A series of Mn 2+ -doped CsPbCl 3 nanocrystals (NCs) was synthesized using reaction temperature and precursor concentration to tune Mn 2+ concentrations up to 14%, and then studied using variable-temperature photoluminescence (PL) spectroscopy. All doped NCs show Mn 2+ 4 T 1g → 6 A 1g d−d luminescence within the optical gap coexisting with excitonic luminescence at the NC absorption edge. Room-temperature Mn 2+ PL quantum yields increase with increased doping, reaching ∼60% at ∼3 ± 1% Mn 2+ before decreasing at higher concentrations. The low-doping regime is characterized by singleexponential PL decay with a concentration-independent lifetime of 1.8 ms, reflecting efficient luminescence of isolated Mn 2+ . At elevated doping, the decay is shorter, multiexponential, and concentration-dependent, reflecting the introduction of Mn 2+ −Mn 2+ dimers and energy migration to traps. A large, anomalous decrease in Mn 2+ PL intensity is observed with decreasing temperature, stemming from the strongly temperature-dependent exciton lifetime and slow exciton-to-Mn 2+ energy transfer, which combine to give a strongly temperature-dependent branching ratio for Mn 2+ sensitization.

Many musculoskeletal tissues exhibit significant anisotropic mechanical properties reflective of a highly oriented underlying extracellular matrix. For tissue engineering, recreating this organization of the native tissue remains a challenge. To address this issue, this study explored the fabrication of biodegradable nanofibrous scaffolds composed of aligned fibers via electrospinning onto a rotating target, and characterized their mechanical anisotropy as a function of the production parameters. The characterization showed that nanofiber organization was dependent on the rotation speed of the target; randomly oriented fibers (33% fiber alignment) were produced on a stationary shaft, whereas highly oriented fibers (94% fiber alignment) were produced when rotation speed was increased to 9.3 m/sec. Non-aligned scaffolds had an isotropic tensile modulus of 2.1 ± 0.4 MPa, compared to highly anisotropic scaffolds whose modulus was 11.6 ± 3.1 MPa in the presumed fiber direction, suggesting that fiber alignment has a profound effect on the mechanical properties of scaffolds. Mechanical anisotropy was most pronounced at higher rotation speeds, with a greater than 33-fold enhancement of the Young's modulus in the fiber direction compared to perpendicular to the fiber direction at a rotation speed reached 8 m/sec. In cell culture, both the organization of actin filaments of human mesenchymal stem cells and the cellular alignment of meniscal fibroblasts were dictated ‡Corresponding Author: Rocky S. Tuan, Ph. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. by the prevailing nanofiber orientation. This study demonstrates that controllable and anisotropic mechanical properties of nanofibrous scaffolds can be achieved by dictating nanofiber organization through intelligent scaffold design. NIH Public Access

Introduction Since the outbreak of coronavirus disease 2019 (COVID-19), more than 3000 (including clinical diagnosis) healthcare workers (HCWs) have been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in China. This study is aimed to investigate the risk perception and immediate psychological state of HCWs in the early stage of the COVID-19 epidemic. Methods This study utilized a cross-sectional survey designed on a convenient sample of 4357 HCWs in China. Its data were collected using anonymous structured questionnaires distributed through social software. 6 questions were set to evaluate the participants' risk perception of COVID-19, and a General Health Questionnaire was used to identify the participants' immediate psychological status. Descriptive statistics were used for data analysis. Risk perception and psychological status were compared by demographic characteristics and COVID-19 exposure experiences. Result A total of 4,600 questionnaires were distributed, and 4,357 qualified ones (94.7%) were collected. The main concerns of HCWs are: infection of colleagues (72.5%), infection of family members (63.9%), protective measures (52.3%) and medical violence (48.5%). And 39.1% of the HCWs had psychological distress, especially working in Wuhan, participating in frontline treatments, having been isolated and having family members or colleagues infected. Conclusions The finding indicating that, faced with the COVID-19 epidemic, HCWs, especially in Wuhan, were worried about the risks of infection and protective measures, resulting in psychological distress, so further actions should be taken.

The photoluminescence stability of all-inorganic perovskite nanocrystals (CsPbBr3) with different size is studied.