1,720,959 research outputs found
AMONG THE GREEKS, AMONG THE NATIVES. PRELIMINARY ANALYSIS OF THE ANTHROPOLOGICAL RECORD FROM THE NECROPOLIS OF PITHEKOUSSAI II, ISCHIA ISLAND (NAPLES).
No full textAMONG THE GREEKS, AMONG THE NATIVES: STRONTIUM ISOTOPIC RATIO ANALYSIS OF HUMAN ODONTOSKELETAL REMAINS FROM PITHEKOUSSAI, ISCHIA (S ITALY)
No full textTen years of Tridacna sclerochemistry at up to daily resolution from a controlled aquarium environment – records of habitat change, induced seasonality and growth variability
No full textGiant clams such as Tridacna sp., with their rapid shell accretion (mm-cm/year), decade-long lifespans and aragonitic shells, are invaluable (palaeo)environmental archives, potentially providing information at (sub-)seasonal timescales. Royal Burgers' Zoo aquarium in Arnhem, The Netherlands, opened a live coral reef eco-display in 2000 and introduced T. squamosa from Vietnam in 2001. One specimen (TS2) that died in 2011 facilitated a decade-long comparison of carefully monitored aquarium conditions with Tridacna sclerochemistry and growth, whose results we present herein. Spatially resolved El/Ca ratios by LA-ICPMS (at up to daily resolution) as well as micromilled δ13C and δ18O data were transferred onto a sclerochronological framework at a daily resolution, which enabled the detailed correlation of aquarium parameters with sclerochemistry. We show that environmental stresses such as transportation, introduction to a new aquarium environment, shifts in water change regimes and artificial seasonality from 2009 onwards have severe impacts on the organism's growth and sclerochemistry, and are particularly manifest in this sample in increased Mg/Ca and Sr/Ca ratios. Growth rates were reduced from ∼20 to ∼7 μm/day during transportation into the aquarium, and from ∼10 to ∼2 μm/day during shifts in water change regimes in the aquarium. A disruption of daily El/Ca cyclicity was marked during transportation-induced stress, but within three weeks of introduction the organism acclimatised to the aquarium and returned to natural growth rates and cyclicity. Three years of induced temperature seasonality (25.0–26.5 °C) most notably affected Na/Ca, while the resulting expected δ18O variability was not resolvable due to TS2's strongly decreased growth rate coupled with our large drill-step size for sampling. Despite a transient spike in aquarium [NO-3] from ∼0.02 to 2.4 mg/L, caused by accidental over-fertilisation, no stress effect was apparent in the organism's sclerochemistry or growth rate. Changes in the water-exchange regime appear to have far more sclerochemical impact, as these are reflected in the overall δ18O, Ba/Ca and associated growth rates. The detailed decade-long Tridacna record shows that even systems with comparatively little environmental variability can produce large degrees of shell heterogeneity, and also highlights the importance of establishing a detailed (counted) chronology for sclerochemical interpretations.</p
Daily to seasonal environmental variability from giant clams revealed via spatially-resolved geochemical analyses and laboratory culture experiments: Case studies from Recent and Miocene Indo-Pacific Tridacna shells
Full text linkThis thesis presents high (weeks-months) and ultra-high (hours-days) resolution time-series proxy records obtained from Miocene, Recent and laboratory cultured giant clam (Tridacna spp.) shells. In order to evaluate the fidelity of two Late Miocene Tridacna shells from East Kalimantan (Indonesia) to preserve any palaeoenvironmental variability, a multi-method approach was applied to assess pristine aragonite preservation. Combined usage of XRD, SEM/CL imaging and LA-ICPMS trace elemental screening has proven effective at detecting diagenetic shell alteration. Seasonally-resolved palaeoproxy records obtained from pristine shell aragonite provide insight into tropical sea surface temperature (SST) variability of the Indo-Pacific region during the late Miocene. 18O time-series records from two fossil shells indicate an average SST variability of 2.7 ± 2.1 and 4.6 ± 1.7 °C, respectively, which exceeds the modern-day seasonality in the Makassar Strait two- to threefold. A novel methodological approach of ultra-high resolution LA-ICPMS analysis is introduced, which utilizes the combined capabilities of a rotating rectangular aperture (spot size 4 x 50 μm), the rapid signal washout of a Laurin two-volume laser ablation cell and slow compositional profiling (1.5 μm/s) and enables resolution of <10 μm compositional variability in B/Ca, Mg/Ca, Sr/Ca and Ba/Ca preserved within microscopically visible growth increments of both Recent and Miocene Tridacna shells. In comparison to a lower-resolution, seasonally resolved Miocene record, the ~10-20 μm element/Ca cycles were determined to be daily in origin, and a further ~14-15 day cyclicity, interpreted to reflect tidal periodicity, is detected in long-term (annual) daily resolved proxy records. Laboratory culture experiments of Tridacna crocea, conducted under controlled environmental conditions including temperature, light level and seawater chemistry, allowed quantifying the temperature and light influence on shell growth rates. Corresponding ultra-high resolution LAICPMS analysis of the isotopically labelled cultured shell domains revealed that both temperature and light influence trace elemental incorporation into shell aragonite, yet biophysiology also controls trace element partitioning
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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