11,302 research outputs found
Noise Power Spectrum Scene-Dependency in Simulated Image Capture Systems
The Noise Power Spectrum (NPS) is a standard measure for image capture system noise. It is derived traditionally from captured uniform luminance patches that are unrepresentative of pictorial scene signals. Many contemporary capture systems apply non- linear content-aware signal processing, which renders their noise scene-dependent. For scene-dependent systems, measuring the NPS with respect to uniform patch signals fails to characterize with accuracy: i) system noise concerning a given input scene, ii) the average system noise power in real-world applications. The scene- and-process-dependent NPS (SPD-NPS) framework addresses these limitations by measuring temporally varying system noise with respect to any given input signal. In this paper, we examine the scene-dependency of simulated camera pipelines in-depth by deriving SPD-NPSs from fifty test scenes. The pipelines apply either linear or non-linear denoising and sharpening, tuned to optimize output image quality at various opacity levels and exposures. Further, we present the integrated area under the mean of SPD-NPS curves over a representative scene set as an objective system noise metric, and their relative standard deviation area (RSDA) as a metric for system noise scene-dependency. We close by discussing how these metrics can also be computed using scene-and-process- dependent Modulation Transfer Functions (SPD-MTF)
Multi-wavelength analysis to constrain the role of AGN in galaxy evolution
It is widely accepted that the formation of stars in galaxies must somehow be regulated to achieve the observed galaxy demographics. In massive galaxies in particular, the supermassive black holes that are known to reside at their centres are the most likely source of this regulation. The growth of these black holes through the accretion of gas releases considerable amounts of energy in the form of radiation and / or bipolar jets of charged particles. During these growth phases they are referred to as `active galactic nuclei' (AGN). This energy has the potential to regulate star formation in the host galaxies, by removing gas through outflows, halting the accretion of new gas onto the galaxy, and/or rendering the gas incapable of forming stars (e.g.\ through heating / turbulence). This is collectively referred to as `AGN feedback'. Around 10~percent of AGN have extreme radio luminosities due to powerful jets which are capable of preventing gas accretion onto the galaxy. However, for the remaining 90~percent of the AGN population, the so called `radio-quiet' AGN, the physical processes at play are less clear. This thesis targets a sample representative of the majority of AGN, and uses multi-wavelength observations to resolve some of the outstanding questions about how `radio-quiet' AGN transfer energy into their host galaxies, impact the surrounding multi-phase gas and, consequently, impact the evolution of their host galaxies.
In the first part of this thesis I study ten local ($z~10^45 erg/s), 'radio-quiet' AGN selected to have powerful ionised gas outflows, combining radio observations (with spatial resolutions up to 20 times better than the pre-existing data), and optical integral field spectroscopy. Jet-like radio emission on ~kpc scales was discovered in 70-80 percent of the sample, and it was revealed that these jets are driving ionised gas outflows in their host galaxies. This challenges the expectation that photon pressure should dominate feedback in these systems, and establishes that jets are playing an important role in the evolution of galaxies even in this 'radio-quiet' regime. I then used observations of the total carbon monoxide emission in nine of the sources studied in the radio to demonstrate that the outflows and jets do not have an immediate, global impact on the total reservoir of molecular, star-forming gas in their host galaxies. Specifically, at least seven of the AGN observed reside in gas-rich, highly star-forming galaxies. Finally, I present the first results on the full Quasar Feedback Survey, expanding the sample studied to 42 targets and removing the pre-selection for known outflows. In this ~four times larger, unbiased sample I showed that radio jet like features are still present in the majority (66 percent) of the sample and found a correlation between radio size and the ionised gas outflow properties, indicative of jet-gas interactions. This work has confirmed a connection between outflows and radio emission, and determined that jets are an important mechanism for driving outflows even in 'radio-quiet' AGN. I also discovered that even in systems with outflows and jets there is no immediate, appreciable impact on the global molecular gas content. These results will require simulations of feedback to be updated, and represent a significant step forward in the quest to form a complete understanding of how galaxies evolve
Nursing health assessment: A meta-analysis
Health assessment is the responsibility of all nurses (McCain, 1965), however, it is frequently discussed without reference to any global definition and studied under a variety of conditions. The purpose of this study was to determine the influence of clinical setting, year of assessment, nursing education and experience in nursing on the scope of nursing health assessment using meta-analysis techniques. Sixty five research journal articles were located of which 16 primary studies were selected and grouped for analysis. The result of this analysis indicates there is a significant difference in the scope of nursing health assessment in varied clinical settings (
The petrogenesis and geochemistry of the dioritic complexes south of Balmoral forest, Angus
The Glen Doll and Juan Jorge Complexes are two contrasting late Caledonian calc-alkaline plutons intruded into Middle Dalradian metasediments at the northern end of Glen Clova, in the Angus district of Tayside, Scotland. The Glen Doll Complex (12 km squared) constitutes a wide range of rock types from olivine gabbro, through diorite to adamellite. The bulk (> 80%) of the succession consists of heterogeneous hornblende- and pyroxene-bearing diorites. Partially assimilated rafted metasedimentary xenoliths, are common in the intermediate rock types. The basic rocks are cumulates which display wall-parallel layering. Mineralogical variation displays a transition from pyroxene-dominated anhydrous assemblages to amphibole-dominated assemblages. The diorites by contrast display floor-parallel layering and typically contain cumulate magnetite and ilmenite. Petrographic and mineralogical data suggests that fractionation played an important role in the evolution of the cumulate rocks
The Effect of Foot and Mouth Disease on Trade and Prices in International Beef Markets
The paper develops and uses a two step quantitative model to analyze the effect of Foot and Mouth Disease (FMD) on international beef markets over time. Using monthly data from 1990-2002 for 7 major beef exporters and for 22 major beef importers, we use a probit equation to estimate the probability that country i exports to country j, taking account of foot and mouth status of exporter, sanitary policy of importer, beef quality, trade preferences, distance, and other factors affecting whether beef trade occurs. We then use OLS to estimate the export prices that are obtained for beef, taking account of beef quality, country per capita, trading preferences, region, per capita income, and a time trend, including terms to adjust for censorship in the first stage. Using the estimated equations, we compare the predicted change in trading partners and in the prices received by the two exporters in our sample that are not FMD free, Brazil and Uruguay, under the assumption that their status switches from having FMD to being FMD free. The model performs well. The results suggest that FMD continues to impede trade between many countries and does accordingly reduce the price received for beef from countries with FMD. Nonetheless, the "sanction" from FMD appears smaller than previously believed.International Relations/Trade,
Multi-wavelength analysis to constrain the role of AGN in galaxy evolution
It is widely accepted that the formation of stars in galaxies must somehow be regulated to achieve the observed galaxy demographics. In massive galaxies in particular, the supermassive black holes that are known to reside at their centres are the most likely source of this regulation. The growth of these black holes through the accretion of gas releases considerable amounts of energy in the form of radiation and / or bipolar jets of charged particles. During these growth phases they are referred to as `active galactic nuclei' (AGN). This energy has the potential to regulate star formation in the host galaxies, by removing gas through outflows, halting the accretion of new gas onto the galaxy, and/or rendering the gas incapable of forming stars (e.g.\ through heating / turbulence). This is collectively referred to as `AGN feedback'. Around 10~percent of AGN have extreme radio luminosities due to powerful jets which are capable of preventing gas accretion onto the galaxy. However, for the remaining 90~percent of the AGN population, the so called `radio-quiet' AGN, the physical processes at play are less clear. This thesis targets a sample representative of the majority of AGN, and uses multi-wavelength observations to resolve some of the outstanding questions about how `radio-quiet' AGN transfer energy into their host galaxies, impact the surrounding multi-phase gas and, consequently, impact the evolution of their host galaxies.
In the first part of this thesis I study ten local ($z~10^45 erg/s), 'radio-quiet' AGN selected to have powerful ionised gas outflows, combining radio observations (with spatial resolutions up to 20 times better than the pre-existing data), and optical integral field spectroscopy. Jet-like radio emission on ~kpc scales was discovered in 70-80 percent of the sample, and it was revealed that these jets are driving ionised gas outflows in their host galaxies. This challenges the expectation that photon pressure should dominate feedback in these systems, and establishes that jets are playing an important role in the evolution of galaxies even in this 'radio-quiet' regime. I then used observations of the total carbon monoxide emission in nine of the sources studied in the radio to demonstrate that the outflows and jets do not have an immediate, global impact on the total reservoir of molecular, star-forming gas in their host galaxies. Specifically, at least seven of the AGN observed reside in gas-rich, highly star-forming galaxies. Finally, I present the first results on the full Quasar Feedback Survey, expanding the sample studied to 42 targets and removing the pre-selection for known outflows. In this ~four times larger, unbiased sample I showed that radio jet like features are still present in the majority (66 percent) of the sample and found a correlation between radio size and the ionised gas outflow properties, indicative of jet-gas interactions. This work has confirmed a connection between outflows and radio emission, and determined that jets are an important mechanism for driving outflows even in 'radio-quiet' AGN. I also discovered that even in systems with outflows and jets there is no immediate, appreciable impact on the global molecular gas content. These results will require simulations of feedback to be updated, and represent a significant step forward in the quest to form a complete understanding of how galaxies evolve
Covariant spinor representation of and quantization of the spinning relativistic particle
A covariant spinor representation of is constructed for the
quantization of the spinning relativistic particle. It is found that, with
appropriately defined wavefunctions, this representation can be identified with
the state space arising from the canonical extended BFV-BRST quantization of
the spinning particle with admissible gauge fixing conditions after a
contraction procedure. For this model, the cohomological determination of
physical states can thus be obtained purely from the representation theory of
the algebra.Comment: Updated version with references included and covariant form of
equation 1. 23 pages, no figure
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