Vidyasagar University

In this article, a Leslie-Gower prey-predator model that incorporates cooperation among the predator populations during hunting and a refuge mechanism for the prey are proposed and then analyzed. Additionally, a strong Allee effect in prey growth is included to address both biological and mathematical considerations. Initially, the topological equivalence method is employed to discuss the dynamical behavior of the system in the neighborhood of the origin. Subsequently, the existence and stability of the model's non-negative equilibria are examined. We identify parameter subsets where the system exhibits co dimension-one local bifurcations, specifically saddle-node and Hopf bifurcations, and demonstrate the presence of bistability. The first Lyapunov number is calculated to determine the stability of limit cycles that emerge from the Hopf bifurcation. Using Sotomayor's theorem, we derive the existence of a saddle-node bifurcation in the system. Furthermore, we analyze the influence of hunting cooperation on the model both analytically and numerically, revealing that hunting cooperation not only reduces the density of the prey population, but also destabilizes the system's dynamics. We also investigate the impact of refuge on the model numerically, finding that refuge stabilizes the system's dynamics.

Perovskite nanocrystals (PNCs) have emerged as promising materials for photocatalytic applications due to their superior optoelectronic properties. Nevertheless, a detailed understanding of charge carrier separation and interfacial charge transfer remains dynamics are crucial for optimizing their photocatalytic and photovoltaic performance. In this work, the charge-transfer dynamics between MA0.5Cs0.5PbBr3 nanocrystals and 8-aminoquinoline (AQ) were investigated using steady-state and time-resolved photoluminescence spectroscopy. Femtosecond photoluminescence upconversion measurements revealed ultrafast hot-carrier cooling with a rate 1.89 × 1012 s-1, indicating rapid relaxation of photogenerated carriers to the band edge. Energy-level analysis demonstrates that hole transfer from photoexcited PNCs to AQ is the dominant quenching pathway. The quenching mechanism involves two distinct processes: an ultrafast hot-hole transfer occurring on the picosecond timescale for AQ molecules located in the immediate vicinity of the nanocrystal surface, and a slower band-edge hole transfer mediated by diffusion-controlled interactions with AQ molecules distributed farther from the surface on the nanosecond timescale. The hot and band edge hole transfer rate, estimated from the time resolved PL measurements 1.23×1012s-1 and 2.3×1010 s-1 respectively. Furthermore, the photoluminescence quantum yield (PLQY) of the PNC–AQ system shows a strong dependence on excitation wavelength and quencher concentration. To predict the PLQY at any given excitation and AQ concentration, machine learning-based soft computing techniques, including fuzzy logic, artificial neural networks (ANNs), and adaptive neuro-fuzzy inference systems (ANFIS), were employed. Among these approaches, ANFIS provided the best predictive performance, closely reproducing the experimentally measured PLQY values.

This study investigates the dynamic connectedness between modern investment assets (MIAs) and stock markets to determine whether the inclusion of MIAs enhances portfolio risk diversification. The study employs a TVP-VAR model to analyze the connectedness between MIAs and stock markets over the period 2020 to 2024, and calculates spillovers, hedge ratios, and portfolio weights. The findings indicate moderate static connectedness, with dynamic spillovers fluctuating over time, reflecting the impact of geopolitical tensions on markets. The US and German stock markets, along with ETF markets, act as net transmitters of spillovers, whereas Japanese, Chinese, and Indian stock markets act as net recipients of spillovers. DeFi, cryptocurrency, and green bond markets exhibit time-varying behavior but remain mostly net recipients. The portfolio analysis confirms that MIAs offer diversification benefits, though effective risk management requires asset-specific hedging strategies. Specifically, DeFi and cryptocurrency markets require different approaches than ETFs and green bonds.

Currently toxicological research in Silver nanoparticle is a leading issue in medical science. The surface chemistry and physical dimensions of silver nanoparticles (Ag-NPs) play an important role in toxicity. The aim of this present study was to evaluate the in vitro and in vivo toxicity of Ag-NPs as well as the alteration of toxicity profile due to surface functionalization (PEG and BSA) and the intracellular signaling pathways involved in nanoparticles mediated oxidative stress and apoptosis in vitro and in vivo system. Ag-NPs released excess Ag+ ions leads to activation of NADPH oxidase and helps in generating the reactive oxygen species (ROS). Silver nanoparticles elicit the production of excess amount of ROS results activation of TNF-α. Ag-NPs activates caspase-3 and 9 which are the signature of mitochondrial pathway. Ag-NPs are responsible to decrease the antioxidant enzymes and imbalance the oxidative status into the cells but functionalization with BSA and PEG helps to protect the adverse effect of Ag-NPs on the cells. This study suggested that Ag-NPs are toxic to normal cells which directly lead with human health. Surface functionalization may open the gateway for further use of Ag-NPs in different area such as antimicrobial and anticancer therapy, industrial use or in biomedical sciences.

A thermostable α-amylase gene (Amyk4) from Bacillus licheniformis k4cm (or similar thermophilic Bacillus), isolated from a Himalayan hot spring in Sikkim, India, was successfully cloned and expressed in Escherichia coli BL21(DE3). The purified recombinant α-amylase (Amyk4) exhibited maximal activity (153.2 ± 1.05 U/mL) at 80 °C and pH 6.0, with a half-life of 30.39 h and enhanced stability in the presence of Ca²⁺, indicating its suitability for high-temperature industrial applications. The cotton fabric desizing was optimized using Response Surface Methodology (Box–Behnken design). Optimal conditions (pH 6.9, 80 °C, enzyme dosage of 190 U/g, and treatment time of 95 min) achieved a TEGEWA rating of 8 and a weight loss of 6.6