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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
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Journal of Science of the University of Kelaniya Sri Lanka
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1391-9210
Published by Sri Lanka Journals Online Homepage  [71 journals]
  • Co-occurrence of microcystin and cylindrospermopsin in hypereutrophic
           Mahakanadarawa and Nachchaduwa reservoirs

    • Abstract: Microcystins (MCs) and cylindrospermopsin (CYN) are the most abundant toxins produced by cyanobacteria in tropical freshwaters. We studied the spatial distribution of MC and CYN in two multipurpose reservoirs, Mahakanadarawa and Nachchaduwa in Anuradhapura district in Sri Lanka in September 2020.  Fourteen water quality parameters, phytoplankton composition, chlorophyll-a, MC and CYN concentrations were analyzed in triplicate in 25 sampling sites from each reservoir. Both reservoirs were at hypereutrophic status.  Microcystis was the dominant cyanobacteria with 0-3.75 x 103 cell/mL in Mahakanadarawa and 1-7 x 103 cell/mL in Nachchaduwa. Besides Microcystis, no other potential MC-producing cyanobacteria were observed. In Mahakanadarawa, MC was detected in the range of 0.11-1.63 µg/L which was above the WHO permissible level (1.0 µg/L) for drinking water. Although comparatively high Microcystis cell density was present in Nachchaduwa, its MC concentration was low (0.06-0.17 µg/L). The CYN concentration in Nachchaduwa was above the WHO permissible level (0.7 µg/L) for drinking water. It was 0.20-1.02 µg/L in Nachchaduwa and 0.03-0.08 µg/L in Mahakanadarawa. We did not observe any potential CYN-producing cyanobacteria in either of the reservoirs. There was no relationship between the spatial distribution pattern of MC and Microcystis cell density in both reservoirs. Although the majority of physico-chemical properties of water indicated suitability for drinking, co-occurrence of high concentrations of MC and CYN indicated their unsuitability for drinking. Hence, this study highlights the necessity for routing detection of cyanotoxins in both reservoirs. Further, our findings alarm potential health risks for the local community that relies on Mahakanadarawa and Nachchaduwa reservoirs for drinking, irrigation and fisheries. Published on 2022-07-05 02:58:44
  • Detection of Clostridium perfringens and associated preventive measures to
           appraise the safe meat curry consumption in the Colombo city

    • Abstract: Sri Lanka is a fabulous tourist destination thus; ensuring food safety has garnered importance in public health. Spicy meat curries are popular among consumers and the majority of them belong to the low-income category. Hence, the aim of this descriptive cross-sectional study was to detect Clostridium perfringens and associated preventive measures to appraise the safe meat curry consumption in Colombo city. This spore bearer is ubiquitous in nature and found in a variety of food commodities. Furthermore, this fastidious bacterium is frequently found in meat curries and meat-based dishes. Two hundred meat curry samples comprising 100 chicken and 100 beef were purchased from proportionately selected 200 eating houses in Colombo which have been registered in the Colombo Municipal Council. Spread plate and enrichment techniques were used to optimize the isolation. Subsequently, presumptive identification was done and confirmed by biochemical tests. Confirmed colonies were enumerated and expressed as colony forming units (cfu) per gram of food.  Thus, C. perfringens was not detected in 61 % of meat curry samples comprising 69 % beef and 53% chicken curries. Safety measures either in preparation and/or storage have been taken by 75- 95% of eating houses, where this cultivable bacterium was not detected. Therefore, as indicated by our findings, safe meat curry consumption in the 21 st century without foodborne pathogens, could not be an over-ambitious goal. Further improvements can be done through the valuable service of Public Health Inspectors (PHIs) about the microbial quality of food. Published on 2022-06-28 00:00:00
  • Effect of five medicinal plant leaves on survival, oviposition and progeny
           development of cowpea bruchid, Callosobruchus maculatus (F.) infesting
           cowpea seeds in storage

    • Abstract: Over 90% of the insect damage to cowpea seeds is caused by Callosobruchus maculatus. Although, many chemicals have proven their efficacy against C. maculatus, they adversely affect the natural environment. Death of non-targeted species which are natural enemies of other insect pests and development of resistance to chemicals is possible. Therefore, the current study was conducted to determine the effect of plant leaves of Murraya koenigii (“Karapincha”), Pandanus amaryllifolius (“Rampe”), Vitex negundo (“Nika”), Pavetta indica (“Pavatta”) and Croton aromaticus (“Wel keppetiya”) on adult mortality, oviposition, and progeny development of C. maculatus. Plant leaves were tested in both fresh form and powdered form. The plant leaves were mixed with cowpea seeds to have two concentrations followed by the introduction of 5 pairs of C. maculatus adults. The maximum adult mortality, minimum oviposition and the minimum progeny development were observed when the cowpea seeds were treated with C. aromaticus leaves. The mortality increased to 100% when the seeds were treated with the combination of C. aromaticus – P. amaryllifolius – V. negundo (WPN) plant leaf powders.  This study suggests that fresh plant leaves or plant leaf powder of C. aromaticus can be used against C. maculatus to protect cowpea seeds in storage. Published on 2022-06-28 00:00:00
  • Low-cost microfluidic electrochemical paper-based device to detect glucose

    • Abstract: Continuous monitoring of the level of glucose is essential to maintain the health of a diabetic patient. The use of invasive methods to obtain blood samples to detect glucose is the current method, but such methods may not be preferred by patients. Non-invasive methods such as the determination of glucose based on saliva or sweat can be preferred by patients for continuous monitoring. A low-cost electrochemical microfluidic paper-based analytical device (µPAD) suitable to monitor glucose levels using sweat and saliva is introduced. This device is extremely low-cost due to the use of a paper matrix and varnish for the fabrication of paper. Pseudo-reference stainless steel is used with a working electrode anodized using sodium potassium tartrate tetrahydrate for the development of a three-electrode system. Cyclic voltammetric-based analysis of glucose with µPAD produced a linear response in the working range of 1-10 mmol dm-3 with a limit of detection of 0.058 mol dm-3. The detection of diabetic conditions using saliva and sweat is possible using the device by correlating to the blood glucose levels using prior literature data. Published on 2022-04-05 00:00:00
  • The abundance of mosquito larvae in relation to associated microbiota and
           physicochemical parameters of marshland habitats in Kelaniya in Gampaha
           district of Sri Lanka

    • Abstract: The abundance of mosquito larvae in relation to associated microbiota and physicochemical parameters of water in marshes from selected habitats in Kelaniya divisional secretariat area, of the Gampaha district, Sri Lanka were studied. Culex gelidus was found to be the dominant mosquito species found in marshes followed by Culex whitmorei, Culex tritaeniorhynchus, Culex quinquefasciatus, Culex fuscocephala, and Anopheles peytoni. Fourteen species/taxa of microbiota were identified. There was a significant positive correlation between the abundance of Cx. gelidus larvae and level of organic pollution in marshes as measured by the five-day Biological Oxygen Demand. A positive correlation for the presence of Cx. fuscocephala and Cx. gelidus in the marshland was also observed. Nevertheless, abundance of Cx. gelidus was negatively correlated with Cx. quinquefasciatus and Cx. whitmorei. The presence of Culex gelidus and Cx. tritaeniorhynchus were positively correlated with Daphnia magna indicating their co-existence in the same habitat requirement. Culex gelidus was negatively affected by the epibiont, Vorticella microstoma, when the latter organisms were present in higher densities. In contrast, the presence of Cx. whitmorei was positively influenced by the Vorticella microstoma, Difflugia corona, nauplius larva, and Keratella valga. There was a negative correlation between Cx. whitmorei and Monostyla bulla (Rotifera; Monogononta) and between the abundance of Cx. fuscocephala and Lecane luna in the same marshland. This study concludes that mosquito larvae and some microbiota are interdependent in marshlands. The level of abundance of mosquito larvae and microbiota varied with the level of water pollution. Cx. gelidus larvae are biologically affected by Vorticella microstoma. Many microbiota species compete with mosquito larvae for the same food items. Published on 2022-04-05 00:00:00
  • Population dynamics and breeding preference of Aedes aegypti and Ae.
           albopictus attributing to dengue threat in Kelaniya medical officer of
           health area in Sri Lanka

    • Abstract: Aedes aegypti and Ae. albopictus are the two species of dengue vector mosquitoes in Sri Lanka. Indoor and outdoor distribution of these species, their population dynamics and breeding preference are important factors determining the dengue transmission. Gampaha district in Sri Lanka reported to have frequent dengue epidemics from recent past, hence this study was conducted. Ovitrap surveillance was conducted to determine the vector species distribution in indoor and outdoor in Kelaniya Medical Officer of Health (MOH) area of the Gampaha district. Larvae were reared until emergence of adults in the laboratory to identify species morphologically. Breeding preference of vector mosquitoes were carried out by physically observing the presence of mosquito larvae in water accumulated  receptacles in  the area. Aedes aegypti and Ae. albopictus were reported to distribute throughout Kelaniya MOH area as a mixed population. Ae. albopictus is the most abundant species both indoor and outdoor in Kelaniya MOH area compared to Ae. aegypti. Weather factors, rain days and wind positively correlated with Aedes population. High risk areas were identified as Kiribathgoda and Hunupitiya in this study. Published on 2021-12-31 00:00:00
  • Calcium ion adsorption of Leucaena leucocephala wood biochar activated
           with coconut vinegar

    • Abstract: A positive correlation has been reported recently among the number of Chronic Kidney Disease of Unknown Etiology (CKDu) patients and the levels of groundwater hardness. Hence, the need for a low cost and a simple domestic process to reduce the hardness of potable water is identified to improve living standards of low-income communities in these disease affected areas. Biochar has emerged as a low cost adsorbent for water treatment, because of its abundance and cost-effectiveness. This study was aimed to evaluate the ability of natural coconut vinegar, in activating Leucaena leucocephala wood biochar to be used in calcium ion (Ca2+) removal from potable water. Column tests showed a 1.7 fold increase of Ca2+ adsorption capacity and a 7 fold increase of Ca2+ retaining capacity upon the vinegar treatment. Batch studies matched with both Langmuir (R2 = 0.9761) and Freundlich (R2 = 0.9785) isotherm models. Ca2+ amount in solutions were measured using flame photometry. Ca2+ adsorption capacities of raw biochar and activated biochar determined by column tests ranged from 3.10-3.82 mg/g and 5.27-6.68 mg/g respectively while Ca2+ retaining capacities ranged from 0.16-0.22 mg/g and 1.28-1.4 mg/g respectively. Fourier transform infrared spectra, suggests hydration of the C-O-C bridges of the biochar surface introducing new -O-H groups and possible introduction of carbonyl/ ester/carboxylic functional groups to the biochar surface upon vinegar treatment. According to scanning electron microscopy porosity of the biochar remained stable after the vinegar treatment. Published on 2021-12-28 17:04:44
  • Photocatalytic activity of GO/Fe3O4 fabricated by Sri Lankan graphite
           under visible light irradiation

    • Abstract: Graphene oxide (GO) was synthesized using Sri Lankan naturally available graphite and Fe3O4 nanoparticles were successfully incorporated fabricating magnetically separable GO/Fe3O4 nanocomposite. The synthesized nanocomposites were characterized by X-ray diffractometry (XRD), Scanning electron microscopy (SEM), and FT-IR spectroscopy. Crystalline phases of GO and Fe3O4 nanoparticles were identified by XRD patterns, while the presence of functional groups such as –COOH, OH, CH2 was confirmed by FT-IR spectroscopy. SEM images show that Fe3O4 nanoparticles with an average particle size of 107 nm ranging between 56-150 nm are dispersed on GO while restacking and folding of the nanosheets have been observed with incorporation of Fe3O4 nanoparticles. The photocatalytic performance of the photocatalysts was evaluated on photodegradation of methylene blue under visible light irradiation. The GO/Fe3O4 shows better adsorption behavior and excellent photocatalytic activity where it could be successfully used for three cycles without significant activity loss. This is due to the enhanced charge separation resulted due to the presence of GO sheets and better interactions between GO and Fe3O4. Published on 2021-11-03 00:00:00
  • Magnetic properties of ferromagnetic thin films with three spin layers as
           described by fourth-order perturbed Heisenberg Hamiltonian

    • Abstract: The magnetic properties of ferromagnetic thin films with three spin layers were investigated for the first time using fourth-order perturbed Heisenberg Hamiltonian. Total magnetic energy was determined for ferromagnetic materials with simple cubic lattice. The simulation was carried out for Heisenberg Hamiltonian with different second-order magnetic anisotropy constants in different spin layers. The total magnetic energy periodically varies with spin-exchange interaction, azimuthal angle of spin, and the second-order magnetic anisotropy constant in each spin layer. The peaks along the axis of the angle are closely packed except in the 3-D plot of energy versus angle and second-order magnetic anisotropy constant of the middle spin layer. 2-D plots were perceived by rotating 3-D plots in MATLAB. According to the 3-D plot, the angle between magnetic easy and hard directions is 90 degrees. The minimum energy range was found in the 3-D plot of energy versus angle and the second-order anisotropy constant of the middle spin layer. The samples with the minimum magnetic anisotropy energies have potential application in transformer cores, magnetic switching, and magnetic amplifiers. Published on 2021-09-10 00:00:00
  • Domestic electricity usage estimation model using socio-economic factors

    • Abstract: In this empirical study, socioeconomic factors that can easily be extracted from families have been used to build a "home electricity usage prediction" model based on two variables, family monthly income and family size. Each of these factors was evaluated individually. Two machine learning models were built using those factors as features. Models are based on “Linear regression” and “Random Forest” algorithms. This study revealed that the socioeconomic factors such as family size and family income are very effective in domestic electricity usage prediction model building, where the end usages are not known. Furthermore, the random forest algorithm was found to be more effective for unseen data than the linear regression algorithm. The accuracy of the models can be further improved by adding more data into the both models. Published on 2021-06-18 00:00:00
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