Search

Introduction: This study aimed to explore the impact of COVID-19 on strength performance in highly trained athletes. Method: A force plate was employed to measure squat jump height (SJH), counter-movement jump height (CMJH), and drop jump reactive strength index (DJRSI) in 27 highly trained athletes before infection, and at one week, two weeks, and four weeks post-recovery. Additionally, an Isometric Mid-thigh Pull (IMTP) test was conducted to record maximum isometric strength (MIS) and the rate of force development of the initial phase (RFD 0–50; RFD 0–100). Repeated measures analysis of variance was utilized to compare variations in these indicators across different time points. Results: One week post-recovery, SJH (-7.71%, P = 0.005), CMJH (-9.08%, P < 0.001), DJRSI (-28.88%, P < 0.001), MIS (-18.95%, P < 0.001), RFD 0–50 (-64.98%, P < 0.001), and RFD 0–100 (-53.65%, P < 0.001) were significantly lower than pre-infection levels. Four weeks post-recovery, SJH (-2.08%, P = 0.236), CMJH (-3.28%, P = 0.277), and MIS (-3.32%, P = 0.174) did not differ significantly from pre-infection levels. However, DJRSI (-11.24%, P = 0.013), RFD 0–50 (-31.37%, P = 0.002), and RFD 0–100 (-18.99%, P = 0.001) remained significantly lower than pre-infection levels. Conclusion: After COVID-19, highly trained athletes exhibited a significant reduction in maximum strength, explosive strength, reactive strength, and initial phase force generation capability. By four weeks post-recovery, their maximum and explosive strength had returned to near pre-infection levels, yet their reactive strength and initial phase force generation capability remained significantly impaired. [ABSTRACT FROM AUTHOR]

Zinc indium sulfide (ZnIn2S4), as a significant visible-light-responsive photocatalyst, has become a research hotspot to tackle energy demand and environmental issues owing to its excellent properties of high stability, easy fabrication, and remarkable catalytic activity. However, its drawbacks, including low utilization of solar light and fast photoinduced charge carriers, limit its applications. Promoting the response for near-infrared (NIR) light (~52% solar light) of ZnIn2S4-based photocatalysts is the primary challenge to overcome. In this review, various modulation strategies of ZnIn2S4 have been described, which include hybrid with narrow optical gap materials, bandgap engineering, up-conversion materials, and surface plasmon materials for enhanced NIR photocatalytic performance in the applications of hydrogen evolution, pollutants purification, and CO2 reduction. In addition, the synthesis methods and mechanisms of NIR light-driven ZnIn2S4-based photocatalysts are summarized. Finally, this review presents perspectives for future development of efficient NIR photon conversion of ZnIn2S4-based photocatalysts. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of fiber orientation on the resistance of seepage-induced erosion in fiber-reinforced sand. To clarify the discrepancy and mechanism of different-oriented fibers improving the resistance of the sand matrix, a series of DEM-Darcy coupling simulations were conducted. The microscopic parameters of fiber-reinforced sand were confirmed by the rigorous calibration procedure. The fibers perpendicular to the seepage direction were found to increase the difficulty of moving fluid through the specimen and significantly reduce the erosion rate of the specimen. These macroscopic behaviors acquired corresponding explanations at the mesoscopic scale, including the evolution of fiber-sand contact orientation, coordination number, average normal contact force, tensile force, and energy dissipation. According to the simulation results, it is found that the highest proportion of tensile force in perpendicular fibers can reach 80%, while the parallel fibers are only 40%, which indicates that the perpendicular fibers have a significant netting effect. The mesoscopic behaviors reasonably revealed the role of the fibers with different orientations on the sand matrix during the seepage. This study is beneficial for further understanding the mechanical behaviors of fiber-reinforced sand under seepage-induced erosion in safety engineering. [ABSTRACT FROM AUTHOR]

Core-shell (C/S) structured upconversion coated Fe₃O₄ nanoparticles (NPs) are of great interest due to their potential as magnetic resonance imaging (MRI) and upconversion luminescent (UCL) imaging agents, as well as near-infrared activated photodynamic therapy (PDT) platforms. When C/S structured Fe₃O₄@Mn 2+ -doped NaYF₄:Yb/Er NPs were prepared previously, well-defined C/S-NPs could not be formed without the doping of Mn 2+ during synthesis. Here, the role of Mn 2+ doping on the synthesis of core-shell structured magnetic-upconversion nanoparticles (MUCNPs) is investigated in detail. Core-shell-shell nanoparticles (C/S/S-MUCNPs) with Fe₃O₄ as the core, an inert layer of Mn 2+ -doped NaYF₄ and an outer shell consisting of Mn 2+ -doped NaYF₄:Yb/Er were prepared. To further develop C/S/S-MUCNPs applications in the biological field, amphiphilic poly(maleic anhydride-alt-1-octadecene) (C 18 PMH) modified with amine functionalized methoxy poly(ethylene glycol) (C 18 PMH-mPEG) was used as a capping ligand to modify the surface of C/S/S-MUCNPs to improve biocompatibility. UCL imaging, T₁-weighted MRI ascribed to the Mn 2+ ions and T₂-weighted MRI ascribed to the Fe₃O₄ core of C/S/S-MUCNPs were then evaluated. Finally, chlorine e6 (Ce6) was loaded on the C/S/S-MUCNPs and the PDT performance of these NPs was explored. Mn 2+ doping is an effective method to control the formation of core-shell structured MUCNPs, which would be potential candidate as multifunctional nanoprobes for future T₁/T₂-weighted MR/UCL imaging and PDT platforms.