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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
671

Development of a Hybrid Carrier System based on DNA Origami Nanostructures and Layer-by-Layer Microcarriers

Scheffler, Florian 12 February 2021 (has links)
Die vorliegende Dissertation untersuchte die Kombination von DNA-Nanostrukturen, so- genannte DNA-Origami-Strukturen, mit Layer-by-Layer (LbL) Mikrotransportern zum Auf- bau eines verbesserten Medikamententrägersystems. Dies sollte die jeweiligen Vorteile der eigenständigen Systeme kombinieren um individuelle Nachteile, wie etwa die li- mitierte Stabilität der DNA-Origami-Strukturen unter physiologischen Bedingungen als auch die schrittweise Freisetzung transportierter Medikamente aus der durchlässigen Polymerschicht der LbL-Mikrotransporter, zu umgehen. Die Untersuchungen bestrebten somit die Oberflächenfunktionalisierung der LbL-Mikrotransporter, um den gerichteten Transport in spezifische Zielzellen zu ermöglichen. Im Weiteren sollte die simultane Aus- schüttung des Medikamentes durch geschützte, in die Polymerschicht integrierte, schalt- bare DNA-Origami-Strukturen erreicht werden. Dahingehend wurde zunächst die Verkapselung des Rinderserumproteins und Strept- avidins mittels eines angehangenen DNA-Stranges gezeigt. Dieser hybridisierte an die Komplementärsequenz im Inneren von DNA-Origami-Röhren und geschlossenen Käfi- gen mit rechteckigem Grundriss. Um die für den späteren Medikamententransport not- wendige Ablösung des Proteins aus der Struktur zu untersuchen, wurde das gebundene Protein durch externe Zugabe eines invasiven Stranges und einem einzelsträngigen Über- hang am Bindungsstrang nach der Technik des toehold-mediated strand displacements, dem Überhang-bedingten Strangaustausch, vom Bindungsstrang abgelöst. Die umfassende Un- tersuchung zeigte, dass die Wände geschlossener DNA-Origami-Käfige sowohl für einzel- strängige DNA als auch für Proteine teilweise permeabel waren. Im Gegensatz zu unge- schützten Strukturen, zeigten die in die LbL-Polymerschicht integrierten DNA-Origami- Strukturen in anschließenden Stabilitätsstudien eine deutliche Resistenz gegenüber phys- iologisch degradierenden Faktoren. Zum Ziel des Medikamententransports wurden die hybriden Transporter daraufhin umfassend im Zusammenspiel mit kultivierten Zellen untersucht, wobei sich eine gute Interaktionsrate bei vernachlässigbarer Toxizität des Sys- tems zeigte. Die weitere Verbesserung der biologischen Kompatibilität und Selektivität der Transporter wurde im letzten Schritt durch Oberflächenfunktionalisierung mittels einer Lipiddoppelschicht erreicht. Die zusätzliche Anbindung spezifischer Antikörper an diese Doppelschicht führte anschließend zu einer Verbesserung der Aufnahmerate bei Expres- sion des entsprechenden Rezeptors an der Zelloberfläche. Diese Arbeit zeigte somit die grundlegende Charakterisierung des hybriden Transport- systems aus DNA-Origami-Strukturen und LbL-Mikrotransportern, sowie dessen weitere Funktionalisierung und bildet daher die Grundlage für weiterführende Studien.
672

Instability and Transition on a Sliced Cone with a Finite-Span Compression Ramp at Mach 6

Gregory R McKiernan (8793053) 04 May 2020 (has links)
<div>Initial experiments on separated shock/boundary-layer interactions were carried out within the Boeing/AFOSR Mach-6 Quiet Tunnel. Measurements were made of hypersonic laminar-turbulent transition within the separation above a compression corner. This wind tunnel features freestream fluctuations that are similar to those in</div><div>flight. The present work focuses on the role of traveling instabilities within the shear layer above the separation bubble.</div><div>A 7 degree half-angle cone with a slice and a finite-span compression ramp was designed and tested. Due to a lack of space for post-reattachment sensors, early designs of this</div><div>generic geometry did not allow for measurement of a post-reattachment boundary layer. Oil flow and heat transfer measurements showed that by lengthening the ramp, the post-reattachment boundary layer could be measured. A parametric study was completed to determine that a 20 degree ramp angle caused reattachment at 45% of the</div><div>total ramp length and provided the best flow field for boundary-layer transition measurements.</div><div>Surface pressure fluctuation measurements showed post-reattachment wave packets and turbulent spots. The presence of wave packets suggests that a shear-layer</div><div>instability might be present. Pressure fluctuation magnitudes showed a consistent transition Reynolds numbers of 900000, based on freestream conditions and distance</div><div>from the nosetip. Pressure fluctuations grew exponentially from less than 1% to roughly 10% of tangent-wedge surface pressure during transition.</div><div>A high-voltage pulsed plasma perturber was used to introduce controlled disturbances into the boundary layer. The concept was demonstrated on a straight 7 degree half-angle circular cone. The perturbations successfully excited the second-mode instability at naturally unstable frequencies. The maximum second-mode amplitudes prior to transition were measured to be about 10% of the mean surface static pressure. </div><div>The plasma perturber was then used to disturb the boundary layer just upstream of the separation bubble on the cone with the slice and ramp. A traveling instability was measured post-reattachment but the transition location did not change for any tested condition. It appears that the excited shear-layer instability was not the dominant mechanism of transition.</div>
673

On the Retrieval of Mixing Height from Ceilometers

Biavati, Gionata 21 March 2014 (has links)
The subject of this thesis is the application of optical backscatter measurements to locate a special property of the lowest part of the atmosphere -- the mixing height. Mixing height is the altitude of the top of the layer where all the fluxes emitted at the ground become well mixed. Since Holzworth in 1967, the knowledge of this altitude is considered relevant when modeling transport of pollutants or general fluxes originating at the ground. Indirect estimations of the mixing height are possible using atmospheric models, but its accuracy is quite low. Since several institutions are attempting to estimate precise ground fluxes, networks of measurement stations are being created. The correct use of the measured fluxes, in order to estimate the evolution of the air masses, is limited by the accuracy of the localization of this layer. It can be detected in several different ways. Most are related to a direct sounding, performed with meteorological balloons. Remote sensing techniques are also attempted with acoustical or optical instruments. Both optical and acoustical methods have advantages and disadvantages. This work is focused on optical instruments like lidar and ceilometers, which are basically small cost-effective lidar systems.
674

La protéine de couche de surface SlpB assure la médiation de l’immunomodulation et de l’adhésion chez le probiotique Propionibacterium freudenreichii CIRM-BIA 129. / Surface layer protein SlpB mediates immunodulation and adhesion in the probiotic Propionibacterium freudenreichii CIRM-BIA 129.

Rosa do carmo, Fillipe Luiz 06 September 2018 (has links)
Propionibacterium freudenreichii est une bactérie Gram-positive bénéfique, traditionnellement utilisée comme levain d’affinage fromager, qui bénéficie du statut GRAS (Generally Recognized As Safe). P. freudenreichii a révélé un effet immunomodulateur qui a été confirmé in vivo par la capacité à protéger des souris d’une colite aigüe induite. L’effet anti-inflammatoire est cependant hautement souche-dépendant. Il est dû, au moins en partie, à des composés de surface clés qui favorisent ces effets probiotiques. Les bactéries Gram-positives, y compris P. freudenreichii, peuvent être recouvertes d’une couche extérieure protéique, appelée « surface-layer », paracristalline, et formée par l’autoassemblage de protéines dites de S-layer (Slps). Les Slps, dans différentes bactéries, sont impliquées dans plusieurs caractéristiques probiotiques, telles que l’adhésion aux cellules de l’hôte et au mucus, la persistance dans l’intestin, ou encore l’immunomodulation. Le but de cette étude est d’étudil’immunomodulation. Le but de cette étude est d’étudier, chez une souche probiotique de P. freudenreichii, la protéine de surface qui joue le principal rôle dans les interactions probiotiques avec l’hôte. La souche P. freudenreichii CIRM-BIA 129, récemment reconnue comme immunomodulatrice prometteuse, possède plusieurs protéines de surface Slps, y compris SlpB. Dans la présente étude, l’inactivation du gène correspondant, dans la souche mutante CB129¿slpB, a provoqué une baisse drastique de l’adhésion aux cellules intestinales épithéliales HT-29, confirmant le rôle clé des Slps dans l’adhési / Propionibacterium freudenreichii is a beneficial Gram-positive bacterium, traditionally used as a cheese ripening starter, with the GRAS status (Generally Recognized As Safe). P. freudenreichii has revealed an immunomodulatory effect confirmed in vivo by the ability to protect mice from induced acute colitis. The anti-inflammatory effect is however highly strain-dependent and due, at least in part, to key surface compounds favouring probiotic effects. Gram-positive bacteria, including P. freudenreichii, can be covered with an external proteinaceous layer called a surface-layer paracrystalin layer and formed by the self-assembly of surface-layer-proteins (Slps). Slps were shown, in different bacteria, to be involved in several probiotics traits, such as adhesion to host cells and mucus, persistence within the gut, or immunomodulation. The aim of this study is to investigate, in a P. freudenreichii probiotic strain, the surface protein that plays the main role in the probioticinteraction with the host. The P. freudenreichii CIRM-BIA 129 strain recently revealed promising immunomodulatory properties and possesses several Slps, including SlpB. In the presented work, inactivation of the corresponding gene, CB129¿slpBa mutant strain, caused a drastic decrease in adhesion to intestinal epithelial HT-29 cells, further evidencing the key role of Slps in cell adhesion. we investigated immune response of HT-29 cells towards P. freudenreichii CIRM-BIA 129 and CB129¿slpB. The wild type strain mainly induced expression of the immunomodulatory IL-10 by the cells. Interestingly, th
675

Empirical bifurcation analysis of atmospheric stable boundary layer regime occupation

Ramsey, Elizabeth 18 May 2021 (has links)
Turbulent collapse and recovery are both observed to occur abruptly in the atmospheric stable boundary layer (SBL). The understanding and predictability of turbulent recovery remains limited, reducing numerical weather prediction accuracy. Previous studies have shown that regime occupation is the result of the net effect of highly variable processes, from turbulent to synoptic scales, making stochastic methods a compelling approach. Idealized stable boundary layer models have shown that under some circumstances, regimes can be related to the stable branches of model equilibria, and an additional unstable equilibrium is predicted. This work seeks to determine the extent to which the SBL regime occupation can be explained using a one-dimensional stochastic differential equation (SDE). The drift and diffusion coefficients of the SDE of an input time series are approximated from the statistics of its averaged time tendencies. These approximated coefficients are fit using Gaussian Process Regression. Probabilistic estimates of the system's equilibrium points are then found and used to create an empirical bifurcation diagram without making any prior assumptions on the dynamical form of the system. This data driven bifurcation diagram is compared to modelled predictions. The analysis is repeated on several meteorological towers around the world to assess the influence of local meteorological settings. This work provides empirical insights into the nature of regime dynamics and the extent to which the SBL displays hysteresis. / Graduate
676

Spatial Operations in a GIS-Based Karst Feature Database

Gao, Yongli 01 May 2008 (has links)
This paper presents the spatial implementation of the karst feature database (KFD) of Minnesota in a GIS environment. ESRI's ArcInfo and ArcView GIS packages were used to analyze and manipulate the spatial operations of the KFD of Minnesota. Spatial operations were classified into three data manipulation categories: single layer operation, multiple layer operation, and other spatial transformation in the KFD. Most of the spatial operations discussed in this paper can be conducted using ArcInfo, ArcView, and ArcGIS. A set of strategies and rules were proposed and used to build the spatial operational module in the KFD to make the spatial operations more efficient and topographically correct.
677

The Effect of Shear Sheltering on Trailing Edge Noise: A Theoretical Study

Unknown Date (has links)
Shear sheltering is defined as the effect of the mean flow velocity profile in a boundary layer on the turbulence caused by an imposed gust. In aeroacoustic applications turbulent boundary layers interacting with blade trailing edges or roughness elements are an important source of sound, and the effect of shear sheltering on these noise sources has not been studied in detail. Since the surface pressure spectrum below the boundary layer is the primary driver of trailing edge and roughness noise, this thesis considers the effect that shear sheltering has on the surface pressure spectrum below a boundary layer. This study presents a model of the incoming turbulence as a vortex sheet at a specified height above the surface and shows, using canonical boundary layers and approximations to numerical results, how the mean flow velocity profile can be manipulated to alter the surface pressure spectrum and hence the associated trailing edge noise. The results from this model demonstrate that different mean velocity profiles drive significant changes in the unsteady characteristics of the flow. The surface pressure fluctuations results also suggest that boundary layers where the shear in the mean velocity profile is significant can be beneficial for the reduction of trailing edge noise at particular frequencies. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection
678

Shock Boundary Layer Interactions - A Multiphysics Approach

Bhide, Kalyani R. January 2018 (has links)
No description available.
679

Optimization of The Absorber/Buffer Interface Region of Cu(In,Ga)Se<sub>2</sub> Photovoltaic Devices: A Numerical Simulation Study

Patikirige, Yasas R A 12 August 2019 (has links)
No description available.
680

Brand X, A Cross-Layer Architecture for Quality of Transport (QoT)

De Hart, Gregory Arthur 30 June 2006 (has links) (PDF)
Computing devices are commonly equipped with multiple transport technologies such as IrDA, Bluetooth and WiFi. Transport switching technologies, such as Quality of Transport (QoT), take advantage of this heterogeneity to keep network sessions active as users move in and out of range of various transports or as the networking environment changes. Autonomous transport switching technologies rely on information regarding current network status and the ambient wireless environment in order to make intelligent decisions. This thesis proposes Brand X, a cross-layer architecture designed for a QoT environment to provide timely and accurate environment information in order to facilitate autonomous transport switching. This thesis also presents a performance analysis of network protocol stack latency in a QoT environment considering the various cross-layer mechanisms utilized in Brand X and other architectures.

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