Search

We present results from direct measurements of the $^{27}{\rm Al}(\alpha,n)$ thick target yield from laboratory incident energies $E_{\alpha}\approx$ 3$-$5~MeV, performed with the $^{3}$HeBF$_{3}$ Giant Barrel (HeBGB) neutron detector at the Edwards Accelerator Laboratory. Our measurements have a small energy cadence in order to address discrepancies and sparseness of thick-target yield data sets existing for this energy region. We find general agreement with existing data sets, including yields derived from cross section data, while resolving a discrepancy between existing thick-target yield data sets for $E_{\alpha}\approx4-5$~MeV. However, for $E_{\alpha}<3.5$~MeV, our results are substantially lower than previous thick-target yield data and somewhat larger than yields calculated from existing cross section data. Our data complete the energy-range needed for estimates of the $^{27}{\rm Al}(\alpha,n)$ contribution to neutrino and dark matter detector backgrounds and result in increased viability of $^{27}{\rm Al}(\alpha,n)$ as a plasma diagnostic tool at fusion facilities such as the National Ignition Facility., Comment: Accepted to Nuclear Science and Engineering

$(\alpha,n)$ reactions play an important role in nuclear astrophysics and applications and are an important background source in neutrino and dark matter detectors. Measurements of total $(\alpha,n)$ cross sections employing direct neutron detection often have a considerable systematic uncertainty associated with the energy-dependent neutron detection efficiency and the unknown initial neutron energy distribution. The $^{3}{\rm He}\,{\rm BF}_{3}$ Giant Barrel (HeBGB) neutron detector was built at the Edwards Accelerator Laboratory at Ohio University to overcome this challenge. HeBGB offers a near-constant neutron detection efficiency of ($7.5\pm 1.2$) \% over the neutron energy range 0.01 MeV -- 9.00 MeV, removing a significant source of systematic uncertainty present in earlier $(\alpha,n)$ cross section measurements.

Our UC Santa Barbara research team engages in ongoing efforts to enhance and validate the Social Emotional Health Surveys (Primary, Secondary, and Higher Education). The initiative to enhance the secondary version is supported by an Institute of Education Sciences grant (#R305A160157, 2016-2020), which provides funding to refine, standardize, and accumulate additional validation evidence for the secondary version. This effort has now produced an updated measure, which we call the Social Emotional Health Survey (2020) version. The SEHS-S (2020) represents our efforts to refine and standardize items and response formats and to further extend validation evidence for the covitality construct.

Euler solved the problem of the collapse of tall thin columns under unexpectedly small loads in 1744. The analogous problem of the collapse of circular elastic rings or tubes under external pressure was mathematically intractable and only fully solved recently. In the context of carbon nanotubes, an additional phenomenon was found experimentally and in atomistic simulations but not explained: the collapse pressure of smaller diameter tubes deviates below the continuum mechanics solution [Torres-Dias et al., Carbon 123, 145 (2017)]. Here, this deviation is shown to occur in discretized straight columns and it is fully explained in terms of the phonon dispersion curve. This reveals an unexpected link between the static mechanical properties of discrete systems and their dynamics described through dispersion curves., Comment: 4 pages, 3 Figures, draft in preparation

Non-virialized dark-matter axions may be present in the Milky Way halo in the form of low-velocity-dispersion flows. The Axion Dark Matter eXperiment performed a search for the conversion of these axions into microwave photons using a resonant cavity immersed in a strong, static magnetic field. The spread of photon energy in these measurements was measured at spectral resolutions of the order of 1 Hz and below. If the energy variation were this small, the frequency modulation of any real axion signal due to the orbital and rotational motion of the Earth would become non-negligible. Conservative estimates of the expected signal modulation were made and used as a guide for the search procedure. The photon frequencies covered by this search are 812$-$852 and 858$-$892 MHz, which correspond to an axion mass of 3.36$-$3.52 and 3.55$-$3.69 {\mu}eV. No axion signal was found, and limits were placed on the maximum local density of non-virialized axions of these masses., Comment: 12 pages, 12 figures

Extending chip performance beyond current limits of miniaturisation requires new materials and functionalities that integrate well with the silicon platform. Germanium fits these requirements and has been proposed as a high-mobility channel material,[1] a light emitting medium in silicon-integrated lasers,[2,3] and a plasmonic conductor for bio-sensing.[4,5] Common to these diverse applications is the need for homogeneous, high electron densities in three-dimensions (3D). Here we use a bottom-up approach to demonstrate the 3D assembly of atomically sharp doping profiles in germanium by a repeated stacking of two-dimensional (2D) high-density phosphorus layers. This produces high-density (10^19 to 10^20 cm-3) low-resistivity (10^-4 Ohmcm) metallic germanium of precisely defined thickness, beyond the capabilities of diffusion-based doping technologies.[6] We demonstrate that free electrons from distinct 2D dopant layers coalesce into a homogeneous 3D conductor using anisotropic quantum interference measurements, atom probe tomography, and density functional theory.

The Liverpool Telescope is one of the world's premier facilities for time domain astronomy. The time domain landscape is set to radically change in the coming decade, with surveys such as LSST providing huge numbers of transient detections on a nightly basis; transient detections across the electromagnetic spectrum from other facilities such as SVOM, SKA and CTA; and the era of `multi-messenger astronomy', wherein events are detected via non-electromagnetic means, such as gravitational wave emission. We describe here our plans for Liverpool Telescope 2: a new robotic telescope designed to capitalise on this new era of time domain astronomy. LT2 will be a 4-metre class facility co-located with the LT at the Observatorio del Roque de Los Muchachos on the Canary island of La Palma. The telescope will be designed for extremely rapid response: the aim is that the telescope will take data within 30 seconds of the receipt of a trigger from another facility. The motivation for this is twofold: firstly it will make it a world-leading facility for the study of fast fading transients and explosive phenomena discovered at early times. Secondly, it will enable large-scale programmes of low-to-intermediate resolution spectral classification of transients to be performed with great efficiency. In the target-rich environment of the LSST era, minimising acquisition overheads will be key to maximising the science gains from any follow-up programme. The telescope will have a diverse instrument suite which is simultaneously mounted for automatic changes, but it is envisaged that the primary instrument will be an intermediate resolution, optical/infrared spectrograph for scientific exploitation of transients discovered with the next generation of synoptic survey facilities. In this paper we outline the core science drivers for the telescope, and the requirements for the optical and mechanical design., Comment: 53 pages including 7 figures and 1 table. Accepted by Experimental Astronomy. First revision modified in light of comments from the anonymous referee. This revision fixed some minor typographical errors introduced in the first revision

We present new deep images of the Coma Cluster from the ESA Herschel Space Observatory at wavelengths of 70, 100 and 160 microns, covering an area of 1.75 x 1.0 square degrees encompassing the core and southwest infall region. Our data display an excess of sources at flux densities above 100 mJy compared to blank-field surveys, as expected. We use extensive optical spectroscopy of this region to identify cluster members and hence produce cluster luminosity functions in all three photometric bands. We compare our results to the local field galaxy luminosity function, and the luminosity functions from the Herschel Virgo Cluster Survey (HeViCS). We find consistency between the shapes of the Coma and field galaxy luminosity functions at all three wavelengths, however we do not find the same level of agreement with that of the Virgo Cluster., Comment: 8 pages, 5 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

The fission Time Projection Chamber (fissionTPC) is a compact (15 cm diameter) two-chamber MICROMEGAS TPC designed to make precision cross section measurements of neutron-induced fission. The actinide targets are placed on the central cathode and irradiated with a neutron beam that passes axially through the TPC inducing fission in the target. The 4$\pi$ acceptance for fission fragments and complete charged particle track reconstruction are powerful features of the fissionTPC which will be used to measure fission cross sections and examine the associated systematic errors. This paper provides a detailed description of the design requirements, the design solutions, and the initial performance of the fissionTPC.

We present the study of a large sample of early-type dwarf galaxies in the Coma cluster observed with DEIMOS on the Keck II to determine their internal velocity dispersion. We focus on a subsample of 41 member dwarf elliptical galaxies for which the velocity dispersion can be reliably measured, 26 of which were studied for the first time. The magnitude range of our sample is $-21

We present a study of the fundamental plane, FP, for a sample of 71 dwarf galaxies in the core of Coma cluster in magnitude range $-21 < M_I <-15$. Taking advantage of high resolution DEIMOS spectrograph on Keck II for measuring the internal velocity dispersion of galaxies and high resolution imaging of HST/ACS, which allows an accurate surface brightness modeling, we extend the fundamental plane (FP) of galaxies to $\sim$1 magnitude fainter luminosities than all the previous studies of the FP in Coma cluster. We find that, the scatter about the FP depends on the faint-end luminosity cutoff, such that the scatter increases for fainter galaxies. The residual from the FP correlates with the galaxy colour, with bluer galaxies showing larger residuals from FP. We find $M/L \propto M^{-0.15\pm0.22}$ in F814W-band indicating that in faint dwarf ellipticals, the $M/L$ ratio is insensitive to the mass. We find that less massive dwarf ellipticals are bluer than their brighter counterparts, possibly indicating ongoing star formation activity. Although tidal encounters and harassment can play a part in removing stars and dark matter from the galaxy, we believe that the dominant effect will be the stellar wind associated with the star formation, which will remove material from the galaxy resulting in larger $M/L$ ratios. We attribute the deviation of a number of faint blue dwarfs from the FP of brighter ellipticals to this effect. We also study other scaling relations involving galaxy photometric properties including the photometric plane. We show that, compared to the FP, the scatter about the photometric plane is smaller at the faint end., Comment: 19 pages, 12 figures and 4 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal. (ref. MN-11-0266-MJ.R1) Accepted 2011 October 10. Received 2011 September 13; in original form 2011 February 4

Using deep, high-spatial resolution imaging from the HST ACS Coma Cluster Treasury Survey, we determine colour profiles of early-type galaxies in the Coma cluster. From 176 galaxies brighter than $M_\mathrm{F814W(AB)} = -15$ mag that are either spectroscopically confirmed members of Coma or identified by eye as likely members from their low surface brightness, data are provided for 142 early-type galaxies. Typically, colour profiles are linear against $\log(R)$, sometimes with a nuclear region of distinct, often bluer colour associated with nuclear clusters. Colour gradients are determined for the regions outside the nuclear components. We find that almost all colour gradients are negative, both for elliptical and lenticular galaxies. Most likely, earlier studies that report positive colour gradients in dwarf galaxies are affected by the bluer colours of the nuclear clusters, underlining that high resolution data are essential to disentangle the colour properties of the different morphological components in galaxies. Colour gradients of dwarf galaxies form a continuous sequence with those of elliptical galaxies, becoming shallower toward fainter magnitudes. Interpreting the colours as metallicity tracers, our data suggest that dwarfs as well as giant early-type galaxies in the Coma cluster are less metal rich in their outer parts. We do not find evidence for environmental influence on the gradients, although we note that most of our galaxies are found in the central regions of the cluster. For a subset of galaxies with known morphological types, S0 galaxies have less steep gradients than elliptical galaxies., Comment: 23 pages, 15 figures. Accepted for publication in MNRAS. Online material available at http://astronomy.swin.edu.au/coma/publications.htm

Photometric and spectroscopic observations of the galaxy population of the galaxy cluster Abell 1367 have been obtained, over a field of 34 by 90 arcmin, covering the cluster centre out to a radius of about 2.2 Mpc. U, B and R broad-band and H alpha narrow-band imaging observations were carried out using the Wide Field Camera (WFC) on the 2.5m INT. J and K near-infrared imaging was obtained using the Wide Field Camera (WFCAM) on the 3.8 m UKIRT, covering a somewhat smaller field of 0.75 square degrees on the cluster centre. The spectroscopic observations were carried out using a multifibre spectrograph (WYFFOS) on the 4.2 m WHT, over the same field as the optical imaging observations. Our photometric data give optical and near-infrared magnitudes for 303 galaxies in our survey regions, down to stated diameter and B-band magnitude limits, determined within R24 isophotal diameters. Our spectroscopic data of 328 objects provide 84 galaxies with detections of emission and/or absorption lines. Combining these with published spectroscopic data gives 126 galaxies within our sample for which recession velocities are known. Of these, 72 galaxies are confirmed as cluster members of Abell 1367, 11 of which are identified in this study. (abridged), Comment: 19 pages, 7 figures, accepted for publication in Astronomy and Astrophysics

Measurement of the three dimensional trajectory and specific ionization of recoil protons using a hydrogen gas time projection chamber provides directional information about incident fast neutrons. Here we demonstrate directional fast neutron detection using such a device. The wide field of view and excellent gamma rejection that are obtained suggest that this device is well suited to searches for special nuclear materials, among other applications., Comment: 9 Pages, 13 Figures. Accepted for publication in Nuclear Instruments and Methods A

Contents: 1. Likelihood Analysis of the Next-to-minimal Supergravity Motivated Model (C. Balazs and D. Carter) 2. The Multiple Point Principle: Characterization of the Possible Phases for the SMG (D.L. Bennett) 3. Does Dark Matter Consist of Baryons of New Stable Family Quarks? (G. Bregar and N.S. Mankoc Borstnik) 4. P, C and T for Truly Neutral Particles (V.V. Dvoeglazov) 5. Relativistic Equations for Spin Particles: What Can We Learn From Noncommutativity? (V.V. Dvoeglazov) 6. Radiative Charged Fermion Masses and Quark Mixing (VCKM)4x4 in a SU(3) Gauged Flavor Symmetry Model (A. Hernandez-Galeana) 7. Low Energy Binding of Composite Dark Matter with Nuclei as a Solution for the Puzzles of Dark Matter Searches (M.Yu. Khlopov, A.G. Mayorov and E.Yu. Soldatov) 8. On the Possibilities and Impossibilities of Random Dynamics (A. Kleppe) 9. Spin Connection Makes Massless Spinor Chirally Coupled to Kaluza-Klein Gauge Field After Compactification of $M^{1+5}$ to $M^{1+3}$ x Infinite Disc Curved on $S^2$ (D. Lukman, N.S. Mankoc Borstnik and H.B. Nielsen) 10. Offering the Mechanism for Generating Families - the Approach Unifying Spins and Charges Predicts New Families (N.S. Mankoc Borstnik) 11. Confusions That are so Unnecessary (R. Mirman) 12. - 17. Discussion Sections 18. Presentation of VIA and Bled 2009 Workshop Videoconferences (M.Yu. Khlopov), Comment: Contains articles by different authors presented at the 12th Workshop 'What Comes Beyond the Standard Models', 14. - 24. July 2009, Bled, Slovenia. Editors were N.S. Mankoc Borstnik, H.B. Nielsen, D. Lukman. vii+182pp. (Revised)

The HST ACS Coma Cluster Treasury Survey is a deep two passband imaging survey of the nearest very rich cluster of galaxies, covering a range of galaxy density environments. The imaging is complemented by a recent wide field redshift survey of the cluster conducted with Hectospec on the 6.5m MMT. Among the many scientific applications for this data are the search for compact galaxies. In this paper, we present the discovery of seven compact (but quite luminous) stellar systems, ranging from M32-like galaxies down to ultra-compact dwarfs (UCDs)/dwarf to globular transition objects (DGTOs). We find that all seven compact galaxies require a two-component fit to their light profile and have measured velocity dispersions that exceed those expected for typical early-type galaxies at their luminosity. From our structural parameter analysis we conclude that three of the sample should be classified as compact ellipticals or M32-like galaxies, the remaining four being less extreme systems. The three compact ellipticals are all found to have old luminosity weighted ages (> 12 Gyr), intermediate metallicities (-0.6 < [Fe/H] < -0.1) and high [Mg/Fe] (> 0.25). Our findings support a tidal stripping scenario as the formation mode of compact galaxies covering the luminosity range studied here. We speculate that at least two early-type morphologies may serve as the progenitor of compact galaxies in clusters., Comment: 23 pages, 11 figures, accepted for publication in MNRAS. Proof typos corrected

We present intermediate-resolution spectroscopic data for a set of dwarf and giant galaxies in the Coma Cluster, with -20.6 < M_R < -15.7. The photometric and kinematic properties of the brighter galaxies can be cast in terms of parameters which present little scatter with respect to a set of scaling relations known as the Fundamental Plane. To determine the form of these fundamental scaling relations at lower luminosities, we have measured velocity dispersions for a sample comprising 69 galaxies on the border of the dwarf and giant regime. Combining these data with our photometric survey, we find a tight correlation of luminosity and velocity dispersion, L \propto \sigma^{2.0}, substantially flatter than the Faber-Jackson relation characterising giant elliptical galaxies. In addition, the variation of mass-to-light ratio with velocity dispersion is quite weak in our dwarf sample: M/L \propto \sigma^{0.2}. Our overall results are consistent with theoretical models invoking large-scale mass removal and subsequent structural readjustment, e.g., as a result of galactic winds., Comment: 15 pages, 11 figures, 1 table. MNRAS, in press