Indian Institute of Science Education and Research Bhopal
Recent publications
Arid and semiarid environments of the world are characterized by extreme environmental changes that affect the availability of scarce, patchily distributed resources such as water. In response to these changes, animals migrate or partition resources to minimize competition, resulting in temporal patterns within assemblages across multiple scales. Here, we demonstrate that the winter dry season bat assemblage in a semiarid grassland of northwestern India exhibits seasonal changes and temporal avoidance between coexisting species. Using a passive acoustic monitoring framework to quantify activity patterns at different points in the season, we show that members of this assemblage (Rhinolophus lepidus and Tadarida aegyptiaca) exhibit seasonal differences in activity, being more frequently detected in the early and late parts of the dry season, respectively. Other species (Pipistrellus tenuis and Scotophilus heathii) do not exhibit seasonal changes in activity, but structure diel activity patterns, minimizing temporal overlap (and thus competition) at water bodies. These data, some of the first on bats from this region, demonstrate the complex temporal patterns structuring bat assemblages in arid and semiarid biomes. Our results hold promise both in understanding bat behavioral ecology and in long-term monitoring efforts.
Au(I)/Au(III) redox catalysis, also known as redox gold catalysis, has evolved as a new technique in the past decade, opening up possibilities for the cross-coupling and 1,2-difunctioalization reactions of C–C multiple bonds that were previously inaccessible with gold(I) or gold(III) catalysis. However, the enantioselective Au(I)/Au(III) redox catalysis was missing until recently. The research group of Patil and Shi independently developed new hemilabile chiral (P,N)-ligands to achieve enantioselective redox gold catalysis for the first time.
The evolution of high-capacity and higher-power lithium-ion batteries with longer battery life, quick charging rate, and low self-discharge rate is a significant achievement in enhancing the performance of Electric Vehicles (EVs). However, overheating is always an issue, just as it is with other known energy sources. As a result, effective battery thermal management system (BTMS) for lithium-ion battery packs is critical for reducing the overheating and thereby prolonging the cycle life of lithium-ion batteries and enhancing the performance of Electric Vehicles. Cooling systems play a major part in keeping the battery cool through heat extraction and maintaining a consistent temperature. In this paper, a detailed analysis of effectiveness of three fluids: Water, Therminol VP-1, and Ethylene glycol towards thermal management of prismatic lithium ion battery is studied on a modelled battery pack consisting of five unit cells in which each unit cell comprises of one cooling fin made up of the materialistic properties of aluminium in between two prismatic battery and the following conclusions was derived from the study: i) The inlet flow rate under optimised condition for ethylene glycol, Therminol VP-1 & water was found to be 3.25 cm^3/s, 5.5 cm^3/s & 2.25 cm^3/s respectively, ii)The residence time of the heat transfer fluid in the cooling fin plate channels was found to be only in the range of few seconds, iii) Temperature difference of 2 K was found within the batteries. The temperature difference between distinct batteries through the y-axis was less than the temperature difference within an individual battery on the xz-plane & iv) Water is more efficient in cooling the prismatic batteries followed by ethylene glycol. Therminol VP-1 was found to be least efficient in cooling the prismatic batteries.
A giant clam shell (Tridacna maxima) collected from the lagoon of Minicoy Island in the southern Lakshadweep Archipelago, India, was used for a high-resolution stable isotope (δ¹⁸O, δ¹³C) analysis. The results reveal a cyclic pattern in δ¹⁸Oshell values, interpreted as combined signatures of seasonal temperature and δ¹⁸Osw fluctuations over the period from 2004 to 2014. These δ¹⁸Oshell cycles are characterized by a slight background scatter governed by rainfall events leading to short-term and limited freshening of the water in the partly restricted lagoon. The most striking features of the isotope data are exceptionally negative outliers in δ¹⁸Oshell values beginning in mid-2010. This first anomalous isotope excursion is followed by a phase of lowered growth rates lasting until the beginning of 2011. It is observed that this sudden change in oxygen isotope composition and shell precipitation was caused by anomalous sea surface warming, which was previously documented for the region in 2010 and caused widespread coral bleaching throughout the Lakshadweep Archipelago. Even though several other negative excursions in δ¹⁸Oshell values follow, the cyclicity in the isotope signal and the growth rates become again more regular in the distal part of the shell, indicating a gradual recovery of the bivalve after the initial thermal stress event. The results reveal that even short high-temperature events can significantly perturb the biology of giant clams and require long recovery phases. This information is particularly significant for conservation efforts for this endangered bivalve group in a world with ongoing global warming.
We use surface soil moisture content as a proxy to assess the effect of drainage congestion due to structural barriers on the alluvial Fan of the Kosi River on the Himalayan Foreland. We used Sentinel-1 satellite images to evaluate the spatial distribution of soil moisture in the proximity of structural barriers (i.e., road network). We applied modified Dubois and a fully connected feed-forward artificial neural network (FC-FF-ANN) models to estimate soil moisture. We observed that the FC-FF-ANN predicts soil moisture more accurately (R = 0.85, RMSE = 0.05 m3/m3, and bias = 0) as compared to the modified Dubois model. Therefore, we have used the soil moisture from the FC-FF-ANN model for further analysis. We identified the road network that traverses on the Kosi Fan horizontally, vertically, and with inclination. We create a buffer of 1 km along either side of the road. Within this, we assessed the spatial distribution of soil moisture. We observed a high concentration of soil moisture near the structural barrier, and decreases gradually as we move farther in either direction across the orientation of the road. The impact of structural barriers on the spatial distribution of soil moisture is prominent in a range between 300 to 750 m within the road buffer. This study is a step towards assessing the effect of structural interventions on drainage congestion and flood inundation.
We report the isotopic composition of the surface water and groundwater of the Kosi River fan on the Himalayan Foreland, India. We have collected 65 water samples from surface water (Kosi River (n = 2), streams (n = 9), waterlogging (n = 29), and canal (n = 4)), and groundwater (n = 21) for δ¹⁸O and δ²H analysis during December 2019. We obtained groundwater level data measured at the observation wells from the Central Groundwater Board, India, for 1996 and 2017. The groundwater level varies from 1.0 to 8.1 m below ground level (bgl) and from 0.5 to 9.0 m bgl during 1996 and 2017, respectively. We have used water table fluctuation approach to estimate the recharge rate. The recharge rate in the Kosi Fan varies from 0.7 to 21.4 mm/year from 1996 to 2017. Further, we have used δ¹⁸O and δ²H values of water samples to identify the source and the interaction between surface water and groundwater. The δ¹⁸O value of groundwater shows a wide variation (from −9.3‰ to −5.6‰) compared to the surface water, i.e., streams (−7.8‰ to −6.4‰) and canals (−6.9‰ to −6.0‰), suggesting mixing in groundwater during recharge processes. Furthermore, we have used a two-component mixing model to assess the fraction contribution from streams and precipitation to groundwater. The estimated fraction contribution from stream water to groundwater ranges from 45 to 83%. We also suggest higher recharge is limited up to the depth of 6 m bgl. We suggest precipitation and surface water actively recharge groundwater. We conclude that marked spatial variation in the isotopic composition of groundwater is mainly due to the local recharge sources and interaction between surface water and groundwater.
In this work, we have synthesized Carbon Dots (CDs) through a single-step microwave-assisted method. The synthesized colloi- dal CDs have narrow size distribution and show excellent optical properties as well as biocompatibility. Folic acid was selected as a carbon precursor to introduce intrinsic folate receptor targeting capabilities of CDs and to achieve high water dispersibility. CDs were characterized by a series of spectroscopic and microscopic techniques followed by anti- cancer drug Doxorubicin (Dox) conjugation for potential drug release applications. In near-physiological conditions, the drug loading and the release of Dox were investigated in detail. CDs- Dox conjugates are sensitive towards pH and showed efficient drug release as monitored kinetically by fluorescence. Further, live-cell fluorescence imaging using confocal microscopy establishes the pH-responsiveness of drug release mechanism and cellular uptake mediated by folate receptors. We believe that such biocompatible nanocomposite will be beneficial in cancer treatment.
The slowly decaying viral dynamics, even after 2–3 weeks from diagnosis, is one of the characteristics of COVID-19 infection that is still unexplored in theoretical and experimental studies. This long-lived characteristic of viral infections in the framework of inherent variations or noise present at the cellular level is often overlooked. Therefore, in this work, we aim to understand the effect of these variations by proposing a stochastic non-Markovian model that not only captures the coupled dynamics between the immune cells and the virus but also enables the study of the effect of fluctuations. Numerical simulations of our model reveal that the long-range temporal correlations in fluctuations dictate the long-lived dynamics of a viral infection and, in turn, also affect the rates of immune response. Furthermore, predictions of our model system are in agreement with the experimental viral load data of COVID-19 patients from various countries.
Transition metal catalysis has contributed immensely to C-C bond formation reactions over the last few decades, and alkylation is no exception. The superiority of such methodologies over traditional alkylation is evident from minimal reaction steps, shorter reaction times, and atom economy while also allowing control over regio- and stereo-selectivity. In particular, hydrocarbonation of alkenes has grabbed increased attention due its fundamental ability to effectively and selectively synthesise a wide range of industrially and pharmaceutically relevant moieties. This review attempts to provide a scientific viewpoint and a systematic analysis of the recent developments in transition-metal-catalyzed alkylation of various C-H bonds using simple and activated olefins. The key features and mechanistic studies involved in these transformations are described briefly.
A concise catalytic asymmetric approach to naturally occurring Amaryllidaceae alkaloids sharing 5,10b-ethanophenanthridine skeleton, (-)-oxomaritidine (1c), (-)-dihydromaritidine (1d), (-)-maritidine (1a), and (-)-epi-maritidine (1e) has been envisioned. The key intermediate of this strategy has been realized via a Pd(0)-catalyzed decarboxylative allylation (DcA) of an 2-arylcyclohexanone derived allylenolcarbonate (87% yield with 96% ee).
This study demonstrated the influence of downscaling using the regional climate model (RCM) driven by Era-Interim reanalysis (EIN) in simulating different aspects of the Indian summer monsoon (ISM). It is also examined, whether increasing the horizontal resolution of RCM will inevitably be capable of adding more information to ISM characteristics and its spatio-temporal variability. In this regard, two RCM (at 50 km: Reg50 and 25 km: Reg25) simulations were conducted for six years from 2000 to 2005 for the South Asia Coordinated Regional Downscaling Experiment (CORDEX) domain. The added value (AV) is found to be strongly dependent on region and considered metrics. A slight improvement towards increasing spatial resolution is observed in the simulation of the mean ISM characteristics, while considerable improvements are noticed for the frequency distribution of extremes. The notable improvement in the daily climatology of precipitation is observed over the region of northeast India (~ 35%) and the Hilly region (~ 32%) and the lowest improvement over north-central India (~ 8%). The reduction of anomalously strong northeasterly flow over the southeastern Arabian Sea and strengthening of the moisture leaden southeasterly wind flow from the Bay of Bengal in Reg25 compared to Reg50 is consistent with the reduction of dry bias over India in Reg25. The robust improvements are noticed for the heavy precipitation events (probability density function: PDF tails) and mean precipitation due to extreme precipitation events, particularly over the areas characterized by complex topographical features (e.g., the Western Ghats, Indo-Gangetic plains, and northeast India and Hilly regions) as well as over the areas having substantial bias (e.g., central India), indicating its strong sensitivity towards model resolution. The increasing latent heat flux in Reg25 contributes to increasing the moisture and hence rainfall over India. Both simulations apparently simulate many of the ISM characteristics better than the EIN, thereby emphasizing the usefulness of finer resolutions in the better simulation of the Indian monsoon, especially for heavy rainfall. However, the RegCM bias is comparable to or even greater in some places than the EIN bias. This suggests that high-resolution models are important for improving performance; however, it does not necessarily mean that they can have AV for every aspect and all places. Apart from this, the substantial difference in the AV over different regions or aspects highlights the importance of carefully selecting AV matrices for the different areas and characteristics being investigated. RegCM exhibits some systematic biases in precipitation despite substantial improvement due to misrepresentation of dynamical and thermodynamical processes, including northward and eastward propagating convective bands.
In complex oxides, electrons under the influence of competing energetics determine the coexistence or phase-separation of two or more electronic or magnetic phases within the same structural configuration. Probing the growth and evolution of such phase-coexistence state is crucial to determine the correct mechanism of related phase transition. Here, we demonstrate the combination of terahertz (THz) time-domain spectroscopy and DC transport as a strategy to probe the electronic phase-coexistence. This is demonstrated in disorder-controlled phase-separated rare-earth nickelate thin films, which exhibit a temperature induced metal-insulator transition in DC conductivity but lack this transition in THz dynamic conductivity. Such pronounced disparity exploits two extreme attributes, namely, the large sensitivity of THz radiation to a spatial range of the order of its wavelength-compatible electronic inhomogeneities, and its insensitivity to a range beyond the size of its wavelength. This feature is generic in nature, depending solely on the size of insulating and metallic clusters. Therefore, our strategy offers a high-sensitivity methodology to investigate electronic phase-coexistence and phase transition in a wide range of complex material systems.
We use massive spinor helicity formalism to study scattering amplitudes in \mathcal{N}=2^* 𝒩 = 2 * super-Yang-Mills theory in four dimensions. We compute the amplitudes at an arbitrary point in the Coulomb branch of this theory. We compute amplitudes using projection from \mathcal{N}=4 𝒩 = 4 theory and write three point amplitudes in a convenient form using special kinematics. We then compute four point amplitudes by carrying out massive BCFW shift of the amplitudes. We find some of the shifted amplitudes have a pole at z=\infty z = ∞ . Taking the residue at z=\infty z = ∞ into account ensures little group covariance of the final result.
Standalone structures with periodic surface undulations or ripples can be spontaneously created upon flowing a liquid metal, e.g., Ga, over a metallic film, e.g., Pt, Au, etc., through a complex “wetting-reaction”-driven process. Due to the ability of 3-dimensional patterning at the small length scale in a single step, the liquid metal “ripple” flow is a promising non-conventional patterning technique. Herein, we examine the effect of a few process parameters, such as distance away from the liquid reservoir, size of the liquid reservoir, and the geometry, thickness, and width of substrate metal film, on the nature of the ripple flow to produce finer patterns with feature sizes of ≤ 2 µm. The height and the pitch of the pattern decrease with distance from the liquid reservoir and decrease in the reservoir volume. Furthermore, a decrease in the thickness and width of the substrate film also leads to a decrease in the height and pitch of the ripples. Finally, the application of an external electric field also controls the ripple patterns. By optimizing various parameters, standalone ripple structures of Ga with height and pitch of ≤ 500 nm are created. As potential applications, the ripple patterns with micro-and nano-scopic features are used to produce a diffraction grating and a die for micro-stamping.
Transparent conducting materials are inevitable in the fast-developing optoelectronic and photovoltaic industries. Correlated metals are emerging classes of materials that possess a charge density comparable to the metals in which the correlation effects provide transparency. So, understanding the fundamental physics of these materials is equally important to improve the performance of devices. We have investigated the low energy and non-equilibrium dynamics of the CaVO 3 (CVO) thin film using terahertz time-domain and time-resolved terahertz spectroscopic measurements. Though the electrical resistivity of the CVO thin film shows a Fermi liquid-like signature, the terahertz conductivity dynamics unveil the presence of metal-insulator transition. Furthermore, the mass renormalization effects indicate the competition between electron correlations and phonon interactions in driving the ground state of this system. It is clear that the relaxation of photo-excited carriers is through electron–phonon thermalization, and comprehensive studies show the metallic nature of the system with electron correlations. Thus, the extracted optical and electrical parameters of CVO are comparable with the existing transparent conducting materials and, hence, make this system another potential candidate for transparent electronics.
Quantum error correction has recently been shown to benefit greatly from specific physical encodings of the code qubits. In particular, several researchers have considered the individual code qubits being encoded with the continuous variable GottesmanKitaev-Preskill (GKP) code, and then imposed an outer discrete-variable code such as the surface code on these GKP qubits. Under such a concatenation scheme, the analog information from the inner GKP error correction improves the noise threshold of the outer code. However, the surface code has vanishing rate and demands a lot of resources with growing distance. In this work, we concatenate the GKP code with generic quantum low-density parity-check (QLDPC) codes and demonstrate a natural way to exploit the GKP analog information in iterative decoding algorithms. We first show the noise thresholds for two lifted product QLDPC code families, and then show the improvements of noise thresholds when the iterative decoder – a hardware-friendly min-sum algorithm (MSA) – utilizes the GKP analog information. We also show that, when the GKP analog information is combined with a sequential update schedule for MSA, the scheme surpasses the well-known CSS Hamming bound for these code families. Furthermore, we observe that the GKP analog information helps the iterative decoder in escaping harmful trapping sets in the Tanner graph of the QLDPC code, thereby eliminating or significantly lowering the error floor of the logical error rate curves. Finally, we discuss new fundamental and practical questions that arise from this work on channel capacity under GKP analog information, and on improving decoder design and analysis.
Nature has beautifully assembled its light harvesting pigments within protein scaffolds, which ensures a very high energy transfer. Designing a highly efficient artificial bioinspired light harvesting system (LHS) thus requires the nanoscale spatial orientation and electronic control of the associated chromophores. Although DNA has been used as a scaffold to organize chromophores, proteins or polypeptides, however, are very rarely explored. Here, we have developed a highly efficient, artificial, bioinspired LHS using polypeptide (poly-d-lysine, PDL) nanostructures making use of their β-sheet structure in an aqueous alkaline medium. The chromophores used herein are compatible for an energy transfer process and are nonfluorescent in an aqueous medium but exhibit high fluorescence intensity when bound to the nanostructure of PDL. The close proximity of the chromophores results in an energy transfer efficiency of ∼92% besides generating white light emission at a particular molar ratio between the chromophores.
Understanding the chirality of molecular reaction pathways is essential for a broad range of fundamental and applied sciences. However, the current ability to probe chirality on the time scale of primary processes underlying chemical reactions remains very limited. Here, we demonstrate time-resolved photoelectron circular dichroism (TRPECD) with ultrashort circularly polarized vacuum-ultraviolet (VUV) pulses from a tabletop source. We demonstrate the capabilities of VUV-TRPECD by resolving the chirality changes in time during the photodissociation of atomic iodine from two chiral molecules. We identify several general key features of TRPECD, which include the ability to probe dynamical chirality along the complete photochemical reaction path, the sensitivity to the local chirality of the evolving scattering potential, and the influence of electron scattering off dissociating photofragments. Our results are interpreted by comparison with high-level ab-initio calculations of transient PECDs from molecular photoionization calculations. Our experimental and theoretical techniques define a general approach to femtochirality.
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1,757 members
Sebastian Wuester
  • Department of Physics
Jeyaraman Sankar
  • Department of Chemistry
Navjeet Ahalawat
  • Department of Chemistry
Kumar Gaurav
  • Department of Earth and Environmental Sciences
Sankar Chakma
  • Department of Chemical Engineering
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Prof Siva Umapathy
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