RESUMEN
Aluminum (Al) plasmonic nanostructures have recently demonstrated remarkable optical nonlinear phenomena, such as enhanced second harmonic (SH) generation. However, the relatively weak field enhancement resulted from large optical losses associated with aluminum nanostructures in combination with the difficulties in controlling the emission polarization pose as a challenge for SH enhancement and tuning. In this paper, we show that the SH emission of aluminum nanostructures can be efficiently enhanced with the polarization properties simultaneously tunable by using metal-insulator-metal (MIM) nanostructures, constituting of Al cross nanoantenna arrays on top of Al mirrors with a SiO2 spacing layer. Specifically, femtosecond laser beam with a linear polarization parallel to one arm illuminates on the structure while the orthogonal arms were physically modified by the laser-induced photothermal reshaping technique to control the SH radiation by the plasmonic resonances. Under the resonance at the SH wavelength, we observed one order of magnitude larger emission enhancement compared to that at the off-resonant condition. Interestingly, the polarization states can be well manipulated simultaneously by controlling the resonances of the orthogonal arms. The enhanced SH conversion and tunable polarization states pave the way for the development of nonlinear optical sources and advanced functional metasurfaces.
RESUMEN
The present study investigated the effects of the Sijunzi decoction (SJZD) at various dosages on the immunological function of rats with 3% dextran sulfate sodium (DSS; molecular weight 5,000)-induced ulcerative colitis (UC). A total of 40 male Wistar rats were randomly divided into 5 groups: Normal, model, low-dose SJZD, moderate-dose SJZD and high-dose SJZD groups. The 3% DSS was intragastrically administered for 7 consecutive days in order to induce the UC model. The normal group consumed distilled water. Subsequently, SJZD (5.0, 10.0 and 30.0 g/kg) was intragastrically administered, and scores of the disease activity index (DAI) were calculated. After 2 weeks, all the rats were sacrificed. Scores of the colon mucosa damage index (CMDI) were evaluated; and secretory immunoglobulin A (sIgA) and interleukin-2 (IL-2) were measured in intestinal tissue by ELISA assays. The model group rats had ulcers, hyperemia and interstitial edema and infiltrated inflammatory cells. SJZD attenuated the severity of the gross lesions and reduced the histopathological injuries. Compared with the normal group, DAI and CMDI were significantly increased (P<0.01), and levels of determined sIgA in the intestinal mucosa and IL-2 in the intestinal tissue were significantly decreased (P<0.05) in the model group. Compared with the model group, moderate and high doses of SJZD showed a restoration effect on all the aforementioned indexes, and the high dose was the most effective. In conclusion, SJZD can ameliorate inflammation in DSS-induced UC rats. The mechanism is most likely due to enhancing intestinal local immunity.