No description available.

Greenhouse studies were conducted to determine effects of zinc chloride compounds on foliar and root growth of Marigold (tagetes patula), Zinnia (zinnia elegans) and Vinca (catharanthus roseus). Four different experiments were conducted using zinc chloride compounds applied as a spray on 288 plug trays at rates of 0 (paint only), 3.5, 7, and 14 percent. Experiment I includes examining uptake of zinc into potting media. Experiment II examined plant growth at the various application rates and included a visual survey. Experiment III used microscopic studies to determine effects of zinc compounds on root growth. Experiment IV examined the effect of zinc compound rates on plant survival and if survival was species and treatment rate dependent.

Salmonella enterica Typhimurium is a common foodborne pathogen, and ready-to-eat (RTE) seafood is a potential source of Salmonella outbreaks. Lactic acid is a classical preservative in the meat industry and it is used with high efficacy to sanitize meat surfaces. Cetylpyridinium chloride (CPC) is a cationic quaternary ammonium compound proposed for use as a pathogen intervention substance. Cetylpyridinium chloride activity can be potentially affected by interactions between cetylpyridinium chloride and lactic acid. Lactic acid treatment (up to 1%) reduced Salmonella Typhimurium counts by less than 0.5 log cfu/g. Cetylpyridinium chloride treatment (up to 1%) reduced Salmonella Typhimurium counts by 0.9 log cfu/g. Cetylpyridinium chloride treatment at 18 and 45°C reduced populations of Salmonella Typhimurium by 1.34 and 1.14 log cfu/g. Combined treatment with cetylpyridinium chloride and lactic acid at 18 and 45°C decreased Salmonella Typhimurium counts by 0.83 log cfu/g and 1.05 log cfu/g. The single intervention of cetylpyridinium chloride was more effective than lactic acid used alone or combination of cetylpyridnium chloride and lactic acid to reduce Salmonella Typhimurium attached on ready-to-eat shrimp.

No description available.

No description available.

The ZEBRA battery based on Na/NiCb chemistry shows promise for powering electric vehicles and load leveling systems. The ZEBRA cell consists of a liquid sodium negative electrode separated from the positive electrode by a W'-alumina solid electrolyte. The current state of development of this battery makes use of glass sealing and thermo compression sealing as an integral part of the cell assembly. One objective of the present research was to reduce the thickness of the W'alumina electrolyte thickness as a means to improve perfomance, by lowering the internal cell resistance. The second objective was to develop a ceramic seal with matching thermal expansion coefficient (TEC) to increase battery durability. An added benefit realized with the new ceramic seal was its use for high temperature applications such as emf measurements ordinary systems to determine thermodynamic properties. Dense electrolyte tubes with reduced thickness of less than 100 J..Lm and supported on a porous substrate were successfully produced by slip casting. The slip casting parameters, sintering conditions and materials were optimized and electrolyte resistance was measured by a DC method. A ceramic seal was developed from a eutectic mixture of Na20 and Al203 and tested in galvanic cells. The reproducibility of the emf data shows that the seal is fully impervious and can sustain a high alkali pressure atmosphere up to 1 000°C without cracking or degradation. The seal microstructure revealed liquid phase formation of the seal and diffusion bonding with the lid and tube. The thermodynamic properties and phase relations of the Na-Si binary system were studied by the emf method using Na|β-alumina|Si-Na galvanic cells over the whole composition range below 600°C. There is very limited solubility of Si in molten Na. Properties of the sodium silicon compounds were determined from the emf measurements. / Thesis / Doctor of Philosophy (PhD)

For concrete, a sustainable design requires considering both mechanical properties and durability. One of the major deterioration modes of reinforced concrete structures is the entry of chloride ions and corrosion of embedded metals, which is mainly controlled by diffusion as the mass transport mechanism. Therefore, it is pivotal to quantify the chloride diffusion coefficient of concrete, which controls the rate of chloride ingress. Several testing methods exist for quantifying diffusivity of concrete. However, the current test methods are time consuming and demanding. The primary goal of this study is to develop models for quantifying the chloride diffusion coefficient of concrete. As such, initially, the most recent and prevailing analytical models proposed in the scientific literature were critically reviewed and the parameters controlling the chloride diffusion coefficient of concrete were identified. Then, the cement degree of hydration of concrete – as a key parameter which controls the properties of concrete – its measurement methods, and the uncertainties associated with different quantification methods were scrutinized. Finally, three models were developed to quantify the chloride diffusivity of concrete. The first model quantifies the chloride diffusivity of concrete in terms of its electrical resistivity based on the modified Nernst-Einstein equation. The model accounts for the ionic concentration of the pore solution through the alkalis released due to hydration of cementing materials and the alkali uptake of hydration products, the pore solution conductivity, and the interaction between the ions in the pore solution. The second model, which provides a phenomenological relationship for chloride diffusivity of concrete in terms of its compressive strength, accounts for the tortuosity factor of the mixture, aggregate volume fraction, porosity, compressive strength, and cementing materials content and composition. The third model is developed based on the mixture constituents and the cement degree of hydration of concrete. The model accounts for tortuosity factor through the volume fraction of aggregate particles, the interfacial transition zone thickness and diffusivity, cementing materials type and chemical composition, bulk cement paste transport properties through water to cementing materials ratio, cement degree of hydration, supplementary cementing materials type and replacement levels. In order to assess the accuracy and precision of the proposed models, an experimental program was developed and conducted. The following variables were considered for the experimental program: the volume fraction of coarse aggregate, water to cementing materials ratio, total cementing materials content, and supplementary cementing materials type and replacement levels. The experimental results along with the reported data in the scientific literature were used to validate the proposed models. The results revealed the capability of the models to capture the documented observations, as well as the high accuracy and precision of the proposed models for quantifying the chloride diffusivity of concrete in a wide range of concrete mixtures composition and age. The developed models provide designers, practicing engineers and standard/code developers with accurate, precise and consistent models for quantifying the chloride diffusion coefficient of concrete as a direct measure of its durability. / Thesis / Doctor of Philosophy (PhD)

Lead corrosion in premise plumbing systems from materials, such as lead pipes, soldered joints, and brass, can cause elevated lead in drinking water. This work examined mechanisms by which galvanic corrosion of lead solder:copper joints is accelerated by high chloride, low sulfate, and high nitrate in the water. Galvanic corrosion studies conducted using simulated copper plumbing joints showed lowered pH and concentrated anions at the lead solder surface. A combination of low pH and high chloride can prevent passivation of the solder surface, indefinitely sustaining high corrosion rates and lead contamination of potable water supplies. The mass of lead leached to water correlated with predictions based on Faraday's law, although a portion of the oxidized lead remained attached to solder in a scale layer. When the level of sulfate in water increased relative to chloride, galvanic currents and associated lead contamination could be greatly reduced. The impact of chloride-to-sulfate mass ratio (CSMR) on lead leaching from 50:50 lead:tin solder galvanically coupled to copper was examined at the bench scale.The CSMR can be affected by coagulant changeover, use of desalinated water, anion exchange, brine leaks, and other treatment changes. Consistent with prior experiences, increasing the CSMR in the range of 0.1 to 1.0 produced dramatic increases in lead leaching from this source. Above this range, while lead leaching was generally very high, there was little correlation between lead release and CSMR. The impact of nitrate was tested at the bench scale using synthesized water. Results consistently showed that increasing nitrate in the range of 0 to 10 mg/L NO??N, could dramatically increase lead leaching from simulated soldered pipe joints. Although higher nitrate slightly increased the galvanic current, the main factor affecting lead release appears to be initiation of non-uniform corrosion, with small pieces of solder detaching into the water. Under some circumstances, the decay of chloramine after it leaves the treatment plant, and formation of nitrate via nitrification, can markedly increase corrosivity of distributed water to lead solder. The bench scale experiments conducted in this work illuminated many issues related to accelerated lead corrosion of solder. However, future research is necessary to further elucidate the mechanisms behind nitrate-accelerated corrosion, as well as methods for inhibition of corrosion due to chloride and nitrate. / Master of Science

Plasticizers are often interchanged with the idea that they will not affect the processing behavior of Polyvinyl Chloride (PVC). However, when the plasticizer type is changed, various complaints are made by the processors that the material no longer processes the same. This research was concerned with the effect of three different plasticizers on the plasticating extrusion behavior of PVC. Di-isodecyl pthalate (DIDP), di-hexyl pthalate (DHP) and 2-ethyl hexyl pthalate (DOP) are the three plasticizers used in this study. First some differences in the extrusion performance of the three differently plasticized PVC compounds were identified. In particular, it was observed that pressure build-up, flow rate and power requirement were affected by the plasticizer type with the DIDP plasticized materials generating higher pressures and requiring more power than the other two plasticized materials. The differences in extrusion characteristics have been observed for two different dies (1/8 and 1/16 inch diameter) attached to the extruder. The differences were most significant between the DIDP and the DHP plasticized mixes. Factors which could influence the processing behavior of plasticized PVC include viscosity, compaction, thermal conductivity, specific heat, and friction coefficient. It was found that all other properties other than the viscosity were unaffected by the plasticizer type. On the other hand, viscosities were significantly affected by the plasticizer type with the DIDP plasticized materials displaying higher values between 160 and 190 °C. The difference in viscosity was larger between the DIDP and DHP plasticized materials than between DIDP and DOP plasticized materials. The differences in viscosity between DIDP and DOP plasticized materials tend to diminish considerably at 190 °C. Two flow regions characterized by different degrees of fusion above and below 165 °C were identified for the plasticized PVC compounds. Plasticized PVC exhibited yield stresses with the DIDP plasticized materials having higher values. The yield stresses were responsible for the significant difference in viscosity at lower shear rates. The yield stress was a more dominant feature at temperatures below 160 °C and this fact was made use of in modeling the solids conveying zone as a fluid with yield stress. Correlation was established between the viscosities and the extrusion behavior of the plasticized PVC compounds. It was observed that the DIDP plasticized mixes had higher viscosities, fused earlier in the screw channel, gave rise to higher pressures, required more power and in general exhibited higher flow rates at the same screw speed. The finite element method was used for the numerical simulations. Based on the experimental results, the numerical modeling of the melt zone was performed in order to predict the differences in the extrusion characteristics. The melt zones were modeled as a temperature dependent power law fluid having two different viscosity expressions above and below 165 °C. The numerical predictions for pressures and flow rates in the extruder with the 1/8 inch diameter die were in good agreement with the experimental results. For the case of the 1/16 inch diameter die attached to the extruder, the numerical and experimental flow rates were in good agreement but the pressure predictions, although indicating the correct trends, were off by 15 to 20% from the experimental results. In general the differences in the physical properties, viz. viscosities, were used to predict the differences in the pressure build-ups and flow rates. Also the solid conveying zone was modeled using a Herschel Bulkley model. It was possible to match the experimental and numerical results for the solids conveying zone by using an average density value for the entire solids conveying zone, but more work needs to be done in order to establish greater validity and applicability of this model. / Ph. D.

It was the purpose of this investigation to study the effect of addition agents on the electrodeposition of aluminum on copper from a fused bath of 80 per cent aluminum chloride and 20 per cent sodium chloride. The agents added and the concentrations studied were lead chloride, 0.5 and 1.0 per cent; aluminum thiocyanate, 0.5 and 1.0 per cent; chromic oxide, 0.5 per cent; sodium cyanide, 0.1 and 0.5 per cent; and vanadium pentoxide, 0.1 per cent. The electrolysis was carried out in a 1000-millimeter beaker in a furnace heated by a 1000-watt element. The plating cell was fitted with a tight lid through which the electrodes could be adjusted. The optimum current density range while plating from a bath of 80 per cent aluminum chloride and 20 per cent sodium chloride was 8.2 to 21.0 amperes per square foot. When aluminum was electroplated from a bath of 75 per cent aluminum chloride, 20 per cent sodium chloride, and 5 per cent lithium chloride, the plates did not adhere to the base metal. Also, the plates corroded to the base metal in a few days. The optimum temperature was found to be 356 °F. Lead chloride, when added at a concentration of 0.5 and 1.0 per cent, produced a smoothening effect. The plates obtained at the former concentration were smoothest. However, the plates were rather easily corroded by the atmosphere. In contrast, chronic oxide at 0.5 per cent did not improve the smoothness of the plate but did improve considerably the corrosion resistance of the plate. Addition of aluminum thiocyanate caused formation of a black powder which was non-adherent. Sodium cyanide at 0.1 and 0.5 per cent did not improve the ductility and corrosive resistance of the plate to any extent. Vanadium pentoxide gave corrosive resistance and ductility to the deposit at lower current densities of 10 to 100 amperes per square foot and thin mirror plates at current densities between 100 and 500 amperes per square foot. The vanadium pentoxide was used at a concentration of 0.1 weight per cent. In attempts to protect the plates from corrosion, applications of chemical treatment to the aluminum plate failed, as also did an application of lacquer. The results obtained with the addition of lead chloride, chromic oxide, and vanadium pentoxide warrant further study to determine optimum operating conditions and limits. / Master of Science