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Van, der Byl Gretchen. "Other observations." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/10890.
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Bibliography: leaves 94-98.Painting presents an almost infinite range of possibilities to convey meaning through the versatility and potential of the medium. It is to this potential for mimicking and representing the real world that I wish to turn; for whilst the word painting refers to the manifestation of the physical object, it also, more importantly for this discussion, refers to the act of painting itself, the application of paint onto a surface in the articulation of an illusory reality. This ability to represent in paint, upon a two-dimensional surface, the real world in such a way as to cause in the viewer an experience which is somehow like that of looking at the world, is called naturalism.
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Ricci, Marina. "Étude des propriétés optiques d’amas de galaxies détectés en rayons X : analyse multi-longueurs d’onde et implications pour les grands relevés du futur." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4070/document.
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Répondre aux questions fondamentales concernant notre compréhension de l’Univers, comme la cause de son expansion accélérée ou la nature de la matière noire, requiert de confronter les théories aux observations. Dans ce contexte, les amas de galaxies peuvent être utilisés comme de puissantes sondes observationnelles. Cependant, à l’heure actuelle, leur utilisation est limitée par des incertitudes et des effets systématiques, qui affectent notamment la mesure de leur masse, que l’on présume dominée par la matière noire. Les amas de galaxies peuvent être étudiés à différentes longueurs d’onde : le gaz chaud qui compose le milieu intra-amas (ICM en anglais) émet des rayons X et est observable dans le domaine millimétrique via l’effet Sunyaev Zel’dovich (SZ), alors que les galaxies rayonnent principalement en optique et infrarouge. Combiner et comparer ces observables permet de réduire les incertitudes et les effets systématiques des contraintes cosmologiques issues des amas. Dans ce contexte, cette thèse a pour but de préparer les grands relevés observationnels du futur comme Euclid et le Large Synoptic Survey Telescope (LSST). Elle présente les analyses multi-longueurs d’onde d’un échantillon d’amas détectés en X dans le relevé XXL, couvrant une large gamme de masses et de redshifts. La première partie de cette thèse introduit le contexte cosmologique et présente les propriétés observationnelles des galaxies et amas de galaxies, ainsi que les ingrédients pour construire des échantillons cosmologiques d’amas. La deuxième partie traite de la caractérisation optique des amas XXL et des propriétés de leurs galaxies membres. Nous commençons par la présentation de XXL et du Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), un relevé optique associé. Ensuite, nous nous concentrons sur la caractérisation de la qualité des redshifts photométriques du CFHTLS et sur leur utilisation pour construire les fonctions de luminosité (LF en anglais) optiques des galaxies d’amas XXL. Il apparaît que la LF des galaxies satellites dépend légèrement de la richesse des amas, le principal proxy de masse en optique, mais ne montre pas d’évolution significative avec le redshift. Ensuite, nous entreprenons l’étude de la couleur et de la fraction de galaxies à noyaux actifs (AGN en anglais) dans les galaxies d’amas XXL et montrons que la masse joue un rôle clé dans la régulation de l’activité de formation stellaire dans les amas. Pour finir, l’algorithme de détection d’amas WaZP est utilisé pour étudier la contrepartie optique des amas XXL. La troisième partie de cette thèse est consacrée au projet observationnel dédié à la cartographie du signal SZ de trois amas XXL distants, avec la camera à haute résolution angulaire NIKA2. La préparation du projet est discutée, en se servant des données optiques et X afin de prédire le signal SZ attendu. Ensuite, nous présentons la procédure d’observation au télescope et la réduction des données, dédiée à la production des cartes SZ étalonnées. Le projet est en cours et un amas, XLSSC102, à z = 0.97, a été observé partiellement. Nous développons ensuite une méthode de détection en aveugle des potentielles galaxies qui peuvent contaminer le signal SZ, permettant la découverte fortuite de galaxies poussiéreuses à haut taux de formation stellaire dans le champ de XLSSC102. La morphologie et l’état dynamique de XLSSC102 sont ensuite caractérisés grâce à la combinaison des données optiques, SZ et X et les profils radiaux de masse et de propriétés thermodynamiques de l’ICM sont mesurés en associant les données X et SZ. Cela permet de montrer que XLSSC102 est un amas en coalescence avec une masse de ∼ 3 × 10^14 Msol et est compatible avec le scénario d’évolution standard de la formation des amasAddressing fundamental questions regarding our understanding of the Universe, such as the cause of its accelerated expansion or the nature of dark matter, requires to confront theories and observations. In this context, galaxy clusters can be used as powerful observational probes. However, their current utilisation is limited by uncertainties and systematic effects, notably affecting the measurement of their mass, which is presumably dominated by dark matter.Galaxy clusters can be studied at different wavelengths: the hot gas composing the Intra Cluster Medium (ICM) shines in X-ray and is observable at millimetre wavelengths via the Sunyaev-Zel’dovich (SZ) effect, whereas galaxies emit principally in the optical and infrared. Combining and comparing these observables allows us to reduce the uncertainties and systematics in the cosmological constraints obtained from clusters. In this context, this thesis aims at paving the way of future large surveys such as Euclid and the Large Synoptic Survey Telescope. It presents the multi-wavelengths analyses of a sample of clusters detected in X-ray in the XXL survey, spanning a wide range of masses and redshifts. The first part of the thesis introduces the cosmological context and presents the observational properties of galaxies and clusters, and the ingredients to build cosmological cluster samples. The second part concentrates on the optical characterisation of XXL clusters and the properties of their member galaxies. It starts by presenting XXL and the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), an optical counterpart survey. Then, it focuses on the characterisation of the CFHTLS photometric redshifts quality and their use to construct the optical galaxy luminosity functions (LF) of XXL clusters. The LF of satellite galaxies is found to slightly depend on cluster richness, the main optical mass proxy, but no significant redshift evolution is observed. Then, the study of the colour and active galactic nuclei (AGN) fraction in XXL cluster galaxies is performed, finding that the mass plays a key role in shaping AGN and star formation activity in clusters. Finally, the WaZP optical cluster finder algorithm is used to investigate the optical counterparts of XXL clusters. The third part of this thesis is dedicated to the observational project dedicated to the mapping of the SZ signal in three distant XXL clusters, with the high angular resolution NIKA2 camera. The preparation of the project is discussed, making use of the X-ray and optical data to predict the expected SZ signal. Then, the observation procedure at the telescope and the data reduction, dedicated to produce calibrated SZ maps, are presented. The project is still ongoing and one cluster, XLSSC102, at z = 0.97, has been partially observed. The development of the blind detection of galaxies potentially contaminating the SZ signal is developed, allowing for the serendipitous discovery of dusty star forming galaxies in the field of XLSSC102. The morphology and dynamical state of XLSSC102 are then characterised using optical, SZ and X-ray data and the radial ICM thermodynamics and mass profiles are measured combining SZ and X-ray data. This allows us to show that XLSSC102 is a merging cluster with a mass ∼ 3 × 10 14 M, and is compatible with the standard evolution scenario of cluster formation
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Le, Gal Romane. "Chimie interstellaire des hydrures d'azote : modélisation - observations." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY081/document.
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La nouvelle fenêtre spectroscopique dans le sub-millimétrique, ouverte par l’avènement del’observatoire spatial Herschel, a permis la détection d’espèces azotées simples, les hydruresd’azote NH, NH2 et NH3, dans les enveloppes froides de proto-étoiles. Ces enveloppes sontconstituées de gaz dense et froid caractéristique des conditions physico-chimiques des nuagesmoléculaires. L’observation d’hydrures d’azote dans de tels environnements a donc permis d’apporterde nouvelles contraintes sur la chimie interstellaire de ces nuages, et nous a donné enparticulier l’occasion de ré-explorer la chimie de l’azote.L’objectif de mon travail de thèse a été d’analyser en détail cette chimie interstellaire etprincipalement la formation en phase gazeuse d’espèces polyatomiques simples : les hydruresd’azote. Dans des conditions de gaz dense et froid (n = 104 cm−3, T = 10 K), la chimie de cesderniers est initiée par une chimie lente (la conversion de N en N2 par réactions neutre-neutre),contrairement à celles de ses analogues oxygénés et carbonés. Nous nous sommes particulièrementintéressés à cette étape de la chimie de l’azote, au vu des récents travaux théoriqueset expérimentaux menés par plusieurs équipes d’experts (Bordeaux, Besançon). De plus, lesrécents travaux concernant la conversion ortho-para de l’hydrogène moléculaire et les nouveauxcalculs de rapports de branchement de spins nucléaires pour les voies de production des hydruresd’azote dans leurs configurations ortho et para, menés à l’IPAG, nous ont permis d’entreprendrele calcul auto-cohérent des différentes symétries de spin des hydrures d’azote et de l’hydrogènemoléculaire. Nous avons ainsi pu développer un nouveau réseau chimique de l’azote, bénéficiantdes taux cinétiques les plus à jour pour les réactions critiques impliquées dans la chimie deshydrures d’azote.Ce nouveau réseau est utilisé pour modéliser l’évolution temporelle des abondances desespèces azotées dans des conditions de gaz dense et froid ( 103 < n < 106 cm−3, T ≤ 50 K).Les résultats à l’état stationnaire sont comparés aux observations de NH, NH2 et NH3, dans lesenveloppes froides de proto-étoiles de faible masse, en étudiant l’influence des abondances totalesen phase gazeuse du carbone, de l’oxygène et du soufre. Nos modèles chimiques reproduisent lesabondances des hydrures d’azote observés et leurs rapports pour un rapport C/O élementaire, enphase gazeuse, de ∼ 0.8 et à condition que l’abondance totale de soufre soit déplétée d’au moinsun facteur 2. Les rapports ortho/para prédits par nos modèles, pour NH2 et NH3, respectivement∼ 2.3 et ∼ 0.7, sont compatibles avec les observations de ces derniers dans des nuages diffusfroids. Les abondances des hydrures d’azote, dans des conditions de nuages sombres, sont donccohérentes avec une synthèse purement en phase gazeuse. De plus, nos résultats soulignent lefait que NH provient d’une voie de formation différente de celle de NH2 et NH3. NH vient de larecombinaison dissociative de N2H+ alors que la formation de NH2 et NH3 est principalementdue à la recombinaison dissociative de l’ion ammonium (NH+4 ), lui même molécule fille deN+. Ainsi, NH2 et NH3 procèdent de l’échange de charge dissociatif N2 + He+, tandis que NHprovient de la réaction N2 + H+3The new spectroscopic window opened by the advent of the Herschel Space Observatory,has enabled the detection of simple nitrogen species, the nitrogen hydrides NH, NH2, and NH3,in the cold envelope of protostars. These envelopes are made of dense cold gas characteristicof the physico-chemical conditions of molecular clouds. The observation of nitrogen hydrides insuch environments has brought new constraints on the interstellar chemistry of these kind ofclouds, and gives, in particular, the opportunity to revisit the chemistry of nitrogen.The aim of my thesis was to comprehensively analyse the interstellar chemistry of nitrogen,focussing on the gas-phase formation of the simplest polyatomic species, namely nitrogen hydrides.Under dense, cold gas conditions (n = 104 cm−3, T = 10 K), the chemistry of theselatter is initiated by a slow chemistry (the conversion from N to N2 with neutral-neutral reactions),in contrast to their carbonated and oxygenated analogues. We have investigated andrevisited this specific part of the nitrogen chemistry in the light of recent theoretical and experimentalwork carried out by several expert teams (Bordeaux, Besançon). In addition, recentwork about the ortho-para conversion of molecular hydrogen and new calculations of nuclearspin branching ratios for the production pathways of nitrogen hydrides in their ortho and paraconfigurations conducted at IPAG, enabled us to treat self-consistently the different spin symmetriesof the nitrogen hydrides together with the ortho and para forms of molecular hydrogen.We were able to develop a new network of chemical nitrogen in which the kinetic rates of criticalreactions involved in the nitrogen chemistry have been updated.This new network is used to model the time evolution of the nitrogen species abundancesin dense cold gas conditions (T ≤ 50 K, 103 < n < 106 cm−3). The steady-state resultsare compared to observations of NH, NH2 and NH3 towards a sample of low-mass protostars,with a special emphasis on the influence of the overall amounts of gaseous carbon, oxygen, andsulphur. Our chemical models reproduced the nitrogen hydrides abundances and their ratios fora gas-phase elemental C/O ratio of ∼ 0.8, provided that the total amount of sulphur is depletedby at least a factor of two. Our predicted ortho-to-para ratios for NH2 and NH3, ∼ 2.3 and∼ 0.7 respectively, are in good agreement with the observations towards cold diffuse clouds.Then, in dark gas conditions, the nitrogen hydride abundances are consistent with a pure gasphasesynthesis. Moreover, our results are based on the fact that NH is coming from a differentpathway than NH2 and NH3. NH is the daughter molecule of N2H+, deriving from the reactionN2+H+3 , while NH2 and NH3 proceed from NH+4 , itself daughter molecule of N+, resulting fromthe dissociative charge exchange N2 + He+
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Ninove, Floriane. "Apports de données Argo pour caractériser les erreurs modèles et contraindre les systèmes d'assimilation." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30230/document.
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Le programme international Argo a révolutionné l'observation globale des océans. Une flotte de plus de 3000 instruments sous-marins autonomes est en place, programmés pour fournir des mesures globales de profils de température et de salinité sur les 2000 premiers mètres de l'océan. Ces mesures sont assimilées dans des modèles océaniques conjointement aux observations satellitaires afin de décrire et prévoir l'océan. Dans cette thèse nous proposons une analyse permettant de caractériser les erreurs d'un modèle global océanique par comparaison aux données du réseau Argo. Ces erreurs sont décrites via leurs amplitudes, leurs variations régionales et temporelles ainsi que via les échelles spatiales associées. Une caractérisation des échelles spatiales à la fois pour la variabilité océanique et pour les erreurs modèles est, en particulier, menée permettant de relier la structure des erreurs modèles à celle du signal. Enfin, des techniques basées sur le contenu en information sont testées afin de pouvoir à terme mieux quantifier l'impact des observations Argo sur les systèmes d'assimilation de Mercator OcéanThe international Argo program has revolutionized the observation of the global ocean. An array of more than 3000 profiling floats is in place and provides global measurements of temperature and salinity on the first 2000 meters of the ocean. These measurements are assimilated into ocean models together with satellite observations to describe and forecast the ocean state. We propose here to characterize model errors using Argo observations. Model errors are described through their amplitude, geographical and temporal variations as well as their spatial scales. Spatial scales of both model errors and ocean signals are, in particular, estimated. This allows a comparison of model errors and ocean variability structure. Finally, techniques based on information content are tested in the longer run quantifying the impact of Argo observations in the Mercator Ocean data assimilation systems
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Nelson, Stephanie Anne. "Associations Between Intelligence Test Scores and Test Session Behavior in Children with ADHD, LD, and EBD." ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/159.
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Individually administered intelligence tests are a routine component of psychological assessments of children who may meet criteria for Attention-Deficit/Hyperactivity Disorder (ADHD), learning disorders (LD), or emotional and behavioral disorders (EBD). In addition to providing potentially useful test scores, the individual administration of an intelligence test provides an ideal opportunity for observing a child’s behavior in a standardized setting, which may contribute clinically meaningful information to the assessment process. However, little is known about the associations between test scores and test session behavior of children with these disorders. This study examined patterns of test scores and test session observations in groups of children with ADHD, LD, EBD who were administered the Stanford Binet Intelligence Scales, Fifth Edition (SB5), as well as in control children from the SB5 standardization sample. Three hundred and twelve children receiving special education services for ADHD (n = 50), LD (n = 234), EBD (n = 28) and 100 children selected from the SB5 standardization sample were selected from a data set of children who were administered both the SB5 and the Test Observation Form (TOF; a standardized rating form for assessing behavior during cognitive or achievement testing of children). The groups were then compared on SB scores and TOF scores. Associations between test scores and TOF scores in children with ADHD, LD, and EBD and normal controls were also examined. The results of this investigation indicated that children with ADHD, LD, and EBD and normal control children differed on several SB5 and TOF scales. Control children scored higher on all of the SB5 scales than children with LD, and scored higher on many of the SB5 scales than children with ADHD and EBD. Children with EBD demonstrated the most problem behavior during testing, followed by children with ADHD. Children with LD were similar to control children with respect to test session behavior. In addition, several combinations of test scores and test session behavior were able to predict diagnostic group status. Overall, the results of this investigation suggest that test scores and behavioral observations during testing can and should be important components of multi-informant, multi-method assessment of children with ADHD, LD, and EBD.
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Atkins, John L. "Personal anthropological observations." Virtual Press, 1987. http://liblink.bsu.edu/uhtbin/catkey/724963.
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The creative project dealt with the artist creating a vocabulary of images derived from past and present cultures in order to create a series of highly personalized anthropological narratives. The artist intended the narrative drawings to invoke archaic moods rather than summon literal responses.The accomplishments of this creative project were further development of the artist's personal imagist style, success in relating personal anthropological observations through narratives, and progress in media experimentation. By creating more contrast between forms, by varying value against value and deep space against shallow space, the artist was able to achieve superior compositional studies.Department of Art
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Bradley, Christine Lavella, and Christine Lavella Bradley. "SpectroPolarimetric Imaging Observations." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624499.
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The capability to map anthropogenic aerosol quantities and properties over land can provide significant insights for climate and environmental studies on global and regional scales. One of the primary challenges in aerosol information monitoring is separating two signals measured by downward-viewing airborne or spaceborne instruments: the light scattered from the aerosols and light reflected from the Earth's surface. In order to study the aerosols independently, the surface signal needs to be subtracted out from the measurements. Some observational modalities, such as multispectral and multiangle, do not provide enough information to uniquely define the Earth's directional reflectance properties for this task due to the high magnitude and inhomogeneity of albedo for land surface types. Polarization, however, can provide additional information to define surface reflection. To improve upon current measurement capabilities of aerosols over urban areas, Jet Propulsion Laboratory developed the Multiangle SpectroPolarimetric Imager (MSPI) that can accurately measure the Degree of Linear Polarization to 0.5%. In particular, data acquired by the ground-based prototype, GroundMSPI, is used for directional reflectance studies of outdoor surfaces in this dissertation. This work expands upon an existing model, the microfacet model, to characterize the polarized bidirectional reflectance distribution function (pBRDF) of surfaces and validate an assumption, the Spectral Invariance Hypothesis, on the surface pBRDF that is used in aerosol retrieval algorithms.
The microfacet model is commonly used to represent the pBRDF of Earth's surface types, such as ocean and land. It represents a roughened surface comprised of randomly oriented facets that specularly reflect incoming light into the upward hemisphere. The analytic form of the pBRDF for this model assumes only a single reflection of light from the microfaceted surface. If the incoming illumination is unpolarized, as it is with natural light from the Sun, the reflected light is linearly polarized perpendicular to the plane that contains the illumination and view directions, the scattering plane. However, previous work has shown that manmade objects, such as asphalt and brick, show a polarization signature that differs from the single reflection microfacet model. Using the polarization ray-tracing (PRT) program POLARIS-M, a numerical calculation for the pBRDF is made for a roughened surface to account for multiple reflections that light can experience between microfacets. Results from this numerical PRT method shows rays that experience two or more reflections with the microfacet surface can be polarized at an orientation that differs from the analytical single reflection microfacet model. This PRT method is compared against GroundMSPI data of manmade surfaces.
An assumption made regarding the pBRDF for this microfacet model is verified with GroundMSPI data of urban areas. This is known as the Spectral Invariance Hypothesis and asserts that the magnitude and shape of the polarized bidirectional reflectance factor (pBRF) is the same for all wavelengths. This simplifies the microfacet model by assuming some surface parameters such as the index of refraction are spectrally neutral. GroundMSPI acquires the pBRF for five prominent region types, asphalt, brick, cement, dirt, and grass, for day-long measurements on clear sky conditions. Over the course of each day, changing solar position in the sky provides a large range of scattering angles for this study. The pBRF is measured for the three polarimetric wavelengths of GroundMSPI, 470, 660, and 865nm, and the best fit slope of the spectral correlation is reported. This investigation shows agreement to the Spectral Invariance Hypothesis within 10% for all region types excluding grass. Grass measurements show a large mean deviation of 31.1%. This motivated an angle of linear polarization (AoLP) analysis of cotton crops to isolate single reflection cases, or specular reflections, from multiple scattering cases of light in vegetation. Results from this AoLP method show that specular reflections off the top surface of leaves follow the Spectral Invariance Hypothesis.
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Dahlqvist, Caroline, and Hanna Eriksson. "Night-Time Observations of Earth : Satellite Orbit Modied for UHECR Observations." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-249172.
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Particles with energies higher than 3. 10.19 eV are generally referred to as Ultra- High Energy Cosmic Rays (UHECRs) and their sources are currently unknown. The observations of these particles are performed during the night from ground observatories or telescopes mounted on stratospheric balloons or, in the near future, from the International Space Station (ISS). In this report, different orbit types are analysed and compared with the ISS in terms of the duration of the sub-point in night-time (umbra), the observed area on the ground in umbra and estimations of the observable number of events.
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Mtema, Kuda. "När leken vänder. : En studie som bygger på mina observationer kring hur leken kan förändras i ett ögonblick." Thesis, Stockholms universitet, Institutionen för didaktik och pedagogiskt arbete, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38678.
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Devogèle, Maxime. "Propriétés des astéroïdes de type L : un lien avec le Système Solaire primordial ?" Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4069/document.
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En 2006, Il a été observé que l'astéroïde (234)~Barbara possède une valeur anormalement élevée d’angle d’inversion polarimétrie. Par la suite, d'autres astéroïdes possédant la même caractéristique que Barbara ont été découverts et nommés ``Barbarians'' en référence à (234) Barbara. L'étude de ces astéroïdes constitue le sujet principal de cette thèse ayant pour but de mieux comprendre la raison de cet angle d'inversion plus élevé que la normale. La première hypothèse formulée afin d’expliquer cette anomalie polarimétrique suppose que les astéroïdes Barbarians possèdent une forme fortement irrégulière induisant une réponse polarimétrique particulière. La deuxième hypothèse stipule que les astéroïdes Barbarians possèdent une abondance anormalement élevée d'inclusions riches en aluminium et en calcium. Au cours de cette thèse, nous avons obtenu de nombreuses nouvelles données aussi bien en photométrie, spectroscopie que polarimétrie. Ces nouvelles observations d’astéroïdes ont permis de tester différentes hypothèses formulées précédemment afin d'expliquer l'anomalie polarimétrique observée. Nos observations ont permis d'éliminer une hypothèse faisant appel à une topologie particulière des astéroïdes Barbarians, mais nous avons confirmé et renforcé une autre hypothèse faisant intervenir une composition particulière de ces astéroïdes. Si cette dernière hypothèse était confirmée, cela en ferait des astéroïdes primitifs s'étant formés lors des premières étapes du Système Solaire. Leur étude permettrait donc d'en apprendre plus sur les mécanismes de formation des astéroïdes et la composition de la nébuleuse ayant donné naissance au Système Solaire. Comprendre les astéroïdes Barbarians sert à mieux comprendre les premières étapes de formation du Système Solaire et aussi celles des planètesA few years ago, asteroid polarimetry allowed to discover a class of asteroids exhibiting peculiar phase polarization curves, collectively called "Barbarians" from the prototype of this class, the asteroid (234) Barbara. All such objects belong to the L visible plus near infrared based taxonomic class. The anomalous polarization has been tentatively interpreted in terms of high-albedo, spinel-rich Calcium-Aluminum inclusions (CAI) that could be abundant on the surfaces of some of these asteroids, according to their spectral reflectance properties and to analogies with CO3/CV3 meteorites. Such CAIs are among the oldest mineral assemblages ever found in the Solar System. Barbarians' surfaces could therefore be rich in this very ancient material and bring information on the early phases of planetary formation. During this thesis, a systematic campaign for photometric, polarimetric and spectroscopic characterization has been conducted. These observation campaigns allowed improving our general knowledge about these peculiar asteroids and highlighting the link between polarization and polarimetric properties. Our observation also allowed discarding the hypotheses involving peculiar shape for these asteroids. However, as it was suggested, a link between the presence of CAI and the polarimetric response was found. Our observations show that the relative abundance of CAI is correlated with the polarimetric inversion angle. This is the first time that a direct link between polarimetric and spectroscopic properties is found
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Stevens, Jason Anthony. "Multifrequency observations of blazars." Thesis, University of Central Lancashire, 1995. http://clok.uclan.ac.uk/20140/.
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Blazars are a class of active galactic nuclei (AGN). Active galaxies are those that host compact sources of non-thermal radiation in their nuclear regions and are usually classified as being radio-loud or radio-quiet. The nature of the central source is ullcertain, but arguments based on energy budget suggest that accretion onto a supermassive black hole is the most probable scenario (Rees 1984). At present, there is no satisfactory theory that can explain the difference between radio-loud and radio-quiet AGN. The emission from radio-quiet AGN is regarded as being thermal in origin. Thermal re-radiation of the nuclear energy by dust in the host galaxy is thought to be an important process in these sources (Bregman 1990; Hughes et al. 1993). Radio-loud sources are dominated by non-thermal radiation which is almost certainly synchrotron in origin. Blazars are the most extreme example of radio-loud AGN and as such, provide the best opportunity to investigate further the emission mechanisms associated with radio-loudness. The term blazar (Angel & Stockman 1980) was originally applied to two groups of AGN which exhibit similar properties, namely BL Lacertae objects and optically violently variable (OVV) quasars. The BL Lac objects can be further split into radio selected BL Lac objects (RBLs) and X-ray selected BL Lac objects (XBLs). The difference between these two groups may only be due to the angleat which the jet (see below) is directed towards the line-of-sight of the observer. In this scenario the RBLs are more closely aligned (e.g. Gear 1994). The BL Lac objects studied in this work are all RBLs. In recent years, differences between OVV quasars and BL Lac objects have become apparent and these, together with the similarities that led to the original unification, will be discussed below. It is now more correct to assign the term blazar to a phenomenon rather than to a distinct class of AGN.
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Cartwright, Ian Martin. "Optical observations of comets." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301755.
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Xystouris, George. "SETI follow-up observations." Thesis, Uppsala universitet, Observationell astrofysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-294436.
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The G-HAT team (G-HAT: Glimpsing Heat from Alien Technologies) compiled a catalogue of 93 galaxies that could host Kardashev-III civilizations [Griffith et al., 2015], using data from the WISE space telescope. Their method was based on the detection of the civilization's "waste heat": as any physical process takes place, heat is being released to the environment and it can be detected as an excess of the IR flux of the object. Garrett [2015] combined the data from the G-HAT catalogue with the 20cm flux from the NRAO VLA Sky Survey (NVSS) and 9 objects with an anomalous flux excess at IR wavelengths were identied. This work is based on the the needed follow-up observations for each of those 9 sources. This work is divided into three parts: in the first part we explain the theory of the "waste heat" search method, in the second part we give details about our submitted proposal for a submillimeter follow-up observation of NGC0814, using the Atacama Pathnder EXperiment (APEX) and in the third part we present a strategy for the required follow-up observations for the rest of the candidates.
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Rostron, J. W. "Observations of exoplanet atmospheres." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/69291/.
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In the past decade the field of extra-solar planetary science has moved beyond simple detections of planets outside of our Solar System into more detailed characterisations of these objects. One avenue that is at the forefront of current research is the study of extra-solar planet atmospheres. This work has focused on a subset of the current exoplanet population: transiting hot Jupiters. The large sizes, high temperatures and bright stellar hosts of these planets make them particularly amenable to atmospheric studies through techniques such as secondary eclipse observations, which can sample the planetary thermal and reflected light. Atmospheric detections have now been made for over 50 extra-solar planets. With such a population, we can begin to look for trends in the atmospheric properties of these planets, in order to shed more light on the physical processes that affect their atmospheres. It is in this context that I present the work in this thesis, which comprises secondary eclipse observations of five transiting hot Jupiter exoplanets. Secondary eclipses of WASP-3b were observed using the Spitzer Space Telescope, giving estimates of the planets thermally emitted flux at 3.6 μm, 4.5 μm and 8.0 μm. These estimates imply the planet is very hot (Teff = 2280+200−150 K) and that it may host an inverted vertical temperature profile. This system probes a cut-off in a proposed correlation between the vertical temperature structures of hot Jupiters and the chromospheric activity of their host stars. I find that my measurements for WASP-3b imply this cut-off is more complex than initial data has suggested. Secondary eclipses of the planets WASP-21b, WASP-28b and WASP-37b, all with low metallicity host stars, were also observed with the Spitzer Space Telescope, at 3.6 μm and 4.5 μm. These systems were studied to explore potential correlations between planetary spectral properties and host star metallicities. In existing data, a hint of a trend between the vertical temperature structures of planets and the metallicities of their host stars is found. However this trend is not supported by the planetary flux estimates derived for the three systems I have studied. Ground-based optical and near infra-red secondary eclipses were also observed for WASP-33b, using the ULTRACAM instrument on the William Herschel Telescope. The emission of WASP-33b, detected in the z’ band, confirms that the planet is extremely hot (Tz = 3170+90−190 K) and supports a trend found for highly irradiated planets to have systematically low albedos and poor heat redistribution properties.
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ALFONSO, THIERY ISABELLE. "Observations comportementales en musicotherapie." Toulouse 3, 1993. http://www.theses.fr/1993TOU31008.
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Hulot, Gauthier. "Observations geomagnetiques et geodynamo." Paris 7, 1992. http://www.theses.fr/1992PA077085.
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Les differentes etudes que nous avons presentees au cours de cette these nous ont amene a constater que le champ magnetique terrestre principal se presente comme la superposition d'un champ dipolaire evoluant lentement (a l'echelle du million d'annees au moins) et d'un champ multipolaire evoluant vite (a l'echelle de quelques centaines d'annees) et de maniere apparemment aleatoire. Parallelement, nous avons montre que cette variation rapide du champ peut etre expliquee en termes de mouvements du fluide a la surface du noyau terrestre. Les mouvements de grande echelle que nous en deduisons sont simples et possedent d'interessantes proprietes de symetrie. Ces resultats suggerent que la convection qui anime le noyau liquide de la terre et qui engendre le champ magnetique principal, s'organise autour de deux grands rouleaux identiques, symetriques par rapport a l'equateur et paralleles a l'axe de rotation de la terre
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Bochinski, Jakub Jaroslaw. "Observations of transiting exoplanets." Thesis, Open University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.699818.
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The field of exoplanetology has evolved significantly from its beginnings in the 1990s, gradually shifting emphasis from the detection of new exoplanets to characterisation of those already discovered. Simultaneously, considerable progress has been made in the area of automatisation of both instruments and data reduction techniques, leading to an ever-growing influx of new data, discoveries and facts about the planets outside of the Solar System. Observations of transiting exoplanets can be divided into two major themes: surveys, designed to find new planetary candidates; and follow-up observations, which offer a chance to learn more about the characteristics of the previously identified candidates and confirm their planetary nature. In this thesis, I introduce both aspects in the context of the current exoplanetary re- search, and go on to describe in considerable detail the objects of two observational follow-up projects, planets WASP-12 band KIC 12557548 b, together with a selection of new techniques I develop to assist in data reduction and analysis of large photometric datasets. In the WASP-12 b study, I use ULTRACAM on the William Rerschel Telescope to search in the visible light for the presence of the early ingress signature, observed previously with the Rubble Space Telescope in the near-ultraviolet. I also investigate claims of a transit timing variation in this system. I use the same instruments to carry out KIC 12557548 b observations, with the aim to measure the colour dependence of the extinction and scattering due to the dust in the tail of the putative planet and provide direct evidence in favour of this object being a disrupting low-mass rocky planet, feeding a transiting dust cloud. I also present a new algorithm used to correct for scattered light in astronomical images, ULTRACorrect, and introduce a bespoke photometry pipeline, ULTRAPhoto, together with a selection of other methods useful in observations planning and data analysis
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Chiesa, M. "COSMOLOGICAL OBSERVATIONS AND BACKREACTION." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/233237.
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Since the very beginning the Friedmann-Robertson-Walker metric has played one of the most important roles in developing cosmology. The underlying assumptions of maximal symmetry have simplified our general view of the Universe but recent developments in observational cosmology, like the discovery of cosmic acceleration, have demonstrated that a more precise approach is required. Dealing with the inhomogeneities of the matter distribution in the Universe has led to the problem of defining averages in a relativistic framework. After having reviewed the basics of the Standard Model, we introduce the longstanding problem of averaging in relativistic cosmology and the cosmological backreaction in the formulation proposed by Buchert. We follow the suggestion of probing backreaction against data applying the method based on a template friedmaniann-like metric developed by Larena et al. in 2008. We test the backreaction model against SN data of the Union2.1 release, clusters and CMB measurements from Planck and WMAP-9yr using different sets of observables. We find that the improvements in SN and cluster data confirm Larena's results providing slightly better constraints. Unfortunately current CMB data shed light on underlying approximations in matching the backreaction model and standard CMB theory, showing that the derived constraints on cosmological parameters are in contrast with predictions from the other data sets and consequently we have to handle them with care.
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Allan, Shawn S. "A study of high wind storms affecting Atlantic Canada, 1979-1995." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ44114.pdf.
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Pluriel, William. "Effets de la structure tridimensionnelle des atmosphères d’exoplanètes chaudes sur les observations et les modèles d’inversion de données." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0167.
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Nous sommes aujourd'hui en mesure non seulement de découvrir de plus en plus d'exoplanètes, mais aussi d'observer leurs atmosphères afin d'obtenir des informations sur leurs propriétés physiques, dynamiques et chimiques. Avec la nouvelle génération de télescopes spatiaux tels que le JWST ou Ariel, nous serons en mesure d'observer des caractéristiques spectrales aujourd'hui non-observables. Cependant, lors des observations en transits, la structure géométrique des atmosphères, et notamment la dichotomie jour--nuit des Jupiters chauds et ultra chauds, affecte le spectre en transmission et génère des biais dans l'interprétation des modèles d'inversion de données.Ma thèse se concentre sur l'étude des effets de la structure tridimensionnelle des atmosphères d'exoplanètes, en particulier des plus chaudes d'entre elles. Le but est de déterminer leurs importances et leurs origines pour permettre une meilleure analyse des données spectrales. Pour y parvenir, j'ai mis en place une expérience numérique simulant des observations de Jupiters chauds où je contrôle l'ensemble de la chaîne observationnelle, de la génération de l'atmosphère à l'inversion de données. En complément, j'ai analysé des observations du télescope spatial Hubble de Kelt-7 b, un Jupiter chaud, pour lier mes analyses numériques à des données réelles.Mes travaux ont montré que la structure particulière des Jupiters les plus chauds affecte significativement les données d'observations, impliquant des biais importants dans les résultats des modèles d'inversion de données 1D. Bien que ces modèles restent valables sur une large gamme de planètes, j'ai démontré que pour les exoplanètes les plus chaudes, ils sont intrinsèquement incapables de trouver l'abondance des espèces. Je suis parvenu à quantifier ces biais et à comprendre leurs origines, apportant une amélioration à l'avenir des interprétations faites à partir des modèles 1D. Par ailleurs, je conclue qu'il est nécessaire de développer en parallèle des modèles 2D pour tenter de résoudre ces biaisNowdays, we are able to discover more and more exoplanets, and even more important we can observe their atmospheres and we are starting to get information on their physical, dynamic and, chemical properties. With the new generation of space telescopes such as the JWST or Ariel, we will be able to observe spectral features that are now unobservable. However, during transit observations, the geometric structure of the atmospheres, and in particular the day to night dichotomy of hot and ultra hot Jupiters, affects the transmission spectrum and generates biases in the interpretations of retrieval outputs analysis.The aim of my thesis is to study the effects of the three-dimensional structure of exoplanet atmospheres, and in particular the hottest ones, in order to determine the importance and the origin of these biases to allow a better analysis of the spectral data. I set up a numerical experiment simulating observations of hot Jupiters where I control the entire observational chain, from the atmosphere's simulation to the retrieval. In addition, I analyzed observations of Kelt-7 b, a hot Jupiter, from the Hubble Space Telescope, to link my numerical analysis to real data.My work has shown that the particular structure of the hottest Jupiters significantly affects observations, implying significant biases in the results of 1D retrieval models. Although these models are valid over a large range of planets, I have demonstrated that for the hottest exoplanets, they are unable to find the abundances of species. I succeeded in quantifying these biases and in understanding their origins, hence an improvement in the interpretation of future results from 1D retrieval models. Furthermore, I conclude that it is necessary to develop 2D retrieval models to try to resolve these biases
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Marseille, Matthieu. "Observations et modélisations de proto-étoiles massives dans le cadre des observatoires Herschel." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13658/document.
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La formation des étoiles massives reste, à ce jour, encore mal connue à cause de l’extrême quantité d’énergie que ces étoiles dégagent, limitant en conséquence leurs masses théoriques et contredisant les observations de ce type d’étoile. Les observatoires du futur (en particulier l’observatoire spatial Herschel) vont tenter de répondre à cette problématique grâce notamment aux émissions moléculaires de l’eau. L’analyse précise et correcte de ces données, dans l’avenir, nécessite donc dès aujourd’hui un travail associant des observations et des modélisations des objets concernés. C’est dans ce but que cette thèse a consisté en l’élaboration d’une méthode de modélisation dite « globale » d’objets protostellaires massifs (proto-amas ou cœurs denses massifs). Celle-ci a permis une description physique et une étude chimique des multiples cœurs denses massifs étudiées, et a ouvert de nombreuses voies vers des aspects évolutifs. Elle a également donné des indices pour a?ner le programme d’observation en temps garanti WISH des raies moléculaires de l’eau et con?rmé le rôle clef de cette molécule pour la compréhension de la formation des étoiles massivesToday the formation of massive stars is still not well understood due to the huge interac- tion of these objects with their environment, leading to a theoretical limit in the ?nal mass that observations contradict. The future observatories, like the Herschel Space Observatory, will try to answer some of the questions linked to this topic, particularly through the water line emissions. The correct and precise analysis of the future data is then necessary and needs a full work linking the observations and the modelling of the objects that will be studied. Hence the main goal of this PhD Thesis was to elaborate a robust and global modeling method of the massive dense cores in which high-mass stars are forming. The method leaded to a physical description and a chemical study of multiple massive dense cores, opening new views on evolution aspects. In addition it gave some tweaks on the guaranteed-time key program WISH for the water line emissions and con?rmed the key role of this molecule for a better understanding of the high-mass star formation
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JORDA, LAURENT. "Atmospheres cometaires : interpretation des observations dans le visible et comparaison avec les observations radio." Paris 7, 1995. http://www.theses.fr/1995PA077211.
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Les observations d'atmospheres cometaires dans le visible permettent de cartographier les poussieres. Leur etalonnage, ainsi que la modelisation de la coma de poussieres, autorise le calcul de la masse de poussieres produite par le noyau. La haute resolution spectrale des donnees radio permet d'etudier la cinematique des molecules et radicaux presents dans le coma et de calculer la quantite de gaz emise par le noyau. Une loi de correlation entre les magnitudes visuelles et le taux de production de l'eau a ete determinee. Elle permet de predire le niveau d'activite de p/wirtanen, cible designee de la mission rosetta de l'agence spatiale europeenne. Le taux de production des grains de six cometes a ete mesure a partir d'observations en imagerie ccd et en photometrie d'ouverture. L'etude des jets de poussieres et de gaz observes dans le coma de p/swift-tuttle permet, a partir d'un modele base sur l'emission de grains par une zone active a la surface d'un noyau en rotation, de determiner plusieurs proprietes physiques du noyau de cette comete exceptionnelle
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Josien, Eric. "La dissection des arteres vertebrales : 9 observations personnelles et 198 observations de la litterature." Lille 2, 1990. http://www.theses.fr/1990LIL2M240.
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Sapp, Brian Keith. "Observations of Laboratory Rip Currents." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10453.
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Laboratory experiments of rip current systems are performed in a wave basin with a bar and rip channel geometry at the Ocean Engineering Laboratory at the University of Delaware. The experiments include both in situ water level and velocity measurements and optical visualization of the flow field under a variety of normal-incident wave conditions. Digital video is used to record surface drifters moving through a rip current system. A method is presented that tracks these digitally-recorded drifters into long Lagrangian sequences. The laboratory measurements capture both an Eulerian and Lagrangian description of the rip current system.
Time-averaged rip current properties are calculated and analyzed using both in situ and video measurements. From the video, Lagrangian velocities are computed with forward differencing of the low-pass filtered drifter tracks. Wave properties are also estimated using the orbital drifter motions and linear (Airy) wave theory. The effects of various wave conditions on the time-averaged rip current systems are investigated to show that wave height is a critical parameter. Measurements of circulation cells are obtained by spatially averaging the drifter track velocity measurements into a polar grid ranging from 0.25 m to 3.25 m from the center of the cell. Circulation cell features, such as the center of circulation and cell width, are calculated to characterize their response to various wave conditions.
Spectral analyses are used to characterize the rip current pulsations in the experimental measurements. Three frequencies are found to be energetic in several of the experiments in the low frequency band: the wave group frequency, a lower frequency, and the interaction of the wave group and lower frequencies. Some experiments have significant energy at each of the three peaks, where others have only one or none. The lower frequency motions have also been found in the video measurements and attributed to rip meandering. Possible causes for the low-frequency pulsations, including wave basin seiching, circulation cell instabilities, and wave-current interaction, are discussed.
This thesis adds to previous rip current studies by providing a spatially-large and time-varying perspective of rip current systems as a whole.
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Cabral, de Barros Susana Cristina. "ULTRACAM observations of interacting binaries." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491889.
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This thesis focuses upon two different aspects of interacting binary stars, the study of the shortest period binary stars known V407 Vul and HM Cnc and the study of stochastic variability in cataclysmic variable stars. V407 Vul and HM Cnc are X-ray emitting stars with X-ray and optical light curves that are modulated on periods of 569 and 321 s, respectively. In chapter 4 we consider geometrical constraints upon the unipolar inductor model for these stars, in particular what parameter values (component masses, orbital inclination and magnetic colatitude) can describe the X-ray and optical light curves. We find that for a dipole field on the primary star, the unipolar inductor model fails to match the data on V407 Vul for any combin?tion of parameters, and can' only match HM Cnc if the sparser set of observations of this star have been unluckily timed. In chapter 5 we present optical light curves of V407 Vul and HM Cnc. The optical and X-ray light curves of HM Cnc have been reported as being in antiphase, but we find that in fact the X-rays peak around 0.2 cycles after the maximum of the optical light, as seen also in V407 Vul. The X-rayjoptical phase shifts are well explained under the accreting models of the systems if most of the optical modulation comes from the heated faces of the mass donors and if the X-ray emitting spots are positioned in advance of the mass donors, as is expected given the angular momentum of the accreting XIV l II , Supplied by The British Library - 'The world's knowledge' 1 material. Some optical emission may also come from the vicinity of the X-ray spot. and we further show that this can explain the non-sinusoidal light curves of HM Cnc. The only significant difference between the two stars is that V407 Vul is observed to have the spectrum of a G star. The variation in position on the sky of a blend of a variable and a constant star can be used as a measure of their separation. and is sensitive to values well below the limit set by seeing. We apply this 'pulsation astrometry' to deduce that .the G star is separated from the variable by about 0.027 arcsec and hence plays no role in the vadability of V407 Vul. We show that light travel time variations could influence the period change in V407 Vul if it forms a triple system with the G star. In chapter 6 we present the study of flickering. Flickering is a characteristic of accreting systems. It is thought that the maximum frequency present in an accretion disc is the dynamic frequency at the inner accretion disc radius. In cataclysmic variable stars this would appear as a break in the power spectrum on frequencies 0.01 - 3 Hz. We use the high speed CCD Camera ULTRACAM to obtain high time resolution data on 14 cataclysmic variables in the hope of seeing the expected break in their power spectrum. We did not find such a break because the power spectra of the cataclysmic variable stars observed was steeper than was expected. We measure a power spectrum proportional to j-2.5 while previous studies reported it to be proportional to j-2. We compared flickering in cataclysmic variable stars with stellar flares and concluded that they have the same colour behaviour so they have could the same origin Le. magnetic reconnection. We also compare the power spectra of cataclysmic variable stars and of X-ray binaries in the optical and concluded that the latter are much shallower than cataclysmic variable stars. We argue that this implies that flickering in X-ray transients comes from the inner accretion disc in both systems since their outer discs are thought to be similar. Supplied by The British Library - 'The world's knowledge'
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Rebentisch, Eric. "Preliminary Observations on Program Instability." Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/7331.
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This white paper reports emerging findings at the end of Phase I of the Lean Aircraft Initiative in the Policy focus group area. Specifically, it provides details about research on program instability. Its objective is to discuss high-level findings detailing: 1) the relative contribution of different factors to a program’s overall instability; 2) the cost impact of program instability on acquisition programs; and 3) some strategies recommended by program managers for overcoming and/or mitigating the negative effects of program instability on their programs. Because this report comes as this research is underway, this is not meant to be a definitive document on the subject. Rather, is it anticipated that this research may potentially produce a number of reports on program instability-related topics. The government managers of military acquisition programs rated annual budget or production rate changes, changes in requirements, and technical difficulties as the three top contributors, respectively, to program instability. When asked to partition actual variance in their program’s planned cost and schedule to each of these factors, it was found that the combined effects of unplanned budget and requirement changes accounted for 5.2% annual cost growth and 20% total program schedule slip. At a rate of approximately 5% annual cost growth from these factors, it is easy to see that even conservative estimates of the cost benefits to be gained from acquisition reforms and process improvements can quickly be eclipsed by the added cost associated with program instability. Program management practices involving the integration of stakeholders from throughout the value chain into the decision making process were rated the most effective at avoiding program instability. The use of advanced information technologies was rated the most effective at mitigating the negative impact of program instability.
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Rodriguez, Luz-Maria. "New observations on cardiac arrhythmias." Maastricht : Maastricht : Universitaire Pers Maastricht ; University Library, Maastricht University [Host], 1994. http://arno.unimaas.nl/show.cgi?fid=6619.
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Updike, Adria C. "Gamma ray burst afterglow observations." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181668208/.
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Morrison, Jonathan David. "Lagrangian observations of rip currents." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Sep%5FMorrison.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, September 2007.Thesis Advisor(s): MacMahan, Jamie H. "September 2007." Description based on title screen as viewed on October 25, 2007. Includes bibliographical references (p. 39-41). Also available in print.
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Kuulkers, Erik. "EXOSAT observations of Z sources." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 1995. http://dare.uva.nl/document/91617.
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Greet, P. A. "Observations on the sodium airglow /." Title page, contents and abstract only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phg8166.pdf.
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Senior, Andrew. "Radio observations of geospace plasmas." Thesis, Lancaster University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429932.
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Ewen, Graham Bruce Lachlan. "Infrared limb observations of cloud." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427868.
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Duke, O. L. "Immunological observations in rheumatoid arthritis." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598674.
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Smale, Peter Rich. "Observations and inhomogeneity in cosmology." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/6868.
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We interpret distance measurements from nearby galaxies, type Ia supernovae, and gamma-ray bursts in the light of a cosmological model that incorporates a spatial averaging technique to account for the inhomogeneous distribution of
structure in the late-epoch Universe and the consequent importance of the location of the observer. In the timescape cosmology it is suggested that dark energy is a misidentification of gravitational energy gradients---and
consequently of the relative calibration of clocks and rulers---in a complex inhomogeneous structure. This model is consistent with the current supernova and gamma-ray burst data within the limits imposed by our understanding of the
systematic uncertainties, to the extent that a Bayesian model comparison with the standard model yields a preference for the timescape model that is “not worth more than a bare mention”.
In the spirit of the timescape model, of attempting to understand
the astrophysics with as few cosmological assumptions as possible, we
perform a model-independent analysis of galaxy distances in the local
Universe. We find that the rest frame of the Local Group provides a
more uniform Hubble expansion field than the rest frame of the CMB.
We find that the dipole in the Hubble expansion field coincides with
the dipole in the CMB temperature with a correlation coefficient of
-0.92, and that this pattern is induced within 60 h⁻¹ Mpc, provided
the variation in the distance-redshift relation due to the formation of
structure is taken into account.
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關志威 and Chi-wai Kwan. "Influential observations in factor analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B29803895.
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Dandy, C. L. "Observations of near-earth objects." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403268.
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Sim, David Anthony James. "Ultrasonographic observations on human pregnancy." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334475.
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Clayton, C. A. "Echelle observations of HII complexes." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382745.
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Leighton, P. "Observations on some bridged porphyrins." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355269.
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Johnson, Rosie Eleanor. "Infrared observations of Jupiter's ionosphere." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42409.
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In this thesis I have used infrared observations of Jupiter to investigate the flows of ions in the ionosphere and how they are coupled to the ionospheric heating in the auroral regions, determining the drivers of the heating and how they are related to the thermosphere and the magnetosphere. I investigated the H3+ line-of-sight velocity in the mid-to-low latitude region, derived from the Doppler shift of the Q(1,0-) emission line taken by IRTF-CSHELL. No evidence of flows in the region of the H Ly-α bulge predicted by a global circulation model were measured, and the H3+ ions in the mid-to-low latitude region were found to be corotating. Using observations taken by VLT-CRIRES, polar projections of the intensity and line-of-sight velocity of the H3+ ions in Jupiter’s northern auroral region were created. This revealed the ionospheric flows and how they relate to different morphological regions of the northern aurora. These flows vary from extremely sub-rotational to super-rotational, and the drivers of the flows range from the solar wind and magnetospheric interaction to a potential thermospheric driver. The same set of VLT-CRIRES observations are then used to derive the rotational temperature, column density, and total emission of the H3+ ions in the northern auroral regions. These properties were mapped onto polar projections, which revealed changes in temperature during the observations (over a short period of ~80 minutes). The changes in temperature could be caused by local time changes in particle precipitation energy, or they could be caused by the thermospheric response to a transient enhancement of solar wind dynamic pressure, as predicted by models. By comparing all of the H3+ properties, the complex interplay between heating by impact from particle precipitation and Joule heating, as well as cooling by the H3+ thermostat effect was revealed.
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Rhodes, Christophe Sebastian. "Cosmological observations in braneworld models." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615727.
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Lindsay, Simon Thomas. "X-ray observations of Mercury." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31433.
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Data from MESSENGER and the GOES solar activity archive are used to deduce properties of Mercury and its X-ray environment in preparation for the forthcoming ESA/JAXA BepiColombo mission to Mercury. Data from MESSENGER’s X-ray spectrometer operations at Mercury exhibit background X-ray enhancements which are identified as the results of astrophysical sources crossing the instrument field of view and of electron bombardment of the X-ray spectrometer causing fluorescence within the instrument. These electron enhancements are analysed and mapped, leading to a three-dimensional representation of low-energy electron populations in the Mercury environment, the distributions of which are associated with features of Mercury’s magnetosphere, including the sunward magnetopause and magnetic equator. The population is characterised, producing estimates of low-energy electron number densities which are consistent with previous observations. Thus, the X-ray spectrometer functions as a proxy detector for electrons with energies below the threshold of dedicated electron detectors. Variations in seasonal X-ray background flux observed by the MESSENGER X-ray spectrometer are investigated, with a modulation visible with a periodicity of one Mercury year. Several telemetry parameters, including temperature, show corresponding variations. The origin of the variation in background flux is identified as the calculation in spacecraft telemetry relating instrument live time to instrument integration time, which varies on the same yearly period. The GOES solar activity archive is used to generate a model of solar X-ray flux levels, with the intention of providing an estimate of the levels of X-ray flux the BepiColombo mission will encounter, and subsequently the volume and rate of data that the MIXS instrument will produce. This model is used to predict the likelihood of the instrument experiencing data loss events by exceeding the data storage available, and how this likelihood varies with the level of solar flux and the onboard storage space that is allocated to the instrument.
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Maxwell, Michael. "Multiband observations of recurrent novae." Thesis, University of Central Lancashire, 2014. http://clok.uclan.ac.uk/10719/.
Full textAbstract:
Recurrent novae are binary systems which undergo outbursts due to a thermonuclear runaway on a timescale of decades. Two systems, U Scorpii and RS Ophiuchi, are the main focus of this thesis having gone into outburst in 2010 and 2006 respectively. Optical and near-IR spectroscopy of U Sco obtained with facilities including the Liverpool Telescope, the Very Large Telescope, and the Southern African Large Telescope, as well as ultra-violet and optical spectroscopy of RS Oph obtained with the Ultra-Violet and Optical Telescope, are presented here. Observations of U Sco obtained in outburst are used to determine the helium abundance of the ejecta, with observations in quiescence used to constrain the nature of the companion star and the accretion disc. Observations of RS Oph are used to produce lightcurves of the decline from maximum to the post-outburst minimum. Analysis of optical and near-IR spectra following the 2010 outburst of U Sco leads to the determination of the reddening and the helium abundance. The reddening is found to be E(B-V) = 0.17 ± 0.14, consistent with previous estimates. The helium abundance, N(He)/N(H), is determined to be 0.122 ± 0.018, lower than previous estimates and suggesting that the companion is not helium rich. The fitting of model stellar atmospheres to observations of U Sco in quiescence, obtained ∼18-30 months after the 2010 outburst, constrains the effective temperature of the companion and indicates that it is a cool F or hot G star. The accretion disc is found to be still in a state of development until at least ∼18 months after outburst, contrary to previous studies. The strength of the Heii 4686 ̊A line in quiescence is found to be consistent with a high mass white dwarf accreting solar-abundance material at a high rate. The He line strengths do not require an overabundance of helium, as has been previously suggested, consistent with the solar abundance of helium found in the ejecta of the 2010 outburst. UVOT observations of RS Oph following the 2006 outburst are used to produce B and u′ lightcurves of the decline to minimum. These lightcurves are used in con- junction with published V and B lightcurves to show the change in the colour of the system throughout the outburst. Spectra of RS Oph show the spectroscopic evolution during the initial decline, plateau, final decline, and post-outburst minimum phases. SALT spectra obtained during the late decline phase of the 2011 outburst of a third recurrent nova, T Pyxidis, are used to derive a helium abundance of N(He)/N(H)= 0.161 ± 0.013, approximately twice the solar value. Very strong [O iii] lines are also detected.
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Hakansson, Nieto Carlos Guillermo. "Some observations to unconstitutional process." Derecho & Sociedad, 2017. http://repositorio.pucp.edu.pe/index/handle/123456789/117683.
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The unconstitutional process at the Peruvian Constitution (1993) has a progressive development in the jurisprudence of his top judicial institution to make constitutional interpretations; but the Congress needs to take a politic decision to promote some amendments at the future.
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Minini, Pascal. "Modélisation des observations longitudinales incomplètes." Paris 11, 2004. http://www.theses.fr/2004PA11T060.
Full textAbstract:
Au cours des études longitudinales, des sujets sont observés afin de mesurer l'évolution une réponse d'intérêt. Le protocole de ces études prévoit de recueillir un certain nombre de réponses pour chaque sujet. Cependant, il est extrêmement rare que toutes les mesures prévues soient effectivement réalisées. L'analyse des données incomplètes est devenu un thème majeur de la statistique au cours des dernières années. De nombreuses méthodes ont été proposées, mais il est généralement impossible de s'assurer de leur validité. Il est désormais recommandé de réaliser une analyse de sensibilité, afin d'évaluer dans quelle mesure les résultats d'une étude peuvent être affectés par différentes hypothèses concernant le processus de données manquantes. Ce rapport souligne la nécessité de l'analyse de sensibilité, et montre comment cet objectif peut être atteint dans trois situations différentes, les données normales, les données binaires et les données de survieIn longitudinal studies, subjects are repeatedly observed to obtain measurements of some response. The protocol of such studies plans to collect a fixed number of responses for each subject, during a predefined follow-up period. However, it is extremely rare that all the planned measurements are actually performed. The analysis of incomplete data has become a major topic in statistics during the last years. Many methods have been proposed, but it is generally impossible to check their validity. It is now recommended to perform a sensitivity analysis, to evaluate the extent to which the results from a study can be affected by different assumptions regarding the missing data process. This report highlights the need for a sensitivity analysis, and shows how this aim can be achieved in three different situations, normal data, binary data and survival data
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De, Michele Marcello. "Remote sensing observations of seismotectonics." Paris 6, 2010. http://www.theses.fr/2010PA066647.
Full textAbstract:
Pendant les 20 dernières années, notre connaissance de la déformation de la Terre a été complètement bouleversée par l’introduction de deux techniques de Géodésie spatiale. D’une part, ce que l’on appelle positionnement satellitaire (‘point positioning’) pas seulement à partir du système GPS (Global Positioning System) mais également à partir du système DORIS (Doppler Orbitography and Radio-positioning Integrated from Space). D’autre part, ont été développées des techniques d’imagerie satellitaire de corrélation d’images et d’interférométrie SAR (Synthetic Aperture Radar) ainsi que les méthodes de mesures de décalages sur des images panchromatiques à haute résolution spatiale. Ces nouvelles techniques, ont permis une série d’avancement scientifiques notamment la confirmation et l’amélioration de la théorie de la tectonique de plaques, la cartographie fine de déplacements sismiques et asismiques, l’amélioration de la compréhension des phénomènes de relaxation post sismiques, la détection de séismes lents et ‘silencieux’, la détection de signaux précurseurs de séismes ou d’éruptions volcaniques. Actuellement des nombreuses questions clés restent ouvertes. Notamment : l’importance relative de la déformation accommodée sismiquement en bords de plaques par rapport à la déformation totale et à la contrainte tectonique ; la contribution des séismes à la déformation par rapport au déplacement asismique sur les discontinuités. Le but de la présente Thèse de Doctorat, est d’étudier le potentiel, les limitations et la complémentarité des données issues de l’Observation de la Terre pour prendre en compte et essayer de répondre à certains aspects des questions exposées ci-dessus.
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Wilson, Sara R. "Control Charts with Missing Observations." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37623.
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Traditional control charts for process monitoring are based on taking samples from the process at regular time intervals. However, it is often possible in practice for observations, and even entire samples, to be missing. This dissertation investigates missing observations in Exponentially Weighted Moving Average (EWMA) and Multivariate EWMA (MEWMA) control charts. The standardized sample mean is used since this adjusts the sample mean for the fact that part of the sample may be missing. It also allows for constant control limits even though the sample size varies randomly. When complete samples are missing, the weights between samples should also be adjusted.
In the univariate case, three approaches for adjusting the weights of the EWMA control statistic are investigated: (1) ignoring missing samples; (2) adding the weights from previous consecutive missing samples to the current sample; and (3) increasing the weights of non-missing samples in proportion, so that the weights sum to one. Integral equation and Markov chain methods are developed to find and compare the statistical properties of these charts. The EI chart, which adjusts the weights by ignoring the missing samples, has the best overall performance.
The multivariate case in which information on some of the variables is missing is also examined using MEWMA charts. Two methods for adjusting the weights of the MEWMA control statistic are investigated and compared using simulation: (1) ignoring all the data at a sampling point if the data for at least one variable is missing; and (2) using the previous EWMA value for any variable for which all the data are missing. Both of these methods are examined when the in-control covariance matrix is adjusted at each sampling point to account for missing observations, and when it is not adjusted. The MS control chart, which uses the previous value of the EWMA statistic for a variable if all of the data for that variable is missing at a sampling point, provides the best overall performance. The in-control covariance matrix needs to be adjusted at each sampling point, unless the variables are independent or only weakly correlated.Ph. D.
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Jia, Xianzhe. "Ganymede's magnetosphere observations and modeling /." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1925733131&sid=9&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Kwan, Chi-wai. "Influential observations in factor analysis /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19003110.
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