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Journal Cover Journal of the National Science Foundation of Sri Lanka
  [SJR: 0.166]   [H-I: 8]   [2 followers]  Follow
    
  This is an Open Access Journal Open Access journal
   ISSN (Print) 1391-4588
   Published by Sri Lanka Journals Online Homepage  [48 journals]
  • A taxonomic synopsis of Nymphaea nouchali Burm. f. And infraspecific taxa

    • Abstract: Nymphaea nouchali exhibits a range of flower colours, where some taxonomic circumscriptions consider the character as of taxonomic significance in recognising infraspecific taxa. The revision of the Sri Lankan Nymphaeaceae has not recognised any infraspecific taxa. N. nouchali populations exhibiting morphological variations within a range of floral colours were encountered during the field studies conducted in different parts of the country. Therefore, the present study was conducted with the objective of evaluating the morphological variations of N. nouchali populations using multivariate analyses of morphological and molecular sequence data. Both morphometric analysis using 59 characters and matK and trnH-psbA sequence data supported two subgroups within N. nouchali, clearly corresponding to the differences in flower colour; one group with blue flowers and the other with white and pink flowers. In addition, colour of the petiole and the leaf abaxial surface also supported the grouping. The study recognised two infraspecific taxa for N. nouchali in Sri Lanka, N. nouchali var. nouchali with blue flowers [‘Nil-manel’ (S); Blue water-lily (E)] and N. nouchali var. versicolour (Sims) Guruge and Yakandawala with either white or pink flowers. Recognising infraspecific taxa of N. nouchali in Sri Lanka is significant to the country not only to acknowledge its natural diversity, but in addition most importantly, as N. nouchali is the declared national flower of Sri Lanka. In this context, the recognition of the blue-flowered group as N. nouchali var. nouchali would strengthen its identity over the other flower-colour groups of N. nouchali. A taxonomic key for the Sri Lankan Nymphaea and descriptions for the two infraspecific taxa are also produced. Published on 2017-09-26 07:03:22
       
  • Bayesian estimation of 3-component mixture of Gumbel type-II distributions
           under non-informative and informative priors

    • Abstract: This paper deals with 3-component mixture of the Gumbel type-II distributions when the scale parameter is known under Bayesian view point. The type-I right censored sampling scheme is considered due to its extensive use in reliability theory and survival analysis, taking different non-informative and informative priors. Bayes estimates of the parameters of the mixture model along with their posterior risks are derived under different loss functions. In case where no or little prior information is available, elicitation of hyperparameters is given. In order to numerically study the execution of the Bayes estimators under different loss functions, their statistical properties have been simulated for different sample sizes and test termination times. The comparisons among the estimators have been made in terms of the corresponding posterior risks. A real life data example is also given to illustrate the study. Published on 2017-09-26 06:52:51
       
  • Morphometric analysis of watersheds in Kelani river basin for soil and
           water conservation

    • Abstract: Geomorphic behaviour of watersheds influences the soil erosion characteristics in river basins and is used to prioritise the watersheds for soil and water conservation. There is evidence of higher rates of soil erosion occurring in the Kelani river basin. Thus, soil conservation in this basin is crucial at present. This study was carried out to identify the priority within the Kelani river basin for soil and water conservation using GIS spatial environment. Kelani river basin was first delineated on the digital elevation model (DEM) of 15 × 15 m resolution. It was further sub divided into 20 watersheds (KB1 to KB20) using spatial analysis techniques in GIS. Morphometric parameters such as areal, linear and relief were calculated for the 20 watersheds and ranked considering the susceptibility to erosion. Final priority was assessed based on the compound value. Hypsometric integral was also calculated for the 20 watersheds, and the watersheds were classed as young, mature and old. The results showed that upstream sub watersheds KB18 and KB20 fell under very high priority for soil and water conservation and they were further sub divided (KB18.1 to KB18.6 and KB 20.1 to KB 20.8, respectively) to investigate the most prioritised areas for soil and water conservation. The results showed that KB18.5 and KB18.6, and KB20.1, KB20.2 and KB20.3 are the most susceptible areas for soil erosion in KB18 and KB20 watersheds, respectively. Significant higher correlation (- 0.529 at significant level 0.01) between the compound value and observed turbidity data validated the morphometric base priority for soil and water conservation in Kelani river basin. Results of the study can be utilised in watershed prioritisation for soil and water conservation in Kelani river basin in Sri Lanka. Published on 2017-09-26 06:40:53
       
  • Responses of explant type of wheat (Triticum aestivum L.) genotypes to
           different tissue culture media

    • Abstract: Wheat recalcitrance to in vitro culture is one of the most important and crucial steps for its genetic transformation, and is directly associated with the ability of the explant to regenerate, composition of the media and genotype. Callus induction and regeneration potential of various explants, viz, mature embryo, immature embryo, endosperm supported (ES) mature embryo and shoot apical meristem, taken from the same plants of two wheat genotypes (AS-2002 and GA-2002) were investigated using Murashige and Skoog (MS) basal callus induction medium supplemented with 2, 4, 6 or 8 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) and regeneration media comprising various combinations of auxins and cytokinins. In vitro culture response of the explants taken from the same plant varied from each other and was influenced by the genotype and media composition. Immature embryo culture of genotype AS-2002 exhibited the highest callusing ability (84.75 %) followed by the mature embryo culture of genotype GA-2002 (78.50 %). Similarly, immature embryos cultured on MS basal medium supplemented with 4 mg/L 2,4-D and mature embryos cultured on MS basal medium supplemented with 6 mg/L 2,4-D exhibited the highest callusing ability of 90.83 and 88.33 %, respectively. Immature embryos of genotype GA-2002 cultured on MS based regeneration medium supplemented with 0.2 mg/L 2,4-D, 0.5 mg/L zeatin and 0.5 mg/L benzylaminopurine (BAP) showed a significantly higher regenerating potential. ES mature embryos of genotypes GA-2002 and AS-2002 cultured on regeneration medium comprising 0.4 mg/L 2,4-D, 1.0 mg/L zeatin and 1.5 mg/L BAP showed maximum regeneration potentials of 59.67 and 59.0 %, respectively. Appraisal of the responses of the four explants used showed that endospermsupported mature embryo is the most suitable explant for plant regeneration in wheat. Published on 2017-09-26 06:37:32
       
  • Morphological, SSR and ISSR marker based genetic diversity assessment of
           mountain papaya germplasm in comparison with Carica papaya

    • Abstract: The genetic diversity in papaya cultivars is essentially important as it provides the basis for varietal improvement. In this regard a study was initiated to assess the genetic diversity of the commercial Carica papaya cultivars in Sri Lanka and to introduce mountain papaya (Vasconcellea cundinamarcensis), which is reported to contain cold resistance and papaya ring spot virus (PRSV-P) resistant trait. Twenty one accessions of Carica papaya and mountain papaya were assessed by morphological, simple sequence repeat (SSR) and inter simple sequence repeat (ISSR) markers. A total of 33 alleles were generated with an average frequency of 2.5 alleles per marker from 11 SSR and 2 ISSR markers. Morphological and molecular marker based cluster analyses revealed that there was no clear distinction among the C. papaya cultivars grown in different geographical areas in Sri Lanka, while mountain papaya was highly distinct from the other C. papaya accessions. Except three SSR markers, all the other markers were polymorphic between mountain papaya and C. papaya accessions. Of the 33 alleles produced, 12 alleles were common for both C. papaya and mountain papaya indicating the potential relatedness to C. papaya. This investigation revealed both the genetic diversity and the relatedness of mountain papaya with C. papaya so as to use it as a potential source for the improvement of C. papaya by hybridisation. Published on 2017-09-26 06:18:10
       
  • Phenol degradation by Acinetobacter sp. in the presence of heavy metals

    • Abstract: The purpose of this study was to investigate the ability of Acinetobacter sp. strain AQ5NOL 1 immobilised in gellan gum beads to degrade phenol in the presence of heavy metals. Seven different heavy metals, namely, As5+, Cu2+, Cd2+, Ni2+, Cr6+, Pb2+, and Hg2+ at 1 ppm were tested. Results of the study showed that degradation of phenol by free cells was inhibited by Hg2+, Cu2+ and Cr6+ after 48 hours of incubation by 97.91 %, 77.58 % and 75.26 %, respectively. Only Hg2+ and Cr6+ inhibited phenol degradation by immobilised Acinetobacter cells in 18 hours by 67.55 % and 53.19 %. Phenol degradation by immobilised cells was affected when Cr6+ and Hg2+ concentrations exceeded 0.5 and 0.1 ppm, respectively. However, inhibitory effects of heavy metals can be overcome by prolonging the incubation time for immobilised Acinetobacter sp. strain AQ5NOL 1 from 18 hours to 24 and 30 hours for Cr6+ (46.80 %) and Hg2+ (21.40 %), respectively. Published on 2017-09-26 06:01:43
       
  • Use of artificial neural networks and support vector machines to predict
           lacking traffic survey data

    • Abstract: The aim of this paper was to predict lacking data from a traffic survey along a principal highway in Bangladesh using artificial neural network (ANN) combined with the support vector machine (SVM). Traffic data were obtained at an hourly rate using a methodical inquiry over a four-year period at the Jamuna toll collection point, which is located along the North Bengal corridor of Bangladesh. Two evolutionary computational statistical procedures were used along with its corresponding numerical model. The neural network and SVM were fed with data from 13 recurring weeks over a fouryear period. The missing data were predicted with significant accuracy using both methods. Accuracy of the methods was compared, which showed that the SVM method is much more accurate than the ANN technique. Combination of both the ANN and SVM models can be used to obtain trends in traffic data more accurately. Published on 2017-09-26 05:54:13
       
  • The molecular evolution of Ghd7 orthologs is not in line with the
           speciation events in genus Oryza

    • Abstract: Under long day conditions, the grain number, plant height, and heading date7 (Ghd7) is a key regulatory gene in the rice specific flowering pathway, with significant pleotropic effects on yield related traits such as the number of spikelets per panicle, and heading date. The Ghd7 codes for a CO, COLIKE and TIMING OF CAB1 (CCT) domain, which is unique from the other CCT family proteins. In the current study, the evolutionary relationships of putative orthologs of Ghd7 within the genus Oryza is assessed via computational approaches. The relationships were deduced based on the nucleotide diversity, gene tree and synteny of Ghd7 orthologs of nine Oryza species using genomic, coding, and polypeptide sequences of the putative Ghd7 orthologs and adjacent genes retrieved from the Gramene database. The coding sequences (CDS) were found to be highly conserved (> 95 %) across the Oryza species, including the CCT domain. The length and the composition of the exons were not conserved between species. The exonintron boundaries depicted an intron phase where codons in exons were not interrupted by introns. The reconstructed gene tree revealed earlier divergence of Oryza brachyantha (diploid F genome) and Oryza punctata (diploid B genome) from the diploid species carrying an A genome. The A genome carriers were grouped into two strongly supported monophyletic clades, with clear separation of the Asian-origin species from the African-origin species. The movement of the syntenic blocks comprising putative orthologs of Ghd7 and its adjacent genes in 0.5 Mbp region revealed complex relationships, especially in ancestral species and species with African descent as the 1:1 putative orthologs were found in non-predictor chromosomes. Hence, the evolutionary pathway of Ghd7 was found to be complex and was governed by geographic origins, and gene movement across syntenic and non-syntenic regions. Published on 2017-09-26 05:43:56
       
  • Synthesis of novel porous tannin-phenol-formaldehyde cation exchange resin
           from Terminalia arjuna (Kumbuk)

    • Abstract: Natural tannins have a high affinity to absorb metal ions, proteins and some other biomolecules. In this study, tannins extracted from Terminalia arjuna (Kumbuk) were used to synthesise renewable tannin-phenol-formaldehyde resin systems and a porous modified resin system. A series of resin systems was synthesised by varying the incorporated phenol content. The ion exchange capacities of the resins produced were studied and the resin with the highest ion exchange capacity was selected. It was sulfonated to increase the properties further. A monovalent cation, Na+ was used to estimate the adsorption properties of both sulfonated and unsulfonated resin systems. Solubility and swelling properties of the resins were measured to check their applicability as an ion exchanger in aqueous media at different pH values. Fourier transform infrared spectroscopy (FTIR) analysis was carried out to characterise the synthesised resins. Scanning electronic microscopic (SEM) images were obtained to study the morphology of the resins produced. Sulfonated tannin-phenolformaldehyde resin with the tannin/phenol ratio of 1:1 showed the highest adsorption capacity for the metal ion used (Na+), which was 1.552 meq/g.To increase the surface area and to gain an efficient flow rate, a porous tannin-phenol-formaldehyde resin system was prepared. Synthesis was carried out using hexamethylenetetramine as both the cross linker and the catalyst. Coconut oil was used as the porogenic agent to create the porous structure through emulsion templating process. Synthesised porous resin contains μm and nm scale porous structures. Published on 2017-09-26 05:41:08
       
  • Aerodynamics and right-left symmetry in wind dispersal of maple,
           dipterocarps, conifers and some genera of apocyanaceae and magnoliaceae

    • Abstract: The wind dispersing seeds have evolved remarkable aerodynamic optimisation to minimise the speed of descent on detachment from the tree, so that they could be carried away by the wind and deposited a distance away from the parent. An efficient physical mechanism that enables slowing down the descent is rotation, which reduces the translational kinetic energy. Rotation and translation always define a right or left-handedness. The present work examines the aerodynamics of the dispersal of seeds of many species in relation to right-left asymmetry, giving examples to show that in nature this symmetry is broken either spontaneously or intrinsically. In the former situation, seeds have no geometrical right-left asymmetry, but an initial instability chooses one sense of rotation (right or left). Whereas in the latter, geometrical asymmetry dictates the sense of rotation. Seeds of the maple familiy belongs to the first category and a theortical model is presented to explain the motion. Seeds of dipterocarps, conifers and some genera of apocyanaceae and magnoliaceae are found to possess a handedness, which determines the rotation during seed fall. In dipterocarps, conifers and magnoliaceae, both right-handed and left-handed seeds are produced in the same tree but correlated to the handedness of the sprial phyllotaxy of the branch that bears the fruit. Apocyanaceae is found to be unique and seeds of all genera have the same handedness. The details of extensive field observations, experiments and theoretical interpretations are presented to illustrate the relationship of right-left asymmetry to the aerodynamics of seed wind dispersal, pointing out the implications of evolutinary optimisation in practical aerodynamics. Published on 2017-09-26 05:30:29
       
 
 
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