Damming disrupts natural sediment flow to downstream resulting in legacy sediment accumulation. Legacy sediments have been well investigated in streams throughout the Piedmont region; however, there is no research of legacy sediments following dam removal in low-gradient Coastal Plain streams. Research objectives were to: characterize legacy sediments in a low-gradient stream restoration, quantify pre-impoundment accretion and carbon dynamics, and assess current sediment deposition rates via 14C analyses within sediment cores and sediment collection tiles. Carbon accumulation and accretion rates of modern tidal sediment have reached that of the tidal relic benchmark and current sediment deposition rates are similar between the natural reference and restored tidal wetlands. At this site, the pattern of legacy sediment accumulation and stream incision was reversed relative to previous studies in higher gradient systems. Results suggest in dam impacted Coastal Plain streams, legacy sediment may become a benefit rather than a liability for downstream tidal wetlands.

This thesis presents the results of a combined magnetic fabric and palaeomagnetic analysis of lower crustal rocks exposed in the Oman (Semail) ophiolite. This has long been an important natural laboratory for understanding the construction of oceanic crust at fast spreading axes and its subsequent tectonic evolution, but magnetic investigations in the ophiolite have been limited. Analyses presented here involve using: (i) magnetic anisotropies as a proxy for magmatic petrofabrics in lower crustal rocks in order to contribute to outstanding questions regarding the mode of accretion of fast-spread oceanic crust; and (ii) classical palaeomagnetic analyses to determine the nature of magnetization in these rocks and gain further insights into the regional-scale pattern of tectonic rotations that have affected the ophiolite. The extensive layered gabbro sequences exposed in the Semail ophiolite have been sampled at a number of key localities. These are shown to have AMS fabrics that are layer-parallel but also have a regional-scale consistency of the orientation of maximum anisotropy axes. This consistency across sites separated by up to 100 km indicates large-scale controls on fabric development and may be due to consistent magmatic flow associated with the spreading system or the influence of plate-scale motions on deformation of crystal mushes emplaced in the lower crust. Detailed analysis of fabrics in a single layer and across the sampled sections are consistent with either magmatic flow during emplacement of a melt layer into a lower crustal sill complex, or traction/drag of such layers in response to regional-scale stresses (e.g. mantle drag). Together, results support formation of the layered gabbros by injection of melt into sill complexes in the lower crust. New anisotropy data from the overlying foliated gabbros sampled at two key localities also provide insights into the style of melt migration at this crustal level. Fabrics are consistent with either focused or anastomosing magmatic upwards flow through this layer, reflecting melt migration beneath a fossil axial melt lens. Previous palaeomagnetic research in lavas of the northern ophiolitic blocks has demonstrated substantial clockwise intraoceanic tectonic rotations. Palaeomagnetic data from lower crustal sequences in the southern blocks, however, have been more equivocal due to complications arising from remagnetization. Systematic sampling resolves for the first time a pattern of remagnetized lowermost gabbros and retention of earlier magnetizations by uppermost gabbros and the overlying dyke-rooting zone. Results are supported by a positive fold test that shows that remagnetization of lower gabbros occurred prior to Campanian structural disruption of the Moho. NW-directed remagnetized remanences in the lower units are consistent with those used previously to infer lack of significant rotation of the southern blocks. In contrast, E/ENE-directed remanences in the uppermost gabbros imply a large, clockwise rotation of the southern blocks, of a sense and magnitude consistent with that inferred from extrusive sections in the northern blocks. Hence, without the control provided by systematic crustal sampling, the potential for different remanence directions being acquired at different times may lead to erroneous tectonic interpretation.

Orientadores: Alberto Vazquez Saa, Marcus Aloizio Martinez de Aguiar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-27T13:28:54Z (GMT). No. of bitstreams: 1 Vieira_RonaldoSavioliSume_D.pdf: 9121576 bytes, checksum: eab8bcedfd86d048afd51f4b65fe9501 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho analisamos aspectos dinâmicos de sistemas astrofísicos que possuem uma componente discoidal proeminente. Estudamos o movimento de partículas de teste (estrelas) que cruzam discos galácticos bidimensionais e axialmente simétricos, obtendo uma fórmula para o envelope das órbitas que depende somente da densidade superficial $\Sigma$ do disco. Essa fórmula nos dá uma terceira integral de movimento aproximada para o sistema. Também analisamos a estabilidade das órbitas circulares equatoriais nesses discos, chegando à condição de estabilidade vertical $\Sigma>0$. Esse formalismo é estendido para discos tridimensionais, assim como para a relatividade geral (em que obtivemos que a \textit{condição de energia forte} é suficiente para a estabilidade vertical das órbitas circulares em discos infinitesimais, no caso estático e axialmente simétrico). Trabalhamos também com a aproximação pós-newtoniana (1PN), obtendo o formalismo hamiltoniano para uma distribuição arbitrária de matéria, assim como as correções 1PN nas frequências epicíclicas radial e vertical para configurações estacionárias e axialmente simétricas e a terceira integral de movimento aproximada para discos infinitesimais (estacionários). Outro resultado obtido foi a dependência das frequências epicíclicas com a curvatura riemanniana do espaço-tempo para distribuições suaves de matéria-energia, no caso estático e axialmente simétrico em relatividade geral. A segunda parte desta tese corresponde aos resultados para discos de acreção. Analisamos o movimento de partículas de teste na métrica de Kehagias & Sfetsos (solução esfericamente simétrica da gravitação de Horava no caso em que o espaço-tempo é assintoticamente plano), na região de parâmetros em que a singularidade central é nua. Por fim, estudamos a espessura dos discos de acreção super-Eddington obtida por simulações globais recentes de radiation magnetohydrodynamics em relatividade geral. O resultado foi comparado com modelos de discos slim para taxas de acreção similares, levando à conclusão de que o estado final (estacionário) dos fluxos de acreção gerados por essas simulações é um disco slim, e não um disco espesso, como seria esperado pelas características das configurações iniciais do tipo Polish Doughnuts usualmente adotadas / Abstract: In this work, we analyze dynamical aspects of astrophysical systems containing a prominent discoidal component. We study the motion of test particles (stars) which cross bidimensional, axially symmetric galactic disks, obtaining a formula for the orbits' envelope which depends solely on the disk's surface density. This formula gives us an approximate third integral of motion for the system. We also analyze the stability of equatorial circular orbits in these disks, arriving at the vertical stability condition $\Sigma>0$. This formalism is extended to three-dimensional disks, as well as to general relativity (in which we obtained that the \textit{strong energy condition} is sufficient for vertical stability of circular orbits in infinitesimal disks, in the static and axially symmetric case). We also worked with the post-Newtonian approximation (1PN), obtaining the Hamiltonian formalism for an arbitrary matter distribution, as well as the 1PN corrections to the radial and vertical epicyclic frequencies for stationary and axially symmetric configurations, and the approximated third integral of motion for (stationary) infinitesimal disks. Another result obtained was the dependence of the epicyclic frequencies on the Riemannian spacetime curvature for smooth matter-energy distributions, in the static and axially symmetric case. The second part of this thesis corresponds to the results concerning accretion disks. We analyzed the motion of test particles in the Kehagias & Sfetsos metric (spherically symmetric solution to Horava's gravity in the case in which the spacetime is asymptotically flat), in the parameter region in which the singularity is naked. Finally, we studied the thickness of super-Eddington accretion disks, obtained via recent global radiation magnetohydrodynamics simulations in general relativity. The result was compared with slim-disk models for similar accretion rates, leading to the conclusion that the final (stationary) state of accretion flows generated by these simulations is a slim disk, and not a thick disk, as it would be expected by the characteristics of the usually adopted Polish Doughnuts initial configurations / Doutorado / Física / Doutor em Ciências

Neste trabalho estudamos a dinâmica de discos torcidos finos e espessos para compreender melhor a propagação da deformação nestes discos. No caso dos discos finos, estudamos a física do efeito Bardeen-Petterson e aplicamos este modelo para explicar o jato em escalas de parsec e kilo-parsec da galáxia NGC 1275. Encotramos que o efeito Bardeen-Petterson reproduziu muito bem a forma do jato e com isto derivamos os parâmetros do disco como raio, valores das viscosidades azimutal e vertical, lei de potência da densidade superficial e spin do buraco negro. Para uma melhor compreensão da física destes discos, realizamos simulações GRMHD de discos moderadamente finos tanto planos como inclinados para estudar a evolução do ângulo de inclinação entre os momentos angular do buraco negro e do disco de acresção assim como o ângulo de torção que está associado com a precessão do disco. Encontramos que quando o disco de acresção e o buraco negro rotacionam no mesmo sentido, o ângulo de inclinação entre os momentos angular apresentou um comportamento oscilatório na parte interna do disco e permaneceu constante na parte externa em acordo com as previsões teóricas. Já quando o buraco negro rotacina no sentido oposto ao disco de acresção, encontramos pela primeira vez numa simulação GRMHD evidências de alinhamento, ocorrendo um alinhamento de 10\\% do angulo entre os momentos angulares do disco e buraco negro. Além disso, comprovamos pela primeira vez numa simulação GRMHD a não isotropia do stress. Utilizando um modelo semi-analítico, comparamos os resultados de nossas simulações com este modelo, utilizando os dados da simulações de disco plano como entrada e obitivemos os mesmos comportamentos das simulações tanto no caso prógrado quanto no caso retrógrado mostrando que o alinhamento é devido ao regime onda. / In this work we studied the dynamics of twisted thin and thick disks to better understand how the warp propagates in these discs. In the case of thin discs, we studied the physics of the Bardeen-Petterson effect and we applied this model to explain the shape of the jet in both parsec and kilo-parsec scales of the galaxy NGC 1275. We found that the Bardeen-Petterson effect could explain very well the shape of the jet and with that we derived the disc parameters such as its radius, the values of the kinematic azimutal and vertical viscosities, the power-law of the surface density and the spin of the black hole. To better understand the physics of such discs, we have performed GRMHD simulations of moderatelly thin tilted disks to study the evolution of the tilt angle between the angular momentum of the accretion disk and black hole and also the twist angle which is associated with the precession of the disc. We found that when the accretion disc and the black hole are rotating in the same direction, the tilt angle showed an oscillatory behavior in the inner parts of the disk while in the outer parts it remained constant in agreement with the theorical modelos. However, when both rotate in the opposite direction, we found for the very first time in a GRMHD simulation, evidences of alignment of 10\\% of the tilt angle. Besides that, we prove for the first time in a GRMHD simulation that the stress is far from being isotropic. Using a semi-analitic model, we compared the results of our simulations with this model, using the datas of the untilted simulations as inputs and we found the same behaviors found in the simulations even in prograde case as in the retrograde case showing that the alignment is due to bending waves.

Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...

Sgr A*, le trou noir supermassif le plus proche de nous, émet une luminosité quiescente très faible ainsi que des éruptions en infrarouge proche (NIR), rayons X et radio. Cette thèse a pour but d'étudier l'effet du passage de DSO/G2 près de Sgr A* sur les éruptions. J'ai utilisé et amélioré trois méthodes pour l'étude en rayons X : les blocs Bayésiens en deux passes pour détecter les éruptions avec une certaine probabilité, le lissage des courbes de lumières pour diminuer le bruit de Poisson et la méthode de Monte Carlo par chaînes de Markov pour l'ajustement des spectres des éruptions. J'ai contraint les paramètres physiques de la source pour une des 3 éruptions détectées en rayons X en 2011 et pour 3 éruptions détectées en rayons X et NIR durant la campagne multi-longueurs d'onde de février-avril 2014. L'activité en rayons X et NIR de février-avril 2014 correspond à celle observée avant le passage de DSO/G2 près de Sgr A*. J'ai calculé le taux d'éruption intrinsèque en rayons X de Sgr A* en 1999-2015 et détecté une plus faible activité à partir du 28 octobre 2013. L'énergie stockée pendant cette période peut expliquer la plus forte activité observée du 30 août au 9 septembre 2014. / Sgr A*, the closest supermassive black hole, is an extremely low luminosity black hole emitting flares in near-infrared (NIR), X-rays and radio. The goal of this Ph.D. is to study the impact of the pericenter passage of the Dusty S-cluster Object DSO/G2 close to Sgr A* on the flaring activity. I used and improved three methods for the study in X-rays: the two-steps Bayesian blocks method to detect flares with a given false detection probability, the light curve smoothing to reduce the Poisson noise and the Monte Carlo Markov chains method for the fitting of the flare spectra. I constrained the physical parameters of the flaring region for one of the three X-ray flares detected in 2011 and for three NIR/X-ray flares detected during the 2014 Feb.-Apr. multiwavelength campaign. The X-ray and NIR activity during the 2014 Feb.-Apr. is not different from those observed before the DSO/G2 pericenter passage. I computed the intrinsic flaring rate in X-rays from Sgr A* in 1999-2015 and I detected a smaller flaring activity beginning on 2013 Oct. 28. The energy saved during this time period could explain the largest activity observed from 2014 Aug. 30 to Sept. 9.

Swedish EPA (Naturvårdsverket) noise level guide-lines suggest that equivalent A-weighted sound pressure levels (SPL) must not exceed 40 dBA at residents. Thus, in the planning of new wind farms and their location it is crucial to estimate the disturbance it may cause to nearby residents. Wind turbine noise emission levels are guaranteed by the wind turbine manufacturer only under ice-free conditions. Thus, ice accretion on wind turbine may lead to increased wind turbine noise resulting in noise levels at nearby residents to exceed 40 dBA SPL. The purpose of the project is to evaluate the effect on wind turbine noise emission due to ice accretion. This, by trying to quantify the ice accretion on rotor blades and correlate it to any change in noise emission. A literature study shows that the rotor blades are to be considered the primary noise source. Hence, ice accretion on rotor blades are assumed to be the main influence on noise character. A field study is performed in two parts; as a long term measurement based on the method out-lined by IEC 61400-11 and as a short term measurement in strict accordance with IEC 61400-11. These aim to obtain noise emission levels for the case of icing conditions and ice-free conditions (reference conditions) as well as background noise levels. An analysis is performed, which sets out to correlate ice measurements with wind turbine performance and noise emission. Data reduction procedures are performed according to IEC 61400-11.The apparent sound power levels are evaluated. This is performed for the case of icing conditions as well as for the case of ice-free onditions. A statistical evaluation of icing event is carried out. The results show that ice accretion on wind turbine (rotor blades) may lead to drastically higher noise emission levels. The sound power levels show an average increase of 10.6 dB at 8 m/s. However, this can occur at all wind speeds from 6 m/s to 10 m/s. Higher levels of noise, (55 to 65 dBA SPL) may be caused by very small amounts of ice accretion. Occurrences of higher levels of noise, in the range of 50 to 65 dBA SPL, are not common. Noise levels exceeding 50 dBA SPL are to expected 10.3 % of the time during the winter or 3 % of the time during one year. Correlation between measured ice accumulation and noise level is weak apart from large amounts of ice. This due to statistical noise. Taking into account the noise level guide-lines of 40 dBA SPL at residents, as is recommended by Swedish EPA (Naturvårdsverket), the increased levels of windturbine noise under icing conditions may force the power production to a halt.

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