1,720,984 research outputs found
Sviluppo e studio di biosensori sostenibili e performanti dedicati alla determinazione di composti nutraceutici e contaminanti di interesse agroalimentare
No full textThe ability of a biosensor to respond to an analyte lies in the nature of the biological component. Based on the evidence that aflatoxin is able to inhibit the enzymatic activity of the acetyl cholinesterase enzyme (ACE) (Arduini et al., 2007), an amperometric biosensor based on enzymes ACE and choline oxidase has been developed. The biosensor was tested with different mixtures of mycotoxins (aflatoxin, patulin, type B trichothecene and ochratoxin) and reported the presence of aflatoxins and patulin in a biological matrix (Chapter 1), showing different sensitivity to the two mycotoxins.In parallel, new chemical components from sustainable sources were synthesized and evaluated in order to improve the performance of the biosensor. To solve the problem of the interfering signals present in the matrix, such as ascorbic acid (AA) and dopamine (DA), the transducer is commonly covered with polymeric films derived from orthofenilendiammine (PPD) (Killoran and O'Neill, 2008), a monomer toxic and mutagenic (Murata et al., 2006).In a first step, the monomers chosen as candidates for obtaining new permselctive films were represented by non-toxic phenols, naturally occurring in nature, such as eugenol, isoeugenol, magnolol and dehydrodieugenol. Among these, for practical reason, dehydrodieugenol was obtained through chemical synthesis starting from eugenol. Molecules were elettropolymerized using two techniques: constant potential amperometry and cyclic voltammetry. The polymers were characterized through permselectivity studies and Scanning Electron Microscopy (SEM); the studies were repeated over time to assess the stability of obtained polymers. High electropolymerization potentials were used, in order to overoxidate polymers and enhance charge repulsion characteristics of the polymer. Through the calculation of the permselectivity parameter (S%), permselective properties of the polymer films were quantified. The poly-magnolol proved the best alternative for PPD and it was included in the construction of a biosensor based on the enzyme glucose oxidase (Chapter 2).The next step’s study of alternative polymers from natural monomers comprised the addition of a further molecule, guaiacol. This compound presents a simpler structure compared to the other molecules studied, being constituted of one guaiacyl unit. Taking into account the significant changes in permselectivity imparted by the polymerization conditions applied, in this part of the work the different phenols were polymerized by constant potential amperometry exploring a discrete range of electropolymerization potentials. Each phenol was subject to four different potentials and the characteristics of the resulting film were observed compared to H2O2, ascorbic acid and dopamine, and accompanied by images obtained by scanning electron microscopy (SEM). The experiments showed that the permeability characteristics are strongly related to the potential applied during polymerization; also permselectivity values were improved compared to previously reported work (Chapter 3).
Several molecules, that can alter the characteristics of βCD, have been selected in order to strengthen and widen βCD use in biosensors. The introduction of a bridge, created by a covalent bond between a linker molecule and two βCD, can enhance the ability of inclusive power of macrocycle; also the nature of the linker may make new functional groups and / or charges that help the interaction with the enzyme. A good attachment site is represented by the primary OH present on C6 of βCD, where, under certain conditions, can take place an esterification reaction between linker and βCD. As linker molecules have been used the polycarboxylic acid (PCA), the glyceroldiglycidilether (GDGE) and dimethyl carbonate (DMC). The products of the reactions were examined by means of nuclear magnetic resonance (NMR). Under the experimental conditions used, the reaction between the anhydride of 1,2,3,4-butanetetracarboxylic acid (BTCAa) and the βCD shows the formation of a mixture of different complexes. The complex was tested with carvacrol, a molecule that easily forms stable complexes with the βCD. The strong interaction BTCA-βCD has prevented the formation of the βCD-carvacrol complex and esterification between BTCAa and βCD (Chapter 4).
To include the βCD during electropolymerization various procedures were developed to obtain complexes between βCD and phenols. The βCD-eugenol complex, obtained in 85% of yield, was characterized by NMR spectroscopy; the analysis in D2O show a modification of the signal of the H5 βCD and the presence of well resolved eugenol signals in solution. Also the formation of βCD-guaiacol complex was confirmed by NMR with a yield of 47%. Repeated NMR analysis have confirmed a long-term stability for at least 2 weeks. Different conditions of complexation, all sustainable, including the technology to microwaves, have not been successful in obtaining a βCD- magnolol inclusion complex (Chapter 4).
The properties of a sulfur-containing phenol (S-PhOH) derivative product from Chemiplastica Specialties SpA were evaluated. The formation of strong complexes between S-PhOH and the βCD was studied by NMR spectroscopy under different experimental conditions, such as microwave, coprecipitation, sonication and solvent evaporation under vacuum (Rotavapor). These complexes are highly soluble and stable in water. The electro-deposition of S-PhOH is able to modify a platinum electrode imparting interesting characteristics towards ascorbic acid presence (Chapter 5)
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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