Dissertations / Theses on the topic 'Channelling'
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Ferguson, Dorothy Helen. "Channelling discomfort in learning." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443129.
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Lawton, David Neil. "Electron channelling in varying magnetic potentials." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760810.
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King, Philip J. C. "Crystal defect imaging using transmission ion channelling." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358679.
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Beard, Katherine F. M. "Investigating metabolite channelling in primary plant metabolism." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:8172377f-5eca-4825-b6f1-5c10f02bede5.
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The tricarboxylic acid (TCA) cycle is one of the central pathways in respiration and also plays an important role in a variety of metabolic processes including the synthesis of secondary metabolites and the provision of carbon skeletons for ammonium assimilation and amino acid biosynthesis. Effective regulation of these multiple demands on the TCA cycle is likely to be very important for plant fitness. One way that this regulation could be achieved is through metabolite channelling. This occurs when metabolites are transferred between enzyme active sites without diffusing into the bulk aqueous phase of the cell, and is known to be important in regulating demands in metabolic pathways. Although there is evidence that metabolite channelling exists in animals, there have been no attempts to investigate it in plant. The first aim of this thesis was therefore to investigate whether metabolite channelling exists in the plant TCA cycle. Isotope dilution experiments were developed to investigate metabolite channelling, and were able to show that metabolite channelling was present between certain enzymes of the TCA cycle in both S. tuberosum and A. thaliana mitochondria. The second aim of the thesis was investigate whether metabolite channelling is important in regulating the TCA cycle in plant mitochondria. The pattern of metabolite channelling did not change in mitochondria isolated from the light and the dark, or from mitochondria with increased or decreased TCA cycle rates, but it was not possible to say whether the metabolite channelling altered in a quantitative fashion. Overall the thesis provides the first direct evidence of channelling in the TCA cycle in plants, and further work should help to elucidate what role, if any, it plays.
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Lim, Anthony Craig. "Ion channelling and electronic excitations in silicon." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/29867.
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When a high-energy (MeV) atom or neutron collides with an atom in a solid, a region of radiation damage is formed. The intruding atom may cause a large number of atoms to leave their lattice sites with low energies (keV) in a collision cascade. Alternatively, it may cause a single lattice atom to be removed from its crystal lattice site and travel large distances without undergoing any further atomic collisions/scatterings in a process known as channelling. Any moving atom may lose energy via collisions with other atoms or by the excitation of electrons. The microstructural evolution of the irradiated material depends on the rate at which the damaged region cools, which in turn depends on the rate at which electrons are excited and carry energy away. Since silicon is a semiconductor with a band gap of 1.1 eV, it is normally assumed that the rate of excitation of electrons by atoms with low kinetic energies (< 100 eV) is negligible. However, the atomic kinetic energy threshold required for electronic excitation is not understood. This thesis uses large-scale quantum mechanical simulations to investigate how a moving atom loses energy to the electrons in a crystal of silicon. It is possible to calculate the energy transfer from a channelling atom to the host material's electrons using time-dependent density functional theory (TDDFT) and we have done so. However, these highly accurate calculations are computationally expensive and cannot be used to study very large systems. Hence, we also use a less accurate method called time-dependent tight binding (TDTB). We show that TDTB and TDDFT simulations of channelling in small silicon systems are in good qualitative agreement and use the cheaper TDTB method to investigate finite-size effects. We also investigate how an atom oscillating around its lattice site transfers energy to the crystal's electrons. To understand the complex behaviour of the electronic energy transfer, we utilise non-adiabatic perturbation theory. Our simulations and the perturbative analysis both show that the presence of a gap state with a time-dependent energy eigenvalue allows electronic excitations for very low energy (eV) channelling atoms.
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Kurt, Nilufer, and nilf_k@yahoo com au. "A Study of Channelling Behaviour in Batch Sedimentation." RMIT University. School of Civil and Chemical Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061220.120258.
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Batch sedimentation is a method that enables us to understand the mechanism of compaction and compression of sedimenting slurry. However, batch settling behaviour is a very complex phenomenon that is not easily described fully by a mathematical model. This causes unrealistically large empirical calculations when the thickener size estimations are required. Channelling, reverse concentration gradients and the initial concentration of the slurry have large effects on batch settling. Existing procedures do not provide clear relationships involving these three significant variables. In this study, batch sedimentation phenomena are examined in detail and possible explanations are given to clarify the complex behaviour using recent theories. Modern research has shown that channelling is an unwanted formation because channels can change the concentration at the bottom and top of the bed by carrying a great amount of flocs upwards. Batch sedimentation tests were performed using flocculated slurry of Calcium Carbonate at various initial concentrations such as 250 g/l, 500 g/l, 750 g/l and 1000 g/l to observe channelling and reverse concentration gradients. Flux plots for the batch system reveal behaviour which can be attributed to the upward flow of solids. In addition, photographic methods were used to observe settling processes, channelling mechanisms and flocs in the channels. One of the purposes of this work was to examine the phenomenological solid-liquid separation theory of Buscall and White (1987), which employs the material properties of the local volume fraction, compressive yield stress Py ()ö and hindered settling function R()ö to identify the material behaviour in batch sedimentation. Stepped-pressure filtration and batch settling tests were used to measure the material characteristics for the flocculated CaCO3 suspension. Experimental data were demonstrated using Height versus Time and Height versus Concentration graphs and displayed the possible region of reverse concentration gradients and channelling in the settling bed. Mathematical predictions adopted from Usher (2002) were performed employing material characteristics of the material and graphical documentations were presented. The results of mathematical predictions were compared to the experimental results and the modes of sedimentation explained by Lester et al. (2005). Fundamental theoretical models and experimental observations highlight that the main driving force for channelling is the high-pressure gradient at the bottom of the bed and the most important factors that cause channelling are high initial concentration of slurry and settling time. The predictions also show that the material and flocculant used for the batch settling tests demonstrate important effect on the settling process. The knowledge and information gained from this study is valuable to maximize the thickening process.
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Simmonds, Helen Margaret. "Channelling change : evolution in Guernsey Norman French phonology." Thesis, University of Exeter, 2012. http://hdl.handle.net/10871/9246.
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This thesis examines evolution in the phonology of Guernesiais, the endangered variety of Norman French indigenous to the Channel Island of Guernsey. It identifies ways in which modern Guernesiais phonology differs from previous descriptions of the variety written between 1870 and 2008, and identifies new patterns of phonological variation which correlate with speaker place of origin within the island. This is accomplished through a combination of quantitative and qualitative analyses of a new corpus of speech data. The relationship between the data and other extralinguistic variables such as age and gender is also explored. The Guernsey 2010 corpus was gathered during linguistic interviews held with forty-nine adult native speakers of Guernesiais between July and September 2010. The interviews featured a word list translation task (English > Guernesiais), a series of socio-biographical questions, and a self-assessment questionnaire which sought to elicit information about the participants’ use of Guernesiais as well as their responses to questions relating to language revitalisation issues. The interviews resulted in over 40 hours of recorded material in addition to a bank of written socio-biographical, behavioural and attitudinal data. Analysis of the phonetically transcribed data revealed that a number of phonological features of Guernesiais have evolved, perhaps owing to greater contact with English or through other processes of language change such as levelling. Shifting patterns of diatopic variation indicate that south-western Guernesiais forms are spreading northwards, and this is echoed in the findings of the socio-biographical data. New evidence of diatopic variation in final consonant devoicing and word-final post-obstruent liquid deletion was also found. This thesis concludes that there is still considerable variation in the pronunciation of modern native speakers of Guernesiais, and that this correlates with place of origin within the island. While northern Guernesiais forms have not disappeared entirely, south-western Guernesiais appears set to become the de facto standard for the variety, especially as the political impetus for revitalisation is generated from this area of the island.
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Jones, Darran Dafydd. "Protein-domain interactions and substrate channelling in multienzyme complexes." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621518.
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Gunasekar, Naresh Kumar. "Electron channelling contrast imaging of nitride semiconductor thin films." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18575.
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This work reports on the development of a scanning electron microscopy based technique known as electron channelling contrast imaging for characterising extended defects in nitride semiconductors. Extended defects in nitride semiconductors act as scattering centres for light and charge carriers and thus limit the performance of optoelectronic devices. Developing the capability to rapidly analyse extended defects, namely threading dislocation and stacking fault densities without any sample preparation represents a real step forward in the development of more efficient nitride-based semiconductor devices. In electron channelling contrast imaging, changes in crystallographic orientation, or changes in lattice constant due to local strain, are revealed by changes in grey scale in an image constructed by monitoring the intensity of backscattered electrons as an electron beam is scanned over a suitably oriented sample. Extremely small orientation changes are detectable, enabling small an gle tilt and rotation boundaries and extended defects to be imaged. Images with a resolution of tens of nanometres are obtainable with electron channelling contrast imaging. Vertical threading dislocations are revealed as spots with black-white contrast in electron channelling contrast imaging. A simple geometric procedure was developed which exploits the differences observed in the direction of this black-white contrast for screw, edge, and mixed dislocations for two electron channelling contrast images acquired from two symmetrically equivalent crystal planes. By using this procedure, an order of magnitude reduction in the time required to obtain quantitative information on dislocations is envisaged compared to the presently available techniques. The use of electron channelling contrast imaging to reveal and characterise basal plane stacking faults and partial dislocations in m-InGaN thin films and quantifying threading dislocations in InAlN thin films is also demonstrated. Preliminary work on combining electron channelling contrast imaging and cathodoluminescence imaging has been demonstrated for the first time to understand the effect of threading dislocations on light emission characteristics in nitride semiconductors.
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Roos, Lizelle. "Channelling endogenous knowledge through civil litigation in South Africa." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60088.
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The main aim of this thesis is to expose and address some of the current problems of the civil litigation system with specific reference to the issue of access to justice. I will argue that there is a tension between the ideals strived for by and within the Constitution and how they are realised within the context of access to justice considerations.1
With access to justice I refer to a broader notion of justice. It does not merely entail being able to enter the Courts for purposes of litigation. It also involve an alternative conceptualization of the nature of rights and the attainment and enhancement of such rights by and on behalf of members of the general public. Moving away from a strict contractarian approach where there is a focus on ?just institutions? to what Amartya Sen refers to as the behaviours, freedoms, choices and interactions of people involved in ordering their lives.2 Sen posits this idea of justice as a framework for developing a civil justice system not based only on ?ideal institutions? but also on the facilitated behaviours and interactions of parties in the pursuit of what they deem to be justice.
I am of the opinion that it is this difference of perception with regards to the notion of justice (and by implication access to justice) that is the catalyst behind the tension between the ideals strived for by and within the Constitution on the one hand and how they are realised within the context of access to justice considerations.
In my study I investigate how the utilization of endogenous knowledge could be of value to the civil litigation system in an attempt to alleviate the tension as mentioned above.Dissertation (LLM)--University of Pretoria, 2016.
Jurisprudence
LLM
Unrestricted
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Kuraoka, Hisayo. "Channelling domestic conflict within globalisation : Iran and the search for development." Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403241.
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Chauhan, Hitesh. "Protein-protein interaction and substrate channelling in the pyruvate dehydrogenase complex." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620982.
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Nguyen, Tien Hien. "Channelling investigation of the behaviour of urania under low-energy ion irradiation." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00966967.
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This thesis is dedicated to the investigation of the structural destabilisation of UO2 single crystal. Irradiations with 470-keV Xe, 500-keV Ce and 500-keV La ions (with corresponding ion range of Rp 85 nm and range straggling of Delta Rp _ 40 nm according to SRIM calculation) have been performed to investigate the destabilisation of UO2 single crystals induce by (i) the radiation damage effects due to the nuclear stopping process of a fission fragment at the end of their trajectories (ballistic contribution) and by (ii) the incorporation of a fission product at high concentration (chemical contribution). The energies and masses of bombarding ions were deliberately chosen so that they would have very similar projected range in UO2 in order to compare the effects induced by solubles (La and Ce) versus non soluble Xe species in UO2. Rutherford Backscattering Spectrometry in channelling geometry (RBS/C) was applied to study the defects induced. Channelling data were analysed afterwards by Monte-Carlo simulation with McChasy code assuming a two-class model of defects comprising (i) the randomly displaced atoms (RDA) and the bent channels (BC) defects. The accumulation of RDA with increasing ion fluence leads to a steep increase (build-up of defects) observed from 4 to 7 dpa regardless of nature of ions and a dramatic increase observed from 300 dpa (corresponding to _ 5 at. % of implanted ions) only for Xe irradiated crystal. The difference due to the soluble versus insoluble species was clearly observed. Such a difference was observed via the dramatic increase of RDA when the crystal is implanted at very high concentration only for crystal implanted with insoluble species. Moreover, the difference is also observed via the higher fraction of RDA created in the crystal irradiated with insoluble element. This phenomenon is mostly due to the size of implanted species in the matrix. Insoluble Xe atoms have the atomic radius which is larger than twice the atomic radius of U sub-lattice while soluble La and Ce atoms have the atomic radii of similar size as compared to U atom. Xe creates a much stronger stress field in UO2 crystal in comparison to La or Ce; a higher fraction of RDA is thus created. Conversely, the accumulation of BC with increasing ion fluence leads to very similar evolution versus ion fluence in all crystals implanted with the three elements . A regular increase of BC versus fluence which reveal the dramatic
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Georgiacodis, D. N. "Low temperature ion-irradiation effects in silicon studied by ion-channelling techniques." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304345.
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Larsson, Martin. "Heterogeneity-Induced Channelling, Flow-Wetted Surface, and Modelling of Transport in Fractured Rock." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-180409.
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Heterogeneities in fractured rock are found at all scales; from the scale of individual fractures, to the scale of fracture networks, and to the largest regional scales. These heterogeneities cause challenges for modelling and parameter estimation of flow and solute transport. The heterogeneities in fracture aperture, characterization of the flow channelling they are causing, and implementation of this information into numerical simulation models of the solute transport in fractured media are the subjects of this thesis. Aperture variability within a fracture causes the flow channelling, where the water flow is focused in a few channels and other areas of the fracture have practically stagnant water. The flow-wetted surface is the area where the flowing water is in contact to the fracture area. Contaminants are transported with the flowing water and therefore the flow-wetted surface is an important parameter that influences the diffusion into the rock matrix and sorption to the fracture rock surface. The specific flow-wetted surface (sFWS) is the flow-wetted surface divided by the total fracture area. The sFWS is systematically analyzed for different fracture aperture distribution characteristics. The local aperture is linked to the local hydraulic conductivity K. Increasing standard deviation of the hydraulic conductivity K field (σln K) leads to decreased sFWS. The sFWS is found to be independent of the correlation length (λ) of the field. An empirical relationship is developed, which describes the sFWS as a function of the σln K. A method is also introduced to determine this key parameter by analysis of the breakthrough curve from a single-well injection-withdrawal (SWIW) test. Further, an approach is presented to incorporate the effect of fracture level heterogeneity into fracture network models and to analyze the effect on sorption and matrix diffusion, by including the sFWS parameter into the transport calculations. The results show that the median transport time is proportional to the square of the sFWS-value. The results also suggest that there are an averaging behaviour in the fracture network, the sFWS-value of each individual fracture is not important for the transport over the domain, but a mean-value can be utilized in the numerical model.Heterogeniteter i sprickigt berg finns i alla skalor, från millimeterskala till en skala på hundratals kilometer. Dessa heterogeniteter orsakar problem vid beräkning av vattenflöde och ämnestransport. Aperturen i en spricka är öppningen mellan de två omslutande bergsidorna, den varierar både inom och mellan olika sprickor. Ämnet för denna avhandling är heterogeniteter i aperturerna inom enskilda sprickor, karaktärisering av den flödeskanalisering som uppstår på grund av dessa heterogeniteter och hur man kan använda denna information till en numerisk modell.Variabilitet av aperturen i en enskild spricka gör att vattenflödet blir fokuserat i ett fåtal kanaler, medan andra områden av sprickan kan ha praktiskt taget stillastående vatten. Den flödesvätta ytan är det område där det strömmande vattnet kommer i kontakt med sprickytan. Den flödesvätta ytan som påverkar diffusionen in i bergmatrisen och sorptionen till sprickytan är en viktig parameter eftersom föroreningar transporteras med det strömmande vattnet. Den specifika flödesvätta ytan (sFWS) är den flödesvätta ytan dividerad med den totala sprickarean. I avhandlingen analyserades sFWS systematiskt för olika statistik över sprickaperturen. Den lokala aperturen är kopplad till den lokala hydrauliska konduktiviteten K. En ökad standardavvikelse för det hydrauliska konduktivitetsfältet (σln K) ledde till minskad sFWS. sFWS visades vara oberoende av konduktivitetsfältets korrelationslängd (λ). En empirisk relation utvecklades som beskriver sFWS som en funktion av σln K. Ett SWIW-test är en typ av spårämnesförsök, där ett spårämne injiceras i en brunn följt av vatten i en bestämd tidsperiod, innan flödet vänds och en genombrottskurva registreras. Testet används traditionellt för att bestämma bergets diffusions- och sorptionsegenskaper. En metod presenterades för att bestämma den specifika flödesvätta ytan genom analys av genombrottskurvan för ett SWIW-test. Ett tillvägagångssätt introducerades för att analysera effekterna av sorption och matrisdiffusion i heterogena sprickor i en spricknätverksmodell genom att inkludera sFWS-parametern i transportberäkningar. Resultaten visade att medianvärdet för transporttiden är proportionell mot kvadraten på sFWS-värdet. Resultaten visade också att transporten genom spricknätverket inte är beroende av sFWS-värdet i de individuella sprickorna, utan att medelvärdet kan användas för modellering.
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Bjerre, Lise M. "Channelling in non-experimental pharmacoepidemiologic research : its role in understanding confounding by indication." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84476.
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When a new drug is introduced onto the market, patients treated with it often tend to be sicker than those who are not. Once a drug has been released onto the market, its safety and efficacy can usually only be assessed using non-experimental studies. However, these methods cannot account for the differential assignment of sicker patients to new drugs, which can make a new drug seem detrimental or even dangerous, if these systematic differences are not accounted for. This is a prototypical example of confounding by indication, which is often viewed as an insurmountable problem in pharmacoepidemiologic research. Confounding by indication consists of two components, namely channelling and the risk factor effect.In this thesis, the index of apparent channelling (IAC) is introduced as a novel tool for the measurement of the degree of channelling. The IAC makes use of propensity scores to quantify the proportion of the variance in treatment assignment that can be accounted for by documented patient characteristics. However, the IAC can only account for channelling due to documented factors. Thus, it is always possible that there be residual channelling due to undocumented factors. Such residual channelling is of concern mostly to the extent that it leads to confounding of the treatment effect. Consequently, the index of residual channelling (IRC) is developed to estimate residual channelling and a novel approach is proposed to assess the strength of the resulting confounding bias. This model-based approach is based on estimating the interaction between treatment effect and the expected strength of residual channeling on treatment assignments of individual patients, measured by the discrepancy between their predicted treatment and the treatment they actually received.
The combination of the index of apparent channelling and the model-based approach to residual channelling provides a practical approach to the problem of assessing the impact of confounding by indication in non-experimental studies in the post-marketing evaluation of the safety and efficacy of new drugs. The application of these methods may enhance the validity of the conclusions drawn in such studies.
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Ahmed, Jaoued. "A study of fatigue in single crystal copper using electron channelling contrast imaging." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298467.
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Kasolo, Pius Chilufya-Bwalya. "Fluid-channelling and gold mineralization within the Late Proterozoic Mwembeshi Shear Zone,Zambia." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315515.
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Whyte, David. "Channelling oceanic energy : investigating intimacy among surfers and waves along Ireland's Atlantic coast." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10059254/.
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This thesis examines the entangled relationships of humans, waves, and the wider nonhuman environment in surfing. It is based on an ethnographic study of surfing along the Atlantic coast of Ireland, and also on how these communities are tied to a global surfing imaginary via online magazines, digital swell forecasts, and international travel. The argument at the core of this thesis is that surfing describes a collection of practices which transforms humans into channels for Oceanic energy. This becoming is both what allows the human body and technology to make lives as surfers in the littoral environment, and also produces the practical context whereby Irish terrestrial sociality is transformed into Irish surfer sociality with its own rules, hierarchies, and environmental understandings. The thesis departs from established tendencies in anthropology, geography and popular literature to theorise the coast as a liminal/peripheral space that is distinct from 'everyday' life and in which social norms are relaxed, transformed or perhaps even absent. Instead, I develop an alternative ecological analysis of Irish surfing using surfers' own concepts which examines how surfing practice refigures the coast as the centre of certain human lives while at the same time blurring conceptual and physical boundary lines which separate land, littoral and ocean. By going beyond a strictly materialist approach to examine the energies which animate material relations, the ecological explanation developed herein argues that an anthropological explanation of surfing social relations benefits from a thorough understanding of the various ways that people become affectively tied to environments through practice.
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Svensson, Sjöbom Ludvig. "Channeling of MeV ion beams : Improving sample alignment at the tandem accelerator, Ångström laboratory." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230962.
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At the Tandem accelerator in the Ångström laboratory, Uppsala, Rutherford backscattering spectrometry (RBS) is one of the methods used for thin film analysis, providing information on thickness and composition. The films are commonly grown on silicon substrates, whose crystal structure gives rise to channelling effects (a strong angular dependence in the intensity of the signal), which can cause faulty results. For other samples, channelling may also be used to get information on crystal structure and quality. This work demonstrates new functions to the existing software, aiming at minimizing these effects. The new methods have been tested by measurements both in channelling directions and in directions determined by the old method. In comparison with the earlier method the worst-case error is of order 80 %,commonly around 20 %, but it is possible to achieve an error which is not detectable. It is worth to note that the stated errors appear in tests oriented for maximum channelling, where effects without the new methods give an error corresponding to an apparent thin-film thickness almost 18 times that of the actual thickness.Vid Tandemlabbet i Ångströmlaboratoriet, Uppsala, används bland annat Rutherford backscattering spectrometry (RBS) för att undersöka egenskaper, t.ex tjocklek och sammansättning, hos tunnfilmer som ofta är odlade på kiselsubstrat. Kiselkristallernas struktur ger upphov till kanaliseringseffekter, d.v.s starkt vinkelberoende intensitet, som i detta sammanhang kan ge felaktiga resultat. För andra prover kan kanaliseringseffekter användas för att få information om kristallstruktur och kvalitet. I det här arbetet demonstreras nyskrivna funktioner till befintlig mjukvara med syfte att minimera dessa effekter. De nya funktionerna har testats genom provtagningar i orienteringar som är gynnsamma och icke gynnsamma för kanalisering. Vid jämförelse med tidigare metoder ger de nya metoderna ett fel på i värsta fall ca. 80%, med bättre parametrar sjunker felet till ca 20 % och med rätt val av parametrar försvinner felet jämfört med tidigare metod. Värt att notera är att ovanstående maximala fel uppstår vid test orienterat för maximal kanalisering, där effekterna utan de nya metoderna ger ett fel på uppemot en faktor 18.
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Heyns, Eva Hutton. "Channelling metabolic flux away from ethanol production by modification of gene expression under wine fermentation conditions." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80137.
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Thesis (MSc)--Stellenbosch University, 2013.ENGLISH ABSTRACT: There is a global demand for technologies to reduce ethanol levels in wine without compromising wine quality. While several chemical and physical methods have been developed to reduce ethanol in finished wine, the target of an industrially applicable biological solution has thus far not been met. Most attempted biological strategies have focused on developing new strains of the main fermentative organism, the yeast Saccharomyces cerevisiae. Gene modification approaches have primarily focused on partially redirecting yeast carbon metabolism away from ethanol production towards glycerol production. These techniques have met with some moderate success, thus the focus of the current study was to re-direct carbon flux towards trehalose production by moderate over-expression of the TPS1 gene. This gene encodes trehalose-6-phosphate synthase, which converts glucose 6-phosphate and UDPglucose to α,α-trehalose 6-phosphate. Previous data have shown that the overproduction of trehalose restricts hexokinase activity reducing the amount of glucose that enters glycolysis. Nevertheless, preliminary TPS1 over-expression studies using multiple copy plasmids have shown some promise, but also indicated significant negative impact on the general fermentation behaviour of strains. In order to reduce such negative impacts of excessive trehalose production, a new strategy consisting in increasing the expression of TPS1 only during specific growth phases and by a relatively minor degree was investigated. Our study employed a lowcopy number episomal vector to drive moderate over-expression of the TPS1 gene in the widely used industrial strain VIN13 at different stages during fermentation. The fermentations were performed in synthetic must with sugar levels representative of those found in real grape must. This, as well as the use of an industrial yeast strain, makes it easier to relate our results to real winemaking conditions. A reduction in fermentation capacity was observed for all transformed strains and controls. Expression profiles suggest that the DUT1 promoter certainly results in increased TPS1 expression (up to 40%) during early exponential growth phase compared to the wild type strain (VIN13). TPS1 expression under the control of the GIP2 promoter region showed increased expression levels during early stationary phase (up to 60%). Chemical analysis of the yeast and the must at the end after fermentation showed an increase in trehalose production =in line with the expression data of TPS1. Importantly, glycerol production was also slightly increased, but without affecting acetic acid levels for the transformed strains. Although ethanol yield is not significantly lower in the DUT1-TPDS1 strain, s statistically significantly lower ethanol yield is observed for over-expression under the GIP2 promotor. Increasing trehalose production during stationary phase appears therefore to be a more promising approach at lowering ethanol yield and redirecting flux away from ethanol production. This controlled, growth phase specific over expression suggests a unique approach of lowering ethanol yield while not impacting on the redox balance.
AFRIKAANSE OPSOMMING: Wêreldwyd is daar ‘n aanvraag na tegnologie wat die etanol vlakke in wyn kan verminder sonder om wyngehalte te benadeel. Terwyl verskeie chemiese en fisiese metodes ontwikkel is om etanol in die finale wynproduk te verminder, is die soeke na 'n industrieel gebaseerde biologiese oplossing tot dusver nie gevind nie. Meeste biologiese strategieë fokus op die ontwikkeling van nuwe rasse van die primêre fermentatiewe organisme, naamlik Saccharomyces cerevisiae. Geen modifikasie benaderings het hoofsaaklik gefokus op die gedeeltelike kanalisering van koolstof metabolisme weg van etanol produksie na gliserol produksie. Hierdie benadering is net matiglik suksesvol, dus is ons huidige fokus om koolstof te kanaliseer na trehalose produksie deur gematigde oor-uitdrukking van die TPS1 geen. Hierdie geen kodeer vir trehalose-6-fosfaat sintase, wat glukose-6-fosfaat en UDP-glukose omskakel na α, α-trehalose-6-fosfaat. Vorige data het getoon dat die oorproduksie van trehalose hexokinase aktiwiteit beperk en die hoeveelheid glukose wat glikolise binne gaan. Voorlopige TPS1 ooruitdrukking studies met behulp van multi-kopie plasmiede toon matige sukses, maar het ook ‘n negatiewe impak op die algemene fermentasie kapasiteit van die gis. Ten einde so 'n negatiewe impak van oormatige trehalose produksie te oorkom, is 'n nuwe strategie gevolg wat bestaan uit die verhoogde uitdrukking van die TPS1 geen slegs gedurende spesifieke groei fases met baie lae vlakke van oor-uitdrukking. Ons studie gebruik 'n lae-kopie episomale vektor met matige oor-uitdrukking van die TPS1 geen in die industriële ras VIN13 op verskillende stadiums tydens fermentasie. Die fermentasie is uitgevoer in sintetiese mos met suiker vlakke verteenwoordigend van dié van werklike wyn mos. Hierdie, sowel as die gebruik van 'n industriële gisras, maak dit makliker om ons resultate te vergelyk met regte wyn fermentasie kondisies. Verlaagde fermentasie kapasiteit is waargeneem vir alle getransformeerde stamme en hul kontroles. Geen uitdrukkings profiele dui op verhoogde TPS1 uitdrukking (tot 40%) onder beheer van die DUT1 promotor gedurende die vroeë eksponensiële groeifase wanneer vergelyk word met die wilde tiepe (VIN13). TPS1 uitdrukking onder die beheer van die GIP2 promotor het verhoogde uitdrukking van tot 60% gedurende die vroeë stasionêre fase. Chemiese analise van die gis aan die einde van fermentasie dui op ‘n toename in trehalose produksie wat korreleer met die uitdrukking profiele van TPS1. Gliserol produksie is ook effens verhoog, maar sonder ‘n toename in asynsuur vlakke vir die getransformeerde rasse. Alhoewel etanol opbrengs nie aansienlik laer vir die DUT1-TPS1 ras is nie, is etanol opbrengs vir die oor-uitdrukking onder beheer van die GIP2 promotor wel laer. Toenemende trehalose produksie gedurende stasionêre fase blyk dus 'n meer belowende benadering op die verlaging van etanol opbrengs en her-kanaliseering weg van etanol produksie. Hierdie benadering met die fokus op groeifase spesifieke oor-uitdrukking dui op 'n unieke strategie vir die verlaging van etanol opbrengs sonder om die redoks balans te beinvloed.
The NRF, IWBT and Stellenbosch University for funding
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Qvarnström, Yvonne. "Sulphonamide Resistance in Neisseria meningitidis and Commensal Neisseria Species." Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3750.
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Extensive use of the sulphonamide drugs against the bacterium Neisseria meningitidis has resulted in drug resistance development. Sulphonamide resistance in N. meningitidis is caused by alterations in the chromosomal folP gene, coding for DHPS (dihydropteroate synthase). One type of resistant DHPS has high sequence divergence compared to DHPS from susceptible strains. This divergent DHPS has a duplication of two amino acids, crucial for resistance, and an altered amino acid in position 68, important for both resistance and substrate binding. When introduced into a susceptible DHPS, these two alterations did not incur resistance and resulted in abnormal substrate binding properties. This indicated that the divergent DHPS was not directly developed by mutations, but rather had been acquired by horizontal transfer of folP from another species. Commensal Neisseria species are implied as the origin of the horizontally transferred resistance. Sulphonamide-resistant commensal Neisseria isolates were detected in throat swabs from healthy individuals not exposed to these drugs; however, transformation of resistance from these commensals to N. meningitidis was restricted in the laboratory. A comparison of the genomic region surrounding folP revealed differences in gene organisation and in the DNA uptake sequence between N. meningitidis and distantly related commensals. These differences are likely to restrict transformation between distantly related Neisseria species. DHPS participates in the folate biosynthesis pathway. The enzyme preceding DHPS in the pathway, HPPK (hydroxymethyl-dihydropterin pyrophosphokinase), from N. meningitidis was characterised and a method for studying substrate channelling from HPPK to DHPS was developed. The information gained could be exploited in the search for new antibiotics. In conclusion, well-adapted sulphonamide-resistant strains of N. meningitidis and commensal Neisseria are established in the bacterial population and resistance can be horizontally spread by natural transformation. This may explain the abundance of sulphonamide-resistant N. meningitidis, although these drugs are no longer used against this bacterium.
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Joch, Vítězslav. "Nízkoenergiový rozptyl iontů inertních plynů na zlatých strukturách." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229500.
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This diploma thesis deals with comparison of experimental and simulated low energy ion scattering spectra. There is a theoretical description of basic principles of low energy ion scattering and description of the spectrometer, which is situated at Institute of physical engineering. It is shown, how to prepare samples using the colloidal gold solution. The deposition of gold nanoparticles is characterized. The usage and meaning of time and energy spectra of low energy ion scattering is explained. There is also shown the effect of channeling in Si substrate.
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Cheng, Hamilton Chung-Ming Carleton University Dissertation Journalism and Communication. "Channelling the industrial oil; the establishment of Taiwan telecommunications from 1950 to 1976 for serving the U.S. semiconductor assembly industry; the domination and limit of the Taiwan state in a telecommunications-mediated development." Ottawa, 1994.
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Menchaca, Roa Ane. "Analyse numérique des hydroliennes à axe vertical munies d'un carénage." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI050/document.
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Cette thèse s'inscrit dans le cadre des énergies renouvelables au sein du programme HARVEST du laboratoire LEGI, qui consiste à développer un concept d'hydrolienne de type Darrieus. L'hydrolienne peut être équipée d'un dispositif appelé carénage afin de transformer une portion plus grande de l'énergie cinétique contenue dans le courant d'eau en électricité. Les travaux présentés se sont focalisés sur ces systèmes de carénage, autour de trois axes : l'explication du principe de fonctionnement hydrodynamique du carénage, la quantification des performances de l'hydrolienne carénée et la mise en évidence des grandeurs géométriques clés du carénage permettant d'améliorer ou d'optimiser la performance du système. Toutes les études ont été réalisées à l'aide des calculs RANS 2D et des données expérimentales mises à disposition et, comparées aux résultats obtenus pour une hydrolienne non-carénéeThe general context of the present thesis is renewable energies within the HARVEST program initialized at LEGI laboratory, which consists in developing a Darrieus-type water current turbine (WCT). The WTC can be equipped with a channelling device which allows transforming a bigger amount of the kinetic energy contained in the flowstream into electricity. The present work is focused on the channelling devices. Studies concern three main topics: the explanation of the channelling device hydrodynamic functioning, the evaluation of the performance of the shrouded WCT and the revealing of the system geometrical parameters which allow its improvement or optimisation. All studies have been carried out by 2D RANS calculations and available experimental data, and have been compared to bare WTC results
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Lanaro, Flavio. "Geometry, Mechanics and Transmissivity of Rock Fractures." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3168.
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Templeton-Parker, Christine. "Utopias, magic realism and rebellious spirits : films of Christine Parker 1990 to 2000." Thesis, University of Derby, 2015. http://hdl.handle.net/10545/582854.
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“The More You Look, the more THERE IS to see…” From Hinekaro Goes on a Picnic and Blows up Another Obelisk (Christine Parker, Oceania Parker, 1995) In the 1990s New Zealand was in the grip of free market fundamentalism, neo-liberal deregulation of the economy having begun in the mid-eighties. The Maori protest movement was a major source of societal conflict and feminism had become the ‘F’ word. This study examines my writing and directing during the 1990s in New Zealand. It is proposed that the films contributed to national and international conversations around feminism, colonial struggles, spirituality and the supernatural. It is argued that these works offer a social critique of neoliberalism and the divisive effects of it, on women in particular. In the context of this appraisal neoliberalism is understood to be a set of beliefs that support the functioning of the global free market, with minimal government regulation, except to protect the functioning of private enterprise and the ownership of private property. The short films One Man’s Meat (1991), Peach (1993), and Hinekaro Goes on a Picnic and Blows up Another Obelisk (1995) and the feature film Channelling Baby (1999) are located in an oeuvre of female, Gay, and Maori film makers and artists responding to this environment. The recurrence of alternative utopias, the use of magic realism and the representation of the spiritual and supernatural in my work are also considered in relation to other films made in the period. A case is made that the films were part of a small vanguard of films responding to the 1990s status quo by offering alternative modes of discourse to the dominant economic rationalism. Rich in visual intensity and heightened narrative tropes, such as irony and fragmented narratives, my aesthetic choices, together with recurring themes of chance and fate, agency and identity, are considered to link the films together as a coherent study. While the works are located in an evolving feminist tradition in the 1990s, their continued relevance today, particularly in relation to foregrounding marginal voices and the disruption of dominant paradigms and expectations of female behaviour and identity, underpin the claim for originality.
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Guerrero, Karen. "Organisation structurale et fonction métabolique des unités énergétiques intracellulaires (ICEUs) dans le muscle cardiaque et squelettique : conditions physiologiques et pathophysiologiques : [Thèse soutenue sur un ensemble de travaux]." Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10244.
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Ce travail de thèse s'intéresse principalement à la régulation de la respiration mitochondriale in situ dans les cellules de muscle cardiaque et squelettiques. L'oxygraphie, la spectrophotométrie et la microscopie confocale sur cellules isolées ou fibres musculaires perméabilisées à la saponine ont été utilisées ainsi que la modélisation mathématique. Dans les cellules musculaires, les mitochondries sont organisées de manière très précise tel un ‘cristal'. Cet arrangement intracellulaire serait la base d'une organisation à la fois structurale et fonctionnelle au sein desquelles les mitochondries sont couplées fonctionnellement par le cytosquelette aux autres organelles : réticulum sarcoplasmique et myofibrilles : les ICEUs (ou unités énergétiques intracellulaires). Au sein des cellules cardiaques, il existe 2 niveaux de régulation de la respiration mitochondriale par l'ADP exogène : la perméabilité de la membrane mitochondriale externe (VDAC) et des restrictions localisées de diffusion de l'ADP au voisinage des mitochondries. La β-tubuline participe indirectement à ces mécanismes de régulation de même que la protéine STOP, une protéine associée aux microtubules. Ces données expérimentales sont utiles pour expliquer les aspects métaboliques de la loi de Frank-Starling dans le cœur. Cette notion d'ICEU peut servir de diagnostic lors de l'étude clinique du métabolisme énergétique chez des transplantés pulmonaires avant et après un programme d'entraînement à domicileThe aim of this work was to study the regulation of mitochondrial respiration in situ in cardiac and skeletal muscle cells. Oxygraphy, spectrophotometry and confocal microscopy on saponin-permeabilized muscle cells or fibers were used as well as mathematic modelisation. In muscle cells, mitochondria are ordered very precisely in ‘a crystal like pattern'. This intracellular arrangement could be the basis of a structural and functional organisation within which mitochondria are functionally coupled by cytoskeleton to the other organelles: sarcoplasmic reticulum and myofibrils: ICEUs (intracellular energetic units). In cardiac cells, there are two levels of regulation of mitochondrial respiration by exogenous ADP: permeability of the outer mitochondrial membrane (VDAC) and localized restrictions of ADP diffusion in the neighbourhood of mitochondria. β-tubulin and STOP protein, a microtubule-associated protein, participate indirectly to these mechanisms of regulation. These experimental data are useful for explaining the metabolic aspects of the Frank-Starling law of the heart. The notion of ICEU can be diagnostically used in clinical study of energetic metabolism of lung recipients transplants before and after a home-interval training program
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Harlow, Sage. "Giving voice to the extra-normal self with the extra-normal voice: Improvised exploration through the realms of shamanic chaos magick, insight meditation and gender performance." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2019. https://ro.ecu.edu.au/theses/2210.
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This thesis documents practice-led research exploring the intersections of, and tensions between, improvised invocation ritual within a chaos magick paradigm and Buddhist insight meditation. I explore the extra-normal self—those aspects of consciousness not usually present, or not usually accessible, in day-to-day life—by mean of improvised ritual work with the extra-normal voice and seek to maintain a Buddhist ‘witness’ consciousness throughout these explorations. I also explore the tensions between politics, aesthetics and spiritual practice; in particular, queer and trans politics, a timbre-centred vocal aesthetics and chaos magick, shamanic and Buddhist spiritual practices. This work constitutes part of a larger project of attempting to secularise and democratise spiritual practice greatly influenced by Sam Harris’ book Waking Up: A Guide to Spirituality Without Religion (2014) and to some extent from chaos magick, some iterations of which strive to ‘free’ the western esoteric tradition from its religious trappings. I also take cues from Hakim Bey (1985) as one of the few anarchist writers who sees spiritual practice as profoundly important and not at odds with anarchism. I make use of a ‘radical agnosticism’ (Wilson, 1977) in my practice, privileging subjective experience and critical engagement over the search for an objective truth. I take an autoethnographic approach to this project with a focus on process rather than outcome, with the final project consisting of a description of these approaches and their value (and limitations), accompanied by selected musical examples (recordings).
The thesis also explores a practice that functions as a navigation away from the normative, phallogocentric western esoteric tradition taking cues from feminism, trans and queer politics as well as anarchism. My improvised possession rituals seek to give voice to aspects of the extra-normal self and/or spirits or demons. The different Belief Systems used in this work frame these experiences in different language. My practice strives to accept ‘whatever arises’ (a meditation term) with compassion—whatever their ontological status.
The main text of this thesis consists of three sections: Improvising Theory, Workings and Scores. The first section presents some of my thinking through concepts and theoretical paradigms that I have engaged with over the last few years of my research. I explore the illusion of free will, the intersection of gender and timbre theory and the use of the cut-up technique in chaos magick generally and my practice specifically. The second section of the thesis presents in-depth discussion of some of the explicit ritual performances and recordings that I have explored over the course of the research. This section explore more fully concepts central to my practice such as the interweaving of insight meditation and improvised ritual work. I present reflections on my explorations of dada ‘anti-magick’ ritual which critiques the normative, phallogocentric western esoteric tradition, taking cues from feminism, trans and queer politics as well as anarchisms. This culminates in an exploration of the concept of ‘True Shamanic Black Metal’—a tongue-in-cheek gesture towards a serious exploration of rhythm inspired by my understanding of shamanic drumming, particularly from Tuva, Mongolia and Korea, merged with an interest in extreme metal traditions, particularly black metal. I explore what shamanic black metal might sound like, centring the discussion around the album I recorded in 2017 invocations of unknown entities. The third section of this thesis presents thoughts on playing scores and on writing scores. I explore scores as open invitations to explore either extra-normal states of consciousness or particular aesthetic or ethical interests.
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Derry, Trevor Ernest. "Ion channelling in diamond." Thesis, 2015. http://hdl.handle.net/10539/17165.
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Sanford, Christopher. "Modelling and Computational Prediction of Metabollic Channelling." Thesis, 2009. http://hdl.handle.net/1807/18870.
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Metabolic channelling occurs when two enzymes that act on a common substrate pass that intermediate directly from one active site to the next without allowing it to diffuse into the surrounding aqueous medium. In this study, properties of channelling are investigated through the use of computational models and cell simulation tools. The effects of enzyme kinetics and thermodynamics on channelling are explored with the emphasis on validating the hypothesized roles of metabolic channelling in living cells. These simulations identify situations in which channelling can induce acceleration of reaction velocities and reduction in the free concentration of intermediate metabolites. Databases of biological information, including metabolic, thermodynamic, toxicity, inhibitory, gene fusion and physical protein interaction data are used to predict examples of potentially channelled enzyme pairs. The predictions are used both to support the hypothesized evolutionary motivations for channelling, and to propose potential enzyme interactions that may be worthy of future investigation.
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Fearick, Roger Worsley. "Studies of ion channelling and dechannelling in diamond." Thesis, 2015. http://hdl.handle.net/10539/17250.
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Maciejewski, James Michael. "An application of KAM theory to a model for particle channelling in crystals and some related numerical simulations." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1092.
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It has been seen in physical experiments as early as the 1960’s that when a positively charged particle is injected into a crystal in certain directions and with sufficiently
high energy, the particle can penetrate into the crystalline structure to a depth which is
unexpectedly long. Such motions in the crystal are referred to as channelling trajectories.
Herein, we consider a Hamiltonian model for particle motion in a crystal. We then proceed
to show that the results of KAM theory are applicable to the model, and moreover that these
result predict the existence of trajectories for the fired particle which do indeed penetrate
the crystal deeply. Finally, we present the results of two series of numerical simulations
which strongly suggest that this behaviour is observable in our model.text
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Naseri, Neda. "Relativistic Self-Focusing, Magnetic Field Generation and Particle Acceleration in Underdense Plasmas." Phd thesis, 2010. http://hdl.handle.net/10048/1506.
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In this thesis the following problems are studied:
1-Relativistic self-focusing and channelling of intense laser pulses have been studied in underdense plasma using 2D PIC simulations, for different laser powers and plasma densities. Analytical solutions for the stationary evacuated channels have been recovered in PIC simulations. It is shown that otherwise stable channels can accelerate electrons due to surface waves on the walls of the channels. Relativistic filaments with finite electron density are unstable to transverse modulations which lead in the nonlinear stage to the break-up of laser pulses into independent filaments.
2-Although 3D simulations are limited, they are more realistic. Azimuthal stability of the laser pulses in interaction with underdense plasma can only be studied in 3D geometry.
Relativistic self-focusing and channelling of intense laser pulses have been studied in underdense plasma using 3D PIC simulations, for different laser powers and plasma densities. Analytical solutions for the stationary evacuated channels and ring structure have been recovered in PIC simulations. The stability of ring structure due to azimuthal perturbations has been studied both in theory and in simulations. The gain length of such instability is smaller at higher densities $(>0.1n_{cr})$. It is shown that the azimuthal perturbation can break up the azimuthal symmetry of the laser pulse.
3-Working with circularly polarized laser pulses, gave us a motivation to study Inverse Faraday Effect in interaction of circularly polarized laser pulses with plasma. Axial magnetic field generation by intense circularly polarized
laser beams in underdense plasmas has been studied with 3D particle-in-cell (PIC) simulations and by means of theoretical analysis. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach maximum strength of several tens of MG for laser pulses undergoing relativistic self-focusing and channelling in moderately relativistic regime.
4-Electron wakefield acceleration was studied in support of the experiment which was carried on using 7 TW laser beam at Canadian Advanced Laser Light source facility. 2D simulations were performed to study this problem. The energy the electrons gained in the process was peaked at 20-30 Mev close to the experimental results.
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Buinho, Miguel André Fernandes. "Desenvolvimento da tecnologia Friction Stir Channelling - estudo da influência da base no processamento de ligas de alumínio." Master's thesis, 2020. http://hdl.handle.net/10362/118342.
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A presente dissertação visa contribuir para o desenvolvimento da tecnologia Friction
Stir Channelling, que é um processo no estado sólido que permite, através da fricção
linear, produzir canais contínuos no interior de uma peça maciça numa única passagem
e com a trajetória que se pretender. O intuito específico desta investigação foi avaliar a
influência da base (local onde a chapa a processar é fixada) no processo. Para tal
optou-se por utilizar duas bases com características térmicas distintas. Sendo uma delas
mais convencional (base de aço CK45) e que permite um fácil escoamento do calor,
enquanto a outra de um material isolante (baquelite).
Através da análise dos ensaios realizados e da caracterização dos canais
produzidos concluiu-se que a base é um fator preponderante para que este processo
possa ser realizado com sucesso, pois os ensaios realizados com a base isolante
(baquelite) permitiram concluir que o calor excessivo no processo pode impedir a
formação de canais. Nesses ensaios foram observadas diversas contraindicações para
a utilização deste tipo de base, desde canais não estanques, a canais completamente
abertos e instáveis, por não ser possível manter o processo estacionário, verificando-se
um aumento constante da temperatura.
Deste modo, desenvolveu-se e produziu-se uma base de cobre refrigerada, com o
intuito de se retirar dependência dos parâmetros do processo no fabrico do canal. Assim
sendo, o que se espera é que se possa estabilizar a temperatura do processo através
da utilização de uma base refrigerada e que os parâmetros do processo possam apenas
fazer variar a geometria do canal.
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王蔚鈞. "The Study of Structure Reversion Toward Atomic Resolution Tomogaphy Using Reverse Multislice Theory and Reverse Channelling Theory." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/11513448197106651096.
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碩士國立清華大學
工程與系統科學系
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Finding the structure of nanocrystals to atomic scale can provide a greater understanding of the properties of nano-materials which may realize in many different applications. It has been widely studied that high resolution transmission electron microscope (HRTEM) can provide the information to a finer scale. However, atomic resolution tomography has not yet proposed. Electrons interact with atoms strongly which cause hundreds of diffractions simultaneously resulting in multiple scattering. Therefore, the exit wave function does not reveal the structure information exactly. Dynamical scattering in the crystal can be described from the multislice theory and the channelling theory. The multislice theory presents the electrons are transmitted through a set of N two dimensional phase- and amplitude-objects in equal separation distances. The channelling theory derives the motion of electrons passing through an atom column in real space. This motion can be fairly expressed only by the most bound state of the electrons. This thesis discusses the potential of structure reversion from exit wave based on the two methods: reverse multislice method and reverse channelling method. From the reverse multislice method, it is intended to find the number of slices of atomic planes perpendicular to the incident electron beam direction. The reverse channelling method is mainly retrieving the thickness and the bound eigenenergy of the atom column. These two methods apply to analyze the number of atoms in every atom column and to distinguish chemically the different elements. Both methods are tested with a simulated wedge-shaped crystal NiSi2 and an experimental SrTiO3 [110] exit wave. The results show that these two methods can effectively determine the number and the type of the atoms. A primary concept of discrete tomography is introduced. At the atomic level materials are made out of a discrete set of atoms. By representing the structure projection information as matrices, atomic resolution tomography can be obtained.
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"Non steroidal anti-inflammatory drugs and cardiovascular risk: identifying evidence for channelling bias in a population based study." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-07-2098.
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ABSTRACT
The non-steroidal anti-inflammatory drug (NSAID), diclofenac, has been associated with a high risk for cardiovascular events in observational studies. However, majority of studies identifying this association were conducted when diclofenac was the only NSAID that could be obtained as a combination product (i.e., formulated with misoprostol). As a result, channelling bias might have resulted if prescribers selected the combination of diclofenac/misoprostol (Diclo-Miso) in patients with poor health status frequently than other NSAID products.
The main purpose of this study was to identify evidence for channelling bias in a cohort of patients with coronary heart disease (CHD) prescribed NSAIDs.
Three independent, retrospective analyses were carried out using Saskatchewan’s health administrative databases. Patients were eligible if they were hospitalized with CHD event between January 1, 1994 and December 31, 2008. In the first analysis, a time series was conducted to examine trends in the use of NSAIDs following discharge from original hospitalization. In the second analysis, multivariate logistic regression models were constructed to identify characteristics of patients prescribed with Diclo-Miso in comparison to single-entity diclofenac. Finally, a nested case-control study was conducted to examine the risk for recurrent myocardial infarction (MI)/ Unstable Angina (UA) or death among patients prescribed with Diclo-Miso versus single-entity diclofenac. For each case, up to five controls were matched by age and sex.
Between 1994 and 2008, NSAIDs were used by 20.1% (3,099/15,393) of patients in the year following discharge from their original MI/UA hospitalization. Use of these agents was relatively stable until 2004 when the COX-2 selective agent rofecoxib was withdrawn from the market. Following this date (i.e., September 30, 2004), the use of Diclo-Miso and single-entity diclofenac appeared to follow different trends. However, available patient and disease specific factors could not explain diverging utilization trends. Further, no differences were observed in the risk of experiencing recurrent MI/UA between patients receiving Diclo-Miso (OR 0.88, 95% CI 0.72-1.08, p=0.22) or single-entity diclofenac (OR 0.78, 95% CI 0.60-1.00, p=0.06) versus patients not exposed to NSAIDs.
Based on the study’s result, channelling bias does not appear to be a major threat to the analysis of cardiovascular toxicity of diclofenac products.
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Keyes, Bruce A. "Pruning the growth buds a proposed view of sustained urban growth and the role of sewerage in channelling growth /." 1995. http://catalog.hathitrust.org/api/volumes/oclc/32952440.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1995.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 181-185).
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Mowbray, Duncan John. "Hydrodynamic Modelling of the Electronic Response of Carbon Nanotubes." Thesis, 2007. http://hdl.handle.net/10012/2723.
Full textAbstract:
The discovery of carbon nanotubes by Iijima in 1991 has created a torrent of new research activities. Research on carbon nanotubes ranges from studying their fundamental properties, such as their electron band structure and plasma frequencies, to developing new applications,
such as self-assembled nano-circuits and field emission displays. Robust models are now needed to enable a better understanding of the electronic response of carbon nanotubes. We use time-dependent density functional theory to derive a two-fluid two-dimensional (2D)
hydrodynamic model describing the collective response of a multiwalled carbon nanotube with dielectric media embedded inside or surrounding the nanotube.
We study plasmon hybridization of the nanotube system in the UV range, the stopping force for ion channelling, the dynamical image potential for fast ions, channelled diclusters and point dipoles, and the energy loss for ions with oblique trajectories. Comparisons are made of results obtained from the 2D hydrodynamic model with those obtained from an extension of the 3D Kitagawa model to
cylindrical geometries.
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Carvoeira, Laura da Costa. "Modelação Experimental e Numérica de Incêndios em Topografia Complexa." Master's thesis, 2018. http://hdl.handle.net/10316/86005.
Full textAbstract:
Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaO presente trabalho tem como principal objetivo o estudo do comportamento extremo do fogo em duas colinas, tendo em consideração o fenómeno já estudado por vários autores e conhecido fire channelling. Este fenómeno acontece na face a sotavento da colina e é caracterizado pelo facto de o fogo exibir uma rápida propagação na direção transversal à do vento, para além da rápida propagação na direção do vento.O estudo foi repartido em duas fases: a realização de ensaios experimentais e a criação de simulações numéricas.Na primeira fase, foram realizados nove ensaios experimentais no túnel de vento do Laboratório de Estudos sobre Incêndios Florestais (LEIF), que tiveram como principal objetivo o estudo da influência, no comportamento do fogo, da alteração de alguns parâmetros tais como: os ângulos de inclinação das colinas, o ângulo entre a direção do vento e a linha do cume, o local de ignição e a existência de vento. Nestes ensaios, foram obtidas e analisadas as velocidades de propagação do fogo e tiradas algumas conclusões. Entre estas conclusões, está o facto de o fenómeno fire channelling, na primeira colina, não mostrar simetria quando existe um ângulo diferente de 90º entre a direção do vento e a linha do cume.Na segunda fase, foram criadas simulações numéricas no programa Fire Dynamics Simulator (FDS) e que, fazendo a comparação com testes experimentais realizados anteriormente na Universidade de Coimbra, foram tiradas algumas conclusões acerca da sua veracidade. Os resultados destas simulações são apresentados como um mapa de propagação que na sua criação tem como base as frentes de fogo.
The main objective of this work is the study of the extreme behavior of fire in two hills, considering the phenomenon already studied by many authors and known as fire channelling. This phenomenon occurs on the leeward face of the hill and is characterized by the fact that the fire exhibits a rapid propagation in the transverse direction of the wind, in addition to the rapid propagation towards the wind.The study was divided into two phases: experimental tests and the creation of numerical simulations.In the first phase, nine experimental tests were carried out in the wind tunnel of Laboratório de Estudos sobre Incêndios Florestais (LEIF), whose main objective was to study the influence of changes in some fire parameters such as: the slope angles of the hills, the angle between the direction of the wind and the ridge line, the location of ignition and the existence of wind. In these tests, fire propagation velocities were obtained and analyzed. Among these conclusions is the fact that the fire channeling phenomenon on the first hill does not show symmetry when there is a different angle of 90° between the direction of the wind and the ridge line.In the second phase, numerical simulations were created in the Fire Dynamics Simulator (FDS) program and, after comparing them with experimental tests carried out previously at the University of Coimbra, some conclusions were drawn about their veracity. The results of these simulations are presented as a propagation map based on fire fronts.
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Wang, Xiang. "Long-term under-deposit corrosion of carbon steel pipes in seawater environment." Thesis, 2017. http://hdl.handle.net/1959.13/1335468.
Full textAbstract:
Research Doctorate - Doctor of Philosophy (PhD)Water injection is the most commonly used method to increase the yield from oil and gas reservoirs. Seawater is typically the most convenient water source, and aquifer water and produced water (recovered from crude oil) or some combination is also used. The water injection pipelines (WIP) usually are carbon steel and often are many kilometres long. Because the insides of the pipes usually are not coated, the adverse operational environment means that internal corrosion is an on-going problem for many water injection pipelines. A corrosion problem of much concern in practice is the severe internal corrosion at the lower part of water injection pipelines in near-horizontal positions, in some cases, severe metal loss threatening the integrity of the pipelines. This type of corrosion is known variously as channelling corrosion, 6 o’clock corrosion, and bottom of the line corrosion. The examination of field observations suggests both under-deposit corrosion (UDC) and microbiologically influenced corrosion (MIC) are likely to be associated with the phenomenon. However, the mechanism of this phenomenon is still not fully understood. This thesis reports the observations of long-term corrosion of model steel pipes in a pilot laboratory study aimed at improving the understanding of development of channelling corrosion in offshore water injection pipelines. Half-pipe steel specimens were exposed continuously to stagnant and simulated deoxygenated seawater in the presence of mixed deposits for up to 365 days. The relative contributions of MIC, UDC and nitrate addition to corrosion development were investigated using four different test environments. The steel specimens were recovered after 12, 180 and 365 days of exposure and the changing surface topography was examined by Scanning Electron Microscopy (SEM) and optical microscope. The evolution of corrosion products were analysed by SEM and Energy-dispersive X-ray spectroscopy (EDS). The pit depths were measured by digital Linear Variable Differential Transformer (LVDT). These techniques present detailed graphical, morphological and chemical results of the corrosion process of mild steel in presence of deposits exposed to deoxygenated seawater. The observations show the synergistic effect of MIC and under-deposit corrosion led to severe localized corrosion. Nitrate addition caused most severe localized corrosion. This is linked to the enhanced MIC and the added nitrate plays the role of a source of critical nutrient. The progression of maximum pitting depth with increased exposure period was evaluated and a preliminary extreme value analysis of variability in maximum pit depth is presented. It is found that extreme value distribution examination shows Gumbel function is not appropriate to describe all the pit depth data. Frechet distribution is a better model to deal with the variability of the deepest pits. Finally, it is proposed that the continuous propagation of broad pits with the initiation of newer pits may explain the ultimate formation of channelling corrosion seen in practical water injection pipelines. Suggestions are provided for industrial practice on controlling rust deposition and MIC. The extreme value analysis of the pit depth data is also important for predicting failure probability due to pitting corrosion. In sum, the results in this thesis have implications for the corrosion management of water injection pipelines in the offshore oil industry.
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Viljoen, Nina Susara. "The feasibility of rainwater and stormwater harvesting within a winter rainfall climate context: a commercial building focus." Diss., 2014. http://hdl.handle.net/10500/14391.
Full textAbstract:
Cape Town, South Africa, falls within a winter rainfall region, making it difficult to assess the feasibility of rain- and stormwater harvesting. The reason for this is because the region’s high water demand period coincides with the low rainfall summer season, thereby limiting the availability of this alternative water resource when most needed. During this study, rainwater harvesting for toilet flushing purposes, collected from roof surfaces, was practically assessed by means of inserted flow meters at a pilot study site in Kommetjie, Cape Town. The combined and single system roof- and land surface runoff yields and savings of commercial buildings within the Kommetjie business area, were also theoretically assessed by making use of a mathematical roof- and land surface runoff model specifically developed during this study. The statistical testing of the hypotheses statements relating to the pre- and post-harvesting savings at the pilot study building, compared against the average actual municipal water usage, were performed. Hypotheses testing were also performed in order to compare the theoretical rain- and stormwater runoff yields for the commercial business area against the average actual municipal water consumption. The conclusions drawn from this study indicated that valuable potable water, as well as related financial savings, can be achieved within a winter rainfall region, thereby making rain- and stormwater harvesting a feasible option for commercial businesses in Cape Town.Environmental Sciences
M.Sc. (Environmental Management)