1,721,038 research outputs found
On-chip food safety monitoring: multi-analyte screening with imaging surface plasmon resonance-based biosensor
No full textFood safety is an increasing health concern, recognised and promoted by many institutions across the globe. Food products can be contaminated with pathogenic microorganisms, environmental pollutants, veterinary drug residues, allergens and toxins. Public health concerns which have been raised in relation to hazardous agents found in food include, among others, increased cancer risk, endocrine, reproductive and neurobehavioral systems disruption, teratogenesis, antibiotic resistance and even death in cases of allergic reactions and acute poisoning. Some of the food hazardous agents (e.g. pathogenic microorganisms and toxins) can even be used as biological warfare, spread through food and agricultural chains. Thus, an adequate detection of these compounds is also important for biosecurity. In order to safeguard consumers’ health, legislations have been put in place both in the US and the EU. These laws specify for each health threatening compound the maximal acceptable amounts in different food products. Besides health issues, food safety and quality has an economical impact on the food industry, where quality control expenses amount to about 1.5 – 2 % of the total sales. Since more and more food products nowadays contain multiple and processed ingredients, which are often shipped from different parts of the world, and share common production lines and storage spaces, food safety and quality monitoring becomes a challenging task. Traditional analytical methods require dedicated laboratories, equipment and highly trained personnel for detection and identification of each type of hazardous agent (e.g. antibiotics, bacteria, allergens). These techniques are also time-consuming and often expensive. There is a growing need for multi-analyte screening methods, which will enable rapid and simultaneous detection of multiple compounds in complex food samples. In recent years, biosensors have been applied successfully to food analysis, incorporating the same bioassay principals as traditional methods with transducers (optical, electrochemical, etc) in novel, usually miniaturized, integrated analytical devices. However, most of these biosensors still lack the desired level of the multiplexicity. Recent developments in the field of Surface Plasmon Resonance (SPR) technology in the direction of high-throughput systems and multi-analyte measurements present a promising alternative for the existing systems. One of such systems is imaging SPR (iSPR); it enables real-time and label free read-out of spatially modified surfaces (e.g. microarrays). The aim of this study was to develop an iSPR–based biosensor, for simultaneous and quantitative detection of different health-threatening compounds in food. To obtain a comprehensive overview on the analytical applicability of such a system, several points were addressed. The intrinsic sensor properties, such as optical sensitivity and robustness, of the iSPR instrument were studied. Further on, both direct and competitive immunoassay formats for high and low molecular weight compounds detection using the iSPR platform were evaluated. Then, the iSPR-based biosensor was applied for detection of regulated substances in food such as antibiotic residues in milk and allergens in cookies and chocolates. Finally, the most common drawback of using SPR for screening in complex biological matrices, the nonspecific binding to the sensor chip surface, was tackled. The sensitivity of both high and low molecular weight compounds was proven to be sufficient for some of the hazardous agents detection at the maximum residue levels, established in the EU legislation, as was demonstrated by simultaneous detection of seven antibiotic residues in milk and twelve allergens in cookies and dark chocolates. The analysis time takes about 10 minutes and provides quantitative information on multiple targets, producing a fingerprint (allergenic fingerprint for instance) of the tested food. This detailed food profile contributes to the decision making process on the quality and safety of foods, basing it on the total picture of all target compounds present. In order for iSPR-based biosensing to reach its full potential and to become a widely applied routine analytical tool, the instrumental cost needs to be reduced and the analysis further simplified, becoming cost-effective and approachable to non-trained personnel. An additional drawback in analytical applications of a SPR sensor is the nonspecific binding of the matrix components of complex samples to the sensor surface. Many assays based on SPR fail due to inapplicability to measure in “real” samples. As a possible solution to this problem, sensor chip surface engineering was suggested in this thesis. A nanopatterned filter layer covering the sensor chip surface was found to be effective in reducing nonspecific binding when the measurements were performed in “raw” samples by keeping the non-soluble aggregates and big sample matrix components beyond the sensing region of the SPR. With respect to other existing biosensors, iSPR still lags behind in terms of sensitivity and portability. In summary, the results of this study demonstrate that iSPR-based biosensor is a versatile platform, which can be applied for a wide variety of fundamentally different analytes and offers several advantages over already existing methods. SPR detection principle eliminates the need in labelling and the instrumental set-up allows automated analysis. High multiplexing capabilities and short measurement times are obtained with no need for complex and time consuming sample preparation steps. By using iSPR-based biosensor, one can obtain robust and quantitative information on the target analyte concentration, in real time and with high specificity (or broad spectrum, depending on the assay). In conclusion, on-chip screening using iSPR, described here, presents a powerful analytical approach towards food safety and quality monitoring which satisfies the current need in rapid and multi-analytical devices. <br/
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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