Palladium catalyzed Heck coupling with aryl and alkenyl halides has become a powerful means of carbon-carbon bond formation. This standard synthetic method has been developed to a high level of utility using various catalysts, conditions and substrates. Yet significant drawbacks remain, including poor reactivity, the need for high temperatures and base, limited substrate generality, and selectivity. Mixed products often suffer from olefin migration following insertion. N-Heterocyclic carbenes (NHC) have proven to be electron-rich donors which provide higher stability and reactivity than phosphines. In a previous paper reported by our research group the imidazolium-palladium carbene has proven to be highly efficient for the Suzuki-Miyaura cross couplings. The most active bis-2,6- diisopropylphenyl dihydroimidazolium chloride ligand 1 in that series together with palladium acetate were employed as the catalyst, to efficiently catalyze the Heck coupling of aryl diazonium ions with olefins with useful yields at room temperature. Added base is not needed either to form the carbene catalyst or for alkene product formation. Phase-Transfer Catalysis (PTC) is a very useful approach and has been widely used in synthetic organic chemistry. A novel class of fluoroanthracenylmethyl PTC catalysts were synthesized and explored for asymmetric glycolate and glycine alkylation. Phosphorous pentoxide was used for the challenging electron-deficient electrophilic aromatic substitution step. These new catalysts proved to have high selectivities for glycine alkylation under mild conditions.

No description available.

The extensive use of tetrachloroethene (PCE) and trichloroethene (TCE) as cleaning solvents has resulted in widespread contamination of groundwater systems with vinyl chloride (VC). VC, a known human carcinogen, is primarily formed in groundwater via incomplete anaerobic reductive dechlorination of PCE and TCE. Aerobic, methane-degrading bacteria (methanotrophs), which are capable of VC cometabolism while growing on methane, could be important in natural attenuation of VC plumes that escape anaerobic treatment. Real-time PCR (qPCR) represents an innovative approach for detecting and quantifying the presence and activity of these VC-degrading microbes. Immediate applications of this technique include use in a laboratory setting to help elucidate the potential bacterial-substrate interactions occurring in the subsurface environments at these contaminated sites; interactions that could ultimately affect the role of methanotrophs in VC degradation. This technique could also provide lines of evidence for natural attenuation of VC, thus support existing anaerobic bioremediation technologies that generate VC as a metabolic intermediate. In this work, we evaluated several PCR primer sets from the literature for use in methanotroph qPCR assays of groundwater samples. PCR primers targeting two functional genes involved in VC cometabolism, pmoA (sub-unit of particulate methane monooxygenase (pMMO)) and mmoX (sub-unit of soluble MMO (sMMO)), as well as 16S rRNA gene primers that targeted Bacteria, and Type I and Type II methanotrophs were tested. These assays were made quantitative by constructing standard curves with DNA from Methylococcus capsulatus (Type I) and Methylocystis sp. strain Rockwell (Type II). Primer sets were evaluated by comparing gene abundance estimated against known amounts of Type I and Type II methanotroph DNA. After primer validation, an effort to substantiate this methanotroph qPCR method was made by attempting to investigate methanotroph populations in groundwater samples from VC-contaminated sites. Some samples studied were also subjected to 16S rRNA gene pyrosequencing, allowing for relative abundance comparisons with qPCR analyses. Following our primer assessment experiments, effective primer sets were used to estimate the presence of methanotrophs at environmental sites in Soldotna, Alaska; Naval Air Station Oceana, Virginia Beach, Virginia; and Carver, Massachusetts. Results showed that methanotrophs were present in nearly all wells sampled from all environmental sites. Estimations of methanotroph relative abundance in environmental samples were determined by comparing the Type I and Type II primer estimates to those of the 16S universal primers. Methanotrophs in these groundwater samples ranged from 0.2% to 6.6% of the total bacterial population. Pyrosequencing analysis of the same samples showed methanotroph relative abundances that ranged from 1.7% to 54%. In groundwater samples where both DNA and RNA was extracted, the quantities of functional gene transcripts per gene copy was compared, revealing that the transcripts/gene ratio for both pmoA and mmoX was less than one, implying relatively low methanotroph activity. Analysis of mmoX environmental sample dissociation curves revealed a double peak, indicating possible non-specific PCR products. Our data suggests that most of the qPCR primer sets used in the environmental samples adequately detect methanotrophs, though the mmoX primers need to be further validated. These primer sets will be useful for supporting VC bioremediation strategies by providing a rapid, convincing, and cost effective alternative the enrichment culture technique currently employed. Comparison of qPCR and pyrosequencing analysis revealed biases in either one, or both techniques. Finally, our preliminary transcripts/gene data suggests that the methanotrophs at the Carver site are not actively expressing pMMO and sMMO genes above basal levels.

A number of toxicities associated with methylene chloride have been found in both human subjects and mice. However, relatively few studies have probed immunotoxicities of methylene chloride. In order to examine possible immunotoxicities or immunomodulating effects of methylene chloride, several tests of cellular immune function were performed using both human in In Vitro studies and a mouse model. Body weights and specific organ weights of thymus, spleen, liver, and kidney were normal in CD-1 mice given various concentrations of methylenechloride. However, a significantly reduced mitogenic response to phytohemagglutinin (PHA} and reduced interleukin-2 (IL-2} production was found in these methylene-chloride-treated mice. The findings in the mouse model provide additional evidence that immune suppression may be associated with exposure to methylene chloride. Splenic mononuclear cells isolated from CD-1 mice were incubated with various concentrations of methylene chloride in vitro and investigated for blastogenic response to mitogen PHA and IL-2 production. The results show no significant difference between methylene-chloride-treated cells and the cells treated with growth media. Peripheral blood mononuclear cells isolated from healthy donors were incubated with various concentrations of methylene chloride and tested for blastogenic activity, natural killer (NK) cell activity, and IL-2 production. The findings showed that the NK cell activity, the T-cell blastogenesis in response to PHA mitogen, and IL-2 production activity were not affected.

Concrete cylinder piles produced by a centrifugally cast, vibrated, roller compacted process have shown promising corrosion durability in marine environments. Three bridges in the Florida Panhandle with approximately 40 years of service in aggressive marine service were examined. A newly constructed marine bridge utilizing concrete cylinder piles was also examined to verify corrosion performance of piles manufactured with modern building materials and construction compared to piles built several decades ago. Survey of the marine bridges showed minimal corrosion distress despite low design concrete cover to steel hoop reinforcements (20-40 mm). Typical concrete distress included minor rust staining but not necessarily indicating corrosion of reinforcement steel. Thin longitudinal cracks were frequently observed but were likely caused by mechanical damage from pile driving rather than stemming from corrosion distress. Chloride ion diffusivity was low, in the order of 1x10-13 m2/s. Other measured parameters such as concrete resistivity, porosity, and water absorption indicate low permeability. Chloride analysis of cracked and uncracked concrete cores from the older bridges in this study did not show pronounced preferential chloride penetration. Chloride analysis from the contemporary marine bridge did show some preferential transport of chloride ions at shallow depths through cracks with further evidence of lower electrical resistivity indicating enhanced electrolyte transport. The pore water pH of concrete samples from the contemporary bridge was high despite the presence of pozzolanic materials suggesting that normal chloride threshold values may be valid.

>Magister Scientiae - MSc / The current study aimed at providing groundwater recharge estimates in a fractured rock aquifer environment that is occupied by pine plantation and indigenous forests in order to improve the understanding of the effect of pine plantation forests on recharge. This was based on the argument that for the trees to affect recharge, they do not necessarily need to tap directly from the saturated zone, as vegetation may indirectly affect groundwater recharge by interception and abstracting the infiltrating water in the vadose zone before reaching the water table. The study was conducted along the Southern Cape coastline of Western Cape Province in South Africa. This area is 7 km east of George in an area characterized by the occurrence of the Table Mountain Group aquifer. The research presented in this thesis formed part of a Water Research Commission (WRC) project titled “The Impacts of Commercial Plantation Forests on Groundwater Recharge and Streamflow”. To achieve the aim of the current study, three objectives were formulated: i) to characterize the dominantly occurring recharge mechanism ii) to determine long-term groundwater recharge estimates, and iii) to assess the effect of plantation forests on groundwater recharge. As part of characterizing the dominant recharge mechanism in the area, a conceptual groundwater recharge model of the area was developed to explain the recharge mechanism and facilitate an improved understanding of recharge estimates. The model was based on a theoretical understanding and previous investigations conducted in the study area. Methods such as environmental stable isotopes and hydrochemistry were used to refine the conceptual model by identifying the source of recharge and the dominant recharge mechanism. The occurrence and density of lineaments were used as a proxy to delineate potential recharge zones in the area. Recharge was estimated using the Rainfall Infiltration Breakthrough (RIB) and the Chloride Mass Balance (CMB) methods. Additionally, the effect of plantation forests on recharge was assessed using the HYDRUS-2D numerical model. The recharge estimates derived from the RIB and CMB techniques were verified using the published maps by Vegter (1995).

No description available.

Assessement of effects of cadium chloride exposure on the anaphylaxis reaction to food was done on six week old Swiss and BALB/c female mice. The animals were exposed to cadium as cadium chloride for either three days or six weeks. Intra-peritonal dose of cadium chloride was injected once a day, five days per week for three successive weeks. The animals were then sensitised to cow's milk by force-feeding with cow's milk for three consecutive days. Oral exposure of mice to a high dose of cadium resulted in cytotoxicity of liver and kidney cells. Retardation in growth rate and haematology change were detected. Proliferative response to the T-cell epitope from the circumsporozoite protein of plasmodium falsiparum was decreased in cultures of lymph node cells from cadium chronically treated mice and sensitised with the same peptide. In contrast, an increase of cell proliferation was observed when cow's milk was used instead. Significant increase in Immunoglobulin E level and Anaphylactic reaction dependent on the quantity of cadium exposed were recorded. No protective effect of ascorbic acid or zinc acetate on cadium alteration of immune response was observed / Master of Science (Hons) (Food Science)

Earthworking activities have the potential to accelerate soil erosion through vegetation clearance and soil compaction processes. The eroded sediment can have many detrimental effects on receiving aquatic environments, and thus its discharge is controlled under the Resource Management Act, 1991. Two chemically dosed sediment retentions ponds at the SH20 extension project in Mount Roskill, Auckland were investigated, and the impact of the discharge of one of these ponds on a receiving waterbody was assessed using the Stream Ecological Valuation (SEV) method. Rainfall and suspended solid data was collected for a nine month period between November 2006 and August 2007, although sampling did not commence at one of the ponds until March 2007. Two SEV samples were undertaken within the receiving waterbody; one in November 2006 and the other in November 2007 to assess environmental changes resulting from the sediment retention pond discharge. The suspended solids results measured within the sediment retention ponds during this study were much lower than those reported by other studies on earthwork sites. This is believed to be due to the effective implementation of sediment and erosion control measures onsite. The Somerset Road pond was very effective at removing suspended solids throughout the sampling period, with the majority of suspended solid removal occurring in the forebay as it typically did not become full enough to overflow into the main pond. When the forebay was full of water, the PAC dosing system resulted in large reductions in suspended solid levels over a short horizontal distance within the forebay. A smaller amount of suspended solid reduction was achieved in the main pond, predominately through dilution, with the major function of the main pond being additional storage capacity for runoff. Discharge from the Somerset Road Pond was not continuous due to low water levels in the main pond. However, when discharge did occur, the suspended solids levels were very low compared with other studies investigating sediment retention pond discharge. The Richardson Road pond was less effective at removing suspended solids due to the flow regime within the forebay. There were two runoff channels entering the forebay, as well as a continual flow of groundwater. Only one of the runoff channels was directly dosed with PAC, and as the water level in the forebay was typically at, or just below, the level spreader at all times, there was a decreased potential for the PAC to become evenly distributed through the forebay and achieve dosing of all runoff. Furthermore, the main pond discharged continuously during the study period, resulting in reduced residence times of runoff within the pond system. Nonetheless, the discharge from the main pond was much lower than other studies, implying suspended solid reduction was being achieved. The SEV method indicated that the receiving environment was already degraded due to modifications to the riparian vegetation, increased dissolved oxygen demand, and moderate bank erosion. This was reflected in the macroinvertebrate population, with only pollution tolerant taxa being collected, thus limiting the use of macroinvertebrates as an assessment tool in this study. However, the SEV method, which assesses a wide range of ecological functions, implied that very little environmental change occurred as a result of the sediment retention pond discharge. A small increase in deposited sediment was observed on the stream bed, however indications are that deposited sediment is rapidly washed away once earthworks are completed. Thus this deposited sediment may not have a permanent impact within the receiving environment.

The study presented here consists in an original piece of work to better understand complex food packaging interactions. The majority of investigations on food polymer interactions related to orange juice and this provided a good base to our study (Literature reviews: cf. Chapters 1a and b). Additionally a rather remarkable finding in 1994 was that limonin, a trace bitter material found in some varieties of orange juice was rapidly absorbed by highly plasticised polyvinyl chloride (PVC plastisol) (Chapter 2). Several commercial absorbants are available for debittering, relying on limonin absorption on the large surface area of the highly porous absorbant pellets. However, the absorptive properties of the smooth plastisols apparently relied on a different mechanism. Limonin is a very large (470.5 g/mol) compound, but some preliminary experiments with another much smaller orange juice constituent d- of absorbates in plastisols, methods used earlier (Moisan 1980, Holland and Santangelo 1988) to measure solubilities and diffusion constants in packaging films could be advantageously used to survey these properties in a wide range of materials, including model compounds of various types, and a number of compounds which may be found in citrus juices (Chapters 3, 4 and 5). Experimentally, the method found most suitable was to use a ‘test film’ of pure plastisol which was wrapped tightly on both sides by a similar ‘supply film’ blended with 1 Molar test material (also called ‘absorbate’), setting up a concentration gradient. The inner test film was removed at regular intervals (minutes to hours) to measure (mainly by weighing) the uptake of the test reagent with time. Rather unexpectedly, it was found in a number of cases that the test film lost weight, either from the beginning, or after a period of time. Three main types of behaviour were identified: Type A lost weight from the beginning and over a long period of time, Type B gained weight initially and then lost weight, and Type C gained weight until a steady state was reached. Often the maximum, or near maximum, mass increase occurred within around 100 minutes, indicating a very rapid, liquid-like diffusion mechanism, in harmony with the rapid uptake of d-limonene and limonin. The major parameters of interest with these compounds are their diffusion rates and their solubilities, and in the presence of aqueous media (orange juice and other foodstuffs) the partition coefficient between the plastisol and water, which is related to the hydrophobicity function LogP for the compound. The major complicating factor in these measurements is the observation that the plasticiser materials themselves also migrate, in the reverse direction, because of the lower effective concentration in the supply film. This effect tends to be small, but is one explanation for the mass loss observed above, and cannot be ignored over the long term, nor in its practical applications to contamination in foods. There are many possible applications for the techniques described above. The removal or addition of compounds in food packaging itself is one. Upgrading foods, such as orange juice, commercially, is another. In many cases ‘scalping’ off-flavours or other minor components takes place exclusively through solid or liquid contact with the packaging. The removal from the headspace measured by the current gas permeation methods is irrelevant for the vast numbers of involatile, but easily diffusable compounds. For such compounds these novel applications are simple and rapid, require little specialised equipment, and fill a niche in the armoury of food and packaging chemists. / Doctor of Philosophy (PhD)