PURSE 1998

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Verrucous carcinoma in the oral cavity
(University of Peradeniya, 1998-11-07) Baheerathan, N. N.; Mendis, B. R. R.; Amemiya, A.
The verrucous carcinoma (VC) is a distinct variant of squamous cell carcinoma. It has low grade malignancy, slow growth and low metastatic potential. VC is chiefly exophytic. However VC can invade and destroy oral tissues including bone. Although it has been reported in other sites such as larynx and genitalia, the tumour is most frequently found in the oral cavity. As VC runs a relatively benign course, it could be effectively treated surgically and is prognostically favourable. Thirty-eighty cases ofVC of the oral cavity were reviewed for their clinical and histopathological characteristics. Data for this study was gathered from specimens available at the Department of Pathology at the Faculty of Dental Sciences from 1978 to 1998. All biopsies diagnosed histopathologically as VC was reviewed by using the histologic criteria defined by Ackerman in 1948. The criteria are: 1) Papillary or verrucous projections on the surface 2) No connective tissue invasion at the basement membrane zone 3) Mild or no dysplasia of the epithelium 4) Parakeratin or orthokeratin plugging on the surface 5) A broad and advancing front of the lesion into the subjacent connective tissue and 6) A chronic inflammatory cell infiltrate in the connective tissue, mainly lymphocytes and plasma cells. The cases which did not meet the above histopathologic criteria were eliminated.Clinical data were collected from the submitted biopsy request forms. The tumour occurred chiefly in older patients ( age range from 15 to 76 years,mean age 54.3) and more often in males than in females (32 males- 84.2% and 5 females-13.15%) The sex of one patient (2.65%)was not available. The site of lesion was known only in 19 patients. The most common site of occurrence was the buccal mucosa (10 cases). Macroscopic appearance of lesion was reported as either exophytic or warty and white. All the cases showed marked epithelial thickening with series of irregular papillary projections .All the biopsies showed broad rete ridges .These rete ridges showed no evidence of invasion at the connective tissue interface and basement membrane was intact.71.1% (27) of the cases showed no epithelial dysplasia and 28.9% (II) of biopsies showed mild epithelial dysplasia .Moderate to intense inflammatory cells infiltration was present in 84.2% (32)of cases, predominantly lymphocytes.Less intense inflammatory cells present in 15.8%(6) of cases.In 94.8%(36) of the cases,keratin plugging was present but the absence of keratin plugging did not exclude our diagnosis of VC
Novel gas sensors based on polyaniline
(University of Peradeniya, 1998-11-07) Premasiri, H. D. S.; Rajapakse, R. M. G.; Bandara, H. M. N.; Tennakoon, D. T. B.; Perera, J. S. H. Q.
Polyaniline is a conjugated organic polymer that can exist in six different structural forms depending upon the extent of oxidation andlor protonation of the polymer backbone. These forms are called leuco-emaraldine base, leuco-emaraldine salt, emaraldine base, emaraldine salt, pernigraniline base and pernigraniline salt. First two polymers are in completely reduced forms with neutral and positively charged backbones respectively. These two forms are transparent yellow in colour. The third form which is blue in colour is partially oxidised but deprotonated. Forth form is an electronic conductor with a conductivity around 100 S em" and is green in colour. This form of the polymer exists with a partially oxidised and protonated structure. Fifth and sixth forms of polyaniline are in their fully oxidised states with the former being deprotonated and the latter being protonated. These two forms are violet in colour. These forms of polyaniline are interconvertible by redox andlor acid/base treatments. These changes of the same material can be utilised in several technological applications. In this presentation, we describe novel sensors for gases such as NH3,H2S, CO, CO2, Ch and HCI which are based upon polyaniline attached glass templates. A novel method was developed to covalently attach polyaniline on to ordinary glass surfaces. Such templates were dried at 110 DCand stored in a dry desiccator. The templates were exposed to gases at different pressures and changes of conductivity and the optical absorption were measured. The conductivity of the emaraldine salt form decreases upon exposure to basic gases such as NH3. The colour of the template is changed from green to blue concomitantly. The changes of absorbance and the conductivity were proportional to the gas pressure, while with acidic gases the opposite changes occur. Corresponding changes were observed for reducing and oxidising gases also. With the suitable choice of the polyaniline form it is therefore possible to fabricate electrical and optical sensors for gases that are important environmental pollutants. Since most of the above forms of polyaniline are stable under remote and hostile environmental conditions, these sensors are attractive for the monitoring of industrial atmospheres and those at which geological changes take place. The performance of common gas sensors based upon semiconducting oxides and membranes in remote andlor hostile environments is not very satisfactory.
School processes: a study of the taching-learning Processes within the classroom based on a selected sample drawn from the schools in the educational deistrict of Kandy.
(University of Peradeniya, 1998-11-07) Embakke, E. K. S. K.
This is an ethnographic study conducted to ascertain the quality and to evaluate the teaching -learning process in the schools. The research was conducted using eight schools, which represented different social class backgrounds in the Kandy District as research sites. In addition to the data obtained from observing the teaching-learning process in the classrooms, the researcher collected data from analyzing documents and by interviewing students and teachers as well. This enabled the researcher to triangulate and maintain the reliability and the validity of the data. The different stages of a classroom lesson namely planning, beginning, development and evaluation and feedback were continuously observed in the selected subject areas using various ethnographic research methods. The data thus collected and analyzed enabled the researcher to arrive at the following conclusions. 1. A majority of the teachers do not resort to yearly, termly, weekly or daily planning of their classroom lessons. Consequently the teaching-learning process is done without any prior planning. 2. The teachers do not care to plan their work because they are not subjected to any evaluation or supervision process. 3. Most of the teachers do not understand the significance of planning their classroom lessons. 4. The teachers in the schools attended by the lower socio-economic class children pay better attention prior preparation than those teachers in the superior schools in the urban areas. 5. Since the teachers do not resort to planning they are unable to motivate their students or to do any effective teaching. 6. In the daily teaching-learning process there is plenty of teacher talk which is carried on using only the blackboard and the textbook only. The result is a boring lesson. 7. Most of the teachers do not make any attempt to evaluate and ascertain whether the objectives of the lessons are achieved by using proper and suitable evaluation procedures. It is the opinion of a large number of them that evaluation and feedback unnecessary. The ultimate result is that half-baked knowledge is transmitted. The above conclusions clearly indicate the realistic picture of what is happening in our classrooms. The eradicate the weaknesses and the drawbacks in the existing systems, various remedial measures have been suggested by the researcher. Among these suggestions the significant ones are, that a close monitoring of teacher activities in the classrooms are essential in addition to the step that should be undertaken to educate the teachers of the teaching methodologies that could be adopted in our classrooms. It is also suggested that various teacher education institutions should be given the opportunity to get involved in the implementation of such programs. The researcher sincerely hopes that this study would lead to the improvement in the quality of the teaching-learning process and that the future researchers would study as to how these suggested programs could be successfully implemented so as to maintain the quality of the teaching-learning process in our schools.
Evaluation of vertebrate habitats in the Knuckles region
(University of Peradeniya, 1998-11-07) Ranawana, K. B.
The Knuckles range of forests, covering an area of 20,000 hectares, is located within the Kandy and Matale districts of Sri Lanka. This range is geologically a part of central massif of the island but isolated from the main mountain mass by the upper middle part of the Mahaweli river basin known as the Dumbara valley. The mountain range runs from Laggala-Pallegama in the northwest to Medamahanuwara in the southeast, for a lengthof 22 miles. The main ridge has many peaks rising over 1000 meters. Some of the important peaks are Gombaniya-the highest (1952 m) Knuckles (1669 m), Kalupahana peak (1942 m), Dotalugala (10630 m) and Lakegala (1356 m) situated in the eastern sector of the Knuckles range. Several streams, both perennial and seasonal originate form this range of hills and therefore have a high watershed value. Climatically the Knuckles region is unique in that the entire variety of climatic conditions of the island is reproduced within 'asmall area ranging from the extreme wet to the almost dry. The Knuckles range probably containsa more diverse set of forest types than any like-sized area elsewhere in Sri Lanka. TheKnuckles forest range harbors a high diversity of fauna, of which majority are endemic and relict forms. Fish species such as Puntius srilankensis, P'martenstyn, Garra phillipsi and Danio aequipinnatus are restricted to the Knuckles range. Of the amphibians present in this region, the endemic and relict species Nannophrys marmorata is found no where else in Sri Lanka. Seventeen species of reptiles were recorded from the area, of which 11 were endemic. These include the endemic and relict lizard Ceratophora tennenti found onlyin the Knuckles region. Fifteen species of endemic birds have been recorded from this region. Rare mammals found in the knuckles region include the leopard, otter and loris, which are globally threatened as well. Habitats of these unique faunal types have been badlyaffected due to agricultural expansion, conversion of lands to plantation crops such as coffee and tea, shifting cultivation, cardamom cultivation, and illicit felling and gem mining. In order to determine the wildlife-habitat correlation, habitat use of some selected vertebratesin the knuckles region was evaluated using a Life-Form model.
Self-Medication in a defined community in Sri Lanka
(University of Peradeniya, 1998-11-07) Wijeratne, P. D. P.; Paranathala, D. M. L. B.
To findout the extent and practice of self-medication in a defined community and compare the results with a control group. (Medical students) A randomly selected 144 subjects aged> 18 years in the MOH area Hindagala and 100 first year medical students (95/96) formed the study subjects. Data was collected using a pre- printed questionnaire from August to December 1997 and the results analysed statistically. 112 completed questionnaires received from the community. The prevalence of self-medication in the community (77.68% n=87/112) was lower than that in the student population (p < 0.001). In the community, self-medication was associated with literacy and there was a tendency to self-medicate both 'over-the-counter' and 'prescription only' drugs; 60.9% (n=53) self-medicated 1 to 5 times frequency in the previous 6 months, "Good past experience" was the main reason for their self-medication. 89.65% (n=78) in the community expressed satisfaction with their self-medication. None in either population stated any untoward effects of their self-medication. This study reveals that a significant percentage of subjects in the community indulge in self-medication practice. Furthermore it was associated with literacy, the educated beingpracticing more (P < 0.05). The self-medication of 'prescription only drugs' in the community as in the student population is a cause for concern. According to this study self-medication appears to have been practiced without untoward effects that merit mention.
Electrochemical properties of chemically and electrochemically synthesized polyniline
(University of Peradeniya, 1998-11-07) Chandrakanthi, R. L. N.; Gunaratne, L. M. W. K.; Vidhanapathirana, K.; Careem, M. A.
Polyaniline(P ANI) is one of the most promising electronically conducting polymers for technological applications such as rechargeable batteries, electrochromic displays and sensors. Further, PANI is highly electroactive and it has relatively high doping levels than the other electronically conducting polymers. Therefore it is a suitable candidate for cathode materials in plastic batteries. The PANI system differs from other conducting polymers because of the presence of more than one redox process and because of the possibility of protonation of the polymer chain itself, in addition to the negative counterions more loosely doped to the chain. Therefore, its properties depend on both the pH of the solution it is treated with and on the oxidation potential. Due to this complexity, the reported results on PANI in the literature differ considerably. Unlike many other conducting polymers, PANI can be prepared by chemical or electrochemical synthesis. The work reported in the literature is mostly confined to systems prepared by one of these methods. In this study, electrochemical behaviour of PANI films prepared by both process are reported. Electrochemical synthesis was carried out in 0.1 M aqueous ethanedisulfonic acid (EDSA) solution. PANI films of 0.25 11m thickness were obtained galvanostatically at a constant current density of 62.5 IlAlcm2 using the standard two compartment, three electrode cell arrangement. Films were also prepared by momentarily dipping a clean platinum wire in solution containing chemically synthesised PANI in formic acid. Cyclic voltarnetry and in-situ electrical conductivity variation studies were carried out in aqueous electrolytes containing ethanedisulfonic acid. The cyclic voltarnmograms for both type of films have identical features indicating the films obtained may be the same form. PANI changes from non conducting state to conducting state on partial oxidization and reverts back to non conducting state when it is fully oxidized. In the conducting state the electrical conductivity seemed to vary with applied potential. The conductivity has the highest value at a potential close to the first anodic peak of the corresponding voltammograme.
An examination of learning styles of undergraduates in different academic disciplines
(University of Peradeniya, 1998-11-07) Perera, E. B. P.
The objectives of this study is to investigate whether there is a pattern of distribution in the learning styles of undergraduates in different academic disciplines of Sri Lankan universities. Some of the background variables associated with learning styles were also investigated. The sample consisted of 1138 first year undergraduates of three Sri Lankan universities in the disciplines of arts, Engineering, Medicine, Management, Science and Agriculture. A Sinhala version of Kolb's Learning style inventory was used to identify the learning styles of Undergraduates. In addition to this a short questionnaire was utilized to obtain relevant information for the identification of background factors associated with student learning styles. The investigation revealed some important findings. There is a clear differentiation of learning styles between students in Arts, and Science disciplines and this is parallel to Hudson's Arts/Science converger/ diverger differentiation. The learning styles of undergraduates in Engineering , Medicine, Management, Science and Agriculture except in the arts discipline were significantly unequal in distribution. The learning styles in these disciplines were directed towards the converger style. This shows a similarity between universities in western counties and in Sri Lanka. Occupations of the fathers and parental education were found to be background factors in the accentuation of learning styles of students. It was revealed that the children of fathers in higher occupational levels were convergers while children of fathers in lower occupational levels were divergers and the children of parents who had obtained a higher educational level were convergers. These findings show Kolb's Inventory could be successfully used in the identification of students learning styles and confirms the validity of further use as an instrument in the identification of student learning styles.
Factors affecting the conductivity of surface immobilised polyaniline
(University of Peradeniya, 1998-11-07) Wickramanayake, D. K. W. W. M. S.; Rajapakse, R. M. G.
Polyaniline exists in six different structural forms depending upon the extent of oxidation and protonation of the polymer backbone. One of these forms is an electronic conductor with maximum recorded conductivity of 100 S cm-I. Some of these forms can be easily and quickly interconverted while the most oxidised form is prone to various chemical reactions leading to the degradation of the polymer. The extent of conductivity of the conducting form of the polymer, known as emaraldine salt, depends strongly on various parameters such as the acidity, the counter ion etc. The properties of the materials are such that innumerable possible technological applications for the material can be found. However, most of such applications depend on the processibility of the material. We have already designed and developed a method to retain polyaniline on ordinary glass surfaces. This involves the reaction of surface hydroxyl groups of glass with SOCh followed by aniline at ca. 400°C and subsequent deposition of polyaniline by oxidative polymerisation of aniline in aqueous acidic solution containing functionalised glass plates. This procedure ensures a permanent attachment of polyaniline on glass surfaces though the conductivity of the surface is relatively poor owing to the discontinuity of the polyaniline layer on the surface. During this project we have attempted to increase the smoothness and conductivity of the polyaniline coat attached to ordinary glass surfaces by further improving the immobilisation procedure and studying the factors affecting the conductivity of the immobilised polyaniline layer. Ordinary silica glass surfaces contain some hydroxyl groups and Si-O-Si linkages and bound water molecules. Refluxing the glass with concentrated hydrochloric acid results in the hydrolysis of the Si-O-Si linkages to yield Si-OH groups. As such pre-cleaned glass pieces were refluxed with cone. HCI for different periods from 1 hour to 24 hours. The plates were then rinsed with water and dried. The above procedure was then followed on such glass plates. Also the effect of concentration ratio of the oxidant to the monomer and the effect of various oxidants and their concentrations were studied in order to investigate the best oxidant, optimum concentration ratio for obtaining highly conducting smooth glass plates. Our results have clearly shown that the refulxing with cone. HCI for a minimum of 6 hour period ensures the increased amount of surface -OH groups and hence better contrast for the surface deposited polyaniline layer. Further, we found that Fe3+ is a better oxidant than all the other oxidants tested ( 6 in number ranging various redox potential values above that of aniline/aniline"). The optimum concentration ratio is 1:6 in monomer:oxidant when Fe3+ was used as the oxidant. The resultant polyaniline layer is smooth to microscopic examination and has a sheet resistance of8.5 kQ cm-I.
Optimal anti windup compensator designto handle a wide range of setpoints
(University of Peradeniya, 1998-11-07) Maithripala, D. H. S.; Walgama, K. S.
Actuator saturation is a very commonly encountered controller Non-Linearity that gives rise to the so called Windup phenomena. This usually causes severe performance degradation in control systems, especially if the closed-loop is very fast and/or the open-loop is very slow or unstable. To reduce these undesirable consequences of windup, many techniques known as Anti Windup Compensators(A WC) have been proposed in the literature. They could generally be classified as either tunable parameter AWCs or fixed parameter AWCs. It is generally felt that the applicability of fixed parameter methods are limited and that it is preferable to use tunable parameter methods in industrial controllers. However no proper guide lines are available yet for the tuning of them and there is also the problem of the range of operation being limited for even a properly tuned AWC. The Conditioning Technique (CT) is a fixed parameter AWC based on the concept of a realizable setpoint and it exhibits a performance that is independent of the setpoint. However it suffers from the so called shortsightedness problem and results in a degraded performance. To overcome this problem an optimization based modification is proposed by Cheng & Pemg(1996) for the AWCs that fit into the class of the CT. This scheme contains a single tuning parameter and we in this paper show that this parameter could easily be tuned with the aid of simulations to achieve optimal performance conditions for a particular setpoint. However this optimal setting would not perform optimally for other setpoints. Cheng & Pemg(l996) have provided some guidelines as to the design of a time varying mechanism for this tunable parameter with respect to an example so that a wide range of setpoints may be handled effectively. An improved design criterion for the optimal tuning of this time varying parameter to handle a wide range of setpoints as well as unmeasured disturbances is proposed in this paper.
Carrot callus tissue-based biosensor for the detection of hydrogen peroxide.
(University of Peradeniya, 1998-11-07) Navaratne, Ayanthi.; Susantha, Nalaka.
Monitoring and quantitative determination of hydrogen peroxide is very important since, it is highly used in various industrial fields such as food, textile and dye industries. Hydrogen peroxide is also produced in living organisms during the normal cellular metabolism. The carrot callus tissues which contain a high peroxidase activity was utilized to construct an amperometric biosensor for the detection of hydrogen peroxide. The tissue was incorporated into a carbon paste matrix along with ferrocene as an electron mediator. This biosensor is based on enzymatic reduction of hydrogen peroxide into water. The enzymatic reduction of hydrogen peroxide is monitored and quantitatively related to the amperometric current of ferrocene/ferrocenium couple at the electrode surface. Amperometric responses of this bioelectrode for the sequential addition of 2.0 x 10-5 M hydrogen peroxide were obtained. The linear dynamic range of the sensor for hydrogen peroxide was found to be 1.99 x 10-5 M to 1.99 X 10-4M and the lower detection limit 1.02 x 10-7 M hydrogen peroxide and the sensitivity of 17.8 uA mol with the optimized pH of 6.5 (0.1 M Phosphate buffer) and 6.4% tissue content. Other important characteristics of the sensor include fast response time of 2.5 sec. The co-efficient of variation and the life time of the sensor were also evaluated. Financial support from NARESA (Grant No RG/96/C/02) is gratefully acknowledged
Glycaemic status of Sri Lankan diabetics and its relationship to serum lipids
(University of Peradeniya, 1998-11-07) Sivakanesan, R.; Illangasekara, V. L. U.; Nantini, S.
Diabetes mellitus is a condition where derangements in glucose and lipid metabolism are commonly observed. An attempt is made in this study to correlate the concentration of serum glucose with that of serum lipids. Blood samples were collected after 14 hrs overnight fasting from diabetic subjects (n=212) attending the diabetic c1inic,Teaching hospital, Peradeniya and healthy volunteers (n=126). A questionnaire was used to collect dietary, family and other information. Glucose and lipid estimations were done on serum by enzymatic methods using Randox assay kits and fructosamine by the nitroblue tetrazolium method using Sigma kits. Diabetics had significantly (p<0.05) elevated fasting serum glucose compared to the controls (l49.5±3.7 mg/dl vs 90.O±1.0 mg/dl; Mean±SEM). The prevalence of hyperglycaemia (glucose concentration> 111.6 mg/dl) in diabetics was 79.4 %. Similarly, the diabetic males (144.0±5.3 vs 91.4±1.4 mg/dl) and females (153.8±5.1 vs 88.3± 1.4 mg/dl) showed elevated serum glucose compared to the controls. The prevalence of hyperglycaemia in diabetic males (glucose concentration> 113.7 mg/dl) was 73.6 % and in diabetic females (glucose concentration >109.0 mg/dl) was 83.9 %. The difference in serum glucose concentration between men and women of both groups was not significant. Serum fructosamine, a marker used to assess short term glycaemic control, in diabetics was significantly (p<0.05) higher compared to the controls (3.15±0.06 mmol/l vs 2.24± 0.03 mmol/l). The prevalence of elevated concentration of fructosamine (fructosamine concentration >2.50 mmol/l) in diabetics was 83.8%. Similarly, the mean concentration of serum fructosamine in diabetic males (3. 16±0.09 vs. 2.26±0.05 mmol/I) and females (3.14±0.09 vs 2.20±0.05) was significantly higher than the controls. The prevalence of elevated concentration of fructosamine (fructosarnine concentration >2.50 mmolll) in diabetic males was 65.3 % and in diabetic females (fructosamine concentration > 2.44 mmol/I) was 87.1 %. However, the difference between males and females of both groups was not significant. Correlation analysis between serum glucose and lipids showed significant positive associations between serum glucose and triglycerides (r = 0.177, p=0.009) and total cholesterol (r = 0.133, p=0.05). Significant positive associations were also seen between serum glucose and duration of disease (r = 0.179, P = 0.016) and fructosamine (r = 0.607, p=O.OOOI). There is a direct relationship between serum triglyceride and cholesterol concentrations and serum glucose concentration in diabetics. Furthermore, the glucose concentration tend to increase with increase in duration. Therefore it is necessary to exercise tight glycaemic control to prevent elevations in serum lipids which are proven risk factors of cardiovascular diseases.
Effect of the maternal factors during pregnancy on the birth weight of neonates.
(University of Peradeniya, 1998-11-07) Athaudaarachchi, P. M.; De Silva, Y. A. S.; Gunaratne, C.; Jayasinghe, C. P.; Jayaweera, T. S.
The effect of maternal physical activity, nutrition, psycho-social stress and socio-economic status during pregnancy, on the birth weight of neonates was studied. A quota sampling method was used to collect data from 258 eligible Sinhalese postnatal women and their neonates, by direct interviews and by anthropometric measurements at 3 hospitals in Kandy, on randomly decided dates between 27/03/1997 and 20/0411997. Using a scoring system which considered severity and duration of physical activity during pregnancy, the mothers were divided in to high and low work groups and the mean birth weights of their neonates compared using Student's t-test. The body fat content of the mother was estimated using triceps skinfold thickness and used as an index of her overall nutritional status to analyse it's correlation with the birth weight of the neonates using Pearson'scorrelation test. Maternal height, postnatal weight and postnatal body mass index was also similarly used for correlation, but the latter two were found to be inconsistent indices. The responses given to a questionnaire on psycho-social stress at work and at home was used to group the mothers in to "minimally stressed" and "stressed" groups, and the mean birth weights of their neonates compared using Student's t-test. Employing a scoring systemdivided by us, which considered percapita income, house and property, education andoccupation the mothers were divided in to three classes and the mean birth weights of their neonates compared using Student's t-test. The significance of difference of the incidence of low birht weights was also assessed using Chi square test. The significance of the difference of mean birth weight of neonates was very high (p
Biological and mineralogical aspects of the development of some selected soil profiles from the Central Highlands of Sri Lanka
(University of Peradeniya, 1998-11-07) Yatigammana, S. K.; Dahanayake, K.
Biological aspects of the development of soil profiles were studied by field observations and collection of samples. The mineralogy, chemistry, petrology and biological activities in 15 different soil profiles in different climatic regions were examined. The results reveal that biological agents influence the development of soil by weathering the parent material and transforming primary minerals into secondary minerals. These processes involve the decomposition and mixing of organic and inorganic components of soil. The X- Ray Diffractometry (XRD), Differential Thermal Analysis (DTA) and Scanning Electron Microscopy (SEM) studies show the occurrence of secondary minerals in different climatic regions as follows ; (a) Up Country Wet Zone: kaolinite, vermiculite and goethite. (b) Mid Country Wet Zone: vermiculite, smectite. (c) Mid Country Intermediate Zone: vermiculite, smectite, goethite, and mica. (d) Low Country Wet Zone: kaolinite, gibbsite and goethite. The SEM studies reveal that the dominating fungal genera of weathering surfaces belong to Penicillium and Mucor. A Blue-Green algal genus Scytonema is widely distributed in the partially weathered marble as well as on other rock surfaces where optimum environmental conditions occur. Gram-positive (+ve) bacteria are also well distributed in the weathering surfaces. Soil organisms and plants are also involved in the development of soil profiles. The interactions of microbes, macro organisms and minerals seem to operate in mutual harmony to develop the soil profiles.
Abuse, harassment and torture University style: a study of the forms and practices of ragging in the University of Peradeniya
(University of Peradeniya, 1998-11-07) Athukorale, K.; Pinnawala, S.
Department of Sociology, Faculty of Arts, University of Peradeniya. Legitimization of change of social status of individual members in traditional societies is done through a ritualistic process called initiation. A number of contemporary institutions are known to maintain similar traditions as part of their sub-culture. Ragging in the Universities is one such sub-cultural tradition. However, unlike the initiation rituals in traditional societies many of the modem day initiation practices are harmful to society and the individual. The aim of the paper is to understand the types and forms of ragging and to examine whether it can be considered an initiation ritual. The analysis is based on a survey that was carried out in 1995 in the University of Peradeniya. The use of 1995 data is justified as two years is not long enough to have any significant changes in the types and forms of ragging and its social basis. The study showed that ragging practices can be classified into two groups. The first is the activities that cause physical pain, leading even to injuries, on those who are ragged. The second is those that take the form of verbal abuse causing mental strain. The injuries caused by the latter are not often visible and immediate. Of the activities of ragging the majority fall into the first group. Ragging activities in the University show a parallel between hazing in the United States and ragging here indicating to a gradual Americanization of ragging in this country. Ragging in its physical form is predominantly a male activity. The clear majority of the students who are engaged in this form of ragging and those who are subjected to it are males. In inflicting mental abuse however both males and females showed similar involvement. Ragging across gender almost exclusively takes place in the form of verbal abuse. Ragging showed a close association with the socio-economic background of those who are involved. Contrary to the popular belief it is those who come from rural areas, regional schools and those who belong to low income groups are the ones who often get ragged and are very often the perpetrators of ragging. There is also a close relationship between ragging and political activities in the campus. Ragging is manipulated by political groups to recruit members. This happens in two ways. One way is to win the student over through sympathy. The other way is by subjecting one to extreme ragging. It helps to identify the stronger personalities and those who are won over in this manner remain loyal to the cause and the leadership. The claim that ragging promotes solidarity and friendship and also a great leveler is unfounded. Only a very small minority of those who get ragged continued to be friends with the raggers. Neither has it succeeded in promoting equality among the students. There is little evidence to show that ragging in its present form serves any function in the University community.
Acoustic quality of buildings
(University of Peradeniya, 1998-11-07) Dilhani, M. P. P.; Hussain, F. M.; Karunasinghe, D. S. K.; Somaratna, A. P. N.
Department of Civil Engineering, Faculty of Engineering, University of Peradeniya There are certain types of buildings whose acoustic qualities assume great importance. Some examples are: auditoria, concert halls, recording studios, and lecture theatres etc. In the design of such buildings careful attention has to be paid to achieving superior acoustic qualities. This study was aimed at exploring the available design practices with respect to acoustic quality and also at investigating the methods for the assessment of acoustic quality in buildings after construction. The acoustic requirements of different types of buildings are different. Rooms meant for speech such as lecture theatres should ensure that every member of the audience hears the speaker clearly. A concert hall needs to ensure that the music lingers on for a short time without dying down too rapidly. A recording studio for speech should minimize the reverberations. The most important parameter that governs the acoustic quality of such a room is the reverberation time. It is defined as the time taken for a sound to decay by 60 db. In addition, the sound level distribution within a room also is an important consideration. Both these depend on the geometric shape and the dimensions of the room, and the acoustic properties of the materials used in the construction of the room including the furniture. Some guidelines are available for the design of buildings with good acoustic qualities. For example, there are recommended values for reverberation time, volume per seat, ratios of room dimensions etc. There are recommendations regarding the shapes of rooms, roofs, ceilings etc. These guidelines were compiled as the first step in the present study. In order to investigate their effectiveness two lecture rooms in the Faculty of Engineering - viz. room no. 9 (considered to have poor acoustic qualities) and room no. 2 (thought to have good acoustic qualities) - were selected for experimental testing. The dimensions of these rooms were compared against the recommendations. The reverberation times of each of these two lecture rooms were first computed using analytical methods. Then they were measured experimentally and the values were compared with the recommended values. In addition the sound level distributions within each room were studied to see whether there were any areas of poor reception. Based on the results the following conclusions were drawn: (a) The guidelines given in literature for good acoustic design of buildings do in fact help to produce good results. (b) The analytical procedures available for the calculation of reverberation times are capable of yielding satisfactory estimates and the reverberation time is a good measure of the acoustic quality of a room. (c) Proper design procedures which pay adequate attention to guidelines regarding acoustics can improve the acoustic quality of buildings a great deal.
A mathematical model to predict groundwater contamination due to pesticide application
(University of Peradeniya, 1998-11-07) Kumaragamage, D
Mathematical models are often used to describe the transport of agro-chemicals in soils. Such models have been successfully used in many countries to predict the extent of groundwater contamination by various pesticides under certain soil and environmental conditions. The objective of this study was to formulate and validate a mathematical model to describe pesticide transport in soils, which can be used to predict the extent of groundwater contamination. The classical convective-dispersive transport equation was used considering irreversible removal of pesticide from solution due to adsorption and degradation. Preliminary experiments using carbofuran indicated that adsorption by soil particles is rapid and equilibrium was reached quickly, and that adsorption data in most soils fitted well to linear isotherm. Therefore, when formulating the model, a local equilibrium assumption with linear isotherm was used to characterize pesticide adsorption. The degradation of pesticide was assumed to be a first order kinetic process, and the degradation constants were obtained from literature. The model was validated using data obtained for carbofuran in a column leaching study, where the soil column was initially saturated with water. Four soils were used, including two ultisols, one alfisol and one inceptisol. A known carbofuran concentration was applied to the surface of the column and was thereafter followed by carbofuran free solution. The leachate samples were analyzed for carbofuran concentrations and leaching was continued until the carbofuran concentration in the leachate is undetectable. In curve fitting the numerical solution of the transport equation to the observed data, it was assumed that the solution sample represents volume-averaged concentrations. The average pore velocity was calculated by dividing the soil water flux by volumetric moisture content. In all soils, the model prediction fitted well to the observed data for carbofuran. This model therefore can be used to predict the concentration of carbofuran in moving water at any soil depth, given the soil conditions. However, to use this model for other pesticides, preliminary information regarding adsorption and degradation should be available and the transport model should be modified accordingly.
Protected culture for yield stability and high quality of tomato under different weather and agro-climatic conditions
(University of Peradeniya, 1998-11-07) Weerakkody, W. A. P.; Peiris, B. C. N.
Protected (indoor) culture is renowned for high yield, quality and production stability of crops in a range of undesirable environments. Therefore, the applicability of protected culture to Sri Lankan vegetable cultivation was investigated in two steps. In the first step, indoor structures and few improved technologies were compared with the conventional open-field culture in two seasons. In the second step, the treatments were further modified and tested under different farmer situations and agro-ecological conditions. In the first step, the highest yield was reported by the polythene house under rainy conditions (during Yala) and the shed house under dry conditions (during Maha). The effect of indoor culture on marketable fruit number, fruit damages and locular materials varied with the weather. Improved technology produced high quality fruits under rainy conditions. Improvements in the yield and fruit quality indicated a potential increase in farmer income despite the high cost of protected culture. In the second step, protected culture (modified) and the location, Rahangala assured enhanced yield components, fruit size and damage-free fruits. In addition, the interactions gave rise to higher yield components and fruit size at Rahangala and high acidity and locular material content at Peradeniya under protected culture. The fruits at Peradeniya had the highest Brix value. High and stable farmer income was reported due to high fruit quality, and yield assurance at Rahangala during extremely high rainy season. The polythene house with improved technology was more productive and economical for the agro-ecological conditions at Rahangala in terms of yield and external fruit quality of tomato while it was more suitable for Peradeniya in terms of internal fruit quality of tomato.
Ambewalamides A and B, Novel Antineoplastic Compounds from a Sri Lankan USNEA SP
(University of Peradeniya, 1998-11-07) Karunaratne, V.; Bombuwala, K.; De Silva, E. D.
Department of Chemistry, University of Peradeniya *Department of Chemistry, University of Colombo Lichens produce a wide range of natural products and many are unique to lichens and an appreciable number have been shown to have antimicrobial, and other biological activities of potential medicinal value. The present study describes the isolation of two novel endodisulphides from an Usnea species. Specimens of the Usnea sp. were collected from the surface of a decaying tree, identified asAcacia deccurens in Ambewala, Central Province, Sri Lanka. The air- dried lichen (950 g) was exhaustively extracted with CH2Cl2 at room temperature to give a crude gum (5.1 g) that was fractionated via silica gel medium pressure liquid chromatography (eluent: step gradient from hexane to MeOH/CH2CI2, 4:96), silica gel preparative chromatography (eluent CH2CI2) and Sephadex LH-20 chromatography (eluent: CH2CI2/MeOH, 2:8) to give a crystalline fraction that contained the mixture of ambewelamides A and B. Final purification was accomplished using normal phase HPLC (Waters Radical PAK cartridge; eluent: CH2CI2/McOH, 20: 1) to give 13.4 mg of ambewelamide A and 1.4 mg of anbewelamide B, both as optically active, clear crystalline plates. The structure of the compounds were elucidated by a combination of high resolution FAB mass spectroscopy, and lD and 2D NMR (COSY & HMBC) spectroscopy. The final confirmation was arrived at by single crystal X-ray diffraction techniques. Ambewelarnide A exhibited potent in vitro cytotoxicity (murine leukemia P388: IC50 = 8.6 ng/ml.) and it also showed significant in vivo antineoplastic activity (P388: % CIT 140 @ 160 ~lg/Kg). To [he best of our knowledge, this is the most potent and most promising anticancer compound to be discovered from a Sri Lankan source (both terrestrial and marine). Diagram(See the pdf version of the Scanned copy) Ambewelamide A: R = (CHz) ZCH3 Ambewelamide B: R = (CHz) 4CH3
LP gas conversion in petrol engines
(University of Peradeniya, 1998-11-07) Sumanasiri, K. E. D.
Conversion of Petrol engine to run by Liquified Petroleum (LP) gas is becoming increasingly common in Sri Lanka due to the high price of petrol compared to cheaper LP gas option. Even though the diesel engines can be converted, it has not been paid much attention due to the low price of diesel. Many petrol vehicle owners are still searching for advantages and disadvantages of different conversion systems for which the cost varies from Rs. 10,000 to 50,000 depending on the conversion system. The paper presents a study which involves identifying the differences of the engine performance when converted to run from petrol to LP gas, rather than the cost effectiveness. The Nissan petrol engine test bed (carburettor system) available at the Department of Mechanical Engineering was converted to be operated using gas from a domestic LP gas cylinder. Different arrangements were tested to understand the engine performance by changing the air: fuel ratio, by heating of gas supply, by changing cylinder pressure etc. Indicator diagrams were obtained to study the pressure variation inside the engine cylinder when petrol and LP gas are combusted. Exhaust gas emissions were analysed using the Orsat's apparatus. It was found that the volumetric consumption of LP gas is higher than that of petrol. Heating of the gas supply reduced the gas consumption and reduced the engine temperature. No significant difference in the exhaust emission was identified perhaps due to the accuracy of the gas analyser. The ignition advance angle should be altered for better performance of the engine when running using LP gas which are preset for best performance when running with petrol. The trails were made in a test engine with variation of brake loads and the performance during actual running conditions of vehicles should be studied separately. It is to be pointed out that the facilities of an advanced carburettor are not fully utilised when the engine is converted to run on LP gas. The engine performance could be enhanced if petrol and LP gas are used together to run the engine.
Surface sensitive v-shaped switching in chiral smectic liquid crystals.
(University of Peradeniya, 1998-11-07) Chandani Perera, A. D. L.
Antiferroelectricity in chiral smectic liquid crystals shows tristable switching, which is the electric-field-induced transition between antiferroelectric (AF) and ferroelectric (F) phases and has characteristic DC threshold and hysteresis. Although antiferroelectric liquid crystals has some display characteristics superior to ferroelectric liquid crystals, the pretransitional effect in the electric-field-induced AF-F phase transition, which appears as a slight increase in the transmittance below the threshold prevents antiferroelectric liquid crystal displays from achieving much higher contrast. During the development of materials to suppress this pretransitional behaviour, liquid crystalline materials showing thresholdless, hysteresis-free, V-shaped switching have been discovered. This V -shaped switching has attractive display characteristics such as wide viewing angle with high contrast ratio, fast response to applied field etc. suggesting potential for active matrix or thin film addressing in display devices. This paper presents a study of the influence of the alignment layer coated on the substrate on the V -shaped switching. The liquid crystalline material 4-[(1- trifluoromethyl- 5 - ethoxy) phenyloxycarbonyl- 3 - fluoro] phenyI4'-(n-undecyloxy) biphenyl- 4 -carboxylate used has the following phase sequence. Isotropic (82 oc) Sm A (81 oc) Sm X* This material shows V -shaped switching in the phase denoted by Sm X'" in thin homogeneous cells. Several polyimides with different chemical structures were used as the alignment layer. In this study, we investigated the influence of the alignment layer on the V -shaped switching by measuring the optical transmittance of the liquid crystal cells made with various alignment layers, under crossed nicols while applying a triangular wave voltage at various frequencies and temperatures. One side rubbed thin homogeneous cells were prepared. The polarization switching current peaks were also observed in the same cells by applying a 1 Hz triangular wave voltage. In order to confirm the surface sensitiveness of V -shaped switching, typical ferroelectric and antiferroelectric liquid crystalline materials were used and carried out similar measurements. It was found that this V -shaped switching strongly depends on the thickness of the alignment layer coated on the substrate surface. Thick alignment layers give rise to ideal V-shaped switching while thin layers change V -shaped switching to W-shaped switching. Further, it was found that typical ferroelectric and antiferroelectric switching unlike V -shaped switching have essentially no dependence on the thickness of the alignment layer. Very broad switching current peaks were observed for V-shaped switching which is quite different from the shape of the typical switching current peaks of ferroelectric/antiferroelectric liquid crystals. This broad switching current peak would be a characteristic feature of V-shaped switching.

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