Search Results (986)

Electron fields (and more generally spinor fields) with a vortex structure in free space that allows them to have arbitrary integer orbital angular momentum along the direction of motion have been studied for some time. We point out that there are several ways to calculate the local velocity of the electron field, defined as the ratio of momentum density to energy density, and that all but one show a singular vorticity at the vortex line. That one, using the Dirac bilinear current with no derivatives, is the only one so far (to our knowledge) studied in the literature in this context and we further show how to understand an apparent conflict in the existing results. The momentum densities corresponding to the three possible velocity fields give different physical results, in particular regarding the electron induced quantum superkicks given to small electron-absorbing test objects. Full article

Intelligent soft open points (SOPs) and energy storage systems (ESSs) are effective ways to absorb distributed new energy in the spatial and temporal dimensions, and play an important role in improving the new-energy-carrying capacity of distribution networks. Existing planning models for SOPs and ESSs in distribution networks are often nonlinear and non-convex, and are usually transformed into a mixed-integer second-order cone optimization (MISOCP) model. However, this transformation often needs stringent relaxation conditions, and the solution speed and convergence performance of the model are poor. These disadvantages make traditional MISOCP models unsuitable for optimal planning for complex hybrid networks. To overcome these limitations, a joint planning method for AC/DC hybrid networks based on an improved DC power flow (IDCPF) algorithm is proposed in this paper. The proposed method transforms the original nonlinear model into an approximate linear model, improving the solution speed and accuracy of the model. The effectiveness of the proposed method is validated through case studies on an improved AC/DC 43-node network, which demonstrates the accuracy and numerical stability of the planning model. Full article

Material-extrusion (MEX) printing with automated filament switching enables single-build multi-material laminates, but interfaces between dissimilar polymers may govern failure. Here, monolithic PETG, monolithic PC–ABS, and an alternating PETG/PC–ABS laminate (COMP) with 0.2 mm laminae (4 mm total) were fabricated and benchmarked. Tensile behavior was measured using ISO 527-2 Type 1B specimens at 5 and 50 mm/min, complemented by three-point bending in horizontal/vertical orientations, unnotched Charpy impact (ISO 179), Shore D hardness (ISO 868), and SEM fractography. COMP delivered the highest horizontal flexural strength (159.82 ± 25.42 MPa), exceeding both single-material baselines, indicating improved bending load capacity in the preferred orientation. In Charpy impact, COMP absorbed more energy than PETG in the horizontal condition (0.86 ± 0.14 J vs. 0.57 ± 0.06 J) but remained below PC–ABS. In tension, COMP strength decreased by ~21–23% relative to PETG and by ~5–6% relative to PC–ABS at both speeds, consistent with interface-controlled damage. SEM revealed void-assisted crack initiation and interfacial debonding aligned with raster paths, highlighting interfacial strengthening and porosity reduction as key routes to improve tensile performance while retaining favorable flexural and impact response. Full article

This study investigates the hydrodynamic responses and energy harvesting performance of a hemispherical point-absorber wave energy converter (WEC) in uniform current. A frequency-domain Rankine source method (RSM) is developed to rigorously account for current-modified free-surface conditions, and an approximate free-surface Green-function method (AFSGM) is implemented to assess practical applicability under weak-current assumptions. The numerical settings for body, free-surface, and radiation-boundary discretizations are determined through convergence tests. Model validation is performed by comparing motion responses against published benchmark results under both zero-current and current conditions. The effects of current and motion constraints are examined for surge–heave free and heave-only cases. Results show that current can amplify the heave response and that surge freedom enhances heave motion through coupling effects, leading to increasing discrepancies between RSM and AFSGM as current strengthens. For heave-only motion, AFSGM provides practically acceptable predictions within $\mid F_r\mid \le 0.045$, while noticeable differences appear near resonance beyond this range, for which RSM is recommended. Energy harvesting is evaluated using a linear PTO damping model, revealing that current alters the capture width ratio (CWR) and shifts the optimal PTO damping and frequency, indicating the necessity of considering current in performance assessment and PTO design. Full article

Additive manufacturing enables the fabrication of personalized protective equipment with locally tailored mechanical properties. In this work, a low-cost scan-to-print workflow is proposed for the fused filament fabrication (FFF) of personalized dual-zone shin guards combining a stiff outer load-distribution layer with a compliant inner energy-absorbing layer. Subject-specific leg geometry was acquired via structured-light 3D scanning and used to design a shin guard with two 3.5 mm thick zones (total thickness 7 mm). Foamable filaments of PLA, ASA, and TPU were employed to manufacture unfoamed and foamed regions by controlling extrusion temperature. Mechanical performance was assessed through three-point bending tests and dynamic finite element impact simulations. Unfoamed PLA and ASA exhibited flexural strengths of approximately 88 MPa and 72 MPa, respectively, while foaming reduced these values by about 74%. Dual-zone configurations partially restored stiffness, reaching 41 MPa for PLA and 29 MPa for ASA. TPU showed lower flexural stresses with a smaller reduction of 23% upon foaming. Impact simulations revealed maximum deformations of 1.97 mm and 2.02 mm for PLA and ASA outer zones, respectively, while TPU exhibited large deformations leading to penetration of the 3.5 mm thick inner layer. The results demonstrate that dual-zone designs manufactured via foaming-enabled FFF can effectively balance stiffness, weight, and impact response for personalized shin guard applications. Full article

Background/Objectives: Cannabidiol is a non-psychoactive substance that possesses properties suitable for the treatment of several disorders related to the central nervous system. However, successful administration of cannabidiol remains challenging due to low and variable bioavailability and potential adverse effects. Intranasal delivery of cannabidiol may help overcome these limitations, but the pharmacokinetics of such administration has not been fully established. Methods: Starch-based cannabidiol-loaded nanoparticles were used as carriers and were administered to rats via the intranasal route. Cannabidiol levels in plasma and the brain were examined at different time points and compared to cannabidiol levels in plasma and the brain following intravenous administration of cannabidiol solution for injection. Pharmacokinetic parameters were calculated for each delivery route, and a pharmacokinetic model was fitted for the intranasal administration. Results: Intranasal administration resulted in a bioavailability of 47.9%. Systemic absorption accounted for 44% of the absorbed drug, while 56% was absorbed by direct brain entry. Intranasal administration resulted in rapid brain penetration with a brain t_max of 10 min and demonstrated a brain bioavailability of 28.5% compared to bioavailability after intravenous bolus injection of cannabidiol solution. Conclusions: Intranasal administration of cannabidiol-loaded nanoparticles was found to be effective for the delivery of cannabidiol to the brain with significantly lower systemic exposure compared to intravenous administration. A proposed pharmacokinetic model was found to be appropriate in describing and predicting the disposition pathways following intranasal administration, especially when designing drug delivery systems for brain targeting. Full article

The emergence of large-scale models and machine learning has transformed the modeling of complex nonlinear systems, such as postseismic stress evolution. However, purely data-driven approaches often lack interpretability and numerical stability, leading to physically inconsistent long-term predictions. This study addresses these limitations by introducing a coupled Kolmogorov–Petrovsky–Piskunov–Rate-and-State (KPP–RS) reaction–diffusion system as a rigorous physical prior for large-scale modeling of stress-driven dynamics. Using analytic semigroup theory and Banach’s fixed-point theorem, we establish the global existence and uniqueness of solutions, ensuring that the governing dynamics are mathematically well posed—a necessary prerequisite for stable learning-based frameworks. We further prove the global dissipativity of the system and identify a bounded absorbing set in the H¹ phase space, which imposes intrinsic physical constraints and limits unphysical parameter exploration in large-scale optimization or black-box modeling. In addition, a Courant–Friedrichs–Lewy (CFL) stability condition is derived, providing a theoretical benchmark for time-step selection in numerical implementations, including physics-informed or hybrid neural architectures. This analytical framework supplies a mathematically controlled foundation for developing robust, interpretable, and stable pattern-recognition or time-series representations in complex geophysical systems. Full article

Background/Objectives: Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is a global health crisis, but current diagnostics are limited. Liver biopsy is invasive, magnetic resonance imaging-proton density fat fraction (MRI-PDFF) is expensive, and quantitative ultrasound methods are low-accuracy, especially in patients with a high body mass index (BMI). This study introduces a novel thermo-acoustic (TA) method that generates ultrasound signals based on tissue electrical conductivity, where lean tissue (high in water and electrolytes) absorbs more radio-frequency (RF) energy than fatty tissue, providing a direct molecular contrast for fat. Methods: A prospective, cross-sectional feasibility study compared a new thermo-acoustic fat fraction (TAFF) score with the reference standard MRI-PDFF in 40 subjects with suspected fatty liver disease. Bland–Altman analysis, Deming regression, and Binary classification performance were tested. To establish system stability, a dedicated Repeatability and Reproducibility (R&R) study (N = 14) evaluated inter-operator and intra-operator consistency using an Intraclass Correlation Coefficient (ICC) derived from a two-way random-effects ANOVA model. Results: TAFF estimates demonstrated a substantial correlation (r = 0.89) with MRI-PDFF and an average absolute error of 3.04% fat fraction. Classification performance was high, with an Area Under the Receiver Operating Characteristic Curve (AUROC) of 0.92 at the 12% fat fraction threshold and 0.99 at the 20% fat fraction threshold. The R&R study confirmed robust stability (intraclass correlation = 0.89) and a negligible mean inter-operator difference of 0.36%. Estimation errors showed no statistically significant correlation with BMI or other body habitus measurements. Conclusions: These findings support thermoacoustics’ potential as an accurate, non-invasive, point-of-care solution that can serve as a new imaging biomarker. By providing predictive values closely aligned with MRI-PDFF across the full MASLD spectrum, TAFF can complement currently available ultrasound methods to address the cost and access constraints of MRI for the assessment, diagnosis, and monitoring of MASLD. Full article

This work investigates the reciprocal adhesion of Polybenzoxazole (PBO) and silicon nitride (SiN) with a focus on the combined effects of surface chemistry and environmental conditions, i.e., temperature (T) and relative humidity (RH). A set of six samples, including standard and silicon-rich SiN substrates treated with oxygen (O₂) or carbon tetrafluoride (CF₄) plasma, was fabricated and characterized by AFM, XPS, and TEM/EDX to quantify surface roughness and interfacial chemical modifications. Adhesion with PBO was then assessed through nanoindentation both in situ, during ambient control, and ex situ, after aging in a climatic chamber. Compared to PBO adhesion with as-deposited standard and silicon-rich SiN, O₂ plasma treatment was shown to improve adhesion by 13% and 24%, respectively, whereas CF₄ plasma treatment was still beneficial but more limited, improving adhesion by 8% for both substrates. The different effects were ascribed to the formation of a surface oxide layer after O₂ plasma, enhancing chemical affinity and substantially equalizing the adhesion on the two SiN substrates, while CF₄ plasma was impacting adhesion by reducing the substrates’ activity and, thus, increasing the efficiency of the PBO curing procedure. Notably, the adhesion loss with increasing dew point of the ambient (dependent on temperature and relative humidity) was observed across all samples regardless of surface treatment, reinforcing the critical role of absorbed moisture on polymeric film adhesion. However, this trend was observed for all samples only for in situ testing, with a loss of 25% in the critical load of delamination for the most critical environment, while ex situ tests showed a marked recovery of adhesion properties, leading to measurements no longer reflecting the actual state of the samples inside the altered environment. The results presented in this paper highlight the effect of substrate preparation on the adhesion of an organic compound and a substantial difference in environmental control methods for adhesion testing, providing an alternative approach to classical aging treatments and subsequent characterization for qualifying polymer/inorganic interfaces exposed to stressful operational conditions. Full article

Purpose: The present study aimed to assess the radiation dose associated with low-dose (LD) CT pelvimetry compared with conventional radiography and to evaluate the adequacy of the resulting image quality. Methods: The absorbed dose was measured using thermoluminescent dosimeters positioned in an anthropomorphic female phantom, including uterine locations, to estimate the fetal dose. Conventional radiographic pelvimetry and LD-CT pelvimetry were performed using clinically implemented protocols. Effective dose was calculated using Monte Carlo–based modeling applying acquisition parameters and retrospective patient dose registry data. Image quality of LD-CT pelvimetry was independently evaluated in 14 consecutive clinical cases using a four-point ordinal scale. Results: LD-CT pelvimetry reduced the mean absorbed pelvic dose by approximately 50% compared with conventional pelvimetry (0.18 vs. 0.39 mGy) and decreased estimated fetal dose by 40% (0.21 vs. 0.37 mGy). These estimates were based on standardized single acquisitions and did not incorporate additional radiation from retakes commonly observed in conventional practice. CT demonstrated substantially more homogeneous dose distribution, whereas conventional pelvimetry exhibited marked heterogeneity with peak values up to 2.3 mGy. The maternal effective dose was lower for LD-CT (0.16 mSv) than for conventional pelvimetry (0.36 mSv); inclusion of retakes increased the conventional effective dose to 0.71 mSv. All CT examinations were diagnostically adequate, and no recalls were required. Conclusions: Optimized low-dose CT pelvimetry significantly reduces radiation dose compared with conventional radiographic pelvimetry while maintaining reliable diagnostic image quality. These results support the clinical adoption of CT-based pelvimetry as a dose-efficient and reproducible alternative to conventional techniques. Full article

We develop a minimal thermodynamic model to predict Titan’s surface temperature based on radiative–convective equilibrium and the principle of maximum entropy production (MEP). The model retains only the essential atmospheric constituents: gaseous methane, which absorbs both longwave and near-infrared radiation, and stratospheric haze, which scatters and absorbs solar flux. Subject to Clausius–Clapeyron scaling of methane vapor pressure together with energy balances at the surface, tropopause, and stratopause, the model links the convective flux to the surface temperature, which exhibits a pronounced maximum due to competing radiative effects of tropospheric methane. As the surface warms, enhanced greenhouse effect would strengthen the convection, whereas the rising anti-greenhouse effect would suppress convection. The resulting convective peak corresponds to MEP, which thus selects a surface temperature slightly above methane’s triple point. To assess its long-term evolution, we consider a 20% dimmer early Sun and a hypothetical 20% enrichment of the oceanic methane. Even in combination, they only cool the surface by ~2 K, in sharp contrast to the ~20 K cooling inferred in studies that prescribe haze abundance. This study suggests a critical role of self-adjusting haze in providing the internal degree of freedom necessary for MEP closure, thereby stabilizing Titan’s temperature. Full article

Menstruation, a biological phenomenon experienced by more than half of the global population, remains stigmatized and poorly addressed in the context of research and public discourse. One overlooked issue is that of “period pollution,” the waste generated by millions of feminine hygiene pads (menstrual pads) that end up in landfills or the environment. Simultaneously, Japanese knotweed (Reynoutria japonica), a non-native invasive plant which disrupts native species, leads to the disruption of ecological systems. This experimental study assesses the Japanese knotweed plant for its potential to serve as the absorbent core in a sustainable menstrual pad, helping to address both environmental challenges in tandem. As control groups, commercial pads (Natracare and Saathi) were tested for their performance as absorbent materials, as defined by the absorbency ratio (AR) test. All preliminary studies were done using normal saline solutions dyed with red food coloring. Saathi pads demonstrated significantly higher levels of AR compared to Natracare and knotweed pads due to the presence of superabsorbent polymers, making it an unreliable benchmark. Because Japanese knotweed is composed of cellulosic fibers that absorb water through hydrogen bonding to hydroxyl groups and capillary imbibition within porous fiber networks, lignin removal via alkaline processing was employed to enhance absorbency prior to experimental testing. The inner lumen of the knotweed was selected and delignified using a sodium hydroxide bath, later being shaped into an absorbent core akin to the measurements of the commercial pads and inserted into Natracare shells for proof-of-concept testing. Although knotweed-based pads exhibited lower AR values than Natracare, the testing places the knotweed prototype at approximately 40% of the fluid capacity, indicating a strong starting point for a natural fiber. To further evaluate the processing feasibility of Japanese knotweed beyond laboratory-scale pad prototyping, Japanese knotweed biomass was subjected to conventional Kraft pulping, which helps to remove lignin and increase absorbency. The Kraft pulping produced a moderately delignified brown pulp with a Kappa number of 20. Due to limiting factors, the absorbency of the pulp was not tested. However, the pulp’s fiber dimensions were comparable to hardwood pulps that are commonly used in absorbent applications, suggesting feasibility for future development into bleached fluff pulp and sustainable menstrual hygiene products. Full article

Optimizing the mechanical response of structures with triple periodic minimal surfaces (TPMS) is key to their use in lightweight applications focused on energy absorption. This study evaluated the influence of cell geometry and uneven material distribution on the bending behavior of Primitive, Gyroid, and Diamond structures. Nylon 12 CF samples were produced using an additive method (FDM) with volume fractions of 35%, 40%, 45%, and 55%. The mechanical response was quantified using a three-point bending test according to ISO 178, from which the maximum force (F_max), flexural strength (σ_f), absorbed energy (E_abs), and ductility index (µ_d) were determined. The Primitive structure achieved the highest strength at a volume fraction of 45% (σ_f = 28.35 MPa; F_max = 756 N). The Primitive structure also demonstrated the highest toughness with a ductility index of up to µ_d = 8.62 at 55%. The study identified a significant deformation phenomenon in the Gyroid structure, where the sample with a volume fraction of 45% showed higher absorbed energy (34.58 J) than the sample with a higher fraction of 55% (26.81 J). This finding suggests that targeted material inhomogeneity (gradient) can, under specific conditions, lead to stabilization of the deformation mechanism through progressive collapse, thereby increasing energy efficiency. The Primitive structure proved to be the most resistant to uneven material distribution and, with a volume fraction of 45–55%, offers an optimal compromise between high strength and toughness, making it most suitable for the design of gradient structures subjected to bending loads. Full article

Bio-epoxy composites were fabricated by casting a resin–hardener–filler mixture into 3D-printed molds, using different sea-originated secondary raw materials: mussel shell powder (MSP) (63–83 μm) and Posidonia oceanica short fibers (POF) (1–2 mm). Monofiller composites were prepared with 5 or 10 wt.% MSP, or 5 or 10 wt.% POF. Hybrid formulations were also produced, containing both MSP and POF in two combinations, where the total amount of filler again summed up at 10 wt.%. A subset of the samples was conditioned by immersion in a 35 ‰ NaCl solution reproducing seawater composition until saturation was reached. Characterization was carried out on unconditioned and conditioned samples by Shore D hardness and Charpy impact tests while performing three-point flexural loading only on unconditioned ones. Fracture morphology was also investigated. Adding MSP slightly enhanced resin hardness, whereas impact absorption exhibited, to a variable extent, a two-phase behavior, reproducing crack initiation and propagation. The MSP6-POF4 hybrid configuration provided the greatest improvement in absorbed energy (25–30% higher), which was retained after conditioning. The introduction of fillers, first separately, then in combination, resulted in a reduction in flexural strength to a similar extent for all unconditioned configurations. Finally, composite panels containing 10 wt.% MSP, 10 wt.% POF, and a 6MSP–4POF hybrid formulation, intended for prospective boat deck applications, were fabricated and compared with neat bio-epoxy, showing satisfactory consolidation. Density and post-molding dimensional shrinkage were measured on the panels. Full article

Background/Objectives. This research supports the development of long-acting injectables (LAIs) via in situ gel (ISG) technology by illustrating the influence of drug properties and formulation variables on in vitro drug release (Part 1), and providing an example of a point-to-point in vitro–in vivo correlation (IVIVC) for celecoxib ISGs (Part 2). Methods/Results. Part 1 evaluated the in vitro release (IVR) for ISGs containing 10 mg/g of five model drugs—paracetamol, theophylline, felbinac, indomethacin, and celecoxib—using two different poly(D,L-lactide-co-glycolide) (PLGA) grades with lactide/glycolide ratios (L/G) of 50:50 or 85:15 in N-methyl-2-pyrrolidone (NMP) at polymer/solvent ratios of 30/70% or 40/60% (w/w). The results demonstrated sustained IVR, with approximately 80% of the drug released within 1 to 5 days for the sparingly soluble compounds paracetamol and theophylline ISGs, and within 1.5 to 11 days, 3 to over 20 days, and 19 to 74 days for the slightly soluble compounds felbinac, indomethacin, and celecoxib, respectively. The IVR rate increased with decreasing polymer lipophilicity and concentration and with increasing drug solubility in the IVR medium. In Part 2, the pharmacokinetics of celecoxib ISGs were assessed following subcutaneous (SC) injection in rats. A point-to-point IVIVC was established between the fraction of drug absorbed derived via deconvolution (deconvoluted F_abs) and the fraction dissolved (observed F_diss) obtained in Part 1, based on Korsmeyer–Peppas fitting and release phase-specific scaling. Conclusions. In summary, this research highlights the significant impact of drug solubility, polymer grade, and concentration on the IVR rates of ISGs and provides an example of a point-to-point IVIVC for celecoxib ISGs with varying polymer concentrations and grades, following SC injection in rats. Full article