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Papers by Chandra Shekhar Singh
Lepidium sativum Linn. has been used in traditional and folklore medicine for the treatment of br... more Lepidium sativum Linn. has been used in traditional and folklore medicine for the treatment of bronchial asthma, diabetes, local and rheumatic pain. The present study deals with the investigation of the neurobehavioral effects of the total alkaloid from seeds of Lepidium sativum [LSAF].The effect of LSAF on general pharmacology, thiopental induced hypnosis, locomotor activity, motor coordination, antianxiety and analgesic effect were studied. The animals were intraperitonealy treated with 50, 150 and 250 mg/kg LSAF to the respective treatment groups. The results revealed that LSAF considerably potentiated the thiopental induced hypnosis, decreased locomotor activity and motor coordination, and increased preference to plus maze open arm. LSAF also increase the reaction time in caudal immersion and decrease in number of wriths in acetic acid induced writhing. It has been concluded that LSAF exhibited sedative, anxiolytic, myorelaxant and analgesic activity.
Metallurgical and Materials Transactions A, 2013
A large class of modern structural alloys derives its strength from precipitation hardening. Prec... more A large class of modern structural alloys derives its strength from precipitation hardening. Precipitates obstruct the motion of dislocations and thereby increase alloy strength. This paper examines the process using an atomistic-based hierarchical multiscale modeling framework. Atomistic modeling is employed to (1) compute solute-dislocation interaction energies for input into a semi-analytic solute hardening model and (2) evaluate precipitate strengths for use in dislocation line tension simulations. The precipitate microstructure in the dislocation line tension simulations is obtained from simple analytic precipitation kinetics relations. Fitting only the rate constants in the precipitation kinetics model, the macroscopic strength predictions of the hierarchical multiscale model are found to correspond reasonably well with experiments. By analyzing the potential sources of discrepancy between the model's macroscopic predictions and experiments, this work illuminates the importance of specific atomic-scale processes and highlights important challenges that remain before truly predictive mechanism-based plasticity modeling can be realized.
Mechanics of Materials, 2009
This paper treats the problem of elastic response of composite laminates containing matrix cracks... more This paper treats the problem of elastic response of composite laminates containing matrix cracks in plies of multiple orientations. The approach taken has been described as synergistic damage mechanics (SDM) and has been previously illustrated for ½0 m = AE h n =0 m=2 s laminates with cracks of equal density in þh and Àh plies [Singh, C.V., Talreja, R., 2008. Int. J. Solids Struct. 45(16), 4574-4589]. The current work extends the approach to ½0 m = AE h n =90 r s and ½0 m =90 r = AE h n s laminates with cracks additionally in the 90°-plies. The interaction between the AEh-cracks and the 90°-cracks is analyzed in terms of the crack surface displacements using a three-dimensional finite element (FE) model and found to be significant only for crack orientations close to 90°. The stiffness degradation of the laminate with all cracking modes simultaneously present is formulated by continuum damage mechanics using a second order tensor characterization of damage. The elastic moduli changes predicted by the SDM procedure are validated by independent three-dimensional FE calculations. For a particular case of quasi-isotropic ½0=90= Ç 45 s laminate, the elastic moduli predictions are evaluated against experimental data. Finally, a parametric study is performed to examine the effects of ply thickness changes on stiffness properties.
Journal of Composite Materials, 2012
We treat selected test cases in the third world wide failure exercise by the approach described a... more We treat selected test cases in the third world wide failure exercise by the approach described as synergistic damage mechanics. This approach utilizes micromechanics and continuum damage mechanics to predict the overall mechanical response of composite laminates with ply cracking in multiple orientations. The material constants needed in the continuum damage mechanic formulation are calculated from stiffness property changes incurred in a reference laminate. For other laminate configurations, the stiffness changes are derived using a relative constraint parameter which is calculated from the constraint on the opening displacement of ply cracks within the given cracked laminate evaluated numerically by a finite element analysis of appropriately constructed representative unit cell. The number density of ply cracks (cracks per unit length normal to the crack planes) under quasi-static loading is calculated by an energy-based approach. Finally, the stress–strain response of a laminate...
Indian Journal of Pharmacology, 2013
Objectives: The present study was undertaken to evaluate the radioprotective and cytoprotective p... more Objectives: The present study was undertaken to evaluate the radioprotective and cytoprotective potential of cordifolioside-A, a primary active constituent of n-butanol fraction of Tinospora Cordifolia (NBTC) against 4 Gy-γ radiation in mice and cyclophosphamide induced genotoxicity. Materials and Methods: Presence of cordifolioside-A in NBTC stem ethanolic extract was confirmed by high performance thin layer chromatography (HPTLC) analysis. Radioprotective activity was evaluated at 80 and 120 mg/kg, intraperitoneal (i.p.) dose of NBTC administered 15 days prior to whole body radiation exposure by observing survival rate, change in body weight, hematology, spleen colony forming unit (CFU), and micronucleus (MN) expression. Cytoprotective activity of NBTC was evaluated at 5, 10, and 15 mg/ml concentrations on Allium cepa root meristem growth against cyclophosphamide. Results: HPTLC analysis of standard cordifolioside A, and NBTC confirmed the presence of cordifolioside-A in NBTC with the retention factor value of 0.86. Administration of NBTC (120 mg/kg, i.p.) produced significant protection against radiation in terms of increased survival rate, body weight retention, hematological parameters, spleen CFU assay (P < 0.01), and decreased MN expression (P < 0.01). Cytoprotectivity was observed maximally at 10 mg/ml NBTC concentration with significant increase in root growth (P < 0.01), non-toxic mitotic index (MI) (65.9%) and lesser chromosomal aberrations (15.4%). NBTC at 10 mg/ml concentration showed very few C-anaphase compared to aberrations like fragmentation, C-anaphase, multipolarity and sticky chromosome in cyclophosphamide alone. Conclusion: The results suggest that enriched NBTC containing cordifolioside-A has a potential in vivo radioprotective effect as well as in vitro cytoprotective activity.
Food Chemistry, 2012
The present study investigates the hypoglycemic and antiobesity effect of sesame seed cake (SSC) ... more The present study investigates the hypoglycemic and antiobesity effect of sesame seed cake (SSC) on rats fed with high fructose diet (HFD). SSC contained dietary fibre, lignans and phenolic compound. One month of HFD feeding induced significantly the obesity, hyperglycemia, hyperlipidaemia, insulin insensitivity and increased atherogenic index (AI). Treatment of SSC along with feed material decreased the weight gain, normalised the blood glucose (BG) level, reduced the serum cholesterol and improved the glucose tolerance significantly. In the oral glucose tolerance test (OGTT), rats fed with HFD supplemented with 2% and 4% SSC significantly reduced the plasma glucose after 120 min of glucose loading, indicating an improved glucose tolerance. In conclusion, the intake of SSC supplementation can be adopted as a therapeutic strategy for the prevention of obesity induced Type 2 hyperglycemia.
Chemical Engineering Science, 1982
Lepidium sativum Linn. has been used in traditional and folklore medicine for the treatment of br... more Lepidium sativum Linn. has been used in traditional and folklore medicine for the treatment of bronchial asthma, diabetes, local and rheumatic pain. The present study deals with the investigation of the neurobehavioral effects of the total alkaloid from seeds of Lepidium sativum [LSAF].The effect of LSAF on general pharmacology, thiopental induced hypnosis, locomotor activity, motor coordination, antianxiety and analgesic effect were studied. The animals were intraperitonealy treated with 50, 150 and 250 mg/kg LSAF to the respective treatment groups. The results revealed that LSAF considerably potentiated the thiopental induced hypnosis, decreased locomotor activity and motor coordination, and increased preference to plus maze open arm. LSAF also increase the reaction time in caudal immersion and decrease in number of wriths in acetic acid induced writhing. It has been concluded that LSAF exhibited sedative, anxiolytic, myorelaxant and analgesic activity.
Metallurgical and Materials Transactions A, 2013
A large class of modern structural alloys derives its strength from precipitation hardening. Prec... more A large class of modern structural alloys derives its strength from precipitation hardening. Precipitates obstruct the motion of dislocations and thereby increase alloy strength. This paper examines the process using an atomistic-based hierarchical multiscale modeling framework. Atomistic modeling is employed to (1) compute solute-dislocation interaction energies for input into a semi-analytic solute hardening model and (2) evaluate precipitate strengths for use in dislocation line tension simulations. The precipitate microstructure in the dislocation line tension simulations is obtained from simple analytic precipitation kinetics relations. Fitting only the rate constants in the precipitation kinetics model, the macroscopic strength predictions of the hierarchical multiscale model are found to correspond reasonably well with experiments. By analyzing the potential sources of discrepancy between the model's macroscopic predictions and experiments, this work illuminates the importance of specific atomic-scale processes and highlights important challenges that remain before truly predictive mechanism-based plasticity modeling can be realized.
Mechanics of Materials, 2009
This paper treats the problem of elastic response of composite laminates containing matrix cracks... more This paper treats the problem of elastic response of composite laminates containing matrix cracks in plies of multiple orientations. The approach taken has been described as synergistic damage mechanics (SDM) and has been previously illustrated for ½0 m = AE h n =0 m=2 s laminates with cracks of equal density in þh and Àh plies [Singh, C.V., Talreja, R., 2008. Int. J. Solids Struct. 45(16), 4574-4589]. The current work extends the approach to ½0 m = AE h n =90 r s and ½0 m =90 r = AE h n s laminates with cracks additionally in the 90°-plies. The interaction between the AEh-cracks and the 90°-cracks is analyzed in terms of the crack surface displacements using a three-dimensional finite element (FE) model and found to be significant only for crack orientations close to 90°. The stiffness degradation of the laminate with all cracking modes simultaneously present is formulated by continuum damage mechanics using a second order tensor characterization of damage. The elastic moduli changes predicted by the SDM procedure are validated by independent three-dimensional FE calculations. For a particular case of quasi-isotropic ½0=90= Ç 45 s laminate, the elastic moduli predictions are evaluated against experimental data. Finally, a parametric study is performed to examine the effects of ply thickness changes on stiffness properties.
Journal of Composite Materials, 2012
We treat selected test cases in the third world wide failure exercise by the approach described a... more We treat selected test cases in the third world wide failure exercise by the approach described as synergistic damage mechanics. This approach utilizes micromechanics and continuum damage mechanics to predict the overall mechanical response of composite laminates with ply cracking in multiple orientations. The material constants needed in the continuum damage mechanic formulation are calculated from stiffness property changes incurred in a reference laminate. For other laminate configurations, the stiffness changes are derived using a relative constraint parameter which is calculated from the constraint on the opening displacement of ply cracks within the given cracked laminate evaluated numerically by a finite element analysis of appropriately constructed representative unit cell. The number density of ply cracks (cracks per unit length normal to the crack planes) under quasi-static loading is calculated by an energy-based approach. Finally, the stress–strain response of a laminate...
Indian Journal of Pharmacology, 2013
Objectives: The present study was undertaken to evaluate the radioprotective and cytoprotective p... more Objectives: The present study was undertaken to evaluate the radioprotective and cytoprotective potential of cordifolioside-A, a primary active constituent of n-butanol fraction of Tinospora Cordifolia (NBTC) against 4 Gy-γ radiation in mice and cyclophosphamide induced genotoxicity. Materials and Methods: Presence of cordifolioside-A in NBTC stem ethanolic extract was confirmed by high performance thin layer chromatography (HPTLC) analysis. Radioprotective activity was evaluated at 80 and 120 mg/kg, intraperitoneal (i.p.) dose of NBTC administered 15 days prior to whole body radiation exposure by observing survival rate, change in body weight, hematology, spleen colony forming unit (CFU), and micronucleus (MN) expression. Cytoprotective activity of NBTC was evaluated at 5, 10, and 15 mg/ml concentrations on Allium cepa root meristem growth against cyclophosphamide. Results: HPTLC analysis of standard cordifolioside A, and NBTC confirmed the presence of cordifolioside-A in NBTC with the retention factor value of 0.86. Administration of NBTC (120 mg/kg, i.p.) produced significant protection against radiation in terms of increased survival rate, body weight retention, hematological parameters, spleen CFU assay (P < 0.01), and decreased MN expression (P < 0.01). Cytoprotectivity was observed maximally at 10 mg/ml NBTC concentration with significant increase in root growth (P < 0.01), non-toxic mitotic index (MI) (65.9%) and lesser chromosomal aberrations (15.4%). NBTC at 10 mg/ml concentration showed very few C-anaphase compared to aberrations like fragmentation, C-anaphase, multipolarity and sticky chromosome in cyclophosphamide alone. Conclusion: The results suggest that enriched NBTC containing cordifolioside-A has a potential in vivo radioprotective effect as well as in vitro cytoprotective activity.
Food Chemistry, 2012
The present study investigates the hypoglycemic and antiobesity effect of sesame seed cake (SSC) ... more The present study investigates the hypoglycemic and antiobesity effect of sesame seed cake (SSC) on rats fed with high fructose diet (HFD). SSC contained dietary fibre, lignans and phenolic compound. One month of HFD feeding induced significantly the obesity, hyperglycemia, hyperlipidaemia, insulin insensitivity and increased atherogenic index (AI). Treatment of SSC along with feed material decreased the weight gain, normalised the blood glucose (BG) level, reduced the serum cholesterol and improved the glucose tolerance significantly. In the oral glucose tolerance test (OGTT), rats fed with HFD supplemented with 2% and 4% SSC significantly reduced the plasma glucose after 120 min of glucose loading, indicating an improved glucose tolerance. In conclusion, the intake of SSC supplementation can be adopted as a therapeutic strategy for the prevention of obesity induced Type 2 hyperglycemia.
Chemical Engineering Science, 1982