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The effect that organic urinary macromolecules have on the crystallization of calcium oxalate from a synthetic urine-like solution was studied in a mixed suspension-mixed product removal (MSMPR) continuous crystallizer. Precipitation of calcium oxalate crystals occurs during the continuous passage of urine through the renal system (kidney, bladder and tubules). While in normal circumstances these crystals remain small in size and exit the system unimpeded, in the pathologic condition calcium oxalate crystals are observed to aggregate and grow beyond a critical size where there is a significant probability of being trapped inside the renal system, e.g., on the kidney wall or in the tubules. Once trapped, the crystals become a nidus for further solute deposition and aggregation, giving origin to a renal calculus or stone. It is shown that this process is significantly affected by the presence or absence of organic macromolecules that act as modifiers of crystal growth, nucleation, and aggregation. An ultrafiltration technique was used to fractionate urine specimens from normal (N) and stone-forming (SF) persons into organic compounds of different molecular weight. These compounds were then added to the MSMPR system to test their effect on calcium oxalate crystallization. Significant differences were found to exist between N and SF urines in the composition, molecular weight distribution, and total quantity of these organic macromolecular compounds. The fraction of macromolecules responsible for the major effects on calcium oxalate crystallization was isolated, and its effect on crystal growth and nucleation rates was quantified. The steady state driving force (supersaturation) in the MSMPR system was measured. Striking differences in supersaturation versus residence time behavior between N and SF macromolecules were observed. The experimental conditions under which calcium oxalate crystals agglomerate were identified. Evidence which supports agglomeration as a key mechanism in urinary stone formation is presented.

Deposition of amorphous silica (SiO2) and calcium oxalate (CaOx) on the calandria tubes of juice evaporators cause serious processing problems in Australian cane sugar mills. The removal of these deposits by mechanical and chemical means is a timeconsuming and costly experience. The cost of downtime and chemical cleaning can be several million dollars per year for the Australian sugar industry. The interactions between CaOx and SiO2 have not been investigated previously because conventional studies only address fouling by individual components. The present work evaluates their interactions using two experimental approaches: batch tests for assessing kinetic and thermodynamic behaviour, and fouling-loop experiments for examining composite fouling behaviour under different operating conditions. The above two approaches were employed both in the absence and in the presence of sugar to elucidate the effect of sugar on composite fouling mechanisms and to determine the controlling species responsible for composite fouling. The composite fouling experiments were performed in a novel closed-loop circulation system simulating the effect of feed composition of successive stages of evaporation cycle in a single run. In addition, the fouling-loop system was operated in a constant composition mode to study the effects of thermal hydraulic conditions on composite fouling. The combined information obtained from both the batch and fouling-loop tests in this study offer a unique insight into the mechanisms of composite fouling of CaOx and SiO2. Some of the highlights of the obtained results are as follows: ??? Identification of a complex interactive process in calcium oxalate monohydrate ??? silica (COM-SiO2) systems by investigation of the kinetics and thermodynamics of COM-SiO2 coprecipitation in water and sugar solutions, and an understanding of the mechanisms of these interactions; ??? Development of a novel fouling-loop system, which is simple, efficient and cost effective for the study of the effect of juice composition on scale formation in various stages of juice evaporation; ??? Elucidation of composite fouling mechanisms, e.g., a feed composition dependent fouling mechanism is proposed; ??? Isolation and verification of the existence of certain species in composite deposits, which is known to be thermodynamically unstable. In other words, it is established that calcium oxalate trihydrate is stable under certain conditions; ??? Evaluation of the role of thermal hydraulic operating parameters in determining the characteristics of subcooled flow boiling heat transfer and in determining the strength of the composite deposit; ??? Development and validation of an empirical model to predict the subcooled flow boiling heat transfer coefficients in water and sugar solutions; ??? Development of an analytical model incorporating the effects of operating parameters for COM and SiO2 composite fouling in sugar solutions. This model predicted the experimental data better than available models. Results of this work are significant, not only because they have made a valuable contribution to advance the fundamental understanding of heat exchanger fouling, but also because they may play a key role in the development of scale control and removal strategies to minimize the composite fouling in Australian sugar mill evaporators. For example it was found that, in order to effectively minimize the rate of composite fouling and reduce the scale tenacity, it would be necessary to control thermal hydraulic operating conditions, especially the fluid velocity, and to adjust the initial CaOx/SiO2 supersaturation ratio to the optimum value. To achieve the optimal CaOx/SiO2 ratio, certain device can be developed to sequentially measure oxalic acid and SiO2 concentrations in juice so that the correct proportions of chemicals can be added. Model simulations of the composite fouling rate may also effectively and economically provide comparative and relevant information essential for process optimisation and evaporator design

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 180-212).

The broad aim of the work presented in this thesis was to examine the relationship between the mineral and organic phases of calcium oxalate monohydrate (COM) crystals, which are the principal components of human kidney stones. The results presented, clearly demonstrate the presence of some amino acids and urinary proteins in the crystals and suggest a role for intracrystalline proteins in urolithiasis. The adsorptive affinities of twenty amino acids to COM, calcium hydrogen phosphate, tricalcium phosphate and hydroxyapatite were assessed over the physiological urinary pH range (pH 5-8) in aqueous solutions. In all cases adsorption was strongest at pH 5 and decreased as the pH increased as a result of the increasing negative charge of both substrate and adsorbate. Binding was higher to COM than to the phosphate minerals, owing to differences in the surface charge or coordination-site availability. Aspartic acid (Asp), glutamic acid (Glu) and y- carboxyglutamic acid (Gla), which each have at least two carboxyl groups, exhibited the highest binding affinities, suggesting that binding occurs by chelation. Further, binding affinity was reasoned to result from the ability of the zwitterions of Asp, Glu and Gla to adopt favourable conformations in which two carboxyl groups, and possibly the amino group, can interact with the mineral surface without further rotation. Although free amino acids are unlikely to fulfil a prominent inhibitory role in stone pathophysiology, they could, nonetheless, fulfil an important function as terminal residues or as exposed components of calcium-binding domains of proteins involved in stone formation. The existence of intracrystalline proteins and amino acids in COM crystals was demonstrated by Synchrotron X-ray Diffraction (SXRD) analysis. / Non-uniform strains and crystallite sizes were derived from SXRD whole pattern line widths using Rietveld analysis, which showed an increase in average non-uniform strain and a decrease in average crystallite size. These were attributed to intracrystalline molecules. Occluded molecules were Glu, Gla, human prothrombin (PT) and to a lesser extent, human serum albumin (HSA), as well as crystal matrix extract (CME), which comprises a complex mixture of soluble organic molecules remaining after demineralization of COM crystals grown in centrifuged and filtered (CF) urine. COM grown in CF urine possessed greater non-uniform strain and smaller crystallite size than COM grown in ultrafiltered (UF) urine, indicating that the majority of intracrystalline macromolecules in crystals derived from CF urine were >10kDa in molecular mass. Asp, AspAsp, GluGlu and Tamm Horsfall glycoprotein (THG) were non-occluded molecules. Proteinase treatment of COM crystals grown in CF urine produced a marked decrease in non-uniform strain and an increase in crystallite size, suggesting that smaller crystallite material, more intimately associated with proteins than the bulk COM, was liberated during the treatment. A reciprocal relationship was found between non-uniform strain and crystallite size, which was dependent upon the type of molecule(s) in which the COM crystals were grown. For a given increment in non-uniform strain, the corresponding decrease in crystallite size was found to be considerably greater for occluded macromolecules, than for amino acids. This difference was attributed to the capacity of macromolecules, once incorporated into the crystal, to disrupt a larger volume of the mineral bulk than amino acids. Alternatively, unlike amino acids, macromolecules might possibly stabilise an amorphous phase. / Amorphous contributions resulting from the occlusion of PT and molecules from CF urine and UF urine in COM were found to range between 5-9%. The SXRD data derived from the COM crystals were further analysed for anisotropy using Williamson-Hall plots and individual peak analysis (SHADOW). Crystals grown in distilled water COM (distilled water) and COM (Asp, AspAsp, GluGlu, Gla, HSA, THG and PT) were isotropic with respect to both non-uniform strain and crystallite size. Although COM (Glu) and COM (UF) were isotropic with respect to non-uniform strain, the crystallite sizes were smaller along the (100) and (001) principal axes, respectively. COM (CF urine) and COM (CME) were also anisotropic, but with respect to crystallite size, with the shortest lengths occurring along the (100) and (001) axes. The absence of anisotropy in non-uniform strain was ascribed to experimental error. The data also showed that stacking faults contributed significantly to crystal disorder. Largest stacking faults, highest non-uniform strain and lowest crystallite sizes were generally found along the (13i) plane. Computer- generated models showed that molecules as large as proteins could not effectively be incorporated along the (13i) plane in COM. It was concluded therefore, that they transmit disorder from the principal (100,010, 001) planes in the crystal to the (13i) plane by diagonal sliding of one or more rows of oxalate ions, calcium ions and water molecules. SXRD single peak and whole pattern analysis of COM crystals grown in aqueous solutions of increasing concentrations of PT, HSA, CME and Gla showed that non- uniform strain increased, crystallite size decreased and stacking faults increased, to limiting values. / This was also found for crystals grown in UF urine containing CME and HSA. When crystals with occluded proteins were treated with proteinase K, their stacking faults and non-uniform strain decreased, and crystallite size increased, indicating that the non-crystalline material is more intimately associated with the protein and is physically removed or solubilised when the protein is destroyed. FESEM observations of the internal architecture of fractured CaOx crystals grown in human urine and synthetic solutions containing PT, revealed an inhomogeneous microstructure containing low density zones not observed in COM crystals grown in water or UF urine. Proteolytic treatment of the fractured crystals, created an internal honey combed structure that replaced the “low-density” zones. A timed growth study showed the internal ultrastructure of urinary COM crystals depended to a significant extent, upon the ratio of crystal-binding proteins to the available quantities of solute ions during growth. Dissolution studies of COM crystals showed that the process obeyed the Shrinking Core model and was therefore surface area-dependent. Pure COM dissolved more rapidly than crystals derived from UF urine, which dissolved at a faster rate than crystals precipitated from CF urine. This was attributed to shielding of the exposed COM surface by occluded molecules, which would reduce the effective surface area and slow dissolution. There is also the possibility that the macromolecules would have bound to the ions and retard their release into solution. The use of proteinase inhibitors verified the presence of proteinases in fresh urine and showed that they were capable of attacking proteins occluded in COM, in particular, proteins with Mr > 10kDa. / Although COM (CF) crystals were more difficult to dissolve than COM (UF) crystals in aqueous solutions, they were far more susceptible to endogenous proteolytic degradation in urine. Collectively, these findings have formed the basis of a novel hypothesis, which proposes that the type and concentration of urinary proteins incorporated inside CaOx crystals are fundamental to the disposal of CaOx crystals precipitated and retained within the renal system, and may therefore play an important role in the prevention of urolithiasis.

Bibliography: leaves 278-289. / xi, 324 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis reports on experimental investigation of the growth and aggregation of calcium oxalate mono-dydrate in metastable saline solutions using batch and continuous systems. The physical chemistry of calcium oxalate mono-hydrate in aqueous solutions is considered. A tubular crystalliser to be used as an in vitro system is described. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1996?

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [140]-152).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 174).

The intent of this research is to identify a simple diagnostic test to detect abnormal calciuresis and predict calcium oxalate (CaOx) urolith presence in Miniature Schnauzers. We investigated the impact of postprandial time on the specificity of urine calcium:creatine (UCa/Cr) in identifying affected dogs. The hypotheses were: 1) Significant differences exist in fasted and postprandial UCa/Cr between urolith-forming and control schnauzers. 2) UCa/Cr increases significantly from fasted baseline at one or more postprandial time point(s). Urine samples were collected from Miniature Schnauzers with (urolith-formers) and without (controls) CaOx uroliths in a fasted state and 1, 2, 4, and 8 hours after feeding a standardized diet. The change in UCa/Cr from baseline was calculated for each postprandial time. Urolithiasis status and the time point were assessed for impact on the UCa/Cr and change in UCa/Cr using a mixed model ANOVA. Based on 9 urolith-forming and 15 control dogs enrolled, urolith-forming Miniature Schnauzers have significantly higher mean UCa/Cr at 1 hour and 8 hours postprandial timepoints indicating altered calciuresis. The change in UCa/Cr was not significant at any post-prandial time point between or within groups. This pilot study shows male urolith-forming Miniature Schnauzers have excessive calciuresis throughout the day, providing insight into the mechanism behind their formation of CaOx uroliths. If using the Ca/Cr ratio, the postprandial sampling time is not critical. This simple urine measurement has potential as a marker of urolith presence and possibly risk of urolith formation. / Master of Science

Calcium (Ca) is an essential macronutrient that is increasingly recognized as a biogeochemical factor that influences ecosystem structure and function. Progress in understanding the sustainability of ecosystem Ca supply has been hampered by a lack of information on the various forms and pools of Ca in forest ecosystems. In particular, few studies have investigated the role of Ca-oxalate (Ca-ox), a ubiquitous and sparingly soluble biomineral formed by plants and fungi, on Ca cycling. I investigated Ca-ox pools in two young Douglas-fir forests in the Oregon Coast Range, and found that Ca-ox comprised 4 to 18% of total ecosystem Ca in high- and low-Ca sites, respectively, with roughly even distribution in vegetation, detritus and mineral soil to 1 m depth. The proportion of ecosystem Ca existing as Ca-ox varied by ecosystem compartment but was highest in needle litterfall, foliage and branches. Calcium-ox could be a large amount of Ca in mineral soil; across nine sites comprising a local soil Ca gradient, we found as much as 20% of available Ca in 0 - 10 cm depth mineral soil occurs as Ca-ox. Ca-ox was the dominant form of Ca returned from plants to soil, but disappeared as rapidly as bulk Ca from decomposing litter, suggesting an important pathway for Ca recycling. In mineral soil, Ca-ox was a larger portion of total available Ca in the low-Ca site, which had lower Ca-ox concentrations overall, suggesting that Ca-ox has limited potential to buffer against Ca depletion in forests where Ca is in shortest supply. I investigated foliar chemistry as a method for diagnosis of nutrient deficiencies in high and low-Ca sites where Ca varied inversely with soil nitrogen (N), and which had received fertilization with urea (for nitrogen, N), lime, and calcium chloride three years prior. Foliar vector diagrams suggested N limitation at the low-N site and N sufficiency at the high-N site, but did not suggest Ca deficiency at either site after urea, lime and Ca-chloride fertilization. The high-Ca site displayed 20-60 times higher concentrations of foliar Ca-oxalate than the low-Ca site, although this was unaffected by fertilization. Soil nitrification responded to both N and lime fertilization at both sites, suggesting that fertilization with N may stimulate nitrification that could accelerate soil Ca loss. I also investigated how Ca-ox may influence cation tracers such as Ca and strontium (Sr) ratios (i.e., Ca/Sr) and Ca-isotopes (⁴⁴Ca/⁴⁰Ca), which are used to identify sources and pathways of Ca cycling in ecosystem studies. Laboratory synthesis of Ca-ox crystals exhibited preference for Ca over Sr, and for ⁴⁰Ca over ⁴⁴Ca. In the field, discrimination between Ca and Sr was detected in bulk plant tissues due to Ca-ox accumulation, suggesting that Ca-ox accumulation related to tree Ca supply status could influence interpretations of Ca/Sr as a tracer of Ca cycling. I also found that standard methods of soil exchangeable Ca extraction could dissolve Ca-ox crystals and potentially contribute an additional 52% to standard measurements of exchangeable-Ca pools in low-Ca sites, thus complicating long-standing interpretations of available soil Ca pools and dynamics in many studies. Results of this work show overall that Ca-ox is found in large quantities in plants, detritus, and mineral soil in forest ecosystems, and is a more dynamic component of ecosystem Ca cycling than previously recognized. / Graduation date: 2012