Browsing by Author "Pradeep Kumar Shukla"

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A new subspecies of Isoetes coromandelina (Isoetaceae) from Gujarat, India
(College of Life Science, 2017) Santosh Kumar Shukla; Sarvesh Kumar Singh; Pradeep Kumar Shukla; Nawal Kishor Dubey; Husnara Khanam; Gopal Krishna Srivastava
In the present study Isoetes coromandelina ssp. thanensis S.K. Shukla, S.K. Singh, P.K. Shukla, N.K. Dubey, H. Khanam & G.K. Srivastava a micro endemic new subspecies is described from the Than in Rajkot District of Gujarat state in coastal zone of India. Morphologically, the new subspecies is most similar to I. coromandelina ssp. coromandelina but differs in its microspore with levigate surface ornamentation and chromosome number 2n = 22 + 1. Different morphological features of I. coromandelina ssp. thanensis are discussed. Images and a distributional map are also provided. In the present study, we made a correlation between microspore ornamentation and ploidal status at the infra-specific level which helpful in taxonomy of closely related taxa. © 2017, College of Life Science. All rights reserved.
Anisotropy analysis in shallow marine gas hydrate bearing sediments: a case study from the offshore Mahanadi basin, India
(Springer Science and Business Media B.V., 2022) Pradeep Kumar Shukla; Dip Kumar Singha; Kalachand Sain
Analysis of anisotropy from velocity data is essential for improving the hydrocarbon reservoir characterization. The anisotropy of a medium is affected by the mechanical strength, presence of fracture, mineral distribution of the rock, and its degree affects the seismic velocity. We attempted to characterize the anisotropy of the gas hydrate bearing sediments in the offshore Mahanadi basin using three wells. Initially, the presence of anisotropy was investigated by estimating the stiffness coefficients and Thomsen’s parameters (epsilon, gamma and delta) assuming a horizontal transversely medium using dipole S-wave (upper and lower) velocities. The natural fractures were identified from the formation image data. The strong anisotropy is associated with the presence of natural fractures and lower values of the elastic modulus. Most of the strong and weak anisotropy zones are oriented in the NW to W direction of the study area. Our study suggests that the anisotropy in gas hydrate bearing sediment is stress-induced due to the presence of pore filling fractures, and the change of mechanical behavior. The higher positive values of epsilon and delta with gamma represent either dry solid gas hydrate or free gas filled in the fracture of the sediments as observed in the crossplot analysis. Finally, we modeled P-wave and S-wave velocities by incorporating the Thomsen’s parameters. S-wave velocity is less effective than P-wave velocity at 90° angle of fracture relative to the symmetry axis and the modeled P-wave velocity increases upto 2.8% in the gas hydrate bearing sediments. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Base pairing patterns of DNA base lesion spiroiminodihydantoin: A DFT study
(2013) Pradeep Kumar Shukla; P.C. Mishra
The DNA base lesion spiroiminodihydantoin (Sp) is produced in biological systems endogenously and can cause mutation and cancer. It is considered to be more mutagenic and deleterious than 8-oxoguanine and other oxidized guanine products such as guanidinohydantoin (Gh) and imidazolone. In this work, the base pairing patterns of Sp with each of the normal nucleic acid bases of DNA have been investigated thoroughly using the B3LYP, M06-2X, and wB97X-D functionals of density functional theory in conjunction with the aug-cc-pVDZ basis set. It is found that the magnitudes of interaction energies between the bases and Sp follow the order: Sp-guanine >> Sp-cytosine > Sp-adenine > Sp-thymine. The strong Sp-guanine abnormal base pairing may be the main cause of the observed mutagenicity of Sp. © 2013 Wiley Periodicals, Inc. DNA in living organisms is attacked by reactive oxygen and nitrogen oxide species, free radicals, alkylating agents, and so forth, produced endogenously and exogenously, leading to diseases like cancer. Spiroiminodihydantoin (Sp) is formed due to the oxidation of guanine and 8-oxoguanine. This work investigates the base pairing patterns of Sp with each of the normal DNA bases and finds that the strong Sp-guanine abnormal base pairing may be the main cause of the observed mutagenicity of Sp. © 2013 Wiley Periodicals, Inc.
Isoetes bilaspurensis (Isoetaceae – Lycopodiopsida), New to Southern India: An Extended Distribution and Redescription
(American Fern Society, 2024) Pradeep Kumar Shukla; Sarvesh Kumar Singh; Daniel F. Brunton; Santosh Kumar Shukla; Anant Prakash Patil; Nawal Kishor Dubey
The authors discovered a previously unknown population of Isoetes at Badami in Bagalkot district of Karnataka state, India in October 2022 which is determined to be I. bilaspurensis. This represents a new record for the Deccan plateau of Southern India and a significant disjunction from its previously known distribution in Chhattisgarh and Madhya Pradesh, Central India. In light of this additional information a revised, detailed description of I. bilaspurensis is presented. Morphological comparisons with closely related taxa, its conservation status, and the phytogeographic implications of its distribution are also provided. © 2024 American Fern Society. All rights reserved.
Isoetes ×gopalkrishnae (Isoetaceae), a new interspecific sterile hybrid from Central India
(Magnolia Press, 2018) Sarvesh Kumar Singh; Santosh Kumar Shukla; Nawal Kishore Dubey; Pradeep Kumar Shukla
Isoetes ×gopalkrishnae hybr. nov., is described, illustrated and compared with possible parent species. Based on morphological characteristics and habitat conditions, this taxon is considered to represent a sterile hybrid between I. coromandelina and I. panchananii. The new hybrid is amphibious and grows on the exposed shore of an artificial pond. It is known only from a single locality on the Vindhya plateau in Uttar Pradesh, India. It can be distinguished from other taxa by a combination of characters including the lack of a scale, the leaf which is terete in transverse section, velum absent to rudimentary, a sporangial wall with internal pigmentation, rugulate megaspores with a smooth equatorial girdle and microspores with densely echinate to short-cristate ornamentation. It is the first Isoetes hybrid reported from the Indian subcontinent. © 2018 Magnolia Press.
Modeling of in-situ horizontal stresses and orientation of maximum horizhontal stress in the gas hydrate-bearing sediments of the Mahanadi offshore basin, India
(Springer Science and Business Media Deutschland GmbH, 2022) Pradeep Kumar Shukla; Dip Kumar Singha; Kalachand Sain
Abstract: Horizontal stresses are key parameters of reservoir geomechanics and wellbore stability modeling. For scientific well drilling, where direct measurements are not always available, modeling of horizontal stresses is challenging, especially for highly porous un-compacted gas hydrate-bearing sediments below the seafloor. We have estimated the minimum (Sh) and maximum (SH) horizontal stresses by using rock poro-elastic models based on three wells data which are situated at the national gas hydrate program (NGHP)-01 sites of the offshore Mahanadi basin. The stress magnitudes are validated by wellbore breakout. We have computed the stress magnitudes using 2D seismic for mapping the gas hydrate-bearing sediments. The average gradients of SH and Sh (10.58 MPa/km and 10.48 MPa/km) are less than the gradient of vertical stress, SV (10.67 MPa/km). The present-day stress distribution at the NGHP-01 site is principally a normal faulting (SV > SH > Sh) regime as obtained from stress polygons. The breakouts identified from both formation image and caliper data, suggest a NNW-SSE orientation for SH in the Pleistocene age, which is slightly anti-clock wise relative to the northward oriented of the Indian sub-continent. This change in the orientation of SH could be due to a local structure/fault system cross-cutting the bottom simulating reflector, and mass sliding/slumping on the seafloor. The orientation of SH varies from N11.25°W to N25.7°W of D-quality. We have analysed wellbore stability using the Mohr–Coulomb circle and hoop stress techniques. These results will enable numerical modeling of production from gas hydrate reservoirs planned for the future. Article Highlights: 1.Identification of breakout from formation image and caliper log data and hence, orientation of horizontal stress in the gas hydrates-bearing sediments of the offshore Mahanadi basin.2.Magnitude of the maximum horizontal stress at breakout intervals and the continuous profile of the horizontal stresses using both well data at NGHP-01 sites and multi-channel seismic data.3.Analysis of stress polygons, Mohr circles and hoop stress distributions at the selected depth intervals near the gas hydrate-bearing sediments. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
Morphological studies of the ligules of selected Indian species of Selaginella (Selaginellaceae)
(Elsevier GmbH, 2019) Sarvesh Kumar Singh; Santosh Kumar Shukla; Nawal Kishore Dubey; Pradeep Kumar Shukla; Richard V. Lansdown
The article presents the results of a study of the ligule morphology of both vegetative and reproductive leaves of four species of Selaginella, i.e. S. delicatula, S. ganguliana, S. plana and S. tenera, occurring in India. Ligules of S. ganguliana, S. plana and S. tenera are described for the first time, and the occurrence of shuttlecock-like ligules is described for the first time. Ligule shape is generally constant across the species studied but some minor morphological variations are observed within species. However, in combination with other morphological characters, the ligule may be a useful tool in the taxonomic delimitation of closely related Selaginella species. In addition, we propose that ligule size may be influenced by the habitat conditions, whereas the presence of glandular cells at their tip margins possibly indicate a water secreting function. © 2019 Elsevier GmbH
Multi-channel 2D seismic constraints on pore pressure- and vertical stress-related gas hydrate in the deep offshore of the Mahanadi Basin, India
(Elsevier Ltd, 2019) Dip Kumar Singha; Pradeep Kumar Shukla; Rima Chatterjee; Kalachand Sain
Estimation of pore pressure and in-situ vertical stress magnitude is essential for understanding the geomechanical behavior of the gas hydrate sediments in deep offshore of the Mahanadi basin. The basin located at northern side of eastern continental margin of India (ECMI) contains gas hydrate in clay/silt sediments. The pore pressure and vertical stress are mapped on two 2D-multi channel seismic data of lines (MH-38A and MH-38B) with aid of information of three wells (namely NGHP-01-19, NGHP-01-09 and NGHP-01-08). Initially, the coefficients of best fit curve have been computed from velocity-effective stress plot for the individual wells and applied on the seismic velocity to transform into the effective stress. The vertical stress has been computed from both the seismic and log data. Therefore, the pore pressure is predicted by subtracting the effective stress from the vertical stress. The pore pressure have been mapped in gas hydrate stability zone (GHSZ) and sediments below bottom simulating reflector (BSR). The pore pressure and vertical stress gradient are 10.11 MPa/km and 10.67 MPa/km, respectively. The pore pressure and vertical stress from seismic data are closely matched at well location with excellent goodness of fit (R2) varying from 0.82 to 0.95. Normal pressure is observed in the gas hydrate bearing sediments but slightly high pressures are noticed below the BSR indicating presence of free gas. The pore pressure from seismic data will guide drillers for choosing the mud weight during well drilling and casing optimizing in other part of deep offshore in the Mahanadi basin. © 2019 Elsevier Ltd
Petro-physics Analysis and Rock Physics Modeling for Estimation of Gas Hydrate Saturation: A Case Study in the Mahanadi Offshore Basin
(Springer, 2022) Pradeep Kumar Shukla; Dip Kumar Singha; Pradeep Kumar Yadav; Kalachand Sain
Gas hydrate saturation (Sh) is the most challenging key parameter of petrophysical evaluations for reservoir characterization. In total three wells were used (namely, NGHP-01-19, NGHP-01-09, and NGHP-01-08) to compute the petrophysical parameters in the gas hydrate-bearing sediments of the Mahanadi offshore basin. Initially, effective porosity and volume of shale are computed using conventional log data varying from 11–36% and 55–75% respectively. The most prominent technique responding to the physical property has been used to compute the Sh by using Archie’s empirical electrical resistivity method. The presence of gas hydrate, free gas, and other lithology affects the sonic velocity which is widely used to quantify the hydrate saturation. Therefore, an attempt is made to quantify the Sh from the wellbore sonic velocity using a rock physics model at higher porosity (∼62%) for unconsolidated marine sediments below the seafloor. The model is best suited for gas hydrate zones where velocity increases with the hydrate saturation but underestimates the saturation for free gas zones below the bottom simulating reflector. In the study area, Sh ranges from 5–13% in the depth interval of 175–200 mbsf for well NGHP-01-19 whereas, small amount of 3–10% and 2–8% for well NGHP-01-09 and NGHP-01-08 respectively. The Sh obtained from the rock physics model is insignificantly mismatched with the saturation obtained from temperature and resistivity data due to the presence of an isotropic layer with fracture filling sediments having anisotropic properties. © 2022, Geological Society of India.
Rediscovery of presumed extinct Isoetes divyadarshanii (Isoetaceae—Lycopodiopsida) in India: New insight on its morphology, taxonomy and conservation status
(Magnolia Press, 2025) Sarvesh Kumar Singh; Daniel Francis Brunton; Pradeep Kumar Shukla; Paul Clayton Sokoloff; Santosh Kumar Shukla; Anant Prakash Patil; N. K. Dubey
A population of Isoetes divyadarshanii, a species previously known only from its type location in Maharashtra State, India and considered extinct since at least 2013, was discovered on the Sada Plateau in the Belagavi District of Karnataka state, India in October 2023. This represents a significant disjunction (over 465 km) from its type location into a different phytogeographic division of the Indian subcontinent. The new information provided by this discovery permits verification of critical elements of the original description. It also allows for an updated and more precise description of the morphology, ecology and taxonomy of this poorly understood taxon. A detailed morphological comparison with closely related taxa, especially I. udupiensis, is presented. The cytology of the new population is reported (2n = 2× = 22) and the IUCN conservation status criteria designation of the species is revised from Critically Endangered (Extinct) to Endangered. Finally, the phytogeographic implications of this new discovery are discussed. © © 2025 Magnolia Press.
Screening of essential oils of angiospermic plants for their fungitoxicity against Aspergillus Flavus and Aspergillus Niger
(International Journal of Pharma and Bio Sciences, 2015) Atul Srivastava; Pradeep Kumar Shukla; Ashwini Kumar Mishra; Subhashini; Suchit John
Essential oils obtained from plants have recently gained a great scientific interest as a potent source of antimicrobials of natural origin. The present study highlights the antifungal activity of essential oils against Aspergillus flavus and Aspergillus niger. During screening of essential oils of six selected Angiospermic plants at 2000 ppm (mg/l) against the test fungus, Mentha arvensis and Citrus aurantifolia, being most effective was selected for further study. The selected oils were subsequently standardized through physicochemical and fungitoxic properties. The MIC values of Mentha arvensis and Citrus aurantifolia were found to be 1000 and 2000 ppm (mg/l) respectively. Fungitoxicity of both oils represents fungicidal, as well as fungistatic behavior at their respective MIC(s). Study also revealed that oil of Mentha arvensis and Citrus aurantifoila are highly thermo stable (up to 80°C) and had the potency to withstand high inoculum density. The fungitoxicity of both the oils remained unaltered up to 180-210 days at room temperature. The antifungal potency of oils was found greater when compared with some prevalent synthetic commercial fungicides. Therefore oils could be recommended as a potential source of ecofriendly herbal fungicide and might have role as pharmaceutical and preservatives.
Selaginella odishana (Selaginellaceae: Lycopodiophyta), a new species from Odisha, Eastern Ghats of India
(Springer Science and Business Media Deutschland GmbH, 2020) Sarvesh Kumar Singh; Pradeep Kumar Shukla; Nawal Kishore Dubey
Selaginella odishana (subg. Stachygynandrum) is described as a new terrestrial species (probably a local endemic) from the Sal tree (Shorea robusta) forest on hill slopes of Daringbadi, Daringbadi Udayagiri forest range, Kandhamal district, Odisha state, Eastern Ghats region of India, and compared to morphologically close taxa (S. reticulata and its allied taxa). The new species is characterised by sub-erect stems, membranous leaf, lateral and axillary leaf, ciliate at the base and serrate distally (towards stem tips) and only serrate (outside face) or serrate margin, lanceolate median leaf with entire-serrate margins, dorsal sporophyll with serrate margins and laminar flap up to ¾ as long as lamina length with ciliate margins, ventral sporophyll ciliate along basal ½ and serrate along distal ½, creamy white megaspores with foveolate surface ornamentation and microspores with smooth surface ornamentation. The conservation status of S. odishana is assessed as Critically Endangered. © 2020, The Board of Trustees of the Royal Botanic Gardens, Kew.
The significance of a new umbellate ornamentation in Isoetes (Isoetaceae: Lycopodiopsida) megaspores
(Taylor and Francis A.S., 2021) Sarvesh Kumar Singh; Pradeep Kumar Shukla; Nawal Kishore Dubey; Santosh Kumar Shukla
A new umbellate ornamentation pattern is described in Isoetes megaspores based on scanning electron microscopy and thorough comparisons with sculptural patterns documented in lycophytes and ferns. The umbellate ornamentation is quite distinct from other vertically projected megaspore sculptural patterns (baculate, clavate, gemmulate, pustulate, tuberculate, saccate and verrucate). In addition, megaspore ornamentations described previously for I. dixitei as tuberculate or pustulate have now been corrected as umbellate. This species also possesses a rudimentary velum and internal pigmentation in sporangial wall which has not been reported in other Indian species of the genus. Further, this taxa has a range restricted to the Western Ghats and is confined to a higher elevational range than Indian species characterised by vertically projected megaspore surface ornamentation patterns. © 2020 Collegium Palynologicum Scandinavicum.
The taxonomy and conservation status of Isoetes (Isoetaceae; Lycopodiopsida) in India
(Taylor and Francis Ltd., 2021) Sarvesh Kumar Singh; Pradeep Kumar Shukla; Daniel F. Brunton; Nawal Kishore Dubey; Santosh Kumar Shukla
In many cases over the years the diversity of Isoetes in India has been defined by inconsistent morphological analyses and questionable data. This has resulted in substantial confusion, dramatically different taxonomic interpretations and a low level of global acceptance. That in turn has prevented the reliable determination of conservation priorities. The present study reviews the most reliable morphological, distributional and cytological Indian data available with techniques and standards that have guided successful taxonomic investigations of Isoetes elsewhere in the world. This results in the enumeration of nine readily distinguishable species for India. One named hybrid is also discussed as is the probable occurrence of other unnamed hybrids. All Indian Isoetes species except I. coromandelina subsp. coromandelina are endemic. Two possible but unresolved taxa are also discussed. A clearer determination of the highest national priorities for Isoetes conservation has resulted. Most Indian taxa are rare, some qualifying as Endangered and others probably being extinct. Suggestions for conservation strategies and actions to protect and sustain vulnerable Isoetes species and their habitats are offered. © 2020 Société botanique de France.