1,721,039 research outputs found
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
Reactivity studies of the 2-phosphaethynolate anion: a pathway to phosphinecarboxamides
Full text linkThis thesis summarises the research carried out during my PhD on the phosphinecarboxamide family. Inspired by Wöhler’s seminal synthesis of urea, the phosphinecarboxamides are obtained by the reaction of the 2-phosphaethynolate anion, PCO–, a heavier congener of the cyanate anion, with ammonium salts. These species are phosphorus-containing analogues of urea, RHPC(O)NHR’. These compounds are prime examples of primary phosphines that exhibit remarkably air- and moisture stability. Several examples of these compounds were obtained by the reaction of the 2-phosphaethynolate anion with a variety of amines such as amino acids, leading to N-functionalised chiral products and bidentate amines. The reactivity of these compounds was explored by promoting deprotonation of the molecules, which allowed post functionalisation, affording new P-functionalised species. These phosphinecarboxamides were also shown to be able to act as Lewis bases, as they were able to use the phosphorus lone-pair to coordinate to transition metals centres. Finally, this thesis underlines the reactivity of the PCO– anion with amines bearing a ferrocenyl group as well the reactivity of the resulting products
Solution reactivity studies of group 15 Zintl ions
Full text linkThe reactivity of group 15 Zintl ions, E73– (E = P, As), towards a number of transition and post-transition metal reagents has been studied. The synthesis and characterisation of the resulting novel cluster anions are described herein. The reactions of E73– with [Cu5(mes)5], MPh2 (M = Zn, Cd) and InPh3 yielded the Cu–Cu bridged species [Cu2(E7)2]4– (E = P, As), the group 12 bridged cluster anions [M(E7)2]4– (M = Zn: E = P, As; M= Cd: E = P), and the In-functionalised Zintl ions [E7InPh2]2–, respectively. P73– and As73– have been found to react with a number of metal salts, namely [M(nbe)3][SbF6] and MCl (M = Ag, Au), InCl3, TlCl and MI2 (M = Sn, Pb). These reactions formed the Ag–Ag and Au–Au bridged complexes [M2(HP7)2]2– (M = Ag, Au), the In-bridged species [In(E7)2]3– (E = P, As), the Tl-derivatised Zintl ions [TlE7]2– (E = P, As), and the sixteen vertex cluster anions [ME15]3– (M = Sn, Pb; E = P, As). The reactivity of P73– towards a series of group 8 compounds has also been studied. The reactions of P73– with FeCl2 and [Ru(PPh3)3Cl2] produced [M(HP7)2]2- (M = Fe, Ru). NMR studies showed that these species can be deprotonated to form [M(P7)2]4– (M = Fe, Ru). These Fe and Ru complexes are isoelectronic with ferrocene. In addition, P73– reacts with [Ru(COD)(η3-CH2C(CH3)CH2)2] to form [(C4H7)P7Ru(COD)]2–. Both P73– and As73– undergo transition metal mediated activation reactions in the presence of [Co(PEt2Ph2)(mes)2], yielding [Co(η5-P5){η2-HP2(mes)}]2– and [Co([η3-As3){η4-As4(mes)2}]2–, respectively
Chemical reactivity of group 14 [E9]4– and 15 [E'7]3– Zintl ions
Full text linkThis thesis describes the reactivity of Zintl ions of groups 14 [E9]4– (E = Ge and Sn)and 15 [E'7]3– (E' = P and As) towards a number or transition, post-transition and main group reagents. The synthesis and characterisation of the resulting novel cluster anions is described herein. Coordination compounds of group 14 Zintl ions were synthesised when K4Ge9 was reacted with Zn[N(SiMe3)2]2 to give the simple coordination compound [Ge9ZnN(SiMe3)2]3–. The heavier analogue K4Sn9 reacts with the same metal precursor to give the paramagnetic species [Sn9ZnNSiMe3]3– where a trimethylsilyl group has been lost. K4Ge9 reacts with [Ru(COD)(η3-CH2C(CH3)CH2)2] to form the paramagnetic endohedral compound [Ru@Ge12]3– and with [Co(PEt2Ph)2(mes)2] to form the prolate endohedral compound [Co2@Ge16]4–, which has two metal centres encapsulated inside the sixteen atom germanium cage. Regarding group 15 Zintl ion reactivity, the reactions between pyridine solutions of [HP7]2– and E[N(SiMe3)2]2 (E = Ge, Sn and Pb) have been found to yield coordination compounds of the type [P7E(N(SiMe3)2]2–. The germanium containing species [P7GeN(SiMe3)2]2– quickly decomposes at room temperature to give rise to the thermodynamic product [(P7)2Ge2N(SiMe3)2]3–, a process that involves the loss of an amide moiety. Activation products were also synthesised from the reaction of [E'7]3– with varying stoichiometries of VCp2. The reaction with 0.7 equivalents of VCp2 yields the sandwich complexes [CpV(η5-E'5)]n– (E' = P: n = 1; E' = As, n = 1 and 2) whereas with 2.5 equivalents the products are the triple-decker sandwich complexes [(CpV)2(ηx-E'x)]– (E' = P: x = 6; E' = As: x = 5)
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
Solution reactivity studies of group 15 Zintl anions towards unsaturated substrates
Full text linkThis thesis describes selected reactivity studies of group 15 Zintl anion [E7]3– (E = P, As) derived cages towards a series of unsaturated organic molecules. The synthesis and characterization of forty-two compounds derived from [E7]3– cages are detailed herein. A high yielding procedure for the synthesis of [HE7]2– (E = P, As) from the K3E7 Zintl phase has been developed. This solves prior issues with poor solubility and variable purity of the Zintl phases. The conditions required for the deprotonation of the phosphorus congener to [P7]3– are described. The reactivity of both [P7]3– and [HP7]2– towards carbon dioxide and isolobal isocyanates and carbodiimides was explored. This yielded a series of monofunctionalized [E7R]2– cages, via a net hydropnictination of a C=N double bond of the organic substrate. The protonation chemistry of these anions was further investigated, resulting in the formation of the protic [HP7C(NHDipp)(NDipp)]– cluster. This anion is capable of further hydrophosphination chemistry to give a series of difunctionalized heptaphosphide cages. The reaction of [E7]3– with alkynes results in the formation of the relatively unusual 1,2,3-tripnictolide anions. A series of such anions have been prepared, encompassing all of the previously reported anions and several novel species. Investigation of the coordination properties of these cyclopentadienyl analogues shows that they are superior π acceptor ligands. A synthetic route to [P5]– as a compositionally pure solid, and some initial studies on its protonation chemistry are also additionally presented
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
Dioxygen Splitting by a Tantalum(V) Complex Ligated by a Rigid, Redox Non‐Innocent Pincer Ligand**
No full textThe reaction of TaMe3Cl2 with the rigid acridane-derived trisamine H3NNN yields the tantalum(V) complex [TaCl2(NNNcat)]. Subsequent reaction with dioxygen results in the full four-electron reduction of O2 yielding the oxido-bridged bimetallic complex [{TaCl2(NNNsq)}2O]. This dinuclear complex features an open-shell ground state due to partial ligand oxidation and was comprehensively characterized by single crystal X-ray diffraction, LIFDI mass spectrometry, NMR, EPR, IR and UV/VIS/NIR spectroscopy. The mechanism of O2 activation was investigated by DFT calculations revealing initial binding of O2 to the tantalum(V) center followed by complete O2 scission to produce a terminal oxido-complex
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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