My research has focused on locating and measuring star formation and AGN activity in different environments with interferometric and single-dish radio observations. As my first PhD project, I studied the complex interaction between an intermediate redshift (z 0.3) starburst galaxy and a nearby ( 7 kpc separation) QSO using sub-arcsecond VLA observations. I found new evidence for jet-induced star formation activity in the companion galaxy, making the system a strong candidate for this rare, and potentially important process in the early Universe. In my second paper, I investigated the infrared-radio correlation (IRRC) of spheroid- and disc-dominated galaxies in the COSMOS field out to z 1.5. With 1.4 GHz data and Herschel photometry I found that the redshift evolution reported in recent works is due to an increasing radio excess emission associated with spheroid-dominated galaxies, compared to disc-dominated ones, i.e. the ‘purest' star-forming systems in our sample. I theorize that the extra radio power in spheroid-dominated systems is due to low-level AGN activity, even though these sources were not identified by most commonly-used diagnostics as AGN hosts. This finding will significantly increase the accuracy of future high-redshift radio surveys measuring star formation. In my third project I assembled and analysed the largest-to-date low-z IRRC sample of galaxies. I demonstrated the importance of selection effects influencing IRRC statistics, and carried out an improved IRRC analysis that yielded more accurate measures of the correlation's properties. With rich ancillary data it will provide insight into the physical processes that give rise to the IRRC. Finally, I adopted an MCMC-based model optimization to fit a radiative transfer model to ammonia line spectra of a binary molecular cloud core. I determined the physical structures and the masses of the cores and found they are gravitationally unbound.

Over the last three decades, the far-infrared emission from distant galaxies has been revealed to us. This far-infrared light is emitted by dust clouds heated by UV radiation from young stars. This reveals to us some of the most remarkable and highly star-forming galaxies in the Universe. The Herschel space observatory was able to capture this light. With this thesis I have attempted to get a better understanding of the underlying galaxy population. I have done this by observing the most extreme forms of star formation in the early Universe seen in maps obtained by the SPIRE instrument and using prior information from deep high resolution surveys. In particular I have examined the dependencies of dusty galaxy properties on their environment. I have confirmed that star formation is primarily dependent on both galaxy mass and whether a galaxy lies in the "blue cloud". Environment is the primary influence on the fraction of galaxies lying in the blue cloud and has a minor, but significant, affect on the average star formation rate of star forming galaxies. The highest redshift galaxies directly detected in the Herschel SPIRE maps are very rare, but due to the large area of the HerMES surveys we are able to find a statistical significant sample. With the addition of longer wavelength SCUBA-2 data I further confine the redshift of the dusty galaxies and find that the star formation rates of those sources are extremely high and exceed 1000 M_ a year. The observed number counts of these extremely bright sources have been a problem for galaxy evolution models. I am able to explain the observed number count of red SPIRE sources by adding correlated confusion noise and Gaussian instrumental noise to simulated galaxy catalogues. My results emphasise that it is crucial to correct for noise and selection effects for comparison with simulations. I exploit a novel way of fitting the full SPIRE maps using prior information from deep high resolution surveys, obtained from wavelengths ranging from optical to radio. In doing so I obtain the most accurate values of the cosmic infrared background (CIB) at the SPIRE wavelengths. With these results we have a better indication of which sources are producing the CIB, and therefore the bulk of star formation. My results indicate that future large area surveys like LSST are likely to resolve a substantial fraction of the population responsible for the CIB at 250 μm ≤ λ ≤ 500 μm.

In artificial evolution, selection and evaluation are separate and distinct steps. This distinction is rather different in natural evolution, where fitness (corresponding to evaluation) is a direct consequence of selection rather than a precursor to it. This thesis presents a new way of thinking about artificial evolution that separates evaluation and selection and consequently opens up the space of potential evolutionary algorithms beyond the limitations imposed by ignoring this distinction. In Part I of the thesis we explore how varying the level of evaluation and selection impacts evolution. Using novel genetic algorithms (GAs) we show how group level evaluation allows evolution to find solutions to problems that require niching or a division of labour amongst component parts, something that cannot be accomplished using a standard GA. One of the inspirations for testing GAs with group-level evaluation was recent research into bacterial evolution which shows in bacterial colonies, distinguishing between the individual and group is very difficult because of the symbiotic relationship between different bacteria. We find that depending on the task it sometimes makes sense to select the individual while in other cases simply selecting groups is the best choice. Finally, we present a method for evolving the group size in these types of GAs that has the benefit of avoiding the need to know the optimal division of labour ahead of time. In Part II we move away from studying the relationship between evaluation and selection to show how our novel view of evolution can be used to develop GAs that implement horizontal gene transfer which was again inspired by looking at bacterial evolution. By testing these GAs on a variety of different tasks we show how this promiscuous gene swapping is often beneficial to evolution because it can reduce the probability of the population getting stuck on a sub-optimal solution. The thesis demonstrates the benefits of of looking at artificial evolution in terms of both evaluation and selection when it comes to algorithm development, and thus provides the GA community with a new context in which they can choose different algorithms appropriate to different tasks.

acase@tulane.edu / A comprehensive understanding of sexual dichromatism and sexual selection depends on understanding selective pressures on females, which may differ from those experienced by males. Conventional theory suggests that ornamentation in females evolves as the byproduct of selection pressures on males, and is non-adaptive. My dissertation challenges this assumption through a series of linked studies related to female ornamentation in a species of tropical passerine bird, the White-shouldered Fairywren (Malurus alboscapulatus), of New Guinea. The White-shouldered Fairywren is ideally suited to evaluate the evolution of female ornamentation, because populations are characterized by divergence in female plumage coloration from brown (unornamented) to black-and-white (ornamented), with no variation in males, which are uniformly black- and-white. My thesis research employed field-based observation and experimentation with contemporary genomic, endocrine, and microscopy techniques to identify proximate mechanisms, current adaptive function, and evolutionary history of female ornamentation in this system. / 1 / Erik Enbody

acase@tulane.edu / The Louisiana coast is an invaluable asset to the nation's human, economic, and ecological welfare. However, due to the combined effects of coastal erosion, subsidence, and sea level rise, Louisiana is losing on average 25 km2 of its valuable coastal wetlands per year. Terrebonne Bay and the associated Lafourche deltaic lobe headland is a critical section of this coast for wetlands and infrastructure protection and restoration in the State’s Master Plan. Historical imagery and bathymetry clearly show the rapid transgression and erosional degradation of both sets of headland-flanking barrier island shorelines due to wave attack and relative sea level rise in the past 150 y. The focus of the present study is a barrier island system: an ocean-fronting modern- barrier shoreline (Timbalier) and a paleo-deltaic headland barrier arc (Terrebonne) inland of the active barrier. The evolution of the modern barrier arc is closely tied to the shallow geologic framework over which it is transgressing, and specifically the sand re-activation capacity of the antecedent geology once erosional forces are introduced. To understand the evolution of these barrier systems and how to address their protection and re-nourishment, it is important to quantify (1) the depositional facies geometry and (2) the volume of sand in these back-barrier sandy lithosomes. Here we present new observations from CHIRP sub-bottom seismic, multibeam bathymetry, and surface grab and vibracore sampling in an effort to quantify the sediment availability within the underlying geologic framework and reconstruct the geomorphic evolution of these barrier shorelines. Observations of sandy units agree with results from Kulp et al. (2005), who showed the presence and extent of sandy lithofacies within 3 m of the surface proximal to the Raccoon Pass tidal-inlet. We provide evidence to suggest that this sand is an important potential resource for the longevity of proximal sandy barrier islands as transgression continues. / 1 / Daniel Culling

In the history of life, we can observe an astounding diversity of life forms. However, we still lack a thorough understanding of how different species form and even what constitutes a species. In some groups of organisms, especially in plants, hybridization between species is very common. Hybridization has the potential to create new combinations of traits, which can lead to speciation, but hybridization can also lead to extinction or demographic decline of natural populations. Within and between species, genetic variation is ubiquitous in natural populations, which can be observed on various levels. Here, I present several ways to assess such variation in the plant genus Boechera (Brassicaceae). First, I present the evolutionary history and patterns of admixture within a subgroup in the genus, the B. puberula clade. I further show through admixture analyses, that that there is variation in the extent of admixture within the group, but especially when it comes to admixture with two widespread congeners, not part of the B. puberula clade. In a second study, I assessed levels of genetic diversity and patterns of population genetic structure within a member of the B. puberula clade, the montane endemic diploid B. lasiocarpa from Utah. After excluding all hybrids based on estimated admixture proportions, I show that levels of genetic diversity based on genomic data from this rare species are higher than in the widespread B. stricta. Additionally, I assessed common and rare SNVs and show that populations of B. lasiocarpa exhibit variation in genetic diversity and population genetic structure, which seem to be consistent with assumed population sizes. Further, I investigated patterns of gene expression in an experiment under drought-stress in four Boechera species, which exhibit differences in reproductive mode and ploidy level. Across all four species, I did not find a uniform response to drought-stress, and I present evidence for apomixis-specific gene expression, for differential expression associated with ploidy as well as differentially-expressed genes under a model of potential reversal from apomixis to sexual reproduction in B. lignifera.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (viewed Feb. 8, 2007). PDF text: iv, 319 p. UMI publication number: AAT 3218216. Includes bibliographical references. Also available in microfilm and microfiche format.

Megalagrion damselflies have radiated into new breeding habitats independently at least six times in the Hawaiian archipelago, and have evolved bright body coloration numerous times. We hypothesize that these radiations are correlated with specific changes in the opsin proteins. We isolated and characterized two opsin genes from nine different Megalagrion species. The opsin phylogeny is consistent with the phylogeny based on breeding habitat preference of Megalagrion species supporting the correlation between the evolutionary changes of vision and habitat shifts. dN/dS ratios of opsin sequences show that these genes are evolving under purifying selection, though some sites of the opsin genes might be evolving under positive selection. Two terrestrial-breeding Megalagrion species show higher rates of opsin gene evolution that are correlated with a rapid transformation in their breeding habitats from aquatic to terrestrial. These results support the hypothesis that opsin gene evolution has played a role in Megalagrion radiation in Hawaii.