1,721,006 research outputs found
Flexible and Ultrathin Metal-Oxide Films for Multiresonance-Based Sensors in Plastic Optical Fibers
No full textWe have exploited a laser-based integration process of ultrathin metal-oxide (MO) films to improve the plasmonic effect in sensors based on D-shaped plastic optical fibers (POFs). More specifically, using ultrathin MO films, the performances of the surface plasmon resonance (SPR) phenomenon improve and a lossy mode resonance (LMR) can occur. Although the role of this kind of materials has been already presented, when they are deposited as overlayer (upside the thin metal film), we have used a different approach by depositing MOs, especially zirconium oxide (ZrO2) and titanium oxide (TiO2), as flexible intermediate layers between the exposed core of POFs and the gold film. The MO layer is prepared from sol-gel solution, and deep-UV laser curing allows us to densify the thin film and tune the refractive index, with a room-temperature process fully compatible with the flexible polymer substrates. In a preliminary step, we have carried out numerical results, based on transfer matrix formalism, to predict the SPR response. Subsequently, we have experimentally characterized the developed sensor configurations. Numerical and experimental results have shown above all an enhancement of the sensor performances, in terms of SPR sensitivity, with respect to a reference sensor based on a polymer instead of MOs. Moreover, in some proposed sensor configurations, together with the SPR phenomenon, an LMR phenomenon was observed. It occurred in a different wavelength range, for a typical refractive index range present when considering receptors for biochemical sensing applications. Therefore, both resonances (SPR and LMR) could be used in several application fields
In situ synthesis of molecularly imprinted polymers by near-field photopolymerization for ultrasensitive PFOA plasmonic plastic fiber optic sensors
No full textPer- and polyfluoroalkylated substances (PFAS), in particular perfluorooctanoic acid (PFOA), are persistent environmental pollutants that constitute major health risks due to their toxicity and bioaccumulation potential. Their detection is therefore a crucial and immediate challenge. This study presents an innovative nanofabrication approach for preparing highly sensitive sensors to detect PFOA. This approach is based on molecularly imprinted polymers (MIPs) obtained by near-field photopolymerization (NFPP). These MIPs are grafted onto a gold-coated plastic optical fiber (POF), thanks to near-field light enhancement by surface plasmon resonance (SPR). This approach enables nanoscale functionalization of POFs by MIPs, promoting accessibility to specific sites and optimizing coupling with surface plasmon. By adjusting the thickness of the MIPs through light irradiation, scalable limits of detection (LOD) from 53 aM to 6.3 pM were obtained, enabling coverage of concentrations ranging from attomolar to nanomolar scales, with a response time of only 10 min. POF@MIP sensors also show excellent selectivity, with no response in the presence of two analogues even at concentrations 100 times higher than that of PFOA. This PFAS sensor, exploiting SPR, is the first to achieve an LOD in the attomolar range, paving the way for advanced monitoring of these environmental contaminants
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Soft molecularly imprinted nanoparticles with simultaneous lossy mode and surface plasmon multi-resonances for femtomolar sensing of serum transferrin protein
No full textThe simultaneous interrogation of both lossy mode (LMR) and surface plasmon (SPR) resonances was herein exploited for the first time to devise a sensor in combination with soft molecularly imprinting of nanoparticles (nanoMIPs), specifically entailed of the selectivity towards the protein biomarker human serum transferrin (HTR). Two distinct metal-oxide bilayers, i.e. TiO2–ZrO2 and ZrO2–TiO2, were used in the SPR–LMR sensing platforms. The responses to binding of the target protein HTR of both sensing configurations (TiO2–ZrO2–Au-nanoMIPs, ZrO2–TiO2–Au-nanoMIPs) showed femtomolar HTR detection, LODs of tens of fM and KDapp ~ 30 fM. Selectivity for HTR was demonstrated. The SPR interrogation was more efficient for the ZrO2–TiO2–Au-nanoMIPs configuration (sensitivity at low concentrations, S = 0.108 nm/fM) than for the TiO2–ZrO2–Au-nanoMIPs one (S = 0.061 nm/fM); while LMR was more efficient for TiO2–ZrO2–Au-nanoMIPs (S = 0.396 nm/fM) than for ZrO2–TiO2–Au-nanoMIPs (S = 0.177 nm/fM). The simultaneous resonance monitoring is advantageous for point of care determinations, both in terms of measurement’s redundancy, that enables the cross-control of the measure and the optimization of the detection, by exploiting the individual characteristics of each resonance
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Sensing Approaches Exploiting Molecularly Imprinted Nanoparticles and Lossy Mode Resonance in Polymer Optical Fibers
No full textIn this work, two different lossy mode resonance (LMR) platforms based on plastic optical fibers (POFs) are developed and tested in a biochemical sensing scenario. The LMR platforms are based on the combination of two metal oxides (MOs), i.e., zirconium oxide (ZrO2) and titanium oxide (TiO2), and deposited on the exposed core of D-shaped POF chips. More specifically, two experimental sensor configurations were obtained by swapping the mutual position of the Mos films over to the core of the D-shaped POF probe. The POF–LMR sensors were first characterized as refractometers, proving the bulk sensitivities. Then, both the POF–LMR platforms were functionalized using molecularly imprinted nanoparticles (nanoMIPs) specific for human transferrin (HTR) in order to carry out binding tests. The achieved results report a bulk sensitivity equal to about 148 nm/RIU in the best sensor configuration, namely the POF-TiO2-ZrO2. In contrast, both optical configurations combined with nanoMIPs showed an ultra-low detection limit (fM), demonstrating excellent efficiency of the used receptor (nanoMIPs) and paving the way to disposable POF–LMR biochemical sensors that are easy-to-use, low-cost, and highly sensitive
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