Browsing Faculty of Science by Title
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Murray-Hudson, M.; Mmopelwa, G. (Global Science Books, http://www.globalsciencebooks.info/, NaN, 2011)[more][less]
Abstract: Most work globally on Phragmites spp. has been done in temperate northern hemisphere localities, where winter low temperatures and short day lengths cause a seasonal decrease in growth. In this study, we report above-ground stem length-mass relationships, stem densities and daily growth rates in 3 Phragmites australis reedbeds in the flood-pulsed, subtropical Okavango Delta, with the aim of assessing the economic value of this plant, which is widely used throughout north-western Botswana for cladding house walls and fencing yards. Stem density averaged 77m¯² in 32 plots. Length-mass relationships were best represented by a power function y = 8.05x¹•⁸⁵, where y is the dry mass in grams and x is the length in meters (r²=0.895). The mean daily growth rate was 0.015 m and did not appear to vary systematically with season. The maximum standing crop calculated from stem length was 2.89 kg m¯², and occurred in May 2005. Annual above-ground production was conservatively estimated at 20-30 t ha¯¹. Assuming that harvesting takes place not more than once annually, reed beds in the Okavango Delta are worth ~US$ 45,000 ha¯¹ at market. This land use value is over 90 times that of flood recession agriculture in the same area. URI: http://hdl.handle.net/10311/918 Files in this item: 1
Murray-Hudson_AJPSB_2011.pdf (1.180Mb) -
Keter, F.K.; Ojwach, S.O.; Oyetunji, O.A.; Guzei, I.A.; Darkwa, J. (Elsevier Science Ltd, www.elsevier.com/locate/ica, NaN, 2009)[more][less]
Abstract: A series of pyrazolyl palladium(II), platinum(II) and gold(III) complexes, [PdCl2(3,5-R2bpza)] {R = H (1), R = Me (2), bpza = bis-pyrazolyl acetic acid}, [PtCl2(3,5-R2bpza)] {R = H (3a), R = Me (4)}, [AuCl2(3,5- R2bpza)]Cl {R = H (5a), R = Me (6a)} and [PdCl2(3,5-R2bpzate)] {R = Me (7)} have been synthesised and structurally characterised. Single crystal X-ray crystallography showed that the pyrazolyl ligands exhibit N^N-coordination with the metals. Anticancer activities of six complexes 1–6a were investigated against CHO cells and were found to have low activities. Substitution reactions of selected complexes 1, 2, 3a and 5a with L-cysteine show that the low anticancer activities compounds and that the rate of substitution with sulfur-containing compounds is not the cause of the low anticancer activities. URI: http://hdl.handle.net/10311/1032 Files in this item: 1
Keter_ICA_2009.pdf (1.240Mb) -
Jain, P.K.; Lungu, E.M.; Prakash, J. (Elsevier Science Ltd. www.elsevier.com/locate/renene, NaN, 2003)[more][less]
Abstract: The Republic of Botswana is one of the sunniest countries in Southern Africa. It has very little cloud cover, insufficient rainfall, very low humidity, and very low wind speed throughout the year for most parts of the country. The daily extremum temperatures appear to be very much related to solar irradiation which in turn depends on sunshine duration. In Botswana, solar irradiation on a horizontal surface is measured only at Sebele, but sunshine duration and extremum temperatures are measured at several locations throughout the country. This paper presents bivariate models that relate solar irradiation to sunshine duration, and solar irradiation to extremum temperatures for Sebele, Botswana. Autocorrelation analysis revealed that the solar irradiation series is stationary for d=2 and D=0, sunshine duration series is stationary for d=0 and D=0, while the extremum temperatures series are stationary for either d=0 and D=N where N=1, 2, . . . or d=1 and D=1. It is found that there is a lag of three months between the peaks of the differenced series of fractional sunshine duration and fractional solar irradiation. On the other hand it is found that there is at most a lag of one month between the peaks of the differenced series of maximum temperature and solar irradiation, and that there is no lag between the peaks of the differenced series of minimum temperature and solar irradiation. Analysis of the noise component revealed that the bivariate processes under consideration behaved either as a purely seasonal MA processes of order (0,1,1) or as ARIMA processes of order (0, 1, 1)x (0, 1, 1)12 or as a purely nonseasonal, autoregressive process of order 2. We claim that the relationships found for Sebele can be applied to estimate solar irradiation at other locations with climatic conditions similar to Botswana. URI: http://hdl.handle.net/10311/177 Files in this item: 2
jain_RE_2003.pdf (1.288Mb)license.txt (1.998Kb) -
Asare, S.D.; Mashwama, P.M.; Cunningham, S. (Elsevier Science Ltd, http://www.elsevier.com/locate/cag, NaN, 2003)[more][less]
Abstract: This note discusses issues in building the educational base for computer graphics growth in developing countries, particularly in southern Africa. It is based on a delegation’s visit to southern Africa in the spring of 2001 and on a workshop organised by the authors at the University of Botswana in June 2002. URI: http://hdl.handle.net/10311/844 Files in this item: 1
Asare_CG_2003.pdf (448.1Kb) -
Mapeo, R.B.M.; Armstrong, R.A.; Kampunzu, A.B.; Modisi, M.P.; Ramokate, L.V.; Modie, B.N.J. (Elsevier B.V. www.elsevier.com/locate/epsl, NaN, 2006)[more][less]
Abstract: The Segwagwa Group of southeastern Botswana, a correlate of the Pretoria Group of the Transvaal Supergroup of South Africa, consists of a major sequence of siliciclastic sedimentary rocks, minor carbonates and basaltic to andesitic lavas and tuffs straddling the Western and Central Domains of the Kaapvaal Craton. The Segwagwa Group unconformably overlies the Taupone Dolomite Group, a correlative of the South African Chuniespoort/Ghaap Groups of the Transvaal Supergroup. SHRIMP U–Pb analyses of 123 detrital zircons from the top, middle and bottom of the Segwagwa Group sedimentary rocks include 96 concordant to nearconcordant zircons defining three main age groups: N3.0–2.9 Ga (n=12), 2.8–2.5 Ga (n=27) and 2.45–2.20 Ga (n=57). The ≥2.90 Ga zircons were sourced from granitoids emplaced before and around 2915±12 Ma and are related to the amalgamation of the Western, Northern and Central Domains of the Kaapvaal Craton. Concordant zircons with a mean age of 2781±8 Ma originate from the Gaborone Igneous Complex. The detrital zircons in the range 2.7–2.5 Ga were likely sourced from the Kalahari continental fragment made up of the Kaapvaal Craton, Limpopo Belt and the Zimbabwe Craton, specifically from the Limpopo Belt and/or the Zimbabwe Craton where igneous rocks in this age range are widespread. The igneous sources for the Palaeoproterozoic (ca. 2.45–2.20 Ga) zircons are difficult to identify since igneous rocks in that age are not widely known or documented by reliable dates in the Kalahari Craton. The youngest zircons of ca. 2.2 Ga occur in all the sandstones and form the main group (N90%) in the sample from the top of the Segwagwa Group. The youngest detrital zircon of 2193±20 Ma sets the maximum time of deposition of the Segwagwa Group. Published data suggest that the minimum deposition age of Chuniespoort/Ghaap Group sedimentary rocks is 2431±31 Ma [D.R. Nelson, Compilation of SHRIMP U-Pb zircon Geochronological Data, 1996 Record 1997/2, pp. 189, Western Australia Geological Survey, 1997.]. Therefore, the unconformity between the Lower and Upper Transvaal represents a ∼200 Ma hiatus, and the lithostratigraphic units on the two sides of the unconformity should not be grouped in the same supergroup. Detrital zircon ages suggest that the time of deposition of the Segwagwa/Pretoria Group which ranges from ca. 2.40 to 2.20 Ga is coeval with the Palaeoproterozoic global glacial deposits in North America, Australia and Fennoscandia; and with sedimentary rocks from the Palaeoproterozoic Magondi Belt. Therefore, the Segwagwa/Pretoria Group and the Magondi metasedimentary succession were deposited during the first global glacial period, are possibly related to the same geodynamic cycle, and should be part of the same supergroup. URI: http://hdl.handle.net/10311/273 Files in this item: 1
A ca. 200Ma.pdf (11.14Mb) -
Mapeo, R.B.M.; Armstrong, R.A.; Kampunzu, A.B.; Modisi, M.P.; Ramokate, L.V.; Modie, B.N.J. (Elsevier www.elsevier.com/locate/epsl, NaN, 2006)[more][less]
Abstract: The Segwagwa Group of southeastern Botswana, a correlate of the Pretoria Group of the Transvaal Supergroup of South Africa, consists of a major sequence of siliciclastic sedimentary rocks, minor carbonates and basaltic to andesitic lavas and tuffs straddling the Western and Central Domains of the Kaapvaal Craton. The Segwagwa Group unconformably overlies the Taupone Dolomite Group, a correlative of the South African Chuniespoort/Ghaap Groups of the Transvaal Supergroup. SHRIMP U–Pb analyses of 123 detrital zircons from the top, middle and bottom of the Segwagwa Group sedimentary rocks include 96 concordant to nearconcordant zircons defining three main age groups: >3.0–2.9 Ga (n=12), 2.8–2.5 Ga (n=27) and 2.45–2.20 Ga (n=57). The ≥2.90 Ga zircons were sourced from granitoids emplaced before and around 2915±12 Ma and are related to the amalgamation of the Western, Northern and Central Domains of the Kaapvaal Craton. Concordant zircons with a mean age of 2781±8 Ma originate from the Gaborone Igneous Complex. The detrital zircons in the range 2.7–2.5 Ga were likely sourced from the Kalahari continental fragment made up of the Kaapvaal Craton, Limpopo Belt and the Zimbabwe Craton, specifically from the Limpopo Belt and/or the Zimbabwe Craton where igneous rocks in this age range are widespread. The igneous sources for the Palaeoproterozoic (ca. 2.45–2.20 Ga) zircons are difficult to identify since igneous rocks in that age are not widely known or documented by reliable dates in the Kalahari Craton. The youngest zircons of ca. 2.2 Ga occur in all the sandstones and form the main group (N90%) in the sample from the top of the Segwagwa Group. The youngest detrital zircon of 2193±20 Ma sets the maximum time of deposition of the Segwagwa Group. Published data suggest that the minimum deposition age of Chuniespoort/Ghaap Group sedimentary rocks is 2431±31 Ma [D.R. Nelson, Compilation of SHRIMP U-Pb zircon Geochronological Data, 1996 Record 1997/2, pp. 189, Western Australia Geological Survey, 1997.]. Therefore, the unconformity between the Lower and Upper Transvaal represents a ∼200 Ma hiatus, and the lithostratigraphic units on the two sides of the unconformity should not be grouped in the same supergroup. Detrital zircon ages suggest that the time of deposition of the Segwagwa/Pretoria Group which ranges from ca. 2.40 to 2.20 Ga is coeval with the Palaeoproterozoic global glacial deposits in North America, Australia and Fennoscandia; and with sedimentary rocks from the Palaeoproterozoic Magondi Belt. Therefore, the Segwagwa/Pretoria Group and the Magondi metasedimentary succession were deposited during the first global glacial period, are possibly related to the same geodynamic cycle, and should be part of the same supergroup. URI: http://hdl.handle.net/10311/742 Files in this item: 1
Mapeo2006Transvaal Groups.pdf (1.993Mb) -
Mpuchane, S.; Allotey, J.; Matsheka, I.; Simpanya, M.; Coetzee, S.; Jordaan, A.; Mrema, N.; Gashe, B.A. (ICIPE - African Insect Science for Food and Health, http://journals.cambridge.org/action/displayJournal?jid=JTI, NaN, 2006)[more][less]
Abstract: Domestic cockroaches Blattella germanica were trapped from various homes in Gaborone, Botswana using ‘Dyroach’ traps. Isolations of bacteria, yeasts and moulds were done on external body parts and on the faecal pellets using various selective media. Body parts of cockroaches were also fixed with OsO4 vapour for 24 h, sputter coated with gold under special conditions and examined in a Phillips (1) XL30 ESEM in low vacuum mode. Awide spectrum of bacteria including common food spoilage and pathogenic organisms, such as Bacillus spp., Staphylococcus spp., Escherichia coli, Pseudomonas spp., Enterobacter spp., Klebsiella spp., Erwinia spp. Salmonella sp., Shigella sp. and Serratia spp. were isolated. Yeasts commonly associated with food spoilage, such as Pichia sp., Candida sp. and Torulopsis spp. were found on many cockroaches. In addition, various groups of moulds, some associated with food spoilage and others known to produce mycotoxins, such as Aspergillus flavus, Aspergillus fumigatus and Aspergillus parasiticus were isolated. Antimicrobial sensitivities of bacterial isolates revealed resistance patterns to various agents. Since cockroaches are prevalent in homes, particularly in food preparation areas and since their body parts and faecal pellets have been found in food storage areas, concern about their impact on food quality and safety is raised and possible control measures including education of communities on proper sanitation are suggested. URI: http://hdl.handle.net/10311/1005 Files in this item: 1
Matsheka_IJTIS_2006.pdf (193.3Kb) -
Abegaz, B.M.; Ngadjui, B.T.; Dongo, E.; Ngameni, B.; Nindi, M.N.; Bezabih, M. (Elsevier Science Ltd. www.elsevier.com/locate/phytochem, NaN, 2002)[more][less]
Abstract: The twigs of Dorstenia prorepens furnished the digeranylated chalcone, 5,30-(3,7-dimethyl-2,6-octadienyl)-3,4, 20,40-tetrahydroxychalcone while Dorstenia zenkeri yielded the 30,40-(3-hydroxy-2,2-dimethyldihydropyrano)-4,20-dihydroxychalcone and a bichalcone. 4-Hydroxylonchocarpin was found in both plants. D. prorepens also yielded the known compounds: psoralen, bergapten, b-sitosterol and its D-glucopyranosyl derivative. D. zenkeri yielded p-hydroxybenzaldehyde, dorsmanin A, 4,20,40-trihydroxychalcone and 4,20,40-trihydroxy-30-prenylchalcone. Structures of the new compounds were established by UV, IR, MS and 2-D NMR analysis. URI: http://hdl.handle.net/10311/254 Files in this item: 2
Chalcones and other constituents.pdf (3.760Mb)license.txt (1.998Kb) -
Mabaleha, M.B.; Yeboah, S.O. (AOCS Press., NaN, 2004)[more][less]
Abstract: Seed oils from six legume cultivars of Phaseolus vulgaris, grown in the Kingdom of Lesotho, were extracted and their physicochemical properties and FA compositions were determined in order to compare their dietary lipids with those in P. vulgaris cultivars grown in other parts of the world. The oil content of the beans was very low, ranging from 1.5 to 2.0% (w/w). The acid values ranged from 11.0 to 19.2 mg KOH/g, whereas a combination of the PV and the p-anisidine values in Holm’s equation gave oxidation values that ranged from 11.0 to 15.0. Thus, considerable enzymatic hydrolysis and oxidation had taken place in the beans during storage. Iodine values ranged from 80.5 to 92.3 (Wijs method), indicating moderate unsaturation in the oils. However, capillary GC analysis, supported by proton NMR analysis of the FAME, gave a total unsaturation range from 79.67 to 84.24%. The dominant FA were α-linolenic acid (36.47–48.81%) and linoleic acid (20.96–36.10%), with appreciable amounts of palmitic acid (14.33–18.23%). This FA composition pattern is quite similar to the FA distribution reported for low oil-bearing legume seeds. Thus, notwithstanding the different climatic and soil conditions, the general properties of lipids in the southern African legume cultivars were quite similar to those of lipids in P. vulgaris cultivars grown in other parts of the world. The high content of α-linolenic acid in the cultivars of P. vulgaris could very likely play a beneficial role in reducing the risk of coronary heart disease among the large populations consuming them in the southern African region. URI: http://hdl.handle.net/10311/303 Files in this item: 1
Characterization and compositional.pdf (3.533Mb) -
Kayombo, B.; Meulenburg, F.; Moganane, B. G.; Dikinya, O.; Aliwa, J. N.; Nsinamwa, M.; Gaboutloeloe, G.; Patrick, C.; Mzuku, M.; Machacha, S. (University of Botswana, http://www.ub.bw, April NaN, 2005)[more][less]
Abstract: A study was carried out during 1998-2001 with the objective of, firstly, assessing the impact of cultivation on soil quality, and secondly, evaluating the effects of human and animal activities on soil erosion and range resources. A Topical Rapid Rural Appraisal (TRRA) based on rapid appraisal approaches, was conducted in three benchmark villages in Bobirwa Sub-district. A diagonistic survey report provided similar information for Kgalagadi District. Three benchmark sites were located in Bobirwa Sub-district and two others in Kgalagadi District. Soils were characterized at benchmark sites and in the laboratory for physiochemical properties. Soil erosion was monitored using embedded nail technique. At all benchmark sites, trends show a deterioration of soil quality, both in terms of nutrient depletion and poor physical properties for cultivated soils in comparison to uncultivated soils. There is visible evidence of environmental degradation of land resources resulting partly from considerable soil trampling and loosening during the dry season by livestock. During the wet season, the loosened soil is washed down elsewhere and/or deposited at watering points. The confounding effects of drought, overgrazing, poor management and ever-increasing utilization of veld products have led to the decline of a considerable number of tree and grass species. URI: http://hdl.handle.net/10311/645 Files in this item: 1
Kayombo_BJT_2005.pdf (3.655Mb) -
Døssinga, L.N.; Frei, R.; Stendal, H.; Mapeo, R.B.M. (Elsevier www.elsevier.com/locate/precamres, NaN, 2009)[more][less]
Abstract: Major and trace element, samarium (Sm)–neodymium (Nd) and lead (Pb) isotopic analyses of individual mesobands of five Banded Iron Formations (BIFs) and associated volcanic and sedimentary rocks from the Neoarchean Tati Greenstone Belt (TGB, Northeastern Botswana) were conducted in order to characterize the source(s) and depositional environment(s). Rare earth element (REE)–yttrium (Y) patterns of individual BIF mesobands showfeatures characteristic of other Archean BIFs with LREE depletion relative to MREE and HREE, positive La/La∗PAAS, Eu/Eu∗PAAS, Y/Ho ratios and no Ce/Ce∗PAAS anomalies. The REY patterns are comparable to modern seawater and together with low concentrations of high-field strength elements these features are indicative of an essentially detritus-free precipitation. Elevated Eu anomalies in the TGB BIFs are a general feature observed in ∼2.7 Ga BIFs worldwide and possibly result from widespread magmatic activity and associated high-temperature fluid fluxes to the oceans at around this time. Uranogenic Pb isotope data for the BIFs define correlation lines with slopes corresponding to apparent ages of ∼2.7 Ga which brackets the depositional timeframe. Pb isotope data on sulfides and Pb-stepwise leaching (PbSL) data on garnets define a correlation line with an apparent age of 1976±88 Ma. This age is similar to tectono-metamorphic events within the adjacent Limpopo belt. Elevated 207Pb/204Pb relative to 206Pb/204Pb ratios of BIFs are indicative of a high- (238U/204Pb) prehistory of their source materials which can best be modeled by a 3.0–3.2 Ga extraction of these sources from an older Archean mantle reservoir. The TGB BIFs show evidence of two periodically interacting water masses during the deposition. The first is characterized by elevated Sm/Nd ratios and a negative inferred εNd(2.7 Ga) value of −2.5 and is associated with high Fe fluxes. The second source, associated with high Si fluxes, is characterized by lower Sm/Nd ratios and a less negative inferred εNd(2.7 Ga) value of −0.4. While the association of high Fe concentrations and elevated Sm–Nd in BIF mesobands is characteristic of hydrothermal seawater input, the Sm–Nd isotopic characterization of this source, unlike other Archean BIFs, points to a significantly LREE enriched mantle source. This finding is compatible with the potential existence of a sub-continental lithospheric mantle reservoir beneath the Zimbabwe and Kaapvaal craton. The old (up to ∼3.5 Ga) Nd (TDM) model ages, particularly of iron-rich mesobands of the TGB BIFs, support such a scenario. In contrast, Si-rich solutes were likely derived from weathering of mafic continental crust. URI: http://hdl.handle.net/10311/389 Files in this item: 1
Mapeo2009Characterization.pdf (2.630Mb) -
Metuno, R.; Ngandeu, F.; Tchinda, A.T.; Ngameni, B.; Kapche, G.D.W.F.; Djemgou, P.C.; Ngadjui, B.T.; Bezabih, M.; Abegaz, B.M. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2007)[more][less]
Abstract: Three species of the genus Treculia namely, Treculia acuminata Baill., Treculia africana Decne ex. Treà ´cul and Treculia obovoidea N.E.Br. grow in the humid rain forest of southwest Cameroon. They are also widely distributed in tropical Africa. T. africana is commonly known as African bread fruit. These three species are commonly used in folk medicine against skin diseases and dental allergies (Berg et al., 1985). The twigs, stem and wood of T. acuminata and the leaves of T. africana, whose chemical constituents are reported herein, were collected from Kumba, Cameroon, in August 2004, and identified by Mr Victor Nana of the National Herbarium in Yaounde, Cameroon where voucher specimens (N 2921/Srf/CAM and 29053/SRF/Cam, respectively) are deposited. URI: http://hdl.handle.net/10311/291 Files in this item: 1
Chemical constituents of Treculia.pdf (2.209Mb) -
Dikinya, O.; Mufwanzala, N. (Academic Journals, http://www.academicjournals.org/JSSEM, May NaN, 2010)[more][less]
Abstract: The utilization of chicken manure as an organic fertilizer is essential in improving soil productivity and crop production. We carried out the study to assess the effects of chicken manure on soil chemical properties and the response of application rate on the yield of spinach (Spinacia oleracea) as well as the uptake of nitrogen and phosphorus nutrients. To quantify these effects, we added chicken manure to samples of Calcisols, Arenosols and Luvisols at application rates: 5, 10, 20 and 40% chicken manure. The addition of chicken manure irrespective of application rate did not change the acidity or pH of Calcisol, suggesting its hypo-buffering capacity. While the results reveal increases of EC with increasing rate, at rate above 40%, the ECs were above the critical salinity level of 4 mS/cm indicating potential threat to soil productivity. The exchangeable bases increased with application rate, suggesting the positive effects of chicken manure in enhancing soil fertility. Similarly significant increase of nitrogen and phosphorus were observed following the addition of chicken manure. Initially the spinach yield increases up to optimum rate of 0.06, 0.07 and 0.16 g/plant for Luvisol, Arenosol and Calcisol, respectively and subsequently drops after critical threshold values; 15, 5 and 1% for Calcisol, Arenosol and Luvisol, respectively. Interestingly above the rate of 40%, the yield was almost zero for all soils, suggesting the ineffectiveness of chicken manure in enhancing soil productivity. URI: http://hdl.handle.net/10311/1003 Files in this item: 1
Dikinya_JSSEM_2010.pdf (514.6Kb) -
Dikinya, O.; Areola, O. (Springer, http://link.springer.com/, March NaN, 2010)[more][less]
Abstract: The use of treated urban wastewater for irrigation is a relatively recent innovation in Botswana and knowledge is still limited on its impact on soil heavy metal levels. The aim of this study is to analyze and compare heavy metal concentration in secondary wastewater irrigated soils being cultivated to different crops: olive, maize, spinach and tomato in the Glen Valley near Gaborone City, Botswana. The studied crop plots have been cultivated continuously under treated wastewater irrigation for at least 3 years. Most crop farms have sandy loam, loamy sand soils. Based on food and agriculture organization, heavy metal threshold values for crop production have been studied. Results showed that the wastewater irrigated soils in the Glen Valley have higher cadmium, nickel and copper than desirable levels, while the levels of mercury, lead and zinc are lower than the maximum threshold values recommended for crop production. The control sites show that the soils are naturally high in some of these heavy metals (e.g copper, zinc, nickel) and that crop cultivation under wastewater irrigation has actually lowered the heavy metal content. Comparing between the crops, mercury and cadmium levels are highest in soils under maize and decline linearly from maize to spinach to olive to tomato and control site. By contrast, concentrations of the other metals are at their lowest in maize and then increase from maize to spinach to olive to tomato and to control site. URI: http://hdl.handle.net/10311/1105 Files in this item: 1
ijest 2010 dikinya and areola.pdf (685.3Kb) -
Moroke, T.S.; Dikinya, O.; Patrick, C. (Elsevier Science Ltd, http://www.elsevier.com/locate/pce, NaN, 2009)[more][less]
Abstract: Water infiltration is an important component of water balance for improving crop production potential in dryland soil tillage systems in Botswana, particularly in the eastern region. Hardsetting soils common in arable lands of Botswana, often require some kind of tillage such as mouldboard ploughing, chiselling and ripping to improve waterharvesting and crop growth conditions. The objective of this study was to compare ponded cumulative infiltration, steady state infiltration rate and sorptivity of soils cultivated using deep ripping, single and double mouldboard ploughing. This study was conducted on Chromic Luvisols (sandy loam), Haplic Luvisols (sandy clay loam), Ferric Luvisols (clay loam), and Ferric Arenosols (sand). Infiltration was measured using double ring infiltrometer method for 4 h. Although infiltration was smaller on traffic line of deep ripping system at all sites, it was only significantly (P < 0.05) different on Ferric Luvisols and Ferric Arenosols. Compared with conventional ploughing, steady state infiltration was greater but not significantly (P > 0.05) different under deep ripped. Cumulative and steady state infiltration rate was greater under sandy than loamy soils, smaller under double ploughing compared with single ploughed and deep ripped soils. Sorptivity was not significantly (P > 0.05) different among tillage systems but was greater under sandy than sandy loam soils. Information on tillage and infiltration can improve implementation of waterharvesting technologies and crop production in Botswana. URI: http://hdl.handle.net/10311/1007 Files in this item: 1
Moroke_PCE_2009.pdf (666.4Kb) -
Areola, O.; Dikinya, O.; Mosime, L. (Global Science Books, http://www.globalsciencebooks.info/Journals/AJPSB.html, NaN, 2011)[more][less]
Abstract: This study compares soil quality parameters, and salinity and heavy metal levels in soils cultivated with different crops under secondary treated wastewater irrigation in the Glen Valley, near Gaborone City, Botswana. The hypothesis being tested is that the impact of wastewater on soil quality varies with soils and crop types. The study covers 4 selected crops, maize (Zea mays L.), spinach (Spinacia oleracea), olive (Olea europaea), and tomato (Solanum lycopersicum), most widely cultivated by the farmers. Three farm plots per crop type were sampled at 5 sampling points and at two soil depths, 0-15 and 15-30 cm. Samples were also collected at 5 sampling points from two control sites. Irrigation water samples were collected from microbiological analysis from 2 farms per crop type. The most significant differences and relationships are between those crop farms, such as maize and two of the spinach plots, with predominantly sandy soils (loamy sands – sand loams) on the one hand, and the olive, tomato and one of the spinach plots with sandy clay loams on the other. The importance of soil texture was confirmed by the strong correlations between the sand and silt contents, several soil quality parameters, heavy metals and other elements. With the exception of Cd and Hg, most soil heavy metal contents were lower on the irrigated plots than on the control plot. The EC values also show that soil salinity levels were still low on the irrigated fields, but SAR and ESP values were high. The secondary treated wastewater being used in the Glen Valley is biologically clean, but one recorded case of E. coli emphasizes the importance of avoiding sprinkler irrigation at all costs to protect human health. URI: http://hdl.handle.net/10311/1002 Files in this item: 1
Dikinya_AJPSB_2011.pdf (249.7Kb) -
Nijegorodov, N.; Luhanga, P.V.C.; King, J.G. (Regional Energy Resources Information Center (RERIC) Asian Institute of Technology. http://www.rericjournal.ait.ac.th/index.php/reric/index, December NaN, 2005)[more][less]
Abstract: Please refer to the attached article for the ABSTRACT. Due to technical problems with some scientific formulae it was not possible to upload the abstract HERE. URI: http://hdl.handle.net/10311/408 Files in this item: 1
Nijegorodov_IEJ_2005.pdf (2.539Mb) -
Comprehensive study of solar conditions in Mozambique: the effect of trade winds on solar componentsNijegorodov, N.I.; Devan, K.R.S.; Simao, H.; Mabbs, R. (Elsevier Science Ltd. www.elsevier.com/locate/renene, NaN, 2003)[more][less]
Abstract: A new algorithm to simulate all solar components and optimum slopes, Bopt, based on new models for direct normal beam and diffuse radiation and an analytical model to predict Bopt, developed at the University of Botswana is applied for complete study of solar conditions in Mozambique. The components of solar radiation depend to a large extent on the number of h of sunshine. However, it is obvious that cloud-cover is determined mainly by the prevailing trade winds, which carry moisture and rain clouds. This is of especial concern in coastal areas. In the current work, hourly, I, daily, H and monthly mean, H¯ components of solar radiation and the optimum slopes of a north-south aligned collector are simulated and analyzed for 21 synoptic stations in Mozambique. Monthly mean daily direct normal, H¯ bn solar radiation maps are plotted for December and June and discussed. It is found that, to a great extent, isoinsolation curves are determined by the prevailing trade winds, mountain chains and coastal conditions. Plotted maps of annual mean daily direct normal and global solar radiation also show tremendous dependence on the prevailing winds. Several special locations in Mozambique with quite high or very low solar radiation components are pointed out and the reasons explained. URI: http://hdl.handle.net/10311/267 Files in this item: 1
Nijegorodov_RE28_2003.pdf (2.514Mb) -
Ayalew, Y.; Mbero, Z.A.; Nkgau, T.Z.; Motlogelwa, P.; Masizana-Katongo, A. (The Science and Information Organization, http://thesai.org/Publication/Default.aspx, NaN, 2011)[more][less]
Abstract: This paper presents the results of a content analysis of computing job adverts to assess the types of skills required by employers in Botswana. Through the study of job adverts for computing professionals for one year (i.e., January 2008 to December 2008), we identified the types of skills required by employers for early career positions. The job adverts were collected from 7 major newspapers (published both daily and weekly) that are circulated throughout the country. The findings of the survey have been used for the revision and development of curricula for undergraduate degree programmes at the Department of Computer Science, University of Botswana. The content analysis focused on the identification of the most sought after types of qualifications (i.e., degree types), job titles, skills, and industry certifications. Our analysis reveals that the majority of the adverts did not set a preference to a particular type of computing degree. Furthermore, our findings indicate that those job titles and computing skills which are on high demand are not consistent with previous studies carried out in the developed countries. This requires further investigation to identify reasons for these differences from the perspective of the practices in the IT industry. It also requires further investigation regarding the degree of mismatch between the employers computing skills demands and the knowledge and skills provided by academic programmes in the country. URI: http://hdl.handle.net/10311/916 Files in this item: 1
Mbero_IJACSA_2011.pdf (417.6Kb) -
Akande, A.R. (Elsevier Science Ltd. www.elsevier.com/locate/elstat, NaN, 2005)[more][less]
Abstract: The charge transfer between metals and some solution-cast polymers has been investigated by employing intermittent soft contact under a controlled condition. The result of our measurements reveals that the measured charge is unaffected by our attempt at purifying the polymer samples and so we conclude that the charge transfer is an intrinsic property of the polymers. The histogram of the charge distribution for all the polymers studied is not Gaussian but skewed towards larger charges. The metal work function influences the charge transfer to the polymer except polyvinyl chloride, which behaves as Teflon, already reported in our earlier work. URI: http://hdl.handle.net/10311/277 Files in this item: 1
Akande_JE63_2005.pdf (891.9Kb)