Indian Institute of Technology Gandhinagar

• Gandhinagar, Gujarat, India
Recent publications
We obtain a three-parameter q-series identity that generalizes two results of Chan and Mao. By specializing our identity, we derive new results of combinatorial significance in connection with N(r,s,m,n), a function counting certain overpartition pairs recently introduced by Bringmann, Lovejoy and Osburn. For example, one of our identities gives a closed-form evaluation of a double series in terms of Chebyshev polynomials of the second kind, thereby resulting in an analogue of Euler's pentagonal number theorem. Other applications include expressing a multi-sum involving N(r,s,m,n) in terms of the partition function p(n) and relating a certain double series to a weight 7/2 theta series.
Understanding the groundwater-surface water interactions and groundwater recharge mechanism is paramount in the arid and semi-arid region which covers nearly 1/3rd of the continental area globally and depends on groundwater to sustain the ecology and livelihood of the people. One such region is semi-arid western India. This study uses seasonal isotopic (δ¹⁸O and d-excess) differences to study groundwater dynamics in semi-arid western India, in conjunction with the isotopic composition of India Summer Monsoon (ISM) to understand the rainfall - groundwater relationship, variation in recharge characteristics and quantification of groundwater recharge by rain. Some of the Important results of this study are (1) Temporal variation in the isotopic composition of shallow groundwater reveals that only ∼47% of the area is recharged by ISM rainfall; (2) Isotopic enrichment in post-monsoon season in certain regions (∼25%) indicates that deep static non-replenishable groundwater is extracted for irrigation which finds its way into shallower aquifers; (3) ∼25% (0.52 Billion Cubic Meters) of the available dynamic groundwater resource in South Gujarat is lost as submarine groundwater discharges into the Arabian Sea; (4) Groundwater in the coastal area near the Gulf of Kachchh is recharged by hypersaline waters from salt pan.
Ribes nigrum, commonly known as blackcurrants, is an economically important species and considered a super fruit due to its immense health-promoting properties. The temperate hardy perennial shrub with dark purple-colored berries grows indigenously in Europe, Central Asia, and the Himalayas. Blackcurrants are widely used in medicines and food industries for its significant levels of polyphenols, flavonoids, anthocyanins, organic acids, and vitamin C. The species has depicted a range of pharmacological actions including antitumor, antioxidant, anti-diabetic, antiinflammatory, antimicrobial activities. R. nigrum vasomodulatory, cardiovascular and immunomodulatory effects have been proven through several clinical researches. The plant is widely used in the commercial production of juice, jam, wines, beverages, and nutritive value products in food industries. The present chapter highlights the phytochemical, nutraceutical importance of blackcurrants, pharmacological and pharmacokinetic studies, factors affecting the nutritional value and commercial production of blackcurrants, case studies of available product formulations along with encountered challenges and future recommendations.
Neural signatures for the western classification of emotions have been widely discussed in the literature. The ancient Indian treatise on performing arts known as Natyashastra categorizes emotions into nine classes, known as Rasa s. Rasa —as opposed to a pure emotion—is defined as a superposition of certain transitory, dominant, and temperamental emotional states. Although Rasa s have been widely discussed in the text, dedicated brain imaging studies have not been conducted in their research. Our study examines the neural oscillations, recorded through electroencephalography (EEG) imaging, that are elicited while experiencing emotional states corresponding to Rasa s. We identify differences among them using network-based functional connectivity metrics in five different frequency bands. Further, Random Forest models are trained on the extracted network features, and we present our findings based on classifier predictions. We observe slow (delta) and fast brain waves (beta and gamma) exhibited the maximum discriminating features between Rasa s, whereas alpha and theta bands showed fewer distinguishable pairs. Out of nine Rasa s, Sringaram (love), Bibhatsam (odious), and Bhayanakam (terror) were distinguishable from other Rasa s the most across frequency bands. On the scale of most network metrics, Raudram (rage) and Sringaram are on the extremes, which also resulted in their good classification accuracy of 95%. This is reminiscent of the circumplex model where anger and contentment/happiness are on extremes on the pleasant scale. Interestingly, our results are consistent with the previous studies which highlight the significant role of higher frequency oscillations in the classification of emotions, in contrast to the alpha band that has shows non-significant differences across emotions. This research contributes to one of the first attempts to investigate the neural correlates of Rasa s. Therefore, the results of this study can potentially guide the explorations into the entrainment of brain oscillations between performers and viewers, which can further lead to better performances and viewer experience.
Sterols play a significant role in many physiological processes affecting membrane organization, transport, permeability, and signal transduction. The development of fluorescent sterol analogs that have immediate functional relevance to the natural biomolecules is one approach to understanding the sterol-driven physiological processes. Visualizing cellular compartments with tailor-made fluorescent molecules through specific labeling methods enables organelle targeting and reveals dynamic information. In this review, we focus on the recent literature published between 2020 and 2022, with particular emphasis on extrinsic fluorophores and their investigations of sterol-driven biological processes involving sterol transport, biomolecular interactions, and biological imaging.
Airglow emissions from the thermosphere act as tracers of the behaviour of the upper atmosphere. OI 630 nm nightglow emissions that originate from an altitude of around 250 km in the thermosphere have been investigated using a large field-of-view ground-based optical spectrograph from Mt. Abu (24.6°N, 72.7°E, 19°N Mag.), a low-latitudinal location in India. The latitudinal movement of the crest of the equatorial ionization anomaly (EIA) in both poleward in the evening and equatorward in the night has been reported using the OI 630 nm nightglow emissions. The EIA crest is found to shift away from the equator after the sunset, which has been shown to be directly related to the strength of the twilighttime equatorial electrodynamics. Later in the night, after 20 LT, a clear movement of the crest back towards the equator, known as the reversal of EIA, has been observed. The speeds of the EIA reversals for forty nights in the years 2014 and 2015 have been obtained and are found to be in the range of 10–55 ms⁻¹. As the global equatorial electric fields (E) are irrotational in nature (∇×E=0), simultaneous variations in the daytime electrojet strength over Jicamarca in the American sector have been compared with the nighttime reversal speeds of the EIA over the Indian sector, which show a remarkable relationship with each other. Thus, it is hereby demonstrated that the reversal in EIA as inferred by the OI 630 nm nightglow emissions in our measurements is due to the westward equatorial electric field. It is hereby proposed that the reversal speed derived from optical nightglow measurements can serve as a proxy for the determination of westward electric field over equator for that longitude sector.
The present study investigates concentrated coal ash slurries' rheological and pipe flow characteristics. Our results reveal coal ash slurries' shear thinning flow behavior regardless of solid volume fraction (ϕ) = 0.17–0.6. Rheo-microscopy study explains the thixotropy, yielding where slurry microstructure varies with time and applied shear. Experimental viscosity data fit with Dabak and Yucel model with a maximum coal ash packing fraction (ϕm) = 0.63. The yield stress (τy) determined using the creep test, stress sweep, Herschel-Bulkley model, and oscillatory sweep tests indicate the exponential relationship of τy with ϕ = 0.43–0.6. The head loss (hL) during pipeline transportation of slurries increases with coal ash concentration (ϕ = 0.272–0.349) and slurry velocity (vm = 0.5–3 m/s). hL estimated from the rheological data is comparable with the experimental pipe-loop data with pipe length, L = 12 m, and pipe diameters, D = 25 and 50 mm at higher vm (∼2–3 m/s).
Microscopic fluctuations over sunlit locations on Moon due to dominant photoelectric charging might induce a sufficient fluctuating electric field that can electrostatically detach the overlying charged dust by overcoming surface adhesion and lunar gravity. A formulation based on the dynamical evolution of the statistical variables, viz., the mean charge and the variance, at microscopic scale is established to calculate the local charge and electric field fluctuations and illustrate this effect. The formulation has been coupled with the charged particle dynamics to derive the optimum launch velocity of the dust particles near the surface just after detachment. Fowler's treatment of the photoemission, dominant Extreme Ultraviolet (EUV) Lyman α radiation of the solar spectrum and subsequent collection of the emitted photoelectrons, measured particle size distribution of the regolith sample, and typical solar wind plasma have been consistently accounted for illustrating the concept. Our analysis suggests that the intense fluctuations in the electric field locally detach the submicron-charged particles with a launch velocity of a few ms−1–for instance, the charge fluctuations might induce ∼ 10 Mv/m field that can launch 100 nm particles with a speed of ∼5 ms−1.
One of the biggest challenges limiting the biological applications of fluorescent carbon-based nanoparticles is their capacity to emit in the red region of the spectrum and simultaneously maintaining the smaller size. These two parameters always go in inverse proportion, thus lagging their applications in biological imaging. Endocytic pathways play important roles in regulating major cellular functions such as cellular differentiation. The Spatio-temporal dynamics of endocytic pathways adopted by various ligands (including nanoparticles) over longer durations in cellular differentiation remain unstudied. Here we have used red-emitting fluorescent carbon nanoparticles to study the endocytic pathways in neuronal cells at different stages of differentiation. These small-sized, bright, red-emitting carbon nanoparticles (CNPs) can be internalized by live cells and imaged for extended periods, thus capturing the Spatio-temporal dynamics of endocytic pathways in model SH-SY5Y derived neuroblastoma neurons. We find that these nanoparticles are preferably taken up via clathrin-mediated endocytosis and follow the classical recycling pathways at all the stages of neuronal differentiation. These nanoparticles hold immense potential for their size, composition, surface and fluorescence tunability, thus maximizing their applications in spatio-temporally tracking multiple cellular pathways in cells and tissues simultaneously.
We statistically validated a sample of hot Neptune candidates applying a two-step vetting technique using DAVE and TRICERATOPS. We performed a systematic validation of 250 transit-like events in the Transiting Exoplanet Survey Satellite (TESS) archive in the parameter region defined by P ≤ 4 d and 3 R⊕ ≤ R ≤ 5 R⊕. Through our analysis, we identified 18 hot Neptune-sized candidates, with a false positive probability $< 50\%$. Nine of these planet candidates still need to be confirmed. For each of the nine targets we retrieved the stellar parameters using ARIADNE and derived constraints on the planetary parameters by fitting the lightcurves with the juliet package. Within this sample of nine candidates, we statistically validated (i.e, with false positive probability $< 0.3\%$) two systems (TOI-277 b and TOI-1288 b) by re-processing the candidates with TRICERATOPS along with follow-up observations. These new validated exoplanets expand the known hot Neptunes population and are high-priority targets for future radial velocities follow-up.
We establish the existence of a solution to the following problem: Δ2u−α|∇u|r=μS2(D2u)+λfinΩ,u=0=∂u∂non∂Ω,\begin{equation*}\hskip7pc \def\eqcellsep{&}\begin{array}{ll}\Delta ^2u-\alpha |\nabla u|^r=\mu S_2(D^2 u)+\lambda f & \mbox{in } \Omega , \\[3pt] u=0=\displaystyle \frac{\partial u}{\partial n} &\mbox{on } \partial \Omega , \end{array} \end{equation*}where Ω⊂RN,N=2,3$\Omega \subset {\mathbb {R}}^N,\, N=2,3$, is a smooth and bounded domain and S2(D2u)(x)=∑1≤i<j≤Nλi(x)λj(x)$S_2(D^2 u)(x)=\sum _{1\le i<j\le N}\lambda _i(x)\lambda _j(x)$, where λi(x)=1,2,…N$\lambda _i(x)=1,2,\ldots N$ is the ith eigenvalue of symmetric matrix D2u(x)$D^2 u(x)$. We assume that f∈L1(Ω),α>0,λ>0$f\in L^1(\Omega ),\, \,\alpha >0,\,\lambda >0$ and 0≤μ≤1$0\le \mu \le 1$ are parameters. Moreover, we assume that r≥1$r\ge 1$ if N=2$N=2$ and 1≤r≤6$1\le r\le 6$ if N=3$N=3$. We use variational arguments and an iterative technique to prove our results.
Hydrogels have long been developed for a plethora of applications such as soft electronics, energy storage, the development of actuators, sensors, and, most importantly, biomedical applications. The biomedical applications of hydrogels are the most sought after and highly researched because of the various advantages of hydrogels. Having said that, the practical applications of the hydrogels are still restricted and efforts are being made to introduce other materials that add to the advantages of the hydrogels and impart new and exciting properties to the formed composite. In this regard, 2D materials beyond graphene such as phosphorene, antimonene, and germanene have gained significant attention. These are the newest addition to the existing 2D material family. These materials are highly optically active, which is vital while considering biomedical applications. The biomedical applications include antibacterial activity, chemotherapy, photothermal therapy, wound treatment, drug delivery, tissue engineering, and many more. This review intends to give the readers a brief overview of the trends and advancements in using these beyond graphene 2D material/hydrogel composites for biomedical applications. Graphical abstract
In this paper, we consider an optimal control problem governed by linear parabolic differential equations with memory. Under the assumption that the corresponding linear parabolic differential equation without memory term is approximately controllable, it is shown that the set of approximate controls is nonempty. The problem is first viewed as a constrained optimal control problem, and then it is approximated by an unconstrained problem with a suitable penalty function. The optimal pair of the constrained problem is obtained as the limit of the optimal pair sequence of the unconstrained problem. The result is proved by using the theory of strongly continuous semigroups and the Banach fixed point theorem. The approximation theorems, which guarantee the convergence of the numerical scheme to the optimal pair sequence, are also proved. Finally, we present an algorithm to compute an optimal control with a numerical example.
We report various phase transitions in half-Heusler TbPtBi compound using Density Functional Theory (DFT). Specifically, the inclusion of spin-orbit coupling (SOC) leads to the band inversion resulting in the transition from the metallic to the topological semimetallic phase. However, in the presence of SOC, there is a phase transition from the topological semimetal to trivial semimetal when the material is subjected to compressive strain (<-7%). Subsequently, under the further increase of compressive strain (≥-7%), we find an opening of a direct band gap at the Γ point, driving the system from the trivial semimetallic to semiconducting state with changes in the sequence of the bands. In the absence of SOC, only the transition from the metallic to the semiconducting phase is noticed. Under tensile strain, the TbPtBi compound maintains its phase as in the unstrained condition but with an increase in the hole pocket at the Fermi level, both in the absence and presence of SOC. These tunable phase transitions (especially as a fraction of strain) make this compound very promising for application in various quantum devices such as highly sensitive strain gauges.
Moist heat stress can lead to the inability of the human body to cool itself due to the impact of high temperature and humidity. The co-occurrence of tropical cyclones (TCs) and moist heat stress has considerable implications for India's dense population and infrastructure. However, the crucial linkage between TCs and moist heat extremes remains unrecognized. We used the cyclone eAtlas and ERA5 reanalysis to examine the temporally compounding TC and moist heat extremes over India from 1980 to 2021. We find that TC-Heat stress events in India have increased recently, which can be attributed to the high-intensity TCs originating from the Arabian Sea. The risk of TC-Heat stress events is higher (than in other parts of the world) in India due to an overlap of peak moist heat and TCs occurrence during the pre-monsoon (April-June) season. Landfalling TCs alter the thermodynamic environment causing the moist heat to peak over the region with increased frequency and intensity. The direct and compounded influence of TCs on moist heat can have substantial implications.
The Indian Government has committed to educate 90,000 midwives in accordance with international norms. This goal is critical as midwives provide evidence-based, high-quality midwifery care. There is a need to explore the contextual factors influencing this new midwifery education programme. Hence, the aim of this study is to explore contextual factors influencing the implementation of the national midwifery education programme for midwifery educators and the future Nurse Practitioners in Midwifery (NPMs) in India. A qualitative research design was used, with data collected through focus group discussions (n = 8) with a total of 27 participants representing seven national and international organisations supporting the Indian Government in its midwifery initiative. Transcribed interviews were analysed using content analysis. This study on contextual factors influencing the implementation of the new midwifery education programme in India showed that organisational and administrative processes are complex and the development of midwifery educators and nurse practitioners in midwifery needs to be fast tracked. The education of educators and future midwives in India, and elsewhere in similar settings, could benefit from efforts to simplify the organisational and administration processes and, in parallel, mobilize innovative teaching and learning approaches to bridge theory and practice.
Conventional direction-of-arrival (DOA) estimation algorithms like MUSIC only allow localization of fewer number of sources than the number of physical sensors. In this paper, underdetermined azimuth localization (localizing more sources than the number of sensors) using arbitrary planar arrays has been proposed, using only second-order statistics of the received data. To achieve this, we utilize the difference coarray of the actual array and express the elements of the array covariance matrix as the signal received by the virtual sensors of the coarray. We explore the structure and geometry of the difference coarray of an $N$ -element planar array and show that the coarray can provide an increased degree-of-freedom (DOF) of $\mathcal {O}(N^{2})$ which enables underdetermined localization. Then, we extend the manifold separation (MS) technique to the coarray to expresses the coarray steering matrix in terms of a Vandermonde structured matrix by designing a signal independent coarray characteristic matrix. As the signal model of a coarray is a single snapshot model, the Vandermonde structure enables us to perform a spatial smoothing type operation to restore the rank of the coarray covariance matrix. This allows us to propose a novel subspace-based algorithm, which we call the coarrayMS-MUSIC, to perform underdetermined source localization using arbitrary planar arrays. We have also introduced the polynomial rooting version of our algorithm called the coarrayMS-rootMUSIC. Finally, we have conducted extensive numerical simulations to verify the effectiveness and usefulness of the proposed methods.
In this work, electronic structure of several doped TiO2 anatase systems is computed using DFT+U. Effective masses of charge carriers are also computed to quantify how the dopant atoms perturb the bands of the host anatase material. U is computed systematically for all the dopants using the linear response method rather than using fitting procedures to physically known quantities. A combination of d and f block elements (Nb, Ta, V, Mo, W, Cr, La, Cu, Co and Ce) are considered as dopants. Depending upon the energies of their outer d or f electrons, the dopants are found to form defect states at various positions in the band structure of host anatase system. Some dopants like Cr, Mo etc. form mid-gap states, which could reduce transparency. Other dopants like Nb, Ta and W are found to have the Fermi levels positioned near the conduction band edge, indicating these systems to exhibit n-type conductivity. From the effective mass analysis, dopants are found to increase the effective mass of charge carriers and the non-parabolic nature of bands. Based on electronic structure and effective mass analysis, Nb, Ta and W are identified to exhibit higher transparency and conductivity as compared to the other dopants considered here. The theoretical results presented here, increase our understanding and show the potential of dopants to alter the properties in anatase TiO2.
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