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1
Saida, Myriam. « Composition and structure of murine sperm chromatin ». Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522979.
Texte intégral
2
Chatzantonis, Ioannis. « Deleuze and mereology : multiplicity, structure and composition ». Thesis, University of Dundee, 2010. https://discovery.dundee.ac.uk/en/studentTheses/e2d2398c-2b38-4174-944b-971c741bbf6f.
Texte intégralRésumé :
This investigation constitutes an attempt towards(1) understanding issues and problems relating to the notions of one, many, part and whole in Parmenides and Plato; (2) extracting conditions for a successful account of multiplicity and parthood;(3) surveying Deleuzian conceptions and uses of these notions; (4) appraising the extent to which Deleuze’s metaphysics can answer some of these ancient problems concerning the status of multiplicity and the nature of mereological composition, that is, of the relations that pertain between parts and the wholes that they compose.
3
Watts, Sally. « Composition-structure-property relationships in bioactive glasses ». Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5678.
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Hench developed the first bioactive material, Bioglass®, based on a soda-lime phospho-silicate glass. Most materials, elicit a neutral response when implanted into the human body. Bioglass®, however, was seen to create a positive response by depositing the body’s natural bone substance, Hydroxyapatite on its surface. Although it is recognised that compositional modifications effect bioactivity, there is very little comprehension of the composition-structureproperty relationships that result in such bioactivity. The objective of this investigation, therefore, was to study such fundamental relationships with respect to two components often found in bioactive glass compositions – P2O5 and MgO. The first component studied was P2O5. The design of two series was undertaken – the first, a straight substitution of silicon for phosphorus, varying the network connectivity, NC, and the second, a charge compensating series, keeping the NC constant. 31P and 29Si MAS NMR of the two series provided evidence that the glasses were phase separated, with a predominantly Q2 silicate structure co-existing with phosphorus in a predominantly Q0 orthophosphate environment. Raman, FTIR, density measurements, differential thermal analysis and dilatometric analysis all further supported the existence of this structure. Dissolution studies in SBF highlighted the importance of phosphorus on bioactivity, with the glass dissolution rates of both series increasing with the addition of phosphorus. Instead of the dissolution of a glass depending solely on ion exchange reactions, as previously thought, it is proposed that dissolution depends upon the balance existing between the NC of the silicate phase and the existence of isolated orthophosphate rich domains. It is hypothesised that phosphorus in a phase separated structure is far more important than previously suspected, with its ability to preferentially dissolve into solution, dominating over the effect of NC on the resultant bioactivity of the glass and apatite formation. The second component investigated was magnesium oxide and its influence on the glass structure when substituted for calcium oxide. Two series of glasses were designed, the first series with a high sodium content and the second series with a low sodium content. In order to eliminate any influence due to silicate network disruption, all glasses were designed to have a constant NC of 2.04. All physical parameters were seen to be related strongly to the substitution of magnesium oxide, in both series. 31P, 29Si and 25Mg MAS-NMR of the high sodium magnesium glasses highlighted that magnesium, rather than acting to depolymerise the silicate network by acting as a network modifier, was acting partially as an intermediate oxide with a proportion entering the network as MgO4 tetrahedra. The decreasing Tg and Ts values and increasing thermal expansion coefficients, with increasing MgO substitution, supported this theory; with the significantly weaker bond strength of Mg-O, compared to Si-O, explaining the experimentally observed weakening of the network. The corresponding results for the low sodium magnesium glasses also pointed to magnesium acting as an intermediate oxide, however, with a smaller proportion entering the silicate network as MgO4 tetrahedra. It is suggested that magnesium acts as an intermediate oxide in highly disrupted glasses, with a more disrupted glass giving a higher proportion of MgO4. Dissolution studies in SBF settled the previously controversial subject of magnesium and bioactivity, with the addition of magnesium resulting in decreased glass dissolution rates and apatite formation in both series. This work has highlighted the importance of having a detailed understanding of the composition-structure-property relationships which exist in a bioactive glass. It is suggested that, from the contribution this work makes to this understanding, coupled with the knowledge gained from parallel studies, we are now at the point where a specific bioactive glass composition could be engineered, and tailored for a particular biomedical application.
4
Groenewald, Alphonso. « Psalm 69 : its structure, redaction and composition / ». Münster : Lit, 2003. http://catalogue.bnf.fr/ark:/12148/cb392315962.
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5
Zhi, Dan. « Structure and composition of InAs/GaAs quantum dots ». Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414000.
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6
Fletcher, Leigh Nicholas. « Saturn's atmosphere : structure and composition from Cassini/CIRS ». Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445756.
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7
Al-Masri, Mohammed. « The Jordanian bourgeoisie : composition and structure, 1967-1989 ». Thesis, Durham University, 2005. http://etheses.dur.ac.uk/2808/.
Texte intégralRésumé :
This study analyzes the composition and structure of the Jordanian bourgeoisie over the period 1967-1989. Both the study of the structure and composition of the social classes and their role in the political and social change are neglected topics when Jordan is concerned. On this basis, the main argument of this thesis is that the bourgeoisie is an important social class, whose study andanalysis can yield a better understanding of socio-economic structure and change inJordan. This study uses the Marxist paradigm as a theoretical framework to define the bourgeoisie as the social class that has the economic ownership of the means of production and appropriates the surplus value. Some Marxist theorems had to be modified to be operative in studying the bourgeoisie in particular and the class in general. This thesis adopts an empirical approach in studying the bourgeoisie. It first locates and defines the bourgeoisie members within the domain of the private sector, which is their objective context. It then analyzes their activities and investment strategies. This study analyzes the bourgeoisie into the possible fractions that come to exist according to their activities, investments and assets. It also examines the possibility of the existence of fractions in the domain of the bourgeoisie according to vertical dimensions such as religion or country of origin.
8
Fuller, R. J. « Composition and structure of bird communities in Britain ». Thesis, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363417.
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9
Allen, Kathryn. « Composition and structure of foraminiferal agglutinated test walls ». Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284673.
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Edgington, A. L. « The structure, composition and evolution of Mercury's core ». Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1532824/.
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This thesis presents the results of ab initio molecular dynamics calculations of the adiabatic gradient of pure liquid iron and a liquid Fe-S-Si mixture with the relative atomic percentages, 80:10:10. Laser-heated diamond-anvil-cell experiments have been conducted to measure the liquidus and solidus relationships of Fe0.8S0.1Si0.1. First-principles molecular dynamics is combined with thermodynamic integration and free-energy minimisation to simulate the spin transition in pure liquid iron and liquid Fe0.8S0.1Si0.1. From the magnetic transition, the equations of state, thermodynamic properties and adiabatic gradients of pure liquid iron and liquid Fe0.8S0.1Si0.1 are determined. The calculated adiabatic gradients are used alongside the gradients of published melting curves of iron and the measured liquidus of Fe0.8S0.1Si0.1 to provide insight into the crystallisation regime of the core of Mercury. The suggested crystallisation regime of a hypothetical pure iron or Fe0.8S0.1Si0.1 Mercurian core depends strongly on the derivative of the melting curve. Results suggest that a Fe0.8S0.1Si0.1 core of Mercury may start in a ‘top-down’ crystallisation regime resulting in a complex core structure with a possible stratified Fe-S layer at the top of the core, which, may in-part explain the observed weak magnetic field of Mercury.
11
Huang, Jing-Lun. « Prediction of avian species composition from assemblage structure ». Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/417922/.
Texte intégralRésumé :
This research focuses on how capitalising on community pattern, a character of ecological communities, could improve the predictability of community models, thus facilitating research in conservation. Patterns of communities not only depict phenomena but are also useful for predicting potential changes in species composition when patterns are governed by specific mechanisms. Most conventional prediction models do not take community pattern into consideration, despite the fact that incorporating community patterns into conventional models for predicting species richness and composition may enhance predictability. In this thesis, I assessed if incorporating two community patterns, nestedness and species co-occurrence, into conventional prediction models could improve the model predictability. Nestedness is a non-random species distribution pattern in which species in depauperate sites are contained in species-rich sites. Co-occurrence networks categorise species assemblages that reflect differential habitat requirements. I demonstrate that capitalising on nestedness provides a novel approach for improving the predictive power of species accumulation curves for species richness in unsampled areas. Specifically, while species richness is usually overestimated when the data are inputted in random order (the conventional approach), species richness is underestimated when the data are inputted in nested order. Taking an average of projected species richness of these two inputting orders dramatically lowers the prediction error rate, indicating that using nestedness in addition to random orders can greatly improve the predictive power of species distribution curves. I also show that network analysis can improve the ability to correctly classify site groups, which is the basis for calculating the indicator species value, by accurately reflecting similar ecological requirements of co-occurred species. Indicator species identified by network modularity, comparing to conventionally based on the k-means clustering method, can more successfully assign unsampled sites to the correct species groups and recognise representative species for the groups. These methods were tested using both British and Taiwanese bird assemblages. Both case studies supported the above conclusions, suggesting that the methods developed in this thesis have real promise for conservation applications. However, further work is required to assess whether these two novel pattern-based approaches are similarly applicable in other geographic regions or taxas.
12
Glimenez, Frédéric. « Nucleation, croissance, composition et structure d'agregats bimetalliques supportes ». Aix-Marseille 2, 1997. http://www.theses.fr/1997AIX22044.
Texte intégralRésumé :
Cette these est consacree a la mise au point d'une methode d'elaboration de collections homogenes et bien caracterisees d'agregats bimetalliques d'alliage pd-cu, supportees par des faces de clivage (100) de nacl afin d'etudier, par la suite, leur reactivite en fonction de leur taille et de leur composition chimique. Nous avons utilise la methode de nucleation-croissance epitaxique, par condensation simultanee sous ultra-vide, des atomes des 2 constituants, emis par 2 cellules de knudsen. Les echantillons sont caracterises a l'aide des techniques de microscopie electronique et de fluorescence x. Nous montrons que la germination des particules d'alliage pd-cu est gouvernee par le palladium qui impose la frequence de nucleation. La croissance se fait essentiellement par 2 mecanismes : diffusion des atomes de palladium absorbes, et capture a la peripherie des agregats, et aussi par impact direct sur les particules des atomes de cuivre de la phase vapeur. Apres croissance a 280c les agregats sont monocristallins et ont la structure c. F. C. De la solution solide desordonnee. Les plus petits (< 5 nm) sont accoles au support suivant un plan (100) avec une orientation azimutale unique. Sur chaque echantillon tous les agregats ont la meme composition chimique. La comparaison des cinetiques de croissance et de l'evolution de la composition chimique, avec des modeles de croissance, a permis d'estimer les libres parcours moyens des atomes de palladium et de cuivre sur nacl(100) a 280c. A partir de ces deux valeurs une estimation des energies d'adsorption et de diffusion des atomes de palladium et de cuivre sur nacl(100) et donnee. Par recuit a 365c des collections d'agregats de composition voisine de 50% en cuivre, nous observons la transformation de la structure c. F. C. Vers la structure c. C. Prevue par le diagramme de phases du materiau massif. Ces experiences ont permis d'observer un effet de taille sur la temperature limite d'existence de la phase ordonnee de l'alliage.
13
Reinhardt, Deborah Ann. « The effect of repeated composition experience on the tonal structure of fifth-grade students' compositions ». Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054922982.
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14
Uthayakumaran, Surjani. « Structure/function studies on systematically altered wheat flours ». Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27689.
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The gluten proteins have unique physico-chemical properties which enable use of the wheat flour to produce bread. This project was undertaken to study the chemistry of the different wheat storage proteins and to evaluate their contribution to the breadmaking process in a controlled system where all parameters other than the varied one remained constant. In a systematic study of the functionality of different storage proteins, gluten and starch were separated from seven flour samples having a range of protein contents and functionality. Gliadin- and glutenin-rich fractions, high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMWGS), HMW-GS 7 (x-type), HMW-GS 8 (y-type), and a range of gliadin types (a., P, y, co) were isolated. In addition HMW-GS 5 and 10 obtained by bacterial expression were also purified. Protein content, glutenin-to-gliadin ratio, HMW-GS-to-LMW-GS ratio, amounts of HMW-GS 7, 8, 5 and 10 and the different gliadin types were altered by blending these fractions into the test flours in calculated amounts using addition or incorporation. Mixing properties, extension-tester parameters and baking performance of composite flours were determined using small-scale techniques. New incorporation methods were developed to investigate the effects of glutenin subunits on extension and baking parameters. For the first time, basic principles of physics (basic rheological tests for elongation and viscosity) have been used to separate the effects of protein content and glutenin-gliadin ratio.
The mixing time increased with increase in protein content, glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio. There was a general increase in peak resistance with increase in protein content, glutenin-to-gliadin ratio (in five out of seven flours) and HMW-GS-to-LMW-GS ratio. There was a decrease in resistance breakdown observed with increase in glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio. However resistance breakdown was different in samples as the protein content was increased. Three samples showed a general increase in resistance breakdown, two others showed an initial decrease in resistance breakdown followed by an increase and two samples showed a consistent decrease in resistance breakdown. The maximum resistance to extension increased with increase in protein content and glutenin-to-gliadin ratio. The maximum resistance to extension slightly increased with increase in HMW-GS-to-LMW-GS ratio (strongly in one cultivar, Hartog). Extensibility increased with protein content but decreased with increase in glutenin-to-gliadin ratio and HMW-GS-to-LMWGS ratio (except in Osprey derivative). Increases in loaf height were observed with increase in protein content, glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio.
Since this work confirmed that glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio had important effects on bread-making quality, there was potential to evaluate near infrared spectroscopy (NIR) as a tool for measuing the content of these four classes ofprotein non-destructively. Its use for measuring total protein content is very widespread and well established. NIR calibrations were developed for two blends of proteins, with 2308 nm distinguishing glutenin from gliadin and 2300 nm HMW-GS from LMW-GS. When a third component, starch, was added, however, the differences in spectra at these single wavelengths were no longer detectable. Nevertheless, the potential for nondestructive and indirect measurement of these two key ratios was demonstrated and its eventual application may depend on more sophisticated data processing.
In incorporation studies of single and paired glutenin subunits, HMW-GS 5 + 10 gave a synergistic effect, increasing mixing time, maximum resistance to extension and loaf height as compared to HMW-GS 5 or 10 separately. However, HMW-GS 7 + 8 did not show any synergistic effects, and HMW-GS 7 incorporated separately had a higher mixing time, maximum resistance to extension and loaf height than those of HMW-GS 7 + 8 and HMW-GS 8. All gliadin fractions decreased mixing time, maximum resistance to extension and loaf height and increased resistance breakdown and extensibility. The various gliadin fractions showed differences in functional properties, with y-gliadin reducing the mixing time and maximum resistance to extension to the greatest extent, rogliadin contributing to the greatest reduction in loaf height and a + -gliadins having the least effect on reducing loaf height.
Dough measurements determined by traditional Mixograph, Farinograph, Extensograph and Al veograph methods are empirical and not founded on parameters of basic physics. The application of methods of basic physics was also used in this study to differentiate the effect of protein content and glutenin-to-gliadin ratio on dough properties. Parmeters such as extension to rupture, tensile force, extensional viscosity, tensile stress (United Testing Machine), steady shear viscosity and time to peak viscosity (rheometer) were determined. The increase in protein content increased extension to rupture, tensile force, extensional viscosity and tensile stress but decreased steady shear viscosity. The increase in glutenin-to-gliadin ratio increased tensile force, extensional viscosity, tensile stress and steady shear viscosity but decreased extension to rupture. High correlations of extension to rupture and extensibility, tensile force and maximum resistance to extension (measured in traditional extension testing machine and United Testing Machine) confirmed the validity of traditional empirical measures of dough quality.
The results obtained from the systematic study have allowed the separation of the effects of flour protein quantity and quality on functional properties.
15
Cook, Kathryn B. « Epipelagic zooplankton community structure : spatial patterns in abundance, species composition and size structure ». Thesis, Swansea University, 2001. https://cronfa.swan.ac.uk/Record/cronfa42911.
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Åkerlund, Eva-Brita. « Composition, properties and surface structure of tribochemically deposited coatings ». Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-151881.
Texte intégralRésumé :
Five tribochemically deposited coatings on honed cast iron cylinder liner segments has been studied with respect to surface properties, material composition, coating thickness, hardness and friction. Methods like Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), 3D topography using white light interferometry (VSI) and Electron Spectroscopy for Chemical Analysis (ESCA) were used to study the surface, coating thickness and material composition. Lubrication regimes (friction) were studied using a test set-up in a Lathe. An in-situ scratcher and nano indenter were used to study the hardness. It was found that the honing plateau surface is smoothened by the coating process while the honing scratches are kept more or less intact. The deposited coating thickness is approximately 10-100 nm. The coating is softer than the substrate and shows a butter-like behavior when scratched. Using only sulfur additive in the process fluid gives a smooth surface and an evenly distributed coating. Tungsten additive in the process fluid gives a thicker coating but a more irregular material distribution. Tungsten additive in the process fluid does not seem to stimulate the formation of WS2, but rather WO3 is formed.
17
Siddiqui, Mohammad Nahid. « Studies on structure and chemical composition of Arabian asphalt ». Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/671.
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Bumajdad, Ali Y. E. A. « Phase structure and interfacial composition of mixed surfactant microemulsions ». Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322358.
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Huang, Kevin J. (Kevin Joon-Ming). « Composition, structure, and performance of nanocrystal bulk heterojunction photovoltaics ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98742.
Texte intégralRésumé :
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 131-134).
We describe the fabrication and study of bulk heterojunction solar cells composed of PbS quantum dots and TiO2. In particular, we study the effects that bulk heterojunction composition and structure have on resulting device performance. We find that PbS and titania are extremely evenly distributed throughout our bulk heterojunction devices, such that charge carriers generated anywhere within the blend are well within a carrier collection length of the charge separating driving force required to separate them and enable their collection. Of the compositions we studied, we found that devices with a TiO2 rich bulk heterojunction composition outperformed devices employing other compositions. As a result of the size difference between the PbS quantum dots and the titania nanocrystals which compose the blends, the likelihood of forming a truly complete, bicontinuous bulk heterojunction network is maximized at a TiO2-rich blend composition. We find that diffuse interfaces exist between adjacent layers of our devices as a result of interfacial surface roughness. Rather than being deleterious, this increased interfacial area extends the spatial extent of the depletion region over a greater volume of our devices. Our bulk heterojunction blends form well packed, high density binary particle mixtures, particularly at a TiO2-rich composition. Device efficiency was maximized for bulk heterojunctions employing the smallest titania nanocrystals, an indication that at constant volume fractions, larger titania nanocrystals decrease the total number of titania particles available to form complete and continuous pathways through the depth of the bulk heterojunction. Furthermore, a peak in device performance was observed at intermediate blend layer thicknesses. This results from the balance between two opposing effects: an increase in light absorption and photocurrent with thicker bulk heterojunctions and an increased likelihood of charge carrier recombination with thicker bulk heterojunctions. Finally, enhanced light absorption and current generation was observed at red and infrared wavelengths, validating the ability of bulk heterojunctions to spatially extend the reach of the charge separating driving force, such that the previously missed red and infrared photons may be captured.
by Kevin J. Huang.
Ph. D.
20
Ballering, Nicholas, et Nicholas Ballering. « Measuring the Structure and Composition of Circumstellar Debris Disks ». Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621759.
Texte intégralRésumé :
In this dissertation, I measure the structure and composition of circumstellar debris disks to probe the underlying planetary systems. In Chapter 1, I provide an introduction to the field of debris disks. I highlight our current observational and theoretical understanding of the field, rather than providing a detailed history. This is intended to give the reader context and motivation for the subsequent chapters. I also describe important developments in debris disk science that are not the focus of this dissertation, but are nevertheless vital for a complete overview. In Chapter 2, I describe my analysis of a large sample of cold (≲130 K) debris disks seen in Spitzer/IRS data. Previous work had suggested a common temperature for these disk components, regardless of spectral type. I find that there is trend with spectral type and argue that the locations of cold disks are not set by snow lines, but more likely by the formation/evolution of planets. This work was published in Ballering et al. (2013). In Chapter 3, I turn my focus to the warm (~190 K) debris components identified in Chapter 2---specifically those exhibiting silicate emission features. I show that these features arise from exozodiacal dust in the habitable zones around these stars. This was published in Ballering et al. (2014). In Chapter 4, I examine the remainder of the warm disks to investigate what mechanism sets their location. I find that for many systems, the locations trace the water snow line in the primordial protoplanetary disk, rather than the current snow line. This favors the interpretation that warm debris components arise from asteroid belts in these systems. This study will be published soon. In Chapter 5, I analyze images of the debris disk around beta Pictoris at five different wavelengths, including in thermal emission and scattered light. I find that matching the disk brightness at all wavelengths constrains the composition of the dust, with a mixture of astronomical silicates and organic refractory material fitting the data well. This was published in Ballering et al. (2016). In Chapter 6, I conclude with a summary of this dissertation and prospects for future progress in these areas.
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Lisachuk, G. V., R. V. Krivobok, E. V. Chefranov, O. Lapuzina, P. S. Korablova et I. G. Krasyuk. « The structure and phase composition of the radiotransparent ceramics ». Thesis, Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/38983.
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Unocic, Kinga Angelika. « Structure-Composition-Property Relationships In 5xxx Series Aluminum Alloys ». The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218473077.
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Santos, Jean Daniel dos. « Structure development in confectionery products : importance of triacylglycerol composition ». Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/9190.
Texte intégralRésumé :
Mestrado em Biotecnologia - AlimentarThe objective of this thesis was to study the effect of the ratio symmetric/asymmetric TAG on the crystallization properties, storage stability and fat migration of fat blends. In order to do that, eight blends with varying ratios of symmetric/asymmetric TAG, but with an equal amount of saturated fatty acids (40%) were prepared. The preparation of the blends involved the mixing of different fractions of shea butter with high oleic sunflower oil. The ratio of symmetric/asymmetric TAG decreased from blend 1 to 8. These blends were crystallized at 15°C and 20°C and stored at various temperatures according to the experiment. The research was divided in four parts: part one focused on the determination of the composition of the starting materials and blends and their preparation, the investigation of the crystallization behaviour of the blends was done in part two while the storage stability was studied in part three, in part four the fat migration from hazelnut filling to tempered and untempered samples of the blends was studied. The starting materials and blends were characterized in terms of both fatty acid profile (through the use of GC) and TAG composition (through the use of HPLC). Based on the results of the starting materials the eight blends were prepared with different ratios of symmetric/asymmetric TAG. The crystallization behaviour was investigated using pNMR, DSC (both the isothermal and the stop and return method) and XRD. Regarding the DSC, results showed a two-step crystallization for all blends. The stop and return data gave an indication that polymorphic transitions occurred in most of the blends. This was confirmed by WAXD data that demonstrated a polymorphic transition from á to either â’ or â for almost all of the XRD experiments done. The storage stability of the blends was studied with hardness measurements and the analysis of the microstructure was done with polarized light microscopy. The hardness measurements showed that there was no direct pattern regarding the evolution of the hardness with time and/or ratio of symmetric/asymmetric TAG. It was observed that the two blends with the highest amount of SSO had the highest value of hardness directly after the crystallization at 15°C and the value drops substantially during storage whether it was stored at 18 or 23°C. The obtained values suggest that no post-hardening occurred. Through polarized light microscopy it was observed that blends 1, 2 and 3 formed big crystals imbedded in a matrix of small crystals, independently of the crystallization and storage temperature. Regarding to the other blends, they presented numerous crystals of very small size and very small gaps between them. In the study of the fat migration it could be observed that excluding blend 1, the effect of tempering on the prevention of the migration of the TAG seemed to be almost negligible. Between all of the blends, the tempered samples of blend 1 were the most effective in preventing the migration of TAG from the hazelnut filling to the stearic-based blend, while the untempered blend 1 was the less effective of them all.
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Chapman, Nicholas. « Dust structure and composition within molecular clouds and cores ». College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7613.
Texte intégralRésumé :
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Astronomy. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lingg, Linda Jeanne. « Lanthanide trifluoride thin films : Structure, composition, and optical properties ». Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185031.
Texte intégralRésumé :
This study characterizes thin films of eleven lanthanide trifluorides which are potentially useful for optical applications. The natural and controlled transparency and real refractive index of single layers of these trifluorides are examined and accompanied by studies of composition and crystal structure of the films which are made by conventional, high temperature, and ion-assisted thermal evaporation. Additionally, since these particular fluoride compounds provide an excellent opportunity for doing so, the mechanisms active in film modification through high temperature and ion-assisted thermal evaporation are explored.
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Dzianach, Paulina Agnieszka. « Modelling the Composition and Structure of Campylobacter jejuni Biofilms ». Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/82785.
Texte intégralRésumé :
The goal of this research project was to study the effects of environmental and genetic factors on biofilm formation of Campylobacter jejuni with the use of mathematical modelling, experimental and bioinformatics techniques. Potential reasons for some puzzling observations regarding C. jejuni biofilm formation have been proposed as a result of this study, and a number of genes and SNPs have been identified, which may play a role in biofilm formation of this pathogen.
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Giles, Rohini. « Jupiter's tropospheric composition and cloud structure from 5-μm spectroscopy ». Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:04619240-ba40-4ee2-afcc-7f911f364d05.
Texte intégralRésumé :
This thesis uses infrared observations from spacecraft and ground-based telescopes to investigate the composition and cloud structure of the jovian atmosphere. It focuses on a single spectral region, known as the 5-μm window, where Jupiter's upper atmosphere becomes optically thin. This allows us to probe down beneath the planet's thick cloud decks to the 4{8 bar region in the middle troposphere. Two different data sources are combined to build up a three-dimensional picture of Jupiter's troposphere. The first dataset is from the Cassini VIMS instrument, and was taken during the 2000-2001 Jupiter yby. These observations cover a wide spectral range, provide global coverage and include both the nightside and the dayside of the planet, making them well suited to studying clouds. The VIMS spectra can be modelled using a single tropospheric cloud deck, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; and (iii) the cloud is sufficiently spectrally at. The second dataset is from the CRIRES instrument at the Very Large Telescope in Chile. These observations have a very high spectral resolution, allowing the absorption lines of individual molecular species to be resolved. The CH3D line shape varies between belts and zones, which can be interpreted as variations in the opacity of a deep cloud, located at around 5 bar. There is also evidence for spatial variability in two disequilibrium species, AsH3 and PH3, both of which show an enhancement at high latitudes. This is in contrast to a third disequilibrium species, GeH4, which shows no evidence for spatial variability. The CRIRES dataset also includes several strong emission lines, which are identified as H3+, an auroral species in Jupiter's ionosphere. The strengths of these lines were measured in order to determine the ionospheric temperatures. The work in this thesis contributes to our understanding of the dynamical, chemical and cloud-forming processes shaping Jupiter's troposphere and provides a reference point for future work, including observations made by NASA's Juno mission.
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Everard, David Alexander. « Composition, structure and processes along woodland gradients in the Weald ». Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385319.
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Bayat, Alireza [Verfasser]. « Composition and geometric structure of ultrathin oxide films / Alireza Bayat ». Halle, 2018. http://d-nb.info/1175950572/34.
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Li, Ming. « Composition-structure-property relationships in high permittivity oxide-bassed perovskites ». Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489139.
Texte intégralRésumé :
The composition-structure-property relationships of several important oxides are reported. The effect of sintering atmosphere, cooling rate and post annealing in N2 on the composition, B-site cation ordering, electrical conductivity and microwave dielectric loss of BCN ceramics have been investigated. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy (RS) results confirm that a slow cooling rate from the sintering temperature and/or post annealing below the order-disorder phase transition temperature increases the degree of B-site cation 1:2 ordering regardless of the oxygen partial pressure (pOj) of the sintering and/or annealing atmosphere.
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Comtois, Audrey. « Structure et composition du milieu riverain en forêt boréale québécoise ». Master's thesis, Université Laval, 2013. http://hdl.handle.net/20.500.11794/25413.
Texte intégralRésumé :
Ce projet visait à mieux comprendre la répartition de la végétation riveraine en forêt boréale québécoise. La végétation adjacente à cinq types de plans d’eau ou cours d’eau a été inventoriée dans quatre provinces naturelles recoupant d’est en ouest tout le Nord de la forêt boréale commerciale québécoise en paysage forestier vierge. Certaines caractéristiques physiques du milieu ont été évaluées. La végétation riveraine variait selon la province naturelle principalement en fonction de la topographie. Les profils d’élévation particuliers à certains types de lacs et cours d’eau ont généré des communautés végétales distinctes dont les patrons de répartition ont été résumés en toposéquences. Celles-ci révèlent la présence récurrente de trois différentes sous-zones au milieu riverain : le dénudé humide, la forêt riveraine humide et la forêt riveraine sèche. Ces trois sous-zones, qui couvraient en général environ 40 m à partir de la rive, s’étendaient davantage dans les régions au relief plat.The aim of this project was to improve the knowledge of riparian plant distribution in the boreal forest of Quebec. Vegetation adjacent to five types of water bodies or watercourses was sampled in the four ecoregions covering from East to West all the northern part of Quebec’s commercial boreal forests restricted to natural landscapes. Some physical factors of the riparian area were also evaluated. Mainly, riparian vegetation varied among ecoregions in relation with topography. Particular elevation profiles for some types of water bodies and watercourses supported distinct plant communities. Patterns of plant communities were summarized in toposequences that consistently reveal the existence of three different sub-areas in the riparian area: untreed wetland, riparian wet forest, and riparian dry forest. Those three sub-areas generally covered about 40 m from the shore and extended even more in flat regions.
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Szekeres, Gergő Péter. « Structure and Composition of the Protein Corona in Animal Cells ». Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21656.
Texte intégralRésumé :
Die Charakterisierung der Protein-Nanopartikel-Wechselwirkungen in komplexen biomolekularen Systemen wie einer lebenden Zelle ist für die Pharma-, Medizin- und Umweltforschung von entscheidender Bedeutung. In solchen biomolekularen Systemen adsorbieren Proteine leicht auf der Oberfläche von Nanopartikeln, die die Proteinkorona bilden. Diese Arbeit konzentriert sich auf die Charakterisierung der Proteinkorona in lebenden Zellen, wobei verschiedene analytische Ansätze kombiniert werden. Experimente mit oberflächenverstärkter Raman-Streuung (SERS) an reinen Proteinlösungen zeigten die Konzentrationsabhängigkeit der Protein-Gold-Nanopartikel-Wechselwirkungen, die zu unterschiedlichen SERS-Spektren führten und ermöglichten die Bestimmung von Proteinsegmenten, die an Citrat-stabilisierte Gold-Nanopartikel binden. In SERS-Experimenten mit lebenden Zellen wurde die Anwesenheit von Proteinfragmenten in der innersten Schicht der Proteinkorona, die als harte Proteinkorona bezeichnet wird, festgestellt. Eine analytische Methode, die Natriumdodecylsulfat-Polyacrylamid-Gelelektrophorese und Hochleistungs-Flüssigchromatographie-gekoppelte Elektrospray-Ionisations-Massenspektrometrie kombiniert, wurde entwickelt, um die Bestandteile der Hartproteinkorona zu identifizieren. Die Proteomics-, SERS- und Cryo-Soft-X-Ray-Nanotomographiedaten, wobei letztere Informationen über die dreidimensionale Ultrastruktur der Zelle liefern, zeigen den Aufnahmemechanismus, die Verarbeitung, die Akkumulationsstelle, die molekulare Umgebung und die induzierten zellulären Reaktionen internalisierter Goldnanopartikel. Diese Arbeit validiert die Verwendung von SERS bei der Analyse der Proteinkorona in der Lösung von Modellproteinen und in lebenden Zellen und präsentiert eine geeignete Methode zur Analyse der unveränderten harten Proteinkorona, die in lebenden Zellen gebildet wird.The characterization of the protein-nanoparticle interactions in complex biomolecular systems such as a living cell is vital for pharmaceutical, medical, and environmental research fields. In such biomolecular systems, proteins readily adsorb on the surface of nanoparticles forming the protein corona. This thesis focuses on the characterization of the protein corona in living cells combining different analytical approaches. Surface-enhanced Raman scattering (SERS) experiments on pure protein solutions revealed the concentration dependence of the protein-gold nanoparticle interactions resulting in different SERS spectra, and allowed for the determination of protein segments binding to citrate-stabilized gold nanoparticles. In live cell SERS experiments, the presence of protein fragments in the innermost layer of the protein corona, called the hard protein corona, was revealed. An analytical method combining sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-performance liquid chromatography-coupled electrospray ionization mass spectrometry was developed to identify the constituents of the hard protein corona. The proteomics, SERS, and cryo soft X-ray nanotomography data, the latter providing information of the three dimensional ultrastructure of the cell, reveal the uptake mechanism, processing, accumulation site, molecular environment, and the induced cellular responses of internalized gold nanoparticles. This work validates the use of SERS in the analysis of the protein corona in the solution of model proteins and in living cells, and presents a suitable method for the analysis of the unaltered hard protein corona formed in living cells.
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Tabibi, Makaye. « Dispersant Effects on Zinc Dialkyldithiophosphate (ZDDP) Tribofilm Structure and Composition ». VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/4059.
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For decades, global regulations and government mandates have driven technological developments to improve vehicle fuel economy. Tribological components found in all automotive engines contain metal-on-metal contact zones that may result in increased friction and wear, reducing overall engine efficiency. Lubricant additives such as antiwear and friction modifying components are added to motor oils to prevent some of the damages that may occur at contact zones and improve friction. The effects of other additive components, such as dispersants, that are prevalent in a lubricant additive package on the anti-wear layer remain relatively unknown. Polyisobutenyl Succinimide (PIBSI) dispersants were evaluated for their interactions with the ZDDP antiwear component. The physical and chemical properties and friction of the tribofilms formed in presence of dispersants were defined revealing a previously unknown structure-activity relationship. Further analysis of ZDDP and dispersants revealed surface and bulk fluid interactions.
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Tajuelo, Rodriguez Elena. « Relation between composition, structure and morphology in C-S-H ». Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9292/.
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The aim of this study was to determine if there is a relationship between the morphology of C-S-H (calcium silicate hydrates) with its chemical composition and structure or the morphological change is kinetically driven. The morphology of C-S-H, the binding phase of cement, has been an open subject of debate for decades. C-S-H morphology affects the shape of the capillary pores, as the capillary porosity is defined by the outer product C-S-H. Thus, the morphology of C-S-H partially determines transport properties and the durability of cementitious materials. This underlines the importance of understanding it to model the degradation and predict the service life of such materials. The Op C-S-H (outer product) exhibits different morphologies from fibrillar to sheet-like foils in different cementitious systems. It is not clear whether the change in morphology is determined by the structure and chemical composition or it is kinetically driven [1]. Finding suitable synthetic analogues of materials formed under normal conditions remains a challenge. However, synthetic analogues are ideal systems for the aim of this project. Their fabrication is controlled under synthesis parameters which can affect the morphology and can be tailored. Therefore synthetic C-S-H, with Ca/Si ratios between 0.75 to ~1.7 (covering part of the range that commercial cements exhibit) were proposed as model systems to be compared with real cementitious systems in this study. TEM and NMR were the main techniques to analyze the morphology, chemical composition and structure of the samples. Other techniques such as STA, XRD, XRF, TG-FTIR-DSC and SEM were used to get complementary information. The results obtained indicate that C-S-H morphology of samples fabricated via silica-lime reactions with bulk Ca/Si ratios from 0.75 to 1.5, and C-A-S-H samples with Ca/Si=1 and Al/Si=0-0.05 is foil-like. The morphology of C-S-H in samples hydrated via the controlled hydration of C3S at fixed lime concentrations was found to be dependent on the lime concentration in solution; being foil-like for lime concentrations from 12 to 20mmol/l (Ca/Si ratios from ~1.25 to ~1.4), a mixture of foils and fibrils for 22mmol/l (Ca/Si ratio of ~1.58) and fibrillar for concentrations ≥ 25mmol/l (Ca/Si ratios of ~1.60-1.65). For each lime concentration, the morphology was found to be independent of the growth rate, being the same for the acceleration period (fast growth) and the deceleration period (slow growth). This implies the morphology is composition dependent and not kinetically driven. However, a link between the silicate structure of C-S-H and its morphology was also found. Samples fabricated via the controlled hydration of C3S, with an ultrasound gun, at lime concentrations of 27-29mmol/l, were found to have higher percentages of Q2 silicate species and more flattened surfaces, than samples fabricated at the same lime concentrations but with the use of C-S-H seeds (Xseed). This agrees with the fact that flattened surfaces could accommodate longer silicate chains while surfaces with more features would accommodate more Q1 end-chains.
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Dolly, Adeline. « Cachexie cancéreuse : composition corporelle, structure et métabolisme du muscle squelettique ». Thesis, Tours, 2019. http://www.theses.fr/2019TOUR3808.
Texte intégralRésumé :
La cachexie cancéreuse est un syndrome multifactoriel caractérisé notamment par une perte progressive du muscle squelettique, qui entraîne une diminution de la qualité de vie, de la réponse aux traitements anticancéreux, et de la survie des patients. De par la complexité physiopathologique de ce syndrome clinique, il n’existe pour le moment aucun traitement curatif.Malgré de récentes découvertes, les mécanismes à l’origine de la fonte musculaire squelettique ne sont pas clairement élucidés. Les résultats des études précliniques et cliniques pointent sur de possibles altérations des métabolismes mitochondrial et lipidique. De plus, si la composition corporelle est affectée par la tumeur, elle l’est aussi par les traitements anti-cancéreux.Au cours de ce travail de thèse, nous nous sommes donnés comme objectifs d’étudier les liens entre la composition corporelle et un traitement par chimiothérapie à base de bévacizumab (étude clinique STIC-Avastin (NCT00489697)) ; ou avec la structure et le métabolisme du muscle squelettique, dans le contexte de la cachexie cancéreuse (protocoles cliniques METERMUCADIG (NCT02573974) et METERMUS-IMC (NCT03027479))Cancer cachexia is a multifactorial syndrome characterized by progressive loss of skeletal muscle, leading to decreased quality of life, response to cancer treatments, and patient survival. Due to the physio pathological complexity of this clinical syndrome, there is currently no cure to cancer cachexia.Despite recent discoveries, the mechanisms underlying skeletal muscle wasting are not clearly understood. Recent preclinical and clinical studies highlighted possible alterations in mitochondrial and lipid metabolism. Furthermore, body composition could be affected not only by the tumor, but also by anti-cancer treatments.During this PhD, the aims were to study the links between body composition and bevacizumab-based chemotherapy treatment (clinical study STIC-Avastin (NCT00489697)); or with skeletal muscle structure and metabolism, in the context of cancer cachexia (clinical protocols METERMUCADIG (NCT02573974) and METERMUS-IMC (NCT03027479))
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Byron, Robert Griffin. « Variations on the theme of metamorphosis as applied to musical compositional structure ». Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2009. https://ro.ecu.edu.au/theses/1890.
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Atgié, Marina. « Composition and structure of gum Arabic in solution and at oil-water interfaces ». Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0024/document.
Texte intégralRésumé :
La gomme arabique est un exsudat d’arbre qui est essentiellement utilisée pour ses propriétés stabilisantes et émulsifiantes. Ce produit naturel est un mélange complexe de protéines et de polysaccharides liés de façons covalentes, qui différent de part leur masse molaire et leur hydrophobicité. Malgré le grand nombre d’études existantes dans littérature sur la structure et les propriétés interfaciales de la gomme arabique, la compréhension de la relation entre la composition interfaciale, la structuration interfaciale et la métastabilité d’émulsions restent mal comprises à ce jour compliquée. La gomme arabique est classiquement décrite comme un mélange de trois fractions : une fraction riche en polysaccharide (arabinogalactan), une fraction composée de conjugués protéine-polysaccharides et enfin des glycoprotéines. Les propriétés émulsifiantes et stabilisantes de la gomme sont attribuées à la fraction de conjugués dont la partie protéinée s’adsorbe à la surface des gouttes d’huiles et les espèces carbonées apportent des répulsions stériques entre les gouttes. Dans cette thèse, nous avons étudié le comportement microscopique des espèces de la gomme en solution et aux interfaces huile/eau. La première étape a consisté à caractériser la structure des molécules de la gomme en solution. Une séparation bi-dimensionnelle de la gomme a été réalisée par exclusion stérique suivie d’une séparation par affinité hydrophobe, ce qui nous a permis de confirmer la nature très hétérogène de la gomme. Des expériences de diffusion des rayons-X et des neutrons aux petits angles sur la gomme arabique et ses fractions nous ont amené à proposer un modèle structural des espèces conjuguées. Nous avons ensuite étudié la composition de films de gomme arabique adsorbés en émulsion en la comparant avec celle de la gomme en solution. Une augmentation du taux de protéine dans le film interfacial a montré le rôle crucial des espèces polypeptidiques sur l’adsorption. Nous avons observé que la composition du film adsorbé diffère de la gomme en solution mais reste hétérogène en taille et en hydrophobicité. Un bilan massique a révélé une forte dépendance entre la formulation d’émulsion (concentration en gomme et paramètres physicochimiques) et la concentration surfacique alors que la composition de l’interface a très peu changé. Ces résultats suggèrent une modification de conformation des espèces adsorbées en fonction des conditions d’émulsification. Dans un troisième temps, nous nous sommes intéressés aux mécanismes de stabilisation provenant de l’adsorption des espèces amphiphiles de la gomme arabique. Pour cela, nous avons développé une méthode permettant de récupérer les espèces adsorbées dans une émulsion huile dans eau. Cette méthode nous a permis de mettre à jour une structuration du film adsorbé. Les espèces récupérées de l’interface ont montré la présence d’une agrégation, dont l’intensité dépend directement du taux de couverture et du taux de protéine de l’interface. La métastabilité d’émulsions stabilisées par de la gomme arabique est ainsi favorisée par l’augmentation de la structuration interfaciale, i.e. quand le taux d’agrégation des espèces adsorbées augmente. Un tel comportement n’a pas encore été reporté dans la littérature et nous pensons qu’il s’agit d’un mécanisme clef dans le cadre d’émulsions stabilisées par la gomme arabique. Enfin, des expériences de diffusion de neutrons aux petits angles (avec un contraste identique entre les phases continue et dispersée) ont révélé des différences de structuration entre deux régimes de concentration surfacique. Ces observations ont été discutées au regard des spectres de diffusion de la gomme en solution. Pour conclure, cette thèse porte sur la relation entre composition et structuration dans des émulsions stabilisées par la gomme arabique et démontre notamment un mécanisme original de stabilisation qui joue un rôle important dans ce système complexeGum arabic, a tree exudate, is essentially used for its binding and emulsifying properties. This natural product is a complex mixture of covalently linked proteins and charged polysaccharides moieties, differing in their molecular mass and hydrophobicity. A large body of literature now exists on the structure and interfacial properties of gum Arabic but a comprehensive description of the relationship between interfacial composition, interfacial structuration and emulsion metastability remains elusive. In the literature, gum Arabic is described as a mixture of three fractions: an arabinogalactan rich polysaccharide fraction, a polysaccharide-protein conjugates fraction and a fraction of glycoproteins. The conjugate fraction is thought to be responsible for the emulsifying and stabilizing properties of the gum, with the protein part adsorbing at oil droplets surface and the carbohydrate moieties providing steric repulsion between droplets. In this work, we have investigated the microscopic behavior of the gum species in solution and at oil/water interfaces. The first step was to characterize the structure of gum Arabic species in solution. A twodimensional separation of the gum molecules was performed using size exclusion chromatography followed with by hydrophobic interaction separation, which confirmed the highly heterogeneous composition of the gum. Small angle X-ray and neutron scattering measurements on the gum and its fractions led us to propose a structural representation of the gum conjugated moieties. Then the composition of adsorbed gum Arabic films as compared to gum Arabic solutions has been investigated. An increase in the protein rate of the interfacial film showed the crucial role of the polypeptide moieties on the adsorption. The composition of the adsorbed film was shown to differ from the bulk but remained heterogeneous in size and hydrophobicity. A mass balance revealed a strong dependence between the emulsion formulation (gum concentration and physico-chemical parameters) and the surface concentration, while the composition of the interface was only slightly changed. These results suggest that gum Arabic adsorbing species must adopt conformational changes depending on emulsification conditions. In a third stage, we have addressed the stabilization mechanisms resulting from the adsorption of gum Arabic amphiphilic species. For that purpose, we have developed a method to recover the adsorbed species within an oil-in-water emulsion. This method allowed us to unveil a structuration of the adsorbed film. Species recovered from the interface displayed aggregation, the magnitude of which directly depended on the coverage density and protein rate of the adsorbed film. The metastability of emulsions, stabilized with gum Arabic, increased upon promoting interfacial structuration, i.e. when the aggregation rate of adsorbed species was enhanced. Such behavior has not been reported so far in the literature and we believe that it is a key mechanism of gum Arabic-based on emulsions. Finally, small angle neutron scattering experiments (contrast match between the continuous and dispersed phases) disclosed differences of structuration between two regimes of interface coverage. These observations were discussed in the light of the comparison with the scattering spectra of gum Arabic solutions. To conclude, this thesis revolves around the composition/structuration relationship in gum Arabic-stabilized emulsion stabilized and demonstrates that an original mechanism is at play in this complex system
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Nicolas, Anne. « Etudes structure-fonction d'une cutinase recombinante de Fusarium solani pisi ». Aix-Marseille 2, 1996. http://www.theses.fr/1996AIX2A002.
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Merrill, Julia Carlson. « Focus in the structure of concepts in analytic discourse ». CSUSB ScholarWorks, 2007. https://scholarworks.lib.csusb.edu/etd-project/3255.
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The primary focus of this thesis was to find out what makes workable topic sentences different from inadequate ones. A group of topic sentences was collected from the author's eight grade students and reviewed.
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Adams, Ruth. « Structure-composition-property relations in B-site deficient hexagonal perovskite systems ». Thesis, University of Huddersfield, 2010. http://eprints.hud.ac.uk/id/eprint/9697/.
Texte intégralRésumé :
This thesis describes the structural and preliminary electrical characterisation of various “shifted” hexagonal B-site deficient perovskites, of generic formula, A4B3O12. These ceramics are reported to possess promising microwave dielectric properties, which are a requirement for use in the ever evolving mobile telecommunications industry. The 12R crystal structures of the Ba3-xSrxLaNb3O12 series (x = 1 – 3) were refined at variable temperatures using NPD data in space group R-3 and some interesting behaviour was exhibited. All compositions were found to be antiphase tilted, the extent of which being dependent on the A-cation size. Upon heating, the tilt angle for all members of the series was found to decrease, although no tilt transitions from R-3 to R-3m were witnessed for all phases up to 900 °C, and a change in the magnitude of permittivity at 1 MHz was observed for all members except, BaSr2LaNb3O12. Additionally evidence from preliminary low temperature data suggest relaxor ferroelectric type behaviour. Ba2SrLaNb3O12 was found to possess the most promising dielectric properties although room exists for further improvement of the quality factor (Q value). To facilitate further tuning of the dielectric properties, specifically Q, the Ba3- xSrxLaNb3-yTayO12 series (x = 0 - 3, y = 1 - 2) was investigated, with the introduction of Ta5+ on the B-site. Some interesting ordering of A- and B-sites was found to occur, and furthermore, Nb5+ was found to display a preference to inhabit the distorted environment of B(1), adjacent to the “shifted” region, compared to the undistorted B(2) site, in the perovskite block. Unusual microwave dielectric properties were displayed with all compositions exhibiting small and positive temperature coefficient of resonant frequency (TCF) values and significantly small Q values, the reverse of what is expected, thus implying that the B-site has some influence on TCF values in this case. The interesting dielectric properties may be explained by several factors, including, the increased strength associated with the covalency of the Ta-O bond compared to that of Nb-O and the presence of some significant impurity phases, particularly in the intermediate compositions that are richer in Ta5+. The LCR data collected revealed similar results as found for the Ba3-xSrxLaNb3O12 series (x = 1 – 3), highlighting the limiting nature of the temperature range which did not, in fact reflect the true response of the compositions’ behaviour. All of the compositions are antiphase tilted at room temperature therefore the collection of variable temperature diffraction data is warranted. A range of novel Ta-based intergrowth compounds were synthesised and preliminarily characterised. No detailed structural or electrical data were collected for these compounds, however, the ability to form Ta-based intergrowths, in the first instance, has been established. It is postulated that by the formation of these intergrowth phases, the dielectric properties will be effectively tuned in comparison to those of the parent oxides that they are composed of, due to the regularisation of the octahedral layers that occurs upon the formation of such intergrowth structures. This often leads to improved TCF values, and by the introduction of Ta5+, can also give improved Q values. Ta5+ was substituted for Nb5+ in the untilted 5x6y (x = 1 – 3, y = 1) layered compounds, however, it was found that to facilitate this, the replacement of Ba2+ for Sr2+ was also required on the A-site. This double substitution was a requirement to obtain compositions closer to single phase Ta-rich phases compared to Nb-rich compositions.
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Boyd, Adrian. « Composition, structure and properties of sputter deposited calcium phosphate thin films ». Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311526.
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Lee, Jae Min. « Retrieval of atmospheric structure and composition of exoplanets from transit spectroscopy ». Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:9daa5af9-040d-47eb-a2ca-57aefcc36f21.
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Recent spectroscopic observations of transiting exoplanets have permitted the derivation of the thermal structure and molecular abundances of H2O, CO, CO2, CH4, metallic oxides and alkali metals in these extreme atmospheres. Here, for the first time, a fully-fledged retrieval algorithm has been applied to exoplanet spectra to determine the thermal structure and composition. The development of a suite of radiative transfer and retrieval tools for exoplanet atmospheres is described, building upon an optimal estimation retrieval algorithm extensively used in solar system studies. Firstly, the collection of molecular line lists and the pre-tabulation of the absorption coefficients (k-distribution tables) for high temperature application are discussed. Secondly, the best-fit spectra for hot Jupiters are demonstrated and discussed case by case. Available sets of primary and secondary transit observations of exoplanets are used to retrieve atmospheric properties from these spectra, quantifying the limits of our knowledge of exoplanetary atmospheres based on the current quality of the data. The contribution functions and the vertical sensitivity to the molecules are fully utilised to interpret these spectra, probing the structure and composition of the atmosphere. Finally, the retrievals provide our best estimates of the thermal and compositional structure to date, using the covariance matrices to properly assess the degeneracy between different parameters and the uncertainties on derived quantities for the first time. This sheds light on the range of diverse interpretations offered by other authors so far, and allows us to scrutinise further atmospheric features by maximising the capability of the current retrieval algorithm and to demonstrate the need for broadband spectroscopy from future missions.
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Cui, Yi. « Factor Structure And Affective Composition Of The Chills : Replication And Extension ». W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1616444531.
Texte intégralRésumé :
“The chills” refers to a set of bodily sensations (goosebumps, tingling, coldness, and shivers) that sometimes accompany strong emotion (Maruskin, Thrash & Elliot, 2012). Past factor analyses of the chills identified a multi-factor, hierarchical structure, consisting of four lower-order factors (goosebumps, tingling, coldness, and shivers) and two higher-order factors (goosetingles and coldshivers). Research on the affective nomological nets of particular chills factors provided additional evidence of the discriminant validity of the two higher-order and the four-lower-order factors (Maruskin, Thrash & Elliot, 2012; Wadsworth, 2019). Despite evidence of discriminant validity, most researchers have continued to treat the chills as a unitary construct. The goal of the present study is to replicate and extend evidence that the chills consists of a set of distinguishable sensations with distinct affective correlates. Specifically, I aim to (a) replicate the factor structure of the chills and (b) further test whether the four lower-order sensations show distinct relations to core affect variables. Using the narrative recall method, the present study assessed chills sensations and core affect during recalled chills experience. Results of factor analyses replicated the factor structure of the chills established by Maruskin et al. (2012). Results of circumplex analyses provided additional evidence of the discriminant validity of higher-order and lower-order sensations. Goosetingles tended to accompany pleasant states, whereas coldshivers tended to accompany unpleasant states. Furthermore, relative to goosebumps, tingling accompanied states lower on activation and higher on pleasure. Relative to coldness, shivers accompanied states lower on displeasure and higher on activation. These findings are consistent with but refine the conclusions of Maruskin et al. (2012) and point to the value of incorporating the affect circumplex in understanding the chills.
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Schiffman, Paula M. « Environmental determinism and forest structure and composition : a naturally replicated experiment ». Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/37397.
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Morin, Nathalie. « Les Microcodium : architecture, structure et composition, comparaison avec les racines calcifiées ». Montpellier 2, 1993. http://www.theses.fr/1993MON20025.
Texte intégralRésumé :
Les microcodium sont des fossiles calcaires, arborescents, de dimension millimetrique, dont la nature n'est toujours pas etablie avec certitude. Ces fossiles correspondent aux restes d'etres vivants souterrains endolithes, qui apparaissent au campanien et semblent s'eteindre au pliocene. Recemment, plusieurs auteurs ont decrit dans des sols actuels des racines calcifiees de structure comparable a celle des microcodium. Ce travail a pour objectif de comparer l'architecture, la structure et la composition des microcodium et des racines calcifiees actuelles, afin de tester l'hypothese d'une origine racinaire des microcodium. Les principaux resultats acquis consistent en la mise en evidence chez les microcodium de ramifications de type lateral monopodial en la mise en evidence de la presence systematique de stries d'accroissement au sein des prismes constitutifs, et en l'analyse de la composition isotopique des carbonates constitutifs. La comparaison avec les racines calcifiees actuelles montre que les microcodium consistent tres probablement en des racines de vegetaux superieurs, mais appartenant a un groupe fossile disparu actuellement. Differents elements suggerent qu'il pourrait s'agir d'un groupe apparente aux premieres monocotyledones
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Quet, Aurélie. « Composites de friction à matrice céramique : relation composition / structure / comportement tribologique ». Bordeaux 1, 2007. http://www.theses.fr/2007BOR13512.
Texte intégralRésumé :
Les composites C/C sont acutellement les matériaux les mieux adaptés aux exigences du freinage aéronautique. Ils présentent cependant un taux d'usure accru pour les freinages de taxiage. Les composites à matrice SiC se caractérisent par un lissage de cette bosse d'usure observée aux basses températures mais ils ne satisfont pas aux exigences du freinage de détresse. L'objectif de la thèse est d'introduire un autre carbure que le SiC dans la matrice des composites de friction et d'évaluer son influence sur le comportement tribologique des composites élaborés. Des composites C/C-ZrC et C/CTiC ont ainsi été élaborés via le procédé RMI (Reactive Melt Infiltration). Ces matériaux ont été caractérisés à travers des analyses morphologiques, chimiques et structurales. Une décohésion est présente à l'interface matrice de carbone/carbure. L'utilisation d'alliages, notamment à base de silicium, permet de limiter ce phénomène de décohésion. Les matériaux éléborés ont ensuite été testés sur un banc de simulation de freinage. Les composites C/C-ZrC e C/CTiC satisfont les conditions du RTO. Cependant, les composites à matrices ZrC montrent une usure très élevée à haute température en relation avec leur comportement à l'oxydation. Les composites à matrice TiC présentent une usure acceptable à haute température et une troncature de la bosse d'usure observée aux faibles températures, ce qui est lié à des coefficents de frottement faiblesC/C composites are nowadays the most suitable materials for needs of aircraft braking. However, they show a high wear during taxiing. SiC matrix composites are characterised by a smoothing of the wear peak noticed at low temperatures but they don't meet requirements of rejected take-off (RTO). The aim of this work is to put another carbide than SiC in the matrix of friction composites and to assess its influence on tribological properties of materials. C/C-ZrC and C/C-TiC composites were manufactured using RMI processing route (Reactive Melt Infiltration). Materials were characterised with mophological, chemical and structural analysis which reveal especially a decohesion between carbon phase and carbide phase. This gap can be limited using alloys as Zr-Si and Ti-Si alloys. Triboligical behaviour of the resulting materials was then investigated with an inertial dynamometer simulating brake stops. C/C-ZrC and C/C-TiC composites meet RTO requirements. Neverless, ZrC matrix composites have a high wear for high temperature brake stops linked to their oxidation behaviour. TiC matrix composites present moderate wear at high temperature and a lower wear at low temperature compared to C/C composites in relation to low friction coefficients
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White, Madeline Eve. « Investigation of the optical properties, composition and local structure of InGaN ». Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248841.
Texte intégral
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Guggenbühl, Claudia. « Recherches sur la composition et la structure du ms. Arsenal 3516 / ». Basel ; Tübingen : A. Francke, 1998. http://catalogue.bnf.fr/ark:/12148/cb36969816r.
Texte intégral
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Hu, Yu. « Structure-composition-property relationships of stoichiometric and non-stoichiometric "Bi12MO20" sillenites ». Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4489/.
Texte intégralRésumé :
The structure-composition-property relationships of sillenite-type compounds Bi12MxO20±δ, where M = Zn2+, Mg2+, Fe3+, Al3+, In3+, Ga3+, B3+, Si4+, V5+ and P5+ have been investigated. This has enabled improved understanding associated with the following aspects: (i) approval of the structural model of Radaev and co-workers’ (R model); (ii) validity of the general formula for sillenites suggested by Valant and Suvorov (VS); (iii) rationalisation of the linear trend(s) between dopant ion (M) size and unit cell length as reported by Poleti et al.; (iv) the origins of the low (LT) and high temperature (HT) bulk dielectric relaxation effects in sillenites; (v) the variation in bulk conductivity of stoichiometric and non-stoichiometric sillenites; (vi) potential physical applications of sillenites as Low Temperature Co-fired Ceramics (LTCC) dielectrics and/or mixed ionic-electronic conductors.
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Jain, Saumya. « The Analysis of mRNP Granule Composition and Structure in Saccharomyces cerevisiae ». Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556224.
Texte intégralRésumé :
A recurring theme in biology is the aggregation of mRNA-protein complexes (mRNPs) into higher order assemblies. Often these complexes play important roles in the regulation of gene expression, but the function of the conserved cytoplasmic mRNP assemblies - P bodies and stress granules, is not known. It is believed that the misregulation of granule assembly is related to disorders like Amyotrophic Lateral Sclerosis and Frontotemporal Lobe Degeneration. Determining the complete composition of these granules may hold the key to understanding the function and mechanism of assembly of these granules. This work describes multiple approaches taken to identify new protein and mRNA components of P bodies and stress granules. New members of the P body and stress granule proteome reveal a role for these granules in diverse cellular processes including signal transduction, transcription and metabolism. Additionally, a new stress granule resident complex - the CCT complex, was also identified as a novel regulator of granule disassembly. This work also describes the first purification scheme for stress granules and presents a new system for in vitro study of stress granules. Together, the findings shed new light on the composition, function, structure and regulation of P bodies and stress granules in yeast.