1,720,962 research outputs found
From Craton to Present Mountains - The Scandinavian Lithosphere Imaged by Rayleigh Surface Waves and Ambient Noise
Get PDFThe Scandes mountain range along the western rim of the Archean Baltic craton with
elevation up to 2500 m forms an exceptional setting as the orogeny terminated 420 Ma ago and the Caledonides were deeply eroded afterwards. Since this region lacks recent compressional tectonic forces, a comprehensive explanation for the topography, which shows north-south and lateral variations along the Scandes, is missing. In my dissertation, I use earthquake surface waves and ambient noise to image the crustal and mantle structure aiming to provide new clues about the topography’s origin. The focus is also on exploring structural differences between the various tectonic domains. Here, I benefit from the seismic recordings by the ScanArray network supplemented by permanent and previous projects, distributed over entire Scandinavia.
First, I performed a beamforming of Rayleigh surface waves which yielded average phase
velocities for the study region and several of its sub-regions. An unusual 360° or sin(1θ) phase velocity variation with propagation azimuth is observed in northern Scandinavia and southern Norway/Sweden but not in the central area. For periods >35 s, a 5% variation between the maximum and minimum velocities was measured for opposite backazimuths of 120° and 300°, respectively. Such a variation is incompatible with the intrinsic azimuthal anisotropy and the path average approximation made in tomography. I assumed an eastward dipping lithosphere-asthenosphere boundary (LAB) to be the causing structure, inspired by some preliminary velocity models and observations made in previous studies.
To test this hypothesis, I carried out 2D full-waveform modeling of the Rayleigh wave propagation. The models include a steep gradient at the LAB in combination with a pronounced reduction in the shear velocity below the LAB. The synthetic results are consistent with the observations: Faster phase velocities are obtained for propagation towards the thinning lithosphere, and lower ones for propagation in the direction of deepening LAB. The interference of reflected surface wave energy at the steep LAB with the forward propagating fundamental mode probably causes this peculiar effect.
Second, the joint inversion of Rayleigh surface waves and ambient noise provides structural
imaging down to 250 km depth. Resultant from my velocity model, I derive a new crustal
model from which maps of the Moho depth as well as of the high-density lower crustal layer
(LCL) are obtained. I observe crustal thickening from west to east below the Precambrian
low-topography terranes, which is mainly a consequence of eastward thickening of the LCL. In contrast to the southern Scandes, with the overall highest topography (2,500 m), a crustal root below the northern Scandes (max. 2,100 m) is seen which diminish towards the central Scandes (max. 1,000 m). The LAB below the Scandes is deepening from west to east. The sharp steps in the LAB and strong velocity reductions both in the south (90–120 km LAB depth with 5.5% Vsv contrast) and the north (150 km LAB depth with 9% Vsv contrast) surprisingly correlate with the Caledonian mountain front. Whereas smoother laterally varying structures (150–170 km LAB depth with 4% Vsv contrast) are found below the central Scandes. The correlation of the lithosphere thickening with the Caledonian front might be related to metasomatism as result of the orogeny and/or the passive margin rifting. In Precambrian Scandinavia, low-velocity areas below 150 km depth are observed beneath the Archean Karelia craton in northern Finland. At mantle depth, the Paleoproterozoic Norrbotten craton can be separated from the Karelia craton, Caledonides and Paleoproterozic Svecofennian likely due to different degrees of metasomatism.
Based on the structural differences, I conclude that different mechanisms are responsible for the compensation of the topography. The northern Scandes are likely compensated by a
combined Airy-Pratt isostasy as implied by low-density rocks in the shallow crust (<15 km
depth), a high-density layer in the deep crust (>10 km LCL thickness) and the mountain root.
The strongly reduced velocities at sub-lithospheric depth additionally suggest an uplift
contribution from the upper mantle. Since the southern Scandes lacks these crustal attributes, they experience mainly mantle-driven buoyancy. In both cases, however, I assume the influence of small-scale edge-driven convections (EDC) that can arise at sharp LAB gradients. EDC emplaces thereby low-density material at sub-lithospheric depths by the upwelling of hot asthenosphere which implies additional buoyancy of the lithosphere. Moreover, the lateral topography differences along the Scandes can be explained by varying EDC cell dimensions. Primarily, Pratt isostasy compensates the low topography central Scandes, but a contribution from dynamic support could act as well.
Ultimately, I see the strong gradients at the LAB below the southern and northern Scandes
as the cause of the observed 1θ phase velocity variation. While the smoother velocity structure in the central study area explains the absence of the 1θ effect
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
- …
