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- 저자 : D. Kumar (검색결과 417 건)
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Kumar, D. Praveen,Park, Hanbit,Kim, Eun Hwa,Hong, Sangyeob,Gopannagari, Madhusudana,Reddy, D. Amaranatha,Kim, Tae Kyu Elsevier 2018 Applied catalysis. B, Environmental Vol.224 No.-
<P><B>Abstract</B></P> <P>The hollow materials have played a significant role in cutting-edge innovations for energy conversion due to their peculiar properties and their wide range of potential applications. These materials show great promise for the development of cleaner power sources to address growing environmental concerns at a time of increasing global demand for energy. Noble metal-free MOF-derived onion slice-type hollow structured Co<SUB>4</SUB>S<SUB>3</SUB> was developed and embedded with CdS nanoparticles for photocatalytic hydrogen production. The incorporation of Co<SUB>4</SUB>S<SUB>3</SUB> with the CdS particles effectively accelerated charge separation and transfer in photocatalytic reactions due to the low density, hollow interior, and shell permeability of the onion-type composite. The optimized Co<SUB>4</SUB>S<SUB>3</SUB>/CdS photocatalyst led to an enhanced rate of H<SUB>2</SUB> production of 12,360μmolh<SUP>−1</SUP> g<SUP>−1</SUP> under simulated solar light irradiation; this value is 26-fold greater than that of the pristine CdS nanoparticles. The Co<SUB>4</SUB>S<SUB>3</SUB>/CdS composite exhibited remarkably stable photocatalytic performance for up to 65h and could be reused in five successive cycles. Furthermore, to the best of our knowledge, this is the highest H<SUB>2</SUB> production rate achieved with cobalt sulfide-based CdS nanoparticle photocatalysts in the photocatalysis of water under simulated solar light irradiation. Owing to its low cost and high efficiency, this photocatalytic system should hold great potential for the development of highly efficient photocatalytic materials for use in various fields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Noble metal-free MOF-derived onion slice-type hollow structured Co<SUB>4</SUB>S<SUB>3</SUB> was developed. </LI> <LI> The Co<SUB>4</SUB>S<SUB>3</SUB> with the CdS particles effectively accelerated charge separation. </LI> <LI> The low density, hollow interior, shell permeability of Co<SUB>4</SUB>S<SUB>3</SUB> improves the transfer property. </LI> <LI> The optimized Co<SUB>4</SUB>S<SUB>3</SUB>/CdS shows high rate of H<SUB>2</SUB> production of 12,360μmolh<SUP>−1</SUP> g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Noble metal-free MOF-derived onion slice-type hollow cobalt sulfide nanostructures: Enhanced activity of CdS for improving photocatalytic hydrogen production by D.P. Kumar et al.</P> <P>[DISPLAY OMISSION]</P>
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G Thamizharasan,Eithiraj R,D,Enhbayar Enhtuwshin,So Jung Kim,Niroj Kumar Sahu,Arpan Kumar Nayak,HyukSu Han 한국세라믹학회 2020 세라미스트 Vol.23 No.4
Electronic band structure of bismuth ferrite (BFO) is studied by computational and experimental methods. Bandgap of BFO is precisely determined using optical absorption spectra as well as density functional calculation (DFT). Both methods give a comparable result that BFO can have both of direct or indirect (very close to direct) bandgap of about 2.0~2.2 eV. Furthermore, electronic transition in BFO occurs via the unoccupied O 2p to the occupied Fe 3d states or the d-d transition in Fe 3d states. Intriguing electronic structure of BFO, a narrow bandgap and a multiple electronic transition route, render it as a promising candidate for a visible light photocatalyst.
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Ratnam, B.V.,Jayasimhadri, M.,Bhaskar Kumar, G.,Jang, K.,Kim, S.S.,Lee, Y.I.,Lim, J.M.,Shin, D.S.,Song, T.K. Elsevier Sequoia 2013 JOURNAL OF ALLOYS AND COMPOUNDS Vol.564 No.-
<P>An efficient green emitting Tb3+ doped NaCaPO4 (NCP) phosphor was synthesized by using conventional solid-state reaction for solid-state lighting applications. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), FT-IR, emission and excitation properties were extensively investigated for NCP phosphors. X-ray diffraction analysis confirmed the formation of NaCaPO4 with orthorhombic structure. The excitation spectrum consists of strong 4f-4f transition at around 370 nm, which has higher intensity than the f-d transition. Emission spectra indicated that this phosphor can be efficiently excited by UV light in the range from 250 to 400 nm, and shows strong emission band centered at 547 nm. Analysis of the emission spectra with different Tb3+ concentrations revealed that the optimum dopant concentration for these NCP phosphors is about 5 mol% of Tb3+. Diminishing of D-5(3) level and increasing of D-5(4) level emission intensity with the Tb3+ concentration explained successfully. The emission color was analyzed and confirmed with the help of chromaticity coordinates and color temperature. The excellent luminescent properties of NaCaPO4: Tb3+ phosphor makes it as a potential green phosphor upon near-UV LED excitation. (C) 2013 Elsevier B.V. All rights reserved.</P>
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( E. Gnana Desigan ),( D. Raj Kumar ) 대한간학회 2020 춘·추계 학술대회 (KASL) Vol.2020 No.1
Background: Nonalcoholic fatty liver disease (NAFLD) is a condition in which excessive fat accumulates in the liver of a patient who drinks little or no alcohol. The development of NAFLD is associated with obesity, insulin resistance, and hyperlipidemia and is characterized by the accumulation of fatty acids, especially excess triglycerides, in hepatocytes. The increasing prevalence of obesity, metabolic syndrome, and NAFLD has been connected to excess caloric intake, such as the excessive consumption of refined food with high fructose levels. Recent research suggests diets specifically high in fructose have been shown to contribute to a metabolic disturbance in animal models. NAFLD is a component of the metabolic syndrome. High fructose consumption has been implicated in the progression and severity of NAFLD by promoting de novo lipogenesis and increasing insulin resistance, oxidative stress, inflammation, and fibrosis. However the mechanism responsible is still unknown. Aim: The aim of the present study is to assess relationship between high fructose diet and risk, progression of NAFLED. Methods: Thirty six female albino mice of 21 years old were divided into six groups. Group A: normal control diet for 30 days (control 30), Group B: High fructose diet for 30 days (HFD 30 days), Group C: Palm jaggery diet for 30 days (PJD 30), Group D: normal control diet for 90 days (Control 90), Group E: High fructose diet for 90 days (HFD 90), Group F: Palm jaggery diet for 90 days (PJD 90). The mice are fed control diet, refined high sugar diet, Palm jaggery diet, tap water ad libitum. The body weight was measured at regular intervals. At the end of the experimental period the animals were sacrificed and blood samples were collected by cardiac puncture for biochemical analysis and liver tissues were processed for histoarchitecture analysis. Results: HFD 90 mice shows liver parenchyma with partially effaced architecture. Many hepatocytes show apoptotic changes and cytoplasmic vaculations around central vein. The concentration of collagen fibres were increased apparently. Fat droplets were observed with degenerative changes of hepatocyes in some regions of liver. PJD 90 mice shows apoptotic changes in some part of liver also shows less number of fat droplets was observed. Most of the perivenular and periportal hepatocytes appear normal. Control groups (control 30, 90) show normal liver parenchyma with intact architecture. No significant changes were observed in HFD30 & PJD30 liver architecture. Serum insulin level was increased significantly in PJD 30, HFD 30 & HFD 90. Increased TBARS level in HFD 90 with other findings shows features of dyslipidemia (P<0.01). Conclusion: This study concludes that chronic exposure to high fructose diet (HFD) in mice induces oxidative stress and this manifested as structural changes in liver similar to non alcoholic fatty liver disease (NAFLD). Our study suggests that intake of palm jaggery will be a good alternative to fructose to maintain the normal liver morphology.
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Effect of low levels of hydrotropes on micellization of phenothiazine drug
Sulaiman Y. M. Alfaifi,Dileep Kumar,Malik Abdul Rub,Farah Khan,Naved Azum,Anish Khan,Abdullah M. Asiri,Hurija Džudžević-Čančar 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.2
Interactions within mixtures of the phenothiazine drug promethazine hydrochloride (PMH) and cationic hydrotropes ortho-toluidine hydrochloride (o-TDH) and para-toluidine hydrochloride (p-TDH) were investigated at different ratios and temperatures via conductometry to understand various physicochemical properties. Critical micelle concentration (cmc) was less than values of cmcid (cmc in ideal mixed system), indicating significant interaction among the studied constituents in solution mixtures. The cmc of pure PMH was also determined by measuring the surface tension for comparison. A variety of micellization thermodynamic parameters (Gibbs free energy [Gm 0 ], change in standard enthalpy [Hm 0 ], and change in entropy [Sm 0 ]) were computed using conductometry. The micellar mole fraction (X1 Rb, X1 Rod, and X1 id) of hydrotropes estimated by various theoretical models (Rubingh, Rodenas, and Motomura) was assessed, and the results showed a greater contribution of hydrotropes in mixed micelles along with their values increasing via an increase in mole fraction (1) of hydrotropes (o-TDH/p-TDH). Negative values suggest extremely favorable attractive interaction/synergism, as declines occurred in the whole quantity of amphiphile used for the desired purpose, leading to a drop of expenditure along with ecological concern. Obtained activity coefficients (f1 and f2) were always beneath unity, meaning nonideality was found between PMH and o-TDH/p-TDH. Like the conductivity method, the UV-visible and FT-IR techniques also demonstrate the interaction between the PMH and o-TDH/p-TDH.
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Kim, J. S.,Han, K. S.,Kim, S. J.,Kim, S. D.,Lee, J. Y.,Han, C.,Rajesh Kumar, J. Springer Science + Business Media 2016 Journal of Radioanalytical and Nuclear Chemistry Vol.307 No.2
<P>Synergistic extraction of uranium using amine combined with phosphorous based extractant systems was described. The present study focused on the continuous extraction processing of uranium to form precipitation under higher pH conditions and higher aqueous phase ratios. To address this, synergistic extraction studies were carried out with P-based extractants as synergists and investigations were done with better pairs with an aminebased extractant system. Finally, all of the developed synergistic extraction methodologies were compared with each other. This showed that Alamine 336 and D2EHPA was the best pair for uranium extraction, offering as much separation as possible from other associated metals.</P>
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Association of Serum Vitamin D Levels with Bacterial Load in Pulmonary Tuberculosis Patients
( B. Yuvaraj ),( M. G. Sridhar ),( D. N. B. ),( S. Vinod Kumar ),( T. Kadhiravan ) 대한결핵 및 호흡기학회 2016 Tuberculosis and Respiratory Diseases Vol.79 No.3
Background: Vitamin D is known to have diverse effects on various systems in the body. There is evidence to suggest that a link exists between the serum vitamin D status and tuberculosis. The present study was designed to assess the alterations in serum 25-hydroxyvitamin D levels in newly diagnosed sputum acid fast bacilli (AFB) positive pulmonary tuberculosis patients and to study the association, if any, between serum vitamin D levels and different levels of sputum smear positivity. Methods: Serum 25-hydroxyvitamin D levels were estimated in 65 sputum AFB positive pulmonary tuberculosis patients and 65 age and gender-matched healthy controls. Results: The levels of serum 25 hydroxy-vitamin D in tuberculosis patients were not statistically different from the levels of serum 25 hydroxy-vitamin D in healthy controls. However, among patients with pulmonary tuberculosis, there was a significant negative correlation between the levels of serum 25 hydroxy-vitamin D and levels of sputum positivity. Conclusion: Serum vitamin D levels negatively correlates with bacterial load in patients with active pulmonary tuberculosis.
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Rangappa, A. Putta,Kumar, D. Praveen,Gopannagari, Madhusudana,Reddy, D. Amaranatha,Hong, Yul,Kim, Yujin,Kim, Tae Kyu Elsevier 2020 APPLIED SURFACE SCIENCE - Vol.508 No.-
<P><B>Abstract</B></P> <P>The development of low-cost and noble-metal-free catalysts for the photoconversion of water into hydrogen (H<SUB>2</SUB>) is of great interest. Here, 2D tin(IV) sulfide (SnS<SUB>2</SUB>) ultrathin nanosheets as co‐catalysts are coupled with 1D cadmium sulfide (CdS) nanorods for the photosplitting of water into H<SUB>2</SUB>. The design of the catalyst can facilitate the passivation of the physiochemical properties of CdS and enhance H<SUB>2</SUB> evolution activity. The prepared CdS/SnS<SUB>2</SUB> composite catalyst increases the H<SUB>2</SUB> generation activity and exhibits excellent and continuous long-term photostability. The H<SUB>2</SUB> evolution rate of the optimized CdS/SnS<SUB>2</SUB> composite is approximately 9-fold that of pristine CdS nanorods. The characterization results of the CdS/SnS<SUB>2</SUB> composite reveal that the loading of SnS<SUB>2</SUB> can enhance the synergistic effects of the photocatalyst due to the effective separation, large number of exposed catalytic sites, and highly dispersed nature of the layered SnS<SUB>2</SUB>. Several characterization outcomes of CdS/SnS<SUB>2</SUB> are examined in detail (e.g., structural and surface elemental results of transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy). Further, the optoelectrical properties and charge-carrier excitations are investigated via ultraviolet diffuse reflectance spectroscopy, photoluminescence spectroscopy, and photoelectrochemical analysis. The proposed CdS/SnS<SUB>2</SUB> composite is a promising low-cost, noble-metal-free, and high-efficiency catalyst for the photocatalytic water-reduction reaction.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Superior hydrogen evolution rate which is nine folds higher than the CdS. </LI> <LI> Excellent separation of photo generated charge carriers on CdS/SnS<SUB>2</SUB> hybrid with SnS<SUB>2</SUB> insertion. </LI> <LI> Excellent photo stability (30 h) of the catalyst for long term practical applications. </LI> <LI> Uniform deposition of ultrathin SnS<SUB>2</SUB> sheets onto CdS by simple methods. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Optimal hydrogen evolution rate of 20.2 mmol h<SUP>−1</SUP> g<SUP>−1</SUP> facilitated by enhanced absorption and prolonged life time of charge carriers by SnS<SUB>2</SUB> as co-catalyst on CdS.</P> <P>[DISPLAY OMISSION]</P>
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