Thermal and electrical switchable wide-angle multi-band terahertz absorber.

Multi-band terahertz (THz) absorbers have recently gained attention due to their favorable application prospects in communication, imaging, detection, and other fields. However, many multi-band THz absorbers are tuned by a single method, which limits their tuning effect. To address this issue, we propose a multi-band THz absorber that can be co-modulated by thermal and electrical methods. Our proposed absorber uses vanadium dioxide (VO2) to achieve this co-modulation. When VO2 is insulating, the frequency of the absorbing peaks originating from the lateral Fabry-Pérot resonance mode can be changed by adjusting the VO2 width. When VO2 is a conductor, the quality factor of the absorbing peak based on the inductor-capacitor resonance mode can be tuned by adjusting the width of VO2. By varying the top dielectric layer thickness, the frequency of the absorbing peaks can be tuned over a wide range. For devices with two or three layers of graphene nanoribbons-dielectric stacks, a modulation effect similar to that of varying dielectric layer thickness in a single-layer graphene device can be achieved simply by applying a 1 eV Fermi energy to graphene nanoribbons in different layers. By combining thermal and electrical modulation, the two or three-layer stacked device can be dynamically switched between four or six absorbing states, and a wider range of dynamic peak frequency modulation can be realized. Furthermore, the performance of the absorber does not deteriorate significantly at an incident angle of up to 70°. Our proposed thermal-electrical switchable wide-angle multi-band THz absorber provides a reference for the design, fabrication, and application of high-performance THz absorbers in different fields.

Construction and validation of a nomogram for predicting fear of falling related activity restrictions in community-dwelling older adults.

Fear of falling related activity restrictions are widespread among older adults, leading to several adverse effects. Given these consequences, there is an urgent need for a comprehensive assessment tool that integrates various risk factors to predict the likelihood of older adults experiencing such activity restrictions. This cross-sectional study investigated fear of falling related activity restrictions and its influencing factors, simultaneously constructed and validated a nomogram among older adults residing in the communities in China. The model includes variables like age, gender, self-rated health, past year injurious falls, gait stability, anxiety, and cognitive impairment. It showed an AUC of 0.892. Internal validation had an AUC of 0.893, and external validation had an AUC of 0.939. Calibration curve showed good fit, and decision curve showed high clinical benefits. It's an intuitive tool for medical professionals to identify older adults at high risk of activity restrictions due to fear of falling.