124,777 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
From the Pharmacophore to the Homology Model of the Benzodiazepine Receptor: The Indolyglyoxylamides Affair
No full textInteraction between the so-called benzodiazepine receptor (BzR) and the chemically heterogeneous class of its ligands is still one of the most challenging objects of theoretical studies. In the mid-90s our group began to collaborate with Prof. Antonio Da Settimo and coworkers to a project of synthesis and biological evaluation of indolylglyoxylamides designed as BzR ligands. Herein we review our efforts in designing these compounds and in interpreting their structure-affinity relationships. Our investigations were carried out for years by adopting the pharmacophore/topological model for BzR ligands set up by Cook's group. In an attempt to rationalize some puzzling structure-affinity relationships we speculated in 1998 that our ligands interact with the BzR by assuming one of two alternative binding modes (called "A" and "B") depending on whether or not they were substituted at the 5-position of the indole nucleus. Such a model received support from a considerable amount of experimental data accumulated throughout our researches. About a decade later, docking calculations performed on a homology-built model of the α 1 BzR subtype were found in agreement with the hypothesis of mode A and mode B of binding accessible to 5-H and, respectively, 5-Cl/NO 2 indole derivatives. © 2012 Bentham Science Publishers
Natural and synthetic geiparvarins are strong and selective MAO-B inhibitors. Synthesis and SAR studies.
No full textNatural geiparvarin 1 and a number of its analogues were prepared and tested as inhibitors of both monoamine oxidase isoforms, MAO-B and MAO-A. The desmethyl congener 6 of geiparvarin, proved potent and selective MAO-B inhibitor (pIC(50)=7.55 vs 4.62). X-ray crystallography and molecular modelling studies helped the understanding of the observed structure-activity relationships
Selective Internal Radiotherapy (SIRT) Using Resin Yttrium-90 Microspheres for Chemotherapy-Refractory Metastatic Colorectal Cancer: An Italian Cost-Effectiveness Analysis
No full textDispelling 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
On the reactivity of nitrosoimidazoles with acids (the Cusmano-Ruccia reaction): a continuous source of new ring- into-ring interconversion
No full textAn extension of the ‘Cusmano–Ruccia’ reaction is reported. 6-(4-chlorophenyl)-3-methyl-5-nitrosoimi-dazo[2,1-b]oxazole by the action of hydrochloric acid gives 3-(4-chlorobenzoyl)-5-methyl-1,2,4-oxadiaz-ole (13); presumably via ammonium ion, CO2 and methanol elimination. The relevance of the nature of the atom of the B-ring linked to C-2 of the imidazole for the occurrence of the ring-into-ring interconver-sion has been once more confirmed
A novel approach to the evaluation of the importance of steric and electronic effects in SNAr reactions: a computational, thermodynamic and 1H and 13C NMR study of "Meisenheimer-type" adducts in the benzo[b]thiophene series
No full textThe synthetically useful nucleophilic attack on nitrobenzo[b]thiophenes, a starting point for ring-opening/ring-closure pathways to different heterocyclic systems, has been investigated in detail. 3-Nitrobenzo[b]thiophene (9) and 2 nitrobenzo[b]thiophene (10) react with sodium methoxide in either DMSO or methanol to give the relevant “Meisenheimer-type” adducts 9’ and 10’, identified by NMR spectroscopy. A UV study indicated that the equilibrium constants for the formation of 9’ at 293 K are 10.1 and 40700 Lmol–1 in methanol and in DMSO, respectively. Competition reactions showed that the stability constant of 10’ is lower than that of 9’: accordingly, DFT [B3LYP/6-31+G(d,p)] calculations indicate that the formation of 9’ is thermodynamically more favoured than that of 10’ both in the gas phase and in DMSO. The reason for the opposite sequence in the stability constants previously found for the corresponding gem-dimethoxy Meisenheimer adducts 7’ and 8’ was therefore investigated in depth and appears to be a consequence of different steric interactions in the starting compounds, 2-methoxy-3-nitro- (7) and 3-methoxy-2-nitrobenzo[b]thiophene (8), respectively. A study of 13C NMR chemical shift changes accompanying the formation of adducts 9’ and 10’ confirms that the formation of the adduct exhibiting the larger stability constant is accompanied by a smaller π electron density redistribution, as we have previously found in other cases all governed by electronic effects. The opposite behaviour is observed in the formation of the gem-dimethoxy adducts 7’ and 8’, which is a consequence of the predominance of steric effects. Further outcomes of more general interest deal with the aromatic character of benzo[b]thiophenes. NMR spectroscopic data and calculated bond lengths show that in the studied reactions the benzene ring, unlike the thiophene one, is scarcely affected by methoxide addition, retaining its nearly “full” aromatic character. Benzocondensation increases the stability constants of σ-adducts mainly because of a marked reduction in the aromatic character of the thiophene ring in the substrates
Reazioni di interconversione di anello. Sintesi e reattività di Z-2,4-dinitrofenilidrazone del 5-ammino-3-benzoil-1,2,4-ossadiazolo
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