Browsing by Author "A.K. Shukla"

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A new class of Bianchi cosmological models in f(R,T) gravity
(Kluwer Academic Publishers, 2013) R. Chaubey; A.K. Shukla
The new class of cosmological model of the early Universe is considered with f(R,T) modified theories of gravity (Harko et al. in Phys. Rev. D 84:024020, 2011). The exact solutions to the corresponding field equations are obtained in quadrature form. The cosmological parameters have been discussed in detail. We have also discussed the well-known astrophysical phenomena, namely the Hubble parameter H(z), luminosity distance (dL) and distance modulus μ(z) with redshift. © 2012 Springer Science+Business Media B.V.
A New Class of Bianchi Cosmological Models in Lyra's Geometry
(Springer Science and Business Media, LLC, 2013) R. Chaubey; A.K. Shukla
The new class of cosmological model of the early Universe filled with perfect fluid in Lyra's geometry has been considered. We obtain two classes of exact solutions of the field equations in Lyra's geometry with a time-dependent displacement vector. The exact solutions to the corresponding field equations are obtained in quadrature form. The cosmological parameters have been discussed in detail and it is also shown that the solutions tend asymptotically to isotropic Friedmann-Robertson-Walker cosmological model. We have also discussed the well-known astrophysical phenomena, namely the Hubble parameter H(z), luminosity distance dL and distance modulus μ(z) with redshift. © 2012 Springer Science+Business Media New York.
Aspects of non-interacting and interacting universe: a complete scenario
(Canadian Science Publishing, 2023) Rakesh Raushan; A.K. Shukla; R. Chaubey
The evolution of the dark energy within the scope of a spatially homogeneous and isotropic Friedmann–Robertson–Walker model filled with barotropic fluid and dark energy is examined. We have considered the two cases of an interacting and non-interacting two-fluid (barotropic and dark energy) scenario and obtained the exact solutions to the corresponding field equations. In an interacting model, we have considered linear as well as quadratic interaction between dark sectors of the universe. We have also given the quadrature form for general interaction coupling parameter via Q = αρnm, n ≥ 1 and discussed the evolution of energy densities and effective equation of state with cosmic time for flat, closed, and open universes. It is also examined that the matter energy density is dominated in early phase of the universe, whereas the dark energy density is dominated in later phase of the universe for both scenarios, which is in concurrence with current observations. © 2022 The Author(s).
Bianchi type I cosmological model with a cosmological constant (Λ) in creation-field cosmology
(Maik Nauka Publishing / Springer SBM, 2015) R. Chaubey; A.K. Shukla; A. Singh; T. Singh
Solutions of Einstein’s field equations with a cosmological constant Λ in the presence of a creation field have been obtained for Bianchi type I cosmological models in the Hoyle-Narlikar creation field theory. The cosmological parameters are calculated. We examine the nature of the creation field and the cosmological constant which dominate at the early stage of the universe, but they do not survive for a long time and finally tend to zero at large cosmic times. © 2015, Pleiades Publishing, Ltd.
General class of Bianchi cosmological models with Λ in creation-field cosmology
(Kluwer Academic Publishers, 2014) R. Chaubey; A.K. Shukla; Ashutosh Singh; T. Singh
The solutions of Einstein's equations with cosmological constant (Λ) in the presence of a creation field have been obtained for general class of anisotropic cosmological models. We have obtained the cosmological solutions for two different scenarios of average scale factor. In first case, we have discussed three different types of physically viable cosmological solutions of average scale factor for the general class of Bianchi cosmological models by using a special law for deceleration parameter which is linear in time with a negative slope. In second case, we have discussed another three different forms of cosmological solutions by using the average scale factor in three different scenarios like Intermediate scenario, Logamediate scenario and Emergent scenario. All physical parameters are calculated and discussed in each physical viable cosmological model. We examine the nature of creation field and cosmological constant is dominated the early Universe but they do not survive for long time and finally tends to zero for large cosmic time t. We have also discussed the all energy conditions in each cases. © 2014 Springer Science+Business Media Dordrecht.
Holographic dark energy model with quintessence in general class of Bianchi cosmological models
(Canadian Science Publishing, 2014) R. Chaubey; A.K. Shukla
In this paper, we study the general class of Bianchi cosmological models with holographic dark energy component. We have discussed three types of solutions of the average scale factor for the general class of Bianchi cosmological models by using a special law for the deceleration parameter, which is linear in time with a negative slope. The exact solutions to the corresponding field equations are also obtained. All the physical parameters are calculated and discussed in each physically viable cosmological model. For large time (i.e., t →∞) the models tend asymptotically to an isotropic Friedmann-Robertson-Walker cosmological model. Quintessence scalar field and quintessence potential are also obtained for three different scenarios of scale factor. © 2014 Published by NRC Research Press.
Locally rotationally symmetric Bianchi type-I cosmological model with dynamical Λ and G in f(R) gravity
(Springer, 2019) Rakesh Raushan; A.K. Shukla; R. Chaubey; T. Singh
In this paper, we have studied the locally rotationally symmetric (LRS) Bianchi type-I cosmological model filled with a bulk viscous cosmological fluid in f(R) gravity in the presence of time-varying gravitational and cosmological constant. We have used the power-law and intermediate scenario for scale factor to obtain the solution of the field equations. The evolution of temperature of a viscous Universe is also analysed. © 2019, Indian Academy of Sciences.
Management of micronutrients in soil for the nutritional security
(Springer Singapore, 2019) Dileep Kumar; K.P. Patel; V.P. Ramani; A.K. Shukla; Ram Swaroop Meena
Availability of soil micronutrient is a major limiting factor in crop productivity and its quality. The micronutrient deficiencies of zinc (Zn) 40%, iron (Fe) 12.6%, copper (Cu) 4.5%, manganese (Mn) 6.0%, and boron (B) 22.8% in soils have been reported across the country. The manganese deficiency is emerging extremely fast, particularly in wheat crops grown after rice in Haryana (12%) and Punjab (18%) due to leaching of Mn from the upper surface of the coarse-textured soils. In acid soils of India, the majority of the soil samples indicated a sufficient supply of Cu, Fe, and Mn, low deficiencies of Zn (30%), and higher deficiencies of B (46%) and Mo (50%). Application of soil or foliar spray of Zn, Mo, and B and foliar spray of Fe and Mn has been recommended as the most suitable method for the management of micronutrients for the better nutrition of the crops. The average response of Zn application to cereals, oilseeds, and pulses was around 20, 18, and 24%, respectively. The average yield increase due to iron (ferrous sulfate) has been recorded as 450 kg ha-1 in chickpea, 780 kg ha-1 in wheat, and up to 1500 kg ha-1 in paddy. The average yield increase recorded in paddy and wheat is 360 kg ha-1 and 560 kg ha-1, respectively, due to Mn supple- mentation in Punjab. The average yield increase in cereals and pulses crops was recorded up to 400 kg ha-1 due to boron application in the northeast region. Cereals, mainly rice and wheat, are inherently very low in concentration of Zn and Fe in grain, particularly when grown under Zn- and Fe-deficient soils. Deficiency of these nutrients in soil is affecting crop productivity, quality of food, and human nutrition. In rice out of the total micronutrients absorbed by the crop, only 31% Zn, 33% B, 18% Fe, 9% Mn, and 67% Cu remain in grains, and they are removed from the field. In cereals, Fe uptake varies from 150 to 1200 g ha-1 year-1. Micronutrient malnutrition now afflicts over two billion peoples across the world which causes health problems especially in women and children in developing countries. Besides agronomic strategy, microbial and physiological interventions help to mobilize micronutrients from source to sink and resulted in micronutrient-dense grain production with an increase in crop yields which helps to combat malnutrition in animals and humans. Hence, there is need to improve micronutrient quality through fortifying the grains with micronutrients. © Springer Nature Singapore Pte Ltd. 2020.
Observational constraints in modified Chaplygin gas cosmological model
(Elsevier B.V., 2023) A.K. Shukla; R. Raushan; S. Mandal; R. Chaubey
Bianchi type-V cosmological model with modified Chaplygin gas having the equation of state p=γρ−[Formula presented], where C is a positive constant and 0≤α,γ≤1, has been investigated. To find the deterministic solution, we have considered power-law and intermediate expansions which predicts the decelerating and accelerating phases of expansion of the Universe. Here, we have also constructed cosmographic parameters like H,j,l,s∗ and studied their evolution in the background of Bianchi type-V Universe with modified Chaplygin gas. The geometric diagnostics, the state-finder (r,s) in our cosmological model to discriminate from the ΛCDM model are studied. We have performed the statistical analysis and obtained best fit values of the parameters using MCMC technique for intermediate model. We have also compared our models with observed Hubble data for both scenarios. We have noted some new and interesting cosmological solutions which is relevant for the model building, including present accelerating phase of the Universe. © 2023 Elsevier B.V.
Pre-harvest forecasting of rice yield using weather indices in pantnagar (UTTARAKHAND)
(2012) Y.A. Garde; A.K. Shukla; S. Singh
The present article deals with forecasting of rice crop yield using time series data of yield and weekly weather parameters. The association between yearly crop yields and weekly weather parameters was studied by using Karl-Pearson's correlation technique. The forecasting models utilized yearly yield and weekly weather data of University Farm at G. B. Pant University of Agriculture and Technology, Pantnagar. The techniques included development of weather indices which were used as explanatory variables (predictors) in the model. The technique was further modified by incorporating technical and statistical indicators along with developed predictors. Comparative studies of the developed models were carried out from forecast error percentage along with mean square error (MSE). The study proposed that modified model incorporating technical and statistical indicators effectively used for early pre-harvest forecasting of crop yield particularly up to two and half month before harvest.
Soil potassium fertility and management strategies in South Asian agriculture
(Academic Press Inc., 2023) Ch. Srinivasarao; Sumanta Kundu; K.V. Rao; A.K. Shukla; A. Subba Rao; Patricia Imas; Nanthi S. Bolan; Rattan Lal; J.V.N.S. Prasad; P.C. Abhilash; G. Ranjith Kumar; R.S. Meena; G. Pratibha; G. Narayanaswami; S.K. Bansal; K.C. Nataraj; M. Jagadesh; K. Mrunalini; S. Jayaraman; M.L. Jat; S.N. Malleswari; Anthony Whitbread; B. Venkateswarlu
Almost one-fourth of the global population live in South Asia (SA) countries with 14% of cultivable land. Most of the countries in the South Asian region are facing multiple challenges like high population growth, declining farm land area, and low productivity in primary and secondary sectors leading to limited employment opportunities. Consequently, both availability and access to food are adversely affected. Regions exposed to natural disasters, tribal and the hilly regions of SA are amongst the most vulnerable in terms of food security. Accelerated efforts are required to ensure that conflicts do not exacerbate the already fragile food situation in SA. Despite recent strong gains in economic growth and agricultural productivity, food and nutritional security remains a major concern in SA. The region has the largest concentration of poverty and hunger in the world, with nearly 40% of the world's impoverished and 45% of the world's undernourished people. The enormity of malnutrition in SA can be gauged from the fact that it is the home to nearly two-thirds of the world's undernourished children. More than 56% of the world's low-birth-weight babies are born in SA. Furthermore, food and nutrition security remain major challenges with a large proportion of the world's poor living here and global hunger index (GHI) at 30.9. Overcoming these twin challenges require actions both at the national and regional level. Among production constraints and yield gaps, imbalanced nutrient use is a critical issue in many of the SA countries, with nutrient application focused mainly on nitrogen (N), leaving the possibility for other plant nutrient deficiencies including phosphorus (P) and potassium (K). In some cases, the use efficiency of N may be low due to losses in the form of N2O emissions, a potent greenhouse gas (GHG), or via leaching with the undesirable offsite effects. Among the primary nutrients, K is an essential nutrient for productivity, food quality and numerous functions in the plant system. It plays a major role in activating ∼60 enzymes, regulating stomatal functions, controlling water relations especially under rainfed crop production, influencing the water balance of plant systems, and underpinning agronomic productivity and sustainability. Negative K balance in soil under intensive cropping is reported because of low external input and large crop removal, leading to large scale K mining in soils. Declining yield trends were observed in several fertilizer experiments 30–40 years long with continuous application of either N alone or NP without K under both irrigated and rainfed crop production systems in the region. Recent K fertility analysis indicates widespread K deficiency in light-textured alluvial soils, red and lateritic soils beside acid soil types in India, Bangladesh, Sri Lanka, and Pakistan. The countries in SA depend largely on imported K fertilizers. Such imported fertilizer should be utilized most efficiently in the light of limited global K mineral reserves and 93% of world total K exports are from five countries viz. Canada (37.12%) followed by the Russian Federation, Belarus, Germany and Israel. Therefore, the current review addresses issues related to the K supplying capacity of soils in various crop production systems in SA, crop K responses, soil test methods followed, emerging issues in soil K fertility, K balance in major cropping systems and rationalizing K recommendations among crops, soil types and agro-ecological regions. The role of K in balanced nutrition, farm productivity, food and nutritional security in these countries is examined. The review also covers the critical role of K in climate change adaptation, mitigation of nitrous oxide (N2O) emissions and improving overall nitrogen use efficiency (NUE) in the SA region. © 2023 Elsevier Inc.
The anisotropic cosmological models in f (R, T) gravity with Δ(T )
(Indian Academy of Sciences, 2017) R. Chaubey; A.K. Shukla
The general class of anisotropic Bianchi cosmological models in f (R, T) modified theories of gravity with Δ(T ) has been considered. This paper deals with f (R, T) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar R and the trace of the stress-energy tensor T has been investigated for a specific choice of f (R,T ) = f1(R) + f2(T ). The exact solutions to the corresponding field equations are obtained in quadrature form. We have discussed three types of solutions of the average scale factor for the general class of Bianchi cosmological models by using a special law for deceleration parameter which is linear in time with a negative slope. The solutions to the Einstein field equations are obtained for three different physical viable cosmologies. All physical parameters are calculated and discussed in each model. © Indian Academy of Sciences.
The general class of Bianchi cosmological models in f(R, T) gravity with dark energy in viscous cosmology
(Scientific Publishers, 2016) R. Chaubey; A.K. Shukla; Rakesh Raushan; T. Singh
The general class of Bianchi cosmological models in f(R, T) gravity with dark energy in the form of standard and modified Chaplygin gas and bulk viscosity have been considered. We have discussed three types of average scale factor by using a special law for deceleration parameter which is linear in time with negative slope. The model describes an accelerating universe for large value of time t, wherein the effective negative pressure induced by Chaplygin gas and bulk viscous pressure are driving the acceleration. © 2015, Indian Association for the Cultivation of Science.
The general class of Bianchi cosmological models with dark energy and variable Δ and G in viscous cosmology
(Indian Academy of Sciences, 2017) R. Chaubey; A.K. Shukla; Rakesh Raushan
The general class of Bianchi cosmological models with dark energy in the form of modified Chaplygin gas with variable Δ and G and bulk viscosity have been considered. We discuss three types of average scale factor by using a special law for deceleration parameter which is linear in time with negative slope. The exact solutions to the corresponding field equations are obtained. We obtain the solution of bulk viscosity (? ), cosmological constant (Δ), gravitational parameter (G) and deceleration parameter (q) for different equations of state. The model describes an accelerating Universe for large value of time t , wherein the effective negative pressure induced by Chaplygin gas and bulk viscous pressure are driving the acceleration. © Indian Academy of Sciences.
The general class of Bianchi cosmological models with varying EoS parameter
(Springer Netherlands, 2015) R. Chaubey; A.K. Shukla
This paper deals with the general class of Bianchi cosmological models with varying equation of state (EoS) parameter. We have discussed three different types of physically viable cosmological solutions of average scale factor by using a special law for deceleration parameter which is linear in time with a negative slope. The exact solutions to the corresponding field equations are obtained for three different physical viable cosmologies. The EoS parameter for deceleration parameter as well as dark energy is found to be the time varying function. We have using the latest observational data to draw a qualitative picture of the evaluation of the universe. In our constructed model, the equation of state parameter of dark energy is obtained as time varying and it is evolving with negative sign which is consistent with recent observation. We also shows that, at the early stage, the equation of state (EoS) parameter (γ) is positive i.e. the universe was matter dominated but at large time, the universe evolving with negative values i.e. the present epoch. All physical parameters are calculated and discussed in each physical viable cosmological model. © 2014, Springer Science+Business Media Dordrecht.
Use of some essential oils as post-harvest botanical fungicides in the management of grey mould of grapes caused by Botrytis cinerea
(2008) Pramila Tripathi; N.K. Dubey; A.K. Shukla
During screening of twenty six essential oils against Botrytis cinerea, the essential oils of the ten plants viz. Chenopodium ambrosioides, Eucalyptus citriodora, Eupatorium cannabinum, Lawsonia inermis, Ocimum canum, O. gratissimum, O. sanctum, Prunus persica, Zingiber cassumunar and Z. officinale were found to exhibit absolute fungitoxic activity (100% growth inhibition). The essential oils of O. sanctum, P. persica and Z. officinale were selected for further investigation because these oils showed lower Minimum Inhibitory Concentration (MIC) as compared to the other fungitoxic oils. The selected oils were subsequently standardized through physico-chemical and fungitoxic properties. The MIC values of O. sanctum, P. persica and Z. officinale were found to be 200, 100 and 100 ppm (mg/l) respectively. The oils showed fungistatic nature at their respective MIC. The oils were thermostable, and exhibited a wide range of fungitoxicity against 15 other post-harvest fungal pathogens. The oils had the potency to withstand high inoculum density. The antifungal potency of oils was found to be greater in comparison to some prevalent synthetic fungicides. Practical applicability of the essential oils was observed in control of grey mould of grapes caused by B. cinerea during storage. The O. sanctum- and P. persica-oil-treated grapes showed enhancement of storage life up to 5 and 4 days respectively. The storage life of Z. officinale-oil-treated grapes was found to be enhanced up to 6 days. The oils did not exhibit any phytotoxic effect on the fruit peel. Therefore, the oils could be recommended as a potential source of ecofriendly botanical fungicide, after long term and wide ranging trials. © 2007 Springer Science+Business Media B.V.