379
1,515.33
4.00
1,630

Publication History View all

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Poly- and single-crystal thin films of U-Mo alloys have been grown both on glass and sapphire substrates by UHV magnetron sputtering. X-ray and Electron Backscatter Diffraction data indicate that for single-crystal U1-xMox alloys, the pure cubic uranium gamma-phase exists for x > 0.22 (10 wt.% Mo). Below 10 wt.% Mo concentration, the resulting thin film alloys exhibited a mixed alpha-gamma uranium phase composition.
    Thin Solid Films 11/2013; 550. DOI:10.1016/j.tsf.2013.11.087
  • [Show abstract] [Hide abstract]
    ABSTRACT: Transmission and scanning electron microscopy are used to examine the sulphidation of hydrother- mally grown [0001]-oriented ZnO nanorods in aqueous thioacetamide (CH3C(S)NH2) solution. At the early stages of growth, the reaction occurs preferentially on the (0001) top surface,confirmed to be Zn- polar by convergent beam electron diffraction, and on the lines of intersection of the {1010} facets. It is shown that the reaction involves surface migration of Zn species towards ZnS deposits.The presence of voids at the ZnS/ZnO interface also confirms a Kirkendall mechanism where ZnS grows from the top surface of the deposit.
    Journal of Solid State Chemistry 01/2013; 199(2013):109-115. DOI:10.1016/j.jssc.2012.12.009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We predict the splitting of a high-order optical vortex into a constellation of unit vortices, upon total internal reflection of the carrier beam, and analyze the splitting. The reflected vortex constellation generalizes, in a local sense, the familiar longitudinal Goos-Hänchen and transverse Imbert-Fedorov shifts of the centroid of a reflected optical beam. The centroid shift is related to the center of the constellation, whose geometry otherwise depends on higher-order terms in an expansion of the reflection matrix. We derive an approximation of the amplitude around the constellation as a complex analytic polynomial, whose roots are the vortices. Increasing the order of the initial vortex gives an Appell sequence of complex polynomials, which we explain by an analogy with the theory of optical aberration.
    Physical Review Letters 11/2012; 109(18):183903. DOI:10.1103/PhysRevLett.109.183903
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In nonrelativistic quantum mechanics, measurements performed by separate observers are modeled via tensor products. In algebraic quantum field theory, though, local observables corresponding to spacelike separated parties are just required to commute. The problem of determining whether these two definitions of separation lead to the same set of bipartite correlations is known in nonlocality as Tsirelson's problem. In this article, we prove that the analog of Tsirelson's problem in steering scenarios is false. That is, there exists a steering inequality that can or cannot be violated depending on how we define spacelike separation at the operator level.
    Physical Review Letters 10/2012; 109(16):160405. DOI:10.1103/PhysRevLett.109.160405
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract I summarize the early developments of the more quantitative aspects of exoplanet detection. After a brief overview of the observational methods currently applied to exoplanet searches and a summary of the first true exoplanet detections resulting from these various techniques, the more relevant historical background is organized according to the observational techniques that are currently most relevant. Key Words: Exoplanets-History of astronomy. Astrobiology 12, 928-939.
    Astrobiology 09/2012; 12(10):928-39. DOI:10.1089/ast.2011.0784
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present single-Sérsic two-dimensional (2D) model fits to 167 600 galaxies modelled independently in the ugrizYJHK bandpasses using reprocessed Sloan Digital Sky Survey Data Release Seven (SDSS DR7) and UKIRT Infrared Deep Sky Survey Large Area Survey imaging data available from the Galaxy And Mass Assembly (GAMA) data base. In order to facilitate this study we developed Structural Investigation of Galaxies via Model Analysis (SIGMA), an R wrapper around several contemporary astronomy software packages including SOURCE EXTRACTOR, PSF EXTRACTOR and GALFIT 3. SIGMA produces realistic 2D model fits to galaxies, employing automatic adaptive background subtraction and empirical point spread function measurements on the fly for each galaxy in GAMA. Using these results, we define a common coverage area across the three GAMA regions containing 138 269 galaxies. We provide Sérsic magnitudes truncated at 10re which show good agreement with SDSS Petrosian and GAMA photometry for low Sérsic index systems (n < 4), and much improved photometry for high Sérsic index systems (n > 4), recovering as much as Δm= 0.5 mag in the r band. We employ a K-band Sérsic index/u-r colour relation to delineate the massive (n > ˜2) early-type galaxies (ETGs) from the late-type galaxies (LTGs). The mean Sérsic index of these ETGs shows a smooth variation with wavelength, increasing by 30 per cent from g through K. LTGs exhibit a more extreme change in Sérsic index, increasing by 52 per cent across the same range. In addition, ETGs and LTGs exhibit a 38 and 25 per cent decrease, respectively, in half-light radius from g through K. These trends are shown to arise due to the effects of dust attenuation and stellar population/metallicity gradients within galaxy populations.
    Monthly Notices of the Royal Astronomical Society 03/2012; 421(2):1007-1039. DOI:10.1111/j.1365-2966.2012.20355.x
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fitted over a range of more than ten magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue-plus-red sample, require double power-law Schechter functions to fit a dip in their LF faintwards of the characteristic magnitude M * before a steepening faint end. This upturn is at least partly due to dust-reddened disc galaxies. We measure evolution of the galaxy LF over the redshift range 0.002 < z < 0.5 both by using a parametric fit and by measuring binned LFs in redshift slices. The characteristic lumi-nosity L * is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. The comoving number density of blue galaxies in-creases with redshift, while that of red galaxies decreases, consistent with prevailing move- 2 J. Loveday et al. ment from blue cloud to red sequence. As well as being more numerous at higher redshift, blue galaxies also dominate the overall luminosity density beyond redshifts z 0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, by blue galax-ies in u and g.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new classification of circular polarization C points in three-dimensional polarization ellipse fields is proposed. The classification type depends on the out-of-plane variation of the polarization ellipse axis, in particular, whether the ellipse axes are in the plane of circular polarization one or three times. A minimal set of parameters for this classification is derived and discussed in the context of the familiar in-plane C point classification into lemon, star, and monstar types. This new geometric classification is related to the Möbius index of polarization singularities recently introduced by Freund.
    Optics Letters 10/2011; 36(19):3765-7. DOI:10.1364/OL.36.003765
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Figure 1: Catastrophic disruption data from this work and the literature: rubble piles (+, ,), ice (hexagon), and basalt (strong: *, , , hourglass; weak: ; hydrodynamic: • ; porous: ⊗,). A. Data adjusted for impact angle to equivalent normal im-pact. B. Data adjusted to equivalent equal mass (1:1) impact. The 1:1 data define the principal disruption curve (black line).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Collisions are the core component of planet formation. Using new high-resolution simulations of collisions between planetesimals for a wide range of projectileto- target mass ratios, impact angles, and impact velocities, we have derived a complete analytic description of the dynamical outcome for any collision between gravity-dominated bodies (100 m planetesimals to planets). The range of impact parameters encountered during growth from planetesimals to planets span multiple collision outcome regimes: cratering, merging, disruption, hit-and-run, and erosive hit-and-run events. We have derived equations to demarcate the transition between collision regimes and to describe the size and velocity distributions of the post-collision bodies. The scaling laws include only four material parameters, which are tightly constrained by the available data. All collision outcomes are described in terms of the impact conditions and the catastrophic disruption criteria, Q? RD, the specific energy required to disperse half the total colliding mass. The selfconsistent scaling laws will significantly improve the physics of collisions between gravity-dominated bodies in numerical simulations of planet formation and collisional evolution. This corpus of work, [1], has been split into two abstracts. In this abstract, we focus on the transitions between collisional regimes. In our companion abstract [2], we focus on describing a general catastrophic disruption law for planet formation.
Information provided on this web page is aggregated encyclopedic and bibliographical information relating to the named institution. Information provided is not approved by the institution itself. The institution’s logo (and/or other graphical identification, such as a coat of arms) is used only to identify the institution in a nominal way. Under certain jurisdictions it may be property of the institution.