1,721,014 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
Formation of [Ir(CO)2Cl]x (x = 2, n) Species by Mild Carbonylation of [Ir(cyclooctene)2Cl]2 Supported on Silica or in Solution: A New Convenient Material for the Synthesis of Iridium(I) Carbonyl Complexes
No full textA pale-blue Ir(I) dicarbonyl chloride surface species is obtained by carbonylation of [Ir-(cyclooctene)(2)Cl](2) supported on the silica surface working under. mild conditions (1 atm of CO, room temperature). This species is probably weakly bound to the surface silanol groups. It can be extracted only with weak donor solvents like, acetone and acetonitrile, affording a solution of the dimer [Ir(CO)(2)Cl](2). This dimer can be also obtained by carbonylation under mild conditions of [Ir(cyclooctene)(2)Cl](2) in the latter solvents. Evaporation of the donor solvents transforms [Ir(CO)(2)Cl](2) into a dark-brown, almost black, amorphous carbonyl material, probably polymeric via strong Ir-Ir interactions. Likewise, in nondonor solvents like toluene and pentane, carbonylation of [Ir(cyclooctene)(2)Cl](2) produces. the same insoluble material of formula [Ir(CO)(2)Cl](2). This material may be reversibly dissolved by donor solvating solvents, to form again a solution of the dimer. The acetonitrile solution of [Ir-(CO)(2)Cl](2) is a very convenient starting material for the high-yield preparation of many Ir(I) carbonyl derivatives such as, for instance, [Ir(CO)(2)Cl-2](-), [Ir(CO)(2)(amine)Cl], [Ir(CO)(PPh(3))(2-)Cl], and [Ir(CO)(2)(acac)], where acacH is acetylacetone
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
Modern Surface Organometallic Chemistry
No full textCovering everything from the basics to recent applications, this monograph represents an advanced overview of the field. Edited by internationally acclaimed experts respected throughout the community, the book is clearly divided into sections on fundamental and applied surface organometallic chemistry. Backed by numerous examples from the recent literature, this is a key reference for all chemist
New diruthenium acetylide donor complexes for bulk-heterojunction solar cells
No full textConjugated polymers and oligomers have received a lot of attention as active materials for organic photovoltaic devices because of their potential for the development of plastic solar cells that are lightweight, flexible, and low cost. Bulk heterojunctions fabricated by blending polymers with fullerene derivative have resulted in great improvements in the polymer photovoltaic cell efficiencies.
The most commonly used materials are poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) [1], these cells with optimized device structure and fabbrication conditions can reach efficiencies in the range of 5-5.5%.
However, to produce highly efficient organic photovoltaic devices, it is necessary to extend the light absorption into the near-infrared region and at the same time preserve the high IPCE and open-circuit voltage.
Several papers have been recently dedicated to the investigation of the use of conjugated polymers incorporating heavy atoms; in particular Pt acetylide polymers as donors in solar cells using PCBM as acceptor [2] were proposed as a tool to enhance charge photogeneration. For instance, Mei et al. reported on a Pt acetylide-based polymer using a 2,1,3-benzothiadiazole (BTD) acceptor moiety flanked on either side by 2,5-thienyl (Th) donor units ([-Pt(L2)-t-Th-BTD-Th-t-]n, where L = PBu3), which absorbs strongly throughout the visible region. [3]
The use of Ru acetylides is a novel interesting tool for the design of donor materials [4] to combine with electron-withdrawing fullerides in bulk heterojunction solar cells.
New dinuclear Ru(II) complexes where two Ru atoms are separated by a bridge consisting of a 2,1,3 benzothiadiazole acceptor moiety flanked on either side by 2,5-thienyl or 3-hexyl substituted 2, 5 thienyl donor units were synthesized. (Figure 1)
These rather simple complexes appears to behave as a photoactive donor when blended with a fullerene as acceptor, thus being a first step toward novel bulk heterojunction solar cells, based on Ru donor systems
Figure 1
1. F. Padinger, R. S. Rittberger, N. S Sariciftci, Adv. Funct. Mater, 13 (2003) 85–88.
2. W.-Y. Wong, C.-L. Ho, Acc. Chem. Res. 43 (2010) 1246.
3. J.Mei, et al. Appl. Mater. Interfaces 1 (2009) 150.
4. A. Colombo, C. Dragonetti, D. Roberto, R. Ugo, L. Falciola, S. Luzzati, and D. Kotowski Organometallics (2011) doi: 10.1021om100846
Surface-mediated organometallic synthesis: the role of the oxidation state and of ancillary ligands in the high-yield and selective syntheses of platinum carbonyl dianions [Pt3(CO)6]n 2- (n = 6, 5, 4, 3) by reductive carbonylation under mild conditions and in the presence of surface basicity of various silica-supported Pt(IV) or Pt(II) compounds.
No full textThe reductive carbonylation under 1 atm of CO and in the presence of surface basicity of silica-supported Na-2[PtCl6], K-2[PtCl4], [Pt(CH3CN)(2)Cl-2], or [Pt(COD)Cl-2] (COD = cis,cis-1,5-cyclooctadiene) leads to the formation in high yields of platinum carbonyl dianionic clusters [Pt-3(CO)(6)](n)(2-) (n = 6, 5, 4, 3). Remarkably the silica surface plays a key role in these reductive carbonylations since no carbonyl cluster is obtained by reductive carbonylation of solid Na-2[PtCl6] in the absence of silica. The selectivity of the reaction can be easily tuned by controlling the surface metal loading, the basicity of the surface, and the nature of the platinum precursor (platinum oxidation state and nature of the coordination sphere). In particular, the one-step silica-mediated synthesis of [Pt-18(CO)(36)](2-) from K-2[PtCl4] (90% yield) is very convenient when compared to the traditional synthesis in methanol solution (67% yield), which requires two steps: (i) formation of [Pt-12(CO)(24)](2-) and (ii) addition of Na-2[PtCl6] drop by drop (molar ratio [Pt-12(CO)(24)](2-):Na-2[PtCl6] = 1:1) under a flow of CO
Surface mediated organometallic synthesis: Formation of [H5Os10(CO)(24)](-) by hydrogenation of silica-supported [Os(CO)(3)(OH)(2)](n) as a springboard for a high-yield synthesis of [H4Os10(CO)(24)](2-) starting from alpha-[Os(CO)(3)Cl-2](2) and working in ethylene glycol solution
No full textNew high yield routes to the high nuclearity hydrido carbonyl clusters [H5OS10(CO)24]- and [H4OS10(CO)24]2-, model systems for the chemisorption of CO and H2 on metal surfaces, are reported. [H5OS10(CO)24]- is obtained in good yields by hydrogenation (1 atm) at 200°C of physisorbed [Os(CO)3(OH)2]n whereas in refluxing ethylene glycol solution, that is less acidic than the silica surface, [H4OS10(CO)24]2- is obtained in high yield start-ing from [Os(CO)3(OH)2]n or, more conveniently, from α-[Os(CO)3Cl2]2 in the presence of the stoichiometric amount of sodium carbonate. The quantitative equilibrium [H4OS10(CO)24]2- +OH-⇄+H+ [H5OS10(CO)24]- is confirmed
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
The sulphonated nature of the ligand as origin of the "triflate effect" on the NLO properties of [ZnY2L2] (L = 4-trans-NC5H4(CHCH)C6H4NMe2) complexes
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