1,720,966 research outputs found
Assessment of small intestinal viability: A bioimpedance approach
No full textThis thesis describes how bioimpedance measurements can be used to assess the viability (live or die) of the small intestines, after a period without sufficient blood supply (ischemia). Using machine learning we were able to classify intestinal tissue injury and viability based on bioimpedance data, with accuracies similar to or better than what is reported by using the present clinical method.
The thesis describes how electrical parameters measured on the small intestine change during ischemia and reperfusion and describes the creation of a reference model for intestinal viability in a pig model. It also discusses how machine learning can be a relevant tool for analysis of longitudinal bioimpedance data.
As a part of the methodology, the thesis discusses intraluminal microdialysis for detection and monitoring of ischemia and reperfusion, and the use of histology to provide a reference for the viability limit. The thesis combines knowledge and research from the fields of physics and medicine, in order to investigate a solution to a medical problem
Assessment of Ischemic Small Intestine using Bioimpedance Measurements
No full textBACKGROUND AND OBJECTIVES:
In gastrointestinal surgery related to intestinal ischemia, the surgeon has to assess the viability of intestines that have been exposed to ischemic injury. There are at present limited means by which tissue viability can be assessed. The standard clinical method is still visual inspection and palpation. This method is non-specific and unreliable, and requires a high level of clinical experience. Bioimpedance has been utilized to measure changes in electrical parameters during ischemia in tissues like the liver, skeletal muscle, and the heart. The physical changes on the cellular and structural levels after the onset of ischemia, results in time-variant changes in the electrical properties of the tissue. The aim of this thesis is to investigate the possibility of utilizing bioimpedance measurements to aid in intraoperative assessment of the viability of ischemic small intestinal tissue.
MATERIALS AND METHODS:
We have accomplished 5 initial pilot studies in a porcine model of small intestinal ischemia, and 7 further studies on porcine models based on the initial findings. After induction of anesthesia, a warm ischemic model with full mesenteric occlusion in a small part of the jejunum was implemented. Measurements were conducted by placing electrodes on the serosa of the jejunum, applying a constant voltage, and measuring the resulting admittance. Several electrode setups were tested. We used the recognized and commonly used Solartron 1260/1294 impedance analyzer setup. As a control we used measurements on parts of the jejunum with full perfusion in the same porcine model.
RESULTS:
The 2 electrode Silver-Silver chloride setup appeared the best of the tested setups for measuring small intestinal ischemia interoperably. The collected data from the porcine models show significant changes in electrical parameters of modulus, phase, and tan d as a function of ischemic time, compared to the control. A Matlab program with pilot algorithms has been developed that show 78,2% sensitivity, 94,2% specificity, 92,7% positive predictive value, and 82,0% negative predictive value in assessing if the porcine small intestine is ischemic or not, based upon analysis of the collected data. The program also show promising results in discerning the time duration of ischemic small intestine within the tested 6 hour time frame. Histological samples show ischemic changes to the small intestinal tissue that correlate with the measured time variable changes.
CONCLUSIONS:
The time development of the electrical properties measured within a 6 hr period of ischemia is statistically significant, and can be correlated with the onset and duration of ischemia. These changes in electrical parameters can be utilized in programs to assess the ischemic status of porcine small intestine. Based on the results from the porcine models, it is not yet possible to assess the viability of the small intestine to the point of irreversible ischemic damage, as the 6 hour ischemic period of porcine model 2 (PM2) did not create a 100% certain ischemically irreversible damaged porcine small intestine. The animal model developed through these experiments seems suitable for further studies related to the determination of the viability of ischemic small intestine
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
Detection of physiological concentrations of GABA using dielectric spectroscopy - A pilot study
No full textGamma-aminobutyric acid (GABA) is a major inhibitory neurotransmitter that is present at a relatively low level throughout the normal adult human brain. Abnormal GABA levels are found in people with neurodegenerative disorders such as Parkinson’s disease, epilepsy, schizophrenia, depression, and others. Being able to measure the GABA concentration would be beneficial for patient groups with fluctuating GABA levels for better diagnosis and treatment. In this study, we explore the feasibility of using dielectric relaxation spectroscopy for the detection of GABA concentrations within a physiological range, with the perspective of miniaturization and use during implantation. Utilizing machine learning techniques, we were able to differentiate GABA concentrations down to 5 μm. This work investigates a novel use of dielectric relaxation spectroscopy, to assess if physiological GABA concentrations can be detected through permittivity measurements
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
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