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- 저자 : M. Kumar (검색결과 812 건)
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Analgesic and antipyretic actions of Muntingia calabura leaves chloroform extractin animal models
ZA Zakaria,G Hanan Kumar,Siti NH Mohd Zaid,Marwiza A Ghani,G Hanan Kumar,Siti NH Mohd Zaid,MH Hassan,Nurul AMN Hazalin,Mahirah M Khamis,G Rathna Devi,MR Sulaiman 경희대학교 융합한의과학연구소 2007 Oriental Pharmacy and Experimental Medicine Vol.7 No.1
The present study was carried out to elucidate the potential of Muntingia (M.) calabura leaves chloroform extract (MCCE) as antinociceptive, anti-inflammatory and antipyretic agents using various animal models. The dried powdered leaves of M. calabura (20 g) were soaked in chloroform for 72 h and the supernatant obtained was then evaporated to dryness. The crude dried extract (0.912 g), dissolved in dimethyl sulfoxide (1 : 20; w/v) and considered as a stock solution (100% concentration/strength), was then diluted to the concentrations of 10 and 50% and used together in all experimental models. The MCCE was found to show significant (P < 0.05) antinociceptive and antipyretic activities, but less remarkable anti-inflammatory activity. Only the antinociceptive activity of MCCE measured using the abdominal constriction test and in the first phase of the formalin test occurred in a concentration-dependent manner. The anti-inflammatory activity of 50 and 100% concentrations MCCE was observed only at the range of time interval of 60 - 120 and 60 min, respectively. Based on the results, we conclude that the M. calabura leaves chloroform extract possessed remarkable antinociceptive and antipyretic, but less effective anti-inflammatory, activities and thus justifies the Peruvian folklore claims of its medicinal values. The present study was carried out to elucidate the potential of Muntingia (M.) calabura leaves chloroform extract (MCCE) as antinociceptive, anti-inflammatory and antipyretic agents using various animal models. The dried powdered leaves of M. calabura (20 g) were soaked in chloroform for 72 h and the supernatant obtained was then evaporated to dryness. The crude dried extract (0.912 g), dissolved in dimethyl sulfoxide (1 : 20; w/v) and considered as a stock solution (100% concentration/strength), was then diluted to the concentrations of 10 and 50% and used together in all experimental models. The MCCE was found to show significant (P < 0.05) antinociceptive and antipyretic activities, but less remarkable anti-inflammatory activity. Only the antinociceptive activity of MCCE measured using the abdominal constriction test and in the first phase of the formalin test occurred in a concentration-dependent manner. The anti-inflammatory activity of 50 and 100% concentrations MCCE was observed only at the range of time interval of 60 - 120 and 60 min, respectively. Based on the results, we conclude that the M. calabura leaves chloroform extract possessed remarkable antinociceptive and antipyretic, but less effective anti-inflammatory, activities and thus justifies the Peruvian folklore claims of its medicinal values.
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Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point
Kumar, Pankaj,Nakariakov, Valery M.,Cho, Kyung-Suk American Astronomical Society 2017 The Astrophysical journal Vol.844 No.2
<P>This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 (A) over circle. channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120. s, and the speed of the wavefronts was in the range of similar to 664-1416. km s(-1). Almost simultaneously, quasi-periodic bursts with similar instant periods, similar to 70 and similar to 140. s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of the flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70-140. s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 (A) over circle we observed quasi-periodic EUV disturbances with periods of 95 and 240. s propagating downward at apparent speeds of 172-273. km s(-1). The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.</P>
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Electrical and Magnetic Properties of BiFeO₃ Multiferroic Ceramics
M. Roy,Sumit Jangid,Shiv Kumar Barbar,Praniti Dave 한국자기학회 2009 Journal of Magnetics Vol.14 No.2
The multiferroic BiFeO₃ has been investigated extensively in both thin film and ceramic form. However, the synthesis of a perfect sample with high resistivity is a prerequisite for examining its properties. This paper reports the synthesis of multiferroic BiFeO₃ along with its structural, electrical and magnetic properties in ceramic form. Polycrystalline ceramic samples of BiFeO₃ were synthesized by solid-state reaction using high purity oxides and carbonates. The formation of a single-phase compound was confirmed by x-ray diffraction and its lattice parameters were determined using a standard computer program. The microstructural studies and density measurement confirmed that the prepared samples were sufficiently dense for an examination of its electrical and magnetic properties. The dc electrical conductivity studies show that the sample was resistive with an activation energy of ~0.81 eV. The magnetization measurement showed a linear (M~H) curve indicating antiferromagnetic characteristics.
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OBSERVATION OF A QUASIPERIODIC PULSATION IN HARD X-RAY, RADIO, AND EXTREME-ULTRAVIOLET WAVELENGTHS
Kumar, Pankaj,Nakariakov, Valery M.,Cho, Kyung-Suk American Astronomical Society 2016 The Astrophysical journal Vol.822 No.1
<P>We present a multiwavelength analysis of a quasiperiodic pulsation (QPP) observed in the hard X-ray (HXR), radio, and extreme-ultraviolet (EUV) channels during an M1.9 flare that occurred on 2011 September 23-24. The nonthermal HXR emission in 25-50 keV observed by RHESSI shows five distinct impulsive peaks of decaying amplitude with a period of about 3 minutes. A similar QPP was observed in the microwave emission recorded by the Nobeyama Radioheliograph and Polarimeter in the 2, 3.75, 9.4, and 17 GHz channels. Interestingly, the 3-minute QPP was also observed in the metric and decimetric radio frequencies (25-180, 245, 610 MHz) as repetitive type III bursts. Multiwavelength observations from the Solar Dynamics Observatory/Atmospheric Image Assembly, Hinode/SOT, and Solar TErrestrial RElations Observatory/SECCHI suggest a fan-spine topology at the eruption site, associated with the formation of a quasi-circular ribbon during the flare. A small filament was observed below the fan loops before the flare onset. The filament rose slowly and interacted with the ambient field. This behavior was followed by an untwisting motion of the filament. Two different structures of the filament showed an approximately 3-minute periodic alternate rotation in the clockwise and counterclockwise directions. The 3-minute QPP was found to highly correlate with 3-minute oscillations in a nearby sunspot. We suggest that the periodic reconnection (modulated either by a sunspot slow-mode wave or by an untwisting filament) at a magnetic null point most likely causes the repetitive particle acceleration, generating the QPP observed in HXR, microwave, and type III radio bursts.</P>
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Kumar, P.,Shahzad, F.,Yu, S.,Hong, S.M.,Kim, Y.H.,Koo, C.M. Pergamon Press ; Elsevier Science Ltd 2015 Carbon Vol.94 No.-
In this work, we fabricated reduced large-area graphene oxide (rLGO) with maximum surface area of 1592μm<SUP>2</SUP> through a cost-effective chemical reduction process at low temperature. The product revealed large electrical conductivity of 243+/-12Scm<SUP>-1</SUP> and thermal conductivity of 1390+/-65Wm<SUP>-1</SUP>K<SUP>-1</SUP>, values much superior to those of a conventional reduced small-area graphene oxide (with electrical conductivity of 152+/-7.5Scm<SUP>-1</SUP> and thermal conductivity of 900+/-45Wm<SUP>-1</SUP>K<SUP>-1</SUP>). The rLGO thin film also exhibited not only excellent stiffness and flexibility with Young's modulus of 6.3GPa and tensile strength of 77.7MPa, but also an efficient electromagnetic interference (EMI) shielding effectiveness of ~20dB at 1GHz. The excellent performance of rLGO is attributed to the fact that the larger area LGO sheets include much fewer defects that are mostly caused by the damage of graphene sp<SUP>2</SUP> structure around edge boundaries, resulting in large electrical conductivity. The manufacturing process of rLGO is an economical and facile approach for the large scale production of highly thermally conducting graphene thin films with efficient EMI shielding properties, greatly desirable for future portable electronic devices.
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M.I. Sayyed,F. Akman,M.R. Kaçal,A. Kumar 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.3
The lead element or its salts are good radiation shielding materials. However, their toxic effects are high. Due to less toxicity of bismuth salts, the radiation shielding properties of the bismuth salts have beeninvestigated and compared to that of lead salts to establish them as a better alternative to radiationshielding material to the lead element or its salts. The transmission geometry was utilized to measure themass attenuation coefficient (m/r) of different salts containing lead and bismuth using a high-resolutionHPGe detector and different energies (between 81 and 1333 keV) emitted from point sources of 133Ba,57Co, 22Na, 54Mn, 137Cs, and 60Co. The experimental m/r results are compared with the theoretical valuesobtained through WinXCOM program. The theoretical calculations are in good agreement with theirexperimental ones. The radiation protection efficiencies, mean free paths, effective atomic numbers andelectron densities for the present compounds were determined. The bismuth fluoride (BiF3) is found tohave maximum radiation protection efficiency among the selected salts. The results showed that presentsalts are more effective for reducing the intensity of gamma photons at low energy region.
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Schur M-power convexity of related function for holders inequality with application
Chowdappa M R,Sreenivasa Reddy Perla,S Padmanabhan,Uday Kumar K N 장전수학회 2023 Proceedings of the Jangjeon mathematical society Vol.26 No.4
Schur M-power convexity of related function for holders inequality with application
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Himanshu Kumar,Gaurav A. Bhaduri,S. G. K. Manikandan,M. Kamaraj,S. Shiva 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.3
The primary focus of the study is to explore the influence of annealing on the various properties like phase formation,microstructure evolution and wear analysis of equiatomic AlCoCrFeNiTi high entropy alloy (HEA) coatings developed byatmospheric plasma spray technique. Post deposition, annealing was performed at three different temperatures of 700 °C,900 °C and 1200 °C, respectively, for a time period of 180 min. X-ray diffraction (XRD) studies revealed that AlCoCrFeNiTiHEA coating comprises two BCC solid solution phases. The deposited samples were characterized using scanning electronmicroscopy (FESEM), surface profilometer, chemical analysis using x-ray photoelectron spectroscopy (XPS) and Fouriertransform infra-red spectroscopy (FTIR). The dilution level study revealed the strong metallurgical bonding between coatingand substrate. Microhardness of the AlCrCoFeNiTi was found to be marginally decreased by increasing the annealingtemperature due to coarsening of grains and the deposited coating microhardness was found to be 768.48 ± 16 HV0.2. Weartest analysis performed using the ball-on disc test revealed that, there is a significant decrease in wear resistance after heattreatment at 1200 °C. Beyond 900 °C, annealing decreased the microhardness and wear resistance due to coarsening ofgrains. The wear volume rate of the unannealed as-deposited coating was found to be 2.8 × 10–7 mm3N−1 m−1 and the coatingannealed at 700 °C, 900 °C, and 1200 °C had a wear volume rate of about 2.89 × 10–7 mm3 N−1 m−1, 2.87 × 10–7 mm3 N−1 m−1,7.29 × 10–7 mm3 N−1 m−1, respectively.
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Himanshu Kumar,Gaurav A. Bhaduri,S. G. K. Manikandan,M. Kamaraj,S. Shiva 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2
The primary focus of the study is to explore the influence of annealing on the various properties like phase formation,microstructure evolution and wear analysis of equiatomic AlCoCrFeNiTi high entropy alloy (HEA) coatings developed byatmospheric plasma spray technique. Post deposition, annealing was performed at three different temperatures of 700 °C,900 °C and 1200 °C, respectively, for a time period of 180 min. X-ray diffraction (XRD) studies revealed that AlCoCrFeNiTiHEA coating comprises two BCC solid solution phases. The deposited samples were characterized using scanning electronmicroscopy (FESEM), surface profilometer, chemical analysis using x-ray photoelectron spectroscopy (XPS) and Fouriertransform infra-red spectroscopy (FTIR). The dilution level study revealed the strong metallurgical bonding between coatingand substrate. Microhardness of the AlCrCoFeNiTi was found to be marginally decreased by increasing the annealingtemperature due to coarsening of grains and the deposited coating microhardness was found to be 768.48 ± 16 HV0.2. Weartest analysis performed using the ball-on disc test revealed that, there is a significant decrease in wear resistance after heattreatment at 1200 °C. Beyond 900 °C, annealing decreased the microhardness and wear resistance due to coarsening ofgrains. The wear volume rate of the unannealed as-deposited coating was found to be 2.8 × 10–7 mm3N−1 m−1 and the coatingannealed at 700 °C, 900 °C, and 1200 °C had a wear volume rate of about 2.89 × 10–7 mm3 N−1 m−1, 2.87 × 10–7 mm3 N−1 m−1,7.29 × 10–7 mm3 N−1 m−1, respectively.
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