• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 545
  • 153
  • 134
  • 124
  • 76
  • 42
  • 34
  • 23
  • 17
  • 15
  • 13
  • 8
  • 6
  • 6
  • 5
  • Tagged with
  • 1479
  • 239
  • 207
  • 133
  • 119
  • 100
  • 97
  • 91
  • 90
  • 86
  • 85
  • 77
  • 65
  • 64
  • 61
  • 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.
341

Automated Micropipette Aspiration of Single Cells

Shojaei-Baghini, Ehsan 26 November 2012 (has links)
This research presents a system for mechanically characterizing single cells using automated micropipette aspiration. Using vision-based control and position control, the system controls a micromanipulator, a motorized translation stage, and a custom-built pressure system to position a micropipette (4 $\mu$m opening) to approach a cell, form a seal, and aspirate the cell into the micropipette for quantifying the cell's elastic and viscoelastic parameters as well as viscosity. Image processing algorithms were developed to provide controllers with real-time visual feedback and to accurately measure cell deformation behavior on the fly. Experiments on both solid-like and liquid-like cells demonstrated that the system is capable of efficiently performing single-cell micropipette aspiration and has low operator skill requirements. Once the system was validated, it was used to study voided urine cells. In this study, the mechanical properties of bladder carcinoma cells were investigated.
342

Automated Micropipette Aspiration of Single Cells

Shojaei-Baghini, Ehsan 26 November 2012 (has links)
This research presents a system for mechanically characterizing single cells using automated micropipette aspiration. Using vision-based control and position control, the system controls a micromanipulator, a motorized translation stage, and a custom-built pressure system to position a micropipette (4 $\mu$m opening) to approach a cell, form a seal, and aspirate the cell into the micropipette for quantifying the cell's elastic and viscoelastic parameters as well as viscosity. Image processing algorithms were developed to provide controllers with real-time visual feedback and to accurately measure cell deformation behavior on the fly. Experiments on both solid-like and liquid-like cells demonstrated that the system is capable of efficiently performing single-cell micropipette aspiration and has low operator skill requirements. Once the system was validated, it was used to study voided urine cells. In this study, the mechanical properties of bladder carcinoma cells were investigated.
343

Digital Microfluidics for Integration of Lab-on-a-Chip Devices

Abdelgawad, Mohamed Omar Ahmad 23 September 2009 (has links)
Digital microfluidics is a new technology that permits manipulation of liquid droplets on an array of electrodes. Using this technology, nanoliter to microliter size droplets of different samples and reagents can be dispensed from reservoirs, moved, split, and merged together. Digital microfluidics is poised to become an important and useful tool for biomedical applications because of its capacity to precisely and automatically carry out sequential chemical reactions. In this thesis, a set of tools is presented to accelerate the integration of digital microfluidics into Lab-on-a-Chip platforms for a wide range of applications. An important contribution in this thesis is the development of three rapid prototyping techniques, including the use of laser printing to pattern flexible printed circuit board (PCB) substrates, to make the technology accessible and less expensive. Using these techniques, both digital and channel microfluidic devices can be produced in less than 30 minutes at a minimal cost. These rapid prototyping techniques led to a new method for manipulating liquid droplets on non-planar surfaces. The method, called All Terrain Droplet Actuation (ATDA), was used for several applications, including DNA enrichment by liquid-liquid extraction. ATDA has great potential for the integration of different physico-chemical environments on Lab-on-a-Chip devices. A second important contribution described herein is the development of a new microfluidic format, hybrid microfluidics, which combines digital and channel microfluidics on the same platform. The new hybrid device architecture was used to perform biological sample processing (e.g. enzymatic digestion and fluorescent labeling) followed by electrophoretic separation of the analytes. This new format will facilitate complete automation of Lab-on-a-Chip devices and will eliminate the need for extensive manual sample processing (e.g. pipetting) or expensive robotic stations. Finally, numerical modeling of droplet actuation on single-plate digital microfluidic devices, using electrodynamics, was used to evaluate the droplet actuation forces. Modeling results were verified experimentally using an innovative technique that estimates actuation forces based on resistive forces against droplet motion. The results suggested a list of design tips to produce better devices. It is hoped that the work presented in this thesis will help introduce digital microfluidics to many of the existing Lab-on-a-Chip applications and inspire the development of new ones.
344

La relation de confiance en relations publiques : vers un modèle d'adéquation contextuelle optimale

Gagné, Anne-Marie 02 1900 (has links) (PDF)
Bien que les relations publiques constituent une industrie en pleine croissance, que leur enseignement soit intégré dans de nombreux programmes universitaires et que celles-ci soient représentées par de nombreuses associations professionnelles, le métier de relationniste n'a pas bonne presse. Dans le discours populaire, tout comme dans celui de certains théoriciens, les relationnistes sont accusés d'être à la solde des entreprises qui les emploient et de tenter de manipuler l'opinion publique en « maquillant » la réalité. Alors que les diverses parties prenantes sont de plus en plus nombreuses à faire valoir leurs points de vue et à réclamer que les entreprises prennent leurs attentes et leurs intérêts en considération, le niveau de confiance envers la grande organisation (et ses porte-parole) est bas. Plus particulièrement, lorsque les activités de l'entreprise ont des conséquences ou des retombées potentiellement négatives (ou perçues comme étant potentiellement négatives) chez les parties prenantes, les critiques à l'endroit du relationniste ayant à promouvoir ou à défendre ces activités sont particulièrement acerbes et son discours est accueilli avec grand scepticisme. Dans ce contexte, comment le relationniste, qui a le mandat d'établir et de maintenir les relations entre l'entreprise et ses parties prenantes peut-il, sans cette confiance, exercer son métier? L'objectif de la présente recherche est d'identifier les éléments constitutifs permettant l'établissement d'une relation de confiance entre les relationnistes et les parties prenantes de l'entreprise dans le contexte actuel de préoccupation à l'égard des externalités négatives des entreprises et des enjeux sociaux liés à son activité économique et, ultimement, le développement d'un modèle de la relation de confiance en relations publiques. Pour répondre à cet objectif, les types de confiance et éléments constitutifs propres aux différents modèles de la relation de confiance répertoriés à travers de nombreuses disciplines connexes aux relations publiques (la sociologie, les sciences économiques et de la gestion, le marketing et la psychologie) ont été mises en relation avec les pratiques de professionnels des relations publiques et de parties prenantes. Au total, 40 entretiens semi-directifs ont été conduits auprès de relationnistes et de parties prenantes répondant à des critères spécifiques en lien avec l'objet de cette recherche. L'analyse et l'interprétation des données qualitatives issues de ces entretiens a permis d'identifier, pour chaque type de confiance, des éléments constitutifs de la relation de confiance propres aux relations publiques dans un contexte de promotion ou de défense d'un projet comportant un fort potentiel d'externalités négatives chez les parties prenantes. Il a également permis de développer un modèle de la relation de confiance en relations publiques : le modèle de l'adéquation contextuelle optimale, modèle qui laisse entrevoir la possibilité d'un modèle de la relation de confiance et de la relation de méfiance en relations publiques. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : relations publiques, confiance, méfiance, modèle, relationnistes
345

Cell Manipulations with Dielectrophoresis

Lin, James Ting-Yu January 2007 (has links)
Biological sample analysis is a costly and time-consuming process. It involves highly trained technicians operating large and expensive instruments in a temperature and dust controlled environment. In the world of rising healthcare cost, the drive towards a more cost-effective solution calls for a point-of-care device that performs accurate analyses of human blood samples. To achieve this goal, today's bulky laboratory instruments need to be scaled down and integrated on a single microchip of only a few square centimeters or millimeters in size. Dielectrophoresis (DEP), a phenomenon where small particles such as human blood cells are manipulated by non-uniform electric fields, stands to feature prominently in the point-of-care device. An original device that enhances DEP effect through novel geometry of the electrodes is presented. When activated with two inverting sinusoidal waveforms, the novel-shaped electrodes generate horizontal bands of increasing electric fields on the surface of the microchip. With these bands of electric fields, particles can be manipulated to form a straight horizontal line at a predictable location. Experimental results showing the collection, separation, and transportation of mammalian cells are presented. A strategy for simultaneous processing of two or more types of particles is also demonstrated. With capabilities for an accurate position control and an increased throughput by parallel processing, the novel microchip device delivers substantial improvements over the existing DEP designs. The research presented here explores the effects of novel electrode geometries in cell manipulations and contributes to the overall progress of an automated blood analysis system.
346

Manipulation and Hard Compatibilism

Coates, Daniel Justin 07 August 2007 (has links)
In this paper I consider a recent objection to compatibilism—the manipulation argument. This argument relies on two plausible principles: a manipulation principle that holds that manipulation precludes free will and moral responsibility, and a ‘no difference principle’ that holds that manipulation is relevantly similar to determinism. To respond to this argument, the compatibilist must reject either the manipulation principle or the ‘no difference principle.’ I argue that rejecting the manipulation principle offers the compatibilist the most compelling response to the manipulation argument. Incompatibilists claim that this strategy is implausible because it requires that some victims of manipulation are free and responsible. I aim to show that this consequence is not as implausible as it might initially appear.
347

Cell Manipulations with Dielectrophoresis

Lin, James Ting-Yu January 2007 (has links)
Biological sample analysis is a costly and time-consuming process. It involves highly trained technicians operating large and expensive instruments in a temperature and dust controlled environment. In the world of rising healthcare cost, the drive towards a more cost-effective solution calls for a point-of-care device that performs accurate analyses of human blood samples. To achieve this goal, today's bulky laboratory instruments need to be scaled down and integrated on a single microchip of only a few square centimeters or millimeters in size. Dielectrophoresis (DEP), a phenomenon where small particles such as human blood cells are manipulated by non-uniform electric fields, stands to feature prominently in the point-of-care device. An original device that enhances DEP effect through novel geometry of the electrodes is presented. When activated with two inverting sinusoidal waveforms, the novel-shaped electrodes generate horizontal bands of increasing electric fields on the surface of the microchip. With these bands of electric fields, particles can be manipulated to form a straight horizontal line at a predictable location. Experimental results showing the collection, separation, and transportation of mammalian cells are presented. A strategy for simultaneous processing of two or more types of particles is also demonstrated. With capabilities for an accurate position control and an increased throughput by parallel processing, the novel microchip device delivers substantial improvements over the existing DEP designs. The research presented here explores the effects of novel electrode geometries in cell manipulations and contributes to the overall progress of an automated blood analysis system.
348

Computational Voting Theory: Game-Theoretic and Combinatorial Aspects

Xia, Lirong January 2011 (has links)
<p>For at least two thousand years, voting has been used as one of the most effective ways to aggregate people's ordinal preferences. In the last 50 years, the rapid development of Computer Science has revolutionize every aspect of the world, including voting. This motivates us to study (1) <bold>conceptually, how computational thinking changes the traditional voting theory</bold>, and (2) <bold>methodologically, how to better use voting for preference/information aggregation with the help of Computer</p><p>Science</bold>.</p><p>My Ph.D. work seeks to investigate and foster the interplay between Computer Science and Voting Theory. In this thesis, I will discuss two specific research directions pursued in my Ph.D. work, one for each question asked above. The first focuses on investigating how computational thinking affects the game-theoretic aspects of voting. More precisely, I will discuss the rationale and possibility of using computational complexity to protect voting from a type of strategic behavior of the voters, called <italic>manipulation</italic>. The second studies a voting setting called <italic>Combinatorial Voting</italic>, where the set of alternative is exponentially large and has a combinatorial structure. I will focus on the design and analysis of novel voting rules for combinatorial voting that balance computational efficiency and the expressivity of the voting language, in light of some recent developments in Artificial Intelligence.</p> / Dissertation
349

Surface Biological Modification and Cellular Interactions of Magnetic Spinel Ferrite Nanoparticles

Heintz, Eva Liang-Huang 23 November 2004 (has links)
Surface Biological Modification and Cellular Interactions of Magnetic Spinel Nanoparticles Eva Liang-Huang Heintz 191 Pages Directed by Dr. Z. John Zhang The interest in magnetic nanoparticles is multi-dimensional. Fundamentally, it is important to be able to control their magnetic properties and to correlate to specific applications. In biology, magnetic nanoparticles offer promising potential as magnetic carriers or chaperones for magnetic localization and manipulation of therapeutic reagents. The synthesis of superparamagnetic CoFe2-xSmxO4 nanoparticles and the tunability of their magnetic properties by size and composition variations are discussed. An increase in size of CoSm0.19Fe1.81O4 nanoparticles produced an increase in blocking temperature and saturation magnetization, but a non-linear coercitivity response was observed with change in size. By varying the composition, the saturation magnetization of CoFe2-xSmxO4 decreased dramatically while the coercitivity increased when compared to native cobalt spinel ferrite (CoFe2O4) nanoparticles. These results demonstrate how the magnetic properties of cobalt spinel ferrite nanoparticles can be tailored to specific applications. Surface modifications of cobalt spinel ferrite nanoparticles facilitated the conjugation of oligonucleotides. Using a transfection reagent, CoFe2O4 ??igonucleotide conjugates were delivered into mammalian cells. Post transfection, synchronized movement of cells in response to an external magnetic field was observed. This demonstrated the possibility of magnetic manipulation and localization of therapeutic reagents coupled to CoFe2O4 magnetic nanoparticles. Results from this thesis demonstrate the potential role of magnetic spinel nanoparticles in cell biology and will facilitate the progress towards in vivo testing.
350

Orienting Deformable Polygonal Parts without Sensors

Kristek, Shawn 2011 December 1900 (has links)
Parts orienting is an important part of automated manufacturing. Sensorless manipulation has proven to be a useful paradigm in addressing parts orienting, and the manipulation of deformable objects is a growing area of interest. Until now, these areas have remained separate because existing orienting approaches utilize forces that if applied to deformable parts violate the assumptions used by existing algorithms, and could potentially break the part. We introduce a new algorithm and manipulator actions that, when provided with the geometric description and a deformation model of choice for the part, exploits the deformation and generates a Plan that consists of the shortest sequence of manipulator actions guaranteed to orient the part up to symmetry from any unknown initial orientation and pose. Additionally, the algorithm estimates whether a given manipulator is sufficiently precise to perform the actions which guarantee the final orientation. This is dictated by the particular part geometry, deformation model, and the manipulator action path planner which contains simple end-effector constraints and any standard motion planner. We illustrate the success of the algorithm with multiple parts through 192 trials of experiments that were performed with low-precision robot manipulators and six parts made of four types of materials. The experimental trials resulted in 154 successes, which show the feasibility of deformable parts orienting. The analysis of the failures showed that for success the assumptions of zero friction are essential for this work, increased manipulator precision would be beneficial but not necessary, and a simple deformation model can be sufficient. Finally, we note that the algorithm has applications to truly sensorless manipulation of non-deformable parts.

Page generated in 0.0993 seconds