1,721,016 research outputs found
Nanoscale heterogeneity at the aqueous electrolyte–electrode interface
No full textUsing molecular dynamics simulations, we reveal emergent properties of hydrated electrode interfaces that while molecular in origin are integral to the behavior of the system across long times scales and large length scales. Specifically, we describe the impact of a disordered and slowly evolving adsorbed layer of water on the molecular structure and dynamics of the electrolyte solution adjacent to it. Generically, we find that densities and mobilities of both water and dissolved ions are spatially heterogeneous in the plane parallel to the electrode over nanosecond timescales. These and other recent results are analyzed in the context of available experimental literature from surface science and electrochemistry. We speculate on the implications of this emerging microscopic picture on the catalytic proficiency of hydrated electrodes, offering a new direction for study in heterogeneous catalysis at the nanoscale
The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like
Full text linkWith molecular simulation for water and a tunable hydrophobic substrate, we apply the instantaneous interface construction [A. P. Willard and D. Chandler, “Instantaneous liquid interfaces,” J. Phys. Chem. B114, 1954–1958 (2010)] to examine the similarity between a water-vapor interface and a water-hydrophobic surface interface. We show that attractive interactions between a hydrophobic surface and water affect capillary wave fluctuations of the instantaneous liquid interface, but these attractive interactions have essentially no effect on the intrinsic interface. The intrinsic interface refers to molecular structure in terms of distances from the instantaneous interface. Further, the intrinsic interface of liquid water and a hydrophobic substrate differs little from that of water and its vapor. The same is not true, we show, for an interface between water and a hydrophilic substrate. In that case, strong directional substrate-water interactions disrupt the liquid-vapor-like interfacial hydrogen bonding network.United States. Dept. of Energy. Office of Science (Contract DE-AC02-05CH11231
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
A Model of Charge-Transfer Excitons: Diffusion, Spin Dynamics, and Magnetic Field Effects
No full textIn this Letter, we explore how the microscopic dynamics of charge-transfer (CT) excitons are influenced by the presence of an external magnetic field in disordered molecular semiconductors. This influence is driven by the dynamic interplay between the spin and spatial degrees of freedom of the electron-hole pair. To account for this interplay, we have developed a numerical framework that combines a traditional model of quantum spin dynamics with a stochastic coarse-grained model of charge transport. This combination provides a general and efficient methodology for simulating the effects of magnetic field on CT state dynamics, therefore providing a basis for revealing the microscopic origin of experimentally observed magnetic field effects. We demonstrate that simulations carried out on our model are capable of reproducing experimental results as well as generating theoretical predictions related to the efficiency of organic electronic materials.Massachusetts Institute of Technology. Department of Chemistr
Characterizing Hydration Properties Based on the Orientational Structure of Interfacial Water Molecules
No full textIn this work, we present a general computational method for characterizing the molecular structure of liquid water interfaces as sampled from atomistic simulations. With this method, the interfacial structure is quantified based on the statistical analysis of the orientational configurations of interfacial water molecules. The method can be applied to generate position dependent maps of the hydration properties of heterogeneous surfaces. We present an application to the characterization of surface hydrophobicity, which we use to analyze simulations of a hydrated protein. We demonstrate that this approach is capable of revealing microscopic details of the collective dynamics of a protein hydration shell
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
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