1,721,057 research outputs found
Ab Initio Computational Study on Fe2NiP Schreibersite: Bulk and Surface Characterization
No full textPhosphorus is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorus is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and nonreactive materials, making it unavailable for ready incorporation in living organisms. A possible source of phosphorus is from exogenous meteoritic bombardment and, in particular, iron/nickel phosphides. These materials, by simple interaction with water, produce oxygenated phosphorus compounds, which can easily react with organic molecules, thus forming C-O-P bonds. In the present work, periodic ab initio simulations at the PBE level (inclusive of dispersion interactions) have been carried out on metallic Fe2NiP schreibersite, as a relatively abundant component of metallic meteorites, in order to characterize the structural, energetic, and vibrational properties of both bulk and surfaces of this material. The aim is to study the relative stability among different surfaces and also to characterize the nanocrystal morphology of the mineral
Hydroxyapatite as a key biomaterial: quantum-mechanical simulation of its surfaces in interaction with biomolecules
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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
H2Formation on Interstellar Grains and the Fate of Reaction Energy
No full textMolecular hydrogen is the most abundant molecular species in the universe. While no doubts exist that it is mainly formed on the interstellar dust grain surfaces, many details of this process remain poorly known. In this work, we focus on the fate of the energy released by the H2 formation on the dust icy mantles: how it is partitioned between the substrate and the newly formed H2, a process that has a profound impact on the interstellar medium. We carried out state-of-the-art ab initio molecular dynamics simulations of H2 formation on periodic crystalline and amorphous ice surface models. Our calculations show that up to two-thirds of the energy liberated in the reaction (∼300 kJ mol-1 ∼3.1 eV) is absorbed by the ice in less than 1 ps. The remaining energy (∼140 kJ mol-1 ∼1.5 eV) is kept by the newly born H2. Since it is 10 times larger than the H2 binding energy on the ice, the new H2 molecule will eventually be released into the gas phase. The ice water molecules within ∼4 Å from the reaction site acquire enough energy, between 3 and 14 kJ mol-1 (360-1560 K), to potentially liberate other frozen H2 and, perhaps, frozen CO molecules. If confirmed, the latter process would solve the long standing conundrum of the presence of gaseous CO in molecular clouds. Finally, the vibrational state of the newly formed H2 drops from highly excited states (ν = 6) to low (ν ≤ 2) vibrational levels in a timescale of the order of picoseconds
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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