Faculty of Science and Technology
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Item Open Access Surface smoothing of metallic glasses by swift heavy ion irradiation(Elsevier Ltd., 1999) Narayan, Himanshu; Agrawal, H. M.; Kushwaha, R. P. S.; Kanjilal, D.; Sharma, S. K.Self supporting samples of Metglass 2204 (Ti50Be40Zr10) and substrate bound samples of Metglass 2705M (Co69B12Si12Fe4Mo2Ni1) have been irradiated with 260 MeV 107Ag and 130 MeV 28Si ions, respectively at liquid nitrogen temperature. The surfaces have been examined by Scanning Electron Microscopy prior to and after irradiation. It is found that the surfaces have been smoothened after irradiation in both cases. The heights of the ÔhillsÕ have been decreased and the ÔvalleysÕ have been ®lled, without any detectable mass loss. The observed surface smoothing has been explained on the basis of shear ¯ow mechanism within the framework of the viscoelastic model. Ó 1999 Elsevier Science B.V. All rights reserved.Item Open Access Afm, stm and sts studies of grain boundaries And ion-beam induced defects in MGB2(Nova Science Publishers, 2001-06) Narayan, Himanshu; Narlikar, A. V.; Herrmann, P. S. P.; Samanta, S. B.; Gupta, Anurag; Kanjilal, D.; Muranaka, T.; Akimitsu, J.; Vijayaraghavan, R.Item Open Access Er1−yCayBa2Cu3−x(Fe, Zn)xO7−δ superconductors: a study of microstructure and resistive transitions in a dc magnetic field(IOP Publishing Ltd, 2001-10-15) Chaudhuri, Sukalpa; Gupta, Anurag; Ganesan, V.; Das, I.; Kumar, Anil; Zaleski, A. J; Narayan, Himanshu; Narlikar, A. V.We report an investigation of structure by x-ray diffraction, microstructure by atomic force microscopy (AFM) and broadening of resistive transitions in high dc magnetic fields (0–20 kOe) in Er1−yCayBa2Cu3−x(Fe, Zn)xO7−δ (y = 0.1, 0.2; and 0 x 0.20) ceramic superconductors. The XRD shows that the presence of Ca does not alter the known effect of Fe/Zn substitution on the structure of the pure (y = 0) system. Substitution of both Fe and Zn leads to a decrease in the grain size and micro-hardness. Interesting results were obtained on the influence of various dopants on the broadening of resistive transitions in dc magnetic fields, in general: (1) an increase in Ca content suppresses it; (2) Zn substitution has no effect; and (3) Fe substitution enhances it. We show that these results can be interpreted in terms of a thermally activated flux motion (TAFM), and the effect of various dopants on the properties like pinning barrier and anisotropy.Item Open Access Study of magnetization and pinning mechanisms in MgB2 thin film superconductors: effect of heavy ion irradiation(IOP Publishing Ltd, 2003) Narayan, Himanshu; Gupta, Anurag; Astill, D.; Kanjilal, D.; Ferdeghini, C.; Paranthaman, M.; Narlikar, A. V.We report magnetization studies on MgB2 superconducting thin films in a temperature range 4.2–40 K and magnetic field range 0–6 T. Thin films prepared by both pulsed laser deposition (PLD) and electron beam evaporation (EBE) methods were investigated. In addition, both films were studied before and after heavy ion irradiation by 200 MeV Ag ions with a dose of 1011 ions cm−2. Variation of sweep rates during the measurement of the magnetization loop reveals the presence of flux creep in both films. The PLD film, after irradiation, shows a severe degradation of Tc, critical current densities (Jc) in low fields and irreversibility line (B∗(T )). In contrast, the EBE film shows a slight enhancement in Tc, and nearly no change in Jc(B) and the position of irreversibility line after irradiation. For both pristine films, the obtained volume pinning forces Fp versus reduced field b = B/B∗ shows a good scaling for T 10 K, which matches well with the theoretical curve based on the flux line shear (FLS) pinning model. These and other results can be interpreted in terms of grain boundaries in MgB2 films acting as FLS channels.Item Open Access Moisture Absorption, Dimensional Stability Properties and Applications of Composites made from Thermosetting Resins, Reinforced with Sandstone, Diorite, and Corn Stalk.(National University of Lesotho, 2011-05) Osiki, I.O; Dr. Thamae, T.Moisture absorption and dimensional stability of materials is one major concern in any engineering design, as well as in any environment. This is because moisture absorption and poor dimensional stabilities in any material is capable of leading to the degradation and ultimate failure of such a material. The purpose of this research however, was to study the moisture absorption as well as dimensional stability properties of composites made from thermosetting polymers, reinforced with diorite, sandstone, and cornstalk. Other objectives of the research were to determine possible applications of the different composite materials as well as determine which of the thermosetting polymer resins would be most applicable as matrix material. Moisture absorption was carried out using the long term immersion procedure based on the ASTM D 570 - 98 standard. From the results of moisture absorption, the corn stalk-polyester composite was found to absorb more moisture than the other synthesized composite. The diorite-polyester composite absorbed the least moisture and results indicate that moisture decreases with increasing amount of the diorite filler added. The dimensional stability tests indicate that the sandstone-polyester composite is the most dimensionally stable of all the composite materials made in this research, and comparism of this composite with the water based acrylic resinsandstone composite indicates that the polyester composite is the preferable choice of polymer resin as matrix material for the production of composites. This conclusion was based on facts obtained from dimensional stability tests that indicate that the polyester resin is more stable dimensionally when filled with sandstone. Finally, designs were made from the various composites and this include table tops made from polyester-diorite composites, wall tiles made from polyester-sandstone composite, artifacts made from polyester-cornstalk composite, and wall tiles were also made using the water-based acrylic resin. A cost analysis was also carried out and although cornstalk was estimated as possible material for production of cost effective composites but its undesirable properties such as high moisture intake , made the sandstone a preferable choice of filler material for production of cost effective materials.Item Open Access Synthesis and characteristics of Phthalocyanines(National University of Lesotho, 2011-05) Ts'enoli, Sidwell; Dr. Sekota, M;The phthalocyanine compounds K2[(CN)2FePc], K2[(CN)2CoPc], FePc(Py)2 and CoPc(Py)2 were successfully synthesized and characterized by UV-Visible and IR spectrometry. This was done for application of these compounds as electrode modifiers and as chemical sensors. These coordination compounds were synthesized by the synthesis of the metal-free phthalocyanines followed by the introduction of the axial ligands. The characteristic UV-Visible and IR spectral bands were observed for the four complexes. Therefore it can be concluded that the complexes were successfully synthesized.Item Metadata only Antimicrobial activity of the cyclic peptides, Cyclo(D-Phe-4I-Pro) and Cyclo(L-Phe-4I-Pro).(2013) Qhola, P. J.; Milne, J.Item Metadata only Software Support for Creating Digital Health Training Materials in the Field(University of Cape Town, 2013) Molapo, M.; Marsden, G.In this paper, we present the design, implementation, and deployment of a tool developed to help rural health trainers to create digital training content for low-literate Community Health Workers (CHWs) in Lesotho; the digital content being mobile videos created from combining images, voice-over, and/or video clips. Our results show that when health professionals who are based in rural areas were empowered by the tool to create their own content, they were able to supplement nationally and globally produced health training materials with more locally relevant content that addresses unique information needs within their communities. We discuss other lessons learned from an eight-months deployment of this tool in Lesotho, and conclude with recommendations on how a similar project can be implemented in other developing regions.Item Metadata only Laboratory assessment of insecticidal properties of Tagetes minuta crude extracts against Brevicoryne brassicae on cabbage(Journal of Entomology and Nematology, 2013) Phoofolo, M. W.; Mabaleha, S.; Mekbib, Sissay BekeleThe cabbage aphid, Brevicoryne brassicae is one of the most serious insect pests of cabbage in Lesotho. Chemical insecticides for efficient control of this pest are often unaffordable for resource-poor farmers. As a first step in a search for effective pest management techniques that can be affordable and easily available to these farmers, the aphicidal activities of Tagetes minuta crude extracts were evaluated against the cabbage aphid. A comparison was made on lethal and sub-lethal effects of T. minuta crude extracts from acetone, methanol, water and a mixture of acetone/methanol/water (7:7:1, v:v). The solvent system that produced the most toxic extract was the mixture, followed by methanol and water, whereas acetone produced the least toxic extract. The sub-lethal effect on cabbage aphid fecundity was well described by linear regression equations that showed significant reduction in fecundity as the concentration of crude extracts increased. The extract from the mixture solvent system had the strongest effect on fecundity.Item Open Access Microbial and Physicochemical Characterization of Maize and Wheat Flour from a Milling Company, Lesotho(FoodHACCP.com Publishing, 2013) Ntuli, V.; Mekbib, Sissay Bekele; Asita, A. O.; Molebatsi, Ntseliseng; Makotoko, Makotoko; Chatanga, PeterMaize meal flour and wheat flour are the most widely consumed cereals in Lesotho. The present study was undertaken to investigate the physicochemical and microbiological quality of special, super and extra super brands of maize meal flour; cake, white wheat and whole brown wheat brands of wheat flour produced by a mill company in Maseru, Lesotho. Three samples of each flour were collected on each of five sampling trips during January to May 2012, making a total of 90 samples, and were analysed physico-chemically for ash, fat, protein, moisture content and pH. Microbiologically, total plate count, total coliforms, Bacillus cereus, Salmonella spp, E. coli, yeasts and moulds were also determined. A series of biochemical tests were done to characterize the isolated micro-flora. Moisture content (9.89±0.76% to 13.31±0.64%) and pH (5.83±0.06 to 6.40±0.12) of the flours were within recommended legal limits. However, fat content (33% (n=90)) in maize samples exceeded the maximum recommended limit. The fat content (2.00±0.08% to 5.29±0.10%) of all maize meal brands was significantly higher (P<0.05) than that of wheat flour (0.90±0.03% to 1.87±0.02%). Protein content in maize meal was significantly lower than that of wheat flour, ranging from 7.01±0.91% to 9.64±0.09%. Ash content for the samples ranged from 0.29-1.21%. Statistically, bacterial counts in the different brands of flours showed significant differences (p < 0.05). In a more qualitative assessment, microbes of the genera Escherichia, Klebsiella, Aerobacter, Enterobacter, Salmonella, Bacillus, Aspergillus, Penicillium, Fusarium, Candida, Saccharomyces and Rhodotorula were identified in the flours. Pathogens (Bacillus cereus and Salmonella spp) and indicator organisms (coliforms and E. coli) were above World Food Programm (WFP) recommended limits. This study highlighted the need for stringent cleaning and sanitation regimes to be fully implemented in such companies for consumer safety and public health protection.Item Metadata only Growth of graphene underlayers by chemical vapor deposition(AIP Publishing, 2013) Fabiane, M.; Khamlich, S.; Bello, A.We present a simple and very convincing approach to visualizing that subsequent layers of graphene grow between the existing monolayer graphene and the copper catalyst in chemical vapor deposition (CVD). Graphene samples were grown by CVD and then transferred onto glass substrates by the bubbling method in two ways, either direct-transfer (DT) to yield poly (methyl methacrylate) (PMMA)/graphene/glass or (2) inverted transfer (IT) to yield graphene/PMMA/glass. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to reveal surface features for both the DT and IT samples. The results from FE-SEM and AFM topographic analyses of the surfaces revealed the underlayer growth of subsequent layers. The subsequent layers in the IT samples are visualized as 3D structures, where the smaller graphene layers lie above the larger layers stacked in a concentric manner. The results support the formation of the so-called �inverted wedding cake�stacking in multilayer graphene growth.Item Metadata only Symmetry classification and invariant solutions of the variable coefficient BBM equation(Elsevier, 2013) Molati, M.; Khalique, C. M.We perform Lie symmetry classification of a time-variable coefficient BBM equation, which arises in the modeling of long waves of small amplitude in �1 � 1� dimensions. The direct method of group classification is employed to specify the forms of these time-dependent coefficients. Some exact solutions are derived.Item Metadata only Thermal Expansion in Zinc Oxide Nanomaterials(Nanoscience and Nanotechnology Research, 2013) Singh, M.; Singh, Madan.Thermal expansion of rock salt and wurtize phases of Zinc Oxide nanomaterials has been studied using various relationships between volume thermal expansivity and temperature. The numerical values of volume thermal expansion coefficient for rs-ZnO and w-ZnOnanomaterials have been calculated in low and high temperature ranges. It is observed that in low temperature range i.e. upto room temperature, volume thermal expansion coefficient increases with slow rate with temperature for both the phases of Zinc Oxide while in high temperature range, thermal expansion coefficient increases with high rate with increase in temperature in the case of rs-ZnO and with slow rate in the case of w-ZnO. The available experimental predictions that demonstrates the validity of the work.Item Metadata only Lie Group Analysis of a Forced KdV Equation(Hindawi Publishing Corporation, 2013) Molati, M.; Khalique, C. M.Item Metadata only Qualitative Assessment of Livestock Faeces and Sewage for Antibiotic Resistant Strains of E. coli in Roma, Lesotho(Greener Journals, 2013) Mekbib, Sissay Bekele; Marole, T. A.; Asita, A. O.Sewage water (SW) and fresh livestock faeces: Chicken (ChNF), Sheep (SF), and Cattle (CF) were taken randomly from the farm of the National University of Lesotho aseptically during the 2012 academic year. Twenty ml of sewage water or 20 grams of fresh animal faeces was dissolved in 80 ml of sterilized Ringer�s solution and serially diluted. A 0.1 ml of sample suspension at 10-4 dilution was spread plated on Nutrient Agar (NA) and Eosine Methyl Blue (EMB) and plates were incubated for 24-48h at 24 and 37�C, respectively. A disc diffusion method was used to test the reaction of selected strains of Enterobacteriaceae to nine antibiotics. In total, 24 strains under Enterobacteriaceae were isolated from the respective sources and the number of each that were Escherichia coli, as confirmed by the biochemical tests were: SW (7 and 3); ChNF (5 and 3); SF (8 and 6) and CF (4 and 2). Thirteen E. coli strains fermented lactose and were Catalase positive, while only one E. coli strain from SW was non-lactose fermenter and Catalase negative. The lethal potencies, as number of isolates sensitive to the 9 antibiotics, ranked as: Colistin = Amikacin (24/24) > Kanamycin (23/24) > Chloramphenicol (22/24) > Cefotaxime (21/24) > Sulphafurazole (7/24) > Methicillin (1/24) > Penicillin G = Rifampicin (0/24). Sensitivity of the E. coli strains ranked as follows, Colistin = Amikacin = Kanamycin (14/14) > Chloramphenicol (13/14) > Cefotaxime (12/14) > Sulphafurazole (6/14) > Methicillin (1/14) > Penicillin G = Rifampicin (0/14). This result showed that the development of antibiotic resistant E. coli strains, which can pass through food chain to humans and other organisms if stringent control measures are not taken. Strict quarantine procedures have to be applied to control such potential health risks.Item Metadata only Graphene: Synthesis, Transfer, and Characterization for Dye-Sensitized Solar Cells Applications(ACS Publications, 2013) Dodoo-Ahrin, D.; Fabiane, M.; Bello, A.Large area graphene films with varying growth time thicknesses were synthesized by chemical vapor deposition (CVD) on copper foil and transferred to other substrates for characterization and photovoltaic applications. Scanning tunneling microscopy, Raman spectroscopy, and imaging show films with high crystallinity, low defect density, I2D/IG ratio of 0.52?2.26, and the presence of continuous graphene sheets with optical transparency of 75.7%?96.8%. The use of CVD graphene sheets as counter electrode in dye-sensitized solar cells was explored. The short circuit current density (Jsc), the open circuit current (Voc), the fill factor (FF), and the overall conversion efficiency under AM 1.5, 100 mW cm?2 illumination are 12.7 mA/cm2 57.5% and 3.8%, respectively.Item Metadata only Teacher knowledge of error analysis in differential calculus(Pythagoras, 2014) Moru, E. K.; Nchejane, J.; Qhobela, M. et.al.The study investigated teacher knowledge of error analysis in differential calculus. Two teachers were the sample of the study: one a subject specialist and the other a mathematics education specialist. Questionnaires and interviews were used for data collection. The findings of the study reflect that the teachers' knowledge of error analysis was characterised by the following assertions, which are backed up with some evidence: (1) teachers identified the errors correctly, (2) the generalised error identification resulted in opaque analysis, (3) some of the identified errors were not interpreted from multiple perspectives, (4) teachers' evaluation of errors was either local or global and (5) in remedying errors accuracy and efficiency were emphasised more than conceptual understanding. The implications of the findings of the study for teaching include engaging in error analysis continuously as this is one way of improving knowledge for teaching.Item Metadata only Direct approach to a group classification problem: Fisher equation with time-dependent coefficients(World Scientific Publishing, 2016) Molati, M.; Khalique, C. M.We perform Lie symmetry analysis of a time-variable coefficient Fisher equation which models reaction–diffusion–convection phenomena in biological, chemical and physical systems. These time-dependent coefficients (model parameters or arbitrary elements) are specified via the direct integration of the classifying relations.Item Metadata only An efficient linear numerical scheme for the Stefan problem, the porous medium equation and nonlinear cross-diffusion systems(SPEKTRUM STU Publishing, 2017-12-29) Molati, M.; Murakawa, H.This paper deals with nonlinear diffusion problems which include the Stefan problem, the porous medium equation and cross-diffusion systems. We provide a linear scheme for these nonlinear diffusion problems. The proposed numerical scheme has many advantages, namely, it is very easy-to-implement, the ensuing linear algebraic systems are symmetric, it requires low computational cost, the accuracy is comparable to that of the well-studied nonlinear schemes, the computation is much faster than the nonlinear schemes to obtain the same level of accuracy. In this paper, numerical experiments are carried out to demonstrate efficiency of the proposed scheme.Item Open Access Simultaneous determination of Nitrate, nitrite and Phosphate in environmental samples by high performance liquid Chromatography with UV detection(South African Chemical Institute, 2018-06-15) Moshoeshoe, Mohau N; Obuseng, VeronicaAn HPLC method using an UV detector was developed for the simultaneous determination of nitrites, nitrates and phosphates in environmental samples. Chromatographic separation was achieved isocratically on a Phenomenex Synergi Polar-RP LC column using acetonitrile and acidified water (pH 2.7) at 60:40 v/v as mobile phase. Baseline resolution of all the three analytes was achieved within 3 min. The developed method was applied to water samples obtained from the wastewater treatment plant in Gaborone, Botswana. The use of HPLC technique in this study demonstrated its ability to carry out a simultaneous determination of NO 2 – , NO 3 – and PO 4 3– in water samples. The treatment plant was found to be functioning within expectations, removing 97.6 % NO 2 – , 88.0 % NO 3 – and 90.9 % PO 4 3– from the received wastewater. Results of the developed method were comparable with those of the traditional ion chromatography method, showing accuracy values between 95.22 % and 98.04 %. The precision of the method for the determination of all analytes was determined by RSD values, all of which were lower than 5 %. The method is of low cost, fast, has an easy procedure and avoids the use of many reagents – some of which may be hazardous.