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Modeling the Ionic Strength Effect on Diffusion in Clay. the DR-A Experiment at Mont Terri
Get PDFSolute diffusion in compacted clays depends on ionic strength through its control on the thickness of the electrical double layer (EDL) on the charged clay surfaces. In the DR-A field experiment (Mont Terri, Switzerland), synthetic porewater was circulated through a borehole for 189 days, leading to the out-diffusion of a variety of tracers into the Opalinus Clay. The borehole solution was then replaced with a higher-salinity solution for an additional 540 days, leading to the diffusion of Cs + , Ca 2+ , Mg 2+ , and Sr 2+ back into the borehole and to an increase in the out-diffusion of anions (I - , Br - ) and 3 H. The experimental results were interpreted using the CrunchClay code, which includes a mean electrostatic potential model for the EDL. The EDL corresponds to a second continuum in addition to bulk electrically neutral porewater. Species-specific diffusion (Nernst-Planck equation) occurs through both domains. A 1D radial model considered a single pore diffusion coefficient (D p = 10 -9 m 2 /s) for cations and 3 H in the bulk porosity, and a smaller D p (3 × 10 -10 m 2 /s) for anions. D p values in the EDL were smaller (10 -11 m 2 /s), except for Cs + and K + (5 × 10 -10 and 2 × 10 -10 m 2 /s, respectively). The model reproduced well the experimental results and showed the capability to consider temporal changes in geochemical conditions affecting the transport and retention of potentially important radionuclide contaminants (e.g., 137 Cs + , 90 Sr 2+ , 129 I - ) in underground geological nuclear waste repositories. Coupled multicomponent diffusion together with the electrostatic properties of the charged surfaces are essential in the development of predictive models for ion transport in clays. © 2019 American Chemical Society.Partial financial support was provided by the Mont Terri Project (Switzerland), thanks to the partners of the DR-A experiment (NAGRA, Switzerland; NWMO, Canada; Department of Energy, U.S.A.). C.S. acknowledges funding support from the Director, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 to Lawrence Berkeley National Laboratory. The detailed comments from two anonymous reviewers and the suggestions from the Associate Editor, Prof. Sumit Chakra-borty, were substantial to the improvement of the manuscript.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
A stroboscopic control for the confinement of swarms in a spherical domain around the Earth
No full textSwarms of spacecraft are an idea that has been growing in interest in the last few years. This work focuses on the strategies and costs for the maintenance of a swarm of a large number of spacecraft in a close neighborhood (in our case represented by an sphere but any other confining geometry could be considered) for long periods of time. One of the main issues that one encounters when optimizing the sequence of control maneuvers for a large group of spacecraft is the huge number of variables and constraints. Our methodology considers a hierarchical structure that accounts both for collision avoidance and degradation of the con- finement region of the spacecraft swarm. In an strobe way, usually counted in one or few orbital periods, a few spacecraft of the set are selected and a suitable and efficient control procedure is applied to them, assuring this way computational efficiencyPostprint (author's final draft
A stroboscopic control for the confinement of swarms in a spherical domain around the Earth
No full textSwarms of spacecraft are an idea that has been growing in interest in the last few years. This work focuses on the strategies and costs for the maintenance of a swarm of a large number of spacecraft in a close neighborhood (in our case represented by an sphere but any other confining geometry could be considered) for long periods of time. One of the main issues that one encounters when optimizing the sequence of control maneuvers for a large group of spacecraft is the huge number of variables and constraints. Our methodology considers a hierarchical structure that accounts both for collision avoidance and degradation of the con- finement region of the spacecraft swarm. In an strobe way, usually counted in one or few orbital periods, a few spacecraft of the set are selected and a suitable and efficient control procedure is applied to them, assuring this way computational efficiencyPostprint (author's final draft
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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