1,720,960 research outputs found
Enhancing the reactivity of clean, defect-free epitaxial graphene by the substrate-Experiment and theory
No full textExperimental and theoretical evidence is presented that a sulfur compound dissociates on clean, defect-free epitaxial graphene (Gr) in ultrahigh vacuum (UHV). Together with density functional theory calculations (DFT), experimental kinetics and spectroscopic data suggest an auto-(/self)catalytic process. The results could open a pathway to a carbocatalyst. While adsorbing H2S in UHV at low temperatures on single-layer graphene/ruthenium (Gr/Ru), H-2 desorbs and sulfur remains on the surface. Vacancy and grain boundary defects, respectively, can be excluded as active sites. DFT results indicate the importance of the Ru(0001) support in facilitating a reaction pathway with small activation energy for H2S dissociation. Gr becomes reactive due to a complex interplay of structural and electronic effects, including the corrugation of the graphene layer and the hybridization of ruthenium's d orbital with antibonding states of H2S
Quantum-Mechanically Enhanced Water Flow in Subnanometer Carbon Nanotubes
Full text linkWater flow in carbon nanotubes (CNTs) starkly contradicts classical fluid mechanics, with permeabilities that can exceed no-slip Haagen-Poiseuille predictions by 2-5 orders of magnitude. Semiclassical molecular dynamics accounts for enhanced flow rates that are attributed to curvature-dependent lattice mismatch. However, the steeper permeability enhancement observed experimentally at about nanometer-size radii remains poorly understood, and suggests emergence of puzzling nonclassical mechanisms. Here, we address water-CNT friction from a quantum mechanical perspective, in terms of water-energy loss upon phonon excitation. We find that combined weak water-phonon coupling and selection rules hinder water-CNT scattering, providing effective protection to water super flow, whereas comparison with a semiclassical theory evidences a friction increase that can exceed the quantum mechanical prediction by more than 2 orders of magnitude. Quasi-frictionless flow up to subnanometer CNTs opens new pathways toward minimally invasive trans-membrane cellular injections, single-water fluidics, and efficient water filtration
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
One-step approach to Quaternary (B, N, P, S)-Doped hierarchical porous carbon derived from Quercus Brantii for highly selective and efficient CO2 Capture: A combined experimental and extensive DFT study
No full textRecently, the enhancement of atmospheric carbon dioxide (CO2) concentration has a negative impact on the environment and human health. Adsorption is well recognized as a promising technology to control CO2 emission in which the design of an optimum adsorbent is one of the most critical challenges. In this article, multiheteroatoms doped porous carbons have been successfully derived from Quercus Brantii by one-step doping-activation to investigate the textural characteristics and heteroatoms doping effects on CO2 capture application. Based on the physicochemical properties of the adsorbents, which were characterized using varied techniques (FE-SEM, EDS, HR-TEM, XRD, FT-IR, XPS, BET, and BJH), the introduction of heteroatoms provides more active sites in carbon networks and develops the porous architecture of each activated carbon, resulting in diverse CO2 capture performances. The low content of phosphorus (P) incorporated in P-doped activated carbon (PAC) perfected the performance of CO2 capture to reach a high uptake (7.13 mmol g-1 at 1 bar and 20 degrees C) on a heterogeneous surface. Apart from the high equilibrium and dynamic CO2 uptake, these Quercus Brantii-based carbonaceous adsorbents present superior CO2 selectivity over N2, CH4, and H2, prominent cyclic regeneration capacity, high turnover frequency (TOF) and turnover number (TON) for commercial scale as well as fast kinetic adsorption. The density functional theory (DFT) method was performed to reveal the adsorption mechanisms as well as electronic properties of the systems
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
Investigating the effect of PDA/KH550 dual functionalized h-BCN nanosheets and hybrided with ZnO on corrosion and fouling resistance of epoxy coating: Experimental and DFT studies
No full textIn this work, two-dimensional hexagonal boron carbonitride nanosheets co-functionalized with polydopamine (PDA) and 3-aminopropyltriethoxysilane (KH550) (abbreviated as Fh-BCNNS) are introduced as nanofillers for promoting the fouling and physical barrier resistance of solvent-based epoxy coatings. The material characterization conducted with X-ray techniques of photoelectron spectroscopy and diffraction as well as Brunauer-Emmett-Teller confirm that the synthesized h-BCNNS has 353 m(2)/g specific surface area with microporous structure, while field emission scanning electron microscopy and Fourier transform infrared spectroscopy indicate that the co-functionalization is successfully achieved. After dispersing the Fh-BCNNS in the epoxy matrix at 0.3, 0.6, and 1.0 wt% followed by mixing with the curing agent, the coating is applied by a spray method on the steel surface. The data derived by electrochemical impedance spectroscopy show that the optimum corrosion resistant properties is achieved by loading 0.6 wt% Fh-BCNNS, and the coating resistance of the optimized nanocomposite is 3.7 x 10(7 )and 2.85 x (10)(6)omega.cm(2) after immersion in the corrosive electrolyte of 3.5 wt% NaCl aqueous solution for 1 day and 28 days, respectively. Furthermore, density functional theory (DFT) alongside the experimental investigations proves the mechanisms involved in corrosion protection properties through considering interactions and electronic properties. For EP/Fh-BCNNS@F-ZnO nanohybrid, the value of Z(f)= 0.01 Hz of EP/Fh-BCNNS@F-ZnO hybrids after 1 day and 4 weeks of immersion, are 9 x 10(7) and 3.3 x 10(7) omega.cm(2) which are two order of magnitude higher than EP/Fh-BCNNS. According to anti-fouling results, the growth rate of algae is less than 10% for the EP/Fh-BCNNS@F-ZnO sample and between 30% and 60% for the control sample (EP/Fh-BCNNS at 0.6 wt%) after 28 days of immersion
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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