1,720,972 research outputs found
Sensibilité du C profond des sols aux changements climatiques : Minéralisation des matières organiques du sol à différentes teneur en eau en profondeur dans un PODZOSOL amazonien
No full textLes changements de régime hydrique seront une des composantes principales des
changements climatiques à venir. Or,
si l’effet de la température sur les stocks de C des sols
a fait l
’objet de nombreuses études récentes, il n’en est pas de même pour l’effet du rég
ime
hydrique, alors que
l’humidité du sol influence fortement l’activité microbienne (Moyano et al.
2013)
. Il a récemment été montré que les horizons BpH des podzols amazoniens
représentent un stock de carbone organique très important, de 13.6 PgC (Montes et al.
2011). Or, la région amazonienne est sujette au changement climatique ainsi
qu’a des
changements d’usage des terres ce
qui induit des changements de régime hydrique. Les
horizons B
pH
des podzols équatoriaux sont généralement saturés en eau ce qui limite la
minéralisation du carbone organique. Des régimes hydriques plus secs ou plus variables
pourraient donc induire une augmentation de la minéralisation des stocks de C avec une
libération significative de CO
2
vers l'atmosphère. Pour pouvoir estimer l'importance de ce flux
de CO
2,
il faut comprendre
la
réponse du C organique des sols à des régimes hydriques
différents : une modification du potentiel matriciel vers des valeurs plus faibles et des cycles
de dessiccation et ré-humectation pouvant induire une augmentation importante et rapide de
la minéralisation du C organique des sols (Birch, 1958).
Notre objectif est de mesurer la minéralisation du C de différents horizons
de
podzols
à
différents potentiels matriciels pour ainsi connaitre la sensibilité du C à des changements de
régime hydrique.
Pour parvenir à cet objectif, des échantillons non perturbés provenant de 4 horizons
différents (OH, E, BpH, IIM) de podzols amazoniens de trois sites distincts ont été incubés
dans un dispositif qui permet de suivre les émissions de CO
2
.
A l’aide d’une
presse à
membrane de Richards, les échantillons ont été placés dans des microcosmes à 5 potentiels
contrastés (pF 0, 1.7, 2.5, 3.5, 4.2) puis directement mis en incubation à 28°C. Le suivi de la
minéralisation est effectué pendant 1 mois et demi par mesure régulière des flux de CO
2
à
l’aide d’un μGC
.
A la fin
de
l’
incubation, la structure des communautés microbiennes a été
analysée par quantification des PLFAs.
Nos premiers résultats indiquent que les horizons OH sont peu sensibles à la variation à
l’humidité,
ce qui est en accord avec Manzoni et al. (2012). Les horizons E et IIM ont un
optimum de minéralisation à
pF
2.5. L
a minéralisation dans l’horizon
BpH est en revanche
faible
aux pF bas, soit de 0 à 2.5, et l’on observe une augmentation de l’activité vers 3.5 qui
12es
Journées
d'Etude
des
Sols,
30
juin
-
4
juillet
2014,
Le
Bourget
du
Lac
223
diminue à pF 4.2. Nous supposons que cet horizon est saturé lorsque le pF est inférieur à
3.5 ce qui limite la minéralisation comme le décrit dans Moyano et al. (2013). Nous faisons
l’hypothèse que la principale limite de la minéralisation est le manque d’azote dans les
horizons profonds et la
teneur en eau qui limite l’oxygénation du milie
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
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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