2,887 research outputs found

    Clyde superficial deposits and bedrock models released to the ASK Network 2013 : a guide for users

    Get PDF
    This report draft provides an overview of the Clyde superficial deposits models to be released in 2013 and detail on the Central Glasgow Superficial Deposits Model currently released to the ASK network. The geological models are an interpretation of digital datasets held by the British Geological Survey. A summary of the construction and limitations of the models and a brief description of the modelled units is given. The report will be updated and revised as more models become available for release to the ASK network. More details on the models can be found in the previous reports Merritt et al. (2009), Monaghan (2012a) and Monaghan et al. (2012)

    Star Formation Around Super-Massive Black Holes

    Full text link
    The presence of young massive stars orbiting on eccentric rings within a few tenths of a parsec of the supermassive black hole in the Galactic centre is challenging for theories of star formation. The high tidal shear from the black hole should tear apart the molecular clouds that form stars elsewhere in the Galaxy, while transporting the stars to the Galactic centre also appears unlikely during their stellar lifetimes. We present numerical simulations of the infall of a giant molecular cloud that interacts with the black hole. The transfer of energy during closest approach allows part of the cloud to become bound to the black hole, forming an eccentric disc that quickly fragments to form stars. Compressional heating due to the black hole raises the temperature of the gas to 100-1000K, ensuring that the fragmentation produces relatively high stellar masses. These stars retain the eccentricity of the disc and, for a sufficiently massive initial cloud, produce an extremely top-heavy distribution of stellar masses. This potentially repetitive process can therefore explain the presence of multiple eccentric rings of young stars in the presence of a supermassive black hole.Comment: 20 pages includingh 7 figures. "This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science, 321, (22 August 2008), doi:10.1126/science.1160653". Reprints and animations can be found at http://star-www.st-and.ac.uk/~iab1

    SPH Simulations of Counterrotating Disk Formation in Spiral Galaxies

    Get PDF
    We present the results of Smoothed Particle Hydrodynamics (SPH) simulations of the formation of a massive counterrotating disk in a spiral galaxy. The current study revisits and extends (with SPH) previous work carried out with sticky particle gas dynamics, in which adiabatic gas infall and a retrograde gas-rich dwarf merger were tested as the two most likely processes for producing such a counterrotating disk. We report on experiments with a cold primary similar to our Galaxy, as well as a hot, compact primary modeled after NGC 4138. We have also conducted numerical experiments with varying amounts of prograde gas in the primary disk, and an alternative infall model (a spherical shell with retrograde angular momentum). The structure of the resulting counterrotating disks is dramatically different with SPH. The disks we produce are considerably thinner than the primary disks and those produced with sticky particles. The time-scales for counterrotating disk formation are shorter with SPH because the gas loses kinetic energy and angular momentum more rapidly. Spiral structure is evident in most of the disks, but an exponential radial profile is not a natural byproduct of these processes. The infalling gas shells that we tested produce counterrotating bulges and rings rather than disks. The presence of a considerable amount of preexisting prograde gas in the primary causes, at least in the absence of star formation, a rapid inflow of gas to the center and a subsequent hole in the counterrotating disk. In general, our SPH experiments yield stronger evidence to suggest that the accretion of massive counterrotating disks drives the evolution of the host galaxies towards earlier (S0/Sa) Hubble types.Comment: To appear in ApJ. 20 pages LaTex 2-column with 3 tables, 23 figures (GIF) available at this site. Complete gzipped postscript preprint with embedded figures available from http://tarkus.pha.jhu.edu/~thakar/cr3.html (3 Mb

    Magnetic field structure due to the global velocity field in spiral galaxies

    Full text link
    We present a set of global, self-consistent N-body/SPH simulations of the dynamic evolution of galactic discs with gas and including magnetic fields. We have implemented a description to follow the evolution of magnetic fields with the ideal induction equation in the SPH part of the Vine code. Results from a direct implementation of the field equations are compared to a representation by Euler potentials, which pose a div(B)-free description, an constraint not fulfilled for the direct implementation. All simulations are compared to an implementation of magnetic fields in the Gadget code which includes also cleaning methods for div(B). Starting with a homogeneous seed field we find that by differential rotation and spiral structure formation of the disc the field is amplified by one order of magnitude within five rotation periods of the disc. The amplification is stronger for higher numerical resolution. Moreover, we find a tight connection of the magnetic field structure to the density pattern of the galaxy in our simulations, with the magnetic field lines being aligned with the developing spiral pattern of the gas. Our simulations clearly show the importance of non-axisymmetry for the evolution of the magnetic field.Comment: 17 pages, 18 figure

    IMPORTANCE OF INTERPROFESSIONAL EDUCATION, PRACTICE AND RESEARCH IN THE PHARMACY CURRICULUM IN THE ERA OF GLOBALIZATION

    Get PDF
    The profession of pharmacy has evolved gradually for more than a century and has seen many educational challenges and reforms. The pharmacy curriculum is science-based and varies widely in different parts of the world in both content and outcomes. The global pharmacy curriculum could be broadly categorized as product/industry-focused or patient-focused. In the United States (US), the baccalaureate degree has been replaced with the entry level Doctor of Pharmacy (Pharm.D.) curriculum. This change was designed to enable practicing pharmacists to provide patient care services that optimize medication therapy outcomes and promote health, wellness and disease prevention. This shift from a product-centered to a patient-centered curriculum has offered tremendous benefits to patients, society and healthcare. It has further been realized that working as a collaborative team with an inter-professional approach produces effective patient-centered outcomes. Implementation of inter-professional education (IPE), practice and research was recognized by pharmacy educators and accreditation authorities in the US in the early part of 21st century. IPE is now considered a standard for pharmacy accreditation. This review will compare some of the pharmacy curriculums of the world and the difficulty in harmonization of pharmacy curricula. The factors that facilitate and hinder IPE, practice and research in the curriculum will be discussed

    IMPORTANCE OF INTERPROFESSIONAL EDUCATION, PRACTICE AND RESEARCH IN THE PHARMACY CURRICULUM IN THE ERA OF GLOBALIZATION

    Get PDF
    The profession of pharmacy has evolved gradually for more than a century and has seen many educational challenges and reforms. The pharmacy curriculum is science-based and varies widely in different parts of the world in both content and outcomes. The global pharmacy curriculum could be broadly categorized as product/industry-focused or patient-focused. In the United States (US), the baccalaureate degree has been replaced with the entry level Doctor of Pharmacy (Pharm.D.) curriculum. This change was designed to enable practicing pharmacists to provide patient care services that optimize medication therapy outcomes and promote health, wellness and disease prevention. This shift from a product-centered to a patient-centered curriculum has offered tremendous benefits to patients, society and healthcare. It has further been realized that working as a collaborative team with an inter-professional approach produces effective patient-centered outcomes. Implementation of inter-professional education (IPE), practice and research was recognized by pharmacy educators and accreditation authorities in the US in the early part of 21st century. IPE is now considered a standard for pharmacy accreditation. This review will compare some of the pharmacy curriculums of the world and the difficulty in harmonization of pharmacy curricula. The factors that facilitate and hinder IPE, practice and research in the curriculum will be discussed

    Δ14C balance for the Gulf of Maine, Long Island Sound and the northern Middle Atlantic Bight: Evidence for the extent of the Antarctic Intermediate Water contribution

    Get PDF
    The radiocarbon signatures of the western Sargasso Sea and the atmosphere as a function of time over the past 200 years are known. These can be combined with seawater dissolved inorganic carbon (DIC) radiocarbon data from the Gulf of Maine and the northern Middle Atlantic Bight (MAB), including Long Island Sound (LIS), for 1983 and pre-1955 shell analyses for radiocarbon, to set the amount of Antarctic Intermediate Water (AAIW) required to balance the 14C budget in the northern MAB. Approximately 40% of the water entering the Middle Atlantic Bight from the north must be AAIW, the other 60% being Sargasso Sea water. Contemporary water from LIS, a part of northern MAB, can be explained as a mixture of Sargasso Sea water and Gulf of Maine water but at times in the past more low-14C water (AAIW) was added to this mixture as recorded in shells from LIS. This implies variations in upwelling rates over time in the region of the Middle Atlantic Bight

    Enhancement of thrust reverser cascade performance using aerodynamic and structural integration

    Get PDF
    This paper focuses on the design of a cascade within a cold stream thrust reverser during the early, conceptual stage of the product development process. A reliable procedure is developed for the exchange of geometric and load data between a two dimensional aerodynamic model and a three dimensional structural model. Aerodynamic and structural simulations are carried out using realistic operating conditions, for three different design configurations with a view to minimising weight for equivalent or improved aerodynamic and structural performance. For normal operational conditions the simulations show that total reverse thrust is unaffected when the performance of the deformed vanes is compared to the un-deformed case. This shows that for the conditions tested, the minimal deformation of the cascade vanes has no significant affect on aerodynamic efficiency and that there is scope for reducing the weight of the cascade. The pressure distribution through a two dimensional thrust reverser section is determined for two additional cascade vane configurations and it is shown that with a small decrease in total reverse thrust, it is possible to reduce weight and eliminate supersonic flow regimes through the nacelle section. By increasing vane sections in high pressure areas and decreasing sections in low pressure areas the structural performance of the cascade vanes in the weight reduced designs, is improved with significantly reduced levels of vane displacement and stress

    Electrical characterization of the soft breakdown failure mode in MgO layers

    Get PDF
    The soft breakdown (SBD) failure mode in 20 nm thick MgO dielectric layers grown on Si substrates was investigated. We show that during a constant voltage stress, charge trapping and progressive breakdown coexist, and that the degradation dynamics is captured by a power-law time dependence. We also show that the SBD current-voltage (I-V) characteristics follow the power-law model I = aVb typical of this conduction mechanism but in a wider voltage window than the one reported in the past for SiO2. The relationship between the magnitude of the current and the normalized differential conductance was analyzed

    The X-ray Ridge Surrounding Sgr A* at the Galactic Center

    Full text link
    We present the first detailed simulation of the interaction between the supernova explosion that produced Sgr A East and the wind-swept inner ~ 2-pc region at the Galactic center. The passage of the supernova ejecta through this medium produces an X-ray ridge ~ 9'' to 15'' to the NE of the supermassive black hole Sagittarius A* (Sgr A*). We show that the morphology and X-ray intensity of this feature match very well with recently obtained Chandra images, and we infer a supernova remnant age of less than 2,000 years. This young age--a factor 3--4 lower than previous estimates--arises from our inclusion of stellar wind effects in the initial (pre-explosion) conditions in the medium. The supernova does not clear out the central ~ 0.2-pc region around Sgr~A* and does not significantly alter the accretion rate onto the central black hole upon passage through the Galactic center.Comment: 10 pages, 3 figures, submitted to ApJ
    corecore