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  Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 374 journals)
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Journal of the National Science Foundation of Sri Lanka
Journal Prestige (SJR): 0.157
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1391-4588
Published by Sri Lanka Journals Online Homepage  [71 journals]
  • Assessment of submergence stress responses and mining allelic variations
           of submergence tolerance gene Sub1A in Sri Lankan rice germplasm

    • Abstract: Development of submergence tolerant (ST) rice cultivars is a priority in rice breeding programs globally, as floods significantly curtail rice production. Sub1A is the major known gene conveying submergence tolerance in rice, carrying two variants; Sub1A-1 (tolerance allele) and Sub1A-2 (susceptible allele). Sri Lanka hosts a genetically diverse rice germplasm; however, the allelic diversity of Sub1A gene among the Sri Lankan rice germplasm remains unknown. Hence, the current study focuses on assessment of submergence stress responses and identification of the allelic diversity of Sub1A gene in a panel of 64 Sri Lankan rice varieties/accessions. Submergence stress responses of the rice panel were evaluated and Sub1A allelic variations were assessed using a modified gel-based marker, ABUOP0003. A Bayesian approach was used to assess the genetic structure of the rice panel and its association to the Sub1A alleles was explored. Thirteen rice accessions/varieties showed significantly similar (p>0.05) survival percentages (SP - 77 to 93%) as ST reference FR13A. ABUOP0003 marker assay revealed that 13 rice accessions/varieties carry Sub1A-1. The rice accessions Godaheenati, Heenkarayal, Goda wee and Dik wee carried the Sub1A-1 allele as well as expressed a tolerance response to submergence stress. No significant association (p
  • Effect of oviposition-site deprivation on reproductive performance and
           life history parameters of dengue vector Aedes aegypti

    • Abstract: Dengue and dengue haemorrhagic fever constitute one of the most significant arthropod-borne viral diseases that occur in tropical and subtropical regions in the world.  Annually 390 million new dengue cases are being reported from the 128 dengue-endemic countries. Aedes aegypti is the primary vector that transmits the disease. Since the primary vector is a container breeder, source reduction appears to be a good vector control method. Source reduction limits the oviposition of females through oviposition-site deprivation. Therefore, the current study was conducted to determine the effect of oviposition-site deprivation on the fecundity, fertility, life-history parameters, and longevity of Ae. aegypti. Oviposition-site deprivation was enabled by delaying the access to the oviposition substrate. Female mosquitoes were allowed to access the oviposition substrate separately on the day of blood feeding and 2, 4, 6, and 8 days after blood feeding. The results showed that oviposition-site deprivation significantly increased fecundity with an increase in the number of egg retention days. The number of eggs laid by the female increased by 69% when the female was compelled to retain the eggs for 8 days. The highest recorded fecundity was 100 ± 5. Nevertheless, fertility, percentage larval mortality, total larval duration, pupal duration, and longevity were not affected by the number of egg retention days. Thus, it is imperative to have a clear awareness about the effect of oviposition-site deprivation on the reproductive performance of the vector mosquitoes when adopting vector control strategies. Published on 2023-04-10 10:51:01
  • Quantification of metabolite cinnamic acid of cinnamon (Cinnamomum
           zeylanicum) in human plasma

    • Abstract: Cinnamomum zeylanicum (CZ) is known to have numerous beneficial medicinal effects. The mechanism of action and compounds which account for these effects are not yet clearly defined. The present study aims to develop and validate a method to quantify the metabolites of CZ in human plasma and study its pharmacokinetic profile. Cinnamic acid (CA) was identified as the main metabolites of CZ in human plasma and was used to develop and validate the method.  HPLC with a UV-detector was used to identify and quantify CA. Linearity, precision, bias, repeatability, and lower limit of detection (LOD) were determined. CZ (5 g) was orally administered to 5 healthy volunteers and serial blood samples were taken, to determine maximal plasma concentration (Cmax), time to reach maximal concentration (Tmax) and elimination half-life (T½) of CA. The precision, bias, and repeatability, of the method were 7.73%, 4.20%, and 5.63%, respectively. LOD was 1.11 µmol/L and samples were stable up to five days at 4 oC. Recovery of the method was 95% -125%. The retention time of CA was 16 minutes at 254 nm. Concentrations of CA between 0.5 and 200.0 µmol/L in a plasma matrix showed a linear response. Cmax was 1.9 ± 1.5 μmol/L, while Tmax and T½ were 15 and 36 minutes respectively. The study developed a sensitive and specific HPLC method to detect CA, a key metabolite of CZ in humans, which is suitable for human pharmacokinetic studies. These pharmacokinetic parameters (Cmax, Tmax, T½) would help in further development of CZ as a pharmaceutical agent for use in humans. Published on 2023-04-10 00:00:00
  • Temperature control in an exothermic continuous stirred tank reactor

    • Abstract: A continuous stirred tank reactor (CSTR) is a batch reactor fortified with an impeller or additional mixing device to provide resourceful mixing.  In chemical engineering, the name CSTR is often used to describe an idealised agitated tank reactor used to model manoeuvre variables necessary to achieve a specified output. Most chemical plants have a process involving a continuous stirred tank reactor (CSTR), and it has more nonlinearity in real-world implementation due to disturbances like change in surrounding temperature, non-uniformity in mixing, and change in the temperature of the coolant. The aim of the work is to study the dynamic behaviour of a continuous stirred tank reactor with coolant flow rate as input and reactor temperature as output and to design a suitable controller to control the temperature of the continuous stirred tank reactor by conducting an exothermic reaction in real-time. A continuous stirred tank reactor was modelled with the help of a transfer function model in the MATLAB environment. For controlling the temperature of the reactor fluid, the design of proportional integral derivative, proportional integral derivative (PID) – particle swarm optimization (PSO), proportional integral derivative (PID) – artificial bee colony optimization (ABC) and model predictive control (MPC) controller were carried out. The simulation results show that model predictive control has better tracking performance compared to conventional PID, PID–PSO or PID–ABC.  Published on 2023-04-10 00:00:00
  • On recurrence relations for moments of dual generalized order statistics
           for a general transmuted power function distributions with

    • Abstract: Dual generalized order statistics is a unified method for random variables that are arranged in decreasing order. The moments of dual generalized order statistics are helpful to study the properties of any distribution. Often, the moments of dual generalized order statistics are not easy to compute and recursive computation is done. The recurrence relations for moments of generalized and dual generalized order statistics are helpful to compute the higher order moments from the lower order moments. In this paper, the methods for recursive computation of moments of dual generalized order statistics for general transmuted power function distributions are presented. The general transmuted power function distributions are first defined and then the recurrence relations are obtained. These recurrence relations include relations for single, inverse, product, and ratio moments. The recurrence relations are used to obtain the relations for moments of special cases, which include lower record values and reversed order statistics. Some characterizations of the general transmuted power function distributions are also presented based on the basis of single and product moments of dual generalized order statistics. These characterizations are unique results for the general transmuted power function distributions. The results given in the paper are useful to obtain the results for special cases of general transmuted power function distribution which includes power function and transmuted power function distributions. Published on 2023-04-10 00:00:00
  • Removal of methylene blue from aqueous solution using raw laterite: an
           adsorption study

    • Abstract: Existing methods for dye removal have their limitations and can be expensive and not very effective. Therefore, the search for efficient, effective, less expensive, and environmentally-friendly ways to remove industrial dyes from water remains open. Methylene blue (MB) removal from aqueous solutions is studied using raw laterite soil as a low-cost adsorbent. The physico-chemical properties and surface area were determined. Effects of parameters such as contact time, laterite dosage, pH, and ionic salts on MB adsorption by raw laterite were examined. The results showed that the maximum removal efficiency of MB adsorption was observed at pH values above 10, after 60 min of contact time, and with an adsorbent (raw Laterite) dose of 1.00 g in 100mL of dye solution. Increasing the salt concentration decreased the absorption of dye from solution. Ionic salt media containing, CaCl2 and KCl have shown maximum and minimum influence, respectively, on the adsorption of MB by raw laterite soil. At the optimum conditions, the experimental adsorption capacity of raw laterite was 2.930 mg/g. The experimental data fitted the pseudo-second order kinetic model (R2 = 0.99). The Freundlich adsorption isotherm model (R2 = 0.99) showed the best fit to the experimental adsorption data. According to the Freundlich isotherm model, the calculated adsorption capacity of raw laterite was 2.949 mg/g. Desorption studies with several solvents revealed that the adsorbent could successfully retain MB, up to 33.89%. Therefore, it can be considered that raw laterite soil is effective in removing MB from aqueous solutions. Published on 2023-04-10 00:00:00
  • Comparison of physicochemical and sensory properties of African butter
           seed (Pentadesma butyracea) and cocoa fats for potential use in future
           food applications

    • Abstract: African butter (Pentadesma butyracea) seeds are rich in edible fat, while cocoa butter is an expensive product obtained from fermented and dried cocoa beans. The aim of our study was to analyze the physicochemical and sensory properties of African butter seed fat and cocoa fat while determining their potential food applications. Chemically extracted fat was utilized for determination of physicochemical properties according to AOCS guidelines. Physically extracted fat was utilized for preparation of cookies and determination of sensory properties. Acid value, free fatty acid value and iodine value of African butter seed fat and cocoa fat were 1.05 ± 0.17 vs. 2.06 ± 0.14 mg KOH/g, 0.53 ± 0.09% vs. 1.14 ± 0.07% and 48.65 ± 3.03 vs. 34.31 ± 0.97 g I2/100g respectively. Saponification values of African butter seed fat and cocoa fat were 177.0 ± 0.6 mg KOH/g and 194.2 ± 1.1 mg KOH/g respectively. Between 25 and 30 °C, the solid fat content ranged from 31.8 ± 0.05% to 6.85 ± 0.07% for African butter seed fat and 36.14 ± 0.87% to 11.15 ± 0.11% for cocoa fat. The contents of stearic and oleic acids which are abundant in African butter seed fat were 39.05 ± 0.16% and 56.97 ± 0.27% respectively while those of in cocoa fat were 37.75 ± 0.06% and 34.12 ± 0.14%. Results of hedonic test performed for cookies prepared by incorporating the two kinds of fats highlighted that there was a significant difference relative to the preference (p < 0.05) for colour, while there was no significant difference with respect to the preference for flavour, texture and overall acceptability (p > 0.05). There is a high potential to develop African butter seed fat as a fat spread, a cocoa butter alternative and in preparation of cookies.  Published on 2023-04-10 00:00:00
  • A comparison of model parameter estimation methods for complex survey
           survival data

    • Abstract: When estimation of model parameters is the target in survey data, the inference on the model can be based on a pure model-based approach or a model-assisted approach which is a hybrid approach combining design-based and model-based methods. This study aims to compare these methods for survival data that are gathered from a stratified random sampling design.  The Accelerated Failure Time (AFT) model was fitted to describe the relationship between the censored response variable and the explanatory variables. Resampling methods with different sample sizes and different sampling designs from a real dataset were considered in the study to generate samples. The AFT models were fitted to each of the samples using, firstly a pure model-based method ignoring the survey design and weights, secondly a model-based method with survey weights, and finally a model-assisted method considering both survey design and weights. Squared bias, variance, and mean squared error (MSE) were used to compare the three approaches. The AFT model, with all covariates and the best AFT model with the best set of covariates and distribution, were analyzed. Even though it was challenging to select the best method for all cases, the second and third approaches worked better for small samples than the first approach.  Published on 2023-04-10 00:00:00
  • Mechanically exfoliated graphene from Sri Lankan vein graphite for field
           effect transistor application

    • Abstract: In this work, a single layer of graphene was exfoliated from Sri Lankan vein graphite obtained from the Kahatagaha graphite mines, and field effect transistors (FETs) were fabricated to study their electronic properties. Graphite pieces were carefully examined, and a small piece of graphite was separated with possible large graphene sheets. A simple Scotch tape technique was used to transfer graphene from the selected graphite pieces onto a 300 nm SiO2 coated Si (SiO2/Si) substrate for FET fabrication. The thickness and the uniformity of the graphene layers were tested using atomic force microscopy (AFM). The thickness of the transferred single layer graphene was confirmed to be 0.4 nm. The AFM images also confirmed the presence of double layer graphene with thickness of 0.9 nm. FETs were fabricated by creating electrical contacts using successive thermal evaporation of chrome and gold on the transferred graphene layers with a channel length of 5 µm. Results showed that the graphene FETs showed an ambipolar current response with a positive Dirac voltage. The calculated average electron and hole mobility in the graphene channel were 252 (±57) and 592 (±125) cm2V-1s-1 respectively. The positive Dirac voltage could be attributed to the sulphur content in the graphite obtained from Kahatagaha graphite mines. Our studies suggests that the Sri Lankan graphite can be used as a raw material for graphene exfoliation and device application. Published on 2023-04-10 00:00:00
  • Assessment of transverse thermal conductivity of coir fibre using
           experimental, analytical, and numerical methods

    • Abstract: Researchers aim to produce sustainable insulation materials using lignocellulose fibres (natural plant fibres). Lignocellulose fibres are readily available, biodegradable, and low-cost materials for insulation. However, these materials are formulated as composites and not as fibres alone. Thus, the thermal properties of these composites depend on the volume fraction of each phase. The evaluation of thermal conductivity can be followed by experimental, analytical, and numerical methods. Numerical and analytical methods are convenient investigational methods; they are more cost-effective, have a higher degree of flexibility in design enhancement, and are faster methods of analysing results than the experimental method. The thermal conductivity value of each phase should be used to analyse the thermal properties of composite materials. However, there is no specific method to determine the thermal conductivity of natural fibres. Therefore, this work suggests a new method to find the thermal conductivity of coir fibres. The method follows the inverse calculation of the analytical methods to find the thermal conductivity of coir fibres, and the substitution values for the equations will be determined by an experimental method. The two-phase composite was fabricated by coir fibres and epoxy with different volume fractions. Next, the thermal conductivity was measured for the fabricated composite and epoxy using the hot disk method. Finally, the transverse thermal conductivity of the fibre was calculated using available analytical models namely, the Rule of mixture, Maxwell’s model, Rayleigh’s model, and the Lewis-Nielsen model. The thermal conductivity value determined was 0.3058 W/mK. The results were validated through numerical modelling. The thermal conductivity of fibres was determined using a binderless compacted fibre disk, and the obtained value was 0.2797 W/mK.  This value was correlated with the results obtained with the analytical and numerical methods. Published on 2023-04-10 00:00:00
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