Succinate is a metabolic intermediate of the tricarboxylic acid (TCA) cycle in all aerobic organisms, and is also a vital microbial metabolite in the gut. Although succinate is known to regulate intestinal metabolism and immune function, its role in the protection of the intestinal epithelial barrier function and inflammation is poorly characterized. In this study, we evaluated the effects of succinate on intestinal epithelial barrier function and inflammation in pigs. Twenty-four growing pigs were distributed into three groups (n = 8) and received either a basal diet (control group) or the same diet supplemented with 0.1% succinate or 1% succinate. The diet supplemented with 1% succinate led to alterations in the intestinal morphology. We confirmed in vitro that 5 mM succinate treatment modulated intestinal epithelial permeability by increased transepithelial electrical resistance (TEER) in intestinal porcine epithelial cell (IPEC)-J2 cells. Furthermore, succinate treatment increased the abundance of tight junction proteins claudin-1, zona occluden (ZO)-1, and ZO-2 in the jejunum in vivo and in vitro. In addition, dietary succinate supplementation promoted the expression of inflammatory cytokines interleukin (IL)-25, IL-10, IL-8, and IL-18 in the jejunum. Taken together, these data identify a novel role of succinate in the modulation of intestinal epithelial barrier function, which may be a nutritional target to improve gut health in animals.

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Utilizing the transfer matrix method, a multifunctional infrared device possessing the properties of the wide-angle broadband absorption and the polarization separation based on the one-dimensional (1-D) magnetized ferrite photonic crystals (MFPCs) arranged by the Dodecanacci sequence is designed theoretically under the modulation of the external magnetic field. The magneto-optical effect generated in the proposed MFPCs gives birth to the ultra-broadband absorption regions under the transverse electric (TE) mode, one runs at 16.22 THz –30.89 THz and the other covers at 33.52 THz–70.00 THz. The mechanism of the wide-angle (at most 80.89° for TE mode) absorption is analyzed by the interference cancellation condition. Moreover, owing to the different effective permeabilities of the MFPCs under the two polarization modes, the propagation behaviors of the electromagnetic (EM) wave are diverse which present the absorption features under the TE mode and show the transmission properties under the transverse magnetic (TM) mode in the structure. Compared with the periodic and Thue-Morse structures, the complex symmetry of the Dodecanacci sequence makes the absorption features of the MFPCs superior to that of the former. Besides, the influences of the magnetic field intensity and the dielectrics’ thicknesses on the angle-insensitive absorption and polarization separation characteristics are discussed explicitly. This research provides meaningful guidance for the modulation and absorption of the infrared light wave and the design of the multifunctional magnetically tunable optoelectric device.

Based on the solid-state plasma (SSP), a metamaterial analog of electromagnetically induced transparency (EIT-like) with superior properties is theoretically proposed, including tunability, a large group index, and delay-bandwidth product (DBP), polarization independence, and low-loss. By exciting different specific parts of the SSP, the EIT-like peak frequency switches from 8.518 GHz with 90.92% transmissivity in state I to 11.26 GHz with 93.76% transmissivity in state II, i.e. a 2.742 GHz shift. Meanwhile, the metamaterial has 0.679 ns or 1.314 ns group delay, 453 or 876.1 group index, and 0.422 or 1 DBP in state I or II. Additionally, the transmission curves are the same under the circular polarization waves or linear polarization waves at any angle. The low-loss feature is likewise demonstrated. Therefore, the EIT-like metamaterial has superior properties for related applications, especially in slow light, sensing, switching, and communication.

A tunable multifunctional modulator of the stacked graphene-based hyperbolic metamaterial (HM) cells is proposed. The dielectric constant and group index of HM are theoretically investigated. The calculated results show that, for the cell structure, a transmission window in the reflection zone (TWRZ) can be obtained at the normal incidence, but all reflections are converted to the transmission when the incident angle is near 82°. Concurrently, a single frequency absorption in the transmission zone (SFATZ) is realized, which can be adjusted by the chemical potential of graphene. For the whole structure composed of cell structures with different chemical potentials, the ultra-wideband absorption and transmission window in the absorption zone (TWAZ) can be achieved, which can work in different frequency bands if the given structural parameters can be tailored. Those computed results can apply for switchable frequency-dependent and angle-dependent reflection-transmission modulations, single frequency and ultra-wideband absorbers, and a logic switch based on the TWAZ.