1,721,031 research outputs found
Thallium isotope constraints on the water fluxes of ridge flank hydrothermal systems (abstract of paper presented at: 16th Annual V.M. Goldschmidt Conference 2006, Melbourne, Australia, 27 Aug-1 Sept 2006)
No full textHydrothermal activity in the oceans is not restricted to the high-temperature (T) vents that are found at mid-ocean ridge axes. Rather, ridge flanks have a total hydrothermal power output which exceeds the axial output by at least a factor of 3. As the temperatures are comparatively low at ridge flanks, the respective water flux must be several orders of magnitude larger than on-axis, to remove the inferred power output. Even small changes in the composition of the circulating fluids can therefore produce very significant chemical fluxes. Our understanding of the importance of these chemical fluxes with respect to global geochemical budgets is limited, however, because the partitioning of heat between warmer, more reactive fluids with T 40 °C and cooler fluids, which have T 20 °C, is only poorly constrained.In this study, we have used Tl isotope and concentration data for altered ocean crust and hydrothermal fluids to constrain the water fluxes and average fluid exit temperatures of ridge flank hydrothermal systems. The calculations are based on the observation that the upper ocean crust, which has been altered at low temperature, has fractionated Tl isotope compositions and elevated Tl concentrations. The observed systematics can be exploited to calculate the flux of low-T hydrothermal fluids (FLT) by mass balance:FLT×[Tl]sw×fupt=Fuoc×?[Tl]uoc Here [Tl]sw is the Tl concentration of seawater, fupt is the fraction of Tl removed from seawater by alteration, Fuoc is the mass flux of upper ocean crust affected by low-T hydrothermal alteration, and ?[Tl]uoc is the average change of Tl concentration observed for low-T altered ocean crust.The calculations indicate that the hydrothermal water flux of ridge flanks is (0.2–5.4) × 1017 kg/yr. This implies that the fluids have an average temperature anomaly of only about 0.1–3.6° relative to ambient seawater. Such low temperatures should severely restrict the effect of ridge flank hydrothermal systems on the marine budgets of 87Sr/86Sr and Mg. This conclusion is in accord with the results of previous rock alteration studies, which concluded that the fluxes of low-T hydrothermal systems are insufficient to balance the oceanic budgets of these elements. <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
Relevance of a truncated PRESENILIN 2 transcript to Alzheimer's disease and neurodegeneration.
No full textBACKGROUND: The PRESENILIN genes (PSEN1, PSEN2) encoding for their respective proteins have critical roles in many aspects of Alzheimer's disease (AD) pathogenesis. The PS2V transcript of PSEN2 encodes a truncated protein and is upregulated in AD brains; however, its relevance to AD and disease progression remains to be determined. OBJECTIVE: Assess transcript levels in postmortem AD and non-AD brain tissue and in lymphocytes collected under the Australian Imaging Biomarker and Lifestyle (AIBL) study. METHODS: Full length PSEN2 and PS2V transcript levels were assessed by quantitative digital PCR in postmortem brain tissue (frontal cortex and hippocampus) from control, AD, frontotemporal dementia (FTD), and Lewy body dementia (LBD). Transcript levels were also assessed in lymphocytes obtained from the Perth subset of the AIBL study (n = 160). Linear regression analysis was used to assess correlations between transcript copy number and brain volume and neocortical amyloid load. RESULTS: PS2V levels increased in AD postmortem brain but PS2V was also present at significant levels in FTD and LBD brains. PS2V transcript was detected in lymphocytes and PS2V/PSEN2 ratios were increased in mild cognitive impairment (p = 0.024) and AD (p = 0.019) groups compared to control group. Increased ratios were significantly correlated with hippocampal volumes only (n = 62, β= -0.269, p = 0.03). CONCLUSION: Taken together, these results suggest that PS2V may be a marker of overall neurodegeneration.Nik Moussavi, Hani Seyyed, Tenielle Porter, Morgan Newman, Bartlett Benjamin, Imranc Khan ... et al
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
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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