Deficiency of endothelial FGFR1 alleviates hyperoxia-induced bronchopulmonary dysplasia in neonatal mice.

Disrupted neonatal lung angiogenesis and alveologenesis often give rise to bronchopulmonary dysplasia (BPD), the most common chronic lung disease in children. Hyperoxia-induced pulmonary vascular and alveolar damage in premature infants is one of the most common and frequent factors contributing to BPD. The purpose of the present study was to explore the key molecules and the underlying mechanisms in hyperoxia-induced lung injury in neonatal mice and to provide a new strategy for the treatment of BPD. In this work, we reported that hyperoxia decreased the proportion of endothelial cells (ECs) in the lungs of neonatal mice. In hyperoxic lung ECs of neonatal mice, we detected upregulated fibroblast growth factor receptor 1 (FGFR1) expression, accompanied by upregulation of the classic downstream signaling pathway of activated FGFR1, including the ERK/MAPK signaling pathway and PI3K-Akt signaling pathway. Specific deletion of Fgfr1 in the ECs of neonatal mice protected the lungs from hyperoxia-induced lung injury, with improved angiogenesis, alveologenesis and respiratory metrics. Intriguingly, the increased Fgfr1 expression was mainly attributed to aerosol capillary endothelial (aCap) cells rather than general capillary endothelial (gCap) cells. Deletion of endothelial Fgfr1 increased the expression of gCap cell markers but decreased the expression of aCap cell markers. Additionally, inhibition of FGFR1 by an FGFR1 inhibitor improved alveologenesis and respiratory metrics. In summary, this study suggests that in neonatal mice, hyperoxia increases the expression of endothelial FGFR1 in lung ECs and that deficiency of endothelial Fgfr1 can ameliorate hyperoxia-induced BPD. These data suggest that FGFR1 may be a potential therapeutic target for BPD, which will provide a new strategy for the prevention and treatment of BPD.

Value of heparin-binding protein in the diagnosis of severe infection in children: a prospective study. / è‚ç´ ç»“åˆè›‹ç™½å¯¹å„¿ç«¥é‡ç—‡æ„ŸæŸ“è¯Šæ–­ä»·å€¼çš„å‰çž»æ€§ç ”ç©¶.

OBJECTIVES: To study the value of heparin-binding protein (HBP) in the diagnosis of severe infection in children. METHODS: This study was a prospective observational study. The medical data of children who were admitted to the pediatric intensive care unit due to infection from January 2019 to January 2020 were collected. According to the diagnostic criteria for severe sepsis and sepsis, the children were divided into a severe sepsis group with 49 children, a sepsis group with 82 children, and a non-severe infection group with 33 children. The three groups were compared in terms of related biomarkers such as plasma HBP, serum C-reactive protein, serum procalcitonin, and platelet count. The receiver operating characteristic (ROC) curve was plotted to investigate the value of plasma HBP level in the diagnosis of severe infection (including severe sepsis and sepsis). RESULTS: The severe sepsis and sepsis groups had a significantly higher plasma HBP level on admission than the non-severe infection group (P<0.05). Compared with the sepsis and non-severe groups, the severe sepsis group had significantly higher serum levels of C-reactive protein and procalcitonin and a significantly lower platelet count (P<0.05). Plasma HBP level had an area under the ROC curve of 0.590 in determining severe infection, with a sensitivity of 38.0% and a specificity of 82.4% (P<0.05). CONCLUSIONS: There is an increase in plasma HBP level in children with severe infection, and plasma HBP level has a lower sensitivity but a higher specificity in the diagnosis of severe infection and can thus be used as one of the markers for the judgment of severe infection in children.

Theoretical derivation of slip boundary conditions for single-species gas and binary gas mixture.

A theoretical derivation of slip boundary conditions for single-species gas and binary gas mixture based on two typical gas-surface scattering kernels is presented. If the Maxwell model is assumed, then the derived slip boundary conditions are consistent with the previous conclusions. Considering the limitation of the Maxwell model in describing the complexity of gas-surface scattering behavior, we further perform theoretical analyses based on the Cercignani-Lampis-Lord (CLL) model, where separate accommodation coefficients in the tangential and normal directions are defined. Our results demonstrate that for both single-species gas and binary gas mixture, the velocity slip predicted by the CLL model is only dependent on the tangential accommodation coefficient, while the temperature jump determined by the CLL model is related to the accommodation coefficients in both tangential and normal directions. To account for the collision effect in the Knudsen layer, we propose to add correction terms to the theoretical models, and the corrected slip coefficients agree well with the previous numerical results obtained by solving Boltzmann equation for single-species gas. Moreover, the slip boundary conditions for binary gas mixture based on the CLL model are determined theoretically for the first time. Since at most situations the tangential and normal accommodation coefficients are not equal, the temperature jump boundary condition based on the CLL model is expected to give more accurate predictions about temperature distribution and heat flux at the boundaries, particularly for hypersonic gas flows with strong nonequilibrium effect.

Enhancement of toughness of SiC through compositing SiC-Al interpenetrating phase composites.

Silicon carbide has excellent properties such as high hardness and decomposition temperature, but its applications are limited by its poor toughness. Here, we investigate the enhancement of SiC's toughness by compositing silicon carbide-aluminum (SiC-Al) interpenetrating phase composites (IPCs) via molecular dynamics simulations. IPCs are a class of composites consisting of two or more phases that are topologically continuous and three-dimensionally interconnected through the microstructure. The Young's modulus and ultimate strength gradually increases with an increment of the volume fraction of SiC, opposite to the fracture strain. The interface between SiC and Al affects the mechanical properties of SiC-Al IPCs. When the volume fraction of SiC is less than 0.784, the attenuation rate of ultimate strength and fracture strain decreases. The attenuation rate increases when the volume fraction of SiC is more than 0.784. There are a minimum of ultimate strength and fracture strain at the 0.784, 0.7382 and 2.8610, respectively. The hardness of SiC-Al IPCs is about 48% of SiC. The change of SiC-Al IPCs hardness is more stable than that of SiC in the later stage of the nanoindentation test.

Nonlinear diffusion, bonding, and mechanics of the interface between austenitic steel and iron.

We investigate the atomic diffusivity and mechanics of the interface between bulk austenitic steel (fcc structure) and bcc iron at various temperatures and strain rates using molecular dynamics simulations. We adopt the system of Fe74Cr16Ni10 corresponding to 316L steel as a representative model of austenitic steels, denoted as FeCrNi. We find that the compressive strength of the FeCrNi/Fe system decreases by 44.3% and the corresponding strain decreases by 7.2% when the temperature increases from 1500 K to 1800 K. The temperature enhances nonlinearly the diffusion of interfacial atoms and improves the cohesion of FeCrNi/Fe by forming a thicker diffusion layer, of which the thickness increases by 56.3% when the temperature increases from 1600 K to 1700 K, and by nearly 48% when the temperature increases from 1700 K to 1800 K. However, the thickness of the diffusion layer decreases by 33.3% when the compressive strain rate increases from 1 × 109 s-1 to 4 × 109 s-1. Our study sheds light on the atomistic mechanism of the interfaces of bimetals and might be helpful in optimizing the process of the fabrication of bimetal composites.