Sediment accumulation and loss were measured in a water tupelo (Nyssa aquatica)- baldcypress (Taxodium distichum) forested wetlandin years 2, 7, 10 and 12 following harvesting disturbance. A 3 X 3 Latin Square design was replicated three times and compared to a psuedo-replicate reference stand (REF). Disturbance treatments were chainsaw fellind of trees with (1) helicopter removal of logs (HELI), (2) helicopter removal of logs followed by a simulated skidder removal (SKID), and helicopter removal of logs follwed by glyphosphate application (GLYPH). Measurements of sediment accretion show little difference between treatments and reference in the first two years following harvest. After two years the harvest treatments accumulate more sediment than the REF. Of the harvest treatments, the GLYPH plots accumulate the greatest quantities of sediment. The difference in sediment accretion between the harvest treatments begins to fade in the 12th year of recovery. Results show that skidder and helicopter removal of logs differ very little in the amount of sediment trapped, while glyphosphate application increased the wetland's ability to trap sediment beginning in the second year. In addition, sediment trappin is associated with herbaceous cover that slows flood waters and allows soil particles to precipitate from flood water. / Master of Science

Multimessenger astrophysics represents a new paradigm in our understanding of the universe, transcending traditional observational boundaries by combining information from various cosmic messengers. One of the most notable events in multimessenger astrophysics is the merger of two neutron stars, which was first detected in 2017 through the simultaneous observation of gravitational waves (GW) and electromagnetic radiation across the entire spectrum. This groundbreaking discovery provided many insights on different physical phenomena, from the properties of matter at very high densities to the origin of heavy elements. In this thesis we mainly focus on the study of the second binary neutron star (BNS) merger GW190425, detected by the Ligo and Virgo interferometers on the 25th of April, 2019, on the characterization of the accretion discs formed from the merger of a binary system composed by two neutron stars and on the effects of a hadron to quark phase transition that can occurs during such mergers.

Neste trabalho é apresentado um estudo observacional de discos de acresção em Variáveis Cataclísmicas (VCs). São analisadas medidas espectrofotométricas com resolução temporal dos perfis de linhas de emissão. A emissividade em linhas dos sistemas é mapeada utilizando a técnica de tomografia Doppler. Os parâmetros básicos das binárias, tais como período orbital, massas, inclinação orbital, são determinados quando necessário. Um código foi desenvolvido para simular a variabilidade das linhas de emissão em sistemas binários, além da presença de vento. O código foi utilizado para quantificar os parâmetros necessários para um estudo adequado de tomografia do flickering, tais como número de espectros, relação sinal-ruído destes, e frequência e amplitude do flickering em questão. Três sistemas são abordados: V3885 Sgr, RR Pic e V841 Oph. A variabilidade intrínseca de V3885 Sgr é mapeada através da técnica de tomografia do flickering. O flickering foi simulado e verificou-se que a fonte principal de flickering observada em V3885 Sgr não poderia se originar em um disco de acresção Kepleriano, mas sim na face iluminada da estrela secundária. Uma interpretação proposta para este fenômeno seria de um cenário onde o flickering no contínuo UV originado nas regiões centrais do disco ou na mancha quente é reprocessado na face iluminada da secundária. Obtivemos a primeira confirmação, para uma Variável Cataclísmica de curto período (RR Pic), de uma secundária com relação massa/raio distante da sequência principal. No caso de V841 Oph determinamos o período orbital e obtivemos uma razão de massas um pouco inferior a 1. Verificamos a existência de uma região de emissão mais intensa localizada no quadrante oposto ao esperado para a mancha quente, sendo esta região particularmente brilhante em HeI. O disco de acresção de V841 Oph foi verificado como sendo de baixa emissividade em linhas. / An observational study of accretion disks in Cataclysmic Variables (CVs) is presented in this work. Time-resolved spectrophotometric data of the emission line profiles are analyzed. The line emissivity of the systems is mapped using the Doppler tomography technique. The basic orbital parameters of the systems, like the orbital period, mass, orbital inclination, are determined when needed. A code was developed to simulate the emission line profile variability in binary systems, also including the presence of a wind. Such a code was used to quantify the parameters involved in a flickering tomography study, like the number of spectra, signal-to-noise ratio, frequency and amplitude of the flickering. Three systems are analyzed: V3885 Sgr, RR Pic and V841 Oph. The intrinsic variability in V3885 Sgr is mapped using the flickering tomography technique. The flickering was simulated and we have verified that the main flickering source in V3885 Sgr could not be located on the Keplerian accretion disk. The inner face of the secondary star is proposed instead. One interpretation of this phenomenon is a scenery where flickering in the UV continuum from the inner parts of the accretion disk is reprocessed at the illuminated face of the secondary star. The first confirmation of a secondary star with a mass-radius relation far from the main sequence values was obtained for a CV with a short period (RR Pic). In the case of V841 Oph we determined the orbital period and obtained a mass-ratio slightly below 1. We verified the presence of a region of enhanced emission in the quadrant opposite to the one expected for the hot spot. The emission of this region is particularly enhanced in HeI. The V841 Oph accretion disk was verified as being of low emissivity in lines.

L’émission X associée à l’accrétion sur un objet compact présenter une important variabilit photométrique et spectroscopique. Quand l’accréteur est en orbite autour d’une étoile Supergéante, il capture une fraction du vent stellaire supersonique qui forme des chocs dans son voisinage. L’amplitude et la stabilité de cette focalisation gravitationnelle conditionnent le taux d’accrétion de masse responsable, in fine, de la luminosité X des Binaires X Supergéantes (SgXB). La capacité de ce flot à faible moment angulaire à former un disque susceptible de présenter des instabilités est en jeu.Grâce à des setups numériques sophistiqués, nous caractérisons la structure du flot de Bondi- Hoyle-Lyttleton sur un objet compact, depuis le choc jusqu’au voisinage de l’accréteur, typiquement 5 ordres de grandeur plus petit. L’évolution du choc détaché qui se forme autour de l’accréteur (structure transverse, angle d’ouverture, stabilité, profil de température) avec le nombre de Mach est détaillé. La fiabilité de ces simulations basées sur le code hautes performances MPI-AMRVAC est étayée par la topologie de la surface sonique, en accord avec le attentes théoriques.Nous développons un modèle synthétique de transfert de masse dans les SgXB qui couple le lancement du vent, les paramètres stellaires, l’évolution orbital du flot et l’accrétion. Nous montrons que la forme du flot est entièrement détermimée par les facteur de remplissage et d’Eddington, le rapport de masse et le multiplieur de force alpha. Avec les paramètres d’échelle, nous pouvons en déduire, eg, la luminosité X, le processus d’accrétion et le cisaillement du flot. / X-ray emission associated to accretion onto compact objects displays important levels of photometric and spectroscopic time-variability. When the accretor orbits a Supergiant star, it captures a fraction of the supersonic radiatively-driven wind which forms shocks in its vicinity. The amplitude and stability of this gravitational beaming of the flow conditions the mass accretion rate responsible, in fine, for the X-ray luminosity of those Supergiant X-ray Binaries (SgXB). The capacity of this low angular momentum inflow to form a disc susceptible to be the stage of instabilities remains at stake.Using state-of-the-art numerical setups, we characterize the structure of a Bondi-Hoyle- Lyttleton flow onto a compact object, from the shock down to the vicinity of the accretor, typically five orders of magnitude smaller. The evolution of the bow shock which forms around the accretor (transverse structure, opening angle, stability, temperature profile...) with the Mach number of the flow is detailed. The robustness of those simulations based on the High Performance Computing MPI-AMRVAC code is supported by the topology of the inner sonic surface, consistent with theoretical expectations.We develop a synthetic model of mass transfer in SgXB which couples the launching of the wind the stellar parameters, the orbital evolution of the streamlines and the accretion process. We show that the shape of the permanent flow is entirely determined by the filling and Eddington factor, the mass ratio and the alpha force multiplier. Provided scales are known, we can trace back, eg, the X-ray luminosity, the accretion mechanism (stream or wind-dominated) and the shearing of the inflow.

Black hole jets and accretion discs are the most extreme objects in modern astrophysics whilst dark energy is undoubtedly the most mysterious. This thesis focuses on understanding these three topics. The majority of this thesis is dedicated to investigating the structure and properties of black hole jets by modelling their emission. I develop an inhomogeneous jet model with a magnetically dominated parabolic accelerating base, transitioning to a slowly decelerating conical jet, with a geometry set by radio observations of M87. This model is able to reproduce the simultaneous multiwavelength spectra of all 38 Fermi blazars with redshifts in unprecendented detail across all wavelengths. I constrain the synchrotron bright region of the jet to occur outside the BLR and dusty torus for FSRQs using the optically thick to thin synchrotron break. At these large distances their inverse-Compton emission originates from scattering CMB photons. I find an approximately linear relation between the jet power and the transition region radius where the jet first comes into equipartition, transitions from parabolic to conical and stops accelerating. The decreasing magnetic field strength and increasing bulk Lorentz factor with jet power are the physical reasons behind the blazar sequence. I calculate the conditions for instability in a thin accretion disc with an α parameter which depends on the magnetic Prandtl number, as suggested by MHD simulations. The global behaviour of the instability induces cyclic flaring in the inner regions of the disc, for parameters appropriate for X-ray binary systems, thereby offering a potential solution to a long standing problem. Finally, I calculate the effect of an interacting quintessence model of dark energy on cosmological observables. I find that a scalar-tensor type interaction in the dark sector results in an observable increase in the matter power spectrum and integrated Sachs-Wolfe effect at horizon scales.

The local universe is dominated by quiescent galaxies with little or no ongoing star formation. Once star formation has been shut down in a possible quasar phase, energy feedback in the form of outflows from a supermassive black hole (SMBH) accreting at a low rate is one of the leading candidates for heating up or removing gas accreted afterwards. In this work we performed hydrodynamic simulations of radiatively inefficient accretion flows around supermassive black holes and investigate the generation of outflows by the accretion flow. We found that hot accretion flows can produce powerful subrelativistic winds that carry considerable amounts of energy away and they can provide feedback inside the host galaxy. / O universo local é dominado por galáxias quiescentes com pouca, ou nenhuma, taxa atual de formação estelar. Uma vez que a formação estelar é suprimida numa possível fase de quasar do núcleo ativo da galáxia, o feedback de energia na forma de outflows do buraco negro supermassivo acretando a pequenas taxas é um dos principais candidatos a aquecer ou remover o gás do sistema. Nesse trabalho, executamos simulações hidrodinâmicas de escoamentos acretivos radiativamente ineficientes ao redor de buracos negros supermassivos e investigamos a geração de outflows pelo escoamento. Encontramos que escoamentos acretivos quentes podem produzir ventos subrelativísticos poderosos que carregam para fora consideráveis quantidades de energia e que podem providenciar feedback dentro da galáxia hospedeira.

O presente trabalho tem como objetivo estudar a evolução térmica de corpos intrusivos em diferentes níveis da crosta formados por múltiplas injeções de magma em forma de sils, levando em consideração mudança de fase e liberação de calor latente em um intervalo finito de temperaturas. A análise proposta inclui o estudo dos modelos de transferência de calor puramente condutivos utilizando a equação da evolução da entalpia que integra a mudança composicional dos magmas. A evolução térmica do corpo ígneo gerado por introdução do magma basáltico através de sils na crosta inferior obtém-se usando o método das diferenças finitas em uma dimensão, além disso se desenvolvem duas formas de construção do corpo ígneo neste nível: acréscimo por cima e acréscimo por baixo, sendo o primeiro caso o mais eficiente em manter o sistema a temperaturas elevadas durante mais tempo. Na crosta superior a evolução térmica do corpo ígneo de composição próxima ao tonalito introduzido por meio de sils é resolvida em duas dimensões com o método dos elementos finitos utilizando uma geometria com simetria axial no eixo z. O desenvolvimento destes corpos depende do ritmo de acréscimo do magma e das propriedades térmicas tanto da crosta como do magma injetado, podendo desenvolver-se como uma câmara magmática, um repositório de fusão ou um corpo altamente cristalino. A segunda fase do trabalho consistiu na solução da equação de condução de calor com mudança de estado em câmaras magmáticas esféricas, esferóides oblatos e esferóides prolatos com o método de elementos finitos para analisar evolução do sistema crosta-câmara magmática e introduzir o estudo da variação da viscosidade em função da temperatura. A geometria da câmara magmática influencia fortemente os fluxos de calor à crosta e portanto a criação de um halo dúctil que pode afetar a estabilidade dela mesma. / The purpose of this work is to study the thermal evolution of intrusive bodies formed by successive sills injection in different levels of the crust, taking into account the phase change and latent heat release in a finite temperatures interval. Our numerical models involve heat transfer only by conduction. Thermal evolution of the system is found with the energy balance equation of enthalpy that includes phase and composition change of magmas. The thermal evolution of the basaltic igneus body intruded into the lower crust is evaluated using finite difference scheme. At this level of the crust we develop two different ways of igneus body construction: over- accretion and under-accretion. Over-accretion is the more efficient way for keeping high temperatures in the time. In the upper crust, the thermal evolution of a tonalite igneus body formed by successive sils injection is computed with finite elements method in a geometry with rotational symmetry about z axis. Thermal and geological development of this igneus bodys strongly depends on magma emplacement rate and magma and crust thermal proprerties. These features defines if the igneus body develops in a magmatic chamber, a melt reservior or a high crystalline body. In the second part of this work we examine heat transfere from magamatic chambers of different geometries into the country rock, solving the entalphy equation with latent heat release effects with finite element method. The magmatic chambers geometries constructed are oblate spheroid, prolate spheroid and spherical. The viscosity of the rock is also obteined from temperature field.

O presente trabalho tem como objetivo estudar a evolução térmica de corpos intrusivos em diferentes níveis da crosta formados por múltiplas injeções de magma em forma de sils, levando em consideração mudança de fase e liberação de calor latente em um intervalo finito de temperaturas. A análise proposta inclui o estudo dos modelos de transferência de calor puramente condutivos utilizando a equação da evolução da entalpia que integra a mudança composicional dos magmas. A evolução térmica do corpo ígneo gerado por introdução do magma basáltico através de sils na crosta inferior obtém-se usando o método das diferenças finitas em uma dimensão, além disso se desenvolvem duas formas de construção do corpo ígneo neste nível: acréscimo por cima e acréscimo por baixo, sendo o primeiro caso o mais eficiente em manter o sistema a temperaturas elevadas durante mais tempo. Na crosta superior a evolução térmica do corpo ígneo de composição próxima ao tonalito introduzido por meio de sils é resolvida em duas dimensões com o método dos elementos finitos utilizando uma geometria com simetria axial no eixo z. O desenvolvimento destes corpos depende do ritmo de acréscimo do magma e das propriedades térmicas tanto da crosta como do magma injetado, podendo desenvolver-se como uma câmara magmática, um repositório de fusão ou um corpo altamente cristalino. A segunda fase do trabalho consistiu na solução da equação de condução de calor com mudança de estado em câmaras magmáticas esféricas, esferóides oblatos e esferóides prolatos com o método de elementos finitos para analisar evolução do sistema crosta-câmara magmática e introduzir o estudo da variação da viscosidade em função da temperatura. A geometria da câmara magmática influencia fortemente os fluxos de calor à crosta e portanto a criação de um halo dúctil que pode afetar a estabilidade dela mesma. / The purpose of this work is to study the thermal evolution of intrusive bodies formed by successive sills injection in different levels of the crust, taking into account the phase change and latent heat release in a finite temperatures interval. Our numerical models involve heat transfer only by conduction. Thermal evolution of the system is found with the energy balance equation of enthalpy that includes phase and composition change of magmas. The thermal evolution of the basaltic igneus body intruded into the lower crust is evaluated using finite difference scheme. At this level of the crust we develop two different ways of igneus body construction: over- accretion and under-accretion. Over-accretion is the more efficient way for keeping high temperatures in the time. In the upper crust, the thermal evolution of a tonalite igneus body formed by successive sils injection is computed with finite elements method in a geometry with rotational symmetry about z axis. Thermal and geological development of this igneus bodys strongly depends on magma emplacement rate and magma and crust thermal proprerties. These features defines if the igneus body develops in a magmatic chamber, a melt reservior or a high crystalline body. In the second part of this work we examine heat transfere from magamatic chambers of different geometries into the country rock, solving the entalphy equation with latent heat release effects with finite element method. The magmatic chambers geometries constructed are oblate spheroid, prolate spheroid and spherical. The viscosity of the rock is also obteined from temperature field.

<p>Städer och regioner runt om i världen konkurrerar ständigt med varandra i strävan efter ett gemensamt mål; en ökad tillväxt. För att nå målet måste platserna både attrahera resurser utifrån och mobilisera de interna resurser som redan finns. Platser som förknippas med tillväxt, attraktiva boendemiljöer eller exklusiva turistupplevelser har ett försprång gentemot regioner som förknippas med utflyttning, nedläggningar och sociala problem. Piteå är en mindre kommun i Norrbotten, en region som brottas med utflyttning och negativa befolkningsutvecklingar. Syftet med föreliggande uppsats är att ta reda på vad Piteås kommun och näringsliv gör och vad de kan göra för att öka sin attraktivitet, som i sin tur skall leda till en ökad besöksnäring, ökad inflyttning och nyetableringar av företag. Vidare undersöks vilka faktorer som påverkar attraktiviteten för en stad. Ytterligare är ett syfte att se hur samverkan fungerar mellan kommunen och olika aktörer i Piteå. För att kunna uppfylla syftet har kvalitativa metoder i form av djupintervjuer använts med några betydande aktörer samt Piteå kommun. Resultatet av studien har visat att samverkan i Piteå kommun är väl fungerande men att tillgängligheten till och från staden för godstrafik är begränsad samtidigt som passagerartrafik med tåg är obefintlig. Piteå är en stark evenemangsstad och i dagsläget sker även stora satsningar inom energiområdet, vilket kan öppna för stora möjligheter i framtiden.</p> / <p>Cities and regions all over the world are constantly competing in the will for the same goal; an increased accretion. To reach the goal the places have to attract resources from the outside and mobilise the internal resources they already have. Places that are associated with accretion, attractive living environments, or exclusive tourist experiences have a head-start to the places that are associated with out-migration, discontinuation, and social problems. Piteå is a smaller municipality in Norrbotten; a region that struggles with emigration and negative population developments. The purpose with the following thesis is to find out what the municipality and the commercial and industrial life in Piteå does to increase their attractiveness. Which will lead to an increased tourist business, an increased in-migration and establishments of new business corporations? A further examination is about what factors that affect the attractiveness for a city. Another purpose is to see how interactivity between the municipality in Piteå and the commercial and industrial life works. To fulfil the purpose qualitative methods in the shape of interviews with some significant enterprisers and the municipality in Piteå has been used. The result of the study has shown that the interaction between the municipality and the commercial and industrial life in Piteå is in working order, but the accessibility to and from the city with goods traffic is limited at the same time as passenger traffic is nonexistent. Piteå is a strong in arranging events and in the present situation big investments in the energy field is made, which opens up for big opportunities in the future.</p>

<p>This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. The current picture of TTS is based on rather simple models assuming that accretion is a homogeneous and axisymmetric process. Although these models have been successful in explaining some observational signatures of TTS such as the shape of emission lines, the static nature of these models makes them unsuitable for describing the strong variability of the veiling spectrum and emission lines of TTS. An improved understanding of this variability is of key importance to study the dynamic processes related to the accretion flow and the winds.</p><p>This study is based on a set of high-quality spectroscopic observations with the UVES spectrograph at the 8-m VLT in 2000 and 2002. These spectra, with exposure times as short as 10-15 minutes, have high spectral resolution and high signal-to-noise ratios and cover a large part of the optical wavelength range. From this dataset we determine the basic physical parameters of several TTS and model their photospheres. These models then serve as a basis for a detailed investigation of variations of the veiling continuum and line emission. We confirm that the level of veiling correlates with some of the strongest emission lines and that coherent changes in accretion occur on a timescale of a few hours, comparable to the free-fall time from the disk to the star. From the properties of the emission lines formed close to the central star and in the stellar wind we derive restrictions on the geometry of the observed systems.</p><p>Because the intrinsic axial symmetry of a single star makes it almost impossible to disentangle rotational modulation from inhomogeneity and axial asymmetry of the accretion flow, we study a series of spectra of a close spectroscopic binary at different orbital phases and derive the 3D structure of flows between the disk and the star. Finally, we calculate the profiles of hydrogen emission lines by iteratively solving 3D NLTE radiative transfer in a state-of-the-art magnetospheric model.</p>