[en] Light absorption enhancement of aged soot aerosols is highly sensitive to the morphologies and mixing states of soot aggregates and their non-absorbing coatings, such as organic materials. The quantification of these effects on the optical properties of thinly coated soot aerosols is simulated using an effective model with fixed volume fractions. Fractal aggregated soot was simulated using the diffusion limited aggregation (DLA) algorithm and discretized into soot dipoles. The dipoles of non-absorbing aerosols, whose number was fixed by the volume fraction, were further generated from the neighboring random edge dipoles. Their optical properties were calculated using the discrete dipole approximation (DDA) method and were compared with other commonly used models. The optical properties of thinly coated soot calculated using the fixed volume fraction model are close to (less than ~10% difference) the results of the fixed coating thickness model, except their asymmetry parameters (up to ~25% difference). In the optical simulations of thinly coated soot aerosols, this relative difference of asymmetry parameters and phase functions between these realistic models may be notable. The realizations of the fixed volume fraction model may introduce smaller variation of optical results than those of the fixed coating thickness model. Moreover, the core-shell monomers model and homogeneous aggregated spheres model with the Maxwell-Garnett (MG) theory may underestimate (up to ~20%) the cross sections of thinly coated soot aggregates. The single core-shell sphere model may largely overestimate (up to ~150%) the cross sections and single scattering albedo of thinly coated soot aggregates, and it underestimated (up to ~60%) their asymmetry parameters. It is suggested that the widely used single core-shell sphere approximation may not be suitable for the single scattering calculations of thinly coated soot aerosols. - Highlights: • Fixed volume fraction model is applied for optical simulations of thinly coated soot. • Optical diversity between different models may be caused by morphological differences. • This model simulated similar (<10%) cross sections from fixed coating thickness model. • Differences of asymmetry parameters between these models may be obvious (up to ~25%). • Three other widely used models were investigated with large diversities (up to ~150%).

[en] The effects of soot aggregate quantities on the optical properties of their semi-external mixture with sulfate host particle were investigated. In this study, the individual soot-containing mixtures were simulated as sulfate host point-contact attached to a specified amount of soot aggregates with the same monomer numbers and fractal parameters. The total numbers and volumes of soot monomers were also constant. Optical properties of this type of aerosol mixture were calculated using the numerically exact superposition T-matrix method (STM). The random-orientation averaging results indicated that the optical properties of the soot-containing mixtures may be influenced by the soot aggregate quantities. In these simulations, the absorption Ångström exponent (AÅE) values ranged from 0.9 to 1.1, which agree with the observations. The relative deviations of scattering Ångström exponent (SÅE) values between different numbers of soot aggregates attached to the surface of a sulfate host were upwards of ~11%. The results showed that the greater number of attached soot aggregates may lead to smaller SÅE values in the soot-containing mixtures. For most cases of simulated mixtures, a more compact morphology of soot aggregates, larger soot monomer radii and smaller soot volume fractions (F_s_o_o_t) may also generate smaller SÅE values. Moreover, in the visible range, the simulated scattering cross sections of soot-containing mixtures with two, three, four, and six soot aggregates (D_f=1.8) were ~5%, ~10%, ~15%, and ~30% larger than those with only one soot aggregate, respectively, on the condition that volumes of soot and sulfate are comparable. However, these relative deviations between different numbers of attached soot aggregates on the scattering cross sections of mixtures may be weakened for larger volume of non-absorbing sulfate particle (<5% for the cases of F_s_o_o_t=1/10, sulfate volume is 9 times of soot). - Highlights: • Optical properties of sulfate mixing varying numbers of soot aggregates are simulated. • Absorption Ångström exponents ranged from 0.9 to 1.1, which agree with observations. • Effect of soot number on scattering is raised (5–30%) for more soot volume fractions. • More attached soot aggregates may bring stronger effect on scattering of the mixture.

[en] Anthropogenic soot aerosols are shown as complex, fractal-like aggregated structures with high light absorption efficiency. In atmospheric environment, soot monomers may tend to acquire a weakly absorbing coating, such as an organic coating, which introduces further complexity to the optical properties of the aggregates. The single scattering properties of soot aggregates can be significantly influenced by the coated status of these kinds of aerosols. In this article, the monomers of fractal soot aggregates are modelled as semi-external mixtures (physical contact) with constant radius of soot core and variable sizes of the coating for specific soot volume fractions. The single scattering properties of these coated soot particles, such as phase function, the cross sections of extinction and absorption, single scattering albedo (SSA) and asymmetry parameter (ASY), are calculated using the numerically exact superposition T-matrix method. The random-orientation averaging results have shown that the single scattering properties of these coated soot aggregates are significantly different from the single volume-equivalent core–shell sphere approximation using the Mie theory and the homogeneous aggregates with uncoated monomers using the effective medium theory, such as Maxwell-Garnett and Bruggemann approximations, which overestimate backscattering of coated soot. It is found that the SSA and cross sections of extinction and absorption are increased for soot aggregates with thicker weakly absorbing coating on the monomers. Especially, the SSA values of these simulated aggregates with less soot core volume fractions are remarkably (∼50% for core volume fraction of soot aggregates of 0.5, ∼100% for a core volume fraction of 0.2, at 0.67 μm) larger than for uncoated soot particles without consideration of coating. Moreover, the cross sections of extinction and absorption are underestimated by the computation of equivalent homogeneous fractal aggregate approximation (within 5% for the T-matrix method and 10–25% for the Rayleigh–Debye–Gans approximation due to different soot volume fractions). Further understanding of the optical properties of these coated soot aggregates would be helpful for both environment monitoring and climate studies. -- Highlights: • Optical properties of soot aggregates with coated monomers are calculated. • Homogeneous aggregated approximations overestimate backscattering of coated soot. • A relationship between absorption cross section and core volume fraction is built

[en] TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800 °C can limit their further high-temperature structural applications. To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy (Ti-45Al-8.5Nb, in units of at.%), a chromium (Cr) coating is prepared by using the plasma surface alloying technique, separately, at 800 °C and 1000 °C. The x-ray diffraction (XRD) patterns reveal that an oxide surface layer consisting of Cr₂O₃, Al₂O₃, and TiO₂ is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr₂O₃ is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage (≤ 90 h) and a biquadratic law stage (≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process, the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45Al-8.5Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers. (paper)

[en] Si/a-C:H(Ag) multilayer films with different modulation periods are prepared to test their potential applications in human body. The composition, microstructure, mechanical and tribological properties in the simulated body fluid are investigated. The results show the concentration of Ag first decreases and then increases with the modulation period decreasing from 984 nm to 250 nm. Whereas the C content has an opposite variation trend. Notably, the concentration of Ag plays a more important role than the modulation period in the properties of the multilayer film. The a-C:H sublayer of the film with an appropriate Ag concentration (8.97 at.%) (modulation period of 512 nm) maintains the highest sp³/sp² ratio, surface roughness and hardness, and excellent tribological property in the stimulated body fluid. An appropriate number of Ag atoms and size of Ag atom allow the Ag atoms to easily enter into the contact interface for load bearing and lubricating. This work proves that the Ag nanoparticles in the a-C:H sublayer plays a more important role in the tribological properties of the composite-multilayer film in stimulated body fluid condition. (paper)

[en] Ti/Al/Mg/Al/Ti laminated composites were fabricated via hot-pressing at 350 °C, 400 °C and 450 °C successfully. The influences of interface morphology, diffusion zone, constraint effect on the mechanical properties were investigated. At Ti/Al interface, intermetallic compounds aren't found. Whereas, they form at Al/Mg interface. With the increasing temperature, the bonding strength of Al/Mg interface doesn't change linearly, and the maximum strength is obtained at 400 °C because of intermetallic compounds with appropriate thickness. With the increase of temperature, the hardness at both Ti/Al and Al/Mg interfaces increases owing to the solid solution and the intermetallic phases. Also, the ultimate tensile strength of LMCs increases with sacrificing the fracture elongation. The rule of mixture is used to predict the theoretical strength. It is found that the theoretical values are less than the measured, and the reasons may relate to interfaces in Ti/Al/Mg/Al/Ti laminated composites. (author)

[en] A consistent and unified picture for critical phenomena of charged AdS black holes in f ( R ) gravity is drawn in this paper. Firstly, we investigate the phase transition in canonical ensemble. We derive the explicit solutions corresponding to the divergence of C _Q . The two solutions merge into one when the condition Q _c =√(−1/3 R ₀) is satisfied. The curve of specific heat for Q < Q _c has two divergent points and can be divided into three regions. Both the large radius region and the small radius region are thermodynamically stable with positive specific heat while the medium radius region is unstable with negative specific heat. However, when Q > Q _c , the specific heat is always positive, implying the black holes are locally stable and no phase transition will take place. Secondly, both the T − r ₊ curve and T − S curve f ( R ) AdS black holes are investigated and they exhibit Van der Vaals like behavior as the P − v curve in the former research. Critical physical quantities are obtained and they are consistent with those derived from the specific heat analysis. We carry out numerical check of Maxwell equal area law for the cases Q =0.2 Q _c , 0.4 Q _c , 0.6 Q _c , 0.8 Q _c . The relative errors are amazingly small and can be negligible. So the Maxwell equal area law holds for T − S curve of f ( R ) black holes. Thirdly, we establish geometrothermodynamics for f ( R ) AdS black hole to examine the phase structure. It is shown that the Legendre invariant scalar curvature R would diverge exactly where the specific heat diverges. To summarize, the above three perspectives are consistent with each other, thus providing a unified picture which deepens the understanding of critical phenomena of f ( R ) AdS black holes.

[en] Oxide dispersion-strengthened materials W-1wt%Pr₂O₃ and W-1wt%La₂O₃ were synthesized by wet chemical method and spark plasma sintering. The field emission scanning electron microscopy (FE-SEM) analysis, XRD and Vickers microhardness measurements were conducted to characterize the samples. The irradiations were carried out with a 5 keV helium ion beam to fluences up to 5.0 × 10²¹ ions/m² under 600 °C using the low-energy ion irradiation system. Transmission electron microscopy (TEM) study was performed to investigate the microstructural evolution in W-1wt%Pr₂O₃ and W-1wt%La₂O₃. At 1.0 × 10²⁰ He⁺/m², the average loops size of the W-1wt%Pr₂O₃ was 4.3 nm, much lower than W-1wt%La₂O₃ of 8.5 nm. However, helium bubbles were not observed throughout in both doped W materials. The effects of pre-irradiation with 1.0 × 10²¹ He⁺/m² on trapping of injected deuterium in doped W was studied by thermal desorption spectrometry (TDS) technique using quadrupole mass spectrometer. Compared with the samples without He⁺ pre-irradiation, deuterium (D) retention of doped W materials increased after He⁺ irradiation, whose retention was unsaturated at the damage level of 1.0 × 10²²D₂+/m². The present results implied that irradiation effect of He⁺ ions must be taken into account to evaluate the deuterium retention in fusion material applications

[en] Atmospheric black carbon (BC) is the most important aerosol contributor to global warming. However, there is a lack of understanding about the climate impact of BC aerosols because of systematic discrepancies between model and observation estimates of light absorption enhancements (Eabs) in atmospheric processes after emissions, and such discrepancies are transferred directly into large uncertainties of aerosol radiative forcing assessments. In this study, we quantify Eabs of atmospheric BC aerosols with diverse particle morphology distributions using a multi-dimensional aerosol model. We show that current widely used Mie method may overestimate BC Eabs by ∼50% because variations in particle morphology are not considered. Although absorption calculation can be improved by including complex particle morphology and heterogeneity in composition, we find that neglect of the diverse particle morphology distributions in modeling may lead to 15% ∼ 30% relative deviations on Eabs estimations of BC aerosol ensembles. The results thus imply that particle morphology distribution should be included in models to accurately represent the radiative effects of BC aerosols. (letter)

[en] We aimed to determine whether initial tumour responses measured during short-term follow-up computed tomography (CT) examinations after baseline examinations would correlate with clinical outcomes in patients with non-small cell lung cancer (NSCLC) who received epidermal growth factor receptor (EGFR)-targeted therapy. A total of 86 gefitinib-treated patients with advanced adenocarcinoma of the lung were retrospectively reviewed. All patients underwent baseline and short-term follow-up CT examinations. The new response criteria (NRC) by Lee et al. were used for the response evaluations. A Cox proportional hazards multiple regression model and Kaplan-Meier survival analyses were used to evaluate correlations between the initial tumour changes and progression-free and overall survival (PFS, OS). Better separation and smaller p values were observed for both PFS and OS when good and poor disease responses (as defined by NRC) were compared after excluding tumours with characteristic morphologies. Early tumour changes correlated with PFS in a size-dependent manner. Moreover, a stronger association was observed between size changes and PFS when characteristic morphology was also considered. Initial changes in tumour size during short-term post-treatment CT examinations could act as a potential prognostic imaging surrogate for PFS in gefitinib-treated patients with advanced adenocarcinoma of the lung. (orig.)