Acoustic scattering from an infinitely long cylindrical shell with periodic internal lengthwise ribs.

The acoustic scattering from an infinitely long cylindrical shell with periodic lengthwise ribs is studied. The shell motion is described by the Donnell equations, and the lengthwise rib is modeled as an elastic beam whose motion is decomposed into longitudinal and flexural vibrations. A circumferential mode expansion is used to obtain numerical results for the scattering sound field. The backscattering characteristics in the far-field can be explained by the resonance and interference phenomena. It is shown that subsonic flexural waves can be generated and radiated by the ribs. Due to the periodical distribution of the ribs, there exist multi-order flexural Bloch waves in the circumferential direction. The multi-order flexural Bloch waves can form standing circumferential waves, which lead to a complex acoustic resonance. The attachments of the ribs to the shell can reflect an acoustic wave directly and the reflected wave will interfere with the specular reflection, which is dominant in the frequency-angle spectra with an increasing number of ribs. Furthermore, the flexural wave and flexural Bloch waves can radiate through the attachments and interfere with the specular reflection. However, the interference fringes in the frequency-angle spectra caused by the flexural wave and flexural Bloch waves are coincident at broadside.

Phylogenetic and biological characterization of three K1203 (H5N8)-like avian influenza A virus reassortants in China in 2014.

Three H5N8 avian influenza viruses isolated from domestic geese in China in 2014 were characterized phylogenetically and biologically. Phylogenetic analysis of the complete genomic sequences of the three isolates from this study and those of 61 other H5N8 viruses retrieved from the GISAID platform indicated that, chronologically and geographically, all H5N8 viruses of the Asian H5N1 HA lineage of clade 2.3.4.4 are the direct descendents of the K1203 (H5N8)-like viruses first isolated in China in 2010. The three viruses from this study shared high sequence similarity in all eight gene segments with three other isolates from China in 2013, and two Korean isolates were distinct from the recently circulating reassortants causing outbreaks in Asia, Europe and the United States in 2014 and 2015. In vitro viral growth curves indicated that these H5N8 viruses replicated to high titers in CEF, DEF, MDCK and A549 cells but to significantly lower titers in Vero cells. Pathogenicity studies in vivo indicated that these viruses were all highly virulent to chickens and mallard ducks, while they varied from moderate to high virulence in mice. Additionally, hemagglutination assays using α-2,3-sialidase-treated goose red blood cells and solid-phase direct binding assays with different glycans demonstrated that the three viruses could bind to both avian-type SAα-2,3Gal and human-type SAα-2,6Gal receptors. Our findings confirmed the progenitor nature of the K1203-like viruses in generating recent prevalent clade 2.3.4.4 H5N8 reassortants, which have caused tremendous damage to the poultry industry and are a potential threat to public health.