A magnetic wormhole

Wormholes are fascinating cosmological objects that can connect two distant regions of the universe. Because of their intriguing nature, constructing a wormhole in a lab seems a formidable task. A theoretical proposal by Greenleaf et al. presented a strategy to build a wormhole for electromagnetic waves. Based on metamaterials, it could allow electromagnetic wave propagation between two points in space through an invisible tunnel. However, an actual realization has not been possible until now. Here we construct and experimentally demonstrate a magnetostatic wormhole. Using magnetic metamaterials and metasurfaces, our wormhole transfers the magnetic field from one point in space to another through a path that is magnetically undetectable. We experimentally show that the magnetic field from a source at one end of the wormhole appears at the other end as an isolated magnetic monopolar field, creating the illusion of a magnetic field propagating through a tunnel outside the 3D space. Practical applications of the results can be envisaged, including medical techniques based on magnetism

Drivers of population structure of the bottlenose dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea

The drivers of population differentiation in oceanic high dispersal organisms, have been crucial for research in evolutionary biology. Adaptation to different environments is commonly invoked as a driver of differentiation in the oceans, in alternative to geographic isolation. In this study, we investigate the population structure and phylogeography of the bottlenose dolphin (Tursiops truncatus) in the Mediterranean Sea, using microsatellite loci and the entire mtDNA control region. By further comparing the Mediterranean populations with the well described Atlantic populations, we addressed the following hypotheses: (1) bottlenose dolphins show population structure within the environmentally complex Eastern Mediterranean Sea; (2) population structure was gained locally or otherwise results from chance distribution of preexisting genetic structure; (3) strong demographic variations within the Mediterranean basin have affected genetic variation sufficiently to bias detected patterns of population structure. Our results suggest that bottlenose dolphin exhibits population structures that correspond well to the main Mediterranean oceanographic basins. Furthermore, we found evidence for fine scale population division within the Adriatic and the Levantine seas. We further describe for the first time, a distinction between populations inhabiting pelagic and coastal regions within the Mediterranean. Phylogeographic analysis suggests that current genetic structure, results mostly from stochastic distribution of Atlantic genetic variation, during a recent postglacial expansion. Comparison with Atlantic mtDNA haplotypes, further suggest the existence of a metapopulation across North Atlantic/Mediterranean, with pelagic regions acting as source for coastal environments

Aqueous-Phase Synthesis of Silver Nanodiscs and Nanorods in Methyl Cellulose Matrix: Photophysical Study and Simulation of UV–Vis Extinction Spectra Using DDA Method

We present a very simple and effective way for the synthesis of tunable coloured silver sols having different morphologies. The procedure is based on the seed-mediated growth approach where methyl cellulose (MC) has been used as soft-template in the growth solution. Nanostructures of varying morphologies as well as colour of the silver sols are controlled by altering the concentration of citrate in the growth solution. Similar to the polymers in the solution, citrate ions also dynamically adsorbed on the growing silver nanoparticles and promote one (1-D) and two-dimensional (2-D) growth of nanoparticles. Silver nanostructures are characterized using UV–vis and HR-TEM spectroscopic study. Simulation of the UV–vis extinction spectra of our synthesized silver nanostructures has been carried out using discrete dipole approximation (DDA) method

Breaking the diffusion limit with super-hydrophobic delivery of molecules to plasmonic nanofocusing SERS structures

n/

Analogue Transformations in Physics and their Application to Acoustics

Transformation optics has shaped up a revolutionary electromagnetic design paradigm, enabling scientists to build astonishing devices such as invisibility cloaks. Unfortunately, the application of transformation techniques to other branches of physics is often constrained by the structure of the field equations. We develop here a complete transformation method using the idea of analogue spacetimes. The method is general and could be considered as a new paradigm for controlling waves in different branches of physics, from acoustics in quantum fluids to graphene electronics. As an application, we derive an analogue transformation acoustics formalism that naturally allows the use of transformations mixing space and time or involving moving fluids, both of which were impossible with the standard approach. To demonstrate the power of our method, we give explicit designs of a dynamic compressor, a spacetime cloak for acoustic waves and a carpet cloak for a moving aircraft.This work was developed under the framework of the ARIADNA contract 4000104572/11/NL/KML of the European Space Agency. A. M. and J. S.-D. also acknowledge support from Consolider EMET project (CSD2008-00066), A. M. from project TEC2011-28664-C02-02, J.S.-D. from US Office of Naval Research, and C. B. and G. J. from the project FIS2008-06078-C03-01. We thank Reme Miralles for her help with Fig. 2.García Meca, C.; Carloni, S.; Barcelo, C.; Jannes, G.; Sánchez-Dehesa Moreno-Cid, J.; Martínez Abietar, AJ. (2013). Analogue Transformations in Physics and their Application to Acoustics. Scientific Reports. 3(2009):1-5. https://doi.org/10.1038/srep02009S1532009Pendry, J. B., Schurig, D. & Smith, D. R. Controlling electromagnetic fields. Science 312, 1780–1782 (2006).Leonhardt, U. Optical conformal mapping. Science 312, 1777–1780 (2006).Schurig, D. et al. Metamaterial Electromagnetic Cloak at Microwave Frequencies. Science 314, 977–980 (2006).Shalaev, V. M. Transforming Light. Science 322, 384–386 (2008).Greenleaf, A., Kurylev, Y., Lassas, M. & Uhlmann, G. Invisibility and inverse problems. B. Am. Math. Soc. 46, 55–97 (2009).Genov, D. A., Zhang, S. & Zhang, X. Mimicking celestial mechanics in metamaterials. Nat. Phys. 5, 687–692 (2009).Chen, H., Chan, C. T. & Sheng, P. Transformation optics and metamaterials. Nat. Mater. 9, 387–396 (2010).Leonhardt, U. & Philbin, T. Geometry and light. The science of invisibility (Dover Publications, 2010).Pendry, J. B., Aubry, A., Smith, D. R. & Maier, S. A. Transformation Optics and Subwavelength Control of Light. Science 337, 549 (2012).Post, E. G. Formal Structure of Electromagnetics: General Covariance and Electromagnetics (Interscience Publishers, New York, 1962).Cummer, S. A. & Schurig, D. One path to acoustic cloaking. New J. Phys. 9, 45 (2007).Chen, H. & Chan, C. T. Acoustic cloaking in three dimensions using acoustic metamaterials. Appl. Phys. Lett. 91, 183518 (2007).Norris, A. N. Acoustic metafluids. J. Acoust. Soc. Am. 125, 839 (2009).Chen, H. & Chan, C. T. Acoustic cloaking and transformation acoustics. J. Phys. D: Appl. Phys. 43, 113001 (2010).Zhang, S., Genov, D. A., Sun, C. & Zhang, X. Cloaking of Matter Waves. Phys. Rev. Lett. 100, 123002 (2008).McCall, M. W., Favaro, A., Kinsler, P. & Boardman, A. A spacetime cloak, or a history editor. J. Opt. 13, 024003 (2011).Fridman, M., Farsi, A., Okawachi, Y. & Gaeta, A. L. Demonstration of temporal cloaking. Nature 481, 62–65 (2012).Cummer, S. A. & Thompson, R. T. Frequency conversion by exploiting time in transformation optics. J. Opt. 13, 024007 (2011).Barceló, C., Liberati, S. & Visser, M. Analogue Gravity. Living Rev. Relativity 14, 3 (2011).Visser, M. Acoustic black holes: Horizons, ergospheres and Hawking radiation. Class. Quant. Grav. 15, 1767 (1998).Barceló, C. & Jannes, G. A Real Lorentz-FitzGerald contraction. Found. Phys. 38, 191 (2008).Bergmann, P. G. The Wave Equation in a Medium with a Variable Index of Refraction. J. Acoust. Soc. Am. 17, 329 (1946).Torrent, D., Håkansson, A., Cervera, F. & Sánchez-Dehesa, J. Homogenization of two-dimensional clusters of rigid rods in air. Phys. Rev. Lett. 96, 204302 (2006).Torrent, D. & Sánchez-Dehesa, J. Effective parameters of clusters of cylinders embedded in a nonviscous fluid or gas. Phys. Rev. B 74, 224305 (2006).Unruh, W. G. Experimental black hole evaporation? Phys. Rev. Lett. 46, 1351 (1981).Li, J. & Pendry, J. B. Hiding under the Carpet: A New Strategy for Cloaking. Phys. Rev. Lett. 101, 203901 (2008).Popa, B. I., Zigoneanu, L. & Cummer, S. A. Experimental acoustic ground cloak in air. Phys. Rev. Lett. 106, 253901 (2011).Garay, L. J., Anglin, J. R., Cirac, J. I. & Zoller, P. Black holes in Bose-Einstein condensates. Phys. Rev. Lett. 85, 4643 (2000).Lahav, O., Itah, A., Blumkin, A., Gordon, C. & Steinhauer, J. Realization of a sonic black hole analogue in a Bose-Einstein condensate. Phys. Rev. Lett. 105, 240401 (2010).Castro Neto, A. H., Guinea, F., Peres, N. M. R., Novoselov, K. S. & Geim, A. K. The electronic properties of graphene. Rev. Mod. Phys. 81, 109 (2009).Cortijo, A. & Vozmediano, M. A. H. Electronic properties of curved graphene sheets. Europhys. Lett. 77, 47002 (2007).Vakil, A. & Engheta, N. Transformation optics using graphene. Science 332, 1291 (2011)

Tunable plasmonic lattices of silver nanocrystals

Silver nanocrystals are ideal building blocks for plasmonicmaterials that exhibit a wide range of unique and potentially usefuloptical phenomena. Individual nanocrystals display distinct opticalscattering spectra and can be assembled into hierarchical structures thatcouple strongly to external electromagnetic fields. This coupling, whichis mediated by surface plasmons, depends on their shape and arrangement.Here we demonstrate the bottom-up assembly of polyhedral silvernanocrystals into macroscopic two-dimensional superlattices using theLangmuir-Blodgett technique. Our ability to control interparticlespacing, density, and packing symmetry allows for tunability of theoptical response over the entire visible range. This assembly strategyoffers a new, practical approach to making novel plasmonic materials forapplication in spectroscopic sensors, sub-wavelength optics, andintegrated devices that utilize field enhancement effects

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised