Modelling of Atherosclerotic Plaque for Use in a Computational Test-Bed for Stent Angioplasty

A thorough understanding of the diseased tissue state is necessary for the successful treatment of a blocked arterial vessel using stent angioplasty. The constitutive representation of atherosclerotic tissue is of great interest to researchers and engineers using computational models to analyse stents, as it is this in silico environment that allows extensive exploration of tissue response to device implantation. This paper presents an in silico evaluation of the effects of variation of atherosclerotic tissue constitutive representation on tissue mechanical response during stent implantation. The motivation behind this work is to investigate the level of detail that is required when modelling atherosclerotic tissue in a stenting simulation, and to give recommendations to the FDA for their guideline document on coronary stent evaluation, and specifically the current requirements for computational stress analyses. This paper explores the effects of variation of the material model for the atherosclerotic tissue matrix, the effects of inclusion of calcifications and a lipid pool, and finally the effects of inclusion of the Mullins effect in the atherosclerotic tissue matrix, on tissue response in stenting simulations. Results indicate that the inclusion of the Mullins effect in a direct stenting simulation does not have a significant effect on the deformed shape of the tissue or the stress state of the tissue. The inclusion of a lipid pool induces a local redistribution of lesion deformation for a soft surrounding matrix and the inclusion of a small volume of calcifications dramatically alters the local results for a soft surrounding matrix. One of the key findings from this work is that the underlying constitutive model (elasticity model) used for the atherosclerotic tissue is the dominant feature of the tissue representation in predicting tissue response in a stenting simulation

The Effect of Physiological Cyclic Stretch on the Cell Morphology, Cell Orientation and Protein Expression of Endothelial Cells

In vivo, endothelial cells are constantly exposed to pulsatile shear and tensile stresses. The main aim of this study was to design and build a physiological simulator, which reproduced homogenous strain profiles of the tensile strain experienced in vivo, and to investigate the effect of this cyclic tensile strain on the cell morphology, cell orientation and protein expression of endothelial cells. The biological response of human umbilical vein endothelial cells to a uniaxial cyclic stretch, in this newly developed simulator, was examined experimentally using immunohistostaining and confocal imaging and it was found that the cells elongated and oriented at 58.9± 4.5. This value was compared to a mathematical model where it was revealed that endothelial cells would orient at an angle of 60. This model also revealed that endothelial cells have an axial strain threshold value of 1.8% when exposed to a 10% cyclic strain at 1 Hz for 3 h. Cells cultured under conditions of cyclic strain showed increased ICAM-1 immunostaining when compared to static cells whereas, a marked decrease in the levels of VCAM-1 receptor staining was also observed. Haemodynamic stresses can modulate the endothelial cell adhesion response in vivo thus, taken together; this data validates the bioreactor as replicating the physiological environment

Measurement of CP asymmetries and branching fraction ratios of B− decays to two charm mesons

The $CP$ asymmetries of seven $B^-$ decays to two charm mesons are measured using data corresponding to an integrated luminosity of $9\text{fb}^{-1}$ of proton-proton collisions collected by the LHCb experiment. Decays involving a $D^{*0}$ or $D^{*-}_s$ meson are analysed by reconstructing only the $D^0$ or $D^-_s$ decay products. This paper presents the first measurement of $\mathcal{A}^{CP}(B^- \rightarrow D^{*-}_s D^0)$ and $\mathcal{A}^{CP}(B^- \rightarrow D^{-}_s D^{*0})$, and the most precise measurement of the other five $CP$ asymmetries. There is no evidence of $CP$ violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.The CP asymmetries of seven B$^{−}$ decays to two charm mesons are measured using data corresponding to an integrated luminosity of 9 fb$^{−1}$ of proton-proton collisions collected by the LHCb experiment. Decays involving a D$^{*0}$ or ${D}_s^{\ast -}$ meson are analysed by reconstructing only the D$^{0}$ or ${D}_s^{-}$ decay products. This paper presents the first measurement of $\mathcal{A} ^{CP}$(B$^{−}$→${D}_s^{\ast -}$D$^{0}$) and $\mathcal{A} ^{CP}$(B$^{−}$→${D}_s^{-}$D$^{∗0}$), and the most precise measurement of the other five CP asymmetries. There is no evidence of CP violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.[graphic not available: see fulltext]The $CP$ asymmetries of seven $B^-$ decays to two charm mesons are measured using data corresponding to an integrated luminosity of $9\text{ fb}^{-1}$ of proton-proton collisions collected by the LHCb experiment. Decays involving a $D^{*0}$ or $D^{*-}_s$ meson are analysed by reconstructing only the $D^0$ or $D^-_s$ decay products. This paper presents the first measurement of $\mathcal{A}^{CP}(B^- \rightarrow D^{*-}_s D^0)$ and $\mathcal{A}^{CP}(B^- \rightarrow D^{-}_s D^{*0})$, and the most precise measurement of the other five $CP$ asymmetries. There is no evidence of $CP$ violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured

Is the coactivation of biceps femoris during isometric knee extension affected by adiposity in healthy young humans?

This study aimed to verify if the level of biceps femoris antagonist activity measured during isometric knee extension was affected by the individual degree of adiposity in 14 young healthy subjects of both genders aged between 18 and 24. Surface EMG signals were recorded from the biceps femoris muscle of the dominant leg during isometric knee extension at three levels of voluntary contraction: maximum (MVC), 80% MVC and 200 N, respectively. In addition, whole-body percentage of fat, volume of the thigh and skinfold thickness below the electrodes were achieved. Biceps femoris coactivation values were: 28.5±17.9%, 30.9±17.7% and 25.3±17.5% for MVC, 80% MVC and 200N trials, respectively (NS). Neither the whole-body percentage of fat nor the skinfold thickness influenced percentage coactivation, irrespective of the intensity of contraction. However, an increase in the whole-body percentage of fat showed a tendency to augment the biceps femoris coactivation (PI=0.079; PII=0.575). No differences in coactivation were observed between genders. In addition, the duration of contraction did not affect the level of coactivation

Local and regional mechanical characterisation of a collagen-glycosaminoglycan scaffold using high-resolution finite element analysis

Artificial tissue growth requires cells to proliferate and differentiate within the host scaffold. As cell function is governed by mechano-sensitive selection, tissue type is influenced by the microscopic forces exposed to the cells, which is a product of macroscopically straining the scaffold. Accordingly, the microscopic strain environment within a CG scaffold is offered here. Using muCT to characterise CG scaffold architecture, two high-resolution 3D FE models were used to predict the deformation mechanics. While also providing an analysis of region-specific features, such as relative density, pore diameters and microstructural elastic stability, the deformation patterns afforded strains to be inferred for seeded cells. The results indicate a regional dependence, in terms of architectural and mechanical properties. Specifically, the peripheral regions demonstrated the lowest volume fraction, the highest stress concentrations and the greatest potential for elastic instability. Conversely, the mid-region exhibited the most homogeneous environment. Based on the proviso of mechano-sensitive proliferation and differentiation, the findings suggest cell function will vary between CG scaffold regions. Further work should investigate the possibility of improving the fabrication process in order to deliver a construct in line with the mid-region, or alternatively, isolation of the mid-region may prove beneficial for cell culturing