37 research outputs found

    Quantum cellular automata quantum computing with endohedral fullerenes

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    We present a scheme to perform universal quantum computation using global addressing techniques as applied to a physical system of endohedrally doped fullerenes. The system consists of an ABAB linear array of Group V endohedrally doped fullerenes. Each molecule spin site consists of a nuclear spin coupled via a Hyperfine interaction to an electron spin. The electron spin of each molecule is in a quartet ground state S=3/2S=3/2. Neighboring molecular electron spins are coupled via a magnetic dipole interaction. We find that an all-electron construction of a quantum cellular automata is frustrated due to the degeneracy of the electronic transitions. However, we can construct a quantum celluar automata quantum computing architecture using these molecules by encoding the quantum information on the nuclear spins while using the electron spins as a local bus. We deduce the NMR and ESR pulses required to execute the basic cellular automata operation and obtain a rough figure of merit for the the number of gate operations per decoherence time. We find that this figure of merit compares well with other physical quantum computer proposals. We argue that the proposed architecture meets well the first four DiVincenzo criteria and we outline various routes towards meeting the fifth criteria: qubit readout.Comment: 16 pages, Latex, 5 figures, See http://planck.thphys.may.ie/QIPDDF/ submitted to Phys. Rev.

    Entropic C-theorems in free and interacting two-dimensional field theories

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    The relative entropy in two-dimensional field theory is studied on a cylinder geometry, interpreted as finite-temperature field theory. The width of the cylinder provides an infrared scale that allows us to define a dimensionless relative entropy analogous to Zamolodchikov's cc function. The one-dimensional quantum thermodynamic entropy gives rise to another monotonic dimensionless quantity. I illustrate these monotonicity theorems with examples ranging from free field theories to interacting models soluble with the thermodynamic Bethe ansatz. Both dimensionless entropies are explicitly shown to be monotonic in the examples that we analyze.Comment: 34 pages, 3 figures (8 EPS files), Latex2e file, continuation of hep-th/9710241; rigorous analysis of sufficient conditions for universality of the dimensionless relative entropy, more detailed discussion of the relation with Zamolodchikov's theorem, references added; to appear in Phys. Rev.

    Implications of Space-Time foam for Entanglement Correlations of Neutral Kaons

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    The role of CPTCPT invariance and consequences for bipartite entanglement of neutral (K) mesons are discussed. A relaxation of CPTCPT leads to a modification of the entanglement which is known as the ω\omega effect. The relaxation of assumptions required to prove the CPTCPT theorem are examined within the context of models of space-time foam. It is shown that the evasion of the EPR type entanglement implied by CPTCPT (which is connected with spin statistics) is rather elusive. Relaxation of locality (through non-commutative geometry) or the introduction of decoherence by themselves do not lead to a destruction of the entanglement. So far we find only one model which is based on non-critical strings and D-particle capture and recoil that leads to a stochastic contribution to the space-time metric and consequent change in the neutral meson bipartite entanglement. The lack of an omega effect is demonstrated for a class of models based on thermal like baths which are generally considered as generic models of decoherence

    The SARAO MeerKAT 1.3 GHz Galactic Plane Survey

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    We present the SARAO MeerKAT Galactic Plane Survey (SMGPS), a 1.3 GHz continuum survey of almost half of the Galactic Plane (251○ ≤l ≤ 358○ and 2○ ≤l ≤ 61○ at |b| ≤ 1 5). SMGPS is the largest, most sensitive and highest angular resolution 1 GHz survey of the Plane yet carried out, with an angular resolution of 8″ and a broadband RMS sensitivity of ∼10–20 μJy beam−1. Here we describe the first publicly available data release from SMGPS which comprises data cubes of frequency-resolved images over 908–1656 MHz, power law fits to the images, and broadband zeroth moment integrated intensity images. A thorough assessment of the data quality and guidance for future usage of the data products are given. Finally, we discuss the tremendous potential of SMGPS by showcasing highlights of the Galactic and extragalactic science that it permits. These highlights include the discovery of a new population of non-thermal radio filaments; identification of new candidate supernova remnants, pulsar wind nebulae and planetary nebulae; improved radio/mid-IR classification of rare Luminous Blue Variables and discovery of associated extended radio nebulae; new radio stars identified by Bayesian cross-matching techniques; the realisation that many of the largest radio-quiet WISE H II region candidates are not true H II regions; and a large sample of previously undiscovered background H I galaxies in the Zone of Avoidance

    Multi-ancestry GWAS of the electrocardiographic PR interval identifies 202 loci underlying cardiac conduction

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    The electrocardiographic PR interval reflects atrioventricular conduction, and is associated with conduction abnormalities, pacemaker implantation, atrial fibrillation (AF), and cardiovascular mortality. Here we report a multi-ancestry (N = 293,051) genome-wide association meta-analysis for the PR interval, discovering 202 loci of which 141 have not previously been reported. Variants at identified loci increase the percentage of heritability explained, from 33.5% to 62.6%. We observe enrichment for cardiac muscle developmental/contractile and cytoskeletal genes, highlighting key regulation processes for atrioventricular conduction. Additionally, 8 loci not previously reported harbor genes underlying inherited arrhythmic syndromes and/or cardiomyopathies suggesting a role for these genes in cardiovascular pathology in the general population. We show that polygenic predisposition to PR interval duration is an endophenotype for cardiovascular disease, including distal conduction disease, AF, and atrioventricular pre-excitation. These findings advance our understanding of the polygenic basis of cardiac conduction, and the genetic relationship between PR interval duration and cardiovascular disease

    Phylogenomics and the rise of the angiosperms

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    Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

    Thysanotus racemoides (Asparagales: Asparagaceae), a new species from South Australia and western Victoria

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    The new species Thysanotus racemoides Sirisena, T.D.Macfarl. & Conran, from South Australia and western Victoria, is described and distinguished from the previously conspecific T. juncifolius (Salisb.) J.H.Willis & Court, by the presence of sessile subterminal umbels and relatively longer anthers and perianth segments. The revised distribution of T. juncifolius is New South Wales and eastern Victoria. Descriptions, photographic plates and a map are provided for the new species and T. juncifolius. The key in the Flora of Australia is amended to accommodate the new species.Udani M. Sirisena, Terry D. Macfarlane, and John G. Conra

    Embryo and seedling morphology in Trithuria lanterna (Hydatellaceae, Nymphaeales): new data for infrafamilial systematics and a novel type of syncotyly

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    Keywords: anatomy; cotyledon; embryology; evolution; gravitropism; heterocotyly; monocots; seed germination; vasculature The monogeneric early-divergent angiosperm family Hydatellaceae (Trithuria) was formerly placed in the monocots and shows several features that are at least superficially monocot-like. Seedlings of Hydatellaceae are unusually diverse and have been interpreted as either dicotylar or monocotylar. We provide the first detailed developmental description of seedlings of Trithuria lanterna (including the first data on mature embryos of tropical Hydatellaceae) as a basis for the general discussion of seedling diversity in Hydatellaceae. Seedlings at various stages after germination were studied using serial sections and scanning electron microscopy. The embryo is dicotylar. It lacks pronounced asymmetry and lacks a plumule before seed germination. In the majority of seedlings, the cotyledons are free and appear attached to the seedling axis at different levels. In other seedlings, the cotyledons are united via a non-haustorial leaf-like organ; this alternative condition represents a novel type of syncotyly for seed plants and a second type of syncotyly recorded for Hydatellaceae. Seedling morphology is determined by strong one-sided growth of the hypocotyl, which is an unusual way of overcoming the basic seed plant spatial constraint at germination. The direction of one-sided growth is independent of cotyledon orientation and could be environmentally determined. Seedlings provide synapomorphies for the two major clades of Trithuria, which can be regarded as subgenera. Although no direct homology is inferred, the exceptional degree of morphological variation in Hydatellaceae seedlings, including the variable occurrence of several superficially monocot-like features, leads us to hypothesize that the stem group of monocots could have exhibited an analogous degree of variation in cotyledon morphology. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 201
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