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Seigenfuse, Matthew David. "Lamellar / Woven database." Master's thesis, Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/94139.
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KinesiologyM.S.
INTRODUCTION: Pubertal growth is an important time during development for bone accrual and attainment of peak bone mass. Suboptimal bone gain has been observed in females with reproductive abnormalities such as primary and secondary amenorrhea and these conditions are very prevalent in female athletes. Amenorrhea is associated with decreased estradiol levels. Previous research has shown that in prepubertal animals a low estrogen environment significantly decreased mechanical strength, but there was no significant loss in bone area and actually an increase in moment of inertia. The decrease in mechanical properties may be related to the microstructure of the bone. Two types of bone are involved in growth-- woven bone, which is added for structural support in the short term, and lamellar bone , which is highly organized and has a greater contribution to overall strength. We will test the hypotheses that suppressed estradiol will result in bones with no change in cortical area and decreased strength properties but will have a larger composition of non lamellar bone as opposed to lamellar bone. PURPOSE: The goal of this study was to determine the relative amounts of woven and lamellar tissue in a bone and the relationship with the bone's mechanical strength in two models of low estrogen-- pre- and post-pubertal onset. METHODS: Fifty-Five female Sprague-Dawley rats were randomly assigned into four groups: a control group (n=14) and three experimental groups injected with gonadotropin releasing-hormone antagonist (GnRH-a)-- the Dose 1 group was injected with 1.25 mg/kg/dose daily (n=14), the Dose 2 was injected with 2.5 mg/kg/dose daily (n=14), and the Dose 3 group was injected with 5.0 mg/kg/dose, 5 days per week (n=13). All groups were sacrificed at Day 49. Additionally, twenty-nine Sprague Dawley rats were randomly assigned into three groups. The baseline day 65 group (BL 65) was sacrificed on day 65 (n=9). There was an aged match control group that was sacrificed on day 90 (n=12). Finally, there was an AMEN experiment group injected with 2.5 mg/kg/dose daily that was sacrificed on day 90 (n=9). All experimental groups for both protocols received injections of gonadotropin releasing hormone antagonists (GnRH-a) (Zentaris GmbH) intraperitoneally. Left femora were mechanically tested under 3-point bending. The right femora were dehydrated, embedded in polymethylmethacrylate, cut and ground to 100 µm thickness. Bones were analyzed under polarized light using Stereo Investigator Software (MBF Bioscience, VT). The proportion of the cortex with primary lamellar vs. non-lamellar/other primary tissue type was measured and expressed as percent of the total cortical bone area. Outcome measures included lamellar endocortical area, lamellar periosteal area, cortical area, endocortical area, % lamellar area and % non-lamellar area. RESULTS: There was a significant decrease (p<.05) in the distribution of lamellar versus non-lamellar cortical tissue type in the experimental group in the model of delayed puberty. Additionally, the pre-pubertal bones had a lower percentage of lamellar periosteal and endocortical area. The post-pubertal group showed no significant differences between the control and experimental group in any of the outcome measures. CONCLUSION: There were significant differences in relative bone distribution throughout the femoral cortex. Relative decreases in lamellar tissue distribution, especially on the periosteal surface, will result in decreased mechanical strength due to increased percentage of woven bone in pre-pubertal models.
Temple University--Theses
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Mohamed, Bragheeth Mohamed Abd El-Naby. "Lamellar corneal refractive surgery." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403907.
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Hill, Patricia Grace. "Properties of lamellar metal thiophosphates." Thesis, Kingston University, 1999. http://eprints.kingston.ac.uk/20630/.
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Castiglione, Andrea. "Liquid crystalline macromolecular architectures based on regioregular poly(3-alkylthiophene) as backbone and calamitic mesogens as side-groups : towards ambipolar materials." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066693.
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Très récemment, le potentiel des semi-conducteur organiques (OSC) ambipolaires à attiré l'attention par de nombreuses applications technologiques. Dans le domaine de la microélectronique organique, l'un des obstacles majeurs pour le développent des OSC est le design de systèmes capables de transporter à la fois les électrons et les trous. Les matériaux semi-conducteurs ambipolaires ordonnés, peuvent répondre à cette problématique. Dans ce contexte nous avons développé la synthèse et la caractérisation d'une architecture macromoléculaire originale, fondée sur l'association d'un polymère semi-conducteur régiorégulier d'une part, avec des molécules ?-conjuguées cristal liquides ayant la propriété de s'auto-organiser spontanément d'autre part. Afin d'améliorer les propriétés mésomorphes et électroniques de ce système macromoléculaire, une gamme de composés différant par (i) la nature chimique du groupement pendant et (ii) le dégrée de polymérisation moyen du polymère à été synthétisée. La présence d'une mesophase a été confirmée pour chacun de ces composés par diffraction des rayons X et une mesophase de type lamello-lamellaire, présentant une alternance de couches électron-donneur ou électron-accepter à également pu être mis en évidenceVery recently ambipolar organic semi-conductors (OSC) have gaining attention for their potential use in numerous technologically relevant applications. Representative technological examples are the area of organic microelectronics where patterning of p- and n-channel semiconductors is one of the major hurdles for the implantation of OSC in organic complementary logic circuit. To achieve this objective, well-ordered ambipolar semiconducting materials are needed. In this work we investigated the self-organization and the electronic properties of a series of side chain liquid crystal (SCLC) semiconducting polymers where: (i) the backbone is a π-conjugated polymer and (ii) the side-groups are π-conjugated calamitic mesogens. We present our results on the design, synthesis, and structural characterization of this new liquid crystal regioregular poly(3-alkylthiophene) polymer family post-functionalized with side-on calamitic moieties. The parameters of these materials are: (i) the chemical nature of the side-group moieties and (ii) the degree of polymerization. As a result we will show that this strategy leads to the supramolecular self-assembly of this SCLC semiconducting polymer in a peculiar lamello-lamellar mesophase, where the two different lamellas present two different electronic properties, such as electron donor and electron acceptor behaviors
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Poulos, Andreas-Stavros. "Lyotropic lamellar phases doped with polyoxometalates." Paris 11, 2008. http://www.theses.fr/2008PA112357.
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Les systèmes hybrides organiques-inorganiques sont actuellement l'objet d'une grande attention parce qu'ils peuvent combiner les propriétés électroniques des matériaux inorganiques avec les propriétés d'autoassemblage des molécules organiques. Nous avons formulé un tel système, en associant des nanoparticules de polyoxométallates (POMs) avec une phase lamellaire Iyotrope. La diffusion de rayons X et la microscopie en lumière polarisée ont démontré que ce système hybride, très chargé en POMs, est un nanocomposite de structure lamellaire cristal-liquide (La), avec des propriétés viscoélastiques proches de celles des gels. L'interprétation des données de rayons X suggère fortement que les POMs sont localisés près des groupements -OH terminaux du tensio-actif, dans la couche aqueuse. De plus, le système présente du photochromisme réversible, associé à la photoréduction de l'anion polyoxométallate. D'un point de vue plus fondamental, ces matériaux hybrides peuvent servir comme modèles pour étudier les propriétés statiques et dynamiques des nanoparticules confinées dans des phases lamellaires. Ainsi, la diffusion de rayons X a été utilisée pour étudier l'effet du confinement sur le potentiel d'interaction entre les particules. En outre, nous avons mesuré les coefficients de diffusion des particules, en utilisant la RMN en gradient de champ. Nous avons démontré que le coefficient de diffusion est très réduit dans la phase, ce qui confirme la forte interaction entre les particules et la bicouche. Finalement, des expériences simples ont permis l'étude des propriétés rhéologiques du systèmeOrganic-inorganic hybrid systems have recently attracted a lot of attention. They can potentially combine the electronic properties of inorganic materials with the self-assembly properties of organic molecules. We have developed such a hybrid system, in which polyoxometallate nanoparticles (POMs) are inserted between the bilayers of a Iyotropic lamellar phase. X-ray scattering and polarized light microscopy demonstrate that these hybrid materials, highly loaded with POMs, are nanocomposites of liquid-crystalline lamellar structure (La), with viscoelastic properties reminiscent of those of gels. The interpretation of X-ray scattering data strongly suggests that the POMs are located close to the terminal -OH groups of the nonionic surfactants, within the aqueous sublayers. Moreover, these materials exhibit a reversible photochromism associated to the photoreduction of the polyoxometallate anion. From a more fundamental point ofview, these hybrid materials can serve as models for the study ofboth static and dynamic properties of nanoparticles confined within soft lamellar structures. X-ray scattering was used to study the effect of confinement on the interparticle interaction potential. Furthermore, pulsed-field gradient NMR was used to measure the translational diffusion coefficients of the POMs as a function of the inter-bilayer distance. It was demonstrated that the dynamics of the particles are significantly slowed down, and, thus, that they strongly interact with the bilayer. Finally, sorne simple experiments were done to determine the rheological behaviour of the system in question
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Ha, Yung-Hoon Sam 1975. "Hierarchical layered-silicate-- lamellar triblock copolymer nanocomposites." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29969.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2003.Includes bibliographical references.
The fundamental role of the layered-silicates in a styrene-butadiene-styrene triblock copolymer (SBS) as a function of layered-silicate dispersion during deformation was investigated. Predominantly immiscible composites of mixed morphology provided the initial proof that dramatic alteration of the SBS deformation behavior exists, but a clear understanding of the nature of reinforcement was precluded due to the fiber symmetric orientation of the SBS and the mixed clay morphologies. Following the theory of Vaia and Giannelis, use of a more hydrophobic organically modified clay resulted in an intercalated morphology with a near single crystalline texture of the SBS due to roll-casting. Significant heterogeneous deformation was observed at ambient conditions as well as at elevated temperature as verified through Cohen's affine deformation model in combination with Kratky's scattering pattern model. The intercalated morphology shows little or modest mechanical property enhancements at all temperatures studied. Exfoliated nanocomposite was produced by functionalization of the clay surfaces with polystyrene, altering the enthalpic interactions. Entropic interactions were also controlled by varying the molecular weight of the surfactant and the grafting density and shows remarkable agreement with the theory proposed by Balazs et al. Due to the increase surface volume ratio of the clay, a flipping transition of the block copolymer morphology was observed during roll-casting producing a near single crystalline parallel/parallel clay/BCP orientation. The modulus was relatively unaffected whereas the toughness increased significantly due to an earlier onset of strain hardening.
by Yung-Hoon Sam Ha.
Ph.D.
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Buchanan, Mark. "Dynamics of interfaces in surfactant lamellar phases." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/13235.
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The hydrophilic and hydrophobic properties of surfactant molecules enable them to organise in large structures when dissolved in water. Under certain conditions they can organise in bilayers forming the lamellar phase. The equilibrium properties of this phase have been well studied. In this study we observe the dynamic and kinetic behaviour during the swelling and dissolution of the lamellar phase. We have performed penetration scan experiments under different thermodynamic conditions using video microscopy. When the lamellar phase is insoluble in water classic myelin instabilities are observed. These instabilities have been studied with microscopy and in some cases we use tracer particles to follow fluid flow in between the myelins. We report qualitative features of the myelin growth as well as provide some quantification of the swelling process. Specifically, we determine an effective diffusion coefficient for the swelling lamellar phase. In the case of a soluble lamellar phase myelin instabilities are not observed. Also, we report instabilities observed at the liquid surfactant/lamellar interface. These instabilities appear to create multilayer vesicles which move into the liquid surfactant. We have found these to be attached to the surface of a wedge of lamellar phase that moves along the surface of the cell into the liquid surfactant phase. Also, we have conducted contact experiments using a presheared lamellar phase the so called “onion” texture. The onion phase does not form myelins as in the normal case. Instead the onions dissolve into an isotropic (“sponge”) phase. During the onion dissolution a small stable core remains. If the sample is observed over a more extended period the onions are observed to coalesce. These features were investigated at different temperatures.
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Bogahawatta, Vimarsha. "CO2 Adsorption on Polyethylenimine-Impregnated Lamellar Silica." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41557.
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The increasingly stringent environmental regulations worldwide demand the use of efficient methods for air purification. Moreover, the alarming effect of greenhouse gases on the world climate requires the removal and sequestration of large quantities of anthropogenic carbon dioxide (CO2). This work is contributed towards the development of efficient, amine-containing, lamellar structured silica adsorbents for CO2 removal. Seven different materials were prepared by impregnation of various amounts of PEI, over as synthesized, or partially extracted or calcined lamellar silica. Materials were characterized by powder XRD and SEM. CO2 adsorption capacity was measured by thermogravimetry.
The effects of PEI loading, temperature, CO2 partial pressure and surface alkyl chains were investigated. PEI seems to be dispersed better in a consistent surface alkyl chain network, leading to enhanced CO2 uptake. VB-13, the material with 50 wt% of PEI, recorded the highest CO2 uptake at 75 °C, in the presence of both 15% CO2/N2 and 100% CO2 with values of 3.02 and 3.50 mmol/g respectively. The optimum temperature for CO2 uptake was found to be 75 °C for samples with high PEI loading. Moreover, higher uptake was recorded in the presence of 100% CO2 versus 15% CO2/N2 for all temperatures.
Another objective of this study was to investigate the effect of humidity on the CO2 adsorption process. In that case use of the column-breakthrough technique coupled with mass spectrometry to discriminate between CO2 and water was considered. Complete understanding of the technique and the different effects of moisture on CO2 adsorption over amine-containing materials, namely promotion of CO2 uptake and stabilization of the adsorbent, were achieved, based on a thorough scrutiny of the literature. Nonetheless, because of the Covid-19 pandemic and several technical issues, some experiments could not be undertaken.
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Theodorou, Antri. "Mixed surfactant lamellar phases : studies under shear." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/mixed-surfactant-lamellar-phases-studies-under-shear(4ac8336d-5747-4f45-8735-cdd8613e16e3).html.
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'Structured liquid' detergent products have received much attention as a means of providing liquid detergent compositions with special rheological and other properties. These include the ability to suspend particles and storage stability at ambient temperatures. The challenge is to prevent separation of the product into two or more layers (which requires a high viscosity) while controlling the rheology to allow a sufficient ease of pouring acceptable to the consumer. Liquid laundry detergent compositions are generally formulated with a variety of active ingredients, typically one or more anionic surfactants, often in combination with a nonionic surfactant and detergent builder materials such as electrolytes. The microstructure of these 'liquids' (determined by the product formulation, process conditions and procedures) strongly influences the macroscopic properties such as rheology. In this work, the microstructure, rheology and aging of a range of model structured liquid have been studied. The model systems are complex aqueous mixtures of sodium alkylbenzene sulphate (LAS), sodium alkyl ether sulphate (SLES) and primary alcohol ethoxylate (NEODOL 25-7). The dependence of the phase microstructure on sample composition was investigated by added different amount of electrolyte (tri-sodium citrate, TSC) in the model system. The physical appearance of these systems varied from transparent to milky depending on the concentration of the electrolyte. All were viscous 'gels'. Optical microscopy and SAXS have been used to elucidate the basic microstructure, its variation with electrolyte concentration and temperature on the angstrom to micrometer length scale. Deuterium nuclear magnetic resonance (2H NMR) spectroscopy on 2H2O-enriched samples has been used to provide information about the phase behaviour of the liquid crystalline systems. Changes in spectral line shape and water quadrupole splittings are presented and discussed as a function of sample composition, temperature and aging process. The shear-alignment process of the lamellar microstructure has been examined including Linkam optical shear cell, AR 2000 rheometer and 2H Rheo-NMR. A variety of rheological patterns including simple stress sweeps and oscillatory rheology have been investigated and provided information about the effect of shear, shear time and nature of deformation of the model structured liquids. In this context, the relaxation kinetics of the shear-induced structures has been investigated using 2H Rheo-NMR spectroscopy.
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Castiglione, Andrea. "Liquid crystalline macromolecular architectures based on regioregular poly(3-alkylthiophene) as backbone and calamitic mesogens as side-groups : towards ambipolar materials." Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066693.
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Très récemment, le potentiel des semi-conducteur organiques (OSC) ambipolaires à attiré l'attention par de nombreuses applications technologiques. Dans le domaine de la microélectronique organique, l'un des obstacles majeurs pour le développent des OSC est le design de systèmes capables de transporter à la fois les électrons et les trous. Les matériaux semi-conducteurs ambipolaires ordonnés, peuvent répondre à cette problématique. Dans ce contexte nous avons développé la synthèse et la caractérisation d'une architecture macromoléculaire originale, fondée sur l'association d'un polymère semi-conducteur régiorégulier d'une part, avec des molécules ?-conjuguées cristal liquides ayant la propriété de s'auto-organiser spontanément d'autre part. Afin d'améliorer les propriétés mésomorphes et électroniques de ce système macromoléculaire, une gamme de composés différant par (i) la nature chimique du groupement pendant et (ii) le dégrée de polymérisation moyen du polymère à été synthétisée. La présence d'une mesophase a été confirmée pour chacun de ces composés par diffraction des rayons X et une mesophase de type lamello-lamellaire, présentant une alternance de couches électron-donneur ou électron-accepter à également pu être mis en évidenceVery recently ambipolar organic semi-conductors (OSC) have gaining attention for their potential use in numerous technologically relevant applications. Representative technological examples are the area of organic microelectronics where patterning of p- and n-channel semiconductors is one of the major hurdles for the implantation of OSC in organic complementary logic circuit. To achieve this objective, well-ordered ambipolar semiconducting materials are needed. In this work we investigated the self-organization and the electronic properties of a series of side chain liquid crystal (SCLC) semiconducting polymers where: (i) the backbone is a π-conjugated polymer and (ii) the side-groups are π-conjugated calamitic mesogens. We present our results on the design, synthesis, and structural characterization of this new liquid crystal regioregular poly(3-alkylthiophene) polymer family post-functionalized with side-on calamitic moieties. The parameters of these materials are: (i) the chemical nature of the side-group moieties and (ii) the degree of polymerization. As a result we will show that this strategy leads to the supramolecular self-assembly of this SCLC semiconducting polymer in a peculiar lamello-lamellar mesophase, where the two different lamellas present two different electronic properties, such as electron donor and electron acceptor behaviors
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Hellström, Kristina. "Density variations during solidification of lamellar graphite iron." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-37869.
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Senapati, Sephalika. "Evolution of Lamellar Structures in AL-AG Alloys." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3067.
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In the present study, the formation and the evolution of lamellar structures in different Al-Ag alloys were investigated by transmission electron microscopy (TEM). Plates of the hexagonal [gamma] phase form semi-coherently on the {111} planes of the face centered cubic lattice of the alloy after the formation of Guinier-Preston zones. Guinier-Preston zones are metastable coherent preprecipitates which are silver rich in the aluminum-rich Al-Ag alloys. The decomposition of aluminum rich Al-Ag alloys, particularly the sequence of the later stages of precipitate formation was studied. With scanning electron microscopy and high-resolution transmission electron microscopy the development of the [gamma] phase was investigated. Samples cut from different Al-Ag alloys were homogenized at temperatures between 530 degrees C to 560 degrees C to obtain a single phase f.c.c solid solution. The samples were then quenched to room temperature, followed by heat treatments at temperatures between 140 degrees C and 220 degrees C for varying lengths of times. While Guinier-Preston zones increase in diameter with increasing aging duration, silver rich platelets of the [gamma] phase form. The [gamma] phase is the next metastable phase in the decomposition sequence before finally the [gamma] phase transforms to the stable silver-rich phase, termed [gamma]. For samples with silver contents above 12 at.% a parallel lamellar alignment of fine [gamma] plates and Alrich matrix is found after extended heat treatments. For all alloys with Ag concentrations below 12 at.% individual [gamma] plates are found on all four possible (111) planes of the [alpha] matrix. A method is presented to calibrate the medium-magnification high-angle annular dark-field contrast in scanning transmission electron microscopy. This calibration allows for the quantitative measurement of plate thicknesses from high-angle annular dark-field scanning transmission electron micrographs of Ag2Al plates inclined to the electron beam. Results from these measurements are in good agreement with direct bright-field micrographs of plates viewed edge-on.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science and Engineering
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Yang, Jing. "Fatigue crack propagation threshold in lamellar TiAl alloys." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5620/.
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In the present study, the effect of lamellar spacing, volume fraction of equiaxed gamma grains and lamellar orientation on fatigue crack propagation threshold have been assessed for three as-cast γ-TiAl alloys, Ti45Al2Mn2Nb1B (4522XD), Ti45Al2Mn2Nb (4522) and Ti46Al8Nb (at %). The influence of alloying elements, Nb and Ta on fatigue threshold was also studied with five forged alloys, Ti45Al2Mn2Nb1B, Ti45Al2Nb2Ta1B, Ti45Al2Mn2Ta1B, Ti45Al2Mn4Ta1B and Ti45Al2Mn4Nb1B. The fatigue crack propagation threshold tests were carried out at 650°C in air at a stress ratio R=0.1 and frequency of 10HZ. In addition, the microstructural characterisation of fatigue crack growth fracture surface was also examined by SEM. The samples assessed for fatigue crack propagation threshold failed mainly by translamellar fracture and interlamellar fracture. Interlamellar cracking occurs in lamellar colonies at any lamellar orientation at high stress intensity factor, ΔK, while at low ΔK cracking occurs in lamellar colonies only when the lamellar interface is parallel to the fracture plane. Therefore, the fracture behaviour is determined by both lamellar orientation and ΔK. The fatigue crack propagation threshold shows little sensitivity to lamellar spacing and volume fraction of equiaxed gamma grains with 4522XD variants in the studied range.
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Clapp, Paula Jean 1968. "Visible-light induced reactions in lamellar phospholipid assemblies." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282185.
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Cyanine photosensitizers are visible-light absorbing dyes commercially useful in photography and available in a variety of structures with tunable redox, absorptivity and excited state properties. The areas of research described in this dissertation all utilize cyanine dyes to photosensitize various processes to visible-light within the confines of lamellar phospholipid assemblies. In Chapter III, an efficient three component, liposome-bound photochemical molecular device for transfer of energy and electrons is described. A porphyrin (free base or metallated) serves as the energy donor, a cyanine functions as the energy acceptor/electron acceptor and Ph₃BnB- acts as an electron donor. In Chapter IV, the first example of visible-light sensitized bilayer polymerization is presented. Sensitizing the polymerization of two-dimensional lipid assemblies to visible-light is part of a current research effort to exploit the properties of polymerized supramolecular structures. Extending the polymerization sensitivity of such amphiphile aggregates to lower energy visible-light creates possibilities for applications where UV photolysis would not be useful. Applications of liposomes as drug delivery vehicles thus far have relied upon such release mechanisms as pH sensitivity or target specific interactions to empty the liposome contents to the cell. Chapter V describes a new system for the successful destabilization of liposomes at pH 4.5 via visible-light sensitive polymerization of lipids. Visible-light sensitized polymerization induces the release of liposome aqueous contents providing temporal and spatial control over the release event and lower energy irradiation with more tissue penetration than UV photolysis.
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Li, Jianxiong. "The lamellar structure and deformation mechanisms of [beta]-polypropylene." Click to view the E-thesis via HKUTO, 1997. http://sunzi.lib.hku.hk/hkuto/record/B31237368.
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李建雄 and Jianxiong Li. "The lamellar structure and deformation mechanisms of {221}-polypropylene." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31237368.
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Khairullah, Noor Hasnah Mohamed. "Preparation and characterisation of polymeric lamellar substrate particles (PLSP)." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252022.
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Wilkins, Georgina Mary Heather. "Characterisation of a lyotropic lamellar phase under shear flow." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426847.
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Jimenez, Palomar Ines. "Mechanical properties of bone at the sub-lamellar level." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8471.
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Bone is a complex fibrous biological nanocomposite material optimized to avoid catastrophic failure and to perform a variety of mechanical functions, most notably load bearing. The fracture behaviour of bone is expected to be controlled by the various structural features present across the many existing hierarchical length scales. Micron sized bone lamellae present the simplest composite unit in bone consisting of mineralized collagen fibrils within a protein matrix, with some work suggesting that this length scale dominates the fracture of whole bone. However, the synergy between the bone components even at these relatively small length scales is poorly understood. The aim of this work is to therefore examine the mechanical properties of bone at length scales where the bone material itself can be considered as a composite material. To achieve this, discrete volumes of bone corresponding to the sub-lamellar unit were mechanically tested using an in situ Atomic Force Microscope (AFM) while monitoring using Scanning Electron Microscope (SEM). The elastic modulus of sub-lamellar bone units mechanically tested by the AFM in a bending configuration within the SEM was shown to be similar in both wet and SEM vacuum conditions, indicating that the SEM vacuum is insufficiently strong to drive off water from hydrated bone samples at lamellae length scales. AFM-SEM mechanical testing was extended to determine the structural effects of collagen fibril orientation in bone sub-lamellar units on both elastic modulus and fracture. Final experiments examined small scale mechanical properties of osteoporotic Mechanical Properties of Bone at the Sub-lamellar Level Queen Mary University of London 3 bone, with results highlighting how osteoporosis has little effect on the strength of the bone material but lowers the elastic modulus. This work therefore highlights the use of small scale mechanical testing using AFM and SEM to determine the influence of structural organization, specifically collagen fibril orientation, and compositional changes induced by osteoporosis on resultant bone material behaviour.
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Cracknell, Roger Francis. "Monte Carlo and theoretical studies of aqueous lamellar systems." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47827.
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Perkins, John Dillard. "Mid-infrared optical absorption in undoped lamellar copper oxides." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12228.
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Schmitt, Anke [Verfasser]. "Creep behavior of lamellar FeAl/FeAl2 alloys / Anke Schmitt." München : Verlag Dr. Hut, 2020. http://d-nb.info/121947844X/34.
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Triantafillou, Jim Carleton University Dissertation Engineering Mechanical and Aerospace. "The Creep behaviour of lamellar near gamma-titanium aluminides." Ottawa, 1996.
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Li, Jianxiong. "The lamellar structure and deformation mechanisms of b-polypropylene /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18865410.
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Meklesh, Viktoriia. "Effect of confined polymer on the properties of lyotropic lamellar mesophases." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE024/document.
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Cette thèse porte sur l'effet de l'incorporation du polymère adsorbant polyéthylène glycol (PEG) sur les propriétés structurelles et élastiques des mésophases lamellaires lyotropes. En particulier, ces phases lamellaires dopées au polymère sont d'un grand intérêt pour la compréhension des interactions inter-membranaires médiées par la macromolécule. Dans un premier temps, le module élastique de courbure des membranes a été étudié le long de plusieurs lignes de dilution de polymère. Il a été obtenu à partir des mesures des couplages quadrupolaires par spectroscopie de résonance magnétique nucléaire (RMN) à l'état solide de deutérium des molécules de cotensioactif perdeuteré incorporée dans la membrane. En présence du polymère adsorbé, nous avons constaté que la valeur du module élastique de courbure augmentait d'environ 20% dès que la solution de polymère était semi-diluée. Deuxièmement, nous discutons le coefficient de diffusion du polymère dans l'eau et confiné dans la phase lamellaire. La structure des mésophases a été étudiée par diffusion aux petits angles par rayons X et par microscopie électronique après cryofracture. Finalement, les mesures directes du module de compressibilité des mésophases lamellaires ont également été réaliséesThis thesis deals with the effect of the incorporation of the adsorbing polymer polyethylene glycole (PEG) on the structural and elastic properties of lyotropic lamellar mesophases. In particular, these polymer doped-lamellar phases are of great interest for understanding the intermembrane interactions mediated by the macromolecule. Firstly, the bending elastic modulus of the membranes has been investigated along several dilution lines of polymer. It was obtained from the measurements of quadrupolar splittings by deuterium solid state Nuclear Magnetic Resonance (NMR) spectroscopy of the perdeuterated cosurfactant molecule embedded in the membrane. In the presence of the adsorbed polymer the value of the bending elastic modulus was found to increase of about 20% as soon as the polymer solution becomes semi-diluted. Secondly, the diffusion coefficient of the polymer in water and confined in the lamellar phase is discussed. The structure of the mesophases was investigated by small angle X-ray scattering and freeze-fracture electon microscopy. Finally, the direct measurements of the compressibility modulus of the lamellar mesophases were also carried out
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Wang, Yanhui. "Hybridization of lamellar oxides : from insertion to in situ synthesis." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAE037/document.
Full textAbstract:
Dans cette thèse, nous avons développé l'utilisation de l'activation microondes pour fonctionnaliser des pérovskites lamellaires et notamment la phase d'Aurivillius Bi2SrTa2O9 (BST), connue pour ses propriétés ferroélectriques. Nous sommes parvenus à protoner cette phase (HST) et à la fonctionnaliser par diverses amines et polyamines, avec des temps de réaction considérablement réduits par rapport aux fonctionnalisations en conditions classiques. Cette approche nous a permis de fonctionnaliser HST par des amines plus encombrées et plus complexes. Cette stratégie a ensuite été étendue au greffage d'alcools et de polyols. Nous avons également établi une stratégie de modification post-synthèse, pour synthétiser in situ la molécule désirée, en utilisant la chimie "click" et l'activation microondes. Enfin, nous sommes parvenus à insérer des ions métalliques et des complexes de métaux de transition, ce qui constitue une première étape vers la synthèse de nouveaux hybrides multiferroïquesDuring this PhD thesis, we have developed the use of microwave activation to functionalize layered perovskites, among which the Aurivillius phase Bi2SrTa2O9 (BST), known for its ferroelectric properties. We managed to protonate this phase (leading to HST) and to functionalize it by various amines and polyamines, with reaction times much shorter than using classical conditions. This approach allowed us to functionalize HST by bulkier and more complex amines. This strategy has further been extended to the grafting of alcohols and polyols. We have also established a postsynthesis modification strategy, in order to synthesize the desired molecule in situ, within the interlamellar space, using "click" chemistry and microwave activation. Finally, we managed to insert transition metal ions and complexes, which constitutes a promising step towards the synthesis of new multiferroic hybrid materials
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Dutton, Helen Marie. "The behaviour of surfactant lamellar and gel phases under flow." Thesis, University of Manchester, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529230.
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Myers, Randall T. (Randall Todd) 1972. "Grains and grain boundaries in lamellar styrene--butadiene block copolymers." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85277.
Full text
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Oda, Reiko. "X-ray diffraction study of a three-component lamellar phase." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38037.
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Patel, Manish. "Morphological stability of lamellar structures in γ-TiAl based alloys." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/844309/.
Full textAbstract:
Two gamma-TiAl alloy groups were the subject of this investigation. From the first group, Ti-40Al-5Mn and Ti-40Al-10Mn alloy ingots, produced by cold-hearth plasma arc melting were characterised using light and electron microscopy and XRD. Their dendritic microstructures comprised of alpha2/gamma lamellar areas and single-phase gamma, beta and Laves (Mn2Ti) grains or precipitates. The lamellar alpha2/gamma Volume fraction was less in the Ti-40Al-10Mn alloy, due to the influence of its higher Mn content. The alloys were heat treated at 1200°C for 4 hours, resulting in nearly lamellar and duplex microstructures in the Ti-40Al-5Mn and Ti-40Al-10Mn alloys, respectively, hi both cases, the lamellar colonies contained poorly formed, discontinuous alpha2 lamellae. Raising the heat treatment temperature to 1300°C provided both alloys with fully lamellar microstructures with well formed, linear and continuous alpha2 lamellae. From the second alloy group, the Ti-47Al-4(Nb, Mn, Cr, Si, B) alloy known as gamma-TAB, was produced as hot isostatically pressed billets. Its microstructure comprised of some "feathery" lamellar colonies and single phase gamma-matrix. Unique phases based on Ti-B and Ti-Si were identified as being TiB and Ti5Si3, respectively. The boride stringers were profusely spread in the microstructure, whereas the Ti5Si3 was very elusive and found only once in TEM analysis. Heat treatment at 1400°C for 6 hours resulted in a fully lamellar Ti-47Al-4(Nb, Mn, Cr, Si, B) alloy with wide interlamellar spacing and greater gamma lamellae volume fraction; however the lamellar morphology was generally linear and continuous. In order to assess microstructural and lamellar morphological stability of the fully lamellar alloys, isothermal ageing at 800°C for durations of 500, 1000, 1500 and 2000 hours was conducted. Major microstructural changes took place in the Ti-Al-Mn alloys, whereby Ostwald ripening of alpha2 agglomerates and beta grains in the early stages, gave way to Laves phase lamellae and grains in the latter stages of ageing. This was more extensive in the Ti-40Al-10Mn alloy due to phase equilibrium requirements, whereby more of the alpha2/gamma lamellar content was eliminated. However, the specific resilience of alpha2 lamellae was inferior in the Ti-40Al-5Mn, as greater serration, fragmentation and termination migration within lamellar regions was witnessed. Termination migration within lamellar regions was considered as being independent to termination migration of the colony boundaries, which was distinguished as recession or contraction of the lamellar region, with an equivalent extension of the gamma-matrix. Boundary splitting was not precisely seen, but must have been the precursor to termination migration. In the Ti-47Al-4(Nb, Mn, Cr, Si, B) alloy, no Ostwald ripening of alpha2 agglomerates or formation of beta or Laves phases was observed. The gamma-matrix did progressively extend to eliminate alpha2/gamma lamellar grains to some degree, and gamma lamellae coarsened profoundly. Fragmentation and termination migration of alpha2 lamellae was more prominent after 1500 hours ageing. Mean interlamellar spacing (lambda) and coarsening ratio (r) increased the most in the Ti-40Al-5Mn alloy, due to the extent of alpha2 lamellar fragmentation and termination migration, followed by the Ti-47Al-4(Nb, Mn, Cr, Si, B) and Ti-40A1-10Mn alloys, respectively. Modes of morphological evolution that had not taken place during thermal ageing in all alloys studied, were direct cylinderisation, edge spheroidisation and discontinuous coarsening. Overall, the Ti-47Al-4(Nb, Mn, Cr, Si, B) alloy provided the best model for development of gamma-TiAl alloys with enhanced morphological stability, if issues such as the low alpha2 phase volume fraction and coarse gamma lamellae could be resolved. The role of silicon in gamma-TiAl alloys also needs to be examined, and whether it has any bearing on lamellar morphological stability.
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Dal, Corso Francesco. "Cracks, Shear Bands and Lamellar Inclusions in Homogeneously Prestressed Materials." Doctoral thesis, Università degli studi di Trento, 2009. https://hdl.handle.net/11572/368338.
Full textAbstract:
Localized deformation patterns are experimentally observed to prelude failure in many ductile materials (such as metal, alloy, granular material and plastic) and in quasi–brittle materials (such as concrete and rock). Moreover,
the presence of a second phase in composites may promote failure due to stress concentrations at the inclusion boundaries.
In order to investigate shear bands nucleation, propagation and interaction with a second phase or a defect, analytical solutions for an infinite nonlinear elastic solid subject to a uniform far–field deformation increment are obtained
for the following types of inclusion:
i) A crack, revealing features related to the interaction between shear bands and crack tip fields. This solution is also fundamental to the understanding of the shear band problem;
ii) A rigid line inclusion, the so-called ‘stiffener’, showing the emergence of shear bands at the stiffener tips in highly deformed ductile materials. For null prestress the solution is shown to match correctly with photoelastic
experiments and to predict the fracture patterns for a brittle material containing a stiffener;
iii) A pre–existing shear band, showing that the deformation is highly focussed and aligned coaxial to the shear band and the energy release rate to blow up to infinity, for incremental loading occurring when the prestress approaches the elliptic boundary, so that the propagation becomes ‘unrestrainable’.
All these analytical results substantiate the experimental observations that shear bands emerge at the inclusion tips and they are preferential near-failure deformation modes.
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Dal, Corso Francesco. "Cracks, Shear Bands and Lamellar Inclusions in Homogeneously Prestressed Materials." Doctoral thesis, University of Trento, 2009. http://eprints-phd.biblio.unitn.it/71/1/Dal_Corso_PHD_thesis.pdf.
Full textAbstract:
Localized deformation patterns are experimentally observed to prelude failure in many ductile materials (such as metal, alloy, granular material and plastic) and in quasi–brittle materials (such as concrete and rock). Moreover,
the presence of a second phase in composites may promote failure due to stress concentrations at the inclusion boundaries.
In order to investigate shear bands nucleation, propagation and interaction with a second phase or a defect, analytical solutions for an infinite nonlinear elastic solid subject to a uniform far–field deformation increment are obtained
for the following types of inclusion:
i) A crack, revealing features related to the interaction between shear bands and crack tip fields. This solution is also fundamental to the understanding of the shear band problem;
ii) A rigid line inclusion, the so-called ‘stiffener’, showing the emergence of shear bands at the stiffener tips in highly deformed ductile materials. For null prestress the solution is shown to match correctly with photoelastic
experiments and to predict the fracture patterns for a brittle material containing a stiffener;
iii) A pre–existing shear band, showing that the deformation is highly focussed and aligned coaxial to the shear band and the energy release rate to blow up to infinity, for incremental loading occurring when the prestress approaches the elliptic boundary, so that the propagation becomes ‘unrestrainable’.
All these analytical results substantiate the experimental observations that shear bands emerge at the inclusion tips and they are preferential near-failure deformation modes.
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Shearman, Gemma Claire. "X-ray structural studies of the stability of charged lamellar mesophases." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419859.
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Tzianetopoulou, Theodora 1974. "Micro-and macromechanics of single crystal and polygrannular lamellar block copolymers." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42293.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaves 181-186).
Block copolymers (BCPs) are a relatively new class of thermoplastic elastomers. Their macromolecular chain consists of covalently bonded repeating blocks of thermoplastic and elastomeric molecular chains. When given the thermodynamic freedom, the chain constituents phase separate into domains of various morphologies with sizes that can range between ten to hundreds of nanometers. BCPs are in essence nanocomposites with chemically bonded interfaces. As such, their mechanical behavior is consistent both with that of elastomers, and of thermoplastics. Due to this unique behavior, BCPs are among the most popular polymeric materials with diverse commercial applications that cover a number of industries. Furthermore, BCPs are emerging as instrumental for the future of nanotechnology as an increasing number of new techniques and applications seek to utilize their nanostructural features. BCPs, whether as polycrystalline configurations or as "highly" oriented single-crystals, attract an accumulating number of applications, and the increasing demand for efficient material design and product development extends over a range of length scales. Hence, there exists a need for continuum models that will predict both the oriented as well as the polycrystalline response of block-polymer materials to generic loading conditions. This thesis presents a general micromechanical framework for the derivation of large-strain continuum constitutive models for hyperelastic materials with layered micro- or macro-structures. The framework was implemented for the case of oriented (single-crystal) lamellar BCPs with Neo-Hookean phase behavior, and an analytical continuum model was derived for their large-strain hyperelastic response.
(cont.) The model was used to study the behavior of styrene-butadiene-styrene (SBS) triblock polymers, the behavior and micromechanics of which have been extensively investigated experimentally. Micromechanical unit-cell calculations were used as direct parallels to experimental (x-ray, microscopy, and stress-strain) data in order to verify the model's predictions. The presented continuum model describes the stress and deformation response of an oriented microstructure accurately, and was further implemented in multigranular numerical studies for the mechanical behavior of polycrystalline lamellar configurations. Simulations of the polycrystal structures reveal the manner in which the individual grains collectively deform and interact with each other to accommodate the macroscopic deformation. These results reveal the key roles of interlamellar shearing, lamellar dilation, rotation, and buckling.
by Theodora Tzianetopoulou.
Ph.D.
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Fan, Yin Ph D. Massachusetts Institute of Technology. "Self-assembly and selective swelling in Lamellar block copolymer photonic gels." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87534.
Full textAbstract:
Thesis: Ph. D. in Polymer Science and Technology, Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Materials with responsive structural color have broad applications ranging from sensing to smart coating. Nature provides inspirations for the design of such materials. Mimicking the structure of the skin elements responsible for cephalopod's fast camouflage, we made photonic gels using lamellar block copolymer (BCP) films. Diblock copolymer poly(styrene-b-2-vinylpyridine) (PS-P2VP) of symmetric composition self-assembles into alternating PS and P2VP layers parallel to the substrate after solvent vapor annealing. In solvents that are selective to P2VP, the P2VP layers swell while the PS layers remain glassy. The glassy PS layers restrict the lateral expansion of the P2VP layers, and therefore the swelling of P2VP layers occurs only along the direction normal to the layer surface. The 1D swelling turns the lamellar BCP film into a Bragg stack comprised of alternating gel and glass layers, which reflects light in the visible regime. The BCP gels display responsive structural color to a variety of stimuli triggered by the swelling/deswelling of the gel layers, and can be used to indicate changes in the solution properties of the gel block in the selective solvent. The thesis first looks into developing temperature-responsive or thermochromic photonic gels. The first example is a PS-P2VP/acetic acid photonic gel. P2VP has a temperature-dependent basicity and its swelling ratios in acetic acid solutions vary with temperature as degrees of protonation change. The PS-P2VP/acetic acid photonic gels showed blue-shifts in the reflection color at high temperatures which can be tuned by acid concentration, valency and counterion species. The second example of temperature-responsive photonic gels is PS-P2VP/ cyclohexane. The PS - cyclohexane pair has an upper critical solution temperature (UCST) and the photonic gel's structural color red-shifts at high temperature. The temperature dependence can be tuned by the molecular weight of the PS-P2VP. Next we show that the PS-P2VP photonic gels are also responsive to the composition of alcohol-water co-solvents. A model based on Flory-Huggins mixing and line defect network strain energy quantitatively relates the photonic gel's reflectivity to the Flory-Huggins interaction parameter X between P2VP and the co-solvent and the average defect density. The results indicate that the edge and screw dislocation line defects in lamellar self-assembly serve to create an interconnected network of glassy PS layers that restrict the selective swelling and hence the photonic response. The co-solvent quality responsive photonic gels provide a method to measure the Flory-Huggins y parameter and the defect density in the lamellar BCP film. Proteins can form ionic complexation with polyelectrolytes. The P2VP block in the lamellar PS-P2VP is converted into a polycation QP2VP by quatemization reactions. The ionic complexation between proteins and QP2VP triggers the swelling/deswelling of the QP2VP gel block, which changes the structural color of the lamellar PS-QP2VP photonic gels. We demonstrate that counterion coacervation as a novel mechanism to trigger the photonic responses of the BCP gels. Exposure to aqueous solutions of proteins alters the swelling ratios of the QP2VP gel layers in the PS-QP2VP gels due to the ionic interactions between proteins and the polyelectrolyte block. The real-time photonic responses of the PS-QP2VP gels are characterized by the reflective spectra recorded as a function of time and are related to the dynamic swelling behaviors of the QP2VP gel layers in protein solutions. The results suggest that the BCP gels and their associated structural colors provide a fast and visually interpretable method to differentiate different proteins due to their differences in size and charge.
by Yin Fan.
Ph. D. in Polymer Science and Technology
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Diaz, Mesa Ivonne Marcela. "Studies of some lamellar inorganic host compounds and their organic intercalates." Thesis, Kingston University, 2014. http://eprints.kingston.ac.uk/28760/.
Full textAbstract:
For many years organic conducting polymers have been used for electronic and photonic applications. Although there are many advantages of using these sorts of polymers, their poor environmental stability is still an issue that needs further investigation. Intercalation of organic polymer into the interlayer space of inorganic host materials is an effective way of producing well organised nanocomposites with properties that can be used for various industrial applications, including the production of electronic devices which are environmentally more stable. The preparation of a number of luminescent semiconducting nanocomposites of manganese phosphorus trisulphide (MnPS3), cadmium phosphorus trisulphide (CdPS3) and vanadyl phosphate (VOP04) containing the organic polymer poly(phenylene vinylene ) (PPV) by intercalation is herein described along with the characterisation by thermogravimetric analysis (TGA), infrared (IR) and raman spectroscopy, and X ray diffraction (XRD). In addition to this we used scanning electron microscopy (SEM) to monitor the physical changes in crystallinity of the host materials. An average increase of 5.05 A in the interlayer distance was observed through XRD, a strong indicator of intercalation of the polymer. It was also found that the environmental stability of the composites was enhanced in comparison with PPV alone by doing fluorescence analysis. Moreover, electrical conductivity studies showed that the composites presented higher conductivity relative to the constituent inorganic hosts.
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Pirisola, Isaac. "Maximising resource efficiency for the manufacture of lamellar based consumer products." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2003579/.
Full textAbstract:
The work disseminated within this Thesis pertain to an industrially funded study whose primary aims were to enhance the understanding of the effect of a range of process variables on the underlying microstructure of a rinse-off Hair Conditioner. The study utilised a range of analytical techniques namely; rheology, microscopy, SAXS and thermal transition. Findings herein have demonstrated that through process optimisation, more resource efficient processes are achievable which offer the possibility to significantly reduce raw materials use whilst maintaining a desired viscosity. In some cases a significant raw material reduction of 40 % could be realised (calculated on the amount of FA, CS & QUAT in the formulation) if the following steps are applied; i. Initial formation of the FA, CS & QUAT lamellar system such that the morphological makeup is predominantly a QUAT/CS rich Lβ microstructure - this is primarily a function of process temperature whilst ensuring fine state of dispersion of this product intermediate. ii. Followed by a dispersive and distributive mixing step to reduce QUATS rich Lβ microstructure domain size via a low temperature, high shear post processing operation – a function of increasing deformation rates within mixing equipment. In addition to this, the Controlled Deformation Dynamic Mixing technology was found to be an efficient device at delivering the required deformation rates to the hair conditioner product, compared to the other mixing technologies tested. Deformation rates have been characterised with respect to [1] extensional (a function of process flow-rate), [2] rotational shear rates (a function of mixer rotational speed) and more importantly [3] Mixer design (a function of equipment geometry). The trio determines the deformation rates available to process fluids during an operation, and likewise vital to any scale-up operation for geometrically similar CDDM devices. The main commercial outputs for this work therefore can be estimated using Euromonitor figures, which state that the total UK market for hair conditioner alone is £324.4 million per annum. Thus if we assume even a fraction of the raw material costs can be realised in the supply chain, saving of several million per annum are conceivable.
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Briceño-Ahumada, Zenaida Cenorina. "Propriétés rhéologiques et moussantes des phases lamellaire et éponge du système dodécylsulfate de sodium-hexanol-saumure." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS331.
Full textAbstract:
Dans cette thèse, on a étudié les propriétés rhéologiques et moussantes de phases de bicouches, de type lamellaire et éponge, en utilisant le système expérimental SDS/hexanol/saumure. On a également préparé des mousses avec ces deux phases de bicouches, dont on a étudié la stabilité et les mécanismes d’évolution dans le temps. En premier lieu, les propriétés rhéologiques de la phase éponge ont été examinées. Les échantillons ayant une fraction volumique de membrane phi ≥ 0.08 se comportent comme des fluides Newtoniens. Avec les moins concentrés, phi = 0.05 et 0.024, un changement de viscosité est observé à environ 1000 et 100 s⁻¹, respectivement. Ce changement pourrait être lié à une transition de la phase éponge vers une phase lamellaire induite par cisaillement. Les changements de viscosité qui suggèrent une transition éponge-lamellaire induite par l’écoulement ont été plus facilement détectés pour l'échantillon de fraction volumique phi = 0.024. Pour cet échantillon, il a été constaté qu’à des températures plus basses ou lors de l’ajout d’un polymère hydrosoluble (PEG), la variation de la viscosité liée à la transition de phase éponge-lamellaire se produit à des valeurs inférieures de la vitesse de cisaillement. L’étude des propriétés rhéologiques de la phase lamellaire a ensuite été menée. Les expériences ont révélé le comportement de gel faible des échantillons. A une fréquence de 10 rad/s et dans un intervalle de température compris entre 5 à 50 °C, il n’y a aucun changement perceptible des modules G’ et G’’, donc pas de transition de phase, sauf pour les échantillons les moins concentrés : dans ce cas, la température a un effet plus marqué, et la structure lamellaire évolue probablement. Lorsque le taux de cisaillement augmente, il a été observé que les échantillons avec phi ≥ 0.10 présentent une forte augmentation de la viscosité à partir d’une valeur seuil du taux de cisaillement. Cette observation, combinée avec des résultats de Rhéo-SAXS, a permis de conclure qu’il y a une transition vers une phase de vésicules (ou oignons) induite par l’écoulement. Les expériences de Rhéo-SAXS ont montré que, après l’arrêt du cisaillement, la phase de vésicules relaxe vers la phase lamellaire initiale au bout d’un temps typique d’une demi-heure. Enfin, des mousses ont été obtenues par incorporation de bulles d’air dans les phases lamellaire et éponge précédemment étudiées. Les mousses faites avec les phases lamellaires présentent une grande stabilité, probablement en raison de la viscosité élevée de ces gels. De plus, ces gels présentent des contraintes seuils d’écoulement faibles. Lorsque les bulles sont petites, la contrainte seuil est supérieure à la contrainte de pesanteur sur les bulles de la mousse (force d’Archimède). Mais ces bulles grossissent avec le temps (mûrissement dû aux différences de pression de Laplace entre bulles) et lorsque la contrainte de pesanteur dépasse la contrainte seuil du gel, le drainage de la mousse commence. On a constaté que la taille des bulles évoluait avec le temps en suivant une loi de puissance. Cependant, l’exposant (≈ 0.25) est plus petit que ceux trouvés pour le mûrissement d’Ostwald (0.333, valable pour des bulles isolées) ou le mûrissement des mousses (0.5). Le fait que l’exposant trouvé soit plus petit pourrait être lié à la réorientation des domaines lamellaires lors du mûrissement. Enfin, les mousses préparées avec des phases éponge présentent une faible stabilité probablement due aux passages internes entre bicouches qui forment la structure éponge, passages qui pourraient faciliter la coalescence des bulles. Deux scénarii ont été détectés lors de l’évolution de ces mousses: à basse fraction volumique de membrane, l’effondrement de la mousse commence pendant son drainage, alors que les mousses faites avec les échantillons les plus concentrés ont le temps de mûrir avant de s’effondrerIn this thesis a study of the rheological and foaming properties of the lamellar and sponge phases of the SDS/hexanol/brine system was performed. Shear rate and temperature sweeps were done to analyze the rheology of the lamellar and sponge phases, adding frequency sweeps for the lamellar phase samples. Also, foamability and foam stability tests of foams made with these two phases were done. Sponge phase samples with membrane volume fractions phi ≥ 0.08 showed a Newtonian behavior, whereas in the less concentrated ones, phi 0.05 and 0.024, a change in viscosity was seen at shear rate values near to 1000 and 100 s ⁻¹, respectively. This change can be linked to a shear induced transition sponge to lamellar phase. Results indicate that temperature and the addition of the hydrosoluble polymer PEG affect the shear rate value at which this transition occurs. Lamellar phase samples with phi ≥ 0.10 presented a sharp increase in viscosity at intermediate shear rate values. The standard rheology technique together with Rheo-SAXS experiments allowed us to infer that there is a shear induced phase transition to vesicle phase. Rheo-SAXS data confirmed that the average interlamellar vesicle phase decreases by the effect of shear rate, and, when shear is stopped, the vesicle structure is relaxed and goes back to the lamellar phase after certain time. Foams made with lamellar phase samples showed a high stability and it was found that the time evolution of the bubble diameter follows a power law equation with exponents smaller than those reported for coarsening and Ostwald ripening. The small values of these exponents seem to be related with orientation defects of the liquid crystalline phase. On the opposite, the foams made with the sponge phase samples presented poor stability, as a possible consequence of the passages that form their structure that could facilitate coalescence of bubbles
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Kilian, Dewald. "A comparative study between two lamellar gel phase systems and Emzaloids as delivery vehicles for the transdermal delivery of 5-fluorouracil and idoxuridine / Dewald Kilian." Thesis, North-West University, 2004. http://hdl.handle.net/10394/602.
Full textAbstract:
The distinctive architecture of the stratum corneum with its unique nature of an
interstitial lipoidal environment plays the major role in regulating the barrier function of
the skin.
The major problem with the transdermal delivery of 5-fluorouracil or idoxuridine is the
permeation of sufficient amounts to the deeper layers of the skin and into the systemic
circulation.
In an attempt to enhance the transdermal permeability of 5-fluorouracil and idoxuridine,
the aim of this study was to evaluate two lamellar gel phase systems (Physiogel
dermaquadrille® and Physiogel NT®) and Emzaloids® as transdermal delivery vehicles
for the two actives. Lamellar gel phase systems (LGPS) and Emzaloids® are both novel
drug delivery systems.
The epidermis of female abdominal skin was used in vertically mounted Franz diffusion
cell experiments. An average amount of 250 mg of the 1% m/m LGPS was applied to
cover the entire diffusion area of 1,075 cm2 of the skin, which contained 2,5 mg of the
active. Samples of the actives in Emzaloids® were prepared and applied in the same way.
The control solutions of the actives in water were prepared so that 1 ml of the applied
solution contained the same amount of drug that was applied to the experimental cells.
The entire receptor phase of the cells was removed at 2,4,6, 8, 10, 12 and 24 hours and
was replaced with fresh 37°C receptor phase. The amount of active in the receptor phase
was determined by HPLC analysis. Graphs of the cumulative amount of the active that
permeated the skin over the 24 hour period were drawn and the slope of the graphs
represented the flux in µg/ml/h. The average flux values of six experimental cells and six
control cells were compared. Entrapment of the actives in the Emzaloid® vesicles was
confirmed with the use of confocal laser scanning microscopy.
Results for the LGPS indicate an enhancement ratio in the order of 4,2 for 5-fluorouracil
and 1,7 for idoxuridine when compared to the control cells. There were no viscosity
changes in the LGPS samples containing 1% m/m of the active when compared with the
blank LGPS samples, suggesting that no change in the internal structure of the LGPS
occurred after the addition of the actives to it. There were also no significant changes in
the pH of the samples.
Entrapment of the actives in the Emzaloid® vesicles occurred readily. The Emzaloid®
vehicle showed a lower rate of release for idoxuridine than the LGPS did during the
VanKel dissolution experiments. This suggests that higher flux values would be obtained
with the LGPS for idoxuridine than with the Emzaloid® formulation, since more drug was
available for permeation through the skin.
This was, however, not the case. The Emzaloid® formulation showed much higher flux
values, showing that even with a smaller amount of active available to permeate the skin
higher flux values were obtained.
Enhancement ratios of 20,33 and 3,50 were achieved with the Emzaloid® formulation for
5-fluorouracil and idoxuridine respectively.
The internal LGPS structure which mimics the skins lipid components remained
unchanged after the addition of the actives. Greater success might be achieved with the
LGPS for different model drugs, since the drugs' physicochemical properties play an
important part in its permeation through the skin.
The Emzaloid® formulation, which is closely related to liposomes and transfersomes,
showed great potential for commercially marketable formulations for the drugs tested but
further research on the formulation has to be done.Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2005.
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Pramatarova, Radina. "The lamellar structure of the shell of Patella crenata a crystallographic study /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967134315.
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Greven, Martin. "Neutron scattering study of magnetism in insulating and superconducting Lamellar copper oxides." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32649.
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Seigenfuse, Matthew David. "Low Estrogen Model and Percent Lamellar Bone Pre and Post Puberty [thesis]." Master's thesis, Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/94126.
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KinesiologyM.S.
INTRODUCTION: Pubertal growth is an important time during development for bone accrual and attainment of peak bone mass. Suboptimal bone gain has been observed in females with reproductive abnormalities such as primary and secondary amenorrhea and these conditions are very prevalent in female athletes. Amenorrhea is associated with decreased estradiol levels. Previous research has shown that in prepubertal animals a low estrogen environment significantly decreased mechanical strength, but there was no significant loss in bone area and actually an increase in moment of inertia. The decrease in mechanical properties may be related to the microstructure of the bone. Two types of bone are involved in growth-- woven bone, which is added for structural support in the short term, and lamellar bone , which is highly organized and has a greater contribution to overall strength. We will test the hypotheses that suppressed estradiol will result in bones with no change in cortical area and decreased strength properties but will have a larger composition of non lamellar bone as opposed to lamellar bone. PURPOSE: The goal of this study was to determine the relative amounts of woven and lamellar tissue in a bone and the relationship with the bone's mechanical strength in two models of low estrogen-- pre- and post-pubertal onset. METHODS: Fifty-Five female Sprague-Dawley rats were randomly assigned into four groups: a control group (n=14) and three experimental groups injected with gonadotropin releasing-hormone antagonist (GnRH-a)-- the Dose 1 group was injected with 1.25 mg/kg/dose daily (n=14), the Dose 2 was injected with 2.5 mg/kg/dose daily (n=14), and the Dose 3 group was injected with 5.0 mg/kg/dose, 5 days per week (n=13). All groups were sacrificed at Day 49. Additionally, twenty-nine Sprague Dawley rats were randomly assigned into three groups. The baseline day 65 group (BL 65) was sacrificed on day 65 (n=9). There was an aged match control group that was sacrificed on day 90 (n=12). Finally, there was an AMEN experiment group injected with 2.5 mg/kg/dose daily that was sacrificed on day 90 (n=9). All experimental groups for both protocols received injections of gonadotropin releasing hormone antagonists (GnRH-a) (Zentaris GmbH) intraperitoneally. Left femora were mechanically tested under 3-point bending. The right femora were dehydrated, embedded in polymethylmethacrylate, cut and ground to 100 µm thickness. Bones were analyzed under polarized light using Stereo Investigator Software (MBF Bioscience, VT). The proportion of the cortex with primary lamellar vs. non-lamellar/other primary tissue type was measured and expressed as percent of the total cortical bone area. Outcome measures included lamellar endocortical area, lamellar periosteal area, cortical area, endocortical area, % lamellar area and % non-lamellar area. RESULTS: There was a significant decrease (p<.05) in the distribution of lamellar versus non-lamellar cortical tissue type in the experimental group in the model of delayed puberty. Additionally, the pre-pubertal bones had a lower percentage of lamellar periosteal and endocortical area. The post-pubertal group showed no significant differences between the control and experimental group in any of the outcome measures. CONCLUSION: There were significant differences in relative bone distribution throughout the femoral cortex. Relative decreases in lamellar tissue distribution, especially on the periosteal surface, will result in decreased mechanical strength due to increased percentage of woven bone in pre-pubertal models.
Temple University--Theses
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Ghasemi, Rohollah. "Tribological and Mechanical Behaviour of Lamellar and Compacted Graphite Irons in Engine Applications." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-25724.
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There has been much discussion about the beneficial uses of lamellar graphite iron in piston rings–cylinder liner systems, where a good combinations of both thermal and tribological properties are essential. The excellent tribological performance of lamellar iron under such sliding conditions is principally associated with lubrication behaviour of the graphite particles which are distributed as lamellas throughout the matrix. During sliding, graphite particles are extruded and smeared onto the counterfaces, act as solid lubricating agents and form a thin graphite film between the sliding surfaces. Although this process especially, during the running-in period significantly changes the sliding wear response of the components, the exact mechanism behind of this phenomenon has rarely been discussed in previous studies. It is tribologically beneficial to keep the graphite open, particularly in applications where the scuffing issues do matter. In this thesis, the main causes involved in closing the graphite lamellas are discussed, with a focus on matrix plastic deformation that occurs during sliding. In first step, the relationship between graphite lamellae orientation and plastic deformation was investigated. To do so, two piston rings, belonging to the same two-stroke marine engine operated for different periods of time, were selected and compared to the unworn sample. The worn piston rings displayed a substantial decrease in both frequency and area fraction of the graphite lamellas. Most of the lamellas were closed as a result of plastic deformation of matrix. This happening was caused mainly by the interaction between abrasive particles and metallic matrix. Additionally, it was found that graphite lamellas parallel or near-parallel to the sliding direction exhibited maximum closing tendency under sliding condition. In next step, to have a better understanding of the graphite film formation mechanism and matrix deformation role in closing the graphite lamellas, microindentation and microscratch testing were performed on typical lamellar iron. The qualitative results showed a similar mechanism involving in graphite contribution to lubricate the sliding surfaces. Moreover, microindentations made nearby the graphite lamellas demonstrated that the deformation of the matrix causes the formation of cracks in the centre of the graphite lamellas, compressing and then extruding the graphite from its natural position, irrespective of the lamellas′ size. Furthermore, it was found that subsurface graphite orientation had a large influence on the extrusion behaviour, in that, for graphite lamellas oriented towards the indenter, the effect was observed more pronounced. Furthermore, an improved fully ferritic solution strengthened compacted graphite iron was produced for future wear studies. The effects of different Si levels and section thicknesses on tensile properties and hardness were investigated as well. The influence of Si content and section thickness on mechanical properties was revealed by improving the materials strength and slightly enhancing the hardness through increasing Si content. Besides, Si addition up to 4.5 wt% significantly affected the strength and elongation to failure of cast samples.Helios
FFI
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Abukhdeir, Nasser. "Growth, dynamics, and texture modeling of the lamellar smectic-A liquid crystalline transition." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86888.
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This thesis is focused on the study of material transformations from the disordered state to the lamellar-ordered/smectic-A liquid crystalline state via multi-scale multi-transport modeling and simulation. This approach utilizes a high-order Landau-de Gennes phenomenological model able to bridge the gap between experimentally observed macro-scale phenomena and the nano-scale growth and structure inherent to liquid crystalline ordering. A unique feature of this simulation-based thesis is the direct verification of predictions with past experimental observations. In this context, the main contributions of this thesis work focuses on three experimental systems: free growth of an isolated domain, defect/texture formation, and the evolution of texture/defect interactions as the system approaches equilibrium.Simulation studies of free growth were first performed under conditions of deep undercooling, where non-isothermal effects can be neglected. The growth/shape kinetic evolution of initially textured and homogeneous spherulites growing into an unstable isotropic matrix phase was found, elucidating nano-scale morphology/texture processes and growth instabilities inaccessible experimentally. Undulation instabilities in growing smectic-A spherulites discovered in this work shed light on a possible mechanism for the formation of experimentally observed anisotropic "batonnet" morphologies and two-dimension focal conic defect structures. Recent experimental observations of growth kinetic phenomena of meta-stable nematic pre-ordering was studied, showing that the high-order model both predicts this phenomenon and explains the underlying mechanisms for experimentally determined morphological trends. A non-isothermal extension to the high-order model is derived and applied to study free growth under shallow undercooling conditions, where latent heat and anisotropic thermal diffusion are non-negligible. Growth laws, agreeing with experimental observations, are determined and novel diffusional/diffusionless growth kinetics found.
The effects of surfaces, focusing on the experimentally/industrially prevalent thin-film geometry, were studied using a de Gennes surface model allowing for energetic self-selection. Layer transitions and defect-mediated surface-enhanced growth phenomena were studied and used to simulate equilibrium defect core structure (of the smectic-A elementary edge dislocation), inaccessible via previous theory and experiment.
Finally, the last stages of phase transformation, texture formation and coarsening, are studied. The obtained simulation results are compared directly to relevant experimental data of a system with the same symmetries, self-assembled cylindrical block copolymer films. Multi-body defect interactions are studied and both compared to experimental macro-scale results and analyzed at the nano-scale, as is resolved by the simulations. The formation, structure, and complex interactions of "giant" split-core edge dislocations, composite structures composed of both orientational and translational defects, are presented and validated by experimental observations of this phenomena.
The models, computational techniques, and predictions developed in this thesis work provide a substantial basis on which to further develop the computational material science of anisotropic soft matter.
Cette thèse se concentre sur l'étude de la transformation des matériaux d'un état isotrope à une phase cristalline liquide ordonnée lamellaire de type smectique A par l'entremise de modélisations et de simulations de multi-échelles. Cette approche s'appuie sur le modèle phénoménologique de Landau-de Gennes qui est capable de faire le lien entre les observations expérimentales de phénomènes macroscopiques et la croissance nanoscopique associé à la structure inhérente d'un cristal liquide. L'un des attraits principaux de cette thèse basée sur les simulations provient du fait qu'elle vérifie directement des données expérimentales observées par le passé. Dans la même optique, les apports majeurs de ce travail de thèse se répartissent en trois principaux systèmes expérimentaux: la croissance libre d'un domaine isolé, la formation de texture/défauts, l'évolution de l'interaction entre les textures/défauts à mesure que le système atteint l'équilibre . fr
Les études de la croissance libre réalisé au moyen de simulations ont tout d'abord été effectuées dans des conditions où l'ordre liquide cristallin est très prononcé et dans laquelle les effets non-isothermaux peuvent être négligés. L'étude de la cinétique de croissance durant laquelle se forme des sphérulites texturés et homogènes se développant dans une matrice de isotrope instable a pu être mettre en évidence les processus de changement morphologie à une échelle nanoscopique ainsi que les instabilités de croissances, phénomènes inaccessibles sur le plan expérimental. Les ondulations instables des sphérulites de phase smectique A découvertes dans ce travail ont permis de mettre en évidence un possible mécanisme responsable des morphologies anisotropiques de type bâtonnets et des défauts de structure en deux-dimensions de type coniques focaux observés expérimentalement. Un phénomène de cinétique de croissance pré-ordonné en nématique metastable, phénomène qui a été récemment observé expérimentalement, a ensuite été étudié, démontrant qu'un modèle d'ordre supérieur à la fois prédit ce phénomène et les mécanismes sous-jacents régissant aux tendances morphologiques déterminées expérimentalement. Une extension non-isothermale au modèle d'ordre supérieur a été dérivée et employée pour l'étude de la croissance libre dans des conditions de faible congélation, où la chaleur latente et la diffusion thermique anisotropique sont non-négligeables. Les lois de croissance, en accord avec les observations expérimentales, sont déterminées et une nouvelle cinétique de croissance de diffusion et de non-diffusion est développée. fr
Les effets de surfaces, et plus particulièrement la géométrie expérimentale/industrielle prédominante des films fins, ont été étudiès à l'aide d'un modèle de surface de de-Gennes permettant une auto-sélection énergétique. Les phénomènes de transition de couches et de croissance de surface augmentée gérés par les dèfauts ont été étudiés et utilisés afin de simuler un équilibre dans la structure des défauts (les dislocations des bordures du smectique A), non-accessible via les anciennes théories et expériences. Finalement, les dernières étapes de transformation de phase, de formation de texture et d'alignement de texture ont été étudiées. Les résultats obtenus de la simulation ont été directement comparés aux données expérimentales issues d'études similaires, démontrant les mêmes symétries que des blocs cylindriques de co-polymères auto-assemblés. Les interactions entre les défauts de différents corps sont à la fois comparés aux résultats expérimentaux obtenus à une échelle macroscopique et analysés à une échelle nanoscopique, tel qu'obtenu par les simulations. La formation, la structure, et les interactions complexes entre les dislocations de bordures à noyaux divisés, structure composite formée à la fois de défauts orientationnels et translationnels, sont présents et validés par des observations expérimentales de ce phénomène. fr
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Halford, Timothy Paul. "Fatigue and fracture of a high strength, fully lamellar γ-tial based alloy." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289746.
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Colombo, Cristian Carlos Puig. "The absence of lamellar thickening in a blend of linear and branched polyethylene." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385530.
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Greenan, Kathleen A. "Controlled Folding in Precisely Functionalized Polyethylenes| Designing Nanoscale Lamellar Structures for Ion Transport." Thesis, Purdue University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10790087.
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This qualitative, phenomenological study explored Sexual Health Education (SHE) through the lens of 11 public school teachers who formally taught sex education. It explored the levels of comfort and barriers that educators possessed when they communicated SHE to adolescents. One community within the State of Indiana was examined. Eleven 7-12th grade educators among three school districts shared their beliefs, values, and feelings regarding SHE instruction and levels of sexuality comfort. As a result, the concept of sexuality comfort was reconstructed, and three findings emerged from the data that can contribute to further research in the fields of education, communication, and health. They include: (1) An inclusive sexual health education program can provide educators with more sexuality comfort, (2) Teacher training and instructional materials relate to an educator’s sexuality comfort level and willingness to communicate SHE, and (3) An educator’s level of sexuality comfort will likely increase if engaged in SHE decision-making policies.
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Bangert, D. E. "Computational studies of gratings." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344034.
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Machado, Margarete Oliveira. "Fosfato de bario, intercalação e termoquimica." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250040.
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Orientador: Claudio AiroldiDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-04T03:16:55Z (GMT). No. of bitstreams: 1 Machado_MargareteOliveira_M.pdf: 2375635 bytes, checksum: f083ccbf844356a5d576d3d1a2311e97 (MD5) Previous issue date: 2004
Mestrado
Quimica Inorganica
Mestre em Química
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Zeng, Xiangbing. "Study of lamellar structures in pure and mixed long chain n-alkanes and derivatives." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340143.
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