1,720,976 research outputs found
The Campbell ferromanganese nodule field in the southern part of New Zealand’s Exclusive Economic Zone
No full textA refined geochemical dataset of volcanic rocks from the Kermadec intra-oceanic arc venting (abstract of paper presented at: 16th Annual V.M. Goldschmidt Conference 2006, Melbourne, Australia, 27 Aug-1 Sept 2006)
No full textOccurrence and physical setting of ferromanganese nodules beneath the Deep Western Boundary Current, SW Pacific
No full textAn extensive ferromanganese nodule field adjacent to the Campbell Plateau in the Southwest Pacific Ocean forms beneath the Deep Western Boundary Current (DWBC) and Antarctic Circumpolar Current (ACC). West of c. 174°E, between 59 and 48°S, the field is inferred to be 300–500 km wide, but east of 174°E, where the currents impinge on the eastern slope of the Campbell Plateau, the field narrows from c. 200 km at 55°S to c. 120 km at 49°S. This coincides with deflection of current flow eastward, and consequent reduction in bottom-current velocity and eddy kinetic energy. Based on seafloor photographs, dredge samples, and 3.5 kHz profile data, five principal nodule facies form broadly parallel zones eastwards from the lowermost Campbell escarpment. These are defined based on location, presumed nodule genesis, and seafloor nodule density: (1) slope hydrogenous, high-density (SHH); (2) abyssal diagenetic/hydrogenous, low-density (ADHL); (3) abyssal hydrogenous, high-density (AHH); (4) abyssal diagenetic, high-density (ADH); and (5) abyssal diagenetic, low-density (ADL). Several nodule morphotypes are identified including distinctive discoidal forms with overgrowths possibly resulting from overcrowding and partial sediment burial. Seafloor abundance, surficial textures, and chemistry indicate a predominantly hydrogenous nodule growth and very low net sedimentation beneath the core of the DWBC. Increasing Mn, Ni, and Cu contents, and decreasing detrital silicate contents from core to rim, reflect intensifying abyssal DWBC circulation since c. 6 Ma. Because of the DWBC’s high velocity, the nodules provide no record of an increasing terrigenous bedload from New Zealand since c. 3 Ma. However, in regions of reduced flow velocity eastwards from the main DWBC pathway, relatively higher sedimentation rates prevail, and nodules have a higher diagenetic component
Methane release at the top of the gas hydrate stability zone of the Hikurangi margin, New Zealand
No full textDissolved methane and high resolution bathymetry surveys were conducted over the Rock Garden region of Ritchie Ridge, along the Hikurangi margin, eastern New Zealand. Multibeam bathymetry reveals two prominent, northeast trending ridges, parallel to subduction along the margin, that are steep sided and extensively slumped. Elevated concentrations of methane (up to 10 nM, 10× background) within the water column are associated with a slump structure at the southern end of Eastern Rock Garden. The anomalous methane concentrations were detected by a methane sensor (METS) attached to a conductivity-temperature-depth-optical backscatter device (CTDO) and are associated with elevated light scattering and flare-shaped backscatter signals revealed by the ship’s echo sounder. Increased particulate matter in the water column, possibly related to the seepage and/or higher rates of erosion near slump structures, is considered to be the cause of the increased light scattering, rather than bubbles in the water column. Methane concentrations calculated from the METS are in good agreement with concentrations measured by gas chromatography in water samples collected at the same time. However, there is a c. 20?min (c. 900?m) delay in the METS signal reaching maximum CH4 concentrations. The maximum methane concentration occurs near the plateau of Eastern Rock Garden close to the edge of a slump, at 610?m below sea level (mbsl). This is close to the depth (c. 630?mbsl) where a bottom simulating reflector (BSR) pinches out at the seafloor. Fluctuating water temperatures observed in previous studies indicate that the stability zone for pure methane hydrate in the ocean varies between 630 and 710?mbsl. However, based on calculations of the geothermal gradients from BSRs, we suggest gas hydrate in the study area to be more stable than hydrate from pure methane in sea water, moving the phase boundary in the ocean upward. Small fractions of additional higher order hydrocarbon gases are the most likely cause for increased hydrate stability. Relatively high methane concentrations have been measured down to c. 1000?mbsl, most likely in response to sediment slumping caused by gas hydrate destabilisation of the sediments and/or marking seepage through the gas hydrate zone
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
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
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