scholarly journals Modelling of fibre dispersion and its effects on cardiac mechanics from diastole to systole

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Debao Guan ◽  
Xin Zhuan ◽  
William Holmes ◽  
Xiaoyu Luo ◽  
Hao Gao
Keyword(s):  
Mathematical Modelling ◽  
Dispersion Model ◽  
Fibrous Tissue ◽  
Experimental Studies ◽  
Cardiac Mechanics ◽  
Distribution Functions ◽  
Diastolic Filling ◽  
Myocardial Mechanics ◽  
Pump Function ◽  
Out Of Plane

AbstractDetailed fibre architecture plays a crucial role in myocardial mechanics both passively and actively. Strong interest has been attracted over decades in mathematical modelling of fibrous tissue (arterial wall, myocardium, etc.) by taking into account realistic fibre structures, i.e. from perfectly aligned one family of fibres, to two families of fibres, and to dispersed fibres described by probability distribution functions. It is widely accepted that the fibres, i.e. collage, cannot bear the load when compressed, thus it is necessary to exclude compressed fibres when computing the stress in fibrous tissue. In this study, we have focused on mathematical modelling of fibre dispersion in myocardial mechanics, and studied how different fibre dispersions affect cardiac pump function. The fibre dispersion in myocardium is characterized by a non-rotationally symmetric distribution using a $$\pi $$ π -periodic Von Mises distribution based on recent experimental studies. In order to exclude compressed fibres for passive response, we adopted the discrete fibre dispersion model for approximating a continuous fibre distribution with finite fibre bundles, and then the general structural tensor was employed for describing dispersed active tension. We first studied the numerical accuracy of the integration of fibre contributions using the discrete fibre dispersion approach, then compared different mechanical responses in a uniaxially stretched myocardial sample with varied fibre dispersions. We finally studied the cardiac pump functions from diastole to systole in two heart models, a rabbit bi-ventricle model and a human left ventricle model. Our results show that the discrete fibre model is preferred for excluding compressed fibres because of its high computational efficiency. Both the diastolic filling and the systolic contraction will be affected by dispersed fibres depending on the in-plane and out-of-plane dispersion degrees, especially in systolic contraction. The in-plane dispersion seems affecting myocardial mechanics more than the out-of-plane dispersion. Despite different effects in the rabbit and human models caused by the fibre dispersion, large differences in pump function exist when fibres are highly dispersed at in-plane and out-of-plane. Our results highlight the necessity of using dispersed fibre models when modelling myocardial mechanics, especially when fibres are largely dispersed under pathological conditions, such as fibrosis.

Abstract 17184: CMR Derived Myocardial Mechanics in Patients With Systemic Sarcoidosis

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Veronica Rolim S. Fernandes ◽  
Beatriz Jauregui Garrido ◽  
Maria E Siqueira ◽  
Jonathan Katz ◽  
Adam Jacobi ◽  
...  
Keyword(s):  
Myocardial Dysfunction ◽  
Myocardial Strain ◽  
Prognostic Significance ◽  
Cardiac Mechanics ◽  
Structural Heart Disease ◽  
Left Ventricular ◽  
Gadolinium Enhancement ◽  
Myocardial Mechanics ◽  
Systemic Sarcoidosis ◽  
Lv Ejection Fraction

Objective: To assess myocardial mechanics by cardiac magnetic resonance (CMR)-derived strain in patients with biopsy-proven systemic sarcoidosis. Methods: We included 50 consecutive patients (age 51 ± 11 years old, 30 males) with biopsy-proven systemic sarcoidosis who underwent gadolinium-enhanced CMR for suspected cardiac sarcoid involvement. Late gadolinium enhancement (LGE) was considered positive if showing an intramyocardial/subepicardial location with a nonischemic pattern. From cine images and using dedicated software (TomTec©), we quantified mean left ventricular (LV) longitudinal, radial, and circumferential peak strains as the average of 16 standard myocardial segments. We also randomly selected from our database 15 control subjects without structural heart disease (age 41 ± 11 years old, 5 males). Results: Both mean longitudinal strain (LS) and LV ejection fraction (LVEF) were lower in sarcoid patients than controls (-11.8 ± 7.3% vs. -18.1 ± 3.9%, p55%, n=32) mean LS was reduced compared to controls (-12.2 ± 7.8% vs. -18.1 ± 3.9% respectively, p=0.01; Fig 1B). There was no correlation between LVEF and mean LS (r=-0.11, p=0.65). We found no significant differences in circumferential or radial strains. LGE was present in 16 patients (32%). Sarcoid patients with LGE showed significantly less mean LS than those without (-8.5 ± 8.4% vs. -13.6 ± 6.4%, p<0.001; Fig 1A) although LVEF did not differ significantly (52% vs. 59%, p=0.35). No significant differences in circumferential or radial strains were found. Conclusions: In patients with systemic sarcoidosis, evaluation of cardiac mechanics with CMR detects myocardial dysfunction even in the presence of preserved LVEF. This is more pronounced in patients with positive LGE. The potential diagnostic and prognostic significance of CMR-derived myocardial strain in sarcoidosis deserves further investigation.

Effect of fixation stitches on out-of-plane response of textile non-crimp fabric composites

2018 ◽  
Vol 48 (7) ◽  
pp. 1151-1166 ◽  
Author(s):  
Somen K Bhudolia ◽  
Kenneth KC Kam ◽  
Pavel Perrotey ◽  
Sunil C Joshi
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Peak Load ◽  
Experimental Studies ◽  
Critical Energy ◽  
Critical Energy Release Rate ◽  
Mode I Fracture Toughness ◽  
Out Of Plane ◽  
Static Indentation ◽  
Sem Investigation

Non-crimp fabrics are fabric tapes stitched to an adjacent orthogonal fabric with no associated crimp. In the current research, the effect of fixation polyester stitches in improving through-the-thickness properties of non-crimp fabric composite laminates is investigated. Detailed experimental studies on interlaminar fracture toughness and static indentation properties of stitched and unstitched thin ply carbon fibre epoxy composites have been conducted. About 23% higher peak load and 37% higher energy absorption were noticed during static indentation tests for the stitched ply composites. A detailed SEM investigation has shown that the stitch-stitch interaction ‘within a bi-angle ply’ and ‘between the bi-angle ply’ plays a significant role in reducing the delamination extent. The critical energy release rate during Mode I fracture toughness of stitched composites was found to be 26.5% higher and SEM investigation depicted that the stitches promote the intra-laminar delamination and enhance the toughness of the composite.

Analytical and experimental studies on out-of-plane dynamic instability of shallow circular arch based on parametric resonance

2016 ◽  
Vol 87 (1) ◽  
pp. 677-694 ◽  
Author(s):  
Airong Liu ◽  
Hanwen Lu ◽  
Jiyang Fu ◽  
Yong-Lin Pi ◽  
Youqin Huang ◽  
...  
Keyword(s):  
Parametric Resonance ◽  
Dynamic Instability ◽  
Experimental Studies ◽  
Circular Arch ◽  
Out Of Plane

scholarly journals Mathematical modelling of heat transfer in a greenhouse with surface soil heating system

2019 ◽  
Vol 28 (4) ◽  
pp. 569-583
Author(s):  
Volodymyr Hud ◽  
Ievgenii Gerasimov ◽  
Petro Martyniuk ◽  
Oleg Pinchuk ◽  
Pavlo Volk
Keyword(s):  
Mathematical Model ◽  
Mathematical Modelling ◽  
Surface Soil ◽  
Experimental Studies ◽  
Soil Surface ◽  
Heating System ◽  
System Structure ◽  
Soil Heating ◽  
Berry Crops ◽  
Comparison Of The Results

The use of low-temperature heat of industrial and natural origin for heating the soil in greenhouses allows practitioners to get very early vegetable and berry crops. The paper suggests a mathematical model of greenhouse heat exchange with a system of soil surface heating for substantiating the system structure and its efficiency in different conditions. The solution of the mathematical model was performed using the method of least squares in COMSOL Multiphysics software. The comparison of the results of experimental studies with the results of mathematical modelling revealed that the proposed mathematical model with a high degree of reliability allows predicting the thermal regime in greenhouses with surface soil heating using cover sleeves.

scholarly journals RESEARCH PROGRAMME ON SEISMIC PERFORMANCE OF REINFORCED CONCRETE WALLS: KEY RECOMMENDATIONS

2020 ◽  
Vol 53 (2) ◽  
pp. 54-69
Author(s):  
Alex Shegay ◽  
Farhad Dashti ◽  
Lucas Hogan ◽  
Yiqiu Lu ◽  
Arsalan Niroomandi ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Research Programme ◽  
Concrete Walls ◽  
Damage And Failure ◽  
Reinforced Concrete Walls ◽  
Wide Range ◽  
Out Of Plane ◽  
Assessment Guidelines ◽  
Precast Walls

A wide range of reinforced concrete (RC) wall performance was observed following the 2010/2011 Canterbury earthquakes, with most walls performing as expected, but some exhibiting undesirable and unexpected damage and failure characteristics. A comprehensive research programme, funded by the Building Performance Branch of the New Zealand Ministry of Business, Innovation and Employment, and involving both numerical and experimental studies, was developed to investigate the unexpected damage observed in the earthquakes and provide recommendations for the design and assessment procedures for RC walls. In particular, the studies focused on the performance of lightly reinforced walls; precast walls and connections; ductile walls; walls subjected to bi-directional loading; and walls prone to out-of-plane instability. This paper summarises each research programme and provides practical recommendations for the design and assessment of RC walls based on key findings, including recommended changes to NZS 3101 and the NZ Seismic Assessment Guidelines.

Ultimate Strength of Steel and Glass Fibre Reinforced Composite Plates With Square Opening Under Axial and Out of Plane Loads

2010 ◽  
Author(s):  
R. Sundaravadivelu ◽  
P. Alagusundaramoorthy ◽  
M. Suneel Kumar ◽  
S. Rahima Shabeen
Keyword(s):  
Steel Plate ◽  
Slenderness Ratio ◽  
Experimental Studies ◽  
Composite Plates ◽  
Offshore Structures ◽  
Combined Loading ◽  
Glass Fiber Reinforced ◽  
Gfrp Composite ◽  
Out Of Plane ◽  
Glass Fibre Reinforced

The weight of glass fiber reinforced polymer composite (GFRP) plate is about one fourth of the steel plate and can be used in ship and offshore structures, so that the payload can be increased. However comparative studies on the behaviour of steel and GFRP composite plates with square opening have not been studied in detail. The experimental studies on steel and GFRP plates with and without openings are carried out for the combined loading of axial compression and out-of-plane loads. The in-plane and out-of-plane deflections are measured. The reduction in the axial load carrying capacity of the plates due to out-of-plane load is quantified. The effect of column slenderness ratio and plate slenderness ratio on the collapse load of simply supported stiffened plates is presented. Two sets of interaction equations are developed, one for the steel plate and another for the GFRP composite plate.

scholarly journals Of mitogens and morphogens: modelling Sonic Hedgehog mechanisms in vertebrate development

2020 ◽  
Vol 375 (1809) ◽  
pp. 20190660 ◽  
Author(s):  
Ian Groves ◽  
Marysia Placzek ◽  
Alexander G. Fletcher
Keyword(s):  
Mathematical Modelling ◽  
Mathematical Models ◽  
Sonic Hedgehog ◽  
Mechanism Of Action ◽  
Concentration Gradient ◽  
Experimental Studies ◽  
Theoretical Framework ◽  
Vertebrate Development ◽  
Complex Mechanism ◽  
Proliferation And Differentiation

Sonic Hedgehog (Shh) Is a critical protein in vertebrate development, orchestrating patterning and growth in many developing systems. First described as a classic morphogen that patterns tissues through a spatial concentration gradient, subsequent studies have revealed a more complex mechanism, in which Shh can also regulate proliferation and differentiation. While the mechanism of action of Shh as a morphogen is well understood, it remains less clear how Shh might integrate patterning, proliferation and differentiation in a given tissue, to ultimately direct its morphogenesis. In tandem with experimental studies, mathematical modelling can help gain mechanistic insights into these processes and bridge the gap between Shh-regulated patterning and growth, by integrating these processes into a common theoretical framework. Here, we briefly review the roles of Shh in vertebrate development, focusing on its functions as a morphogen, mitogen and regulator of differentiation. We then discuss the contributions that modelling has made to our understanding of the action of Shh and highlight current challenges in using mathematical models in a quantitative and predictive way. This article is part of a discussion meeting issue ‘Contemporary morphogenesis’.

Experimental Studies on Dispersion of Fine Non-Spherical Particles in Enclosed Spaces

2013 ◽  
Vol 310 ◽  
pp. 3-6 ◽  
Author(s):  
Zi Biao Song ◽  
Xiao Lu Wu ◽  
Yu Qian Ye ◽  
Chang Jun Rong
Keyword(s):  
Fine Particle ◽  
Indoor Environment ◽  
Carbon Nanofiber ◽  
Dispersion Model ◽  
Experimental Studies ◽  
Particle Dispersion ◽  
Spherical Particles ◽  
Dispersion Process ◽  
Aerosol Dispersion ◽  
Mass Concentrations

Study on the fine particle dispersion in the room is very important for creating and maintaining a healthy indoor environment. An experiment of a carbon nanofiber material blown in smoke box was taken and the mass concentrations of the aerosol formed by this material were measured. Dispersion process of this material in the smoke box was simulated by random walk model, spherical particles aerosol dispersion model and non-spherical particles aerosol dispersion model, respectively. The setting velocities of the aerosol in the smoke box were calculated according to the mass concentrations at different times and the influences of gravity and non-spherical particles’ shape on its dispersion process were analyzed in theory.

Sign in / Sign up

Export Citation Format

Share Document