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Ključne besede: olive knot disease, olive genotype susceptibility, phenols, plant-based antibacterial agents, strain virulence
Objavljeno v DiRROS: 03.02.2026; Ogledov: 213; Prenosov: 153
Celotno besedilo (3,99 MB)
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Povzetek: Myocardial strain imaging by echocardiography or cardiac magnetic resonance (CMR) is a powerful method to diagnose cardiac disease. Strain imaging provides measures of myocardial shortening, thickening, and lengthening and can be applied to any cardiac chamber. Left ventricular (LV) global longitudinal strain by speckle-tracking echocardiography is the most widely used clinical strain parameter. Several CMR-based modalities are available and are ready to be implemented clinically. Clinical applications of strain include global longitudinal strain as a more sensitive method than ejection fraction for diagnosing mild systolic dysfunction. This applies to patients suspected of having heart failure with normal LV ejection fraction, to early systolic dysfunction in valvular disease, and when monitoring myocardial function during cancer chemotherapy. Segmental LV strain maps provide diagnostic clues in specific cardiomyopathies, when evaluating LV dyssynchrony and ischemic dysfunction. Strain imaging is a promising modality to quantify right ventricular function. Left atrial strain may be used to evaluate LV diastolic function and filling pressure.
Ključne besede: cardiac magnetic resonance, cardiomyopathy, myocardial function, myocardial work, speckle-tracking echocardiography, strain
Objavljeno v DiRROS: 08.01.2026; Ogledov: 705; Prenosov: 566
Celotno besedilo (10,00 MB)
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Povzetek: Background: Acute myocarditis (AM) affects myocardial structure and function, assessed by cardiac magnetic resonance late gadolinium enhancement (CMR-LGE) and speckle tracking echocardiography (STE), respectively; however, the correlation between the two techniques at the segmental level is inconsistent. We studied natural heterogeneity and anatomical orientation mismatch as potential causes of correlation discrepancy. Methods: A total of 30 AM patients underwent left ventricle LGE-CMR and STE measurement, acquiring 18 segmental values depicting edema extent and peak longitudinal strain, respectively. Baseline segmental correlation was compared to average patient segmental correlation and to segmental correlation after spatial resolution reduction achieved by averaging adjacent segments in four successive iterations, where the degree of spatial resolution reduction was evaluated based on the relative decrease in segmental standard deviation. Results: Baseline segmental correlation was weak, i.e., r = 0.24 (p < 0.05) but improved in fitted SLGE and SpLS baseline correlation (r0 = 0.44, p < 0.05) and in average patient correlation (r = 0.55, p < 0.05). Iterative spatial resolution reduction increased the correlation to r1 = 0.49 and r2 = 0.51 and then decreased it to r3 = 0.11 (p < 0.05) and r4 = 0.07 (p > 0.05), with corresponding decreases in segmental standard deviation relative to baseline from σ0 = 12.87 to σ/σ0 = 0.68, 0.51, 0.38, and 0.29 in SLGE values and σ0 = 4.77 to σ/σ0 = 0.57, 0.41, 0.31, and 0.23 in SpLS. Conclusions: Improved correlation in average patients is associated with natural heterogeneity, which indicates a need to develop more robust indicators of ventricular function. The improved correlation in moderate spatial resolution reduction indicates a potential solution for anatomic orientation mismatch between CMR-LGE and STE techniques.
Ključne besede: acute myocarditis, anatomical orientation mismatch, cardiac magnetic resonance, late gadolinium enhancement, natural heterogeneity, segmental peak systolic strain, spatial resolution reduction, speckle tracking echocardiography
Objavljeno v DiRROS: 10.11.2025; Ogledov: 341; Prenosov: 162
Celotno besedilo (3,07 MB)
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Povzetek: This study explores a robust and computationally efficient two-dimensional solution procedure for phase-field modelling of crack propagation under tensile, compressive, and shear loadings by using the meshless local radial basis function collocation method (LRBFCM). The mechanical model is based on the brittle elastic material, and the crack propagation is governed by the fourth-order phase field equation coupled in a staggered way. The spectral-split method for strain tensor decomposition of a brittle elastic material is used with LRBFCM for crack propagation for the first time. It ensures that the crack is propagated physically correctly under different loading types, filling the gap in our previous study [1], where crack propagation only under tensile loading was possible. The strong-form LRBFCM is constructed on 13-noded subdomains with augmented third- order polyharmonic spline shape functions. A novel adaptive loading step size criterion is introduced to increase computational efficiency by removing cumbersome internal iteration processes. The method’s performance is assessed with three benchmark tests subjected to mixed-mode tension, shear and compressive loading. The results are validated with the reference solutions regarding accuracy and convergence rates for scattered and regular node arrangements. The effects of the iterative and non-iterative processes with different loading step sizes are shown.
Ključne besede: strong form LRBFCM, higher-order phase field, crack propagation, PHSs, spectral-split, strain decomposition, shear test
Objavljeno v DiRROS: 13.05.2025; Ogledov: 659; Prenosov: 383
Celotno besedilo (9,95 MB)
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Povzetek: The Strain Gradient Crystal Plasticity (SGCP), based on cumulative shear strain, is developed to regularize and simulate the size effect behavior of polycrystalline aggregates, specifically in the formation of localization bands in terms of slip and kink bands, influenced by strain softening during the initial stages of plastic deformation. In this respect, the thermodynamically consistent derivation of the SGCP equations is presented, establishing their connection to the kinematics of classical crystal plasticity (CCP) framework. The governing balance equations are solved using the fixed-point algorithm of the fast Fourier transform (FFT)-homogenization method, involving explicit coupling between the classical and SGCP balance equations. To address this problem, a strong 21-voxel finite difference scheme is established. This scheme is considered to solve the higher order balance equation inherent to SGCP. Additionally, three types of interface conditions are implemented to explore the impact of grain boundaries on the transmission of localization bands. These conditions yield consistent intragranular/transgranular localization patterns in the MicroFree and MicroContinuity cases, while in the MicroHard condition all localization bands are intragranular with stress concentrations appearing at the grain boundaries. Analytical solutions corresponding to different material behaviors are developed and compared with numerical results to validate the numerical implementation of the FFT fixed-point algorithm. It is observed that both the macroscopic behavior and microscopic variables in CCP framework are highly influenced by grid resolutions (non-objective), leading to numerical instabilities arising from the material softening and subsequent formation of localization bands, both in single crystals and polycrystalline aggregates. Remarkably, the developed SGCP model provides results that are independent of grid resolutions (objective) and effectively regularizes the material behavior on local scale. Moreover, the non-local parameter of the model is capable of controlling the localization band widths. Finally, the proposed SGCP model, together with employed MicroHard condition on grain boundaries, is demonstrated to qualitatively reproduce main microstructural features of irradiated polycrystalline materials.
Ključne besede: strain localization A, strain gradient crystal plasticity B, polycrystalline material B, FFT-homogenization method C
Objavljeno v DiRROS: 11.04.2025; Ogledov: 758; Prenosov: 402
Celotno besedilo (9,87 MB)
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