415,923 research outputs found

    Affordances of Historic Urban Landscapes: an Ecological Understanding of Human Interaction with the Past

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    Heritage has been defined differently in European contexts. Despite differences, a common challenge for historic urban landscape management is the integration of tangible and intangible heritage. Integration demands an active view of perception and human-landscape interaction where intangible values are linked to specific places and meanings are attached to particular cultural practices and socio-spatial organisation. Tangible and intangible values can be examined as part of a system of affordances (potentialities) a place, artefact or cultural practice has to offer. This paper discusses how an ‘affordance analysis’ may serve as a useful tool for the management of historic urban landscapes

    Diffractive Results from the Tevatron

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    Hard diffraction in events with dijets and rapidity gaps has been studied by D\O and CDF for three processes: hard color singlet exchange, hard single diffraction, and hard double pomeron exchange, using Tevatron pˉp\bar pp data at s\sqrt{s} = 630 GeV and 1.8 TeV. Measurements of rates, η,ET\eta, E_T and s\sqrt{s} dependencies are presented and comparisons made with predictions of several models.Comment: Presented at DPF99, 8 pages, 6 figure

    Orion Revisited - I. The massive cluster in front of the Orion Nebula Cluster

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    The aim of this work is to characterize the stellar population between Earth and the Orion A molecular cloud where the well known star formation benchmark Orion Nebula Cluster (ONC) is embedded. We use the denser regions the Orion A cloud to block optical background light, effectively isolating the stellar population in front of it. We then use a multi-wavelength observational approach to characterize the cloud's foreground stellar population. We find that there is a rich stellar population in front of the Orion A cloud, from B-stars to M-stars, with a distinct 1) spatial distribution, 2) luminosity function, and 3) velocity dispersion from the reddened population inside the Orion A cloud. The spatial distribution of this population peaks strongly around NGC 1980 (iota Ori) and is, in all likelihood, the extended stellar content of this poorly studied cluster. We infer an age of ~4-5 Myr for NGC 1980 and estimate a cluster population of the order of 2000 stars, which makes it one of the most massive clusters in the entire Orion complex. What is currently taken in the literature as the ONC is then a mix of several intrinsically different populations, namely: 1) the youngest population, including the Trapezium cluster and ongoing star formation in the dense gas inside the nebula, 2) the foreground population, dominated by the NGC 1980 cluster, and 3) the poorly constrained population of foreground and background Galactic field stars. Our results support a scenario where the ONC and L1641N are not directly associated with NGC 1980, i.e., they are not the same population emerging from its parental cloud, but are instead distinct overlapping populations. This result calls for a revision of most of the observables in the benchmark ONC region (e.g., ages, age spread, cluster size, mass function, disk frequency, etc.). (abridged)Comment: Version 2 includes comments and clarifications from John Tobin, Nicola Da Rio, and Lynne Hillenbrand (minor clarifying changes were made to Figures 1, 8, and 10). A&A accepted (15 pages, 10 figures). Higher resolution figures available upon reques

    Theses towards a new natural philosophy

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    In this paper I address some philosophical questions regarding the impact quantum mechanics has in the classical conceptions about reality and knowledge. I stress that onto-gnosiological realism still is an option to the issues regarding the relationship between knowledge and reality. Rejecting some radical aspects of Copenhagen interpretation of quantum formalism, I emphasize the advantages of de Broglie’s realistic and causal model. To finish with, I discuss the limits of the Cartesian concept of matter and the split between matter and mind
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