1,720,972 research outputs found
Synthese en karakterisering van arylsystemen : stille-chemie toegepast op de koppeling van pyrrool-, thiofeen-, benzeen- en etheenderivaten
No full textA mild and convenient method for the preparation of multi-isocyanates starting from primary amines
No full textA mild and convenient method for the synthesis and isolation of multi-isocyanates, obtained from the reaction of the corresponding primary amines with di-t-butyltricarbonate (1) is described
Synthesis and Characterization of axially chiral molecules containing dendritic substituents
No full textEnantiomerically pure, axially chiral (S)-1,1'-bi-2-naphthol was used as a core material to which Frechet-type dendritic wedges of the 0th up to the 4th generation were attached, yielding the axially chiral dendrimers. The chiroptical features of these compds. were studied and revealed an increasing molar optical activity for higher generations of dendrimers. This effect can be explained by a larger torsional angle between the naphthyl units, caused by steric repulsions between the dendritic wedges. However, the effect is marginal, indicating a high degree of flexibility present in the axially chiral dendrimer
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Chiral dendrimers with backfolding wedges
No full textDendritic wedges with a substitution pattern that forces the growth inwards are introduced and the use of this new building strategy is exemplified in the synthesis and chiroptical properties of a chiral dendrime
Fast and convenient construction of carbamate/urea-based dendrimers by making use of a diisocyanate building block
No full textA novel, fast, and simple synthetic procedure for polycarbamate/urea dendrimers, based on an AB-CD2 coupling strategy, is presented. The reactivity difference of the two isocyanate functionalities of the AB building block allows the construction of these dendrimers without the necessity of activation or deprotection steps. This makes it possible to construct dendrimers within 2-3 days, even the largest dendrimers. The resulting dendrimers could be fully characterized by 13C NMR, IR spectroscopy, and mass spectrometry. The synthetic strategy necessitates only techniques such as stirring, heating, and accurate dosing, and there is no workup required for the purification of the compounds. On account of a wide variety of polyols, amines, and aminoalcohols, this new procedure is not limited to the synthetic strategy followed but allows the incorporation of a large variety of functional molecules in the core, in the branching units, or at the end groups. The method is even applicable when organometallic species are incorporated into the dendritic structure, thereby showing its versatility. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3112-3120, 200
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