RESUMEN
Metamaterials have demonstrated significant potential for enhancing nonlinear processes at the nanoscale. The presence of narrowband hot-spots and highly inhomogeneous mode-field distributions often limit the enhancement of nonlinear interactions over larger spatial scales. This has posed a formidable challenge in achieving simultaneous enhancement across a broadband spectral range, significantly constraining the potential of photonic nanostructures in enhancing nonlinear frequency conversion. Here, we propose a broadband resonant mode matching method through near-field examinations that supports the multipole modes and enables the development of an ultrabroadband-enhanced 3-5 µm mid-infrared frequency upconversion technique utilizing a hyperbolic triangular pyramidal metasurface. The gap-plasma mode of the hyperbolic metamaterial multilayer system excites narrowly high-order resonances at near-infrared pump light wavelengths, while the slow-light effect generated by the dipoles achieves ultrabroadband near-field enhancement at mid-infrared wavelengths. The symmetry breaking of the triangular structure localizes these resonant modes at the tips, enabling mode-matched modulation at different wavelengths, and thus boosting the nonlinear frequency conversion process. Our approach provides a promising platform for metasurface-based frequency conversion techniques.
RESUMEN
Confined evaporation-induced self-assembly (C-EISA) is a powerful technique to guide disordered nanoparticles into long-range organized structures. Herein, we investigate the C-EISA behavior of 1-butyl-3-vinylimidazolium cation ([VBIm]+) grafted cellulose nanocrystals (CNC-C) in a parallel-plates confined geometry. Interestingly, CNC-C can spontaneously assemble into maze-like patterns with branch dimensions on the micrometer scale and uniformly distributed throughout the confined space, which is completely different from the lamellar self-assembly patterns of unmodified CNCs. Combining in situ observations and microscopic characterization, we speculate that the formation of maze-like patterns originates from the reduction of colloidal stability induced by the grafted imidazolium cations. The electrostatic attraction between CNC-C aggregated bundles and glass substrates acts as anchor points, thereby leading to the unstable motion of the liquid-air menisci during the inward intrusion of air. Due to the physicochemical properties and unique C-EISA behavior, the CNC-C based adhesive can maintain adhesion at temperatures of ca. 200 °C, while rapidly debonding when immersed in water, demonstrating the potential to be used as stimuli-responsive temporary or removable adhesives. Furthermore, the strategy proposed in this work for achieving CNCs patterning is also promising to be extended to other anisotropic rod-shaped nanoparticles.
RESUMEN
Background: Currently, ischemic stroke is the leading cause of death in China. To compare regional differences of ischemic stroke, we analyzed the clinical characteristics of patients with ischemic stroke in four regionally representative hospitals in China. Methods: We conducted a retrospective study at four tertiary hospitals in east China, with regionally representative patients. The associated factors include hypertension, diabetes mellitus, coronary heart disease, hyperlipidemia and a combination of these factors. The standardized ratio (SR), estimated as the observed number divided by the expected number, computed as the sum of predicted probabilities from a multivariable logistic regression model derived using data from all other cities, was used to compare to average levels. Results: A total of 34,707 patients were included. The number of patients increased with age in all four hospitals and patients were predominantly male. The number of ischemic stroke cases with related factors increased with age, except for hyperlipidemia. There was no significant gender difference when multiple related factors existed simultaneously. Coronary heart disease had a more significant impact on ischemic stroke in Qingdao Municipal Hospital and the First Hospital of Qinhuangdao, while hyperlipidemia had a significant influence on ischemic stroke in the First Hospital of Qinhuangdao. Conclusions: At four hospitals in east China, with the increase of age, the risk factors associated with ischemic stroke increased, and the distribution of ischemic stroke-related factors showed regional differences.