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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.
121

Tungsten is Essential for Long-Term Maintenance of Members of Candidate Archaeal Genus Aigarchaeota Group 4

Dimapilis, Joshua Robert Reyes 01 September 2019 (has links)
Aigarchaeota, a deeply branching archaeal lineage with no cultivated representatives, is found in geothermal and hydrothermal systems worldwide and consists of at least 9 genus-level groups, each predicted to have diverse metabolic capabilities. This candidate archaeal phylum is part of the TACK superphylum, members of which possess eukaryotic-signature proteins, thus suggesting that they may represent evolutionary steps along the way to the genesis of the first eukaryotic cells. Cultivating members of Aigarchaeota would elucidate how eukaryotes arose in evolutionary history and provide biotechnological applications. Aigarchaeota Group 4 (AigG4), one genus in Aigarchaeota, was previously found to be abundant in corn stover in situ enrichments in Great Boiling Spring (GBS). AigG4 has been maintained in mixed laboratory cultures, where it composes ~ 0.5-1% of the community. However, these cultures could only be maintained when GBS water, which contains ~300 nM tungsten, was included in the medium. In addition, AigG4 metagenome bins from the in situ enrichments and laboratory cultures contained multiple genes encoding putative tungsten-containing aldehyde:ferredoxin oxidoreductases (TAORs). These observations led to the hypothesis that tungsten was the key component in GBS water that allowed for growth of AigG4. The requirement of tungsten for AigG4 long-term maintenance in mixed culture was tested using three different approaches: (1) Assessing the phylogeny of tungsten transporters and TAORs across the Aigarchaeota lineage, followed by confirmation of transcription of hypothesized AigG4 tungsten-associated genes in lab cultures, (2) Measuring tungsten levels in Great Boiling Spring (GBS) using ICP-OES (Inductively coupled plasma-optical emission spectroscopy), and (3) determining minimum amount of tungsten for long-term AigG4 maintenance in corn stover and in a defined mix of sugars (1% glucose, 1% xylose, 1% D-arabinose, 1% L-arabinose, 1% mannose). In addition, FISH (Fluorescent in situ hybridization) probes were designed to target the AigG4 lineage in the hopes that in conjunction with nanometer-scale secondary ion mass spectroscopy (Nano-SIMS), this would test whether tungsten has indirect or direct effects on AigG4 to track carbon substrate intake. Most Aigarchaeota lineages possess a tungsten transporter complex (TTC). AigG4 TTC groups most closely with the Tup family while other Aigarchaeota group with the Wtp family. Group 4 and Group 5 Aigarchaeota contained TAORs that grouped to other hypothesized TAORs but not to characterized counterparts suggesting diverse functional capabilities. Group 4 and Group 5 TAORs clustered together suggesting that these are conserved within these lineages. Gene expression of predicted AigG4 tungsten-associated enzymes was detected in culture. Tungsten was detected in GBS water as previously observed in 2005. In both corn stover and sugar mix, 1 nM tungsten was sufficient for long term AigG4 maintenance. In corn stover, AigG4 decreased to levels below detection after three 3-week transfer periods in 0 nM and 20 nM tungsten. In sugar mix, AigG4 abundance levels varied wildly in 0 nM tungsten after the fifth transfer period suggesting tungsten contamination. Two newly designed FISH probes exhibited lower fluorescence signal intensity than the previously designed FISH probe suggesting issues with either target site accessibility or conjugation of the fluorescent moiety to oligonucleotide probes.
122

Distribution of Available Phosphorus in the Subsoil of Selected Pedons of the Warm Springs Series

Lammers, Duane Altman 01 May 1975 (has links)
The Warm Springs soil series which contained variable amounts of subsoil available (sodium bicarbonate extractable) phosphorus was studied to explain the variability and distribution of the NaHCO3-P in the subsoil. Four pedons ranging in subsoil NaHCO3-P from less than 10 ppm to greater than 30 ppm were selected in an area of less than 200 ha located on a nearly level, low lake terrace east of the Great Salt Lake in Weber County, Utah. The morphology of each pedon was described in the field and samples collected from each genetic horizon or contrasting layer. Each soil sample was analyzed for total phosphorus, NaHCO3-P, water- soluble phosphorus, pH, extractable iron , calcium carbonate equivalent, electrical conductivity and water-soluble sodium. Four horizons were selected from each pedon for anal ysis of parti cle-size distribution, clay-size carbonate and non-carbonate clay. The very fine sand fraction of four horizons from two of the pedons were studied petrographically to determine the amount of apatite present. Thin strata with higher chroma were separated from adjacent layers and analyzed for extractable iron and NaHCO3-P. Cicada casts and their surrounding matrix were separated and analyzed Selected soil samples were shaken with sodiumphosphate solutions and then analyzed for NaHCO3-P to determine the influence of the amount of phosphorus in solution on the amount of phosphorus extracted. NaHCO3-P below the calcic horizons was highly variable, 10 ppm or less in two pedons and up to 40 ppm in the other two. Subsoil horizons with pH values greater than 10.0 and relatively large amounts of water-soluble sodium contained more than 10 ppm NaHCO3-P. Extractable iron and NaHC03-P were concentrated in subsoil strata with higher chroma. The results indicated that large amounts of NaHCO3-P in the subsoil were primarily due to the presence of readily soluble sodium phosphate. Weathering of apatite in the surface horizons did not contribute the NaHCO3-P below the calcic horizons. The most likely source of NaHCO3-P in the Warm Springs subsoil , however, was the sediments deposited in the low lake terraces and river flood plains by the Weber and Bear Rivers. Lateral flow and vertical fluctuations of the water table were suggested as a means by which the NaHCO3-P could be extracted from some areas and concentrated in others. Although certain soil properties might indicate the probable occurrence of more than 10 ppm NaHCO3-P in the subsoil, this study did not provide a method for identifying all subsoils with appreciable amounts of NaHCO3-P.
123

Does Revolution Breed Radicalism? An Analysis of the Stalled Revolution in Syria and the Radical Forces Since Unleashed

Little, Ryan King 03 November 2014 (has links)
This thesis examines the turn to conflict in Syria during 2011 to see if it is revolutionary in nature and if so, why has it not succeeded? This thesis aims to analyze the anatomy of Syria's "revolution" in order to determine the causes behind the initial popular mobilization and transition to conflict. Then, further analysis of the essential elements of successful revolutionary movements will be undertaken to reveal what conditions remain unmet for Syria to culminate in a full revolutionary transformation. Special attention will be paid to the revolutionary Opposition itself, since, to date, it has proved unable to generate the power necessary to destroy the old order and rebuild a new system. The significant role of external intervention will also be addressed, since these forces have simultaneously helped cause the conflict, prolong the conflict and prop up the regime. Finally, the negative consequences of undertaking a revolutionary process, especially when left only partially complete, will be highlighted throughout the study. Syria's own "rise of the radicals," has manifested itself in the phenomenon of ISIL or ISIS, which has proven the strongest and most violent Opposition group to emerge from Syria's revolutionary environment.
124

Molecular and microscopic studies of a <i>Fusarium</i>-associated biotrophic mycoparasite

Goh, Yit Kheng 14 May 2010
Environmental hazards and health problems due to the application of chemical pesticides in agricultural sectors incite huge public concerns. Therefore, one of the better solutions is through introduction of biological control means to manage the outbreaks of plant diseases. To date, only small numbers of beneficial microorganisms - belonging to the category of hyperparasitic or mycoparasitic fungi have proven to keep plants or protect crops from plant pathogen infection. The objective of this study was to characterize a group of <i>Fusarium</i>-associated melanosporaceous biotrophic mycoparasitic fungal isolates, which were identified and pre-selected by Dr. Vladimir Vujanovic and deposited in the Saskatchewan Microbial Collection and Database (SMCD). Particular objectives were to examine spore germination of a biotrophic mycoparasite, to test effects of this fungus on seed germinations, to study interactions between the mycoparasite and Fusarium hosts, and to investigate relationships between the mycoparasite-the <i>Fusarium</i> host-wheat root under controlled conditions in the university Phytotron facilities.<p> Information related to this group of fungi is relatively limited. In order to characterize potential biotrophic mycoparasitic fungal isolate(s), molecular and microscopy methods were performed to accomplish taxonomical, phylogenetical and morphological studies. Since, spore germination is a very crucial stage in fungal life cycle and growth, ascospores (sexual spores) of the biotrophic mycoparasite were isolated from a fungal colony. These spores were inoculated on media supplemented with different <i>Fusarium</i>-filtrates or suspended in different <i>Fusarium</i>-filtrates to examine spore germination rates and growth patterns. Together with other mycoparasitic fungi, this biotrophic mycoparasite was inoculated on spring wheat seeds, to test effects of these fungal inoculants on seedlings growth using <i>in vitro</i> assays. Dual-culture, slide culture, and microscopy approaches were carried out to elucidate intimate and special relationship between the biotrophic mycoparasite and <i>Fusarium</i>-hosts. In order to study tritrophic interactions (biotrophic mycoparasite-<i>Fusarium</i> host-wheat root), spring wheat was grown in the phytotron with different treatments of fungal inoculations. Wheat roots were then subjected to genus-specific quantitative real-time PCR analyses.<p> One melanosporaceous biotrophic mycoparasitic strain was identified as a new species in the genus <i>Sphaerodes</i>. This biotrophic mycoparasite was isolated from <i>Fusarium</i>-infected fields in Saskatchewan and Quebec, and named <i>Sphaerodes mycoparasitica</i>. Germination of <i>S. mycoparasitica</i> sexual spores was improved when treated with filtrates or extracellular extracts from the <i>Fusarium</i>-host as compared to <i>Fusarium</i>-non-host filtrates. No pathogenic effects on wheat seeds were observed when inoculated with <i>S. mycoparasitica</i>. Furthermore, seedlings growth was enhanced with this biotrophic mycoparasite compared to other mycoparasitic fungi. Later, this biotrophic mycoparasitic strain was found to establish biotrophic fusion and haustorial contact relations with <i>F. avenaceum, F. oxysporum</i>, and two F. graminearum chemotypes. Since, 3-Acetyldeoxynivalenol-producing <i>F. graminearum</i> is one of the most highly toxigenic and aggressive wheat pathogens in Saskatchewan and North America, therefore, this pathogen strain was chosen for tritrophic interaction study. Under controlled conditions in the phytotron, <i>S. mycoparasitica</i> improved seedlings growth when these were challenged with <i>F. graminearum</i> as compared to seedlings only inoculated with the <i>Fusarium</i> pathogen. In conclusion, S. mycoparasitica could be a potential candidate for biological control of <i>Fusarium</i> diseases in wheat.
125

Molecular and microscopic studies of a <i>Fusarium</i>-associated biotrophic mycoparasite

Goh, Yit Kheng 14 May 2010 (has links)
Environmental hazards and health problems due to the application of chemical pesticides in agricultural sectors incite huge public concerns. Therefore, one of the better solutions is through introduction of biological control means to manage the outbreaks of plant diseases. To date, only small numbers of beneficial microorganisms - belonging to the category of hyperparasitic or mycoparasitic fungi have proven to keep plants or protect crops from plant pathogen infection. The objective of this study was to characterize a group of <i>Fusarium</i>-associated melanosporaceous biotrophic mycoparasitic fungal isolates, which were identified and pre-selected by Dr. Vladimir Vujanovic and deposited in the Saskatchewan Microbial Collection and Database (SMCD). Particular objectives were to examine spore germination of a biotrophic mycoparasite, to test effects of this fungus on seed germinations, to study interactions between the mycoparasite and Fusarium hosts, and to investigate relationships between the mycoparasite-the <i>Fusarium</i> host-wheat root under controlled conditions in the university Phytotron facilities.<p> Information related to this group of fungi is relatively limited. In order to characterize potential biotrophic mycoparasitic fungal isolate(s), molecular and microscopy methods were performed to accomplish taxonomical, phylogenetical and morphological studies. Since, spore germination is a very crucial stage in fungal life cycle and growth, ascospores (sexual spores) of the biotrophic mycoparasite were isolated from a fungal colony. These spores were inoculated on media supplemented with different <i>Fusarium</i>-filtrates or suspended in different <i>Fusarium</i>-filtrates to examine spore germination rates and growth patterns. Together with other mycoparasitic fungi, this biotrophic mycoparasite was inoculated on spring wheat seeds, to test effects of these fungal inoculants on seedlings growth using <i>in vitro</i> assays. Dual-culture, slide culture, and microscopy approaches were carried out to elucidate intimate and special relationship between the biotrophic mycoparasite and <i>Fusarium</i>-hosts. In order to study tritrophic interactions (biotrophic mycoparasite-<i>Fusarium</i> host-wheat root), spring wheat was grown in the phytotron with different treatments of fungal inoculations. Wheat roots were then subjected to genus-specific quantitative real-time PCR analyses.<p> One melanosporaceous biotrophic mycoparasitic strain was identified as a new species in the genus <i>Sphaerodes</i>. This biotrophic mycoparasite was isolated from <i>Fusarium</i>-infected fields in Saskatchewan and Quebec, and named <i>Sphaerodes mycoparasitica</i>. Germination of <i>S. mycoparasitica</i> sexual spores was improved when treated with filtrates or extracellular extracts from the <i>Fusarium</i>-host as compared to <i>Fusarium</i>-non-host filtrates. No pathogenic effects on wheat seeds were observed when inoculated with <i>S. mycoparasitica</i>. Furthermore, seedlings growth was enhanced with this biotrophic mycoparasite compared to other mycoparasitic fungi. Later, this biotrophic mycoparasitic strain was found to establish biotrophic fusion and haustorial contact relations with <i>F. avenaceum, F. oxysporum</i>, and two F. graminearum chemotypes. Since, 3-Acetyldeoxynivalenol-producing <i>F. graminearum</i> is one of the most highly toxigenic and aggressive wheat pathogens in Saskatchewan and North America, therefore, this pathogen strain was chosen for tritrophic interaction study. Under controlled conditions in the phytotron, <i>S. mycoparasitica</i> improved seedlings growth when these were challenged with <i>F. graminearum</i> as compared to seedlings only inoculated with the <i>Fusarium</i> pathogen. In conclusion, S. mycoparasitica could be a potential candidate for biological control of <i>Fusarium</i> diseases in wheat.
126

Intermittency and Irreversibility in the Soil-Plant-Atmosphere System

Rigby, James January 2009 (has links)
<p>The hydrologic cycle may be described in essence as the process of water rising and falling in its various phases between land and atmosphere. In this minimal description of the hydrologic cycle two features come into focus: intermittency and irreversibility. In this dissertation intermittency and irreversibility are investigated broadly in the soil-plant-atmosphere system. The theory of intermittency and irreversibility is addressed here in three ways: (1) through its effect on components of the soil-plant-atmosphere system, (2) through development of a measure of the degree of irreversibility in time-series, and (3) by the investigation of the dynamical sources of this intermittency. First, soil infiltration and spring frost risk are treated as two examples of hydrologic intermittency with very different characters and implications for the soil plant system. An investigation of the water budget in simplified soil moisture models reveals that simple bucket models of infiltration perform well against more accurate representation of intra-storm infiltration dynamics in determining the surface water partitioning. Damaging spring frost is presented as a ``biologically-defined extreme event'' and thus as a more subtle form of hydrologic intermittency. This work represents the first theoretical development of a biologically-defined extreme and highlights the importance of the interplay between daily temperature mean and variance in determining the changes in damaging frost risk in a warming climate. Second, a statistical measure of directionality/asymmetry is developed for stationary time-series based on analogies with the theory of nonequilibrium thermodynamics. This measure is then applied to a set of DNA sequences as an example of a discrete sequence with limited state-space. The DNA sequences are found to be statistically asymmetric and further that the local degree of asymmetry is a reliable indicator of the coding/noncoding status of the DNA segment. Third, the phenomenology of rainfall occurrence is compared with canonical examples of dynamical intermittency to determine whether these simple dynamical features may display a dominant signature in rainfall processes. Summer convective rainfall is found to be broadly consistent with Type-III intermittency. Following on this result we studied daytime atmospheric boundary layer dynamics with a view toward developing simplified models that may further elucidate the interaction the interaction between land surface conditions and convective rainfall triggering.</p> / Dissertation
127

Thermomechanical modeling of a shape memory polymer

Ghosh, Pritha B. 15 May 2009 (has links)
The aim of this work is to demonstrate a Helmholtz potential based approach for the development of the constitutive equations for a shape memory polymer undergoing a thermomechanical cycle. The approach is motivated by the use of a simple spring-dashpot type analogy and the resulting equations are classified as state-equations and suitable kinetic equations for the recoverable-energy elements and the dissipative elements in the model respectively. These elements have mechanical properties which vary with temperature. The governing equations of the model are developed starting from the basic conservation laws together with the laws of thermodynamics. The entire set of equations are written in a state-evolution form as a set of ordinary differential equations to be solved using Matlab. It is shown that the results of the simulation in Matlab are in qualitative and quantitative agreement with experiments performed on polyurethane. Subsequently, we study the dependence of the yield-stress on temperature to be similar and different functions of heating or cooling processes.
128

Effects of Winter Overseeding and Three-demensional Clipping Management on Warm-season Turfgrasses

Fontanier, Charles H. 2010 May 1900 (has links)
Perennial ryegrass (Lolium perenne L.) is commonly overseeded into hybrid bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt Davy] turfs during autumn in the southern United States. Overseeding can provide a green, actively-growing turf throughout the winter dormancy period. Improved persistence of perennial ryegrass cultivars has increased management inputs during the spring transition period. Lower input turf systems that provide acceptable winter overseeding quality are preferred, and research aimed at evaluating alternative overseeding species are warranted. Grooming reel attachments allowing for threedimensional clipping management (3DCM) have become increasingly used by turf managers for reducing grain and thatch, but scientific information on best management practices and canopy effects of 3DCM-grooming are lacking. A field study was conducted at the Texas A&M Turfgrass Field Laboratory in College Station, TX (30.6191 degrees N, 96.3576 degrees W), to investigate the effects of overseeding using annual (Lolium multiflorum Lam.) and perennial ryegrasses on 3DCM-groomed and non-groomed fairway turfs of 'Tifway' hybrid bermudagrass, zoysiagrass [Zoysia matrella (L.) Merr. 'Cavalier'], and seashore paspalum (Paspalum vaginatum Sw. 'Sea Isle 1'). The study was arranged as a randomized complete block split-split-plot with three replications. Species whole main plots were split into three grooming intervals, which were further split into four overseeding treatments. Data were collected assessing visual turf quality, visual turf cover, leaf area index, clipping yield, shoot density, and biomass partitioning. Results indicate annual ryegrass alone and an annual/perennial ryegrass overseeding mix provided acceptable turf quality, but did not improve turf recovery over perennial ryegrass alone in 'Tifway' or 'Sea Isle 1' turfs. In 'Cavalier' turfs, summer quality was affected by overseeding treatment as follows: control > annual > annual/perennial > perennial. The overseeding tolerance of the warm-season turfgrasses was as follows: 'Sea Isle 1' > 'Tifway' &gt; 'Cavalier'. Differences in canopy architecture of warm-season turfgrasses were related to the overseeding tolerance of each species and used to explain plant competition during the spring transition period. Grooming by 3DCM improved late-season turf quality and reduced scalping in 'Tifway'. Overseeding establishment and canopy architecture were not affected by 3DCM.
129

The Study about "Songs about Spring" of Dominick Argento

Chen, Ya-ting 30 June 2009 (has links)
Dominick Argento (1927-) is one of America¡¦s most distinguished contemporary composers. He composed ten song cycles. Songs about Spring is his first vocal work which composed in 1950 and 1955. This song cycle contains five songs. Argento selected five poems about spring season from American poem Edward Estlin Cummings¡¦ collections of poem, and named the song cycle as Songs about Spring. The study of the lecture recital document contains five main sections: the biography about Argento, the characteristics of Argento¡¦s art songs, a brief introduction of poet Edward Estlin Cummings, the compositional background of Songs about Spring, and a performance analysis of Songs about Spring. The purpose of this study is to explore how Argento made use of music device to express variable sentences, telescoped words, harmony of sound and poem¡¦s frame of mind from Edward Estlin Cummings¡¦s poem, and expects to reinforcing profundity in performance.
130

Near-Threshold Photoproduction of £N(1520) from Protons and Deuterons at SPring-8/LEPS

Chen, Jia-ye 13 July 2009 (has links)
GeV photon beams are provided at SPring-8/LEPS facility by backward-Compton scattering (BCS) from Argon laser photon against the 8-GeV electrons inside the SPring-8 storage ring. The energy range of tagged photon by measuring the recoil electron is from 1.5 to 2.4 GeV, and enables us to study the strange meson- and baryon-photoproduction, such as £p(1020), £N(1405) and £N(1520) . In the past 30 years, other than the high-energy £N(1520) photoproduction at NINA/LAMP2 experiment, there is no further study of the £N(1520) photoproduction near the threshold. Based on this exclusive measurement at NINA/LAMP2 experiment, several theoretical calculations predict that the £N(1520) photoproduction near the threshold can be explained by t-channel K* exchange, t-channel K exchange or the contact term together with the t-channel K exchange under the gauge invariance. This experiment was performed at SPring-8/LEPS facility with liquid hydrogen and deuterium targets by a forward spectrometer from 2002 to 2003. The electroproduction experiment with similar c.m. energy region performed by JLab/CLAS is included for comparison. We study three two-track detection modes to reconstruct the £N(1520) resonance and other resonant/non-resonant backgrounds by the invariant mass and missing mass spectra. Utilizing the one-/two-step side-band subtraction methods and Monte Carlo simulation method, we measure the differential cross sections, K^- decay asymmetries in t-channel helicity frame and photon beam asymmetries to understand the production mechanism of £N(1520) . This is the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K^{+/0} angles. It can be explained by the dominance of the contact term along with the t-channel K exchange under the satisfaction of gauge invariance. This interpretation was also compatible with the differential cross sections, K^- decay asymmetry, and the photon beam asymmetry measured in the production from protons in the forward K^+ angles. A detector upgrade for the acceptance complement is done by introducing a time projection chamber, the configuration and operation principles except for the physics results will also be discussed in this thesis.

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