• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 126
  • 42
  • 36
  • 30
  • 18
  • 6
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 318
  • 49
  • 44
  • 42
  • 41
  • 39
  • 39
  • 37
  • 28
  • 28
  • 27
  • 21
  • 21
  • 21
  • 20
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Bio-structuration à l'échelle micro et nanométrique

Massou, Sophie 11 July 2011 (has links)
Les substrats structurés aux échelles micrométriques et nanométriques sont intéressants pour des applications biomédicales, par exemple dans des puces à ADN/protéines, pour la miniaturisation des « lab-on-chip » ou pour préparer des implants permettant le contrôle de l'adhésion de cellules. Dans la dernière décennie des études ont montrées, que les cellules vivantes peuvent détecter la présence de nano-structures sur les substrats sur lesquels elles adhèrent. Bien que ces mécanismes soient étudiés depuis une dizaine d'années, les mécanismes fondamentaux sont encore en cours d'études. Tant pour une étude au niveau fondamental que dans le but d'applications concrètes, il est important de développer des techniques simples pour structurer des substrats sur de grandes surfaces. Nous avons réalisé une nouvelle méthode alliant un faible coût de fabrication et la biocompatibilité pour structurer et biofonctionnaliser des substrats à l'échelle nanométrique en utilisant des membranes d'alumine poreuses comme masque. Les membranes d'alumine poreuses, préparées par électrochimie, sont naturellement organisées en un réseau hexagonal sur une surface de quelques cm². Nous les utilisons comme masque pour la structuration de surfaces. Des trous réguliers sont gravés dans le substrat à travers les membranes d'alumine poreuses. Ce substrat est ensuite utilisée lors d'une application biologique : une bicouche lipidique est déposée sur le substrat structuré pour imiter les hétérogénéités de la membrane cellulaire. La mobilité de la bicouche est étudiée par corrélation de spectroscopie de fluorescence à rayon variable. Une autre série d'expériences est faite en utilisant des membranes d'alumine poreuses comme masque d'évaporation pour créer des réseaux organisés d'îlots d'organo-silanes. Deux molécules sont utilisées elles possèdent soit une fonction amine réactive soit une longue chaîne carbonée inerte. La bio-fonctionnalisation est ensuite effectuée en utilisant la fonction amine pour accrocher un anticorps. Des études sont effectuées en parallèle, sur des substrats bio-fonctionnalisés à l'échelle micrométrique grâce au micro-contact printing. Le but de cette étude est de mettre au point une biochimie de surface permettant le contrôle de l'adhésion de cellules immunitaires, avec le but de transférer ensuite la biochimie à l'échelle nanométrique. / Substrates patterned at the micro-scale and nano-scale are interesting for biomedical applications, for example, in DNA/protein nano-arrays, for miniaturized lab-on-chip applications or for making smart implants that can control adhesion of cells. In the last decade, some studies showed that living cells can detect nano-scale structures on substrates to which they adhere. Although this behaviour has been observed now for over a decade, the fundamental detection mechanism is still under investigation. Both for fundamental studies and for applications, it is important to develop facile techniques to pattern substrates on a large scale. We have realized a novel technique for patterning and bio-functionalizing substrates at the nano-scale using porous anodic alumina membranes as masks. The ordered porous anodic alumina membranes, prepared by classical electro-chemistry, are naturally organized in an hexagonal array over surface area of few square centimeters. Here we use them as mask for surface patterning. To create an array of nano holes, the substrate is dry etched through the alumina pores. In a biologically relevant application, a lipid bilayer is deposited on the patterned substrate to mimic a heterogeneous cell membrane. The mobility of the bilayer is studied by fluorescent correlation spectroscopy. In a different set of experiments, the porous alumina membranes are used as evaporation mask to create an organized array of alkyl-silane islands - either with a short carbon chain and with a reactive amine group or with a long carbon chain and non-reactive. Afterwards, biochemical functionalization is achieved by exploiting the amino-function of the amino-silane to bind an antibody. In parallel, we have started some studies of adhesion on a pattern substrate at micro-scale with immunological cells. The substrate is pattern by micro contact printing and the cell adhesion is observed by RICM. The aim of this studies is to prepare the biochemistry for the immunological cells adhesion, with the aim or transferring this to the nano-scale.
222

The Joycean Sublime

Moreno, Anthony 17 June 2013 (has links)
The purpose of my thesis is to analyze notions of the sublime in James Joyce’s Ulysses and how the sublime is evoked and presented in Joyce’s work. The present work will examine concepts of the sublime from the Classical and Medieval period, through the Enlightenment, and into the Romantic era to develop my own definition. Placing the sublime in a historical perspective allows me to discover how the sublime is at work through Joyce’s creative use of complex narrative approaches. The beauty of aesthetic perfection was achieved by employing all of Joyce’s artistic faculties. My thesis investigates how Ulysses’ experimental writing technique, unique structuring, and difficult prose created a work of genius which evokes the sublime. By analyzing Joyce’s use of language, unconventional narrative, and ambiguity in Ulysses I will explore how the sublime is aroused.
223

Coexistência microscópica de antiferromagnetismo e supercondutividade não-convencional / Microscopic coexistence of antiferromagnetism and unconventional superconductivity

Almeida, Dalson Eloy, 1989- 20 February 2017 (has links)
Orientador: Eduardo Miranda / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-01T08:41:01Z (GMT). No. of bitstreams: 1 Almeida_DalsonEloy_D.pdf: 2470369 bytes, checksum: 93d3b945f62f374cfd686217575dda95 (MD5) Previous issue date: 2017 / Resumo: Nesta tese estudamos a relação entre antiferromagnetismo e supercondutividade em pnictídeos à base de ferro. Este estudo será feito através da análise de uma energia livre de Ginzburg-Landau de parâmetros de ordem acoplados que será derivada de um modelo microscópico. Em particular, estamos interessados em saber se a transição entre os estados ordenados é de primeira ordem ou se as duas ordens podem coexistir. Para o caso de supercondutividade convencional as duas fases puras nunca coexistem. Entretanto, quando a supercondutividade é não-convencional e a condição de nesting perfeito não é satisfeita, pode haver um regime intermediário de coexistência microscópica das duas ordens. Nesta nova fase termodinâmica, as simetrias de rotação no espaço de spins, de reversão temporal e U(1) são quebradas simultânea e localmente. Logo, os canais de supercondutividade singleto e tripleto se misturam quanticamente. Em outras palavras, uma componente tripleto secundária do estado supercondutor é gerada. Os diagramas de fases do sistema são apresentados e analisamos também como flutuações magnéticas, acima da temperatura de Néel pura, afetam a temperatura de transição tripleto. Investigamos também o efeito da magnetização alternada no efeito Josephson, i.e., na supercorrente que flui através de uma junção entre dois supercondutores na fase de coexistência. Por fim, mas não menos importante, estudamos o efeito de proximidade em uma interface entre um supercondutor e um antiferromagneto. Veremos que os pares de Cooper podem penetrar a região magnética e em consequência, uma componente tripleto é induzida próximo da interface / Abstract: In this thesis, we study the interplay between antiferromagnetism and superconductivity in iron pnictides. This study will be done analyzing a free energy of coupled order parameters which will be derived from a microscopic model. In particular, we are interested if the phase transition between the ordered states is first order or if the two orders can coexist. For the case of conventional superconductivity, the two phases cannot coexist. However, when superconductivity is unconventional and the perfect nesting condition is not satisfied, there can exist an intermediary state of microscopic coexistence of the two orders. In this new thermodynamic phase, spin rotation, time reversal and U(1) symmetries are simultaneously and locally broken. Therefore, the singlet and triplet superconductivity channels are quantum mechanically mixed. In other words, a secondary triplet component is generated. The phase diagrams of the system are presented and we also analyze the effect of magnetic fluctuations above the pure Néel temperature on the triplet temperature transition. We also investigate the effects of the staggered magnetization on the Josephson effect, i.e., on the supercurrent that flows through a junction of two superconductors in the coexistence phase. Last, but not least, we study the proximity effect at an interface between a superconductor and an antiferromagnet. We will see that the Cooper pairs can penetrate the magnetic region and consequently a triplet component is induced near the interface / Doutorado / Física / Doutor em Ciências / 140834/2013-3 / 2342/15-4 / CNPQ / CAPES / BEX
224

Optimal policies in international macroeconomics / Politiques optimales en macroéconomie internationale

Alla, Zineddine 17 March 2017 (has links)
La crise financière mondiale qui a débuté en 2008, et la crise des dettes souveraines en zone euro qui l'a suivie, ont successivement forcé les macroéconomistes à repenser leur cadre conceptuel. Cette thèse est une modeste contribution aux efforts colossaux déployés par les macroéconomistes à travers le monde pour faire face à ce défi: renforcer la compréhension de l'utilisation optimale des outils de politique économique non conventionnels. A cette fin, elle est construite en deux parties. Chaque partie vise à explorer au plan théorique un "contexte macroéconomique-type" au sein duquel des outils de politique économique non conventionnels ont été employés ces dernières années. La première partie, intitulée "Politique Non Conventionelle Optimale en Economie Ouverte", analyse l'utilisation optimale d'instruments de politique économique non conventionels par une banque centrale en économie ouverte. En présence de frictions financières qui modifient la manière dont la politique monétaire affecte l'économie, ou en présence de chocs exogènes qui mettent en défaut la "divine coïncidence", cette partie décrit comment un banquier central devrait combiner un instrument de politique monétaire non conventionnelle et la politique monétaire conventionnelle à des fins de stabilisation macroéconomique. La seconde partie, "Politique Budgétaire Optimale en Union Monétaire", adopte le point de vue du gouvernement d'un pays situé en union monétaire (typiquement la zone euro). Un tel pays ne disposant d'une politique monétaire autonome (au plan national), cette partie étudie la possibilité pour un tel pays d'utiliser la politique budgétaire comme un outil de stabilisation, et décrit l'utilisation optimale des dévaluations fiscales en réponse à des chocs exogènes idiosyncratiques. / The 2008 global financial crisis and the subsequent euro area sovereign debt crisis successively forced macroeconomists to reassess this conceptual framework. This thesis is a modest contribution to the huge efforts undertaken by macroeconomists following the crisis to meet this challenge, i.e. to develop some insights about the optimal use of unconventional policy tools. To do so, this thesis is twofold. Each part intends to explore from a theoretical perspective a fundamental macroeconomic situation that called for the use of unconventional policy instruments in the recent years. The first part, ”Optimal Unconventional Policy in An Open Economy” analyzes the optimal use of unconventional policy instruments by the central bank in an open economy framework. Assuming that the presence of financial frictions changes the way monetary policy affects the economy, or that the occurence of exogenous shocks breaks the ”divine coincidence”, this part describes how a central bank should combine an unconventional policy instrument and conventional monetary policy to favor macroeconomic stabilization. The second part, ”Optimal Fiscal Policy in a Currency Union”, takes the standpoint of the governement of a country located in a currency union (typically the euro area). Such a country being deprived of monetary policy autonomy, this part considers the opportunity of using fiscal policy as a stabilization tool, and describes the optimal use of fiscal devaluations following idiosyncratic exogenous shocks.
225

Utilizing noble gases to identify hydraulic fracturing “sweet spots” and evaluate the occurrence of carbon isotopic reversals of hydrocarbons within the Northern Appalachian Basin

Lary, Brent Alexander January 2020 (has links)
No description available.
226

Parametry laserového paprsku / Parameters of the laser beam

Hort, Zbyněk January 2017 (has links)
The diploma thesis consists of the three main parts. The first part deals with the theoretical description of the laser technology and other unconventional technologies. In the second part, the thesis is focused on testing the parameters of the laser and evaluating the most suitable parameters. In the last part the diploma thesis deals with comparison of unconventional technologies in terms of cut quality
227

Obrábění těžkoobrobitelných materiálů pomocí vodního paprsku s abrazivem / Abrasive water jet machining of hard-to-machine materials

Kubín, Matěj January 2019 (has links)
The diploma thesis deals with unconventional technology of material separation by water jet with abrasive. It describes the influence and specification of technological parameters of the water jet on the quality of the cutting surface. The work contains an experiment, where the aim was to achieve from the theory the influence of tech-nological parameters on surface roughness on composite materials from glass fiber and carbon fiber.
228

Manipulation of time reversal symmetry breaking superconductivity in Sr₂RuO₄ by uniaxial pressure

Ghosh, Shreenanda 30 September 2021 (has links)
Unconventional superconductivity continues to be one of the most striking chapters in condensed matter physics, by posing challenges to our theoretical understanding of its origin. During the last three decades a large number of unconventional superconductors with exotic properties have been found arising great interest, such as the heavy fermion systems, high Tc cuprates as well as the Iron based superconductors etc. Sr2RuO4, the material I have studied, can be considered as an exemplary case in this regard. In spite of more than two decades of comprehensive research, Sr2RuO4 remains one of the most compelling superconductors till date. Various experimental results give evidence that the superconductivity of Sr2RuO4 is chiral: including measurements of the Kerr effect, sound velocities, critical currents across junctions, and muon spin relaxation(μSR), the experimental technique at the heart of this dissertation. Recent NMR Knight shift measurements suggests that the pairing is most likely spin-singlet, and in the tetragonal lattice of Sr2RuO4, the combination of singlet pairing and chirality compels consideration of an seemingly unlikely order parameter: dxz ± idyz. It is unlikely because it comes along with a horizontal line node at kz = 0, whereas Sr2RuO4 has a very low c-axis conductivity. And that makes the question whether or not the superconductivity of Sr2RuO4 is chiral, of great importance. This calls for an unique scenario in regard to our understanding of unconventional superconductivity, as the presence of chirality in Sr2RuO4 might imply a new form of pairing, which is yet to be firmly determined. Chiral superconductors break time reversal symmetry by definition, and in general time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two component order parameters. Probing Sr2RuO4 under uniaxial pressure offers the possibility to lift the degeneracy between such components. However, despite strenuous efforts, a splitting of the superconducting and TRSB transitions under uniaxial pressure has not been observed so far. In this thesis, I report muon spin relaxation measurements on Sr2RuO4 samples, placed under uniaxial stress. The relatively large sample size suitable for μSR demanded for a customized uniaxial pressure cell in order to perform our experiments. It has been a technically challenging task to have a fully fledged uniaxial pressure cell with stringent requirements, that is suitable for time restricted facility experiments like μSR. The technical advancement has been documented thoroughly in this thesis. Using the dedicated uniaxial pressure cell, we observed the much awaited stress induced splitting between the onset temperatures of superconductivity and time reversal symmetry breaking, consistent with the qualitative expectations for a chiral order parameter in Sr2RuO4. In addition to that, we report the appearance of a bulk magnetic order in Sr2RuO4 under higher uniaxial stress for the first time, above the critical pressure at which a Lifshitz transition is known to occur. The signal in the state appearing at high stress qualitatively differs from that in the TRSB state in unstressed Sr2RuO4, which provides evidence that the enhanced muon spin relaxation at lower stresses is not a consequence of conventional magnetism. As a whole, our results strongly support the idea of two-component superconducting order parameter in Sr2RuO4, that breaks time-reversal symmetry.
229

Racionalizace malosériové výroby výpalků v podmínkách firmy PARS Nova a.s. / Rationalization of small-lot production of slops in conditions of company PARS Nova a.s.

Jurka, Pavel January 2008 (has links)
Analysis of the technological possibility ray methods of protoplasm, laser and water jet on the part of needs company Pars Nova a.s.. Propsal concrete of unconventional method. Process layout and exigencies of working designed method. Security and ecological diversification of designed method. Technical – economics evaluation contribution designed of unconventional technology.
230

Abrazivní vodní paprsek / Abrasive Water Jet

Kopečný, Libor January 2011 (has links)
This dissertation thesis is focused on explaining the broad issue of the non-conventional machining by an abrasive water jet. Introductory chapters deal with various techniques and methods of water-jet cutting and analyze them. Then the following text provides us with a detailed description of the machine itself so that people can understand the way how this technology works. The third chapter is focused on the quality of the resulting surface and the possibility of affecting it by technological parameters. This part is connected with the practical part of my thesis, in which the resultant surfaces of various materials made by different cutting parameters were compared. Subsequent section outlines the development of this technology. The last chapter contains technical and economic evaluation.

Page generated in 0.1067 seconds