An analysis is made on the Flat Spectrum Radio Quasar PKS 0426-380 using two sets of data. The first set of data is the Fermi-LAT data collected over the time 54682.66 − 59317.66 in Modified Julian Date within the energy range of 100 MeV to 500 GeV. The second set of data is a multi-wavelength spectral energy distribution within the approximate frequencies of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%0A%0A%5Cleft%5B10%5E%7B10%7D,%2010%5E%7B27%7D%20%5Cright%5D" data-classname="equation" data-title="" />. First, the Fermi-LAT data were analysed and after modelling a lightcurve over the entire available time, a period of interest was located. The next step was to obtain a multi-wavelength spectral energy distribution of said period. Then, using JetSeT modelling, the data were analysed and a model of the Synchrotron Self-Compton, External-Compton and Synchrotron curves was fitted to the data. The final model which contained the best fit provided a set of physical parameters that described the source. These parameters were finally compared to two other Flat Spectrum Radio Quasars and conclusions regarding the properties of PKS 0426-380 were eventually drawn. A discussion comparing a related work on the same source to the results in this thesis followed. With the large differences in the constrained data between the Flat Spectrum Radio Quasars as background, three predictions concluded the thesis. These are, firstly, a cautioned approach to future searches for periodicity in AGN's. Secondly, in time, local periodicity for AGN's might be more common and interesting for future research. Finally, no certain values for the physical parameters of the AGN can be assessed and the results can only be wived as indications of the actual properties. / <p>Passed</p>

No description available.

Let $M_v$ denotes a complete mixed graph on $v$ vertices, and let $S_6^i$ denotes the partial orientation of the 6-star with twice as many arcs as edges. In this work, we state and prove the necessary and sufficient conditions for the existence of $\lambda$-fold decomposition of a complete mixed graph into $S_6^i$ for $i\in\{1,2,3,4\}$. We used the difference method for our proof in some cases. We also give some general sufficient conditions for the existence of $S_6^i$-decomposition of the complete bipartite mixed graph for $i\in\{1,2,3,4\}$. Finally, this work introduces the decomposition of a complete mixed graph with a hole into mixed stars.

In the present work we study the properties of accretion tori orbiting black hole. Our approach to this problem comes from the solving of general relativistic magnetohydrodynamic equations, which follow from conservation of the energy-momentum tensor, the particle number and from Maxwell's equations. We solve these equations by numerical methods which are described in Chapter 1. The formalism of tori which we consider here is described in Chapter 2. We are interested in tori with constant density of angular momentum and Fishbone-Moncrief tori mainly. We study accretion rates in these tori when the mass of black hole is increased suddenly and so the equilibrium in the torus is corrupted. For tori with constant density of angular momentum we study the influence of the presence of toroidal magnetic field on accretion rates.

Necessary and sufficient conditions are given for the existence of isomorphic decompositions of the complete bipartite graph, the complete graph with a hole, and the λ-fold complete graph into copies of a 4-cycle with a pendant edge.

We explore the optical parametric amplifier, an optical device where a pump field creates a pair of lower-frequency fields: signal and idler. The pump field is usually treated classically, but this thesis focuses on scenarios where the pump must be treated quantum mechanically. One of these scenarios is the growing field of nonlinear interferometry, where the fundamental sensitivity of a probed relative phase can beat the classical bounds and reach the maximum limit allowed by quantum mechanics, the Heisenberg limit. Indeed, we show that a fully quantum nonlinear interferometer displays a Heisenberg scaling in terms of the mean number of input pump photons. This result goes beyond the well-accepted Heisenberg scaling with respect to the down-converted photons inside the interferometer, which predicts unphysical phase sensitivities starting at a particular input pump energy. Our theoretical findings are particularly useful when designing a nonlinear interferometer with bright pump fields or optimized optical parametric amplifiers for quantum metrology and quantum imaging applications. The quantum nature of the pump field may also play a central role concerning other physical phenomena, like Hawking radiation in the context of black holes. As suggested by several authors, both the optical parametric amplifier and Hawking radiation comprise the creation of fundamental particle pairs. Thus, if the optical parametric amplifier is fully treated quantum mechanically, we may get insight into an open problem in modern physics, namely the black hole information paradox. According to this paradox, the information stored in a black hole can be destroyed once the black hole has evaporated by emitting Hawking radiation, contradicting quantum mechanics. Despite the experimental efforts to build systems that reproduce event horizons and gravitational effects in the laboratory, the evaporation of black holes due to the emission of Hawking radiation remains a challenging task. In this thesis, we experimentally investigate the impact of an evolving pump field in an optical parametric amplifier by optimizing a parametric down-conversion process. We measure the pump and signal photon number properties, finding that the pump field gets chaotic and the signal coherent when the pump displays some sizeable depletion. We arrive at similar conclusions about the pump field from its measured Wigner function. Our experiment is the first step towards a successful experiment that could suggest that information in the black hole is not destroyed but encoded in the emitted Hawking radiation starting at some point in the black hole evolution. We finally discuss further experimental improvements to investigate the parallel between the optical parametric amplifier and Hawking radiation.

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), May, 2020 / Cataloged from the official PDF of thesis. / Includes bibliographical references (pages 161-183). / Highly productive marine microbial communities in the coastal Southern Ocean sustain the broader Antarctic ecosystem and play a key role in Earth's climate via the biological pump. Regional phytoplankton growth is primarily limited by iron and co-limited by cobalamin (vitamin B₁₂), a trace cobalt-containing organometallic compound only synthesized by some bacteria and archaea. These micronutrients impact primary production and the microbial ecology of the two keystone phytoplankton types: diatoms and Phaeocystis antarctica. This thesis investigates microbe-driven cobalamin cycling in Antarctic seas across multiple spatiotemporal scales. I conducted laboratory culture experiments with complementary proteomics and transcriptomics to investigate the B₁₂-ecophysiology of P. antarctica strain CCMP 1871 morphotypes under iron-B₁₂ co-limitation. / We observed colony formation under higher iron treatments, and a facultative use of B₁₂-dependent (MetH) and B₁₂-independent (MetE) methionine synthase isoforms in response to vitamin availability, demonstrating that this strain is not B₁₂-auxotrophic. Through comparative 'omics, we identified a putative MetE protein in P. antarctica abundant under low B₁₂, which is also found in other marine microbes. Across Antarctic seas, community-scale cobalt and B₁₂ uptake rates were measured by ⁵⁷Co radiotracer incubation experiments and integrated with hydrographic and phytoplankton pigment data. I observed significant correlations between uptake fluxes and environmental variables, providing evidence for predominantly diatom-driven uptake of these micronutrients in warmer, fresher surface waters with notable regional differences. / To date, this work is the most comprehensive attempt to elucidate the processes governing the co-cycling of cobalt and B₁₂ in any marine system. At the ecosystem-scale, I developed and tested a hypothesis of micronutrient-driven community dynamics through a trait-based model with cross-feeding interactions. The model demonstrates how the observed seasonal succession of springtime P. antarctica from solitary to colonial cells, bacterioplankton, and summertime diatoms may be explained by the microbial cycling of iron, dissolved organic carbon, and B₁₂. Overall, this dissertation provides new information about the micronutrient-driven ecology of Antarctic marine microbes and adds to our understanding of the interconnections between organismal life cycle, trace metals, and trace organics in marine environments. / by Deepa Rao. / Ph. D. / Ph.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)

Endwall contouring has been widely studied as an effective measure to improve aerodynamic performance by reducing secondary flow strength. The effects of endwall contouring with discrete holes and an upstream purge slot for a high turning (127") airfoil passage under transonic conditions are investigated. The total pressure loss and secondary flow field were measured for two endwall geometries. The non-axisymmetric endwall was developed through an optimization study [1] to minimize secondary losses and is compared to a baseline planar endwall. The blade inlet span increased by 13 degrees with respect to the inlet in order to match engine representative inlet/exit Mach number loading in a HP turbine.  The experiments were performed in a quasi-2D linear cascade with measurements at design exit Mach number 0.88 and incidence angle. Four cases were analyzed for each endwall -- the effect of slot presence (with/without coolant) and the effect of discrete holes (with/without coolant) without slot injection. The coolant to mainstream mass flow ratio was set at 1.0% and 0.25% for upstream purge slot and discrete holes, respectively.  Aerodynamic loss coefficient is calculated with the measured exit total pressure at 0.1 Cax downstream of the blade trailing edge. CFD studies were conducted in compliment. The aero-optimized endwall yielded lower losses than baseline without the presence of the slot. However, in presence of the slot, losses increased due to formation of additional vortices. For both endwall geometries, results reveal that the slot has increased losses, while the addition of coolant further influences secondary flow development. / Master of Science

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998. / Includes bibliographical references (leaves 156-158). / by François W. Primeau. / Ph.D.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998. / Includes bibliographical references (leaves 150-157). / Double-diffusive processes are studied and parameterized, and their impacts on the oceanic thermohaline circulation are investigated by single-hemisphere numerical models and scaling analysis. Scaling analysis on the thermohaline circulation has been done under three types of surface boundary conditions. (a) Under "relaxation" conditions, there is a two-thirds power law dependence of the meridional overturning rate (and the poleward heat transport) on the diapycnal diffusivity. For any given external forcing, there is only one equilibrium state for the thermohaline circulation. (b) Under "flux" boundary conditions, there is a half power law dependence of the meridional overturning rate on the diapycnal diffusivity. Only one mode is possible for given external forcing. (c) Under "mixed" boundary conditions, multiple equilibria become possible. For given thermal forcing, the existence of multiple equilibria depends on the relative contributions of diapycnal diffusivity and the hydrologic forcing. Numerical experiments are implemented to test the above scaling arguments. Consistent results have been obtained under the above three types of boundary conditions. These provide a basis for understanding how the thermohaline circulation depends on the diapycnal diffusivity, which we know is influenced by the double-diffusive processes of "salt fingering" and "diffusive layering" in some parts of the ocean. In order to examine this issue, the double-diffusive processes are parameterized by diapycnal eddy diffusivities for heat and salt that are different and depend on the local density ratio, ... A background diffusivity is applied to represent turbulent mixing in the stratified environment. The implementation of this double-diffusive - parameterization in numerical models has significant impacts on the thermohaline circulation. (a) Under "relaxation" boundary conditions, the meridional overturning rate and the poleward heat transport are reduced, and water mass properties are also changed. Similar results are obtained under "flux" boundary conditions. (b) Under "mixed" boundary conditions, the critical freshwater flux for the existence of the thermal mode becomes smaller with the double-diffusive parameterization. The extent to which the thermohaline circulation is affected by double-diffusive processes depends on the magnitude of the freshwater forcing. / by Jubao Zhang. / Ph.D.