http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
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.3
Thiazolidinediones (TZDs) act as potent activators of the adipose differentiation program in established preadipose cell lines. TZD's have also been investigated in diabetic patients and reported to act as PPAR-${\gamma}$ ligands. In this report, the effects of TZDs on the differentiation pathway of myoblasts have been investigated. C2C12 mouse myoblasts were grown in Dulbecco's Modified Eagles medium for 4-5 days until they reached almost 100% confluency. Post-confluent cells (day 0) were further exposed to adipogenic induction medium along with TZDs for 48 hours. Thereafter, cells were exposed only to TZDs every 48 h until day 10. The control was provided with differentiation medium without any treatment. Alterations in the cells during the differentiation programme were analyzed on the basis of fusion index, oil-red-o staining, adipocyte index, adipocyte stain uptake measurement, immuno-histochemistry and western blotting. Exposure of C2C12 mouse myoblasts to TZDs prevented the expression of myosin heavy chain with parallel increase in the expression of C/EBP-${\alpha}$ and PPAR-${\gamma}$ and acquisition of adipocyte morphology, thus abolishing the formation of multinucleated myotubes. TZDs exert their adipogenic effects only in non-terminally differentiated myoblasts; myotubes were insensitive to the compound. Continuous exposure (at least 4-5 doses) to inducers after the growth arrest was essential to provide a sustained environment to the cells converting to fully matured adipoctyes. The results indicate that TZDs specifically converted the differentiation pathway of myoblasts into that of adipoblasts.
Studies of Radiation-Induced Defects in Li2SiO3:Sm Phosphor Material
Singh, N.,Singh, V.,Watanabe, S.,Gundu Rao, T. K.,Chubaci, J. F.,Cano, N. F.,Pathak, M. S.,Singh, P. K.,Dhoble, S. J. Springer Science + Business Media 2017 Journal of electronic materials Vol.46 No.1
<P>Li2SiO3:Sm was synthesized by the solution combustion method. Powder x-ray diffraction technique was used to find the phase formation. Li2SiO3:Sm exhibits thermoluminescence (TL) peaks at approximately 140 degrees C, 155 degrees C, 190 degrees C, 250 degrees C, and 405 degrees C. Three defect centers contribute to the observed electron spin resonance spectrum from the gamma irradiated phosphor. Center I with principal g-values g(parallel to) = 2.0206 and g(perpendicular to) = 2.0028 is identified as an O-2(-) ion while center II, with an isotropic g-factor 2.0039, is assigned to an F+-type center. Center III is assigned to a Ti3+ center. The Ti3+ center is related to the 250 degrees C TL peak while the O-2(-) ion also correlates with the main TL peak at 250 degrees C. An additional defect center is observed during thermal annealing experiments, and the center (assigned to F+ center) seems to originate from an F center. The F center appears to be associated with the high temperature TL peak in a Li2SiO3: Sm phosphor. The luminescence spectrum reveals the dominant emission peaks at 605 ((4)G(5/2) -> H-6(7/2)) nm under the excitation wavelength of 402 nm.</P>
Singh, N.,Singh, V.,Sivaramaiah, G.,Rao, J.L.,Singh, P.K.,Pathak, M.S.,Dhoble, S.J.,Mohapatra, M. Elsevier [etc.] 2016 Journal of luminescence Vol.178 No.-
<P>Strong blue-green light emitting MgSrAl10O17:Eu2+,Mn2+ phosphor was synthesized by a low temperature initiated, self-propagating and gas producing combustion process in a very short time (< 5 min). Structural characterization of the luminescent material was studied with X-ray diffraction analysis and energy-dispersive X-ray analysis. The absorption spectrum exhibits bands due to Eu2+ and Mn3+ ions. The excitation spectrum shows a peak at 337 nm. Upon excitation at 337 nm, the emission spectrum exhibits an intense band centered at 462 nm due to transitions from the 4f(6)5d(1) to the 4f(7) configuration of the Eu2+ ions, whereas sharp peak at 513 nm attributed to T-4(1) -> (6)A(1) transition of Mn2+ ions. The X-band EPR spectra of MgSrAl10O17:Eu2+,Mn2+ showed the presence of Eu2+ and Mn2+ ions. (C) 2016 Elsevier B.V. All rights reserved.</P>
Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Pathak, M. S.,Jirimali, H. D.,Singh, P. K.,Srivastava, A. K.,Dhoble, S. J.,Mohapatra, M. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.8
<P>Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g approximate to 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.</P>
Singh, A.N.,Gautam, Kirti A.,Dalela, D.,Sankhwar, S.N.,Natu, S.M.,Sankhwar, P.L.,Srivastava, A.N. Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.3
Background: Formation of new blood vessels is necessary for the development and spread of neoplasms more than 1 mm3 in volume, angiogenesis being responsible for formation of new from pre-existing blood vessels. Vascular endothelial growth factor (VEGF) is pivotal and the best studied angiogenic factor in all human cancers. Therefore we designed this study to investigate the role of VEGF-A and VEGF-C in prostate cancer in comparison with BPH controls in a north Indian population. Methods: In this case-control study a total of 100 subjects were included on the basis of confirmed histopathological reports, out of which 50 were prostate cancer patients and the other 50 were BPH patients with PSA levels >2 ng/ml and abnormal digital rectal examination (DRE) findings during September 2009 to August 2011 from the Department of Urology, KGMU, Lucknow, India. Plasma levels of VEGF were determined using quantitative immunoassay (ELISA-enzyme linked immunosorbent assay). Statistical analysis was carried out using SPSS 15.0 version. Results: The mean age of prostate cancer ($67.6{\pm}5.72$) patients was significantly higher (p=0.005) than BPH ($63.6{\pm}7.92$) patients. Expression of VEGF-A was not significantly higher in disease stage C1 than D1 or D2 and A or B (p=0.13) while the level of VEGF-A was significantly higher (p=0.04) in prostate cancer as compared to BPH subjects (PCa=13.0 pg/ml, BPH=6.8 pg/ml). Levels of VEGF-C were similar in both groups (PCa=832.6 pg/ml, BPH=823.7 pg/ml). In ROC curve, the area under curve (AUC) was 0.70 (95%CI: 0.60-0.80) and the cut-off value for which a higher proportion of patients was correctly classified (20%) was 26.0 pg/mL. Conclusion: Although VEGF-A is increased in cancer prostate patients a statistically significant correlation could not be established in this study. VEGF-C was not found to be a useful biomarker.
Singh, Vijay,Shinde, K.N.,Pathak, M.S.,Singh, N.,Dubey, Vikas,Singh, Pramod K.,Jirimali, H.D. Elsevier 2018 OPTIK -STUTTGART- Vol.164 No.-
<P><B>Abstract</B></P> <P>A series of Tb<SUP>3+</SUP>-doped CaLaAl<SUB>3</SUB>O<SUB>7</SUB> phosphors were successfully synthesized via a sol-gel method. The formation of the synthesized phosphors was confirmed using X-ray powder diffraction (XRPD) studies. A scanning electron microscope (SEM) was used to characterize the surface morphology and to investigate the photoluminescence behaviors in detail. Under the excitation of 235 nm, the emission spectrum consists of the characteristic Tb<SUP>3+</SUP> transitions that mainly peak at 543 nm and correspond to the <SUP>5</SUP>D<SUB>4</SUB> → <SUP>7</SUP>F<SUB>5</SUB> transition. The intensity was greatly improved due to the Tb<SUP>3+</SUP> concentration in the present phosphors. The optimum Tb<SUP>3+</SUP>-doping concentration was determined to be 0.05 mol. The chromaticity coordinates of the CaLaAl<SUB>3</SUB>O<SUB>7</SUB>:Tb<SUP>3+</SUP> were fixed to make it tunable for the blue-to-green region. The typical photographs of the CaLaAl<SUB>3</SUB>O<SUB>7</SUB>:Tb<SUP>3+</SUP> under a 254-nm UV light revealed an intense-green powder. The results showed that this kind of phosphor is potentially applicable in terms of UV-excited white LEDs.</P>
UV emission from Gd<sup>3+</sup> ions in LaAl<sub>11</sub>O<sub>18</sub> phosphors
Singh, Vijay,Singh, N.,Pathak, M.S.,Watanabe, S.,Gundu Rao, T.K.,Singh, Pramod K.,Dubey, Vikas Elsevier 2018 Optik Vol.157 No.-
<P><B>Abstract</B></P> <P>Phosphors with the composition La<SUB>1-x</SUB>Gd<SUB>x</SUB>Al<SUB>11</SUB>O<SUB>18</SUB> (x = 0.01–0.10) were synthesized by combustion at a furnace temperature of 500 °C. The formation of the as-prepared combustion products was confirmed by X-ray diffraction analysis. On excitation with 273 nm, an emission band for the Gd<SUP>3+</SUP> ion was observed at 314 nm. This band progressively enhanced with increasing Gd<SUP>3+</SUP> concentration. The phosphor with low concentrations of Gd<SUP>3+</SUP> ions exhibits prominent ESR lines with <I>g</I> <SUB>eff</SUB> ∼ 1.9, 2.0, 4.7, and 5.9. With high dopant concentrations, the spectrum shows features similar to those of a U-spectrum with dominant lines with <I>g</I> <SUB>eff</SUB> ∼ 2.0, 2.9, 4.6, and 6.1. Low field lines arise from distortions in the immediate environment of the Gd<SUP>3+</SUP> ion.</P>