6,702 research outputs found

    The Effects of a Modified Cover, Copy, Compare on Spelling Third Grade Core Words for a Student with Autism

    Get PDF
    Since cover copy compare CCC has not been widely implemented for students with autism one purpose of this study was to evaluate the effectiveness of modified CCC on spelling third grade core words for an elementary school student with autism ASD This study adds to the literature by having the participant trace the first time she wrote a word using CCC the form on which the student wrote her words was modified so she could not view her previous performance The present case report provides a replication of employing CCC with a student with autism This intervention required the student to trace the spelling word copy it cover it write it from memory then compare the copied word to the original correct model The effectiveness of CCC was assessed using a non-concurrent multiple-baseline across word sets The results indicated that the intervention was successful for teaching spelling words to a single student with autism in a self-contained special education classroom setting The use of a modified CCC with students with autism was discusse

    Unusual glitch activity in the RRAT J1819-1458: an exhausted magnetar?

    Get PDF
    We present an analysis of regular timing observations of the high-magnetic-field Rotating Radio Transient (RRAT) J1819-1458 obtained using the 64-m Parkes and 76-m Lovell radio telescopes over the past five years. During this time, the RRAT has suffered two significant glitches with fractional frequency changes of 0.6×1060.6\times10^{-6} and 0.1×1060.1\times10^{-6}. Glitches of this magnitude are a phenomenon displayed by both radio pulsars and magnetars. However, the behaviour of J1819-1458 following these glitches is quite different to that which follows glitches in other neutron stars, since the glitch activity resulted in a significant long-term net decrease in the slow-down rate. If such glitches occur every 30 years, the spin-down rate, and by inference the magnetic dipole moment, will drop to zero on a timescale of a few thousand years. There are also significant increases in the rate of pulse detection and in the radio pulse energy immediately following the glitches.Comment: accepted for publication in MNRAS, 7 pages, 7 figures, 1 tabl

    Pulsar J1411+2551: A Low Mass New Double Neutron Star System

    Get PDF
    In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 ±\pm 0.7) ×1020ss1\times 10^{-20}\, \rm s\, s^{-1}; from these, we derive a characteristic age of 10\sim 10\,Gyr and a surface magnetic field strength of 2.5 ×109\times 10^{9} G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric (e=0.17e\, = \, 0.17) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, ω˙=0.07686±0.00046 yr1\dot{\omega} = 0.07686 \pm 0.00046 ^{\circ}~{\rm yr}^{-1}. Assuming general relativity accurately models the orbital motion, this implies a total system mass M = 2.538±0.022M2.538 \pm 0.022 M_{\odot}. The minimum companion mass is 0.92M0.92\, M_{\odot} and the maximum pulsar mass is 1.62M1.62\, M_{\odot}. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW 170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.Comment: Accepted for publication in APJ letter

    K-Shell Photoabsorption Studies of the Carbon Isonuclear Sequence

    Full text link
    K-shell photoabsorption cross sections for the isonuclear C I - C IV ions have been computed using the R-matrix method. Above the K-shell threshold, the present results are in good agreement with the independent-particle results of Reilman & Manson (1979). Below threshold, we also compute the strong 1s -> np absorption resonances with the inclusion of important spectator Auger broadening effects. For the lowest 1s -> 2p, 3p resonances, comparisons to available C II, C III, and C IV experimental results show good agreement in general for the resonance strengths and positions, but unexplained discrepancies exist. Our results also provide detailed information on the C I K-shell photoabsorption cross section including the strong resonance features, since very limited laboratory experimental data exist. The resultant R-matrix cross sections are then used to model the Chandra X-ray absorption spectrum of the blazar Mkn 421

    Rapid human-assisted, obstacle avoidance system using sparse range point clouds

    Get PDF

    On the dc Magnetization, Spontaneous Vortex State and Specific Heat in the superconducting state of the weakly ferromagnetic superconductor RuSr2_{2}GdCu2_{2}O8_{8}

    Full text link
    Magnetic-field changes << 0.2 Oe over the scan length in magnetometers that necessitate sample movement are enough to create artifacts in the dc magnetization measurements of the weakly ferromagnetic superconductor RuSr2_{2}GdCu2_{2}O8_{8} (Ru1212) below the superconducting transition temperature TcT_{c} \approx 30 K. The observed features depend on the specific magnetic-field profile in the sample chamber and this explains the variety of reported behaviors for this compound below TcT_{c}. An experimental procedure that combines improvement of the magnetic-field homogeneity with very small scan lengths and leads to artifact-free measurements similar to those on a stationary sample has been developed. This procedure was used to measure the mass magnetization of Ru1212 as a function of the applied magnetic field H (-20 Oe \le H \le 20 Oe) at T<TcT < T_{c} and discuss, in conjunction with resistance and ac susceptibility measurements, the possibility of a spontaneous vortex state (SVS) for this compound. Although the existence of a SVS can not be excluded, an alternative interpretation of the results based on the granular nature of the investigated sample is also possible. Specific-heat measurements of Sr2_{2}GdRuO6_{6} (Sr2116), the precursor for the preparation of Ru1212 and thus a possible impurity phase, show that it is unlikely that Sr2116 is responsible for the specific-heat features observed for Ru1212 at TcT_{c}.Comment: 17 pages, 6 figure

    Discovery of the Optical Counterparts to Four Energetic Fermi Millisecond Pulsars

    Get PDF
    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified gamma-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modelling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irradiated pulsar binaries and offers insights about the energetics of the pulsar wind and the production of gamma-ray emission. In addition, this provides a simple way of estimating the brightness of irradiated pulsar companions given the pulsar spin-down luminosity. Our analysis also suggests that two of the four new irradiated pulsar companions are only partially filling their Roche lobe. Some of these sources are relatively bright and represent good targets for spectroscopic follow-up. These measurements could enable, among other things, mass determination of the neutron stars in these systems.Comment: 11 pages, 5 tables, 1 figure, 4 online tables. ApJ submitted and referee

    Quantum Hall Fluids on the Haldane Sphere: A Diffusion Monte Carlo Study

    Full text link
    A generalized diffusion Monte Carlo method for solving the many-body Schr\"odinger equation on curved manifolds is introduced and used to perform a `fixed-phase' simulation of the fractional quantum Hall effect on the Haldane sphere. This new method is used to study the effect of Landau level mixing on the ν=1/3\nu=1/3 energy gap and the relative stability of spin-polarized and spin-reversed quasielectron excitations.Comment: 13 pages, Revtex + psfig, figures include

    Neutrino-nucleus interaction rates at a low-energy beta-beam facility

    Full text link
    We compute the neutrino detection rates to be expected at a low-energy beta-beam facility. We consider various nuclei as neutrino detectors and compare the case of a small versus large storage ring.Comment: 6 pages, 3 figure

    Coral Disease and Health Workshop: Coral Histopathology II

    Get PDF
    The health and continued existence of coral reef ecosystems are threatened by an increasing array of environmental and anthropogenic impacts. Coral disease is one of the prominent causes of increased mortality among reefs globally, particularly in the Caribbean. Although over 40 different coral diseases and syndromes have been reported worldwide, only a few etiological agents have been confirmed; most pathogens remain unknown and the dynamics of disease transmission, pathogenicity and mortality are not understood. Causal relationships have been documented for only a few of the coral diseases, while new syndromes continue to emerge. Extensive field observations by coral biologists have provided substantial documentation of a plethora of new pathologies, but our understanding, however, has been limited to descriptions of gross lesions with names reflecting these observations (e.g., black band, white band, dark spot). To determine etiology, we must equip coral diseases scientists with basic biomedical knowledge and specialized training in areas such as histology, cell biology and pathology. Only through combining descriptive science with mechanistic science and employing the synthesis epizootiology provides will we be able to gain insight into causation and become equipped to handle the pending crisis. One of the critical challenges faced by coral disease researchers is to establish a framework to systematically study coral pathologies drawing from the field of diagnostic medicine and pathology and using generally accepted nomenclature. This process began in April 2004, with a workshop titled Coral Disease and Health Workshop: Developing Diagnostic Criteria co-convened by the Coral Disease and Health Consortium (CDHC), a working group organized under the auspices of the U.S. Coral Reef Task Force, and the International Registry for Coral Pathology (IRCP). The workshop was hosted by the U.S. Geological Survey, National Wildlife Health Center (NWHC) in Madison, Wisconsin and was focused on gross morphology and disease signs observed in the field. A resounding recommendation from the histopathologists participating in the workshop was the urgent need to develop diagnostic criteria that are suitable to move from gross observations to morphological diagnoses based on evaluation of microscopic anatomy. (PDF contains 92 pages
    corecore