903 research outputs found
Termination of scroll waves by surface impacts
No full textThree-dimensional scroll waves direct cell movement and gene expression, and induce chaos in the brain and heart. We found an approach to terminate multiple three-dimensional scrolls. A pulse of a properly configured electric field detaches scroll filaments from the surface. They shrink due to filament tension and disappear. Since wave emission from small heterogeneities is not used, this approach requires a much lower electric field. It is not sensitive to the details of the excitable medium. It may affect future studies of low-energy chaos termination in the heart
Far field pacing supersedes anti-tachycardia pacing in a generic model of excitable media
No full textRemoving anchored spirals from obstacles is an important step in terminating cardiac arrhythmia. Conventional anti-tachycardia pacing (ATP) has this ability, but only under very restrictive conditions. In a generic model of excitable media, we demonstrate that for unpinning spiral waves from obstacles this profound limitation of ATP can be overcome by far field pacing (FFP). More specifically, an argument is presented for why FFP includes and thus can only extend the capabilities of ATP in the configurations considered. By numerical simulations, we show that in the model there exists a parameter region in which unpinning is possible by FFP but not by ATP. The relevance of this result regarding clinical applications is discussed
Phase-resolved analysis of the susceptibility of pinned spiral waves to far-field pacing in a two-dimensional model of excitable media
No full textLife-threatening cardiac arrhythmias are associated with the existence of stable and unstable spiral waves. Termination of such complex spatio-temporal patterns by local control is substantially limited by anchoring of spiral waves at natural heterogeneities. Far-field pacing (FFP) is a new local control strategy that has been shown to be capable of unpinning waves from obstacles. In this article, we investigate in detail the FFP unpinning mechanism for a single rotating wave pinned to a heterogeneity. We identify qualitatively different phase regimes of the rotating wave showing that the concept of vulnerability is important but not sufficient to explain the failure of unpinning in all cases. Specifically, we find that a reduced excitation threshold can lead to the failure of unpinning, even inside the vulnerable window. The critical value of the excitation threshold (below which no unpinning is possible) decreases for higher electric field strengths and larger obstacles. In contrast, for a high excitation threshold, the success of unpinning is determined solely by vulnerability, allowing for a convenient estimation of the unpinning success rate. In some cases, we also observe phase resetting in discontinuous phase intervals of the spiral wave. This effect is important for the application of multiple stimuli in experiments
Alf Nilsen-Børsskog — The Author Chosen by the Language
Get PDFThis article discusses Alf Nilsen-Børsskog’s four-volume series of novels Elämän jatko [Continuation of life, 2004–2015], seen as the first literary works treating the Kven culture from a native perspective. Nilsen-Børsskog’s novels are analysed as constituting a “counterstory”, a term coined in the postcolonial cultural research paradigm to refer to self-representation. The Kvens have been considered a national minority in Norway since 1999, and their language has been an official minority language since 2005. The present author scrutinizes how Nilsen-Børsskog’s work differs from previous literary descriptions of this minority, often marked by the frequent use of stereotypes of the Kven language and culture
LIBS and LA-SD-OES Analysis of Minor and Trace Elements in Steel Samples
No full textAuthor Valentin Ehrentraut, BScMasterarbeit Universität Linz 2022Arbeit nach Ablauf der Sperre auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
Termination of Atrial Fibrillation Using Pulsed Low-Energy Far-Field Stimulation
No full textElectrically based therapies for terminating atrial fibrillation (AF) currently fall into 2 categories: antitachycardia pacing and cardioversion. Antitachycardia pacing uses low-intensity pacing stimuli delivered via a single electrode and is effective for terminating slower tachycardias but is less effective for treating AF. In contrast, cardioversion uses a single high-voltage shock to terminate AF reliably, but the voltages required produce undesirable side effects, including tissue damage and pain. We propose a new method to terminate AF called far-field antifibrillation pacing, which delivers a short train of low-intensity electric pulses at the frequency of antitachycardia pacing but from field electrodes. Prior theoretical work has suggested that this approach can create a large number of activation sites ("virtual" electrodes) that emit propagating waves within the tissue without implanting physical electrodes and thereby may be more effective than point-source stimulation
Johann Siegmund Valentin Popowitsch (Janez Žiga Valentin Popovič), Vocabula Austriaca et Stiriaca 1-2 (Frankfurt am Main 2004)
No full textThe Austrian dictionary composed by the Slovenian scho-lar Janez Žiga Valentin Popovič (1705-1774) in the third quarter of the 18th century was only published in 2004, and edited by Richard Reutner, who wrote an extensive introduction to it. The dictionary comprises many language-geographical data for the German language, excellent explanations and many comparisons with much information provided regarding Popovic's mother tongue. The author broad horizon is admirable, especially with regard to the German language area and the linguistic literature of that time.Avstrijski slovar, ki ga je v tretji četrtini 18. stoletja sestavil slovenski učenjak Janez Žiga Valentin Popovič (1705-1774), je izšel šele leta 2004 v uredništvu Richarda Reutnerja, kije k njemu napisal obsežen uvod. Slovar vsebuje mnogo jezikovnogeografskih podatkov za nemščino, odlične razlage in marsikaj primerjalnega, veliko pa se najde tudi v zvezi s Popovičevo materinščino. Občudovanja vredna je avtorjeva razgledanost predvsem po nemškem jezikoslovnem prostoru in po takratni jezikoslovni literaturi
Vortices Termination in the Cardiac Muscle
No full textMethods for termination of three-dimensional electrical vortices in the heart are needed for development of patient-friendly cardiac defibrillation techniques (Nature 475, 235, 2011). The defibrillation technique used today is the delivery of a high-energy electric shock (360 J, 1 kV, 30 A, 12 ms, when applied externally) often associated with severe side effects. Developing low-energy defibrillation methods are hampered by two problems: the unknown locations of the cores of the vortices, and the unpredictable phases of the vortex waves rotating around these cores. The first problem has been resolved through the use of electric field pulses to excite the cores of all pinned vortices simultaneously. Approaches to solve the second problem are being developed. One of them is based on the phase scanning of all pinned vortices in parallel to hit the critical time window (“Vulnerable Window”, VW) of every pinned vortex. We investigate the related physical mechanisms and describe problems created by scanning. We describe also a mechanism by which a 3-dim scroll vortex may be terminated with a VW of the full 2π radians. It makes knowledge of the wave phase no longer required. We describe a mechanism terminating also a free (not pinned) vortex, when the vortex’s core passes not very far from a defect. About 500 experiments with termination of vortices during ventricular fibrillation in pig isolated hearts confirm that pinned vortices, hidden from direct observation, are significant in fibrillation. These results form a physical basis needed for creation of new effective methods for termination vortices underlying fibrillation
Valentin N. Volóchinov: um filósofo da ciência da linguagem
Get PDFThis text address the work of Russian scholar Valentin N. Vološinov, author of the book Marxism and the Philosophy of Language. The objective is to demonstrate a set of characteristics that place Vološinov as a participant in the critique of science movement, which had its epicenter in Germany, between the years 1840 and 1900. To this end, in addition to a general reflection, which recovers the meaning of the term “criticism” most present in the academic environment of the time, this text considers two points of the much mentioned – and, apparently, somewhat misunderstood – opposition of the Russian thinker to the linguistics of Ferdinand de Saussure, as this linguistics is presented in the Course in General Linguistics. Finally, by way of provocation, this text outlines a few words about the proximity between the epistemological works of Valentin N. Vološinov and Wilhelm Dilthey.Este texto aborda la obra del estudioso ruso Valentin N. Voloshinov, autor de la obra Marxismo y filosofía del lenguaje. El objetivo es demostrar un conjunto de características que sitúan a Voloshinov como participante del movimiento de crítica científica, que tuvo su epicentro en Alemania, entre los años 1840 y 1900. Para ello, además de una reflexión general, que recupera el significado del término “crítica” más presente en el ambiente académico de la época, se consideran dos puntos de la tan mencionada –y, aparentemente, algo incomprendida– oposición del pensador ruso a la lingüística de Ferdinand de Saussure, tal como se presenta esta última en el curso de lingüística general. Al final, a modo de provocación, se esbozan algunas palabras sobre la proximidad entre las obras epistemológicas de Valentin N. Voloshinov y Wilhelm Dilthey.O presente texto aborda o trabalho do estudioso russo Valentin N. Volóchinov, autor da obra Marxismo e filosofia da linguagem. O objetivo é demonstrar um conjunto de características que situam Volóchinov como um partícipe do movimento de crítica das ciências, o qual teve seu epicentro na Alemanha, entre os anos 1840 e 1900. Para isso, além de uma reflexão geral, que recupera a acepção do termo “crítica” mais presente no ambiente acadêmico da época, são considerados dois pontos da muito mencionada – e, ao que tudo indica, um tanto mal compreendido – oposição do pensador russo à linguística de Ferdinand de Saussure, tal como essa última é apresentada no Curso de linguística geral. Ao fim, a título de provocação, são esboçadas algumas palavras a respeito da proximidade entre os trabalhos epistemológicos de Valentin N. Volóchinov e Wilhelm Dilthey
Shifting patterns of fruit production in tropical forests with negative outnumbering positive trends
No full textAnalysis related to Shifting patterns of fruit production in tropical
forests with negative outnumbering positive trends from Hacket-Pain et al.
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corresponding author: Andrew Hacket-Pain; [email protected]
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