8,797 research outputs found
The Earth as a living planet: human-type diseases in the earthquake preparation process
The new field of complex systems supports the view that a number of systems
arising from disciplines as diverse as physics, biology, engineering, and
economics may have certain quantitative features that are intriguingly similar.
The earth is a living planet where many complex systems run perfectly without
stopping at all. The earthquake generation is a fundamental sign that the earth
is a living planet. Recently, analyses have shown that human-brain-type disease
appears during the earthquake generation process. Herein, we show that
human-heart-type disease appears during the earthquake preparation of the
earthquake process. The investigation is mainly attempted by means of critical
phenomena, which have been proposed as the likely paradigm to explain the
origins of both heart electric fluctuations and fracture induced
electromagnetic fluctuations. We show that a time window of the damage
evolution within the heterogeneous Earth's crust and the healthy heart's
electrical action present the characteristic features of the critical point of
a thermal second order phase transition. A dramatic breakdown of critical
characteristics appears in the tail of the fracture process of heterogeneous
system and the injury heart's electrical action. Analyses by means of Hurst
exponent and wavelet decomposition further support the hypothesis that a
dynamical analogy exists between the geological and biological systems under
study
Influence of cardiac tissue anisotropy on re-entrant activation in computational models of ventricular fibrillation
The aim of this study was to establish the role played by anisotropic diffusion in (i) the number of filaments and epicardial phase singularities that sustain ventricular fibrillation in the heart, (ii) the lifetimes of filaments and phase singularities, and (iii) the creation and annihilation dynamics of filaments and phase singularities. A simplified monodomain model of cardiac tissue was used, with membrane excitation described by a simplified 3-variable model. The model was configured so that a single re-entrant wave was unstable, and fragmented into multiple re-entrant waves. Re-entry was then initiated in tissue slabs with varying anisotropy ratio. The main findings of this computational study are: (i) anisotropy ratio influenced the number of filaments Sustaining simulated ventricular fibrillation, with more filaments present in simulations with smaller values of transverse diffusion coefficient, (ii) each re-entrant filament was associated with around 0.9 phase singularities on the surface of the slab geometry, (iii) phase singularities were longer lived than filaments, and (iv) the creation and annihilation of filaments and phase singularities were linear functions of the number of filaments and phase singularities, and these relationships were independent of the anisotropy ratio. This study underscores the important role played by tissue anisotropy in cardiac ventricular fibrillation
Quantitative comparison of myocardial fiber structure between mice, rabbit, and sheep using diffusion tensor cardiovascular magnetic resonance
<p>Abstract</p> <p>Background</p> <p>Accurate interpretations of cardiac functions require precise structural models of the myocardium, but the latter is not available always and for all species. Although scaling or substitution of myocardial fiber information from alternate species has been used in cardiac functional modeling, the validity of such practice has not been tested.</p> <p>Methods</p> <p>Fixed mouse (n = 10), rabbit (n = 6), and sheep (n = 5) hearts underwent diffusion tensor imaging (DTI). The myocardial structures in terms of the left ventricular fiber orientation helix angle index were quantitatively compared between the mouse rabbit and sheep hearts.</p> <p>Results</p> <p>The results show that significant fiber structural differences exist between any two of the three species. Specifically, the subepicardial fiber orientation, and the transmural range and linearity of fiber helix angles are significantly different between the mouse and either rabbit or sheep. Additionally, a significant difference was found between the transmural helix angle range between the rabbit and sheep. Across different circumferential regions of the heart, the fiber orientation was not found to be significantly different.</p> <p>Conclusions</p> <p>The current study indicates that myocardial structural differences exist between different size hearts. An immediate implication of the present findings for myocardial structural or functional modeling studies is that caution must be exercised when extrapolating myocardial structures from one species to another.</p
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Quantitative analysis of hypertrophic myocardium using diffusion tensor magnetic resonance imaging
Systemic hypertension is a causative factor in left ventricular hypertrophy (LVH). This study is motivated by the potential to reverse or manage the dysfunction associated with structural remodeling of the myocardium in this pathology. Using diffusion tensor magnetic resonance imaging, we present an analysis of myocardial fiber and laminar sheet orientation in ex vivo hypertrophic (6 SHR) and normal (5 WKY) rat hearts using the covariance of the diffusion tensor. First, an atlas of normal cardiac microstructure was formed using the WKY b0 images. Then, the SHR and WKY b0 hearts were registered to the atlas. The acquired deformation fields were applied to the SHR and WKY heart tensor fields followed by the preservation of principal direction (PPD) reorientation strategy. A mean tensor field was then formed from the registered WKY tensor images. Calculating the covariance of the registered tensor images about this mean for each heart, the hypertrophic myocardium exhibited significantly increased myocardial fiber derangement (p ¼ 0.017) with a mean dispersion of 38.7 deg, and an increased dispersion of the laminar sheet normal (p = 0.030) of 54.8 deg compared with 34.8 deg and 51.8 deg, respectively, in the normal hearts. Results demonstrate significantly altered myocardial fiber and laminar sheet structure in rats with hypertensive LVH
Chinese Expert Consensus on Critical Care Ultrasound Applications at COVID-19 Pandemic
The spread of new coronavirus (SARS-Cov-2) follows a different pattern than previous respiratory viruses, posing a serious public health risk worldwide. World Health Organization (WHO) named the disease as COVID-19 and declared it a pandemic. COVID-19 is characterized by highly contagious nature, rapid transmission, swift clinical course, profound worldwide impact, and high mortality among critically ill patients. Chest X-ray, computerized tomography (CT), and ultrasound are commonly used imaging modalities. Among them, ultrasound, due to its portability and non-invasiveness, can be easily moved to the bedside for examination at any time. In addition, with use of 4G or 5G networks, remote ultrasound consultation can also be performed, which allows ultrasound to be used in isolated medial areas. Besides, the contact surface of ultrasound probe with patients is small and easy to be disinfected. Therefore, ultrasound has gotten lots of positive feedbacks from the frontline healthcare workers, and it has played an indispensable role in the course of COVID-19 diagnosis and follow up
Vascular remodeling of the mouse yolk sac requires hemodynamic force
The embryonic heart and vessels are dynamic and form and remodel while functional. Much has been learned about the genetic
mechanisms underlying the development of the cardiovascular system, but we are just beginning to understand how changes in
heart and vessel structure are influenced by hemodynamic forces such as shear stress. Recent work has shown that vessel
remodeling in the mouse yolk sac is secondarily effected when cardiac function is reduced or absent. These findings indicate that
proper circulation is required for vessel remodeling, but have not defined whether the role of circulation is to provide mechanical
cues, to deliver oxygen or to circulate signaling molecules. Here, we used time-lapse confocal microscopy to determine the role of
fluid-derived forces in vessel remodeling in the developing murine yolk sac. Novel methods were used to characterize flows in
normal embryos and in embryos with impaired contractility (Mlc2a^(–/–)). We found abnormal plasma and erythroblast circulation in
these embryos, which led us to hypothesize that the entry of erythroblasts into circulation is a key event in triggering vessel
remodeling. We tested this by sequestering erythroblasts in the blood islands, thereby lowering the hematocrit and reducing shear
stress, and found that vessel remodeling and the expression of eNOS (Nos3) depends on erythroblast flow. Further, we rescued
remodeling defects and eNOS expression in low-hematocrit embryos by restoring the viscosity of the blood. These data show that
hemodynamic force is necessary and sufficient to induce vessel remodeling in the mammalian yolk sa
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