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Diversity within yeast involved in spontaneous fermentation of pito
(2007-11-11) Glover, Richard Lander Kwame
A survey was conducted in ten (10) “Dagarti pito” production sites located in nine towns within eight administrative regions of Ghana to investigate diversity within yeast varieties involved in the spontaneous fermentation of Dagarti pito. Samples of dry yeast were obtained from commercial Dagarti pito producers from Tamale and Nyankpala (Northern Region); Ayigya- Kumasi and Monaco-Kumasi (Ashanti Region); Accra (Greater- Accra Region); Cape Coast (Central Region); Takoradi (Western Region); Sunyani (Brong Ahafo Region); Ho (Volta Region) and Suhum (Eastern Region). For purposes of comparison, dry yeast was also sampled from three dolo production sites in Ouagadougou, Burkina Faso. Yeast populations ranged between 106 and 108 cfu g-1. Twenty-five yeast isolates from each site were characterized phenotypically by colony and cell morphology as well as carbohydrate assimilation profiling, using the API ID 32 C Kit (Biomerieux SA, Marcy L’Etoile, France). Ninety-nine percent (247) of the isolates showed colony and cell morphologies typical of S. cerevisiae. Of these, 72 % (179) had fifty-three carbohydrate assimilation profiles similar to S. cerevisiae (according to Vaughan-Martini and Martini, 1998) and were subsequently identified as such while 28 % (68) which had four carbohydrate assimilation profiles atypical of S. cerevisiae or any other member of the sensu stricto complex could not be identified in API galleries. Two isolates (1%) which had colony and cell morphologies atypical of S. cerevisiae, and a broad-spectrum assimilation profile, were identified as Candida kefyr. Genotyping of five randomly selected isolates from each site was carried out using the Polymerase Chain Reaction (PCR) to amplify the region spanning the two intergenic transcribed spacers (ITS) and the 5.8S ribosomal gene (ITS1-5.8S rDNA-ITS2), followed by restriction analysis (ITS-PCR+RFLP) of the product, as well as Pulsed Field Gel Electrophoresis (PFGE). The genetic analyses indicated that all of them belonged to S. cerevisiae, notwithstanding the phenotypic differences. The mitochondrial cytochrome-c oxidase II gene (COX 2) of four isolates representing the four chromosome profile groupings that emerged after PFGE, were then sequenced to confirm their close relatedness to S. cerevisiae, particularly type strain CBS1171. Two isolates randomly selected from each of the ten production sites, (one with a broad carbohydrate assimilation spectrum and the other with a narrow carbohydrate assimilation spectrum) and assessed for technological properties showed different patterns of growth and flocculation without much change in pH during fermentation, and most of them produced pito having sensory attributes which compared favorably with commercially produced pito. Pito produced with each of ten out of the twenty yeast strains from Ghana used for the earlier investigations and three from Burkina Faso was analyzed by headspace, for its aroma constituents. All ten Ghanaian isolates could form aromatic compounds representing the alcohols, esters, and ketones which are among reported typical flavor compounds of conventional beer. This study has demonstrated diversity within S. cerevisiae strains involved in fermentation of pito wort. These strains possess desirable technological properties, including sufficient growth during fermentation and efficient hydrolysis of sugars for biomass enhancement. They also demonstrated fermentation activities, particularly, ethanol production, formation of aroma compounds and metabolites, which impart appropriate sensory attributes to pito.
Malaria Transmission Dynamics and Pyrethroid Insecticide Resistance Status of Anopheles Gambiae Sensu Lato Gilles (Diptera: Culicidae) in two Districts of the Brong Ahafo Region, Ghana
(2009) Hayford, Daniel
Malaria results from infection with Plasmodium species transmitted mostly through the bite of female Anopheles species. The Brong Ahafo Region (BAR) of Ghana is endemic for malaria with endemicity greater than 75%. The Ghana National Malaria Control Programme (NMCP) has prioritised the use of pyrethroid-treated bednet and/or indoor residual spraying as a key strategy for combating malaria transmission. Control of malaria transmission using insecticide treated bed-nets and/or IRS impacts on both morbidity and mortality due to malaria. Evidence of insecticide resistance in malaria vectors in different areas necessitates surveillance studies to allow prompt detection of resistance should it arise and thus enable its management. Also, in preparation for the future IRS expansion programme planned by the NMCP, data on indices of malaria transmission would be required from several parts of Ghana, including the BAR. Hence, density, diversity, biting habits, feeding behaviour, parity rates, survival rates, sporozoite rates and entomological inoculation rates (EIRs) as well as pyrethroid insecticide resistance in the main malaria vector were investigated in some communities in two districts of the BAR. Mosquito larvae were collected using the dipping technique and reared to the adult stage and used for the insecticide susceptibility bioassays. Adult mosquitoes were also collected using human landing catches. The susceptibility bioassays were carried out using the standard WHO diagnostic bioassay kits. Bioassays were performed on non-blood fed female mosquitoes 2- to 4-day old. Knockdown rates were recorded after 5, 10, 15, 20, 30, 40, 50, 60, and 80 minutes. Mortality rates 24 hours post-exposure were also noted. Anopheles gambiae complex mosquitoes were analysed using the An. gambiae species specific PCR protocol. DNA from specimens identified as An. gambiae s.s. were subjected to PCR assays for the identification of the M and S molecular forms, and the detection of the leucine to phenylalanine knockdown resistance (kdr) gene mutation. Ovaries of wild-captured adult mosquito samples were dissected to examine the ovarian tracheations in order to determine parity, survival rates and life expectancy. The heads and thoraces of the parous mosquito samples were tested for the presence of circumsporozoite antigens of P. falciparum using enzyme-linked immunosorbent assay. A total of 15,384 Anopheles was collected, 13,088 in the rainy season and 2,296 in the dry season. Three Anopheles species were identified in both seasons: An. gambiae s.l. Gilles (98.80%), An. hancocki Edwards (1.20%) and An. coustani Laveran (0.03%). Anopheles gambiae s.s. was the only member of the An. gambiae s.l. found, consisting of both the M and S molecular forms but the S form was predominant (72.30%). No M/S hybrids were found. The susceptibility tests showed resistance to deltamethrin and permethrin. That is, mortality rates below 80% were observed ranging from 45% to 59% for the 0.05% deltamethrin bioassays conducted at Ahafo Kenyasi and Sunyani respectively. Mortality rates for the 0.75% permethrin bioassays ranged from 27% to 35% for the Ahafo Kenyasi and Sunyani samples respectively. Lastly, 46% mortality was observed for the Ahafo Kenyasi samples tested with 1.5% permethrin. The leucine to phenylalanine kdr gene mutation was detected in the two molecular forms but it was more frequent in the S form. That is, approximately 80.1% and 31.0% of the S and M molecular forms of the An. gambiae s.s. respectively, had the mutation. Anopheles gambiae s.s had its peak biting activity in the third and fourth quarters of the night in the rainy season but activity in the dry season peaked in the third quarter. In the rainy season, human-biting rates did not differ significantly between Sunyani, Ahafo Kenyasi and Hwidiem but the rates in these communities were significantly higher than in Chiraa (p = 0.034). In the dry season, however, there were no significant differences in HBR between the study sites (p = 0.898). Overall biting rates were higher in the rainy season (p < 0.001). Parity and survival rate did not differ significantly between sites but they were higher in the dry season. The sporozoite rate of both the An. hancocki and An. coustani was zero. There were no significant differences in P. falciparum sporozoite rates of An. gambiae between sites and seasons, however, EIRs were higher in the rainy season. The average inoculation rate was 2.864 infective bites per man per night (ib/m/n) in the rainy season, which gives an estimated 85.92 infective bites per man per month (ib/m/m). Comparative figures for the dry season were 0.468 ib/m/n and 14.07 ib/m/m. An overall average inoculation rate was 1.649 ib/m/n, which gives an estimated 49.48 ib/m/m. The results of this study suggest that the An. gambiae s.s. populations are resistant to the pyrethroid (deltamethrin and permethrin) insecticides tested. The implication of this is that malaria vector control measures in these communities using pyrethroid insecticides may be compromised due to the existence of insecticide resistance in the main malaria vector, An. gambiae s.s. The results of this study also suggest that the present study communities are areas of high malaria transmission intensity with transmission occurring all year round even though it is significantly higher in the rainy season.
The anti-termite properties and basic phytochemicals of eight local plants and the chemical characterisation of thevetia peruviana (pers) k. schum in Ghana
(2009) Tagbor, Trinity Ama
There is an increasing interest in the use natural products for termite control because of their environmental safety. Some local plant materials have been mentioned as potential alternatives to synthetic termiticides. The objective of this work was to determine the antitermitic efficacy of locally available plants such as; Thevetia peruviana (pers) K Shum Carapa procera DC, Jatropha curcus L ,Cassia nigricans Vahl, Cymbopogon ginganteus (Hachst) Chiov), Hyptis spicigera Lam., Vetiver zizaniodes Nash (vetiver grass) and Chromolaena odorata (L). Following the identification and collection of the experimental plants and termite samples, a series of field and laboratory experiments were conducted using parts of the plants to determine their antitermite efficacy. Antitermite efficacy was measured as their tolerance to termite damage, repellency and toxicity to termites. This was followed by extraction into petroleum ether, ethanol and water and the analysis of the most efficacious extract by chromatography (thin layer, column and high pressure) and spectrometry (mass spectrometry, nuclear magnetic resonance and infra red) methods to identify the active ingredients in the extract of the most efficacious plant. Resistance to termite destruction was measured by the loss in weight of stakes buried in treated and untreated soil and by visual assessment of extent of destruction. Repellency or attrantancy was determined by counting the number of termites that moved towards or away from filter paper pads treated with extracts of the test material. The results showed that soil treated with pulverised materials from T. peruviana offered the best protection to buried stakes against damage by subterranean termites. Field tests conducted with petroleum ether, ethanol and water extracts of T. peruviana suggested that the ethanol extract of T. peruviana resisted the destructive effects of termites most. In the repellency/attrantancy test, the ethanol extract was found to be an attractant. When the fractionated components of the ethanol extract were tested on brine shrimps, fraction 1 was found to be highly toxic suggesting obvious cytotoxicity. Analysis of fraction 1 by chromatography and spectrometry methods indicated the presence of two components digitoxin and digitoxigenin which were found to be toxic to brine shrimp. Sucrose was also isolated from the crude ethanolic extract of T. peruviana. Thus this work has shown that the potential for the use of anti-termite agents from T. peruviana is promising.
Quantum Mechanical Studies of the Mechanisms of Some Transition Metal Organometallic Reactions
(2009-07-18) Tia, Richard
The 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.
Characterization of water yam (Dioscorea Alata) for existing and potential food products
(2009-08-05) Baah, Faustina Dufie
The yam species, Dioscorea alata has an advantage for sustainable cultivation due to its comparatively good agronomic characteristics. This research was aimed at identifying the major chemical and physical characteristics of D. alata tubers that affect food and industrial processing qualities. Tubers from 20 varieties of D. alata were compared to a reference variety, D. rotundata. The tubers were processed into flour for the determination of quality characteristics. Pounded yam, boiled yam and amala products were also prepared for sensory assessment against the reference. The influences of tuber maturity and length of storage on the quality characteristics were also evaluated, as well as the tuber tissue microstructure. On the average, most of the characteristics evaluated were relatively higher in D. alata varieties as compared to D. rotundata: moisture (72.2%), sugar (5.7%), protein (6.0%) and total dietary fibre (6.9%) contents; higher water binding capacity (163.3%), solubility (11.0%), and amylose (29.4%); breakdown (198.7 RVU), peak time (6.3 min) and pasting temperature (84.2 oC). However, dry matter (27.8%) and starch contents (68.4%), peak, setback, and final viscosities (215.7, 57.3 and 256.0 RVU respectively) were comparatively lower. D. alata varieties equally had appreciable contents of minerals. Based on the physicochemical and chemical properties, D. alata could be processed to flour for use in bakery products and diet formulations. The measured physicochemical properties in conjunction with pasting properties of the D. alata varieties suggest the presence of strong bonding forces within their starch granules. The relatively higher pasting temperatures required, and the lower pasting viscosities make D. alata suitable for producing weaning foods and other products that require low viscosity. Pasting properties of D. alata revealed relatively higher thermal and mechanical stability which will make it a good ingredient for processed foods, especially those that require thermal sterilization. The sensory analyses showed that D. alata varieties have comparative advantage over D. rotundata for amala production. However, specific promising varieties (TDa 98-159, TDa 291, TDa 297 and TDa 93-36) would need further genetic improvement to render them suitable for boiled yam and pounded yam dishes. Microstructural studies of the cooked cells in majority of the D. alata varieties (71%) showed incomplete disruption of the cells and consequently reducing exudation of starch contents. This feature partly accounts for less suitability of D. alata for sticky and doughy yam products in production areas. Moisture content of D. alata tubers decreased significantly from 5 to 9 months after planting (MAP) (74.53 to 71.76%) and throughout the 5 months storage period (71.76 to 68.06%) as a result of dehydration. Sugar and starch contents increased from the 5MAP to 9MAP (4.54 to 4.70%; 65.92% to 72.01% respectively), however, starch content decreased at the end of 5 months storage period (72.01 to 66.55%) with concomitant increase in sugar content (4.70-6.83%). The observations are due to photosynthetic materials accumulation during growth period and breakdown of starch to sugars as a result of respiration during storage. Amylose content generally decreased with the storage period but swelling power increased (6.26-9.02%). Pasting viscosities increased throughout the growth period to the end of storage. The increases in dry matter and sugar contents, swelling power and pasting viscosities of stored D. alata tubers would have significant improvement in their organoleptic and textural properties. Contribution to Science From this study, the following have been established and therefore add onto the scientific knowledge on D. alata yam species: 1. D. alata varieties had higher total dietary fibre than what is reported for brown rice (5%) (Best, 2005) with a few varieties having comparable values to whole wheat flour. The specific varieties with high TDF will be useful in diet formulation because of its health benefits 2. D. alata flour (elubo) is very good for amala product. This product should be promoted in Ghana due to the high flour storability and ease of preparation. 3. Significant mineral variations were observed among D. alata varieties which suggest the potential for improvement through breeding programmes.
Diversity in Anopheles gambiae s.s and Wuchereria bancrofti, and the Distribution of Lymphatic Filariasis in Ghana
(2010) Dziedzom, Komi de Souza
Lymphatic Filariasis (LF) is a disease transmitted by the filarial worm Wuchereria bancrofti. It is a disease of public health importance, and has been earmarked for elimination by the year 2020 through Mass Drug Administration (MDA) programs. In Ghana, the distribution of LF reveals a pattern of endemicity separated by a continuous area of non-endemicity. As such, this study hypothesized that genetic differences – probably not revealed by current identification methods, within LF vectors and parasite populations, may be responsible for the observed distribution pattern. The main aim of this project was therefore to explain the current observed distribution of LF based on the diversity in the Anopheles gambiae s.s and Wuchereria bancrofti in Ghana. Mosquito samples were collected from 14 sites across Ghana, divided into 4 ecological zones, and falling into endemic and non-endemic areas. W. bancrofti samples were picked from dissected mosquitoes -using dissecting pins, collected from previous studies in Ghana. The samples were morphologically and molecularly identified using routine methods. Using the PCR, the Cytochrome C Oxidase subunit 1 (COI) from W. bancrofti and An. gambiae s.s was amplified, sequenced and analyzed. To better understand the effects of environmental factors on the diversity in the An. gambiae s.s, the spatial distribution of the An. gambiae M and S molecular forms and associated environmental factors were examined, and their relationship with disease prevalence was determined. A total of 10274 mosquitoes were collected, out of which 6150 (59.9%) were morphologically identified as An. gambiae s.l; 1494 (24.3%) of the An. gambiae s.l were further classified into sibling species. The S form of An. gambiae s.s predominated in the middle belt, while the M form predominated in the northern and coastal Savannah belts. Bivariate correlation analysis between the M and S forms indicated that their prevalences were negatively correlated (-0.763). Spatial analyses carried out, indicated a positive spatial clustering for both the An. gambiae M (MI =0.19, Z score=4.2, P< 0.01) and An. gambiae S (MI =0.19, Z score=4.2, P< 0.01) forms. Multiple regression analyses of all data (n=70 sites), indicated that temperature was an important variable for both forms, explaining for An. gambiae M, 28% (R2=0.28, F=25.8, P<0.001) and for An. gambiae S, 36% (R2=0.36, F=37.9, P<0.001) of the variance in the model. An. gambiae M was significantly correlated with LF, and 2.5 to 3 times more prevalent in the high LF zone than low to medium LF zones. Phylogenetic analyses of An. gambiae s.s revealed the samples to be grouped according to endemicity and ecological zones. The equality of evolutionary rate between the consensus sequences from the endemic and non-endemic areas, revealed a χ2 test statistic of 3.71 (P = 0.054), rejecting the null hypothesis of equal rates between lineages. Seven and 15 W. bancrofti specimens from Gomoa District (in the South) and Bongo District (in the North) respectively were sequenced. There was a significant difference in the evolutionary rate between the consensus sequences of W. bancrofti from the North and the South, with a χ2 test statistic of 7.44 (P = 0.00637). The results of this study indicate that environmental factors, especially temperature, play an important role in the distribution of LF and its vectors in Ghana. The observed genetic differences in An. gambiae s.s and W. bancrofti populations in Ghana may affect the vector-parasite interactions in various areas, and may explain the observed distribution of LF in the country.
Impact Attenuation System Using a Passive Damper
(2010-03-18) Agyei-Agyemang, Anthony
The goal of this work is to mitigate the degree of damage to passengers caused by automobile collisions. Crash phenomena involving road vehicles were investigated for the purpose of developing an impact attenuation design that can withstand speeds higherthan the current specified range of up to 4 km/h (for a bumper). Different impact attenuation systems in the vehicle were studied with emphasis on the bumper modeling, analysis and design. A mathematical model for a bumper was developed. Simulation of impact of the bumper against a fixed barrier was performed. A passive friction element was introduced into the bumper system to improve on the attenuation of the impact and kinetic energy absorption capacity. A mathematical model of the bumper-damper system was formulated and used to simulate impact phenomena for a 1900 kg mass moving at a speed of 70 km/h (19.4 m/s), 17.5 times the speed of a typical design specification. The simulation revealed that the energy absorption capacity of the bumper was improved with the addition of a frictionelement. Design parameters for the friction damper were extracted from the results of the simulation. The extracted design parameters includestiffness, k, and coefficient of the damping, c, of the bumper. The use of the results from ii the simulation in the design of the bumper was pursued with success. Friction damper designs were proposed. Two of thesedesigns were built and used in experiments to verify their effectiveness and to validate the simulation results. The experiments revealed that higher energy absorption could be achieved with the addition of afriction element to traditional bumpers. From simulation, it was observed that a combinationof material stiffness and damping factors could influence energy absorption ability of the damper. It was observed that the addition of a friction element to an ordinary bumper-damper system with the new design parameters can improve its energy absorption capacity by 103.6 kJ,that is about 146 %. Additionally, it was also observed that the addition of the friction element to a traditional vehicle could increase the critical design speed from 4 km/h (1.11 m/s) to 14.9 km/h (4.1 m/s). It was concluded that a passive friction damper system could be used to attenuate road vehicle impact energy in collisions (of vehicles of mass similar to that of a typical sedan car) at speeds 3times higher than the speed for which current conventional bumpers are designed to attenuate (i.e. 4 km/h).
Spatio-temporal Variability of Phytoplankton Community Species Composition, Biomass and Primary Productivity of Lake Bosomtwe (Ghana)
(2010-07-12) Awortwi, Francis Emmanuel
In this thesis, the community composition, biomass and primary productivity of the phytoplankton of Lake Bosomtwe on spatio-temporal scales are presented for the first time in relation to the physico-chemical environment. Horizontal and temporal/seasonal variabilities in the wet weight biomass, chlorophyll a, gross productivities, and community respiration as well as growth rates are also assessed. Phytoplankton community composition and biomass were assessed from 14 different stations in spatial surveys and 1 index central station for temporal studies. Samples were collected biweekly (temporal study) and in stratified and mixing periods (spatial study) with a 6-Litre van Dorn sampler and preserved with acid Lugol. Samples were counted using inverted microscopy and converted to wet weight biomasses by approximating cell volume through routine measurements of 30-50 cells of an individual species and the application of the geometric formula best fitted to the shape of the cell. Identifications were performed on preserved whole and net (10 µm mesh) samples. The in situ light and dark bottle oxygen method was used for studying photosynthesis. An adapted version of the phytoplankton production model was employed to quantify phytoplankton photosynthesis and community respiration. Both chlorophyll a and total phosphorus were estimated. Coefficient of variance, t-test, ANOVA and the Levine test of homogeneity of variance were used to assess annual, inter-annual and seasonal variability of the means of physico-chemical and biological variables. Community species composition consisted of a total of 56 in horizontal and 75 in temporal studies in 7 major groups dominated by the Chlorophyceae. But the biomass dominated by the Cyanobacteria. Mean biomass of phytoplankton was 1570.0 in the first year (2004-2005) and 2262.3 mg m-3 in the second year (205-2006). Annual mean gross primary productivity of 4.73 gC m-2d-1 is high but net productivity was very low i.e. 0.38 gC m-2d-1. This was due to the very high community respiration that represented 90 % of the gross primary productivity and may imply higher loss rates. Mean growth rate in the Zeu of 0.13 d-1 is low and is commensurate with the low biomasses observed in the lake. Very weak relation between biomass and chlorophyll a and the little change in community composition in an annual cycle show that the changes in the chlorophyll a concentration are due to adaptation of the same community to differing conditions within the water column. Variabilities in the community biomass that range from a Coefficient of Variance of 28-79 % and that of the gross primary productivity of 33.1 % are high and seem to be regulated by the similarly high variabilities in the physico-chemical parameters. Significant inter-annual differences in the community biomass were observed. Physical factors such as Zmix and Zeu seem to exert more control in the dynamics of the phytoplankton growth and productivity compared to chemical factors even though nitrogen limitation is suggestive because of the abundance of heterocyst-bearing filamentous Cyanophyceae. Selective grazing may also be contributing to some extent to the observed dynamics.
Evaluation of the microbiological and physicochemical quality of borehole water in the Offinso District of Ashanti Region
(2010-08-11) Amankona, Benjamin Kwasi
The quality of borehole water from seven administrative town councils namely Asuoso (AS), Akenkaasu (AK), Samproso (SA), Abofour (AB), Offinso (OF), Afrancho (AF) and Bonsua (BO) in the Offinso District of Ashanti region were analysed from January 2007 to June 2007. Water samples were collected from thirty-five boreholes comprising five boreholes in each town council and analysed for temperature, pH, colour, turbidity, conductivity, total dissolved solids, alkalinity, hardness and some selected anions PO3-4, NO2-,SO2-4) some heavy metals (Cd, Cu, Zn, Mn and Pb), total and faecal coliforms. From the results, pH of the water was slightly acidic (5.03-6.53) and was unaffected by the seasonal variation. The water was moderately soft to slightly hard (12.8-226.80mg/l CaCO3). The nutrient loads observed in the water were slightly low and fell within the WHO standards. There were isolated cases of cadmium contamination at Asuoso (AS), Abofour (AB) and Bonsua (BO) recording 0.00198, 0.00124, 0.00158 and 0.00164, respectively. With the exception of pH, all the other parameters analysed were influenced by seasonal variations. There was a general increase in all the parameters during the wet season with turbidity, conductivity and total dissolved solids recording high values. The mean total coliforms ranged between 10 and 20CFU/100ml while all the samples analyzed recorded zero for faecal coliforms. The results suggest that borehole water sources in the Offinso district were of acceptable quality.
Biting Patterns of Mosquitoes, the dynamics of Malaria Transmission and Existence of the Knockdown Resistance (kdr) Gene in parts of the Central Forest Belt of Ghana
(2010-8-24) Abonuusum, Ayimbire
Malaria is presumed to be holoendemic in the forest belt of Ghana, through no comprehensive transmission studies have been conducted...
New Cone Metrics on the Sphere
(2011-06-13) Boadi, Richard Kena
We give an explicit construction of lattices in P U (1, 2). A family of these lattices was originally constructed by Livn´e [15]. Parker [19] constructed these lattices of Livn´e as the modular group of certain Euclidean cone metrics on the sphere. In this work we give a construction of these lattices which includes that of Parker’s as the modular group of certain Euclidean cone metrics on the sphere. Our cone metrics on the sphere had five cone points with cone angles (π − θ + 2φ, π + θ, π + θ, π + θ, 2π − 2θ − 2φ) Where θ > 0, φ > 0 and θ + φ < π. These corresponds to a group of five tuples lattices generated by Thurston [27] in his paper Shapes of Polyhedra and Triangulations of the Sphere . Hence our choice of θ and φ in order to obtain discreteness are as follows: θ 2π/3 2π/3 2π/3 2π/4 2π/4 (2π/5) 2π/5 2π/6 φ π/4 π/5 π/6 π/3 π/4 (2π/5) π/3 π/3 Certain automorphisms which we considered on our cone metrics yielded unitary matrices R1, R2 and I1. Using these matrices, we obtained our fundamental polyhe- dron D by constructing our vertices, edges and faces to define the polyhedron. Our vertices were obtained by the degeneration of certain cone metrics. The polyhedron D is contained in bisectors whose intersection give us the edges of the polyheron. The faces are also contained in the bisectors. Then finally we proved using Poincar´e’s polyhedron theorem that the group Γ generated by the side pairings of D is a dis- crete subgroup of P U (1, 2) with fundamental domain D and presentation: J 3 = Rp = Rp = (P −1J )k = I , \ 1 2 Γ = J, P, R1, R2 : R2 = P R1P −1 = J R1J −1, P = R1R2
Assessment of Public Exposure to Naturally Occurring Radioactive Materials from Mining and Mineral Processing Activities of Tarkwa Goldmine in Ghana
(2011-06-14) Faanu, Augustine
Mining has been identified as one of the potential sources of exposure to naturally occurring radioactive materials (NORM). However, mining companies are not being regulated for NORM in Ghana. Whilst the developed countries have identified NORM as potential problems and measures are being taken to address the issues, very little is being done in the developing countries. However, most of the NORM industries such as mining and mineral processing are located in developing countries such as Ghana. Currently, there are over two hundred (200) registered mining companies operating small, medium and large scale mining in Ghana. Tarkwa Goldmine is one of the largest gold mining companies in Ghana and has been in operation for the past 200 years with no data on radioactivity levels. The mine currently undertakes only surface mining and the process produces large volumes of tailings and waste that may contain NORM. Some of the NORM are soluble in water and have the tendency to leach into water bodies and farm lands. These studies have been carried out to determine the exposure of the public to NORM from processing of gold ore at the Tarkwa Goldmine in Ghana. Direct gamma spectrometry and neutron activation analysis (NAA) techniques were used to analyse for U/Th series and K-40 in soil, rock, water, food and particulate (dust) samples from the mining environment. The mean activity concentrations measured for 238U, 232Th and 40K in the soil/rock samples were 15.2 Bq/kg, 26.9 Bq/kg and 157.1 Bq/kg respectively. For the water samples the mean activity concentrations were 0.54 Bq/L, 0.41 Bq/L and 7.76 Bq/L for 226Ra, 232Th and 40K respectively. The mean activity concentrations of 226Ra, 232Th and 40K in the food samples were 0.18, 0.14 and 45.00 Bq/kg respectively. The mean activity concentrations measured in the dust samples were 4.90 and 2.75 µBq/m3 for 238U and 232Th respectively. The total annual effective dose to the public was estimated to be 0.74 mSv. The results in this study compared well with typical world average values. The results indicate an insignificant exposure of the public to technologically enhanced NORMS from the activities of the Goldmine. The radiological hazard due to226Ra, 232Th and 40K were carried out. The radium equivalent activity (Raeq) and the calculated external and internal hazard indices, the absorbed dose rates and the corresponding annual effective dose were estimated in the soil and rock materials that might possibly be used as building materials. The results obtained in this study shows insignificant radiological hazards for the materials considered for use as construction materials for dwellings by the inhabitants in the study area. The results obtained in this study also shows that the background radiation levels are within the natural limits and compared well with similar studies for other countries. The study assessed the concentration of U, Th and K as well as other trace metals, anions and the physical parameters in water and soil samples in the goldmine and its surrounding areas. The mean concentrations of the U, Th and K were 0.020, 0.029 and 1.19 mg/L. The concentration of U, Th and K were variable in soil and rock samples taken from different locations in the study area with mean values varying in a range of 0.2 to 1.8 µg/g, 0.9 to 2.6 µg/g and 7037 to 71360 µg/g respectively. The concentrations of U, Th and K are comparable to world average values of similar studies. The calculated Th/U ratios show that there has not been significant fractionation during weathering of the radioelements with a mean value of 2.5. The concentrations of the other trace metals, anions and the physical parameters are within the WHO guideline levels in drinking water. The mean values of the gross-α and gross-β activity concentrations were 0.012 and 0.137 Bq/L which are also below the WHO recommended guideline values for drinking water.
New cone metrics on the sphere
(2011-10-05) Boadi, Richard Kena
Modelling Mean Lenght of Stay at the Hospital, A Case Study of Kwame Nkrumah University of Science and Technology Hospital, Male Medical Ward.
(2011-10-18) Adobah, Emmanuel
The purpose of this study was to model mean length of stay (LOS) given several factors at KNUST Hospital (Male ward), Kumasi...
Modelling Customers Response to Service offers using game Theory Case Study; MTN and Vodafone in Bolgatanga Polytechnic
(2011-11-18) Issahaku, Abdul-Majeed
Game 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...
Anti-Wolbachia Treatment of Lymphatic Filariasis and Genetic Analysis of the Pathology of Lymphedema as a Clinical Manifestation of the Disease
(2012) Batsa, Linda
Lymphatic filariasis (LF) caused by Wuchereria bancrofti is a disease of considerable public health and socio-economic burden in the tropics. The recommended drugs (ivermectin and albendazole) for the control of lymphatic filariasis are only microfilaricidal. The regimen of the standard treatment with doxycycline which has proven macrofilaricidal is 200mg/d for 4 weeks. This is considered a long period and dissuades complaince by patients receiving treatment. Therefore reducing the duration or the dosage from the current 200mg/d to 100mg/d would be a better option and will also increase compliance. In search of a more effective drug to complement the existing ones, in an area endemic for bancroftian filariasis in Ghana, 261 adult worm positive men were recruited for a double blind placebo-controlled study in the Ahanta West District of Ghana. Six groups of patients were treated with the gold standard (4 weeks 200mg/d doxycycline), 5 weeks and 4 weeks 100mg/d doxycycline, 3 and 2 weeks combination of 200mg/d doxycycline and 10mg/kg rifampicin and 5 weeks placebo. The effect of the treatment on Wolbachia depletion was assessed at 4 months after treatment; adult worm vitality assessed at pre-treatment, 12, 18 and 24 months, and microfilarial depletion assessed at pre-treatment, 4, 12, 18 and 24 months follow up time points. In accordance with the national mass drug administration programme, all the study participants were given 150mg/kg ivermectin and 400mg albendazole four months after treatment. The treatment drugs were well tolerated with no serious adverse effects in both the treated and the placebo groups. There was significant Wolbachia depletion at 4 months time point in the standard group (p=0.001), 5 weeks 100mg doxycycline (p=0.019), 4 weeks 100mg doxycycline (p=0.03) and 3 weeks combination treatment (p=0.028). However there was no significant Wolbachia depletion in the 2 weeks combination group as well as the placebo group (p>0.05). Microfilarial assessment at 12, 18 and 24 months follow up time points showed a significant depletion in the standard group, 5 weeks and 4 weeks 100mg doxycycline groups as well as the 3 weeks combination of 200mg plus rifampicin group but not in the 2 weeks and placebo groups (p>0.05). The macrofilaricidal activity was significant at 12, 18 and 24 months in the standard and the 5 weeks groups. In the 4 weeks group, it was significant at 18 and 24 months time point and in the 3 weeks group it was significant at 18 months follow up time point, but no significant difference was observed for the 2 weeks and the placebo groups. On the other hand, there is the need to know the genetic markers associated with LF. Such knowledge will be beneficial in terms of diagnosis and possible therapy of various forms of the pathology. For this reason, a cross-sectional study of unrelated Ghanaian volunteers were designed to genotype single nucleotide polymorphisms (SNPs) in 266 lymphedema patients as cases and 691 infected patients without pathology as well as 346 endemic controls. Out of the 147 chosen SNPs that were genotyped, 11 SNPs in eight genes were found to be associated with lymphedema. The associated SNPs were in the vascular endothelial growth factor receptor 3 (VEGFR3), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (NFKB- inhibition alpha), carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1), tissue inhibitor of metallopeptidase 2 (TIMP) genes, interleukin 10 and two SNPs in insulin like growth factor-1 (IGF-1) and matrix metallopeptidase 2 (MMP-2). A SNP in the interleukin 17 gene revealed a trend but there was significant haplotype association. In conclusion 5 weeks, 4 weeks and 3 weeks combination regimens of doxycycline were effective in treating LF infections, and SNPs in the angiogenic pathway were found to be associated with the pathology of lymphatic filariasis.
Synthesis and Characterization of Cadmium Zinc Sulphide (Cd1-xZnxS) Thin Films from Acidic Chemical Baths
(2012-05-18) Ampong, Francis Kofi
Cadmium zinc sulphide thin films with the required composition were successfully deposited from chemical baths containing zinc chloride, cadmium chloride, urea and thioacetamide at modestly acid pH values...
An 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, Reuben
Plasmodium 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.
Max-Plus Algebra for Genetic Algorithms
(2012-08-18) Ackora-Prah, Joseph
We investigate the redesigning of the general Genetic Algorithms (GAs) using concepts from max-plus algebra...
Solution of Inverse Eigenvalue Problem of Certain Singular Hermitian Matrices
(2012-12-18) Gyamfi Kwasi Baah
We investigate solutions to the Inverse Eigenvalue Problem (IEP) of certain singular Hermitian matrices. Based on a solvability lemma, we propose an algorithm to reconstruct such matrices from their eigenvalues. That is, we develop algorithms and prove that they solve 𝑛×𝑛, singular Hermitian matrices of 𝑟𝑎𝑛𝑘𝑟. In the case of 𝑛×𝑛 matrix, the number of independent matrix elements would reduce to the extent that there would be an isomorphism between the elements and the nonzero eigenvalues. We initiate a differential geometry and numerical analytic interpretation of the Inverse Eigenvalue problem for Hermitian matrices using fibre bundle with structure group 𝑂(𝑛). In particular, Newton type algorithm is developed to construct non singular symmetric matrices using certain singular symmetric matrices as the initial matrices for the iteration.

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