1,720,963 research outputs found
Charakterisierung von Wehentätigkeit: Ein magnetomyographischer Ansatz
No full textPremature labor and delivery is a major cause of infant mortality and morbidity. Advances in the fields of medicine and engineering together with a better understanding of the preterm birth related risk factors have successfully reduced their incidence. Despite such advances, in most developed countries the preterm birth rate is still high, accounting for about 85% of infant mortality and more than 50% of the surviving infant's morbidity. The timely prediction of premature labor and delivery can improve the effectiveness of the required treatments. Unfortunately, the techniques employed in current obstetrical practice proved to be inaccurate for the prediction of premature labor and delivery.
The contractile element of the uterus is the myometrium, which consists of smooth muscle cells. The electrical activity (always accompanied by magnetic activity) in form of action potentials (AP) propagates through the myometrial cells causing the contraction of the uterus. Magnetomyography (MMG) is the noninvasive measurement of the uterine magnetic activity by means of equally spaced magnetic sensors arranged in a concave array. The MMG recordings display advantages which renders them suitable for the analysis and characterization of the uterine activity. Compared to electromyography signals, the MMG signals are detectable outside the boundary of the skin without making any contact with the body. Also they are independent on conductivity geometry, i.e. tissue conductivity. The measured electrical activity arises from volume currents owing (in the body) to the electrode sites and not directly due to the primary current generators.
The current work presents a set of methods designated to identify and characterize uterine contractile activity and its dynamics in MMG signals. The basic process controlling the uterine contraction is the underlying electrical activity in the form of APs which propagate between muscle cells and open ion channels allowing the influx of calcium ions to produce a contraction. APs occur in groups and form a burst of activity which in humans can last more than a minute. The ultimate goal is to provide a timely prediction of delivery. More precisely, a multi-sensor analysis of the spatial propagation properties of the MMG signals is carried out to identify time segments of uterine burst activity. This type of analysis is of particular relevance because the spreading of magnetic activity in the myometrium results in coordinated contractions (close to term), capable to push the fetus into the birth canal and ultimately lead to delivery. Therefore, the analysis of the spatial propagation properties (within segments of contractile activity), i.e. conduction velocity (CV), could provide a fundamental contribution for the prediction of delivery.
It could be shown that the HTWD approach can be used for the successful identification of uterine contractions. To mark the contractile intervals, a discrete-time binary decision signal was created in each magnetic sensor. The information provided by this approach was further used to determine the CV of the uterine contraction bursts and it was shown that the increase in the CV can be considered as a possible predictor of preterm labor. Significant benefits could be expected from the introduction of MMG signal analysis for routine contraction monitoring. Further clinical validations are required to assess the robustness of the presented methods and to account for physiological differences among subjects.Frühgeburt ist die Hauptursache für Säuglingssterblichkeit und Säuglingsmorbidität. Die Inzidenz der Frühgeburt konnte durch Fortschritte in der biomedizinischen Forschung und ein besseres Verständnis der Risikofaktoren erfolgreich reduziert werden. Trotz solcher Erfolge, ist die Häufigkeit der Frühgeburt auch in entwickelten Ländern noch hoch und erklärt etwa 85% der Säuglingssterblichkeit und mehr als 50% der überlebenden Säuglingsmorbidität. Eine zeitliche Vorhersage des Eintretens einer Frühgeburt kann die Effektivität der benötigten Behandlungen erhöhen, jedoch sind die gegenwärtig eingesetzten Methoden für die Vorhersage der Frühgeburt zu ungenau.
Das kontraktile Gewebe der Gebärmutter ist das Myometrium, das aus einer glatten Muskulatur besteht. Die elektrische Aktivität (immer begleitet von einer magnetischen Aktivität) in Form von Aktionspotentialen (AP) breitet sich entlang der myometrischen Zelloberäche aus und verursacht Kontraktionen des Uterus. Die Magnetomyographie (MMG) ist eine nicht invasive Methode für die Messung der magnetischen Aktivität des Uterus. Dabei werden hochsensitive magnetische Sensoren eingesetzt, die es erlauben magnetische Aktivität über das gesamte Abdomen einer Schwangeren zu registrieren. Aus den biomagnetischen Signalen kann die kontraktile Aktivität des Uterus extrahiert werden. Im Vergleich zu elektromyographischen Signalen können MMG Signale auch ohne direkten Kontakt mit der Hautoberäche erfasst werden. Zusätzlich werden die MMG Signale nicht von der Leitfähigkeit des Gewebes beeinusst und können auch referenzfrei registriert werden.
In der vorliegenden Arbeit wurden mehrere Methoden entwickelt, implementiert und validiert, die für die Identifizierung und Charakterisierung der kontraktilen Aktivität des Uterus und seiner Dynamik geeignet sind. Das Hauptziel der Arbeit war die Entwicklung eines Methodensets, das die zeitliche Vorhersage der Geburt ermöglichen kann. Dabei wurde die kontraktile Aktivität anhand einer Multi-Sensor Analyse der räumlich-zeitlichen Muster der MMG Signale untersucht. Die Ausbreitung der magnetischen Aktivität im Myometrium verursacht koordinierte, die den Fötus in den Geburtskanal drücken und schließlich zur Geburt führen.
Es wurde gezeigt, dass der HTWD Ansatz für eine erfolgreiche Identifizierung der Wehentätigkeit im MMG Signal verwendet werden kann. Um die kontraktilen Abständen zu markieren, wurde ein zeitdiskretes, binäres Auswahlsignal in jedem magnetischen Sensor erzeugt. Die von diesem Ansatz zur Verfügung gestellten Informationen wurden weiter verwendet, um die CV der kontraktilen Aktivität im Uterus zu bestimmen. Es wurde auch gezeigt, dass die CV als möglicher Prädiktor für vorzeitige Wehen betrachtet werden kann. Der Einsatz der MMG Signalanalyse für die routinemäßige überwachung der Wehentätigkeit im klinischen Setting könnte wichtige medizinische Nutzen zeigen. Weitere klinische Validierungen, die die physiologische Unterschiede zwischen Probanden berücksichtigen, sind erforderlich, um die Robustheit der vorgestellten Methoden zu bewerten
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
