Research Articles

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https://hdl.handle.net/20.500.14155/199

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Antimicrobial activity of the cyclic peptides, Cyclo(D-Phe-4I-Pro) and Cyclo(L-Phe-4I-Pro).
(2013) Qhola, P. J.; Milne, J.
Antimicrobial wound healing properties of indigenous medicinal plants of Lesotho and the pharmacist's role in minor wound care
(2021) Hlokoane, O.K.; Sello, M.
Lesotho has a rich supply of indigenous medicinal plant resources. More than a dozen Lesotho medicinal plants have been used to treat minor wound infections among Basotho for over 100 years. The aim is to provide scientifi validation of their antimicrobial activities against microorganisms relevant to the skin. The anti-infective activities of plants are thought to be due to the presence of active phytochemicals in parts of the plants, especially phenolic compounds, anthraquinones, glycosides, and alkaloids. Although there is limited research that establishes the structure-activity relationship of those phytochemicals, there are reports that attributed the phytochemical constituents with the antimicrobial effcts through a variety of mechanisms ranging from inhibition of cytoplasmic membrane function, inhibition of energy metabolism to inhibition of bacterial nucleic acid synthesis. The role of the pharmacist is to provide medical information on these compounds to promote the safe use of herbal products and in combination with conventional medicines.
Approximate Model for a Merge Configuration of Multiservers With Finite Capacity Intermediate Buffers
(International Journal of Applied Mathematics, 2013) Nikolov, A. V.
We consider a queueing network consisting of multiservers in parallel and connected to a merger queue. All servers have an infinite capacity buffers. The configuration is decomposed into two subsystems: merging multi-servers and merger server and then analyzed in isolation. All times are assumed to be exponentially distributed. First we set and solve the equations for the aggregated merger queue, then express the occupancy probabilities of the original queue through the probabilities of the aggregated one, which reduces significantly the number of equations describing the behavior of the network. Using the fore-mentioned result, we derive expressions for the occupancy probabilities and other parameters of the merging queue.
Bile acids as specific faecal pollution indicators in water and sediments
(European Scientific Journal, 2013-04) Obuseng, Veronica; Moshoeshoe, Mohau; Nareetsile, Florence
Microbiological indicators such as Escherichia coli (E. coli) have been extensively applied to monitor sewage contamination in waters and sediments. However, it has been accomplished by many researchers that microorganism indicators of faecal pollution in aquatic environments have limited applicability, owing to their lack of specificity and variable life span induced by environmental factors such as sunlight and chlorination. This review highlights the use of chemical indicators for faecal or sewage pollution monitoring. It highlights that the differences in bile acid distributions in animal faeces could be utilized to differentiate inputs in an environment. Furthermore, the high resistance to degradation by some of the bile acids would make them better suited for long standing pollution compared to coprostanol, as it is more readily degraded. Bile acid data could be used in conjunction with other available evidence, be it ethnographic or as part of a multi-biomarker approach, employing 5 ฀-stanols and bacterial indicators, such as C. perfringens, to distinguish amongst the different environmental inputs.
Chaos-based Encryption Keys and Neural Key-store for Cloudhosted Data Confidentiality
(Technological University Dublin, 2017-09) Mosola, N.N.; Dlamini, M.T.; Blackledge, J.M.; Eloff, J.H.P.; Venter, H.S.
Cloud computing brings flexible and cost effective services. However, security concerns plague the cloud. Data confidentiality is one of the concerns inhibiting the adoption of cloud computing. This concern stems from various cyberattacks directed towards gaining unauthorised access to cloud-bound or cloud-hosted data. This paper proposes a client-end encryption and key management system to curb attacks that targets compromising the confidentiality of cloud-hosted data. The proposed system uses chaotic atmospheric noise to generate a fitness function. The fitness function generates random numbers which create encryption keys. The strength of the encryption keys is derived from the chaotic and random nature of the atmospheric noise. The keys are then used for encrypting cloud-bound data using Advanced Encryption Standard (AES-128, 192 and 256), Data Encryption Standard (DES), 3-DES, and our novel cryptosystem named Cryptor, before it can be sent to the cloud. However, encryption bears no significance if the key management is flawed. To address the inherent key management problem, the solution uses a neural network to learn patterns of an encryption key. Once learnt, the key is then discard to thwart possible key attacks. The key is reconstructed by the neural network for decryption purposes.
Chemical adsorption of NiO nanostructures on nickel foam-graphene for supercapacitor applications
(J. Mater Sci (2013), 2013) Bello, A.; Fabiane, M.; Dodoo-Arhin, D. et al
Few-layer graphene was synthesized on a nickel foam template by chemical vapor deposition. The resulting three-dimensional (3D) graphene was loaded with nickel oxide nanostructures using the successive ionic layer adsorption and reaction technique. The composites were characterized and investigated as electrode material for supercapacitors. Raman spectroscopy measurements on the sample revealed that the 3D graphene consisted of mostly few layers, while X-ray diffractometry and scanning electron microscopy revealed the presence of nickel oxide. The electrochemical properties were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and potentiostatic charge�discharge in aqueous KOH electrolyte. The novelty of this study is the use of the 3D porous cell structure of the nickel foam which allows for the growth of highly conductive graphene and subsequently provides support for uniform adsorption of the NiO onto the graphene. The NF-G/NiO electrode material showed excellent properties as a pseudocapacitive device with a high-specific capacitance value of 783 F g-1 at a scan rate of 2 mV s-1. The device also exhibited excellent cyclestability, with 84 % retention of the initial capacitance after 1000 cycles. The results demonstrate that composites madeusing 3D graphene are versatile and show considerable promise as electrode materials for supercapacitor applications.
Clastogenic and Cytotoxic Effects of Four Pesticides Used to Control Insect Pests of Stored Products on Root Meristems of Allium cepa
(Environment and Natural Resources Research, 2013) Asita, A. O.; Mokhobo, M. M
While the use of pesticides of stored product has increased productivity in agriculture, there is concern about their use because some are mutagens and/or carcinogens, harm non-target organisms or cause pest resistance. In this study Grain Treat (GT) (Mercaptothion, 10 g kg-1, Permethrin 1.5 g kg-1); QuickPhos (QP) (Aluminium Phosphide, 560 g kg-1); Nuvan Profi (NP) (Dichlorvos, 124 g kg-1) and Eriocephalus punctulatus plant smoke condensate (EPSC) were evaluated for cytotoxicity and the induction of genotoxicity in the onion (Allium cepa) test. Onion seeds were germinated and exposed to pesticides (mg ml-1), GT (12.5, 25, 50); QP (0.75, 1.5, 3.0); NP (0.064, 0.128, 0.256); EPSC (0.0025, 0.0049, 0.0098) for 24 hours. For each concentration, three root tips were transferred to three microscope slides, stained with aceto-carmine, covered with cover slip, squashed and observed microscopically. The cytotoxicity and genotoxicity induced by each pesticide concentration was compared with the value for the concomitant negative control using t-test. Only QP (3.0 mg mL-1) and NP (0.256 mg mL-1) significantly depressed the MI, i.e. cytotoxic (P < 0.05). Genotoxicity was determined by examining, 100 anaphase and telophase cells on each of three slides per concentration for chromosome aberration (CA). The three concentrations of each pesticide induced CAs (P < 0.05) in the following general order of frequency; stickiness > multipolarity > c-mitosis > anaphase and telophase bridges > chromosome Largards. The induction of sticky chromosomes indicated that the pesticides caused abnormal DNA condensation, abnormal chromosome coiling and inactivated the spindles. Because abnormalities of the cell division process results from the genotoxic effects of environmental chemicals, the four pesticides have the potential to cause aneuploidy in exposed organisms and adverse human health and environmental effects.
Control of Penicillium digitatum on Citrus Fruit Using Two Plant Extracts and Study of Their Mode of Action
(Springer, 2007-05-07) Mekbib, Sissay Bekele; Regnier, Thierry J. C.; Korsten, Lise
Extracts from two plants from Ethiopia, Withania somnifera and Acacia seyal, were evaluated for their potential as natural biopesticides and to study their mode of action. Methanolic extracts of these plants were tested in vivo on citrus fruit for their efficacy to control Penicillium digitatum when applied on wounded or unwounded fruit surfaces. Relative to the control, 70% and 75% of wound – inoculated fruit did not develop decay symptoms for up to 21 days of storage at 25◦C and >85% r.h. An increase in cell wall-bound phenolics was evident in wounded fruit treated with plant extracts and inoculated with a spore suspension of P. digitatum. Scanning electron microscopy revealed deposition of crystalline plant material sticking to the pathogen and around the wound site. The application of the plant extracts increased the epiphytic background total microbial population but decreased diversity. KEY WORDS: Citrus fruit; postharvest diseases; natural compounds; plant phenolics; host resistance.
Designing Pattern & Performance Analysis of Rectangular Microstrip Patch Antenna using IE3D
(International Journal of Advance Research in Science and Engineering, 2013) Ahirwar, K.; Singh, S. K.; Chauhan, R. et al
In the recent years the development in communication systems has received considerable attention from the research community and this results the development of low cost, minimal weight, low profile antennas that are capable of maintaining high performance over a wide spectrum of frequencies. This technological trend has focused much effort into the design of a Microstrip patch antenna. In this Paper two designs have been considered, results of these two designs have been compared with each other by using IE3D an electromagnetic simulation package by Zeland Software Inc. and design parameters are calculated using MATLAB software. We compared the results of the design1 and design 2 with this we will suggest the optimum configuration of antenna with maximum radiated efficiency that can be used in practice.
A detailed investigation of surface modification in metallic glasses subjected to 130 MeV 28Si ion irradiation
(2002-05) Narayan, Himanshu; Samanta, S. B.; Agrawal, H. M.; Kushwaha, R. P. S.; Gupta, Anurag; Sharma, S. K.; Narlikar, A.V.; Kanjilal, D.
Surface modification induced in four metallic glasses by4.64 MeV/u 28Si ion irradiation has been investigated in detail using optical microscopy, SEM and STM. Results obtained in two separate runs have been presented here. The effects of ion fluence (/) and tilt angle (h) on surface modification have been studied both qualitativelyand quantitatively. It has been found that for Se values smaller than that for track formation, swift heavyion irradiation leads to smoothing of the irradiated surfaces. The smoothing is evident from decreasing mean roughness Rq and reduction in height of the hills and filling up of the valleys in the SEM and STM pictures. The observations have been explained on the basis of the theoryof shear flow within the framework of the viscoelastic model.
A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition
(AIP Publishing, 2016-01-07) Fabiane, M.; Madito, M. J.; Bello, A.; Oliphant, C. J.; Dangbegnon, J. K.; Jordaan, W. A.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Manyala, N.
A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.
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.
The ecology and plant functional composition of the afromontane palustrine wetlands in Lesotho
(National University of Lesotho, 2020-02) Chatanga, P; Seleteng-Kose, L.
The classification and description of wetland vegetation is important for biodiversity conservation and water resource management as it provides an understanding of the wetland vegetation-environment relationships and information to interpret spatial variation in plant communities. This study characterises the Afromontane palustrine wetlands of Lesotho in terms of plant communities, plant functional types and plant functional composition. Relationships of plant communities and functional traits were also explored. Vegetation, environmental and plant functional trait data were collected using the Braun-Blanquet method and standard methods. The data were analysed mainly by means of clustering, ordination and diversity analysis techniques. Twenty-two communities were produced by the classification of the Afromontane wetland vegetation and seven plant functional types, as well as seven functional communities were obtained from the classification. The wetland plant communities are diverse in terms of species richness. The ordination revealed that the wetland vegetation is mainly influenced by altitude, longitude, slope, soil parent material, landscape, inundation, peat, potassium content, soil texture, total organic carbon, nitrogen, sulphur, electrical conductivity, calcium, soil depth, wetness, magnesium, aspect and latitude. Plant functional traits and functional composition of the communities were found to be broadly influenced by altitude, slope, longitude, soil parent material, landscape and inundation, and more finely by edaphic factors that include electrical conductivity, calcium, sodium, magnesium, nitrogen, organic matter, total organic carbon, clay percentage, pH, sand percentage and potassium. Regarding species composition and diversity, plant communities in the Highlands were more diverse and were distinctively different from those in the Lowlands. Although a few wetlands, particularly in the Highlands are still in their near-pristine condition, many wetlands in the country are showing severe signs of degradation. While some communities are either restricted to the Highlands or Lowlands, others exhibit a wide ecological amplitude and occur in both regions. The study further highlights the possibility of alterations in plant functional traits, types and functional composition in the face of environmental changes, including climate change. The diversity of most of the wetlands, coupled with their restricted habitat and distribution at high altitudes and their role in supplying ecosystem services that include water resources, highlights the high conservation value associated with these wetlands, particularly in the face of climate change and loss of biodiversity.
Efficacy and mode of action of yeast antagonists for control of Penicillium digitatum in oranges
(Brazilian Phytopathological Society, 2011-08) Mekbib, Sissay Bekele; Thierry, J. C.; Regnier; Korsten, Lise
Three yeast antagonists (two strains of Cryptococcus laurentii and one of Candida sake) from orange trees reduced incidence of green mold by 80 to 95% when tested in wounded orange fruits inoculated with Penicillium digitatum and incubated at 7ºC for 30 days. The yeasts inhibited conidial germination of the pathogen, but did not kill the spores. Effectiveness of the three yeasts as antagonists was associated in part with their ability to rapidly colonize wound sites, despite low nutrient availability. Observations suggested that production of extracellular matrix by the yeasts may have facilitated rapid wound colonization. Germination of P. digitatum conidia was significantly inhibited when the pathogen and antagonists were in direct physical contact in a
Efficacy of Cellulose Degrading Microbial Strains on the Decomposition of Sewage Water Microalgae for the Production of Biogas
(International Journal of Sciences: Basic and Applied Research (IJSBAR), 2014-12) Mekbib, Sissay Bekele; Ayele, Adebe Seyoum; Mosotho, George J.; Tebello, Samosamo
Sewage water microalgae are potential sources of feed stock for the production of biofuel. In this study, six treatment combinations of microbial strains (C, N1 and N2) in single and combined treatments were used in a 5L plastic container as anaerobic digester. The use of sewage water microalgae alone was used as a negative control; and a separate application of effective microorganisms (EM) were used for comparison. A volume of 3L sewage water suspension containing 300g of microalgae biomass were used in all plastic containers as a feedstock. All treatment applications including the control showed some activity of pressure development in each bag per treatment per cycle except the combined treatment of strain (C, N1, N2). Significant volume of biogas production (4-5L/300g)) and pressure development (517.80 and 544.35 Nm-2 was observed in the first cycle when using cellulose degrading microorganism (C) alone and the combined treatment with nitrogen fixing strain (N1), respectively. High efficacy of shortening the retention time was observed while using strain C alone and combined treatment of C+N1 compared to other treatments including the control. Overall, strain C exhibited an increase of the final gas volume by 148.6% utilizing 60% of the microalgae biomass compared to the control. These results highlight the importance of the tested strains on efficiency of converting these algae to biofuel. However, further investigation of strain efficiency in a pilot scale application, outside the laboratory is recommended.
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.
Evaluation of Ethiopian plant extracts, Acacia seyal and Withania somnifera, to control green mould and ensure quality maintenance of citrus (Citrus sinensis L.)
(EDP Sciences, 2009) Mekbib, Sissay Bekele; Regnier; Thierry, J. C.; Korsten, Lise; Sivakumar, Dharini
Green mould, Penicillium digitatum (Pers.: Fr.) Sacc., causes economically important postharvest disease in citrus. Materials and methods. Ethiopian plant extracts of Acacia seyal (Del. Var. Seyal) and Withania somnifera (L.) Dual were used to test the control of green mould in wound-inoculated fruit, stored for 21 d at 7 °C and at > 85% RH. The chemical compositions of the two extracts were determined using high-performance chromatography. Thereafter, freshly harvested (naturally infected) fruit were subjected to different postharvest treatments and stored for 50 d to investigate the effects of the two plant extracts on fruit quality parameters. Treatments included (pre-wax + leaf extracts), (wax + leaf extracts incorporated into wax, Citrosol A®), (leaf extract alone), (fruit washed in chlorinated water at 5.25%), (untreated fruit) and (commercially treated fruit). Results. Extracts of A. seyal and W. somnifera reduced the incidence of green mould by 56.1% and 50%, respectively, in wound-inoculated fruit. A. seyal extract contained a high concentration of gallic acid (60.3 mg·mL–1) whilst W. somnifera contained low concentrations of caffeic acid (8.7 mg·mL–1), salicylic acid (6.3 mg·mL–1) and 3,4 dihydroxy benzoic acid (3.8 mg·mL–1). Green mould was absent in naturally infected fruit subjected to (pre-wax + leaf extracts), (wax mixed with leaf extracts) and (leaf extracts) treatments. (Pre-wax + leaf extracts) and (wax mixed with leaf extract) treatments significantly reduced weight loss; retained firmness and colour; and they maintained eating qualities and a maturity index (SSC/TA) similar to commercial treatment. Conclusion. Both extracts of A. seyal and W. somnifera showed potential to be used as an alternative in combined applications with wax application under low temperature storage to replace synthetic fungicides, to ultimately control green mould and retain overall fruit quality.
Exact solution of a mathematical model for human muscular motion
(Elsevier, 2024-09-29) Molati, Motlatsi
An ordinary differential equation (ODE) which models human muscular movement is considered. A functional form of the model parameter is specified through the Lie symmetry approach, yielding a different expression from the one derived in the previous study (Kosugi et al., 2019). The Lie point symmetries corresponding to the model parameter are employed for derivation of exact solution.
Exact solutions of nonlinear diffusion-convection-reaction equation: A Lie symmetry analysis approach
(Elsevier, 2019) Molati, M.; Murakawa, H.
We derive some exact solutions of a nonlinear diffusion-convection-reaction equation which models biological, chemical and physical phenomena. The Lie symmetry classification approach is employed to specify the model parameters and then the symmetries of resulting submodels are utilized for construction of exact solutions.
Fast and complete degradation of Congo red under visible light with Er3+ and Nd3+ ions doped TiO2 nanocomposites
(PAGEPress, 2012) Narayan, Himanshu; Alemu, Hailemichael; Alotsi, Ntjamang Daniel; Macheli, Lebohang; Thakurdesai, Madhavi; Jaybhaye, Sandesh; Singh, Arvind
We report fast and complete destruction of the dye Congo red (CR) under visible light in the presence of Nd3+ and Er3+ doped TiO2 nanocomposites (NCs). TiO2 NCs with general composition TiO2[R2O3]x, {x=0.1, 0.2; R≡ Nd, Er} and particle size 12-16 nm were synthesized through co-precipitation/hydrolysis (CPH). A set of similar composites was also prepared through solid state reaction (SSR) route, which produced 31- 47 nm particles. After characterization, visible light photocatalytic activity of all the samples was recorded for the degradation of CR. NCs with molar concentration x=0.2 of both doping types produced close to 100% degradation in 180 min. The apparent rate constant (kobs) was found to be 2.91×10–2 min–1 and 2.36×10–2 min–1, for these Nd3+ and Er3+ doped NCs, respectively. The other NCs with x=0.1, also showed significant degradation of CR, but the samples prepared through SSR performed worse. The excellent degradation obtained with the NCs may be attributed to their small particle size. Moreover, the doping of Nd3+ and Er3+ ions further supported the photocatalysis through formation of intermediate energy levels within the band gap of TiO2. These new levels not only acted as electron traps for efficient suppression of the undesired e–/h+ recombination, but also facilitated to a certain extent the absorption of visible irradiation.

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