. Indeed the solution structure of H169TDntR appears very like that of open-form homotetramers seen in the crystal structure of TsaR. This same effect was observed in solution scattering studies of inducer bound-and thus activated, DntR.The work presented in this thesis thus appears to confirm, as previously hypothesized, that upon activation DntR, and presumably all homotetrameric LTTRs, undergo a conformational change from a compact, to a much more open form that allows the relaxation of the bound DNA promoter region, exposing it to solvent and allows RNA polymerase access and thus initiate transcription
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Chavan, Harshad S. "Investigation of ß-phase poly (vinylidene fluoride) films using small-angle x-ray scattering." Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1145990710.
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Böhmert, Jürgen, Gudrun Müller, and Krist'l van Ouytsel. "A Small Angle X-ray Scattering Method to Investigate the Crack Tip in Metals." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29045.
Full textAbstract:
The work in this report, financed by the European Union through the Marie Curie Fellowship Association, was carried out at the FZ-Rossendorf. The subject of the research was to develop a method to investigate the damage, the high defect gradients at the tip of a ductile crack by means of Small Angle X-ray Scattering. The work explains the objectives and entails a brief introduction and background; it portrays and discusses the results which can be summarized as follows. Different damage parameters were investigated: the integral intensity, the total intensity on the detector, the anisotropy parameter and the fractal dimension. Of these, the anisotropy parameter is the most robust and most clearly depicts a damage region and the fractal dimension provides an idea of the structure of the scattering defect. The integral and total intensity provide comparable results only in some cases and are therefore not reliable. From supportive investigations: Scanning and Transmission Electron Microscopy (S-TEM), Finite Element Analysis and X-Ray Diffraction, it is suggested that the scatterer created after deformation is related to large oriented dislocation networks.
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Mitropoulos, Nasos. "Characterization of some porous materials by physical adsorption and small angle X-ray scattering." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330305.
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Böhmert, Jürgen, Gudrun Müller, and Krist'l van Ouytsel. "A Small Angle X-ray Scattering Method to Investigate the Crack Tip in Metals." Forschungszentrum Rossendorf, 2003. https://hzdr.qucosa.de/id/qucosa%3A21731.
Full textAbstract:
The work in this report, financed by the European Union through the Marie Curie Fellowship Association, was carried out at the FZ-Rossendorf. The subject of the research was to develop a method to investigate the damage, the high defect gradients at the tip of a ductile crack by means of Small Angle X-ray Scattering. The work explains the objectives and entails a brief introduction and background; it portrays and discusses the results which can be summarized as follows. Different damage parameters were investigated: the integral intensity, the total intensity on the detector, the anisotropy parameter and the fractal dimension. Of these, the anisotropy parameter is the most robust and most clearly depicts a damage region and the fractal dimension provides an idea of the structure of the scattering defect. The integral and total intensity provide comparable results only in some cases and are therefore not reliable. From supportive investigations: Scanning and Transmission Electron Microscopy (S-TEM), Finite Element Analysis and X-Ray Diffraction, it is suggested that the scatterer created after deformation is related to large oriented dislocation networks.
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Zhang, Mingqiang. "Morphological Characterization and Analysis of Ion-Containing Polymers Using Small Angle X-ray Scattering." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/77256.
Full textAbstract:
Small angle X-ray scattering (SAXS) has been widely used in polymer science to study the nano-scale morphology of various polymers. The data obtained from SAXS give information about sizes and shapes of macromolecules, characteristic distances of partially ordered materials, pore sizes, and so on. The understanding of these structural parameters is crucial in polymer science in that it will help to explain the origin of various properties of polymers, and guide design of future polymers with desired properties.
We have been able to further develop the contrast variation method in SAXS to study the morphology of Nafion 117CS containing different alkali metal ions in solid state. Contrast variation allows one to manipulate scattering data to obtain desired morphological information. At room temperature, only the crystalline peak was found for Na⁺-form Nafion, while for Cs⁺-form Nafion only the ionic peak was observed. The utilization of one dimensional correlation function on different counterion forms of Nafion further demonstrates the necessity of contrast variation method in obtaining more detailed morphological information of Nafion. This separation of the ionic peak and the crystalline peak in Nafion provides a means to independently study the crystalline and ionic components without each other's effect, which could be further applied to other ionomer systems.
We also designed time resolved SAXS experiments to study the morphological development during solution processing Nafion. As solvent was removed from Nafion dispersion through evaporation, solid-state morphological development occurred through a variety of processes including phase-inversion, aggregation of interacting species (e.g., ionic functionalities), and crystallization of backbone segments. To probe the real-time morphological development during membrane processing that accurately simulates industrial protocols, a unique sample cell has been constructed that allows for through-film synchrotron SAXS data acquisition during solvent evaporation and film formation. For the first time, this novel experiment allows for a complete analysis of structural evolution from solution/dispersion to solid-state film formation, and we were able to show that the crystallites within Nafion develop later than the formation of ionic domains, and they do not reside in the cylindrical particles, but are dispersed in solution/dispersion.
Besides bulk morphology of Nafion, we have also performed Grazing Incident SAXS to study the surface morphology of Nafion. We were able to manipulate the surface morphology of Nafion via neutralizing H⁺-form Nafion with different large organic counterions, as well as annealing Nafion thin films under different temperatures. This not only allows to obtain more detailed information of the nano-structures in Nafion thin films, but also provides a means to achieve desired morphology for better fuel cell applications.
We have also been able to study the polymer chain conformation in solution via measuring persistence length by utilizing solution SAXS. Different methods have been applied to study the SAXS profiles, and the measured persistence lengths for stilbene and styrenic alternating copolymers range from 2 to 6 nm, which characterizes these copolymers into a class of semi-rigid polymers. This study allows to elucidate the steric crowding effect on the chain stiffness of these polymers, which provides fundamental understanding of polymer chain behaviors in solution.
Self-assembling in block copolymers has also been studied using SAXS. We established a morphological model for a multiblock copolymer used as a fuel cell material from General Motors®, and this morphological model could be used to explain the origins of the mechanical and transport properties of this material. Furthermore, several other block copolymers have been studied using SAXS, which showed interesting phase separated morphologies. These morphological data have been successfully applied to explain the origins of various properties of these block copolymers, which provide fundamental knowledge of structure-property relationship in block copolymers.Ph. D.
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CHAVAN, HARSHAD S. "INVESTIGATION OF β-PHASE POLY (VINYLIDENE FLUORIDE) FILMS USING SMALL- ANGLE X-RAY SCATTERING." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145990710.
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Schroer, Martin [Verfasser]. "Small angle X-ray scattering studies on proteins under extreme conditions / Martin A. Schroer." Dortmund : Universitätsbibliothek Technische Universität Dortmund, 2011. http://d-nb.info/1018126767/34.
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Patel, Mushtaq. "Counterion distribution around a macroion in polyelectrolytes probed by anomalous small-angle X-ray scattering." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975952854.
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Skjønsfjell, Eirik Torbjørn Bakken. "Mapping Orientation Distribution of Talc Particles in Polypropylene by Small-Angle X-ray Scattering Tomography." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23619.
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Small-angle X-ray scattering tomography has for the first time been used toinvestigate the spatially resolved orientation distribution of talc particles in asample of injection molded isotactic polypropylene, where the particles had apreferred orientation along the axis of the injection. The scattering patternsin the direction perpendicular to the rotation axis of the tomography scanwere used to retrieve the orientation distribution in a 2D cross section of thesample.Two different methods are presented, one using a numerical approach ofsimulated annealing and one method using a linear set of equations to findthe distances the X-ray beam travels through the different orientation regions.The method of simulated annealing showed little to no promise inretrieving the orientation distribution while the method using a linear setof equations is successful at retrieving the main features of the orientationdistribution. The resolution is however not yet good enough to distinguishfine details inside the sample.It is believed that with further work on the model used and additional constraintson the reconstruction algorithm higher precision in the retrievedorientation distribution can be achieved.
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Hartl, Caroline [Verfasser], and Tim [Akademischer Betreuer] Liedl. "Characterization of DNA nanostructures with small-angle X-ray scattering / Caroline Hartl ; Betreuer: Tim Liedl." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1201274214/34.
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Pontoni, Diego. "Small-angle X-ray scattering studies of phase transitions and growth processes on colloidal dispersions." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271227.
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Jergel, M., P. Šiffalovič, K. Végsö, E. Majková, S. V. Roth, O. Konovalov, and H. Y. Lee. "Grazing-incidence Small-angle X-ray Scattering Technique for Probing Nanostructures and Processes at Nanoscale." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42696.
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The paper presents the grazing-incidence small-angle X-ray scattering technique and its application to the studies of self-assembly and re-assembly effects of colloidal nanoparticles. Two basic cases are exemplified - solvent evaporation driven self-assembly and self-assembly driven by barrier movement in the Langmuir-Blodgett trough. Studies of the nanoparticle re-assembly effects due to the surfactant removal
complete the overview. These examples document strength of GISAXS for an in situ tracking of processes at nanoscale. The results have direct implications for tailored preparation of the self -assembled nanoparticle templates for sensing, plasmonics and other applications.
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Mykhaylyk, O. O. "Structural Characterization of Colloidal Core-shell Polymer-based Nanoparticles Using Small-angle X-ray Scattering." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34779.
Full textAbstract:
Colloidal particle complexes are often characterized by small angle X-ray scattering (SAXS) techniques.
The present work demonstrates SAXS analysis of inhomogeneous core-shell nanoparticles with complex
shell morphologies. Different experimental techniques such as variation of particle composition and
contrast variation method, and analytical techniques such as Monte Carlo simulation and indirect Fourier
transformation are applied to obtain structural parameters of polymer-based core-shell nanoparticles. It is
shown that the SAXS results are consistent with other measurements performed by electron microscopy,
atomic force microscopy, dynamic light scattering, thermogravimetry, helium pycnometry and BET.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34779
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Zhao, Wenhan ZHAO. "SMALL ANGLE X-RAY SCATTERING AND RHEOLOGY STUDIES OF POLYISOBUTYLENE WITH OLIGO(ß-ALANINE) GRAFTS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1528983070278315.
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Pflüger, Mika. "Using Grazing Incidence Small-Angle X-Ray Scattering (GISAXS) for Semiconductor Nanometrology and Defect Quantification." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/22207.
Full textAbstract:
Hintergrund:
Die Entwicklung von Nanotechnologien und insbesondere integrierten Schaltkreisen beruht auf dem Verständnis von Struktur und Funktion auf der Nanoskala, wofür exakte Messungen erforderlich sind.
Kleinwinkel-Röntgenstreuung unter streifendem Einfall (GISAXS) ist eine Methode zur schnellen, berührungs- und zerstörungsfreien dimensionellen Messung von nanostrukturierten Oberflächen.
Ziele:
Es soll die Möglichkeit untersucht werden, die zunehmend komplexeren Proben aus Wissenschaft und Industrie mit Hilfe von GISAXS präzise zu vermessen.
Ein weiteres Ziel ist es, Messtargets aus der Halbleiter-Qualitätskontrolle mit einer Größe von ca. 40x40 µm² zu messen, deren Signal typischerweise nicht zugänglich ist, weil ein Bereich von ca. 1x20 mm² auf einmal beleuchtet wird.
Methoden:
Synchrotron-basierte GISAXS-Messungen verschiedener Proben werden mit Hilfe einer Fourier-Konstruktion, der "distorted wave Born approximation" und einem Maxwell-Gleichungs-Löser basierend auf finiten Elementen analysiert.
Ergebnisse:
Aus GISAXS-Messungen kann die Linienform von Gittern mit einer Periode von 32 nm rekonstruiert werden und sie weicht weniger als 2 nm von Referenzmessungen ab.
Eine sorgfältige Bayes'sche Unsicherheitsanalyse zeigt jedoch, dass wichtige dimensionelle Parameter innerhalb der Unsicherheiten nicht übereinstimmen.
Für die Messung von kleinen Gittertargets entwerfe ich ein neuartiges Probendesign, bei dem das Target in Bezug auf die umgebenden Strukturen gedreht wird, und stelle fest, dass dadurch parasitäre Streuung effizient unterdrückt wird.
Fazit:
GISAXS-Messungen von komplexen Nanostrukturen und kleinen Targets sind möglich, jedoch würde GISAXS enorm von effizienteren Simulationsmethoden profitieren, die alle relevanten Effekte wie Rauhigkeit und Randeffekte einbeziehen.
Hier gibt es vielversprechende theoretische Ansätze, so dass GISAXS eine zusätzliche Methode für die Halbleiter-Qualitätskontrolle werden könnte.Background. The development of nanotechnology such as integrated circuits relies on an understanding of structure and function at the nanoscale, for which reliable and exact measurements are needed. Grazing-incidence small angle X-ray scattering (GISAXS) is a versatile method for the fast, contactless and destruction-free measurement of sizes and shapes of nanostructures on surfaces. Aims. A goal of this work is to investigate the possibility of precisely measuring the increasingly complex samples produced in science and industry using GISAXS. A second objective is to measure targets used in semiconductor quality control with a size of approx. 40x40 µm², whose signal is typically not accessible because an area of approx. 1x20 mm² is illuminated at once. Methods. I take synchrotron-based GISAXS measurements and analyze them using reciprocal space construction, the distorted wave born approximation, and a solver for Maxwell's equations based on finite elements. Results. I find that the line shape of gratings with a period of 32 nm can be reconstructed from GISAXS measurements and the results deviate less than 2 nm from reference measurements; however, a careful Bayesian uncertainty analysis shows that key dimensional parameters do not agree within the uncertainties. For the measurement of small grating targets, I create a novel sample design where the target is rotated with respect to the surrounding structures and find that this efficiently suppresses parasitic scattering. Conclusions. I show that GISAXS measurements of complex nanostructures and small targets are possible, and I highlight that further development of GISAXS would benefit tremendously from efficient simulation methods which describe all relevant effects such as roughness and edge effects. Promising theoretical approaches exist, so that GISAXS has the potential to become an additional method in the toolkit of semiconductor quality control.