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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.
301

Extrathyroidal thyroid hormone activation in ring doves

Rieman, James Davis 14 March 2009 (has links)
The characteristics of 5’deiodinase (5’D) were studied in the postmitochondrial fraction (PMF) of liver homogenates from adult and developing ring doves (Streptopelia risoria). The 5’D assays were performed in the presence of abundant substrate, reverse triiodothyronine (rT3), cofactor (dithiothreitol) and trace amounts of I¹²⁵-rT3. 5’D activity was measured as I¹²⁵ released from the labelled rT3 during the assay incubation time. The 5’D assay was validated for all ages studied to assure that the initial reaction velocity of the enzyme was measured. Using the validated assay conditions the following characteristics were found in adult doves: the apparent K<sub>m</sub> was 0.44 μM rT3, V<sub>max</sub> was 255 pmol rT3 degraded/min-mg PMF protein. The 5’D activity was completely inhibited by 1.0 mM PTU and 50% inhibited by the addition of 18.0 μM thyroxine (T4) in the presence of 4.0 μM rT3. Activity was maximal at pH 8.04 and at 37.5 C. The K<sub>m</sub> of the enzyme did not change throughout development (1 day prehatch to adult). The 5’D specific activity (rT3 degraded/min-mg PMF protein) was highest during early development (1 day prehatch to 7 days post-hatch), after which it gradually decreased with increasing age. The liver 5’D activity/gram of body weight was highest during the first seven days posthatch. This period of high potential triiodothyronine (T3) production corresponds with the observed period of greatest increase in plasma thyroid hormone concentrations during the first 6-8 days posthatch in ring doves. These results are the first demonstration of initial velocity 5’D activity during development in an altricial bird species and demonstrate a correlation between hepatic 5’D activity and plasma thyroid hormone concentrations during development in ring doves. / Master of Science
302

The root of all evils: creation science and the fundamentalist mission

Holshoe, Joseph Marian 08 April 2009 (has links)
This work examines creation science and its relationship to American Protestant fundamentalism. The thesis argues that scientific creationism is inextricably linked to American Protestant fundamentalism. More specifically, this thesis demonstrates that creation science is a direct historical product of fundamentalist thought, theology, social character, and organizational structure. Indeed, creation science is most clearly understood in light of its historical and social relationship to fundamentalism. Scientific creationism is the newest phase in the fundamentalist rejection of modernist thought and evolutionary theory. The thesis concludes that creation science is not a valid scientific endeavor, and is in instead a form of Biblical apologetics. / Master of Arts
303

Incorporating global information into local nonlinear controllers

Stewart, Chris G. 07 April 2009 (has links)
For a particular equilibrium point, the local performance is determined by the partial derivatives of the control law evaluated at the equilibrium point. For a linear controller, the derivatives are equal to the state-feedback gains and the gains on the external inputs. These gains can be changed to vary the local performance of the system. An extended-linear controller links together the desired local controllers of various equilibrium points producing a nonlinear controller with the desired characteristics in a neighborhood of the equilibrium curve. Global performance is the behavior of the system away from the equilibrium curve. Although the extended-linear controller has good local performance, the global performance might be poor or even unstable. This thesis uses cubic spline techniques to investigate the coupling of global information into local controllers without affecting the local performance. Although “stand-alone” interpolative spline structures do not give the desired local performance, global information can be splined into linear and extended-linear controllers to provide both good global and good local performance. / Master of Science
304

Influence of lipid antioxidants on soybean seed storage life

Aho, David W. 13 February 2009 (has links)
In-storage losses of seed vigor, i.e., aging, that occur between harvest and planting may leave soybeans essentially worthless as seed. Peroxidation of lipids, with resultant loss of membrane integrity, is theorized to be a primary event in seed aging. Lipid antioxidants might have the potential to protect dry seed by neutralizing free radicals, which propagate lipid peroxidation and other destructive events. Seed were treated with antioxidants in dimethyl sulfoxide (DMSO) to investigate possible protective effects of antioxidants during storage and thus also provide evidence for the lipid peroxidation model of seed aging. The toxicity of DMSO to soybean seed was found to be minimal at treatment times of 15 min or less. Seed were treated for 15 min with 0, 5, 25, and 50 mM solutions in DMSO of propyl gallate (PG), butylated hydroxyanisore (BHA), butylated hydroxy toluene (BHT), and tert-butylhydroquinone (TBHQ). Germination, seed leakage, seedling vigor, and phospholipids in the embryonic axis were monitored following storage at 40 C for up to 90 days. / Master of Science
305

An integrated approach to the optimal runway exit locations

Kim, Byung Jong 24 March 2009 (has links)
The airport capacity problem has recently received a great deal of attention due to airport congestion and delays. Capacity improvements of airfield and airspace component of an airport are currently being addressed by several researchers and federal and state agencies. The optimal location of runway turnoffs is the focus of this research. Although the current airport capacity limitations are dictated by airspace separation rules, it is expected that runway occupancy time (ROT) will become an important factor In the near future as the interarrival separations between landing aircraft are reduced. The intent of this research is to show that the use of high speed exits on runway contributes to the reduction of ROT, and therefore provides enhancement in runway capacity. However, locating the high speed exits is a complex and dynamic problem stemming from the aircraft landing behavior. The landing behavior of an aircraft is affected by many factors such as approach speed, deceleration rate, design exit speed, airport elevation, wind, temperature, etc .. Some of these factors are probabilistic in nature. A simulation model and an optimization algorithm that take into consideration all above factors developed to address the problem. The simulation model consists of a series of dynamic equations of motion that models the aircraft landing behavior under various airport conditions, and determines the best exit location for that aircraft. The optimization model takes the simulation results as input for various aircraft mix, and finds a given number of exit locations which minimize the average ROT for the total aircraft fleet. / Master of Science
306

A feasibility study of PVDF piezoelectric sensors to detect damage in adhesive joints

Mommaerts, Joseph 08 April 2009 (has links)
Poly(vinylidene fluoride) (PVDF) films can be easily etched into sensor devices. Since these sensors are relatively inexpensive, thin and light-weight, they can be attached to adhesively bonded joints permanently to measure bond integrity. The present study shows the different steps to design such sensors and proper techniques to attach them near the adhesive bondline. PVDF sensors have been successfully used as NDT transducers in pulse-echo, through-transmission, and acousto-ultrasonic techniques to monitor curing, to detect porosity and crack propagation in different model joint geometries. The potential of using these techniques for practical bonded structures has then been evaluated. / Master of Science
307

Laboratory evaluation of conditioning requirements for sludge dewatering using belt filter press

Burgos, William David 14 March 2009 (has links)
The purposes of this study were to develop a reliable bench-scale testing procedure to adequately predict polymer conditioning requirements for full-scale belt filter presses, and to determine the additional polymer demand exerted by applied pressure during the expression stage of a dewatering process. Bench-scale experiments performed with anaerobically digested, alum, and secondary sludges used a high-speed mixer to gauge mixing intensity effects, and a wedge zone tester to gauge applied pressure effects on conditioning requirements. Full-scale experiments varied Sludge throughput, belt speed, and polymer dose to evaluate polymer performance. The polymer requirements to optimize performance of a full-scale belt filter press can be predicted with a bench-scale mixing device, where the shear (Gt) of the mixer matches that of the full-scale press. An estimate of the Gt value of the full-scale belt filter presses used in this study was 10,000. Alternatively, a bench-scale wedge zone tester, operated in an applied pressure range between 5 psi and 20 psi, can predict polymer doses for optimum belt filter press performance. The range of applied pressures used to simulate the expression phase of a dewatering process did not exert a Significant additional polymer demand for optimum conditioning. The shear (Gt) associated with mixing sludge and polymer during conditioning can exert a greater polymer demand than the expression phase of the wedge zone tester. / Master of Science
308

Survival equations for loblolly pine trees in cutover, site- prepared plantations

Avila, Olga B. 12 March 2009 (has links)
The probability of mortality for an individual tree with certain characteristics growing under certain conditions was modeled. A particular algorithm SCREEN was used to fmd the best set of predictors variables. This algorithm was specially created to be used when the dependent variable can take only two values like in this binary case (dead or alive tree). The logistic model with different independent variables, which were found to be significant through the SCREEN algorithm, was fitted to the data. For the unthinned plots the logistic model with the following variables, CR (crown ratio), HH (total height/height of dominant and co-dominant trees) and CI (competition index) was compared with the survival model applied in a published distance-dependent model PTAEDA. The logistic model with CR, HH and DD (quadratic mean diameter/dbh) was compared with the survival model already used in a distance-independent model TRULOB. In both cases the behavior of the logistic model was quite similar to the published models. For the thinned plots the predictor variables DDt HH, CI and CR raised to 1.5 were used in the logistic model to predict mortality for individual trees. Mortality is difficult to predict. In this particular study the logistic model was used. The final distance-dependent model for unthinned plots includes as predictor variables CR, HH and CI. For thinned plots the final logistic model employs HH, CI and CR raised to 1.5 as independent variables. The final distance-independent model for unthinned plots includes as predictor variables HH, DD and CR. For thinned plots the final logistic model uses HH, DD and CR raised to 1.5 as independent variables. Differences between deterministic and the stochastic treatments of mortality were also studied. No practical differences in several stand characteristics such as average height, total volume, basal area were found when using these two approaches. Further, no significant differences were found in the diameter distribution for dead or alive trees. / Master of Science
309

Simultaneous process control of several independent quality variables

Wise, Marshall Alan 12 March 2009 (has links)
A method for multivariate quality control with the dual objectives of providing a true level of sampling error probabilities for the joint control of several quality variables while also giving problem diagnoses for the quality variables individually. The method is comprised of an afine transformation of the multiple quality variables which creates a univariate test statistic used to monitor the quality and provide problem diagnoses. In practice, realized values of this statistic would be plotted as a time series on a control chart with multiple diagnosis intervals. For the analysis of the method’s effectiveness, the quality variables are assumed to be independent and normally distributed. The method is shown to be successful in achieving desired sampling error probabilities for any m quality variables in the case of positive shifts in the means of the variables. A second transformed variable is added for the diagnosis of shifts of unrestricted direction, and its effectiveness is analyzed. The sample size requirement of the afine transformation method is compared to the total sample size necessary when a separate Shewhart chart for the mean is maintained for each quality variable with the same overall sampling plan objectives. The power of the method to detect quality problems in general while disregarding specific diagnoses is compared to the power of Hotelling’s T² test for multivariate quality control. A comprehensive evaluation of the relative worth of the two methods is not possible since the T² statistic does not consider diagnoses of the individual quality variables. / Master of Science
310

A framework to guide the incremental implementation of a computer- integrated manufacturing system

Perko, Margery Leigh 12 March 2009 (has links)
This thesis develops a framework to guide the incremental design and implementation of a Computer-Integrated Manufacturing System (CIMS). The framework is premised upon the facts that: (1) CIMS design is accomplished through a series of evaluation decisions sequenced through time and (2) evaluation is accomplished by decomposing the entire manufacturing organization into its essential activities and transactions. The effects of computerization on these activities and transactions are determined and these effects are then related to impacts on a set of selected evaluation criteria. Formal methods for benefit quantification are not included. The user of this framework is required to: (1) specify a set of relevant evaluation criteria, (2) define essential activities and transactions of their organization, and (3) derive organization-specific affect/impact relationships. The framework structures these activities for the user and suggests a series of matrices that can be used to guide the user through the steps of the framework. Use of the framework is demonstrated as various aspects of an implementation decision currently being faced by a manufacturing organization are analyzed. The implementation decision concerns whether to implement a computerized production planning and scheduling system and aspects of the decision which are considered include impacts on organizational flexibility, responsiveness, and skills. The required changes in authority relationships and the assignment of task responsibilities are also considered. Using results from this case study, the usefulness and appropriateness of the framework was assessed. Although there was no quantitative measure available, the client deemed the framework useful for analyzing and guiding their implementation decision. Suggested improvements to the framework are presented. / Master of Science

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