Hydrochloric acid leaching of saprolite nickel ores has been proposed as an effective means of recovering nickel and cobalt. However, the leach produces a concentrated brine of magnesium chloride which must be hydrolyzed to recover the HCl lixiviant. The processing of carnallite similarly produces a concentrated MgCl2 brine; converting this brine into HCl and MgO provides an attractive way of adding value while effectively disposing of this waste product. Direct pyrohydrolysis of magnesium chloride brines by the reaction, MgCl2,a + H2Oa  MgOs + 2HClg is energy-intensive as large volumes of water must be evaporated. The energy cost is high, and the HCl stream produced is limited to approximately 20 wt% HCl. This thesis explores alternative methods of obtaining HCl from aqueous magnesium chloride solutions. Two methods are considered: the hydrolysis, under autogenous pressure, of concentrated MgCl2 molten salt hydrates; and the precipitation of magnesium hydroxychloride compounds such as 2MgO·MgCl2·6H2O and 3MgO·MgCl2·11H2O, which are subsequently decomposed at high temperature. Considerable experimental difficulties were encountered in studying pressure hydrolysis of molten salt hydrates, despite extensive equipment modifications. Ultimately, the work moved on to precipitation and decomposition of hydroxychlorides. This was found to bear promise, and conceptual flowsheets based on these reactions are presented. A phase stability diagram giving the areas of predominance of the different hydroxychloride phases is presented, and fundamental thermochemical data are derived. The results of a kinetic study on magnesium hydroxychloride thermal decomposition are also presented. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2011-03-11 10:14:53.455

Adrenomedullin (ADM) is a 52 amino acid vasodilator peptide isolated, in 1993, from human pheochromocytoma. It has been demonstrated in the adrenal medulla of several mammalian species, including humans and rats. There have been conflicting results of the tissue distribution in the adrenal cortex. Hypertension is a complex trait with multiple genetic and environmental influences. Furthermore, salt-sensitive hypertension is characterized by a cluster of renal, hormonal, and metabolic derangements that might favour the development of cardiovascular and renal complications. Therefore the objective of this study was to investigate the adrenal distribution of ADM as well as to semi-quantitatively assess the adrenomedullin secretory capacity of the adrenal gland in the rat model of salt sensitive hypertension. Fourty-four male weanling rats were divided into 4 experimental groups and placed on a dietary regimen for 6 weeks viz. Dahl salt sensitive (DSS) rats on a high sodium diet (8% NaCl), DSS on a normal sodium diet (1% NaCl) matched with normotensive Dahl salt resistant (DSR) rats on the same dietary treatments. Blood pressure was monitored by tail-cuff readings and by the end of the six weeks, the DSS rats developed hypertension with tachycardia irrespective of the diet they were fed. The normal sodium diet was found to delay the development of hypertension, whilst the high sodium diet exacerbated the development of hypertension. Kidney weights and heart weights were greater in DSS rats than DSR rats probably due to their renal pathology or cardiac hypertrophy. Adrenomedullin immunopositivity was found predominantly in the adrenal medulla, and to varying degrees in the zona glomerulosa and zona reticularis of the adrenal cortex. The semi-quantitative analysis indicate that there was a 6.3 fold increase in ADM content of DSS rats compared to the DSR rats, where both consumed the 1% NaCI supplemented diet (DSR : 5.98 ± 0.3 vs. DSS : 37.85 ± 0.5, P / Thesis (M.Sc.)-University of Durban-Westville, 2003.

No description available.

The effect of salinity on phosphorus (P) absorption kinetics by 'Russet Burbank' cv. potato propagated by tissue culture technique was studied in the laboratory. Nine clones of the cultivar were evaluated for their salt tolerance at the vegetative stage by using in vitro culture. Four concentrations of NaCl (0, 40, 80, and 120 mM) were used in the experiments. The first experiment was carried out to study the effect of salinity on P absorption by using radiophosphorus ($ sp{32}$P) as a marker. P absorption showed a quadratic relationship with time. In general, there was a significant reduction in P absorption as the NaCl concentration increased in the nutrient medium. However, the root tip concentration of $ sp{32}$P increased with increased salt concentration. When P concentration in the nutrient medium was increased, $ sp{32}$P activity was also increased with time at 120 mM salt concentration. The activity of radiophosphorus decreased on root tips when P concentration in the nutrient medium was increased to 2.5 mM P. The second experiment was conducted in tissue culture using nodal cutting bioassay. The plant morphological parameters of shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, and root dry weight were reduced for all nine clones as salinity increased. The clone PEI#1 (tu) exhibited high salt tolerance characteristics.

This study examines modern relationships among salt marsh plant species and their pollen in three salt marshes located on the northwest coast of the Bay of Fundy, New Brunswick. Linear regression analysis of pollen in 35 surface sediment samples and vegetation cover on small (<15 m) and broad (>15 m) scales show that, with the exception of Poaceae and Cheno Am, pollen corresponds well with fine-scale patterns of salt marsh vegetation. Scatter diagrams of paired pollen and cover data illustrate that cover of Triglochin is over-represented by its pollen, Glaux is under-represented, and Poaceae, Cheno Am, and Plantago are inconsistent. Tidal mixing and differential inputs from local, regional, and extra-regional sources with elevation limit the establishment of plant-pollen relationships for Cheno Am and Poaceae but not for other taxa. Comparison of 35 modern analogs from five vegetation zones using squared chord distance show that zones are distinct such that the marsh-terrestrial interface can be tracked with the greatest degree of certainty in a salt marsh paleo-ecological record and other marsh zones can be tracked when a conservative threshold of dissimilarity is used.

This thesis presents the study of films derived from the reduction of aryldiazonium salts at gold surfaces. The properties of bare polycrystalline surfaces were investigated via the observation of the electrochemical oxidation and reduction of the gold. Films derived from diazonium salts were electrochemically grafted to the gold surface. The structure and stability of these interfaces was examined through the use of redox probes, gold oxide electrochemistry and water contact angle measurements. The spontaneous reduction of aryldiazonium salts at gold surfaces was investigated and the possible applications it presented towards printing and patterning of the gold surface with films were explained. Polycrystalline gold surfaces were prepared and subjected to various treatments, to observe the behaviour of gold oxide formation and reduction at the surface. Various effects on the surface structure were observed after treatment in solvents and electrolyte solutions. The surface structure of the gold atoms frequently changed due to the high mobilities of the gold atoms, and it is difficult to achieve a reproducibly stable surface. The electrochemical modification of gold surfaces via the reduction of aryldiazonium salts was investigated. Surfaces were modified with methylphenyl and carboxyphenyl films and exposed to various treatments. Monitoring the gold oxide reduction changes enabled the surface coverage of modifier directly attached to the surface to be calculated. The films appear to be stable, loosely packed and porous. The films are flexible in nature; redox probe responses showed reversible changes after repeated sonication in solvents of differing polarities and hydrophilicities. Contact angle measurements further support the notion of films that can reorganise in response to their environment. The spontaneous reduction of aryldiazonium salts at gold surfaces was observed. Film coverage was significantly lower at the spontaneously grafted surface than for films grafted electrochemically. Gold surfaces were successfully modified via microcontact printing, and surface coverages similar to the spontaneously grafted film were achieved. Microcontact printing was also used to pattern surfaces with films derived from diazonium salts. Feature sizes down to 100 µm were successfully achieved.

In order to understand and predict the geochemical conditions in Antarctic meltwater ponds during winter, the geochemical extremes in Bratina Island meltwater ponds over a seasonal cycle were determined and compositional variation related to key physical, chemical and biological processes. A high resolution record of vertical temperature gradients in Skua Pond during freezing, winter and thaw, highlighted a significant seasonal temperature variation (10.3˚C to -41.8˚C) driven by air temperatures and the release of latent heat of fusion. A conceptual model of freeze-thaw involved heterogeneous melting, and explained how the presence of an ice plug near the base of the pond supports the strong chemical stratification observed, which can persist throughout summer. The geochemistry of Bratina Island meltwater ponds was shown to be catchment specific with correlation between geochemical parameters within ponds, but not between ponds. Basal brines that develop during freezing were nearer in composition to the brines preserved during summer, than to those present immediately post-melting. This is due to mineral precipitation during winter removing selected dissolved ions. Therefore winter brine predictions should be based on mid-late summer conditions, and allow for existing geochemical stratification. Nutrient concentrations were vertically stratified, by the same physical processes controlling major ion concentrations. However, the relatively low nutrient concentrations meant that biological processes exerted little influence over winter brine geochemistry. FREZCHEM62 modeled winter brine compositions were consistent with those of brines present during progressive freezing. Predicted mineral precipitation was also consistent with the presence of halite (NaCl), mirabilite (Na₂SO₄.10H₂O), thenardite (Na₂SO₄), magnesite (MgCO₃), gypsum (CaSO₄), sodium carbonate (NaCO₃) and calcite (CaCO₃) in pond sediments. FREZCHEM62 can therefore be used with confidence to predict winter conditions, as long as a reliable initial bulk pond water composition is calculated, and limitations, such as the over-prediction of carbonate mineral formation, are borne in mind.

Feed intake is a key factor affecting pig performance; thus, the objective of these studies was to assess a variety of factors that could potentially affect intake in pigs in different production stages. Studies were conducted to determine the effects of flavor and diet complexity, Appetein™ (an alternative protein source), and graded levels of salt on swine feed intake and feed preference. Two newly developed flavors were used in nursery pig diets. The use of the two flavors did not increase feed intake (P > 0.05). Nursery pigs actually showed a preference for the control diet. Complex diet formulation does increase feed intake (P < 0.03) in nursery pigs when diets are not over-formulated. When flavor was added to lactation diets sow feed intake did not change compared to the control. The flavor did not affect litter performance (P > 0.05). When Appetein™ was added to lactation diets at 0.5%, pig weight and litter weight were numerically greater for the sows fed Appetein™ but not significantly so. Appetein™ did not affect feed intake. When nursery pigs were fed graded levels of salt (0.1, 0.5, and 0.8%) feed intake increased (P < 0.01) as salt level increased. Nursery pigs also preferred (P < 0.05) 0.8% salt over other levels the first two weeks after weaning when given a choice among diets.

It had been generally accepted that salinity adversely affects the growth of plants. This study examined how the salinity level affects the growth of H. jubatum. A green house study was conducted to determine the effects of salinity levels on growth, and anatomy of root and leaf of H. jubatum. One week-old seedlings were transplanted and grown on 10-cm plastics pots filled with sand at Ball State University green house. Plants were subirrigated with hydroponic solution Dyna gro liquid 9-7-5 (NPK) and 0%, 0.5%, 1 %, and 1.5% NaCl for each treatment. The solutions were changed bi-weekly, evaporation losses were replaced daily. After aproximately 45 days, randomly chosen plants were harvested, washed, measured and weighted, to determine their growth such as: root biomass, shoot biomass, shoot height, leaf lenght, and leaf width. Slides of root and leave tissues were prepared with microtechnic standard using rotary microtome and N-butyl alcohol series. Anatomical variables measured included; root diameter, stele diameter, ratio of stele to root, thickness of leaf at mid vein, diameter of vb in mid vein, diameter of metaxylem in midvein, thickness of leaf at second lateral vein (left and right), diameter of vb at second lateral vein (left and right). The slides then were potoghraped with Olympus camera. Statistical analysis supported that salinity significantly affected the growth, morphology, and anatomy of H. jubatum. / Department of Biology

Cultured tobacco cells (Nicotiana tabacum L., cv Wisconsin-38) were subjected to temporary sub-lethal heat and salt shock treatments to determine the effects of these treatments on various physiological parameters after subsequent lethal heat or salt stresses. Tobacco cells developed a tolerance to a non-permissive temperature stress (54C for 14 min) when pretreated with heat shock of 38C for 2h but not when pretreated at 42C for 2h. Cells pretreated at 38 (2h) exhibited less than 30% normal growth when the 54C stress came immediately after the 38C treatment. Tolerance to the 54C stress developed with increased interval between shock and stress with cells exhibiting 95% normal regrowth when the 54C stress was administered 8h after the 38C shock. The developement of heat tolerance was inhibited if heat shock was done in the presence of a non-injuring level of EGTA (.0.5mM). Cells treated with EGTA during heat shock grew normally at 23C but not after a 54C heat stress. EDTA (0.5mM) had little effect on the acquisition of tolerance to heat stress.Wisconsin-38 cells developed a tolerance to a non-permissive salt stress (2% NaCl for 16h) when pretreated at a lower salt level (1.2% NaCl) for 3h. Cells heat shocked at 38C exhibited increased tolerance of the lethal salt stress up to 8h. Conversely, cells heat shocked at 42C exhibited immediate tolerance to lethal salt stress and this tolerance decayed over eight hours. The heat shock-induced acquisition of salt tolerance was inhibited by both EGTA and EDTA.Proteins synthesized during heat and salt stress treatments were labeled with [35S]-methionine and/or [3H]-leucine and separated using Sodium dodecylsulfate polyacrylamide gel electrophoresis. Fluorographic analysis of the gels indicate that a number of proteins are produced in response to heat shock. Similar analysis of proteins from salt shocked cells indicates that no salt shock proteins are produced in response to a brief low-level sodium chloride shock.