1,720,975 research outputs found
Colorimetric andfluorescence“turn-on”recognition offluoride by a maleonitrile-based uranyl salen-complex
No full textThe synthesis and characterization of two new uranyl-salen complexes, 1e2, based on a 1,2-diaminomaleonitrile unit, is described. Spectroscopic studies to evaluate their potential as colorimetric
probes forfluoride detection in chloroform and dichloromethane were undertaken. Compound 2 exhibits a‘turn-on’ response characterized by a naked-eye colorimetric change for the selective recognition of
fluoride in both solvents. DFT calculations show that the stabilization energy for the formation of the host:guest complex follows the trend F>Cl>Br hence supporting the experimental data
Fluoride binding in water with the use of micellar nanodevices based on salophen complexes
Full text linkThe use of micelles to transpose lipophilic receptors, such as uranyl-salophen complexes, into an aqueous environment is a valuable and versatile tool. Receptor 1 incorporated into CTABr micelles forms a supramolecular system that exhibits excellent binding properties towards fluoride in water, despite the competition of the aqueous medium. To fully evaluate the potential of micellar nanodevices, we extended our previous study to other types of surfactants and to a uranyl-salophen receptor with a more extended aromatic surface. Paramagnetic relaxation enhancement experiments were used to obtain information on the location of the two receptors within the micelles and complementary information was obtained from dynamic light scattering experiments. With these data it is possible to account for the key factors necessary to obtain an efficient supramolecular device for anion binding 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
Development and physico-chemical characterization of supramolecular systems for anion recognition in aqueous media
No full textAnion recognition is a topical area of research warranted by the potential applications of anion receptors in environmental and biological monitoring. Anions are indeed widespread in nature, are involved in many biochemical processes and are also major aqueous pollutants. Molecular receptors able to recognize anions with high affinity and selectivity in organic solvents are well documented in the literature but only few systems are efficient in aqueous media. Water is undeniably a particularly challenging solvent to work with due to the competition of water in the recognition process. Moreover, most of the receptors that are known to bind anions with high affinity and selectivity in organic solvents are not soluble in water. One strategy used to make hydrophobic molecular receptors “water-compatible” is micellar incorporation. This strategy is straightforward as no synthetic modifications of the receptor are required and has furthermore been seen to enhance the apparent properties, in particular binding properties, of the receptors. Following previous work undertaken in the laboratory, this thesis was devoted to the study of the micellar incorporation of different anion receptors. The first part of this thesis focused on the potential of Nuclear Magnetic Resonance (NMR) and more precisely Paramagnetic Relaxation Enhancement (PRE) experiments to provide robust information on the localisation of receptors within micelles. We studied the effect of various parameters and were able to rationalize the effect of the nature and concentration of the counterion and of the surfactant concentration on the PRE values obtained with cationic cetyltrimetylammonium (CTAX) micelles. By applying a normalization procedure we were then able to compare different receptor/micelle systems. This work has been reported in the Journal of Physical Chemistry (“Paramagnetic Relaxation Enhancement Experiments: a Valuable Tool for the Characterization of Micellar Nanodevices”, F. Keymeulen, P. De Bernardin, A. Dalla Cort, and K. Bartik, J. Phys. Chem. B, 2013, 117, 11654–11659).The second part of our work consisted in the study of the role played by the surfactant on the efficiency of the supramolecular system formed. Using UV-vis and/or NMR titrations, we studied the impact of the nature of the surfactant (cationic, zwitterionic or neutral) as well as its concentration on the apparent binding affinity for fluoride of two uranyl-salophen receptors. We showed that the supramolecular systems formed with cationic micelles are the most efficient, due to the favourable electrostatic interaction between the positively charged micelle and the fluoride despite the competition of the surfactant counter-ion. The concentration of the cationic surfactant does however have an impact as the apparent affinity decreases with surfactant concentration as a consequence of this non-specific interaction of the guest with the micelles. PRE and DLS (Dynamic Light Scattering) experiments allowed us to better understand the differences between the different types of micelles. This work has been reported in Organic & Biomolecular Chemistry (“Fluoride binding in water with the use of micellar nanodevices based on salophen complexes”, F. Keymeulen, P. De Bernardin, I. Giannicchi, L. Galantini, K. Bartik, and A. Dalla Cort, Org. Biomol. Chem. 2015, 13, 2437–2443).The final part of our study was devoted to the investigation of the applicability of micellar incorporation to other receptors. Two other uranyl-based receptors were studied in cationic CTAX and neutral Triton X-100 micelles. One suffered from chemical stability issues and the other receptor did not perform any better than the ones previously studied. We also studied trimesitylborane which can bind fluoride via Lewis acid-base interactions. This system, which is highly efficient in organic solvents, was shown to be ineffective once incorporated into micelles, probably because the change in the hybridization of the boron atom upon fluoride binding is not favourable in the confined micellar environment. Indolocarbazole-based anion receptors, which recognize acetate and benzoate via hydrogen bonding, were successfully incorporated into DPC micelles, albeit at low concentrations, and were observed to be efficient as the apparent binding affinity measured in water is of the same order of magnitude or higher as the one observed in organic solvents.Doctorat en Sciences de l'ingénieur et technologieinfo:eu-repo/semantics/nonPublishe
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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