1,720,990 research outputs found
From Au11 to Au13: Tailored Synthesis of Superatomic Di-NHC/PPh3-Stabilized Molecular Gold Nanoclusters
Full text linkHerein, we report a new method to synthesize molecular gold nanoclusters (AuNCs) stabilized by phosphine (PR3) and di-N-heterocyclic carbene (di-NHC) ligands. The interaction of di-NHC gold(I) complexes, with the general formula [(di-NHC)Au2Cl2] with well-known [Au11(PPh3)8Cl2]Cl clusters provides three new classes of AuNCs through a controllable reaction sequence. The synthesis involves an initial ligand metathesis reaction to produce [Au11(di-NHC)(PPh3)6Cl2]+ (type 1 clusters), followed by a thermally induced rearrangement/metal complex addition with the formation of Au13 clusters [Au13(di-NHC)2(PPh3)4Cl4]+ (type 2 clusters). Finally, an additional metathesis process yields [Au13(di-NHC)3(PPh3)3Cl3]2+ (type 3 clusters). The electronic and steric properties of the employed di-NHC ligand affect the product distribution, leading to the isolation and full characterization of different clusters as the main product. A type 3 cluster has been also structurally characterized and was preliminarily found to be strongly emissive in solution
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
Tailoring thermally activated delayed fluorescence emitters for efficient electrochemiluminescence with tripropylamine as coreactant
No full textUsing a unified metal-free procedure, a selection of Thermally Activated Delayed Fluorescence (TADF) emitters has been synthesized and characterized. Different acceptor and donor moieties have been explored in order to develop red emitting dyes with reduction potentials suitable for the application in ECL using tri-propylamine as coreactant. The most promising compound shows terephthalonitrile as the acceptor and diphenylamines as donors, and it displayed an ECL efficiency that is double the one of the standard [Ru(bpy)3](PF6)2. Based on such findings, a novel water-soluble TADF emitter (Na4[4DPASO3TPN]) has been synthesized and characterized to enable electrochemiluminescence in an aqueous medium
Comparative Evaluation of Intestinal Absorption and Functional Value of Iron Dietary Supplements and Drug with Different Delivery Systems
Full text linkIron is a fundament micronutrient, whose homeostasis is strictly regulated. Iron deficiency anemia is among the most widespread nutritional deficiencies and its therapy, based on dietary supplement and drugs, may lead to severe side effects. With the aim of improving iron bioavailability while reducing iron oral therapy side effects, novel dietary supplements based on innovative technologies-microencapsulation, liposomes, sucrosomes-have been produced and marketed. In the present work, six iron dietary supplements for different therapeutic targets were compared in terms of bioaccessibility, bioavailability, and safety by using an integrated in vitro approach. For general-purpose iron supplements, ME + VitC (microencapsulated) showed a fast, burst intestinal iron absorption kinetic, which maintained iron bioavailability and ferritin expression constant over time. SS + VitC (sucrosomes), on the other side, showed a slower, time-dependent iron absorption and ferritin expression trend. ME + Folate (microencapsulated) showed a behavior similar to that of ME + VitC, albeit with a lower bioavailability. Among pediatric iron supplements, a time-dependent bioavailability increase was observed for LS (liposome), while PIC (polydextrose-iron complex) bioavailability is severely limited by its poor bioaccessibility. Finally, except for SS + VitC, no adverse effects on intestinal mucosa vitality and barrier integrity were observed. Considering obtained results and the different therapeutic targets, microencapsulation-based formulations are endowed with better performance compared to the other formulations. Furthermore, performances of microencapsulated products were obtained with a lower iron daily dose, limiting the potential onset of side effects
Use of a mixed cationic-reverse phase column for analyzing small highly polar metabolic markers in biological fluids for multiclass lc-hrms method
Full text linkThe determination of small highly polar metabolites at low concentrations is challenging when reverse-phase (RP) chromatography is used for multiclass analysis. A mixed cationic-RP column coupled to high-resolution tandem MS (HR-MS/MS) was tested for highly polar compounds in biological fluids, i.e., trimethylamine N-oxide (TMAO) and the isobaric molecules beta-methylamino-L-alanine (BMAA) and 2,4-diaminobutyric acid (DAB). The efficient retention and separation of the above compounds were obtained with common and MS-friendly RP conditions, reaching high selectivity and sensitivity. The method was firstly assessed in plasma and urine, showing good linearity in the range 50–1000 μg/L and 500–10,000 μg/L for TMAO and both BMAA and DAB, respectively. Excellent precision (RDS < 3%) and good accuracies (71–85%) were observed except for BMAA in plasma, whose experimental conditions should be specifically optimized. Preliminary tests performed on compounds with biological relevance and a wider range of polarities proved the effectiveness of this chromatographic solution, allowing the simultaneous analysis of a larger panel of metabolites, from very small and polar compounds, like trimethylamine, to quite lipophilic molecules, such as corticosterone. The proposed LC-HRMS protocol is an excellent alternative to hydrophilic interaction liquid chromatography and ion-pairing RP chromatography, thus providing another friendly analytical tool for metabolomics
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
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