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Production of nematode free plantlets in Polianthes tuberosa using in vitro culture techniques
Kanchan B. M. Singh,Jayanthi Madhavan,Raghunath Sadhukhan,Shivani Chandra,Uma Rao,Pranab Kumar Mandal 한국원예학회 2020 Horticulture, Environment, and Biotechnology Vol.61 No.5
Tuberose ( Polianthes tuberosa ) cultivation is tremendously aff ected due to Meloidogyne incognita infection. Histologicalstudy of in vitro nematode infected tuberose roots showed that the root infection initiated within 2 days post inoculation(DPI) and root gall formation occurred at 6 DPI indicating established infection on the roots. The life cycle of M. incognitain tuberose roots completed within 45 DPI evident by the formation of large number of eggs. Our study established in vitromethods like shoot tip culture and callus mediated regeneration of tubers collected from nematode infection fi elds to obtaincompletely nematode free plantlets. Tubers of diff erent varieties produced multiple shoot bud on Murashige and Skoog (MS)media containing 4 mg L −1 6-benzylaminopurine (BAP) and 0.1 mg L −1 α-naphthaleneacetic acid (NAA). Maximum numbersof plantlets were obtained for Calcutta Single (14.4 ± 2.0 per plant). Embryogenic callus was induced on MS medium supplementedwith altered concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), NAA and BAP from leaf, fl ower, root andtuber explant. The maximum callus induction was obtained on MS containing 1 mg L −1 2,4-D, 1 mg L −1 NAA and 0.5 mg L −1BAP (100%) and 1 mg L −1 2,4-D and 2.25 mg L −1 BAP (96.7%). Regeneration of tuber callus was achieved on MS with0.5 mg L −1 Kinetin (KIN) within 3 weeks. Plantlets were rooted on ½ MS with 0.5 mg L −1 Indole-3-butyric acid for 25 days. The in vitro regeneration protocol developed can thus be used for producing disease free plantlets for mass propagation.
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>
M. Mohana Rao,M. Joy Thomas,B. P. Singh 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.3
The transient fields generated during switching operations in a Gas Insulated Substation (GIS) are associated with high frequency components in the order of few tens of ㎒. These transient fields leak into the external environment of the gas-insulated equipment and can interfere with the nearby electronics. Measurements of the transient fields are thus required to characterise the interference caused by switching phenomena in such substations. In view of the above, E-field emission measurement during a switching operation bas been carried out for a 245 ㎸ GIS model, using a resonant dipole antenna and D-dot sensor. The characteristics of the E-fields i.e., frequency spectra and their levels have been analysed and are reported in the paper. Suitability of the measurements has been confirmed by comparing frequency spectra of the measured and computed transient fields.
Rao, M. Mohana,Thomas, M. Joy,Singh, B.P. The Korean Institute of Electrical Engineers 2007 Journal of Electrical Engineering & Technology Vol.2 No.3
The transient fields generated during switching operations in a Gas Insulated Substation (GIS) are associated with high frequency components in the order of few tens of MHz. These transient fields leak into the external environment of the gas-insulated equipment and can interfere with the nearby electronics. Measurements of the transient fields are thus required to characterise the interference caused by switching phenomena in such substations. In view of the above, E-field emission measurement during a switching operation has been carried out for a 245 kV GIS model, using a resonant dipole antenna and D-dot sensor. The characteristics of the E-fields i.e., frequency spectra and their levels have been analysed and are reported in the paper. Suitability of the measurements has been confirmed by comparing frequency spectra of the measured and computed transient fields.
Rao, M.Mohana,Rao, T. Prasad,Ram, S.S. Tulasi,Singh, B.P. The Korean Institute of Electrical Engineers 2008 Journal of Electrical Engineering & Technology Vol.3 No.1
In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) are generated due to switching operations and ground faults. These fast transients are associated with high frequency components of the order of a few hundreds of MHz. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420kV graded bushing for high frequency pulses of rise time 1 to 50ns, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with different equivalent layers has been considered. The effect of different equivalent layers modeling circuits on the non-uniform voltage factor has been analysed. The influence of copper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients.
PL and ESR of Gd3+ in LaMgAl11O19 phosphors
Singh, Vijay,Singh, N.,Pathak, M. S.,Watanabe, S.,Gundu Rao, T. K.,Singh, Pramod K.,Kwon, Young-Wan Springer-Verlag 2018 Journal of materials science Materials in electron Vol.29 No.6
<P>LaMgAl11O19 doped with different concentrations of gadolinium phosphors were synthesized by combustion and characterized using X-Ray diffraction to identify the crystalline phase. Photoluminescence studies on the sample showed emission peaks at 313 and 306 nm with lambda(exi) = 273 nm corresponding to the P-6 (J) -> S-8(7/2) transitions of Gd3+ ions. In phosphors with low dopant concentrations, dominant electron spin resonance lines are observed with g (eff) similar to 1.96, 1.98, 4.2, and 6.0. With increasing concentrations, the spectrum appears to be U-shaped, and main lines are seen at g (eff) similar to 1.98, 2.04, 2.8, 4.1 and 6.2. Distortions in the immediate environment of Gd3+ ions lead to relatively strong crystal fields and the appearance of lines in the low field region of the spectrum.</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, 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>
UV emitting Pb<sup>2+</sup> doped SrZrO<sub>3</sub> phosphors prepared by sol-gel procedure
Singh, N.,Kaur, Sumandeep,Jayasimhadri, M.,Pathak, M.S.,Watanabe, S.,Gundu Rao, T.K.,Lee, Jung-Kul,Singh, Vijay Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.14
<P><B>Abstract</B></P> <P>A series of Pb<SUP>2+</SUP>-doped SrZrO<SUB>3</SUB> phosphors with a varying Pb<SUP>2+</SUP> concentration has been successfully synthesized using the sol-gel method. The structural, morphological, and luminescence properties along with the electron paramagnetic resonance (EPR) properties have been investigated in details. The structural analysis was carried out by recording X-ray diffraction (XRD) patterns, which confirms the pure-phase formation of the synthesized phosphors. The morphological study was performed using a scanning electron microscope (SEM) that showed micron-sized particles with irregular morphologies. The photoluminescence excitation and emission spectra were also recorded. The emission intensity shows the maximum at 360 nm that was pumped at 278 nm for SrZrO<SUB>3</SUB>:Pb<SUP>2+</SUP>. The optimized Pb<SUP>2+</SUP> concentration is 0.015 mol. Investigations of un-doped and Pb<SUP>2+</SUP> doped SrZrO<SUB>3</SUB> phosphor have been carried out using electron paramagnetic resonance (EPR) technique. Pure SrZrO<SUB>3</SUB> exhibits an axially symmetric EPR line with <SUB> g || </SUB> = 1.93 and <SUB> g ⊥ </SUB> = 1.99. These lines are ascribed to Zr<SUP>3+</SUP> ion. Additional lines are not observed in the Pb<SUP>2+</SUP> doped phosphors.</P>