1,720,955 research outputs found
Do retinal microvascular abnormalities shed light on the pathophysiology of lacunar stroke?
Full text linkBackground. Lacunar strokes account for 25% of all ischaemic stroke but the exact
nature of the causative cerebral small vessel abnormality remains unknown.
Pathological studies are technically difficult and brain imaging cannot adequately
characterise the cerebral small vessels. The retinal blood vessels are of similar size
and physiology to the cerebral small vessels and may act as a surrogate marker for
these cerebral small vessels. We therefore investigated retinal microvascular
abnormalities in lacunar stroke.
Methods. We performed a systematic review of retinal microvascular abnormalities
in lacunar stroke to clarify associations and identify where further research was
required. We then established a cohort of patients presenting with lacunar stroke
with cortical stroke controls to investigate differences in retinal microvascular
abnormalities between stroke subtypes. All patients had MRI brain at presentation
and digital retinal photography of both eyes. We investigated the prevalence of
retinopathy (hard and soft exudates or haemorrhages/microaneurysms), focal
arteriolar narrowing and arteriovenous nicking . We developed, validated and used
novel semi-automated techniques for measuring retinal arteriolar and venular widths,
retinal arteriolar geometry (branching co-efficients (change in arteriolar cross
sectional area across a bifurcation) and branching angles) and fractal dimensions
(reflecting branching complexity) of the vasculature. We also assessed MRI
parameters in lacunar stroke. We used multivariable analysis to correct for baseline
imbalances in vascular risk factors.
Results. From the systematic review we demonstrated that retinal microvascular
abnormalities are associated with incident and prevalent stroke but that in general,
strokes were inadequately characterised and there were no data regarding retinal
microvascular abnormalities in ischaemic stroke subtypes. We recruited 253
patients, 129 lacunar strokes and 124 cortical strokes, mean age 68 years. We found
no difference in the prevalence of retinopathy, arteriovenous nicking, focal arteriolar
narrowing or arteriolar widths between lacunar and cortical stroke subtypes. We
found that venules were wider in lacunar stroke. We found no differences in
arteriolar branching co-efficients or arteriolar branching angles between lacunar and
cortical strokes but found that deep white matter white matter hyperintensities on
MRI were associated with increased branching co-efficients and periventricular
white matter hyperintensities associated with decreased branching co-efficients. We
found that the fractal dimension of the vascular tree was decreased in lacunar stroke.
Furthermore we found that enlarged perivascular spaces on MRI are associated with
lacunar stroke and white matter disease.
Conclusions. We have clearly demonstrated that retinal microvascular abnormalities
differ between lacunar and cortical stroke suggesting that a distinct small vessel
vasculopathy may cause lacunar stroke. We have also identified MR markers of
lacunar stroke. These results suggest that venular disease (a hitherto underresearched
area) may play a role in the pathophysiology of lacunar stroke. Retinal
microvascular abnormalities can act as markers for cerebral small vessel disease. We
plan collaborative analyses with colleagues who have performed similar studies to
further assess retinal abnormalities in lacunar stroke
Do retinal microvascular abnormalities shed light on the pathophysiology of lacunar stroke?
No full textBackground. Lacunar strokes account for 25% of all ischaemic stroke but the exact nature of the causative cerebral small vessel abnormality remains unknown. Pathological studies are technically difficult and brain imaging cannot adequately characterise the cerebral small vessels. The retinal blood vessels are of similar size and physiology to the cerebral small vessels and may act as a surrogate marker for these cerebral small vessels. We therefore investigated retinal microvascular abnormalities in lacunar stroke. Methods. We performed a systematic review of retinal microvascular abnormalities in lacunar stroke to clarify associations and identify where further research was required. We then established a cohort of patients presenting with lacunar stroke with cortical stroke controls to investigate differences in retinal microvascular abnormalities between stroke subtypes. All patients had MRI brain at presentation and digital retinal photography of both eyes. We investigated the prevalence of retinopathy (hard and soft exudates or haemorrhages/microaneurysms), focal arteriolar narrowing and arteriovenous nicking . We developed, validated and used novel semi-automated techniques for measuring retinal arteriolar and venular widths, retinal arteriolar geometry (branching co-efficients (change in arteriolar cross sectional area across a bifurcation) and branching angles) and fractal dimensions (reflecting branching complexity) of the vasculature. We also assessed MRI parameters in lacunar stroke. We used multivariable analysis to correct for baseline imbalances in vascular risk factors. Results. From the systematic review we demonstrated that retinal microvascular abnormalities are associated with incident and prevalent stroke but that in general, strokes were inadequately characterised and there were no data regarding retinal microvascular abnormalities in ischaemic stroke subtypes. We recruited 253 patients, 129 lacunar strokes and 124 cortical strokes, mean age 68 years. We found no difference in the prevalence of retinopathy, arteriovenous nicking, focal arteriolar narrowing or arteriolar widths between lacunar and cortical stroke subtypes. We found that venules were wider in lacunar stroke. We found no differences in arteriolar branching co-efficients or arteriolar branching angles between lacunar and cortical strokes but found that deep white matter white matter hyperintensities on MRI were associated with increased branching co-efficients and periventricular white matter hyperintensities associated with decreased branching co-efficients. We found that the fractal dimension of the vascular tree was decreased in lacunar stroke. Furthermore we found that enlarged perivascular spaces on MRI are associated with lacunar stroke and white matter disease. Conclusions. We have clearly demonstrated that retinal microvascular abnormalities differ between lacunar and cortical stroke suggesting that a distinct small vessel vasculopathy may cause lacunar stroke. We have also identified MR markers of lacunar stroke. These results suggest that venular disease (a hitherto underresearched area) may play a role in the pathophysiology of lacunar stroke. Retinal microvascular abnormalities can act as markers for cerebral small vessel disease. We plan collaborative analyses with colleagues who have performed similar studies to further assess retinal abnormalities in lacunar stroke.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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