The effect of transition metal oxide doping on the sintering behaviour of yttria-stabilised tetragonal zirconia

H.C. Alexander Chee,R.S.K. Singh,K.Y. Sara Lee 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.4

The effect of small amounts (0.2 wt% and 0.5 wt%) of transition metal oxide (CuO) doping on the sintering behavior of 3mol% yttria-stabilized zirconia (Y-TZP) was investigated over the temperature range of 1250 oC to 1500 oC. Sintered sampleswere characterized to determine the phase present, relative density, microstructural evolution and Vickers hardness. Thestudies revealed that the addition of 0.2 wt% CuO dopant was most effective in enhancing the densification of the Y-TZP inparticularly at low temperatures below 1350 oC. The phase analysis revealed that the tetragonal phase was disrupted as evidentfrom the high monoclinic phase formation in the 0.5 wt% CuO-doped zirconia. This phenomenon was associated withmechanism involving transient liquid phase which believed to have destabilized the tetragonal structure. Nevertheless, thestudy revealed that compared to the undoped Y-TZP, the sample with addition of 0.2 wt% CuO resulted in enhanced hardnessand finer grain sizes when sintered at relatively low temperatures.

Rapid degradation of phenol by ultrasound-dispersed nano-metallic particles (NMPs) in the presence of hydrogen peroxide: A possible mechanism for phenol degradation in water

Singh, J.,Yang, J.K.,Chang, Y.Y. Academic Press 2016 Journal of Environmental Management Vol. No.

<P>The present study was carried out to investigate the degradation of phenol by ultrasonically dispersed nano-metallic particles (NMPs) in an aqueous solution of phenol. Leaching liquor from automobile shredder residue (ASR) was used to obtain the NMPs. The prepared NMPs were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by X-ray diffraction (XRD). The SEM images show that the diameters of the NMPs were less than 50 nm. An SEM-EDX elemental analysis reveals that Fe was the most commonly found element (weight %) in the NMPs. The FTIR and XRD peaks indicate the presence of metals oxides on the surfaces of the NMPs. The results of the XPS analysis indicate that various elements (e.g., C, O, Zn, Cu, Mn, Fe) are present on the surfaces of the NMPs. The effects of the NMP dose, the initial solution pH, and of different concentrations of phenol and H2O2 on the phenol degradation characteristics were evaluated. The results of this study demonstrate that phenol degradation can be improved by increasing the amount of NMPs, whereas it is reduced with an increase in the phenol concentration. The degradation of phenol by ultrasonically dispersed NMPs followed the pseudo-first-order kinetics. The probable mechanism of phenol degradation by ultrasonically dispersed NMPs was the oxidation of phenol caused by the hydroxyl radicals produced during the reaction between H2O2 and the NMPs during the ultrasonication process. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Transdifferentiation of porcine satellite cells to adipoblasts with ciglitizone1

Singh, N. K.,Chae, H. S.,Hwang, I. H.,Yoo, Y. M.,Ahn, C. N.,Lee, S. H.,Lee, H. J.,Park, H. J.,Chung, H. Y. Oxford University Press 2007 Journal of animal science Vol.85 No.5

2, 4-Thiazolidindion Induced Plasticity of Myoblast (C2C12) and Satellite Cells (Porcine) - A Comparative Study

Singh, N.K.,Chae, H.S.,Hwang, I.H.,Yoo, Y.M.,Ahn, C.N.,Lee, H.J.,Park, H.J.,Chung, H.Y. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.7

This study was conducted to determine the difference between satellite cells (porcine) and myoblasts (C2C12) in their differentiation under the influence of 2, 4-thiazolidindion. C2C12 myoblast cells and porcine satellite cells (isolated from 10 d old $Landrace{\times}Duroc$ piglets) were grown to absolute confluency. Post confluent cells (day 0) were further exposed to adipogenic induction medium along with 2, 4-thiazolidindion ($8{\mu}M$) for 2 d. Thereafter, cells were exposed to 2, 4-thiazolidindion alone every 2 d till day 10 and analysed. The control was cultured in differentiation medium without any treatment. Increased (p<0.05) expression of transcriptional factors i.e. C/EBP-${\alpha}$ and PPAR-${\gamma}$ and transition of cells to adipocyte morphology was noticed from 2 d and 4 d onwards in satellite cells (Porcine) and myoblasts (C2C12) respectively. Myogenesis was observed to be suppressed completely in case of satellite cells compared to myoblasts in response to 2, 4-thiazolidindion. Pax-7 (transcriptional factor) appeared as a sole entity to satellite cells only, as it was not identified in case of myoblasts. Although both the cells were converting to adipoblasts, the degree of their conversion was different in response to 2, 4-thiazolidindion. Therefore, the hypothesis that satellite cells contribute various domains to the growing myoblasts appeared obscured and found to be dependent on the proliferative energy/or degree of fusion. However, it revealed satellite cells as currency to myoblasts/muscle.

Articular Cartilage Repair with Autografting Under the Influence of Insulin-Like Growth Factor-1 in Rabbits

Singh, N. K.,Singh, G. R.,Kinjavdekar, P.,Sharma, A. K.,Mohanty, T. R.,Kumar, S.,Chae, H. S.,Yoo, Y. M.,Ahn, C. N. Wiley (Blackwell Publishing) 2007 Journal of veterinary medicine. A, Physiology, pat Vol.54 No.4

PA-824 Kills Nonreplicating Mycobacterium tuberculosis by Intracellular NO Release

Singh, R.,Manjunatha, U.,Boshoff, H. I. M.,Ha, Y. H.,Niyomrattanakit, P.,Ledwidge, R.,Dowd, C. S.,Lee, I. Y.,Kim, P.,Zhang, L.,Kang, S.,Keller, T. H.,Jiricek, J.,Barry, C. E. American Association for the Advancement of Scienc 2008 Science Vol.322 No.5906

<P>Bicyclic nitroimidazoles, including PA-824, are exciting candidates for the treatment of tuberculosis. These prodrugs require intracellular activation for their biological function. We found that Rv3547 is a deazaflavin-dependent nitroreductase (Ddn) that converts PA-824 into three primary metabolites; the major one is the corresponding des-nitroimidazole (des-nitro). When derivatives of PA-824 were used, the amount of des-nitro metabolite formed was highly correlated with anaerobic killing of Mycobacterium tuberculosis (Mtb). Des-nitro metabolite formation generated reactive nitrogen species, including nitric oxide (NO), which are the major effectors of the anaerobic activity of these compounds. Furthermore, NO scavengers protected the bacilli from the lethal effects of the drug. Thus, these compounds may act as intracellular NO donors and could augment a killing mechanism intrinsic to the innate immune system.</P>

Extracellular synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 and their biological applications

Singh, P.,Singh, H.,Kim, Y.J.,Mathiyalagan, R.,Wang, C.,Yang, D.C. IPC Science and Technology Press ; Elsevier Scienc 2016 Enzyme and microbial technology Vol.86 No.-

<P>The present-study highlights the microbial synthesis of silver and gold nanoparticles by Sporosarcina koreensis DC4 strain, in an efficient way. The synthesized nanoparticles were characterized by ultraviolet visible spectrophotometry, which displayed maximum absorbance at 424 nm and 531 nm for silver and gold nanoparticles, respectively. The spherical shape of nanoparticles was characterized by field emission transmission electron microscopy. The energy dispersive X-ray spectroscopy and elemental mapping were displayed the purity and maximum elemental distribution of silver and gold elements in the respective nanoproducts. The X-ray diffraction spectroscopy results demonstrate the crystalline nature of synthesized nanoparticles. The particle size analysis demonstrate the nanoparticles distribution with respect to intensity, volume and number of nanoparticles. For biological applications, the silver nanoparticles have been explored in terms of MIC and MBC against pathogenic microorganisms such as Vibrio parahaemolyticus, Escherichia coli, Salmonella enterica, Bacillus anthracis, Bacillus cereus and Staphylococcus aureus. Moreover, the silver nanoparticles in combination with commercial antibiotics, such as vancomycin, rifampicin, oleandomycin, penicillin G, novobiocin, and lincomycin have been explored for the enhancement of antibacterial activity and the obtained results showed that 3 mu g concentration of silver nanoparticles sufficiently enhance the antimicrobial efficacy of commercial antibiotics against pathogenic microorganism. Furthermore, the silver nanoparticles potential has been reconnoitered for the biofilm inhibition by S. aureus, Pseudomonas aeruginosa and E. coli and the results revealed sufficient activity at 6 mu g concentration. In addition, gold nanoparticles have been applied for catalytic activity, for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride and positive results were attained. (C) 2016 Elsevier Inc. All rights reserved.</P>

Pedobacter panacis sp. nov., isolated from Panax ginseng soil

Singh, P.,Singh, H.,Kim, Y. J.,Yang, D. C. Kluwer Academic Publishers [etc.] 2017 Antonie van Leeuwenhoek Vol.110 No.2

<P>A novel strain, DCY108(T) was isolated from soil of a Panax ginseng field, Yeoncheon province (38A degrees 04'N 126A degrees 57'E), Republic of Korea. Strain DCY108(T) is Gram-negative, non-motile, non-flagellate, rod-shaped, and aerobic. The bacterium grows optimally at 25-30 A degrees C, pH 6.5-7.0 and 1 % NaCl. Phylogenetically, strain DCY108(T) is closely related to Pedobacter jejuensis JCM 18824(T), Pedobacter aquatilis JCM 13454(T), Pedobacter kyungheensis LMG 26577(T) and the type strain of the genus Pedobacter heparinus DSM 2366(T). The DNA-DNA relatedness values between strain DCY108(T) and its close phylogenetic neighbors were below 30.0 %. The DNA G+C content of strain DCY108(T) was determined to be 45.1 mol%. The predominant quinone was menaquinone 7 (MK-7). The major polar lipids were identified as phosphatidylethanolamine and three unidentified aminolipids AL1, AL13 and AL17. Iso-C-15:00, iso-C(17:0)3OH and summed feature 3 (C-16:1 omega 7c/C-16:1 omega 6c) were identified as the major fatty acids present in strain DCY108(T). The results of physiological and biochemical tests allowed strain DCY108(T) to be differentiated phenotypically from other recognized species belonging to the genus Pedobacter. Therefore, it is suggested that the newly isolated organism represents a novel species, for which the name Pedobacter panacis sp. nov is proposed with the type strain designated as DCY108(T) (=CCTCCAB 2015196(T) = KCTC 42748(T)).</P>

Effect of pH values on recovery of nano particles (NPs) from the fine fraction of automobile shredder residue (ASR): An application of NPs for phenol removal from the water

Singh, J.,Lingamdinne, L.P.,Yang, J.K.,Chang, Y.Y.,Lee, B.K.,Koduru, J.R. Institution of Chemical Engineers ; Hemisphere Pub 2017 PROCESS SAFETY AND ENVIRONMENTAL PROTECTION Vol.105 No.-

Nano particles (NPs) were synthesized from leachate of fine fraction (<0.25mm) of automobile shredder residue (ASR) at pH levels of 3, 5, 7, 9 and 12. The removal of phenol using NPs in water was investigated to determine whether applying NPs for phenol removal from wastewater would be feasible. The recovered NPs were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In this research, phenol degradation was studied with hydrogen peroxide to assess the potential applicability of NPs for the treatment of wastewater. The results of the SEM and TEM analyses show that the separated NPs were <50nm in size. The FTIR spectra indicate the presence of C?O and O?H bonds in the NPs. The XRD results show the presence of metals oxides of Fe, Zn, and Cu, among others, on the surfaces of the NPs. The results of the XPS analyses show that various elements (e.g., C, O, Zn, and Fe) existed in the recovered NPs. The degree of phenol degradation by NPs in the presence of hydrogen peroxide was significant. Phenol degradation was found to be 100% for NPs synthesized at pH levels of 3 and 7 at a reaction time of 210min. A pseudo-first-order kinetic model showed a very good fit to the phenol degradation results. The probable mechanism for the removal of phenol by NPs was the degradation of phenol by hydroxyl radicals which were produced during the reaction between H<SUB>2</SUB>O<SUB>2</SUB> and NPs in a liquid medium. The results of the present study indicate that NPs recovered from low-grade ASR can be applied for the removal of phenolic compounds from water.

Electronic and mechanical properties of (6,1) single-walled carbon nanotubes with different tube diameters: a theoretical study

Singh Y. T.,Patra P. K.,Obodo K. O.,Rai D. P. 한국탄소학회 2022 Carbon Letters Vol.32 No.2

We investigated the electronic and mechanical properties of single-walled carbon nanotubes (SWCNTs) with different tube diameters using density functional theory (DFT) and molecular dynamics (MD) simulation, respectively. The carbon nanotubes’ electronic properties were derived from the index number (n1 , n2 ), lattice vectors, and the rolled graphene sheet orientation. For (6,1) SWCNT, (n1 -n2 )/3 is non-integer, so the expected characteristic is semiconducting. We have considered (6,1) Chiral SWCNT with different diameters ‘d’ (4.68 Å, 4.90 Å, 5.14 Å, 5.32 Å, 5.53 Å) corresponds to respective bond lengths ‘δ ’ (1.32 Å, 1.38 Å, 1.45 Å, 1.50 Å and 1.56 Å) and then analyze the electronic properties from the Linear Combination of Atomic Orbitals (LCAO) based on DFT. We have used both the DFT-1/2 and GGA exchange energy correlation approximations for our calculation and compared the results. In both cases, the energy bandgap is decreasing order with the increase in bond lengths. The lowest value of formation energy was obtained at the bond length δ=1.45 Å (d=5.14 Å). For the mechanical properties, we have calculated Young’s modulus using molecular dynamics (MD) simulations. From our calculation, we have found that the (6,1) SWCNT with bond length 1.45 Å (d=5.14 Å) has Young’s modulus value of 1.553 TPa.