物理最新文献

Micro-machining with ultra-short (sub-ps) and short (ns) pulsed lasers is used to minimize thermal effects, as the heat-affected zone depends on pulse duration. The distinction between ’cold’ (ultra-short regime) and ’hot’ (short regime) ablation holds for single-shot processes, but for high-repetition-rates, it involves additional effects such as incubation, plasma shielding, and thermal accumulation, making the choice of optimal pulse duration more complex. This study compares laser cutting and engraving using sub-picosecond and nanosecond lasers at the same repetition rate of 0.5 MHz. Experiments on graphite determined ablation properties and optimal processing parameters. A thermal model was used to understand the heat accumulation resulting in incubation phenomenon and allows us to characterize the heat affected zone for a given process. Results highlight the influence of pulse duration and process parameters on efficiency and thermal effects, offering insight for high-repetition rates laser processing of sensitive materials.

Reliable, non-invasive glucose monitoring remains essential for improving diabetes management, motivating the development of highly sensitive terahertz (THz) biosensors. This study proposes a hybrid Graphene/Au/MXene/Cu metasurface biosensor on a SiO₂ substrate featuring a central copper rectangular resonator, MXene–WS₂-coated V-shaped resonators, concentric gold rings, and a graphene layer to enhance plasmonic field confinement. Full-wave COMSOL simulations and parametric optimization investigated graphene chemical potential (0.1–0.9 eV), incidence angle (0°–80°), and resonator dimensions across four structural configurations. The optimized design achieved a maximum local sensitivity of 1000 GHz/RIU over a glucose refractive index range of 1.335–1.338, with a figure of merit of 10.753 RIU⁻¹ and a quality factor of 4.250 at 0.391 THz. Electric field enhancement reached 9.15 × 10⁷ V/m, while a 1D-CNN surrogate model predicted sensor responses with R² > 0.9992 and MAPE < 0.18%. These numerical findings establish a computationally efficient platform with potential for rapid, label-free THz glucose sensing and provide a basis for subsequent experimental validation.

Dy₀.₅Ba₀.₅CrO₃ was synthesized using a citrate-based sol–gel method and investigated through structural, microstructural, dielectric, impedance, electrical-transport, and electronic-structure analyses. X-ray diffraction and Rietveld refinement indicated the formation of a predominantly single-phase orthorhombic perovskite structure with Pnma symmetry. The refinement produced (R_p = 4.2%, R_wp = 5.6%, χ² = 2.17), and a goodness-of-fit value of 1.47. Williamson–Hall analysis gave an average crystallite size of approximately 44 nm and a microstrain of. The conductivity increased with temperature, confirming thermally activated semiconducting behavior. Activation energies of approximately eV for DC transport and eV for relaxation were obtained from Arrhenius analysis. The frequency-dependent conductivity followed Jonscher’s universal power law, while the impedance response exhibited thermally activated non-Debye relaxation and a decreasing overall resistance with increasing temperature. Because no equivalent-circuit fitting was performed, separate grain and grain-boundary parameters were not extracted. Oxygen-related defects and chromium mixed valence are discussed as possible contributors to localized transport but are not considered conclusively established without complementary bulk oxygen-stoichiometry measurements.

The Mg₀.₅₊₀.₅ₓAlₓTi₂₋ₓ(PO₄)₃ samples (x = 0.1, 0.3, 0.5, 0.7 and 0.9) were investigated to evaluate the effect of Al³⁺ substitution on the structural and ionic transport properties of Mg₀.₅Ti₂(PO₄)₃. XRD results confirmed that the samples predominantly exhibited a rhombohedral R-3c crystal structure similar to that of the parent compound. The Al³⁺ substitution for Ti⁴⁺ is proposed to promote charge compensation, which may facilitate the incorporation of additional Mg²⁺ ions and consequently enhance ionic transport. Among the investigated compositions, x = 0.5 (AL5) exhibited the highest ionic conductivity, reaching 2.61 × 10⁻⁸ S cm⁻¹ at room temperature and 5.41 × 10⁻⁶ S cm⁻¹ at 500 °C. The enhancement in conductivity is consistent with the proposed charge-compensation mechanism, although direct confirmation of interstitial Mg²⁺ occupancy requires further structural characterization. The frequency-dependent conductivity and temperature dependence of the frequency exponent further indicate thermally activated ionic transport in AL5. The Arrhenius analysis of total ionic conductivity yielded apparent activation energies of 0.04 eV and 0.62 eV for the low and high temperature regions, respectively. These findings demonstrate that Al substitution can effectively enhance the ionic transport properties of Mg₀.₅Ti₂(PO₄)₃ and provide useful insight into the development of NASICON-type magnesium-ion solid electrolytes.

We assess the prospects for inclusive heavy-quark-pair electroproduction in electron–proton (ep) and electron–nucleus (eA) collisions, alongside double-charm-pair ((D^0 bar{D}^0) and (D^0D^0)) electroproduction in ep collisions, during the early operational phase of the Electron-Ion Collider (EIC). Based on the anticipated beam energies and luminosities of the EIC, we estimate the total cross sections and differential distributions for photon virtuality (Q^2), heavy-quark transverse momentum, and rapidity. This analysis evaluates different Bjorken-x ((x_textrm{Bj})) intervals across a range of (Q^2) values. Expected event yields are estimated from the projected integrated luminosities of the early science programme, demonstrating the substantial improvement in statistical precision over previous HERA measurements at moderate and large (x_{textrm{Bj}}). For electron–nucleus collisions, we compute the nuclear modification ratio (R^{etext {A}}) within collinear factorisation using nuclear parton distribution functions, and identify the kinematic regimes in which shadowing, anti-shadowing, and EMC-like suppression are accessible with early EIC data. These results are intended to serve as a parton-level baseline to support feasibility studies and to provide a reference for future higher-order theoretical and experimental investigations at the EIC.

We have numerically calculated energy spectrum of electron in isolated GaAs-AlGaAs Quantum Well in conduction band in presence of uniform static magnetic field applied parallel to GaAs-AlGaAs interfaces. We have numerically solved eigenvalue equation of energy using a two-point boundary value problem in this regard. This is the first use of the numerical method to this classic problem of nanostructure physics. There is no need to use any analytical expression for eigenfunctions in the calculations. We have also shown that results of our method agree very well with known standard results where available; we analyzed two different cases in this regard. Thus the work introduces a novel numerical approach in computational nanostructure physics.

Galaxy clusters are among the most powerful laboratories to probe fundamental physics, from the formation of cosmic structures to the nature of dark matter, dark energy, and gravity. Realizing their full potential requires accurate and unbiased determinations of their mass profiles, a longstanding challenge in cluster cosmology. In this context, the kinematics of member galaxies in clusters has become a key tool to reconstruct the mass distribution and investigate the dynamical properties of clusters. The advent of large spectroscopic datasets has enabled the application of increasingly sophisticated models and robust techniques, which make kinematic analyses competitive with other probes of cluster dynamics. In this review, we provide a comprehensive overview of cluster kinematics, covering the main methods to infer dynamical masses and mass profiles, their physical assumptions, and the impact of systematics, such as deviation from dynamical equilibrium, triaxiality, and substructures. We discuss the complementarity with other techniques to investigate the structure of clusters and highlight recent applications to tests cosmological models. We focus in particular on the role of kinematical studies in constraining the dark sector (dark matter and dark energy) and in providing novel insights into the behavior of gravity at Mpc scales. Finally, we outline current limitations and future prospects, emphasizing that the combination of improved modeling and forthcoming spectroscopic surveys will establish cluster kinematics as a fundamental probe in the era of precision cosmology.

The Kaup–Kupershmidt equation is used to study nonlinear wave propagation associated with ocean currents, capturing the combined effects of nonlinearity and dispersion. Due to the many solitons exhibited by the fractional Kaup–Kupershmidt (K–K) equation, which represent the many solitary waves observed in ocean currents, plasma physics, and optics, several analytical methods have been developed and consistently applied to study these phenomena. One such method is the homogeneous balance method (HBM), which invariably relies on the embedded Riccati equation. Thus, the workability of the HBM largely depends on the embedded Riccati equation, which by and large determines the number and type of solitons yielded when the HBM is applied to the fractional K–K equation. Undeniably, several Riccati equations appear in the literature, each with unique properties. Therefore, if the HBM is embedded with a particular Riccati equation for solving the fractional K–K equation, the underlying mechanisms of the solitary waves in ocean current, plasma physics and optics are unveiled. The HBM and its modified methods explored only by the researchers have not been exhaustively observed a fractional Riccati equation with a quadratic term as the dependent variable, where coefficient of the second term is one and coefficient of the linear term is zero, (frac{d^{gamma }phi }{dxi ^{gamma }} = p + phi ^2(xi ),) quadratic term as the dependent variable and applied this modified homogeneous balance method (MHBM) to obtain the exact solitons of the fractional K–K equation. Applying the MHBM in solving the fractional K–K equation yielded five solitons: a bright soliton with a flat top, a gray soliton, a dark soliton with a flat bottom, an L-tilted soliton, and a halfway dark soliton. Three of the five solitons, a bright soliton with a flat bottom, a dark soliton with a flat bottom, and an L-tilted soliton, were new solitons that have not been observed in literature. These three new solitons of the fractional K–K equation have been observed in this paper as a result of a new embedded Riccati equation in HBM. The soliton properties, such as the kinetic and potential energies of the gray soliton and L-tilted soliton, are similar, whereas in the bright soliton and in the flat top and dark soliton with flat bottom, the potential and kinetic energies are in opposite directions. Lastly, the kinetic energy of the halfway dark soliton increases exponentially.