Advances in unsupervised learning and deep neural networks have led to increased performance in a number of domains, and to the ability to draw strong comparisons between the biological method of self-organization conducted by the brain and computational mechanisms. This thesis aims to use real-world data to tackle two areas in the domain of computer vision which have biological equivalents: feature detection and motion tracking. The aforementioned advances have allowed efficient learning of feature representations directly from large sets of unlabeled data instead of using traditional handcrafted features. The first part of this thesis evaluates such representations by comparing regularization and preprocessing methods which incorporate local neighbouring information during training on a single-layer neural network. The networks are trained and tested on the Hollywood2 video dataset, as well as the static CIFAR-10, STL-10, COIL-100, and MNIST image datasets. The induction of topography or simple image blurring via Gaussian filters during training produces better discriminative features as evidenced by the consistent and notable increase in classification results that they produce. In the visual domain, invariant features are desirable such that objects can be classified despite transformations. It is found that most of the compared methods produce more invariant features, however, classification accuracy does not correlate to invariance. The second, and paramount, contribution of this thesis is a biologically-inspired model to explain the emergence of motion tracking behaviour in early development using unsupervised learning. The model’s self-organization is biased by an original concept called retinal constancy, which measures how similar visual contents are between successive frames. In the proposed two-layer deep network, when exposed to real-world video, the first layer learns to encode visual motion, and the second layer learns to relate that motion to gaze movements, which it perceives and creates through bi-directional nodes. This is unique because it uses general machine learning algorithms, and their inherent generative properties, to learn from real-world data. It also implements a biological theory and learns in a fully unsupervised manner. An analysis of its parameters and limitations is conducted, and its tracking performance is evaluated. Results show that this model is able to successfully follow targets in real-world video, despite being trained without supervision on real-world video.

This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.” Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles. In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines. Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force. The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.

Aktive Filament-Systeme, wie zum Beispiel das Zellskelett, sind Beispiele einer interessanten Klasse neuartiger Materialien, die eine wichtige Rolle in der belebten Natur spielen. Viele wichtige Prozesse in lebenden Zellen wie zum Beispiel die Zellbewegung oder Zellteilung basieren auf dem Zellskelett. Das Zellskelett besteht aus Protein-Filamenten, molekularen Motoren und einer großen Zahl weiterer Proteine, die an die Filamente binden und diese zu einem Netz verbinden können. Die Filamente selber sind semifexible Polymere, typischerweise einige Mikrometer lang und bestehen aus einigen hundert bis tausend Untereinheiten, typischerweise Mono- oder Dimeren. Die Filamente sind strukturell polar, d.h. sie haben eine definierte Richtung, ähnlich einer Ratsche. Diese Polarität begründet unterschiedliche Polymerisierungs- und Depolymerisierungs-Eigenschaften der beiden Filamentenden und legt außerdem die Bewegungsrichtung molekularer Motoren fest. Die Polymerisation von Filamenten sowie Krafterzeugung und Bewegung molekularer Motoren sind aktive Prozesse, die kontinuierlich chemische Energie benötigen. Das Zellskelett ist somit ein aktives Gel, das sich fern vom thermodynamischen Gleichgewicht befindet. In dieser Arbeit präsentieren wir Beschreibungen solcher aktiven Filament-Systeme und wenden sie auf Strukturen an, die eine ähnliche Geometrie wie zellulare Strukturen haben. Beispiele solcher zellularer Strukturen sind Spannungsfasern, kontraktile Ringe oder mitotische Spindeln. Spannungsfasern sind für die Zellbewegung essentiell; sie können kontrahieren und so die Zelle vorwärts bewegen. Die mitotische Spindel trennt Kopien der Erbsubstanz DNS vor der eigentlichen Zellteilung. Der kontraktile Ring schließlich trennt die Zelle am Ende der Zellteilung. In unserer Theorie konzentrieren wir uns auf den Einfluß der Polymerisierung und Depolymerisierung von Filamenten auf die Dynamik dieser Strukturen. Wir zeigen, dass der kontinuierliche Umschlag (d.h. fortwährende Polymerisierung und Depolymerisierung) von Filamenten unabdingbar ist für die kontraktion eines Rings mit konstanter Geschwindigkeit, so wie in Experimenten mit Hefezellen beobachtet. Mit Hilfe einer mikroskopisch motivierten Beschreibung zeigen wir, wie "filament treadmilling", also Filament Polymerisierung an einem Ende mit der gleichen Rate wie Depolymerisierung am anderen Ende, zur Spannung in Filament Bündeln und Ringen beitragen kann. Ein zentrales Ergebnis ist, dass die Depolymerisierung von Filamenten in Anwesenheit von filamentverbindenden Proteinen das Zusammenziehen dieser Bündel sogar in Abwesenheit molekulare Motoren herbeiführen kann. Ferner entwickeln wir eine generische Kontinuumsbeschreibung aktiver Filament-Systeme, die ausschließlich auf Symmetrien der Systeme beruht und von mikroskopischen Details unabhängig ist. Diese Theorie erlaubt uns eine komplementäre Sichtweise auf solche aktiven Filament-Systeme. Sie stellt ein wichtiges Werkzeug dar, um die physikalischen Mechanismen z.B. in Filamentbündeln aber auch bei der Bildung von Filamentringen im Zellkortex zu untersuchen. Schließlich entwickeln wir eine auf einem Kräftegleichgewicht basierende Beschreibung für bipolare Strukturen aktiver Filamente und wenden diese auf die mitotische Spindel an. Wir diskutieren Bedingungen für die Bildung und Stabilität von Spindeln. / Active filament systems such as the cell cytoskeleton represent an intriguing class of novel materials that play an important role in nature. The cytoskeleton for example provides the mechanical basis for many central processes in living cells, such as cell locomotion or cell division. It consists of protein filaments, molecular motors and a host of related proteins that can bind to and cross-link the filaments. The filaments themselves are semiflexible polymers that are typically several micrometers long and made of several hundreds to thousands of subunits. The filaments are structurally polar, i.e. they possess a directionality. This polarity causes the two distinct filament ends to exhibit different properties regarding polymerization and depolymerization and also defines the direction of movement of molecular motors. Filament polymerization as well as force generation and motion of molecular motors are active processes, that constantly use chemical energy. The cytoskeleton is thus an active gel, far from equilibrium. We present theories of such active filament systems and apply them to geometries reminiscent of structures in living cells such as stress fibers, contractile rings or mitotic spindles. Stress fibers are involved in cell locomotion and propel the cell forward, the mitotic spindle mechanically separates the duplicated sets of chromosomes prior to cell division and the contractile ring cleaves the cell during the final stages of cell division. In our theory, we focus in particular on the role of filament polymerization and depolymerization for the dynamics of these structures. Using a mean field description of active filament systems that is based on the microscopic processes of filaments and motors, we show how filament polymerization and depolymerization contribute to the tension in filament bundles and rings. We especially study filament treadmilling, an ubiquitous process in cells, in which one filament end grows at the same rate as the other one shrinks. A key result is that depolymerization of filaments in the presence of linking proteins can induce bundle contraction even in the absence of molecular motors. We extend this description and apply it to the mitotic spindle. Starting from force balance considerations we discuss conditions for spindle formation and stability. We find that motor binding to filament ends is essential for spindle formation. Furthermore we develop a generic continuum description that is based on symmetry considerations and independent of microscopic details. This theory allows us to present a complementary view on filament bundles, as well as to investigate physical mechanisms behind cell cortex dynamics and ring formation in the two dimensional geometry of a cylinder surface. Finally we present a phenomenological description for the dynamics of contractile rings that is based on the balance of forces generated by active processes in the ring with forces necessary to deform the cell. We find that filament turnover is essential for ring contraction with constant velocities such as observed in experiments with fission yeast.

Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund's sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called TRIDER (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as 'cleanest' possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general, sputtering is not the dominant driving force responsible for the ripple formation. Processes like bulk and surface defect kinetics dominate the surface morphology evolution. Only at grazing incidence the sputtering has been found to be a direct cause of the ripple formation. Bradley and Harper theory fails in explaining the ripple dynamics because it is based on the second-order-effect 'sputtering'. However, taking into account the new mechanisms, a 'Bradley-Harper equation' with redefined parameters can be derived, which describes pattern formation satisfactorily. (ii) Kinetics of (bulk) defects has been revealed as the dominating driving force of pattern formation. Constantly created defects within the collision cascade, are responsible for local surface topography fluctuation and cause surface mass currents. The mass currents smooth the surface at normal and close to normal ion incidence angles, while ripples appear first at incidence angles larger than 40°. The evolution of bimetallic interfaces under ion irradiation is another application of TRIDER described in this thesis. The collisional mixing is in competition with diffusion and phase separation. The irradiation with He ions is studied for two extreme cases of bimetals: (i) Irradiation of interfaces formed by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters show a self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co. The TRIDER program package has been proven to be an appropriate technique providing a complete picture of mixing mechanisms.

Background: Since the 1980s, society has been hit hard by economization and deprofessionalization through neoliberal abstract forms of governance. Control is achieved by measuring efficiency through simplified models. The demand for measurability has also hit the art field where administration and paperwork have increased. As an effect, a large part of cultural funding goes to non-artistic activities. Values other than those of art are focused on and art institutions are having to adapt to the logic of the market and meet commercial interests. In addition, the conditions of artistic production have deteriorated: there are no resources, space or time yet, which threatens art production. The situation is, to say the least, strained for many artists, who are more or less forced into their own corporate activities by the field's surrounding organizations and institutions. However, there are those who work against this development and act for change. Artists have collectively organized themselves outside the city that no longer meets the condition for artistic production. They are about 40 organisations spread across Sweden. Through networks, they have united under one designation; the self-organized. They could be said to constitute a micro-resistance to the current order. Purpose: The purpose of this study is to investigate what the self-organized means. Which ideas and practices make sense and distinction concerning the self-organised? We want to understand and highlight how the self-organised are motivated and how they go about trying to alter and expand the artistic field and the society at large. Methodology: Using a qualitative approach, the study has been a case study of a central actor in the self-organized fields; Art Lab Gnesta. Materials have been collected through a group interview, participant observation and through written sources produced by the study object itself. This is to better understand underlying ideas and what it is that makes sense for self-organized arts organizations. Conclusions: This study is about a possible institutionalisation process in its future. The self-organised is a kind of avant-garde of the 20th century. In this study, we conclude that the self-organised should be understood as a concept that provides alternative frameworks in a world characterized by an unsustainable order. The self-organised opens up opportunities and shows other ways to go. If many join the concept, changes can possibly be achieved. We have seen that they succeed in reaching out and are legitimized by both the authorities, the art world and the local population. When enough people act on similar ideas, they can constitute institutional pressure and possibly create change. We understand the self-organised as a predestination and a strategy for a potential future. It is about change, nothing else can be determined since we are in the initial stage of the course of event. They are a grassroots movement. / Bakgrund: Samhället har allt sedan 1980-talet drabbats av en hårt driven ekonomisering och avprofessionalisering via nyliberala abstrakta styrformer. Kontroll uppnås genom att via förenklade modeller mäta effektivitet. Kravet på mätbarhet har även drabbat konstfältet där administrationen har ökat. Således går en stor del av kulturfinansieringen åt till icke-konstnärlig verksamhet. Andra värden än den av konsten fokuseras och konstinstitutioner har i större utsträckning marknadsanpassas och möter kommersiella intressen. Utöver detta har konstnärers produktionsförhållandena försämrats: det finns inte rum, tid och resurser nog, varvid konsten hotas. Situationen är minst sagt ansträngd för många konstnärer, som mer eller mindre tvingats in i egen företagsverksamhet av fältets omgivande organisationer och institutioner. Det finns dock dem som tar spjärn mot denna utveckling och verkar för en förändring. Konstnärer har kollektivt organiserat sig utanför staden som inte längre erbjuder. De är ett fyrtiotal verksamheter spridda över Sverige. Genom nätverk har de förenat sig under en beteckning; de självorganiserade. De skulle kunna sägas utgöra ett mikro-motstånd mot rådande ordning. Syfte: Syftet med denna studie är att undersöka vad de självorganiserade betyder. Vilka idéer och vad för praktiker ger mening och distinktion gällande de självorganiserade? Vi vill förstå och belysa hur de självorganiserade motiveras och hur de går tillväga för att försöka uppnå förändring av den ordning som de tar spjärn emot på det konstnärliga fältet och i samhället i stort. Metod: Utifrån en kvalitativ ansats har studien utgjorts av en fallstudie på en central aktör på de självorganiserades fält; Art Lab Gnesta. Material har samlats in genom en gruppintervju, en deltagande observation samt genom skriftliga källor producerade av studieobjektet själv. Detta för att bättre förstå bakomliggande idéer och vad det är som ger mening för självorganiserade konstorganisationer. Slutsatser: Denna studie handlar om en eventuell institutionaliseringsprocess i sitt blivande. De självorganiserade är ett slags 2020-talets avantgarde. I studien kommer vi fram till att de självorganiserade ska förstås som ett koncept som ger alternativa ramverk i en värld präglad av ohållbar ordning. De självorganiserade öppnar upp för möjligheter och visar på andra vägar. Ansluter många till konceptet kan eventuellt förändringar uppnås. Vi har sett att de lyckas nå ut och legitimeras av både makthavare, konstvärld och lokalbefolkning. När tillräckligt många handlar utifrån liknande koncept kan de utgöra ett institutionellt tryck och eventuellt skapa förändring på fältet. Vi förstår de självorganiserade som en predistination och en strategi för en potentiell framtid. Det handlar om förändring, inget annat kan slås fast då vi är i skeendets initiala stadie. De är en gräsrotsrörelse.

The development of shape in multicellular organisms has intrigued human minds for millenia. Empowered by modern genetic techniques, molecular biologists are now striving to not only dissect developmental processes, but to exploit their modularity for the design of custom living systems used in bioproduction, remediation, and regenerative medicine. Currently, our capacity to harness this potential is fundamentally limited by a lack of spatiotemporal control over gene expression in multicellular systems. While several synthetic genetic circuits for control of multicellular patterning have been reported, hierarchical induction of gene expression domains has received little attention from synthetic biologists, despite its fundamental role in biological self-organization. In this thesis, I introduce the first synthetic genetic system implementing population-based AND logic for programmed hierarchical patterning of bacterial populations of Escherichia coli, and address fundamental prerequisites for implementation of an analogous genetic circuit into the emergent multicellular plant model Marchantia polymorpha. In both model systems, I explore the use of bacteriophage T7 RNA polymerase as a gene expression engine to control synthetic patterning across populations of cells. In E. coli, I developed a ratiometric assay of bacteriophage T7 RNA polymerase activity, which I used to systematically characterize different intact and split enzyme variants. I utilized the best-performing variant to build a three-color patterning system responsive to two different homoserine lactones. I validated the AND gate-like behavior of this system both in cell suspension and in surface culture. Then, I used the synthetic circuit in a membrane-based spatial assay to demonstrate programmed hierarchical patterning of gene expression across bacterial populations. To prepare the adaption of bacteriophage T7 RNA polymerase-driven synthetic patterning from the prokaryote E. coli to the eukaryote M. polymorpha, I developed a toolbox of genetic elements for spatial gene expression control in the liverwort: I analyzed codon usage across the transcriptome of M. polymorpha, and used insights gained to design codon-optimized fluorescent reporters successfully expressed from its nuclear and chloroplast genomes. For targeting of bacteriophage T7 RNA polymerase to these cellular compartments, I functionally validated nuclear localization signals and chloroplast transit peptides. For spatiotemporal control of bacteriophage T7 RNA polymerase in M. polymorpha, I characterized spatially restricted and inducible promoters. For facilitated posttranscriptional processing of target transcripts, I functionally validated viral enhancer sequences in M. polymorpha. Taking advantage of this genetic toolbox, I introduced inducible nuclear-targeted bacteriophage T7 RNA polymerase into M. polymorpha. I showed implementation of the bacteriophage T7 RNA polymerase/PT7 expression system accompanied by hypermethylation of its target nuclear transgene. My observations suggest operation of efficient epigenetic gene silencing in M. polymorpha, and guide future efforts in chassis engineering of this multicellular plant model. Furthermore, my results encourage utilization of spatiotemporally controlled bacteriophage T7 RNA polymerase as a targeted silencing system for functional genomic studies and morphogenetic engineering in the liverwort. Taken together, the work presented enhances our capacity for spatiotemporal gene expression control in bacterial populations and plants, facilitating future efforts in synthetic morphogenesis for applications in synthetic biology and metabolic engineering.

L'équilibre arbre-herbe dans la savane tropicale est reconnu comme l'une des principales<p>énigmes de l'écologie des plantes. Les origines du difficile équilibre entre ces formes de vie<p>sur des dizaines de millions de kilomètres carrés à l'échelle mondiale sont en partie attribuées<p>aux perturbations fréquentes induites par les feux de végétation dont les effets varient dans<p>l'espace et dans le temps selon les conditions environnementales. Les résultats de recherche<p>dépendent de l’échelle et les conclusions tirées d’études locales sont rarement transposables à<p>d’autres échelles. La question du transfert d'échelle s’avère donc cruciale dans l'étude des<p>effets du feu, et nécessite une approche transdisciplinaire.<p>En raison de la variété des échelles couvertes, cette étude constitue une première dans la<p>confrontation de données sur l’historique des feux dérivé de l'imagerie satellitaire à des<p>données de terrain incluant des mesures détaillées sur la structure et la composition de<p>végétation, ainsi que des propriétés édaphiques et topographiques. Elle s’est focalisée sur la<p>composante ligneuse de par son caractère pérenne et son influence sur les processus<p>écologiques majeurs. Sur une zone de plus de 2000 km², le Parc National du W du Niger<p>(PNWN), où le feu est utilisé comme outil pour la gestion et la conservation des écosystèmes<p>semi-arides, une carte de l'historique des feux a été élaborée à partir d'images MODIS de 250<p>m de résolution spatiale et de résolution temporelle journalière couvrant une période de sept<p>années (2002-2009). Pour comprendre la variabilité, à la fois dans l'espace et le temps, de la<p>propagation du feu dans la végétation, nous avons étudié les caractéristiques de distribution<p>des feux en termes de régime du feu (i.e. période d'occurrence et fréquence) et de structure<p>spatiale (métriques paysagères). Les relations causales plausibles entre les régimes du feu, les<p>conditions édaphiques et topographiques à l'échelle régionale comme locale, et les<p>caractéristiques de la végétation ligneuse (composition et structure) ont été examinées à<p>travers des analyses multivariées et des modèles d'équations structurales. Nous avons aussi<p>examiné plus en détails les stratégies adaptatives mises en oeuvre par les ligneux, et les<p>interactions biologiques qui sous-tendent l'organisation spatiale des ligneux à travers une<p>approche des processus ponctuels.<p>Les résultats montrent que l'activité du feu dans le PNWN se caractérise par une hétérogénéité<p>spatio-temporelle induite principalement par les conditions édapho-topographiques via la<p>structure de la végétation ligneuse. Les feux précoces de gestion créent des pare-feux<p>efficaces, limitant une large extension des feux de saison tardifs. Cependant, ces feux tardifs<p>pourraient ne pas être aussi destructifs comme qu’on le suppose généralement. En effet,<p>l'adaptation des espèces aux différents régimes defeu correspond à des stratégies de croissance<p>contrastées. Dans le cas des feux tardifs, les surfaces terrières et hauteurs moyennes les plus<p>fortes sont rencontrées, permettant aux arbres de résister au feu. Quant aux zones non<p>affectées par les feux l'analyse "patron-processus" désigne clairement la facilitation entre<p>ligneux comme un processus fondamental de l'organisation spatiale périodique du couvert, une<p>structure émergente qui empêche le passage du feu. Bien qu’ils ne se substituent pas aux<p>études expérimentales, ces résultats basés sur une expérimentation naturelle à large échelle<p>apportent des informations nouvelles précieuses tant au niveau fondamental que pour la mise<p>en place d'une gestion raisonnée du PNWN.<p><p><p>The tree-grass equilibrium in tropical savanna is recognized as one of plant ecology's main<p>conundrums. The origins of the difficult balance between these life forms over tens of millions<p>of square kilometers worldwide are in part attributed to the frequent disturbances caused by<p>vegetation fires effects of which vary in space and time depending on local environmental<p>factors. Research results are scale-dependent and findings from local studies are rarely<p>transposable to higher levels of ecosystem organization. The question of scaling (scale<p>transfer) is therefore crucial in the study of fire effects, and requires a multidisciplinary<p>approach.<p>Because of the variety of scales covered, this study is a premiere in the confrontation of<p>satellite-imagery derived fire history data with detailed field data including measurements of<p>vegetation parameters (structure and composition), as well as soil and topographic properties.<p>The study focuses on the woody component, because of its perennial character and its<p>influence on major ecological processes. On an area of more than 2000 km², the W National<p>Park of Niger (WNPN) where fire is used as a tool for the management and conservation of<p>semi-arid ecosystems, a fire history map was elaborated from MODIS images with a 250 m<p>spatial resolution and a daily temporal resolution over a period of seven years (2002-2009). To<p>understand the variability, both in space and time, of fire propagation in vegetation, we studied<p>the fire distribution characteristics in terms of fire regime (i.e. timing and frequency) and<p>spatial structure (landscape metrics). Plausible causal relationships at regional and local scales<p>between fire regimes, edaphic and topographic conditions, and the woody vegetation<p>(composition and structure) characteristics were examined through multivariate analyses and<p>structural equations models. We also examined in detail the woody species adaptive strategies<p>as well biological interactions, which underlie their spatial organization, using point statistics.<p>Results show that the WNPN fire's activity is characterized by spatial and temporal<p>heterogeneity induced mainly by edaphic and topographic conditions via the structure of the<p>ligneous component. Prescribed early season fires create effective firewalls, limiting wide late<p>season fires. However, these late fires might not be as destructive as is commonly assumed.<p>Indeed, species adaptation to different fire regimes corresponds to contrasting growth<p>strategies. In the case of late fires, increased basal areas and mean tree heights were<p>encountered, enabling trees to resist fire and escape flames. As for the unburned areas, the<p>"pattern-process" analysis clearly indicates that facilitation between shrubs is a fundamental<p>process determining the woody cover periodic spatial organization, an emergent structure that<p>prevents fire spread.<p>Although they do not replace experimental studies, these results based on a large-scale natural<p>experiment provide valuable new information both on a fundamental level and for setting up<p>the rational management of the WNPN. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

「内発的地域イノベーション・エコシステム」とは、地域課題の革新的な解決を可能にする多様なプレイヤーによる機能的ネットワークであり、相互作用と共進化により持続する自律的システムである。人口減少を迎える小規模自治体において、いかにそうしたエコシステムを生み出し、地域公共財としての社会関係資本を蓄積しながら、しなやかに地域社会を維持・発展させていくことが可能なのかについて、国内の先進事例をもとに分析を行った。 / "Endogenous Regional Social Innovation Ecosystem" is that enable innovative solutions to regional challenges. It is a functional network of multi-sectoral players that is autonomous, sustained by interaction and co-evolution among the players. I analyzed based on advanced cases in Japan, about how it is possible for domestic small municipalities with declining populations to maintain and develop the local community in a flexible manner by creating such an ecosystem while accumulating social capital as local public goods. / 博士(ソーシャル・イノベーション) / Doctor of Philosophy in Social Innovation / 同志社大学 / Doshisha University