1,720,955 research outputs found
BIS(ARENE)VANADIUM(0) COMPLEXES AS A SOURCE OF VANADIUM(II) DERIVATIVES BY BOTH DISPROPORTIONATION OF THE [V(ETA-6-ARENE)2]+ CATIONS AND OXIDATION OF [V(ETA-6-ARENE)2]
No full textThe [V(eta6-arene)2]+ Cation (arene = benzene, toluene or mesitylene) is disproportionate to [V(eta6-arene)2] and V(II) compounds in ether solvents such as THF or 1,2-dimethoxyethane (DME). The extent of disproportionation depends on the nature of both the counteranion and the arene ligand. Addition of the filtered crude reaction mixtures, presumably containing the [V(eta6-arene)2][Al2X7] derivatives, to THF gave [V2(mu-X)3(THF)6[AlX4] (arene = benzene or toluene; X = Cl or Br). For X = Cl and arene = toluene, addition to a THF solution of Lil yielded [V2(mu-Cl)3(THF)6]I. The atom connectivity was established for [V2(mu-Cl)3(THF)6][AlCl4], while [V2(mu-Cl)3(THF)6]I was fully characterized by X-ray diffraction methods. Crystal data: [V2(mu-Cl)3(THF)6]I: monoclinic, space group C2/c (no. 15), a 25.199(8), b 13.865(6), c 9.879(4) angstrom, beta 103.98(2)-degrees, V 3349.3 angstrom3, Z = 4, D(c) 1.523 g cm-3, mu 17.256 cm-1, F(000) = 1560. The vanadium(II) derivative VI2(THF)0.7 was obtained, together with [V(eta6-mesitylene)2] in the reaction of [V(eta6-mesitylene)2][AlI4] with THF. By reaction of [V(eta6-mesitylene)2] with CPh3X (X = Br or 1) in 1,2-dimethoxyethane (DME), the dihalides of vanadium(II), [VX2(DME)2] have been isolated in good yields. The crystal and molecular structure of the monomeric cis-[VI2(DME)2] of pseudo-octahedral geometry has been studied by X-ray diffraction methods. Crystal data: 2(DME)2]: monoclinic, space group P2(1)/n (non-standard No. 14), a 7.819(4), b 13.150(4), c 15.535(5) beta 90.23(3)-degrees, V 1597.3(1) angstrom3, Z = 4, D(c) 2.017 g cm-3, mu 44.231 cm-1, F(000) = 916
Cyclopentadienyl-N,N-diethylcarbamato Derivatives of Zirconium(IV) and Hafnium(IV), MCp(O2CNEt2)3: Synthetic Procedures and Use as Precursors for the Chemical Implantation of Organometallic Fragments on a Silica Surface
No full textReaction of Mg(C5H5)2 with the homoleptic diethylcarbamato derivatives of zirconium(IV) or hafnium(IV),
M(O2CNEt2)4, gave the mixed cyclopentadienyl–diethylcarbamato complexes [M(C5H5)(O2CNEt2)3]. These
derivatives have also been obtained by reaction of Fe(O2CNEt2)2 with M(C5H5)4 in the appropriate stoichiometric
ratio. The compound [Zr(C5H5)(O2CNEt2)3] crystallizes in the space group P1 ̄ , Z = 2, a = 9.734(4), b = 10.234(2),
c = 12.948(6) Å; a = 83.41(4), b = 86.13(4) and g = 67.43(3)8. On reaction of [Zr(C5H5)(O2CNEt2)3] with
dehydrated silica, 1 mol of CO2 per zirconium was evolved. The organometallic fragment Zr(C5H5)(O2CNEt2)2
grafted on silica has been characterized by analytical methods and by CP MAS 13C NMR spectroscopy
Synthesis and crystal structure of a self-assembled, octanuclear oxo-tantalum(V) derivative containing the first example of a transition metal M8(mu-O)12 cage
No full textBy reduction with CoCp*(2) in THF or toluene, the tantalum(V) chlorocarbamato complex TaCl2(O2CNEt2)(3), 1, gives high yields of the tantalum(III) N,N-diethylcarbamate, Ta(O2CNEt2)(3), 2. On the other hand, good yields of the octanuclear mu-oxo-N,N-diethylcarbamato cage compound Ta-8(mu-O)(12)(O2CNEt2)(16), 3, were secured by reaction of 1 with sodium in THF. Compound 3 has been characterized by analytical and spectroscopic methods and by X-ray diffractometry. Crystal data for C80H160N16O44Ta8: M = 3497.84, triclinic, space group P (1) over bar (no. 2), (1) over bar a = 15.440(3) Angstrom, b = 15.710(1).Angstrom, c = 16.090(2) Angstrom, alpha = 101.53(4)degrees, beta = 107.51(5)degrees, gamma = 118.79(3)degrees, V = 2971.4(3) Angstrom(3), Z = 1, D-c = 1.955: Mg/m(3), mu = 7.416 mm(-1), F(000) = 1688, R1 = 0.0350, wR2 = 0.0798, T = 213 K. The eight tantalum atoms are located at the vertexes of a cube whose edges are occupied by 12 bridging oxo groups; Hexacoordination at tantalum is completed by bridging and terminal N,N-diethylcarbamato ligands. Both THF and the carbon dioxide fragments of the carbamato groups are involved in the formation of the mu-oxo cage oxides
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
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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