2,519 research outputs found

    Thoughts on the Unification of U.S. Labor and Employment Law: Is the Whole Greater than the Sum of the Parts

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    As the need for fundamental reform of our nation\u27s labor laws has grown more and more evident since the 1970s, major reform efforts have focused narrowly on adjusting the provisions of the National Labor Relations Act (NLRA), but have repeatedly foundered amidst intense polarization over tipping the existing balance between labor and management.\u27 At the same time, at the federal, state, and, increasingly, municipal levels, U.S. labor laws governing worker organization and collective bargaining have been surrounded by a growing thicket of other laws governing the workplace

    Different Faces in the Crowd: A Happiness Superiority Effect for Schematic Faces in Heterogeneous Backgrounds

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    Recently, D.V. Becker, Anderson, Mortensen, Neufeld, and Neel (2011) proposed recommendations to avoid methodological confounds in visual search studies using emotional photographic faces. These confounds were argued to cause the frequently observed Anger Superiority Effect (ASE), the faster detection of angry than happy expressions, and conceal a true Happiness Superiority Effect (HSE). In Experiment 1, we applied these recommendations (for the first time) to visual search among schematic faces that previously had consistently yielded a robust ASE. Contrary to the prevailing literature, but consistent with D.V. Becker et al. (2011), we observed a HSE with schematic faces. The HSE with schematic faces was replicated in Experiments 2 and 3 using a similar method in discrimination tasks rather than fixed target searches. Experiment 4 isolated background heterogeneity as the key determinant leading to the HSE

    Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae

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    We present spectral and long-timescale variability analyses of \textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) with precisely known positions in the globular cluster 47 Tucanae. The X-ray emission of the majority of these MSPs is well described by a thermal (blackbody or neutron star hydrogen atmosphere) spectrum with a temperature Teff∌(1−3)×106T_{\rm eff}\sim(1-3)\times10^6 K, emission radius Reff∌0.1−3R_{\rm eff}\sim0.1-3 km, and luminosity LX∌1030−31L_{X}\sim10^{30-31} ergs s−1^{-1}. For several MSPs, there is indication that a second thermal component is required, similar to what is seen in some nearby field MSPs. The radio-eclipsing binary MSPs 47 Tuc J, O, and W show a significant non-thermal component, with photon index Γ∌1−1.5\Gamma\sim 1-1.5, which may originate in an shock formed due to interaction between the relativistic pulsar wind and matter from the stellar companion. We re-examine the X-ray--spindown luminosity relation (LX−E˙L_{X}-\dot{E}) and find that due to the large uncertainties in both parameters the result is consistent with both the linear LX−E˙L_{X}-\dot{E} relation and the flatter LX∝E˙0.5L_X\propto\dot{E}^{0.5} predicted by polar cap heating models. In terms of X-ray properties, we find no clear systematic differences between MSPs in globular clusters and in the field of the Galaxy.Comment: 13 pages, 6 figures, accepted for publication in the Astrophysical Journa

    Constraints on the Universal CIV Mass Density at z~6 from Early IR Spectra Obtained with the Magellan FIRE Spectrograph

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    We present a new determination of the intergalactic CIV mass density at 4.3 < z < 6.3. Our constraints are derived from high signal-to-noise spectra of seven quasars at z > 5.8 obtained with the newly commissioned FIRE spectrograph on the Magellan Baade telescope, coupled with six observations of northern objects taken from the literature. We confirm the presence of a downturn in the CIV abundance at =5.66 by a factor of 4.1 relative to its value at =4.96, as measured in the same sightlines. In the FIRE sample, a strong system previously reported in the literature as CIV at z=5.82 is re-identified as MgII at z=2.78, leading to a substantial downward revision in ΩCIV\Omega_{CIV} for these prior studies. Additionally we confirm the presence of at least two systems with low-ionization CII, SiII, and OI absorption but relatively weak signal from CIV. The latter systems systems may be of interest if the downward trend in ΩCIV\Omega_{CIV} at high redshift is driven in part by ionization effects.Comment: 14 pages, 6 figures, 2 tables. Submitted to Ap

    Chandra X-ray Observations of 12 Millisecond Pulsars in the Globular Cluster M28

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    We present a Chandra X-ray Observatory investigation of the millisecond pulsars (MSPs) in the globular cluster M28 (NGC 6626). In what is one of the deepest X-ray observations of a globular cluster, we firmly detect seven and possibly detect two of the twelve known M28 pulsars. With the exception of PSRs B1821-24 and J1824-2452H, the detected pulsars have relatively soft spectra, with X-ray luminosities 10^30-31 ergs s^-1 (0.3-8 keV),similar to most "recycled" pulsars in 47 Tucanae and the field of the Galaxy, implying thermal emission from the pulsar magnetic polar caps. We present the most detailed X-ray spectrum to date of the energetic PSR B1821-24. It is well described by a purely non-thermal spectrum with spectral photon index 1.23 and luminosity 1.4x10^33Theta(D/5.5 kpc)^2 ergs s^-1 (0.3-8 keV), where Theta is the fraction of the sky covered by the X-ray emission beam(s). We find no evidence for the previously reported line emission feature around 3.3 keV, most likely as a consequence of improvements in instrument calibration. The X-ray spectrum and pulse profile of PSR B1821--24 suggest that the bulk of unpulsed emission from this pulsar is not of thermal origin, and is likely due to low-level non-thermal magnetospheric radiation, an unresolved pulsar wind nebula, and/or small-angle scattering of the pulsed X-rays by interstellar dust grains. The peculiar binary PSR J1824-2452H shows a relatively hard X-ray spectrum and possible variability at the binary period, indicative of an intrabinary shock formed by interaction between the relativistic pulsar wind and matter from its non-degenerate companion star.Comment: 9 pages, 6 figures. Accepted for publication in the Astophysical Journa

    Orbitofrontal cortex mediates pain inhibition by monetary reward

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    Pleasurable stimuli, including reward, inhibit pain, but the level of the neuraxis at which they do so and the cerebral processes involved are unknown. Here, we characterized a brain circuitry mediating pain inhibition by reward. Twenty-four healthy participants underwent functional magnetic resonance imaging while playing a wheel of fortune game with simultaneous thermal pain stimuli and monetary wins or losses. As expected, winning decreased pain perception compared to losing. Inter-individual differences in pain modulation by monetary wins relative to losses correlated with activation in the medial orbitofrontal cortex (mOFC). When pain and reward occured simultaneously, mOFCs functional connectivity changed: the signal time course in the mOFC condition-dependent correlated negatively with the signal time courses in the rostral anterior insula, anterior-dorsal cingulate cortex and primary somatosensory cortex, which might signify momentto-moment down-regulation of these regions by the mOFC. Monetary wins and losses did not change the magnitude of pain-related activation, including in regions that code perceived pain intensity when nociceptive input varies and/or receive direct nociceptive input. Pain inhibition by reward appears to involve brain regions not typically involved in nociceptive intensity coding but likely mediate changes in the significance and/or value of pain

    Evidence for Large-Scale Fluctuations in the Metagalactic Ionizing Background Near Redshift Six

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    The observed scatter in intergalactic Lyman-α\alpha opacity at zâ‰Č6z \lesssim 6 requires large-scale fluctuations in the neutral fraction of the intergalactic medium (IGM) after the expected end of reionization. Post-reionization models that explain this scatter invoke fluctuations in either the ionizing ultraviolet background (UVB) or IGM temperature. These models make very different predictions, however, for the relationship between Lyman-α\alpha opacity and local density. Here we test these models using Lyman-α\alpha emitting galaxies (LAEs) to trace the density field surrounding the longest and most opaque known Lyman-α\alpha trough at z<6z < 6. Using deep Subaru Hyper Suprime-Cam narrow-band imaging, we find a highly significant deficit of z≃5.7z \simeq 5.7 LAEs within 20 Mpc/hh of the trough. The results are consistent with a model in which the scatter in Lyman-α\alpha opacity near z∌6z \sim 6 is driven by large-scale UVB fluctuations, and disfavor a scenario in which the scatter is primarily driven by variations in IGM temperature. UVB fluctuations at this epoch present a boundary condition for reionization models, and may help shed light on the nature of the ionizing sources.Comment: 13 pages, 9 figure, submitted to ApJ, comments welcom
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