Search

In order to solve the problems of uneven component diffusion, weak mass transfer capability and flow field flooding in the conventional flow field of proton exchange membrane fuel cell (PEMFC), and to improve the cell output power. In this paper, a novel folded porous cathode flow field is proposed. A numerical model of three-dimensional multiphase flow is established for comparative study, which reveals the relationship between the component flow characteristics and mass transfer performance of PEMFC. The folding rib structure of the novel flow field triggers gas vortices in the channel and generates secondary flow, improves the mass transfer capability of reactants between the channel and the GDL, and alleviates the drainage problem of the porous layer under the rib. The angle, length and number of folding at the rib of the flow field were mainly changed, and the mass fraction difference coefficient (CV Mi) was used to compare the uniformity of the distribution of the components of the flow field, and the optimal flow field structure was obtained as FP6-7, which increased the current density by 44.9% compared with the traditional linear flow field. For the first time, the secondary flow evaluation criterion absolute vortex flux number J ABS n was introduced to evaluate the mass transfer performance. The influence of fluid flow characteristics on the mass transfer performance is revealed. • The folded porous (FP) flow field improves the mass transfer capacity. • The current density of PEMFC based on FP6-7 flow field was increased by 44.9%. • The mass fraction difference coefficient (CV Mi) was used to evaluate the uniformity of water-air distribution in the flow field. • The absolute vortex flux (J ABS n ) is used for the first time to evaluate the mass transfer characteristics. • The relationship between the flow characteristics of components and the mass transfer capacity in the flow field is revealed. [ABSTRACT FROM AUTHOR]

Evidence indicates that prolonged low-level inflammation and elevated-glucose–induced oxidative stress in diabetic wounds can accelerate senescence. The accumulation of senescent cells, in turn, inhibits cellular proliferation and migration, aggravating the inflammatory response and oxidative stress, ultimately impeding wound healing. In this study, we exploited the heightened lysosomal β-galactosidase activity detected in senescent cells to develop an innovative drug delivery system by encapsulating Fe 3 O 4 with galactose-modified poly (lactic-co-glycolic acid) (PLGA) (F@GP). We found that F@GP can selectively release Fe 3 O 4 into senescent cells, inducing ferroptosis via the Fenton reaction in the presence of elevated intracellular H 2 O 2 levels. This showed that F@GP administration can serve as a chemodynamic therapy to eliminate senescent cells and promote cell proliferation. Furthermore, the F@GP drug delivery system gradually released iron ions into the diabetic wound tissues, enhancing the attenuation of cellular senescence, stimulating cell proliferation, promoting re-epithelialization, and accelerating the healing of diabetic wounds in mice. Our groundbreaking approach unveiled the specific targeting of senescence by F@GP, demonstrating its profound effect on promoting the healing of diabetic wounds. This discovery underscores the therapeutic potential of F@GP in effectively addressing challenging cases of wound repair. The development of galactose-modified PLGA nanoparticles loaded with Fe 3 O 4 (F@GP) represents a significant therapeutic approach for the treatment of diabetic wounds. These nanoparticles exhibit remarkable potential in selectively targeting senescent cells, which accumulate in diabetic wound tissue, through an enzyme-responsive mechanism. By employing chemodynamic therapy, F@GP nanoparticles effectively eliminate senescent cells by releasing iron ions that mediate the Fenton reaction. This targeted approach holds great promise for promoting diabetic wound healing by selectively eliminating senescent cells, which play a crucial role in impairing the wound healing process. The innovative utilization of F@GP nanoparticles as a therapeutic intervention offers a novel and potentially transformative strategy for addressing the challenges associated with diabetic wound healing. [Display omitted] [ABSTRACT FROM AUTHOR]

Schematic diagram of "Ludwigia sedioides" inspired substance-exchangeable spacer PTMS@P with PRP incorporated and its therapeutic effects for skin flap repair. [Display omitted] • A "Ludwigia sedioides" inspired ultra-thin microporous spacer is developed. • Slow-released growth factors from PRP strengthen revascularization and ECM synthesis. The spacer facilitates vascular shuttling and substance exchange. Extended vascular networks promoted skin flap survival and regeneration. Adequate substance exchange is an important prerequisite for tissue repair, and how to efficiently establish mature vascular networks to enhance the graft-host substance exchange is a challenge. Herein, inspired by the special structure of the aquatic plant "Ludwigia sedioides", ultra-thin microporous scaffolds (TMS) of bovine Achilles tendon derived collagen were fabricated as "floating leaves" via pyridine reaction, and cleverly combined with platelet-rich plasma (PRP) after the Schiff base and Michael additions reactions of polydopamine to construct a biomimetic "Ludwigia sedioides" spacer (PTMS@P), allowing blood vessels (as a "rhizome") freely shuttling and substance exchange. In this spacer, growth factors were efficiently released to peak concentrations in the first 12 h, thereby facilitating rapid blood vessel growth. In the subsequent 96 h, these slow-released growth factors retained at 11.6 % to 45.8 % of the peak concentrations, sustainedly promoting vascular networks shuttling through the spacer, graft-host substance exchange and extracellular matrix synthesis in fibroblasts. In vitro, the spacer significantly fostered fibroblasts and endothelial cells' proliferation, adhesion and migration, which were fundamental for revascularization and substance exchange. Immunohistochemical staining of CD31 and Ki67 in vivo demonstrated that abundant vascular networks shuttled through PTMS@P and extended from flap base to the farther flap body, promoting more robust substance exchange and cellular metabolism, which significantly enhanced the survival of ischemic flaps in nude mice. Altogether, this "Ludwigia sedioides" inspired spacer PTMS@P with strengthened revascularization and substance-exchange functionality holds promising applications for tissue repair and regeneration. [ABSTRACT FROM AUTHOR]

At high current density, the mass transfer in proton exchange membrane fuel cells (PEMFC) is significantly influenced by the flow field structure. In this paper, a bilateral track flow field (BTFF) is proposed to improve the transverse and longitudinal mass transfer as well as the water removal capacity of PEMFC. The geometry of the BTFF is optimized by orthogonal tests to obtain the optimal combination of geometric parameters and levels. Then using numerical modeling, the impact of the optimized BTFF (BT6) on the efficiency of the PEMFC was examined. The results show that BT6 significantly improves the utilization of the under-rib region by shortening the reactive gas diffusion path length to obtain a more uniform oxygen distribution, and the average oxygen concentration in the midline of the under-rib of the BT6 is increased by 102.60%, furthermore, the current density is increased by 16.32% compared with that of the parallel flow field (case0). In addition, by reducing the cross-sectional area of the gas flow channel, the BT6 has a higher gas flow velocity, which accelerates the removal of cathode liquid water, and the average liquid water saturation in the midline of the under-rib of the BT6 is reduced by 15.26% compared with case0. Finally, by analyzing the net power density of PEMFC, it can be found that the net power density of BT6 is increased by 15.68% compared with case0, which has good practical application value. • A novel bilateral track flow field is proposed and optimized by orthogonal test. • Locally improved structure enhances transverse and longitudinal mass transfer. • The average oxygen concentration under-rib of the optimized flow field has increased by 102.60%. • The optimized flow field net power density has increased by 15.68%. [ABSTRACT FROM AUTHOR]

How to identify important nodes in multi-layer networks is still an unresolved issue in network science, which has aroused the interest of many researchers. In addition, the relationships between entities in many real-world systems are diverse and can be modeled as multi-layer networks. In the past few decades, scholars have defined various centrality methods from different perspectives to find influential nodes in multi-layer networks, but they only utilize the local or global topology information. Recently, various gravity centralities that utilize both the local and global topological structure information have been defined for identifying key nodes in single-layer networks. In the gravity model, the interaction between two nodes is related to their mass and distance. In consideration of the advantages of gravity model, in this paper, we define an improved gravity centrality for identifying key nodes in multi-layer networks based on multi-PageRank centrality, referred to as the PRGC. Unlike the existing gravity centralities that treat each node degree as its mass, our proposed centrality views the multi-PageRank centrality value of each node as its mass. Furthermore, PRGC weights the shortest path distance between any two nodes across all network layers to define their distance in multi-layer networks. Finally, to illustrate the effectiveness and superiority of the proposed centrality approach, numerical experiments are conducted on six real-world multi-layer networks show that our proposed centrality method outperforms state-of-the-art centralities. • Each node's PageRank value is treated as its mass. • A novel method is proposed to compute the distance between two nodes. • An improved gravity centrality is proposed for identifying key nodes in multilayer networks. • The proposed centrality outperforms state-of-the-art centralities. [ABSTRACT FROM AUTHOR]