Browsing Faculty of Science by Title
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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) -
Cailteux, J.L.H.; Kampunzu, A.B.H.; Batumike, M.J. (Elsevier www.elsevier.com/locate/jafrearsci, NaN, 2005)[more][less]
Abstract: The Neoproterozoic Katangan R.A.T. ("Roches Argilo-Talqueuses") Subgroup is a sedimentary sequence composed of red massive to irregularly bedded terrigenous-dolomitic rocks occurring at the base of the Katangan succession in Congo. Red R.A.T. is rarely exposed in a continuous section because it was affected by a major layer-parallel de´collement during the Lufilian thrusting. However, in a number of thrust sheets, Red R.A.T. is in conformable sedimentary contact with Grey R.A.T which forms the base of the Mines Subgroup. Apart from the colour difference reflecting distinct depositional redox conditions, lithological, petrographical and geochemical features of Red and Grey R.A.T. are similar. A continuous sedimentary transition between these two lithological units is shown by the occurrence of variegated to yellowish R.A.T. The D. Strat. "Dolomies Stratifie´es" formation of the Mines Subgroup conformably overlies the Grey R.A.T. In addition, a transitional gradation between Grey R.A.T. and D. Strat. occurs in most Cu–Co mines in Katanga and is marked by interbedding of Grey R.A.T.-type and D. Strat.-type layers or by a progressive petrographic and lithologic transition from R.A.T. to D. Strat. Thus, there is an unquestionable sedimentary transition between Grey R.A.T. and D. Strat. and between Grey R.A.T. and Red R.A.T. The R.A.T. Subgroup stratigraphically underlies the Mines Subgroup and therefore R.A.T. cannot be comprised of syn-orogenic sediments deposited upon the Kundelungu (formerly ‘‘Upper Kundelungu’’) Group as suggested by Wendorff (2000). As a consequence, the Grey R.A.T. Cu–Co mineralisation definitely is part of the Mines Subgroup Lower Orebody, and does not represent a distinct generation of stratiform Cu–Co sulphide mineralisation younger than the Roan orebodies. URI: http://hdl.handle.net/10311/391 Files in this item: 1
Kampunzu2005Lithostratigraphic.pdf (1.922Mb) -
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) -
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) -
Nijegorodov, N.; Mabbs, R. (Elsevier Science BV; www.elsevier.com/locate/saa, January 15, 2002)[more][less]
Abstract: [Please note that the mathematical symbols have not transposed into this abstact].The luminescent and laser properties of heteroaromatic and aromatic compounds are reviewed and discussed on the basis of all possible mutual arrangements of singlet and triplet states. All heteroaromatic compounds are divided into five classes. It is shown that a heteroaromatic compound can only be an effective laser dye if it belongs to class V (a situation where the Tn_* level lies at higher energy than the S__* 1 level). Moreover, it is shown that the energy interval between the Tn_* and S__* 1 states must be no less than 1000 cmâ 1 since the rate constant of the non-radiative process S__*1 _Tn_*_T__1 is usually 100 times greater than the fluorescence rate constant. The classification is extended to compounds with orbitals of _l,_*, _,__* and _l,__* nature. Pure aromatic compounds, the spectral-luminescent properties of which are solely determined by transitions of _-electrons (_ _ _*), are also divided into five classes, depending on the mutual arrangement of the Sp(1La), S_(1Lb), Tp(3La) and T_(3Bb) states. It is found that only aromatic compounds of classes IV and V can be effective scintillators and laser dyes. It is also shown that the energy interval S_â Sp (for class IV) and T_â Sp (for class V) must be no less than 1000 cmâ 1. To illustrate the classifications for heteroaromatic and aromatic compounds, 12 specifically chosen compounds were studied experimentally and quantum chemically. The quantum yields, _ and decay times, _f of fluorescence in aerated and non-deaerated ethanol or cyclohexane solutions were measured. The oscillator strength, fe, fluorescence rate constant, kf, natural lifetimes, _0 T and intersystem crossing rate constants, kST are calculated. The laser ability of each of the compounds studied is tested. The suggested classification schemes can be extremely useful in the quest for effective scintillators and laser dyes among hypothetical heteroaromatic and aromatic molecules, enabling evaluation of these properties for a particular compound using only quantum chemical simulations. URI: http://hdl.handle.net/10311/136 Files in this item: 2
license.txt (1.998Kb)nijegorodov_sa_2002.pdf (1.811Mb) -
Muxworthy, A.R.; King, J.G.; Odling, N. (AGU and the Geochemical Society. http://www.agu.org/journals/gc/index.shtml, NaN, 2006)[more][less]
Abstract: The magnetic hysteresis properties for well-defined micron-sized magnetite samples produced by electron beam lithography (EBL) are presented. In addition to measuring standard hysteresis parameters, first-order reversal curve (FORC) diagrams are also reported. EBL produces samples that consist of particles with very tightly constrained size distributions, and spatial distributions that govern the degree of intergrain magnetostatic interactions are accurately controlled and known. Thus EBL samples are significantly better characterized compared to powdered samples, which are conventionally used to characterize the size dependency of magnetic hysteresis properties of naturally occurring magnetic minerals. Compared with the hysteresis properties of powdered samples of the same nominal sizes, EBL samples display more multidomain-like (MD) behavior. The influence of magnetostatic interactions fields on hysteresis properties is analyzed. When magnetostatic interactions are effectively in only one direction, the hysteresis properties become more single domain-like, and if the interactions are in more than one direction, hysteresis becomes more MD-like, in agreement with numerical models. URI: http://hdl.handle.net/10311/360 Files in this item: 1
Muxworthy_GGG_2006.pdf (1.589Mb) -
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) -
Kampunzu, A.B.; Tombale, A.R.; Zhaia, M.; Bagai, Z.; Majaule, T.; Modisi, M.P. (Elsevier www.elsevier.com/locate/lithos, NaN, 2003)[more][less]
Abstract: The Neoarchaean Tati granite–greenstone terrane occurs within the southwestern part of the Zimbabwe craton in NE Botswana. It comprises 10 intrusive bodies forming part of three distinct plutonic suites: (1) an earlier TTG suite dominated by tonalites, trondhjemites, Na-granites distributed into high-Al (Group 1) and low-Al (Group 2) TTG sub-suite rocks; (2) a Sanukitoid suite including gabbros and Mg-diorites; and (3) a younger high-K granite suite displaying I-type, calc-alkaline affinities. The Group 1 TTG sub-suite rocks are marked by high Sr/Y values and strongly fractionated chondrite-normalized rare earth element (REE) patterns, with no Eu anomaly. The Group 2 TTG sub-suite displays higher LREE contents, negative Eu anomaly and small to no fractionation of HREE. The primordial mantle-normalized patterns of the Francistown TTGs are marked by negative Nb–Ti anomalies. The geochemical characteristics of the TTG rocks are consistent with features of silicate melts from partial melting of flat subducting slabs for the Group 1 sub-suite and partial melting of arc mafic magmas underplated in the lower crust for the Group 2 sub-suite. The gabbros and high-Mg diorites of the Sanukitoid suite are marked by Mg#>0.5, high Al2O3 (>>16%), low TiO2 ( < 0.6%) and variable enrichment of HFSE and LILE. Their chondrite-normalized REE patterns are flat in gabbros and mildly to substantially fractionated in high-Mg diorites, with minor negative or positive Eu anomalies. The primordial mantle-normalized diagrams display negative Nb–Ti (and Zr in gabbros) anomalies. Variable but high Sr/Y, Sr/Ce, La/Nb, Th/Ta and Cs/La and low Ce/Pb ratios mark the Sanukitoid suite rocks. These geochemical features are consistent with melting of a sub-arc heterogeneously metasomatised mantle wedge source predominantly enriched by earlier TTG melts and fluids from dehydration of a subducting slab. Melting of the mantle wedge is consistent with a steeper subduction system. The late to post-kinematic high-K granite suite includes I-type calc-alkaline rocks generated through crustal partial melting of earlier TTG material. The Neoarchaean tectonic evolution of the Zimbabwe craton is shown to mark a broad continental magmatic arc (and related accretionary thrusts and sedimentary basins) linked to a subduction zone, which operated within the Limpopo– Shashe belt atf2.8–2.65 Ga. The detachment of the subducting slab led to the uprise of a hotter mantle section as the source of heat inducing crustal partial melting of juvenile TTG material to produce the high-K granite suite. URI: http://hdl.handle.net/10311/381 Files in this item: 1
Kampunzu2003Majorandtrace element.pdf (2.863Mb) -
Simon, R.E.; Wright, C.; Kwadiba, M.T.O.; Kgaswane, E.M. (Elsevier Science Ltd. www.elsevier.com/locate/lithos, NaN, 2003)[more][less]
Abstract: Average one-dimensional P and S wavespeed models from the surface to depths of 800 km were derived for the southern African region using travel times and waveforms from earthquakes recorded at stations of the Kaapvaal and South African seismic networks. The Herglotz–Wiechert method combined with ray tracing was used to derive a preliminary P wavespeed model, followed by refinements using phase-weighted stacking and synthetic seismograms to yield the final model. Travel times combined with ray tracing were used to derive the S wavespeed model, which was also refined using phase-weighted stacking and synthetic seismograms. The presence of a high wavespeed upper mantle lid in the S model overlying a low wavespeed zone (LWZ) around 210- to - 345-km depth that is not observed in the P wavespeed model was inferred. The 410-km discontinuity shows similar characteristics to that in other continental regions, but occurs slightly deeper at 420 km. Depletion of iron and/or enrichment in aluminium relative to other regions are the preferred explanation, since the P wavespeeds throughout the transition zone are slightly higher than average. The average S wavespeed structure beneath southern Africa within and below the transition zone is similar to that of the IASP91 model. There is no evidence for discontinuity at 520-km depth. The 660-km discontinuity also appears to be slightly deeper than average (668 km), although the estimated thickness of the transition zone is 248 km, similar to the global average of 241 km. The small size of the 660-km discontinuity for P waves, compared with many other regions, suggests that interpretation of the discontinuity as the transformation of spinel to perovskite and magnesiowu¨ stite may require modification. Alternative explanations include the presence of garnetite-rich material or ilmenite-forming phase transformations above the 660-km discontinuity, and the garnet– perovskite transformation as the discontinuity. URI: http://hdl.handle.net/10311/265 Files in this item: 1
Simon_L71_2003.pdf (2.274Mb) -
De Waele, B.; Kampunzu, A.B.; Mapani, B.S.E.; Tembo, F. (Elsevier www.elsevier.com/locate/jafrearsci, NaN, 2006)[more][less]
Abstract: The Mesoproterozoic Irumide belt is a northeast-trending structural province stretching from central Zambia to the Zambia–Tanzania border and northern Malawi. Mesoproterozoic and Neoproterozoic transcurrent shear zones within reactivated parts of the Palaeoproterozoic Ubendian belt define its northeastern limit. The northwestern margin is defined by the largely undeformed basement lithologies of the Bangweulu block. An intensely folded and sheared zone at the southeastern margin of the Mporokoso Group sedimentary depocentre on the Bangweulu block, interpreted to have developed above a thrust at the basement-cover interface, indicates that far-field effects of the Irumide Orogen also affected the southeastern part of the Bangweulu block sedimentary cover. To the west and southwest, Irumide and basement lithologies were reworked by the Damara–Lufilian–Zambezi Orogen within the Neoproterozoic Zambezi and Lufilian belts. The Choma–Kalomo block, previously regarded as the southwesterly continuation of the Irumide belt, is a distinct Mesoproterozoic province, while a succession of structurally juxtaposed tectonic terranes in eastern Zambia record a deformation event related to the Irumide Orogen. The lithological units identified in the Irumide belt include: (1) limited Neoarchaean rocks emplaced between 2.73 and 2.61 Ga and representing the oldest rocks in the Bangweulu block; (2) ca. 2.05–1.85 Ga volcano-plutonic complexes and gneisses representing the most important components in the Bangweulu block; (3) an extensive quartzite–metapelite succession with minor carbonate forming the Muva Supergroup, and deposited at ca. 1.85 Ga; (4) granitoids emplaced between 1.65 and 1.55 Ga; (5) a minor suite of anorogenic plutons (nepheline syenite and biotite granite) restricted to the far northeastern Irumide belt and emplaced between 1.36 and 1.33 Ga; (6) voluminous syn- to post-kinematic Irumide granitoids emplaced between 1.05 and 0.95 Ga. Crustal shortening and thickening in the Irumide belt are shown by northwestward-directed thrusts and related folds and metamorphic parageneses recording a clockwise medium-pressure/medium-temperature P–T–t path. Metamorphic grades range from greenschist facies in the foreland to the northwest to upper amphibolite facies in the southeast, with local granulites. Peak metamorphism is diachronous across the belt and bracketed between 1.05 in the southeast and 1.02 Ga in the northwest. URI: http://hdl.handle.net/10311/398 Files in this item: 1
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Becker, T.; Schreiber, U.; Kampunzu, A.B.; Armstrong, R. (Elsevier www.elsevier.com/locate/jafrearsci, NaN, 2006)[more][less]
Abstract: Two main Mesoproterozoic provinces occur in southern Namibia: (1) The high-grade Namaqua Metamorphic Complex (NMC) composed of a supracrustal sedimentary succession and interpreted as a passive margin sequence in the west of the Kalahari craton; (2) The Sinclair Group and its northeastern correlatives, composed of two main magmatic and metamorphic units, reflecting northeast-directed subduction, which started before 1.37 Ga and lasted until about 1.1 Ga. These two units were tectonically juxtaposed during the 1.1– 1.03 Ga Namaqua orogenic event. The Kairab–Kumbis Metamorphic Complex comprises metasedimentary and metavolcanic rocks intruded by the 1.37 Ga arc-related Aunis tonalite. The mafic volcanic rocks from this complex have geochemical features of island arc calcalkaline basalts; they were emplaced and metamorphosed along an active margin before 1.37 Ga. The 1.2–1.1 Ga low-grade unmetamorphosed volcanic and immature sedimentary rocks of the Sinclair Group and its northwestern equivalents rest disconformably on the Kairab–Kumbis Complex. They occur in fault-bounded depocenters defining a regional arc-shape structure up to 100 km-wide and with a minimum length of 2000 km. The plate tectonic setting of this arc is best constrained by the composition of volcanic rocks from the 1.2 Ga Barby Formation and coeval granitoids; they comprise high-K calcalkaline rocks suggesting emplacement in an active continental margin setting. The final stage of this continental arc evolution is recorded in the <1.1 Ga tholeiites of the Opdam Formation. High Ti-content and flat REEpatterns in the tholeiites suggests an extensional event, whereas high Th/Ta and La/Nb ratios, low Ce/Pb values and negative anomalies for Nb–Ta suggest a subduction-related setting for the mantle source from which the mafic magmas were derived. Docking of continents led to the slab detachment, allowing interaction between the asthenospheric mantle and the mantle wedge enriched during the subduction process. The magmatic underplating related to this event induced the genesis of large-scale batholitic granitoid bodies in the NMC and a 1.1–1.0 Ga high-grade LP/HT metamorphism, with mineral assemblages indicating an anti-clockwise P–T–t path. URI: http://hdl.handle.net/10311/385 Files in this item: 1
Kampunzu2006RocksofNamibia.pdf (3.444Mb) -
Atlhopheng, J.R.; Ekosse, G. I. E. (Bioline http://www.bioline.org, NaN, 2007)[more][less]
Abstract: A mineralogical investigation of duricrust suites in Letlhakeng valley, and five pans around Jwaneng in Botswana was undertaken in order to know the mineral assemblages and infer on their landscape formation. In Letlhakeng, duricrusts comprised calcretes, silcretes and ferricretes. Calcretes were dominated by the minerals: calcite, quartz and to a lesser extent dolomite. Silcrete mineralogy was dominated by quartz, opal, and some occurrences of palygorskite, microcline and rutile. The intermediate forms of cal-silcretes yielded quartz, muscovite, and kaolinite. Ferricretes occurred on an area of the valley capping, with minerals dominated by goethite and haematite. The indurates are believed to have been formed through groundwater mechanisms. The general lowering of the valley, led to precipitation of the duricrusts. The pans were dominated by calcrete and silcrete only. The calcretes mineralogy was mainly calcite, dolomite and quartz. Illite-montmorillonite and sepiollite were also present. Samples of pan clay floor, other than being dominated by calcite, dolomite and quartz, also had sepiollite ferrian. Pans and valleys are accumulation sites, with polygenetic modes of genesis. The duricrusts have undergone several alterations throughout time. URI: http://hdl.handle.net/10311/679 Files in this item: 1
Atlhopheng_JASEM_2007.pdf (494.4Kb) -
Meck, M.L.; Atlhopheng, J.; Masamba, W.R.L.; Ringrose, S.; Diskin, S. (Bentham Open, http://www.benthamscience.com/open/tomj/index.htm, NaN, 2011)[more][less]
Abstract: This study set out to establish the major minerals at Dorowa and determine which of those are likely to host metals that may leach into surface and groundwater. This study comes after a preliminary assessment of the water quality in the Save River downstream of the Dorowa phosphate mine in Zimbabwe showed an increase in conductivity, iron content, manganese content, nitrates and hardness when compared to those taken before the mining area. X-Ray Diffractometry (XRD) was used to establish the major minerals at Dorowa whilst Inductively Coupled Plasma Mass Spectrometry (ICP- MS) was used to establish the chemistry of the rocks. The results from this study show that the major minerals in the rocks around Dorowa are feldspars, pyroxenes, apatite, magnetite and calcite. The metals hosted by the rocks include Ag, As, Be, Cd, Co, Cu, Pb, Hg, Ni, Sb, Se and Zn. The study concludes that the minerals likely to host metals are calcite and apatite. Metal hosting is higher in apatite minerals than in calcite. Metal hosting by the other minerals observed in the study area is low. URI: http://hdl.handle.net/10311/1109 Files in this item: 1
Atlhopheng_OMJ_2011.pdf (848.6Kb) -
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) -
Mogobe, K.D.; Tshiamo, W.; Bowelo, M. (Elsevier, www.rhmjournal.org.uk, NaN, 2007)[more][less]
Abstract: This paper describes the maternity monitoring system in Botswana, developed in 1998, and the main methods used: maternal death and morbidity reviews at service delivery level, analysis by the National Maternal Mortality Audit Committee of data from the reviews as reported on two forms, perinatal reviews and surveys using process indicators. We carried out a study of these findings to examine whether the system was working well. Surveys using process indicators in 2001 and 2006 were analysed. Other data examined were from 2004–2006 and early 2007. The Maternal Death Notification Form was found to be comprehensive but not all health facilities were submitting them and some gave incomplete information. In 2001, 70% of pregnant women attended antenatal care but access to emergency obstetric care was uneven. In 2006, 28 facilities with maternity services surveyed were providing 24-hour delivery care, but laboratory, theatre and blood supplies were more limited, and only 50% of doctors and 67% of midwives had life-saving skills. Antibiotics were widely available, but there were shortages of magnesium sulphate, diazepam, oxytocics and manual vacuum aspiration kits. Recommendations for improvements have been made, training for skilled attendants is ongoing and a medical school has just opened at the University of Botswana. URI: http://hdl.handle.net/10311/498 Files in this item: 1
DintleMogobe2007Mortality.pdf (944.3Kb) -
Gnonlonfin, G.J.B.; Hell, K.; Fandohan, P.; Siame, A.B. (Elsevier B.V. www.elsevier.com/locate/ijfoodmicro, NaN, 2008)[more][less]
Abstract: The presence of fungi, aflatoxins and fumonisin B1 in cassava and yam chips (during 28 processing and storage) were evaluated during two consecutive seasons in two agroecological zones of Benin (Northern Guinea Savannah, NGS and Sudan Savannah, SS). The Benin samples were assessed for moisture content, fungal infestation and total aflatoxin and fumonisin B1 contamination. During the two seasons, samples collected from the NGS, had moisture contents ranging from 10.0 to 14.7% in cassava chips and from 11.4 to 15.3% in yam chips. In samples from the SS, moisture content ranged from 10.1 to 14.5% and 11.1 to 14.5% in cassava and yam chips, respectively. A. flavus was the predominant fungal species. The maximum cfu/g in cassava and yam chips was 8950 and 6030, respectively. Other fungal species isolated included P. chrysogenum, M. piriformis, Phoma sorghina, F. verticillioides, R. oryzae and Nigrospora oryzae. High performance liquid chromatography analysis of both cassava and yam chips showed no contamination by either aflatoxins or fumonisin B1. URI: http://hdl.handle.net/10311/317 Files in this item: 1
Mycoflora and natural occurrence.pdf (5.959Mb) -
Cao, Y.; Allameh, S.; Sethiaraj, S. (Elsevier, NaN, 2006)[more][less]
Abstract: This paper presents the results of nanoindentation experimental studies of the contact-induced deformation in Au and Ag thin films. The paper examines the effects of film thickness and substrate deformation restraint on the mechanical properties of electron beam (e-beam) deposited Au and Ag films. Following a brief description of film microstructure, surface topography, and contact-induced pile-up deformation, film mechanical properties (hardness and Young’s modulus) were determined using nanoindentation techniques. The indentation size effects (ISE) observed in films with different thicknesses were explained using a mechanism-based strain gradient (MSG) theory. The intrinsic film yield strengths and hardnesses extracted from the MSG theory are shown to exhibit classical Hall–Petch dependence on the inverse square root of the average film grain size. Displacement bursts were also found to occur in Ag films at indentation load levels of 100 N. These were attributed to the initial onset of dislocation slip activity, when the shear stress exceeds the estimated theoretical shear strengths of the materials. URI: http://hdl.handle.net/10311/537 Files in this item: 1
Nanoindentation measurements.pdf (1.173Mb)