PURSE 2001

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Use of cation exchange membrane in the electridiaysis treatment of black liquor
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11) Ariyaratna, S. M. W. T. P. K.; Shantnini, R.; Walgama, K. S.
The liquid effiuent from the Embillipitiya pulp mill, known as black liquor, is an extremely complex substance containing chemicals such as residual sodium hydroxide, sodium carbonate, sodium silicate, sodium lignite, phenolic compounds, and some organic acids. Its black color is due to the presence oflignate ions which are almost impossible to decompose by biodegradation. A continuous release of black liquor into a water body has the potential to kill all the aquatic life in the water body and eventually turn it into a dead one. Black liquor has successfully been converted into a colorless liquor in an electrodialysis unit used to fractionate Embillipitiya black liquor into sodium hydroxide, lignin and organic acids cellophane was used as the anode and cathode side membranes in this electrodialyser. As a further improvement to the system, the cathode-side cellophane membrane was replaced by a cation exchange membrane, and the performances by the two membranes was compared. The system with the cation exchange membrane yielded a considerably higher rate of separation than the cellophane one. It gained almost half of energy that used for the same separation in the system with cellophane. When operating beyond limiting current densities, unlike cellophane membranes, the cation exchange membrane encourages the water splitting phenomenon. The side effects of water splitting, such as high-energy consumption and damage to membranes, were identified and quantified. Methods to minimize these effects were tested, and were found to be successful. For inctance using dilute NaOH solution, instead of distilled water in the cathode chamber, reduce water splitting. Beside these, the durability of the membranes was also studied and the methods to preserve the membrane for the subsequent runs were also examined. After using the membrane, it was found out to store in 0.1M NaOH solution.
A preliminary study to detect antibiotic residues in fresh milk
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Hathurusinghe, M. H.; Piyankarage, R. H.; Abeynayake, P.; Jayaweera, W.
Due to the wide usage of antibiotics in the treatment and prevention of diseases in dairy cows, there is a likelihood of antibiotic residues occurring in milk. Such residues can cause several adverse effects in humans including hypersensitivity reactions. These residues may also interfere with bacterial starter cultures used for preparing of curd, yoghurt and cheese. This study was designed to screen milk for the presence of antibiotic residues. The study was carried out in 74 dairy cows reared in certain selected areas of the Kandy district. After taking the history of each cow, milk samples from each animal were obtained into sterile bottles at the time of milking. Before performing the screening test, the samples were heated at 100°C for 5 minutes to destroy natural inhibitory substances in raw milk. For negative control, 2 ml of 10 % skimmed milk heated at 110°C for 10 minutes was used. The positive control was a 2 ml milk sample containing 0.006 ug/ml of benzathene benzyl penicillin. A prepared test culture of 0.2 ml of Streptococcus thermophilus strain T.J. containing yeast-extract and bromocresol purple (as pH indicator), were added to each 2 ml of milk sample and placed in a water bath at 45°C ± 0.5 for 2.5 hours. Bromocresol purple is purple at the beginning and turns yellow due to acidification during the growth of the bacteria. Retention of the original purple colour indicates that the bacterial growth has been inhibited and such samples were considered as positive. The samples that gave a yellow colour were considered as negative. Out of the 74 samples tested, 7 samples (9.5 %) were found to be positive and 63 samples (85.1 % ) were negative for chemical inhibitory substance. Four samples (5.4%) gave intermediate colours indicating doubtful results. The positive results could be due to the presence of antibiotic residues or other inhibitory chemicals in raw milk. Serial dilutions of antibiotics prepared in skimmed milk were used to detect the level of sensitivity of the test. Penicillin and oxytetracycline gave the colour change at >0.005 ug/ml. Cloxacillin gave the colour change at 0.5 ug/ml where as gentamycin changed the colour at 0.5j.tg/ml concentrations. Chloramphenicol gave the colour change at 100 ug/ml. Therefore the test was found to be highly sensitive to penicillin and oxytetracycline antibiotics, whereas Chloramphenicol was found to be the least sensitive antibiotic for this test. The results revealed that the fresh milk is not totally devoid of inhibitory substances and further studies are necessary to specify the chemical and to quantitatively determine its concentration.
Recent trends of urban development in the city of Kurunegala
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Tennakoon, T. M. B. P. K.
'Urban development' is an important phenomenon in modern society. It is essential to design proper urban plans that would develop the economic sector while enhancing the environment in the recent past, the government of Sri Lanka has paid special attention to the rapid development of urban areas. The objective of this research has been to investigate the progress that the city of Kurunegala has made since 1980s. The most notable finding of this research is that, in the city of Kurunegala, commercial and public transport, education and health sectors have rapidly developed, while production sector has lagged behind. It appears that the rapid development of commercial and public facilities is largely a result of the rapid expansion of the city area of increasing population. In the light of these developments, the following recommendations can be made to ensure sustainable urban development preventing potential problems in the city of Kurunegala. It is recommended that (a) Lands in the city area not be allocated for residential, industrial an institutional purposes to save the limited space available for the development of the commercial sector: (b) Investors of small industries be given land close to the city, (c) The main bus stand and its buildings be reorganized to suit current t demands; (d) Railway station be shifted to a suitable place in the city, (e) Certain areas unsuitable for productive activities be developed into recreational areas; (f) - new rules and regulations be prepared to make Kurunegala an eco-friendly city. It will be ideal, if this can be combined with public awareness and monitoring programmes.
Use of cyclogram technique for the interpretation of water supply borehole data
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Malaviarachchi, M. A. S. P. K.; Dharmagunawardhane, H. A.
Cyclogram mapping technique represents and illustrates well strata logs that depict penetrating lithologies of the boreholes together with other hydrogeologic parameters. This method has been successfully utilized in some other countries, to describe borehole data from sedimentary areas. However, the method has not been applied in crystalline rock areas. Since 90% of the land area of Sri Lanka is a crystalline rock terrain and a large number of water supply boreholes have been drilled in it, an attempt was made to illustrate borehole data using the cyclogram technique. Under the present study, interpretation of borehole data using cyclograms was done for one hundred water supply boreholes in the Polonnaruwa 1:50 000 topographic map. Drawing of cyclograms was done using Microsoft Paint and plotting on map layers was done with Adobe Photoshop 5.5 software packages. Cyclograms were set on a map illustrating all available geological and hydrogeological information on the same layout. Mapping of water supply borehole data using the cyclograms revealed that the method could be successfully applied for showing location of wells and boreholes, three-dimensional illustration of penetrated strata and presentation of other technical and hydrogeologic data from wells, all on a single map. Consequently, it was found that the cyclogram map could be used as a base map of well records, which is essential for proper interpretation of groundwater conditions in crystalline rock areas.
Porphyrin derivatives as mosquito photopesticides
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Amerasinghe, P. H.; Karunaratne, V.; Karunaratne, S. H. P. P.; Wickramasinghe, A.; Samarasinghe, D.; Disanayake, N.
Phototoxic effects of porphyrin derivatives have been demonstrated previously. These compounds act on biological systems, only when activated by direct sunlight or artificial light, and are described as environmentally friendly. This study investigated a novel approach to larval control, by testing the toxicity of four porphyrin derivatives, namely, protoporphyrin dimethyl ester (PPDME), haematoporphyrin dimethyl ester (HPDME), haematoporphyrin dihydrochloride (HPD) and haematoporphyrin (HP) on 4th instar larvae of Aedes aegypti, during the period of April 1999- July 2001. Laboratory and field studies were carried out at 1.25,2.5,5 and 10 ppm in aqueous and aqueous-acetone (few drops) solutions, at a unit volume of2.5 or 4 ml per larva in clear plastic containers. Field experiments (Nagastenna, Kandy) were carried out inside and outside the houses (n=10) simulating the natural breeding habitats of mosquitoes. Larvicidal activity was dependent on the derivative concentration, duration of exposure to sunlight and the unit volume per larva. Overall, a higher level of larvicidal activity was observed with aqueous solutions of HPD and HP than aqueous solutions containing acetone. In contrast, mortality rates with PPDME and HPDME in aqueous solutions with acetone generated better phototoxic effects than its aqueous counterpart. A mortality of 55% (n=50; 2.5ml/larva in 10 ppm PPDME), after 4 days of exposure to light, doubled (100%) at 2 days, when the unit volume of PPDME was increased up to 4 ml/larva. Increased mortality levels (90-92%) were also observed after 7 days of exposure, at a unit volume of 2.5 ml/larva, with 18% accounted for natural mortality. In contrast, larvicidal activity was low with HPDME, with only 50% mortality observed after 7days. One hundred percent mortality was observed with HPD (2.5 ppm; 4ml/larva) after 2 days of exposure to sunlight, during which natural mortality was not observed. Although HPD at 1.25 ppm (4 ml/larva), gave similar results, larval mortality in the controls without HPD accounted for 30% of the mortality. Field experiments carried out in home gardens, revealed that, mortality was only 12- 25% (n=100) higher than the controls, even at 5 days, using PPDME and HPDME at 2.5 ppm concentrations. In contrast, with HPD phototoxicity resulted in 100% mortality within 3 days, 16% being accounted for natural mortality. In contrast, there were no appreciable levels of larval mortality, observed in the experiments carried out, inside houses. Porphyrin compounds tested have phototoxic effects on 4th instar larvae of Aedes aegypti. HPD has a higher phototoxic efficiency than other compounds tested. HPD is recognized as a potential photoinsecticidal agent that could be safely used in the field. Experiments are underway to study the effect of HPD on larvae, found in other types of artificial breeding containers.
A Study of electrical conductivity of Peo-X solid polymer electrolytes with X= LiCf3 So3 ZnC7 H5 O3 and PbI 2
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Bandara, L. R. A. K.; Abeykoon, A. M. S. B.; Bokalawela, R. S. P.; Dissanayake, M. A. A. K.
Solid polymer electrolytes occupy a unique posrtion in the development of a new generation of power source applications ranging from small portable electronic equipment to larger electric vehicles. These polymers, in thin film form, display many advantages over liquid electrolytes such as leakage proof and gassing. further, they show dual action both as ionic conductors and mechanical separators, which make them the most attractive solid polymer electrolyte in conducting polymer-based batteries. A wide range of salts can be dissolved in poly(ethylene oxide) (PEO) to form solid polymer electrolytes whose transport ions may be cations or anions. In this work, PEO based electrolyte films with three types of salts, namely lithium triflorosulfonate (LiCF3S03), zinc salizelate (ZnC7Hs03) and lead iodide (Pbh) were used and their electrical conductivity measurements were carried out. Samples have been prepared by the solvent casting technique. The complex impedance measurements were performed over the frequency range of 5 Hz to 13 MHz, using a computer controlled HP4192A impedance analyzer with an applied signal of 0.1 V. The impedance data were collected in the temperature range of 25°C to 85 "C. DC polarization test was carried out on all the samples, using both the blocking and non blocking electrodes, to estimate the tranfrerency numbers of the polymer electrolytes. Compared to the other two systems, PEO-LiCF3S03 system shows higher ionic conductivities. With both ZnC7Hs03 and Pbl- salts, PEO based solid polymer electrolytes show almost the same conductivity values within the studied temperature range. In all three systems, the ionic conductivity increases linearly with increasing temperature. The knee observed in these conductivity curves are assumed to be due to the melting of the crystalline phase of pure PEO. It was observed that the ionic conductivity is high in the amorphous phase above 55°C, in the presence of a flexible polymer chain. Results of the dc polarization test showed that all the studied samples had low electronic conductivities. According to the above results, PEO- LiCF3S03 and PEO-ZnC7Hs03 systems can be mainly considered as cationic conductors while the PEO-PbI2 system acts as anionic conductors.
The May 2001 Riots in Mawanella: A Sociological Account
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Silva, K. T.; Saif Deen, N. T. M.; Gunasekera, A. M. A. S.
The riots that broke out in the Mawanella town on May 2, 2001 took most people by surprise. First, these riots had no apparent relation to the ongoing civil war in Sri Lanka. Second, the riots developed from a confrontation between Sinhala and Muslim elements within the Mawanella bazaar. Given the peaceful relations that had so far prevailed between the two communities, these riots came as a shock to many people. Third, in terms of their possible impact on the future course of ethnic relations in the country the Mawanella riots and similar eruptions around Hatton following the Bindunuwewa incident last year can be seen as the most significant chain of riots Sri Lanka since the nation wide outbreak of anti-Tamil riots in July 1983. Fourth, the Mawanella riots led to a chain of events that finally brought about the downfall of the regime in power. Using available reports and preliminary field inquiries, this paper examines factors contributing to the outbreak of riots in Mawanella in May 2001. Media accounts and some "official inquiries" into these events have sought to apportion the blame among various actors including the thugs, their political masters and the police. While the specific role of these various actors must be examined in any investigation of the relevant events, undue attention on trigger factors (i.e. those that sparked the initial confrontation) tends to under emphasize the underlying causes of the riots. This paper explores why a seemingly private dispute between two narrowly defined parties (extortionist thugs versus owners of /workers in certain business houses) quickly turned into a riot where the battle lines were clearly drawn along ethnic lines. Also it must be noted that the Mawanella riots were not an isolated event but a culmination of a series of tremors that surfaced in Mawanella and nearby locations. In trying to identify the underlying causes of the Mawanella riots, attention must be drawn to a pattern of population distribution. While the Muslims vastly outnumber the Sinhalas a narrowly defined urban corridor (bazaar), the pattern is reversed in the surrounding rural hinterland-where the Sinhalas are an overwhelming majority. This, in turn, is related to a pattern business competition where a heavy Muslim domination in business has come under some chalenge from an emerging layer of Sinhala entrepreneurs with the strong backing of certain politicians. Even though each ethnic group is internally divided along class lines, a rising .c fervor has guided business competition and political action. Within this context all that needed to spark a major communal disturbance were some unlawful Anti-Muslim acts of thugs who obviously enjoyed police protection. As in all other ethnic riots vicious rumour played a major role in inciting the two communities against each other. The Mawanella riots point to the for law enforcement machinery, the police in particular, to be more sensitive to ethnic relations and to reflect the ethnic heterogeneity of each area in its composition. More importantly, community and school based programmes are needed to promote mutual understanding and to diffuse any existing tensions between ethnic communities.
Investigation of Root Anatomy of Rice (Oryza Sativa) and Maize (Zea Mays) Grown in Aerated and Stagnant Conditions
(Unviersity of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Naganathan, M.; Gunawardena, A. H. L. A. N.
Plants in the environment face different types of stresses such as salinity, drought, an water logging. Water logging is considered as a major stress in some areas. Plants have sever mechanisms to survive under flooded condition. Development of adventitious roots, superficial roots, increased branching of roots and the formation of Aerenchyma are considered to be the mechanisms to survive under flooded conditions. Aerenchyma facilitates gas diffusion between roots and the aerial environment. Some cells in the cortical region die to form aerenchyma. Bo the casparian bands and the suberin deposits in endo- and exodermis and suberized sclerenchyma layer act as main barriers to water flow and air movement in monocot roots. As a result radial oxygen loss is prevented. Rice and Maize plants were grown hydroponically in an incubator at 25C under aerated and stagnant conditions. Root lengths were measured daily and a mark was given at a distance of 10 mm from the root tip of the plants. Free hand cut sections of roots were taken using a razon blade and stained with Sudan 7B. These sections were viewed under light microscope an photographed. Some sections were stained with Berberine Aniline Blue and observed under Fluorescent microscope. Root growth was high under aerated condition in maize compared to the stagnant condition over time. However, in rice, root growth was more or less similar in aerated and stagnant conditions. Increased pH was observed under aerated condition, while a declined pH in stagnant condition over time. The different layers of a monocot root (epidermis, exodermis, scierenchyma layer, cortical parenchyma, endodermis, pericycie and stele core) were observed clearly. Formation of aerenchyma was observed in maize roots grown in stagnant conditions, but not in aerated condition. In rice roots aerenchyma was observed in both aerated and stagnant conditions. Initiation of aerenchyma was observed in the mid cortex region in rice and maize root (stagnant condition). Both the casparian bands and suberization in endodermis and exodermis, were prominent in rice and maize roots grown under stagnant condition than in aerated condition. In addition, a very thick scierenchyma layer also was present in rice roots grown under stagnant condition. The results of this anatomical study will be useful in plant breeding programs especially in the production of varieties with constitutive aerenchyma and in the production of drought tolerant varieties.
An Odontometric Study of the Permanent Molars in two Ethnic Groups in Sri Lanka
(University of Peradeniya, Peradeniya,Sri Lanka, 2001-11-16) Peiris, H. R. D.; Nanayakkara, C. D.
The shape and the size of the teeth are known to vary. Evolutionary anthropologists have highlighted that the size and the shape of the teeth change due to selective forces, technological and dietary changes during human evolution. These dimensions also furnish human biologists and clinicians with an insight into the genetic relation between populations and environmental adaptation. A study was undertaken to establish mesiodistal, buccolingual and occlusal dimensions of the permanent molars of the Sinhalese and Sri Lankan Tamil adult males. Eighty males belonging to the Sinhalese and Sri Lankan Tamil ethnic groups (40 Sinhalese and 40 Sri Lankan Tamils) in the age range of 20 - 35 were selected. Three generation pedigree was recorded for each individual in order to check the ethnicity. Teeth were selected for measurements only if they were morphologically normal and fully erupted, not noticeably affected by attrition and caries and not restored. Only individuals having the normal occlusion were included in the study. Measurements were obtained on the dental casts taken from each subject. The measurements included, mesiodistal and buccolingual crown diameters (MD and BL) of the maxillary and mandibular molars, MD and BL diameters of the trigonid and talonid (TRMD, TLMD, TRBL, TLBL) of the mandibular molars. All measurements were recorded to the nearest 0.01 mm. using a digital vernier caliper by one investigator. The means and SDs of the MD and BL crown diameters of the maxillary and mandibular molars, TRMD, TLMD, TRBL, and TLBL of the mandibular molars were computed. Differences between the means were tested for significance using the student's t- test. Mean values of all measurements of teeth were larger in Sri Lankan Tamils than in the Sinhalese. However, significant differences were observed for the MD and TLMD of the mandibular second molar tooth and MD of the maxillary first molar tooth between Sri Lankan Tamil and Sinhalese males.
Observation on the Behaviouf of the Southern Common Babbler Turdoides Affinis Taprobanus in the Campus of the University of Peradeniya, Sri Lanka
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Hapukotuwa, N. K.; Santiapillai, C.
The Southern Common Babbler Turdoides affinis taprobanus is a very common bird in Sri Lanka. It lives in flocks ranging in size from 4 to 20 (seldom exceeding 20) birds. Each flock maintains a home range that varies from 1 - 11 ha. They show various types of behaviour not only within the flock (intra-specific behaviour) but also with other bird species (inter- specific behaviour). Intra-specific behaviour includes, spatial behaviour (such as movements in space range, hopping, resting, perching), maintenance behaviour (manipulation of body including preening, stretching, bathing, sun-bathing, scratching, sleeping, shaking), nutritional behaviour (foraging and feeding), agonistic behaviour (physical interactions such as fighting, playing and communicative interactions such as vocalization), sexual behaviour (songs, mating, courtship, copulation, territorial defense), nesting behaviour (nest-building, egg-laying, incubation) and parental behaviour (brooding, nourishing, feeding the young by bringing food such as larval and adult insects). Most of these behaviour types are common among other species of birds as well as in the common babbler. But certain behaviour patterns, such as preening and feeding for instance, are different from other birds and are very interesting. Preening includes nibbling with the tip of the bill that may remove foreign matter and ectoparasites. The birds sit on tree branches and preen especially in between feeding. There are two types of preening, allopreening and autopreening ..When several individuals are clumped together they often perch facing the same or opposite directions and preen each other. This type of preening is called allopreening. But some individuals move a little away from the group and do self-preening. This is called autopreening. The southern common babbler is an omnivore and it forages in groups of varying size. They feed mainly on insects, vegetable matter and some fruits. They also feed on wild figs, waste rice and curry, and bread thrown out of the houses, canteens. Mainly their two types of inter-specific behaviour types: with the competitors and with the predators. Mainly they forage with squirrels and common mynahs. They share the same feeding ground and do not show any serious fights because of the high abundance of food and wide food habits of babblers. The predator-babbler relationship is different: the babblers become aggressive towards their predators such as rat snakes, cats, and dogs that enter their territory. The behaviour patterns and the activities of the Southern Common Babbler vary according to the changes in the weather. On sunny days: they are very active and forage through the entire day (0630 to 1700 h) while on rainy days, they are less active and hence, their foraging time is much less. They are not aggressive. These birds spend most of their time foraging on the ground. The habitats of the Southern Common Babbler in the University Campus include home gardens, grasslands, pine forests, and woodlands. Of these, home gardens are the most preferred type of habitat. This is due to the high abundance of food such as waste rice, curry and bread.
Synthesis of black beetle aggregation pheromone
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Wickramasinghe, A.; Vicente, G. M.
The rhinoceros beetle, Oryctes rhinoceros L., is an important pest of coconut in all coconut growing countries including Sri Lanka. Gas chromatography and gas chromatographic- electroantennographic detection analysis ofPorapak Q-trapped volatiles obtained from aeration of male Oryctes rhinoceros shows three sex specific compounds'. One of these compounds, ethyl 4-methyloctanoate was reported to be an aggregation pheromone. Ethyl 4- methyloctanoate is being promoted by the Coconut Research Institute for mass trapping of the beetle as part of its plant protection strategy for the coconut palm. The methods available for the synthesis of ethyl 4-methyloctanoate are laborious and expensive. We were interested in developing a synthesis of the pheromone, which could be conveniently carried out using cheap raw materials. Three possible approaches were derived from retrosynthetic analysis, using cane sugar, succinic anhydride and hexanal respectively as starting materials. The aggregation pheromone was synthesized using cane sugar as the starting material. Cane sugar was treated with cone. hydrochloric acid to give 4-oxopentanoic acid in 20% yield. Fischer esterification of levulinic acid with ethanol and cone. sulfuric acid gave ethyl levulinate in 90% yield. Wittig olefination reaction of ethyl levulinate with triphenylphosphoniumbutylylid gave ethyl 4-methyloct-4-enoate in only 12% yield. Hydrogenation of the alkene using hydrogen with palladised carbon afforded the pheromone in 90% yield. The hydrogenation gives racemic ethyl 4-methyloctanoate but since both R and S compounds are reported to be attractive to the beetle, the racemic product can be used in plant protection without resolution.
A preliminary study on the gut parasites of Ramanella Obscura (anura: Microhylidae)
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Lokuhewage, S.; Amerasinghe, P. H.
Ramanella obscura (Gunther, 1864) is an endemic species of frog in Sri Lanka. Although some aspects of its biology are known, studies on endoparasites of this frog are lacking. Present study investigates the gut parasites of Ramanella obscura. A total of 155 tadpoles and 2 adults collected from two man-made ponds (A and B) at Sarasavigama (Kandy District) were examined for gut parasites. Tadpoles (n = 5) were dissected at weekly intervals for parasite counts and species identification. Light microscope measurements of parasites (n = 30-50 parasites/observation) were made after staining with Delafield's Haematoxylin and alcoholic Eosin. Morphological features and light microscope measurements were used for species identification. The two frogspawns examined contained 327 and 220 eggs respectively. Embryonic development from fertilization to hatching took 48-72 hours. Emergence of adults from the two ponds observed was observed at 80 and 101 days respectively. Protozoan parasites belonging to three genera (Opalina, Protoopalina, and Nycototherus), their juvenile and sexual forms were observed in the guts of tadpoles. The species identification of juveniles was not possible, as all morphological features were not developed. Only Opalina and one nematode parasite species (unidentified) was observed in the limit number of adults examined. In general, prevalence of infection in tadpoles, for all protozoan species ranged from 20-80%. The parasite abundance in tadpoles from both spawns ranged from, Opalina 5-1902, Protoopalina 6-816 and Nyctoterus 1-28. Mean length (Jim) and width (11m) of parasites collected at weekly intervals, from tadpoles and adults of ponds A and B ranged from, Opalina, 70.06±28.06 - 106.12±15.28 and 23.78±7.69 - 79.04±19.40; 43.89±4.95 - 153.54±49.53 and 16.23±2.50 - 41.17±11.03; Protoopalina, 97.79±8.50 - 113.22± 2.67 and 19.9±1.70 - 31.30±3.19; 75.58±19.81 - 116.23±22.17 and 13.83±6.89 - 20.24±4.74; Nyctotherus, 19.54 - 155.50 ± 59.22 and 10.66- 114.65±51.69; 60.38 - 154.88± 76.26 and 37.29 - 108.97±73.68 respectively. At both ponds, infections with Opalina, occurred first (42 and 27 days respectively), followed by the other two protozoan infections (50 and 34 days respectively). For all parasite species, the highest number of parasites was collected from tadpoles in Pond B. Only a limited number of adults were available for observation. Tadpoles of Ramanella obscura become infected with protozoan parasites (Opalina, Protoopalina, Nyctotherus) during early development. Infections occur through the ingestion of cysts of the parasite, which are usually discharged into water by the adult frogs during the breeding season. The abundance and sizes of protozoan parasites varied, probably due to the available nutrients, overall density of the parasites per host and also environmental conditions. The absence of Protoopalina and Nyctotherus, in the frogs cannot be explained due to the small sample size examined during this study. Nematode infections occur only after tadpoles reach adult stage. To the best of our knowledge, this is the first record of the parasite fauna of Ramonaella obscura. Further studies need to be done for the identification of the parasite species. Studies such as these contribute to the knowledge and understanding of co-evolution of hosts and their parasites.
Insecticide Tolerance in the Bruchid Callosobruchus Maculatus
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Bogamuwa, M. M. S; Karunaratne, S. H. P. P.
Bruchid Callosobruchus maculatus is a storage pest of legumes. Status and the mechanisms of insecticide resistance were investigated in adults. Insects were collected from a culture in Horticultural Research and Development Institute (HORDI) Gannoruwa and reared at the Department of Zoology, University of Peradeniya. Adults were subjected to insecticide bioassays by topical application using a microapplicator. Different dosages of four insecticides; carbamate carbosulfan, organophosphate dimethoate and pyrethroid permethrin were used. LD50 and LD90 values were obtained using log-probit mortality curves. Percentage mortality for fixed dosages of malathion (50 [ ]) and DDT (40 [ ]) were also obtained. LD50 [ ] values for carbosulfan, dimethoate and permethrin were 6.23,2.17 and 5.21 respectively. LD90 [ ] values were 371.23, 48.85 and 3842.81 respectively. Resistance percentages (percentage survivals) to malathion and DDT were 11.25% and 10% respectively. Activity of insecticide metabolizing enzymes such as glutathione S-transferases (GST), carboxylesterases and monooxygenases, in insect crude homogenates (n> 200) were investigated using a kinetic spectrophotometer. Mean' GST specific activity for the reduced glutathione/chlorodinitrobenzine was 0.55 ± 0.28 [ ]". Mean specific activity of carboxylesterases with the substrate para-nirtophenylacetate was 0.49 ± 0.36 [ ]". Native polyacrylamide gel electrophoresis resolved two elevated esterase isoenzymes in adult bruchids. Mean monooxygenase level was 0.14 ± 0.21 OD/mg. Sensitivity of the insecticide target-site, acetylcholinesterase (AChE), to insecticides was monitored by inhibiting AChE with the carbamate propoxur. Inhibition co-efficient (Ki) for the inhibition reaction was 0.10 x 105 M-1 min-1 indicating a high sensitivity of the target-site. Results show that the resistance to insecticides in C. maculatus is mainly due to increased activity of insecticide metabolizing enzymes.
Intercalation of Conducting Polymers Within Layered Materials
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Manoratne, C. H.; Krishantha, D. M. M.; Rajapakse, R. M. G.; Perera, J. S. H. Q.; Tennakoon, D. T. B.; Dissanayake, M. A. K. L.
Inorganic/organic heterostructure materials have attracted much attention of the research community as a result of potential applications of these interesting advanced materials. More importantly, these materials can be synthesised relatively easily by simple wet chemical methods as opposed to sophisticated vapour deposition techniques generally required for inorganic/inorganic quantum-well type heterostructure materials. During this work, we have developed wet chemical methods to exchange protons in the interstitial sites of bentonite, a layered clay material, with various metal ions, ammonium ions, and organic cations. The d-spacings of the resulting modified clay materials were measured by powder XRD technique. The anilinium-exchanged bentonite was treated with a strong oxidant and the anilinium ions entrapped within interstitial spaces were polymerised accordingly. The resulting material has a dark green colour and measurable electronic conductivity. These materials were also characterised by UV-visible absorption spectroscopy, FTIR spectroscopy, and AC impedance measurements. In this communication, we present novel techniques developed in our research group for the preparation of clay/conducting polymer heterostructure materials and their characterisation using several physical techniques.
Insecticidal Activity of Latex of Euphorbia Antiquorum on Agricultural Insect Pests
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) De Silva, W. A. P. P.; Manuweera, G. K.; Karunaratne, S. H. P. P.
Euphorbia antiquorum (Euphorbiacea) (Sinhalese name: Daluke), a plant native to Sri lanka, has various medicinal uses. Its latex has been described as having emetic, purgative, diuretic and poisonous properties. The latex is used to control paddy pests such as Scirpophaga insertulas and Sitophelus orizae in rural areas of Sri Lanka. This study was undertaken to investigate the potential use of E. antiquorum latex as an insect pest control agent and to isolate the compounds that are responsible for insect control. Latex of E. antiquorum was collected from Ebbagala (Kurunegala District) and dissolved separately in 7 solvents dichloromethane, distilled water, n-hexane, petroleum ether, methanol, diethyl ether and acetone. Activity of each solution was tested against laboratory colonies of the aphids Myzus persicae and Aphis gossipii, using a potters 'sprayer. Both species showed 100% mortality at levels of 10,000ppm of the xylene solution. At this concentration the degree of activity was much lower in acetone (20% mortality), distilled water (8% mortality) and methanol (38% mortality) solutions. The latex when dissolved in dichloromethane, n-hexane and diethyl ether formed a white precipitation when applied on insects. Insecticidal activity of the xylene solution (10,000ppm)was further tested on paddy bug Leptocoriza oratorius (48% mortality) black bug Scotinophara lurida (0% mortality) brown plant hopper Nilaparvata lugens (50% mortality) and cabbage looper Chrysodeixis erisoma. Predatory ladybird beetles, Harmonia octomaculata and Menochilus sexmaculates showed 0% mortality whereas predatory the spider Lycosa pseudoannulata showed 100% mortality at this concentration. control experiments were done using seven solvents dichloromethane, distilled water, n-hexane, petroleum ether, methanol, diethyl ether and acetone. Of the seven latex solutions, latex in xylene gave clear spots on thin layer chromatography (TLC). Column chromatography (florisil 60-80 mesh size) was used for the separation of xylene solution. Sample was eluted with n-hexane (120ml) and 5ml fractions were collected. Bioassays were carried out using Myzus persicae with each fraction (0.25microliter) of each solution was topically applied on to the thorax of the insect using a microapplicator). Fraction 17 had the highest bioefficacy (80%mortality). Separated fractions were studied by TLC and high performance liquid chromatography (HPLC). Fraction 17 showed one clear spot on TLC and showed three separated peaks on HPLC. LD50 values for the xylene latex solution (10,000ppm) and the 17th fraction were 0.06721ppm and 3.221ppm respectively when tested on Myzus persicae.
A study on the developmental cycle of dactylogyrus intermedius in Gold -Fish ( Carassius Auratus)
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Perera, U. F. R.; Rajapakse, R. P. V. J.; Arulkanthan, A.
Dactylogyrus intermedius (gill fluke) is a monogenean trematode known to cause heavy morbidity and mortality in gold-fish (particularly in young fry) in many commercial aquariums in Sri Lanka. Information on the clinical presentation of the disease and the life cycle pattern of D. intermedius infection in gold-fish under local conditions are scarce. Therefore, with a view of proposing measures to control this infection in Sri Lankan aquariums, the above mentioned aspects were studied. Four hundred gold-fish fry (age; 3-4 weeks), which were naturally infected with D. intermedius, was obtained from an aquarium in Colombo. After observing the clinical features, 50 randomly selected fry were sacrificed and gross lesions in the gills were noted. Ten infected fry were kept in a tank for 48 hours to determine the mean spawning rate. The rest of the infected fry were used to obtain eggs for life-cycle studies. Freshly spawned eggs (n=250) were incubated in de-chlorinated water at room temperature (26-29 °C) and the eggs were examined twice daily for larval development. In a subsequent experiment, two groups (A and B) of uninfected gold-fish fry (n=10/group) were kept in separate tanks and on Day 0 of the experiment freshly spawned eggs (250 eggs/tank) were added to each tank. On Day 7 of the experiment, fish from group A was removed from the tank and kept individually in 10 petri dishes and examined twice daily for the presence of freshly spawned eggs. Group B was transferred to a new tank on Day 7 of the experiment; thereafter one fish was sacrificed on every other day and skin scrapings and gills were examined for developmental stages. The common clinical signs observed in infected gold-fish fry varied but the salient features were widely opened operculum, rapid breathing, and crowding near the surface with gaping mouths. At necropsy, varying numbers of D. intermedius (range; 4-52) were found to be attached to the gills which were pale in colour with a heavy blanket of mucus. The mean spawning rate was 11 eggs/fluke/day and the operculated eggs (dimensions; 40-47.5 x 72.5-80 urn) sunk to the bottom of the tank after spawning. The larval development within the eggs was evident by 24 to 48 hours post incubation. Free swimming ciliated oncomiracidium (110 - 115 x 40 - 45 µm) emerged from the eggs by 2.5 to 6 days post incubation and the percentage of hatching was 85-90 %. Immature flukes were present on the skin and gills, whereas the mature flukes (112.5-137.5 x 312.5-337.5 µm) were attached either on the primary or secondary lamellae of the gills. The duration taken to complete the life cycle (eggs to eggs) at 26-29 °C was found to be 12-15 days. It is suggested that physical removal of eggs from the tank by bi-weekly siphoning off the sediment and coupled with a chemical treatment in the form of continuous immersion for a minimum period of 15 days would control this infection by disrupting the life cycle.
High Densed Tin Doped Indium Oxide Ceramics from a Hydrothemally Derived Power
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Udawatte, C. P.; Yanagisawa, K.
Tin doped Indium oxide (ITO) has received much attention because of its desirable properties such as high conductivity (formula) and high transparency to visible light. Due to these characteristics, thin and thick films of ITO are used for several useful applications such as transparent electrodes for display devices and transparent coating for solar energy heat mirrors. Among various processing methods, one of the best techniques to make the ITO films is magnetron sputtering, which utilizes either In-Sn alloy or In2O3-SnO2 oxide as the sputtering target. The sputtering efficiency and properties of the sputtered films, strongly depend on the characteristics of the sputtering targets. The densification of ITO is usually accomplished by the conventional solid state reaction of oxides above 1600 °C, but it is difficult to obtain a dense and homogenous target due to poor densification of In2O3. In order to enhance the densification, either an oxidizing sintering atmosphere or sintering aids should be used. The aim of the present study was to fabricate additive free, compositionally homogeneous, dense ITO ceramics with air as the sintering atmosphere. In the process, well-crystallized microcrystalline, homogeneous Sn-doped indium hydroxide [In(OH)3:Sn] or Sn-doped indium oxyhydroxide [InOOH:Sn] powders were prepared by hydrothermally treating a co-precipitated indium-tin amorphous gel, which was formed from a mixed solution of tin and indium chlorides. Low temperature calcination (300- 450·C) of the hydrothermally prepared powders form a cubic structured Sn doped In2O3 and a substitutional vacancy type solid solution of In2Sn1-xO5-y respectively. Sintering of both types of calcined powder compacts at 1350-1450·C for 3h in air resulting in high dense (>95% of theoretical density) C-type rare-earth oxide structured Sn-doped Inz03 ceramics with a fine grained microstructure and less pores. One of main advantages of this process is that the sintering was performed in air without sintering aids.
Synthesis of soluble polyanilines and their technological applications
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Rajapakse, R. M. G.; Perera, A. D. L. C.; Perera, J. S. H. Q.
Electronically conducting polymers belong to the special class of polymers possessing a long-range conjugation in their structures. Their electronic conductivities can be changed reversibly, in a range exceeding 20 orders of magnitude, and hence the same material can be made to have insulating, semiconducting, and fully conducting properties with concomitant change of their physico-chemical properties. Hence these materials have various technological applications. Electronically conducting polymers can be prepared by chemical and electrochemical polymerisation routes. During their synthesis, these materials generally precipitate, and are highly insoluble in common solvents. Technological applications of these materials are, therefore, hampered by their intractability. Hence the development of processing techniques for these materials is very important. During last ten years of research activities, we have designed and developed several novel techniques for processing electronically conducting polymers. We have discovered that although polyaniline is insoluble in common solvents, by substituting a methyl- or methoxy group to ortho position of aniline, substituted polyanilines can be prepared. These materials also possess electronic conductivity and their reduced forms are soluble in chloroform. Hence these polymers can be processed by solution casting. Methods were also developed to prepare conducting polymer-coated glass and plastic substrates, and conducting polymer grafted substrates. Conducting polymer intercalated layered materials were also prepared and characterised. In particular, polyaniline and polypyrrole intercalated clays (bentonite, montmorrilonite, fuller's earth) were prepared and characterised. Applications of these advanced materials in liquid crystal display technology, and in gas sensing, were documented. In this communication, we reveal the progress we made in developing processing techniques for electronically conducting polymers and, technological applications of these highly valuable materials.
Hydropower Potential of Nalanda Reservoir
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Nandalal, K. D. W.; Ratnayake, U. R.
Nalanda reservoir was built across Nalanda Oya during the period from 1954 to 1957. Primarily the intention was to store and divert the Nalanda Oya to Kalawewa while supplying irrigation water to lands downstream. The need for such diversion does not exist presently, as the Mahaweli water is available to the Kalawewa. The dam and the reservoir are now mainly utilized to augment Dewahuwa reservoir by diverting through Ebbawala regulator. The reservoir is not fully utilized at present due to appearance of several cracks in the dam. A study was carried out to assess the availability of water for irrigation and hydropower generation. Further it investigates the hydropower generation potential at the dam and along the diversion path. A simulation model was developed to study the system behaviour with hydropower generation introduced to the system. The simulation considers irrigation releases, mandatory releases, releases for hydropower generation and drinking water supply requirements. As the repairs of the dam are presently under consideration this simulation assumes full utilization of its design capacity. One simulation considers irrigation releases at Ebbawala distributed throughout the year and the other considers releases made only during September to June. Several simulations were performed varying the releases for irrigation through Ebbawala regulator from 100acre-ft to 130acre-ft and for each irrigation release, the release at the dam for hydropower was varied from 2 to 30cusec. The following table presents hydropower generations for selected releases at the dam. (Table) Comparison of the different scenarios is through the quantity based reliability, time based reliability, average interarrival time, average interevent time and resilience in addition to hydropower generations. The results of the simulations carried out indicate that an irrigation water supply up to about 130acre-ft can be supplied with a reasonable reliability as applied to irrigation water supplies. Energy generation on the diversion path is significantly higher than that at the dam. Also, generation on diversion path associates with high reliabilities for both irrigation water supply and hydropower generation.
Innate Immunity to Rhinosporidium Seeberi in Guinea Pigs
(University of Peradeniya, Peradeniya, Sri Lanka, 2001-11-16) Tilakaratne, W. M.; Arseculatne, S. N.
No farm or laboratory animal has supported the growth of R. Seeberi after experimental inoculation. Inocula in congenitally immuno deficient mice also failed to reproduce the disease, suggesting that specific adaptive immunity was not involved in preventing the establishment of infection. The testing of the possibility that non-specific immune mechanisms, notably the phagocytes, were responsible for the elimination of experimental inocula was planned with the guinea pigs skin as the test tissue, with H & E examination of sections of the intrademally-injected sites at serial intervals. PAS stained sections of these sites for the rhinosporidial bodies were performed. Identification of the specific lymphocytes with fluorescent antibody markers for macrophages, B and T cell subsets was planned as the second step. Method Intradermal inocula of 0.1 ml of suspensions of purified rhinosporidial endospores and juvenile sporangia (containing endospores 550/ml and sporangia 365/ml) were injected into the flanks of two guinea pigs (Hartley strain), and 1 injected site (total skin thickness) was excised from each animal under local anesthesia at intervals of 1.3.5.7.10.15.18.21 days. The tissue was fixed in buffered formal-saline and processed for H &E and PAS staining. Results The tissues showed host cell infiltration beginning around the 3rd day, consisting of neutrophils, macrophages and lymphocytes. Some free endospores were seen. Between the 7th - 15th days, the macrophages infiltration was marked, with some containing PAS debris possibly of endospore origin. Sporangia were not seen. In later stages, the endospores were absent. Conclusion The tentative conclusion is that rhinosporidial endospores are phagocytosed and destroyed by macrophages. Further detailed tests on the guinea pig skin were abandoned on account of the failure to obtain the specific markers for specific cells from abroad. Alternative experiments are planned with mouse macrophages in vitro for tests of phagocytosis and with liposome-blockaded macrophages in vivo in mice for the ability of these mice to support rhinosporidiosis.

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