Browsing Faculty of Science by Title
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Sathiaraj, T.S. (Elsevier Ltd, NaN, 2008)[more][less]
Abstract: Indium tin oxide (ITO) thin films were prepared by RF sputtering of ceramic ITO target in pure argon atmosphere at a high base pressure of 3 10 4mbar without substrate heating and oxygen admittance. The use of pure argon during deposition resulted in films with high transparency (80–85%) in the visible and IR wavelength region. The films were subsequently annealed in air in the temperature range 100–400 1C. The annealed films show decreased transmittance in the IR region and decreased resistivity. The films were characterized by electron microscopy, spectrophotometry and XRD. The predominant orientation of the films is (2 2 2) instead of (4 0 0). The transmission and reflection spectra in the wavelength range 300–2500 nm are used to study the optical behaviour of the films. The optical transmittance and reflectance spectra of the films were simultaneously simulated with different dielectric function models. The best fit of the spectrophotometric data was obtained using the frequency-dependent damping constant in the Drude model coupled with the Bruggeman effective medium theory for the surface roughness. It has been found that the sputtering power and the chamber residual pressure play a key role in the resulting optical properties. This paper presents the refractive index profile, the structure determined from the XRD and the electrical properties of ITO films. It has been found from the electrical measurement that films sputtered at 200W power and subsequently annealed at 400 1C have a sheet resistance of 80O/& and resistivity of 1.9 10 3Ocm. Description: Some mathematical symbols may not come as they are in the abstract. URI: http://hdl.handle.net/10311/690 Files in this item: 1
Effect of annealing.pdf (1.308Mb) -
Sathiaraj, T.S. (Elsevier Science Ltd. http://www.elsevier.com/locate/mejo, NaN, 2008)[more][less]
Abstract: Indium tin oxide (ITO) thin films were prepared by RF sputtering of ceramic ITO target in pure argon atmosphere at a high base pressure of 3×10−4 mbar without substrate heating and oxygen admittance. The use of pure argon during deposition resulted in films with high transparency (80–85%) in the visible and IR wavelength region. The films were subsequently annealed in air in the temperature range 100–400 °C. The annealed films show decreased transmittance in the IR region and decreased resistivity. The films were characterized by electron microscopy, spectrophotometry and XRD. The predominant orientation of the films is (2 2 2) instead of (4 0 0). The transmission and reflection spectra in the wavelength range 300–2500 nm are used to study the optical behaviour of the films. The optical transmittance and reflectance spectra of the films were simultaneously simulated with different dielectric function models. The best fit of the spectrophotometric data was obtained using the frequency-dependent damping constant in the Drude model coupled with the Bruggeman effective medium theory for the surface roughness. It has been found that the sputtering power and the chamber residual pressure play a key role in the resulting optical properties. This paper presents the refractive index profile, the structure determined from the XRD and the electrical properties of ITO films. It has been found from the electrical measurement that films sputtered at 200 W power and subsequently annealed at 400 °C have a sheet resistance of 80 Ω/□ and resistivity of 1.9×10−3 Ωcm. URI: http://hdl.handle.net/10311/631 Files in this item: 1
Sathiaraj_MJ_2008.pdf (763.9Kb) -
Kumar, J.; Kumar, P.; Suri, N.; Ahmad, M.; Thangaraj, R.; Sathiaraj, T.S. ( NaN, 2008)[more][less]
Abstract: Optical properties of Pb doped ternary Ge-Sb-Te chalcognide films prepared by thermal evaporation have been studied in the visible and near-infrared spectral regions. The straightforward analysis proposed by Swanepoel has been successfully employed and it has allowed us to accurately determine the refractive index and extinction coefficient of the films. The refractive index has been determined from the upper and lower envelopes of the transmission spectra. The absorption coefficient and extinction coefficient have been determined from the transmission spectra in the strong-absorption region. The dispersion of the refractive index is discussed in terms of the Wemple–DiDomenico single oscillator model. URI: http://hdl.handle.net/10311/544 Files in this item: 1
Effect of composition.pdf (950.3Kb) -
Chaturvedi, P.; George, S.; Milinganyo, M.; Tripathi, Y.B. (John Wiley & Sons, Ltd, http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-1573, NaN, 2004)[more][less]
Abstract: In this study, the methanol extract of Momordica charantia fruit extract was administered to diabetic rats to assess the long term effect of the extract on the lipid profile and the oral glucose tolerance test. Treatment for 30 days showed a significant decrease in triglyceride, low density lipoprotein and a significant increase in high density lipoprotein level. A significant effect on oral glucose tolerance was also noted. Chronic administration showed an improvement in the oral glucose tolerance curve. The effect was more pronounced when the test was done in rats fed the extract on the day of the test compared with tests done in rats which were not fed the extract on the same day. URI: http://hdl.handle.net/10311/1017 Files in this item: 1
Chaturvedi_PR_2004.pdf (258.2Kb) -
Moseki, B.; Dintwe, K. (Global Science Books, http://www.globalsciencebooks.info/, NaN, 2011)[more][less]
Abstract: The effects of water stress on the photosynthetic characteristics of two locally-cultivated sorghum cultivars (‘Segaolane’ and ‘Town’) were investigated over a period of weeks. Water stress was imposed on 1-week-old plants by withholding water. Measurements of chlorophyll fluorescence were used to determine changes in the efficiency of light utilization for electron transport, the occurrence of photoinhibition of photosystem II photochemistry on the sorghum cultivars. Drought treatment significantly decreased leaf area in all species, an important factor in drought-induced decreases in photosynthetic productivity. Water-stressed ‘Town’ exhibited a decrease in maximum photochemical efficiency of PSII (estimated from dark-adapted Fν⁄Fм ratio) with increasing period of withholding water. Light-adapted Fν’⁄Fм’ estimated the efficiency of excitation energy transfer to open PSII centres. Water-stressed ‘Town’ displayed a decrease in the efficiency of excitation energy transfer to open PSII reaction centres throughout the entire study period. The quantum yield of PSII electron transport (фPSII), which represents electron flow beyond PSII, decreased markedly in water-stressed ‘Town’ compared with that of water-stressed ‘Segaolane’. These initial findings indicate that ‘Town’ is more prone to photoinhibition than ‘Segaolane’. URI: http://hdl.handle.net/10311/962 Files in this item: 1
Moseki_AJPSB_2011.pdf (96.03Kb) -
Murty, V.R.K. (Elsevier Science Ltd. www.elsevier.com/locate/radphyschem, NaN, 2004)[more][less]
Abstract: The study of interaction of photons with matter finds wide application in areas such as industry, medical radiation dosimetry and radiation shielding. A careful review of these measurements indicates that the studies are exhaustive in respect of pure elements. However, measurements on photon attenuation in alloys are meagre. This is mainly due to the difficulty in procuring targets in suitable form for experimentation. Such studies play a prominent role in selecting alternative shielding materials on the cost-effective basis. URI: http://hdl.handle.net/10311/268 Files in this item: 1
Murty_RPC71_2004.pdf (223.2Kb) -
Chaturvedi, P.; Segale, M. (Academic Journals http://www.academicjournals.org/SRE/index.htm, NaN, 2007)[more][less]
Abstract: Four types of extracts were prepared from Melia azedarach fruits. These were methanol extract and three types of water decoctions; urine treated water decoction (UE), milk treated water decoction (ME) and plain water decoction (WE). Different doses of these four extracts were tried in normal rats to estimate the hypoglycemic activity of these extracts against glucose induced hyperglycemia. Most potent doses of all the extracts were assessed for their effects on lipid peroxidation, toxic effects on liver and reduced glutathione which is considered as first line of defense against free radicals in normal rats after 10 days of oral administration. All the extracts were found to posses hypoglycemic properties. Methanol extract showed toxic effects on the liver as indicated by high activities of Serum glutamate oxaloacetate (SGOT) and serum glutamate pyruvate tranasaminase (SGPT). It also indicated high rate of lipid peroxidation and depleted reduced glutathione levels of plasma. On the other hand three water decoctions showed very low activities of SGOT, SGPT, very low rates of lipid peroxidation and high levels of reduced glutathione. Extract prepared by the Ayurvedic method reduce blood glucose in glucose induced hyperglycemic rats and impart no toxicity. URI: http://hdl.handle.net/10311/181 Files in this item: 2
Effects of different types of water.pdf (836.9Kb)license.txt (1.998Kb) -
Mpoloka, S.W. (Academic Journals. http://www.academicjournals.org/AJB, NaN, 2008)[more][less]
Abstract: Over the past few decades, there has been a depletion of the stratospheric ozone layer due to emissions of halogen-containing compounds of anthropogenic origin. This has resulted in a concomitant increase in solar ultraviolet-B radiation. High levels of UV-B radiation are responsible for multiple biologically harmful effects in both plants and animals. In plants, these effects include DNA damage, which often causes heritable mutations affecting various physiological processes, including the photosynthetic apparatus, protein destruction and signal transduction via UV-B photoreceptors. High UV-B levels introduce a number of different lesions, predominantly cyclobutane pyrimidine dimmers (CPDs) and pyrimidine (6-4) pyrimidinone products [(6-4) PPs] in the genome. These could adversely affect plant growth, development and morphology, especially the productivity of sensitive crop species. This paper reviews the genetic effects of long-term UV-B exposure in plants. URI: http://hdl.handle.net/10311/491 Files in this item: 1
Effects of prolonged.pdf (2.345Mb) -
Siele, M.P.; Mubyana-John, T.; Bonyongo, M.C. (Global Science Books http://www.globalsciencebooks.com/index.php?page=shop.product_details&category_id=1&flypage=shop.flypage&product_id=5&option=com_virtuemart&Itemid=56&vmcchk=1&Itemid=56, NaN, 2008)[more][less]
Abstract: Soil cover influences soil biological and chemical processes in various ways. The effects of soil cover (bare soil without litter, litter cover, Mopane tree canopy and grass cover) on soil respiration and microbial population at four sites in the Mopane woodland of north western Botswana were investigated. Soil respiration rates were measured using an infrared gas analyzer. Nitrifying bacterial populations were quantified by MPN on ammonium and nitrite calcium carbonate media, oligotrophs on 1% nutrient agar, actinomycetes on starch casein agar, bacteriovorous protozoans by MPN on sodium chloride agar baited with Enterobacter, and fungal biomass carbon using buried slides were also determined. Soil respiration in different habitats was significantly influenced by type of cover, diurnal temperature variations and soil moisture. Soils under cover showed significantly higher soil respiration than the bare soils. Autochthonous bacterial populations in the Mopane woodland soils consisted mostly of oligotrophs which varied insignificantly between seasons. Fungi were the most dominant microorganisms in all the Mopane woodland soils, with biomass of 162.05 to 282.14 μg C/g soil in the wet season and 11.84 to 44.16 μg C/g soil in the dry season. Microscopic observation of buried slides revealed that fungi play a vital role in holding soil particles together in these soils. The results showed a strong positive relationship between changes in fungal biomass and fluctuation of soil respiration. However, no clear correlation was observed between the variation of soil respiration and other microbial populations (oligotrophic bacteria, actinomycetes, and nitrifying bacteria). Overall these results indicate that in soils under Mopane tree canopy, fungi contribute significantly to soil structure and soil respiration. Other microbial populations consist mostly of oligotrophs which show minimal seasonal variations. Soil moisture significantly influences seasonal fluctuation in soil respiration. URI: http://hdl.handle.net/10311/292 Files in this item: 1
The Effects of Soil Cover.pdf (6.625Mb) -
Toteng, E.N. (Routledge http://dx.doi.org/10.1080/02508060802475415, NaN, 2008)[more][less]
Abstract: This article examines the adverse effects of a fragmented water management framework and the role of domestic water users on water conservation in Gaborone, the rapidly growing capital city of Botswana. There was a major drought in Botswana in 2004, which recurred in 2007. The drought seriously affected water availability in Gaborone, re-igniting the water conservation debate. Most urban households prior to 2004 did not practise water conservation, except in cases of enforced temporary measures, such as water restrictions and increased water tariffs imposed by the Water Utilities Corporation. From secondary evidence, the situation had not changed much in 2007. URI: http://hdl.handle.net/10311/363 Files in this item: 1
Toteng_WI_2008.pdf (851.6Kb) -
Mazimba, O.; Masesane, I.B.; Majinda, R.R. (Elsevier Science Ltd, http://www.elsevier.com/locate/tetlet, NaN, 2011)[more][less]
Abstract: An efficient total synthesis of flavans from the reactions of salicylaldehyde and acetophenone derivatives is reported. The synthesis involves preparation of chalcones through an aldol reaction followed by reduction of both the double bond and the ketone using NaBH4 and an acetic acid mediated cyclization. Methoxy groups on the aromatic rings did not affect significantly the yields of the procedure. URI: http://hdl.handle.net/10311/1027 Files in this item: 1
Mazimba_TL_2011.pdf (204.0Kb) -
Masale, M. (Elsevier Science Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/622948/description#description, NaN, 2008)[more][less]
Abstract: A calculation is presented on the scattering rates of electrons via the bulk spectrum of longitudinal optical phonons near a current-carrying core of radius R employing the Frohlich interaction Hamiltonian. The electrons are mainly confined near the core by an electric potential and are also under the influence of the current-induced spatially inhomogeneous static azimuthal magnetic field. The external magnetic field lifts the double degeneracy of the non-zero electron's axial wave number (kz ) states, while that of the nonzero azimuthal quantum number (m) states is preserved. In fact, the kz < 0 electron's energy subbands are found to be characterized by minima in their variations with the field. The intrasubband scattering rates show a remarkable behavior in their variations with the field. First, for weak electric potential of the nanosystem, these exhibit a strong, nonetheless inharmonic, oscillatory behavior in their variations with the field. The oscillations are, however, smoothed out as the strength of the electrical potential is increased, commencing at lower values of the field, within the same range of values of the field used. Second, for the same strength of the electric potential, there arise phase variations of the scattering rates in their variations with the field, resulting from the variation in the electron's axial wave number. URI: http://hdl.handle.net/10311/232 Files in this item: 2
license.txt (1.998Kb)Masale_SM_2008.pdf (1.267Mb) -
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) -
Mbaiwa, J.E. (Elsevier http://www.doi:10.1016/j.tourman.2003.11.005, NaN, 2005)[more][less]
Abstract: This paper draws on the dependency paradigm to explain the development of enclave tourism and its socio-economic impacts in the Okavango Delta, Botswana. Using both primary and secondary data source, the study indicates that international tourists, foreign safari companies and investors dominate the tourism industry in the Okavango Delta. The foreign domination and ownership of tourism facilities has led to the repatriation of tourism revenue, domination of management positions by expatriates, lower salaries for citizen workers, and a general failure by tourism to significantly contribute to rural poverty alleviation in the Okavango region. Tourism as a result has a minimal economic impact on rural development mainly because it has weak linkages with the domestic economy, particularly agriculture. Because of its nature, tourism in the Okavango Delta cannot be described as being sustainable from a socio-economic perspective. In order to address problems of enclave tourism development and promote more inclusive and beneficial tourism development in the Okavango, there is need to adopt policies and strategies that will ensure that substantial amounts of tourism revenue are retained in the Okavango and Botswana. These strategies should also ensure that tourism development in the Okavango Delta has strong linkages with the rest of the economy in Botswana. URI: http://hdl.handle.net/10311/429 Files in this item: 1
Mbaiwa_TM_2005.pdf (2.402Mb) -
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) -
Totolo, O.; Chanda, R. (Elsevier Science Ltd, http://www.elsevier.com/wps/find/journaldescription.cws_home/622855/description#description, NaN, 2003)[more][less]
Abstract: The collection of papers in this special edition of the Journal of Arid Environments is a sequel to a Workshop held in Maun, Botswana, in October 2000, on the theme Climate Change, Biodiversity and Multi-species Production Systems in the Kalahari Region. Constituting only about one-third of the workshop papers delivered, this set of articles survived a rigorous peer-review process and are being published as one of the planned outputs of the Maun meeting. Except for the keynote paper by Darkoh which is a review article with a continental purview, the collection is based on research conducted by natural and social scientists within the Southern African Kalahari region either as part of the Southern African Science Initiative (SAFARI 2000) co-ordinated from the University of Virginia in the U.S.A. or of the Kalahari Transect project based at the University of Botswana. URI: http://hdl.handle.net/10311/316 Files in this item: 1
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Ekosse, G.; van den Heever, D.J.; de Jager, L.; Totolo, O. (Elsevier www.elsevier.com/locate/mineng, NaN, 2004)[more][less]
Abstract: This study aimed at chemically and mineralogically characterizing whole particulate air matter (PAM) occurring at the Selebi Phikwe nickel–copper (Ni–Cu) area in Botswana, and postulating its possible environmental implications.Heavy metals concentrations in PAM samples around the Selebi Phikwe Ni–Cu plant were determined by atomic absorption spectrometry and the mineral phases identified by X-ray powder diffraction technique.The particles consisted of quartz, pyrrhotite, chalcopyrite, albite and djurleite.Concentration levels of heavy metals contained in PAM samples could be related to mineral phases present.Quite significantly is the occurrence of djurleite, which has not been found in both the orebody and surrounding soils.Djurleite polymorphs formed from secondary mineralization of chalcocite and the gases H2S and SO2 released from concentration/smelting processes.Possible environmental chemistry of the whole PAM based on its mineralogy at Selebi Phikwe area is discussed. Description: Technical Note URI: http://hdl.handle.net/10311/545 Files in this item: 1
Ekosse2004Environmental Chemistry1.pdf (511.2Kb) -
Gwebu, T.D. (Pergamon, www.elsevier.com/locate/habitatint, NaN, 2003)[more][less]
Abstract: This study investigates the profile, dynamics and dimensions ofenvironm ental problems at Old Naledi, a low income urban neighbourhood in Gaborone, the capital city ofBotsw ana. It is based on documentary and field research. The field research has a participatory component involving meetings, discussions and open- ended interviews with the interested and affected persons. It also involves the administration of a structured survey questionnaire to 171 resident respondents. The main findings ofthe study are that residents have made great efforts in improving the availability of the housing stock. However, in the process they have failed to abide by the stipulated Development Control code and Urban Development Standards. This essentially reflects the increasing non-affordability of land and costs of construction materials to urban low income groups due to evolving state policy in the provisioning ofshelt er. The direct result has been a congested, overcrowded settlement. Because ofthis , and a rapidly increasing population, there has been underservicing and the emergence oflif e-threatening home and neighbourhood environmental problems. URI: http://hdl.handle.net/10311/496 Files in this item: 1
GWEBU2003Environmental Problems.pdf (2.409Mb) -
Shoeb, M.; Jaspars, M.; MacManus, S.M.; Majinda, R.R.T.; Sarker, S.D. (Elsevier Ltd. www.elsevier.com/locate/biochemsyseco, NaN, 2004)[more][less]
Abstract: A study focusing on Centaurea cyanus L. (family: Asteraceae alt. Compositae), otherwise known as "cornflower" or "bachelor's button. The seed is purchased from B & T World Seeds sarl, Pauguignan, 34210 Olonzac, France and the voucher specimen (PHSH0002) kept in the Plant and Soil Science Department, University of Aberdeen, UK for testing. The result shows the occurrence of epoxylignans, berchemol (1) and lariciresinol 4-O-b-d-glucopyranoside (2) in the seeds of C. cyanus. URI: http://hdl.handle.net/10311/300 Files in this item: 1
epoxylignans from the seeds.pdf (1.594Mb) -
Evaluation of methods for the isolation, detection and quantification of cyanobacterial hepatotoxinsMsagati, T.A.M.; Siame, B.A.; Shushu, D.D. (Elsevier Ltd. http://www.elsevier.com/wps/find/journaldescription.cws_home/505509/description#description, NaN, 2006)[more][less]
Abstract: Cyanobacterial hepatotoxins such as microcystins and nodularins have been responsible for the poisoning of both animals and humans who ingest or come into contact with toxic blooms. They are extremely stable in water due to their stable chemical structure and can tolerate radical changes in water chemistry, including pH and salinity. Different methods for the extraction and detection of these compounds have been reported. Extraction methods utilizing both aqueous and organic solvent systems have been reported. The detection methods ranging from immunological or biochemical assays such as enzyme linked immunosorbent assays (ELISA) and enzyme activity assays, to chemicals methods such as high performance liquid chromatography (HPLC) and more sophisticated liquid chromatographyà ¢ mass spectrometry (LC-MS) have been documented as well. We review some important aspects of cyanobacterial hepatotoxins and methods of analysis for these toxins. URI: http://hdl.handle.net/10311/218 Files in this item: 2
license.txt (1.998Kb)