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- ItemA Modal Approach To Price An Option In Continuous Time(KNUST, 2018) Osei AntwiAverage value options or Asian options have been priced using geometric and arithmetic averages of the underlying asset. However, these methods do not give accurate results especially in very low volatility regimes. In this study, we develop a new option pricing model based on the modal average of the underlying asset to price options. Using data from the NASDAQ in the United States of America we use the proposed model to price options sold on some stocks listed on the exchanges using software. The results consistently showed that for volatilities less than 3% of the underlying asset, the modal average option pricing model gives a better option price when compared to existing average option pricing models. Moreover, the modal average consistently does better at all levels of volatility when compared to the Black-Scholes model. We further proved analytically that the modal average model indeed does better than the geometric or arithmetic average models especially for low volatility stocks.
- ItemAn Integrated Approach To Buruli Ulcer Transmission Studies: From Aquatic Environments To Human Infection(KNUST, 2018-04) Charles QuayeBuruli ulcer (BU) is a debilitating skin infection usually of impoverished tropical rural populations. BU is caused by Mycobacterium ulcerans (MU), a pathogen described as a non-tuberculous mycobacteria (NTM). The exact mode of transmission of BU is not known and involvement of insect vectors including mosquitoes, animal and small mammal reservoirs and aerosols in transmission and dispersal has been proposed. A holistic approach to studies that involve NTM is proposed especially in transmission and control studies. This study related human MU infections to MU types in identified risk areas and establishing sources of human infections. Water body type preferences of members of the two most implicated insect families in BU transmission, Family Belostomatidae (Hemiptera: Heteroptera) and Family Naucoridae (Hemiptera: Heteroptera) collected from water bodies in Ghana and Cote d’Ivoire were also related to their probability of being involved in transmission of BU. Four BU endemic communities (Bepotenten, Sukuumu, Monia-Gyaman and Wromanso) in the Amansie Central District of the Ashanti Region of Ghana were selected for the study. Two hundred and twenty-four (224) questionnaires administered proportionally to population were used to elicit responses to water use and areas of contact, BU knowledge, animal contact and infection status. Ground truthing of the four communities and the capturing of geographical information allowed the reconciliation of questionnaire water contact points and the subsequent mapping to reveal all surface water contact points. M. ulcerans from environmental sources was detected using 16S rRNA and then IS2404 detections. M. ulcerans genetic material from both human BU cases and identified environmental sources were VNTR (viable number tandem repeats) typed at four loci (VNTR targets: MIRU1, Locus 6, ST1 and Locus 19. Swimming and bathing (p=0.04) in risk environments and the capture of squirrels (p=0.04) were associated with an increased in the risk of acquiring BU in the study communities (OR= 3.28 and OR=5.85 respectively). Rigorous activity in infected water was found to increase the risk of infection laying credence on a direct trauma infection route for M. ulcerans. VNTR typing of MU from human BU disease and environmental samples revealed localized infection with inhabitants mostly being infected from community associated water bodies. Four main VNTR types were detected in human disease MU based on number of copies of four loci: MIRU1, Locus 6, ST1 and Locus 19. These were ‘W’ (1,1,2,1), ‘X’ (1.1.2.2), ‘Y’ (1,2,2,1) and ‘Z’ (1,2,2,2) in the copy number order MIRU1, Locus 6, ST1, Locus 19. The ‘Y’ VNTR type was common to all communities being detected in human as well as environmental samples and is therefore the profile causing the most infections in the study communities. A total of 125 and 321 individual Naucoridae (Hemiptera: Heteroptera) and Belostomatidae (Hemiptera: Heteroptera) respectively were classified to at least genus level. Eight species of the Naucoridae were identified; Ctenopocoris africanus (Leach, 1815), Aneorocoris insolitus (Montandon, 1897), Laccocoris limicola (Stal, 1855), Laccocoris spurcus congoensis (Poisson, 1949), Neomacrocoris bondelaufa (Sites, 2015), Neomacrocoris vuga (Sites, 2015), Naucoris obscuratus (Montandon, 1913) and Neomacrocoris usambaricus (Montandon, 1913). Differences in habitat preference of the Naucoridae were observed. Naucoris spp and Laccocoris spp showed the least preference for lotic water bodies (p<0.05). Four genera of the family Belostomatidae; Abedus, Diplonychus, Lethocerus and Benacus, were identified in collections from 82 water bodies in Ghana and 7 water bodies in Cote d’Ivoire. Abedus spp were the most abundant and most widely distributed. Belostomatidae showed no preference to type of water flow (p=0.2068). The integrated approach of the study offered complementary information, observations and deductions which together enabled verifiable conclusions to be drawn on the transmission of the environmental mycobacterium. The use of few communities facilitated a more concentrated search for risk areas and their link to BU infections in the study communities. A study involving a higher number of communities in a similar geographical range is recommended. In insect transmission studies, individual species competence should be considered and generalizations minimized as species preferences to habitat are important especially in studies involving NTMs.
- ItemDehydration Characteristics, Quality Evaluation And Consumer Assessment Of Solar Dried Tomato.(KNUST, 2018-11-29) Mavis Owureku AsareTomato (Lycopersicon esculentum) is an important vegetable used in cooking most local foods in Ghana. At the peak season of harvesting, high loses are incurred because of the absence of facilities to process fresh tomato and extend the shelf life. Solar drying has been proven to be a more efficient and low cost method of enhancing quality and adding value to tomato and other vegetables. However, there are concerns on the usage, functionality and sensory appeal of the dried products by consumers. In this study a natural mixed mode solar dryer suitable for drying tomato was adapted and used to investigate the dehydration characteristics, quality and consumer acceptability of the dried products. An initial baseline survey was conducted using semi structured questionnaires administered to 395 randomly selected respondents in the Accra Metropolis. Information was obtained on the demographics, consumption pattern, knowledge and acceptance of tomato processing technologies and assessment of quality attributes of tomato. The efficiency of a passive solar dryer was evaluated and used in the processing of fresh tomato to powder. The processing involved the pre-treatment of 6mm slices of fresh roma tomato by dipping in (a) 1% potassium metabisulphite solution (b) 1 % ascorbic acid solution (1:1) for 10 minutes respectively. Untreated tomato slices served as control. Samples were then dried in the passives and in the open sun, with the open sun drying serving as control. The moisture content, moisture ratio and dehydration rate of solar dried tomato was assessed. The quality of dried tomato was assessed for their physicochemical, nutritional and microbiological characteristics. Physicochemical analysis involved determination of pH, total titratable acidity, dry matter, ash, tristimulus colour, total soluble solids, water activity and moisture. Nutritional quality was assessed for lycopene, beta-carotene, total carotenoid acids using high performance liquid chromatography (HPLC) procedures. Flowability, smoothness and compressibility (or packing porosity), particle size and shape distribution of the tomato powder was determined using a Morphologi G3-ID. Scanning electron microscopy of pre-treated solar and sundried tomato samples were imaged with an FEI Quanta 3D FEG scanning electron microscope. Quantitative Descriptive Analysis (QDA) was carried out to compare the sensory descriptive profiles of solar dried tomato powder with existing products on the market using a trained descriptive panel of nine (9). Home Use Test (HUT) was conducted using a trained panel to assess the acceptability of solar dried tomato powder in local foods. The results showed that, most consumers (74%) preferred tomato powder that was conveniently packaged to retain the characteristic intense taste and the flavour. The first day dryer efficiency of 24.2 % facilitated the drying process of tomato (final moisture content of 12-14%). The ash content was slightly higher in the sun-dried tomato (9.3 -10.14 %) compared with the solar dried tomato (9.4 - 9.68 %), an indication of potential contamination with extraneous materials from the environment. Water activity for solar dried tomato powder were significantly lower (0.35 - 0.38) than sundried tomato powder (0.53 - 0.57) and water activity lower than 0.6 is considered microbiologically safe for storage. Lower tristimulus colour L* values (37.81 - 40.31) observed for sun-dried tomato samples indicated that these samples were darker in colour than the solar dried samples with L* values (50.35 - 46.44). Aerobic mesophile counts were lower in solar dried (3.90 CFU/g) tomato pre-treated with potassium metabisulphite compared with sun-dried samples (4.85 CFU/g). Sulphur dioxide content (740.8 ppm) of solar dried tomato pre-treated with potassium metabisulphite was lower than the maximum legal limit (2000 ppm) recommended in fruits and vegetables, indicating its safety for human consumption. A strong, negative correlation between sulphur dioxide 740.9 ppm concentration and microbial load was observed for solar dried tomato. QDA results indicated a strong tomato aroma intensity (scored 127 out of 150) for solar dried tomato powder with the market samples having an extremely low intensity score of 0.7 out of 150 for tomato. Sensory profiling of the two products differed extremely in aroma, appearance and texture. Sensory characteristics of reconstituted solar dried tomato powder was similar to that of fresh tomato and tomato paste (two products commonly used in cooking). It had a very coarse appearance and texture (as predicted by the particle size distribution and shape profile and parameters of convexity and circularity) and a strong boiled/cooked aroma compared to tomato paste which had a higher intensity of red colour, metallic and stewed tomato concentrate aroma and flavour. Most of the participants used tomato powder to prepare local dishes such as “jollof “rice, tomato stew and light soup because of the good swelling characteristics of the product. The mixed mode solar dryer developed in this study was efficient in processing tomato powder which appealed to consumers and had varied uses in food production. The dryer has the potential of enhancing post-harvest loses, extending the shelf life of tomato and creating an alternative processing method which is simple and convenient.
- ItemGreen Approach To Metal Chalcogenide Semiconductor Nanomaterials: Syntheses And Characterization Of Cds, Pbs, Zns, Mns And Mnxzn1-Xs Nanoparticles(KNUST, 2018-07) Micheal Baah MensahMetal chalcogenide nanomaterials such as CdS, PbS, ZnS, MnS and MnxZn1-xS are very useful compound semiconductors with potential applications in sensing, bioimaging, drug delivery, data storage and photovoltaic devices as well as in catalysis. However, the syntheses of good quality nanomaterials usually include toxic chemical reagents and therefore limit their application and adaptation to large scale production. Castor oil and single source precursors (SSPs) are suitable alternative green reagents for the syntheses of undoped and doped metal chalcogenide nanocrystals. In this thesis, green syntheses of (i) CdS nanoclusters and PbS nanorods/belts via thermal decomposition of xanthate complexes in castor oil, and (ii) ZnS, MnS and MnxZn1-xS nanocrystals via the thermal decomposition of diricinoleate carboxylate and heterocyclic dithiocarbamate complexes in oleylamine are reported. The dopant (Mn) feed concentration was varied in the range 0 ≤ x ≤ 0.1. The CdS displayed a band gap of 2.63 – 2.84 eV and a strong emission in the near-UV (λmax = 393 nm) region and formed small clusters of nanocrystals with average particle size of 6.78 1.89 nm. The PbS nanocrystals showed variety of morphologies. The average width and length of the PbS nanorods observed were 22.2 ( 2.3) nm and 225.9 ( 23.3) nm respectively. The activation energy obtained for the growth of ZnS nanoparticles in oleylamine was 53.41 kJ/mol. Powder-X-ray diffraction (p-XRD) patterns showed that the ZnS and MnxZn1-xS nanocrystals synthesized by different precursor routes were sphalerite and the shift in the lattice parameter indicated distortion due to the incorporation of the Mn(II) into the ZnS. The MnS nanocrystals were pure alabandite. The p-XRD patterns of the nanocrystals synthesized by the dithiocarbamate route showed some wurtzitic characteristics of ZnS and MnxZn1-xS. The band gap energy was found to decrease with increasing Mn(II) dopant concentration which indicated the introduction of trap states into the forbidden zone of the host ZnS. Luminescence was observed for MnxZn1-xS (for x ≤ 0.01) nanocrystals at 587 – 599.7 nm characteristic of Mn 4T16A1 transition suggesting possible incorporation of the Mn(II) into the ZnS host lattice. Electron paramagnetic resonance (EPR) studies confirmed the presence of Mn(II) ions dispersed at substitutionary sites for x ≤ 0.01 MnxZn1-xS nanocrystals. However, at high concentrations of Mn dopant (≥ 0.01), the Mn(II) ions were found bound to the surface/interstitial sites in ZnS. Thus, useful morphologies and interesting properties of important metal chalcogenide semiconductors were achieved by the use of environmentally benign materials.
- ItemAn In Vitro Model of Endemic Burkitt’s Lymphoma (eBL) Pathogenesis; Cooperation of Plasmodium Falciparum and Epstein Barr Virus in DNA Damage Mediated Via Activation Induced Cytidine Deaminase.(2012-06-15) Ayivor-Djanie, ReubenPlasmodium falciparum (P. falciparum) and Epstein-Barr virus (EBV) infections are contributors in the pathogenesis of endemic Burkitt’s lymphoma (eBL), although the precise mechanism of their synergy remains elusive. Reports suggest that the role of P. falciparum is indirect, creating a permissive environment for the outgrowth of EBV. EBV on the other hand invades and immortalizes lymphocytes in vitro and upregulates activation-induced cytidine deaminase (AID), a DNA repair enzyme responsible for diversifying the antibody repertoire and a potent mutagen capable of inducing the genetic damage characteristic of eBL. It is yet to be shown how exposure to P. falciparum affects the expression of AID in lymphocytes. The aim of this work was to investigate the possible direct role of P. falciparum in eBL lymphomagenesis by exploring parasite-lymphocyte interactions and AID expression after exposure to P. falciparum and/or EBV. Malaria positive slides were examined for parasite-lymphocyte interactions and primary tonsillar mononuclear cells (MNCs) were co-cultured with RBCs infected with up to 5% parasitemia of the 3D7 strain of P. falciparum. Geimsa stained thin smears were made from these co-cultures and examined for parasite-MNC interactions over a five day period. No direct parasite-MNC interaction was observed from all slides examined. The levels of AID mRNA in MNCs was measured by qPCR after in vitro exposure to P. falciparum and/or EBV, and in the presence or absence of 2µg/ml cyclosporine. P. falciparum induced up to a 6-fold increase in AID over unstimulated controls, EBV induced a 13-fold maximum increase, and both pathogens together induced up to a 22-fold increase in AID. With cyclosporine, AID mRNA levels in the P. falciparum stimulated cultures remained unchanged. EBV alone induced a 22- fold increase in AID and both pathogens together induced a 42-fold increase in AID. DNA damage was estimated by Comet Assay and quantified with an algorithm from the Comet Assay Project Lab (CASP). DNA comets revealed that P. falciparum induced moderate DNA damage in MNCs with up to 5.6% and 10% DNA in tails of comets with and without cyclosporine respectively. Cultures stimulated with EBV recorded DNA damage of up to 16% and 13% DNA in tails of comets with and without cyclosporine respectively; and both pathogens induced DNA damage with up to 11% and 16% DNA in tails of comets with and without cyclosporine respectively. The levels of DNA damage in these cells correlated with AID levels and demonstrate that P. falciparum plays a direct role in eBL pathogenesis, by inducing AID expression to levels similar to that expressed in BL cells and cooperating with EBV to induce abnormally high levels of AID and DNA damage.
- ItemThe kinetics of mycolactone in relation to the microbiological, clinical and immunological responses to antibiotic therapy for mycobacterium ulcerans disease.(2014-11-20) Sarfo, Fred StephenBackground: Mycobacterium ulcerans is the causative agent for a chronic necrotising skin infection called Buruli ulcer. Pathology of the disease is closely linked with the elaboration of a unique lipid toxin, mycolactone, which has potent cytotoxic and immunomodulatory properties. In this study, assays were developed to detect and quantify mycolactone concentrations in tissues during curative antibiotic therapy in mice and in humans to understand its dynamics in pathogenesis and to explore its potential as a biomarker for diagnosis and monitoring of patients with Buruli ulcer disease on antibiotic therapy. The currently recommended antibiotic regimen for the management of Buruli ulcer is a combination of daily intramuscular injections of streptomycin and oral rifampicin for 8 weeks (RS8). This regimen was compared with streptomycin/rifampicin for 2 weeks followed by clarithromycin/rifampicin (RS2RC6) for 6 weeks in patients to determine the clinical and bacteriological effectiveness in a pilot study. Methods: Biopsies were obtained from infected human skin tissues and BALB/c mouse hind footpads before, during and after 8-weeks of rifampicin-containing combination antibiotic therapy. Lipids were extracted from tissues using organic solvents, mycolactone concentrations were measured using a cytotoxicity assay and mass spectrometry. Trends in mycolactone concentrations and clinical, bacteriological and immuno-histopathological responses were determined. Concentrations of cytokines in supernates of whole blood assays in humans or murine splenocytes after stimulation with mycobacterial antigens/T-cell mitogens were measured using ELISA. iv Results: Eighty-three patients with confirmed Buruli ulcer were randomized to RS8 or RS2RC6 and monitored for recurrence free-healing. Bacterial load in tissue samples before and after treatment for 6 and 12 weeks was monitored in samples obtained by 4mm punch biopsy by semi-quantitative culture. There was no difference in using RS8 or RS2RC6 with respect to healing rate or the proportion healed in each group after 4, 8, 12, 16, 20, 24 and up to 52 weeks. The success rate was 93% in each group and there was no recurrence after 12-month follow-up. There was no difference in the number of bacteria cultured at the different time points for the two regimens. Mycolactone was detectable in 92% and 77% of human samples (n=80) using cytotoxicity assays and mass spectrometry respectively. Antibiotic therapy was associated with a decline in tissue concentration of mycolactone in both human and murine-infected tissues which was paralleled by resolution of clinical lesions, reductions in bacteriological counts and restoration of local and systemic immune responses. Discussions/Conclusions: This study shows that mycolactone concentrations in tissues is closely associated with the presence of M. ulcerans and provides useful proof-of-concept data that mycolactone detection could potentially be used to monitor response to antibiotic therapy as well as for diagnosis of Buruli ulcer disease. The findings from the pilot study indicate that rifampicin combined with clarithromycin can replace rifampicin and streptomycin for the continuation phase after rifampicin-streptomycin treatment for 2 weeks without any apparent loss of efficacy. The implication is that a controlled trial of fully oral therapy using rifampicin and clarithromycin for 8 weeks (RC8) is justified.
- ItemThe kinetics of mycolactone in relation to the microbiological, clinical and immunological responses to antibiotic therapy for mycobacterium ulcerans disease.(2014) Sarfo, Fred StephenBackground: Mycobacterium ulcerans is the causative agent for a chronic necrotising skin infection called Buruli ulcer. Pathology of the disease is closely linked with the elaboration of a unique lipid toxin, mycolactone, which has potent cytotoxic and immunomodulatory properties. In this study, assays were developed to detect and quantify mycolactone concentrations in tissues during curative antibiotic therapy in mice and in humans to understand its dynamics in pathogenesis and to explore its potential as a biomarker for diagnosis and monitoring of patients with Buruli ulcer disease on antibiotic therapy. The currently recommended antibiotic regimen for the management of Buruli ulcer is a combination of daily intramuscular injections of streptomycin and oral rifampicin for 8 weeks (RS8). This regimen was compared with streptomycin/rifampicin for 2 weeks followed by clarithromycin/rifampicin (RS2RC6) for 6 weeks in patients to determine the clinical and bacteriological effectiveness in a pilot study. Methods: Biopsies were obtained from infected human skin tissues and BALB/c mouse hind footpads before, during and after 8-weeks of rifampicin-containing combination antibiotic therapy. Lipids were extracted from tissues using organic solvents, mycolactone concentrations were measured using a cytotoxicity assay and mass spectrometry. Trends in mycolactone concentrations and clinical, bacteriological and immuno-histopathological responses were determined. Concentrations of cytokines in supernates of whole blood assays in humans or murine splenocytes after stimulation with mycobacterial antigens/T-cell mitogens were measured using ELISA. iv Results: Eighty-three patients with confirmed Buruli ulcer were randomized to RS8 or RS2RC6 and monitored for recurrence free-healing. Bacterial load in tissue samples before and after treatment for 6 and 12 weeks was monitored in samples obtained by 4mm punch biopsy by semi-quantitative culture. There was no difference in using RS8 or RS2RC6 with respect to healing rate or the proportion healed in each group after 4, 8, 12, 16, 20, 24 and up to 52 weeks. The success rate was 93% in each group and there was no recurrence after 12-month follow-up. There was no difference in the number of bacteria cultured at the different time points for the two regimens. Mycolactone was detectable in 92% and 77% of human samples (n=80) using cytotoxicity assays and mass spectrometry respectively. Antibiotic therapy was associated with a decline in tissue concentration of mycolactone in both human and murine-infected tissues which was paralleled by resolution of clinical lesions, reductions in bacteriological counts and restoration of local and systemic immune responses. Discussions/Conclusions: This study shows that mycolactone concentrations in tissues is closely associated with the presence of M. ulcerans and provides useful proof-of-concept data that mycolactone detection could potentially be used to monitor response to antibiotic therapy as well as for diagnosis of Buruli ulcer disease. The findings from the pilot study indicate that rifampicin combined with clarithromycin can replace rifampicin and streptomycin for the continuation phase after rifampicin-streptomycin treatment for 2 weeks without any apparent loss of efficacy. The implication is that a controlled trial of fully oral therapy using rifampicin and clarithromycin for 8 weeks (RC8) is justified.
- ItemMechanistic Studies and Mathematical Models for Mycolactone Toxin and Autoinhibitory WASP: Model Mechanisms for Buruli ulcer Initiation and Spread.(2015-11-09) Nyarko, Peter RomeoThe Wiskott-Aldrich Syndrome Protein (WASP) has been implicated in many diseases such as Wiskott-Aldrich Syndrome (WAS) and Buruli ulcer. Mycobactrium ulcerans is the main causative organism of Buruli ulcer (BU) disease. The bacteria secretes a polyketide lipid toxin (Mycolactone). The toxin not only di uses through the cell membranes, but also binds, hijacks and disrupts the normal functions of WASP in the cytoplasm leading to over polymerization of actin lament, cytoskeletal rearrangement and eventually cell death through necrosis. In pre-ulcerative BU disease, toxins extend beyond the actual size of the lesion. A mathematical model is developed to describe the binding mechanism of the two conformations of WASP and the complexes formed using the idea of isomerization. The formulation utilizes ligand concentration-dependence (ligand-receptor), equilibrium and conservation principles. By this approach, we are able to determine the fractional response of WASP against change in concentration of its activators;
- ItemModelling Customers Response to Service offers using game Theory Case Study; MTN and Vodafone in Bolgatanga Polytechnic(2011-11-18) Issahaku, Abdul-MajeedGame theory is being found to be one of the useful tools for analysing strategic situations that involve competitors or rivals who struggle against each other for supremacy...
- ItemOn The Trapped Surface Characterization Of Black Hole Regions In The Spherically And Axially Symmetric Spacetimes(KNUST, 2018-04) Mohammed KumahThe characterization of black holes by means of classical event horizon is a global concept since one need to have the knowledge of the whole spacetime in order to locate a black hole region and the event horizon. To surmount these issues, we investigate alternative approach based on the concept of trapped surfaces in a variety of spacetimes. Specifically, to compute the expansions of the appropriate null vectors in both spherically and axiallysymmetric spacetimes and thus explicitly determine the existence of trapped and marginally trapped surfaces in their respective black hole regions
- ItemOptimizing The Conditions Of Ethanol Production From Cassava And Sweetpotato(KNUST, 2018-02) Gregory Afra KomlagaCassava and sweetpotato are root and tuber crops cultivated in Ghana that could serve as industrial raw material for ethanol production. Investigations were conducted to optimize the yield of ethanol from two (2) varieties each of Cassava and Sweetpotato. Response surface methodology was used to model the optimum liquefaction, saccharification and fermentation conditions for ethanol production from the cassava and sweetpotato varieties. Three starch hydrolytic enzymes (Liquozyme SC DS, Spirizyme Fuel, Viscozyme L) and two strains of yeast (Bio-Ferm XR, Baker’s yeast) were used for fermentation. The best liquefaction, saccharification and fermentation times established were 2.1 hours, 4 hours and 57.4 hours at 34oC respectively with Liquozyme SC DS, Spirizyme Fuel/Viscozyme L and Bio-Ferm XR (Lallemand) yeast. The combination of Viscozyme L and Spirizyme Fuel enzymes in a ratio of 1:1 was the best enzyme mix for saccharification for a duration of 4 hours. The yeast to employ for best fermentation was Bio-Ferm XR at temperature of 34oC for 57.4 hours duration. The results also indicated that 10 months matured Sika bankye and 3 months old Apomuden were the best cassava and sweetpotato varieties respectively for ethanol production. The best ethanol yield established from the study was 16.2% v/v from a 50:50 cassava:sweetpotato flour combination. Ethanol production with Sika bankye and Apomuden in a 50:50 ratio with GH¢ 119.00 as cost of fresh roots and tubers, ethanol yield of 15.5% v/v, selling price of GH¢ 4.7 per litre of ethanol and the use of a 10,000 litres per day capacity ethanol distilling plant generates net profit of between 11% and 31% over a period of five years. Ethanol production with cassava and sweetpotato is therefore a profitable venture.
- ItemPerformance Assessment of Satellite and DACCIWA Optical Gauge Rainfall Products for the Analysis of Trends and Drivers of Rainfall Extremes in Ghana(KNUST, 2018-11) Atia Winifred AyinpogbillaRainfall plays an important role in the socio-economic development of any nation. Below or above normal rainfall conditions have serious consequences on key socioeconomic sectors such as agriculture. This is particularly true for countries where rain-fed agriculture is a predominant practice as such, rainfall impact studies are important. In this thesis, rainfall impact studies in Ghana were examined in three different areas. The first part of the study evaluated the performance of satellites and merged rainfall products over Ghana in order to examine their reliability as surrogate ground-based gauge measurements for areas where gauge networks are sparse. Satellite products (TAMSAT, TRMM, ARC2, CMAP, GPCP and CHIRPs) and gauge-only products (CRU and GPCC) were validated with gridded rainfall data from the Ghana Meteorological Agency (GMet) on monthly to annual time scales using a suite of statistical analysis. The results showed that, the performance of the satellites and merged rainfall products is a function of the scales and locations used in the validation. While ARC2 showed large biases on both monthly and annual time scales, all other products, especially, TRMM and TAMSAT showed relatively good skills on the monthly scale (r > 0.90) than the annual. On the countrywide basis, CHIRPs and CRU markedly revealed better skills on both time scales. In all the four agro-ecological zones of the country, the products were able to capture the respective rainfall patterns, onset, cessation and spells (wet and dry) of each zone. Thus, TRMM and TAMSAT will serve as better surrogates at monthly time scale whereas CHIRPS and CRU would be better substitutes to ground-based gauge data for both time scales over the entire country and in the four ecological zones. In the second part of the study, the performance of the new Dynamic Aerosol Chemistry-Cloud Interactions in West Africa (DACCIWA) optical rain gauge (DOG) measurements over the Ashanti region of Ghana were assessed. The study further examined the validities of subdaily rainfall data from IMERG and TRMM over the region for their exploits in the key socio-economic activities of the country such as agriculture, hydrology and water resource management. Daily rainfall data for nine co-located stations from the Ghana Meteorological agency (GMet) were used to assess the validity of the DOGs. A point-point assessment of IMERG and TRMM from 2016–2017 for the nine stations were then performed using the DOGs. The outcome of the assessment revealed that the DOGs were able to capture the diurnal and monthly rainfall patterns in the region. IMERG revealed a better skill in capturing the daily rainfall than TRMM although both products showed some similarities in the June–August (JJA) season. Both products slightly over-estimated gauge measurements (<2 mm/day) in all selected stations. The third part of the study examined the climatologies and trends of extreme rainfall events in Ghana. The study further probed the links between the rainfall extremes and SST anomalies at the oceanic basin. The trend analysis revealed that CDD, CWD, R10mm and R20mm were in the range of 5–140, 5–14, 25–60 and 2–26 days per year respectively. Moreover, PRCPTOT, R95p, R99p, SDII, RX1day and RX5day were in the range of 800-1800 mm, 150–450 mm, 30–130 mm, 6–14 mm, 30–100 mm and 60–190 mm per year respectively. The maximum of temporally averaged intensity rainfall indices have shown to cover southwestern Ghana while the minimum of these indices covered northwestern and eastern coasts of Ghana. Significant decreasing trends in wet indices were observed over the Volta lake and central Ghana while low positive trends were dominant over the northern sectors of the country. In most cases, with the exception of the CDD and CWD indices, there were significant positive (negative) correlations with the Atlantic (Pacific and Indian) basins SSTs. IOD had a dipole effect on rainfall indices with the central and southern sectors generally covered by negative correlations while northern and coastal Ghana have shown positive correlations. The R95p index over central Ghana had negative correlations with AMO while positive correlations dominated some isolated parts of the country in the south and northeast. The impacts of AMO on PRCPTOT index were insignificant over most parts of the country with a few exceptions over southeastern and northern boarder regions. These results have implications on the improvement of monthly-annual forecasts of the Ghanaian rainfall and its extremes, and also provides prior knowledge for better understanding of multidecadal modulations of global inter-annual teleconnections
- ItemPhysicochemical And Functional Characterization Of Pectin Extracts From Different Okra Genotypes(KNUST, 2018-04) Fidelis Mawunyo Kwasi KpodoOkra (Abelmoschus spp.) is a plant of the Malvaceae family cultivated for its immature pods. The pectin content is responsible for the slimy texture of okra extracts and is of major technological interest for food, non-food and medicinal applications. A preliminary study on isolation of pectins from eight different okra types obtained from different geographical zones in Ghana revealed that the okra pods had considerable pectin yield and different physicochemical properties which can be exploited for their potential applications. Six different okra (Abelmoschus spp) genotypes were then cultivated under the same environmental conditions and their genetic diversity determined using fragment length analysis (FLA) of ten simple sequence repeat (SSR) markers. Pectins were extracted from the pods of the different okra genotypes using 0.1 M phosphate buffer (pH 6). Physicochemical, functional and rheological characteristics of the pectins were evaluated using FT-IR and NMR spectroscopy, Size-exclusion chromatography (SEC) and dilute solution viscometry. Neutral sugars composition was evaluated using GC-MS. Emulsifying properties of the pectins were determined by analyzing the interfacial protein and pectin concentrations, emulsion rheology, particle size distribution, zeta potential and the emulsion morphology using fluorescence microscopy. Genotypic studies confirmed unique genotypes for each okra sample used with each SSR markers detecting an average of 4.1 alleles. Physicochemical results showed that okra genotypes had pectin yields between 11–14 %. Resultant pectins were all low methoxyl pectin with varied degree of methylation (17–25 %), total carbohydrate (66.2–87.5 %), protein (3.3–7.1 %), sugar composition, degree of acetylation (20– 40 %), GalA content (43–63 %) and weightaverage molar mass (700–1700 x 103 g mol-1). FT-IR and NMR spectroscopy showed structural similarities between the pectins from the different genotypes. Intrinsic viscosity of the okra pectins ranged from 2.91 to 5.10 dL g-1. Huggins constant values calculated for okra pectins ranged from 0.3 to 0.7 revealing flexible chain conformation. Coil overlap plots revealed three concentration regimes with two critical concentrations. Stability of emulsions to creaming varied from 0.8 to 16.9 % and surface coverage of pectins (0.6 – 3.6 mg m-2) were relatively higher than that of the proteins (0.3-1.0 mg m-2). The okra pectins demonstrated good emulsifying abilities with initial surface weighted mean diameter (d3,2) ranging between 1.3 and 3.7 μm. Emulsion destabilization occurred in all samples after five days of storage and the viscosity of samples remained constant with aging. The differences between genetic variations have potential applications in the food industry as emulsifying agents.
- ItemPreparation and characterization of fat particles-in-water emulsions for the encapsulation of bioactive compounds using allanblackia seed fat and tween 20 and sodium alginate as emulsifying agents(2015-11-09) Badu, MercyEffective delivery of poorly water-soluble bioactive ingredients has been considered a great challenge in the pharmaceutical, food and cosmetic industries. The compartmentalized hydrophobic and hydrophilic regions of emulsion systems give them the advantage to encapsulate polar and non-polar compounds for effective delivery. However, the challenge associated with emulsions is their thermodynamic instability. This study investigated the stabilisation process of fully crystallised fat globules as a dispersed phase in an oil-in-water emulsion system prepared from a naturally occurring vegetable fat, a nonionic surfactant and a polysaccharide biopolymer. The crystallisation profiles of the fats from Allanblackia seed and shea nuts were determined. Based on the results Allanblackia seed fat was selected and used as the dispersed phase in the oil-in-water emulsion system. The emulsion was formulated in the presence of Tween 20 and sodium alginate. The mixed emulsifier system gave stability against aggregation of the fat particles hence preventing coalescing, creaming and flocculation and this was more significant at 2 % to 4 % sodium alginate content. The emulsion particle size and microstructure were dependent on the fat/water ratio and a viscoelastic system with G′ > G′′ at the lower frequencies and G′′ > G′ at higher frequencies (where G and G are….). The dispersed fat particles emulsion system was used to encapsulate sudan orange dye (a water insoluble dye) and the efficiency of the encapsulation was characterized by an increase in particle size (ranging from 246 to 250 nm) and varying size distribution. UV-Vis spectrophotometric analysis of the dye loading capacity, release rate and leaching capacity showed a successful entrapment of the dye in the fat matrix. This confirms Allanblackia seed fat as a potential solid fat for its application in the formulation of oil-in-water emulsions.
- ItemQuantum Mechanical Studies of the Mechanisms of Some Transition Metal Organometallic Reactions(2009-07-18) Tia, RichardThe mechanistic pathways of three organometallic reactions, namely the oxidation of ethylene by chromyl chloride leading to the formation of epoxide, 1,2-dichloroethane, 1,2-chlorohydrin, acetaldehyde, and vinyl alcohol precursors; the olefin metathesis reaction involving ethylene and 20 metal methylidene Cl4MCH2(M=Cr, Mo, W, Ru, Re) and metal oxo-methylidene Cl2(O)MCH2(M=Cr, Mo, W, Ru, Re) complexes; and the transition-metal-assisted formation of 1,2-dinitroso complexes of cobalt and its congeners have been studied using hybrid density functional theory at the B3LYP/LACVP* level of theory. The formation of the epoxide precursor (Cl2(O)Cr-OC2H4) was found to take place via initial [2+2] addition of ethylene across the Cr=O bond of CrO2Cl2 to form a chromaoxetane intermediate, as opposed to [3+2] addition across the two Cr=O bonds of CrO2Cl2 as suggested in earlier studies. The hitherto unexplored pathway involving initial [3+2] addition of ethylene across the Cr=O and Cr-Cl bonds of CrO2Cl2 was found to be more favorable than the [3+2] addition across the two Cr-O bonds of CrO2Cl2. The formation of the 1,2-dichloroethane precursor was found to take place via [3+2] addition of ethylene across the two Cr-Cl bonds of CrO2Cl2. The 1,2-chlorohydrin precursor was also found to originate from [3+2] addition of ethylene across the Cr-O and Cr-Cl bonds of CrO2Cl2 as opposed to [2+2] addition of ethylene across the Cr-Cl bond. Also the vinyl alcohol and acetaldehyde precursors were found to arise from a direct attack of one of the carbon atoms of ethylene on an oxygen atom of CrO2Cl2 through a triplet intermediate. In the reactions of Cl4MCH2(M=Cr, Mo, W, Ru, Re) with ethylene it was found that the formation of the metallacyclobutane through formal [2+2] cycloaddition, a key step in the olefin metathesis reaction according to the Herrison-Chauvin mechanism, is a low-barrier process in each of the complexes studied. It was also found that the active species for the formation of the metallacyclobutane is a carbene complex and not a carbenoid complex. One key factor was found to be responsible for the difference in metathesis activity in these complexes: the stability of the carbenoid complexes relative to the carbenes. In Cr and Ru, the carbenoid complexes are more stable than the carbenes and thus Cl4CrCH2 and Cl4RuCH2 are likely to exist in the lower- 21 energy carbenoid Cl3MCH2Cl form as opposed to the carbene Cl4M=CH2 form. This is likely to deplete the reaction surface of the active species of the process, making Cl4MCH2(M=Cr, Ru) not suitable for olefin metathesis. This suggests that whereas Cl4MCH2 (M = Mo, W, Re) may catalyze olefin metathesis, Cl4MCH2 (M = Cr, Ru) may not. The W and Re complexes have been found to have greater metathesis activity than the Mo complex. In the Cl2(O)MCH2 (M=Mo, W, Re) complexes the metathesis reaction has favorable energetics and is found to be more feasible than the side-reactions studied while in the Cl2(O)MCH2(M=Cr, Ru) complexes, the olefin metathesis is found to be less favorable than the side reactions. In the transition-metal-assisted formation of 1,2-dinitrosoalkanes, it was found that the activation barriers for the one-step [3+2] addition pathway for the formation 1,2-dinitrosoalkanes are generally very low while the activation barriers for the [2+2] addition of the C=C bond of the olefins across the M-N bonds of CpM(NO)2 (M=Co, Rh, Ir) to form an intermediate are generally very high. A transition state for the re-arrangement of the products of [2+2] addition to the products of [3+2] addition could not be located, indicating that the re-arrangement of the products of [2+2] addition by reductive elimination involving the second metal-nitrogen π-bond to form the observed 1,2-dintrosoalkanes as suggested in the work of Rappé and Upton may not be possible. Therefore it is concluded that the direct one-step [3+2] addition pathway proposed by Bergman and Becker for the formation of 1,2-dinitrosoalkanes is a more plausible pathway.
- ItemSecuring Cloud Data On Multiple Infrastructure Using Erasure Coding, Dispersal Technique And Encryption(KNUST, 2017-12) Frimpong TwumCloud computing is a technology that has come to save organisations from investing in and owning high cost IT infrastructure including its management and maintenance. The technology enables an organisation to outsource its IT needs to the care of a remote third party Cloud Service Provider (CSP) while focusing on its core business processes. It enables the usage of IT resources remotely as a service on subscription basis at a per usage fee on demand. The service models available are Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). These service models are deployed in one of four cloud deployment models as Public, Private, Community or Hybrid cloud. Despite the technology’s numerous benefits, it also poses serious security threats to vital business data assets as the subscriber has to surrender control over its management and maintenance to a remote CSP. The threats include: the CSP using the data for their own gains, the location of the data not known to the subscriber, the ownership of the data (for example, on contract termination or in the event of conflict or dispute?), and also the subscriber not knowing who has unauthorised access to their data resource. The challenge therefore, is how to create a secure and vigorous data security solution that can mitigate these threats and alleviate the cloud subscriber fear to freely enjoy using cloud computing services. Hence, this study proposes and implements a Six-level Cloud Data Distribution Intermediary (CDDI) Framework that enables the cloud subscriber to effectively secure its data against these threats. The framework employs Erasure Coding (based on the Galois Field Theory and Reed Solomon Coding), Data Dispersion technique with a proposed Transposition Encryption technique based on Rubiks cube transformation. In addition, it also uses this study’s proposed Erasure Coding technique based on checksum dubbed “Checksum Data Recovery”. The CDDI framework implemented on the cloud subscriber’s gateway system encrypts and splits the subscriber’s data into chunks of data fragments and distributes them randomly to the subscribers selected multiple CSP storage infrastructures. This alleviates threats of data usage, location, ownership, and access, identified. By employing design research methodology, the CDDI framework is developed into software following a Plan-Driven Incremental software development approach. The system dubbed ‘SecureMyFiles (SMF)’ was developed in an experimental lab set-up using JAVA, SQL, and PHP. The SMF system provides users a choice of selecting one of four data priority levels (Low, Normal, Important, Critical) at the time of uploading data resources to the cloud. The priority level selected determines the uploading and downloading process the system uses, the amount of data that can be recovered in the event of data corruption and the performance during recovery. The security strength of the SMF system in relation to assuring the cloud subscriber of the Confidentiality, Integrity, and Availability of their data was found to be much stronger than the existing direct architecture model provided by DropBox, Box, Google, Backblaze B2, or the indirect architecture model provided by CASB/SECaaS providers. This is because with the SMF system the subscriber data does not reside with one single provider but distributed across many providers distributed storage infrastructure.
- ItemSignificance of Genetic Mutations in the Molecular Pathogenesis of Human Orofacial Clefts in Ghana(KNUST, 2017-06) Lord Jephtha Joojo GowansHuman orofacial clefts (OFCs) are congenital craniofacial dysmorphologies, with a global prevalence of 1 per 700 live births. OFCs may be syndromic or nonsyndromic, with the syndromic forms presenting with extra congenital anomalies. Nonsyndromic OFCs (NSOFCs) account for about 70% of all OFCs. The aetiology of the more common NSOFCs is complex, with both genes and environmental factors playing vital roles. The main objective of the present study was to demonstrate association between genetic variants and the pathogenesis of OFCs in Ghanaians. The specific objectives were fivefold: (i) determine pattern of inheritance of OFCs, (ii) establish the role of environmental and other risk factors in OFC aetiology, (iii) ascertain genetic susceptibility loci for OFCs, (iv) detect rare aetiologic mutations in affected individuals and, (v) subsequently validate the pathogenic mechanism of action of some selected rare variants in zebrafish embryos. A questionnaire was administered to participating families mainly at KATH to collect environmental and phenotypic data. Saliva and cheek swab samples were collected from participants using Oragene DNA collection kits. DNA was extracted from samples using Oragene saliva processing protocol and Quibit assay was used to quantify extracted DNA, with subsequent validation of sexes of participants through XY-Genotyping that employed Real Time PCR. A total of 3,585 individuals (872 cases, 1635 relatives and 1078 unrelated controls) were genotyped at 48 SNPs using Fluidigm SNP Genotyping Protocol. Eight genes were also directly sequenced in 184 NSOFC cases and IRF6 gene only on 80 individuals with multiple congenital anomalies (MCAs), using Sanger sequencing technology. Primers used for DNA sequencing were designed with Primer3 software based on human genome assembly GRCh37/hg19, 2009 (http://genome.ucsc.edu), followed by ascertainment of their optimal PCR conditions through Gradient PCR. Initial PCR was used to amplify exons and flanking intronic sequences as well as 5’ and 3’ untranslated regions (UTRs) of the eight genes. PCR amplicons were examined by gel electrophoresis. The Initial PCR product was then sequenced with ABI 3730XL DNA Sequencer. Employing genetic engineering, site-directed mutagenesis and developmental biology techniques, two selected variants of IRF6 were also functionally validated in zebrafish embryos. The study established multifactorial pattern of inheritance for OFCs in Ghana. Low socio-economic status, delayed antenatal attendance and folate deficiency were significantly associated with families with OFCs by increasing OFC susceptibility. In SNP association studies, case-control meta-analyses demonstrated that PAX7 (rs742071, p=5.10×10-03), 8q24 (rs987525, p=1.22×10-03) and VAX1 (rs7078160, p=0.04) were nominally associated with NSCL/P. MSX1 (rs115200552, p=0.01), TULP4 (rs651333, p=0.04), CRISPLD2 (rs4783099, p=0.02) and NOG (rs17760296, p=0.04) were nominally associated with NSCP. Many other loci exhibited threshold association with NSOFCs in TDT and DFAM analyses. Coding, splice site and/or regulatory region variants were observed in all eight sequenced genes. Novel pathogenic mutations were observed in both NSOFCs (p.Glu69Lys, p.Asn185Thr and c.175-2A>C) and MCA (p.Gly65Val, p.Lys320Asn and c.379+1 G>T) cases in IRF6, including probable genetic modifiers. In functional validation of p.Glu69Lys and p.Gly65Val, these variants, through dominantnegative effect, disrupted craniofacial structures, such as pharyngeal arches, in zebrafish. These observations are relevant for prenatal diagnosis of high risk families, understanding the genetic architecture of OFCs and genetic counseling. This is the first ever genetic study on OFCs in Ghana and also the most extensive done in African populations on the African continent to date. The study has for the first time, demonstrated associations between the studied genetic loci and NSOFCs among continental Africans, with striking racial differences.
- ItemSyntheses And Characterization Of Bismuth And Lead Chalcogenides And Their Ternary Alloys From Single Source Precursors(KNUST, 2018-07) Selina Ama SaahThis research describes the syntheses and characterization of lead and bismuth chalcogenide nanoparticles and thin films from single source precursors. The single source precursors used were dithiocarbonates, dithio- and diselenoureas, and dithiocarbamates. These precursors were characterized using micro-elemental analyses, thermogravimetric analyses, infrared spectroscopy, nuclear magnetic resonance spectrometry and mass spectrometry. The single crystal structures of bismuth ethyl xanthate and its 1, 10 phenanthroline adduct were determined. The complexes were used for the syntheses of nanoparticles using the hot injection and thin films using the spin coating technique. The as-synthesized nanoparticles and thin films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, energy dispersive X-ray spectroscopy and absorption measurements. Optical band gaps were estimated from the absorption data using Tauc’s plots. For the PbS thin films from lead dithiocarbonates, the effect of the alkyl chain length on the morphology and size of the nanocrystals were investigated. There was a change in morphology from cubes to fibrous structures as the alkyl chain changed from ethyl to dodecyl, thus confirming the anisotropic nature of PbS. SEM analyses of Bi2S3 thin films also showed a change in shape from nanowires of the bismuth ethyl xanthate to clusters of nanorods (triethylamine, pyridine) and nanodots (1,10 phenanthroline) depending on the choice of nitrogen adduct. Ternary PbSxSe(1-x) thin films deposited from lead xanthate and lead selenourea showed a gradual shift in p-XRD pattern to lower 2 theta values as the mole fraction of the lead selenourea complex in the coating mixture changed from 0 to 1 at an interval of 0.1. Estimated optical band gaps for the parent binaries (PbS and PbSe) and their ternary alloys (PbSxSe(1-x)) were all blue shifted from their respective bulk materials. PbSxSe(1-x) nanoparticles synthesized from lead thio- and selenourea complexes also exhibited a similar trend in both p-XRD and optical band gap. EDX analyses confirmed the presence of Pb, S and Se in all the PbSxSe(1-x) alloys formed at different atomic percentages depending on the ratios of the starting materials. The effects of different concentrations of Bi doping on the optical and structural properties of PbS nanoparticles have been investigated. Morphological studies showed cubes at 50% Bi doping suggesting the incorporation of the Bi atoms into the crystal lattice of the PbS nanoparticles. However, an interplay between rods and cubes were seen at 80% Bi doping. The estimated band gaps for PbS and Bi2S3 were 0.72 and 1.94 eV respectively with the alloy having band gaps in between the two binaries.
- ItemThe Design And Implementation Of Convoluted Os Kernel Architecture For Secured Network Infrastructure(KNUST, 2017-12) Edward Danso AnsonResearch into security enhanced kernel architecture has been on going by computer corporations, research institutions and Kernel development engineers for several decades now. Even though the paradigm-shift from performance enhanced kernel development to application level security operating systems improved the safety of operating systems use, it was apparent that more kernel retrofitting need to be implemented at the kernel level since it is a highly privileged section of the architecture, and therefore a compromise in the kernel could affect the security of the entire systems including the performance of security applications which runs on the kernel. This research introduces the Convoluted Kernel Architecture (CKA) which is a security enhanced Linux server based monolithic architecture that re-modifies the original monolithic kernel architecture with additional layer of virtual module within the kernel to improve the security and availability of the Kernel. The system make use of Operating System level virtualization with an integrated security module, which otherwise would have been implemented at the application layer, with a novel authentication module called the Stealth Obfuscation Zero Knowledge Proof algorithm. This research describes how the CKA abstracts the hardware and software layers of conventional servers to implement the operating system all in one security appliance that at the same time, providing High Availability. Finally, this work describes how the CKA protects the core kernel from attacks when upper kernel becomes compromised through vulnerabilities of applications that executes on them or the kernel utilities itself.