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RISS 인기검색어
- 검색키워드
- 저자 : Ram P. Sharma (검색결과 6 건)
- 무료
- 기관 내 무료
- 유료
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Ram P. Sharma,Johannes Breidenbach 한국산림과학회 2015 Forest Science And Technology Vol.11 No.1
We developed nonlinear mixed effects height-diameter models for three major tree species: Norway spruce (Picea abies[L.] Karst.); Scots pine (Pinus sylvestris L.); and downy birch (Betula pubescens [Ehrh.]) in Norway. We used data fromfour Norwegian national forest inventory (NFI) cycles (7th10th NFI cycle) as model fitting data and data from the 6thNFI cycle as validation data. Among several bi-parametric functions tested as base functions in a preliminary analysis, theN€aslund function showed the smallest residual variations, and therefore it was extended by incorporating stand variables ascovariates that act as modifiers of the original parameters of the N€aslund function. Sample plot-level random effects werealso included in order to account for inter-plot variations within the populations. Unlike a basic mixed effects model, theextended mixed model described larger parts of variations in the height-diameter relationships and predicted heightswithout significant bias for validation data from the sample plots, where all measured heights of the focused species(species used for species-specific model) were used to predict random effects. For species independent models, whenmeasured heights of other than focused species were used to predict random effects, a significant height prediction biasoccurred. This bias could be reduced for certain diameter ranges by applying an extended ordinary least square model. Werecommend using extended mixed effects models to estimate the missing heights on NFI sample plots and other sampleplots, where measured tree heights of the focused species are available for prediction of random effects. When measuredheights are not available, the extended ordinary least square model can be used.
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Geetha, S.,Ram, M.Sai,Sharma, S.K.,Ilavazhagan, G.,Banerjee, P.K.,Sawhney, R.C. The Korean Society of Food Science and Nutrition 2009 Journal of medicinal food Vol.12 No.1
This study was designed to determine the cytoprotective activity of flavones of seabuckthorn (Hippophae rhamnoides L.) against tert-butyl hydroperoxide (tert-BOOH), used as an oxidant to induce oxidative damage, with lymphocytes as the model system. Addition of tert-BOOH ($250\;{\mu}M$) to the cells resulted in enhanced cytotoxicity and free radical production. The intracellular calcium levels, caspase activity, and apoptosis were significantly increased following tert-BOOH treatment. Seabuckthorn flavones at the concentration of $100\;{\mu}g/mL$ significantly inhibited tert-BOOH-induced cytotoxicity and free radical production and also restored the antioxidant status to that of control cells. Seabuckthorn flavones also significantly restricted tert-BOOH-induced apoptosis by decreasing intracellular calcium levels and caspase activity. The extract also decreased tert-BOOH-induced formation of DNA breaks by 30%. These observations suggest that the flavones of seabuckthorn have marked cytoprotective properties, which could be attributed to the antioxidant activity.
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Modeling above-ground biomass for three tropical tree species at their juvenile stage
Tolak R. Chapagain,Ram P. Sharma,Shes K. Bhandari 한국산림과학회 2014 Forest Science And Technology Vol.10 No.2
Accurate prediction of biomass for juveniles (sapling and seedling) of any stand is important to estimate total biomass orcarbon stock in the stand. In this study allometric biomass models were developed for prediction of above-ground biomassfor three major tropical tree species (Shorea robusta, Terminalia tomentosa, and Acacia catechu) at their juvenile stage. Biomass data for this study were acquired from 120 destructively sampled juvenile individuals (40 for each species) ofthese species in the lowland of western Nepal. Among several mathematical models tested, an exponential model withdiameter and total height as explanatory variables showed the best fits to the data (i.e. smallest root mean square error(RMSE) and Akaike information criterion (AIC), and largest R2adj). Also the same model form with diameter, height andwood density as explanatory variables fitted the data equally well. All other models with diameter alone or its combinationwith other variables showed relatively poorer fits. The first two best models of the forms yi ¼ expfb1ðD2i HiÞb2g andyi ¼ expfb1ðrD2i HiÞb2g explained >92% above-ground biomass proportion, resulting in a small random variation ofresiduals around zero (RMSE ¼ 62 g). Thus, for more accuracy, one of these two models was recommended to predictabove-ground biomass of juveniles of three species. Since the models developed in this study are explicitly site-specific,their application should be restricted to site, size and stand conditions similar to the basis of this study. Further works forvalidation and verification of the presented models with new data from a wider range of site, size and stand conditions ofShorea robusta, Terminalia tomentosa, and Acacia catechu are recommended.
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Bishnu Hari Wagle,Ram P. Sharma 한국산림과학회 2012 Forest Science And Technology Vol.8 No.1
Individual tree growth models are important decision-making tools for forest management. We developed individual tree basal area growth models with Blue pine (Pinus wallichiana) data from Lete and Kunjo areas of Mustang district in Nepal. The sample trees were identified from all applicable ages, sizes, site qualities, and stand conditions and were cut. Diameters and ages were measured on the cut surface of stump (at 30 cm above ground). With the application of the auto-regressive error-structured modelling approach, we fitted Bertalanffy function to the data from 94 stumps by using basal area growth per year as dependent variable and stump age or stump diameter as independent variable. The age-independent individual tree basal area growth model showed better fits (R^2_adj=0.8324) than its agedependent counterpart (R^2_adj=0.8174). Because of having better fits and being easier for application, the ageindependent model is recommended for predicting basal area growth per year at an individual tree level for Blue pine across Lete and Kunjo areas of Mustang district.
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S. Geetha,S.K. Sharma,G. Ilavazhagan,P.K. Banerjee,R.C. Sawhney,M. Sai Ram 한국식품영양과학회 2009 Journal of medicinal food Vol.12 No.1
This study was designed to determine the cytoprotective activity of flavones of seabuckthorn (Hippophae rhamnoides L.) against tert-butyl hydroperoxide (tert-BOOH), used as an oxidant to induce oxidative damage, with lymphocytes as the model system. Addition of tert-BOOH (250 μM) to the cells resulted in enhanced cytotoxicity and free radical production. The intracellular calcium levels, caspase activity, and apoptosis were significantly increased following tert-BOOH treatment. Seabuckthorn flavones at the concentration of 100 μg/mL significantly inhibited tert-BOOH-induced cytotoxicity and free radical production and also restored the antioxidant status to that of control cells. Seabuckthorn flavones also significantly restricted tert-BOOH-induced apoptosis by decreasing intracellular calcium levels and caspase activity. The extract also decreased tert-BOOH-induced formation of DNA breaks by 30%. These observations suggest that the flavones of seabuckthorn have marked cytoprotective properties, which could be attributed to the antioxidant activity.
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