1,720,954 research outputs found
Complex Monge-Ampère flows on compact Hermitian manifolds
No full textL'origine de la zone de transition dunitique (DTZ) à l'interface manteau-croûte est mal connue, ainsi que les processus physico-chimiques impliqués dans sa genèse. Pour aborder cette question, ce travail a porté sur l'étude pétrologique, géochimique et structurale de 20 coupes (600 échantillons) levées dans la DTZ du massif de Sumail (ophiolite d'Oman), épaisse de plus de 400 mètres à l'aplomb d'un paléo-diapir mantellique. Au-delà des données in situ sur minéraux (microsonde, LA-ICP-MS) et des compositions en éléments majeurs des roches totales, le développement d'une procédure analytique a permis l'acquisition des compositions en éléments en traces des dunites dont les teneurs sont de l'ordre du ng.g-1. La DTZ est faite de dunites pures (olivine et chromite) et de dunites imprégnées, contenant une quantité variable de minéraux interstitiels ayant cristallisé à partir d'un magma percolant. Ces faciès renferment des minéraux d'une variété insoupçonnée incluant, en plus de ceux clairement issus d'un MORB (clinopyroxène et plagioclase), de l'orthopyroxène, amphibole, grenat, et des diopsides témoignant d'un processus d'hybridation entre le MORB et des fluides hydratés. Les forts rapports Mg# et teneurs en TiO2 des orthopyroxènes et amphiboles ainsi que la composition des clinopyroxènes, intermédiaire entre clinopyroxènes magmatiques et diopsides hydrothermaux, a permis de contraindre la composition du magma hybride qui résulterait du mélange entre un magma d'affinité tholéiitique et un fluide supercritique riche en silice, voire trondhjémitique issu de la fusion incongruente hydratée des orthopyroxènes mantelliques, similaire au produit de fusion hydratée des roches environnantes (péridotites serpentinisées, troctolites, gabbros). Ces minéraux sont observés en position interstitielle et en inclusion dans les chromites, témoignant de leur origine précoce et du fait que les magmas hybrides ont participé à la formation de la DTZ. La combinaison des interprétations des données in situ et des données roches totales a permis la déconvolution du message polyphasé enregistré par les dunites : la signature du protolithe, celles de la dunitisation et du rééquilibrage de la matrice d'olivine avec un MORB percolant (métasomatisme cryptique), la signature de refertilisation par la cristallisation des minéraux interstitiels (métasomatisme modal), ainsi que les effets de la serpentinisation. Il apparaît que les dunites pures, caractérisées par un spectres de terres rares en forme de U ou de V, semblent avoir acquis cette signature très précocement, probablement lors de la phase initiale de leur genèse sous l'effet de rééquilibrages avec des liquides très riches en éléments incompatibles (REE, Th, U, HFSE) et pouvant correspondre au magma hybride. L'étude structurale de la DTZ dans le massif de Sumail a montré l'influence de la tectonique synmagmatique sur la structuration de la DTZ, se traduisant par l'alternance d'horizons imprégnés ou non ainsi que par l'évolution verticale sur plusieurs dizaines de mètres des compositions chimiques à l'approche des zones de failles. On l'observe notamment pour les teneurs en éléments immobiles dans les fluides tels que le Ti, les REE ou le Th. La DTZ semble s'être développée dans un environnement transtensif dont les deux systèmes de failles principaux N130 et N165-180 ont accommodé la percolation des magmas et fluides responsables de la dunitisation ainsi que l'introduction des fluides hydrothermaux pouvant conditionner les échanges globaux avec les enveloppes externes.La comparaison avec les DTZ d'autres massifs en Oman ou à Trinity (Californie), ayant évolué dans un contexte magmatique différent, montre également l'importance des failles synmagmatiques dans la structuration de la DTZ. Les liquides qui ont percolé dans ces DTZ apparaissent systématiquement sous-saturés en Al et saturés en H2O, amenant à interpréter le caractère hydraté comme une condition critique pour la genèse des dunites.The origin of the dunitic transition zone (DTZ) between the mantle and the crust is still largely unknown, as well as the physical and chemical processes involved in its genesis. To address this topic, this thesis focused on the petrological, geochemical and structural study of 20 cross-sections (600 samples) collected along the DTZ from the Sumail massif, Oman ophiolite, 400 meters thick and located above a former paleo-mantle diapir. In addition to mineral compositions acquired using in situ methods (microprobe, LA-ICP-MS) and to whole rock major elements, the development of an analytical procedure permitted to determine trace element contents in dunites that display low concentrations (regularly about one ng.g-1). The DTZ is made of pure dunites (olivine and minor chromites), and of impregnated ones, containing a variable amount of interstitial minerals that crystallized from a percolating melt. These latter rocks contain an unexpected mineralogical variety with, in addition to clinopyroxene and plagioclase showing a MORB affinity, the presence of orthopyroxene, amphibole, garnet and diopsides that highlights a hybridization process between the MORB and hydrated fluids. The high Mg# ratio and TiO2 content in orthopyroxene and amphibole together with the clinopyroxene composition, intermediate between igneous clinopyroxene and pure hydrothermal diopside, allow deciphering the nature of the parent melt as the result of the mixing between tholeiitic melt and a supercritical water enriched in silica, or trondhjemitic fluid issued from the hydrated incongruent melting of mantle orthopyroxene, similar to melts produced by the hydrated melting of country rocks (serpentinized peridotites, troctolites, gabbros). All these minerals are observed both in interstitial position and as inclusions in chromite, showing that they crystallized early and that hybrid melts participated to the genesis of the DTZ. The comparison between mineral and whole rock compositions permitted to highlight the different processes that led to the observed chemical signatures of dunites: the protolithe signature, the dunitization process, chemical reequilibration between the olivine matrix and the percolating MORB, refertilization following the crystallization of interstitial minerals, as well as the effects of later serpentinization. Pure dunites, characterized by U or V-shaped REE patterns, seem to have acquired early the LREE-enriched signature that probably results from the reequilibration with silica- and incompatible trace elements-rich fluids (REE, Th, U, HFSE) generated through the harzburgite orthopyroxenes incongruent melting and probably reflecting the hybrid melt that crystallized interstitial hydrous minerals. The structural study of the DTZ in Sumail highlights the effect of synmagmatic faults on the DTZ development, resulting in the alternation between pure and impregnated horizons as well as in the vertical chemical structuration with compositions evolving on few tens of meters until fault zones. This is particularly true for chemical species expected as immobile during weathering as Ti, REE or Th. The DTZ seems to have been developed in a transtensional environment structured by two main faults systems, oriented N130 and N165-180. These faults spatially constrained both the melt flow, thus the dunitization, and the introduction of hydrothermal fluids probably oceanic in origin. This meeting zone between igneous and hydrothermal fluids can strongly influence the chemical exchanges and distribution between the deep lithosphere and the surface. The comparison between the Sumail DTZ and other ones from Oman or Trinity (California) ophiolites, which evolved in a different magmatic setting, shows the systematic role of synmagmatic faults. Melts that percolated these other DTZ were under-saturated in Al and saturated in water, allowing to interpret the hydrated component as an essential condition for dunites genesis at the mantle-crust transition
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
- …
