Search Results (304)

This study investigates subauroral phenomena during the main phase of the 10 May 2024 geomagnetic storm using a combination of ground-based observations from the WD IZMIRAN observatory (magnetometer, ionosonde, and all-sky imager) and Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) simulations. During 18:00–20:00 UT, we identified the simultaneous occurrence of ionospheric signatures of Polarization Jets (PJ)/Sub-Auroral Ion Drifts (SAID) and Strong Thermal Emission Velocity Enhancement (STEVE) over Kaliningrad, consistent with previously reported PJ/SAID identification from DMSP drift velocity measurements. This identification is supported by: (1) characteristic purple emissions (clearly visible in all three channels) moving rapidly westward; (2) U-shaped structures in ionogram sequences; (3) the reproduction of supersonic westward plasma drifts within a narrow latitudinal band by the first-principles model; and (4) observed and simulated significant Ne depletion. The estimated ion drift velocity from all-sky imaging (assuming an emission altitude of 200 km) is consistent with GSM TIP simulations, which predicted PJ/SAID velocities of ~750 m/s driven by a latitudinally narrow (~3°) but longitudinally extended (>50°) poleward electric field (40 mV/m). Simulations reveal that this PJ/SAID phenomenon causes a reversal of the zonal thermospheric wind at 250 km and induces Ne disturbances across the 200–700 km altitude range. The electron temperature enhancement (up to 1500 K) exhibits a “falling drop” shape, peaking at 350 km, while ion heating exceeds 150 K. The neutral temperature shows a dual response: frictional heating at 120–160 km and localized cooling at 175–250 km due to drop in electron density. Additionally, an increase in atomic oxygen concentration was predicted within the 90–200 km range across the PJ/SAID longitudinal sector. Full article

This study investigates the antioxidant and anticorrosive properties of Mentha pulegium L. essential oil (MP EO) as a sustainable and eco-friendly alternative to synthetic oxidation inhibitors. The antioxidant activity of MP EO was evaluated using the ferric reducing antioxidant power (FRAP) assay, which demonstrated a strong electron-donating capacity and effective reduction of ferric ions, indicating promising antioxidant potential. The anticorrosive performance was assessed on mild steel in 0.5 M H₂SO₄ using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed inhibition efficiencies of up to 75.8% at a concentration of 2 g/L. Molecular docking simulations revealed favorable binding interactions between the key oil components (pulegone and menthone) and the ROS-generating enzyme model (PDB ID: 2CDU), providing complementary mechanistic insight into their potential role in oxidative stress modulation. Additionally, quantum chemical calculations highlighted electronic properties favoring adsorption on metallic surfaces. Surface morphology analysis using SEM/EDX confirmed the formation of a protective film on steel in the presence of MP EO. These combined findings position Mentha pulegium essential oil as a potent, biodegradable candidate for both antioxidant applications and corrosion prevention in acidic environments. Full article

The detection of plastic explosives in vapor form is extremely challenging due to the very low volatility of their primary components, such as RDX and PETN. To overcome this limitation, volatile chemical markers like 2,3-dimethyl-2,3-dinitrobutane (DMNB) are added to explosive formulations to enable indirect vapor detection. This study presents a rapid method for detecting and quantifying DMNB vapors using a handheld ion mobility spectrometer (IMS) operating near ambient temperature, ammonia-doped and equipped with a non-radioactive corona discharge ionization source. The instrument, model LCD-3.2E (Smiths Detection Ltd.), is based on a twin drift–cell time-of-flight configuration and simultaneously records ion mobility spectra in both positive and negative modes. DMNB generated distinct product ion peaks in both modes, with reduced mobility values (K₀) of 1.42 cm²V⁻¹s⁻¹ (positive) and 1.37 cm²V⁻¹s⁻¹ (negative). The method demonstrated high sensitivity, with limits of detection calculated at 1.4 ppb_v (10.2 × 10⁻³ mg m⁻³) in positive mode and 3.1 ppb_v (22.7 × 10⁻³ mg m⁻³) in negative mode. The IMS system provided rapid responses within seconds and covered a quantifiable concentration range of 5–3000 ppb_v, with saturation estimated to appear above approximately 5 ppm_v (36.6 mg m⁻³). The simultaneous dual-polarity response of the DT IMS enhances both the selectivity and reliability of identification. These findings confirm the capability of portable IMSs for fast trace vapor detection in DMNB, supporting its application in field-based screening scenarios such as luggage inspection or container interrogation, where indirect detection of plastic explosives is required. Full article

Fluorite (CaF₂) and barite (BaSO₄) commonly occur together in the same deposits. Due to their similar surface chemical properties, their flotation separation is often challenging. In flotation pulps, dissolved metal ions can further interfere with separation and exert a pronounced influence on the flotation behavior of these minerals. This study investigated the effects of metal ions frequently encountered in industrial pulps (Fe³⁺, Al³⁺, Mg²⁺, Ca²⁺, and Zn²⁺) on the floatability of fluorite and barite in a sodium oleate (NaOL) collector system. The aims were to clarify how metal ions affect flotation behavior and to evaluate the feasibility of enhancing fluorite–barite separation via metal-ion regulation. Flotation results showed that, in the NaOL system, the largest floatability difference between fluorite and barite occurred at pH 10. Al³⁺ exhibited the strongest depression on barite while only weakly affecting fluorite flotation. Fe³⁺ and Mg²⁺ caused slight depression of barite, whereas Ca²⁺ and high concentrations of Zn²⁺ (>20 mg/L) promoted barite flotation. Overall, these metal ions had little influence on fluorite flotation. Adsorption measurements indicated that Al³⁺ reduced NaOL adsorption by more than 40% and decreased the contact angle from 35.6° to 23.1°, resulting in a sharp loss of surface hydrophobicity. ICP adsorption tests revealed that Al³⁺ showed the highest uptake on barite surfaces. Density functional theory (DFT) calculations further confirmed that surface SO₄²⁻ groups on barite form strong chemisorption with hydrolyzed Al species (adsorption energy: −436.19 kJ/mol), whereas only weak physisorption occurs on hydroxylated fluorite surfaces (adsorption energy: −43.73 kJ/mol). This study provides insights into the flotation separation of non-metallic minerals dominated by polar ionic bonding and offers practical guidance for efficient fluorite–barite separation under complex ionic environments. Full article

The corrosion behavior and passive-film stability of a β-TiZrNbTa (β-TZNT) alloy were investigated in artificial seawater (ASW), focusing on the effects of pH, temperature, immersion time, fluoride ion concentration, and potential scan rate. In addition to electrochemical methods such as open-circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed for surface characterization. The establishment of a stable and efficient passive layer enriched in Zr-, Nb-, and Ta-oxides was responsible for the β-TZNT alloy’s superior corrosion resistance in fluoride-free ASW when compared to commercially pure titanium. Reduced passive-film resistance resulted from corrosion kinetics being greatly accelerated by decreasing the pH and increasing the temperature. The presence of fluoride ions strongly affected the passivity of the alloy due to the chemical dissolution of TiO₂ through the formation of soluble fluoride complexes, resulting in an increase in the corrosion current densities by more than one order of magnitude. A bilayer passive structure with a compact inner barrier layer and a porous outer layer was identified by EIS analysis. The stability of this structure gradually decreased with increasing fluoride concentration and acidity. Over time, passive-film degradation was dominant in fluoride-free seawater, whereas prolonged exposure in fluoride-containing media promoted partial re-passivation. Overall, these results highlight the potential and limitations of the β-TZNT alloy for marine and offshore applications by offering new mechanistic insights into the synergistic effects of fluoride ions and environmental factors on corrosion performance. Full article

The escalation of thermal runaway in lithium-ion batteries presents severe safety hazards that necessitate advanced monitoring protocols to ensure early warning of potential failures. Carbon dioxide (CO₂) is released during preliminary decomposition well before catastrophic failure occurs, thereby providing a strategic advantage for early-stage warning. Consequently, identifying materials with high-selective CO₂ recognition is an essential prerequisite for developing reliable sensing platforms. This study integrates Grand Canonical Monte Carlo simulations with Random Forest (RF) models to systematically screen 1470 MOFs from the CoRE-MOF 2019 database. The screening process evaluates selective CO₂ recognition under multicomponent competitive adsorption conditions involving CO₂, C₂H₄, and O₂. The performance evaluation is based on working capacity, selectivity, and the trade-off between working capacity and selectivity (TSN). The RF model achieves high predictive accuracy, with tested R² exceeding 0.92 on the test samples. Shapley Additive Explanations (SHAP) interpretability analysis identifies Q⁰_st(CO₂), Q⁰_st(C₂H₄), WEPA, K_H(C₂H₄), and ETR as key performance drivers. The results indicate that CO₂ selectivity is constrained by the binding strength of competing C₂H₄. Optimal materials tend to have hard Lewis acid centers and polar inorganic clusters to minimize non-specific π-interactions with interfering species. Top-performing MOFs require balanced structural features, concentrating in moderate surface areas (965–1975 m²/g), narrow pore windows (PLD ≈ 4–7 Å, LCD ≈ 5.5–9.6 Å), high void fractions above 0.6, and low densities below 1.3 g/cm³. AJOTEY emerges as the optimal candidate with a TSN of 6.43 mol/kg, combining substantial working capacity (4.57 mol/kg) with strong selectivity (25.52). These results will accelerate the discovery of sensing materials and provide a practical pathway for MOF-based CO₂ sensor development to enhance lithium-ion battery safety. Full article

Physicochemical modification of titanium implants aims to enhance early osseointegration by improving bioactivity. This study deposited and evaluated an anatase TiO₂ film on clinically relevant sandblasted, acid-etched titanium (Ti-SLA) to enhance in vitro bioactivity and osteogenic responses. An ~8 µm TiO₂-anatase coating was deposited on Ti-SLA by reactive pulsed DC magnetron sputtering. Surface characterization included FE-SEM, helium ion microscopy, and XRD. Wettability and surface free energy (SFE) were evaluated by contact angle analysis. In vitro bioactivity was assessed by hydroxyapatite (HA) formation in twofold-concentrated simulated body fluid (2× SBF). Osteoblast responses were evaluated through cell adhesion, viability, alkaline phosphatase activity, gene expression, and mineralization. The coating produced hierarchical multi-globular microstructures decorated with faceted anatase nanocrystals. Ti-SLA’s initial hydrophobicity converted to a superhydrophilic, high-energy surface with increased polar SFE. Homogeneous HA crystallites deposited exclusively on SLA-anatase in 2× SBF. SAOS-2 cells showed enhanced metabolic activity, ALP activity, osteogenic gene upregulation, and improved mineralized matrix, while primary human osteoblasts exhibited increased metabolic activity and calcium deposition. The anatase coating produced a superhydrophilic, high-energy micro-nano surface that accelerates HA formation and enhances osteoblast function in vitro, warranting in vivo validation for early osseointegration. Full article

This study aims to enhance the corrosion property of 17-4PH martensitic stainless steel, a material commonly used in industrial applications including nuclear power components, to enhance its performance in borate buffer solutions. The study employed plasma-based low-energy nitrogen ion implantation at temperatures ranging from 350 °C to 550 °C for 4 h to modify the steel surface. Microstructural characterization via XRD and TEM revealed the formation of a nanocrystalline nitrided layer, with thickness increasing from 11 to 27 μm and surface nitrogen concentration rising from 29.7 to 33.1% as temperature increased. Correspondingly, the nanocrystalline grains coarsened from an average size of 2 nm to 15 nm. The main findings showed that all nitrided layers significantly improved general corrosion resistance in pH 8.4 borate solution compared to the unmodified steel. An optimal performance with a corrosion potential of −169.4 mV(SCE) and a passive current density of 0.5 μA/cm² was achieved at 450 °C, accompanying the development of a denser passive film with high polarization resistance and lower defect density. It is concluded that the high interstitial nitrogen concentration within the nanocrystalline γ′_N accelerates passivation kinetics and enhances corrosion resistance, with the applied point defect model clarifying the underlying improvement mechanism. Full article

This work presents integrated flux and velocity channel maps of the planetary nebula Abell 30 (A30) inner knot system. The observations were taken with the INTEGRAL spectrograph at the William Herschel Telescope (WHT), La Palma, Spain. Our IFU data cube has a field of view (FoV) of 12.3″× 16″ that partially covers knots J1 and J2, and completely covers knots J3 and J4 in the system. Optical Recombination Lines (ORLs) of C II, He I, He II, N III, O II and Collisionally Excited Lines (CELs) of [Ar IV], [Ar V], [N II], [Ne III], [Ne IV], and [O III] were detected. Our integrated flux maps visualise the ionisation structure and the chemical inhomogeneity in the system previously reported by other groups. We find that ORLs are concentrated in the polar region (J1, J3), whereas the equatorial knots (J2, J4) are dominated by CELs. The flux ratio map of the diagnostic [O III $\lambda$ 5007/4363 Å] lines reveals the electron temperature distribution, which shows cold cores of 15,000 K in knots J3 and J4 surrounded by a hot outer layer of above 20,000 K. Our channel maps show positive and negative velocity excursions from the systemic value among the ions. Several ions show variation in their velocity structures from their lower-energy-level counterparts, including [Ar IV] and [Ar V], [Ne III] and [Ne IV], and He I and He II. New recurrent velocity structures are identified in the low-density regions where the ions move much faster compared to their surrounding environments. The velocity dispersion measurements highlight extreme turbulence in some of the ions (${\sigma }_{{\mathrm{v}}_{\mathrm{rad}}}\approx 140$ km/s), consistent with supersonic/hypersonic motion driven by shocks. The forbidden line species [N II] exhibits lower turbulence (${\sigma }_{{\mathrm{v}}_{\mathrm{rad}}}\approx$ 50–60 km/s), tracing denser, less-turbulent gases. Based on our data, we conclude that both the ionisation and kinematic studies hint at shock heating and multiple ejection history in the evolutionary pathway of A30. Full article

This work investigates the corrosion behavior of 18%Ni high-strength steel (00Ni18Co-8Mo5TiAl, solution-treated at 820 °C for 3 h and aged at 480 °C for 3 h) in NaCl solutions with 1%, 3.5%, and 6% chloride ions, as well as chloride ions’ effect on passive film properties. The corrosion process was systematically studied via chemical immersion tests (GB/T 17897-1999, 144 h, solution-to-sample contact area ratio 20:1) and electrochemical methods, including EIS (frequency range: 100 kHz–0.01 Hz) and Tafel polarization curves (scan rate: 10 mV/min). Passive film evolution was analyzed via Mott–Schottky curves (fixed frequency: 1000 Hz, scanning potential: −1 V to 1 V vs. SCE). Microstructural observations show the steel exhibits pitting corrosion in chloride environments, with corrosion products transforming from loose outer α-FeOOH/γ-FeOOH to dense inner Fe₃O₄/β-FeOOH. These dense products inhibit anodic reactions. Electrochemical results reveal polarization resistance decreases and corrosion current density rises with increasing chloride concentration. Mott–Schottky curves indicate that flat band potential increases from −0.2177 V to −0.1258 V with rising chloride concentration, increasing point defects in the passive film and weakening its self-healing ability. Full article

Early oxidative stress caused by titanium implants can impair osseointegration. Manganese dioxide (MnO₂) nanozyme coatings have the potential to scavenge H₂O₂ and simultaneously generate O₂ to alleviate hypoxia, but their activity is mostly static, and the ion release is detrimental. A nano-MnO₂/Ti/P(VDF-TrFE) sandwich-structured composite was fabricated, and ferroelectric polarization was applied to preset a tunable surface potential. Kelvin probe force microscopy (KPFM) verified a presettable potential within ±500 mV. Steady-state kinetics confirmed an enhancement in overall catalytic efficiency (higher V_max and lower K_m). This translated to a faster initial decomposition rate at a low, physiologically relevant H₂O₂ concentration (300 μM). Correspondingly, under these oxidative stress conditions, cell survival in the polarized group was higher than that in the unpolarized group, indicating that the enhanced initial rate can have a positive effect in such conditions. Overall, this study demonstrates a proof-of-concept strategy to tune MnO₂ nanozyme catalysis using a polarization-preset surface potential, targeting implantation-relevant ROS-rich conditions. Full article

This study aims to investigate the effects of Cr and Mo added to Fe-Al alloys on their corrosion behavior in acidic and chloride-containing environments. Corrosion tests were carried out in 0.5 M H₂SO₄ and 3.5 wt.% NaCl aerated aqueous solutions. X-ray diffraction analyses reveal that all alloys exhibited predominantly body-centered cubic structures in the homogenized states. In the 0.5 M H₂SO₄ solution, the addition of Cr can effectively reduce the critical current density; however, the anodic and cathodic polarization curves still intersected three times, similar to the alloy without the addition of Cr, resulting in three corrosion potentials. With the further addition of Mo, the critical current density became much lower, leading to a single corrosion potential. In the 3.5 wt.% NaCl solution, the addition of Cr alone markedly improved the pitting resistance of Fe-Al alloys, while the further addition of Mo broadened the passive region and increased the pitting potential. The analysis of ion concentrations was consistent with the potentiodynamic polarization results, verifying the stabilization of Mo on the passive film. It is evident that the addition of Cr promotes passivation of the Fe-Al alloy, and the further incorporation of Mo enhances this effect even more significantly. The related corrosion mechanisms are discussed with Nerst equations of metal–metal oxides and their solubility products (K_sp). Full article

Electrokinetics has established itself as a central pillar in microfluidic research, offering a powerful, non-mechanical means to manipulate fluids and analytes. Mechanisms such as electroosmotic flow (EOF), electrophoresis (EP), and dielectrophoresis (DEP) re-main central to the field, once more layers of complexity emerge heterogeneous interfaces, viscoelastic liquids, or anisotropic droplets are introduced. Five research directions have become prominent. Field-driven manipulation of droplets and emulsions—most strikingly Janus droplets—demonstrates how asymmetric interfacial structures generate unconventional transport modes. Electrokinetic injection techniques follow as a second focus, because sharply defined sample plugs are essential for high-resolution separations and for maintaining analytical accuracy. Control of EOF is then framed as an integrated design challenge that involves tuning surface chemistry, engineering zeta potential, implementing nanoscale patterning, and navigating non-Newtonian flow behavior. Next, electrokinetic instabilities and electrically driven micromixing are examined through the lens of vortex-mediated perturbations that break diffusion limits in low-Reynolds-number flows. Finally, electrokinetic enrichment strategies—ranging from ion concentration polarization focusing to stacking-based preconcentration—demonstrate how trace analytes can be selectively accumulated to achieve detection sensitivity. Ultimately, electrokinetics is converging towards sophisticated integrated platforms and hybrid powering schemes, promising to expand microfluidic capabilities into previously inaccessible domains for analytical chemistry and diagnostics. Full article

This study quantitatively investigates the corrosion behavior of aluminum (Al1070) under salt water acetic acid test (SWAAT) conditions, focusing on the effects of chloride ions (Cl⁻) and acetic acid (CH₃COOH) concentration on the pitting corrosion. Potentiodynamic polarization tests showed that increasing Cl⁻ concentration caused a negative shift in corrosion potential (E_corr) and an increase in corrosion current density (i_corr), indicating accelerated passive film breakdown and enhanced pitting susceptibility. Immersion tests and SEM analysis revealed intensified surface discoloration, oxide formation, and crack propagation at higher Cl⁻ levels, confirming localized dissolution. The effect of acetic acid was evaluated for concentrations ranging from 0 to 2000 µL L⁻¹. Higher acetic acid levels lowered solution pH and slightly increased E_corr and elevated i_corr while reducing ΔE(E_pit − E_corr), indicating increased localized corrosion susceptibility. SEM and 3D XCT analyses showed increased pit density, corrosion loss, and pitting showed temporary pit coalescence at intermediate concentrations. Mechanistically, the acidic SWAAT environment (pH 2.8–3.0) positions aluminum in the active corrosion region. Cl⁻ destabilizes the passive oxide layer, initiating pitting, while acetic acid promotes metal dissolution via hydrogen evolution reactions. Their combined action exerts a specific effect, accelerating localized corrosion through chemical oxide layer degradation. These results provide quantitative insights into aluminum corrosion under SWAAT conditions. They could inform the design of corrosion resistant materials and reliability assessments in industrial applications. Full article

Alkaline water electrolysis is a widely researched method for hydrogen generation due to its low cost, scalability and its advantage of being able to produce hydrogen using only renewable energy. Enhancing the efficiency of electrolysis systems relies mainly on the development of high-performance ion-conductive membranes. The incorporation of ceramic fillers into polyvinyl alcohol (PVA) membranes as a composite material has shown considerable promise in enhancing the performance of electrolyzers. In this work, novel composite separator membranes for use in alkaline electrolyzers were developed from aqueous PVA solutions and physically crosslinked through a freeze–thawing process. To enhance the membrane properties, two types of ceramic fillers—titanium dioxide (TiO₂) and zirconium dioxide (ZrO₂)—were incorporated into the starting crosslinking solution. The thermal stability of these membranes was studied by a Differential Scanning Calorimetry (DSC) technique where we can conclude that addition of TiO₂ and ZrO₂ significantly influences the thermal properties of PVA membranes. These metal oxides enhance thermal stability, as shown by the shift in exothermic peaks toward higher temperatures and alterations in the degradation mechanism, evidenced by changes in the intensity and number of DSC peaks. The effect is concentration-dependent for TiO₂, where higher contents produce more pronounced yet increasingly complex thermal behavior. Compared with commercial membrane (Zirfon Perl), these types of membranes exhibit better electrochemical performance at ambient temperature and pressure; however, the process of preparation is simpler, reducing the cost of the hydrogen production process. The polarization curves (U-I curves) indicated a decrease in voltage with the addition of an ionic activator based on cobalt and molybdenum. Conductivity measurements performed using electrochemical impedance spectroscopy utilizing a two-probe method revealed that PVA membranes with TiO₂ exhibit ionic conductivity comparable to that of the commercial membrane. Compared to the commercial membrane, these types of membranes demonstrated similar mechanical properties and improved electrochemical performance at ambient temperature and pressure, along with a simplified production process and lower cost of hydrogen production. Full article