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The aim of current study was to investigate risk perception of COVID‐19 pandemic, sleep quality and time change of leisure activity and their correlations with posttraumatic stress disorder (PTSD) in healthcare workers (HCWs) from four designated hospitals in China. Medical staffs (n = 317) from three designated hospitals in Guangdong Province and one designated hospital in Guangxi Province were surveyed on their demographic information, sleep quality and time change of leisure activity, risk perception of pandemic and PTSD symptoms (by using PTSD checklist for DSM‐5 (PCL‐5)). Hierarchical regression and structural equation model (SEM) were used to examine the correlated factors of PTSD. The prevalence of high level of PTSD symptoms (PCL‐5 > =33, a probable diagnosis of PTSD) was 10.7%. Regression analysis found that risk perception (dread: β = 0.142, p < 0.01; familiarity: β = 0.203, p < 0.01), sleep quality (β = 0.250, p < 0.001), time change of leisure activity (β = −0.179, p < 0.01), were independently correlated with PTSD severity, which was further confirmed by SEM. Locations of COVID‐19‐related hazards were significant different in cognitive map of risk perception between groups with high and low levels of PTSD symptoms. Risk perception of COVID‐19 pandemic influenced PTSD symptoms in HCWs. Adequate time for leisure activity and good sleep quality protected some HCWs against PTSD symptoms under the influence of pandemic. More researches were warranted to understand the path from pre‐factors of risk perception to its psychological consequences among HCWs.

Sodium-ion batteries (SIBs) are a promising alternative for the large-scale energy storage owing to the natural abundance of sodium. However, the practical application of SIBs is still hindered by the low working voltage, poor rate performance, and insufficient cycling stability. A sodium-ion based full battery using a multi-ion design is now presented. The optimized full batteries delivered a high working voltage of about 4.0 V, which is the best result of reported sodium-ion full batteries. Moreover, this multi-ion battery exhibited good rate performance up to 30 C and a high capacity retention of 95 % over 500 cycles at 5 C. Although the electrochemical performance of this multi-ion battery may be further enhanced via optimizing electrolyte and electrode materials for example, the results presented clearly indicate the feasibility of this multi-ion strategy to improve the electrochemical performance of SIBs for possible energy storage applications.

High-anisotropy NiAs-type MnBi films are produced by in situ annealing of Bi/Mn/Bi trilayers, [Bi/Mn/Bi]n multilayers, and subsequent magnetic field annealing. Phase components, crystallographic anisotropy, and magnetic properties of the MnxBi100−x thin films exhibits strong dependence on Mn concentration. High-purity MnBi thin films with perfect c-axis orientation are obtained by carefully controlling the Mn/Bi ratio. An energy product of 16.3 MGOe, which is the highest value reported so far, is achieved for the x = 50 film of thickness t = 100 nm. The MnBi thick film (t = 2 μm) changes from isotropic to anisotropic after magnetic field annealing. Depending on the direction of the applied field during magnetic field annealing, the MnBi thick film may have out-of-plane or in-plane anisotropy. This control of anisotropy direction enables applications of MnBi films in permanent-magnet, spintronic devices, or magnetic micro-electro-mechanical systems. In addition, the room-temperature magnetocrystalline anisotropy constant and saturation polarization of the hard magnetic MnBi phase are determined to be K = K1 + K2 = 15.0 Mergs cm−3 and Js = 8.2 kG, respectively.

Novel nanostructured Zr2 Co11 -based magnetic materials are fabricated in a single step process using cluster-deposition method. The composition, atomic ordering, and spin structure are precisely controlled to achieve a substantial magnetic remanence and coercivity, as well as the highest energy product for non-rare-earth and Pt-free permanent-magnet alloys.

Pr2Fe14B/(Fe3B,α-Fe) nanocomposite magnets with high coercivity have been prepared by devitrification of Pr9Fe88.5–x Ti2.5Bx (x = 7, 9, 11, 13, and 15) amorphous ribbons. Similar to Zr and Nb, Ti substitutes rare earth sites and participates in forming the (Pr,Ti)2Fe14B phase. The increasing amount of nonmagnetic TiB2 with increasing x in the nanocomposite magnets may precipitate along the grain boundaries and refine the microstructure by inhibiting the grain growth, and results in a continuous increase of coercivity. It also leads to an increase of the fraction of soft phases in the nanocomposites, which enhances the remanence. The squareness of the demagnetization curves is also improved by appropriate B addition. As a result, the energy product attains a maximum value of 129.6 kJ/m3 for x = 13. A more obvious shoulder and significantly enhanced coercivity (2424 kA/m) in the hysteresis curves at 70 K was observed for the sample with x = 15 in comparison with the ribbon with x = 7. This further demonstrates that B addition promotes the formation of TiB2 and the Fe3B soft phase in good agreement with XRD results. Accordingly, the introduction of a proper amount of nonmagnetic phases can enhance the magnetic properties of the nanocomposite magnets. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)