1,720,961 research outputs found
Structure and function of the extracellular layer of airspaces and its configuration following deposition of solid and liquid particles
No full textBibliography: p. 243-278.The purpose of this dissertation is to examine the structure and function of the extrace11ular layer from large airways to alveoli. Surface tension (y) was directly measured at the air-liquid interface of tracheas from rats and guinea pigs with a droplet spreading technique. A non-aqueous fixation method was used to preserve the extracellular layer
including the surface active film for examination by electron microscopy ('EM). The function of the extracellular layer including the surface film was also studied in terms of its effect on particle displacement. Finally, a mode1 of injury to the airspaces was used to study the changes in the configuration of the extracellular layer after exposure to an acid aerosol.
The extracellular layer of the airspaces was shown by EM to be continuous with a predominantly multilayered osmiophilic film at its surface. In the large airways, y was 33.3 ± 0.70 (SE) mN/m and 32.3 ± 0.68 (SE) mN/m for the normal rat and guinea pig trachea respectively. Guinea pigs exposed for 4 hours to sulphuric acid aerosol(43.3 • 4.57 (SD)
mg/m3) developed a several-fold increase in the thickness of the mucus layer, with exudation of protein-Iike material. The osmiophilic surfactant film became irregularly thickened and multilayered. Despite these morphological changes, y remained normal. The capacity of the
surface film to displace particles into the subphase was not compromised.
The wetting and displacement of particles of different sizes and shapes were also studied in vitro. Small spherical particles (<30 µm in diameter) were more easily submersed into the liquid phase than larger particles; this effect was attributed to surface and line tension forces.
Alveolar surfactant was studied using a captive bubble surfactometer to characterize the minimum surface tension (y min) obtained upon compressing surfactant films. The y min measured for lavaged material from the lungs of acid exposed guinea pigs was 12.1 ± 8.48 (mean ± SD) mN/m, significantly higher than for control guinea pigs-2.0 ± 0.43 mN/m-or for acid exposed rats-1.29 ± 0.11 mN/m. Both protein inhibition and lipid peroxidation appear to be involved in this model of injury to the extracellular layer
A Biophysical study of surface properties of the mesothelium and trachea: injury caused by inhaling asbestos and acid aerosols
No full textBibliography: p. 137-155
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
The development of the pulmonary surfactant system in California sea lions
No full textPulmonary surfactant has previously been shown to change during development, both in composition and function. Adult pinnipeds, unlike adult terrestrial mammals, have an altered lung physiology to cope with the high pressures associated with deep diving. Here, we investigated how surfactant composition and function develop in California sea lions (Zalophus californianus). Phosphatidylinositol was the major anionic phospholipid in the newborn, whereas phosphatidylglycerol was increased in the adult. This increase in phosphatidylglycerol occurred at the expense of phosphatidylinositol and phosphatidylserine. There was a shift from long chain and polyunsaturated phospholipid molecular species in the newborn to shorter chain and mono- and disaturated molecular species in the adult. Cholesterol and SP-B concentrations were also higher in the adult. Adult surfactant could reach a lower equilibrium surface tension, but newborn surfactant could reach a lower minimum surface tension. The composition and function of surfactant from newborn California sea lions suggest that this age group is similar to terrestrial newborn mammals, whereas the adult has a “diving mammal” surfactant that can aid the lung during deep dives. The onset of diving is probably a trigger for surfactant development in these animals
An optimized in vitro model of the respiratory tract wall to study particle cell interactions
No full textAs a part of the respiratory tissue barrier, lung epithelial cells play an important role against the penetration of the body by inhaled particulate foreign materials. In most cell culture models, which are designed to study particle-cell interactions, the cells are immersed in medium. This does not reflect the physiological condition of lung epithelial cells which are exposed to air, separated from it only by a very thin liquid lining layer with a surfactant film at the air-liquid interface. In this study, A549 epithelial cells were grown on microporous membranes in a two chamber system. After the formation of a confluent monolayer the cells were exposed to air. The morphology of the cells and the expression of tight junction proteins were studied with confocal laser scanning and transmission electron microscopy. Air-exposed cells maintained monolayer structure for 2 days, expressed tight junctions and developed transepithelial electrical resistance. Surfactant was produced and released at the apical side of the air-exposed epithelial cells. In order to study particle-cell interactions fluorescent 1 microm polystyrene particles were sprayed over the epithelial surface. After 4 h, 8.8% of particles were found inside the epithelium. This fraction increased to 38% after 24 h. During all observations, particles were always found in the cells but never between them. In this study, we present an in vitro model of the respiratory tract wall consisting of air-exposed lung epithelial cells covered by a liquid lining layer with a surfactant film to study particle-cell interactions
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
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