1,720,954 research outputs found
Cryogenic origin for brine in the subsurface of southern McMurdo Sound, Antarctica
No full textSampling of interstitial fl uids during deep coring in southern McMurdo Sound, Antarctica,
revealed the presence of seawater-sourced, hypersaline brine at depths >200 m below the seafl
oor. Na-Cl-Br and SO4-Cl-Br relationships are consistent with a concentration mechanism
that involves the removal of pure H2O as ice and precipitation of mirabilite (Na2SO4·10H2O)
during progressive freezing of seawater. The brine is in Neogene subglacial, glacimarine, and
marine facies that record advance and retreat of glaciers through the Ross Sea embayment.
In this environment, sea ice formation in semi-isolated marine basins that occupied fl exural
troughs along ice sheet margins produced dense brines that sank and infi ltrated the permeable
subglacial sediment. Repeated cycles of glacial advance and retreat provided multiple
opportunities for batches of seawater to be transformed into brine that now is in the subsurface
of southern McMurdo Sound. Results demonstrate the feasibility of brine formation via
seawater freezing and attest to the potential of a cryogenic origin for subsurface brines in
high-latitude regions of the Northern Hemisphere, as proposed by some workers
Early and middle Miocene Antarctic glacial history from the sedimentary facies distribution in the AND-2A drill hole, Ross Sea, Antarctica
No full textIn 2007, the Antarctic Geological Drilling
Program (ANDRILL) drilled 1138.54 m of
strata ~10 km off the East Antarctic coast,
includ ing an expanded early to middle Miocene
succession not previously recovered
from the Antarctic continental shelf. Here,
we pre sent a facies model, distribution, and
paleoclimatic interpretation for the AND-2A
drill hole, which enable us, for the fi rst time,
to reconstruct periods of early and middle
Miocene glacial advance and retreat and
paleo environmental changes at an ice-proximal
site. Three types of facies associations
can be recognized that imply signifi cantly
different paleoclimatic interpretations. (1) A
diamictite-dominated facies association represents
glacially dominated depositional environments,
including subglacial environments,
with only brief intervals where ice-free coasts
existed, and periods when the ice sheet was
periodically larger than the modern ice sheet.
(2) A stratifi ed diamictite and mudstone facies
association includes facies characteristic of
open-marine to iceberg-infl uenced depositional
environments and is more consistent
with a very dynamic ice sheet, with a grounding
line south of the modern position. (3) A
mudstone-dominated facies association generally
lacks diamictites and was produced in a
glacially infl uenced hemipelagic depositional
environment. Based on the distribution of
these facies associations, we can conclude that
the Antarctic ice sheets were dynamic, with
grounding lines south of the modern location
at ca. 20.1–19.6 Ma and ca. 19.3–18.7 Ma and during the Miocene climatic optimum, ca.
17.6–15.4 Ma, with ice-sheet and sea-ice minima
at ca. 16.5–16.3 Ma and ca. 15.7–15.6 Ma.
While glacial minima at ca. 20.1–19.6 Ma
and ca. 19.3–18.7 Ma were characterized by
temperate margins, an increased abundance
of gravelly facies and diatomaceous siltstone
and a lack of meltwater plume deposits suggest
a cooler and drier climate with polythermal
conditions for the Miocene climatic
optimum (ca. 17.6–15.4 Ma). Several periods
of major ice growth with a grounding line traversing
the drill site are recognized between
ca. 20.2 and 17.6 Ma, and after ca. 15.4 Ma,
with evidence of cold polar glaciers with ice
shelves. The AND-2A core provides proximal
evidence that during the middle Miocene climate
transition, an ice sheet larger than the
modern ice sheet was already present by ca.
14.7 Ma, ~1 m.y. earlier than generally inferred
from deep-sea oxygen isotope records.
These fi ndings highlight the importance of
high-latitude ice-proximal records for the interpretation
of far-fi eld proxies across major
climate transitions
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
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