Les cours d’eau sont des vecteurs de dispersion efficaces pour les espèces végétales colonisant les berges, y compris pour celles qui ne sont pas a priori adaptées à ce mode de dispersion. Dans le cas d’espèces invasives, l’étude des traits de dispersion et de colonisation, et leur variabilité, permet la compréhension du potentiel de propagation d’une espèce dans son aire d’invasion et du potentiel d’adaptation à de nouveaux environnements. Le complexe invasif Fallopia est un taxon génotypiquement diverse qui colonise les berges. Son succès reposerait en partie sur la dispersion des propagules végétatives et sexuées. L'objectif de ce travail a été d’étudier les stratégies de dispersion par les cours d’eau, de ce taxon terrestre. Ce travail a permis de quantifier le potentiel de dispersion et de colonisation de Fallopia par l’étude de la flottaison et la viabilité en fonction de la durée d’immersion des propagules. Ce travail a montré que les rhizomes ne flottent pas contrairement aux tiges et aux akènes. La durée de flottaison est liée aux traits morphologiques. La germination des akènes dans l’eau peut allonger cette durée de flottaison. La durée d’immersion ne réduit la viabilité des propagules qu’à partir de 3 semaines. La variabilité observée des traits a permis d’identifier différentes stratégies de propagation du taxon en milieu aquatique. La régénération dans l’eau des tiges et akènes permet leur installation rapide sur le site du dépôt tandis que les rhizomes régénèrent qu’une fois sur le site de dépôt si les conditions sont favorables. Bien que la variation des traits des propagules soit continue entre les taches, il est possible d’identifier, en particulier sur les akènes, des individus ayant des aptitudes à la dispersion sur des longues distances, pouvant participer à la progression du front d’invasion du taxon. Ces résultats montrent que les capacités de dispersion et colonisation des propagules peuvent participer au succès de propagation du taxon par les cours d'eau / Watercourses are efficient dispersal vectors for plant species colonising riverbanks, including those that are not primarily adapted to this dispersal mode. In the case of invasive species, the study of plant traits participating to dispersal and colonization, and their variability, is important to understand the spread potential of one species in the invasive area, as well as its adaptive potential to new environments. The invasive complex Fallopia displays a high genotypic diversity and highly colonises riverbanks. Dispersal of sexual and vegetative propagules could explain their colonization success. The aim of this work is to study the dispersal strategies by watercourses displayed by this terrestrial taxon.This work has quantified the dispersal and colonization potential of Fallopia propagules through the study of their floatation ability and their viability after water exposure. This work demonstrated that rhizomes do not float unlike stem fragments and achenes. Floatability is related to morphological traits. Achene germination in water may increase the floatation time. Il was also demonstrated that viability was only reduced after 3 weeks of water exposure. The variability observed for the traits allows to identify different spread strategies in this taxon. Stem and achene regeneration in water enables a rapid installation in the riverbanks, while rhizomes regenerate after deposition in the riverbank, if environmental conditions are favourable to the development and the survival of the plant. Even if variability of propagule traits is continuous, it is possible to identify, in particular for achenes, individuals that have the capacity to disperse over long distances, and that could participate to the progression of the invasive front of the taxon. These results demonstrated that dispersal and colonization abilities of Fallopia propagules might participate to the spread potential of the species through watercourses

O presente trabalho tem como objetivo apresentar o resultado da análise e identificação de padrões e comportamentos de postagens na rede social Twitter monitorando um termo específico em um período definido de tempo. Após a extração e tratamento dos dados obtidos do Twitter, explicitando dentre as postagens quais são oriundas de usuários geradores de notícias, foram analisadas informações de topologia da rede de usuários do experimento, inclusive com o detalhamento das informações de propagação e duração das postagens: dados e comportamentos os quais buscamos reproduzir utilizando simulação por agentes / The present work aims to present the result of the analysis and identification of patterns and behaviors of Twitter posts monitoring a specific term in a period. After the extraction and treatment of the data obtained from Twitter, emphasizing among the posts which are generated from news agency users, were analyzed the topology information about the network of users of the experiment, including details of propagation information and duration of the posts: data and behaviors that we seek to reproduce using agent simulation

For roughly the past 200 years land-managers have used the practice of “muirburning” to manipulate the structure of heather (Calluna vulgaris) to create a patchwork of habitat structures able to provide forage and nesting sites for red grouse (Lagopus lagopus scoticus) as well as grazing for sheep (Ovis aries) and red deer (Cervus elaphus). This thesis investigates both the behaviour and impact of management fires in recognition of the need to develop multi-aim land management practices that ensure both continued productivity and protection of biodiversity in the face of climatic and environmental change. Fuel structure and loading are crucial controlling factors on both fire behaviour and impact governing both rate of spread and heat release to the ground surface. A visual obstruction method is developed that estimates total and fine fuel loading as well as the structure of the heather canopy. In order to adequately understand fire impact a dimensional analysis approach is taken to estimating the mass of burnt heather stems. Experiments at a number of spatial and temporal scales relate variation in heather fuel moisture content to stand structure and variation in weather conditions. Monitoring shows moisture contents to be relatively stable temporally, but spatially variable. Periods of extreme low moisture contents in early spring are associated with frozen ground, winter cuticle damage and physiological drought. Such conditions may have contributed to the large number of wildfires in 2003. A replicated plot design was used to investigate the effect of weather conditions and fuel loading on fire behaviour. An empirical approach is taken to fire behaviour modelling with equations describing rate of spread and fireline intensity being developed on the basis of fuel structure descriptors and windspeed. The theoretical negative correlation between fuel bed density and rate of spread is demonstrated to hold true for heather stands, while the impact of heterogeneity in fuel bed structure is also investigated. Redundancy Analysis is used to investigate the influence of multiple predictors on a number of aspects of fire behaviour including: rate of spread, fireline intensity, flame length and ground surface heating. Data from this and previous studies are used to ground-truth a number of fire behaviour prediction systems including BehavePlus and the Canadian Fire Behaviour Prediction System. Finally linkages between fire behaviour, fire severity and heather regeneration are investigated. A number of proxy measures of ‘Immediate Severity’ are tested and used to examine the influence of fires on plant regeneration. The post-fire development of stands is shown to relate primarily to stand age and structure before burning, and to post-fire substrates rather than variation in fire behaviour and severity.

Project finance has become a vital financing vehicle for undertaking capital-intensive and infrastructure investments. In 2017 alone, the value of deals signed using project finance was estimated at approximately $229 billion. Despite its increasing importance, little is known regarding the impact of project-level, and country characteristics on the loan terms. This thesis proceeds in examining these determinants along three empirical essays. The first essay (Chapter 3) focuses on how domestic lead arrangers certification (in emerging markets) impact the pricing of project finance loans. Using a sample 1270 project finance loan tranches signed between 1998 and 2011, and worth over $300 billion, the chapter posits that domestic lead arrangers certification reduce search and information cost, which in turn, reduces the financing cost. The results, after controlling for endogeneity of certification decision, indicate a reduction of 47 basis points in the spread offered on PF loans. The magnitude of this reduction differs across industries, geographic region, and income classification of the project countries. The second essay (Chapter 4) examines the relationship between PF contractual structures and loan outcomes, using a sample of 5872 project finance loan tranches signed between 1998 and 2013, and worth approximately $1.2 trillion. The chapter hypothesises that (i) non financial contracts (NFCs) (that is, contracts used to manage the various project functions), reduces overall project risk, (ii) the involvement of project sponsors as key counterparties to the non-financial contracts is an additional signal of project s potential worth, and (iii) the effects observed in (i and ii) are stronger, if sponsor counterparties have verifiable credit ratings. After matching loan tranches with NFCs to those without, the results indicate that the use of NFCs reduce both the loan spreads and leverage ratios. This impact is higher if the sponsor counterparties are credit-rated. The results are also stronger for developing countries. The third essay examines the impact of country-level institutions on project finance loan spread and leverage ratio, using a sample of 3,362 loan tranches signed between the year 1998 - 2012. The chapter investigates whether political and legal institutions are substitutes (or complements), that is, if improvement in one absorbs the weakness of the other, and vice versa. Further, the essay examines if project finance network of contracts substitutes for these institutions. The results indicate that political and legal institutions are substitutes. Specifically, improvements in political institutions lead to a reduction in both the loan spread and leverage ratio for countries with weak legal and governance institutions. The chapter also finds that where NFCs are included in PF, the impact of political institutions on loan spread reduces. On the other hand, the impact of political institutions on leverage ratio is higher when NFCs are used. The findings from the three research chapters provide interesting insights on how lenders and sponsors create value through contract design.

<p>Osnovni cilj ovog istraživanja je utvrđivanje mogućnosti proizvodnje funkcionalnog niskoenergetskog prehrambenog namaza na bazi bra&scaron;na od semena tikve golice i hidrokoloida ugljenohidratnog porekla.<br />Utvrđivanju ove mogućnosti prethodilo je potpuno karakterisanje i definisanje sastavnih komponenti namaza. To su bra&scaron;no od semena tikve golice i prehrambeni hidrokoloidi na bazi vlakana. Bra&scaron;no od semena tikve golice analizirano je radi određivanja njegovih fizičko&ndash;hemijskih karakteristika, funkcionalnih svojstava, mikrobiolo&scaron;ke ispravnosti i mikrostrukturalne prirode. Analizama bra&scaron;na stečen je uvid u fizičke, nutritivne i mikrobiolo&scaron;ke karakteristike i u svojstva pona&scaron;anja, s ciljem utvrđivanja mogućnosti primene bra&scaron;na od semena tikve u daljem radu. Takođe, ispitane su dve vrste hidrokoloida ugljenohidratnog porekla metodom mikrostrukturalne analize, metodom određivanja raspodele veličina čestica, reolo&scaron;kim određivanjima i teksturalnim karakterisanjem sistema. Cilj ovog ispitivanja je definisanje vrste i koncentracije vlakana u gel strukturi hidrokoloida, koja ima sposobnost da ostvari ulogu nosača bra&scaron;na, odnosno kontinualne faze u namazu. Time je predviđeno i pona&scaron;anje ugljenohidratnih hidrokoloida u prehrambenom sistemu tipa namaza.<br />Nakon definisanja sastavnih komponenti, radi utvrđivanja optimalnih svojstava namaza, analizirani su namazi sa različitom vrstom i koncentacijom vlakana u gel sistemu i različitim udelom primenjenog hidrokoloida u sastavu namaza. Pri ispitivanju značajnosti uticaja promenljivih faktora na svojstva dobijenih namaza kori&scaron;ćena je metoda planiranja eksperimenta (DOE&ndash;design of experiment) u okviru koje je primenjen potpuni faktorijalni dizajn. Takođe, međusobna linearna zavisnost<br />između pojedinih promenljivih određena je metodom korelacije sa ciljem utvrđivanja povezanosti parametara senzorske analize sa instrumentalno određenim karakteristikama.<br />Cilj objedinjenja svih analiza je definisanje sastava namaza optimalnih svojstava i formulacija niskoenergetskog prehrambenog namaza na bazi bra&scaron;na od semena tikve.<br />Na osnovu prikazanih rezultata istraživanja u okviru ove doktorske disertacije izvedeni su zaključci da je bra&scaron;no od semena tikve golice nutritivno i biolo&scaron;ki vrlo vredna sirovina dobre održivost, bez patogenih mikroorganizama i da predstavlja pogodnu sirovinu za proizvodnju namaza. Takođe, hidrokoloid Vivapur MCG 611F se odlikuje<br />povoljnijim reolo&scaron;kim i teksturalnim svojstvima od hidrokoloida Vitacel WFG HS73, jer tiksotropno protiče, ima veći stepen uređenosti i povezanosti strukture sa izraženom elastičnom prirodom koja mu omogućava manju podložnost deformacijama i čini ga pogodnim za proizvodnju namaza.<br />Na osnovu analize uticaja promenljivih faktora, koji se odnose na sastav namaza, zaključeno je da posmatrani namazi predstavljaju realne reolo&scaron;ke sisteme i da sastav namaza izraženo utiče na njihove reolo&scaron;ke, teksturalne i senzorske osobine.<br />Na osnovu sprovedenih istraživanja zaključuje se da je moguća proizvodnja niskoenergetskog namaza na bazi bra&scaron;na od semena tikve golice. Pri tome namaz treba da sadrži 80% MCG zamenjivača masti (na masu namaza) koncentracije hidrokoloidnog gela 7% i 20% bra&scaron;na od semena tikve golice (na masu namaza). Namaz optimalnih svojstava je polidisperzan sistem sa uređenom strukturom u<br />kojoj su čestice primenjene količine bra&scaron;na uklopljene u kontinuiranu mrežu hidratisanih MCG vlakana i potpuno obložene dostupnom količinom zamenjivača masti. Zahvaljujući takvoj organizaciji i strukturi sistema optimalni namaz ispoljava dobre reolo&scaron;ke karakteristike, optimalnu mazivost, dobro prijanjanje na povr&scaron;inu i laku manipulaciju namazom tokom proizvodnje i tokom primene. Dobijeni namaz predstavlja nutritivno vredan proizvod koji se na osnovu sastava i zdravstvenog uticaja komponenti može svrstati u funkcionalne prehrambene proizvode.</p> / <p>The main objective of this study was to determine the possibility of production the low-fat functional food spreads based on flour of pumpkin seed and carbohydrate<br />hydrocolloids.<br />That included complete characterization of components of the spreads, the flour of hull&ndash;less pumpkin seed and fiber based food hydrocolloids. Flour of pumpkin seed was analyzed in order to determine its physico&ndash;chemical characteristics, functional characteristics, microbiological safety and microstructural nature. These analyses of flour defined the physical, nutritional and microbiological characteristics and behavior of flour, with the aim of determine the possibilities of its application in further work.<br />Also, two types of carbohydrate based hydrocolloids were examined by microstructural aspect, by particle size distribution, rheological determinations and textural characterization. The aim of these analysis was to define the type and concentration of fibers in the gel structure of hydrocolloids, which has the ability of to flour carrier and the role of continuous phase in the spread. This predicted<br />the behavior of carbohydrate based hydrocolloids in the food system such as spreads.<br />The determination of main components of the spreads was followed by determination of optimal properties of the spreads, which included analysis of spreads with different type and concentrations of fibers in the gel system and the<br />different amount of the applied hydrocolloid. To determine the significance of the influence of variable factors on the properties of the obtained spreads, the method of design of experiment (DOE) was used, with applied full factorial design. Also, correlation between certain sensory and instrumentally determined parameters was defined.<br />The aim of all analysis was to define the composition of the spread with optimal properties and to formulate the low&ndash;fat food spread based on flour of pumpkin seed<br />Based on the results obtained within this doctoral thesis, it was concluded that the flour of pumpkin seed cake is nutritionally and biologically very valuable raw material<br />with good sustainability, without pathogenic microorganisms, thus it is a suitable raw material for the production of spread. Also, Vivapur MCG 611F was characterized as hydrocolloid with better rheological and textural properties than the hydrocolloid Vitacel WFG HS73, because of its thixotropic flow properties, higher degree of<br />networking and pronounced elastic nature of structure that provides lower susceptibility to deformation and makes it suitable for the production of spread.<br />Based on the influence of variable factors, related to the composition of spreads, it was concluded that the observed spreads were real rheological systems and that the<br />composition of spreads signifficantly influenced on their rheological, textural and sensory characteristics. Obtained resultes of this research suggested that the production of low&ndash;fat food spread based on flour of pumpkin seed is possible. This spread contains 80% of MCG 611F fiber based hydrocolloid ( on the mass of the spread) with gel concentration of 7% and 20% of flour of pumpkin seed cake ( on the mass of the spread). The spread with optimal properties is poydisperse system with compact structure in which the flour particles are incorporated into continious network of hydrated MCG fibers and completly coated with avaliable amount of fat relacer. Due to this organization and structure of the system, optimal spread exhibits good properties for manipulation during production and application, such as good rheological characteristics, optimal spreadability and good adhesion to the surface. Obtained spread is nutritionaly valuable food product which can be classified into functional food product based on the composition and health inffluance.</p>

Esse trabalho objetiva avançar nas pesquisas acerca da difusão da arquitetura moderna brasileira para fora dos grandes centros, descobrindo seus reflexos ante as peculiaridades locais da mesorregião mineira do Triângulo Mineiro e Alto Paranaíba, identificando, além dos seus protagonistas, os vários mecanismos de apropriação da nova linguagem projetual inserida, que também se refletem na produção de novos valores, novas formas, novos procedimentos técnicos e nos diálogos com a produção dos grandes centros. Parte da arquitetura moderna documentada em vinte e uma cidades da mesorregião pelo projeto de pesquisa intitulado \"Documentação da Arquitetura Moderna no Triângulo Mineiro e Alto Paranaíba: História e Preservação\", desenvolvido pelo Núcleo de Pesquisa em Teoria e História da Arquitetura e Urbanismo (NUTHAU), da Faculdade de Arquitetura, Urbanismo e Design da Universidade Federal de Uberlândia (FAUeDUFU). O trabalho foi desenvolvido no curso de mestrado em Teoria e História da Arquitetura e Urbanismo, do Instituto de Arquitetura e Urbanismo da Universidade de São Paulo (IAU/USP), com auxílio da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes). / This work, which is entitled \"Modern Architecture in the Triângulo Mineiro and Alto Paranaína region: some indications for the development of an architectural culture\", aims at progressing the research on the spread of Brazilian modern architecture outside major centers, finding out its consequences on local peculiarities of the Triângulo Mineiro and Alto Paranaíba mesoregion and also identifying - in addition to its protagonists -, the numerous mechanisms for appropriation of the new projectual language added, which is reflected in the production of new values, new forms and new technical procedures as well as in the dialogues with production from major centers. Part of the modern architecture was documented in twenty-one mesoregion cities through a research project entitled \"Documentation of Modern Architecture in Triângulo Mineiro and Alto Paranaína: History and Preservation\", undertaken by the Center for Research in Theory and History of Architecture and Urbanism (NUTHAU, in Portuguese), from the School of Architecture, Urbanism and Design at the Federal Univerity of Triângulo Mineiro (FAUeD-UFU, in Portuguese). The work was developed at the Master´s Program in Theory and History of Architecture and Urbanism - Architecture and Urbanism Institute of the University of São Paulo (IAU/USP) with support from CAPES (Coordination for Improvement of Higher Education Personnel).

Esta tese propõe um método de avaliação de sistemas de obtenção de imagem radiológica através das Funções de Transferência simuladas para qualquer região do campo de radiação. Esse processo de simulação reflete as mudanças sofridas pelo ponto focal e, portanto, pela Função de Espalhamento de Ponto (FEP) ao longo do campo. A avaliação utiliza informações obtidas de Funções de Transferência ótica bi-dimensionais calculadas através da aplicação de Transformadas de Fourier sobre as Funções de Espalhamento de Ponto simuladas. O método permite realizar um mapeamento da resposta em freqüências espaciais dos sistemas radio1ógicos para todo o campo de radiação, comparar a nitidez da imagem de sistemas distintos com relação a regiões equivalentes e estudar uma região especifica para prever as distorções que serão inseridas na imagem. / In this work a method of evaluation for the radiological imaging systems performance by simulated transfer functions for any X-ray field region is proposed. The simulation procedures provide information of the changes of the focal spot sizes and, therefore, of the Point Spread Function (PSF) along the field. The evaluation yields the bi-dimensional optical Transfer Functions calculated from Fourier Transformation of the simulated PSFs. This method provides: the spatial frequency response for the entire radiation field of the radiological systems; comparisons of the image sharpness relative to equivalent field regions for different systems; and the study of a singular region in order to predict image distortions.

Es centres de rayonnement synchrotron sont des accélérateurs de particules qui génèrentun faisceau de lumière bien intense et collimaté en courbant la trajectoire d'un faisceau d´électronrelativiste. Le champ le plus simple utilisé pour courber la trajectoire d'un électron est unchamps magnétique constant généré par un dipôle. Des rayonnements plus intense peuventêtre émis dans une insertion. Une insertion est composée d'une séries de dipôle de polaritésinverses. Les insertions comprennent en général deux types : onduleurs et wigglers. Leswigglers sont très importants pour une source de rayonnement synchrotron. Ils peuvent êtreutilisé pour objectives différents, comme moduler le structure temporel de paquets d´électron,la production de faisceau de photon de haut énergie et réduire la taille transverse de faisceau.Ce travail est consacré pour l´étude de deux wigglers différent pour deux objective différents :le wiggler W164 et wiggler Robinson. Le W164 a étéconstruit pour la production des impulsionsde courte durée (femtosecond ) en utilisant le principe de femtoslicing. Dans le principede femtoslicing, si un faisceau d´électron se propage avec un faisceau de laser de durée defemtosecond dans le wiggler, ce dernier fait le rôle d'un modulateur qui extrait un “ slice “du paquet de durée de femtosecond qui émet à son tour un rayonnement X de durée de femtosecond.En plus, W164 fait un autre rôle d' une source rayonnement de photon des hautsénergies pour une autre ligne de lumière. La deuxième partie de ce travail est dédiée à l´étude d'unwiggler Robinson pour réduire l´emittance horizontal. L'effet Robinson à été étudié et observéexpérimentalement à SOLEIL avant la construction de wiggler. Les résultats sont présentés.Un pré-design a été aussi proposé. / Synchrotron light sources are particle accelerators that generate intense and highly collimatedradiation by bending the trajectory of a relativistic electron beam. The most commonsimple field used to deflect a relativistic electron beam trajectory is a constant magnetic fieldgenerated by bending magnet. More intense radiation can produced through insertion devices.An insertion device is made by combining short bending magnets of opposite polarities. Theyinclude in general two types: undulators and wigglers. Wigglers play an important role ina synchrotron radiation source, since they can be employed for different objectives such asmodulating the time structure of the electron bunch, generating high energy photons, andreducing the transverse beam size. This work studies two different wigglers for different purposes:W164 and Robinson wiggler. The wiggler W164 was constructed for the production offemtosecond light pulses based on the femtoslicing principle. Femtoslicing implies that if anelectron beam co-propagates through the wiggler with a femtosecond laser pulse, the wiggleracts on the electron beam as a modulator and extracts a femtosecond slice of the bunch thatcreates in turn a femtosecond X-ray pulse. Moreover, the W164 plays another role of being ahigh energy photon source for another beamline. The second topic studied here is reducing thehorizontal emittance by using Robinson wiggler. Robinson effect was studied and observedexperimentally at SOLEIL before the wiggler construction. A preliminary wiggler design isproposed

La mise en œuvre de méthodes d'assimilation d'ensemble est une technique assez récente visant à simuler les erreurs d'analyse et de prévision d'un système d'assimilation de données. Cela permet d'une part d'estimer des covariances spatiales des erreurs de prévision, qui sont un ingrédient essentiel des systèmes d'assimilation de données, dans la mesure où elles permettent de filtrer et de propager spatialement l'information observée. La dépendance de ces covariances d'erreur à la situation météorologique devient ainsi accessible avec ces techniques d'ensemble. D'autre part, l'assimilation d'ensemble est également une méthode de plus en plus utilisée pour fournir des perturbations initiales aux systèmes de prévision d'ensemble. Une telle approche peut être mise en place non seulement dans un système modélisant l'atmosphère sur l'ensemble du globe, mais aussi dans un système régional à aire limitée, en utilisant dans ce cas des conditions limites latérales appropriées. Le sujet de thèse proposé consiste à examiner certaines propriétés de sensibilité de ces techniques d'assimilation d'ensemble dans ces deux types de contextes (à savoir global et régional, respectivement). Il s'agit premièrement d'étudier la sensibilité d'un système global d'assimilation d'ensemble à son initialisation. Cela sera mené en comparant une technique d'initialisation "à froid" (basée sur des perturbations initiales nulles) avec une méthode basée sur des perturbations initiales tirées d'un modèle de covariance. Dans une deuxième partie, la sensibilité d'une assimilation d'ensemble régionale aux conditions limites latérales sera examinée. Dans cette perspective, une comparaison entre différentes techniques de production des perturbations latérales sera réalisée. Il s'agit notamment de comparer les approches basées sur des perturbations latérales qui sont soit nulles, soit tirées d'un ensemble global, ou encore produites à l'aide d'un modèle de covariance. Ces études de sensibilité seront menées d'une part en utilisant des expérimentations avec les systèmes global Arpege et régional Aladin. Ce travail s'appuiera d'autre part sur une formalisation des équations qui gouvernent l'évolution des perturbations au sein d'une assimilation d'ensemble. Ces études devraient permettre de documenter les propriétés de ces assimilations d'ensemble, et de définir des stratégies de mise en œuvre en grandeur réelle pour l'assimilation de données ainsi qu'éventuellement pour la prévision d'ensemble. / The implementation of ensemble assimilation methods is a fairly recent technique used to simulate the analysis and forecast errors within a data assimilation system. On the one hand, this allows to estimate the spatial covariances of forecast errors, which are an essential component in data assimilation systems, insofar as they are used to filter and disseminate spatially the observed information. The dependence of such error covariances to the weather situation becomes accessible with these ensemble techniques. On the other hand, the ensemble assimilation is a method increasingly used to provide initial perturbations to ensemble prediction systems. Such approach may be implemented not only in a system modeling the atmosphere throughout the globe, but also in a regional system with limited area using suitable lateral boundary conditions. The proposed thesis consists on examining some sensitivity properties of these ensemble assimilation techniques in both contexts (global and regional, respectively). In the first part, the sensitivity of a global ensemble assimilation system to its initialization will be examined. This will be conducted by comparing a "cold" initialization technique (initial perturbations equal to zero) with a method based on initial perturbations drawn from a covariance model. In the second part, the sensitivity of a regional ensemble assimilation to lateral boundary conditions will be considered. In this context, a comparison between different techniques producing lateral boundaries will be achieved. It involves comparing approaches using lateral boundaries which are equal to zero or drawn from a global ensemble, or generated using a covariance model. These sensitivity studies will be conducted using experiments using the global and regional modeling systems, Arpège and Aladin respectively. Furthermore, this work will be based on a formalization of the equations governing the evolution of perturbations in an ensemble assimilation. These studies should help to document the ensemble assimilation properties, and develop strategies for implementing in real scale for data assimilation and possibly for ensemble prediction system.

The naturalisation and subsequent spread of non-indigenous plant species (NIPS) is a major problem for most regions of the world. Managing plant invasions requires greater understanding of factors that determine initial naturalisation and distribution of wild NIPS. By the year 2000, 2252 NIPS were recorded as wild (1773 fully naturalised and 479 casual) in New Zealand. From published literature and electronic herbaria records, I recorded year of discovery of wild populations, and regional distribution of these wild NIPS. I also recorded species related attributes hypothesised to affect naturalisation and/or distribution, including global trade, human activities, native range and biological data; and regional attributes hypothesised to affect distribution, including human population densities, land use/cover, and environmental data. I used interval-censored time-to-event analyses to estimate year of naturalisation from discovery records, then analysed the importance of historical, human activity, biogeographical and biological attributes in determining patterns of naturalisation. Typically, NIPS that naturalised earlier were herbaceous, utilitarian species that were also accidentally introduced and/or distributed, with a wide native range that included Eurasia, naturalised elsewhere, with a native congener in New Zealand. In the year 2000, 28% of wild NIPS occupied only one region, 18% occupied two regions, decreasing incrementally to 2.5 % for nine regions, but with 13.5% occupying all ten regions. I used generalised linear models (GLMs) with binomial distribution to determine predictors of whether a wild NIPS occupied ten regions or not, and GLMs with Poisson distribution for wild NIPS occupying 0 – 9 regions. As expected, the dominant effect was that species discovered earlier occupied more regions. Utilitarian wild NIPS that were also accidentally introduced and/or distributed, and wild NIPS with a native congener tended to be more widely distributed, but results for other attributes varied between datasets. Although numbers of wild NIPS recorded in regions of New Zealand were sometimes similar, composition of wild NIPS was often very different. I used nonmetric multidimensional scaling (NMDS) to determine dissimilarity in composition between regions. Then, after reducing correlation between predictor variables using principal components analyses (PCAs), I tested the importance of regional variables in determining the regional composition of wild NIPS using metaMDS. The density of human populations best explained the dissimilarity in composition, but temperature gradients and water availability gradients were also important. In the year 2000 more than 1100 (60%) of the 1773 fully naturalised NIPS in mainland New Zealand had each been recorded in Northland/Auckland and Canterbury, and at the other end of the scale, Southland and Westland each had fewer than 500 (30%). I used GLMs to analyse the importance of people and environment in determining the numbers of wild NIPS in each region. Because I conducted multiple tests on the same dataset I used sequential Bonferroni procedures to adjust the critical P-value. Only human population density was important in explaining the numbers of NIPS in the regions. Overall, humans were the dominant drivers in determining the patterns of naturalisation and spread, although environment helps determine the composition of NIPS in regions. Incorporating human associated factors into studies of wild NIPS helps improve the understanding of the stages in the naturalisation and spread process.