Impact of cyclic bending on coronary hemodynamics

It remains unknown that the degree of bias in computational fluid dynamics results without considering coronary cyclic bending. This study aims to investigate the influence of different rates of coronary cyclic bending on coronary hemodynamics. To model coronary bending, a multi-ring-controlled fluid–structural interaction model was designed. A coronary artery was simulated with various cyclic bending rates (0.5, 0.75 and 1 s, corresponding to heart rates of 120, 80 and 60 bpm) and compared against a stable model. The simulated results show that the hemodynamic parameters of vortex Q-criterion, temporal wall shear stress (WSS), time-averaged WSS (TaWSS) and oscillatory shear index (OSI) were sensitive to the changes in cyclic rate. A higher heart rate resulted in higher magnitude and larger variance in the hemodynamic parameters. Whereas, the values and distributions of flow velocity and relative residence time (RRT) did not show significant differences between different bending periods. This study suggests that a stable coronary model is not sufficient to represent the hemodynamics in a bending coronary artery. Different heart rate conditions were found to have significant impact on the hemodynamic parameters. Thus, cyclic bending should be considered to mimic the realistic hemodynamics in future patient-specific coronary hemodynamics studies

Reproducibility of the computational fluid dynamic analysis of a cerebral aneurysm monitored over a decade

Computational fluid dynamics (CFD) simulations are increasingly utilised to evaluate intracranial aneurysm (IA) haemodynamics to aid in the prediction of morphological changes and rupture risk. However, these models vary and differences in published results warrant the investigation of IA-CFD reproducibility. This study aims to explore sources of intra-team variability and determine its impact on the aneurysm morphology and CFD parameters. A team of four operators were given six sets of magnetic resonance angiography data spanning a decade from one patient with a middle cerebral aneurysm. All operators were given the same protocol and software for model reconstruction and numerical analysis. The morphology and haemodynamics of the operator models were then compared. The segmentation, smoothing factor, inlet and outflow branch lengths were found to cause intra-team variability. There was 80% reproducibility in the time-averaged wall shear stress distribution among operators with the major difference attributed to the level of smoothing. Based on these findings, it was concluded that the clinical applicability of CFD simulations may be feasible if a standardised segmentation protocol is developed. Moreover, when analysing the aneurysm shape change over a decade, it was noted that the co-existence of positive and negative values of the wall shear stress divergence (WSSD) contributed to the growth of a daughter sac

Impact of Speckle Deformability on Digital Imaging Correlation

Digital Image Correlation (DIC) has been widely used as a non-contact deformation measurement technique. Nevertheless, its accuracy is greatly affected by the speckle pattern on the specimen. To systematically evaluate how speckle deformability affects the precision of DIC algorithms. In this study, a test dataset of 2D speckle patterns with various prescribed deformation fields was numerically generated, containing two categories of speckles, i.e., the deformable and the non-deformable (rigid) ones. This dataset was used to evaluate the performance of inverse compositional Gauss-Newton (ICGN)-based DIC algorithms with two types of shape function (first-order and second-order), in the different scenarios of the deformation field. The results showed that imaging noise had a significant influence on the DIC algorithm. The first-order shape function (ICGN-1) performed better when tracking the simple linear deformation field. While the second-order shape function (ICGN-2) was proved to perform better on non-linear deformations. Moreover, the deformability of the speckle was found to have an obvious impact on the performance of the DIC algorithm. ICGN-2 could effectively reduce so-called speckle rigidity induced (SRI) error. Conclusively, ICGN-2 should be chosen as priority, because of its feasibility on non-linear deformation fields and speckle rigidity. While in the linear deformation scenarios, ICGN-1 was still a robust and efficient method

An isothermal titration and differential scanning calorimetry study of the G-quadruplex DNA-insulin interaction

The binding of insulin to the G-quadruplexes formed by the consensus sequence of the insulin-linked polymorphic region (ILPR) was investigated with differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). The thermal denaturation temperature of insulin was increased by almost 4 oC upon binding to ILPR G-quadruplex DNA as determined by DSC. The thermodynamic parameters (KD, H, G and S) of the insulin-G-quadruplex complex were further investigated by temperature-dependent ITC measurement over 10-37 °C. The binding of insulin to the ILPR consensus sequence displays micromolar affinity in phosphate buffer at pH 7.4, which and is mainly driven by entropic factors at below 25 °C but by enthalpic factors terms at above 30 °C. The interaction was also examined in several different buffers and results showed that observed H is dependent on the ionization enthalpy of the buffer used. This indicates proton release upon the binding of G-quadruplex DNA to insulin. Additionally, the large negative change in heat capacity for this interaction may be associated with the dominant hydrophobicity of the amino acid sequence of insulin’s beta subunit, which is known to bind to the ILPR G-quadruplex DNA