1,720,972 research outputs found
Recognition processes based on molecular cages and tripodal receptors
Full text linkQuesta tesi di dottorato riguarda la sintesi e lo studio di nuovi sistemi molecolari, tripodali e a forma di gabbia, adatti per il riconoscimento di specie ioniche in soluzione. Questi leganti, dotati di un’elevata preorganizzazione, presentano una maggiore selettività nel riconoscimento molecolare rispetto ai sistemi lineari. Il riconoscimento host:guest è basato su una sinergia di interazioni: elettrostatiche, legame a idrogeno e ad alogeno e coordinazione a centri metallici
Synthesis and study in solution of a new dansyl-modified azacryptand
Full text linkThe synthesis of a new asymmetric azacryptand (L1), characterized by three p-xylyl spacers, one of which carries a dansyl
side arm is reported. The fluorescent sensor has been studied by potentiometric, UV-Vis, and emission studies in MeOH: water 3 : 2 mixture
(0.07M NaNO3), determining, in particular, the protonation constants of the free ligand and metal ion complexation equilibria.
Interestingly, the obtained results revealed that the new receptor is fluorescent at neutral pH with a typical emission band of the
dansyl group. Metal addition induced a partial quenching of the dansyl emission band; this behavior is more pronounced with
Cu(II) that reduces the receptor’s emission by 60%. With all the studied cations, quenching follows the formation of a dimetallic
complex. Similar studies on the model compound L2 confirmed that fluorescence quenching ismainly driven by a static mechanism,
attributable to the formation of the inclusion dicopper complex [L1Cu2]4+. In order to test the stability of copper complexes under
physiological conditions, spectrofluorimetric titrations with Cu(II) were performed in water buffered at pH = 8 (HEPES 0.07 M)
and the values of binding constants, K11 and K12, were determined
Azacryptands as molecular cages for anions and metal ions
No full textThis is a short overview on azacryptands, as molecular receptors for cations and anions. A particular
attention was devoted to the results obtained by women researchers working in the field. The terms
‘cryptand’ and ‘cryptate’ were coined by Lehn. Since then, much work has been done to improve
the knowledge on this class of receptors. Small azacryptands, as free bases, were found to bind a
single metal ion within their cavities. When fully protonated, the same systems could also behave
as selective hosts for anions, through the cooperation of H-bonding and electrostatic interactions.
Proceeding to systems with larger cavities, the inclusion of two metal ions and a bridging anion
was possible, forming the so-called ‘cascade’ complexes. Azacryptates carrying fluorescent spacers
or exploiting the indicator displacement paradigm allowed the sensing of anionic species in water
at micromolar concentrations. Moreover, immobilisation on solid matrices and surfaces yielded
new materials for the solid-phase extraction of anionic pollutants and the construction of selective
electrodes for analytes in water
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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