Mapana Journal of Sciences

Thermal convection of a Oldroyd-B nanofluid with magnetic effect: Linear and weakly nonlinear analyses

2025-07-04T07:14:55+00:00

Onset of convection in a horizontal layer with Oldroyd-B nanofluid investigated. The normal mode technique has been employed to work out the non dimensional governing equations and this leads to eigenvalue problem. The analytical expressions of stationary and oscillatory Rayleigh numbers are obtained. Critical values of Rayleigh number for
the prescribed values of other parameters are obtained. Amplitude equation is derived in weakly nonlinear analysis.

Spectrophotometric Investigations of Charge Transfer Complexes formed between Imidazoles and DMAD

2025-08-01T10:19:40+00:00

Four novel charge transfer (CT) complexes were synthesized between imidazole-based donors and dimethyl acetylenedicarboxylate (DMAD) as the electron acceptor, in dichloromethane and acetone at room temperature. The formation of CT complexes was confirmed by characteristic n → π* and π → π* electronic transitions in the UV-Vis spectra. Stoichiometric analysis using Job's method revealed 1:1 and 2:1 donor–acceptor ratios for imidazole and N-methylimidazole, respectively. Among the synthesized complexes, those involving N-methylimidazole exhibited the highest formation constants (K_CT), molar extinction coefficients (ε), and negative Gibbs free energy changes (ΔG⁰), indicating spontaneous and stable complexation. Additionally, the lowest CT transition energies (E_CT) in dichloromethane confirmed stronger donor–acceptor interactions in this less polar solvent.

To further validate donor strength, DFT calculations were performed at the B3LYP/6-31+G(d) level. N-methylimidazole exhibited the highest HOMO energy, lowest HOMO–LUMO energy gap (ΔE), and the most favorable global reactivity descriptors—chemical softness and chemical potential—affirming its better electron-donating ability.

An accelerating flat universe with an inverse square variation of the equation of state parameter with scale factor.

2025-08-02T04:35:10+00:00

The omega parameter in the equation of state of the cosmic fluid that varies inversely as the square of the scale factor is a possibility to explain the evolution of our flat universe, presently expanding with an increasing acceleration under the negative pressure of dark energy. The model is an attempt to demonstrate the shift of the universe from a phase of decelerating expansion rate to an acceleration using a simple equation of state consistent with the cosmological observations by introducing an effective omega parameter in the equation of state for the cosmic fluid which comprises of radiation, matter and dark energy.

INTERCONNECTING PERCEPTION AND INTENTIONAL UNDERSTANDING VIA MIRROR NEURONS

2025-08-13T04:44:40+00:00

Typically, when an observer witnesses an action being performed by an agent, their Mirror Neuron System initiates a motor simulation of that action. It has been argued that mirror neurons and the cortical areas of the action observation network (AON) enable our capacity to comprehend activities at these levels. The empirical evidence for this suggested role is scant but according to existing theories, the visual brain of primates is split into two functionally separate networks. The dorsal route calculates an object's position and any activities associated with it, while the ventral pathway computes an object's identity. The ventral route employs semantic retrieval and selection to forecast the likely intentions and objectives associated with observed behaviors. Encoding of the representation of the needed action for accomplishing the expected goal happens throughout this procedure. In this two-route paradigm, mirror neurons encode this concrete representation of the event, which serves as a precedent to forecast the sensory effects of this action through the dorsal AON pathway. Although still popular, the two visual pathways concept needs to be updated. This review gives an idea about mirror neurons and discusses their role in action observation network.

Synthesis of nano materials and study of the effect of Shock waves on their nano composites

2025-08-08T09:11:39+00:00

Abstract: Vanadium Carbide-Carbon Shells nano material was synthesized using hydrothermal method with the help of several steps and also, nano alpha-aluminium oxide was synthesized using solid combustion synthesis process. Preparation of aluminium oxide/vanadium carbide-carbon shells composite was done through as aluminium oxide reinforced with 5 wt. % vanadium carbide-carbon shells. Test samples were prepared with the help of die. Samples were sintered and the pre-sintered samples were then sintered in a microwave furnace. From the SEM images of aluminium oxide, a platelet like structure was observed and for vanadium carbide-carbon shell, they were appears to a shell-like structure encapsulating small nanoparticles. The XRD pattern of α-aluminium oxide was shown the sharp peak which indicates that the nano material was crystalline and pattern of vanadium carbide-carbon shells was shown semi crystalline nature. Shockwaves of the magnitude of 8 bar and 700 K was produced and impacted on the surface of the specimen held at the driven end. T

Theoretical approach to study the electroclinic effect very near to the Smectic C* –Smectic A* transition point of FLC molecules

2025-08-04T07:36:25+00:00

We propose a theoretical approach considering Landau type free energy expansion in order to understand the electroclinic effect appearing very close to the transition region between Smectic-C* to Smectic-A* phases. A new secondary order parameter is considered, and expressing it as the fluctuations of the applied field very close to the transition point, the capacitive nature of the system is addressed successfully at this very region. More over we have been able to show that the modulated Smectic-C* phase may be considered to be responsible for the origination of the electroclinic behavior.