Singhal R.K.,University of Rajasthan |
Kumar S.,khadia University |
Kumari P.,University of Rajasthan |
Xing Y.T.,Brazilian Center for Research in Physics (CBPF) |
Saitovitch E.,Brazilian Center for Research in Physics (CBPF)
Applied Physics Letters | Year: 2011
In this work, we demonstrate that room temperature ferromagnetism can be induced in pristine anatase TiO2 paramagnetic bulk powder through extended hydrogenation. Defect complexes, Ti3+ - VO (Ti3+ ions accompanied by oxygen vacancies) are clearly identified in hydrogenated TiO2 by combining x-ray diffraction and photoemission spectroscopy. The observed ferromagnetic ordering is reversible that can be switched between "on" and "off" by inducing or removing, respectively, these defect complex. We convincingly elucidate that the factors (i) Ti 3d-O 2p hybridization (iii) F+ centers (the electrons in singly occupied oxygen vacancies), and (iii) oxygen vacancy assisted fragmentation of grains, compositely contribute to the ferromagnetic ordering. © 2011 American Institute of Physics.
Vyas B.M.,khadia University
International Journal of Remote Sensing | Year: 2013
This paper focuses on the long-term declining change in total ozone column (TOC) derived from satellite measurements over a 25 year period over two neighbouring tropical Asian sites, Karachi, and Mt Abu. A strong declining trend was observed in TOC at both sites, with a significance level of over 95% and a higher magnitude of 4 to 10 DU per decade in September to December and a weak statistical significance level of below 85% and a lower magnitude of 2 to 4 DU per decade in pre-monsoon months. However, during the monsoon months, a small declining trend of about 1 DU per decade was observed, but this variation is statistically insignificant. Further, the long-term changes in TOC exhibit seasonal dependence with a more negative change of 10 DU per decade in winter over Karachi and 7 DU per decade over Mt Abu. The consequence of such a net long-term declining change in TOC as high as 10 DU per decade is expected to have serious environmental implications due to an overall increase in ground-level solar UV radiation of 18% over the normal values in the tropics. In order to identify some plausible causes of this depletion trend in ozone concentration with stratospheric temperature and solar activity, it is clear that there is a strong relationship between the seasonal dependence of the long-term declining trend of TOC on air temperature at 10 mb or stratospheric cooling. At the same time, there is a less significant long-term variation in TOC due to altered solar activity levels. © 2013 Copyright Taylor and Francis Group, LLC.
Vyas B.M.,khadia University |
Dayanandan B.,The University of Nizwa
Indian Journal of Radio and Space Physics | Year: 2011
The paper presents variation of percentage occurrences of nighttime VHF ionospheric scintillation characteristics in amplitude of radio beacon signals of 244/250 MHz transmitted from Fleet Satellite (positioned at 73°E longitude) received over Udaipur (24.6°N, 73.7°E, dip angle 35°) during different levels of solar activity from March 1986 to April 2000. These long time observations of VHF scintillations phenomenon, spanning a solar cycle (1986 to 2000), which covers low, mid as well as high solar activity period, have shown nighttime temporal hourly, seasonal and solar cycle variations in scintillations occurrences. The percentage occurrences of nighttime VHF radio wave scintillations have been observed with maximum percentage occurrences mostly during the equinoxes months, less during winter and the least during summer months in different phases of solar cycle. The average monthly variations of percentage occurrences of VHF ionospheric scintillations activities have been seen to be enhanced during high solar activity year and reduced during low solar activity year. The peculiar feature of discrete or patchy nature of nighttime VHF amplitude scintillations, specifically over Appleton anomaly region, has also been discussed in the light of seasonal and solar activity dependence of scintillations occurrences and their patch duration. The present observations have been compared with the earlier results reported by researchers at Indian stations specifically over similar Appleton anomaly zone and almost similar behaviour of ionospheric scintillations occurrence has been found. An attempt has been made to interpret the present findings on the basis of similarities observed between seasonal solar activity dependence of scintillations events in the present work with the earlier reported statistical observations of seasonal solar activity dependence of maximum electron density of F- region (NmF2), occurrence, and duration of range and frequency type of ESF. Furthermore, the present finding of ionospheric scintillations events have also been linked with the coincidence of numerous precursors of equatorial ionospheric parameters like rising of F-region height due to abrupt increase of upward vertical drift resulting in enhancement in eastward electric field as well as eastward drift after the sunset time over equator with experimentally observed by other researchers. The combined effect of equatorial low ionospheric irregularities phenomena such as development of equatorial ionization anomaly strength over off side of equatorial region is also discussed in view of active precursors to produce the scintillations occurrence in patchy nature away from the equatorial side from the reported studies.
Shekhawat M.S.,khadia University |
Prabhulingaiah G.,Wharton Overseas F.Z.E
Journal of the Geological Society of India | Year: 2010
Two large, chemically similar, SMS grade limestone deposits occur in Sanu area of Jaisalmer and Gotan area of Nagaur, Rajasthan. The Sanu deposit belongs to Khuiala Formation of Tertiary sequence of lower Eocene age, while Gotan deposit belongs to Bilara Group of Marwar Supergroup of late Neoproterozoic to early Cambrian. These deposits are being developed and utilised as flux in the steel plants of India. The Sanu limestone of Jaisalmer is more suitable compared to Gotan and other limestone deposits of the country due to its superior and favourable physical properties. Mineralogicaliy, it consists of fine-grained, sub-rounded to rounded grains of calcite mainly replacing tests of the larger foraminifera. While, the Gotan limestone is composed of fine to coarse-grained, angular to sub-rounded grains of calcite. In Sanu area, about 54% of the limestone produced is being generated as -30 mm grit during the process of sizing for SMS grade. This lower size of limestone is suitable for making cement but due to non-avaibility of rail transport facility from Sanu to Jaisalmer for a distance of about 60 km, it remains unutilised as mineral reject. © GEOL. SOC. INDIA.
Chauhan N.P.S.,khadia University |
Ameta R.,University of Kota |
Ameta R.,HASETRI |
Ameta S.C.,khadia University
Indian Journal of Chemical Technology | Year: 2011
Emeraldine base (EB) form of polyaniline (PANI) powder is prepared by chemical oxidative polymerization using different acidic media (HCl or CF3COOH) at different temperatures (-15°C to + 5°C). The chemical structure, thermal characterization and conducting behaviour are studied by means of Fourier transform infra-red (FTIR) spectroscopy, differential scanning calorimetery (DSC) and two-probe conductivity method. These polyanilines are soluble in N-methyl-2- pyrrolidone, dimethyl sulfoxide (DMSO) and dimethylpropylene urea (DMPU). The softening temperatures of different EB range from 87.8-116.4°C, which is believed to be an indication of cross-linking. Conductivity of emeraldine base of PANI is around (0.8-1.5) × 10-6 S/cm and energy band gap is approximately 0.5 eV, and no detectable crystallinity is observed. Wide-angle XRD technique indicates that PANI- EB base is amorphous in nature.