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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.
141

The effect of exercise on thermo-tolerance in pregnant Holstein heifers

Johnson, Jessica January 1900 (has links)
Doctor of Philosophy / Department of Animal Sciences and Industry / Timothy G. Rozell / Dairy cows require a low-stress environment in order to efficiently produce milk, and thus stress management is a common focal point for both researchers and producers. A primary source of stress for dairy cattle is associated with the environment, particularly heat, and therefore a considerable amount of research has been done in an attempt to find ways of reducing heat stress. Most of the research, however, has focused on using heat abatement techniques to cool the cow, using evaporative cooling systems to reduce temperature in the environment thus also cooling the cow, and selective breeding to improve thermal tolerance. Whereas cow comfort has been improved, there are still negative responses to heat stress today including decreased milk production and altered milk composition. Cattle remove excess body heat primarily through evaporative and convective cooling in the respiratory system and exercise is likely to improve blood flow and efficiency of heat transfer within the lungs. Furthermore, exercise has been proven to improve performance in humans and horses. This study was designed to determine whether or not exercise improved fitness and heat tolerance, and to observe whether there were any resulting effects on milk production and parturition. Two experiments were carried out during the late summer/early fall of 2014 and summer of 2015. Each experiment utilized a different exercise regimen: experiment 1 used a combination of high-intensity intervals and endurance training, whereas experiment 2 involved an endurance regimen performed during the afternoon in early summer. Pregnant Holstein heifers (Experiment 1, n = 24; Experiment 2, n = 24) were exercised in an 8-panel motorized walker over a period of 8 wk that ended approximately 21 d prior to parturition. In experiment 1, fitness was improved in heifers that were exercised compared with their non-exercised counterparts based on their duration of exercise and speed of exercise at failure (P < 0.05). During a cool hour of the day after 6 wk of exercise, exercised heifers spent more time in body temperature zone 1 (< 39.0°C) compared with their non-exercised counterparts (P < 0.05). Exercised heifers also spent less time (P < 0.05) than non-exercised heifers in body temperature zone 3 (> 40.0°C) during the hottest hour of a hot day during the 6th week. No treatment effects (P > 0.10) were found for weekly milk components or milk production. In experiment 2, exercise resulted in greater milk protein and solids-not-fat (SNF) percentage (P < 0.05) compared with contemporaries that did not exercise; however, there was no difference in weekly milk production during the first 150 days (P > 0.10). Fat-corrected milk and energy-corrected milk were calculated and no difference was detected between treatments (P > 0.10). These results are the first to show that high-intensity intervals and endurance training exercise in pregnant dairy heifers can improve heat tolerance, increase production of milk protein and SNF, and perhaps increase animal comfort and well-being during hot weather.
142

Experiences of Conservative Orthodox Christian Students Attending Public Secular Accredited Counseling and Counseling Psychology Graduate Programs

Schaefer, Paul 22 May 2006 (has links)
The purpose of this qualitative study was to explore the experiences of conservative orthodox Christian students attending public, secular, accredited counseling and counseling psychology graduate programs. Conservative orthodox Christian students who were attending public, secular, accredited counseling and counseling psychology graduate programs were recruited by email. A prescreening interview was conducted with each respondent. Seven respondents participated in three rounds of individual interviews. The overall research question was: What are the experiences of conservative orthodox Christian students attending public, secular, accredited counseling and counseling psychology graduate programs? Follow-up questions explored the participants' perceptions and experiences in depth. Data were analyzed through within case and cross case displays using a phenomenological approach. Emergent categories, themes, and descriptors were gathered from each round of interviews. Data were organized into three major categories: reflections on secular programs, experiences attending secular programs and Christian identity, and further organized into underlying themes and descriptors. Implications related to conservative orthodox Christian students attending public, secular, accredited counseling and counseling psychology graduate programs were discussed. Finally, suggestions for future research were provided.
143

Thermo-acidophilic Algae: pH and Metal Tolerances

Lowell, Christina, Lowell, Christina January 2012 (has links)
The class Cyanidiophyceae (the "cyanidia") includes three genera, the walled Cyanidium and Galdieria and the "naked" Cyandioschyzon. All of these algae are unicellular and asexual and live at high temperature and low pH. The cyanidia grow optimally at a pH of 2-3 but can tolerate a higher pH and lower their surrounding pH if it is above the optimal level. They can also tolerate high concentrations of potential toxins that are often found in their natural environments. This thesis shows that strains of cyanidia from Yellowstone National Park and other geographic locations have differing abilities to lower their surrounding pH and tolerate environmental toxins that are found in many environments in which they live. These unique characteristics of this class of algae allow them to be optimally adapted for life in extreme environments with few competitors. This thesis includes unpublished co-authored material.
144

Static and fatigue propagation of buckle-driven delaminations under bending and compressive loads

Kinawy, Moustafa January 2011 (has links)
No description available.
145

Techniques for optimisation and analysis of composite structures for damage tolerance and buckling stiffness

Baker, Neil January 2012 (has links)
This thesis explores methods by which carbon fibre reinforced polymers may be fficiently designed with the inclusion of damage tolerance criteria. An efficient method of modelling the compression after impact (CAI) strength of composite materials is selected, and this forms the basis of analysis performed. The CAI model is initially used as the objective in an optimisation routine using a simple genetic algorithm. This indicates features of a damage tolerant composite laminate, namely that plies near the surface are less axially sti® in the loading direction than those nearer the laminate midplane, with a lower Poisson's ratio than the full laminate. This delays sublaminate buckling under laminate uniaxial compression, thus restricting delamination propagation. The designs produced by the optimisation are verified experimentally. In order to improve the computational efficiency of the CAI model a simple surrogate modelling technique for sublaminate buckling is presented. This allows a complete database of results to be produced for a given set of ply angles, in this case standard 0/90/§45± plies. This is used in the full analysis of a collection of layups produced elsewhere to be fully uncoupled, but without the stipulation of midplane symmetry. The surrogate method is shown to reduce computation time by over 99%, and produce results with an average error of less than 0.1% compared to exhaustive analysis. The analysis of the damage tolerance of fully uncoupled laminates shows that the relaxation of midplane symmetry as a design rule gives the designer far more flexibility in layup, and may allow for more damage tolerant laminates to be selected. Finally, the CAI model is incorporated into a stiffened panel design optimisation problem as a constraint. Firstly the panel is optimised using the in¯nite strip analysis tool VICONOPT, with three stiffener geometries. The objective function is minimum mass for a panel subject to compressive and out-of-plane loading, with buckling and strain allowable constraints applied. Damage tolerance constraints are then applied in place of a strain allowable, using a bi-level optimisation approach. This method is shown to allow efficient inclusion of damage tolerance as a constraint in stiffened panel design, although it does not account for interactions in global buckling and local sublaminate buckling which may reduce the strength of the panel. Results indicate that the inclusion of damage tolerance analysis in stiffened panel design shows little benefit for low load panels, but can give significant reductions in mass (up to 30%) for higher load panels.
146

Evaluation of free leaf proline concentration as a practical method for measuring drought stress in plants

Waldren, Richard P January 2010 (has links)
Digitized by Kansas Correctional Industries
147

SELECTION FOR HEAT TOLERANCE IN JAPANESE QUAIL (Coturnix coturnix japonica)

Abdullaziz Al-abdullatif Unknown Date (has links)
ABSTRACT This study reports on the results of a selection experiment using Japanese quail (Coturnix coturnix japonica) with the aim of assessing the impact of a number of selection regimes on tolerance to heat stress as measured by growth rate. Four lines were selected for six generations for increased weight gain from 14-28 days of age under either high (W, 32ºC) or normal (C, 25ºC) temperature conditions on either a high (H, 250 g/kg) or low (L, 150 g/kg) protein diet. Both diets contained 13.0 MJ ME/kg. The four selected lines were thus designated WH, CH, WL and CL. Fortnightly hatches were produced each generation from matings between 12 males and 36 females per line, with the parents of the next generation selected from approximately 100 birds per sex per line. A randomly selected control line (line C) of similar size was also maintained and reared in all cages with the selected line birds. Each generation, a third hatch of birds was reared and approximately 20 birds per line per environment were placed in single-bird cages to measure correlated responses in weight gain and feed efficiency in all four temperature/ dietary protein environments. In addition, correlated responses were measured in body composition and an assessment of the relative responses of the lines to early post-hatch epigenetic heat conditioning and to dietary addition of betaine (an osmolyte) were undertaken. The final study involved measurement of correlated response in the lines in the components of reproductive performance. On the high protein diet, response in growth rate relative to the control line in all selected lines was positive under both temperature environments, and by generations 5 and 6 growth rate was higher in the WH than in the CH line birds in both temperature environments. As weight gain was the selection criterion, these results suggest that selection for increased growth rate under high temperature conditions may not only be beneficial for progeny reared under high temperature conditions, but might also be at least as effective as selection under normal temperatures for progeny reared under normal temperature conditions. Whilst there was no equivalent advantage in feed efficiency in the WH line birds in either temperature environment, and the results arise from a comparison between un-replicated lines, they certainly indicate that such a selection approach is unlikely to have deleterious consequences. There was no benefit in either growth rate or feed efficiency under either temperature environments achieved through selection of birds on a low protein diet, irrespective of the selection temperature conditions. This indicates that irrespective of environmental temperature either during selection or subsequently, any possible advantage obtained through a reduction in the protein breakdown rate conferred through selection on a diet limiting in protein is outweighed by other factors contributing to a lower heritability and poorer response in these lines. In contrast to the WH line, the CH line birds in the normal temperature conditions were significantly (P<0.01) leaner under high than normal temperature conditions, although these differences were not reflected in differences in feed efficiency. On the low protein diet, females were considerably fatter than males and the CL line birds had a considerably higher proportion of body fat than either their WL or C line counterparts. Responses in body composition emphasise the inadvisability of selecting birds for growth rate under protein deficient diets, particularly if they are expected to perform under high temperature conditions on either high or low protein diets. In a study of the effect of early post-hatch epigenetic heat conditioning on subsequent performance in the single-bird cages, half of the chicks from each line were exposed at 2 days of age to 38OC for 24 hours. The results of the study showed that there was a positive effect of heat conditioning, as measured by subsequent growth rate, in birds selected for increased growth rate under normal temperatures. However, selection for increased heat tolerance appeared to render the birds refractory to the beneficial effects of epigenetic conditioning. This suggests that the physiological pathways exploited by epigenetic heat conditioning are also utilised in selection for heat tolerance. Inclusion of betaine in the diet at 0.5 g/kg had a beneficial effect upon growth performance from 14-28 days of age in birds kept under high temperature conditions, but the degree of the effect was influenced by other factors possibly associated with the nutrient (and particularly the amino acid) composition of the diet. There was a lack of consistency in the relative responses of the lines to betaine supplementation indicating that it is unlikely that osmoprotection contributes in any meaningful way to heat tolerance expressed by the lines selected under high temperature conditions. A study of reproductive performance of the birds at generation six lent support to previous published findings showing deleterious effects upon the components of reproductive performance from selection for increased growth rate. There were, however, significant differences between the selection lines which suggested beneficial outcomes from selection for growth rate under moderately high temperature conditions, particularly in breeders housed under these same conditions. Relative to selection under normal temperatures, these benefits included: early onset of lay, increased egg production, increased egg weight and improved fertility.
148

Potential for improving the drought resistance of soybean (Glycine max (L.) Merr.) using the transpiration efficiency trait

White, Damien Scott. January 1998 (has links) (PDF)
Bibliography: leaves 134-145. The improvement of drought tolerance of commercial soybean varieties via indirect selection for transpiration efficiency (TE) in breeding programs was investigated. The extent and nature of variation for TE among soybean genotypes were established through glasshouse experiments under well watered conditions, and confirmed in the field under contrasting water stress conditions. The results suggest that increasing TE will be a beneficial strategy to improve soybean grain yield at the crop level, and a protocol developed suited to indirect selection for high TE soybean genotypes under a range of environments. This will have immediate application in the development of soybean varieties specifically adapted to the dryland production areas of the Australian sub-tropics.
149

Molecular and functional characterization of sn-glycerol-3-phosphate acyltransferase of plants

Chen, Xue 06 1900 (has links)
sn-Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the acylation of sn-1 position of sn-glycerol-3-phosphate to produce lysophosphatidic acid and Coenzyme A. GPATs are involved in several lipid synthetic pathways and play important physiological roles in plant development. The present doctoral thesis includes three related studies, which aim to molecularly and functionally characterize several plant GPAT genes and the encoded enzymes. The first study characterized three endoplasmic reticulum-bound GPAT4s encoded by three homologous GPAT4 genes of Brassica napus (oilseed rape), focusing primarily on their functional divergence and physiological roles in plant development and lipid biosynthesis. The three homologous GPAT4 genes exhibited different expression patterns and altered epigenetic features. Phenotypic rescue of a gpat4 gpat8 Arabidopsis double mutant and analysis of the gpat4 RNAi B. napus lines suggested physiological roles for the GPAT4s in cuticle formation of the rosette leaves, early flower development, pollen development and storage lipid biosynthesis. The second study investigated stable internal reference genes for gene expression studies in B. napus. This project identified four reliable reference genes to be used in gene expression analysis of BnGPAT4 homologues in both vegetative tissues and developing seeds. The third study focused on molecular cloning and biochemical characterization of a soluble plastidial GPAT isolated from a chilling-tolerant plant, western wallflower (Erysimum asperum). A truncated form of recombinant EaGPAT, with the putative transit peptide deleted, was functionally expressed in yeast. A series of enzymatic assays were performed in order to determine the optimum in vitro reaction conditions for the recombinant EaGPAT. The recombinant EaGPAT was further assayed with different acyl-CoAs and exhibited a substrate preference for 18 carbon unsaturated acyl-CoAs. With this substrate preference, the EaGPAT could potentially be used as a biotechnological tool for improving plant chilling-tolerance or increasing unsaturated fatty acid content of seed oil. Overall, the present doctoral studies revealed the functional divergence and important physiological roles of the GPAT4s in B. napus, and biochemically characterized a plastidial GPAT from E. asperum. The knowledge obtained from these studies provides new insights into the role of GPAT in plants and will be useful for further development of biotechnological approaches to modify seed oil biosynthesis in oleaginous crops. / Plant Science
150

Vagueness and Domain Restriction

Pagin, Peter January 2011 (has links)
This paper develops an idea of saving ordinary uses of vague predicates from the Sorites by means of domain restriction. A tolerance level for a pred- icate, along a dimension, is a difference with respect to which the predicate is semantically insensitive. A central gap for the predicate+dimension in a domain is a segment of an associated scale, larger than this difference, where no object in the domain has a measure, and such that the extension of the predicate has measures on one side of the gap and the anti-extension on the other. The domain restriction imposes a central gap. / <p>Author count: 1;</p> / Vagueness and Context Factors

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