Characteristics of Pu contamination in atmospheric particulate matter in Beijing: seasonal variation, particle size distribution, and source identification.

Interpretable machine learning prediction of biochar characteristics based on laser-Raman spectroscopy.

Abstract CO 2 curing can greatly enhance the properties of concrete while actively sequestering CO 2 . However, the influencing mechanisms of CO 2 curing on the passivation film of steel bars in concrete remains unclear. In this study, the passivation and depassivation behaviors of steel bars in CO 2 -cured mortar were investigated via electrochemical measurements, and the microscopic morphology and chemical composition of the passivation film were examined using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that CO 2 curing can accelerate the passivation of steel bars, which can be attributed to the higher oxygen partial pressure around the steel bars when compared to standard curing. Although the thickness of passivation film on steel bars in CO 2 -cured specimens (4.06 nm) is less than that in standard-cured specimens (4.73 nm), the charge transfer resistance in CO 2 -cured specimens (458.54 kΩ·cm 2 ) is higher than that in standard-cured specimens (384.49 kΩ·cm 2 ). Specifically, the dense and ordered microstructure observed by SEM, together with the relatively high Fe 2+ /Fe 3+ atomic ratio (0.90 vs. 0.63) of the passivation film detected by XPS, contributes to the enhanced electrochemical stability. In addition, it is found that CO 2 curing significantly delays the depassivation onset of steel bars in mortar when subjected to chloride drying-wetting cycles, with the depassivation of standard-cured specimens initiating after 18 cycles and that of CO 2 -cured specimens being postponed to 30 cycles. Consequently, the protective performance of the passivation film in CO 2 -cured specimens surpasses that in standard-cured specimens despite the slightly thinner thickness.

The bitumen shale facies in the Paleocene Palana Formation serves as a key oil-shale resource in the Bikaner-Nagaur Basin, Western India. It has a high organic matter concentration, which provides the necessary foundation for significant oil accumulation. Therefore, the purpose of this work is to characterize the molecular structure of kerogen within the Palana oil shale facies in order to assess the potential of shale oil resources and comprehend the mechanisms of hydrocarbon generation. In this study, comprehensive chemical analyses, including elemental analysis (CHNS), FTIR, TG/DTA, Py-GC, and kinetics of the kerogen decomposition, incorporated with microscopic investigation, were employed to decipher the elemental composition and molecular structure of Palana's kerogen. The microscopic analysis of kerogen indicates that the Palana oil shale sediments are characterized by high abundance marine organic matter assemblages, including bituminite, fluorescence AOM, and algae, consistent with the presence of hydrogen-rich kerogen. The predominance of hydrogen-enriched kerogen, primarily classified as Type II, with moderate-to-low sulfur content is substantiated by the kerogen's elemental profile and molecular structure. This includes a high hydrogen-to-carbon atomic ratio (H/C ˃1.40), low sulfur-to-carbon atomic ratio (S/C < 0.04), and predominance of aliphatic compounds with relatively low concentrations of aromatic compounds. The petroleum type of the Palana's kerogen is corresponding to P-N-A oils with high wax content, and it is released at a subsurface temperature regime of 107 to 153°C, which is consistent with the computed vitrinite reflectance values of 0.62-1.07%VRo, as demonstrated by the bulk and compositional kinetic results. The highlight results of the elemental composition and molecular structure provide a strong basis for further in-situ conversion processes and development of the shale oil system, as well as the mechanism of petroleum generation in the oil shale of the Palana Formation.

Rare-earth (RE) elements are often employed to optimize electrocatalytic performance due to their tunable electronic structures and surface properties. Herein, a yttrium oxide-doped Pt-based catalyst (Pt-Y2O3/C) is engineered for the electrocatalytic methanol oxidation reaction (MOR), and the surface Y/Pt atomic ratio is precisely modulated to optimize its performance. Pt-Y2O3/C-2 (1/0.17 Pt/Y atomic ratio, Pt loading of 4.73 wt %) exhibits optimal mass activity (MA) for MOR, 5.10 A mgPt-1 in 1.0 M KOH with 1.0 M CH3OH, obviously outperforming commercial 20 wt % Pt/C by a factor of ∼12.8. It also shows superior CO-poisoning tolerance and stability; its MA for the MOR remains at 3.80 A mgPt-1 after the 10 000 s stability test. Integrated characterization results demonstrate that Y2O3 doping induces an electronic interaction with Pt, thereby reducing the electron density of Pt and optimizing its electronic structure, attenuating the adsorption of CO* intermediates at the Pt sites. Y2O3 doping also decreased the charge transfer resistance (Rct) in the MOR. The superior MOR performance of the Pt-Y2O3/C-2 catalyst originates from its uniformly sized Pt-Y2O3 nanoparticles and unique electronic effect. This work highlights the regulatory role of the rare-earth metal in Pt-based catalysts for the MOR, offering a general strategy for achieving excellent catalytic performance.

Abstract This study proposes a novel high-frequency impact electrospark treatment (HFIET) method to fabricate Al/AlN composite layers on 2024-T3 aluminum alloy substrates. The HFIET process utilized nitrogen as both the shielding gas and reactive nitrogen source for in situ synthesis of AlN, with precisely controlled discharge parameters to minimize substrate thermal damage. Analysis revealed a dense Al/AlN composite layer with near-stoichiometric composition (Al:N atomic ratio ≈ 1:1), confirmed by EDS and XRD. The microhardness profile exhibited a gradient distribution, decreasing from 450 HV at the surface to the substrate hardness (∼120 HV), attributed to the gradual reduction in AlN volume fraction from the top layer to the interior. Tensile tests demonstrated simultaneous improvements in ultimate tensile strength (∼10 % increase) and elongation (∼30 % increase) compared to untreated 2024-T3 alloy, indicating enhanced strength-ductility synergy. Corrosion resistance was significantly enhanced, and the Al/AlN layer acts as an effective barrier against corrosive media infiltration, suppressing pitting initiation at the coating–substrate interface.

Reliable quantification of the chemical composition of graphene-related 2D materials (GR2M) as powders and liquid suspensions is a challenging task. Analytical methods such as X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) are recommended by standardization bodies. The specific parameters to be measured are also defined, e.g., the oxygen-to-carbon (O/C) atomic ratio, the trace metal impurities, or the functional groups. In this contribution, for the first time, results of a systematic study on the capability of energy-dispersive X-ray spectroscopy (EDS) at a scanning electron microscope (SEM) to reliably quantify the O/C ratio and impurities remained from the synthesis of selected GR2M are reported. The robustness of SEM/EDS analysis is verified for various measurement conditions (different excitations and EDS detectors) and the validity of the results is tested by comparison to the established XPS analysis. Moreover, an ionic liquid is used as a reference material for the quantification of the light elements such as C, N, O and F. The study clearly demonstrates the reliability of the fast and widely available SEM/EDS as a standard method for the quantification of the elemental composition of GR2M and generally of light materials.

The burnup, initial enrichment, and cooling time of spent nuclear fuel collectively determine the activities of key gamma-emitting nuclides (e.g., 134Cs, 137Cs, 154Eu). In safeguards verification, a non-destructive assay (NDA) using radiation detectors can directly acquire the gamma-ray emission signatures associated with these characteristic nuclides. Previous studies have reported empirical relationships between the activities of nuclides such as 134Cs, 137Cs, and 154Eu and the assembly burnup. However, the non-uniform axial power distribution in fuel assemblies leads to variations in axial-segment burnup. Accordingly, this study utilizes a nuclide sample database of a typical pressurized water reactor (PWR) assembly generated by OpenMC 0.15.3 depletion calculations. The calculated results are analyzed, and a sensitivity analysis of the hydrogen-to-uranium atomic ratio (H/U) on the characteristic nuclides is presented, confirming the necessity of incorporating the H/U ratio as an input parameter to improve the cross-condition generalization of the surrogate models. Subsequently, MLP and CNN based on PyTorch 2.9.1 (CUDA 13.0 build: 2.9.1+cu130), and XGBoost 3.0.2 models are implemented to invert axial-segment burnup, initial enrichment, and the number densities of selected actinides under various discrete operating conditions based on characteristic nuclide activities. A comparative analysis of the prediction results from different feature inversion methods is provided. The results indicate that the MLP model performs best with Method A, which incorporates absolute 137Cs activity and the 154Eu/137Cs ratio, achieving a relative prediction deviation of only 5.2% for initial enrichment. Under Method C, the XGBoost model attains a relative prediction deviation of only 0.9% for axial-segment burnup (BU_zone).

Wafer-scale synthesis of metal telluride films has been hindered by the high volatility and limited reactivity of tellurium. To overcome this, we introduce a confined tellurization strategy utilizing in situ formed metal-tellurium (M-Te) alloys as controllable Te sources. Systematic investigation on appropriate metal species through cohesive energy calculations and experiments demonstrates that the cohesive energy of the source metal and metal-to-Te atomic ratio in the source bilayer are the key parameters dictating Te flux. Among many metals, Au-Te and Ag-Te alloys provide steady Te flux while preventing the delamination of M/Te bilayer (observed with Pt, Mo, Cu) after metal deposition on Te layer and the undesired co-evaporation of metal (observed with In, Zn) during Te supply for MxTey synthesis. With the Au-Te alloy, atomically-smooth, single-crystalline 4-inch Si2Te3 thin films are produced, which are the largest reported to date. The film thickness can be modulated by adjusting the Au/Te ratio, verified by structural and spectroscopic characterization. The generality of this concept is verified by synthesizing other tellurides, including MoTe2 and Cr2Te3. The M-Te alloy source is recyclable by replenishing Te on the alloy, establishing this methodology as a robust and versatile platform for producing a wide range of high-quality metal telluride films.

Multifaceted-optimization on PtFeCoNiMnX high entropy alloy confined in macroporous carbon fibers towards superior oxygen catalysis.

The effect of atomic ratio of phase change material on solidification properties of the modeled porous ceramics based on steel slag and fly ash solid wastes using molecular dynamics simulation

Seasonal redistribution of Pu and 237Np in the North Yellow Sea: Implications for sediment transport and hydrodynamic shifts.

ABSTRACT This study evaluates the influence of hydrothermal carbonization (HTC) conditions on the chemical composition and quality of sugarcane bagasse-based hydrochars, with potential relevance for agricultural applications. A limitation in current literature is the lack of detailed assessments of HTC operating conditions when organic matter quality is the primary focus. Sugarcane bagasse was subjected to HTC using a combined 3² × 2¹ experimental design, varying reaction time (10, 12, and 14 h), temperature (180, 190, and 200 °C), and reaction medium (H₂O and HNO₃ 0.1 mol L⁻1). Hydrochar yield, organic matter (OM), total organic carbon (TOC), and atomic ratios (H/C and O/C) were determined. Structural and chemical features were evaluated by FTIR and SEM, while Py-GC/MS was applied to investigate molecular composition, with emphasis on compounds associated with plant growth. Principal component analysis (PCA) was used to correlate chemical profiles with hydrochar quality. Hydrochars produced in acidic medium exhibited lower yields but higher OM and TOC contents compared to those obtained in water, indicating enhanced carbon concentration. FTIR results suggested progressive biomass carbonisation, whereas SEM revealed marked surface modifications, including fibre grooving, reduced interstitial material, and increased surface area under more severe HTC conditions. Py-GC/MS revealed distinct chemical profiles, with higher concentrations of bioactive compounds in acid-assisted treatments. PCA indicated that reaction medium and temperature were the dominant factors controlling organic matter transformation, followed by residence time. Overall, HTC conditions strongly influenced hydrochar chemical quality, and samples A/200/12 and A/200/14 exhibited the most favourable combination of quality-related chemical indicators.

Interaction of Molybdenum with Boron at an Atomic Ratio of 1 : 2 in an Equimolar NaCl–KCl Melt at 750°C

Identifying presumed epileptogenic region (PER) in MRI-negative epilepsy patients is crucial for successful surgical outcomes. This study aims to determine whether dynamic deuterium metabolic imaging (DMI) at 7Tesla can detect region-specific metabolic alterations in MRI-negative, 18FDG-PET-positive temporal-lobe epilepsy. Five drug-resistant MRI-negative, 18FDG-PET-positive epilepsy patients underwent dynamic DMI. 3D 2H FID-MRSI scans (11:44 min each) were acquired at 7T over ~ 100min following oral [6,6'-2H2]glucose intake. Venous plasma glucose and 2H glucose atom percent enrichment (APE) were measured in blood samples taken during scanning. Plasma glucose and 2H-glucose APE were analyzed using a General Linear Model with Repeated measures. From DMI, brain 2H-glucose and 2H glutamate/glutamine levels were analyzed using a two-level linear mixed model (factors: time and tissue type) comparing the PER and contralateral (contra-PER), hippocampus and temporal pole regions. Plasma glucose and 2H-Glucose (Glc) atom-percent excess rose within 40 min post ingestion and then stabilized. Brain 2H-Glc and 2H-glutamate/glutamine (Glx) increased over time (p < 0.001). For 2H-Glc, regional differences were small, with only a modest elevation in hippocampus-PER relative to temporal-contra (p = 0.04). In contrast, 2H-Glx showed clear regional variation (p < 0.001), with the highest levels in hippocampus-PER, significantly exceeding PER, Temporal-PER, and Temporal-Contra (p ≤ 0.01). These findings remained consistent when averaging the final four time points. Ultra-high-field DMI revealed elevated hippocampal glutamatergic turnover in MRI negative epilepsy patients, with the highest levels in the epileptogenic hippocampus. These findings indicate the presence of subtle metabolic alterations in hippocampal tissue, supporting the potential of DMI to capture pathophysiological changes that remain invisible to conventional imaging.

This study investigates the deposition of amorphous silicon carbon nitride (a-SiCN) films using a microwave sheath-voltage combination plasma (MVP) source under duty-cycle-controlled deposition conditions. Duty ratios of 10, 30, 50, and 70% resulted in substrate temperatures of 180, 600, 980, and 1040 °C, respectively. The deposition rate reached a maximum of approximately 208 μm/h at a duty ratio of 30%. The atomic ratios of C, N, and Si remained nearly constant for duty ratios from 30% to 70%. X-ray diffraction confirmed that all films were amorphous. Raman spectra revealed features characteristic of amorphous carbon (a-C) for duty ratios of 30% or higher, suggesting the incorporation of a-C-like structures into the a-SiCN matrix. The film hardness increased as the duty-cycle-controlled deposition conditions shifted from 10% to 50% (180 to 980 °C), reaching a maximum of 22.65 ± 6.78 GPa at a duty ratio of 50%, and then decreased at 70% (1040 °C). These variations in hardness are suggested to be associated with coupled changes in hydrogen incorporation, C-N bonding, and the evolution of sp2-rich carbon clustering (graphite-like short-range ordering) under elevated temperature and ion-bombardment conditions.

Dispersion of acoustic and optic collective excitations are comparatively studied in two Al-based liquid metallic alloys, which contain ten atomic percent of Si with four valence electrons or Mg with two ones. Partial density-density and current-current time correlation functions are analyzed by a combination ofab initiomolecular dynamics simulations and theoretical generalized collective modes approach. We obtain and analyze the dispersion of acoustic and optic collective excitations and wave number dependence of the slowest relaxation process as eigenmodes of the generalized Langevin equation in matrix form. These findings allow understanding of different factors responsible for features in collective dynamics of the two liquid metallic alloys.

Point defects can strongly affect the mechanical properties of two-dimensional (2D) materials, causing an overall detrimental effect on the strength, stiffness, and elasticity. However, the opposite has also been reported in the literature, which indicates that our understanding of the role of defects at the atomic level remains incomplete. This computational study provides a systematic assessment, based on first-principles calculations, of the mechanical properties of the archetypal 2D materials (h-BN and graphene monolayers) containing substitutional impurities and vacancies, which is further extended to 2D BCN alloys representing the case of high concentration of substitutional impurities in h-BN and graphene. In general, the stiffness of these materials, as described by Young's modulus, decreases in the presence of point defects. The Young's modulus of h-BN decreases rapidly with increasing concentration of C atoms in the N positions, while the drop is smaller for C impurities in the B positions. Notably, a defect configuration, in which carbon atoms replace the neighboring N and B atoms as a pair, results in the values of the Young's modulus in the range between that of pristine graphene and h-BN. In h-BN, B vacancies give rise to a greater decrease in stiffness than N vacancies, as explained by the analysis of the local defect-mediated strain fields formed near the point defects. The effects of graphene weakening through the introduction of substitutional defects and vacancies are similar to those observed in h-BN. This mechanical behavior persists in materials with few atomic percent of point defect concentration and agrees with most experimental results found in the literature. As the mechanical properties of 2D BCN alloys can be manipulated by a preferential substitution of B and N atoms with C atoms, our predictions may guide future efforts in defect-mediated engineering of the mechanical properties of 2D materials.

The current study investigated the deposition behaviour of the tool particles made from powder metallurgical (PM) green compact tool of W-Cu for coatings on Inconel 800 superalloy substrate using the electric discharge alloying (EDA) process. The effect of process variables such as compact load (CL), voltage (V) and duty factor (DF) is systematically analysed over the output responses, i.e., material deposition rate (MDR), tool wear rate (TWR) and surface roughness (Ra). The results indicated a maximum TWR of 225.325 mg/min, a maximum MDR of 47.250 mg/min and a minimum Ra of 3.5 µm. The alloyed layer is further characterized by FESEM analysis. The weight and atomic percentage of the migrated particles are determined by EDS analysis. The elemental mapping further confirmed the enrichment of tool particles and other base material constituents within the alloyed surface. The XRD analysis further showed the existence of tool elements and the development of new compounds in the alloyed layer. The alloyed layer exhibited an average layer thickness of 11.354 µm.

The current state and prospects of microreactor synthesis of functional materials in single- and two-phase flows with a liquid continuous phase are analyzed. Microreactors allow fine control over the size, composition, structure, and properties of synthesized particles in co-precipitation processes. The results obtained by various teams provide grounds to expect fairly extensive capabilities for controlling the processes of nucleation and particle growth in microreactors-by controlling the pH, reagent concentrations, micromixing quality, and residence time in each of the reactor zones-in the nucleation growth zones. The advantages of microreactor synthesis have been demonstrated with a high quality of micromixing in a volume of 0.2-0.5 mL, which ensures the production of nanoparticles without impurities, a stoichiometric ratio of atoms in the product, and limitation of agglomerate growth due to a short residence time (in the order of several milliseconds). The transition to an industrial scale is very easy due to the fairly high productivity of a single microreactor (up to 10 m3/day for suspension, up to 200-300 kg/day for solid phase). Intensive mixing in microreactors with a diameter of 2-4 mm or less, due to Taylor vortices, contributed to the use of two-phase microreactors for the synthesis of both organic and inorganic substances.