Physica Scripta

Many researchers have argued that humanity will create artificial general intelligence (AGI) within the next twenty to one hundred years. It has been suggested that AGI may inflict serious damage to human well-being on a global scale ('catastrophic risk'). After summarizing the arguments for why AGI may pose such a risk, we review the fieldʼs proposed responses to AGI risk. We consider societal proposals, proposals for external constraints on AGI behaviors and proposals for creating AGIs that are safe due to their internal design.

X-ray diffraction (XRD) is routinely used to characterise Ti alloys, as it provides insight on structure-related aspects. However, there are no dedicated reports on its accuracy are available. To fill this gap, this work aims at examining the benefits and limitations of XRD analysis for phase identification in Ti-based alloys. It is worth mentioning that this study analyses both standard and experimental Ti alloys but the scope is primarily on alloys slow cooled from high temperature, thus characterised by equilibrium microstructures. To be comprehensive, this study considers the all spectrum of Ti alloys, ranging from alpha to beta Ti alloys. It is found that successful identification and quantification of the phases is achieved in the majority of the different type of Ti-based alloys. However, in some instances like for near-alpha alloys, the output of XRD analysis needs to be complemented with other characterisation techniques such as microscopy to be able to fully characterise the material. The correlation between the results of XRD analysis and the molybdenum equivalent parameter (MoE), which is widely used to design Ti alloys, was also investigated using structural-analytical models. The parallel model is found to be the best to estimate the amount of β-Ti phase as a function of the MoE parameter.

Squeezed light generation has come of age. Significant advances on squeezed light generation have been made over the last 30 years—from the initial, conceptual experiment in 1985 till today's top-tuned, application-oriented setups. Here we review the main experimental platforms for generating quadrature squeezed light that have been investigated in the last 30 years.

Alena Tensor is a recently discovered class of energy-momentum tensors that provides mathematical framework in which, as demonstrated in previous publications, the description of a physical system in curved spacetime and its description in flat spacetime with fields are equivalent. The description of a system with electromagnetic field based on Alena Tensor can be used to reconcile physical descriptions. (1) In curvilinear description, Einstein Field equations were obtained with Cosmological Constant related to the invariant of the electromagnetic field tensor, which can be interpreted as negative pressure of vacuum, filled with electromagnetic field. (2) In classical description for flat spacetime, three densities of four-forces were obtained: electromagnetic, against gravity (counteraction to gravitational free-fall), and the force responsible for the Abraham-Lorentz effect (radiation reaction force). Obtained connection of Einstein tensor with gravity and radiation reaction force, after transition to curvilinear description, excludes black hole singularities. There was obtained Lagrangian density and generalized canonical four-momentum, containing electromagnetic four-potential and a term responsible for the other two forces. In this description charged particles cannot remain at complete rest and should have spin, their energy results from the existence of energy of magnetic moment and the density of this energy is part of the Poynting four-vector. The distribution of charged matter was expressed as polarization-magnetization stress-energy tensor, what may explain why gravity is invisible in QED. 3) In quantum picture, QED Lagrangian density simplification was obtained, and the Dirac, Schrödinger and Klein–Gordon equations may be considered as approximations of the obtained quantum solution. Farther use of Alena Tensor in unification applications was also discussed.

The solar system started to form about 4.56 Gyr ago and despite the long intervening time span, there still exist several clues about its formation. The three major sources for this information are meteorites, the present solar system structure and the planet-forming systems around young stars. In this introduction we give an overview of the current understanding of the solar system formation from all these different research fields. This includes the question of the lifetime of the solar protoplanetary disc, the different stages of planet formation, their duration, and their relative importance. We consider whether meteorite evidence and observations of protoplanetary discs point in the same direction. This will tell us whether our solar system had a typical formation history or an exceptional one. There are also many indications that the solar system formed as part of a star cluster. Here we examine the types of cluster the Sun could have formed in, especially whether its stellar density was at any stage high enough to influence the properties of today's solar system. The likelihood of identifying siblings of the Sun is discussed. Finally, the possible dynamical evolution of the solar system since its formation and its future are considered.

We present an alternative formulation of quantum mechanical angular momentum, based on spatial wavefunctions that depend on the Euler angles $\varphi ,\theta ,\chi$, and have an additional internal projection $n$. The wavefunctions are Wigner D-functions, ${D}_{\mathrm{nm}}^{s}(\varphi ,\theta ,\chi )$, for which the body-fixed projection quantum number $n$ has the unusual value $n=\left|{\boldsymbol{s}}\right|=\sqrt{s\left(s+1\right)}{\mathscr{=}}{\mathscr{s}}$, or $n=0$. We show that the states ${D}_{{\mathscr{s}}m}^{s}(\varphi ,\theta ,\chi )$ of elementary particles with spin $s$ give a gyromagnetic ratio of $g=2$ for $s\gt 0$, and we identify these as the spatial angular-momentum wavefunctions of known fundamental charged particles with spin. All known Standard-Model particles can be categorized with either value $n={\mathscr{s}}$ or $n=0$, and all known particle reactions are consistent with the conservation of its projection in the internal frame, and with internal-frame Clebsch-Gordan coefficients of unity. Therefore, we make the case that the ${D}_{{\rm{nm}}}^{s}(\varphi ,\theta ,\chi )$ are useful as spatial wavefunctions for spin. Some implications and new predictions related to the quantum number $n$ for fundamental particles are discussed, such as the proposed Dirac-fermion nature of the neutrino, the explanation of some Standard-Model structure, and some proposed dark-matter candidates.

First conceptualised in Olaf Stapledon's 1937 novel 'Star Maker', before being popularised by Freeman Dyson in the 1960s, Dyson Spheres are structures which surround a civilisation's sun to collect all the energy being radiated. This article presents a discussion of the features of such a feat of engineering, reviews the viability, scale and likely design of a Dyson structure, and analyses details about each stage of its construction and operation. It is found that a Dyson Swarm, a large array of individual satellites orbiting another celestial body, is the ideal design for such a structure as opposed to the solid sun-surrounding structure which is typically associated with the Dyson Sphere. In our solar system, such a structure based around Mars would be able to generate the Earth's 2019 global power consumption of 18.35 TW within fifty years once its construction has begun, which itself could start by 2040 using biennial launch windows. Alongside a 4.17 km² ground-based heliostat array, the swarm of over 5.5 billion satellites would be constructed on the surface of Mars before being launched by electromagnetic accelerators into a Martian orbit. Efficiency of the Dyson Swarm ranges from 0.74–2.77% of the Sun's 3.85 × 10²⁶ W output, with large potential for growth as both current technologies improve, and future concepts are brought to reality in the time before and during the swarm's construction. Not only would a Dyson Swarm provide a near-infinite, renewable power source for Earth, it would also allow for significant expansions in human space exploration and for our civilisation as a whole.

The concept of the Fermi surface is at the very heart of our understanding of the metallic state. Displaying intricate and often complicated shapes, the Fermi surfaces of real metals are both aesthetically beautiful and subtly powerful. A range of examples is presented of the startling array of physical phenomena whose origin can be traced to the shape of the Fermi surface, together with experimental observations of the particular Fermi surface features.

In this work, strange quark matter (SQM) and normal matter (NM) attached to domain wall (DW) matter distributions have been examined for locally rotationally symmetric (LRS) Bianchi-I space-time has been investigated. The model has been constructed in the framework of f(R, T) theory for f(R, T) = R + 2μT which is suggested as an alternative gravitation theory instead of Einstein's General Relativity Theory. Obtained modified field equations have been solved by using scale factors equation A = B^m come from the proportion of expansion scalar θ to shear scalar ϖ². SQM and NM are added to DW with the help of equations of state (EoS) ${p}_{m}=\frac{1}{3}({\rho }_{m}-4{B}_{c})$ and p_m = (γ − 1)ρ_m. Pressure and energy densities of all matter distributions have been obtained depending on cosmic time t and their effects decrease by the time. It is found that DW matter behaves like stiff matter due to attaining DW pressure equal to DW energy density p^DW = ρ^DW. Also obtained values of scale factors and some kinematic quantities give an expanding universe for the model. Energy conditions and kinematic quantities of the model have been examined in the last section. In addition, General Relativity solutions of the model have been attained by assuming μ = 0 in f(R, T) = R + 2μT. All solutions have been concluded in detail.

Within a decade, the power congversion efficiency (PCEs) of metal-halide perovskite solar cells (PSCs) moves upward from 3.9% to 25.7%, making them competitive with current state-of-the-art silicon-based counterparts. This steepest growth of the PCEs suggests that the commercialization of this technology might be easing the energy transition from fossil fuel to renewable energy. However, a wide range of factors restrict the commercial viability of PSCs like their toxicity and instability. A crucial and difficult task in the field of PSCs is the replacement of Pb-based perovskite with non-toxic and eco-friendly material while maintaining high-performance with improved stability. Cs₂AgBiBr₆ halide double perovskites (HDP) material seems to be very promising in this regard. This article reviews the recent progress in Cs₂AgBiBr₆ double PSC devices, especially fabrication techniques including the advancement of its efficiency and stability. Here, the evolution of Cs₂AgBiBr₆ towards the application and fabrication of PSCs has also been discussed. This study also analyzed the impact of numerous environmental stresses, such as mechanical, thermal, and optical stresses including the potential prospects in the case of Pb-free PSCs.

The potential of local surface plasmon resonance (LSPR) in the aspect of high sensitivity optical sensors has attracted wide attention. Nevertheless, the application of LSPR sensors is limited by material's inherent ohmic loss and far-field radiation loss, resulting in a lower quality-factor (Q). In this research, a novel all-metal metasurface based on the continuum bound state principle is theoretically designed. Under the conditions of vertical incidence, based on the principle of controlling far-field radiation loss by modifying the structure parameters of metasurface, the metasurface exhibits symmetry protection and Friedrich-Wintgen quasi-bound states in the continuum (quasi-BIC) characteristics, making its Q-factor higher than that of a single quasi-BIC excitation device. The simulation results confirm that the Q-factor of this dual quasi-BIC plasma refractive index sensor can reach about 300, the sensitivity is up to 860 nm RIU⁻¹, and the figure of merit (FOM) is 43 RIU⁻¹, another figure of merit (FOM^I) is 85. In addition, it is also realized that the transition between BIC and quasi-BIC states through the design of the graphene-metal boat structure. These research results may bring new application prospects to the fields of biosensing and optical display.

The field of optimization problems has garnered significant attention due to its importance across various applications, particularly driven by the demand for efficient solutions to complex engineering challenges. Numerous metaheuristic algorithms inspired by animal behaviour or swarm intelligence have been proposed; however, these algorithms often pursue a multitude of strategies, resulting in excessive parameters that complicate tuning and hinder convergence and balance. Additionally, algorithms based on human behaviour remain scarce. To address these limitations, extensive research has been conducted on the interplay between social memory and individual memory, leading to the introduction of a novel human-behaviour-inspired metaheuristic algorithm, named Advanced Social Memory Optimization (ASMO). This algorithm seeks to address the complexities of parameter management, convergence, and balance more effectively with a streamlined set of strategies. Furthermore, a mathematical model based on the mechanisms of social memory formation and individual memory updating underpins the algorithm. Rigorous performance evaluations, utilizing the Wilcoxon Rank-Sum Test and the Friedman Test across multiple benchmark suites (CEC2017, CEC2019, and CEC2022), demonstrate that ASMO, with only two algorithmic strategies, outperforms or matches established algorithms on more than half of the test functions. These findings suggest promising new avenues for research in the field of optimization and, given the succinctness of ASMO's strategies, underscore its potential as a powerful tool for enhancing and developing solutions to complex engineering design problems. The code for the ASMO algorithm is available in appendix D.

Deposition penetration depth into nanofibrous materials is a crucial but underexplored parameter for their modification using low-pressure plasma polymerisation. This work studies it using Monte Carlo simulations and two analytical approaches, a classic continuum diffusion model and a new abstract discrete model, which is fully solvable using the method of generating functions. The discrete model represents the material as a stack of cells with no further geometry and is only characterised by the sticking coefficient η of film-forming species. The models are used to investigate other properties, such as directional coverage of fibres by the deposited film, anisotropy of the mean free path in the nanofibrous material, or the effective sticking coefficient of the material as a whole. The two very different analytical approaches are found to complement each other. When the derived expressions are compared with Monte Carlo results, we find that the discrete model can provide surprisingly relevant formulae despite the very high level of abstraction. The clearest example is the sticking coefficients of the material as a whole, for which the discrete model achieves almost perfect agreement. The other two properties require dimensional scaling factors. It shows that certain aspects of the process are fundamental and mostly independent on details of the interactions and that the dependencies on the sticking coefficient are in some sense separable. By combining the analytical and Monte Carlo results we can also obtain elementary practical formulae for the studied quantities as functions of the sticking coefficient and/or porosity. They are directly applicable to the deep penetration of low-η species or deposition of thin coatings and can be used as local description in more complex cases.

This study reports the generation of dissipative soliton resonance (DSR) mode-locked pulses in an erbium-ytterbium doped fiber laser using a hybrid configuration combining graphene oxide/zinc oxide (rGO/ZnO) nanocomposite on an arc-shaped fiber as a saturable absorber (SA) with a nonlinear amplified loop mirror (NALM). Implementing the hybrid configuration gave an output spectrum with center wavelength and signal-to-noise ratio (SNR) of 1564 nm and 55 dB respectively. The hybrid setup generates 80 ns pulses with a pulse energy of 99.51 nJ. The system is very stable over time. This study highlights the performance of hybrid configuration in enhancing the generation of DSR mode-locked pulses that could be useful for practical applications in optical technologies.

Bragg reflection waveguides (BRW) enable the generation of photon pairs in non-birefringent AlGaAs through spontaneous parametric down conversion (SPDC). Furthermore, the development of an electrically driven laser source from a passive BRW by introducing a suitable doping profile and an active region allows the simultaneous lasing of the pump field and the SPDC process within the same cavity. Here, we present an optimized design of a BRW to allow lasing at 775 nm and simultaneous conversion into photon pairs at 1550 nm. Based on the computed modes at 775 nm and 1550 nm, the non-linear emission characteristics of both SPDC and second harmonic generation of the proposed device is calculated. The design is particularly optimized regarding the monolithic integration of a distributed Bragg reflector (DBR) section to stabilize the laser wavelength. This is necessary because SPDC is highly sensitive to the pump wavelength. By using an eigenmode expansion approach, we calculate the reflection spectra of a 1 mm long, 9th order surface grating in dependence of various parameters. We demonstrate that a peak reflectivity of  > 80% can be achieved with technologically feasible etch depths and groove widths. This paves the way for the promising application of DBR surface gratings for the selection of the pump wavelength for the SPDC process in BRW lasers, with the objective of improving the photon output.

Despite their many advantages, the widespread application of magnesium (Mg) alloys is hindered by their high corrosion rates and poor ductility and formability. One effective method for enhancing both the corrosion resistance and mechanical properties, such as ductility, of Mg alloys is through alloying with Rare Earth (RE) elements. These elements have recently garnered significant attention due to their beneficial properties, including an electrode potential similar to that of Mg and their capacity to refine grain size, which contributes to reduced corrosion rates and enhanced alloy strength. This paper explores the common forms of Mg corrosion and elucidates the mechanisms by which RE elements improve corrosion resistance and mechanical behavior in Mg-RE alloys. It also provides a detailed analysis of how each RE element alters the corrosion behavior of Mg-based alloys. By integrating RE elements, it is possible to control corrosion and improve mechanical properties through mechanisms like solid solution strengthening, grain refinement, and the formation and distribution of secondary phases.

Heat transfer enhancement has become an important research area to improve the efficiency of thermal systems. This chronological review focuses on approaches for heat transfer enhancement by incorporating inputs into strategies. An in-depth review has been carried out with inserts such as twisted tapes, turbulators, vortex generators, dimple surfaces and porous materials to improve heat transfer in a variety of applications like heat exchangers, renewable energy devices, automotive systems and electronic cooling systems. A comprehensive literature review across several decades was conducted to examine the progress in improving heat transfer efficiency. Various numerical, analytical and experimental methods used in the study were examined to correct the processes and effects of different insert designs. The study includes various insert geometries, structures and materials providing a detailed analysis of the state-of-the-art in heat transfer enhancement. The review highlights key findings from studies of various inputs and their effects on heat transfer enhancement. It provides insight into efficiency metrics such as the Nusselt number, coefficient of heat transfer and pressure drop associated with each insertion method. In addition, the chronological presentation allows trends and improvements to be identified in insert-based heat transfer enhancement over the years. The results in various applications show the effectiveness of certain insert geometries and configurations in improving heat transfer performance. This chronological analysis provides a comprehensive overview of the progress in heat transfer enhancement through the use of different approaches. Knowledge gathered from various studies demonstrates the potential of insert-based methods to significantly improve the thermal conductivity of various thermal systems. Insights gained from this study can guide future research efforts, contributing to efficient and sustainable heat transfer technologies that have been developed. The conclusion highlights the importance of continued research in this area to address the growing challenges of thermal management and energy efficiency.

Two-dimensional (2D) Boron Carbon Nitride (BCN) has recently gained significant attention as a convoluted ternary system owing to its remarkable capability to exhibit a wide range of finely tunable physical, chemical, optical, and electrical properties. In this review, we discuss a variety of stable structure forms of BCN nanosheets. In addition, this review provides recent approaches for synthesizing BCN nanostructures, and properties of BCN derivatives. BCN is a promising material for sustainable energy and energy storage devices. Since BCN application is a challenge in the field of energy, we present potential applications of BCN in the field of energy including supercapacitors and batteries, wastewater treatment, electrochemical sensing, and gas adsorption.

The widespread application of synthetic dyes across industries poses significant environmental problems, particularly concerning with degradation of water quality. Concerning the possible solutions, copper oxide (CuO) considered as a feasible candidate. CuO a p-type heterogeneous semiconductor with a bandgap of 1.2–2.71 eV, It is a reasonable choice and widely studied photocatalyst for addressing such challenges. The functionality of CuO deteriorated, when the wavelength exceeded the UV–visible region. In this manner difficulties associated with reproducibility and reusability, as well as rapid electron–hole recombination, prevent the widespread application of this technology. In an attempt to eliminate this defect, researchers have been investigating strategies to activate CuO under visible light, with one promising approach being carbon nanomaterials such as graphene to form carbon-CuO composites. The unique properties of graphene, i.e., its higher surface area and excellent electron mobility, make it a remarkable candidate for the enhancement of CuO photoactivity. This study highlighted the recent progress in the synthesis of graphene-based CuO photocatalysts, with the main characteristic of extending the light absorption capacity of CuO into the visible spectrum. It reveals achievements in material innovations and applications, with a focus on photocatalytic. It has been observed from the documented studies, catalysis is considered as next generation emerging field for the researcher.

Within a decade, the power congversion efficiency (PCEs) of metal-halide perovskite solar cells (PSCs) moves upward from 3.9% to 25.7%, making them competitive with current state-of-the-art silicon-based counterparts. This steepest growth of the PCEs suggests that the commercialization of this technology might be easing the energy transition from fossil fuel to renewable energy. However, a wide range of factors restrict the commercial viability of PSCs like their toxicity and instability. A crucial and difficult task in the field of PSCs is the replacement of Pb-based perovskite with non-toxic and eco-friendly material while maintaining high-performance with improved stability. Cs₂AgBiBr₆ halide double perovskites (HDP) material seems to be very promising in this regard. This article reviews the recent progress in Cs₂AgBiBr₆ double PSC devices, especially fabrication techniques including the advancement of its efficiency and stability. Here, the evolution of Cs₂AgBiBr₆ towards the application and fabrication of PSCs has also been discussed. This study also analyzed the impact of numerous environmental stresses, such as mechanical, thermal, and optical stresses including the potential prospects in the case of Pb-free PSCs.

This study presents the synthesis of nano-sized titanium dioxide (TiO2) powder from titanium powder utilizing a co-precipitation method followed by calcination at varying temperatures of 100°C, 200°C, 500°C, and 700°C. X-ray diffraction (XRD) analysis reveals that the anatase phase of TiO2 is predominantly formed at a calcination temperature of 200°C, with a gradual transition to the rutile phase observed as the temperature is elevated to 700°C. Notably, an increase in the lattice parameters for both the anatase and rutile phases was recorded, indicating significant structural modifications resulting from thermal treatment. Optical characterization further demonstrates that the synthesized TiO2 exhibits pronounced activity within the ultraviolet (UV) spectrum, with band gap energies ranging from 3.89 eV to 4.19 eV. These findings underscore the potential of the synthesized TiO2 powder for photocatalytic applications, suggesting its applicability in environmental remediation and energy conversion technologies. Future work will focus on optimizing the synthesis parameters to enhance photocatalytic efficiency and exploring the mechanisms underlying the observed phase transitions.

We recently presented leading-order semiclassical expressions for the matrix elements 
of the evolution operator between wave functions constructed in the vicinity of unstable 
periodic orbits. By employing a novel canonical transformation, these expressions remain 
valid for arbitrarily long times. In this work, we analyse this transformation within the framework 
of a perturbed cat map 
and compare it with the analytical method of hyperbolic normal forms, revealing a connection 
between them. Based on these insights, we hypothesise that by introducing a small number 
of transverse excitations to the wave functions, the semiclassical expressions can also 
incorporate the next-order correction in $ \hbar $. To validate this hypothesis, we test our 
approach in a quantum version of the perturbed cat map.

Designing a good transfer channel for arbitrary quantum states in spin chains implies optimising a cost function, usually the averaged fidelity of transmission. The fidelity of transmission measures how much the transferred state resembles the state prepared at the beginning of the transfer protocol. When averaged over all the possible initial states, the figure of merit quantifies the quality of the protocol. There are proposals for optimising a given Hamiltonian to accomplish a particular task. The transfer of quantum states is one of them. In particular, we consider the design of Heisenberg spin chains using a genetic algorithm. This very efficient algorithm allows us to study different properties of Hamiltonians with good to excellent transfer ability. Using an evolutionary population method results in exchange coefficient strengths that change abruptly from site to site, which could hinder implementing an actual physical system with such exchange coefficients. By modifying the cost function, we obtain Hamiltonians with exchange coefficients varying smoothly along the chain length without compromising their transfer ability concerning the rough ones. Besides, both kinds of chain Hamiltonians show similar robustness against static disorder. By studying the statistical properties of the eigenvalues of Hamiltonians with varying transfer abilities, we determine the ensemble of random matrices to which the spectra belong.

In this paper, the Die-Sinker Electrical Discharge Texturing (DSEDT) is utilized to machine closed cell titanium foam using pure brass tool electrode. Discharge time, current and discharge voltage were taken as input factors. By varying these input factors, discharge energy generated in between the tool and workpiece gets altered. Therefore, the influence of discharge energy on the average crater diameter, re-solidified layer thickness and chemical alteration of machined surface are analysed. The stochastic nature of DSEDT process is studied using microscopic images and energy dispersive X-ray spectroscopy profiles. Through micrographs it is perceived, increase in the discharge energy from 5.12 J to 10.13 J, leads to an increase in average crater diameter from 29.26 to 66.29 μm respectively. It is observed that combined effect of crater overlap phenomena and re-solidification of material seals the cells in a foam material. A minimum re-solidified layer thickness of 44.29 μm is achieved. The machined surface of closed cell titanium foam shows significant rise in carbon, copper and zinc elements owing to the disintegration of the dielectric liquid and tool electrode during spark erosion. The study on DSEDT of closed cell titanium foam revealed the possibility to create surfaces with uniform crater diameter and establish titanium carbide on the machined surface.

Nanosecond high-peak-power vortex-pulsed lasers show application in material processing, high-capacity optical communication, and quantum information processing. This study generated nanosecond, high-peak-power LG_0,1 vortex beams in a Yb:YAG/Cr⁴⁺:YAG passively Q-switched microchip laser (PQSML) pumped with an annular beam. An annular pump beam, irradiated at 940 nm, was shaped by aligning the uneven distribution of light emitters in a laser diode bar and emitting light from a multimode fiber. An optical coupling system was constructed using two spherical lenses (f = 8 mm). The diameter was 80 μm at the focus spot. A linear increase in the average output power was achieved with a slope efficiency of 12.4%. The average output power of the vortex laser was 256 mW at an incident pump power (P_in) of 5.7 W. Vortices oscillated in a single-longitudinal mode when P_in < 4.2 W, and the laser attained a pulse width of 2 ns and peak power of 28 kW. Conversely, when A P_in > 4.2 W, vortices oscillated in a multi-longitudinal mode, and the laser attained a peak power of approximately 19 kW and pulse width of less than 2.2 ns. The vortex laser with a pulse energy of 42 μJ operated at a repetition rate of 6.3 kHz. A high-beam-quality and high-purity vortex-pulsed laser generated in the compact PQSML shows potential applications in integrated photonics, such as quantum communication and optical trapping.

Deposition penetration depth into nanofibrous materials is a crucial but underexplored parameter for their modification using low-pressure plasma polymerisation. This work studies it using Monte Carlo simulations and two analytical approaches, a classic continuum diffusion model and a new abstract discrete model, which is fully solvable using the method of generating functions. The discrete model represents the material as a stack of cells with no further geometry and is only characterised by the sticking coefficient η of film-forming species. The models are used to investigate other properties, such as directional coverage of fibres by the deposited film, anisotropy of the mean free path in the nanofibrous material, or the effective sticking coefficient of the material as a whole. The two very different analytical approaches are found to complement each other. When the derived expressions are compared with Monte Carlo results, we find that the discrete model can provide surprisingly relevant formulae despite the very high level of abstraction. The clearest example is the sticking coefficients of the material as a whole, for which the discrete model achieves almost perfect agreement. The other two properties require dimensional scaling factors. It shows that certain aspects of the process are fundamental and mostly independent on details of the interactions and that the dependencies on the sticking coefficient are in some sense separable. By combining the analytical and Monte Carlo results we can also obtain elementary practical formulae for the studied quantities as functions of the sticking coefficient and/or porosity. They are directly applicable to the deep penetration of low-η species or deposition of thin coatings and can be used as local description in more complex cases.

This study reports the generation of dissipative soliton resonance (DSR) mode-locked pulses in an erbium-ytterbium doped fiber laser using a hybrid configuration combining graphene oxide/zinc oxide (rGO/ZnO) nanocomposite on an arc-shaped fiber as a saturable absorber (SA) with a nonlinear amplified loop mirror (NALM). Implementing the hybrid configuration gave an output spectrum with center wavelength and signal-to-noise ratio (SNR) of 1564 nm and 55 dB respectively. The hybrid setup generates 80 ns pulses with a pulse energy of 99.51 nJ. The system is very stable over time. This study highlights the performance of hybrid configuration in enhancing the generation of DSR mode-locked pulses that could be useful for practical applications in optical technologies.

Bragg reflection waveguides (BRW) enable the generation of photon pairs in non-birefringent AlGaAs through spontaneous parametric down conversion (SPDC). Furthermore, the development of an electrically driven laser source from a passive BRW by introducing a suitable doping profile and an active region allows the simultaneous lasing of the pump field and the SPDC process within the same cavity. Here, we present an optimized design of a BRW to allow lasing at 775 nm and simultaneous conversion into photon pairs at 1550 nm. Based on the computed modes at 775 nm and 1550 nm, the non-linear emission characteristics of both SPDC and second harmonic generation of the proposed device is calculated. The design is particularly optimized regarding the monolithic integration of a distributed Bragg reflector (DBR) section to stabilize the laser wavelength. This is necessary because SPDC is highly sensitive to the pump wavelength. By using an eigenmode expansion approach, we calculate the reflection spectra of a 1 mm long, 9th order surface grating in dependence of various parameters. We demonstrate that a peak reflectivity of  > 80% can be achieved with technologically feasible etch depths and groove widths. This paves the way for the promising application of DBR surface gratings for the selection of the pump wavelength for the SPDC process in BRW lasers, with the objective of improving the photon output.

Overactive bladder (OAB) significantly affects an individual's quality of life by disrupting daily routines and social interactions. The hallmark symptom of OAB is a sudden, uncontrollable urge to urinate, often resulting in involuntary leakage. Diagnosing OAB is challenging due to the subjective nature of symptom reporting and the absence of definitive biomarkers. Existing diagnostic methods, such as urodynamic testing and symptom questionnaires, provide valuable insights but often lack conclusive reliability. This research leverages a data-driven approach to diagnose and predict the severity of OAB symptoms using comprehensive questionnaire data. Participants of varying ages provided demographic information, medical history, and details such as urination frequency. OAB severity was classified into three levels: no OAB, mild OAB, and moderate OAB, reflecting an increasing intensity of symptoms. The collected data were used to train multiple machine learning (ML) models, including support vector machine (SVM), artificial neural networks (ANN), linear discriminant analysis (LDA), and random undersampling boosted (RUSBoost). Model performance was evaluated using K-fold cross-validation (K = 5 and 10), measuring accuracy, recall, and F1 score to ensure generalizability. Among the models, SVM achieved the highest accuracy, with a 10-fold cross-validation accuracy of 93.33%. To address limitations such as small dataset size and class imbalance, the synthetic minority oversampling technique (SMOTE) was applied, further enhancing model performance. Explainable artificial intelligence (XAI) techniques were also implemented, showing how individual features influenced model predictions. This eliminated the need for manual intervention by uncovering intricate patterns in symptom data and making the diagnostic process more accessible and interpretable. This study underscores the potential of integrating machine learning into OAB diagnosis. The results demonstrate that questionnaire-based predictions of OAB severity are highly accurate and cost-effective, surpassing the performance of human experts. This approach offers a promising solution for enhancing patient care and streamlining OAB management by reducing diagnostic costs and improving clinical decision-making.

We introduce a new method to derive solutions of the Dirac equation in external static fields that have a direct connection to classical physics. Using it, we derive new analytic solutions of the Dirac equation in a magnetic field, which reproduce the motion of relativistic classical particles. We also generalize this method to the case of crossed electric and magnetic field.

Assuming the beam spectrum at the accelerator output follows a Gaussian distribution and its attenuation in air is described by a Landau distribution, the ill-posed problem of electron energy spectrum reconstruction using depth-dose distribution was reduced to finding the electron spectrum at the phantom surface as a convolution of the Landau and Gaussian distributions. The algorithm proposed in the study uses the experimentally measured depth dose distributions generated by Varian TrueBeam medical accelerator operating at 6 MeV and 9 MeV modes in water-equivalint and aluminium phantoms and reconstructs the electron spectra in targeted materials. The algorithm uses reference depth dose distributions from monoenergetic electrons calculated using Geant4 toolkit. It was found that the spectra reconstructed using experimental depth dose distributions in solid water and aluminium differ by less than 5%, and reconstructed depth dose distributions corresponding to the reconstructed spectra deviate from experimentally measured ones by no more than 5%.

In this paper, we characterize all discrete-time systems in quasi-standard form admitting coalgebra symmetry with respect to the Lie–Poisson algebra ${{\mathfrak{h}}}_{6}$. The outcome of this study is a family of systems depending on an arbitrary function of three variables, playing the rôle of the potential. Moreover, using a direct search approach, we classify discrete-time systems from this family that admit an additional invariant at most quadratic in the physical variables. We discuss the integrability properties of the obtained cases, their relationship with known systems, and their continuum limits.

Following a comprehensive analysis of the historical literature, we model the geometry of the Stern–Gerlach experiment to numerically calculate the magnetic field using the finite-element method. Using this calculated field and Monte Carlo methods, the semiclassical atomic translational dynamics are simulated to produce the well-known quantized end-pattern with matching dimensions. The finite-element method used provides the most accurate description of the Stern–Gerlach magnetic field and end-pattern in the literature, matching the historically reported values and figures.

This study establishes a unified approach to utilising symmetry methods to uncover diverse analytical solutions and provides deeper insights into the nonlinear phenomena governed by the Kadomtsev-Petviashvili (KP) framework. The (3+1) dimensional generalized Kadomtsev-Petviashvil (gKP) equation with arbitrary nonlinearity f(u) is examined for its underlying symmetry properties, optimal systems, and exact solutions. We employ Lie symmetry methods to classify the algebraic structure and develop one-dimensional optimal systems for different nonlinearities, including power and exponential forms of f(u). Additionally, using square-law nonlinearity, we derive the modified Korteweg-de Vries-Kadomtsev-Petviashvili (mKdV-KP) equation, which is then subjected to symmetry analysis. By utilising the invariants, we systematically reduce the (3+1)-gKP equation to lower-dimensional forms, facilitating the discovery of static and travelling wave solutions. Notably, the square-law nonlinearity reveals rich solution behaviour, which includes elliptic and Jacobi function representations. Furthermore, graphical illustrations provide a better understanding of underscoring their relevance to soliton theory and nonlinear wave dynamics.

We report on the defect engineering in n-type Bi1.8Sb0.2Te3 end-compound via Te non-stoichiometry (Bi1.8Sb0.2Te3-x) intending to enhance the thermoelectric performance at low and near room temperature regime (10 - 350 K). Contemplating the asymmetry in electronic and phonon transport, the extrinsic anionic disorders successfully modulate the thermoelectric transport. Systematic manipulation of Te and Bi/Sb vacancies increases the electrical conductivity, leading to the highest power factor of 534 μW/mK2 at 350 K. The self-doping effect created via anionic disorders resulted in an enhancement in the thermoelectric performance compared to the Bi1.8Sb0.2Te3 compound. Increased ZT values, accompanied by the thermoelectric quality factor, confirm the quality factor as one of the decisive parameters in elevating the thermoelectric performance. The sample with x = 0.08 has the highest ZT value of 0.081 at 350 K. A 174% increase in compatibility factor is also observed, indicating the state-of-the-art applicability of Bi1.8Sb0.2Te3 in segmented thermoelectric generators.&#xD;