1,720,957 research outputs found
General anesthesia impairs muscle microvascular compliance
No full textIntroduction Drugs used to induce and maintain general
anesthesia have deep effects on the cardiovascular system. To our knowledge there are no studies investigating microvascular
compliance during general anesthesia with a noninvasive approach
based on near-infrared spectroscopy (NIRS) technology.
Methods We randomized 36 healthy subjects undergoing maxillofacial surgery to receive general anesthesia with a sevofluorane–remifentanil (Group S) or a propofol–remifentanil association (Group P). We collected noninvasive measures of hemoglobin concentration from the gastrocnemius muscle of the subjects using a NIRS device (NIMO, NIROX srl, Italy), which performs quantitative assessments of the [HbO2] and [Hb] exploiting precise absorption measurements close to the absorption peak of the water. Data were collected during a series of venous occlusions at different cuff pressures, before and after 30 minutes from induction of general anesthesia. The muscle blood volume and microvascular compliance were obtained with a process previously described elsewhere [1]. Data were analyzed with a one-way analysis of variance test.
Results Demographic data of the 36 subjects were similar in both
Groups S and P. General anesthesia reduced the heart rate and
mean arterial pressure and increased the total muscle blood
volume in both groups (Group S: from 2.4 ± 0.9 to 3.2 ± 1.2 ml/
100 ml; Group P: from 2.4 ± 1.2 to 3.5 ± 1.8 ml/100 ml;
P < 0.05). During general anesthesia, despite no differences in
muscle blood volume between the two groups, sevofluorane–
remifentanil significantly decreased microvascular compliance
(from 0.15 ± 0.08 to 0.09 ± 0.04 ml/mmHg/100 ml; P = 0.001)
whereas propofol–remifentanil did not (from 0.15 ± 0.08 to
0.16 ± 0.11 ml/mmHg/100 ml; P = 0.39).
Conclusion General anesthesia affects the microvascular bed of
skeletal muscle. An association between opioid and ipnotic agents
increases the muscle blood volume, whereas microvascular compliance
is reduced only by the sevofluorane–remifentanil association.
Reference
1. De Blasi RA, Palmisani S, Alampi D, et al.: Microvascular
dysfunction and skeletal muscle oxygenation assessed by phase modulation near-infrared spectroscopy in patients with septic shock. Intensive Care Med 2005, 31:1661-1668
Numerical study on active and passive trailing edge morphing applied to a multi-MW wind turbine section
Full text linkA progressive increasing in turbine dimension has characterized the technological development in offshore wind energy utilization. This aspect reflects on the growing in blade length and weight. For very large turbines, the standard control systems may not be optimal to give the best performance and the best vibratory load damping, keeping the condition of maximum energy production. For this reason, some new solutions have been proposed in research. One of these is the possibility of morphs the blade surface in an active way (increasing the performance in low wind region) or passive (load reduction) way.
In this work, we present a numerical study on the active and passive trailing edge morphing, applied to large wind turbines. In particular, the study focuses on the aerodynamic response of a midspan blade section, in terms of fluid structure interaction (FSI) and driven surface deformation.
We test the active system in a simple start-up procedure and the passive system in a power production with turbulent wind conditions, that is, two situations in which we expect these systems could improve the performance.
All the computations are carried out with a FSI code, which couples a 2D-CFD solver, a moving mesh solver (both implemented in OpenFOAM library) and a FEM solver.
We evaluate all the boundary conditions to apply in the section problem by simulating the 5MW NREL wind turbine with the NREL CAE-tools developed for wind turbine simulation
Effects of remifentanil-based general anaesthesia with propofol or sevoflurane on muscle microcirculation as assessed by near-infrared spectroscopy.
No full textAbstract BACKGROUND: Although anaesthetics are known to alter microcirculation no study has, to our knowledge, documented changes in human skeletal microcirculatory function during general anaesthesia. METHODS: Forty-four patients undergoing maxillofacial surgery at a university hospital were prospectively randomized to receive general anaesthesia with remifentanil combined with propofol or sevoflurane. Muscle microcirculation was investigated with near-infrared spectroscopy (NIRS) before general anaesthesia was induced and 30 min later. An NIRS device (NIMO, Nirox) was used to quantify calf deoxyhaemoglobin [HHb], oxyhaemoglobin [HbO2], and total haemoglobin [HbT] concentrations, coupled to a series of venous and arterial occlusions to measure calf blood flow, muscle oxygen consumption, calf vascular resistance, microvascular compliance, and haemoglobin resaturation rate (RR). RESULTS: In both the groups, general anaesthesia induced marked changes in muscle microcirculation: the tissue blood volume increased (+33% in remifentanil-sevoflurane and +45% with remifentanil-propofol groups), microvascular resistance decreased (-31% and -38%, respectively), and the post-ischaemic haemoglobin RR decreased (-48% and -36%, respectively). In the remifentanil-propofol group, the muscle blood flow increased (P0.001), whereas in the remifentanil-sevoflurane group microvascular compliance and muscle oxygen consumption decreased (P0.01). CONCLUSIONS: Remifentanil-based general anaesthesia with propofol or sevoflurane altered the muscle microcirculation in different ways. Quantitative NIRS, a technique that takes into account the optical tissue properties of the individual subject, can effectively measure these changes non-invasively
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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