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Journal Cover 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  [48 journals]
  • Assessment of the egg parasitoid guild of rice leaf folder, Cnaphalocrocis
           medinalis (Guenee): a search for biocontrol agents

    • Abstract: Biological control of rice leaf folder (RLF), Cnaphlocrocis medinalis by augmentative release of egg parasitoids has been suggested. This study was conducted to assess the egg parasitoid guild associated with the RLF and to determine their parasitism levels under local conditions. A survey was conducted in three districts at 14 sites using 16 fields where rice was cultivated under conventional, pesticide free and organic farming practices. RLF eggs were collected and incubated at room temperature with 60 % RH under natural daylight in the laboratory. The emerging parasitoids were identified and their parasitism levels were calculated. Four egg parasitoid species: Troichogrammatoidea bactrae, Troichogrammatoidea nana, Trichogramma sp. and Lithromeromyia sp. (Hymenoptera: Trichogrammatidae) were found parasitising RLF eggs. These species collectively parasitised 17 % of RLF eggs and the level of parasitism significantly varied between 0 and 57 % among sampling sites. Mean parasitism in conventional and pesticide free fields were 1.62 ± 0.81 % and 24.39 ± 16.8 %, respectively, which was significantly different. T. bactrae was the most prevalent parasitoid species, which was found in nine sites, while T. nana and Lithromeromyia sp. were found only in one site. Trichogramma sp. was found in four sites. Mean parasitism caused by T. bactrae, T. nana, Trichogramma sp. and Lithromeromyia sp. were 8.2 ± 5.7 %, 15.2 %, 3.7 ± 1.3 % and 2.5 %, respectively. The parasitoids did not affect beneficial arthropods such as spiders and coccinellids. The results suggest that T. bactrae is a potential egg parasitoid of RLF to manage RLF populations in local rice fields through augmentative release. Published on 2016-06-30 09:21:44
       
  • Multi-level threshold based edge detector using logical operations

    • Abstract: Edge detection is a very significant feature of image processing and refers to the algorithms, which are intended for identifying points in a digital image where the image intensity changes significantly. The need of edge detection is to find the discontinuities in intensity, surface direction, change in texture properties, and variation in scene illumination. This paper proposes a rapid and superior edge detection technique, which uses the logical operations on circularly shifted images to efficiently detect the edges with lesser computational complexity. The results are compared with other edge detectors using 2-dimensional Fourier transform. Experimental results show that the proposed algorithm improves detection accuracy and possesses encouraging robustness when applied to different images, in comparison to several other edge detection algorithms. Moreover, the algorithm is also applied on a bio-medical application to segment blood cells to show the diversified nature of the proposed algorithm. Published on 2016-06-30 09:04:32
       
  • Country-specific emission factors for methane emission from enteric
           fermentation: a case study from a non-annex 1 country

    • Abstract: Methane emission from enteric fermentation is a subcategory considered under the Agriculture sector greenhouse gas emissions under the United Nations Framework Convention on Climate Change (UNFCCC). So far, most non-annex 1 member countries have used the default IPCC 1996 revised guidelines in estimating such emissions. The latest IPCC 2006 revised guidelines for national greenhouse gas inventories provide better guidelines for developing country-specific emission factors. Countryspecific methane emission factors were developed for estimating methane emission from enteric fermentation in livestock in Sri Lanka, using a Tier 2 approach with energy calculations (IPCC, 2006) based on country-specific activity data. Each animal category was further subdivided for the analyses, and emission estimates incorporated population characteristics in the different agro-climatic zones of the country. Separate emission factors were calculated for sub categories within the local (indigenous) and improved (Indian and European) breeds. The population-weighted methane emission factor (50 kg head-1 yr-1) estimated for dairy cows (i.e. lactating females) was lower than the IPCC default value. The methane emission factors calculated for other cattle categories ranged between 11 – 58 kg head-1 yr-1. However the population-weighted emission factor (32 kg head-1 yr-1) was slightly higher than the IPCC default value (27 kg head-1 yr-1), as the proportion of the calves in the other cattle population was relatively lower (~47 percent) than what the IPCC default emission factor has considered. Overall, the population-weighted emission factors for buffaloes (49 kg head-1 yr-1) and sheep (3 kg head-1 yr-1) were lower than the IPCC default values. Published on 2016-06-30 08:57:48
       
  • Multi-label classification of computer science documents using fuzzy logic
           

    • Abstract: Classification has been already used for the prediction of predefined topics in many diversified domains including research paper classification task. A research paper may belong to one or more than one topic (classes). The state-ofthe- art techniques in this area have the following limitations such as: (1) most of the techniques classify documents to at most one principal topic and do not identify all of the topic associations for research papers, (2) considers the classification problem of research documents in discrete domain and the accuracy of these techniques remain low when considering multiple classes for a single document. These limitations led us to explore the fuzzy domain for the classification of Computer Science documents because we are not sure whether the documents belong to one category or more than one category. Furthermore, fuzzy classification will help to identify the degree to which papers belong to different topics. To validate the findings of our research, we need a comprehensive dataset. Such a dataset has been made available by the scientific community for Computer Science domain. Therefore, in this paper, we restrict our focus to the Computer Science domain. Key features are extracted from the Title and Keywords of the research paper. We used term frequency (TF) as the weight scoring methodology. As a paper may belong to more than one category, we used fuzzy classifier, which automatically identifies all possible categories. Subsequently based on a threshold, the final one or more than one topic is assigned. We propose a generic framework and two algorithms for category (ies) identification. Our rules have been evolved (updated) by rules updater after the classification has been done by the fuzzy classifier. Performance of the technique with respect to accuracy has been compared with different classification techniques. The proposed approach has outperformed the state-of-the-art approaches. Published on 2016-06-30 09:08:13
       
  • Release behaviour of amoxicillin from chitosan coated liposomes derived
           from eggs

    • Abstract: A delivery system consisting of chitosan coated liposomes was tested for its ability to deliver drugs over a period of time. Amoxicillin was used as the drug of choice and was entrapped in liposomes made of egg yolk lecithin and coated with chitosan with the aid of Tween 80 and sodium tripolyphosphate. These nanoparticles were monitored for the release of the drug in vitro. The activity of the released amoxicillin was measured against Staphylococcus aureus (NCTC-6571 strain) in BHI broth medium. The percentage of drug released with time was measured by HPLC. The nanoparticles showed sustained release of amoxicillin over a period of 24 hours. Approximately 80 % of the encapsulated drug was released in the first 10 hours. A sufficient drug release to kill the bacteria was obtained in 4 hours and a steady increase in drug concentration was observed up to 8 hours of testing. This study has enabled the model formulation of a sustained release delivery system for amoxicillin in vitro capable of delivering the drug over a period of 8 hours, which may enable drug activity such that the number of times of administration is reduced. Published on 2016-06-30 09:14:12
       
  • Identification and substrate utilisation of fungi associated with low
           country live wood termite, Glyptotermes dilatatus Bugnion & Popoff and the
           host plant, Camellia sinensis L.O. Kuntze

    • Abstract: The low country live wood termite (Glyptotermes dilatatus) is known to be associated with wood decaying fungi on decayed tea (Camellia sinensis var Assamica) stems. The diversity and prevalence of wood decaying fungi in decayed tea stems however have not been studied extensively. In this study, wood decaying fungi were isolated from decayed tea stems of TRI 4042 cultivar, living termites (G. dilatatus) and termite galleries collected from St. Joachim Tea Estate, Ratnapura, Sri Lanka. Of the fifteen fungi isolated, thirteen were identified using molecular taxonomy. This is the first report of isolation and identification of wood decaying fungi associated with decayed tea stumps. Among the identified fungi species, seven, six, and twelve fungal strains were recovered from the living termites, termite occupied galleries and decayed tea stems, respectively. Fusarium solani, Fusarium sp.1, Fusarium sp. 2, and Rhizomucor variabilis were the common fungi isolated. Results on substrate utilisation patterns of seven fungal species revealed that all the fungi were able to produce at least two enzymes to utilise the test substrates. Further, except with R. variabilis and Neosartorya fischeri, these fungi could digest cellulose and pectin either by producing polygalactouronase or pectate lyase. In utilisation of lignin, none of the test fungi produced laccase although all were able to produce peroxidase. Published on 2016-06-30 09:19:09
       
  • Heavy metals in road deposited sediments and road dusts of Colombo
           Capital, Sri Lanka

    • Abstract: Road deposited sediment (RDS) and road dust analyses are useful techniques to understand the heavy metal (HM) pollution in an urban area. Therefore, this study focused on the chemical characteristics of RDS and road dust in order to evaluate the pollution conditions in the Colombo Metropolitan Region (CMR) in terms of HMs. Forty six (46) RDS samples and forty eight (48) road dust samples were collected, and elemental concentrations of Zn, Cu, Pb, Fe, Mn and Cr were determined. Out of these measured elements, the most abundant element in all the samples was Fe, which is a common element in the basement lateritic soil in the area. Cu, Pb, Fe and Cr concentrations in RDS are high in industrial areas, while Zn and Mn are high in commercial areas. Except Fe, all the other element levels were higher in road dust than in RDS. Data analysis revealed that vehicle-related activities are the dominant source for the metals in the city. Zn, Cu, Mn and Fe contents were significantly higher than the background levels of the area. Statistical analysis reconfirms that road dust is more polluted than RDS in terms of Zn and Cu. According to the geoaccumulation index, road dust is moderate to strongly polluted and RDS are moderately polluted. Higher pollution conditions of road dust may be due to the resuspension of dust particles. Spatial distribution patterns show that HMs of anthropogenic origin were accumulated towards the North and Northwestern parts where the transportation related activities are centered in the CMR. However, the prevailing natural conditions such as wind direction, geomorphology and basement soil also control the level of contamination in the area. Published on 2016-06-30 09:32:31
       
  • Finite element simulation of the effect of loading rate on the
           stress-strain behaviour of Albany sand

    • Abstract: In this research, the effect of strain rate on Albany sand has been studied by elastic visco-plastic constitutive model within the framework of three component model. Strain rate effect can be modelled by using any one of the (i) Isotach, (ii) TESRA (temporary effects of strain rate and acceleration) or Viscous Evanescent and (iii) P&N (positive and negative viscosity) models of the three component framework. Usually ‘Isotach’ is appropriate for clay and soft rock, ‘TESRA’ for sand and ‘P&N’ is appropriate for sand with less angularity like Albany sand. In this research triaxial compression (TC) test results of Albany sand at different strain rates have been modelled successfully into a commercially available package called ‘ABAQUS’. The P&N model was implemented into a generalised elasto-plastic isotropic strain-hardening non-linear model in C++. The model was then embedded in the finite element computer programme ABAQUS, which was used for the actual analysis. In order to define the P&N model user subroutine of ABAQUS ‘UMAT’ was written in C++ and used hereafter. ABAQUS is a robust FEM software that allows writing subroutines for describing different material behaviour. Generally UMAT is written in FORTRAN but in this study the main model is written in C++ and then it is called by FORTRAN with appropriate change in ABAQUS environment file. The effect of strain rate on the stress-strain behaviour of Albany sand has been modelled by using the TESRA model with the help of user subroutine UMAT of commercially available FEM software ABAQUS. Published on 2016-06-30 09:39:38
       
  • Combining ability analysis for evaluation of maize hybrids under drought
           stress

    • Abstract: The present study was conducted to evaluate the genetic basis of yield related traits under drought conditions. A high heritability and genetic advance was found for plant height, 100-grain weight, grain rows per cob and grain yield per plant, suggesting that the selection of high yielding maize genotypes is possible through this approach. The high specific combining ability of W64SP, A495, A509 and A50-2 suggested that the pre-screening of inbred lines may be an efficient approach to develop higher yielding maize hybrids through heterosis breeding under drought. Published on 2016-06-30 09:47:44
       
  • Chi-square based hierarchical agglomerative clustering for web
           sessionization

    • Abstract: Clustering is one of the fundamental techniques to organise similar objects into proper groups based on features in the domain of data mining, machine learning and pattern recognition. In each cluster, objects are more similar to each other on the basis of particular features. Clustering has numerous applications in multiple domains such as information retrieval, data mining, machine learning, pattern recognition, mathematics, medical and bioinformatics. Web centric applications are expanding day by day and the web has become one of the largest data repositories. During the last decade, information and knowledge retrieval from the web has become a challenging research area. Similarity computation among the data objects (web sessions) is complex, however is a significant problem in unsupervised learning. This research is an attempt to overcome these challenges and problems. The objective of this research paper is to introduce a chi-square based similarity measure to compute the similarity among the sessions. A chi-square based approach is being applied to compute the statistically significant relationship between observed and expected frequencies of the number of pages visited and the time consumed by a user during a session. Moreover, a chi-square based hierarchical agglomerative clustering (Chi-HAC) technique is proposed to extract useful knowledge from web log. The Chi-HAC helps to improve the visualisation of web logs and is equally important for website designers, developers and owners for the improvements of websites at each level. Experimental results with two different log files reveal that the proposed similarity measure with Chi-HAC algorithm has significantly improved the computation among data objects in web sessions. Published on 2016-06-30 09:42:02
       
 
 
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