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Hydrolysis and chemical speciation of dioxouranium(VI) ion in aqueous media simulating the major composition of seawater
No full textThe hydrolysis and chemical speciation of the dioxouranium(VI) ion at 25 jC was studied in a number of binary electrolytes (LiCl, NaCl, MgCl2, CaCl2, Na2SO4) and some mixtures (NaCl–Na2SO4, NaNO3–Na2SO4, CaCl2–MgCl2) as
well as artificial seawater (SSWE) as a function of ionic strength. The results in LiCl, CaCl2 and MgCl2 solutions confirmed
the formation of (UO2)2(OH)22 +, (UO2)3(OH)42 +, (UO2)3(OH)5+ and (UO2)3(OH)7- species (at I = 0 mol l- 1: log beta22 =-5.76, logbeta34 =-11.82, log beta35 =-15.89 and log beta37 =-29.26). For NaNO3, NaCl and artificial seawater the hydrolysis constant for the formation of the UO2(OH)+ species was also determined (at I = 0 mol l-1: log beta11 =-5.19). The results in Na2SO4,
Na2SO4/NaNO3 and Na2SO4/NaCl required the formation of UO2(SO4)0, UO2(SO4)22-, UO2(OH)SO4- , (UO2)2(OH)2SO40, (UO2)3(OH)4SO40 and (UO2)3(OH)5SO4- , whose estimated values of each complex formation constant at I = 0 mol
(kg H2O)- 1 are (log betapqr standard deviation, species in parenthesis): 3.32F0.02 [UO2SO4
0], 4.26F0.04 [UO2(SO4)22-],
2.30F0.01 [UO2(OH)(SO4)-], 2.64F0.04 [(UO2)2(OH)2(SO4)0], 8.45F0.04 [(UO2)3(OH)4(SO4)0], 13.58F 0.04
[(UO2)3(OH)5(SO4) ]. All the results were examined using the Pitzer model by considering the interactions of the cation hydrolytic species with Cl- and NO3- and anion hydrolytic species with Li+, Na+ , Ca2 + and Mg2 + and, in addition, the ‘‘same sign’’ and ‘‘triple’’ interaction parameters. The resulting Pitzer parameters give an adequate representation of all the hydrolysis constants measured in the binary, ternary and artificial seawater solutions. Alternatively to the interpretation of the dependence of uranyl hydrolysis constants on ionic strength and on ionic medium in terms of variations of activity coefficients of
ions, the formation of ion pairs was considered and some complex formation constants among dioxouranium(VI) species and different ions of background salts were calculated. Interactions of uranyl with major components of seawater were taken into account using the ‘‘single salt’’ BA approximation according to which SSWE is considered as a single sea salt (BA) where cation
B and anion A, having charge z = +-1.117, are representative of all major cations (Na+, K+, Ca2 +, Mg2 +) and
anions (Cl- and SO42-) of seawater, respectively. Pitzer parameters were also calculated for both the interactions of uranyl with Bz+ and Az- ions and for the internal BA interactions. The last ones are: b(0) = 0.1081 and b(1) = 0.4238 for B1.117 +–A1.11
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
Modelling S-carboxymethyl-L-cysteine protonation and activity coefficients in NaClaq and (CH3)4NClaq by SIT and Pitzer equations
No full textDispelling 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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Speciation of trialkyltin (IV) cations in natural fluids
No full textThe hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in different ionic media (NaNO(3), NaCl, Na(2)SO(4) and SSW) are used to determine Pitzer interaction parameters. Predictive equations for the calculation of unknown hydrolysis constants and Pitzer interaction parameters of other trialkyltin(IV) cations, such as tributyltin(IV), are proposed
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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