Indian Institute Of Science Education and Research, Thiruvananthapuram

• Thiruvananthapuram, Kerala, India
Recent publications
The emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants made emerging novel coronavirus diseases (COVID-19) pandemic/endemic/or both more severe and difficult to manage due to increased worry about the efficacy and efficiency of present preventative, therapeutic, and sensing measures. To deal with these unexpected circumstances, the development of novel nano-systems with tuneable optical, electrical, magnetic, and morphological properties can lead to novel research needed for (1) COVID-19 infection (anti-microbial systems against SARS-CoV-2), (2) early detection of mutated SARS-CoV-2, and (3) targeted delivery of therapeutics using nano-systems, i.e., nanomedicine. However, there is a knowledge gap in understanding all these nano-biotechnology potentials for managing mutated SARS-CoV-2 on a single platform. To bring up the aspects of nanotechnology to tackle SARS-CoV-2 variants related COVID-19 pandemic, this article emphasizes improvements in the high-performance of nano-systems to combat SARS-CoV-2 strains/variants with a goal of managing COVID-19 infection via trapping, eradication, detection/sensing, and treatment of virus. The potential of state-of-the-art nano-assisted approaches has been demonstrated as an efficient drug delivery systems, viral disinfectants, vaccine productive cargos, anti-viral activity, and biosensors suitable for point-of-care (POC) diagnostics. Furthermore, the process linked with the efficacy of nanosystems to neutralize and eliminate SARS-CoV-2 is extensively highligthed in this report. The challenges and opportunities associated with managing COVID-19 using nanotechnology as part of regulations are also well-covered. The outcomes of this review will help researchers to design, investigate, and develop an appropriate nano system to manage COVID-19 infection, with a focus on the detection and eradication of SARS-CoV-2 and its variants. This article is unique in that it discusses every aspect of high-performance nanotechnology for ideal COVID pandemic management.
Anti-microbial resistance (AMR) has recently emerged as an area of high interest owing to the rapid surge of AMR phenotypes. Metal oxide NPs (MeONPs) have been identified as novel phytomedicine and have recently peaked a lot of interest due to their potential applications in combating phytopathogens, besides enhancing plant growth and yields. Numerous MeONPs (Ti2O, MgO, CuO, Ag2O, SiO2, ZnO, and CaO) have been synthesized and tested to validate their antimicrobial roles without causing toxicity to the cells. This review discusses the application of the MeONPs with special emphasis on anti-microbial activities in agriculture and enlists how cellular toxicity caused through reactive oxygen species (ROS) production affects plant growth, morphology, and viability. This review further highlights the two-facet role of silver and copper oxide NPs including their anti-microbial applications and toxicities. Furthermore, the factor modulating nanotoxicity and immunomodulation for cytokine production has also been discussed. Thus, this article will not only provide the researchers with the potential bottlenecks but also emphasizes a comprehensive outline of breakthroughs in the applicability of MeONPs in agriculture.
Delaminating cells undergo complex, precisely regulated changes in cell–cell adhesion, motility, polarity, invasiveness, and other cellular properties. Delamination occurs during development and in pathogenic conditions such as cancer metastasis. We analyzed the requirements for epithelial delamination in Drosophila ovary border cells, which detach from the structured epithelial layer and begin to migrate collectively. We used live imaging to examine cellular dynamics, particularly epithelial cells’ acquisition of motility and invasiveness, in delamination-defective mutants during the time period in which delamination occurs in the wild-type ovary. We found that border cells in slow border cells (slbo), a delamination-defective mutant, lacked invasive cellular protrusions but acquired basic cellular motility, while JAK/STAT-inhibited border cells lost both invasiveness and motility. Our results indicate that invasiveness and motility, which are cooperatively required for delamination, are regulated independently. Our reconstruction experiments also showed that motility is not a prerequisite for acquiring invasiveness.
We report a comprehensive study of the static susceptibility, high-field magnetization and high-frequency/high-magnetic field electron spin resonance (HF-ESR) spectroscopy of polycrystalline samples of the bismuth cobalt oxyphosphate BiCoPO5. This compound features a peculiar spin system that can be considered as antiferromagnetic (AFM) chains built of pairs of ferromagnetically coupled Co spins and interconnected in all three spatial directions. It was previously shown that BiCoPO5 orders antiferromagnetically at TN≈10K and this order can be continuously suppressed by magnetic field towards the critical value μ0Hc≈15 T. In our experiments we find strongly enhanced magnetic moments and spectroscopic g factors as compared to the expected spin-only values, suggesting a strong contribution of orbital magnetism for the Co2+ ions. This is quantitatively confirmed by ab initio quantum chemical calculations. Within the AFM ordered phase, we observe a distinct field-induced magnetic phase transition. Its critical field rises to ∼6 T at T≪TN. The HF-ESR spectra recorded at T≪TN are very rich comprising up to six resonance modes possibly of the multimagnonic nature that soften towards the critical region around 6 T. Interestingly, we find that the Co moments are not yet fully polarized at Hc which supports a theoretical proposal identifying Hc as the quantum critical point for the transition of the spin system in BiCoPO5 to the quantum disordered state at stronger fields.
In this paper, the problem of reconstruction of signals in mixed Lebesgue spaces from their random average samples has been studied. Probabilistic sampling inequalities for certain subsets of shift-invariant spaces have been derived. It is shown that the probabilities increase to one when the sample size increases. Further, explicit reconstruction formulae for signals in these subsets have been obtained for which the numerical simulations have also been performed.
Phage Tail Like bacteriocins (PTLBs) has been an area of interest in the last couple of years owing to their varied application against multi-drug resistant (MDR), anti-microbial resistant (AMR) pathogens and their evolutionary link with the dsDNA virus and bacteriophages. PTLBs are defective phages derived from Myoviridae and Sipho-viridae phages, PTLBs are distinguished into R-type (Rigid type) characterized by a non-flexible contractile nanotube resembling Myoviridae phage contractile tails, and F-type (Flexible type) with a flexible non-contractile rod-like structure similar to Siphoviridae phages. In this review, we have discussed the structural association, mechanism, and characterization of PTLBs. Moreover, we have elucidated the symbiotic biological function and application of PTLBs against MDR and XDR pathogens and highlighted the evolutionary role of PTLBs. The difficulties that must be overcome to implement PTLBs clinically are also discussed. It is imperative that these issues be addressed by academics in future studies before being implemented in clinical settings. This article is novel in its way as it will not only provide us with a gateway that acts as a novel strategy for scholars to mitigate and control the uprising issue of AMR pathogens but also promote the development of clinical studies for PTLBs.
In this paper, we investigate a problem of Halmos on various generalizations of the numerical range. We generalize a finite-dimensional result of Gau, Li and Wu, by showing that for k∈N, the closure of the rank-k numerical range of a contraction T acting on a separable Hilbert space H is the intersection of the closure of the rank-k numerical ranges of all unitary dilations of T to H⊕H. The same is true for k=∞ provided the rank-∞ numerical range of T is non-empty. We also show that when both defect indices of a contraction are equal and finite (=N), one may restrict the intersection to a smaller family consisting of all unitary N-dilations. We also investigate this problem in the matricial range and the C-numerical range. We obtain a few interesting results and conclude the answers in negative.
Transformation chemistry has advanced significantly in recent years as an excellent methodology for synthesizing new nanoclusters and functionalizing the existing ones. However, rational synthesis and fundamental understanding of the structural evolution among clusters have not yet been achieved in nanocluster science. A deeper understanding of the fundamental aspects of structure-property correlation is necessary for the employment of befitting nanoclusters for specific applications. Very recently, the transformation of nanoclusters without the use of conventional co-reactants has been brought to light. These co-reactant-less transformations are triggered by various conditions, such as pH, solvent, light, temperature, etc. In this perspective, we discuss how this unique method of transformation without any co-reactant benefits the basic understanding of growth patterns and the corresponding property evolution in nanoclusters.
Excited state aromaticity is a stimulating area of research, widely used as a probe to describe and rationalize many photochemical phenomena. Herein we review some of the recent findings of unprecedented aromatic stabilization in spin singlet excimer and through‐space aromatic character in triplet excimers of a series of linear [n]acenes, as paramount examples of polycyclic aromatic hydrocarbons (PAHs). This review also provides insights on the aromatic stabilization profile of singlet benzene excimer formation, which can be related to antiaromaticity alleviation of the molecular (localized) S1 through exciton delocalization. The theoretical investigation of excimer stabilization using magnetic, electronic, and geometric aromatic indices manifested the presence of through‐space ring current in triplet cofacial excimers. The antiaromaticity of the sandwich (D6h) spin singlet and triplet benzene excimers were also investigated by decomposing the excimer wave function as a linear combination of local exciton (LE) and charge transfer (CT) diabats and by identifying the contribution of these terms to the nucleus independent chemical shift (NICS) of the two six‐membered rings. These results provide a detailed description of the unique (anti)aromatic properties in PAH excimers, establishing strong connection between this important chemical concept and the electronic structure intricacies of excimers.
Primary and secondary interactions form the basis of substrate activation in Lewis-acid mediated catalysis, with most substrate activations occurring at the secondary binding site. We explore two series of antimony cations, [(NMe2CH2C6H4)(mesityl)Sb]+ (A) and [(NMe2C6H4)(mesityl)Sb]+ (B), by coordinating ligands with varying nucleophilicity at the position trans to the N-donor. The decreased nucleophilicity of the incoming ligands leads to reversal from a primary bond to a secondary interaction in A, whereas a constrained N-coordination in B diminishes the border between primary and secondary bonding. Investigations on carbonyl olefin metathesis reactions and carbonyl reduction demonstrate increased reactivity of a Lewis acid when the substrate activation occurs at the primary binding site.
Human papillomavirus (HPV) contributes to sexually transmitted infection, which is primarily associated with pre-cancerous and cancerous lesions in both men and women and is among the neglected cancerous infections in the world. At global level, two-, four-, and nine-valent pure L1 protein encompassed vaccines in targeting high-risk HPV strains using recombinant DNA technology are available. Therapeutic vaccines are produced by early and late oncoproteins that impart superior cell immunity to preventive vaccines that are under investigation. In the current review, we have not only discussed the clinical significance and importance of both preventive and therapeutic vaccines but also highlighted their dosage and mode of administration. This review is novel in its way and will pave the way for researchers to address the challenges posed by HPV-based vaccines at the present time.
We report an adaptive energy‐compensated synthetic aperture focusing technique (eC‐SAFT) for improving the imaging performance of photoacoustic microscopy (PAM) in terms of depth of field (DOF), spatial resolution (both axial and lateral), and SNR. In addition to coherency and time‐delay (in conventional SAFT), our beamforming‐based reconstruction algorithm takes into account acoustic energy loss ‐ a primary physical parameter in acoustic wave propagation ‐ following Beer‐Lambert's law. Experimental validation studies were performed in tissue‐mimicking (Agar) phantoms, complex leaf veins, and chicken breast tissues. Results demonstrate that our proposed eC‐SAFT+CF outperforms conventional SAFT+CF to improve axial resolution (up to ∼ 5%), lateral resolution (up to ∼ 5 %), SNR (up to ∼ 6%) and CR (up to ∼ 8%). This article is protected by copyright. All rights reserved.
Brain‐inspired artificial neural networks and neuromorphic computing are taking space to a new height based on solid‐state memristor devices. Despite considerable progress already made, the use of lead‐free double perovskite materials with direct bandgap can be recognized as a significant paradigm shift in this field. Here, growth, thin film deposition, and analog electroforming‐free resistive switching property along with promising artificial synaptic and neural activities of lead‐free layered cesium copper antimony chloride (Cs4CuSb2Cl12 or CCAC) double perovskite nanocrystals are reported. Optical and structural characterizations of CCAC microcrystals (MCs) and nanocrystals (NCs) confirm the growth, the existence of direct bandgap, and <111> oriented monoclinic crystal phase of space group C2/m. Interestingly, both the MCs and NCs display an almost equal bandgap of 1.1 eV in thin film even though they have higher bandgaps of 1.3 and 2.2 eV in dispersion, respectively. However, devices of NC thin film exhibit superior memristor behavior along with emulation of various synaptic and neural activities due to having less number of defects. Finally, the analog modulation of synaptic weight using CCAC memristor, in terms of postsynaptic currents, during potentiation and depression represents a significant achievement toward hardware implementation of neural networks and neuromorphic computing. Thin film of a direct bandgap lead‐free cesium copper antimony chloride (Cs4CuSb2Cl12) layered double perovskite nanocrystal is utilized to demonstrate robust electroforming‐free analog resistive switching, which is also capable of emulating various synaptic functionalities and neural activities. This work stimulates further research opportunities to use lead‐free perovskite nanomaterials toward hardware implementation of neural networks and neuromorphic computing.
Investigation into the photoinduced processes of 3-mercaptopyran-4-one is carried out using trajectory-based surface hopping simulations. Excitation into the near-degenerate higher singlet excited states reveals rapid internal conversion (IC) into S1 on a sub-50 fs timescale. Excited-state intramolecular proton transfer (ESIPT) also takes place simultaneously with IC. We observe that following tautomerization, the molecule has multiple relaxation pathways. A channel exists for it to nonradiatively decay into the tautomer ground-state or undergo rapid intersystem crossing (ISC) into the close-lying higher triplet state, which ultimately decays into T1. The simulations show that ISC is significantly enhanced after ESIPT, which is studied by tracking the changes in energy gaps and associated spin-orbit coupling elements.
To acquire the atomic design of new functional Ag(I) clusters, a new synthetic approach of site-specific alloying has been unveiled, by which the neutral CO2 templated Ag20 core is confined...
We have developed Brønsted base-mediated regioselective allenylation and propargylation of various para-quinone methides using unfunctionalized 2-alkynyl azaarenes as pronucleophiles. The appropriate choice of a base provides an opportunity to achieve either an allenylated product or the propargylated product. The use of KOtBu as a Brønsted base promotes the formation of allenylated products, whereas NaN(SiMe3)2 furnishes the propargylated products. Besides, the current strategy is scalable and can be performed on a gram scale.
The ability to see colour at night is known only from a handful of animals. First discovered in the elephant hawk moth Deilephila elpenor , nocturnal colour vision is now known from two other species of hawk moths, a single species of carpenter bee, a nocturnal gecko and two species of anurans. The reason for this rarity—particularly in vertebrates—is the immense challenge of achieving a sufficient visual signal-to-noise ratio to support colour discrimination in dim light. Although no less challenging for nocturnal insects, unique optical and neural adaptations permit reliable colour vision and colour constancy even in starlight. Using the well-studied Deilephila elpenor , we describe the visual light environment at night, the visual challenges that this environment imposes and the adaptations that have evolved to overcome them. We also explain the advantages of colour vision for nocturnal insects and its usefulness in discriminating night-opening flowers. Colour vision is probably widespread in nocturnal insects, particularly pollinators, where it is likely crucial for nocturnal pollination. This relatively poorly understood but vital ecosystem service is threatened from increasingly abundant and spectrally abnormal sources of anthropogenic light pollution, which can disrupt colour vision and thus the discrimination and pollination of flowers. This article is part of the theme issue ‘Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods’.
Feedhorn- and orthomode transducer- (OMT) coupled transition edge sensor (TES) bolometers have been designed and micro-fabricated to meet the optical specifications of the LiteBIRD high frequency telescope (HFT) focal plane. We discuss the design and optical characterization of two LiteBIRD HFT detector types: dual-polarization, dual-frequency-band pixels with 195/280 GHz and 235/337 GHz band centers. Results show well-matched passbands between orthogonal polarization channels and frequency centers within 3% of the design values. The optical efficiency of each frequency channel is conservatively reported to be within the range 0.64-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$-$$\end{document}0.72, determined from the response to a cryogenic, temperature-controlled thermal source. These values are in good agreement with expectations and either exceed or are within 10% of the values used in the LiteBIRD sensitivity forecast. Lastly, we report a measurement of loss in Nb/SiNx\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_x$$\end{document}/Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature.
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• School of Physics (SoP)
• School of Biology
• School of Chemistry
• School of Biology
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Address
Maruthamala P. O, Vithura, 695551, Thiruvananthapuram, Kerala, India
Head of institution
Prof . J. N. Moorthy
Website
http://www.iisertvm.ac.in/