Dissertations / Theses on the topic 'Shock profiles'

Thesis (Ph.D.)--Indiana University, Dept. of Mathematics, 2005.
Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3170. Adviser: Kevin Zumbrun. "Title from dissertation home page (viewed Dec. 4, 2006)."

Gradual SEP events is one of the greatest hazards in space environment, particularly for the launch and operation of spacecraft and for manned exploration. Predictions of their occurrence and intensity are essential to ensure the proper operation of technical and scientific instruments. However, nowadays there is a large gap between observations and models these events that can lead to predictions. This work focuses on the modelling of SEP events, particularly, on the influence of the observer's relative position and of the shock strength, on the simulated SEP flux profiles. Part I of the thesis, deals with 3D MHD simulations of interplanetary shocks. We have studied the potential relevance of the latitude of the observer on the evolution of the strength of the shock and its influence on the injection rate of shock-accelerated particles; thus, on the resulting flux profiles. It is the first time that such dependence on the latitude is quantified from the modelling of SEP events, because most of the codes used so far to simulate interplanetary shocks are not 3D codes or they have been applied to near-ecliptic events. To study the influence of the latitude of the observer and the strength of the shock in the SEP flux profiles, we have simulated the propagation of two shocks (slow and fast) up to several observers placed at different positions with respect to the nose of the shock. We have calculated the evolution of the plasma and magnetic field variables at the cobpoint, and we have derived the injection rate of shock-accelerated particles and the resulting proton flux profiles to be measured by each observer. We have discussed how observers located at different positions in space measure different SEP profiles, showing that variations on the latitude may result in intensity changes of up to one order of magnitude. In Part II, we have used a new shock-and-particle model to simulate the 1 March 1979 SEP event that was observed by three different spacecraft. These spacecraft were positioned at similar radial distances but at significantly different angular positions, with respect to the associated solar source location. This particular scenario allows us to test the capability of the model to study the relevance of longitudinal variations in the shape of the intensity flux profiles, and to derive the injection rate of shock-accelerated particles. Despite the interest of multi-spacecraft events and due to the restrictions that they impose, this is just the second multi-spacecraft scenario for which their shock-particle characteristics have been modelled. For the first time, a simulation of a propagation of an interplanetary shock has simultaneously reproduced the time shock arrival and the relevant plasma jumps across the shock at three spacecraft. We have fitted the proton intensities at the three spacecraft for different energy channels, and we have derived the particle transport conditions in space. We have quantified the efficiency of the shock at injecting particles in its way toward each observer, and we have discussed the influence of the observer's relative position on the injection rate of shock-accelerated particles. We have concluded that in this specific event the evolution of the injection rate can not be completely explained in terms of the normalized velocity jump. The work performed during this thesis shows that the injection rate of shock-accelerated particles and their resulting flux profiles depend both on the latitude and on the longitude of the observer. This implies that more SEP events have to be modelled in order to quantify this conclusion on firm ground.
Els esdeveniments graduals de partícules solars energètiques (SEP) són un risc important per als astronautes i l’ instrumentació espacial. És per això que són necessàries eines de predicció de la intensitat i l'ocurrència de les tempestes de partícules solars per a garantitzar l'operativitat del material tècnic i científic embarcat. Existeix un gran buit, però, entre les prediccions del models actuals (per a ús en meteorologia espacial), i les observacions d'esdeveniments SEP. El treball realitzat durant aquesta tesi doctoral es centra en diversos aspectes de la simulació d'esdeveniments SEP. En particular, analitzem la influència de la posició relativa de l'observador i de la força del xoc en els perfils de flux derivats del nostre model combinat xoc-i-partícula. A partir de simulacions 3D, obtenim que el ritme d'injecció de partícules accelerades pel xoc depèn de la longitud de l'observador i demostrem, per primera vegada, que també depèn de la seva latitud. I es mostra que, conseqüentment, els perfils de flux detectats poden variar en un ordre de magnitud depenent de la connexió magnètica de l'observador amb el front del xoc. A més a més, presentem una simulació 2D d'un esdeveniment solar vist per tres sondes interplanetàries, pel qual s'ha ajustat, per primera vegada, l'arribada del xoc i els perfils de intensitat dels protons de diferents canals d'energia observats per cadascuna de les sondes. Així mateix, hem ajustat els salts en velocitat i camp magnètic a l'arribada del xoc, hem derivat les condicions de transport de les partícules i hem quantificat l'eficiència del xoc com a injector de partícules. La conclusió final del treball és que els futurs models de predicció d'esdeveniments SEP per a meteorologia espacial han de tenir en compte la geometria global de l'escenari solar-interplanetari.

 U okviru ove doktorske disertacije posmatrani su zakoni održanja sa funkcijom fluksa koja ima prekid u x = 0, pri čemu delovi fluksa levo i desno od x = 0 imaju smo po jedan ekstrem. U prvoj glavi se može naći pregled osnovnih pojmova, definicija i teorema. U drugoj  glavi su opisani hiperbolični sistemi zakona održanja, slaba rešenja, kao i numerički postupci za njihovo rešavanje. U trećoj glavi su predstavljeni  diskretni profili darnih talasa. U četvrtoj glavi su opisani zakoni održanja  sa prekidnom funkcijom fluksa i ukratko su predstvaljeni rezultati drugih autora iz ove oblasti. U petoj glavi je najpre analizirana tzv. jednačina sa dva fluksa u slučaju kada oba dela fluksa levo i desno od  x = 0 imaju minimum, a pri tome se seku u najviše jednoj tačci unutar intervala. Primenom regularizacije na intervalu [−ε, ε], za ε > 0 dovoljno malo, dokazano je postojanje diskretnih udarnih profila za postupak Godunova za zakone održanja sa promenljivom funkcijom fluksa. Definisan je i odgovarajući diskretan uslov entropije, a postojanje entropijskog diskretnog  udarnog profila je postavljen kao kriterijum za dopustivost udarnih talasa. Potom je analizirana ista jednačina u slucaju kada deo fluksa levo  od x = 0 ima maksimum, a deo fluksa desno od x = 0 minimum, dok se oba dela fluksa seku na  krajevima posmatranog intervala. U ovom slučaju, uopšten je uslov entropije. U okviru ove glave je prikazano nekoliko numeričkih primera za oba opisana slučaja. Numerički rezultati  su dobijeni korišcenjem softvera razvijenog za potrebe ove teze u programskom paketu Mathematica.
We consider conservation laws with a flux discontinuity at x = 0, where the flux parts from both left and right hand side of x = 0 have at most one extreme on the  observed  domain. The first chapter provides elementary definitions and theorems..The second chapter refers to hyperbolic systems of conservation laws, their solutions, and  numerical procedures. The third chapter is devoted to discrete  shock profiles. The fourth chapter describes conservation laws with discontinuous flux functions and provides basic information upon known results in this field. In the  fifth chapter, we first  analyse the two-flux equation when both flux parts have a minimum and cross at most    at one point in the interior of the domain. Using a flux regularization on the interval [−ε,   ε], for ε > 0 small enough, we show the existence of discrete shock profiles for Godunov’s scheme for conservation laws with discontinuous flux functions. We also define a discrete entropy condition accordingly, and use the existence of an entropy discrete shock profile as an entropy criterion for shocks. Then we analyse the same problem in the case when the flux part on the left of x = 0 has a maximum and the part on the right of x = 0 has a minimum, whereas the fluxes cross at the edges of the interval. We derive a more general discrete entropy condition in this case. We provide several numerical examples in both of the above mentioned flux cases. All the  presented numerical results are obtained using a program written in Mathematica. Finally, in chapter six, we prove the existence of  singular shock waves in the case when the graph of one of the flux parts is above the graph of the other one on the entire domain. For that purpose, we use the shadow wave technique. At the end of this chapter, we provide a numerical verification of the obtained singular solution.

During the past several decades, corals worldwide have been dealing with a considerable increase in water temperature due to climate change, which is predicted to increase the frequency of coral bleaching and mass mortality events. Nevertheless, corals show differences in stress susceptibility and they are not all affected evenly. The symbiotic coral Oculina patagonica from the Eastern Mediterranean Sea can thrive in relatively unstable environments and is considered a stress-tolerant species. In this study, baseline expression and temporal dynamics of induction of a 70-kDa heat shock protein (HSP70) after an acute heat stress were analyzed in O. patagonica to investigate the influence of its peculiar physiological traits on stress responsiveness. Furthermore, data collected were further discussed within a comparative analysis with similar findings reported in 5 temperate corals of the Mediterranean Sea (Franzellitti et al., 2018). Results show that O. patagonica hsp70 transcriptional response aligns with the formerly observed high resistance for elevated sea water temperatures of this species. The multispecies comparison shows that hsp70 expression varies in accordance with the stress sensitivity of coral populations inhabiting different thermal environments and possessing different trophic strategies and morphologies. This study also reports an analysis of the post heat-stress transcriptional regulation of transcripts related to energy metabolism (gadph), redox regulation (sod), and DNA damage (bcl-2 and bax), disclosing the time line of the events occurring in O. patagonica in response to an acute heat stress, which aligns with its quick recovery from bleaching. These molecular processes analysis is particularly demanding for corals inhabiting the Mediterranean Sea, in light of projected scenarios of anthropogenic global change.

Cette thèse aborde l'analyse de la stabilité des profils de chocs totalement discrets pour les systèmes de lois de conservation. Ces profils correspondent à l'approximation d'ondes progressives discontinues par des schémas aux différences finies conservatifs. De telles solutions discontinues apparaissent naturellement dans l'étude des systèmes de lois de conservation qui peuvent modéliser de nombreuses situations physiques comme par exemple la dynamique des gaz. L'étude des profils de choc totalement discrets se divise essentiellement en deux axes, le premier étant de construire de tels profils discrets et donc de prouver leur existence, et le second étant d'étudier leur stabilité. L'objectif principal de cette thèse est d'approfondir cette seconde direction. De nombreux résultats existants sur la stabilité des profils de chocs totalement discrets introduisent des hypothèses contraignantes, telles que la restriction aux lois de conservation scalaires ou encore le fait d'imposer que les discontinuités approchées soient de faible amplitude. Les résultats de cette thèse visent à ouvrir la voie vers des résultats de stabilité non linéaire qui traiterait de systèmes de lois de conservation et non pas seulement de lois scalaires, et qui remplacerait l'hypothèse de faible amplitude des discontinuités par une hypothèse spectrale sur le linéarisé du schéma autour du profil de choc discret considéré. Au niveau des résultats obtenues, dans un premier temps, la thèse se focalise sur l'obtention d'estimées de décroissance fines sur le linéarisé du schéma aux niveaux de solutions particulières. On se concentrera d'abord sur le linéarisé au niveau des solutions constantes avant de passer au cas plus compliqué du linéarisé au niveau des profils de chocs totalement discrets. D'un point de vue spectral, l'analyse du problème des chocs fait apparaitre une valeur propre plongée dans le spectre essentiel. Il en résulte de nouveaux termes dans l'analyse de la fonction de Green du schéma linéarisé et on détaille les propriétés de décroissance de chacun de ces termes. Dans une dernière partie, on utilise les estimations obtenues sur l'opérateur linéarisé pour établir un argument de stabilité non linéaire
This thesis deals with the stability analysis of discrete shock profiles for systems of conservation laws. These profiles correspond to approximations of discontinuous traveling waves by conservative finite difference schemes. Such discontinuous solutions appear naturally in the study of conservation law systems, which can model many physical situations, such as gas dynamics. The study of discrete shock profiles is essentially divided into two directions, the first one focusing on the construction of such discrete profiles and thus on the proof of their existence, and the second one studying their stability. The main objective of this thesis is to investigate this second direction. Many existing results on the stability of discrete shock profiles introduce constraining hypotheses, such as the restriction to scalar conservation laws or the requirement that the approximated discontinuities should be of small amplitude. The results of this thesis aim to pave the way towards nonlinear stability results that would deal with systems of conservation laws and not just scalar laws, and that would replace the smallness assumption on the amplitude of the discontinuities by a spectral assumption on the linearization of the numerical scheme about the discrete shock profile under consideration. In terms of the results obtained, the thesis initially focuses on obtaining sharp decay estimates for the linearization of the numerical scheme about particular solutions. We will first focus on the linearization about constant solutions before moving on to the more complicated case of the linearization about discrete shock profiles. From a spectral point of view, the analysis of the shock problem implies the existence of an eigenvalue located within the essential spectrum. This results in new terms in the analysis of the Green's function of the linearized scheme and decay properties of each of these terms will be presented. In a final section, we use the estimates obtained on the linearized operator to establish a nonlinear stability argument

The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two-component flow structure of wind and clumps using two “beta” velocity laws. While individual bow shocks tend to generate double-horned emission line profiles, a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution is broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted for in modeling X-ray line profile shapes for massive stars.

L'optique adaptative classique est limitée par l'anisoplanétisme. Pour remédier à cette limitation, de nouveaux concepts, appelés optiques adaptatives grand champ, ont été développés. Ces systèmes analysent la turbulence atmosphérique dans le volume, ce qui accroît le champ de correction. Ces techniques requièrent une connaissance précise du profil de Cn2. Mon étude consiste à valider sur le ciel une nouvelle technique de mesure du profil de Cn2, appelée CO-SLIDAR, à partir des corrélations des mesures de pentes et de scintillation réalisées avec un analyseur Shack-Hartmann sur étoile binaire. Elle s'organise autour de deux grands axes. On réalise d'abord une simulation bout-en-bout de la reconstruction du profil de Cn2 dans un cas concret d'observation astronomique. On peut ainsi étudier l'impact des différentes sources d'erreur sur la reconstruction du profil de Cn2. Ceci nous permet d'améliorer la procédure d'estimation du profil de Cn2, en prenant en compte les bruits de détection. La deuxième partie de mon étude se consacre à la validation expérimentale. On dimensionne et caractérise en laboratoire un banc d'acquisition, le banc ProMeO. Ceci conduit à une bonne connaissance du fonctionnement du banc et nous permet de corriger certains effets instrumentaux. Le banc ProMeO est finalement couplé au télescope MeO de 1,5 m de diamètre. Les données acquises permettent une reconstruction du profil de Cn2, du sol jusqu'à 17 km, avec une résolution de 600 m. Les profils obtenus par la méthode CO-SLIDAR sont comparés avec succès à des profils issus de données météorologiques. L'ensemble de ces travaux constitue la première validation sur le ciel de la méthode CO-SLIDAR.

Com a utilização dos atuais protocolos de tratamento, 70-80% dos casos de leucemia linfóide aguda (LLA) na infância têm obtido sobrevida livre de eventos em cinco anos. Entretanto, os 20% restantes, que se mostram resistentes ao tratamento, apresentam recidivas e as causas desse insucesso no tratamento ainda permanecem desconhecidas. Dessa forma, com o intuito de melhor compreender os mecanismos moleculares que participam desse processo, o presente trabalho teve por objetivo avaliar o perfil de expressão de um painel de genes que foram previamente associados à resistência e/ou sensibilidade aos quimioterápicos: prednisona (F8A, CDK2AP1, BLVRB, CD69), vincristina (RPLP2, CD44, TCFL5, KCNN1, TRIM24), daunorrubicina (MAP3K12, SHOC2, PDCH9, EGR1, KCNN4) e asparaginase (GPR56, MAN1A1, CLEC11A, IGFBP7, GATA3). Para a realização do estudo, foram utilizadas inicialmente amostras de medula óssea de pacientes portadores de LLA pertencentes a quatro grandes centros de oncologia pediátrica do Estado de São Paulo e que foram submetidos ao protocolo de tratamento do GBTLI-99. A análise da expressão gênica foi realizada pela técnica de PCR quantitativa em tempo real, utilizando-se o reagente SYBR Green, o gene GUS? como controle endógeno e amostras de medula óssea normais como referência. A análise dos dados de expressão gênica em relação aos diversos parâmetros clínicos e laboratoriais avaliados na LLA, demonstrou associações importantes entre os diversos genes estudados e variáveis clínicas importantes como contagem de glóbulos brancos ao diagnóstico, presença do antígeno CD10 (CALLA), translocação TEL/AML1, presença de doença residual mínima entre outras. Dentre os genes avaliados destacaram -se como possíveis marcadores de bom prognóstico os genes SHOC2 e GPR56. Posteriormente, reavaliou-se o perfil de expressão desses genes em pacientes submetidos ao protocolo de tratamento europeu do grupo BFM com o intuito de verificar o padrão de expressão em pacientes com um background genético distinto e submetidos a um protocolo terapêutico distinto. Os resultados confirmaram os dados encontrados anteriormente e demonstraram a hiperexpressão do gene SHOC2 (que foi previamente associado à sensibilidade à daunorrubicina) associada ao grupo de pacientes bons respondedores, sugerindo a correlação desse gene com critérios favoráveis de prognóstico. Para verificar o nível de interação desse gene avaliou-se ainda a expressão protéica do mesmo, que confirmou os padrões de expressão gênica obtidos por RQ-PCR. A função do gene SHOC2, que embora não esteja completamente elucidada, já foi anteriormente descrita pela literatura, que demonstra a participação do gene no processo de ativação da proteína Erk pela via Ras. Finalmente para melhor compreender os possíveis mecanismos que envolvem o gene SHOC2 no processo de melhor resposta à quimioterapia, utilizou-se a técnica de RNAi para silenciá- lo na linhagem celular leucêmica Jurkat. Os resultados demosntraram a associação da expressão do gene SHOC2 com proliferação celular e também com a indução de apoptose. Esses dados sugerem que a hiperexpressão desse gene pode ser importante para o processo de sensibilidade das células leucêmicas ao tratamento. Como conclusão, este trabalho demonstrou a associação de diversos genes com importantes parâmetros clínicos da LLA e destaca principalmente o papel do gene SHOC2 como possível alvo terapêutico para o tratamento da leucemia linfóide aguda.
Major improvements have been made in the ALL treatment, which achieved successful rates of approximately 80% of long-terms survival. Despite the significant percentage of success, the remaining 20 % still presents treatment failure and the molecular mechanisms involved in the resistance process remains unclear. The present study was undertaken to analyze and validate the gene expression pattern of the previously described genes related to prednisolone (F8A, CDK2AP1, BLVRB, CD69), vincristine (RPLP2, CD44, TCFL5, KCNN1, TRIM24), daunorubicin (MAP3K12, SHOC2, PDCH9, EGR1, KCNN4) and Lasparaginase (GPR56, MAN1A1, CLEC11A, IGFBP7, GATA3) in order to better inderstand these mechanisms. Bone marrow samples of ALL patients, obtained at diagnosis, in four oncology centers and treated according to the Brazilian protocol (GBTLI-99). The relative mRNA expression levels were quantified using real-time PCR analysis. Amplification of the specific sequences was performed with SYBR® Green reagent; GUSB was used as the reference gene and normal bone marrow samples used as calibrator. The expression profile analisis showed important associations among the studied genes and clinical features as WBC count at diagnosis, CALLA, TEL/AML1 translocation and minimal residual disease. Among the analyzed genes, possible therapy targets were found at SHOC2 and GPR56. Further we addressed the expression profile of these genes in ALL patients, treated according to the BFM protocol, which chacarterize a group of distinct genetic\'s background. The results confirmed the data previously obtained. The overexpression of the gene SHOC2, that was primaraly associated to sensibility to dauborubicin, was related to patients who presented good prednisone response, suggesting the correlation of SHOC2 with good prognostic factors. In order to acess the interaction level of this gene, the protein expression was analyzed and confirmed the mRNA expression data. Despite its lack of information, the data on SHOC2 shows its role as na important element in the Erk activation by Ras induced pathway. Finally, to better understand the possible mechanisms which involve SHOC2 gene to the chemotherapy response process, Jurkat cells was transfect with siRNA to silence the gene SHOC2. Further, functional assays were done to characterize the mechanisms involved. The results showed the association of SHOC2 gene expression with processes of cell proliferation and apoptosis induction, thus suggesting that the overexpression of SHOC2 could play an important role in leukemic cell\'s sensibility to chemotherapy agents, and consequently in patients\' treatment outcome. In conclusion, this work demonstrated the association of the expression profile of many genes with important clinical and laboratorial features. Furthermore, this data present the gene SHOC2 as a possible therapy target to acute lymphoblastic leukemia \'s treatment.

Au cours des dernières décennies, l’astronomie infrarouge a changé notre point de vue au sujet de l’évolution des galaxies, en particulier à de grandes distances. Nous avons accès à une grande variété d’informations physiques grâce au domaine spectral infrarouge. Toutefois, les limites de diffraction des instruments infrarouges et l’existence d’un grand nombre de sources font de l’identification individuelle des galaxies une tâché difficile. La première partie de cette thèse est consacrée à Résoudre le fond extragalactique infrarouge avec l’observatoire spatial Herschel, à, l’aide de simulations réalistes, correspondant aux images les plus profondes jusqu’ici obtenues en infrarouge lointain. Nous avons étudié l’origine du bruit de confusion dans les images GOODS-Herschel et résolu une partie de fond cosmique infrarouge en galaxies individuelles. De nouvelles techniques ont été développées pour prédire les flux en infrarouge lointain à partir de la connaissance préalable des positions, décalages spectraux et densités de flux des sources dans l’infrarouge moyen. Les images simulées ont été construites en utilisant les flux prédits afin d’évaluer le rôle du bruit local de confusion et d’identifier des sources individuelles. La deuxième partie de la thèse concerne l’étude de la Destruction de grains de poussières par des jets vus en radio. Nous avons étudié les effets des noyaux actifs de galaxies dans le milieu interstellaire, en particulier le mécanisme qui donne lieu à la région des raies étroites dans les galaxies de type Seyfert. Des spectres en infrarouge proche à fente longue a ont été enregistrés sur un ensemble de galaxies Seyfert de type 2 afin de mesurer les raies d’émission de ([Fe II], [P II] et Paβ) qui révèlent la destruction de poussières par les ondes de choc produites par les jets radio. Nous avons constaté que le mécanisme dominant l’ionisation près du noyau des galaxies Seyfert est le champ de rayonnement produit par l’activité du trou noir. Dans la partie extérieure de la région des raies étroites, des ondes de choc induites par des jets de radio contribuent également au budget énergétique du milieu interstellaire et à la destruction des grains de poussière. Cette thèse s’est déroulée en co-encadrement au Service d’Astrophysique du CEA-Saclay et au Département d’Astronomie de l’Université de Concepción, au Chili
During the last decades, infrared astronomy has changed our view about the evolution of galaxies, especially at large distances. We have access to large variety of physical information in the infrared bands. However, diffraction limits of the infrared instruments and the existence of a large number of sources makes individualization of galaxies a difficult task. The first part of this thesis is entitled Resolving the Cosmic Infrared Background with the Herschel Space Observatory where, by the use of far-infrared realistic simulations of the deepest infrared images of the Universe, we have studied the origin of the confusion noise in the GOODS-Herschel images and resolved a substantive part of the Cosmic Infrared Background into individual galaxies. New techniques were developed to predict the fluxes in the far-infrared from prior knowledge in the mid-infrared. Mock images were built using those predicted fluxes to evaluate the role of local confusion noise and identify individual sources. The second part of the thesis concerns the study of the Destruction of dust grains by radio jets. We study the effects of active galactic nuclei in the insterstellar medium, in particular in the mechanism that gives rise to the narrow-line region in Seyfert galaxies. Long-slit near-Infrared spectra of a set of type-2 Seyfert galaxies were taken to measure diagnostic emission lines ([Fe II], [P II] and Paβ) that reveal the destruction of dust grains due to the shock waves produced by the radio jets. We found that the dominant mechanism of ionization close to the nuclei of the Seyfert galaxies is the radiation field produced by the back hole activity. In the outer part of the narrow-line region, shock waves induced by the radio jets also contribute to the energy budget of the interstellar medium and sputter the dust grains. This was a co-advising thesis performed in the Service d’Astrophysique CEA-Saclay and the Astronomy Department of the University of Concepción, Chile
Durante las últimas décadas, la astronomía infrarroja ha cambiado nuestra visión sobre la evolución de galaxias, en especial revelando que a grandes distancias (z >1) las galaxias individuales son típicamente Galaxias Infrarrojas Ultraluminosas (cuyas siglas en inglés son ULIRGs por Ultraluminous Infrared Galaxies, 1012 < Lbol < 1013 L⊙). Actualmente tenemos acceso a una gran variedad de información física basada en la emisión en bandas espectrales infrarrojas (IR), radiación que en el caso de las galaxias es producida en su mayoría por granos de polvo. Sin embargo, el límite de difracción de los instrumentos infrarrojos junto con el gran número de fuentes de emisión hace de la individualización de galaxias una tarea difícil. La primera parte de esta tesis se titula Resolviendo el Fondo Cósmico Infrarrojo con el Observatorio Espacial Herschel donde, con el uso de simulaciones realistas de las imágenes más profundas del Universo, hemos estudiado el origen del ruido de confusión en las imágenes GOODS-Herschel y resuelto en galaxias individuales una parte sustantiva del Fondo Cósmico Infrarrojo. Nuevas técnicas fueron desarrolladas para predecir los flujos en el infrarrojo lejano a partir del conocimiento a priori en el infrarrojo medio. Las imágenes simuladas fueron construidas usando esos flujos predichos y con ellos evaluar el rol del ruido de confusión local así como identificar fuentes individuales. La segunda parte de la tesis trata del estudio sobre la Destrucción de granos de polvo por chorros en ondas de radio. Este proyecto que se concentró en la observación de galaxias Seyfert y ULIRGS y apunta a entender mejor el ciclo de vida del polvo al estudiar la destrucción de granos en galaxias con nucleos activos y los efectos de la actividad de estas últimas en el medio interestelar, en particular en el mecanismo que da origen a la región de líneas de emisión angostas en las galaxias Seyfert. Se obtuvo espectros infrarrojos de rendija larga de galaxias Seyfert del tipo 2 para medir líneas de emisión ([Fe II], [P II] y Paβ) las cuales revelan la destrucción de granos de polvo debido a las perturbaciones de las ondas de choque producidas por chorros detectados en ondas de radio. Hemos encontrado que el mecanismo dominante de la ionización cerca de los núcleos de las galaxias Seyfers es el campo de radiación producido por la actividad del agujero negro central. En la parte externa de la región de líneas de angostas, las ondas de choque inducidas por los chorros en radio también contribuyen al balance energético del medio interestelar y desintegran los granos de polvo. Esta fue una tesis de co-tutela llevada a cabo en el Departamento de Astronomía de la Universidad de Concepción y en el Service d’Astrophysique del Commissariat á l’Énergie Atomique (CEA), Francia

L’interaction onde de choc/couche limite en écoulement transsonique autour de profils aérodynamiques est étudiée numériquement utilisant différentes classes de modélisation de la turbulence. Les approches utilisées sont celles de modèles URANS et de méthodes hybrides RANS-LES. L’emploi d’une correction de compressibilité pour les fermetures à une équation est aussi évalué. Premièrement, la séparation intermittente induite par le choc sur un profil supercritique en conditions d’incidence proches de l’angle critique d’apparition du tremblement est analysée. Suite à des simulations URANS, la modélisation statistique la mieux adaptée est étudiée et utilisée dans l’approche DDES (Delayed Detached-Eddy Simulation). L’étude de la topologie de l’écoulement, des pressions pariétales et champs de vitesse statistiques montrent que les principales caractéristiques de l’oscillation auto-entretenue du choc sont capturées par les simulations. De plus, la DDES prédit des fluctuations secondaires de l’écoulement qui n’apparaissent pas en URANS. L’étude de l’interface instationnaire RANS-LES montre que la DDES évite le MSD (modeled stress depletion) pour les phases de l’écoulement attaché ou séparé. Le problème de la ‘zone grise’ et de son influence sur les résultats est considéré. Les conclusions de l’étude sur le profil supercritique est ensuite appliquées à l’étude numérique d’un profil transsonique laminaire. Dans ce contexte, l’effet de la position de la transition de la couche limite sur les caractéristiques de deux régimes d’interaction choc/couche limite sélectionnés est étudié. En conditions de tremblement, les simulations montrent une forte influence du point de transition sur l’amplitude du mouvement du choc et sur l’instationnarité globale de l’écoulement
Shock wave/boundary layer interactions arising in the transonic flow over airfoils are studied numerically using different levels of turbulence modeling. The simulations employ standard URANS models suitable for aerodynamics and hybrid RANS-LES methods. The use of a compressibility correction for one-equation closures is also considered. First, the intermittent shock-induced separation occurring over a supercritical airfoil at an angle of attack close to the buffet onset boundary is investigated. After a set of URANS computations, a scale-resolving simulation is performed using the best statistical approach in the context of a Delayed Detached-Eddy Simulation (DDES). The analysis of the flow topology and of the statistical wall-pressure distributions and velocity fields show that the main features of the self-sustained shock-wave oscillation are predicted by the simulations. The DDES also captures secondary flow fluctuations which are not predicted by URANS. An examination of the unsteady RANS-LES interface shows that the DDES successfully prevents modeled-stress depletion whether the flow is attached or separated. The gray area issue and its impact on the results are also addressed. The conclusions from the supercritical airfoil simulations are then applied to the numerical study of a laminar transonic profile. Following a preliminary characterization of the airfoil aerodynamics, the effect of the boundary layer transition location on the properties of two selected shock wave/boundary layer interaction regimes is assessed. In transonic buffet conditions, the simulations indicate a strong dependence of the shock-wave motion amplitude and of the global flow unsteadiness on the tripping location

This work provides an in-depth study into the development of a complex two-dimensional flow field resulting from the interaction of a plane shock wave in air with concave profiles. Of particular interest are the development of reflection patterns of the incident shock wave at the profile wall and the process of gas dynamic focus. These principal flow features are examined across a wide range of different reflector shapes using both experimental and CFD approaches. The size of the various reflector shapes were specified by varying their depth-toaperture where models ranged from 0.2 to 1. Model apertures for numerical test pieces were fixed at 160 mm; experimental test pieces ranged from 140  A 160mm. The strength of the incident plane shock wave was limited to 1.2 1.45 S  M  . The principal flow features were established and examined experimentally using qualitative and quantitative flow visualization techniques supplemented with numerical results. Timeresolved high-speed imaging was used to capture the interaction providing the unique ability to track the various transient flow features over the course of the interaction. The variation of the principal flow features were examined by testing a large group of profiles using an experimentally-validated Euler-based CFD code. The depth-to-aperture ratio of the profile and the incident shock strength were shown to be the two primary factors that influenced the maximum pressure amplification at focus and the focus mechanism. Increases in the depth-to-aperture ratio increased the maximum pressure amplification observed at focus. This occurred due to a combination of factors including: the strengthening of the individual shock waves involved in focus; the duration of focus and the strengthening of a compressive flow field that develops adjacent to the shock system during focus. The compressive flow field adjacent to the shock system at focus was shown to be of great importance to the focus process. Parabolic or weighted catenaries with depth-toaperture ratios between 0.7 and 0.75 developed a new focus mechanism consisting of multiple foci. This new focus mechanism was shown to produce significant peak pressure amplifications. Recommendations for further study include high resolution experimental and/or CFD studies of gas dynamic focus in deep profiles.

碩士
國立臺灣大學
植物科學研究所
102
Transcription factors could be regulated by small single-domain proteins that disturb the formation of active oligomers. Heat shock factor (HSF) binding protein (HSBP) is a 10-kDa protein with a coiled-coil motif that interacts with the oligomerization domain of HSFs and is a negative regulatorof the heat stress response (HSR). In Arabidopsis (Arabidopsis thaliana), HSBP is a cytoplasmic protein that translocates to the nucleus after HS for HSF interaction. To uncover the cytoplasmic interacting proteins of HSBP and characterize the interaction with HSF members, we used mass spectrometry after HSBP co-immunoprecipitation (co-IP) and HSBP–HSF bimolecular fluorescence complementation assays. Mass spectrometry after co-IP revealed 14 cytoplasmic HSBP-interacting candidates responding to HS in Arabidopsis seedlings. The candidates were cytosolic HSP70s and all components of the MAIGO 2 complex; the most robust candidates were COP1-interactive protein 1 and kinesin-like protein for actin-based chloroplast movement 1, predicted to contain at least one coiled-coil domain. As well, 16 HSFs interacted with HSBP, predominantly in the nucleus, and included factors reported to be involved in the HS signaling cascade, antioxidant mechanisms, and seed maturation. As a small regulatory protein, HSBP interacts with HSFs and cytoplasmic coiled-coil–containing partners in response to numerous stress and developmental conditions.

碩士
國立臺灣師範大學
數學系
102
Assume Fi is a viscous shock profile of the viscous hyperbolic conservation laws. We are concerned with the stability and the solution structure for the initial value problem of the viscous hyperbolic conservation laws around the viscous shock wave Fi. The T-C scheme is used to estimate the solution of the linearized equations around viscous shock profile Fi. The detail proofs for the transversal wave operator of the T-C scheme are given in this thesis.

The present Dissertation’s academic research addresses the impact of oil price shocks on the performance of United States banks in the 2009Q1-2020Q3 period. The two hypotheses advanced are that oil price shocks have a direct impact on bank profitability, or that the effect of oil price movements is channeled solely through general economic activity, through an indirect effect. This Dissertation employs an incremental approach based on both Static and Dynamic Panel Data models. Subsequently, two robustness checks are performed, so as to check the possibility that the distance of banks’ Headquarters to Cushing, Oklahoma might affect the severeness of the impact of oil on bank performance; as well as to test the premise that price movements might produce asymmetrical effects. The dependent variable used is ROA, and the independent variables selected are three different oil price shock measures, and vectors of bank-specific and macroeconomic control variables. Bank-specific data were extracted from the Compustat Bank Fundamentals database, while oil and economic data were gathered from Refinitiv Worldscope. This Dissertation’s findings show that oil price shocks have a direct positive impact on U.S. bank performance and are robust for both econometric models. Moreover, several macroeconomic and bank-specific are found to affect bank performance. Additionally, the location of banks is noteworthy, since banks closer to Cushing observe a more significant positive impact of oil price on bank performance. However, no asymmetrical effects were observed. The empirical results of this Dissertation pose multiple management/policy challenges for bank executives, banking supervisors, and energy policymakers.
A presente Dissertação aborda como questão científica o efeito dos choques do preço do petróleo no desempenho dos bancos Norte-Americanos durante o período 2009Q1-2020Q3. As hipóteses avançadas prendem-se na possibilidade de os choques terem um efeito direto no desempenho dos bancos, ou o resultado dos movimentos do preço ser sentido somente na atividade económica, verificando-se um efeito indireto. Esta Dissertação utiliza uma abordagem incremental baseada em modelos estático e dinâmicos de dados em painel. Subsequentemente, dois testes de robustez foram aplicados, de forma a aferir a possibilidade da distância da sede dos bancos a Cushing, Oklahoma poder afetar a severidade do impacto do petróleo no desempenho dos bancos; foi igualmente testada a premissa de que os movimentos no preço poderiam produzir efeitos assimétricos. A variável dependente utilizada é o ROA, e as variáveis independentes selecionadas são três métricas de choques de preço do petróleo, bem como variáveis de controlo especificamente bancárias e macroeconómicas. Os dados dos bancos foram extraídos da base de dados Compustat Bank Fundamentals, enquanto os dados económicos e petrolíferos foram recolhidos do Refinitv Worldscope. Os resultados desta Dissertação mostram que os choques de preço do petróleo emitem um efeito positivo no desempenho dos bancos Norte-Americanos, confirmados para ambos os modelos. Mais, verificou-se que variáveis macroeconómicas e bancárias afetam o desempenho bancário. Adicionalmente, a localização geográfica é significativa, dados que se verificou um efeito do petróleo mais acentuado nos bancos mais próximo de Cushing, Oklahoma. Os resultados desta Dissertação colocam vários desafios a executivos, supervisores e legisladores.