Acoustics in 2D Spaces of Constant Curvature

[EN] In this work, we will consider a locally homogeneous and isotropic (2+1)D spacetime of Robertson-Walker type and therefore with underlying de Sitter space.M. M. T. wishes to thank the Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (ERDF) for financial support under grant TIN2014-59294-PTung, MM.; Gambi, JM.; María Luisa García del Pino (2016). Acoustics in 2D Spaces of Constant Curvature. Springer. 483-489. https://doi.org/10.1007/978-3-319-63082-3_75S483489Beals, R., Szmigielski, J.: Meijer G-functions: a gentle introduction. Not. Am. Math. Soc. 60(7), 866–872 (2013)Chen, H.Y., Chan, C.T.: Acoustic cloaking and transformation acoustics. J. Phys. D 43(11), 113001 (2010)Choquet-Bruhat, Y., Damour, T.: Introduction to General Relativity, Black Holes, and Cosmology. Oxford University Press, Oxford (2015)Cummer, S.A.: Transformation acoustics. In: Craster, V.R., Guenneau, S. (eds.) Acoustic Metamaterials: Negative Refraction, Imaging, Lensing and Cloaking, pp. 197–218. Springer Netherlands, Dordrecht (2013)Cummer, S.A., Schurig, D.: One path to acoustic cloaking. New J. Phys. 9(3), 45–52 (2007)Islam, J.N.: An Introduction to Mathematical Cosmology. Cambridge University Press, Cambridge (2001)Kalnins, E.G.: Separation of Variables for Riemannian Spaces of Constant Curvature. Pitman Monographs and Surveys in Pure and Applied Mathematics. Longman Scientific & Technical, New York (1986)Kuchowicz, B.: Conformally flat space-time of spherical symmetry in isotropic coordinates. Int. J. Theor. Phys. 7(4), 259–262 (1973)Lanczos, C.: The Variational Principles of Mechanics. Dover Publications, New York (1970)Mechel, F.P.: Formulas of Acoustics. Springer, Berlin (2002)Norris, A.N.: Acoustic metafluids. J. Acoust. Soc. Am. 125(2), 839–849 (2009)Redkov, V.M., Ovsiyuk, E.M.: Quantum mechanics in spaces of constant curvature. In: Contemporary Fundamental Physics. Nova Science, New York (2012)Rosenberg, S.: The Laplacian on a Riemannian Manifold: An Introduction to Analysis on Manifolds. London Mathematical Society Student Text, vol. 31. Cambridge University Press, Cambridge (1997)Tung, M.M.: A fundamental Lagrangian approach to transformation acoustics and spherical spacetime cloaking. Europhys. Lett. 98, 34002–34006 (2012)Tung, M.M., Peinado, J.: A covariant spacetime approach to transformation acoustics. In: Fontes, M., Günther, M., Marheineke, N. (eds.) Progress in Industrial Mathematics at ECMI 2012. Mathematics in Industry, vol. 19. Springer, Berlin (2014)Tung, M.M., Weinmüller, E.B.: Gravitational frequency shifts in transformation acoustics. Europhys. Lett. 101, 54006–54011 (2013)Tung, M.M., Gambi, J.M., García del Pino, M.L.: Maxwell’s fish-eye in (2+1)D spacetime acoustics. In: Russo, G.R., Capasso, V., Nicosia, G., Romano, V. (eds.) Progress in Industrial Mathematics at ECMI 2014. Mathematics in Industry, vol. 22. Springer, Berlin (2016)Visser, M., Barceló, C., Liberati, S.: Analogue models of and for gravity. Gen. Rel. Grav. 34, 1719–1734 (2002)Wolf, J.A.: Spaces of Constant Curvature. American Mathematical Society, Providence, Rhode Island (2011

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well

The Bellingshausen Sea, a desert in High Antarctica: an overview from environmental and megabenthos data of the

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Reviewing the role of ecosystems services in the sustainability of the urban environment: A multi-country analysis

The urban environment is characterised by many pressures caused by population growth, transport (and its related emissions), and the damage to green areas. Yet, there is a variety of ecosystem services available in urban areas, which may be deployed to ameliorate the current problems and foster their sustainability. This paper reviews the role of ecosystem services as tools for sustainability, based on an urban setting. It also describes a series of multi-country case studies, where an assessment of their functions using a set of benefits valuation approaches such as health benefits, economic benefits, social benefits and benefits to climate resilience, are provided, along with an appraisal of their role in up-keeping the overall quality of the urban environment in the studied areas. Policy recommendations aimed at enhancing the role of ecosystem services, and fostering sustainability in the sampled sites -and beyond-are provided