124,892 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Synthesis of Water-soluble Triazole Ligands and Application of Their Metal Complexes in Biphasic Hydrogenations of C=C and C=O
No full textAbstract:
Homogenous catalysis is a powerful tool for organic synthesis but its success in industrial application is limited because of difficult catalyst separation and reuse. To overcome these issues, the use of biphasic catalysis is at present of great interest because the catalyst is confined in one of the two-phases and the product in the other phase allowing for a prompt recovery of the product and an easy recycle of the catalyst. In particular, the development of water soluble catalysts for aqueous/organic biphasic reactions is increasingly attractive [1]. Our research group has been involved in the synthesis of triazolyl ligands by taking advantage of the copper-catalyzed azide-alkyne [3+2] cyclization [2]. Recently, we have synthesized a small library of N-N or N-S ligands which have been employed in Suzuki-Miyaura reactions [3,4]. In this work, we wish to present our studies on biphasic (water/toluene) catalytic hydrogenation of C=O and C=C (Schemes 3 & 4) double bonds using a water soluble triazole ligand in combination with Ruthenium and Iridium.
[1] (a) Cornils B.; Herrmann W. A.; Horvath I. T.; Leitner W.; Mecking S.; Olivier-Bourbigou H.; Vogt (Eds.) D. Multiphase Homogeneous Catalysis, Wiley-VCH, Weinheim, 2005. (b) Joo F. Aqueous Organometallic Catalysis, Kluwer Acad. Publ. Dordrecht, 2001. [2] V. V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem., Int. Ed. 2002, 41, 2596. [3] Amadio E.; Scrivanti A.; Chessa G.; Matteoli U.; Beghetto V.; Bertoldini M.; Rancan M.; Venzo A.; Bertani R. J. Org. Chem. 2012, 716, 193. [4] Amadio E.; Bertoldini M.; Scrivanti A.; Chessa G.; Beghetto V.; Matteoli U.; Bertani R.; Dolmella A. Inorg. Chim. Acta 2011, 370, 388
Differential time course of the response to axotomy induced by cut or crush in the leech AP cell.
No full textComplessi di Pd(0) contenenti leganti imino-fosfinici come catalizzatori per la alcossicarbonilazione di alchini terminali
No full textInactivation kinetics of voltage-gated calcium channels in glutamatergic neurons are influenced by SNAP-25
No full textSNAP-25 forms part of the SNARE core complex that mediates membrane fusion. Biochemical and electrophysiological evidence supports an accessory role for SNAP-25 in interacting with voltage-gated calcium channels (VGCCs) to modulate channel activity. We recently reported that endogenous SNAP-25 negatively regulates VGCC activity in glutamatergic neurons from rat hippocampal cultures by shifting the voltage-dependence of inactivation of the predominant P/Q-type channel current in these cells. In the present study, we extend these findings by investigating the effect that manipulating endogenous SNAP-25 expression has on the inactivation kinetics of VGCC current in both glutamatergic and GABAergic cells recorded from 9-13 DIV cultures. Silencing SNAP-25 in glutamatergic neurons significantly slowed the inactivation rate of P/Q-type VGCC current whereas alterations in SNAP-25 expression did not alter inactivation rates in GABAergic neurons. These results indicate that endogenous SNAP-25 plays an important role in P/Q-type channel regulation in glutamatergic neurons
Complessi di Pd(0) contenenti leganti imino-fosfinici come catalizzatori per la reazione di Stille
No full textMechanistic Study on the Cross-Coupling of Alkynyl Stannanes with Aryl Iodides catalyzed by η2-(Dimethyl Fumarate)Palladium(0) Complexes with Iminophosphine Ligands
No full textThe reactions of [Pd(η2-dmfu)(P–N)] [dmfu = dimethyl fumarate; P–N = 2-(PPh2)C6H4-1-CH
NR, R = C6H4OMe-4
(1a), CHMe2 (2a)] and [Pd(η2-dmfu)(P–N)2] with IC6H4CF3-4, ISnBu3 and PhC CSnBu3 have been studied under
pseudo-first-order conditions. The oxidative addition of IC6H4CF3-4 yields [PdI(C6H4CF3-4)(P–N)] (1b or 2b). No
reaction takes place with PhC CSnBu3 and also with ISnBu3 in the presence of an excess of PhC CSnBu3. In the
presence of fumaronitrile (fn), 1b and 2b undergo transmetalation by PhC CSnBu3 followed by fast reductive
elimination to yield [Pd(η2-fn)(P–N)]. The same reaction sequence occurs for the system [PdI(C6H4CF3-4)(P–N)]/P–N
(1 : 1 molar ratio) to give [Pd(η2-fn)(P–N)2]. The palladium(0) complexes are active catalysts in the cross-coupling
of PhC CSnBu3 with aryl iodides ArI (Ar = C6H4CF3-4, Ph). The catalytic efficiency depends on the complex:
[Pd(η2-dmfu)(P–N)2] > [Pd(η2-dmfu)(P–N)], and on the substituent R: C6H4OMe-4 > CHMe2. The reactivity and
spectroscopic data suggest a catalytic cycle involving initial oxidative addition of ArI to a palladium(0) species,
followed by transmetalation of the product and by fast reductive elimination to regenerate the starting palladium(0)
compound. For [Pd(η2-dmfu)(P–N)] as catalyst, the oxidative addition is the rate-determining step, while for
[Pd(η2-dmfu)(P–N)2] the oxidative addition and the transmetalation steps occur at comparable rate
Reazioni di 'cross coupling' di alchinilstannani con alogenuri arilici catalizzate da complessi imminofosfinici di palladio(0)
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