1,720,978 research outputs found
Microbial Biofilms Along a Geochemical Gradient at the Shallow-Water Hydrothermal System of Vulcano Island, Mediterranean Sea
Full text linkShallow water hydrothermal vents represent highly dynamic environments where strong geochemical gradients can shape microbial communities. Recently, these systems are being widely used for investigating the effects of ocean acidification on biota as vent emissions can release high CO2 concentrations causing local pH reduction. However, other gas species, as well as trace elements and metals, are often released in association with CO2 and can potentially act as confounding factors. In this study, we evaluated the composition, diversity and inferred functional profiles of microbial biofilms in Levante Bay (Vulcano Island, Italy, Mediterranean Sea), a well-studied shallow-water hydrothermal vent system. We analyzed 16S rRNA transcripts from biofilms exposed to different intensity of hydrothermal activity, following a redox and pH gradient across the bay. We found that elevated CO2 concentrations causing low pH can affect the response of bacterial groups and taxa by either increasing or decreasing their relative abundance. H2S proved to be a highly selective factor shaping the composition and affecting the diversity of the community by selecting for sulfide-dependent, chemolithoautotrophic bacteria. The analysis of the 16S rRNA transcripts, along with the inferred functional profile of the communities, revealed a strong influence of H2S in the southern portion of the study area, and temporal succession affected the inferred abundance of genes for key metabolic pathways. Our results revealed that the composition of the microbial assemblages vary at very small spatial scales, mirroring the highly variable geochemical signature of vent emissions and cautioning for the use of these environments as models to investigate the effects of ocean acidification on microbial diversity
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
Effects of midline thoracotomy on pulse pressure variations during pressure-control ventilation
No full textObjective During mechanical ventilation, the heart–lung interaction
induces a cyclic oscillation of the arterial pulse pressure. The measure of this respiratory changes, called pulse pressure variation (PPV), is one of the most reliable index of fluid responsiveness. It is used as a functional hemodynamic monitoring in several conditions (general anesthesia, sepsis, ALI/ARDS). During cardiac surgery, midline thoracotomy significantly alters heart–lung interaction and, consequently,
PPV. The aim of the study was the evaluation of the effects of
sternotomy on PPV during pressure-control ventilation (PCV).
Methods Nineteen patients (age 62 ± 10 years) undergoing elective CABG in a tertiary university hospital were enrolled. A Swan–Ganz catheter, an arterial catheter and a central venous catheter was inserted in order to collect pressure waveforms. After the induction of general anesthesia all the patients were mechanically ventilated (PCV), setting pressure values in order to obtain a tidal volume of 8 ml/kg. Hemodynamic data were collected 5 min before and after sternotomy. PPV was calculated offline from the collected waveforms, according to the formula reported by Michard and colleagues [1].
Results The PPV, cardiac index, stroke volume, mean arterial
pressure, airway pressure and tidal volume did not change after
sternotomy. We subsequently differentiated patients according to
PPV values (Fig. 1). In the subgroup of patients with PPV > 13%
(7/19 patients), we found a good correlation between PPV and
Paw (Pearson correlation 0.861 P = 0.03; R2 = 0.74 P = 0.049);
after sternotomy, PPV was significantly reduced (15.4 ± 2.8% vs
8.2 ± 1.6%, P = 0.043) and it was no more correlated with Paw. In the subgroup of patients with PPV < 13% (12/19 patients), we did not find any correlation between PPV and Paw, and sternotomy
had no effects on hemodynamic data.
Conclusions During PCV, airway pressure affects PPV only when
patients are in a ‘fluid responsive’ status (PPV > 13%); similarly,
sternotomy reduces PPV only when baseline is above the hreshold value of 13%. It may thus be possible that midline thoracotomy makes a ‘fluid responsive’ patient unresponsive to a fluid challenge by leading his heart to work on the plateau portion of theFrank–Starling curve. This hypothesis would be confirmed by the lack of correlation between airway pressure and PPV after opening the thorax.
Reference
1. Michard F, Boussat S, Chemla D, et al.: Am J Respir Crit
Care Med 2000, 162:134-138
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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