Global ETD Search

21	Resonant generation and refraction of dispersive shock waves in one-dimensional nonlinear Schrödinger flows Leszczyszyn, Antin M. January 2011 (has links) In the Thesis, two important theoretical problems arising in the theory of one-dimensional defocusing nonlinear Schrödinger (NLS) flows are investigated analytically and numerically: (i) the resonant generation of dispersive shock waves (DSWs) in one-dimensional NLS flow past a broad repulsive penetrable barrier; and (ii) the interaction of counter-propagating DSW and a simple rarefaction wave (RW), which is referred to as the DSW refraction problem. The first problem is motivated by the recent experimental observations of dark soliton radiation in a cigar-shaped BEC by sweeping through it a localised repulsive potential; the second problem represents a dispersive-hydrodynamic counterpart of the classical gas-dynamics problem of the shock wave refraction on a RW, and, apart from its theoretical significance could also find applications in superfluid dynamics. Both problems also naturally arise in nonlinear optics, where the NLS equation is a standard mathematical model and the `superfluid dynamics of light' can be used for an all-optical modelling of BEC flows. The main results of the Thesis are as follows: (i) In the problem of the transcritical flow of a BEC through a wide repulsive penetrable barrier an asymptotic analytical description of the arising wave pattern is developed using the combination of the localised ``hydraulic'' solution of the 1D Gross-Pitaevskii (GP) equation with repulsion (the defocusing NLS equation with an added external potential) and the appropriate exact solutions of the Whitham-NLS modulation equations describing the resolution of the upstream and downstream discontinuities through DSWs. We show that the downstream DSW effectively represents the train of dark solitons, which can be associated with the excitations observed experimentally by Engels and Atherton (2008). (ii) The refraction of a DSW due to its head-on collision with the centred RW is considered in the frameworks of two one-dimensional defocusing NLS models: the standard cubic NLS equation and the NLS equation with saturable nonlinearity, the latter being a standard model for the light propagation through photorefractive optical crystals. For the cubic nonlinearity case we present a full asymptotic description of the DSW refraction by constructing appropriate exact solutions of the Whitham modulation equations in Riemann invariants. For the NLS equation with saturable nonlinearity, whose modulation system does not possess Riemann invariants, we take advantage of the recently developed method for the DSW description in non-integrable dispersive systems to obtain key parameters of the DSW refraction. In both problems, we undertake a detailed analysis of the flow structure for different parametric regimes and calculate physical quantities characterising the output flows in terms of relevant input parameters. Our modulation theory analytical results are supported by direct numerical simulations of the corresponding full dispersive initial value problems (IVP). 530.15
22	司法判決書之「法律論述」考察～以白曉燕案張志輝部分判決書為例蕭旭岑 Unknown Date (has links) 本文以論述（discourse）為切入點，並將觀察的對象明確化為：我們社會上的「法律語言」，或者說「法律論述」（legal discourse）。以「論述」為切入點的前提假設是：我們日常生活世界由各式各樣的論述所構成，而這些論述都對於我們的日常生活世界產生種種的效果，形成我們的世界觀或生活方式。本文將以這個角度切入法律的層次，針對我們社會上現存的「法律論述」對我們產生什麼樣的效果，以及如何產生效果，做有意義的觀察與解讀。　　本文預計分為五章，包括緒論、兩層理論探究、具體案例分析與結論。在第一章裡，主要是研究動機、思考脈絡，以及本文架構。　　第二、三章是針對理論部分，呈現論述、法律論述在定義上、論理上的細部討論。第二章是「論述」的討論部分，先從一般西方discourse的理論開始談起，有意義地挪用、鋪陳理論家的定義和解釋，並特別取法傅柯對「論述」的見解，延伸探討「論述」的細緻化特性（如：論述的稀釋作用）。　　第三章是「法律論述」的討論部分，首先區分「法律論述」的兩個思考方向：「法律即是論述的一種」與「法律文體的論述」，並以後者為描述的重心，但穿插前者的思維模式，在具體操作的分析上作為解讀論述現象的背景預設（見第四章第三節）；「法律文體的論述」藉著西方對legal discourse的模型討論，參照我國法律文書的格式，描述出法律論述的外形及其字句結構。本文相信，掌握「論述」的效果一定要由觀察論述可見的形式部分開始，透過描繪論述的外形，分析論述的結構，歸納出結構的規則，才有可能切實推論出論述的效果。　　第四章則是以張志輝一、二、三審判決書為觀察對象，進入判決文字的字裡行間的搜查，配合參酌第二章與第三章細緻化的「論述」預設，以及法律論述理論，佐以西方理論界提出的legal discourse模型、外部語言特徵，嘗試觀察描述出現下台灣社會中，「法律論述」的樣貌，以及法律論述作用於社會的效果與影響。相關司法新聞報導也列入觀察的對象（第四節），綜合前面討論的結果，檢討法律論述內部，判決文本與新聞文本之間，以及法律論述與日常生活經驗世界之間，所產生的「稀釋化」作用。第五章是結論，自我評估觀察所得的結果，與檢視本次觀察研究所有的種種限制，並期待能對當今社會現存的論述情境，有所反省與思考。論述法律論述傅柯稀釋化司法判決書司法新聞報導張志輝白曉燕案 discourse legal discourse Michel Foucault rarefaction
23	O Problema de Riemann para um modelo de injeção de polímero em meio poroso com efeito de adsorção. / The Riemann Problem for a model of polymer injection in porous medium with adsorption effect. LIMA, Erivaldo Diniz de. 11 August 2018 (has links) Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-11T13:32:15Z No. of bitstreams: 1 ERIVALDO DINIZ DE LIMA - DISSERTAÇÃO PPGMAT 2015..pdf: 2368610 bytes, checksum: 3db3b8e45efcb83c955dae60371f8f4b (MD5) / Made available in DSpace on 2018-08-11T13:32:15Z (GMT). No. of bitstreams: 1 ERIVALDO DINIZ DE LIMA - DISSERTAÇÃO PPGMAT 2015..pdf: 2368610 bytes, checksum: 3db3b8e45efcb83c955dae60371f8f4b (MD5) Previous issue date: 2015-08 / Neste trabalho consideramos um sistema de leis de conservação proveniente da modelagem matemática de um escoamento bifásico unidimensional num meio poroso, preenchido de óleo e água com polímero dissolvido nela e levando em conta a adsorção de parte do polímero pela rocha. Usando a técnica das curvas de onda apresentamos a construção detalhada da solução do problema de Riemann para dados iniciais arbitrários no espaço de estados. Usamos a condição de entropia do per l viscoso para as ondas de choque com salto na concentração do polímero e a condição de Oleinik-Liu para os choques com concentração constante do polímero e salto na saturação da água / In this work we consider a system of conservation laws from the mathematical modeling of a one-dimensional two-phase flow in porous media, filled with oil and water with dissolved polymer in it and taking into account the adsorption of part of the polymer by the rock. Using the wave curves technique, we present a detailed construction of the Riemann problem solution for arbitrary initial data on the state space. We use the entropy condition of the viscous pro le for the shock waves with jumps in the polymer concentration and Oleynik-Liu condition for the shocks with constant concentration of polymer and jumps on the water saturation. Matemática. Problema de Riemann Modelo de injeção de polímero Meios porosos Adsorção Leis de conservação Onda de choque Onda de rarefação Conservation laws Riemann problem Polymer Injection Shock wave Rarefaction Wave Condições de entropia Curva de coincidência
24	Characterization of microvascular stress and cell death responses triggered by renal ischemia-reperfusion injury and their roles in progressive fibrosis Lan, Shanshan 12 1900 (has links) L’insuffisance rénale aiguë (IRA) est une complication clinique associée à une mortalité significative. Parmi les diverses causes d'IRA, l'ischémie-reperfusion (IRI) est une étiologie importante, en particulier dans le contexte de la transplantation rénale. Les types de mort cellulaire programmée (MCP) activées dans l'IRA induite par IRI ont été étudiées par des nombreux groupes. L’atteinte tubulaire épithéliale est classiquement considérée comme le principal contributeur à l'IRA.En effet, plusieurs morts programmées de cellules tubulaires ont été démontrées dans la littérature. Cependant, les lésions endothéliales microvasculaires rénales attirent davantage l'attention en tant qu'inducteurs cruciaux de dysfonctionnement microvasculaire et de fibrose rénale progressive. Ainsi, certaines équipes de recherche, dont la nôtre a rapporté le développement de l'apoptose endothéliale rénale en association avec l’IRI. Le but de mon travail était donc de caractériser les types de mort cellulaire microvasculaires secondaires à l’IRI et leur contribution à la dysfonction rénale. Pour évaluer l'importance de l'apoptose dans l'IRA induite par IRI, nous avons utilisé un modèle murin d’IRI chez des souris caspase-3 knock-out (KO) et sauvages, avec clampage de l'artère rénale pendant 30 minutes (modèle IRA légère) ou 60 minutes (modèle IRA sévère). Dans le modèle IRA légère, notre résultat montre que la carence en caspase-3 empêche la mort apoptotique des cellules endothéliales dans toutes les phases de l'IRA, atténuant la raréfaction microvasculaire, le dépôt de collagène et la fibrose rénale. L’absence de caspase-3 favorise aussi le maintien d’une perméabilité endothéliale microvasculaire normale à long terme. Toutefois, l’invalidation de la caspase-3 aggrave la mort cellulaire tubulaire à court terme en favorisant la nécroptose, mais améliore l’homéostasie tubulaire à long terme grâce à la préservation des capillaires péritubulaires (PTCs) permettant un maintien de la perfusion tubulaire. En outre, le déficit en caspase-3 est également associé à un effet protecteur contre la raréfaction microvasculaire rénale, la fibrose rénale progressive, ainsi qu'une perméabilité endothéliale améliorée et une préservation de la fonction rénale dans le modèle d’IRA sévère. En conclusion, nos résultats démontrent l'effet crucial de l’apoptose endothéliale microvasculaire en tant qu'inducteur de dysfonctionnement microvasculaire rénal, de raréfaction microvasculaire et de fibrose rénale progressive dans la physiopathologie de l'IRA légère et sévère induite par l'IRI. Ils établissent aussi l’importance prédominante de l’atteinte microvasculaire plutôt que tubulaire épithéliale dans la prédiction de la perte de fonction rénale à long terme suite à une IRI. / Acute kidney injury (AKI) is a crucial clinical event, with increasing incidence and mortality. Among various pathogenesis of AKI, ischemia-reperfusion injury (IRI) is an important etiology, especially in the renal post-transplant scenario. The complex of programmed cell deaths (PCD) developed in IRI-induced AKI has been proven in a number of investigations. Renal tubular epithelial injury has been considered as the major contributor in AKI and multiple programmed tubular epithelial cell (TECs) deaths have been demonstrated in the literature. However, renal microvascular endothelial injury is attracting more attention as an important inducer of microvascular dysfunction and renal progressive fibrosis. Some investigators, including our team, have reported the development of renal endothelial apoptosis in the condition of ischemia. Apoptosis, a commonly known programmed cell death, has been elucidated in both renal TECs and microvascular endothelial cells (ECs) post-IRI and the activation of caspase-3 functions as the key effector of caspase-dependent apoptosis. To verify the importance of apoptosis in IRI- induced AKI, we applied the in vivo murine renal IRI model in wild-type and caspase-3 KO mice, with clamping the renal artery for 30 minutes (mild AKI model) or 60 minutes (severe AKI model). In regard to the mild AKI model, our result demonstrates that caspase-3 deficiency prevents ECs apoptotic death in all phases of AKI, attenuating microvascular rarefaction, collagen deposition, and renal fibrosis, while maintaining physical endothelial permeability in the long-term. Meanwhile, caspase-3 deletion aggravates tubular injury in the short-term by promoting TECs necroptosis but ameliorates long-term tubular injury through preserved peritubular capillaries (PTCs) function. Furthermore, caspase-3 deficiency also demonstrated a protective effect against renal microvascular rarefaction, progressive renal fibrosis, as well as enhanced endothelial permeability in the severe AKI model. Conclusively, our findings determine the crucial effect of microvascular endothelial apoptosis as an inducer of renal microvascular dysfunction, microvascular rarefaction, and progressive renal fibrosis in the pathophysiology of mild and severe AKI induced by IRI. Additionally, our results demonstrate the predominant importance of microvascular endothelial injury over tubular epithelial injury in predicting renal function loss at long-term post-IRI. Apoptose Apoptosis Fibrose Fibrosis Perméabilité endothéliale Endothelial permeability Microvascular rarefaction Nécroptose Necroptosis Ischemia-reperfusion injury Lésion rénale aiguë Acute kidney injury Lésion d'ischémie-reperfusion Raréfaction microvasculaire
25	Macroscopic description of rarefied gas flows in the transition regime Taheri Bonab, Peyman 01 September 2010 (has links) The fast-paced growth in microelectromechanical systems (MEMS), microfluidic fabrication, porous media applications, biomedical assemblies, space propulsion, and vacuum technology demands accurate and practical transport equations for rarefied gas flows. It is well-known that in rarefied situations, due to strong deviations from the continuum regime, traditional fluid models such as Navier-Stokes-Fourier (NSF) fail. The shortcoming of continuum models is rooted in nonequilibrium behavior of gas particles in miniaturized and/or low-pressure devices, where the Knudsen number (Kn) is sufficiently large. Since kinetic solutions are computationally very expensive, there has been a great desire to develop macroscopic transport equations for dilute gas flows, and as a result, several sets of extended equations are proposed for gas flow in nonequilibrium states. However, applications of many of these extended equations are limited due to their instabilities and/or the absence of suitable boundary conditions. In this work, we concentrate on regularized 13-moment (R13) equations, which are a set of macroscopic transport equations for flows in the transition regime, i.e., Kn≤1. The R13 system provides a stable set of equations in Super-Burnett order, with a great potential to be a powerful CFD tool for rarefied flow simulations at moderate Knudsen numbers. The goal of this research is to implement the R13 equations for problems of practical interest in arbitrary geometries. This is done by transformation of the R13 equations and boundary conditions into general curvilinear coordinate systems. Next steps include adaptation of the transformed equations in order to solve some of the popular test cases, i.e., shear-driven, force-driven, and temperature-driven flows in both planar and curved flow passages. It is shown that inexpensive analytical solutions of the R13 equations for the considered problems are comparable to expensive numerical solutions of the Boltzmann equation. The new results present a wide range of linear and nonlinear rarefaction effects which alter the classical flow patterns both in the bulk and near boundary regions. Among these, multiple Knudsen boundary layers (mechanocaloric heat flows) and their influence on mass and energy transfer must be highlighted. Furthermore, the phenomenon of temperature dip and Knudsen paradox in Poiseuille flow; Onsager's reciprocity relation, two-way flow pattern, and thermomolecular pressure difference in simultaneous Poiseuille and transpiration flows are described theoretically. Through comparisons it is shown that for Knudsen numbers up to 0.5 the compact R13 solutions exhibit a good agreement with expensive solutions of the Boltzmann equation. kinetic theory of gases rarefied gas flows Grad's moment method nonequilibrium gas dynamics nonequilibrium flow Knudsen boundary layers Couette flow Poiseuille flow transpiration flow kinetic boundary conditions rarefaction effects R13 equations second order velocity slip condition second order temperature jump condition temperature dip in Poiseuille flow Knudsen paradox thermomolecular pressure difference Onsager's reciprocity relation
26	Structure spatiale de la diversité intra- et interspécifique en Afrique centrale: le cas des forêts gabonaises Dauby, Gilles 03 February 2012 (has links) L’origine de la structuration spatiale de la diversité inter spécifique (SSDS) des forêts d’Afrique centrale est l'objet de vigoureux débats quant à l’importance relative des facteurs historiques, stochastiques et déterministes. De plus, la SSDS est le plus souvent mal caractérisée, en particulier la variation spatiale de la composition des communautés (diversité beta).<p>L’hypothèse la plus souvent avancée pour expliquer l’origine des centres de diversité et d’endémisme est historique :ces centres constitueraient d’anciens refuges forestiers formés pendant les périodes sèches du Quaternaire. Cependant, la forte hétérogénéité environnementale de ces régions pourrait tout aussi bien expliquer la SSDS.<p>L'objectif principal de cette thèse est de tester l'importance de ces facteurs (historiques et/ou hétérogénéité environnementale) :si les facteurs historiques sont déterminants, on s’attend à observer une concordance spatiale entre la SSDS et la structure spatiale de la diversité génétique (SSDG). En effet, la variation neutre au sein des espèces est en grande partie soumise aux processus qui affectent également la SSDS (dérive génétique/écologique et dispersion des espèces/flux de gènes). L’approche utilisée dans cette thèse consiste donc à comparer et évaluer la concordance spatiale entre la SSDS et la SSDG.<p>Le modèle biologique et le cadre géographique de cette étude sont les communautés et les populations d’arbres des forêts humides d’Afrique centrale atlantique, avec une attention particulière pour les forêts gabonaises. La SSDS a été étudiée sur la base de relevés de communautés d’arbres (16308 individus) et la SSDG sur la base de séquences d’ADN chloroplastiques de six espèces d’arbres (Greenwayodendron suaveolens, Scorodophloeus zenkeri, Afrostyrax lepidophyllus, Afrostyrax kamerunensis, Santiria trimera et Erythrophleum suaveolens).<p>Quatre objectifs spécifiques ont été retenus :<p>(i)\ / Doctorat en Sciences / info:eu-repo/semantics/nonPublished Biologie Sciences exactes et naturelles Biodiversity -- Gabon Forest biodiversity -- Gabon Coastal forests -- Gabon Phylogeography -- Gabon Biodiversité -- Gabon Biodiversité forestière -- Gabon Forêts littorales -- Gabon Phylogéographie -- Gabon forêts littorales Ivindo diversité alpha diversité béta coastal forests alpha diversity phylogenetic structure of community Erythrophleum forest stratification rarefaction indices effective number of species beta diversity Greenwayodendron nombres effectifs d’espèces biais d’estimation indices de raréfaction DNA chloroplastic sequencing stratification forestière Afrostyrax Scorodophloeus Santiria phylogéographie comparée comparative phylogeography Hurlbert Effective Number of species. refuges forestiers Massif du Chaillu Sanaga forests refuges Monts de Cristal Nombres Effectifs de Hurlbert/Gabon hétérogénéité environnementale séquençage d’ADN chloroplastique Bas-Guinéen Gabon
27	Methodological investigations on vegetation typology and phytogeography of rain forests of tropical Africa Senterre, Bruno B.M.L. 17 June 2005 (has links) I. An original methodological discussion is proposed on the problem of the typology of tropical rain forest’s plant communities, based on the study of forest types across gradients of continentality and elevation, within Atlantic central Africa. These investigations were based on the statement that the main problems in forest typology are related to the non-zonal or zonal character of the different vegetation types and to non considering the relations and differences between forest strata. II. Field data consisted in phytosociological homogeneous sample plots localized within different recognized phytogeographical entities, in a region of tropical Africa where these entities are known to be well conserved. A total of 37 such plots were inventoried in the region extending from the littoral forests of Ndoté, Equatorial Guinea, which are wet evergreen forests, to the continental forests of the Dja, Cameroon, known as evergreen seasonal forests. The studied region also included the oriental Atlantic forests of Equatorial Guinea, known as moist evergreen forests or caesalp forests. In various parts of this continentality gradient, some plots were localized within climax non-zonal formations, namely the submontane rain forests. The emphasis was put on the vegetation of the Monte Alén National Park. The sampling methodology was willing to be as "complete ", including all strata, "quantitative ", enumerating all individuals, and "representative ", within each stratum, as possible. These multi-layers plots were realised using nested sub-plots, with a sampling size of 100 individuals for every ligneous stratum recognized (dominant trees, dominated trees and shrubs) and a sampling size of 200m² for the herbaceous and suffrutex stratum. Forest types were defined independently for each stratum and the differences were analysed. A method was proposed for the simultaneous analysis of all floristic data, converting and standardizing the values from ligneous strata, on the one hand, and from understorey strata, on the other hand. III. Ten forest types were described using IndVal and discussed in the general context of the guineo-congolian region, from a syntaxonomic view point (agglomerative classification) and from a phytogeographical view point (divisive classification). Homologies between these two approaches are described. The proposed phytogeographical system is based on an "open " conception of hierarchical classifications, combining advantages of agglomerative and divisive classifications. In concrete terms, the non-zonal criteria, for example the submontane variants, are categorised separately and in analogy with the zonal criteria, related to the usual phytochoria. Analysis of ecological relationships for the 10 communities showed that the main variables related to the floristic variability in our mainland rain forests are elevation, rainfall, hygrometry (estimated using bryophytes cover levels) and distance to the ocean. The two extremes on the vertical microclimatic gradient, dominant trees stratum and herbaceous stratum, give similar typologies, however canonical analysis showed that for the herbaceous layer, non-zonal variables (hygrometry and elevation) were gaining more importance when the influence of the two zonal variables was attenuated. In every case, spatial autocorrelation was less important than the environment in explaining floristic variability but its role increased in the spatial arrangement of understorey species, whose dispersal capacity is generally lower than canopy trees. The phytosociological, phytogeographical and ecological description of forest types is accompanied by a physiognomical description using biological types spectrum, as well as architectural models, leaf sizes, etc. With regard to diversity, we have demonstrated that species richness was higher from upper to lower strata because of the accumulation in lower strata of species from various strata. On the other hand, the proper stratum diversity, i.e. the structural set, decreased from dominant trees to shrubs. The proper diversity of the herb layer showed relatively high figures mainly due to the higher individual density in relation to the existence of microstrata. Within the 37 sample plots, 1,050 taxa have been identified to species or morpho-species levels, for a total of 25,750 individuals. These taxa represent 442 genus among 104 families. The richest forest type is found on the foothills of the Niefang range, on the windward side. This forest type is also characterised by a high number of oligotypic genus and by species belonging to functional types indicators of glacial refuges. These functional types are defined on the basis of the dispersal capacity and on kind of stand needed for effective germination. We formulated the hypothesis that this kind of "foothills refuge ", characterised by his zonal nature, could have been one of the rare refuges for species from mainland rain forests, while montane and fluvial refuges would mainly have preserved species from non-zonal forest types: (sub)montane and riverine. Based on indicator species of submontane forests, a potential distribution map of this forest type has been realised at the Atlantic central African scale. More than 400 submontane forest localities have been mapped. These forests begin at 400m of altitude near the ocean, and progressively at higher altitude for increasing distance to the ocean. Many lowland localities also comprised submontane species, which could indicate the existence of ecological transgressions. These transgressions would allow migratory tracks for submontane species between isolated mountain ranges, not only during glacial periods, through heights at the northern and southern borders of the congo basin, but also contemporarily through the lowland riverine forest network, in the centre of this basin. Finally, a special attention has been attributed to littoral forests and to some cases of choroecological transgressions, coupled to the ecological equalization phenomenon. plant diversity foothills refuge glacial refuge environmental stability conservation rarefaction curves individuals-area curves species-area curves compensations écologiques Guinée Equatoriale Monte Alén Monts de Cristal Réserve de Ndoté rainforest transgression Monte Alén Cristal mountains strate forestière sous-bois ensemble structural groupe écologique modèles architecturaux guilde types fonctionnels synusie genres monotypiques genres paucispecifiques diversité végétale courbes aire-espèces courbes individus-espèces courbes de raréfaction courbes aire-constance aire minimale morpho-espèces pléistocène constancy-area curves minimal area structural ensemble understorey ecological group synusia oligotypic genus Réserve de Biosphère du Dja Cameroun Quaternaire glaciation refuge glaciaire refuge de pied de massifs montagneux stabilité environnementale conservation transgression forestière phytosociology plant community phytogeography open classification non-zonal nested plots forest types IndVal morphospecies pleistocene littoral forest rain forest afromontane submontane altitudinal belt glaciation Quaternary Equatorial Guinea ecological equalization continentality continentalité étage d’altitude forêt littorale forêt dense humide afromontagnard submontagnard IndVal types forestiers phytosociologie phytogéographie classification ouverte azonal relevés emboîtés multistrates monotypic genus architectural model guild plant functional type Ndoté Reserve Cameroon Dja Biosphere Reserve forest stratum forest layer understory
28	Recherches méthodologiques pour la typologie de la végétation et la phytogéographie des forêts denses d'Afrique tropicale Senterre, Bruno 17 June 2005 (has links) I. An original methodological discussion is proposed on the problem of the typology of tropical rain forest’s plant communities, based on the study of forest types across gradients of continentality and elevation, within Atlantic central Africa. These investigations were based on the statement that the main problems in forest typology are related to the non-zonal or zonal character of the different vegetation types and to non considering the relations and differences between forest strata.<p><p>II. Field data consisted in phytosociological homogeneous sample plots localized within different recognized phytogeographical entities, in a region of tropical Africa where these entities are known to be well conserved. A total of 37 such plots were inventoried in the region extending from the littoral forests of Ndoté, Equatorial Guinea, which are wet evergreen forests, to the continental forests of the Dja, Cameroon, known as evergreen seasonal forests. The studied region also included the oriental Atlantic forests of Equatorial Guinea, known as moist evergreen forests or caesalp forests. In various parts of this continentality gradient, some plots were localized within climax non-zonal formations, namely the submontane rain forests. The emphasis was put on the vegetation of the Monte Alén National Park.<p><p>The sampling methodology was willing to be as "complete ", including all strata, "quantitative ", enumerating all individuals, and "representative ", within each stratum, as possible. These multi-layers plots were realised using nested sub-plots, with a sampling size of 100 individuals for every ligneous stratum recognized (dominant trees, dominated trees and shrubs) and a sampling size of 200m² for the herbaceous and suffrutex stratum.<p><p>Forest types were defined independently for each stratum and the differences were analysed. A method was proposed for the simultaneous analysis of all floristic data, converting and standardizing the values from ligneous strata, on the one hand, and from understorey strata, on the other hand.<p><p>III. Ten forest types were described using IndVal and discussed in the general context of the guineo-congolian region, from a syntaxonomic view point (agglomerative classification) and from a phytogeographical view point (divisive classification). Homologies between these two approaches are described. The proposed phytogeographical system is based on an "open " conception of hierarchical classifications, combining advantages of agglomerative and divisive classifications. In concrete terms, the non-zonal criteria, for example the submontane variants, are categorised separately and in analogy with the zonal criteria, related to the usual phytochoria.<p><p>Analysis of ecological relationships for the 10 communities showed that the main variables related to the floristic variability in our mainland rain forests are elevation, rainfall, hygrometry (estimated using bryophytes cover levels) and distance to the ocean. The two extremes on the vertical microclimatic gradient, dominant trees stratum and herbaceous stratum, give similar typologies, however canonical analysis showed that for the herbaceous layer, non-zonal variables (hygrometry and elevation) were gaining more importance when the influence of the two zonal variables was attenuated. In every case, spatial autocorrelation was less important than the environment in explaining floristic variability but its role increased in the spatial arrangement of understorey species, whose dispersal capacity is generally lower than canopy trees. The phytosociological, phytogeographical and ecological description of forest types is accompanied by a physiognomical description using biological types spectrum, as well as architectural models, leaf sizes, etc.<p><p>With regard to diversity, we have demonstrated that species richness was higher from upper to lower strata because of the accumulation in lower strata of species from various strata. On the other hand, the proper stratum diversity, i.e. the structural set, decreased from dominant trees to shrubs. The proper diversity of the herb layer showed relatively high figures mainly due to the higher individual density in relation to the existence of microstrata. Within the 37 sample plots, 1,050 taxa have been identified to species or morpho-species levels, for a total of 25,750 individuals. These taxa represent 442 genus among 104 families. The richest forest type is found on the foothills of the Niefang range, on the windward side. This forest type is also characterised by a high number of oligotypic genus and by species belonging to functional types indicators of glacial refuges. These functional types are defined on the basis of the dispersal capacity and on kind of stand needed for effective germination. We formulated the hypothesis that this kind of "foothills refuge ", characterised by his zonal nature, could have been one of the rare refuges for species from mainland rain forests, while montane and fluvial refuges would mainly have preserved species from non-zonal forest types: (sub)montane and riverine.<p><p>Based on indicator species of submontane forests, a potential distribution map of this forest type has been realised at the Atlantic central African scale. More than 400 submontane forest localities have been mapped. These forests begin at 400m of altitude near the ocean, and progressively at higher altitude for increasing distance to the ocean. Many lowland localities also comprised submontane species, which could indicate the existence of ecological transgressions. These transgressions would allow migratory tracks for submontane species between isolated mountain ranges, not only during glacial periods, through heights at the northern and southern borders of the congo basin, but also contemporarily through the lowland riverine forest network, in the centre of this basin. Finally, a special attention has been attributed to littoral forests and to some cases of choroecological transgressions, coupled to the ecological equalization phenomenon.<p> / Doctorat en sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished Sciences exactes et naturelles Agronomie générale Phytogeography -- Africa, Sub-Saharan Forest surveys -- Africa, Sub-Saharan Phytogéographie -- Afrique noire Inventaires forestiers -- Afrique noire submontane afromontane rain forest littoral forest pleistocene morphospecies IndVal forest types nested plots non-zonal open classification phytogeography plant community phytosociology transgression forestière conservation stabilité environnementale refuge de pied de massifs montagneux refuge glaciaire glaciation Quaternaire Cameroun Réserve de Biosphère du Dja oligotypic genus synusia ecological group understorey structural ensemble minimal area constancy-area curves pléistocène morpho-espèces aire minimale courbes aire-constance courbes de raréfaction courbes individus-espèces courbes aire-espèces diversité végétale genres paucispecifiques genres monotypiques synusie types fonctionnels guilde modèles architecturaux groupe écologique ensemble structural sous-bois strate forestière Cristal mountains Monte Alén rainforest transgression Réserve de Ndoté Monts de Cristal Guinée Equatoriale compensations écologiques species-area curves individuals-area curves rarefaction curves environmental stability glacial refuge foothills refuge plant diversity altitudinal belt Quaternary Equatorial Guinea ecological equalization continentality continentalité étage d’altitude forêt littorale forêt dense humide afromontagnard submontagnard types forestiers phytosociologie phytogéographie classification ouverte azonal relevés emboîtés multistrates monotypic genus architectural model guild plant functional type Ndoté Reserve Cameroon Dja Biosphere Reserve forest stratum forest layer understory

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