1,721,011 research outputs found
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
Reconstructing Neogene Climate and Glacial History of Southern McMurdo Sound, Antarctica
No full textUnderstanding the glacial changes that have occurred in southern McMurdo Sound throughout the Neogene makes an important contribution to reconstructing Antarctic ice volume changes during past periods of climatic warmth, and provides insight into future possible response of the ice sheet. Fossiliferous glacimarine deposits previously identified throughout McMurdo Sound have provided inferences on past changes in ice volume and the implications for global sea level. This study investigates new stratigraphic sections comprising fossiliferous glacimarine sediments from two locations on the flanks of Mount Discovery and one on Brown Peninsula at ~150m above present day sea-level. The aim of this thesis is to undertake a sedimentological, facies and glacimarine sequence stratigraphic analysis together with a quantitative assessment of the constituent micro and macrofossils in order to determine depositional processes, changes in environment and implications for glacial variability in the southern McMurdo Sound. Up to four distinct sedimentary cycles are evident in the Mt Discovery sections with each cycle consisting of:
1. A basal glacial surface of erosion (GSE) or its correlative conformity (CC) seaward of the grounding line, displaying an abrupt transition from a more distal facies to a more proximal facies.
2. A sharp-based massive diamictite displaying physical intermixing of subjacent lithologies, intra formational clasts, soft sediment deformation features, clast rotation features, and a lack of bioturbation, interpreted as subglacial, or in very close proximity to a marine grounding line. In some cases stratified diamictites overly correlative conformities displaying clast alignment, graded beds, and weak decimeter scale parallel bedding in the matrix, interpreted as grounding-line proximal sediment gravity flows or rain-out from ice melt.
3. In some cases, the diamictite passes gradationally-upwards or is sharply overlain by a conglomerate representing appearance of glacimarine fluvio-deltaic deposition or debris flows as the glacier grounding line begins to retreat.
4. Conglomerates are overlain, often sharply, by hemipelagic laminated or massive mudstone and represent the most ice distal and marine part of the sequence at the interglacial minima.
5. A proglacial facies succession is sometimes preserved below the GSE or correlative conformity marking the top of the sequence and usually consists of a transition from mudstone facies into grounding zone proximal conglomerates during re-advance of the grounding line.
Lithofacies analysis supported by sediment grainsize, the results of a foraminiferal census and macrofaunal identifications conducted on each facies imply deposition on the continental shelf in depths of up to 400 m, during oscillations in the proximity of a marine grounding line.
Radiocarbon dating of constituent macrofauna (barnacle plates) reported only background ¹⁴C implying an age of deposition older than the Last Glacial Maximum. The present day elevation of the site and a model developed here using glacio-iostatic loading and unloading implies that the Mt Discovery sites have been above sea-level for approximately the last ~2.7Ma. Given their inferred association with Scallop Hill Formation and faunal similarity to sequences in the nearby ANDRILL drill cores, a Pliocene age is considered most likely. This finding is consistent with previous investigations that indicate a dynamic, sub-polar marine-terminating ice sheet margin in Southern McMurdo Sound during the Pliocene, with periods of open ice shelf free conditions potentially associated with more frequent regional collapse and retreat events of a marine-based ice sheet in the Ross Sea embayment
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
The response of Antarctic ice volume, global sea-level and southwest Pacific Ocean circulation to orbital variations during the Pliocene to Early Pleistocene
No full textThis thesis investigates orbitally-paced variations in the extent of East Antarctic Ice Sheet (EAIS), and the “downstream” influence of these ice sheet variations on ocean circulation and sea level variability during the Pliocene and Early Pleistocene - a time period characterised by a major global cooling step that culminated in the development of a bipolar glaciated world. Three unique records are examined from (1) the Antarctic margin, (2) the southwest Pacific Ocean, and (3) shallow-marine sedimentary strata exposed in Wangnaui Basin, New Zealand.
The Integrated Ocean Drilling Program (IODP) Site U1361 recovered a continuous sedimentary Early Pliocene to Early Pleistocene (4.3 to 2.0 Ma) record from the lowermost continental rise on the Wilkes Land margin offshore of the EAIS. A facies model and stratigraphic framework were developed that allowed for the identification of glacial advances (massive and laminated mudstones) and retreats (diatom-rich mudstones) across the continental shelf, with evidence for prolonged retreats spanning several glacial to interglacial cycles throughout the Pliocene. These cycles are followed by an extensive Early Pleistocene interval (~2.6 Ma) of diatom-rich mudstone with evidence for reworking by bottom currents, interpreted to be the consequence of downslope density currents associated with increased sea ice production after 2.6 Ma. Frequency analysis on Iceberg Rafted Debris (IBRD) from Site U1361 reveals that under an Early Pliocene warm climate state (4.3 to 3.3 Ma), that ice discharge off the EAIS occurred in response to climate change paced by the 40-kyr cycles of obliquity. Whereas, the colder climate state of Late Pliocene to Early Pleistocene (3.3 to 2.0 Ma) resulted in a transferral of orbital variance to 20-kyr-duration, precession-dominated variability in IBRD preceding the development of a more stable marine-based margin of the EAIS at ~2.6 Ma, which is hypothesized to reflect the declining influence of oceanic forcing as the high-latitude Southern Ocean cooled thereby increasing the seasonal duration and extent of sea-ice. The precession-paced influence on IBRD and ice volume variability of the EAIS was strongly modulated by 100-kyr-eccentricity, which is expressed lithologically in cycles of two alternating lithofacies 1) diatom-rich mudstones and 2) massive and laminted mudstones in the Site U1361 record.
A compilation of benthic stable isotope records from Ocean Drilling Program (ODP) Site 1123 in the southwest Pacific Ocean was also developed. The δ18O record identified a 40-kyr obliquity pacing, consistent with other benthic δ18O records globally for this time period, thus allowing for an orbitally-tuned timescale to be developed for this site. Long-term trends in both the δ18O and δ13C records at ODP Site 1123 coincide with major developments of the Antarctic Ice Sheet and Northern Hemisphere glaciation at 3.33 Ma and ~2.6 Ma respectively. A gradual reduction in the deep water δ13C gradient between the southwest Pacific (ODP Site 1123) and equatorial Pacific (ODP Site 849) between 3.33 and 2.6 Ma coincides with expansion of the Antarctic Ice Sheet, enhanced Antarctic Bottom Water (AABW) production, invigorated atmospheric zonal circulation in the southern hemisphere mid-latitudes, and increased meridional sea surface temperature (SST) gradients in the Pacific Ocean.
Finally, a shallow-marine, continental margin stratigraphic section from the Turakina River Valley in the Wanganui Basin, New Zealand, was used to record local sea-level changes, dominated by orbitally-driven, global glacio-eustasy, during the mid-Pliocene interval (3.2 to 3.0 Ma). This interval was selected as it precedes the build-up of significant Northern Hemisphere Ice Sheet, thus allowing for an independent assessment of the orbtial-scale variability of Antarctic Ice Sheet volume. Grain size based proxy of percent mud was employed to reconstruct paleobathymetric changes, which displayed 100-kyr cycles consistent with ~20 m variations in local water depths during the mid-Pliocene. Combined with IBRD record from Site U1361, this reconstruction suggests that the marine margins of East Antarctica varied at orbital timescale, and provided a significant contribution to global eustatic sea-level variations during the mid Pliocene (consistent with global mean sea-level estimates of up to ~+20 m above present from related studies)
Late Cenozoic (13-0 Myr) Glacimarine Sedimentology, Facies Analysis, and Sequence Stratigraphy from the Western Ross Embayment, Antarctica: Implications for the Variability of the Antarctic Ice Sheets
No full textSedimentary processes related to oscillations of the marine-based sector of Antarctic Ice Sheet (AIS) in the Ross Embayment over the past 13 Myr are examined at various timescales from stratigraphic records of glacial advance and retreat obtained from the McMurdo Sound region. An initial sedimentary model was developed from short (<2 m) sediment cores collected from beneath the present-day McMurdo Ice Shelf and seasonally open water in the Ross Island region. These cores document sedimentary processes associated with subglacial, ice shelf and open marine environments since the Last Glacial Maximum (LGM) in the Ross Sea Embayment. A radiocarbon chronology from these short cores implies that lift-off of grounded ice in the 900 m-deep marine basins surrounding Ross Island occurred by ~10,100 14C yr BP. Following lift-off, the ice shelf calving line retreated toward its present position. By ~8,900 14C yr BP, seasonally open marine conditions extended as far south as Ross Island. Glacial retreat was rapid and preceded the timing of Meltwater Pulse 1B. Since 8,900 14C yr BP, the calving line of the Ross Ice Shelf has remained pinned to Ross Island despite warmer-than-present temperatures during the mid-Holocene. Depositional models developed for the LGM to recent sediments were then applied to the interpretation of the 1284-m-long ANDRILL McMurdo Ice Shelf core (AND-1B) to documenting oscillations of the AIS in the Ross Embayment over the past 13 Myr. A sequence stratigraphic framework for grounding-line fluctuations of under a variety of glacial regimes, with three distinct types of glacimarine cycle (sequence motif) identified. Motif 1 (Pleistocene and Mid to early Late Miocene) is dominated by thick sub-glacial diamictite, deposited during glacial advance, with occasional thin interbeds of sparsely- to non-fossiliferous mudstone that marks an ice shelf setting during interglacial maxima. Motif 2 (Pliocene) comprises subglacial to glacimarine diamictite overlain by thin, proglacial deposits and capped with substantial beds of diatom-bearing mudstone or diatomite formed under open-marine conditions. Motif 3 (Late Miocene) extends from subglacial diamictite into a thick proglacial succession that includes a combination of stratified diamictite, graded sandstone, conglomerate, and rhythmically-stratified mudstone. The differences in these facies successions (motifs) are associated with the long-term evolution of the AIS in the Ross Embayment from a cold glacial regime with limited volumes of subglacial meltwater (Motif 1) to warmer styles (Motifs 2 and 3) of glaciation with increased subglacial meltwater discharge, before passing back to the cold style of glaciation that characterises the present-day AIS (i.e., limited subglacial meltwater). Each motif was interpreted on the basis of modern analogues of glacimarine sedimentation from a range of climatic/glacial settings, recording a fundamental change in the mass balance for the AIS in the Ross Embayment. For cold glacial regimes similar to the present day Antarctic Ice Sheets, ablation was largely controlled by calving at the marine margin and the melting of the underside of ice shelves by oceanic processes. For warmer regimes, in particular for Motif 3, ablation by melting was a significant influence on mass balance. This sedimentary model was then applied in detail to interpret the Pleistocene section of AND-1B (upper 150 m) with a chronostratigraphic interpretation constrained by sequence stratigraphy, 40Ar/39Ar dating of volcanic ashes, and magneto-stratigraphy. The glacimarine sequences in AND-1B drill core correlate one-to-one with cycles in the benthic delta 18 O record for the past ~0.8 Myr (Marine Isotope Stages 20-2), and are interpreted as recording fluctuations of the AIS in the Ross Embayment with a 100-kyr cyclicity. In this "100-kyr world", the AIS is relatively stable, with subglacial to grounding-zone sedimentation dominating at the AND-1B drill site, with only thin intervals of ice-shelf
sedimentation during interglacials and little evidence for open-marine conditions during the Late Pleistocene "super-interglacials". An unconformity spans (~200 kyr) most of the Mid-Pleistocene Transition and is inferred to represent large scale expansion of AIS at ~0.8 Myr. Prior to this, Early Pleistocene glacial/interglacial cycles had a 40-kyr frequency, with interglacial periods characterised by open water deposits that contain volcanoclastic debris and diatomaceous sediments. This upper 150 m of AND-1B provides clear evidence for both a change in the frequency (40- to 100-kyr cycles), and a reduction in the sensitivity of a cooler marine-based AIS in the Ross Embayment
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
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