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FIRST-PRINCIPLE STUDY ON STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF BINARY RARE EARTH INTERMETALLIC COMPOUNDS: GdCu AND GdZn
(World Scientific, 2012) R.P. Singh; R.K. Singh; Shalu; M. Rajagopalan
First principle study on structural, elastic and electronic properties of binary copper and zinc based rare earth intermetallics have been carried out using the full-potential augmented plane waves plus local orbital (APW+ lo) within density functional theory (DFT). Results on elastic properties are obtained using generalized gradient approximation (GGA) for exchange correlation potentials. The equilibrium lattice parameter, bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameters have been calculated. From electronic calculations, it has been found that electronic conduction in copper and zinc based rare earth intermetallics is mainly attributed to 3d-orbital electrons of Cu and Zn. © 2012 Imperial College Press.
Band structure and shape coexistence in 56135Ba79
(American Physical Society, 2010) Suresh Kumar; A.K. Jain; Alpana Goel; S.S. Malik; R. Palit; H.C. Jain; I. Mazumdar; P.K. Joshi; Z. Naik; A. Dhal; T. Trivedi; I. Mehrotra; S. Appannababu; L. Chaturvedi; V. Kumar; R. Kumar; D. Negi; R.P. Singh; S. Muralithar; R.K. Bhowmik; S.C. Pancholi
Excited states of 56135Ba79 at high spins are studied using the reaction Te130(Be9,4n)56135Ba79 at 42.5-MeV beam energy. The earlier known level scheme is extended up to 6.4-MeV excitation energy and (37/2) spin with the addition of several transitions. We have performed polarization asymmetry measurements for some of the strong transitions by using a Clover detector to assign the parity. A comparison of experimental data with the results of tilted axis cranking calculations based on various configurations indicates the coexistence of multiple minima in the triaxial deformation (γ), whereas axial symmetric deformation (ε2) remains constant around 0.09. © 2010 The American Physical Society.
SOME STUDIES ON WO//3 THIN FILMS.
(1986) R.P. Singh; S.L. Agrawal; Y.D. Singh
Surface morphology of as-deposited and annealed WO//3 films have been studied using Scanning Electron Microscopy (SEM). Optical absorption studies of as-deposited and annealed films reveal that the band gap decreases upon annealing. Electrical measurements show that the film resistivity is of the order of 10**4 ohms cm. Relevant semiconductor parameters in contact with acidic H//2O electrolyte have been determined and the potentiality of WO//3 in photoelectrolysis solar cell has been demonstrated.
High spin spectroscopy and shears mechanism in In107
(American Physical Society, 2010) D. Negi; T. Trivedi; A. Dhal; S. Kumar; V. Kumar; S. Roy; M.K. Raju; S. Appannababu; G. Mohanto; J. Kaur; R.K. Sinha; R. Kumar; R.P. Singh; S. Muralithar; A.K. Bhati; S.C. Pancholi; R.K. Bhowmik
High spin states of In107 have been investigated using the reaction Mo94(O16,p2n)In107 at a beam energy of 70 MeV. A total of 62 new γ transitions have been placed in the level scheme and several ΔI=1 sequences and one ΔI=2 sequence have been found. Lifetime measurements using the Doppler-shift attenuation method (DSAM) have been carried out for band states of ΔI=1 and ΔI=2. A decreasing trend of B(M1) strengths with increasing spin deduced for the ΔI=1 band indicates the presence of a shears mechanism. The experimental data for this band are compared with the tilted axis cranking (TAC) calculations. The ΔI=2 band has been found to be a deformed band with β2~0.2. © 2010 The American Physical Society.
Leaf tip necrosis: A phenotypic marker associated with resistance to spot blotch disease in wheat
(Crop Science Society of America, 2004) A.K. Joshi; R. Chand; S. Kumar; R.P. Singh
Spot blotch, caused by Bipolaris sorokiniana (Sacc.) Shoem. syn. Drechslera sorokiniana (Sacc.) Subrm and Jain (syn. Helminthosporium sativum, teleomorph Cochliobolus sativus), is an important disease of wheat (Triticum aestivum L.) in warmer and humid regions of the world. To date, no morphological marker is known to be associated with resistance to this disease. The purpose of this study was to find out the association of leaf tip necrosis (Ltn) with resistance to spot blotch disease. A total of 1407 spring wheat genotypes that originated from the Indian and CIMMYT wheat breeding programs were evaluated for Ltn and resistance to spot blotch for three seasons (1994-1995, 1995-1996, and 1996-1997) under field conditions. Disease severity was recorded at six growth stages under artificially created epidemics. About 75% of the genotypes showing Ltn (Ltn+) were resistant or moderately resistant, whereas 82% not showing it (Ltn-) were moderately susceptible or susceptible. Mean spot blotch rating of the Ltn+ genotypes was significantly lower than the Ltn- genotypes at all growth stages and the genotype x environment interaction was nonsignificant. To confirm the association of Ltn with resistance, individual F2-derived F3, F4, F5, and F6 progenies from the cross of the 'HUW234' near-isogenic pair for Ltn were evaluated for spot blotch severity. In each generation, the Ltn+ homozygons progenies had significantly less disease than those homozygous Ltn-. These results confirm that leaf tip necrosis is associated with moderate resistance to spot blotch and can be used as a morphological marker to facilitate selection for resistance.
Unified theory of whistler mode instability in the presence of a parallel electric field
(1984) Indra Mohan Lal Das; R.P. Singh
The propagation characteristics of right-hand circularly polarized whistler mode waves propagating parallel to the external magnetic field in an anisotropic plasma have been reformulated including the effect of a parallel electric field. Analytical expressions for the real frequency and growth rate have been obtained for the full range of the parameters ß (the ratio of particle pressure to magnetic pressure of the hot particles), A (temperature anisotropy) and P (= ßA(A + 1)2) without any restriction on the magnitude of the imaginary part of the wave frequency. The effect of cold plasma injection on the marginal instability has also been studied. Possible application of the present theory to the atmospheres of Earth and Jupiter has been discussed. © 1984, Cambridge University Press. All rights reserved.
Some features of plasma bubble induced scintillations during the AICPITS campaigns of 1991
(2007) P.N. Vijayakumar; T.R. Tyagi; Lakha Singh; H. Chandra; G.D. Vyas; D.R.K. Rao; B.M. Pathan; A. Iype; B. Ramsekaran; A. Naidu; S.M. Sadique; K.N. Iyer; K.N. Pathak; A.K. Gwal; Sushil Kumar; R.P. Singh; U.P. Singh; Birbal Singh; Pawan Kumar; G.N. Navneeth; P.V.S. Koparkar; P.V.S. Ramarao; P.T. Jaychandran; P. Sriram; R. Sethuraman; A. Dasgupta; K. Basu; R.G. Rastogi
The VHF scintillations were recorded at a chain of low-latitude stations in India as part of the All India Coordinated Programme of Ionospheric and Thermospheric Studies (AICPITS), using the 244 MHz radio beacon from the geo-stationary satellite FLEETSAT which was located at 73° E longitude. Data collected during the second campaign of September-October 1991 and analyzed jointly by the participating investigators are presented. The onset times of scintillation at pairs of stations at similar latitude but different longitudes can be used to estimate the eastward drift of the scintillation patches and its E-W extent. The maximum monthly mean occurrence for September 1991 is about 35% at Trivandrum and Tiruchendur, the stations close to dip equator. Occurrence is maximum for stations Annamalainagar, Payyanur and Anantpur (50 %), located slightly north of the dip equator. It decreases further north to 30 % at Nuzvid, Bombay, 20 % near anomaly crest region, 10 % at Agra and 8 % at Delhi, which is the northern most edge of the present observations. The occurrence frequency is slightly less than that observed during the campaign of March 1991. For the sake of completeness some very interesting features and dynamical characteristics of plasma bubble induced scintillations are included here based on digital records of scintillations made at Delhi during the two equinox data campaigns in March-April 1991 and September-October 1991.
Nivetin, a neoflavonoid from Echinops niveus
(1990) R.P. Singh; V.B. Pandey
From the whole plant of Echinops niveus the previously undescribed neoflavonoid, nivetin has been isolated and its structure established by spectroscopic means. © 1990.
On the association of lightning activity and projected change in climate over the Indian sub-continent
(Elsevier Ltd, 2017) Upal Saha; Devendraa Siingh; A.K. Kamra; Elissavet Galanaki; Animesh Maitra; R.P. Singh; A.K. Singh; Swastika Chakraborty
The association of lightning activity with the long-term as well as seasonal spatio-temporal distribution of convective available potential energy (CAPE), surface convective precipitation, vegetation cover and anthropogenic aerosol loading over the Indian sub-continent has been studied for the period 2000–2014. The north-east to north-west arc including the foothills of the Himalayas is the primary seats of lightning occurrences. The correlations of lightning activity with each of aerosol loading, vegetation cover, convective instability and convective precipitation helps us in understanding the definite entity that is responsible for changing the lightning activity in different parts of this tropical region. Lightning flash rate (LFR) has significant positive correlations (r ~ 0.5–0.7) with AOD, CAPE and surface convective precipitation but significant negative correlation (r ~− 0.4) with Normalized Difference Vegetation Index (NDVI). Using global circulation models from the Climate Model Intercomparison Project Phase 5 (CMIP5), time-series of observed and projected upper tropospheric water vapor, surface convective precipitation and aerosol optical depth (AOD) from the historical simulations (1996–2005) and RCP8.5 emission scenario (2036–2045) are analyzed over the Indian region that are vulnerable to climate change in terms of occurrence of convective events and associated hazardous lightning phenomena. This study indicates that upper tropospheric water vapor (300 hPa) has a significant linkage with the lightning occurrences associated with convective activities and strong updraft. During the mid- 21st century, AOD, surface convective precipitation and specific humidity are projected to increase by 1.42%, 2.01% and 1.40%, respectively which may result in regional changes in lightning activity over the Indian sub-continent. © 2016 Elsevier B.V.
γ -vibration in 198 Hg
(Springer New York LLC, 2019) S. Chakraborty; H.P. Sharma; S.S. Tiwary; C. Majumder; P. Banerjee; S. Ganguly; S. Muralithar; R.P. Singh; G.H. Bhat; J.A. Sheikh; R. Palit
Low lying states of 198 Hg have been investigated via 197 Au( 7 Li,α2nγ) reaction at E beam = 33 , 38 MeV and the members of the γ-vibrational band have been identified. Results are compared with the systematic of this mass region and found in agreement. The observed band structures have been interpreted using the theoretical framework of the microscopic triaxial projected shell model (TPSM) approach and it is shown that TPSM results are in fair agreement with the observed energies. © 2019, Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.

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