L'influence des dirigeants sur la performance (ou contre-performance) de la firme fait l'objet de nombreux débats. Selon la vision déterministe, les pressions internes et externes qui s'exercent sur le dirigeant sont si importantes que ce dernier dispose de très peu de marge de manoeuvre pour influencer les résultats de la firme. D'un autre côté, selon les partisans de l'école du leadership, le dirigeant est l'unique architecte de l'entreprise et c'est à lui qu'incombe la performance de l'entreprise. Ces deux points de vue sont nuancés par le concept de latitude managériale qui mesure la marge de manoeuvre dont le dirigeant qui lui permet de se démarquer significativement des autres entreprises du secteur. Cette thèse s'intéresse à la responsabilité du dirigeant sur la performance de la firme ainsi que sur les décisions qui y sont opérées. Elle porte sur les grands patrons français qui ont, notamment, la particularité de former de puissants réseaux sociaux. Le premier chapitre dresse un portrait des grands dirigeants français et met en évidence les principales caractéristiques des décideurs hexagonaux. Le deuxième chapitre étudie le phénomène d'endogamie observé lors des successions de dirigeants ainsi que l'impact sur la performance de la firme. Le troisième chapitre propose une évaluation de l'effet du dirigeant sur la performance de la firme. Enfin le quatrième chapitre mesure l'impact du pouvoir du dirigeant sur les décisions de de croissance externe de la firme. Cette thèse corrobore l'idée que le pouvoir économique demeure au sein d'une castedirigeante fermée

Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.

Resumos em portugues e ingles / Orientador: Fernando Hatschbach / Dissertaçao (mestrado) -Universidade Federal do Paraná. Curso de Pós-Graduaçao em Ciencias Geodésicas / Resumo: Esta dissertação trata da comparação e analise dos resultados obtidos em determinações, a nível de segunda ordem, realizadas com equipamentos específicos para observações de 2ª ordem (teodolito com leitura direta de 1") e específicos para observações de 1ª ordem (teodolito com leitura direta de 0,1"), procurando verificar se há ou não conveniência em se utilizar equipamento mais sofisticado do que o necessário, quando se dispõe de toda a gama de teodolitos, em determinações com precisão adrede estabelecida. O autor pretendia, a princípio, realizar observações para a determinação do meridiano astronômico (pelo método de Estrelas Próximas ou em Elongação), da hora local (pelo método de Zinger) e da latitude astronômica (pelo método de Horrebow-Talcott simplificado, conhecido no Brasil por método de Sterneck), porém, devido às condições atmosféricas adversas em Curitiba (dez noites úteis em cento e um dias), restringiu as observações somente para a determinação da latitude astronômica. / Abstract: This essay deals with the comparison and analysis of results obtained in second order accuracy determinations, acomplished with equipment specifically for second order observations (theodolites with 1" direct-reading) and specifically for first order observations (theodolites with 0,1" direct-reading) in an attempt to verify if it is warranted to use more sophisticated equipment than necessary when one has at his disposal a complete range of theodolites in pre-determined settings. The author initially had in mind to carry out observations for the determination of the astronomic meridian (by the Stars near or at elongations method), of the civil time (by Zinger method), and of the astronomic latitude (by the simplified Horrebow-Talcott method, known in Brazil as the Sterneck method). However, due to the adverse atmospheric conditions in Curitiba (10 useful nights in one hundred and one days), he has restricted his observations only to the determination of the astronomic latitude.

We used ion drift observations from the DE-2 satellite to study for the first time the longitudinal variations of middle and low latitude F-region zonal plasma drifts during quiet and disturbed conditions. The daytime quiet-time drifts do not change much with longitude. In the dusk-premidnight period, the equinoctial middle latitude westward drifts are smallest in the European sector, and the low latitude eastward drifts are largest in the American-Pacific sector. The longitudinal variations of the late night-early morning drifts during June and December solstice are anti-correlated. During geomagnetically active time s, there are large westward perturbation drifts in the late afternoon-early night sector at upper middle latitudes and in the midnight sector at low latitudes. The largest westward disturbed drifts during equinox occur in the European sector and the smallest in the Pacific region. These results suggest that during equinox, Subauroral Polarization Streams (SAPS) events occur most often at European longitudes. The low latitude perturbation drifts do not show significant longitudinal dependence. We have used five years of measurements on board the ROCSA T-1 satellite to develop a detailed local-time, season, and longitude-dependent quiet-time global empirical model for equatorial F-region vertical plasma drifts. We show that the longitudinal dependence of the daytime and nighttime vertical drifts is much stronger than reported earlier, especially during December and June solstice. The late night downward drift velocities are larger in the eastern than in the western hemisphere at all seasons, the morning and afternoon December solstice drifts have significantly different longitudinal dependence, and the daytime upward drifts have strong wavenumber-four signatures during equinox and June solstice. The largest evening upward drifts occur during equinox and December solstice near the American sector. The longitudinal variations of the evening prereversal velocity peaks during December and June solstice are anti-correlated, which further indicates the importance of conductivity effects on the electrodynamics of the equatorial ionosphere. We have shown that disturbance dynamo largely does not affect daytime drifts. The upward perturbations during the nighttime are largely season independent, but near the prereversal enhancement, the downward perturbation drifts are largest during equinox and smallest during December.

<p> Energy-budget calculations and equilibrium model estimates of evaporation from a lichen-dominated upland site in the Hudson Bay low-lands are presented. The energy budget calculations reveal that the lichen surface is relatively resistant to evaporation with an average of only 54 percent of the daily net radiation being utilized in the evaporative process. Equilibrium estimates of evaporation consistently overestimate actual evaporation by 5 and 8 percent for hourly values and daily totals respectively. A simple model, a function of the equilibrium model, is derived from a comparison of actual and equilibrium evaporation. The only inputs required for the model are net radiation, soil heat flow and screen temperatures. Tests of the model indicate that it will predict actual evaporation within 5 percent and that it can probably be applied to any high latitude surface which exhibits a relatively large resistance to evaporation.</p> / Thesis / Master of Science (MSc)

No description available.

This thesis is missing page 28 from this and all other copies. -Digitization Centre / Glacial and glacially-influenced deposits examined at two sites in west-central Ellesmere Island provide insights into the nature of glaciation during the late-Wisconsinan and Holocene advances, and the modes of deposition from arid, high latitude ice bodies. Glacial lithofacies identified indicate that englacial debris content varied spatially and it is inferred that basal thermal conditions also exhibited a complex pattern. Direct glacial deposits usually consist of unsorted diamicts with a complete size range of matrix components, indicating an absence of meltwater-sorting or winnowing during deposition. Glacially-influenced fluvial, lacustrine, and nearshore marine deposits show that most of the Quaternary sediments were deposited by low-frequency, high magnitude events during deglaciation. A tentative reconstruction of late-glacial history in the Strathcona Fiord area proposes that an ice tongue surged down Strathcona Fiord from a previous maximum position coincident with the present day head of the fiord. This surge destabilised the margin locally, causing rapid collapse in the valleys and melting into ice-cored basins on the higher plateau areas. Periodically these ice-cored basins would drain, providing large water and sediment discharges and reworking in some sites whilst leaving other deposits unaffected. Subsequent reworking has been minimal in the cold, arid environment where continued uplift favours fluvial incision rather than extensive sandur development. Examination of the modern ice margin shows that the ice here is frozen to the substrate but basal debris bands indicate that at some localities basal temperatures must be above pressure melting point. Patterns of debris entrainment and deposition and debris lithologies suggest that much of the transported debris is incorporated where lobes of ice begin to flow out from the main ice cap. / Thesis / Master of Science (MS)

The propagation of radiowaves through ionospheric irregularities can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely impact the performance of Global Navigation Satellite System (GNSS) and communication systems. Research into high latitude scintillation, through statistical analysis and inverse modeling, was completed to provide insight into the temporal and spatial distribution, and irregularity parameters, which can ultimately support the development of impact mitigation techniques, and deepen our understanding of the underlying physics. The work in this dissertation focused on the statistical analysis of Global Positioning System (GPS) scintillation data, data inversion, two-dimensional (2D) and three-dimensional (3D) scintillation modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently and can be treated as stochastic Total Electron Content (TEC); findings which have significant implications for impact mitigation. For the first of two inversion studies, scintillation data associated with a series of Polar Cap Patches (PCPs), which are common large-scale high latitude structures, was inverted to gain insight into the composition of the underlying irregularities. The results of this study suggest that the irregularities can be modeled as rods interbedded with sheets, which is knowledge that is crucial for the anchoring of models used to develop system mitigation techniques. The final study presents the results of modeling and inversion work to identify the conditions under which a 2D analytic version of the 3D numerical Satellite-beacon Ionospheric-scintillation global model of the upper atmosphere (SIGMA) model can be used to perform modeling in high latitude regions. During the study, it was found that the analytic model tends to diverge for electron density variance times irregularity layer thickness values exceeding 2, matched reasonably well for correlation length to thickness ratios up to 0.2, and was incompatible when ratios approached 0.35. An elevation angle limitation was also identified for the 2D model, and inflated values for the electron density variance were observed overall, which are thought to result from the weak scatter limits of the analytic model. These inflated values were particularly acute in the auroral zone during elevated conditions and suggest that the analytic model used in the study is not well suited for modeling the highly elongated irregularities associated with auroral precipitation. / Doctor of Philosophy / The ionosphere is a region of the earth's atmosphere extending from approximately 90 to 1000 km in altitude. Radio wave signals which travel through irregularities in the ionosphere can be distorted in a way that can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely degrade the performance of navigation and communication systems. Research into high latitude scintillation, through statistical analysis, and data and model matching, was completed to provide insight into the time and space distribution, and irregularity parameters, in order to ultimately deepen our understanding of the physics and to help develop better models. The work in this dissertation focused on the statistical analysis of GPS scintillation data, data and model matching, and 2D and 3D irregularity modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently but the impacts can be corrected if measured; findings which have significant implications for impact mitigation. For the first of two model and data matching studies, scintillation data associated with a series of common large-scale high latitude structures called PCPs, was matched to a model to gain insight into the composition of the underlying irregularities. The results of this study suggest that the irregularities can be modeled as vertical rods oriented along the magnetic field interbedded within flat sheets, which is knowledge that is crucial for having confidence in the models used to develop system mitigation techniques. The final study presents the results of modeling and data matching work to identify the conditions under which a 2D or 3D model can be used to perform irregularity modeling in the high latitude regions. During the study, it was found that the 2D model tends to diverge from the 3D model for significant variations in the ionosphere, and when irregularity rods are highly elongated. A signal propagation path elevation angle limitation was also identified for the 2D model, and inflated values for the predicted ionospheric variations were observed overall, which are thought to result from limits of the 2D model compared to the more general 3D version. These inflated values were particularly acute in the auroral region during elevated conditions and suggest that the 2D model used in the study is not well suited for modeling the highly elongated irregularities associated with aurora effects.

The Weather Research and Forecasting model (WRF) was executed with high resolution and three nested grids of 12 km, 3 km and 1 km in the South Shetland and particularly in Deception Island s bay, during the period from 5 to 23 February 2011 at Operation Antarctica 29. Data were obtained in situ by Polar Ship Almirante Maximiano from Brazilian Navy, with a frequency of 1 h. The measured variables are pressure, temperature, dew point temperature, wind speed and direction. The model lateral and boundary conditions were data from NCEP global model, with a horizontal resolution of 1o and updated every 6 hours. Two domain sizes have been tested for the innermost grid, one with 127 and the other with 187 points in each horizontal direction. Besides, two physical configurations have been tested, with the main differences being snow microphysics and soil thermal diffusion. Pressure was the variable best represented by the model, as it is the most dependent on large scale meteorological patterns having only small dependence on the microscale. The wind direction and speed at 10 meters from the surface were also accurate, except when there were sudden fluctuations in wind speed and direction influenced by the topography, in which case there has been an underestimation of the speed. Thermodynamic variables have been very poorly represented by the small inner domain, but improved appreciably when it was expanded. The simulated temperature has an average daily cycle less intense than observed and the underestimation increases in warmer temperatures, probably caused by snow packets in the border areas. The dew point temperature daily average cycle followed the observations. Some observed and simulated patterns in circulation are briefly discussed. Finally, a simulation for a 13-day period during which there were in situ measurements at the Deception Island are presented, showing a good performance when compared to the observations. / O modelo Weather Research and Forecasting (WRF) foi rodado em alta resolução com três grades aninhadas (nesting) de 12 km, 3 km e 1 km, em Shetland do Sul e particularmente na baía da ilha Deception, durante o período de 5 a 23 de fevereiro de 2011, na Operação Antártica 29. Os dados foram medidos in situ, pelo Navio Polar Almirante Maximiano da Marinha do Brasil, com frequência de observação de 1 hora. As variáveis medidas e simuladas são pressão, temperatura, ponto de orvalho, temperatura da água do mar, velocidade e direção do vento. Para a entrada no modelo foram utilizados os dados provenientes do modelo global do National Center for Environmental Prediction (NCEP) com 1º de resolução horizontal, atualizados a cada 6 horas. Foram testadas duas opções de domínios na grade mais interna, uma com 127 e outra com 187 pontos em cada direção horizontal. Também foram consideradas duas configurações para o WRF, sendo as principais diferenças entre elas as parametrizações de microfísica de neve e difusão térmica do solo. A variável melhor representada foi a pressão na superfície, uma vez que esta depende quase que exclusivamente dos padrões meteorológicos de grande escala, tendo pequena variação na microescala. A direção e velocidade do vento a 10 m da superfície também apresentaram uma acurácia, exceto quando ocorrem flutuações bruscas na direção e velocidade do vento influenciado pela topografia próxima, ocorrendo uma subestimação na velocidade. As variáveis termodinâmicas apresentaram uma representação muito deficiente com o domínio interno menor, mas melhoraram consideravelmente quando este foi expandido. A temperatura simulada apresentou um ciclo médio diário menos intenso que o observado e a subestimativa aumenta nos períodos mais quentes, provavelmente pelos pacotes de neve nas áreas de fronteira. Já a temperatura do ponto de orvalho seguiu o ciclo diário médio das observações apresentando boas concordâncias com os dados observados. Alguns padrões observados e simulados de circulação são discutidos brevemente. Por fim, uma simulação para um período de 13 dias em que haviam medidas realizadas diretamente na Ilha Deception é apresentada, apresentando um bom desempenho.

Made available in DSpace on 2016-02-26T12:59:45Z (GMT). No. of bitstreams: 1 ClovisFerreiraTolentinoJr.pdf: 826530 bytes, checksum: 77092114a46071787ede642e6bb947cd (MD5) Previous issue date: 2007-12-17 / The selection of appropriate areas for the production of soybean seeds of high quality requires inquiry studies, especially in tropical regions. Some researchers believe that in the biggest part of the region of the Cerrados, in the Central Brazil, the climatic conditions are not favorable to the production of soybean seeds with good quality, once the quality of the seeds is highly influenced by the climatic conditions under which they had been produced. The objective of this work was to evaluate the physiological and sanitary quality of seeds of six soybean cultivars at four sowing dates in Ponta Porã and Maracaju, Mato Grosso do Sul, Brazil. The physiological quality of the seeds was evaluated by the tetrazolium test and the standard germination test and the sanitary quality by the Blotter test. The temperature and precipitation were registered during the experimental period. The seeds produced in Ponta Porã presented better physiological quality that the ones produced in Maracaju. The reduced precipitations and the high temperatures during the reproductive phase of the cultivars plants in both places had favored the low pathogen incidence in the seeds. It was not possible to establish the best sowing date for harvest of seeds with better physiological and sanitary quality / A seleção de áreas apropriadas para a produção de sementes de soja de alta qualidade requer estudos de investigação, especialmente em regiões tropicais. Alguns pesquisadores acreditam que na maior parte da região do Cerrado do Brasil Central, as condições climáticas não são favoráveis à produção de sementes de soja de boa qualidade, uma vez que a qualidade das sementes é altamente influenciada pelas condições climáticas sob as quais foram produzidas. O objetivo deste trabalho foi avaliar a qualidade fisiológica e sanitária de sementes de seis cultivares de soja produzidas em quatro épocas de semeadura em Ponta Porã e Maracaju, Mato Grosso do Sul. A qualidade fisiológica das sementes foi avaliada pelo teste de tetrazólio e pelo teste padrão de germinação, e a qualidade sanitária pelo Blotter test. Foi realizado o monitoramento da temperatura e precipitação ao longo das épocas experimentais. As sementes produzidas em Ponta Porã apresentaram melhor qualidade fisiológica que as produzidas em Maracaju. As reduzidas precipitações e as altas temperaturas durante a fase reprodutiva das cultivares em ambos os locais favoreceram a baixa incidência de patógenos nas sementes. Não foi possível estabelecer a melhor época de semeadura para colheita de sementes com melhor qualidade fisiológica e sanitária