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1
Ferguson, Andrew Neil. "Production mechanisms of intense events." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/58204/.
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The Restricted Euler equations, taken from the Vieillefosse model for the velocity gradient tensor, are re-investigated using data from direct numerical simulations of an intense event, rather than using data from forced simulations of homogeneous, isotropic turbulence. The goal is to develop ideas for extensions to turbulence models based on the RE equations that can handle these intense events. With this goal in mind, the new numerical data is compared against the evolution of the RE equations towards a finite time limit and its predictions on how ratios of the RE moments converge. The analysis starts by looking at distributions of the invariants in the R-Q phase space. From this, the analysis then compares the Vieillefosse equations to the full equations and notes that there is a significant change in behaviour around t = 0:5. It is suggested that this is associated with a change in ow topology due to the reconnection of vortex tubes in the flow field. To build a higher-order model, more terms from the full RE equations should be used, which is investigated by looking at the co-evolution of the second invariant Q and the third-order moments, Rw and Rs.
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Khouja, Ahmad Yassin. "Mechanisms of prostanoid production : regulation of phospholipase activity." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335838.
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Wales, Shea B. "MECHANISMS UNDERLYING PRODUCTION STABILITY IN TEMPERATE DECIDUOUS FORESTS." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5803.
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A persistent and reliable future terrestrial carbon (C) sink will depend on how stable forest production is under more variable climate conditions. We examined how age, forest structure, and disturbance history relate to the interannual variability of above-ground wood net primary production (NPPw). Our site in northern Michigan spans two experimental forest chronosequences and three late successional stands; the chronosequences have distinct disturbance histories, originating following either clear cut harvesting (“Cut Only”) or clear cut harvesting and fire (“Cut and Burn”), and range from 21 to 108 years old. Annual NPPw was estimated using dendrochronology and site specific allometric equations. We used a portable canopy LiDAR (PCL) system to derive canopy rugosity, a measure of the variability and heterogeneity of vertical and horizontal leaf arrangement, to quantify plot level canopy complexity. Counter to our hypothesis, we found that NPPw stability was greatest in the most frequently disturbed, Cut and Burn stands and lowest in less recently disturbed, late successional forest communities. Opposing trends in chronosequence interannual variation of NPPw indicated that stand age and canopy complexity are not consistently related to production stability. Furthermore, sub-canopy leaf trait properties and breadth were not, as hypothesized, correlated with canopy complexity or NPPw stability. Our mixed findings suggest that multiple factors, including stand age and disturbance history, interact to influence NPPw stability, but also highlight an unexpected dichotomy in which disturbance legacies at our site negatively impact the long-term trajectory of annual forest NPPw, but enhance its interannual stability.
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Humphreys, Gina F. "Linking sentence production and comprehension : the neural mechanisms underlying production and comprehension control processes." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3780/.
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This thesis investigated the relationship between sentence production and comprehension. A combination of behavioural and neuroimaging techniques were used to examine the extent to which sentence production and comprehension engage common or distinct mechanisms, with specific focus on the processes engaged by semantic/syntactic competition. Behavioural studies in Chapter 2 indicated that high-competition cases were more difficult to understand and produce than low-competition cases, and that difficulty varied as a function of the number of alternative associations entertained during performance in both tasks. In Chapter 3, an fMRI study indicated that production and comprehension shared a common competition mechanism within left inferior frontal gyrus (LIFG). However, they engage distinctive networks that interact with LIFG, with production eliciting a larger network including areas involved in sentence planning and memory retrieval. Further asymmetries across tasks were revealed in Chapter 4, in which behavioural results and neural networks were compared across adults and adolescents. This study also demonstrated the occurrence of shifts in the neural networks involved in competition resolution throughout development, thereby providing a strong link between poor behavioural performance and the underdevelopment of pre-frontal inhibitory mechanisms in adolescents. Chapter 5 used an improved experimental paradigm from that in Chapters 3 and 4. The results showed that production elicits more activity than comprehension in the dorsal language route thus confirming the engagement of task-specific control processes. Interestingly, this study also revealed a common area of LIFG involved in both tasks, but also differences within LIFG, suggesting the possibility of task-specific circuitry. Together, the findings suggest that production and comprehension share fronto-temporal areas that store and manage abstract linguistic associations between words and structures. However, they differ in the manner in which linguistic information is used, as is evident by the recruitment of distinct networks. Implications for models of language processing are discussed.
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Branzi, Francesca Martina 1984. "The mechanisms and the scope of bilingual language production." Doctoral thesis, Universitat Pompeu Fabra, 2014. http://hdl.handle.net/10803/316582.
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When bilinguals plan to speak even one word, lexicalization processes of the two languages becomes concurrently activated. Surprisingly, bilingual speech production is not dramatically affected. This observation raises the questions about the control mechanisms that ensure lexicalization in the intended language and their representational scope.
The aim of this dissertation was to increment the general knowledge on these two aspects of bilingual language control. To do so, we measured behavioral, electrophysiological, and neural responses in language switching tasks to investigate the mechanisms and the scope of bilingual language control. Moreover, we measured behavioral and neural responses in linguistic and non-linguistic switching tasks to explore the overlap between bilingual language control and domain-general executive control.
The most consistent findings of this dissertation suggest that the mechanisms of bilingual language control are different from domain-general inhibitory control and that they are applied globally on the dominant language and likely also locally on the non-dominant language.
The evidence presented in the current dissertation not only extends previous knowledge on bilingual language control, but it also provides a clearer understanding of the role of inhibitory control in switching tasks, an information relevant for any model of bilingual language control.En el momento que los bilingües planean hablar, incluso si es sólo una palabra, los procesos de lexicalización se activan simultáneamente en ambas las lenguas. Sorprendentemente, la producción del habla bilingüe no se ve afectada de forma significativa. Esta observación plantea preguntas acerca de los mecanismos de control que garantizan la lexicalización en la lengua deseada así como su alcance. Esta tesis tiene como objetivo incrementar el conocimiento general sobre estos dos aspectos de control lingüístico en los bilingües. Para ello, en diferentes experimentos se midieron respuestas conductuales, electrofisiológicas y neuronales en tareas de cambio lingüísticas para investigar los mecanismos y el alcance del control de las lenguas. Además, se midieron las respuestas conductuales y neuronales en tareas de cambio lingüísticas y no lingüísticas para explorar el solapamiento entre el control lingüístico y el control ejecutivo de dominio general. Los hallazgos más consistentes de esta tesis sugieren que los mecanismos de control lingüístico en los bilingües son diferentes de control inhibitorio de dominio general y que se aplican a nivel global en la lengua dominante y probablemente también a nivel local en la lengua no dominante. La evidencia aportada en esta tesis no sólo extiende el conocimiento previo sobre el control lingüístico en los bilingües, sino que además proporciona una comprensión más clara sobre el papel del control inhibitorio en las tareas de cambio, una información relevante para cualquier modelo de control lingüístico bilingüe.
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Loubser, Max. "Organisational mechanisms in peer production : the Case of Wikipedia." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522764.
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Rafiei, Rezvan. "Production planning mechanisms in demand-driven wood remanufacturing industry." Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25316.
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L'objectif principal de cette thèse est d'étudier le problème de planification de la production dans le contexte d'une demande incertaine, d’un niveau de service variable et d’approvisionnements incontrôlables dans une usine de seconde transformation du bois. Les activités de planification et de contrôle de production sont des tâches intrinsèquement complexes et difficiles pour les entreprises de seconde transformation du bois. La complexité vient de certaines caractéristiques intrinsèques de cette industrie, comme la co-production, les procédés alternatifs divergents, les systèmes de production sur commande (make-to-order), des temps de setup variables et une offre incontrôlable. La première partie de cette thèse propose une plate-forme d'optimisation/simulation permettant de prendre des décisions concernant le choix d'une politique de planification de la production, pour traiter rapidement les demandes incertaines, tout en tenant compte des caractéristiques complexes de l'industrie de la seconde transformation du bois. À cet effet, une stratégie de re-planification périodique basée sur un horizon roulant est utilisée et validée par un modèle de simulation utilisant des données réelles provenant d'un partenaire industriel. Dans la deuxième partie de cette thèse, une méthode de gestion des stocks de sécurité dynamique est proposée afin de mieux gérer le niveau de service, qui est contraint par une capacité de production limitée et à la complexité de la gestion des temps de mise en course. Nous avons ainsi développé une approche de re-planification périodique à deux phases, dans laquelle des capacités non-utilisées (dans la première phase) sont attribuées (dans la seconde phase) afin de produire certains produits jugés importants, augmentant ainsi la capacité du système à atteindre le niveau de stock de sécurité. Enfin, dans la troisième partie de la thèse, nous étudions l’impact d’un approvisionnement incontrôlable sur la planification de la production. Différents scénarios d'approvisionnement servent à identifier les seuils critiques dans les variations de l’offre. Le cadre proposé permet aux gestionnaires de comprendre l'impact de politiques d'approvisionnement proposées pour faire face aux incertitudes. Les résultats obtenus à travers les études de cas considérés montrent que les nouvelles approches proposées dans cette thèse constituent des outils pratiques et efficaces pour la planification de production du bois.The main objective of this thesis is to investigate the production planning problem in the context of uncertain demand, variable service level, and uncontrollable supply in a wood remanufacturing mill. Production planning and control activities are complex and represent difficult tasks for wood remanufacturers. The complexity comes from inherent characteristics of the industry such as divergent co-production, alternative processes, make-to-order, short customer lead times, variable setup time, and uncontrollable supply. The first part of this thesis proposes an optimization/simulation platform to make decisions about the selection of a production planning policy to deal swiftly with uncertain demands, under the complex characteristics of the wood remanufacturing industry. For this purpose, a periodic re-planning strategy based on a rolling horizon was used and validated through a simulation model using real data from an industrial partner. The computational results highlighted the significance of using the re-planning model as a practical tool for production planning under unstable demands. In the second part, a dynamic safety stock method was proposed to better manage service level, which was threatened by issues related to limited production capacity and the complexity of setup time. We developed a two-phase periodic re-planning approach whereby idle capacities were allocated to produce more important products thus increasing the realization of safety stock level. Numerical results indicated that the solution of the two-phase method was superior to the initial method in terms of backorder level as well as inventory level. Finally, we studied the impact of uncontrollable supply on demand-driven wood remanufacturing production planning through an optimization and simulation framework. Different supply scenarios were used to identify the safety threshold of supply changes. The proposed framework provided managers with a novel advanced planning approach that allowed understanding the impact of supply policies to deal with uncertainties. In general, the wood products industry offers a rich environment for dealing with uncertainties for which the literature fails to provide efficient solutions. Regarding the results that were obtained through the case studies, we believe that approaches proposed in this thesis can be considered as novel and practical tools for wood remanufacturing production planning.
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Hsiung, Bor-Kai. "COLOR PRODUCTION MECHANISMS IN SPIDERS AND THEIR BIOMIMICRY POTENTIAL." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1497355826810282.
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Coates, Jane [Verfasser]. "Tropospheric Ozone Production Pathways with Detailed Chemical Mechanisms / Jane Coates." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1115184261/34.
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Gorbatai, Andreea. "Social Structure and Mechanisms of Collective Production: Evidence from Wikipedia." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10304.
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In my dissertation I propose three counterintuitive social mechanisms to alleviate the risk that collective production will fail to maintain participant involvement and respond to demand. My first study, based on a panel dataset of edits and views of articles in the English Wikipedia, shows that, although collective production lacks a price-like mechanism to estimate demand for the goods it produces, consumers’ contributions act as such a signal to expert producers. In the second paper I examine the theory that collective production participation is greatest when social norms of collaboration are obeyed. Using a large panel dataset of production networks and normrelated behavior in Wikipedia, I show that social norm infringement is not completely detrimental to participation because norm enforcement increases the likelihood that the beneficiary producer continues participating. In my third paper, I rely on interviews with experienced Wikipedia producers to examine whether producers’ ties to non-participants in collective production increase the likelihood of turnover, and whether producers’ embeddedness in collective production reduces turnover risk. Surprisingly, I find that producers with networks rich in ties to non-producers and with a task-oriented approach to collective production are those least likely to stop participating.
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Pryde, Kenneth Robert. "Understanding the mechanisms of superoxide production by mitochondrial NADH:ubiquinone oxidoreductase." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607725.
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Cox, Amy M. "Functional Gain and Change Mechanisms in Post-Production Complex Systems." Thesis, The George Washington University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10254316.
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This research was motivated by the need for functional change of complex systems in post-production. Through an initial empirical study, this research found pathways to functional change with minimal change to form; thus avoiding the high risk of material change propagation that has been a concern of both the systems engineering and engineering change literature. This study also revealed the relative importance of system users in the post-production change environment. Through a follow-on study of user innovation in this environment this research was able to reveal pathways for change which are underexplored in both the user innovation and flexibility literature.
While not yet a final solution to the motivating problem, this research has revealed levers for change which system users are adept at exploiting. Key amongst the changes employed by user designers is their unconstrained use of themselves (human change) to realize system function and their exploitation of the expansive operational states (operational change) afforded by complex systems. User driven change poses an important source of post-production functional change. This research unpacks user change and sets the stage for further investigation of this source of system changeability.
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de, Bettignies Thibaut. "Sources and supply of kelp detritus : quantifying mechanisms of production." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/564.
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In temperate waters, rocky reefs dominated by extremely productive kelp beds export considerable primary production. Despite the extensive body of work on kelp detritus as a trophic subsidy, many questions remain about the production of this detritus. The aim of this thesis was to determine the rate and mechanisms of kelp detritus production, for Ecklonia radiata, the dominant kelp species in temperate Australia. Most of the work was conducted in Marmion Lagoon located 20 km North of Perth, south-western Western Australia, a region strongly influenced by oceanic swell and winter storms. The study comprised of four major components: the impact of kelp morphology on the drag forces acting on kelp thalli; investigation of wound patterns in kelp tissue and the biomechanical implications for kelp detritus production; the relative contribution of erosion of frond material and dislodgement of whole thalli to detritus production; and the relationship between kelp dislodgement and peak water velocities, implemented with a kelp dislodgement model.
The initial work in chapter 1 revealed that only size (total area), not morphology, was important in determining the drag acting on E. radiata at peak velocities. This implied that at storm velocities the only way drag forces acting on a kelp can be reduced is by a reduction of total thallus area (biomass) and not by modification of thallus shape. These results constituted the first step to build a mechanistic model of kelp dislodgement.
In chapter 2, it is shown that wounds were highly abundant on kelps before peaks in winter storms and that simulated wounds caused significant loss of tissue integrity and strength. Collectively, these findings suggest that accumulation of wounds over summer results in kelp pruning (tissue fragmentation) in early winter. Paradoxically, this may increase kelp survival during winter storms because the biomechanical drag is much lower on small, pruned kelps (lower biomass).
Results presented in chapter 3 indicated that erosion accounted for 80% of the annual detrital production with a pulse in autumn, whereas dislodgement accounted for a smaller and more constant proportion throughout the year. Neither erosion nor dislodgement correlated with increasing water velocity. Instead, the pulse of detrital 4 production coincided with sporogenesis, leading to the hypothesis that weakening of structural tissue through the formation and release of spores made E. radiata more susceptible to wound accumulation (Ch. 2) and erosion.
In chapter 4, results are presented that show no increase in kelp dislodgement with increasing water velocity, except during the most severe storms. The dislodgement model indicated that the seasonal variation in individual kelp biomass, resulting from erosion of frond tissue (Ch. 3), resulted in lower susceptibility to dislodgement (lower biomass) at times of peak water velocities. The benefit of erosion in reducing drag acting on the thallus, as proposed in the previous chapters, was therefore demonstrated by the model.
The commonly accepted model of wave-driven mortality of kelp during storms in winter was refined by the results. The experimental, field sampling and modelling studies have been synthesised into an alternative model of kelp dislodgement, in which kelp beds are in dynamic equilibrium with wave disturbance. This equilibrium is mediated through erosion-driven adjustment of individual kelp biomass in autumnwinter which lowers drag on kelp thalli during the period of peak water velocity. This relationship between erosion and the susceptibility of E. radiata to dislodgement suggests an adaptation of the kelp E. radiata to its environment, critical to kelp survival in one of the most hydrodynamically challenging environment.
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Llort, Jordi Joan. "Bloom phenology, mechanisms and future change in the Southern Ocean." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066064.
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La production primaire (PP) dans l'Océan Austral joue un rôle crucial dans la capacité des océans à absorber le carbon atmosphérique. Elle est caractérisée par une forte limitation en Fer et par un cycle saisonnier très marqué, présentant un bloom planctonique en fin d'hiver, plus ou moins intense selon les régions. Ma thèse est centrée sur la compréhension des mécanismes qui contrôlent ce bloom et sa variabilité, ainsi que sur les éléments, présents et futurs, qui contrôlent son intensité. J'ai abordé le premier aspect (phénologie et mécanismes) en mettant en place une approche mécaniste basée sur une nouvelle configuration du modèle biogéochimique PISCES forcé par un environnement physique 1D idéalisé. Cette méthodologie m'a permis de réconcilier les différentes théories sur la formation des blooms aux hautes-latitudes, d'identifier les spécificités du bloom de l'Océan Austral et de proposer des critères adaptés à sa détection dans les observations. En outre, les résultats de cette étude de modélisation ont été confrontés à ceux issues d'une deuxième approche, basée sur des observations satellitaires, ce qui a permis la localisation géographique des différentes phénologies de bloom que j'ai identifiées dans l'Océan Austral. Pour répondre au deuxième aspect (altération et changements futurs), j'ai également suivi une double approche. J'ai d'abord examiné comment les limitations par la lumière et par le fer se combinent, via la variabilité du cycle saisonnier du mélange vertical, et pilotent ainsi la production primaire dans l'Océan Austral actuel à l'aide de la configuration idéalisée présentée plus haut. Dans un deuxième temps, cette analyse a permis d'aider à l’interprétation des variations de PP observées dans les projections climatiques issues de 8 modèles couplés (CMIP5). L'ensemble de mes résultats permet de mieux comprendre les processus physiques et biologiques qui contrôlent la croissance du phytoplancton dans l'Océan Austral et d'appréhender comment la modification de ces processus peut entraîner des altérations de la PP dans une région clé pour l'évolution future du climatPrimary production (PP) in the Southern Ocean (SO) plays a crucial role on atmospheric carbon uptake. PP in this ocean is highly iron-limited and presents a marked seasonal cycle. Such a seasonal cycle has a strong productive phase in late winter, called bloom, which distribution and intensity is highly variable. My PhD focus on two specific aspects of the PP in the SO: first, the mechanisms that drive such a bloom and its dynamics and, second, the elements able to control the bloom intensity at present and in the future. The first aspect (bloom phenology and mechanisms) was addressed by setting up a mechanistic approach based on a novel model configuration: a complex biogeochemical model (PISCES) forced by a 1D idealised physical framework. This methodology allowed me to conciliate the different bloom formation theories and to identify the SO bloom specificities. Moreover, I proposed how to use different bloom detection criteria to properly identify bloom from observations. Such criteria were then tested in a complementary observation-based approach (with satellite and in-situ data) to characterise different bloom phenologies and its spatial distribution in the SO. The second aspect (bloom intensity and future change) was also addressed by a twofold approach. First, using the 1D model, I studied how seasonal variability of vertical mixing combine light and Fe limitation to drive PP. Secondly, I used such an analysis to interpret PP trends observed in 8 coupled model climatic projections (CMIP5 models). My PhD thesis results allow for a better understanding of the physical and biological processes controlling phytoplankton growth. My conclusions also suggest how an alteration of these processes by Climate Change may influence PP in the whole SO, a key region for future climate evolution
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Chu, Xiaoyong. "Study of new dark matter production mechanisms and their possible signatures." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209421.
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This thesis is devoted to the study of the nature of Dark Matter (DM). To this end we investigate both its generation mechanisms and detection possibilities. We mainly focus on interesting simple models and follow closely experimental constraints, in order to reveal the features of DM as model-independently as possible.Throughout the whole thesis, we consider the framework of standard cosmology, which is first introduced in Chapter.1 (and supplemented in Appendices). Background knowledges of DM physics from the cosmological and experimental aspects are given in Chapter.2 and Chapter.3, respectively.
Following the scenario that a hidden sector, including DM particles, might decouple from the Standard Model (SM) sector at a very early time of the Universe, we study how through a portal interaction such a hidden sector can be created by the SM sector to yield the proper relic density of dark matter. In Chapter.4 we discuss the case of a massless portal using the gauge kinetic mixing model. It turns out that there are four basic ways to achieve the observed DM relic density for both massless and massive mediator cases: freeze-in from SM sector, reannihilation determined by the balance of the two sectors, freeze-out with hidden or portal interactions. Various models with massive portals, especially $Z'$ and scalar portals, are then explored in Chapter.5. Provided that DM annihilation within the hidden sector is kinetically allowed, similar conclusions would appear. If there is no hidden annihilation for DM, only the first and last ways are allowed. Nevertheless, chemical thermalization in hidden sector can still influence the results significantly.
In Chapter.6, we explore the hypothesis that dark matter particles partially annihilate to photons via a new heavy charged particle which is also "gauged" under SU(3)_C. By applying this hypothesis to the claimed
Fermi-LAT 130 GeV gamma line, it is showed that the correct dark matter relic density could be naturally obtained from the gluon channel and how for such a class of models the cosmic antiproton, diffuse gamma-ray, direct detection and LHC constraints
are fully correlated.
In Chapter.8, concluding remarks and perspectives for future DM research are presented.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Theyab, Muhammad Ali. "Study of fluid flow assurance in hydrocarbon production : investigation wax mechanisms." Thesis, London South Bank University, 2017. http://researchopen.lsbu.ac.uk/2061/.
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The current work is a study of wax deposition, a phenomenon that is one of the main flow assurance problems faced by the oil industry, affecting numerous oil companies around the world. Wax deposition can result in the restriction of crude oil flow in the pipeline, creating pressure abnormalities and causing an artificial blockage that can lead to reduced or interrupted production. Wax can precipitate as a solid phase on the pipe wall when its temperature drops below the wax appearance temperature (WAT). The aim of this research is to study in a lab rig the influence of some of the factors that control and affect the wax deposition process, such as pipe wall temperature (inlet coolant temperature), flow rate, pressure drop, oil temperature, shear stress, recirculation time of crude oil and viscosity. It aims to study the chemical and mechanical methods of inhibiting wax deposition in pipelines. The work also aims to simulate the multiphase flow process in the rig for this study. A new experimental flow loop system was built in the lab to study the variation of wax deposition under single-phase transport through a pipe. A series of experiments were carried out for varying inlet coolant temperatures, flow rates and run times, while the pressure drop was monitored to evaluate the effect of chemical inhibitors and to evaluate the effect of spiral flow on wax deposition. Multiphase flow numerical simulations were undertaken using OLGA software in order to study the effect of the factors that control the wax deposition. Use of mixtures of inhibitors was evaluated, considering their effects on the rheological behaviour of the crude oil. The experimental results show that there is a direct relation between the deposition time, pressure drop and wax deposit thickness, which is also highly dependent on the temperature. The wax deposit increases as the inlet coolant temperature decreases, even if the oil temperature exceeds the WAT, resulting in a larger pressure drop. The wax inhibition percentage was the highest using a combination of spiral flow with the inhibitor polyacrylate polymer (C16-C22) due to the synergy effect of high shear stress and the effect of an inhibitor that interferes with wax crystal growth. Three different mixtures of inhibitors were prepared in this work depending to the inhibitors that provide the greatest reduction in wax deposition; the mixtures of inhibitors presented a high reduction in crude oil viscosity, even at lower temperatures, due to interfere with wax molecules and prevent the growth processes. The findings of the numerical simulation, using a simulator to reproduce the experimental results by tuning analogical properties (assumptions), show agreement with the experimental results. This study presents the spiral flow and the combination of spiral flow with the inhibitor polyacrylate polymer (C16-C22) as efficient mitigation methods to prevent or reduce wax deposition in hydrocarbon pipelines.
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Pedras, Maria Inês Machado. "Investigation of the regulation mechanisms for bioplastics production from industrial residues." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10863.
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Dissertação para obtenção do Grau de Mestre em
BiotecnologiaThe current high demand for plastics has become unsustainable. Polyhydroxyalkanoates are biopolymers stored by bacteria that can potentially replace modern plastics due to: wide range of applications; biodegradability; use of renewable resources as feedstock. High costs of current Polyhydroxyalkanoates production can be reduced using mixed cultures of organisms. Activated sludge from wastewater treatment plants is selected for Polyhydroxyalkanoates production through the imposition of cycles of intermittent feeding. In this study, the acclimation of activated sludge using synthetic volatile fatty acids (VFAs) as substrate resulted in a culture rich in Paracoccus spp. and unidentified filamentous bacteria. Low cost substrates such as sugarcane molasses (SM) or cheese whey (CW) can be employed as feedstock for further cost reduction. This requires an additional step before the microbial selection to ferment the feedstock into VFAs. In this work, the feedstock was changed from SM to CW. The population fed with SM was rich in Actinomycetaceae, while the population fed with CW was rich in Streptococcaceae, affecting the VFA composition. Consequently, the PHA-storing population and the polymer were affected. In the fermented SM (fSM) phase, the population was rich in Azoarcus (41.5 - 64.6%) and in the fCW phase the population was more diverse. Changing the pH in the fermentation reactor also affected the selection stage with an increase in Thauera and Azoarcus and a decrease in Paracoccus. A significant unidentified population of one layer sheet- forming bacteria was observed. Lastly, the occurrence of cell-to-cell communication (QS) in the selection stage was investigated. Possibly, QS molecules were detected when the carbon source was depleted. All steps of polyhydroxyalkanoate production are interconnected and for optimization, all stages must be studied and improved. Moreover, if QS proves to be involved in polyhydroxyalkanoate storage, the addition of QS molecules to the process may be explored for further optimization.
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Kearney-Fischer, Martin A. "The Noise Signature and Production Mechanisms of Excited High Speed Jets." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1318961517.
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Eduafo, Augusta K. "Mechanisms of Hyperglycemia-Induced ROS Production in Osmotically Swollen Glial Cells." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1433185840.
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Taubert, Christina Maria. "Molecular mechanisms underlying the regulation of interleukin-10 production in macrophages." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10034083/.
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Interleukin (IL)-10 is an immunosuppressive cytokine that plays a crucial role in preventing inflammatory and autoimmune pathology. The dysregulation of IL-10 during infection can lead to either an over-exuberant response damaging the host, or conversely ineffective pathogen clearance. Macrophages are important players in inflammatory responses and produce IL-10 in response to Toll-like receptor (TLR) ligation along with protective pro-inflammatory cytokines. The collective regulation of these cytokines is central to the generation of an effective but balanced immune response. We observed that type I IFN is one factor that leads to differential production of IL-10 and pro-inflammatory cytokines in TLR4 stimulated C57BL/6 and BALB/c macrophages. The effects of type I IFN on pro-inflammatory cytokine production were IL-10 dependent and independent. Hence, we further investigated how type I IFN regulates IL-10 production and showed that type I IFN acts as a transcriptional regulator of Il10 mRNA via activation of ERK1/2, and additionally stabilises Il10 mRNA transcripts in TLR4 stimulated macrophages. Using an assay for transposase-accessible chromatin with high throughput sequencing we further unravelled how type I IFN regulates Il10 transcription. We were able to demonstrate that type I IFN increases chromatin accessibility and augments the recruitment of the transcription factors ATF3 and JUNB to the Il10 locus in macrophages upon LPS stimulation. These findings highlight key pathways responsible for the type I IFN-dependent regulation of IL-10, and may provide valuable information for the development of immunomodulatory treatments of inflammatory diseases.
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Selin, Carrie Lynn. "Regulatory Mechanisms Underlying Biological Control Activity of Pseudomonas chlororaphis PA23." FEMS Microbial Ecology, 2010. http://hdl.handle.net/1993/9144.
Full textAbstract:
Biological control is an intriguing alternative to the use of chemical pesticides as it represents a safer, more environmentally friendly approach to managing plant pathogens. Pseudomonas chlororaphis strain PA23 was isolated from soybean root tips and it was found to be an excellent antagonist of sclerotinia stem rot. Our studies have shown that pyrrolnitrin (PRN) is the key metabolite required for S. sclerotiorum inhibition, while phenazine (PHZ) is important for biofilm establishment. For this reason, research efforts were directed towards elucidating the mechanisms governing PA23-mediated antibiotic production. To determine how these compounds were regulated, QS-deficient strains and an rpoS mutant were generated. The QS-deficient strains no longer inhibited the fungal pathogen S. sclerotiorum in vitro and exhibited reduced PRN, PHZ and protease production. Analysis of transcriptional fusions revealed that RpoS has a positive and negative effect on phzI and phzR, respectively. In a reciprocal manner, RpoS is positively regulated by QS. Characterization of a phzRrpoS double mutant showed reduced antifungal activity as well as PRN and PHZ production, similar to the QS-deficient strains. Furthermore, phzR but not rpoS was able to complement the phzRrpoS double mutant for the aforementioned traits, indicating that the Phz QS system is a central regulator of PA23-mediated antagonism.
GacS/GacA, PsrA, RpoS and the PhzI/PhzR QS are members of a complex regulatory hierarchy that influence secondary metabolite production in PA23. An additional system, termed Rsm, was identified, adding yet another layer of complexity to the regulatory network. The Rsm system in PA23 appears to be comprised of a single small non-coding regulatory RNA termed RsmZ, and two RNA binding proteins RsmA and RsmE. We discovered that the expression of rsmZ, rsmA and rsmE all require GacA. In addition, both PsrA and QS were shown to positively regulate rsmZ transcription.
For rsmE, GacA may indirectly regulate expression through PsrA, RpoS and QS, as all three regulators control rsmE transcription. Furthermore, we believe that the positive effects of PsrA and QS on rsmE transcription are likely mediated through RpoS as only RpoS show direct activation of rsmE in an E. coli background.
22
Jermann, Doris. "Membrane fouling during ultrafiltration for drinking water production : causes, mechanisms and consequences /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17811.
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Jones, Ashley Cameron. "Mechanisms of growth factor-induced lysophosphatidic acid production in ovarian cancer cells." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/a_jones_092506.pdf.
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Farrell, Gayle 1959. "Compensatory mechanisms in aphasia : production of syntactic forms that express thematic roles." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63336.
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Mendoza, Antonio Campos. "Regulatory mechanisms associated with egg production and egg activation in Oreochromis niloticus." Thesis, University of Stirling, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417669.
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SANTOS, JANAINA BARRETO. "EXPERIMENTAL STUDY OF MECHANISMS OF SAND PRODUCTION USING X-RAY COMPUTERIZED TOMOGRAPHY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5345@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRODurante a fase produtiva de um poço de petróleo ou gás, muitas vezes há a produção simultânea de partículas sólidas arrancadas da matriz da rocha reservatório. Este fenômeno recebe o nome de produção de areia. Neste caso as tensões e as condições de fluxo nas vizinhanças do poço são fatores fundamentais para a deflagração do processo. As tensões que se concentram na parede do poço com a perfuração do mesmo, pode ser de tal magnitude que pode causar a perda da coesão entre os grãos e criando , assim , uma região de material granular susceptível ao arraste pelas forças de percolação derivadas do fluxo. Este trabalho visou a realização de ensaios em amostras de arenito Rio Bonito e arenito sintético utilizando a técnica da Tomografia Computadorizada de Raios-X para acompanhamento em tempo real dos ensaios. Os ensaios tiveram por objetivo identificar a pressão de início e o modo de propagação da ruptura da parede da cavidade interna da amostra ensaiada. Estes são estágios iniciais dos processos de produção de areia em rochas. As análises das imagens tomográficas adquiridas durante os ensaios permitiram a visualização de breakouts e arrombamentos dos poços. Estudos mais detalhados possibilitaram estimar a quantidade de areia produzida e reconstruir tridimensionalmente o processo de propagação da ruptura.
During productive phase of the well, manytimes there is simultaneous production of the solid particles detached from matrix of the reservoir rock. This phenomenon receive the name of the sand production. In this case stress and flow conditions around of the well are fundamental factors for deflagration of the process. Stress concentration in the wall of the well lead to the loss of cohesion between grains arising, consequently, a granular material region susceptible for dragging by seepage forces derived from fluid flow. The objective of this work was to perform sand production tests in Rio Bonito and synthetic sandstone samples using real-time X-Ray Computerized Tomography. The tests investigated the initial and the evolution of failure at the cavity wall of samples. These are initial stages of the sand production process. The analysis of the CT-scans obtained during tests allowed the visualization of breakouts and collapses of the wells. From studies more details were possible estimate the sand production and produce 3-D images of the propagation of the failure.
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Yokoyama, Fumiaki. "Studies on Production Mechanisms of Extracellular Membrane Vesicles of Cold-Adapted Bacteria." Kyoto University, 2020. http://hdl.handle.net/2433/253343.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第22507号
農博第2411号
新制||農||1078(附属図書館)
学位論文||R2||N5287(農学部図書室)
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 栗原 達夫, 教授 植田 充美, 教授 山口 信次郎
学位規則第4条第1項該当
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Nomura, Takashi. "Molecular mechanisms and control of cellulose carbonization for efficient production of levoglucosan." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/264675.
Full textAbstract:
京都大学新制・課程博士
博士(エネルギー科学)
甲第23394号
エネ博第421号
新制||エネ||80(附属図書館)
京都大学大学院エネルギー科学研究科エネルギー社会・環境科学専攻
(主査)教授 河本 晴雄, 教授 髙野 俊幸, 准教授 奥村 英之
学位規則第4条第1項該当
Doctor of Energy Science
Kyoto University
DFAM
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Zia, Muhammad Irfan. "Production Control MechanismsComparison using Multi-ObjectiveSimulation Optimization." Thesis, University of Skövde, School of Technology and Society, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-3266.
Full textAbstract:
The choice of an efficient and effective production control mechanism (PCM)along with the appropriate buffer allocation pattern is very important for anyproduction engineer/decision maker when designing a production line in order toattain the required system performance. This project work aims to give an insightwith different PCMs, different buffer allocation patterns and arrangement ofworkers of different capability to help the production engineers/decision makersto select the right mechanism and pattern. This study has been performed withmulti-objective simulation optimisation (MOSO) tool. The result from manyexperiments have shown that the ascending buffer allocation pattern stands outas the prominent choice when the goal was to attain maximum throughput (TP)and simultaneously keeping minimum cycle time (CT) and work in process (WIP).The PCMs and workers imbalance patterns performance is different in differentregions of the Pareto-optimal CT-TP data plots obtained from MOSO so theirselection is depending on the interest of the desired level of throughput togetherwith the limit of cycle time.
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Marjoniemi, K. (Kyösti). "Thermogenic mechanisms during the development of endothermy in juvenile birds." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514265424.
Full textAbstract:
Abstract
The use of regulatory and obligatory heat production mechanisms were
studied in
juvenile birds during the development of endothermy.
The development of shivering thermogenesis was studied in the pectoral and
gastrocnemius muscles of the altricial domestic pigeon and in three precocial
galliforms (Japanese quail, grey partridge and domestic fowl). The development of
shivering was the determinant for the beginning of endothermy. Homeothermy also
necessitated avoidance of excess heat loss by insulation and behavioural
thermoregulation. In the precocial species, shivering thermogenesis was present
in the leg muscles of the youngest age groups (1-2 d) studied. Breast muscles
contributed shivering from the second post-hatching week. In the altricial
pigeons, significant thermogenesis was apparent later than in the precocials, at
the age of 6 d. In contrast to the precocials, the pectoral muscles of the
altricials were the most significant heat production tissues. In newly-hatched
partridges and pigeons, incipient shivering did not result in significant heat
production.
The ability to produce heat in cold by putative nonshivering thermogenesis
was
studied in Japanese quail chicks and domestic ducklings. In both species,
three-week cold acclimation resulted in morphometric and physiological changes,
but there was no clear evidence of nonshivering thermogenesis. The lack of NST
was evident because an increase in shivering amplitude at least in one of the
muscles studied paralleled an increase in oxygen consumption. Consequently,
shivering thermogenesis was probably the only mode of regulatory heat
production.
The amplitudes of shivering EMGs measured during cold exposure were
dependent on
the coexistence of postprandial thermogenesis or exercise. Japanese quail chicks
were able to substitute shivering thermogenesis partially with postprandial heat
production when nourished. Bipedal exercise both inhibited shivering in pectorals
directly via inhibitory neural circuits and stimulated it indirectly via
decreased body temperature. Because of increased heat loss, exercise was not used
as a substitute for shivering.
Shivering is a flexible mode of thermogenesis and its magnitude can be
adjusted
according to the magnitude of obligatory thermogenesis. The adjustment works
towards energy saving by avoidance of the summation of different modes of heat
production. The prerequisite for successful adjustment of shivering is adequate
insulation, whose role in preventing excessive heat loss is pronounced during
exercise. It is concluded that the energetics of posthatching thermoregulation
includes the potential for optimizations in energy use in order to avoid
dissipation of waste energy as heat.
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Kühne, Conny [Verfasser], and K. [Akademischer Betreuer] Böhm. "Incentive Mechanisms and Quality Assurance for Peer Production / Conny Kühne. Betreuer: K. Böhm." Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1088553303/34.
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Chabot, Sophie. "Mechanisms of cytokine production from microglia-T cell interaction, relevance to multiple sclerosis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0014/NQ49486.pdf.
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Chung, Elaine Yee-Lin. "Molecular mechanisms in IL-10 production by macrophages during phagocytosis of apoptotic cells /." Access full-text from WCMC:, 2007. http://proquest.umi.com/pqdweb?did=1296119151&sid=6&Fmt=2&clientId=8424&RQT=309&VName=PQD.
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Pouliot, Dominique. "Pion production mechanisms in a microscopic model of intermediate energy heavy ion collisions." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68244.
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Comparative features of the Cascade Model and the BUU model are presented and followed by a Quantum Theory Derivation of the Vlasov equation. Several modifications are made to the BUU model: the inclusion of a momentum-dependent potential instead of the usual Skyrme potential, the replacement of the "old" detailed balance cross section for delta reabsorption by the Danielewicz cross section, and a proper generation of the $ Delta$ mass, using a Monte-Carlo simulation. The effects of these ingredients on pion yields at beam kinetic energies in the range (0.4 AGeV-1.8 AGeV), and pion energy spectra at 90$ sp circ$ are analyzed. It is found that our numerical simulations agree quite well with experiments, except for pion energy spectra at low pion kinetic energies.
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Woodward, Eleanor. "Mechanisms by which interleukin-4 suppresses inflammatory cytokine production by activated human monocytes." Thesis, Woodward, Eleanor (2011) Mechanisms by which interleukin-4 suppresses inflammatory cytokine production by activated human monocytes. PhD thesis, Murdoch University, 2011. https://researchrepository.murdoch.edu.au/id/eprint/14844/.
Full textAbstract:
Improving understanding of how inflammatory responses by monocytes and macrophages are regulated may aid in the development of more targeted therapies for chronic inflammatory disease. In this thesis the mechanisms by which the cytokine, IL-4, can suppress inflammatory cytokine production by LPS-stimulated human monocytes have been examined.
IL-4 suppressed LPS-induced TNFα transcription, without inhibiting LPS signalling through IκB, the mitogen-activated protein kinase (MAPK) pathways, or LPS-mediated activation of the transcription factor NF-κB. Histone acetylation regulated LPS-induced cytokine production but not the suppression of these cytokines by IL-4. IL-4 induced three molecules with potential anti-inflammatory properties, suppressor of cytokine signalling-1 (SOCS1), peroxisome proliferator-activated receptor gamma (PPARγ) and triggering receptors expressed on myeloid cells-2 (TREM-2), but suppressed LPS-induced TNFα production independently of these molecules.
Targeted gene arrays for Toll-like receptor (TLR) signalling pathways revealed that IL-4 down-regulated mRNA levels of LPS-induced inflammatory cytokines and chemokines, without altering other NF-κB-dependent genes or mRNA levels of TLR-related signalling molecules. Instead, the anti-inflammatory actions of IL-4 may be mediated by up-regulation of an unknown signalling molecule or transcriptional regulator. In LPS-treated monocytes, IL-4 up-regulated mRNA levels for IL-10, receptor-interacting serine-threonine kinase 2 (RIPK2), RP105 and c-Maf. However, the anti-inflammatory actions of IL-4 did not require IL-10 or the kinase activity of RIPK2. While the TLR-homolog, RP105, is likely to negatively regulate LPS responses by monocytes, IL-4 had no effect on cell surface expression of RP105. Additional studies may determine whether c-Maf, a transcription factor which induces IL-10, also regulates the suppression inflammatory cytokine production by IL-4.
This study identified novel candidates induced by IL-4 in LPS-stimulated human monocytes. However, the molecules involved in the regulation by IL-4 of LPS-induced TNFα production were not definitively identified. Further studies may identify the mechanisms by which IL-4 is anti-inflammatory. Ultimately, this research will contribute towards the development of novel therapies for inflammatory disease.
36
Furman, Ivo Oznan. "User generated dissent : a biographic case study of peer production mechanisms on Eksisozluk.com." Thesis, Goldsmiths College (University of London), 2016. http://research.gold.ac.uk/18373/.
Full textAbstract:
In a public sphere wherein corporate monopolies of mass media networks prevail and antidemocratic practices suppressing the freedom of speech are the norm, the widespread adoption of the Internet in Turkey has engendered the emergence of a sphere of dissent wherein participants use social media and Web 2.0 platforms to engage in cyberactivism, participate in networked social movements, and express alternative, non-hegemonic political identities and discourses. Sözlüks, a genre of content hosting platforms that can broadly be described as urban dictionaries, are unique within this ecology insofar as they rely on collaborative mechanisms to produce and organize dissent. Affording the oppurtunity to express oneself to the Turkish-speaking online audience in an anonymous manner, sözlüks have become safe havens for free speech within the context of a country historically known for the censure of the press and the public sphere. Although it has been argued that engagement in spaces similar to sözlüks constitute a form of digital labour, this dissertation argues that participation and the collaborative process found in sözlüks constitutes a unique model of peer production. The commons-based peer-production model used by sözlüks generates a constant steam of publicly accessible and at times, subversive information. User generated dissent explores communal, commons and automated aspects to the peer production mechanisms driving Ekşisözlük, the oldest urban dictionary in Turkish cyberspace in a holistic manner. It attempts to link the model of collaboration found on Ekşisözlük with other studies on different peer production models found elsewhere online. Opting for a mixed methodology that combines ethnographic fieldwork with a sociotechnical systems and Biography of Artefacts (BoA) approach, User generated dissent combines conventional data collection methods with using the Wayback Machine (WM) to build a longitudinal case-study to document the collaborative process that has made Ekşisözlük a unique and influential actor within the ecology of Turkish cyberspace.
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Blackett, Ricardo Corey. "Optimal Synthesis of Planar Five-link Mechanisms for the Production of Nonlinear Mechanical Advantage." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31571.
Full textAbstract:
This thesis presents a technique for the optimal synthesis of planar five-link mechanisms that produce a desired mechanical advantage function over a specified path. Since a five-bar linkage has two degrees of freedom, small deviations from the specified path are possible without significantly altering the mechanical advantage function. The research shows one potential application, the design of strength machines, where it is important to control force while allowing the user freedom of motion.
In the past, closed-form analytical synthesis techniques have been used to design mechanical-advantage-generating linkages. This method is time consuming and case specific. However, optimal synthesis techniques apply to the general case and present a robust solution procedure. This thesis uses the non-linear pattern search technique of Hooke and Jeeves to synthesize five-bar linkages. The search technique matches user strength curves and mechanism resistance curves to produce a five-link mechanism. This mechanism produces the desired mechanical-advantage function and serves as the basis for strength training machines. Unlike analytical synthesis, optimization allows direct incorporation of a greater number of design constraints, thus resulting in solutions that are more practical. The pattern search technique aims to minimize a given objective function that depends primarily on the force generating capabilities and kinematic constraints on of the linkage.Master of Science
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Voyle, Roger Bruce. "Mechanisms of intracellular and extracellular cytokine production from the human leukaemia inhibitory factor gene." Title page, contents and summary only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phv975.pdf.
Full textAbstract:
Addendum attached to back facing leaves. Includes bibliographical references (leaves 172-199). The findings establish leukemia inhibitory factor, and possibly oncostatin M, as new members of a small but growing class of cytokines produced in an intracellularly active form and also suggest that the production of alternate transcripts and intercellularly-retained proteins may be a common and important feature of cytokines of the IL-6 and other families.
39
Eriksson, Anders. "Regulatory mechanisms controlling the production of the virulence determinants in Erwinia carotovora subsp. carotovora /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1998. http://epsilon.slu.se/avh/1998/91-576-5519-7.gif.
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Dickson, Kelly. "Systematic reviews to inform policy : institutional mechanisms and social interactions to support their production." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10054092/.
Full textAbstract:
Background: The last 35 years have seen a proliferation of systematic reviews seeking to synthesise the best available and most relevant evidence to inform policy. In response to a growing interest in the process of generating policy relevant evidence, I conducted further which investigated the perspective of policy makers and academics about producing systematic reviews to inform health systems policymaking. We found that models for producing reviews can be distinguished in terms of their starting point and their purpose. For example, reviews could start with or without a wide agreement about their key concepts and with the purpose of addressing common problems for multiple audience or to inform policy decisions within a specific jurisdiction and timescale (Oliver and Dickson, 2016). As the models were developed in a health systems policy context, the next step was to test their applicability with reviews commissioned in other fields. Aims: This thesis aims to demonstrate, with an analysis of my publications, how my approach to conducting systematic reviews contributes to an understanding of the institutional mechanisms and social interactions required to produce policy-relevant evidence across broader policy areas. Methods: Case example of four reviews were used to explore the utility of models for producing policy relevant reviews. This was achieving by taking an analytical framework of institutional mechanisms previously developed and operationalising the higher order themes into questions to interrogate our approach to producing systematic reviews. This ‘analytical interrogation’ was an iterative and interpretive process which required drawing on our ‘use of self’ to reflexively generate new insights and understanding of producing each review (Finlay and Gough 2008). The focus of our analysis was to explore institutional mechanisms informing review production. These were framed according to themes representing the overlapping social worlds of policy and research: harnessing motivations, engagement between policy and research, and the structures and procedures for producing policy-relevant reviews and their resulting impact. Findings: My analysis in this thesis has contributed to an understanding of producing policy-relevant systematic reviews in several ways. By exploring the literature on this topic I have discovered that while there is research on the barriers to policy research use and mechanisms to increase uptake, an understanding of the process of producing reviews to address the range of policy needs is disparate, cutting across different fields of inquiry (e.g. methods, technology, stakeholder engagement) and is yet to be systematically drawn together. I have attempted to elucidate that producing policy-relevant reviews is both a technical and social enterprise requiring a range of institutional mechanisms and social competencies to navigate the policy-research interface. I have also shown that the production of reviews in broad policy areas has implications for the quality of reviews, which requires addressing the relationship between accountability and ensuring the coherence of the review, alongside the use of rigorous and explicit methods.
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Wagner, Daniel Elger. "Cellular and genetic mechanisms of new tissue production in the regenerating planarian Schmidtea mediterranea." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70394.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references.
Regeneration of missing body parts is biologically fascinating, yet poorly understood. Many instances of regeneration, such as the replacement of amphibian limbs or planarian heads, require both a source for new cellular material as well as mechanisms to specify, differentiate, and pattern the regenerate. The planarian Schmidtea mediterranea is a classic system for studies of regenerative biology in which proliferating cells known as "neoblasts" provide the source of new cellular material for regeneration. Stem cells that might be present within the neoblast population, however, have not yet been defined. Such cells could therefore be either pluripotent or, alternatively, a heterogeneous collection of lineage-restricted cell types. In order to distinguish these models experimentally, methods for clonal analysis were developed here and used to assess descendants of individual neoblasts. Individual cells, termed "Clonogenic Neoblasts" (cNeoblasts) were identified that gave rise to large descendant cell colonies in vivo. Individual cNeoblasts generate descendants spanning multiple germ layers and, in single cell transplantation experiments, all cells of the adult body. These data indicate that adult pluripotent stem cells (cNeoblasts) are the source of new tissue for planarian regeneration. Despite a sequenced genome and the availability of RNAi, the genetic basis for stem cell regulation in Schmidtea mediterranea has remained largely unexplored. Using microarrays, a genome-scale approach was taken to identify and characterize genetic factors specifically expressed in proliferating cells (neoblasts) of adult planarians. Genes identified by microarray were RNAi screened using quantitative assays (developed here) for expansion and differentiation of cNeoblast descendants. Several genes encoding proteins with conserved roles in germ cell biology (e.g. Vasa) and chromatin regulation (e.g. Polycomb proteins Ezh, Sz12, and Eed) were identified as required for proliferative cell expansion and/or differentiation, along with additional genes encoding three zinc finger proteins, two transcription factors, and two candidate RNA-binding proteins. These experiments suggest that cNeoblast regulation involves mechanisms shared with germ cells and embryonic stem cells, and provide a powerful framework for future investigations of planarian stem cell function.
by Daniel Elger Wagner.
Ph.D.
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Kawabata, Kyuichi. "Suppressive effects of citrus constituents on matrix metalloproteinase-7 production and underlying molecular mechanisms." Kyoto University, 2006. http://hdl.handle.net/2433/136506.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第12668号
農博第1591号
新制||農||934(附属図書館)
学位論文||H18||N4194(農学部図書室)
UT51-2006-U373
京都大学大学院農学研究科食品生物科学専攻
(主査)教授 大東 肇, 教授 井上 國世, 教授 河田 照雄
学位規則第4条第1項該当
43
Goult, Tracey Alexandra. "Mechanisms of xanthine oxidoreductase-catalysed production of nitric oxide : enzyme inactivation and clinical relevance." Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425869.
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Alabdullatif, Meshari. "Understanding the Resistance and Virulence Mechanisms of Staphylococcus Epidermidis Triggered During Skin Disinfection, Blood Production and Storage." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38661.
Full textAbstract:
Bacterial contamination of platelet concentrates (PCs) represents the highest post-transfusion infectious risk. The skin flora bacterium Staphylococcus epidermidis has been reported to be the predominant aerobic contaminant of PCs. The Ramirez' group has shown that S. epidermidis can form surface-attached bacterial aggregates known as biofilms, and can outcompete other coagulase-negative staphylococci, such as Staphylococcus capitis, in PCs. The ability of S. epidermidis to form biofilms has been linked to increased pathogenicity and missed detection during PC screening with an automated culture system (BacT/ALERT). This thesis aimed at investigating the proliferative advantage and resistance mechanisms displayed by S. epidermidis in the PC milieu. Furthermore, in an effort to enhance PC safety for transfusion patients, I studied the anti-biofilm properties of essential oils and antimicrobial peptides (AMPs). My studies aimed at improving PC safety by focussing on both the point of introduction of bacterial contaminants (blood collection), and the stage at which bacterial contaminants can form biofilms and proliferate (PC storage). S. epidermidis can be found in the skin of blood donors as biofilms, which are resistant to the blood donor skin disinfectant currently used by Canadian Blood Services, chlorhexidine-gluconate and isopropyl alcohol (CHG-IPA). Here, several plant-extracted essential oils were evaluated for their ability to enhance the anti-biofilm activity of CHG-IPA. Data revealed that the Lavandula multifida oil and its main component (linalool) greatly enhanced the activity of CHG-IPA against S. epidermidis biofilms. Furthermore, the ability of a combination of three synthetic AMPs to inhibit S. epidermidis biofilm formation during PC storage was assessed These results showed that the combination of AMPs could inhibit biofilm formation but was ineffective against pre-formed S. epidermidis biofilms. The accumulation associated protein (Aap) encoded by the aap gene, found in most S. epidermidis strains and absent in S. capitis, plays a role in biofilm formation. When S. epidermidis aap is transformed into S. capitis, this bacterium displayed increased biofilm formation and proliferated to higher concentrations compared to untransformed S. capitis and to a S. epidermidis aap deletion mutant. Based on these results, aap appears to play a role in providing S. epidermidis a proliferative advantage in PCs by enhancing biofilm formation. Lastly, the GraRS system and SepA were studied for their role in S. epidermidis resistance to platelet-derived AMPs using the synthetic AMP PD4 as a model molecule.
Results indicate that the GraS mechanism is involved in resistance towards PD4. The work presented in my thesis provides further insights into why S. epidermidis has a proliferative advantage in the PC storage environment and allows for the proposal of alternative methods to enhance PC safety for transfusion patients.
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Deily, Joshua Allen. "Mechanisms of call recognition in three sympatric species of Neoconocephalus (Orthoptera: Tettigoniidae) asymmetrical interactions and evolutionary implications /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4357.
Full textAbstract:
Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 26, 2007) Vita. Includes bibliographical references.
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Lusted, Roderick M. "Direct observation of oil consumption mechanisms in a production spark ignition engine using fluorescence techniques." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/25851.
Full textAbstract:
The oil consumption characteristics of a four cylinder,
normally aspirated spark-ignition engine were investigated for
different piston ring end-gap configurations. A radiotracer
was used to perform direct measurement of the oil consumption
while Laser-induced Fluorescence (LIF) was used to perform the
oil film thickness measurements for consumption predictions
using the "Puddle Theory of Oil Consumption, " which relates
oil consumption to second land film thickness and reverse flow
through top ring gap. The consumption data was evaluated to
determine the impact of top ring end-gap azimuthal location on
oil consumption. The film thickness data was used to evaluate
the extent to which the Oil Puddle Theory predicts variations
seen in the actual oil consumption.
A tritium radiotracer oil consumption measurement system
with an accuracy of 94.6% was designed and constructed. This
was used to perform direct measurements of the test engine oil
consumption in two different test matrices. The first
evaluated a piston ring configuration with the rings free to
rotate. The second evaluated configurations with the top ring
and second piston rings pinned to fix the azimuthal location
of the end-gap; the azimuth of the top ring was varied. In
the second test matrix, the oil film thickness on the piston's
second land was measured, and predictions were made on the
basis of that measurement
.
The first test matrix results indicated only a weak speed
dependence and a large amount of variability in the oil
consumption measurements.
The second test matrix results showed an oil consumption
speed dependence that was a function of top gap azimuth.
Speed normalized results showed that the oil consumption was
larger when the end-gap was on the thrust side of the test
engine than when on the anti-thrust side. Measured oil consumption differed substantially from that
predicted. This was found to be due to difficulties in
determining effective ring gap flow areas and due to a
previously un-documented azimuthal variation in second land
oil film thickness. However, analysis of the results also
indicates that the Puddle Theory is still a plausible oil
consumption mechanism.
47
Lusted, Roderick M. (Roderick Mark). "Direct observation of oil consumption mechanisms in a production spark ignition engine using fluorenscence techniques." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/38353.
Full textAbstract:
Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994.Includes bibliographical references (leaves 114-115).
by Roderick M. Lusted.
M.S.
Nav.E.
48
Lynch, Galen(Galen Forest). "The distinct neural mechanisms underlying the production of stereotyped and exploratory vocal behavior in songbirds." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129923.
Full textAbstract:
Thesis: Ph. D. in Neuroscience, Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, May, 2020Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 213-232).
Whether it is speaking to one another, or nailing a tennis serve, humans can perform an incredible range of behaviors, most of which are learned. How do we and other animals learn complicated sequential behaviors, and once they are learned how are they executed? This thesis is an investigation into the neural basis of the two modes of behavior that occur at the beginning and end of learning a motor skill: the initially highly variable exploratory behavior, and the ultimately stereotyped skilled performance. To understand the start and end points of learned motor behaviors, I present two studies, each on the premotor activity of ensembles of neurons that underlie song production in zebra finches. Executing learned motor behaviors requires animals to produce precisely timed motor sequences.
While cortical motor regions traditionally have been viewed as encoding features of motor gestures (Georgopoulos et al., 1982), more recent studies have suggested that motor regions may have intrinsic dynamics to pattern the production of motor gestures (Churchland et al., 2012). A similar debate has arisen in songbirds. Adult birdsong requires the premotor nucleus HVC (used as a proper noun), in which projection neurons burst sparsely at stereotyped times in the song. It has been hypothesized that projection neuron bursts, as a population, form a continuous sequence, while a different model of HVC function proposes that HVC activity is tightly organized around motor gestures. Using a large dataset of HVC neurons recorded in singing birds, we test several predictions of these models. We find that projection neuron bursts in adult birds are continuously and nearly uniformly distributed throughout song.
Another model posits that LMAN may act as an excitable media producing locally propagating waves of activity, and predicts that all nearby pairs of neurons would be highly correlated. To test these models and to understand how LMAN actively generates behavioral variability, we built a miniature lightweight microdrive to simultaneously record from multiple neurons, as well as a lightweight endoscope to perform functional calcium imaging of ensembles of LMAN neurons. With these new technologies, we observed the simultaneous activity of pairs of single units in singing juvenile and adult birds. We find that most pairs of neurons with small separation (<250 μm) are completely uncorrelated, which is incompatible with the wave model. However, a small subset of pairs have strikingly large correlations, with correlation coefficients of up to 0.81. Intriguingly, these correlated pairs of neurons can be separated by up to 400 μm.
The existence of such highly correlated neurons within LMAN is inconsistent with LMAN being a simple balanced excitatory-inhibitory network with uniformly random connectivity. These results suggest that new models of variability generation are required to explain how LMAN generates exploratory behavioral variability.
by Galen Lynch.
Ph. D. in Neuroscience
Ph.D.inNeuroscience Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences
49
Ovtchinnikov, Mikhail. "An investigation of ice production mechanisms using a 3-D cloud model with explicit microphysics /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1997.
Find full text
50
Pretto, Paolo. "The perception and production of speed during self-motion: evidence for non-optimal compensation mechanisms." Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3425122.
Full textAbstract:
The thesis describes a series of studies on the perception of speed of self-motion in realistically simulated environments. We carried out several experiments in order to explore from both the behavioral and the perceptual point of view how visual changes in the environment lead to a misperception of self-speed. More specifically, we investigated the issues of image contrast reduction, gaze direction and field-of-view and their influence on the perceived and produced speed of self-motion. Virtual environments technology was employed to display visual motion for both driving and walking speeds. Given the first results obtained from the implementation of a realistic contrast reduction in a driving simulation we formulate the hypothesis that changes in the perceived and produced speed are due to a non-optimal combination of the retinal angular velocities during self-motion. Indeed, the retinal projection of the environment during forward self-motion consists of expanding optic-flow patterns in which the angular velocities of the objects on the scene vary gradually according to their position and speed relatively to the moving observer. Objects very far away appear as moving slowly in the centre of the field-of-view, while the proximal regions appear as moving faster at the periphery of the visual field. The second part of the thesis is then dedicated to a systematic investigation on how the angular velocities from central and peripheral regions of the field-of-view contribute to the generation of the percept of a unique speed of forward translation.
In Chapter 1 we present a brief overview of the principal aspects of visual motion processing. We report some psychophysical and physiological findings that have been produced in the last decades of research, together with some models that try to describe the functional aspects of motion and speed processing. Moreover, we introduce and explain the theme of the visual speed of self-motion. Finally, we describe the technical and methodological tools that have been adopted to implement and execute the experiments of the following chapters.
In Chapter 2 experiments are described in which we address the question how image contrast reduction affects the driving behavior. We put particular emphasis to a naturalistic implementation of contrast reduction, namely fog. We show that a realistically simulated fog causes drivers to reduce the driving speed. We provide experimental evidence that this effect has a perceptual origin, due to the increased perceived speed while driving in fog. The behavioral effect of simulated fog is consistent through different experimental setups. Moreover, we show that the effect of an increased perceived speed is enhanced accordingly to the fog density. We hypothesize an explanation for these results based on the fact that the motion signals within the visual field are selectively masked. In fact, the three-dimensional spatial distribution of the exponential fog model used in our experiments reduces mainly the visibility of the lower velocity signals, situated in the distal region of the environment, centrally in the visual field. Furthermore, we compare the effect of simulated fog to the effect of a type of contrast reduction that attenuates the visibility uniformly all over the visual field, independently of the three-dimensional structure of the environment. We demonstrate that the perception of both the driving and walking speed is independent of a spatially uniform contrast reduction and of the region within the visual field in which this reduction is applied (central or peripheral).
The experiments of Chapter 3 show that during self-motion the estimation of the self-speed relies on retinal angular velocities that are likely to be combined in a non-optimal solution. We provide evidence that the speed estimate is biased towards the available motion signals from the environment, both in the driving and in the walking speeds domain. When the visibility of the central region of the field-of-view is precluded the perceived speed is higher, and conversely, when the peripheral region is not visible, the perceived speed is lower. This suggests that the speed estimation process takes into account the velocity signals from both central and peripheral areas of the visual field. However, we provide also evidence that the central area is necessary and nearly sufficient to build a correct speed estimate, even in large field-of-view virtual environments. Finally, we report also that the speed estimate depends on the gaze direction and can be impaired when the vertical field-of-view is limited.
Summary of the results and general discussion are presented in Chapter 4.