| 2. |
- Emile-Geay, J., et al.
(författare)
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Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era
- 2017
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.
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| 3. |
- Cabanettes, Frédéric, 1982-, et al.
(författare)
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Topography of as built surfaces generated in metal additive manufacturing : A multi scale analysis from form to roughness
- 2018
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Ingår i: Precision engineering. - Philadelphia, PA : Elsevier. - 0141-6359 .- 1873-2372. ; 52, s. 249-265
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Tidskriftsartikel (refereegranskat)abstract
- Topographies are one of the challenges for the development of the metal additive manufacturing promising technique. The article investigates multi scale topographies (from form to roughness) of as built surfaces generated by selective laser melting (SLM). Different building inclinations of samples were observed both for upskin and downskin surfaces with a wide range of measuring techniques. The two main aims are: (i) to make a critical review of measuring techniques at different scales, (ii) to enlighten the different surface generation phenomena (and the corresponding scale) occurring during additive manufacturing. The effect of heat treatment on each scale of the topography is also discussed. It is found that the focus variation technique is well suited for AM surfaces. Concerning the observation of the inclined surfaces, some parameters are emphasized as good indicators of typical signatures of AM surfaces: isotropy for the weld track component, the skewness and Rsm for the staircase effect, fractal dimension for the presence of partly melted particles. The different parameters studied helps to model and understand the different surface generation phenomena aforementioned. © 2018 Elsevier Inc.
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| 4. |
- Zumberge, J. Alex, et al.
(författare)
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Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals
- 2018
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Ingår i: Nature Ecology & Evolution. - : NATURE PUBLISHING GROUP. - 2397-334X. ; 2:11, s. 1709-1714
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Tidskriftsartikel (refereegranskat)abstract
- Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100 Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C-30 sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.
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