No description available.

The lack of falcilities for veterinary services, such as analytical laboratories, which are distant from the field and at immense distances are aggravated by the constraint of transporting and preserving the samples. A method where a certain amount of the urine sample is absorbed onto filter paper, but dried in the field and then sent to the laboratory (Dried Filter Paper Method, DFPM), has been used in human medicine, but never applied in the veterinary field. The practice of expressing various urinary minerals/electrolytes relative to till' concentration of creatinine has recently become generally accepted. A single sample obviates the need for collection of urine over a 24-hour period. Fractional excretion (FE) of minerals and electrolytes (which is the mineral or electrolyte to creatinine ratio), is a simple, inexpensive measurement and a reasonable indicator of the renal clearance of minerals/electrolytes, using a single urine sample. The investigation was divided into two phases, The first was conducted entirely in vitro, using simulated urine (artificial and goat urine) dried on filter paper, manipulated in various ways under laboratory conditions, and the second phase was conducted in vivo and in vitro, using urine (collected from water-deprived goats) dried on filter paper and manipulated in various ways under laboratory conditions. Determination of mineral/electrolyte to creatinine ratios using the dried filter paper method consisted of Impregnating a specific filter paper with a specific volume of artificial/goat urine, diluted in a specific eluent, and then analysed for the analytes (creatinine, phosphate, chloride, magnesium, calcium, sodium, and potassium). Due to the wide range of filter papers, which could have been used for the trial, it was necessary to run an experiment to identify the best for the purpose. The experiment used filter papers from :2 different brands (Whatman® and Scheicher&Schuel filter papers). The following filter paper were compared: Whatman® no 2, 3, 5, 6, 42, 43, 44, and 542 and 860, 593, 595. 597, 598 for Schleicher&Schuell (very high quality). There were few significant differences. Whatman filter paper number 6, was chosen, because of the constant and uniform mineral/electrolyte to creatinine ratios. The very high variability of urine mineral/electrolyte concentrations in ruminants, and the limited linearity range of routine analytical equipment, constrains the routine use of laboratory analysers in urine mineral and electrolyte assessment. One of the approaches is to use a diluent, with a particular mineral/electrolyte concentration near to the lower end of the linear/standardised range. Therefore, "mixing" a small volume of urine with the diluent will result in a final mineral/electrolyte concentration, that falls into a linear and controlled/standard range for the particular mineral and electrolyte. A diluent was tested and the results for analytes show a high interclass correlation (R1 >0.75) between the expected and the calculated values of this ratio. The stability of mineral/electrolyte to creatinine ratio (B/Cr) in artificial and goat urine specimens using the dried filter paper method stored at 2 different temperatures during ten days was also evaluated experimently. While it has been found that P/Cr ratio, Mg/Cr ratio, K/Cr ratio are stable for the 10 days, the Cl/Cr ratio, Ca/Cr ratio, and Na/Cr were found to be less stable during the same period of time. The average results do not differ significantly from the control in either the artificial urine or the goat urine. Experiments were conducted to evaluate the reproducibility of artificial urine and artificial urine diluted 1:5 to simulate reproducibility of mineral/electrolyte to creatinine ratios with higher and lower concentrations, respectively. The results indicate a relatively good reproducibility of the method, because the variation, as measured by standard deviation, is small relative to the mean, except for Cl/Cr ratio and Ca/Cr ratio, where the results presented showed a relatively low reproducibility. In theory, since ratios can be obtained, and should be unchanged by taking measurements at different dilutions even if the amount of specimen is unknown, there should be no need to absorb a fixed amount of urine onto the filter paper when urine is collected, using this method. However, there appear to be limits to this in reality, dilution of urine below a 1: 10 dilution and/or the volume impregnated onto the filter paper below 0.525 ml on Whatman® number 6 filter paper. An experiment with goats on the relationship between the influence of water deprivation on minerallelectrulvte to creatinine ratio over a period of time demonstrated that concentrations and excretion of electrolytes vary from animal to animal, but the mineral/electrolyte to creatinine ratios by DFPM hardly vary, even if the goat is deprived of water. Using goat urine to determe mineral/electrolyte to creatinine ratio with the dried filter paper method gives high interclass correlation for mineral/electrolyte to creatinine ratio between the control (fresh urine sample, preserved in freezer) and the dried filter paper method on goats given water ad libitum. Interclass correlation agreement for the two methods was R1 >0.75. On the basis of the results, the method is robust for use as a urine sample preservation and transportation method for the determination of mineral/electrolyte to creatinine ratio with an added advantage of not needing either preservative or refrigeration. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2000. / Companion Animal Clinical Studies / unrestricted

Lithium is a very attractive material for batteries. It has low redox potential (-3.04V vs SHE) and high theoretical capacity of 3860 mAh g-1. So, lithium batteries would have high energy density. During charging and discharging of the batteries, the interface between electrode and electrolyte changes as lithium is deposited or dissolved. If the deposition is dendritic, it can short circuit and cause failure of the battery. During dissolution of lithium from the electrode, pits can form on the surface and some part of lithium is detached. It is called dead lithium since it is not electrochemically active. Solid electrolyte and lithium metal interfaces are characterized by high interfacial resistance. The interface between electrode and electrolyte is critical to the safety and performance of lithium batteries. The aim of this research is to understand the evolution of interface between electrode and electrolyte as charging or discharging occurs. Three kinds of interfaces are considered, interface formed between intercalation anode and liquid electrolyte, interface of metal anode and liquid electrolyte and interface between metal anode and solid electrolyte.<br>Stringent performance and operational requirements in electric vehicles can push lithium-ion batteries toward unsafe conditions. Electroplating and possible dendritic growth are a cause for safety concern as well as performance deterioration in such intercalation chemistry-based energy storage systems. There is a need for better understanding of the morphology evolution due to electrodeposition of lithium on graphite anode surface, and the interplay between material properties and operating conditions. In this work, a mesoscale analysis of the underlying multi-modal interactions is presented to study the evolution of morphology due to lithium deposition on typical graphite electrode surfaces. It is found that electrodeposition is a complex interplay between the rate of reduction of Li ion and the intercalation of Li in the graphite anode. The morphology of the electrodeposited film changes from dendritic to mossy structures due to the surface diffusion of lithium on the electrodeposited film.<br>Dendritic deposition on lithium metal anode during charging poses a safety concern. During discharging, formation of dead lithium results in low Coulombic efficiency. In this work, a comprehensive understanding of the interface evolution leading to the formation of dead lithium is presented based on a mechanism-driven probabilistic analysis. Non-dendritic interface morphology is obtained under reaction controlled scenarios. Otherwise, this may evolve into a mossy, dendritic, whisker or needle-like structures with the main characteristic being the propensity for undesirable vertical growth. During discharging, pitted interface may be formed along with bulk dissolution. Surface diffusion is a key determinant controlling the extent of dead lithium formation, including a higher probability of the same when the effect of surface diffusion is comparable to that of ionic diffusion in the electrolyte and interface reaction.<br>One of the biggest advantages of solid electrolyte over liquid electrolyte is its mechanical rigidity which provides resistance to dendritic deposition. The electrodeposition at the interface of solid electrolyte and lithium metal anode will be affected by the nature of the interface formed between solid electrolyte and lithium metal, i.e. coherent, semi-coherent or incoherent depending on the misfit between the two crystal lattices. A coupled energetics and deposition mesoscale model is developed to investigate the nature of deposition and surface roughness of the deposition. The strength of interaction between metal anode surface and solid electrolyte surface at the interface is key in determining the roughness of the morphology during deposition. The energy is localized to region near the interface. With surface diffusion at the interface, the roughness of the interface as well as the energy near the interfacial region decreases.

Lithium batteries have revolutionized emerging electronic applications and will play more important roles in the future. Unfortunately, the energy density of commercial lithium-ion batteries (100-265 Wh kg-1) cannot satisfy the fast-growing demand for energy storage technologies. Lithium-sulfur (Li-S) batteries stand out for high energy density (2567 Wh kg-1), low-cost, and environmentally benign attributes. However, the development of Li-S full-batteries is still hindered by the dissolution of polysulfides into the organic electrolytes and poor ions transfer at the interfaces of electrolytes and lithium-intercalated electrodes (e.g., lithiated graphite). Improving the electrolytes is a crucial aspect for the development of battery technologies, but the knowledge concerning the electrolyte microstructures remains elusive. This dissertation unravels the microstructures of organic electrolytes and paves the way to the development of Li-S batteries. Firstly, we demonstrate the key role of electrolyte chemistry in the battery performances by showing a synergetic effect of electrolytes coupled with designed sulfur cathodes. Secondly, we investigate the microstructure of electrolytes and discover previously unexplored solvent-solvent and solvent-anion interactions. We show that the interactions are useful to elucidate important battery operations, such as ions transfer at electrolyte-electrode interfaces, and reveal a potential probe for developing battery electrolytes. Thirdly, we optimize the electrolyte composition to obtain a highly reversible Li+ intercalation/deintercalation at the graphite anode, giving high performances of Li-S full-batteries in a dilute electrolyte concentration. Finally, we unravel the key role of additives in suppressing Li+ solvation in the electrolytes. Nitrate (NO3-) anions are observed to incorporate into the solvation shells, change the local environment of Li+ cations, and then lead to an effective Li+ desolvation followed by improved battery performances. Key significances of this dissertation are (i) observation of detailed electrolyte microstructures showing a potential probe for developing battery electrolytes; (ii) evidences of the electrolyte chemistry plays a predominant role in the electrolyte-electrode interfacial reactions, which prevails over the role of commonly believed solid electrolyte interphase (SEI); and (iii) new mechanistic insights into the key role of additives in the electrolyte microstructures. Furthermore, the presented methodology paves the way for developing electrolytes for broad electrochemical applications.

<p> Potassium levels in serum are used in the diagnosis of diseases involving cardiac arrhythmias, neuromuscular weakness, and chronic kidney diseases. These illnesses are becoming more prevalent, therefore, developing new potassium quantification methods would aid in advancing preventative care. Current methods of quantifying potassium mainly rely on the use of glass ion-selective electrodes which are costly, fragile, and requires frequent maintenance and recalibration. For faster and more accessible quantification of potassium, we are developing low cost, portable, and easy to fabricate electrochemical tape-and-paper-based devices. Our sensor bypasses the inconveniences of ion-selective electrodes and could ultimately serve as a point-of-care device to allow for regular monitoring or even home-use. Our sensing method relies on Prussian blue immobilized on the surface of electrodes as a potassium recognition element. Potassium ions intercalate into the Prussian blue lattice and subsequently changes the electrochemical characteristics of Prussian blue such as the redox peak potentials. These devices are highly robust, feature a limit of detection of 1.3 mM potassium and the response is linear to at least 100 mM, which contains the clinically relevant ranges required for diagnostics. Quantification was developed using cyclic voltammetry, demonstrated in Chapter 3. We observed changes in Prussian blue redox peak potentials at different concentrations of potassium and followed the expected Nernstian response. We investigated multiple methods of immobilizing Prussian blue onto the electrode surfaces to investigate stability and reproducibility in Chapter 4. Adsorption, <em>in-situ</em> synthesis, and carbon paste incorporation of Prussian blue was tested. Prussian blue-carbon paste devices had reproducibility issues and featured broad reduction peaks. <em>In-situ</em> synthesis of Prussian blue directly onto the surface of the electrodes also featured broad reduction peaks but the Prussian blue response was reproducible. The issue with <em>in-situ</em> synthesis was the stability of the Prussian blue layer, which was susceptible to degradation after repeated use of the device, which is required for evaluating the performance of the device. Although adsorption using Prussian blue in water had some reproducibility issues as well, this method led to the most stable Prussian blue layer, had distinct reduction peaks, and was simple to perform. Various solvents were used to dissolve Prussian blue in Chapter 5 to investigate methods of increasing device reproducibility when using adsorption. A few organic solvents were able to dissolve Prussian blue to form a stable solution with the goal of forming a more uniform Prussian blue layer and potentially improving consistency of the layer immobilization. While these alternative solvents were able to dissolve Prussian blue, they also damaged the graphite electrodes on the devices, which altered the electrochemical responses of the devices to the point where potassium quantification was no longer possible. Due to incompatibility between these alternative solvents and the devices, adsorption of Prussian blue in water continued to be used. Different modes of adsorption were explored and was optimized in Chapter 6. By altering the adsorption setup and allowing the Prussian blue particles to settle evenly onto a level electrode surface, device reproductivity increased substantially. To understand the applicability of the devices in real samples, interferent studies were performed in Chapter 7. Other cations such as Na+, Li+, Ca2+, Mg2+, and Ba2+ were not observed to enter the Prussian blue lattice in the cyclic voltammograms. Monovalent cations that share the same charge as K+ but have smaller ionic radius, Na+ and Li+, were able to decrease K+ sensitivity. Divalent cations that had a smaller ionic radius than K+ did not alter sensitivity. The exception was Ba2+, which also decreased K+ sensitivity. These results suggested that both ionic radius and charge of a species were important factors in impacting K+ intercalation into the Prussian blue lattice. Other interferents such as sulfates, phosphates, carbonates, urea, and lactic found in serum and sweat samples were tested. The presence of these interferents decreased the current intensity of the reduction peak of Prussian blue, which resulted in less definition in the peaks. For the future of this project, the effects of interferents found in serum and sweat must be investigated further. Additionally, reproducibility of the devices could be improved further if less harsh organic solvents are tested for adsorption, square wave voltammetry could be used for quantification to evaluate the viability of alternative voltametric techniques, and Prussian blue analogues could be implemented into the devices for quantification of other cations. </p>

No description available.

In order that further steps could be taken in the attempt to defeat corrosion, it was desirable to find a method for electrodepositing aluminum on other metal surfaces. To meet this need, an investigation was conducted to attempt to find an electrolyte that would be suitable from the field of molten inorganic aluminum and alkali salts. The principal work by other investigators on the electrodeposition of aluminum has been with aqueous solutions which have been proved unusable and with fused alkali-aluminum halide mixtures that have produced crystalline, poorly adherent aluminum coatings. In the present investigations, seven inorganic, fused salt systems were studied. These systems were chloride, fluoride, cyanide, sulfide, thiocyanate, formate and fluoborate. No electrolyte was found that gave a compact, adherent aluminum deposit. Investigation of a fused electrolyte containing 66 mol per cent aluminum chloride, 20 mol per cent sodium chloride and 14 mol per cent potassium chloride at 160 °C produced poorly adherent, dendritic aluminum deposits on a copper cathode at a current density of 0.833 ampere per square decimeter. This coating formed a surface alloy between aluminum and copper when electroplated pieces of copper were heat treated in an electric furnace at 550 °C for 45 minutes and at 1000 °C for one minute. The piece treated at 1000 °C seemed to have deeper penetration of the aluminum. Ratios of 45 to 55, 42 to 58 and 40 to 60 mol per cent aluminum fluoride to potassium fluoride failed to produce a composition that would have a low viscosity at a temperature below the melting point of aluminum, 660 °C. A fused bath of 70 weight per cent potassium sulfide, K₂S₈, and 30 weight per cent aluminum sulfide, Al₂S₇, did not yield aluminum after electrolysis at current densities of 2.5 and 5.0 amperes per square decimeter for three hours at a temperature of 300 °C and using platinum electrodes. A plot of cell potential versus current for the sulfide system indicated oxidation and reduction of the electrolyte with ultimate passivity of the anode. Systems of cyanide, fluoborate and formate proved to be impractical because of the difficulty in handling or obtaining the chemicals involved. Aluminum thiocyanate showed promise as an electrolyte but limitation of time prevented experimental work on this system. / Master of Science

This thesis describes the results of two process system engineering studies: (1) hydrogen pinch analysis; and (2) application of COSMO-SAC (conductor-like screening model – segment activity coefficient) to electrolytes. Part (1) presents an automated spreadsheet method that can quickly help minimize fresh hydrogen consumption and maximize hydrogen recovery and reuse in petroleum refineries and petrochemical complexes. Part (1) has appeared as a featured article on engineering practice in the Chemical Engineering Magazine, volume 115, pp. 56-61, June 2008. We present an automated spreadsheet on our research group website (www.design.che.vt.edu) and describe procedures for using the spreadsheet in this thesis. Part (2) discusses the application of the conductor-like screening model – segment activity coefficient (COSMO-SAC), a liquid-phase activity-coefficient model, to electrolytes. We offer detailed procedure for obtaining sigma profiles for electrolytes. A sigma profile is a molecular-specific probability distribution of the surface-charge density, which enables the application of solvation-thermodynamic models to predict vapor-liquid and solid-liquid equilibria, and other properties. We propose to add an additional term to the exchange energy to account for ion-ion attractive and repulsive forces. We also look at the resulting exchange energy behavior. Although accurate numerical results are not achieved, we are able to produce results that match literature data by adding an adjustment factor. / Master of Science

Le développement des dispositifs microélectroniques a dopé la recherche dans le domaine des microbatteries tout solide rechargeables. Mais actuellement, les performances de ces microbatteries élaborées par des technologies couche mince (2D) sont limitées et le passage à une géométrie 3D adoptant le concept “Li-ion” ou“rocking chair” est incontournable. Cette dernière condition implique de combiner des matériaux de cathode comme LiCoO2, LiMn2O4 or LiFePO4 avec des anodes pouvant réagir de manière réversible avec les ions lithium. Parmi tous les matériaux pouvant servir potentiellement d'anode, les nanotubes de TiO2 révèlent des propriétés intéressantes pour concevoir des microbatteries Li-ion 3D. Facilement réalisable, la nano-architecture auto-organisée a montré des résultats très prometteurs en termes de capacités à des cinétiques relativement modérées. L'utilisation des nanotubes de TiO2 en tant qu'anode conduit à des cellules présentant de faible autodéchargeet élimine le risque de surcharge grâce au haut potentiel de fonctionnement (1.72 V vs. Li+/Li). Dans ce travail de thèse, nous avons étudié la substitution des ions Ti4+ par Sn4+ et Fe2+ dans les nanotubes de TiO2. Bien que la présence d'ions Fe2+ n'ait pas amélioré les performances électrochimiques des nanotubes, nous avons pu mettre en évidence l'effet bénéfique des ions Sn4+. Nous avons aussi pu montré que la fabrication de matériaux composites à base de nanotubes de TiO2 et d'oxyde de métaux de transition électrodéposés se présentant sous forme de particules (NiO et Co3O4 ) augmentait les capacités d'un facteur 4. / The advent of modern microelectronic devices has necessitated the search for high-performance all-solid-state (rechargeable) microbatteries. So far, only lithium-based systems fulfill the voltage and energy density requirements of microbatteries. Presently, there is a need to move from 2D to 3D configurations, and also a necessity to adopt the “Li-ion” or the “rocking-chair” concept in designing these lithium-based (thin-film) microbatteries. This implies the combination of cathode materials such as LiCoO2, LiMn2O4 or LiFePO4 with the wide range of possible anode materials that can react reversibly with lithium. Among all the potential anode materials, TiO2 nanotubes possess a spectacular characteristic for designing 3D Li-ion microbatteries. Besides the self-organized nano-architecture, TiO2 is non-toxic and inexpensive, and the nanotubes have been demonstrated to exhibit very good capacity retention particularly at moderate kinetic rates. The use of TiO2 as anode provides cells with low self-discharge and eliminates the risk of overcharging due to its higher operating voltage (ca. 1.72 V vs. Li+/Li). Moreover, their overall performance can be improved. Hence, TiO2 nanotubes and their derivatives were synthesized and characterized, and their electrochemical behaviour versus lithium was evaluated in lithium test cells. As a first step towards the fabrication of a 3D microbattery based on TiO2 nanotubes, electrodeposition of polymer electrolytes into the synthesized TiO2 nanotubes was also studied; the inter-phase morphology and the electrochemical behaviour of the resulting material were studied.

The purpose of this study was to determine the effect of stratum corneum (SC) hydration by distilled water on SC ion content and sweat ion concentrations as measured by occlusive sweat patch. 10 men and 10 women completed approximately 40 minutes of moderate exercise in the heat. Select skin sites were hydrated before sweating by adhering cylinders of distilled water to forearm skin. SC samples were taken before and after exercise using the tape stripping (TS) method and sweat samples were taken with homemade filter paper sweat patches with a tegaderm backing. An increase in SC hydration was verified by a reduction in SC potassium concentration (p<0.05). SC hydration caused a significant decrease in sweat potassium (K+), calcium (Ca++), and lactate (Lac-) concentration: K+ =8.14 ± 0.46 to 6.56 ± 0.46, Ca++ = 0.86 ± 0.17 to 0.67 ± 0.18, Lac- = 11.64 ± 1.36 to 8.82 ± 1.11, euhydrated to hyperhydrated respectively(p<0.05). SC sodium (Na+) and K+ concentration increased after sweating without a sweat patch (p<0.05). Our data do not dispute the idea that electrolytes can be leached from the SC by distilled water or sweat trapped within an occlusive dressing. However, our data indicate that during normal sweating the SC "dehydrates" resulting in an increase in the electrolyte concentration. As such, we propose that the occlusive dressing does trap sweat on the skin but the important end result is that it prevents water movement out of the SC and thereby producing a more concentrated sweat.