1,721,022 research outputs found
Thermodynamics beyond dilute solution theory: Steric effects and electrowetting
No full textHere, we address the impact that steric models, introducing finite ion size effects, have on the contact angle for charged
surfaces. We review the two most common steric models, namely the excluded volume (commonly referred to as the
Bikerman model) and the Carnahan-Starling (CS) models. We clarify the thermodynamics of the solid–liquid electrolyte
interface and show that the common case of an electrolyte reservoir characterized by bulk ion concentrations corresponds to
the thermodynamics of the grand potential with fixed ionic chemical potentials. The grand potential gives distinctly different
interfacial energies compared to the free energy, which corresponds to a finite number of ions in an electrolyte solution
(relevant in nanofluidics, for instance). Steric models may be applied to either thermodynamic scenario, and applications to
electrowetting are shown under the grand potential (large droplets with a bulk reservoir in the center). When sufficiently large
potentials are applied to conducting electrodes, the steric models, unlike the classical point charge model, introduce ion
specificity into the electrowetting contact angle via finite ion sizes, which introduces an asymmetry in the contact angle at
positive and negative potentials. For electrowetting on dielectrics (EWOD), the theoretical contact angles match experimental
values well until electrode potentials of 240 V, with CS performing better than Bikerman. We hypothesize that contact angle
saturation at 240 V may arise due to a switch in the thermodynamics of the solid–liquid interfacial energy from grand
potential (bulk reservoir) to free energy (finite ion number) conditions, capping the formation of a counterion adsorption
layer at the electrode surface
Blistering at the solid-liquid interface: The graphite case-study
No full textThe mechanical swelling of a sample surface, which produces bubbles having different dimensions (from the sub-micrometer
up to some tens of micrometer), is termed as blistering. This phenomenon was historically considered as a detriment of the
sample surface, while, more recently, it turned out to be a model system for testing the mechanical properties of confined 3D
objects. In particular, the development of blisters underneath a single layer of atoms (such as graphene) is crucial for the
investigation of permeability of ultrathin sheets. In the variety of materials well-documented in the scientific literature, we
present and discuss the specific case study of blister evolution on the basal plane of graphite, when the crystal undergoes an
ion-intercalation during the oxidation process. Our choice is motivated by the importance of investigating graphite in an
electrolytic environment, because of its electrochemical/mechanical performances that can be exploited in many applications: as an electrode in electrochemical cells, batteries, fuel-cells, but also, as a layered-crystal, in procedures for graphene
production. More generally, the ion intercalation in graphite represents a model system to understand the mechanisms at
molecular length-scale of the insertion of molecules inside a stratified crystal. This process, driven by electrochemistry, can be
followed mainly by investigating the solid-liquid interface. Otherwise, investigating the graphite at the end of the intercalation process after emersion outside of the electrolyte leads to the observation of many residues from the solution on the
graphite surface, which perturb the true morphology of blisters. In this case, rinsing the graphite surface with water would be
even more perturbing, since additional chemical reactions and phenomena would alter both the chemical status and
morphology of the intercalated electrode
Intercalation of graphite in Li-ion batteries: In situ microscopic characterization of the solid-electrolyte interface (SEI)
No full textEnergy storage technologies are crucial in the next green-energy transition. In particular, Li-ion batteries (LIBs) are nowadays
the reference technology for many applications including, in particular, the forthcoming electrical mobility. In the last years,
the deep investigation of the plethora of complex phenomena controlling the charge storage mechanism in LIBs allowed
a considerable improvement in LIBs performance. In this regard, in situ analysis played a fundamental role in the
comprehension of the degradation processes occurring at the electrode/electrolyte interface. In particular, in situ electro chemical atomic force microscopy (EC-AFM), consisting in high-resolution microscopy under electrochemical control,
uniquely allowed to monitor the evolution in morphology and mechanical properties of the solid-electrolyte interface (SEI)
forming at low potential on the graphitic anodic electrodes of LIBs. In this work, we employed in situ EC-AFM measurements
and ex situ ToF-SIMS analysis as representative techniques to provide a comprehensive morphological and compositional
overview of the SEI film formed under cyclic voltammetry experiments. The work aims to provide guidelines in the SEI
evolution when highly oriented pyrolytic graphite (HOPG), which can be considered a model electrode, is employed. The
reported in situ data are in agreement with current interpretative models. The ex situ ToF-SIMS analysis discloses a film
composition where different Li compounds are uniformly distributed on the electrode surfac
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
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