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Reproductive Life History Decisions in a Long-Distance Migrating Iteroparous Fish Model
No full textSteelhead trout (Oncorhynchus mykiss, hereafter referred to as steelhead) display diverse life histories after initial or maiden spawning, with some individuals spawning again after 1 year (consecutive spawning) and others after two or more years (skip spawning). This study seeks to understand how reproductive performance compares between maiden and repeat spawners, how physiological condition is involved in the development of consecutive and skip spawning life histories, and how and when resources are allocated within and between reproductive events. An experimental model employing female, hatchery-origin steelhead was used to test for: (1) physiological trade-offs between maiden reproductive effort and future reproduction, (2) a conditional vs. fixed maturation strategy, (3) a critical period after maiden spawning for rematuration initiation, and (4) the sensitivity of ovarian development in relation to physiological condition. Female steelhead were captured following their upstream spawning migration, manually spawned, fed, sampled, and repeat spawned in captivity. This experimental model represents one of extreme energy depletion associated with an approximately 6 month-long, 800 km freshwater fasting spawning migration. Repeat spawners were larger and had greater absolute fecundity than maiden spawners. Skip spawners had larger eggs and greater total reproductive effort than maiden and consecutive spawners. When standardized for mass, consecutive spawners had more but smaller eggs than maiden spawners, indicating that egg size can vary and is determined early in oogenesis based on energy reserves. These observations imply that excess energy gained during the vitellogenic period is allocated to somatic growth. Mass growth and plasma triglyceride (TG) levels were greater in consecutive than skip spawners 10 weeks after maiden spawning, and muscle lipids and Fulton’s condition factor were greater in consecutive spawners 20 weeks after maiden spawning. These findings suggest that consecutive spawners consumed more food than skip spawners during the period after spawning. Mass growth and TG were positively related to reproductive performance at repeat spawning in consecutive spawners, with the maximal correlation with egg size at 10 weeks, and the maximal correlation with total reproductive investment at 20 weeks. Consecutive maturation was not significantly associated with any measure of physiological condition at maiden spawning. However, post-spawning survival was positively associated with maiden spawning TG, representing the ability to access energy, and plasma osmolality, indicating the ability to maintain homeostasis. Surprisingly, consecutive maturation was positively related to maiden reproductive effort, which is not consistent with a theorized tradeoff between current and future reproduction in animals. Instead, this result suggests that both maiden reproductive effort and consecutive maturation may be condition dependent at time points prior to maiden spawning. This dissertation provides insight into how and when consecutive and skip spawning life history tactics develop physiologically in steelhead. Additionally, this dissertation provides evidence that female steelhead can modulate reproductive investment based on physiological condition early during oogenesis.doctoral, Ph.D., Biology -- University of Idaho - College of Graduate Studies, 2018-1
Magnetic Induction of Conductive Nanosprings
No full textNanosprings grown on a substrate produce a 3D network of randomly connected microscopic springs. The springs are made of silicon dioxide on the order of 10 nm in diameter. The motion of electrical current through the 3D network of nanosprings is of interest for the integration of nanosprings into electronic devices. To make the nanosprings conductive they are coated in graphene by a process called Graphite from the University of Idaho Thermolyzed Asphalt Reaction (GUITAR). The following data demonstrate the equipment configuration necessary to obtain a low noise signal to investigate the electrical response of GUITAR coated nanosprings due to magnetic flux. When comparing the response of a sample of nanosprings to a comparable resistor it was found that the nanospring sample is more sensitive to smaller magnetic flux than to larger magnetic flux.masters, M.S., Physics -- University of Idaho - College of Graduate Studies, 2018-0
ELECTROCHEMISTRY OF LANTHANUM IN ROOM TEMPERATURE IONIC LIQUID EMIM-DCA
No full textIn nuclear engineering, the accumulation of lanthanides, as the main fission products, has detrimental effects on the efficiency of nuclear fuel because of strong neutron absorption properties. Therefore, the lanthanides need to be separated from actinides, a difficult task due to the similarity of chemical and electrochemical properties. One of the avenues for reprocessing nuclear fuels is electrometallurgy from ionic liquids. Ionic liquids can be classified according to temperature of application into (1) high temperature and (2) low temperature. High temperature ionic liquids are eutectic inorganic salts, such as LiCl-KCl. They are operational in the range 400 – 600 °C. Low temperature ionic liquids are made of an organic (cation) and inorganic (anion) components. They are fully ionized, stable, conductive and liquid in a much lower temperature range than ionic liquids based on inorganic salts, typically 25 - 100 °C. For that reason, they are often termed as room temperature ionic liquids (RTILs). Due to lanthanide’s large electronegative deposition potential (~ -2.4 V vs SHE) traditional aqueous electrodeposition processes cannot be used as hydrogen evolution from water occurs prior to any lanthanide metal deposition. RTIL’s provide a unique solution to this problem as these salts are liquid at room temperature and provide a wide electrochemical window (up to 5 V) for deposition of electronegative metals without the detrimental effects from hydrogen ion reduction, as present in aqueous systems. The goal of this study was to examine the electrochemistry and deposition morphology of lanthanum metal in the RTILs 1-ethyl-3- methylimidazolium dicyanamide (EMIM-DCA) and 1-butyl-3-methylimidazolium dicyanamide (BMIM-DCA) ionic liquids. These particular RTILs are stable in the cathodic direction up to -2.4V vs Ag/AgCl, providing the adequate stability to observe the electrodeposition of lanthanum metal. Reduction mechanisms were characterized on the basics of cyclic voltammetry technique. For the determination of kinetic parameters, such as diffusion rate constant and reaction rate constant the rotating disk technique was employed. The effects of water and ethanol concentration were studied in details. The role of water was important to determine in order to evaluate its effect during its eventual absorption from open atmosphere. Ethanol gained in importance because of the solubility of rare earth salts in alcohols, as the only viable route toward solubilization of rare earths in ionic liquids. The diffusion coefficient of water in EMIM-DCA was calculated to be 7.6x10-7 cm2/sec. The reduction of water on platinum in EMIM-DCA exhibited sluggish kinetics and the rate constant was calculated to be 2.15x10-5 cm/sec. Both water and ethanol additions slightly reduced the stability window of the RTIL. Morphology of lanthanum electrodeposits, observed around -2.0V, was characterized by using scanning electron microscope (SEM). Thin dense films were generally produced. However, the organic components of ionic liquids were also intermixed with metallic deposit, which were removed by washing with alcohol.masters, M.S., Materials Science -- University of Idaho - College of Graduate Studies, 2018-0