The gamma distribution is often used as a model for positively skewed distributions. The median is better than the mean as the representative of the 'average' in such situations. Literature is available for inference concerning the mean of a gamma distribution, but the literature concerning the median of a gamma distribution is rare. In this paper we present a method for constructing confidence intervals for the median of a gamma distribution. The method involves inverting the likelihood ratio test to obtain 'large sample' confidence intervals. A difficulty arises as it is not possible to write the likelihood function in terms of the median. In this paper we propose a method to avoid this difficulty. The method works well even for moderately large sample sizes. The methodology is illustrated using an example.
{"title":"Confidence Intervals for the Median of a Gamma Distribution","authors":"B. Banneheka","doi":"10.31357/VJS.V15I0.212","DOIUrl":"https://doi.org/10.31357/VJS.V15I0.212","url":null,"abstract":"The gamma distribution is often used as a model for positively skewed distributions. The median is better than the mean as the representative of the 'average' in such situations. Literature is available for inference concerning the mean of a gamma distribution, but the literature concerning the median of a gamma distribution is rare. In this paper we present a method for constructing confidence intervals for the median of a gamma distribution. The method involves inverting the likelihood ratio test to obtain 'large sample' confidence intervals. A difficulty arises as it is not possible to write the likelihood function in terms of the median. In this paper we propose a method to avoid this difficulty. The method works well even for moderately large sample sizes. The methodology is illustrated using an example.","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130561083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Proximate composition was determined in different body parts (skin, white muscle, red muscle, head muscle and belly flap of five species of tuna; Katsuvonus pelamis (skipjack, balaya), Thunnus Albacares (yellow fin tuna, kellawalla), Auxis rochei (Bullet tuna, ragoduwa), Auxis thazard (frigate tuna, alagoduwa) and Euthvnnus affinis (kawakawa, attawalla) obtained from the Negambo fish landing site. Fatty acid profiles were also analyzed in the akin, red and white muscle of the five species. No significant differences between the tuna species were observed with respect to protein, total fat. and moisture contents. The ash content in Frigate tuna and Kawakawa were significantly higher than the other species. The muscle tissue in all the species was rich in protein (20-25%) and low in fat (
{"title":"Nutritional Evaluation in Five Species of Tuna","authors":"K.A.A.U. Karunarathna, M. Attygalle","doi":"10.31357/VJS.V15I0.211","DOIUrl":"https://doi.org/10.31357/VJS.V15I0.211","url":null,"abstract":"Proximate composition was determined in different body parts (skin, white muscle, red muscle, head muscle and belly flap of five species of tuna; Katsuvonus pelamis (skipjack, balaya), Thunnus Albacares (yellow fin tuna, kellawalla), Auxis rochei (Bullet tuna, ragoduwa), Auxis thazard (frigate tuna, alagoduwa) and Euthvnnus affinis (kawakawa, attawalla) obtained from the Negambo fish landing site. Fatty acid profiles were also analyzed in the akin, red and white muscle of the five species. No significant differences between the tuna species were observed with respect to protein, total fat. and moisture contents. The ash content in Frigate tuna and Kawakawa were significantly higher than the other species. The muscle tissue in all the species was rich in protein (20-25%) and low in fat (","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124558236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mineral spectrum of five species of tuna namely; Skipjack (Balaya, Katsuwonus pelamis ), Yellow fin tuna (Kelawalla, Thunnus albacores ), Bullet tuna (Ragoduwa, Auxis rochei ), Frigate tuna (Alagoduwa, Auxis thazard ) and Kawakawa (Atawalla, Euthynnus affinis ) were detected in skin, red muscle, white muscle, head muscle and belly flap using an Atomic Absorption Spectrophotometer (GBC 932 plus). Both macro and micro elements were detected in all tunas studied. Accordingly from the recorded minerals K was the most abundant macro element as its mean concentration among the tunas studied ranged from 246.94±62.27 to 293.84±77.78 mg/100g and the highest K level among the different body parts, was recorded in the skin (p Key words : Tuna; macro elements; micro elements Vidyodaya Journal of Science Vol.14(2) 103-111
{"title":"Mineral spectrum in different body parts of five species of tuna consumed in Sri Lanka","authors":"K.A.A.U. Karunarathna, M. Attygalle","doi":"10.31357/VJS.V14I2.149","DOIUrl":"https://doi.org/10.31357/VJS.V14I2.149","url":null,"abstract":"The mineral spectrum of five species of tuna namely; Skipjack (Balaya, Katsuwonus pelamis ), Yellow fin tuna (Kelawalla, Thunnus albacores ), Bullet tuna (Ragoduwa, Auxis rochei ), Frigate tuna (Alagoduwa, Auxis thazard ) and Kawakawa (Atawalla, Euthynnus affinis ) were detected in skin, red muscle, white muscle, head muscle and belly flap using an Atomic Absorption Spectrophotometer (GBC 932 plus). Both macro and micro elements were detected in all tunas studied. Accordingly from the recorded minerals K was the most abundant macro element as its mean concentration among the tunas studied ranged from 246.94±62.27 to 293.84±77.78 mg/100g and the highest K level among the different body parts, was recorded in the skin (p Key words : Tuna; macro elements; micro elements Vidyodaya Journal of Science Vol.14(2) 103-111","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126572193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Uluwaduge, P. Jayaweera, N. Ileperuma, E. Jansz, M. Thabrew
The fruit pulp of palmyrah ( Borassus flabellifer) contains flabelliferins which are glycosides of β-sitosterol. Naturally bound to flabelliferins is an UV active compound, phvtofluene, which affects biological activity. This UV active compound shows intense blue fluorescence and can be dissociated from flabelliferins. The objectives of this study were to determine the main carotenoid binder to flabelliferin-II (F-II, a tetraglycoside) in a sample of PFP from Kalpitiya, Sri Lanka by HPLC and some of the chemical features of this complex (F-II+ carotenoid binder). HPLC studies showed that the major binder to F-II in a sample of PFP from Kalpitiya was phytofluene. No correlation was found between the stoichiometry of binding of phytofluene and F-II (r 2 =0.406) as well as for Fb (r 2 =0.007) indicating that the binding ratios of phytofluene with F-II or Fb are not constant in different PFP samples tested. Computational calculations(- ΔΔ H f /KJ mol -1 ) suggest that binding is less stable between F-II and phytofluene compared to the other flabelliferins tested. This was probably due to phytofluene distorting the conformation of the carbohydrate moiety of F-II. Computer modeling provided confirmatory evidence for this assumption. Key Words : Palmyrah; Borassus flabelifer ; Flabelliferins Vidyodaya Journal of Science Vol.14(2) 47-57
棕榈果(Borassus flabellifer)果肉含有棕榈素，它是β-谷甾醇的糖苷。自然结合的黄芪素是一种紫外线活性化合物，苯芴，影响生物活性。这种紫外线活性化合物显示出强烈的蓝色荧光，并能与黄花素解离。本研究的目的是用高效液相色谱法测定斯里兰卡Kalpitiya PFP样品中flabelliferin-II (F-II，一种四糖苷)的主要类胡萝卜素结合剂，以及该复合物(F-II+类胡萝卜素结合剂)的一些化学特征。高效液相色谱法研究表明，在Kalpitiya PFP样品中，与F-II的主要粘合剂是phytofluene。在不同的PFP样品中，phytofluene与F-II (r 2 =0.406)和Fb (r 2 =0.007)结合的化学计量学没有发现相关性，这表明phytofluene与F-II或Fb的结合比率不是恒定的。计算计算(- ΔΔ H f /KJ mol -1)表明，与测试的其他flabelliferins相比，f - ii与植物fluene之间的结合不太稳定。这可能是由于植物流感扭曲了F-II的碳水化合物部分的构象。计算机模拟为这一假设提供了确凿的证据。关键词:巴尔米拉;松果;科学学报，Vol.14(2): 47-57
{"title":"Aspects of the binding of acyclic carotenoids to flabelliferins from palmyrah fruit pulp","authors":"A. Uluwaduge, P. Jayaweera, N. Ileperuma, E. Jansz, M. Thabrew","doi":"10.31357/VJS.V14I2.145","DOIUrl":"https://doi.org/10.31357/VJS.V14I2.145","url":null,"abstract":"The fruit pulp of palmyrah ( Borassus flabellifer) contains flabelliferins which are glycosides of β-sitosterol. Naturally bound to flabelliferins is an UV active compound, phvtofluene, which affects biological activity. This UV active compound shows intense blue fluorescence and can be dissociated from flabelliferins. The objectives of this study were to determine the main carotenoid binder to flabelliferin-II (F-II, a tetraglycoside) in a sample of PFP from Kalpitiya, Sri Lanka by HPLC and some of the chemical features of this complex (F-II+ carotenoid binder). HPLC studies showed that the major binder to F-II in a sample of PFP from Kalpitiya was phytofluene. No correlation was found between the stoichiometry of binding of phytofluene and F-II (r 2 =0.406) as well as for Fb (r 2 =0.007) indicating that the binding ratios of phytofluene with F-II or Fb are not constant in different PFP samples tested. Computational calculations(- ΔΔ H f /KJ mol -1 ) suggest that binding is less stable between F-II and phytofluene compared to the other flabelliferins tested. This was probably due to phytofluene distorting the conformation of the carbohydrate moiety of F-II. Computer modeling provided confirmatory evidence for this assumption. Key Words : Palmyrah; Borassus flabelifer ; Flabelliferins Vidyodaya Journal of Science Vol.14(2) 47-57","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"127 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129068588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bacterial populations were investigated in relation to the environmental parameters in Bolgoda Lake for a period of six months from January 2000 to June 2000. Surface water samples were collected from six sampling stations in the Bolgoda Lake at monthly intervals. Total viable bacterial colony forming units (assumed to be equal to the density of bacterial population), total coliforms and faecal coliforms were studied as biological indicators. Physico-chemical environment parameters included, temperature, pH, electrical conductivity, salinity, Secchi disk depth, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), orthophosphate and nitrate contents. These were measured using standard methods. Correlations among bacterial densities and selected water quality parameters were investigated. High densities of bacterial populations were recorded at several sampling points in the vicinity of outlet drains which bring domestic and industrial effluents. Low densities of bacterial populations were recorded in samples taken at upstream and downstream of the North Lake. Results also revealed that some chemical parameters may have an effect in the density of bacterial populations. Density of bacterial populations showed a significant negative correlation with Biochemical oxygen demand (BOD) and with phosphate concentration. However, the density of bacterial population did not show a significant correlation with the nitrate content of the surface waters of the Lake. Further the DO, BOD values and PO 4 -3 content indicated organic and inorganic nutrient pollution of surface waters of Bolgoda Lake. However, samples collected from downstream had lower values for above parameters indicating that self- purification is taking place to a certain extent in the Lake. However, results revealed that at present Bolgoda Lake is heavily exposed to pollution from industrial and residential effluents. To avoid catastrophe, measures should be taken to reduce pollution by curtailing sewage disposal and treatment of effluents of nearby factories before being discharged into this Lake. Key words: water quality; Bolgoda Lake; evaluation of water quality Vidyodaya Journal of Science Vol.14(2) 113-133
{"title":"A study of water quality of Bolgoda North Lake","authors":"Wmp Gunatilaka, S. Wijeyaratne","doi":"10.31357/VJS.V14I2.150","DOIUrl":"https://doi.org/10.31357/VJS.V14I2.150","url":null,"abstract":"Bacterial populations were investigated in relation to the environmental parameters in Bolgoda Lake for a period of six months from January 2000 to June 2000. Surface water samples were collected from six sampling stations in the Bolgoda Lake at monthly intervals. Total viable bacterial colony forming units (assumed to be equal to the density of bacterial population), total coliforms and faecal coliforms were studied as biological indicators. Physico-chemical environment parameters included, temperature, pH, electrical conductivity, salinity, Secchi disk depth, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), orthophosphate and nitrate contents. These were measured using standard methods. Correlations among bacterial densities and selected water quality parameters were investigated. High densities of bacterial populations were recorded at several sampling points in the vicinity of outlet drains which bring domestic and industrial effluents. Low densities of bacterial populations were recorded in samples taken at upstream and downstream of the North Lake. Results also revealed that some chemical parameters may have an effect in the density of bacterial populations. Density of bacterial populations showed a significant negative correlation with Biochemical oxygen demand (BOD) and with phosphate concentration. However, the density of bacterial population did not show a significant correlation with the nitrate content of the surface waters of the Lake. Further the DO, BOD values and PO 4 -3 content indicated organic and inorganic nutrient pollution of surface waters of Bolgoda Lake. However, samples collected from downstream had lower values for above parameters indicating that self- purification is taking place to a certain extent in the Lake. However, results revealed that at present Bolgoda Lake is heavily exposed to pollution from industrial and residential effluents. To avoid catastrophe, measures should be taken to reduce pollution by curtailing sewage disposal and treatment of effluents of nearby factories before being discharged into this Lake. Key words: water quality; Bolgoda Lake; evaluation of water quality Vidyodaya Journal of Science Vol.14(2) 113-133","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116972206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Powdered leaves of thirty seven plant species were screened under laboratory conditions with the temperature of 29±2°C and 84±2% relative humidity for their repellent properties against rice weevil, Sitophilus oryzae (L). The screening was carried out with the view of producing more eco-friendly agents suitable for post-harvest rice protection and as sustainable alternatives to synthetic pesticides in the control of S. oryzae. Reared weevils were exposed to 15.0g of leaf powders admixed with rice grains in laboratory screening test using a modified cup-bioassay. The results revealed that twenty treatments caused significant repellency of adult S. oryzae than the control. Out of these, Ocimum gratissimum (Lamiaceae), Cinnamomum verum (Lauraceae), Mentha viridis (Lamiaceae), Plectranthus amboinicus (Lamiaceae) and Citrus reticulate (Rutaceae) showed the highest repellent activity. M. viridis elicited the highest and the strongest repellency (89.0 %) in the weevils when compared with the other three treatments. However, the weevils demonstrated considerably high rates of repellency to C. verum, O.gratissimum, C. reticulate and, P. amboinicus which were 76.0%, 74.0%, 68.0% and 64% respectively. When weevils were further tested against 5.0, 10.0 and 15.0g of leaf powders, all treatments showed significantly (p S. oryzae than the control. M. viridis at 15.0g dose elicited the highest and the strongest repellency (89%) in the weevils when compared with the other treatments and concentrations. The overall results indicated that repellency rate increased proportionately with the increase of the dose of the powder. A similar trend of repellency was also observed with time. However, the effects of all plant powders on the insects were highest within 6 hours post treatment. The overall results of the research provide scientific corroboration for the use of the four plant powders as effective grain protectants against the rice weevil. Key words : Sitophilus oryzae; Rice weevil; repellency; plant powders Vidyodaya Journal of Science Vol.14(2) 69-83
{"title":"Laboratory evaluation of some Sri Lankan plants as post-harvest grain protectants for the control of rice weevil Sitophilus oryzae","authors":"T. Gunarathna, M. Karunaratne","doi":"10.31357/VJS.V14I2.147","DOIUrl":"https://doi.org/10.31357/VJS.V14I2.147","url":null,"abstract":"Powdered leaves of thirty seven plant species were screened under laboratory conditions with the temperature of 29±2°C and 84±2% relative humidity for their repellent properties against rice weevil, Sitophilus oryzae (L). The screening was carried out with the view of producing more eco-friendly agents suitable for post-harvest rice protection and as sustainable alternatives to synthetic pesticides in the control of S. oryzae. Reared weevils were exposed to 15.0g of leaf powders admixed with rice grains in laboratory screening test using a modified cup-bioassay. The results revealed that twenty treatments caused significant repellency of adult S. oryzae than the control. Out of these, Ocimum gratissimum (Lamiaceae), Cinnamomum verum (Lauraceae), Mentha viridis (Lamiaceae), Plectranthus amboinicus (Lamiaceae) and Citrus reticulate (Rutaceae) showed the highest repellent activity. M. viridis elicited the highest and the strongest repellency (89.0 %) in the weevils when compared with the other three treatments. However, the weevils demonstrated considerably high rates of repellency to C. verum, O.gratissimum, C. reticulate and, P. amboinicus which were 76.0%, 74.0%, 68.0% and 64% respectively. When weevils were further tested against 5.0, 10.0 and 15.0g of leaf powders, all treatments showed significantly (p S. oryzae than the control. M. viridis at 15.0g dose elicited the highest and the strongest repellency (89%) in the weevils when compared with the other treatments and concentrations. The overall results indicated that repellency rate increased proportionately with the increase of the dose of the powder. A similar trend of repellency was also observed with time. However, the effects of all plant powders on the insects were highest within 6 hours post treatment. The overall results of the research provide scientific corroboration for the use of the four plant powders as effective grain protectants against the rice weevil. Key words : Sitophilus oryzae; Rice weevil; repellency; plant powders Vidyodaya Journal of Science Vol.14(2) 69-83","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126947886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-01-15DOI: 10.31357/FESYMPO.V0I0.1756
P. Yapa, A. Silva, W. Senarath
A new method for the production of chitosan from shrimp waste using dried papaya milk (DPM) has been developed. It involves the treatment of demineralized (with 4% HC1) shrimp waste with DPM followed by deproteinization with 3% NaOH and deacetylation with 50% NaOH. The use of DPM brings about considerable reductions in the amount of HC1 (20%) and NaOH (40%), which are known to cause environmental pollution problems. Typically, the degree of deacetylation (DD) of resulting chitosan was (67%) comparable to DD of conventional methods. Moisture content (9.12%) and ash content (0.09%) of resulting chitosan were significantly low compared to chitosan obtained by 100% chemical methods. Vidyodaya J. of Sci.. (2009) Vol. 14, pp 31-39
{"title":"Use of dried papaya milk in chitosan manufacture","authors":"P. Yapa, A. Silva, W. Senarath","doi":"10.31357/FESYMPO.V0I0.1756","DOIUrl":"https://doi.org/10.31357/FESYMPO.V0I0.1756","url":null,"abstract":"A new method for the production of chitosan from shrimp waste using dried papaya milk (DPM) has been developed. It involves the treatment of demineralized (with 4% HC1) shrimp waste with DPM followed by deproteinization with 3% NaOH and deacetylation with 50% NaOH. The use of DPM brings about considerable reductions in the amount of HC1 (20%) and NaOH (40%), which are known to cause environmental pollution problems. Typically, the degree of deacetylation (DD) of resulting chitosan was (67%) comparable to DD of conventional methods. Moisture content (9.12%) and ash content (0.09%) of resulting chitosan were significantly low compared to chitosan obtained by 100% chemical methods. Vidyodaya J. of Sci.. (2009) Vol. 14, pp 31-39","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130387177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A study of zooplankton was carried out in Kotmale reservoir, from August1990 to December 1991. Vertical and horizontal sampling was done oncea month near the dam of the reservoir, between 1100 hours to 1200 hours.A closing type net with mesh size of 50p m was used for collection ofzooplankton. Ceriodaphnia cornuta is a cosmopolitan species and the dominant formin the cladoceran community of Kotmale reservoir. It represented 98% ofthe whole population at certain months. Its population structure comprisednymphs and adults throughout the year. Ceriodaphnia cornuta showed polymorphism. Two morphologicalforms were identified. One form (horned form) had a comparatively smallerbody (size range of 0.30-0.45 mm) with spines on the head region & theother (unhorned form) with a larger body (size range of 0.48-0.84 mm) withoutbearing spines. Abundance of morphological forms were different in 1990 and 1991. The spined form predominated in the epilimnetic waters where fish predationwas high and the other form was found at all depths. Existence of suchmorphological forms may be an adaptation to minimize selective predationby fish.
{"title":"Population structure and polymorphism of Ceriodaphnia cornuta in kotmale reservoir","authors":"W. Chandrananda, S. Piyasiri","doi":"10.4038/VJS.V4I1.6077","DOIUrl":"https://doi.org/10.4038/VJS.V4I1.6077","url":null,"abstract":"A study of zooplankton was carried out in Kotmale reservoir, from August1990 to December 1991. Vertical and horizontal sampling was done oncea month near the dam of the reservoir, between 1100 hours to 1200 hours.A closing type net with mesh size of 50p m was used for collection ofzooplankton. Ceriodaphnia cornuta is a cosmopolitan species and the dominant formin the cladoceran community of Kotmale reservoir. It represented 98% ofthe whole population at certain months. Its population structure comprisednymphs and adults throughout the year. Ceriodaphnia cornuta showed polymorphism. Two morphologicalforms were identified. One form (horned form) had a comparatively smallerbody (size range of 0.30-0.45 mm) with spines on the head region & theother (unhorned form) with a larger body (size range of 0.48-0.84 mm) withoutbearing spines. Abundance of morphological forms were different in 1990 and 1991. The spined form predominated in the epilimnetic waters where fish predationwas high and the other form was found at all depths. Existence of suchmorphological forms may be an adaptation to minimize selective predationby fish.","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115616214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Results obtained from a fertilizer experiment conducted with thirteentreatments indicate the positive effect of phosphorus and magnesium nutritionon the yield and the fractional composition of essential oil of Cymbopogonnardus. Phosphorus nutrition has increased the "total geraniol" (total acetylisablecompounds) in oil. Magnesium in combination with phosphorusfertilizers significantly increased the total geraniol at the second harvest. Theincrease of total geraniol was always accompanied by the decrease of totalhydrocarbons, which indicates the better utilization of monoterpenes in biosyntheisof constituents of total geraniol in oil as a result of phosphorus nitrition.Phosphorus content in leaves has positive relationships with total geraniol(r=+O.5), essential oil yield (r= +0.58) and output of total geraniol(r=+0.59). The optimum phosphorus concentrations in leaves after fourmonths of planting that produced maximum yields of essential oil and totalgeraniol by this crop were found to be in the range of 0.23-0.26 %.
{"title":"Mineral Nutrition of Cymbopogon nardus (L) Rendle: Part II. Effects of Magnesium and Phosphorus Nutrition on the Fractional Composition of Essential Oil","authors":"S. S. Rsnaweera, W. P. Thilakaratne","doi":"10.4038/VJS.V4I1.6081","DOIUrl":"https://doi.org/10.4038/VJS.V4I1.6081","url":null,"abstract":"Results obtained from a fertilizer experiment conducted with thirteentreatments indicate the positive effect of phosphorus and magnesium nutritionon the yield and the fractional composition of essential oil of Cymbopogonnardus. Phosphorus nutrition has increased the \"total geraniol\" (total acetylisablecompounds) in oil. Magnesium in combination with phosphorusfertilizers significantly increased the total geraniol at the second harvest. Theincrease of total geraniol was always accompanied by the decrease of totalhydrocarbons, which indicates the better utilization of monoterpenes in biosyntheisof constituents of total geraniol in oil as a result of phosphorus nitrition.Phosphorus content in leaves has positive relationships with total geraniol(r=+O.5), essential oil yield (r= +0.58) and output of total geraniol(r=+0.59). The optimum phosphorus concentrations in leaves after fourmonths of planting that produced maximum yields of essential oil and totalgeraniol by this crop were found to be in the range of 0.23-0.26 %.","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130384235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vertical distribution of cyclopid copepcds was studied in Kotmale reservoir,in order to determine the variation in zooplankton at different depths. Theirseasonal distribution and migratory patterns were also studied. Vertical and horizontal sampling were done at monthly intervals fromAugust 1990 to December 1991. Two diurnal samplings were done; onewhen water level was low (40m) and the other when it was high (62m). The two cycIopid species identified were Mesocyclops leukarti andThermocyclops crassus. CycIopid adults and their immature stages were abundant at all depths.However their population density decreased with increasing depth. Highestdensity was found within the range of surface to ten meters. They showed striking diurnal migration which was independent of theintensity of sunlight. The migratory pattern of adults and young was notmuch different. The seasonal variation observed did not show the same pattern duringboth sampling years. During the latter part of the study (October to December1991)a large decrease in cyclopid population was observed which was correlatedwith the collapse of green algae population and the appearance of algal bloomcaused by blue green algae (Microcystis aeruginosat.
{"title":"Seasonal diurnal and vertical distribution patterns of cyclopid copepods in Kotmale reservoir","authors":"W. Chandrananda, S. Piyasiri","doi":"10.4038/VJS.V4I1.6078","DOIUrl":"https://doi.org/10.4038/VJS.V4I1.6078","url":null,"abstract":"Vertical distribution of cyclopid copepcds was studied in Kotmale reservoir,in order to determine the variation in zooplankton at different depths. Theirseasonal distribution and migratory patterns were also studied. Vertical and horizontal sampling were done at monthly intervals fromAugust 1990 to December 1991. Two diurnal samplings were done; onewhen water level was low (40m) and the other when it was high (62m). The two cycIopid species identified were Mesocyclops leukarti andThermocyclops crassus. CycIopid adults and their immature stages were abundant at all depths.However their population density decreased with increasing depth. Highestdensity was found within the range of surface to ten meters. They showed striking diurnal migration which was independent of theintensity of sunlight. The migratory pattern of adults and young was notmuch different. The seasonal variation observed did not show the same pattern duringboth sampling years. During the latter part of the study (October to December1991)a large decrease in cyclopid population was observed which was correlatedwith the collapse of green algae population and the appearance of algal bloomcaused by blue green algae (Microcystis aeruginosat.","PeriodicalId":214405,"journal":{"name":"Vidyodaya Journal of Science","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127644931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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