High-performance terahertz modulators induced by substrate field in Te-based all-2D heterojunctions.

High-performance active terahertz modulators as the indispensable core components are of great importance for the next generation communication technology. However, they currently suffer from the tradeoff between modulation depth and speed. Here, we introduce two-dimensional (2D) tellurium (Te) nanofilms with the unique structure as a new class of optically controlled terahertz modulators and demonstrate their integrated heterojunctions can successfully improve the device performances to the optimal and applicable levels among the existing all-2D broadband modulators. Further photoresponse measurements confirm the significant impact of the stacking order. We first clarify the direction of the substrate-induced electric field through first-principles calculations and uncover the unusual interaction mechanism in the photoexcited carrier dynamics associated with the charge transfer and interlayer exciton recombination. This advances the fundamental and applicative research of Te nanomaterials in high-performance terahertz optoelectronics.

Polar metals in strain-engineered KNbO3/CaNbO3 superlattices: a first-principles study.

Polar metals have generated significant interest since the ferroelectric-like structural transition in metallic LiOsO3 was discovered. Herein, we report on a strain-modulated polar metal in the ferroelectric/metal superlattice of 1 : 1 KNbO3/CaNbO3. Using first-principles calculations, we have investigated the structural distortions, including polar distortions and octahedral rotations, and layer-by-layer electronic structures in the KNbO3/CaNbO3 superlattice under different epitaxial strains. Along the stacking direction, the superlattice has almost parallel polar displacements under compressive strain, whereas both in-plane and out-of-plane antiferroelectric-like polar displacements are robust under intermediate strain, which is connected to the octahedral tilting pattern and interlayer electron transfer. In addition, the in-plane polar distortions are enhanced by tensile strains and have a sudden increase at 4% tensile strain. The metallicity is mainly contributed by d electrons from Nb atoms. And orbital-resolved electron distributions in each layer show that d-orbital splitting is related not only to the epitaxial strain but also to the direction of polar displacements. Our results suggest an efficient way to tune polar distortions as well as local metallicity via epitaxial strains in the superlattice.

Serotonin and dopamine regulate the aggressiveness of swimming crabs (Portunus trituberculatus) in different ways.

Bioamines act as a pivotal part in the regulation of aggressive behavior in animals as a type of neuroendocrine, but the patterns of how they regulate aggressiveness in crustaceans are still unclear due to species-specific responses. To determine the effects of serotonin (5-HT) and dopamine (DA) on the aggressiveness of swimming crabs (Portunus trituberculatus), we quantified their behavioral and physiological characteristics. The results showed that an injection of 5-HT at 0.5 mmol L-1 and 5 mmol L-1 could significantly enhance the aggressiveness of swimming crabs, as well as an injection of DA at 5 mmol L-1. The regulation of 5-HT and DA on aggressiveness is dose-dependent, and these two bioamines have different concentration thresholds that can trigger aggressiveness changes. 5-HT could up-regulate the 5-HTR1 gene expression and increase lactate content at the thoracic ganglion as the aggressiveness enhances, suggesting that 5-HT may activate related receptors and neuronal excitability to regulate aggressiveness. As a result of DA injection at 5 mmol L-1, lactate content in the chela muscle and hemolymph increased, glucose content in the hemolymph increased, and the CHH gene was significantly up-regulated. Pyruvate kinase and hexokinase enzyme activities in the hemolymph increased, which accelerated the glycolysis process. These results demonstrate that DA regulates the lactate cycle, which provides substantial short-term energy for aggressive behavior. Both 5-HT and DA can mediate aggressive behavior in the crab by activating calcium regulation in muscle tissue. We conclude that the enhancement of aggressiveness is a process of energy consumption, in which 5-HT acts on the central nervous system to induce aggressive behavior, and DA affects muscle and hepatopancreas tissue to provide a large amount of energy. This study expands upon the knowledge of regulatory mechanisms of aggressiveness in crustaceans and offers a theoretical foundation for enhancing crab culture management.

High temperatures enhance the strength of multiple predator effects in a typical crab-clam system.

Although marine heatwaves pose urgent threats to marine life, our understanding of how these events influence interactions between key species in marine ecosystems is still inadequate. Herein, we examined the behavioral mechanisms by which heat regulates multiple predator effects in different foraging systems that include Asian paddle crabs (Charybdis japonica) and swimming crabs (Portunus trituberculatus) by quantifying their predation and competition at two temperatures. Our results show that non-independent multiple predator effects occurred in the conspecific treatment of Asian paddle crabs and in the interspecific treatment, whereas independent multiple predator effects occurred in the conspecific treatment of swimming crabs. Asymmetrical behavior responses of these crabs to competition and heat triggered divergences in multiple predator effects. High temperatures increased the strength of multiple predator effects but did not alter their types. The reason is that heat negatively impacts predation by enhancing aggressive interactions, outweighing its direct positive effects on predation.