1,721,010 research outputs found
3-dimensional imaging and mathematical modelling of human pulmonary lymphatics
No full textLymphatics drain fluid, cells, and essential metabolites back to the circulatory system to maintain fluid homoeostasis. The fluid balance is critical for normal tissue function and is often disturbed in lung diseases such as COPD, asthma, and lung cancer. Although 6.5 million people in the UK are undergoing active treatment for these diseases, little is known about how lymphatics influence lung fluid dynamics.This study developed and applied a methodology to assess the anatomical structure and predict the function of the 3D lymphatic network in healthy and diseased peripheral human lung tissue.High-resolution X-ray micro-computed tomography (μCT) provided the 3D structural blueprint of the lung samples down to a voxel size of 5 μm. The pulmonary lymphatic network was subsequently identified and segmented within the same tissue using immunohistochemistry and anti-podoplanin antibodies (D240 and LP21). These micrographs were used to manually segment the lymphatic structures within the μCT dataset alongside the blood vessels, airways and lung parenchyma.A physiologically accurate image-based mathematical model was established using these geometries. Flow in the blood and microlymphatics are described using the Stokes equations and flow through the interstitium using Darcy's law. Starling’s law describes flow across the blood and lymphatic vessel walls, with a uni-directional restraint given to the lymphatic vessel wall to represent the primary valve condition. In addition to changes in input geometry, the model shows sensitivity to pulmonary blood vessel pressure and vessel flow velocities.To validate the methodology, ten formalin-fixed, paraffin-embedded peripheral lung biopsies were used, four controls, four from patients with acute respiratory injury or inflammation and two with severe COPD disease. Inter- and intra-sample lymphatic heterogeneity was assessed by vessel volume, vessel surface area, network branch and junction number, vessel tortuosity and fractal dimension. Two hierarchical lymphatic populations were identified; precollecting lymphatics and microlymphatics. Three microlymphatic subpopulations were also defined based on their structural heterogeneity and anatomical location in the lung: intralobular(IL); subpleural (SP) and bronchovascular(BVB). This suggested pulmonary fluid dynamics may vary in different anatomical locations. In the active disease group, five of the six microlymphatic measures were distinct to both the COPD and control groups (P<0.0001). Whereas, no morphological differences were seen between the control and COPD sample groups, suggesting fluid dynamics in the control and COPD samples would be similar, whilst those in the active disease sample would be different.To test the predictions from the morphometry assessment, a finite element mesh was created for the lymphatics, blood vessels and parenchyma in five random volumes from the IL, SP and BVB regions in the control group, and IL region of the acute disease and COPD samples. Using COMSOL Multiphysics ©, finite element simulation software and the mathematical model, fluid flow within the lung geometries were then simulated and compared. Modelling results predict fluid drainage does vary between anatomical areas of the peripheral lung but in the IL region, the COPD geometries drain fluid less efficiently than the control (0.0015 ml.min1 /mm3 lymphatic volume and 0.0024 ml.min-1 /mm3 lymphatic volume respectively). The model considers both blood vessel and interstitial structural variation and their proximity to the lymphatics in 3D space. This more sophisticated analysis accounts for some of the discrepancies between the morphometry assessment and the modelling predictions. This highlights the benefit of incorporating image-based modelling into biological systems to provide higher-level consideration of structure function relationships of the whole tissue
Dataset supporting article entitled "Correlative 3D Imaging and Microfluidic Modelling of Human Pulmonary Lymphatics using Immunohistochemistry and High-resolution μCT"
No full textThis dataset supports the article entitled "Correlative 3D Imaging and Microfluidic Modelling of Human Pulmonary Lymphatics using Immunohistochemistry and High-resolution μCT" and includes:
20x human lung lymphatics Immunohistochemistry data files
2x COMSOL result modelling files
Location of the micro-CT data set used in this article
This dataset, approx 98Gb, is available on request via the webform at https://library.soton.ac.uk/datarequest </span
"3-Dimensional Imaging and Mathematical Modelling of Human Pulmonary Lymphatics"
No full textThis raw data contributes to the University of Southampton Doctoral thesis entitled "3-Dimensional Imaging and Mathematical Modelling of Human Pulmonary Lymphatics" </span
Students pay attention! Combating the vigilance decrement to improve learning during lectures
No full textMaintaining student concentration in lectures has long been a challenge for lecturers. Pedagogical research consistently finds a drop in attention between 10 and 30 minutes into the lecture, which has been associated with the passive nature of the standard format, and has consequences for learning approaches and outcomes. A similar phenomenon has been observed in ergonomics for some time, known as the vigilance decrement. In this paper, we present an exploratory effort to detect the vigilance decrement in four different lecture formats, by adopting an ergonomics measurement tool which has been related to vigilance, and relating the findings to students’ assessment results. It was found that standard lecture formats do induce a vigilance decrement, and this can adversely affect learning of the material. Conversely, vigilance degradation is avoided when presentation is varied, though this is not necessarily associated with interactive participation techniques. Implications for lecturing styles, learning approaches and pedagogical research methods are discussed
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
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