Showing papers by "University of Peradeniya published in 1983"

Variations in the particles produced at the end of mastication in subjects with different types of dentition.

Abstract: Summary The final composition of the size of particles of food or the swallowable composition (SC) has been investigated in subjects with different types of dentition. A convenient mouthful of hard-baked soya beans was masticated and thereafter the bolus was dried, sieved and weighed. Full denture wearers prepared a SC with a mode value around 4000 μm whereas subjects with mixed dentition prepared a SC with a mode value around 2000 μm. Subjects with partial dentition produced wide variations in the SC. To produce a SC which is usually swallowed by a particular subject the quantity of masticated food should bear an optimum ratio to the area of the healthy oral tissues.

The abbreviated larval development of caridina singhalensis ortmann, 1894 (decapoda, atyidae)

Abstract: The highly abbreviated development of Caridina singhalensis, endemic to Sri Lanka, is described. The peculiar morphological features found in the larvae are compared to those of the two other examples of direct development described in the Atyidae. The marked morphological similarities among the reduced larval phases, independently evolved in C. singhalensis and the Japanese species (C. brevirostris and C. denticulata ishigakiensis), allow the identification of a syndrome associated with direct development in the genus. Caridina singhalensis Ortmann, 1894, is endemic to the highlands of Sri Lanka where its present distribution is restricted to a six mile stretch of the headwaters of the Belihul Oya (6?48'N, 80?48'E). This species lays very large eggs compared to other caridinids and undergoes a direct development. While a number of descriptions of larval development are available for the genus Caridina (Babu, 1963; Benzie, 1982; Chinnaya, 1974; Daday, 1907; Glaister, 1976; Lakshmi, 1975; Nair, 1949; Pillai, 1975; Shen, 1939; Shokita, 1973a, 1976, and 1981), only two examples of direct development have been reported previously-C. brevirostris (Shokita, 1973a) and C. denticulata (Shen, 1939; Mizue and Iwamoto, 1961; Shokita, 1976). (The status of C. denticulata subspecies is not clear and the larval description of Shen (1939) may refer to a species different from those described by the other authors. If the specific difference between these forms is upheld then the number of direct developments described in the Atyidae previous to the present paper would be three. Details are given in the discussion.) The development of C. singhalensis is of interest not only as the third direct development reported for the Atyidae but also because some of the morphological changes associated with extremely abbreviated development have progressed further in this species compared to those described to date. In addition the first stage larva shares a number of peculiar features with C. brevirostris and C. denticulata, although clearly of separate origin, and the description of this form allows the identification of a syndrome associated with direct development in the Atyidae. The present paper describes the larval development of C. singhalensis and discusses these features. Ovigerous females were collected from the Belihul Oya at Black Bridge on Horton Plains (1 inch Haputale Map Sheet M, grid ref. 204179) in February/March 1980 and transported to laboratories in Peradeniya University, Kandy. Each female was placed in a small 10 ml container and checks were made several times daily to establish the presence of larvae. While a number of eggs hatched successfully, none of the larvae moulted to stage II and all died within a few hours of hatching. Mortality was in all probability due to high temperatures in the laboratory. No controlled temperature facilities were available and ambient temperature was approximately 30?C, far in excess of the temperatures of approximately 17-20?C to which the animals are exposed naturally in the highlands. Samples of larvae from field populations at Horton Plains, where C. singhalensis is the only prawn, were therefore obtained and moult stages inferred from size and morphological differences. Individual larvae were preserved in 70% alcohol and later dissected in polyvinyl lactophenol, stained with lignin pink. Drawings were made with the aid of a camera lucida and measurements made using a compound microscope and ocular graticule. Carapace measurements were made from the antero

Humified phenol-rich plant residues and soil urease activity

Abstract: A greenhouse experiment was conducted to examine the comparative effects of phenolrich and phenol-poor plant residues after prolonged decomposition, on the urease activity of an acid soil. Addition of organic residues increased soil urease activity over that of control; but soils amended with phenol-rich residues had a urease activity which was about 50% lower than that of soils amended with phenol-poor residues. This reduction in soil urease activity was attributed to the higher content of soil polyphenols present in the soils amended with phenol-rich residues.

Studies on terpenoids and steroids. Part 3. Structure and synthesis of a new phenolic D:A-friedo-24-noroleanane triterpenoid, zeylasterone, from kokoona zeylanica

Abstract: Zeylasterone, the first of a novel series of natural phenolic nortriterpenes from Kokoona zeylanica(Celastraceae) and ‘ kokum soap ’ has been shown to be 29-methyl hydrogen 2,3-dihydroxy-6-oxo-D:A-friedo-24-noroleana-1,3,5(10),7-tetraene-23,29-dioate (3) on the basis of spectroscopic and chemical evidence. Trimethylzeylasterone (8) has been synthesized from pristimerin, a quinone methide present in K. zeylanica and ‘ kokum soap ’. The biosynthetic importance of some triterpenoids of K. zeylanica is discussed.

Studies on atyidae (decapoda, caridea) of sri lanka. ii. distribution of atyid shrimps in sri lanka

Abstract: [Dix especes de crevette atyides sont recensees du Sri Lanka, a savoir, Caridina costai de Silva, 1982; C. fernandoi Arudpragasam & Costa, 1962; C. pristis Roux, 1931; C. singhalensis Ortmann, 1894; C. zeylanica Arudpragasam & Costa, 1962; C. gracilirostris De Man, 1892; C. propinqua De Man, 1908; C. simoni Bouvier, 1904; C. typus H. Milne Edwards, 1837 et Atya spinipes Newport, 1847. Cinq especes semblent endemiques, alors que les cinq autres sont largement distribuees dans la region Indo-Pacifique. La sous-espece de C. simoni presente dans l'ile, c'est a dire C. simoni simoni, serait endemique. Cette sous-espece, ainsi que C. fernandoi, sont les deux formes les plus largement repandues. C. pristis frequente principalement les zones peu elevees des hauteurs centrales (300-1000 m) et les cours d'eau a faible courant. Ses deux sous-especes, C. pristis pristis et C. pristis cruszi, sont l'une et l'autre confinees au Sri Lanka. Atya spinipes vit dans les eaux a courant rapide. Caridina costai n'est connue que d'une localite. C. gracilirostris, C. propinqua, C. typus et C. zeylanica sont des formes d'eau saumâtre a basse salinite, trouvees dans les zones cotieres, les trois premieres n'etant connues que de la region sud-ouest de l'ile. Des deux sous-especes de C. gracilirostris, seule C. gracilirostris gracilirostris est presente au Sri Lanka. C. singhalensis et la seule crevette connue au-dessus de 1000 metres et sa distribution est restreinte a un cours d'eau aux plus hautes altitudes de l'ile (au dessus de 2000 m). En dehors des barrieres geographiques possibles, il est probable que la temperature est aussi un facteur qui cantonne la majorite des atyides aux basses altitudes et C. singhalensis aux altitudes elevees., Dix especes de crevette atyides sont recensees du Sri Lanka, a savoir, Caridina costai de Silva, 1982; C. fernandoi Arudpragasam & Costa, 1962; C. pristis Roux, 1931; C. singhalensis Ortmann, 1894; C. zeylanica Arudpragasam & Costa, 1962; C. gracilirostris De Man, 1892; C. propinqua De Man, 1908; C. simoni Bouvier, 1904; C. typus H. Milne Edwards, 1837 et Atya spinipes Newport, 1847. Cinq especes semblent endemiques, alors que les cinq autres sont largement distribuees dans la region Indo-Pacifique. La sous-espece de C. simoni presente dans l'ile, c'est a dire C. simoni simoni, serait endemique. Cette sous-espece, ainsi que C. fernandoi, sont les deux formes les plus largement repandues. C. pristis frequente principalement les zones peu elevees des hauteurs centrales (300-1000 m) et les cours d'eau a faible courant. Ses deux sous-especes, C. pristis pristis et C. pristis cruszi, sont l'une et l'autre confinees au Sri Lanka. Atya spinipes vit dans les eaux a courant rapide. Caridina costai n'est connue que d'une localite. C. gracilirostris, C. propinqua, C. typus et C. zeylanica sont des formes d'eau saumâtre a basse salinite, trouvees dans les zones cotieres, les trois premieres n'etant connues que de la region sud-ouest de l'ile. Des deux sous-especes de C. gracilirostris, seule C. gracilirostris gracilirostris est presente au Sri Lanka. C. singhalensis et la seule crevette connue au-dessus de 1000 metres et sa distribution est restreinte a un cours d'eau aux plus hautes altitudes de l'ile (au dessus de 2000 m). En dehors des barrieres geographiques possibles, il est probable que la temperature est aussi un facteur qui cantonne la majorite des atyides aux basses altitudes et C. singhalensis aux altitudes elevees.]

The Genesis of Thorium-Rich Monazite Placer Deposits in Sri Lanka

Abstract: The monazite placers of Sri Lanka are among the world's most thorium rich sediments. This study of the stream sediments and rocks from an area in the southwest of Sri Lanka shows that the highly metamorphosed aluminous schists and gneisses and also granitoid rocks of the Highland and South-west Groups ofthe Precambrian of Sri Lankaare the ~robable source rocks for the thorium-rich monazite. Themanmatic fluids known to have - pervaded the aluminous sediments during the intense folding and metamorphism under granulite facies conditions are considered to have been thorium rich. The P-T conditions of - proved to be ideal for the formation of a variety of gem minerals including gem monazite and other associated heavy minerals.

The effect of oral contraceptive therapy and of pregnancy on serum folate levels of rural Sri Lankan women.

Abstract: Serum folate level packed cell volume and hemoglobin concentration of apparently healthy rural Sri Lankan women between ages 20-45 and earning up to Rs. 500 (Sri Lankan Rs. 35 equals approximately 1 pound Sterling)/month were estimated during pregnancy and when on oral contraceptives (OCs; Ovulen 50/ethinyl estradiol 0.05 mg 1 mg ethynodiol diacetate. Ovulen 50 administration led to a fall in serum folate levels which occurred very rapidly during the 1st 6 months and more slowly thereafter stabilizing at 2.2 ng/ml of very low economic status and at 2.9 ng/ml in the more privileged. There was a steady fall in serum folate concentrations during pregnancy the levels at the end of pregnancy being higher than those in women under OC treatment for 9 months. The need for folate supplementation during OC treatment is stressed. (authors modified)

A survey of aflatoxin contamination of coconut products in Sri Lanka; incidence, origins and recommendations

Abstract: Forty five large scale mills in the 'Coconut Triangle' of Sri Lanka were studied over one year period, for aflatoxin contamination of their products - mainly copra, oil and press cake - to determine the incidence and levels of aflatoxin contamination, and the origin of such contamination. Of 344 samples, approximately 50% contained medium-high levels (0.05 to 1 μg/g, ppm) of aflatoxin B1. None of the samples had levels over 1 ppm. In 99 selected copra kernels with heavy fungal colonisation, the levels ranged from 0.05 t o 4 ppm in 50% of the kernels. Only 2 kernels had higher levels with 10 and 20 ppm: 29% of kernels had levels between trace and 0.05 ppm while no aflatoxin was detected in 18%. The levels detected in cured copra products were lower than those reported in other oilseeds; reasons are discussed. The aflatoxin levels in the products from 25 mills which were in continuous production during the survey period, were classifiable as 'regularly high', 'occasionally high: regularly medium-low' and 'low or nil'. These patterns were correlated with rainfall techniques for curing of copra, conditions of storage, prolonged storage of copra, admixture of high quality copra with substandard kernels for oil extraction and the lack of quality control measures.

Temperature characteristics of turbulent, premixed flames stabilised on a step

Abstract: The paper presents fine-wire thermocouple measurements of temperature and temperature fluctuations in a confined, two-dimensional, premixed methane-air flame of 08 equivalence ratio, stabilised by a backward-facing step, and with bulk flow Reynolds numbers ranging from 2800 to 13000 The results indicate a narrowing of the flame front with decrease in Reynolds number The temperature fluctuation measurements were compensated for thermal inertia and the probability density functions were bimodal with the probability density at the two extremes of the temperature range increasing with fall in Reynolds number Temperature power spectra indicated that the preferred frequencies corresponded to the acoustic frequencies of the combustor system, although the influence of vortex shedding was evident at the lowest Reynolds number

Aflatoxin contamination of coconut oil from small scale mills: toxin levels and their relation to free fatty acid content

Abstract: Coconut oil which was mechanically extracted in small scale mills, from intermittently processed (sun-dried or smoked) Grade 111 or substandard copra kernels. was assayed for free fatty acid and aflatoxin B1. Oil from these samples showed significantly high levels of aflatoxin B1 (mean value 186 ppb in 115 samples of oil) than the levels found in oil from adequately processed copra extracted in large scale industrial mills. The attention of the coconut industry is drawn to this problem as a potential health hazard to humans and animals, from the consumption of the oil and press cake from such inadequately processed kernels. The relationship between free fatty acid (FFA) content and aflatoxin B1 levels in 100 samples of coconut oil from the small scale mills has been investigated. No correlation was found. The conventionally used FFA content as a chemical index of the 'quality' of oil does not reflect the degree of aflatoxin contamination, making it necessary to apply separate assays for aflatoxin contamination in coconut oil, from commercial sources. Possible reasons for the absence of a correlation between FFA and aflatoxin levels in such oils are discussed.

Metal‐organic interactions in environmental pollution

Abstract: The importance of organic matter in complexing heavy metals in polluted environments is now being increasingly recognized. As metal‐scavenging agents, organic matter plays an extremely important role in polluted environments. With the recent discovery of the ability of certain metals such as Hg and As to be methylated and volatilized under environmental conditions by microorganisms, biomethylation is now being intensely studied for a number of industrially important elements such as Sn, Pb, Pt etc. This paper deals with the recent advances in the study of metal‐organic interactions that have an important bearing in environmental pollution.

Studies on terpenoids and steroids. Part 1. Structures of six novel 27-hydroxy and 6β-hydroxy di- and tri-oxygenated D : A-friedo-oleanane triterpenes from Kokoona zeylanica

Abstract: The benzene extract of the inner stem bark of Kokoona zeylanica Thwaites (Celastraceae) contains twelve D : A-friedo-oleananes of which nine are new. The new triterpenes have been classified under three series; kokoonol (3,27-dioxy and 3,21,27-trioxy), zeylanol (3,6-dioxy and 3,6,21-trioxy), and kokzeylanol (3,6,27-trioxy and 3,6,21,27-tetraoxy). Six of these triterpenes belonging to the kokoonol and zeylanol series have been identified as 27-hydroxy-D : A-friedo-oleanan-3-one (4)(kokoonol), 27-hydroxy-D : A-friedo-oleanane-3,21-dione (5)(kokoononol), 21α,27-dihydroxy-D : A-friedo-oleanan-3-one (6)(kokoondiol), 6β-hydroxy-D : A-friedo-oleanan-3-one (21)(zeylanol), 6β-hydroxy-D : A-friedo-oleanane-3,21-dione (22)(zeylanonol) and 6β,21β-dihydroxy-D : A-friedo-oleanan-3-one (23)(zeylandiol), by spectroscopic methods and chemical interconversions. The biosynthetic significance of 6-hydroxy-D : A-friedo-oleananes is discussed.

Preliminary laboratory studies on increasing phosphorous availability in eppawala apatite

Abstract: Preliminary investigations to increase the availability of phosphorus in Eppawala apatite were carried out. Samples of an ultisol (Reddish Brown Latasolic soil) and an alfisol (Reddish Brown Earths) amended with animal manure or straw or sulphur at 2% were incubated separately with finely ground apatite at 50% field capacity or under flooded condition. Olsen's P of the incubated soil samples determined at fortnightly periods indicate that the release of phosphorus in apatite is increased by straw and animal manure under unflooded conditions. Under flooded condition? only animal manure was effective. Straw did not show any significant influence..

Extrapolation of short-term process data to long-term landform development: A case study from southwestern Australia

Abstract: Summary Short-term erosion rates by overland flow under forested conditions are considered in relation to long-term valley development. Five catenas which are representative of the range of valley forms in the study area were selected, and the nine unit landsurface model was used as a sampling framework to locate experimental plots within the catenas. Factors affecting data validity include the spatial and temporal sampling pattern, and human-induced changes to the physical environment. Over the longer time-scale of valley development, problems in extrapolating the short-term data include establishing the time period within which valley development has occurred, and identifying and estimating the effects of climatic fluctuations on process intensities. The results show that, in the long-term context, measured contemporary erosion rates are ‘reasonable’ for three of the five catenas, but that considerable additional experimental work is required to resolve the identified problems. In some instances the means by which relevant data may be obtained are not apparent.

Biotype distribution of vascular wilt pathogen Pseudomonas solanacearum in Sri Lanka

Abstract: $he:bacterial wilt caused by Pseudomonas solanacearum E. F. Smith is one of'the @aj.or diseases of solanaceous crops, The disease occurs mostly in warm climates. It is Briown,to infect various other hosts such as ~anand'~eanuts:~aste/t~in~ed bean'. 'has An erratic distribution.in soil.%lso variation within the species based on nk~rphological, physiological pioperties' has been well d o c ~ t n e n t e d . 2 . ~ ~ ~ ~ ' ~ ~ ~ ~