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Tesi sul tema "Small-angle light scattering"
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1
Dahlgren, Eric D. "Small angle light scattering analysis of tissue." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0111102-171921.
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2
Van, Heiningen Jan. "Ultra-small angle light scattering : apparatus design optimization." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84092.
Testo completoAbstract (sommario):
Ultra-small angle light scattering (USALS) is a technique used to probe large average spatial and temporal structure of soft condensed matter complementary to microscopy. Limited information is available on the design and features of a multi-speckle CCD-based USALS apparatus. The optics of such a setup are described followed by an optimization scheme involving ray tracing that can be used to choose the optimum lenses by taking into account the finite spot size due to lens aberrations, diffraction, and the CCD pixel size. Results of calculations of the optimization scheme are presented for a static light scattering (SLS) setup followed by a few experimental tests of our current apparatus.
3
Saito, Shin. "Light Scattering and Small-Angle Neutron Scattering Studies on Shear-Induced Structures in Semidilute Polymer Solutions." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150694.
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Schmidt, Nico [Verfasser]. "Phase transformation behaviour of polylactide probed by small angle light scattering / Nico Schmidt." Paderborn : Universitätsbibliothek, 2020. http://d-nb.info/1209601370/34.
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5
Mokhtari, Tahereh. "The effect of shear on colloidal aggregation and gelation studied using small-angle light scattering." Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/280.
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Kozan, Mehmet. "CHARACTERIZATION OF COLLOIDAL NANOPARTICLE AGGREGATES USING LIGHT SCATTERING TECHNIQUES." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/567.
Testo completoAbstract (sommario):
Light scattering is a powerful characterization tool for determining shape, size, and size distribution of fine particles, as well as complex, irregular structures of their aggregates. Small angle static light scattering and elliptically polarized light scattering techniques produce accurate results and provide real time, non-intrusive, and in-situ observations on prevailing process conditions in three-dimensional systems. As such, they complement conventional characterization tools such as SEM and TEM which have their known disadvantages and limitations. In this study, we provide a thorough light scattering analysis of colloidal tungsten trioxide (WO3) nanoparticles in the shape of irregular nanospheres and cylindrical nanowires, and of the resulting aggregate morphologies. Aggregation characteristics as a function of primary particle geometry, aspect ratio of nanowires, and the change in dispersion stability in various polar solvents without the use of dispersants are monitored over different time scales and are described using the concepts of fractal theory. Using forward scattered intensities, sedimentation rates as a result of electrolyte addition and particle concentration at low solution pH are quantified, in contrast to widely reported visual observations, and are related to the aggregate structure in the dispersed phase. For nanowires of high aspect ratios, when aggregate structures cannot directly be inferred from measurements, an analytical and a quasiexperimental method are used.
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Mokhtari, Tahereh. "Studies of the effects of shear on colloidal aggregation and gelation using small angle light scattering." Diss., Kansas State University, 2007. http://hdl.handle.net/2097/522.
Testo completoAbstract (sommario):
Doctor of Philosophy<br>Department of Physics<br>Christopher M. Sorensen<br>We investigated the effect of shear on the structure and aggregation kinetics of unstable
colloids using small angle light scattering. We used an aqueous suspension of 20 nm polystyrene
latex microspheres and MgCl[subscript]2 to induce aggregation. The sample was only sheared once for
approximately 33 sec at different times, typically 1 min, 5 min, or 15 min, after the onset of
aggregation. The average shear rate was in the range of 0.13 - 3.56 sec[superscript]−1 , which was in a laminar
regime. The unsheared sample gelled after ca. 45 min. When the sample was sheared soon after
the onset of aggregation, the aggregation followed the diffusion limited cluster cluster
aggregation (DLCA) kinetics to yield D[subscript f] = 1.80 [plus or minus] 0.04 aggregates unaffected by the shear. The
gel time also remained the same as the unsheared gel. Shearing at later stages of aggregation
shortened the gel time and enhanced the scattered light intensity significantly indicating rapid
growth. Then, depending on the shear rate, there were three different behaviors. At high shear
rates, the aggregate structure was inhomogeneous after the shear was stopped with a crossover in
slope in the scattered light intensity versus q, to imply hybrid superaggregates with two different
fractal dimensions. At intermediate shear rates far from the gel point, there was a similar
crossover after the shear was stopped; however, the fractal dimension regained 1.80 [plus or minus] 0.04 at the
gel point. At low shear rates, the aggregation rate was increased, but the aggregate structure was
uniform, and the fractal dimension remained 1.75 [plus or minus] 0.05.
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Mokhtari, Tahereh Mokhtari Tahereh. "Studies of the effects of shear on colloidal aggregation and gelation using small angle light scattering." Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/522.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Kansas State University, 2007.<br>Title from electronic thesis title page. Revision of master's thesis: The effect of shear on colloidal aggregation and gelation studied using small-angle light scattering. 2007. Includes bibliographical references.
9
Ade-Browne, Chandra. "Understanding Surfactant Skin Irritation by Probing the Relationship between the Structure and the Function of Micelles." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1523629545916627.
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Selomulya, Cordelia Chemical Engineering & Industrial Chemistry UNSW. "The Effect of Shear on Flocculation and Floc Size/Structure." Awarded by:University of New South Wales. Chemical Engineering and Industrial Chemistry, 2002. http://handle.unsw.edu.au/1959.4/18226.
Testo completoAbstract (sommario):
The effect of shear on the evolution of floc properties was investigated to analyse the flocculation mechanisms. Little fundamental attention has been given to the shear influence that often creates compact aggregates, while the floc characteristics might differ in other aggregating conditions. It is thus crucial to understand how flocs evolve to steady state, if their properties are to be 'tailored' to suit subsequent solids-liquid separation processes. In this work, flocculation of monodisperse latex particles of various sizes (60, 380, and 810 nm diameter) via electrolyte addition was carried out in a couette-flow and also in shear fields generated by an axial-flow impeller (Fluid foil A310) and a radial-flow impeller (Rushton R100) in standard mixing tanks. A small-angle light scattering technique was used to acquire information regarding the time variation of floc properties in a non-intrusive manner. The structure was quantified by a measure of fractal dimension, signifying the degree of floc compactness. Estimates of the average floc mass were also obtained from the aggregate scattering patterns. By monitoring the changes in floc structure and mass, corresponding to the size evolution; mechanisms of floc formation, fragmentation, and restructuring were identified. Aggregates of 60 and 380 nm particles were observed to grew larger initially, before decreasing to their equilibrium sizes at moderate shear rates (32 - 100 s-1) in a homogeneous shear environment. Floc restructuring at large length scales occurred extensively, and was responsible for the drop in size, particularly at the early stage of the process. Aggregates of 810 nm particles did not, however, display this behaviour. Flocs of larger primary particles were presumably susceptible to breakage rather than deformation, as they were weaker under comparable conditions. Denser aggregates were found when restructuring transpired, while comparatively tenuous flocs were observed when formation and breakage kinetics were the governing mechanisms. The disparity in floc behaviour at higher shear rates (246 s-1 - 330 s-1) was less apparent. The intense hydrodynamic stresses in those instances inevitably caused fragmentation, regardless of the intrinsic particle properties; hence the observed floc compaction was the product of break-up and re-aggregation. A population balance model, incorporating variation in floc structure, displayed comparable trends in size evolution; verifying that restructuring indeed took an important role under certain flocculation conditions. Similar phenomena were likewise observed with the flocculation in stirred tanks. The results reinforced findings in literature; that while circulation time controlled the process kinetics; the floc size was determined by the turbulent stresses. In addition, the maximum shear levels also influenced the floc structures, with denser aggregates produced in a shear field generated using the radial-flow impeller at equivalent energy dissipation per-unit mass. A correlation between non-dimensional floc factor that embodied the aggregate size and structure, and aggregation factor comprising the significant parameters from flocculation conditions, was proposed. The proposed relationship takes into account aspects such as the aggregate structure, interparticle forces, and particle concentration that are often overlooked in existing relationships, which usually only relate the maximum floc size to the applied energy dissipation rate. It thus provides an improved manner of presenting general flocculation data, as well as a means to predict floc properties produced under a specific aggregation condition. Future studies with increasingly complex systems that resemble real conditions are recommended in order to establish a practical understanding of the flocculation mechanisms, for the purpose of optimising the aggregate properties.
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Bastardo, Zambrano Luis Alejandro. "Self assembly of surfactants and polyelectrolytes in solution and at interfaces." Doctoral thesis, KTH, Ytkemi, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-425.
Testo completoAbstract (sommario):
This thesis focuses on the study of the interactions between polyelectrolytes and surfactants in aqueous solutions and at interfaces, as well as on the structural changes these molecules undergo due to that interaction. Small–angle neutron scattering, dynamic, and static light scattering were the main techniques used to investigate the interactions in bulk. The first type of polymer studied was a negatively charge glycoprotein (mucin); its interactions with ionic sodium alkyl sulfate surfactants and nonionic surfactants were determined. This system is of great relevance for several applications such as oral care and pharmaceutical products, since mucin is the main component of the mucus layer that protects the epithelial surfaces (e.g. oral tissues). Sodium dodecyl sulfate (SDS) on the other hand, has been used as foaming agent in tooth pastes for a very long time. In this work it is seen how SDS is very effective in dissolving the large aggregates mucin forms in solution, as well as in removing preadsorbed mucin layers from different surfaces. On the other hand, the nonionic surfactant n-dodecyl β-D-maltopyranoside (C12-mal), does not affect significantly the mucin aggregates in solution, neither does it remove mucin effectively from a negatively charge hydrophilic surface (silica). It can be suggested that nonionic surfactants (like the sugar–based C12-mal) could be used to obtain milder oral care products. The second type of systems consisted of positively charged polyelectrolytes and a negatively charged surfactant (SDS). These systems are relevant to a wide variety of applications ranging from mining and cleaning to gene delivery therapy. It was found that the interactions of these polyelectrolytes with SDS depend strongly on the polyelectrolyte structure, charge density and the solvent composition (pH, ionic strength, and so on). Large solvent isotopic effects were found in the interaction of polyethylene imine (PEI) and SDS, as well as on the interactions of this anionic surfactant and the sugar–based n-decyl β-D-glucopyranoside (C10G1). These surfactants mixtures formed similar structures in solutions to the ones formed by some of the polyelectrolytes studied, i.e. ellipsoidal micelles at low electrolyte concentration and stiff rods, at high electrolyte and SDS concentrations.<br>QC 20100901
12
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.
Testo completoAbstract (sommario):
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 protéine<br>Rhabdoviruses, 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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YOSHIDA, SHUNSUKE. "IN VITRO CHARACTERIZATION OF MESENCHYMAL STEM CELL-SEEDED TENDON IMPLANTS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1070550904.
Testo completo
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Siegemund, Thomas. "Structure and properties of drug-loaded polymeric nanoparticles targeting β-amyloid". Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-70212.
Testo completoAbstract (sommario):
Polymere Nanopartikel sind ein vielversprechender Ansatz für die Diagnose und Therapie von Krankheiten. Sie ermöglichen den Einsatz von schwerlöslichen oder instabilen Wirkstoffen. Ein weiterer Vorteil ist die Möglichkeit das Targetings, durch gezielte Modifikationen des Nanopartikels wird der Wirkstoff zum Zielort transportiert und kann dort in der gewünschten Form freigesetzt werden; dadurch könnten bei erhöhter Wirksamkeit die Nebenwirkungen von Medikamenten reduziert werden.
Ziel dieser Arbeit war die Untersuchung von physikalischen und biochemischen Eigenschaften von Nanopartikeln bestehend aus einem abbaustabilen Polystyren- Kern und einer biologisch abbaubaren Schale aus Polybutylcyanoacrylat. Es werden Methoden beschrieben, um die Größe, Struktur und den Abbau dieser Wirkstoffträger zu untersuchen. Die untersuchten Nanopartikel zeigen RAYLEIGH-Streuung, sowohl Größe als auch Abbau können durch Messung des Absorptionsspektrums bestimmt werden. Weiterhin konnten diese Eigenschaften mit Hilfe von dynamischer und statischer Lichtstreuung sowie Neutronenkleinwinkelstreuung untersucht werden. Bei letzterer Methode konnte gezeigt werden, dass die Schale größtenteils abgebaut werden kann, während der Kern intakt bleibt.
In einem weiteren Teil der Arbeit wurde die Überwindung der Blut-Hirn-Schranke durch polymere Nanopartikel untersucht. Dabei wurde der fluoreszierende Thioflavine als Modellwirkstoffe eingesetzt. Das Durchdringen der Blut-Hirn-Schranke konnte nur mit Nanopartikeln erreicht werden, an deren Oberfläche ein Apolipoprotein E-Peptid gekoppelt war. Es konnte gezeigt werden, das die Nanopartikelschale im Gehirn abgebaut wird, der Wirkstoff freigesetzt wird und an Amyloid β, einem Marker der Alzheimer-Krankheit, bindet.
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Hubbard, Joshua A. "A study of aerodynamic deaggregation mechanisms and the size control of NanoActive™ aerosol particles." Thesis, Kansas State University, 2006. http://hdl.handle.net/2097/173.
Testo completoAbstract (sommario):
Master of Science<br>Department of Mechanical and Nuclear Engineering<br>Steven J. Eckels<br>Christopher M. Sorensen<br>Large specific surface areas and high concentrations of reactive edge and defect sites make NanoActive™ metal oxide powders ideal chemical adsorbents. These powders are dispersed in aerosol form to remediate toxic wastes and neutralize chemical and biological warfare agents.
In the destructive adsorption of toxic chemicals, effective application requires particles be as small as possible, thus, maximizing surface area and number of edge and defect sites. Other applications, e.g. smoke clearing, require particles be large so they will settle in a timely manner. Ideally, particle size control could be engineered into powder dispersion devices. The purpose of this study was to explore particle cohesion and aerodynamic deaggregation mechanisms to enhance the design of powder dispersion devices.
An aerosol generator and four experimental nozzles were designed to explore the most commonly referenced deaggregation mechanisms: particle acceleration, particles in shear and turbulent flows, and particle impaction. The powders were then dispersed through the nozzles with increasing flow rates. A small angle light scattering device was used to make in situ particle size measurements. The nozzle designed for impaction deaggregated the NanoActive™ MgO particles to a lesser degree than the other three nozzles, which deaggregated the particles to a similar degree.
Flows in three of the four nozzles were simulated in a commercial computational fluid dynamics package. Theoretical particle and aggregate stresses from the literature were
calculated using simulated data. These calculations suggest particle acceleration causes internal stresses roughly three orders of magnitude larger than shear and turbulent flows. These calculations, coupled with experimental data, lead to the conclusion that acceleration was the most significant cause of particle deaggregation in these experiments.
Experimental data also identified the dependence of deaggregation on primary particle size and agglomerate structure. NanoActive™ powders with smaller primary particles exhibited higher resistance to deaggregation. Small primary particle size was thought to increase the magnitude of van der Waals interactions. These interactions were modeled and compared to theoretical deaggregation stresses previously mentioned.
In conclusion, deaggregation is possible. However, the ideas of particle size control and a universal dispersion device seem elusive considering the material dependent nature of deaggregation.
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Gallois, Charlotte. "Etude des propriétés physico-chimiques de suspensions de boehmite. Application aux supports catalytiques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066553/document.
Testo completoAbstract (sommario):
La poudre de boehmite, précurseur de l’alumine utilisée pour la production de supports catalytiques variés, est produite suite à une étape de séchage par atomisation. Cet oxyhydroxyde d’aluminium est composé de particules anisotropes chargées. Ces dernières années, il a été ont montré que les propriétés physico-chimiques des suspensions avaient une influence sur les caractéristiques des poudres. La morphologie des grains (sphère creuse, tore…) ainsi que les propriétés des poudres (dispersibilité, résistance mécanique…) peuvent être modifiées en jouant sur les caractéristiques des suspensions.Ce travail de thèse porte sur la compréhension des liens entre les propriétés physico-chimiques et rhéologiques de suspensions de deux boehmites industrielles et les propriétés des grains obtenus après séchage. Dans une première partie, nous avons caractérisé les particules en suspension de ces deux boehmites grâce à une approche multi-technique (SAXS, DLS, MET). Une étude rhéologique des suspensions obtenues par stress osmotique a ensuite permis de construire précisément le diagramme de phase de ces deux boehmites dans le plan force ionique – fraction volumique. La diffusion des rayons X aux petits angles et la diffusion dynamique de la lumière ont été utilisées pour déterminer l’organisation structurale des suspensions. Enfin, des expériences de séchage suivies optiquement et par micro-tomographie X ont été réalisées sur des suspensions de boehmite afin d’étudier l’impact de la concentration et de la force ionique sur l’évolution de la goutte au cours du séchage<br>In the catalyst supports industry, one important step of alumina powder production is the spray-drying of boehmite suspensions. This aluminium oxyhydroxyde is often used as precursor for various types of alumina catalyst supports. Boehmite is composed of anisotropic particles bearing an electric charge. In the past decade, it has been shown that the properties of the dry powder depend not only on the drying conditions but on physico-chemical properties of the sprayed suspensions. For instance, different grains morphologies (doughnut-shaped grains, hollow spheres,…) as well as various dry grains properties (textural properties, mechanical resistance,…) may be obtained by tuning the physico-chemical properties of the suspension.This study focus on the understanding of the links between the physico-chemical properties of suspensions of two industrial boehmites and the characteristics of the final dry grain. Since these two boehmites were not well-known, the first step of the study was to characterize boehmite particles present in suspension thanks to a multi-technical approach. A rheological study was performed on boehmite suspensions obtained thanks to osmotic stress to build precisely the phase diagrams of the both boehmites according to the system of ionic strength vs. volume fraction. Small angle X ray scattering and dynamic light scattering were used to investigate the existence of an orientational order of boehmite particles in suspension. Finally, drying experiments of boehmite suspensions were conducted on an optical set-up and on fast micro-tomography X, to examine the impact of both concentration and ionic strength on the evolution of the droplet during drying
17
Colard-Itté, Jean-Rémy. "Synthèses et études physico-chimiques de matériaux à base de moteurs moléculaires rotatifs photoactivables." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF044.
Testo completoAbstract (sommario):
Ce manuscrit décrit la synthèse d’un moteur moléculaire rotatif photoactivable. Il est montré que la molécule cible peut être intégrée dans un réseau de chaînes PEG, et que l’irradiation UV du matériau obtenu mène à sa contraction à macroscopique. Ces mouvements moléculaires collectifs permettent donc de convertir de l’énergie lumineuse pour produire un travail mécanique de huit ordres de grandeur au-delà de leur échelle. Une combinaison d’études de rhéologie et de diffusion de neutron a permis de définir les paramètres de formation de gels pour obtenir une contraction maximale, mais aussi l’observation expérimentale que la rotation des moteurs initie des enroulements de chaînes PEG, ce qui est responsable de la contraction du matériau. De plus, la synthèse d’une unité modulatrice et son intégration dans ces matériaux sont décrites. Les gels résultants présentent des propriétés de contraction réversibles et le caractère hors-équilibre de l’ensemble du système est ensuite discuté<br>This manuscript describes the gram-scale synthesis of a light-driven rotary molecular motor. It is shown that the target molecule can be integrated into a PEG chains network, and that the UV irradiation of the obtained material leads to its macroscopic contraction. These collective molecular movements are then able to convert light energy to produce a mechanical work of eight orders of magnitude beyond their scale. A combination of rheology and small angle neutron scattering studies defined the of gel formation parameters to obtain maximum contraction, but also the experimental observation that motor rotation initiates PEG chain windings, which is responsible of the contraction of the material.In addition, the synthesis of a modulator unit and its integration into these materials is described. The resulting gels present reversible contraction properties and the out-of-equilibrium behavior of the entire system is then discussed
18
McNamara, Joseph E. "Monte Carlo, small angle light scattering, and dynamic light scattering studies of dilute polymer solutions." 2005. https://scholarworks.umass.edu/dissertations/AAI3193925.
Testo completoAbstract (sommario):
The adsorption of negatively charged polymer, negative/neutral block copolymer and a polyampholyte to patterned surfaces is investigated using off-lattice Monte Carlo simulations. The surface is decorated by stripe and checkerboard patterns of mixed charges. The polymer has periodic charge segments, which potentially match the periodicity of the surface pattern. Results show that the chain entropy of a flexible polymer disrupts and prevents full pattern recognition. Quantities such as average adsorption energy and the radii of gyration of the adsorbed polymer are calculated and found to be dictated by the size of the surface pattern and its correlation to the polymer charge density. We performed small angle light scattering on dilute-solution-grown polyethylene crystals grown from quenches in para-xylene. The quench depths ranged from 60 to 85°C for 0.05 wt.% and 0.1 wt.% linear-low-polydispersity polyethylenes. We found asymmetric scattering patterns for the lower temperature quenches to 65°C, and symmetric scattering patterns for the higher temperature quenches to 80°C. There is a smooth transition from asymmetric to symmetric scattering as we change the quench depth. The correlation lengths d=2π/qmax corresponding to the peaks of intensity versus q ranged from 15 to 30 μm. We find evidence that these length scales correspond to assemblies of single polyethylene crystals. Also, we have performed dynamic light scattering on solutions of sodium-poly(styrene-sulfonate) (NaPSS) and poly(ethylene-oxide) (PEO) in water with BaCl2. The fast mode ( Dfast) and slow mode (Dslow) diffusion coefficients were measured as a function of polymer concentration for both polymers in dilute solution. We found that the diffusion coefficients remained relatively constant in the concentration regimes investigated and Dfast and Dslow for both polymers differed by about 1½ orders of magnitude: 1.1 × 10-6 cm2/s versus 7.8 × 10-8 cm2/s for NaPSS and 6.7 × 10-7 cm2/s versus 4.2 × 10-8 cm2/s for PEO. Also, we studied more concentrated solutions of PEO without salt and used Dfast and Dslow to calculate hydrodynamic radii of single and aggregated PEO chains. Using a concentration-dependent viscosity for PEO in water, we found single chain radii from 1 to 5 nm and aggregate radii from 45 to 60 nm.
19
tung, Hsiao yu, and 蕭有彤. "Calibration and Applications of Small Angle Light Scattering Measuring System." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/11639386475186531918.
Testo completoAbstract (sommario):
碩士<br>國立中正大學<br>化學工程研究所<br>101<br>Light scattering is widely used in various fields to probe the structural and dynamic properties of a wide range of materials. Light scattering is also a nondestructive testing process. The major advantage of SALS (Small angle light scattering) lies in its ability to provide structural information about disordered systems on micrometer scales. SALS is a particularly useful tool for studying polymer aggregation, biological systems and colloids, etc. This study aims at calibrating a homemade SALS apparatus and applying it to C60 solutions. The calibration was carried out using a pinhole as a sample (with a nominal diameter of 50±5 μm.) Afterwards, we tested the SALS apparatus by studying aqueous suspensions of polystyrene (PS) spheres with known size. Furthermore, we studied the aggregate properties of C60 in toluene or chlorobenzene by SALS, and confirmed the existence of micrometer-sized aggregate species in C60 solutions.
20
(8775689), Luis Palacio. "SMALL ANGLE SCATTERING OF LARGE PROTEIN UNITS UNDER OSMOTIC STRESS." Thesis, 2020.
Cerca il testo completoAbstract (sommario):
<div>Large protein molecules are abundant in biological cells but are very difficult to study in physiological conditions due to molecular disorder. For large proteins, most structural information is obtained in crystalline states which can be achieved in certain conditions at very low temperature. X-ray and neutron crystallography methods can then be used for determination of crystalline structures at atomic level. However, in solution at room or physiological temperatures such highly resolved descriptions cannot be obtained except in very few cases. Scattering methods that can be used to study this type of structures at room temperature include small-angle x-ray and neutron scattering. These methods are used here to study two distinct proteins that are both classified as glycoproteins, which are a large class of proteins with diverse biological functions. In this study, two specific plasma glycoproteins were used: Fibrinogen (340 kDa) and Alpha 1-Antitrypsin or A1AT (52 kDa). These proteins have been chosen based on the fact that they have a propensity to form very large molecular aggregates due to their tendency to polymerize. One goal of this project is to show that for such complex structures, a combination of scattering methods that include SAXS, SANS, and DLS can address important structural and interaction questions despite the fact that atomic resolution cannot be obtained as in crystallography. A1AT protein has been shown to have protective roles of lung cells against emphysema, while fibrinogen is a major factor in the blood clotting process. A systematic approach to study these proteins interactions with lipid membranes and other proteins, using contrast-matching small-angle neutron scattering (SANS), small angle x-ray scattering (SAXS) and dynamic light scattering (DLS), is presented here. A series of structural reference points for each protein in solution were determined by performing measurements under osmotic stress controlled by the addition of polyethylene glycol-1,500 MW (PEG 1500) in the samples. Osmotic pressure changes the free energy of the molecular mixture and has consequences on the structure and the interaction of molecular aggregates. In particular, the measured radius of gyration (Rg) for A1AT shows a sharp structural transition when the concentration of PEG 1500 is between 33 wt\% and 36 wt\%. Similarly, a significant structural change was observed for fibrinogen when the concentration of PEG 1500 was above 40 wt\%. This analysis is applied to a study of A1AT interacting with lipid membranes and to a study of fibrinogen polymerization in the presence of the enzyme thrombin, which catalyzes the formation of blood clots. The experimental approach presented here and the applications to specific questions show that an appropriate combination of scattering methods can produce useful information on the behavior and the interactions of large protein systems in physiological conditions despite the lower resolution compared to crystallography.</div>
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Liu, Cheng-Ping, and 劉正平. "Dynamic Light Scattering and Small Angle Neutron Scattering from Dilute and semi-dilute Poly(vunyl alcohol)-Borax-D2O Solution." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83119005031869522727.
Testo completoAbstract (sommario):
碩士<br>元智大學<br>化學工程研究所<br>88<br>Dynamic Light Scattering and Small Angle Neutron Scattering
from Dilute and Semi-dilute
Poly(vinyl alcohol)-Borax-D2O Solutions
Student：Cheng-Ping Liu Advisor：Dr. T.L. Yu
Institute of Chemical Engineering Yuan-Ze Iniversity
Abstract
Poly (vinyl alcohol) forms di-diol complex with borate ion in aqueous solution. In dilute solution, the di-diol complex is formed through intra-molecular crosslinking reaction. In semidilute or high PVA concentrations where the polymer molecules entangle with each other, the di-diol complex forms both through intra- and inter-molecular crosslinking. The formation of H-bond through the -OH functional group is another important factor for the formation of PVA-borax-complex in aqueous solutions. The aggregation of PVA molecules through H-bond causes the formation of clusters. The conformation of PVA-borax complex in aqueous solution is controlled by the following factors：(1) polymer excluded volume effect; (2) intra- and inter- molecuded crosslink through H-bond formation and borate ion di-diol complex formation; (3) charge repulsion among the negative charged borate ions bound on PVA molecules; (4) the screen effect of free Na+ positive ion on the negative charge of PVA-borate complex ; (5) H-bond and cluster formation through intra- and inter-molecular reaction. In this study we report the fractal dimensions, and the correlation length or radius of PVA-borate-D2O complex in dilute and semidilute solution by dynamic light scattering and small angle neutrun scattering.
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Doncom, K. E. B., Anaïs Pitto-Barry, H. Willcock, A. Lu, B. E. McKenzie, N. Kirby, and R. K. O'Reilly. "Complementary light scattering and synchrotron small-angle X-ray scattering studies of the micelle-to-unimer transition of polysulfobetaines." 2015. http://hdl.handle.net/10454/15384.
Testo completoAbstract (sommario):
Yes<br>AB and ABA di- and triblock copolymers where A is the hydrophilic poly(oligoethylene glycol methacrylate) (POEGMA) block and B is a thermo-responsive sulfobetaine block [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (PDMAPS) were synthesised by aqueous RAFT polymerisation with narrow dispersity (ĐM ≤ 1.22), as judged by aqueous SEC analysis. The di- and triblock copolymers self-assembled in salt-free water to form micelles with a PDMAPS core and the self-assembly of these polymers was explored by SLS and TEM analysis. The micelles were shown, by DLS analysis, to undergo a micelle-to-unimer transition at a critical temperature, which was dependent upon the length of the POEGMA block. Increasing the length of the third, POEGMA, block decreased the temperature at which the micelle-to-unimer transition occurred as a result of the increased hydrophilicity of the polymer. The dissociation of the micelles was further studied by SLS and synchrotron SAXS. SAXS analysis revealed that the micelle dissociation began at temperatures below that indicated by DLS analysis and that both micelles and unimers coexist. This highlights the importance of using multiple complementary techniques in the analysis of self-assembled structures. In addition the micelle-to-unimer morphology transition was employed to encapsulate and release a hydrophobic dye, Nile Red, as shown by fluorescence spectroscopy.<br>Engineering and Physical Sciences Research Council (EPSRC), University of Warwick
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Chou, Che-Min, and 周哲民. "Studies on Structural Formation of Polymer Physical Gels by Time-Resolved Small-Angle Light Scattering." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/37046658366203704939.
Testo completoAbstract (sommario):
博士<br>國立臺灣科技大學<br>高分子工程系<br>92<br>Gelation is the phase transition from a collection of finite clusters to a state with the formation of an infinite network. The essential physical feature of a gel is its geometrical connections, and hence theoretical progress generally emphasizes percolation phenomena to gelation theory. In addition to this, an even more noteworthy subject is the nature and formation of network junctions in physical gels. Thermoreversible physical gel is a three-dimensional network of polymer chains cross-linked by physical junctions, and it can arise either as the result of a phase transition or through some specific molecular association or as a result of entanglements. In the present study, we confine our attention to the case of gels associated with phase transition. Physical gels passing through phase transition are especially complex systems; and it is generally accepted that the gelation is typically governed by the coupling of several phase transitions like the liquid-liquid phase separation, the crystallite formation of the polymer chain segments, and percolation phenomena. However, the complexity introduced by these coupling mechanisms has limited theoretical progress largely to purely phenomenological approaches, resulting in difficulties to explain fully in terms of gelation phenomena.
Most studies of gelation behaviors have focused on phase behavior, structural morphology, and rheological properties in physical gels. Experimentally, there is a lack of data on the dynamics of the gelation process, which may be attributed to both the complex nature of the gelation phenomena and practical difficulties in real-time observation of structural development of physical gels. By using the time-resolved small angle light scattering (TRSALS) technique, we present the first real-time measurement of the physical gelation process for a crystalline polymer. The finding is that the light scattering patterns show a unique feature in the Hv and the Vv scattering for PVDF gel electrolytes. To investigate the growth kinetics, a complete picture of the gel structural formation should be differentiated into, the nucleation and growth of the microgels, the diffusive aggregation of the microgels, the percolation in cluster-cluster aggregation process, and the late-stage coarsening by Ostwald ripening process. We propose some phenomenological functions to describe the hierarchical structure of the nucleation gels. The modeling of the late-stage gel structure could be built upon following three relevant categories, the structure of the primary particle, the nonfractal local structure of a random packing of the nearest neighbors, and the fractal correlations between the particles constituting the aggregates. The model is able to reproduce the overall behavior of Hv and Vv scattering intensity distributions over the experimental -range, and holds the truth of the gel structural development in the late-stage coarsening process. It is clear that the experimental results are entirely different from the general concept of “spinodal gels” and also imply that the spontaneous concentration fluctuation by spinodal decomposition is not a prerequisite for the formation of the large-scale heterogeneous gels. In contrast with spinodal gels, now we call it nucleation gels.
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Jiang, Ming-Yu, and 江茗妤. "Studies on Network Structure of Agarose Hydrogels by Time-Resolved Small-Angle Light Scattering Analysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/eu3g3z.
Testo completoAbstract (sommario):
碩士<br>國立臺灣科技大學<br>材料科學與工程系<br>102<br>Time-resolved small-angle light scattering (TRSALS) is an important technique to study the temporal spatial complexity of soft matter on a mesoscopic length scale. In this thesis, from the Hv scattering and time-trace rheological experiments ,we suggest that the molecules should exhibits a worm-like chain with the single helix conformation in sol state and show that the gelation process of the agarose hydrogel can be divide into three stages:
(i) the structural fluid stage (t < tnucl)
(ii) the ripening stage(tnucl < t < taging), the fibrillar network is formation, but the structure and properties are continued enhancement.
(iii) the aging stage (t > taging), no true equilibrium network was observed, the result is consistent with our previous studies that the fibrillar network is a polycrystalline off- equilibrium configuration.
On the other hand, although the Vv scattering does show a ring pattern in gelation process, our detailed analysis rejects the early opinion that the agarose gelation is induced by the spinodal decomposition or by the fractal aggregation. Moreover, we suggest that the network structure of the agarose hydrogel is characterized by a scale-free network. Thus, there is room for reconsidering the current opinion on the formation mechanism of the fibrillar networks. At this point, our coherent structure model is a good starting point in the description of the phenomenon or process.
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Hsu, Di-Yao, and 許迪堯. "Studies on Phase Separation of Poly(ethylene glycol)/Poly(ethylene glycol-ran-propylene glycol) Mixtures by Time-Resolved Small-Angle Light Scattering." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/80688218540134114659.
Testo completoAbstract (sommario):
博士<br>國立臺灣科技大學<br>材料科學與工程系<br>104<br>During the past decades, many remarkable results have been achieved in the phase separation of polymer mixtures, especially for the spinodal decomposition, while the small-angle light scattering (SALS) plays an important role. In view of the improvement of scattering technique and subsequent data analysis, we have enough ability to study the complex phase separation behavior of PEG/PEG-ran-PPG polymer mixtures by using time-resolved small-angle light scattering apparatus.
In this study, since involving different area researches of phase separation, we will focus on the following topics:
(1) Thermodynamics and phase diagram of PEG/RAN mixture: in the temperature-traced turbidity experiments, the boundary of the phase separation can be approximation by the cloud point. However, in order to avoid the artificial distortion, we prefer to use the slice of τ-ϕ profile to analyze the “coexistence points”. Then, we use the Flory-Huggins lattice theory and melting point depression to calculate the coexistence, spinodal, and melting curves, respectively. On the other hand, time-traced peak position q_m is measured by using SALS, while the corresponding growth exponent α can define the kinetic transition to get percolation line. Here, we consider the reason why the percolation line is asymmetric with the diameter, and try to obtain an accurate phase diagram.
(2) Ultra-fast hydrodynamic coarsening in near-critical quench: we have mentioned that the growth exponent for the percolation region is higher than the hydrodynamic coarsening (α>1), which depending on the temperature, composition, and sample thickness; moreover, we also found the existence of double structures. Inasmuch as the wetting effect in our system, we consider the double structures are represented the structures of bulk and surface phases, respectively. However, the preliminary result shows that the prediction seems not to be correct, and these two structures are 3D growth.
(3) Validity of dynamic scaling hypothesis in off-critical quench: since the percolation spinodal decomposition (PSD) region is narrower than the spinodal region, it will inevitably heighten the importance of the droplet spinodal decomposition (DSD) region. In this chapter, we consider the validity of “dynamic scaling hypothesis”, that is, the structural evolution can be scaled by a single length parameter, in the process of DSD structural evolution; however, we believe that it does not hold here. There are several reasons, such as more than one length parameters, the formation of double structures, and the extinction effect of the scattered lights by large droplets (the so-called anomalous diffraction problem). Finally, we try to propose an alternative method to reduce the structure factor of DSD structure, and also superimpose the ultra-wide q-range scattering profiles. We hope to develop an exact scattering modeling for a quantitative analysis of the DSD structure in the future.
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Saldanha, Oliva. "Tracking Assembly Kinetics of Intermediate Filaments." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3E14-3.
Testo completo
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Bogomolova, Anna. "Samoorganizace ve směsích surfaktantů a polymerů s komplexní strukturou citlivých ke změně vnějšího prostředí." Doctoral thesis, 2015. http://www.nusl.cz/ntk/nusl-334588.
Testo completoAbstract (sommario):
Title: Self-assembly in mixture of surfactants and stimuli-responsive polymers with complex architecture Author: Anna Bogomolova Department: Physical and Macromolecular Chemistry Supervisor: PhD. Sergey K. Filippov, IMC AS CR, v.v.i. Supervisor's e-mail address: filippov@imc.cas.cz Abstract: The issue of construction of complex multi-block copolymers is currently one of the most researched areas. It became a logic consequence of the continuous development in polymer chemistry. Nowadays, a great interest is attracted to multi- responsive block copolymers. As a rule, they consist of hydrophilic, hydrophobic and responsive blocks. That responsive block can be either thermo-sensitive or pH-sensitive as well as sensitive to some other external stimuli. In the present work, we will try to cover topic of stimuli-responsive block copolymers and their interactions with different types of surfactants. Understanding of polymer/surfactant interactions can be a crucial step for future modeling of drug/polymer or protein(DNA)/surfactant interactions. There is a great interest in the investigation of polymer-surfactant interactions. However, while the homopolymer-surfactant interactions are characterized well enough, the same interactions for block copolymers are poorly described. The main development in the latter topic...
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Siegemund, Thomas. "Structure and properties of drug-loaded polymeric nanoparticles targeting β-amyloid". Doctoral thesis, 2010. https://ul.qucosa.de/id/qucosa%3A11216.
Testo completoAbstract (sommario):
Polymere Nanopartikel sind ein vielversprechender Ansatz für die Diagnose und Therapie von Krankheiten. Sie ermöglichen den Einsatz von schwerlöslichen oder instabilen Wirkstoffen. Ein weiterer Vorteil ist die Möglichkeit das Targetings, durch gezielte Modifikationen des Nanopartikels wird der Wirkstoff zum Zielort transportiert und kann dort in der gewünschten Form freigesetzt werden; dadurch könnten bei erhöhter Wirksamkeit die Nebenwirkungen von Medikamenten reduziert werden.
Ziel dieser Arbeit war die Untersuchung von physikalischen und biochemischen Eigenschaften von Nanopartikeln bestehend aus einem abbaustabilen Polystyren- Kern und einer biologisch abbaubaren Schale aus Polybutylcyanoacrylat. Es werden Methoden beschrieben, um die Größe, Struktur und den Abbau dieser Wirkstoffträger zu untersuchen. Die untersuchten Nanopartikel zeigen RAYLEIGH-Streuung, sowohl Größe als auch Abbau können durch Messung des Absorptionsspektrums bestimmt werden. Weiterhin konnten diese Eigenschaften mit Hilfe von dynamischer und statischer Lichtstreuung sowie Neutronenkleinwinkelstreuung untersucht werden. Bei letzterer Methode konnte gezeigt werden, dass die Schale größtenteils abgebaut werden kann, während der Kern intakt bleibt.
In einem weiteren Teil der Arbeit wurde die Überwindung der Blut-Hirn-Schranke durch polymere Nanopartikel untersucht. Dabei wurde der fluoreszierende Thioflavine als Modellwirkstoffe eingesetzt. Das Durchdringen der Blut-Hirn-Schranke konnte nur mit Nanopartikeln erreicht werden, an deren Oberfläche ein Apolipoprotein E-Peptid gekoppelt war. Es konnte gezeigt werden, das die Nanopartikelschale im Gehirn abgebaut wird, der Wirkstoff freigesetzt wird und an Amyloid β, einem Marker der Alzheimer-Krankheit, bindet.
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Delisavva, Foteini. "Asociace polymerů s amfifilními sloučeninami (surfaktanty) ve vodných roztocích." Doctoral thesis, 2017. http://www.nusl.cz/ntk/nusl-371354.
Testo completoAbstract (sommario):
Title: Self-assembly of polymers with amphiphilic compounds (surfactants) in aqueous solutions Abstract: This PhD Thesis is devoted to the co-assembly in systems containing electrically charged polymers (polyelectrolytes and block copolymers containing polyelectrolyte sequences). I studied the interactions between block copolymers and oppositely charged surfactants in aqueous solutions, and the structure and properties of co-assembled nanoparticles by a combination of several experimental methods. I found that the spontaneous formation, solubility and stability of complex nanoparticles depend not only on the electrostatic attractive forces but also on the hydrophobic effects. In a major part of my Thesis, I studied the interaction of polyelectrolytes with oppositely charged gemini surfactants (containing two charged head-groups interconnected by a short linker and two hydrophobic tails) which is a relatively new topic - much less studied than the co-assembly with conventional single tail surfactants. Better understanding of the formation and properties of complexes containing gemini surfactants and polymers provides knowledge that should lead to novel tailor-made nanoparticles with desired properties for applications in medicine and new technologies (including nano-technologies). We have shown that the...