Atomistic investigation of homogeneous nucleation in undercooled liquid

<p>Although nucleation, a fundamental physical phenomenon in nature, has long been studied by simulations and experiments, our knowledge of this process is still quite limited. Herein, the atomistic pathways of homogeneous nucleation are studied using the phase-field crystal model. We find that nucleation is of one-step type for low initial densities (solid volume fraction), whereas two-step nucleation (TS) dominates in other cases. For the TS process, the fraction and the lifetime of metastable intermediate phases will increase with increasing density, and these metastable phases can significantly accelerate the nucleation process. By calculating the nucleation barriers, we investigated the origin of the appearance of the metastable phases and the mechanism of two-step nucleation.</p

Investigations on the p‑Type Formation Mechanisms of Group II and VII Elements and N‑Doped β‑Bi₂O₃

In this work, the feasibility of p- and n-type doping modifications in intrinsic n-type β-Bi2O3 via Group VII (F, Cl, Br, I) and Group II (Be, Mg, Ca, Sr) elements as well as N have been systematically investigated using first-principles hybrid functional calculations. Notably, the p-type modification mechanism in N-doped β-Bi2O3 has been extensively, carefully, and comparably explored and analyzed, in contrast to the famous N-doped ZnO case. It is found that the enhancement of the n-type conductivity in β-Bi2O3 by Group VII element doping is easily achieved, and F is the best n-type dopant candidate. However, achieving the transition from an unintentional n-type to a p-type semiconductor in β-Bi2O3 is very difficult via Group II element doping because of the stronger compensation effect from the intrinsic donor O1 vacancy defect and unintentional H interstitial (donor) as well as the self-compensation effects from the doping itself under thermal equilibrium growth conditions. Fortunately, it should be easier to dope and achieve the p-type conductivity in β-Bi2O3 using NO2 rather than these source gases, including N2, N2O, NO, and NH3 or Group II element doping under O-poor conditions. The substitutional defect NO2 is the most possible candidate for the p-type modification. However, because of the charge compensation effect, nonequilibrium conditions such as annealing under high temperatures may be essential in obtaining long-lasting p-type conductivity for β-Bi2O3. Understanding the different element doping effects on the p- or n-type conductivity in β-Bi2O3 can further facilitate relevant experimental preparation and application studies

Longitudinal section of distal femur indicating the region of interest (black box and yellow box for synovium and cartilage, respectively) (A); synovium was stained with H&E (scar bar = 100 μm) (B), and the histopathological score was evaluated at 4, 8 and 12 weeks post-transplantation (C).

<p>Longitudinal section of distal femur indicating the region of interest (black box and yellow box for synovium and cartilage, respectively) (A); synovium was stained with H&E (scar bar = 100 μm) (B), and the histopathological score was evaluated at 4, 8 and 12 weeks post-transplantation (C).</p

Morphological features of synovium.

<p>Morphological features of synovium.</p

Schematic chronogram of experimental design.

<p>Schematic chronogram of experimental design.</p

Schematic illustration of possible mechanisms for remission of collagen-induced arthritis.

<p>Schematic illustration of possible mechanisms for remission of collagen-induced arthritis.</p

Concentrations of IL-1β, TNF-α and anti-COL-II Ab in serum analyzed by ELISA.

<p>Data are represented as means ± SD (<i>n</i> = 3).</p

The procedures of different experimental groups.

<p>The procedures of different experimental groups.</p

Flow cytometry analysis of CD3⁺ T lymphocyte subsets in peripheral blood analyzed using FITC-conjugated anti-CD3, PE-conjugated anti-CD4, and APC-conjugated anti-CD8 mAbs.

<p>Flow cytometry analysis of CD3⁺ T lymphocyte subsets in peripheral blood analyzed using FITC-conjugated anti-CD3, PE-conjugated anti-CD4, and APC-conjugated anti-CD8 mAbs.</p

H&E staining of cartilage sections (scar bar = 100 μm) (A), the modified OARSI score of microscopic observation (B) and the ratio of the thickness of hyaline cartilage to calcified cartilage were evaluated at 4, 8 and 12 weeks post-transplantation (C).

<p>H&E staining of cartilage sections (scar bar = 100 μm) (A), the modified OARSI score of microscopic observation (B) and the ratio of the thickness of hyaline cartilage to calcified cartilage were evaluated at 4, 8 and 12 weeks post-transplantation (C).</p