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The ability to tune the performance of acoustic metamaterials without structural modifications or complex active control circuits is a remarkable challenge. In this work, we present a square piezoelectric side-branch (PSB) pipe-type structure that consists of the piezoelectric composite sheets (PCSs) on its sidewall and propose the corresponding equivalent electroacoustic circuit model. Compared with the traditional side-branch, theoretical and numerical results show that the thickness of the PSB can be up to λ / 200 , and the tunable phase shift of the transmitted wave in the PSB pipe can achieve nearly 2 π by adjusting the capacitances that are connected to the PCSs. The experiment for a square pipe with one PCS is also given to prove the phase control ability of the PSB model. Furthermore, we show that by merely adjusting the external capacitances of the PCSs, switching the functions between the 45° extraordinary transmission and the acoustic focusing for the same incident wave can be exactly realized. Our work provides a promising potential in active controls and integration designs of acoustic metamaterials and devices. [ABSTRACT FROM AUTHOR]

Single-crystal rods with different diameters and deviation angles with respect to the solidification direction were produced by Bridgman rapid solidification method at withdrawal rates of 3 and 6 mm·min-1 and used as grain continuators. The crystallographic orientation of the rods, which cross-sections were perpendicular to the solidification direction at different solidification heights, was measured by electron backscattered diffraction, while the corresponding microstructures were observed by optical microscopy. The mushy zone morphology and the distribution of the temperature gradient were simulated by the finite element analysis software ProCAST. The experimental results indicate that the crystallographic orientation of the single-crystal rods corresponds to the statistical average value of all the dendrite orientations in cross-section. The crystallographic orientation of the primary and secondary dendrites of each single-crystal rod at different cross-sections fluctuates irregularly within a small range (less than 4°). The crystallographic orientation of the dendrite in each single-crystal rod is not exactly consistent with each other and is affected by their branching mode of dendrites in the solidification space. In addition, the simulation results show that the mushy zone shapes and the temperature gradient of single-crystal rods change with the increase of solidification height during the solidification process. Finally, the evolution mechanism of the crystallographic orientations and the corresponding influence factors were analyzed and discussed. [ABSTRACT FROM AUTHOR]

The development of novel antibiotic adjuvants is imminent because of the frequent emergence of resistance in Gram-negative bacteria, which severely restricts the efficiency and longevity of commonly used clinical antibiotics. It is reported that famotidine, a clinical inhibitor of gastric acid secretion, enhances the antibacterial activity of rifamycin antibiotics, especially rifampicin, against Gram-negative bacteria and reverses drug resistance. Studies have shown that famotidine disrupts the cell membrane of Acinetobacter baumannii and inhibits the expression of the outer membrane protein ompA gene, while causing a dissipation of the plasma membrane potential, compensatively upregulating the pH gradient and ultimately increasing the accumulation of reactive oxygen species by leading to increased bacterial mortality. In addition, famotidine also inhibited the efflux pump activity and the biofilm formation of A. baumannii. In the Galleria mellonella and mouse infection models, the combination of famotidine and rifampicin increased the survival rate of infected animals and decreased the bacterial load in mouse organs. In conclusion, famotidine has the potential to be a novel rifampicin adjuvant, providing a new option for the treatment of clinical Gram-negative bacterial infections. [ABSTRACT FROM AUTHOR]