MST-School of Pure and Applied Sciences

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This collections contains bibliographic information and abstracts of Master theses and dissertation in the School of Pure and Applied Sciences held in Kenyatta University Library

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A study on numerical range of operators in a hilbert space
(Kenyatta University, 1987) Oleche, Paul Odhiambo
Determination of water transport numbers in cation exchange membranes by an EMF (streaming potential) method
(Kenyatta University, 1987-10) Onindo, Charles Otieno
Thermal conductivity of EPDM rubber composites as a function of filler concentration and type.
(Kenyatta University, 1988) Oduor, Andrew Odhiambo
Thermal conductivities of EPDM (ethylene propylene diene monomer) rubber loaded with one of the following fillers: carbon black type N339, a reinforcing filler, kaolin, a non-reinforcing filler, and ground charcoal have been studied using a guarded hot plate apparatus designed at Kenyatta University. The hardness and tensile strength as well as the breaking energy of the composites have also been determined. The results show that the thermal conductivity, increases with increasing filler concentration in the composites. The thermal conductivity values also increase with increasing composite hardness. Thermal conductivity and tensile strength values were higher for the composites filled with reinforcing filler than those filled with non-reinforcing ones. The high values are explained in terms of the filler-polymer interaction energies that are higher in composite filled with reinforcing fillers than those filled with the non-reinforcing ones. Using several known thermal conductivity models, for bi component composites, the theoretical values of thermal conductivity were calculated for the various filler concentrations and compared with the experimentally determined values. None of these models, successfully predicted the experimental values of thermal conductivity of rubber composites. In almost all the cases the theoretical values of k for kaolin, charcoal and carbon black samples are at variance with the experimental values. Explanation for this discrepancy is based on the fact that the polymer filler interaction-parameter which is different in the three fillers used plays an important role in facilitating thermal conductivity in the composites. Besides other results, the conductivity-hardness and tensile strength results confirm this observation. As a major finding of this work, it is observed that the theoretical models available have been derived on the basis of conductivities of the individual components, they do not incorporate the interaction parameter which apparently plays an important role in rubber composites.
The use of crown ethers in the von richter reaction
(Kenyatta University, 1988) Langat, Caroline Chelang'at
Electrical Characterization of Cu and Al Doped Amorphous Semiconductor As2Se3
(Kenyatta University, 1988-10) Okumu, John.
The electrical conductivity and thermoelectric power of an amorphous semiconductor As2Se3 in pure and doped forms were studied with temperature. The dopants used were 1 at. % Cu and 1 at. % AI. Measurements on electrical conductivity were performed in the temperature range 223-573 K and that of thermoelectric power in the temperature range 343-473 K. The effects of the impurities on the conductivity and thermoelectric power of amorphous As2Se3 are small. The samples showed conductivity activation energies. The electrical conductivity versus inverse temperature curves showed a break at low temperatures. The activation energy of conduction, E , above room temperature were found to be 0.77 ± 0.09 eV, 0.82 ± 0.09 eV, and 0.64•± 0.03 eV for pure , Cu doped, and Al doped samples respectively. The thermoelectric power varied linearly with inverse temperature and all samples were found to be p-type. The activation energy, ES' from thermoelectric power measurements were found to be 0.96 ± 0.06 eV, 0.87 ± 0.02 eV, and 0.84 ± 0.05 eV for pure, Cu doped, and Al doped samples respectively. Most of the above results have been explained on the basis of the CFO and the dangling bond models. The CFO model postulates a mobility edge and overlapping tails of localized states in the energy gap and in the dangling bond model, charged defects D+, DO, D-, exist in the energy gap, which act as traps to charge carriers.
The jahn-teller effect in the absorption band of activated crystals
(Kenyatta University, 1989) Gathua, Joseph K.; Dod, T. S.
Phytoplankton and Physicochemical Dynamics of Lake Baringo
(Kenyatta University, 1989) Kiplagat, Wilson; Patterson, Graeme; Muthuri, Francis M.
Electrical Characterization of Iodine Doped Organic - Semiconductor Polypropylene
(Kenyatta University, 1989-10) Mulati, David Masabule
Cytogenetic studies of some Kenyan tea clones (camellia Sinensis) l.o. kuntze) karyotype and ploidy.
(Kenyatta University, 1990) Wachira, Francis Nyamu; Njagi, G.D.E.; Magambo, M.J.S.
A comparative intraclonal analysis of ploidy states and karyotypes was performed on eight Kenyan tea clones (Camellia sinensis L.O. Kuntze), by examining shoot meristematic cells. C-metaphase chromosomes were studied by acetopropionic orcein staining methods. Several karyotypic variables VJere determined for each clone; chromosome number, short arm length (S), long arm length (L), total chromosome length (TL), arm ratio (r), relative chromosome 1ength (RL), and the presence or absence of secondary constrictions and satell ites (SAT). Clones 7/9, S15/10, 6/8, 31/8, TN14/3 amd 57/15 were all shown to be diploids w it.h chromosome complements of 2n - 2x = 30. Clones 84/2 and 84/1 we re confirmed to be naturally occurring triploids with chromosome complements of 2n=3x=45. Analysis of variances for the means of chromosomal variables, notably total chromosome lengths, indicated that there were significant (P<0.05) differences between chromosome pairs within each complement. Except for a few instances, corresponding chromosomes among the diploids were, however, shown not to differ significantly in length. In this case, therefore, chromosome lengths failed to yield diagnostic mar ke rs related to the six diploid clones and their phenotypes (yield and quality potentials). vi Corresponding chromosomes among the t.wo triploid clones wo re howave r shown to be more variable. The triploid clones similarly had their chromosomes reduced by as much as 14% in length as compared to their diploid counterparts. Arm ratios for the haploid chromosome complements within all the eight clones decreased along w ith chromosome lengths. Using arm ratios to define centromeric positions, all the eight clones were shown to have ch romosomes wh ich we re essent iall y metacentr ics. The decrease in arm ratios with chromosome length therefore meant that the shortest ch romosomes with in each comp 1ement were either perfect or near perfect metacentrics. Secondary constrictions and satellites were also shown to be consistently absent in all the eight clones. Preliminary wo rk on Giemsa staining did not give positive results and had very limited success in resolution of chromosomal structures for all the eight clones.
Immunization studies in rabbits using midgut membrane bound protein derived from rhipicephalis appendiculatus neumann, rhipicephalus evertsi evertsi neumann and amblyomma variegatum fabricius
(Kenyatta University, 1990) Kutima, Hellen Lydia
The objective of this study was to immunize rabbits with midgut membrane-bound proteins derived from partially engorged Rhipicephalus appendiculatus, R. evertsi evertsi and Amblyomma variegatum female ticks a~d assess whether the immunity elicited was protective against both homologous and heterologous tick ins tars and to isolate and identify the protective antigens. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the Gut Membrane-Bound Protein (GMBP) antigens demonstrated protein bands with molecular weights ranging from 14 to 140 kDa. Approximately 37 protein bands were fractionated from appendiculatus GMBP antigens, approximately 45 protein bands ere fractionated from . evertsi evertsi GMBP antigens and approxi ately 39 protein bands were fractionated from !. variegatum GMBP antigens. Twentytwo of the isolated proteins were shared among the three tick species. The ability of rabbits to acquire resistance 'to ~. appendiculatus, R. evertsi evertsi and !. variegatum was determined by injecting three separate se~s of rabbits with respective GMBP antigens. Resistance was manifested by prolonged feeding, reduction in engorgement weights, egg mass weights, mou ting and percentage hatchability and increa ed mortality. Cross-resistance was evaluated by dividing R. appendiculatus, R. evertsi evertsi and A. variegatum resistant rabbits into three groups each and challenging them with homologous and heterologous live stages. Considerably high cross-resistance was apparent among the three groups. Cross-protection was more pronounced in the homologous than heterologous systems. Enzyme Linked Immunosorbent Assay. (ELISA) technique detected circulating antibodies in the immune sera to GMBP from homologous and heterologous systems one week after the primary dose. Ouchterlony double immunodiffusion reactions with anti-tick GMBP sera formed 2 to 4 precipitin lines with homologous GMBP antigens and 1 to 2 precipitin line(s) with each heterologous GMBP antigens. A line of complete identity was observed when immune sera to GMBP antigens reacted with GMBP from homologous and heterologous tick species, suggesting common antigenic epitopes. Western blot analysis on GMBP of R. appendiculatus, !. evertsi evertsi and !. variegatum with sera from immunized rabbits detected protein bands specific to the homologous GMBP antigens, and revealed considerable cross-reactions in the heterologous systems. In conclusion, there was prolonged feeding periods, reduced engorged weights, egg mass weights hatchability and moulting and increased death rate of both homologous and heterologous challenge ticks which fed on resistant rabbits. This was due to the presence of common antigens. The presence of cross-reacting antigens conferred cross-protection. These results have pointed out that it is possible to protect livestock from R. appendiculatus, R. evertsi evertsi and !. variegatum using an antigen from anyone of the three tick species hence reducing the expence of having to develop an antigen to control each tick species as there are in existence.
Application of canonical correlation analysis ;a comparative study on academic perfomance
(1990-06) Makambi, Kepher Henry
A survey of some cucurbitaceae species in Kenya with an analysis of cucurbitacin content, and an identification guide to poisonous and safe species
(Kenyatta University, 1992) Njoroge, Grace Njeri
The Cucurbitaceae is a family of dicotyledonous plants. For a long time the plants in this family have been cultivated as sources of vegetables and fruits. Many of the wild species are reported to be used locally as sources of vegetables. While others are given to domestic animals as fodder. Some of the wild species however. have been reported to poison people as well as domestic animals that may feed on them. Cases of poisoning could be as a result of misidentification of these species . For investigation into this problem a total of 23 cucurbitaceous species were collected from Nairobi area as well as from the surrounding areas. These plants were identified and voucher specimens deposited at EA. Cases of poisoning in cucurbitaceous species have been attributed to the occurrence of a group of triterpenoid compounds called cucurbitacins. The presence or absence of these compounds in the various organs of these cucurbitaceous species is determined firstly by test and triphenyltetrazolium chloride secondly by the infrared precipitate absorption spectrophotometer. Individual cucurbitacins were provisionally identified by thin-layer chromatography with authentic samples. Presence or absence of the toxic cucurbitacina was assessed in the various organs which are used locally as sources of vegetables or herbal medicines. It is possible from this work to distinguish the plant parts with toxic cucurbitacina and identify the plants in the field using the key presented. To make the results of this study available to the local people who use them an identification key was constructed . This key avoided technical botanical terms . which implies that it can be used by people without botanical training to identify the plants in the field. Simple illustrations are included in the key to aid identification. In addition, the local uses, distribution and flowering times of these species were investigated. It is hoped that the results of this work will reduce incidence of poisoning
Some aspects of the decomposition process in the mangrove swamp at Gazi Bay, Kenya
(1993) Boga, Hamadi Iddi
Kinetics and Mechanisms of Catalysed and Uncatalysed Oxidation of Organic Dyes by Inorganic Species and Indicator Reaction for Determination of Cations
(Kenyatta University, 1998) Ngugi, Sironik Stephen
The rate of oxidation of both the uncatalysed and Vanadium (V) catalysed reaction between indigo carmine (IC) and Chromium (VI) as well as the uncatalysed and Ruthenium (III) catalysed reaction between methylene blue (MB) and cerium (IV) have been studied. Both reactions were performed in sulphuric acid media by monitoring the absorbances of IC and MB at 610 nm and 665 nm respectively at 25°C. The kinetics and the probable mechanisms of these reactions have been elucidated. For the former reaction, the order with respect to IC, H+ and Cr(VI) were 1, 2 and 1.5 respectively and 1 for V(V) in the case of catalyzed reaction while for the latter reaction the partial orders with respect to MB, Ce(IV) and H+ were 2, 1 and 0 respectively and 1 for Ru(III) in the case for the catalysed. The mechanism for the ICCr( VI) reaction involves an initial two electron process which is confirmed by the limiting induction factor of 0.5 from the iodide ion induction reaction. Further the presence of V(V) ion in the reaction mix!ure caused an increase in the rate of the oxidation of IC that was affected by traces of Ru(III) and Mo(VI). The interfering effects of the Ru(III) and Mo(VI) were effectively masked by traces of thiourea and thiocyanate respectively without any appreciable effect on the rate of the uncatalysed reaction. The uncatalyzed and RU(III)-catalyzed reaction between MB and cerium (IV) sulphate in acidic media occurred by means of a chain reaction. The presence of free radicals in the reaction media were established by means of introducing acrylamide which formed a co-polymer with MB whose rate of formation was drastically reduced using 1,4-benzoquinone. In addition a high stoichiometry of MB:Ce(IV) 1:40 was observed for both the catalyzed and uncatalyzed reactions. The presence of Mo(VI), W(VI) and Co(III) ions was found to interfere with the rate of the indicator reaction. The interfering effect of W(VI) and Co(III) were masked by ammonium hydrogen phosphate and sodium fluoride respectively while that of Mo(VI) could be effected by extraction using 2-Methylpropanol followed by ethylacetate prior to oxidation. Further, a fixed time method is described for the determination of V(V) and Ru(III), based on their ability to catalyze the oxidation of IC by Cr(VI) and MB by ceric sulphate respectively and the interference of other cations on their determination studied using synthetic mixtures.
A study of the Reactions of tetrabromopctacarbonyldimolybdenum(II) Complex with 1 ,2-bis(diphcnylphosphino)ethane at Elevated Temperature
(1998) Changamu, Evans O.
The reaction between (Mo(CO)4Br2)2,and 1,2-bis( diphenylphosphino )ethane, (dppe), has been investigated. The results show that at the refluxing temperature of tetralin (about 190 C) (Mo( CO)4Br2h reacts with 1,2-bis( diphenylphosphino )ethane (dppe ),giving disproportionation and decarbonylation products. The decarbonylation products isolated from the reaction mixture wtre a maroon coloured complex of empirical formula Mo( dppe )Br2 and a yellow coloured complex of empirical formula Mo( dppe hBr2. The disproportionation products isolated were a brown coloured Mo(IV) complex, Mo(dppehBq, a yellow coloured Mo(O) complex, Mo(COh(dppeh and a pale flesh complex whose elemental analysis data suggest is Mo(dppe)).CloH12. The UV-VIS and IR spectra of the various complexes isolated have been recorded. The UV-VIS spectroscopy was used to distinguish between the maroon-coloured complex with empircal formula MoBr2(dppe) and the yellow complex MoBr2(dppeh. Electrical conductivity measurements have been done on MoBq( dppe h in nitrobenzene and the results show that it is a 1:1 electrolyte. The possible reaction mechanisms by which these products were formed are suggested.
Efficacy of seed-dressing and organic amendments against fusarium root-rot of French beans (phaseolus vulgaris l. Cv. Monel.) in Kenya.
(Kenyatta University, 1998) Wagichungc., A. G. Richard.
Laboratory, greenhouse and field tests were conducted to (i) compare relative pathogenicity of Fusarium solani fsp. phaseoli and F oxysporum f.sp. phaseoli on ,french beans (Phaseolus vulgaris L. cv. Monel), (ii) evaluate the efficacy of seed dressing with various fimgicides singly and in combinations against the two pathogens (iii) compare efficacy of organic matter and / or fungicides on root-rot caused by the two' pathogens and (iv) compare effects of delay ~ planting after application of cowdung and Tithonia diversifolia on the root-rot. Laboratory experiments were arranged in a completely randomised block design while greenhouse and field experiments were arranged in a randomised complete block design. Five replicates were used in all tests. In-vitro fimgitoxicity potential offimgicides and fungicide combinations was assessed by computing % inhibition of mycelial growth, % spore germination and number of spores produced on fungicide treated dishes relative to that of controls. Plant growth assessment was based on plant shoot height, dry weights of seeds, shoots and roots, and number of pods produced .. per plant. Disease severity was determined using mean length of discoloured root tissue (MLDRT) and mean.root rot index (MRRl). The plant growth parameters stated above were significantly (p=O.05) lower on plants infected with the two Fusarium spp. than control. However, slightly higher % loss in nw:nber of pods and seed dry weight were realised on those plants infected with F oxysporum fsp. phaseoli than F solani fsp. phaseoli. No statistical differences were noted between the effects of the two Fusarium spp. on bean, growth. Disease severity on plants inoculated with the two pathogens was similar. MLDRT and MRRI, were the same in both cases. However, MLDRT and MRRI were relatively higher on plants infected by F oxysporum fsp. phaseoli than 1'. so/ani fsp. phaseoli. This suggests that F oxysporum fsp. phaseoli may have been more pathogenic than F solani fsp. phaseoli under the prevailing experimental conditions. Fungitoxicity was based on the eTfect of fungicides on mycelial growth, spore germination and sporulation. Fungicide -treatments significantly (P=O.05) inhibited mycelial growth, spore germination and sporulation of both test fungi. However, fungal sporulation was higher in plates treated with fungicides than in controls an indication that fungicides stimulated sporulation. Although no fungicide treatment was seen to be an inhibitor of all the three measures of fungitoxicity, the ranking of the best three fungicide treatments was be, thiram 50 + captan 50 >triforine > metalaxyl mancozeb. Individual fungicide treatments had significantly (P=O.05) better effects on plant growth and disease development than fungicide combination or control. Significantly (P=O.05) higher plant growth parameters and lower MLD RT and MRRl were recorded from single fungicide treatment on both the greenhouse and field grown plants. Significantly (P=O.05) better plant growth, more pods and heavier seed dry weights were recorded from plants obtained from seeds treated with fungicides triforine or metalaxyl. Integration of cowdung and T diversifolia with the fungicide metalaxyl revealed that cowdung or a combination of cowdung with metalaxyl significantly (P=O.05) reduced disease development and increased plant performance more than T diversifolia or a combination of T diversifolia with metalaxyl. Plants harvested in soils treated with T diversifolia or a combination of T diversifolia with metalaxyl or controls had the poorest seed and pod yields. Germination was low and no pods wereharvested from plants grown in these soils. A delay in planting french bean in soil treated with cowdung significantly (P=O.05) decreased development of root rot when compared to untreated controls. The greatest decrease was obtained with 2 and 4 week delay. Shoot and root dry weights of plants infected by F. oxysporum fsp. phaseoli or F solani fsp. phaseoli significantly (P=O.05) increased with delay in planting and were highest where planting was delayed 2 and 4 weeks, respectively. A delay from 0 to 4 weeks in planting french beans in soil treated with crushed leaves of T diversifolia significantly (p=O.05) increaseddisease severity and reduced plant performance when compared to untreated control.
Gravity Survey in Magadi Geothermal Area
(Kenyatta University, 1999) Waithaka, J. W.
Kenya has prominent geographical features such as the Rift Valley which gives rise to geothermal reservoirs which can be exploited to produce geothermal energy for power generation and heating. Lake Bogoria, Lake Magadi as well as other areas are considered to have potential for geothermal energy because of the existing hot springs. For above mentioned regions it is known that positive gravity anomalies within the Rift Valley proper are superposed on the generally negative gravity anomaly typically for rift structures. Research has availed that these local gravity highs can be explained as result of high density intrusions in the upper crust. The aim of the project was to study the gravity highs in Magadi and determine whether they could be possible sources of geothermal energy. The area of study comprises a part of the Rift Valley, which has geothermal potential. The Magadi area is located in the southern part of the Kenyan Rift Valley. The gravity prospecting method was used in the project to investigate the gravity anomalies occurring in the area. Both qualitative and quantitative interpretations were attempted and conclusions drawn from the findings. A gravity survey was conducted to fill in the unsurveyed sectors. The data collected was subjected to the necessary corrections and a Bouguer anomaly map of the area was then drawn. The Bouguer gravity values ranges from -1800 g.u. to -1600 g.u. with the maximum peak occurring at the NNE part of the project area. The relationship between the gravity anomalies and the topographic features of the area is clearly noticeable. The quantitative interpretation involved fitting theoretical two-dimensional models to the observed data along profiles. The choice of two-dimensional models was dictated by the shape of the anomalies to be interpreted. The anomalies were interpreted in terms of intrusions of several bodies. The geometries of these bodies were also determined. Quantitative interpretation involved forward modelling along five selected profiles named PQ, MN, UV, CD and RG. The model parameters arrived at suggests that the causative bodies in this area are found to be dikes like structures except the body behind the gravity profile MN which seems to be due to a shallow magma chamber. Gravity body behind PQ is at a depth of 0.2 km to the top, 4 km to the bottom with an average width of 1 km and dips at 110° to the horizontal. It has a density contrast of about positive 280 to 290 kgm" and with an elongation of NNWSSE. The depths to the top of the bodies MN, UV, CD and HG are 0.15, 0.3, 0.5 and 0.15 km respectively while the depths to the bottom are 6.1, 4, 4 and 3.6 km respectively. The profiles mentioned above have positive density contrast ranging between 280 kgm" and 340 kgm" , with dip angles of 90°, 90°, 82° and 90° respectivelywhich are elongated in a nearlyN-S or NNW-SSE directions. It was found that the densities of the rocks causing the positive anomalies in the region is about 3 000 kgm" or slightlyless. The mode of formation of the causative bodies and shallow depths indicate that the area is potential for the generation of geothermal energy. Comparison of the results of this study with other studies in the sameregion, indicate that the anomalies are caused by bodies at shallow depth. The study of the gravity anomalies revealed that the major gravity disturbances were caused by the rifting and the subsequent tectonic activities of the Rift Valley, since the gravity anomalies were found to have north south trending nature which coincidewith the north-south running features such as dykes, fractures e.t.c. that are aligned in the direction of rifting. The agreement between the final geophysical models
Finding the Distribution of a Random Variable from its Moment Function
(2000) Otwombe, N. K.
Consider the problem of r .~/ randomly distributed points in a unit n-ball and the convex hull created by these points. Let ~II be r! times the r-content of an rsimplex whose P vertices are in the interior and r -I- /- p vertices on the boundary of a unit n-ball. Explicit expressions for the exact distribution functions of ~II are given when r I / points are independently, and identically distributed according to the Uniform distribution. The exact distributions are obtained using the technique of Inverse Mellin transforms with the help of the moment functions. The technique is illustrated for the general case p =- r -j J and a particular case p =3, r - 2 . Various representations of the distributions in psi and the generalized zeta functions are given. These representations are also given in the most general case as an H- function distribution. SYMBOLS AND NOTATIONS The following is a list of symbols and notations, with meanings indicated on the right that will frequently occur in this Research. (" ) = 17 1 fII ml(n-m) Binomial Coefficient m-J .(at, =n(a +.j), (a),. = I Pochhammer Symbol j (! r(a) Gamma Function pdf Probability density function The cumulative distribution function The natural logarithm of 10 r-content of the r-simplex generated by r + 1 points 11" = r! 11 r! times the r - content of the simplex R",£" Euclidian n-space Re(.) The real part of (.) arg(.) Argument of (.) GRAPHS AND TABLES Fig. 4.1 Theoretical cdf plot for r=2, n=Z, p=3 Fig. 4.2 Density plot for r=2, n=Z, p=3 Table 1 Table of Theoretical moments and the exact Moments from Equation (4.1.1)
Heavy Metal and Organochlorine Pollutants in Tissues of Marine Fauna along the Coast of Mombasa Island - Kenya
(Kenyatta University, 2000) Kipkosgei, Bor Samuel
Marine pollution is increasingly becoming a problem along the Kenyan coast. Heavy metals and organochlorine pollutants have the potential to damage the delicate marine ecosystem with the result that the country's important foreign exchange earner - tourism - could seriously be affected. This study aimed at assessing the levels of cadmium, lead, copper, zinc, manganese, iron and titanium using Energy Dispersive X-ray Fluorescene (EDXRF) and Atomic Absorption Spectroscopy (AAS) in selected marine fauna. It further assessed the levels of lindane, aldrin, dieldrin, endosulfan (o-, B-), DDT and its metabolites using Gas-Liquid Chromatographic (GLC) techniques. Certified reference material (Mussel Tissue, MA-M-2ITM, IAEA) was analyzed by, both AAS and EDXRF techniques, for quality assurance and control. The two methods are in good agreement and the results are within 10% of the certified values (Appendix III). For statistical analysis, regression analysis was used to calculate the concentration of samples and relationship between pollutant concentrations. Some of the calculations refer to the dry weight of soft tissues. One-way analysis of variance (ANOVA) was applied with the aid of a computer programme to investicate the differences in pollutant concentrations between animal samples and between locations. The level of statistical significance was set at p::;0.05, unless otherwise stated. Tukey's studentized range test was used to separete the means when ANOVA indicated significant differences. Marine animals used for the study were chosen from molluscs, echinoderms, crustaceans and chordates sampled mainly along thexiii coast of Mombasa Island. Some samples were also collected from Vanga in the South Coast, Nyali Beach and Marine Park in the north. The four groups of animals were all found to have accumulated heavy metals and pesticides to some considerable extent. Concentrations of lead and cadmium ranged from 3.68 - 5.70 ppm and 0.47 - 1.45 ppm respectively. Pesticide levels were, however, relatively low (0.227 ± 0.026 ppm ). Lindane which was found in 64% of all the animals studied, ranged from the detection limit (0.01 ppm) - 0.561 ppm. Marine fauna sampled near the Mombasa showground (English Point) contained higher than average (4.25±0.37 ppm against a mean value of 2.295±0.22 ppm) levels of the heavy metals studied. Pesticide concentraion had a similar pattern with a level of 0.383±0.039 ppm against a mean value of 0.235±0.039 ppm. Vanga was another place where marine animals were found to have accumulated the heavy metals and pesticides to a significant (p = 0.0481) extent (4.07±0.25 ppm and 0.242±0.01 pprn respectively). The highest concentration of lead (14.80 ± 0.42 ppm ), recorded in this study was found in Crassostrea sp. sampled from Vanga. Cadmium registered a concentration of 3.49 ± 0.31 ppm in Uca vocans collected from Mbaraki. The same species registered the highest concentration of lindane ( 0.561±0.5 ppm ). Although this study has confirmed that marine fauna from the Kenyan Coast have accumulated both the heavy metals and pesticides studied, the levels are generally low compared to the results from a similar study by Windom (1991). However, unless the pollutants are monitored continuously, the levels are set to increase, with serious implications.
Characterisation of natural immune responses to fal vac-l of plasmodium falciparumin children and adults from a holoendemic area of Western Kenya
(Kenyatta University, 2000) Were, Tom
Previous studies indicate that FAL VAC-1, a recombinant multistage and multicomponent Plasmodium falciparum candidate vaccine containing 12 B cell and 9 T cell epitopes from 9 different antigens of different life cycle stages is immunogenic in animal models and that FAL VAC-1-induced antibodies produced significant antiparasite activities against both sporozoite and blood stages of the parasite. In preparation for vaccine trials in humans, a community based cross-sectional study in a malaria holoendemic area of western Kenya was conducted during April-August 1999, to characterise in vitro natural humoral and cellular immune responses to this candidate vaccine and their association with clinical protection against malaria in young children < 2 years old (N= 180) and their non-pregnant mothers aged 15-48 years (N=139). FAL VAC-1 antigen was used in antibody measurement by ELISA and in lymphoproliferative experiments. Prevalence and level of antibodies were significantly higher in adults than in children when stratified by age groups: 0-6 months; 7-12 months, 13-18 months; 19-24 months; 15-25 years and 26-48 years. Total IgG, IgG1, IgG3 and IgM were the predominant antibodies. IgG2 responses were low and no IgG4 was detected. In children, there were higher IgG 1 levels in parasitaemic group than in the aparasitaemic 'group (F=3.459, p=0.024, t-test). Furthermore, total IgG, IgG1, IgG3 and IgM levels were inversely associated with .' . r '. haemoglobin levels at the time of sampling (total IgG, r=-0.215, p=0.005, IgG1, r=- 0.180, p=0.019; IgG3, r=-0.164, p=0.034; IgM, r=-0.216, p=O.OOl). Parasitaemic children had significantly higher IgG 1 levels at a month prior to sampling. In addition, IgG 1 was positively correlated to the rate of high density parasitaemia and to episodes of clinical malaria (r=0.218, p=0.029 and r=0.237, p=0.018), respectively. However, in adults, aparasitaemic individuals had high total IgG, IgG 1 and IgM levels than parasitaemic individuals (total IgG, F=3.856, p=O.007; IgGl, F=2.701, p=O.007; IgM, F=5.133, p=O.OOl,t-test). In addition, IgG2 was inversely associated with haemoglobin levels at the time of sampling. In contrast to antibody responses, lymphoproliferative responses were higher in children than in adults (one-way ANOV A, F=2.392, p=O.038). Generally, lymphocytes from adults responded at lower antigen concentrations, while those from children responded at higher antigen concentrations. There were no associations between lymphoproliferation and malaria infection or haemoglobin level in either young children or adults. The results of this study therefore indicate that: FAL VAC-l, a multistage multicomponent malaria vaccine candidate is recognised by individuals naturally exposed to malaria. The antibody responses increase whereas lymphoproliferative responses decrease with age. The higher IgG1 levels in children may indicate the presence of a current P. falciparum infection, but in adults from the same holoendemic area, IgG 1, may be associated with protection against parasitaemia.

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