1,720,980 research outputs found
Transient-doped organic electrochemical transistors working in current-enhancing mode as sensing devices for low concentration of oxygen dissolved in solution
Full text linkDissolved oxygen in cell culture media represents an interesting parameter worth monitoring, especially at very low concentrations. Indeed, cells grow faster and live longer in hypoxic conditions, and recent studies relate stronger tumor malignancy, recurrence, and progression with reduced oxygen levels. Standard techniques for dissolved oxygen evaluation rely either on optical investigations or on electrochemical methods. The former requires complex protocols and expensive instrumentations, while for the latter, the presence of a silver/silver chloride electrode hinders the device miniaturization and induces cytotoxic effects. In this work, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (Pedot:Pss)-based Organic Electrochemical Transistors (OECTs) are presented as dissolved oxygen sensors. The catalytic activity of the Pedot chains is exploited for the transduction since oxygen reduction reactions, occurring at the polymer/electrolyte interface, induce Pedot:Pss to switch from the less conductive neutral state (off) to the more conductive oxidized one (on). This transient-doping effect enhances OECT current output, which presents a high signal to noise ratio (i.e., >102-103). The transistor architecture allows for high output/input signal power amplification (i.e., >15 dB-22 dB) and excellent sensitivities [328 ± 11 mV/dec and -0.38 ± 0.02 mA/dec for transfer and Ids(t), respectively], together with a low detection limit (0.9 μM, which represents the 0.07% of oxygen partial pressure). Finally, the here reported OECT sensors are demonstrated to work also in a real-life complex biological environment. This work paves the way for reliable, real-time oxygen monitoring in in vitro cell cultures for various relevant applications, such as investigating the influence of hypoxia conditions on cell lines or tumors
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
Organic Mixed Ionic Electronic Conductor Nanochannels for Vertical Electrochemical and Ionic Transistors
Full text linkThin films of organic mixed ionic electronic conductors (OMIECs) constitute the functional layer in organic electrochemical transistors (OECTs), organic bioelectronic transducers and other ionic-electronic devices. The thin-film configuration constrains devices to be fabricated on impermeable substrates in the form of 2D microstructures with lateral electrodes to drive an electronic current through the thin film. In order to alleviate such constraints, novel OMIEC deposition methods are needed that produce alternatives to thin-film devices and that are compatible with permeable substrates and electronic transport in the vertical direction. Here OMIECs filled nanoporous membranes are introduced as functional layer in devices with mixed ionic electronic transport. Electropolymerization of ethylenedioxythiophene (EDOT) monomers is used to fabricate OMIEC filled nanochannels. Electronic and ionic transport through such nanochannels are investigated and modulation of electronic as well as ionic carrier density by action of a third gate electrode is demonstrated. The novel OMIEC nanochannels enable the fabrication of vertical OECTs with high transconductance and organic ionic transistors using only additive fabrication methods.A method is developed to electropolymerize PEDOT based organic mixed ionic electronic conductors into the nanochannels of tracketched membranes. Gated electronic and ionic transport through the membranes is investigated. The results demonstrate that the method gives access to high transconductance vertical OECTs fabricated without photolithography and to novel ionic transistors. imag
Textile sensors platform for the selective and simultaneous detection of chloride ion and pH in sweat
Full text linkThe development of wearable sensors, in particular fully-textile ones, is one of the most interesting open challenges in bioelectronics. Several and significant steps forward have been taken in the last decade in order to achieve a compact, lightweight, cost-effective, and easy to wear platform for healthcare and sport activities real-time monitoring. We have developed a fully textile, multi-thread biosensing platform that can detect different bioanalytes simultaneously without interference, and, as an example, we propose it for testing chloride ions (Cl−) concentration and pH level. The textile sensors are simple threads, based on natural and synthetic fibers, coated with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and properly functionalized with either a nano-composite material or a chemical sensitive dye to obtain Cl− and pH selective sensing functionality, respectively. The single-thread sensors show excellent sensitivity, reproducibility, selectivity, long term stability and the ability to work with small volumes of solution. The performance of the developed textile devices is demonstrated both in buffer solution and in artificial human perspiration to perform on-demand and point-of-care epidermal fluids analysis. The possibility to easily knit or sew the thread sensors into fabrics opens up a new vision for a textile wearable multi-sensing platform achievable in the near future
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