1,720,984 research outputs found
A study of the green leaf volatile biochemical pathway as a source of important flavour and aroma precursors in Sauvignon blanc grape berries
No full textGreen leaf volatiles (GLVs) are short-chain acylic aldehydes, alcohols and esters produced by plants via enzymatic metabolism of polyunsaturated fatty acids (PUFAs). GLVs are known to affect flavour and aroma of fruits and vegetables, including grapes. It has also been suggested that C6 and C5 GLVs are the precursors of volatile thiols, the aroma compounds that are important in Sauvignon blanc wine. GLVs are produced during grape berry development and released in high quantities upon berry crush.
GLV aldehydes are formed from PUFAs by the action of two enzymes, lipoxygenase (LOX) and hydroperoxide lyase (HPL). This biochemical pathway is well characterised in other plant species and is known as the GLV pathway. To date, the GLV pathway has not been characterised in grapes. This thesis focuses on identification and initial characterisation of LOX and HPL genes and enzymes involved in the GLV-pathway.
LOXs are a group of non-haem iron-containing dioxygenases that catalyse oxygenation of PUFAs producing PUFA-hydroperoxides. The most common PUFA substrates in plants are linoleic acid (LA, 18:2) and α-linolenic acid (LnA, 18:3). Depending on the position of oxygenation of the 18-carbon chain PUFAs, all plant LOXs are classified as 13(S) - and 9(S)-LOXs. 13(S)-LOXs are further regarded as type II and type I enzymes, depending on the presence or absence of transit peptides in the amino acid sequences of these enzymes respectively.
HPLs belong to the CYP74 enzyme family, which is represented by atypical members of cytochrome P450 oxidases superfamily. HPLs cleave PUFA-hydroperoxides, producing aldehydes and oxoacids. Depending on the substrate specificity, HPLs are classified as 13-HPLs, 9/13-HPLs or 9-HPLs.
The research reveals the complexity of the genetic makeup of the GLV metabolic pathway in grapes. Eighteen putative LOX genes and six putative HPL genes were identified in the Pinot noir grape genome. Phylogenetic analysis of the identified grape LOXs classified them as members of two groups, type II 13-LOXs and 9-LOXs, whereas all identified grape HPLs were classified as 13-HPLs (CYP-74B) and 9/13-HPLs (CYP-74C).
Several LOX and HPL genes were expressed at different levels in Sauvignon blanc berry. Study of selected LOX and HPL gene expression revealed different levels of expression and differential tissue distribution of individual LOX and HPL genes within the berry. The studied genes also displayed different patterns of expression across different stages of berry development, upon wounding and in berries infected with Botrytis cinerea. Amongst the four LOX gene studied, transcripts of VvLOXA were the most abundant at all stages during berry development. VvLOXO was induced transiently upon berry damage and was a clear candidate involved in berry response to wounding. Expression levels of VvLOXC and VvLOXO were significantly increased in berries infected with Botrytis cinerea compared to the uninfected berries.
In vitro biochemical analysis of the reaction products of recombinant VvLOXA (LOXA-TP) and VvLOXO (LOXO-TP) confirmed that these two enzymes are 13-LOXs. Both enzymes preferred LnA as a substrate. Both enzymes had the same temperature optima of 25°C, but preferred different pH conditions. Recombinant LOXA-TP preferred acidic environment and had pH optimum of pH 5.5, while LOXO-TP preferred neutral-to-basic conditions and had pH optimum of pH 7.5.
Preliminary experiments with recombinant VvHPLA showed its ability to metabolise 13(S)-hydroperoxides, releasing C6 volatile aldehydes. Recombinant VvHPLA exhibited maximum activity with 13(S)-hydroperoxides of LnA as substrate at pH 5.0
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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