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  Journal of the National Science Foundation of Sri Lanka
  [SJR: 0.16]   [H-I: 5]   [1 followers]  Follow
    
  This is an Open Access Journal Open Access journal
   ISSN (Print) 1391-4588
   Published by Sri Lanka Journals Online Homepage  [45 journals]
  • The host preference of a Ganoderma lucidum strain for
           three tree species of Fabaceae family; Cassia nodosa,
           Cassia fistula and Delonix regia

    • Abstract: Root and butt rot of Cassia nodosa, Cassia fistula and Delonix regia is caused by Ganoderma lucidum. Ganoderma root and butt rot is a lethal disease on C. nodosa, C. fistula, and D. regia trees, and G. lucidum was identified as the causal organism of this disease. Susceptibility of these host trees was higher when infected at a young age. All infected trees regardless of the age died after 6-24 months from the appearance of the first sign of the disease. Of these three susceptible host species, C. fistula was the most susceptible host, dying six months after the first visible sign of the disease. Host preference of G. lucidum was demonstrated when new healthy C. nodosa, C. fistula or D. regia trees were infected while bypassing other tree species including species of Fabaceae family, which were growing in the close vicinity of the infected trees. Keywords: Ganoderma lucidum, landscape trees, root and butt rot.   doi:10.4038/jnsfsr.v36i4.271   Journal of the National Science Foundation of Sri Lanka 36 (4) 323-326 Published on None
       
  • Effects of water borne cadmium on biomarker enzymes and metallothioneins
           in Nile tilapia, Oreochromis niloticus

    • Abstract: Cadmium is widely used in modern industry and ranks among the most toxic metals in the aquatic ecosystems. In the present study, activities of several biomarker enzymes viz. ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST) and cholinesterase (ChE) were determined in Nile tilapia (Oreochromis niloticus) at different waterborne Cd22+ exposure levels (0, 0.001, 0.005, 0.01, 0.1, and 1 mg/L for 28 days) to evaluate the potential influence of environmental cadmium on these enzymes. In addition, hepatic metallothionein (MT) levels in these fish at different waterborne Cd2+ exposure levels were also studied to evaluate their response to waterborne cadmium exposure. The results revealed that hepatic MT levels in the fish exposed to Cd2+ increased 2-26 fold depending on the exposure level and duration. Hence hepatic MT in Nile tilapia is a sensitive biomarker to indicate cadmium pollution in the natural environments. Continuous exposure of fish to ≤ 0.01 mg/L of Cd2+ had no significant effect on hepatic EROD, hepatic GST and brain and muscle ChE activities whereas exposure to ≥ 0.1 mg/L Cd2+ evoked time dependent significant depression of hepatic EROD (41-55%) activity. Brain and muscle ChE activities of the fish exposed to 1 mg/L Cd2+ were depressed to 24-32% and 33-35% respectively. Results revealed that high concentrations of Cd2+ in the natural environments could inhibit the basal activities of the hepatic EROD and brain and muscle ChE in Nile tilapia affecting the normal functioning of these biomarker enzymes and influencing the biomarker response to targeted organic pollutants in the environment. Keywords: Biomarkers, cadmium, metallothionein, tilapia.   doi:10.4038/jnsfsr.v36i4.270   Journal of the National Science Foundation of Sri Lanka 36 (4) 315-322 Published on None
       
  • Copper availability and selective microbiological properties of an
           intensively cultivated ultisol in Nuwara Eliya

    • Abstract: A study was undertaken to assess the effect of copper on microbiological properties of intensively cultivated vegetable fields at Nuwara Eliya. Soil samples were collected from six cultivated fields and an undisturbed forest were assessed for pH, total and DTPA extractable Cu, biomass nitrogen (BN) and substrate induced respiration (SIR). Total and Cu-resistant bacteria were enumerated using four agar media. Soil pH of experimental soils ranged from 4.44 to 5.44. Organic C content in cultivated soils varied from 1.8 to 3.3 % and it was 6.8% in forest soil. Total and DTPA extractable Cu contents varied from 14.4 to 25.6 mg kg-1 and 1.2 to 4.5 mg kg-1, respectively. Forest soil showed the highest SIR (46 μg CO2 g-1 soil h-1) and BN (267 μg N g-1 soil). The highest Cu-resistant bacterial population was 0.43% of the total population reported for the forest. Building up of Cu and increasing of population of Cu-resistant bacteria was not evident due to cultivation. The percentage of Cu-resistant bacteria correlated positively with DTPA extractable Cu (R = 0.49) suggesting that threshold Cu levels for bacterial growth in experimental soils remain within the range of extractable Cu concentrations reported. This relationship was influenced by soil organic C content and pH. Tryptic soy agar (TSA) medium produced higher percentages of Cu-resistant bacteria for both forest and cultivated soils. Those percentages showed linear relationships with total Cu (r2 = 0.95) and percentage of DTPA extractable Cu (r2 = 0.94) indicating suitability of the TSA medium to enumerate Cu-resistant bacteria. Keywords: Bacteria, copper, cultivated ecosystems, organic carbon, pH.   doi:10.4038/jnsfsr.v36i4.269   Journal of the National Science Foundation of Sri Lanka 36 (4) 307-313 Published on None
       
  • Ising model across planar lattices

    • Abstract: The Ising model on a two dimensional lattice with pentagon tiling and greater number of next to neighbours interaction is equivalent to the Ising model on the centered square lattice with nearest and next to nearest neighbour non-crossing interactions. We obtain exact expressions on calculation of critical temperature with ferromagnetic and anti-ferromagnetic interactions. A direct anti-ferromagnetic bond of strength α L can give rise to the transition temperatures for appropriate α. We apply the star-triangle mapping transformation technique and decorating transform to Ising model. Keywords: Exact results, Ising model, square lattice, transformations.   doi:10.4038/jnsfsr.v36i4.268   Journal of the National Science Foundation of Sri Lanka 36 (4) 303-305 Published on None
       
  • Gauge-invariant 3D Ising actions

    • Abstract: We formulate gauge-invariant Ising models in three dimension, which describe the open surface version of the Gonihedric Ising models. The energy of these open surfaces does not depend on their area but rather on the number of plaquettes meeting at right angles and the length of boundaries and "seams" where three plaquettes intersect. The models thus describe a gas of open surfaces with rigidity but no bare surface tension. Using mean field techniques, we obtain solutions to zero temperature phase diagram. Keywords: Ising model, mean field theory, open surface solutions.   doi:10.4038/jnsfsr.v36i4.267   Journal of the National Science Foundation of Sri Lanka 36 (4) 299-302 Published on None
       
  • Phylogenetics of the endemic genus Stemonoporus Thw.
           (Dipterocarpaceae)

    • Abstract: Stemonoporus Thw. is the most species-rich (27 species) endemic dipterocarp genus in Sri Lanka. All its members are categorized as highly threatened or threatened in the IUCN Red Data Book. The existing classifications of the genus are primarily based on traditional taxonomic methods using a limited number of collected material and sometimes mainly on herbarium specimens. A recent study carried out in order to evaluate the species limits of Stemonoporus strengthens its position as the most species-rich endemic dipterocarp genus in Sri Lanka. However, there are no phylogenetic studies being carried out on this important genus. The aim of the study was to construct the phylogeny of the genus Stemonoporus, using morphological and phytochemical data. Specimens of all representative taxa were sampled from different geographical locations. A total of 170 specimens were collected and six individuals per taxon were examined. Cladistic analysis was performed based on morphological and phytochemical data extracted from specimens collected from different geographical locations and herbarium specimens. Combined analysis of morphological and phytochemical data suggests that all the species except for Stemonoporus wightii form a monophyletic group with strong bootstrap support of 82%. The strict consensus tree of the combined analysis identifies eight monophyletic groups within the genus Stemonoporus. S. wightii was resolved as the basal taxon of the genus. The identified 27 species are supported as monophyletic groups. Keywords: Dipterocarpaceae, morphological data, phylogeny, phytochemistry, Stemonoporus.   doi:10.4038/jnsfsr.v36i4.266   Journal of the National Science Foundation of Sri Lanka 36 (4) 281-297 Published on None
       
  • Chromosome substitution lines for the analysis of heterosis in
           Arabidopsis thaliana

    • Abstract: Heterosis is an important phenomenon used in agricultural crop improvement for several decades. The molecular basis of heterosis is still unclear despite the wide exploitation of heterosis for improving economically important traits of crops. The current experiment investigates the heterosis related to several morphological traits in Arabidopsis thaliana on an individual chromosome basis of cr. Whole chromosome substitution lines (CSLs) of chromosomes three, four and five of Arabidopsis, recurrent parent Columbia and the three relevant F1 progenies were grown in a growth chamber in a completely randomised experimental design for the scoring of morphological traits. Data were analysed to detect the presence or absence of heterosis for each trait on per-chromosome basis. The traits rosette width at day 20, flowering time, height at flowering time, rosette and cauline leaf numbers at flowering displayed significant heterosis in different chromosomes. The findings revealed the presence of both positive and negative heterosis for rosette leaf number at flowering on different chromosomes. Genetic components of the means and the potence ratios indicated those parents having more dominant alleles in the cross in each chromosome. The results indicated the appropriateness of CSLs in studying heterosis in a micro scale rather than the whole genome level. The study demonstrates that breeding programmes can be designed to keep the desirable effects and remove the disadvantageous effects of heterosis caused by the genes present in different chromosomal parts in the genome. Keywords: Arabidopsis, chromosome substitution lines, heterosis.   doi:10.4038/jnsfsr.v36i4.265   Journal of the National Science Foundation of Sri Lanka 36 (4) 275-280 Published on None
       
  • Exact critical points for testing subhypotheses in nonreplicated three-way
           experiments

    • Abstract: In the absence of replication, conventional analyses do not provide ways to examine three-way interaction in threeway experiments. Tucker3 analysis based on alternating least squares algorithm is a general approach that can be used in such cases. However, Tucker3 options are not available with standard statistical packages. A few methods for estimating σ2 and testing for three-way interaction using a "single component" Tucker3 model are available in literature. A method based on a convenient approximation to a likelihood ratio test is also available in limited cases for testing three-way interaction in sub-areas once interaction is present. In this paper the null distribution of the above likelihood ratio statistic is simulated using Monte Carlo methods based on exact values obtained from Tucker3 analysis. Critical points are also obtained for the test for selected cases. Though the package 3-WAY PACK® handles Tucker3 analysis it does not conveniently support WINDOWS® based simulations and therefore MATLAB® is used for the simulation. The method is illustrated using two examples involving real data. Keywords: Exact critical points, testing subhypotheses, three-way interaction, tucker3 analysis.   doi:10.4038/jnsfsr.v36i4.264   Journal of the National Science Foundation of Sri Lanka 36 (4) 267-273 Published on None
       
  • What constitutes the enterprise of Modern Science'

    • Abstract: This essay is addressed to young people at the beginning of their careers in scientific research, as much as to those concerned with education and governance in science. It considers the question- what is science, what are the processes of scientific discovery, and what pathways did science take to reach its status as the greatest intellectual achievement of Man' It emphasizes the dichotomy between Moral Philosophy and Natural Philosophy while pointing out that it is Natural Philosophy that is now known as Modern Science. It highlights the lack of knowledge of some critical areas in scientists of the country, notably the philosophy of modern science that characterizes a practitioner as a literate scientist and not as a mere technician. The essay also considers some historical aspects that underlie the growth of Modern Science, and the limitations of science which again seem to be missing from the education in science that is present in our country. Of particular interest are the determinants of the growth of science, an awareness of which is necessary for our education in science if we are to take meaningful steps towards its growth; these include the establishment of a scientific attitude especially in young people, the methodologies that a practitioner should engage in, and the state's support for science through relevant and effective policies, and their implementation. Keywords: Modern Science, scientific enterprise, scientific literacy.   doi:10.4038/jnsfsr.v36i4.263   Journal of the National Science Foundation of Sri Lanka 36 (4) 257-266 Published on None
       
  • Science, technology and sustainable development

    • Abstract: doi:10.4038/jnsfsr.v36i4.262 Journal of the National Science Foundation of Sri Lanka 36 (4) 255-256 Published on None
       
 
 
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