1,721,310 research outputs found
Extension of the Swiss Lateglacial tree-ring chronologies
No full textFossil wood finds reveal a high resolution paleoclimatic proxy record of Lateglacial and Early Holocene. Eighty-one
buried fossil pine stumps have been excavated on the construction site (Gaenziloo) of the A4-highway tunnel through
Uetliberg near Zurich (Switzerland). The trees were buried during their lifetime by loamy alluvia washed down from
the upper part of the slopes. The stumps have remained well preserved for more than 13,500 years. The cross sections
of the trunks were analyzed dendrochronologically. The sections were dated by 14C, and 14C age vs. ring number were
obtained from decadal sample segments.
Three floating chronologies were built. They cover a time span of 428 years in the Mid-Allerød (GAEALLCH_A),
561 years in the Late-Allerød (GAEALLCH_D) and 212 years in the Younger Dryas (GAEYD_A). Visual
synchronization, t-values, percentages of parallel variation (‘Gleichlaeufigkeit’) and radiocarbon wiggle matching
(14C age determinations on a decadal scale) as well as a check by the program Cofecha support the validity of the
resulting chronologies.
The two Allerød-chronologies from Gaenziloo were linked with two chronologies from Daettnau (DAEALCH_1
and DAEALCH_2) published by Kaiser, K.F. (1993. Beitra ̈ ge zur Klimageschichte vom Hochglazial bis ins fru ̈ he
Holoza ̈ n, rekonstruiert mit Jahrringen und Molluskenschalen aus verschiedenen Vereisungsgebieten. Ziegler Druck-
und Verlags-AG, Winterthur. 206pp). They extend the existing floating Swiss chronology in the Late-Allerød by a total
of 186 years. Unfortunately independent chronology GAEYD_A does not overlap with the actual absolute chronology
developed by the tree-ring laboratory of the University of Hohenheim (Friedrich, M. et al., 2004. The 12,460 year
Hohenheim oak and pine tree-ring chronology from Central Europe – A unique annual record for radiocarbon
calibration and paleo-environment reconstructions. Radiocarbon 46(3), 1111–22.)
Back to the future: The advantage of studying key events in human evolution using a new high resolution radiocarbon method
Full text linkRadiocarbon dating is the most widely applied dating method in archaeology, especially in human evolution studies, where it is used to determine the chronology of key events, such as the replacement of Neanderthals by modern humans in Europe. However, the method does not always provide precise and accurate enough ages to understand the important processes of human evolution. Here we review the newest method developments in radiocarbon dating (‘Radiocarbon 3.0’), which can lead us to much better chronologies and understanding of the major events in recent human evolution. As an example, we apply these new methods to discuss the dating of the important Palaeolithic site of Bacho Kiro (Bulgaria)
Exploring different methods of cellulose extraction for 14C dating
Full text linkIn this study we aim to identify the optimal cellulose extraction protocol for 14C dating of wood, with a focus on glacial trees. To achieve this, we compare three cellulose extraction methods on the basis of cellulose yield and 14C age. The study is conducted on 12 wood samples of different species, in varying states of preservation with ages covering the full 14C age range. Cellulose is extracted from each sample following three different protocols selected from the literature: ABA-B, BABAB and 2Chlorox. The extracted cellulose was graphitised and dated with the MICADAS (Mini Carbon Dating System) at the ETH AMS laboratory. Although all three methods are considered efficient, the BABAB protocol, despite being a more aggressive procedure, allows the extraction of a sufficient amount of cellulose to be 14C dated and leads to the most reliable results, particularly for very old and background samples (samples with 14C content of zero)
14C calibration in the 2nd and 1st millennia BC-Eastern Mediterranean radiocarbon comparison project (EMRCP)
No full textWe have measured additional known-age German oak samples in 4 intervals in the 2nd and 1st millennia BC to add to (and to replicate) parts of the international Northern Hemisphere radiocarbon calibration data set. In the 17th, 16th, and 12th centuries BC, our results agree well with IntCal04. In the 14th and 13th centuries BC, however, we observe a significant offset, with our results on average 27 yr older than IntCal04. The previously reported 14C offset between Anatolian juniper trees and central European oaks in the 9th and 8th centuries BC is smaller now, on the basis of our new measurements of German oak, but still evident. In the 17th and 16th centuries BC, the 14C ages from the Anatolian chronology agree well with IntCal04 and our new German oak data. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona
Dendrocronologie del Tardoglaciale dal Palughetto.
No full textLe dendrocronologie basate sui campioni di abete e di larice provenienti da Palughetto datate da 12.500 a 11.000 14C BP si estendono per tutta la cronozona Bølling-Allerød ma non permettono ancora un completo ancoraggio alla cronologia tardoglaciale, che forse sarà facilitato dal ritrovamento di ulteriori pini subfossili in diversi luoghi della Pianura Padana. L’acquisizione di un numero maggiore di campioni consentirà nel futuro di costruire curve per l’Italia Settentrionale e di inserirle nelle dendrocronologie dell’Europa Centrale
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Debates over Palaeolithic chronology - the reliability of C-14 is confirmed
No full textThe debate about the complex issues of human development during the Middle to Upper Palaeolithic transition period (45-35 ka BP) has been hampered by concerns about the reliability of the radiocarbon dating method. Large C-14 anomalies were postulated and radiocarbon dating was considered flawed. We show here that these issues are no longer relevant, because the large anomalies are artefacts beyond plausible physical limits for their magnitude. Previous inconsistencies between C-14 radiocarbon datasets have been resolved, and a new radiocarbon calibration curve, IntCal09 (Reimer et al., 2009), was created. Improved procedures for bone collagen extraction and charcoal pre-treatment generally result in older ages, consistent with independently dated time markers. (C) 2012 Elsevier Ltd. All rights reserved.</p
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