1,721,045 research outputs found
Biochemical composition of sediment from the abyssal Clarion-Clipperton Fracture Zone
No full textSediment samples were collected by multi corer in the eastern Clarion-Clipperton Fracture Zone in 2022. Sediment grain size of freeze-dried sediment was measured by laser diffraction in a Malvern Mastersizer 2000. Total carbon, organic carbon, total nitrogen, δ13TC, δ13org. C, and δ15N content of freeze-dried, pulverized sediment was measured with a elemental analyzer coupled to an isotope ratio mass spectrometer (EA-IRMS). Phospholipid-derived fatty acids (PLFAs) were extracted from the sediment using a Bligh and Dyer extraction. Afterwards, PLFAs were derivatized to fatty acid methyl esters (FAMEs), and their concentrations and δ13 isotopic values measured on a gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS)
Metabolic rates are significantly lower in abyssal Holothuroidea than in shallow-water Holothuroidea
No full textRecent analyses of metabolic rates in fishes, echinoderms, crustaceans and cephalopods have concluded that bathymetric declines in temperature- and mass-normalized metabolic rate do not result from resource-limitation (e.g. oxygen or food/chemical energy), decreasing temperature or increasing hydrostatic pressure. Instead, based on contrasting bathymetric patterns reported in the metabolic rates of visual and non-visual taxa, declining metabolic rate with depth is proposed to result from relaxation of selection for high locomotory capacity in visual predators as light diminishes. Here, we present metabolic rates of Holothuroidea, a non-visual benthic and benthopelagic echinoderm class, determined in situ at abyssal depths (greater than 4000 m depth). Mean temperature- and mass-normalized metabolic rate did not differ significantly between shallow-water (less than 200 m depth) and bathyal (200–4000 m depth) holothurians, but was significantly lower in abyssal (greater than 4000 m depth) holothurians than in shallow-water holothurians. These results support the dominance of the visual interactions hypothesis at bathyal depths, but indicate that ecological or evolutionary pressures other than biotic visual interactions contribute to bathymetric variation in holothurian metabolic rates. Multiple nonlinear regression assuming power or exponential models indicates that in situ hydrostatic pressure and/or food/chemical energy availability are responsible for variation in holothurian metabolic rates. Consequently, these results have implications for modelling deep-sea energetics and processes
Biochemical composition of Echinodermata (Ophiuroidea, Asteroidea) from the abyssal Clarion-Clipperton Fracture Zone
No full textEchinodermata (Ophiuroidea and Asteroidea) were collected by the remotely operating vehicle (ROV) Kiel 6000 (Geomar, Kiel, Germany) and ROV HD14 (Ocean Infinity, Texas, USA) in the eastern Clarion-Clipperton Fracture Zone in 2019 and 2021. Total carbon, organic carbon, total nitrogen, δ13TC, δ13org. C, and δ15N content of freeze-dried, pulverized Ophiuroidea and Asteroidea were measured with a elemental analyzer coupled to an isotope ratio mass spectrometer (EA-IRMS). Phospholipid-derived fatty acids (PLFAs) were extracted from the Echinodermata pulver using a Bligh and Dyer extraction. Afterwards, PLFAs were derivatized to fatty acid methyl esters (FAMEs), and their concentrations and δ13 isotopic values measured on a gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS)
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
Photobiological Effects on Ice Algae of a Rapid Whole-Fjord Loss of Snow Cover during Spring Growth in Kangerlussuaq, a West Greenland Fjord
No full textThe presence of snow on sea-ice can have dramatic effects on the photosynthetically available radiation (PAR) that reaches the ice algae. To better quantify this effect in the high Arctic, an experiment was conducted in Kangerlussuaq, west Greenland, throughout March 2013 where snow was cleared off the sea-ice and measured parameters were compared to a control area. Samples of under-ice algae were then taken to analyse the species composition.
The bottom 30 mm of the sampled ice cores were used to determine the stress on the photosystems of the sea ice algae as they experienced the rapid irradiance via the variable fluorescence of photosystem II (PSII). PSII was measured using pulse amplitude modulated (PAM) fluorometry (Walz Imaging-PAM fluorometer). This provides the effective quantum yield of PSII (Φ_PSII), which is a unitless ratio of ambient (F) and maximum (F_m) fluorescence yields. These measurements were taken every 3 hours over the final day of the study. Periodically over the week of the study, similar measurements were taken (in triplicate) with a Phyto-PAM System II Emitter-Detector (Phyto-ED) to determine how F and F_m values changed at a courser temporal resolution. Also measured were rapid light curves (RLCs), which allowed for the derivation of the relative electron transfer rate (rETR and rETR_max; µmol é/m²/s), the slope of the light-limited portion of the RLC (α; mol é /mol photons), and the irradiance at which rETR was light-saturated (E_k; µmol photon/m²/s).
100 ml samples of thawed sea-ice were also collected and stored in the dark to be used for species identification. This was done by first enumerating the ice algae to the Utermöhl method. A Zeiss Axiovert 135M (40×) inverted microscope was used to identify and count species/morphological groups via a total of four diagonals per sample. Relative abundances of algae were estimated as percent of total count, and the biomass was calculated according to the ALGESYS protocol.
Throughout the experiment the following variables were collected at 5 minute intervals: Air temperature (°C; sun-screened Campbell 107 temperature probe), upwelling and downwelling PAR (µmol photons/m²s; Li-COR Li-191 PAR sensor) at 0.5 m above the sea-ice surface, and under-ice PAR (µmol photon/m²/s; Li-COR –Li-192 submersible PAR sensor). From these data, transmittance (τ) was calculated as the ratio between under-ice PAR and downwelling PAR at the surface, and albedo (0-1 scale) was calculated as the ratio between upwelling and downwelling PAR at the surface
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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