1,359 research outputs found

    Self-organized criticality and synchronization in a lattice model of integrate-and-fire oscillators

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    We introduce two coupled map lattice models with nonconservative interactions and a continuous nonlinear driving. Depending on both the degree of conservation and the convexity of the driving we find different behaviors, ranging from self-organized criticality, in the sense that the distribution of events (avalanches) obeys a power law, to a macroscopic synchronization of the population of oscillators, with avalanches of the size of the system.Comment: 4 pages, Revtex 3.0, 3 PostScript figures available upon request to [email protected]

    SPARTAN: a global network to evaluate and enhance satellite-based estimates of ground-level particulate matter for global health applications

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    Ground-based observations have insufficient spatial coverage to assess long-term human exposure to fine particulate matter (PM2.5) at the global scale. Satellite remote sensing offers a promising approach to provide information on both short-and long-term exposure to PM2.5 at local-to-global scales, but there are limitations and outstanding questions about the accuracy and precision with which ground-level aerosol mass concentrations can be inferred from satellite remote sensing alone. A key source of uncertainty is the global distribution of the relationship between annual average PM2.5 and discontinuous satellite observations of columnar aerosol optical depth (AOD). We have initiated a global network of ground-level monitoring stations designed to evaluate and enhance satellite remote sensing estimates for application in health-effects research and risk assessment. This Surface PARTiculate mAtter Network (SPARTAN) includes a global federation of ground-level monitors of hourly PM2.5 situated primarily in highly populated regions and collocated with existing ground-based sun photometers that measure AOD. The instruments, a three-wavelength nephelometer and impaction filter sampler for both PM2.5 and PM10, are highly autonomous. Hourly PM2.5 concentrations are inferred from the combination of weighed filters and nephelometer data. Data from existing networks were used to develop and evaluate network sampling characteristics. SPARTAN filters are analyzed for mass, black carbon, water-soluble ions, and metals. These measurements provide, in a variety of regions around the world, the key data required to evaluate and enhance satellite-based PM2.5 estimates used for assessing the health effects of aerosols. Mean PM2.5 concentrations across sites vary by more than 1 order of magnitude. Our initial measurements indicate that the ratio of AOD to ground-level PM2.5 is driven temporally and spatially by the vertical profile in aerosol scattering. Spatially this ratio is also strongly influenced by the mass scattering efficiency.Fil: Snider, G.. Dalhousie University Halifax; CanadĂĄFil: Weagle, C. L.. Dalhousie University Halifax; CanadĂĄFil: Martin, R. V.. Dalhousie University Halifax; CanadĂĄ. University of Cambridge; Reino UnidoFil: van Donkelaar, A.. Dalhousie University Halifax; CanadĂĄFil: Conrad, K.. Dalhousie University Halifax; CanadĂĄFil: Cunningham, D.. Dalhousie University Halifax; CanadĂĄFil: Gordon, C.. Dalhousie University Halifax; CanadĂĄFil: Zwicker, M.. Dalhousie University Halifax; CanadĂĄFil: Akoshile, C.. University of Ilorin; NigeriaFil: Artaxo, P.. Governo Do Estado de Sao Paulo; BrasilFil: Anh, N. X.. Vietnam Academy of Science and Technology. Institute of Geophysics; VietnamFil: Brook, J.. University of Toronto; CanadĂĄFil: Dong, J.. Tsinghua University; ChinaFil: Garland, R. M.. North-West University; SudĂĄfricaFil: Greenwald, R.. Rollins School of Public Health; Estados UnidosFil: Griffith, D.. Council for Scientific and Industrial Research; SudĂĄfricaFil: He, K.. Tsinghua University; ChinaFil: Holben, B. N.. NASA Goddard Space Flight Center; Estados UnidosFil: Kahn, R.. NASA Goddard Space Flight Center; Estados UnidosFil: Koren, I.. Weizmann Institute Of Science Israel; IsraelFil: Lagrosas, N.. Manila Observatory, Ateneo de Manila University campus; FilipinasFil: Lestari, P.. Institut Teknologi Bandung; IndonesiaFil: Ma, Z.. Rollins School of Public Health; Estados UnidosFil: Vanderlei Martins, J.. University of Maryland; Estados UnidosFil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas; ArgentinaFil: Rudich, Y.. Weizmann Institute Of Science Israel; IsraelFil: Salam, A.. University Of Dhaka; BangladeshFil: Tripathi, S. N.. Indian Institute Of Technology, Kanpur; IndiaFil: Yu, C.. Rollins School of Public Health; Estados UnidosFil: Zhang, Q.. Tsinghua University; ChinaFil: Zhang, Y.. Tsinghua University; ChinaFil: Brauer, M.. University of British Columbia; CanadĂĄFil: Cohen, A.. Health Effects Institute; Estados UnidosFil: Gibson, M. D.. Dalhousie University Halifax; CanadĂĄFil: Liu, Y.. Rollins School of Public Health; Estados Unido

    Observation of the decay \psip\rar\kstark

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    Using 14 million ψ(2S)\psi(2S) events collected with the BESII detector, branching fractions of \psip\rar\kstarkpm and \kstarknn are determined to be: \calB(\psip\rar\kstarkpm)=(2.9^{+1.3}_{-1.7}\pm0.4)\times 10^{-5} and \calB(\psip\rar\kstarknn)=(13.3^{+2.4}_{-2.7}\pm1.9)\times 10^{-5}. The results confirm the violation of the "12%" rule for these two decay channels with higher precision. A large isospin violation between the charged and neutral modes is observed.Comment: 5 pages, 3 figure

    Asymptotic behaviour and optimal word size for exact and approximate word matches between random sequences

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    BACKGROUND: The number of k-words shared between two sequences is a simple and effcient alignment-free sequence comparison method. This statistic, D(2), has been used for the clustering of EST sequences. Sequence comparison based on D(2 )is extremely fast, its runtime is proportional to the size of the sequences under scrutiny, whereas alignment-based comparisons have a worst-case run time proportional to the square of the size. Recent studies have tackled the rigorous study of the statistical distribution of D(2), and asymptotic regimes have been derived. The distribution of approximate k-word matches has also been studied. RESULTS: We have computed the D(2 )optimal word size for various sequence lengths, and for both perfect and approximate word matches. Kolmogorov-Smirnov tests show D(2 )to have a compound Poisson distribution at the optimal word size for small sequence lengths (below 400 letters) and a normal distribution at the optimal word size for large sequence lengths (above 1600 letters). We find that the D(2 )statistic outperforms BLAST in the comparison of artificially evolved sequences, and performs similarly to other methods based on exact word matches. These results obtained with randomly generated sequences are also valid for sequences derived from human genomic DNA. CONCLUSION: We have characterized the distribution of the D(2 )statistic at optimal word sizes. We find that the best trade-off between computational efficiency and accuracy is obtained with exact word matches. Given that our numerical tests have not included sequence shuffling, transposition or splicing, the improvements over existing methods reported here underestimate that expected in real sequences. Because of the linear run time and of the known normal asymptotic behavior, D(2)-based methods are most appropriate for large genomic sequences

    Using standard keywords in publications to facilitate updates of new fungal taxonomic names

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    The combination of manual curation and the reliance on updates from submitters to the public sequence databases is currently inefficient and impedes the comprehensive and timely release of records with new taxonomic names. This should be improved by making several steps during data release more efficient. This article focuses on one such step by proposing a standard way for publications to flag papers with novel taxonomic information. As a result, the potential for automated searches of publication aggregators are improved, as well as the accurate curation of taxonomic information.This paper resulted from discussions in Group 5 under the auspices of the International Commission on the Taxonomy of Fungi (ICTF).http://www.imafungus.orgam2018Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant Patholog

    Observation of the Decays B0->K+pi-pi0 and B0->rho-K+

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    We report the observation of B^0 decays to the K^+pi^-pi^0 final state using a data sample of 78 fb^-1 collected by the Belle detector at the KEKB e^+e^- collider. With no assumptions about intermediate states in the decay, the branching fraction is measured to be (36.6^{+4.2}_{-4.3}+- 3.0)*10^-6.We also search for B decays to intermediate two-body states with the same K^+pi^-pi^0 final state. Significant B signals are observed in the rho(770)^- K^+ and K^*(892)^+pi^- channels, with branching fractions of (15.1^{+3.4+1.4+2.0}_{-3.3-1.5-2.1})* 10^-6 and (14.8^{+4.6+1.5+2.4}_{-4.4-1.0-0.9})* 10^-6, respectively. The first error is statistical, the second is systematic and the third is due to the largest possible interference. Contributions from other possible two-body states will be discussed. No CP asymmetry is found in the inclusive K^+pi^-pi^0 or rho^-K^+ modes, and we set 90% confidence level bounds on the asymmetry of -0.12<A_{CP}<0.26 and -0.18<A_{CP}<0.64, respectively.Comment: 18 pages, 7 figure

    HighP–TNano-Mechanics of Polycrystalline Nickel

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    We have conducted highP–Tsynchrotron X-ray and time-of-flight neutron diffraction experiments as well as indentation measurements to study equation of state, constitutive properties, and hardness of nanocrystalline and bulk nickel. Our lattice volume–pressure data present a clear evidence of elastic softening in nanocrystalline Ni as compared with the bulk nickel. We show that the enhanced overall compressibility of nanocrystalline Ni is a consequence of the higher compressibility of the surface shell of Ni nanocrystals, which supports the results of molecular dynamics simulation and a generalized model of a nanocrystal with expanded surface layer. The analytical methods we developed based on the peak-profile of diffraction data allow us to identify “micro/local” yield due to high stress concentration at the grain-to-grain contacts and “macro/bulk” yield due to deviatoric stress over the entire sample. The graphic approach of our strain/stress analyses can also reveal the corresponding yield strength, grain crushing/growth, work hardening/softening, and thermal relaxation under highP–Tconditions, as well as the intrinsic residual/surface strains in the polycrystalline bulks. From micro-indentation measurements, we found that a low-temperature annealing (T < 0.4 Tm) hardens nanocrystalline Ni, leading to an inverse Hall–Petch relationship. We explain this abnormal Hall–Petch effect in terms of impurity segregation to the grain boundaries of the nanocrystalline Ni

    A new model for the characterization of infection risk in gunshot injuries:Technology, principal consideration and clinical implementation

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    <p>Abstract</p> <p>Introduction</p> <p>The extent of wound contamination in gunshot injuries is still a topic of controversial debate. The purpose of the present study is to develop a model that illustrates the contamination of wounds with exogenous particles along the bullet path.</p> <p>Material and methods</p> <p>To simulate bacteria, radio-opaque barium titanate (3-6 ÎŒm in diameter) was atomized in a dust chamber. Full metal jacket or soft point bullets caliber .222 (n = 12, v<sub>0 </sub>= 1096 m/s) were fired through the chamber into a gelatin block directly behind it. After that, the gelatin block underwent multi-slice CT in order to analyze the permanent and temporary wound cavity.</p> <p>Results</p> <p>The permanent cavity caused by both types of projectiles showed deposits of barium titanate distributed over the entire bullet path. Full metal jacket bullets left only few traces of barium titanate in the temporary cavity. In contrast, the soft point bullets disintegrated completely, and barium titanate covered the entire wound cavity.</p> <p>Discussion</p> <p>Deep penetration of potential exogenous bacteria can be simulated easily and reproducibly with barium titanate particles shot into a gelatin block. Additionally, this procedure permits conclusions to be drawn about the distribution of possible contaminants and thus can yield essential findings in terms of necessary therapeutic procedures.</p

    Improved Measurements of Branching Fractions for B->Kpi, pipi and KK Decays

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    We report improved measurements of branching fractions for B→KπB\to K\pi, π+π−\pi^+\pi^-, π+π0\pi^+\pi^0 and KKˉK\bar{K} decays based on a data sample of 85.0 million BBˉB\bar{B} pairs collected at the ΄(4S)\Upsilon (4S) resonance with the Belle detector at the KEKB e+e−e^+e^- storage ring. This data sample is almost three times larger than the sample previously used. We observe clear signals for B→KπB\to K\pi, π+π−\pi^+\pi^- and π+π0\pi^+\pi^0 decays and set upper limits on B→KKˉB\to K\bar{K} decays. The results can be used to give model-dependent constraints on the CKM angle ϕ3\phi_3, as well as limits on the hadronic uncertainty in the time-dependent analysis of the angle ϕ2\phi_2.Comment: 10 pages, 1 figure, 4 tables. Submitted to Phys. Rev. D Rapid Communications. Several corrections were mad
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