Chemistry
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Item Repellency and toxicity of four essential oils to Sitophilus oryzae L. (Coleoptera: Curculionidae)(2004) Paranagama, P.A.; Abeysekera, K.H.T.; Nugaliyadde, L.; Abeywickrama, K.P.Item Characterisation of spinifex (Triodia pungens) resin and fibres(Australasian Polymer Symposium, Cairns, QLD, Australia, 2009) de Silva, D.S.M.; Memmott, P.; Flutter, N.; Martin, D.Spinifex grasses have been largely ignored as a sustainable resource despite their widespread distribution throughout Australia. This project involves an in-depth study of the structure and properties of both the leaf and resinous components of various spinifex species and an investigation into the preparation and properties of Spinifex-based composite materials. The present work is comprised of two components, analysis of the resin and mechanical testing of various fibrous components. Resin of the soft Spinifex species (Triodia pungens) was extracted from the resinous stems of Spinifex grasses into methanol by soxhlet extraction. The dried extracts were chromatographed on silica gel, eluted with the solvent mixture of hexane and methanol with increasing polarity to give ten fractions. Resin was also extracted directly by soaking the resinous stems for 8 hours in hexane and methanol in order to study the polar and non-polar volatile compounds. The chemical composition of the fractions of the resin has been studied by means of GC-MS and LC-MS. ATR-FTIR spectroscopy was used to identify the functional groups present in the resin. Thermal analysis was also performed using DSC. GC-MS chromatograms revealedItem Towards Novel Biomimetic Building Materials: Evaluating Aboriginal And Western Scientific Knowledge Of Spinifex Grass(Australian Institute of Bioengineering and Nanotechnology, Brisbane, Australia, 2009) Memmott, P.; Martin, D.; de Silva, D.S.M.; Flutter, N.; Gamage, H.; Schmidt, S.; Fensham, R.Deriving new materials from renewable, non-petrochemical feedstocks is currently an area of great interest to materials engineers. Spinifex grasses have been largely ignored as a sustainable resource despite their widespread availability throughout Australia and their unique biology that has evolved in harsh environments. This project involves an in-depth study of the structure and properties of both the leaf and resinous components of various Spinifex species. The properties will be benchmarked against other natural fibers and natural resins. The objective of this project is to apply traditional Aboriginal knowledge to produce novel biomimetic building materials based on Spinifex.Item Manufacture, properties and use of activated carbon from Cashew nut shells in waste water treatment(Institute of Chemistry Ceylon, 2009) Roshini, P.H.S.; Mortha, J.T.S.; de Silva, D.S.M.Item Effects of pretreatments on extending the self life of minimally processed Rhisomes of Lasia spinosa(Institute of Chemistry Ceylon, 2008) Liyanage, S.; Wimalasena, S.; de Silva, D.S.M.Item Quantification of arsenic and phosphorus in calcium carbide treated mangoes(Sri Lanka Association for the Advancement of Science, 2004) Haturusinghe, L.S.; de Silva, D.S.M.; Wimalasena, S.Item Use of recycled polyethylene teraphthalate and rice hull in polymer concrete(Sri Lanka Association for the Advancement of Science, 2004) Tissera, P.T.N.; Motha, J.T.S.; de Silva, D.S.M.Item Study of disorder in different phases of tetratriacontane and binary alkane mixture, using vibrational spectroscopy(Journal of Physical Chemistry, 2007) Wickremarachchi, P.A.S.R.; Spells, S.J.; de Silva, D.S.M.Raman spectroscopy has been used to investigate the monoclinic crystal f rotator f melt phase transitions in n-C34H70, for both real-time heating and cooling runs. Changes in band intensity and frequency in the CH2 bending, CH2 twisting, skeletal C-C stretching, and CH3 rocking regions revealed both transitions, particularly when using band components related to gauche bonds. In the room temperature infrared spectrum, the CH2 rocking-twisting and CH2 wagging progressions were observed and indexed for n-C34H70 and a 2:1 (w/w) mixture of C34H70 and C36D74. This led to best estimates for the all-trans crystal core in both cases of 33 to 34 carbon atoms, indicating that the core corresponds to almost the whole of the C34H70 molecule.Item Effect of pretreatments on extending the shelf life of minimally processed “Ela Batu” (Solanum surattense)(Tropical Agricultural Research and Extension, 2007) Dharmabandu, P.T.S.; de Silva, D.S.M.; Wimalasena, S.; Wijesinghe, W.A.J.P.; Sarananda, S.Due to the cumbersome nature of the cleaning process and high time consumption for the preparation, most Sri Lankan housewives are reluctant to prepare Solunum surattense (Sinh. Elabatu) as a vegetable for their diet. If S. surattense is available in „ready to cook‟ form it would become a popular vegetable among Sri Lankan housewives. Studies were carried out to identify the best conditions for minimal processing of S. surattense. As pre-treatments 2% (w/v) calcium chloride solution, 0.6% (w/v) turmeric solution, 1% (w/v) vinegar solution, 2% (w/v) calcium chloride + 0.6% (w/v) turmeric solution and 2% (w/v) calcium chloride +1% (w/v) vinegar solution were used. Low density polyethylene (LDPE) pouches (gauge 150) were used to pack pre-treated samples and stored them at 8ºC. In all the pre-treated samples stored at 8ºC, Salmonella and E. coli were absent and coliform counts were at acceptable levels. Sensory evaluation of cooked pre-treated samples showed that the sample pre-treated with 2% (w/v) calcium chloride was the best. In addition to shelf life, colour, and degree of browning of the treatments were also acceptable. Treating S. surattense cut fruits with 2% (w/v) calcium chlo-ride solution before packing in LDPE pouches and storing in 8ºC found to be the best method for extending shelf-life of the fruit. The product could be kept for seven days.Item The effects of self-poisoning on crystal morphology and growth rates(Advances in Polymer Science, 2005) Ungar, G.; Putra, E.G.R.; de Silva, D.S.M.; Shcherbina, M.A.Recent extensive experimental work and the limited theoretical studies of the phenomenon of self-poisoning of the crystal growth face are reviewed. The effect arises from incorrect but nearly stable stem attachments which obstruct productive growth. Experimental data on the temperature and concentration dependence of growth rates and the morphology of long-chain monodisperse n-alkanes from C162H326 to C390H782 are surveyed and compared to some previously established data on poly(ethylene oxide) fractions, as well as on polyethylene. The anomalous growth rate minima in both temperature and concentration dependence of growth rates are accompanied by profound changes in crystal habits, which have been analysed in terms of growth rates on different crystallographic faces, and in terms of separate rates of step nucleation and propagation. In some cases non-nucleated rough-surface growth is approached. The phenomena covered include “poisoning” minima induced by guest species, the “dilution wave” effect, autocatalytic crystallization, pre-ordering in solution, two-dimensional nucleation, and the kinetic roughening and tilt of basal surfaces.