Search Results (7,926)

Hydrogen (H₂) was produced from recycled aluminum microparticles (180–250, 300–425, and 425–500 μm) via alkaline hydrolysis using a 1.0 M NaOH solution to enhance oxide layer removal and aluminum dissolution. Maximum hydrogen flow rates of approximately 13, 15, and 19 mL·min⁻¹ were obtained, confirming that smaller particle sizes promote faster reaction rates due to increased specific surface area. The hydrogen evolution exhibited two-stage kinetic behavior: an initial stage characterized by rapid aluminum dissolution and increasing H₂ production, followed by a gradual decline associated with the formation of a passivating Al(OH)₃ layer. Despite the higher reaction rates observed for smaller particles, the maximum cumulative hydrogen production was obtained for the intermediate particle size (363 µm, 132 mL), compared to 106 mL and 102 mL for 215 µm and 463 µm, respectively, indicating a trade-off between surface area and passivation effects. Kinetic analysis based on the shrinking core model showed excellent agreement (R² = 99.94–99.97%), with rate constants of 0.137, 0.064, and 0.050 min⁻¹. The relationship k ∝ d⁻ⁿ (n ≈ 1.4) suggests a mixed kinetic regime involving both surface reaction and diffusion through the Al(OH)₃ layer. These findings indicate that hydrogen generation can be modulated by particle size; however, the relatively low flow rates and yields limit its immediate practical applicability. Full article

Euphorbia tirucalli, commonly known as Aveloz, is widely used in Brazilian folk medicine for its purported antibacterial, antiviral, and antitumoral properties. However, scientific evidence regarding its systemic in vivo effects, particularly on the cardiovascular system, remains limited. This study investigated the impact of oral E. tirucalli latex ingestion on cardiac hemodynamics and associated molecular alterations in normotensive Wistar rats. Animals received water (control) or E. tirucalli latex (13.47 mg/kg) by oral gavage for 15 days. Hemodynamic parameters were assessed through noninvasive blood pressure monitoring and direct measurements of left ventricular systolic (LVSP) and end-diastolic pressures (LVEDP), cardiac cycle duration, rates of pressure development (dP/dt_max and dP/dt_min), and the left ventricular relaxation constant (Tau). Oxidative stress and inflammation were evaluated by plasma advanced oxidation protein products (AOPP) and myeloperoxidase (MPO), respectively, while reactive oxygen species production and apoptosis were analyzed in isolated cardiomyocytes. Although systemic blood pressure remained unchanged, E. tirucalli increased LVSP, LVEDP, cardiac cycle duration, and dP/dt_max, while reducing Tau. These alterations were accompanied by elevated AOPP and MPO levels, increased cardiomyocyte hydrogen peroxide, and higher rates of early apoptosis, indicating that E. tirucalli latex alters cardiac hemodynamics and promotes oxidative and inflammatory cardiac injury. Full article

Porous, crystalline gamma-Al₂O₃ coatings with a thickness of (6 ± 0.5) μm and a uniform distribution of rare earth (RE) dopants are synthesized by plasma electrolytic oxidation of aluminum at a current density of 150 mA/cm² in a boric acid and borax (BB) solution containing added RE oxide particles (Ho₂O₃, Tb₄O₇, and Pr₆O₁₁) at concentrations of 1, 2, and 4 g/L. The concentration of RE oxide particles in the BB solution determines the amount of RE elements incorporated into the coatings but does not significantly affect their surface morphology, crystal structure, or light absorption properties. The coatings exhibit high absorption in the middle/near-ultraviolet region, characteristic of Al₂O₃. Typical 4f-4f transitions of Ho³⁺, Tb³⁺, and Pr³⁺ are observed in the photoluminescence spectra. Photocatalytic evaluations using methyl orange degradation under simulated solar irradiation show that RE doping significantly enhances photocatalytic efficiency. Peak degradation efficiencies are achieved at a concentration of 4 g/L for all RE oxides. After 8 h of irradiation, maximum degradation reaches 88%, 92%, and 85% with pseudo-first-order rate constants (k_app) of about 0.274 h⁻¹, 0.339 h⁻¹, and 0.232 h⁻¹ for coatings synthesized in BB with 4 g/L Ho₂O₃, Tb₄O₇, or Pr₆O₁₁, respectively. In comparison, the pristine Al₂O₃ coating achieves only about 50% degradation (k_app ≈ 0.087 h⁻¹). Photoluminescence indicates that RE³⁺ ions serve as effective charge-carrier traps, suppressing electron–hole pair recombination. RE-doped Al₂O₃ coatings demonstrate exceptional structural stability and reusability over six cycles, highlighting their potential for sustainable wastewater remediation. Full article

One of the most puzzling and unsolved challenges in molecular biology is understanding how proteins fold. Despite having advanced predictive tools that can accurately estimate the native structures of proteins, we still lack a comprehensive model that explains how amino acid sequences dictate folding pathways and trajectories. This manuscript introduces a novel treatment for the issue by employing the “principle of least action.” This approach enables us to explore an intriguing question: how does a protein achieve its native state at a constant folding rate and within a biologically plausible time frame? A response to this inquiry will help us understand why proteins must fold along specific pathways and identify the boundary conditions that limit their availability. Furthermore, the principle of least action—together with the effective trajectory conjecture—enables us to explain why different proteins could exhibit the same folding rate. Finally, it will enable us to provide an in-depth description of the genesis and solution of Levinthal’s paradox. Our results are expected to pave the way for a more profound understanding of how proteins fold, shedding light on how the amino acid sequence and its surrounding environment encode the protein’s folding pathways and, consequently, the protein’s three-dimensional structure. Full article

Imidazolinone herbicides such as imazethapyr (IMT) pose potential ecological risks due to their high mobility and ecotoxicity. This study synthesized the bismuth-based photocatalyst BiOIO₃ via a facile hydrothermal method and systematically characterized its physicochemical properties. BiOIO₃ features a 2D lamellar structure, pure phase composition, and a built-in internal polarization electric field that efficiently separates photogenerated electron–hole pairs. Photocatalytic experiments exhibited that BiOIO₃ achieved 84.5% elimination of IMT, with a rate constant 66 times higher than that of TiO₂ (Rutile). Mechanistic studies revealed that photogenerated electrons (e⁻), holes (h⁺), and superoxide radicals (·O₂⁻) are the primary reactive species. HPLC-MS/MS identified key intermediates, and QSAR-based toxicity prediction showed reduced mutagenicity for most intermediates. Importantly, BiOIO₃ effectively eliminated five imidazolinone herbicides simultaneously. This work highlights BiOIO₃ as a promising photocatalyst for efficient and practical remediation of imidazolinone herbicide-contaminated water. Full article

Light-responsive hydrogel-based oscillators typically exhibit small oscillation amplitudes because solvent diffusion is intrinsically slow, and their dependence on external periodic light modulation further results in limited amplitude, poor stability, and insufficient autonomy. Inspired by the trigger and sliding mechanism of the ancient crossbow, this study introduces an innovative system that integrates a sliding-block mechanism with time-delay feedback, breaking from conventional approaches that rely on hydrogel inertia or external modulation, within a purely theoretical and simulation-based framework. By establishing a nonlinear dynamic model coupling solvent diffusion, photoisomerization, and optical attenuation, this research shows through numerical simulations that the system can exhibit two distinct modes under constant illumination: a stable state and a self-sustained oscillatory state. The model predicts that the oscillation frequency can be flexibly tuned by varying key parameters, including the crosslinking density, Flory–Huggins interaction parameters of the spiropyran and hydrophilic polymer, ring-opening reaction rate, light intensity, fraction of light-sensitive molecules, and sliding displacement, whereas the initial absorption coefficient has only a minor influence. The slider displacement is also identified as an effective means to regulate the oscillation amplitude. Furthermore, the expansion force at the container bottom is predicted to oscillate synchronously with the hydrogel’s volume change. This theoretical framework represents a paradigm shift from “static small deformation” to “dynamic large-amplitude oscillation”, significantly enhancing the mechanical responsiveness of the material. This work provides a novel and controllable strategy for the conceptual design of autonomous light-driven micromechanical systems. Full article

Estimating in a stream’s cross-section the depth-averaged velocity, V, from the free-surface velocity, v_surf, is an efficient, non-invasive hydrometric method. The ratio f_v = V/v_surf is typically assumed constant at f_v = 0.86 in field applications, despite observations to the contrary. Guidance is, therefore, needed in estimating actual f_v-ratios when velocity profile data are absent. This work provides field-verified guidance based on the hydromechanics of the logarithmic velocity law, which shows that f_v depends on the scaled resistance measure ‘friction length/depth’, y_o/h, with the y_o(k) function of the equivalent sand grain roughness, k. The mean-to-surface-velocity ratio in rough-bed streams is estimated from the bed roughness and stream morphology by modifying Nikuradze’s equation, y_o = k/30, to y_o = ck, with c(h/k) ≥ 1/30, and k ≈ D₈₄—data fit: c ≈ 8.61(h/k)^−1.821, ~5 ≤ h/k < ~30. Field-verification of the ratio’s modified hydromechanics, f_v = f$\left(h/y_o\right),$ with y_o(h/k) evaluated from bed roughness estimated by inspection or sieve analysis shows this ratio holding within ~|10|% error for shallow streamflow over a coarse bed of gravels and rocks, giving submergences of ~5 ≤ h/D₈₄ ≤ ~30; y_o = k/30 suits large streams with smooth beds (h/k ≥ ~30, f_v ≥ ~0.86). Variable roughness-estimated f_v-ratios appear to be more reliable than the fixed default, f_v(h/y_o ≈ 1000) = 0.86. This flow-gauging concept is based on observable physical characteristics of a monitoring cross-section and facilitates the rating of hard-to-access streams draining small basins in ragged upland terrain. Full article

Multi-Robot Systems (MRS) demand optimal spatial resource configuration to ensure systemic efficiency in mission-critical applications. Conventional paradigms rely on rigid coverage-first principles, prioritizing exhaustive spatial scanning over rapid target discovery, thereby compromising systemic responsiveness. To bridge this gap, this study proposes the Attraction of Unknown area Centroid for Exploration (AUCE) architecture, a centralized framework designed to simultaneously optimize global exploration efficiency and early-stage target discovery rates. The control framework incorporates a dynamic region planning strategy that adaptively modulates the systemic search focus based on the specific field of view of autonomous agents, alongside an optimized S-shaped trajectory pattern to establish a rigorous balance between localized path simplicity and global coverage. A versatile profit function synthesizing constant and time-varying coefficient strategies explicitly regulates the systemic trade-off between accelerated early-stage target discovery and global path cost minimization. Quantitative simulations demonstrate that AUCE significantly outperforms established methods by mitigating redundant path costs and generating a distinct front-loading effect to accelerate target localization. Subsequent evaluations confirm the framework’s computational scalability in expanded swarms and its systemic adaptability when navigating static obstacles. Full article

Background and Clinical Significance: Conventional hard sockets are reported to result in skin breakdown for almost half of transtibial prosthesis users. Adjustable sockets have been developed to better accommodate residual limb shape and volume changes. They have demonstrated optimal skin health in prospective adult clinical studies. Case Presentation: We present the case of a 57-year-old male with a transtibial amputation who enrolled in a research study at the University of Pennsylvania. In the year before enrollment, he experienced frequent, near-constant skin breakdown of the distal residual limb at the anterior tibia due to limb volume fluctuations and excessive pressure from a conventional hard socket and was frequently unable to use his socket due to skin breakdown. The subject was fit with an adjustable, immediate fit transtibial prosthesis (iFIT Prosthetics^®). After a two-week home trial, he rated the adjustable prosthesis 62 out of 70 on an adapted Prosthetic Evaluation Questionnaire, compared with a score of 20 for his conventional prosthesis. Due to improved comfort, he discontinued the use of his conventional device. The subject was followed for over one year and wore the adjustable prosthesis exclusively without a recurrence of skin breakdown. Residual limb volume changes commonly lead to poor socket fit and skin irritation in conventionally fabricated hard sockets, often progressing to skin breakdown. In individuals with diabetes, wound healing can be prolonged and functionally limiting. In this case, an adjustable prosthesis successfully eliminated anterior tibial skin breakdown in a subject predisposed to this injury when using conventional hard sockets. Conclusions: Adjustable sockets can prevent skin breakdown in individuals with transtibial limb loss. Full article

Motor vehicle exhaust in urban tunnels can cause nitric oxide (NO) to accumulate, severely degrading air quality both inside the tunnel and in the surrounding environment. Photocatalytic technology is an efficient, secondary-pollution-free approach with clear potential for treating tunnel exhaust; however, parametric analyses for practical tunnel engineering applications remain limited. Using computational fluid dynamics (CFD), this study developed a numerical model to simulate photocatalytic NO degradation in a congested tunnel and examined how the surface reaction rate, coating extent, and longitudinal coated section affect NO reduction performance. The results show that NO reduction efficiency increased with the surface reaction rate; however, once the surface reaction rate constant exceeded 2.11 × 10⁻⁴ m/s, further gains diminished and the efficiency approached a plateau due to mass-transfer limitations. With respect to the coating extent, full four-wall coating (sidewalls, ceiling, and road surface) provided the best performance, followed by three-wall coating (excluding the ceiling). Moreover, because the road surface lies in a region of high pollutant concentration and low air velocity, coating on the road surface achieved a markedly stronger reduction effect than coating on the sidewalls or the ceiling. In the simulated 500 m tunnel, the downstream coated section achieved a markedly higher NO reduction efficiency in the ambient environment outside the tunnel (5.9%) than the upstream coated section (1.0%), approaching that of the full-length (500 m) coated section (6.6%). Therefore, in practical engineering applications, priority should be given to coating strategies targeting the downstream section and the road surface in order to balance NO reduction performance and economic cost. Such a strategy is beneficial not only for improving tunnel air quality, but also for promoting sustainable pavement and tunnel-surface engineering by reducing unnecessary coating area and enabling a more resource-efficient and cost-effective use of photocatalytic materials. These findings provide theoretical and methodological support for the sustainable design and application of photocatalytic coating systems in urban tunnels. Full article

Ultra-high-performance concrete (UHPC) is widely used due to its strength, toughness, and durability. Shrinkage issues are the primary cause of concrete cracking and one of the main factors limiting the widespread application of UHPC in structural engineering. The shrinkage properties of UHPC vary depending on curing conditions. Research indicates that after thermal curing, the pore structure of UHPC is optimized, resulting in a significant reduction in shrinkage values. Based on the superposition principle, temperature creep coefficients and humidity creep coefficients are introduced to correct the temperature and humidity in the test environment to a constant temperature (20 °C) and humidity (75% relative humidity). The B3 coefficient of variation method was used to compare five different creep prediction models. The CEB-FIP2010 model was selected as the benchmark creep model, and curing condition coefficients were incorporated into the model to establish a comprehensive creep calculation model considering curing conditions. After 550 days of steam curing, the shrinkage strain of the UHPC specimens was approximately 28.9% of that of the uncured specimens. The additional creep deformation caused by temperature and humidity in the uncured and steam-cured specimens accounted for approximately 10% and 20% of the total creep deformation over 550 days, respectively. The strain development rates for both tensile and compressive strains in steam-cured specimens were lower than those in uncured specimens. A ten-year long-term creep simulation of UHPC precast joint beams was conducted using the finite element software Midas-Fea, and the comparison results validated the reliability of the comprehensive creep model. Full article

The rapid expansion of the Internet of Vehicles (IoV) necessitates high-capacity backhaul connectivity, yet the deployment of such networks under strict hardware and power constraints poses significant computational challenges for network optimization. To address this challenge, this paper investigates a joint transmit–receive beamforming optimization problem for narrowband wireless backhaul in IoV networks under constant-modulus constraints. Unlike ideal digital architectures, we focus on cost-effective analog phase shifters, which introduce strictly non-convex constant-modulus constraints, rendering the optimization problem mathematically intractable for standard solvers. Since the resulting problem is highly non-convex, we develop two structured numerical methods: an iterative alternating optimization (AO) method and a joint optimization (JO) method, where AO employs auxiliary WMMSE-guided alternating updates together with constant-modulus projection, while JO jointly updates both beamformers over the constant-modulus feasible set. We compare their achievable sum-rate performance with that of a CDO-based benchmark and analyze their dominant computational costs through representative Big-O complexity expressions. Furthermore, we examine the effect of SVD-based and random feasible initializations on empirical convergence behavior, runtime, and final achievable performance. Simulation results demonstrate that the proposed computational methods significantly improve achievable sum-rate performance compared with the CDO benchmark. Moreover, SVD-based initialization provides a more structured starting point and generally leads to better convergence behavior and lower runtime than random feasible initialization. The empirical timing results further show that AO exhibits faster empirical convergence and requires lower runtime, whereas JO achieves better final sum-rate performance after more iterations. Full article

Despite the growing adoption of Ti6Al4V-ELI made by Laser Powder Bed Fusion (LPBF) in tribologically demanding applications, the influence of hybrid nanoparticle additives on its lubrication behavior under starved contact conditions remains insufficiently explored. The tribological performance of Ti6Al4V was investigated under starved boundary-to-mixed lubrication conditions using engine oil modified with Ag-doped TiO₂ nanoparticles. Double-scan LPBF-fabricated discs were tested in a ball-on-disc configuration against AISI 52100 bearing steel using a TRB³ tribometer. Nanolubricants were prepared by dispersing TiO₂ and Ag–TiO₂ nanopowders with different Ag⁺/Ti⁴⁺ ratios (0.5%, 1.5%, and 2.5%) in SAE 10W-40 engine oil at a constant nanoparticle concentration of 0.05 wt%. Comprehensive physicochemical characterization of the nanopowders and nanolubricants was performed through structural, chemical, optical, morphological, rheological, and stability analyses. Tribological experiments were conducted following a full-factorial design combining three normal loads (5–15 N), three sliding speeds (0.10–0.20 m·s⁻¹), and four lubricant formulations. The steady-state coefficient of friction ranged between 0.281 and 0.359, while the specific wear rate varied from 2.81 × 10⁻⁴ to 4.83 × 10⁻⁴ mm³·N⁻¹·m⁻¹. The contact temperature rise remained relatively moderate, within the interval of 1.9–9.4 °C. Among the investigated formulations, the lubricant containing 1.5% Ag–TiO₂ exhibited the lowest friction coefficient, whereas the formulation with the highest Ag content showed improved stability of tribological performance across the investigated operating domain. These results indicate that Ag-modified TiO₂ nanoparticles are consistent with the formation of protective tribofilms and contribute to the stabilization of friction, wear, and thermal behavior under starved lubrication conditions. ANOVA confirmed that sliding speed and the load–lubricant interaction are the dominant factors governing friction and wear, while normal load controls the thermal response. These findings support the use of Ag–TiO₂ nanolubricants as a viable strategy for stabilizing interfacial behavior in LPBF-fabricated titanium components operating under starved lubrication conditions. Full article

The microstructure, phase composition, and high-temperature oxidation behavior of Al_0.5CoCr_0.5NiPt_0.1 and AlCoCr_0.5NiPt_0.1 multi-principal element alloys (MPEAs) at 1100 °C in air were investigated. Depending on the content of aluminum, the microstructure of as-cast samples contains FCC and BCC solid solutions. Similarly, the ratio of two solid solutions varies depending on the aluminum content in the alloy. When the content of aluminum is x = 0.5, the microstructure is dominated by the FCC solid solution, while a BCC solid solution is dominated when the concentration of aluminum is increased to x = 1.0. Moreover, in both MPEAs, platinum exists as a part of solid solutions rather than a separate phase. High-temperature oxidation was carried out in a Plavka.Pro PM-1 SmartKiln muffle furnace under isothermal conditions at 1100 °C for 100 h exposure in air, and weighing was performed every 10 h. The maximum specific weight gain for the Al_0.5CoCr_0.5NiPt_0.1 alloy was 0.965 mg/cm², and 0.675 mg/cm² for the AlCoCr_0.5NiPt_0.1 alloy. Based on the high-temperature oxidation experiment results, it was established that AlCoCr_0.5NiPt_0.1 MPEA exhibits greater resistance towards high-temperature dry air corrosion with the formation of an exclusive Al₂O₃ scale on the surface with 3–5 μm thickness; the parabolic oxidation rate constant for this alloy is k_p = 20.2 × 10^–13 (g²/cm⁴s). Introduction of platinum into the composition of the Fe-free AlCoCr_0.5Ni alloy reduces the value of the parabolic oxidation rate constant by half. Full article

Synthetic dyes frequently persist through conventional wastewater treatment, motivating the use of advanced oxidation processes capable of breaking down these stable molecules. Metal-doped carbon dots (CDs) offer a tuneable platform for catalytic dye degradation in water, although their performance varies strongly with operating conditions. The aim of this work was to determine how temperature, H₂O₂ dosage, and pH influence the catalytic behaviour of Fe-, Cu-, Zn-, and Mg-doped CDs during the degradation of methylene blue (MB) and rhodamine B (RB), optimised using a Taguchi L27 orthogonal array design. Temperature and oxidant loading were the dominant factors: higher temperatures accelerated reactions through Arrhenius-type kinetics, while increasing H₂O₂ availability improved removal until excessive levels began to suppress •OH generation. Across all condition sets, apparent rate constants spanned 7.0 × 10⁻⁴–2.65 × 10⁻² min⁻¹, with t₅₀ values of 26–217 min and t₉₀ extending from ~86 min to >700 min; final decolourisation ranged from ~17% to nearly 100%. pH played a secondary role, mainly affecting dye speciation and surface adsorption. Dopant identity shifted the optimum operating region for each catalyst: Fe- and Cu-CDs achieved complete or near-complete removal of both dyes at pH 7 and 50 °C with relatively low H₂O₂ dosage (0.5–1.0 mL); Zn-CDs reached equivalent performance at pH 7 and 25 °C but required higher oxidant loading (1.5 mL of H₂O₂), reflecting their photo-induced rather than thermally driven activation mechanism; Mg-CDs performed comparably under the same conditions as Fe- and Cu-CDs. The resulting condition–catalyst map highlights the operating regimes that maximise efficiency while minimising chemical input, providing a practical framework for selecting carbon-dot-based catalysts for water treatment applications. Full article