To see the other types of publications on this topic, follow the link: Cascade of turbulent cells.
Dissertations / Theses on the topic 'Cascade of turbulent cells'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 48 dissertations / theses for your research on the topic 'Cascade of turbulent cells.'
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
Kovaľová, Alžbeta. "Kvantifikace turbulence pomocí ekvivalentního teplotního gradientu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442412.
Full textAbstract:
The diploma thesis is focused on the optical beam propagating in the atmosphere in a wireless communication optical link. The first part of the work explains the atmospheric transmission media with turbulence and its effects on reliability of the optical system. The second part introduces methods for turbulence determination based on a statistical approach to turbulence quantification are introduced. In the third part, method of equivalent temperature gradient is described with the advantage of immediate turbulence evaluation. The output of this thesis is the model of turbulent environment formed by the optical elements. Analysis of turbulent properties and non-reciprocal nature of turbulent channel is processed by a 2D simulator based on the mentioned model and method of equivalent temperature gradient.
2
Alves, Portela Felipe. "Turbulence cascade in an inhomogeneous turbulent flow." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/63233.
Full textAbstract:
The inhomogeneous, anisotropic turbulence downstream of a square prism is investigated by means of direct numerical simulations (DNS) and two-point statistics. As noted by Moffatt (2002) “it now seems that the intense preoccupation [...] with the problem of homogeneous isotropic turbulence was perhaps misguided” acknowledging there is now a revived interest in studying inhomogeneous turbulence. The full description of the turbulence cascade requires a two-point analysis which re- volves around the recently derived Kármán-Howarth-Monin-Hill equation (KHMH). This equation is the inhomogeneous/anisotropic analogue to the so-called Kolmogorov equation (or Kármán-Howarth equation) used in Kolmogorov’s 1941 seminal papers (K41) which are the foundation to the most successful turbulence theory to date. Particular focus is placed on the near wake region where the turbulence is anticipated to be highly inhomogeneous and anisotropic. Because DNS gives direct access to all ve- locity components and their derivatives, all terms of the KHMH can be computed directly without resorting to any simplifications. Computation of the term associated with the non-linear inter-scale transfer of energy (Π) revealed that this rate is roughly constant over a range of scales which increases (within the bounds of our database) with distance to the wake generator, provided that the orientations of the pairs of points are averaged-out on the plane of the wake. This observation appears in tandem with a near −5/3 power law in the spectra of fluctuating velocities which deteriorates as the constancy of Π improves. The constant non-linear inter-scale transfer plays a major role in K41 and is required for deriving the 2/3-law (which is real space equivalent of the −5/3). We extend our analysis to a triple decomposition where the organised motion associ- ated with the vortex shedding is disentangled from the stochastic motions which do not display a distinct time signature. The imprint of the shedding-associated motion upon the stochastic component is observed to contribute to the small-scale anisotropy of the stochastic motion. Even though the dynamics of the shedding-associated motion differs drastically from that of the stochastic one, we find that both contributions are required in order to preserve the constant inter-scale transfer of energy. We further find that the inter- scale fluxes resulting from this decomposition display local (in scale-space) combinations of direct and inverse cascades. While the inter-scale fluxes associated with the coherent motion can be explained on the basis of simple geometrical arguments, the stochastic motion shows a persistent inverse cascade at orientations normal to the centreline despite its energy appearing to be roughly isotropically distributed.
3
Cleve, Jochen. "Data-driven theoretical modelling of the turbulent energy cascade." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1103125565484-63361.
Full textAbstract:
Durch eine Modellierung der Energiekaskade gewinnt man wertvolle Einsichten in die Dynamik turbulenter Strömungen. In dieser Arbeit werden multiplikative Kaskadenprozesse untersucht und mit verschiedenen experimentellen Zeitreihen der Energiedissipation verglichen. Zur Berechnung der Energiedissipation ist es unvermeidlich auf eine Hilfskonstruktion zurückzugreifen, die die nicht gemessenen Komponenten des Geschwindigkeitsfeldes ersetzt. Der Schwerpunkt des Vergleichs zwischen Modell und Experiment liegt auf Zweipunktkorrelationen, weil andere Observablen, wie z. B. integrale Momente, durch diese Hilfskonstruktion der Dissipation verfälscht werden. Es werden explizite Ausdrücke für die Zweipunktkorrelationen abgeleitet, die auch Korrekturen, die von einem endlichen Skalierungsbereich stammen,berücksichtigen. Mit diesen Ausdrücken ist es möglich, auch Datensätze mit niedrigen oder moderaten Reynoldszahlen zu fitten und genaue Werte für die Skalierungsexponenten zu bestimmen. Mit einer umfassenden Datenanalyse wird versucht, die freien Parameter des Kaskadengenerators zu bestimmen. Die verfügbare Statistik der Daten ist zu gering, um genauere Aussagen zu treffen, als dass die Verteilung des Kaskadengenerators ähnlich einer log-normal Verteilung sein wird. Mit dem Intermittenzexponenten, der der fundamentalste Skalierungsexponent des Dissipationsfeldes ist, lassen sich die Daten charakterisieren. Die untersuchten Daten teilen sich in zwei Gruppen auf: Die Daten, die aus Luftströmungen gewonnen wurden, weisen einen mit der Reynoldszahl steigenden Intermittenzexponenten auf, der für hohe Reynoldszahlen gegen den konstanten Wert 0.2 konvergiert. Die Daten aus einem Helium-Freistrahl andererseits können am besten mit einem konstanten Intermittenzexponenten 0.1 charakterisiert werden. Diese Unterschiede können nicht vollständig erklärt werden.Um diesen Sachverhalt genauer zu untersuchen wird ein neues Modell vorgeschlagen, das die Kramers-Moyal-Koeffizienten des Geschwindigkeitsfeldes in ein Dissipationsfeld übersetzt, um den Intermittenzexponenten aus einer anderen Perspektive zu berechnen.Schließlich wird eine dynamische Verallgemeinerung des Kaskadenprozesses,die kürzlich vorgestellt wurde, getestet. Das dynamische Modell macht Vorhersagen für allgemeine n-Punktkorrelationen. Die analytischen Ausdrücke für Dreipunktkorrelationen werden mit experimentellen Daten verglichen. Die Übereinstimmung zwischen Modellvorhersage und Experiment ist überzeugend<br>Modelling the turbulent energy cascade gives valuable insight into the dynamics of a turbulent flow. In this work, random multiplicative cascade processes are studied and compared with dissipation time series obtained from various experiments. The emphasis of this comparison is laid on the two-point correlation function because the unavoidable surrogacy of the dissipation field, i.e.the substitution of the multi-component expression by a single component of the velocity signal, corrupts the scaling behaviour of other observables such as integral moments. Finite-size expressions for the two-point correlation function are derived, which make it possible to fit data obtained at moderate or low Reynolds numbers and extract accurate values of scaling exponents. A comprehensive data analysis attempts to determine the free parameters of the cascade generator. The statistics are too limited to claim more than that the cascade generator will be close to having a log-normal distribution. The most basic scaling exponent of the dissipation field is called intermittency exponent and can be used to characterise the data. The investigated data fall into two groups. One set of data obtained from measurements with air show an increasing intermittency exponent with an increasing Reynolds number and saturate for high Reynolds numbers to a value of 0.2. The other set, obtained in a helium jet is best characterised with a constant intermittency exponent of 0.1. The differences are not fully understood. To investigate this issue further, a new construction is suggested, that translates the Kramers-Moyal coefficients of the velocity field into a dissipation field in order to calculate the intermittency exponent from different perspective. Finally, a dynamical generalisation of the cascade process, introduced recently, is tested. The dynamical model makes predictions for point correlation functions. The analytical expressions for three-point correlation functions are compared with their counterparts obtained from experimental data and show remarkable agreement
4
Kishi, Tatsuro. "Scaling laws for turbulent relative dispersion in two-dimensional energy inverse-cascade turbulence." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263445.
Full text
5
Micklow, Gerald J. "Turbomachinery cascade and wake calculation for two-dimensional compressible laminar and turbulent flow." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54244.
Full textAbstract:
A method is presented for the efficient analytical prediction of the two dimensional laminar or turbulent compressor or turbine cascade blade-to-blade flow field and wake. The scheme utilizes a viscous-inviscid interaction routine combining a two-dimensional full potential cascade flow solver with a two-dimensional compressible boundary layer analysis. The boundary layer analysis can compute in the direct mode with pressure gradient specified or in the inverse mode with "boundary layer mass flux" specified. When calculating with the inverse mode, flow separation can be handled easily. Turbulent flow is treated using an algebraic eddy viscosity model with the modified Levy—Lees transformation applied to capture the growth of laminar and turbulent boundary layers. The boundary layer solution is fully implicit and formally second order accurate. The viscous inviscid coupling is performed utilizing thin airfoil theory. Numerical solutions are presented for several numerical test cases and compared with published test data.<br>Ph. D.
6
Wakefield, Bryce Edwin. "Hotwire measurements of the turbulent flow into a cascade of controlled-diffusion compressor blades." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277297.
Full text
7
Tang, Genglin. "Measurements of the Tip-gap Turbulent Flow Structure in a Low-speed Compressor Cascade." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11178.
Full textAbstract:
This dissertation presents results from a thorough study of the tip-gap turbulent flow structure in a low-speed linear compressor cascade wind tunnel at Virginia Tech that includes a moving belt system to simulate the relative motion between the tip and the casing. The endwall pressure measurements and the surface oil flow visualizations were made on a stationary endwall to obtain the flow features and to determine the measurement profiles of interest. A custom-made miniature 3-orthogonal-velocity-component fiber-optic laser-Doppler velocimetry (LDV) system was used to measure all three components of velocity within a 50 mm spherical measurement volume within the gap between the endwall and the blade tip, mainly for the stationary wall with 1.65% and 3.30% tip gaps as well as some initial experiments for the moving wall.
Since all of the vorticity in a flow originates from the surfaces under the action of strong pressure gradient, it was very important to measure the nearest-wall flow on the endwall and around the blade tip. The surface skin friction velocity was measured by using viscous sublayer velocity profiles, which verified the presence of an intense lateral shear layer that was observed from surface oil flow visualizations. All second- and third-order turbulence quantities were measured to provide detailed data for any parallel CFD efforts.
The most complete data sets were acquired for 1.65% and 3.30% tip gap/chord ratios in a low-speed linear compressor cascade. This study found that tip gap flows are complex pressure-driven, unsteady three-dimensional turbulent flows. The crossflow velocity normal to the blade chord is nearly uniform in the mid tip-gap and changes substantially from the pressure to suction side. The crossflow velocity relies on the local tip pressure loading that is different from the mid-span pressure loading because of tip leakage vortex influence. The tip gap flow is highly skewed three-dimensional flow throughout the full gap. Normalized circulation within the tip gap is independent of the gap size. The tip gap flow interacts with the primary flow, separates from the endwall, and rolls up on the suction side to form the tip leakage vortex. The tip leakage vortex is unsteady from the observation of the TKE transport vector and oil flow visualizations. The reattachment of tip separation vortex on the pressure side strongly depends on the blade thickness-to-gap height ratio after the origin of tip leakage vortex but is weakly related to it before the origin of tip leakage vortex for a moderate tip gap. Other than the nearest endwall and blade tip regions, the TKE does not vary much in tip gap. The tip leakage vortex produces high turbulence intensities. The tip gap flow correlations of streamwise and wall normal velocity fluctuations decrease significantly from the leading edge to the trailing edge of the blade due to flow skewing. The tip gap flow is a strongly anisotropic turbulent flow. Rapid distortion ideas can not apply to it. A turbulence model based on stress transport equations and experimental data is necessary to reflect the tip gap flow physics. For the moving endwall, relative motion skews the inner region flow and is decorrelated with the outer layer flow. Hence, the TKE and correlations of streamwise and wall normal velocity fluctuations decrease.<br>Ph. D.
8
Togni, Riccardo. "A numerical study of turbulent Rayleigh-Bénard convection." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6280/.
Full textAbstract:
Il flusso di Rayleigh-Bénard, costituito da un fluido racchiuso fra due pareti a diversa temperatura, rappresenta il paradigma della convezione termica. In natura e nelle applicazioni industriali, il moto convettivo avviene principalmente in regime turbolento, rivelando un fenomeno estremamente complesso. L'obiettivo principale di questo elaborato di tesi consiste nell'isolare e descrivere gli aspetti salienti di un flusso turbolento di Rayleigh-Bénard. L'analisi è applicata a dati ottenuti da tre simulazioni numeriche dirette effettuate allo stesso numero di Rayleigh (Ra=10^5) e a numeri di Prandtl differenti (Pr=0.7,2,7). Sulla base di alcune statistiche a singolo punto, vengono definite nel flusso tre regioni caratteritiche: il bulk al centro della cella, lo strato limite termico e quello viscoso in prossimità delle pareti. Grazie all'analisi dei campi istantanei e delle correlazioni spaziali a due punti, sono state poi individuate due strutture fondamentali della convezione turbolenta: le piume termiche e la circolazione a grande scala. L'equazione generalizzata di Kolmogorov, introdotta nell'ultima parte della trattazione, permette di approcciare il problema nella sua complessità, visualizzando come l'energia cinetica viene immessa, si distribuisce e viene dissipata sia nello spazio fisico, sia in quello delle scale turbolente. L'immagine che emerge dall'analisi complessiva è quella di un flusso del tutto simile a una macchina termica. L'energia cinetica viene prodotta nel bulk, considerato il motore del flusso, e da qui fluisce verso le pareti, dove viene infine dissipata.
9
Lapeyre, Guillaume. "Topologie du mélange dans un fluide turbulent géophysique." Paris 6, 2000. https://hal.archives-ouvertes.fr/tel-01475960.
Full text
10
Kahalerras, Henda. "Etude expérimentale de la profondeur de la cascade de l'intermittence." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10119.
Full textAbstract:
L'evolution de l'intermittence a travers les echelles en turbulence pleinement developpe a ete mesuree par un parametre appele profondeur de la cascade de l'intermittence. L'etude experimentale a consiste a mesurer deux types d'increments de vitesse : longitudinaux et transversaux dans divers ecoulements turbulents et pour une large gamme de nombres de reynolds. L'etude des fonctions de structure a montre que le champ de vitesse n'est pas invariant d'echelle mais admet neanmoins une autosimilarite interne. Une methode des cumulants a ete utilisee pour la premiere fois afin de determiner les trois premiers cumulants (le deuxieme etant la profondeur de la cascade). Les mesures indiquent que ces cumulants sont proportionnels entre eux, au moins pour les echelles inertielles, confirmant ainsi l'hypothese du modele variationnal, a savoir que la cascade de l'intermittence peut etre modelisee par un processus indefiniment divisible. Les deux premiers cumulants presentent une loi de puissance avec l'echelle dont l'exposant evolue de facon universelle avec le nombre de reynolds, ce dernier represente le taux de variation de la profondeur de la cascade de l'intermittence. L'utilisation de cet exposant au concept de la log-similarite a permis de regrouper spectres, fonctions de structure et les deux premiers cumulants a differents nombres de reynolds sur une courbe unique. Enfin, les mesures suggerent qu'en ecoulement stationnaire et localement homogene, les increments transversaux et longitudinaux de vitesse possedent globalement les memes proprietes statistiques et ce independamment du type d'ecoulement et du nombre de reynolds.
11
Liu, Xiaoling. "Polymeric Multicompartmentalized Systems Mimicking Artificial Cells for Controllable Multiple Enzymatic Cascade Reactions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230515.
Full textAbstract:
Engineering artificial cells is currently an emerging area of research that involves constructing mimics of biological cells. These biomimetic cellular systems hold tremendous promise for the different biomedical applications (diagnostics, therapy, tissue engineering, gene transfection, bioactive coatings) as well as aspects of synthetic biology. A key architectural principle of the cell is a multicompartmentalized assembly, which is one of the features of biological cells that enable the performance of multiple complex biochemical reactions within confined environments. For this purpose, this study demonstrates novel artificial cells, not only presenting organelle mimics but also incorporating various stimuli for regulating enzymatic cascade reactions within the artificial cell and for controlled simultaneous and/or subsequent release of the encapsulated (therapeutic) molecules.
To successfully fabricate the multifunctional polymeric multicompartmentalized systems as artificial cells aimed for, in the first step a hollow capsule as biomimetic cellular membrane was developed to simulate a key characteristic of functional artificial cells for the selective uptake and release of (bio)molecules and particles for intra- and intercellular signaling processes. Herein using LbL technique which involved alternate deposition of oppositely charged polyelectrolytes on silica template via electrostatic interaction, the pH and temperature dual-responsive and photo-crosslinked hollow capsule was fabricated and they can be used for the subsequent post-encapsulation process of protein-like macromolecules (≤ 11 nm) and their controllable release triggered by external stimuli for mimicking the controllable bio-inspired functions of cell membranes. The reversible temperature and pH dual-response ability of the hollow capsules has been analyzed. The uptake and release properties of the resulting hollow capsules with different degree of photo-crosslinking for cargos have been further investigated at various temperatures (25, 37 or 45°C) and pH (5.5 or 7.4) of the solution.
Next, the design of the polymersomal subcompartmens as organelle mimics, which divide the interior of the multicompartmentalized systems into subcompartments and can stably encapsulate fragile hydrophobic and hydrophilic cargo, e.g., enzymes in order to conduct encapsulated catalysis-resembling cell organelles, was also an important subject. The fabrication of these subcompartments was starting with the synthesis of suitably end-group block copolymers to realize the enzyme-loaded, multifunctional, pH-responsive, photo-crosslinked and post-labelled polymersomes decorated with adamantane groups. The pH sensitivity and various enzymatic reactions of the established multifunctional Ada-polymersomes have been investigated.
Based on the above concepts, a bottom-up approach was developed to assemble a structural and functional eukaryotic cell mimics, including “membrane-associated” multicompartmentalized system (MS1) and “free-floating” multicompartmentalized system (MS2), by loading pH-sensitive Ada-polymersomes inside the multifunctional cell membrane. The creation of these multicompartmentalized systems was based on the assembly of enzyme-loaded Ada-polymersomes as organelle mimics onto sacrificial particle templates by host-guest interaction, followed by the LbL deposition of temperature-responsive and photo-crosslinkable PMA(β-CD)/[PAH/PNMD]3 multilayers and outer protective capping PAH/PMA(PEG) bilayer as biomimetic cellular membrane. Upon photo-crosslinking the polymer biomimetic membrane and dissolution of the particle templates, multicompartmentalized systems were obtained. Spatial position of the subcompartments can be controlled using non-covalent host-guest concept, which yielded multicompartmentalized systems containing “membrane-associated” and “free-floating” subunits. Moreover, the metabolism mimicry of multicompartmentalized systems by performing multiple successive two-enzyme cascade reactions in the cells and the multiple parallel reactions by using a third enzyme for deactivating the reaction product and interfering the cascade reaction have been investigated.
In conclusion, these multicompartmentalized systems, combining the advantages of both pH-responsive Ada-polymersomes as organelle mimics and multifunctional hollow capsule as biomimetic cellular membrane, present new opportunities for the development of functional cell mimics. The presented studies highlight crucial aspects for the successful applications of such cell mimics for diagnostics, tissue engineering, as nanoreactors, as carriers for multiple drug delivery with controlled release profiles, or as therapeutic artificial cells.
12
Castillo-Castellanos, Andrés Alonso. "Turbulent convection in Rayleigh-Bénard cells with modified boundary conditions." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066200/document.
Full textAbstract:
Une caractéristique remarquable de la convection de Rayleigh-Bénard qui concerne une couche de fluide horizontale chauffée par le bas et refroidie par le haut, est l’établissement spontané de l’ordre spatial et la formation d’une circulation cohérente à grande échelle. Comment les différents facteurs, tels que la géométrie du domaine et les conditions limites, influencent l’écoulement à grande échelle, restent une question ouverte. Malgré sa simplicité apparente, la convection de Rayleigh-Bénard présente une dynamique à grande échelle incroyablement riche et complexe, tels que des modes de torsion et du battement, la rotation du plan et des cessations de la circulation, qui coexistent souvent et se concourent. Une approche couramment utilisée dans l’étude des cessations, consiste à contraindre la circulation à grande échelle à un plan en limitant le domaine fluide à une cellule carrée (2D) ou à une cellule rectangulaire mince (quasi-2D). Cependant, il n’est pas tout à fait clair si les retournements 2-D et (quasi-)2-D correspondent au même phénomène. Le présent document est consacré à l’étude des modes d’écoulement à grande échelle dans la convection turbulente de Rayleigh-Bénard et de l’influence exercée par différents facteurs sur les structures d’écoulement et sur leur évolution temporelle. La caractérisation proposée combine une analyse statistique avec une approche physique s’appuyant sur le moment angulaire ainsi que sur les énergies cinétiques et potentielles pour mettre en évidence les mécanismes physiques sous-jacents. Nous essayons ensuite de relier ces mécanismes à chacun des modes d’écoulement distinctifs observés et à leur évolution<br>One outstanding feature of the Rayleigh-Bénard problem which concerns a horizontal fluid layer heated from below and cooled from above, is the spontaneous establishment of spatial ordering and the formation of a coherent large-scale circulation. How different factors, such as the domain geometry and boundary conditions, influence the sizes and shapes of the large-scale flow remains an open question. Despite its apparent simplicity, Rayleigh-Bénard convection exhibits some incredibly rich and complex large-scale dynamics such as torsional modes, rotation, sloshing, and cessations, which often coexist and compete to each other. One approach, commonly used in the study of cessations is to constrain the large scale circulation to a plane by restricting the fluid domain to a (2-D) square cell or to a slim rectangular cell of small aspect ratio in the transversal direction. However, it is not entirely clear whether the 2-D and (quasi-)2-D reversals correspond to the same phenomenon. The present document is dedicated to the study of the large-scale flow patterns in turbulent Rayleigh-Bénard convection, and of the influence exerted by different factors on the flow structures and on their temporal evolution. The proposed characterization combines a statistical analysis with a physical approach relying on the angular momentum as well as the kinetic and potential energies to highlight the underlying physical mechanisms. We subsequently attempt to tie these mechanisms together to each of the distinctive flow patterns observed and to their evolution
13
Gao, Feng. "Advanced numerical simulation of corner separation in a linear compressor cascade." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0008/document.
Full textAbstract:
La demande croissante pour alléger les moteurs d’avions et diminuer les émissions polluantes de la propulsion aéronautique réclame à rendre plus compact le système de compression des moteurs, qui représente environ 40%-50% de la masse totale. Or, à taux de compression global égal, la réduction du nombre d’étage exige d’un point de vue aérodynamique une augmentation de la charge des aubes de compresseur par étage. La charge d’aube est aujourd’hui limitée car elle induit différents mécanismes de pertes tridimensionnelles très pénalisant. L’un des plus importants est le décollement de coin qui se forme à la jonction entre l’extrados de l’aube et le moyeu ou le carter. Bien que des travaux existent sur les mécanismes et paramètres intervenant dans le décollement de coin, il est encore difficile de proposer une méthode de contrôle efficace. Cela est principalement dû à deux raisons : (i) le manque de compréhension fine des mécanismes physiques, (ii) l’utilisation pour la conception de modèles de turbulence classiques de type RANS (Reynolds-averaged Navier-Stokes) qui ne sont pas capables de prédire précisément le décollement de coin, car ils ne peuvent pas décrire correctement les mécanismes de transport turbulent. Des simulations de type RANS et LES (large-eddy simulation = simulation des grandes échelles) sont présentées dans cette thèse sur une configuration de grille d’aubes de compresseur, et comparées avec les données expérimentales obtenues au LMFA (issues de travaux séparés). L’approche RANS surestime globalement le décollement de coin. Une amélioration significative est obtenue par la méthode LES, en particulier pour le coefficient de pression statique sur l’aube et les pertes de pression totale. Ces résultats montrent que la zone de décollement de coin, qui est la source principale des pertes, génère des tourbillons de grande échelle associés à de forts niveaux d’énergie. Les histogrammes bimodaux de la vitesse tangentielle qui ont été observés expérimentalement semblent confirmés par les résultats LES. En ce qui concerne les amplitudes des fluctuations de vitesse tangentielle, les résultats expérimentaux et ceux de la LES mettent en évidence deux pics sur certains profils perpendiculaires aux parois. Enfin, grâce à l’approche LES, les bilans de l’énergie cinétique turbulente sont calculés et analysés. Ils décrivent l’équilibre entre les termes de production, de dissipation et de transport. Une des perspectives de cette analyse est d’aider à améliorer la modélisation de la turbulence en approche RANS<br>The increasing demand to reduce the mass of aircraft jet engines and emissions of aircraft propulsion requires to make the compression system of engines more compact, since this component accounts for about 40%-50% of the total mass. However, at a given overall pressure ratio, decreasing the number of stages will raise the compressor blade loading per stage. The blade loading is extremely restricted by different three-dimensional flow loss mechanisms. One of them is the corner separation that forms between the blade suction side and the hub or shroud. Although some works previously investigated the mechanisms and the parameters of corner separation, it is still difficult to propose an effective control method of the corner separation. That is mainly due to two reasons: (i) the lack of knowledge of the physical mechanisms, (ii) the nowadays classical RANS (Reynolds-averaged Navier-Stokes) turbulence models are not capable to accurately predict the corner separation, since they cannot correctly describe the turbulent transport mechanisms. RANS (Reynolds-averaged Navier-Stokes) and LES (large-eddy simulation) simulations are here presented on a compressor cascade configuration, in comparison with experimental data obtained at LMFA (from separate works). The RANS approach globally over-estimates the corner separation, whereas a significant improvement is achieved with the LES, especially for the blade surface static pressure coefficient and the total pressure losses. The corner separation region, which is the main source of the total pressure losses, is shown to generate large-scale energy-containing eddies. The bimodal histograms of the streamwise velocity that were observed experimentally seem to be confirmed by the LES results. Concerning the streamwise velocity fluctuations (RMS), both the experiment and the LES show some profiles with two peaks. Finally, thanks to the LES approach, the turbulent kinetic energy budget, which represents the balance between the production, dissipation and transport terms, are computed and analyzed. This may help the improvement of RANS turbulence modeling
14
Kuhl, David Derieg. "Near Wall Investigation of Three Dimensional Turbulent Boundary Layers." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34676.
Full textAbstract:
This report documents the experimental study for four different three-dimensional turbulent flows. The investigation focuses on near wall measurements in these flows. Several experimental techniques are used in the studies; however, the bulk of the investigation focuses on a three-orthogonal-velocity-component fiber-optic laser Doppler anemometer (3D-LDA) system. The control volume of the 3D-LDA is on the order of 50 micro-meter in size, or a y<sup>+</sup> distance of around 2.3 units (using average values of U<sub>τ</sub> and ν from the experiment). An auxiliary small boundary layer wind tunnel (auxiliary tunnel) and a low speed linear compressor cascade wind tunnel (cascade tunnel) are utilized in this study. One of four flow experiments is done in the auxiliary tunnel the other three are in the cascade tunnel. The first three-dimensional turbulent flow is a vortical flow created by two half-delta wing vortex generators. Near wall secondary flow features are found. The second flow is an investigation of the first quarter chord tip gap flow in the cascade tunnel. Strong three-dimensional phenomena are found. The third flow investigated is the inflow to the compressor cascade with the moving wall. The experiment records shear layer interaction between the upstream flow and moving wall. Finally the fourth flow investigated is the inflow to the compressor cascade with the moving wall with half-delta wing vortex generators attached. Phase-averaged data reveal asymmetrical vortex structures just downstream of the vortex generators. This is the first time any near wall data has been taken on any of these flows.<br>Master of Science
15
Ma, Wei. "Experimental investigation of corner stall in a linear compressor cascade." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00728374.
Full textAbstract:
In applied research, a lack of understanding of corner stall, i.e. the three-dimensional (3D) separation in the juncture of the endwall and blade corner region, which has limited the efficiency and the stability of compressors. Both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) still need to be calibrated for turbomachinery applications. In the fundamental research of the turbulent boundary layer (TBL), there are a lot of findings of the effects of curvature and pressure gradients, which also play an important role in physics of corner stall. The purpose of this thesis is (i) to carry out an experiment in a cascade, (ii) to gain a database that could be used to calibrate both RANS and LES, and (iii) to give some basic explanations of corner stall through investigating the TBL on the suction side at the mid-span which is more complex than those in the basic investigations but simpler than those in a real engine. A detailed and accurate experiment of 3D flow field through a linear compressor cascade has been set up. Experimental data were acquired for a Reynolds number of 3.82×10 ^5 based on blade chord and inlet flow conditions. Measurements have been achieved by hot-wire anemometry, pressure taps on blade and endwall, five-hole pressure probe, oil visualization, 2D particle image velocimetry (PIV),and two-component laser Doppler anemometry (LDA). An original and complete database was thus obtained. The TBL on the suction side at mid-span was investigated. The wall-normal negative pressure gradient restrains the separation, on the contrary to its influence in the corner stall. The streamwise adverse pressure gradient can be responsible for the development of Reynolds stresses. The remarkable phenomenon at measurement stations near the trailing edge of blade is that an inflection point occurs in each profile of the mean streamwise velocity. At this inflection point, the magnitudes of the Reynolds stresses reach their maximum values, and the direction of energy diffusion also changes. The velocity field in the corner stall was presented. Bimodal histograms of velocity exist in the experiment. The bimodal points mainly appear in the region around the mean interface of separated flow and non-separated flow. At a bimodal point the local two velocity components are non-independent from each other, due to the aperiodic interplay of two basic modes in the flow field. Two modes were proposed to interpret the physics of bimodal behaviour.
16
Hodge, Jacob G. "Regulation of the MEK/ERK signaling cascade by ADAM12 in triple-negative breast cancer cells." Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/35228.
Full textAbstract:
Master of Science<br>Biochemistry and Molecular Biophysics Interdepartmental Program<br>Anna Zolkiewska<br>Mitogen-activated protein kinase (MAPK) signaling plays an important role in the proliferation, survival, and therapy resistance of breast cancer cells. Two important protein kinases involved in the MAPK pathway are MEK and ERK. The MEK/ERK signaling cascade can be stimulated by activation of the epidermal growth factor receptor (EGFR) upon binding of EGF-like ligands, which are released from cells by ADAM proteases. EGFR is frequently overexpressed in triple-negative breast cancer (TNBC), a particularly aggressive form of breast cancer. Our analysis of clinical data revealed that high expression of ADAM12, but not other ADAMs, in TNBC is associated with poor patient survival. Thus, we hypothesized that ADAM12 plays a critical role in the progression of TNBC, possibly by stimulating MEK/ERK activity in an EGFR-dependent manner. To test this hypothesis, ADAM12 was knocked-down (KD) in SUM159PT TNBC cells, which express high levels of the endogenous ADAM12 protein. An antibody array assay indicated a significant decrease in the activation of the MAPK pathway in SUM159PT cells after ADAM12 KD. The decrease in MAPK activity was further confirmed by Western blotting using phospho-MEK and phospho-ERK specific antibodies. Additionally, conditioned media from ADAM12-deficient SUM159PT cells failed to support the survival of MCF10A cells, suggesting that ADAM12 KD reduced the release of pro-survival growth factors from SUM159PT cells. Based upon this data, we propose that ADAM12 is a novel regulator of the MAPK pathway and a potential therapeutic target in breast cancer.
17
Andrade, João Rodrigo. "Spectral analysis of the turbulent energy cascade and the development of a novel nonlinear subgrid-scale model for large eddy simulation." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I006/document.
Full textAbstract:
L’objectif de cette thèse est d’analyser et d’acquérir de nouvelles connaissances sur le comportement de la dynamique de petites échelles des écoulements turbulents et de proposer un nouveau modèle sous-maille non linéaire pour la simulation des grandes échelles de la turbulence. De cette façon, la présente thèse est subdivisée en trois parties principales. Le premier sujet concerne l’analyse des incertitudes statistiques associées aux données de simulation numérique directe pour des écoulements turbulents en canal plan, fournissant une nouvelle quantification physique de ces erreurs. Dans cette analyse, l’erreur de vitesse moyenne est estimée en prenant en compte le tenseur de contrainte de Reynolds et en utilisant l’équation de forces moyennes. Cette analyse est effectuée afin de vérifier la qualité des données statistiques provenant de la simulation numérique directe appliquée dans le présent travail. Deuxièmement, pour comprendre la physique contenue dans l’ensemble du spectre de nombre d’ondes des écoulements turbulents, une analyse du bilan d’énergie cinétique turbulente dans un écoulement de canal plan turbulent complètement développé est réalisée. L’analyse est centrée sur l’influence du nombre de Reynolds sur la cascade spectrale d’énergie et la cascade d’énergie correspondante dans l’espace physique en présence d’inhomogénéité et d’anisotropie. Finalement, nous présentons un nouveau modèle sous-maille non linéaire, conçu pour la simulation des grandes échelles de la turbulence, basé sur un ensemble de tenseurs objectifs. Dans le modèle de fermeture proposé, le tenseur de contrainte à l’échelle sous-maille est fonction du tenseur de la vitesse de déformation et du tenseur de non-persistance de contraintes, où les deux sont des entités cinématiques locales et objectives. Le tenseur non-persistance de contraintes représente la capacité locale du fluide à ne pas être constamment étiré. Pour vérifier la cohérence du modèle proposé, de tests a priori et a posteriori sont effectués en simulant différents écoulements turbulents délimités par de parois. Des comparaisons avec le tenseur de contrainte exact à l’échelle de sous-maille et de données expérimentales ont révélé que l’inclusion de termes non linéaires dans le modèle sous-maille peut conduire à de meilleurs résultats, montrant le potentiel important de la base tensorielle proposée<br>The purpose of the present work is to analyze and to provide an enhancement of the knowledge about the subgrid-scale behavior and to propose novel nonlinear subgrid-scale models for large eddy simulations of turbulent fluid flows. In this way, the present thesis is subdivided into three main parts. The first topic is an analysis of the statistical uncertainties associated with direct numerical simulation data for turbulent channel flow, showing a novel physicallybased quantification of these errors. In this analysis, the mean velocity error is estimated by considering the Reynolds stress tensor, and using the balance of mean force equation. This analysis is performed in order to verify the quality of the statistical data coming from the direct numerical simulation applied in the present work. Secondly, seeking to understand the contained physics in the whole wavenumber spectrum of turbulent flows, an analysis of the spectral turbulent kinetic energy budget in fully developed turbulent plane channel flow is performed. The analysis is focused on the influence of the Reynolds number on the spectral cascade of energy and the corresponding energy cascade in physical space in the presence of inhomogeneity and anisotropy. Finally, a novel nonlinear subgrid-scale model for large eddy simulation based on a set of objective tensors is presented. In the proposed closure model, the modeled subgrid-scale stress tensor is a function of the resolved rate-of-strain tensor and the resolved non-persistence-of-straining tensor, where both are local and objective kinematic entities. The non-persistence-of-straining tensor represents the local ability of the fluid to avoid being persistently stretched. To check the consistency of the proposed model, a priori and a posteriori tests are performed by simulating different wall-bounded turbulent flows. Comparisons with the exact subgrid-scale stress tensor and experimental data revealed that the inclusion of nonlinear terms on the subgrid-scale model can significantly increase the accuracy of the results, showing the great potential of the proposed tensorial base
18
Zambonini, Gherardo. "Unsteady dynamics of corner separation in a linear compressor cascade." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC049/document.
Full textAbstract:
Le présent travail concerne l'étude du décollement de coin de compresseurs par des investigations expérimentaux sur le banc d'essai subsonique grille d'aubes situé au LMFA (Re = 3.8 x 105, M = 0,12, profil NACA 65-009). Habituellement, cette particulière séparation tridimensionnelle a lieu dans le coin entre l'aubage et la paroi du moyeu des rangées d'aubes, également dans les stators et les rotors.Les performances de l’étage sont ainsi dégradées à cause des pertes de charge et du blocage conséquent à la séparation de l’écoulement. Bien que les caractéristiques stationnaires sont bien connues par la littérature, uniquement des récentes études expérimentales avancées combinées aux améliorations de simulations numériques, telles que URANS et LES, ont permis de découvrir le comportement très instable du décollement de coin. Des études préalables sur le même banc d'essai ont rapporté un comportement intermittent du décollement, appelé comportement bimodal. Dans la présente thèse de doctorat, il est montré que le comportement bimodal correspond à deux états spécifiques du champ fluide: une séparation fermée, presque supprimée, et une séparation ouverte caractérisée par un blocage massif. Il est clair que cette commutation bimodale du décollement de coin apparaissant dans une machine réelle pourrait avoir un impact fortement déstabilisant. En utilisant la méthode de mesure PIV haute vitesse couplée à des mesures de pression résolues en temps sur la surface de l'aubage, l'écoulement d'un canal inter-aube a été étudié pour deux différentes incidences. Les mesures PIV fournissent pour la première fois des visualisations résolues en temps et étendues à toute la section de l'aubage de la variation bimodale du décollement. L'interaction des grandes structures aléatoires de la couche limite à l'amont avec le bord d'attaque de l'aubage déstabilise le front du décollement et agrandit la région de recirculation. Une séparation ainsi massive persiste jusqu'à ce que le blocage dans le canal inter-aube provoque la rupture des plus grandes structures constituant la zone de recirculation. Successivement le débit recommence à accélérer et la séparation est presque supprimée. Cette dynamique coïncide avec le régime d'écoulement hautement instationnaire et apériodique des diffuseurs, appelé large transitory stall, caractérisé par des grandes amplitudes d'énergie dans la gamme des basses fréquences du spectre. Des moyennes conditionnelles de pression et la décomposition orthogonale modale (POD) des champs de vitesse ont été appliquées pour montrer l'effet rétroactif du blocage induit par la séparation ouverte sur l'angle local au bord d'attaque. Ces résultats supportent l’hypothèse d'une instabilité auto-entretenue causée par la diffusion imposée dans le stator. En fin, des mesures de pression totale résolues en temps ont été effectuées en utilisant des capteurs à haute réponse en fréquence, situés à la même position dans les différents canaux adjacents. La cohérence et la linéarité de l'angle de phase trouvée entre les capteurs confirment que l'instabilité du décollement peut se propager d'un canal a l'autre, en analogie avec les perturbations tournantes (rotating instabilities) apparaissant dans les bancs d'essai annulaires. Ceci montre pour la première fois que, même dans une grille d'aubes linéaire de compresseur, l'instabilité intrinsèque du décollement de coin peut déclencher la propagation d'instabilités<br>The present work focuses on the study of the corner separation phenomenon in compressors carried out by experimental investigations on a subsonic linear cascade test rig (Re=3.8x105, M=0.12, blade profile NACA 65-009). Usually, this particular three-dimensional separation takes place in the corner between the blade and the endwall of compressor rows, mostly at hub, both in stators and rotors.Its main features are high total pressure losses and blockage of the flow, with consequent impacts on the efficiency. Whereas time averaged characteristics are well known from the past, only recent advanced experimental studies and improvements of numerical simulations, such as URANS and LES, have permitted to uncover the highly unsteady behavior of corner separation in compressors. Precedent studies on the same test rig have reported an intermittent unsteady behavior of corner separation, called bimodal behavior. In the present thesis it is shown that the bimodal behavior corresponds to two specific states of the flow: a closed separation, almost suppressed, and an open separation characterized by massive blockage and losses. Clearly hub-separation bimodal switches appearing in a real machine could have a first order detrimental effect on the stability of the flow in the compressor. By using high speed PIV coupled with unsteady pressure measurements on the surface of the blade the flow in a single blade passage has been investigated for different incidences. The PIV measurements provide, for the first time, time-resolved flow visualizations of the size switch of the separation with an extended field of view covering the entire blade section. The interaction of random large structures of the incoming boundary layer with the blade is found to be a predominant element that destabilizes the separation boundary and enlarges the recirculation region. Such a massive separation persists until the blockage in the passage causes the breakdown of the largest structures in the aft part of the blade, reestablishing the closed separation state. Such dynamics coincide with the aperiodic intermittent flow regime of diffusers, called transitory stall regime, and the associated Fourier spectra show the largest energy amplitudes in the low frequency range. Conditional ensemble averages of pressure and proper orthogonal decomposition (POD) of velocity fields have been applied to show the feedback effect of the blockage of the separation on the flow angle around the blade leading edge. These results draw the picture of a self-sustained instability caused by the diffusion imposed by the inter-blade passage. To answer the question about the interaction between adjacent corner separations, time-resolved total pressure measurements have been carried out by using high frequency response sensors positioned in bimodal points of multiple passages. The coherent propagation velocity and the linearity of the phase angle found between the signals confirm that the unsteadiness of the separation can propagate in pitch-wise direction. It is interesting to underline that equivalent elements characterize rotating disturbances appearing in annular test rigs. This finally shows that, even in an isolated stator blade row, the intrinsic unsteadiness of corner separation can start the propagation of instabilities. It is the first time that such a propagation effect is observed in a linear compressor cascade
19
Wang, Aibo. "Phosphorylation of Nur77 by MEK-ERK-RSK cascade induces mitochondrial translocation and apoptosis in T cells." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3372283/.
Full text
20
Dunn, Timothy Alan. "The link between neuronal activity and activation of the cAMP/PKA cascade in developing retinal ganglion cells." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3311360.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2008.<br>Title from first page of PDF file (viewed July 30, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
21
Guest, Deborah Sharon Honrado. "Modelling tumour initiating cells and their differentiation cascade, with the effects of photon irradiation and temozolomide, to optimise treatment." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599916.
Full textAbstract:
Glioblastoma murtiforme (GBM) is the most aggressive form of glioma, classified by the Wor1d Health Organisation (WHO) as a grade III or IV tumour [1]. Despite receiving a combination of radiotherapy, chemotherapy and surgical treatment, average survival is poor of 14•6 months and only a two year survival of 27•2% [2]. Present studies on cell surface markers, such as CD15, suggest that GBM is composed of a heterogeneous population of cells, derived from a brain tumour stem cell (BTSC). BTSC cells play an essential role in the growth of tumours and thus treatment therapies may be more beneficial if adapted to inhibit the development of these cells. R10 cells are a patient derived GBM cell line provided by the Addenbrooke's Hospital in Cambridge. Isolating the R10 cell line for the CD15 marker can allow for the sensitivity of the subpopulations within the tumour to be determined. A better understanding of these sensitivities could allow for a more optimal treatment to be developed, which exploits the different sensitivities of each subpopulation. Experimental results showed that each subpopulatian af the R10 cell line has significantly different doubling times and sensitivities to drug and irradiation. A population balance equation is used to model the growth of a BTSC cell. The aim was to model a new fractionation schedule, which improves the treatment of GSM. This was achieved by means of predicting the number of cells killed in each cell line using the data from the R10 cell line. The model implements an asymmetric radiotherapy (ART) treatment that gives two initial low doses followed by a third dose that delivers a total daily dose of 2 Gy. All doses and the inter-fraction intervals could be varied to find the optimum treatment schedule. The optimum schedule from ART delivers two initial doses of 0•7 Gy, followed by a dose of 0-6 Gy with intervals of 1 hour, for 5 days a week for 6 weeks. A daily dose of 2 Gy and a total dose of 60 Gy were given to ensure that jf a patient were to show no signs of hyper-radiosensitivty (HRS) they would still be treated efficiently. However, it was found that the standard radiotherapy treatment was more beneficial with this scenario.
22
Zheng, Fengyuan. "The effect of PMMA stimulated Complement-Macrophage cascade on Osteogenesis of Preosteoblast-like MC3T3-E1 cells on PMMA surface." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275497184.
Full text
23
Cryar, Benjamin Joseph. "Characterisation of the up-stream components in the stretch-induced ERK-1/2 MAP kinase cascade in human myometrial cells." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9581.
Full textAbstract:
The mechanisms underlying stretch-induced signalling in the human myometrium are poorly understood. Previous work in the group has demonstrated that in vitro stretch of human myometrial cells leads to increased expression of the pro-labour factors COX-2 and IL-8 via activation of the ERK-1/2 MAPK cascade, however the identities of components upstream in this pathway have yet to be elucidated. I over expressed constitutively active Ras in human myometrial cells, leading to increased ERK-1/2 phosphorylation and elevated COX-2 and IL-8 mRNA expression. I then inhibited Ras using both the chemical inhibitor manumycin A and transfection with dominant-negative mutant Ras. Each resulted in decreased ERK-1/2 phosphorylation and COX-2 expression in response to stretch. I performed immunoprecipitations to investigate which factors associated with Ras and found that stretch increased its association with SOS-1 and Grb-2. I then confirmed that Grb-2 was essential for the propagation of the stretch signal to ERK-1/2 by using siRNA to silence Grb- 2 and found that this resulted in decreased phosphorylation of ERK-1/2 and COX-2 and IL-8 protein synthesis. Silencing of SOS-1 decreased COX-2 protein expression but had little effect on ERK-1/2 phosphorylation. I then investigated the role of FAK, a constituent of stretch sensing focal adhesions, in the transduction of the stretch signal. First I used the inhibitors Y-27632 and PF-573,228, however neither inhibited the stretch-induced increase in ERK-1/2 phosphorylation or COX-2 and IL-8 mRNA expression In contrast, using siRNA to silence FAK expression reduced both the stretch-induced increase in ERK-1/2 phosphorylation and COX-2 and IL-8 protein synthesis. Moreover, transfection with dominant-negative FRNK reduced ERK-1 phosphorylation and COX-2 protein synthesis. Cells were also treated with the Src family kinase inhibitor PP-2 resulting in a decrease in stretch-induced ERK-1/2 phosphorylation and COX-2 protein synthesis. These data suggest that Ras, Grb-2 and FAK all act upstream of ERK-1/2 to mediate stretchinduced up-regulation of COX-2 and IL-8 in human myometrial cells, the role of SOS-1 is less clear, but also appears to be involved in stretch-induced expression of COX-2.
24
Hadjal, Yasmine. "Role de la cascade p38MAPK-p53 dans la différenciation des cellules souches embryonnaires de souris." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM5031/document.
Full textAbstract:
La réussite de la thérapie cellulaire à l'aide des cellules souches embryonnaires, nécessite une bonne compréhension des mécanismes moléculaires qui contrôlent leur différenciation. Une des voies de signalisation, impliquée dans le contrôle de la différenciation des cellules souches, est la voie p38MAPK. Dans le but de comprendre les mécanismes moléculaires impliqués dans le contrôle de la différenciation précoce des cellules ES, nous avons réalisé un criblage sur puces à ADN. Les résultats du criblage ont montré que certains gènes régulés différentiellement, comme le gène Bcl2, sont des cibles communes de p38MAPK et de p53. En plus de son rôle de répresseur de tumeur, p53 a été impliqué dans le développement embryonnaire et dans la biologie des cellules ES. Ainsi, il est connu que p53 agit comme un répresseur du gène de pluripotence, Nanog. Il est également connu que p53 interfère avec le processus de reprogrammation des cellules adultes ; et que son activité transcriptionnelle augmente avec l'entrée des cellules ES en différenciation. En revanche, son rôle dans la différenciation et dans la formation des différents lignages issus des cellules ES, reste inconnu. Nous avons trouvé que le traitement des cellules ES sauvages avec l'inhibiteur spécifique de p53, la pifithrine-α, durant le processus de différenciation, inhibe les lignages mésodermiques, et à l'inverse, stimule la neurogenèse. De plus, la transfection transitoire des cellules ES avec des siRNAs spécifiques, dirigés contre p53 ainsi que l'utilisation des cellules ES déficientes pour le gène p53, montrent que l'absence de p53, affecte les lignages cardiaques, du muscle lisse et du muscle squelettique<br>Embryonic stem cells (ESCs) differentiate in vitro into all cell lineages. We previously found that p38MAPK controls two independent successive steps during the early mesodermal commitment of ESCs. The first one is Brachyury dependent, a master gene of mesoderm formation whereas the second one is not. In order to understand the molecular mechanism implicated in the second step, we treated ESCs with the p38 specific Inhibitor PD169316 and performed microarray experiments on mRNAs extracted from treated versus untreated cells. Our results show that many regulated genes are common targets of p38MAPK and p53 transcription factor. In addition to its role as a tumor suppressor and cell cycle checkpoint control, p53 has been involved in embryonic development, but its role in ESC differentiation is still unknown. We found that treatment of wild type ESCs with the p53 specific inhibitor pifithrin α during the differentiation process inhibits mesodermal lineages and, by contrast, stimulates neurogenesis. Likewise, ESCs Transfected with p53 siRNAs and p53 KO ESCs show an inhibition of cardiac, endothelial, smooth muscle and skeletal muscle lineage formation. Furthermore, p38MAPK inhibition by PD169316 for 24h induces a strong decrease of p53 protein level. Our results suggest that p53 mediates the p38MAPK control of the commitment of ESCs towards mesodermal lineages. The involvement of the various p53 isoforms in this process will be discussed
25
Bear, Philip Steven. "On the Experimental Evaluation of Loss Production and Reduction in a Highly Loaded Low Pressure Turbine Cascade." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright148464084439115.
Full text
26
Liu, Xiaoling [Verfasser], Brigitte [Akademischer Betreuer] [Gutachter] Voit, and Xinliang [Gutachter] Feng. "Polymeric Multicompartmentalized Systems Mimicking Artificial Cells for Controllable Multiple Enzymatic Cascade Reactions / Xiaoling Liu ; Gutachter: Brigitte Voit, Xinliang Feng ; Betreuer: Brigitte Voit." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1147287376/34.
Full text
27
Liu, Xiaoling [Verfasser], Brigitte Akademischer Betreuer] [Gutachter] Voit, and Xinliang [Gutachter] [Feng. "Polymeric Multicompartmentalized Systems Mimicking Artificial Cells for Controllable Multiple Enzymatic Cascade Reactions / Xiaoling Liu ; Gutachter: Brigitte Voit, Xinliang Feng ; Betreuer: Brigitte Voit." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230515.
Full text
28
Wildroudt, Maria L. "Characterization of the Second Messenger Signaling Cascade Linking Angiotensin II Receptor Activation with Vascular Smooth Muscle Cell Mitogenesis." Kent State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=kent1122480402.
Full text
29
Schoeberl, Birgit. "Mathematical modeling of signal transduction pathways in mammalian cells at the example of the EGF induced MAP kinase cascade and TNF receptor crosstalk." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11406710.
Full text
30
Schoeberl, Birgit [Verfasser]. "Mathematical modeling of signaltransduction pathways in mammalian cells at the example of the EGF induced MAP kinase cascade and TNF receptor crosstalk / Birgit Schoeberl." Aachen : Shaker, 2004. http://d-nb.info/972377360/34.
Full text
31
Rawal, Devika. "Use of a Neurotrophic Factor Mimetic to Block Amyloid Toxicity in Alzheimer's Disease Models." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/69.
Full textAbstract:
Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in the world. The most accepted hypothesis for the cause of this disease is the amyloid cascade hypothesis, which postulates that the formation of extracellular neurotoxic amyloid-beta binds specific receptors on the surface of neuronal and glial cells to increase cell stress leading to cell death. Our laboratory previously showed that treatment of cultured human SHSY neuronal cells with amyloid beta increases the cellular levels of two key components (caspases-2 and -3) of the extrinsic apoptotic pathway, leading to cell death. The amyloid beta induced caspase elevation was blocked by simultaneously treating the cells with a short mimetic of human ependymin neurotrophic factor, hEPN-1, and the hEPN-1 treatment also blocked cell death. This thesis extends the AD investigation to show that treatment of SHSY cells with amyloid beta may also activate an intrinsic apoptotic mitochondrial stress pathway (assaying caspase-9 as a marker enzyme), and that hEPN-1 treatment significantly lowers this activation. In addition, our laboratory previously showed that treating SHSY cells with amyloid beta increases TUNEL staining, an assay for DNA fragmentation (a hallmark of end stage of apoptosis, and a different apoptotic marker than caspase activation). Treatment with hEPN-1 simultaneously with the amyloid beta, or 6 hrs post amyloid beta, significantly lowered the amyloid beta induced TUNEL signal. This thesis extended the earlier TUNEL experiments to show that hEPN-1 treatment can significantly lower the amyloid beta induced TUNEL staining even when added 18 hrs post amyloid beta. With respect to caspase-8, an initiator caspase in the extrinsic pathway, immunoblot assays of brain lysates from 8 month old transgenic AD mice showed that a 2 week oral delivery of hEPN-1 (conjugated to a carrier to deliver it across the blood brain barrier) significantly lowered caspase-8 levels. Finally, an assay of cellular inhibitors of apoptosis (cIAP) showed a significant increase in their cellular levels in SHSY cells, and in transgenic AD mice treated with hEPN-1, showing for the first time that hEPN-1 may aid cell survival by upregulating proteins known to directly bind specific caspases to block their activity leading to their degradation. The cIAP upregulation occurred in the presence or absence of amyloid beta, indicating that hEPN-1 likely does not block cell death by directly interfering with the interaction of amyloid beta with its cell surface receptors, but instead hEPN-1 may activate an independent cell survival signal transduction pathway in neuronal cells.
32
Sato, Masaaki. "NMDA receptor stimulation and brain-derived neurotrophic factor up-regulate Homer 1a mRNA via the mitogen-activated protein kinase cascade in cultured cerebellar granule cells." Kyoto University, 2001. http://hdl.handle.net/2433/150166.
Full text
33
Gupta, Nishith. "An Intimate Dining – Nutritional Interactions between Obligate Intracellular Parasites and Host Cells." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/18657.
Full textAbstract:
Das zu den Protozoen gehörende Phylum der Apicomplexa umfasst nahezu 6000 Parasitenarten. Die meisten Apicomplexa haben sich an eine obligat intrazelluläre Lebensweise angepasst und infizieren verschiedenste Tiere und den Menschen. Zu den bedeutendsten Vertretern der Apicomplexa zählen Toxoplasma, Plasmodium und Eimeria. In dieser Arbeit lag der Schwerpunkt auf den drei repräsentativen Organismen Toxoplasma gondii, Eimeria falciformis und Plasmodium berghei, welche sich alle in einem etablierten Wirt (der Maus) reproduzieren, sich allerdings hinsichtlich ihrer Wirtszellen, Persistenz sowie in ihrem Reproduktionsverhalten deutlich unterscheiden. Somit ermöglichen die genannten Parasiten eine umfassende Untersuchung der Biologie der Apicomplexa. Die meisten Entwicklungsstufen dieser Pathogene sind sehr eng mit der Wirtszelle assoziiert, was auch metabolische Wechselwirkungen beinhaltet. Das Verständnis dieser Interaktionen ist unerlässlich, um die Evolution von Parasiten zu ergründen. Grundsätzlich war das Ziel dieser Arbeit, die metabolischen Netzwerke der genannten Parasiten zu eruieren und den Einfluss des Metabolismus auf Wachstum, Pathogenese und Adaption in verschiedenen Nährstoffumgebungen zu untersuchen. Unsere Vorgehensweise verband biochemische, revers-genetische, zellbiologische und optogenetische Bottom-Up-Methoden mit Top-Down-Methoden wie Lipidomics, Metabolomics und Transcriptomics um folgende Prämissen anzugehen:
• Vergleichender Entwurf der metabolischen Netzwerke in den obengenannten Parasiten
• Nährstoff-Plastizität für die Überlebensfähigkeit des Parasiten in verschiedenen Milieus
• Umregulierung oder Ausbeutung des Wirtsmetabolismus durch intrazelluläre Parasiten
• Stadien-spezifische Regulation des Metabolismus während der asexuellen Reproduktion
• Identifizierung und Validierung potentieller anti-parasitischer Wirkstoffe<br>The protozoan phylum apicomplexa comprises nearly 6000 parasitic species. Most apicomplexans have adapted to obligate intracellular parasitism in a wide range of organisms, including animals and humans. Some notable members of the phylum include Toxoplasma, Plasmodium and Eimeria species. This study focused on three representative parasites, namely Toxoplasma gondii, Eimeria falciformis and Plasmodium berghei, all of which infect a common and well-established model host organism (i.e. mouse), but have diverged from each other considerably with respect to the target host cells, persistence and reproduction behavior. These parasites together therefore enable a fairly inclusive study of the apicomplexan biology. Most developmental stages of these pathogens intimately associate with host cells, involving a metabolic crosstalk between the two entwined entities. A germane understanding of such interactions is vital to appreciate the evolution of parasites. In a nutshell, this work aimed to determine the design of metabolic networks in indicated parasites and the impact of metabolism on growth, pathogenesis and adaptation in discrete nutritional milieus. Our approach blended bottom-up methods of biochemistry, reverse genetics, cell biology and optogenetics with the top-down lipidomics, metabolomics and transcriptomics to address the following major premises:
• Comparative design of the selected metabolic networks in aforementioned parasites
• Nutritional plasticity underlying the parasite survival in variable environments
• Subversion or exploitation of host metabolism by intracellular parasites
• Stage-specific rewiring of parasite metabolism during asexual reproduction
• Identification and endorsement of potential anti-parasitic drug targets
34
Conway, Ann Marie. "Growth factor receptor tyrosine kinase-, G-protein coupled receptor- and sphingolipid-dependent regulation of the extracellular signal-regulated kinase cascade in cultured airway smooth muscle cells." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366970.
Full text
35
梁靜茹 and Ching-yu Leung. "Interactions of pacap and dopamine in regulating growth hormone release from grass carp pituitary cells: functional role of the camp - dependent cascade and ca2+ entrythrough voltage-sensitive ca2+ channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31221312.
Full text
36
Leung, Ching-yu. "Interactions of pacap and dopamine in regulating growth hormone release from grass carp pituitary cells : functional role of the camp - dependent cascade and ca2+ entry through voltage-sensitive ca2+ channels /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20793200.
Full text
37
Ovsyannikov, Mikhail [Verfasser], Jörg [Akademischer Betreuer] Schumacher, Christian [Gutachter] Karcher, and Olga [Gutachter] Shishkina. "Numerical studies of turbulent Rayleigh-Bénard convection in closed cells : boundary layer dynamics and large scale patterns / Mikhail Ovsyannikov ; Gutachter: Christian Karcher, Olga Shishkina ; Betreuer: Jörg Schumacher." Ilmenau : TU Ilmenau, 2018. http://d-nb.info/1178125254/34.
Full text
38
Than, Trong Emmanuel. "Le rôle de la signalisation Notch3 dans le maintien des cellules souches neurales du télencéphale adulte Neural stem cell quiescence and stemness are molecularly distinct outputs of the Notch3 signaling cascade in the vertebrate adult brain her4-expressing neural stem cells are maintained through population asymmetry and embedded into a hierarchy of progenitors responsible for their life-long expansion Radial Glia and Neural Progenitors in the Adult Zebrafish Central Nervous System." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS541.
Full textAbstract:
Un certain nombre de régions du cerveau des vertébrés, y compris chez l’homme, continuent d’être le siège de l’ajout de nouveaux neurones à l’âge adulte. Ces nouveaux neurones sont produits à partir de cellules spécialisées, appelées cellules souches neurales (CSN). Celles-ci sont capables de s’auto-renouveler et sont principalement trouvées dans un état d’arrêt transitoire du cycle cellulaire que l’on appelle quiescence. A l’heure actuelle, les mécanismes cellulaires et moléculaires permettant aux CSN de trouver un équilibre entre maintien et différentiation, ainsi que les règles générales gouvernant l’évolution de leur population, ne sont que partiellement compris. A l’échelle moléculaire, plusieurs facteurs et voies de signalisation apparaissent déterminants pour l’homéostasie des CSN. Notamment, la voie de signalisation du récepteur Notch s’avère essentielle pour maintenir à la fois l’état de quiescence et le caractère souche des CSN. Il demeure néanmoins inconnu si la signalisation Notch affecte ces deux propriétés de manière indépendante ou non. A l’échelle cellulaire, la plupart des modèles actuels suggèrent que les CSN se divisent rarement et principalement de manière asymétrique. Cette dernière propriété permettrait aux CSN de se perpétuer tout en donnant naissance à des cellules filles déterminées à se différencier en neurones. Le pallium du poisson-zèbre abrite une population particulièrement importante de CSN, que l’on appelle glies radiaires (GR), et qui possèdent les mêmes caractéristiques fondamentales que leurs homologues chez les mammifères. Notre laboratoire avait précédemment démontré que le récepteur Notch3 était nécessaire au maintien de la quiescence des GR. Le travail présenté dans ce manuscrit se décompose en deux études complémentaires dont les objectifs respectifs étaient: (1) d’améliorer notre compréhension du rôle de la voie de signalisation Notch3 dans l’homéostasie des GR et (2) d’étudier les schémas de divisions adoptés par les GR afin de maintenir leur nombre sur une longue durée. Dans la première étude, nous démontrons que le rôle de la signalisation Notch3 s’étend au-delà du simple contrôle de la quiescence des GR en contribuant également au maintien de leur caractère souche par l’intermédiaire de son gène cible hey1. Un point important de cette découverte est que l’action du facteur Hey1 sur le caractère souche des GR apparaît indépendante du rôle de Notch3 dans le maintien de leur quiescence. Dans la seconde étude, nous avons réalisé une analyse clonale du devenir des GR exprimant le gène her4.1. Ceci nous a permis de mettre en évidence que leurs choix entre différentiation, amplification et auto-renouvellement apparaissent stochastiques, mais équilibrés, ce qui leur permet de maintenir leur population dans le temps. De façon très intéressante, nous avons aussi observé que le nombre total de GR du pallium augmente au cours de la vie, ce qui, au regard du comportement homéostatique de la population de GR exprimant her4.1, nous amène à proposer que la zone neurogénique du pallium est organisée selon une hiérarchie dans laquelle une population inconnue de progéniteurs produit continuellement de nouvelles GR, qui ensuite se maintiennent grâce à un équilibre probabiliste entre leurs différents lignages<br>New neurons continue to be added into discrete brain regions of most adult vertebrate species, including humans. Adult born neurons arise from precursor cells, called neural stem cells (NSCs), endowed with self-renewal potential and mostly found in a state of reversible cell cycle arrest, named quiescence. Currently, the molecular, cellular and population rules allowing NSC to balance maintenance and differentiation remain incompletely understood. At the single cell level, several factors and signalling pathways were demonstrated to be essential for NSC homeostasis. Among them, the Notch signalling pathway is critically involved in the control of NSC quiescence and stemness. However, whether these two properties represent molecularly distinct or overlapping outputs of the Notch signalling pathway remains unknown. At the cellular level, current models state that NSCs divide rarely and mostly asymmetrically, allowing both self-renewal and the generation of a more committed progeny that ultimately exits the cell cycle and fulfils neuronal differentiation. The adult zebrafish pallium harbours NSCs, called radial glia (RG), which share with their mammalian counterparts the same basic properties. Previously, our laboratory demonstrated that Notch3 was necessary to maintain RG quiescence. Here, in two different and complementary works, we took advantage of the widespread neurogenic ventricular zone (VZ) of the adult zebrafish pallium to (1) explore further the role of Notch3 signalling in RG homeostasis and (2) investigate the division pattern and dynamics allowing the RG population to be maintained on the long run. In the first study, we demonstrate that the role of Notch3 signalling extends beyond the simple maintenance of RG quiescence and that Notch3 also contributes to RG stemness. By overlapping the transcriptomic profiles of both notch3 mutant RG and adult pallial VZ progenitors, we identified different sets of Notch3 target genes potentially responsible for its pleitropic effect in RG. Notably, we show that the Notch3 signalling contribution to RG stemness critically relies on the transcriptional activation of its canonical target gene hey1 and this, independently of Notch3 action on RG quiescence. In the second study, we performed a quantitative analysis of the fates of individual her4.1(Hes5)-expressing RG. We demonstrate that these cells adopt balanced stochastic fates, which allows their population to reach homeostasis. We also report that the overall RG population of the zebrafish pallium continues to grow during adulthood and that this expansion is very likely driven by a yet undefined upstream population of progenitors. As a consequence, we propose that the adult zebrafish is organised into a hierarchy of progenitors dominated by an unknown population that fuels the ongoing production of an intrinsically homeostatic population of RG which, itself, follows neutral drift dynamics
39
Disotell, Kevin James. "Low-Frequency Flow Oscillations on Stalled Wings Exhibiting Cellular Separation Topology." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449162356.
Full text
40
Herberg, Maria, Tüzer Kalkan, Ingmar Glauche, Austin Smith, and Ingo Roeder. "A Model-Based Analysis of Culture-Dependent Phenotypes of mESCs." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-147356.
Full textAbstract:
Mouse embryonic stem cells (mESCs) can be maintained in a proliferative and undifferentiated state over many passages (self-renewal) while retaining the potential to give rise to every cell type of the organism (pluripotency). Autocrine FGF4/Erk signalling has been identified as a major stimulus for fate decisions and lineage commitment in these cells. Recent findings on serum-free culture conditions with specific inhibitors (known as 2i) demonstrate that the inhibition of this pathway reduces transcription factor heterogeneity and is vital to maintain ground state pluripotency of mESCs. We suggest a novel mathematical model to explicitly integrate FGF4/Erk signalling into an interaction network of key pluripotency factors (namely Oct4, Sox2, Nanog and Rex1). The envisaged model allows to explore whether and how proposed mechanisms and feedback regulations can account for different expression patterns in mESC cultures. We demonstrate that an FGF4/Erk-mediated negative feedback is sufficient to induce molecular heterogeneity with respect to Nanog and Rex1 expression and thus critically regulates the propensity for differentiation and the loss of pluripotency. Furthermore, we compare simulation results on the transcription factor dynamics in different self-renewing states and during differentiation with experimental data on a Rex1GFPd2 reporter cell line using flow cytometry and qRT-PCR measurements. Concluding from our results we argue that interaction between FGF4/Erk signalling and Nanog expression qualifies as a key mechanism to manipulate mESC pluripotency. In particular, we infer that ground state pluripotency under 2i is achieved by shifting stable expression pattern of Nanog from a bistable into a monostable regulation impeding stochastic state transitions. Furthermore, we derive testable predictions on altering the degree of Nanog heterogeneity and on the frequency of state transitions in LIF/serum conditions to challenge our model assumptions.
41
Cleve, Jochen [Verfasser]. "Data-driven theoretical modelling of the turbulent energy cascade / vorgelegt von Jochen Cleve." 2004. http://d-nb.info/974154792/34.
Full text
42
Ho, Tzung-Han, and 何宗翰. "Cascade Organic Solar Cells with Two Exciton Dissociation Surfaces." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/84205332698733790633.
Full textAbstract:
碩士<br>臺灣大學<br>物理研究所<br>98<br>Due to the abuse of fossil fuel, there have been a lot of carbon dioxide exhausted into the air.The carbon dioxide will cause climate change and the temperature of earth to rise,which further result in many disasters in the world. To solve this problem, the research of renewable energy become more and more important, especially the development of solar cells.Organic solar cells had been developed quickly since 1986, the efficiency now is about 7%.
The improvement of organic solar cells is divided into two regions, one is the synthesis of new materials,the other is the amelioration of device structure. In this thesis,we focus on the improvement of device structure and try to apply the concept of cascade energy level to the fabrication of organic solar cell devices.Cascade-type organic solar cells have many advantages including large exciton dissociation surfaces, good optical compensation, no restriction of photocurrent, high exciton usage efficiency, etc.There is still a disadvantage that the middle layer material has to have high electron and hole mobility,but the materials having this property are very rare.We found that 10,12-PENTACOSADIYNOIC ACID(PDA) has this bipolar property, so we choose it as our middle layer material,and together with Pentacene and C60 to form the cascade-type organic solar cell.
To fabricate our device, first we spin-coat the PEDOT:PSS on the ITO glass as hole transport layer,then evaporate Pentacene, PDA and C60 as our active layer in turn,last evaporate BCP as the exciton blocking layer and silver as the electrode.Besides the PDA monomer, we also tried polymerizing the PDA monomer to polymer and annealing the devices to improve the performance of the devices.
We found that when inserting PDA into the interface of Pentacene/C60 bilayer structure to form the cascade-type structure,the Voc would increase and the Jsc would decrease. Until now the best efficiency of Pentacene/PDA/C60 cascade-type structure is 1.20%,which is nearly equal to the Pentacene/C60 bilayer device, whose efficiency is 1.14%. If we can improve the orientation of PDA molecules, the efficiency has a big chance to increase further in the future.
43
ju, Hsieh ya, and 謝雅如. "Signaling cascade in photodynamic therapy triggered death of human epidermoid carcinoma A431 cells." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/88242295376158861128.
Full textAbstract:
碩士<br>長庚大學<br>基礎醫學研究所<br>89<br>Photodynamic therapy (PDT) is one kind of photochemo-therapeutic treatment. It had been approved by FDA for treatment of some tumor. When cells uptake photosensitizers and exposed to specific wavelength of light, the photosensitizers can absorb the energy from photon and then transfer the energy to oxygen molecule to form reactive oxygen species (ROS), which can then induce cell death by intracellular signal transduction. Previous work from this laboratory had dissected the apoptotic signal pathway in human epidermal carcinoma A431 cell treated with PDT using Rose Bengal as photosensitizer (Chan et al., 2000). In this thesis, the death pathway of A431 cells treated with Photofrin®-PDT (a clinical PDT regime approved by FDA) was investigated. It was found that the effect of PDT on A431 cell is dependent on the dose of Photofrin®. PDT with low dose (3.5 mg/ml) Photofrin® had little effect on A431 cells. However, cell shrinkage and detachment from culture dish were observed following PDT with medium dose (7-14 mg/ml) Photofrin®. At high dose (28 mg/ml) Photofrin®, cell membrane disruption and cell swelling were detected immediately after PDT. The cell death process induced by high dose (28 mg/ml) Photofrin®-PDT was further studied in details. The results showed that Photofrin®-PDT can induce (i) ROS production, (ii) JNK and ERK phosphorylation/activation, (iii) PARP and PAK2 cleavage, and (iv) mitochondria membrane potential lost. Several scavengers for ROS and inhibitor for mitochondria MPT inhibitor were used to examine the cellular response to Photofrin®-PDT. It was found that, (i) Photofrin®-PDT-induced ROS production can’t be diminished even in the presence of mixed scavengers, and (ii) the MPT inhibitor can’t block Photofrin®-PDT-induced mitochondria membrane potential lost. In addition, the characteristics of typical apoptosis such as externalization of phosphatidylserine, caspase activation and DNA fragmentation can not be detected in the cell death process induced by Photofrin®-PDT. It is concluded that the type of death of A431 cells triggered by high dose (28 mg/ml) Photofrin®-PDT is necrosis but not apoptosis, which is distinctly different from that elicited by Rose Bengal-PDT.
44
Ming-Chang and 謝明璋. "Antizyme induces apoptosis of haematopoietic cells through mitochondrial membrane depolarization and caspases’ cascade." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/92436048107887339418.
Full textAbstract:
碩士<br>中山醫學大學<br>免疫學研究所<br>94<br>Antizymes delicately regulate ornithine decarboxylase (ODC) enzyme activity and polyamine transport. One member of the family, antizyme-1, plays the vital roles in molecular and cellular functions, including developmental regulation, cell cycle, proliferation, cell death, differentiation and tumorigenesis. However, how does it participate in the cell apoptotic mechanism is still unidentified. To elucidate the contribution of human antizyme-1 in haematopoietic cell death, we examine whether inducible overexpression of antizyme enhances the apoptotic cell death. Antizyme reduced the viability in a dose- and time-dependent manner of human leukemia HL-60 cells, acute T leukemia Jurkat cells and mouse macrophage RAW 264.7 cells. The apoptosis-inducing activities were determined by nuclear condensation, DNA fragmentation, sub-G1 appearance, loss of mitochondrial membrane potential (Δym), release of mitochondrial cytochrome c into cytoplasm and proteolytic activation of caspase 9 and 3. Following conditional antizyme overexpression, all protein levels of cyclin-dependent kinases (Cdks) and cyclins are not reduced except cyclin D significantly before their entrance into apoptotic cell death. However, introduced cyclin D1 into Jurkat T tetracycline (Tet)-On cell system still couldn’t rescue cells from apoptosis. Antizyme doesn’t influence the expression of tumor suppressor p53 and its downstream p21, but it interferes in the expressions of Bcl-2 family. Inducible antizyme largely enters mitochondria resulting in cytochrome c release from mitochondria to cytosol following Bcl-xL decrease and Bax increase. According to these data, we suggest that antizyme induces apoptosis mainly through mitochondria-mediated and cell cycle-independent pathway. Furthermore, antizyme induces apoptosis not only by Bax accumulation to decline the function of Bcl-2 family, destroy the Δym, release cytochrome c to cytoplasm but also by the activation of apoptosomal caspase cascade.
45
Huang, Shih-Che, and 黃士哲. "Sensitization of Nanocrystalline TiO2 Solar Cells by Using Organic Dye Cocktails and Bandgap Cascade Approaches." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/12281478064650526764.
Full textAbstract:
碩士<br>國立成功大學<br>化學工程學系碩博士班<br>95<br>Although dye-sensitized solar cells (DSSCs) with ruthenium (Ru) complexes as sensitizers may reach an overall efficiency up to 11%, the limited availability of Ru complexes will become a problem if DSSCs find wide application. Compared with Ru complexes, organic sensitizer dyes which generally have much larger molar extinction coefficients and can be prepared and purified more easily and economically, therefore, exhibit promising potential in DSSC applications. Organic dyes, however, have relatively sharp absorption bands in the visible region, which is a disadvantage for harvesting of solar light. As a result, dye cocktails and bandgap cascade approaches have been proposed to broaden the absorption spectrum. The highest overall efficiencies of 6.5% (Chen et al., 2005) and 1.67% (Perera et al., 2003) for DSSCs by the dye cocktails approach with triple-dye-sensitization and the bandgap cascade approach with dye bilayer sensitization, respectively, have been documented in the literature.
In this work, three commercial cheap organic dyes — that is, C343, Mercurochrome, and Eosin Y─ were employed to sensitize the solar cells. Adsorption properties, adsorption dynamics, interlayer—CuSCN, dye aggregation behavior, and photosensitization properties were investigated systematically. The experimental results indicated that co-sensitization is efficient in light harvesting. The overall efficiencies through dye cocktails approach by using C343 and Mercurochrome and Eosin Y and Mercurochrome binary mixed dyes, however, showed a negative deviation from the ideal mixing calculations. In the other way, the overall efficiencies through bandgap cascade approach by using Mercurochrome╱C343 and Eosin Y╱Mercurochrome layer-by-layer deposited dyes were lower than that of the solar cell sensitized by the single dye with higher efficiency may exhibit a higher efficiency than that of one of the two dyes by using interlayer. The main factors that affect the sensitization performance were discussed further through visible light absorption and IPCE(incident photon-to-electron conversionefficiency)characteristics.
46
Wang, Aibo. "Phosphorylation of Nur77 by MEL-ERK-RSK cascade induces mitochondrial translocation and apoptosis in T cells." 2009. https://scholarworks.umass.edu/dissertations/AAI3372283.
Full textAbstract:
Nur77, an orphan nuclear receptor, plays a key role in T cell apoptosis. As a transcription factor, Nur77 is assumed to exert its functions by driving the expression of target genes. However, Nur77 targets in T cell apoptosis are unknown. In cancer cell lines, Nur77 can induce apoptosis through the intrinsic apoptotic pathway but it remains controversial how Nur77 kills T cells. In this study, we provide biochemical, pharmacological and genetic evidence demonstrating that Nur77 induces apoptosis through the activation of the intrinsic pathway in T cells. We also show that Nur77 is a physiological substrate of the MEK-ERK-RSK-cascade. Specifically, we demonstrate that RSK phosphorylate Nur77 at serine 354 and this modulates Nur77 nuclear export and intracellular translocation during T cell death. Our data reveal that Nur77 phosphorylation and mitochondrial targeting, regulated by RSK, may define a role for the MEK1/2-ERK1/2 cascade in T cell apoptosis.
47
Tzu-YuHuang та 黃子育. "Knockout of STIM1 enhances PDGF-mediated Ca2+ signaling through the PDGFR-PLCγ-STIM2 cascade in MEF cells". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/8fyd32.
Full textAbstract:
碩士<br>國立成功大學<br>生物醫學工程學系<br>104<br>STIM1 (stromal interaction molecule 1) has been reported as a key molecule in store-operated calcium entry (SOCE) which is one of the major mechanisms that allows extracellular Ca2+ refill into cytoplasm to regulate many cell functions. Platelet-derived growth factor-BB (PDGF-BB) induces cell migration and proliferation in MEF (murine embryo fibroblast) cells. Recent studies have suggested that PDGF-BB induces endo-plasm reticulum (ER) Ca2+ release and SOCE through the STIM1-Orai1 complex. In this study, we investigated the role of STIM1 in PDGF-BB-induced Ca2+ oscillation and its functions in MEF cells. PDGF-BB activates Ca2+ elevation by activating the PLCγ sig-naling pathway, and the PIP2 hydrolysis into IP3 and DAG resulted in ER Ca2+ release. The depletion of ER Ca2+ induces SOCE through forming a SOC channel (STIM-TRPC-Orai complex). Also, there are several signaling pathways co-activated by PDGF-BB stimulation, including AKT, JNK, ERK and STAT3. According to data collect-ed from the FlexStation3 microplate reader, unexpectedly, we found PDGF-BB (100 ng/ml) induced manifest Ca2+ elevation in STIM1 knockout MEF cells dramatically with different doses and immunoblots data also indicated that PDGFR (PDGFα and PDGFRβ) overexpression induced PLCγ activity time-dependently with PDGF-BB stimulation in STIM1 knockout MEF cells. Furthermore, we applied SOCE, PLC, PDGFR inhibitors to examine the signaling transduction pathway. 2-APB, SKF96365, YM58483, Gd3+, La3+ were applied to inhibit PDGF-BB-induced Ca2+ elevation, U73122 and D609 were applied to inhibit PLC phosphorylation, and the AG-1295 was applied to inhibit PDGFR activa-tion after PDGF-BB triggering. These data show that PDGFR protein levels are enhanced in STIM1 knockout MEF cells and then raise the PDGF-PLCγ-STIM2 signaling cascade to increase the [Ca2+]i with PDGF-BB stimulation.
48
Chao, Han-Yi, and 趙涵怡. "The effects of polyunsaturated fatty acids on the inflammatory cascade and oxidative stress in human aortic endothelial cells." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50868113440725326851.
Full textAbstract:
碩士<br>國立陽明大學<br>生化暨分子生物研究所<br>95<br>Atherosclerosis is not only one of the metabolic syndromes, but also a chronic inflammatory disease, in which endothelial activation and leukocytes recruitment play critical roles in the initial stage. The effects of polyunsaturated fatty acids (PUFAs) on the regulation of inflammatory responses of vascular endothelial cells help clarify the mechanisms by which PUFAs affect atherosclerosis. The aim of the study was to investigate the effects of PUFAs on the inflammatory cascade and oxidative stress in human vascular endothelial cells. We hypothesized that some PUFAs may down-regulate the oxidative stress and the expression of inflammatory genes induced by cytokines, in a peroxisome proliferators-activated receptor (PPAR)-dependent pathway.
In cellular study of human aortic endothelial cells (HAECs), pretreatment with docosahexaenoic acid (DHA; 22:6n-3) or DHA containing 9-cis retinoic acid (9-cis RA), the ligand for retinoid X receptor (RXR), decreased the mRNA levels of vascular cell adhesion molecule-1 (VCAM-1) induced by tumor necrosis factor-α (TNF-α), while none of the PUFAs or PPAR agonists could attenuate the expression of intercellular adhesion molecule-1 (ICAM-1)、interleukin-6 (IL-6)、interleukin-8 (IL-8) or monocyte chemoattractant protein-1 (MCP-1). PUFAs or the agonists for PPAR including PPARα agonist WY14643 and PPARγ agonist Rosiglitazone decreased the protein levels of VCAM-1 induced by TNF-α. The result from electrophoretic mobility shift assay (EMSA) revealed that linoleic acid (LA; 18:2n-6) or WY14643 alone could inhibit the binding of nuclear factor-κB (NF-κB) to its consensus element, and both DHA and arachidonic acid (AA; 20:4n-6) had the same effect in the presence of 9-cis RA. PUFAs or PPAR agonists (WY14643 and Rosiglitazone) decreased reactive oxygen species (ROS) generation induced by TNF-α. Less ROS generation was found in cells treated with DHA、LA or Rosiglitazone in the presence of 9-cis RA. In conclusion, PUFAs may down-regulate VCAM-1 expression in HAECs through activation of PPAR, down-regulation of ROS generation and inhibition of NF-κB activity, and this may contribute to the benefits of PUFAs against atherosclerosis.