511 research outputs found

    The Global Kinematics of the Globular Cluster M92

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    We report the determination of high-accuracy radial velocities for 306 members of the globular cluster M92 using the Hydra multiobject spectrograph on the WIYN telescope. We have concentrated on stars outside of the central region of the cluster, located up to 14.4&arcmin; from the cluster center. Candidate members were selected for spectroscopy based on a photometric metallicity index determined from three-band Washington photometry, also obtained with the WIYN telescope. The median error in the velocities is 0.35 km s-1. We find the heliocentric radial velocity of the cluster to be -121.2 ± 0.3 km s-1. We have used an improved Bayesian analysis to determine the velocity dispersion profile of M92. The most probable profile is a cored power law with a scale radius of 2&arcmin;, a velocity dispersion at 1&arcmin; of 6.3 km s-1, and an outer power law with a slope of -0.6. We have also reanalyzed the M15 radial velocities of Drukier et al. and find that a pure power law with a 1&arcmin; velocity dispersion of 8 km s-1 and a slope of -0.5 and the combination of a power law with a slope of -0.4 and a scale of 7.5 km s-1 inside 9&arcmin; and a dispersion of 4 km s-1 outside are equally likely. In both clusters there is evidence that the samples include escaping stars. We present results from a GRAPE-based N-body simulation of an isolated cluster that demonstrates this effect. We suggest additional tests to determine the relative importance of tidal heating and stellar ejection for establishing the velocity field in globular cluster halos

    Global Kinematics of the Globular Cluster M15*

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    We present velocities for 230 stars in the outer parts of the globular cluster M15 measured with the Hydra multifiber spectrograph on the 3.5 m WIYN telescope. A new Bayesian technique is used for analyzing the data. The mean velocity of the cluster is -106.9 ± 0.3 km s-1. Rotation with an amplitude of 1.5 ± 0.4 km s-1 and a position angle of 125° ± 19° is observed, and a model including rotation is marginally favored over one without rotation. The velocity dispersion decreases from the center out to about 7&arcmin; and then appears to increase slightly. This behavior is strikingly different from the continued decline of velocity dispersion with increasing radius that is expected in an isolated cluster. We interpret this as an indication of heating of the outer part of M15 by the Galactic tidal field

    Mellin-Barnes Representation for the Genus-g Finite Temperature String Theory

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    The Mellin-Barnes representation for the free energy of the genus-gg string is constructed. It is shown that the interactions of the open bosonic string do not modify the critical (Hagedorn) temperature. However,for the sectors having a spinor structure, the critical temperature exists also for all gg and depends on the windings. The appearance of a periodic structure is briefly discussed.Comment: 9 pages, report UTF 294 (1993

    Results from a Comparison of Approximate Analytical Solutions with a Detailed Numerical Inversion Analysis to Determine the Thermal Conductivity of the Regolith at the Mars InSight Landing Site Using Data from HP3 Heating Experiments

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    A direct measurement of the regolith thermal conductivity at the Mars InSight landing site (4.50°, 132.62°E) was made by heating experiments using the physical properties package (HP3) of the Mars InSight mission. Temperature and time data from these heating experiments, after removal of background temperature variations, were analyzed using a finite element model for which Monte Carlo simulations were run varying regolith thermal conductivity, density, thermal contact conductance between the probe and the regolith to determine parameter combinations that best fit the heating curve. In terms of simulating details of heating experiment this data reduction and numerical inversion is as complete as possible within the current constraints of the experiment. However, no information was included in the model concerning regolith thermal conductivity variations radial to the probe caused during penetration of the probe

    Bioactivity of umbelliprenin, the major component found in the seeds of Angelica sylvestris

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    Se ha evaluado la actividad antibacteriana y antioxidante de la umbelliprenina (1), una cumarina de sesquiterpenil, aislada como el componente principal presente en extractos de n-hexano y diclorometano de semillas de Angelica sylvestris (Apiaceae). También se ha evaluado la toxicidad general de 1 mediante el bioensayo de letalidad de gambas en salmuera (BSL).Umbelliprenin (1), a sesquiterpenyl coumarin, isolated as the major component present in the n-hexane and dichloromethane extracts of the seeds of Angelica sylvestris (Apiaceae), has been assessed for antibacterial and antioxidant activities. General toxicity of 1 has also been evaluated by the brine shrimp lethality (BSL) bioassay

    On the Progenitors of Core-Collapse Supernovae

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    Theory holds that a star born with an initial mass between about 8 and 140 times the mass of the Sun will end its life through the catastrophic gravitational collapse of its iron core to a neutron star or black hole. This core collapse process is thought to usually be accompanied by the ejection of the star's envelope as a supernova. This established theory is now being tested observationally, with over three dozen core-collapse supernovae having had the properties of their progenitor stars directly measured through the examination of high-resolution images taken prior to the explosion. Here I review what has been learned from these studies and briefly examine the potential impact on stellar evolution theory, the existence of "failed supernovae", and our understanding of the core-collapse explosion mechanism.Comment: 7 Pages, invited review accepted for publication by Astrophysics and Space Science (special HEDLA 2010 issue

    Supply of Vertebrate Necropsy and Sample Recovery Services Merged Final Reports

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    The Marine Institute issued a tender for the Supply of Vertebrate Necropsy and Sample Recovery Services Tender (2017-2018). The results are presented in this report. These tenders required i) the recovery and standardised necropsy of three cetacean species with associated case history reporting, ii) the provision of sampling kits to be used for the recovery of tissue samples collected from bycaught animals (birds, seals and cetaceans) by observers on commercial inshore and offshore fishing vessels in Irish waters in order to provide additional data to the MI’s existing catch sampling programme and iii) the storage and subsequent delivery of all samples and associated databases to the client. Recovery of 24 animals from two geographical lots was the target for the initial contract (2017) and was achieved. The contract extension (early 2018) required the collection and necropsy of a further 16 animals, which was exceeded as 19 animals were collected. A target of 30 animals to be recovered was required in the second contract (2018) and was also successfully reached. These 73 animals comprised 53 common dolphins (Delphinus delphis), ten striped dolphins (Stenella coeruleoalba) and ten harbour porpoises (Phocoena phocoena). Forty-one of the 73 (56%) individuals were recovered from Lot 1 from counties Clare to Donegal, while 32 (44%) individuals were recovered from Lot 2 from counties Wexford to Kerry. Thirty-five sampling kits were assembled and delivered to the Marine Institute, and additional kits were prepared and available upon request for distribution to their panel of fishery observers. Between 24 July and 14 December 2017, two adult male grey seals were incidentally captured in tangle nets and reported to the Project Coordinator. Results from these tenders will inform the development of a long-term strategy for necropsy of stranded cetaceans and recovery of tissue samples for further biological studies. Samples requiring long-term storage at -20°C, including those for virology, were transported in a portable refrigerator to the IWDG office in Kilrush, Co. Clare and stored at facilities on site. Formalin fixed tissues, such as reproductive organs and adrenal glands, were stored at the RVL in Cork. All samples have been delivered to the Marine Institute in Oranmore, Co. Galway along with a detailed database of samples collected.EMF

    Field Measurements of Terrestrial and Martian Dust Devils

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    Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types

    Origins of the Ambient Solar Wind: Implications for Space Weather

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    The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure
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