Browsing by Subject "correlation"
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Item Genotypic and phenotypic chacterization of maize testcross hybrids under stressed and non stressed conditions(Texas A&M University, 2007-04-25) Ganunga, Rosan PatersonDrought and low soil nitrogen are major factors limiting maize production in Sub-Saharan Africa. Genotypic and phenotypic characterization of maize testcross hybrids developed from four biparental populations: CML441 x CML444, CML440 x COMPE, CML444 x K64R and CML312 x NAW was conducted. The objectives were (a) to evaluate the performance of F2:3 line testcrosses across stressed and non-stress conditions, (b) to estimate heritabilities for grain yield and secondary traits, (c) to assess the relationship between testing environments, (d) to estimate genetic correlations among relevant traits, (e) to estimate direct and indirect genetic gain from selection, and (e) to have a preliminary assessment of the efficiency of marker-assisted selection. Studies were conducted under no nitrogen fertilization, low nitrogen, drought, well- watered and high nitrogen in Malawi and Zimbabwe. About 100 entries from each population were tested using an alpha lattice design with two replications at all locations. Traits measured were grain yield, plant height, anthesis date, anthesis-silking interval, ears per plant, grain moisture at harvest and leaf senescence. Highest grain yield across environments was obtained from population CML444 x K64R (3.82 Mg ha-1) and the lowest from CML440 x COMPE (3.64 Mg ha-1). Testcrosses from CML441 x CML444 and CML444 x K64R had higher heritability estimates compared to CML440 x COMPE and CML312 x NAW. Drought and high nitrogen environments had higher heritability estimates than low nitrogen and well-watered conditions. Drought and well-watered environments discriminated testcrosses in a similar manner as well as high and low nitrogen environments. All populations had negative correlations between grain yield and anthesis silking interval, while positive correlations were observed between grain yield and ears per plant. No consistent differences were observed between overall means of best and worst marker based selected line testcrosses across populations and environments. Highest direct expected genetic gains were observed from high nitrogen environments. Direct selection under specific environments (e.g. drought ) was estimated to be more beneficial than indirect selection in other environments.Item International baccalaureate: a study in college readinessGurumurthy, UshaItem Multi-Scale Indentation Hardness Testing; A Correlation and Model(2010-01-20) Bennett, Damon W.This thesis presents the research results of a correlation and model based on nano and macroindentation hardness measurements. The materials used to develop and test the correlation include bulk tantalum and O1 tool steel. Following the literature review and a detailed description of the experimental techniques, the results of the nanoindentation hardness measurements are presented. After applying the methods and correlation recommended here, the results should give an accurate value of hardness in the Vickers scale for microstructural features that are too small to be precisely and exclusively measured using the traditional macroindentation hardness technique. The phenomena and influential factors in nanoindentation hardness testing are also discussed. These phenomena and theories are consistent with the microstructural behavior predicted in the Nix and Gao model for mechanism-based strain gradients. Implementing the correlation factors and/or correlation curve, accurate results can be found for metals over a broad hardness range. Initially, this research may impact the pipeline division of the petroleum industry by providing a correlation to the Vickers scale for nanoindentation testing of microstructural features. This thesis may also provide a research methodology to develop hardness correlations for materials other than metals. This thesis consists of eight chapters. Following an introduction in Chapter I, the research motivations and objectives are highlighted in Chapter II. Chapter III explains the multi-scale indentation techniques used in this thesis and Chapter IV presents the materials preparation techniques used. Then, the results are presented in Chapter V, followed by the factors affecting nanoindentation hardness in Chapter VI. Finally, Chapters VII and VIII reveal the indentation contact analysis, correlation, and conclusions of this research, respectively.Item Subsurface conductive isolation of refraction correlative magnetic signals (SCIRCMS)(Texas A&M University, 2004-11-15) Erck, Eric StephensonIsolation of terrestrially-observed magnetic signals by restoring their diffusive loss due to subsurface electrical conductivity sufficiently correlates these signals with those derived from the Alfven ionospheric electron movement of refraction variation. Temporary magnetic observatories were established on a conductive sedimentary basin (with a sampling interval of 5 s) and on a resistive large igneous intrusion (with a sampling interval of 10 s). Conventional modeling techniques estimate and remove the effects of the magnetometer, geomagnetic diurnal changes, whorls (solar quiet current vortices), and some bays from the acquired signals. Conventional one-dimensional skin depth modeling estimates the diffusive attenuation. The residual magnetic signal and the diffusive filter (as applied to the topography) become quantities in the linear system estimation of the geoelectric subsurface. Angular frequency domain least squares solution of the equations yields an isolated magnetic anomaly spectrum. Interpretive refinement, by selection of the zero or near zero curvature onset of either the spectrum's real or imaginary component, critically prepares the signal solution for correlation to a pseudomagnetic anomaly signal. This is an independently-derived sequence of anomalous values derived from Global Positioning System (GPS) refracted ranges. Detailed application of the Biot-Savart law provides independent anomaly signals to which the magnetic anomalies correlations show great correlation improvement by the isolation. These correlation improvements are from 2% to 83% and 9% to 91% for the sedimentary basin and from 2% to 96% and 24% to 78% for the igneous intrusion.Item The dna ?saw puzzle??ructure model: the case studies of the rice and yeast genomes(2009-05-15) Liu, Yun-HuaHow does DNA make the abundant and diverged life world? To address this question, a DNA ?Jigsaw Puzzle? structure model was proposed and first tested by comprehensively analyzing the genome of the model dicot plant, Arabidopsis thaliana. However, it is unknown whether this model is held in other species. Here we report the studies of the DNA structure model using the monocot plant model species, rice (Oryza sativa), and the single-celled model species, yeast (Saccharomyces cerevisiae). Analyses of the genomes sequenced so far revealed that the genome of an organism consists of a limited number of sequence-specialized, so-called fundamental function elements. For a higher organism, these elements often include genes (GEN), retro-transposable elements (RTE), DNA transposable elements (DTE), simple sequence repeats (SSR) and low complex repeats (LCR). Datasets were developed for RTE, DTE, SSR, LCR and GEN as well as genes categorized into different function categories from the sequences of the rice and yeast genomes using appropriate window sizes. The datasets were subjected to statistical analyses to test the DNA ?Jigsaw Puzzle? structure model in terms of the unambiguousness, correlation, uniqueness and selection of their genome-constituting element arrays. The analyses were conducted with a series of window sizes of the sequences at both the whole genome and individual chromosome levels, both including and excluding the centromeric regions. The results showed that all fundamental function elements of the genomes as well as the genes categorized into different function categories were arrayed in the genomes in an unambiguous manner resembling linear ?Jigsaw Puzzles? at the whole genome and/or individual chromosome levels, no matter whether the centromeric regions were included or excluded. The analyses revealed that arraying of the genomic elements was correlated significantly and uniquely for each chromosome and each species. This further confirmed the non-random arraying characteristic of the genomic elements for the DNA ?Jigsaw Puzzle? structure model and suggested that the DNA ?Jigsaw Puzzle? structure is unique for an organism, which has probably resulted from natural selection. These results unambiguously support the hypothesis of the DNA ?Jigsaw Puzzle? structure model. Since the content, arraying and interaction pattern of the fundamental function elements were shown to be unique for each organism, variations of an organism in its DNA ?Jigsaw Puzzle? array would lead to phenotypic variations, thus resulting in different organisms. Moreover, the fundamental function elements constituting a genome, as the four nucleotides (A, T, G and C) of DNA, could be arrayed into an infinite number of DNA molecules, thus giving different forms of organisms. Therefore, the DNA ?Jigsaw Puzzle? structure model would provide a novel, but convincing explanation for the abundance, diversity and complexity of living organisms in the world.