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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  [46 journals]
  • Two new bioactive polyketides from Curvularia trifolii, an endolichenic
           fungus isolated from Usnea sp., in Sri Lanka

    • Abstract: Two new polyketides (compounds 1 and 2) were isolated from the EtOAc extract of an endolichenic fungus, Curvularia trifolii obtained from Usnea sp. in Sri Lanka. The structures of these compounds were elucidated on the basis of spectroscopic methods (UV, IR, MS, 1D NMR and 2D NMR). The bioactivity of the compounds 1 and 2 were studied using DPPH antioxidant assays and they showed radical scavenging activity with IC50 values of 4.0 ± 2.6 and 1.3 ± 0.2 mg/mL, respectively. The radical scavenging activity of compound 2 was higher than that of compound 1 and it was comparable to BHT. Moreover, the new compounds 1 and 2 were evaluated for their anti-inflammatory activity, and only compound 2 exhibited a significant activity comparable to the standard antiinflammatory drug, aspirin. Compound 1 was evaluated for the inhibition of cell proliferation in a panel of five cancer cell lines NCI-H460, MCF-7, SF-268, PC-3M and MIA Pa Ca-2, and exhibited > 90 % inhibitory activity at 5 μg/mL with all of the above cell lines.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3): 217-224 Published on 2015-10-01 09:16:19
  • Using animal communication strategy (ACS) for MANET routing

    • Abstract: A mobile ad-hoc network (MANET) is a network of wireless nodes with high mobility. Mobile nodes change their position quickly in any direction and speed, and follow an infrastructure-less network. Although there are many mobility models and protocols available to find the path between any two nodes, the challenge in retaining the path still remains unchanged. In general, a permanent path between any source and destination does not exist because of the node mobility. Path retention is essential for certain applications like in the military, disaster and rescue operations where an infrastructure-less network like MANET is only feasible. In this paper an algorithm named ‘Animal Communication Strategy (ACS)’ is proposed to improve path construction and retention based on animal behaviour. Most of the time animals are found aggregated in the form of clusters. The cluster may undergo dispersal, reformation and reunion due to sudden changes. Each and every animal, who is aware of the changes, will immediately take the responsibility of communicating with their neighbours in the cluster. This impressive and cooperative behaviour of animals was adopted in the ACS algorithm. ACS algorithm is tested for performance using NS2 simulator. The results show a significant improvement with ACS for the metrics packet loss, delay and overhead when compared to the existing protocol in MANET routing.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3): 199-208 Published on 2015-10-01 09:10:43
  • Improvement of thermal properties of poly (L-lactic acid) by blending with
           zinc lactate

    • Abstract: Zinc lactate (RSX) was synthesised from zinc acetate and L-lactic acid, and the structure was characterised using X-ray diffraction (XRD). Thermal decomposition showed that the decomposition temperature of RSX is higher than the processing temperature of composites based on poly (L-lactic acid) (PLLA). Single factor experiments certified that the optimum reaction conditions are a reaction temperature of 80 oC, and a reaction time of 4 hours. Addition of RSX could significantly decrease the half-time of overall PLLA crystallisation. Compared to pure PLLA, the half-time of PLLA with 7 % RSX decreased from 2359.91 seconds to 152.68 seconds at 115 oC. The kinetics of isothermal crystallisation of PLLA/RSX composites can be described using the Avrami equation.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):247-252 Published on 2015-10-01 09:36:25
  • Stability properties of a delayed HIV model with nonlinear functional
           response and absorption effect

    • Abstract: This study investigated the impact of latent and maturation delay on the qualitative behaviour of a human immunodeficiency virus-1 (HIV-1) infection model with nonlinear functional response and absorption effect. Basic reproduction number (R0), which is defined as the average number of infected cells produced by one infected cell after inserting it into a fully susceptible cell population is calculated for the proposed model. As Ro (threshold) depends on the negatively exponential function of time delay, these parameters are responsible to predict the future propagation behaviour of the infection. Therefore, for smaller positive values of delay and larger positive values of infection rate, the infection becomes chronic. Besides, infection dies out with larger delays and lower infection rates. To make the model biologically more sensible, we used the functional form of response function that plays an important role rather than the bilinear response function. Existence of equilibria and stability behaviour of the proposed model totally depend on Ro. Local stability properties of both infection free and chronic infection equilibria are established by utilising the characteristic equation. As it is crucially important to study the global behaviour at equilibria rather than the local behaviour, we used the method of Liapunov functional. By constructing suitable Liapunov functionals and applying LaSalle’s invariance principle for delay differential equations, we established that infection free equilibrium is globally asymptotically stable if R0 ≤ 1, which biologically means that infection dies out. Moreover, sufficient condition is derived for global stability of chronic infection equilibrium if R0 > 1 , which biologically means that infection becomes chronic. Numerical simulations are given to illustrate the theoretical results.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):235-245 Published on 2015-10-01 09:28:14
  • Diversity and distribution of tick species infesting goats with two new
           host records from Sri Lanka

    • Abstract: An island-wide study on ticks that infest the domestic goat, Capra aegagrus hircus was carried out from June 2011 to May 2013. A total of 2,628 ticks were collected in 22 districts within the three agro-climatic zones in Sri Lanka from 740 goats belonging to various breeds. Eight species of ticks belonging to the two genera Haemaphysalis and Rhipicephalus (Family Ixodidae) including Haemaphysalis bispinosa, H. intermedia, H. cuspidata, Rhipicephalus sanguineus, R. haemaphysaloides, R. turanicus, R. (Boophilus) annulatus and R. (Boophilus) microplus were recorded. The most common species in the overall collection were H. intermedia (44.0 %) and H. bispinosa (43.8 %). Haemaphysalis bispinosa was the dominant species in the Wet and Intermediate Zones, except in a few locations. In these exceptions H. intermedia was the dominant species, which was also the most abundant species found in the Dry Zone. Haemaphysalis bispinosa and R. sanguineus were restricted only to the Wet and Intermediate Zones. Of the eight tick species found, the two species, R. turanicus and R. microplus were new host records from Sri Lanka. More adult stages (70.8 %) were found in goats, where nymphs and larvae formed 25.9 and 3.3 %, respectively. All three stages of the dominant tick species were found on goats except for immature stages of R. haemaphysaloides and R. sanguineus. Most ticks preferred the anterior side of the body with one exception, R. microplus, which was more attracted to the posterior side of the host. This study reports the tick species infesting goats with zoonotic potential and also known vectors of many tick borne diseases of human and livestock.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):225-234 Published on 2015-10-01 09:21:04
  • Effect of silicon and potassium on tomato anthracnose and on the
           postharvest quality of tomato fruit (Lycopersicon esculentum Mill.)

    • Abstract: The resistance against anthracnose was investigated in tomato cutivars ‘Thilina’ and ‘Maheshi’ by soil application of silicon (Si) at 0 (control), 50 and 100 mg/L during the growth stage, flowering stage and both growth and flowering stages. It showed a reduction of lesions by 80 % in ‘Maheshi’ and 87 % in ‘Thilina’, respectively compared to the control irrespective of the cultivar and stage of the plant at which the treatment was given. Application of potassium (K) at twice (X2) and thrice (X3) the recommended dose to the plants reduced lesion size by over 30 % or 85 % in ‘Thilina’ and ‘Maheshi’ cultivars, respectively. In ‘Maheshi, Si applied at 50 and 100 mg/L at all stages showed a significantly higher (p ≤ 0.05) fruit size compared to the control. Plants treated with higher doses (X2 and X3) of K also showed significantly higher fruit sizes compared to the control. Fruit firmness significantly increased in ‘Maheshi’ treated with 50 and 100 mg/L Si applied at the growth or flowering stage. A significantly lower percentage of total acidity (TA %) was observed in ‘Thilina’ treated with 50 or 100 mg/L Si irrespective of the stage of plant. ‘Thilina’ treated with X2 or X3 doses of K showed significantly higher (p ≤ 0.05) total soluble solid (TSS). Also, the percentage number of appressoria formed (number of spores with appressoria/total number of spores × 100) on areas inoculated with the fungus were significantly higher in fruits treated with X3 K dose and all Si treated fruits compared to the control.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):273-280 Published on 2015-10-01 10:12:09
  • In vitro propagation of Santalum album L.

    • Abstract: Santalum album L. (sandalwood) is a valuable tropical plant species that belongs to the family Santalaceae. Santalol - the active compound in S. album, which is commonly known as sandalwood oil is highly valued in the perfumery industry due to its sweet persistent aroma. Sandalwood plants are over-exploited for harvesting their wood. Although the species is naturally regenerated by seeds the success rate is as low as 20 %. Due to the hemi-parasitic nature of S. album, the survival of seedlings is low making the species rare in Sri Lanka. There is a high demand for sandalwood plants for commercial scale plantations. Therefore in the present study, plantlet regeneration through somatic embryogenesis was studied in order to produce a large number of healthy plants to be used in establishing commercial scale plantations.Mature and immature seeds, leaf discs and nodal segments were used as explants for embryonic callus induction. Nodal segments found to be the best explants for embryonic callus production. Murashige and Skoog medium (MS) supplemented with 2.5 mg/L 2,4-dichloro phenoxy acetic acid (2,4-D) and 3.0 mg/L kinetin (kin) induced callus with a mean diameter of 3.22 ± 0.1 cm after 8 weeks of incubation. Somatic embryo induction was optimized by the addition of 0.5 mg/L benzyl amino purine (BAP), 1.0 mg/L indole-3-acetic acid (IAA) and 0.5 mg/L kin to MS medium, which resulted about 10 somatic embryos per 1.0 cm2 of callus. Somatic embryos germinated best in MS medium supplemented with 2.0 mg/L gibberellic acid (GA3). The highest percentage of plantlet regeneration was observed when the germinated embryos were transferred into MS medium supplemented with 0.4 mg/L BAP and 0.2 mg/L IAA.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):265-272 Published on 2015-10-01 10:09:02
  • Major determinants of fruit set and yield fluctuation in coconut (Cocos
           nucifera L.)

    • Abstract: The final yield of coconut (Cocos nucifera L.) is determined by early fruit set. Thus understanding the factors controlling fruit set including climate change is of importance for assessing the yield and its accurate prediction. This study assessed the survival pattern of female flowers produced in different months of the year, the effects of climate factors during early phase of flowering and the competition for assimilates from previously formed fruits on the fruit set of newly opening inflorescences in a 25 ‒ 26 year-old coconut plantation in the intermediate zone (IL1a) of Sri Lanka over a period of three years. The rate of fruit survival since the onset of flowering to maturity varied with the month of inflorescence opening. Abortion of fruits after three months from inflorescence opening was negligible. The optimum (Topt-in vitro) and maximum (Tmax-in vitro) temperatures for in vitro pollen germination were 28 ºC and 39.7 ºC, respectively. The fruit set of an inflorescence/s opened in a given month (number of set fruits palm-1 month-1) was negatively correlated with the total reproductive dry matter requirement of the palm (TDMR) of the month of inflorescence/s opening (first month), and the number of high temperature days (Tmax ≥ 33 ºC) during the first three months of inflorescence opening, whilst it was positively correlated with the number of female flowers produced in the inflorescence. There was a highly significant correlation between the monthly fruit set (at three month stage) and the corresponding harvested fruit yield palm-1 month-1. The lag period between flowering (opening of the female phase) and fruit maturing was eleven months.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3): 253-264 Published on 2015-10-01 10:04:55
  • Appreciation : Emeritus Professor J.N.O. Fernando

    • Abstract: J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):289 Published on 2015-10-01 10:17:06
  • Model assessment of acid deposition potential by SOx in Sri Lanka

    • Abstract: Asia is undergoing tremendous economic development and increased demand for energy, particularly from coal burning. As a result, acidic precursors move to neighbouring countries with the potential to cause serious environmental damage. Such transboundary pollution originating from countries in the Asian region such as India, China and Thailand contribute to acidic depositions in Sri Lanka. India in particular, because of its geographical proximity contributes significantly to sulphur depositions in Sri Lanka. The RAINS-ASIA model was used to calculate future acidic depositions in four major cities of Sri Lanka for the period 1990 ‒ 2030 using baseline data from 1990. The total acid depositions due to Sri Lanka taken as a whole can be compared to those arising from transboundary pollution. It was found that the acidic depositions in all four cities will increase by 400 ‒ 600 % during this period, with Kandy recording the highest increase at 600 %. It was also found that the share from transboundary pollution to acid depositions in Jaffna located close to the Indian peninsula is ~80 % of the total. On the other hand, the transboundary contributions in Colombo is predicted to decrease from 58.5 % in 1990 to 33 % in 2030. This can be attributed to increased local air pollution, resulting from the burning of fossil fuel such as coal and diesel in local power stations and also increased vehicular traffic. Ship movements around Sri Lanka significantly contribute to acid depositions and depending on the city it can vary from 10 ‒ 15 %.J.Natn.Sci.Foundation Sri Lanka 2015 43 (3):281-287 Published on 2015-10-01 10:15:04
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