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King, J.G.; Williams, W. (American Geophysical Union. http://www.agu.org/journals/jd/, NaN, NaN)[more][less]
Abstract: Although several studies have recommended removal of secondary components of magnetic remanence by zero-field cycling from room temperature to a temperature much lower than the low temperature transition for magnetite (about 120 K), the method has not become a standard routine technique. This is partly due to the poor understanding of the behavior of magnetite particles at the low-temperature transition zone. Previous experiments by other researchers have used magnetite powders. In such powders it is always possible to attribute any discrepancy between the results observed and theory to possible existence of magnetostatic interaction effects or existence of elongated particles in samples presumed to contain only equant particles. Such factors need to be eliminated in order to have a better understanding of the low temperature behavior of magnetite particles. Low-temperature magnetic properties of lithographically produced arrays of both interacting and noninteracting cubic magnetite particles as well as those from powder particles have been measured as part of this study. A gradual increase in the amount of saturation isothermal remanent magnetization (SIRM) lost at the Verwey transition Tv with increasing particle size in the pseudo-single-domain size range has been observed. This behavior is consistent with the vortex state domain structure. The grain size dependence of the amount of SIRM lost at Tv is most probably what previous researchers reported as a magnetic memory particle-size-dependent trend. Magnetic memory measured during the cooling and warming process is shown to be a stress-related phenomenon. Such measurements could be useful in assessing the nature of stress in a magnetite sample. URI: http://hdl.handle.net/10311/347 Files in this item: 1
King_JGR_2000.pdf (2.594Mb) -
Abegaz, B.M. (Chemical Society of Ethiopia. http://www.aau.edu.et/faculties/sc/CSE/home.html, NaN, 1996)[more][less]
URI: http://hdl.handle.net/10311/345 Files in this item: 1
progress in the chemistry of.pdf (922.3Kb) -
Ketshajwang, K.K.; Holmback, J.; Yeboah, S.O. (AOCS Press. http://www.springerlink.com/content/120382/, NaN, 1998)[more][less]
Abstract: Seed oils were extracted with n-hexane from three edible Leguminosae seeds: Tylosema esculentum, Xanthocercis zambesiaca, and Bauhinia petersiana, giving yields of 48.2, 17.6, and 20.8% (w/w), respectively. Some physical and chemical parameters were determined to ascertain the general characteristics of the oils. The saponification and iodine values indicated that all three oil samples could be classified among the olive group of oils. This inference was supported by the results of the detailed fatty acid composition of the oils as determined by capillary gas chromatography. The ratio of total unsaturated to total saturated fatty acids in all three oil samples was approximately 70:30, with either oleic or linoleic acid being the dominant fatty acid. These results were in agreement with a proton nuclear magnetic resonance analysis of the fatty acid classes in the seed oils. Thus, the analysis served to justify the use of the three Leguminosae seed oils in food preparations. The work has further indicated that, with their attractive properties, the seed oils from T. esculentum, X. zambesiaca, and B. petersiana are good candidates for further studies to evaluate their future commercial prospects in the Southern African region. URI: http://hdl.handle.net/10311/304 Files in this item: 1
quality and compositional.pdf (1.683Mb) -
Motshegwe, S.M.; Holmback, J.; Yeboah, S.O. (AOCS Press. http://www.springerlink.com/content/0003-021X, NaN, 1998)[more][less]
Abstract: A preliminary investigation of the bulk properties of the oil from the edible mophane caterpillar (phane), Imbrasia belina, showed a significant difference in the iodine values of the oils from mature and young phane. Detailed analysis of the fatty acid composition of the two oil samples was thus carried out by capillary gas chromatography (GC) and complemented with 1H and 13C nuclear magnetic resonance (NMR) studies to investigate the degree of unstauration in the two oil samples. While these studies showed that the oil samples from the mature and young mophane caterpillar were much the same in fatty acid composition, the data revealed a significant divergence from a literature report on phane oil. This earlier report puts the ratio of total saturated to total unsaturated fatty acids at approximately 1:1 (48.2:48.8, in percentages) and estimates the fatty acid composition for the major fatty acids as 16:0 (31.9%), 18:0 (15.2%), 18:1 (20.4%), 18:2 (9.9%), and 18:3 (19%). The data collected from the present work, however, showed the fatty acid composition for total saturated and total unsaturated fatty acids to be 40.5 and 57.0%, respectively. This work estimated the fatty acid composition for the major fatty acids as 16:0 (27.2%), 18:0 (12.3%), 18:1 (16.1%), 18.2 (10.7%), and 18:3 (29.0%). Thus, linolenic acid was the most abundant fatty acid in the phane oil. The GC results of the present analysis were largely corroborated by studies of the composition of fatty acid classes in the phane oil estimated from integrals of 1H and 13C NMR signals. Oils from other edible Lepidoptera larvae are also known to be much richer in unsaturated than saturated fatty acids. URI: http://hdl.handle.net/10311/307 Files in this item: 1
General properties.pdf (1.906Mb) -
Abegaz, B.M.; Ngadjui, B.T.; Bezabih, M.; Mdee, L.K. (International Union of Pure and Applied Chemistry. http://www.iupac.org/publications/pac/, NaN, 1999)[more][less]
Abstract: Marketed plants are an important but a vulnerable group of plants whose investigations as well as conservation should be considered with priority. The chemistry, and in some cases biological activities of novel iso¯avonoids, nor-lignans, anthracene and naphthalene derivatives and poly prenylated ¯avonoids isolated and characterized from Hagenia abyssinica, Salsola somalensis, Hypoxis spp., Taverniera abyssinica, Aloe spp., Bulbine capitata, Rhamnus prinoides and Dorstenia spp. are discussed. URI: http://hdl.handle.net/10311/289 Files in this item: 1
Novel natural products.pdf (4.533Mb) -
Nindi, M.M.; Kgarebe, B.V.; Wolfender, J.L.; Abegaz, B.M. (John Wiley & Sons, Ltd., NaN, 1999)[more][less]
Abstract: Three naphthalenic derivatives, four flavonoids and two of the four anthraquinones previously isolated from the leaves of Rhamnus prinoides were successfully ionised under electrospray ionisation conditions. These compounds were subsequently detected in the leaf extract of the plant using electrospray liquid chromatography–mass spectrometry (LC–ESI–MS). The potential of LC–ESI–MS for screening a leaf extract, with the focus on the suitability of the method for assaying the bitter principle, geshoidin, of this commercially important plant, is presented. URI: http://hdl.handle.net/10311/290 Files in this item: 1
Electrospray Liquid.pdf (1.464Mb) -
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) -
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) -
Goodwin, J.W.; Hughes, R.W.; Kwaambwa, H.M.; Reynolds, P.A. (Elseview Science B.V. www.elsevier.nl/locate/colsurfa, NaN, 2000)[more][less]
Abstract: A series of well characterised cis-polyisoprene polymers have been added to dispersions of PHS coated PMMA particles in dodecane. At a molecular weight of 8000 g mol−1 and above, these systems showed phase separation at low particle volume fractions and above a critical polymer concentration. The rate of separation has been shown to be influenced by the viscosity of the polymer. At high polymer and particle volume fractions long lived metastable phases occurred. Above a critical concentration these were viscoelastic indicating an appreciable change in diffusion dynamics with two relaxation processes present. A significant Bingham yield stress was also observed. The Asakura Oosawa potential was not able to describe the observed rheological properties. At a molecular weight of 1000 g mol−1 no phase separation was observed. At high particle concentrations the yield stress was found to reduce with the addition of polymer. This was due to the polymer acting as a ‘solvent’ and penetrating the stabilising layer on the particles. URI: http://hdl.handle.net/10311/329 Files in this item: 1
Phase separation behaviour.pdf (2.723Mb) -
King, J G; Ranganai, RT (BOSHASTED, NaN, 2000)[more][less]
Abstract: Emissions of vehicles represent a significant contribution to environmental pollution along roads. Pollutants from cars include gases such as (NOx, CO, CO2), solid components such as sort particles from exhaust system, abrasion products from the brakes and engine etc (Leven et al., 1999). Aerosols pollutants can reduce significantly the quality of the environment and seriously affect human health e.g. by contributing to high rates of allergies or diseases of the respiratory system. In this study, samples were collected at various distances from a busy road, Gaborone-Tlokweng road near Game store. Non-magnetic adhesive paper pieces were used as sample collectors. Magnetic properties of the aerosols collected were measured using a highly sensitive magnetometer (AGM-Micromag). Magnetic properties measured include total magnetic moment, hysteresis loops and associated parameters such as coercivity. In general, observed hysteresis loops are typical for magnetite. URI: http://hdl.handle.net/10311/406 Files in this item: 1
King_BOSHASTED_2000.pdf (159.1Kb) -
Mapeo, R.B.M.; Kampunzu, A.B.; Armstrong, R.A. (Geological Society of South Africa. http://sajg.geoscienceworld.org/, June NaN, 2000)[more][less]
Abstract: The Precambrian rocks of northern Botswana comprise poorly exposed igneous complexes, high-grade metamorphic rocks, as well as sedimentary sequences including mainly siliciclastic and carbonate rocks. New U-Pb SHRIMP data are presented for detrital zircons from siliciclastic rocks collected from the Shakawe area in northern Botswana. These data show three main age groups at c. 1020 Ma, 1090 Ma, and 2050 Ma which support contentions for local provenance of the sediments. They also fix the maximum age of the deposition of these siliciclastic rocks at 1020 Ma. The results support field evidence suggesting that the siliciclastic rocks exposed in the Shakawe zone are part of the Ghanzi-Chobe Supergroup. URI: http://hdl.handle.net/10311/371 Files in this item: 1
mapeodoc.pdf (1.611Mb) -
Onibere, E.A.; Morgan, S.; Busang, E.M.; Mpoeleng, D. (Elsevier Science Ltd, www.elsevier.com/locate/intcom, NaN, 2001)[more][less]
Abstract: This paper reports on research carried out to determine whether a localised interface is preferred by users in a multi-cultural and multi-lingual country where a non-local language is nationally used,. We attempted to discover whether local symbols are more acceptable to users as icons and also whether the current phrases used in menus and icon descriptions are clearly understood by the various communities. A survey was conducted nation-wide among computer end-users in Botswana. The results indicate an overwhelming desire from users for a localised interface. However, there appears to be little need for localised icons and no agreement as to which language to use for text-based interfaces. URI: http://hdl.handle.net/10311/887 Files in this item: 1
Mpoeleng_IC_2001.pdf (1.247Mb) -
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) -
King, J.G.; Ranganai, R.T. (Botswana Geoscientists Association, NaN, 2001)[more][less]
Abstract: The Hopkinson effect is the increase of magnetic susceptibility with temperature from near room temperature to near the Curie point. Although this effect has been known for more than a century, it has not been effectively utilised as an analysing tool in palaeo, rock and environmental magnetic studies. This is partly due to the poor understanding of the influence of magnetite (Fe,O.)grain parameters on the Hopkinson effect. In an attempt to study the effects of grain size on the Hopkinson effect, magnetite samples with well-defined grain sizes have been used. it was found that in general, magnetic susceptibility enhancement factor (SEF) obtained by heating the sample in a non-oxidising environment, increase with decreasing grain size. The relation of SEF to grain size is linear when plotted on a log-log scale. This relation has been used to infer grain sizes (hence magnetic domains) for some selected Botswana rocks. The inferred magnetic domains are consistent with independent predictions from hysteresis measurements for the same samples. URI: http://hdl.handle.net/10311/338 Files in this item: 1
King_BJES_2001.pdf (625.5Kb) -
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) -
Matsheka, M.I.; Lastovica, A.J.; Elisha, B.G. (American Society for Microbiology. http://jcm.asm.org/, NaN, 2001)[more][less]
Abstract: A 1.6-kb DNA fragment isolated from a Campylobacter concisus genomic library gave C. concisus-specific restriction fragment length patterns when it was used as a probe in hybridization studies. All of the strains tested, including type strains and clinical isolates, contained a 0.5-kb HindIII fragment that hybridized to the probe. DNA sequencing of the 1.6-kb fragment identified three open reading frames (ORFs). One of the ORFs encodes the carboxy terminus of GyrB, and the translational products of ORF2 and ORF3 showed similarity to hypothetical proteins, previously identified in Campylobacter jejuni. DNA-DNA hybridization studies with a fragment internal to ORF3 showed that this sequence was responsible for the signal observed with the 0.5-kb HindIII fragment. A rapid PCR assay was developed and evaluated. Primers that annealed to the extremities of the 1.6-kb fragment were used to obtain an amplicon of the correct size from both reference and clinical strains of C. concisus. URI: http://hdl.handle.net/10311/306 Files in this item: 1
Molecular identification of.pdf (4.701Mb) -
Majinda, R.R.T; Abegaz, B.M.; Bezabih, M.; Ngadjui, B.T; Wanjala, C.C.W.; Mdee, L.K.; Bojase, G.; Silayo, A.; Masesane, I.; Yeboah, S.O. (IUPAC. http://www.iupac.org/publications/pac/, NaN, 2001)[more][less]
Abstract: Marketed plants are very important items of trade in many parts of the world. The community uses these for a variety of purposes such as foods, cosmetics, flavors, spices, and medicines. It seems that plants that are used for medicinal purposes form the most common category. Four plants used for treatment of microbial infections, viz., Bolusanthus speciosus, Erythrina latissima, Crotalaria podocarpa, and Elephantorrhiza goetzei, were investigated, and these yielded several known and novel structures, some with appreciable antibiotic activity against the test organisms. The activity of some of the isolated plants and the parts of the plant from which these were obtained lend support to their traditional use. Bulbine abyssinica and B. capitata yielded phenylanthraquinones, some of which were shown to possess strong antiplasmodial activity. In addition, these yielded isofuranonaphthoquinones, which were also found to be weakly antiplasmodial and antioxidant. Scilla nervosa yielded several known and novel homoisoflavoinds of the 3-benzylchroman-4-ones and 3-benzylidinechroman- 4-one type, as well as some stilbenoids. The homoisoflavonoids showed strong antitumor activity against various cancer cell lines. Rhus pyroides gave a novel bichalcone, which showed weak antifeedant activity, consistent with the observation by farmers that the plant was avoided by corn cricket. Results from investigated Dorstenia species originating from Cameroon, Ethiopia, and Tanzania yielded styrenes, coumarins, chalcones, and flavonoids. The chalcones and flavonoids showed various levels of prenylation or geranylation, and an observation made so far is that prenylated flavonoids are only found in Dorstenia species of African origin. The only example of a bis-geranylated chalcone is found in Dorstenia. URI: http://hdl.handle.net/10311/308 Files in this item: 1
Recent results from.pdf (4.630Mb) -
Toteng, E.N. (Springer http://www.springerlink.com/index/05CM7XY4DJGUEUQL.pdf, NaN, 2001)[more][less]
Abstract: For the last three and half decades, Botswana has been widely acclaimed to be one of sub-Saharan Africa's longest and most stable liberal democracies, coupled with and sustained by a growing economy. One of the major contradictions, however, within this development scenario, has been the neglect of environmental problems in the country in general, and urban environmental issues in particular. Part of the problem fueling the misconception of environmental issues in Botswana is the state's domination of the country's environmental agenda. This is linked to the power disjunction in decision-making and policy processes between state and nonstate actors over the most appropriate course of action to tackle the problems. Without adopting appropriate analytical frameworks, it is possible that the problem of urban environmental mismanagement in Botswana will persist. This article examines some of the major urban environmental issues in Botswana from neighborhood, citywide, and urban–rural interface perspectives. Further, the elite theory of public policy is used to explain constraints on policy change in the urban environmental management arena in Botswana URI: http://hdl.handle.net/10311/365 Files in this item: 1
Toteng_EM_2001.pdf (933Kb) -
Gwebu, T.D. (Taylor & Francis Ltd, http://www.tandf.co.uk/journals/cepe, NaN, 2002)[more][less]
Abstract: In sub-Saharan Africa, communal land resource utilization and management has reflected changes in sociocultural belief systems, population dynamics, and modes of societal administration and regulation. This paper, based on archival evidence, attempts to substantiate this assumption through an illustrative case study on biomass depletion around large settlements in Botswana. It also suggests that a revisit to certain traditional institutional and sociocultural practices on natural resource management might provide useful insights towards the sustainable utilization of wood resources. URI: http://hdl.handle.net/10311/959 Files in this item: 1
Gwebu_EPE_2002.pdf (597.0Kb) -
Gwebu, T.D. (Kluwer Academic Publishers, http://www.springerlink.com/content/102895/, NaN, 2002)[more][less]
Abstract: Like most African countries, Botswana contributes almost insignificantly to global greenhouse emissions (GHGs). In this context, some have argued that energy policy and legislative measures to regulate emissions in Botswana should not be accorded high priority. This is a misguided view when one considers that each country, no matter how under-industrialized, contributes to the overall global emission problem. Moreover, the least developed countries will have to industrialize in order to meet the increasing economic and social needs of their growing populations. For rapidly growing economies like Botswana, whose annual energy demand is projected to increase by about 4% for the next ten years, the importance of compiling accurate inventories of sources and sinks of GHGs and formulating environmentally-friendly policies can hardly be over- emphasized. The United Nations Framework Convention on Climate Change (UNFCCC) provides the ideal basis for the country-by-country investigations and management of global climatic change; specifically its nature, properties, directionality, characteristics and probable consequences. Botswana was a founding signatory of UNFCCC in 1992 and ratified the Convention in 1994. The country is also involved in regional cooperation efforts, within the Southern African Development Community, to enforce regulatory mechanisms to minimize GHG emissions from the energy sector. There exist certain energy-related institutions, policies, and regulations in the country which could mitigate the impact of GHG emissions on global warming. This paper, based on government and other relevant documentation, critically analyses Botswana’s energy sector policies in as far as they affect climate change. It is clear that much still needs to be done about energy policies in terms of proper formulation, monitoring, co-ordination, energy pricing and the exploration of energy alternatives to mitigate potentially negative impacts on climate change. URI: http://hdl.handle.net/10311/958 Files in this item: 1
Gwebu_GJ_2002.pdf (1.010Mb)
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