Quasi-two-dimensional acoustic metamaterial with negative bulk modulus

We present the experimental realization and characterization of an acoustic metamaterial with negative bulk modulus. The metamaterial consists of a two-dimensional array of cylindrical cavities, and the bulk modulus is controlled by their radius size and length. Experiments are performed in a two-dimensional waveguide where a slab of seven layers is used to extract the parameters of the metamaterial. A complete characterization of the constructed structure is reported, including the dispersion relation of the acoustic bands and the skin depth effect, which both have been measured, and the data are well supported by semianalytical models and by finite-element simulations. © 2012 American Physical Society.This work was supported by the Spanish MICINN under Contracts No. TEC2010-19751 and No. CSD2008-0066 (CONSOLIDER program), and by the USA Office of Naval Research. We acknowledge the technical help by A. Diaz-Rubio and A. Climente. J.S.-D. acknowledges useful discussions with A. Broatch and A. Krokhin. D.T. acknowledges the postdoctoral grant provided by the UPV under the program Campus de excelencia internacional.García Chocano, VM.; Graciá Salgado, R.; Torrent Martí, D.; Cervera Moreno, FS.; Sánchez-Dehesa Moreno-Cid, J. (2012). Quasi-two-dimensional acoustic metamaterial with negative bulk modulus. Physical Review B. 85(18). https://doi.org/10.1103/PhysRevB.85.184102S8518Fok, L., Ambati, M., & Zhang, X. (2008). Acoustic Metamaterials. MRS Bulletin, 33(10), 931-934. doi:10.1557/mrs2008.202Norris, A. N. (2009). Acoustic metafluids. The Journal of the Acoustical Society of America, 125(2), 839-849. doi:10.1121/1.3050288Liu, Z. (2000). Locally Resonant Sonic Materials. Science, 289(5485), 1734-1736. doi:10.1126/science.289.5485.1734Yang, Z., Mei, J., Yang, M., Chan, N. H., & Sheng, P. (2008). Membrane-Type Acoustic Metamaterial with Negative Dynamic Mass. Physical Review Letters, 101(20). doi:10.1103/physrevlett.101.204301Yao, S., Zhou, X., & Hu, G. (2008). Experimental study on negative effective mass in a 1D mass–spring system. New Journal of Physics, 10(4), 043020. doi:10.1088/1367-2630/10/4/043020Park, C. M., Park, J. J., Lee, S. H., Seo, Y. M., Kim, C. K., & Lee, S. H. (2011). Amplification of Acoustic Evanescent Waves Using Metamaterial Slabs. Physical Review Letters, 107(19). doi:10.1103/physrevlett.107.194301Fang, N., Xi, D., Xu, J., Ambati, M., Srituravanich, W., Sun, C., & Zhang, X. (2006). Ultrasonic metamaterials with negative modulus. Nature Materials, 5(6), 452-456. doi:10.1038/nmat1644Wang, Z. G., Lee, S. H., Kim, C. K., Park, C. M., Nahm, K., & Nikitov, S. A. (2008). Acoustic wave propagation in one-dimensional phononic crystals containing Helmholtz resonators. Journal of Applied Physics, 103(6), 064907. doi:10.1063/1.2894914Two-dimensional acoustic metamaterial with negative modulus. (2010). Journal of Applied Physics, 108(7), 074911. doi:10.1063/1.3493155Fey, J., & Robertson, W. M. (2011). Compact acoustic bandgap material based on a subwavelength collection of detuned Helmholtz resonators. Journal of Applied Physics, 109(11), 114903. doi:10.1063/1.3595677Li, J., & Chan, C. T. (2004). Double-negative acoustic metamaterial. Physical Review E, 70(5). doi:10.1103/physreve.70.055602Lee, S. H., Park, C. M., Seo, Y. M., Wang, Z. G., & Kim, C. K. (2010). Composite Acoustic Medium with Simultaneously Negative Density and Modulus. Physical Review Letters, 104(5). doi:10.1103/physrevlett.104.054301Torrent, D., & Sánchez-Dehesa, J. (2011). Multiple scattering formulation of two-dimensional acoustic and electromagnetic metamaterials. New Journal of Physics, 13(9), 093018. doi:10.1088/1367-2630/13/9/093018Torrent, D., & Sánchez-Dehesa, J. (2008). Anisotropic mass density by two-dimensional acoustic metamaterials. New Journal of Physics, 10(2), 023004. doi:10.1088/1367-2630/10/2/023004Pendry, J. B., & Li, J. (2008). An acoustic metafluid: realizing a broadband acoustic cloak. New Journal of Physics, 10(11), 115032. doi:10.1088/1367-2630/10/11/115032Torrent, D., & Sánchez-Dehesa, J. (2010). Anisotropic Mass Density by Radially Periodic Fluid Structures. Physical Review Letters, 105(17). doi:10.1103/physrevlett.105.174301Spiousas, I., Torrent, D., & Sánchez-Dehesa, J. (2011). Experimental realization of broadband tunable resonators based on anisotropic metafluids. Applied Physics Letters, 98(24), 244102. doi:10.1063/1.3599849Li, J., Fok, L., Yin, X., Bartal, G., & Zhang, X. (2009). Experimental demonstration of an acoustic magnifying hyperlens. Nature Materials, 8(12), 931-934. doi:10.1038/nmat2561Fokin, V., Ambati, M., Sun, C., & Zhang, X. (2007). Method for retrieving effective properties of locally resonant acoustic metamaterials. Physical Review B, 76(14). doi:10.1103/physrevb.76.144302Torrent, D., Håkansson, A., Cervera, F., & Sánchez-Dehesa, J. (2006). Homogenization of Two-Dimensional Clusters of Rigid Rods in Air. Physical Review Letters, 96(20). doi:10.1103/physrevlett.96.20430

RICORS2040 : The need for collaborative research in chronic kidney disease

Chronic kidney disease (CKD) is a silent and poorly known killer. The current concept of CKD is relatively young and uptake by the public, physicians and health authorities is not widespread. Physicians still confuse CKD with chronic kidney insufficiency or failure. For the wider public and health authorities, CKD evokes kidney replacement therapy (KRT). In Spain, the prevalence of KRT is 0.13%. Thus health authorities may consider CKD a non-issue: very few persons eventually need KRT and, for those in whom kidneys fail, the problem is 'solved' by dialysis or kidney transplantation. However, KRT is the tip of the iceberg in the burden of CKD. The main burden of CKD is accelerated ageing and premature death. The cut-off points for kidney function and kidney damage indexes that define CKD also mark an increased risk for all-cause premature death. CKD is the most prevalent risk factor for lethal coronavirus disease 2019 (COVID-19) and the factor that most increases the risk of death in COVID-19, after old age. Men and women undergoing KRT still have an annual mortality that is 10- to 100-fold higher than similar-age peers, and life expectancy is shortened by ~40 years for young persons on dialysis and by 15 years for young persons with a functioning kidney graft. CKD is expected to become the fifth greatest global cause of death by 2040 and the second greatest cause of death in Spain before the end of the century, a time when one in four Spaniards will have CKD. However, by 2022, CKD will become the only top-15 global predicted cause of death that is not supported by a dedicated well-funded Centres for Biomedical Research (CIBER) network structure in Spain. Realizing the underestimation of the CKD burden of disease by health authorities, the Decade of the Kidney initiative for 2020-2030 was launched by the American Association of Kidney Patients and the European Kidney Health Alliance. Leading Spanish kidney researchers grouped in the kidney collaborative research network Red de Investigación Renal have now applied for the Redes de Investigación Cooperativa Orientadas a Resultados en Salud (RICORS) call for collaborative research in Spain with the support of the Spanish Society of Nephrology, Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón and ONT: RICORS2040 aims to prevent the dire predictions for the global 2040 burden of CKD from becoming true