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Status of fish diversity and fishing gears in the fishery of Nanthikadal Lagoon, Mullaitivu, Sri Lanka

2022-01-01T00:00:00Z

Title: Status of fish diversity and fishing gears in the fishery of Nanthikadal Lagoon, Mullaitivu, Sri Lanka Authors: Surenthar, P.; Sivashanthini, K. Abstract: The Northern coast of Sri Lanka is home to a larger number of lagoons, totalling up to 804 km2. Nanthikadal lagoon is a significant lagoon that exists in the coastal zone of the Mullaitivu District between 9° 17’ N and 80° 48’E. Species occurrences and their types are good indicators to express the health status of the lagoon ecosystem. The present investigation was carried out for the first time to record the finfish and shellfish diversity, diversity indices and the fishing gears used to capture these fishes in the Nanthikadal lagoon by collecting monthly samples from the fish landing centres from September 2017 to August 2019. Collected species were identified using FAO species identification field guide. During the field survey, the number of organisms caught from all species were also counted. Diversity indices such as Dominance, Simpson, Shannon and Evenness were calculated by using PAST software. Fish numbers were graphically compared through cluster analysis by Unweighted Pair Group Method with Arithmetic mean (UPGMA). Fishing gears used and details on mesh size of nets were collected by using questionnaire and face to face interview with the fishermen. Seventeen finfish and five shellfish species belonging to seventeen families were identified during the study period. Tilapia mossambica made the highest percentage contribution (29.34%). The minimum contribution was reported by species such as Portunus pelagicus, Scylla serrata, Scatophagus argus, Lutjanus johnii, Tricanthus biaculeatus and Chanos chanos (<1%). The highest and lowest abundance was found in post-monsoon and pre-monsoon periods respectively. Simpson index and Shannon index were high in the monsoon season. Strongylura strongylura and Gerres abbreviates showed a close relationship based on month-wise cluster analysis. Cast net was the most commonly used, and legal fishing gear. Part-time fishermen actively participated in shrimp capturing from brackish water. In the present study, the important components of the lagoon fishery such as fish and usage of fishing gears were analyzed to determine the present status of Nanthikadal lagoon fishery. These findings will be helpful for stakeholders in this region for sustainable fishery management and ultimately supporting the Ministry of Fisheries and Aquatic Resource Development by providing required fundamental information to develop a lagoon management plan in the future.

Development of Natural Sodium Montmorillonite as a Cathode Material

2022-01-01T00:00:00Z

Title: Development of Natural Sodium Montmorillonite as a Cathode Material Authors: Goonathilake, W.K.O.W.; Bandaranayake, P.W.S.K. Abstract: Montmorillonite (MMT) is naturally occurring clay mineral in Sri Lanka. It is an aluminosilicate crystalline compound with layered structure. In this structure an octahedral sheet of aluminum-oxygen (Al-O) is sandwiched between two tetrahedral sheets of silicon-oxygen (Si-O). The MMT structure can accommodate various monovalent and divalent cations such as H+, Li+, Na+, Mg2+ within the interlayer spacing. Natural Li-MMT and Na-MMT are found in various parts of the world. The MMT structure has an ability to exchange interlayer cations with various other divalent cations. MMT with interlayer alkali cations show appreciable ionic conductivity. Natural Na-MMT found in Sri Lanka was used for the present study. To improve the ionic conductivity of natural Na-MMT, the structure was further saturated with Na+ ions. The Na+ ion concentration of saturated Na-MMT was measured by Inductive Couple Plasma Mass Spectroscopy. The structural and electrical properties of Na saturated MMT were characterized by SEM and Complex Impedance Spectroscopy. As a result of Na+ ion saturation the bulk conductivity of Na-MMT was increased to 3.41×10-4 S cm-1 at 30 C . Saturated Na-MMT has negligible electronic conductivity which is less than 0.001%. For using Na-MMT as intercalation cathode materials in rechargeable batteries, an appreciable electronic conductivity must also be present. To enhance the electronic conductivity of saturated Na-MMT, carbon black was mixed. The electronic transference number of saturated Na-MMT pellets was measured by the DC polarization technique. The electronic transference number of saturated Na-MMT with 25% and 30% carbon black were 0.81 and 0.87 respectively.

Examining the Influences of the Mathematics Teachers’ Pedagogical Content Knowledge on Learning Algebra in Grade Six

2022-01-01T00:00:00Z

Title: Examining the Influences of the Mathematics Teachers’ Pedagogical Content Knowledge on Learning Algebra in Grade Six Authors: Rupasinghe, D.D.; Amarasinghe, A.K.; Vitharana, P.R.K.A. Abstract: This mixed method study findings indicate that the pedagogical content knowledge (PCK) of the teachers is an influencing factor of learning algebra in grade six in Sri Lankan schools. Reliable and validated two questionnaires followed by 24 of eight mathematics teachers’ classroom observations and post- lesson interviews were administered for collecting data in the explanatory sequential mixed methods research design. Field notes, lesson video recordings and the interview data were triangulated in terms of the reliability of the qualitative data while the two questionnaires were piloted and designed by Delphi method before collecting quantitative data. The Cronbach’s alpha of the questionnaire-2 was 7.59. SPSS statistical software was used in the first phase while the reflexive thematic analysis method was used in the second phase of the data analysis process. The study results of the first phase indicate that the mathematics teachers’ PCK in teaching algebra is at a medium level and not satisfactory. Teachers’ PCK in algebra was found to be multi-functional, indicating no positive relationship with academic qualification, professional qualification and professional experiences. Further analysis showed that there was no correlation between the PCK and the PCK knowledge dimensions, declarative, procedural and conditional knowledge. Qualitative study results revealed that the mathematics teachers’ PCK is low, in building algebraic concepts in the students’ mind, addressing the students’ algebraic misconceptions and understanding of students’ algebraic thinking. Finally, learning algebra in algebraic symbols, variables and algebraic expressions were observed and found to be less effective. Therefore, content knowledge and pedagogical knowledge based professional teacher development programs are recommended for enhancing the students’ learning algebra in the classrooms.

Synthesis, characterisation, ion chelation exchange capability and antibacterial properties of the o-cresol-formaldehyde-catechol-based copolymer

2022-01-01T00:00:00Z

Title: Synthesis, characterisation, ion chelation exchange capability and antibacterial properties of the o-cresol-formaldehyde-catechol-based copolymer Authors: Jayathilake, N.H.A.M.; Arasaretnam, S.; Mahendranathan, C. Abstract: An ion exchange resin chelator was synthesized from o-cresol, catechol and formaldehyde through the condensation process in the molar ratio of 1:3:5 in the presence of 1 M hydrochloric acid as a catalyst. The resulting copolymer was characterized by IR spectral data. The cation exchange capacity was measured; the effect of metal ion concentration, pH effect, and the ratio of the cation exchange reaction were studied. The chelation ion-exchange properties were also studied with the batch equilibrium method. The formed copolymer chelation ion-exchange properties of the copolymer were analyzed for Cd2+, Cr2+, Fe2+ and Mg2+ ions. The resin was proved selective chelating ion- exchange copolymer for the above metals. The study was carried out over a wide pH range and in media of various ionic concentrations for the metals. The antibacterial properties of the synthesized resin were also investigated, using the well diffusion method for the gram-positive bacteria, Staphylococcus aureus and the gram-negative bacteria E coli. The results showed a significant inhibiting effect against the tested bacteria, against the formed resin copolymer.