African Journal Of Science Research Articles

Dietary factors and predominant eye diseases in sub-Saharan African populations: A systematic review protocol.

Evidence linking diet and ocular diseases is growing, yet variations persist, with a paucity of data in sub-Saharan Africa. The proposed review will systematically synthesize evidence on dietary factors associated with predominant eye disorders (cataracts, refractive error, glaucoma, diabetic retinopathy, age-related macular degeneration, and dry eye disease) in the sub-Saharan African population. The systematic review protocol will follow PRISMA-P (Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols) for transparency in reporting. All relevant published studies in the English Language will be identified from PubMed, Scopus, Web of Science, Embase, Health Inter-Network Access to Research Initiative (HINARI), Cumulative Index to Nursing and Allied Health Literature (CINAHL), African Journal of Science, and Cochrane Central Register of Controlled Trials (CENTRAL) using medical subject headings (MeSH) and controlled vocabulary without date restrictions. The reference lists of all retrieved studies will be checked and experts will be contacted for additional relevant studies. The risk of bias for observational studies will be assessed using ROBINS-E (Risk of Bias in Non-Randomized Studies - of Exposure) and for non-interventional and randomized studies ROBINS-V2 (Risk of Bias in Non-Randomized Studies version 2) and ROB2 (Cochrane Risk of Bias 2) will be employed respectively. Study quality will be assessed using the National Heart Lung and Blood Institutes Quality Assessment (NHLBI) tool for Observational Cohort and Cross-Sectional Studies and Controlled Interventional Studies. Meta-analysis will not be considered because of the wide range of dietary factors and the susceptibility to high heterogeneity. Patterns of association between dietary factors and the specific eye diseases will be consolidated by Synthesis Without Meta-analysis (SWiM).

Science, technology and innovation in BRICS countries: Introduction to the special issue

The BRICS (Brazil, Russia, India, China and South Africa) economies have been the subject of many scholarly studies in recent years, as well as featuring in the popular media. This special issue of the African Journal of Science, Technology, Innovation and Development (AJSTID) called for original research contributions in the various aspects of Science Technology and Innovation (STI) studies in the BRICS group of emerging economics. The issue is composed of 11 research papers on different STI topics relevant to the BRICS countries.

Bibliometric analysis of ecosystem monitoring-related research in Africa: implications for ecological stewardship and scientific collaboration

ABSTRACTRegional ecosystem monitoring is a central form of knowledge sharing and collaboration amongst scientists and decision makers on environmental health, land use change, and science-policy development. Despite the proliferation of such research networks on long-term monitoring on many continents, little has been achieved in Africa. This study aims to assess and examine the spatiotemporal trend and categorical patterns in ecosystem monitoring-related research in Africa for the benefits of conserving biodiversity and sustaining natural resource sectors for well-being and livelihood security, environmental planning, and ecological stewardship. A systematic review was conducted using bibliometric tools. Based on a set of search terms and peer-reviewed publications retrieved from various ecosystem monitoring networks and journal databases, further analysis was conducted using social network approaches, mapping tools, and content analysis. About 1442 scientific publications on ecosystem monitoring and related research were documented from 1987 to 2014 mostly published in English. The number of publication increased progressively since 1992 after the Convention on Biodiversity was signed and this trend peaked till 2008. South African Journal of Science was the most leading journal and Nature the most cited. Internationally coauthored and collaborative articles represented majority of the findings with the United Kingdom at the central position in the research network due to colonial relationships. Regional collaboration amongst countries is limited owing to language barriers and other institutional constraints such as funding and short-term projects. These findings have implication for prioritizing national and regional policies toward biodiversity science and its contribution to human well-being, food security, and global change responses.

Separation of cashew nut shell liquid by column chromatography

Cashew nut shell liquid (CNSL) a natural product that consists of a mixture of phenolic compounds was separated into cardanol, cardol, and 2 - methylcardol using column chromatography. The separation was aimed at recovering cardanol that can be used in the synthesis of cation-exchange resin. The separation was effected using a mixture of equal portions of benzene and chloroform as the mobile phase in a column packed with silica gel adsorbent of particle size 60–120 mesh as the stationary phase. The mean RF-values determined from the study were cardanol (0.516), cardol (0.173) and 2-methylcardol (0.148). The corresponding RM-values calculated were cardanol (-0.040), cardol (0.673), 2-methylcardol (0.753). The RF-value is a measure of the affinity of the component for the mobile phase. The results show that the component that eluted first from the column which was cardanol had the highest affinity for the mobile phase, followed by cardol while the 2-methylcardol had the least affinity. The RM-value is a measure of the polarity of the component and its affinity for the stationary phase. The results of this study show that the component that eluted last from the column which was 2-methylcardol was the most polar. The molecular structures of these three components also show that 2-methylcardol is the most polar followed by cardol and the least polar was cardanol. The RF-value of cardanol obtained in this study could be used in the design of an industrial chromatographic column for its separation from CNSL. African Journal of Science and Technology Vol. 5(2) 2004: 92-95

Evaluation of dissolution of nonconventional phosphate fertilizers in Zimbabwe soils: effects of soil properties

Dissolution of phosphate rock (PR) depends on inherent chemical and physical properties of the rock and on external factors such as soils and plants. The objective of this study was to investigate, with a soil incubation experiment, the relationship between selected soil factors and extractable phosphorus (P) in order to assess the potential of using nonconventional phosphate fertilizers derived from unreactive Dorowa (Zimbabwe) PR on Zimbabwe soils. Three phosphate fertilizer materials: finely ground (0.150-mm screen) Dorowa PR (DPR); DPR partially acidulated with 50 % of the sulfuric acid required for complete acidulation (PADPR); and a compacted mixture of DPR + triple superphosphate (TSP) + urea + potassium chloride (DTUK) with half of the P from DPR and half from TSP, were made from Dorowa rock. Their relative effectiveness in supplying P was compared with that of single superphosphate on soils that varied in properties thought to influence PR dissolution and P availability. The effectiveness of the P sources in supplying Bray-I P after a 40-day and Pi P after a 90-day soil incubation period followed the order of SSP>DTUK>PADPR>DPR=Check. Soils high in clay, soil organic matter, and iron oxides content yielded significantly less extractable P than soils with low content. African Journal of Science and Technology Vol. 5(2) 2004: 73-82

Lightning signature as an index for the determination of the beginning of the planting season in Nigeria

West African rains are mainly due to the squall-line activities. Squall lines are groups of active thunderstorm clouds that are aligned with the ITCZ in front. The clouds are electrically active and 90% of lightning recorded occurs during squall lines associated thunderstorms. The results of measurements of lightning count from 1986 to date for Nigeria are presented in this work. Data obtained from other West African countries are also compared with them. The maximum lightning count occur mid-way between the north most position to the ITCZ and the ocean; shows a diurnal variation dependent on the movement of ITCZ that has very strong dependence on solar activities via evaporation and wind speed and direction. The minimum count is recorded during the ITCZ's recession and behind it. The applications to agricultural practices in West Africa are discussed. African Journal of Science and Technology Vol. 5(2) 2004: 28-33

Mathematical programming formulations for the examinations timetable problem: the case of the University of Dar es Salaam

Examinations Timetabling Problem (ETP) is the problem of assigning courses to be examined and candidates to time periods and examination rooms while satisfying a set of constraints. Every University has a different set of constraints and structure of examinations. Thus there is no general ETP model for all Universities around the world [1]. ETP is NP-Hard [2] and therefore no optimal algorithm is known for this problem which can solve a general problem within reasonable time. However, exact methods can be used to provide a benchmark for the heuristic methods. There is no general model for University Timetabling Problems because the problem feature differs from one University to another. In this paper we focus in the formulation of the ETP for the University of Dar as salaam. We formulate, test and compare three Integer Programming models. It is concluded that, although exact methods cannot give a solution to a real-size problem, these models give a good benchmark for testing the performance of other approaches. This paper also gives a direction for better exact models for the University of Dar es salaam's ETP. African Journal of Science and Technology Vol. 5(2) 2004: 34-40

Fracture strength of porous ceramics: stress concentration vs minimum solid area models

In this study, we have reviewed recently published strength-porosity data of porous ceramics, and compared these data with those computed from both the minimum contact solid area (MCA) and the pore stress concentration effect (SCE) models. We observed that the theoretical data (MCA model) matched better the experimental results of ceramics in the low volume fraction porosity range (P 0.25), the SCE model better predicts the experimental results. African Journal of Science and Technology Vol. 5(2) 2004: 19-27

Dimensioning of dog bone specimens and numerical analysis of the effects of different fillet radii, clamp area and pinhole loading on the stresses in such specimens

The effects of different fillet radii, clamp area dimensions, and pinhole loading through a hole located in the clamp area of a dog bone specimen were investigated using the Finite Element Analysis (FEA) software Abaqus. Changes in the fillet radius were shown to have little effect on the distribution and magnitude of the von Mises stresses. Different dimensions of the clamp section gave different von Mises stress distributions within the clamp section, with the maximum values remaining within the gauge section, thus implying that limitations of available cutters and material could be accommodated by varying the dimensions of test specimens. Introduction of pinhole loading in order to minimise torsion, led to a shift of the maximum von Mises stress from the gauge section to the edge of the pinhole, an indication that the benefits of minimising torsion required to be weighed carefully. The observed shift was only significant however, for failure load levels and for cyclic loading. A set percentage change rather than the absolute convergence of the von Mises stresses was shown to be a more economical way of arriving at an optimal mesh density, a characteristic that was seen to vary from one location to another. African Journal of Science and Technology Vol. 5(2) 2004: 60-72

Quasistationary sequences in Hilbert spaces

In this paper the concept of covariance differences of a sequence is introduced and its relationship with the covariance function is established. The criteria of linear representability of sequences in Hilbert space are proved. The necessary and sufficient conditions for a linearly representable sequence to be quasistationary are given and proved. The properties of dissipative random sequences are studied. African Journal of Science and Technology Vol. 5(2) 2004: 83-91

IMPROVED COMBUSTION PROCESSES IN MEDICAL WASTES INCINERATORS FOR RURAL APPLICATIONS

The emergence of sustainable development programmes and the problem associated with continued steady increase in population have increased public awareness and concern for the environment. In particular, the demand for health services has increased to an extent that the health sector produces large quantities of biomedical wastes that can have severe impact on the environment if not properly disposed. Although incineration is not a clean process of disposing these wastes, it is still a preferred method especially when operated at elevated temperatures. The problem in developing countries is that several incinerators either in rural or urban areas operate at low temperatures and are therefore sources of environmental pollution. This paper describes the use of cost effective and appropriate pollution control systems to achieve acceptable combustion conditions. A small rig was designed for conducting tests on the incineration of rural clinical wastes in Botswana. Experimental results showed that if proper combustion conditions are applied to low technology rural clinical waste incinerators, the operating temperatures could increase from around 400 to above 850oC. It was concluded that by increasing the operating temperatures of the current disposal methods and using wet scrubber in rural clinical waste incinerators, the combustion conditions could be improved significantly. African Journal of Science and Technology Vol.5(1) 2004: 67-72

TEMPERATURE DEPENDENCE OF THE THERMAL CONDUCTIVITY OF A GROG MODIFIED KENYAN KAOLINITE REFRACTORY

Thermal conductivity values, in the temperature range 300 – 1200 K, have been measured in air and at atmospheric pressure for a Kenyan kaolinite refractory with 0% - 50% grog proportions. The experimental thermal conductivity values were then compared with those calculated using the Zumbrunnen et al [1] and the Litovsky and Shapiro [2] theoretical models. The experimental values for samples prepared without or low percentages of grog increased with increase in temperature as predicted (reasonably good fit observed) by both the theoretical models, with the Litovsky and Shapiro's model giving theoretical values that were generally closer to experimental values than the Zumbrunnen et al's model. On the contrary, the conductivity values for the sample containing iÝ 40% decreased with increase in temperature in a manner consistent with the Eucken law. African Journal of Science and Technology Vol.5(1) 2004: 6-14

EFFECT OF BLENDING VARIOUS COLLECTORS AT BULK FLOTATION OF COPPER AND COBALT SULPHIDE ORES FROM NKANA CONCENTRATOR

Nkana Concentrator under the ownership of the then Zambia Consolidated Copper Mines Ltd (ZCCM) had been using Sodium Ethyl Xanthate (SEX) mainly as a collector, but with the coming of new Mopani Copper Mines Plc (M.C.M), it was felt that there was a need to test alternative collectors in an attempt to improve the production of the copper and cobalt concentrates. This work reports a series of laboratory testworks which were conducted on four other collectors which included, Potassium Amyl Xanthate (PAX), Sodium Isopropyl Xanthate (SIPX), Phosphorodithioic acid, O,Odiethyl ester, sodium salt or Ethyl - dtp-Na (DANAFLOAT 123) and Phosphorodithioic acid, O,O-bis (2-methylpropyl) ester, Sodium salt or i-butyl-dtp-Na (DANAFLOAT 245). The parameters considered in the evaluation were grade and recovery of both copper and cobalt minerals. Bulk float was characterised by an improvement in grades and recoveries by use of both individual collectors and their blends. Most collectors performed well except for SIPX and SEX: SIPX for the 20:80 ratio which did not give improved grades. Cobalt grades at bulk float were very poor, well below that obtained from the plant practice. It was established that the use of the other reagents such as PAX, SIPX, DANFLOAT123, DANAFLOAT 245 would be costly as compared to SEX. Cost of DANFLOAT 245 and 123 are $1.28 and $1.33 per kg respectively as compared to SEX at $1.23 per kg whereas SIPX and PAX are also slightly higher than SEX making them less favourable. Keywords : Collectors, recovery, grade, flotation. African Journal of Science and Technology Vol.5(1) 2004: 57-66

DESIGN AND CONSTRUCTION OF A WATER HEATER CONTROLLER

A micro-controller based water heater allows consumers to efficiently control domestic water heating system. Hardware and software designs and construction of the controller are done in the laboratory. The controller is interfaced with a real time digital watch, a temperature sensor and a keypad. In this design, a real time emulator driven by software controls a water heater using a micro-controller. Keywords. Micro-controller, geyser, keypad, interface, design, construction. African Journal of Science and Technology Vol.5(1) 2004: 1-5

K-AR AGES, MINERALOGY, MAJOR AND TRACE ELEMENT GEOCHEMISTRY OF THE TERTIARY-QUATERNARY LAVAS FROM THE NDU VOLCANIC RIDGE N.W. CAMEROON

The Ndu Volcanic Ridge occupies the central position amongst the continental sector volcanoes of the Cameroon Volcanic Line. K-Ar age determination coupled with field observations show that there were three episodes of volcanic manifestation: 31-28 Ma; 23-21 Ma and African Journal of Science and Technology Vol.5(1) 2004: 47-56

ACCURATE MAPPING: THE FIRST STEP TO BETTER SPATIAL INFORMATION MANAGEMENT BY AFRICAN UTILITIES

African utilities, faced with the challenge of providing diverse services to some of the fastest growing urban areas in the world, have to improve their management systems, especially the management of their spatial information if they are to rise to this challenge. This paper argues that for this to happen, urgent revision and expansion of large scale base mapping, more investment in thematic mapping by the utilities themselves, plus greater commitment to digital management support systems such as Geographic Information Systems (GIS) are necessary. Reviews of the status of large scale mapping in Kenya's major towns and the level of map usage at Nairobi's major utilities are presented as examples to support this argument. African Journal of Science and Technology Vol.5(1) 2004: 29-33

ASSESSMENT OF BUILDING FAILURES IN NIGERIA: LAGOS AND IBADAN CASE STUDY

The research focused on the causes and possible solutions to common buildings failures in Nigeria. Two major cities, Ibadan and Lagos were taken as case study. Questionnaires were administered to few selected architects, town planners, civil engineers and clients in the case study areas and also field trips were made to selected areas to ascertain common failures of buildings. Secondary data were obtained from the Nigerian Institute of Building (NIOB) and few media houses. The research outcome revealed that all parties in the building industry: Clients, Architects, Design Engineers, Local Authority (Town planners) and Contractors are contributing immensely to building failures in various dimensions. Also, the nation is loosing both human and material resources each time a building fails. Common failures seen on buildings were wall cracking, wall spalling, foundation settlement, column buckling, etc. Proper assurance of competent professionals and strict enforcement of ethical standards by the Nigerian Society of Engineers, the Nigerian Institute of Building, and the Nigerian Institute of Architects would reduce the problems identified to the minimum. African Journal of Science and Technology Vol.5(1) 2004: 73-78

A MODEL FOR INTRODUCING AND IMPLEMENTING E-LEARNING FOR DELIVERY OF EDUCATIONAL CONTENT WITHIN THE AFRICAN CONTEXT

Africa, where we have enormous and varied challenges in accessing higher education, there is need for relevant and customized content that is specific to our needs and challenges. Most of the models that exist to address these challenges have their limitations in terms of flexibility, time and space constraints and hence the need to address the mitigating factors. A blend of different types of information and communication technologies can be used in innovative ways in order to resolve some of these limitations. However, the same technologies brings about other challenges such as the costs that are associated and change of attitude and training on the part of the e-content developers. These challenges must be addressed for successful introduction of the same in an educational setup. In this paper, electronic learning is proposed as one of the main ways of overcoming some of the key challenges in accessing education. We argue that electronic learning models should be sensitive to the level of availability of infrastructure, technical support, and clear policy on implementation, evaluation and curriculum re-orientation. We propose an e-learning implementation model that can be used by educational institutions in introducing e-learning technologies to their staff and students. The model is a modification of Rogers'model of diffusion of innovation in organizations and has been developed from experiences and experiments conducted over a period of three years at the University of Nairobi. The steps involved in the proposed model are described and for each step factors that meliorate the situation are identified and put into perspective. System flowcharts have been developed and used to visualize the processes and the interrelatedness of the steps. We have contextualized the model to suit various parametric values that are dependent on cost, level of infrastructural support and staff motivation and commitment. Key Words: E-learning development process model, e-learning modes, e-content, infrastructure African Journal of Science and Technology Vol.5(1) 2004: 34-46

INVESTIGATION OF THE ANTIULCER PROPERTIES OF THE METHANOLIC LEAF FRACTION OF <i>CISSAMPELOS MUCRONATA</i>

Fraction F1 containing alkaloids and sterols/triterpenes isolated from the methanolic leaf extract of Cissampelos mucronata A.Rich (Menispermaceae) was assayed for anti-ulcer activity using histamine- and stress-induced ulcer models. The fraction and crude methanolic extract (CME) were screened for anti-spasmodic activity using the spontaneously contracting smooth muscle of the rabbit jejunum. Their antimicrobial potency was assessed using different Gram-negative and Grampositive bacteria as well as two species of fungi. The result indicate that the fraction and CME exhibited 63.25 % and 57.26 % inhibition of ulcer induced by histamine while 57.15 % and 47.14 % inhibition were recorded against stress-induced ulcer respectively. The inhibitions of ulcer induction were significant (P Key Words: Cissampelos mucronata, fraction, histamine, stress African Journal of Science and Technology Vol.5(1) 2004:109-114

Comparison of thin layer chromatography (TLC) and gas chromatograph determination of propoxur residues in a cocoa ecosystem

The fate of propoxur in a cocoa ecosystem has been studied using TLC and GC. Residues of propoxur as determined by both TLC and GC were not significantly different. TLC analysis of propoxur residues in soil, cocoa leaves and pods may not need any rigorous clean up since residues measured from cleaned and uncleaned extracts were not significantly different. The residue levels of propoxur in the soil were found to decrease rapidly and, by the 21st day, none was detected in the topsoil (0 – 15cm). Evidence of leaching of propoxur residues in the soil environment has also been demonstrated. The amount left in the top soil after the first seven days were 27%, 23% and 24% as determined by the TLC only, TLC with clean-up and GLC respectively. About 38% of pesticides detected on the cocoa pod on the day of treatment remained as residues on the pod seven days after treatment. The residue detected on the leaves on the day of treatment was higher than that for the soil. This decreased rapidly to 1.7% in 21 days compared to 16% for the soil and 23% for the pod. No propoxur residue was detected 21 days after spraying. African Journal of Science and Technology Vol.4(2) 2003: 24-28