Self-contact snapping metamaterial for tensile energy dissipation.

Mechanical metamaterials for energy dissipation have received significant attention for vibration and impact mitigation. However, existing designs often neglect energy dissipation in the tensile direction, which is crucial for attenuating tensile load and controlling falling descent. Importantly, current energy-dissipating mechanisms including plastic deformation and friction mechanisms, suffer from drawbacks such as reversibility and self-recovery, restricting their effectiveness under tension. To address these limitations, we propose a novel mechanism utilizing self-contact snap-through buckling to develop an energy-dissipating metamaterial. Unlike previous metamaterials, the self-contact snapping metamaterial (SCSM) achieves tensile energy dissipation with fewer unit cells while exhibiting reusability, self-recovery, and low reliance on material selection. A theoretical model is established to explain its energy-dissipating mechanism from the perspective of buckling mode transition. Moreover, the proposed SCSM exhibits sequential snapping behavior and effectively mitigates tensile impacts, as demonstrated through quasi-static and dynamic tests. This work opens new avenues for achieving tensile energy dissipation and inspires future research on energy conversion employing self-contact interactions.

Underwater acoustic metamaterials.

Acoustic metamaterials have been widely investigated over the past few decades and have realized acoustic parameters that are not achievable using conventional materials. After demonstrating that locally resonant acoustic metamaterials are capable of acting as subwavelength unit cells, researchers have evaluated the possibility of breaking the classical limitations of the material mass density and bulk modulus. Combined with theoretical analysis, additive manufacturing and engineering applications, acoustic metamaterials have demonstrated extraordinary capabilities, including negative refraction, cloaking, beam formation and super-resolution imaging. Owing to the complexity of impedance boundaries and mode transitions, there are still challenges in freely manipulating acoustic propagation in an underwater environment. This review summarizes the developments in underwater acoustic metamaterials over the past 20 years, which include underwater acoustic invisibility cloaking, underwater beam formation, underwater metasurfaces and phase engineering, underwater topological acoustics and underwater acoustic metamaterial absorbers. With the evolution of underwater metamaterials and the timeline of scientific advances, underwater acoustic metamaterials have demonstrated exciting applications in underwater resource development, target recognition, imaging, noise reduction, navigation and communication.

Point mutation of 5' noncoding region of BCL-6 gene in primary gastric lymphomas.

AIM: To investigate the mutations of the 5' noncoding region of BCL-6 gene in Chinese patients with primary gastric lymphomas. METHODS: PCR and direct DNA sequencing were used to identify BCL-6 gene mutations in the 5' noncoding region in 29 cases of gastric diffuse large B-cell lymphoma (DLBCL) and 18 cases of gastric mucosa-associated lymphoid tissue (MALT) lymphoma as well as 10 cases of reactive hyperplasia of lymph node (LRH). RESULTS: Six of 29 gastric DLBCLs (20.7%), 4 of 18 gastric MALT lymphomas (22.2%) and 1 of 10 LRHs(10%) were found to have mutations. All mutations were single-base substitutions and the frequency of single-base changes was 0.20 x 10(-2) -1.02 x 10(-2) per bp. CONCLUSION: Point mutations in the 5' noncoding region of BCL-6 gene are found in Chinese patients with primary gastric DLBCLs and MALT lymphomas, suggesting that they may, in some extent, participate in the pathogenesis of primary gastric DLBCLs and MALT lymphomas.