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Dissertations / Theses on the topic 'Observational signatures'
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Sming, Yue-Lin Sming. "Observational signatures of supersymmetric dark matter." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544174.
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Sarkar, Tamal. "Search for some observational signatures of general relativity." Thesis, University of North Bengal, 2017. http://hdl.handle.net/123456789/2643.
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Hamilton, Devon. "Observational signatures of convection in solar type stars." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58914.pdf.
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Harding, Paul. "The formation of the Galactic bulge and halo: Observational signatures." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289743.
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The evolution of tidal debris within the Galactic halo has been simulated to determine its detectability within the constraints imposed by currently available telescopes and instrumentation. Observations of the simulations show that there is a very high probability of detecting and quantifying the presence of tidal debris with a pencil beam survey of 100 square degrees. The debris is readily detectable via the presence of kinematic substructure in the radial velocities. The detection probabilities show surprisingly little change with the age of the debris. Accretion events that occurred up to ≳ 10 Gyr ago can be detected. In the limiting case of a single 10⁷ M(⊙) satellite contributing 1% of the luminous halo mass the detection probability is a few percent using just the velocities of 100 halo stars in a single 1 deg² field. The detection probabilities scale with the accreted fraction of the halo and the number of fields surveyed. Accurate CMDs in the Washington photometric system have been derived for four fields spanning the range of Galactocentric distances from 1.5 to 5.5 kpc. The differential reddening variations within each field were corrected by a new technique optimized for the highly variable reddening variations found in bulge fields. Abundance distributions in the four fields were derived from color-color diagrams in the Washington system. The quality of the photometry which yields photometric abundances with σ[Fe/H] ≲ 0.25 dex (including reddening errors) supplemented by the luminosity information from observations in the 51 filter allows contamination by foreground and background stars to be eliminated from the bulge sample. A clear abundance gradient is seen which is consistent with the change in morphology of the CMDs. The abundance gradient is predominantly due to a decrease in the fraction of stars in the metal-rich shoulder of the abundance distributions. The modal abundance changes little. Relative to Baade's window the magnitude distribution of clump stars in the L354 B-06 field implies a bar angle of ≃ 40 deg.
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Bending, Victoria Louise. "Extra-solar planetary atmospheres and interior structure : implications for observational signatures." Thesis, Open University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701075.
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Hot Jupiter exoplanets are a previously unknown and fascinating field of study. Models of planet formation based only around the Solar System did not predict their existence, occupying as they do the orbital region less than 0.1 AD from their parent stars. Believed to be tidally locked, always presenting the same face to the star, these gas giants are bathed in intense irradiation, and inhabit a regime alien to anything known in the Solar System. As exoplanetary surveys discover an increasing number of planets, the ubiquity of hot Jupiters in the galaxy continues to be confirmed. Both the evolution and the atmospheric dynamics of these unusual planets are natural focuses of study. However, most authors have historically concentrated on one or the other of these two lines of enquiry, although both are linked. In the case of gas giants in particular, which have no true ground or otherwise easily defined surface layer, the two regimes blend towards the outer layers of the planet. This convergence renders the possibility of model overlap ever more relevant, a possibility that is here studied, both independently and together, ultimately continuing to the modelling of the specific known exoplanets HD 209458b, HD 189733b, and WASP-7b. It is found that, while it is reasonable for interior evolution model results to be used to provide boundary conditions and atmospheric characteristics for the purposes of three-dimensional atmospheric modelling, the reverse is a much more difficult propo- sition, providing few truly relevant constraints. Observational characteristics are also predicted, with cyclic variability found in the case of HD 209458b, a more permanently variable state in the case of HD 189733b, and very little longitudinal temperature variation for the calmer atmosphere of WASP-7b.
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Patrick, Antolin Tobos. "Predicting observational signatures of coronal heating by Alfven waves and nanoflares." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/126571.
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Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(理学)<br>甲第14894号<br>理博第3463号<br>新制||理||1507(附属図書館)<br>27332<br>UT51-2009-M808<br>京都大学大学院理学研究科物理学・宇宙物理学専攻<br>(主査)教授 柴田 一成, 教授 一本 潔, 教授 嶺重 慎<br>学位規則第4条第1項該当
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Jürgens, Gero [Verfasser], and Matthias [Akademischer Betreuer] Bartelmann. "Evolution and observational signatures of cosmic structures / Gero Jürgens ; Betreuer: Matthias Bartelmann." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177148463/34.
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Ogawa, Takumi. "Observational Signatures of Super-Eddington Accretors:Views from Radiation Hydrodynamics/Radiation Transfer Simulations." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263470.
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Hall, Cassandra. "Using numerical simulations to identify observational signatures of self-gravitating protostellar discs." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29585.
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In this thesis, I study numerical and semi-analytical models of self-gravitating protostellar discs, with the aim of furthering our understanding of the role of disc-self gravity in planet formation. At the time of writing, the ALMA era of observational astronomy is upon us. Therefore, I place my research into this context with synthetic images of both numerical and semi-analytical models. I begin with an examination into the apparent lack of convergence, with increasing resolution, of the fragmentation boundary in Smoothed Particle Hydrodynamics (SPH) simulations of a protostellar disc. I run a suite of SPH with different numerical implementations, and find that even very similar implementations can fundamentally change the final answer. I analyse a suite of SPH simulations that fragment to form gravitationally bound objects, with the motivation of informing future population synthesis model development. I find that fragment-fragment and fragment-disc interaction dominates the orbital evolution of the system even at very early times, and any attempt to produce a population of objects from the gravitational instability process must include these interactions. Before a disc fragments, it will go through a self-gravitating phase. If the disc cools globally on a timescale such that it is balanced by heating due to gravitational stresses, the disc will be in a state of quasi-equilibrium. So long as the disc mass is sufficiently low, and spirals are sufficiently tightly wound, then angular momentum transport can be described by the local approximation, for which there is an analytical description. Using this analytical description, I develop an existing 1D model into 3D, and examine a wide range of parameter space for which disc self-gravity produces significant non-axisymmetry. Using radiative transfer calculations coupled with synthetic observations, I determine that there is a very narrow range of parameter space in which a disc will have sufficiently large gravitational stresses so as to produce detectable spirals, but the stresses not be so large as to cause the disc to fragment. By developing a simple analytical prescription for dust, I show that this region of parameter space can be broadened considerably. However, it requires grains that are large enough to become trapped by pressure maxima in the disc, so I conclude that if self-gravitating spiral arms are detected in the continuum, it is likely that at least some grain growth has taken place.
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Zach, Juergen Johann. "Observational Signatures of the Macroscopic Formation of Strange Matter during Core Collapse Supernovae." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1053470113.
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Winner, Georg Eckhard Verfasser], and Christoph [Akademischer Betreuer] [Pfrommer. "On the Evolution and Observational Signatures of Cosmic Ray Electrons in Magnetohydrodynamical Simulations / Georg Eckhard Winner ; Betreuer: Christoph Pfrommer." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://nbn-resolving.de/urn:nbn:de:bsz:16-heidok-289531.
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Winner, Georg Eckhard [Verfasser], and Christoph [Akademischer Betreuer] Pfrommer. "On the Evolution and Observational Signatures of Cosmic Ray Electrons in Magnetohydrodynamical Simulations / Georg Eckhard Winner ; Betreuer: Christoph Pfrommer." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1220836303/34.
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Johnston, Katharine G. "Observational signatures of massive star formation : an investigation of the environments in which they form, and the applicability of the paradigm of low-mass star formation." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1895.
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This thesis presents both a study of the cluster-scale environments in which massive stars form, investigating in particular how the ionized gas in these regions relates to the molecular star-forming material, as well as detailed studies of two luminous forming stars, AFGL 2591 and IRAS 20126+4104, to determine whether they are forming similarly to their low-mass counterparts. The results of this work include the identification of 35 HII regions (20 newly discovered) via a radio continuum survey of ionized gas towards 31 molecular cluster-forming clumps. The observed ionized gas was found to be preferentially associated with the clumps, which were shown to have a range of evolutionary stages. The massive star formation efficiency was determined for the clumps with associated ionized gas, and a relationship was found between the mass of the clumps and the mass of their embedded massive stars. By modelling the SEDs and images of AFGL 2591 and IRAS 20126+4104, it was found that the geometry of their circumstellar material was generally consistent with an envelope plus disk, similar to that expected for low-mass protostars. However, within the central ~1800 AU, the mid-IR images of IRAS 20126+4104 were better described by only a flattened envelope, suggesting that the radiation from IRAS 20126+4104 may be affecting the regions closest to the star. Observations of the ionized and molecular gas towards AFGL 2591 were carried out, and a photoionization code was developed to interpret these observations. The results showed that the observed 3.6 cm emission is likely to be produced by both a shock-ionized jet and a hypercompact HII region that does not appear to have disrupted the jet or the large-scale circumstellar environment. In addition, the C¹⁸O(1-0) emission observed towards AFGL2591 traces the densest parts of the outflow, with the blue-shifted emission exhibiting many of the properties of the outflows from low-mass protostars.
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Etienne, Christian. "Réalisation et évaluation d'un sodar monostatique : étude des signatures sodars en fonction de paramètres météorologiques." Orléans, 1986. http://www.theses.fr/1986ORLE0404.
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Le but de ce travail a été la réalisation et l'évaluation d'un sodar simple monostatique à réflectivité. Les signatures très caractéristiques de la basse atmosphère fournies par ce sodar pendant trois mois, après avoir été classées sont comparées a celles obtenues aux USA, au Japon et au Canada. Puis une étude climatologique statistique comparant ces signatures sodars à différentes données météorologiques, permet d'établir des corrélations très étroites entre les différents échos sodars et les observations météorologiques principales telles que la température, l'humidité. . . Mais aussi entre l'évolution de la couche limite observée par le sodar et une donnée relevée au sol, la température du point de rosée
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Trottier, Eric. "Recherche de signatures spectrales d’objets astronomiques variant ultra rapidement dans les relevés spectroscopiques." Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29658/29658.pdf.
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Meng, Huan Y. A., George H. Rieke, Kate Y. L. Su, and András Gáspár. "The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623246.
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We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to similar to 40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, IC 4665, Chamaeleon I, Orion OB1a and OB1b, Taurus, the beta Pictoris Moving Group,. Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius-Centaurus, and Tucana-Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P(D), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 mu m decays relatively slowly initially and then much more rapidly by similar to 10 Myr. However, there is a continuing component until similar to 35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12-20 Myr, including similar to 13% of the original population, and with a post-peak mean duration of 10-20 Myr.
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Alkahtani, Abdulaziz M. A. l.-Musa. "Free hand simulation of Arabic signatures : Forensic examination and statistical observations." Thesis, Staffordshire University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522387.
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Matthews, Sarah H. "Thermal and nonthermal radiation signatures in solar flares : models and observations." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309388.
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Gaspar, Andras. "Observations and Models of Infrared Debris Disk Signatures and their Evolution." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202982.
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In my thesis I investigate the occurrence of mid-infrared excess around stars and their evolution. Since the launch of the first infrared satellite, IRAS, we have known that a large fraction of stars exhibit significant levels of infrared emission above their predicted photospheric level. Resolved optical and infrared images have revealed the majority of these excesses to arise from circumstellar disk structures, made up of distributions of planetesimals, rocks, and dust. These structures are descriptively called debris disks. The first part of my thesis analyzes the Spitzer Space Telescope Observations of δ Velorum. The 24 μm Spitzer images revealed a bow shock structure in front of the star. My analysis showed that this is a result of the star’s high speed interaction with the surrounding interstellar medium. We place this observation and model in context of debris disk detections and the origin of λ Boötis stars. The second part of my thesis summarizes our observational results on the open cluster Praesepe. Using 24 μm data, I investigated the fraction of stars with mid-infrared excess, likely to have debris disks. I also assembled all results from previous debris disk studies and followed the evolution of the fraction of stars with debris disks. The majority of debris disks systems are evolved, few hundred million or a Gyr old. Since the dissipation timescale for the emitting dust particles is less than the age of these systems, they have to be constantly replenished through collisional grinding of the larger bodies. The last two chapters of my thesis is a theoretical analysis of the collisional cascade in debris disks, the process that produces the constant level of dust particles detected. I introduce a numerical model that takes into account all types of destructive collisions in the systems and solves the full scattering equation. I show results of comparisons between my and other published models and extensive verification tests of my model. I also analyze the evolution of the particle size distribution as a function of the variables in my model and show that the model itself is quite robust against most variations.
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Vontrat-Reberac, Aurélie Karine. "Etude des cornets polaires : observations in-situ à haute altitude et modélisation et observations des signatures ionosphériques." Versailles-St Quentin en Yvelines, 2003. http://www.theses.fr/2003VERS0023.
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Au niveau des pôles magnétiques, les lignes du champ magnétique de la Terre convergent et forment des entonnoirs appelés cornets polaires. Ces régions très localisées sont très sensibles aux conditions interplanétaires. Avec ses 4 satellites, la mission CLUSTER permet pour la première fois d'étudier la structure tridimensionnelle des régions frontières et de séparer les effets spatiaux des effets temporels. Nous avons exploité cette capacité pour analyser la dynamique spatio-temporelle de structures de particules observées dans le cornet polaire lors d'événements de reconnexion des champs magnétiques terrestre et interplanétaire. Les observations dans l'ionosphère au pied des cornets polaires par le radar ESR montrent que des particules du cornet polaire entrent en collision avec l'ionosphère et y produisent de l'ionisation, du chauffage. Nous avons interprété ces observations à l'aide de la modélisation de leurs effets immédiats et à plus long terme sur les paramètres ionosphériques<br>Near the magnetic poles, the magnetic field lines converge and form funnels called polar cusps. These very localized regions are very sensitive to interplanetary conditions. With its four satellites in, the CLUSTER mission allows for the first time the study of the tri-dimensional structure of boundary regions and the separation of spatial and temporal effects. We have exploited this capability to analyse the space and time dynamics of particle structures observed in the high-altitude polar cusp during events of reconnection between the terrestrial and interplanetary magnetic fields. Ionospheric observations at the footprint of polar cusps by the radar ESR show that polar cusp particles collide with the ionosphere and create ionization, heating. We have interpreted these observations from the modeling of their immediate and long-term effects on the ionospheric parameters
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Occhipinti, Giovanni. "Observations multi-paramètres et modélisation de la signature ionosphérique du grand séisme de Sumatra." Paris, Institut de physique du globe, 2006. http://www.theses.fr/2006GLOB0012.
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Ce travail de thèse fait l'objet d'une étude sur le couplage entre la Terre solide et ses enveloppes fluides, qu'il s'agisse de l'océan, de l'atmosphère neutre ou de sa partie ionisée. Les anomalies atmosphériques et ionosphériques de nature sismique seront traitées en détail avec une attention particulière aux effets produits par la propagation de l'onde de Rayleigh et de tsunamis. L'effet de la première sur le plasma ionosphérique a été mis en évidence depuis les années soixante grâce aux observations par sondeur Doppler et, récemment, par GPS via la mesure du contenu électronique total (TEC). La perturbation ionosphérique produite par l'onde de Rayleigh du séisme du 28 mars 2005 (M=8. 2) et observée par sondeur Doppler et radar transhorizon a été analysée ici à la lumière des modélisations. Ceci a permis de valider la détection par radar transhorizon, jamais prouvée auparavant, ajoutant un outil très puissant à la sismologie ionosphérique. Concernant la détection de tsunamis par sondage ionosphérique, suggérée théoriquement en 1972, elle restait, jusqu'au 26 décembre 2004, très difficile à prouver vue la difficulté de distinguer les perturbations tsunamigéniques des perturbations ionosphériques itinérantes (TIDs). Sans négliger les anomalies observées dans le plasma ionosphérique lors du tsunami de Sumatra, qui seront passées en revue, l'effort premier de ce travail a été le développement d'une méthode de modélisation 3D du couplage océan- atmosphère-ionosphère. Cela a permis d'une part de reproduire la signature tsunamigénique observée le 26 décembre 2004 dans les données du TEC des satellites Topex/Poseidon et Jason-1, d'autre part d'explorer synthétiquement les méthodes de sondage ionosphérique aptes à la détection des tsunamis. Ces résultats, validant l'existence et la détectabilité de la signature ionosphérique des tsunamis, ouvrent d'excitantes perspective dans la détection et la surveillance des océans
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Boudin, Nathalie. "Recherche de signatures spectrales de cations aromatiques dans l'absorption diffuse interstellaire : confrontation spectroscopie de laboratoire, observations astronomiques." Paris 11, 2001. http://www.theses.fr/2001PA112348.
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Les Hydrocarbures Aromatiques Polycycliques (PAHs) sont maintenant reconnus comme un constituant important de la phase gazeuse du milieu interstellaire. Cette famille de molécules et en particulier leurs dérives ioniques semble être l'un des candidats les plus prometteurs pour l'identification des Bandes Diffuses Interstellaires (DIBs). Ces bandes d'absorption sont observées dans le visible sur des spectres d'étoiles masquées par des nuages. L'identification de PAHs comme molécules responsables de ces bandes ne peut se faire que par comparaison directe avec des spectres de PAHs obtenus dans des conditions se rapprochant le plus possible de celles du milieu interstellaire. Ces conditions de basse température et d'absence de collisions ont été reconstituées en laboratoire grâce à la technique du jet supersonique. Un complexe de van der Waals PAH-Ar est alors ionise par ionisation résonnante à deux photons. L'absorption par cet ion d'un photon laser visible accordable provoque le départ de l'atome d'argon, et la détection de cette dissociation au spectromètre de masse permet, l'obtention du spectre du cation PAR. Grâce a cette technique, les spectres du phénylacétylène(+)-Ar et de l'acénaphthène(+)-Ar ont pu être enregistrés. Le profil spectral des bandes est large et lorentzien, indiquant une dynamique intramoléculaire dominée par des mécanismes de conversion interne ultrarapide. Deux campagnes d'observations au Télescope Bernard Lyot du Pic du Midi ont permis la recherche systématique de ces bandes larges grâce à un protocole d'observation et à un traitement des données spécifiques. Des limites supérieures d'abondance on été déterminées pour cinq cations PAHs. Les zones d'absorption interstellaire repérées dans nos spectres sont de largeur variable et certaines sont vraisemblablement le résultat d'une combinaison de l'absorption de plusieurs espèces. D'après nos mesures entre 525 et 840 nm, l'absorption interstellaire diffuse représente 87 % de l'absorption interstellaire<br>Polycyclic Aromatic Hydrocarbons (PAHs) are now recognized as an important constituent of the interstellar medium gaseous phase. This family of molecules and in particular their ionic derivatives seems to be one of the most promising candidates for identification of the Diffuse Interstellar Bands (DIBs). These absorption bands are observed in the visible spectral range in the spectra of stars partially masked by gas cloud. The possible identification of PAHs as molecules responsible for these bands must be done through direct comparison with PAHs spectra recorded in conditions as close as possible to those of the interstellar medium. These low temperature and collision-free conditions can be recreated in the laboratory with supersonic beams. A van der Waals complex PAH-Ar is then ionized by resonant two-photon ionization. The ion absorption of a tunable visible laser photon causes the argon departure, and the detection of this dissociation by a mass spectrometer allows the recording of the PAH cation spectrum. Using this technique, the spectra of phenylacetylene(+)-Ar and of acenaphthene(+)-Ar could be obtained. The spectral profile is wide and lorentzian, showing an intramolecular dynamics dominated by ultrafast internal conversion. Two observation campaigns with the Télescope Bernard Lyot at the Pic du Midi allowed us to perform a systematic search for this broad bands, thanks to specific observational protocole and data processing. Upper-limits of abundance were determined for five PAH cations. Interstellar absorption zones identified in our spectra are of variable width and some of them are very likely the result of a combination due to several species. According to our measurements between 525 and 840 nm, the diffuse interstellar absorption represents 87 % of the interstellar absorption in front of BD +404220 star
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Bernard, Jérémy. "Signature géographique et météorologique des variations spatiales et temporelles de la température de l'air au sein d'une zone urbaine." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0006.
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Ce travail de thèse propose une modélisation des différences de température d'air observées au sein d'une agglomération. Elle repose sur des formulations simples établies à partir de l'observation des interactions qui existent entre la formation d'un microclimat, son contexte géographique et les conditions météorologiques. Cinq réseaux de capteurs de température d'air sont utilisés,permettant de qualifier les microclimats de trois agglomérations du grand ouest français : Nantes, Angers et La Roche-sur-Yon. Un état de l'art des méthodes d'analyse du climat urbain est réalisé au chapitre 1. Le chapitre 2 est consacré à la présentation et à l'analyse de chacun des réseaux de capteurs. Une méthode de correction des données erronées est également proposée. Au chapitre 3, les différences de température mesurées entre les sites sont expliquées à partir de régressions linéaires multiples utilisant des indicateurs géographiques. Ces indicateurs, descriptifs des formes urbaines et de la typologie des sols de chaque site, sont calculés au sein d'un cercle de rayon de 500 m centré sur chaque station. L'intensité de l'îlot de chaleur urbain est modélisé à partir d'une régression linéaire multiple utilisant des variables météorologiques telles que la vitesse du vent ou le rayonnement solaire comme variables explicatives. Préalablement à la calibration, les données sont triées de différentes manières afin d'élaborer plusieurs modèles. Le plus performant est identifié au chapitre 4 en confrontant les valeurs mesurées par les cinq réseaux de capteurs à celles estimées par chacun des modèles. Au chapitre 5, trois exemples d'application possible du travail réalisé sont présentées<br>This thesis presents a method to model air temperature differences within a conurbation . It relies on the analysis of the existing relationships between urban microclimate,geographical context and weather conditions. To do so, five air temperature networks located in three western France conurbations are utilized : Nantes, Angers and La Roche sur-Yon. A state of the art of the methods used to analyze urban climate is realized in chapter 1. In Chapter 2, air temperature networks are presented and analyzed and a methodology to correct biased data is proposed. In Chapter3 air temperature differences observed between the network sites are modelled from multiple linear regressions, using weather variables such as wind speed or solar radiation as explicative variables. Before the calibration step, data is sorted in a variety of ways in order to elaborate several models. The most performant model is identified in chapter4, confronting data observed using the five temperature networks to data estimated from each of the models.Chapter 5 illustrates the results of the work through three practical applications
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Deligny, Olivier. "Observatoire Pierre Auger : analyse des gerbes inclinées, Observation de neutrinos d'ultra haute énergie, et signatures d'une origine locale pour les rayons cosmiques chargés." Paris 6, 2003. https://tel.archives-ouvertes.fr/tel-00002995.
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Wilson, Belinda R. "The Forgotten Signature: An Observational Study on Policy of Securing Identity in Prevention of Identity Theft and Credit/Debit Card Fraud at Retail Store POS Terminals." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3074.
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Identity theft and credit and bank card fraud is increasing in America and worldwide. Given the current statistics of its prevalence and practices around the world, many in government are starting to take critical notice due to its impact on a nation’s economy. Limited amounts of research have been conducted regarding the practices of applying the Routine Activities Theory (Cohen & Felson, 1979) to better equip store managers in understanding the critical need for capable and effective point of sale guardianship for in-store prevention of credit or bank card fraud due to identity theft. This research has used qualitative observational studies to investigate the presence of or lack of capable guardianship at point of sales transactions in large department stores where a majority of in-store credit and bank card fraud loss occurs. Findings conclude an overwhelming lack of capable guardianship at retail store POS terminals.
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Deligny, Olivier. "Observatoire Pierre Auger : Analyse des gerbes inclinées, observation de neutrinos d'ultra haute énergie, et signature d'une origine locale pour les rayons cosmiques chargés." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2003. http://tel.archives-ouvertes.fr/tel-00002995.
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L'observatoire Pierre Auger se propose de recueillir une statistique sans précédent concernant le spectre des rayons cosmiques d'ultra haute énergie. Les quelques données actuelles suggèrent une absence de coupure GZK, coupure liée à la distance d'atténuation des protons dans un milieu de propagation tel que le rayonnement fossile à 3K.<br> Après avoir étudié l'effet des champs magnétiques extragalactiques sur la propagation des rayons cosmiques et l'influence sur le spectre, une grande partie du chapitre consacré à la description de l'expérience Auger sera laissée au système d'acquisition des données.<br> L'étude des gerbes atmosphériques initiées dans la haute atmosphère sous incidence rasante est riche d'enseignements concernant la possibilité de détection de neutrinos. Une procédure de reconstruction de l'énergie des gerbes rasantes hadroniques est formalisée et appliquée aux événements du prototype dans le chapitre 4, et le calcul de la sensibilité aux neutrinos du détecteur complet est donné dans le chapitre 5.<br> Enfin, l'analyse des données de l'année 2002 du réseau prototype de l'expérience Auger est l'objet du chapitre 6.
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Quentin, Céline. "Etude de la surface océanique, de la signature radar et de ses interactions avec les flux turbulents de quantité de mouvement dans le cadre de l'expérience FETCH." Paris 6, 2002. https://tel.archives-ouvertes.fr/tel-00010934.
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QUENTIN, Céline Gwenaëlle. "Etude de la surface océanique, de sa signature radar et de ses interactions avec les flux turbulents de quantité de mouvement dans le cadre de l'experience FETCH." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2002. http://tel.archives-ouvertes.fr/tel-00010934.
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L'objectif principal est l'étude de l'état de la mer et de ses relations avec les flux turbulents d'énergie et avec le signal radar rétrodiffusé. L'étude est basée sur les données de l'expérience FETCH (« Flux, Etat de la mer et Télédétection en Conditions de fetcH limité ») qui s'est déroulée dans le golfe du Lion, Méditerranée Occidentale, en Mars-Avril 1998. L'état de la mer a été étudié à partir de mesures in situ (bouées), et par télédétection aéroportée (radar RESSAC) et spatiale (altimètres TOPEX et ERS). Plusieurs états de mer (mer en développement, mer mixte et houle) associées à des situations météorologiques variées (Mistral, Tramontane, ou Marin) ont été analysés. La séparation du spectre des vagues en composantes de mer du vent (vagues générées par le vent local) ou houle a permis de classifier les états de mer. La loi de croissance des vagues a été établie pour les cas de pure mer observés localement par la bouée. . Cette loi diffèresensiblement de celles citées dans la littérature. Ce jeu de données a servi de base à une étude comparative entre modèles de prévision et observations, qui a montré la nécessité, pour cette région côtière, d'utiliser un champ de vent et un modèle d'état de mer de fine résolution spatiale. Une analyse de l'influence de l'état de la mer sur les flux de quantité de mouvement a été menée à partir des données de turbulence acquises sur une bouée (ASIS) et du navire de recherche (Atalante). En condition de mer du vent, l'influence de l'âge des vagues sur les flux de quantité de mouvement a été montrée. Mais aucune relation entre la pente significative des vagues et les paramètres des flux turbulents n'a été mise en évidence sur les données de l'expérience FETCH. L'analyse du signal radar à faible incidence (autour de 12°) a montré une dépendance très faible de la moyenne quadratique des pentes de la surface aux paramètres tels que la force du vent, l'âge ou la pente significative des vagues.
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Riccio, Giuseppe. "The Observational Signatures of Cosmic Strings." Tesi di dottorato, 2009. http://www.fedoa.unina.it/3790/1/riccio.pdf.
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Cosmic strings were postulated by Kibble in 1976 and, from a theoretical point of view, their existence finds support in modern superstring theories, both in compactification models and in theories with extended additional dimensions. One of the best observational evidences for cosmic strings is the gravitational lensing effects they produce. A first effect is produced by an intervening string along the line of sight which splits in two components (double images) faint background galaxies, thus forming a chain of lensed galaxies along the path of the string. The second optical method is the serendipity discovery through anomalous lensing of extended objects. The huge ratio existing between the string width and length leads to a sort of step function signature on the gravitationally lensed images of background sources. The optical research of cosmic strings signatures suffers from many spurious effects mainly induced by the fact that, in order to be effective, the detection of background galaxies needs to be pushed down to very low flux limits. At these flux levels photometric errors, as well as noise statistics increase the number of spurious detections and, for instance, an application to the Sloan Digital Sky Survey leads to an huge and unrealistic number of candidate pairs. One way to minimize the contamination introduced in the catalogues by the spurious detection, is to increase the contrast by selecting pairs in the 3D space, i.e. by attributing to each galaxy a redshift estimate. At this purpose, a new method for photometric redshifts estimation has been created. The method is based on multiwavelength photometry and on a combination of various data mining techniques developed under the EuroVO and NVO frameworks for data gathering, pre-processing and mining, while relying on the scaling capabilities of the computing grid. This method allowed us to obtain photometric redshifts with an increased accuracy (up to 30%) with respect to the literature. The second fundamental observational evidence for cosmic strings is the signature they are expected to leave in the CMB a signature which may be sought for in the available WMAP data and in the soon to come Planck data. Theory shows that a moving string should produce a step-like discontinuity of low S/N ratio in the CMB, as a consequence of the Doppler shift due to the relative velocity between the string and the observer, thus causing the temperature distribution to deviate from a Gaussian. In the simplifying assumption that the string is a straight discontinuity in space time, we used the S.Co.P.E. computational grid to produce a large number of simulations covering a wide range of values for the velocity of the string, its direction and its distance from the observer. Simulations are produced using a C++ code that generates realistic maps of the CMB temperature distribution in presence of a straight cosmic string. By varying its characteristic parameters, it is possible to explore the signatures left by various types of moving strings. In order to amplify the step-like discontinuity and smooth the noise, maps are then subjected to a “squeezing” procedure. Successively, on the “squeezed” maps, we tested some filters that recognizes high value differences between close pixels. The excellent results of our filter on simulations prompted us to apply it on WMAP 5 years data.
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Fernandez, Elizabeth Rose. "Observational signatures of the first stars : from the near infrared background to Lyman-[alpha] emitters." 2008. http://hdl.handle.net/2152/17868.
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Bogdanovic, Tamara. "Close encounters of black holes, stars, and gas in galactic nucle a study of the observational signatures /." 2006. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1537/index.html.
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Che-WeiChang and 張哲維. "Observation of Kondo Signatures in Spin-Orbit Coupled Quantum Wires." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/13338835550030194844.
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Law, Colin Christian. "Observations of magnetic signatures and structure in the dayside ionosphere of Venus." Thesis, 1993. http://hdl.handle.net/1911/13753.
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Present models of the Venus solar wind interaction do not allow for changes in the orientation of the field as you approach the planet. Analysis of high resolution magnetic field data from the Pioneer Venus Orbiter spacecraft has revealed two distinct field rotations that are observed to occur in conjunction with the dayside ionosphere and ionopause. These rotations are a result of the velocity shear at the ionopause and indicate an alignment of the magnetic field with the day to night ionospheric plasma flow. From these results a new configuration of the dayside field draping has been determined. In addition, the field diagnostics discovered here can be used to probe the ionosphere of Mars which may otherwise go unobserved due to a lack of ion instrumentation onboard the Mars Observer spacecraft.
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Corlies, Lauren Nicole. "Observationally Constrained Metal Signatures of Galaxy Evolution in the Stars and Gas of Cosmological Simulations." Thesis, 2016. https://doi.org/10.7916/D8FF3SJC.
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The halos of galaxies - consisting of gas, stars, and satellite galaxies - are formed and shaped by the most fundamental processes: hierarchical merging and the flow of gas into and out of galaxies. While these processes are hard to disentangle, metals are tied to the gas that fuels star formation and entrained in the wind that the deaths of these stars generate. As such, they can act as important indicators of the star formation, the chemical enrichment, and the outflow histories of galaxies. Thus, this thesis aims to take advantage of such metal signatures in the stars and gas to place observational constraints on current theories of galaxy evolution as implemented in cosmological simulations.
The first two chapters consider the metallicities of stars in the stellar halo of the Milky Way and its surviving satellite dwarf galaxies. Chapter 2 pairs an N-body simulation with a semi-analytic model for supernova-driven winds to examine the early environment of a Milky Way-like galaxy. At z=10, progenitors of surviving z=0 satellite galaxies are found to sit preferentially on the outskirts of progenitor halos of the eventual main halo. The consequence of these positions is that main halo progenitors are found to more effectively cross-pollute each other than satellite progenitors. Thus, inhomogeneous cross-pollution as a result of different high-z spatial locations of different progenitors can help to explain observed differences in abundance patterns measured today. Chapter 3 expands this work into the analysis of a cosmological, hydrodynamical simulation of dwarf galaxies in the early universe. We find that simple assumptions for modeling the extent of supernova-driven winds used in Chapter 2 agree well with the simulation whereas the presence of inhomogeneous mixing in the simulation has a large effect on the stellar metallicities. Furthermore, the star-forming halos show both bursty and continuous SFHs, two scenarios proposed by stellar metallicity data. However, the metallicity distribution functions of the simulated halos are both too metal rich and too peaked when compared to the data. This comparison reveals that a complex SFH and a broad metallicity distribution can develop rapidly in the early Universe.
The third chapter moves to the present day with a consideration of the circumgalactic medium (CGM) around nearby Milky Way-like galaxies. We compare a cosmological simulation of a Milky Way-like galaxy to recent absorption line data and find that a reduced extragalactic ultraviolet background brings the column density predictions into better agreement with the data. Similarly, when the observationally derived physical properties of the gas are compared to the simulation, we find that the simulation gas is always at temperatures approximately 0.5 dex higher. Thus, similar column densities can be produced from fundamentally different gas. Metal-line emission is then considered as a complementary approach to studying the CGM. From the simulations, we find that the brightest emission is less sensitive to the extragalactic background and that it closely follows the fundamental filamentary structure of the halo. This becomes increasingly true as the galaxy evolves from z = 1 to z = 0 and the majority of the gas transitions to a hotter, more diffuse phase. Finally, resolution is a limiting factor for the conclusions we can draw from emission observations but with moderate resolution and reasonable detection limits, upcoming instrumentation should place constraints on the physical properties of the CGM.
Future work advancing the techniques in this thesis remain promising for putting new observational constraints on our theories of galaxy evolution.
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Liu, Chih-Yuan, and 劉志原. "SEARCH FOR SIGNATURE OF WAVES ON THE SURFACE OF NEUTRON STARS - LONG-TERM X-RAY OBSERVATIONS OF PSR B1509-58." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/07743504838549394738.
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碩士<br>國立清華大學<br>天文研究所<br>91<br>The stable pulsar PSR B1509-58 has been monitored with the Rossi X-ray Timing Explorer (RXTE) for seven years, since the start of that mission in January 1996. The long-term observation has enabled us to determine the first and the se
cond period derivatives which can help us to search for other possible periodicities with data over a long time span. These possible periods may reveal properties of MHD waves on the surface of neutron stars, and thus promote our understand
ing of neutron star physics.
As the first of such attempts, we applied the H-test to RXTE/PCA data of PSR B1509-58 spanning from 1996 to 2002, consisting of more than 3*10^7 photon events, to search for periods other than the spin period. A search in the period
range of 0~0.3 sec with 1-msec steps was conducted. No other periods were found. Some suspicious signatures, however, deserve further investigation. Moreover, the search sampling rate (1 msec per step) is too loose. A study with a higher sampling rate and a wider search range, which requires more computing time, is in preparation.