Browsing by Author "Ankit Singh"

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Anaerobic Digestion of Agri-Food Wastes for Generating Biofuels
(Springer, 2021) Chunjie Gong; Ankit Singh; Pranjali Singh; Archana Singh
Presently, fossil fuels are extensively employed as major sources of energy, and their uses are considered unsustainable due to emissions of obnoxious gases on the burning of fossil fuels, which can lead to severe environmental complications, including human health. To tackle these issues, various processes are developing to waste as a feed to generate eco-friendly fuels. The biological production of fuels is considered to be more beneficial than physicochemical methods due to their environmentally friendly nature, high rate of conversion at ambient physiological conditions, and less energy-intensive. Among various biofuels, hydrogen (H2) is considered as a wonderful due to high calorific value and generate water molecule as end product on the burning. The H2 production from biowaste is demonstrated, and agri-food waste can be potentially used as a feedstock due to their high biodegradability over lignocellulosic-based biomass. Still, the H2 production is uneconomical from biowaste in fuel competing market because of low yields and increased capital and operational expenses. Anaerobic digestion is widely used for waste management and the generation of value-added products. This article is highlighting the valorization of agri-food waste to biofuels in single (H2) and two-stage bioprocesses of H2 and CH4 production. © 2021, Association of Microbiologists of India.
Analysis of citizen science scientific publications: A scientometric study
(University of Idaho Library, 2021) Ajay Kumar Chaubey; Ankit Singh
The purpose of this study is to assess the citizen science publications in journals indexed in the Web of Science database from 1993 to 2020.Major areas of research related to CS are environmental science, ecology, biodiversity & conservation, education & educational research, public environmental & occupational science and computer science. The USA, England, Australia, Canada and Germany were the most productive countries. This study describes some silent characteristics trends of CS research like most prolific authors, institutions and countries. 82% of publications on CS received the citation while 18% of publications did not receive any citation. Although 47% of publications were open access and 53% publications were close access platform. However, Journal on Biological Conservation, Peerj, International Journal of Environment and Pollution, Marine Pollution Bulletin and Journal of Applied Ecology are the leading journals in this field. © 2021
Coulomb Stress Change of the 2012 Indian Ocean Doublet Earthquake
(Springer International Publishing, 2024) Pankhudi Thakur; Rohtash Kumar; Ranjit Das; Amritansh Rai; Raghav Singh; Ankit Singh; S.P. Maurya
The 2012 Sumatra (Mw 8.6) earthquake, which falls into the largest and rarest group of the great intraplate earthquakes, continues to awe many brilliant minds. An enormous aftershock (Mw 8.2) was felt two hours after the Indian Ocean earthquake along the triple intersection of the Indian, Australian, and Sunda plates in the northwest. Over the past 20 years, there have been numerous earthquakes in the Sumatran subduction zone, including the 2004 earthquake (Mw 9.2) of Sumatra-Andaman, the 2005 earthquake (Mw 8.6) of Nias-Simeulue, the 2007 earthquake (Mw 8.4) of Bengkulu, the 2010 earthquake (Mw 7.8) of Mentawai tsunami, and a large number of other minor to moderate-sized events. It often takes a few seconds to a few minutes for the stress brought on by an earthquake to dissipate. This massive discharge disrupts the lithosphere and asthenosphere, which causes more earthquakes to occur nearby. A comprehensive comprehension of stress variations along a fault and its neighboring faults is essential for effectiv ly predicting and mitigating seismic risks. Drawing inspiration from the earthquake finite fault model pioneered by Guangfu Shao, Xiangyu Li, and Chen Ji from UCSB, we have formulated Coulomb stress models tailored to the Sumatran subduction zone and the Sumatran fault. It was discovered that the primary shock’s related coulomb stress change exceeded the stress-triggering threshold. The aftershock struck a place where there was a lot of stress from the mainshock. Therefore, the Coulomb failure stress change brought on by the mainshock is likely what caused the Sumatra aftershock to occur. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Data-Driven Spatiotemporal Assessment of Seismicity in the Philippine Region
(Springer International Publishing, 2024) Amritansh Rai; Rohtash Kumar; S.P. Maurya; Ankit Singh; Pankhudi Thakur; Raghav Singh; Ranjit Das
The present study provides a retrospective analysis of the geographical and chronological fluctuations of three basic statistical characteristics of seismicity using a big dataset of events that occurred between 1940 and 2022 in the Philippine region. For determining the spatial-time changes in a-value (seismic activity), b-value (recurrence graph slope), and z-value, the contemporary expanded software package ZMAP with numerous sophisticated seismological functions for earthquake catalog analysis is employed (parameter of the relative seismic quiescence). For the various statistical interpretations, catalog data from the United States Geological Survey (USGS) occurred in spatial windows 0° N – 20° N and 118°E – 130oN are used. The overall conclusion is that unusually low b-values and high z-values, which define zones of comparatively seismic quiescence, may be a signal of the approaching release of more severe stress in areas near zones of relatively high a-values. Thus, the suggested joint interpretation of the spatial-time fluctuations of these three statistical characteristics of seismicity may be seen as a form of the predictor of the more powerful recent seismic occurrences in the region. Furthermore, the occurrence probability of a seven magnitude event is near about one with a return period of 2 years. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Delayed collapse transitions in a pinned polymer system
(American Physical Society, 2022) Keerti Chauhan; Ankit Singh
Employing Langevin dynamics simulations, we investigated the kinetics of the collapse transition for a polymer of length N when a particular monomer at a position 1=X=N is pinned. The results are compared with the kinetics of a free polymer. The equilibrium ?-point separating the coil from the globule phase is located by a crossover in (Rg2)/N plots of different chain lengths. Our simulation supports a three-stage mechanism for free and pinned polymer collapse: the formation of pearls, the coarsening of pearls, and the formation of a compact globule. Pinning the central monomer has negligible effects on the kinetics as it does not break the symmetry. However, pinning a monomer elsewhere causes the process to be delayed by a constant factor fX depending linearly upon X. The total collapse time scales with N as tc~fXN1.60±0.03, which implies tc is maximum when an end monomer is pinned (X=1 or N), while when pinning the central monomer (X=N/2) it is minimum and identical to that of a free polymer. The average cluster size Nc(t) grows in time as tz, where z=1.00±0.04 for a free particle, whereas we identify two time regimes separated by a plateau for pinned polymers. At longer times, z=1.00±0.04, while it deviates in early time regimes significantly, depending on the value of X. © 2022 American Physical Society.
Earthquake Source Dynamics and High-Frequency Decal Characteristics of Japanese Arc Region
(Springer International Publishing, 2024) Ankit Singh; Rohtash Kumar; Amritansh Rai
The shape of the seismic frequency spectrum and its relationship to the magnitude of earthquakes have been a significant focus. This pursuit aims to extract valuable information about the nature of earthquake source mechanisms. Additionally, it serves as a valuable reference for generating accurate simulations of strong ground motion, which is crucial for engineering applications. A data set of 10 sites, each site having 20 data of surface and well of magnitude equal to 3.8 or greater than 3.8 Japan (Kik), has been used in this study. A MATLAB script was employed to calculate key spectral parameters. These parameters include the corner frequency (fc), which designates the point beyond which the spectrum’s decline follows a specific rate of 2. Furthermore, the high-cut frequency (fmax) was determined, signifying the frequency above which the spectrum’s decay occurs, along with the rate of this decay (p) for frequencies beyond fmax. Previous research conducted by Kumar et al. demonstrates that the relationship involving fmax is not influenced by factors such as focal depth, distances from the epicenter, and the conditions of recording sites. Both fmax and fc exhibited a comparable correlation with seismic moments or magnitudes, indicating that fmax is likewise influenced by the characteristics of the earthquake source process. Across various recording locations, the observed values of fmax consistently exhibit a rise in conjunction with seismic moment or magnitudes. This trend suggests that the primary influencing factor is the seismic source itself, rather than the conditions at the recording sites. Within this particular study, it has been observed that fmax is found independent of site conditions, seismic moment is directly proportional to power (−3) of cornering frequency. Also variation of fmax with epicenter and the Average value of kappa is estimated. The exploration of this field was initiated by Aki (J Geophys Res 72:1217–1231, 1967), who delved into the relationship between the seismic wave’s amplitude spectrum and the dimensions pertaining to the origin of the earthquake. He achieved this by analyzing a pair of fault displacement models for an earthquake, extending his research until 1970. Aki conceived of the origin of an earthquake as an immediate horizontal strain surge acting on a dislocation surface. Within this framework, he introduced triple autonomous factors (source dimensions, fractional stress drop, and moment) that influence the configuration of the pattern of displacement spectrum for seismic body waves in distant regions. He established a connection between the cutoff frequency of the rupture radius and the assumption the efficiency of stress equates to the typical static stress reduction (Aki, J Geophys Res 72:1217–1231, 1967). © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Emergence of cooperatively reorganizing cluster and super-Arrhenius dynamics of fragile supercooled liquids
(American Physical Society, 2021) Ankit Singh; Sarika Maitra Bhattacharyya; Yashwant Singh
In this paper, we develop a theory to calculate the structural relaxation time τα of fragile supercooled liquids. Using the information of the configurational entropy and structure, we calculate the number of dynamically free, metastable, and stable neighbors around a central particle. In supercooled liquids, the cooperatively reorganizing clusters (CRCs) in which the stable neighbors form "stable"nonchemical bonds with the central particle emerge. For an event of relaxation to take place, these bonds have to reorganize irreversibly; the energy involved in the processes is the effective activation energy of relaxation. The theory brings forth a temperature Ta and a temperature-dependent parameter ψ(T) which characterize slowing down of dynamics on cooling. It is shown that the value of ψ(T) is equal to 1 for T>Ta, indicating that the underlying microscopic mechanism of relaxation is dominated by the entropy-driven processes, while for T
Enzyme kinetics: Industrially important enzymes
(Elsevier, 2023) Archana Singh; Pranjali Singh; Ankit Singh; Deepak Pandey; Durgavati Yadav; Kumar Sandeep
Biocatalysts play a key role in biotransformation reactions. Enzymes are a versatile biocatalyst present in almost all kinds of organisms to regulate their metabolism and survival. Biocatalysts exhibited high selectivity and specificity toward their substrate under mild conditions over chemical processes that are carried out under very harsh conditions and led to the undesirable side by-products. Microbes or enzymes recovered from them are widely utilized for biotechnological applications, including industrial and biomedical. Enzymes are more beneficial over the whole cells due to their high selectivity and easy to operate in the specific reaction. Therefore, the selection of a key enzyme as biocatalysts is necessary for successful industrial applications. The purification of enzymes also faces major challenges such as to retain high activity and better stability. Primarily, the enzyme properties such as low activity (rate of reaction), narrow physiological conditions (low stability), and kinetic properties such a low affinity toward the substrate, low turnover number, and catalytic efficiency. In this book chapter, the details about industrial biocatalysts properties production of enzymes, and improvement in their kinetic and stability properties through protein engineering and immobilization of enzymes is discussed to improve biotechnological applications for human welfare and environmental benefits. © 2023 Elsevier Inc. All rights reserved.
Exploring GRACE and GPS and Absolute Gravity Data on the Relationship Between Hydrological Changes and Vertical Crustal Deformation in South India
(Springer International Publishing, 2024) Ankit Singh; Rohtash Kumar; Amritansh Rai; Raghav Singh; S.P. Singh
Rainfall during the monsoon across the Indian subcontinent leads to significant hydrological changes that alter the ground over a range of timescales. In the present study, both GPS and Grace data have been analysed to assess the impact of groundwater variability on ground deformation study region. The amplitudes seasonal vertical deformation phases estimated from Global Positioning System (GPS) and Gravity Recovery and Climate Experiment (GRACE) are reliable, demonstrating that hydrological factors are the main contributors of periodic deformation in the region. We compare the deformation computed from GRACE mass signal with that of altitude variations from non-stop GPS data from three locations, viz. Bangalore, Hyderabad and Lucknow. For the specified period of time, the patterns of the GRACE and GPS plots match well for Hyderabad and Bangalore but not so well for Lucknow. This shows that hydrological loading is mostly to blame for the crustal deformation seen by GPS in Hyderabad and Lucknow. The crustal d formation as determined by the GPS in Lucknow is consistent with that derived from GRACE data over Lucknow to some extent. This shows that GRACE may be used to adjust the deformation detected by GPS for the hydrological effect. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
How attractive and repulsive interactions affect structure ordering and dynamics of glass-forming liquids
(American Physical Society, 2021) Ankit Singh; Yashwant Singh
The theory developed in our previous papers [Phys. Rev. E 99, 030101(R) (2019)10.1103/PhysRevE.99.030101; Phys. Rev. E 103, 032611 (2021)10.1103/PhysRevE.103.032611] is applied in this paper to investigate the dependence of slowing down of dynamics of glass-forming liquids on the attractive and repulsive parts of intermolecular interactions. Through an extensive comparison of the behavior of a Lennard-Jones glass-forming liquid and that of its WCA reduction to a model with truncated pair potential without attractive tail, we demonstrate why the two systems exhibit very different dynamics despite having nearly identical pair correlation functions. In particular, we show that local structures characterized by the number of mobile and immobile particles around a central particle markedly differ in the two systems at densities and temperatures where their dynamics show large difference and nearly identical where dynamics nearly overlap. We also show how the parameter ψ(T) that measures the role of fluctuations embedded in the system on size of the cooperatively reorganizing cluster (CRC) and the crossover temperature Ta depend on the intermolecular interactions. These parameters stemming from the intermolecular interactions characterize the temperature and density dependence of structural relaxation time τα. The quantitative and qualitative agreements found with simulation results for the two systems suggest that our theory brings out the underlying features that determine the dynamics of glass-forming liquids. © 2021 American Physical Society.
How collaborative is Indian academia? A case study of top three ranked institutions
(National Institute of Science Communication and Information Resources, 2022) Bhaskar Mukherjee; Ankit Singh
The present study employs bibliometric methods to examine the pattern of existing collaboration in India’s top three ranked academic institutes using publications indexed in the Web of Science for the period 2000 to 2020. The results show although the number of collaborations and the degree of collaboration have increased over time, however, the collaboration coefficient remains almost the same in the three institutes. The lesser negative Pearson correlation between authors and articles with a higher positive Pearson correlation between articles and citations for JNU publications suggests that collaboration with a smaller group is more successful than a larger group for gaining citations. Collaborative publications of Banaras Hindu University (36%) and Indian Institute of Science (33%) are more inclined towards authors of the same department, while for Jawaharlal Nehru University, it is with other authors from different universities (41%). The foreign collaboration for all three institutes is almost the same. The network visualization of collaboration in three institutes suggests that the collaborative research in IISc is more diverse than JNU or BHU and in national collaboration, distance between two national organizations also play an important role for strong collaboration. Overall, theoretical aspects of physics lead in collaborative publications followed by chemical sciences. Agricultural biotechnology, clinical medicine, polymer sciences and nanoscience are some emerging disciplines where organizations are increasing their participation through collaborative research. © 2022, National Institute of Science Communication and Information Resources. All rights reserved.
Lapse-Time Dependence of Coda Quality Factor Within the Lithosphere of Northern Ecuador
(Springer International Publishing, 2024) Amritansh Rai; Rohtash Kumar; Ankit Singh; Raghav Singh; Indrajit Das; S.P. Maurya
In the current study, a frequency-dependent attenuation relationship based on coda waves is developed for the Ecuador region. The single backscattering model developed by Aki and Chouet (J Geophys Res 80:3322–3342, 1975) is used to investigate the dependence of Coda-Q on lapse time frames. The waveforms of 49 local earthquakes recorded by a one-station local seismological network are used for the analysis. The frequency-dependent Coda-Q relations estimated for the region are: Qc = (65.75) f0.6302 (10 sec lapse time), Qc = (92.48) f0.6868 (20 sec lapse time), Qc = (18.17) f1.3337 (30 sec lapse time), Qc = (30.95) f1.2303 (40 sec lapse time), Qc = (88.22) f0.9117, and Qc = (125.19) f0.9342. Given that greater areas would be sampled by longer lapse time windows, the rise in Qc values with lapse time demonstrates the depth dependency of Qc. The increase in value of Q0 (QC at 1 Hz) with time depicts that the heterogeneities decrease with depth. The observed quality factor is highly variable with the lapse time and frequency. The more significant value of n shows that the area is seismically active. The observed Qc relation is found equivalent to other similar seismically active regions. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Moho Mapping of Northern Chile Region Using Receiver Function Analysis and HK Stacking
(Springer International Publishing, 2024) Amritansh Rai; Rohtash Kumar; Dipankan Srivastava; Raghav Singh; Ankit Singh; S.P. Maurya
In this study, Rfpy software is utilized to compute the receiver functions to map Moho in the Northern Chile region. To obtain the teleseismic waveforms within an epicentral distance of 30° to 90°, the Package makes use of the IRIS station database. The receiver functions over stations AC04 and AC05 indicate a low-velocity layer possible area at a shallower depth. Additionally, the delay periods of the Moho Ps phase at various different back azimuths are used to infer the anisotropy or dipping Moho. With the aid of H-K Stacking the receiver functions for Poisson’s ratio and Moho depth were also inverted. Under the AC07 station, which is situated in Caldera, Atacama, a higher Moho depth of 46 km is discovered. This results in a Poisson’s ratio of 0.24. Below the CO10 station, which is in Coquimbo, an extraordinary poisson ratio is found. Accordingly, a Moho depth of 25 km is discovered. Inverting the acquired P-wave receiver functions may effectively determine the S-wave velocity structure below each station. This would aid in enhancing the region’s crustal imaging. Additionally, harmonic decompositions of the receiver functions might be performed to examine the behavior of anisotropy. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Statistical theory of fluids confined in quenched disordered porous media
(American Institute of Physics, 2024) Mamta Yadav; Ankit Singh; Yashwant Singh
We develop a theory to calculate structural correlations and thermodynamic properties of a fluid confined in a random porous solid medium (matrix). We used density functional formalism to derive an annealed averaged expression for the density profile and excess free energy of fluid arising due to random fields of a particular realization of the matrix. After performing the second average over the quenched-disordered variables, the excess free energy is organized to give one- and two-body potentials for fluid particles. The average over disorder reduces the system to an effective one-component system of fluid in which particles feel one-body (external) potential and interact via effective pair potential. The effective pair potential is a sum of the bare (the one in the pure fluid) and the matrix-induced potential. The resulting partition function involves only fluid variables. Equations are derived for fluid-fluid and fluid-matrix correlation functions and for free energy, pressure, and chemical potential of the fluid. The theory is applied to a model system of hard spheres and results for the effective pair potential, correlation functions, and thermodynamic properties are reported. The effective pair potential is found to be attractive at the contact and develops a repulsive peak before decaying to zero. Results for pair correlation function and structure factor are compared with simulation results for several fluid densities at two matrix densities. In all the cases, a very good agreement has been found. © 2024 Author(s).
Structure ordering and glass transition in size-asymmetric ternary mixtures of hard spheres: Variation from fragile to strong glasses
(American Physical Society, 2023) Ankit Singh; Yashwant Singh
We investigate the structure and activated dynamics of a binary mixture of colloidal particles dispersed in a solvent of much smaller-sized particles. The solvent degrees of freedom are traced out from the grand partition function of the colloid-solvent mixture which reduces the system from ternary to effective binary mixture of colloidal particles. In the effective binary mixture colloidal particles interact via effective potential that consists of bare potential plus the solvent-induced interaction. Expressions for the effective potentials and pair correlation functions are derived. We used the result of pair correlation functions to determine the number of particles in a cooperatively reorganizing cluster (CRC) in which localized particles form "long-lived"nonchemical bonds with the central particle. For an event of relaxation to take place these bonds have to reorganize irreversibly, the energy involved in the processes is the effective activation energy of relaxation. Results are reported for hard sphere colloidal particles dispersed in a solvent of hard sphere particles. Our results show that the concentration of solvent can be used as a control parameter to fine-tune the microscopic structural ordering and the size of CRC that governs the glassy dynamics. We show that a small variation in the concentration of solvent creates a bigger change in the kinetic fragility which highlights a wide variation in behavior, ranging from fragile to strong glasses. We conclude that the CRC which is determined from the static pair correlation function and the fluctuations embedded in the system is probably the sole player in the physics of glass transition. © 2023 American Physical Society.
Super-Arrhenius behavior of molecular glass formers
(American Physical Society, 2019) Ankit Singh; Yashwant Singh
A theory is developed to calculate values of the potential-energy barriers to structural relaxation in molecular glass formers from the data of static pair-correlation function. The barrier height is shown to increase due to an increase in the number of "stable bonds" a particle forms with its neighbors and the energy of each bond as liquids move deeper into the supercooled (supercompressed) region. We present results for a system of hard spheres and compare calculated values of the structural relaxation time with experimental and simulation results. © 2019 American Physical Society.