scholarly journals Computer simulations of three-dimensional propagation in ventricular myocardium. Effects of intramural fiber rotation and inhomogeneous conductivity on epicardial activation.

1993 ◽  
Vol 72 (4) ◽  
pp. 744-756 ◽  
Author(s):  
A E Pollard ◽  
M J Burgess ◽  
K W Spitzer
Keyword(s):  
Computer Simulations ◽  
Three Dimensional ◽  
Ventricular Myocardium ◽  
Inhomogeneous Conductivity

scholarly journals Geometric auxetics

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150033 ◽  
Author(s):  
Ciprian Borcea ◽  
Ileana Streinu
Keyword(s):  
Computer Simulations ◽  
Mathematical Theory ◽  
Three Dimensional ◽  
Numerical Approximations ◽  
Periodic Frameworks ◽  
Infinite Supply

We formulate a mathematical theory of auxetic behaviour based on one-parameter deformations of periodic frameworks. Our approach is purely geome- tric, relies on the evolution of the periodicity lattice and works in any dimension. We demonstrate its usefulness by predicting or recognizing, without experiment, computer simulations or numerical approximations, the auxetic capabilities of several well-known structures available in the literature. We propose new principles of auxetic design and rely on the stronger notion of expansive behaviour to provide an infinite supply of planar auxetic mechanisms and several new three-dimensional structures.

scholarly journals Quantitative Assessment of Myocardial Ischemia in Multi-Vessel Coronary Artery Disease by Multimodal Stress Echocardiography with Semi-Supine Bicycle Ergometry

2020 ◽  
Vol 15 (6) ◽  
pp. 813-819
Author(s):  
S. N. Koretskiy ◽  
O. M. Drapkina ◽  
F. B. Shukurov ◽  
D. K. Vasiliev
Keyword(s):  
Stress Echocardiography ◽  
Peak Load ◽  
Three Dimensional ◽  
Ventricular Myocardium ◽  
Cardiovascular Complications ◽  
Artery Occlusion ◽  
Left Ventricular ◽  
Myocardial Imaging ◽  
Left Ventricular Myocardium ◽  
Bicycle Ergometry

Stress echocardiography is a modern widely used method of noninvasive diagnosis of coronary heart disease and stratification of the risk of cardiovascular complications. In addition, exercise echocardiography is an important tool to clarify the localization of ischemia and establish a symptomassociated artery for management of patient with known coronary angiography data. This is especially important in multivessel lesions, the presence of an occluded artery or borderline stenosis. Currently, various stress agents are used for stress echocardiography in clinical practice: pharmacological drugs (dobutamine or adenosine), transesophageal or endocardial pacing, treadmill, semi-supine bicycle. To detect signs of ischemia usually used only visual estimation of local contractility in the two-dimensional gray-scale mode. Modern modes of myocardial imaging, such as speckletracking echocardiography or three-dimensional visualization, are practically not used. In the presented clinical case, the possibility of combining standard and modern imaging modes to clarify the localization and quantification of ischemia in multivessel coronary lesions, including chronic artery occlusion, is shown. As a stress agent, a semi-supine bicycle was chosen, the use of which allowed to obtain a qualitative image of the left ventricular myocardium at rest and at peak load, suitable for assessing deformation and threedimensional visualization. Evaluation of left ventricular myocardial deformation by speckle-tracking echocardiography was more accurate than standard diagnosis in detecting signs of ischemia in a patient with multivessel lesions. Three-dimensional imaging was inferior in sensitivity to speckletracking stress echocardiography and, at present, seems to have more research value.

Mechanical evaluation of theories of neurulation using computer simulations

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 1013-1023 ◽  
Author(s):  
D. A. Clausi ◽  
G. W. Brodland
Keyword(s):  
Computer Simulations ◽  
Driving Forces ◽  
Shape Change ◽  
Three Dimensional ◽  
Dorsal Surface ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Amphibian Embryo ◽  
Axial Elongation ◽  
Shape Changes

Current theories about the forces that drive neurulation shape changes are evaluated using computer simulations. Custom, three-dimensional, finite element-based computer software is used. The software draws on current engineering concepts and makes it possible to construct a ‘virtual’ embryo with any user-specified mechanical properties. To test a specific hypothesis about the forces that drive neurulation, the whole virtual embryo or any selected part of it is ascribed with the force generators specified in the hypothesis. The shape changes that are produced by these forces are then observed and compared with experimental data. The simulations demonstrate that, when uniform, isotropic circumferential microfilament bundle (CMB) constriction and cephalocaudal (axial) elongation act together on a circular virtual neural plate, it becomes keyhole shaped. When these forces act on a spherical (amphibian) embryo, dorsal surface flattening occurs. Simulations of transverse sections further show that CMB constriction, acting with or without axial elongation, can produce numerous salient transverse features of neurulation. These features include the sequential formation of distinct neural ridges, narrowing and thickening of the neural plate, skewing just medial to the ridges, ‘hinge’ formation and neural tube closure. No region-specific ‘programs’ or non-mechanical cell-cell communications are used. The increase in complexity results entirely from mechanical interactions. The transverse simulations show how changes to the driving forces would affect the patterns of shape change produced. Hypotheses regarding force generation by microtubules, intercellular adhesions and forces extrinsic to the neural plate are also evaluated. The simulations show that these force-generating mechanisms do not, by themselves, produce shape changes that are consistent with normal development. The simulations support the concept of cooperation of forces and suggest that neurulation is robust because redundant force generating mechanisms exist.

scholarly journals Analysis of spatial thermal field in a magnetic bearing

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 52-56
Author(s):  
Dawid Wajnert ◽  
Bronisław Tomczuk
Keyword(s):  
Temperature Field ◽  
Mathematical Models ◽  
Computer Simulations ◽  
Thermal Field ◽  
Three Dimensional ◽  
Magnetic Bearing ◽  
Field Analysis ◽  
Two Dimensional ◽  
Temperature Distributions ◽  
Dimensional Simulation

AbstractThis paper presents two mathematical models for temperature field analysis in a new hybrid magnetic bearing. Temperature distributions have been calculated using a three dimensional simulation and a two dimensional one. A physical model for temperature testing in the magnetic bearing has been developed. Some results obtained from computer simulations were compared with measurements.

Multimodality imaging anatomy of interatrial septum and mitral annulus

Heart ◽  
2020 ◽  
pp. heartjnl-2020-318127
Author(s):  
Francesco Fulvio Faletra ◽  
Laura Anna Leo ◽  
Vera Paiocchi ◽  
Susanne Schlossbauer ◽  
Jagat Narula ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Multimodality Imaging ◽  
Three Dimensional ◽  
Mitral Annulus ◽  
Ventricular Myocardium ◽  
Interatrial Septum ◽  
Atrial Septal Defect Closure ◽  
Hinge Line ◽  
Septum Primum ◽  
Contraction And Relaxation

The detailed anatomy of the interatrial septum (IAS) and mitral annulus (MA) as observed on cardiac magnetic resonance, computed tomography and two-dimensional/three-dimensional transthoracic and transesophageal echocardiography is reviewed. The IAS comprises of two components: the septum primum that is membrane-like forming the floor of the fossa ovalis (FO) and the septum secundum that is a muscular rim that surrounds the FO. The latter is an enfolding of atrial wall forming an interatrial groove. Named Waterston’s groove, it is filled with adipose tissue on the epicardial side. Thus, the safest area for transseptal puncture (TSP) is within the limits of the FO floor, which provides direct interatrial access. While crossing an intact septum is a well-established procedure, TSP is a more complex and time-consuming procedure in the presence of patent foramen ovalis, aneurysmal FO or atrial septal defect closure devices. MA comprises two distinctive segments: an anterior-straight and a posterior-curved segment. The posterior MA is a thin, discontinuous fibrous ‘string’, interspersed with adipose tissue, where four components converge: the atrial and ventricular musculature, epicardial adipose tissue and the leaflet’s hinge line. In parts of where this fibrous string is deficient or absent, the posterior leaflet is inserted directly on ventricular and atrial myocardium rendering the MA less robust and producing an ‘asymmetric’ dilation. The marked vulnerability of posterior MA to calcifications might be due to its insertion on the crest of ventricular myocardium being subject to friction injury due to the contraction and relaxation of LV.

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