1,720,993 research outputs found
An iron(II) complex of trans, trans, trans-bis(azido)bis(4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole): insight into molecular and supramolecular structures using hirshfeld surface analysis and DFT studies
No full textThe solvothermal synthesis and structural characterization of the new high-spin iron(II) complex trans,trans,trans-[bis(azido)bis(4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole)iron(II)] is reported. The complex crystallizes in the triclinic space group Pī with Z = 1, a = 6.6648(3) Å, b = 8.4012(3) Å, c = 11.7970(5) Å, α = 85.063(2)°, β = 95.063(2)°, γ = 98.5080(10)°. It is centrosymmetric with mutually trans pairs of azido, pyridyl and triazole N atoms, the Fe–N distances indicate a high-spin configuration. A combination of N–H···N hydrogen bonds and π···π stacking interactions generates a sheet structure in which the shortest Fe···Fe distance is 6.6648(3) Å. Hirshfeld surface analysis has been performed for visualizing, exploring and quantifying intermolecular interactions that stabilize the crystal packing of the complex. Non-covalent interactions present in the crystal structure have also been analysed by means of computational tools. The interaction energies associated with the different interaction topologies were calculated and QTAIM and NBO analyses were applied to study the origin and nature of the attractive forces.Fil: Setifi, Zouaoui. Université Ferhat Abbas; ArgeliaFil: Setifi, Fatima. Université Ferhat Abbas; ArgeliaFil: Glidewell, Christopher. University of St. Andrews; Reino UnidoFil: Gil, Diego Mauricio. Universidad Nacional de Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria; ArgentinaFil: Kletskov, Alexey V.. University of Russia; RusiaFil: Echeverria, Jorge. Universidad de Barcelona; EspañaFil: Mirzaei, Masoud. University of Mashhad; Irá
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
A combined experimental, Hirshfeld surface analysis, and theoretical study on fac-[tri(azido)(tris(2-pyridyl)amine)iron(III)]
No full textA novel Fe(III) complex with the general formula [Fe(tpa)(N3)3] (1) (tpa = tris(2-pyridyl)amine), has been prepared by solvothermal synthesis and characterized by standard spectroscopic and analytical methods to determine its composition. Crystal structure analysis at 170 K shows that the tris(2-pyridyl)amine ligand is coordinated in tridentate fashion via the pyridyl N atoms and the complex as a whole has approximate threefold rotational symmetry: the Fe–N distances indicate that the metal centre adopts a low-spin configuration at 170 K. A combination of two C-H···N hydrogen bonds and two azido···π(pyridyl) interactions link the molecules into a continuous three-dimensional array. An analysis of the complex total energy evaluated the preference of the high-, intermediate- and low-spin complexes. DFT calculations showed that the high-spin complex is the least energetic of the three possible spin states. The Quantum Theory of Atoms In Molecules (QTAIM), Reduced Density Gradient (RDG), and Natural Bond Orbitals (NBO) analysis showed an azido···azido interactions cooperatively assisted by weak hydrogen bonds and lone-pair···π interactions between N3– and the pyridine fragment from the tris(2-pyridyl)amine ligand. The amine and N3– arrange to bear a caged anion. The azido···azido interaction nature can be related to the donation from the N lone-pair to the π* of the opposite anion.Fil: Setifi, Zouaoui. Université 20 Août 1955-Skikda; Argelia. Université Ferhat Abbas Sétif 1; ArgeliaFil: Cubillán, Néstor. Universidad del Atlántico; ColombiaFil: Glidewell, Christopher. University of St. Andrews; Reino UnidoFil: Gil, Diego Mauricio. Universidad Nacional de Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Orgánica; ArgentinaFil: Torabi, Elham. Ferdowsi University Of Mashhad; IránFil: Morales Toyo, Miguel. Universidad Central del Este; República DominicanaFil: Dege, Necmi. Ondokuz Mayıs University; TurquíaFil: Setifi, Fatima. Université Ferhat Abbas Sétif 1; ArgeliaFil: Mirzaei, Masoud. Ferdowsi University Of Mashhad; Irá
Functional ligand designs for the elaboration of magnetic networks based on iron, cobalt or rare earth ions
No full textL’objectif de cette thèse porte sur la conception de nouveaux composés de coordination à partir de ligands imidazolium fonctionnalisés par différentes fonctions de coordination ou de ligands dérivés du motif 1,2,4-triazole et de cations de transition tels que les ions Fe2+ ou Co2+ ou d’ions lanthanides tels que les ions Dy3+. Le but de ces associations est de générer des réseaux fonctionnels pouvant présenter des propriétés magnétiques voire de luminescence. Plusieurs méthodes de synthèse ont été utilisées pour obtenir ces composés : méthode solvothermale, méthode de diffusion ou encore modification post-synthèse lorsque les méthodes directes ne marchaient pas. La mise en oeuvre de ces différentes méthodologies a permis d’obtenir plusieurs composés qui ont été caractérisés structuralement, spectrocopiquement et magnétiquement en exploitant différentes techniques telles que la diffraction de rayons X, la spectroscopie infrarouge et UV-Visible, la microscopie électronique à balayage, les analyses thermiques et élémentaires ou encore la spectroscopie de photoélectrons et la magnétométrie à SQUID.The aim of this thesis is to progress in the design of new coordination networks using imidazolium ligands functionalized with different coordination functions or ligands based on 1,2,4-triazole and transition metals such as Fe2+ or Co2+ or lanthanide ions such as Dy3+. The goal is to generate magnetic and even luminescent networks. Several synthesis strategies have been used to obtain these compounds : solvothermal and non-solvothermal reactions and post-synthesis modifications when direct reactions were not efficient. The use of these strategies has led to several compounds for which structural characterization have been performed using X ray diffraction. Analysis such as infrared and UV-Visible spectroscopies, scanning electronic microscope, thermal and elementary analysis end even X-ray photoelectron spectroscopy as well as SQUID magnetometry have been carried out to fully characterized all these compounds
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Synthèse, structures et propriétés physiques de matériaux moléculaires conducteurs et magnétiques
No full textCe travail concerne la synthèse, les études structurales par diffraction des rayons X et l'étude des propriétés électriques et magnétiques de matériaux moléculaires à propriétés multiples, associant en particulier conductivité électrique et interactions magnétiques. Ces composés sont formés de donneurs organiques dérivés du tétrathiafulvalène (TTF) ou du tétrathiapentalène (TTP) et de complexes anioniques d'ions de transition. Afin d'établir des interactions entre les électrons mobiles de la partie organique conductrice et les spins localisés de la partie inorganique paramagnétique, trois types de stratégies sont étudiés (i) l'utilisation de donneurs fonctionnalisés, (ii) l'utilisation d'anion dont les ligands possèdent des systèmes pi et (iii) la synthèse de nouveaux complexes de coordination où les systèmes conducteurs et magnétiques sont liés par un pont conjugué.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF
- …
