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Pawan Kumar,Rakesh Kumar Dwivedi,Pawan Kumar,Ravikant Prasad,Praveen Kumar Siwach,Hari Krishna Singh 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1
Thin films of La_(0.80)Sr_(0.20)Mn_(1−x)Cu_xO_3 with x = 0.00, 0.04, 0.08, 0.10, 0.15, and 0.20 were deposited on single-crystal LaAlO_3 (100) (LAO) substrates at 250 ± 10 ℃ by using a nebulized spray pyrolysis technique. Structural, surface, and transport characterizations were done by X-ray diffraction (XRD), atomic force microscopy (AFM) and the standard four probe technique, respectively. XRD patterns revealed the formation of single-phase polycrystalline films with a rhombohedral crystal structure. Cu substitution resulted in a uniform decrease in the metal insulator transition (T_(IM)) temperature up to x = 0.10, followed by a drastic decrease in T_(IM) for x = 0.15. Finally, the metal-insulator transition vanished for higher Cu concentrations (x = 0.20) in the observed temperature range. The variation in T_(IM) with the amount of added Cu is explained on the basis of the double exchange mechanism. Cu substitution has been found to perturb the Mn^(3+)-O-Mn^(4+) network and has a strong influence on T_(IM). The variation in resistivity maxima with temperature for different Cu concentrations showed a systematic trend up to x ∼ 0.10. We also explored the electrical conduction at T > T_(IM) in the framework of small polaron hopping in the adiabatic limit. The activation energy showed a strong dependence on the Cu concentration. The maximum magneto-resistance (MR) up to 10%, was observed for x = 0.15 at low temperatures.
Pawan Kumar,Eric Vejerano,Azmatullah Khan,Grzegorz Lisak,안정현,김기현 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.11
Coordination polymers (CPs) are a unique class of polymers characterized by a molecular structure consisting of repeating metal centers linked by organic ligands in an infinite array connected through coordination bonding. In the last two decades, research interest in CPs, such as metal organic frameworks (MOFs), has grown rapidly owing to their exclusive advantageous properties (e.g., exceptionally high surface area, chemical and thermal stability, molecular functionality, porosity, electron mobility, thermal conductivity, and mechanical strength). In this study, we started with a basic question: Why and how are coordination polymers special and how do they differ from other classes of polymers? Next, we explored the value of unique and innovative CPs in line with the advent of design and synthesis approaches. We focused on the current trends and challenges of CPs/MOFs for application in the control and management of air quality. The intent of this review is to motivate development of CPs/MOFs that can be ultimately applied towards more efficient and effective technology as remediating and managing of the air quality. Ultimately, this review will help us open a new paradigm to pursue the future progress in polymers and materials science that targets specific applications in environmental engineering.
Pawan K. Dubey,Vrajesh Tripathi,Ram Pratap Singh,G. Taru Sharma 대한수의학회 2011 JOURNAL OF VETERINARY SCIENCE Vol.12 No.3
Effect of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on in vitro survival, growth, steroidogenesis, and apoptosis of buffalo preantral follicles (PFs) was investigated. PFs (200~250 μm) were isolated by micro-dissection and cultured in 0 (control), 10^(-3), 10^(-5), 10^(-7), and 10^(-9) M SNP. To examine the reversible effect of SNP, PFs were cultured with 10^(-5 )M SNP + 1 mM N^ω-nitro-L-arginine methyl ester (L-NAME) or 1.0 μg hemoglobin (Hb). The results showed that greater concentrations of SNP (10^(-3), 10^-(5), 10^(-7) M) inhibited (p < 0.05) FSH-induced survival, growth, antrum formation, estradiol production, and oocyte apoptosis in a dose-dependent manner. However, a lower dose of SNP (10^(-9) M) significantly stimulated (p < 0.05) the survival, growth, antrum formation, follicular oocyte maturation, and stimulated progesterone secretion compared to the control. A combination of SNP + L-NAME promoted the inhibitor effect of SNP while a SNP + Hb combination reversed this effect. Nitrate and nitrite concentrations in the culture medium increased (p < 0.05) in a dosedependent manner according to SNP concentration in the culture medium. At higher concentrations, SNP had a cytotoxic effect leading to follicular oocyte apoptosis whereas lower concentrations have stimulatory effects. In conclusion, NO exerts a dual effect on its development of buffalo PFs depending on the concentration in the culture medium.
Correlation between blood glucose and hematocrit: A new estimation methodology
Pawan K. Tiwari,남학현,손영수 한국바이오칩학회 2012 BioChip Journal Vol.6 No.3
The estimation of hematocrit in the enzy me and mediator configured blood glucose monitoring electrochemical strips is proposed conceptualizing an innovative data mining methodology. This methodology demonstrate assimilating the peak current(IP), and time(tP) to achieve the peak current of the amperometry; as a coordinate point in the indigenously nomenclated HMM(Hematocrit Monitoring Method) IP-tP Array. The array consists of onstructing a matrix(9×7 matrix) that could be extended to a matrix of appreciable size within the computational limitations. The computational results of hematocrit estimation are precise in the experimental range of 10-50% hematocrit volume. A mathematical model for the transient current emanating from an lectrochemical strip is also formulated corroborating our experimental results.
Pawan Dahal,Deepak Pathak,Eunju Kwon 한국구조생물학회 2023 Biodesign Vol.11 No.4
Bacteria regulate stress-response transcription using two-component systems to adapt to environmental changes. In Bacillus subtilis, the Css two-component system is responsible for counteracting envelope stress caused by heat, protein misfolding, and peptidoglycan stress. This envelope stress is directly recognized by the extracytoplasmic domain of CssS (CssS-ECD). As preliminary studies to understand the stress-sensing mechanism of CssS, CssS-ECD was expressed, purified, and crystallized. Diffraction data of CssS-ECD were collected at a sub-atomic resolution of 0.92 Å. The crystal belongs to the primitive P1 space group with unit cell parameters of a = 27.2, b = 33.7, c = 33.8 (Å), α = 97.7, β = 109.5, and γ = 104.6 (°). The Matthews coefficient of this crystal is calculated to be 1.75 Å3/Da and the corresponding solvent content is 29.6%, assuming that one CssS-ECD is in the crystallographic asymmetric unit.
Pawan Kumar Shahi,임동윤,Dong Chaun Zuo,최석,Mi Jung Lee,정현숙,전제열 한국생약학회 2013 Natural Product Sciences Vol.19 No.4
In preliminary tests, we examined the effect of several fractions isolated from fermented pine needle extract on pacemaker potentials in cultured interstitial cells of Cajal (ICCs) from the mouse colon using a whole cell patch clamp technique. Among these fractions, Fraction 3 (F3) elicited the most powerful depolarization of membrane. Therefore, the aim of the present study was to investigate the effect of F3 obtained from fermented extract of Pinus densiflora needle on pacemaker potentials in ICCs and to establish its mechanism of action. Colonic ICCs generated spontaneous periodic pacemaker potentials in the current-clamp mode. F3 depolarized the membrane and decreased the frequency and amplitude of pacemaker potentials in a dose-dependent fashion. The F3-induced effects on pacemaker potentials were blocked by methoctramine, a muscarinic M2 receptor antagonist, and by glycopyrrolate, a muscarinic M3 receptor antagonist. The F3-induced effects on pacemaker potentials were blocked by external Na+-free solution and by flufenamic acid, a non-selective cation channel blocker, as well as by the removal of external Ca2+ and in the presence of thapsigargin, a Ca2+-ATPase inhibitor in the endoplasmic reticulum. Taken together, these results suggest that F3 of pine needle extract modulates the pacemaker activity of colonic ICCs by the activation of non-selective cation channels via muscarinic M2 and M3 receptors. And external Ca2+ influx and intracellular Ca2+ release are involved in F3 actions on ICCs.
Controlling Band Gap and Refractive Index in Dopant-Free α-Fe2O3 Films
Pawan Kumar,Nitin Rawat,Da-Ren Hang,이흥노,Rajesh Kumar 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.1
Dopant-free hematite (α-Fe2O3) films are formed at a liquid-vaporinterface by means of an easy method in order to control the bandgap and refractive index of the films. The α-Fe2O3 films after beingtransferred to a glass substrate are studied for their structural andoptical properties. Control over the thickness of the films in therange from 75 to 400 nm and the constituent nanocrystallite sizefrom 3 to 46 nm is achieved by controlling the synthesisparameters. By controlling the film thickness, crystallite size, andcrystallinity of dopant-free α-Fe2O3 films, the optical band gap isincreased significantly (by ≈ 0.64 eV) from 2.30 to 2.94 eV, alongwith increase in the refractive index from 1.35 to 2.8. Theobserved increase in the optical band gap is explained on thebasis of change in lattice symmetry (via change in the c/a ratio) ofα-Fe2O3 crystallites.