Indian Institute of Technology Guwahati

This review highlights important research on anion coordination chemistry for materials applications over the last decade. This field has numerous applications in various areas, such as the environment, industry, and medicine. Despite its enormous potential, real‐world applicability is still pending. However, there has been a new trajectory in the field recently, with rapid advancement in designing sophisticated molecular systems for various materials applications. To keep track of this dynamic advancement, we have discussed some outstanding research work with enormous potential for materials applications soon.

We report a detailed study on the composition (x) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr2O4) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetry Fd-3m was noticed for all the compositions in the range 0 ⩽ x⩽ 1 of Ni(Cr1−xMnx)2O4. However, there is significant alteration in the bond angles ∠B–O–B (90.51°-93.86°) and ∠A–O–B (122.48°–124.90°) (both of which follow completely opposite trend with increasing x) and bond lengths A–O (1.82–1.94 Å) and B–O (2.02–2.08 Å). The corresponding lattice parameter (a) follows Vegard’s law (8.32 ± 0.001 Å ⩽ a ⩽ 8.45 ± 0.001Å). The electronic structure determined from the x-ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin–orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ =8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)A[(Cr1−xMnx)2]BO4 obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (EG) semiconducting nature in which EG varies from 1.16 to 2.40 eV within the range of x = 0.85–0. Such variation of EG (x) is consistent with the compositional variation of the crystal structure data with anomalous change between x = 0.25 and 0.6. Beyond this range, the Eg mode (140 cm⁻¹) in Raman spectra arising from Mn–O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature, TFN due to the unequal magnetic moments of the cations. However, both the ordering temperature TFN and saturation magnetization (MS) increases progressively from 73.3 K (1500 emu mol⁻¹) to 116 K (3600 emu mol⁻¹) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (HK~4.5 kOe, K1~2.5 × 10⁴ erg cc⁻¹) shows an opposite trend with x. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trend JBB > JAB > JAA, (JBB/kB =13.36 K).

Perovskites, both natural and synthetic, form a large class of materials are a vast class of materials with significant technological relevance due to their remarkable physical properties, such as superconductivity, magnetoresistance, ionic conductivity, and diverse dielectric behaviors. In this study, the dielectric relaxation and transport properties of the double perovskite Dy2CoMnO6(DCMO) synthesized via high-energy ball milling are investigated. DCMO exhibits a notably large dielectric constant, attributed to a combination of intrinsic and extrinsic mechanisms. Frequency-dependent dielectric studies reveal non-Debye-like behavior, validated by augmented Havriliak-Negami function fitting. Impedance spectroscopy confirms the semiconducting nature of DCMO, showing a negative temperature coefficient of resistance, and identifies two distinct relaxation processes corresponding to grain boundaries and grain interiors thereby highlighting the impact of microstructure and defects. The Cole-Cole plot further supports the non-Debye behavior, while thermally activated relaxation suggests damped charge carrier dynamics at grain boundaries. Conduction analysis using augmented Jonscher's power law reveals non-overlapping small polaron tunneling as the dominant mechanism driving both the dielectric response and transport properties, with DC conductivity suggesting a three-dimensional variable range hopping model. These results provide significant insights into the dielectric and transport properties of DCMO, highlighting its promising potential for advanced electronic applications.

The application of biochar, a thermochemically converted blackish biomass, is considered an economical and efficient strategy for the remediation of nickel (Ni²⁺) and manganese (Mn²⁺) ions from watery matrix to mitigate environmental contamination and safeguard public health. A wide variety of techniques, ranging from laboratory to industrial scale, have been developed to produce biochar. However, in rural areas of developing countries, biomass is typically used for cooking without being charred. The strategies for producing biochar on a small scale for farmers have not advanced significantly. In this current study, a scraped 200-L oil drum is modified to fabricate a drum kiln setup for producing biochar from areca nut husk (AH), a locally available agro-residue of Northeast India. The prepared areca nut husk biochar (AHB) was further evaluated for adsorptive removal of Ni²⁺ and Mn²⁺ from water. AHB reaches the equilibrium time at 150 min and 180 min for Ni²⁺ and Mn²⁺, respectively. The experimental data has shown a good fit for the pseudo-second-order kinetic model and Freundlich isotherm model for both metals, revealing a chemisorption-driven monolayer adsorption mechanism. The presence of oxygen-containing functional groups on the AHB surface required for chemisorption was confirmed by different spectroscopy methods. AHB could be regarded as an effective adsorbent for the rapid elimination of heavy metals from water, and the biochar production strategy using a drum kiln has been demonstrated to be the simplest and most effective method for achieving self-sustainability.

The evolution of infrastructural development demands using innovative and eco-friendly materials in construction. The net-zero of carbon emission and waste management are booming areas of research. This pivotal work involves reducing decarbonisation by reducing clinker usage and waste management by replacing slag with fine aggregate. The metakaolin of 7, 9, 11, and 13% of weight are investigated as cement replacement. Supplementary Cementitious Material (SCM) concludes that metakaolin of 11% (M3 mix) performs better in mechanical strength. In the M3 mix, the crushed sand (C-sand) is replaced by Ferrochrome slag sand (FeCr-Sg) of 25, 30, 35, 40, and 45% weight. The compressive strength and UPV of the MFS4 mix (40% of FeCr-Sg) are superior at room temperature. The Core temperature of M0, M3, and MFS4 mix is subjected to heat for 2 h at 150◦C, 300◦C, 450◦C and 600◦C respectively. The strength, water absorption and UPV of MFS4 mix at room temperature perform better. The relative mass loss at 600◦C in MFS4 is 93.2%. The MFS4 mix attains a dense microstructure, zero crack surface texture and better passing of pulse velocity rather than M0 and M3 at 600◦C. Metakaolin with FeCr-Sg was effective in enhancing mechanical, durability and thermal properties in both ambient and elevated temperature matrix.

In recent years, additively manufactured metallic scaffolds have generated significant interest among researchers working in the field of bone tissue engineering and orthopaedic implants. Although such intricate, porous architectures are promising as bone substitutes, they need to be thoroughly tested for structural robustness as well as their capacity for bony integration. In this present work, we introduced and preclinically evaluated the biomechanical viability of Weaire-Phelan (WP) Ti-alloy scaffolds as bone replacement components. Two distinct groups of WP scaffolds, namely WPA and WPD, of varying porosities were examined for comparative assessment. Finite element (FE) analysis, computational fluid dynamics (CFD) and uniaxial compression tests were performed on 3D printed as-built scaffolds to comprehensively evaluate the structural, hemodynamic, fatigue and morphometric properties of the two groups. The mechanical performances of the WP scaffolds of 70%, 80% 90% porous group (relative density 0.3 and lower) were found to accord with the natural trabecular bone tissue. However, WPA scaffolds demonstrated slightly superior mechanical performances as compared to WPD scaffolds (22%– 63% greater compressive modulus depending on the porosity). On the other hand, WPD scaffolds showed improved hemodynamic properties thereby implying enhanced osteogenic potential. Moreover, the range of effective elastic moduli corresponding to the WP scaffolds was found to be in good agreement with that of the natural bone tissue. As such, these designs were categorized based on their suitability at different anatomical sites. The overall performance metrics of the WP scaffolds underscore its potential for improved osseointegration, structural conformities and greater capacity for customization with enhanced manufacturability.

Wireless energy transfer (WET) is a promising method to extend the operation time of sensors in energy-constrained wireless networks. Specially, for the low-power applications such as the Internet-of-Things (IoT) and machine-to-machine communications, most of the existing works have so far focused on using fixed-frequency waveforms for WET. In this paper, we investigate the potential of superposed chirp waveforms for downlink (DL) WET from a multi-antenna access point (AP) to a group of sensors over orthogonal subbands while satisfying the peak power constraint. To this end, we first propose the general design of superposed chirp waveforms and establish key properties required to optimize WET. We derive novel closed-form analytical expressions using order statistics for average received energy based on DL WET via superposed chirps and via fixed-frequency waveforms over subbands selected independently for each sensor based on their estimated channel gain, and evaluate average harvested energy (HE) considering both linear and nonlinear energy harvesting models. For both superposed chirps and fixed-frequency based DL-WET, we then derive max-min optimal power control coefficients in closed-form to ensure that the sensors placed at different distances from the AP receive the same amount of energy. As a benchmark, we present the corresponding analysis considering perfect channel knowledge. Through our analytical and numerical results, for the considered setup, we prove and elucidate that superposed chirp-based WET over select subbands and under max-min power control provides an improvement of 40% in average HE performance as compared to multisine waveforms consisting of a set of fixed-frequency cosine signals, and extends the operating range of energy transfer by about 17.5% over fixed-frequency waveforms.

We derive new upper bounds on outage probability (OP) and spectral efficiency (SE) for a simultaneous wireless information and energy transfer system under spatial correlation and optimal phase configuration at intelligent reflecting surface (IRS) when users are served based on round-robin (RR) scheduling, share common source to IRS links and adopt nonlinear energy harvesting. Diversity order for this system is characterized. We then extend our study to a multi-antenna source and analyze OP and SE under random and equal phase shift configurations at IRS. We design beamformers at the source and at IRS under different strategies, namely RR scheduling and simultaneous service with and without signal-to-interference-plus-noise ratio (SINR) constraint. Numerical results are presented to validate the accuracy of our statistical modeling and mathematical analysis and quantify the gain in performance relative to random and equal phase shifts. We illustrate that higher number of users can be served by increasing number of IRS elements while keeping OP fixed. We identify the operational regime where RR scheduling yields better performance than serving users simultaneously without SINR constraint. We show that increasing IRS elements can help maintain target harvested power even under stricter SINR constraint. Impact of estimation error on performance is illustrated.

Intelligent reflecting surface (IRS) has recently emerged as a promising technology for beyond fifth-generation (B5G) networks conceived from metamaterials that smartly tunes the signal reflections via a large number of low-cost passive reflecting elements. However, the IRS-assisted communication model and the optimization of available resources needs to be improved further for more efficient communications. This paper investigates the enhancement of received power in an IRS-assisted wireless communication by jointly optimizing the phase shifts at the IRS elements and its location. Employing the conventional Friss transmission model, the relationship between the transmitted power and reflected power is established. The expression of the received power incorporates the free space loss, reflection loss factor, physical dimension of the IRS panel, and radiation pattern of the transmit signal. Also, the expression of reflection coefficient of IRS panel is obtained by exploiting the existing data of radar communications. Initially exploring a single IRS element within a two-ray reflection model, we extend it to a more complex multi-ray reflection model with multiple IRS elements in 3D Cartesian space. The expression of the received power in both the cases is derived in a more tractable form, and then, it is maximized by jointly optimizing the underlying variables, i.e., the IRS location and the phase shifts. Further, the optimization of resources are investigated in active IRS, multiple access, and joint active and passive beamforming. Numerical insights and performance comparison reveal that joint optimization leads to a substantial 37% enhancement in received power compared to the closest competitive benchmark.

Seeds are the building blocks of food security, and their free exchange amongst the farming community has formed the bedrock for maintaining genetic diversity in addition to food security and sovereignty. The appropriation of production, exchange, and marketing of seeds by the corporate over the past decades has altered the agricultural scene in the Global South. Given the conflicting perspectives, mandates, and practices of multiple stakeholders, this article attempts to critically evaluate seed policies in India considering the cultural, economic, and social undertones that characterise them. From the perspective of the sociology of science, this article attempts to trace the shifts in the decline of the ‘rural,’ erosion of national agriculture, policy gaps, and why values matter in India’s development narratives vis-à-vis science and technology solutions. Further, this article investigates, through a case study of Vrihi Community Seed Bank (CSB), ¹ located in the eastern state of Odisha, how CSBs are progressively being seen as a possible long-term solution to combat the diverse challenges posed by changing agro-climatic conditions, increasing corporatisation, and industrialisation of agricultural and allied practices of food production.

This paper addresses the attitude stabilization problem of unmanned aerial vehicles (UAVs) like quadrotors with uncertain inertia, external disturbances, and actuator faults simultaneously in predefined time. The adaptive predefined-time sliding mode control (SMC) incorporated with a radial basis function neural network (RBFNN) is designed to track the desired trajectory and estimate the uncertainty of the system effectively to enhance the control performance. The proposed control strategy utilizes the sliding manifold, which ensures state convergence in a predefined time. The settling time of the presented control scheme can be arbitrarily chosen in advance compared to the traditional fixed-time and finite-time control strategies. The boundedness of the complete system is verified using Lyapunov stability theory. Finally, comparative results are presented to demonstrate the effectiveness of the proposed control scheme.

Mission-critical Internet of Things (MC-IoT) applications span from the industrial field to the battlefield and from smart homes to healthcare. Reliability is one of the stringent requirements of such applications. Routing in low-power and Lossy Networks (RPL) is a standard routing protocol traditionally used in IoT applications. Unlike the traditional single-path-based RPL, the reliable multi-path RPL (RMP-RPL) selects k parents for each transmitting node to achieve the hard reliability requirement in MC-IoT applications. However, the RMP-RPL fails to achieve the reliability requirement when the number of source nodes and traffic rate increases. In this paper, a multi-path game theoretic congestion control (GTMP-RPL) approach is proposed on top of the RMP-RPL to reduce congestion at the parent nodes of any child. In case of congestion at any one of the selected k parents, its child node replaces the congested parent by a non-congested parent with minimum rank from the set of remaining nodes. The rank of a node is calculated based on the Data Packet Drop Ratio (DPDR), Expected Transmission Count (ETX), and Node Mobility (NM) of that node. If no non-congested parent is available for that child node, a non-cooperative game is played among siblings to adjust their data transmission rates based on congestion occurrence at the parent, energy spent by the child, and parent connectivity of the child node. The solution obtained for the proposed game, using the Lagrange multiplier and Karush–Kuhn–Tucker (KKT) conditions, is used to reduce congestion at the parent node. The proposed scheme is validated using the cooja simulator in Contiki OS. Simulation results show that GTMP-RPL achieves a 99% packet delivery ratio for at most 50 source nodes with a traffic rate of 30 pkts/min present in a random topology of 101 nodes. In addition, it outperforms the other benchmark schemes by a significant margin to achieve hard reliability.

Calibration transfer techniques aim to standardize secondary instruments to a primary instrument, enabling the utilization of the primary instrument’s calibration model with minimal additional experiments. While widely employed in spectroscopic datasets, their application in environmental sensors and sensor arrays is less common despite the pressing need due to issues like sensor batch variability and time drift. This study assesses 10 calibration transfer techniques on three experimental gas sensor datasets that have a small number of transfer standards. Model-based (linear regression) and model-free (K-nearest-neighbour) calibration methods are also compared. Results unexpectedly show that, despite the reduced data availability, direct recalibration of the secondary sensor (eg. without transfer) may be sufficient for the secondary sensor to reach the same performance as the primary one. In the other cases, Partial-Least-Square Standardization and Direct Standardization are the most robust transfer methods across the use cases, and they can outperform direct recalibration. Other methods, such as Single Sensor Standardization, Mean Correction, Principal Component Standardization, and Procrustes Transform, have consistently lower performance in this small data context.

This letter describes the development and characterization of an optical fiber humidity sensor employing intensity modulation via evanescent wave (EW) absorption technique. For the development of the sensor, humidity-sensitive SiO ₂ -coated ZnO nanoparticle doped PVA film was synthesized over the centrally decladded plastic cladding silica (PCS) fiber. In order to achieve optimal response, rigorous experimental investigations were conducted by varying the film thickness and composition. The optimized sensing probe demonstrated a linear response over 45.5-94.4% RH, with a linear sensitivity of 0.0137RH ^-1 (47.6mV/%RH). The response and recovery times were observed to be 1s and 1.25s during humidification and dehumidification, respectively. Additionally, the proposed sensor demonstrates a very high degree of repeatability, reversibility, and stability.

A novel design strategy for the development of FBG based all optical, temperature insensitive tilt sensor is proposed. Response characteristics of the proposed sensor is theoretical analyzed and experimentally established. An excellent sensitivity of 0.0415 nm/°, that can be further tuned to the desired value, along with remarkable accuracy of ±0.024°, extremely low maximum discrepancy of ±0.001 nm and an angular resolution of 0.012° are observed for the sensor. Sensor is also characterized with high degree of reversibility, reliability and repeatability.

The main objective of the present research is to develop an optical fiber relative humidity (RH) sensor having ultrahigh sensitivity, linear response over a wide dynamic range, and optimum response/recovery times while utilizing the simple optical fiber sensing configuration. The proposed sensor, developed to achieve these objectives, exploits the phenomena of intensity modulation via evanescent wave (EW) absorption in the sensing region, which is designed by employing TiO ₂ -GO nanocomposite doped silica sol-gel nanostructured thin sensing film onto a short centrally decladded region of a plastic-clad silica (PCS) fiber. Detailed experimental investigations are carried out to analyze the response characteristics of the proposed sensor. The developed sensor is characterized by a significantly enhanced sensitivity of 0.0094 RH ^-1 while responding linearly over a large dynamic range of 9%−92%RH. In addition, the sensor exhibits a high degree of reversibility, repeatability, reliability, and fast response and recovery time.

Industry 5.0 refers to the next-generation industrial revolution, where significantly more industrial things such as production machines, industrial robots, and uncrewed vehicles will be easily connected with advent technologies like the Industrial Internet of Things (IIoT), blockchain, 6G communication, and distributed edge-cloud. Despite these technological advancements, current industries still face several issues related to human-centric design, data interoperability, sustainability and standardized design. To deal with these issues and to promote Industry 5.0 revolution, the necessity of Zero-Touch Network Management (ZTNM) techniques in industries is inevitable. Therefore, this work presents a novel ZTNM-enabled Industry 5.0 architecture and validates its importance using two industrial use-case scenarios. Furthermore, we discuss several ZTNM-supported technologies, potential challenges and possible solutions for upcoming Industry 5.0 automation.

Research on induced pluripotent stem cells (iPSCs) has a broad impact on basic biology and biomedical applications, ranging from disease modeling to drug screening to personalized medicine. In addition, the recent advances in genome editing technologies have made the human genome amenable to experimental genetics. This is either via the introduction of de novo mutations in healthy iPSCs to investigate their biological role and thereby model disease in a culture dish or via the correction of inherent mutations in patient-specific iPSC lines for cell transplantation. Owing to these multifaceted applications, various studies have reported the generation of iPSCs from adult stem cells and specialized cells using integration-based and integration-free approaches. iPSCs generated using integration-based methods have limited applications since they carry an enormous risk of permanent genomic modifications. To obviate this, integration-free reprogramming techniques are established that have minimal or no genomic modifications to derive clinical-grade cells. This chapter provides an overview that primarily focuses on the generation of iPSCs using safe, integration-free reprogramming approaches such as transducible versions of the stem cell-specific recombinant proteins and small molecules employed in our lab. In addition, research in our lab focuses on the differentiation of these integration-free iPSCs into cardiomyocytes and β-cells, prospectively for the treatment of cardiovascular diseases and diabetes mellitus (DM), respectively. In addition, the applications of CRISPR-Cas technology to understand the role of the gene of interest in iPSC generation, self-renewal, and pluripotency are also an integral part of our research objectives. Thus, iPSCs and their differentiated derivatives can be used for biobanking, disease modeling, drug screening, cell therapy, and tissue engineering applications.

To ascertain upon the ideal configuration of physico-mechanical qualities, efficient processing techniques, and network stability of the prepared bio-composite films in real-world applications, the polymeric materials shall be subjected to a careful manipulation. Such bio-composite films have outstanding combinations of biocompatibility and toxicity-associated safety qualities. Such research interventions will be beneficial for the packaging, pharmaceutical, and biomedical industries that wish to target and adopt them for commercial applications. In this article, three alternate organic acids, i.e., citric acid (CA), tartaric acid (TA), and malic acid (MA), are blended separately into polyvinyl alcohol (PVA)-starch (St)-glycerol (Gl) composite films and for the targeted purpose of enhanced crosslinking, plasticizing, and antibacterial capability of the polymer network. The organic acid-based bio-composite polymeric films were assessed in terms of swelling index (SI), in vitro degradation, tensile strength (TS), percentage elongation (%E), antibacterial activity, and cytotoxicity attributes. Among these, the MA-based PVA composite films outperformed the CA-based PVA composite film in terms of absorbency (SI 739.29%), mechanical strength (TS 4.88 MPa), and elasticity (%E 103.68%). Furthermore, following a 24-h incubation period, the MA-based films exhibited the highest proliferative effect of 215.59% for the HEK cells. In conclusion, the MA has been inferred to be the most relevant organic acid for the desired optimality of film composition, physical and biological properties, and cost.

Bicyclic diaziridines are important heterocyclic scaffolds, which can be cleaved into 1,3‐zwiterionic species to serve as a versatile precursor in fabricating biologically important N‐hetero‐ and spiro‐cyclic structural frameworks. Owing to their staple architecture, inherent ring strain and ease of synthesis, considerable advancements have been made by employing bicyclic diaziridines towards the construction of heterocyclic systems of biological importance. A significant surge with appreciable efforts in the adoption of such strategies has led to their implementation by the synthetic chemists. This article focuses on the developments in ring expansion of bicyclic diaziridines employed in N‐heterocycle synthesis.