Metasurfaces with subwavelength thicknesses have exhibited unconventional phenomena in ways that could not be mimicked by traditional materials. Here we report on the analytical design and experimental realizations of acoustic metasurfaces with hitherto inaccessible functionality of manipulating the reflected waves arbitrarily. By suitably designing the phase-shift profile with a 2π span induced by labyrinthine units, the metasurface can reflect acoustic waves in an unusual yet controllable manner. Anomalous reflection and ultrathin planar lenses are both demonstrated with carefully designed metasurfaces. Remarkably, the free manipulation of phase shifts offers great flexibility in the design of nonparaxial acoustic self-accelerating beams with arbitrary trajectories. With extraordinary wave-steering ability, the metasurface should open exciting possibilities for designing compact acoustic components with versatile potential and may find a variety of applications ranging from ultrasound imaging to caustic engineering where designing the shape of a focused trajectory of sound is required.

An angiosperm phylogeny was reconstructed in a maximum likelihood analysis of sequences of four mitochondrial genes, atp1, matR, nad5, and rps3, from 380 species that represent 376 genera and 296 families of seed plants. It is largely congruent with the phylogeny of angiosperms reconstructed from chloroplast genes atpB, matK, and rbcL, and nuclear 18S rDNA. The basalmost lineage consists of Amborella and Nymphaeales (including Hydatellaceae). Austrobaileyales follow this clade and are sister to the mesangiosperms, which include Chloranthaceae, Ceratophyllum, magnoliids, monocots, and eudicots. With the exception of Chloranthaceae being sister to Ceratophyllum, relationships among these five lineages are not well supported. In eudicots, Ranunculales, Sabiales, Proteales, Trochodendrales, Buxales, Gunnerales, Saxifragales, Vitales, Berberidopsidales, and Dilleniales form a basal grade of lines that diverged before the diversification of rosids and asterids. Within rosids, the COM (Celastrales-Oxalidales-Malpighiales) clade is sister to malvids (or rosid II), instead of to the nitrogen-fixing clade as found in all previous large-scale molecular analyses of angiosperms. Santalales and Caryophyllales are members of an expanded asterid clade. This study shows that the mitochondrial genes are informative markers for resolving relationships among genera, families, or higher rank taxa across angiosperms. The low substitution rates and low homoplasy levels of the mitochondrial genes relative to the chloroplast genes, as found in this study, make them particularly useful for reconstructing ancient phylogenetic relationships. A mitochondrial genebased angiosperm phylogeny provides an independent and essential reference for comparison with hypotheses of angiosperm phylogeny based on chloroplast genes, nuclear genes, and non-molecular data to reconstruct the underlying organismal phylogeny.

Despite the prior use of approximately 9000 bp, deep-level relationships within the angiosperm clade, Saxifragales remain enigmatic, due to an ancient, rapid radiation (89.5 to 110 Ma based on the fossil record). To resolve these deep relationships, we constructed several new data sets: (1) 16 genes representing the three genomic compartments within plant cells (2 nuclear, 10 plastid, 4 mitochondrial; aligned, analyzed length = 21,460 bp) for 28 taxa; (2) the entire plastid inverted repeat (IR; 26,625 bp) for 17 taxa; (3) "total evidence" (50,845 bp) for both 17 and 28 taxa (the latter missing the IR). Bayesian and ML methods yielded identical topologies across partitions with most clades receiving high posterior probability (pp = 1.0) and bootstrap (95% to 100%) values, suggesting that with sufficient data, rapid radiations can be resolved. In contrast, parsimony analyses of different partitions yielded conflicting topologies, particularly with respect to the placement of Paeoniaceae, a clade characterized by a long branch. In agreement with published simulations, the addition of characters increased bootstrap support for the putatively erroneous placement of Paeoniaceae. Although having far fewer parsimony-informative sites, slowly evolving plastid genes provided higher resolution and support for deep-level relationships than rapidly evolving plastid genes, yielding a topology close to the Bayesian and ML total evidence tree. The plastid IR region may be an ideal source of slowly evolving genes for resolution of deep-level angiosperm divergences that date to 90 My or more. Rapidly evolving genes provided support for tip relationships not recovered with slowly evolving genes, indicating some complementarity. Age estimates using penalized likelihood with and without age constraints for the 28-taxon, total evidence data set are comparable to fossil dates, whereas estimates based on the 17-taxon data are much older than implied by the fossil record. Hence, sufficient taxon density, and not simply numerous base pairs, is important in reliably estimating ages. Age estimates indicate that the early diversification of Saxifragales occurred rapidly, over a time span as short as 6 million years. Between 25,000 and 50,000 bp were needed to resolve this radiation with high support values. Extrapolating from Saxifragales, a similar number of base pairs may be needed to resolve the many other deep-level radiations of comparable age in angiosperms.

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We investigate the conditions yielding plasmon-exciton strong coupling at the single emitter level in the gap between two metal nanoparticles. A quasi-analytical transformation optics approach is developed that makes possible a thorough exploration of this hybrid system incorporating the full richness of its plasmonic spectrum. This allows us to reveal that by placing the emitter away from the cavity center, its coupling to multipolar dark modes of both even and odd parity increases remarkably. This way, reversible dynamics in the population of the quantum emitter takes place in feasible implementations of this archetypal nanocavity.PACS numbers: 73.20. Mf, 42.50.Nn, 71.36.+c Plasmon-exciton-polaritons (PEPs) are hybrid lightmatter states that emerge from the electromagnetic (EM) interaction between surface plasmons (SPs) and nearby quantum emitters (QEs) [1,2]. Crucially, PEPs only exist when these two subsystems are strongly coupled, i.e., they exchange EM energy coherently in a time scale much shorter than their characteristic lifetimes. Recently, much attention has focused on PEPs, since they combine the exceptional light concentration ability of SPs with the extreme optical nonlinearity of QEs. These two attributes makes them promising platforms for the next generation of quantum nanophotonic components [3].A quantum electrodynamics description of plasmonic strong coupling of a single QE has been developed for a flat metal surface [4], and isolated [5,6] and distant nanoparticles [7][8][9], where SP hybridization is not fully exploited. From the experimental side, in recent years, PEPs have been reported in emitter ensembles [10][11][12][13], in which excitonic nonlinearities are negligible [14][15][16]. Only very recently, thanks to advances in the fabrication and characterization of large Purcell enhancement nanocavities [17][18][19], far-field signatures of plasmonexciton strong coupling for single molecules have been reported experimentally [20].In this Letter, we theoretically investigate the plasmonic coupling of a single emitter in a paradigmatic cavity: the nanometric gap between two metallic particles [13,19,20]. We consider spherical-shaped nanoparticles, and develop a transformation optics (TO) [21,22] approach that fully accounts for the rich EM spectrum that originates from SP hybridization across the gap. Our method, which is the first application of TO concepts to treat quantum optical phenomena, yields quasianalytical insight into the Wigner-Weisskopf problem [23] for these systems, and enables us to reveal the prescriptions that nanocavities must fulfil to support single QE PEPs. (1) level system (with transition frequency ω E and z-oriented arXiv:1605.09443v2 [cond-mat.mes-hall]

Three mitochondrial (atp1, matR, nad5), four chloroplast (atpB, matK, rbcL, rpoC2), and one nuclear (18S) genes from 162 seed plants, representing all major lineages of gymnosperms and angiosperms, were analyzed together in a supermatrix or in various partitions using likelihood and parsimony methods. The results show that Amborella + Nymphaeales together constitute the first diverging lineage of angiosperms, and that the topology of Amborella alone being sister to all other angiosperms likely represents a local long branch attraction artifact. The monophyly of magnoliids, as well as sister relationships between Magnoliales and Laurales, and between Canellales and Piperales, are all strongly supported. The sister relationship to eudicots of Ceratophyllum is not strongly supported by this study; instead a placement of the genus with Chloranthaceae receives moderate support in the mitochondrial gene analyses. Relationships among magnoliids, monocots, and eudicots remain unresolved. Direct comparisons of analytic results from several data partitions with or without RNA editing sites show that in multigene analyses, RNA editing has no effect on well supported relationships, but minor effect on weakly supported ones. Finally, comparisons of results from separate analyses of mitochondrial and chloroplast genes demonstrate that mitochondrial genes, with overall slower rates of substitution than chloroplast genes, are informative phylogenetic markers, and are particularly suitable for resolving deep relationships.

Although most of wealth and innovation have been the result of human interaction and cooperation, we are not yet able to quantitatively predict the spatial distributions of three main elements of cities: population, roads, and socioeconomic interactions. By a simple model mainly based on spatial attraction and matching growth mechanisms, we reveal that the spatial scaling rules of these three elements are in a consistent framework, which allows us to use any single observation to infer the others. All numerical and theoretical results are consistent with empirical data from ten representative cities. In addition, our model can also provide a general explanation of the origins of the universal super- and sub-linear aggregate scaling laws and accurately predict kilometre-level socioeconomic activity. Our work opens a new avenue for uncovering the evolution of cities in terms of the interplay among urban elements, and it has a broad range of applications.