Browsing by Subject "morphology"
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Item A geological framework for temporal sedimentary dynamics(2009-05-15) Noll, Christian JohnGeophysical, geochemical and geotechnical methods were used to investigate the spatial and temporal aspects of sediment distribution, accumulation, post-depositional alterations, and seafloor response and recovery to major events in a temperate, paraglacial, turbid outwash fjord. The goals of this study are to generate a complete geological model and compare the results to the global distribution of fjords. The over arching theme of this study is that the ratio of the area of the watershed to the area of the receiving basin can provide a first order indicator of many factors including glacial mass; the timing of glacial retreat; sediment input, accumulation, and preservation; and other factors. Temporal observations reveal the change of this fjord from a glaciated basin to and estuarine environment. These observations become important when viewed in the context of global climate change and the continued loss of ice. Preserved strata provide a 2800 yr record of changing modes of sedimentation as the system evolved from a glaciated basin to a non-glaciated fjord revealing a detailed chronology of change between end-member systems which can be used to infer changes as glaciers retreat from other fjords. Short lived radio isotopes were used to investigate post-depositional alteration of modern sediments. Without an understanding of how biological and physical processes work to modify sedimentary fabric during preservation, changes seen in sediment and rock core data cannot be accurately resolved. Physical processes can cause erosion and lateral transport; winnowing and armoring; and instantaneous sedimentation, all of which may be preserved. Biological processes can modulate the preservation of strata by destroying sedimentary fabric and integrating signals. The final fundamental need is to investigate the seafloor response and recovery to these events. Massive earthquakes are frequent in the study area and cause perturbations to sediment input and preservation. By understanding how lakes and deltas modulate sediment discharge after the event; how shorelines are modified after the event; and where sediment is deposited we can determine the influence these changes have on the environment and on humans.Item A Study of Unbalanced Morphological Understanding: Morphological Land Use Patterns Analysis of U.S. Megaregions(2012-07-16) Ko, YounghoProblem: This study identifies some issues in the definitions of US megaregions which have strongly emphasized functional relationships without considering morphological characteristics. An extensive review of the literature revealed that the morphological approach and accompanying spatial statistical analysis described in this paper have not been done before, and represent a potentially useful refinement of current practice. Research strategy: This study examines morphological characteristics of the 11 US megaregions to represent morphologically-oriented US megaregions. A primary research hypothesis is that the megaregions spatially defined by morphological characteristics may not be the same as the current representation of the 11 US megaregions. The research hypothesis is tested by two distinct analyses which spatially examine the morphological characteristics at global and local scales. The global scale spatial patterns were examined with a density-based sprawl index, spatial scattering index, and spatial clustering index. Local scale spatial patterns were examined with the Getis-Ord Gi* hot spots analysis and the Anselin Local Moran?s I cluster and outlier analysis. In order to represent the megaregion-scale urban built environment, the morphological characteristics of total population, population density, impervious land cover, and nighttime light emissions were examined. All 11 megaregions were subjected to detailed GIS-based analysis and mapping for each morphological characteristic, and the results was analyzed using mapping, tables and graphs. Findings: The analysis results showed that global scale spatial distributions of morphological characteristics were inconsistently concentrated and clustered in high density subareas of each US megaregion. The morphological clustering representation of the 11 US megaregions clearly showed that the morphologically identified US megaregions were not the same as the current US megaregions. Takeaway for practice: This study asks the urban and regional planning profession to realize the incompleteness of a functional perspective, add a complementing morphological viewpoint, and balance the perspective between functional relations and morphological characteristics in identifying US megaregions.Item An ecophysiological framework for the morphological evolution of bluegill sunfish(2009-05-15) Papadopoulos, AnthonyBody shape affects the capacity and efficiency of swimming in fishes, and places constraints on foraging and reproductive performance. Hence, fitness components, such as aerobic swimming capacity and efficiency, can be determined from analysis of swimming energetics using active respirometry. In particular, body shape adaptations, such as streamlining, aim at reducing hydrodynamic drag (resistance), thereby increasing swimming efficiency in the presence of water flow, which is a principal contributor to resistance for fish inhabiting rivers. For two populations of bluegill sunfish, one from the Brazos River and the other from Moelman?s Slough (a Brazos River oxbow lake), the metabolic transport rate (MTR) was determined to evaluate differences in swimming efficiency. The standard cost of swimming (SCOS) was also determined to evaluate differences in swimming capacity, which represents the overall capacity of the skeletal muscles to generate mechanical power to overcome hydrodynamic resistance. The MTR and the SCOS describe holistic swimming performance, where the MTR specifies the hydrodynamic response due to swimming, and the SCOS specifies the physiologic response due to swimming. The differences in swimming performance are mainly attributed to factors affecting hydrodynamic resistance and could be predicted by morphology; because body shape, like water flow, is also a principal contributor to resistance. Multivariate body shape, from generalized Procrustes analysis, was used to assess the influence of multiple shape traits on swimming costs. This measure of shape related to swimming performance using partial least-squares analysis showed the two bluegill populations to be significantly different. The results were as follows: the shallow-bodied condition in bluegills was highly correlated with efficient swimming and low swimming capacities; whereas, deep-bodied bluegills were highly correlated with inefficient swimming and high swimming capacities. This is an empirical case of divergent natural selection. For convergence, however, the position of the caudal peduncle is consistent with optimal swimming speed (Um), which depends on standard metabolic rate (SMR), or metabolic maintenance. Bluegills with erect caudal peduncles have a high range of swimming speeds without suffering much cost of swimming ability compared to bluegills with prone caudal peduncles. The adaptive physiological response to high Um is due to a low SCOS because swimming efficiency is low and metabolic maintenance is high. In other words, bluegills that are inefficient swimmers and require a high energy intake cannot survive unless they gain the ability to increase their foraging capacity by thrust or metabolic power reduction. This is perhaps one of the most remarkable adaptive physiological responses due to the joint effects of shape and SMR.Item Characterization of Zr-Fe-Cu Alloys for an Inert Matrix Fuel for Nuclear Energy Applications(2013-08-09) Barnhart, Brian A.An ultra-high burnup metallic inert matrix nuclear fuel concept is being characterized and evaluated by Lawrence Livermore National Laboratory based on a metal matrix fuel concept originally developed at the Bochvar Institute in Russia. The concept comprises a dispersion of uranium metal microspheres in a Zr-based alloy matrix that provides thermal bonding between the fuel particles and the cladding material. The objective of this study was to experimentally evaluate both the microstructural and thermophysical properties of Zr-Fe-Cu alloys. The experiments and analyses described were divided into three main parts, nominally based on the analysis methods used to examine the alloys. An Electron Probe Microanalyzer (EPMA) was used to characterize the metallurgical properties of the proposed matrix alloys. The groups of alloys were cast using a high temperature inert atmosphere furnace. The cast alloys showed the expected combination of phases with the exception of the ZrFe2 Laves phase which was predicted for the Zr-12Fe-15Cu1 alloy but was not detected. The Zr-12Fe-5Cu alloy consisted of a Zr solution phase dispersed in a matrix of two different intermetallic phases. The second alloy, Zr-12Fe-10Cu, did not produce a homogenous mixture and consisted of two distinct phase morphologies. The top half of the sample was Zr rich and contained Zr precipitates dispersed in a matrix of intermetallic compounds while the bottom half consisted solely of intermetallic compounds. The third alloy, Zr-12Fe-15Cu, was comprised of four different intermetallic phases three of which had the same apparent Zr_(2)(Fe,Cu) structure but had distinct phase morphologies based on the Backscatter Electron (BSE) images. Upon determining the phase morphologies of each of the fabricated alloys Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were used to measure phase transformation and melting temperatures. Little difference was observed between the as-cast and annealed samples. The transitions shifted slightly to higher temperatures and the annealed Zr-12Fe-15Cu alloy only had two transitions compared to three seen in the as-cast samples. Slight changes were observed in the melting temperatures between the as-cast and annealed alloys. Zr-12Fe-5Cu had the largest melting temperature (886.3?C) while Zr-12Fe-10Cu had the smallest melting temperature (870?C). The third alloy, Zr-12Fe-15Cu, had a melting point just below that of Zr-12Fe-5Cu at 882.7?C. Light Flash Analysis (LFA) was implemented to determine the low temperature (20-260?C) thermal diffusivity values of each alloy. The as-cast measurements were more precise than the annealed samples, most likely the result of non-ideal sample integrity prior to loading. Each of the three alloys showed a linear increase in thermal diffusivity over the temperature range. Values for Zr-12Fe-5Cu ranged from 3.54 ? 0.06 mm2/s to 4.42 ? 0.10 mm^(2)/s. The Zr-12Fe-10Cu alloy had maximum and minimum values of 4.19 ? 0.22 mm^(2)/s and 3.17 ? 0.16 mm^(2)/s, respectively. Lastly, Zr-12Fe-15Cu had the largest thermal diffusivity ranging from 3.52 ? 0.15 mm^(2)/s at 20?C to 4.64 ? 0.16 mm_(2)/s at 260?C. Overall, the data from the LFA measurements showed that the Zr-Fe-Cu alloy system had similar diffusivity values compared to other common reactor materials.Item Comparative Analysis of the Morphology and Materials Properties of Pinniped Vibrissae(2012-02-14) Ginter, Carly C.Vibrissae (whiskers) are important components of the mammalian tactile sensory system, and primarily function as detectors of environmental vibrotactile cues. Pinnipeds possess the largest and most highly innervated vibrissae among mammals and their vibrissae demonstrate a diversity of shapes and likely mechanical properties. These two characteristics are important for vibrotactile sensory perception. Vibrissae of most phocid seals exhibit a beaded morphology with repeated sequences of crests and troughs along their length. I comparatively characterized differences in vibrissae morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods to test the hypothesis that vibrissal morphologies are species-specific manipulations of a common pattern. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to taxon based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. At least three separate morphologies were identified since phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Another important characteristic that influences the transduction of vibrotactile information to the mechanoreceptors in the follicle-sinus complex is the materials properties of the vibrissae. Vibrissae were modeled as cantilever beams and flexural stiffness (EI) was measured to test the hypotheses that the shape of beaded vibrissae reduces flexural stiffness and that vibrissae are anisotropic (orientations differ in EI). Species were significantly different and smooth vibrissae were generally stiffer than beaded vibrissae. Beaded vibrissae decrease vibrations in flow, which, combined with lower flexural stiffness values, may enhance detection of small changes in flow from swimming prey. The anterior plane of the vibrissae is likely the most biologically significant in tracking hydrodynamic trails but had lower flexural stiffness values than the dorsoventral orientation. There is likely a complex interaction between shape and mechanical properties in pinniped vibrissae but the ecological and functional implications are currently unknown.Item Comparative feeding biomechanics and behavioral performance of feeding in the family kogiidae and tursiops truncatus (odontoceti, cetacea)(Texas A&M University, 2007-09-17) Bloodworth, Brian EdwardHyolingual biomechanics and kinematics in three species of two odontocete genera were investigated to compare adaptations and performance of divergent feeding strategies. Ram and suction feeding are two ends of a continuous spectrum that is poorly-studied in odontocetes. Comparative anatomy identified characters associated with feeding patterns of morphologically dissimilar and evolutionary distant genera. Hyolingual investigations included measurements of hyolingual muscle vectors and hyoid surface area/robustness. ANOVA's revealed Kogia basihyal and thyrohyal surface areas were significantly greater than T. truncatus. However, most predicted muscle tension values were not significantly different between genera. The presence of lateral gape occlusions, broad basihyal and thyrohyals near the caudal oral cavity, and a broad, short tongue were likely responsible for Kogia's effective suction mechanism. These features were absent, or reduced, in T. truncatus. The feeding kinematics of dwarf and pygmy sperm whales (Kogia sima and K. breviceps), and bottlenose dolphins (Tursiops truncatus) were characterized and compared incorporating the Ram-Suction Index (RSI). Mean RSI data support a suction feeding strategy for the phylogenetically basal Kogia (-0.67; S.D.????0.29) and a ram feeding strategy for the more-derived Tursiops (0.94; S.D.????0.11). Tursiops displayed two ram-based feeding behaviors, closed gape approach, where gape increased near food items, and open gape approach, where gape was at least 50% of maximum in the first video field. Four feeding phases were identified in both odontocetes: preparatory, jaw opening, gular depression, and jaw closing. The mean Kogia feeding cycle duration (470 ms; S.D.????139) was significantly shorter (P<0.003) than all Tursiops groups (pooled: 863 ms; S.D.????337, closed gape approach: 662 ms; S.D.????207, open gape approach: 1211 ms; S.D.????207). Kogia mean maximum gape angle (39.8????; S.D.????18.9), mean maximum opening, and closing gape angle velocities (293????/s; S.D.????261 and 223????/s; S.D.????121, respectively) were significantly greater (P<0.005) than pooled Tursiops mean maximum gape angle (24.8????; S.D.????6.6), mean maximum opening and closing gape angle velocities (84????/s; S.D.????56 and 120????/s; S.D.????54, respectively). Negative Kogia RSI values were correlated with increasing maximum hyoid depression and retraction, wide gape angle, and rapid opening gape velocity. Kinematic data support functional hypotheses that odontocetes generate suction by rapid depression of the hyoid and tongue.Item Morphology in Word Recognition: Hindi and Urdu(2011-08-08) Rao, ChaitraThe present research examined whether morphology influences word recognition independently of form-level word properties. Prevailing views attribute cross-linguistic differences in morphological processing to variations in morphological structure and/or productivity. This study tested whether morphological processing is additionally influenced by the orthographic depth of written language, by comparing primed word naming among biliterate readers of Hindu and Urdu, languages written in distinct orthographies but sharing a common morphophonology. Results from five experiments supported the view that morphological processing in orthographically shallow (transparent) Hindi script diverged significantly from that in the deeper (opaque) Urdu orthography. Specifically, morphological priming was differently affected in Hindi vs. Urdu by prim presentation conditions (Exps. 1-3): very briefly exposed (48ms), forward masked morphological primes facilitated word naming in Hindi but not in Urdu. Neither briefly presented, unmasked primes nor longer prime exposures (80ms/240ms) produced priming in Hindi, but Experiment 2 showed priming by unmasked Hindi primes at a 240 ms exposure. By contrast, Urdu exhibited morphological priming only for forward masked primes at the long exposure of 240ms. Thus, early-onset priming in Hindi resembled morpho-orthographic decomposition previously recorded in English, whereas Urdu evinced priming consistent with morpho-semantic effects documented across several languages. Hemispheric asymmetry in morphological priming also diverged across Hindi and Urdu (Exps. 4 and 5); Hindi revealed a non-significant numerical trend for facilitation by morphological primes only in the right visual field (RVF), whereas reliable morphological priming in Urdu was limited to left visual field (LVF) presentation.Disparate patterns in morphological processing asymmetry were corroborated by differences in baseline visual field asymmetries in Hindi vs. Urdu word recognition- filler words elicited a consistent RVF advantage in Hindi, whereas in Urdu, one-syllable fillers, but not two- and three-syllable words revealed the RVF advantage. Taken together, the findings suggest that the variable of orthographic depth be integrated more explicitly into mainstream theoretical accounts of the mechanisms underlying morphological processing in word recognition. In addition, this study highlights the psycholinguistic potential of the languages Hindi and Urdu for advancing our understanding of the role of orthography as well as phonology in morphological processing.Item Root Morphological and Physiological Bases to Understand Genotypic Control of Mineral Acquisition in Rice Grains(2012-11-28) Chittoori, Ratnaprabha 1982-Rice (Oryza sativa L.) supports half of the human population. However, predominant rice consumption leads to malnutrition due to mineral deficiencies. The research goal was to support identification of genes responsible for the uptake/accumulation of potassium (K), iron (Fe), zinc (Zn) and molybdenum (Mo), thus promoting the breeding for rice with high grain concentrations of these elements. Prior studies identified rice genotypes with high grain-K, -Fe, -Zn or -Mo concentrations that were hypothesized to be due to differences in root traits. The research objective was to identify root traits associated with these elements. These traits could be bases for identifying genes. The first study determined if these genotypes showed similar accumulation patterns in leaves as in grains, which would hint at influences of the roots and enable identifying distinct root traits and possible genes in vegetative growth stages. The second study determined if root traits of high grain-Mo genotypes displayed an acid-tolerance mechanism as these genotypes originated from Malaysia where acidic soils strongly adsorb Mo making it unavailable for plants. The third study identified root trait differences of high grain-K, -Fe, -Zn and -Mo genotypes in hydroponics media, while the fourth determined root trait differences in these genotypes in sand-culture media including a 1-Naphthalene Acetic Acid (NAA) seed treatment for perturbation. The first study identified several high grain-Mo genotypes with similar Mo accumulation patterns in V4 to V6 stage-leaves as in grains, suggestive of a root influence. The second study established that gross morphological and physiological root traits of a high grain-Mo genotype were not part of an acid-tolerance mechanism. Neither the third nor fourth study identified root traits related to shoot K, Fe, Zn or Mo concentration, however positive associations of seedling vigor traits with several beneficial elements, including K, and negative associations with numerous toxic elements were established. Lack of correlation with root traits suggests other mechanisms (e.g. active uptake transporters) instead control the observed grain accumulation differences. Based on the fourth study, either direct effects of NAA on element uptake/transfer or indirect effects on soil pH and redox potential altered tissue Fe and Zn levels.Item Synopsis of the morphology and taxonomy of Carex section Glaucescentes in North America(Texas A&M University, 2004-11-15) McLaughlin, Diane CostonField studies were used to characterize habitat and evaluate morphological characters of Carex glaucescens, C. joorii and C. verrucosa. Morphometric analysis of herbarium specimens along with field studies, Environmental Scanning Electron Microscopy (ESEM), pollen viability and phenology show C. glaucescens, C. joorii and C. verrucosa to be taxonomically distinguishable at the species level. The taxonomy of Carex section Glaucescentes is presented in an artificial dichotomous key to the taxa and in species descriptions.Item The Architecture of Phenotypes in a Naturally Hybridizing Complex of Xiphophorus Fishes(2013-04-08) Johnson, James BradleyThe origin and maintenance of phenotypic variation has generated considerable interest among students of functional morphology, sexual selection and behavioral ecology. In particular, hybridization has been suggested as a phenomenon which may generate novel phenotypic variation. In this dissertation I focus on the Xiphophorus birchmanni - X. malinche hybrid system to assess the role of hybridization in altering behavioral, morphological, sexual and non-sexual traits. I determine the relationship between the sword sexual ornament and body condition to support previous work which suggests that the sword is an inexpensive means to increase apparent size. My findings support the prediction that, while body size is condition-dependent, the sword is not. I show a trend toward hybrid populations displaying increased phenotypic variance and reduced phenotypic integration in sexual ornaments and body size. These findings provide evidence for a potential answer to a central question in the study of sexual selection, that of reduced genetic and phenotypic variance in sexual ornaments as the result of persistent direction selection generated by female choice. I take advantage of reduced phenotypic integration in hybrids allowing the evaluation of locomotor performance across a broad range of multivariate trait values. Sexual ornaments did not impair swimming performance per se. Rather, the sword negatively affected performance only when paired with a sub-optimal body shape. I evaluated how natural hybridization changes the relationship between boldness and anti-predator response. In poeciliid fishes, bold individuals have increased survival in the presence of predators. This non-intuitive observation may result from bold individuals being more likely to engage in anti-predator behaviors. Counter to my prediction, bold individuals were less likely to perform a fast-start response to a predator threat. This correlation was consistent among populations and species but was only significant in hybrids. My findings suggest that hybridization could influence correlations between behavioral traits in a manner similar to that documented for morphological traits.