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Gradients in benthic community structure and bioturbation potential along the Nordic Seas continental marginShields, Mark Aiden January 2008 (has links)
The Nordic Seas region marks a transitional zone between the temperate North Atlantic Ocean and the polar Arctic Ocean. The influence of contrasting fluxes of organic matter on benthic community structure and function within the deep waters of the region were investigated. Samples of the macrofaunal community were collated throughout the region employing a standardised method. In the summer of 2002, during the RRS James Clark Ross 75 cruise, replicated samples were obtained with the SMBA multiple corer and the USNEL boxcorer from four stations located at similar sampling depths along a latitudinal transect at the Norwegian Sea continental margin. Additional replicated samples were obtained with a megacorer at six stations located along two bathymetric transects across the Norwegian Sea continental margin in the summer of 2005 during the RRS James Clark Ross 127 cruise. Contrasting fluxes of organic matter influenced benthic community structure, functional ecology and bioturbation potential. Species known to adopt the feeding strategy of the sub-surface storage of organic matter occurred in areas characterised by a seasonal input of organic matter. Species richness and diversity was highest at the Svalbard Margin, located within the marginal ice zone. Bathymetric patterns of macrofaunal biomass were comparable with previously reported global patterns. However, bathymetric patterns of macrofaunal abundance were higher than global patterns. The previously reported rapid subduction of organic matter by the sipunculan Nephasoma sp. and associated deep burrow networks on the Voring Plateau was linked to the species Nephasoma lilljeborgi. It is proposed that N. lilljeborgi is an ecosystem engineer.
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Kinks in a model for two-phase lipid bilayer membranesHelmers, Michael January 2011 (has links)
In the spontaneous curvature model for two-phase lipid bilayer membranes the shape of vesicles is governed by a combination of an elastic bending energy and an interface energy that penalises the size of phase boundaries. Each lipid phase induces a preferred curvature to the membrane surface, and these curvatures as well as phase boundaries may lead to the development of kinks. In a rotationally symmetric setting we introduce a family of energies for smooth surfaces and phase fields for the lipid components and study convergence to a sharp-interface limit, which depends on the choice of the bending parameters of the phase field model. We prove that, if kinks are excluded, our energies $Gamma$-converge to the commonly used sharp-interface spontaneous curvature energy with the additional assumption of $C^1$-regularity across interfaces. For a choice of parameters such that kinks may appear, we obtain a limit that coincides with the $Gamma$-limit on all reasonable membranes and extends the classical model by assigning a bending energy also to kinks. We illustrate the theoretical result by some numerical examples.
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O desenvolvimento conceitual de estudantes sobre a estrutura da matéria e sua utilização na explicação de fenômenos: um estudo longitudinal / Students\' concept development of structure of matter and its application to explain phenomena: a longitudinal studyCarmo, Miriam Possar do 07 August 2015 (has links)
Este estudo teve como objetivo verificar como ocorre e se desenvolve a construção dos conceitos acerca da estrutura da matéria e quais as dificuldades envolvidas nesse processo de aprendizagem. Para esta finalidade foi realizado um estudo longitudinal com um grupo de alunos ao longo do ensino médio. O estudo apresenta a análise do desenvolvimento conceitual desses estudantes, ao manifestarem explicações sobre fenômenos do seu cotidiano, utilizando ideias sobre a estrutura da matéria. Foram empregadas três dimensões de análise: natureza corpuscular da matéria (1ª dimensão), natureza elétrica da matéria (2ª dimensão) e interações intra e interpartículas (3ª dimensão). O estudo foi dividido em duas etapas. Na primeira etapa, participaram 91 alunos de 1ª a 3ª séries de uma escola de Ensino Médio de São Paulo, cujo ensino esteve a cargo de uma mesma professora. A compreensão dos conceitos acerca da estrutura da matéria foi extraída de suas respostas a um questionário contendo questões abertas e fechadas. O conhecimento dos alunos foi avaliado considerando suas respostas em níveis de adequação e compreensão elaborados a partir de uma comparação com respostas de professores especialistas na área de química e de ensino ao mesmo questionário. Verificou-se que as respostas dos alunos se apresentaram entre os níveis de inadequação e parcial adequação com vaga à alguma compreensão na 1ª dimensão de análise para todas as séries. Na 2ª dimensão de análise as respostas foram inadequadas com insuficiente compreensão, entre os alunos da 1ª série, inadequadas com vaga compreensão entre os alunos da 2ª e 3ª séries. Na 3ª dimensão, as respostas foram inadequadas, com insuficiente compreensão entre os alunos das 1ª e 3ª séries, o que implica em avanços e retrocessos do conhecimento dos conceitos e, para a 2ª série, as respostas foram inadequadas com vaga compreensão. Na segunda etapa do estudo, foram acompanhados quatro alunos (A, B, C e D) durante os três anos do Ensino Médio. O conhecimento individual de cada aluno foi extraído de suas respostas a questionários, entrevistas e representações pictóricas. O desenvolvimento conceitual de cada aluno foi avaliado por meio da elaboração de mapas cognitivos a partir de suas manifestações verbais e escritas. Os resultados indicaram que dois dos estudantes desenvolveram uma compreensão gradual dos conceitos acerca da estrutura da matéria, um deles finalizou o ensino com vaga compreensão (A), outro com alguma compreensão (D) e dois deles alcançaram bom nível de compreensão (B e C), estes últimos parecem ter integrado de maneira mais coesa seus conhecimentos, o que indicou que reestruturaram e reorganizaram suas estruturas de conhecimento. O estudo sugere que é necessária uma retomada constante dos conceitos sobre estrutura da matéria, possibilitando ao aluno estabelecer inter-relações conceituais na explicação de fenômenos, de maneira a facilitar uma reestruturação das concepções dos estudantes, tornando a aprendizagem mais significativa. / This study aims to investigate how High School students understand and develop concepts related to structure of matter and how they apply these concepts to explain everyday phenomena related to Chemistry. For this purpose, we conducted a longitudinal study with 91 High School students from 2012 to 2014. The conceptual development of these students was investigated by analyzing their answers to a questionnaire applied in the beginning of the 1st and 2nd grades and in the end of the 3rd grade of High School. In addition, four students were chosen to answer to five interviews conducted over the three years of High School. The students had the same Chemistry teacher in these three years. Students\' answers were categorized in three dimensions of analysis elaborated by the researcher: particle model of matter (1st dimension), electrical nature of matter (2nd dimension) and intra- and inter-particle interactions (3rd dimension). The analyses were conducted in two steps. In the first step, the concepts expressed by the 91 students were analyzed according to the three dimensions. Adequacy and comprehension levels were created to categorize students\' responses. These levels were elaborated by comparing students\' answers to Chemistry experts\' answers. The second step consisted of analysis of each of four students (A, B, C, D) during learning process on 1st, 2nd and 3rd grades of High School. The concept development of each student was evaluated through cognitive maps elaborated by the researcher from student\'s verbal and written manifestations. On the first step, concerning to the 1st dimension of analysis, the students on the three grades showed answers classified in inadequacy and partial adequacy levels, and low comprehension level. For the 2nd dimension, 1st graders\' ideas were classified as inadequate with insufficient understanding, the students of 2nd and 3rd grades showed a low level of understanding. On the 3rd dimension, the answers given by students of the 1st and 3rd grades were classified as inadequate, with insufficient understanding. The responses of 2nd grade students were also inadequate but with a little better level of understanding. On the second step, results indicated that students A and D developed a gradual understanding of the concepts concerning the structure of matter. Although, student A has achieved a low level of comprehension, student D has achieved the level of some comprehension. Students B and C achieved good level of understanding and their concepts seem to be closely integrated, which indicates that they have restructured and reorganized their knowledge structures. In conclusion, this study suggests that concepts related to structure of matter should be frequently reviewed in order to enable the student to establish conceptual interrelationships to explain phenomena at sub-microscope level, promote students\' conceptions restructuration, and provide meaningful learning during the teaching-learning process.
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Macroscopic models of superconductivityChapman, S. J. January 1991 (has links)
After giving a description of the basic physical phenomena to be modelled, we begin by formulating a sharp-interface free-boundary model for the destruction of superconductivity by an applied magnetic field, under isothermal and anisothermal conditions, which takes the form of a vectorial Stefan model similar to the classical scalar Stefan model of solid/liquid phase transitions and identical in certain two-dimensional situations. This model is found sometimes to have instabilities similar to those of the classical Stefan model. We then describe the Ginzburg-Landau theory of superconductivity, in which the sharp interface is `smoothed out' by the introduction of an order parameter, representing the number density of superconducting electrons. By performing a formal asymptotic analysis of this model as various parameters in it tend to zero we find that the leading order solution does indeed satisfy the vectorial Stefan model. However, at the next order we find the emergence of terms analogous to those of `surface tension' and `kinetic undercooling' in the scalar Stefan model. Moreover, the `surface energy' of a normal/superconducting interface is found to take both positive and negative values, defining Type I and Type II superconductors respectively. We discuss the response of superconductors to external influences by considering the nucleation of superconductivity with decreasing magnetic field and with decreasing temperature respectively, and find there to be a pitchfork bifurcation to a superconducting state which is subcritical for Type I superconductors and supercritical for Type II superconductors. We also examine the effects of boundaries on the nucleation field, and describe in more detail the nature of the superconducting solution in Type II superconductors - the so-called `mixed state'. Finally, we present some open questions concerning both the modelling and analysis of superconductors.
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O desenvolvimento conceitual de estudantes sobre a estrutura da matéria e sua utilização na explicação de fenômenos: um estudo longitudinal / Students\' concept development of structure of matter and its application to explain phenomena: a longitudinal studyMiriam Possar do Carmo 07 August 2015 (has links)
Este estudo teve como objetivo verificar como ocorre e se desenvolve a construção dos conceitos acerca da estrutura da matéria e quais as dificuldades envolvidas nesse processo de aprendizagem. Para esta finalidade foi realizado um estudo longitudinal com um grupo de alunos ao longo do ensino médio. O estudo apresenta a análise do desenvolvimento conceitual desses estudantes, ao manifestarem explicações sobre fenômenos do seu cotidiano, utilizando ideias sobre a estrutura da matéria. Foram empregadas três dimensões de análise: natureza corpuscular da matéria (1ª dimensão), natureza elétrica da matéria (2ª dimensão) e interações intra e interpartículas (3ª dimensão). O estudo foi dividido em duas etapas. Na primeira etapa, participaram 91 alunos de 1ª a 3ª séries de uma escola de Ensino Médio de São Paulo, cujo ensino esteve a cargo de uma mesma professora. A compreensão dos conceitos acerca da estrutura da matéria foi extraída de suas respostas a um questionário contendo questões abertas e fechadas. O conhecimento dos alunos foi avaliado considerando suas respostas em níveis de adequação e compreensão elaborados a partir de uma comparação com respostas de professores especialistas na área de química e de ensino ao mesmo questionário. Verificou-se que as respostas dos alunos se apresentaram entre os níveis de inadequação e parcial adequação com vaga à alguma compreensão na 1ª dimensão de análise para todas as séries. Na 2ª dimensão de análise as respostas foram inadequadas com insuficiente compreensão, entre os alunos da 1ª série, inadequadas com vaga compreensão entre os alunos da 2ª e 3ª séries. Na 3ª dimensão, as respostas foram inadequadas, com insuficiente compreensão entre os alunos das 1ª e 3ª séries, o que implica em avanços e retrocessos do conhecimento dos conceitos e, para a 2ª série, as respostas foram inadequadas com vaga compreensão. Na segunda etapa do estudo, foram acompanhados quatro alunos (A, B, C e D) durante os três anos do Ensino Médio. O conhecimento individual de cada aluno foi extraído de suas respostas a questionários, entrevistas e representações pictóricas. O desenvolvimento conceitual de cada aluno foi avaliado por meio da elaboração de mapas cognitivos a partir de suas manifestações verbais e escritas. Os resultados indicaram que dois dos estudantes desenvolveram uma compreensão gradual dos conceitos acerca da estrutura da matéria, um deles finalizou o ensino com vaga compreensão (A), outro com alguma compreensão (D) e dois deles alcançaram bom nível de compreensão (B e C), estes últimos parecem ter integrado de maneira mais coesa seus conhecimentos, o que indicou que reestruturaram e reorganizaram suas estruturas de conhecimento. O estudo sugere que é necessária uma retomada constante dos conceitos sobre estrutura da matéria, possibilitando ao aluno estabelecer inter-relações conceituais na explicação de fenômenos, de maneira a facilitar uma reestruturação das concepções dos estudantes, tornando a aprendizagem mais significativa. / This study aims to investigate how High School students understand and develop concepts related to structure of matter and how they apply these concepts to explain everyday phenomena related to Chemistry. For this purpose, we conducted a longitudinal study with 91 High School students from 2012 to 2014. The conceptual development of these students was investigated by analyzing their answers to a questionnaire applied in the beginning of the 1st and 2nd grades and in the end of the 3rd grade of High School. In addition, four students were chosen to answer to five interviews conducted over the three years of High School. The students had the same Chemistry teacher in these three years. Students\' answers were categorized in three dimensions of analysis elaborated by the researcher: particle model of matter (1st dimension), electrical nature of matter (2nd dimension) and intra- and inter-particle interactions (3rd dimension). The analyses were conducted in two steps. In the first step, the concepts expressed by the 91 students were analyzed according to the three dimensions. Adequacy and comprehension levels were created to categorize students\' responses. These levels were elaborated by comparing students\' answers to Chemistry experts\' answers. The second step consisted of analysis of each of four students (A, B, C, D) during learning process on 1st, 2nd and 3rd grades of High School. The concept development of each student was evaluated through cognitive maps elaborated by the researcher from student\'s verbal and written manifestations. On the first step, concerning to the 1st dimension of analysis, the students on the three grades showed answers classified in inadequacy and partial adequacy levels, and low comprehension level. For the 2nd dimension, 1st graders\' ideas were classified as inadequate with insufficient understanding, the students of 2nd and 3rd grades showed a low level of understanding. On the 3rd dimension, the answers given by students of the 1st and 3rd grades were classified as inadequate, with insufficient understanding. The responses of 2nd grade students were also inadequate but with a little better level of understanding. On the second step, results indicated that students A and D developed a gradual understanding of the concepts concerning the structure of matter. Although, student A has achieved a low level of comprehension, student D has achieved the level of some comprehension. Students B and C achieved good level of understanding and their concepts seem to be closely integrated, which indicates that they have restructured and reorganized their knowledge structures. In conclusion, this study suggests that concepts related to structure of matter should be frequently reviewed in order to enable the student to establish conceptual interrelationships to explain phenomena at sub-microscope level, promote students\' conceptions restructuration, and provide meaningful learning during the teaching-learning process.
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The evaluation and expansion of methodologies relating to the reporting and analyses of intermediate test results : improving the clinical utility of diagnostic researchShinkins, Bethany January 2014 (has links)
<b>Background and objectives:</b> It has been argued that the binary framework frequently adopted to analyse test accuracy does not represent the clinical reality of diagnostic practice, and the recognition of an intermediate category of test result could make the utility of diagnostic tests more transparent. The objective of this thesis is to explore the value of moving away from the binary framework when evaluating and interpreting quantitative diagnostic tests. <b>Methods:</b> This thesis starts with an overview of the key arguments against dichotomising quantitative test results and a summary of some of the alternative methods proposed. Four distinct studies are then reported: 1) a systematic review of the methods currently used to evaluate the accuracy of quantitative cancer biomarkers, 2) a survey of GPs exploring preferences for threshold guidance 3) an evaluation of existing methods for identifying an intermediate range of test values, and 4) an assessment of the feasibility of applying these methods to the results of a meta-analysis. <b>Results:</b> The binary framework remains the most common method for evaluating the accuracy of quantitative tests, despite the survey of GPs indicating that a single threshold interpretation is less helpful than identifying rule-in and rule-out thresholds. Existing methods for identifying an intermediate range of values require some adaptation to incorporate the cost trade-offs relating to different outcomes but, given complete reporting at the primary research, could be applied to the results of a meta-analysis. <b>Conclusion:</b> The 2 x 2 diagnostic framework frequently fails to capture many of the realities and complexities of clinical research questions. Standardised methods that facilitate complete reporting of test accuracy in primary diagnostic accuracy studies are required to allow for greater flexibility when producing threshold recommendations further down the evidence pathway.
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New Directions In The Direction Of TimeBagci, Gokhan Baris 01 June 2006 (has links) (PDF)
This thesis analyzes the direction of time problem in the framework of philosophy of science. The radiation arrow, Newtonian arrow, thermodynamical arrow and quantum mechanical arrow have been studied in detail. The importance of the structure of space-time concerning direction of time is emphasized.
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Wittgenstein And Zen: A ComparisonErcan, Ahmet Bora 01 April 2010 (has links) (PDF)
This thesis is a comparison of the philosophical systems of Zen Buddhism, which is an Eastern Philosophy, with Ludwig Wittgenstein&rsquo / s philosophical studies, who is an extraordinary name of the Western Philosophy in the 20th century. The history and sources of Zen Buddhism were given with its adoption in the use of language and arts. Besides, this study exemplifies the philosophy of Zen Buddhism with the examples from the life story of Wittgenstein. The thesis is written with a full awareness of the sensitivity of comparing different systems which always embody counterexamples and speculations. This is the reason why speculative ideas and resources were deliberately ignored. The aim is to contribute the cultural life of Turkey by taking such a subject to the academic milieu. Moreover, Turkey is the passage of the East and the West both geographically and culturally. There are resemblances between Zen and Wittgenstein by means of method and the useof language. Furthermore, it was given the names of the books that Wittgenstein read and the philosophers who influenced Wittgenstein. The parallels between Zen and Wittgenstein are justified.
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Random graph processes with dependenciesWarnke, Lutz January 2012 (has links)
Random graph processes are basic mathematical models for large-scale networks evolving over time. Their systematic study was pioneered by Erdös and Rényi around 1960, and one key feature of many 'classical' models is that the edges appear independently. While this makes them amenable to a rigorous analysis, it is desirable, both mathematically and in terms of applications, to understand more complicated situations. In this thesis the main goal is to improve our rigorous understanding of evolving random graphs with significant dependencies. The first model we consider is known as an Achlioptas process: in each step two random edges are chosen, and using a given rule only one of them is selected and added to the evolving graph. Since 2000 a large class of 'complex' rules has eluded a rigorous analysis, and it was widely believed that these could give rise to a striking and unusual phenomenon. Making this explicit, Achlioptas, D'Souza and Spencer conjectured in Science that one such rule yields a very abrupt (discontinuous) percolation phase transition. We disprove this, showing that the transition is in fact continuous for all Achlioptas process. In addition, we give the first rigorous analysis of the more 'complex' rules, proving that certain key statistics are tightly concentrated (i) in the subcritical evolution, and (ii) also later on if an associated system of differential equations has a unique solution. The second model we study is the H-free process, where random edges are added subject to the constraint that they do not complete a copy of some fixed graph H. The most important open question for such 'constrained' processes is due to Erdös, Suen and Winkler: in 1995 they asked what the typical final number of edges is. While Osthus and Taraz answered this in 2000 up to logarithmic factors for a large class of graphs H, more precise bounds are only known for a few special graphs. We close this gap for the cases where a cycle of fixed length is forbidden, determining the final number of edges up to constants. Our result not only establishes several conjectures, it is also the first which answers the more than 15-year old question of Erdös et. al. for a class of forbidden graphs H.
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Incoherent neutron scattering studies of select inorganic systems : I. Nuclear momentum measurements of multiple masses, II. The dynamics of coordinated ammonia in zeolite ASeel, Andrew G. January 2012 (has links)
Spectroscopic measurements are detailed within this thesis, utilising incoherent neutron scattering to examine the dynamics of various condensed-matter systems, from nanosecond to sub-femtosecond timescales. The body of this work is divided into two distinct areas of research. I. Nuclear Momentum Measurements of Multiple Masses Deep inelastic neutron scattering (DINS) is used to probe the nuclear momentum distributions and kinetic energies of individual atomic species in sodium hydride (both in bulk and as nanoparticulates within a silica matrix), enriched lithium-7 fluoride and lithium tetra-ammoniate. Extension of DINS to examine heavier (M>4amu) nuclei is detailed, accomplished by the application of a simple stoichiometric fixing technique within the standard DINS theory and analysis protocols. The validity and accuracy of such simultaneous measurements are discussed. II. The Dynamics of Coordinated Ammonia in Zeolite A Inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) are utilised in the examination of vibrational and stochastic dynamics of the ammonia molecule, as coordinated to the internal surface of a zeolite host. Both sodium and copper-exchanged forms of zeolite-A are studied, with proton-weighted, low energy phonon-modes and rotational processes being observed and assigned.
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