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Detection of the mycotoxin citrinin using silver substrates and Raman spectroscopy
Singh, D.K.,Ganbold, E.O.,Cho, E.M.,Cho, K.H.,Kim, D.,Choo, J.,Kim, S.,Lee, C.M.,Yang, S.I.,Joo, S.W. Elsevier Scientific Pub. Co 2014 Journal of hazardous materials Vol.265 No.-
We detected a trace amount of the mycotoxin citrinin using surface-enhanced Raman scattering (SERS) on silver nanoparticle (Ag NP) surfaces. The SERS substrate on hydrophobic Teflon films was also introduced to observe the citrinin peaks. A broad band at ~1382cm<SUP>-1</SUP>, which was ascribed to the symmetric carboxylate stretching mode, was observed in addition to an antisymmetric carboxylate stretching mode at ~1568cm<SUP>-1</SUP> in the Raman spectra. The spectral feature indicated that citrinin would adsorb on Ag NPs via its carboxylate form. Based on density functional theory (DFT) calculations, vibrational mode analysis was performed to compare the Raman spectra of citrinin. DFT calculations also predicted that a bidentate bridge configuration through O15 and O16 atoms in citrinin would be the most stable on three Ag atoms. After treating with Ag NPs, observation of citrinin peaks was attempted in fungal cells of Penicillium citrinum. This work may provide useful insights into the direct observation of the hazardous citrinin mycotoxin using SERS by understanding its adsorption behaviors on Ag surfaces.
Consequences of electronic excitations in CoFe<sub>1.90</sub>Dy<sub>0.10</sub>O<sub>4</sub>
Kumar, H.,Singh, J.P.,Srivastava, R.C.,Negi, P.,Agrawal, H.M.,Asokan, K.,Won, S.O.,Chae, K.H. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.12
Present work reports the irradiation induced effects in Dy<SUP>3+</SUP> doped cobalt ferrite nanoparticles in the regime of dominant electronic excitation processes induced by 100 MeV O<SUP>7+</SUP> ion irradiation. Irradiation leads to the deterioration of crystalline phase as envisaged by X-ray diffraction. Crystallite size decreases with the increase of irradiation fluence. Disappearance of certain bands in Raman spectra at higher fluence of irradiation confirms the crystalline disorder induced by electronic excitations. Fourier transform infrared spectra show onset of cation migration from tetrahedral site to octahedral site and vice versa. X-ray absorption fine structure measurements depict the preservation of valence state of metal ions after irradiation. These measurements further infer bond breaking process in irradiated materials. Magnetic measurements carried out on these materials indicate slight increase of saturation magnetization at room temperature followed by the decrease of coercive field. Obtained results are discussed on the basis of appropriate mechanism.
Pathak, M.S.,Gopal, N.O.,Singh, N.,Mohapatra, M.,Rao, J.L.,Lee, Jung-Kul,Singh, Vijay Elsevier 2018 Journal of non-crystalline solids Vol.500 No.-
<P><B>Abstract</B></P> <P>Iron doped lithium metasilicate sample was synthesized using a combustion technique and characterized by XRD (X ray diffraction), SEM (scanning electron microscopy), FTIR (Fourier transform infrared spectroscopy), optical, and EPR (electron paramagnetic resonance) analyses. The phase purity of the combustion synthesized products was confirmed by XRD analysis. SEM data suggested the formation of a porous compound by virtue of the entrapment of the gases that evolved during the sample synthesis. FTIR data confirmed the formation of SiO bonds in the system. Optical data confirmed the existence of both divalent and trivalent iron in the system. Characteristic absorption bands in the region 215–270 nm and 535–620 nm were observed due to the presence of Fe<SUP>3+</SUP> in Oh and Td geometry respectively. On the other hand, the presence of bands at 967 and 1442 nm suggested the stabilisation of Fe<SUP>2+</SUP> also in both Oh and Td geometries, respectively. The divalent iron being a non-Kramer ion, could not be observed by EPR. However, strong temperature-dependent EPR signals were observed in the sample owing to Fe<SUP>3+</SUP>. By analyzing the EPR data, super-paramagnetic type of behaviour was observed in the system. Furthermore, the relaxation times along with other EPR spectroscopic parameters were estimated for the system.</P>
On balance of uncertainty in shadowed sets
M. A. Ibrahim,T. O. William-West,A. F. D. Kana,D. Singh 원광대학교 기초자연과학연구소 2020 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.19 No.3
A shadowed set, $S$, facilitates crisp decision-making with a fuzzy set $F$. It is constructed with the aid of different optimization-based principles. Among these principles, the requirement of uncertainty balance guarantees preservation of the uncertainty of $F$ in $S$. In order to gain further insight on uncertainty balance, some essential mathematical properties which characterize uncertainty-balance-based objective function, $J(\alpha)$, are studied. These properties provide theoretical explanation for interpreting and analyzing $J(\alpha)$ and its ensuing optimum partition threshold $\alpha$. Two senses of uncertainty balance are discussed in this paper. Their combined efficiency in enhancing clustering results is illustrated with the aid of synthetic data set used in shadowed $C$-means clustering. Finally a need for five-region shadowed sets, $S_5$, is pointed out. A closed-form formula for determining its optimum thresholds is proposed and exemplified on typical fuzzy set and synthetic dataset.
L-cysteine recognition triggered by Zn<sup>2+</sup> complexation with ligand
Kim, M.J.,Sharma, H.,Singh, N.,Jang, D.O. Elsevier 2013 Inorganic chemistry communications Vol.36 No.-
A new type of benzimidazole-based imine-linked fluorescence chemosensor for Zn<SUP>2+</SUP> was synthesized. Coordination of Zn<SUP>2+</SUP> with the receptor led to enhanced fluorescence while other metals quenched the receptor fluorescence. The resulting complex had a supramolecular assembly with a 1:1 host-guest ratio with variable size. The (1.Zn<SUP>2+</SUP>)<SUB>n</SUB> assembly showed high selectivity towards the complexation of L-cysteine even in the presence of other potentially competitive biologically important anionic species.
Adedeji, Adeyemi O.,Singh, Kamalendra,Kassim, Ademola,Coleman, Christopher M.,Elliott, Ruth,Weiss, Susan R.,Frieman, Matthew B.,Sarafianos, Stefan G. American Society for Microbiology 2014 Antimicrobial Agents and Chemotherapy Vol.58 No.8
<P>We have previously shown that SSYA10-001 blocks severe acute respiratory syndrome coronavirus (SARS-CoV) replication by inhibiting SARS-CoV helicase (nsp13). Here, we show that SSYA10-001 also inhibits replication of two other coronaviruses, mouse hepatitis virus (MHV) and Middle Eastern respiratory syndrome coronavirus (MERS-CoV). A putative binding pocket for SSYA10-001 was identified and shown to be similar in SARS-CoV, MERS-CoV, and MHV helicases. These studies show that it is possible to target multiple coronaviruses through broad-spectrum inhibitors.</P>
Cho, E.-M.,Singh, D.K.,Ganbold, E.-O.,Dembereldorj, U.,Jang, S.-W.,Kim, D.,Choo, J.,Kim, S.,Lee, C.M.,Yang, S.I. SOCIETY FOR APPLIED SPECTROSCOPY 2014 APPLIED SPECTROSCOPY Vol.68 No.3
Surface-enhanced Raman scattering (SERS) of an antifungal reagent, myclobutanil (MCB), was performed on Au and Ag nanoparticles (NPs) to estimate the drug-release behaviors in fungal cells. A density functional theory (DFT) calculation was introduced to predict a favorable binding site of MCB to either the Ag or Au atom. Myclobutanil was presumed to bind more strongly to Au than to Ag in their most stable, optimized geometries of the N4 atom in its 1,2,4-triazole unit binding to the metal atom. Strong intensities were observed in the Ag SERS spectra only at acidic pH values, whereas the most prominent peaks in the Au SERS spectra of MCB matched quite well with those of 1,2,4-triazole regardless of pH conditions. The Raman spectral intensities of the MCB-assembled Ag and Au NPs decreased after treatment with either potato dextrose agar (PDA) or glutathione (GSH). Darkfield microscopy and confocal SERS were performed to analyze the MCB-assembled metal NPs inside Penicillium digitatum fungal cells. The results suggested that MCB was released from the metal NPs in the intracellular GSH in the fungi because we observed only fungal cell peaks.