We experimentally demonstrate a mode-locked erbium-doped fiber laser (MLEDFL) employing lead phthalocyanine (PbPc) as a saturable absorber (SA). The PbPc-based SA was fabricated through a simple and cost-effective solution-processing approach, in which PbPc powder was incorporated into a polyvinyl alcohol host matrix to form a thin film. The resulting PbPc–PVA SA exhibited a modulation depth of 3.7
Ba0.2 [Na0.5 Bi0.5]0.8Sn0.2Ti0.8O3 (BTSn – 0.8NBT) ceramics was fabricated using the solid-state reaction technique. Its crystal structure was investigated by means of X-ray diffraction (XRD), and Raman spectroscopy, while impedance spectroscopy was used to study their electrical properties. At room temperature, XRD pattern revealed a perovskite phase with a rhombohedral structure (R3c space group). Raman-spectroscopy analyses were used investigate the fundamental phase transitions of Ba0.2[Na0.5Bi0.5]0.8Sn0.2Ti0.8O3. Complex impedance spectroscopy, carried out over 10 000Hz–1MHz and 773–833 K, demonstrated two semicircles in the plots, reflecting relaxation processes from both the grains and the grain boundaries. These relaxation behaviors were further examined using electrical modulus data. Direct and alternating current conductivity measurements (DC and AC) indicated that electrical conduction is thermally activated. Furthermore, in order to elucidate conduction mechanisms within different regions, the temperature dependence of the frequency exponent (s) was investigated. The findings revealed that conduction is controlled by a non-overlapping small polaron tunneling (NSPT) mechanism.
The Kelvin–Helmholtz instability (KHI) is fundamentally a velocity-shear–driven instability that occurs in neutral fluids as well as in magnetized plasmas. In dusty (complex) plasmas, it plays an important role in explaining a wide range of astrophysical and laboratory phenomena. The effect of dust polarization and ion-beam dynamics on KHI in a magnetized dusty plasma is studied using a linear fluid model. The plasma consists of electrons, ions, charged dust grains, and an ion-beam propagating along an external magnetic field. The polarization force, dust charge fluctuation, and beam dynamics have been incorporated into the dispersion relation. Dust polarization modifies KHI by introducing additional electrostatic restoring forces, thereby changing the instability threshold, and the growth rate in dusty plasmas. The dust polarization tends to reduce the real frequency and suppress the instability growth rate, particularly in the long-wavelength regime. In contrast, an increase in ion-beam density and velocity enhances the growth rate of Instability through stronger beam–plasma interaction. Increasing ion beam density (from 2 × 109 cm−3 − 5 × 109 cm−3) and beam velocity (from 5.5 × 105 cm/s − 7 × 105 cm/s) corresponds to an increase in energy from (6 eV–10 eV) which enhances the growth rate of the Kelvin–Helmholtz Instability (KHI) through Cerenkov interaction.
Unlike previous studies on neuronal networks that assume a constant membrane capacitance, this investigation considers the robust nature of membrane in managing ion exchanges through ion-gated channels. Experimental and theoretical studies have shown that membrane capacitance may depend on the transmembrane voltage due to membrane deformation, charge redistribution, among other physiological effects. Motivated by these observations, we extend the magnetized FitzHugh-Nagumo neural network by incorporating a voltage-dependent membrane capacitance. Consequently, we employ the discrete multiple-scale expansion method to obtain a nonlinear differential difference equation from a magnetized FitzHugh-Nagumo system with nonlinear membrane capacitance. The dynamic interplay between the capacitive-feedback parameter and magnetic coupling reveals new stable and unstable regions for plane-wave solutions, in the neuronal network via modulational-instability (MI) analysis. Analytical and numerical results consistently show localized nerve-impulse profiles, whose amplitudes depend on the nonlinear membrane capacitance. Our proposed neural model therefore provides a biophysical mechanism for pulse sharpening, excitability regulation and amplitude control, strongly suggesting that nonlinear membrane capacitance may contribute to improved metabolic efficiency during the generation and transmission of action potentials.
In this work, the nonlinear dynamics of granular (dust)-acoustic waves (GAWs) in a dusty plasma with a non-ideal granular component are investigated within a three-dimensional hydrodynamic framework governed by the Dieterici equation of state. Using the standard reductive perturbation method, a three-dimensional nonlinear Schrödinger equation (3D-NLSE) is derived to describe the evolution of weakly nonlinear wave packets. Modulational instability and bifurcation analyses are performed to determine the conditions governing stable and unstable wave propagation. The results demonstrate that the Dieterici non-ideal parameters significantly modify the nonlinear and dispersive coefficients of the 3D-NLSE, thereby shifting the modulational-instability threshold and regulating the formation of coherent nonlinear structures. Exact envelope-soliton, dromion, and second-order rational rogue-wave solutions are obtained using Hirota’s bilinear method combined with the method of separation of variables. Increasing the attractive-interaction parameter enhances nonlinear self-focusing, resulting in higher rogue-wave amplitudes and stronger localization of dromion and rogue-wave structures. In contrast, increasing the excluded-volume parameter suppresses nonlinear amplification and reduces the corresponding localization. Thus, the attractive-interaction and excluded-volume parameters produce distinct and competing effects on multidimensional nonlinear wave dynamics by respectively strengthening and weakening the nonlinear response relative to dispersion. These findings demonstrate that non-ideal granular thermodynamics provides an effective mechanism for regulating coherent nonlinear structures in strongly coupled dusty plasmas, with potential relevance to laboratory, space, and astrophysical plasma environments.
