PURSE 2002

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/49

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    Student teacher interaction and learing outcome
    (The University of Peradeniya, 2002-10-30) Wickramarachchi, W. A. R.; Sugathapala, R. D.
    In student learning, a variety of theoretical perspectives focus on the contrast between the organizations of knowledge as discrete, serial elements to be remembered and the integration and transformation of knowledge in to a personally constructed meaning full entity. Marton (1975) first made this distinction when he described approaches to learning in terms of either deep or surface processing of information. This conceptualization has led to much further theoretical development (Biggs. 1987: Entwiste, et al. 1991). Biggs (1989, 1982) has developed an interactive system model of teaching and learning map how students' general conception of learning, interact with characteristics in the learning environment to produce learning outcomes. This system has three components: Presage, Process and Product. Presage factors include not only the students characteristics but also the learning context involving teacher and teaching methods. The specific learning strategies that they consequently adopt for that learning task is the process. The product of learning outcome is largely influenced by the strategy adopted and the presage factors. As a presage factors teacher and teaching methods mainly influenced to the learning outcome. Present study is based on above theoretical perspective. In this study 54 lessons conducted by student teachers who are following the Post Graduate Diploma in Education course were observed by the researches to examine the effects of teaching strategies on students' learning process and product, direct observations and semi structured interviews were conducted for four students from each class. Data were analyzed qualitatively. From the analyzes of data, some important facts were revealed. On the strength of revealed facts following conclusions were made. 1. Whcn teachers focus strongly on active participation of students and creating a supporting environment, students focused on student-centered aspects of the class. 2. In contrast, when traditional expository teaching methods were used students mainly focused on transmission and reproduction.
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    Local changes in contraction related substences in Bovine Oviducts exposed to ovarian steroids and peptides; investigation by in vitro microdiaysis system
    (The University of Peradeniya, 2002-10-30) Wijayagunawardane, M. P. B.; Weerathunga, H. A. S. K.
    The microenvironment in the oviduct is controled by the endocrine, paracrine and autocrine interactions mediated by ovarian and pituitary hormones as well as by the local oviductal products. Thus, in this study, microdialysis system (MDS) was utilized to investigate the effect of luteinizing hormone (LH), oxytocin (OT) and ovarian steroids (progesterone; P4 and estradiol-l Zp; E2) added to the incubation medium on the local secretion of prostaglandins (pG), endothelin-l (ET-I) and angiotensin II (Ang II). A 7 em long microdialysis capillary membrane was implanted in to the lumen of the oviducts collected from post ovulatory phase of the estrous cycle, incubated in TCM 199 in simple organ culture chambers, and the system was gently perfused with Ringer's solution. Addition of LH, ET -1 and LH+ET -1 to the incubation medium induced PGE2 release and the highest stimulatory effect on PGE2 secretion was observed with the combination ofLH+ET- l+E2+P4. The administration of LH, ET-l, P4+E2, LH+ET-l, LH+ET-l+ E2+P4 show a stimulatory effect on PGF2a release. LH, LH+ET-l, LH+ET-l+ E2+P4 stimulate ET-l and Ang II releases. ET-l in the incubation medium stimulate it's own release. When OT was added to the incubation medium it hinders the effect of all these stimulations. The overall results of this study indicated that LH with the E2 and low P4 and/or ET-I bearing the highest stimulatory effect on the production of contraction related substances such as PGE2, PGF2a, ET -1 and Ang II. The administration of OT resulted in an inhibition of the LH stimulated effect on the oviduct. Moreover, the locally produced ET-l acted as an up regulator of it's own secretion. This results provide further evidences for our previously suggested concept on the regulation of oviductal contraction that the preovulatory LH surge, together with a locally recirculated high level of E2 from the Graafian follicle and basal P4 level from regressing corpus Iuteum (CL) induces the maximum stimulation in the oviductal production of PG and ET-l, resulting in the active oviductal contraction for a rapid transport of gametes. OT released from the newly formed CL may block these mechanisms, thus inhibiting the contraction to secure a slow transport of the embryo to the uterus.
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    Establishment cell cultures of tea (Camellia sinensis L.) to study programmed cell death (PHD) in plants.
    (The University of Peradeniya, 2002-10-30) Thilalakarathne, C. L.; Gunawarena, A. H. L. A. N.; Gunasekare, M. T. K.
    Tea (Camellia sinensis L.) is highly heterozygous and predominantly cross-pollinated woody perennial crop. Therefore, the development of improved plant materials through conventional breeding is a laborious and time-consuming task. Alternatively, cell cultures hold great promise in the production of improved cultivars of tea. As there are no studies done in the past to perfect the conditions necessary for establishing cell cultures isolated from plant tissues of tea, the present study aimed at perfecting such conditions. There is clear evidence that Programmed Cell Death (PCD) occurs during plant development and environment response. However, the signals that trigger PCD in plants are unknown. In plants, selective cell death is necessary for growth and survival. Therefore, cell cultures are used to study PCD in vitro. A system was established for isolation of single cells from surface sterilized leaf tissues by digesting them in an enzyme mixture containing 1% (w/v) Macerozyme in cell and protoplast washing medium and mannitol (CPW 1.6 M) for 3 hours. Cells were purified by centrifugation followed by washing in CPW l.6 M solution. Culture density (5x104) was adjusted by counting purified cell suspension on a haemocytometer. Purified isolated cells were then, cultured in Murashige and Skoog basal medium containing 3 % (w/v) sucrose and 1.6 % (w/v) mannitol devoid of growth regulators. Cell viability was determined by staining cells with 0.25 % (w/v) Evan's blue. Characteristics related to PCD were observed using a light microscope. For optimizing yield and viability of isolated cells, factors such as concentrations of enzymes and mannitol, stage or the age of the leaf, type of explant and digestion time were examined. Of the factors tested, optimum yield and viability of cells were obtained when second leaf from the shoot apex was digested with 1% (w/v) Macerozyme in CPW 1.6 M for 3 hours. Under these conditions, it was possible to achieve 1.6 x 106 - 2.0 x 106 cells per gram fresh weight of leaf tissue with viability ranging from 75 - 78 %. Under similar conditions however, in vitro leaf tissues resulted inferior quality cells as well as more protoplasts than cells. Cell division started at 24 hours after culture. Percentage of dividing cells reached its peak 144 hours (6 days) after culture and declined afterwards. One of the characteristics of PCD, condensation of cytoplasm was observed in freshly isolated cells and dividing cells. Dead cells were stained in blue color whereas viable cells were remained unstained. For further studies of PCD characteristics, transmission electron microscopic observations are needed
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    Engineering analysis and fatigue evaluation of ancient riveted wrought iron railway bridges
    (The University of Peradeniya, 2002-10-30) Siriwardane, S. A. S. C.; Adasooriya, A. M. N. D.; Herath, K. R. B.; Dissanayake, P. B. R.; Mauroof, A. L. M.; Ranweera, M. P.
    Evaluation of load carrying capacity and remaining service life of railway bridges in Sri Lanka has become of primary importance since most of the major bridges in the country are more than 50 to 100 years old. The task of dealing with these old bridges has become complex as many codes of practice do not provide necessary guidelines for identification of the condition and for evaluating the remaining service life. The analysis of a railway bridge was carried out as a case study. The method adopted in evaluating the remaining service life of the bridge was the Miner-Palmgren cumulative damage rule. The bridge considered was a semi-through bridge having eight double system Warren girders supported by cylindrical piers. Several member sets were used in the analysis of the structure considering various cross-sectional properties. The most highly stressed member, i.e. the critical member of each of the member sets was taken into consideration for life evaluation. The aim of this exercise was to find out the remaining service life of each set of members. Out of the various forms of structural failures applicable to bridges the bridge considered was most likely to fail due to the effect of fatigue. The service stresses in the bridge were evaluated using a validated 3D finite element model and the stress cycle distribution of the service conditions were found from the analyses and as well as from the field tests. An impact factor based on the measured strains in dynamic field tests was used for this evaluation. The Miner's summation rule was used in the prediction of the fatigue life of the bridge. Elements of a structure may be subjected to many forms of stress cycles varying both in range and in magnitude. Each element of the structure should be designed considering the number of cycles of different magnitude to which the element is likely to be subjected during the expected life of the structure. The number of cycles of each magnitude must be estimated by the designer in the light of available data, considering the probable frequency of occurrence of each type of loading. Due to fatigue under current loadings, speeds, and frequencies of operation, the lowest remaining life found for a member under the investigation was found to be 20 years. Thus, it may be concluded that the Bridge deck can be used for another 20 years provided that the speed, frequency, and the weight of the trains are not increased from the present value. If proper maintenance work is carried out and critical members are replaced by new members having longer life, the bridge may be able to provide service for a further period.
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    The effect of fish type, marination and smoke source on the quality of smoked fish product
    (The University of Peradeniya, 2002-10-30) Ananthi, K.; Cyril, H. W.; Ganepola, M.
    Smoking is an ancient technique that is commonly used in contribution with brining and curing. In industrialized countries, smoking of fish is done for enhancement of flavor and texture. it adds considerable value to the fish. Smoking provide partial protection against microbiological, enzymatic and chemical deterioration. Fish is main seafood act as protein rich source. Since smoking of fish act as value adding process and preservative measure, smoked fish product was developed to fulfill the requirements of producer and consumers. Five fish types namely seer, mallet, lo-musso, travelly and shark were filleted and, smoked after dipping into the standard brine solution (7ppm). Then samples were subjected to an untrained taste panel to select the best types for smoking. Sensory evaluation was conducted based on 5-point Hedonic scale and result was analyzed using Friedman test. Subsequently, selected fishes seer and mallet were dipped into different recipies of brines, soy source with white wine brine, honey cured brine, onion cheese spread, and mayonnaise and, smoked. Through sensory analysis honey cured brine was selected as best marination for seer fish and soy source with white wine brine was selected as best marination for mallet fish. Thereafter seer fish which was marinated with honey cured brine and mallet fish which was marinated with soy source with white wine brine were smoked using different smoke sources such as Cinnamon saw dust and Clove leaves. Through sensory analysis best product was selected. Finally Seer fish marinated with Honey cured brine and smoked by Cinnamon wood dust and saw dust combination (2: 1) was selected as best product. The overall acceptability was considered mainly to select best treatment. Then the selected best product was packed in vacuum and normal packing and stored at the temperature of 4 ± 2°C and quality of the product was checked weekly by measuring pH, color, water holding capacity, rancidity(TBA value), water activity and total plate count until 4 weeks of time. Even though water activity was higher in the smoked seer fish, microbial level was satisfactory (less than 105 CFU/g of smoked fish) for both packaging types up to 4th weeks of storage at 4 ± 2°C. The pH, TBA value and water holding capacity were increased rapidly with storage period on smoked seer fish, which packed under normal conditions than that packed under vacuum. This indicates vacuum packing was improved storage life of smoked fish product