247,363 research outputs found

    The PL calibration for Milky Way Cepheids and its implications for the distance scale

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    The rationale behind recent calibrations of the Cepheid PL relation using the Wesenheit formulation is reviewed and reanalyzed, and it is shown that recent conclusions regarding a possible change in slope of the PL relation for short-period and long-period Cepheids are tied to a pathological distribution of HST calibrators within the instability strip. A recalibration of the period-luminosity relation is obtained using Galactic Cepheids in open clusters and groups, the resulting relationship, described by log L/L_sun = 2.415(+-0.035) + 1.148(+-0.044)log P, exhibiting only the moderate scatter expected from color spread within the instability strip. The relationship is confirmed by Cepheids with HST parallaxes, although without the need for Lutz-Kelker corrections, and in general by Cepheids with revised Hipparcos parallaxes, albeit with concerns about the cited precisions of the latter. A Wesenheit formulation of Wv = -2.259(+-0.083) - 4.185(+-0.103)log P for Galactic Cepheids is tested successfully using Cepheids in the inner regions of the galaxy NGC 4258, confirming the independent geometrical distance established for the galaxy from OH masers. Differences between the extinction properties of interstellar and extragalactic dust may yet play an important role in the further calibration of the Cepheid PL relation and its application to the extragalactic distance scale.Comment: Accepted for Publication (Astrophysics & Space Science

    Alessi 95 and the short period Cepheid SU Cassiopeiae

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    The parameters for the newly-discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically-observed B and A-type stars near SU Cas follow a reddening relation described by E(U-B)/E(B-V)=0.83+0.02*E(B-V), implying a value of R=Av/E(B-V)~2.8 for the associated dust. Alessi 95 has a mean reddening of E(B-V)_(B0)=0.35+-0.02 s.e., an intrinsic distance modulus of Vo-Mv=8.16+-0.04 s.e. (+-0.21 s.d.), d=429+-8 pc, and an estimated age of 10^8.2 yr from ZAMS fitting of available UBV, CCD BV, NOMAD, and 2MASS JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B-V)=0.33+-0.02 and a luminosity of =-3.15+-0.07 s.e., consistent with overtone pulsation (P_FM=2.75 d), as also implied by the Cepheid's light curve parameters, rate of period increase, and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, its pulsation parallax derived from the infrared surface brightness technique, and Hipparcos parallaxes, which all agree to within a few percent.Comment: Accepted for Publication (MNRAS

    The Cepheid Impostor HD 18391 and its Anonymous Parent Cluster

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    New and existing photometry for the G0 Ia supergiant HD 18391 is analyzed in order to confirm the nature of the variablity previously detected in the star, which lies off the hot edge of the Cepheid instability strip. Small-amplitude variability at a level of \Delta V = 0.016+-0.002 is indicated, with a period of P=123.04+-0.06 d. A weaker second signal may be present at P=177.84+-0.18 with \Delta V = 0.007+-0.002, likely corresponding to fundamental mode pulsation if the primary signal represents overtone pulsation (123.04/177.84 = 0.69). The star, with a spectroscopic reddening of E(B-V) = 1.02, is associated with heavily-reddened B-type stars in its immediate vicinity that appear to be outlying members of an anonymous young cluster centered ~10 arcmin to the west and 1661+-73 pc distant. The cluster has nuclear and coronal radii of r_n=3.5 arcmin and R_c=14 arcmin, respectively, while the parameters for HD 18391 derived from membership in the cluster with its outlying B stars are consistent with those implied by its Cepheid-like pulsation, provided that it follows the semi-period-luminosity relation expected of such objects. Its inferred luminosity as a cluster member is M_V=-7.76+-0.10, its age (9+-1)x10^6 years, and its evolutionary mass ~19 M_{\sun}. HD 18391 is not a classical Cepheid, yet it follows the Cepheid period-luminosity relation closely, much like another Cepheid impostor, V810 Cen.Comment: Accepted for Publication (Astronomische Nachrichten

    Chemical structure matching using correlation matrix memories

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    This paper describes the application of the Relaxation By Elimination (RBE) method to matching the 3D structure of molecules in chemical databases within the frame work of binary correlation matrix memories. The paper illustrates that, when combined with distributed representations, the method maps well onto these networks, allowing high performance implementation in parallel systems. It outlines the motivation, the neural architecture, the RBE method and presents some results of matching small molecules against a database of 100,000 models

    Optically-stimulated luminescence profiling and dating of historic agricultural terraces in Catalonia (Spain)

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    Dating agricultural terraces is a notoriously difficult problem for archaeologists. The frequent occurrence of residual material in terrace soils and the potential for post-depositional disturbance mean that conventional artefactual and lab-based dating methods often provide unreliable dates. In this paper we present a new technique using luminescence field profiling coupled with OSL dating to produce complete (relative) sequences of dates for sedimentary stratigraphies associated with agricultural terraces and earthworks. The method is demonstrated through a series of case-studies in western Catalonia, Spain, in which we reconstruct the formation sequence of earthwork features from the Middle Ages through to the present day. OSL profiling at the time of archaeological survey and excavation permitted spatially and temporally resolved sediment ‘chronologies’ to be generated, and provides the means to interpret the environmental and cultural archives contained in each. The case-studies presented here show that luminescence approaches are a valuable tool to reconstruct landscape histories

    Stitching together the fabric of space and society: an investigation into the linkage of the local to regional continuum

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    To date, space syntax models have focused typically on relatively small areas up to the city scale. There have been very few models that take into account the entire network up to the regional scale, so the cumulative effects of micro-scale connections on regional networks is unknown, and the performance of the regional network as a function of the local area cannot be assessed. As such, a complete understanding of the ways in which regional centres are co-dependent and cities relate to their surrounding sub-centres is lacking. This study models the entire road network at the regional scale, by dispensing with axial lines entirely and moving to a road-centre line model of the UK, the Ordnance Survey's Integrated Transport Network (ITN) layer. This layer includes the topological connections between roads, so that a complete topological model of the road network including the directionality of streets can be constructed quickly. A region of the North of England - including Manchester, Bradford, Sheffield and Leeds - is analysed. Regional level angular analysis is shown to correlate well with overall movement in the network, while local level metric analysis is shown to correlate with the population density. It is hypothesised that combined measures that link the global to the local will uncover discontinuities in the continuum of space, and that these disruptions to the network will correspond to social deprivation. However, although such discontinuities exist, experimental linkage of the analysis to deprivation indices by census areas shows little conclusive evidence. In particular, it is clear that the complex web of spatial factors uncovered need investigation with more sensitive tools and smaller units of aggregation. The study highlights the need for a set of combined measures using microscopic spatial, economic, demographic, and land-use data, in order to further understand the relationship of spatial factors with social activity, while reinforcing standard space syntax results at the regional level

    Social Partnership in Germany: Lessons for U.S. Labor and Management

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    German industrial relations in the postwar period have made a major contribution to German industrial success. The German system is rooted in the explicit recognition of well organized interests: strong, assertive employers and employers\u27 associations not afraid to demand what they think is right, including wage restraint as well as reorganization of production toward lean production ; and strong, assertive unions not afraid to demand what they think is right, including broad skills training, high wages, a shorter workweek, and a human-centered work organization. Amazingly, these strong forces end up with negotiated outcomes in a system that is accurately called social partnership

    Conclusion: Uncertain Outcomes of Conflict and Negotiation

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    [Excerpt] To elaborate on each of these points, the findings presented in this book can be summarized as follows. First of all, the German model, that is, a social partnership approach to the negotiation of terms and conditions for the organization of an advanced market economy has worked in the past. We believe, on the basis of extensive collective research on different aspects of the political economy of the Federal Republic, both before and after unification, that the preservation of a reformed social partnership in Germany is highly desirable as an alternative to less regulated forms of capitalism in the contemporary world economy. Thus we disagree rather sharply with both conservative and liberal analysts who see the social market economy as an expensive and outdated relic of a welfare-state past. The evidence presented in this book also shows not only that social partnership is desirable but that it remains relatively intact. We have identified problems that must be solved for this to continue to be the case, but whatever the future holds, the basic institutions and practices of social partnership have been transferred into eastern Germany and continue to characterize political-economic relations in unified Germany. This remains true even in the face of major challenges presented by European integration, intensified global competition, a rapidly appreciating deutschmark, market imperatives for production reorganization (driven by Japanese-style lean production), and escalating collective bargaining conflict. Both employer associations and unions continue to play pattern-setting roles in wage negotiations, to set the framework for firm-level codetermination, and to engage in national, regional, and local negotiations over important aspects of economic and labor-market policy

    Energy efficiency and the rebound effect

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    In recent years the argument that rebound effects, triggered by economy-wide price and income effects, may partially or wholly offset reductions in energy consumption expected from energy efficiency improvements has gained a great deal of attention in both academic and policy arenas. In the UK, a report by the House of Lords (2005) raised the question as to whether this argument provides an explanation as to why total energy consumption in the UK hasn’t fallen in line with increased energy efficiency. In response, the UK Research Councils have funded research, first through the UK Energy Research Centre (UKERC) and now at the University of Strathclyde to investigate the conditions under which rebound effects may occur in the UK economy

    Developing 'authentic leaders' - the leaders' coaching journey

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    Jane Turner suggests that traditional leadership development programmes do not spend enough time focussing upon the inner person and that the modern leader needs to develop additional skills to flourish
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