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In this article, 316L stainless steel hollow spheres (316L HS) and polyurethane (PU) resins were used to prepare a novel metallic-hollow-sphere/polyurethane (MHSP) acoustic composite by casting. The acoustic experimental results of this composite revealed that compared to monolithic PU, the sound transmission loss of the composites increased and the maximum sound absorption peak shifted to lower frequency with the change of acoustic impedance and resonance frequency. When the surface of metallic hollow sphere used in MHSP composite was modified by silane coupling agent, the sound insulation and sound absorption performance of MHSP composites were further improved. This is related to the addition of the molecular layer of coupling agent between MHSP matrix. In addition, the addition of silane coupling agent creates PU foaming in matrix, resulting in a large number of pores and gaps that can increase the sound waves energy loss through air friction and heat exchange.

In this investigation, a variety of polyurethane composites with different syntactic hollow spheres were prepared by casting method, using 316 L stainless steel hollow spheres and 316 L stainless steel–Al2O3 double‐layer hollow spheres as reinforcements. The sound insulation and absorption properties of polyurethane composites with different syntactic hollow spheres were tested by impedance tube. The effects of the hollow spheres on the acoustic properties of composites were analyzed and compared with polyurethane resin and polyurethane/solid spheres composites. The experimental results reveal that the sound transmission loss of polyurethane can be improved by the addition of hollow spheres, and the range of sound absorption frequency of polyurethane tends to move to lower frequency. Otherwise, the sound insulation and absorption frequency range of polyurethane can be broadened by the effect of 316 L stainless steel–Al2O3 double‐layer hollow spheres. In addition, the compressive strength and stiffness of polyurethane composites have been significantly improved after hollow spheres added. Comparing with polyurethane, the compressive strength and stiffness of PU/316 L–Al2O3 HS increased by 47.9% and 115.9%, respectively.

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Buzhong Yiqi decoction (BZYQD) has been developed for preventing or reducing the recurrence of ischemic stroke for a long time in China. However, the mechanism of action of the BZYQD is not completely understood. Our research aims to determine whether the mechanism of action of BZYQD is by regulating gut microbiota using 16SR RNA and fecal microbiota transplantation. In a cerebral ischemia mouse model, the results showed that prophylactic administration of BZYQD could reduce brain infarct volume and improve neurological function and behavior. The prophylactic administration of BZYQD could regulate intestinal microbiota and increase the abundance of butyrate-producing Prevotellaceae_NK3B31_group and probiotic Akkermansia in mice 72 h after surgery. Transplanting BZYQD-administered bacterial flora into antibiotic-depleted mice could reproduce the therapeutic effects of BZYQD. Overall, our study provided molecular insights into the mechanism and impact of BZYQD in the prevention of cerebral ischemic damage and highlighted the potential of regulation of intestinal microbiota as a therapeutic approach for ischemic stroke.