DEVENDRA KUMAR - Academia.edu (original) (raw)

Papers by DEVENDRA KUMAR

Research paper thumbnail of Advances in conductive polymers

European Polymer Journal, 1998

AbstractÐConductive polymers are a new class of materials which exhibit highly reversible redox b... more AbstractÐConductive polymers are a new class of materials which exhibit highly reversible redox behaviour and the unusual combination of properties of metal and plastics. The prospective utility of conductive polymers with a potent application in number of growing technologies in biomolecular electronics, telecommunication, display devices and electrochemical storage systems, etc. has further enhanced the interest of researchers in this novel area. An eort has been made in this article to present an updated review on the various aspects of conductive polymers, viz. synthesis of conductive polymers, doping, structure analysis and proposed utility for further study of the future scienti®c and technological developments in the ®eld of conductive polymers. #

Research paper thumbnail of Cytoprotective and antioxidant activity of Rhodiola imbricata against tert -butyl hydroperoxide induced oxidative injury in U-937 human macrophages

Molecular and Cellular Biochemistry, 2005

The present study reports cytoprotective and antioxidant activity of aqueous and alcoholic extrac... more The present study reports cytoprotective and antioxidant activity of aqueous and alcoholic extracts of Rhodiola imbricata rhizome on tert-butyl hydroperoxide (tert-BHP) induced cytotoxicity in U-937 human macrophages. There was an increase in cytotoxicity and apoptosis significantly in the presence of tert-BHP over control cells. The tert-BHP induced cytotoxicity can be attributed to enhanced reactive oxygen species (ROS) production which in turn is responsible for fall in reduced glutathione (GSH) levels; further there was a significant decrease in mitochondrial potential and increase in apoptosis and DNA fragmentation. Both aqueous and alcoholic extracts of Rhodiola rhizome at a concentration of 250 μg/ml were found to inhibit tert-BHP induced free radical production, apoptosis and to restore the anti-oxidant levels to that of the control cells. The alcoholic extract of Rhodiola showed higher cytoprotective activities than aqueous extract. These observations suggest that the alcoholic and aqueous extracts of Rhodiola have marked cytoprotective and antioxidant activities.

Research paper thumbnail of Cyto-protective and immunomodulating properties of Amla ( Emblica officinalis) on lymphocytes: an in-vitro study

Journal of Ethnopharmacology, 2002

The fruits extracts of Emblica officinalis (Amla) has been reported to have strong anti-oxidant p... more The fruits extracts of Emblica officinalis (Amla) has been reported to have strong anti-oxidant properties. There is a paucity of studies on the immunomodulatory properties of fruit extracts of Amla in immuno-compromised states, with the emphasis on lymphocytes. Therefore, the aim of the study was to determine the anti-oxidant and immunomodulatory properties of Amla using chromium (VI) as an immunosuppressive agent. Chromium (Cr) treatment results in enhanced cytotoxicity, free radical production, lipid peroxidation and decreased glutathione peroxidase (GPx) activity and diminished glutathione (GSH) levels. There was a significant inhibition of both lipopolysaccharide and concanavalin-A-stimulated lymphocyte proliferation. Chromium also inhibited Con A stimulated interleukin-2 and g-interferon production significantly. Further, there was enhanced apoptosis and DNA fragmentation in the presence of Cr. Amla significantly inhibited Cr-induced free radical production and restored the anti-oxidant status back to control level. Amla also inhibited apoptosis and DNA fragmentation induced by Cr. Interestingly, Amla relieved the immunosuppressive effects of Cr on lymphocyte proliferation and even restored the IL-2 and g-IFN production considerably.

Research paper thumbnail of Immunomodulatory effects of NIM76, a volatile fraction from Neem oil

Journal of Ethnopharmacology, 1997

The immunomodulatory properties of NIM-76 have been described in this paper. Pre-treatment of rat... more The immunomodulatory properties of NIM-76 have been described in this paper. Pre-treatment of rats with a single i.p. injection of NIM-76 resulted in an increase in polymorphonuclear (PMN) leukocytes with a concomitant decrease in lymphocyte counts. The immunomodulatory activity of NIM-76 was found to be concentration-dependent. At 120 mg/kg body weight, there was an enhanced macrophage activity and lymphocyte proliferation response, while the humoral component of immunity was unaffected. At higher concentrations of NIM-76 (300 mg/kg body weight), there was a stimulation of mitogen-induced lymphocyte proliferation, while macrophage activity remained unaffected. However, a fall in primary and secondary antibody titres was observed. The study indicates that NIM-76 acts through cell-mediated mechanisms by activating macrophages and lymphocytes.

Research paper thumbnail of Thermal Unit Commitment Solution Using an Improved Lagrangian Relaxation

to the thermal unit commitment problem (UCP) is proposed in this paper. The algorithm is characte... more to the thermal unit commitment problem (UCP) is proposed in this paper. The algorithm is characterized by: (1) a new Matlab function to determine the optimal path of the dual problem, (2) new initialization procedure of Lagrangian multipliers, based on both unit and time interval classification, (3) a flexible adjustment of Lagrangian multipliers, and (4) a dynamic search for uncertain stage scheduling, using a Lagrangian relaxation -dynamic programming method (LR-DP). After the LR best feasible solution is reached, and when identical or similar units exist, a unit decommitment is used to adjust the solution. The proposed algorithm is tested and compared to conventional Lagrangian relaxation (LR), genetic algorithm (GA), evolutionary programming (EP), Lagrangian relaxation and genetic algorithm (LRGA), and genetic algorithm based on unit characteristic classification (GAUC) on systems with the number of generating units in the range of 10 to 100. The total system production cost of the proposed algorithm is less than the others especially for the larger number of generating units. Computational time was found to increase almost linearly with system size, which is favorable for large-scale implementation. t t λ μ : Lagrangian multipliers at hour t ($/MWh); J, Q: primal and dual solution of the LR based UC algorithm; ε : Pre-specified tolerance.

Research paper thumbnail of Advances in conductive polymers

European Polymer Journal, 1998

AbstractÐConductive polymers are a new class of materials which exhibit highly reversible redox b... more AbstractÐConductive polymers are a new class of materials which exhibit highly reversible redox behaviour and the unusual combination of properties of metal and plastics. The prospective utility of conductive polymers with a potent application in number of growing technologies in biomolecular electronics, telecommunication, display devices and electrochemical storage systems, etc. has further enhanced the interest of researchers in this novel area. An eort has been made in this article to present an updated review on the various aspects of conductive polymers, viz. synthesis of conductive polymers, doping, structure analysis and proposed utility for further study of the future scienti®c and technological developments in the ®eld of conductive polymers. #

Research paper thumbnail of Cytoprotective and antioxidant activity of Rhodiola imbricata against tert -butyl hydroperoxide induced oxidative injury in U-937 human macrophages

Molecular and Cellular Biochemistry, 2005

The present study reports cytoprotective and antioxidant activity of aqueous and alcoholic extrac... more The present study reports cytoprotective and antioxidant activity of aqueous and alcoholic extracts of Rhodiola imbricata rhizome on tert-butyl hydroperoxide (tert-BHP) induced cytotoxicity in U-937 human macrophages. There was an increase in cytotoxicity and apoptosis significantly in the presence of tert-BHP over control cells. The tert-BHP induced cytotoxicity can be attributed to enhanced reactive oxygen species (ROS) production which in turn is responsible for fall in reduced glutathione (GSH) levels; further there was a significant decrease in mitochondrial potential and increase in apoptosis and DNA fragmentation. Both aqueous and alcoholic extracts of Rhodiola rhizome at a concentration of 250 μg/ml were found to inhibit tert-BHP induced free radical production, apoptosis and to restore the anti-oxidant levels to that of the control cells. The alcoholic extract of Rhodiola showed higher cytoprotective activities than aqueous extract. These observations suggest that the alcoholic and aqueous extracts of Rhodiola have marked cytoprotective and antioxidant activities.

Research paper thumbnail of Cyto-protective and immunomodulating properties of Amla ( Emblica officinalis) on lymphocytes: an in-vitro study

Journal of Ethnopharmacology, 2002

The fruits extracts of Emblica officinalis (Amla) has been reported to have strong anti-oxidant p... more The fruits extracts of Emblica officinalis (Amla) has been reported to have strong anti-oxidant properties. There is a paucity of studies on the immunomodulatory properties of fruit extracts of Amla in immuno-compromised states, with the emphasis on lymphocytes. Therefore, the aim of the study was to determine the anti-oxidant and immunomodulatory properties of Amla using chromium (VI) as an immunosuppressive agent. Chromium (Cr) treatment results in enhanced cytotoxicity, free radical production, lipid peroxidation and decreased glutathione peroxidase (GPx) activity and diminished glutathione (GSH) levels. There was a significant inhibition of both lipopolysaccharide and concanavalin-A-stimulated lymphocyte proliferation. Chromium also inhibited Con A stimulated interleukin-2 and g-interferon production significantly. Further, there was enhanced apoptosis and DNA fragmentation in the presence of Cr. Amla significantly inhibited Cr-induced free radical production and restored the anti-oxidant status back to control level. Amla also inhibited apoptosis and DNA fragmentation induced by Cr. Interestingly, Amla relieved the immunosuppressive effects of Cr on lymphocyte proliferation and even restored the IL-2 and g-IFN production considerably.

Research paper thumbnail of Immunomodulatory effects of NIM76, a volatile fraction from Neem oil

Journal of Ethnopharmacology, 1997

The immunomodulatory properties of NIM-76 have been described in this paper. Pre-treatment of rat... more The immunomodulatory properties of NIM-76 have been described in this paper. Pre-treatment of rats with a single i.p. injection of NIM-76 resulted in an increase in polymorphonuclear (PMN) leukocytes with a concomitant decrease in lymphocyte counts. The immunomodulatory activity of NIM-76 was found to be concentration-dependent. At 120 mg/kg body weight, there was an enhanced macrophage activity and lymphocyte proliferation response, while the humoral component of immunity was unaffected. At higher concentrations of NIM-76 (300 mg/kg body weight), there was a stimulation of mitogen-induced lymphocyte proliferation, while macrophage activity remained unaffected. However, a fall in primary and secondary antibody titres was observed. The study indicates that NIM-76 acts through cell-mediated mechanisms by activating macrophages and lymphocytes.

Research paper thumbnail of Thermal Unit Commitment Solution Using an Improved Lagrangian Relaxation

to the thermal unit commitment problem (UCP) is proposed in this paper. The algorithm is characte... more to the thermal unit commitment problem (UCP) is proposed in this paper. The algorithm is characterized by: (1) a new Matlab function to determine the optimal path of the dual problem, (2) new initialization procedure of Lagrangian multipliers, based on both unit and time interval classification, (3) a flexible adjustment of Lagrangian multipliers, and (4) a dynamic search for uncertain stage scheduling, using a Lagrangian relaxation -dynamic programming method (LR-DP). After the LR best feasible solution is reached, and when identical or similar units exist, a unit decommitment is used to adjust the solution. The proposed algorithm is tested and compared to conventional Lagrangian relaxation (LR), genetic algorithm (GA), evolutionary programming (EP), Lagrangian relaxation and genetic algorithm (LRGA), and genetic algorithm based on unit characteristic classification (GAUC) on systems with the number of generating units in the range of 10 to 100. The total system production cost of the proposed algorithm is less than the others especially for the larger number of generating units. Computational time was found to increase almost linearly with system size, which is favorable for large-scale implementation. t t λ μ : Lagrangian multipliers at hour t ($/MWh); J, Q: primal and dual solution of the LR based UC algorithm; ε : Pre-specified tolerance.