1,720,975 research outputs found
A New Water-Soluble Calix[4]arene Ditopic Receptor Rigidified by Microsolvation: Acid-Base and Inclusion Properties
No full textThe coordination of a water molecule, bridging two distal phenolate anions of the tetrasulphonated calix[4]arene 1,3-dicarboxylic acid, has a remarkable influence on the acid base and inclusion properties of the ditopic receptor
Charge Assisted Hydrophobic Binding of Ethanol Into the Cavity of Calix[4]Arene Receptors in Aqueous Solution
No full textEthanol is included into the hydrophobic cavity of the water soluble calixarenes 1 and 2 in aqueous solution, with the alkyl residue pointing towards the cavity and the hydroxyl group facing the bulk of the solvent. No inclusion is detected for 3, and this suggests that the sulphonate groups serve as anchoring points
A New Chiral Rigid Cone Water Soluble Peptidocalix[4]arene and its Inclusion Complexes with a-Amino Acids and Aromatic Ammonium Cations
No full textA remarkable influence of the rigidity of the calix[4]arene platform in determining the recognition properties of mobile 2 and rigid cone 6 water soluble peptidocalix[4]arene receptors towards alpha-amino acids and aromatic quaternary ammonium cations has been foun
Water Soluble Calix[4]arenes. A Themodynamic Investigation of Proton Complex Formation
No full textThermodynamic parameters of protonation of calix[4]arene-p-tetra sulphonate were potentiometrically and calorimetrically determined in aqueous solution at 25 °C and I = 0.1 mol dm−3 (NaNO3). These values were compared with literature findings. ΔH° and ΔS° values reveal that the penta-anion protonation is energetically costly. In this connection the role played by hydrogen bonding and the cone conformation stabilization are critically discussed. Proton formation constants of the calix[4]arene-p-tetrasulphonate-tetra-carboxylate derivative in the cone conformation were also potentiometrically determined under the same experimental conditions
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
Inclusion of naturally occurring amino acids in water soluble calix[4]arenes: a microcalorimetric and 1HNMR investigation supported by molecular modeling
No full textThe thermodynamic parameters for the inclusion of some naturally occurring amino acids into a series of p-sulfonated calix[4]arenes, were determined via both H-1 NMR and calorimetric titrations in buffered aqueous solution at 25 degrees C. The calorimetric data show that inclusion is enthalpically driven in all cases, regardless of flexibility of the host and the nature of the guest. The most efficient receptor is the calix[4]arene tetrasulfonate 1, which exists in solution at pH 7 in a cone conformation, stiffened by H-bonding at the lower rim.
Molecular mechanics data help in the understanding of why some hosts do not form inclusion complexes at all. The comparison of our data with literature reports shows that there are dramatic buffer-dependent changes in the binding affinities
Synthesis of New Calixcrowns and their Anchoring to Silica Gel for the Selective Separation of Cs+ and K+
No full textNew 1,3-alternate calix[4]arenecrown-6 and calix[4]arene-crown-5, which are selective for caesium and potassium ions respectively, have been synthesized and linked covalently to silica gel via hydrosilanization and successfully employed for the chromatographic separation of Cs+ and K+ from alkali metal ions
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
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