A desorption technique was employed to evaluate chemisorption of ammonia by clays under moist conditions. In equilibria involving ammonia, all factors favoring volatilization losses of gaseous ammonia would undoubtedly exert an influence on the ultimate equilibria which are reached. Investigation of the relationship between pH and ammonia equilibria in soils revealed that an increase in the concentration of ammonium ions, applied as ammonium sulfate, stimulated ammonia losses from fine-textured soils at pH's ranging from 4.5 to 7.1. Ammonia volatilization was directly related to the initial pH of the soil and increased with an increase in pH. It was postulated that ammonia may be volatilized, even from acid soils, due to the equilibrium NH₄⁺ + OH⁻ ⇌ NH₃ + H₂O. By using initial concentrations of ammonium ions from ammonium sulfate applied, initial pH of an aqueous suspension of the soil and a value K_b = 1.80 x 10⁻⁵, values of ammonia losses were predicted. The linear relationship found between predicted and measured amounts of ammonia losses from acid as well as neutral soils, was interpreted as evidence of the existence of the proposed volatilization mechanism in soils. In attempting to evaluate the characteristics of ammonia retention by homo-ionic bentonites and kaolinites under moist conditions, it was found that base-saturated clays did not chemisorb ammonia in a fashion which could be described by Langmuir's adsorption isotherms. The S-shaped curves did not necessarily reflect polymolecular sorption. In strong contrast, chemisorption of ammonia by Al-saturated clays, followed Langmuir's equation almost perfectly. Evaluation of the inverse values of the differential slopes of two straight line segments obtained in the desorption isotherms corresponded closely to values obtained for the permanent charge (CEC) and the total charge (total CEC) developed at a specific pH higher than 6 respectively. It was shown that if sufficient ammonia is applied, exchangeable Al⁺⁺⁺ of Al-compounds may be precipitated as Al(OH)₃. An attempt to evaluate pseudo-equilibrium constants for aluminum-clay ammonia equilibria by using Langmuir's adsorption equation, was unsatisfactory. Chemical kinetic studies indicated that ammonia volatilization reactions could be described by a fast reaction and a slow reaction. The slow reaction represented chemisorption of ammonia on the permanent charge exchange sites. Extrapolation of the slow reaction to zero time yielded values corresponding closely to the CEC permanent charge. Investigation of the effects of CO₂, the NH₄⁺ concentration is increased, resulting in more effective replacement of basic cations for "permanent charge" exchange spots. The lower pH and higher effective NH₄⁺ concentration resulted in higher retention of NH₄⁺ in Na⁺- and K⁺-clays. The most striking retention of NH₄⁺ was obtained in Mg- and particularly in Ca-bentonites. It is believed that the Ca and Mg ions, exchanged by NH₄⁺ ions, are effectively removed from the soil solution as a result of the precipitation of these compounds which are sufficiently insoluble to ensure conservation of ammonia as chemisorbed ammonium ions. / Ph. D.

Ammonium ionenes are macromolecules with quaternized nitrogen groups in the main chain. Ionenes are commonly referred to as x,y-ionene, where x and y represent the number of methylene groups between quaternized nitrogens. Synthesis of aliphatic ammonium ionenes has been studied since the early twentieth century; however, absolute molecular weight characterization has only been performed using extensive light scattering and viscosity experiments. Performing aqueous size exclusion chromatography (SEC) on ammonium ionenes provides absolute molecular weight determinations while eliminating the need for separate viscosity and light scattering experiments. We developed a mobile phase composition that provides reliable separation of aliphatic ammonium ionenes using aqueous SEC. For the first time, we report absolute molecular weights of aliphatic ammonium ionenes using this technique. We investigated the influence of charge density and structural symmetry on thermal and mechanical properties of ammonium 6,6-, 12,6- and 12,12-ionenes. Thermal properties were measured using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and mechanical properties were measured using dynamic mechanical analysis (DMA) and an Instron. Incorporating low molecular weight polymer segments into the main chain of the ionene allows tailoring of polymer characteristics. Poly (tetramethylene oxide) segments decrease hydrophilicity and increase elastomeric character. Linear PTMO based ionenes have been synthesized previously, and we were interested in how branching affected thermal and mechanical properties. We synthesized bis(dimethylamino) poly(tetramethylene oxide) segments, and subsequently, synthesized linear and branched ionenes to study the effects of topology on thermal and mechanical properties. Polymers were analyzed using DMA, DSC, TGA, SAXS, and an Instron. / Master of Science

Quaternary ammonium compounds (QACs) are antimicrobial disinfectants commonly used in commercial and household settings. While these compounds have been used for decades, reproductive toxicity has not been thoroughly evaluated. Extensive use of QACs results in ubiquitous human exposure to potentially toxic compounds. Reproductive toxicity of two common QACs, alkyl dimethyl benzyl ammonium chloride (ADBAC) and didecyl dimethyl ammonium chloride (DDAC), was investigated to determine gender-specific toxicity with an emphasis on male reproductive function. Breeding pairs of mice exposed for six months to ADBAC+DDAC exhibited decreases in fertility and fecundity, with fewer pregnancies and decreased numbers of pups over a six month period. Females proceeded through significantly fewer estrus cycles, and both ovulation and implantation rates were reduced. Males exhibited declines in both sperm concentration and motility. Male reproductive toxicity was further assessed in a series of in-vitro and in-vivo experiments. ADBAC+DDAC were cytotoxic to testicular Sertoli cells in culture at concentrations greater than or equal to 0.0005%. Changes in blood-testis-barrier integrity (BTB) were observed at 0.01% ADBAC+DDAC using a two-compartment culture system that measures transepithelial electrical resistance (TER). Sertoli cell cytotoxicity correlated with decreased TER at ADBAC+DDAC concentrations above 0.001%. In-vitro fertilization capacity of epididymal sperm was reduced in males given a 10-day rest period following ADBAC+DDAC exposure. Multigenerational changes in sperm parameters and in mRNA expression of enzymes involved with epigenetic modifications were evaluated across three generations. Sperm concentration and motility were reduced in F0 males exposed directly to ADBAC+DDAC. In F1 males, sperm concentration was increased and motility decreased, while there was no change in the F2 progeny. Genes involved in epigenetic modifications were altered in the exposed F0, with upregulation of two histone acetyltransferases (Hat1 and Kat2b) and downregulation of one lysine-specific demethylase (Kdm6b). F1 and F2 generations were not different from controls except for downregulation of the methyltransferase Dnmt1 in F1 progeny. The reproductive toxicity of ADBAC+DDAC identified in these studies, particularly to the male, compels further investigation into the potential effects that these compounds may have on human reproduction. / Ph. D.

Increased nitrogen (N) costs and environmental concerns have created a need to reevaluate current sidedress N application recommendations for corn. Injection of Urea Ammonium-Nitrate (UAN) may reduce N-loss via ammonia (NH?) volatilization compared to current surface application methods. This study evaluated injection and surface-banding application techniques of UAN in two ways: (1) by conducting a laboratory experiment where NH?-N loss was measured from UAN applied by both techniques across varying residue covers; and (2) by performing a field study where the application methods were compared by their effect on corn grain yield, ear leaf tissue N content, and stalk nitrate (NO3). The laboratory system used to compare the NH?-N loss from the UAN application methods was evaluated and found to be capable of providing rapid, accurate, and precise measurements of N loss throughout a range of N rates and conditions. In the laboratory study, injection of UAN reduced NH?-N losses to <1% of applied N. Surface-banding of UAN resulted in NH?-N losses between 15.3 and 32.5% of applied N. Results from the field study suggest that differences between application methods were commonly seen in ear leaf tissue N, where injection of UAN was often found to increase tissue N compared to surface-banding. Also, injection of UAN reduced the optimal N rate by 25 kg N ha?? compared to surface-banding. The results suggest that injection of UAN reduces the potential of NH?-N losses and is a practice worth considering in developing an efficient N fertilizer program. / Master of Science

As anthropogenic nutrient loads threaten the health of the Chesapeake Bay, lotic processes throughout its headwaters may buffer increased nitrogen inputs by converting them to stable forms, ultimately through denitrification to N2 gas. However, the temporal environmental factors controlling baseflow nitrogen retention are poorly understood, particularly temperature, shading, and dissolved organic matter dynamics. This study therefore attempts to elucidate the effects of these environmental variables on nitrogen cycling within the Fair Hill Natural Resources Management Area (Fair Hill), a forested watershed within the Piedmont physiographic province of the Chesapeake Bay. As expected, groundwater and allochthonous organic matter inputs set the foundation for lotic biogeochemistry at Fair Hill, creating a nutrient-limited, heterotrophic reach. Within this setting, three temporal "hot-moments" of in-stream nutrient processing were observed: the release of ammonium and phosphate during the warm - but shaded - growing season; nitrate uptake during autumnal leaf-fall; and a unique spike of nitrate uptake and respiration-induced degradation of labile organic matter during a drought. Consequently, the baseflow capacity of this headwater stream to buffer nutrient exports to the Chesapeake Bay constantly varies throughout the year in response to light availability, temperature, and in-stream organic matter dynamics. / Master of Science / Throughout the Chesapeake Bay watershed, ecological processes known as nitrogen retention can naturally remove nitrogen pollution from small streams (a.k.a. headwater streams), and hence the Chesapeake Bay watershed. However, in-stream nitrogen retention varies throughout the year due to seasonal changes in temperature, shading (as leaves grow in the spring or fall off in the fall), and the amount and type of organic matter in the stream. This study examines how these three variables (temperature, shading, and dissolved organic matter dynamics) affect nitrogen retention in a headwater, forested stream within the Fair Hill Natural Resources Management Area (Fair Hill) located in the Piedmont region of the Chesapeake Bay watershed. As expected, groundwater and organic matter inputs set the foundation for in-stream conditions at Fair Hill, creating an environment with low concentrations of nitrate and phosphate (thus causing the stream to be nutrient-limited), while also creating a heterotrophic environment, which is an environment where more oxygen is consumed by microbes than produced by algae and plants. Additionally, three seasonal patterns regarding in-stream nutrient dynamics were observed at Fair Hill. Firstly, in-stream ammonium and phosphate concentrations increased during the warm - but shaded - growing season. Secondly, in-stream nitrate concentrations decreased when leaves fell in the fall. Thirdly, during a drought, in-stream nitrate removal increased while in-stream organic matter became more degraded. Consequently, in-stream nutrient retention at Fair Hill varies constantly throughout the year in response to light availability, temperature, and in-stream organic matter dynamics.

Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover. / Master of Science

The construction of an adiabatic demagnetization cryostat has been outlined in detail along with the associated electrical apparatus for supplying power to the cryostat and for temperature measurement. Various magnet electrical configurations have been suggested and tried, and the degree of success of each noted. Two types of working coolants, Ferric Ammonium Sulphate and Pink Ruby have been considered and the advantages and disadvantages of each have been discussed. Suggestions for further improvements have also been made. / Thesis / Master of Engineering (ME)

Black Cottonwood (Populus trichocarpa) is a fast-growing, economically important tree species. P. trichocarpa was the first tree to have its genome fully sequenced and is considered the model organism for genomic research in trees. Of the macronutrients in plants, Nitrogen (N) is required in the greatest amounts and is generally the limiting nutrient in terrestrial ecosystems. Inorganic N-transport is performed by four families of transporter proteins, AMT1 and AMT2 for ammonium (NH4+) and NRT1 and NRT2 for nitrate (NO3-). I have created phylogenetic reconstructions of each of these transporter families in 22 members of Viridiplantae whose genomes have been fully sequenced. Based on these phylogenies, I have introduced a new classification system for the transporter families that better represents the evolutionary and functional relatedness of the proteins. These phylogenies were supplemented with topology predictions, subcellular localization predictions, and in silico expression profiling in order to suggest functional characterization of the groups. This facilitated candidate gene selection for NH4+ and NO3- uptake transporters from P. trichocarpa. Expression profiling was performed on two of these candidates. Results suggest that PtAMT1-1 may be a high-affinity, root-localized NH4+ transporter. In contrast, PtNRT2-6 is a high-affinity NO3- transporter localized to the dormant bud, but its physiological functions remain largely enigmatic. Flux profiles of NH4+, NO3-, and H+ in the first 1.4 cm of root tips of three-week-old P. trichocarpa seedlings and cuttings were measured using the Microelectrode Ion Flux mEasurement (MIFE) system to demonstrate the activity of AMTs and NRTs under nutrient-abundant and nutrient-deficient conditions. I found mainly N-efflux from roots of cuttings while seedling roots exhibited N-uptake. This is the first report of such a difference. This highlights an unexpected but clear physiological difference between seedling and cutting roots, which are frequently used in experimental setups. / Graduate / 0817 / 0369 / 0715 / neilvonw@gmail.com

This thesis details investigations into the generation and synthetic utility of α,β-unsaturated acyl ammonium intermediates using isothioureas as Lewis base organocatalysts to generate a range of heterocyclic products. Initial investigations focussed on the development of a Michael addition-lactonisation protocol utilising α,β-unsaturated acyl ammonium intermediates (generated in situ from HBTM 2.1 and α,β-unsaturated homoanhydrides) and a range of 1,3-dicarbonyl nucleophiles. Products could be isolated as lactones or as ring-opened highly functionalised esters, giving good yields and excellent enantioselectivity. 1,3-Diketones were shown to generate a mixture of regioisomers and whereas 1,3-ketoesters afforded only a single regioisomer. A crystal structure of an α,β-unsaturated acyl ammonium intermediate was obtained that clearly demonstrated steric blocking of the Si- face of the alkene by the catalyst stereodirecting groups, therefore it can be postulated that enantiocontrol in the addition occurs by selective nucleophilic addition from the Re- face. α,β-Unsaturated acyl ammonium species were then shown to participate in asymmetric annulation processes with benzazole nucleophiles to afford highly functionalised heterocyclic products, with both lactone and lactam formation observed. The relationship between nucleophile structure and process regioselectivity was investigated and it was demonstrated that benzothiazole and benzimidazole nucleophiles afforded preferential N-cyclisation to give lactams whilst benzoxazoles exhibited O-cyclisation to form lactones. It was also possible to influence the regioselectivity by changing the electronic properties of the acyl group (R'). Due to the reactivity of this class of nucleophiles it was possible to access products with quaternary centres. Palladium-catalysed cross coupling reactions were also successful on 3-bromo substituted lactams, demonstrating the potential for further derivatising these interesting heterocyclic products. Finally, a cascade protocol was developed that employed Michael-Michael-lactonisation steps to give tricyclic products from enone malonate nucleophiles and α,β-unsaturated acyl ammonium intermediates (generated in situ by addition of HBTM 2.1 into acid chlorides). Interestingly, the reaction showed higher enantioselectivity at elevated temperatures (70 ˚C) and moderate regioselectivity (1,4- vs. 1,2-addition), which could not be improved after extensive screening. A range of lactones was isolated in moderate yields and enantioselectivity.

Dans les sédiments marins, la conversion de l'azote en diazote est traditionnellement supposée avoir lieu via le processus de nitrification-dénitrification bactérienne ou par l'oxydation anaérobie de l'ammonium (anammox). Mais, les faibles concentrations d'ammonium observées dans les sédiments riches en oxyde de manganèse suggèrent l'existence d'une voie alternative qui pourrait avoir lieu via un processus chimique. Parmi les oxydes de manganèse, la birnessite est la forme la plus existante dans les sols et les sédiments. C'est un oxyde lamellaire contenant à la fois du Mn (III) et du Mn (IV) dans sa structure et caractérisé par sa haute réactivité. Ce travail vise à mettre en évidence la nature de la réactivité de la Na-birnessite triclinique synthétisée par une méthode redox avec l'ammonium. Cette interaction était soupçonnée, dans des études antérieures, d'impliquer un mécanisme d'échange cationique seulement. La première partie de ce manuscrit est consacrée à la synthèse d'une birnessite pure via un processus redox. Le rapport Mn (VII): Mn (II) de 0,33 a été choisi et trois méthodes ont été utilisées consistant en un mélange rapide sous agitation vigoureuse de deux des trois réactifs et ensuite en l’ajout goutte à goutte du troisième. L'étude de paramètres réactionnels (ordre de mélange des réactifs, temps d'addition du troisième réactif, méthode de vieillissement, nature du cation utilisé et présence ou absence de l'oxygène dissous) a mis en évidence le rôle clé de l'oxygène dans la formation de la birnessite pure et un mécanisme de formation a été proposé. La deuxième partie a porté sur l'interaction de la Na-birnessite avec l'ammonium. L'étude de nombreux paramètres réactionnels (concentration initiale en ammonium, temps de contact, pH et température du milieu), en suivant à la fois les changements solides et liquides, a permis de démontrer que la birnessite n'agit pas seulement comme échangeuse cationique envers NH4+. En effet, l'analyse de surface réalisée par XPS a montré que les spectres N1s sont caractérisés par l'existence de deux environnements différents : un attribuable à NH4+ dans le domaine interfoliaire et le second à une espèce N chimisorbée. Des transformations structurales et chimiques ont été observées sur la birnessite avec un déficit de bilan massique d'azote. L’analyse des espèces en solution : NH4+, Na+, Mn2+, NO3- et NO2- et solides (état d'oxydation moyen de Mn, capacité d'échange cationique, teneur en azote solide et évolution de symétrie identifiée par DRX et FTIR) indique sans ambiguïté que NH4+ réagit chimiquement avec la birnessite / In marine and sediments, the conversion of combined nitrogen to dinitrogen is traditionally assumed to take place via the coupled bacterial nitrification-denitrification process or through the anaerobic ammonium oxidation (anammox). But, the low ammonium concentrations observed in the Mn-oxide rich sediments suggested the existence of an alternative pathway that might take place via a chemical process. Among manganese oxide, birnessite was found to be the most existing form in soils and sediments. It is a lamellar oxide containing both Mn(III) and Mn(IV) in its structure and characterized by its high reactivity. This work aims to highlight the nature of the reactivity of the triclinic Na-birnessite synthesized via a redox method with ammonium. This interaction was suspected, in previous studies, to involve a cationic exchange mechanism only. The first part of this manuscript is dedicated to the synthesis of a pure phase birnessite via a redox process. The Mn(VII):Mn(II) ratio of 0.33 was chosen and three methods were used consisting in a quick mixing under vigorous stirring of two of the three reagents and then on the dropwise addition of the third one. The study of numerous reaction parameters (the order of reagent mixing, the addition time of the third reagent, the aging method, the nature of the cation used and the dissolved oxygen effect) highlighted the key role played by oxygen in the formation of a pure birnessite and a mechanism of formation has been proposed. The second part focused on the interaction of Na-birnessite with ammonium. The study of numerous reaction parameters (the initial ammonium concentration, the contact time, the pH and the temperature of the medium) by monitoring both solid and liquid changes allowed us to demonstrate that birnessite is not only acting as a cationic exchanger toward NH4+. Indeed, the surface analysis performed by XPS showed that N1s spectra are characterized by the existence of two different environments: one assignable to an interlayer NH4+ and the second to a chemisorbed N-species. Structural and chemical transformations were observed on birnessite with nitrogen mass balance deficit. The monitoring of NH4+, Na+, Mn2+, NO3- and NO2- and solid changes (average oxidation state of Mn, cation exchange capacity, solid nitrogen content and symmetry evolution identified by XRD and FTIR) indicate unambiguously that NH4+ reacts chemically with the birnessite