published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Temperature effects on the development of the zebrafish embryos and larvae and adults were examined. It was found that the earlier in development a temperature change was performed on an embryo, the more significant the change in survival and/or subsequent development. Thus, viable temperature ranges for zebrafish widened significantly as development proceeded. Adults reared and bred at 25oC produced embryos that were significantly more successful at the lower range of rearing temperatures compared to embryos produced from adults reared at 28oC. The majority of this study focused on the physiological effects of swim training during development in the zebrafish. The earlier in development the zebrafish larvae were trained, the greater the mortality. Trained free swimming larvae had a significantly higher routine oxygen consumption after 11 days of training, and a higher mass specific routine metabolic rate after 8 and 11 days of training. Trained free swimming larvae consumed significantly less oxygen during swimming and were more efficient at locomotion, compared to control larvae. Training enhanced survival during exposure to extreme hypoxia in all age groups. Performance aspects of training were investigated in attempt to quantify training effects and in most cases, trained fish performed significantly better than controls. As blood vessels formed during development, they decreased in cross sectional area from days two to six. It was also shown that the variability in visual stroke volume measurements could be reduced significantly by using a third dimension in the analysis with a more accurate volume equation. Finally, the ontogeny of cardiac control was evaluated. The adrenergic receptors were the first to respond to pharmacological stimulation but were closely followed by cholinergic pharmacological stimulation a few days later. There was a significant cholinergic tone present in day 15 zebrafish larvae which persisted. Although an adrenergic tone was not documented in this study, this does not prove its lack of existence.

Acclimation temperature had a significant effect on the lethality of copper to fathead minnows in replicated 96-hour lethality tests. Lowest median lethal copper concentrations (LC50) were recorded at 12 and 22°C, with LC50s at 5 and 32°C at least 140 μg/1 higher. This research found LC50 copper concentrations in the 300 to 500 μg/1 range and a polynomial relationship between LC50s and acclimation temperature. Following a 24-hour exposure to three sublethal concentrations of copper, critical thermal maxima (CTMax) were tested in minnows acclimated to four temperatures. Sublethal exposure to copper significantly decreased the CTMaxs relative to controls at three of the four temperatures. Control CTMaxs ranged from 28.6 to 40.4°C and increased 0.46°C for each 1°C increase in acclimation temperature.

Genetic variation and thermal tolerance were surveyed for variation attributed to nonuniform selection pressures for five populations of the red shiner, Notropis lutrensis, collected from regulated and unregulated portions of a Texas river. Populations within 30 km of a hypolimnion-release dam that experience large thermal perturbations were found to have higher levels of heterozygosity, higher levels of polymorphism, significantly depressed levels of upper thermal tolerance endpoints, and greater variances in tolerance endpoints. These populations have evolved enzyme systems differing from the unregulated populations in response to a variable and depressed thermal regime.

Electrophoretic variation at twenty gene loci, patterns of behavioral thermoregulation, and genotype-specific malate dehydrogenase kinetics were investigated among populations of the red shiner, Notropis lutrensis, and the blacktail shiner, N. venustus, collected from thermally altered and thermally unaltered portions of their ranges. Genic variation was found to be high among red shiners and low among blacktail shiners. The behavioral response of the blacktail shiner to temperature was fixed among the populations sampled, whereas the response of the red shiner was mutable. Finally, blacktail shiners have incorporated into their genome an Mdh-B allele which functions well at low temperatures; red shiners, displaying high levels of Mdh-B polymorphism, maintain a more complex set of allozymes which function well over a wide range of environmental temperatures. These data are consistent with reported ecotypic distributions of the species in Texas waters; i.e., blacktail shiners occur in cool, thermally static habitats, and red shiners are tolerant of wide temperature ranges.

Call number: LD2668 .T4 1986 H534 / Master of Science / Horticulture, Forestry, and Recreation Resources

In recent years, high strength concrete (HSC) is becoming an attractive alternative to traditional normal strength concrete (NSC), and is used in a wide range of applications. With the increased use of HSC, concern has developed regarding the behavior of such concrete in fire. Until now, the fire performance of HSC is not fully understood and more research is needed. Full-scale fire testing is time consuming and expensive, and the real fire scenario is different from the standard fire. Performance-based assessment methods, including numerical analysis and simplified method, are being accepted in an increasing number of countries. In this dissertation, the fire testing results both of HSC and NSC are presented, performance-based numerical models are developed to study the fire performance of reinforced concrete (RC) members, and simplified calculation methods are proposed to estimate the load capacity of fire-damaged RC columns/beams. A detailed and comprehensive literature review is presented that provides background information on the high temperature behavior of concrete materials and RC members, as well as information on fire performance assessment procedures and objectives. The fire testing results of seven batches of HSC and NSC are presented and discussed. The test results indicated that the post-fire re-curing results in substantial strength and durability recovery, and its extent depends upon the types of concrete, temperature level, and re-curing age. The fire tests also showed that violent explosive reduced the risk of HSC explosive spalling. The surface crack widths were also reduced during the re-curing process, and in most cases, they were found within the maximum limits specified by the American Concrete Institute (ACI) building code. / Numerical models are developed herein to investigate the behavior in fire of RC columns and beams. The models have been validated against fire test data available in literature, and used to conduct parametric studies, which focused on the size effect on fire resistance of RC columns, and the effect of concrete cover thickness on fire endurance of RC beams. Simplified calculation methods have been developed to predict the load capacity of fire damaged RC columns/beams. This method is validated by five case studies, including thirty-five RC columns tested by other investigators. The predicted results are compared with the experimental results, and the good agreement indicates the adequacy of the simplified method for practical engineering applications. / by Lixian Liu. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Florida’s sea turtle populations are increasing due to conservation efforts; however, sea turtle species are vulnerable to climate change. Turtles exhibit temperaturedependent sex determination, in which nest environment influences sex. Environmental changes may produce altered sex ratios that limit reproduction potential; therefore hatchling sex ratios should be monitored. Hatchlings are not externally sexually dimorphic, making sex identification difficult. This study established baseline plasma hormone concentrations in hatchling and post-hatchling green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles using High Performance Liquid Chromatography. Five hormones were assayed and were present in the majority of samples (testosterone: N.D.-10.12, progesterone: N.D.-0.43, estradiol: N.D.-4.78, estriol: N.D.-5.55 and estrone: N.D.-1.67 μg/mL). Plasma hormones did not distinguish hatchling sex because male and female ranges overlapped. Hormone concentrations varied with sex but also with incubation temperature, indicating that climate change could impact hatchling and posthatchling hormone profiles and thus could impact future fitness. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Pubagem é o processo de fermentação natural de raízes de mandioca para produção de puba, um alimento tradicional nas regiões Norte e Nordeste do Brasil. Além da fermentação lática, uma ação combinada da pectina-metil-esterase endógena e enzimas microbianas despolimerizantes causa o amolecimento das raízes, que é importante para sua completa desintegração. No entanto, o reconhecimento do ponto final de fermentação e as condições que propiciam puba de boa qualidade não são completamente esclarecidos. O objetivo do trabalho foi estudar a influência da temperatura de fermentação e da adição de enzima como auxiliar de pubagem na textura das raízes e rendimento de puba, procurando associar estes parâmetros para detectar o ponto final desta etapa do processo. Cerca de 1Kg de raízes descascadas e 2 litros de água foram colocados em recipientes plásticos. Diferentes concentrações (0,1 e 2mL) de pectinase comercial de Aspergillus aculeatus/Kg de raiz foram adicionadas em tratamentos separados. Amostras foram incubadas a 25, 30 e 35ºC, por períodos de 48, 72 e 96 horas. Foram efetuadas análises de acompanhamento do processo fermentativo (pH, textura e rendimento) e da composição da farinha de puba obtida. O maior rendimento, de 77% após 72 horas, foi observado no tratamento a 25ºC com 2mL de enzima por Kg de raiz, quando a textura que era de 18,62lbf/g na matériaprima passou para 3,92lbf/g na raiz pubada. Outros rendimentos mais próximos desse valor, 75,7 e 74,7%, foram obtidos respectivamente na fermentação natural a 35ºC e na amostra tratada com 2mL de enzima incubada a 30ºC/48 horas. Os valores de textura foram de 2,50lbf/g para o primeiro tratamento e 2,89lbf/g para o segundo. A relação entre textura e rendimento foi significativa para a temperatura de 30ºC e todos os períodos de 72 horas. A associação entre os dados de textura e rendimento permite concluir que quando a textura alcança valores da ordem de 4lbf/g os rendimentos de puba são maiores, indicando o final do processo. Os rendimentos mais baixos ocorreram para os valores de textura próximos a 2,30lbf/g de amostra, geralmente obtidos em fermentações mais longas e com maior concentração de enzima. / "Retting" is a natural fermentation of cassava roots for the production of puba, a traditional food in the North and Northeast of Brazil. Besides the lactic fermentation, the combined action of the endogenous pectin-methyl-esterase and depolymeryzyng enzymes, causes a softening of the roots which is important for its complete disintegration. However, the recognition of the end point of fermentation and the conditions that lead to good quality puba are not completely understood. The objective of this work was to study the influence of the temperature and enzyme concentration on the yield and texture, aiming at associating these parameters to detect the end point of fermentation. The physicochemical properties of the puba flour were also determined. About 1Kg of peeled roots and 2 liters of water were placed in plastic containers. One or two milliliters of commercial pectinase from Aspergillus aculeatus were added / Kg root, in separate treatments. In the control treatment no enzyme was added. Samples were incubated at 25, 30 and 35ºC and portions removed after 48, 72 and 96 hours for the determination of pH, texture, yield and dry matter. Fibers, starch, total soluble sugars and amylose were determined in the flour of the dried puba. The highest yield of 77% was obtained after 72 hours for the treatment at 25ºC with 2mL of enzyme/kg of root, when the texture values decreased from 18.62lbf/g (raw material) to 3.92lbf/g (retted root). A high yield of 75.7% was also observed in same period, for the natural fermentation at 35ºC, when texture values of 2.50lbf/g were reached. The relation between texture and yield was significant for a temperature of 30ºC and a period of 72 hours. The association between the texture and yield data suggests that when the texture reaches values of the order of 4lbf/g, the yields are higher, indicating the end of the process. The yields were lower when texture values were close to 2.30lbf/g, usually achieved for long fermentations and higher enzyme concentrations.

"Microelectromechanical systems (MEMS) technology has been evolving for about two decades and, now it is integrated in many designs, including radio frequency (RF) switches characterized by µm dimensions. Today, designers are attempting o develop the ideal RF MEMS switch, yet electro-thermo-mechanical (ETM) effects still limit the design possibilities and adversely affect reliability of these microswitches. The ETM effects are a result of Joule heat generated at the microswitch contact areas. This heat is due to the current passing through the microswitch, characteristics of the contact interfaces, and other parameters characterizing a particular design. It significantly raises temperature of the microswitch, thus affecting the mechanical and electrical properties of the contacts, which may lead to welding, causing a major reliability issue. Advanced research was performed, in this thesis, to minimize the Joule heat effects on the contact areas, thus improving performance of the microswitch. Thermal analyses done computationally on a cantilever-type RF MEMS switch indicate heat-effected zones and the influences that various design parameters have on these zones. Uncertainty analyses were also performed to ensure accuracy of the computational results, which indicate contact temperatures on the order of 700˚C, for the cases considered in this thesis. Although these temperatures are well below the melting temperatures of the materials used, new designs of the microswitches will have to be developed, in order to lower their maximum operating temperatures and reduce temporal effects they cause, to increase reliability of the RF MEMS switches."