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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.
51

To investigate the effect of a change in hard gelatin capsule supplier on a phenytoin sodium capsule formulation

Marx, Amor January 2004 (has links)
Stability studies were undertaken at ambient (25ºC/60%RH) and accelerated conditions (40ºC/75%RH) to determine the effect of changing of hard gelatin capsule supplier on a phenytoin sodium (100 mg) capsule formulation. Three hard gelatin capsule suppliers: RP Scherer (Supplier A), Capsugel (supplier B) and Associated Caps (Supplier C) were used in the study. Capsules were analyzed just after filling of the capsules (T0), after 1 month (T1), after 2 months (T2) and after 3 months (T3) after being stored in securitainers under the above-mentioned conditions. The moisture content of the empty shells as well as the capsule contents were analysed at each time-point. The capsule disintegration time was recorded at each time point. Multi-point dissolution testing was performed at each time point to determine the release of the active substance in each case. Based on the achieved results, the best capsule shell supplier was recommended, and other suggestions were made to improve the capsule formulation.
52

Preparation and characterisation of nanocomposites of biomass and montmorillonite clay for use as biofuels

Nyamutswa, Lavern Tendayi January 2014 (has links)
The aim of the study was to prepare composites of clay and biomass which burn longer than unmodified biomass. Montmorillonite clay was converted to mono-ionic clay by ion exchange with sodium using sodium chloride solution. The mono-ionic clay was organically modified with an organic surfactant, methyl triphenyl phosphonium bromide. Nanocomposites were then prepared by combining the modified forms of the clay with sawdust. The three forms of clay used for the formation of composites were unmodified montmorillonite, mono-ionic montmorillonite and organically modified montmorillonite. The solution blending method was used to make the nanocomposites. FT-IR and XRD analysis showed that organic surfactant increases the interlayer space of the clay since it is bulkier than the inorganic cations that are naturally present in the interlayer space of montmorillonite. The combination of clay and sawdust resulted in the formation of exfoliated nanocomposites as shown by the absence of peaks in the low 2 theta angle in the x-ray diffraction data of the nanocomposite. The nanocomposite which was made from sawdust and 1% organically modified clay showed the best results in terms of burning time and thermal stability, as well as giving a calorific value closest to unmodified sawdust and the least amount of residue.
53

Ethanol production from lignocellulosic sugarcane leaves and tops

Dodo, Charlie Marembu January 2014 (has links)
Various methods for the production of bioethanol using different feedstocks have been researched on. In most work on bioethanol synthesis from sugar cane, tops and leaves have been regarded as waste and generally removed and thrown away. In this work, lignocellulosic sugarcane leaves and tops were not discarded but instead used as biomass to evaluate their hydrolyzate content. The leaves and tops were hydrolysed using different methods, namely concentrated acid, dilute acid pre-treatment with subsequent enzyme hydrolysis and compared with a combination of oxidative alkali pretreatment and enzyme hydrolysis. Subsequent fermentation of the hydrolyzates into bioethanol was done using the yeast saccharomyces cerevisae. Acid hydrolysis has the problem of producing inhibitors, which have to be removed and this was done using overliming with calcium hydroxide and compared to sodium hydroxide neutralization. Oxidative alkali pre-treatment with enzyme hydrolysis gave the highest yields of fermentable sugars of 38% (g/g) using 7% (v/v) peroxide pre-treated biomass than 36% (g/g) for 5% (v/v) with the least inhibitors. Concentrated and dilute acid hydrolysis each gave yields of25% (g/g) and 22% (g/g) yields respectively although for acid a neutralization step was necessary and resulted in dilution. Alkaline neutralization of acid hydrolyzates using sodium hydroxide resulted in less dilution and loss of fermentable sugars as compared to overliming. Higher yields of bioethanol, 13.7 (g/l) were obtained from enzyme hydrolyzates than 6.9 (g/l) bioethanol from dilute acid hydrolyzates. There was more bioethanol yield 13.7 (g/l) after 72h of fermentation with the yeast than 7.0 (g/l) bioethanol after 24h. However, the longer fermentation period diminishes the value of the increase in yield by lowering the efficiency of the process.
54

Ni(II) and Pb(II) dithiocarbamate complexes as precursors for the synthesis of HDA-capped NiS and PbS nanoparticles

Chintso, Thobani January 2015 (has links)
Ni(II) and Pb(II) dithiocarbamate complexes were synthesized and characterized by elemental analysis, UV-Vis, FTIR and TGA and some of the Ni(II) complexes and one Pb(II) were further analyzed by 1H-NMR and 13C-NMR spectroscopy. Generally all the dithiocarbamate ligands are soluble in water while the complexes were soluble mostly in solvents such as chloroform, toluene, DMSO and DCM. Based on the elemental analysis, the dithiocarbamate complexes are formulated as four coordinate (tetrahedral or square planar) compounds. However, the FTIR showed that each of the dithiocarbamate ligands acted as bidentate ligand through two sulfur atoms. The TGA of the most complexes showed one major decomposition step to give respective metal sulfide above 200 oC. In this research project, dithiocarbamate complexes were used as single source precursor for the synthesis of metal sulfide nanoparticles. We studied the optical and structural properties of metal sulfide nanoparticles using UV-Vis, photoluminescence (PL), powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorption spectra of the metal sulfide nanoparticles are blue shifted in respect to bulk material and they also showed broad emission. The XRD of the NiS nanoparticles were indexed to the cubic and rhombohedral phase, with crystallite sizes of 15 - 18 nm. The XRD of PbS nanoparticles were indexed to the face centered cubic and cubic rock salts, with the crystallite sizes 12 - 18 nm. The TEM images of the metal sulfide nanoparticles showed particles with spherical and rectangular shapes with crystallite sizes 4 - 35 nm.
55

The characterization and electrochemistry of dye-sensitized solar cells

Caga, Noloyiso January 2013 (has links)
In this study a presentation of the technology behind dye-sensitized solar cells, their design as well as the role of the different parts of the cell. The characterization of the cell is divided into four sections namely: the characterization of the paste required to make the TiO2 film and its optical properties using SEM-EDX and XRD analytical techniques; Analysis of the various absorptions of three Ru-based dyes using UV-Vis spectroscopy, Photoluminescence and Fourier Transform Infra-Red spectroscopy; the characterization and the analyses of the entire cell using Electrochemical Impedance Spectroscopy. The nine cells were prepared by examining RuL2(CN)2 , RuL2(NCS)2 or N3 dye and RuL2(NCS)2 TBA+ or N719 dye. [L = 2,2'-bipyridyl-4,4'-dicarboxylic acid ;TBA = tetra-butyl ammonium] were combined with three electrolytes namely: Z–150 , AN–50 and PN–50. The Iodolyte PN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called propionitrile (PN). The Iodolyte AN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called acetonitrile (AN). The Iodolyte Z–150 is an iodide based low viscosity electrolyte with 150 mM of tri-iodide dissolved in a solvent called 3-methoxypropionitrile (MPN) and with additives such an ionic liquid, malkylbenziimidazole and guanidine thiocyanate. A solar simulator was utilized with which the standard solar irradiation can be created in laboratory conditions. The fill factors as well as overall performance efficiencies of the these cells are quite low < 1.0%,.
56

Investigation into the characteristics and possible applications of biomass gasification by-products from a downdraft gasifier system

Melapi, Aviwe January 2015 (has links)
Biomass gasification has attracted the interest of researchers because it produces zero carbon to the atmosphere. This technology does not only produce syngas but also the byproducts which can be used for various application depending on quality.The study conducted at Melani village in Alice in the Eastern Cape of South Africa was aimed at investigating the possible applications of the gasification byproducts instead of being thrown away. Pine wood was employed as the parent feedstock material for the gasifier. Biomass gasification by-products were then collected for further analysis. The studied by-products included tar(condensate), char, soot and resin. These materials were also blended to produce strong materials.The essence of the blending was to generate ideal material that is strong but light at the same time.The elemental analysis of the samples performed by CHNS analyser revealed that carbon element is in large quantities in all samples. The FTIR spectra showed almost similar results for all the studied samples, since the samples are end products of lignocellulosegasification. SEM gave the sticky images of resin as well as porous char structures. Char showed a higher heating value of 35.37MJ/Kg when compared to other by-products samples.
57

Isolation, Characterisation, and biological activity evaluation of essential Oils of Cymbopogon validus (Stapf) Stapf ex Burtt Davy and Hyparrhenia hirta (L.) Stapf

Rungqu, Pamela January 2014 (has links)
Cymbopogon validus and Hyparrhenia hirta belong to the Poaceae botanical family. Both plants are used as thatching material; H. hirta is also used for weaving mats and baskets. In this study, we investigated the anti-inflammatory effects of C. validus and H. hirta essential oils on fresh egg-albumin induced edema on Wistar rats. To fully understand the chemically induced anti-inflammatory properties of these plants, we first analyzed the chemical composition of the essential oils. The essential oils were analyzed using gas chromatography-mass spectrometry (GC-MS). In C. validus, 13 compounds accounted for 74.3% of fresh leaves oil, 14 compounds 71.8% of dried leaves oil and 12 compounds 73.3% of flower oil were identified from the GC-MS Chromatogram. The percentage yields were as follows fresh leaves oil 2.2%, dried leaves oil 2.0% and flower oil 2.4% v/w respectively. Linalool (3.2-29.6%) and northujane (4.4-16.9%) were the dominant compounds found in the 3 oils analyzed. While, α-terpineol 37.5% and verbenone 13.5% was only found in the fresh leaf oil, this was absent in the dried leaves oil and the flowers oil of C. validus. In H. hirta, 25 compounds accounted for 68.1% of fresh leaves oil, 40 compounds 71.9% of dried leaves oil, 23 compounds 77.6% of fresh flowers oil and 18 compounds 80.1% of dried flowers oil were identified from the GC-MS Chromatogram. The percentage yields obtained from the different parts were 3.4% for fresh leaves oil, 2.8% for dried leaves oil, 2.8% for fresh flowers oil and 0.7% for dried flowers oil v/w respectively. Northujane (8.5-30.0%), diisooctyl phthalate (4.4-26.5%), phytone (1.1-10.4%) were the dominant compounds found in the 4 oils analyzed. While, dibutyl phthalate 26.9% was only found in the fresh flowers and was absent in the dried flowers oil. Moreover, caryophyllene oxide (1.7-9.6%) was found in fresh leaves and dried flowers oil of H. hirta. In vivo analysis revealed that the two essential oils displayed significant edema inhibition effect overtime. They displayed strong anti-inflammatory properties when compared to control group. However, the H. hirta essential oil was more effective than that of C. validus. Linalool, α-terpineol, and northujane extracted from C. validus and H. hirta essential oils might have contributed to the anti-inflammatory effects observed in Wistar rats. This study, confirms the anti-inflammatory properties of C. validus and H. hirta suggesting that they may be used in diseases related to anti-inflammation.
58

Development of a bench scale single batch biomass to liquid fuel facility

Zhang, Yusheng January 2014 (has links)
The research described in this dissertation was motivated by the global demand for energy that is not dependent on coal, oil, natural gas and other non-renewable fossil fuels. The technology used in this project is related to the use of biomass to produce a viable alternative to conventional sources of fuel. A bench scale biomass to liquid (BTL) facility was built and tested. This produced results confirming the feasibility of the BTL process. The findings of the pilot study outlined in this dissertation justified the conclusion that the next step will be to expand the capacity and productivity of the BTL pilot plant to an industrial scale. Biomass comes from a variety of renewable sources that are readily available. In this case, the material used in the fixed bed biomass gasification facility to generate wood gas was agricultural and forestry waste, such as straw and wood chips. The gasifier had the capacity to produce up to 10 cubic metres/hr of gas with a carbon monoxide and hydrogen content of between 20–40% by volume, when it was operated at ambient pressure and with air as the oxidizer. The gas, produced at a temperature above 700º C, was cooled in a quench/water scrubber in order to remove most of the mechanical impurities (tars and water-soluble inorganic particles), condensed and dried with corn cobs before being compressed in cylinders at over 100 bar (g) for use in the Fischer-Tropsch Synthesis (FTS). The syngas was subjected further to a series of refining processes which included removal of sulphur and oxygen. The sulphur removal technology chosen entailed applying modified activated carbon to adsorb H2S with the help of hydrolysis in order to convert organic sulphur impurities into H2S which reduced the sulphur content of the gas to less than 5 ppbv. Supported cobalt catalyst (100 grams), were loaded into a single-tube fixed bed FT reactor with an inner diameter of 50 mm. The reactor was fitted with a heating jacket through which, heated oil ran to cool the reactor during a normal reaction occurring at < 250 ºC, while nitrogen was used in the heating jacket during reduction, which occurred at temperatures up ~ 350 ºC. The FTS reaction was carried out at different pressures and temperatures. Liquid and wax products were produced from the facility. The properties of the liquid and solid hydrocarbons produced were found to be the same as FT products from other feed stocks, such as natural gas and coal.
59

Preparation of photocatalytic TiO₂ nanoparticles immobilized on carbon nanofibres for water purification

Nyamukamba, Pardon January 2011 (has links)
Titanium dioxide nanoparticles were prepared using the sol-gel process. The effect of temperature and precursor concentration on particle size was investigated. The optimum conditions were then used to prepare carbon and nitrogen doped titanium dioxide (TiO2) nanoparticles. Doping was done to reduce band gap of the nanoparticles in order to utilize visible light in the photocatalytic degradation of organic compounds. A significant shift of the absorption edge to a longer wavelength (lower energy) from 420 nm to 456 nm and 420 nm to 428 nm was observed for the carbon doped and nitrogen doped TiO2 respectively. In this study, the prepared TiO2 photocatalyst was immobilized on carbon nanofibres to allow isolation and reuse of catalyst. The photocatalytic activity of the catalyst was tested using methyl orange as a model pollutant and was based on the decolourization of the dye as it was degraded. The doped TiO2 exhibited higher photocatalytic activity than the undoped TiO2. The materials prepared were characterized by XRD, TEM, SEM, FT-IR, DSC and TGA while the doped TiO2 was characterized by XPS, ESR and Raman Spectroscopy.
60

Development of a visible light active, photo-catalytic and antimicrobial nanocomposite of titanium dioxide and silicon dioxide for water treatment

Mungondori, Henry Heroe January 2012 (has links)
The aim of this study was to prepare composite materials based on titanium dioxide (TiO2) and silicon dioxide (SiO2), and to evaluate their photo-catalytic and antimicrobial properties. Carbon and nitrogen doped TiO2nano-particles were prepared via a sol gel synthesis, which is a simple hydrolysis and condensation technique. In situ doping was carried out using glucose and urea as carbon and nitrogen sources respectively. Doping increased the spectral response of titanium dioxide photo-catalyst, allowing it to utilise the visible region which is much wider than the UV region (about 40 % of the solar spectrum), thus making it a more efficient photo-catalyst. The carbon and nitrogen doped TiO2-SiO2nano-particles were immobilized on glass support material to allow for easy separation of the spent photo-catalyst after the photo-degradation process. Tetraethyl orthosilicate (TEOS) was employed as both a binder and precursor for silicon dioxide. A mixture of TiO2 and TEOS in a 1:1 ratio was allowed to polymerize on a glass support which had been treated with hydrofluoric acid to introduce OH groups. The prepared photo-catalytic material was characterized by FT-IR, XRD, DRS, TEM, EDX, and BET analyses. Carbon was found to be more effective as a dopant than nitrogen. It brought about a band gap reduction of 0.30 eV and a BET surface area of 95.4 m2g-1 on the photo-catalyst as compared to a gap reduction of 0.2 eV and surface area of 52.2 m2g-1 for nitrogen doped TiO2. On the other hand, introduction of SiO2 allowed utilization of visible light by the TiO2-SiO2 nano-composite leading to an improved rate of photo-degradation of both methyl orange and phenol red. However, the immobilization of TiO2 on support material made it less effective towards inactivation of E. coli ATCC 25922 bacterial cells when compared to powdered TiO2 which was able to inactivate about 98 % of the bacterial cells within an hour of treatment.

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