The European Physical Journal Plus最新文献

This study presents a comprehensive analysis of the influence of temperature on bioconvective patterns in an algal suspension, exposed to collimated irradiation from above and heating or cooling from below. The linear stability analysis predicts that the critical bioconvective Rayleigh number is inversely related to the thermal Rayleigh number, suggesting a pronounced destabilization when the system is heated from below, and enhanced stability under cooling conditions. Additionally, the pattern wavelength increases as the thermal Rayleigh number decreases. Furthermore, the results reveal that reducing the critical light intensity and increasing cell motility can significantly bolster the system’s stability. This study also predicts the emergence of limit cycles and/or orbits via bifurcation analysis. These insights advance our understanding of thermal convective interactions in photo-driven bioconvection, with potential implications for optimizing bioreactor designs and other applications involving microalgal systems.

We review the problem of flavour tracing back to the days when the standard model was just coming together. We focus on the recently discussed new solutions of this problem, namely the Froggatt and Nielsen mechanism based on a novel discrete (mathcal {Z}_{textrm{N}} times mathcal {Z}_{textrm{M}}) flavour symmetry, and the standard hierarchical VEVs model. The standard HVM, and the Froggatt and Nielsen mechanism based on the (mathcal {Z}_{textrm{N}} times mathcal {Z}_{textrm{M}}) flavour symmetry, can be recovered from a new dark-technicolour paradigm, where the hierarchical VEVs or the flavon VEV may appear as the chiral multi-fermion condensates. In particular, there appears a novel feature that the solution of the flavour problem based on the discrete flavour symmetry can provide the so-called flavonic dark matter. This predicts a specific relation between the mass and the symmetry-breaking scale, which can be contrasted with the standard QCD axion. Moreover, a possible direction towards the Grand Unified framework is also discussed.

In this study, the dual magnetic curves of the corresponding flux surfaces are determined, and the use of these dual curves enables the definition of magnetic offsets. The kinematic properties of these curves are explored, emphasizing their role in describing the motion and transformations of the flux surfaces. The integral invariants of the flux surfaces and developable are investigated by the utilization of the dual magnetic angle between dual magnetic curves. Additionally, we identify connections between Mannheim offsets and spherical images associated with dual quaternions. Furthermore, the study utilizes dual quaternions to perform a geometric and kinematic analysis of magnetic curves and screw motion, providing a comprehensive framework to link magnetic geometry and kinematic motion.

The rapid cycling synchrotron (RCS) of the China spallation neutron source accumulates 1.56 (times) (10^{13}) protons and accelerates them from 80 MeV to 1.6 GeV at a repetition rate of 25 Hz, delivering a 100 kW proton beam to the target. Despite predictions that no instabilities would occur at high beam intensity, an unexpected coherent oscillation of the beam was observed during the beam commissioning. To confirm and address the instability, a series of systematic measurements and studies were conducted, revealing that the issue is a transverse coupled bunch instability and identifying a narrow-band impedance with a low frequency in the RCS. Further bench measurements confirmed that ceramic chambers with RF shields are the source of this impedance, which is consistent with the analysis of the experimental data. Based on these findings, a tune curve during the ramping process and chromaticity optimization have been implemented to completely mitigate the instability in the RCS at 100 kW.

The sol-gel spin coating method, an easily applicable, low-temperature, and inexpensive method, was used to grow Patent Blue V (PBV) organic thin films placed between metal and semiconductor. Atomic force microscope images were taken to reveal the morphological structure of the resulting organic film. FTIR, NMR, and UV-Vis measurements were taken to investigate the chemical features and optical structure of the PBV molecule. Using the traditional I-V, Cheung, and Norde methods of the produced Al/PBV/p-Si diode structure, ideality factor (n), barrier height (Φ_b), series resistance (R_s), and interfacial density of states (N_ss) parameters were calculated. The differences between the results obtained with these methods arise from calculating the I-V characteristic of the methods from different regions. The ideality value of n for the produced diodes is much greater than one (n >  > 1). Deviating the calculated n value from 1 indicates possible mechanisms, such as generation-recombination effect, organic PBV layer, and interfacial states. It was observed that the electronic parameters of the Al/p-Si conventional junction can be controlled using an organic PBV interlayer.

Graphical abstract

In response to the increasing need for energy, supercapacitors developed to store an additional energy level and exhibit superior efficiency in accumulating energy compared to traditional batteries that undergo several charge–discharge cycles. Transition metal carbides/nitrides, known as MXenes (Nb₄C₃ MXene), have been the primary subject of advanced research by scientists in energy storage. MXenes, a promising class of 2D materials, offer a unique combination of high conductivity, hydrophilicity, tunable surface chemistry, mechanical resilience, and outstanding electrochemical properties, making them ideal candidates for electrode applications. The recently developed pseudocapacitive material optimizes electrochemical energy storage through its abundant interlayer ion diffusion channels and ion storage sites. Moreover, the MXene has some low conductivity issues; to overcome these issues, the Nb₄C₃ MXene structure was decorated with Tin monosulfide (SnS). Furthermore, the GQDs were introduced as 6 wt.% dopants to improve the additional conductivity level. The alterations above lead to enhanced porosity, surface area, density, particle structure, shape, and size. These features substantially contribute to improving the electrochemical process (energy storage and hydrogen evaluation reaction). The resulting SnS/Nb₃C₄(GQDs)-fabricated electrode displayed an excellent specific capacity of 300 C/g and maintained significant charge–discharge cycle stability; capacity retention and coulombic efficiency are 95.52 and 98.61% over 12,000 cycles. The resulting symmetric device achieved a high E_d of 68.2 Wh/kg and Pd of 1315 W/kg at a current density of 2 A/g. Moreover, the SnS/Nb₃C₄(GQDs) electrode demonstrated a significantly lower HER overpotential of 88.7 mV and Tafel slope values of 83.7 mV/dec. The proposed approach offers a hydrothermal method to combine electrochemically active metal sulfide-based and 2D nanostructured materials, enhancing their energy storage and conversion performance. After the stability test, we have performed the CV, GCD and EIS analyses which show the optimal performance with minor change (Fig. S1).

Predator movement determined by prey density is known as prey-taxis, which plays a crucial role in ecosystem dynamics. This study considers the effect of prey-taxis in a predator–prey system with hunting cooperation in predators. Linear stability analysis is used to establish the condition for diffusive instability. Analytical investigation was carried out in the temporal system to investigate the existence of biologically possible equilibrium points and their stability, positivity, and boundedness of solutions and the presence of transcritical and Hopf bifurcations. The transcritical and Hopf bifurcations observed in the predator–prey system for predator death rate and predator hunting cooperation, respectively. As the level of hunting cooperation rises, the system becomes unstable. The stability switches between predator-free and interior equilibrium as predator death rates increase. In the spatially extended system, prey-taxis plays a crucial role in Turing pattern formation.

This paper presents an analytical technique and NLSE-NLSE transformations to discover new spatial soliton solutions, Akhmediev breather (AB) solutions, and first-order rogue waves in photorefractive media backgrounds. The study includes non-centrosymmetric and centrosymmetric photorefractive media, as well as media exhibiting both linear and quadratic electro-optic effects. Using the proposed technique, we discovered exact spatial soliton solutions that can be steered in all these media. Exact AB solutions for all three media types were derived using NLSE-NLSE transformations. We found that AB solutions exhibit a plane-wave profile when photorefractive nonlinearity is high and transform into Peregrine solitons (first-order rogue waves) when nonlinearity is low. By taking the limit of the electro-optic parameter to zero from the AB solutions, we derived analytical solutions for first-order rogue waves across all the media. The characteristics of spatial solitons, AB, and first-order rogue waves, as examined in each media background, show significant differences according to the intrinsic nature of each medium. The NLSE-NLSE transformation has proven to be a powerful and invertible tool, and, in addition to its application in the AB case, can also be widely used to recover spatial soliton and first-order rogue wave solutions found in this study.

In this work, we extend the Kugo–Ojima–Nakanishi covariant operator formalism to quantize two higher derivative systems, considering their extended phase space structures, more specifically, the one describing spin-0 particles by a vector field and the generalized electrodynamics. We investigate the commutator structure of these theories and present the definition of their physical Hilbert subspaces. The first model presents a reducible gauge symmetry, implying the necessity of two sets of auxiliary fields. The massless limit is also carefully analyzed. After this prelude, the generalized QED(_4) can be investigated with such machinery. Regarding the interacting regime, the positive norm subspace is no longer time invariant, since the interaction can create negative norm states from an initially ghost-free one. Then, we furnish an alternative description of the situation by analyzing a set of spectral representations highlighting the lack of positivity associated with the well-known ultraviolet improvement. Finally, based on these efforts and also on recent discussions about Lee–Wick-like models, we prove that it is possible to establish a specific higher derivative interacting model compatible with establishing a time-invariant positive norm subspace.

Cholera is mainly spread by the ingestion of contaminated food or water, especially in areas where poor sanitation is prevalent. The bacteria responsible for cholera, Vibrio cholerae, are observed to multiply in environments lacking proper water treatment and sewage management systems. A novel exploration of machine learning solutions is presented in this paper, with supervised neural structures being applied to a nonlinear stochastic cholera epidemic (SCE) model that incorporates quarantined impact and Brownian motion uncertainty. Artificial neural networks optimized by the Levenberg–Marquardt algorithm (ANNs-LMA) are utilized to predict the dynamics of the SCE model. The probabilistic dynamics of the representative nonlinear SCE model are described in terms of susceptible, infected, quarantined, and recovered individuals, along with the bacterial population represented by the concentration of cholera bacteria in water and food sources. Synthetic data for the execution of ANNs-LMA are generated using the Euler–Maruyama numerical method, with variations in key parameters, including the migration rate into the susceptible group, the transmission rate of cholera through contaminated food and water, the rate at which immunity is lost, natural death rates, the disease progression, and mortality rates among infected individuals, and the recovery or severe disease progression rates among quarantined individuals. The effectiveness of the proposed ANNs-LMA approach is demonstrated by its close alignment with the reference numerical results of the SCE model, as indicated by an error value approaching zero, and is further validated through various assessment metrics, including mean square error-based convergence, adaptive governing parameters, error histograms, and autocorrelation analyses.