Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 85-91).

Techn. Univ. Diss., 1999--Darmstadt

Calcium phosphate compounds have been widely utilised in the interdisciplinary field of biomaterials research and are used clinically in a number of medical devices. In the present work, calcium phosphate compositions were prepared by two precipitation methods: a classic aqueous precipitation method and a novel biomimetic precipitation method. The aqueous precipitation method was used to produce a range of hydroxyapatite and carbonate-substituted hydroxyapatite compositions that would act as reference materials, but more importantly to allow a method of determining the Ca/P molar ratio of these compositions using X-ray diffraction data. The importance of this was that a simple technique would be required for studying the calcium phosphates produced later by biomimetic methods, as the very low yields prevents traditional methods such as XRF. It was found that Rietveld refinement of XRD data from precipitated apatites that had been heated at between 800 and 1200°C in air provided quantitative phase compositions that could then be used to calculate Ca/P molar ratios. In order to use synthesis conditions that were more similar to in vivo mineralisation, calcium phosphate compositions were directly prepared by using alkali-induced 'biomimetic' precipitation from Simulated Body Fluid (SBF) under controlled conditions. The key parameters that were studied were the effect of precipitation pH, the SBF concentration, the reaction time, the soaking time, and the magnesium and the carbonate ion concentration of the SBF solution. The key finding was that while the precipitated product obtained from 'conventional' SBF was an amorphous calcium phosphate with a Ca/P molar ratio of 1.5, irrespective of the pH, SBF concentration, reaction time or carbonate ion concentration, the gradual removal of magnesium ions from the SBF solution led to the precipitation of firstly a Ca-deficient apatite and eventually (for low Mg concentrations and a Mg-free SBF) a stoichiometric hydroxyapatite with a Ca/P molar ratio of 1.67. This method resulted in very low yields, typically (50 mg from 100 ml of SBF) but control of parameters could yield different phase compositions and could also affect the crystal size and the crystallinity of the product. These observations highlighting the important role of magnesium ions in the SBF on the composition of the calcium phosphate phase that would precipitate raised the question of what effect does SBF magnesium ion content have on the surface apatite precipitation on various biomaterials when incubated in SBF, which is the classic in vitro bioactivity test. Studies that incubated bioactive glass discs and powder (45S5 composition) and dense hydroxyapatite ceramic discs in conventional SBF and an Mg-free SBF showed that the rate of surface apatite precipitation was significantly affected by the Mg content in the SBF. For the case of bioactive glass discs, a surface apatite layer formed in 2 hours when incubated in an Mg-free SBF compared to 24 hours in conventional SBF.

An investigation is made of the interactions between a variety of small molecule phosphates and amines, and in particular of triethylenetetramine with hexametaphosphate, pyrophosphate, tripolyphosphate, ADP and ATP and of cyclic triethylenetriamine with hexametaphosphate. For each phosphate/amine pair, observed changes in the pH dependence of ¹H and ³¹P nmr chemical shift are used to calculate the effect of interaction on the pK_a of the two species present and an association constant is evaluated at one particular pH value. These data are then combined to evaluate association constants for a variety of protonation states of the phosphate and amine. Strength of association is interpreted in terms of electrostatic charge and its spatial distribution, comparison is made with Mg²⁺ and Ca²⁺ complexes and biological relevance is discussed. The interaction of yeast PGK with its substrates is investigated by using the (500MHz and 300MHz) ¹H nmr spectrum of the enzyme and (250MHz) ³¹P nmr spectra of its substrates. On the basis of pH dependence, comparison with the spectrum of horse PGK and T₂ relaxation data,¹H nmr resonances are assigned to surface residues. In particular, resonances are assigned to the three active site histidines (nos. 62,167 and 170), and to the exposed histidine and methionine residues. A series of comparatively well-resolved upfield shifted aromatic peaks, including a relatively exposed tyrosine peak is tentatively assigned to the interdomain hinge region of the protein. The effects of MgADP, MgATP and the non-reacting nucleotide analogue MgAMPPNP on the yeast PGK spectrum are characterised. The line-broadening reagent Gd³⁺is used to distinguish between direct influence and conformational effects. The triose phosphate substrate 3-PG is added to the enzyme as are the anionic probes [Co(CN)₆]<sup3-</sup> , [Cr(CN)₆]<sup3-</sup>and [Fe(CN)₆]<sup3-</sup> I and the nature of anion binding in the active groove of the protein and elsewhere on its surface is investigated. Movement of the two PGK domains is investigated in three models of the ternary complex: (i) with MgAMPPNP and 3-PG, (ii) with the elongated nucleotide A4P, and (iii) with a mutant form of the enzyme (his388 -gln388). The PGK/substrate interaction is interpreted in terms of the phosphate/amine model.

A study was undertaken to assess the feasibility of using a combination trickling filter-activated sludge (fixed growth-suspended growth) treatment process for enhanced biological phosphorus removal from municipal wastewater, and to evaluate the operating conditions at a full-scale fixed growth-suspended growth (FGR-SGR) demonstration facility in Salmon Arm, British Columbia, Canada. The results of the study, based on full-scale plant data and bench-scale batch test results obtained over the first year of operation, showed that enhanced biological phosphorus removal was established in the combined FGR-SGR process. The phosphate release and uptake rates of the biomass cultured in the full-scale FGR-SGR system were comparable to the findings of others for activated sludge-type biological phosphorus removal systems. The study was designed to include an assessment of the effects of plant operating MLSS concentration on effluent quality; the average effluent total phosphorus concentration increased from 2.1 mg P/L (75% removal) to 2.6 mg P/L (79% removal) to 4.6 mg P/L, for average operating MLSS concentrations of 4090 mg/L, 3250 mg/L, and 2360 mg/L, respectively, over an 11 month operating period. However, the effects of the planned changes in MLSS may have been confounded with the effects of (unknown) seasonal variations in plant operating conditions. Seasonal changes in process organic loading appeared to have a significant effect on bacterial phosphate release and uptake rates in the full-scale process, but had no apparent effect on effluent quality. The average effluent concentrations of total suspended solids and BOD₅ were both in the range 8-14 mg/L over the entire 11 month period. Process liquid temperatures as low as 8° C had no detrimental effect on effluent quality. The average phosphorus content of the SGR total suspended solids was 4.4% by dry weight over the 11 month study period. Diurnal fluctuations in flow and load to the full-scale process were found to have a significant effect on phosphorus removal. The concentration of total phosphorus in the plant final effluent was consistently less than 1 mg P/L during the morning low flow-low organic load condition; after the onset of the afternoon high flow-high organic load condition, plant effluent orthophosphate concentrations were generally greater than 1 mg P/L. Batch test simulations indicated that lowering the secondary sludge return flow rate would increase bacterial PO₄ release in the anaerobic phase, but would have no short-term effect on aerobic bacterial PO₄ uptake rates, or on the aerated volume required for complete PO₄ removal. Batch test results also indicated that the biomass cultured in the full-scale FGR-SGR process had an average total PO₄ uptake capacity of 40-60 mg P/L (19-21 mg P/g MLSS), compared to the plant design phosphorus loading of 7-8 mg P/L (the aeration periods for the batch tests used to calculate the average total PO₄ uptake capacity of the biomass were 2-3.5 times longer than the actual aeration time available in the full-scale process, and the initial PO₄ concentration used in the batch tests was approximately 10 times the plant design loading). / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Porcine Semimembranosus muscles were vacuum tumbled with phosphate, without phosphate, fiber dry vinegar, or whey protein concentrate (WPC). Consumers preferred (P<0.05) deli ham with phosphate, without phosphate and WPC over the oat fiber with vinegar treatment. In addition, the phosphate treatment had less cooking loss, (P<0.05) greater bind strength (P<0.05) and more intact slices (P<0.05) than other treatments. In addition, WPC produced ham with a higher (P<0.05) CIE l* and a lower (P<0.05) b* value than other treatments. Consumers preferred (P<0.05) chicken breasts marinated with phosphate with respect to flavor and aroma over the negative phosphate treatment and oat fiber treatments. Chicken breast with phosphate increased pH and had less cooking loss (P<0.05) as compared to chicken with WPC and without phosphate. Results indicated that oat fiber has potential as a phosphate replacer in marinated chicken, and WPC has potential as a phosphate replacer in deli ham.

No description available.

Phosphate (Pi) is an essential nutrient for plants, required for plant growth and seed viability. When Pi is limited, plants undergo dynamic morphological and metabolic changes to leverage available Pi, known as the Phosphate Starvation Response (PSR). The inositol phosphate (InsP) signaling pathway is a crucial element of the plant's ability to regulate the PSR and respond to changing energy conditions. InsPs are synthesized from the cyclic 6-carbon polyol scaffold, myo-inositol. Inositol hexakisphosphate (InsP6) is the most abundant InsP signaling molecule and can be phosphorylated by the multifunctional inositol tetrakisphosphate 1-kinase 1 (ITPK1) and diphosphoinositol pentakisphosphate (VIP) kinases, resulting in inositol pyrophosphates (PP-InsPs). PP-InsPs have high energy bonds and have been linked to Pi maintenance and energy homeostasis in yeast, plants, and mammals. However, the precise mechanism(s) by which PP-InsPs act within plant signaling pathways remains to be determined. Two approaches to understand the role of PP-InsPs in plants are described within this dissertation. The first approach analyzes genetic loss-of-function vip1/vip2 double mutants, and their responses to low Pi conditions. Specifically, vip1/vip2 double mutant gene expression and lipid remodeling patterns in response to low Pi were characterized. We found that vip1-2/vip2-2 had an impacted lipid remodeling response under low Pi conditions, whereas ipk1 had altered lipid composition under Pi-replete conditions. In a complementary approach, a gain-of-function in either the ITPK1 or the kinase domain of VIP (VIP2KD) were constructed in transgenic Arabidopsis thaliana plants. Both ITPK1 and VIP2KD transgenic plants contain elevated levels of the specific inositol pyrophosphate, InsP8. Elevated InsP8 in both types of plants results in changes in growth and senescence phenotypes, delayed time to flowering, Pi accumulation, and altered PSR gene expression. The data from both approaches suggest new roles for PP-InsPs in the regulation of the PSR and other signaling pathways in plants. To enhance my teaching and leadership skills, I participated in the Graduate Teaching Scholars (GTS) program. As a GTS, I worked with the Virginia Tech Research and Extension Experiential Learning (VT-REEL) program where I developed a structured mentorship program for undergraduate and graduate students and created a professional development workshop series. During the COVID-19 pandemic, I developed an online version of the VT-REEL program. Using inclusive pedagogy practices and surveys from the participants, we compiled the best practices for moving a summer undergraduate research program online. These practices come from surveyed participants in the 2020 and provides strategies that can be tailored to various online research experiences and be implemented in both online and in-person formats. / Doctor of Philosophy / Phosphate (Pi) is crucial for plant development and crop yield, but is often limited in soils. Pi-containing fertilizers are often added to supplement soils. Overuse of Pi-containing fertilizers can lead to Pi runoff and can devastate aquatic ecosystems. In addition, Pi is a limited, nonrenewable resource, with U.S. stores projected to be depleted in as little as 30 years. It is now crucial to develop crops that can feed a growing population with less Pi input. Here, we describe how changing levels of plant messenger molecules known as inositol pyrophosphates (PP-InsPs) impact the ability of plants to sense and respond to Pi. This knowledge advances understanding f how mineral nutrient physiology affects many plants traits, and can be harnessed to develop novel strategies to reduce Pi-application and overuse.

Corrosion is one of the most complicated and costly problems facing drinking water utilities. Corrosion of iron pipes can lead to economic losses and customer complaints, while lead corrosion poses a serious health risk. This work first synthesizes nearly 100 years of iron corrosion research to provide the water industry with an updated understanding of factors that influence iron pipe corrosion including water quality and composition, flow conditions, biological activity, and corrosion inhibitors. Potential impacts of upcoming regulations on iron corrosion are also considered. Next, a four-year study is presented that evaluated the effect of water quality and phosphate inhibitors on the corrosion of iron pipes under extended stagnant water conditions. Surprisingly, many of the water quality parameters traditionally thought to influence iron corrosion were not controlling under these "worst case" stagnant conditions. Moreover, addition of phosphate inhibitors often had either no statistically significant effect or actually increased iron concentration, scale build-up and overall weight loss. Temperature is often overlooked when corrosion of distribution systems pipes is considered. Temperature impacts many parameters that are critical to pipe corrosion including physical properties of the solution, thermodynamic and physical properties of corrosion scale, chemical rates, and biological activity. Moreover, variations in temperature and temperature gradients may give rise to new corrosion phenomena worthy of consideration by water treatment personnel. In laboratory experiments, cast iron samples at 5°C had 23% more weight loss, ten times higher iron release to water, and twice as much tuberculation compared to samples at 25°C. For lead corrosion, hexametaphosphate inhibitors were proven to increase release of both particulate and soluble lead to drinking water by 200 - 3500% over a wide range of water qualities when compared to orthophosphate, effectively ending a long term debate as to their impacts. Utilities should consider these adverse effects whenever polyphosphate is used to prevent scaling or iron precipitation. / Ph. D.