1,721,014 research outputs found
Miocene barnacle facies: a review with examples from the Old World (Italy and France) and the New World (Peru)
No full text"Excess Ar" by laboratory alteration of biotite
Full text linkMany biotite phenocrysts from marine tephra layers have substoichiometric potassium concentrations and alkali occupation << 2.0 atoms per formula unit. Diagenetic alteration is an expected effect of exposure of fresh magmatic minerals to interstitial water and brine intrusions after the deposition and burial of sediments. To test the effect of diagenetic alteration on potassium-argon ages, we irradiated and step heated untreated Fish Canyon biotite (t = 28.2 Ma) and several aliquots leached to various extents in strong and weak acids. Laboratory alteration caused loss of K, age spectrum discordance, high step ages and total gas ages, Ar release at lower furnace temperature, higher Cl/K and Ca/K, and a slight decrease in 36Ar concentration. Potassium loss was always higher than 40Ar* loss. Electron microprobe element maps document that acids preferentially penetrate in phyllosilicate interlayers, removing K (and Na). Because Ar* is removed to a lesser extent than K, we propose that natural 40K decay partly implants radiogenic Ar* into the tetrahedral-octahedral-tetrahedral (T-O-T) phyllosilicate layer, where Ar is shielded from interlayer leaching. The recoiled 39Ar, which was produced by irradiation after the leaching, also partitioned between T-O-T and the interlayer; age spectrum discordance was probably enhanced by the heterogeneous partition of 39Ar and 40Ar* in leached samples
Evidence of dietary niche partitioning in the Squalodelphinidae (Cetacea, Odontoceti): a new large-sized taxon from the early Miocene of Peru
No full textThe South Asian river dolphin (Platanista gangetica) is the only extant survivor of the superfamily Platanistoidea (Cetacea, Odontoceti), a clade characterized by a diversified fossil record since the late Oligocene. The early Miocene family Squalodelphinidae differs from other members of the Platanistoidea by having a moderately elongated and tapered rostrum, single-rooted posterior teeth retaining ornamentation, and marked skull asymmetry. Similar to the extant common dolphin, the few squalodelphinids described are all relatively small in size, having an estimated body length (based on the bizygomatic width of the skull) between ca 2 m (Huaridelphis raimondii) and ca 2.5 m (Squalodelphis fabianii).
Based on a partial skeleton (MUSM 2545), including a well-preserved skull, collected from the Chilcatay Formation (Peru), we report here a new squalodelphinid genus and species. A volcanic ash layer sampled near MUSM 2545 yielded a 40Ar/39Ar age of 18.80 ± 0.06 Ma (early Burdigalian, early Miocene). In addition to several morphological characters, this new squalodelphinid differs from all the other genera of the family in its markedly larger size: condylobasal length of the skull greater than 770 mm and bizygomatic width equal to 370 mm. Based on this last measurement, the body length of MUSM 2545 can be estimated to ca 3.5 m. Combined with some cranial features, such as the robust rostrum less tapered than in other squalodelphinids, the large temporal fossa, and the prominent nuchal and temporal crests, this large body size suggests that the new taxon consumed larger prey than other members of its family. Together with Huaridelphis raimondii and Notocetus vanbenedeni, both of them also found in the Chilcatay Formation, this new archaic platanistoid increases further the peculiar local diversity of squalodelphinids along the southeastern Pacific coast, a diversity possibly related to their partition in different, size-related dietary niches
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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