1,720,973 research outputs found
Optical Detection of Antioxidant Capacity in Food Using Metal Nanoparticles Formation. Study on Saffron Constituents
Full text linkA simple metal nanoparticles (MNPs) based colorimetric assay for the antioxidant capacity of Saffron polyphenolics is proposed. The proposed method has been compared with the commonly used classical assays (FC and ABTS); a significant similar response trend was found with the ABTS. Additionally, it was also found that the proposed approach was polyphenols selective versus other endogenous antioxidants as safranal and crocin
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
Colorimetric determination of polyphenols via a gold nanoseeds–decorated polydopamine film
Full text linkA polystyrene ELISA plate (EP) modified with a thin film based on gold nanoseeds (AuSDs) assembled onto polydopamine (PDA) is proposed. The nanodecorated film (PDA@AuSD) allows to evaluate the polyphenols antioxidant capacity (AOC) through a colorimetric approach based on a seed-mediated growth strategy. Polyphenols, in the presence of the nanodecorated (PDA@AuSD) surfaces are able to drive an increase in size of the AuSDs according to their AOC; this produces an increase of the localized surface plasmon resonance (LSPR; maximum at λ ~ 550 nm) that is taken as analytical signal. The PDA@AuSD EP manufacturing shows good intraplates repeatability (RSD ≤ 6.6%, n = 96 wells) and interplates reproducibility (RSD ≤ 7.4%, n = 748 wells), resulting stable for 1 year. The AuSDs growth kinetic has been studied using 11 polyphenols belonging to different chemical classes and 4 different food samples. The PDA@AuSD film is able to return quantitative information on the AOC of food polyphenols. Good repeatability (RSD ≤ 5.7%, n = 12 EP wells) and reproducibility (RSD ≤ 8.1%, n = 12 EP wells) was achieved, with acceptable linear correlation coefficients (R2 ≥ 0.990) and useful limits of detection (LODs ≤ 2.5 10−5 mol L−1). The samples analyzed with the PDA@AuSD device have been successfully ordered according to their AOC in agreement with conventional optical methods. The PDA@AuSD plate allows multiple measurements (96 wells per EP) with a one-step strategy, overcoming the limitations related to the use of colloidal nanoparticles; in addition, since absorbance is measured after washing, it is not affected by sample color or turbidity. [Figure not available: see fulltext.
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
Single-Stroke Metal Nanoparticle Laser Scribing on Cellulosic Substrates for Colorimetric Paper-Based Device Development
No full textA straightforward CO2 laser-plotter-based technique to obtain different types of metal nanoparticles on paper is presented. This strategy allows the instantaneous laser-induced generation of metal nanoparticles (LIMs) anchored onto cellulosic substrates with micrometric resolution and customizable patterns; Au, Ag, Pt, Ni, and Cu LIMs have been obtained. LIM features were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. LIMs are plasmonic-active and characterized by colorimetric features consistent with nanostructure chemistry and density. Arrays of LIMs were assembled in two paper-based formats: (i) a nanocatalytic multimetal comb-shaped device to prove LIMs' remediation ability for the switch-off of organic dyes and (ii) a paper-based nano colorimetric LIM array challenged for peracetic acid (PAA) vapor sensing, useful in the area of environmental sanitization. LIM nanochemistry allows (i) rapid (<1 min) organic dye catalytic conversion and (ii) sensitive PAA detection (LOD <= 0.3 mu g mL(-1)) capable of discriminating PAA exposure levels from 0.5 to 60 mg m(-3). LIM-based devices returned reproducible data (RSD <= 15%, n = 3). Summing up, the proposed strategy is particularly prone to generate catalytic/sensing zones in tailored paper-based devices, resulting in a new sustainable nanopatterning technique appealing in the (bio)sensing and nanochemistry fields
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
Integrated cloverleaf-like paper-based analytical device for quantitative colorimetric sensing of maleic hydrazide
No full textPaper-based analytical devices (PADs) are becoming pivotal tools in the sensing field; however, the integration of molecularly imprinted polymers (MIPs) on them deserves further exploration to obtain all-in-one selective devices. Herein, a cloverleaf-like PAD integrating a MIP for the smartphone-based selective colorimetric determination of maleic hydrazide (MH), a widely used plant growth regulator, is proposed. The device encompasses the complete MH analysis in a 4-leaved format (4L-μMIP/PAD), where the μMIP is housed at the center and each leaf encloses an analytical step (i.e., sample excess removal, washing, analyte elution, and MH colorimetric detection). The μMIP was synthesized with a UV lamp on fiberglass, while the entire paper device was manufactured via laser plotter and wax printer. The μMIP displays an imprinting factor of 17 and was characterized via FTIR, SEM, and elemental mapping, resulting selective toward MH. The colorimetric sensing, integrated on the sensing leaf, was attempted on 13 different paper types. The final 4L-μMIP/PAD allows the selective MH determination in the range 5–60 mg kg−1 (R2 = 0.995; RSD ≤ 11 %, n = 3) with a LOD of 0.7 mg kg−1, meeting the requirements for MH analysis in samples at Maximal Residual Levels admitted by the law. The device ensures the complete MH analysis in 50 min, with 40 μL of sample, resulting stable and ready-for-use, for 1 month (RSD = 9 %). Eventually, the 4L-μMIP/PAD was successfully tested for MH analysis in garlic, onions, and carrots, obtaining recoveries between 89 % and 110 % and reproducible data (RSD ≤ 15 %, n = 3)
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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