Browsing Faculty of Science by Title
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Banda, A.; Mubyana-John, T.; Taylor, J.E. (Global Science Books, http://www.globalsciencebooks.info/, NaN, 2011)[more][less]
Abstract: The influence of burning on soil microbial dehydrogenase activity, nitrogen content and fungal population along the Boro route in the Okavango Delta was assessed in the flood and dry seasons. Soil samples from the burnt plots and the adjacent control un-burnt plots were cultured on agar plates using dilution methods. Fusarium spp. were dominant while Aspergillus species were low in burnt plots. The other fungi such as Drechslera sp., Exophiala jeanselmmei, Penicillium compactum and Chrysosporium merdarium were only in the burnt plots as compared to unburnt control plots. However, fungal diversity and soil dehydrogenase activity reduced after 6 months of burning showing significant increase in Chrysosporium merdarium in almost all the burnt plots. The influence of burning on soil nitrogen was insignificant instead flooding had a stronger influence on nitrogen content than burning. The results indicate that burning increased fungal diversity and biomass, however, reduces overall microbial enzyme activity after burning without influencing soil nitrogen and pH. URI: http://hdl.handle.net/10311/919 Files in this item: 1
Mbuyana_AJPSB_2011.pdf (220.0Kb) -
Mubyana, T.; Krah, M.; Totolo, O.; Bonyongo, M. (Journal of Arid Environments. http://www.elsevier.com/wps/find/journaldescription.cws_home/622855/description#description, NaN, 2003)[more][less]
Abstract: The effect of flooding on soil total nitrogen, phosphorus and microbial population in different vegetation zones (floodplain, island and woodland) and profile depth (0?1, 0?5, 2?0, 3?0, 4?0 and 5?0m) of the Okavango Delta was studied from February to July 1999. Total nitrogen significantly differed with soil profile depth, moisture regime and months. In the woodlands, insignificant total nitrogen was detected at all depths except at 0?1m, where 0?03% and 1?17% were detected in February and March, respectively. In the island samples, only 0?05% was detected at 4m in February. Nitrogen in the floodplain samples was concentrated in the A1 horizon where 0?12%, 0?61% and 0?03% were detected in February, March, and May, respectively. Organic phosphorus significantly differed with vegetation zone but not with months and depth. Although organic phosphorus was low (0?02–0?52%) at all sites, it was liberally distributed throughout the profiles. On the island, actinomycetes were only detected up to 2m in February and up to 3m in July. Fungi concentrated in the top 0?5m (103–105). In both the floodplain and island samples, bacteria concentrated in the upper 3m. However, after May, populations decreased significantly. In the floodplain, significant actinomycetes populations were only detected in the upper 0?5m. Generally, organic phosphorus showed positive correlations with fungal populations. This study indicates that these soils are low in total nitrogen and phosphorus. URI: http://hdl.handle.net/10311/293 Files in this item: 1
Influence of seasonal flooding.pdf (3.953Mb) -
Dikinya, O.; Hinz, C.; Aylmore, L.G. (Csiro, http://www.publish.csiro.au/nid/84.htm, NaN, 2007)[more][less]
Abstract: The paper examines the effects of electrolyte concentration and sodium adsorption ration (SAR) on the relative saturated hydraulic conductivity (RHC) and the ionic behaviour of calcium (Ca) and sodium (Na) ions in the Na-Ca echange complex. Batch binary exchange and saturated column transport experiments were carried out to quantify these effects using agricultural Balkuling soil and mining residue. Generally, RHC has been found to decrease with time, with increasing SAR and with decreasing electrolyte concentration. The more rapid decrease in RHC in the mining residue, particularly at the lowest concentration (1 mmol/L), was consistent at all SAR values. The decreases in RHC were likely to be caused by partial blocking of pores by dispersed clay particles, as evidenced by the appearance of suspended clay particles in the effluent during leaching. Significant differences in RHC were abserved in the passage of fronts of decreasing electrolyte concentration for CaCl2 and SAR 15 solutions through the soil columns. These differences were attributable to structural alterations (slaking) of the media and the nature of the particles released and mobilised within the porous structure at a given point in the column. Measurements at the critical threshold concentration and turbidity increase in SAR to 15 is initially accompained by erractic RHC, presumably due to the break up of soilaggregates under the increased swelling forces. The less coherent mining residue soil was substantially more vulnerable to blockage of pores than the Balkuling soil in which clay particles are likely to be more readily mobilised, and hence available to re-deposit and occlude the matrix pores. URI: http://hdl.handle.net/10311/312 Files in this item: 1
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Nijegorodov, N.; Winkoun, D.P.; Nkoma, J.S. (Elsevier Science Ltd http:www.elsevier.com/locate/saa, NaN, 2003)[more][less]
Abstract: Please refer to the attached article for an ABSTRACT. The abstract was not uploaded here due to formula appearance problem in UBRISA. URI: http://hdl.handle.net/10311/403 Files in this item: 1
Nijegorodov_SAa60_2004.pdf (1.056Mb) -
Nijegorodov, N.; Winkoun, D.P.; Nkoma, J.S. (Elsevier Science Ltd. www.elsevier.com/locate/saa, NaN, 2004)[more][less]
Abstract: The fluorescence and laser properties of seven specially chosen aromatic compounds are studied at 293 ◦C. The quantum yield of fluorescence, γ, decay times, τf , of the deaerated and non-deaerated solutions are measured. The oscillator strength, fe, fluorescence rate constants, kf , natural lifetimes, τT 0 , and intersystem crossing rate constants, kST, are calculated. Some laser parameters are calculated or measured experimentally. It is found that the position of the T level plays an important role in the fluorescence and laser properties of aromatic compounds. If the T level is situated below the Sp level, it decreases the quantum yield of fluorescence and the decay time and increases the threshold of laser action. If, due to some structural changes of a molecule, the T level is situated higher than the Sp level, then the quantum yield of fluorescence and the decay times are increasing and the threshold of laser action is decreasing. Such influence of the position of the T level upon fluorescence and laser properties of aromatic compound is explained by the fact that the Sp level mixes with the T level more readily than with other τ ∗ levels. URI: http://hdl.handle.net/10311/366 Files in this item: 1
Nijegorodov_SAa60_2004.pdf (1.056Mb) -
Nijegorodov, N.; Mabbs, R.; Winkoun, D.P. (Elsevier Science Ltd. www.elsevier.com/locate/saa, NaN, 2003)[more][less]
Abstract: Please refer to the attached article for an ABSTRACT. The abstract was not uploaded here due to formula appearance problem in UBRISA. URI: http://hdl.handle.net/10311/402 Files in this item: 1
Nijegorodov_SAa59-2003.pdf (1.367Mb) -
Chaturvedi, P. (Oxford University Press, Oxford Journals; http://ecam.oxfordjournals.org/, March NaN, 2008)[more][less]
Abstract: In the present study, inhibitory effect of the methanol extract of Raphanus sativus root on lipid peroxidation has been carried out in normal rats. Graded doses of methanol extract of root of the plant (40, 80 and 120 mg kg 1 body weight) were administered orally for 15 days to experimental treated rats. Distilled water was administered to experimental control rats. At the end of experiment, rats were killed by decapitation after ether anesthesia. Blood and liver were collected to measure thiobarbituric acid reactive substance, reduced glutathione and activity of catalase. Results indicated that the extract of R. sativus root reduced the levels of thiobarbituric acid reactive substance significantly in all experimental treated groups (P50.05) as compared to the experimental control group. It also increased the levels of reduced glutathione and increased the activity of catalase. In vitro experiments with the liver of experimental control and experimental treated rats were also carried out against cumene hydroperoxide induced lipid peroxidation. The extract inhibited in vitro cumene hydroperoxide induced lipid peroxidation. R. sativus inhibits lipid peroxidation in vivo and in vitro. It provides protection by strengthening the antioxidants like glutathione and catalase. Inclusion of this plant in every day diet would be beneficial. Description: eCAM Advance Access originally published online on February 20, 2007 eCAM 2008 5(1):55-59; doi:10.1093/ecam/nel077 Version available here is the 2007 version. URI: http://hdl.handle.net/10311/182 Files in this item: 2
Inhibitory response of raphanus.pdf (861.5Kb)license.txt (1.998Kb) -
Kgathi, D.L.; Bolaane, B. (Sage http://wmr.sagepub.com/cgi/content/abstract/19/4/342, NaN, 2001)[more][less]
Abstract: Sustainable solid waste management is a strategy for achieving environmental quality in both the developed and the developing world. Environmental quality is a necessary condition for an increase in per capita welfare over time. The paper suggests alternative instruments for solid waste reduction, re-use and recycling. But to be able to apply the suggested economic instruments, the quantities and composition of the waste must be known. Having identified the current instruments of Botswana’s solid waste management (regulatory measures, environmental education, and economic instruments of property rates, service levy, and sanitation fees), the paper argues that these do not go far enough in enhancing environmental protection. Alternative instruments such as solid waste collection and disposal levies, deposit refund schemes, and product levies are suggested. It is also suggested that public environmental education and regulatory measures should be strengthened. URI: http://hdl.handle.net/10311/480 Files in this item: 1
Kgathi_WMR_2001.pdf (1.278Mb) -
Swatuk, L. A.; Rahm, D. (Elsevier, http://www.linkinghub.elsevier.com/retrieve/pii/S1474706504001834, NaN, 2004)[more][less]
Abstract: Botswana is generally regarded as an African success story. Nearly four decades of unabated economic growth, multi-party democracy, conservative decision-making and low-levels of corruption have made Botswana the darling of the international donor community. One consequence of rapid and sustained economic development is that water resources use and demands have risen dramatically in a primarily arid/semi-arid environment. Policy makers recognize that supply is limited and that deliberate steps must be taken to manage demand. To this end, and in line with other members of the Southern African Development Community (SADC), Botswana devised a National Water Master Plan (NWMP) and undertook a series of institutional and legal reforms throughout the 1990s so as to make water resources use more equitable, efficient and sustainable. In other words, the stated goal is to work toward Integrated Water Resources Management (IWRM) in both policy and practice. However, policy measures have had limited impact on de facto practice. This paper reflects our efforts to understand the disjuncture between policy and practice. The information presented here combines a review of primary and secondary literatures with key informant interviews. It is our view that a number of constraints—cultural, power political, managerial—combine to hinder efforts toward sustainable forms of water resources use. If IWRM is to be realized in the country, these constraints must be overcome. This, however, is no small task. URI: http://hdl.handle.net/10311/405 Files in this item: 1
Swatuk_PCE_2004.pdf (1.142Mb) -
Gwebu, T.D. (Taylor & Francis (Routledge), http://jir.ucsur.pitt.edu/, NaN, 2008)[more][less]
Abstract: Based on the intergenerational wealth flows conceptual framework, this paper investigates how the AIDS pandemic threatens to disrupt the transfer of resources between generations by using a typical low income urban area in sub-Saharan Africa as a case study. It explores the everyday living conditions of orphans, their guardians, and the primary home caregivers, with the intention of gaining a deeper insight into their current and future life chances, as a result of parental morbidity and mortality due to HIV/AIDS. The research employs a qualitative methodology and relies on documentary information from secondary sources. Short- and long-term recommendations on how to mitigate the negative impacts of HIV/AIDS on wealth transfers among the affected populations are suggested based on the study findings. URI: http://hdl.handle.net/10311/1019 Files in this item: 1
Gwebu_JIR_2008.pdf (1.160Mb) -
Ogunlusi, G.O.; Ige, J.; Oyetunji, O.A.; Ojo, J.F. (Springer Science+Business Media B.V., http://www.springer.com/chemistry/journal/11243, NaN, 2009)[more][less]
Abstract: The kinetics of the reactions between azidopentacyanocobaltate(III), Co(CN)5N3 3-, and iron(II) polypyridyl complexes, Fe(LL)3 2? (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol dm-3 NaCl. The reactions were carried out under pseudo-first-order conditions in which the concentration of Fe(LL)32+ was kept constant, and the second-order rate constants obtained for the reactions at 35 C were within the range of 0.156–0.219 dm3 mol-1 s-1 for LL = bipy and 0.090–0.118 dm3 mol-1 s-1 for LL = phen. Activation parameters were measured for these systems. The dependence of reaction rates on acid was studied in the range [H+] = 0.001–0.008 mol dm-3. The reaction in acid medium shows interesting kinetics. Two reactive species were identified in acid medium, namely, the protonated cobalt complex and the azido-bridged binuclear complex. The electron-transfer process is proposed to go by mixed outerand inner-sphere mechanisms in acid medium, in which electron transfer through the bridged inner-sphere complex (k5) is slower than through the outer-sphere path (k4). Description: Symbols may not appear as they are in the original abstracts. URI: http://hdl.handle.net/10311/1035 Files in this item: 1
Ogunlusi_TMC_2009.pdf (948.9Kb) -
Mpoloka, S.W. (American-Eurasian Network for Scientific Information. http://www.aensi.org/aeb_online.html, NaN, 2008)[more][less]
Abstract: The nuclear 18S rDNA and chloroplast encoded rbcL gene sequences were used to investigate the evidence of residual UV-B induced mutagenesis in Dimorphotheca sinuata plants. The probes were generated by the polymerase chain reaction and labelled with a non-radioactive Digoxigenin label and used in Southern hybridization studies. High levels of variability in the 18S rDNA gene were found, pointing to genome rearrangements and possibly genome instability due to UV-B effects. URI: http://hdl.handle.net/10311/484 Files in this item: 1
Investigating evidence.pdf (1.233Mb) -
Alemaw, B.F.; Chaoka, T.R.; Totolo, O. (Elsevier Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/413/description#description, NaN, 2006)[more][less]
Abstract: The agricultural economic sector of Botswana is limited mainly to range resources-based livestock and pockets of arable farming based on rainfall and limited irrigated agriculture at several places. In this study agricultural sustainability of rain-fed agriculture is investigated in Botswana by considering the Pandamatenga plains as a case study. Daily soil moisture regimes with respect to crop growth cycle were modelled using a water balance model based on 42 years of daily hydroclimatic inputs and corresponding simulated components of soil moisture, evaporation, surface runoff, and deep percolation. Using a sustainability criterion on crop water requirement and soil moisture availability during the cropping periods, it was found that rain-fed agriculture of maize, sunflower, and sorghum crops is sustainable. The relative sensitivity to drought of these crops was also found to conform to the Agromisa recommendations. In the pursuit to explore more IWRM opportunities, through the simulation of the corresponding direct runoff, we have also explored that more water harvesting opportunities exist in order to manage rainfall excesses effectively. URI: http://hdl.handle.net/10311/155 Files in this item: 4
alemaw_chaoka_totolo_06.pdf (2.112Mb)license.txt (1.998Kb)license.txt (1.998Kb)license.txt (1.998Kb) -
Moseki, B.; Buru, J.C. (Academic Journals, http://www.academicjournals.org/, NaN, 2010)[more][less]
Abstract: The aim of this study was to assess the growth response of Sesuvium portulacastrum (L.) (a halophyte) to various NaCl concentrations and hence determine how it is adapted to grow optimally under saline conditions. S. portulacastrum was grown hydroponically in various NaCl concentrations (that is, 0, 100, 200, 400 and 600 mol m-3 NaCl). It was found to exhibit a growth pattern typical of dicotyledonous halophytes. It attained maximal growth at 200 mol m-3 NaCl concentration in hydroponic cultures. It accumulated large concentrations of Na+ and Cl- with the leaves having the highest ion content. These ions are believed to be sequestered in the vacuole. S. portulacastrum also accumulated proline in high concentrations and this proline appeared to adjust the cytoplasmic ion concentration to balance that of the vacuole. URI: http://hdl.handle.net/10311/961 Files in this item: 1
Moseki_SRE_2010.pdf (102.5Kb) -
Ngamga, D.; Yankep, E.; Tane, P.; Bezabih, M.; Ngadjui, B.T.; Fomum, Z.T.; Abegaz, B.M. (Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com, NaN, 2005)[more][less]
Abstract: Three new isoflavonoids, griffonianone F, G and H were isolated from the seeds of Millettia griffoniana, along with the known prebarbigerone, pseudobaptigenin, pseudobaptigenin methyl ether, tephrosin, dipterixine, odorantine, 7,4’,5’-tetramethoxyisoflavone and isojamaicin. Their structures were assigned on the basis of spectroscopic data and chemical transformations. URI: http://hdl.handle.net/10311/274 Files in this item: 1
Isoflavonoids from Seeds.pdf (1.353Mb) -
Baloi, B.; Matsheka, M.I.; Gashe, B.A. (Global Science Books, http://www.globalsciencebooks.info/, NaN, 2011)[more][less]
Abstract: Halophilic bacteria from the Makgadikgadi salt pans in north central Botswana were isolated using culture-dependent methods. Polymerase chain reaction (PCR) amplification of the 16S rRNA gene and phylogenetic analysis were used to identify the strains. Culturing was done aerobically in six different complex salt media. Salt concentrations used were 1Halophilic bacteria from the Makgadikgadi salt pans in north central Botswana were isolated using culture-dependent methods. Polymerase chain reaction (PCR) amplification of the 16S rRNA gene and phylogenetic analysis were used to identify the strains. Culturing was done aerobically in six different complex salt media. Salt concentrations used were 15, 20, 25 and 30% (2.6, 3.4, 4.3 and 5.1 M, respectively) NaC1, at pH 7.2 to pH 8.0. Four colony morphology types were isolated in axenic cultures comprising Gram-positive cells. Universal bacterila primers were used to amplify 16S rDNA from chromosomal DNA isolated from three of the four distinct colony groups. Restriction enzyme digest analysis of the 16S rDNA revealed seven RFLP types. Five of the RFLP types were subjected to sequencing. Comparison of the 16S rDNA sequence alignment to reference sequence data bases showed samples S2012A3, S2012B2 and S2012B3 to have between 95 and 99% homology to Bacillus sp. BH 164 and Bacillus sp. HS 136T, a novel species recently described as Bacillus persepolensis. Isolate S4102D4 showed 95 to 99% homology to Thalassobacillus sp. JY0201 and Thalassobacillus sp. FIB228 and Halobacillus sp. MO56 species. All five isolates had at least 95% similarity to published sequences implying they could be species within the described genera. A sub-tree drawn to compare the isolates indicated two phyletic lines with S4102D4 being an outlying strain and S2012A3, S2012B and S2012B3 being a closely related clonal group all of which branch from Bacillus sp. BH 164. Pending conclusive culture, biochemical and polar lipid composition data these microorganisms are regarded as previously un-described and therefore novel species of halophilic bacteria. URI: http://hdl.handle.net/10311/920 Files in this item: 1
Matsheka_AJPSB_2011.pdf (525.8Kb) -
Jourdan, F.; Fe´raud, G.; Bertrand, H.; Kampunzu, A.B.; Tshoso, G.; Le Gall, B.; Tiercelin, J.-J.; Capiez, P. (Elservier www.elsevier.com/locate/epsl, NaN, 2004)[more][less]
Abstract: The lower Jurassic Karoo–Ferrar magmatism represents one of the most important Phanerozoic continental flood basalt (CFB) provinces. The Karoo CFB province is dominated by tholeiitic traps and apparently radiating giant dyke swarms covering altogether ca. 3 106 km2. This study focuses on the giant N110j-trending Okavango dyke swarm (ODS) stretching over 1500 km across Botswana. This dyke swarm represents the main (failed) arm of the so-called Karoo triple junction that is generally considered as a key marker of the impingement of the Karoo starting mantle plume head. ODS dolerites yield six new plagioclase 40Ar/39Ar plateau (and miniplateau) ages ranging from 178.7F0.7 and 180.9F1.3 Ma. The distribution of the ages along a narrow Gaussian curve suggests a short period of magmatic activity centered around 179 Ma, i.e., f5 Ma younger than the emplacement age of Karoo mafic magmas in the southern part of the Karoo CFB province (f184). This age difference indicates that Karoo magmatism does not represent a short-lived event as is generally the case for most CFB but lasted at least 5Ma over the whole province. In addition, small clusters of plagioclase separated from 28 other dykes and measured by ‘‘speedy’’ step-heating experiments (with mostly two to three steps), gave either ‘‘Karoo’’ or Proterozoic ages. Integrated ages of the Proterozoic rocks range from 851F6 to 1672F7 Ma, and one plateau age (959.1F4.6 Ma) and one possibly geologically significant weightedmean age (982.7F4.0 Ma) were obtained. Proterozoic and Karoo mafic rocks are petrographically similar, but Proterozoic dykes display clear geochemical differences (e.g., TiO2 < 2.1%) with the Karoo high-Ti ODS (TiO2>2.1%). Geochemical data combined with available Ar/Ar dates allow the identification of the two groups within a total set of 77 dykes investigated: f10% of the bulk ODS dykes are Proterozoic. Thus, the Jurassic Karoo ODS dykes were emplaced along reactivated Proterozoic structures and there is no pristine Jurassic Nuanetsi triple junction as commonly proposed. This throws into doubt the validity of the ‘‘active plume head’’ Karoo CFB rift models as being responsible for the observed ‘‘triple junction’’ dyke geometry URI: http://hdl.handle.net/10311/383 Files in this item: 1
Kampunzu2004KarooTripleJunction.pdf (1.306Mb) -
Oyetunji, O.A.; Paphane, B.D.; Becker, C.A.L. (Springer, http://www.springer.com/chemistry/journal/11243, NaN, 2006)[more][less]
Abstract: The interaction of pyridine with four tetraki(arylisocyanide)cobalt(II) complexes, [Co(CNR)4(ClO4)2] R = 2,6- Me2C6H3 (A), 2,4,6-Me3C6H2 (B), 2,6-Et2C6H3 (C) and 2,6-iPr2C6H3 (D), have been studied in 2,2,2-trifluoroethanol medium. The kinetics of the reactions were investigated over the 293–318 K temperature range. The reaction profile exhibited two distinct processes, proposed to be an initial fast substitution followed by a slow reduction, for each of the reactions. The pseudo first-order rate constants for both processes increased with increasing concentration of pyridine with the reduction processes exhibiting saturation kinetics at high pyridine concentrations. Steric hindrance plays a significant role in the rates of the reactions, as the rates decrease in the order k(A) > k(B) > k(C) > k(D). The activation enthalpies, DH , increase from A to D while the activation entropies, DS , are relatively similar for the four reactions, indicating similar transition states and hence similar mechanisms. Complex B was first synthesized and characterized in this study. URI: http://hdl.handle.net/10311/1033 Files in this item: 1
Oyetunji_TMC_2006.pdf (911.4Kb) -
Kalabamu, F.T. (Elsevier Science Ltd. http://www.elsevier.com/locate/landusepol, NaN, 2000)[more][less]
Abstract: Since attainment of independence, almost every country in East and Southern Africa has introduced some kind of land reform aimed at reconciling indigenous land tenure practices and those introduced by colonial regimes. The reforms have centred on modi"cation of tenurial rules on access, ownership, administration and transfer of land rights coupled with land redistribution and/or restitution in some countries. With the exception of a few countries, such as Botswana, land reforms have largely remained on statute books with little to show on the ground. The paper gives an overview of land reforms in East and Southern Africa, taking Botswana as a case study. It notes that although Botswana has largely been successful in implementing land reforms, it is currently experiencing land tenure problems, especially in peri-urban settlements and inner city low-income areas, despite government's enhanced control over local land administrative structures. The paper ends with suggestions on how to contain the current problems. URI: http://hdl.handle.net/10311/1134 Files in this item: 1
Kalabamu_LUP_2000.pdf (1.757Mb) -
Kapche, G.; Laatsch, H.; Fotso, S.; Kouam, S.; Wafo, P.; Ngadjui, B.; Abegaz, B. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2007)[more][less]
Abstract: The genus Lannea belongs to the family Anacardiaceae and consists of 40 species. Lannea nigritana (Sc. Elliot) Keay is a small tree of 3e6 m of height found in the tropical rain forest (Berhaut, 1971; Letouzey, 1972). It is used in the traditional medicine for the treatment of various infectious diseases (Berhaut, 1971; Burkill, 1985). The stem bark of this plant was collected in Makenene, Centre Province of Cameroon in December 2003. The identification was done by Mr. Nana from the National Herbarium of Yaounde where a voucher specimen (N 40408/HNC) documenting the collection is deposited. URI: http://hdl.handle.net/10311/252 Files in this item: 2
Lanneanol.pdf (2.606Mb)license.txt (1.998Kb)