African Journal of Science and Technology最新文献

{"title":"Detection and quantification of toxins in cultures of microcystis aeruginosa (pcc 7820) by hplc and protein phosphatase inhibition assayffect of blending various collectors at bulk","authors":"G. Akin-Oriola, L. Lawton","doi":"10.4314/AJST.V6I1.55157","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55157","url":null,"abstract":"Increasing anthropogenic eutrophication in lakes, drinking water reservoirs and coastal waters is a world-wide phenomenon leading to the formation of blooms of toxic cyanobacteria. These pose a significant threat to human and animal health hence the need for sensitive methods for their detection, identification and quantification. This report presents two methods: analytical high power liquid chromatography coupled with photo-diode array detection and protein phosphatase inhibition assay for the analysis of the most frequently encountered cyanobacterial hepatotoxins – the microcystins. Four microcystin variants: microcystin - LR, - LY, - LW and - LF were identified and quantified by HPLC in cells and growth media of cultured Microcystis aeruginosa PCC 7820. The protein phosphatase inhibition assay was used to estimate potential toxicity of cyanobacterial extracts and both methods showed good correlation (R2 = 0.91). Although HPLC provides accurate and specific information on the identity and quantity of each microcystin variant, it is quite expensive. The assay method on the other hand is relatively cheaper and can be modified to measure milligramme quantities of sample on a benchtop spectrophotometer but individual microcystin variants cannot be identified","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87790022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INTERSYSTEM INTERFERENCE DUE TO HYDROMETEOR SCATTERING ON SATELLITE DOWNLINK SIGNALS IN TROPICAL LOCATIONS","authors":"M. Ajewole, John Sunday Ojo","doi":"10.4314/AJST.V6I2.55176","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55176","url":null,"abstract":"This paper computes intersystem interference due to scattering by hydrometeors into the downlink receiver terminal of a communication satellite in three tropical locations, Ile-Ife (Nigeria), Nairobi (Kenya) and Douala (Cameroon). The evaluation procedure used was the simplified 3-D bistatic radar equation and the exponential rain-cell model. The results obtained in this study show that the cumulative distribution of effective transmission loss (Le) is much lower than the cumulative distribution of transmission loss in all the locations. For instance, at time percentage unavailability of 0.01%, the effective transmission loss is lower than the transmission loss by 20 dB in Douala, 15 dB at Ile-Ife and 11 dB in Nairobi. The lower the effective transmission loss, the higher is the interference in the satellite receiver. Also,a comparison of the effective transmission loss in the regions shows that Douala has the worst effective transmission loss, that is, highest interference at all frequencies and time percentages. Therefore, while it is acknowledged that satellite fade outs at frequencies greater than 10 GHz is a problem in these locations, it may be deduced that Douala has comparatively the highest frequency of outages.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"561 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91552028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DETERMINATION DE LA QUALITÉ DU PAIN DE SUCRE A PARTIR DES CONCENTRATIONS DES SUCRES REDUCTEURS","authors":"M. Amrani","doi":"10.4314/AJST.V7I1.55185","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55185","url":null,"abstract":"Ce travail fait reference a un procede automatise pour l’elaboration du pain de sucre a partir du jus de canne a sucre. Les caracteristiques du produit traditionnel sont maintenues tout en veillant a conserver ses qualites intrinseques qui en font un aliment naturel, peu altere par ce procede technique. Un procede semi-continu a ete developpe pour elaborer le pain de sucre. Le procede se subdivise en 3 etapes principales : l’extraction du jus de canne, l’epuration et la concentration du jus, enfin le moulage du pain de sucre. La durete et la texture du produit fini sont les parametres majeurs qui conditionnent la qualite du produit. Les fluctuations des concentrations en sucres reducteurs directs SRD influent significativement sur les parametres durete et texture. Ces derniers demeurent les indicateurs majeurs de critere de qualite du pain de sucre. Cette etude est un descriptif detaille du procede d’elaboration du pain de sucre dont la qualite depend etroitement de la concentration en SRD tout au long de la chaine de fabrication. Les correlations entre les concentrations SRD et les parametres qualite y sont egalement developpes.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75717520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Essai d’optimisation de la capacite de retenue d’eau d’un lac par caracterisation geophysique du recouvrement Argileux","authors":"S. Bakkali, J. Bouyalaoui","doi":"10.4314/AJST.V6I2.55173","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55173","url":null,"abstract":"Les auteurs proposent une etude geophysique par mesures de resistivites geoelectriques en vue d’optimiser les capacites de retenue d’eau d’un lac artificiel d’une commune rurale. Le lac Rahrah de la commune dite Rahrah dans la province de Tanger au Nord du Maroc est le reservoir principal de la dite commune pour ses besoins considerables en arrosage agricole. Cette etude a pour objectif la reconnaissance et la determination de la profondeur optimale du lac : il s’agit de definir la nature geologique des terrains et de delimiter soit la base des couches impermeables soit le toit du substratum resistant. Afin de determiner la nature lithologique des terrains et leurs epaisseurs, 25 sondages electriques Schlumberger de direction Nord-Sud ont ete implantes et realises de maniere a couvrir la surface totale du lac Rahrah.. L’appareil de mesure de la resistivite apparente est le resistivimetre GTR-2 a sommation de signaux et a compensation automatique de la polarisation spontanee de Geotrade Instruments. Le traitement des donnees de resistivites apparentes mesurees a ete realise a l’aide du logiciel WinSev 3.3 de Geosoft. Les sondages electriques realises sont analogues et integrent un modele de terrain caracterise par le passage d’une formation argileuse en surface a une formation greso-calcaire en profondeur. Ces sondages electriques attestent egalement de l’homogeneite des terrains sur toute la surface du lac. Du Sud vers le Nord, il existe une variation de la profondeur du toit du substratum resistant, et par consequent des epaisseurs du recouvrement argileux, qui peuvent atteindre 15 metres vers le sud et 35m vers le nord. Les cartes de distribution des epaisseurs et des profondeurs, issues de l’interpretation des sondages electriques, sont realisees a l’aide du logiciel Surfer (Win32) V.6.04 de Golden Software.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89237408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The beneficiation of mumbwa phosphate deposit by various techniques","authors":"C. Lukomona, J. B. Mwalula, L. K. Witika","doi":"10.4314/AJST.V6I2.55182","DOIUrl":"https://doi.org/10.4314/AJST.V6I2.55182","url":null,"abstract":"The Mumbwa phosphate ore constitutes of Apatite(43.6wt%) as the major mineral, Feldspar(29.0wt%), Iron oxides(14.4wt%), minor quantities of Quartz(8wt%) and the rest being trace minerals. The chemical composition of the ore averages 22.7 % P2O5 with the other constituents being 22.8% SiO2, 19.0% CaO, 7.0% Fe2O3, 4.0 % Al2O3 and 0.2% MgO. Beneficiation studies were performed to investigate methods of concentrating the phosphate values. Preliminary investigations involved detailed identification of mineralogical and chemical properties of the constituents minerals which would form the basis of selective separation of the phosphate values from the gangue. The results of these studies showed that liberation of apatite occurred below the average grain size of 500 μm. On the basis of the identified mineralogical and chemical properties of the minerals, heavy media separation using Bromoform and subsequently flotation were applied in the beneficiation tests. The results indicate that heavy media separation techniques could not be used to give a final phosphate concentrate. It has to be a pre-concentration process prior to another concentration process. Encouraging concentrate grades were obtained after flotation with a cationic collector, petroleum sulphonate. The optimum pH being 9.5 and the concentration of petroleum sulphonate 1200 g/ton. Under these conditions, the grade was 40.8% P2O5 with 1.65% SiO2 while the combined grade was 50.2% P2O5. On the basis of this test, a treatment flow sheet for this deposit has been proposed.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"106 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80396937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Antiphase phenomena in 2d ising square lattice","authors":"Y. B. Sitamtze, S. Zekeng, J. Ndjaka, S. Domngang","doi":"10.4314/AJST.V7I1.55188","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55188","url":null,"abstract":"Monte Carlo simulations of the two dimensional Ising model were carried out to determine the impact of Antiphase Boundaries (APBs) in some thermodynamic functions of the system. We considered several lattice sizes and sometimes both Ferromagnetic (FM) and Antiferromagnetic (AFM) interactions for the same lattice. The analysis of the curves obtained shows that APBs appears only in AFM interaction and their effect is the creation of an energy gap that prevents the system from reaching the ground state. This happens only in lattices with odd linear size L (L = 9, 15, 31 …). However, these boundaries do not change the critical temperature of the Antiferromagnetic/Paramagnetic (AFM/PARA) phase transition which remains approximately at 2.26 (in unit of J/kB). Nevertheless, they impose on the curve of the specific heat a jittery behaviour as a function of the temperature and with no clear peak as opposed to the case of even L (L = 16 ,20, 48,…) where there is a clear peak and a smooth curve. There is also a fluctuating magnetization around the value zero at low temperature (AFM phase). We show that this energy gap is proportional to 1/L where L is the linear size of the lattice, thus this gap should vanish if L becomes high. A similarity has been established with the role played by APB in some crystal structures and more especially in the binary alloys that are moreover described by the Ising model.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80144380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of collector, frother and depressant addition on the copper recovery and concentrate grade of the nchanga underground scavenger circuit of konkola copper mine - Zambia","authors":"M. K. Mpongo, E. Siame","doi":"10.4314/AJST.V7I1.55186","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55186","url":null,"abstract":"Nchanga copper ore is a complex mixture of sulphide and oxide minerals and processing involves sulphide flotation and the sulphide rougher/scavenger tails rich in oxide minerals (acid soluble copper) are sent to the Tailings Leach Plant for the recovery of the acidsoluble copper. Currently, the acid insoluble copper (sulphides) losses on the scavenger banks are very high, from about 0.3 % TCu to 0.77 % TCu. Mineralogical tests carried out on the scavenger feed samples showed that the valuable minerals were liberated. This indicated that the chemical environment might have an effect on the recovery of the sulphide minerals (acid insoluble copper) lost to the tailings. In this paper the effect of collector, frother and depressant addition on thecopper recovery and concentrate grade of the Nchanga Underground Scavenger circuit was studied. The investigation involved the flotation recovery of sulphide minerals from the scavenger feed uponaddition of the collector, frother and depressant. The reagent dose rates were varied as follows: collector (10, 30, 50 and 80 g/t), frother (10, 20, and 30 g/t), and depressant (40, 60, and 100 g/t). The results showed that the addition of TDSC 39/R9004A frother (maximum recovery 72.49 % TCu with a concentrate grade of 29.5 % TCu at a dose rate of 30 g/t) to the scavenger feed is more effective than the addition of SIPX collector (maximum recovery of 23.99 % TCu with a concentrate grade of 26 % TCu at a dose rate of 50 g/t). The depressant (Deptan 100) was more effective at lower dose rate of 40 g/t at which the level of insolubles reduced to 35 %.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87647369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization by factor analysis of the chemical facies of groundwater in the deltaic plain sands aquifer of Warri, western Niger delta, Nigeria","authors":"S. Olobaniyi, F. B. Owoyemi","doi":"10.4314/AJST.V7I1.55201","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55201","url":null,"abstract":"This paper examines the hydrochemical facies of groundwater present in the Deltaic Plain Sands aquifer of Warri and its immediate environs, maps their areal distribution and attempts to explain the controlling processes responsible for the various facies. 60 water samples were collected from wells tapping the Deltaic Plain Sands aquifer of Warri and environs and analyzed for various parameters including pH, total dissolved solids (TDS), K, Na, Ca, Mg, Cl, HCO3 and SO4 after standard procedures. The data obtained were subjected to R-mode factor analysis. Three factors were extracted. Factor 1 includes K, Na, Cl, and EC and reflects the signature of saline water incursion resulting from seepages into the aquifer of water from the tide-influenced River Warri. Factor 2 has high loading values of Mg, Ca, HCO3 and pH and represents the processes of natural rainwater recharge and water-soil/rock interaction. Factor 3 includes SO4 and can be related to the dissolution of sulphides from interstratified peat within the geological formation, heavy vehicular activity and the petroleum refining process in the town. The areal distributions of the various factor scores indicate that factors 1 and 2 are enhanced close to the banks of River Warri and decreases away from them. A broad zone of groundwater interaction (mixing) between water species represented by factors 1 and 2 is thus created towards the riverbanks. The implication of this is that ionic concentration in the water decreases away from the banks of the river an indication that the quality of groundwater improves away from the river. Factor 3 is enhanced in the southeastern portion of the town where it is deemed to be caused by the dissolution by groundwater of sulphur bearing minerals within the geological formaton, and also in the central and northwestern portions of the town were it could be related to the rain-dissolution of sulphur bearing compounds from gaseous emanations arising from vehicles and the petroleum refining process respectively, which eventually as acid-rain recharges aquifers in the vicinity. This paper demonstrates the effectiveness of factor analysis in evaluating hydrochemical processes in coastal and industrial areas","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78762152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An evaluation of the effectiveness of nonconventional p fertilizers derived from Zimbabwe phosphate rock using ryegrass as a test crop","authors":"E. Govere, S. Chien, R. Fox","doi":"10.4314/AJST.V6I1.55164","DOIUrl":"https://doi.org/10.4314/AJST.V6I1.55164","url":null,"abstract":"Zimbabwe and many other African countries lack high-quality phosphate ores for the production of conventional phosphate fertilizers. The objective of this study was to investigate the agronomic potential of an igneous phosphate rock derived from Dorowa (Zimbabwe) in a greenhouse experiment using rye grass (Lolium perenne) as test crop on a Hartsells silt loam. Three phosphate fertilizer materials: finely ground (0.150-mm screen) Dorowa phosphate rock (DPR); DPR partially acidulated with 50 % of the sulfuric acid required for complete acidulation (PADPR); and a compacted mixture of DPR + triple superphosphate + urea + potassium chloride (DTUK) with half of phosphorus from DPR and half from TSP were made from Dorowa rock and their agronomic effectiveness compared with that of single superphosphate. The relative agronomic effectiveness of the fertilizers based on dry matter yield of ryegrass followed the orders: DTUK=SSP>PADPR>DPR=Check and SSP>DTUK=PADPR>DPR=Check during the first 12 weeks and the second 12 weeks, respectively. For phosphorus uptake by ryegrass, the orders were: DTUK>SSP>PADPR>DPR=Check, DTUK=SSP>PADPR>DPR=Check, and SSP>DTUK>PADPR>DPR=Check during the first six, second six, and last 12 weeks, respectively. The results confirmed that the effectiveness of DPR could be greatly enhanced by partially acidulating DPR or compacting DPR with TSP, urea, and KCl.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78930492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Some Aspects Of Water Quality Characteristics In Small Shallow Tropical Man-made Reservoirs In Kenya","authors":"F. Mwaura","doi":"10.4314/AJST.V7I1.55203","DOIUrl":"https://doi.org/10.4314/AJST.V7I1.55203","url":null,"abstract":"The water quality in eight small reservoirs (0.065-0.249 km2) in both the rugged escarpment landscape above the rift valley floor and the stepped plateau above them were studied  between 1998 and 2000. Water transparency was measured using a 20cm Secchi visibility disk. Total dissolved solids (TDS) and electrical conductivity (specific conductance) with temperature compensation at 25oC were recorded in situ from a portable Jenway probe model 4075. Water pH, dissolved oxygen (DO), percentage oxygen saturation (POS) were recorded on site from a portable WTW probe model ProfiLine Oxi 197/197-S. The overall range of mean water pH was 7.0 – 8.4 while the overall range of mean TDS was 29-82 mg/l. The TDS was slightly higher in the plateau reservoirs. The overall range of specific conductance was 37-101 μS/cm. The range of TDS and specific conductance in the reservoirs was quite low compared to other reservoirs in Kenya. The mean range of dissolved oxygen and percentage oxygen saturation was 2.0-7.2 mg/l, 23.4.2-33.6%, respectively. The level of dissolved oxygen was quite low in most reservoirs with dry season hypolimnial oxygen deficits in some sites and higher dissolved oxygen content in the more transparent reservoirs. The summary results showed a clear difference in water quality between the plateau and escarpment reservoirs in the study area. The water quality in the reservoirs was found to be suitable for domestic and livestock utilization. However, additional water quality parameters are required to confirm this conclusion. The reservoirs were found to possess a good potential for multipurpose development.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79473737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}