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Cruywagen, Gerhard C. "Tissue interaction and spatial pattern formation." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:f242b785-9b46-4c21-a789-477b025ce4b3.
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The development of spatial structure and form on vertebrate skin is a complex and poorly understood phenomenon. We consider here a new mechanochemical tissue interaction model for generating vertebrate skin patterns. Tissue interaction, which plays a crucial role in vertebrate skin morphogenesis, is modelled by reacting and diffusing signal morphogens. The model consists of seven coupled partial differential equations, one each for dermal and epidermal cell densities, four for the signal morphogen concentrations and one for describing epithelial mechanics. Because of its complexity, we reduce the full model to a small strain quasi-steady-state model, by making several simplifying assumptions. A steady state analysis demonstrates that our reduced system possesses stable time-independent steady state solutions on one-dimensional spatial domains. A linear analysis combined with a multiple time-scale perturbation procedure and numerical simulations are used to examine the range of patterns that the model can exhibit on both one- and two-dimensions domains. Spatial patterns, such as rolls, squares, rhombi and hexagons, which are remarkably similar to those observed on vertebrate skin, are obtained. Although much of the work on pattern formation is concerned with synchronous spatial patterning, many structures on vertebrate skin are laid down in a sequential fashion. Our tissue interaction model can account for such sequential pattern formation. A linear analysis and a regular perturbation analysis is used to examine propagating epithelial contraction waves coupled to dermal cell invasion waves. The results compare favourably with those obtained from numerical simulations of the model. Furthermore, sequential pattern formation on one-dimensional domains is analysed; first by an asymptotic technique, and then by a new method involving the envelopes of the spatio-temporal propagating solutions. Both methods provide analytical estimates for the speeds of the wave of propagating pattern which are in close agreement with those obtained numerically. Finally, by numerical simulations, we show that our tissue interaction model can account for two-dimensional sequential pattern formation. In particular, we show that complex two-dimensional patterns can be determined by simple quasi-one-dimensional patterns.
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COLOMBO, EDUARDO HENRIQUE FILIZZOLA. "SPATIAL PATTERN FORMATION IN POPULATION DYNAMICS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24777@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO<br>BOLSA NOTA 10<br>Motivado pela riqueza de fenômenos produzidos pelos seres vivos,
este trabalho busca estudar a formação de padrões espaciais de populações
biológicas. De um ponto de vista mesoscópico, definimos os processos básicos
que podem ocorrer na dinâmica, construindo uma equação diferencial parcial
para a evolução da distribuição da população. Essa equação incorpora
duas generalizações de um modelo pre-existente para a dinâmica de um
espécie, que leva em conta interações de longo alcance (não locais). A
primeira generalização consiste em considerar que a difusão é não linear,
isto é, é afetada pela densidade local de tal modo que o coeficiente de difusão segue uma lei de potência. Por outro lado, visto a alta complexidade
envolvida na natureza dos parâmetros do modelo, introduzimos como segunda
generalização parâmetros que flutuam no tempo. Idealizamos estas
flutuações como um ruído descorrelacionado temporalmente e que obedece
uma distribuição gaussiana (ruído branco). Para estudar o modelo resultante,
utilizamos uma abordagem analítica e numérica. As ferramentas analíticas se baseiam na linearização da equação de evolução e portanto são aproximadas. Todavia, complementadas com resultados numéricos, conseguimos extrair conclusões relevantes. A não localidade das interações induz a formação de padrões. O alcance dessas interações é o que determina o modo dominante presente nos padrões. Assim, para valores dos parâmetros acima de um limiar crítico, emergem padrões. Analiticamente, mostramos que, mesmo abaixo desse limiar, as flutuações nos parâmetros podem induzir a aparição de ordem espacial. Os efeitos da difusão não-linear são captados superficialmente pela análise linear. Numericamente, mostraremos que sua presença modifica a forma dos padrões. Observamos, especialmente, a existência de uma transição quando alternamos entre o caso em que a difusão é facilitada por altas densidades e o caso oposto. Para o primeiro caso, verificamos que os padrões se tornam fragmentados, ou seja, a população é agora composta de sub-grupos desconectados.<br>Motivated by the richness of phenomena produced by living beings,
this work aims to study the formation of spatial patterns in biological
populations. From the mesoscopic point of view, we define the basic
processes that may occur in the dynamics, building a partial differential
equation for the evolution of the population distribution. This equation
incorporates two generalizations of a pre-existing model for the dynamics
of one species, which takes into account long-range (nonlocal) interactions.
The first generalization is to consider that diffusion is nonlinear, i.e., it is
affected by the local density such that the diffusion coeficient follows a
power law. On the other hand, because of the high complexity involved in
the nature of model parameters, we introduced as a second generalization
time-fluctuating parameters. We idealize these fluctuations as Gaussian
temporally uncorrelated (white) noises. To study the resulting model, we
use an analytical and numerical approach. Analytical tools are based on
the linearization of the evolution equation and are therefore approximate.
However, as evidenced by numerical results, we draw important conclusions.
The nonlocal feature of the interaction is the main mechanism which
induces pattern formation. We show that the extent of these interactions
is what characterizes the dominant mode. Thus, for parameter values
above a critical threshold patterns emerge. Analytically, we also show that
even below this threshold, fluctuations in the parameters can induce the
appearance of spatial order. The effects of nonlinear diffusion are only
superficially captured by the linear analysis. Numerically, we show that their
presence modifies the patterns shape. We mainly observed the existence of
a qualitative difference between the cases when diffusion is facilitated or
not by high densities. In the first case, we note that the patterns become
fragmented, that is, population becomes composed of disconnected clusters.
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Tse, Dawn Po-Ling. "Spatial period-multiplying bifurcations in pattern formation." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616060.
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Julien, Keith Anthony. "Strong spatial resonance in convection." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386110.
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Irvine, Michael Alastair. "Pattern formation and persistence in spatial plant ecology." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/67166/.
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The main aim of the thesis is to explore the interaction between pattern and process in vegetation ecology using a variety of mathematical and statistical methods. Of particular interest is what information about the dynamics of the underlying system can be gained through a single spatial snapshot, such as an aerial photograph or satellite image. The hypotheses are related to seagrass ecology, whose growth is primarily clonal and broadly exists as a monoculture and thus makes it an ideal candidate to study these interactions. The thesis broadly concerns two forms of spatial pattern and the underlying dynamics that give rise to them. The first concerns regular pattern formation, where the pattern has a characteristic length scale. Examples are abundant in natural systems, such as mussel beds, semi-arid ecosystems as well as seagrass. The developments concerned with regular pattern formation include methods of detection in a large spatial dataset, a novel stochastic model of vegetation that produces regular pattern with plausible mechanisms, the development of a new methodology to fit regular spatial pattern data to the model and the impact as well as evolutionary mechanisms of regular patterning in the presence of disease. The second form of spatial pattern exhibited in a wide variety of sessile species is scale-free or fractal patterning. Certain scaling heuristics, such as the boundary dimension of a vegetation cluster or the power-law exponent of the patch-size distribution have been used to infer properties of the dynamics. We explore these heuristics using a variety of plausible models of vegetation growth and find the circumstances under which there is a clear relationship between the spatial heuristics and the dynamics. These are then supplemented by viewing vegetation growth as an aggregation process. A novel model of vegetation aggregation with death is produced to find the origin of the ubiquitous power-law patch-size distribution found in nature. Finally the impact of scaling on the spread of disease is explored.
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Kose, Semra. "Spatial Formation Of The Interface Between University And City." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612586/index.pdf.
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Universities have a significant role in society as they are generators of economic activity, as land developers, as neighbors and as property owners. Therefore it is a focal point in the community. Every university lives within a surrounding community. They have been creating their own relations with the neighborhoods. The space that the university confronts with the city is shaped according to the needs of the people from the university and the inhabitants of the area. Between the university and the city, every university creates their own interface in accordance with the location and the inhabitants of the area. While planning the city or the university the interface zone did not take into account. It has been behaved as a part of the city although it has been a neighbor with university. While designing the university there has been no attempt to design this zone or making decisions including this zone. Therefore this space creates its own character in time. As it is locating between the city and the university it has been carrying both the character of the university and the city.
The main aim of this study is to examine the spatial formation of the interface of university and city in respect to the planning decisions and spatial features of the area by investigating the two different types of universities in their own contexts in Ankara<br>Ankara University and METU. In this context, the spatial character of interface area is defined by examining this space as a transitional area, boundary and threshold. Then universities and their historical developments are examined in urban space and the relations between these two domains are investigated through the selected universities in Europe and USA. Finally, the situation of the university in Turkey is handled and searched the formation of the interface areas around the campuses of the two selected universities in Ankara.
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Ali, Adnan. "Stochastic pattern formation in growth models with spatial competition." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/54323/.
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The field of stochastic growth encompasses various different processes which are ubiquitously seen across the physical world. In many systems, stochasticity appears quite naturally, where inherent randomness provides the right setting for the tone of motion and interaction, whose symphony leads to the surprising emergence of interesting patterns and structure. Although on the microscopic scale one can be overwhelmed by the randomness arising from the fluctuating interactions between components, on the macroscopic scale, however, one is mesmerized by the emergence of mathematical beauty and symmetry, leading to complex structures with fractal architecture. Competition between components adds an extra degree of complexity and leads to the possibility of critical behaviour and phase transitions. It is an important aspect of many systems, and in order to provide a full explanation of many natural phenomena, we have to understand the role it plays on modifying behaviour. The combination of stochastic growth and competition leads to the emergence of interesting complex patterns. They occur in various systems and in many forms, and thus we treat competition in growth models driven by different laws for the stochastic noise. As a consequence our results are widely applicable and we encourage the reader to find good use for them in their respective field. In this thesis we study stochastic systems containing interacting particles whose motion and interplay lead to directed growth structures on a particular geometry. We show how the effect of the overall geometry in many growth processes can be captured elegantly in terms of a time dependent metric. A natural example we treat is isoradial growth in two dimensions, with domain boundaries of competing microbial species as an example of a system with a homogeneously changing metric. In general, we view domain boundaries as space-time trajectories of particles moving on a dynamic surface and map those into more easily tractable systems with constant metric. This leads to establishing a generic relation between locally interacting, scale invariant stochastic space-time trajectories under constant and time dependent metric. Indeed “the book of nature is written in the language of mathematics” (Galileo Galilei) and we provide a mathematical framework for various systems with various interactions and our results are backed with numerical confirmation.
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Madzvamuse, Anotida. "A numerical approach to the study of spatial pattern formation." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343437.
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Moss, Jennifer Leigh. "The spatial and temporal distribution of pipe and pockmark formation." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54111/.
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This research concentrates on two study areas. A family of blowout pipes from North Namibia imaged in 3D seismic data; and a group of large buried pockmarks and a field of small seabed pockmarks from the Western Nile Deep Sea Fan (NDSF) imaged in ultra high resolution 2D data. The general themes of this research are pipe and pockmark morphology and formation process, their spatial and temporal distribution and the magnitude and frequency of fluid flux through the conduit. A family of blowout pipes from Namibia exhibit a variety of seismic characteristics, with the largest pipes containing a blowout crater and evidence of possible stacked palaeo-pockmarks. Pipe formation is shown to be intermittent and persistent throughout the Neogene. The spatial position of pipes adheres to both basinal and local controls. A group of large buried pockmarks on the NDSF are interpreted to have formed between 15,000 yrs BP and 125,000 yrs BP, the majority of which are believed to have formed at the same time c. 60,000-80,000 yrs BP. These buried pockmarks show evidence for highly focused, episodic fluid flow following burial of the pockmark. The longevity of post formation fluid migration is estimated to be ~50,000-100,000 yrs. A field of > 13,800 small seabed pockmarks (Nile Deep Sea Fan) are interpreted to have formed within the last 1,000 yrs. Spatial statistics identified an exclusion zone or drainage cell surrounding each pockmark which is not penetrated by the formation of any other pockmark. A conceptual model for a drainage cell is proposed whereby pockmark formation dissipates, a radius/area of fluid and overpressure, thereby preventing the formation of another pockmark within that cell.
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Sasaki, Yuya. "Dynamics of Spatial Pattern Formation: Cases of Spikes and Droplets." DigitalCommons@USU, 2007. https://digitalcommons.usu.edu/etd/7131.
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This thesis studies the gradient system that forms spatial patterns such that the minimum distances of pairs among various points are maximized in the end. As this problem innately involves singularity issues, an extended system of the gradient system is proposed. Motivated by the spatial pattern suggested by a numerical example, this extended system is applied to a three-point problem and then to a two-point problem in a quotient space of R2 modulo a lattice.
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Kendall, Bruce Edward. "Spatial structure and transient periodicity in biological dynamics." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/187496.
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Structure, in its many forms, is a central theme in theoretical population ecology. At a mathematical level, it arises as nonuniformities in the topology of nonlinear dynamical systems. I investigate a mechanism wherein a chaotic time series can have episodes of nearly periodic dynamics interspersed with more 'typical' irregular dynamics. This phenomenon frequently appears in biological models, and may explain patterns of alternating biennial and irregular dynamics in measles epidemics. I investigate the interaction between spatial structure and density-dependent population regulation with a simple model of two logistic maps coupled by diffusive migration. I examine two different consequences of spatial structure: scale-dependent interactions ("nonlocal interactions") and spatial variation in resource quality ("environmental heterogeneity"). Nonlocal interactions allow three general dynamical regimes: in-phase, out-of-phase, and uncorrelated. With environmental heterogeneity, the dynamics of the total population size can be approximated by a logistic map with the mean growth parameter of the two patches; the dynamics within a single patch are often less regular. Adding environmental heterogeneity to non-local interactions has little qualitative effect on the dynamics when the differences between patches are small; when the differences are large, uncorrelated dynamics are most likely to be seen, and there are interesting consequences for the stability of source-sink systems. A third type of structure arises when individuals differ from one another. Accurate prediction of extinction risk in small populations requires that a distinction be made between demographic stochasticity (variation among individuals) and environmental stochasticity (variation among years or sites). I describe and evaluate two tests to determine whether all the variation in population survivorship can be explained by demographic stochasticity alone. Both tests have appropriate probabilities of type I error, unless the survival probability is very low or very high. Small amounts of environmental stochasticity are often not detected by the tests, but the hypothesis of demographic stochasticity alone is consistently rejected when environmental stochasticity is large. I also show how to factor out deterministic sources of variability, such as density-dependence. I illustrate these tests with data on a population of Acorn Woodpeckers.
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Kyureghian, Hrachya Henrik. "Theory and Simulations in Spatial Economics." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26077.
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Chapter 2 deals with a linear city model à la Hotelling where the two firms share linear transport costs with their customers. Mill pricing and uniform delivery pricing are special limiting cases. We characterize the conditions for the existence of a pure strategy equilibrium in the two-stage location-price game. These enable us to identify the causes for non-existence in the two limiting cases. We solve for the equilibrium of a location game between the duopolists with an exogenously given price. When the two firms are constrained to locate at the same central spot, we show the nonexistence of pure strategy equilibria, conjecture the existence of mixed strategy equilibria, and show that any such possible equilibria will always yield positive expected profits.
Chapter 3 provides simulations as well as theoretical analysis of potential spatial separation of heterogeneous agents operating on a two-dimensional grid space that represents a city. Heterogeneity refers to a characteristic which is also a determinant of individual valuation of land. We study spatial separation with respect to the distinguishing characteristic and investigate the details of emerging spatial patterns. Simulations suggest that the process of interaction with little trade friction goes through stages which resemble its end-state with high trade friction. Several theoretical examples exhibit a distinguishing characteristic upon which the simulations are based. They reflect some of the causes for spatial separation. Examples for the absence of spatial separation are also given.
In Chapter 4 simulations, in addition to some theory, are used to investigate certain aspects of a city formation process. The model assumes two types of economic agents, workers and employers, operating on a two-dimensional grid. The agents have simple preferences, positive for the opposite type and negative for the own type in the own location. In addition, they have positive or negative preference for agglomeration in the own location. The model helps build intuition about a potentially important factor for agglomeration formation, namely, the disparity between entrepreneurial and technical skills in localities. We also determine the minimum level of positive preference for agglomeration that leads to agglomeration formation.<br>Ph. D.
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Smith, Craig W. "The effects of spatial arrangement on group formation, productivity, and satisfaction." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/28576.
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Sinclair, Scott. "Pattern formation and control of spatial structures in optical parametric oscillators." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249142.
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Ferguson, James. "THE SPATIAL AND TEMPORAL ROLE OF EZH2 IN SKULL BONE FORMATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1530898825341447.
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Fabacher, Emilien. "Guidage et pilotage d’un remorqueur magnétique spatial." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0037/document.
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Remorquer des satellites peut être utiles pour de nombreuses raisons : les désorbiter ou ré-orbiter, nécessaire dans le cas des satellites en fin de vie, ou pour finaliser les lancements par exemple. Dans ce cas, cette manœuvre augmenterait la capacité des étages supérieurs de lanceurs. Plusieurs moyens peuvent être envisagés pour modifier l’orbite d’un satellite cible grâce à un autre satellite. Parmi eux, les concepts sans contact sont intéressants, car ils fournissent un moyen d’éviter le besoin d’interfaces normalisées. Ils permettent ausside ne pas réaliser d’amarrages non coopératifs, qui représentent une grande difficulté. Enfin, ils contribuent à réduire le risque de créer de nouveaux débris par collision. Dans cette thèse, nous proposons d’utiliser les forces magnétiques pour remorquer le satellite cible. En effet, de nombreux satellites, en particulier en orbite terrestre basse, sont équipés de magnéto-coupleur, utilisés pour le contrôle d’attitude. Un satellite chasseur équipé d’un dipôle magnétique puissant pourrait donc générer des forces sur la cible. Cependant, la création d’une force entre deux dipôles magnétiques génère automatiquement des couples sur les deux dipôles. Par conséquent, la viabilité d’un remorqueur magnétique spatial n’est a priori pas assurée, étant donné qu’appliquer en permanence des couples sur les deux satellites ne serait pas acceptable<br>Satellite tugging can be undertaken for various reasons: de-orbiting or reorbiting,necessary in the case of satellites at the end-of-life, or for instance to finalise launches,in which case this manoeuvre would increase the capacity of launchers’ upper stages. Severalmeans can be considered to modify the orbit of a target satellite by tugging it with anothersatellite. Contact-less concepts are interesting, as they provide a way to avoid standardisedinterfaces and hazardous docking phases. They also help to prevent the creation of new debrisby reducing the risk of collision. In this thesis, we suggest using magnetic forces to tug the target. Indeed many satellites, especially in Low Earth Orbit, are equipped with Magnetic Torque Bars used for attitudecontrol. A chaser satellite equipped with a powerful magnetic dipole could hence generateforces on the target. However, creating a force between two magnetic dipoles automaticallycreates torque on both of them. Therefore, the feasibility of magnetic tugging is a priori notassured, considering that applying constant torques on both satellites would not be acceptable
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Hilal, Muna. "Role of Scribble1 in hippocampal synaptic maturation, bidirectional plasticity and spatial memory formation in mice." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22037/document.
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La formation de la mémoire spatiale est un mécanisme complexe qui transforme les informations récemment acquises en traces mnésique robustes à long terme. D’un point de vue moléculaire, ces phénomènes sont dépendants de l’expression de deux formes opposées de plasticité synaptique ; la potentialisation à long terme (LTP) et la dépression à long terme (LTD). L’induction de la LTP/LTD dépend de la fine régulation entre des kinases et des phosphatases sensibles au Ca2+ qui vont activer respectivement la LTP et la LTD dans la densité postsynaptique (PSD). Cette régulation met également en jeu des interactions en avale entre les récepteurs et des protéines d’échafaudages spécialisées au sein de la PSD. Scribble1 (Scrib1) est une de ces protéines d’échafaudage appartenant à la famille des LAP (leucine-rich repeats & PDZ domains) avec 16 répétitions riches en leucine et 4 domaines PDZ (PSD-95/Dlg/ZO-1). Lors de cette étude, nous avons développé de souris « knock-out » conditionnelles avec une délétion complète de la Scrib1 dans les principaux neurones de l’encéphale antérieur, dont les neurones excitateurs de l’hippocampe, grâce au système Cre-lox (Scrib1f/f,CaMKII-cre). Les souris Scrib1f/f,CaMKII-cre présentent une altération de la morphologie des dendrites apicales sans modification de la morphologie ni de la densité des épines dans la région CA1 de l’hippocampe. Sur le plan fonctionnel, les neurones du CA1 des souris Scrib1f/f,CaMKII-cre présentent une augmentation du nombre de synapses silencieuses (non-fonctionnelles). Ceci réduit le nombre de synapses actives et entraine une diminution globale de la transmission basale des synapses CA3-CA1 comparée aux synapses Scrib1f/f. Les souris Scrib1f/f,CaMKII-cre montrent une augmentation de la LTP mais sont incapables d’exprimer une LTD ni la depotentiation à long terme. De plus, des protocoles de LTD induisent une LTP chez ces souris. Au niveau moléculaire, nous avons mis en évidence une interaction directe au sein des synapses entre Scrib1 et la phosphatase PP2A impliquée dans la LTD. De plus, l’absence de Scrib1 entraine une réduction des niveaux de PP2A dans la PSD chez les souris Scrib1f/f,CaMKII-cre. Ceci implique une diminution de l’activation de la voie de signalisation de la LTD via PP2A au profit de celle de la CAMKII et la LTP, ce qui pourrait expliquer l’induction d’une LTP à la place d’une LTD chez les souris Scrib1f/f,CaMKII-cre. Sur le plan cognitif, les souris Scrib1f/f,CaMKII-cre présentent des déficits dans la flexibilité de l’apprentissage spatial comparées aux souris Scrib1f/f. Chez les souris Scrib1f/f,CaMKII-cre, la la mémoire spatiale à court terme n’était pas altérée tandis que la mémoire à long terme était déficiente. Ainsi, ces données révèlent un rôle majeur de Srib1 dans consolidation de la mémoire spatiale. Lors de cette étude, nous avons montré un rôle pour Scrib1 dans les connections et la morphologie des neurones CA1, ainsi que la conversion fonctionnelle des synapses silencieuses en synapses actives. D’une manière importante, Scrib1 permet l’expression de la plasticité synaptique bidirectionnelle à travers une interaction avec PP2A et module la formation de la mémoire spatiale à long terme<br>Spatial memory formation is a complex process that transforms newly-acquired information into long-lasting and solid memories. Molecularly, these phenomena rely on the expression of two opposite forms of synaptic plasticity; long-term potentiation (LTP) and long-term depression (LTD). LTP/LTD induction relies on a fine balance between Ca2+-sensitive kinases and phosphatases that activate specific pathways of either LTP or LTD, respectively. This regulation also involves downstream interactions between receptors and highly specialized scaffold proteins, at the PSD. Scribble1 (Scrib1) is a scaffold protein that belongs to the LAP (leucine-rich repeats and PDZ domains) protein family, with 16 leucine rich repeats and 4 PDZ (PSD-95/Dlg/ZO-1) domains. Here, we developed conditional knock-out mice with a complete loss of Scrib1 expression in the major neurons of the postnatal forebrain, including hippocampal excitatory neurons, using the Cre-Lox system (Scrib1f/f,CaMKII-cre). Scrib1f/f,CaMKII-cre presented altered morphology of apical dendrites but intact spine density and spine morphology in the CA1 region. Functionally, we found increased number of silent (non-functional) synapses that decreases the number of active synapses in Scrib1f/f,CaMKII-cre CA1 neurons leading to a global decrease in basal glutamatergic synaptic transmission at CA3-CA1 synapses compared to Scrib1f/f synapses. Scrib1f/f,CaMKII-cre synapses displayed enhanced LTP but were unable to express LTD or long-term depotentiation. More strikingly, LTD-inducing protocols generated LTP in Scrib1f/f,CaMKII-cre synapses. Molecularly, we revealed a direct interaction between Scrib1 and the phosphatase PP2A that signals LTD at the synapse. Moreover, we found that the absence of Scrib1 results in a reduction of synaptic PP2A levels in Scrib1f/f,CaMKII-cre mice. This probably leads to a decrease in PP2A signaling pathway activation which favors the competing pathway downstream CaMKII resulting in LTP induction instead of LTD in Scrib1f/f,CaMKII-cre mice. On the cognitive level, we found that spatial learning was slower and inflexible in Scrib1f/f,CaMKII-cre compared to Scrib1f/f mice. Short-term spatial memory was intact while long-term memory was impaired. These results argue for an important role of Scrib1 in spatial memory consolidation. We here report that Scrib1 is important for appropriate neuronal shaping and wiring of CA1 neurons as well as functional conversion of silent synapses into active ones. Importantly, it allows bidirectional synaptic plasticity through interaction with PP2A and modulates long-term spatial memory formation
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Maréchal, Rozenn. "Contribution au SAR spatial distribué." Toulouse, ENSAE, 2006. http://www.theses.fr/2006ESAE0005.
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L'obtention d’images à partir de l'émission, de la réception et du traitement d'impulsions radar (SAR) est soumise à différentes contraintes qui limitent les performances telles que la résolution en distance, la résolution en azimut ou la largeur de la Zone imagée (fauchée). Ces limites sont en partie liées à la dimension finie de l’antenne, en particulier dans le cas du SAR spatial. Pour cette raison, on a cherché à étudier la possibilité de mettre au point des systèmes SAR spatiaux distribués, c'est-à-dire dont la surface d'antenne globale est répartie sur plusieurs plates-formes (généralement microsatellites pour des raisons de coût). Ce concept a déjà été instruit dans des concepts de formations comme la Roue lnterferométrique, le Pendulum ou TechSat21. Dans le cadre de mes travaux, deux configurations seront présentées. La première repose sur N antennes réparties successivement sur une même orbite («Train SAR»). On montre que, moyennant des contraintes de positionnement fortes, une telle formation permet, à surface globale d'antenne égale, d’augmenter d’un facteur N le rapport fauchée sur résolution azimut par rapport à une antenne monolithique. Cependant, les simulations effectuées montrent que le positionnement strict nécessaire pose un problème, dont une solution étudiée est l'utilisation de formes d’ondes à spectre étalé. Par ailleurs, le passage d’une antenne monolithique sur un satellite de grande taille à un ensemble de petites antennes sur des microsatellites, a fait l’objet d’une étude de dimensionnement. La deuxième formation repose sur deux satellites fonctionnant à la même fréquence, ayant la même bande émise, placés de telle manière qu’ils observent la même fauchée à deux incidences proches. Cette situation peut être ramenée à une observation à la même incidence, avec deux bandes émises décalées. On peut alors obtenir une bande émise virtuelle plus large, donc une résolution distance plus fine. Après avoir appliqué l'algorithme à des signaux simulés, il a été utilisé sur des images réelles ENVISAT. Les résultats seront présentés, ainsi qu’une première étude de dimensionnement. Enfin, on conclura sur les pistes d’études futures mises en évidence par ces travaux, et sur l’apport possible des systèmes distribués dans le cadre du SAR spatial.
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Vries, Miranda Wilhelmina Maria de. "Governing with your closest neighbour : an assessment of spatial coalition formation theories /." [S.l. : s.n.], 1999. http://www.gbv.de/dms/sub-hamburg/309517354.pdf.
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Hao, Jingyan [Verfasser]. "Araneiform terrain on Mars — spatial configuration and mechanism of formation / Jingyan Hao." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1219904821/34.
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Vries, Miranda W. M. de. "Governing with your closest neighbour : an assessment of spatial coalition formation theories /." Enschede : Ipskamp, 1999. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=008991203&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Stevenson, Cassie Hayley. "Investigating the role of the hippocampal formation in episodic and spatial memory." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5632.
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This thesis aims to explore the two dominant functional roles of the hippocampal formation, in the relational encoding of episodic memory and the neural representation of allocentric space, using a combination of pharmaceutical manipulations and single-unit recording techniques in rodents. The first part of this thesis focuses on episodic-like memory, defined by the original episodic memory triad: ‘what-where-when’ (Tulving 1972), which enables the behavioural aspects of episodic memory to be tested in non-human animals. Permanent neurotoxic lesions of the hippocampus and it’s subregions were induced to assess their role in a putative episodic-like memory task developed by Eacott and Norman (2004). In view of the difficulties encountered in successfully demonstrating the temporal component of episodic-like memory in rats, this task tested integrated memory for ‘what-where-which’, where the temporal component (when) was replaced with another event specifier: context (on ‘which’ occasion). Disruption of the hippocampal circuitry led to a specific impairment in the integration of all three event components, whereas the associative recognition of any combination of these features in isolation was left intact. These results confirm the hippocampal dependence of this episodic-like memory task and further reveals the necessity of both CA3 and CA1, hypothetically due to the underlying autoassociative role of CA3 with CA1 functioning as the vital output pathway for this associated information and/or as a mismatch detector. There has been much debate over the inclusion of the temporal component and sceptics may argue that any such interpretations of task-dependence on episodic-like memory processing are invalid considering the requirement for temporal processing is absent. Due to the proposal that a temporal framework necessarily provides the foundation on which episodic memories are built, the second chapter focuses on the development of a suitable protocol in which integrated memory for the original ‘what-where-when’ episodic memory triad can be reliably tested. The other main function attributed to the hippocampus was brought to light by the fascinating revelation that it’s neurons selectively fire in different regions of an environment, termed ‘place cells’ (O’Keefe and Dostrovsky 1971). From the numerous publications resulting from this discovery it has emerged that place cells not only respond to the spatial features of the environment but are also sensitive to a multitude of non-spatial features. These characteristics support the logical assumption that the primary firing patterns of the hippocampus should underlie it’s main purported roles, leading to speculations that they reflect episodic memory processes. The second part of this thesis aims to examine the relationship between hippocampal cells and behaviour by extending the work of Ainge et al. (2007a), in which a subset of hippocampal place cells were found to encode both current and intended destination in a double Y-maze ‘win-stay’ task. The development of these ‘goal-sensitive’ cells were initially investigated during the learning phase of this task. An exciting pattern of results showed a strong positive correlation between the emergence of goal-sensitive firing and behavioural performance on the task, tempting speculations that these firing patterns may underlie spatial learning and future planning, necessary to support performance. To ensure these firing patterns were not a mere reflection of greater experience on the maze, a second study was conducted in which the task demands changed over set periods of days. A significant increase in the proportion of cells demonstrating goal-sensitive firing was revealed when the protocol shifted to incorporate the spatial memory demands of the ‘win-stay’ task, with all other parameters of the protocol remaining constant. These results support the theory that goal-sensitive firing patterns are specifically related to the learning and memory demands of the spatial task, not a result of increased exploration of the maze. The last of this series of studies assessed hippocampal-dependence of this task and revealed that bilateral hippocampal lesions induced an impairment in spatial ‘win-stay’ performance. Collectively, these experiments demonstrate that goal-sensitive firing of hippocampal cells emerge in line with behavioural performance in a hippocampal-dependent task and the emergence of these firing patterns are specific to the learning and memory demands of a spatial ‘win-stay’ protocol. The functional role of the hippocampus in allocentric spatial processing may thus underpin it’s function in episodic memory and potentially in the imagining and planning of future events, whereby the hippocampus provides a ‘space’ in which retrieved information can be integrated in a coherent context to support the fluent and flexible use of information. This hippocampal function would necessarily require visual information to be accessed, concerning the arrangement of landmarks and cues within the environment, in association with information regarding internal orientation and direction and this leads to the question assessed in the final part of this thesis of where this integration occurs. Based on anatomical evidence and the current literature, the postsubiculum, an input structure to the hippocampus, emerged as a potential site for the convergence of sensory cues into the internally generated head direction cell and place cell networks to enable hippocampal-dependent spatial processing. Thus, the effects of temporary pharmacological blockade of AMPARs and NMDARs in the postsubiculum were assessed on the encoding of spatial memory in an object recognition paradigm. The impairment revealed in the ability to recognise novel object-place configurations demonstrates a key role for NMDAR-dependent plasticity within the postsubiculum itself in the formation of allocentric spatial memory. In summary, the experimental results reported in this thesis further elucidate the critical role the hippocampal formation plays in spatial and episodic memory by combining evidence from cellular physiology and neuroanatomy to the behaving animal and extends these findings to discuss a more general role for the hippocampus in imagining both past and future events, in order to successfully navigate, learn and enable past experience to influence our intended future plans and decisions.
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Hazir, Cilem Selin. "Spatial dynamics of knowledge networks." Thesis, Saint-Etienne, 2014. http://www.theses.fr/2014STETT108.
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La littérature économique attribuant des rôles endogènes à l'évolution technologique et à lagéographie pour expliquer la croissance économique suggère que la compréhension des fluxde connaissances dans l'espace et de leurs conséquences sur les activités d'innovation est aucoeur de l'explication des disparités dans la croissance économique. À cet égard, cette thèsemet l'accent sur les réseaux de connaissances comme un mécanisme permettant la circulationdes connaissances dans l'espace et le temps. Parmi les différents types de réseaux deconnaissances, elle étudie les réseaux de collaboration de R&D et explore deux questionsprincipales.Tout d'abord, elle examine l'effet de la géographie sur la formation du réseau pour savoir si lesflux de connaissances par les réseaux de collaboration en R&D sont limités dans l'espace oupas. Elle s'enquiert de cette question à la fois pour le réseau multilatéral entre lesorganisations et le réseau inter-régional entre les régions européennes dans le domaine desbiotechnologies en utilisant les données sur les collaborations de R&D promues par lesProgrammes-Cadres Européens.Deuxièmement, elle explore comment un réseau évolutif de collaborations de R&D entre lesrégions affecte les performances des régions en matière d'innovation. Elle utilise l'économétriespatiale pour quantifier les effets statiques et dynamiques des flux de connaissances desvoisins spatiaux et d'un ensemble évolutif de partenaires de collaboration sur l'activitéinventive des régions dans le domaine des TIC au cours de la période 2003-2009<br>The economic literature attributing endogenous roles to technological change and geography inexplaining economie growth suggests that understanding knowledge flows in space and theirconsequences on innovative activities is central to explaining disparities in economie growth. Inthis regard, this PhD thesis focuses on knowledge networks as a mechanism that enablesknowledge flows in space and time. Among different types of knowledge networks, it studiesR&D collaboration networks and addresses two main issues.First, it investigates the effect of geography on network formation to figure out whetherknowledge flows through R&D collaboration networks are constrained in space or not. It inquiresthis question both for multilateral R&D collaboration network among organizations and theresulting inter-regional network among European regions in the field of biotechnology using dataon R&D collaborations promoted via European Framework Programmes.Second, it addresses how an evolving network of R&D collaborations among regions affectsregional innovation performances in time. It employs a spatial econometric approach to quantifythe static and dynamic effects of knowledge flows from spatial neighbors and an evolving set ofcollaboration partners on inventive activity of regions in the field of ICT durin 2003-2009
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Rival, Muriel. "Impacts hypervitesse de micrométéorites et débris orbitaux sur les satellites : formation d'éjecta et implications pour l'environnement." Toulouse, ENSAE, 1997. http://www.theses.fr/1997ESAE0012.
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L'objectif de cette thèse est de préciser la contribution des débris secondaires au flux de particules solides en orbite basse terrestre, dans la gamme de taille allant du micron au millimètre. Les débris secondaires sont créés lors de l'impact hypervitesse d'un débris ou d'un micrométéoroïde sur un satellite en orbite. Une étude bibliographique poussée, associée à l'analyse d'échantillons provenant d'expériences au sol ou embarquées, a permis de mettre en évidence les différents phénomènes responsables de la formation et de l'éjection de particules secondaires lors d'un impact hypervitesse. Les matériaux fragiles, en particulier les cellules solaires, génèrent un nombre important de petits fragments éjectés à grande vitesse, auxquels s'ajoutent des éclats de grande taille libérés à faible vitesse. Un modèle est proposé qui, à partir des caractéristiques du projectile primaire et de la vitesse d'impact, donne la distribution en taille, vitesse et direction d'éjection des particules secondaires émises lors du choc. L'application de ce modèle permet de quantifier les flux secondaires induits dans l'environnement proche du satellite sur lequel a eu lieu l'impact primaire. Les résultats montrent que le flux des éjecta sur une surface en regard de l'impact primaire peut être très largement supérieur au flux primaire. Cette pollution locale fausse les mesures de flux sur les détecteurs embarqués et peut nuire à l'efficacité de surfaces sensibles. Les éjecta qui ne sont pas stoppés par une surface en regard s'éloignent du stellite parent et suivent leur propre orbite. Le modèle d'éjecta, couplé à un module d'extrapolation d'orbite, permet de simuler l'évolution orbitale des particules secondaires générées sur les panneaux solaires d'un satellite en orbite soumis au flux primaire. Les résultats montrent que les plus gros fragments secondaires ont une durée de vie de plusieurs années et polluent à la fois l'altitude du satellite parent et les altitudes inférieures. Ils induisent une pollution à long terme de l'environnement orbital et constituent une source prmanente de débris de petite taille.
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Mangan, Peter Anthony. "Spatial memory abilities and abnormal development of the hippocampal formation in Down syndrome." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185800.
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The recent evidence concerning the nature of cognitive development in Down Syndrome (DS) suggests that it is different than normal development. The neuropathology seen in DS implicates a prenatal interruption of normal neural development as a possible basis for these differences. Since the hippocampal formation (HF) undergoes extensive postnatal maturation and is found to be abnormal in DS, it is proposed that cognitive deficits associated with DS would be most evident in tasks requiring hippocampal function. The performance of DS children at 16-18 months and 28-30 months of age was compared to that of age-matched control groups of normal children on two cognitive tasks requiring abilities that develop during the first postnatal year shown not to involve hippocampal function, and a task requiring abilities that develop during the second postnatal year shown to require hippocampal functioning. The results show that the DS performed comparably on the nonhippocampal tasks but differently on the hippocampal task. The normal children's performance supports the position that the ability to perform HF tasks develops during the second postnatal year while the performance of the older DS children suggested that this development does not occur in DS. The specificity of the deficits to the hippocampal task was interpreted as indicative of a lack of HF development in DS.
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Giovannoli, Elodie. "Les galaxies observées de l'ultraviolet à l'infrarouge. Les résultats du télescope spatial Herschel." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10095/document.
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Ma thèse s'inscrit dans l'étude de la physique extragalactique. Pendant mes trois années de thèse j'ai travaillé sur les méthodes d'ajustement de la distribution d'énergie spectrale des galaxies (ou SED fitting) en effectuant un bilan énergétique entre l'émission en ultraviolet et l'émission en infrarouge. A cet effet j'ai très largement utilisé le code CIGALE (Burgarella et al. 2005, Noll et al. 2009) qui permet d'estimer les paramètres physiques des galaxies à partir de l'analyse de leur émission dans des bandes larges et intermédiares de l'ultraviolet au submillimétrique. J'ai procédé pendant ma thèse à des améliorations de ce code en rajoutant des paramètres d'extinction en sortie et j'ai implémenté plusieurs modèles d'émission de noyaux actifs de galaxies pour compléter les modèles existants.En parallèle de l'étude de la méthode de SED fitting avec des données en bandes larges et intermédiaires, j'ai développé la construction originale d'un catalogue de galaxies artificielles, dont le but est de déterminer la fiabilité des paramètres de sortie du code CIGALE et des codes de SED fitting en général. La technique du SED fitting m'a permis d'analyser plusieurs échantillons de galaxies dans l'univers proche et dans l'univers lointain possédant des données multi longueurs d'onde. Pratiquement j'ai travaillé avec des données allant de l'ultraviolet (GALEX) à l'infrarouge lointain avec les téléscopes spatiaux AKARI et Herschel. Les données AKARI couplées à des données ancillaires ont été à la base d'une étude de galaxies de l'univers local pour lesquelles j'ai pu déterminer la quantité d'atténuation.J'ai également travaillé avec les données Herschel en tant que membre des consortiums HerMES et GOODS-H. Dans le cadre du projet GOODS-H j'ai participé à la mise en évidence et à l'étude du "bump" à 2175 A d'un échantillon de galaxies distantes ainsi qu'à la formulation d'une loi d'atténuation pour ces objets. Dans le cadre d'un groupe de travail sur le SED fitting au sein d'HerMES j'ai participé à l'étude d'un échantillon de galaxies avec 0<br>My PhD thesis takes part of extragalactic physics. During three years I have worked on the fit of the spectral energy distribution (SED fitting) of galaxies by doing an energetic budget between the emission at ultraviolet wavelengths and the one at infrared wavelengths. I have extensively used the code CIGALE (Burgarella et al. 2005, Noll et al. 2009) allowing to estimate the physical parameters of galaxies from their broad bands and intermediate bands emission from ultraviolet wavelengths to submillimetric wavelengths. During my thesis I have improved this code by adding output parameters and several templates of active galactic nuclei to those already available.While I have studied the SED fitting technics I have also built original mock catalogues of galaxies to determine the reliability of the output parameters of CIGALE and, more generally, the reliability of parameters estimated by SED fitting codes.I have used the SED fitting method to analyse several samples of galaxies from low redshift to high redshift, with multi wavelength detections. I have used data from the ultraviolet (GALEX) to the far infrared using data from AKARI and Herschel space observatory. I have matched the AKARI data to ancillary data at other wavelengths to study nearby galaxies and determine their dust attenuation quantity. I have used Herschel data as part of HerMES and GOODS-H consortium members. In the framework of the GOODS-H project I have worked on the determination and the study of the so-called ultraviolet bump at 2175 A for a sample of high-redshift galaxies, and on the formulation of an attenuation law for these objects. In the framework of HerMES I have worked with the SED fitting working group to study a sample of galaxies with 0
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Nyadjro, Ebenezer S. "Spatial and temporal dynamics of benthic chlorophyll formation on the northwest Florida continental shelf." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-2/r1/nyadjroe/ebenezernyadjro.pdf.
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Allred, Isaac John. "Spatial Trends and Facies Distribution of the High-Energy Alluvial Cutler Formation, Southeastern Utah." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6253.
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The Cutler Formation is composed of thick, arkosic, alluvial conglomerate, sandstone, and mudstone shed southwestward from the Uncompahgre Uplift into the Paradox Basin. More basin-ward the Cutler is recognized as a group consisting of differentiable formations. Discrete formations historically have not been distinguished near the uplift, but this study identified several separate successions in the Richardson Amphitheater. Research at the Richardson Amphitheater, ~12 km southwest of the uplift and ~30 km northeast of Moab, Utah, led to a systematic subdivision of the Permian Cutler Formation proximal to the uplift. Likely driven by channel cutting and migration across the alluvial fan, six 10-20 m thick successions are partially exposed. The dominant observed facies are basal conglomerate and channel-fill trough cross-stratified sandstone overlain by finer-grained distal sheetflood and frequently pedogenically altered sandstone. Down-warping of identified successions and the presence of additional sands within the area of flexure suggest that localized salt withdrawal created a sediment depocenter in the Richardson Amphitheater, ~6 km northwest of the Onion Creek salt diapir. The identified salt withdrawal feature is more proximal to the Uncompahgre Uplift than any of the major documented salt structures in the area and was not previously documented. Six measured stratigraphic sections and hundreds of high-precision differential GPS data points outlining major lateral erosional surfaces form the basis for interpretation. Five mapped erosional surfaces (bounding surfaces based upon differential GPS point interpolation) are laterally extensive within the approximately one square kilometer study area, and as such, represent stratigraphically significant surfaces. Within the generated structural geocellular model, stratigraphic data from measured sections informed facies modeling between major surfaces. This outcrop model may serve as an analogue for subsurface systems deposited in similar settings.
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Nelson, Erica June. "The Spatial Distribution of Star Formation in Galaxies| Observing the Emergence of Galactic Structure." Thesis, Yale University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10160870.
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<p>A high resolution measurement of the distribution of star formation within galaxies is key to understanding the emergence of galactic structure. The aim of this thesis is to understand how the structure of galaxies is built by developing a new method to spatially resolve their star formation. Using Ha maps for 2676 galaxies, this thesis shows where star formation is distributed in galaxies during the epoch 0.7 < <i>z</i> < 1.5 when a third of the total star formation in the history of the universe occurred. Across the star formation rate - stellar mass plane (the "main sequence"), star formation is `spatially coherent': in galaxies with higher than average star formation rates, Ha is enhanced throughout the disk; similarly, in galaxies with low star formation rates Ha is depressed throughout the disk. This places constraints both on the mechanisms for enhancing and quenching star formation as well as on how the structure of galaxies is built. The disk scale length of star formation in galaxies is larger than that of the stars, a direct demonstration that the disks of galaxies grow inside-out. While most star formation in most galaxies occurs in disks, not all of it does. With the first spatially resolved measurement of the Balmer decrement at <i>z</i> > 1, it can be seen that galaxies with M<sub>*</sub> > 10<sup>10</sup>M[special characters omitted] have significant dust attenuation toward their centers. This means that we are witnessing the build-up of the dense stellar cores of massive galaxies through dust-obscured in-situ star formation. The most massive galaxies are thought to have formed their dense stellar cores at even earlier cosmic epochs. This thesis presents the first confirmed example of a massive galaxy core in the process of formation at <i>z</i> = 2.3. It has one of the highest velocity dispersions ever measured for a normal star forming galaxy and also appears to be building through very dense, dust-enshrouded star formation. </p>
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PANT, MOHAN MOORTI. "A STUDY ON THE SPATIAL FORMATION OF KATHMANDU VALLEY TOWNS-THE CASE OF THIMI." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149798.
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Fontdecaba, i. Baig Jordi. "Dynamics of formation flying : applications to earth and universe observation." Observatoire de Paris, 2008. https://theses.hal.science/tel-01958557.
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Le mouvement relatif est un élément clé pour le développement des futures missions spatiales qui utiliseront les vols en formation. Dans cet ouvrage je développe trois méthodes différentes pour son étude, utilisant différentes représentations. Les coordonnées cartésiennes ont été pendant de nombreuses années l’outil principal pour étudier le mouvement relatif, même si elles présentent des limitations en terme de linéarisation des équations ou des perturbations. Ces limitations peuvent être dépassées grâce à l’utilisation d’une représentation alternative : les différences d’éléments orbitaux. Une troisième représentation qui s’avère très intéressante pour l’étude des trajectoires utilise les éléments orbitaux locaux. L’utilisation des différences d’éléments orbitaux nous a permis d’étudier l’influence des perturbations les plus importantes. Pour les orbites basses, la perturbation dominante est le champ de gravité, et en particulier le second harmonique zonal lié à l’aplatissement de la Terre. Pour les orbites très hautes, la pression de radiation solaire joue un rôle dominant quand les satellites ne présentent pas le même rapport surface sur masse. J’ai développé des études concrètes du mouvement relatif pour deux missions particulières. D’abord je me suis intéressé à l’intérêt des vols en formation pour l’étude du champ de gravité. Pour cela, j’ai obtenu les équations de sensibilité des mesures intersatellitaires aux paramètres géophysiques. Je me suis également intéressé aux difficultés liées aux orbites très excentriques (HEO) pour les vols en formation en étudiant une mission du type SIMBOL-X<br>Relative motion is a key technology for future missions using formation flying. In my thesis, I have developed three different methods to study it, as function of its representation. Cartesian coordinates have been the main tool to study the relative motions, even if they present some drawbacks in terms of equations linearisation and introduction of perturbations. These limitations can be overcome using differential orbital elements. A third representation of the relative motion is the local orbital elements. They are very interesting to study relative trajectories. The use of differential orbital elements enable the introduction of the main perturbations. For low orbits, the dominant perturbation is the gravity field, and in particular, the oblateness of the Earth. For very high orbits, solar radiation pressure plays a main role when satellites do not have the same ratio surface to mass. The study of relative motion is concluded with the analysis of two missions. First, I have analyzed the interest of formation flying for gravity field determination. In order to do so, I have obtained the sensitivity equations of intersatelllite measurements to geophysical parameters. Second, I have worked on the characteristics of high eccentric orbits (HEO) for formation flying. I have analyzed different aspects of Simbol-X mission
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Serrano-Lopez, Maria A. "Three-dimensional clay modeling instruction: A pathway to spatial concept formation in second language learners." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289954.
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This dissertation contributes to the area of Applied Linguistics and foreign language teaching and learning by investigating whether formal instruction, as opposed to no specific instruction, plays a significant role in the acquisition of Spanish spatial prepositions: "en", "sobre", "de," and "a." The study investigates the effect of formal instruction for spatial concepts for which English native speakers could use the L1 to generate correct responses in the L2 and for spatial concepts that created confusion between the L1 and the L2. It also investigates the effect of formal instruction when prepositions are taught by rules. The study introduces a visual/spatial/kinesthetic methodology based on the Davis Symbol MasteryRTM program, originally designed to be used with juvenile and adult dyslexics. The study investigates whether 3-D clay modeling can create new mental representations of spatial concepts not existent in the L1 or resolve overlapping spatial concepts between the L1 and the L2. Advanced university learners of Spanish as a Second Language participated in this study. Results show that (a) formal instruction has a significant general effect for the mixed spatial concepts chosen for this study; (b) formal instruction has no significant effect over no specific instruction for concepts for which English native speakers could use the L1 to generate correct responses in the L2; (c) formal instruction, specifically 3-D clay intervention, can either help resolve the confusion in case of overlapping of spatial concepts between the L1 and L2 or create new mental representations not existent in the L1; and (d) formal instruction has no significant effect in the case of instruction by rules. The dissertation offers a novel theoretical explanation for why 3-D clay modeling may help resolve confusion in the case of overlapping of spatial concepts between the L1 and L2 or create new mental representations not existent in the L1. Vygotsky's Tools for Cognitive Development are extended: 3-D clay modeling provides a tool that is both concretely grounded and consciously systematically accessible. The dissertation also discusses motivation in learning based on Csikszentmihalyi's "Flow Theory".
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Stukins, Stephen. "Spatial and temporal palynological trends in marginal marine depositional system : Lajas Formation, Neuquén Basin, Argentina." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=167073.
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In order to better understand the relationship of tidally dominated depositional environments and their palynological assemblages, the Middle Jurassic sediments of the Lajas Formation, Neuquén Basin were examined. The ambition was to present models and trends which can be used for studies of other such deposits. In order to integrate the palynoassemblages with the environment of deposition, additional granulometric data and nutrient data from XRF analysis were used in combination with the palynology. A new method using correspondence analysis was used for understanding the palaeoecology and floral dynamics. An updated, dynamic model for the Middle Jurassic floral palaeoecology of the Neuquén Basin has been presented and the drivers of floral succession are interpreted as disturbance tolerance and substrate water content. Taphonomic expressions of seral groupings show that later seral stage community palynomorphs are preferentially deposited within or close to distributary systems, whereas earlier seral stage palynomorphs are preferentially deposited in environments of greater accommodation space, such as bayfills. Taphonomic signatures, using palaeoecological groupings provide trends in low (4th/5th) order cycles and lateral variations relating to tidal channels and surrounding bayfill mudstones. A model for 4th/5th order boundaries is also presented using new interpretations of the distribution of pinaceous pollen and microforaminiferal test linings. Using Canonical Correspondence Ananlysis (CCA), a model is presented of depositional environments incorporating palynological data and granulometric proxies for grain size and grain sorting. The relationship between sediment processes in a tidal flat dominated palaeoenvironment and the hydrodynamic properties of some palynomorphs is investigated and presented. The weathering and nutrient status of the substrates throughout the Lajas Formation is presented using XRF proxy data. The proxies are also used with CCA to create nutrient related floral groupings. When plotted stratigraphically, these show cycles of eutrophication and subsequent weathering of the substrates.
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Ijambo, Bertha Deshimona. "An econometric analysis of spatial market integration and price formation in the Namibian sheep industry." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/65897.
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The Namibian government introduced the Small Stock Marketing Scheme (SSMS) for the sheep market in 2004. The SSMS is a quantitative export restriction. Quantitative export restriction policies decrease the tradable quantity of a commodity, and increases domestic supply of a commodity, causing a lack of equilibrium in spatial markets. This, therefore, has the capacity to hinder market integration. Moreover, a quantitative export restriction disrupts the domestic supply and demand, and ultimately the equilibrium prices. A policy such as the quantitative export restriction therefore determines the domestic price levels. The effect of the SSMS on spatial market integration and price formation remains unclear. A lack of empirical evidence on spatial sheep market integration and domestic price levels can create challenges for policy makers. This is because a lack of evidence could prevent policy makers from implementing evidence-based policies, which might buffer poor consumers and producers from adverse price shocks, and lead to improved resource allocation. This study hypothesises that the SSMS policy negatively affected the long-run equilibrium relationship and short-run dynamics between the Namibian and South African markets. The study further hypothesises that the policy negatively influenced the level of equilibrium prices. As a result, this study hence observes spatial price integration in the presence of the SSMS, by defining the long-run equilibrium and short-run dynamics. The spatial price integration analysis is evaluated by subdividing price series data into pre-SSMS (1999M01-2003M12) and post-SSMS (2004M01-2015M12). The long-run equilibrium relationship is conducted with the Engle and Granger (1987) method and the Johansen (1988) cointegration approach. Short-run dynamics are, in turn, determined with an error correction model (ECM) and vector error correction model (VECM). The study also examined the impact of the SSMS on domestic price levels. This was done by recognising the reaction of the domestic supply, demand, and price functions to the SSMS. The analysis is conducted within the partial equilibrium framework (PEF). Additionally, the synthesis generated a simulation with the PEF to determine the impact on price changes were the SSMS to be removed. The analyses acknowledged a long-run equilibrium relationship between the spatial markets. As predicted, the long-run equilibrium relationship is not the same, pre- and post-SSMS. The price transmission elasticity (0.94) post-SSMS is marginally higher than pre-SSMS (0.88) is, which contradicts a priori expectation that quantitative export restrictions weaken price transmission. The pre-SSMS evaluation indicated a presence of short-run dynamics. Post-SSMS, the VECM revealed no bidirectional effect. The VECM also specified that the Namibian prices are effecting the adjustments in the short run to return to the long-run equilibrium position. This implies that if there is a shock that disturbs the equilibrium between the two spatial prices, Namibian prices would move to restore equilibrium. Likewise, the study appraised the response of the supply and demand functions to the policy in the PEF, incorporating the SSMS as an export ratio variable. The PEF results displayed that the SSMS influenced the supply function negatively, because of the negative elasticity of 0.013. This denotes that in the presences of the SSMS a 10 per cent increase in the quantitative export ratio decreases supply by 0.13 per cent, in which the response is slow. A negative effect is bound to decrease supply, and increase domestic price levels. Furthermore, the SSMS had a positive influence on the demand function, with an elasticity of 0.03 for the export abattoir demand, and 0.93 for the non-export abattoir demand. A positive impact on demand means a decrease in the producer price increases demanded for live sheep. The price equation outcome revealed that the SSMS had an insignificant effect of -0.0044 on the domestic producer prices. The price equation result is attributed to the low elasticity of the SSMS in the domestic supply and demand equation; the continued increase in producer prices post-SSMS due to the drought; and finally, because the SSMS is allowed to vary. Based on the simulation results, the removal of the SSMS policy would increase domestic producer prices by 4 per cent and 6 per cent, in 2017 and 2018, respectively. The percentage increase is considered low, as a result, this suggests that other dynamic factors, such as drought and market structure, affecting prices. This study therefore rejects the hypothesis stating that the long-run equilibrium relationship and short-run dynamic forces had reduced post-SSMS price transmission. The price transmission and speed of adjustment improved, post-SSMS. The study concludes that the SSMS policy did not have a detrimental effect, which was contrary to what was anticipated. The synthesis further fails to reject the hypothesis stating that the SSMS influenced domestic price levels, but the influence was very minimal and negligible. Both the spatial price integration and price formation analyses conclude that the SSMS had no detrimental effect on the sheep market. As a result, the study indicates that a quantitative export restriction policy, which varies, is better than an export control policy that does not allow any variation.<br>Dissertation (MSc (Agric))--University of Pretoria, 2017.<br>Agricultural Economics, Extension and Rural Development<br>MSc (Agric)<br>Unrestricted
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Harjoko, Triatno Yudo, and n/a. "Urban kampung: its genesis and transformation into metropolis, with particular reference to Penggilingan in Jakarta." University of Canberra. Resources, Environmental and Heritage Sciences, 2003. http://erl.canberra.edu.au./public/adt-AUC20050411.145222.
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Urbanism in the discipline of architecture has largely been confined to the
analysis of physical appearance of cities. Such an analysis may overlook the crucial
issue, which is political, on the spatial formation of a city like Jakarta This formation
results from the structuration process of a society where the production and
reproduction of society assumes domination from one another. In a dual society, such
as in the city of Jakarta, such a process has an implication of the urban form, that is,
the dual quality of urbanism.
This study examines this dual image of Jakarta, with a particular concern for
the transformation of the inner dynamic of its social life. It concerns the triad of
knowledge-power-space in which the society is produced and reproduced in the timespace
dimension. The kampung is investigated as a locale of social practices,
especially in regard to the low-income urban population. The idea and term
tropotopia is introduced to describe urban form or spatiality that is in a continuous
process of formation and transformation.
The study looks particularly the history of the reproduction of society in
Indonesia, where dominant social systems control allocative and authoritative
resources. Such practices primarily govern the spatial formation of Jakarta. In these
systems, planners and designers acting as agents have played crucial roles in the
structuration of society, and of the space. Planners and designers are seen to be part
of the episteme that develops and informs the poor relation of society. The
dissertation concludes with a reflection on the ways in which the dual quality of
Jakarta is revealed in the interplay in social practices within a triadic knowledge-power-
space.
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Jean-Amans, Philippe. "Contribution à la connaissance de l'élaboration du programme individuel de formation dans le cadre de la loi du 4 mai 2004 : l'exemple du secteur aéronautique et spatial en Midi-Pyrénées." Toulouse 1, 2006. http://www.theses.fr/2006TOU10027.
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Ces travaux de recherche portent sur l'approfondissement des connaissances quant à l'élaboration des programmes individuels de formation depuis la loi de 1971 en passant par le Livre Blanc de Nicole PERY, jusqu'à la loi du 4 mai 2004. Depuis la signature de l'accord interprofessionnel du 20 septembre 2003 qui a conduit à la promulgation de la loi du 4 mai 2004 portant réforme du dispositif de Formation Professionnelle Continue, de nombreux questionnements ont émergé quant à la mise en oeuvre et à l'utilisation du DIF (Droit Individuel à la Formation) par les entreprises et les salariés, et ce conformément aux orientations fixées par le législateur. Un modèle d'analyse est développé et teste plusieurs hypothèses relatives à l'efficacité des pratiques dans le cadre de la gestion du Programme Individuel de Formation au sein des entreprises du Pôle de Compétitivité AESE (Aéronautique et Espace - Systèmes Embarqués en Midi-Pyrénées). Une étude empirique est menée auprès du Pôle de compétitivité AESE et plus particulièrement à partir d'un échantillon de 25 entreprises représentant plus de 25 000 salariés du secteur. Les principaux résultats mettent en évidence que la mise en oeuvre du DIF est accrue lorsque l'entreprise est dotée d'un service ressources humaines développé et d'un responsable formation. Dans ce sens, l'utilisation du DIF est en relation positive avec la population de femmes salariées dans l'entreprise et enfin, la présence d'un responsable formation est favorable à la communication sur le DIF. Les apports principaux de cette recherche sont une approche du programme individuel de formation, au travers de la mise en place effective du DIF et le test du modèle de notre recherche<br>This research aims at increasing our knowledge of the development of the individual programs of training since the law of 1971 while passing by the White Paper of nicole Pery, until the law of May 4, 2004. Since the signature of the interprofessional agreement of September 20 2003 which led to the promulgation of the law May 2004 device of Continuous Vocational training reforms, many questions emerged as for the implementation and use of the DIF (Individual Right to the Formation) by the companies and the employees, and this in accorda,ce with the orientations fixed by the legislator. A model of analysis is developed and tests several assumptions relating to the effectiveness of the practices within the framework of the management of the individual Programme of Formation within the companies of the Pole of Competitiveness AESE (Aerospace industry and Spaces-Systems Embarked in Midi-Pyrénées). An empirical study is undertaken near the Pole of Competitiveness AESE and more particulary to started from a sample of 25 companies representing more than 25 000 employees. The main results highlight that the setting in action of the DIF is increased when the company has a developed service human resources and a person in charge formation. In this direction, the use of the DIF is in positive relation with the population of women employees in the company and finally, the presence of a person in charge of training programs is favorable to the communication on the DIF. The principal contributions of this research are an approach of the individual program of formation, through the effective installation of the DIF and the test of the model of our research
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Weng, Huibin. "A Social Interaction Model with Endogenous Network Formation." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159317152899108.
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Burns, Jonathan Allen. "Prehistoric Rockshelters of Pennsylvania: Revitalizing Behavioral Interpretation from Archaeological Spatial Data." Diss., Temple University Libraries, 2009. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/48182.
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Anthropology<br>Ph.D.<br>The size of archaeological data collection units and provenience controls affect data resolution, types of analyses, and the interpretations that archaeologists draw from the spatial patterning of material evidence. This research examines the use of fine-grained data collection units and the analyses that they support in the study of two Pennsylvania rockshelters to: 1) provide a better understanding of rockshelter use and the importance of rockshelters in Pennsylvania and Middle Atlantic region prehistory and, 2) reveal the impact that archaeological units can have on the reconstruction and interpretation of human behaviors in general. Insights from behavioral theory, ethnoarchaeology and previous archaeological research influenced the units and methods employed in the excavation of the Mykut and Camelback rockshelters. This analysis reveals the range of behaviors that can be reconstructed from these data, which can then be compared and contrasted with interpretations of other rockshelters and site contexts in the region.<br>Temple University--Theses
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Giusti, Domenico [Verfasser], and Katerina [Akademischer Betreuer] Harvati. "Application of spatial statistics to the study of site formation processes / Domenico Giusti ; Betreuer: Katerina Harvati." Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/1172716315/34.
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Kinvig, Helen Susan. "Spatial and temporal variations in the causative processes of caldera formation; an example from Nisyros, Greece." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629005.
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Collapse calderas are associated the most violent volcanic eruptions on Earth. Their destructive potential makes understanding their processes of formation crucial in assessing their vo1canic hazard. This thesis investigates the formation of a central caldera on Nisyros volcano,Greece. It reviews the volcanic stratigraphy of Nisyros; particularly addressing the deposits of its most recent explosive eruptions: the Lower Pumice and Upper Pumice. The eruption stratigraphy of the Lower Pumice and Upper Pumice is reconstructed and discussed, and their contribution to caldera formation is assessed. Lithic component analyses of xenoliths contained within the Lower and Upper Pumice pyroclastic deposits reveal important insights into their eruption chronologies, and vent locations . Circum-caldera lithic variations indicate the use of multiple vents during the caldera forming eruptions. Tephra distribution maps are used to estimate physical eruption parameters for the Pumice eruptions, and aid identification of vent-sites. It is concluded that the Nisyros caldera formed by incremental collapse, involving the cumulative magma withdrawal associated with the Lower pumice and Upper Pumice, and additionally the intercalated, high volume Nikia Rhyolite. A new model of Nisyros caldera formation is presented, in which regional tectonics are considered to have been an important influence on collapse and vent location. A new geological map implementing a revised volcanic stratigraphy is additionally presented. Finally, numerical models that implement an FEA method to investigate the effects of crustal layering on local stress field distribution during an eruption are presented and compared with existing criteria for ring fault initiation. Their results indicate that mechanical layering may be influential in facilitating or inhibiting caldera collapse. The results of the numerical study are discussed with reference to Nisyros volcano.
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Carney, David. "Spatial Analyses of Gray Fossil Site Vertebrate Remains: Implications for Depositional Setting and Site Formation Processes." Digital Commons @ East Tennessee State University, 2021. https://dc.etsu.edu/etd/3930.
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This project uses exploratory 3D geospatial analyses to assess the taphonomy of the Gray Fossil Site (GFS). During the Pliocene, the GFS was a forested, inundated sinkhole that accumulated biological materials between 4.9-4.5 mya. This deposit contains fossils exhibiting different preservation modes: from low energy lacustrine settings to high energy colluvial deposits. All macro-paleontological materials have been mapped in situ using survey-grade instrumentation. Vertebrate skeletal material from the site is well-preserved, but the degree of skeletal articulation varies spatially within the deposit. This analysis uses geographic information systems (GIS) to analyze the distribution of mapped specimens at different spatial scales. Factors underpinning spatial association, skeletal completeness, and positioning of specimens were examined. At the scale of the individual skeleton, analyses of the Mastodon Pit explore how element completeness and orientation/inclination of the mastodon reflect post-depositional processes.
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Chukwuma, Kenneth. "Spatial and temporal variations in the geometry and composition of the Permian Whitehill Formation South Africa." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25057.
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The Lower Permian Whitehill Formation (WHF) is an important hydrocarbon resource unit in the main Karoo Basin where it occurs in outcrops and up to 4 400 m in the subsurface and thus it is distributed over an area in excess of 260 000 km² in the southern half of South Africa. Although the formation is composed predominantly of black laminated carbonaceous shales, earlier studies detected significant spatiotemporal variability in its stratigraphy and composition, particularly the distribution of its organic carbon content across the basin. Because these stratigraphic variations and compositional heterogeneities remained largely uninvestigated, there are conflicting interpretations of not only the hydrocarbon potential of this resource unit but also the paleoenvironmental conditions that prevailed in the Karoo Basin during its accumulation. Following the recent global proliferation of unconventional hydrocarbon resources originating in organic-rich shale successions, the WHF is seriously being considered for gas shale exploitation in South Africa. Consequently, re-characterizing and explaining the spatiotemporal variations in its geometry and composition would be invaluable to the energy industry as well as the larger scientific community. With this aim, this study applied a combination of field descriptions, vintage borehole data, micro- to nano-scale petrographic observations, and multiple geochemical data so that a more critical understanding of the sedimentological controls responsible for the variability can be established. Using this integrated approach, five primary sedimentary facies (F1-F5, i.e., stratigraphic subunits in the WHF) were identified, which show specific and systematic variations in nature and content of organic carbon, stable isotopic composition (of δ¹³Corg and δ¹⁵N), C/N ratio, major and trace elemental enrichment, nature and content of iron sulfides, quartz texture, and CIA across the basin. The lower dark grey to black thinly laminated pyritic, carbonaceous fine shales (facies F1 and F2) contain up to 16.5 % TOC, δ¹³Corg of -15.57‰, δ¹⁵N of 12.49‰, C/N ratio of 1.50, average CIA of 68.11, Rb/K (x10⁻³) and Sr/Ba ratios of 6.56 and 0.67, respectively. Relative to average shale, this unit is up to 6.27 and 3.11 times richer in Mo and Fe, respectively. The organic materials in this facies comprise Tasmanites cysts, colonial algae cells, and amorphous macerals and occur in well-defined laminae (lamalginites) as well as in discrete organic domains loosely associated with mineral grains (organo-minerallic aggregates). At least 25% of the silicate in this facies is of early diagenetic origin, possibly derived from alteration of air-fall volcanic ash. Iron sulfides occur dominantly in form of framboidal aggregates of pyrite. Marcasite in form of lags cement and nodules is also reported. A binary mixture of organic matter and phosphorites with botryoidal textures is also abundant. The upper medium to light grey calcareous-siliceous silty lenticular shale (F3-F5) contain up to 2.04% TOC, δ¹³Corg of -24.71‰, δ¹⁵N of 4.93‰, C/N ratio of 17.62, average CIA of 74.33, Rb/K (x10⁻³) and Sr/Ba ratios of 3.83 and 0.36, respectively. Relative to average shale, this unit was up to 2.65 and 0.43 times richer in Mo and Fe, respectively. Their organic macerals comprise disarticulated plant remains in disseminations with few amorphous macerals. At least 85% of the quartz content is of detrital origin likely sourced from the basin margins and transported to the basin by the action of bottom-hugging currents. Few iron sulfides occur dominantly in form of octa- and euhedral pyrite grains. The data presented in this thesis suggest that the lower WHF (subunits F1 and F2) may have accumulated in a marine setting with high bioproductivity of organic carbon delivered in form of flocculated organo-minerallic aggregates (pelagic snow) onto an anoxic seabed overlain by dysoxic to oxic waters. Reduced terrigenous input, presence of phosphorites, increasing CIA and increasing δ¹³Corg values with higher TOC point to a depositional setting that resulted from an interplay of sea-level highstand and climatic warm-ups. In contrast, the upper WHF (subunits F3-F5) was deposited largely under non-marine conditions with OM in the company of great detrital debris sourced from terrestrial settings, transported into the basin mainly in form of fluid mud flows and deposited above storm wave base. The presence various body and trace fossils, as well as the variations in bioturbation styles and intensities in subunits F3-F5, indicate that colonisation of the basin by invertebrate and vertebrate organisms is related to the different stages in the oxygenation of the sediment-water interface in an increasingly oxygenated setting.
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Niemiec, Anna. "Influence of the environment on galaxy formation." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0260/document.
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Dans le modèle de formation hiérarchique des structures, les amas de galaxies se forment et grandissent par l'accrétion de groupes plus petits ou de galaxies isolées. Dans ce scenario, comprendre comment les galaxies accrétées interagissent avec cet environnement très dense est une étape importante pour comprendre le schéma global de l'évolution des galaxies et de la formation des structures. En effet, pendant leur chute au coeur de l'amas, les galaxies sont sujettes à diverses interactions avec l'amas hôte, au niveau de leur composante baryonique aussi bien que matière noire, et ces interactions vont modifier les propriétés de la galaxie. Au niveau de la matière noire, les simulations numériques suggèrent que la friction dynamique fait plonger les galaxies vers le centre de l'amas, et que les forces de marée exercées par l'hôte peuvent arracher une partie de la matière de la galaxie, et même détruire celle-ci. Ce processus, au cours duquel une partie de la matière noire de la galaxie est arrachée, est appelé stripping. La détection du stripping de matière noire contient d'importantes informations sur l'évolution des groupes et des amas. Le travail principal de cette thèse se concentre sur l'étude des galaxies dans les amas, et en particulier sur l'étude du stripping des galaxies par les forces de marées des amas. Les profils de densité des halos sont mesurés à l’aide de l’effet de lentille gravitationnelle faible, en utilisant les catalogues de formes de galaxies des relevés CFHTLenS, CFHT Stripe 82 et DES-SV, alliés au catalogue d’amas redMaPPer<br>Galaxy clusters are large structures in the Universe, composed of tens or hundreds of galaxies bound by gravity. In the hierarchical formation model, they are formed and grow by accretion of smaller groups or isolated galaxies. In this scenario, understanding how these accreted galaxies interact with the very dense cluster environnement is an important step towards explaining the global picture of galaxy evolution and structure formation. Indeed, during infall, galaxies are subject to numerous interactions with the host cluster, both at the level of the baryonic and dark matter component, and these interactions influence the properties of the infalling galaxy. At the level of dark matter, numerical simulations suggest that dynamical friction sinks galaxies towards the center of clusters, and tidal forces of the host can strip part of the satellite's matter away, and even disrupt it. The detection of this stripping contains important informations on the evolution of groups and clusters: what quantity of dark matter is associated to the cluster galaxies as a function of the distance to the centre of the cluster ? How does this depend on the redshift and dynamical state of the cluster ? Does stripping depend on the morphological type of cluster galaxies ? The main work of this thesis is focused on studying galaxies in clusters, in particular tidal stripping of their dark matter haloes. The dark matter halo profiles are measured with weak gravitational lensing, using galaxy shape catalogues from the CFHTLenS, CFHT Stripe 82 and DES-SV surveys, combined with the redMaPPer cluster catalogue
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Wearmouth, Curran. "Spatial, Temporal and Physical Origin of Matrix-Poor to Matrix-Rich Sandstones, Neoproterozoic, Windermere Supergroup, British Columbia, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37567.
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At the Castle Creek study area a remarkably well exposed section in the Isaac Formation, Windermere Supergroup, was measured to document potential lateral and vertical changes in facies. Here, a consistent lateral succession of facies was observed consisting of matrix-poor sandstone to clayey sandstone to bipartite bed to sandy claystone, collectively overlain by a thin-bedded turbidite and mudstone cap. These changes are interpreted to reflect particle settling in a negligibly-sheared sand-mud suspension following detachment from the margins of an avulsion jet. Vertically, similar facies stack to form packages 2-7 beds thick implying temporary stabilization of jet-margin dynamics. At a larger scale facies stack to form three stratal assemblages. SA-1: intercalated matrix-rich and matrix-poor strata and SA-2: matrix-rich strata stack vertically and laterally but then are sharply overlain everywhere by classical turbidites of SA-3, indicating a dramatic change from deposition immediately downflow of an avulsion node to conventional levee deposition.
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O'Malley, Paul W. "Understanding Formation and Evolution of Dune Fields by Spatial Mapping and Analysis: Upper Muskegon River Valley, Michigan." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1557841176226706.
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Gaulocher, Sebastian. "Commande boucle fermée multivariable pour le vol en formation de vaisseaux spatiaux." Toulouse, ISAE, 2007. http://www.theses.fr/2007ESAE0011.
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Cette thèse traite du contrôle du vol en formation de vaisseaux spatiaux. Le vol en formation permet de réaliser de nouveaux scénarios de missions. De par la diversité des applications envisageables, les travaux sont divisés en deux parties. Dans la première partie, restreinte au contrôle des centres de masse des vaisseaux, une approche est proposée pour modéliser les orbites relatives entre deux satellites en orbite terrestre, tenant compte de l'aplatissement de la Terre. Fondée sur le scénario d‘une mission en orbite de transfert géostationnaire, la problématique d‘une dynamique à paramètre variant est illustrée. Deux manières différentes d'asservir la position relative sont présentées : la première a recours à la représentation linéaire fractionnaire pour obtenir un correcteur auto-séquencé ; la seconde utilise la synthèse H2 et un modèle de référence pour synthétiser un correcteur interpolé. Dans la deuxième partie, traitant des 6 degrés de liberté de chaque vaisseau, des modèles génériques pour la cinématique, la dynamique et la métrologie d'une formation de vaisseaux spatiaux en orbite non planétaire sont proposés. La mission exemplaire Pegase est composée de trois vaisseaux. Dans son mode d'observation, qui requiert un maintien précis des positions et des attitudes des vaisseaux, il est possible d'utiliser des techniques de commande multivariable. La commande H2 est utilisée pour satisfaire les spécifications de la mission Pegase. Ensuite, deux problématiques particulières sont traitées. Premièrement, la commutation entre correcteurs conçus pour différents modes est considérée. Deuxièmement, un correcteur H2 décentralisé est synthétisé grâce à un algorithme itératif.
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Clark, Amy Elizabeth. "Spatial Structure and the Temporality of Assemblage Formation: A Comparative Study of Seven Open Air Middle Paleolithic Sites in France." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556880.
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The spatial arrangements of artifacts and features within archaeological sites have often been used to isolate activity areas and draw inferences about site function. This approach assumes that objects found in close proximity were used for the same task, and that artifacts are usually discarded where they were used. However, the location of artifact abandonment often has more to do with patterns of discard and use/reuse of the site throughout time than with the function or location of activities. This dissertation uses a comparative framework to address how the observed spatial structure of Middle Paleolithic sites in France sites was formed through centrifugal dispersion of lithic artifacts, i.e. the displacement of artifacts between their creation and the final location of their abandonments. Seven Middle Paleolithic sites were included in this study. The sites were excavated over large areas, from 200 to more than 2000 m². They range from small single component occupation sites to lithic raw material workshops with assemblages of more than 15,000 artifacts. The movement of artifacts is tracked through an analysis of sets of refitted lithics and through comparisons of the distributions of multiple classes of artifact across areas of the sites with differing artifact densities. Studying the distribution of lithic technological classes and tracking their movement through refitting sets provides new perspectives on the ways Paleolithic archaeological assemblages and sites were formed. The temporality of site use had a much greater impact on site structure than did activities that took place at any one point during a site's occupation. These data enabled me to assess the relative lengths and numbers of occupations for the seven sites in this study. The approach taken in this study not only provides a clearer understanding of site formation and structure than do studies that strive to isolate "activity areas," but it also provides information about the sizes of past human groups and the ways they moved among different localities on the landscape. Such insights are integral to the study of land use, mobility and economic adaptations among Paleolithic hunter-gatherers.
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Kahn, Meghan Cornelia. "Goal Location Memory in Pigeons: Roles of the Hippocampal Formation and Visual Wulst." Bowling Green, Ohio : Bowling Green State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1242383665.
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Zaytseva, Sofya. "Investigation of Pattern Formation in Marine Environments Through Mathematical Modeling and Analysis of Remotely Sensed Data." W&M ScholarWorks, 2019. https://scholarworks.wm.edu/etd/1582642586.
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Pattern formation in ecological systems refers to a nonuniform distribution of animal and plant species across a landscape. Pattern formation can be observed in many aquatic and terrestrial systems and can provide important insights into their dynamics and ability to cope with environmental changes. In this dissertation, we focus on pattern formation in tidal marshes and oyster reefs, two important habitats that provide a number of essential ecosystem services. Both of these systems have also experienced dramatic losses, prompting much research to investigate their dynamics as and viable restoration and management strategies. The first part of this dissertation focuses on understanding the spatial patterning of the marsh shoreline, which can range from a uniform to a more wave-like shoreline. We present a mathematical framework for modeling the spatial variation of the shoreline as a result of interactions between marsh vegetation, mussels and their impact on marsh sedimentation and erosion. While both species are known to significantly impact marsh dynamics, no mathematical model describing this phenomenon has been previously proposed. Numerical and analytical investigation of our model indicates that the interactions between these species can drive the spatial variation of the marsh edge, increase the system’s productivity and allow it to withstand harsh erosion conditions. The second part of this dissertation focuses on pattern formation in intertidal oyster reef communities, where both round and elongated reefs of various orientations dominate the landscape. Most of what is currently known about reef geometry has been anecdotal, with no comprehensive, quantitative study of reef pattern formation carried out. In particular, the interaction of oyster reefs of various geometric configuration with tidal flow remains poorly understood. This is important in reef restoration, where understanding the interaction of reef geometry with flow and other environmental factors can inform the construction of artificial oyster reefs. In this dissertation, we present a comprehensive analysis of remotely sensed aerial imagery of an intertidal oyster reef network in conjunction with information on tidal flow dynamics and bathymetry. Using texture and color properties of the aerial imagery, we identify and delineate over six thousand individual reefs. We then classify reefs into natural classes based on geometric attributes such as reef shape, size and orientation. Finally, we use multiple spatial analysis techniques to determine the spatial clustering of different reef types and investigate the role of flow and bathymetry in their spatial distribution.
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Maurin, Tiphaine. "Occupations humaines de l’Oldowayen ancien et facteurs en-vironnementaux : interrelations et évolutions à partir des en-sembles archéologiques de la Formation de Shungura (Basse Vallée de l'Omo, Éthiopie)." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0891/document.
Full textAbstract:
Dans la Formation de Shungura l’apparition du comportement de taille de la pierre coïncide avec l’apparition de l’Oldowayen ancien et se concentre sur un laps de temps relativement resserré (Membre F et partie inférieure du Membre G ; 2,32 Ma à 2 Ma), bien que les hominidés fossiles soient présents tout au long de la séquence (3,6 à 1 Ma). Afin de questionner les interrelations et l’évolution entre les occupations humaines de l’Oldowayen ancien et les facteurs environnementaux, une approche multi-scalaire a été développée. Elle permet d’intégrer les très nombreuses données archéologiques (une centaine d’occurrences dans le Membre F et une cinquantaine dans la partie inférieure du Membre G) et paléoenvironnementales (incluant plusieurs milliers de spécimens pa-léontologiques des Membres E et F et les données géologiques de terrain). Selon le degré de préci-sion spatio-temporelle de ces différents registres de données, trois échelles d’analyse ont été rete-nues (complexe archéologique, zone d’étude, formation). L’analyse spatiale et taphonomique des données archéologiques couplée à l’analyse des cortèges fauniques a permis de démontrer que seul un petit nombre d’occurrences correspond à des occupations initiales dans le Membre F. Elles sont localisées à la base du Membre F, à proximité du paléo-fleuve Omo, dans un contexte général d’ouverture et d’aridification croissantes du milieu. À cela s’ajoute une répartition spatiale différen-tielle de certains taxons entre la partie nord et la partie sud de l’aire Type, qui pourrait être le mar-queur d’une plus grande emprise des zones humides dans le paysage de la partie sud de la Formation de Shungura<br>The appearance of stone tool making behavior In the Shungura Formation coincides with the appearance of the early Oldowan. It lasts over a limited time period (Member F and the lower part of Member G: 2.32 Ma to 2 Ma), while hominid fossils are present in all members, from 3.6 Ma to 1 Ma. A multi-scalar approach was developed for assessing potential interrelations and co-evolution be-tween Early Oldowan human occupations and environmental factors. This approach has allowed to include an extensive set of archaeological and paleoenvironmental data (a hundred of occurrences in Member F and ca. fifty occurrences in the lower part of Member G, thousands of faunal remains from Members E and F, and field geological data). Depending on the spatial and temporal resolution of these different records, I have defined three scales of analysis, from archeological complex scale, to study area and formation scales. The combination of spatial and taphonomical analyses of archeo-logical data, coupled with the analysis of faunal assemblages, suggest that only few archeological occurrences correspond to primary occupations in Member F. They are all located in the lower part of Member F, in the vicinity of the Omo paleoriver, in a global context of opening up and drying of the environment. Additionally, the differential spatial distribution of several faunal taxa between the northern and southern parts of the Type area could mark a greater extension of wet areas in the southern part of the Shungura Formation