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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development of an optimized process for commercial production of (-) ambrafuran

Mongwe, Joy 11 May 2016 (has links)
Dissertation submitted for the qualification Master of Science in Molecular and Cell biology (full time) University of Witwatersrand 01 February 2016 / Ambergris is a large lump excreted by whales, when exposed to sunlight, air and sea water, it oxidatively decomposed through inorganic reactions to form different compounds including (-) ambrafuran. (-) Ambrafuran is a highly fragrant compound and it is considered to be a stronger perfume ingredient than other constituents in ambergris. It is used as a fixative agent to stabilize perfumes by reducing the rate of evaporation of volatile substances. A two-step process for production of (-) ambrafuran starting from sclareol was developed at CSIR for an industrial partner, Teubes cc. The current commercial production of (-) ambrafuran entails a chemical process consisting of at least 8 steps and require very harsh chemicals and elevated temperatures. In the current study, relevant technologies for the optimization of a process for commercial production of (-) ambrafuran were investigated. The project objective has been to optimize fermentation conditions on laboratory scale for the conversion of sclareol to an intermediate diol using the microorganism Hyphozyma roseoniger and to subsequently test different zeolites for conversion of diol to (-) ambrafuran. Production of ambradiol was achieved in potato dextrose broth media in 13 days compared to a patented method which took 16 days. The method was also scaled-up in a 2 L fermentation bioreactor and the yield of 93% was achieved after 24 hours of reaction. Following the initial use of the zeolite CBV320, two new zeolites (CFG-1 and ZD0614) were identified which have the potential to convert ambradiol to (-) ambrafuran without undergoing an activation process. Zeolite CFG-1 have been recognized to be highly effective for converting the intermediate ambradiol to the resulting (-) ambrafuran. One of the greatest outcomes of this research project is that the amount of zeolite required per substrate has been reduced from between 1:6 and 1:9 to 1:2. The substrate concentration has been increased from 5 mg/mL to 100 mg/mL which also resulted in the reduction of the volume of solvent required for the cyclodehydration step. The study allowed for scale-up and following further optimisation on larger scale should result in a process on commercial scale.
2

An analysis of stone tool use in the Maya coastal economies of Marco Gonzalez and San Pedro, Ambergris Caye, Belize /

Stemp, William James. January 2000 (has links)
No description available.
3

An analysis of stone tool use in the Maya coastal economies of Marco Gonzalez and San Pedro, Ambergris Caye, Belize /

Stemp, William James. January 2000 (has links)
The Maya sites of Marco Gonzalez and San Pedro are located on the southern end of Ambergris Caye, a limestone-based coral island off the coast of modern-day Belize. When combined, the archaeological settlements at these sites represent some of the longest occupations in coastal Belize. Evidence suggests the earliest occupation occurred at Marco Gonzalez in the Late Preclassic and extended into the Late Postclassic, while San Pedro's population thrived well into the Historic period. An analysis of the stone tools recovered from excavations at Marco Gonzalez and San Pedro and a study of the use-wear patterns on these artifacts has revealed that the Maya from both sites were primarily engaged in subsistence-based activities with a limited amount of small-scale craft production. Use-wear evidence suggests that the majority of these activities focused on the exploitation of local resources necessary in everyday Maya life. The activities included the acquisition of seafoods such as fish and molluscs, and the preservation and/or processing of fish and other marine by-products, such as shell, coral, and stingray spines for both local use and trade. As consumer sites, the Caye inhabitants offered many of these products in exchange for stone tools produced in mainland workshops, such as Colha, in the 'chert-bearing zone' of Northern Belize. In addition to the local and regional trade of marine resources and salt, the sites of Marco Gonzalez and San Pedro served as transshipment points for the long-distance exchange of valuable wealth or prestige goods along the coast. The large inland site of Lamanai likely served as ally and trade partner with these sites based on archaeological evidence for socioeconomic and sociopolitical ties between this mainland centre and the smaller Caye settlements. This relationship assisted the Maya from southern Ambergris Caye in surviving the breakdown in trade relations and depopulation that plagued other Maya centres in the Late to Terminal

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