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Dikinya, O. (University of Botswana, Faculty of engineering and technology, http://www.ajol.info/index.php/bjt/index, NaN, 2008)[more][less]
Abstract: Characterisation of soil water, in particular water flow dynamics is fundamental in assessing the environmental implications to soil management. Soil water characterisation was assessed by measuring soil water content and soil water potential in a draining profile of sandy and loamy soils. Mercury manometers and Neutron probe meter were connected to a 1.2 m high metal-reinforced container filled with soil samples, to simultaneously measure soil water potential and volumetric water content, respectively. Soil water contents (SWC) were found to decrease monotonically with time, with a rapid decrease in the first 50 hrs of free drainage in both soils. Sandy soil was more prone to huge losses of water than loamy soil attributed to numerous large drainable pores in sandy soil. An appreciable difference of SWC in the upper layer (SWC= 0.22 cm3/cm3) and the bottom layer (SWC= 0.35 cm3/cm3), in the case of loamy soil was attributable to its poor drainage properties. URI: http://hdl.handle.net/10311/1006 Files in this item: 1
Dikinya_BJT_2008.pdf (116.4Kb) -
Huntsman-Mapila, P.; Ringrose, S.; Mackay, A.W.; Downey, W.S.; Modisi, M.; Coetzee, S.H.; Tiercelin, J.-J.; Kampunzu, A.B.; Vanderpost, C. (Elsevier, www.sciencedirect.com, NaN, 2006)[more][less]
Abstract: Sediment samples from a continuous 4.6m profile in the dry bed of Lake Ngami in NW Botswana were analysed for geochemistry and dated using both 14C and TL methods. Certain units in the profile were found to be diatom rich and these, with the geochemical results, were used as indicators of high and low lake levels within the basin. The Lake Ngami sediments contain a high proportion of SiO2 (51–92.5 wt%, avg. 72.4 wt%) and variable levels of Al2O3 (2.04–17.2 wt%, avg. 8.88 wt%). Based on elevated Al2O3 and organic matter (LOIorgC) results, lacustrine conditions occurred at ca. 42 ka until 40 ka and diatom results suggest that relatively deep but brackish conditions prevailed. At 40 ka, the lacustrine sedimentary record was terminated abruptly, possibly by tectonic activity. At ca. 19 ka, shallow, aerobic, turbulent conditions were prevalent, but lake levels were at this time increasing to deeper water conditions up until ca. 17 ka. This period coincides with the Late Glacial Maximum, a period of increased aridity in the central southern Africa region. Generally, increasing Sr/Ca ratios and decreasing LOIorgC and Al2O3, from ca. 16 to 5 ka, suggest decreasing inflow into the basin and declining lake levels. Based on the enrichment of LREE results, slightly alkaline conditions prevailed at ca. 12 ka. Diatom results also support shallow alkaline conditions around this time. These lake conditions were maintained primarily by local rainfall input as the region experienced a warmer, wetter phase between 16 and 11 ka. Lake levels rose rapidly by 4 ka, probably in response to enhanced rainfall in the Angolan catchment. These results indicate that lake levels in the Lake Ngami basin are responding to rainfall changes in the Angolan catchment area and local rainfall. The results confirm that the present-day anti-phase rainfall relationship between southern Africa and regions of equatorial Africa was extant during the late Quaternary over the Angolan highlands and NW Botswana. URI: http://hdl.handle.net/10311/891 Files in this item: 1
Modisi2006SedimentaryRecord.pdf (1.674Mb) -
Dikinya, O.; Lehmann, P.; Hinz, C.; Aylmore, G. (Wiley http://www.interscience.doi.wiley.com/10.1002/hyp.6299, NaN, 2008)[more][less]
Abstract: A pore-scale model based on measured particle size distributions has been used to quantify the changes in pore space geometry of packed soil columns resulting from a dilution in electrolyte concentration from 500 to 1 mmol l 1 NaCl during leaching. This was applied to examine the effects of particle release and re-deposition on pore structure and hydraulic properties. Two different soils, an agricultural soil and a mining residue, were investigated with respect to the change in hydraulic properties. The mining residue was much more affected by this process with the water saturated hydraulic conductivity decreasing to 0Ð4% of the initial value and the air-entry value changing from 20 to 50 cm. For agricultural soil, there was little detectable shift in the water retention curve but the saturated hydraulic conductivity decreased to 8Ð5% of the initial value. This was attributed to localized pore clogging (similar to a surface seal) affecting hydraulic conductivity, but not the microscopically measured pore-size distribution or water retention. We modelled the soil structure at the pore scale to explain the different responses of the two soils to the experimental conditions. The size of the pores was determined as a function of deposited clay particles. The modal pore size of the agricultural soil as indicated by the constant water retention curve was 45 μm and was not affected by the leaching process. In the case of the mining residue, the mode changed from 75 to 45 μm. This reduction of pore size corresponds to an increase of capillary forces that is related to the measured shift of the water retention curve. URI: http://hdl.handle.net/10311/490 Files in this item: 1
Dikinya_HP_2008.pdf (1.769Mb) -
Om, S.; Talib, M. (The Science and Information Organization Inc., www.ijacsa.thesai.org, NaN, 2011)[more][less]
Abstract: Security is always a major concern and a topic of hot discussion to users of Wireless Mesh Networks (WMNs). The open architecture of WMNs makes it very easy for malicious attackers to exploit the loopholes in the routing protocol. Cooperative Black-hole attack is a type of denial-of-service attack that sabotages the routing functions of the network layer in WMNs. In this paper we have focused on improving the security of one of the popular routing protocols among WMNs, Ad-hoc on demand distance vector (AODV) routing protocol and present a probable solution to this attack using Merkle hash tree. URI: http://hdl.handle.net/10311/1067 Files in this item: 1
Om_IJACSA_2011.pdf (294.4Kb) -
Saab, P.; Robdera, M.A. (Glasgow Mathematical Journal Trust, http://journals.cambridge.org/action/displayJournal?jid=GMJ, NaN, 2011)[more][less]
Abstract: Let G be a compact metrizable abelian group, and let X be a Banach space. We characterize convolution operators associated with a regular Borel X-valued measure of bounded semivariation that are compact (resp; weakly compact) from L1(G), the space of integrable functions on G into L1(G)ˇ⊗X, the injective tensor product of L1(G) and X. Along the way we prove a Fourier Convergence theorem for vector measures of relatively compact range that are absolutely continuous with respect to the Haar measure. Description: the symbols on the abstract may differ from the original script URI: http://hdl.handle.net/10311/1004 Files in this item: 1
Saab_GMJ_2012.pdf (83.98Kb) -
Goodwin, J.W.; Hughes, R.W.; Reynolds, P.A.; Kwaambwa, H.M. (Elsevier B.V. www.elsevier.com/locate/colsurfa, NaN, 2004)[more][less]
Abstract: A series of well characterised cis-poly(isoprene) (PIP) polymers (Mw = 1180, 8000, 28 300, 31 500, 86 000, 115 000 and 130 000) have been added to dispersions of poly(12-hydroxystearic acid) (PHS) coated poly(methylmethacrylate) (PMMA) particles in dodecane. The ratio of particle size to adsorbed layer was also varied. For a given added polymer molecular weight, the polymer concentration in the continuous phase covered the dilute, semi-dilute and concentrated regimes as defined by the critical concentrations c and c . The viscosity behaviour of latex dispersions with added polymer were similar for all latex/polymer combinations except when polymer Mw = 1180 was added. In the latter case, the effect of adding polymer reduced both the viscosity and shear thinning behaviour. This supports the contention that the lower molecular weight polymer acts more like a diluent than a depletent. The behaviour of the viscosity ratio (the viscosity of the dispersion relative to that of the medium) as a function of polymer concentration increased with an increase in the polymer concentration until some critical concentration (cmax) for all polymers except for a polymer molecular weight 1180 Daltons. The addition of the polymer Mw = 8000 gave the highest viscosity ratio values in the polymer concentration range studied. It was found that the viscosity of all latex/polymer combinations decreased with an increase in temperature. The results suggest that the viscosity behaviour cannot be explained on the basis of a simple steric–elastic model and require a modified theoretical treatment. URI: http://hdl.handle.net/10311/324 Files in this item: 1
Viscosity behaviiour of particles.pdf (4.522Mb) -
Kwaambwa, H.M.; Goodwin, J.W.; Hughes, R.W.; Reynolds, P.A. (Elsevier B.V. www.elsevier.com/locate/colsurfa, NaN, 2007)[more][less]
Abstract: Aseries of six well characterised homopolymers of cis-polyisoprene (PIP) ranging from 1180 to 115,000 molecular weight were utilised to explore viscosity and the scaling relationship between viscosity and concentration in dodecane (good solvent). For each polymer molecular weight, the relative viscosity of PIP in dodecane at 298K was measured at several polymer concentrations using capillary viscometry. The linear extrapolation of experimental data based on Huggins, Kramer, Martin and Schulz-Blaschke equations was used to find the intrinsic viscosity at infinite dilution for each polymer molecular weight. The single-point method of evaluation of the intrinsic viscosity was also used for comparison. The Mark-Houwink fit of the data gave power index of 0.72 indicating that dodecane is good solvent for PIP and the latter exists in solution as open flexible coil. Both the radius of gyration and critical chain overlap concentration, c*, were derived from measured intrinsic viscosities. Plot of the relative viscosities versus the scaled concentration c/c*, resulted in single curve with slope value 4.44×10−2 and correlation coefficient r2 = 0.996, indicating good linear fit. URI: http://hdl.handle.net/10311/328 Files in this item: 1
Viscosity molecular weight.pdf (3.079Mb) -
Ddamba, W.A.A.; Mokate, O. (Journal of Solution Chemistry., NaN, 2006)[more][less]
Abstract: Densities (ρ) of the binary systems of {difurylmethane+(ethanol or propan-1- ol or butan-1-ol or pentan-1-ol or hexan-1-ol)} have been measured with an Anton Paar DMA 4500 vibrating-tube densimeter over the entire composition range at 298.15K and atmospheric pressure. Excess molar volumes (V E m ) of each binary system were determined and correlated by the Redlich-Kister equation. Limiting (Vi E,∞) and excess partial molar volumes (V E i ) of components of each binary system have been calculated to provide insight into the intermolecular interactions present and the packing efficiencies. The results have been discussed in terms of specific intermolecular interactions, dispersive forces and structural effects. URI: http://hdl.handle.net/10311/318 Files in this item: 1
Volumetric prop.pdf (3.737Mb) -
Thior, I.; Gabaitiri, L.; Grimes, J.; Shapiro, R.; Lockman, S.; Kim, S.; Kebaabetswe, P.; Garmey, E.; Montano, M.; Peter, T.; Chang, S.; Marlink, R.; Essex, M. (Elsevier www.elsevier.com/locate/pateducou, NaN, 2007)[more][less]
Abstract: Objective: To determine uptake and socio-demographics predictors of acceptance of voluntary counseling and testing (VCT) among postpartum women in Botswana. Methods: Women attending maternal and child health clinics for their first post-partum or well baby visit in three sites in Botswana were offered VCTafter a written informed consent. A standardized questionnaire was used to collect socio-demographic characteristics and reasons for declining VCT. Results: From March 1999 to November 2000, we approached 1735 post-partum women. Only 937 (54%) of those approached accepted VCT. In multiple logistic regression analysis, younger maternal age, not being married, and less formal education were significant predictors of acceptance of VCT. Thirty percent of women who accepted VCT were HIV-positive. Conclusion: Our results indicated that in Botswana prior to the initiation of a government Mother to Child Transmission (MTCT) prevention program, younger, unmarried, and less educated post-partum women were more likely to undergo VCT. Practice implications: Our results have shown that interventions to improve VCT among post-partum women and more generally among women of reproductive age are warranted in Botswana. These interventions should account for differences such age, marital status, education, and partner involvement to maximize VCT uptake. URI: http://hdl.handle.net/10311/588 Files in this item: 1
GABAITIRI2007VOLUNTARY COUNSELING.pdf (642.1Kb) -
Chipanshi, A.C.; Chanda, R.; Totolo, O. (Springer http://www.springerlink.com/content/p88867543584713, NaN, 2004)[more][less]
Abstract: This study examines the sensitivity of maize and sorghum crops to global warming in Botswana, a country with arid climatic conditions and shortfalls in locally produced grain. The vulnerability of the maize and sorghum crops to climate change were studied using crop simulation models while climate change scenarios were generated from Global Circulation Models. Simulated yields indicated that rain-fed crop production under the observed climate was a small fraction of what could be produced under optimal conditions. The gap was attributed to both physical (especially lack of rain) and socio-economic constraints. Using the southern African core climate change scenario, simulated yields declined by 36% in the case of maize and 31% for sorghum in the sand veldt region. Yield reductions from the hard veldt region were in the order of 10% for both maize and sorghum. The growing season became shorter, the average reduction in days in the sand veldt region being 5 and 8 days for maize and sorghum respectively, and correspondingly, 3 and 4 days over the hard veldt region. The food security option currently followed in Botswana was found to be a good adaptive strategy under a changed climate. URI: http://hdl.handle.net/10311/412 Files in this item: 1
chipanshi_CC_2003.pdf (1.144Mb) -
Masike, S.; Urich, P. (Academic journals http://hdl/handle.net/10289/973, NaN, 2008)[more][less]
Abstract: Cattle’s rearing in Botswana is undertaken in two sectors: the communal and commercial. The communal sector is exclusively free range and therefore depends on biomass production. This makes the systems highly susceptible to drought. One strategy that has been devised by farmers to adapt to drought has been to overstock. However, this strategy may not be the best adaptation strategy as it leads to overgrazing and quick depletion of scarce biomass during the drought years. Climate change may increase the vulnerability of the communal cattle sector in the country mostly through changes and variability of rainfall. In the article, we determine the reliability of the rainfall in the Khurutshe area, Botswana. Vulnerability of the cattle sector to system severe failure is also determined. Lastly, the effects of climate change on return period of drought are investigated. Results indicate that the reliability index of rainfall in the Kgatleng District is 0.5. The vulnerability index of the cattle is estimated at 8000 per year. Lastly, using SimCLIM computer model climate change will shorten the return period of mild drought from 2 years to 1.6 years by 2050. These findings have serious implications on the recovery period of the cattle to withstand the next drought period. URI: http://hdl.handle.net/10311/542 Files in this item: 1
Masike_JGRP_2008.pdf (555.0Kb) -
Mbaiwa, J.E. (Elsevier http://www.doi:10.1016/j.jenvman.2005.03.007, NaN, 2005)[more][less]
Abstract: This paper uses the concept of sustainable development to examine the utilisation of wildlife resources at Moremi Game Reserve (MGR) and Khwai community area (NG 18/19) in the Okavango Delta, Botswana. Using both secondary and primary data sources, results show that the establishment of MGR in 1963 led to the displacement of Khwai residents from their land; affected Basarwa’s hunting and gathering economy; marked the beginning of resource conflicts between Khwai residents and wildlife managers; and, led to the development of negative attitudes of Khwai residents towards wildlife conservation. Since the late 1980s, a predominately foreign owned tourism industry developed in and around MGR, however, Khwai residents derive insignificant benefits from it and hence resource conflicts increased. In an attempt to address problems of resource conflicts and promote sustainable wildlife utilisation, the Botswana Government adopted the Community-Based Natural Resource Management (CBNRM) programme, which started operating at Khwai village in 2000. The CBNRM programme promotes local participation in natural resource management and rural development through tourism. It is beginning to have benefits to Khwai residents such as income generation, employment opportunities and local participation in wildlife management. These benefits from CBNRM are thus having an impact in the development of positive attitudes of Khwai residents towards wildlife conservation and tourism development. This paper argues that if extended to MGR, CBNRM has the potential of minimising wildlife conflicts between Khwai residents and the wildlife-tourism sectors. This approach may in the process promote the sustainable wildlife use in and around MGR. URI: http://hdl.handle.net/10311/439 Files in this item: 1
Mbaiwa_JEM_2005.pdf (2.041Mb) -
Ahmad, J.; Ddamba, W.A.A. (Chemic Publishing Co., http://www.asianjournalofchemistry.com/, NaN, 2006)[more][less]
Abstract: The expression for mechanical work obtained in the expansion of a gas commonly used in physical chemistry textbooks is critically examined. The mathematical form of the first law of thermodynamics is arrived at by a procedure that is consistent with the common definition of mechanical work. The treatment is extended to explain the concept of reversible and irreversible work. URI: http://hdl.handle.net/10311/225 Files in this item: 2
license.txt (1.998Kb)Work in thermodynamics.pdf (1.197Mb)
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Now showing items 222-234 of 234