Browsing Faculty of Science by Title
-
Mbaiwa, J. E.; Ngwenya, B.N.; Kgathi, D.L. (Blackwell http://www.wiley.com/10.1111/j.1467-9493.2008.00332.x, NaN, 2008)[more][less]
Abstract: This paper reviews how state policy and regulatory instruments, including protected area alienations and concessions, have altered or denied the access to land and natural livelihood resources of the indigenous Basarwa and minority subsistence-oriented communities in the Okavango Delta (OD) in Botswana. Drawing on field research and guided by a sustainable rural livelihoods framework, the paper provides an overview of key institutional interventions – in particular the setting up of the Moremi Game Reserve, Wildlife Conservation Policy, Tourism Policy, Agricultural Development Policy and the erection of veterinary fences – that have served to privilege a foreign-owned and dominated commercialized wildlife and nature tourism sector and the export-oriented beef industry in the OD. The officially sanctioned barriers to customary and usufructory rights and access, and the non-recognition of historically embedded traditional land uses have decimated already marginalized resource-based subsistence livelihoods, and precipitated intergroup conflicts over preferential rights and access to resources and opportunities, notably wildlife, non-timber veld products, agriculture and community-based tourism schemes. Such outcomes, moreover, will have consequences for the longer-term sustainability of the OD both as a socioeconomic resource base and as a natural ecosystem. URI: http://hdl.handle.net/10311/483 Files in this item: 1
Mbaiwa_SJTG__2008.pdf (966.6Kb) -
Alemaw, B.F.; Chaoka, T.R. (Pergamon www.elsevier.com/locate/pce, NaN, 2003)[more][less]
Abstract: A distributed GIS-based hydrological model is developed using GIS and computational hydrology techniques. The model is based on water balance consideration of the surface and subsurface processes. The surface water balance processes include precipitation infiltration, overland runoff, evapo-transpiration and canopy surface interception losses on daily time steps; The subsurface process considers soil moisture accounting on a monthly basis. The model was used to estimate generated runoff from matrix of specific geo-referenced grids representing Southern Africa. All regional and seasonal dispensation of water balances have been based on standard GIS formats for storage, spatial display and interpretation of results. Considering the 1961–1990 climatic period, we have mapped the regional variation of the mean annual soil moisture (SM), actual evapo-transpiration (AET), and generated runoff (ROF) across Southern Africa or known as the SADC region. The model estimates the mean SM of the region to be about 148 mm/year. There is a wide spatial range in the distribution of SM over the region due to the fact that the absolute soil moisture is dependent on the water retention properties of the soils considered across the region. The model prediction of the mean annual AET in the region reaches a maximum of 1500 mm, with mean 420 mm. The mean annual generated runoff from the land catchment in the region is about 151 mm/year although there is a significant inter-regional variation among the SADC countries, which is a function of the variation in the vegetation cover, soil and climate variation. Lower runoff regimes are dominant in arid areas in Botswana, Namibia and south-western part of the Republic of South Africa. Higher runoff regimes are the Northern and Western Tanzania, along the east coastal portions of Mozambique, central Mozambique, western Zambia and Malawi. URI: http://hdl.handle.net/10311/494 Files in this item: 1
ALEMAW2003CONTINENTAL SCALE.pdf (623.4Kb) -
Alemaw, B.F.; Chaoka, T.R. (Pergamon www.elsevier.com/locate/pce, NaN, 2003)[more][less]
Abstract: A distributed GIS-based hydrological model is developed using GIS and computational hydrology techniques. The model is based on water balance consideration of the surface and subsurface processes. The surface water balance processes include precipitation infiltration, overland runoff, evapo-transpiration and canopy surface interception losses on daily time steps; The subsurface process considers soil moisture accounting on a monthly basis. The model was used to estimate generated runoff from matrix of specific geo-referenced grids representing Southern Africa. All regional and seasonal dispensation of water balances have been based on standard GIS formats for storage, spatial display and interpretation of results. Considering the 1961–1990 climatic period, we have mapped the regional variation of the mean annual soil moisture (SM), actual evapo-transpiration (AET), and generated runoff (ROF) across Southern Africa or known as the SADC region. The model estimates the mean SM of the region to be about 148 mm/year. There is a wide spatial range in the distribution of SM over the region due to the fact that the absolute soil moisture is dependent on the water retention properties of the soils considered across the region. The model prediction of the mean annual AET in the region reaches a maximum of 1500 mm, with mean 420 mm. The mean annual generated runoff from the land catchment in the region is about 151 mm/year although there is a significant inter-regional variation among the SADC countries, which is a function of the variation in the vegetation cover, soil and climate variation. Lower runoff regimes are dominant in arid areas in Botswana, Namibia and south-western part of the Republic of South Africa. Higher runoff regimes are the Northern and Western Tanzania, along the east coastal portions of Mozambique, central Mozambique, western Zambia and Malawi. URI: http://hdl.handle.net/10311/492 Files in this item: 1
ALEMAW2003CONTINENTAL SCALE.pdf (623.4Kb) -
Huntsman-Mapila, P.; Kampunzu, A.B.; Ringrose, S.; Vink, B. (Elsevier www.elsevier.com/locate/sedgeo, NaN, 2005)[more][less]
Abstract: The siliciclastic sediments of the Okavango inland Delta of northwest Botswana have a modal composition of quartz arenites and result from a complex history, including transport by river and deposition in a nascent rift basin located in a desert environment with input of aeolian sands. The geochemical composition of sediments from the Okavango Delta was determined in order to constrain the role of weathering at the source and the composition of the source rocks. The chemical analyses and the interelement ratios show a broad compositional range usually encompassing the PAAS composition. The chemical index of alteration (CIA) values and the A–CN–K diagram define an evolution trend which can be interpreted using a mixing model involving a strongly weathered component which corresponds to the sedimentary fraction transported by the Okavango River and a relatively immature component which corresponds to the aeolian sand component of the Okavango sediments. Field geological data supported by geochemical ratios involving elements with affinity for mafic–ultramafic and felsic rocks such as Th/Cr, Th/Sc, La/Sc, La/Co and Eu/Eu* support a source area including mafic–ultramafic and felsic rocks, with or without intermediate rocks. The relationships between certain elements (Cr–Ni, Na2O–Al2O3, K2O–Al2O3) refine the interpretation by pointing to the existence of at least three source rock end-members, including a felsic rock source and pyroxene-rich and olivine-rich mafic–ultramafic source rocks. Proterozoic granitoid–gabbro and related volcanic and ortho-metamorphic rock complexes exposed in NW Botswana and adjacent Angola and Namibia are the source rocks of the sediment component which was mixed with aeolian sand and interacted with a variable proportion of diagenetic carbonates to produce the Okavango sediments. URI: http://hdl.handle.net/10311/382 Files in this item: 1
Kampunzu2005OkavangoDeltasediments.pdf (1.941Mb) -
Mbaiwa, J.E.; Sakuze, L. K. (Taylor and Francis http://dx.doi.org/10.1080/14766820902829551, NaN, 2009)[more][less]
Abstract: This paper uses the livelihoods framework to analyse how cultural tourism can diversify livelihoods at XaiXai village in the Okavango Delta, Botswana. Both primary and secondary data sources were used in this study. Primary data sources included household and key informant’s interviews conducted at XaiXai village and Gcwihaba Caves. Secondary data included both published and unpublished materials on cultural tourism, XaiXai village and Gcwihaba Caves. Results indicate that the San(Basarwa) of XaiXai’s traditional life of hunting and gathering has become a cultural tourism product in the Okavango Delta. Gcwihaba Caves’ geological formation particularly the stalagmites, stalactites and channels also attract tourists that visit the Okavango Delta. The caves also have a cultural history in that they were used as a hiding place by the Basarwa in times of wars, rainy season and cold winters. As such, the cultural values of the San of XaiXai and Gcwihaba Caves are cultural tourism products that can diversify livelihoods at XaiXai village. Therefore, policies and strategies that address cultural tourism and rural livelihoods in tourism destination areas need to be developed. The Gcwihaba Caves and Xaixai Village case study demonstrates that cultural tourism can be a tool for rural livelihoods diversification in tourism destination areas of developing countries. URI: http://hdl.handle.net/10311/482 Files in this item: 1
Mbaiwa_JTCC_2009.pdf (899.2Kb) -
Meck, M.; Atlhopheng, J.; Masamba, W.R.L. (Elsevier http://www.linkinghub.elsevier.com/retrieve/pii/S1464343X09000491, NaN, 2009)[more][less]
Abstract: Alkaline rocks (phosphate deposits in particular) of igneous origin are currently being mined in Zimbabwe. Exploitation of these deposits, which are associated with metals and non-metals, provides a potential for changing the river water quality in the surrounding areas by increasing metal and phosphates levels in the water, thereby endangering the beneficial use of the river. The aim and objectives of this paper are to enumerate the current impacts associated with mining alkaline rocks on Save River water quality in Zimbabwe using the Dorowa mine as a case study. Though there are several impacts associated with the mining of alkaline rocks, this paper deals only with impacts on water quality. A preliminary assessment of the water quality in the Save River downstream of the Dorowa phosphate mine showed an increase in conductivity, iron content, manganese content, nitrates and hardness when compared to those taken before mining activity began. However, there was no notable increase in phosphate and metals except for Fe and Mn. A plausible explanation for the low phosphate values in the water is that the phosphates are precipitating and settling as sediments. Phosphate is known to effectively remove metals from the surface water through the formation of metal–phosphate minerals. Thus, various pollutants may be adsorbed into sediments accumulated on the bottom of the river. These sediments may accumulate pollutants over long periods and act as new pollutant sources to the overlying water when phosphate desorbs from sediments due to changes in water conditions. Therefore, the sediments can act as a source of water pollution in the future URI: http://hdl.handle.net/10311/409 Files in this item: 1
Meck_JAES_2009.pdf (495.8Kb) -
Masale, M. (Elsevier Science Ltd. www.elsevier.com/locate/physc, August 15, 2002)[more][less]
Abstract: The azimuthal surface nucleation field of an infinitely long type II superconducting cylindrical filament is calculated from the linearized Ginzburg-Landau equation for the order parameter. A current is thought to be passed along the axis of the filament which induces a magnetic field in the azimuthal direction. On increasing the current, the field increases to a value whereby a phase transition from the superconducting to the normal state occurs. The magnetic field lines are parallel to the surface of the cylindrical filament so that the required critical field is Hc3; the parallel surface nucleation field of a type II superconductor. The systems considered are a solid cylinder; free-standing and in a metallic matrix; and a very thin-walled hollow cylinder. The full numerical analysis is carried out only for a solid cylinder. In the case of a thin-walled cylindrical shell, the quantitative description of the superconducting- normal phase is given in terms of the limiting form of the temperature for small fields. URI: http://hdl.handle.net/10311/196 Files in this item: 2
license.txt (1.998Kb) -
Ahmad, J.; Bothata-Nareetsile, F.; Becker, C.A.L. (NRC Research Press, http://www.nrcresearchpress.com/loi/cjc, NaN, 2003)[more][less]
Abstract: Nine pairs of corresponding [CoI(CNR)3(PR3 ′ )2]X, [CoII(CNR)3(PR3 ′ )2]X2 complexes — where X = ClO4, BF4; CNR = CNCMe3, CNCHMe2, CNC6H11, CNCH2Ph; PR3′ = PPh3, P(C6H4Me-p)3, P(C6H4OMe-p)3 — have been studied using cyclic voltammetry in CH3CN solutions. All cycles are reversible, and E1/2 for the Co(I) complexes, initially oxidized, are within experimental error identical to E1/2 values for the corresponding Co(II) complexes, initially reduced. E1/2 values are strongly dependent on the triarylphosphine ligand, decreasing in the order PPh3 > > P(C6H4Me-p)3 > P(C6H4OMe-p)3, and weakly dependent on the alkylisocyanide ligand, decreasing in the order CNCH2Ph > CNCMe3 > CNC6H11 ≥ CNCHMe2. Solution ν(-N C) IR patterns reveal that the [CoI(CNR)3(PR3′)2]X complexes do not have regular trigonal bipyramidal coordination, their structure being determined by the particular CNR ligand, while the [CoII(CNR)3(PR3′)2]X2 complexes, specifically in CF3CH2OH, appear to have regular trigonal bipyramidal coordination. Description: Signs on the abstract may be different to the original document URI: http://hdl.handle.net/10311/1034 Files in this item: 1
Ahmad_CJC_2003.pdf (782.1Kb) -
Dikinya, O.; Hinz, C.; Aylmore, G. (Elsevier http://www.linkinghub.elsevier.com/retrieve/pii/S0016706108001365, NaN, 2008)[more][less]
Abstract: The dynamics of the process of self-filtration in soil columns have been evaluated for two soils with different structural cohesion (Balkuling agricultural soil and a mining residue) by carrying out experiments focusing on microscopic particle behaviour during filtration. Soil column experiments were set up to simultaneously measure changes in hydraulic gradients (ΔH/ΔL) along the columns and outflow particle sizes and concentrations during pressure leaching with solutions of 100, 10 and 1 mmol/L NaCl and deionised water. The lowest ionic strength has resulted in more reduced hydraulic conductivity and relatively more release of colloids associated with hydrodynamic shear and dispersion. Steady increases in hydraulic gradient (ΔH/ΔL) and corresponding decreases in relative saturated hydraulic conductivity (K/Ko) with time were observed for both soils and follow similar trends at all column depths. The most severe increases in ΔH/ΔL and decreases in K/Ko always occurred near the inlet to the columns and the decline gradually decreased along the column. The decrease in K/Ko and increase in ΔH/ΔL were clearly influenced by the size as well as the concentration of migrating particles in the porous medium. The finer mobile particles in the mining residue were clearly more readily self-filtered at the lower concentration than the larger Balkuling soil particles producing more rapid increases in ΔH/ΔL and decreases in K/Ko. This was attributable to more effective self-filtration and more pore clogging probably due to increased development of the diffuse double layer, swelling and dispersion within the soil matrix at these concentrations. URI: http://hdl.handle.net/10311/488 Files in this item: 1
Dikinya_Geoderma_2008.pdf (1.429Mb) -
Daka, P.S.; Obuseng, V.C.; Torto, N.; Huntsman-Mapila, P. (Water SA Pretoria; Water Research Commission; http://www.wrc.org.za/, October NaN, 2006)[more][less]
Abstract: Deltamethrin concentrations were determined in 35 sediment samples collected from three different habitats: channel, lagoon and pool sites from Xakanaxa in the Okavango Delta, NW Botswana. The samples were Soxhlet-extracted in acetone to extract deltamethrin residues and subsequently cleaned-up with silica gel 60. The final determination was carried out with a gas chromatograph equipped with an electron capture detector (GC-ECD). The sample work-up and determination gave deltamethrin recoveries of 54 to 97%, and detection limits of 0.004 mg/kg dw. The concentration of deltamethrin residues in the sediment samples collected from the three sprayed areas in the Okavango delta ranged between 0.013 and 0.291 mg/kg dw, with the highest concentrations observed in samples obtained from the pool sites. Analysis of samples for organic matter content showed percentage total organic carbon (% TOC) ranging between 0.19% and 8.21%, with samples collected from the pool having the highest total organic carbon. The concentrations of deltamethrin residues and the % TOC in sediment samples showed a similar trend with the highest levels recorded in the pool samples. These data confirmed that a simple method based on GC-ECD, after Soxhlet extraction, was robust enough to enable quantification of deltamethrin in the sediments, because comparable results were obtained with a more sophisticated system consisting of a GC coupled to a mass spectrometer with a time of flight (TOF) analyser. URI: http://hdl.handle.net/10311/140 Files in this item: 2
dakaetal.pdf (463.1Kb)license.txt (1.998Kb) -
Bernard, T.; Moetapele, N. (Elsevier http://www.doi:10.1016/j.jaridenv.2005.02.001, NaN, 2005)[more][less]
Abstract: For at least 200 years, Gomoti River people and their neighbours lived interactively with the Okavango flood pulse system, travelling widely in dugout canoes, practicing flood recession agriculture, fishing, hunting, and collecting wild foods. Today they are wetlanders without wetlands. A major outflow channel of the eastern Okavango Delta in the 1930s, the Gomoti River rarely flows these days. This paper explores the Gomoti’s demise, through the lenses first of science and second of Gomoti basin residents. Models developed over the past 20 years attribute the Gomoti’s drying to a complex set of bio-hydrologic processes and feedback loops that begin with sedimentation and conclude with channel switching, peat fires, and purging of toxic salts. Such models essentially omit the long history of human habitation and ecological interaction with the delta. Local people, on the other hand, tell of deliberate and systematic management of channels and floodplains, and they argue this management kept the river healthy and flowing. The picture is confounded by colonial era interventions and by Botswana government policies partitioning the Gomoti and restricting access to its headwaters. We conclude with a model combining meso-scale scientific explanation with micro-scale indigenous constructions as a context for new thinking about Okavango Delta resource management. URI: http://hdl.handle.net/10311/467 Files in this item: 1
Bernard_JAE_2005.pdf (2.556Mb) -
Mpoloka, S.W.; Kgotlele, T.; Wally, A. (Academic Journals, www.academicjournals.org, April 17, 2008)[more][less]
Abstract: Allele frequencies for nine short tandem repeat (STR) loci from the AmpFlSTR® Profiler Plus PCR Amplification Kit were determined in five subpopulations across Botswana and tested for suitability for use in individual identification. DNA was extracted from whole blood samples collected from 150 unrelated individuals. Targeted regions of DNA (vWA, FGA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D18S51, D21S11 and the sex determining locus Amelogenin) were amplified using multiplexed PCR. The alleles showed a high degree of polymorphism, with heterozygosity above 67%, indicating that there is no significant inbreeding within the subpopulations. Matching probability was below 0.2 hence power of discrimination was high, indicating that the alleles from the five subpopulations can be used in human identifications. The present study is the first reported attempt at determining allele frequencies of subpopulations in Botswana and could possibly be used in developing a national DNA database. URI: http://hdl.handle.net/10311/1010 Files in this item: 1
mpoloka ajb paper.pdf (292.5Kb) -
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) -
Ngadjui, B.; Dongo, E.; Abegaz, B.; Fotso, S.; Tamboue, H. (Elsevier Science Ltd. www.elsevier.com/locate/phytochem, NaN, 2002)[more][less]
Abstract: Three prenylated flavonoids, dinklagins A, B and C identified, respectively, as ( )-6-(3,3-dimethylallyl)-7-hydroxy-6000, 6000-dimethylchromeno-( 40,30,2000,3000)-flavanone, (+)-5,40,500x-trihydroxy-600,600-dimethylchromano-(7,6,200,300)-flavone and (+)6-(2x-hydroxy- 3-methyl-3-butenyl)-5,7,40-trihydroxyflavone were isolated from the twigs of Dorstenia dinklagei together with the known 6-prenylapigenin, 4-hydroxylonchocarpin, stipulin and 5,40-dihydroxy-600,600-dimethylchromano-(7,6,200,300)-flavone. Their structures were determined on the basis of spectral data and by comparison with data reported in the literature and with authentic specimens for known compounds. URI: http://hdl.handle.net/10311/262 Files in this item: 2
license.txt (1.998Kb) -
Ngameni, B.; Ngadjui, B.; Folefoc, G.; Watchueng, J.; Abegaz, B. (Elsevier Ltd; www.elsevier.com/locate/phytochem, NaN, 2003)[more][less]
Abstract: The twigs of Dorstenia barteri var. subtriangularis yielded three diprenylated chalcones: ( )-3-(3,3-dimethylallyl)-50-(2-hydroxy-3- methylbut-3-enyl)-4,20,40-trihydroxychalcone, (+)-3-(3,3-dimethylallyl)-40,50-[2000-(1-hydroxy-1-methylethyl)-dihydrofurano]-4,20- dihydroxychalcone and 3,4-(600,600-dimethyldihydropyrano)-40,50-[2000,-(1-hydroxy-1-methylethyl)-dihydrofurano]-20-hydroxychalcone for which the names bartericins A, B and C, respectively, are proposed. Stipulin, b-sitosterol and its 3-b-D-glucopyranosyl derivative were also isolated. The structures of these secondary metabolites were determined on the basis of spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC. The structural relationship of bartericins B and C was further established by the chemical cyclization of one to the other. URI: http://hdl.handle.net/10311/258 Files in this item: 2
Diprenylated chalcones and other.pdf (3.479Mb)license.txt (1.998Kb) -
Ngadjui, B.T.; Abegaz, B.M.; Keumedjio, F.; Folefoc, G.N.; Kapchec, G.W.F. (Elsevier Science Ltd. www.elsevier.com/locate/phytochem, NaN, 2002)[more][less]
Abstract: Three clerodane diterpenoids, crotozambefurans A, B and C were isolated from the stem bark of Croton zambesicus together with the known clerodane crotocorylifuran and two trachylobanes: 7b-acetoxytrachyloban-18-oic acid and trachyloban-7b, 18-diol. Betulinol, lupeol, sitosterol and its 3b-glucopyranosyl derivative were also obtained. The structures of crotozambefurans A, B and C were determined, respectively, as: 15,16-epoxy-1,3,13(16),14-clerodatetraen-20,12-olide-18,19-dioic acid dimethylester, 15,16-epoxy- 1,3,13(16),14-clerodatetraen-18,19,20-trioic acid trimethylester and 15,16-epoxy-3,13(16),14-clerodatrien-19,1a:20,12-diolide-18-oic acid methylester, using spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HSQC, HMBC and TOCSY. URI: http://hdl.handle.net/10311/251 Files in this item: 2
Diterpenoids from the stem bark.pdf (2.493Mb)license.txt (1.998Kb) -
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)