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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Large-scale layered systems and synthetic biology : model reduction and decomposition

Prescott, Thomas Paul January 2014 (has links)
This thesis is concerned with large-scale systems of Ordinary Differential Equations that model Biomolecular Reaction Networks (BRNs) in Systems and Synthetic Biology. It addresses the strategies of model reduction and decomposition used to overcome the challenges posed by the high dimension and stiffness typical of these models. A number of developments of these strategies are identified, and their implementation on various BRN models is demonstrated. The goal of model reduction is to construct a simplified ODE system to closely approximate a large-scale system. The error estimation problem seeks to quantify the approximation error; this is an example of the trajectory comparison problem. The first part of this thesis applies semi-definite programming (SDP) and dissipativity theory to this problem, producing a single a priori upper bound on the difference between two models in the presence of parameter uncertainty and for a range of initial conditions, for which exhaustive simulation is impractical. The second part of this thesis is concerned with the BRN decomposition problem of expressing a network as an interconnection of subnetworks. A novel framework, called layered decomposition, is introduced and compared with established modular techniques. Fundamental properties of layered decompositions are investigated, providing basic criteria for choosing an appropriate layered decomposition. Further aspects of the layering framework are considered: we illustrate the relationship between decomposition and scale separation by constructing singularly perturbed BRN models using layered decomposition; and we reveal the inter-layer signal propagation structure by decomposing the steady state response to parametric perturbations. Finally, we consider the large-scale SDP problem, where large scale SDP techniques fail to certify a system’s dissipativity. We describe the framework of Structured Storage Functions (SSF), defined where systems admit a cascaded decomposition, and demonstrate a significant resulting speed-up of large-scale dissipativity problems, with applications to the trajectory comparison technique discussed above.
72

Routing protocols for indoor wireless ad-hoc networks: a cross-layer perspective

Dricot, Jean-Michel 01 June 2007 (has links)
The all-over trend for an universal access and ubiquitous access to the Internet is driving a revolution in our societies. In order to support this era of nomadic applications, new flexible network architectures have emerged. They are referred to as “wireless ad-hoc networks.” <p><p>Since human-operated devices will more likely be used indoor, it leads to many issues related to the strength of the fading in this environment. Recently, it has been suggested that a possible interaction might exist between various parameters of the ad-hoc networks and, more precisely, between the propagation model and the routing protocol. <p><p>To address this question, we present in this dissertation a cross-layer perspective of the analysis of these indoor ad-hoc networks. Our reasoning is made of four stages. First, the cross-layer interactions are analyzed by the means of multivariate statistical techniques. Since a cross-layering between the physical layer and the routing protocol has been proven to be significant, we further investigate the possible development a physical layer-constrained routing algorithm. <p><p>Second, fundamental equations governing the wireless telecommunications systems are developed in order to provide insightful informations on how a reliable routing strategy should be implemented in a strongly-faded environment. After that, and in order to allow a better spatial reuse, the routing protocol we propose is further enhanced by the adjonction of a power control algorithm. This last feature is extensively analyzed and a closed-form expression of the link probability of outage in presence of non-homogeneous transmission powers is given. Numerous simulations corroborate the applicability and the performance of the derived protocol. Also, we evaluate the gain, in terms of radio channel ressources, that has been achieved by the means of the power control algorithm. <p><p>Third, an architecture for the interconnection with a cellular network is investigated. A closed-form expression of the relaying stability of a node is given. This equation expresses the minimal requirement that a relaying node from the ad-hoc network must fullfil in order to bridge properly the connections to the base-station. <p><p>Finally, a real-life implementation is provided as a validation of the applicability of this novel ad-hoc routing protocol. It is concluded that, both from the performance and the spatial re-use point-of-views, it can be taken advantage from the cross-layering between the physical and the routing layers to positively enhance the networking architectures deployed in an indoor environment. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished
73

Magma chamber dynamics in the peralkaline magmas of the Kakortokite Series, South Greenland

Hunt, Emma J. January 2015 (has links)
Understanding crystallisation in magma chambers is a key challenge for igneous petrology. It is particularly important to understand the origins of layering in peralkaline rocks, e.g. the kakortokite (nepheline syenite), Ilímaussaq Complex, S. Greenland, as these are commonly associated with high value multi-element economic deposits. The kakortokite is a spectacular example of macrorhythmic (>5 m) layering. Each unit consists of three layers comprising arfvedsonite-rich (sodic-amphibole) black kakortokite at the base, grading into eudialyte-rich (sodic-zirconosilicate) red kakortokite, then alkali feldspar- and nepheline-rich white kakortokite. Each unit is numbered -19 to +17 relative to a characteristic well-developed horizon (Unit 0), however there is little consensus on their development. This project applies a multidisciplinary approach through field observations combined with petrography, crystal size distributions (CSDs), mineral and whole rock chemistries on Units 0, -8 to -11 and a phonolite/micro-nephelinolite (“hybrid”) sequence that crosscuts the layered kakortokite. Textures and compositions are laterally consistent across outcrop and indicators of current activity are rare. CSDs indicate in situ crystallisation with gravitational settling as a minor process. Chemical discontinuities occur across unit boundaries. The layering developed through large-scale processes under exceptionally quiescent conditions. The discontinuities reflect open-system behaviour; units were formed by an influx of volatile-rich magma that initiated crystallisation in a bottom layer. Nucleation was initially suppressed by high volatile element concentrations, which decreased to allow for crystallisation of arfvedsonite, followed by eudialyte, then alkali feldspar and nepheline to form each tripartite unit. The chemistry of the hybrid indicates mixing between a primitive (sub-alkaline) magma and kakortokite. Thus injections of magmas of varying compositions occurred, indicating a complex plumbing system below current exposure. The lessons learned at Ilímaussaq, which is extremely well exposed and preserved, are relevant to understanding magma chamber dynamics in the more common instances of pervasively altered peralkaline rocks.
74

Desarrollo de andamiajes con porosidad estratificada basados en poliésteres como soportes en co-cultivo celular indirecto.

Herrero Herrero, María 23 December 2022 (has links)
[ES] El desarrollo de la sociedad ha estado siempre ligado a los avances científicos y tecnológicos. Sin embargo, algunos de estos avances han supuesto la aparición de nuevos problemas, sobre todo de tipo ético, dando lugar a nuevos movimientos asociativos contrarios a ellos. Un ejemplo de ello es el uso de la experimentación animal, fundamentalmente en el campo de la medicina, y más concretamente en el ensayo de fármacos y dispositivos implantables en contacto con medios biológicos. En este sentido, desde el ámbito de los biomateriales y la ingeniería tisular se trabaja para buscar alternativas a la experimentación animal. Una de estas alternativas es el desarrollo de modelos in vitro a partir de soportes poliméricos para el crecimiento celular in vitro. Estas estructuras, además, podrían emplearse no sólo en ensayos de fármacos o investigación in vitro para reducir el uso de animales en experimentación, sino también para regeneración tisular, simulando desde tejidos simples en los que se tienen un único tipo celular, a tejidos más complejos a partir del co-cultivo celular. Así pues, en esta tesis se ha desarrollado un sistema tridimensional con estructura porosa estratificada que permite tanto el co-cultivo celular indirecto, como la realización de ensayos de liberación de fármacos. Para ello, se ha obtenido soportes porosos (scaffolds) por medio de la técnica de solvent-casting particle-leaching empleando como porógeno sal, cuyo tamaño de poro permite albergar células en su interior, sobre los que se han dispuesto, formando una estructura tipo sándwich, membranas electrohiladas. Estas membranas forman una estructura de fibras entrecruzadas, dejando entre ellas espacios de tamaño muy inferior al tamaño celular, de modo que permiten el paso de nutrientes y moléculas a través de ellas, pero actúan de barrera para las células impidiendo su migración a otras zonas del sistema tridimensional. Este tipo de estructuras permiten simular, por ejemplo, la arquitectura tubular renal, con la zona porosa intersticial central y las dos capas epitelial y endotelial externas, que estarían en contacto con la orina y la sangre, respectivamente. Para obtener estas estructuras, se ha optado por emplear polímeros de la familia de los poliésteres, en particular ácido poliláctico y poli(¿-caprolactona), así como su mezcla y copolímeros con ácido poliglicólico. Estas combinaciones permiten ajustar la hidrofilicidad, y por tanto la biodegradabilidad, la cinética de liberación de fármacos y el comportamiento biológico, según interese. Además, el uso de la técnica de electrospinning para el desarrollo de las membranas, permite obtener diferentes diámetros de fibra a partir de la modificación de los principales parámetros del electrohilado, permitiendo también regular las propiedades de estos materiales. Finalmente, para estudiar la liberación de fármacos desde el sistema anterior, las membranas electrohiladas se han cargado con curcumina mediante dos métodos diferentes: a través del método de electrohilado en disolución y con electrospinning coaxial, para obtener así diferentes perfiles de liberación. / [CA] El desenvolupament de la societat ha estat sempre lligat als avanços científics i tecnològics. Malauradament, alguns d'aquests avanços han suposat l'aparició de nous problemes, sobretot de tipus ètic, donant lloc a nous moviments associatius contraris a ells. Un exemple d'això és l'ús de l'experimentació animal, fonamentalment al camp de la medicina, i més concretament en el testatge de fàrmacs i dispositius implantables en contacte amb medis biològics. En aquest sentit, des de l'àmbit dels biomaterials i l'enginyeria tissular es treballa per a buscar alternatives a l'experimentació animal. Una d'aquestes alternatives és el desenvolupament de models in vitro a partir de suports polimèrics per al creixement cel·lular in vitro. Aquestes estructures, a més a més, podrien emprar-se no sols en testatge de fàrmacs o investigació in vitro per a reduir l'ús d'animals en experimentació, sinó també per a regeneració tissular, simulant des de teixits simples en què es té un únic tipus cel·lular, a teixits més complexos a partir del co-cultiu cel·lular. Així doncs, en aquesta tesi s'ha desenvolupat un sistema tridimensional amb estructura porosa estratificada que permet tant el co-cultiu cel·lular indirecte, com la realització d'assajos d'alliberació de fàrmacs. Per a això, s'ha obtingut suports porosos (scaffolds) mitjançant la tècnica solvent-casting particle-leaching emprant com a porògen sal, amb una grandària de porus que permet albergar cèl·lules en el seu interior, sobre els que s'han disposat, formant una estructura tipus sandvitx, membranes electrofilades. Aquestes membranes formen una estructura de fibres entrecreuades, deixant entre elles espais de grandària molt inferior a la grandària cel·lular, de mode que permeten el pas de nutrients i molècules a través d'elles, però actuen de barrera per a les cèl·lules impedint la seua migració a altres zones del sistema tridimensional. Aquest tipus d'estructures permeten simular, per exemple, l'arquitectura tubular renal, amb la zona porosa intersticial central i les dues capes epitelial i endotelial externes, que estarien en contacte amb l'orina i la sang, respectivament. Per a obtindre aquestes estructures, s'ha optat per emprar polímers de la família dels polièsters, en particular àcid polilàctic i poli(¿-caprolactona), així com la seua mescla i copolímers amb àcid poliglicòlic. Aquestes combinacions permeten ajustar la hidrofilicitat, i per tant la biodegradabilitat, la cinètica d'alliberació de fàrmacs i el comportament biològic, segons interesse. A més, l'ús de la tècnica d'electrospinning per al desenvolupament de les membranes, permet obtindre diferents diàmetres de fibra a partir de la modificació dels principals paràmetres de l'electrofilat, permetent també regular les propietats d'aquests materials. Finalment, per a estudiar l'alliberació de fàrmacs des del sistema anterior, les membranes electrofilades s'han carregat amb curcumina mitjançant dos mètodes diferents: a través del mètode d'emulsió i amb electrospinning coaxial, per a obtindre així diferents perfils d'alliberació. / [EN] The development of society has always been linked to scientific and technological advances. However, some of these advances have led to the appearance of new problems, especially of an ethical nature, giving rise to new associative movements opposed to them. An example of this is the use of animal experimentation, mainly in the field of medicine, and more specifically in the testing of drugs and implantable devices in contact with biological media. In this sense, the field of biomaterials and tissue engineering is working to find alternatives to animal experimentation. One of these alternatives is the development of in vitro models based on polymer supports for in vitro cell growth. These structures, moreover, could be used not only in drug testing or in vitro research to reduce the use of animals in experimentation, but also for tissue regeneration, simulating from simple tissues in which there is a single cell type, to more complex tissues from cell co-culture. Thus, in this thesis, a three-dimensional system with a stratified porous structure have been developed to allow both indirect cell co-culture and drug release assays. For this purpose, porous supports (scaffolds) have been obtained by means of the solvent-casting particle-leaching technique using salt as porogen, whose pore size allows cells to be housed in its interior, on which electrospun membranes have been arranged, forming a sandwich structure. These membranes form a structure of cross-linked fibers, leaving spaces between them that are much smaller than the cell size, so that they allow the passage of nutrients and molecules through them, but act as a barrier to the cells, preventing their migration to other areas of the three-dimensional system. This type of structure allows us to simulate, for example, the renal tubular architecture, with the central interstitial porous zone and the two outer epithelial and endothelial layers, which would be in contact with urine and blood, respectively. To obtain these structures, we have chosen to use polymers of the polyester family, in particular polylactic acid and poly(¿-caprolactone), as well as their blend and copolymers with polyglycolic acid. These combinations allow adjustment of hydrophilicity, and thus biodegradability, drug release kinetics and biological behavior, as desired. In addition, the use of the electrospinning technique for the development of membranes allows to obtain different fiber diameters by modifying the main electrospinning parameters, allowing also to regulate the properties of these materials. Finally, to study drug release from the previous system, the electrospun membranes have been loaded with curcumin by two different methods: through the emulsion method and with coaxial electrospinning, in order to obtain different release profiles. / Herrero Herrero, M. (2022). Desarrollo de andamiajes con porosidad estratificada basados en poliésteres como soportes en co-cultivo celular indirecto [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/190919
75

Ion Permeation through Membrane Channels: Molecular Dynamics Simulations Studies

Mustafa, Morad 10 July 2008 (has links) (PDF)
Molecular dynamics simulation was used to study ion permeation through different membrane proteins embedded in a lipid bilayer (DMPC) with different saline solutions. The potential of mean force (PMF) for ion transport was obtained by umbrella sampling simulations. A revised MacKerell force field for tryptophan residues was studied using gramicidin A (gA) channel as a test model. The revised force field contribution to the Na+ PMF was consonant with the prediction from the experimental results, but in stark contrast to the prediction of the CHARMM force field, version 22, for the tryptophan side-chain. A new grid-based correction map algorithm by MacKerell group, called CMAP, was introduced into the CHARMM force field, version 31. The CMAP algorithm focused on optimizing phi, psi dihedral parameters for the peptide backbone. The CMAP corrections reduced the excessive translocation barrier. Decomposition demonstrated the reduction in the translocation barrier was due to effects on the K+ PMFH2O rather than on K+ PMFgA. The presence of negatively charged sulfonate group at the entrance and exit of the gA channel affected the depth and the location of the highly occupied sites. The negatively charged sulfonate group produced a strong attraction for the cations in the bulk towards the channel mouth. In the M2 transmembrane domain channel (M2-TMD), three M2-TMD structures were studied, differing only in whether the selectivity-filter (four His37 side-chains) was uncharged, +2 charged, or +3 charged. M2-TMD structural properties were compared with the structural properties of other models extracted from NMR and X-ray studies. The spontaneous cation and anion entry into the charged selectivity-filter was different from that into a neutral selectivity-filter. Cl- ions had a lower free-energy barrier in the selectivity-filter than either Na+ or NH4+ ions through the M2-TMD channel. NH4+ ions had a lower free-energy barrier in the selectivity-filter than Na+ ions. Based on accessible rotamer conformations, a revised conductance mechanism was proposed. In this conductance mechanism, the His37 side-chain functioned as an acceptor and donor group, whereas the Trp41 side-chain functioned as a carrying group.
76

Dinâmica da matéria orgânica em solo tratado com resíduos orgânicos nos Tabuleiros Costeiros do Estado de Sergipe / Organic matter dynamics in soil treated with organic waste in the Coastal Plains of the state of Sergipe

Moura, Juliana Augusta 15 October 2013 (has links)
In the state of Sergipe, more precisely in the center-south region of the Coastal Plains serves as the stage for one of the largest citrus production in the country. The intensive cultivation of these soils reduces the content of organic matter that is the key component to ensure its quality. Thus, the use of alternate layering residues format, can be a viable alternative to the revitalization of citrus orchards. The objective of this study was the evaluation of the labile and stable soil organic matter, carbon management index and microbial activity in soil treated with organic waste and citrus cultivation in the state of Sergipe. Soil samples were collected in the layers 0-5 cm, 5-10 cm, and 10-15 cm in a citrus (Citrus sinensis, L. Osbeck) orchard treated either with organic residues or mineral fertilizer, or a combination of the two (conventional management, where the projection of the plant canopy was kept clean of weeds, and no mineral fertilization; humus residues; alternate layering residues (in situ made compost); alternate layering residues + NPK; only NPK; humus residues + NPK; and a native forest soil as reference). The results were submitted to analysis of variance and means were compared by the Scott-Knott test at 5% probability by the software SISVAR. To evaluate the microbial activity was also determined the coefficient of correlation (p . 5) via the computer application SAEG. The study of C in the labile and stable organic matter were more effective than isolated evaluation of total organic carbon (TOC) to check for changes in the dynamics of C in the soil. The C in particulate organic matter (C-POM) was more sensitive than the content of C in complexed organic matter (C-COM). Overall, the treatments that have provided incorporation of organic residues showed carbon management index (CMI) close to the native forest. The fulvic acids fraction (FAF) helped identify the changes in soil for different types of management. The humin fraction (HUMF) showed the highest levels of C relative to FAF and humic acids fraction (HAF). The incorporation of organic waste to the crowning of the orange zone also caused an increase in microbial respiration rates, in total content of organic matter, as well as the elevation of pH, P, Ca and Mg treatments when compared to native forest and conventional management. The ratio stratification was effective to evaluate the influence of different management practices between depths indicating treatments Humus, Humus + NPK and altenate layering residues + NPK as the most effective in increasing the organic matter content in the soil. The benefits caused to soil after the incorporation of organic waste show that the use of practices more conservationist contributes to the improvement of the soil. / No estado de Sergipe, mais precisamente no centro-sul, a regiao de Tabuleiros Costeiros serve de palco para uma das maiores producoes citricolas do pais. O cultivo intensivo feito de forma inadequada nesses solos reduz o teor de materia organica que e o componente fundamental para assegurar a sua qualidade. Dessa forma, o aproveitamento dos residuos organicos no formato de compostagem laminar, pode ser uma alternativa viavel para a revitalizacao de pomares citricolas. O objetivo do presente trabalho foi a avaliacao das fracoes labeis e estaveis da materia organica do solo, do indice de manejo do carbono e da atividade microbiana em solo tratado com residuos organicos e cultivado com citros no estado de Sergipe. Foram coletadas amostras de solo em tres profundidades (0-5, 5-10 e 10-15 cm) em area cultivada com laranja pera (Citrus sinensis, L. Osbeck) sob diferentes tratamentos (manejo convencional onde a area sob a copa da planta e mantida limpa e sem aplicacao de fertilizantes; humus, aplicado sob a copa da planta; compostagem laminar, com residuos organicos como restos culturais e estercos dispostos em camadas alternadas sob a copa da planta; compostagem laminar + NPK; NPK; humus + NPK; o mesmo solo sob mata nativa foi usado como referencia). Os resultados foram submetidos a analise de variancia e as medias foram comparadas pelo teste de Scott-Knott a 5% de probabilidade por meio do software SISVAR. Para avaliacao da atividade microbiana tambem foi determinado o coeficiente de correlacao de Pearson (p.5) atraves do aplicativo computacional SAEG. O estudo do C nas fracoes labeis e estaveis da materia organica foram mais eficazes do que avaliacao isolada do carbono organico total (COT) para verificar alteracoes na dinamica do C no solo. O C da materia organica particulada (CMOP) se mostrou mais sensivel do que o teor de C na materia organica complexada (CMOC). No geral, os tratamentos que tiveram incorporacao de residuos organicos proporcionaram indices de manejo de carbono (IMC) proximos ao da mata nativa. A fracao acidos fulvicos (FAF) ajudou a identificar as mudancas ocorridas no solo em funcao dos diferentes tipos de manejo. A fracao humina (FHUM) apresentou os maiores teores de C em relacao a FAF e a fracao acidos humicos (FAH). A incorporacao de residuos organicos a zona de coroamento da laranjeira tambem promoveu um aumento das taxas de respiracao microbiana, nos teores totais de materia organica, assim como, a elevacao de pH, P, Ca e Mg dos tratamentos quando comparados a mata nativa e ao manejo convencional. A relacao de estratificacao mostrou-se eficaz ao avaliar a influencia das diferentes praticas de manejo entre as profundidades indicando os tratamentos Humus, Humus + NPK e compostagem laminar + NPK como os mais eficazes em aumentar o teor de materia organica no solo. Os beneficios ocasionados ao solo, apos a incorporacao de residuos organicos demonstram que a utilizacao de praticas mais conservacionistas contribui em muito para a melhoria do solo.
77

ALISON AND PETER SMITHSON: THE TRANSIENT AND THE PERMANENT

Ábalos Ramos, Ana 05 April 2016 (has links)
[EN] Exhibitions are a cornerstone of Alison and Peter Smithsons' multifaceted approach to their work. A powerful medium for conveying and materialising their ideas which provided them, throughout their career, with the opportunity to freely create experimental constructions to relay their thoughts. The exhibitions they staged in the 1950s and 60s, such as 'Parallel of Life and Art', 'House of the Future', and 'Patio & Pavilion' were, and still are, at least as important to architectural critics as their few built works or many writings. However, from the 1970s onwards little is known about their prolific work in the realm of exhibitions. In his lecture 'The Masque and the Exhibition: Stages Towards the Real' in 1980, Peter Smithson mentioned the importance of exhibitions in shaping the Smithsons' architecture as places of opportunity in which to experiment with reality. This comment makes it logical to think that if the exhibitions held before then had always been a powerful tool - a tool used, furthermore, by the Smithsons to create some of their most intense productions - then those staged after said lecture, which acknowledged and highlighted this aspect of their work might, despite being little known, be at least as intense as the previous exhibitions with greater media visibility. This idea, together with the expectations raised by the 'Christmas-Hogmanay' exhibition - not only because it was staged whilst said lecture was being drafted but also because of the ideas that sprang from the analysis of a related collage mentioned in the prelude to this doctoral thesis - channelled the research towards this final period of the Smithsons' exhibition architecture. The research herein focuses specifically on two groups of exhibitions that stand out amongst the Smithsons' wide range of documented exhibitions on account of their inherent intellectual cohesion enabling the concepts staged by Alison and Peter Smithson to be seen more clearly. This doctoral thesis consists of four chapters. It begins with an introductory chapter which firstly analyses and contextualises architecture in the shape of exhibitions; then outlines the importance of exhibitions in Alison and Peter Smithson's work; and finally puts the specific period under study into context in terms of both their career and the discourse of architecture in general. The two main chapters in this thesis are entitled 'Christmas Exhibitions' and 'Tecta Exhibitions', each organised in a similar fashion: a short introduction to the group of exhibitions followed by an in-depth analysis of each exhibition in the group based mainly on the unpublished documentation to which the author had access in the three main archives devoted to Alison and Peter Smithson: The Alison and Peter Smithson Archive in the Special Collections Department of the Frances Loeb Library at Harvard Design School (USA); the Alison and Peter Smithson Archive / Tecta Archive at Lauenförde (Germany); and the Smithson Family Archive in Stamford (United Kingdom). Finally, each chapter ends with an essay which analyses and links up the different concepts conveyed by each individual exhibition and the exhibitions in the group as a whole. The last chapter is a short epilogue that gathers up all the concepts set out previously in relation to the Christmas and Tecta exhibitions, and shows how they all tie in together in the Smithsons' most experimental work: the Hexenhaus at Bad Karlshafen. / [ES] Dentro del enfoque polifácetico del trabajo de Alison and Peter Smithson, las exposiciones son pieza fundamental. Un medio poderoso para comunicar y materializar sus ideas que les brindó a lo largo de toda su trayectoria la oportunidad de abordar con libertad la construcción experimental de su pensamiento. Sus propuestas expositivas de la década de los cincuenta y sesenta, como Parallel of Life and Art, House of the Future, o Patio & Pavilion, han sido y son tanto o más relevantes para la crítica arquitectónica como sus escasas obras construidas o sus abundantes escritos. Sin embargo, a partir de la década de los setenta, poco se conoce de su prolífica producción expositiva. Peter Smithson en la conferencia "The Masque and the Exhibition: Stages Towards the Real" en 1980 expresaba el importante significado que tenían las exposiciones para la conformación de su arquitectura como lugares de oportunidad para experimentar con la realidad. A partir de esta reflexión, parece lógico pensar que si hasta ese momento dichas instalaciones siempre fueron una herramienta con la que los Smithson han ofrecido algunos de sus momentos más intensos, las realizadas a partir de ese momento de reconocimiento consciente y puesta en valor de esta faceta de su trabajo, pese a su poca difusión, podrían entrañar una intensidad al menos similar a las que ya han destacado hasta el momento en los medios. Esta consideración, unida a las expectativas generadas en torno a la exposición Christmas-Hogmanay, tanto por ser simultánea a la elaboración de dicha conferencia, como por las ideas que se desprenden del análisis de un collage vinculado a la misma que aparece como preludio de esta tesis doctoral, ha dirigido la investigación hacia este último periodo de su arquitectura expositiva. En concreto, el estudio se centra en dos grupos que, dentro del amplio abanico de montajes expositivos realizados, destacan por poseer una cohesión intelectual propia que permitirá descubrir con mayor claridad las reflexiones que Alison y Peter Smithson ponen en escena. La tesis doctoral se estructura en cuatro grandes apartados. Arranca con un capítulo de introducción dedicado a enmarcar el tema de estudio en el que primero se analiza y contextualiza la arquitectura hecha exposición; después, se presenta la relevancia que tiene la obra expositiva en el trabajo de Alison y Peter Smithson; y finalmente se contextualiza el periodo concreto en el que se centra el estudio atendiendo tanto a su propia trayectoria como al discurso arquitectónico general. Los dos grandes apartados de la disertación son las exposiciones de Navidad y las realizadas junto a TECTA, estructurándose ambos de manera similar. Tras una breve introducción al grupo de exposiciones que se va a analizar, aparecen ampliamente documentadas cada una de las exposiciones que conforma el grupo a partir, principalmente, de la documentación inédita a la que se ha tenido acceso en los tres principales archivos dedicados a Alison and Peter Smithson: The Alison and Peter Smithson Archive en el Special Collections Department de la Frances Loeb Library de la Harvard Design School (Estados Unidos); The Alison and Peter Smithson Archiv / TECTA Archiv en Lauenförde (Alemania); y The Smithson Family Archive en Stamford (Inglaterra). Finalmente, cada capítulo se cierra con un ensayo en el que se analizan y relacionan las diferentes reflexiones que las exposiciones ofrecen, de manera individual y en su conjunto. El último capítulo es un breve epílogo que reúne y entrelaza todo lo anteriormente expuesto, a través de las exposiciones de Navidad y TECTA, en su obra más experimental, la Hexenhaus en Bad Karlshafen. / [CAT] Dins de l'enfocament polifacètic del treball d'Alison i Peter Smithson, les exposicions en són una peça fonamental. Un mitjà poderós per a comunicar i materialitzar les idees que, al llarg de tota la seua trajectòria, els van brindar l'oportunitat d'abordar amb llibertat la construcció experimental del seu pensament. Les seues propostes expositives de la dècada dels cinquanta i seixanta, com ara Parallel of Life and Art, House of the Future, o Patio & Pavilion, han sigut i són tant o més rellevants per a la crítica arquitectònica com les seues escasses obres construïdes o els seus abundants escrits. No obstant això, a partir de la dècada dels setanta, poc es coneix de la seua prolífica producció expositiva. Peter Smithson, en la conferència "The Masque and the Exhibition: Stages Towards the Real" al 1980, expressava l'important significat que tenien les exposicions per a la conformació de la seua arquitectura com a llocs d'oportunitat per a experimentar amb la realitat. A partir d'aquesta reflexió, sembla lògic pensar que, si fins a eixe moment les dites instal·lacions sempre van ser una eina amb la qual els Smithson han ofert alguns dels seus moments més intensos, les que van realitzar a partir d'aquest moment de reconeixement conscient i posada en valor d'aquesta faceta del seu treball, tot i la poca difusió, podrien contenir una intensitat com a mínim similar a la d'aquelles que ja han destacat fins al moment en els mitjans. Aquesta consideració, unida a les expectatives generades entorn a l'exposició Christmas-Hogmanay, tant per ser simultània a l'elaboració de la dita conferència, com per les idees que es desprenen de l'anàlisi d'un collage vinculat a la mateixa que apareix com a preludi d'aquesta tesi doctoral, ha dirigit la investigació cap a aquest últim període de la seua arquitectura expositiva. En concret, l'estudi se centra en dos grups que, dins de l'ampli ventall de muntatges expositius realitzats, destaquen per posseir una cohesió intel·lectual pròpia que permetrà descobrir amb una major claredat les reflexions que Alison i Peter Smithson posen en escena. La tesi doctoral s'estructura en quatre grans capítols. Arrenca amb un apartat d'introducció dedicat a emmarcar el tema d'estudi, en què primer s'analitza i contextualitza l'arquitectura feta exposició; després, es presenta la rellevància que té l'obra expositiva en el treball d'Alison i Peter Smithson; i finalment es contextualitza el període concret en què se centra l'estudi, atenent tant a la seua pròpia trajectòria com al discurs arquitectònic general. Els dos grans capítols de la dissertació són les exposicions de Nadal i les realitzades junt amb TECTA, i s'estructuren tots dos de manera similar. Després d'una breu introducció al grup d'exposicions que s'analitzarà, apareixen amplament documentades cadascuna de les exposicions que conforma el grup, a partir principalment de la documentació inèdita a la qual s'ha tingut accés en els tres principals arxius dedicats a Alison i Peter Smithson: The Alison and Peter Smithson Archive a l'Special Collections Department de la Frances Loeb Library de la Harvard Design School (Estats Units d'Amèrica); The Alison and Peter Smithson Archiv / TECTA Archiv a Lauenförde (Alemanya); i The Smithson Family Archive a Stamford (Anglaterra). Finalment, cada capítol es tanca amb un assaig en què s'analitzen i relacionen les diferents reflexions que les exposicions ofereixen, de manera individual i en conjunt. L'últim capítol és un breu epíleg que reuneix i entrellaça tot allò exposat anteriorment, a través de les exposicions de Nadal i TECTA, en la seua obra més experimental, la Hexenhausen Bad Karlshafen. / Ábalos Ramos, A. (2016). ALISON AND PETER SMITHSON: THE TRANSIENT AND THE PERMANENT [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62223 / TESIS
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Mindre hackspettens (Dryobates minor) habitatanvändning i Karlstads kommun / Habitat use of the lesser spotted woodpecker (Dryobates minor) in the municipality of Karlstad, Sweden

Hultberg, Sarah January 2022 (has links)
Mindre hackspett (Dryobates minor) är en vanligen icke-migrerande fågel som är väldigt trogen till sitt hemrevir. Reviret bör vara minst 40 hektar och bestå av en dominerande andel lövträd samt innehålla död ved och grova träd. Studiens syfte var att undersöka den mindre hackspettens habitatanvändning i Karlstads kommun genom att bedöma antalet individer i förhållande till fyra ekologiska faktorer: mängd stående död ved och grova träd, trädskikt samt habitatstorlek. Data togs från en rapport från 2017 där en inventering hade utförts i 77 områden i Karlstads kommun. Rapporten registrerade antal mindre hackspettsindivider och flera ekologiska faktorer i varje område. Hypoteserna var att antalet individer skulle skilja sig i förhållande till: 1) mängden stående död ved, 2) mängden grova träd, 3) antal trädskikt, och 4) habitatstorlek. Resultaten visade att det fanns fler individer av mindre hackspett i områden med en riklig mängd stående död ved och grova träd jämfört med enstaka-och måttlig mängd. Områden med flera trädskikt resulterade även i ett högre antal individer jämfört med en-och två trädskikt. En positiv korrelation mellan habitatstorlek och frekvensen av individer noterades även. Den mindre hackspettens population minskar i Sverige och börjar närma sig att listas som sårbar på IUCN:s rödlista. Det innebär att förvaltare behöver ha ekologiska faktorer i åtanke vid bevaringsåtgärder. Utöver de välkända ekologiska faktorerna döda och stora träd i förhållande till mindre hackspett visade studien även att trädskikt är en viktig faktor att ha i åtanke. Dessutom var endast fem av de 77 habitatområdena i Karlstads kommun större än 40 hektar; vilket innebär att ett landskapsperspektiv är nödvändigt för att bevara konnektivitet mellan habitat, vilket är nödvändigt för en framgångsrik hackspettspopulation. / The lesser spotted woodpecker (Dryobates minor) is usually a nonmigratory bird with a high fidelity towards their home territory. The territory should be at least 40 hectares in size, consisting mostly of deciduous trees and containing dead wood and large-diameter trees. The purpose of this study was to explore the habitat use of the lesser spotted woodpecker in the municipality of Karlstad by assessing the number of individuals in relation to four ecological factors: the amount of standing dead wood and large trees, forest canopy layering and habitat patch size. Data was extracted from a 2017 report, where a field study was conducted in 77 areas in the municipality of Karlstad, Sweden. The report recorded the number of lesser spotted woodpecker individuals and several ecological factors in each area. The hypotheses were that the numbers of individuals would differ in relation to: 1) the amount of standing dead wood, 2) the amount of large trees, 3) forest canopy layering, and 4) habitat patch size. The results showed that there was a greater number of lesser spotted woodpecker individuals in areas with a rich amount of standing dead wood and large trees, versus low-or moderate amounts. Areas with a multiple forest canopy cover also resulted in greater numbers of individuals versus in single-or two-layer canopies. A positive correlation between habitat size and frequency of individuals was also noted. The lesser spotted woodpecker population in Sweden is declining and they are nearing vulnerable on the IUCN red list. This means that managers need to have ecological factors in mind when conducting conservation efforts for the species. In addition to the well-known factors of dead and large trees in relation to the lesser spotted woodpecker, this study also showed that forest canopy layering is an important factor to consider. Furthermore only five of 77 habitat patches in the municipality of Karlstad were larger than 40 hectares; thus, a landscape-level-perspective is required for maintaining connectivity among habitats, which is essential for a thriving woodpecker population.
79

Characterization of heterogeneous diffusion in confined soft matter

Täuber, Daniela 26 October 2011 (has links) (PDF)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
80

Characterization of heterogeneous diffusion in confined soft matter

Täuber, Daniela 20 October 2011 (has links)
A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.

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