Browsing by Author "R.K. Gupta"

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A heuristic analysis for an inhomogeneously loaded tape helix used in a practical travelling wave tube
(2001) S. Ghosh; A.K. Sinha; R.K. Gupta; S.N. Joshi; P.K. Jain; B.N. Basu
The analysis of an inhomogeneously loaded helix in the tape model, reported elsewhere, considering the effect of space harmonics as well as the different radial propagation constants over the different structure regions, is quite tedious and rigorous. So, to avoid the rigorous analysis here, a heuristic analysis has been developed by combining the results of the tape model analysis of a helix in free space with those of the sheath helix model analysis of a loaded helix. The results presented here in terms of dispersion characteristics have been compared with those results obtained from a rigorous approach (both for homogeneously and inhomogeneously loaded structures) in the tape helix model. However, the results obtained from this approach agree closely with those of the rigorous approach for a practical situation in which the discrete supports are smoothed out into a single continuous region. The approach is valid for an inhomogeneously loaded helix for optimum conditions of structure parameters, namely, helix pitch angle, helix to barrel gap, support material and inhomogeneity. Moreover, the results predicted by this heuristic approach have also been validated with those experimental results published in the literature and are found to be in good agreement.
AC impedance studies on the molecular semiconductors based on aromatic diamines-iodine charge-transfer complexes
(2004) R.K. Gupta; R.A. Singh
Molecular semiconductors based on charge-transfer complexes of benzidine, o-olidine and N, N′-diphenylbenzidine with iodine having different mole ratios have been prepared and characterized by thermal, spectral and electrical methods. The thermal decomposition behaviour of these materials indicate that they are thermally stable up to 130°C and then proceed to stoichiometric weight loss corresponding to iodine and aromatic diamines respectively. The electrical conductivity has its highest value for N, N′-diphenylbenzidine- iodine complexes and lowest for benzidine-iodine complexes which may be due to more extensive conjugation of radical cation in the former than in the later. Impedance studies show (RC(RC), R (RC) and (RC) equivalent circuit for benzidine, o-tolidine and N, N′-diphenylbenzidine-iodine complexes respectively. The electrical data have been discussed in light of dynamic bond percolation model in which the distribution, density and availability of potential hopping sites change as a result of electronic and structural changes in the material.
Assessment of lichens as bioindicator of ambient air heavy metal pollution in far-west Nepal
(Triveni Enterprises, 2023) P. Nag; H. Rai; D.K. Upreti; R.K. Gupta
The aim of this research was to identify a suitable lichen species as a bio-indicatorfor heavy metals in the Himalayan habitats. Methodology: The study was conducted in a sacred grove located in Western Nepal. The grove was situated alongside the busy Mahakali National highway. Lichen samples were collected from different areas of the grove, ranging from the edge adjacent to the highway to the center. Standard protocols were employed to identify the collected lichen species. The heavy metal content in the samples were analyzed by subjecting them to acid digestion followed by AAS estimation. Results: Three lichen species were discovered: Bulbothrixmeizospora, Parmotrema tinctorum, and Pyxine berteriana. Pyxine berteriana was collected near the highway, while Bulbothrix meizospora and Parmotrema tinctorum were collected away from it. The heavy metal bioaccumulation pattern observed was as follows: Fe>AI>Mg>Zn>Cu>Pb>Mn>Ni>Cd>Cr. Notably, Pyxine berteriana exhibited the highest metal concentrations among the three species. Interpretation: Based on the findings, it can be concluded that the Physcioid lichen Pyxine berteriana is the most resilient species in the region and can serve as an appropriate bio-indicatorfor studying the deposition of heavy metals in the ambient air. © 2023 Triveni Enterprises. All rights reserved.
Early down regulation of the glial Kir4.1 and GLT-1 expression in pericontusional cortex of the old male mice subjected to traumatic brain injury
(2013) R.K. Gupta; S. Prasad
Astroglia play multiple roles in brain function by providing matrix to neurons, secreting neurotrophic factors, maintaining K+ and glutamate homeostasis and thereby controlling synaptic plasticity which undergoes alterations during aging. K+ and glutamate homeostasis is maintained by astrocytes membrane bound inwardly rectifying K+ channel (Kir4.1) and glutamate transporter-1 (GLT-1 or EAAT-2) proteins, respectively in the synapse and their expression may be altered due to traumatic brain injury (TBI). Also, it is not well understood whether this change is age dependent. To find out this, TBI was experimentally induced in adult and old male AKR strain mice using CHI technique, and expression of the Kir4.1 and GLT-1 in the pericontusional cortex at various time intervals was studied by Western blotting and semi quantitative RT-PCR techniques. Here, we report that expression of both Kir4.1 and GLT-1 genes at transcript and protein levels is significantly down regulated in the pericontusional ipsi-lateral cortex of old TBI mice as compared to that in the adult TBI mice as function of time after injury. Further, expression of both the genes starts decreasing early in old mice i.e., from the first hour after TBI as compared to that starts from fourth hour in adult TBI mice. Thus TBI affects expression of Kir4.1 and GLT-1 genes in age- and time dependent manner and it may lead to accumulations of more K+ and glutamate early in the synapse of old mice as compared to adult. This may be implicated in the TBI induced early and severe neuronal depolarization and excito-neurotoxicity in old age. © 2013 Springer Science+Business Media Dordrecht.
Earthworms for Eco-friendly Resource Efficient Agriculture
(Springer Singapore, 2020) Rahul Kumar; Pankaj Sharma; R.K. Gupta; Sandeep Kumar; Mayur Mukut Murlidhar Sharma; Sonia Singh; Gourisankar Pradhan
Waste production became the main concern in the era of the increasing world population. Millions of tons of waste are being generated everyday worldwide, and now, it is a big challenge for managing the financial and ecological expense of these wastes. An additional significant problem is arising from the disposal of municipal solid wastes, which cause emission of greenhouse gases. For sustainable development, a chief part of municipal wastes has biological garbage which can be converted into eco-friendly material like vermicompost (VCM) by using earthworm. Earthworm's activities increase the soil fertility by improving soil formation, soil porosity, water infiltration, decomposition of organic material, humus formation, suppression of soil-borne diseases & pests, and by promoting nutrient cycles which ultimately help in plant growth. Due to their beneficial activities, they cause the main change in soil properties; therefore, they are known as “Ecological engineer.” Earthworms also act as a bioindicator. Earthworm forms a significant portion of soil invertebrate's biomass about 40-90% in different soil condition. The earthworm species have great diversity across the globe, which is the deciding factor to earthworm's potent towards soil improvement. Indian earthworms are dominant by indigenous species that contribute approximately 89% of total earthworm diversity and are represented by nine families, 67-69 genera, and 418-509 species of earthworms out of them, approximately 51 are exotic species. The present chapter highlights in depth the role of earthworm in efficient and sustainable agriculture. © The Editor(s) (if applicable) and The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2020
Effect of tillage and straw return on carbon footprints, soil organic carbon fractions and soil microbial community in different textured soils under rice–wheat rotation: a review
(Springer, 2020) S.S. Dhaliwal; R.K. Naresh; R.K. Gupta; A.S. Panwar; N.C. Mahajan; Ravinder Singh; Agniva Mandal
Measuring the influence of long-term agricultural tillage practices on soil organic carbon (SOC) is of great importance to farmers and policymakers. Different management practices affected SOC mainly at the soil surface level. The different fractions of SOC viz. total SOC, particulate organic carbon, soil microbial biomass carbon, and potentially mineralizable carbon, were reported to be strongly correlated over a diversity of soils and management systems. Frequent tillage deteriorates soil structure and weakens soil aggregates, causing them to be susceptible to decay. The mixing of residues/surface retention into the soil increases SOM mineralization due to greater exposure to microbial decomposers and optimal moisture and temperature. Increased efficiency of N fertilizers use can result in reduced carbon footprints of field crops, because the contribution of N fertilizers is 36–52% of total emissions while increased soil C sequestration reduces the carbon footprint, because the input carbon as CO2 from atmospheric is converted into the plant biomass and eventually deposited to the soil. Decreasing soil tillage integrated with crop residues retention can increases SOC and decreases carbon footprint, and the mixing of key agricultural practices could increase the crop yields, reduce the emissions and carbon footprint respectively. © 2019, Springer Nature B.V.
Electrical properties of junction between aluminium and poly(aniline)-poly(vinyl chloride) composite
(2004) R.K. Gupta; R.A. Singh
Schottky barrier diode based on composite of polyaniline with polyvinyl chloride has been fabricated and characterized using aluminium as Schottky contact and platinum as an Ohmic contact. Current-voltage (I-V) plots were non-linear and capacitance-voltage (C-V) plots were almost linear in reverse bias indicating rectification behavior. The observed current-voltage characteristics can be satisfactorily fitted using the modified Schottky equation. Various junction parameters were calculated from the temperature-dependent I-V and C-V data and discussed. These results indicate that the composite materials have better mechanical strength and diode quality compared to that of pure polymer. © 2004 Elsevier B.V. All rights reserved.
How extensive are yield declines in long-term rice-wheat experiments in Asia?
(2003) J.K. Ladha; D. Dawe; H. Pathak; A.T. Padre; R.L. Yadav; Bijay Singh; Yadvinder Singh; Y. Singh; P. Singh; A.L. Kundu; R. Sakal; N. Ram; A.P. Regmi; S.K. Gami; A.L. Bhandari; R. Amin; C.R. Yadav; E.M. Bhattarai; S. Das; H.P. Aggarwal; R.K. Gupta; P.R. Hobbs
The rice-wheat cropping system, occupying 24 million hectares of the productive area in South Asia and China, is important for food security. Monitoring long-term changes in crop yields and identifying the factors associated with such changes are essential to maintain and/or improve crop productivity. Long-term experiments (LTE) provide these opportunities. We analyzed 33 rice-wheat LTE in the Indo-Gangetic Plains (IGP) of South Asia, non-IGP in India, and China to investigate the extent of yield stagnation or decline and identify possible causes of yield decline. In treatments where recommended rates of N, P and K were applied, yields of rice and wheat stagnated in 72 and 85% of the LTE, respectively, while 22 and 6% of the LTE showed a significant (P < 0.05) declining trend for rice and wheat yields, respectively. In the rice-wheat system, particularly in the IGP, rice yields are declining more rapidly than wheat. The causes of yield decline are mostly location-specific but depletion of soil K seems to be a general cause. In over 90% of the LTE, the fertilizer K rates used were not sufficient to sustain a neutral K input-output balance. Depletion of soil C, N and Zn and reduced availability of P, delays in planting, decreases in solar radiation and increases in minimum temperatures are the other potential causes of yield decline. A more efficient, integrated strategy with detailed data collection is required to identify the specific causes of yield decline. Constant monitoring of LTEs and analysis of the data using improved statistical and simulation tools should be done to unravel the cause-effect relationships of productivity and sustainability of rice-wheat systems. © 2002 Elsevier Science B.V. All rights reserved.
Inhibition of corrosion by poly(N-hexadecylaniline)/docosanol mixed Langmuir-Blodgett films on copper in sea water
(2006) R.K. Gupta; R.A. Singh
Electrochemical and weight loss techniques have been used for investigation of inhibition of corrosion on copper metal by Langmuir-Blodgett (LB) films of poly(N-hexadecylaniline)/docosanol in sea water. LB films of poly(N-hexadecylaniline)/docosanol were deposited onto the copper specimens. The open-circuit potential and potentiodynamic polarization curves were observed to shift in noble direction, which indicated that these LB films could inhibit the corrosion of copper metal in sea water. © 2005 Elsevier B.V. All rights reserved.
Integral‐breadth analysis of X‐ray line broadening in cold‐worked natural molybdenite (MoS2) crystals
(1972) R. Pratap; R.K. Gupta
An anomalous X‐ray line broadening effect has been studied in cold‐worked natural molybdenite (MoS2)crystals using the integral‐breadth method. The stacking‐fault probability is calculated on the basis of simple h.c.p. structure and is found to be approximately 0.03 on taking account the glide on S–S (sulphur–sulphur) slip planes only. Also, lattice strain and domain‐size parameter have been estimated. The dislocation density calculated from the domain‐size is found to be ≈2.6 × 1010 cm/cm3. A justification for using the simple h.c.p. structure theory for molybdenite has also been given. Copyright © 1972 WILEY‐VCH Verlag GmbH & Co. KGaA
Ionic transport in the (Agl:AgCl) mixed-system
(Kluwer Academic Publishers, 1994) R.C. Agrawal; R.K. Gupta; R. Kumar; Ajay Kumar
Ionic mobility, conductivity, number of charge carriers and transference number are reported for annealed and rapidly quenched [xAgl:(1-x)AgCl] mixed systems, these results are compared with Agl. Of these three materials the quenched mixed-system had the highest Ag+ ion conductivity. Further, preliminary studies are reported where the high conductivity system (i.e. quenched 0.75 Agl:0.25 AgCl) has been used as host material for the preparation of Ag+ ion conducting glasses and composites. Detailed thermal/phase diagram studies have also been carried out on the quenched composition. The conductivity enhancement in the quenched system is attributed to the formation of new disordered phases and the introduction of amorphisity, the simple space-charge model applicable to the annealed system failed to explain these results. © 1994 Chapman & Hall.
Junction properties of Schottky diode based on composite organic semiconductors: Polyaniline-polystyrene system
(2005) R.K. Gupta; R.A. Singh
Schottky barrier diode based on composite of polyaniline with polystyrene has been fabricated and characterized using aluminium as Schottky contact and platinum as an ohmic contact. The observed current-voltage characteristics can be satisfactorily fitted using the modified Schottky equation. Current-voltage (I-V) plots were non-linear and capacitance-voltage (C-V) plots were almost linear in reverse bias indicating rectification behavior. Various junction parameters were calculated from the temperature dependent I-V and C-V data and discussed. These results indicate that the composite materials have better mechanical strength and diode quality compared to the pure semiconducting polymer.
Lattice spacings and stacking fault probabilities in Ag-Cd-In alloys
(Springer-Verlag, 1971) R.G. Krishnan; R.K. Gupta; P.Rama Rao
Lattice spacing values in ternary Ag-Cd-In alloys containing 5 to 30 at. pct Cd and 5 to 15 at. pct In have been determined from X-ray powder patterns using the Nelson-Riley extrapolation procedure. The values are shown to lie, in a ternary plot, on iso-parameter lines obtained by joining equal lattice spacing values in the relevant binary alloys. The intrinsic stacking fault probabilities (α) in these alloys obtained from measurement of X-ray peak displacements are found to follow the empirical relation α=α0 exp k|ΔZ|p, where α0 is the intrinsic fault probability in Ag, |ΔZ| is the weighted mean of solvent-solute valence differences, p is the combined solute content, and k is a constant approximately equal to 0.08 in agreement with the value found earlier for binary alloys based on silver. © 1971 The Metallurgical Society of American Institute of Mining, Mitallurgical and Petroleum Engineers, Inc., and American Society for Metals.
Multi-environment analysis to unravel bread wheat core collection to identify donors for grain quality, phenology, and yield traits
(CSIRO, 2024) Jyoti Kumari; R.K. Gupta; Arun Gupta; B.K. Honrao; S.S. Vaish; Achla Sharma; Sewa Ram; Gopalareddy Krishnappa; Shivani Sharma; Rakesh Bhardwaj; Sherry Rachel Jacob; Sundeep Kumar; V.K. Vikas; Sushil Pandey; J.C. Rana; Ashok Kumar; G.P. Singh; Kuldeep Singh
Context. Untapped wheat germplasm is conserved globally in genebanks. Evaluating it for grain quality and yield will help achieve nutritional and food security. Aims. We aimed to evaluate the Indian National Genebank bread wheat core collection for grain quality, phenology and yield, to identify potential donor germplasm. Methods. 1485 accessions were grown at three locations in India during winter 2015–2016 to evaluate test weight, grain protein content, sedimentation value (SV), days to spike emergence, days to maturity, grain yield and thousand-grain weight (TGW). Key results. Best linear unbiased estimates indicated mean protein of 13.3%, 14.7%, and 13.0% and yield of 73.0 g/m, 70.9 g/m and 66.6 g/m at Ludhiana, Pune, and Varanasi locations, respectively. The SV ranged from 26.6–65.6 mL and 17.7–66.6 mL at the Ludhiana and Pune locations, respectively. The top 10 accessions were identified for all the studied traits. Six high protein accessions, with consistent protein of more than 15% along with moderate Thousand-grain and test weights were further validated and assessed for stability across environments. Grain protein content was correlated negatively with thousand-grain weight and yield, but positively with days to maturity and spike emergence. Conclusion. The identified accessions with high trait values could be used in future breeding programmes to develop high yielding biofortified cultivars to address protein malnutrition and also cultivars with suitable end-product quality. Implications. The diversity in a core collection can be exploited to develop modern high yielding bread wheat cultivars with higher grain protein content and suitable end-product quality. © 2024 The Author(s).
Nitrate reductase activity of the cyanobacterium Synechococcus cedrorum
(1984) R.K. Gupta; E.R.S. Talpasayi
[No abstract available]
Nitrogen fixation by cyanobacteria associated with moss communities in Schirmacher Oasis, Antarctica
(1993) K.D. Pandey; A.K. Kashyap; R.K. Gupta
[No abstract available]
Nitrogen-fixation by non-heterocystous cyanobacteria in an Antarctic ecosystem
(2000) K.D. Pandey; A.K. Kashyap; R.K. Gupta
Unicellular, non-heterocystous, diazotrophic cyanobacteria Gloeocapsa sp. isolated from Schirmacher Oasis, Antarctica, showed N2-fixation (C2H2-reduction) which was comparable to that of Gloeocapsa sp. isolated from a tropical rice field. The optimum temperature of the Antarctic isolate for nitrogenase activity was 20°C, whereas the tropical isolate expressed its maximum activity at 30°C. Sucrose supported the nitrogenase activity of both the isolates in darkness. The results indicated that the Antarctic isolate behaved differently with respect to temperature compared to the tropical isolate.
Nitrogenase activity of the antarctic cyanobacterium Nostoc commune: Influence of temperature
(Springer Netherlands, 1991) A.K. Kashyap; K.D. Pandey; R.K. Gupta
Nitrogenase activity (C2H2 reduction) of Nostoc commune isolated from Schirmacher Oasis (Antarctica) was compared with Nostoc muscorum, N. calcicola, Anabaena doliolum and Gloeocapsa sp. The temperature profile of acetylene reduction (5-30 °C) for N. commune revealed (a) that the highest rate of nitrogenase activity was at 25±1 °C, (b) that it was low (69 %) in comparison with N. muscorum, and (c) that nitrogenase activity continued at lower temperatures, which was not evident for other cyanobacteria. The results suggest that N. commune is adapted to lower temperatures in terms of nitrogen fixation. © 1991 Folia Microbiologica.
Nutrient status, algal and cyanobacterial flora of six fresh water streams of Schirmacher Oasis, Antarctica
(Kluwer Academic Publishers, 1995) K.D. Pandey; A.K. Kashyap; R.K. Gupta
The algal and cyanobacterial flora and the chemical environment of six freshwater streams of Schirmacher Oasis, Antarctica were investigated. Over 30 species of algae, predominantly cyanobacteria (Cyanophyceae), were recorded. N2-fixing species, both heterocystous and unicellular diazotrophs, contributed more than 50% to the counts and their dominance was greatest in the middle of the stream where nitrogen and other nutrients were low. Green algae and diatoms also contributed to the flora. The species composition varied between streams. Glacial and snow drift meltwater streams contained a distinctive community. Based on diversity indices, these streams could be classified into two clusters. © 1995 Kluwer Academic Publishers.
Optical, mechanical, and electrical studies of polymer composites based on charge transfer complex of phenothiazine-iodine with poly(vinyl chloride)
(2009) S.K. Singh; R.K. Gupta; R.A. Singh
Charge transfer complex (CTC) of phenothiazine and iodine (1:2 molar ratio) was prepared by solvent evaporation method in diethyl ether and its composite with poly(vinyl chloride) was prepared in benzene by diffusion method. Infra-red spectra showed overlapped peaks for both components and intensity of individual component was proportional to feed ratio. Optical photographs and scanning electron microscopy of composites showed template growth and connectivity in insulator matrix was proportional to wt% of CTC. Mechanical strength of composites was found to increase with wt% of PVC. The current-voltage study showed percolation threshold of 8 wt% of CTC. The temperature dependence of conductivity showed semiconducting nature of the materials. Transport property of charges were explained by regression analysis of σdc vs. T-1/1+n data and meets the basis for the Mott's 2D, 3D variable range hopping or thermoionic emission model, depending on temperature and wt% of CTC content. The impedance spectroscopy was performed between 40 Hz-100 kHz range. Circuit elements consists only combination of resistance and capacitance, which showed homogeneous nature of composites. Thermoelectric factor 'S' was also evaluated and has value of <1 at 303 K in all cases. © 2009 Elsevier B.V. All rights reserved.