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6484. Dislocation dynamics - analytical description of the interaction force between dipolar loops

Creator:
Minárik, Vojtěch and Kratochvíl, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
dislocation dynamics and interaction force between dipolar loops
Language:
English
Description:
The interaction between dislocation dipolar loops plays an important role in the computation of the dislocation dynamics. The analytical form of the interaction force between two loops derived in the present paper from Kroupa's formula of the stress field generated by a single dipolar loop allows for faster computation.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

6485. Disordered myocardial Ca2+ homeostasis results in substructural alterations that may promote occurrence of malignant arrhythmias

Creator:
Narcisa Tribulová, Knezl, V., Szeiffova Bačová, B., Egan Beňová, Viczenczova, C., Eva Gonsalvesová, and Ján Slezák
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, fyziologie, morčata, prasata, physiology, Guinea pigs, pigs, Ca2+ overload, heart ultrastructure, malignant arrhythmias, rat, 14, and 612
Language:
English
Description:
We aimed to determine the impact of Ca2+-related disorders induced in intact animal hearts on ultrastructure of the cardiomyocytes prior to occurrence of severe arrhythmias. Three types of acute experiments were performed that are known to be accompanied by disturbances in Ca2+ handling. Langedorffperfused rat or guinea pig hearts subjected to K+-deficient perfusion to induce ventricular fibrillation (VF), burst atrial pacing to induce atrial fibrillation (AF) and open chest pig heart exposed to intramyocardial noradrenaline infusion to induce ventricular tachycardia (VT). Tissue samples for electron microscopic examination were taken during basal condition, prior and during occurrence of malignant arrhythmias. Cardiomyocyte alterations preceding occurrence of arrhythmias consisted of non-uniform sarcomere shortening, disruption of myofilaments and injury of mitochondria that most likely reflected cytosolic Ca2+ disturbances and Ca2+ overload. These disorders were linked with non-uniform pattern of neighboring cardiomyocytes and dissociation of adhesive junctions suggesting defects in cardiac cell-to-cell coupling. Our findings identified heterogeneously distributed high [Ca2+]i-induced subcellular injury of the cardiomyocytes and their junctions as a common feature prior occurrence of VT, VF or AF. In conclusion, there is a link between Ca2+-related disorders in contractility and coupling of the cardiomyocytes pointing out a novel paradigm implicated in development of severe arrhythmias., N. Tribulova, V. Knezl, B. Szeiffova Bacova, T. Egan Benova, C. Viczenczova, E. Gonçalvesova, J. Slezak., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

6486. Disparity between two-dimensional echocardiographic and electroanatomic left and right atrial volumes in patients undergoing catheter ablation for long-standing persistent atrial fibrillation

Creator:
Lucyna Škňouřil, Štěpán Havránek, Veronika Bulková, Miloslav Dorda, Tomáš Paleček, Jan Šimek, Fingrová, Z., Aleš Linhart, Jaroslav Januška, Dan Wichterle, and Martin Fiala
Format:
print, bez média, and svazek
Type:
article, články, journal articles, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, echoencefalografie, echoencephalography, long-standing atrial fibrillation, atrial volume, electroanatomic mapping, 14, and 612
Language:
English
Description:
Left atrial (LA) volume (LAV) is used for the selection of patients with atrial fibrillation (AF) to rhythm control strategies. Calculation of LAV from the LA diameters and areas by two-dimensional (2D) echocardiography may result in significant error. Accuracy of atrial volume assessment has never been studied in patients with long-standing persistent AF (LSPAF) and significant atrial remodeling. This study investigated correlation and agreement between 2D echocardiographic (Simpson method) and electroanatomic (CARTO, Biosense Webster) left and right atrial (RA) volumes (LAVECHO vs. LAVCARTO and RAVECHO vs. RAVCARTO) in patients undergoing catheter ablation for LSPAF. The study enrolled 173 consecutive subjects (females: 21 %, age: 59±9 years). There was only modest correlation between LAVECHO (92±31 ml) and LAVCARTO (178±37 ml) (R=0.57), and RAVECHO (71±29 ml) and RAVCARTO (173±34 ml) (R=0.42), respectively. LAVECHO and RAVECHO underestimated LAVCARTO and RAVCARTO with the absolute bias (±1.96 standard deviation) of -85 (-148; -22) ml and -102 (-169; -35) ml, respectively, and with the relative bias of -48 (-75; -21) % and -59 (-88; -30) %, respectively (all P<0.000001 for their mutual difference). Significant confounders of this difference were not identified. In patients with LSPAF, 2D echocardiography significantly underestimated both LA and RA volumes as compared with electroanatomic reference. This disagreement was independent of clinical, echocardiographic and mapping characteristics., L. Škňouřil, Š. Havránek, V. Bulková, M. Dorda, T. Paleček, J. Šimek, Z. Fingrová, A. Linhart, J. Januška, D. Wichterle, M. Fiala., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

6487. Dispersion of cell-to-cell uncoupling precedes low K+-induced ventricular fibrillation

Creator:
Narcisa Tribulová, Manoach, M., Varon, D., Ľudmila Okruhlicová, Zinman, T., and Shainberg, A.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, fyziologie, physiology, hypokalemia, ventricular fibrillation, connexin-43, intercellular junction, 14, and 612
Language:
English
Description:
a1_We hypothesize that hypokalemia-related electrolyte imbalance linked with abnormal elevation of intracellular free Ca2+ concentration can cause metabolic disturbances and subcellular alterations resulting in intercellular uncoupling, which favor the occurrence of malignant arrhythmias. Langendorff-perfused guinea pig heart (n = 44) was subjected to a standard Tyrode solution (2.8 mmol/l K+) followed by a K+-deficient solution (1.4 mmol/l K+). Bipolar ECG of the left atria and ventricle was continuously monitored and the incidence of ventricular fibrillation was evaluated. Myocardial tissue sampling was performed during stabilization, hypokalemia and at the onset of fibrillation. Enzyme activities of succinic dehydrogenase, glycogen phosphorylase and 5-nucleotidase were determined using in situ catalytic histochemistry. The main gap junction protein, connexin-43, was labeled using mouse monoclonal antibody and FITC conjugated goat antimouse antibody. Ultrastructure was examined by transmission electron microscopy. The free Ca2+ concentration was measured by the indo-1 method in ventricular cell cultures exposed to a K+-free medium. The results showed that sustained ventricular fibrillation appeared within 15-30 min of low K+ perfusion. This was preceded by ectopic activity, episodes of bigeminy and tachycardia. Hypokalemia induced moderate reversible and sporadically irreversible subcellular alterations of cardiomyocytes and impairment of intercellular junctions, which were heterogeneously distributed throughout myocardium. Patchy areas with decreased enzyme activities and diminished immunoreactivity of connexin-43 were found. Furthermore, lack of external K+ was accompanied by an increase of intracellular Ca2+. The prevention of Ca2+ overload by either 1 mmol/l Ni2+ (Na+/Ca2+ inhibitor), 2.5 mmol/l verapamil, 10 mmol/l d-sotalol or 10 mmol/l tedisamil was associated with the protection agains fibrillation., a2_The results indicate that hypokalemia induces Ca2+ overload injury and disturbances in intercellular coupling. Dispersion of these changes throughout the myocardium may serve as the basis for microreentry circuits and thus favor fibrillation occurrence., N. Tribulová, M. Manoach, D. Varon, L. Okruhlicová, T. Zinman , A. Shainberg., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6488. Disperzní metody v sériové výrobě

Creator:
Kůr, Jan and Weigl, Martin
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
optical dispersive methods, shape deviances, surface roughness, serial production, disperzní optické metody, úchylky tvaru, drsnost, and sériová výroba
Language:
Czech
Description:
Measuring of shape deviances, a surface roughness or a surface defects belongs to newly formed requirements in a serial production, especially in production of precise automotive parts. Methods, which are used so far, usually does not meet such requirements - their measuring capacity is not suitable, they cannot check a whole or at least a significant segment of a surface in a short time, they do not cover all the mentioned measuring parameters in one device, they are highly dependent on vibrations and fluctuation of temperature, etc. All of this can be solved using optical contactless dispersive methods. and Měření tvarových úchylek, drsnosti a často i povrchových defektů patří k novým požadavkům sériové výroby, zejména přesných autodílů. Dosud používané metody tyto požadavky většinou nesplňují - nevyhovují výkonem, neumožňují v krátkém čase oskenovat celou kontrolovanou plochu nebo alespoň její část, nezaručí jedním systémem proměřit uvedené parametry, jsou citlivé na vibrace, kolísání teploty atd. Problém je řešitelný až pomocí bezkontaktních optických disperzních metod.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6489. Displacement estimation methods for elastography - a phantom study

Creator:
Cygan, Szymon, Kałużyński, Krzysztof, and Leśniak, Beata
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
elastography, sonoelastography, phantom, strain, and displacement
Language:
English
Description:
Estimation of shift between signals of two ultrasound images is the key of sonoelastography. Comparison of three methods - cross-correlation function and two versions of SAD (sum of absolute differences) has been conducted for various displacements and estimation parameters using a soft tissuemimicking gelatin phantom with harder inclusion. Resulting displacement maps were evaluated by comparison of average values and their standard deviations. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6490. Displacement field around an uplifting innovated plate anchor

Creator:
Sabermahani, Mohsen and Nasirabadi, Mehrzad Shojaee
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
anchor plate, pullout capacity, sand deformation zone, PIV, and opening anchor plate
Language:
English
Description:
This paper introduces an innovated plate anchor, increasing its bearing section area during uplift. In this experimental study, the influences of embedment depth of plate anchor and soil surface condition (restricted or free) on sand deformation field during uplift test are investigated. In order to study the soil deformation around the anchor, Particle Image Velocimetry (PIV) is used. The experimental setup consists of a camera, a new designed box, load cell, encoder and computer. During the uplift test on physical models, images are captured and used by PIV to depict the soil displacement field. Based on this study, it is found that pullout capacity and sand deformation zone are significantly influenced by anchor embedment depth. In shallow anchors, sand deformation zone lines are similar to a curve and cross the soil surface; however, in deep anchors, sand deformation zone is a bulb-shaped zone that extends from anchor to a distance of approximately two times its diameter above. Soil surface restriction increases anchor pullout capacity in shallow anchors up to 37 %, but in deep ones, there is no significant difference. Soil surface restriction changes shallow anchor behavior to deep anchors; however, it has no notable influence on deep anchors.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

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