Browsing Faculty of Science by Title
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Kizza, S; Areola, O (Academic Journals, November NaN, 2010)[more][less]
Abstract: This study investigated the influence of the accumulation of animal wastes on the soils of active kraal sites through time. This investigation involved the sampling and analysis of the soils of kraals that had been in use for periods ranging from 2 to over 45 years. Soil sampling and analysis were done both in the dry and wet seasons for comparative purposes. The properties of the kraal soils were compared with those of control sites. Samples were taken from 25 kraals categorized into 5 age (length of use) groups: < 5years; 6 - 10; 11 - 20; 21 - 40; > 40 years. The soils were sampled at two depths, 0 – 15 and 15 – 35 cm. Soil parameters analyzed included particle size distribution (%), bulk density (g/cm3), pore space (%), moisture content (%), pH in water and in potassium chloride solution, EC (μS/cm), organic matter (%), CEC (meq/100g), exchangeable bases: Ca++(cmolc/kg), Mg++(cmolc/kg), K+(cmolc/kg), Na+(cmolc/kg); nitrogen: NH4-N (mg/kg), NO3-N (mg/kg), TKN (%), and Olsen P (mg/kg). Results showed a direct correlation between length of active kraal utilization and impact of animal waste concentration on the soil with correlation coefficients as high as r = 0.99 and r = 0.95 for pH and OM respectively. Nutrient levels in kraal soils of all ages were significantly higher (P = 0.05) than those of the control site soils. Most nutrient elements showed increases ranging from about 2 - 30 times greater than in the control site soils. Soil nutrient levels were higher in the dry season than in the wet season. The nutrient enrichment in the kraals extended deep into the soil, at least, to the 35 cm depth. The organic and nutrient enrichments of the soils also had very positive effects on soil moisture and structural characteristics. However, this highly localized nutrient enrichment of kraal soils is detrimental to the long term sustainability of arid ecosystems and soil productivity. The nutrients concentrated in kraals have been harvested from the surrounding areas by grazing animals and transferred to the kraal sites. In a situation of sedentary kraaling that exists in semi arid lands of Botswana where rotation of kraal sites or the harvesting of animal manure from kraals for use as soil manure is not commonly practiced, the concentration of soil nutrients at scattered kraal spots causes an imbalance in the spatial pattern of soil and plant productivity in the arid land ecosystem. The entire ecosystem is made poorer by this phenomenon. Description: Full Length Research Paper URI: http://hdl.handle.net/10311/1095 Files in this item: 1
Kizza and 0Areola.pdf (293.8Kb) -
Abusukhon, A.; Talib, M. (The Science and Information Organization Inc., http://ijacsa.thesai.org/, NaN, 2011)[more][less]
Abstract: In parallel (IR) systems, where a large-scale collection is indexed and searched, the query response time is limited by the time of the slowest node in the system. Thus distributing the load equally across the nodes is very important issue. Mainly there are two methods for collection indexing, namely document-based and term-based indexing. In term-based partitioning, the terms of the global index of a large-scale data collection are distributed or partitioned equally among nodes, and then a given query is divided into sub-queries and each sub-query is then directed to the relevant node. This provides high query throughput and concurrency but poor parallelism and load balance. In this paper, we introduce new methods for terms partitioning and then we compare the results from our methods with the results from the previous work with respect to load balance and query response time. URI: http://hdl.handle.net/10311/1068 Files in this item: 1
Talib_IJACSA_2011.pdf (325.8Kb) -
Chacha, M.; Mapitse, R.; Afolayan, AJ; Majinda, R.R.T. (Natural Product Inc. http://www.naturalproduct.us/, NaN, 2008)[more][less]
Abstract: Investigation of the roots of Ceriops tagal led to the isolation of a new isopimarane, together with the known diterpenes isopimar-8(14)-en-15,16-diol and erythroxyl-4(17),15(16)-dien-3-one. The structure of the new compound was identified as isopimar-8(14)-en-16-hydroxy-15-one. These structures were determined from extensive spectroscopic data analysis. The isolates were screened for antibacterial activity using the agar dilution method against ten test bacterial strains (Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Micrococcus kristinae, Pseudomonas aeruginosa, Salmonella pooni, Serratia marcescens, Staphylococcus aureus, S. epidermidis and Streptococcus pyrogens). Isopimar-8(14)-en-16-hydroxy-15-one exhibited activity, with MIC values of 0.5 mg/mL against Streptococcus pyrogens; 0.25 mg/mL against Salmonella pooni and 0.1 mg/mL against Bacillus cereus, Staphylococcus aureus and Micrococcus kristinae. URI: http://hdl.handle.net/10311/224 Files in this item: 2
license.txt (1.998Kb) -
Mbaveng, A.; Ngameni, B.; Kuete, V.; Simo, I.K.; Ambassa, P.; Roy, R.; Bezabili, M.; Etoa, F.X.; Ngadjui, B.; Abegaz, B.; Meyer, J.J.M.; Lall, N.; Beng, V.P. (Elsevier Ireland Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/506035/description#description, NaN, 2008)[more][less]
Abstract: The aim of this study was to evaluate the antimicrobial activity of the crude extract of the twigs of Dorstenia barteri (DBT) as well as that of four of the five flavonoids isolated from this extract. Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and fungi (four species) were used. The agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that DBT, isobavachalcone (1), and kanzonol C (4) prevented the growth of all the 22 tested microbial species. Other compounds showed selective activity. The inhibitory activity of the most active compounds namely compounds 1 and 4 was noted on 86.4% of the tested microorganisms and that of 4-hydroxylonchocarpin (3) was observed on 72.7%. This lowest MIC value of 19.06 g/ml was observed with the crude extract on seven microorganisms namely Citrobacter freundii, Enterobacter aerogens, Proteus mirabilis, Proteus vulgaris, Bacillus megaterium, Bacillus stearothermophilus and Candida albicans. For the tested compounds, the lowest MIC value of 0.3 g/ml (on six of the 22 organisms tested) was obtained only with compound 1, which appeared as the most active compound. This lowest MIC value (0.3 g/ml) is about 4-fold lower than that of the RA, indicating the powerful and very interesting antimicrobial potential of isobavachalcone (1). The antimicrobial activities of DBT, as well as that of compounds 1, 3, 4, amentoflavone (5) are being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extracts from DBT as well as some of the isolated compounds in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/234 Files in this item: 2
Antimicrobial activity of the crude.pdf (2.258Mb)license.txt (1.998Kb) -
Kuete, V.; Ngameni, B.; Tsafack, A.M.; Ambassa, P.; Simo, I.K.; Bezabih, M.; Etoa, F.; Ngadjui, BT; Abegaz, B.M.; Beng, V.P. (Pharmacologyonline. http://www.pharmacologyonline.org/, NaN, 2007)[more][less]
Abstract: The crude extract from the twigs of Dorstenia elliptica (DET) as well one of the five compounds isolated from this extract namely O-[3-(2, 2-dimethyl-3-oxo-2H-furan-5-yl)-3- hydroxybutyl]bergaptol (5) were tested for their antimicrobial activity against bacteria and fungi. The Agar disc diffusion test was used to determine the sensitivity of the tested samples while the well micro-dilution was used to determine the minimal inhibition concentrations (MIC) and the minimal microbicidal concentration (MMC) of the active samples. The results of the disc diffusion assay showed that DET prevented the growth of all the 22 tested microbial species while the two tested compounds showed selective activity. At the tested MIC interval ranged from 1.22 to 156.25 μg/ml for the crude extracts and 0.08 to 39.06 μg/ml for the compounds, the activity of DET was noted on 20 of the 22 microbial species. The antimicrobial activities of DET as well as that compound 5 are being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extract in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/287 Files in this item: 1
ANTIMICROBIAL ACTIVITY OF THE.pdf (4.398Mb) -
Kuete, V.; Metuno, R.; Ngameni, B.; Ngandeu, F.; Bezabih, M.; Etoa, F-X.; Ngadjui, B.; Abegaz, B.; Beng, V. (Elsevier Ltd. www.elsevier.com/locate/sajb, NaN, 2007)[more][less]
Abstract: The crude methanolic extracts from Treculia africana and Treculia acuminata, three compounds isolated from T. africana and identified as, Phyllocoumarin (1), Catechin (2) and 6, 9-dihydroxy-megastigmane-3-one (3), four compounds namely 2, 3, 2,3-dihydroxypropyl-heptadecanoate (4), and Ferulic acid (5) isolated from T. acuminata were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gramnegative bacteria (12 species) and three Candida species. The micro-dilution method for the determination of the minimal inhibition concentration (MIC) and the Minimal microbicidal concentration (MMC) was used. The MIC values obtained with the crude extracts varied from 78 to 156 à ¼g/ ml against 12 (57.14%) and 20 (95.24%) of the 21 tested microorganisms respectively for T. acuminata and T. africana. Apart from compound 2 that prevented the growth of all the tested microorganisms, other bioactive compounds showed selective activity. The obtained results provide promising baseline information for the potential use of these crude extracts as well as some of the isolated compounds in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/245 Files in this item: 2
license.txt (1.998Kb) -
Kuete, V.; Metuno, R.; Ngameni, B.; Tsafack, A.M.; Ngandeu, F.; Fotso, G.W.; Bezabih, M.; Etoa, F.; Ngadjui, B.T.; Abegaz, B.M.; Penlap, B.V. (Elsevier Ireland Ltd. www.elsevier.com/locate/jethpharm, NaN, 2007)[more][less]
Abstract: The crude extract from Treculia obovoidea was subjected to purification by repeated chromatography. Eight compounds were isolated from Treculia obovoidea and identified as Psoralen (1), Bergapten (2), 7-methoxycoumarin (3), 7-hydroxycoumarin (4), 4,2 ,4 -trihydroxychalcone (5), 4,2 ,4 -trihydroxy-3-prenylchalcone (6), 3-hydroxy-4-methoxybenzoic acid (7) and O-[3-(2,2-dimethyl-3-oxo-2H-furan-5-yl) butyl] bergaptol (8). These compounds together with the extract were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and three Candida species using micro-dilution methods for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC). The MIC values obtained with the crude extracts varied from 78.12 to 156.25 g/ml against 17 (80.95%) of the 21 tested microorganisms. All the isolated compounds showed selective activity. The antimicrobial activity of this plant as well as that of compounds 6 and 8 is being reported for the first time. The obtained results provide promising baseline information for the potential use of these crude extract as well as some of the isolated compounds in the treatment of bacterial and fungal infections. URI: http://hdl.handle.net/10311/288 Files in this item: 1
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Erasto, P.; Bojase-Moleta, G.; Majinda, R.T. (Elsevier Ltd. www.elsevier.com/locate/phytochem, NaN, 2004)[more][less]
Abstract: Three new flavonoids-5,7,4'-trihydroxy-6-[1-hydroxy-2-methylbuten-2-yl]isoflavone (isogancaonin C), 7,2'-dihydroxy-4'-methoxyisoflav- 3-ene (bolusanthin III), 6,6'-dihydroxy-4'-methoxy-2-arylbenzofuran (bolusanthin IV), in addition to eight known flavonoids; derrone, medicarpan, genistein, wighteone, lupiwighteone, gancaonin C, 7-hydroxy-4'-methoxyisoflavone and 7,3'-dihydroxy-4'- methoxyisoflavone were isolated from the root wood of Bolusanthus speciosus.The compounds showed strong antimicrobial activity against Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Candida mycoderma.The isolated compounds also showed moderate to strong radical scavenging properties against DPPH radical with the highest activities shown by the 2-arylbenzofuran, the isoflav-3-ene and 7,3'-dihydroxy-4'-methoxyisoflavone in decreasing order. URI: http://hdl.handle.net/10311/299 Files in this item: 1
Antimicrobial and antioxidant.pdf (3.228Mb) -
Chacha, M.; Bojase-Moleta, G.; Majinda, R.R.T. (Elsevier Ltd; http://www.elsevier.com/wps/find/journaldescription.cws_home/273/description, November 20, 2004)[more][less]
Abstract: From the stem wood of Erythrina latissima, two isoflavones and a flavanone were isolated and characterized as 7,3'-dihydroxy-4'-methoxy-5'-(y,y-dimethylallyl)isoflavone (erylatissin A), 7,3'-dihydroxy-6".6"-dimethyl-4".5"-dehydropyrano [2",3":4'.5']isoflavone (erylatissin B), (-)-7,3'-dihydroxy-4'-methoxy-5'-(y,y-dimethylallyl)flavanone (erylatissin C), respectively, in addition to 10 known flavonoids. Structures of these compounds were determined on the basis of their spectroscopic data. These compounds showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida mycoderma. The isolated compounds also exhibited weak radical scavenging properties towards DPPH radical. URI: http://hdl.handle.net/10311/216 Files in this item: 2
license.txt (1.998Kb) -
Omisore, N.; Adewunmi, C.; Iwalewa, E.; Ngadjui, B.; Watchueng, J.; Abegaz, B.; Ojewole, J. (Elsevier Ltd. www.elsevier.com/locate/jethpharm, NaN, 2004)[more][less]
Abstract: The present studywas undertaken to investigate the antinociceptive and anti-inflammatory activities of the leaf and twig extracts of Dorstenia barteri (Moraceae) in mice. Both the leaf and twig extracts of Dorstenia barteri at 50, 100 and 200 mg/kg showed significant (P < 0.05-0.01) antinociceptive activities in chemical-, mechanical- and thermal-induced pain test models. Intraperitoneal administration of the plant extracts at 50, 100 and 200 mg/kg significantly (P < 0.05-0.01) inhibited carrageenin-induced acute inflammation in oedema paw weight, pulmonary oedema and number of pleural leucocytes in a dose-dependent way. The twig extract was found to be more active than the leaf extract in all the experimental models used. The inhibitory effects of the plant extracts were comparable to those of the reference drugs acetylsalicyclic acid (ASA) and phenylbutazone (PBZ) at 100 mg/kg i.p. The significant reduction in acetic acid-induced abdominal contractions, the decrease in oedema paw weight as well as in the number of leucocytes in the pleural cavity exudates, and the significant increase in the reaction time and pain threshold of mice observed in this study suggest that Dorstenia barteri extracts possess both anti-inflammatory and antinociceptive activities. The present study, therefore, lend pharmacological support to the folkloric uses of Dorstenia barteri extracts in the treatment, control and/or management of arthritis, rheumatism, gout, headache and other forms of body pains in some parts of Africa. URI: http://hdl.handle.net/10311/256 Files in this item: 2
license.txt (1.998Kb) -
Antioxidant activity of prenylated flavonoids from the West African medicinal plant Dorstenia manniiDufall, K.; Ngadjui, B.; Simeon, K.; Abegaz, B.; Croft, K. (Elsevier Science Ireland Ltd. www.elsevier.com/locate/jethpharm, NaN, 2003)[more][less]
Abstract: The antioxidant activities of three prenylated flavonoids from Dorstenia mannii (6,8-diprenyleriodictyol, dorsmanin C and dorsmanin F) were compared to the common, non-prenylated flavonoid, quercetin. The prenylated flavonoids were found to be potent scavengers of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), and are more potent than butylated hydroxy toluene (BHT), a common antioxidant used as a food additive. The prenylated flavonoids also inhibited Cu2+-mediated oxidation of human low density lipoprotein (LDL). Dose-response studies indicated that the prenylated flavonoids were effective inhibitors of lipoprotein oxidation with IC50 values <1 M and had similar inhibitory potency compared to quercetin, but was not directly related to Cu binding. Unlike quercetin, they did not show any pro-oxidant activity at high doses in the Cu2+-mediated lipoprotein oxidation system. The medicinal action of Dorstenia mannii may be related to the high concentration of potent antioxidant prenylated flavonoids in this species. URI: http://hdl.handle.net/10311/261 Files in this item: 2
license.txt (1.998Kb) -
Omisore, N.O.A.; Adewunmi, C.O.; Iwalewa, E.O.; Ngadjui, B.T.; Adenowo, T.K.; Abegaz, B.M.; Ojewole, J.A.; Watchueng, J. (Brazilian Journal of Medical and Biological Research. http://www.scielo.br/scielo.php?pid=0100-879X&script=sci_serial, NaN, 2005)[more][less]
Abstract: Dorstenia barteri and D. convexa extracts and some isolated components of the former were investigated for effectiveness against Trichomonas gallinarum and compared with quercetin and quercitrin. The antioxidant activity of the extracts/compounds was also determined. The minimum lethal concentrations (MLCs) for the extract of D. barteri leaves and twigs at 24 h were found to be 15.625 and 15.625 μg/ml, respectively. However, the MLCs of the leaf and twig extract of D. convexa were 125 and 437.5 μg/ml, respectively. The prenylated and geranylated chalcones were as active as the prenylated flavones, 6- prenylapigenin and the diprenylated derivative 6,8-diprenyleridictyol. The order of the antitrichomonal activity of the compounds at 24 h was: quercetin (0.121 μg/ml) > quercitrin (0.244 μg/ml) ≥ bartericin B (0.244 μg/ml) > bartericin A (0.73 μg/ml) > stigmasterol (0.98 μg/ml) > 6,8-diprenyleridictyol = isobavachalcone = dorsmanin F (31.25 μg/ ml). D. barteri extracts, quercitrin, and bartericin A, and the prenylated flavonoids had potent antioxidant properties. The twig extract of D. barteri was more potent than the leaf extract. Moderate (EC50 >50 μg/ ml) and high (EC50 <50 μg/ml) antioxidant activities were detected in the leaf and twig extracts of D. barteri and the prenylated flavonoids. Prenylated flavonoids and the isolated compounds with antioxidant properties described here may account for the anti-inflammatory action of these extracts. The antitrichomonal and antioxidant activities shown by the extracts and compounds in this study are consistent with the ethnomedicinal and local use of the Dorstenia species studied. URI: http://hdl.handle.net/10311/284 Files in this item: 1
Antitrichomonal and antioxidant.pdf (2.508Mb) -
Alemaw, B.F.; Shemang, E.M.; Chaoka, T.R. (Elsevier Science Ltd, http://www.elsevier.com/locate/pce, NaN, 2004)[more][less]
Abstract: Botswana is a semi-arid country with limited recharge to groundwater resources. Groundwater however is a major source of water for domestic, industrial and agricultural uses. There is therefore the need to ensure that the groundwater resources are of drinking quality, by protecting them against pollution sources such as landfills, pit latrines, industries, agricultural pesticides and waste. In this study a preliminary assessment of vulnerability of groundwater to pollution in Kanye well field in SE Botswana is undertaken. In order to assess the vulnerability of this aquifer to pollution, soils types, mapped geology and information from 82 boreholes were input into a GIS system to classify pollution vulnerability using Theissen polygons of the study area. Results indicate that 58% of the well field area is highly or very highly vulnerable to pollution, 34% is moderately vulnerable to pollution, and only 9% has low vulnerability. Estimates of the aquifer media characteristics in areas with only a few observations or few geological logs were considered to have higher uncertainty than areas with many observations. However, the use of the polynomial estimator enabled consideration of simple uncertainty for the aquifer media characteristics and pollution vulnerability modelling process. URI: http://hdl.handle.net/10311/888 Files in this item: 1
Alemaw_PCE_2004.pdf (375.0Kb) -
Muzila, M.; Setshogo, M.P.; Moseki, B.; Morapedi, R. (Global Science Books, http://www.globalsciencebooks.info/, NaN, 2011)[more][less]
Abstract: The genus Prosopis comprises 44 species. Extensive introgression and hybridization is suspected in the genus, which makes identification of the species very difficult. Accurate identification of the species is crucial in controlling invasive species, within this genus. That is so because the method of control is species specific. The objective of the study was to determine the taxonomic structure of Prosopis species in Southern Botswana. A systematic qualitative approach was used to sample the species such that specimen selection was based on observable morphological discontinuities. The morphological characters were subjected to multivariate analysis since the analysis has been reported to be good at identifying hybrids. The multivariate analysis included anova, cluster analysis, factor analysis and canonical correlation. The study revealed four pure lines of Prosopis and nine hybrid species. The pure lines are Prosopis chilensis, P. juliflora, P. velutina and P glandulosa and they all belong to one section, ALGAROBIA. The observed hybrids were P. chilensis x P. glandulosa, P. glandulosa x P. chilensis, P. juliflora x P. glandulosa, P. chilensis x P. juliflora, Acacia karroo x P. juliflora, P. glandulosa x P. pallid, P. juliflora x P. pallid, P. chilensis x P. juliflora x P. glandulosa and P. chilensis x P. pallida. It was therefore concluded that the Prosopis species in Southern Botswana have formed a hybrid swam. And for the hybrids P. chilensis x P. glandulosa and P. glandulosa x P. chilensis it was concluded that gene flow between P. chilensis and P. glandulosa is bidirectional. For the hybrid P. juliflora x P. glandulosa it was concluded that gene flow was from P. juliflora to P. glandulosa. URI: http://hdl.handle.net/10311/921 Files in this item: 1
Muzila_AJPSB_2011.pdf (252.4Kb) -
Moleele, N.; Ringrose, S.; Arnberg, W.; Lunden, B.; Vanderpost, C. (Taylor and Francis http://www.clas.ufl.edu/lueci/southworth/RS-class-advanced/Discussion-readings/Moleele%20et%20al%202001%20Assessment%20of%20veg%20indexes%20i.pdf, NaN, 2001)[more][less]
Abstract: Considerable signi® cance is placed on the mapping and monitoring of degraded areas in semi-arid regions of the world, including Botswana. Degraded areas include those suVering from bush encroachment, believed to result from heavy cattle grazing over a number of years. However, certain bush encroachment species have been found to be relatively nutrient-rich.The present work considers the extent to which a series of quanti® ed layers throughmainly bush encroachment canopies can be identi® ed using conventional and newly derived vegetation indexes and transforms based on Thematic Mapper (TM) imagery. Field work involved the strati® cation of green biomass into ® rstly the herbaceous cover layer; secondly the 0.3± 1.5m browse layer; then the 1.5± 2.5m browse layer; and ® nally the >2.5m browse layer. Biomass measurements from these layers were statistically associated with conventional vegetation indexes and transforms such as the NormalizedDiVerenceVegetation Index (NDVI), brightness and greenness values, and relatively newly derived darkening indexes involving the mid-infrared bands. When green biomass and transformed pixel data were averaged per classi® ed vegetation unit, weak negative correlations emerged between grass biomass and the transformed pixel data and no signi® cant correlations developed with the woody biomass (browse) layers. However, when point data were used in the analyses, results showed that most indexes and the brightness transform were signi® cantly correlated with the lower browse layer. Only the darkening indexes and brightness function were sensitive to the browse layers individually and the browse plus grass layers. This work shows the limitations of conventional indexes such as the NDVI in terms of browse and herbaceous layer assessment. New indexes for forage assessment based on relationships between the mid-infrared bands, such as those found in the new MODIS TERRA platform, are urgently required for semi-arid areas. URI: http://hdl.handle.net/10311/410 Files in this item: 1
Moleele_IJRS_2001.pdf (903.7Kb) -
Jourdan, F.; Fe´raud, G.; Bertrand, H.; Watkeys, M.K.; Kampunzu, A.B.; Le Gall, B. (Elsevier www.elsevier.com/locate/epsl, NaN, 2006)[more][less]
Abstract: Continental flood basalts consist of vast quantities of lava, sills and giant dyke swarms that are associated with continental break-up. The commonly radiating geometry of dyke swarms in these provinces is generally interpreted as the result of the stress regime that affected the lithosphere during the initial stage of continental break-up or as the result of plume impact. On the other hand, structures in the basement may also control dyke orientations, though such control has not previously been documented. In order to test the role of pre-dyke structures, we investigated four major putative Karoo-aged dyke swarms that taken together represent a giant radiating dyke swarm (the so-called btriple-junctionQ) ascribed to the Jurassic Karoo continental flood basalt (N3 106 km2; southern Africa). One of the best tests to discriminate between neoformed and inherited dyke orientation is to detect Precambrian dykes in the Jurassic swarms. Accordingly, we efficiently distinguished between Jurassic and Precambrian dykes using abbreviated low resolution, 40Ar/39Ar incremental heating schedules. Save-Limpopo dyke swarm samples (n =19) yield either apparent Proterozoic (728–1683 Ma) or Mesozoic (131–179 Ma) integrated ages; the Olifants River swarm (n =20) includes only Proterozoic (851–1731 Ma) and Archaean (2470–2872 Ma) dykes. The single age obtained on one N–S striking dyke (1464 Ma) suggests that the Lebombo dyke swarm includes Proterozoic dykes in the basement as well. These dates demonstrate the existence of pre-Karoo dykes in these swarms as previously hypothesized without supporting age data. In addition, aeromagnetic and air-photo interpretations indicate that: (1) dyke emplacement was largely controlled by major discontinuities such as the Zimbabwe and Kaapvaal craton boundaries, the orientation of the Limpopo mobile belt, and other pre-dyke structures including shear zones and (2) considering its polygenetic, pre-Mesozoic origin, the Olifants River dyke swarm cannot be considered part of the Karoo magmatic event. This study, along with previous results obtained on the Okavango dyke swarm, shows that the apparent btriple junctionQ formed by radiating dyke swarms is not a Jurassic structure; rather, it reflects weakened lithospheric pathways that have controlled dyke orientations over hundreds of millions of years. One consequence is that the btriple-junctionQ geometry can no longer be unambiguously used as a mantle plume marker as previously proposed, although it does not preclude the possible existence of a mantle plume. More generally, we suggest that most Phanerozoic dyke swarms (including triple junctions) related to continental flood basalts were probably controlled in part by pre-existing lithospheric discontinuities. URI: http://hdl.handle.net/10311/386 Files in this item: 1
Kampunzu2006BasementControl.pdf (2.119Mb) -
Masesane, I.B.; Yeboah, S.O.; Liebscher, J.; Mugge, C.; Abegaz, B.M. (Elsevier Science Ltd, http://www.elsevier.com/locate/phytochem, NaN, 2000)[more][less]
Abstract: The twigs of Rhus pyroides yielded a novel bichalcone 2',40,21-trihydroxy-4',41-dimethoxy-4-O-51-bichalcone. It was identified on the basis of spectroscopic data including 1D and 2D NMR spectroscopy. The name rhuschalcone-1 is proposed. URI: http://hdl.handle.net/10311/1028 Files in this item: 1
Masesane_P_2000.pdf (321.5Kb) -
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)