1,720,955 research outputs found
Application of Mesoporous Silica Materials for the Immobilization of Polyphenol Oxidase
Full text link[ES] La principal reacción que afecta tanto a frutas como a verduras y que causa un detrimento en su color, sabor, olor y valor nutricional es el pardeamiento enzimático. La polifenol oxidasa (PPO), también llamada tirosinasa, es la principal responsable de esta reacción, ya que oxida los compuestos fenólicos generando pigmentos parduzcos. Los materiales mesoporosos han tenido una gran variedad de aplicaciones en las últimas dos décadas, como por ejemplo catálisis y separación de gases, y estos materiales son una interesante opción para inmovilizar la PPO como alternativa a los tratamientos térmicos implementados en la industria. El objetivo de este trabajo es estudiar la posibilidad de retener este enzima o incluso inhibir su actividad aplicándolo sobre zumo de manzana, puesto que, como esta bebida es rica en compuestos fenólicos, es más susceptible de sufrir esta reacción de pardeamiento. Se han estudiado diferentes materiales mesoporosos de sílice con diferentes estructuras, morfologías y porosidades para poder dilucidar su influencia en la tasa de inmovilización. Además, otros factores que han sido ampliamente estudiados han sido la influencia del pH de la solución de inmovilización y el tiempo de contacto entre el material y el enzima. La característica textural que parece ser decisiva en los ensayos de inmovilización es el volumen de poro. Aeroperl® y SBA-15 son los dos materiales que pueden atrapar mayor cantidad de PPO cuando la solución tiene un valor de pH de 4.00, puesto que a ese valor de pH pueden establecerse las interacciones electrostáticas necesarias para que el enzima pueda quedar adsorbido en las paredes del material. Ajustando los modelos de Higuchi y power law podemos deducir que el proceso de entrada de la PPO dentro de los poros está controlado difusionalmente. El material comercial testado es el que presenta mayores tasas de inhibición en extractos de manzana.[EN] Enzymatic browning is one of the most important reactions that occur in fruits and vegetables, resulting in negative effects on color, taste, flavour and nutritional value. The main agent responsible for this reaction is polyphenol oxidase (PPO), also called tyrosinase, because it oxidises phenolic compounds and generates dark pigments. Mesoporous materials have been popular for a variety of applications in the last two decades, such as catalysis and gas separation, and they are an interesting option to immobilize the PPO as an alternative to the established industry process based on heat treatments. The objective of the present work is to study the possibility to remove this enzyme or even inhibit its activity from apple juice, since this beverage is rich in polyphenols and it is susceptible to suffering enzymatic browning. Different mesoporous silica materials were tested with different structures, morphologies and porosities in order to see their influence on the immobilization rate. Besides, the pH value of the solution and time were fully analysed and they provide results to obtain a good immobilization capacity. Pore volume, is the textural characteristic which affects the most the immobilization assay. Aeroperl® and SBA-15 are the materials which can adsorb larger quantity of PPO at pH 4.00, because electrostatic interactions can exist between the enzyme and the silica walls. Fitting power law and Higuchi models, we can assume that the PPO loading into mesoporous materials is a diffusion controlled. The commercial mesoporous material reveals highest inhibition rates in real apple extracts.[CA] La principal reacció que afecta tant fruites com a verdures i que causa un detriment en el seu color, sabor, olor i valor nutricional és l'enfosquiment enzimàtic. La polifenol oxidasa (PPO), també anomenada tirosinasa, és la principal responsable d'aquesta reacció, ja que oxida els compostos fenòlics generant pigments terrosos. Els materials mesoporosos han tingut una gran varietat d´aplicacions en els últims 20 anys, com per exemple catàlisi i separació de gasos, i aquéstos són una interessant opció per a encapsular la PPO com a alternativa als tractaments tèrmics implementats en la industria. L'objectiu d´aquest treball és estudiar si és possible retindre aquest enzim o fins i tot inhibir la seua activitat aplicant-ho sobre suc de poma, ja que, com aquesta beguda és rica en compostos fenòlics, és més susceptible de patir aquesta reacció d'enfosquiment. En el present treball, s'han estudiat diversos materials mesoporosos de sílice amb diferents estructures, morfologies i porositats per a poder dilucidar la seua influència en la taxa d'immobilització. A més, altres factors que han sigut àmpliament estudiats han sigut el pH de la solució d'immobilització i el temps de contacte entre el material i la solució enzimàtica. La característica textural que sembla ser decisiva en els assajos d'immobilització és el volum de porus. Aeroperl® i SBA-15 són els dos materials que poden atrapar major quantitat de PPO quan la solució té un valor de pH de 4.00, ja que per a aquest valor de pH poden establir-se les interaccions necessàries perquè l'enzim puga quedar adsorbit en les parets del material. Ajustant el model de Higuchi i power law podem deduir que el procés d'entrada de la proteïna dins dels porus està controlat difusionalment. El material comercial testat és el que presenta majors taxes d'inhibició en extractes de poma.Corell Escuin, P. (2014). Application of Mesoporous Silica Materials for the Immobilization of Polyphenol Oxidase. https://riunet.upv.es/handle/10251/57097.Archivo delegad
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
- …
