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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
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Ruhuna Journal of Science
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  This is an Open Access Journal Open Access journal
ISSN (Print) 1800-279X
Published by Sri Lanka Journals Online Homepage  [71 journals]
  • Elastic and mechanical properties of cubic metal arsenides (Ga, In and Al)
           under high-pressure: a simulation study

    • Abstract: Semiconducting materials have played an important role in modern technological age. Group III-V materials have attracted much attention in electronic industry due to their structural, mechanical, electronic and thermodynamic properties predicted by calculations. This paper simulated the effect of pressure within the range of 0-100 GPa on the elastic constants and other related parameters, such as Young’s, bulk and shear moduli, Pugh ratio, Poisson ratio, anisotropy factor, degree of anisotropy and Kleinman parameter for gallium arsenide (GaAs), indium arsenide (InAs) and aluminum arsenide (AlAs) materials, using the Tersoff classical potential within ATK-force field.  Results showed that, increase in pressure enhanced the ductility of GaAs and InAs within the entire pressure domain, and between 10-40 GPa for AlAs material. AlAs was found to be brittle under 50-90 GPa, and unstable at 100 GPa. This may be due to occurrence of phase transition at these pressures. The obtained results at zero pressure are consistent with available experimental and theoretical data in literature. Published on 2021-09-15 00:00:00
  • Mass production of the nematode Acrobeloides longiuterus using Tribolium
           castaneum and artificial solid media

    • Abstract: Free-living nematode Acrobeloides longiuterus (Rhabditida: Cephalobidae) exhibits a potential to kill some insect pests. Mass production of this species is a requirement for use it in pest management programs. Tribolium castaneum has been used as a primary host for this nematode as an alternative for Galleria mellonella. Use of artificial media is another option for mass culturing and such recipes based on soy flour are available. Production of A. longiuterus using cost effective method and easily available insect host is important in setting up of small-scale production unit. Therefore, this study has the objectives of evaluating the production feasibility of A. longiuterus on T. castaneum larvae, pupae and adults as in vivo production method. Further, feasibility of using different solid media such as soy flour, palmyra tuber flour, corn flour, black gram flour and dhal flour with other basic ingredients as in vitro conditions system was evaluated. Results revealed that pupa of T. castaneum yielded the highest number of infective juveniles (36112 IJs/ pupa) compared to other life stages tested. In vitro production of A. longiuterus on soy flour and black gram flour media yielded 21530 and 16538 IJs/20g, respectively. Pathogenicity against T. castaneum was shown up to 93% by the infective juveniles produced from the in vitro cultures. In conclusion, T. castaneum is an alternative insect that can be used as a host to produce the A. longiuterus. In addition, soy flour and black gram flour can be used as the sources for this nematode production without losing their entomopathogenicity. Published on 2021-09-15 00:00:00
  • Forest resources as ecotourism attraction: Cross River National Park,

    • Abstract: Cross River National Park (CRNP) in Nigeria with its natural resources of tourist significance can help to foster a culture of conservation and recreation among the public. This study identified ecotourism attractions in CRNP aiming to promote its sustainable use and to enhance its planning as a haven for ecotourism in Nigeria. A field survey of ecotourism resources was conducted in the park during 2010-2014. Fauna resources were identified along the 5 km transects that covered existing trails and jeep tracks in both dry and wet seasons. Quadrat method (15 sample plots of 50 m x 20 m) was used for the vegetation assessment and Shannon-Weiner Diversity Index (H) and descriptive statistics were calculated. Findings revealed that the rainforest, game viewing, birdwatching, mountain climbing, camping, rock formation, village tour, botanical garden tour and water recreation as core ecotourism attractions in CRNP. Fifteen wild animal species belonging to nine families were observed (endangered 01, least concerned 12, near threatened 01, vulnerable 01). Wild animals included drill monkey Mandrillus leucophaecus (endangered), elephant Loxodonta africana cyclotis (vulnerable), bat Eidolon helvum (near threatened), and bare-headed rock fowl Picarthates oreas (endemic) which are “ecostars” and “a must see” that warrant a visit to the park. Other animals were least concerned. A total of 81 tree species belonging to 26 families were identified. Shannon-Wiener Diversity index (H’) of 3.88 and 3.84 were recorded for Oban and Okwango divisions respectively. The most dominant family in Oban was Leguminosae (12 species) and in Okwango, it was Apocynaceae (10 species). Managing and promoting the sustainable use of the park’s numerous resources to actualize the potential value non-consumptively through ecotourism is hereby recommended. Published on 2021-09-15 00:00:00
  • Environmental and social impact of a mini-hydropower plant based on Sudu
           Ganga in Sri Lanka

    • Abstract: Hydropower plants are generally considered as economical and sustainable sources of energy, yet they can create unintended disruptions to sensitive ecosystems. The objective of this study was to assess the environmental and social impact of a proposed mini-hydropower plant based on Sudu Ganga (Matale district) in Sri Lanka. Data for the environmental impact assessment were obtained via species observation and from secondary sources. Data for social impact assessment were obtained through the views of the residents and other stakeholders in the area. The regulation degree was 0.052% which indicated minor impact on the hydrological flow regime. In the project area, the study identified 28 flora species and 30 fauna species including five flora and fauna species at high risk of disappearance, and another five species at the risk of falling into a threatened category. The estimated value of the Shannon biodiversity index for flora species was 1.71 and was lower compared to other ecologically sensitive areas in surrounding districts. The environmental impact values for the physical and biological environment, and the social environment were -0.65 and 1.4, respectively, on a scale of [-5, 5]. These values indicate a slight negative impact on the physical and biological environment but a positive impact on the social environment. The proposed reforestation project and fish bypass gate were recognized as significant mitigation measures. We recommend further precautionary measures, particularly, during the construction phase to minimize disturbance to wildlife and damages to plant species, proper management of site excavation and construction waste, careful use of machinery and vehicles, environmental awareness of employees, and involvement of community and stakeholders to reduce adverse impacts. Published on 2021-09-15 00:00:00
  • Analysis of rainfall trends and variabilities for three decades in Sub
           – Sahara Africa

    • Abstract: Rainfall trend is an important climatic factor that influences agricultural products, groundwater production, drainage planning, commercial and industrial activities. The research aims to determine the trends and variability of monthly, seasonal, and annual rainfall for 30 years (from 1980 to 2010) in Sokoto (13.0059° N, 5.2476° E) and Maiduguri (11. 8333° N, 13.1500° E) using archives data obtained from the Nigeria Meteorological Agency (NiMet), Oshodi Lagos Nigeria. Statistical models were used to analyze the data. The results reveal that the maximum rainfall recorded was 371.60 mm at Maiduguri station and 374.90 mm at Sokoto station which shows a higher rainfall peak in Sokoto than Maiduguri. The coefficient of variation in the Sokoto station (126.39%) was higher than that of Maiduguri station (61.78%) which indicates that there was more rainfall variability in Sokoto than in Maiduguri. Seasonally, the average rainfall recorded in both stations was 61.78% and 126.39% respectively. No rainfall was recorded in January, February, and November for Maiduguri station, more so, no rainfall was recorded in January, November, and December for Sokoto station. According to Man-Kendal trend analysis, significant trends (p<0.5) were observed in Maiduguri and Sokoto. Therefore, the modelled statistical approach on rainfall trends and variability revealed that the peak month of annual rainfall is between June and September for the two stations. It can be recommended that the government should make favourable policies to utilize the rainfall received during this period to store more water in reservoirs and construction of water channels across the country. Published on 2021-09-15 00:00:00
  • Free radical scavenging potential and antibacterial activity of Cola
           nitida and Garcinia kola extracts against bacterial strains isolated from
           patients with urinary tract infections

    • Abstract: Cola nitida and Garcinia kola are found and widely consumed in West Africa. The seeds of these plants have various traditional uses and are reported to exhibit several bioactivities. Their phytochemical, antioxidant and antibacterial properties of methanol, ethanol and aqueous extracts were investigated in the present study. Phytochemical screening and quantification of total phenolic contents analysis were carried out for phytochemical investigation. Preliminary phytochemical screening revealed the presence of flavonoids, alkaloids, tannins, saponins, protein and glycosides in the seed extracts. Quantitative phytochemical constituents revealed 0.818 ± 0.021and 0.700 ± 0.017mg of phenolic compounds and total flavonoid content of 25.63 ± 1.60 and 25.10 ± 1.85mg in G. kola and C. nitida respectively. The extracts showed potent antioxidant activities compared to standard antioxidants by significantly inhibiting 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical (∙OH), and superoxide anion radicals (O2∙) dose dependently. The methanol extracts of G. kola and C. nitida showed significant inhibitory action (p<0.05) against the bacterial isolates. The minimum inhibitory concentration obtained for methanol extract of the plants and both the mixture was 12mm at 31.25mg/ml for Klebsiella pneumoniae while the ethanol and aqueous extract of the plants and both the mixture was 13mm and 12.33mm at 31.25mg/ml and 125mg/ml respectively for E. coli. A direct correlation was observed between total phenolic content of extracts and radical scavenging potential, thus linking the observed bioactivities of these extracts to the presence of the phytochemical. The mixture of these seed extracts showed greater effect against the bacterial isolates, therefore providing a platform for advance studies in the development of drugs against infectious diseases.  Published on 2020-12-31 00:00:00
  • Modelling non-life insurance in Sri Lanka using Cox Hazard Model and
           classification of risky customers

    • Abstract: Some of the major factors that help the decision-making process of an insurance company include Time of the first claim (TFC), claim Size and the frequency of claims. However, in most situations researchers focus mainly on the second and third factors mentioned above. We hypothesize the importance of the TFC of an insurance contract in the decision-making process. Empirical evidence of motor vehicle insurance data in Sri Lanka suggests that nine covariates are responsible for the claim sizes. In the current study, our main objective is to find the key factors of those nine that are responsible for the TFC of the insurance contract. This study is based on the claim data in the whole year of 2016 of non-life insurance policies of a particular insurance company in Sri Lanka. Considering the TFC as right-censored data, selected nonparametric methods, i.e., Kaplan-Meier, Nelson-Aalen estimators, and Cox Proportional Hazard Model are used to analyze the data. We identified the five most influential covariates namely, vehicle type, log of Premium Value and that of Assured Sum, the lease type and the age range via fitting the Cox Model to TFC data. After a thorough residual analysis, the Logistic regression model has been used to identify the important covariates to classify future customers as risky or not. Published on 2020-12-31 00:00:00
  • Antioxidant and anti-inflammatory potential, and chemical composition of
           fractions of ethanol extract of Annona muricata leaf

    • Abstract: Serious health challenges have been associated with inflammation which is a major cause of mortality in the world. This study evaluated the antioxidant, anti-inflammatory potential, and chemical compositions of fractions of ethanol extract of Annona muricata leaf. The leaves were dried at room temperature, blended and extracted in sequential with solvents of varying degree of polarities, i.e., n-hexane, ethyl acetate and ethanol. Ethanol extract was fractionated via solvent-solvent partitioning into five fractions, i.e., n-hexane fraction (F1), dichloromethane fraction (F2), dichloromethane/ methanol (1:1) fraction (F3), methanol fraction (F4), and ethanol fraction (F5). These fractions were examined for their in-vitro antioxidant activities on DPPH, ABTS and H2O2 while the anti-inflammatory activities were investigated using lipoxygenase inhibition, proteinase inhibition and membrane stabilization assays. The F4 being the most active fraction was further analyzed with GCMS to determine its chemical compositions. The results showed that F4 had the highest H2O2 scavenging activity at 10–100 µg/mL. The activity of F4 at 50 µg/mL was significantly higher (P<0.05) than that of other treatments including the standard (Vitamin C). Activity of F4 also showed significantly higher (P<0.05) membrane stabilization than other fractions at 50-100 µg/mL. F4 exhibited higher antioxidant and anti-inflammatory activities than the other fractions. The activity of this fraction could be attributed to the synergetic effect of various antioxidant compounds present in the fraction. Some of the bioactive compounds identified in the GC-MS of F4 were coumaran, tyrosol, phytol, tetracosanol, elaidic acid methyl ester and β-sitosterol.  Published on 2020-12-31 00:00:00
  • Survival modelling of teenage childbirth among Nigerian women

    • Abstract: Childbearing is an essential event in woman’s life when she neglects her education and career for motherhood. The main cause of population growth in Nigeria is teenage childbearing as reported by many researchers with no significant intervention to reduce this menace. This work is designed to compare the results of Cox, Gompertz and Weibull models with a view to determine the model that best fits the data. To evaluate the effect of some risk factors on the hazard of teenage childbirth among Nigerian women, data obtained from National Demographic Health Survey 2013 was analysed. Results of the analysis showed that having a child at teen age depends on geopolitical zone, location, educational level, circumcision, household wealth index, religion belief, use of contraceptive, whether had a terminated pregnancy, forced sexual acts, awareness of HIV/AIDS, STI and the age of first sexual acts. Akaike Information Criterion (AIC) was employed to evaluate performances of the three models. Weibull regression model has the minimum AIC value compared to both Gompertz and Cox regression models. This shows that Weibull regression model provides best fit to the data. Published on 2020-12-31 00:00:00
  • Ethnobotanical study of Buru Community Forest, Taraba State, Nigeria

    • Abstract: An ethnobotanical study of Buru Community Forest was conducted using Participatory Rural Appraisal techniques. A total of 91 species of plants belonging to 43 Families with high endemicity were recorded. The dominant families were Fabaceae, Euphorbiaceae, and Meliaceae. Many species such as Tetrapleura tetrapetra, Phyllanthus mullerianus, Sarcocephalus latifolius and Aframomum melegueta had multiple uses. The three major uses of the species are for medicinal (39 species), edible (33 species) and construction purposes (30 species).  Published on 2020-12-31 00:00:00
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