1,720,957 research outputs found
Small scale physical processes and phytoplankton growth in self seas
No full textDetailed physical and biological observations collected in shelf sea regions, dominated by tidal mixing fronts or internal tides, are analysed in terms of the effect of physical forcing on phytoplankton growth. Microstructure measurements are used to quantify differences in vertical mixing and hence nutrient and light supply across regimes. The Fast Repetition Rate Fluorometer (FRRF) is used to obtain high-resolution data on the physiological state of the associated phytoplankton communities, with the aim of testing hypotheses relating growth to changing environmental conditions. Observations were made during three research cruises, RRS Challenger, in the Western English Channel, 1999 and RV Kaharoa, off the North East New Zealand coast, 1998 and 2000. The work represents one of the first attempts to collect and interpret FRRF data in a defined physical context within natural ecosystems.Results from the 1999 cruise indicate that physical forcing in the region of a tidal mixing front has a pronounced influence on the physiology of the associated phytoplankton communities. FRRF based observations were consistent with nutrient limitation towards the stratified side of tidal mixing fronts, while deep vertical mixing caused light limitation within the mixed region. The observed enhancement of chlorophyll in the region of tidal mixing fronts therefore results, at least partly, from in situ growth.Results from the 1998 and 2000 cruises demonstrate that internal tide dissipation can be responsible for high vertical nitrate fluxes and pronounced variations in phytoplankton light climate. Interpretation of physiological data from the 2000 cruise was difficult due to the complexity of the physical processes observed. However, physiological variability due to vertical motions and upwelling in the region is demonstrated.Changes in FRRF derived photophysiology, as described by the photosynthetic efficiency (Fv/Fm) and the functional absorption cross section (σPSH), are shown to be related to photosynthetic parameters measured by 14C derived carbon fixation. In particular a striking inverse correlation between FRRF derived σPSH and 14C P* vs. E derived maximal photosynthetic rates (P*max) was observed. FRRF derived photosynthetic rates are shown to compare favourably with 14C derived rates, given the limitations of both techniques.</p
Iron limitation of the postbloom phytoplankton communities in the Iceland Basin
No full textMeasurements performed on a cruise within the central Iceland Basin in the high-latitude (>55°N) North Atlantic Ocean during late July to early September 2007 indicated that the concentration of dissolved iron (dFe) in surface waters was very low, with an average of 0.093 (<0.010–0.218, n = 43) nM, while nitrate concentrations ranged from 2 to 5 ?M and in situ chlorophyll concentrations ranged from 0.2 to 0.4 mg m?3. In vitro iron addition experiments demonstrated increased photosynthetic efficiencies (Fv/Fm) and enhanced chlorophyll accumulation in treatments amended with iron when compared to controls. Enhanced net growth rates for a number of phytoplankton taxa including the coccolithophore Emiliania huxleyi were also observed following iron addition. These results provide strong evidence that iron limitation within the postspring bloom phytoplankton community contributes to the observed residual macronutrient pool during summer. Low atmospheric iron supply and suboptimal Fe:N ratios in winter overturned deep water are suggested to result in the formation of this seasonal high-nutrient, low-chlorophyll (HNLC) condition, representing an inefficiency of the biological (soft tissue) carbon pump in the region. <br/
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
Tapping the unused potential of photosynthesis with a heterologous electron sink
Full text linkIncreasing the efficiency of the conversion of light energy to products by photosynthesis represents a grand challenge in biotechnology. Photosynthesis is limited by the carbon-fixing enzyme Rubisco resulting in much of the absorbed energy being wasted as heat, fluorescence or lost as excess reductant via alternative electron dissipation pathways. To harness this wasted reductant, we engineered the model cyanobacterium Synechococcus PCC 7002 to express the mammalian cytochrome P450 CYP1A1 to serve as an artificial electron sink for excess electrons derived from light-catalysed water-splitting. This improved photosynthetic efficiency by increasing the maximum rate of photosynthetic electron flow by 31.3%. A simple fluorescent assay for CYP1A1 activity demonstrated that the P450 was functional in the absence of its native reductase, that activity was light-dependent and scaled with irradiance. We show for the first time in live cells that photosynthetic reductant can be redirected to power a heterologous cytochrome P450. Furthermore, PCC 7002 expressing CYP1A1 degraded the herbicide atrazine, which is a widespread environmental pollutant
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
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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