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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]
  • Gel properties of agar from two Gracilaria species in Sri Lanka and
           development of food jellies

    • Abstract: Gracilaria species are found to be a rich source of natural hydrocolloid agar-agar but are currently under-exploited in Sri Lanka. The gel characteristics of agar extracted from Gracilaria corticata and Gracilaria edulis from Sri Lankan waters were investigated in this study. The agar yields (%, dry weight basis) obtained from G. corticata and G. edulis by hot-water extraction at 90℃ for 1 h, were 39.91 ± 0.17 and 67.52 ± 1.43, respectively. The gel properties of both agar gels (1.5%, w/v) such as pH, viscosity, gelling and melting temperatures, and syneresis were examined. The viscosity of agar gels (cP) at 80°C was lower than that at 70°C for both species, while G. edulis has shown higher viscosities at both temperatures (1.96 ± 0.06 and 2.76 ± 0.39, respectively). Moreover, the textural analysis revealed that G. corticata has a higher gel hardness (316.7 ± 20.8 g) than G. edulis (113.33 ± 12.58 g). Strawberry-flavored food jellies were developed from agar gels of two Gracilaria species with either artificial (Carmoisine, E122) or natural food color (Annato). Collectively, this study revealed that agar from both red seaweed species has the potential to be developed as plant-based food jellies, and G. edulis can be suggested as the best source to extract agar with higher yield compared to G. corticata. Published on 2022-08-18 00:00:00
  • Generalized Stochastic Restricted LARS Algorithm

    • Abstract: The Least Absolute Shrinkage and Selection Operator (LASSO) is used to tackle both the multicollinearity issue and the variable selection concurrently in the linear regression model. The Least Angle Regression (LARS) algorithm has been used widely to produce LASSO solutions. However, this algorithm is unreliable when high multicollinearity exists among regressor variables. One solution to improve the estimation of regression parameters when multicollinearity exists is adding preliminary information about the regression coefficient to the model as either exact linear restrictions or stochastic linear restrictions. Based on this solution, this article proposed a generalized version of the stochastic restricted LARS algorithm, which combines LASSO with existing stochastic restricted estimators. Further, we examined the performance of the proposed algorithm by employing a Monte Carlo simulation study and a numerical example. Published on 2022-08-18 00:00:00
  • Trends in appliance usage and electricity consumption in households: A
           case study in Hambantota District, Sri Lanka

    • Abstract: The study aimed to develop interrelationships among electricity consumption, the plan area of the house, period of construction and appliance availability in Hambantota district in Sri Lanka. For this survey, the data was collected from 385 houses by means of door-to-door visits. Electricity consumption increases with the increase in the number of family members and the plan area of a house, but it is reduced with the age of the house. The availability of air conditioner, refrigerator, electric kettle, electric iron, vacuum cleaner, laptop computer, and incandescent bulbs significantly influences the electricity consumption in a particular housing unit. An increasing trend in energy demand for thermal comfort was observed in the region. Houses built after 2008 use an average of 100 kWh of electricity per month, which is a 30 kWh increase over older houses (built within or before 2008) in the area, resulting in an increase in energy demand in the area. The results of this study are a valuable reference in policymaking related to market availability of appliances, deciding electricity tariffs, and identifying potential ways to improve energy use efficiency in the domestic sector. Published on 2022-08-18 00:00:00
  • Characterization and risk evaluation of water samples collected from
           boreholes situated around a dumpsite in Obalende, Lagos, Nigeria

    • Abstract: Dumpsites are used worldwide for waste disposal because they are cost-effective and have the capacity to contain enormous amounts of waste. However, concerns are rife about the impact of dumpsites on the quality of nearby groundwater. The present study assessed the quality of borehole water near a dumpsite in Obalende, Lagos, Nigeria. Heavy metal, physico-chemical, and microbiological tests were performed on the samples of the water using standard techniques, and the results were compared to the WHO permissible limits. The average daily oral ingestion (A
      DOI ), average daily dermal ingestion (ADDI), and hazard quotient (HQ) of the heavy metals were also estimated. The heavy metal analysis revealed non-permissible levels of zinc, iron, lead, and manganese, while nickel, cadmium, and silicon were within the permissible limits. Physico-chemical analysis showed that turbidity, total suspended solids, total dissolved solids, nitrate, and phosphate were within the permissible limits, but not the pH, electrical conductivity, chloride ion, sulphate and dissolved oxygen. The microbiological examination indicated that the water had high levels of bacteria and coliform counts. The HQ of Zn, Fe, and Pb, mainly through dermal exposure was above the recommended limits (>1). Overall, the results suggest that the water may predispose consumers in the area to Zn, Fe, Pb, and Mn toxicities as well as microbial infections. Consequently, consumers are advised to treat the water before consuming it. Published on 2022-08-18 00:00:00
  • Abundance and ecological classification of fish Species: A case study of
           Owalla Reservoir, Osun State, Nigeria

    • Abstract: Globally, we are experiencing higher species extinction rates than ever before which can critically affect food and nutrition security. The ecological classification of fish species was assessed in Owalla reservoir, Okinni, Osun State, Nigeria. Fish landings of fishermen were sampled for 12 months from September 2019 to August 2020). The species were identified and grouped into herbivores, carnivores, and omnivores, and the fish abundance was recorded. The Forage-Carnivore ratio (F/C ratio) was calculated to express the ecological structure of the reservoir. A total of 15 fish species (n=1035 fish) were identified. In the dry and wet seasons,  15 species (692 fish) and 11 species (343 fish) were recorded, respectively, and herbivores were more abundant than carnivores. Chrysichthys nigrodigitatus (25.9%) was the most abundant species and Cichlidae (55.5%) was the most abundant family. The overall F/C ratio during the combined, dry and wet seasons were 1.35, 1.01 and 2.57, respectively. The ecological structure as indicated by the F/C ratio was unbalanced, but in the wet season, it was close to being balanced. We proposed management measures such as fishing across the trophic levels, efficient monitoring and surveillance, regulation of mesh sizes, and registration of fishermen in addition to routine data collection. Published on 2022-08-18 00:00:00
  • Classification of the level and the type of hearing loss based on the
           analysis of audiograms of workers exposed to high level of occupational

    • Abstract: This paper presents some health effects of workers exposed to high occupational noise for a long period. The main objective of this study was to classify the level and the type of hearing loss of such workers plus to study the effects on their health. Out of a sample of 99 workers exposed to 85 dB(A) or more occupational noise, 73 (74%) workers who were exposed over 40 hours per week for five years or more were selected for this study. Their hearing levels were tested audio-metrically and audiograms of Air Conduction (AC) and Bone Conduction (BC) measurements were taken. Depending on the degree of Hearing Loss (HL) of audiograms, the sample was classified into Normal hearing (0-25 dB(A)) : 10.5%, Mild HL (26-40 dB(A)) : 67.0%, Moderate HL (41-55 dB(A)) : 21.75%, Moderate-to-severe HL (56-70 dB(A)) : 0.75%. None of these fall in to Severe HL or Profound HL categories. Based on the HL and the configuration of audiograms of AC and BC measurements, 89.5% of the sample was classified as Conductive Hearing Loss (CHL 2.25%), Sensorineural Hearing Loss (SNHL 85.75%), and Mixed Hearing Loss (MHL 1.5%). Some SNHL samples were identified as Meniere’s disease 19%, Acoustic Trauma 12%, and Noise-Induced Hearing Loss (NIHL) 6%. NIHL were recorded among highly exposed workers to noise in the frequency range 3000-6000 Hz. Percentage statistics of various levels of hearing levels along–with associated symptoms based on the response to the questionnaire are also presented. Published on 2022-08-18 00:00:00
  • Analysis of Statistical Downscaling Model (SDSM) projected future rainfall
           in Northwestern, Western and Southern provinces of Sri Lanka

    • Abstract: Even though an extensive amount of climate change studies have been carried out in different parts of the world, Sri Lanka is one of the least focused countries in this regard. Climate projections are important and encouraged to manage the futuristic adverse impacts. Identifying this research gap, future rainfall projections were carried out in three provinces in Sri Lanka, i.e. Northwestern (Puttalam and Kurunegala), Western (Katunayake and Colombo), and Southern province (Galle and Hambantota). The Canadian Earth System Model (CanESM2) under the Representation Concentration Pathways (RCP8.5) was downscaled using the Statistical DownScaling Model (SDSM). Non-parametric tests, including Mann-Kendall (MK) test and the Sen’s Slope estimator, were used to determine the significance of trends and magnitude of the slope of the historical trends (1990-2019) and future projected trends (2020-2100). The trends were analyzed for four major seasons in Sri Lanka, including First Inter-monsoon (FIM), Southwest monsoon (SWM), Second Inter-monsoon (SIM), and the Northeast monsoon (NEM). The standard error and model bias at rainfall stations were 0.014-0.034 mm and 1-1.1 respectively, which are acceptable when compared to previous studies. Several significant rainfall trends were identified, including positive trends in the mid-future (2041-2070), and negative trends in the far-future (2071-2100). In addition, rainfall indices, including Rx5day, R20mm, Consecutive dry days (CDD), and Consecutive wet days (CWD) were tested in future projected and historical rainfalls. The results of the present study will be useful for policymakers for decision-making processes in water resources management and agriculture. Published on 2022-08-18 00:00:00
  • Exploring marketing channels and market margins of tuna species: A case
           study of Negombo fishery harbour in Sri Lanka in 2018

    • Abstract: This study was carried out to determine the domestic level marketing channels, marketing cost, and marketing margin for four commercially important marine fish species in Negombo fishery harbour, Western Province, Sri Lanka, with a focus on marketing efficiency. Data related to fish catch and prices were collected by direct observation during the period of January to December 2018. About 80 to 105 tons of fish catch per day were being landed. The annual average wholesale prices of fish (kg-1)g varied from LKR 450 to 670 for Yellowfin tuna, LKR 233 to 414 for Skipjack tuna, LKR 320 to 385 for Frigate tuna, and LKR 140 to 190 for Indian scad, which is typical market behaviour. Though the net profit per 100 kg of fish received by the wholesaler was higher than the assembler, the retailer has made a significant amount of profit, nearly six times higher than the assembler. Ten marketing channels were identified from fish producers to the ultimate consumer and some channels involved more than three intermediaries. As typical for long marketing channels, high prices were paid by the consumer for the low freshness quality of fish. Though, the retail price of skipjack tuna at the Negombo landing center is moderately correlated (r=0.634), the other three fish species did not give a clear indication. Thus, the price factor of selected marine fish at the landing site was not having a significant impact on the market integration. Consumers were concerned about both price and quality when purchasing the fish. To improve the marketing efficiency of the marine fish market, it is recommended to implement shortening of the fish market channel with less involvement of intermediaries and to develop the fish market facilities appropriately. Published on 2021-12-31 00:00:00
  • Formulation and quality assessment of tomato (Lycopersicon esculentum)
           cordial with xanthan stabilizer

    • Abstract: Tomato fruit is a nutritious part of the human diet providing a variety of health benefits. Searching for other means of utilization than direct consumption of tomatoes seems a timely need to reduce post-harvest losses caused by the rapid perishability of ripened tomatoes. In the present study, three tomato cordial formulations with xanthan gum as a stabilizer were tested for sensory properties, and the best formula was tested for its physico-chemical properties and stability over one month period. Well-ripened and healthy fruits were chosen to prepare the cordial. According to the Sri Lankan Standards (SLS 730), three different cordial samples were prepared only changing the concentration of xanthan gum stabilizer as 0.3%, 0.4% and 0.5% (w/v). Using 30 semi-trained panellists, prepared samples were subjected to sensory testing on a 5-point Hedonic scale, and 0.5% of xanthan gum containing cordial was selected as the best formula. The shelf-life evaluation of the best sample was conducted weekly for one month through physicochemical and microbiological analysis. Significant changes (p<0.05) were observed only in vitamin C content and total soluble solids (TSS) during the shelf-life evaluation. At end of the storage period, the cordial with 0.5% xanthan gum possessed pH 3.26, titratable acidity 1.35%, vitamin C 31.9 mg/100ml, TSS 44.9 °Brix, total sugar 19.8% and polyphenol content 0.0021 mg/ml GAE. Changes in the total plate counts during the one month of storage are within the acceptable limit (less than 50 per ml) according to the Sri Lankan Standards (SLS 516). It can be concluded that tomato cordial can be formulated by using 5% of xanthan gum stabilizer and that was found to be stable for one month without any deterioration. Published on 2021-12-31 00:00:00
  • Analysis of physicochemical parameters and selected potentially toxic
           elements to assess the water quality of Kattakaduwa reservoir in
           Hambanthota district, Sri Lanka

    • Abstract: The study was aimed to assess the water quality of Kattakaduwa reservoir in Hambantota district, Sri Lanka. Reservoir water is not directly used for drinking purposes until purification, but people use it for different purposes such as bathing and irrigation. A comprehensive study on the water quality of this reservoir water was timely needed due to the scarcity of such information. Monthly variation in seven physicochemical parameters and five potentially toxic elements (Mn, Fe, Cu, Cd and Pb) of water at five different sites compared to treated reference water samples were studied for 2017. Sediment analysis of the five elements at four different sites was also carried out. At the site closer to the inlet of the pump house before purification (site 3S), the mean values (± SD) of water temperature, pH, dissolved oxygen, sulphate concentration, turbidity, conductivity, and alkalinity were 33 ± 1°C, 7.5 ± 0.1, 7.19 ± 1.80 mg/L, 57.40 ± 23.60 mmol/L, 36.74 ± 18.87 NTU, 605.3 ± 119.8 µS, and 176.0 ± 32.0 mg/L, respectively. The maximum Fe concentration was observed in March (1.73 mg/L) while the minimum was in January (0.70 mg/L) exceeding the United States federal limits (USFL) and Sri Lankan Standard level (SLSL) of Fe (0.3 mg/L) throughout the year. However, Mn concentration in the same site exceeded the USFL and SLSL (0.05 mg/L) slightly in May, July, and October. The concentrations of the rest of the elements were below the minimum detection limit (MDL) of 1 mg/L. All elements in the treated reference water sample (TR) were below MDL. The concentrations of Fe (15291 ± 10486 mg/kg) in sediments were greater than Mn (1178 ± 1007 mg/kg). These values reflect the higher Fe concentration in the reservoir water compared to Mn concentration that may be due to the leaching of Fe from the sediments to the water. Published on 2021-12-31 00:00:00
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