No description available.

The effects of single-step and two-step aging treatments on the tensile properties of an A1-4.5%Cu-1.4%Mg- 0.5%Ag alloy have been investigated. Results showed that a maximum ultimate tensile strength of 75 ksi can be attained by single-step aging 24 hr at 170°C. The two-step aging treatments consisting of first aging one week at 80°C followed by aging at 160° and 190°C led to lower strength properties than simple one-step aging. Reversion treatments applied to fully age-hardened alloy resulted in an almost progressive loss of strength in the 250° to 375° range.

Three experiments were carried out to explore the effects of magnesium deficiency on the activities of the hepatic gluconeogenic enzymes. In Experiment I rats were fed, ad libitum, diets adequate (control) or deficient in magnesium for 12 days. One half of the rats from each treatment group were then fasted for 24 hours. The remaining rats were allowed to eat. The rats were subsequently sacrificed and the following parameters were measured: blood glucose and plasma magnesium, liver magnesium and protein, and the activities of liver glucose-6-phosphatase (G6Pase), fructose 1, 6-bisphosphatase (FDPase), and phosphoenolpyruvate carboxykinase (PEPCK). In Experiments II and III rats were meal-fed diets adequate or deficient in magnesium; in addition, a group of rats was pair-fed to the magnesium-deficient group to test for the effects of anorexia. After 17 days the rats were fasted for 20 hours then sacrificed. The parameters measured in Experiment I were again assessed except liver FDPase and G6Pase were not measured in Experiment III. Feeding a diet deficient in magnesium to the rat produced symptoms characteristic of the deficient state. These symptoms included hyperemia, skin lesions, anorexia, decreased weight gain, and decreased plasma magnesium levels. Anorexia accounted for part, but not all of the decreased weight gain. The concentration of magnesium in the liver of the magnesium-deficient rat was unchanged relative to control values. In the fasted rat, relative to the fed rat, the activities of liver glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) were increased while that of FDPase was decreased. The response to fasting was similar in magnesium deficient and control rats. In the magnesium-deficient rat, relative to the control rat, the activities of G6Pase and FDPase were unchanged, while that of PEPCK was increased. Anorexia was not responsible for the changes in the activity of PEPCK. Since magnesium was not lost from the liver in magnesium deficiency a direct action of this cation on the activity of PEPCK appears untenable. Magnesium is involved in the secretion of insulin, glucagon, epinephrine and corticosterone. These hormones all affect the gluconeogenic enzymes. A change in the circulating level of one or more of these hormones may be responsible for the effects of magnesium depletion on PEPCK. / Ph. D.

Two metabolism trials were conducted with 12 wethers surgically equipped with abomasal and ileal cannulae. A 2 x 2 factorial arrangement was used with diets containing 3 and 23% soluble carbohydrate and .6 and 4% potassium, dry basis. Each trial consisted of a 10-d preliminary period followed by a 7-d collection of feed, feces and urine and a 6-d sampling of feed, abomasal and ileal contents and feces. Chromic oxide was used as an indicator to measure the flow of minerals along digestive tract. The pH of the rumen and ileal fluid was decreased (P<.05) by high levels of soluble carbohydrate. Increased dietary potassium increased (P<.05) ruminal pH. Magnesium absorption and retention were not affected by the level of dietary soluble carbohydrate. High potassium levels decreased (P<.05) magnesium absorption, expressed a g/d or percent of intake. The primary site of magnesium absorption in all animals was the preintestinal region. A net secretion of magnesium into the small intestine was followed by a small net absorption in the large intestine. High levels of dietary potassium tended to depress preintestinal magnesium absorption and increase flow through the small and large intestine. Soluble carbohydrate level had no effect on potassium absorption or retention. Increased potassium intake increased (P<.05) apparent absorption, retention and urinary excretion of potassium. In animals fed the low potassium diet, potassium was absorbed primarily in the small intestine, but at the high level the stomach was also important. The addition of soluble carbohydrate had no consistent effects on calcium and phosphorus balance and absorption. Sodium absorption in the small intestine was increased (P<.05) by the high level of soluble carbohydrate. Increased dietary potassium increased sodium availability and urinary excretion (P<.05). Calcium was absorbed primarily in the preintestinal region. Sodium and phosphorus were secreted into the preintestial region and absorbed from the large and small intestine, respectively. Serum magnesium and calcium levels wei:e not. affected by soluble carbohydrate level, but tended to be depressed at the high potassium level. Bigb dietary potassium increased serum potassium level (P<.05), whereas high soluble carbohydrate intake decreased the level (P<. 05). / Master of Science

Magnesium oxide (MgO) is a cost-effective and environmentally sustainable alternative to magnesium chloride (MgCl2) and sodium hydroxide (NaOH) used for sidestream struvite recovery from anaerobically digested supernatant (centrate) through the Pearl® process. MgO is produced from magnesite (MgCO3) calcination, and different calcination conditions can alter the quality and characteristics of the MgO product. It was hypothesized that the insolubility of MgO could provide a "slowly available" form of Mg2+ in the reactor and consequently allow the reactor to be operated beyond design phosphorus (P) reactor loading. MgO has been utilized in other P recovery technologies, e.g. the Phospaq™ Process, but operation and performance of MgO using a full-scale Pearl® 500 fluidized bed reactor was investigated. Performance at rated reactor loading utilizing MgO was initially comparable to baseline conventional MgCl2 reactor operation, ≥50% struvite yield (P recovered/theoretical P recovery) and ≥70% total phosphorus (TP) removal. However, the pilot reactor operated at 2X reactor loading showed comparable results to baseline performance at 1.5X reactor loading. During the full-scale pilot, optimization of the reactor utilizing MgO was limited by the struvite product size that the struvite post-processing equipment could effectively harvest. Additionally, the MgO characteristics due to calcination conditions were hypothesized to affect struvite precipitation kinetics. In struvite precipitation jar testing, MgO products were used to analyze the saturation index, measure precipitation kinetics, and understand the effect that MgO hydration and reactivity had on struvite precipitation. Jar testing showed that initial P removal increased with increasing MgO product reactivity. The most reactive MgO used, Timab AK98, showed 1-40% P removal and substantial decrease in solution saturation index immediately after dosing MgO to centrate. The slower P removal and decrease in saturation index observed with the less reactive material suggests that MgO can provide a "slowly available" Mg2+ reserve throughout the struvite precipitation reaction. / Master of Science / Phosphorus is an essential element for human, plant and animal health. Necessary bodily functions cannot be performed without inputting phosphorus to cell metabolic pathways, such as cell repair and formation of nucleic acids, bone mineral and stored energy. Phosphates are the most common form of phosphorus found in the environment and are a component of many common substances, such as detergents, fertilizers, food and urine. Due to the increasing population and food demand the need for phosphorus-based fertilizers has soared since the 1940s. In 2018, 240 megatons of phosphate rock were mined, and 17 megatons of phosphorus were extracted from mined ore. 15 megatons of the extracted phosphorus were used in fertilizer production. Because of phosphorus loss from the soil and inefficient agro-practices, only 20% of the extracted phosphorus is consumed by humans and animals from food and little is then recycled from our waste systems. There is a major gap in the agricultural phosphorus cycle that is necessary to address with sustainable practices (Oster, M. et al. 2018). Phosphorus can be recovered from wastewater in the form of struvite, which is a mineral that can be utilized a slow-release fertilizer. Conventional methods of phosphorus recovery from wastewater have the potential to be costly. By utilizing an alternative chemical, struvite recovery can be more cost-effective and environmentally sustainable.

A study was made cf the cost per pound of magnesium sulfate monohydrate produced by a "Krystal" crystallizer at recirculation rates from 20 to 40 gallons per minute and operating temperatures from 150 to 180 °F. From these tests, the optimum operating conditions within the range of these variables were derived. The problem was studied by operating the equipment at all sixteen combinations of these variables in unit steps of ten. The crystallizer was operated at each set of conditions, the product collected, and the cost per pound determined. The operating conditions were found to affect power and steam costs greatly, varying from 1.689 mills/lb at 50 gallons per minute and 170 °F to 0.737 mills/lb at 20 gallons per minute and 180 °F, representing a decrease. cf 0.952 mills per pound upon correct choice of operating temperature and recirculation rate. / Master of Science

In an effort to save weight, transportation and aerospace industries have increasing investigated magnesium alloys because of their high strength-to-weight ratio. Further efforts to save on material use and machining time have focused on the use of additive manufacturing. However, anisotropic properties can be caused by both the HCP structure of magnesium alloys as well as by layered effects left by typical additive manufacturing processes. Additive Friction Stir (AFS) is a relatively new additive manufacturing technology that yields wrought microstructure with isotropic properties. In this study, Additive Friction Stir (AFS) fabrication was used to fabricate WE43 magnesium alloy, with both atomized powder and rolled plate as filler material, into multilayered structures. It was found that the WE43 alloy made by AFS exhibited nearly isotropic tensile properties. With aging these properties exceeded the base material in the T5 condition. The toughness measured by Charpy impact testing also showed an increase over the base material. The relationships among tensile properties, Vickers microhardness, impact toughness, microstructure and thermal history are developed and discussed. / Master of Science

No description available.

Recent advances in high-resolution analytical methods have brought about a paradigm shift in our understanding of how crystalline materials are formed. The scientific community now recognizes that many earth materials form by multiple pathways that involve metastable intermediates. Biogenic calcium carbonate minerals are now recognized to develop by aggregating molecules or clusters to form amorphous phases that later transform to one or more crystalline polymorphs. Amorphous calcium carbonate (ACC) is now recognized as a precursor to CaCO₃ biominerals in a wide variety of natural environments. Recent studies suggest an ACC pathway may imprint a different set of dependencies from those established for classical growth processes. Previous ACC studies provided important insights, but a quantitative understanding of controls on ACC composition when formed at near-physiological conditions is not established. The Mg content of ACC and calcite is of particular interest as a minor element that is frequently found in final crystalline products in calcified skeletons. This three-part dissertation investigated biological and well-characterized synthetic ACC using high-energy x-ray methods, Raman spectroscopy, and mechanical tests. The findings establish chemical and physical properties of ACC in the exoskeleton of crustaceans and show Mg and P levels are tuned in the mineral component to optimize exoskeleton function that could be sensitive to ecological or environmental conditions. Calcite and chitin crystallinity exhibit a similar body-part-specific pattern that correlates directly with the mechanical strength of the exoskeleton. Insights from this study suggest precise biological control of ACC chemistry in the to regulate exoskeleton properties. Laboratory measurements using quantitative methods and compositions that approximate the physiological conditions of crustaceans, demonstrate at least two types of ACC are formed by controlling Mg concentration and alkalinity. We also find temporal changes in the short-range ordering of ACC after precipitation that is dependent upon carbonate content. The findings from this study provide a quantitative basis for deciphering relationships between ACC structures, solution chemistry, and the final transformation products under biologically relevant conditions. / Ph. D. / With the development of new imaging methods for nano-scale materials, scientists across diverse disciplines have recognized that many earth materials can form complex shapes by the formation and aggregation of nanocrystals or structureless (amorphous) particles. Biological minerals, such as shells and skeletons, are well-documented to form CaCO₃ via both of these attachment pathways, particularly amorphous calcium carbonate (ACC). However, little is known about the ACC properties and the factors that determine the final composition of skeletal minerals. This three-part dissertation focuses on ACC and calcite in the exoskeletons of crustaceans to understand how animals form composite exoskeletons of calcium carbonate minerals. This knowledge is important because CaCO₃ minerals are the primary component of the shells and skeletons of many economically important marine species. These minerals are also prevalent in the geological record as roadmaps for the evolutionary record. Amorphous and crystalline forms of CaCO₃ are also used as inert 'filler' materials for pharmaceutical products. By designing a series of experiments to characterize ACC in exoskeletons from lobsters and crabs, one part of the dissertation shows relationships between chemical composition and physical behavior of the materials. Building on this biomineral information, a separate experimental study synthesizes ACC under near-physiological conditions to show how amorphous CaCO₃ forms under controlled conditions. The findings have far-reaching consequences for understanding the complex chemistry that underlies the formation of calcium carbonate as a component of shells and skeletons, and what physical properties are optimized by the composition of these materials.

The compatibility of home water softeners and septic tanks is of concern for the on-site wastewater treatment community. Research has shown that high sodium levels in activated sludge plants can lead to deflocculation and poor effluent quality. Therefore, it is logical to assume that high sodium levels that result from the exchange of calcium and magnesium for sodium in home softeners could give rise to poor effluent quality from septic tanks, leading to shortened lives of drain fields. Additionally, the release of regeneration discharges to the septic tank might further damage performance. This study was undertaken to investigate the effect home ion-exchange softeners have on septic tank performance. A column study was set up and varying levels of sodium were added to wastewater influent and these were fed to columns that contained solids collected from operating septic tanks. In addition, slug influent solutions, which mimic regeneration flow, with varying amounts of excess sodium were investigated. To reinforce the lab column experiments, data were obtained from private septic tanks to determine the effluent quality from septic tanks both diverting and receiving the regeneration flow. Also utilized were graduated cylinder experiments, where the effect of sodium on grease flocculation was determined, and batch anaerobic digestion studies, which determined the effect sodium has on the production of gases and the degradation of solids. The study showed that the addition of sodium to septic tanks is likely to impact the effluent quality of sewage discharged from a septic tank to a drain field. The common way of measuring ion concentrations for comparison in this study was to obtain the monovalent to divalent ratio (M/D Ratio). This is simply the concentration of the sodium ions in solution divided by the concentrations of magnesium and calcium, on an equivalent weight basis (all other monovalent and divalent ions were negligible). Slug solutions of high levels of salts (Septic Tank Effluent M/D = 11), mimicking regeneration wastes from water softeners with an inefficient regeneration cycle, increased the effluent solids, COD and BOD. However, if the regeneration wastes contained the same amount of calcium and magnesium, but a smaller amount of sodium (Septic Tank Effluent M/D = 5), the negative effect on these effluent characteristics was greatly lessened. In an optimum case with a regeneration solution containing a minimal amount of excess sodium (Septic Tank Effluent M/D = 3), the effluent characteristics were often actually more favorable than in similar situations where the regeneration wastes were diverted (Septic Tank Effluent M/D = 2). The case studies reinforced these data, showing that sodium concentrations correlated with an increased discharge of solids to the drain field. The studies on grease flocculation as well as anaerobic digestion suggest that these processes are not affected by the sodium level. Overall, it appears that the use of home softeners with septic tanks may have an effect on solids discharge to the drain field and the level of impact will depend on the level of hardness in the water, whether the regeneration waste is discharged to the septic tank, and the amount of excess sodium present in regeneration wastes. / Master of Science