1,721,009 research outputs found
Multinuclear and multifrequency NMR study of the interactions between Ln(III) ions complexes and fluoride anions
Full text linkSolution and Solid State NMR Approaches To Draw Iron Pathways in the Ferritin Nanocage
No full textIron pathways in ferriti
Mn(II)-Conjugated silica nanoparticles as potential MRI probes
No full textNovel Mn(II)-based nanoprobes were rationally designed as high contrast enhancing agents for magnetic resonance imaging (MRI) and obtained by anchoring a Mn(II)-CDTA derivative to the surface of organo-modified silica nanoparticles (SiNPs). Large payloads of paramagnetic metal-chelates have been immobilized on biocompatible SiNPs with spherical shape and narrow size distribution of 80-90 nm, resulting in a relaxivity gain of 250% at clinical fields (0.5 T) as compared to the free chelate. Such substantial efficacy enhancement of the nanoprobes is mainly attributed to the restriction of the rotational dynamics of the conjugated complex, as revealed by comprehensive 1H-NMR relaxometric investigations. The paramagnetic nanospheres exhibit good colloidal stability over time in biological matrices, allowing for MRI applications. High image contrast was found in T1w-MRI images collected at 1 T on phantoms containing relatively small amounts of contrast agent (CA), for which low cellular toxicity was observed on three different cell lines. Preliminary in vivo studies on healthy mice demonstrated the efficiency of the novel Mn-based silica nanoparticle as T1w-MRI probes, resulting in significant contrast enhancement in the liver. These findings demonstrate that these novel Mn-SiNPs are high efficacy CAs suitable for preclinical MRI applications
High resolution iron derivative of bullfrog M ferritin: structural insight into ferroxidase process
Full text link
Fluoride binding in unlikely partners: the formation of anion–anion complexes with [M(EGTA)]− and [M(OBETA)]− (M = Gd3+, Y3+)
No full textAnionic metal complexes (M = Gd3+, Y3+) with two homologous acyclic aminopolycarboxylate ligands, heptadentate (OBETA) and octadentate (EGTA), were prepared and characterized using both relaxometric NMR (for Gd3+) and high-resolution NMR (for Y3+) techniques. The addition of fluoride to aqueous solutions of these complexes led to the formation of ternary complexes where F− displaces a coordinated water molecule from the metal ion’s inner coordination sphere. In the Gd3+ complexes, this exchange process was tracked by monitoring changes in the nuclear magnetic relaxation rate of water protons, allowing calculation of the binding affinity. For the diamagnetic Y3+ complexes, the exchange was followed through variable-temperature high-resolution 19F NMR experiments. Calculated enthalpic and entropic contributions to the activation free energy suggest a dissociative exchange mechanism for the monohydrated [M(EGTA)(H2O)]− and an associative mechanism for the dihydrated [M(OBETA)(H2O)2]−. Additionally, an unusual dimeric structure was observed for the dihydrated complexes, where two anionic complexes are bridged by fluoride. Detailed DFT calculations confirmed the presence of the dimer, showing a Y–F bond length of 2.33 Å and a 1JY–F NMR coupling constant of 38.0 Hz, in excellent agreement with the experimental value
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
- …
