Avoiding Pandemic Fears in the Subway and Conquering the Platypus.

Metagenomics is increasingly used not just to show patterns of microbial diversity but also as a culture-independent method to detect individual organisms of intense clinical, epidemiological, conservation, forensic, or regulatory interest. A widely reported metagenomic study of the New York subway suggested that the pathogens Yersinia pestis and Bacillus anthracis were part of the "normal subway microbiome." In their article in mSystems, Hsu and collaborators (mSystems 1(3):e00018-16, 2016, http://dx.doi.org/10.1128/mSystems.00018-16) showed that microbial communities on transit surfaces in the Boston subway system are maintained from a metapopulation of human skin commensals and environmental generalists and that reanalysis of the New York subway data with appropriate methods did not detect the pathogens. We note that commonly used software pipelines can produce results that lack prima facie validity (e.g., reporting widespread distribution of notorious endemic species such as the platypus or the presence of pathogens) but that appropriate use of inclusion and exclusion sets can avoid this issue

A Model of Temporal Intensity Modulation for Laser Generated Ultrasound

Q-switched lasers are often used as a non-contact ultrasound source in non-destructive evaluation (NDE) of materials [1]. Q-switched lasers typically have ns pulse durations and generate broadband ultrasound waves, though longer laser pulses, of 100 microseconds or greater, have also been used [2] for NDE. These longer pulses tend to produce somewhat lower center frequencies than do Q-switched pulses, though they are still a broadband source. But it would be desirable in some NDE applications to narrow the signal bandwidth to improve the signal to noise ration (SNR), and also to have direct control over the center frequency of the generated ultrasound. In principle, this may be achieved by temporal [3,4] or spatial modulation [5,6] of the laser pulse, or both [7]. The purpose of this work was to develop a numerical model of a single, temporally modulated laser source of ultrasound in the thermoelastic regime, for isotropic metals

Raising argument strength using negative evidence: A constraint on models of induction

Both intuitively, and according to similarity-based theories of induction, relevant evidence raises argument strength when it is positive and lowers it when it is negative. In three experiments, we tested the hypothesis that argument strength can actually increase when negative evidence is introduced. Two kinds of argument were compared through forced choice or sequential evaluation: single positive arguments (e.g., “Shostakovich’s music causes alpha waves in the brain; therefore, Bach’s music causes alpha waves in the brain”) and double mixed arguments (e.g., “Shostakovich’s music causes alpha waves in the brain, X’s music DOES NOT; therefore, Bach’s music causes alpha waves in the brain”). Negative evidence in the second premise lowered credence when it applied to an item X from the same subcategory (e.g., Haydn) and raised it when it applied to a different subcategory (e.g., AC/DC). The results constitute a new constraint on models of induction

Superconductivity. Quasiparticle mass enhancement approaching optimal doping in a high-T(c) superconductor.

In the quest for superconductors with higher transition temperatures (T(c)), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. Recent experiments have suggested the existence of the requisite broken-symmetry phase in the high-T(c) cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. We used magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa2Cu3O(6+δ) over a wide range of doping, and observed magnetic quantum oscillations that reveal a strong enhancement of the quasiparticle effective mass toward optimal doping. This mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum critical point at a hole doping of p(crit) ≈ 0.18.This work is supported by the US Department of Energy BES \Science at 100 T," the National Science Foundation, the State of Florida, the Natural Science and Engineering Research Council of Canada and the Canadian Institute for Advanced Research. S.E.S. ac- knowledges support from the Royal Society and the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC Grant Agree- ment no. 337425.This is the accepted manuscript. The final version is available at http://www.sciencemag.org/content/348/6232/317.abstract?sid=a882093c-ded2-481c-b62b-2f79a56b5689

Effects of Laser Source Parameters on the Generation of Narrow Band and Directed Laser Ultrasound

The successful application of laser techniques for ultrasonic testing depends on the efficient coupling of optical energy into elastic energy so that laser probe detection sensitivity may be maximized. Through optimization of the laser source which is used to generate ultrasonic waves, the overall performance of laser ultrasonic systems may be enhanced by improving the efficiency with which optical energy is converted to elastic energy. This optimization depends primarily on the source laser wavelength which governs the physical interaction of the optical energy with the material of interest. For a given laser source wavelength, several techniques have been demonstrated which modify the laser source to enhance the detectability of laser ultrasonic waves and include the repetitively pulsed laser source [1,2], or temporal array, and the phased array laser source [3],or phased array. These techniques directly address the wave detectability issue by controlling the amplitude and/or the frequency content of the laser ultrasonic wave. Even though the overall conversion efficiency of optical energy to elastic energy is not improved primarily by repetitive pulsing or phasing laser arrays, the detectability of a given laser ultrasonic wave may be enhanced beyond that obtained using a single laser source

Secluded Dark Matter Coupled to a Hidden CFT

Models of secluded dark matter offer a variant on the standard WIMP picture and can modify our expectations for hidden sector phenomenology and detection. In this work we extend a minimal model of secluded dark matter, comprised of a U(1)'-charged dark matter candidate, to include a confining hidden-sector CFT. This provides a technically natural explanation for the hierarchically small mediator-scale, with hidden-sector confinement generating m_{gamma'}>0. Furthermore, the thermal history of the universe can differ markedly from the WIMP picture due to (i) new annihilation channels, (ii) a (potentially) large number of hidden-sector degrees of freedom, and (iii) a hidden-sector phase transition at temperatures T << M_{dm} after freeze out. The mediator allows both the dark matter and the Standard Model to communicate with the CFT, thus modifying the low-energy phenomenology and cosmic-ray signals from the secluded sector.Comment: ~50p, 8 figs; v2 JHEP versio

The effectiveness of early lens extraction with intraocular lens implantation for the treatment of primary angle-closure glaucoma (EAGLE) : study protocol for a randomized controlled trial

Peer reviewedPublisher PD

A new twist on the geometry of gravitational plane waves

The geometry of twisted null geodesic congruences in gravitational plane wave spacetimes is explored, with special focus on homogeneous plane waves. The role of twist in the relation of the Rosen coordinates adapted to a null congruence with the fundamental Brinkmann coordinates is explained and a generalised form of the Rosen metric describing a gravitational plane wave is derived. The Killing vectors and isometry algebra of homogeneous plane waves (HPWs) are described in both Brinkmann and twisted Rosen form and used to demonstrate the coset space structure of HPWs. The van Vleck-Morette determinant for twisted congruences is evaluated in both Brinkmann and Rosen descriptions. The twisted null congruences of the Ozsvath-Schucking,`anti-Mach' plane wave are investigated in detail. These developments provide the necessary geometric toolkit for future investigations of the role of twist in loop effects in quantum field theory in curved spacetime, where gravitational plane waves arise generically as Penrose limits; in string theory, where they are important as string backgrounds; and potentially in the detection of gravitational waves in astronomy.Comment: 60 pages, 2 figures. Extended version with new material on Rosen geodesics and isometries. Title change

Groups without cultured representatives dominate eukaryotic picophytoplankton in the oligotrophic South East Pacific Ocean

Background: Photosynthetic picoeukaryotes (PPE) with a cell size less than 3 µm play a critical role in oceanic primary production. In recent years, the composition of marine picoeukaryote communities has been intensively investigated by molecular approaches, but their photosynthetic fraction remains poorly characterized. This is largely because the classical approach that relies on constructing 18S rRNA gene clone libraries from filtered seawater samples using universal eukaryotic primers is heavily biased toward heterotrophs, especially alveolates and stramenopiles, despite the fact that autotrophic cells in general outnumber heterotrophic ones in the euphotic zone. Methodology/Principal Findings: In order to better assess the composition of the eukaryotic picophytoplankton in the South East Pacific Ocean, encompassing the most oligotrophic oceanic regions on earth, we used a novel approach based on flow cytometry sorting followed by construction of 18S rRNA gene clone libraries. This strategy dramatically increased the recovery of sequences from putative autotrophic groups. The composition of the PPE community appeared highly variable both vertically down the water column and horizontally across the South East Pacific Ocean. In the central gyre, uncultivated lineages dominated: a recently discovered clade of Prasinophyceae (IX), clades of marine Chrysophyceae and Haptophyta, the latter division containing a potentially new class besides Prymnesiophyceae and Pavlophyceae. In contrast, on the edge of the gyre and in the coastal Chilean upwelling, groups with cultivated representatives (Prasinophyceae clade VII and Mamiellales) dominated. Conclusions/Significance: Our data demonstrate that a very large fraction of the eukaryotic picophytoplankton still escapes cultivation. The use of flow cytometry sorting should prove very useful to better characterize specific plankton populations by molecular approaches such as gene cloning or metagenomics, and also to obtain into culture strains representative of these novel groups