1,721,219 research outputs found
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
Insights into the Hydration Layer of Reduced Graphene Oxides: A Computational Study
Full text linkReduced graphene oxide (rGO) has emerged as a versatile material with diverse applications, particularly in aqueous environments. Understanding its interactions with water molecules is crucial for various fields, ranging from energy storage to sensing. In this study, we investigate the behavior of graphene and rGO in water, focusing on elucidating their wetting properties and the influence of oxygen-containing functional groups. Through extensive molecular dynamics simulations, we analyze the orientation and electrostatic dipole of water molecules near the rGO interface, revealing a direct correlation between rGO hydrophilicity and oxidation level. Specifically, we observe stronger hydrogen bonding networks near higher coverage rGO monolayers, indicating enhanced hydrophilicity. Furthermore, by studying water confined between rGO layers, we find uniform water transport with lateral self-diffusion coefficients comparable to bulk water, highlighting the potential of rGO membranes in various applications. Our findings provide insights into the atomic-scale interactions governing rGO-water interfaces, paving the way for the rational design of graphene-based materials for application in aqueous environments
Unravelling electrocatalytic properties of metal porphyrin-like complexes hosted in graphene matrices
No full textCarbon-based materials are a promising class of catalysts for oxygen and carbon dioxide reduction reactions to value-added chemicals. Here we study the electrocatalytic properties of nitrogen doped graphene structures hosting four pyrrolic rings able to coordinate metal ions in a porphyrin-like configuration. The analysis is carried out by means of density functional theory (DFT) with hybrid functionals, employed to estimate the overpotentials of oxygen reduction reaction to water and hydrogen peroxide, as well as carbon dioxide reduction to carbon monoxide and formic acid. The competing hydrogen evolution reaction is also studied. We predict that Co- and Mn-doped structures exhibit low overpotentials for oxygen reduction to water, with the concurrent suppression of hydrogen peroxide production in the Mn case. Carbon dioxide reduction to formic acid is instead favored by Ti and Mn doping with overpotentials lower than 1 V, while hydrogen evolution reaction is disfavored
Ab initio simulations of semiconductor surfaces and interfaces
No full textCalculations of the electronic properties of solids and surfaces span years of research activity and have produced an enormous amount of publications over the last decades. However, only recently have quantum simulations reached the degree of accuracy to be predictable against experimental data, and this is particularly true for systems with reduced periodicity, such as surfaces, interfaces, and nanostructures. In this review, we present a survey about the characterization of low-dimensional semiconductor-based systems by ab initio density functional methods and compare them with the experimental data available. Several computational issues afflict the description of the different systems; we will not enter into the details of the theoretical approach and of the very many refinements, which cover a broad chapter by themselves. Rather, a discriminating analysis of the single computational protocols to describe and complement specific experimental problems is presented. Prototypical examples that can be considered as templates for the specific problem, with particular emphasis on surface and interface effects, will be addressed
Gemcitabine plus Oxaliplatin Folinic Acid and 5-Fluorouracil in patients with advanced gastric cancer
No full textBACKGROUND AND AIMS:
oxaliplatin in combination with folinic acid (FA) and infusional 5-fluorouracil (5-FU) has shown significant anti-tumor activity in gastric cancer patients (FOLFOX). Previous studies have shown that gemcitabine (GEM), a new fluorinated anti-metabolite, enhances the individual anti-tumor activity of either 5-FU or oxaliplatin. We have therefore designed a multi-center phase II trial in order to test a novel GEM+FOLFOX-4 regimen in patients with metastatic gastric cancer.
METHODS:
we enrolled 36 patients, 28 males and 8 females, with an average age of 64.4 years (range 37-78), who received bi-weekly treatment with GEM (1,000 mg/m2 on day 1), levo-FA (100 mg/m2 on days 1 and 2), a 5-FU (400 mg/m2) bolus injection followed by 22-h continuous infusion (800 mg/m2) on days 1 and 2, and oxaliplatin 85 mg/m2 in a 4-6 h intravenous (i.v.) infusion before the second FUFA administration on day 2.
RESULTS:
the most frequent side effect was grade 1-2 hematological toxicity and late sensorial neurotoxicity. Two patients developed hypersensitivity to oxaliplatin while another developed an aseptic eosinophilic pneumonitis. Two patients refused to continue the treatment after two cycles of chemotherapy and were lost at the follow-up. Among the remaining 34 patients four achieved a complete response, 15 a partial response, 12 had a stable disease and three progressed.
CONCLUSIONS:
these results may grant the rationale to evaluate this multi-drug combination in randomized phase III trials in advanced gastric cancer
Molecular dynamics study of the pore formation in single layer graphene oxide by a thermal reduction process
Full text linkNanoporous graphene is considered the next-generation material for reverse osmosis water desalination providing both high water permeability and almost complete salt rejection. The main problem with graphene is the difficulty of synthesizing membranes with a consistent subnanometer pore size distribution. A recently proposed solution involves processing as-grown graphene oxide (GO) monolayersviaa mild temperature annealing pre-treatment causing GO functional groups to cluster into small oxidized islands. A following harsh thermal reduction process creates pores only in the small oxidized regions. However, a suitable relationship between the area of the GO islands and the pore dimension is still missing. Here, we study in detail the effects of such a thermal reduction process on the graphene oxide sheet by means of molecular dynamics simulations, particularly highlighting and analysing the process parameters affecting the final pore area. Besides proving that epoxides represent the most suitable functional group to induce carbon removal and, thus, pore generation in reduced GO, we find a twofold way to achieve control over the pore size: tuning the dimension and shape of the initial clustered GO areas or changing the harsh reduction process temperature. An accurate balance of these parameters consistently gives rise to targeted pore dimensions in graphene membranes
Controlled Pore Generation in Single-Layer Graphene Oxide for Membrane Desalination
Full text linkNanoporous graphene was proposed as an efficient material for reverse osmosis water desalination membranes because it allows water molecules to pass at high flux while rejecting hydrated salt ions. Nevertheless, from an experimental point of view it is still difficult to control the pore size. A scalable method to generate pores is urgently required for the diffusion of this technology. We propose, by theoretical calculations, an innovative and scalable strategy to better control the dimension of the pores in graphene-based membranes by reduction of single-layer graphene oxide (GO). The latter is first annealed at a controlled mild temperature to induce the aggregation of its randomly distributed oxygen-containing functional groups into small nanometric clusters. The layer then undergoes a high-temperature reducing treatment that causes the desorption of the functional groups along with carbon removal only in the oxidized areas, producing subnanometric pores while leaving unchanged the remaining pristine graphene areas
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
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