463 research outputs found

    Predatory Organisms with Untapped Biosynthetic Potential:Descriptions of Novel Corallococcus Species C. aberystwythensis sp. nov., C. carmarthensis sp. nov., C. exercitus sp. nov., C. interemptor sp. nov., C. llansteffanensis sp. nov., C. praedator sp. nov., C. sicarius sp. nov., and C. terminator sp. nov

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    Corallococcus spp. are common soil-dwelling organisms which kill and consume prey microbes through the secretion of antimicrobial substances. Two species of Corallococcus have been described previously (Corallococcus coralloides and Corallococcus exiguus). A polyphasic approach was taken to characterise antimicrobial, biochemical and phenotypic properties of eight Corallococcus spp. strains and the two type strains. We also report here the genome sequence of the C. exiguus type strain (DSM 14696T). The genomes of the eight candidate strains, C. exiguus DSM 14696T and C. coralloides DSM 2259T, had an average nucleotide identity below 95% and digital DNA-DNA hybridisation scores less than the 70% lower bound for species identity, indicating they belong to distinct species. All ten strains, including the two type strains, were thoroughly characterised, including biochemical analysis of their fatty acid methyl esters, substrate utilisation and sugar assimilation. Each strain gave a distinct profile of properties, which together with their genomic differences supports the proposal of the eight candidate strains as novel species: Corallococcus exercitus sp. nov. (AB043AT = DSM 108849T = NBRC 113887T), Corallococcus interemptor sp. nov. (AB047AT = DSM 108843T = NBRC 113888T), Corallococcus aberystwythensis sp. nov. (AB050AT = DSM 108846T = NBRC 114019T), Corallococcus praedator sp. nov. (CA031BT = DSM 108841T = NBRC 113889T), Corallococcus sicarius sp. nov. (CA040BT = DSM 108850T = NBRC 113890T), Corallococcus carmarthenensis sp. nov. (CA043DT = DSM 108842T = NBRC 113891T), Corallococcus llansteffanensis sp. nov. (CA051BT = DSM 108844T = NBRC 114100T) and Corallococcus terminator sp. nov. (CA054AT = DSM 108848T = NBRC 113892T)

    Magnetic Field Strength in the Upper Solar Corona Using White-light Shock Structures Surrounding Coronal Mass Ejections

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    To measure the magnetic field strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the magnetic field strengths are consistent in both methods; (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.Comment: Accepted for publication in ApJ, 11 Figures, 1 Tabl

    The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption

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    We exploit the high sensitivity and moderate spectral resolution of the HSTHST-Cosmic Origins Spectrograph to detect far-ultraviolet spectral features of carbon monoxide (CO) present in the inner regions of protoplanetary disks for the first time. We present spectra of the classical T Tauri stars HN Tau, RECX-11, and V4046 Sgr, representative of a range of CO radiative processes. HN Tau shows CO bands in absorption against the accretion continuum. We measure a CO column density and rotational excitation temperature of N(CO) = 2 +/- 1 ×\times 1017^{17} cm−2^{-2} and T_rot(CO) 500 +/- 200 K for the absorbing gas. We also detect CO A-X band emission in RECX-11 and V4046 Sgr, excited by ultraviolet line photons, predominantly HI LyA. All three objects show emission from CO bands at λ\lambda >> 1560 \AA, which may be excited by a combination of UV photons and collisions with non-thermal electrons. In previous observations these emission processes were not accounted for due to blending with emission from the accretion shock, collisionally excited H2_{2}, and photo-excited H2; all of which appeared as a "continuum" whose components could not be separated. The CO emission spectrum is strongly dependent upon the shape of the incident stellar LyA emission profile. We find CO parameters in the range: N(CO) 1018−19^{18-19} cm−2^{-2}, T_{rot}(CO) > 300 K for the LyA-pumped emission. We combine these results with recent work on photo- and collisionally-excited H2_{2} emission, concluding that the observations of ultraviolet-emitting CO and H2 are consistent with a common spatial origin. We suggest that the CO/H2 ratio in the inner disk is ~1, a transition between the much lower interstellar value and the higher value observed in solar system comets today, a result that will require future observational and theoretical study to confirm.Comment: 12 pages, 7 figures, 3 tables. ApJ - accepte

    Ethnographic perspectives on global mental health

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    The field of Global Mental Health (GMH) aims to influence mental health policy and practice worldwide, with a focus on human rights and access to care. There have been important achievements, but GMH has also been the focus of scholarly controversies arising from political, cultural and pragmatic critiques. These debates have become increasingly polarized, giving rise to a need for more dialogue and experience-near research to inform theorizing. Ethnography has much to offer in this respect. This paper frames and introduces five articles in the issue of Transcultural Psychiatry that illustrate the role of ethnographic methods in understanding the effects and implications of the field of global mental health on mental health policy and practice. The papers include ethnographies from South Africa, India and Tonga, that show the potential for ethnographic evidence to inform GMH projects. These studies provide nuanced conceptualizations of GMH’s varied manifestations across different settings, the diverse ways that GMH’s achievements can be evaluated, and the connections that can be drawn between locally observed experiences and wider historical, political and social phenomena. Ethnography can provide a basis for constructive dialogue between those engaged in developing and implementing GMH interventions and those critical of some of its approaches

    Confirmation of a Faraday Rotation Measure Anomaly in Cygnus

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    We confirm the reality of a reversal of the sign of the Faraday Rotation Measure in the Galactic plane in Cygnus (Lazio et al, 1990), possibly associated with the Cygnus OB1 association. The rotation measure changes by several hundred rad/m2^2 over an angular scale of 2−5∘2-5^{\circ}. We show that a simple model of an expanding plasma shell with an enhanced density and magnetic field, consistent with observations of Hα\alpha emission in this part of sky, and physically associated with a superbubble of the Cygnus OB1 association, can account for the magnitude and angular scale of this feature.Comment: Submitted to the Astrophysical Journa

    Photoevaporation as a Truncation Mechanism for Circumplanetary Disks

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    We investigate the conditions under which the regular satellites of Jupiter and Saturn formed. The final stage of giant planet accretion is thought to occur slowly over a relatively long, 10 Myr, timescale. Gas accretion during this stage, through a completely or partially opened gap in the solar nebula, occurs slowly allowing for the condensation of ices, and incomplete differentiation, seen in the regular satellites of the giant planets. Furthermore, the dichotomy seen in the Jovian and Saturnian systems may be explained as this infall wanes or is completely shutoff as a result of gap opening or global depletion of gas in the solar nebula. We present one-dimensional simulations of circumplanetary disks that couple the viscous transport of material with the loss of mass at the disk outer edge by ultraviolet photoevaporation as well as the infall of material from the solar nebula. We find that the circumplanetary disks of these protoplanets are truncated, as a result of photoevaporation, at a range of values with the mean corresponding to ≈\approx 0.16 Hill radii. These truncation radii are broadly consistent with the current locations of the regular satellite systems of Jupiter and Saturn. We also find that photoevaporation can successfully act as a clearing mechanism for circumplanetary nebulae on the potentially short timescales, 100-10,000 yr, over which mass accretion from the solar nebula wanes as a result of gap opening. Such a rapid clearing of the circum-Jovian disk may be required to explain the survival of the Galilean satellites.Comment: 6 pages, 6 figures, accepted for publication in the Astronomical Journa
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