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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.
1

THE Origin of the 4.5 μM Excess From Dwarf Galaxies

Smith, Beverly J., Hancock, Mark 03 August 2009 (has links)
Dwarf galaxies tend to have redder [3.6 μm] - [4.5 μm] Spitzer broadband colors than spirals. To investigate this effect, for a large sample of dwarf galaxies we combine Spitzer fluxes with data at other wavelengths and compare to population synthesis models. Lower metallicity systems are found to have redder [3.6] - [4.5] colors on average, but with considerable scatter. The observed range in [3.6] - [4.5] color is too large to be accounted for solely by variations in stellar colors due to age or metallicity differences; interstellar effects must contribute as well. For the reddest systems, the 4.5 μm luminosity may not be a good tracer of stellar mass. We identify three factors that redden this color in dwarfs. First, in some systems, strong Brα emission contributes significantly to the 4.5 μm emission. Second, in some cases high optical depths lead to strong reddening of the starlight in the Spitzer bands. Third, in some galaxies, the nebular continuum dominates the 4.5 μm flux, and in extreme cases, the 3.6 μm flux as well. The harder UV radiation fields in lower metallicity systems produce both more gaseous continuum in the infrared and more Brα per star formation rate. The combination of these three factors can account for the 4.5 μm excess in our sample galaxies, thus it is not necessary to invoke a major contribution from hot dust to the 4.5 μm band. However, given the uncertainties, we are not able to completely rule out hot dust emission at 4.5 μm. More spectroscopic observations in the 3-5 μm range are needed to disentangle these effects.
2

The Effects of Probiotics on High Sugar-Induced Type 2 Diabetes Mellitus Symptoms in Drosophila melanogaster

Al-Ghamdi, Yasser January 2019 (has links)
Background: Type 2 diabetes mellitus is a metabolic disorder characterized by the rise of fasting plasma glucose from its normal range (≥125mg/dl). It is marked by insufficient production of insulin from pancreatic β-cells as a result of failed compensation due to insulin resistance. Several treatments are available for the disorder, which mainly focus on improving the sensitivity of insulin in different body tissues. Recently, probiotics were suggested as candidate treatments for type 2 diabetes and for extending lifespan as well. This experiment aims to investigate such claims using Drosophila melanogaster as a disease model.   Results: Other than the observed low average weights in treated larva samples, probiotics did not show any other significant results in affecting the length, glucose, glycogen, and trehalose levels (One-Way ANOVA and Kruskal-Wallis, p>0.05). Real-time PCR was only carried out once. Thus, no statistical tests were reliable enough to analyse the data obtained. The longevity study, on the other hand, did show significance (Log-rank (Mantel-Cox) test and Gehan-Breslow-Wilcoxon test, p<0.0001), as the probiotic Bifidobacterium lactis extended the lifespan of adult flies feeding on a high sugar diet significantly when compared to the control ones feeding on only high sugar diet without probiotics.   Conclusion: Except for weight measurements, none of the other results was reliable enough to make a concrete conclusion on whether the treatments indeed worked in reversing type 2 diabetes symptoms or not. Real-time PCR results did show some effects of some of the treatments at different developmental stages. However, unless Real-time PCR is repeated at least once using the same protocol, no deduction can be made. Additionally, the data obtained hint that the dosage used (0.025 g) was too high for larvae and adult flies and might have caused malnutrition by blocking their midgut and decreasing food absorption. Hence, false significant or non-significant results were acquired instead.   Further studies are required using a much lower probiotic dosage if Drosophila is used as a disease model. Although, other models such as mice or rats are recommended in this case, in order to reach a solid conclusion about the effectiveness of probiotics in treating type 2 diabetes mellitus. Baring these thoughts in mind and based on the results of this experiment, the null hypothesis indicating that there is no significant relationship between the use of probiotics and reversing type 2 diabetes mellitus symptoms is therefore accepted.
3

The HI Chronicles of LITTLE THINGS Blue Compact Dwarf Galaxies

Ashley, Trisha L 27 May 2014 (has links)
Star formation occurs when the gas (mostly atomic hydrogen; H I) in a galaxy becomes disturbed, forming regions of high density gas, which then collapses to form stars. In dwarf galaxies it is still uncertain which processes contribute to star formation and how much they contribute to star formation. Blue compact dwarf (BCD) galaxies are low mass, low shear, gas rich galaxies that have high star formation rates when compared to other dwarf galaxies. What triggers the dense burst of star formation in BCDs but not other dwarfs is not well understood. It is often suggested that BCDs may have their starburst triggered by gravitational interactions with other galaxies, dwarf-dwarf galaxy mergers, or consumption of intergalactic gas. However, there are BCDs that appear isolated with respect to other galaxies, making an external disturbance unlikely. Here, I study six apparently isolated BCDs from the LITTLE THINGS1sample in an attempt to understand what has triggered their burst of star formation. LITTLE THINGS is an H I survey of 41 dwarf galaxies. Each galaxy has high angular and velocity resolution H I data from the Very Large Array (VLA) telescope and ancillary stellar data. I use these data to study the detailed morphology and kinematics of each galaxy, looking for signatures of starburst triggers. In addition to the VLA data, I have collected Green Bank Telescope data for the six BCDs. These high sensitivity, low resolution data are used to search the surrounding area of each galaxy for extended emission and possible nearby companion galaxies. The VLA data show evidence that each BCD has likely experienced some form of external disturbance despite their apparent isolation. These external disturbances potentially seen in the sample include: ongoing/advanced dwarf-dwarf mergers, an interaction with an unknown external object, and external gas consumption. The GBT data result in no nearby, separate H I companions at the sensitivity of the data. These data therefore suggest that even though these BCDs appear isolated, they have not been evolving in isolation. It is possible that these external disturbances may have triggered the starbursts that defines them as BCDs. 1Local Irregulars That Trace Luminosity Extremes, The H I Nearby Galaxy Survey; https://science.nrao.edu/science/surveys/littlethings
4

The algebra of entanglement and the geometry of composition

Hadzihasanovic, Amar January 2017 (has links)
String diagrams turn algebraic equations into topological moves that have recurring shapes, involving the sliding of one diagram past another. We individuate, at the root of this fact, the dual nature of polygraphs as presentations of higher algebraic theories, and as combinatorial descriptions of "directed spaces". Operations of polygraphs modelled on operations of topological spaces are used as the foundation of a compositional universal algebra, where sliding moves arise from tensor products of polygraphs. We reconstruct several higher algebraic theories in this framework. In this regard, the standard formalism of polygraphs has some technical problems. We propose a notion of regular polygraph, barring cell boundaries that are not homeomorphic to a disk of the appropriate dimension. We define a category of non-degenerate shapes, and show how to calculate their tensor products. Then, we introduce a notion of weak unit to recover weakly degenerate boundaries in low dimensions, and prove that the existence of weak units is equivalent to a representability property. We then turn to applications of diagrammatic algebra to quantum theory. We re-evaluate the category of Hilbert spaces from the perspective of categorical universal algebra, which leads to a bicategorical refinement. Then, we focus on the axiomatics of fragments of quantum theory, and present the ZW calculus, the first complete diagrammatic axiomatisation of the theory of qubits. The ZW calculus has several advantages over ZX calculi, including a computationally meaningful normal form, and a fragment whose diagrams can be read as setups of fermionic oscillators. Moreover, its generators reflect an operational classification of entangled states of 3 qubits. We conclude with generalisations of the ZW calculus to higher-dimensional systems, including the definition of a universal set of generators in each dimension.
5

Etude des bases moléculaires du déterminisme sexuel et de la différenciation chez une espèce hétérogamétique femelle ZZ-ZW : Schistosoma mansoni / Molecular basis of sex determination and differentiation of a female heterogametic species ZZ/ZW : Schistosoma mansoni

Picard, Marion 01 December 2015 (has links)
Parmi plus de 20000 espèces de trématodes hermaphrodites, les Schistosomatidae ont un statut particulier car ils sont gonochoriques (i.e. deux sexes séparés). Le gonochorisme chez ces espèces, et leur dimorphisme sexuel, seraient en fait une stratégie d’adaptation à leur habitat : le système veineux des vertébrés à sang chaud, dont l’Homme. Malgré un mode chromosomique de déterminisme du sexe (i.e. hétérogamétie femelle ZW), les individus mâles et femelles demeurent phénotypiquement identiques durant tous les stades larvaires de leur cycle de vie hétéroxène. La différenciation sexuelle n’a lieu qu’après l’infestation de leur hôte définitif. Dans ce travail, nous nous sommes intéressés aux facteurs moléculaires déclenchant cette différenciation chez Schistosoma mansoni. Nous avons établi le profil d’expression sexe-dépendant de gènes conservés de la cascade de détermination/différenciation chez les animaux : les DMRT (Double-sex and Male-abnormal-3 Related Transcription Factors). Nous avons par ailleurs généré un transcriptome comparatif mâle/femelle (RNA-seq) sur 5 stades de développement in vivo, dont 3 stades « schistosomules » inédits. Cela nous a permis d’identifier de potentiels gènes « clés » de la différenciation sexuelle et de souligner l’importance de l’interaction hôte-parasite. Enfin, par la combinaison de cette approche transcriptomique et d’une analyse épigénomique (ChIP-seq), nous avons montré une dynamique de la compensation de dose génique au cours du cycle de vie chez les femelles ainsi que la mise en place d’une stratégie transcriptionnelle particulière chez les mâles, optimisant leur développement dans l’hôte et ainsi, leur succès reproducteur. / Parasitic flatworms include more than 20.000 species that are mainly hermaphrodites. Among them, the hundred species of Schistosomatidae are intriguing because they are gonochoric. The acquisition of gonochorism in these species is supposed to provide genetic and functional advantages to adapt to their hosts: warm-blooded animals. Sex of schistosomes is genetically determined at the time of fertilization (i.e. ZW female heterogametic system). However, there is no phenotypic dimorphism through all the larval stages of its complex lifecycle: sexual dimorphism appears only in the definitive host. The molecular mechanisms triggering this late sexual differentiation remain unclear, and this is precisely the topic of our present work. We performed transcriptomic (RNA-Sequencing and quantitative-PCRs) and structural (ChIP-Sequencing) analyses at different stages of Schistosoma mansoni development. Here, we present data suggesting that the sexual differentiation relies on a combination of genetic and epigenetic factors. In a genetic point of view, we show a sex-associated expression of the DMRT genes (Double-sex and Mab-3 Related Transcription Factors) that are known to be involved in sex determination/differentiation through all the animal kingdom. In addition, we propose new potential sex-determining key genes and a pivotal role of host-pathogen interaction at the time of development. In a structural point of view, we highlight a dynamic status of dosage compensation in females and chromatin modifications in males. This intense remodeling reveals a specific transcriptomic strategy which optimizes male development and beyond that, schistosomes reproductive success.

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