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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.
191

Seasonal variation in the number of dogs and cats entering four animal shelters in Mississippi and the characterisitics [i.e. characteristics] influencing their adoption

Lefebvre, Sarah Elizabeth 07 August 2010 (has links)
The pet overpopulation problem is a multiactorial problem that many organizations such as animal shelters attempt to manage. Many studies have focused on the reasons animals are relinquished by their owners but few have also looked at the characteristics that may influence adoption. Identifying which characteristics that influence adoption may help shelters provide more detailed adoption programs based on their dog and cat profile. Increases in the number of dogs and cats entering animal shelters during the spring and summer month is a perception among shelter staff. Investigating the seasonal trends in the number of animals entering a shelter may help the facility prepare to provide additional space and resources. The focus of this study was to identify any seasonal variation in the number of dogs and cats entering animal shelters in Mississippi and to determine the characteristics of dogs and cats that influenced their adoption.
192

The effect of environmental variability on heritabilities and genetic correlations of traits in the field cricket, Gryllus pennsylvanicus /

Simons, Andrew M. (Andrew Michael) January 1993 (has links)
No description available.
193

Genetic analysis of the steps involved in the conversion of sulphate to sulphite in Aspergillus nidulans

Niklewicz, Anne M. T. January 1970 (has links)
No description available.
194

Heritability of Egg Size in Captive American Kestrels

Stewart, Katherine Glenna January 1986 (has links)
No description available.
195

The evolution of intraspecific variation, growth, and body size in early theropod dinosaurs

Griffin, Christopher T. 24 June 2016 (has links)
Understanding the changes undergone during the life of an organism is often crucial to properly interpreting the evolutionary history of a group. For extinct organisms, this process can only be directly studied through growth series of fossils representing individuals at different stages of maturity. The growth patterns of the earliest dinosaurs (230–190 million years ago), in particular the morphological changes undergone during the life history of an individual (i.e., ontogeny) is poorly understood. To tackle this problem, I studied the changes undergone during growth of two early theropod dinosaurs, Coelophysis bauri and Megapnosaurus rhodesiensis. To reconstruct the growth of these dinosaurs I used ontogenetic sequence analysis (OSA). I found that, unlike living birds, early dinosaurs possessed an extremely high amount of intraspecific variation in growth. This variation had been previously interpreted as sexual difference; however, I found no evidence of this. Because this variation is widespread among early dinosaurs and their relatives, I hypothesize that this is the ancestral condition of dinosaurian growth, and that this was lost along the evolution to birds. These ontogenetic events are conserved through evolution, and I used this to assess the maturity of large Triassic theropods: I suggest that all known large-bodied Triassic theropods were still growing rapidly at death, and that the maximum body size of Triassic theropods was higher than previously supposed. Theropods were large before the end Triassic mass extinction, unlike what has been previously hypothesized. / Master of Science
196

Évolution et symbiose chez des populations d'une espèce de mousse dans la région subarctique.

Escolástico Ortiz, Dennis Alejandro 10 June 2024 (has links)
Les régions arctiques et subarctiques constituent un défi pour la recherche sur la biodiversité en raison de leur éloignement et des conditions environnementales extrêmes. Cependant, il est essentiel d'acquérir une compréhension fondamentale du biote polaire. Les bryophytes sont une composante importante des écosystèmes polaires à cause de leur abondance et de leurs rôles écologiques, tels que la production primaire, la stabilisation des sols et le cycle des nutriments par le biais d'interactions bactériennes. Malgré leur rôle vital dans les écosystèmes polaires, l'écologie des bryophytes est loin d'être comprise. Cette thèse contribue à la connaissance des bryophytes de l'Arctique et du Subarctique, en mettant l'accent sur les populations de mousses. Je me suis concentré sur trois sujets principaux : l'histoire évolutive, la diversité génétique locale et les interactions microbiennes en utilisant la mousse *Racomitrium lanuginosum* comme espèce modèle. Une approche intégrative a été utilisée pour étudier ces sujets, englobant le séquençage Sanger, le génotypage par séquençage (GBS), des modèles de répartition des espèces, le séquençage des amplicons, les essais de réduction de l'acétylène (ARA) et la spectrométrie de masse à plasma inductif (ICP-MS). Le premier chapitre dévoile l'histoire évolutive de la mousse dans l'hémisphère nord, en découvrant quatre groupes génétiques cryptiques repartis dans des environnements subarctiques et arctiques et en montrant l'impact des dernières glaciations sur la diversité génétique des populations. Le deuxième chapitre illustre comment la reconnaissance de lignées cryptiques peut avoir un impact sur les évaluations de la diversité génétique dans les habitats et peux aider à comprendre la répartition de la variation génétique dans des populations clonales de *R. lanuginosum*. Le troisième chapitre étudie les communautés microbiennes associées à la mousses et leurs capacités de fixation d'azote dans l'écotone forêt-toundra, en mettant en évidence le microbiote central des mousses, les différences de communautés bactériennes entre les habitats et les bactéries diazotrophes qui façonnent la fixation d'azote. En résumé, cette thèse contribue de manière significative à la connaissance des aspects évolutifs et écologiques des plantes de la région subarctique, en se concentrant sur un organisme clé de la toundra. L'étude souligne l'importance des bryophytes et de leurs relations symbiotiques dans les écosystèmes polaires, et met en évidence la nécessité de poursuivre les recherches sur ces systèmes complexes. Afin d'assurer la préservation à long terme de ces écosystèmes vulnérables, il est essentiel d'acquérir une compréhension approfondie de leur dynamique et de développer des stratégies de conservation efficaces, tout en évaluant la manière dont les organismes réagissent aux changements environnementaux. / The Arctic and subarctic regions pose a challenge to biodiversity research due to their remote location and harsh environmental conditions. However, gaining a fundamental understanding of the polar biota is crucial. Bryophytes are significant components of polar ecosystems due to their abundance and ecological roles, such as primary producers, soil stabilization, and nutrient cycling through bacterial interactions. Despite their vital role in polar ecosystems, bryophyte ecology remains far from being understood. This thesis contributes to the knowledge of Artic and Subarctic bryophytes, with a focus on mosses. I covered three main topics: evolutionary history, local genetic diversity and microbial interactions using the moss *Racomitrium lanuginosum* as a model species. An integrative approach was used to study these topics, encompassing Sanger sequencing, genotyping-by-sequencing (GBS), species distribution modeling, amplicon sequencing, acetylene reduction assays (ARA), and inductively coupled plasma mass spectrometry (ICP-MS). The first chapter unveils the evolutionary history of the moss in the Northern Hemisphere, uncovering four cryptic genetic groups scattered across subarctic and arctic environments and showing the impact of the last glaciations on the population's genetic diversity. The second chapter illustrates how recognizing cryptic lineages can impact genetic diversity assessments in habitats and help to understand the partition of genetic variation in clonal populations of *R. lanuginosum*. The third chapter delves into the moss-associated microbial communities and their N₂ fixation capabilities in the forest-tundra ecotone, highlighting the moss core microbiome, the bacterial community differences between habitats and the diazotrophic bacteria influencing this process. In summary, this thesis significantly contributes to the knowledge of the evolutionary and ecological aspects of plants in the subarctic region, focusing on a key tundra organism. The study emphasizes the importance of bryophytes and their symbiotic relationships in polar ecosystems, highlighting the need for further investigations into these intricate systems. A deep understanding of plant dynamics in Arctic and Subarctic environments will be crucial to ensure the long-term preservation of these vulnerable ecosystems
197

Plant genotype and environment interact to influence soil carbon and nitrogen dynamics

Pregitzer, Clara Christina 01 May 2010 (has links)
Abiotic and biotic variation has been shown to be important in regulating nutrient cycling and belowground communities in natural systems. However, genetic variation in dominant plants as a driver of rates of nutrient cycling is still poorly understood and few studies have looked at genotype interactions across multiple environments. Using Populus angustifolia and a common garden approach, we hypothesized that all three factors: tree genetic variation, environmental conditions and genetic by environment (G x E) interactions would affect soil carbon (C) storage and nitrogen (N) cycling. Replicated copies of five different reciprocally planted Populus genotypes were studied in three separate 18-21 year old common gardens at different elevations (1300m, 1384m and 1587m) in northern Utah, to measure the genotype and environmental effects on pools of soil C and N as well as rates of soil net N nitrification and net mineralization. Our results indicate that genotypes influence pools of soil C, total N and C:N, but genotype did not influence net rates of nitrogen mineralization. Environmental variation significantly influenced pools of soil C, total N, soil C:N and rates of net nitrification and net N mineralization. As predicted, G x E interactions significantly influenced both pools and processes of soil C and N cycling. Overall, we found that genetic variation in plant traits (tree diameter and leaf/root chemistry) as well as soil texture across gardens were significant predictors of soil C and N pools and fluxes across seasons. These data help us understand the relative role of genotypic variation on above- and belowground interactions in different environments and the consequences of these interactions on ecosystem processes. The results from this study show that across an environmental gradient Populus angustifolia genotypes can influence nitrogen mineralization through feedbacks between environmental variation, tree phenotype and soils.
198

Plant genotype and environment interact to influence soil carbon and nitrogen dynamics

Pregitzer, Clara Christina 01 May 2010 (has links)
Abiotic and biotic variation has been shown to be important in regulating nutrient cycling and belowground communities in natural systems. However, genetic variation in dominant plants as a driver of rates of nutrient cycling is still poorly understood and few studies have looked at genotype interactions across multiple environments. Using Populus angustifolia and a common garden approach, we hypothesized that all three factors: tree genetic variation, environmental conditions and genetic by environment (G x E) interactions would affect soil carbon (C) storage and nitrogen (N) cycling. Replicated copies of five different reciprocally planted Populus genotypes were studied in three separate 18-21 year old common gardens at different elevations (1300m, 1384m and 1587m) in northern Utah, to measure the genotype and environmental effects on pools of soil C and N as well as rates of soil net N nitrification and net mineralization. Our results indicate that genotypes influence pools of soil C, total N and C:N, but genotype did not influence net rates of nitrogen mineralization. Environmental variation significantly influenced pools of soil C, total N, soil C:N and rates of net nitrification and net N mineralization. As predicted, G x E interactions significantly influenced both pools and processes of soil C and N cycling. Overall, we found that genetic variation in plant traits (tree diameter and leaf/root chemistry) as well as soil texture across gardens were significant predictors of soil C and N pools and fluxes across seasons. These data help us understand the relative role of genotypic variation on above- and belowground interactions in different environments and the consequences of these interactions on ecosystem processes. The results from this study show that across an environmental gradient Populus angustifolia genotypes can influence nitrogen mineralization through feedbacks between environmental variation, tree phenotype and soils.
199

Variant-curation and database instantiation (Variant-CADI): an integrated software system for the automation of collection, annotation and management of variations in clinical genetic testing

Hallier, Andrea Rae 01 December 2016 (has links)
One of the tools a clinician has in disease diagnosis and treatment is genetic testing. To generate value in genetic testing, the link between genetic variants and disease must be discovered, documented, and shared within the community. Working with two existing genomic variation tools, Kafeen and Cordova, a new set of features referred to as Variant-Curation and Database Instantiation (Variant-CADI) was identified, designed, implemented and integrated into the existing Cordova system to unite data collection, management and distribution into one cohesive tool accessible through user interfaces. This eliminates the user needing specialized knowledge of the underlying implementation, data pipeline or data management to collect desired disease specific genetic variations. Using this tool, new disease-specific variation database instances have been initialized and created as demonstrations of the utility of these applications.
200

Within-person variation in personality and psychological well-being

Churchyard, Jamie Stuart January 2014 (has links)
Personality is one of the most broad and complex areas in psychology. This has led to many researchers attempting to reduce this complexity by focusing solely on how habitual personality differs between each individual (inter-individual differences). This is important to study, but it has been focused on so heavily that research into how each individual personality varies within the person (intra-individual differences) has been neglected in comparison. Recent research has started to examine intra-individual variation in personality more thoroughly. One research aim of this programme was to establish the nature of several different types of within person variability including inter-item variation (variation within the test responses for a personality trait), and cross-contextual variation in personality (variation according to context), to see whether these types of variability are associated with psychological outcomes. Three research questions were examined to this end: 1) What is the extent of meaningful variability in personality trait test responding? 2) What are the predictors of intra-individual variability in personality? 3) What is the relative importance of the person and situational factors in personality variability? The first question was developed to try and determine whether the individual can display meaningful inter-item variation in ratings of specific behaviours within personality trait measures. Trait questionnaires are usually only analysed at the between subject level, and within subject variation in inter-item ratings have not been extensively examined in relation to meaningful psychological outcomes. The second and third questions were developed to look into the nature of cross-contextual personality, and establish whether within person personality differences are influenced more strongly by the person or situation. The studies conducted towards answering these questions demonstrated a person-based capacity to display intra-individual variability. A second aim of the research programme was to see whether the capacity to display these types of variability can be utilised in behaviour change. The fourth research question was developed to try and understand how a person can display intra-individual variability, yet still be resistant to changing negative habits: 4) How do the different aspects in personality variability help explain why some people are resistant to change, especially with regard to behaviours that are bad for them? This question was answered by theoretically discussing the findings from the three previous studies which proposed that positive or problematic behaviour could be interpreted with a simple path to understand the process of behavioural action: The individual receives feedback from a behaviour response which either validates or invalidates their action in the situation context (does or does not receive a desired outcome). Reinforcement of the behaviour happens if it is validated by positive feedback. Alternately reconstruction of the situation happens if the behaviour is invalidated. This allows for two types of intra-individual variability. One is flexibility in behaviour responses to different situations under the individual’s control. The other is change according to the situation, where the behaviour is invalidated and an alternative is attempted. A problematic behaviour may have benefit in stopping something invalidating, but if repeated it may become a habit needed for psychological functioning. As part of the second research aim a behaviour change strategy was developed and piloted to try and bring the individual closer to their construct of the ideal self. Instructions were provided for the individual to experiment with that differed from their disposition. The programmes had varied degrees of success depending on the participant. The implications for personality research and behaviour change are discussed.

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