Search Results (8,201)

Robust age measurements for isolated neutron stars (NSs) are not easily available. That is why the characteristic age ${\tau }_{\mathrm{ch}}=P/2\dot{P}$ is often used as a proxy. Here, P is the spin period of the NS and $\dot{P}$ is the time derivative of P. Additional assumptions related to the initial properties and spin-down evolution are made to derive ${\tau }_{\mathrm{ch}}$. As a result, it is expected that ${\tau }_{\mathrm{ch}}$ is an upper limit for the real age ${\tau }_{\mathrm{real}}$. Recently, Chrimes et al. presented measurements of kinematic ages ${\tau }_{\mathrm{kin}}$ for several magnetars. Surprisingly, for the majority of these sources, ${\tau }_{\mathrm{kin}}>{\tau }_{\mathrm{ch}}$. We present a simple model that includes a realistic approximation for magnetic field decay in magnetars and a simple phenomenological description of field re-emergence following fallback after the birth of an NS. We demonstrate that this simple model can explain the observed relation ${\tau }_{\mathrm{kin}}>{\tau }_{\mathrm{ch}}$ for a realistic set of parameters. Full article

High-viscosity sodium alginate solutions (4.5% by mass, apparent viscosity 1 × 10⁴–2 × 10⁴ cP) are widely used in the preparation of hydrogels, wet spinning, and biomedical materials. Residual bubbles can cause internal voids in hydrogels, mechanical heterogeneity, fiber breakage during spinning, and reduced strength, and can severely affect the cell compatibility and clinical safety of biomaterials. Due to the difficulty of bubble migration, coalescence, and rupture in high-viscosity systems, traditional vacuum-standing degassing takes up to 24 h and is extremely inefficient, severely limiting the quality of subsequent processing. To address this issue, this study proposes a novel vacuum-assisted centrifugal recirculating degassing method for highly viscous sodium alginate solutions and aims to establish a kinetic framework for describing its overall degassing behavior. Using the number density of bubbles larger than 0.5 mm in diameter as an evaluation metric, we conducted vacuum-standing control experiments and univariate experiments with different screen mesh apertures (5, 1.5, 0.3, and 0.07 mm). We experimentally verified a continuous kinetic model of bubble number decay based on vacuum bubble expansion, centrifugally enhanced migration, and removal probability during the cycle. The results indicate that the bubble removal effect of 40 min of vacuum–centrifugal cyclic degassing is equivalent to that of 4 h of vacuum static settling, representing a 450% increase in degassing efficiency. There is an optimal range for a screen aperture, with the best degassing effect observed at 0.3 mm, achieving a bubble removal rate of 83.69%. The established kinetic model exhibits good fitting accuracy (RMSE = 0.17, MAPE = 5.9%) and can accurately predict degassing efficiency under different process conditions. This study provides a quantifiable, modelable, and optimizable process scheme for rapid degassing of high-viscosity sodium alginate solutions, and offers a theoretical reference for the development of degassing technologies for high-viscosity polysaccharide fluids. Full article

Electrospinning (ES) can produce nonwoven fibrous mats with high surface area and interconnected porosity, making them attractive for biomedical and functional material applications. However, conventional ES often relies on volatile organic solvents, raising safety, environmental, and translational concerns. Fully aqueous (“green”) ES offers an appealing alternative, although many water-soluble polymers remain difficult to spin and may show limited stability under hydrated conditions. In this study, two fully aqueous binary systems, poly(vinylpyrrolidone)–sodium alginate (PVP–SA) and poly(vinylpyrrolidone)–riboflavin (PVP–RF), were investigated to decouple the roles of sodium alginate (SA) and riboflavin (RF) on solution behaviour, fibre formation, morphology, dry-state mechanical properties, and surface chemistry. Aqueous PVP solutions (20% w/v; molecular weight 1.3 MDa) were blended with SA (1–5 wt% relative to PVP) or RF (1–10 wt% relative to PVP). Electrical conductivity and rheological properties were evaluated prior to ES under controlled conditions, with simultaneous ultraviolet (UV) exposure at 344 nm during fibre collection. RF did not significantly alter conductivity (~0.74–0.75 µS·cm⁻¹), whereas SA increased conductivity up to 2.75 ± 0.03 µS·cm⁻¹ at 5 wt%. All formulations exhibited shear-thinning behaviour, while 10 wt% RF increased the zero-shear viscosity relative to neat PVP. Morphological analysis showed that low SA contents produced uniform fibres, whereas higher SA levels (4–5 wt%) led to bead defects and reduced fibre diameter (down to 85 ± 25 nm). Dry-state mechanical performance decreased with increasing SA content, while 10 wt% RF improved tensile strength and toughness, reaching an ultimate tensile strength of 5.21 ± 0.15 MPa and toughness of 40.51 ± 1.53 MJ·m⁻³. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated subtle UV-driven redistribution of surface chemical states, consistent with mild photo-oxidative microstructural modification rather than extensive covalent network formation. Because the UV irradiance was not directly measured and wet-state stability was not assessed, the UV-related findings are interpreted as preliminary chemical evidence rather than confirmation of stabilized fibre mats. Overall, this work establishes a solvent-free aqueous ES platform in which ionic and photoactive additives can be used to tailor fibre morphology, dry-state mechanical behaviour, and surface characteristics without toxic reagents. Full article

Superheavy and hyperheavy nuclei are one of the frontiers of nuclear structure nowadays, while for many actinides rather limited experimental information exists. Therefore, theoretical methods providing parameter-independent predictions for these nuclei are of particular interest. Such a method is the proxy-SU(3) approximation to the shell model, which has been adequately tested against experimental data in medium-mass and heavy nuclei up to the rare-earth region, and it has been found to provide reliable, parameter-independent predictions for the collective deformation variables $\beta$ and $\gamma$. Within the proxy-SU(3) approach, the SU(3) symmetry of the three-dimensional harmonic oscillator, which is destroyed beyond the $sd$ shell by the strong spin–orbit interaction, is restored through a unitary transformation. For each nucleus, the most symmetric irreducible representation (irrep) allowed by the Pauli principle and the short-range nature of the nucleon–nucleon interaction, called the highest-weight (hw) irrep in mathematical language, is found to suffice, except in cases in which the hw irrep turns out to be completely symmetric, so that the next highest weight (nhw) irrep has also to be included. In this article we provide a full collection of the hw and nhw irreps, as well as of the corresponding parameter-free predictions for the deformation variables $\beta$ and $\gamma$, for all atomic nuclei ranging from $Z=82$, $N=82$ to $Z=126$, $N=258$. Several cases exemplifying the use of the collected results for studying the prolate-to-oblate shape transition, mirror symmetries, and the evolution of the collective variables along the valley of stability are also considered. Full article

The anomalous magnetic moment of the tau lepton, $a_{\tau }$, represents a fundamental test of the Standard Model (SM) and a high-sensitivity probe for New Physics in the third generation of leptons. Due to the tau’s extremely short lifetime, traditional spin-precession measurements remain inaccessible, necessitating innovative experimental strategies at high-energy colliders. This review provides a comprehensive overview of the current experimental landscape, highlighting the recent paradigm shift from LEP-era constraints to the unprecedented precision reached at the LHC. We emphasize the importance of Ultra-Peripheral Heavy-Ion Collisions (UPCs), which act as a “photon-photon collider” of extreme intensity. By leveraging the $Z^4$ enhancement of the coherent photon flux in Lead–Lead ($PbPb$) interactions, these collisions provide a theoretically robust “quasi-static” environment. To interpret these developments, we first establish the general theoretical framework within the Standard Model Effective Field Theory (SMEFT). This allows us to critically compare the UPC results with the latest measurements from proton–proton collisions—including the recent CMS observation of the $\gamma \gamma \to \tau \tau$ process and the ATLAS constraints from the high-mass Drell–Yan tail—evaluating their complementarity and the challenges related to Effective Field Theory validity at the TeV scale. Finally, we outline the future prospects for $a_{\tau }$ at Belle II and the Future Circular Collider (FCC) stages. While FCC-hh in $PbPb$ mode provides a theoretically clean environment, its sensitivity remains limited to $\mathcal{O}\left({10}^{-2}\right)$. Conversely, the next generation of lepton facilities, specifically Belle II and FCC-ee, aims for the $\mathcal{O}\left({10}^{-5}\right)$ level, required to probe SM electroweak loop corrections. Long-term projections for a high-energy Muon Collider suggest a potential reach of $\mathcal{O}\left({10}^{-6}\right)$. Full article

Thermoacoustic oscillations are excited sound waves in systems with large temperature gradients. Thermoacoustic engines and refrigerators can be constructed using porous materials to enhance the acoustic power produced and facilitate heat pumping for refrigeration. Porous materials can also be utilized as catalytic beds to convert between the two spin-isomers of hydrogen: orthohydrogen and parahydrogen. The conversion between ortho- and parahydrogen is either endothermic or exothermic, and the composition of the isomers manipulates the heat capacity of the fluid. This study experimentally investigates ortho-parahydrogen conversion in a thermoacoustic standing-wave engine with different oxidized catalytic materials. Recorded experimental measurements include the onset temperature ratio, acoustic pressure amplitude, and frequency of the thermoacoustic engine. The results depict a relationship between the oxidized materials and the acoustic amplitude. All oxidized materials promoted an increase in acoustic amplitude versus the pure metallic components. Steady-flow conversion was measured for brass oxide and iron oxide pellets; however, no conversion was detected for aluminum oxide or copper oxide pellets. The initial datapoints provide evidence that future cryogenic hydrogen thermoacoustic devices will need to account for the spin isomer conversion inside the stack. New flow-through regenerating liquefiers can also be constructed, which convert orthohydrogen to parahydrogen during liquefaction. Full article

In this work, we report an exactly solvable quantum model featuring a spin-dependent Coulomb interaction, described by the spin vector potential $\overrightarrow{\mathcal{A}}=k(\overrightarrow{r}\times \overrightarrow{S})/r^2$ together with a Coulomb-type scalar potential $\phi =\kappa /r$. The model is governed by the Schrödinger-type Hamiltonian ${\mathcal{H}}_{\mathrm{S}}={\overrightarrow{\Pi }}^2/\left(2M\right)+q\phi$ in nonrelativistic quantum mechanics and by the Dirac-type Hamiltonian ${\mathcal{H}}_{\mathrm{D}}=c\overrightarrow{\alpha }·\overrightarrow{\Pi }+\beta M{c}^2+q\phi$ in relativistic quantum mechanics, where $\overrightarrow{\Pi }=\overrightarrow{p}-(q/c)\overrightarrow{\mathcal{A}}$ is the canonical momentum. We demonstrate two main results: (i) Just as the Coulomb-type scalar potential ${\mathcal{S}}_{\mathrm{Maxwell}}=\{\overrightarrow{\mathcal{A}}=0,\phi =\kappa /r\}$ is a local exact solution of Maxwell’s equations on $r\ne 0$, the gauge potential ${\mathcal{S}}_{\mathrm{YM}}=\{\overrightarrow{\mathcal{A}}=k(\overrightarrow{r}\times \overrightarrow{S})/r^2,\phi =\kappa /r\}$ constitutes a local exact solution of the Yang–Mills equations on the punctured region $r\ne 0$. (ii) Both Hamiltonians ${\mathcal{H}}_{\mathrm{S}}$ and ${\mathcal{H}}_{\mathrm{D}}$ can be solved exactly in the presence of this spin-dependent Coulomb interaction. The resulting energy spectra are derived, and they naturally reduce to those of the ordinary hydrogen atom when the spin-dependent terms are neglected. Finally, we clarify the quantization conditions and the fixed-background interpretation of the model. Full article

This article presents an integrated approach that combines Virtual Reality (VR), Augmented Reality (AR), and an Intelligent Virtual Assistant (IVA) to support training, on-the-job assistance, and maintenance in a textile manufacturing environment. The solution spans three systems: RioRV, a Unity-based VR platform for immersive, step-by-step procedure rehearsal, instructional videos, and simplified 3D animations; RiAR, a mobile AR application for assisted maintenance and access to real-time and historical machine data using marker-based (VuMark) identification; and Ria, a web-based IVA that delivers document-grounded answers, operational queries over a secure plant API, short-horizon forecasting, and a narrow set of guarded remote actions. The architecture prioritizes human-centered Industry 5.0 principles—safety, usability, and resilience—by enabling operators to learn procedures in VR, execute tasks with AR overlays and maintenance media at the workstation, and obtain concise, source-cited guidance via the IVA without leaving immersion. In the case study with a spinning section at RIOPELE, the convergence of VR, AR, and IVA reduced reliance on bulky manuals, shortened time-to-information for machine status, and established a feedback loop in which training and operational experience continuously enrich the knowledge base. Full article

This study aimed to characterize cortical dysfunction and frequency-specific network reorganization following optic nerve injury using spin-exchange relaxation-free magnetoencephalography (SERF-MEG), and to assess the potential of MEG-derived multiscale features as sensitive functional biomarkers for clinical evaluation. In this prospective case–control study, SERF-MEG recordings were acquired during a pattern-reversal visual stimulation paradigm. Time-domain evoked components (M100/M135), global electrophysiological indices, energy-based metrics, and alpha- and beta-band phase-based functional connectivity were extracted. Network topology was quantified using graph-theoretical measures, including global and local efficiency, clustering coefficient, and assortativity. Group-level differences between patients and healthy controls were statistically analyzed. Patients showed significantly reduced M100/M135 amplitudes, prolonged M100 latency, and a lower early-component energy ratio. Functional connectivity was significantly decreased in the alpha and beta bands, accompanied by reduced global and local efficiency, mean strength, and clustering coefficient. Seed-based analyses revealed reduced connectivity predominantly in occipito-parietal and occipito-temporal pathways. SERF-MEG provides sensitive identification of cortical- and network-level functional impairments following optic nerve damage. MEG has significant clinical potential for disease diagnosis and therapy monitoring, providing a novel objective assessment tool for neuro-ophthalmological disorders. Full article

Sweep-field operation in a single-beam spin-exchange relaxation-free (SERF) magnetometer requires stable extraction of the dispersion zero-crossing. A frequency mismatch between the modulation signal and the demodulation references, or an unsuitable low-pass filter, can shift this zero-crossing and affect working-point determination. This paper presents a zero-crossing-stability-oriented FPGA quadrature lock-in module for SERF sweep-field demodulation. The module is designed around two requirements of sweep-field operation: maintaining a common frequency basis between the modulation output and the demodulation references, and preserving the dispersion zero-crossing when the low-pass-filter cutoff frequency is adjusted. A shared direct digital synthesizer generates both the sinusoidal modulation output and the I/Q references, keeping the excitation and demodulation signals on the same frequency basis. After quadrature multiplication, CIC decimation and a reloadable Kaiser-window FIR filter are used for low-pass processing. Board-level tests show a 1000.054 Hz spectral peak for a 1000 Hz setting and a loopback amplitude of 0.496 V, close to the ideal 0.500 V baseband amplitude. On the SERF platform, I/Q rotation reduces the quadrature residual ratio from 32.1% to 0.10%. When the FIR cutoff frequency is changed from 3 to 15 Hz, the maximum zero-crossing difference is about 0.58 ms, corresponding to 0.12% of the 2 Hz sweep period. These results show that the module supports stable zero-crossing extraction and working-point determination during sweep-field operation in a single-beam SERF magnetometer. Full article

Polymer-based active packaging systems incorporating natural bioactive agents have attracted growing interest as eco-friendly alternatives to traditional food packaging materials. In this study, Pistacia lentiscus essential oil (PLEO) was incorporated into PCL/gelatin nanofibrous mats fabricated via solution blow spinning (SBS) to develop multifunctional and biodegradable active packaging materials. Neat PCL, gelatin-blended PCL (PCL–G) and PCL–G mats containing 5, 10 and 20 wt.% PLEO were produced and thoroughly analyzed for their morphological, chemical and functional characteristics. Morphological investigation revealed a smooth, bead-free fibrous structure in all samples. The average fiber diameter (AFD) increased from 239 nm to 320 nm with the addition of gelatin to the PCL matrix, while the incorporation of different concentrations of PLEO caused only minor changes. The results showed that as the concentration of PLEO increased, the antioxidant activity of the nanofibrous mats also increased. This enhancement is potentially linked to the rich content of bioactive molecules such as β-pinene, terpineol and verbenol. The 2,2-diphenyl-1-picrylhydrazyl scavenging activity improved from 6.4% (PCL) to 60% (PCL–G–20PLEO), and ABTS activity rose from 8.7% to 72%. In addition, antimicrobial evaluation showed inhibition zones of 12.5 mm against Escherichia coli and 14.2 mm against Staphylococcus aureus for the PCL–G–20PLEO nanofibrous mats. In 14-day storage tests on Kashar cheese, PCL–G–10PLEO and PCL–G–20PLEO mats reduced microbial counts by more than 2 log units compared with the control and effectively slowed yeast and mold growth. These findings confirm the potential of the PCL–G–PLEO nanofibrous mat as novel active packaging materials for preserving dairy products such as Kashar cheese. Full article

Transition-metal phosphides are promising non-noble-metal electrocatalysts for alkaline hydrogen evolution, yet further improving their performance remains challenging. In this work, a Co-doped nanoporous Fe₃P self-supported electrode was fabricated by vacuum high-frequency induction and melt spinning of Fe₇₅Co₅P₂₀ precursor alloys, followed by electrochemical dealloying. Nanoporous Fe₃P prepared from Fe₈₀P₂₀ was used as the reference. Structural analyses show that dealloying selectively removes the α-Fe phase while preserving the Fe₃P framework, resulting in a three-dimensional nanoporous architecture. XPS results further confirm successful Co incorporation and reveal that Co doping modifies the local chemical environment of Fe and P. Benefiting from the combined effects of Co incorporation and the nanoporous structure, np-Co-Fe₃P exhibits significantly improved HER performance in 1.0 M KOH, requiring only 70 mV to reach 10 mA cm⁻², much lower than that of np-Fe₃P (199 mV). In addition, np-Co-Fe₃P shows a smaller Tafel slope of 94 mV dec⁻¹, lower charge-transfer resistance, and a larger double-layer capacitance of 109.4 mF cm⁻². This work demonstrates an effective strategy for enhancing the alkaline HER performance of Fe-based phosphides through the combination of Co incorporation and dealloying-derived nanoporous architecture. Full article

Strong chiral responses in planar dielectric metasurfaces are important for polarization-selective nanophotonic devices, but achieving large and reversible circular dichroism (CD) in simple dielectric structures remains challenging. This work proposes a symmetry-broken silicon metasurface that realizes near-infrared chiral response based on bound states in the continuum (BICs). The unit cell consists of a silicon nanoblock with two through-air grooves. The in-plane displacement of the air grooves breaks the C₂ rotational symmetry and splits the BIC-related polarization singularity into two circularly polarized points (C points) with opposite handedness. By further introducing out-of-plane tilting, one of the C points is shifted to the Г point, enabling spin-selective coupling between normally incident circularly polarized light and the quasi-BIC mode. Reversing the out-of-plane tilt switches the sign of CD, with values reaching −0.98 and 0.98, approaching the theoretical limits of ±1. Under oblique incidence, the structure can also exhibit near-limit CD responses. Finally, by introducing graphene, the structure achieves tunable circular-polarization-selective absorption, with the absorption of CD approaching the theoretical limits of ±0.5 for the coupled system. This work provides a new design idea for compact chiral nanophotonic materials by using symmetry breaking to control spin-selective quasi-BIC coupling and tunable chiral absorption. Full article

Permalloy (Py) is a crucial component in spin nano-oscillators due to its excellent soft magnetic properties. Due to orbital angular momentum quenching, Py exhibits very low magnetic damping. It reduces intrinsic energy dissipation during precession, which is beneficial for lowering operational power consumption and enhancing the thermal stability of certain memory devices. But lower magnetic damping limits its application in fast-switching spintronic devices. Thus, in this work, the rare earth element Gd is introduced into Py to further enhance the spintronic performance of Py_100−xGd_x alloys. Through spin-torque ferromagnetic resonance measurements (ST-FMRs), the maximum spin Hall angle of the system was calculated to be 0.149 when x = 20, significantly exceeding that of 0.042 in the pure Py sample. Additionally, Gd doping significantly enhances the ability to modulate the magnitude of the linewidth. Also, as the Gd content in the alloy increased, the magnetic damping coefficient of the device gradually rose, reaching a peak in the sample with 17% Gd content. The maximum magnetic damping coefficient of the Py-Gd alloy was 0.051, representing an approximate 2.4-fold increase compared to that of pure Py. The findings of this study confirm that the use of rare-earth elements is highly effective in tuning the performance of spintronic devices and provide support for the development of highly efficient SOT devices. It is noted that the regulation of magnetic damping by Py-Gd holds significant implications for enhancing the magnetization switching speed of SOT devices and reducing the drive current density for microwave emission in spin nano-oscillators. Full article

The amniotic membrane is widely recognized in regenerative medicine due to its rich content of extracellular matrix proteins and growth factors that confer anti-inflammatory and pro-regenerative properties. However, its rapid degradation restricts its standalone clinical use. To overcome these limitations, we developed biofilms by incorporating decellularized human amniotic membrane matrix (dHAM) into polycaprolactone (PCL) and polyvinylpyrrolidone (PVP) matrices using spin-coating. Bone marrow-derived mesenchymal stem cells (BM-MSCs) were used to evaluate film biocompatibility through cell viability, proliferation, and wound healing migration assays. Surface characterization was performed using contact angle measurements, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, and scanning electron microscopy. Soluble dHAM extracts (4–6 mg/mL) significantly enhanced BM-MSC proliferation at 48 h compared to controls (p ≤ 0.01 and p ≤ 0.0001). Both PCL-dHAM and PVP-dHAM biofilms exhibited high cell viability (>90%) and improved initial adhesion. Notably, dHAM incorporation significantly increased wound closure rates at 24 h, reaching 98.47% for PCL-dHAM and 93.13% for PVP-dHAM, compared to 76.56% and 64.20% for pure polymers (p = 0.0001). All scaffolds maintained hydrophilic surfaces (<90°), favorable for cell interaction. The integration of dHAM into PCL and PVP by spin-coating produces biofilms biocompatible with enhanced regenerative potential, representing promising candidates for wound healing applications. In conclusion, these coatings support BM-MSC adhesion, proliferation, and migration, while significantly accelerating wound closure, underscoring their value as advanced bioactive coatings for regenerative medicine. Full article