Search Results (71,070)

Solar flares are among the most powerful and dynamic events in the solar system, resulting from the sudden release of magnetic energy stored in the Sun’s atmosphere. These energetic bursts of electromagnetic radiation can release up to ${10}^{32}$ erg of energy, impacting space weather and posing risks to technological infrastructure and therefore require accurate forecasting of solar flare occurrences and intensities. This study evaluates the predictive performance of three machine learning algorithms—Random Forest (RF), k-Nearest Neighbors (kNN), and Extreme Gradient Boosting (XGBoost)—for classifying solar flares into four categories (B, C, M, X). Using 13 parameters of the SHARP dataset, the effectiveness of the models was evaluated in binary and multiclass classification tasks. The analysis utilized 8 principal components (PCs), capturing 95% of data variance, and 100 PCs, capturing 97.5% of variance. Our approach uniquely combines binary and multiclass classification with different levels of dimensionality reduction, an innovative methodology not previously explored in the context of solar flare prediction. Employing a 10-fold stratified cross-validation and grid search for hyperparameter tuning ensured robust model evaluation. Our findings indicate that RF and XGBoost consistently demonstrate strong performance across all metrics, benefiting significantly from increased dimensionality. The insights of this study enhance future research by optimizing dimensionality reduction techniques and informing model selection for astrophysical tasks. By integrating this newly acquired knowledge into future research, more accurate space weather forecasting systems can be developed, along with a deeper understanding of solar physics. Full article

Medicinal plants play an essential role in the food, pharmaceutical, and cosmetic industries due to their ability to prevent and treat diseases. In this study, a three-factor, three-level Box–Behnken experimental design (BBD) with response surface methodology (RSM) was used to maximize the conditions of ultrasound-assisted extraction (UAE) of bioactive compounds from matico and chacruna leaves in terms of total extraction yield (TEY), total phenolic content (TPC) and antioxidant activity (AA) using ABTS and DPPH assays. The effect of methanol concentration (X1: 25%, 50%, and 75%), time (X2: 3, 6, and 9 min), and power (X3: 90, 270, and 450 W) was evaluated as independent variables. The experimental results were fitted to second-order polynomial models, and multiple regression analysis and analysis of variance were used to determine the suitability of the models, using which 3D response surface plots were generated. Considering the multivariable optimization, the best extraction conditions were 73.68% v/v methanol, 9 min, 269.32 W for matico, and 64.84% v/v methanol, 3 min, 344.44 W for chacruna. Under these conditions, the maximum value of 18.33 and 20.83% for TEY, 7.16 and 40.86 mg GAE/g dm for TPC, 56.88 and 526.38 µmol TE/g dm for DPPH were predicted for matico and chacruna, respectively. Practical Applications: This research focused on the modeling by response surface methodology (RSM) of Ultrasound-Assisted Extraction of bioactive compounds from matico and chacruna, Peruvian plants used in traditional medicine. The methodologies used allow the maximization of bioactive extraction, which presented a high recovery of phenolics with high antioxidant activity. These results highlight the use of Amazon plants in traditional medicine and their possible use in other industries such as cosmetic or food safety. Full article

The title compound has been fully characterised using ¹H and ¹³C NMR spectroscopy, which reveals (E) to (Z) isomerisation upon dissolution. In the solid state, X-ray diffraction shows exclusively the (E)-isomer with two geometrically near-identical independent molecules each with the outer rings tilted with respect to the central ring. Full article

The photocatalytic activity of silica–titania (S-T) fibers synthesized via sol–gel and electrospinning was evaluated using methyl orange (MO), eriochrome black T (EB), and methylene blue (MB) as model dyes. Characterization by X-ray diffraction confirmed the presence of anatase and rutile TiO₂ phases, while UV-Vis spectroscopy determined a bandgap energy of 3.2 eV. Scanning electron microscopy revealed fibers with an average diameter of 214 nm. Under UV irradiation, nearly complete dye removal (initial concentration: 30 mg/L; catalyst dosage: 0.1 g/L) was achieved within 8 h. The reaction kinetics followed the Langmuir–Hinshelwood model, with significant differences in apparent reaction rates (k_a) among the dyes, attributable to their distinct structural and functional properties. This study establishes silica–titania fibers as a high-performance, highly versatile composite photocatalyst. Achieving 98% degradation efficiency, their key innovation is their fibrous morphology, which solves the critical problem of powder catalyst recovery. This enables a paradigm shift from simple lab efficiency to practical, sustainable application. Full article

Molybdenum oxide (MoO_X) has been widely utilized as a hole transport layer (HTL) in crystalline silicon (c-Si) solar cells, owing to characteristics such as a wide bandgap and high work function. However, the relatively low conductivity of MoO_X films and their poor contact performance at the MoO_X-based hole-selective contact severely degrade device performance, particularly because they limit the fill factor (FF). Oxygen vacancies are of paramount importance in governing the conductivity of MoO_X films. In this work, MoO_X films were modified through ultraviolet irradiation (UV-MoO_X), resulting in MoO_X films with tunable oxygen vacancies. Compared to untreated MoO_X films, UV-MoO_X films contain a higher density of oxygen vacancies, leading to an enhancement in conductivity (2.124 × 10⁻³ S/m). In addition, the UV-MoO_X rear contact exhibits excellent contact performance, with a contact resistance of 20.61 mΩ·cm², which is significantly lower than that of the untreated device. Consequently, the application of UV-MoO_X enables outstanding hole selectivity. The power conversion efficiency (PCE) of the solar cell with an n-Si/i-a-Si:H/UV-MoO_X/Ag rear contact reaches 24.15%, with an excellent FF of 84.82%. Full article

Copper (Cu) doping is recognized as an effective strategy to enhance the electrochemical properties of LiNi_1−x−yCo_xMn_yO₂ (NCM) cathode materials. However, the influence of Cu²⁺ doping on particle size and grain boundary fusion remains insufficiently explored. A simple microwave-assisted solution combustion synthesis method was used to introduce Cu²⁺ into LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523), aiming to regulate particle size and grain boundary fusion. The results demonstrate that increasing the Cu²⁺ doping content promotes particle growth, while an appropriate doping level reduces the degree of grain boundary fusion and cation mixing. Benefiting from these structural improvements, the optimized LiNi_0.5Co_0.2Mn_0.29Cu_0.01O₂ (Cu‒1) cathode exhibits significantly enhanced electrochemical performance, delivering a discharge capacity of 128.6 mAh g⁻¹ after 100 cycles at 0.2 C, which is 32 mAh g⁻¹ higher than value of the undoped sample (96.6 mAh g⁻¹). These findings underscore that tailored Cu²⁺ doping can effectively optimize the microstructure of NCM523, leading to superior cycling stability, and provide new insights into the design of high-performance NCM cathodes. Full article

Bronze materials are indispensable across numerous industries for enhancing the durability and performance of components, primarily due to their excellent tribological properties, corrosion resistance, and machinability. This study investigates the impact of different atmospheric conditions on the properties of WAAM (wire arc additive manufacturing) cladded bronze coatings on 09G2S steel substrate. Specifically, the research examines how varying atmospheres—including ambient air (N₂/O₂, no shielding gas), pure argon (Ar), carbon dioxide (CO₂), and 82% Ar + 18% CO₂ (Ar/CO₂) mixture—influence coating defectiveness (porosity, cracks, non-uniformity), wettability (manifested as uniform layer formation and strong adhesion), and the extent of intergranular penetration (IGP), leading to the formation of characteristic infiltrated cracks or “bronze whiskers”. Modern investigative techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were employed for comprehensive material characterization. Microhardness testing was also carried out to evaluate and confirm the homogeneity of the coating structure. The findings revealed that the bronze coatings primarily consisted of a dominant, highly textured FCC α-Cu phase and a minor BCC α-Fe phase, with Rietveld refinement quantifying a α-Fe volume fraction of ~5%, lattice parameters of a = 0.3616 nm for α-Cu and a = 0.2869 nm for α-Fe, and a modest microstrain of 0.001. The bronze coating deposited under a pure Ar atmosphere exhibited superior performance, characterized by excellent wettability, a uniform, near-defect-free structure with minimal porosity and cracks, and significantly suppressed formation of bronze whiskers, both in quantity and size. Conversely, the coating deposited without a protective atmosphere demonstrated the highest degree of defectiveness, including agglomerated pores and cracks, leading to an uneven interface and extensive whisker growth of varied morphologies. Microhardness tests confirmed that while the Ar-atmosphere coating displayed the lowest hardness (~130 HV_0.1), it maintained consistent values across the entire analyzed area, indicating structural homogeneity. These results underscore the critical role of atmosphere selection in WAAM processing for achieving high-quality bronze coatings with enhanced interfacial integrity and functional performance. Full article

This study investigated the chemical and autogenous shrinkage behaviour of limestone calcined clay cement (LC³) pastes incorporating calcined clays sourced from Australia, France, and India. Hydration development and microstructural evolution were examined using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and pore-size distribution analysis. Results showed that LC³ mixes hydration accelerates during early phases, with the main silicate hydration peak appearing more prominently than that in the GP and FA reference pastes, indicating increased nucleation and growth of hydration products due to the limestone filler effect. LC³ pastes exhibited higher autogenous shrinkage overtime, strongly influenced by calcined clay reactivity and particle fineness. A clear correlation was observed between pore refinement and autogenous deformation during the early phases (7 days): pastes with a greater volume of fine pores showed higher early-age autogenous shrinkage during the first 7 days of hydration. In contrast, the chemical shrinkage of LC³ mixes was comparable to that of the GP and FA systems at early ages (≤7 days) but became lower after 28 days, attributed to both the matrix densification and additional nucleation sites provided by the limestone. Overall, LC³ reduces long-term chemical shrinkage and densifies the microstructure; however, the refined pore structure and increased internal water demand lead to higher autogenous shrinkage. These findings demonstrate a direct link between hydration-driven microstructural evolution (phase formation and pore refinement) and the resulting shrinkage behaviour. Full article

Roselle (Hibiscus sabdariffa L.) is a plant rich in bioactive constituents, serving as a unique material for the food and beverage industry and therapeutic applications. Despite its significant utility, few studies have focused on the molecular breeding of the plant. Chloroplasts are organelles in plant cells with independent genetic information, making them ideal for investigating plant phylogeny and genetic evolution. In this study, the roselle breeding material ‘Zhe Xiao Luo 1’ was selected to assemble and analyze the entire chloroplast genome using the Illumina NovaSeq X Plus platform. The phylogenetic relationships between roselle and other species within Malvaceae family, particularly within the genus Hibiscus, were clarified. The results showed that the complete chloroplast genome of roselle was 162,428 bp in length, with nucleotide proportions of 31.14% (A), 18.73% (C), 18.01% (G), 32.12% (T), and 36.74% (GC). It exhibited a typical tetrad structure consisting of four segments: the large single copy (LSC) region (90,327 bp), the small single-copy (SSC) region (19,617 bp), and two inverted repeat sequences (IRa and IRb, each 26,242 bp). A total of 130 genes were identified, including 37 tRNA genes, 8 rRNA genes, and 85 mRNA genes, and no pseudogenes were detected. Phylogenetic analysis using 23 revealed a clear phylogenetic relationship between H. sabdariffa and H. esculentus (okra) among all tested species. Building on previous research, this study further explored the functional annotation of genes in the roselle chloroplast genome, as well as its codon preference, repetitive sequences, simple sequence repeats (SSR), Ka/Ks ratio, nucleotide diversity (pi) analysis, and boundary analysis. The complete gene sequences have been uploaded to the NCBI database (accession number PX363576). This study provides evidence for elucidating the phylogenetic relationships and taxonomic status of H. sabdariffa, laying a theoretical foundation for studies on molecular mechanism resolution and cultivar development. Full article

In this work, two novel nanoscale zero-valent iron (nZVI) composites (nanoscale zero-valent iron and copper-intercalated montmorillonite (MMT-nFe⁰/Cu⁰) and carbon microsphere-supported sulfurized nanoscale zero-valent iron (CMS@S-nFe⁰)) were used to treat soil contaminated with both Cr(VI) and p-nitrophenol (PNP), and added persulfate (PMS). Experiments found that the pollutant removal effect has a great relationship with the ratio of water to soil, the amount of catalyst, the amount of PMS, and the pH value. When the conditions are adjusted to the best (water–soil = 2:1, catalyst 30 g/kg, PMS 15 g/kg, pH 7–9), both materials fix Cr(VI) well and decompose PNP. The removal rates of Cr(VI) and PNP by the MMT-nFe⁰/Cu⁰ system are 90.4% and 72.6%, respectively, while the CMS@ S-nFe⁰ system is even more severe, reaching 94.8% and 81.3%. Soil column leaching experiments also proved that the fixation effect of Cr can last for a long time and PNP can be effectively decomposed. Through detection methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), we found that Cr(VI) was effectively reduced to Cr(III) by Fe⁰ and Fe²⁺ ions and subsequently transformed into stable FeCr₂O₄ spinel oxides, and the groups produced after the decomposition of PNP could also help fix the metal. This work provides a way to simultaneously treat Cr(VI) and PNP pollution, and also allows the use of multifunctional nZVI composites in complex soil environments. Full article

This paper proposes a post-quantum secure key agreement protocol tailored for vehicular networks (V2X), addressing the dual challenges of quantum resistance and lightweight deployment. The hybrid scheme integrates two lattice-based Key Encapsulation Mechanisms (KEMs)—Kyber and Saber—to construct a dual-path handshake framework that enhances cryptographic redundancy and ensures robustness against quantum attacks. The protocol achieves secure and authenticated key exchange through RSU public-key broadcasting, OBU dual-path encapsulation, and session-key derivation using HMAC and timestamps. To support efficient execution in embedded vehicular environments, several algorithm-level optimizations are incorporated, including Number Theoretic Transform (NTT) acceleration for Kyber, AVX2-based parallelism for Saber, and integer inner-product techniques to minimize computational overhead. Experimental validation on a Veins + SUMO vehicular simulation platform demonstrates that the proposed protocol reduces handshake latency by nearly 60% compared with RSA, achieves delay performance comparable to ECDH, and lowers total resource consumption by around 40%. These results confirm that the Kyber + Saber hybrid protocol provides a practical, scalable, and quantum-resistant solution for secure V2X communication in dynamic, resource-constrained, and latency-sensitive environments. Full article

Background: Accurate digital transfer of implant positions is critical for the long-term success of full-arch prosthetic rehabilitation. Photogrammetry remains the benchmark for accuracy, but its high cost and complexity limit clinical adoption. Artificial intelligence (AI)-driven intraoral scanning protocols incorporating real-time library matching and irregular, individually coded scan bodies have been proposed as accessible alternatives to improve accuracy and reproducibility. Methods: This in vitro study evaluated the trueness and precision of a full-arch implant scanning workflow using an AI-assisted real-time library matching system in combination with irregular multi-geometry titanium scan bodies. A high-accuracy structured-light scanner served as the reference standard. Six implant positions (35, 33, 31, 41, 43, 45) were scanned across 20 datasets (n = 120). Mean surface deviations were calculated against the reference STL using CloudCompare v.2.14. and a two-way ANOVA (α = 0.05) in SPSS tested the effects of implant position and scan iteration. Results: The workflow achieved a mean deviation of 13.55 ± 9.70 μm (range 0.77–43.46 μm) across all positions. Anterior sites showed the lowest deviations (e.g., position 31: 3.95 μm; 45: 5.96 μm), while posterior sites exhibited higher deviations (e.g., position 43: 26.15 μm). No mean deviation exceeded 30 μm, and no individual measurement surpassed 45 μm. Implant position significantly affected accuracy (p < 0.001), whereas scan iteration did not (p > 0.05). Conclusions: Within the limitations of this in vitro model, an AI-assisted real-time library matching workflow used in conjunction with irregular multi-geometry scan bodies achieved accuracy levels well within clinically acceptable ranges for full-arch implant impressions. Although comparable to values reported for photogrammetry under laboratory conditions, clinical equivalence should not be assumed. Further in vivo validation is required to confirm performance under routine clinical conditions. Full article

I analyze recent X-ray data from the literature of the type Ia supernova remnant (SNR Ia) Tycho and conclude that Tycho is a SN Ia inside a planetary nebula (SNIP), strengthening such a previous suggestion from 1985. The observations reveal two opposite protrusions, termed ears, projected on the main shell of Tycho. The pair of ear structures qualitatively resembles that of the SNRs Ia Kepler, SNR G299-2.9, and SNR G1.9+0.3, which earlier studies considered as SNIPs. The requirement that the explosion occurs within hundreds of thousands of years after the formation of the planetary nebula (by the second star to evolve) makes the core-degenerate scenario the most likely for Tycho, with the double-degenerate with merger to explosion delay time scenario somewhat less likely. Several other possible scenarios lead to a SNIP, but they are unlikely for Tycho. The identification of Tycho as a SNIP leads to two general conclusions. (1) The fraction of SNIPs among normal SNe Ia is very large, $\approx 70-90\%$. Thus, the vast majority of normal SNe Ia are SNIPs. (2) To accommodate the large fraction of SNIPs, the delay time distribution of normal SNe Ia includes not only the stellar evolution timescale (as usually assumed), but also includes pockets of younger stellar populations in galaxies without ongoing star formation; the SNIPs come from the younger stellar populations in galaxies. Full article

Aiming at the drawbacks of the classic CoCrFeNi high-entropy alloy (HEA)—low room-temperature strength and softening above 600 °C, which fail to meet strict material requirements in high-end fields like aerospace—this study used the vacuum hot-pressing sintering process to prepare CoCrFeNiTa_x HEAs (x = 0, 0.5, 1.0, 1.5, 2.0 atom, designated as H4, Ta_0.5, Ta_1.0, Ta_1.5, Ta_2.0, respectively). This process effectively inhibits Ta segregation (a key issue in casting) and facilitates the presence uniform microstructures with relative density ≥ 96%, while this study systematically investigates a broader Ta content range (x = 0–2.0 atom) to quantify phase–property evolution, differing from prior works focusing on limited Ta content or casting/spark plasma sintering (SPS). Via X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), microhardness testing, and room-temperature compression experiments, Ta’s regulatory effect on the alloy’s microstructure and mechanical properties was systematically explored. Results show all alloys have a relative density ≥ 96%, verifying the preparation process’s effectiveness. H4 exhibits a single face-centered cubic (FCC) phase. Ta addition transforms it into a “FCC + hexagonal close-packed (HCP) Laves phase” dual-phase system. Mechanically, the alloy’s inner hardness (reflecting the intrinsic property of the material) increases from 280 HV to 1080 HV, the yield strength from 760 MPa to 1750 MPa, and maximum fracture strength reaches 2280 MPa, while plasticity drops to 12%. Its strengthening mainly comes from the combined action of Ta’s solid-solution strengthening (via lattice distortion hindering dislocation motion) and the Laves phase’s second-phase strengthening (further inhibiting dislocation slip). Full article

The Qitai silicified wood from Xinjiang, NW China, provides an exceptional archive for investigating the mechanisms of wood silicification. This study applies microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) to characterize the microstructural and mineralogical features of these fossils. The results show that the samples are primarily composed of microcrystalline–macrocrystalline α-quartz having anhedral–euhedral shapes, with minor occurrences of moganite. A well-preserved structure exhibits distinct anatomic details of cellular networks, such as growth rings and rays. Magnified observation revealed that the microcrystalline quartz within cell walls grew outward from the innermost layer of the wall, suggesting silica infiltration from lumina to walls. The opposite growth of elongated columnar quartz within adjacent cell walls terminated at the position of the middle lamellae. Cell lumen infilling exhibits greater variability on filling degree and phase type. The permeation silicification of cell walls and the oligoblastic to polyblastic structure inside cell frameworks contribute to high fidelity preservation. This interpretation helps us understand how the wood structure was perfectly preserved during the silicification, thus emphasizing its significance for wood identification through its preserved structure. Full article