Serine signaling governs metabolic homeostasis and health.

Serine has functions that are involved in metabolic homeostasis and health in pathological or stressful situations. Notably, the de novo serine synthesis pathway (SSP) plays a vital role in targeted regulation of immune responses, cell proliferation, and lipid/protein metabolism. The presentation of serine residues derived from SSP may be a signal of stress and provide novel insights into the relationship between metabolic homeostasis and diseases. Here, we summarize the current trends in understanding the regulatory mechanisms of serine metabolism, discuss how serine signaling governs metabolic and antistress processes, including oxidative stress, immunity, energy and lipid metabolism, intestinal microbiota, and the neurological system. We present a possible framework by which serine metabolism maintains metabolic homeostasis and treats human diseases.

Polarization-independent and angle-insensitive tunable electromagnetically induced transparency in terahertz metamaterials.

A metamaterial with a polarization-independent and angle-insensitive electromagnetically induced transparency (EIT)-like effect is theoretically investigated in the terahertz regime. The proposed metamaterial is composed of square rings and split isosceles triangle rings, which behave as bright elements and quasi-dark elements, respectively. An EIT-like phenomenon, which is caused by the destructive interference between different scattering paths via the bright and quasi-dark elements, is observed with a transparent window. This EIT mechanism is revealed with simulated field distributions as well as the analysis based on coupled-mode theory. Full wave simulations show that EIT-like phenomenon in the proposed metamaterial is independent of polarization and is robust to the angle of the incident light. This structure may have potential applications in terahertz detectors, sensors, and modulators.

Experimental demonstration of the robust edge states in a split-ring-resonator chain.

One of the fascinating topological phenomena is the edge state in one-dimensional system. In this work, the topological photonics in the dimer chains composed by the split ring resonators are revealed based on the Su-Schrieffer-Heeger model. The topologically protected photonic edge state is observed directly with the in situ measurements of the local density of states in the topological nontrivial chain. Moreover, we experimentally demonstrate that the edge state localized at both ends is robust against a varied of perturbations, such as losses and disorder. Our results not only provide a versatile platform to study the topological physics in photonics but also may have potential applications in the robust power transfer.

Z-type control of populations for Lotka-Volterra model with exponential convergence.

The population control of the Lotka-Volterra model is one of the most important and widely investigated issues in mathematical ecology. In this study, assuming that birth rate is controllable and using the Z-type dynamic method, we develop Z-type control laws to drive the prey population and/or predator population to a desired state to keep species away from extinction and to improve ecosystem stability. A direct controller group is initially designed to control the prey and predator populations simultaneously. Two indirect controllers are then proposed for prey population control and predator population control by exerting exogenous measure on another species. All three control laws possess exponential convergence performances. Finally, the corresponding numerical simulations are performed. Results substantiate the theoretical analysis and effectiveness of such Z-type control laws for the population control of the Lotka-Volterra model.

Subwavelength electromagnetic switch: bistable wave transmission of side-coupling nonlinear meta-atom.

We propose a scheme for subwavelength electromagnetic switch by employing nonlinear meta-atom. Bistable response is conceptually demonstrated on a microwave transmission line, which is side-coupled to a varactor-loaded split ring resonator acting as a nonlinear meta-atom. Calculations and experiments show that by applying conductive coupling instead of near-field interaction between the transmission line and the nonlinear meta-atom, switch performances are improved. The switch threshold of low to -5.8 dBm and the transmission contrast of up to 4.0 dB between the two bistable states were achieved. Subwavelength size of our switch should be useful for miniaturization of integrated optical nanocircuits.