for Journals by Title or ISSN
for Articles by Keywords
Followed Journals
Journal you Follow: 0
Sign Up to follow journals, search in your chosen journals and, optionally, receive Email Alerts when new issues of your Followed Journals are published.
Already have an account? Sign In to see the journals you follow.
Journal Cover Journal of the National Science Foundation of Sri Lanka
  [SJR: 0.166]   [H-I: 8]   [1 followers]  Follow
  This is an Open Access Journal Open Access journal
   ISSN (Print) 1391-4588
   Published by Sri Lanka Journals Online Homepage  [48 journals]
  • Effect of genotype, embryo maturity and culture medium on in vitro embryo
           germination of Sri Lankan coconut (Cocos nucifera L.) varieties

    • Abstract: Poor in vitro germination of embryos of exotic varieties was reported as one of the major constraints faced during coconut germplasm exchange programmes. In this study, the effect of genotype, embryo maturity and culture medium on in vitro germination of coconut embryos was investigated. A significant effect (p < 0.05) of genotype on in vitro germination was observed between the selected cultivars, San Ramon Tall (SNRT) (77.48 %), Sri Lanka Red Dwarf (SLRD) (67.28 %), Sri Lanka Green Dwarf (PGD) (71.85 %) and King Coconut (RTB) (52.5 %). Embryo germination percentages were improved in solid media (91.66 % and 92.22 % in 75 g/L and 60 g/L sucrose respectively, p < 0.05) than in liquid media (56.66 % and 60.46 % in 75 g/L and 60 g/L sucrose, respectively) and the sucrose concentration has no effect on germination of SLRD embryos. Furthermore, maturity of the nut significantly affected the germination (p < 0.05) of embryos of PGD and the highest in vitro embryo germination was achieved by culturing embryos of the 12 month old bunch (97.67 %), while the lowest was observed in the 10 month old bunch (52.17 %). Addition of growth hormones favoured root growth of in vitro raised SLRD plants with a significant increase in the number of primary roots and the number of leaves (p < 0.05) when 10 μM BAP, 10 μM Kinetin and 200 μM NAA were added to the embryo culture medium. Published on 2016-09-28 08:00:29
  • An information rich subspace separation for non-stationary signal

    • Abstract: This paper proposes a novel automated approach for the classification of highly non-stationary signals based on a non-principal component analysis (non-PCA) methodology. This method generates an eigen analysis based pseudospectrum to emulate the spectral characteristic variations of the non-stationary signals to be classified. Then, the estimated pseudo-spectrum is used to implement a comb like subspace filter structure, which captures the variations of all significant spectral components throughout the whole observation period. It is shown that this filter implementation method yields better results than the existing dimensionality reduction methods, which only utilise the principal k components of the eigen space. Finally, a novel probabilistic approach which creates a signature vector representing each class of signals in the training phase is proposed for the classification process. It is also shown that the proposed method can be effectively used not only for classification but also for the extraction of hidden stationary signature features from a non-stationary signal. Further, it is also proven that the proposed subspace filtering scheme can be used as a dynamic spectral estimation technique, which can eliminate the time frequency resolution tradeoff that exists in techniques such as short-time fourier transform (STFT). Published on 2016-09-28 07:52:46
  • Zero-current-switching pulse charger for high capacity batteries in
           renewable energy applications

    • Abstract: Fast charging of high capacity batteries is of great concern, especially in renewable energy and electric vehicle (EV) applications. Pulse charging has become the preferred method for fast charging with heavy currents. However, it presents drawbacks due to switching losses involved in hardswitching of semiconductor devices. This paper presents a soft switched pulse charging mechanism for high capacity Pb-acid and Li-ion batteries, which minimises switching losses that makes the methodology very suitable for implementing the National Electric Code (NEC) level-1, level-2 chargers or specially the level-3 charger more conveniently for EVs. The fully clamped quasi-resonant DC link (FCQDL) converter generates current pulses to charge the battery in a zero-current switching (ZCS) manner to minimise switching losses. The simulated and experimental results show that the proposed charger can implement constant current (CC) and constant voltage (CV) modes of charging. The experimental results show that the proposed charging methodology reduces the charging time of Pb-acid batteries by 14.01 % in contrast to the conventional CC-CV charging method. Furthermore, discharging curves for the conventional and pulse charging methods are compared to evaluate the effective useful charge that is put into the battery. The results reveal that the effective charge capacity of a battery is significantly improved due to the use of pulse charging. Published on 2016-09-28 08:20:25
  • Application of pollution indices to quantify the pollution status of
           shallow sediments of the Bolgoda Lake, Sri Lanka

    • Abstract: The present study was conducted to assess the pollution status of the shallow sediments of the Bolgoda Lake in Sri Lanka using sediment pollution indices. Shallow sediment samples were collected as replicates from five sites with different land uses in the monsoonal and nonmonsoonal seasons in 2013. The samples were acid digested and analysed for Cd, Cr, Cu, Ni, Fe and Zn. The heavy metal concentrations were used to calculate: (1) contamination factor (Ci f ); (2) degree of contamination (Cd); (3) pollution loading index (PLI); (4) enrichment ratio (ER); (5) geoaccumulation index (Igeo) and (6) ecological risk factor (Eri ) of the shallow sediment samples. In addition, the quality of the sediments were also assessed by comparing with the numerical sediment quality guidelines (SQGs) and consensus-based sediment quality guidelines (CBSQGs).Significant spatial variations of element concentrations and sediment quality indices were identified in the study area. The pollution level of the study sites ranged from unpolluted to heavily polluted due to heavy metals. The contamination factors for all the heavy metals except Zn indicated moderate, considerable or very high level of pollution in both sampling sessions. The potential ecological risk factor for the heavy metals ranked as Cd > Ni > Cr > Cu > Zn for both sampling sessions indicating the highest potential ecological risk from Cd. The pollution load index for all the study sites except site E in both sampling sessions showed human associated pollution with a PLI higher than 1. All the samples were categorised into class 1 (unpolluted to moderately polluted status) with respect to Cr, Ni, Cu and Zn and to class 0 (unpolluted status) with respect to Cd.The concentrations of Zn and Cd in the present study were lower than the threshold effect concentration (TEC) level of CBSQGs and therefore, was indicated as unlikely to be causing toxicity to benthic organisms. The concentrations of Cr and Ni were higher than the probable effect concentration (PEC) level of CBSQGs and indicated a probable toxicity to benthic organisms. Published on 2016-09-28 08:08:35
  • Zinc content and prediction of bio-availability of zinc in some locally
           grown rice (Oryza sativa L.) varieties in Sri Lanka

    • Abstract: Rice is the staple food in Sri Lanka and the country has a large number of traditional and improved rice varieties. Since their zinc content and bio-availability has not been studied systematically, the present study focused on the zinc content in some traditional rice varieties with high demand and also some improved rice varieties, and their predictable bioavailability.Thirty nine rice varieties from Bombuwala and Bathalagoda Regional Agricultural Research and Development Centres, grown during Yala (March - August, 2006) and Maha (September - March, 2006 ⁄2007) seasons were analysed for stable high zinc rice varieties. Mean zinc content (mg/100 g, on dry weight basis) in the varieties from Bathalagoda varied from 2.17 (Masuran) to 4.49 (Wanni Dahanala), while in the varieties from Bombuwala it varied from 2.46 (Bg 352) to 3.71 (Dahanala) with average values of 3.19 ± 0.55 and 3.11 ± 0.32, respectively. Overall mean zinc content (mg/ 100 g, on dry basis) in the two locations varied from 2.51 (Masuran) – 3.91 (Kalu Bala Wee) with an average value of 3.18 ± 0.45. The mean zinc contents varied significantly (p ≤ 0.05) with varieties. A significant variation (p ≤ 0.05) was observed with respect to the site, season, variety, site*var and ses*var in two way ANOVA, while site*ses*var showed a significant variation in three way ANOVA. The reduction of zinc and phytic acid contents in the selected fifteen polished rice varieties (at polishing rate 8 – 10 %) were 18.2 – 60.7 % and 18.8 – 40.8 %, respectively and no significant correlation was observed between zinc and phytic acid. A moderate bio-availability of zinc was shown by the molecular ratio of zinc:phytic acid and these values ranged from 8.3 – 12.5 and 9.3 – 18.9 in brown rice and polished rice, respectively. Published on 2016-09-28 08:13:45
  • Kirigala forest fragments and the identity as a dipterocarp plantation or
           Hora Kele of Ingiriya

    • Abstract: Fragmentation has exposed the Kirigala forest to the influence of various neighbourhood land-use practices. The present study investigated the floristic, soil and micro-climatic conditions of the forest and demonstrated its degradation due to influences by human induced disturbances. Ten 50 m × 5 m gradsects each accommodating 3 pairs of 10 m × 5 m plots, a total of 60 soil samples and 20 seed traps provided floristic details, seedling emergence from seed bank and annual seed rain of the forest, respectively. Diversity of the edge and the forest interior were compared for the different neighbourhood land use types using the Shannon and Weiner (H) and Simpsons reciprocal (D) indices. Change in the forest structure was illustrated using profile diagrams. Differences in soil pH, soil moisture, nitrogen, available phosphorous and potassium, organic matter content, air temperature, humidity and light intensity between the forest edge and the interior were determined. Soil, microclimate and species richness were combined for clustering of similar areas. The site reported the presence of 55 tree, 12 shrub, 15 herb, 07 climber and 02 vine species including a total of 23 endemic species and 06 invasive species. A higher diversity was observed at the edge, and the highest was observed beside roads as indicated by both diversity indices H and D. Soil and microclimate of the forest varied significantly between the edge and the interior and reflected anthropogenic influences and neighbourhood land use practices. Dominance hierarchy of the trees was Dipterocarpus zeylanicus > Gaertnera vaginans > Aporusa lanceolata, while that for undergrowth/shrubs herbaceous species was Ochlandra stridula > Dracaena thwaitesii > Piper sylvestre. Annual seed rain contained propagules of 23 plant species, while invasive Alstonia macrophylla provided the highest density of seeds. Establishment of foot paths, selective removal of juveniles by root-balling technique and encroachment for crop cultivation have also facilitated the degradation process. It is vital to pay attention on maintaining the ecological stability of this forest before it loses its identity as the Hora Kele of Ingiriya. Published on 2016-09-28 08:36:36
  • White root disease of Murraya koenigii from Sri Lanka caused by
           Rigidoporus microporus

    • Abstract: J.Natn.Sci.Foundation Sri Lanka 2016 44 (3): 347 – 348 Published on 2016-09-28 08:47:57
  • Estimation of parameters of the 3-component mixture of Pareto
           distributions using type-I right censoring under Bayesian paradigm

    • Abstract: As compared to simple probability models, a mixture model of some suitable lifetime distributions may be more capable of capturing the heterogeneity of nature. In this study, a 3-component mixture of Pareto distributions was investigated by considering the type-I right censoring scheme to obtain data from a heterogeneous population. First, considering a Bayesian structure, some mathematical properties of the 3-component mixture of Pareto distributions are discussed. These mathematical properties include Bayes estimators and posterior risks for the unknown component and proportion parameters using the uninformative (uniform and Jeffreys’) and informative (gamma) priors under squared error loss and DeGroot loss functions. Then, the performance of the Bayes estimators for different sample sizes and test termination times under different loss functions were examined. In addition, limiting expressions of Bayes estimators and posterior risks are derived. Finally, the superiority of the Bayes estimators was established through a simulation study and a real life example. Published on 2016-09-28 08:42:05
  • Characterisation of purified protease from Bacillus subtilis BS166

    • Abstract: Proteases are enzymes that break up the peptide bonds of proteins to release amino acids. Proteases showing better stability at alkaline pH and higher temperatures have potential applications in several industrial processes. The present study was aimed at determining the kinetic properties of the partially purified protease obtained from Bacillus subtilis BS166. Bacillus subtilis BS166 can produce protease above 30 oC and at pH 7.0. The protease was extracted with 0.1 M phosphate buffer of pH 7.0 and precipitated with ammonium sulfate. The activity of the purified protease was higher at pH 9.0 and 40 οC and showed zero order kinetics for 10 minutes. When the optimum enzyme concentration was 95.52 μg, a straight line was obtained in the Lineweaver-Burk plot graph. Michaelis constant for the purified enzyme was 50.9 μM and Vmax was 2833.4 pmolmin-1 at pH 9.0 and 40 oC. Published on 2016-09-28 06:34:39
  • Molecular detection and characterisation of begomovirus causing bean
           yellowing disease in Sri Lanka

    • Abstract: Bean (Phaseolus vulgaris L.) is one of the major vegetable crops cultivated in tropical, sub-tropical and temperate regions in the world. Bean yellowing disease (BYD), which was first reported in 1999 from Sri Lanka is still a serious viral threat to bean cultivation causing severe yield reduction. In this study, polymerase chain reaction (PCR) assays using degenerate (universal) primers were conducted with the aim of developing molecular techniques to detect the virus. Two degenerate primer pairs, namely, Deng 540/541 and AV494/AC1048 used in the PCR reactions confirmed the association of a begomovirus with the BYD by giving the desired core coat protein amplicons of 520 bp and 550 bp, respectively. The resulting amplicons were subjected to DNA sequencing and the sequence data were analysed to determine the phylogenetic and molecular evolutionary relationships with other related begomovirus sequences obtained from the GenBank. The analysis revealed that the virus associated with BYD (BYVD-GN-SL-Partial) is closely related to Horsegram [Macrotyloma uniflorum (Lam.) Verdc.] yellow mosaic virus isolate (HgYMV-LK: 09-Bean) reported in Sri Lanka. Further, the DNA sequence of BYVD-GN-SL-Partial was distinctively clustered with the Indian HgYMV sequences and positioned in between the Mungbean yellow mosaic virus (MYMV) sequences. Published on 2016-09-28 06:40:27
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016