1,720,961 research outputs found
[Yb(C2O4)4]5-- a versatile metal-organic building block for layered coordination polymers
No full textRemarkable structural similarities between organic co-crystals and a metal–organic coordination network—insights into hydrogen bonded aliphatic ammonium chlorides
No full textThe mononuclear and dinuclear dimethoxyethane adducts of lanthanide trichlorides [LnCl3(DME)2]n, n = 1 or 2, fundamental starting materials in lanthanide chemistry: preparation and structures
No full textABSTRACT Some new dimethoxyethane (DME) adducts of lanthanide trichlorides of formula [LnCl3(DME)2]n, n=1 or 2; (n=2, Ln=La, Ce, Pr, Nd; n=1, Ln=Eu, Tb, Ho, Tm, Lu) have been prepared by treating Ln2O3, or LnCl3 · nH2O, or Ln2(CO3)3, in DME as medium, with thionyl chloride at room temperature, eventually in the presence of water in the case of Ln2O3 and Ln2(CO3)3. The complexes from lanthanum to praseodymium included are chloro-bridged dimers. In the case of neodymium, the new results complement the literature data, showing that both the mononuclear and dinuclear species exist: neodymium can therefore be regarded as the turning element from dinuclear to mononuclear structures along the series. Only mononuclear complexes were isolated in the Eu–Lu sequence. The lanthanide contraction has been evaluated on the basis of the Ln–O and Ln–Cl bond distances on the isotypical series of the mononuclear complexes LnCl3(DME)2 covering a range of 12 atomic numbers
Reaction of a tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) with dioxygen: synthesis and X-ray characterization of both the oxidation product and its precursor
No full textABSTRACT The tetranuclear N,N-di-iso-propylcarbamato complex of cerium(III) Ce-4((O2CNPr2)-Pr-i)(12), 1, has been synthesized and its crystal structure solved through X-ray diffraction methods. The oxidation of the cerium(Ill) complex by dioxygen produces the mu(3)-OXO tetranuclear cerium(IV) derivative Ce-4(mu(3)-O)(2)((O2CNPr2)-Pr-i)(12), 2, which has been characterised by single crystal X-ray diffractometry. Structural rearrangements on going from the cerium(111) derivative to the corresponding cerium(IV) product have been established. This is the first case of a mu-oxo-carbamato complex being obtained by oxygenation, whereby product and precursor maintain the basic structural features
N,N-dialkylcarbamato lanthanide complexes, a series of isotypical coordination compounds
No full textABSTRACT: The preparations of the N,N-dialkylcarbamato complexes with analytical formulae [Ln(O2CNR2)3] (Ln = Pr, Nd, Eu, Gd, Ho, Er, Yb, Lu, R = iPr; Ln = Nd, Eu, Gd, R = Bu; Ln = Nd, R = Et), using [LnCl3(ether)x] (ether = THF or dimethoxyethane, DME), NHR2, and CO2 are reported. X-ray diffraction of the diisopropylcarbamato derivatives, including a reinvestigation of [Yb4(O2CNiPr2)12], showed these complexes to be tetranuclear and isotypical over a range of 12 atomic numbers. The lanthanide contraction has been evaluated based on the lengths of four different types of Ln-O bond
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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