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Journal of the National Science Foundation of Sri Lanka     [SJR: 0.144]   [H-I: 4]
   [3 followers]  Follow    
  This is an Open Access Journal Open Access journal
   ISSN (Print) 1391-4588
   Published by Sri Lanka Journals Online Homepage  [45 journals]
  • Subject Index Vol 42-2014

    • Authors: The Editor
      PubDate: 2014-12-29
      Issue No: Vol. 42 (2014)
       
  • List of Referees volume 42 (2014)

    • Authors: The Editor
      PubDate: 2014-12-29
      Issue No: Vol. 42 (2014)
       
  • Author Index Vol 42-2014

    • Authors: The Editor
      PubDate: 2014-12-29
      Issue No: Vol. 42 (2014)
       
  • Back-bending phenomena in even-even 110-118Te isotopes

    • Authors: I Hossain, M Hussein, SA Mansour, J Islam
      Abstract: In the present study the back-bending phenomena of moment of inertia are described at high-spin yrast bands of even-even 110-118Te isotopes. The Fermi energy, square of rotational frequency and the moment of inertia of the nuclei have been calculated from available experimental data. An interesting nuclear feature emerging from this study concerns the evolution of the moment of inertia, and the yrast line indicates about the nuclear shape. Fermi energy and the moment of inertia as a function of even neutron number of 110-118Te isotopes have been studied systematically. The moment of inertia as a function of the square of the rotational energy for even neutrons N = 58 to 66 in Te isotopes indicates the nature of back-bending properties. The investigation of back-bending phenomena in ordinary space for even-even Te isotopes with even neutron N = 58 to 66 are carried out and compared with gauge space.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7732 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 335-339
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Bayesian analysis of doubly censored lifetime data using two component
           mixture of Weibull distribution

    • Authors: Navid Feroze, Muhammad Aslam
      Abstract: In recent years analysis of the mixture models under Bayesian framework has received considerable attention. However, the Bayesian estimation of the mixture models under doubly censored samples has not yet been reported. This paper proposes a Bayesian estimation procedure for analyzing lifetime data under doubly censored sampling when the failure times belong to a two-component mixture of the Weibull model. An extended version of the likelihood function for doubly censored samples for the analysis of a mixture of lifetime models has been introduced. The posterior estimation has been considered under the assumption of gamma prior using a couple of loss functions. The performance of the different estimators has been investigated and compared through the analysis of simulated data. A real-life example has been included to demonstrate the practical applicability of the results. The results indicated the preference of the estimates under squared logarithmic loss function (SLLF) for the estimation of the mixture model. The proposed method can be extended for more than two component mixtures.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7731 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 325-334
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • A new record of Fulvifomes fastuosus from Sri Lanka

    • Authors: SS Ediriweera, RLC Wijesundera, CM Nanayakkara, OVDSJ Weerasena
      Abstract: The fungus Fulvifomes fastuosus has not been described from Sri Lanka to date. Morphological studies and DNA analysis were carried out to characterize the fungus. Accordingly, F. fastuosus produces perennial, pileate, solitary and hard basidiomes with a concentrically sulcate pileal surface and homogenous context. It consists of a dimitic hyphal system and yellowish brown acyanophilous basidiospores but lacks hymenial setae. Eventhough the same species has been recorded in China with similar characters, the size of spores and hyphae are comparatively less in the specimen described in the present study. The identity was confirmed by sequencing the internal transcribed spacer (ITS) region in the nuclear ribosomal repeat unit, using the primers ITS1F and ITS4B. The resultant DNA sequence showed the highest similarity with Fulvifomes fastuosus strain CBS 213.36, reported from South Korea.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7737 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4):369-371
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Anticancer and antioxidant effects of selected Sri Lankan marine algae

    • Authors: HH Chaminda Lakmal, Kalpa W Samarakoon, WonWoo Lee, Ji-Hyeok Lee, DTU Abeytunga, Hyi-Seung Lee, You-Jin Jeon
      Abstract: For the investigation of bioactive components from Sri Lankan seaweeds, three species of red algae (Chondrophycus ceylanicus, Gelidiella acerosa, Gracilaria corticata), two species of green algae (Chaetomorpha crassa, Caulerpa racemosa) and one species of brown algae (Sargassum cassifolium) were evaluated. For the bioactivity evaluations, total phenol content (TPC), free radical scavenging activity using electron spin resonance (ESR) spectroscopy and anticancer activity against different cancer cell lines including a human promyelocytic leukemia (HL-60), a human lung carcinoma (A549) and a mouse melanoma (B16F10) were assessed in vitro. Among the extracts, C. racemosa showed significantly higher radical scavenging activity against DPPH (34.34 %), alkyl (85.17 %) and hydroxyl radicals (81.16 %), respectively. The MTT assay confirmed that all the extracts were not cytotoxic at 50 and 100 μg/mL concentrations against vero cells in vitro. In addition, a significant cancer cell growth inhibitory effect (IC50 value 30.17 μg/mL) was observed by C. racemosa methanol extract against HL-60 cells and it was the highest anticancer effect compared to the other extracts. Apoptotic body formation in HL-60 cells and the accumulation of DNA in sub-G1 phase were determined by C. racemosa extract in a dose-dependent manner. This study is the first report of Sri Lankan seaweeds with the potential of pharmacological effects including antioxidant and anticancer activity in vitro.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7730 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 315-323
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Antimicrobial and antioxidant activities of Kingiodendron pinnatum (DC.)
           Harms and Humboldtia brunonis Wallich: endemic plants of the Western Ghats
           of India

    • Authors: Sana Sheik, KR Chandrashekar
      Abstract: The leaf and stem extracts of two endemic plants, Kingiodendron pinnatum (DC.) Harms and Humboldtia brunonis Wallich of the family Fabaceae were subjected to phytochemical analysis, antimicrobial and antioxidant assay. Phytochemicals such as phenols, flavonoids, tannins, glycosides and terpenes were present in both plants. The antibacterial and antifungal activity assays were carried out using the disc diffusion method. Antioxidant activity was carried out using DPPH radical scavenging and reducing power assays with ascorbic acid as the standard. The extracts inhibited six bacterial strains and one fungal strain. Among the solvent extracts, the methanol extract was the most effective against the tested microorganisms and it also exhibited the highest antioxidant activity. Total phenols and flavonoids were determined using the Folin-Ciocalteau and aluminium chloride methods and correlated with the antioxidant activity.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7729 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 307-313
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Purification of xylanase produced by Bacillus pumilus

    • Authors: Ranganathan Kapilan, Vasanthy Arasaratnam
      Abstract: This study was aimed at purifying xylanase produced by Bacillus pumilus. The spent medium contained 27.9 UmL-1 xylanase activity and 1.5 mgmL-1 protein. The highest specific activity (33.7 Umg-1 protein) was achieved with 50 % (NH4)2SO4 saturation and the xylanase recovery was 94.8 %. The dialyzed and DEAE-Sepharose purified enzyme showed 6.7-fold increase in specific activity with a yield of 84.2 %. Molecular weight of the purified xylanase was 55.4 KDa. Thus B. pumilus xylanase can be purified by precipitating with 50 % (NH4)2SO4 saturation and DEAE-Sepharose ion exchange chromatography.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7736 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4):365-368
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Austroeupatorium inulifolium invasion increases arbuscular mycorrhizal
           abundance in Cymbopogon-dominated grasslands in Knuckles Conservation Area
           

    • Authors: HMSP Madawala
      Abstract: Plant invasions can interfere with above- and belowground dynamics of ecosystems, which eventually alter the ecosystem functions. However, relatively less attention has been drawn to assess the impacts of invasion on the soil microbial community. Austroeupatorium inulifolium has been spreading into different landuse types in the Knuckles Conservation Area (KCA) for the last few years, including Cymbopogondominated grasslands. Therefore, the study investigated whether this invasion has altered the arbuscular mycorrhizal fungal (AMF) abundance and the diversity in these grasslands through isolation and identification of AMF spores in three different habitats, namely less- and highly-invaded grasslands (LIG and HIG, respectively) and nearby lower montane forest patch (LMF), which is free of Austroeupatorium invasion. The results revealed that the invasion has significantly increased the AMF spore abundance. However, the LMF reported the highest AMF diversity compared to invaded grasslands. AMF richness showed no difference between the habitats. The results highlighted the importance of investigating the changes caused to the soil microbial community due to invasions and their implications for site restoration.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7735 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 361-364
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Surface modification of silica with a hydrophilic polymer and its
           influence on reinforcement of natural rubber latex

    • Authors: MCW Somaratne, NMVK Liyanage, S Walpalage
      Abstract: Surface modification of precipitated silica particles was carried out in both aqueous and non aqueous media separately with a polyacrylic based hydrophilic polymer synthesized in the laboratory. FTIR spectroscopy and thermo gravimetric analysis of the modified and unmodified silica particles were performed to confirm successful surface modification. Colloidal stability of the aqueous dispersions of the unmodified/modified silica particles were observed at different pH levels. The dispersions at neutral pH were incorporated in different proportions to un-compounded and compounded natural rubber latex (NRL) separately and thin latex films were produced from them by casting. Dispersability of silica particles within the rubber matrix was examined through microstructure studies of films cast from unmodified/modified silica incorporated un-compounded NRL. The influence of surface modification upon the reinforcement of NRL was investigated through tensile and tear strength properties of vulcanized NRL cast films containing modified silica. The uniform dispersion of silica particles and the improved mechanical properties envisaged better compatibility of modified silica particles with NRL by means of interfacial interactions. A significant improvement in the mechanical properties was observed in the films produced with 5 – 7 phr of modified silica.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7734 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 351-360
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • A reaction-diffusion type mathematical model for the formation of coral
           patterns

    • Authors: LW Somathilake, JR Wedagedera
      Abstract: A reaction-diffusion type mathematical model for the growth of corals in a tank has been proposed based on the model suggested by Mistr and Bercovici, emphasizing the effect of nutrient concentration and domain size on growth patterns. The Turing type pattern formation of the proposed model has been considered and the pattern formation parameter spaces (Turing spaces) of the model were determined. The model is solved numerically when the parameters lie in Turing space and the results are represented graphically. These numerical solutions resemble branching structures of some branching corals. It has been observed that the behaviour of the branching structures vary with parameter values as well as the considered domain size (dimensions of the tank).
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7733 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 341-349
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Genetic parameters and correlations of yield attributing characteristics
           of weedy rice in Sri Lanka

    • Authors: UIP Perera, Disna Ratnasekera, SGJN Senanayake, D Sumith de Z Abeysiriwardena
      Abstract: Weedy rice possesses a high diversity in yield attributing characteristics and is an important resource for rice improvement programmes. The present investigation was carried out to estimate the genetic parameters and the correlations of yield attributing characteristics of weedy rice using 370 weedy rice accessions in Sri Lanka. Analysis of variance revealed significant differences (p < 0.05) among the weedy rice accessions for all the characteristics studied, implying the presence of a substantial amount of genetic variability and scope for selection. Shattering percentage, total number of spikelets per plant and the number of filled seeds per panicle exhibited high genotypic and phenotypic coefficients of variation. The degree of difference between phenotypic and genotypic coefficients of variation was relatively low for all the characteristics, except for the total number of spikelets per panicle, indicating comparatively less environmental influence. Very high heritability values coupled with very high genetic advance were observed for the shattering percentage, total number of spikelets per plant and the number of filled seeds per panicle. High heritability values coupled with high genetic advance were recorded for height at the booting stage, number of panicles per plant and tiller number at the seedling and booting stages suggesting the prevalence of additive gene action in the expression of these characteristics and the possible selection for effective improvement based on their phenotypic performance. Correlation studies showed that simply selecting comparatively taller plants with long seeds would identify high yielding weedy rice plants, which may be used in rice improvement programmes.
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7728 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 299-306
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
  • Computer modelling and simulation: essential research tools

    • Authors: ND Kodikara
      Abstract:
      DOI : http://dx.doi.org/10.4038/jnsfsr.v42i4.7727 J.Natn.Sci.Foundation Sri Lanka 2014 42 (4): 297-298
      PubDate: 2014-12-03
      Issue No: Vol. 42 (2014)
       
 
 
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