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

Effect of penehyclidine hydrochloride on IL-6, TNF-α, HIF- 1α and oxidative stress in lung tissue of young rats with acute lung injury

Purpose: To investigate the effect of penehyclidine hydrochloride (PHC) on interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), hypoxia inducible factor-1α (HIF-1α), and oxidative stress levels in lung tissues of acute lung injury (ALI) neonatal rats.Methods: 40 male Sprague-Dawley (SD) rats were assigned to model, low-dose PHC, high-dose PHC, and control groups (n = 10). Levels of IL-6, TNF-α and HIF-1α were evaluated by enzyme-linked immunosorbent assay (ELISA). Pulmonary lesions were determined histologically using H&E staining.Results: The lung tissue levels of IL-6, TNF-α and HIF-1α were significantly higher in model rats than in control rats, and significantly lower in PHC-treated rats than in model group, with decrease in levels as PHC dose increased (p < 0.05). The lung tissue activity of MPO and level of MDA in model rats were significantly higher than those in control rats, but significantly lower in the lung tissues of the two PHC groups than in the model group; decrease in levels occurred as PHC dose increased (p < 0.05).Conclusion: PHC decreases the lung and serum levels of IL-6, TNF-α and HIF-1α in a rat model of ALI, and mitigates pulmonary oxidative stress and lung tissue damage. Thus, penehyclidine hydrochloride may be useful to mitigate ALI-induced damage in patients. However, further studies and clinical trials are required to ascertain this Keywords: Penehyclidine hydrochloride, Alveolar septum, Acute lung injury, Inflammatory cells, IL-6, TNF-α, HIF-1α, Oxidative stres

Exact analytical solution of average path length for Apollonian networks

The exact formula for the average path length of Apollonian networks is found. With the help of recursion relations derived from the self-similar structure, we obtain the exact solution of average path length, $\bar{d}_t$, for Apollonian networks. In contrast to the well-known numerical result $\bar{d}_t \propto (\ln N_t)^{3/4}$ [Phys. Rev. Lett. \textbf{94}, 018702 (2005)], our rigorous solution shows that the average path length grows logarithmically as $\bar{d}_t \propto \ln N_t$ in the infinite limit of network size $N_t$. The extensive numerical calculations completely agree with our closed-form solution.Comment: 8 pages, 4 figure