Дисертації: "Top-down and bottom-up interactions"

1

Grellmann, Doris. "Top-down and bottom-up effects in a Fennoscandian tundra community." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96883.

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The objective of this thesis was to investigate the effects of mammalian grazers, such as microtine rodents and reindeer, (top-down effects) and nutrient availability (bottom- up effects) on the plant community of a tundra heath. I conducted a large-scale fertilization experiment and studied the impact of grazers using exclosures. I measured the effects of fertilization and grazing on soil microbial activity and nutrient cycling. I investigated the responses to fertilization of the invertebrate community, I studied the effects on the quality of bilberry as food for mammalian herbivores, and I looked at how concentrations of nutrients and carbon-based secondary defences against herbivory fluctuated between seasons in unfertilized and fertilized treatments. The results of my thesis show that the plant community investigated is exposed to a strong top-down control by mammalian herbivores. On the fertilized and grazed areas the aboveground biomass of the vascular plant community did not increase compared to unfertilized areas. However, the productivity of the plant community was clearly nutrient- limited. During the eight years of the experiment, on the fertilized areas plant biomass was significantly increased inside the herbivore exclosures In my study mammalian herbivores at comparatively low densities and grazing outside the growing season were sufficient to control the biomass of a heterogeneous plant community. Microtine rodents (Norwegian lemmings and grey-sided voles) preferred the fertilized areas for overwintering. The food plant quality of bilberry for grey-sided voles was improved on the fertilized areas throughout the year. Grazing decreased the nitrogen storage in the aboveground plant biomass. Reindeer and rodents had also important indirect effects on the plant community by decelerating soil nutrient cycling and soil microbial activity. This effect may be accelerated by the impact of herbivore on plant species composition. Graminoids, which contained the highest nitrogen concentrations in their tissues, increased rapidly on the fertilized areas, but their abundance was significantly lower on grazed fertilized areas. The invertebrate community was detritus-based and received their energy indirectly from the litter via soil microbes and detritivores. Fertilization increased the biomass of invertebrate carnivores, but had no effect on the biomass of invertebrate herbivores. Apparent competition between detritivores and invertebrate herbivores, mediated by carnivorous invertebrates predating on both of them, is supposed to keep the densities and grazing pressure of invertebrate herbivores low. Grazing damage by invertebrates was very low and only 0.021 % of the total vascular plant biomass was removed.

Diss. (sammanfattning) Umeå : Umeå universitet, 2001, härtill 6 uppsstser.

digitalisering@umu

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2

Garrett, James Samuel. "Interaction of Top-Down and Bottom-Up Search with Magnocellular- and Parvocellular-Mediated Stimuli." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464278964.

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3

Freier, Livia. "The development of bottom-up and top-down interaction in the processing of goal-directed action." Thesis, Birkbeck (University of London), 2016. http://bbktheses.da.ulcc.ac.uk/176/.

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The study of action-cognition is driven by the assumption that what one can do motorically depends on what one can conceive of mentally, given a set of external opportunities (Rosenbaum, Cohen, & Jax, 2007). Therefore, a comprehensive theory of action development ought to integrate perceptual aspects of action processing with conceptual changes that give rise to increasingly abstract behaviours. How and why children progress to higher levels of organization in the processing and coordination of purposeful behaviour is a question that has been at the core of developmental research for decades. Various competences underlying early action processing and decision-making have been identified and linked to sophisticated mental operations later in life. However, considerably less is known about the relationships between perceptual and conceptual abilities and how they interact to shape action development. Goal-pursuit is achieved with increasing efficiency during the preschool period. In fact, by the age of first grade children show substantial abilities to regulate actions into hierarchically structured sequences of events that can be transferred across contexts (e.g., Levy, 1980; Bell & Livesey, 1985; Livesey & Morgan, 1991). The aim of this project was to investigate the perceptual and conceptual processes that drive these remarkable advances as they emerge during the preschool years. The studies in this thesis investigate top-down and bottom-up interactions in the processing of actions at various levels of abstraction. Employing a range of novel paradigms, the results of four studies highlight considerable advances in preschoolers’ abilities to organise actions in terms of goal hierarchies. Findings further highlight that the ability to extract structure at a basic level is readily achieved early in life, while higher-level action comprehension and planning abilities continue to develop throughout the childhood years.

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4

Han, Peng. "Effets bottom-up et top-down des variations de fertilisation et d'irrigation sur des réseaux tri-trophiques en agroécosystèmes." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4057/document.

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Le système « plante-ravageur-ennemi naturel » fournit un modèle de base idéal pour comprendre comment les communautés d'arthropodes sont structurées et comment les interactions (directes et indirectes) entre les différents acteurs contribuent à façonner la structure des communautés. Dans les agroécosystèmes, les forces "top-down" correspondent aux effets de contrôle que les organismes arthropodes des niveaux trophiques supérieurs (par exemple, les prédateurs) ont sur les espèces des niveaux inférieurs (par exemple, leurs proies). Les communautés d'arthropodes peuvent également être influencées par des forces "bottom-up" induites par des variations dans les régimes de fertilisation ou d'irrigation ou par des variations de certains traits des plantes (résistance aux herbivores ou adaptations aux stress environnementaux). De plus, les forces "bottom-up" peuvent affecter l'impact "top-down" des ennemis naturels sur les herbivores soit directement (par exemple, les effets sur prédateur omnivore) ou médiées par les insectes herbivores intermédiaires. Dans ce contexte, les objectifs de cette thèse ont été de comprendre comment les variations de l'apport des ressources dans les agroecoécosytsèmes (disponibilité en azote et en eau) peuvent influencer les interactions entre les plantes, les herbivores et les ennemis naturels. Cette question a été étudiée aussi bien à l'échelle individuelle (traits d'histoire de vie des insectes) que populationnelle (dynamique des populations). Les études ont été réalisées sur deux agroécosystèmes basés sur les cultures de la tomate et du coton
The “Plant-herbivorous insect-natural enemy” system provides an ideal basic model to understand how the plant-inhabiting arthropod communities are structured and how various mechanisms (i.e. direct and indirect interactions) contribute to shape the community structure. In agro-ecosystems, top-down forces encompass the controlling effects that arthropod organisms of the higher trophic level (e.g., predators) have on species at the next lower level (e.g., prey). Arthropod communities may also be influenced by bottom-up forces induced by environmental variations (e.g. fertilization or irrigation regimes) or plant traits (plant insect-resistance or plant-adaptive traits). Furthermore, bottom-up forces may affect top-down forces on herbivores either directly (e.g., effects on omnivorous predator) or mediated by the intermediate herbivorous insects. In this context, the aims of the PhD study were to disentangle how variations in resource inputs (i.e. nitrogen and water availability) affect interactions among plant, herbivores and their natural enemies at both the individual (life-history traits) and population (population dynamic) levels. The studies were carried out on two agrosystems based on tomato and cotton. On tomato, the system 'Solanum lycopersicum L - leafminer Tuta absoluta - omnivorous predator Macrolphis pygmaeus' was used under laboratory and greenhouse conditions in France. We found strong evidence of bottom-up effects of nitrogen and/or water inputs on the herbivore and the omnivorous predator. Feeding ecology of the predator was also strongly influenced by water availability

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5

Henzell-Thomas, J. "Learning from informative text : Prediction protocols as a means of accessing the interaction between top-down and bottom-up processes." Thesis, Lancaster University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371079.

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6

Quevreux, Pierre. "Conséquences des interactions entre voies vertes et brunes sur la stabilité des réseaux trophiques." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC142/document.

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Cette thèse a pour but de comprendre les implications des relations entre réseau trophique vert et réseau trophique brun sur la stabilité et le fonctionnement des réseaux trophiques. Les interactions entre ces deux réseaux, respectivement fondés sur la photosynthèse et la consommation de la matière organique morte, sont essentielles au fonctionnement des écosystèmes : l'un produit de la matière organique à partir de nutriments minéraux et l'autre recycle les nutriments contenus dans la matière organique morte. Cette question est abordée à l'aide de deux modèles théoriques et d'une étude expérimentale. Mon premier modèle montre que la boucle de rétroaction induite par le recyclage des nutriments dans un réseau trophique exclusivement vert a un effet stabilisant sur les dynamiques d'une chaîne trophique et un effet enrichissement à cause de la remise à disposition pour les producteurs primaires des nutriments excrétés par l'ensemble des organismes du réseau trophique. Cependant seul l'effet enrichissement, qui est déstabilisant, persiste dans un modèle de réseau trophique. Mon second modèle intègre le réseau brun de manière explicite et montre que ce réseau est davantage déstabilisé que le réseau vert lorsque la disponibilité en nutriments augmente. Cette effet est amplifié si la majeure partie de l'excrétion se fait sous forme de détritus qui déstabilisent le réseau brun par un effet d'enrichissement. Ce modèle montre également que la survie des consommateurs est améliorée lorsqu'ils peuvent consommer des proies provenant des deux réseaux. Mon expérience en mésocosmes aquatiques a permis d'étudier les effets en cascades entre réseaux vert et brun via une filtration de la lumière (manipulation directe du réseau vert), l'ajout de carbone organique dissous (manipulation directe du réseau brun) et l'ajout de poissons (manipulation de la structure du réseau trophique). Nous n'avons pas observé d'effets en cascade du réseau vert sur le réseau brun et inversement, notamment à cause d'un ajout probablement trop faible de carbone dissout. Les poissons ont eux eu un fort effet sur les deux réseaux avec des effets positifs sur le phytoplancton lorsque la lumière est réduite à cause de la diminution de la limitation par les nutriments grâce à l'excrétion des poissons, une augmentation de la concentration en carbone organique dissout et une modification du profil métabolique de la communauté bactérienne benthique. Un modèle annexe montre quant à lui que la plasticité du métabolisme chez les organismes, c'est-à-dire leur capacité à réduire ou à augmenter leur métabolisme en fonction de la disponibilité en ressources afin de maximiser leur bilan énergétique permet de stabiliser les dynamiques d'une chaine trophique en diminuant la variabilité temporelle des biomasses des espèces. Dans un réseau trophique, cette stabilisation se traduit par une augmentation de la persistance des espèces. Cette thèse a permis de mieux relier l'écologie des communautés à l'écologie fonctionnelle, améliorant ainsi notre compréhension des conséquences de grands processus écosystémiques comme le recyclage des nutriments sur la stabilité des réseaux trophiques et des effets de la structure de ces réseaux sur le fonctionnement des écosystèmes
The aim of this thesis is to understand the implications of the relationships between green and brown food webs on the stability and functioning of food webs. The interactions between these two food webs, based respectively on photosynthesis and the consumption of dead organic matter, are essential for the functioning of ecosystems: one produces organic matter from mineral nutrients and the other one recycles the nutrients contained in dead organic matter. I address this by using two theoretical models and an experimental study. My first model shows that the feedback loop induced by nutrient cycling in an exclusively green food web has a stabilising effect on species dynamics in a food chain and an enrichment effect due to the excretion of nutrients that are available again for primary producers. However, only the enrichment effect, which is destabilising, persists in a food web model. My second model integrates a true brown food web and shows that this food web is more destabilised than the green food web when nutrient availability increases. This effect is amplified if most of nutrients are excreted as detritus that destabilises the brown food web through an enrichment effect. This model also shows that consumer survival is improved when they can consume prey from both green and brown food webs. My experiment in aquatic mesocosms enabled me to study the cascading effects between green and brown food webs thanks to light filtration (direct manipulation of the green food web), the addition of dissolved organic carbon (direct manipulation of the brown food web) and the addition of fish (manipulation of food web structure). We did not observe any cascading effects of the green food web on the brown food web and vice versa, probably because of a too low addition of dissolved carbon. The fish had a strong effect on both green and brown food webs with positive effects on phytoplankton when light is filtered because of the decreased nutrient limitation thanks to fish excretion, an increased concentration of dissolved organic carbon and a change in the metabolic profile of the benthic bacterial community. An additional model shows that the plasticity of metabolic rate, that is the ability of organisms to increase or decrease their metabolic rate depending on resource availability in order to optimise their energy budget, stabilises species dynamics in a food chain model by decreasing biomass time variability. Such a stabilising effect results in increase of species persistence in a complex food web model. This thesis is an additional step to better link community ecology to functional ecology, thus improving our understanding of the consequences on food web stability of major ecosystem processes such as the nutrient cycling and the effects of food web structure on ecosystem functioning

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7

Filiz, Nur. "Impacts Of Nutrients On Periphyton Growth And Periphyton-macroinvertebrates Interactions In Shallow Lakes: A Mesocosm Experiment." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614911/index.pdf.

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Periphyton biomass on artificial strips was observed monthly to see the impacts of nutrient differences on periphyton and periphyton-macroinvertebrates interaction. The experiment was conducted for four months in a mesocosm which were runned at six countries at the same time and with the same steps. Eight enclosures at two meters depth were used that four of them had high nutrient level and the other four had low nutrient level. Sediment, macrophyte, fish, plankton, benthic invertebrates and water were added at the same time and with the same way in all of the countries. Periphyton growth which formed on artificial 32 cm2 strips for June, July, August and September were brushed to filtered mesocosm water and dry mass, ash free dry mass, phosphorus content and chlorophyl-a concentrations were measured. Grazer pressure on the periphyton was observed with a laboratory experiment for July, August and September months. At the end of the mesocosm experiment macrophytes and fish were harvested. Macrophytes&rsquo
dry mass and fish&rsquo
abundance were measured. Moreover at the end of the experiment epiphyton was also measured. Three kajak cores were taken from sediment for macroinvertebrates at the end of the experiment and identified. All physical features of mesocosm enclosures and PVI data were recorded for every 2 weeks. Periphyton biomass was higher concentrations in HN enclosures than LN tanks. Only dry mass of periphyton biomass showed the opposite because of the marl deposition in LN tanks. This finding was also reinforced by epiphyton samples which was taken at the end of the experiment. LN enclosures had the more abundance of macroinvertebrate. The groups we found in sediment which had big grazer effect on periphyton such as gastropods and Chironomidae. Grazer experiment showed that grazer effect on periphyton increased in time. Although this raise, periphyton growth also increased in LN enclosures with nutrient increasing. This may be indicate that nutrient effect has a stronger effect than grazer pressure on periphyton. As it is explained before in the beginning of the experiment all of the conditions were the same except nutrient level. Thus, bottom-up effect changed the top-down control and at the end of the experiment we saw the more periphyton less macroinvertebrate and more fish in HN tanks while the opposite was seen in LN tanks.

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8

Giacaglia, Giuliano Pezzolo. "Integrating bottom-up and top-down information." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91813.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-70).
In this thesis I present a framework for integrating bottom-up and top-down computer vision algorithms. I developed this framework, which I call the Map-Dictionary Pixel framework, because my intuition is that there is a need for tools that make it easier to build computer vision systems that mimic the way human visual systems process information. In particular, we humans humans create models of objects around us, and we use these models, top-down, to interpret, analyze and discern objects in the information that comes bottom-up from the visual world. After introducing my Map-Dictionary Pixel framework, I demonstrate how it empowers computer vision algorithms. I implement two different systems that extract the pixels of the image that correspond to a human. Even though each system uses different sets of algorithms, both use Map-Dictionary Pixel framework as the connecting pipeline. The two implementations demonstrate the utility of the Map-Dictionary Pixel framework and provide an example of how it can be used.
by Giuliano Pezzolo Giacaglia.
M. Eng.

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ROCHA, Cacilda Michele Cardoso. "O papel de macrófitas submersas na estrutura e interações entre fitoplâncton e zooplâncton em reservatórios." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18683.

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Macrófitas submersas promovem atributos das comunidades zooplanctônicas mediante estrutura física, transparência da água, habitat, e abrigo de predadores. Enquanto competem por luz e nutrientes, afetando negativamente o crescimento do fitoplâncton atuando nas interações de controle base-topo e promovendo efeito de controle topo-base do zooplâncton. Pouco foi investigado sobre o papel da vegetação submersa nas interações do zooplâncton e fitoplâncton em áreas sobre influência de reservatório no semiárido brasileiro. Nesse sentido, de maneira a identificar principais lacunas e perspectivas para estudos futuros sobre as macrófitas e interações tróficas enfatizando buscas por estudos realizados na América do Sul, realizamos uma análise cienciométrica, e acreditamos que o número de artigos na área exibirá uma tendência crescente ao longo dos anos, onde a América do Sul apresentará participação significativa tanto no número de publicações quanto na cooperação internacional. Além disso, com a finalidade de investigar se nas áreas com pressões pelos usos em reservatório e solo, plantas submersas são afetadas positivamente, e estruturam riqueza e abundância para o zooplâncton, e suas interações afetam negativamente o fitoplâncton durante quatro períodos, coletamos evidências de efeitos de controle base-topo e topo-base de macrófitas sobre o plâncton. Para tanto, comparamos atributos de comunidades e nutrientes dissolvidos em bancos de plantas na zona litorânea e centros correspondendo à pelágica. Para análise Cienciométrica, acessamos publicações usando base de dados internacional entre 1980 a 2015. A coleta do material no campo mediante navegação pelas áreas em distâncias superiores de 3.5km, com coletas simultâneas da cobertura vegetal, comunidades planctônicas e nutrientes nitrogenados e fósforo total dissolvido. Áreas de cobertura das plantas submersas foram estimadas por medição da proporção de presença e ausência de espécies em 24 pontos em transectos paralelos às margens em área superior a 3.5 km. Coletamos 24 amostras do fitoplâncton e de nutrientes. Para o zooplâncton, realizamos amostragem composta da coluna d’água na vertical e horizontal através de arrastos totalizando 48 amostras. A Cienciometria mostrou que o número de pesquisas sobre essas interações tróficas cresceram nos últimos anos na América do Sul, com contribuições do Brasil, Argentina e Uruguai. O conhecimento sobre as interações tróficas em tem norteado abordagens técnicas e pesquisas científicas em países temperados para melhorar a qualidade da água e restaurar lagos e reservatórios eutrofizados, mas a América do Sul avançou pouco. Constamos que o maior volume de artigos indexados tratou sobre a dinâmica e estrutura das assembléias aquáticas, teias e interações tróficas, para as quaias reservatórios e áreas alagadas receberam pouca atenção. Grande número de estudoscontemplam toda comunidade aquática e interações entre macrófitas, fitoplâncton zooplâncton e peixes. Com relação à pesquisa de campo, a macrófitas ocorreram em alta densidade e cobertura vegetal em 12 pontos por baía (60%; 70%) a diferentes profundidades (2m a 6m). Nas baías, fósforo (médias= 0.03 e 0.05 mg/L) e nitrogênio (0.4 e 0.9 mg/L) apresentaram baixas concentrações. A transparência de Secchi foi alta nas duas baías (>3.8). O fitoplâncton teve riqueza de 17 táxons, dos quais Cyanophyta e Bacillariophyta foram mais representativos. Baixas densidades registradas refletiram nos baixos valores clorofilaa (médias= 9 e 12 µg/l). O zooplâncton apresentou alta dissimilaridade na riqueza (97 spp.) dos Rotifera, Cladocera e Copepoda e abundância relativa, com densidades variando significativamente na zona pelágica (24 a 2013 ind./m³) e litorânea (28 a 1260 ind./m³) de ambas as baías. Nesse contexto, confrontando esses resultados com os dados encontrados da vegetação, juntamente com as baixas concentrações de nutrientes dissolvidos, clorofila-a e alta transparência da água (Secchi), há forte indício da ocorrência de interações com controles base-topo e topo-base sobre o fitoplâncton. Nossos dados suportam a hipótese de prováveis efeitos dessas interações estejam contribuindo para a manutenção das condições de transparência da água nas baías, favorecendo baixa riqueza e biomassa algal. Uma vez que o conhecimento sobre as interações tróficas, particularmente as que ocorrem em cascata tem sido desenvolvido com sucesso em na reestruturação e restauração da qualidade da água em diversos países. Esta pesquisa contribui para o conhecimento das interações mediadas pelas macrófitas, sobre o zooplâncton e fitoplâncton em áreas de influência de reservatórios. Contudo, estudos na área das interações tróficas mediadas pelas macrófitas poderão ser direcionados de maneira a atenuar assimetrias internacionais, encorajando o aumento da produtividade científica na América do Sul. Esforços para restaurar as baías no entorno do reservatório no Brasil poderão ser despendidos usando técnicas combinadas para aumentar a qualidade da água e incrementar atributos das comunidades aquáticas.
Submerged macrophytes promote attributes of planktonic communities by physical structure, water transparency, habitat, and shelter from predators. As they compete for light and nutrients, affecting negatively the phytoplankton growing, mediated bottom-up and topdown control interactions of zooplankton. Little has been investigated on the role of submerged vegetation in the interactions of zooplankton and phytoplankton in areas of reservoir influence in the Brazilian semiarid region. In order to identify major gaps and perspectives for future studies of macrophytes and trophic interactions, emphasizing searches for studies in South America, we conducted a scientometric analysis. We believe that the number of articles in the area show an increasing tendency to over the years, where South America will present significant participation in both the number of publications and in international cooperation. In order to investigate the impact of land use areas surrounding reservoir in submerged plants on planktonic communities, during four periods, we collect evidence of bottom-up and top-down controls of macrophyte on plankton. Our hypothesis is that the macrophytes are affected positively in that areas, and at the same time, can provide structure for richness and abundance to zooplankton and their interactions affect phytoplankton negatively. In the field we compare attributes of communities and dissolved nutrients in plant beds in the littoral and pelagic zones. For scientometrical analysis, we access publications using international database from 1980 to 2015. In the field, the samples were collected by boat, where greater distances with simultaneous sampling of vegetation, plankton communities and nitrogenous nutrients and total phosphorus dissolved. The submerged plant coverage areas were estimated by reducing the proportion of presence and absence of species in 24 points in parallel transects an area greater than 3.5 km. We collected 24 samples of phytoplankton and nutrients. For zooplankton, carry out sample composed of the water column vertically and horizontally, through hauls totaling 48 samples. The scientometrical analysis results showed that the number of trophic interactions researches grown in recent years in South America, with contributions from Brazil, Argentina and Uruguay. We found that the highest volume of indexed articles deals with the dynamics and structure of aquatic assemblages, webs and trophic interactions. Reservoirs and wetlands have received little attention. The large number of studies includes all aquatic community and interactions between macrophytes, phytoplankton, zooplankton and fish. Macrophytes occurred in high density and vegetation cover at 12 points per bay (60%; 70%) at different depths (2m to 6m). In the bays, phosphorus (mean = 0.03 and 0.05 mg / L) and nitrogen (0.4 and 0.9 mg / L) had lower concentrations. We found high Secchi transparency (>3.8) for both bays. The phytoplankton richness was 17 taxa, of which Cyanophyta Bacillariophyta were most representative. Low densities recorded reflected in lower values Chlorophyll-a (mean = 9.12 µg/l). Zooplankton showed high dissimilarity in the richness (97 spp.) of rotifers, Cladocera and Copepoda, with relative abundance. Densities varying significantly in the pelagic (24-2013 ind./m³) and littoral zones (28-1260 ind./m³) of both the bays. In this context, comparing these results with data from the vegetation, along with low concentrations of dissolved nutrients, chlorophyll-a and high water transparency, there is strong evidence of the occurrence of macrophytes and zooplankton interactions with bottomup and top-down controls on phytoplankton. Our data support the hypothesis that probably, effects of these interactions are contributing to the maintenance of conditions of water transparency, favoring low richness and algal biomass. The knowledge of trophic interactions, particularly which occur in cascades, has been successfully developed in the restructuring and restoration of water quality in several countries. This research brings to contributes to the knowledge of macrophytes, zooplankton and phytoplankton interactions in areas influenced by reservoirs. However, studies in the area of trophic interactions mediated by macrophytes may be directed in order to mitigate international asymmetries by encouraging increased scientific productivity in South America. Efforts to restore the bays around the reservoir in Brazil may be spent using combined techniques to increase the quality water and increase attributes of aquatic communities.

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Itti, Laurent Koch Christof. "Models of bottom-up and top-down visual attention /." Diss., Pasadena, Calif. : California Institute of Technology, 2000. http://resolver.caltech.edu/CaltechETD:etd-12022005-103530.

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11

Best, Maisy Jane. "Top-down and bottom-up influences on response inhibition." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/24650.

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Following exposure to consistent stimulus–stop mappings, response inhibition can become automatised with practice. What is learned is less clear, even though this has important theoretical and practical implications. The main contribution of this thesis is to investigate how stimulus-stop associations are acquired and the conditions under which they influence behaviour. To this end, this thesis addressed several outstanding issues concerning the associative architecture of stop learning, the role of expectancies, and the specificity of learning in inhibition tasks. Experiments 1-4 provide evidence that participants can acquire direct associations between specific stimuli and the stop goal without mediation via a single representation of the stop signal. However, these experiments also suggest that the influence of stimulus-stop associations on behaviour depends on top-down attentional settings: if participants begin to ignore the stop-associated stimuli, the effects of stop learning are diminished or eliminated entirely. Across eight experiments, this thesis provides evidence that participants generate expectancies during stop learning that are consistent with the stimulus-stop contingencies in play. However, Experiments 5-6 indicate that there may be some differences in the relationships between stimulus-stop expectancies and task performance under instructed and uninstructed conditions; stimulus-stop associations that are acquired via task instructions or via task practice have similar effects on behaviour, but seem to differ in how they trigger response slowing for the stop-associated items. Experiments 7-8 investigated the role of signal detection processes during the acquisition of stimulus-stop associations. To distinguish between stimulus-stop learning and stimulus-signal learning, the contingencies between specific stimuli and the stop goal and the contingencies between specific stimuli and the spatial location of the stop signal were independently manipulated. Although these experiments showed evidence of stop/go (goal) learning, there was no evidence that participants acquired the stimulus-signal associations. Across four experiments, this thesis investigated the specificity of stop learning. Experiments 9-10 compared the effects of training on behavioural performance in inhibition (go/no-go) and non-inhibition (two-choice) tasks. The results of these experiments revealed that learning in inhibition and non-inhibition tasks could arise through similar associative mechanisms, but suggest that the effects of training in these tasks could also depend on top-down response settings and general non-associative processes. Experiments 11-12 investigated the neural specificity of stop learning. These experiments also revealed similar effects of training across the go/no-go and two-choice tasks adding weight to the claim that training in inhibition tasks primarily influences task-general processes. Combined, the overall conclusion of this thesis is that bottom-up control can influence response inhibition but what is learned depends on top-down factors. It is therefore important to consider bottom-up factors and top-down factors as dependent, rather than independent, influences on response inhibition.

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12

Burke, Madeline Jane. "Top-down and bottom-up approaches to tissue engineering." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720837.

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13

Widman, Börjesson Sara. "Taluppfattning i ofördelaktiga förhållanden : Hur påverkar kognitiv förmåga perceptionen av enstaviga ord i brus bestående av talande röster?" Thesis, Linköpings universitet, Institutionen för datavetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-108950.

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Inom disciplinen kognitiv hörselvetenskap tillämpas en integrerad ansats där taluppfattning beskrivs ur både ett auditivt bottom-up-perspektiv och ett kognitivt top-down-perspektiv. Studien undersökte hur taluppfattning varierar med, respektive utan top-down-stöd och vad de kognitiva förmågorna uppmärksamhet, minne och inhiberingsförmåga hade för inverkan. Taluppfattningsförmåga utvärderades med hjälp av ett Speech-In-Noise-test (SIN-test) som bestod av tre deltest där enstaviga ord presenterades i en ofördelaktig miljö bestående av röster som talande i mun på varandra. I deltest 1 presenterades ord i uppåtgående förhållande till rösterna utan kognitivt stöd, i deltest 2 presenterades ord i nedåtgående förhållande till rösterna med kognitivt stöd och i deltest 3 presenterades ord i uppåtgående förhållande till rösterna med kognitivt stöd. Detta resulterade i identifiering av tre tröskelnivåer för taluppfattning. Kognitiva förmågor utvärderades med hjälp av Reading span test, Size Comparison span task (SIC-span) och Paced Auditory Serial-Addition Test (PASAT). Envägs variansanalys av taluppfattningstesten visade på signifikanta skillnader mellan alla tre testen. I test 2 identifierades lägst tröskelvärde, därefter test 3 och slutligen test 1. Korrelationsanalys visade på icke signifikanta samband mellan de tre SIN-testen. Av de kognitiva förmågorna och SIN- testen visade endast PASAT A på ett signifikant samband med SIN-test 2. Analys av de kognitiva förmågorna och differenserna mellan SIN-testen gav inga signifikanta samband. Slutligen vid analys av de kognitiva förmågorna hade PASAT A och PASAT B ett starkt positivt samband medan PASAT B och Reading span test hade ett starkt negativt samband. Resultaten i studien talade för att top-down-stöd ger bättre taluppfattningsförmåga och att uppmärksamhetskapacitet är en förmåga som har en signifikant inverkan på taluppfattning i nedåtgående förhållande till ett brus av röster.

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14

Hicks, Jeremy David. "A combined top-down/bottom-up route to fabricating graphene devices." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49100.

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The purpose of this work is to explore a method that combines both top-down and bottom-up elements to fabricate electronic devices made from graphene, a single sheet of carbon atoms related to carbon nanotubes and graphite. This material has garnered interest in the semiconductor industry for many reasons, including its potential for ballistic conduction, natural ambipolar (both n- and p-type) carrier transport, and impermeability to nearly all elements. However, its lack of a band gap, and a lack of viable options for creating one in the material, suggests a limited future as a silicon replacement material. A solution to this problem is presented that uses a recently-reported technique of creating pre-patterned graphene features from the thermal decomposition of specially-structured silicon carbide (SiC) surfaces. We employ a combination of direct band structure measurements and electrical results to suggest that a semiconducting bent graphene nanostructure exists in this structured SiC system, creating a possible route toward a broad class of future graphene electronics.

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15

Abdussalam, S. S. "Bottom-up and top-down approaches to low energy supersymmetry breaking." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595324.

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In this thesis we address the phenomenology of SUSY breaking from the superstring scale to the electroweak scale in order to produce a guide map for discovery at the LHC. From the top-down approach we study SUSY breaking at low-energies from a well defined superstring theory scenario and extract its phenomenological implications. From the bottom-up approach (independent of string theory), using Bayesian inference techniques, we make the first complete model-independent scan of the low energy phenomenological MSSM (pMSSM) parameter space. We perform the first statistically convergent pMSSM global fit to all current collider and DM data. We demonstrate the application of Bayesian model selection methodology to high energy SUSY breaking models with modest number of free parameters. We found that SUSY breaking from superstring theory should eventually help test its reality and that direct data is required in order to assign unambiguous preferences between different high energy SUSY breaking models. We predict that the Higgs boson mass lies between 117 GeV and 128 GeV at 95% confidence level. We believe this is a robust prediction that should be confirmed once SUSY is discovered at the LHC. Our pMSSM parameters fit provides an appropriate arena for the LHC studies of the MSSM which we wish to pursue further in future work.

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16

Goncharov, Alexander. "Magnetization reversal processes in 'bottom-up' and 'top-down' magnetic structures." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414612.

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17

Muhsin, Ali, and Nikola Rusevski. "Kartläggning av Top down och Bottom up i tre fallföretag : Informationsstrategier." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Logistik och verksamhetsledning, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-46759.

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Purpose – The purpose of the study is to map out the top-down and bottom-up perspectives and investigate the information strategies on how it relates to daily operations in three case companies. To fulfill the purpose, the following three questions have been answered: What approach do the organization have on information strategies and what characterizes them? To what extent do the case organization use the information strategies? What opportunities and difficulties do organizations see with the information strategies? Method – To fulfill the purpose, a case study was carried out on three case companies. The empirical data has been collected through interviews and surveys. The theoretical framework together with the empirical data, has then contributed to achieving the purpose. Findings – First the map out was conducted within three case companies and how the information strategies have been chosen in relation to the daily operations perspective. Based on the mapping, it has then been framed the potential possibilities and difficulties with the respective strategy choices and its implementation. Limitations – The definition of the information strategies within the study is defined as Top-down and Bottom-up and how the choice in how companies choose to coordinate and be responsible for tasks. The authors do not know whether the study can be adapted to the business of other organisations when mapping information strategies. Keywords – information strategies, top-down, bottom-up, information flow, communication.

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18

Pule, Lebohang. "Constructing efficient multi-asset class portfolios: Top-down or bottom-up?" Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27753.

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This dissertation concerns itself with the problem of constructing multi asset class portfolios. The investment process is aimed at solving two problems. The first problem is estimating the future returns of individual securities, which is an exercise fraught with uncertainty as the future is fundamentally unpredictable. This uncertainty means that the investor must allocate his portfolio to a number of assets instead of just one, in case his predicted future returns do not materialize. This leads the investor to the second problem of how best to construct the portfolio. It is this part of the investment process which is the subject of this dissertation which examines whether it is best to construct multi-asset class portfolios using a top-down or bottom-up approach. In the top-down approach one begins by creating independent single asset class portfolios which are then combined to create a multi-asset class portfolio. The bottom-up approach constructs the portfolio by considering all the securities available to the investor (irrespective of asset class) at the same time. The Mean-Variance and Black- Litterman models are reviewed in detail. Portfolios are then created using these portfolio construction methods in order to compare the two approaches. In constructing these portfolios, the commonly encountered problem of missing data in financial return series is also examined. The main result is that the top-down and bottom-up approaches create similar efficient frontiers, though the bottom-up approach results in an extended frontier which allows investors to obtain efficient portfolios with either a higher expected return or a lower volatility.

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19

Kondo, Michio. "TOP-DOWN AND BOTTOM-UP FORCES STRUCTURING BIOLOGICAL COMMUNITIES : THEORETICAL CONSIDERATIONS." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150859.

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20

Larsson, Therese, and Louise Pettersson. "Perspektiv på goodwill : En studie om användningen av teoretiska begrepp i praktiken." Thesis, Karlstads universitet, Avdelningen för företagsekonomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-31524.

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Det finns två typer av goodwill, den första typen är internt upparbetad goodwill och den andra typen är goodwill som uppkommer vid förvärv av företag. Fokus i denna uppsats kommer att ligga på den förvärvade goodwill, som kan upplevas som en svart låda då det kan vara oklart vad posten faktiskt består av. Förvärvad goodwill kan definieras på olika sätt av företagen, i den akademiska världen har främst två perspektiv identifierats, top-downperspektivet och bottom-upperspektivet. Ur den första synvinkeln ses goodwill som en restpost och ur den andra synvinkeln kan goodwill ses som en summa av de komponenter som posten består av. Genom att betrakta dessa perspektiv är tanken att få en inblick i hur företagen väljer att redovisa sin goodwill. Det kan vara lättare sagt än gjort, teori och praktik går inte alltid hand i hand. Det finns ett glapp mellan hur praktiker jobbar med goodwill och teoretikers åsikt om posten. Varför det finns meningsskiljaktigheter växer successivt fram under studiens gång. Det finns än så länge bara ett fåtal studier som behandlar själva begreppet goodwill och dess olika perspektiv samt hur företagen ser på goodwill. För att försöka bidra till ökad förståelse på detta område, har vi i denna uppsats undersökt om teorin och praktiken kommit varandra närmare. Det främsta syftet med studien är att ta reda på om företag inom bemanningsbranschen definierar sin goodwill olika i sina årsredovisningar. För att undersöka detta på ett begripligt sätt har tre professionella respondenter intervjuats i ett försök att klargöra komplexiteten av posten. Slutsatsen är att det inte går att identifiera vilket perspektiv som används i en årsredovisning på grund av att dessa är väldigt standardiserade, vilket gör att det blir svårt för intressenten att utläsa särskilt mycket information om goodwillposten. Det alternativ som kändes mest relevant att använda och som skulle hjälpa oss att kunna få klarhet i vår frågeställning, var att vända sig till en urvalsgrupp av representanter på området. Den analys som efterföljde resulterade i att vi kunde konstatera att samtliga svarande på det praktiska området såg goodwillposten mer eller mindre som en restpost. Ingen värdering eller starkare reflektion gjordes kring det andra teoretiska perspektivet. Sammanfattningsvis vågar vi påstå att det inte skett någon märkbar förändring som gjort att teori och praktik närmat sig varandra.
There is two ways to understand goodwill. Number one, internally generated goodwill and number two, acquired purchase goodwill. The main topic for this research is acquired purchase goodwill. Many people believe that goodwill is a sort of black box. It is unclear what goodwill actually is. There is no limit on how you can define acquired purchase goodwill. In academia we talk about two perspectives, top-down perspective and bottom-up perspective. The first perspective sees goodwill as a residual and the second perspective sees goodwill as a sum of its components. When you put on these two glasses, the idea is that you may be able to see how businesses account for their goodwill. It is easier said than done, many times theory and practice does not get along. There is a big space between the theories on how you work with goodwill in the reality. Only a few have studied the definition of goodwill. Because of that we really wanted to investigate this phenomenon. We have analyzed if the gap between theory and reality has been reduced. The purpose of this study is to investigate if the staffing companies define goodwill different in their annual reports. The tool we have used is to interview professional accountants to get their opinion. The conclusion is that the annual report is quite standardized which means it is difficult to understand what goodwill actually is. Everybody we interviewed have the same opinion, that goodwill is a residual. They made no reflections or additions on that subject. In summary, we know now that after our study, no big change has been made between theory and practice.

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21

Erdem, Mehmet Erkut. "Simultaneous Bottom-up/top-down Processing In Early And Mid Level Vision." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610167/index.pdf.

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The prevalent view in computer vision since Marr is that visual perception is a data-driven bottom-up process. In this view, image data is processed in a feed-forward fashion where a sequence of independent visual modules transforms simple low-level cues into more complex abstract perceptual units. Over the years, a variety of techniques has been developed using this paradigm. Yet an important realization is that low-level visual cues are generally so ambiguous that they could make purely bottom-up methods quite unsuccessful. These ambiguities cannot be resolved without taking account of high-level contextual information. In this thesis, we explore different ways of enriching early and mid-level computer vision modules with a capacity to extract and use contextual knowledge. Mainly, we integrate low-level image features with contextual information within uni&
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ed formulations where bottom-up and top-down processing take place simultaneously.

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22

Sharma, Vinay. "Simultaneous object detection and segmentation using top-down and bottom-up processing." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196372113.

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23

Löw, Caroline Anna Elisabeth [Verfasser], and Friederike [Akademischer Betreuer] Lang. "Quellenidentifikation der Phosphorernährung von Buchenwäldern mittels Bottom-up- und Top-down-Ansätzen." Freiburg : Universität, 2019. http://d-nb.info/121641727X/34.

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24

Roberts, James W. "The contribution of top-down and bottom-up processes during observational practice." Thesis, Liverpool John Moores University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582848.

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The primary aim of this thesis was to examine the nature of the representation developed during observational practice. Chapter 2 (Experiment 1-2) investigated the stimulus properties required to learn novel motor skills and the processing mechanisms responsible for learning. Participants attempted a novel relative timing pattern performed on a computer. Following the observation of a novel relative timing pattern via an expert human model (biological motion, BM), constant velocity model (non-biological motion, NBM) or end-state timing information without the trajectory (goal-directed model, GOAL), there was significantly more accurate relative timing error for BM and NBM groups (BM < GOAL, CTL; NBM < CTL (ps < 0.05)) (Experiment 1). Therefore, sequence learning through observation requires the presence of motion information, irrespective of the biological properties. These findings were extended with participants observing biological- or non-biological motion after receiving an instruction that the stimuli were in fact human- or computer-generated (BM-H, BM-C, NBM-H, NBM-C) (Experiment 2). In addition to the test of motor learning, participants completed a crecognition test featuring the detection of previously observed (trained) or novel (new) sequences. The results confirmed significantly more accurate relative timing error for the experimental groups compared to a CTL group. However, the recognition test revealed an attenuation of explicit recognition toward the observation of new sequences for the BM-H group compared to BM-C (p = 0.06), NBM-H and NBM-C groups (ps < 0.05). This indicated implicit motor learning that was specific to BM-H group. Thus, the coding of motion information was subject to top-down processes (i.e., belief), which modulate automatic bottom-up processes sensitive to biological motion. 3 Chapter 2 (Experiment 3-7) focused on the coding of biological kinematics. Thus, the natural movement profile adopted by humans was manipulated by forming an unnatural biological motion model featuring a shift in the proportion of time to peak velocity. The coding of biological kinematics would be indicated by the transition from natural movement kinematics, characterised by an early-to-mid time to peak velocity, toward a novel movement profile featuring a delayed time to peak velocity. Performance was measured by calculating the absolute difference between participant and model pTTPV (imitation error) and pTTPV of segment 1. The results revealed that the observation of unnatural biological motion produced significantly more accurate imitation error and an extended pTTPV, as per the unnatural model (p < 0.05) (Experiment 3). Subsequent experiments were intended to examine the processing mechanisms responsible for the coding of kinematics. Indeed, issuing a secondary movement task during observational practice led to an attenuation of the unnatural kinematics as indicated by no significant differences in imitation error and pTTPV between participants observing natural and unnatural biological motion (p > 0.05) (Experiment 4). This motor interference was effector-independent as indicated by the corresponding attenuation of imitation error and pTTPV after performing secondary movements of an unrelated effector (i.e., foot) (Experiment 5). These results indicate the coding of novel biological kinematics incorporate motor processes typically associated with action-execution. Meanwhile, the coding of biological kinematics was also subject to the direction of attention. That is, a secondary attention demanding counting task attenuated the coding of biological kinematics as there were no significant differences for imitation error and pTTPV (p > 0.05) (Experiment 6). Finally, the instruction to primarily attend to the trajectory compared to a general pre-cue led to a significantly more accurate imitation 4 error score, although significantly attenuated relative timing ~rror (ps < 0.05) (Experiment 7). Together, these results demonstrate the contribution of bottom-up and top-down processes during observational practice.

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Shelley, Elwyn James Bacchus. "Toward positional self-assembly : integration of top-down and bottom-up methodologies." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396185.

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26

Uygun, David. "Top-down and bottom-up control of drug-induced sleep and anaesthesia." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/43958.

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In recent decades, research has unravelled fascinating detail about the molecular mechanisms underpinning pharmacologic loss of consciousness (LOC). However, the systems-level mechanisms are far less clear. Recent genetic approaches, however, enable unprecedented dissection on neural pathways, and they are paving a way for this line of research. The focus of this thesis is to investigate the neuroanatomical substrates of commonly used drugs which reversibly render us unconscious. Zolpidem is a positive allosteric modulator (PAM) of the GABAA receptor which binds to the benzodiazepine (BZ) site. Because zolpidem binds α1-3,β,γ2 containing GABAA receptors, which are widespread, it acts virtually everywhere. We do not know if zolpidem causes sleep by enhancing GABAergic inhibition throughout the entire brain, or if the therapeutic sleep-inducing property depends upon specific brain circuitry. γ2I77 mice are devoid of zolpidem-sensitivity. But, zolpidem-sensitivity can be restored selectively in brain regions, enabling dissection of the circuitry involved in zolpidem's effect. To isolate the therapeutic effect of zolpidem we deleted GABAA-γ2I77-subunits and replaced them with GABAA-γ2F77-subunits in HDC neurons or frontal-cortex in isolation. We were able to selectively restore zolpidem-sensitivity in target neurons. This conferred zolpidem-enhanced IPSCs locally. Compared with wild-type mice and zolpidem-insensitive γ2I77lox mice, we found that GABAA-γ2F77 receptors in either HDC-neurons or frontal cortex alone were enough to rescue the majority of zolpidem-mediated sleep. The response in HDC-γ2F77 mice was similar to that of an H1-receptor antagonist. By producing a null effect in a negative-control area - the superior colliculus - we show that HDC neurons and the frontal cortex are both substrates involved in zolpidem-mediated sleep. We also investigated the role of synaptic-inhibition onto corticothalamic-neurons in anaesthetic-induced LOC and sleep-wake. To do this, we genetically ablated γ2-subunits from layer-6 corticothalamic-cells by crossing Ntsr1-Cre mice with GABAA-γ2I77lox mice. We found this reduced isoflurane sensitivity, but left sleep-wake behaviours virtually unaffected.

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27

Lowe, Andrea Jane. "The relative contribution of top-down and bottom-up information during lexical access." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/6604.

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The research reported in this thesis examines the relative contributions of top-down and bottom-up information during lexical access. I evaluate the Cohort Model of lexical access (Marslen-Wilson and Welsh, 1978; Marslen-Wilson and Tyler, 1980; and Marslen-Wilson, 1987) which specifies that the first stage in lexical access is fully autonomous and that during this stage all processing proceeds in terms of analysis of the acoustic-phonetic input. Implicit in this model is the assumption that bottom-up processing is immune to any effects of contextual or top-down information. I examine the extent to which listeners ever rely exclusively on bottom-up information during lexical access and investigate this issue empirically, by measuring effects of context on both the production and the perception of words in various contexts. I test the hypothesis that a word uttered in a constraining context will be acoustically indistinguishable from its competitors by, first, measuring one acoustic parameter (VOT) across constraining and non-constraining contexts and, then, examining the intelligibility of tokens of that parameter taken from the varyingly constraining contexts. The data from these experiments suggest that the realization of VOT is not an aspect of bottom-up information which would create problems for a bottom-up processor in terms of providing ambiguous acoustic-phonetic information. I then investigate whether bottom-up processing during lexical access is immune to effects of context. Following Grosjean (1980) and Tyler (1984), I utilize the Gating Paradigm. Using incongruous contexts, I argue that direct assessment of the contributions made by different information sources during lexical access can be made. By presenting bottom-up information which is inappropriate to the contextual (topdown) information, I evaluate the extent to which one information source is given priority over the other. I vary both the contextual constraints available to the listener and the acoustic clarity of bottom-up information. The observed pattern of listeners' identifications of the words suggested that whilst bottomup information was given priority, top-down information was available and was utilized during lexical access. I present data which support the working structure of the Cohort Model of lexical access. I conclude, however, that the model places disproportionate emphasis on initial bottom-up processing. It appears that top-down information is not prohibited from contributing to processing during the initial stage of lexical access.

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SEVERIANO, Juliana dos Santos. "Efeitos top-down e bottom-up sobre a comunidade fitoplanctônica: uma análise experimental." Universidade Federal Rural de Pernambuco, 2013. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/4842.

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Submitted by (edna.saturno@ufrpe.br) on 2016-06-21T13:39:09Z No. of bitstreams: 1 Juliana dos Santos Severiano.pdf: 1153405 bytes, checksum: fb7c8b63673224521d85d2d6e04afa79 (MD5)
Made available in DSpace on 2016-06-21T13:39:09Z (GMT). No. of bitstreams: 1 Juliana dos Santos Severiano.pdf: 1153405 bytes, checksum: fb7c8b63673224521d85d2d6e04afa79 (MD5) Previous issue date: 2013-02-21
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
The phytoplankton community can be regulated by the bottom-up controls (nutrients) and top-down (predators). The availability of nutrients has been considered as the most significant factor in this regulation, however, studies show that phytoplankton can also be strongly regulated by zooplankton. Experiments were conducted to study the effects of varying the concentration of nutrients (N: P ratio) and herbivory exercised by zooplankton on the structure and biomass of phytoplankton, with emphasis on species-specific response of phytoplankton to the effects of these factors. Sub-samples of 700 ml of water in a eutrophic environment (Apipucos reservoir, Brazil) were placed in 1 liter Erlenmeyer flasks and maintained in the laboratory for 7 days. Three experiments were conducted separately and maintained for each of these treatments included the addition of nutrients to maintain DIN different reasons: E (N: P ratio 16, 60 and 5), presence and absence of zooplankton. The nitrogen source used was a phosphorus NaNO3 and the KH2PO4. Zooplankton added was obtained in the reservoir water. Phytoplankton community in terms of total biomass was not affected when kept under different nitrogen and phosphorus reasons while herbivory caused significant reduction. The community composition has changed, with the response to the effects of these factors are species-specific. The diatom Cyclotella meneghiniana Kützing was dominant in the treatments and the main species preyed upon by zooplankton. In the absence of zooplankton, this species showed exponential growth in all the experiments, mainly in the N: P ratio 60. The ratio N: P optimal for the growth of green algae ranged from 5: 1 to 60: 1, with species with more a great reason to grow. The green algae Desmodesmus protuberans (Fritsch and Rich) E. Hegewald, D. quadricauda (Turpin) Hegewald and Pediastrum duplex Meyen did not have growth negatively affected by zooplankton, while Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju, growth was stimulated by the presence zooplankton. These results demonstrate the importance of both nutrients as of herbivory in regulating the composition and biomass of phytoplankton and reinforce the need for evaluation of phytoplankton response to specific level for a better understanding of the importance and magnitude of these factors.
A comunidade fitoplanctônica pode ser regulada pelos controles bottom-up (nutrientes) e top-down (predadores). A disponibilidade de nutrientes vem sendo considerada como o fator mais expressivo nesta regulação, entretanto, estudos mostram que o fitoplâncton também pode ser fortemente regulado pelo zooplâncton. Experimentos foram realizados para estudar os efeitos da variação na concentração dos nutrientes (razão N:P) e da herbivoria exercida pelo zooplâncton sobre a estrutura e biomassa do fitoplâncton, dando ênfase na resposta espécie-específica do fitoplâncton aos efeitos desses fatores. Sub-amostras de 700 ml da água de um ambiente eutrófico (Reservatório de Apipucos, Brasil) foram colocadas em Erlenmeyers de 1 litro e mantidas em laboratório, durante 7 dias. Três experimentos foram conduzidos separadamente, sendo mantidos para cada um destes, tratamentos que incluíam a adição de nutrientes de forma a manter diferentes razões DIN:PT (razão N:P 16, 60 e 5), com presença e ausência do zooplâncton. A fonte de nitrogênio utilizada foi o NaNO3 e a de fósforo o KH2PO4. O zooplâncton adicionado foi obtido da água do reservatório. A comunidade fitoplanctônica, em termos de biomassa total, não foi afetada quando mantida sob as diferentes razões nitrogênio e fósforo, enquanto a herbivoria provocou redução significativa. A composição da comunidade foi alterada, com a resposta aos efeitos desses fatores sendo espécie-específica. A diatomácea Cyclotella meneghiniana Kützing foi dominante nos tratamentos e a principal espécie predada pelo zooplâncton. Na ausência dos organismos zooplanctônicos, esta espécie apresentou crescimento exponencial em todos os experimentos, principalmente, na razão N:P 60. A razão N:P ótima para o crescimento das clorofíceas variou de 5:1 a 60:1, com espécies apresentando mais de uma razão ótima para crescer. As clorofíceas Desmodesmus protuberans (Fritsch e Rich) E. Hegewald, D. quadricauda (Turpin) Hegewald e Pediastrum duplex Meyen não tiveram o crescimento negativamente afetado pelo zooplâncton, enquanto Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju, teve o crescimento estimulado pela presença do zooplâncton. Estes resultados demonstram a importância tanto dos nutrientes quanto da herbivoria na regulação da composição e biomassa do fitoplâncton e reforçam a necessidade da avaliação da resposta do fitoplâncton a nível específico para uma melhor compreensão da importância e magnitude desses fatores.

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Woodgate, Zoe Anne. "Determinants of predator abundance in northern KwaZulu-Natal: top-down or bottom-up?" Bachelor's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13032.

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Includes bibliographical references.
As protected areas ultimately aim to successfully conserve natural predator populations, an understanding of the non-anthropogenic drivers of their population change is critical. Both bottom-up (e.g. food limitation, competition) and top-down (e.g. predation, interference) processes play an important role in structuring predator guilds, yet there is a poor understanding of their relative importance. Here, I investigated whether the relative abundance of mesopredators, facultative scavengers, and an apex predator were affected primarily by bottom-up processes (prey abundance) or by top-down processes (predator abundance), or a combination of the two. Central to this study was elucidating the complex relationship between mesopredators and apex predators. Caracal (Caracal caracal), blackbacked jackal (Canis mesomelas), sidestriped jackal (Canis adustus), honey badger (Mellivora capensis) and serval (Leptailurus serval) were classed together as Mesopredators. Facultative scavengers included two hyaena species (spotted Crocuta crocuta and brownhyaena Hyaena brunnea). Leopards (Panthera pardus) were included as an example of an apex predator. Data was obtained from camera-trap surveys conducted in four protected areas located in northern KwaZulu-Natal (South Africa). Results of both a nested analysis of variance and generalised linear mixed models revealed that there was no mesopredator suppression present in protected areas with complete predator guild. In addition, prey and similarly sized predator relative abundance indices (RAIs) had a significant positive effect on mesopredator, hyaena and leopard RAI. The findings suggest that bottom-up drivers are more important than top-down processes in determining the relative abundance of mammalian predators in these protected areas. My study highlights the importance of monitoring prey populations in a protected area when attempting to successfully manage mammalian predator trophic guilds.

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Norén, Emma. "Top-down eller bottom-up? : En kvalitativ studie om lärares val av läsinlärningsmetoder." Thesis, Karlstads universitet, Institutionen för språk, litteratur och interkultur, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-55102.

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Syftet med undersökningen är att söka svar på hur yrkesverksamma lärare inom skolans tidi-gare åldrar åk.1–3 arbetar med läsinlärning. Jag vill även undersöka vilka läsinlärningsme-toder lärarna använder i undervisningen samt vilka faktorer som påverkat dessa lärares val av läsinlärningsmetoder. Min undersökning består av sex semistrukturerade kvalitativa intervjuer med lärare, all verksamma inom samma mellansvenska kommun. Flera intressanta aspekter har framkommit genom undersökningen. Bland annat att ingen av de intervjuade lärarna använder sig av en enda renodlad metod. Istället blandar de och tar ”det bästa” från olika metoder samt anpassar sitt arbetssätt delvis efter den barngrupp de arbe-tar med. Faktorer som påverkat lärarnas val av läsinlärningsmetoder är exempelvis trender, erfarna kollegor och kommunalt inflytande.
The aim of this study has been to find answers as to how primary teachers in the early ages (grades 1–3) help children in the process of learning to read. I also wanted to investigate wich methods teachers use in teaching their students in learning to read. My interest also lies in what has affected the teachers choice of reading methods. My study is based on six semistructured qualitative interviews with teachers, who all work in the same town, but in different schools. Several interesting aspects emerged from the interviews. For example, none of the teachers use only one reading method. The mix and match and adapt their teaching according to their class and preconditions. Factors that have influenced their choice of method is, among other things, trends older colleges and municipal influence.

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Jachim, Stephen. "Investigating the balance of bottom-up and top-down processing in autistic perception." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/investigating-the-balance-of-bottomup-and-topdown-processing-in-autistic-perception(e6b4935d-2599-40b1-b0e1-003f7d636500).html.

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Autism spectrum disorder (ASD) is a neurodevelopmental disorder emerging in the first few years of life. Currently, three characteristics are required for a diagnosis of ASD, impaired social interactions, impaired verbal communication and restricted and repetitive patterns of behaviour or interests. This last category can optionally include hyper- or hypo-reactivity to sensory input. Individuals with autism can also display superior performance on visual tasks where it may help to ignore global detail, behaviour sometimes described as ‘not seeing the forest for the trees’. At present, the exact mechanisms underlying the perceptual differences between autistic and neurotypical groups remain unknown, but they may reflect an imbalance in the contributions that bottom-up and top-down processing make in perceptual processing. Visual perception is thought to rely on interactions between the ‘bottom-up’ flow of ambiguous information from the retina and the ‘top-down’ flow of disambiguating information from higher cortical areas, via cortical circuits that have been shaped by a lifetime’s experience. These interactions lead to the activation of internal representations (of objects) which are necessary for the successful navigation of our environment. In order to investigate these perceptual differences, we employed three well-known experimental paradigms with a group of thirteen autistic participants and their matched controls. We investigated visual integration (involving bottom-up and top-down interactions) across low and intermediate stage neural mechanisms. A dim line (target) is easier to detect when flanked by two brighter collinear lines (flankers), an effect known as collinear facilitation, and we used two variations of this task to investigate low-level visual integration. In the first, we varied the orientation of the collinear flankers and found reduced integration for an autistic compared to a neurotypical group, a finding that conflicts with previous research. In a second collinear facilitation experiment with neurotypical participants, in which the target could be presented before, during or after flanker presentation, we were able to isolate facilitation that we believe was due to feedforward and feedback processing. However, in a subsequent study in which we compared autistic and neurotypical performance on this task, we found no significant difference. Moving onto intermediate level visual integration, we used a contour integration task consisting of open (lines) and closed (square) contours and found reduced integration for the autistic compared to the neurotypical groups when integrating closed contours. In our final study, we looked at global motion integration, and made use of a translating diamond. This is a bistable stimulus in which four lines can be perceived as independent line fragments moving vertically, or as a single integrated shape - a diamond moving horizontally. In this experiment, the autistic group showed an unexpected bias to perceiving the stimuli in its integrated form as a diamond. Perceptual processing of shapes based on squares or diamonds reflects visual integration at a global level, and so the differences we have found in shape processing between our experimental groups (reduced integration for the square and increased integration for the diamond in autism) are more likely to be the result of differences in top-down processing.

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Düpont, Daniel [Verfasser]. "Merging Bottom-up and Top-down Availability for realistic Analysis of Safety-related Loops : Verzahnung von Bottom-Up- und Top-Down-Verfügbarkeit zur Abbildung realen Verhaltens von PLT-Schutzeinrichtungen / Daniel Düpont." Aachen : Shaker, 2010. http://d-nb.info/108453634X/34.

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Spivak, Amanda C. "Bottom-up and top-down controls on sedimentary ecosystem functioning in a seagrass habitat." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539616861.

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Coastal seagrass ecosystems are complex habitats that are increasingly influenced by human perturbations. Disturbances that affect the strength of bottom-up (i.e. resource availability) and top-down (i.e. consumer) controls may also influence biomass distribution between trophic levels, sediment biogeochemistry, and seagrass ecosystem metabolism. Here, I experimentally tested how top-down and bottom-up perturbations interact with community structure (diversity, food chain length of epibenthic consumers) to alter sediment biogeochemistry and ecosystem metabolism in an experimental eelgrass (Zostera marina ) system. My data indicated that resource availability influenced SOM composition and ecosystem metabolism. Light availability tended to be a stronger determinant of SOM composition while nutrient enrichment affected secondary production of invertebrate grazers more strongly than primary producers or SOM. Top-down predator effects on SOM composition and ecosystem flux rates tended to be weak. However, the strength of the trophic cascade may partly be a function of grazer community composition and grazer susceptibility to predation. Finally, my results indicated that grazer species identity and community composition strongly influenced SOM composition. In addition to the main effects of light, nutrients, predators, and grazers there were a variety of interactive effects between resources and food web composition. Consequently, the effects of resource availability and food web composition on seagrass ecosystem functioning should not be considered in isolation.

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Wirsch, Anton. "Analysis of a top-down bottom-up data analysis framework and software architecture design." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/107346.

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Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, System Design and Management Program, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 70-71).
Data analytics is currently a topic that is popular in academia and in industry. This is one form of bottom-up analysis, where insights are gained by analyzing data. System dynamics is the opposite, a top-down methodology, by gaining insight by analyzing the big picture. The merging of the two methodologies can possibly provide greater insight. What greater insight that can be gained is research that will be required in the future. The focus of this paper will be on the software connections for such a framework and how it can be automated. An analysis of the individual parts of the combined framework will be conducted along with current software tools that may be used. Lastly, a proposed software architecture design will be described.
by Anton Wirsch.
S.M. in Engineering and Management

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Benicasa, Alcides Xavier. "Sistemas computacionais para atenção visual Top-Down e Bottom-up usando redes neurais artificiais." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-29042014-162209/.

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A análise de cenas complexas por computadores não é uma tarefa trivial, entretanto, o cérebro humano pode realizar esta função de maneira eficiente. A evolução natural tem desenvolvido formas para otimizar nosso sistema visual de modo que apenas partes importantes da cena sejam analisadas a cada instante. Este mecanismo de seleção é denominado por atenção visual. A atenção visual opera sob dois aspectos: bottom-up e top-down. A atenção bottom-up é dirigida por conspicuidades baseadas na cena, como o contraste de cores, orientação, etc. Por outro lado, a atenção top-down é controlada por tarefas, memórias, etc. A atenção top-down pode ainda modular o mecanismo bottom-up através do enviesamento de determinadas características de acordo com a tarefa. Além do mecanismo de modulação considerado, o que é selecionado a partir da cena também representa uma importante parte para o processo de seleção. Neste cenário, diversas teorias têm sido propostas e podem ser agrupadas em duas linhas principais: atenção baseada no espaço e atenção baseada em objetos. Modelos baseados em objeto, ao invés de apenas direcionar a atenção para locais ou características específicas da cena, requerem que a seleção seja realizada a nível de objeto, significando que os objetos são a unidade básica da percepção. De modo a desenvolver modelos de acordo com a teoria baseada em objetos, deve-se considerar a integração de um módulo de organização perceptual. Este módulo pode segmentar os objetos do fundo da cena baseado em princípios de agrupamento tais como similaridade, proximidade, etc. Esses objetos competirão pela atenção. Diversos modelos de atenção visual baseados em objetos tem sido propostos nos últimos anos. Pesquisas em modelos de atenção visual têm sido desenvolvidas principalmente relacionadas à atenção bottom-up guiadas por características visuais primitivas, desconsiderando qualquer informação sobre os objetos. Por outro lado, trabalhos recentes têm sido realizados em relação ao uso do conhecimento sobre o alvo para influenciar a seleção da região mais saliente. Pesquisas nesta área são relativamente novas e os poucos modelos existentes encontram-se em suas fases iniciais. Aqui, nós propomos um novo modelo para atenção visual com modulações bottom-up e top-down. Comparações qualitativas e quantitativas do modelo proposto são realizadas em relação aos mapas de fixação humana e demais modelos estado da arte propostos
Perceiving a complex scene is a quite demanding task for a computer albeit our brain does it efficiently. Evolution has developed ways to optimize our visual system in such a manner that only important parts of the scene undergo scrutiny at a given time. This selection mechanism is named visual attention. Visual attention operates in two modes: bottom-up and top-down. Bottom-up attention is driven by scene-based conspicuities, such as the contrast of colors, orientation, etc. On the other hand, top-down attention is controlled by task, memory, etc. Top-down attention can even modulate the bottom-up mechanism biasing features according to the task. In additional to modulation mechanism taken into account, what is selected from the scene also represents an important part of the selection process. In this scenario, several theories have been proposed and can be gathered in two main lines: space-based attention and object-based attention. Object-based models, instead of only delivering the attention to locations or specific features of the scene, claim that the selection it be performed on object level, it means that the objects are the basic unit of perception. In order to develop models following object-based theories, one needs to consider the integration of a perceptual organization module. This module might segment the objects from the background of the scene based on grouping principles, such as similarity, closeness, etc. Those objects will compete for attention. Several object-based models of visual attention have been proposed in recent years. Research in models of visual attention has mainly focused on the bottom-up guidance of early visual features, disregarding any information about objects. On the other hand, recently works have been conducted regarding the use of the knowledge of the target to influence the computation of the most salient region. The research in this area is rather new and the few existing models are in their early phases. Here, we propose a new visual attention model with both bottom-up and top-down modulations. We provide both qualitative and quantitative comparisons of the proposed model against an ground truth fixation maps and state-of-the-art proposed methods

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Sauquet, Alexandre. "Three contributions to the top-down and bottom-up approaches to global environmental problems." Thesis, Clermont-Ferrand 1, 2014. http://www.theses.fr/2014CLF10429.

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Pour résoudre les problèmes environnementaux mondiaux, la formation d'accords multilatéraux est une solution privilégiéee. Dans cette approche, des objectifs en matière de protection de l'environnement sont définis au cours d'un cycle de négociations internationales. Une fois ces objectifs définis, une étape cruciale est de recueillir l'engagement des pays au respect de cesobjectifs. Dans la première partie de cette thèse, nous nous intéressons à deux déterminants importants de l'engagement des pays: l'influence des pairs, à travers le chapitre 3, et la tenue d'élections dans le pays, à travers le chapitre 4. Néanmoins, le relatif échec de cette approche descendante à résoudre les problèmes environnementaux globaux a poussé à s'intéresser au rôle de l'approche ascendante. En effet, alors qu'une approche descendante consiste à définir, lors de néegociations internationales, des objectifs qui vont s'imposer à chaque pays, une approche ascendante consiste à partir d'initiatives unilatérales pour aller vers des actions au niveau international.La protection de la biodiversité est un domaine où l'approche ascendante occupe une place prépondérante. Nous avons choisi de nous intéresser à une initiative innovante, l'ICMS-Ecologico. Nous présentons ce mécanisme de transfert fiscal mis en place au Brésil depuis le début des années 1990 dans le chapitre 5, et testons une condition de son efficience dans le chapitre 6. Un résumé des contributions analytiques et méthodologiques, ainsi qu'une discussion des possibles extensions de cette thèse, sont fournis au chapitre 7
The primary approach to dealing with global environmental problems is to conclude international environmental agreements. In this top-down approach, a crucial step is to obtain the participation of countries. This thesis attempts to examine two prominent drivers/obstacles to participation : countries' interactions, in Chapter 3, and national elections, in Chapter 4.Yet, the relative failure of the top-down approach to solve environmental challenges has pushed interest toward bottom-up approaches. While a top-down approach consists in defining targets during multilateral negotiations and in obtaining the agreement of countries to respect these targets, a bottom-up approach begins with a unilateral initiative and moves toward globalsolutions. An environmental issue for which the bottom-up approach plays a crucial role is biodiversity conservation. In Chapter 5, we present the ICMS-Ecologico, an innovative conservation instrument that has been considered to be an interesting tool for the implementation of commitments in international environmental agreements, and, in Chapter 6, we test one condition for its efficiency. We synthesize the analytical and methodological contributions of this thesis and discuss their potential extensions in Chapter 7

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Jamroensan, Aditsuda. "Improving bottom-up and top-down estimates of carbon fluxes in the Midwestern USA." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2530.

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Carbon dioxide (CO2) is the leading contributor to global warming and climate change. The increases in fossil fuel emissions, deforestation, and changes of land use have resulted in increased CO2 levels in the atmosphere from 280 ppm in 1765 to 390 ppm in 2010. Carbon mitigation policies for managing the biosphere to increase net CO2 uptake are dependent upon accurate knowledge of the biosphere fluxes. However, Northern Hemisphere bottom-up and top-down biosphere flux estimates show significant discrepancies, especially in North America. In this study, we design an analysis framework that integrates observations with models with the goal of reducing some of the key uncertainties in estimating CO2 fluxes and concentrations in the Midwest, USA. In this research, the biosphere model, WRF-VPRM model (Ahmadov et al., 2007) is used to simulate CO2 biosphere fluxes and atmospheric CO2 concentrations in the Midwest, USA at high spatial resolution. Reducing uncertainties in the predictions is accomplished by improving the model transport configurations (i.e. the WRF planetary boundary layer (PBL) scheme, the number of vertical layers and the horizontal resolution), utilizing a more detailed land cover map, optimizing VPRM photosynthesis and respiratory parameters for major crops (i.e. corn and soybean) against flux towers, and integrating CO2 tall tower observations and model through a top-down data assimilation method to improve the VPRM model parameters and in turn improving the flux and concentration estimates. The WRF-VPRM model configuration with the YonSei University PBL scheme produced the most accurate CO2 concentration predictions at the WBI tower at all three tower levels with the maximum error reduction of 17.1%. Increasing the number of vertical layers improved the CO2 estimates during nighttime and early morning, especially at 30 m, where the error was reduced by a maximum of ~ 20%. The differences in the monthly average net fluxes over the State of Iowa between the high resolution WRF-VPRM model and coarse resolution Carbon Tracker were significant, 71%, 18%, and 62% in June, July, and August, respectively. The fluxes calculated by the VPRM model are primarily dependent on 4 model parameters, half saturation value of photosynthesis (PAR0), light use efficiency (ë), and respiration parameters (á and â). These parameters are specific to vegetation types, regions, and time period. The default settings do not distinguish between corn and soybean, which are major crops in the Midwest and have significant different photosynthesis rates. When corn and soybean are explicitly included in the model, the flux estimate changed by 31.3% at 12 pm and 24.5% at 12 am. Two different methods were used to optimize for the VPRM model parameters which are optimization against Ameriflux NEE and using a top-down variational method. The simulation using optimized parameters from the variational method reduced the error during the daytime from 11.6 ppm to 7.8 ppm. The average fluxes optimized using the variational method changed by 17% and 38.6% at 12 pm and 12 am, respectively. The more accurate VPRM parameters lead to the more accurate biosphere fluxes, which will ease the evaluation of benefits of different carbon mitigation policies.

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Calderwood, Lily. "Top-down and bottom-up tools for integrated pest management in Northeastern hop production." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/328.

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The demand for locally sourced hops from Northeastern microbreweries began the recent resurgence in local hop production. The farming community has increased acreage and improved the quality of hops grown and processed in the Northeast region over the past five years. There was a sharp increase in the number of Northeast hop producers from six in 2009 to over 175 in 2014. Hop growers in the Northeast are new to the crop and have limited experience with pest identification and management. This dissertation encompasses three research projects that were conducted over the 2012-2014 growing seasons. These projects were the first critical steps taken to develop arthropod integrated pest management (IPM) tactics for Northeastern hop growers. First, the arthropod community in seven Vermont hop yards was evaluated. The objectives of Chapter 2 are to 1) present current hop pest biology and management strategies, 2) report the phenology of arthropod pests observed over three growing seasons, 3) report abundance and peak date for each pest, and 4) document natural enemy abundance in Vermont hop yards. The survey indicates that in cool, wet seasons hop aphid (Phorodon humuli Schrank) is expected to be a pest of concern. Two-spotted spider mite (Tetranychus urticae Koch) is expected to be a pest of concern in hot, dry conditions. Potato leafhopper (Empoasca fabae Harris) is an unpredictable pest of special concern for first year hop plants. When hop aphid or potato leafhopper are sprayed for with broad-spectrum insecticide, two-spotted spider mite secondary outbreak can be expected. Second, the abundance of major arthropod pests and their natural enemy groups were evaluated under drive row flowering cover crop treatments. The objectives of this study were to 1) measure the effect of cover crops on natural enemy group abundance, 2) measure the effect of cover crops on the three major Northeastern hop pests, and 3) measure the effect of cover crop presence on hop yield and quality. Natural enemy groups and pests were positively correlated yet cover crop treatments had no significant effect on natural enemy abundance. Red clover cover crop treatments served as a trap crop for potato leafhopper. No significant difference in hop yield or quality was observed between flowering cover crop treatments. Finally, potato leafhopper is a documented but understudied regional pest of hops. The objectives of this study were to 1) measure the physiological response of eight hop cultivars to adult potato leafhopper feeding and 2) measure hop leaf recovery from potato leafhopper injury. Gas exchange (net photosynthesis and transpiration) and chlorophyll content were measured to quantify injury by adult potato leafhopper to first year hop leaves in field and greenhouse studies. Cultivars did not vary significantly in their physiological response to potato leafhopper feeding. Injury significantly reduced gas exchange measures in the field (P < 0.05) and greenhouse (P < 0.05) and when leafhoppers were removed, gas exchange was restored.

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McHardy, Robin G. "Bottom-up or top-down, a comparison of two methods for teaching a motor skill." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0004/MQ42665.pdf.

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Trinko, Tara Rae. "Bottom-Up and Top-Down Controls on Algal Bloom Frequency in Two Shallow Mesotrophic Lakes." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/TrinkoTR2008.pdf.

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Bahrami, Balani Alex. "Top-down and bottom-up modulation of selective attention and the role of working memory." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.532266.

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Pearson, Anthony Craig. "Nanoscale Surface Patterning and Applications: Using Top-Down Patterning Methods to Aid Bottom-Up Fabrication." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3757.

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Bottom-up self-assembly can be used to create structures with sub-20 nm feature sizes or materials with advanced electrical properties. Here I demonstrate processes to enable such self-assembling systems including block copolymers and DNA origami, to be integrated into nanoelectronic devices. Additionally, I present a method which utilizes the high stability and electrical conductivity of graphene, which is a material formed using a bottom-up growth process, to create archival data storage devices. Specifically, I show a technique using block copolymer micelle lithography to fabricate arrays of 5 nm gold nanoparticles, which are chemically modified with a single-stranded DNA molecule and used to chemically attach DNA origami to a surface. Next, I demonstrate a method using electron beam lithography to control location of nanoparticles templated by block copolymer micelles, which can be used to enable precise position of DNA origami on a surface. To allow fabrication of conductive structures from a DNA origami template, I show a method using site-specific attachment of gold nanoparticles to and a subsequent metallization step to form continuous nanowires. Next, I demonstrate a long-term data storage method using nanoscale graphene fuses. Top-down electron beam lithography was used to pattern atomically thin sheets of graphene into nanofuses. To program the fuses, graphene is oxidized as the temperature of the fuse is raised via joule heating under a sufficiently high applied voltage. Finally, I investigate the effect of the fuse geometry and the electrical and thermal properties of the fuse material on the programming requirements of nanoscale fuses. Programming voltages and expected fuse temperatures obtained from finite element analysis simulations and a simple analytical model were compared with fuses fabricated from tellurium, a tellurium alloy, and tungsten.

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Bishop, Wilsie. "Integrating IPE into an Academic Health Sciences Center: A Bottom-Up and Top-Down Approach." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/ijhse/vol3/iss2/2.

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Best, Lawrence L. (Lawrence Lee). "Institutions which promote social services integration : an analysis of top-down vs. bottom-up approaches." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/54430.

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45

Dittrich, Ruth. "Top-down and bottom-up decision-making for climate change adaptation : an application to flooding." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/28676.

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There is strong scientific consensus on the evidence of anthropogenic climate change which will increasingly present social, economic and institutional challenges. The Fifth Assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) established that ‘human influence on the climate system is clear’ and that ‘changes in many extreme weather and climate events have been observed since about 1950’ (IPCC 2014a). Associated impacts include sea level rise and increased likelihood of extreme weather worldwide such extreme rainfall, heat waves, hurricanes and tornados (IPCC 2014a; Klijn et al. 2015). Climate change adaptation is the adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects in order to minimise the impacts and to take advantage of new opportunities (IPCC 2007). Many vulnerable countries, regions and cities have accepted that some form of adaptation is inevitable (Swart et al. 2014). This thesis contributes to the research on decision-making for climate change adaptation in order to reduce vulnerability. Both bottom-up and top-down analyses are applied to complement one another with an application to flooding. Flood risk is expected to increase in the UK under climate change (Alfieri et al. 2016; Scottish Government 2016) associated significant economic damage (CEA 2007). From a top-down perspective, the thesis explores how to enhance economic decision-making under climate change uncertainty. In a situation of uncertainty the costs may be clear and immediate whereas the benefits are uncertain and often only realised in the distant future. This impedes the use of standard decision-making tools such as cost-benefit analysis that rely on the quantification of (expected) costs and benefits. The thesis begins on the macro scale with a taxonomy of economic decision-making tools for climate change adaptation, discusses the sector level and subsequently proceeds to the case study micro-scale with applications of adaptation decision-making. First, the potential of alternative decision-making tools, so-called robust decision-making approaches, is examined. The strengths and weaknesses of these tools relative to traditional decision-making processes such as CBA are explored and their future potential in the adaptation process evaluated. It is found that robust decision-making tools under uncertainty provide performance across a range of climate change scenarios, but they may yield lower overall performance if compared with the alternative strategy under the actual climate outturn. Furthermore, they are resource intense and decision makers need to balance the resources required for employing the methods with the added value they can offer. A flow-chart is developed to provide guidance on which decision-making tool should be applied depending on the scale and type of adaptation project. On the sector level, the economic appraisal of adaptation options for agriculture is explored. Agriculture is particularly vulnerable to climate change due to the direct impacts of weather and climate on agricultural output and the sector plays an indispensable role in providing (and improving) food security as well as creating employment. Many of the adaptation options in agriculture involve short-term managerial changes and can be appraised with standard economic decision-making and the options can be carried out after the climate signal has been observed. For those adaptations that do require a longer time to take effect or are long-lived and are (partly) irreversible in nature, robust approaches have a valuable role to play in decision-making. Suggestions are made regarding how robust decisionmaking tools under uncertainty can be practically applied to adaptations in agriculture, outlining the data needs and the steps of the data analysis for three different applications. On the micro level, for a case study in the Eddleston Water catchment in the Scottish borders, UK, two different economic appraisal tools are applied. These include a cost-benefit analysis of afforestation as a flood management measure under different climate change scenarios which can provide important insights for adaptation decisions when robust decision-making tools under uncertainty are not feasible due to resource constraints. It is found that the flood risk under climate change increases substantially in the case study area which needs to be taken into consideration for economic appraisal. The results of the CBA reveal that all modelled scenarios of afforestation have positive NPVs which are driven by further eco-system services (including climate regulation, water quality and recreation) rather than flood regulation benefits. It is concluded that eco-system services beyond flood regulation should be considered for the appraisal of NFM to enable policy-makers to make informed decisions. Second, the Expected values can be used in situations of quantifiable uncertainty, i.e risk. But for climate change we do not have a strong methodology to assess these subjective probabilities. They cannot be fully based on the past, because climate change is a new process for which we have no historical equivalent. Models share common flaws in their assumptions and their dispersion in results cannot be used to assess the real uncertainty (Hallegatte, 2012). The term deep uncertainty (Lempert et al., 2003) or severe uncertainty is used (Ben-Haim, 2006) in these contexts. Such uncertainty is characterised as a condition where decision makers do not know or cannot agree upon a model that adequately describes cause and effect or its key parameters (Walker et al., 2012). This leads to a situation where it is not possible to say with confidence whether one future state of the world is more plausible than another. The robust decision-making tool under uncertainty real option analysis is applied to the same case study to allow for adjusting adaptation options over time by integrating lessons learned about climate change in the appraisal process. A simplified ROA is presented to minimise the life cycle cost of a system that aims to prevent flooding of a return period of 1/20 using tools which should be available to most public authorities. This includes the use of UKCP09 climate data, analysis of changes of peak flow under the measure implemented, cost structures for the measure and damage cost under different outcomes. The analysis can be carried out in an excel spread sheet with the aforementioned types of input. The results of the analysis demonstrate that the obtained strategy is significantly cheaper than planting for the worst case scenario and presents the potential for learning under climate change uncertainty as a way to allocate resources in a more efficient way. The complementing bottom up approach investigates behavioural barriers to decisionmaking for adaptation. Standard economic theory tells us that self-interest will motivate most actors to engage in efficient private adaptation as long as the costs do not exceed the benefits. Thus, we would expect households at flood risk to invest in flood adaptation measures. However, it has been observed that households do not necessarily take action to protect themselves and their assets from flooding. In a study carried out in co-operation with 36 communities around Scotland, protection motivation theory is used to explain the uptake of household flood protection and whether community led flood action groups can increase uptake. It is found that flood action groups directly and indirectly influence the uptake of some flood protection measures positively in particular if tailored information is provided. Overall, it is concluded that both top-down and bottom-up approaches play an important role to move towards an economically efficient adaptation in the context of flooding.
From a top-down perspective, uncertainty should be explicitly acknowledged and included in economic decision-making for adaptation (to flooding) to make an informed decision. The type of analysis will depend on the adaptation project and resources at hand. Developing and fostering bottom-up tools such as flood action groups to increase the uptake of the type of household flood protection with a benefit-cost ratio above 1 may also contribute towards the more efficient allocation of resources.

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Martin, Christel. "Développement, par une approche mixte top-down / bottom-up, de dispositifs planaires pour la nanoélectronique." Toulouse, INSA, 2005. http://www.theses.fr/2005ISAT0020.

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Le travail présenté est une contribution au développement de dispositifs pour la nanoélectronique en associant les techniques de fabrication top-down et bottom-up. Notre choix s'est porté sur l'intégration de nano-objets (réseau 3D ou 2D ou bien objet unique) dans un dispositif à géométrique planaire composé de deux électrodes séparées par un intervalle nanométrique. Nous présentons tout d'abord les différents procédés technologiques (basé principalement sur la lithographie électronique) utilisés pour la fabrication de nanoélectrodes métalliques (or) ou métalliques magnétiques (cobalt) sur un substrat de SiO2/Si. Puis, nous montrons qu'il est ensuite possible de contrôler localement le dépôt d'une monocouche auto-organisée de silane (Octadécyltriméthoxysilane), destinée à favoriser l'adsorption de manière contrôlée et dirigée de nano-objets, en combinant la nano-impression et un dépôt chimique en phase vapeur. Pour finir, nous présentons les premiers résultats de réalisation du dispositif complet et ses premières caractéristiques
The work presented is a contribution to the development of nanoelectronic devices by combining the top-down and bottom-up approaches. Our aim is the integration of nano-objects (3D or 2D arrays or single objects) into a device of planar geometry composed of two electrodes separated by a nanometric gap. First of all, we present the various technological processes (based mainly on Electron Beam Lithography) used for the fabrication of metallic (Gold) or magnetic (Co) nanoelectrodes on a SiO2/Si substrate. Then, we show that it is possible to locally control the deposition of a self-organized silane (Octadecyltrimethoxysilane) monolayer, intended to support the adsorption of nano-objects in a controlled and directed way, by combining NanoImprint Lithography and Chemical Vapour Deposition. Finally, we present preliminary results of the fabrication of the complete device and its characteristics

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Wei, Hongguo. "Top-down and Bottom-up Effects: An Examination of Relational Compassion in Leader-follower Dyads." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491559697964869.

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Lueken, U., B. Straube, I. Reinhardt, N. I. Maslowski, H. U. Wittchen, A. Ströhle, A. Wittmann, et al. "Altered top-down and bottom-up processing of fear conditioning in panic disorder with agoraphobia." Cambridge University Press, 2014. https://tud.qucosa.de/id/qucosa%3A39007.

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Background: Although several neurophysiological models have been proposed for panic disorder with agoraphobia (PD/AG), there is limited evidence from functional magnetic resonance imaging (fMRI) studies on key neural networks in PD/AG. Fear conditioning has been proposed to represent a central pathway for the development and maintenance of this disorder; however, its neural substrates remain elusive. The present study aimed to investigate the neural correlates of fear conditioning in PD/AG patients. Method: The blood oxygen level-dependent (BOLD) response was measured using fMRI during a fear conditioning task. Indicators of differential conditioning, simple conditioning and safety signal processing were investigated in 60 PD/AG patients and 60 matched healthy controls. Results: Differential conditioning was associated with enhanced activation of the bilateral dorsal inferior frontal gyrus (IFG) whereas simple conditioning and safety signal processing were related to increased midbrain activation in PD/AG patients versus controls. Anxiety sensitivity was associated positively with the magnitude of midbrain activation. Conclusions: The results suggest changes in top-down and bottom-up processes during fear conditioning in PD/AG that can be interpreted within a neural framework of defensive reactions mediating threat through distal (forebrain) versus proximal (midbrain) brain structures. Evidence is accumulating that this network plays a key role in the aetiopathogenesis of panic disorder.

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Adel, Enayatulla. "Democracy Promotion in Afghanistan : The top-down or bottom-up approaches of EU or US." Thesis, Södertörns högskola, Institutionen för samhällsvetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-30455.

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Democracy promotion is a key objective in both US and EU foreign development policy. The study attempts to provide a better understanding of both actors democracy promotion in Afghanistan. The US and the EU are perceived to have different approaches regarding democracy promotion. Therefor the study examines if US used top-down and EU bottom-up approaches respective coercive and persuasive methods. Approaches used by actors are examined in the study regarding democracy promotion in the case of Afghanistan. It is a case study with qualitative text analysis and the theories used are top-down and bottom up channels of democracy, and persuasive and stick methods. The survey has looked at the both actors’ commitment in Afghanistan during period of 2001-2014. The result shows that the US and EU have more similarities than differences in the case of Afghanistan and actors have combined both top-down and bottom-approaches in promotion of democracy and focused on cooperation and partnership.

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Van, Zyl Hannes. "A pre-money valuation of a hi-tech start-up, utilising both top-down and bottom-up valuation approaches." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/6435.

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