An Improved Second-Order Multisynchrosqueezing Transform for the Analysis of Nonstationary Signals

Second-order multisynchrosqueezing transform(SMSST),an effective tool for the analysis of nonstationary signals,can significantly improve the time-frequency resolution of a nonstationary signal.Though the noise energy in the signal can also be enhanced in the transform which can largely affect the characteristic frequency component identification for an accurate fault diagnostic.An improved algorithm termed as an improved second-order multisynchrosqueezing transform(ISMSST)is then proposed in this study to alleviate the problem of noise interference in the analysis of nonstationary signals.In the study,the time-frequency(TF)distribution of a nonstationary signal is calculated first using SMSST,and then aδfunction is constructed based on a newly proposed time-frequency operator(TFO)which is then substituted back into SMSST to produce a noisefree time frequency result.The effectiveness of the technique is validated by comparing the TF results obtained using the proposed algorithm and those using other TFA techniques in the analysis of a simulated signal and an experimental data.The result shows that the current technique can render the most accurate TFA result within the TFA techniques employed in this study.

3D nano-printed geometric phase metasurfaces for generating accelerating beams with complex amplitude manipulation

Metasurface,a forefront in emerging optical devices,has demonstrated remarkable potential for complex amplitude manipulation of light beams.However,prevailing approaches face challenges in spatial resolution and complexities associated with integrating dynamic phases,impeding the simplified design and reproducible fabrication of metasurfaces.Here,we introduce an innovative approach for complex amplitude modulation within 3D nano-printed geometric phase metasurfaces.Our approach enables the generation of self-accelerating beams by encoding amplitude through phase-only manipulation,achieving high spatial resolution.Notably,this method circumvents the conventional need to adjust the geometric parameters of metasurface unit structures for amplitude manipulation,offering a streamlined and efficient route for design and fabrication complexity.This novel methodology holds promise for expedited and low-cost manufacturing of complex amplitude manipulation metasurfaces.

An antioxidant system through conjugating superoxide dismutase onto metal-organic framework for cardiac repair

Acute myocardial infarction(AMI)remains a dominant origin of morbidity,mortality and disability worldwide.Increases in reactive oxygen species(ROS)are key contributor to excessive cardiac injury after AMI.Here we developed an immobilized enzyme with Superoxide Dismutase(SOD)activity cross-link with Zr-based metal-organic framework(ZrMOF)(SOD-ZrMOF)for mitigate ROS-caused injury.In vitro and in vivo evidence indicates that SOD-ZrMOF exhibits excellent biocompatibility.By efficiently scavenging ROS and suppressing oxidative stress,SOD-ZrMOF can protect the function of mitochondria,reduce cell death and alleviate inflammation.More excitingly,long-term study using an animal model of AMI demonstrated that SOD-ZrMOF can reduce the infarct area,protect cardiac function,promote angiogenesis and inhibit pathological myocardial remodeling.Therefore,SOD-ZrMOF holds great potential as an efficacious and safe nanomaterial treatment for AMI.