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The misleading effect of cerebrovascular autoregulation variability on pressure-volume index assessment in clinical practice.
No full textTranscranial Doppler ultrasonography in intensive care.
No full textSummary
Transcranial Doppler is an innovative, flexible, accessible tool for the bedside monitoring of static and
dynamic cerebral flow and treatment response. Introduced by Rune Aaslid in 1982, it has become indispensable
in clinical practice. The main obstacle to ultrasound penetration of the skull is bone. Low frequencies,
1–2 MHz, reduce the attenuation of the ultrasound wave caused by bone. Transcranial Doppler also provides
the advantage of acoustic windows representing specific points of the skull where the bone is thin enough to
allow ultrasounds to penetrate. There are four acoustic windows: transtemporal, transorbital, suboccipital and
retromandibular. The identification of each intracranial vessel is based on the following elements: (a) velocity
and direction; (b) depth of signal capture; (c) possibility of following the vessel its whole length; (d) spatial
relationship with other vessels; and (e) response to homolateral and contralateral carotid compression. The
main fields of clinical application of transcranial Doppler are assessment of vasospasm, detection of stenosis of
the intracranial arteries, evaluation of cerebrovascular autoregulation, non-invasive estimation of intracranial
pressure, measure of effective downstream pressure and assessment of brain death. Mean flow velocity is
directly proportional to flow and inversely proportional to the section of the vessel. Any circumstance that
leads to a variation of one of these factors can thus affect mean velocity. The main pathological condition
affecting flow velocity is the vasospasm. Vasospasm is a frequent complication of subarachnoid haemorrhage, it
often remains clinically silent and the factors that make it symptomatic are largely unknown. Threshold
velocities above which vasospasm comes into place are well defined as regards the median cerebral artery, while
there is no consensus for the other vessels. Nevertheless, an increase in velocity alone is not sufficient to arrive
at a diagnosis of vasospasm; a condition of hyperaemia also presents with an increase in flow velocity. The
Lindegaard Index has therefore been introduced, which is defined by the ratio between the mean flow velocity
in the median cerebral artery and the mean flow velocity in the internal carotid artery. Criteria for diagnosis
of a stenosis .50% of an intracranial vessel with transcranial Doppler include: (a) segmentary acceleration of
flow velocity; (b) drop in velocity below the stenotic segment; (c) asymmetry; and (d) circumscribed flow
disturbances (turbulence and musical murmur). The transcranial Doppler enables us to assess both components
of self-regulation. The static component is measured by observing changes in flow velocity caused by pharmacologically
induced episodes of hypertension and hypotension. The dynamic component of autoregulation
can be measured using a method devised by Aaslid known as the ‘cuff test’. A very effective and safe device for
measuring cerebral autoregulation is the transient hyperaemic response test. This test is based on the compensatory
vasodilatation of the arterioles, which occurs after brief compression of the common carotid.
Csonyka proposed the following formula based on clinical observation for the calculation of cerebral perfusion
pressure: CPP5MAP3FVd/FVm114. Brain death is defined as the irreversible cessation of all functions of
the whole brain. The clinical criteria are usually considered sufficient to establish a diagnosis of brain death;
however, they might not be sufficient in patients who have been on sedatives or when there are ethical or lega
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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