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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.
31

Brandpåverkan på lastbärande trä-glasväggar / Fire impact on loadbearing timber-glass walls

Karlsson, Viktor, Wärnelöv, Morgan January 2017 (has links)
Denna rapport undersöker möjligheten för en bärande trä-glaskonstruktion att behålla sin bärförmåga under brand. En bärande konstruktion måste uppfylla särskilda krav under en brand. Rapporten sammanfattar vilka regler och krav som finns på en bärande konstruktion. Rapporten bryter ner konstruktionen och undersöker de olika materialens egenskaper. Materialens termiska egenskaper undersöks för att ta reda på om trä-glaskonstruktionen kan uppfylla brandkraven. På marknaden finns brandklassade glas. Rapporten undersöker möjligheterna att applicera brandglas i trä-glaskonstruktionen. Detta för att skydda det bärande glaset från hög temperatur.
32

Exploring the roles of LIM domain binding proteins in zebrafish development

Gu, Wenchao January 2014 (has links)
As some of the most important and widely utilised intercellular signalling molecules, transforming growth factor βs (TGFβs) play critical roles in normal development and in human disease. Establishing appropriate levels of signalling involves positive and negative feedback, driven by the same signal transduction components, but whether or how the two are distinguished has not previously been understood. Here we show that LIM domain binding proteins (Ldbs) drive the Smad6/7-mediated negative feedback of TGFβ signalling, but they are not required for the ligand-driven positive feedback or other downstream transcriptional activation. In Ldb-deficient zebrafish embryos, the homeostasis of TGFβ signalling is perturbed. As a consequence, signalling of TGFβ family members, Nodal and BMP, is stably enhanced, giving rise to excess mesoderm and endoderm, an effect that can be rescued by reducing Nodal and BMP. Later in development, conditional ldb2a knockdown causes defective vascular, angiogenic and haemogenic development, likely also by elevating TGFβ signalling. Thus, Ldbs control the homeostatic regulation of TGFβ signalling and therefore play critical roles in diverse developmental processes.
33

Effektivt materialutnyttjande vid tillverkning av golvstommar / Efficient use of materials in the manufacture of flooring frames

Andersson, Linn January 2020 (has links)
I ett samhälle med allt större fokus på miljön och användning av förnybara resurser så har efterfrågan på trä som material ökat. En ökad efterfrågan på material kan i sin tur leda till att det kan bli svårt att få tag i material och då gäller det att företagen kan utnyttja sina resurser på bästa sätt och på det viset även kunna minska sina kostnader. Trä är ett organiskt material och har därmed egenskaper som inte förekommer hos andra material. Egenskaperna varierar mellan olika trädslag, inom varje trädslag samt inom varje enskilt träd. Detta beror bland annat på cell och kviststrukturen samt hur träden har växt. Med materialutnyttjande i fokus växte detta examensarbete fram för att kartlägga en produktionslina för golvstommar. Syftet var även att studera möjligheterna att minska materialförlusterna genom att limma ihop materialet två och två innan de gick vidare i processen. För att studera detta genomfördes först en bakgrundsstudie kring trä som material samt limfogning av trä. Därefter genomfördes ett antal fallstudier för att kunna beräkna materialförlusterna i produktionen. Det följdes av en praktisk studie i en testmiljö där det studerades möjligheten att minska materialförlusterna genom att sammanfoga materialet med lim innan sönderdelning till lameller. Resultatet visade att det blev materialförluster både i form av sågspån, som är svårt att göra något åt, samt material som faller sönder till följd av främst kvistar. Materialförlusterna på grund av kvistar finns det möjlighet att minska på genom, vilket de partiska testerna av att sammanfoga materialet med lim innan sönderdelning visade. Att studera sina processer och dess materialutnyttjande är relevant för alla träförädlande företag så att råvaran utnyttjas på bästa möjliga sätt. Det går inte att eliminera alla materialförluster men en åtgärd för att minska materialförlusterna kan i detta fall vara att sammanfoga materialet innan sönderdelning. / In a society with an ever-growing focus on the environment and renewable recourses, the demand for wood as a material will increased. An increase in demand can, however, lead to a shortage in materials. This in turn puts pressure on companies to utilize their resources optimally to both conserve materials and to minimize the costs. Wood is an organic material which gives it unique properties compared to other materials. These properties are not however uniform and can change based on the type of wood. Differences in properties might occur between trees of the same wood species, and even in singular trees. This variety depends on the tree’s cellular and knots structure in addition to how it was grown. The focus of this bachelor thesis was the use of materials in a production line of flooring frames. The aim of this study was also to see if it was possible to minimize the loss of materials by gluing together two pieces of material before processing. The first step in completing this study was to perform a background study which focused on wood as a material and the usage of bonding agents for wood. The background study was then followed by a number of case studies where the loss of materials in the production line was calculated. The case studies were then in turn followed by a practical study performed in a test environment concerning the ability of minimizing material losses by adhering two pieces of material before processing them into lamina. The result showed a loss of materials in form of sawdust and materials breaking after processing, mainly due to knots. The sawdust is difficult to avoid but as the practical study showed, it was possible to reduce the loss of materials caused by knots, by adhering material together before processing it. To study the production and its use of materials is relevant for all wood manufacturing industries to ensure the optimal usage of the material. It is not possible to eliminate all material losses but one possible way to minimize it could be, in this case, to adhere material before it is processes.
34

The Role of LIM Kinase 1 and its Substrates in Cell Cycle Progression

Ritchey, Lisa 01 January 2014 (has links)
LIM Kinase 1 (LIMK1), a modulator of actin and microtubule dynamics, has been shown to be involved in cell cycle progression. In this study we examine the role of LIMK1 in G1 phase and mitosis. We found ectopic expression of LIMK1 resulted in altered expression of p27Kip1, the G1 phase Cyclin D1/Cdk4 inhibitor. Overexpression of LIMK1 resulted in lower levels of p27Kip1 and p27Kip1-pY88 (inactive p27Kip1). Knockdown of LIMK1 resulted in elevated levels of p27Kip1 and p27Kip1-pY88. Together, these results suggest LIMK1 regulates progression of G1 phase through modulation of p27Kip1 expression. LIMK1 is involved in the mitotic process through inactivating phosphorylation of Cofilin. Aurora kinase A (Aur-A), a mitotic kinase, regulates initiation of mitosis through centrosome separation and proper assembly of bipolar spindles. Phosphorylated LIMK1 is recruited to the centrosomes during early prophase, where it colocalizes with ?-tubulin. Here, we report a novel functional cooperativity between Aur-A and LIMK1 through mutual phosphorylation. LIMK1 is recruited to the centrosomes during early prophase and then to the spindle poles, where it colocalizes with Aur-A. Aur-A physically associates with LIMK1 and activates it through phosphorylation, which is important for its centrosomal and spindle pole localization. Aur-A also acts as a substrate of LIMK1, and the function of LIMK1 is important for its specific localization and regulation of spindle morphology. Taken together, the novel molecular interaction between these two kinases and their regulatory roles on one other's function may provide new insight on the role of Aur-A in manipulation of actin and microtubular structures during spindle formation. The substrates of LIMK1, Aur-A and Cofilin, are also involved in the mitotic process. Aur-A kinase regulates early mitotic events through phosphorylation and activation of a variety of proteins. Specifically, Aur-A is involved in centrosomal separation and formation of mitotic spindles in early prophase. The effect of Aur-A on mitotic spindles is mediated by modulation of microtubule dynamics and association with microtubule binding proteins. In this study we show that Aur-A exerts its effects on spindle organization through regulation of the actin cytoskeleton. Aur-A phosphorylates Cofilin at multiple sites including S3 resulting in inactivation of its actin depolymerizing function. Aur-A interacts with Cofilin in early mitotic phases and regulates its phosphorylation status. Cofilin phosphorylation follows a dynamic pattern during progression of prophase to metaphase. Inhibition of Aur-A activity altered subcellular localization of Cofilin and induced a delay in the progression of prophase to metaphase. Aur-A inhibitor also disturbed the pattern of Cofilin phosphorylation, which correlated with the mitotic delay. Our results establish a novel function of Aur-A in the early mitotic stage through regulation of actin cytoskeleton reorganization. ?
35

Monteringsstudie av träfackverk med förband av björkplywood / Assembly study of wooden trusses with joints of birch plywood

Säfwe, Glenn, Wåhlander, Robert January 2021 (has links)
Trä blir allt vanligare som konstruktionsmaterial i stommar, i både hus och anläggningar för att sträva mot mindre klimatpåverkan och kostnader. Ett förslag är att byta ut materialet för de inslitsade plåtar som finns i fackverkskonstruktioner i limträ, från stål till björkplywood. Den huvudsakliga frågan som besvaras i detta examensarbete är hur dessa björkplywoodskivor ska monteras. Genom att studera den ursprungliga metoden med inslitsade stålplåtar och dymlingar samt ett fackverk levererat av Moelven till Åkersberga föreslås en monterings-beskrivning på en knutpunkt. Ritningar togs fram med hjälp av AutoCAD och Tekla Structures till byggnation av en knutpunktsmodell i skala 1:2. Modellen tas fram för att utreda monteringsmomenten i detalj och utvärdera arbetsgången. När en metod för monteringen hade framtagits, applicerats den på hela fackverket för att göra en materialåtgångsanalys och ekonomisk jämförelse över mängden björkplywoodskivor och dymlingar. Slutsatsen från detta arbete är att björkplywood har en stor potential och kan tillverkas med lika hög montagenoggrannhet som den konventionella förbandstekniken med stålplåtar. En stor reduktion av stålanvändningen kan erhållas med en bibehållen bärförmåga i fackverket. / Wood is becoming more and more common as a construction material in structural frames, in both houses and civil engineering structures to strive for less climate impact and costs. One proposal is to replace the material on the gusset plates found in glulam truss structures, from steel to birch plywood. The main question that is answered in this thesis is how these birch plywood plates should be mounted. By studying the original method with steel plates and dowels and a truss delivered by Moelven to Åkersberga, an assembly description of a truss node is proposed. Drawings were produced with the help of AutoCAD and Tekla Structures for the construction of a truss node in scale 1: 2. The model was developed to investigate the assembly steps in detail and evaluate the workflow. Once a method of assembly had been developed, it was applied to the entire truss to make a material consumption analysis and economic comparison of the amount of birch plywood plates and dowels. The conclusion from this work is that birch plywood has great potential and can be manufactured with as high assembly accuracy as the conventional joint technology with steel plates. A large reduction in steel can be obtained with a maintained load-bearing capacity in the truss.
36

Régulation de la migration des cellules endothéliales induite par le VEGF via la phosphorylation de l'annexine 1 par la LIM kinase 1

Côté, Maxime 17 April 2018 (has links)
L'angiogénèse est un processus physiologique soutenu par la migration des cellules endothéliales. Le facteur pro-angiogénique VEGF (vascular endothelial growth factor) induit la réorganisation du cytosquelette d'actine en fibres de tension et la migration cellulaire en activant la stress-activated protein kinase-2 (SAPK2/p38 : p38) via le VEGFR-2 (vascular endothelial growth factor receptor-2). Cette étude vise à caractériser les mécanismes moléculaires, en aval de p38, impliqués dans la phosphorylation de l'annexine Al (ANXA1) chez les cellules endothéliales activées par le VEGF et de démontrer leur rôle dans la migration cellulaire. Les résultats suggèrent que l'ANXAl est une nouvelle cible du sentier p38/MAPKAP K2 (mitogen-activated protein kinase activated-protein kinase 2) et qu'elle régule la migration des cellules endothéliales stimulées par le VEGF. Premièrement, à l'aide d'une électrophorèse en 2D et d'une analyse de spectrométrie de masse, nous avons identifié l'ANXAl comme une protéine dont la phosphorylation est induite par le VEGF et diminuée suite à une inhibition de l'activité de p38. Deuxièmement, en utilisant des essais kinases in vitro et des essais de phosphorylation in vivo, nous avons découvert que l'activation de la LIMK1 (lin-ll/Isl-l/Mec-3 domain-containing protein kinase) par le VEGF en aval de p38 entraîne la phosphorylation de l'ANXAl. Troisièmement, nous avons démontré que l'ANXAl joue un rôle dans la migration des cellules endothéliales et dans la tubulogénèse, du fait que ces processus initiés par le VEGF sont inhibés à la suite de l'invalidation de l'ANXAl par un ARNi (ARN interférant). Toutefois, cette inhibition est renversée en ajoutant un plasmide contenant de l'ADN de l'ANXAl insensible au ARNi. En conclusion, nos résultats suggèrent que la LIMK1 activée par le sentier p38 phosphoryle l'ANXAl, une protéine indispensable à la migration des cellules endothéliales et à la formation de tubules induites par le VEGF.
37

Hydrogen peroxide oxidized starch and dextrin with retention of depolymerized small molecular mass fractions / Väteperoxid-oxiderad stärkelse och dextrin med kvarhållande av depolymeriserade fraktioner med låg molmassa

Chu, Victoria January 2024 (has links)
Trälim utgör en stor del av alla lim globalt och är avgörande för skapandet av träkompositmaterial, som många industrier och produkter är beroende av. Bland de vanligaste trälimmen använder flera formaldehyd som en väsentlig komponent i deras polymera struktur. Medan formaldehyd är ett allmänt använt, billigt och pålitligt material, är det också giftigt och har generellt ursprung från petroleumkällor. Ett ersättningsmaterial med di- eller polyaldehydisk funktionalitet av grönt ursprung är därför önskvärt för framtida trälimkemi. En potentiell lösning involverar att oxidera polysackarider såsom stärkelse och dextrin för att funktionalisera de upprepande glukosenheterna med aldehyder, ketoner och karboxylsyror. Här visas att Fenton-liknande förhållanden, med väteperoxid som oxidationsmedel och järn som katalysator, kan användas för att utföra reaktionen effektivt under atmosfäriska förhållanden, vilket producerar minimala biprodukter såsom vätgas, vatten och järnkomplex. Betydande funktionalisering observerades i en lågmolekylviktsfraktion som frigörs från polysackariden vid oxidation, en fraktion som traditionellt förloras under upparbetning via centrifugering. Detta arbete antyder att retention av denna lågmolekylviktsfraktion i produktblandningen kan förbättra framtida limegenskaper vid låg grad av oxidation i material med hög polymerisationsgrad, även om kvarhållande av depolymeriserade fraktioner från material med lägre polymeriseringsgrad, såsom dextrin, kanske inte ger de önskade polyaldehydiska produkterna i tillräckliga koncentrationer. Kvarhållandet av lågmolekylviktsfraktionen antyder också att stora mängder oxidationsmedel och katalysator bör undvikas, eftersom högre oxidationsgrad kan resultera i oönskade monofunktionella molekyler på grund av hög depolymerisation. / Wood adhesives comprise a large part of all adhesives globally and are essential in creation of wood composite materials, which many industries and products are entirely reliant on. Amongst the most common wood adhesives, several utilize formaldehyde as an essential component of their polymeric structure. While formaldehyde is a widely used, cheap and reliable material, it is also toxic, and generally derived from petroleum sources. A replacement with di- or poly-aldehydic functionality of green origin is therefore desirable for future wood adhesive chemistry. One potential solution involves oxidizing polysaccharides such as starch and dextrin, to functionalize the repeating glucose units with aldehydes, ketones, and carboxylic acids. Herein, it is demonstrated that Fenton-type conditions, using hydrogen peroxide as oxidant and iron as catalyst, can be used to perform the reaction efficiently in atmospheric conditions, producing minimal byproducts such as hydrogen gas, water, and iron complexes. Significant functionalization was observed in a small molecular weight fraction released from the polysaccharide upon oxidation, a fraction which is traditionally lost during workup via centrifugation. This work suggests that retention of this small molecular weight fraction in the product mixture may enhance future adhesive properties at low degrees of oxidation in materials with high degrees of polymerization, though retention of depolymerized fractions of lower chain length materials such as dextrin may not provide the targeted poly-aldehydic products in sufficient concentrations. The retention of the small molecular weight fraction also suggests that large amounts of oxidant and catalyst should be avoided, as higher degree of oxidation may result in undesired mono-functional molecules due to higher degrees depolymerization.
38

Estudo do motor de indução linear utilizado como posicionador e simulações computacionais / not available

Martins Filho, Geraldo Macias 24 April 2003 (has links)
Desde a idealização das máquinas elétricas girantes, o motor de indução linear (MIL) fora também considerado viável e, ao longo do tempo, foi pesquisado e foram desenvolvidas novas tecnologias para sua melhoria e para o seu acionamento. Muitos trabalhos acadêmicos foram realizados em todos os centros de pesquisa do mundo e, no Brasil, os primeiros a estudá-lo com rigor científico foram os professores Morency Arouca e Délio Pereira Guerrini, no início da década de 70, no departamento de Engenharia Elétrica da EESC/USP. Até hoje no Brasil, pouco se desenvolve neste campo de estudo da Engenharia Elétrica e, quando se desenvolve, ficam restritos à simulações e levantamentos de parâmetros característicos aos MIL\'s específicos. O presente trabalho tem como objetivo fazer uma explanação teórica e matemática que servirá de base ao estudo e compreensão do MIL e propor uma aplicação ao mesmo: o MIL acionado por inversor de freqüência e utilizado para obtenção de posicionamento com auxílio de simulação computacional de algumas malhas de controle para tal posicionamento. / Since the rotating machines had been idealized, the Linear Induction Motor (LIM) has been researched and, along the time, new technologies are being developed in order to improve it. Many academic works were accomplished in several research centers and universities around the world. In Brazil, the first ones to study it with scientific approach were Professors Morency Arouca and Délio Pereira Guerrini, in the early 70\'s. Even nowadays, works are seldom developed, and most of them are dedicated to simulation of the LIM or obtaining of parameters of specific LIM\'s. The present work has as objective to study the mathematical and theoretical modeling, which will be used as basis in order to study and understand the LIM and to propose an application: the LIM fed by Frequency Inverter, used in order to obtain positioning, with simulation of specific control systems.
39

Högtrycket-Initierande undersökning av nytt limträmaterial / High Pressure-Initial examination of new glue-laminated wood material

Larsson, Olof January 2005 (has links)
<p>The present study examines a new production line of glue-laminated wood (glulam). </p><p>The glulam is produced from non-planed boards of spruce, which also is convex, that is pressed together with high pressure during the gluing. According to a economic calculation, the material has a economical potential mainly on account of the absent planning. </p><p>The study mainly found out that the shear strength of the material tolerated the demanded values in standard SS-EN 386, but the delaminating values did not. Since there are more areas to be studied around the material, the prospect to achieve the right delamination values is seen as positive.</p>
40

Högtrycket-Initierande undersökning av nytt limträmaterial / High Pressure-Initial examination of new glue-laminated wood material

Larsson, Olof January 2005 (has links)
The present study examines a new production line of glue-laminated wood (glulam). The glulam is produced from non-planed boards of spruce, which also is convex, that is pressed together with high pressure during the gluing. According to a economic calculation, the material has a economical potential mainly on account of the absent planning. The study mainly found out that the shear strength of the material tolerated the demanded values in standard SS-EN 386, but the delaminating values did not. Since there are more areas to be studied around the material, the prospect to achieve the right delamination values is seen as positive.

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