1,720,961 research outputs found
Nylon nanofibrous membrane for mediated glucose biosensing
No full textThis work illustrates how polyamide nanofibrous membranes, prepared by the electrospinning process, can act as a new type of biosensor element. The sensing unit is based on a glassy carbon electrode coated with polyamide nanofibrous membranes, in which glucose oxidase is covalently tethered. The work is carried out by means of transient electrochemical techniques, such as cyclic voltammetry and amperometry, in which ferrocene methanol was employed as mediator. The results show that nanofibrous membranes are an excellent support for the development of biosensors thanks to their high-surface to volume ratio, high porosity and permeability of the cosubstrate and minimal effect on both the biocatalytic kinetics and the selectivity of the biorecognition event. The optimization, characterization, and attractive performance of the nanofibrous biosensor are reported in connection with the detection of glucose in a variety of food beverages
Carbon nanotube-adsorbed electrospun nanofibrous membranes as coating for electrochemical sensors for sulfhydryl compounds
No full textA new method to modify electrodes with carbon nanotubes (CNT) was developed. Multiwalled carbon nanotubes (MWNT) were adsorbed on the electrospun nylon-6 nanofibrous membranes (Ny-6-NFM) and used as a coating to modify conventional glassy carbon electrodes. The modified electrode was designed for the amperometric detection of sulfhydryl compounds with the potential held at +0.3 V vs. Ag/AgCl. The modified electrode showed a linear response for cysteine up to 0.4 mM (R2=0.997), with a sensitivity of 5.1 μA/mM and a detection limit of 15 μM. Other sulfhydryl compounds showed similar results. After use, the Ny-6-NFM was easily peeled off, leaving the bare electrode surface back to its original electrochemical behaviour. This is the first attempt to use a disposable membrane functionalized with MWNT for electroanalytical purposes
Biocatalytic nylon nanofibrous membrane
No full textNylon-6 nanofibrous membranes (NFM) have
been prepared, characterized and used to build-up electrochemical biosensing devices. The assembly and the functioning of biocatalytic NFM are described in connection with the physical and the covalent immobilization of glucose oxidase for the detection of glucose. Effects of the
enzyme loading, the mediator, the pH, the surface acidity and the kinetic of the catalysis have been thoroughly investigated. The results show that NFM allow the binding of proteins without the need for the hydrolysis step, in contrast to the nylon film. Furthermore, the high surface-tovolume ratio of the NFM allow superior loading of the enzyme with respect to thin film technology. The immobilization step does not affect the permeability of the coating
to the mediator used. These results give evidence that NFM are a promising and inexpensive coating for a novel electrochemical transducer
Nylon Nanofibrous Biosensors for Glucose Determination
No full textNanofibrous membranes have been produced by electrospinning to develop first generation glucose biosensors. The direct immobilization of glucose oxidase onto the polyamide nanofibrous surfaces by drop coating revealed a simple and efficient method for the development of sensitive, stable, and reproducible electrochemical biosensors. The biosensor showed a linear response over the range 1 – 9X10-3 glucose (R-2=0.9997) with a sensitivity of 1.11 muA/mM and a limit of detection of 2.5X10-6 M (S/N=3). The uncertainty of repeatability was 2% (RSD%, n=30). After one month of storage, the signal decreased of 35%. The recovery of glucose, evaluated in real samples of honey, was 98% (RSD%=1%, n=3)
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
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