1,272 research outputs found

    Measuring galaxy [OII] emission line doublet with future ground-based wide-field spectroscopic surveys

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    The next generation of wide-field spectroscopic redshift surveys will map the large-scale galaxy distribution in the redshift range 0.7< z<2 to measure baryonic acoustic oscillations (BAO). The primary optical signature used in this redshift range comes from the [OII] emission line doublet, which provides a unique redshift identification that can minimize confusion with other single emission lines. To derive the required spectrograph resolution for these redshift surveys, we simulate observations of the [OII] (3727,3729) doublet for various instrument resolutions, and line velocities. We foresee two strategies about the choice of the resolution for future spectrographs for BAO surveys. For bright [OII] emitter surveys ([OII] flux ~30.10^{-17} erg /cm2/s like SDSS-IV/eBOSS), a resolution of R~3300 allows the separation of 90 percent of the doublets. The impact of the sky lines on the completeness in redshift is less than 6 percent. For faint [OII] emitter surveys ([OII] flux ~10.10^{-17} erg /cm2/s like DESi), the detection improves continuously with resolution, so we recommend the highest possible resolution, the limit being given by the number of pixels (4k by 4k) on the detector and the number of spectroscopic channels (2 or 3).Comment: 5 pages, 1 figur

    Energy dependence of {\rm K}S0^0_{\rm S} and hyperon production at CERN SPS

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    Recent results on KS0^0_{\rm S} and hyperon production in Pb-Pb collisions at 40 and 158 AA GeV/cc beam momentum from the NA57 experiment at CERN SPS are presented. Yields and ratios are compared with those measured by the NA49 experiment, where available. The centrality dependence of the yields and a comparison with the higher collision energy data from RHIC are discussed.Comment: 4 pages, 3 figures, proceedings of QM2004 conferenc

    The Impact of Business Ownership Change on Employee Relations: Buy-outs in the UK and the Netherlands

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    A buy-out is a fundamental change in the structure of ownership that may affect the way employee relations develop within an organisation. Little is known about the impact of buyouts upon employee relations. This paper aims to address this gap. We focus on two main questions. First, what are the effects of a buy-out on employee relations in an organisation? Second, does the national institutional context affect the impact of buy-outs on employee relations? The paper reports changes to employee relations in buy-outs in the contrasting institutional environments of the UK and the Netherlands. Overall, we find that buy-outs positively affect HR practices with increases in training, employee involvement, the number of employees and pay levels. The positive effects appear to be significantly stronger in a less institutionalised environment like the UK than the more institutionalised environment of the Netherlands. Buy-outs raised HRM practices in the UK to a level closer although still below that of Dutch buy-outs

    An Upper Palaeolithic Proto-writing System and Phenological Calendar

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    In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper Palaeolithic Homo sapiens groups drew, painted and engraved non-figurative signs from at least ~42,000 BP and figurative images (notably animals) from at least 37,000 BP. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line , the dot , and the —functioned as units of communication. We demonstrate that when found in close association with images of animals the line and dot constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning . The position of the within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history of Homo sapiens

    M32+/-1

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    WFPC-2 images are used to study the central structure of M31, M32, and M33. The dimmer peak, P2, of the M31 double nucleus is centered on the bulge to 0.1", implying that it is the dynamical center of M31. P2 contains a compact source discovered by King et al. (1995) at 1700 A. This source is resolved, with r_{1/2} approx0.2 pc. It dominates the nucleus at 3000 A, and is consistent with late B-early A stars. This probable cluster may consist of young stars and be an older version of the cluster of hot stars at the center of the Milky Way, or it may consist of heavier stars built up from collisions in a possible cold disk of stars orbiting P2. In M32, the central cusp rises into the HST limit with gamma approx0.5, and the central density rho_0>10^7M_sol pc^-3. The V-I and U-V color profiles are flat, and there is no sign of an inner disk, dust, or any other structure. This total lack of features seems at variance with a nominal stellar collision time of 2 X 10^10 yr, which implies that a significant fraction of the light in the central pixel should come from blue stragglers. InM33, the nucleus has an extremely steep gamma=1.49 power-law profile for 0.05"<r<0.2" that becomes shallower as the HST resolution limit is approached. The profile for r<0.04" has either a gamma approx 0.8 cusp or a small core with r_c ~<0.13 pc. The central density is rho_0 > 2 10^6M_sol pc^-3, and the implied relaxation time is only ~3 X 10^6 yr, indicating that the nucleus is highly relaxed. The accompanying short collision time of 7 X 10^9 yr predicts a central blue straggler component quantitatively consistent with the strong V-I and B-R color gradients seen with HST and from the ground.Comment: 44 pages, 22 figures (7 as separate JPEG images), submitted to The Astronomical Journal. Full postscript image available at http://www.noao.edu/noao/staff/lauer/lauer_paper

    The thermodynamic balance of the Weddell Gyre

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    The thermodynamic balance of the Weddell Gyre is assessed from an inverse estimate of the circulation across the gyre's rim. The gyre experiences a weak net buoyancy gain that arises from a leading-order cancellation between two opposing contributions, linked to two cells of water mass transformation and diapycnal overturning. The lower cell involves a cooling-driven densification of 8.4 ± 2.0 Sv of Circumpolar Deep Water and Antarctic Bottom Water near the gyre's southern and western margins. The upper cell entails a freshening-driven conversion of 4.9 ± 2.0 Sv of Circumpolar Deep Water into lighter upper-ocean waters within the gyre interior. The distinct role of salinity between the two cells stems from opposing salinity changes induced by sea ice production, meteoric sources and admixture of fresh upper-ocean waters in the lower cell, which contrasts with coherent reductions in salinity associated with sea ice melting and meteoric sources in the upper cell
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