1,720,972 research outputs found
Quantum Chemical Characterization of Structural Single Fe(II) Sites in MIL-Type Metal–Organic Frameworks for the Oxidation of Methane to Methanol and Ethane to Ethanol
No full textSingle
non-heme Fe(II) ions present as structural moieties in several
metal–organic frameworks (e.g., MIL-100, MIL-101, and MIL-808,
where MIL indicates Materials of Institute Lavoisier) are identified
by Kohn–Sham density functional calculations as promising catalysts
for C–H bond activation, with energetic barriers as low as
40 kJ mol–1 for ethane and 60 kJ mol–1 for methane following the oxidative activation of iron. The rate-determining
step is the activation of N2O and has a barrier of 140
kJ mol–1. Through consideration of the full reaction
profile leading to the corresponding alcohols, ethanol and methanol,
we have identified key changes in the chemical composition of the
node that would modulate catalytic activity. The thermal and chemical
stabilities of these materials, together with the scalability of their
syntheses, make them attractive catalysts for the selective low-temperature
conversion of light alkanes to higher-value oxygenates
Probing the relationship between silicalite-1 defects and polyol adsorption properties
No full textThe relationship between polyol adsorption affinity and silanol defect density was investigated through the development of vapor and aqueous adsorption isotherms on silicalite-1 materials which vary in structural and surface properties. Silicalite-1 crystals prepared through alkaline synthesis, alkaline synthesis with steaming post-treatment, and fluoride synthesis routes were confirmed as crystalline mordenite framework inverted (MFI) by SEM and XRD and were shown to contain ~8.5-0 silanol defects per unit cell by (29)Si MAS, (1)H MAS, and (1)H-(29)Si CPMAS NMR. A hysteresis in the Ar 87 K adsorption isotherm at 10(-3)P/P0 evolved with a decrease in silanol defects, and, through features in the XRD and (29)Si MAS NMR spectra, it is postulated that the hysteresis is the result of an orthorhombic-monoclinic symmetry shift with decreasing silanol defect density. Gravimetric and aqueous solution measurements reveal that propylene glycol adsorption at 333 K is promoted by silanol defects, with a maximum 20-fold increase observed for aqueous adsorption at ~10(-3) g/mL with an increase from ~0 to 8.5 silanols per unit cell. A comparison of vapor and aqueous propylene glycol adsorption isotherms on defect-free silicalite-1 at 333 K, both of which exhibit the Type-V character, indicates that water enhances adsorption by a factor of ~2 in the Henry's Law regime. Henry's constants for aqueous C2-C4 polyol adsorption (concentrations below 0.004 g/mL) at 298 K are shown to have a linear dependence on the silanol defect density, demonstrating that these molecules preferentially adsorb at silanol defects at dilute concentrations. This systematic study of polyol adsorption on silicalite-1 materials highlights the critical role of defects on adsorption of hydrophilic molecules and clearly details the effects of coadsorption of water, which can guide the selection of zeolites for separation of biomass-derived oxygenates.This material is based upon work supported in part by the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE SC0001004. Financial support for M.N. from the Aragon Government, ESF, and the Spanish Ministry of Education, Culture and Sport (FPU program and MAT2010-15870) is gratefully acknowledged. Partial support for this work was also provided by the National Science Foundation: CBET 0855863. We thank Professor Miguel Camblor for guidance on fluoride synthesis of defect-free silicalite-1. We acknowledge Dr. Sonjong Hwang at the Caltech Solid State NMR Facility for the NMR analyses.Peer reviewe
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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