To see the other types of publications on this topic, follow the link: Filamenty.
Dissertations / Theses on the topic 'Filamenty'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Filamenty.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Gutjahr, Petra. "Conformations of semiflexible polymers and filaments." Phd thesis, kostenfrei, 2007. http://opus.kobv.de/ubp/volltexte/2008/1591/.
Full text
2
Janiš, Adam. "Mechanické vlastnosti materiálů pro 3D tisk." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442479.
Full textAbstract:
This thesis focuses on the description of 3D printing technologies using the FDM method, which uses deposition of molten thermoplastics and their subsequent cooling and solidification layer by layer. This unique structure then shows a strong anisotropy of mechanical properties and, as a result, their testing and print settings are very important. Tensile testing of plastic materials, including indicators of mechanical properties, are described in this thesis according to ČSN EN ISO standard. The practical part presents the concept of a device capable of performing these tests. The block diagram indicates the functional elements and the connections among them. Tensile strength test is described together with results processing. Necessary product documentation is also included.
3
Mackay, Duncan Hendry. "Basic magnetic field configurations for solar filament channels and filaments." Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/14188.
Full textAbstract:
The three-dimensional magnetic structure of solar filament channels and filaments is considered. A simple analytical potential model of a filament channel is setup with line sources representing the overlying arcades and point sources the flux of the filament. A possible explanation of the distinct upper and lower bounds of a filament is given. A more detailed numerical force-free model with discrete flux sources is then developed and the effect of magnetic shear on the separatrix surface explored. Dextral channels are shown to exist for a wider range of negative values of the force-free alpha and sinistral channels for positive values of alpha. Potential models of a variety of coronal structures are then considered. The bending of a filament is modelled and a method of determining the horizontal component of a filament's magnetic field is proposed. Next, the observed opposite skew of arcades lying above switchbacks of polarity inversion lines is shown to be produced by a local flux imbalance at the corner of the switchback. Then, the magnetic structure of a particular filament in a filament channel is modelled using observations from a photospheric magnetogram. It is shown that dips in the filaments magnetic field could result from opposite polarity fragments lying below the filament. Finally, the formation of a specific filament channel and filament is modelled. The formation of the channel is shown to be due to the emergence of new flux in a sheared state. It is shown that convergence and reconnections between the new flux and old remnant flux is required for the filament to form. The field lines that represent the filament form a thin vertical sheet of flux. The changing angle of inclination of the sheet gives the appearance of twist. The method of formation is then generalised to other cases and it is shown that a hemispheric pattern consistent with the results of Martin et al. (1995) can be obtained.
4
Meiklejohn, Bruce Ian 1959. "ISOLATION AND SEPARATION OF HUMAN CYTOKERATINS USING VARIOUS CHROMATOGRAPHIC TECHNIQUES." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276475.
Full textAbstract:
The cytokeratins from various human tissue were isolated using chromatographic techniques. The cytokeratins were first extracted from crude tissue using high and low salt buffers. It was necessary to use a denaturing agent such as urea to solubilize the resulting cytokeratin pellet. Imidazole also seemed to help solubilize the pellet and a reducing agent such as 2-Mercaptoethanol was not needed as previously believed. The acidic cytokeratins were separated from the neutral-basic cytokeratins using a DEAE ion-exchange column. The acidic cytokeratin fraction was further separated on a moderately polar reverse phase column with an acetonitrile gradient to eluted the proteins. Tetramethylammonium tetrafluoroborate was added to the mobile phase to react with any unreacted silanol groups on the stationary phase and trifluoroacetic acid was added to ion pair with the protein. The peaks were analyzed for purity using two dimensional electrophoresis and monoclonal antibodies that recognize the cytokeratins.
5
Golzar, Mohammad. "Melt spinning of fine PEEK filaments Schmelzspinnen von feinen PEEK Filamenten /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973384654.
Full text
6
Nam, Gi-moon. "Dynamics of confined biofilaments." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE048/document.
Full textAbstract:
Cette thèse est consacrée à la mécanique et à la mécanique statistique de biofilaments/biopolymères et de leur modèle le plus répandu le Worm-Like Chain (WLC) qu’il s’avère nécessaire d’étendre. Nous étudions WLC à 2-d en présence d’obstacles plus proches que la longueur de persistance. Nous caractérisons le mouvement aux temps courts par des simulations numériques complétées par des calculs analytiques. Des concepts similaires servent à décrire des ADN greffés balayés par le front d’une vésicule en cours d’étalement, l’adhésion de la vésicule est promue par des paires biotine/streptavidine qui contraignent les molécules d'ADN sur des chemins étroits où ils peuvent être imagés. Les microtubules (MT) ici stabilisés au taxol, présentent par contre certains comportements qui échappent au WLC et doivent être ramenés à leur structure interne : i)les déflexions latérales d’un MT attaché par un bout correspondent à une longueur de persistance apparente qui augmente avec la longueur ii) les MT adoptent des formes super-hélicoïdales. Ces deux points sont établis au moyen d’analyses de forme des MT. Des transitions de forme corrélées le long du MT mises en évidence sont compatibles avec un modèle basé sur la bistabilité du dimère de tubuline. Finalement un modèle de chaîne super-hélicoïdale comprenant une courbure et une torsion spontanées élargi le WLC. Confiné à 2-d, HWLC peut adopter un état fondamental circulaire ou sinueux caractérisé par le nombre de points d’inflexion où se concentre la torsion (twist-kink). Dans le cas circulaire, il existe des états métastables proches, à petit nombre de twist-kinks, hyperflexiblesThis PhD is devoted to the mechanics and statistical mechanics of biofilaments and their most widespread model, the Worm-Like Chain (WLC) model, which, as it turns out, needs to be extended. We study the WLC in 2-d in the presence of obstacles closer than their persistence length. We characterize the short time motion by numerical simulations complemented by analytical calculations. Similar concepts serve to describe grafted DNAs swept by the front of a spreading vesicle whose adhesion is promoted by biotin/streptavidin bonds, which constrain the DNAs on narrow paths where they can be imaged. Microtubules (MT), here stabilized by taxol, show features which cannot be rationalized by the WLC and shall be related to their internal structure : i)lateral deflections of a clamped MT correspond to an effective persistence length growing with the MT size ii) MT adopt super-helical shapes. These two points are proven by refined image analysis. We analyze shape transitions correlated along the MT which are compatible with a model based on dimer bi-stability. Finally, a super helical chain model (HWLC) allowing for spontaneous curvature and twist is developed which extends the WLC. When confined to 2-d, the HWLC can adopt a ground state which is circular or wavy with inflection points where twist accumulates, so-called twist-kinks. In the circular case there exist close metastable states, with a small number of twist-kinks, which are hyperflexible
7
Rutherford, Sharon Ann. "Construction of a single-chain antibody against intermediate filaments." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68253.
Full textAbstract:
Intermediate filaments are fibrous proteins, appearing in a wide variety of tissue specific forms. The function of these proteins is poorly understood, although they are commonly believed to perform a structural role in the cell. Evidence suggests that the role these proteins play may be more dynamic than was previously believed. To gain more insight into their normal in vivo function, a single-chain monoclonal antibody has been constructed to serve as a specific reagent which can disrupt the intermediate filament network in vivo. The work presented in this thesis represents the first step in an approach which involves the use of single-chain monoclonal antibodies as specific reagents to target and disrupt the function of intracellular proteins.The polymerase chain reaction was used for the cloning and modification of the heavy and light chain variable regions of the murine monoclonal antibody produced by the TIB 131 hybridoma. The variable regions of the light and heavy IgG chains were initially amplified from cDNA using degenerate 5$ sp prime$ primers and 3$ sp prime$ primers complementary to the constant region of the appropriate chain. The amplification products were cloned individually, sequenced, then modified to include restriction sites suitable for cloning into an expression vector. The two modified variable regions were cloned into an expression vector, and when expressed in either bacteria or in a rabbit reticulocyte lysate system, yielded a protein of the expected molecular weight.
8
Roskey, Daniel Eric. "On the Role of Linear Processes in the Development and Evolution of Filaments in Air." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194509.
Full textAbstract:
It is well known that ultrashort, high intensity pulses with peak powers exceedinga certain critical value (Pcr) undergo self-focusingleading to collapse and filamentation. During the initial stagesof propagation at low intensities the beamdynamics are dominated by diffraction and dispersion. During filamentation, self-focusing resulting from the nonlinear Kerr effect is balanced by higher order nonlinearities such as plasma induced defocusing and absorption.This work examines the role that linear processes combined with initial spatial and temporal conditioningplay in the generation and subsequent evolution of filaments within nonlinearbeams. It is demonstrated that, because of linear diffraction, initial spatial beam shaping can have a dramatic effect on the filament pattern, the number of filaments and the energy contained in each filament. These ideas are applicable to cases that arequite common, such as circularly apodized beams, and help to explain interestingbehavior observed in these types of beams. Finally, it is demonstrated thatwith appropriate preconditioning of multiple subcritical pulses, linear effects can be employed to accurately control when and where filamentation occurs during long distance propagation through conditional collapse of overlapping pulses.
9
Ansari, Mubashir Qamar. "Generation of Thermotropic Liquid Crystalline Polymer (TLCP)-Thermoplastic Composite Filaments and Their Processing in Fused Filament Fabrication (FFF)." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/99885.
Full textAbstract:
One of the major limitations in Fused Filament Fabrication (FFF), a form of additive manufacturing, is the lack of composites with superior mechanical properties. Traditionally, carbon and glass fibers are widely used to improve the physical properties of polymeric matrices. However, the blending methods lead to fiber breakage, preventing generation of long fiber reinforced filaments essential for printing load-bearing components. Our approach to improve tensile properties of the printed parts was to use in-situ composites to avoid fiber breakage during filament generation. In the filaments generated, we used thermotropic liquid crystalline polymers (TLCPs) to reinforce acrylonitrile butadiene styrene (ABS) and a high performance thermoplastic, polyphenylene sulfide (PPS). The TLCPs are composed of rod-like monomers which are highly aligned under extensional kinematics imparting excellent one-dimensional tensile properties. The tensile strength and modulus of the 40 wt.% TLCP/ABS filaments was improved by 7 and 20 times, respectively. On the other hand, the 67 wt.% TLCP/PPS filament tensile strength and modulus were improved by 2 and 12 times, respectively.
The filaments were generated using dual extrusion technology to produce nearly continuously reinforced filaments and to avoid matrix degradation. Rheological tests were taken advantage of to determine the processing conditions. Dual extrusion technology allowed plasticating the matrix and the reinforcing polymer separately in different extruders. Then continuous streams of TLCP were injected below the TLCP melting temperature into the matrix polymer to avoid matrix degradation. The blend was then passed through a series of static mixers, subdividing the layers into finer streams, eventually leading to nearly continuous fibrils which were an order of magnitude lower in diameter than those of the carbon and glass fibers.
The composite filaments were printed below the melting temperature of the TLCPs, and the conditions were determined to avoid the relaxation of the order in the TLCPs. On printing, a matrix-like printing performance was obtained, such that the printer was able to take sharp turns in comparison with the traditionally used fibers. Moreover, the filaments led to a significant improvement in the tensile properties on using in FFF and other conventional technologies such as injection and compression molding.Doctor of Philosophy
10
Friend, Lexie Robyn. "An analysis of intermediate filament end domains /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17114.pdf.
Full text
11
Peng, Fang. "CORE-SHELL STRUCTURED FILAMENTS FOR FUSED FILAMENT FABRICATION THREE-DIMENSIONAL PRINTING & ROLL-TO-ROLL MANUFACTURING OF PIEZORESISTIVE ELASTOMERIC FILMS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542976477808743.
Full text
12
Baczyński, Krzysztof Konrad. "Buckling instabilities of semiflexible filaments in biological systems." Phd thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3792/.
Full textAbstract:
In dieser Arbeit werden Knickinstabilitäten von Filamenten in biologischen Systemen untersucht. Das Zytoskelett von Zellen ist aus solchen Filamenten aufgebaut. Sie sind für die mechanische Stabilität der Zelle verantwortlich und spielen eine große Rolle bei intrazellulären Transportprozessen durch molekulare Motoren, die verschiedene Lasten wie beispielsweise Organellen entlang der Filamente des Zytoskeletts transportieren. Filamente sind semiflexible Polymere, deren Biegeenergie ähnlich groß ist wie die thermische Energie, so dass sie auch als elastische Balken auf der Nanoskala gesehen werden können, die signifikante thermische Fluktuationen zeigen.
Wie ein makroskopischer elastischer Balken können auch Filamente eine mechanische Knickinstabilität unter Kompression zeigen. Im ersten Teil dieser Arbeit wird untersucht, wie diese Instabilität durch thermische Fluktuationen der Filamente beeinflusst wird. In Zellen können Kompressionskräfte durch molekulare Motoren erzeugt werden. Das geschieht zum Beispiel während der Zellteilung in der mitotischen Spindel. Im zweiten Teil der Arbeit untersuchen wir, wie die stochastische Natur einer von Motoren generierten Kraft die Knickinstabilität von Filamenten beeinflusst.
Zunächst stellen wir kurz das Problem von Knickinstabilitäten auf der makroskopischen Skala dar und führen ein Modell für das Knicken von Filamenten oder elastischen Stäben in zwei Raumdimensionen und in Anwesenheit thermischer Fluktuationen ein. Wir präsentieren eine analytische Lösung für
Knickinstabilitäten in Anwesenheit thermischer Fluktuationen, die auf einer Renormierungsgruppenrechnung im Rahmen des nichtlinearen Sigma-Models basiert. Wir integrieren die kurzwelligen Fluktuationen aus, um eine effektive Theorie für die langwelligen Moden zu erhalten, die die Knickinstabilität bestimmen. Wir berechnen die Änderung der kritischen Kraft für die Knickinstabilität und zeigen, dass die thermischen Fluktuationen in zwei Raumdimensionen zu einer Zunahme der kritischen Kraft führen. Außerdem zeigen wir, dass thermische Fluktuationen im geknickten Zustand zu einer Zunahme der mittleren projizierten Länge des Filaments in Richtung der wirkenden Kraft führen. Als Funktion der Konturlänge des Filaments besitzt die mittlere projizierte Länge eine Spitze an der Knickinstabilität, die durch thermische Fluktuationen abgerundet wird. Unser Hauptresultat ist die Beobachtung, dass ein geknicktes Filament unter dem Einfluss thermischer Fluktuationen gestreckt wird, d.h. dass seine mittlere projizierte Länge in Richtung der Kompressionskraft auf Grund der thermischen Fluktuationen zunimmt.
Unsere analytischen Resultate werden durch Monte-Carlo Simulationen der Knickinstabilität semiflexibler Filamente in zwei Raumdimensionen bestätigt. Wir führen auch Monte-Carlo Simulationen in höheren Raumdimensionen durch und zeigen, dass die Zunahme der projizierten Länge unter dem Einfluss thermischer Fluktuationen weniger ausgeprägt ist und stark von der Wahl der Randbedingungen abhängt.
Im zweiten Teil der Arbeit formulieren wir ein Modell für die Knickinstabilität semiflexibler Filamente unter dem Einfluss molekularer Motoren. Wir untersuchen ein System, in dem sich eine Gruppe von Motoren entlang eines fixierten Filaments bewegt, und dabei ein zweites Filament als Last trägt. Das Last-Filament wird gegen eine Wand gedrückt und knickt. Während des Knickvorgangs können die Motoren, die die Kraft auf das Filament generieren, stochastisch von dem Filament ab- und an das Filament anbinden. Wir formulieren ein stochastisches Model für dieses System und berechnen die “mean first passage time“, d.h. die mittlere Zeit für den Übergang von einem Zustand, in dem alle Motoren gebundenen sind zu einem Zustand, in dem alle Motoren abgebunden sind. Dieser Übergang entspricht auch einem Übergang aus dem gebogenen zurück in einen ungebogenen Zustand des Last-Filaments. Unser Resultat zeigt, dass für genügend kurze Mikrotubuli die Bewegung der Motoren von der durch das Last-Filament generierten Kraft beeinflusst wird. Diese Ergebnisse können in zukünftigen Experimenten überprüft werden.We study buckling instabilities of filaments in biological systems. Filaments in a cell are the building blocks of the cytoskeleton. They are responsible for the mechanical stability of cells and play an important role in intracellular transport by molecular motors, which transport cargo such as organelles along cytoskeletal filaments. Filaments of the cytoskeleton are semiflexible polymers, i.e., their bending energy is comparable to the thermal energy such that they can be viewed as elastic rods on the nanometer scale, which exhibit pronounced thermal fluctuations. Like macroscopic elastic rods, filaments can undergo a mechanical buckling instability under a compressive load. In the first part of the thesis, we study how this buckling instability is affected by the pronounced thermal fluctuations of the filaments. In cells, compressive loads on filaments can be generated by molecular motors. This happens, for example, during cell division in the mitotic spindle. In the second part of the thesis, we investigate how the stochastic nature of such motor-generated forces influences the buckling behavior of filaments. In chapter 2 we review briefly the buckling instability problem of rods on the macroscopic scale and introduce an analytical model for buckling of filaments or elastic rods in two spatial dimensions in the presence of thermal fluctuations. We present an analytical treatment of the buckling instability in the presence of thermal fluctuations based on a renormalization-like procedure in terms of the non-linear sigma model where we integrate out short-wavelength fluctuations in order to obtain an effective theory for the mode of the longest wavelength governing the buckling instability. We calculate the resulting shift of the critical force by fluctuation effects and find that, in two spatial dimensions, thermal fluctuations increase this force. Furthermore, in the buckled state, thermal fluctuations lead to an increase in the mean projected length of the filament in the force direction. As a function of the contour length, the mean projected length exhibits a cusp at the buckling instability, which becomes rounded by thermal fluctuations. Our main result is the observation that a buckled filament is stretched by thermal fluctuations, i.e., its mean projected length in the direction of the applied force increases by thermal fluctuations. Our analytical results are confirmed by Monte Carlo simulations for buckling of semiflexible filaments in two spatial dimensions. We also perform Monte Carlo simulations in higher spatial dimensions and show that the increase in projected length by thermal fluctuations is less pronounced than in two dimensions and strongly depends on the choice of the boundary conditions. In the second part of this work, we present a model for buckling of semiflexible filaments under the action of molecular motors. We investigate a system in which a group of motors moves along a clamped filament carrying a second filament as a cargo. The cargo-filament is pushed against the wall and eventually buckles. The force-generating motors can stochastically unbind and rebind to the filament during the buckling process. We formulate a stochastic model of this system and calculate the mean first passage time for the unbinding of all linking motors which corresponds to the transition back to the unbuckled state of the cargo filament in a mean-field model. Our results show that for sufficiently short microtubules the movement of kinesin-I-motors is affected by the load force generated by the cargo filament. Our predictions could be tested in future experiments.
13
Marques, Ivo de Almeida. "Estudos estruturais de septinas: explorando interações entre subunidades de filamentos de septinas humanas." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-09122010-101622/.
Full textAbstract:
Septinas constituem uma família conservada de proteínas de citoesqueleto pertencentes à superclasse das P-loop GTPases. Tais proteínas estão envolvidas em vários processos celulares. Em humanos, algumas septinas também estão relacionadas a casos de patologia. Suas seqüências são divididas em três domínios: domínio N-terminal, domínio GTPase e domínio C-terminal, que geralmente possui predição de coiled coil. A principal característica da família está na capacidade de seus membros formarem filamentos compostos por septinas diferentes. Em 2007, Sirajuddin et al apresentaram a primeira e única estrutura cristalográfica de um complexo de septinas, formado pelas septinas 2, 6 e 7. Embora os domínios C-terminal estivessem presentes, eles não apresentaram densidade eletrônica. Assim, a estrutura não trouxe informação estrutural sobre tais domínios. Atualmente, existem quatro estruturas de septinas depositadas no PDB: complexo 2/6/7 e três estruturas SEPT2 sem o C-terminal. Dada a inexistência de informações estruturais a nível atômico para os domínios C-terminal e baixa qualidade das poucas estruturas existentes, propusemos a obtenção de informações bioquímicas e estruturais dos domínios C-terminal de septinas humanas e a obtenção da estrutura cristalográfica de SEPT3-GC (GTPase mais C-terminal). Vale ressaltar que SEPT3 pertence ao único grupo de septinas que possui predição de não apresentar um coiled coil no C-terminal e para o qual não há nenhuma estrutura disponível. Expressamos e purificamos os domínios C-terminal de SEPT2, SEPT6 e SEPT7 (SEPT2-C, SEPT6-C e SEPT7-C). Mostramos que eles formam homo dímeros e que SEPT6-C e SEPT7-C formam um hetero dímero (KD 15,8 nM), nomeado por SEPT67-C. Tanto SEPT6-C quanto SEPT7-C tendem a precipitar, ao passo que SEPT67-C e SEPT2-C (KD 4 μM) são estáveis à altas concentrações. Tentamos, sem sucesso, cristalizar SEPT2-C e SEPT67-C. Via ressonância magnética nuclear, vimos que SEPT2-C possui duas regiões dinamicamente diferentes, uma central, em α-hélice, e duas extremidades desestruturadas. Neste ponto, planejamos construções para as regiões centrais dos domínios C-terminal, nomeadas SEPT2-CC, SEPT4-CC, SEPT6-CC e SEPT7-CC, referente às septinas 2, 4, 6 e 7. Obtivemos cristais para SEPT2-CC, SEPT4-CC e SEPT6-CC. Contudo, resolvemos apenas a estrutura de SEPT4-CC, mostrando que a construção forma um coiled coil anti-paralelo. Então, propusemos, pela primeira vez, um possível mecanismo de formação de ligações cruzadas entre filamentos de septinas. Por outro lado, obtivemos cristais para uma construção contendo os domínios GTPase e C-terminal de SEPT3 (SEPT3-GC) e resolvemos sua estrutura (2,9 Å). Vimos que SEPT3-GC forma filamentos no cristal, utilizando as mesmas duas interfaces já descritas anteriormente para as outras estruturas. Comparamos a estrutura obtida com estruturas da literatura e observamos diferenças significativas em algumas regiões, além de diferença em relação à orientação das duas subunidades adjacentes. Deve ser notado que a estrutura de SEPT4-CC é a primeira estrutura de um coiled coil de septina e que a estrutura de SEPT3-GC é a primeira estrutura de uma septina do grupo I. Em conclusão, o presente trabalho apresentou um conjunto de resultados os quais auxiliará no entendimento desta intrigante família de proteínas, inclusive em relação à formação de filamentos e as interações entre estes.Septins are a conserved family of cytoskeletal proteins belonging to the superclass of the Ploop-GTPases, involved in various cellular processes. In humans, some septins are also linked to cases of pathology. Their sequences are divided into three domains: an N-terminal domain, a GTPase domain and a C-terminal domain, which usually is predicted to form a coiled coil. The main feature of the family is the ability of its members to form filaments composed of different septins. In 2007, Sirajuddin et al presented the first and only crystal structure of acomplex of septins, formed by septins 2, 6 and 7. Although the C-terminal domains were present, they showed no electron density, indicating disorder. Thus, this structure provides little structural information concerning their nature. Currently, there are four septin structures deposited in the PDB: the 2/6/7 complex and three structures of SEPT2 lacking the Cterminal domain . Based on the absence of structural information at atomic resolution about the C-terminal domains and the low quality of the few existing structures we set out to characterize both biochemically and structurally the C-terminal domains of selected human septins as well as to obtain the crystal structure of SEPT3-GC (a construct containing the GTPase and C-terminal domains). It is noteworthy that SEPT3 belongs to the only group of septins that are predicted to lack the C-terminal coiled coil and for which no crystal structure is available. We have expressed and purified the C-terminal domains of SEPT2, SEPT6 and SEPT7 (SEPT2-C, SEPT6-C and SEPT7-C). We show that they form homo-dimers and that SEPT6-C and SEPT7-C form a hetero-dimer (KD 15.8 nM), SEPT67-C. Both SEPT6-C and SEPT7-C were unstable, but SEPT67-C and SEPT2-C (KD 4 μM) were both stable at high concentrations. NMR measurements showed that SEPT2-C has two dynamically different regions, a central one which is -helical, and two extremities which are unstructured. Constructs were designed for the central regions of the C-terminal domains of septins 2, 4, 6 and 7 (SEPT2-CC, SEPT4-CC, SEPT6-CC and SEPT7-CC). We have obtained crystals of SEPT2-CC, SEPT4-CC and SEPT6-CC and have solved the structure of SEPT4-CC which unexpectedly is observed to form an anti-parallel coiled coil. We use this observation to propose, for the first time, a possible mechanism for the formation of cross-links between septin filaments. Crystals were obtained for SEPT3-GC its structure solved at 2.9 Å. We observe that SEPT3-GC forms filaments in the crystal, employing the same two interfaces previously described for other structures. We compare the structure obtained with those from the literature and observe significant differences in some regions of the molecule as well as differences in the relative orientation of the subunits. It should be noted that the structure of SEPT4-CC is the first structure of a septin coiled coil and that the structure of SEPT3-GC is the first structure of a septin from group I. In conclusion, this study presentsm results which will assist in the understanding of this intriguing protein family, including observations pertinent to filament formation and cross-linking.
14
Soeira, Lucas Emanuel. "Projeto e elaboração de um dispositivo para remodelagem de fibras como subsistema do processo de enrolamento filamentar." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-27102009-192514/.
Full textAbstract:
Essa dissertação trata da modelagem física de filamentos de fibras visando adequá-las a aplicações em equipamentos de enrolamento filamentar - filament winding. No decorrer do trabalho é abordada a criação do subsistema para condução e posicionamento dos fios que compõem as bobinas - rovings. São feitas análises por elementos finitos e realizados testes de bancada com os componentes mecânicos visando validar o subsistema como parte integrante das máquinas de filament winding. É estudada a forma de impregnação dos fios, a tensão e o grau de espalhamento dos fios no decorrer da sua passagem pelo sistema, o qual é composto por um conjunto de polias, um tracionador e um enrolador desses fios.This dissertation deals with the use of fiber reinforcements, in order to improve its appliance in filament winding machines. Throughout this work it is created a mechanism system to remodel the fiber filaments from rovings to the part that is been produced. Finite element analyses and experimental tests are performed to validate the system as part of the filament winding machines. Its is studied the impregnation characteristics, the tensioning and the spreading of the fibers along the designed system, which is composed by a set of pulleys and tensioners. The system is built and satisfactory results are obtained. The results obtained as well as proposals to improve the system are presented and the results discussed.
15
Andrijauskas, Fábio 1986. "Detecção de filamentos solares utilizando processamento paralelo em arquiteturas híbridas = Detection of solar filaments using parallel processing in hybrid architectures." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267769.
Full textAbstract:
Orientadores: André Leon Sampaio Gradvohl, Vitor Rafael ColuciDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia
Made available in DSpace on 2018-08-21T23:26:09Z (GMT). No. of bitstreams: 1 Andrijauskas_Fabio_M.pdf: 2796809 bytes, checksum: 9fd4e03f6038d482ed05a64517bb1780 (MD5) Previous issue date: 2013
Resumo: A quantidade de imagens astronômicas geradas cresce diariamente, além da quantidade já obtida e armazenada. Uma grande fonte de dados são imagens solares, cujo estudo pode detectar eventos que têm a capacidade de afetar as telecomunicações, transmissão de energia elétrica e outros sistemas na Terra. Para que tais eventos sejam detectados, torna-se necessário analisar essas imagens de forma eficiente, levando em conta os aspectos de armazenamento, processamento e visualização. Agregar algoritmos de processamento de imagem e técnicas de computação de alto desempenho facilita o tratamento da informação de forma correta e em tempo reduzido. As técnicas de computação para alto desempenho utilizadas neste trabalho foram desenvolvidas para sistemas híbridos, isto é, aqueles que utilizam uma combinação de sistemas de memórias compartilhada e distribuída. Foram produzidas versões paralelas para sistemas híbridos de técnicas já estabelecidas. Além disso, novas técnicas foram propostas e testadas para esse sistema tais como o Filamento Diffusion Detection. Para avaliar a melhora no desempenho, foram feitas comparações entre as versões seriais e paralelas. Esse texto também apresenta um sistema com capacidade para armazenar, processar e visualizar as imagens solares. Em uma das técnicas de detecção de filamentos, o processo foi acelerado 120 vezes e um processo auxiliar para a detecção de áreas mais brilhantes foi 155 vezes mais rápido do que a versão serial
Abstract: The number of astronomical images produced grows daily, in addition to the amount already stored. Great sources of data are solar images, whose study can detect events which have the capacity to affect the telecommunications, electricity transmission and other systems on Earth. For such events being detected, it becomes necessary to treat these images in a coherent way, considering aspects of storage, processing and image visualization. Combining image processing algorithms and high performance computing techniques facilitates the handling of information accurately and in a reduced time. The techniques for high performance computing used in this work were developed for hybrid systems, which employ a combination of shared and distributed memory systems. Parallel version of some established techniques were produced for hybrid systems. Moreover, new techniques have been proposed and tested for this system. To evaluate the improvement in performance, comparisons were made between serial and parallel versions. In addition to the analysis, this text also presents a system with capacity to store, process and visualize solar images. In one of the techniques for detecting filaments, the process was accelerated 120 times. Also an auxiliary process for the detection of brighter areas was 155 times faster than the serial version
Mestrado
Tecnologia e Inovação
Mestre em Tecnologia
16
Oliveira, Marcel Nogueira de. "Sinais ao nível do solo de partículas relativísticas associadas a erupção de um filamento solar no dia 1 de Novembro de 2014." Niterói, 2017. https://app.uff.br/riuff/handle/1/4019.
Full textAbstract:
Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-07-14T19:20:36Z
No. of bitstreams: 1
Marcel N Oliveira_Mestrado_UFF.pdf: 4519413 bytes, checksum: c433d3349c9b78949e508a919bf89ad8 (MD5)Made available in DSpace on 2017-07-14T19:20:36Z (GMT). No. of bitstreams: 1 Marcel N Oliveira_Mestrado_UFF.pdf: 4519413 bytes, checksum: c433d3349c9b78949e508a919bf89ad8 (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Um filamento solar entrou em erupção no dia 1 de Novembro de 2014, com início às 04:44 UT e uma duração de cerca de três horas, resultando em uma explosão solar (flare) do de classe C2.7. O flare foi associado com o desaparecimento súbito de um grande filamento. O filamento foi ejetado para o espaço, formando um núcleo de uma emissão de massa coronal (CME). A localização da explosão foi na região sudeste do sol (perto da borda oriental do sol), isto significa que a região não é geoefetiva. Uma tempestade de radiação, isto é, partículas energéticas solares (SEP) começaram a chegar à Terra em torno de 14:00 UT, atingindo a condição do nível S1 (menor) na escala NOAA de tempestades de radiação, em 2 de Novembro. Em coincidência com o início da tempestade de radiação S1 (SEP acima de 5 MeV), os telescópios Tupi localizados no IF-UFF, em Niterói – RJ, região que está localizada dentro da Anomalia do Atlântico Sul (SAA) detectou um excesso de múons, originados por partículas (prótons) relativísticas emitidas na explosão solar. Além disso, também foi encontrado em um aumento na intensidade de partículas observado no monitor de nêutrons localizado no Polo Sul. Isto significa que houve uma propagação transversal ao campo magnético interplanetário de partículas energéticas solares. No entanto, mostra-se que a difusão perpendicular sozinha não pode explicar estas observações, é necessária uma combinação com outros processos como uma velocidade muito alta, pelo menos de uma fração dos choques CME, perto do plano da eclíptica.
A solar filament erupted on November the 1st, 2014, started at 04:44 UT with a duration of about 3 hours, resulting in a solar flare of the type C2-7. The flare was associated with the sudden disappearance of a big filament. The filament was ejected to the space, forming the nucleus of a coronal mass ejection (CME). The explosion was localized in the southeast region of the sun (near sun’s oriental border), this means that the region is not geoeffective. A radiation storm i.e solar energetic particles (SEP) started to arrive on Earth around 14:00 UT, reaching the level S1 (minor) condition on the NOAA scale of radiation storms, on November the 2nd. Coinciding with the start of the S1 radiation storm (SEP above 5 MeV), the Tupi telescopes localized in IF-UFF, Niterói – RJ, region that is localized within the South Atlantic Anomaly (SAA) detected an excess of muons, originated from relativistic particles (protons) emitted on the solar explosion. Furthermore, an increase of the intensity of particles observed on the neutron monitor localized on the south pole. This means that a transversal, to the interplanetary magnetic field, propagation of solar energetic particles occurred. Nonetheless, is shown that the perpendicular diffusion alone can not explain this observations, a combination with other processes is necessary like a very high speed, of at least a fraction of the CME shocks, around the ecliptic plane.
17
Silva, Márcio Marques da. "Desenvolvimento e implementação de um sistema integrado para o projeto, otimização e fabricação de peças através do processo de filamento winding." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-19072018-160209/.
Full textAbstract:
Na busca de materiais de baixa densidade, alta resistência e baixo custo, o processo de Filament Winding, ou Enrolamento Filamentar, surge como uma das opções de processo automatizado para a fabricação de componentes em materiais compósitos reforçados por fibras (FRP – Fiber Reinforced Polymers). Tendo uma ampla aplicação estrutural, o tipo de fibra, o tipo de matriz, a orientação das fibras, as camadas de reforço, o mandril a ser utilizado e a otimização da trajetória de deposição das fibras são características essenciais para obtenção de uma peça com as características desejadas no processo. Dentre as necessidades para a utilização deste processo, exerce um papel de destacada influência a geração dos dados da trajetória de deposição da fibra, bem como a geração dos dados operacionais do processo. Este trabalho tem por objetivos desenvolver um programa para a geração destes dados, bem como os dispositivos necessários para a execução do processo de Filament Winding em torno CNC comercial. Os dados das trajetórias são gerados de modo integrado ao sistema CAD, representados por meio dos ângulos das trajetórias, e são alimentados em um programa computacional desenvolvido para este fim, que gera o código CN para a fabricação da peça no equipamento. Para a execução deste código na máquina CNC, foram desenvolvidos sistema de fixação do mandril e alimentador da fibra (incluindo tensionador) que possibilitam a execução do processo neste tipo de equipamento. Todo o sistema desenvolvido foi implementado e utilizado para a confecção de tubos com diferentes trajetórias de preenchimento, validando o sistema computacional e o processo desenvolvido.In the search of low density, high strength and low cost materials, Filament Winding seems to be an option of automated process to manufacture components in Composite Materials Reinforced by Fibers (FRP – Fiber Reinforced Polymers). Due to its large application in structural engineering, aspects such as fibers, matrices, fiber paths and laminate sequence are essential characteristics to obtain the desired final part. Among the requirements to use the Filament Winding Process, the definition of the fiber paths as well as the laminate sequence play fundamental roles in order to achieve the optimum structural performance of the composite part. This work aims to develop the necessary program to generate this data and devices required for the implementation of Filament Winding process in a commercial CNC machine tool. The data of the trajectories are generated in the CAD system, represented by the angles of the trajectories, and are fed in a computer program developed for this purpose, which generates the NC code for the manufacture of the part in the machine. In order to carried out this code in the CNC machine there were developed mandrel fixation system and fiber feeder (including tensioner were deverloped) that enable to wind the part in this type of equipment. The system developed has been implemented and used for the manufacture of tube parts with different fiber paths, validating the integrated system and the process developed.
18
Noble, Christopher J. "Forecasting vortex filaments." Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8165.
Full textAbstract:
The accuracy of stratospheric forecasts from the United Kingdom Meteorological Office's (UKMO) assimilation system in the Southern Hemisphere (SH) are studied primarily for a period in October 1994 and also February 1995. Conventional root mean square error (RMSE) calculations for different regions show that stratospheric forecasts are a large improvement over persistence in October 1994 (SH winter) even at five days but not so during February 1995 (SH summer). Systematic errors in the temperature and zonal wind fields were found to occur in relation with the stratopause and polar jet respectively. Studies also show that in general the vortex minimum temperature is forecast too cool and the maximum wind in the polar jet is forecast too strong. An advection scheme on specialised parcel location fields is used to study the differences in the meridional component of the wind vector with results indicating the forecast winds are highly consistent with the analysed winds even after five days in most cases. A back-trajectory mapping technique is employed to generate high-resolution maps of isentropic potential vorticity to permit the study of small-scale structure. The overall structure in a total hemisphere field produced from forecast winds is very similar to that from analysed winds even for filamentary structure near the polar vortex. Qualitative comparisons of aircraft measured tracer structure during the Airborne Southern Hemisphere Ozone Experiment (ASHOE) 1994 with structure from the high-resolution potential vorticity maps shows that large-scale features are represented well by the back-trajectory mapping technique with possibly less success for small-scale structure.
19
Schlordt, Tobias [Verfasser]. "Robocasting: From Solid Filaments to Hollow Filaments and Coextrusion / Tobias Schlordt." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219471135/34.
Full text
20
Atwell, Scott. "Force et couple dans les pinces magnétiques : paysage énergétique de la protéine hRad51 sur ADN double-brin." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066606/document.
Full textAbstract:
Hautement conservé, de la bactérie jusqu'à l’Homme, la recombinaison homologue est indispensable à la survie de tout organisme vivant. Chez l’humain, la protéine hRad51 (human Rad51) y joue un rôle clé en s’autoassemblant au site de cassure sur les extrémités simple-brin d’une molécule d’ADN endommagée pour former le filament nucléoprotéique. Ce filament est capable à lui seul d’effectuer la plupart des opérations nécessaires au bon déroulement de la recombinaison homologue; il va permettre la reconnaissance d’homologie, l’appariement des séquences homologues et l’invasion de brins requise pour la synthèse de l’ADN manquant.La recombinaison homologue est un processus complexe impliquant de multiples partenaires. Pour mieux comprendre le rôle du filament nucléoprotéique au sein de la réaction, on se propose d’étudier ce dernier en l’absence de tout partenaire. Plus précisément, on observe le comportement mécanique de filaments hRad51-ADNdb en fonction des conditions chimiques. La formation du filament nucléoprotéique modifie la conformation de l’ADN sur lequel il s’assemble, l’allongeant de 50% et le déroulant de 43% dans le cas d’une molécule double-brin. Les pinces magnétiques sont un outil permettant de contrôler la force et la torsion appliquées à une unique molécule d’ADN double-brin (ADNdb), elles sont donc l’outil idéal pour sonder les propriétés mécaniques de filaments nucléoprotéiques. Le système des pinces magnétiques a été modifié afin de mesurer des paramètres mécaniques précédemment inaccessibles tel que le couple ressenti ou exercé par le filament. Le but de cette thèse a été d’étudier les propriétés mécano-chimiques des filaments nucléoprotéiques tout en essayant de tracer le paysage énergétique qui régit les transitions de ces systèmesHighly conserved throughout the species, homologous recombination is crucial to the survival of any living organism. In humans, the hRad51 protein (human Rad51) plays a key role by self-assembling at the break site on the single stranded extremities of damaged DNA molecules thus forming the nucleoprotein filament. This filament is able by itself to accomplish most of the necessary operations of homologous recombination; it allows the homology search, the pairing of the homologous sequences and the strand exchange.Homologous recombination is a complex process involving many partners. In order to better understand the role of the nucleoprotein filament in this process, we propose to study it in the absence of any partners. We will focus on the study of the mechanical properties of hRad51-dsDNA filaments as a function of chemical conditions. The formation of the nucleoprotein filament modifies the conformation of the DNA molecule on which it assembles, stretching it by 50% and unwinding it by 43% in the case of a double stranded DNA. The magnetic tweezers are a tool allowing the control of the force and torsion applied to a single dsDNA molecule; they are therefore the ideal tool to probe the mechanical properties of nucleoprotein filaments. We modified the magnetic tweezers as to allow the measurement of previously inaccessible mechanical parameters such as the torque applied or felt by the filament. The goal of this thesis has been to study the mechano-chemical properties of nucleoprotein filaments while drawing the energy landscape that governs the various transitions of these systems
21
Matthews, Richard. "Knotted polymers and filaments." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533834.
Full text
22
Meunier, Thomas. "Dynamique des filaments d'upwelling." Brest, 2011. http://www.theses.fr/2011BRES2022.
Full textAbstract:
Cette thèse traite de la dynamique des filaments d’upwelling. Trois mécanismes de formation sont étudiés au travers de deux études de processus et de données in-situ et télédétectées. L’impact de la topographie de fond sur la génération et le piégeage de filaments sont étudiés à l’aide d’un modèle shallow water à deux couches. Il est montré que la génération d’anomalie de vorticité potentielle piégée au dessus d’un promontoire induit une circulation permanente qui pince le front et l’entraîne loin au large. La sensibilité du processus à de nombreux paramètres est étudIée. L'interaction entre un jet de surface et un courant profond séparés par une couche intermédiaire sans anomalie de PV est également étudiée à l’aide d’un modèle shallow water. Une analyse de stabilité linéaire montre que ce système de courant est instable barocliniquement et qu’il existe toujours une longueur d’onde instable quelle que soit l’épaisseur de la couche intermédiaire. Il est montré que l’interaction entre des structures vorticales profondes et un front de surface stable peut générer des méandres et des filaments. Enfin, la dynamique des filaments d’upwelling au large de Cap Blanc (Mauritanie) est étudiée à l’aide de données in-situ et télédétectées. La présence de tourbillons issus du front du Cap Vert joue un rôle clé dans la formation des filaments. La topographie semble également jouer un rôle important, avec la formation d’un anticyclone au dessus d’un large promontoire. De manière générale, il est montré que les filaments d’upwelling résultent de l’interaction de structures vorticales et d’un front côtierThe nature and dynamics of upwelling filaments are investigated. A numerical process study is performed in order to elucidate the trapping of filaments near topographic anomalies. The generation of potential vorticity anomalies is shown to induce a trapped circulation which pinches the coastal front and pulls it far offshore. The process is shown to be sensitive to the shape of the topographic anomalies and other parameters. The interactions of a surface boundary current and a deep remote counter-current are also studied using a shallow water model. First, a quasi geostrophic linear stability analysis showed that this current system is unstable whatever the thickness of the intermediate layer. The various non-linear regimes are shown, and the sensitivity of the process to various parameters is studied. It is also shown that deep remote eddies could also trigger meanders and filaments from a surface front. Finally, the dynamics of the upwelling filaments forming off Cap Blanc (Mauritania) is investigated using in-situ and remotely sensed data. It is shown that the eddies related with the Cape Verde Frontal Zone were mainly responsible for the offshore-entrainment of coastally upwelled water. Topographic effects are shown to be important too in advecting the water into the external eddy field. In all cases, it is shown that upwelling filaments arise from the interactions of vortical structures and coastal fronts
23
de, Mourgues Marius. "Composite Cellulose Nanofibrils Filaments." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277919.
Full textAbstract:
Biodegradable polymers are emerging as a new solution to satisfy the increasing demand of greenenvironmentally friendly material. At the same time, the interest for lighter and stronger structures never stops growing. In this paper, we report the production steps to achieve cellulose nanofibrils (CNF) composite filaments via a new green synthesis route known as wet spinning. This new technique avoids the traditional harmful viscose process and produces biodegradable CNF filaments with interesting mechanical properties. This approach is then applied to produce never seen before composite CNF filaments using a three-layered head extruder. In order to obtain conductive filaments, PEDOT/PPS is successfully mixed with CNF to produce in-situ composite filaments. Scanning electron microscopy (SEM), atomic force measurements and tensile tests are employed to characterize the properties of the filaments.Biologiskt nedbrytbara polymerer börjar framträda som en lösning för det ökade behovet avmiljövänliga material. Samtidigt så växer intresset för lättare och starkare strukturer. I denna rapport tar vi upp produktionsstegen för att uppnå nanofibril komposit cellulosa fibrer (CNF), med hjälp av en ny grön polymerisation mest känd som ”wet spinning”. Med denna nya teknik så behövs inte dem traditionella miljöfarliga viskosprocesserna och man producerar biologiskt nedbrytbara CNF filaments med intressanta mekaniska egenskaper. Denna metod appliceras sen för att producera en komposit som aldrig setts innan. CNF fibrer som består av tre lager ”head-extruder”. För att få fibrer med ledningsförmåga så mixas PEDOT/PPS med CNF för att producera ”in-situ komposit fibrer”. Svepelektronmikroskop (SEM), atomkraftsmikroskopi och töjningstester används för att karaktärisera egenskaperna av fibrerna.
24
Farah, Chuck Shaker. "Funções estruturais e regulatórias das regiões N- e C-terminal da troponina I." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-08082012-152838/.
Full textAbstract:
O complexo troponina-tropomiosina regula a contração muscular esquelética e cardíaca. A ligação do cálcio nos sítios regulatórios localizados no domínio N-terminal da troponina C (TnC) induz uma mudança conformacional que remove a ação inibitória da troponina I (TnI) e inicia a contração muscular. Nós usamos fragmentos recombinantes da TnI e uma série de mutantes da TnC para estudar as interações estruturais e regulatórias das diferentes regiões da TnI com os domínios da TnC, TnT e actina-tropomiosina. Nossos resultados indicam que a TnI é organizada em regiões que apresentam funções estruturais e regulatórias e que se ligam de modo antiparalelo com os correspondentes domínios estruturais e regulatórios da TnC. Estudos funcionais mostram que a região inibitória (aminoácidos 103-116) em combinação com a região C-terminal da TnI (TnI103-182) pode regular a atividade ATPásica da acto-miosina de maneira dependente de Ca2+. A regulação não é observada com a região inibitória em combinação com a região N-terminal (TnI116) Estudos de ligação mostram que a região N-terminal da TnI (TnI1-98) interage com o domínio C-terminal da TnC na presença e na ausência de Ca2+ e também interage com a TnT. A região inibitória/C-terminal da TnI (TnI103-182) interage com o domínio N-terminal da TnC de maneira dependente de Ca2+. Baseados nestes resultados, propomos um modelo para a mudança conformacional induzida pelo Ca2+. Neste modelo, a região N-terminal da TnI está ligada fortemente com o domínio C-terminal da TnC na presença ou na ausência de Ca2+. As regiões inibitórias e C-terminal da TnI ligam-se à actina-tropomiosina na ausência de Ca2+ e nos domínios N-terminal e C-terminal da TnC na presença de Ca2+.The troponin-tropomyosin complex regulates skeletal and cardiac muscle contraction. Calcium binding to the regulatory sites in the N-terminal domain of troponin C (TnC). induces a conformational change which removes the inhibitory action of troponin I (TnI) and initiates muscular contraction. We used recombinant TnI fragments and a series of TnC mutants to study the structural and regulatory interactions between different TnI regions and the domains of TnC, TnT and actin-tropomyosin. Our results indicate that TnI is organized into regions with distinct structural and regulatory functions which bind, in an antiparallel manner, with the corresponding structural and regulatory domains of TnC. Functional studies show that a fragment containing the inhibitory and C-terminal regions of TnI (TnIl03-182) can regulate the actomyosin ATPase in a Ca2+- dependent manner. Regulation was not observed with a fragment containing the N-terminal and inhibitory regions (TnIl-116). Binding studies show that the N-terminal region of TnI (TnI1-98) interacts with the C-terminal domain of TnC in the presence of Ca2+ or Mg2+. The inhibitory/C-terminal region of TnI (TnI103-182) binds to the N-terminal domain of TnC in a Ca2+-dependent manner. Based on these results, we propose a model for the Ca2+ -induced conformational change. In this model the N-terminal region of TnI is bound strongly to the C-terminal domain of TnC in the presence or absence of Ca2+. The inhibitory and C-terminal regions of TnI bind to actin-tropomyosin in the absence of Ca2+ and to tne N- and C-terminal domains of TnC in the presence of Ca2+.
25
Zumdieck, Alexander. "Dynamics of Active Filament Systems: The Role of Filament Polymerization and Depolymerization." Doctoral thesis, Technische Universität Dresden, 2005. https://tud.qucosa.de/id/qucosa%3A24642.
Full textAbstract:
Aktive Filament-Systeme, wie zum Beispiel das Zellskelett, sind Beispiele einer interessanten Klasse neuartiger Materialien, die eine wichtige Rolle in der belebten Natur spielen. Viele wichtige Prozesse in lebenden Zellen wie zum Beispiel die Zellbewegung oder Zellteilung basieren auf dem Zellskelett. Das Zellskelett besteht aus Protein-Filamenten, molekularen Motoren und einer großen Zahl weiterer Proteine, die an die Filamente binden und diese zu einem Netz verbinden können. Die Filamente selber sind semifexible Polymere, typischerweise einige Mikrometer lang und bestehen aus einigen hundert bis tausend Untereinheiten, typischerweise Mono- oder Dimeren. Die Filamente sind strukturell polar, d.h. sie haben eine definierte Richtung, ähnlich einer Ratsche. Diese Polarität begründet unterschiedliche Polymerisierungs- und Depolymerisierungs-Eigenschaften der beiden Filamentenden und legt außerdem die Bewegungsrichtung molekularer Motoren fest. Die Polymerisation von Filamenten sowie Krafterzeugung und Bewegung molekularer Motoren sind aktive Prozesse, die kontinuierlich chemische Energie benötigen. Das Zellskelett ist somit ein aktives Gel, das sich fern vom thermodynamischen Gleichgewicht befindet. In dieser Arbeit präsentieren wir Beschreibungen solcher aktiven Filament-Systeme und wenden sie auf Strukturen an, die eine ähnliche Geometrie wie zellulare Strukturen haben. Beispiele solcher zellularer Strukturen sind Spannungsfasern, kontraktile Ringe oder mitotische Spindeln. Spannungsfasern sind für die Zellbewegung essentiell; sie können kontrahieren und so die Zelle vorwärts bewegen. Die mitotische Spindel trennt Kopien der Erbsubstanz DNS vor der eigentlichen Zellteilung. Der kontraktile Ring schließlich trennt die Zelle am Ende der Zellteilung. In unserer Theorie konzentrieren wir uns auf den Einfluß der Polymerisierung und Depolymerisierung von Filamenten auf die Dynamik dieser Strukturen. Wir zeigen, dass der kontinuierliche Umschlag (d.h. fortwährende Polymerisierung und Depolymerisierung) von Filamenten unabdingbar ist für die kontraktion eines Rings mit konstanter Geschwindigkeit, so wie in Experimenten mit Hefezellen beobachtet. Mit Hilfe einer mikroskopisch motivierten Beschreibung zeigen wir, wie "filament treadmilling", also Filament Polymerisierung an einem Ende mit der gleichen Rate wie Depolymerisierung am anderen Ende, zur Spannung in Filament Bündeln und Ringen beitragen kann. Ein zentrales Ergebnis ist, dass die Depolymerisierung von Filamenten in Anwesenheit von filamentverbindenden Proteinen das Zusammenziehen dieser Bündel sogar in Abwesenheit molekulare Motoren herbeiführen kann. Ferner entwickeln wir eine generische Kontinuumsbeschreibung aktiver Filament-Systeme, die ausschließlich auf Symmetrien der Systeme beruht und von mikroskopischen Details unabhängig ist. Diese Theorie erlaubt uns eine komplementäre Sichtweise auf solche aktiven Filament-Systeme. Sie stellt ein wichtiges Werkzeug dar, um die physikalischen Mechanismen z.B. in Filamentbündeln aber auch bei der Bildung von Filamentringen im Zellkortex zu untersuchen. Schließlich entwickeln wir eine auf einem Kräftegleichgewicht basierende Beschreibung für bipolare Strukturen aktiver Filamente und wenden diese auf die mitotische Spindel an. Wir diskutieren Bedingungen für die Bildung und Stabilität von Spindeln.Active filament systems such as the cell cytoskeleton represent an intriguing class of novel materials that play an important role in nature. The cytoskeleton for example provides the mechanical basis for many central processes in living cells, such as cell locomotion or cell division. It consists of protein filaments, molecular motors and a host of related proteins that can bind to and cross-link the filaments. The filaments themselves are semiflexible polymers that are typically several micrometers long and made of several hundreds to thousands of subunits. The filaments are structurally polar, i.e. they possess a directionality. This polarity causes the two distinct filament ends to exhibit different properties regarding polymerization and depolymerization and also defines the direction of movement of molecular motors. Filament polymerization as well as force generation and motion of molecular motors are active processes, that constantly use chemical energy. The cytoskeleton is thus an active gel, far from equilibrium. We present theories of such active filament systems and apply them to geometries reminiscent of structures in living cells such as stress fibers, contractile rings or mitotic spindles. Stress fibers are involved in cell locomotion and propel the cell forward, the mitotic spindle mechanically separates the duplicated sets of chromosomes prior to cell division and the contractile ring cleaves the cell during the final stages of cell division. In our theory, we focus in particular on the role of filament polymerization and depolymerization for the dynamics of these structures. Using a mean field description of active filament systems that is based on the microscopic processes of filaments and motors, we show how filament polymerization and depolymerization contribute to the tension in filament bundles and rings. We especially study filament treadmilling, an ubiquitous process in cells, in which one filament end grows at the same rate as the other one shrinks. A key result is that depolymerization of filaments in the presence of linking proteins can induce bundle contraction even in the absence of molecular motors. We extend this description and apply it to the mitotic spindle. Starting from force balance considerations we discuss conditions for spindle formation and stability. We find that motor binding to filament ends is essential for spindle formation. Furthermore we develop a generic continuum description that is based on symmetry considerations and independent of microscopic details. This theory allows us to present a complementary view on filament bundles, as well as to investigate physical mechanisms behind cell cortex dynamics and ring formation in the two dimensional geometry of a cylinder surface. Finally we present a phenomenological description for the dynamics of contractile rings that is based on the balance of forces generated by active processes in the ring with forces necessary to deform the cell. We find that filament turnover is essential for ring contraction with constant velocities such as observed in experiments with fission yeast.
26
Klemm, Sandy. "The virtual filament model." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3872.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2006.Thesis research directed by: Dept. of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
27
Gomes, Edgar dos Santos. "Implementação de rotinas computacionais para o cálculo de trajetórias geodésicas no processo de filament winding." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-27092013-095037/.
Full textAbstract:
Materiais compósitos são conhecidos pela alta resistência mecânica e baixo peso, desempenho superior, resistência à corrosão e baixa densidade. A produção de um material composto possui vários processos com particularidades diferentes. O enrolamento filamentar (Filament Winding) é um processo no qual fibras de reforço contínuas são posicionadas de maneira precisa e de acordo com um padrão predeterminado para compor a forma do componente desejado. As fibras, submetidas à tração, são enroladas continuamente ao redor de um mandril que tem a forma do produto final, em geral utilizando equipamentos automáticos. No final do processo, após a cura da resina, o mandril é geralmente removido. Desta forma, é de fundamental importância que o projetista disponha de recursos computacionais adequados para o cálculo das trajetórias e sequenciamento de posicionamento das fibras. Esse trabalho tem como objetivo o desenvolvimento de procedimentos matemáticos para cálculo de trajetórias geodésicas no processo de \"Filament Winding\" e implementá-los em um ambiente computacional em linguagem de alto nível Java, considerando-se os casos de revestimento circunferencial, helicoidal e polar. São desenvolvidos dois estudos de caso: tubos cônicos e vasos de pressão, e os resultados apresentados e discutidos, validando os procedimentos e ambiente implementado.Composite materials are well known by the high strength and low weight, superior performance, resistance to the corrosion and low density. The production of a composite material part involves some processes with different requirements. The filament winding process is an automated process in which continuous reinforcement fibers are lay down in prescribed paths on the surface of a mandrel, which is generally removed after the cure of the resin. In such a way, it is fundamental that the designer uses computational resources for the calculation of the paths and sequence of the fibers. In this work is developed the mathematical procedures for calculation of geodesic trajectories in the Filament Winding process and implements them in a computational environment in high level language Java, considering the circumferential, helical and polar strategies. Two case studies are developed successfully: conical pipes and pressure vessels, and the results presented and discussed, validating the procedures and implemented environment.
28
Tatýrek, Lukáš. "Prototyp zařízení pro recyklaci filamentu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442859.
Full textAbstract:
Master thesis is focusing on possibility of recycling waste from 3D prints. Goal was to degin a make lament extruder and winder. Design is based on research of avaible comercial and OpenSource solutions. The result is working machine with compact oor prejction, which is able to produce 110 grams of lament per hour. Deviation from diameter was ±0, 07. Conclusion place great emphasis on further improving and testing, beacuse it has not been reached limits of machine.
29
Colakoglu, Gulsen. "Assembly Dynamics of Intermediate Filaments." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1247691189.
Full text
30
Moreira, Inês de Castro Luís Lopes. "Filamentos metropolitanos." Doctoral thesis, Universidade de Lisboa, Faculdade de Arquitetura, 2016. http://hdl.handle.net/10400.5/20173.
Full textAbstract:
Tese de Doutoramento em Urbanismo, com a especialização em Urbanismo apresentada na Faculdade de Arquitetura da Universidade de Lisboa para obtenção do grau de Doutor.As alterações do contexto físico, económico e político, ocorridas desde a segunda metade do século XX, vieram potenciar as transformações no território metropolitano de Lisboa e a emergência de filamentos metropolitanos (áreas urbanas especializadas). Estas, produto de processos de infraestruturação e densificação metropolitana, caracterizam-se pela ocupação de áreas periféricas ao centro consolidado, em localizações estratégicas da rede rodoviária e elevado grau de especialização funcional. O resultado consiste num sistema urbano polinucleado, com a existência de áreas de grande concentração de atividades económicas ligadas ao sector terciário e quaternário e, simultaneamente, o abandono e a posterior reestruturação das áreas industriais periféricas. De forma a analisar o processo subjacente ao seu aparecimento e consolidação, exploram-se as transformações que se verificaram, os principais motores e as consequências da especialização do território. Com o objectivo de identificar e tipificar as formações urbanísticas emergentes, descodificar as suas lógicas espaciais e os seus processos de formação/transformação, propõe-se a seguinte estrutura metodológica: - Enquadramento conceptual e comparativo das transformações do território metropolitano de Lisboa; - Análise das novas configurações urbanas especializadas a nível funcional e da sua correlação com o território metropolitano; - Operacionalização das dinâmicas identificadas e tradução em princípios de atuação exportáveis para realidades semelhantes.
ABSTRACT: The changes in the physical, economic and political context that occurred since the second half of the twentieth century have contributed to the transformations of Lisbon metropolitan territory and the emergence of metropolitan filaments (specialized urban areas). These areas are the product of metropolitan infrastructuration and densification, and are characterized by their peripheral location, in strategic points of the mobility network and a high degree of functional specialization. The result is a polynuclear urban system with areas of great concentration of economic activities related to the tertiary sector and, simultaneously, the abandonment and afterwards the restructuring of peripheral industrial areas. In order to analyze the process underlying its emergence and consolidation, the research focuses on the transformations, the main drivers and the consequences of the territorial specialization. The following methodological structure is applied with the goal of identifying and typifying the emerging urban formations, as well as decoding their spatial logics and the formation / transformation processes: - Conceptual and comparative framework of the transformations occurred in Lisbon metropolitan territory; - Analysis of the new specialized urban forms and their correlation with the metropolitan territory; - Operationalization of the identified dynamics and translation into guidelines applicable to similar realities.
N/A
31
Klein, Gernot A. "Theoretical aspects of motor protein induced filament depolymerisation." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979172691.
Full text
32
Perera, Nirmali. "Effect of filament properties and twist on the bending behaviour of continuous filament yarns." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539322.
Full text
33
Mitra, Smita. "Design and manufacture of base/filament interconnects and filament patterning of piezoelectric cochlear implant." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1092405861.
Full text
34
MITRA, SMITA. "DESIGN AND MANUFACTURE OF BASE / FILAMENT INTERCONNECTS AND FILAMENT PATTERNING OF PIEZOELECTRIC COCHLEAR IMPLANT." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092405861.
Full text
35
Buchwald, Rajko. "Optoelektrische Magnetfelduntersuchungen an Solarsilizium." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-39445.
Full textAbstract:
Es werden die Ergebnisse der Untersuchungen von Stromverteilungen an Solarzellen und Solarmaterial durch magnetische, elektrische und optische Messmethoden gezeigt. Die neue magnetfeldtopographische Messmethode CAIC wird hierbei erläutert und deren Stromverteilungen mit Ergebnissen der IR-Durchlichtmikroskopie, der LBIC- und der LIT-Methode verglichen und ausgewertet. Auf Basis der durchgeführten Untersuchungen und der Annahme des Vorhandenseins einer Korngrenzendekoration werden die Stromverlaufsmodelle einer elektrisch aktiven Korngrenze für eine Probe mit pn-Übergang sowie für eine Probe ohne pn-Übergang gezeigt. Anhand von CAIC-Messungen können die Position und die Orientierung leitfähiger und oberflächennaher SiC- und Si3N4-Ausscheidungen in mc-Silizium ohne pn-Übergang ermittelt werden. Hierfür wird ein Stromverlaufsmodell gezeigt. Weiterhin werden Zellmikrobrüche, Fehler in der Kontaktstruktur und Layoutunterschiede der Kontaktstruktur durch CAIC-Messungen an Solarzellen eindeutig nachgewiesen.
36
Zumdieck, Alexander. "Dynamics of Active Filament Systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1139849910030-68242.
Full textAbstract:
Aktive Filament-Systeme, wie zum Beispiel das Zellskelett, sind Beispiele einer interessanten Klasse neuartiger Materialien, die eine wichtige Rolle in der belebten Natur spielen. Viele wichtige Prozesse in lebenden Zellen wie zum Beispiel die Zellbewegung oder Zellteilung basieren auf dem Zellskelett. Das Zellskelett besteht aus Protein-Filamenten, molekularen Motoren und einer großen Zahl weiterer Proteine, die an die Filamente binden und diese zu einem Netz verbinden können. Die Filamente selber sind semifexible Polymere, typischerweise einige Mikrometer lang und bestehen aus einigen hundert bis tausend Untereinheiten, typischerweise Mono- oder Dimeren. Die Filamente sind strukturell polar, d.h. sie haben eine definierte Richtung, ähnlich einer Ratsche. Diese Polarität begründet unterschiedliche Polymerisierungs- und Depolymerisierungs-Eigenschaften der beiden Filamentenden und legt außerdem die Bewegungsrichtung molekularer Motoren fest. Die Polymerisation von Filamenten sowie Krafterzeugung und Bewegung molekularer Motoren sind aktive Prozesse, die kontinuierlich chemische Energie benötigen. Das Zellskelett ist somit ein aktives Gel, das sich fern vom thermodynamischen Gleichgewicht befindet. In dieser Arbeit präsentieren wir Beschreibungen solcher aktiven Filament-Systeme und wenden sie auf Strukturen an, die eine ähnliche Geometrie wie zellulare Strukturen haben. Beispiele solcher zellularer Strukturen sind Spannungsfasern, kontraktile Ringe oder mitotische Spindeln. Spannungsfasern sind für die Zellbewegung essentiell; sie können kontrahieren und so die Zelle vorwärts bewegen. Die mitotische Spindel trennt Kopien der Erbsubstanz DNS vor der eigentlichen Zellteilung. Der kontraktile Ring schließlich trennt die Zelle am Ende der Zellteilung. In unserer Theorie konzentrieren wir uns auf den Einfluß der Polymerisierung und Depolymerisierung von Filamenten auf die Dynamik dieser Strukturen. Wir zeigen, dass der kontinuierliche Umschlag (d.h. fortwährende Polymerisierung und Depolymerisierung) von Filamenten unabdingbar ist für die kontraktion eines Rings mit konstanter Geschwindigkeit, so wie in Experimenten mit Hefezellen beobachtet. Mit Hilfe einer mikroskopisch motivierten Beschreibung zeigen wir, wie "filament treadmilling", also Filament Polymerisierung an einem Ende mit der gleichen Rate wie Depolymerisierung am anderen Ende, zur Spannung in Filament Bündeln und Ringen beitragen kann. Ein zentrales Ergebnis ist, dass die Depolymerisierung von Filamenten in Anwesenheit von filamentverbindenden Proteinen das Zusammenziehen dieser Bündel sogar in Abwesenheit molekulare Motoren herbeiführen kann. Ferner entwickeln wir eine generische Kontinuumsbeschreibung aktiver Filament-Systeme, die ausschließlich auf Symmetrien der Systeme beruht und von mikroskopischen Details unabhängig ist. Diese Theorie erlaubt uns eine komplementäre Sichtweise auf solche aktiven Filament-Systeme. Sie stellt ein wichtiges Werkzeug dar, um die physikalischen Mechanismen z.B. in Filamentbündeln aber auch bei der Bildung von Filamentringen im Zellkortex zu untersuchen. Schließlich entwickeln wir eine auf einem Kräftegleichgewicht basierende Beschreibung für bipolare Strukturen aktiver Filamente und wenden diese auf die mitotische Spindel an. Wir diskutieren Bedingungen für die Bildung und Stabilität von SpindelnActive filament systems such as the cell cytoskeleton represent an intriguing class of novel materials that play an important role in nature. The cytoskeleton for example provides the mechanical basis for many central processes in living cells, such as cell locomotion or cell division. It consists of protein filaments, molecular motors and a host of related proteins that can bind to and cross-link the filaments. The filaments themselves are semiflexible polymers that are typically several micrometers long and made of several hundreds to thousands of subunits. The filaments are structurally polar, i.e. they possess a directionality. This polarity causes the two distinct filament ends to exhibit different properties regarding polymerization and depolymerization and also defines the direction of movement of molecular motors. Filament polymerization as well as force generation and motion of molecular motors are active processes, that constantly use chemical energy. The cytoskeleton is thus an active gel, far from equilibrium. We present theories of such active filament systems and apply them to geometries reminiscent of structures in living cells such as stress fibers, contractile rings or mitotic spindles. Stress fibers are involved in cell locomotion and propel the cell forward, the mitotic spindle mechanically separates the duplicated sets of chromosomes prior to cell division and the contractile ring cleaves the cell during the final stages of cell division. In our theory, we focus in particular on the role of filament polymerization and depolymerization for the dynamics of these structures. Using a mean field description of active filament systems that is based on the microscopic processes of filaments and motors, we show how filament polymerization and depolymerization contribute to the tension in filament bundles and rings. We especially study filament treadmilling, an ubiquitous process in cells, in which one filament end grows at the same rate as the other one shrinks. A key result is that depolymerization of filaments in the presence of linking proteins can induce bundle contraction even in the absence of molecular motors. We extend this description and apply it to the mitotic spindle. Starting from force balance considerations we discuss conditions for spindle formation and stability. We find that motor binding to filament ends is essential for spindle formation. Furthermore we develop a generic continuum description that is based on symmetry considerations and independent of microscopic details. This theory allows us to present a complementary view on filament bundles, as well as to investigate physical mechanisms behind cell cortex dynamics and ring formation in the two dimensional geometry of a cylinder surface. Finally we present a phenomenological description for the dynamics of contractile rings that is based on the balance of forces generated by active processes in the ring with forces necessary to deform the cell. We find that filament turnover is essential for ring contraction with constant velocities such as observed in experiments with fission yeast
37
Shotton-Gale, Nicholas Edward Harry. "Clean filament winding : process optimisation." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/3960/.
Full textAbstract:
This thesis reports on a modified wet-filament winding method, termed ‘clean filament winding’, which was developed to address multiple issues associated with the conventional method. The modified method comprised of a resin dispensing unit, static mixer and resin impregnation unit; these were incorporated to replace the practice of commonly used resin baths. Adaptations and developments of this method, such as impregnation modelling, fibre spreading and composite recycling were also used to further enhance the process. It was shown that the modified method was able to produce filament wound tubes with comparable (or superior) mechanical properties when compared the conventional technique. It was also shown that the modified method had considerable economic viability whilst providing substantial environmental impact reductions. These results were attributed to the use of a patented resin impregnation method which reduced the amount of waste resin, solvent for cleaning and production-time needed to fabricate filament wound components. This thesis concludes with details of a closed-loop composites recycling sitetrial. Here, waste-fibre materials were used to manufacture filament wound tubes as replacements for cardboard tubes for the storage of glass-fibre fabrics.
38
Deng, Daosheng. "In-fiber semiconductor filament arrays." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59705.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 107-112).
One-dimensional nanostructures with high aspect-ratios and nanometer cross-sectional dimensions have been the focus of recent studies in the persistent drive to miniaturize devices. Conventional bottom-up methods such as vapor-liquid-solid growth have been widely applied for the fabrication of uniform and high quality nanowires. Two challenges toward nanoelectronics and other applications remain: on the single-nanowire level, precisely manipulating an individual nanowire for the sophisticated functionalities, and on the multiple-nanowire level, integrating nanowires into designed architecture at large scale. Thus, an alternative approach with the capacity to achieve ordered and extended nanowires is highly desirable. In this thesis, we observe an intriguing phenomenon that a cylindrical shell upon reaching a characteristic thickness breaks up into filament arrays during optical-fiber thermal drawing. This structural evolution occurs exclusively in the cross-sectional plane, while the uniformity along the axial direction remains intact. We demonstrate crystalline semiconductor nanowires by post-drawing annealing procedure and characterize their electrical and optoelectric properties for the devices such as optical switch. This top-down thermal drawing approach provides new opportunities for nanostructure fabrication with high throughput and at low cost, and offers promising applications in renewable energy and data storage. In order to understand the stability (or instability) of thin shells and filaments, we explore a physical mechanism during the complicated thermal drawing. A perspective of capillary instability from fluid mechanics is focused. Axial stability of continuous filaments is consistent with capillary instability. Axial stability of a thicker cylindrical shell arises from large radius and high viscosity. These results provide theoretical guidance in the understanding of attainable feature sizes and in materials selection to expand the potential functionalities of devices in microstructured fibers.
by Daosheng Deng.
Ph.D.
39
Verdú, Blasco Pau. "Filamentos elásticos de elastolefina de alta durabilidad obtenidos a partir de copolímeros de bloque de etileno-octeno de baja densidad mediante la tecnología de polimerización por transferencia de cadena para aplicaciones en indumentaria de uso profesional." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/84166.
Full textAbstract:
En la actualidad el mercado carece de prendas elásticas para uso
profesional puesto que los elastanos habitualmente utilizados son
inestables frente a altas temperaturas y químicos agresivos, e.g.
termofijado, mantenimiento de indumentaria industrial etc.
Recientemente se han venido utilizado filamentos olefínicos
obtenidos a partir de copolímeros al azar de etileno-octeno (Dow
XLA™ fibers producidos por The Dow Chemical Company). Aunque más
resistentes a las temperaturas debido a la reticulación, su bajo
punto de fusión, alrededor de 50ºC, limita el comportamiento
elástico en tejidos pesados y tupidos para indumentaria
profesional.
La investigación tiene por objeto la obtención de monofilamentos
elásticos a partir copolímeros de bloque de etileno-octeno (cuyo
punto de fusión es más elevado) y con éstos, tejidos para
indumentaria profesional que ofrezcan mayor fuerza de
encogimiento a las temperaturas típicas de los pre-tratamientos,
tintura y acabado (50ºC-120ºC). El objetivo es hacer que los
tejidos encojan más durante las operaciones en húmedo bajo
temperatura para mejorar así su elasticidad y aumentar el peso en
comparación con los tejidos actuales manufacturados con los
convencionales copolímeros homogéneos de etileno-octeno
reticulados
Los tejidos deberán garantizar las siguientes propiedades durante
todo su ciclo de vida: estabilidad dimensional, relación
elasticidad-crecimiento mejorado, resistencia química,
resistencia térmica, durabilidad ante los lavados industriales y
un mejor confort termofisiológico y sensorial.Due to the lack of stability of elastane based materials against high temperatures and harsh chemicals, e.g. thermofixation and professional wear maintenance, elastic garments with elastane content are not yet fully commercial products. The Dow Chemical Company has recently commercialized a random ethylene-octene copolymer based fiber named Dow XLA™ fiber. Despite its higher temperature resistance as one of the crosslinking effects, its very low melting point, around 50ºC, establishes some limitations in elasticity such in heavy weight and high densely woven fabric cases typically found in professional wear applications. The target for the investigation is to produce block ethyleneoctene copolymer based filaments in which the melting point is supposed to be higher than in random copolymer materials. Different workwear fabrics will be manufactured with yarns containing such elastic filaments. It is supposed these fabrics to show high shrinkage forces even at dyeing and finishing temperatures, (50ºC-120ºC). The goal is to produce fabrics with superior shrinkage performance in order to achieve an excellent elastic power and the final desired fabric weight. Properties such as dimensional stability, stretch and growth ratio, temperature and chemical resistance and durability against industrial laundering should not be affected by the passage of the time. To validate this point these properties will be measured in the fabrics off loom and after the garment cycle life. These fabrics are also supposed to show better thermophysiological and sensorial properties than random copolymer fiber based textiles
40
Brun, Pierre-Thomas. "Dynamique des filaments élastiques et visqueux." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00761399.
Full textAbstract:
Ce manuscrit porte conjointement sur la dynamique des filaments élastiques et visqueux. Leur dynamique est décrite par les équations de Kirchhoff qui sont très largement discutées dans le manuscrit. La description Lagrandienne des filaments visqueux a conduit au code numérique pour leur simulation : Discrete Viscous Rods . Il est validé par l'exemple des enroulements de filaments visqueux similaires à ce qu'on voit en faisant chuter du miel sur une tartine. Nous en étudions ensuite une variante : la machine à coudre fluide. Le filament s'écoule alors sur un tapis roulant dont la vitesse est contrôlée et forme une myriade de motifs complexes ressemblant à ceux d'une véritable machine à coudre. Nous en produisons un diagramme de phase numérique et les décrivons dans un formalisme cinématique unifié. La cinématique de leur contact avec le tapis est d'ailleurs à l'origine de leur formation. Le filament compose avec des fractions exactes de sa fréquence propre pour s'adapter à la vitesse prescrite par le tapis roulant. Les motifs sont une trace de cette adaptation. Ensuite, nous étudions un exemple élastique de dynamique filamentaire : le repliement d'un ressort à courbure constante initialement déposé à plat sur une surface, maintenu par une extrémité, l'autre étant libérée à t = 0. L'énergie élastique de flexion est convertie à mesure que le ressort décolle du support. Son enroulement est inertiel et est formé d'une zone de rayon deux fois supérieur à celui du ressort repos. L'enroulement a une forme autosimilaire, et avance à vitesse constante. On finit par l'étude de la dynamique du lasso dont la dynamique est étudiée avec un modèle minimal de chaîne et d'un noeud coulant.
41
Niedermayer, Thomas. "On the depolymerization of actin filaments." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6360/.
Full textAbstract:
Actin is one of the most abundant and highly conserved proteins in eukaryotic cells. The globular protein assembles into long filaments, which form a variety of different networks within the cytoskeleton. The dynamic reorganization of these networks - which is pivotal for cell motility, cell adhesion, and cell division - is based on cycles of polymerization (assembly) and depolymerization (disassembly) of actin filaments. Actin binds ATP and within the filament, actin-bound ATP is hydrolyzed into ADP on a time scale of a few minutes. As ADP-actin dissociates faster from the filament ends than ATP-actin, the filament becomes less stable as it grows older. Recent single filament experiments, where abrupt dynamical changes during filament depolymerization have been observed, suggest the opposite behavior, however, namely that the actin filaments become increasingly stable with time. Several mechanisms for this stabilization have been proposed, ranging from structural transitions of the whole filament to surface attachment of the filament ends.
The key issue of this thesis is to elucidate the unexpected interruptions of depolymerization by a combination of experimental and theoretical studies. In new depolymerization experiments on single filaments, we confirm that filaments cease to shrink in an abrupt manner and determine the time from the initiation of depolymerization until the occurrence of the first interruption. This duration differs from filament to filament and represents a stochastic variable. We consider various hypothetical mechanisms that may cause the observed interruptions. These mechanisms cannot be distinguished directly, but they give rise to distinct distributions of the time until the first interruption, which we compute by modeling the underlying stochastic processes. A comparison with the measured distribution reveals that the sudden truncation of the shrinkage process neither arises from blocking of the ends nor from a collective transition of the whole filament. Instead, we predict a local transition process occurring at random sites within the filament.
The combination of additional experimental findings and our theoretical approach confirms the notion of a local transition mechanism and identifies the transition as the photo-induced formation of an actin dimer within the filaments. Unlabeled actin filaments do not exhibit pauses, which implies that, in vivo, older filaments become destabilized by ATP hydrolysis.
This destabilization can be identified with an acceleration of the depolymerization prior to the interruption. In the final part of this thesis, we theoretically analyze this acceleration to infer the mechanism of ATP hydrolysis. We show that the rate of ATP hydrolysis is constant within the filament, corresponding to a random as opposed to a vectorial hydrolysis mechanism.Aktin ist eines der am häufigsten vorkommenden und am stärksten konservierten Proteine in eukaryotischen Zellen. Dieses globuläre Protein bildet lange Filamente, die zu einer großen Vielfalt von Netzwerken innerhalb des Zellskeletts führen. Die dynamische Reorganisation dieser Netzwerke, die entscheidend für Zellbewegung, Zelladhäsion, und Zellteilung ist, basiert auf der Polymerisation (dem Aufbau) und der Depolymerisation (dem Abbau) von Aktinfilamenten. Aktin bindet ATP, welches innerhalb des Filaments auf einer Zeitskala von einigen Minuten in ADP hydrolysiert wird. Da ADP-Aktin schneller vom Filamentende dissoziiert als ATP-Aktin, sollte ein Filament mit der Zeit instabiler werden. Neuere Experimente, in denen abrupte dynamische Änderungen während der Filamentdepolymerisation beobachtet wurden, deuten jedoch auf ein gegenteiliges Verhalten hin: Die Aktinfilamente werden mit der Zeit zunehmend stabiler. Mehrere Mechanismen für diese Stabilisierung wurden bereits vorgeschlagen, von strukturellen Übergängen des gesamten Filaments bis zu Wechselwirkungen der Filamentenden mit dem experimentellen Aufbau. Das zentrale Thema der vorliegenden Dissertation ist die Aufklärung der unerwarteten Unterbrechungen der Depolymerisation. Dies geschieht durch eine Kombination von experimentellen und theoretischen Untersuchungen. Mit Hilfe neuer Depolymerisationexperimente mit einzelnen Filamenten bestätigen wir zunächst, dass die Filamente plötzlich aufhören zu schrumpfen und bestimmen die Zeit, die von der Einleitung der Depolymerisation bis zum Auftreten der ersten Unterbrechung vergeht. Diese Zeit unterscheidet sich von Filament zu Filament und stellt eine stochastische Größe dar. Wir untersuchen daraufhin verschiedene hypothetische Mechanismen, welche die beobachteten Unterbrechungen verursachen könnten. Die Mechanismen können experimentell nicht direkt unterschieden werden, haben jedoch verschiedene Verteilungen für die Zeit bis zur ersten Unterbrechung zur Folge. Wir berechnen die jeweiligen Verteilungen, indem wir die zugrundeliegenden stochastischen Prozesse modellieren. Ein Vergleich mit der gemessenen Verteilung zeigt, dass der plötzliche Abbruch des Depolymerisationsprozesses weder auf eine Blockade der Enden, noch auf einen kollektiven strukturellen Übergang des gesamten Filaments zurückzuführen ist. An Stelle dessen postulieren wir einen lokalen Übergangsprozess, der an zufälligen Stellen innerhalb des Filaments auftritt. Die Kombination von weiteren experimentellen Ergebnissen und unserem theoretischen Ansatz bestätigt die Vorstellung eines lokalen Übergangsmechanismus und identifiziert den Übergang als die photo-induzierte Bildung eines Aktindimers innerhalb des Filaments. Nicht fluoreszenzmarkierte Aktinfilamente zeigen keine Unterbrechungen, woraus folgt, dass ältere Filamente in vivo durch die ATP-Hydrolyse destabilisiert werden. Die Destabilisierung zeigt sich durch die Beschleunigung der Depolymerisation vor der Unterbrechung. Im letzten Teil der vorliegenden Arbeit untersuchen wir diese Beschleunigung mit theoretischen Methoden, um auf den Mechanismus der ATP-Hydrolyse zu schließen. Wir zeigen, dass die Hydrolyserate von ATP innerhalb des Filaments konstant ist, was dem sogenannten zufälligen Hydrolysemechanismus entspricht und im Gegensatz zum sogenannten vektoriellen Mechanismus steht.
42
Wong, Kai-lun, and 黃棨麟. "Nanomechanical studies of vimentin intermediate filaments." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799617.
Full textAbstract:
Intermediate filaments, microtubules and microfilaments are the major components of the cytoskeleton. Though it is known that intermediate filaments play an important role in the mechanical behaviour of cells, it is surprising that their mechanical properties are far from being fully understood.
The morphology and assembly process of the vimentin intermediate filaments (IFs) were studied using transmission electron microscopy (TEM) and atomic force spectroscopy (AFM). The width of the vimentin was found to change as the assembly proceeded. This finding agrees with the literature about the compaction process of vimentin IFs. The width of the IFs decreased gradually, while the range of width increased within the first few minutes after assembly initiation, and then decreased at last and became stable at 12.80±2.20nm. The average length of the IFs increased with decreasing rate. The length attained 485.60±162.23nm at 120 minutes. The range of length increased which revealed the assembly process was randomly occurring between filaments in the solution. The height of the IFs obtained with AFM did not show the periodicity in contrary to the literature. It may be due to the flattening of IFs on the functionalized mica(AP-mica) surface, or the periodicity was not prominent to be observed morphologically.
In the force spectroscopy study, the nanomechanical properties of individual vimentin intermediate filaments were studied using AFM. Fresh vimentin intermediate filaments and samples fixed with glutaraldehydewere examined, and force-displacement curves with nano-scale resolutions of different vimentin intermediate filament samples were analysed. The use of glutaraldehydefixative provided cross-linking of the IF, and the structural change will result in differences in their force-displacement curves which helped to provide comparison with the non-fixed samples in order to identify the structure-mechanical property relationship. Statistical studies of these curves revealed that tearing off of protofilaments from the mature intermediate filaments (with and without glutaraldehyde) occurred inthe low force regime below 100pN, and successive tearing off events were observed readily below 25 nm separations, which were comparable with the lengths of domains of around 20 nm. Different features of sawtooth indicated the possibility of sliding mechanism in vimentin IF, and the sliding was found to occur at 30.44±13.41pN. Helical domain unfoldings were observed only in the non-fixed samples to start at 10.19±5.63pN on average witha mean increase of 42.12±26.74nm. This force agreed with the prediction of the extended Bell model described in the literature and the length increase was around double of the domain length, which indicated the uncoiling of the coiled-coils. The force-displacement curves also reveal different modes of failure of the vimentin intermediate filaments including protofilaments slippage/sliding and entropic elasticity. A new tearing off model was hence proposed based on different modes of failure and a previous model developed for desmin filaments reported in literature.published_or_final_version
Orthopaedics and Traumatology
Doctoral
Doctor of Philosophy
43
Strehle, Dan. "Bundles of Semi-flexible Cytoskeletal Filaments." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-144750.
Full textAbstract:
Schaut man durch ein Mikroskop auf eine biologische Zelle mit angefärbten Zytoskelett, so erblickt man lange, mehr oder minder gerade Objekte. Mit ziemlicher Sicherheit gehören diese zu einer von drei Arten von Zytoskelettfilamenten -- Aktin- oder Mikrofilamente, Intermediärfilamente und Mikrotubuli. Schon seit mehreren Jahrzehnten versucht man die mechanischen Eigenschaften lebender Zellen nicht nur zu beschreiben, sondern ihr Verhalten von zwei tieferen Ebenen ausgehend zu verstehen: Inwiefern beschreiben die Eigenschaften von Filamentnetzwerken und -gelen die Zellmechanik und, noch tiefgreifender, wie bestimmen eigentlich die einzelnen Filamente die Netzwerkmechanik. Das Verständnis der Mechanik homogener und isotroper, verhedderter als auch quervernetzter Gele ist dabei erstaunlich detailreich, ohne jedoch vollständig dem jüngeren Verständnis von Zellen als glassartige Systeme zu entsprechen. In den letzten Jahren sind daher anisotrope Strukturen mehr und mehr in den Fokus gerückt, die die Bandbreite möglichen mechanischen Verhaltens enorm bereichern. Die vorliegende Arbeit beschäftigt sich mit solch einem hochgradig anisotropen System -- nämlich Aktinbündeln -- unter drei Gesichtspunkten. Mit Hilfe von aktiven Biegedeformationen wird ein funktionales Modul, das eine differentielle Antwort auf verschiedenen Zeitskalen liefert, identifiziert. Es handelt sich um Aktinfilamente, die durch transiente Quervernetzer gebündelt werden. Während sich das System nach kurz anhaltenden Deformation völlig elastisch verhält, sorgt eine Restrukturierung der Quervernetzer während langanhaltender Deformationen für eine plastische Verformung des Bündels. In einem weiteren Aspekt widmet sich die Arbeit der frequenz- und längenabhängigen Biegesteifigkeit. Die Methode des Bündel-Wigglings, das Induzieren von \"Seilwellen\", wird dabei genutzt, um aus der Wellenform die Biegesteifigkeit zu berechnen. Bündel von Aktinbündeln zeigen dabei ein Verhalten, das vom klassischen Worm-like-chain-Modell abweicht und stattdessen durch das Worm-like-bundle-Modell beschrieben werden kann. Der letzte Aspekt dieser Arbeit untersucht den Musterbildungsprozess bei der Entstehung von Aktinbündeln. Gänzlich unerwartet entstehen quasi-isotrope Strukturen mit langreichweitiger Ordnung, wenn der Bündelungsprozess erst nach der Polymerisation von Filamenten frei von zusätzlichen mechanischen Einwirkungen einsetzt. Da dieser Zustand nicht von der klassischen Flüssigkristalltheorie vorhergesagt wird, soll eine Simulation eine Hypothese zum Entstehungsmechanismus testen. Die Annahme einer lateralen Kondensation von Filamenten zu Bündeln reicht demnach aus, um die beobachteten Strukturen zu erzeugen. Diese Arbeit leistet somit einen Beitrag zum Verständnis hochgradig anisotroper Strukturen und deren Überstrukturen, wie sie auch in lebendigen Zellen reichlich vorhanden sindBeing the most basic unit of living organisms, the cell is a complex entity comprising thousands of different proteins. Yet only very few of which are considered to play a leading part in the cell’s mechanical integrity. The biopolymers actin, intermediate filaments and microtubules constitute the so-called cytoskeleton – a highly dynamic, constantly restructuring scaffold endowing the cell not only with integrity to sustain mechanical perturbations but also with the ability to rapidly reorganize or even drive directed motion. Actin has been regarded to be the protagonist and tremendous efforts have been made to understand passive actin networks using concepts from polymer rheology and statistical mechanics. In bottom-up approaches isotropic, homogeneous actin-gels are well-characterized with rheological methods that measure elastic and viscous properties on different time scales. Cells, however, are not exclusively isotropic networks of any of the mentioned filaments. Rather, actin alone can already be organized into heterogeneous and highly anisotropic structures like bundles. These heterogeneous structures have only come into focus recently with theoretical work addressing bundle networks. and, in the case of the worm-like bundle theory, individual bundles. This work aims at characterizing bundles and bundle-crosslinker systems mechanically in two complementary approaches – in the time as well as in the frequency domain. In addition, it illuminates a bundle formation mechanism that leads to bundle networks displaying higher ordering
44
Silva, Pedro Emanuel Santos. "Modelling the dynamics of elastic filaments." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/7422.
Full textAbstract:
Mestrado em FísicaIn this master's thesis an algorithm for modelling a three-dimensional elastic lament was developed. The model considers chains of beads that are constrained by stretching, bending and torsional forces. Equations that describe the dynamics of the system were derived from potential energies related to the di erent degrees of freedom. A set of numerical results that were obtained in several systems is analysed in this thesis, as a test bed for the algorithm. Force-extension curves of laments were obtained to compare the simulated results with the theoretical models from statistical physics of polymers. In this thesis, numerical techniques are also presented in order to perform the simulation, visualization and audition of the obtained results, so that this thesis may become an useful guide to a beginner in this eld. This thesis should also be regarded as the starting point for the investigation of new physical phenomena related to physical pseudoknots (PPKs). PPKs mechanisms seek to explain, in an innovative way, the arising of certain localized entanglements that occur in nature and which do not explicitly require chemical interactions.
Nesta tese de mestrado desenvolveu-se um algoritmo para simular o movimento de filamentos elásticos em três dimensões. O modelo é composto por uma cadeia de massas acopladas por forças de elongação,flexão e torção. As equações que descrevem a dinâmica do sistema foram deduzidas a partir da energia potencial associada aos vários graus de liberdade. Nesta tese analisa-se um conjunto de resultados numéricos obtidos em diversos sistemas, de forma a validar a simulação. Foram obtidas curvas para ensaios de força-extensão tendo como finalidade a comparação com resultados da Física estatística de polímeros. Nesta tese há também o cuidado de apresentar as técnicas numéricas desenvolvidas com vista à simulação, visualização e até percepção auditiva dos resultados obtidos, com o propósito de que este texto possa servir um potencial leitor interessado em iniciar-se nesta área. Esta tese deve também ser vista como um ponto de partida para a investigação de novos fenómenos físicos associados a pseudonós físicos (Physical PseudoKnots PPKs). Os mecanismos dos pseudonós físicos procuram explicar, de uma forma inovadora, o aparecimento de certos entanglements localizados que ocorrem na Natureza e que não requerem explicitamente interações químicas.
45
Barros, Gustavo de Ara?jo. "Tubula??es de PRFV com adi??o de areia quartzosa visando sua aplica??o na ind?stria do petr?leo." Universidade Federal do Rio Grande do Norte, 2007. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15730.
Full textAbstract:
Made available in DSpace on 2014-12-17T14:58:25Z (GMT). No. of bitstreams: 1
GustavoAB.pdf: 2461248 bytes, checksum: 0536be02b6961005820ca67a7e2765de (MD5)
Previous issue date: 2007-01-19Fillers are often added in composites to enhance performance and/or to reduce cost. Fiberglass pipes must meet performance requirements and industrial sand is frequently added for the pipe to be cost competitive. The sand is added to increase pipe wall thickness, thus increase pipe stiffness. The main goal of the present work is to conduct an experimental investigation between pipes fabricated with and without de addition of sand, to be used in the petroleum industry. Pipes were built using E-glass fibers, polyester resin and siliceous sand. The fabrication process used hand lay up and filament winding and was divided in two different parts: the liner and the structural wall. All tested pipes had the same liner, but different structural wall composition, which is the layer where siliceous sand may be added or not. The comparative investigation was developed considering the results of longitudinal tensile tests, hoop tensile tests, hydrostatic pressure leak tests and parallel-plate loading stiffness tests. SEM was used to analyze if the sand caused any damage to the glass fibers, during the fabrication process, because of the fiber-sand contact. The procedure was also used to verify the composite conditions after the hydrostatic pressure leak test. The results proved that the addition of siliceous sand reduced the leak pressure in about 17 %. In the other hand, this loss in pressure was compensated by a stiffness increment of more than 380 %. MEV analyses show that it is possible to find damage on the fiber-sand contact, but on a very small amount. On most cases, the contact occurs without damage evidences. In summary, the addition of sand filler represented a 27.8 % of cost reduction, when compared to a pipe designed with glass fiber and resin only. This cost reduction combined to the good mechanical tests results make siliceous sand filler suitable for fiberglass pressure pipes
Cargas de adi??o s?o utilizadas com freq??ncia, em materiais comp?sitos, para atingir propriedades mec?nicas requeridas por normas e para redu??o de custos. As tubula??es em pl?stico refor?ado com fibras de vidro (PRFV), utilizadas para aplica??es com altas press?es, devem atender a requisitos m?nimos de projeto estabelecidos em normas. Para tanto, a areia vem sendo utilizada como carga de adi??o, no sentido de manter os tubos em PRFV competitivos no mercado. A areia ? adicionada para aumentar a espessura da parede, aumentando com isso a rigidez. Este trabalho teve como principal objetivo analisar a influ?ncia da areia nas propriedades mec?nicas de tubula??es de PRFV, visando sua aplica??o na ind?stria do petr?leo e do g?s, atrav?s de ensaios comparativos entre tubos com e sem a adi??o de areia. Os tubos foram fabricados com fibras de vidro tipo E na forma de fios cont?nuos e manta, resina poli?ster ortoft?lica e areia quartzosa. A fabrica??o foi realizada em duas etapas distintas, sendo a primeira camada do tubo denominada de barreira qu?mica (processo de lamina??o manual) e a segunda camada denominada estrutura (fabricada pelo processo de filamento cont?nuo). A areia ? adicionada no tubo juntamente com as camadas de filamento cont?nuo e, portanto, ? um constituinte da estrutura do tubo. A an?lise comparativa foi conduzida atrav?s de ensaios de tra??o axial e ircunferencial, press?o hidrost?tica e rigidez, al?m de an?lises com microsc?pio eletr?nico de varredura (MEV). Foram avaliadas as for?as resultantes de ruptura e o m?dulo de elasticidade circunferencial, al?m da rigidez. As an?lises com MEV foram conduzidas para verificar a presen?a de danos causados as fibras, durante o processo de fabrica??o, e para verificar as condi??es do laminado ap?s os ensaios de press?o hidrost?tica. Os resultados mostraram que a adi??o de areia causou uma redu??o na press?o de ruptura do tubo de 17 %. Por?m esta perda foi compensada pelo grande acr?scimo na rigidez que foi da ordem de 380 % . As an?lises no MEV mostraram que ocorrem danos durante o processo de fabrica??o, mas em quantidades muito pequenas. Na maioria dos casos o contato areia/fibras ocorre sem evid?ncias de danos. Em resumo, a areia representa uma redu??o de 27,8 % no custo final do tubo, que somado aos bons resultados obtidos nos ensaios mec?nicos, faz deste material uma excelente op??o de carga de adi??o para tubula??es de PRFV utilizadas com altas press?es
46
Margerit, Daniel. "Mouvement et dynamique des filaments et des anneaux tourbillons de faible épaisseur." Vandoeuvre-les-Nancy, INPL, 1997. http://docnum.univ-lorraine.fr/public/INPL_T_1997_MARGERIT_D.pdf.
Full textAbstract:
Un filament tourbillon est un cas particulier d'écoulement rotationnel, pour lequel la vorticité se trouve uniquement autour d'une courbe tridimensionnel, dite fibre centrale du filament. Calculer l'écoulement, c'est déterminer l'évolution de cette zone de vorticité, dite filament tourbillon, c'est à dire trouver le mouvement de la fibre centrale. Cette thèse reprend la démarche de Callegari et Ting pour obtenir l'équation d'évolution de la fibre centrale d'un anneau tourbillon en la complétant avec divers remarques et commentaires et, bien sur, en donnant des ordres supérieurs du développement. Nous mettons en valeur le développement des intégrales singulières de Biot et Savart à l'aide de la méthode des développements asymptotiques raccordés. Puis, les résultats obtenus sont utilisés pour justifier des méthodes de cut-off et pour les généraliser au cas visqueux et avec vitesse axiale. Nous complétons les résultats de Widnall et Sullivan sur l'étude linéaire d'un anneau circulaire perturbé en donnant la période d'oscillation des différents modes et en comparant ces résultats avec une simulation numérique de l'équation d'évolution. Enfin, nous étudions l'hélicité d'anneaux tourbillons, les oscillations d'un filament droit et la stabilité de filaments parallèles contrarotatifs.
47
Rato, Leila Sofia Coelho. "Vimentin interacts with the Akt/mTOR pathway mediating cell growth." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22372.
Full textAbstract:
Mestrado em Bioquímica - Bioquímica ClínicaA vimentina é uma proteína da classe III dos filamentos intermédios que promove processos tais como proliferação, migração e invasão celular através da interação com diferentes vias de sinalização. No entanto, o papel da vimentina no crescimento celular é ainda pouco conhecido. Neste estudo, observamos que fibroblastos isolados de embriões de ratinhos sem vimentina (Vim -/- MEFs) eram mais pequenos que o tipo normal (WT). Assim, o objetivo deste estudo era entender de que forma a vimentina regula o crescimento celular. Com recurso a modelos in vitro, técnicas de microscopia e técnicas bioquímicas descobrimos que Vim -/- MEFs tinham menor volume e concentração de proteínas quando comparadas com WT MEFs. Adicionalmente, a síntese proteica e ativação de mTORC1 estavam significativamente reduzidas em Vim -/- MEFs. Através de co-imunoprecipitação, descobrimos que a vimentina interage com os complexos mTORC2 e TSC. Assim, postulamos que a vimentina regula o crescimento celular por interação com proteínas da via de sinalização AKT/mTO
Vimentin is a type III intermediate filament protein that takes part in cell proliferation, migration and invasion, by acting as a signalling scaffold. The role of vimentin in cell growth, however, is poorly understood. We observed that vimentin knockout mouse embryonic fibroblasts (Vim -/- MEFs) were smaller than the wild type (WT). Therefore, this work aimed to understanding how vimentin regulates cell growth. Using in vitro models, imaging techniques and biochemical approaches, we have found that the volume and protein concentration of Vim -/- MEFs is lower when compared to WT MEFs. Further, protein synthesis and mammalian target of rapamycin complex 1 (mTORC1) activation was attenuated in Vim -/- MEFs. By co-immunoprecipitation we found that vimentin interacts with mammalian target of rapamycin complex 2 (mTORC2) and tuberous sclerosis protein complex (TSC) after insulin stimulation. Consequently, we postulate that vimentin regulates cell growth by interacting with proteins of the AKT/mTOR pathway
48
Korte, F. Steven. "Thick filament regulation of myocardial contraction." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4383.
Full textAbstract:
Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. "August 2006" Includes bibliographical references.
49
Seth, A. K. "Filament blending in air-jet texturing." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235149.
Full text
50
Liversage, Alexander Duncan. "Investigations into titin/thick filament stoichiometry." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310804.
Full text