1,720,969 research outputs found
The role of stratum corneum and dermal microvascular perfusion in penetration and tissue levels of water-soluble drugs investigated by microdialysis
No full textBACKGROUND: Hydrophilic drugs are poorly absorbed when applied topically, due to low partitioning through the lipid matrix of the stratum corneum. Cutaneous blood flow rapidly clears the absorbed drug, which may result in low tissue levels. This is of importance for topically applied drugs whose site of action is within the epidermis or dermis. Dermal drug levels can be measured using cutaneous microdialysis, which is a means of continuously sampling substances from the dermal extracellular fluid. OBJECTIVES: To measure the contribution of stratum corneum barrier and microvascular perfusion in determining dermal tissue levels of hydrophilic drugs (aciclovir and penciclovir) in vivo. METHODS: Studies were performed using microdialysis of the volar surface of the forearm of healthy volunteers (n = 55) over a 5-h collection period. Stratum corneum was removed by tape stripping, and barrier disruption quantified by measurement of transepidermal water loss (TEWL); dermal microvascular perfusion was modulated by inclusion of noradrenaline in the microdialysis perfusate. RESULTS: With intact skin and normal cutaneous blood flow the concentration of penciclovir recovered was below assay threshold (0.05 ng x mL(-1). With noradrenaline-induced local vasoconstriction, the area under the curve of drug absorbed through normal skin (+/- SEM) was 13.3 +/- 2.9 ng mL(-1) h(0-5) for penciclovir and 27.6 +/- 10.6 ng mL(-1) h(0-5) for aciclovir. Removal of the stratum corneum (to glistening) by tape stripping increased penciclovir absorption by 1300-fold and aciclovir absorption by 440-fold, confirming the stratum corneum as the major barrier to hydrophilic drug absorption. Sequential barrier disruption by tape stripping gave a close correlation between penciclovir concentration absorbed per hour and barrier disruption measured by TEWL (r2 = 0.9283). There was a 15.6-fold difference in the recovery of penciclovir through barrier-deficient skin with and without cutaneous blood flow. There was no relationship between fibre depth and amount of drug dialysed, which suggests free movement of antiviral drug on reaching the aqueous environment of the dermis. CONCLUSIONS: This study defines for the first time the relationship between the degree of mechanical barrier impairment and drug absorption at the same anatomical site in humans, and the role of blood flow in drug clearance in vivo
Multiple Spitz naevi: a report of both variants with clinical and histopathological correlation
No full textSpitz naevi are usually solitary lesions. Multiple Spitz naevi are extremely rare and reported as widespread (disseminated) or grouped (agminated). We report two cases of multiple Spitz naevi and review their aetiology and treatment
The publication rate of abstracts presented at the British Association of Dermatologists annual meeting
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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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