The purpose of this study was to characterize the catalytic activity of rhenium trioxide and rhenium trichloride as hydrogenation catalysts. Work was also undertaken to further study the catalytic properties of rhenium heptoxide. The activity of this latter compound had received some study in a previous project. A complete review of the literature has been made on the organic and inorganic chemistry of rhenium trioxide and rhenium trichloride. A survey of the literature on catalytic hydrogenation and the chemistry of rhenium heptoxide has also been included. Rhenium trioxide was prepared by three similar methods. The first two involved the formation of a complex between rhenium heptoxide and anhydrous dioxane. The complex was isolated and subsequently decomposed by gentle heating to give the pure trioxide. The third method employed tetrahydropyran as a complexing agent. The complex was isolated and decomposed in the same manner as previously indicated. All three methods appeared to give the trioxide in high purity, and little difference was apparent in their catalytic activities. Rhenium heptoxide and rhenium trichloride were commercially available, and thus required no special preparation. Both were generally reduced in situ to the active catalyst. In three instances rhenium heptoxicid was reduced ex situ. It was found that the in situ derived catalysts were generally more active than those derived ex situ. All reductions were carried out in a high pressure hydrogenation vessel. The reduction products were analyzed in a gas chromatograph, by refractive indicies, distillation and/or chemical extraction. Catalysts were analyzed by dissolving in concentrated nitric acid or a 30% hydrogen peroxide and ammonia solution. The resulting perrhenate was precipitated from the solution with tetraphenylarsonium chloride. Generally the analytical data obtained was not of sufficient accuracy to determine the exact chemical structure of the catalyst. The activities of the catalysts were determined by performing a large variety of hydrogenations. Results indicated that the heptoxide and trioxide derived catalysts were generally very similar in their catalytic activities. The trichloride proved to be slightly lower in its activity than the oxides. The catalysts used in this study generally required slightly more drastic conditions for the reduction of a carbonyl group than was generally necessary for a rhenium derived catalyst. The reduction of cyclohexanone was catalyzed at 123° with rhenium tioxide, while the heptoxide and trichloride required temperatures of ca. 150°. The olefinic compounds such as 1-hexene were reduced at temperatures of 95-100°, while styrene required slightly higher conditions due to its conjugation with the benzene ring. Nitro compounds and benzenoid compounds were found the most difficult to reduce with the trioxide and trichloride derived catalysts. Nitrobenzene yielded aniline only under temperatures of 226-275° depending on the catalyst used. Benzene yielded slight reduction with the trichloride catalyst at 200°. The trioxide, heptoxide and trichloride catalysts were outstanding in their ability to reduce the carboxylic acids. In most cases reduction could be effected 150-160°. The catalysts were superior to any reported in the literature for the reduction of the cargoxyl group. Most rhenium catalysts exhibit this high activity toward the carboxyl group to some extent. The oxide catalysts were also found to possess an extremely high activity toward the hydrogenation of amides and anilides. The reduction generally took place at ca. 225° giving a good yield of the primary amine in most cases tried. These catalysts compared very favorably with the better catalysts reported in the literature.

No description available.

<p>By studying the boron isotope composition of marine carbonates, the effectiveness of the tracer to reconstruct the ancient seawater pH and, in turn, atmospheric pCO₂ can be assessed. The boron isotope-pH proxy relies on the hypothesis that only B(OH)₄^-, which has a known boron isotope composition with respect to pH, is incorporated into the carbonate crystal lattice. This research synthesized inorganic aragonite from a range of stable pH values to quantify the dependence of aragonite <em>δ</em>¹¹B on the pH of the precipitating solution. The increasing boron isotope composition of aragonite with increasing pH is consistent with sole incorporation of B(OH)₄^- into the carbonate. The sensitivity of the acid dissociation and isotope equilibrium constants make it difficult to confirm whether or not B(OH)₄^- is the only species contributing to the boron isotope composition of aragonite. The relationship between the boron isotope composition of marine carbonates and ocean pH has wide appeal and, if properly understood, could provide tremendous insight into the history of Earth’s climate.</p> <p>This research also evaluated carbon isotope fractionation between aragonite and dissolved inorganic carbon (DIC) in high ionic strength systems at 25 °C and found it to be consistent with carbon isotope fractionation in low ionic strength environments. The analysis of various isotopic compositions within this study led to the development of new methodology to simultaneously measure the oxygen isotopes of water and carbon isotopes of DIC from small solution samples using continuous flow isotope ratio mass spectrometry (CF-IRMS).</p> / Master of Science (MSc)

I investigated the use of nitrogen isotopes as a tracer of sewage contamination on coral reefs. Sewage is isotopically distinct from marine nitrogen, allowing its use as a tracer in this environment. Emphasis was placed on sampling modem coral tissues, as modern coral reefs are in a rapid state of decline, possibly as a result of sewage contamination. Samples were collected in Zanzibar for two separate studies. The first study involved sampling over a depth/light gradient on large coral heads. These data, when combined with data from Jamaica, show light is a controlling factor on the nitrogen isotopic composition of coral tissue. Regression of delta15N of coral tissue with depth/light attenuation explains 75-90% of the variance. Results indicate increased fractionation with depth, which is related to the symbiotic nature of corals. Light-sufficient, nitrogen-limited zooxanthellae ( in the coral tissue ) must diffusl! all available nitrogen, and there is little fractionation. At depth, light-limited, nitrogen-sufficient zooxanthellae fractionate nitrogen during assimilation processes. These results have important implications for the use of nitrogen isotopes as a sewage tracer on reefs. In general, increased nutrients to the reef environment result in decreased water clarity, or lowered available light to the coral. This could lower the zooxanthellae's nitrogen requirements and allow fractionation (isotopic depletion). Corals have been shown to become reliant on heterotrophy in non-limiting nutrient conditions, related to loss of control over their zooxanthellae. This suggests the delta15N of their tissues would reflect their diet (and therefore the source of contamination). The counteractive effects of these two factors suggests it may not be possible to resolve the source of eutrophication to corals using the isotopic signatures of their tissue. That is, if the contamination gradient is coincident with a gradient in the symbiotic relationship (i.e. from nutrient limited to nutrient non-limited) or trophic status, there is little possibility of resolution of sewage effects. Results from the second sample suite from Zanzibar and a sample suite from Jepara Bay, Indonesia confirm this hypothesis. Zanzibar samples were collected at a eutrophied and non-eutrophied reef, and show no significant difference between isotopic data. This may be a result of distance from source, or the counter-effects of light. At Jepara Bay, samples were collected along a contamination gradient, from 2 point source discharges. Isotopic data show significant change along the gradient, with the entire bay eutrophied. Without delta15N from all potential nitrogen sources it is impossible to adequately conclude whether sewage was the contaminant using isotopes. Other data collected from these reefs do support the interpretation of anthropogenic contamination. These data include decline in coral and fish communities (determined using biological assays, Zanzibar), and increased heavy metal and chlorophyll-a concentrations (Jepara). One control on nitrogen isotope composition of modern corals was identified, and others suggested. Results will remain enigmatic until sample suites including complete water chemistry, source chemistry, and light regime are interpreted. / Thesis / Master of Science (MSc)

The isotopic fractionation of sulphur in the plant metabolism of sulphate by chlorella was investigated; and for this purpose an apparatus was devised for growing chlorella under sterile conditions. A green alga from the shores of Lake Erie, and mustard plants from the field were also investigated. No isotopic fractionation was found in the plant metabolism of sulphate either in the laboratory or in nature. A new method for the reduction of sulphate to hydrogen sulphide was also developed. / Thesis / Master of Science (MS)

Teotihuacan, Mexico, is an example of an early city that supported a substantial population in the absence of large, domesticated animals. This dissertation examines the diverse animal acquisition strategies employed by Teotihuacan’s inhabitants as part of the urban subsistence economy during its apogee (c. 200-550 CE). It integrates zooarchaeological methodologies with proteomic and isotopic techniques to analyze faunal material recovered from Tlajinga and Tlailotlacan, two neighborhoods on the urban periphery. The study has three components. The first component employs Zooarchaeology by Mass Spectrometry (ZooMS) to examine the archaeological remains of birds at Tlajinga. It presents the first major set of avian collagen peptide biomarkers and demonstrates the utility of ZooMS for identifying birds to family and sub-family levels. This technique provides the means to categorize archaeological bird remains, which demonstrates that the residents of Tlajinga had access to a diversity of aquatic birds, illustrating lake exploitation in Teotihuacan’s urban subsistence. The second component analyzes excavated animal remains in two adjacent apartment compounds in the Tlajinga district to understand urban subsistence. It documents how animal consumption varies over space, while controlling for factors that affect taxonomic composition, such as depositional context, excavation strategies, wealth, and cultural affiliations. It appears that the variability found among different faunal assemblages at Teotihuacan may be due to local hunting practices and the choice of which activity areas of the residential compounds were excavated, rather than wealth differences among households. The third component examines the role of animals in the urban economy of Tlailotlacan and Tlajinga using new isotopic data from turkeys, deer, rabbits, and hares. The residents of these two neighborhoods employed diversified strategies to acquire wild animals for urban consumption from multiple natural and anthropogenic niches around the city. Hunting and trapping wild animals was supplemented with lake resources from the extensive lacustrine system in the Basin of Mexico, and small-scale turkey husbandry. Overall, Teotihuacan’s animal economy is relevant to understanding diversity in global urban subsistence systems; it reflects a diversified system of animal production at the household level, distinct from the specialized, and often institutionalized, large-animal economies that supported preindustrial Afro-Eurasian cities. / 2024-10-03T00:00:00Z

Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) in human tissues, which reflect the stable isotope composition of the diet, offer numerous applications in the field of nutrition. One of the biggest contributors to uncertainty in stable isotope dietary reconstruction applications is potential variability in the isotopic composition of foods. No prior studies have evaluated the existing food carbon and nitrogen stable isotope data in an effort to determine broad-scale patterns and characterize the degree of variability of stable isotopes within the American diet. The purpose of this investigation was to improve our understanding of the isotopic composition of the modern American food supply by 1.) Determining geographically representative means and inter-sample variability of animal foods 2.) Assessing the impact of cooking on food stable isotope composition.To define the range of δ¹³C and δ¹⁵N values of animal proteins within the American food supply, we analyzed nationally-collected milk, fish, and shellfish samples from the USDA’s National Nutrient Database for Standard Reference and compared these to previously published data from the international literature. USDA milk samples were characterized by low overall variability, although regional variations in δ¹³C values were present. In contrast, seafood samples exhibited high overall variability but were consistent throughout the domestic and international samples. No variations in δ¹³C or δ¹⁵N values were detected throughout the baking or fermentation process in yeast buns or cookies. The representative values determined in this study can be used as a foundation for interpreting the stable isotope composition of the American diet. / Master of Science

This paper discusses the development of a microprocessor-based instrument to measure boron concentration in the cooling water of a pressurized water reactor. The technique used to develop the boronimeter is neutron transmission entailing the use of a neutron source and a bank of detectors to measure the absorbed neutrons in a sample of borated water. A unique feature of the boronimeter is the inclusion of a servo-operated absorber sleeve which is automatically positioned to compensate for changes in boron concentration. The sleeve is positioned to keep the count rate constant and the position of the sleeve is then used to determine the concentration of the sample. The null operation feature makes the boronimeter particularly adaptable to on-line operations owing to the improved counting statistics. Tests completed on the boronimeter demonstrate its usefulness for accurate, rapid analysis of boron concentration. The system was calibrated over the concentration range 0-2500 ppm boron. At a concentration of 1000 ppm the standard deviation was ± 2% for an analysis time of < 4 minutes. / Master of Science

No / Although the origins of domestic animals have been well-documented, it is unclear when livestock were first exploited for secondary products, such as milk. The analysis of remnant fats preserved in ceramic vessels from two agricultural sites in central and eastern Europe dating to the Early Neolithic (5900-5500 cal BC) are best explained by the presence of milk residues. On this basis, the authors suggest that dairying featured in early European farming economies. The evidence is evaluated in the light of analysis of faunal remains from this region to determine the scale of dairying. It is suggested that dairying ¿ perhaps of sheep or goats ¿ was initially practised on a small scale and was part of a broad mixed economy.

No / This study presents the results of an isotopic analysis of nine naturally mummified individuals—three adults, two adolescents, one juvenile, and three infants—recovered from the Hets Mountain Cave site in southern Mongolia, where they had been secondarily deposited. All of the individuals show evidence of violent perimortem trauma, but no skeletal indicators of nutritional or disease-related stress. Multi-isotopic data (δ13C, δ15N, δ18O, 87Sr/86Sr, and 20nPb/204Pb) were characterized in multiple tissues from each individual when possible, in order to reconstruct diet composition and residential origin at different points in life. Specifically, δ13C and δ15N in bone carbonate and collagen (N = 8) and hair keratin (N = 4) were coupled with enamel carbonate δ18O and δ13C (N = 3) and enamel 87Sr/86Sr, and 20nPb/204Pb (N = 3) to assess diet and residential mobility in relation to skeletal indicators of health and trauma. Results are consistent with a persistence of mixed C3/C4 pastoral subsistence and general stability of diet composition over the life course, in contrast to contemporary accounts of widespread famine and a dependence on grains imported from China throughout the region. However, results also suggest that at least some individuals may have migrated to this region of southern Mongolia from elsewhere during life, meaning that their dietary isotopic profiles may not represent local subsistence patterns near the Hets Mountain Cave site. Overall, these results speak to the utility of life course oriented multi-isotopic analysis in complementing more top-down historical analyses in understanding variation in subsistence, nutrition, and migration in regions undergoing significant political and economic turmoil.