Wave propagation in one-dimensional nonlinear acoustic metamaterials

The propagation of waves in the nonlinear acoustic metamaterials (NAMs) is fundamentally different from that in the conventional linear ones. In this article we consider two one-dimensional NAM systems featuring respectively a diatomic and a tetratomic meta unit-cell. We investigate the attenuation of the wave, the band structure and the bifurcations to demonstrate novel nonlinear effects, which can significantly expand the bandwidth for elastic wave suppression and cause nonlinear wave phenomena. Harmonic averaging approach, continuation algorithm, Lyapunov exponents are combined to study the frequency responses, the nonlinear modes, bifurcations of periodic solutions and chaos. The nonlinear resonances are studied and the influence of damping on hyper-chaotic attractors is evaluated. Moreover, a "quantum" behavior is found between the low-energy and high-energy orbits. This work provides an important theoretical base for the further understandings and applications of NAMs

Programmable gear-based mechanical metamaterials

Elastic properties of classical bulk materials can hardly be changed or adjusted in operando, while such tunable elasticity is highly desired for robots and smart machinery. Although possible in reconfigurable metamaterials, continuous tunability in existing designs is plagued by issues such as structural instability, weak robustness, plastic failure and slow response. Here we report a metamaterial design paradigm using gears with encoded stiffness gradients as the constituent elements and organizing gear clusters for versatile functionalities. The design enables continuously tunable elastic properties while preserving stability and robust manoeuvrability, even under a heavy load. Such gear-based metamaterials enable excellent properties such as continuous modulation of Young’s modulus by two orders of magnitude, shape morphing between ultrasoft and solid states, and fast response. This allows for metamaterial customization and brings fully programmable materials and adaptive robots within reach

A multicentre single arm phase 2 trial of neoadjuvant pyrotinib and letrozole plus dalpiciclib for triple-positive breast cancer.

peer reviewedCurrent therapies for HER2-positive breast cancer have limited efficacy in patients with triple-positive breast cancer (TPBC). We conduct a multi-center single-arm phase 2 trial to test the efficacy and safety of an oral neoadjuvant therapy with pyrotinib, letrozole and dalpiciclib (a CDK4/6 inhibitor) in patients with treatment-naïve, stage II-III TPBC with a Karnofsky score of ≥70 (NCT04486911). The primary endpoint is the proportion of patients with pathological complete response (pCR) in the breast and axilla. The secondary endpoints include residual cancer burden (RCB)-0 or RCB-I, objective response rate (ORR), breast pCR (bpCR), safety and changes in molecular targets (Ki67) from baseline to surgery. Following 5 cycles of 4-week treatment, the results meet the primary endpoint with a pCR rate of 30.4% (24 of 79; 95% confidence interval (CI), 21.3-41.3). RCB-0/I is 55.7% (95% CI, 44.7-66.1). ORR is 87.4%, (95% CI, 78.1-93.2) and bpCR is 35.4% (95% CI, 25.8-46.5). The mean Ki67 expression reduces from 40.4% at baseline to 17.9% (P < 0.001) at time of surgery. The most frequent grade 3 or 4 adverse events are neutropenia, leukopenia, and diarrhoea. There is no serious adverse event- or treatment-related death. This fully oral, chemotherapy-free, triplet combined therapy has the potential to be an alternative neoadjuvant regimen for patients with TPBC

FLEXURAL VIBRATION BAND GAPS IN PERIODIC SANDWICH BEAMS WITH AUXETIC CORE

ABSTRACT The flexural vibration band gaps in one-dimensional periodic sandwich beams with auxetic core are studied basing on the theory of Phononic crystals. The band structures of onedimensional periodic sandwich beams with auxetic core are presented with the plane wave expansion method, the regular calculation method in phononic crystals. Further, the effects of material parameters and structure parameters on the gaps are analyzed. The vibration band gaps in the sandwich beams provide a new idea for the vibration controlling of the structure

Wave propagation in nonlinear metamaterial multi-atomic chains based on homotopy method

This paper studies the dispersion properties and wave propagation in the tetratomic nonlinear acoustic metamaterial chain based on the homotopy analysis method (HAM). We perform a comparison between HAM and Perturbation approach, harmonic balance method (HBM) and equivalent method. Results indicate that HAM can filter the unstable multiple periodic solutions fined by HBM and be more accurate. The succinct equivalent formulas can estimate the bandgaps. There is a limit of the dispersion solution when the nonlinearity tends to infinity. Analyses demonstrate that the energy dispersion in spectrum replaces the linear energy localization because of the hyperchaos that is induced by period-doubling bifurcations. The hyper-chaotic phenomena are demonstrated with frequency spectra, bifurcation diagram and Lyapunov Exponents. This paper further proves the chaotic bands can significantly expand the bandwidth for wave suppression. Enhancing the nonlinearity will vary the behavior of nonlinear bandgaps from independent state to coupling state and then experience a transition. Approaches to manipulate bands are elucidated. The strong nonlinearity is beneficial to expand the total width about 6 times. Moreover, lightweight, low-frequency and broadband characteristics are compatible so can be achieved simultaneously for nonlinear acoustic metamaterial

Ultrabroad acoustical limiting in nonlinear metamaterials due to adaptive-broadening band-gap effect

International audienc