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  • Journal article
    Cookson AN, Doorly DJ, Sherwin SJ, 2019,

    Efficiently Generating Mixing by Combining Differing Small Amplitude Helical Geometries

    , FLUIDS, Vol: 4, ISSN: 2311-5521
  • Journal article
    Alpresa P, Sherwin S, Weinberg P, van Reeuwijk Met al., 2018,

    Orbitally shaken shallow fluid layers. II. An improved wall shear stress model

    , PHYSICS OF FLUIDS, Vol: 30, ISSN: 1070-6631

    A new model for the analytical prediction of wall shear stress distributions at the base of orbitally shaken shallow fluid layers is developed. This model is a generalisation of the classical extended Stokes solution and will be referred to as the potential theory-Stokes model. The model is validated using a large set of numerical simulations covering a wide range of flow regimes representative of those used in laboratory experiments. It is demonstrated that the model is in much better agreement with the simulation data than the classical Stokes solution, improving the prediction in 63% of the studied cases. The central assumption of the model—which is to link the wall shear stress with the surface velocity—is shown to hold remarkably well over all regimes covered.
  • Journal article
    Alpresa P, Sherwin S, Weinberg P, van Reeuwijk Met al., 2018,

    Orbitally shaken shallow fluid layers. I. Regime classification

    , PHYSICS OF FLUIDS, Vol: 30, ISSN: 1070-6631

    Orbital shakers are simple devices that provide mixing, aeration, and shear stress at multiple scales and high throughput. For this reason, they are extensively used in a wide range of applications from protein production to bacterial biofilms and endothelial cell experiments. This study focuses on the behaviour of orbitally shaken shallow fluid layers in cylindrical containers. In order to investigate the behaviour over a wide range of different conditions, a significant number of numerical simulations are carried out under different configuration parameters. We demonstrate that potential theory—despite the relatively low Reynolds number of the system—describes the free-surface amplitude well and the velocity field reasonably well, except when the forcing frequency is close to a natural frequency and resonance occurs. By classifying the simulations into non-breaking, breaking, and breaking with part of the bottom uncovered, it is shown that the onset of wave breaking is well described by Δh/(2R) = 0.7Γ, where Δh is the free-surface amplitude, R is the container radius, and Γ is the container aspect ratio; Δh can be well approximated using the potential theory. This result is in agreement with standard wave breaking theories although the significant inertial forcing causes wave breaking at lower amplitudes.
  • Journal article
    Ghim M, Alpresa P, Yang S, Braakman ST, Gray SG, Sherwin SJ, van Reeuwijk M, Weinberg PDet al., 2017,

    Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow.

    , AJP - Heart and Circulatory Physiology, Vol: 313, Pages: H959-H973, ISSN: 1522-1539

    Transport of macromolecules across vascular endothelium and its modification by fluid mechanical forces are important for normal tissue function and in the development of atherosclerosis. However, the routes by which macromolecules cross endothelium, the hemodynamic stresses that maintain endothelial physiology or trigger arterial disease, and the dependence of transendothelial transport on hemodynamic stresses are controversial. Here we visualised pathways for macromolecule transport and determined the effect on these pathways of different types of flow. Endothelial monolayers were cultured under static conditions or on an orbital shaker producing different flow profiles in different parts of the wells. Fluorescent tracers that bound to the substrate after crossing the endothelium were used to identify transport pathways. Maps of tracer distribution were compared with numerical simulations of flow to determine effects of different shear stress metrics on permeability. Albumin-sized tracers dominantly crossed the cultured endothelium via junctions between neighbouring cells, high-density-lipoprotein-sized tracers crossed at tricelluar junctions whilst low-density-lipoprotein-sized tracers crossed through cells. Cells aligned close to the angle that minimised shear stresses across their long axis. The rate of paracellular transport under flow correlated with the magnitude of these minimised transverse stresses, whereas transport across cells was uniformly reduced by all types of flow. These results contradict the long-standing two-pore theory of solute transport across microvessel walls and the consensus view that endothelial cells align with the mean shear vector. They suggest that endothelial cells minimise transverse shear, supporting its postulated pro-atherogenic role. Preliminary data show that similar tracer techniques are practicable in vivo.
  • Journal article
    Chooi KY, Comerford A, Sherwin SJ, Weinberg PDet al., 2017,

    Noradrenaline has opposing effects on the hydraulic conductance of arterial intima and media.

    , Journal of Biomechanics, Vol: 54, Pages: 4-10, ISSN: 1873-2380

    The uptake of circulating macromolecules by the arterial intima is thought to be a key step in atherogenesis. Such transport is dominantly advective, so elucidating the mechanisms of water transport is important. The relation between vasoactive agents and water transport in the arterial wall is incompletely understood. Here we applied our recently-developed combination of computational and experimental methods to investigate the effects of noradrenaline (NA) on hydraulic conductance of the wall (Lp), medial extracellular matrix volume fraction (ϕ(ECM)) and medial permeability (K1(1)) in the rat abdominal aorta. Experimentally, we found that physiological NA concentrations were sufficient to induce SMC contraction and produced significant decreases in Lp and increases in ϕ(ECM). Simulation results based on 3D confocal images of the extracellular volume showed a corresponding increase in K1(1), attributed to the opening of the ECM. Conversion of permeabilities to layer-specific resistances revealed that although the total wall resistance increased, medial resistance decreased, suggesting an increase in intimal resistance upon application of NA.
  • Journal article
    Mohamied Y, Sherwin SJ, Weinberg PD, 2016,

    Understanding the fluid mechanics behind transverse wall shear stress

    , Journal of Biomechanics, Vol: 50, Pages: 102-109, ISSN: 1873-2380

    The patchy distribution of atherosclerosis within arteries is widely attributed to local variation in haemodynamic wall shear stress (WSS). A recently-introduced metric, the transverse wall shear stress (transWSS), which is the average over the cardiac cycle of WSS components perpendicular to the temporal mean WSS vector, correlates particularly well with the pattern of lesions around aortic branch ostia. Here we use numerical methods to investigate the nature of the arterial flows captured by transWSS and the sensitivity of transWSS to inflow waveform and aortic geometry. TransWSS developed chiefly in the acceleration, peak systolic and deceleration phases of the cardiac cycle; the reverse flow phase was too short, and WSS in diastole was too low, for these periods to have a significant influence. Most of the spatial variation in transWSS arose from variation in the angle by which instantaneous WSS vectors deviated from the mean WSS vector rather than from variation in the magnitude of the vectors. The pattern of transWSS was insensitive to inflow waveform; only unphysiologically high Womersley numbers produced substantial changes. However, transWSS was sensitive to changes in geometry. The curvature of the arch and proximal descending aorta were responsible for the principal features, the non-planar nature of the aorta produced asymmetries in the location and position of streaks of high transWSS, and taper determined the persistence of the streaks down the aorta. These results reflect the importance of the fluctuating strength of Dean vortices in generating transWSS.
  • Journal article
    Serbanovic-Canic J, de Luca A, Warboys C, Ferreira PF, Luong LA, Hsiao S, Gauci I, Mahmoud M, Feng S, Souilhol C, Bowden N, Ashton JP, Walczak H, Firmin D, Krams R, Mason JC, Haskard DO, Sherwin S, Ridger V, Chico TJ, Evans PCet al., 2016,

    Zebrafish model for functional screening of flow-responsive genes

    , Arteriosclerosis Thrombosis and Vascular Biology, Vol: 36, ISSN: 1524-4636

    OBJECTIVE: Atherosclerosis is initiated at branches and bends of arteries exposed to disturbed blood flow that generates low shear stress. This mechanical environment promotes lesions by inducing endothelial cell (EC) apoptosis and dysfunction via mechanisms that are incompletely understood. Although transcriptome-based studies have identified multiple shear-responsive genes, most of them have an unknown function. To address this, we investigated whether zebrafish embryos can be used for functional screening of mechanosensitive genes that regulate EC apoptosis in mammalian arteries. APPROACH AND RESULTS: First, we demonstrated that flow regulates EC apoptosis in developing zebrafish vasculature. Specifically, suppression of blood flow in zebrafish embryos (by targeting cardiac troponin) enhanced that rate of EC apoptosis (≈10%) compared with controls exposed to flow (≈1%). A panel of candidate regulators of apoptosis were identified by transcriptome profiling of ECs from high and low shear stress regions of the porcine aorta. Genes that displayed the greatest differential expression and possessed 1 to 2 zebrafish orthologues were screened for the regulation of apoptosis in zebrafish vasculature exposed to flow or no-flow conditions using a knockdown approach. A phenotypic change was observed in 4 genes; p53-related protein (PERP) and programmed cell death 2-like protein functioned as positive regulators of apoptosis, whereas angiopoietin-like 4 and cadherin 13 were negative regulators. The regulation of perp, cdh13, angptl4, and pdcd2l by shear stress and the effects of perp and cdh13 on EC apoptosis were confirmed by studies of cultured EC exposed to flow. CONCLUSIONS: We conclude that a zebrafish model of flow manipulation coupled to gene knockdown can be used for functional screening of mechanosensitive genes in vascular ECs, thus providing potential therapeutic targets to prevent or treat endothelial injury at atheroprone sites.
  • Journal article
    Chooi KY, Comerford A, Sherwin SJ, Weinberg PDet al., 2016,

    Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study

    , Journal of the Royal Society Interface, Vol: 11, ISSN: 1742-5689

    The hydraulic resistances of the intima and media determine water flux and the advection of macromolecules into and across the arterial wall. Despite several experimental and computational studies, however, these trans- port processes and their dependence on transmural pressure remain incompletely understood. Here we use a combination of experimental and computational methods to ascertain how the hydraulic permeability of the rat abdominal aorta depends on these two layers and how it is affected by structural rearrangement of the media under pressure. Ex vivo experiments determined the conductance of the whole wall, the thickness of the media, and the geometry of medial smooth muscle cells and extracellular matrix. Numerical methods were used to compute water flux through the media. Intimal values were obtained by subtraction. A mechanism was iden- tified that modulates pressure-induced changes in medial transport properties: compaction of the extracellular matrix leading to spatial reorganisation of smooth muscle cells. This is summarised in an empirical constitutive law for permeability and volumetric strain. This led to the physiologically interesting observation that, as a consequence of the changes in medial microstructure, the relative contributions of the intima and media to the hydraulic resistance of the wall depend on the applied pressure; medial resistance dominated at pressures above ∼93mmHg in this vessel.
  • Journal article
    Cantwell CD, Roney CH, Ng FS, Siggers JH, Sherwin SJ, Peters NSet al., 2015,

    Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping

    , Computers in Biology and Medicine, Vol: 65, Pages: 229-242, ISSN: 0010-4825

    Measurements of cardiac conduction velocity provide valuable functional and structural insight into the initiation and perpetuation of cardiac arrhythmias, in both a clinical and laboratory context. The interpretation of activation wavefronts and their propagation can identify mechanistic properties of a broad range of electrophysiological pathologies. However, the sparsity, distribution and uncertainty of recorded data make accurate conduction velocity calculation difficult. A wide range of mathematical approaches have been proposed for addressing this challenge, often targeted towards specific data modalities, species or recording environments. Many of these algorithms require identification of activation times from electrogram recordings which themselves may have complex morphology or low signal-to-noise ratio. This paper surveys algorithms designed for identifying local activation times and computing conduction direction and speed. Their suitability for use in different recording contexts and applications is assessed.
  • Conference paper
    Tzortzis KN, Roney CH, Qureshi NA, Ng FU, Lim PHANGBOON, Sherwin S, Peters NS, Cantwell Cet al., 2015,

    Influence of left atrial geometry on rotor core trajectories in a model of atrial fibrillation

    , Computing in Cardiology, Publisher: IEEE, Pages: 481-484, ISSN: 2325-8861

    Left atrial anatomy and myocardial architecture areknown to influence rotor initiation and maintenance.However, identifying their relative contribution clinicallyis challenging. The present study aims to investigate insilico the effect of left atrial geometry in isolation onrotor generation and evolution through thespatiotemporal tracking of phase singularities. Aftermeandering for a short period of time, rotors areattracted to specific areas of the chamber where there ishigh curvature, primarily near the base of the left atrialappendage and the junctions of the pulmonary veins. Thissuggests that the left atrial anatomy could play a key rolein the perpetuation of fibrillatory activity.
  • Conference paper
    Ali RL, Cantwell CD, Qureshi NA, Roney CH, Phang Boon Lim, Sherwin SJ, Siggers JH, Peters NSet al., 2015,

    Automated fiducial point selection for reducing registration error in the co-localisation of left atrium electroanatomic and imaging data.

    , 2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 1989-1992, ISSN: 1557-170X

    Registration of electroanatomic surfaces and segmented images for the co-localisation of structural and functional data typically requires the manual selection of fiducial points, which are used to initialise automated surface registration. The identification of equivalent points on geometric features by the human eye is heavily subjective, and error in their selection may lead to distortion of the transformed surface and subsequently limit the accuracy of data co-localisation. We propose that the manual trimming of the pulmonary veins through the region of greatest geometrical curvature, coupled with an automated angle-based fiducial-point selection algorithm, significantly reduces target registration error compared with direct manual selection of fiducial points.
  • Journal article
    Cantwell CD, Moxey D, Comerford A, Bolis A, Rocco G, Mengaldo G, de Grazia D, Yakovlev S, Lombard J-E, Ekelschot D, Jordi B, Xu H, Mohamied Y, Eskilsson C, Nelson B, Vos P, Biotto C, Kirby RM, Sherwin SJet al., 2015,

    Nektar++: An open-source spectral/hp element framework

    , Computer Physics Communications, Vol: 192, Pages: 205-219, ISSN: 1879-2944

    Nektar++ is an open-source software framework designed to support the development of high-performance scalable solvers for partial differential equations using the spectral/hphp element method. High-order methods are gaining prominence in several engineering and biomedical applications due to their improved accuracy over low-order techniques at reduced computational cost for a given number of degrees of freedom. However, their proliferation is often limited by their complexity, which makes these methods challenging to implement and use. Nektar++ is an initiative to overcome this limitation by encapsulating the mathematical complexities of the underlying method within an efficient C++ framework, making the techniques more accessible to the broader scientific and industrial communities. The software supports a variety of discretisation techniques and implementation strategies, supporting methods research as well as application-focused computation, and the multi-layered structure of the framework allows the user to embrace as much or as little of the complexity as they need. The libraries capture the mathematical constructs of spectral/hphp element methods, while the associated collection of pre-written PDE solvers provides out-of-the-box application-level functionality and a template for users who wish to develop solutions for addressing questions in their own scientific domains.
  • Journal article
    Mohamied Y, Rowland EM, Bailey EL, Sherwin SJ, Schwartz MA, Weinberg PDet al., 2015,

    Change of direction in the biomechanics of atherosclerosis

    , Annals of Biomedical Engineering, Vol: 43, Pages: 16-25, ISSN: 0090-6964

    The non-uniform distribution of atherosclerosis within the arterial system has been attributed to pro-atherogenic influences of low, oscillatory haemodynamic wall shear stress (WSS) on endothelial cells (EC). This theory is challenged by the changes in lesion location that occur with age in human and rabbit aortas. Furthermore, a number of point-wise comparisons of lesion prevalence and WSS have failed to support it. Here we investigate the hypothesis that multidirectional flow—characterized as the average magnitude of WSS components acting transversely to the mean vector (transWSS)—plays a key role. Maps of lesion prevalence around aortic branch ostia in immature and mature rabbits were compared with equivalent maps of time average WSS, the OSI (an index characterizing oscillatory flow) and transWSS, obtained from computational simulations; Spearman’s rank correlation coefficients were calculated for aggregated data and 95% confidence intervals were obtained by bootstrapping methods. Lesion prevalence correlated positively, strongly and significantly with transWSS at both ages. Correlations of lesion prevalence with the other shear metrics were not significant or were significantly lower than those obtained for transWSS. No correlation supported the low, oscillatory WSS theory. The data are consistent with the view that multidirectional near-wall flow is highly pro-atherogenic. Effects of multidirectional flow on EC, and methods for investigating them, are reviewed. The finding that oscillatory flow has pro-inflammatory effects when acting perpendicularly to the long axis of EC but anti-inflammatory effects when acting parallel to it may explain the stronger correlation of lesion prevalence with transWSS than with the OSI.
  • Journal article
    Mohri Z, Rowland EM, Clarke LA, De Luca A, Peiffer V, Krams R, Sherwin SJ, Weinberg PDet al., 2014,

    Elevated Uptake of Plasma Macromolecules by Regions of Arterial Wall Predisposed to Plaque Instability in a Mouse Model

    , PLoS One, Vol: 9, ISSN: 1932-6203

    Atherosclerosis may be triggered by an elevated net transport of lipid-carryingmacromolecules from plasma into the arterial wall. We hypothesised that whetherlesions are of the thin-cap fibroatheroma (TCFA) type or are less fatty and morefibrous depends on the degree of elevation of transport, with greater uptake leadingto the former. We further hypothesised that the degree of elevation can depend onhaemodynamic wall shear stress characteristics and nitric oxide synthesis. Placinga tapered cuff around the carotid artery of apolipoprotein E -/- mice modifiespatterns of shear stress and eNOS expression, and triggers lesion development atthe upstream and downstream cuff margins; upstream but not downstream lesionsresemble the TCFA. We measured wall uptake of a macromolecular tracer in thecarotid artery of C57bl/6 mice after cuff placement. Uptake was elevated in theregions that develop lesions in hyperlipidaemic mice and was significantly moreelevated where plaques of the TCFA type develop. Computational simulations andeffects of reversing the cuff orientation indicated a role for solid as well as fluidmechanical stresses. Inhibiting NO synthesis abolished the difference in uptakebetween the upstream and downstream sites. The data support the hypothesis thatexcessively elevated wall uptake of plasma macromolecules initiates thedevelopment of the TCFA, suggest that such uptake can result from solid and fluidmechanical stresses, and are consistent with a role for NO synthesis. Modificationof wall transport properties might form the basis of novel methods for reducingplaque rupture.
  • Conference paper
    Roney CH, Cantwell C, Qureshi NA, Ali RL, Chang ETY, Lim PB, Sherwin SJ, Peters NS, Siggers JH, Ng FSet al., 2014,

    An Automated Algorithm for Determining Conduction Velocity, Wavefront Direction and Focal Source Location using a Multipolar Catheter

    , IEEE Engineering in Medicine and Biology Conference

    Determining locations of focal arrhythmia sources and quantifying myocardial conduction velocity (CV) are two major challenges in clinical catheter ablation cases. CV, wavefront direction and focal source location can be estimated from multipolar catheter data, but currently available methods are time-consuming, limited to specific electrode configurations, and can be inaccurate. We developed automated algorithms to rapidly identify CV from multipolar catheter data with any arrangement of electrodes, whilst providing estimates of wavefront direction and focal source position, which can guide the catheter towards a focal arrhythmic source. We validated our methods using simulations on realistic human left atrial geometry. We subsequently applied them to clinically-acquired intracardiac electrogram data, where CV and wavefront direction were accurately determined in all cases, whilst focal source locations were correctly identified in 2/3 cases. Our novel automated algorithms can potentially be used to guide ablation of focal arrhythmias in real-time in cardiac catheter laboratories.
  • Journal article
    Warboys CM, de Luca A, Amini N, Luong L, Duckles H, Hsiao S, White A, Biswas S, Khamis R, Chong CK, Cheung W-M, Sherwin SJ, Bennett MR, Gil J, Mason JC, Haskard DO, Evans PCet al., 2014,

    Disturbed flow promotes endothelial senescence via a p53-dependent Ppathway

    , Arteriosclerosis, Thrombosis and Vascular Biology, Vol: 34, Pages: 985-995, ISSN: 1079-5642

    Objective—Although atherosclerosis is associated with systemic risk factors such as age, high cholesterol, and obesity, plaque formation occurs predominately at branches and bends that are exposed to disturbed patterns of blood flow. The molecular mechanisms that link disturbed flow–generated mechanical forces with arterial injury are uncertain. To illuminate them, we investigated the effects of flow on endothelial cell (EC) senescence.Approach and Results—LDLR−/− (low-density lipoprotein receptor−/−) mice were exposed to a high-fat diet for 2 to 12 weeks (or to a normal chow diet as a control) before the assessment of cellular senescence in aortic ECs. En face staining revealed that senescence-associated β-galactosidase activity and p53 expression were elevated in ECs at sites of disturbed flow in response to a high-fat diet. By contrast, ECs exposed to undisturbed flow did not express senescence-associated β-galactosidase or p53. Studies of aortae from healthy pigs (aged 6 months) also revealed enhanced senescence-associated β-galactosidase staining at sites of disturbed flow. These data suggest that senescent ECs accumulate at disturbed flow sites during atherogenesis. We used in vitro flow systems to examine whether a causal relationship exists between flow and EC senescence. Exposure of cultured ECs to flow (using either an orbital shaker or a syringe-pump flow bioreactor) revealed that disturbed flow promoted EC senescence compared with static conditions, whereas undisturbed flow reduced senescence. Gene silencing studies demonstrated that disturbed flow induced EC senescence via a p53-p21 signaling pathway. Disturbed flow–induced senescent ECs exhibited reduced migration compared with nonsenescent ECs in a scratch wound closure assay, and thus may be defective for arterial repair. However, pharmacological activation of sirtuin 1 (using resveratrol or SRT1720) protected ECs from disturbed flow&ndas
  • Conference paper
    Bailey EL, Peiffer V, Mohamied Y, Chooi KY, Rowland EM, Sherwin SJ, Weinberg PDet al., 2014,

    SPATIAL CORRELATION BETWEEN PATTERNS OF WALL PERMEABILITY AND PATTERNS OF MULTIDIRECTIONAL DISTURBED BLOOD FLOW IN RABBIT AORTA

    , Autumn Meeting of the British-Atherosclerosis-Society (BAS), Publisher: ELSEVIER IRELAND LTD, Pages: E2-E2, ISSN: 0021-9150
  • Journal article
    Cantwell CD, Yakovlev S, Kirby RM, Peters NS, Sherwin SJet al., 2014,

    High-order spectral/hp element discretisation for reaction-diffusion problems on surfaces: application to cardiac electrophysiology

    , Journal of Computational Physics, Vol: 257, Pages: 813-829, ISSN: 0021-9991

    We present a numerical discretisation of an embedded two-dimensional manifold using high-order continuous Galerkin spectral/hp elements, which provide exponential convergence of the solution with increasing polynomial order, while retaining geometric flexibility in the representation of the domain. Our work is motivated by applications in cardiac electrophysiology where sharp gradients in the solution benefit from the high-order discretisation, while the compu- tational cost of anatomically-realistic models can be reduced through the surface representation. We describe and validate our discretisation and provide a demonstration of its application to modeling electrochemical propagation across a human left atrium.
  • Journal article
    Comerford A, Chooi KY, Nowak M, Weinberg PD, Sherwin SJet al., 2014,

    A combined numerical and experimental framework for determining permeability properties of the arterial media

    , Biomechanics and Modeling in Mechanobiology, accepted
  • Conference paper
    Ali RL, Cantwell CD, Roney CH, Qureshi NA, Lim PB, Siggers JH, Sherwin SJ, Peters NSet al., 2014,

    A novel method for quantifying localised correlation of late-gadolinium intensity with conduction velocity

    , Computing in Cardiology (CinC) 2014, Pages: 193-196

    Patient-specific computer models of the human atria have the potential to aid clinical intervention in the treatment of cardiac arrhythmias. However, quantifying and integrating the heterogeneous qualities of the myocardium through imaging is particularly challenging due to the unknown relationship between voxel intensity and tissue conductivities. We establish a method to determine the relationship between local conduction velocity and scar density, extracted through the analysis of late-gadolinium enhanced magnetic resonance imaging data.
  • Journal article
    Peiffer V, Sherwin SJ, Weinberg PD, 2013,

    Computation in the rabbit aorta of a new metric - the transverse wall shear stress - to quantify the multidirectional character of disturbed blood flow

    , JOURNAL OF BIOMECHANICS, Vol: 46, Pages: 2651-2658, ISSN: 0021-9290

    Spatial variation of the haemodynamic stresses acting on the arterial wall is commonly assumed to explain the focal development of atherosclerosis. Disturbed flow in particular is thought to play a key role. However, widely-used metrics developed to quantify its extent are unable to distinguish between uniaxial and multidirectional flows. We analysed pulsatile flow fields obtained in idealised and anatomically-realistic arterial geometries using computational fluid dynamics techniques, and in particular investigated the multidirectionality of the flow fields, capturing this aspect of near-wall blood flow with a new metric – the transverse wall shear stress (transWSS) – calculated as the time-average of wall shear stress components perpendicular to the mean flow direction. In the idealised branching geometry, multidirectional flow was observed downstream of the branch ostium, a region of flow stagnation, and to the sides of the ostium. The distribution of the transWSS was different from the pattern of traditional haemodynamic metrics and more dependent on the velocity waveform imposed at the branch outlet. In rabbit aortas, transWSS patterns were again different from patterns of traditional metrics. The near-branch pattern varied between intercostal ostia, as is the case for lesion distribution; for some branches there were striking resemblances to the age-dependent patterns of disease seen in rabbit and human aortas. The new metric may lead to improved understanding of atherogenesis.
  • Journal article
    Peiffer V, Sherwin SJ, Weinberg PD, 2013,

    Does low and oscillatory wall shear stress correlate spatially with early atherosclerosis? A systematic review

    , CARDIOVASCULAR RESEARCH, Vol: 99, Pages: 242-250, ISSN: 0008-6363
  • Journal article
    Peiffer V, Bharath AA, Sherwin SJ, Weinberg PDet al., 2013,

    A Novel Method for Quantifying Spatial Correlations Between Patterns of Atherosclerosis and Hemodynamic Factors

    , JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 135, ISSN: 0148-0731
  • Journal article
    Steinman DA, Hoi Y, Fahy P, Morris L, Walsh MT, Aristokleous N, Anayiotos AS, Papaharilaou Y, Arzani A, Shadden SC, Berg P, Janiga G, Bols J, Segers P, Bressloff NW, Cibis M, Gijsen FH, Cito S, Pallares J, Browne LD, Costelloe JA, Lynch AG, Degroote J, Vierendeels J, Fu W, Qiao A, Hodis S, Kallmes DF, Kalsi H, Long Q, Kheyfets VO, Finol EA, Kono K, Malek AM, Lauric A, Menon PG, Pekkan K, Moghadam ME, Marsden AL, Oshima M, Katagiri K, Peiffer V, Mohamied Y, Sherwin SJ, Schaller J, Goubergrits L, Usera G, Mendina M, Valen-Sendstad K, Habets DF, Xiang J, Meng H, Yu Y, Karniadakis GE, Shaffer N, Loth Fet al., 2013,

    Variability of Computational Fluid Dynamics Solutions for Pressure and Flow in a Giant Aneurysm: The ASME 2012 Summer Bioengineering Conference CFD Challenge

    , JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 135, ISSN: 0148-0731
  • Conference paper
    Alastruey J, Parker KH, Sherwin SJ, 2012,

    Arterial pulse wave haemodynamics

    , Pages: 401-442

    The shape of the arterial pulse wave is intimately related to the physical properties of the cardiovascular system. Understanding the mechanisms underlying this relation is clinically relevant, since pulse waveforms carry valuable information for the diagnosis and treatment of disease. We overview some numerical, theoretical and experimental efforts (using in vivo and in vitro data) made in this field of research, focusing on the physical aspects of arterial pulse wave propagation in the systemic circulation. The mathematical and numerical tools that we describe are based on the one-dimensional formulation in the time-domain. © BHR Group 2012 Pressure Surges 11.
  • Journal article
    Peiffer V, Rowland EM, Cremers SG, Weinberg PD, Sherwin SJet al., 2012,

    Effect of aortic taper on patterns of blood flow and wall shear stress in rabbits: Association with age

    , ATHEROSCLEROSIS, Vol: 223, Pages: 114-121, ISSN: 0021-9150
  • Journal article
    Alastruey J, Siggers JH, Peiffer V, Doorly DJ, Sherwin SJet al., 2012,

    Reducing the data: Analysis of the role of vascular geometry on blood flow patterns in curved vessels

    , PHYSICS OF FLUIDS, Vol: 24, ISSN: 1070-6631
  • Conference paper
    Peiffer V, Weinberg PD, Sherwin SJ, 2012,

    THE WALL SHEAR STRESS VECTOR: METHODS FOR CHARACTERISING TRULY DISTURBED FLOW

    , ASME Summer Bioengineering Conference (SBC), Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 21-22
  • Conference paper
    Peiffer V, Rowland EM, Cremers SG, Weinberg PD, Sherwin SJet al., 2012,

    AGE-RELATED DIFFERENCES IN HAEMODYNAMICS OF THE RABBIT AORTA AND COMPARISON WITH AVERAGE MAPS OF ATHEROSCLEROTIC LESION PREVALENCE

    , ASME Summer Bioengineering Conference (SBC), Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 495-496
  • Journal article
    De Luca A, Warboys CM, Amini N, Ferreira P, Gatehouse P, Firmin D, Mason J, Sherwin S, Evans PCet al., 2012,

    IMAGE-BASED COMPUTATIONAL HEMODYNAMICS AND MICROARRAY ANALYSIS OF THE PORCINE AORTIC ARCH REVEALS A CORRELATION BETWEEN SHEAR STRESS AND ENDOTHELIAL CELL APOPTOSIS

    , PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B, Pages: 923-924

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