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Solar flares and geomagnetic storms of September 2017: Their impacts on the TEC over 75°E longitude sector
(Elsevier Ltd, 2021) Monti Chakraborty; A.K. Singh; S.S. Rao
This study investigates the ionospheric Total Electron Content (TEC) responses over 75°E longitude to the solar flares and geomagnetic storms of September 6–9, 2017. The results of this study provide the impacts of solely solar flares on the ionosphere and such impact when the effects of solar flares and geomagnetic storm are combined. On September 6, two X class solar flares, namely X2.2 at 0857 UT and X9.3 at 1153 UT, were recorded with quiet geomagnetic conditions. The EUV/X-ray intensity of X9.3 flare was significantly greater than that of X2.2 flare, and the recovery phase of both the flares was slower than their respective impulsive phase. The slower recovery rate in EUV/X-ray intensity is reflected as a delayed TEC response. A nearly 8% higher crest to trough TEC change on flare day than the pre-flare day suggests an enhanced level of the equatorial electrojet. The overall weak TEC response to X9.3 solar flare is attributed to solar zenith angle dependency and shifting of solar flare location from disk center to west limb. The solar flares on September 7–8 were co-occurred with geomagnetic storms and observed large increments in TEC are additionally induced by prompt penetration electric field and the enhanced level of thermospheric compositional changes. On September 9, an increase in TEC is observed during M class solar flares under effect of solar flares and disturbed dynamo electric field. © 2021 COSPAR
Detection of 238U ions using a Triafol plastic track detector
(1988) R.K. Jain; A.K. Singh; S. Mukherjee; J. Rama Rao; S.K. Bose
Triafol plastic track detectors have been exposed to 238U ions of energy 17.17 MeV u−1 at UNILAC, GSI, Darmstadt. The bulk etch rate VG, the track etch rate VT and the sensitivity of the track detector VT/VG are measured for different etchant temperatures and ion energies. The various activation energies used in fitting the Arrhenius equations are also calculated. The maximum etched track lengths of the 238 U ions have been experimentally measured. Surface etching and overetching corrections have been applied to the observed track lengths in order to obtain the true track lengths which have been reported for different etching times and incident-ion energies. These results have been compared with the theoretical energy range calculations; they are found to conform to them reasonably well. © 1988 IOP Publishing Ltd.
Natural convection in vertical concentric annuli under a radial magnetic field
(Elsevier Science Ltd, 1997) S.K. Singh; B.K. Jha; A.K. Singh
Exact solutions for fully developed natural convection in open-ended vertical concentric annuli under a radial magnetic field are presented. Expressions for velocity field, temperature field, mass flow rate and skin-friction are given, under more general thermal boundary conditions. It is observed that both velocity as well as temperature of the fluid is more in case of isothermal condition compared with constant heat flux case when gap between cylinders is less or equal to radius of inner cylinder while reverse phenomena occur when the gap between cylinders is greater than radius of inner cylinder.
Lack of effect of microtubule poisons on the 93D or 93D-like heat shock puffs in Drosophila
(1984) A.K. Singh; S.C. Lakhotia
[No abstract available]
Inheritance study in tomato (Solanum lycopersicum) for Tomato leaf curl virus (ToLCV) resistance
(Indian Council of Agricultural Research, 2015) R.K. Singh; N. Rai; P. Kumar; A.K. Singh
A breeding programme was developed from an initial S. lycopersicum × S. lycopersicum (H 88-78-1) cross. The objective of this study was to determine the inheritance of resistant to leaf curl virus and yielding capacity in four crosses made within and between gene pools (TLBR 3 × H 88-78-1, PKM 1 × H 88-78-1, FLA 7421 × H 88-78-1 and Vaibhaw × H 88-78-1) using generation means analysis with five generations (P1, P2, F1, F2and F3) of each population under two environment (field and glasshouse). Results showed that the character of plants and fruits morphology was fit on 1:2:1 (P1: intermediate: P2) and ToLCV (PDI) value was fit on 3:1 (resistant: susceptible) Mendalian ratio in each four F2 populations. In the present study, it was concluded that the generation mean analysis showed monogenic and partial recessiveness and incomplete penetrance. Each population displayed the additive and dominant gene action according to their heritability for using characters. The partial resistance derived from H 88-78-1 will be useful in homozygosis or may be combined with other resistance genes from other sources and can be grown in any climate challenging area.
Preparation of high-Tc superconducting thin films of Tl-Ca-Ba-Cu-O by the chemical spray pyrolysis technique
(1992) K.K. Verma; A.K. Sexena; A.K. Singh; R.S. Tiwari; O.N. Srivastava
Thin films of the Tl-Ca-Ba-Cu-O system have been prepared on MgO and YSZ single-crystal substrates by a simple chemical process (the spray pyrolysis technique). Since Tl is toxic, the Tl-Ca-Ba-Cu-O films were prepared by a two step process. Firstly, precursor (Ca-Ba-Cu-O) films were prepared followed by diffusion of Tl derived by vaporizing Tl2O3 in a closed system under oxygen flow. A new feature found in the present investigation is that the Tc (R=0) of the Tl-Ca-Ba-Cu-O films has been found to depend upon the microstructural characteristics of the precursor films which can be varied by annealing these films. The Tc (R=0) of the Tl-Ca-Ba-Cu-O HTSCs films prepared from the annealed precursor films has been found to be higher than in the films prepared from the as-deposited precursor films. As, for example, in the case of a film on a MgO substrate, the Tc (R=0) has been enhanced from approximately 90 K to approximately 98 K. The highest T c obtained by the authors for the films synthesized from the annealed precursor films on YSZ substrates corresponds to approximately 103 K. The XRD reveals the biphasic (2223/2122) nature of the films. The microstructural characteristics of the films as monitored by SEM reveals the partially oriented nature of the Tl-Ca-Ba-Cu-O film.
Magnetospheric electron temperatures inferred from whistler observations at low latitudes
(2008) Krishna K. Singh; A.K. Singh; M. Altaf; M.M. Ahmad; B.L. Koul; Lalmani; R.P. Singh; Jaipal Singh; Balraj Kumar
Whistler observations during night times made at low latitude Indian ground stations Jammu (geomag.lat.22° 26'N; L= 1.17), Nainital(geomag.lat., 19° 1' N; L= 1.16) and Varanasi (geomag.lat., 14°55'N; L = 1.11) are used to deduced electron temperatures in the vicinity of the magnetospheric equator. The accurate curve fitting and parameter estimation technique are used to compute nose frequency and equatorial electron densities from the dispersion measurements of short whistlers recorded at Jammu, Nainital and Varanasi. These computed parameters are further used to estimate the magnetospheric electron temperatures from the dispersion analysis of short whistlers observed at low latitudes which are in good agreement with the results reported by other workers. © 2008 IACS.
Supplementation of corn seed with regular diet modulates immune function and antioxidant status in Capra hircus
(Blackwell Publishing Ltd, 2017) A.K. Singh; C. Haldar
Melatonin modulates the functional activation of antioxidative enzymes to maintain the oxidant–antioxidant balance in the physiological system. Melatonin administration via subcutaneous injection increases endogenous melatonin concentration that has been used to modulate the immune function in rodents and reproductive activity in small ruminant like goats. However, to date, no report exist which could suggest the effect of corn seed supplementation on the endogenous melatonin concentration and its impact on cellular-immune function and antioxidative enzymes activity in any small ruminant like goats. Therefore, in this study, Zea mays (corn seeds), as source of melatonin, were supplemented with regular diet to explore its impact on endogenous melatonin concentration in goat, Capra hircus. Zea mays supplementation with regular diet for 40 days significantly elevated the endogenous melatonin concentration, proliferative response of peripheral blood mononuclear cells and antioxidative enzymes activity along with total antioxidant capacity of the plasma. An increase in circulatory IL-2 and IL-6 level along with declined TNF-α, malondialdehyde and nitric oxide was noted with elevated endogenous melatonin concentration. In conclusion, it might be suggested that corn seed could be used as supplement to modulate endogenous melatonin concentration that may improve cellular-immune function and antioxidant status. The corn seed might also be included as nutraceutical in regular diet to maintain immune-antioxidant homoeostasis in other species. Journal of Animal Physiology and Animal Nutrition © 2017 Blackwell Verlag GmbH
Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low-latitude Indian sector
(Blackwell Publishing Ltd, 2012) Ajeet K. Maurya; Rajesh Singh; B. Veenadhari; Sushil Kumar; M.B. Cohen; R. Selvakumaran; P. Pant; A.K. Singh; D. Siingh; U.S. Inan
A total of 19,308 tweeks recorded during April 2007 to March 2008, at Allahabad, a low-latitude station in the Indian sector, has been used to study seasonal occurrence which shows maximum tweek occurrence of about 63% during summer season and about 19% and 18% occurrences during equinox and winter seasons. Maximum occurrence of tweeks during summer season is consistent with the larger number of lightnings detected by World Wide Lightning Location Network in the Indian and Asia Oceania regions during summer as compared to that during equinox and winter. Seasonally, tweek (ionospheric) reflection height in the premidnight (18:00-00:00 LT) during winter is less as compared to that during equinox and summer. Annual (seasonal average) variation of the mean ionospheric reflection height shows a gradual increase in the reflection height from about 19:30 to 04:30 LT. The annual average of postmidnight (00:00-06:00 LT) reflection height is about 5 km higher as compared to that in the premidnight. Our initial results on the variability in the ionospheric reflection height under pure nighttime propagation (21:00-03:00 LT) on magnetically quiet days show a day-to-day variability of up to 8 km. Theoretically calculated attenuation of the Earth-ionosphere waveguide for first six tweek modes in the early and late night periods (21:00-00:00 LT; 00:00-03:00 LT) is less compared to that in the dusk (18:00-21:00 LT) period. The higher attenuation in the dusk period and most of the tweeks in the dawn period traveling partially under daytime conditions explain the lower occurrence of tweeks in these periods. Copyright 2012 by the American Geophysical Union.
Variability, character association and path coefficient analysis of green pod yield and its related traits in pea (Pisum sativum L.)
(Agricultural Research Communication Centre, 2017) Keshav K. Gautam; M.M. Syamal; A.K. Singh; Nakul Gupta
Genetic variability, character association and path coefficient studies were carried out for yield and yield contributing characters for twenty-four diverse genotype of pea. The results revealed a wide range of phenotypic variation, along with high heritability in pea. Highest pod yield per plant was recorded in VRP-229 followed by VRP-372 and VRP-305. The characters namely, plant height and weight of seeds per pod showed high magnitude, while number of pods per plant, number of branches per plant and pod yield per plant showed moderate magnitude for phenotypic and genotypic coefficient of variation. The heritability and genetic advance were high for days to first pod initiation, plant height and pod yield per plant indicating its additive gene action for their expression. Character association studies revealed that pod yield per plant exhibit positive and highly significant correlation with number of pods per plant, number of branches per plant and days to fifty percent flowering. The path coefficient studies also revealed that maximum positive direct effect was observed through number of pods per plant followed by days to first flowering, single pod weight and pod length towards yield indicated that these characters may be considered as the most reliable selection indices while making selection for high yielding genotypes. © 2017, Agricultural Research Communication Centre. All rights reserved.

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