Incorporation of Graphitic Porous Carbon for Synthesis of Composite Carbon Aerogel with Enhanced Electrochemical Performance

Singh, Ashish,Kohli, D.K.,Singh, Rashmi,Bhartiya, Sushmita,Singh, M.K.,Karnal, A.K. The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.2

We report, synthesis of high surface area composite carbon aerogel using additive based polymerization technique by incorporating graphitic porous carbon as additive. This additive was separately prepared using sol-gel polymerization of resorcinol-furfuraldehyde in iso-propyl alcohol medium at much above the routine gelation temperature to yield porous carbon (CA-IPA) having graphitic layered morphology. CA-IPA exhibited a unique combination of meso-pore dominated surface area (~ 700 m²/g) and good conductivity of ~ 300 S/m. The composite carbon aerogel (CCA) was synthesized by traditional aqueous medium based resorcinol-formaldehyde gelation with CA-IPA as additive. The presence of CA-IPA favored enhanced meso-porosity as well as contributed to improvement in bulk conductivity. Based on the surface area characteristics, CCA-8 composition having 8% additive was found to be optimum. It showed specific surface area of ~ 2056 m²/g, mesopore area of 827 m²/g and electrical conductivity of 180 S/m. The electrode formed with CCA-8 showed improved electrochemical behavior, with specific capacitance of 148 F/g & ESR < 1 Ω, making it a better choice as super capacitor for energy storage applications.

ANION INDUCED BLUE TO PURPLE TRANSITION IN BACTERIORHODOPSIN

Singh, Anil K.,Kapil, Mrunalini M. Korean Society of Photoscience 1996 Journal of Photosciences Vol.3 No.2

Anil K. Singh, Mrunalini M. Kapil, Department of Chemistry, Indian Institute of Technology Bombay - 400076, INDIA Purple membrane (PM, $\lambda$$_{max}$ 570 nm) of H. halobium on treatment with sulphuric acid changes its colour to blue ($\lambda$$_{max}$ 608 nm). The purple chromophore can be regenerated from the blue chromophore by exogeneous addition of anions such as CI$^-$ and HPO$_4^{2-}$. Chloride ion is found to be more effective than the dibasic phosphate ion in regenerating the purple chromophore. Nevertheless, one thing common to the anion regeneration is that both CI$^-$ and HPO$_4^{2-}$ show marked pH effect. At pH 1.0 the efficiency of regeneration of the purple chromophore is greater than at pH 2.0, for the same anion concentration. Fluorescence and circular dichroic studies indicate that the proteins do not undergo drastic changes at the secondary' or tertiary structure level and the native structure is preserved during this transition. However, chromophoric-site interactions between retinal and the apoprotein are affected during this colour transition. A molecular mechanism is advanced for this transition.

Mechanistic insights into the interaction between energetic oxygen ions and nanosized ZnFe₂O₄: XAS-XMCD investigations

Singh, Jitendra Pal,Kaur, Baljeet,Sharma, Aditya,Kim, So Hee,Gautam, Sanjeev,Srivastava, Ramesh Chandra,Goyal, Navdeep,Lim, Weol Cheol,Lin, H.-J.,Chen, J. M.,Asokan, K.,Kanjilal, D.,Won, Sung Ok,Lee, The Royal Society of Chemistry 2018 Physical Chemistry Chemical Physics Vol.20 No.17

<P>The interactions of energetic ions with multi-cation compounds and their consequences in terms of changes in the local electronic structure, which may facilitate intriguing hybridization between O 2p and metal d orbitals and magnetic ordering, are the subject of debate and require a deep understanding of energy transfer processes and magnetic exchange mechanisms. In this study, nanocrystals of ZnFe2O4 were exposed to O<SUP>7+</SUP> ions with an energy of 100 MeV to understand, qualitatively and quantitatively, the metal-ligand field interactions, cation migration and magnetic exchange interactions by employing X-ray absorption fine structure measurements and X-ray magnetic circular dichroism to get deeper mechanistic insights. Nanosized zinc ferrite nanoparticles (NPs) with a size of ∼16 nm synthesized in the cubic spinel phase exhibited deterioration of the crystalline phase when 100 MeV O<SUP>7+</SUP> ions passed through them. However, the size of these NPs remained almost the same. The behaviour of crystal deterioration is associated with the confinement of heat in this interaction. The energy confined inside the nanoparticles promotes cation redistribution as well as the modification of the local electronic structure. Prior to this interaction, almost 42% of Zn<SUP>2+</SUP> ions occupied AO4 tetrahedra; however, this value increased to 63% after the interaction. An inverse effect was observed for metal ion occupancies in BO6 octahedra. The L-edge spectra of Fe and Zn reveal that the spin and valence states of the metal ions were not affected by this interaction. This effect is also supported by K-edge measurements for Fe and Zn. The t2g/eg intensity ratio in the O K-edge spectra decreased after this interaction, which is associated with detachment of Zn<SUP>2+</SUP> ions from the lattice. The extent of hybridization, as estimated from the ratio of the post-edge to the pre-edge region of the O K-edge spectra, decreased after this interaction. The metal-oxygen and metal-metal bond lengths were modified as a result of this interaction, as determined from extended X-ray absorption fine structure measurements. These measurements further support the observation of cation migration from AO4 tetrahedra to AO6 octahedra and <I>vice versa</I>. The Fe L-edge magnetic circular dichroism spectra indicate that Fe<SUP>3+</SUP> ions occupying sites in AO4 tetrahedra and BO6 octahedra exhibited antiferromagnetic-like ordering prior to this interaction. The NPs that interacted with energetic O ions displayed a different kind of magnetic ordering.</P>

Optical and EPR Spectroscopic Studies of Deep Red Light Emitting Fe-Doped LiAl5O8 Phosphor Prepared Via Propellant Combustion Route

Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Mohapatra, M.,Singh, P. K.,Pathak, M. S.,Dhoble, S. J. Minerals, Metals & Materials Society and the Insti 2017 Journal of Electronic Materials Vol. No.

<P>LiAl5O8 doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe3+-O2-. On excitation with 293 nm, emission band for the Fe3+ ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe3+ ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe3+ present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe3+ ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K.</P>

Synthesis, magnetic and Mossbauer spectroscopic studies of Cr doped lithium ferrite nanoparticles

Srivastava, M.,Layek, S.,Singh, J.,Das, A.K.,Verma, H.C.,Ojha, A.K.,Kim, N.H.,Lee, J.H. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.591 No.-

Lithium-based ferrites are promising and potential magnetic materials for microwave applications. They possess a spinel (AB<SUB>2</SUB>O<SUB>4</SUB>) type crystal structure, where the distributions of metal cations over the tetrahedral (A) and octahedral (B) voids play a crucial role for exhibiting different physical properties. Among various parameter of synthesis, pH is an important factor that influences the cation distribution over A and B voids, overall growth of the nanoparticles and different physical properties. In the present work single phase Cr substituted lithium ferrite nanoparticles have been synthesized by the sol-gel method at different pH. The phase identification and crystallite size have been probed by X-ray diffraction studies. The crystallite size changes by 44.2-48.8nm upon varying the pH from 3.5 to 11.5. In order to investigate the cations distribution at A/B sites, Mossbauer spectroscopic measurements were done. The values of magnetic hyperfine field obtained from the Mossbauer data for the A and B sites are ~49.5T and 51T, respectively. Moreover, it is observed that the area ratio of B site to A site increases with increasing the pH. This observation further suggests that the B site is more preferable for Fe<SUP>3+</SUP> cations at higher pH than the A site. The magnetic parameter such as saturation magnetization (M<SUB>s</SUB>), remanent magnetization (M<SUB>r</SUB>), coercive field (H<SUB>C</SUB>) and squareness (S) are determined by vibrating sample magnetometer (VSM) measurements, which show a consistent increase with increasing pH. The reason for the variation in magnetic properties has been explained on the basis of increased Fe<SUP>3+</SUP> cation occupancies at the B site and size effect, which is well supported by Mossbauer spectroscopic and XRD studies.

Keratinocyte growth factor and thiazolidinediones and linolenic acid differentiate characterized mammary fat pad adipose stem cells isolated from prepubertal Korean black goat to epithelial and adipogenic lineage

Reza, A. M.,Shiwani, S.,Singh, N. K.,Lohakare, J. D.,Lee, S. J.,Jeong, D. K.,Han, J. Y.,Rengaraj, D.,Lee, B. W. Springer Science + Business Media 2014 In vitro cellular & developmental biology Animal Vol.50 No.3

The study was conducted to know and investigate the mechanism involved during mesenchymal to epithelial transition to unravel questions related to mammary gland development in prepubertal Korean black goat. We, therefore, biopsied mammary fat pad and isolated adipose cells and characterized with stemness factors (CD34, CD13, CD44, CD106, and vimentin) immunologically and through their genetic expression. Furthermore, characterized cells were differentiated to adipogenic (thiazolidinediones and alpha-linolenic acid) and epithelial (keratinocyte growth factor) lineages. Thiazolidinediones/or in combination with alpha-linolenic acid demonstrated significant upregulation of adipo-Q, PPAR-gamma, CEBP-alpha, LPL, and resistin. Adipose stem cells in induction mixture (5 mu g/ml insulin, 1 mu g/ml hydrocortisone, and 10 ng/ml epidermal growth factor) and subsequent treatment with 10 ng/ml keratinocyte growth factor revealed their trans-differentiating ability to epithelial lineage. From 2 d onwards, the cells under keratinocyte growth factor influenced cells to assume rectangular (2-4 d) to cuboidal (8-10 d) shapes. Ayoub-Shklar stain developed brownish-red pigment in the transformed cells. Though, expressions of K8 and K18 were noted to be highly significant (p < 0.01) but expressions of epithelial membrane antigens and epithelial specific antigens were also significant (p < 0.05) compared to 0 d. Conclusively, epithelial transformations of mammary adipose stem cells would add up knowledge to develop therapeutic regimen to deal with mammary tissue injury and diseases.

Observation ofX(3872)inB→X(3872)Kπdecays

Bala, A.,Bhardwaj, V.,Trabelsi, K.,Singh, J. B.,Abdesselam, A.,Adachi, I.,Aihara, H.,Arinstein, K.,Asner, D. M.,Aulchenko, V.,Aushev, T.,Ayad, R.,Aziz, T.,Bahinipati, S.,Bakich, A. M.,Bansal, V.,Barbe American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.5

오리육의 화염 처리 수준에 따른 이화학적 특성

채현석,유영모,안종남,정석근,함준상,이종문,Chae, H.S.,Yoo, Y.M.,Ahn, C.N.,Jeong, S.G.,Ham, J.S.,Lee, J.M.,Singh, N.K. 한국가금학회 2006 韓國家禽學會誌 Vol.33 No.4

본 연구는 오리육의 품질 고급화를 위하여 도축 과정에서 내장 적출 후 화염을 처리하여 도체의 육색 변화와 저장 과정 중 육질 변화 여부를 확인하며, 도체 표면 미생물에 대한 특성을 살펴보고자 수행하였다. 45일령된 오리를 도압장에서 탈모, 내장 제거, 수세 과정에 이어서 화염 처리를 실시하였는데, 화염 처리 수준은 $6kgf/cm^2$ 압력으로 LPG를 무처리, 중처리(50초), 과다 처리(70초)로 구분하여 화염을 처리한 후 저장 특성을 구명하였다. 화염을 처리한 처리구에서는 드립 발생율의 증가율이 적은 반면에 무처리 구에서는 드립 발생 비율이 저장 5일까지 급격히 오르다가 서서히 감소하는 경향을 보였다. 육색에서 명도$(L^*)$ 값은 화염을 처리하지 않은 무처리구가 가장 높은 명도 값을 나타내었고 중, 과 처리구는 서로 비슷한 경향을 나타내었고, 화염 처리 수준별 총 균수의 변화는 무처리구에서 가장 높은 값을 나타내었고, 화염 처리구에서는 처리 수준에 따라 약간씩 저하되는 것을 알 수 있었다. TBARS 값은 화염 처리를 하였을 경우 증가하는 경향을 나타내어 보존성의 저하를 가져왔으나 화염 처리 수준에 따라서는 큰 차이가 없었다. K값 변화는 저장 3일까지는 처리간에 차이가 없었으나 저장 5일이 경과하면서 화염 처리 수준이 증가할수록 K 값이 증가하여 신선도가 감소하는 경향을 나타내었다. 실험을 종합할 때 오리육의 화염을 처리하였을 경우, 화염을 처리할 때 드립발생율 및 육색의 명도 값은 감소되었고, 총 균수도 약간씩 저하되는 경향을 보였으나 지방 산패도를 나타내는 TBARS 값은 증가하는 경향을 나타내었다. Singeing has always been equated with meat color alteration through lipid oxidation and microbial population. Singeing method has always been employed far removing duck feathers, however, the effect of singeing on storage characteristic of duck meat has not been investigated extensively. The study was therefore, designed to Investigate the effect of singeing on duck meat during storage extensively. For the purpose, study was categorized into three groups namely A, B, and C, representing 0, 50 and 70 seconds of singeing time. Singeing was performed on 100 birds in each group, however, only 20 singed birds from each treatment groups were further selected to analyse them subsequently during storage. Analysis revealed that with 70 seconds singeing time drip loss was significantly (p<0.05) higher at $6mgf/cm^2$ compared to 50 seconds of singeing. With 70 seconds treatment breast meat apparently appeared black, where as with 50 seconds treatment no change was observed. Breast showed low redness with more duration of treatment compared to less treatment duration. Yellowness increased, springiness declined and no change was observed in cohesiveness and chewiness with high treatment time. There was increase in the TBARS and VBN, freshness did not change for first 5 days, however, K values started to increase later on indicated decline in freshness. Conclusively, it was inferred from the study that 50 seconds singeing does not make much alternation in the quantitative traits and at the same time maintains the microbial level under permissible limit.

Calculation of electron and hole impact ionization coeffcients in SiGe alloys

Yeom, K.,Hinckley, J.M.,Singh. J. 대전산업대학교 반도체기술연구소 1999 半導體技術硏究所報 Vol.1 No.-

Silicon-germanium alloys offer a system where the ratio of the electron impact ionization coefficiend (a) and hole impact ionization coefficient (B) varies from a value larger the unity (in high silicon content alloys), to a value smaller than unity (in high germanium content alloys). We report results for a and B for this alloy system. The electron results are based on a multivalley nonparabolic band structure. The hole results are based on a six-band k.p model for low energies coupled to an eight0band model for high energies. We find that for the alloy Si_0.4Ge_0.6, a~B. Alloy scattering is found to play an important role in determining the impact ionization coefficient. For compositions around Si_0.5Ge_0.5, the strong alloy scattering is found to suppress the impact ionization coefficient.

Diverse fate of ubiquitin chain moieties: The proximal is degraded with the target, and the distal protects the proximal from removal and recycles

Sun, Hao,Mali, Sachitanand M.,Singh, Sumeet K.,Meledin, Roman,Brik, Ashraf,Kwon, Yong Tae,Kravtsova-Ivantsiv, Yelena,Bercovich, Beatrice,Ciechanover, Aaron National Academy of Sciences 2019 Proceedings of the National Academy of Sciences Vol.116 No.16

<P><B>Significance</B></P><P>The canonical targeting signal for degrading proteins by the ubiquitin (Ub) system—a chain composed of multiple Ub moieties—has remained a mystery. The structure of the proteasome, the enzyme that recognizes the signal and degrades the target substrate cannot explain why such a long chain is needed. To better understand this problem, we synthesized α-globin to which chains with different number of Ubs were attached. In long adducts, the proximal Ub remains on the substrate, likely securing its attachment to the proteasome, and is degraded with it. The distal Ub protects the proximal from removal by deubiquitinating enzymes and is then removed and recycled. In short adducts, the Ub moieties are rapidly removed, and the substrate remains stable.</P><P>One of the enigmas in the ubiquitin (Ub) field is the requirement for a poly-Ub chain as a proteasomal targeting signal. The canonical chain appears to be longer than the distance between the two Ub-binding proteasomal receptors. Furthermore, genetic manipulation has shown that one receptor subunit is sufficient, which suggests that a single Ub can serve as a degradation signal. To shed light on this mystery, we chemically synthesized tetra-Ub, di-Ub (K<SUP>48</SUP>-based), and mono-Ub adducts of HA-α-globin, where the distal or proximal Ub moieties were tagged differentially with either Myc or Flag. When incubated in a crude cell extract, the distal Ub moiety in the tetra-Ub adduct was mostly removed by deubiquitinating enzymes (DUBs) and reconjugated to other substrates in the extract. In contrast, the proximal moiety was most likely degraded with the substrate. The efficacy of degradation was proportionate to the chain length; while tetra-Ub globin was an efficient substrate, with mono-Ub globin, we observed rapid removal of the Ub moiety with almost no degradation of the free globin. Taken together, these findings suggest that the proximal moieties are necessary for securing the association of the substrate with the proteasome along the proteolytic process, whereas the distal moieties are important in protecting the proximal moieties from premature deubiquitination. Interestingly, when the same experiment was carried out using purified 26S proteasome, mono- and tetra-Ub globin were similarly degraded, highlighting the roles of the entire repertoire of cellular DUBs in regulating the degradation of proteasomal substrates.</P>