1,720,994 research outputs found
Major artifacts encountered in studying biological samples containing ferric protoporphyrin IX
No full textHeme (ferric protoporphyrin IX, FP) dissolves very rapidly into the lipid phase of membranes, and a large number of studies have focused attention on its possible toxic effect in whole cells or isolated membranes. However, because of its molecular structure and reactivity, different problems can be encountered during the course of studying biological samples containing FP. In this article, we discuss important interferences by FP and artifacts that can affect the experimental values. First, FP interferes with the Lowry's protein determination; therefore, membranes containing FP are overestimated in their protein content determined by this procedure. Second, freezing membranes at -20°C artifactually increases the local concentration of FP, thereby enhancing FP-induced lipid peroxidation. Third, in the presence of thiol compounds such as N-acetyl cysteine, FP is degraded to products that interfere with the thiobarbituric acid assay, one of the most widely used methods to measure the extent of lipoperoxidation
Antioxidant metabolism in Xenopus laevis embryos is affected by stratospheric balloon flight
No full textTo test the effects of low levels of radiation from space on living organisms, we flew Xenopus laevis embryos at different stages of development on a stratospheric balloon (BI.R.BA mission). After recovery, different parameters were analyzed to assess the effects of flight, with particular regard to oxidative stress damage. Because of failed temperature control during flight, the flight shielded embryos (FC) could not be used for biochemical or morphological comparisons. In contrast, the incubation conditions (i.e. temperature, containers, volumes) for the flight embryos (F) were parallel to those for the ground controls. Mortality data show that younger embryos (16 h) flown on the balloon (F) are more sensitive to radiation exposure than older ones (40 h and 6 days). Exposure during flight lowered the antioxidant potential in all embryos, particularly older ones. These preliminary data demonstrate that flight on a stratospheric balloon might affect antioxidant metabolism, though it is not yet possible to correlate these results with low radiation exposure during fligh
Space Flight Effects on Antioxidant Molecules in Dry Tardigrades: The TARDIKISS Experiment
No full textThe TARDIKISS (Tardigrades in Space) experiment was part of the Biokon in Space (BIOKIS) payload, a set of multidisciplinary experiments performed during the DAMA (Dark Matter) mission organized by Italian Space Agency and Italian Air Force in 2011. This mission supported the execution of experiments in short duration (16 days) taking the advantage of the microgravity environment on board of the Space Shuttle Endeavour (its last mission STS-134) docked to the International Space Station. TARDIKISS was composed of three sample sets: one flight sample and two ground control samples. These samples provided the biological material used to test as space stressors, including microgravity, affected animal survivability, life cycle, DNA integrity, and pathways of molecules working as antioxidants. In this paper we compared the molecular pathways of some antioxidant molecules, thiobarbituric acid reactive substances, and fatty acid composition between flight and control samples in two tardigrade species, namely, Paramacrobiotus richtersi and Ramazzottius oberhaeuseri. In both species, the activities of ROS scavenging enzymes, the total content of glutathione, and the fatty acids composition between flight and control samples showed few significant differences. TARDIKISS experiment, together with a previous space experiment (TARSE), further confirms that both desiccated and hydrated tardigrades represent useful animal tool for space research
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
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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