1,721,012 research outputs found
The historic built environment as a long-term geochemical archive: telling the time on the urban “pollution clock”
Full text linkThis study introduces a novel methodology for utilizing historic built environments as reliable long-term geochemical archives, addressing a gap in the reconstruction of past anthropogenic pollution levels in urban settings. For the first time, we employ high-resolution laser ablation mass spectrometry for lead isotope (206Pb/207Pb and 208Pb/206Pb) analysis on 350-yearold black crust stratigraphies found on historic built structures, providing insights into past air pollution signatures. Our findings reveal a gradual shift in the crust stratigraphy toward lower 206Pb/207Pb and higher 208Pb/206Pb isotope ratios from the older to the younger layers, indicating changes in lead sources over time. Mass balance analysis of the isotope data shows black crust layers formed since 1669 primarily contain over 90% Pb from coal burning, while other lead sources from a set of modern pollution including but not limited to leaded gasoline (introduced after 1920) become dominant (up to 60%) from 1875 onward. In contrast to global archives such as ice cores that provide integrated signals of long-distance pollution, our study contributes to a deeper understanding of localized pollution levels, specifically in urban settings. Our approach complements multiple sources of evidence,enhancing our understanding of air pollution dynamics and trends, and the impact of human activities on urban environments
Simultaneous lead isotope ratio and gold-lead-bismuth concentration analysis of silver by laser ablation MC-ICP-MS
Full text linkA new approach is presented for the simultaneous analysis of lead isotope ratios and gold, lead, and bismuth concentrations in metallic silver using nanosecond laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS). Corrections for both isotope and concentration analyses are performed using an in-house matrix matched silver reference material RM3834. Accuracy and external reproducibility are demonstrated by repeat analyses of a further seven silver reference materials all characterised by solution (MC)-ICP-MS approaches. Typical internal precisions, expressed as two relative standard errors (S.E.) of the mean of the cycles comprising one analysis, are <0.5% for
206Pb/
204Pb,
207Pb/
204Pb and
208Pb/
204Pb, and <0.03% for
207Pb/
206Pb and
208Pb/
206Pb. External reproducibilities, based on repeat analyses over a 10 month period and expressed as two relative standard deviations (S.D.) of the mean, are <0.4% for
206Pb/
204Pb,
207Pb/
204Pb and
208Pb/
204Pb and <0.2% for
207Pb/
206Pb and
208Pb/
206Pb. Internal precisions and external reproducibilities of gold, lead and bismuth concentration analyses are typically <25%. Data are consistent with solution-based approaches. Methods are further demonstrated through analyses of a set of Islamic silver dirhams from the mint of al-Muhammadiyya, highlighting their applicability to geochemical studies of archaeological artefacts.
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Hand stencil discoveries at Lene Hara Cave hint at Pleistocene age for the earliest painted art in Timor-Leste
No full textThe distribution of known Pleistocene painted rock art in Island South-east Asia is currently limited to islands on the northern dispersal route to Australia. Here we report the discovery of at least 16 hand stencil motifs in Lene Hara Cave, Timor-Leste; a site on the alternate southern arc route. Superimposition, preservation state, differing ‘canvas’ materials (i.e. painted surfaces), and the location of the stencils in the internal (darker) part of the cave chamber together suggest that they represent an independent artistic phase that pre-dates the Holocene Austronesian Painting Tradition. The stencils are therefore recognised as a chronologically distinct painted rock art tradition, with a Pleistocene age considered most likely. Such findings have important implications for our understandings on the origins and spread of art in south-east Asia
Faces in the stone: Further finds of anthropomorphic engravings suggest a discrete artistic tradition flourished in Timor-Leste in the Terminal Pleistocene
No full textEngraving sites are rare in mainland and Island Southeast Asia (ISEA) where painted art dominates the prehistoric artistic record. Here we report two new engraving sites from the Tutuala region of Timor-Leste comprising mostly humanoid forms carved into speleothem columns in rock-shelters. Engraved face motifs have previously been reported from Lene Hara Cave in this same region, and one was dated to the Pleistocene–Holocene transition using the Uranium–Thorium method. We discuss the engravings in relation to changes in technology and material culture that took place in the terminal Pleistocene and early Holocene archaeological records in this region of Timor as well as neighbouring islands. We suggest that the engravings may have been produced as markers of territorial and social identity within the context of population expansion and greater inter-group contacts at this time
Mapping coral calcification strategies from in situ boron isotope and trace element measurements of the tropical coral Siderastrea siderea
No full textBoron isotopic and elemental analysis of coral aragonite can give important insights into the calcification strategies employed in coral skeletal construction. Traditional methods of analysis have limited spatial (and thus temporal) resolution, hindering attempts to unravel skeletal heterogeneity. Laser ablation mass spectrometry allows a much more refined view, and here we employ these techniques to explore boron isotope and co-varying elemental ratios in the tropical coral Siderastrea siderea. We generate two-dimensional maps of the carbonate parameters within the calcification medium that deposited the skeleton, which reveal large heterogeneities in carbonate chemistry across the macro-structure of a coral polyp. These differences have the potential to bias proxy interpretations, and indicate that different processes facilitated precipitation of different parts of the coral skeleton: the low-density columella being precipitated from a fluid with a carbonate composition closer to seawater, compared to the high-density inter-polyp walls where aragonite saturation was ~5 times that of external seawater. Therefore, the skeleton does not precipitate from a spatially homogeneous fluid and its different parts may thus have varying sensitivity to environmental stress. This offers new insights into the mechanisms behind the response of the S. siderea skeletal phenotype to ocean acidification
Materials in movement: gold and stone in process in the Upton Lovell G2a burial
No full textExcavated over two centuries ago, the Upton Lovell G2a ‘Wessex Culture’ burial has held a prominent place in research on Bronze Age Britain. In particular, was it the grave of a ‘shaman’ or a metalworker? We take a new approach to the grave goods, employing microwear analysis and scanning electron microscopy to map a history of interactions between people and materials, identifying evidence for the presence of Bronze Age gold on five artefacts, four for the first time. Advancing a new materialist approach, we identify a goldworking toolkit, linking gold, stone and copper objects within a chaîne opératoire, concluding that modern categorisations of these materials miss much of their complexity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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