1,720,956 research outputs found
Synthonic Modeling of Quercetin and Its Hydrates: Explaining Crystallization Behavior in Terms of Molecular Conformation and Crystal Packing
No full textHydrated structures of a specific compound can often have different physiochemical properties compared to the anhydrous form. Therefore, being able to predict and understand these properties, especially the stability, is critical. In this study, quercetin, a flavonoid molecule, is modeled in three different states of hydration to gain an understanding of the effect of water molecules on the structure, packing, and conformation energetics of the three forms. Conformational analysis and modeling of intermolecular interactions (synthonic modeling) have been performed. It was found that in the anhydrous form hydrogen bonding is the strongest type of interaction, while in the two hydrate structures, the incorporation of water within the lattice leads to the formation of hydrogen bonds between the quercetin and water molecules. Within hydrates, quercetin molecules adopt a more planar conformation, which allows them to pack more closely by strong π-πstacking interactions, thus resulting in a higher relative stability. The modeling results highlight the importance of water in the stabilization of the lattice and explain the preferential nucleation of the dihydrate form. It is further demonstrated how synthonic modeling can be a predictive tool for the product's properties, leading to more efficient product design and faster development
Solid-State Characterization and Role of Solvent Molecules on the Crystal Structure, Packing, and Physiochemical Properties of Different Quercetin Solvates
No full textIn this work, a novel quercetin and dimethyl sulfoxide (DMSO) solvate (QDMSO) crystal structure was grown from a mixture of DMSO and water as solvent. Quercetin is a naturally occurring bioflavonoid widely used in the nutraceutical industry due to its many health benefits. Understanding quercetin solvates formation is essential for the design of novel particulate products with tailored quality attributes, including solubility, thermal resistance, and bioavailability. Here, the physiochemical properties and phase transitions of QDMSO were characterized by a wide range of experimental techniques, and the crystal structure, molecular packing, and intermolecular interactions (synthons) within the crystal lattice were modeled. Modeling and experimental results were compared to those of other known quercetin crystal structures, an anhydrous, a monohydrate, and a dihydrate form, to elucidate the role of the solvent molecules on the molecular packing and intermolecular interactions and, ultimately, on the physiochemical properties of each crystal form. It was found that in QDMSO, hydrogen bonds and dipole-dipole interactions had a greater contribution to the total lattice energy, and quercetin-solvent hydrogen bonds were stronger in energy compared to those of the other quercetin structures. These findings were used to explain the superior thermal stability of the QDMSO structure as well as its moisture-dependent behavior. This work demonstrates a coupled modeling and experimental methodology that relates intermolecular interactions and molecular packing in different solvated forms to physiochemical properties and can help in a better prediction and design of particulate products via the rational choice of the solid form
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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