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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

The threespine stickleback adaptive radiation| Salinity, plasticity, and the importance of ancestry

King, Richard W. 01 April 2016 (has links)
<p> Adaptive radiations offer unique insight into how diversification is initiated in novel or changing environments but the value of such studies is often limited by incomplete or lacking information on the ancestral species. The threespine stickleback species complex is proving to be particularly valuable in enhancing our understanding of evolutionary processes because there is reason to believe a surrogate for the ancestral group is extant and representative of the oceanic form that gave rise to most post-glacial freshwater populations during the last ~12,000 years. If we are to maximize the value of this radiation a thorough understanding of the putative ancestor group is needed. This dissertation explores the degree of phenotypic variation in oceanic stickleback in Cook Inlet, AK as well as the relative contributions of genetic and plastic aspects shaping the phenotypic variation revealed.</p><p> Geometric morphometrics were used to describe shape differences in two oceanic forms of stickleback, anadromous and fully marine. These groups differ in shape along the same benthic-limnetic axis described within the freshwater derived populations in the same region. A common-garden rearing study revealed high levels of body shape plasticity in both groups as well as likely genetic influences maintaining important aspects of shape differences between their stocks of origin. Interestingly, plasticity related to the salinity of early rearing environment differed across types suggesting that there may be a flexible dual stem in the threespine stickleback radiation, a surprising result that has not been considered to date in any system to my knowledge.</p><p> Additionally, because life-history traits are intimately linked to reproductive success and thus fitness, differences in life-history strategies between these two oceanic types should reflect meaningful adaptive variation, whether plastic or strictly genetic based. Established methodologies in stickleback life-history studies were employed to assess phenotypic variation across populations, types, and years in many important traits (e.g., egg and clutch size, reproductive effort, allometric relationships between reproductive effort and female body size). Life-history strategies differed significantly across type and year. Generally, marine females exhibit greater reproductive investment and have larger and more numerous eggs per clutch. Anadromous populations experience an apparent reproductive cost to the migration to freshwater relative to their fully-marine counterpart. It&rsquo;s unclear from these studies then where the fitness advantage to anadromy lies in the primitively oceanic species complex. However, important differences in mortality on the breeding grounds for adults and young as well as a possibly faster clutch production frequency in the anadromous lifestyle explains the apparent paradox in these data.</p><p> The finding of differences in genetic and plastic contributions to oceanic stickleback phenotypes body shape and life histories across two types in close geographic proximity which correlates with salinity regime suggest a flexible dual stem in the oceanic group(s). This could then influence evolution within the freshwater radiation. Thus, depending upon the freshwater populations (or watersheds) studied, the choice of representative oceanic type would need to be carefully considered. These data suggest that any near shore or inland sea areas within the stickleback oceanic distribution which experience a wide range of salinities is likely to show associated clinal variation in stickleback population reaction norms for (at least) body shape, life history strategies, and likely many other traits which are sensitive to salinity, such as genes involved in osmoregulation. Recent studies of Baltic and Sea of Japan oceanic stickleback further support this conclusion.</p>
92

The palaeorotation of the Troodos microplate

Clube, Tristan Mark Murray January 1985 (has links)
No description available.
93

An approach to implementing cloud service oriented legacy application evolution

Zheng, Shang January 2013 (has links)
An emerging IT delivery model, Cloud Computing, can significantly reduce IT costs and complexities while improving workload optimisation and service delivery. More and more organisations are planning to migrate their existing systems into this internet-driven computing environment. This investigation is proposed for this purpose and will be undertaken with two main aims. The first aim is to establish a general framework and method to assist with the evolution of legacy systems into and within the Cloud environment. The second aim is to evaluate the proposed approach and demonstrate that such an approach can be more effective than developing Cloud services from scratch. The underlying research procedure of this thesis consists of observation, proposition, test and conclusion. This thesis contributes a novel evolution approach in Cloud computing. A technical solution framework is proposed through a three-dimensional software evolution paradigm, which can cover the relationships of software models, software functions and software qualities in different Cloud paradigms. Finally, the evolved service will be run in the Cloud environments. The approach framework is implemented by three phases: 1) legacy system analysis and extraction, which proposes an analysis approach to decide the legacy system in the Cloud environment and to adopt the techniques of program slicing with improved algorithm and software clustering for extracting legacy components. 2) Cloud-oriented service migration including evolving software into and within Cloud. The process of evolving software 'INTO' Cloud can be viewed mainly as changing software qualities on software models. The process of evolving software 'WITHIN' Cloud can be viewed mainly as changing software functions on software models, the techniques of program and model transformation and software architecture engineering are applied. 3) Cloud service integration, which integrates and deploys the service in the Cloud environment. The proposed approach is proved to be flexible and practical by the selected case study. Conclusions based on analysis and future research are discussed at the end of the thesis.
94

Identification of ejaculated proteins in the house mouse (Mus domesticus) via isotopic labeling

Dean, Matthew, Findlay, Geoffrey, Hoopmann, Michael, Wu, Christine, MacCoss, Michael, Swanson, Willie, Nachman, Michael January 2011 (has links)
BACKGROUND:Seminal fluid plays an important role in successful fertilization, but knowledge of the full suite of proteins transferred from males to females during copulation is incomplete. The list of ejaculated proteins remains particularly scant in one of the best-studied mammalian systems, the house mouse (Mus domesticus), where artificial ejaculation techniques have proven inadequate. Here we investigate an alternative method for identifying ejaculated proteins, by isotopically labeling females with 15N and then mating them to unlabeled, vasectomized males. Proteins were then isolated from mated females and identified using mass spectrometry. In addition to gaining insights into possible functions and fates of ejaculated proteins, our study serves as proof of concept that isotopic labeling is a powerful means to study reproductive proteins.RESULTS:We identified 69 male-derived proteins from the female reproductive tract following copulation. More than a third of all spectra detected mapped to just seven genes known to be structurally important in the formation of the copulatory plug, a hard coagulum that forms shortly after mating. Seminal fluid is significantly enriched for proteins that function in protection from oxidative stress and endopeptidase inhibition. Females, on the other hand, produce endopeptidases in response to mating. The 69 ejaculated proteins evolve significantly more rapidly than other proteins that we previously identified directly from dissection of the male reproductive tract.CONCLUSION:Our study attempts to comprehensively identify the proteins transferred from males to females during mating, expanding the application of isotopic labeling to mammalian reproductive genomics. This technique opens the way to the targeted monitoring of the fate of ejaculated proteins as they incubate in the female reproductive tract.
95

Advances in the social evolution and ecology of bacterial public goods

O'Brien, Siobhan Elizabeth January 2015 (has links)
The altruistic production of public goods is one of most popular puzzles in evolutionary biology, and is most commonly explained by the indirect fitness benefit accrued by producers. I develop our understanding of the ecology and evolution of public good production by considering how inter- and intraspecific interactions can affect indirect fitness benefits, and ultimately, the evolutionary trajectory of public good cooperation in a bacterial public good system: 1) I demonstrate the ability of public good cooperators to adapt to the presence of cheats by reducing their own cooperative output, constraining cheat fitness as a consequence. 2) I examine the relative contributions of inter- (bacteriophage) and intraspecific (social cheats) parasites on shaping bacterial mutation rates, and demonstrate that social cheats can gain a fitness advantage in the presence compared with the absence of interspecific parasites. 3) I formally show for the first time, that siderophore-mediated detoxification can be an altruistic trait, rapidly selecting for the evolution of de novo cheats, and discuss the implications this process may have for community structure and function. 4) I extend (3) to assess the impact the natural microbial community has on the fitness consequences of siderophore-mediated detoxification in a natural soil environment. 5) I discuss the interplay between rapid microbial evolution and community context, and propose the impacts such interplay may have for biotechnological applications.
96

Massive galaxies at 1 < z < 3

Bruce, Victoria Ashley January 2014 (has links)
This thesis explores the evolution of massive galaxies (M * > 1011M ʘ) by conducting the largest multiple-component Sersic light-profile fitting study to date of the rest-frame optical and ultra-violet morphologies of galaxies at redshifts 1 < z < 3. Despite many of the recent advances in galaxy formation and evolution models, the physical processes which are responsible for driving morphological transformations and star-formation quenching remain unclear. By undertaking a detailed study of the individual bulge and disk components of these massive systems, the work presented in this thesis addresses these outstanding issues by exploring not only how the sizes of the individual components evolve with redshift, but also how the overall bulge and disk fractions evolve, and how these trends are connected to star-formation quenching of the separate components. In order to perform this analysis, I have combined the latest high-resolution near-infrared HST WFC3/IR and ACS imaging provided by the CANDELS survey in the UDS and COSMOS fields and have presented a robust procedure for morphological multiple-component Sersic light-pro le model fitting across the 0:6μ m to 1:6μ m wavelength range sampled by CANDELS. This procedure is discussed in depth along with the tests I have undertaken to assess its reliability and accuracy. This approach has enabled me to generate separate bulge and disk component model photometry, allowing me to conduct individual component SED fitting in order to determine decomposed stellar-mass and star-formation rate estimates for the separate bulge and disk components. The results presented in this work reveal that the sizes of the bulge and disk components lie both on and below the local size-mass relations, confirming that the size evolution required by the previously reported compact sizes of high-redshift galaxies extends to both galaxy components. However, I find evidence that the bulge components display a stronger size evolution with redshift than the disks as, at 1 < z < 3, the bulges are a median factor of 3:09 ± 0:2 times smaller than similarly massive local early-type galaxies, whereas the disks are a median factor of 1:77 ± 0:1 times smaller than similarly massive local late-type galaxies. By including decomposed star-formation rates for the individual bulge and disk components, this work also reveals that while the growth of individual components through, for example, inside-out processes such as minor merging, are consistent with the size evolution of these systems, the addition of larger newly quenched systems to the galaxy population, for the disk components at least, may also play an important role in the observed size evolution of massive galaxies. By exploring the evolution of the bulge and disk-dominated fractions with redshift, I find that 1 < z < 3 marks a key transition era in cosmic time where these most massive galaxies appear to be undergoing dramatic structural transformations. Within this redshift range there is a decline in the population of disk-dominated galaxies and a gradual emergence of increasingly bulge-dominated systems. However, despite the rise of S0-type galaxies, even by z = 1 I do not yet find a significant fraction of "pure" bulges comparable to the giant ellipticals which comprise the majority of the local massive galaxy population. In addition to studying how the overall bulge and disk dominated fractions evolve with redshift, by incorporating the star-formation rate and stellar-mass estimates for the separate components and imposing new, highly conservative criteria, I con firm that a significant fraction of passive galaxies are disk-dominated (18± 5%) and a significant fraction of star-forming galaxies are bulge-dominated (11 ±4%). The presence of passive disks and star-forming bulges has interesting implications for the models of galaxy evolution as they suggest that the processes which quench star-formation may be distinct from the mechanisms which cause morphological transformations. Finally, the detailed morphological analysis presented in this work has also allowed me to explore the axial ratio distributions of these most massive high-redshift galaxies, which provides additional insight into the structure of the passive and star-forming bulge and disk-dominated sub-populations. Whilst the overall axial ratio distributions for star-forming disks are peaked, I find tentative evidence that the largest and most active star-forming disks are flatter. I have also been able to further demonstrate that by selecting the most active star-forming disks and comparing to extreme star-forming (sub-)mm selected galaxies, the axial ratio distributions of the two samples appear to be comparably flat, thus reconciling the observed structures of these populations.
97

Long-chain alkenone and alkyl alkenoate, and total pigment abundancies as climatic proxy-indicators in the the northeastern Atlantic : analytical methods, calibration and stratigraphy

Mele, Antoni Rosell i. January 1994 (has links)
No description available.
98

The molecular basis of convergent and divergent evolution in Heliconius butterflies

Pardo Diaz, Geimy Carolina January 2014 (has links)
No description available.
99

Evolution in multi-enzyme systems

Beeby, Richard Ben January 1986 (has links)
No description available.
100

Garnet- and clinopyroxene-liquid equilibria at high pressure : an experimental study in part of the system CaO-MgO-FeO-Al₂O₃-SiO₂ with relevance to garnet-lherzolites

Armshaw, Derek January 1987 (has links)
No description available.

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