Cette étude a eu pour but d'étudier la possibilité de couplage de modèles dynamiques de croissance de l'herbe avec des données de télédétection, et ce pour deux terrains contrastés : La Réunion et le Kalahari (Afrique du Sud). Deux phases se sont succédé. Une première phase exploratoire, basée sur des images SPOT5 et SPOT5take5 (satellites désorbités en cours d'étude) a permis de tirer plusieurs enseignements. A La Réunion l'ajustement d’un modèle empirique entre indices de végétation et biomasse engendre trop d'erreur. Il est en revanche possible d'estimer le Leaf Area Index (LAI) grâce au NDVI (Normalized Difference Vegetation Index). Les parcours du Kalahari, plus complexes, avec différentes strates de végétation (graminées, arbustes, arbres) n'ont pas permis d'estimer l'état du couvert de graminées. Cette phase a ouvert la voie au travail effectué sur un capteur plus pérenne dans le temps, Sentinel-2. Les données Sentinel-2 ont permis d'estimer le LAI des prairies réunionnaises avec une RMSE (Root Mean Square Error) de 0,63 (r²=0,82). Le LAI ainsi estimé a été utilisé dans le couplage du modèle dynamique permettant une baisse générale de la RMSE de l'ordre de 40% par rapport au modèle sans couplage. Ces résultats ont été obtenus durant l'hiver austral, la saison sèche. Durant la période d'été austral les pluies plus abondantes accélèrent la croissance des plantes et les cycles de pousse se raccourcissent. Les images satellites sans couvert nuageux se font plus rares. La prise en compte de cette combinaison de facteurs pouvant impacter les prédictions de biomasse fourragère fera partie des principale perspectives de ce travail. / The purpose of this study was to explore the possibility of coupling dynamic models of grass growth with remote sensing data for two contrasting countries: Reunion Island and Kalahari (South Africa). Two phases followed one another. A first exploratory phase, based on SPOT5 and SPOT5take5 images (desorbed satellites under study) allowed us to learn from this experience. In Reunion the adjustment of an empirical model between vegetation indices and biomass generates too much error. However it is possible to estimate the Leaf Area Index (LAI) thanks to the NDVI (Normalized Difference Vegetation Index). More complex Kalahari rangelands with different vegetation strata (grasses, shrubs, trees) failed to estimate grass cover conditions. This phase set the stage to work on a more durable sensor over time, Sentinel-2. Sentinel-2 data made it possible to estimate the LAI of Reunion Island grasslands with a RMSE (Root Mean Square Error) of 0.63 (r² = 0.82). The LAI thus estimated was used in the coupling of the dynamic model, allowing a general decrease of the RMSE of the order of 40% compared to the model without coupling. These results were obtained during the austral winter, the dry season. During the austral summer, the more abundant rains speed up the growth of the plants and the growth cycles become shorter. Satellite images without cloud cover are becoming scarce. Taking into account this combination of factors that may impact predictions of forage biomass will be one of the main perspectives of this work.

abstract: Researchers who conduct longitudinal studies are inherently interested in studying individual and population changes over time (e.g., mathematics achievement, subjective well-being). To answer such research questions, models of change (e.g., growth models) make the assumption of longitudinal measurement invariance. In many applied situations, key constructs are measured by a collection of ordered-categorical indicators (e.g., Likert scale items). To evaluate longitudinal measurement invariance with ordered-categorical indicators, a set of hierarchical models can be sequentially tested and compared. If the statistical tests of measurement invariance fail to be supported for one of the models, it is useful to have a method with which to gauge the practical significance of the differences in measurement model parameters over time. Drawing on studies of latent growth models and second-order latent growth models with continuous indicators (e.g., Kim & Willson, 2014a; 2014b; Leite, 2007; Wirth, 2008), this study examined the performance of a potential sensitivity analysis to gauge the practical significance of violations of longitudinal measurement invariance for ordered-categorical indicators using second-order latent growth models. The change in the estimate of the second-order growth parameters following the addition of an incorrect level of measurement invariance constraints at the first-order level was used as an effect size for measurement non-invariance. This study investigated how sensitive the proposed sensitivity analysis was to different locations of non-invariance (i.e., non-invariance in the factor loadings, the thresholds, and the unique factor variances) given a sufficient sample size. This study also examined whether the sensitivity of the proposed sensitivity analysis depended on a number of other factors including the magnitude of non-invariance, the number of non-invariant indicators, the number of non-invariant occasions, and the number of response categories in the indicators. / Dissertation/Thesis / Doctoral Dissertation Psychology 2016

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No. of bitstreams: 2 Dissertação - Rafaela Wolff de Pina - 2013.pdf: 5542701 bytes, checksum: c4321bba896962c7daf170cb3d0f88f0 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-11-29 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Human activities of natural resources exploration can have negative impacts on lakes and reservoirs. The increase in the amount of nitrogen and phosphorus in water cause deterioration in the water quality and eutrophication. Eutrophication by algae and cyanobacteria may hinder the use of water for several purposes. João Leite’s reservoir, located in the state of Goiás, is an important water resource for the public supply; approximately, 2.300.000 inhabitants are in need of its water. The present work aimed to study the dynamics of variation of a phytoplankton community in João Leite’s reservoir by a bioreactors board studies in order to evaluate the population growth of phytoplankton in different conditions of light and nutrients. The experiments were performed in nine bioreactors with controlled light conditions (22 μmol de fótons.m-2 .s-1, 44 μmol de fótons.m-2 .s-1,, 67 μmol de fótons.m-2 .s-1) and nutrients (N / P = 10) (N / P = 16) and (N / P = 20) and according with a factorial experimental design with two factors at three levels (3 Meters). The bioreactors were submitted to a photoperiod of 12/12 hours and kept at a temperature of 25 ± 2 ° C. The natural water samples were collected in 5 sampling campaigns in the months of April, May, June and July 2013 from João Leite’s reservoir and monitored for five consecutive days in the laboratory. The results showed a significant positive correlation between light and nutrients on the growth of algae and cyanobacteria. A principal component analysis (PCA) indicated light intensity and nitrate as the factors that most influenced the increase of phytoplankton density. The paired t-test and Tukey tests showed that the effect of light, however, was more significant than the effect of nutrients. The growth of algae and cyanobacteria were modeled as logistic model that adjusted well to the data with R ² value ranging between 0.80 and 0.99. The laboratory experiment corroborated the data of seasonal variations in the reservoir, in which occurred as the increase of algae and cyanobacteria density as was the increase in nitrate concentration and light intensity. / As atividades humanas de exploração dos recursos naturais podem gerar impactos negativos em lagos e em reservatórios. O aumento do aporte de nitrogênio e fósforo nas águas causam a deterioração da qualidade da água e eutrofização. A eutrofização por algas e cianobactérias pode dificultar o uso compartilhado da água para diversos fins. O reservatório do João Leite, situado no estado de Goiás, é um importante recurso hídrico destinado ao abastecimento público de aproximadamente, 2.300.000 habitantes. O presente trabalho teve como objetivo estudar a dinâmica da variação da comunidade fitoplanctônica no reservatório do João Leite por meio de estudo de bancada em biorreatores com a finalidade de avaliar o crescimento da população de fitoplâncton em diferentes condições de luz e nutrientes. Os experimentos foram realizados em nove biorreatores com condições controladas de luz (22 μmol de fótons.m-2 .s-1, 44 μmol de fótons.m-2 .s-1,, 67 μmol de fótons.m-2 .s-1) e nutrientes (N/P=10), (N/P=16) e (N/P=20) e de acordo com um planejamento experimental do tipo fatorial com dois fatores em três níveis (3²). Os biorreatores foram submetidos a um fotoperíodo de 12/12 horas e mantidos a uma temperatura de 25±2ºC. As amostras de água natural foram coletadas em 5 campanhas amostrais nos meses de Abril, Maio, Junho e Julho de 2013 no Reservatório do João Leite e monitoradas por 5 dias consecutivos em laboratório. Os resultados mostraram uma correlação positiva e significativa entre a luz e nutrientes sobre o crescimento de algas e cianobactérias. Uma análise de componentes principais (ACP) indicou a intensidade de luz e concentração de nitrato como os fatores que mais influenciaram o aumento da densidade do fitoplâncton. O teste t pareado e Tukey mostraram que, todavia o efeito da luz foi mais significativo do que o efeito dos nutrientes. O crescimento de algas e cianobactérias foram modelados conforme modelo logístico que se ajustou bem aos dados com o valor de R² variando entre 0,80 e 0,99. O experimento em laboratório corroborou com os dados de variação sazonal no reservatório, em que ocorreu aumento da densidade de algas e cianobactérias à medida que ocorreu o aumento da concentração de nitrato e intensidade de luz.

The instantaneous mortality rate (M) is an important parameter in elasmobranch management and conservation, but is difficult to estimate directly. Thus, indirect estimates based on relatively easily obtained life history parameters are commonly used. Many indirect methods incorporate one or more parameters from the von Bertalanffy growth model (VBGM), which is often criticized for its inability to describe changes in growth associated with maturity. The Lester growth model (LGM) is a biphasic alternative to the VBGM that incorporates trade-offs between reproduction, growth, and survival, and may therefore more accurately estimate M. I used published data from 29 elasmobranch species to compare the performance of the LGM to four conventional growth models and nine conventional methods for indirectly estimating M. For three species (Heterodontus portusjacksoni, Rhizoprionodon taylori, and Carcharhinus limbatus), I obtained direct estimates of M to evaluate the accuracy of indirect M methods. According to AICc, the LGM was the best fitting model for 80.8% of datasets. Using one-sample t-tests, I found that five indirect M methods (two of which are dependent on the LGM) consistently generated estimates of M that were in close agreement with direct estimates. The most common methods in elasmobranch literature appear to be overestimating M by factors of 1.34 – 1.91. However, further research is needed to verify these results across a wider range of species. Overall, I recommend using the LGM to describe the lifetime growth of sharks, and estimating M by averaging across five indirect methods.

Doctor of Philosophy / Department of Chemistry / Mark D. Hollingsworth / The ferroelastic urea inclusion compound (UIC) of 2,10-undecanedione/urea exhibits a striking pseudoelastic memory effect. Although pseudoelasticity is possible for UICs containing only 2,10-undecanedione, introduction of a structurally similar guest impurity (2-undecanone) gives rise to rubber-like behavior, a form of pseudoelasticity. This phenomenon depends on both the crystal strain and the concentration of monoketone: above 13-14% 2-undecanone, pseudoelastic behavior is observed reliably, even at strains as high as 2.4%. The dramatic change in ferroelastic behavior over a small range of impurity content indicates that this is a critical threshold phenomenon. Because the impurity concentration has such a dramatic effect on domain switching, it was important to determine the sector-dependent patterns of incorporation of this relaxive impurity. Preliminary HPLC analyses of guest populations suggest that preferential incorporation of monoketone guests occurs between nonequivalent growth sectors, and that these patterns can be rationalized using a symmetry specific growth model. Birefringence mapping and HPLC studies of optically anomalous UICs containing mixtures of 2,9-decanedione and 2-decanone (which possess trigonal metric symmetry) suggest analogous patterns in guest incorporation and/or ordering that can also be rationalized. Although crystals of 2,9-decanedione/urea exhibit no ferroelastic strain at ambient temperature, they exhibit a proper ferroelastic phase transition near -170[degrees]C. It is proposed that differential perfection of domains gives rise to pseudoelasticity in UICs, and that relaxive impurities play an important role in the energetics of this process. Because ultrafast video studies of domain reversion kinetics demonstrate no clear correlation of observed rates with impurity content, it is proposed that the relaxive impurities facilitate spontaneous domain reversion by annealing stressed defect sites that would otherwise lead to irreversible or plastic domain switching. Following earlier work using synchrotron white beam X-ray topography, the driving force for domain reversion is thought to involve the presence of nanoscopic twins whose strain is epitaxially mismatched with neighboring daughter domains. The behavior of these nanoscopic twins was monitored with in-situ X-ray diffraction studies of stressed crystals, and this has led to a more thorough understanding of the role of these nanoscopic twins in the ferroelastic domain switching and rubber-like behavior in this class of materials.

Nous nous sommes intéressés à la croissance et la caractérisation de nanofils de silicium (Si) et de germanium (Ge). Les nanofils ont été synthétisés par le mécanisme VLS (Vapeur Liquide Solide) dans un réacteur LPCVD (Low Pressure Chemical Vapor Deposition), en utilisant l'or (Au) comme catalyseur et le silane (SiH4) ou le germane (GeH4) comme gaz précurseur. Pour que ce procédé de croissance conduise à l'obtention de nanofils, le catalyseur Au doit être nano-structuré sous la forme de nanoparticules de diamètre si possible contrôlé. Ceci est fait dans cette étude par « démouillage » d'une couche continue déposée initialement par effet Joule sur le substrat choisi. L'épaisseur de cette couche continue initiale est un paramètre essentiel dans l'étude. Une partie préliminaire de ce travail a concerné l'étude de la façon dont se démouillage s'effectue, en fonction des divers paramètres. Nous avons ensuite effectué une étude exhaustive du rôle de tous les paramètres (nature du substrat, température, pression, épaisseur de la couche continue d'or, temps de croissance, durée et température de démouillage) qui contrôlent le procédé de croissance LPCVD sur les caractéristiques des nanofils de Ge notamment. Nous avons fait varier ces paramètres dans de larges fenêtres de valeurs afin de maîtriser et contrôler leur croissance. La caractérisation structurale des nanofils par microscopie électronique en transmission montre leur structure monocristalline avec une direction de croissance <111> pour les nanofils de Si et <110> pour les nanofils de Ge. Enfin, dans le cas des nanofils de Ge coniques isolés et déposés sur différents substrat, l'analyse micro-Raman nous a permis de mettre en évidence un phénomène de résonance optique à l'intérieur du nanofils et qui dépend fortement du diamètre local du nanofil. L'intensité Raman augmente avec la diminution du volume excité. Ces effets sont expliqués par les modes optiques apparaissant selon le diamètre local du nanofil, la longueur d'onde d'excitation et la nature du substrat utilisé. En plus, Le profil de la fréquence obtenu a montré qu'aucune anomalie particulière n'est observée. Ces profils obtenus en fonction du substrat et de la longueur d'onde utilisés sur différents nanofils montrent une faible variation de la fréquence. Le profil de la largeur à mi-hauteur est constant. Ces résultats montrent l'absence des effets de confinement de modes de phonons dans les nanofils individuels caractérisés. / This work deals with the growth and characterization of silicon (Si) and germanium (Ge) nanowires. The nanowires were synthesized by the growth mechanism VLS (Vapor Liquid Solid) in a LPCVD reactor (Low Pressure Chemical Vapor Deposition) using gold (Au) as the catalyst and silane (SiH4) and germane (GeH4) as precursor gas. In order to grow nanowires, the Au catalyst must be nano-structured in the form of nano-particles with controlled diameter if possible. This is done in this study by “dewetting” of a continuous layer evaporated on the chosen substrate. The thickness of this initial continuous layer is an essential parameter in the study. A preliminary part of this work deals with the problem of how the “dewetting” occurs, depending on various parameters (type of substrate, temperature, pressure, thickness of the continuous gold layer, growth duration and “dewetting” temperature) that control the LPCVD growth process. We varied these process parameters over wide ranges to determine how the influence the properties of Ge nanowires grown. The structural characterization of nanowires by transmission electron microscopy shows their single crystal structure with growth direction along <111> in the case of Si nanowires and along <110> for Ge nanowires. Finally, in the case of conical Ge nanowires isolated and deposited on different substrates, the micro-Raman analysis allowed us identifies an optical resonance phenomenon inside the nanowires which strongly depends on their local diameter. The Raman intensity increases with the decrease of volume excited. These effects are explained by the optical modes appearing according to the local diameter of the nanowire, the excitation wavelength and the nature of the substrate used. In addition, the Raman lines recorded along the same profiles did not show any spectral shift, reinforcing the idea that the behavior of their intensity has to be related to resonances associated with the development of local optical modes. These effects were observed to be dependent upon the type of substrate on which the isolated nanowires were transferred (dielectric versus metallic substrates). No effect of the confinement of phonon mode in our nanowires was observed.

This dissertation examines from a comparative perspective the growth experience for a sample of twelve countries of the former Soviet Union over the period from 1991 to 2008. Two meth- ods of econometric analysis are applied: cross-section regressions and dynamic panel data esti- mation techniques. The main focus of the study has been to empirically establish whether coun- tries in the region are converging or diverging in terms of their income per capita and to find important sources of cross-country differences which determine the shape of this process. I did not find statistically significant support for conditional convergence in any cross-section period. It is partly supported by the increased dispersion of per capita income levels during the sample period. Meanwhile, panel data fixed-effects and GMM methods provide strong support for con- ditional convergence hypothesis. The first-differenced GMM estimator indicates a rate of con- vergence of around 2 per cent a year, which is surprisingly similar to the standard cross-section findings in empirical literature. However, it could be the result of the cyclical behaviour of out- put during transition. In general, results indicate that structural transformation is not yet over in most of the countries. Therefore progress in market-oriented reforms and...

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The evolution of the U.S. skill premium over the past century has been characterized by a U-shaped pattern. The previous literature has attributed this observation mainly to the existence of exogenous, unexpected technological shocks or changes in institutional factors. In contrast, this paper demonstrates that a U-shaped evolution of the skill premium can also be obtained using a simple two-sector growth model that comprises both variants of skill-biased technological change (SBTC): technological change (TC) that is favorable to high-skilled labor and capital-skill complementarity (CSC). Within this framework, we derive the conditions necessary to achieve a non-monotonic evolution of relative wages and analyze the dynamics of such a case. We show that in the short run for various parameter constellations an educational, a relative substitutability, and a factor intensity effect can induce a decrease in the skill premium despite moderate growth in the relative productivity of high-skilled labor. In the long run, as the difference in labor productivity increases, the skill premium also rises. To underpin our theoretical results, we conduct a comprehensive simulation study.

There is now increasing evidence that for the U.S. economy, the elasticity of substitution between capital and labor, “sigma”, is rising over time. To account for this, we propose a microfounded model, where the evolution of “sigma”, and, hence, the shape of the aggregate production function occur endogenously. We develop a Schumpeterian growth model in which firms can undertake R&D activities that stochastically lead to the discovery of production technologies characterized by a higher elasticity of substitution between capital and labor. Improved possibilities for factor substitution mitigate the diminishment of the marginal product of capital and spur capital accumulation. Due to successful innovations, the steady state of the economy entails higher levels of the capital stock and the output good. Moreover, our numerical simulations show that the timing of innovations is important: two economies with the same steady-state elasticity of substitution between capital and labor can differ in terms of their steady-state levels of the capital stock and the output good.