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Michael D Stokes, Brendan C Greene, Luke W Pietrykowski, Taylor M Gambon, Caroline E Bales, John D DesJardins
Current total knee replacement designs work to address clinically desired knee stability and range of motion through a balance of retained anatomy and added implant geometry. However, simplified implant geometries such as bearing surfaces, posts, and cams are often used to replace complex ligamentous constraints that are sacrificed during most total knee replacement procedures. This article evaluates a novel total knee replacement design that incorporates synthetic ligaments to enhance the stability of the total knee replacement system...
January 1, 2018: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
Nicholas R Hess, Stephen A Esper, Marie Tuft, Matthew Morrell, Jonathan D'Cunha
INTRODUCTION: Patient foramen ovale (PFO) is a common and often incidental intraoperative finding during lung transplantation (LTx). We sought to characterize the potential outcomes related to the decision-making of whether the PFO was repaired or left unrepaired. METHODS: We retrospectively evaluated bilateral LTx recipients between 2005 and 2015 from our prospective database. Incidence of postoperative stoke, 90-day mortality, and overall survival was compared between the PFO-positive and PFO-negative groups, and secondly compared between repaired PFO (rPFO) and non-repaired PFO (nrPFO) groups...
January 19, 2018: Clinical Transplantation
Christopher R Brown, Michael R Brown
Intrathoracic common carotid artery bifurcations are an anatomic anomaly with such rarity that only six cases have been reported to date. The true incidence of and preferred treatment options for a diseased intrathoracic common carotid artery bifurcation or internal carotid artery (ICA) have not been clearly described. This case report describes a 72-year-old man who experienced a postoperative right hemispheric stoke after an aortic valve replacement, radiofrequency maze procedure, and left atrial appendage clip...
September 2017: Journal of Vascular Surgery Cases and Innovative Techniques
Lynne Turner-Stokes, Christian U Krägeloh, Richard J Siegert
PURPOSE: This first psychometric evaluation of the Patient Categorisation Tool examined its properties as an instrument to measure complexity of needs in a mixed population of patients presenting for specialist neurorehabilitation. MATERIALS/METHODS: Analysis of a large multicentre cohort of patients (n = 5396) from the national clinical dataset representing 63 specialist rehabilitation services across England. Structural validity was examined using exploratory and confirmatory factor analysis...
January 18, 2018: Disability and Rehabilitation
X Xu, K Burgin, M A Ellis, I Halliday
We present a challenging validation of phase field multicomponent lattice Boltzmann equation (MCLBE) simulation against the Re=0 Stokes flow regime Taylor-Einstein theory of dilute suspension viscosity. By applying a number of recent advances in the understanding and the elimination of the interfacial microcurrent artefact, extending to a three-dimensional class of stability-enhancing multiple relaxation time collision models (which require no explicit collision matrix, note) and developing new interfacial interpolation schemes, we are able to obtain data that show that MCLBE may be applied in new flow regimes...
November 2017: Physical Review. E
Cheng Peng, Zhaoli Guo, Lian-Ping Wang
It is well known that standard lattice Boltzmann (LB) models allow the strain-rate components to be computed mesoscopically (i.e., through the local particle distributions) and as such possess a second-order accuracy in strain rate. This is one of the appealing features of the lattice Boltzmann method (LBM) which is of only second-order accuracy in hydrodynamic velocity itself. However, no known LB model can provide the same quality for vorticity and pressure gradients. In this paper, we design a multiple-relaxation time LB model on a three-dimensional 27-discrete-velocity (D3Q27) lattice...
November 2017: Physical Review. E
Chuandong Lin, Aiguo Xu, Guangcai Zhang, Kai Hong Luo, Yingjun Li
A discrete Boltzmann model (DBM) is proposed to probe the Rayleigh-Taylor instability (RTI) in two-component compressible flows. Each species has a flexible specific-heat ratio and is described by one discrete Boltzmann equation (DBE). Independent discrete velocities are adopted for the two DBEs. The collision and force terms in the DBE account for the molecular collision and external force, respectively. Two types of force terms are exploited. In addition to recovering the modified Navier-Stokes equations in the hydrodynamic limit, the DBM has the capability of capturing detailed nonequilibrium effects...
November 2017: Physical Review. E
James Chen
A high order morphing continuum theory (MCT) is introduced to model highly compressible turbulence. The theory is formulated under the rigorous framework of rational continuum mechanics. A set of linear constitutive equations and balance laws are deduced and presented from the Coleman-Noll procedure and Onsager's reciprocal relations. The governing equations are then arranged in conservation form and solved through the finite volume method with a second-order Lax-Friedrichs scheme for shock preservation. A numerical example of transonic flow over a three-dimensional bump is presented using MCT and the finite volume method...
October 2017: Physical Review. E
Giorgia Guccione, Daniela Pimponi, Paolo Gualtieri, Mauro Chinappi
We analyzed the effect of confinement on the effective diffusion of a run-and-tumble E. coli-like flagellated microswimmer. We used a simulation protocol where the run phases are obtained via a fully resolved swimming problem, i.e., Stokes equations for the fluid coupled with rigid-body dynamics for the microorganism, while tumbles and collisions with the walls are modeled as random reorientation of the microswimmer. For weak confinement, the swimmer is trapped in circular orbits close to the solid walls. In this case, optimal diffusivity is observed when the tumbling frequency is comparable with the angular velocity of the stable orbits...
October 2017: Physical Review. E
Nicolas Mordant, Benjamin Miquel
We report numerical investigations of wave turbulence in a vibrating plate. The possibility to implement advanced measurement techniques and long-time numerical simulations makes this system extremely valuable for wave turbulence studies. The purely 2D character of dynamics of the elastic plate makes it much simpler to handle compared to much more complex 3D physical systems that are typical of geo- and astrophysical issues (ocean surface or internal waves, magnetized plasmas or strongly rotating and/or stratified flows)...
October 2017: Physical Review. E
Marie Farge, Naoya Okamoto, Kai Schneider, Katsunori Yoshimatsu
We present numerical simulations of the three-dimensional Galerkin truncated incompressible Euler equations that we integrate in time while regularizing the solution by applying a wavelet-based denoising. For this, at each time step, the vorticity field is decomposed into wavelet coefficients, which are split into strong and weak coefficients, before reconstructing them in physical space to obtain the corresponding coherent and incoherent vorticities. Both components are multiscale and orthogonal to each other...
December 2017: Physical Review. E
J Meibohm, L Pistone, K Gustavsson, B Mehlig
We investigate the distribution of relative velocities between small heavy particles of different sizes in turbulence by analyzing a statistical model for bidisperse turbulent suspensions, containing particles with two different Stokes numbers. This number, St, is a measure of particle inertia which in turn depends on particle size. When the Stokes numbers are similar, the distribution exhibits power-law tails, just as in the case of equal St. The power-law exponent is a nonanalytic function of the mean Stokes number St[over ¯], so that the exponent cannot be calculated in perturbation theory around the advective limit...
December 2017: Physical Review. E
C A Davy, P M Adler
The macroscopic permeability of a natural shale is determined by using structural measurements on three different scales. Transmission electron microscopy yields two-dimensional (2D) images with pixels smaller than 1 nm; these images are used to reconstruct 3D nanostructures. Three-dimensional focused ion beam-scanning electron microscopy (5.95- to 8.48-nm voxel size) provides 3D mesoscale pores of limited relative volume (1.71-5.9%). Micro-computed tomography (700-nm voxel size) provides information on the mineralogy of the shale, including the pores on this scale which do not percolate; synthetic 3D media are derived on the macroscopic scale by a training image technique...
December 2017: Physical Review. E
Aaron J Mowitz, T A Witten
We formulate a numerical method for predicting the tensorial linear response of a rigid, asymmetrically charged body to an applied electric field. This prediction requires calculating the response of the fluid to the Stokes drag forces on the moving body and on the countercharges near its surface. To determine the fluid's motion, we represent both the body and the countercharges using many point sources of drag known as Stokeslets. Finding the correct flow field amounts to finding the set of drag forces on the Stokeslets that is consistent with the relative velocities experienced by each Stokeslet...
December 2017: Physical Review. E
Oleg Schilling, Nicholas J Mueschke
Data from a 1152×760×1280 direct numerical simulation [N. J. Mueschke and O. Schilling, Phys. Fluids 21, 014106 (2009)PHFLE61070-663110.1063/1.3064120] of a Rayleigh-Taylor mixing layer modeled after a small-Atwood-number water-channel experiment is used to investigate the validity of gradient diffusion and similarity closures a priori. The budgets of the mean flow, turbulent kinetic energy, turbulent kinetic energy dissipation rate, heavy-fluid mass fraction variance, and heavy-fluid mass fraction variance dissipation rate transport equations across the mixing layer were previously analyzed [O...
December 2017: Physical Review. E
Idris Adebayo, Zhihua Xie, Zhizhao Che, Omar K Matar
The interaction patterns between doubly excited pulse waves on thin liquid films flowing down an inclined plane are studied both experimentally and numerically. The effect of varying the film flow rate, interpulse interval, and substrate inclination angle on the pulse interaction patterns is examined. Our results show that different interaction patterns exist for these binary pulses, which include solitary wave behavior, partial or complete pulse coalescence, and pulse noncoalescence. A regime map of these patterns is plotted for each inclination angle examined, parametrized by the film Reynolds number and interpulse interval...
July 2017: Physical Review. E
Manash Pratim Borthakur, Gautam Biswas, Dipankar Bandyopadhyay
This paper presents a numerical investigation of the dynamics of pinch-off in liquid drops and jets during injection of a liquid through an orifice into another fluid. The current study is carried out by solving axisymmetric Navier-Stokes equations and the interface is captured using a coupled level-set and volume-of-fluid approach. The delicate interplay of inertia and viscous effects plays a crucial role in deciding the dynamics of the formation as well as breakup of liquid drops and jets. In the dripping regime, the growth and breakup rate of a drop are studied and quantified by corroborating with theoretical predictions...
July 2017: Physical Review. E
Narendra Singh, Ravi Sudam Jadhav, Amit Agrawal
A set of constitutive relations for the stress tensor and heat flux vector for the hydrodynamic description of rarefied gas flows is derived in this work. A phase density function consistent with Onsager's reciprocity principle and H theorem is utilized to capture nonequilibrium thermodynamics effects. The phase density function satisfies the linearized Boltzmann equation and the collision invariance property. Our formulation provides the correct value of the Prandtl number as it involves two different relaxation times for momentum and energy transport by diffusion...
July 2017: Physical Review. E
Huan Yang, Christopher J Hogan
Like and oppositely charged particles or dust grains in linear shear flows are often driven to collide with one another by fluid and/or electrostatic forces, which can strongly influence particle-size distribution evolution. In gaseous media, collisions in shear are further complicated because particle inertia can influence differential motion. Expressions for the collision rate coefficient have not been developed previously which simultaneously account for the influences of linear shear, particle inertia, and electrostatic interactions...
September 2017: Physical Review. E
Fabian B Wadsworth, Jérémie Vasseur, Edward W Llewellin, Katherine J Dobson, Mathieu Colombier, Felix W von Aulock, Julie L Fife, Sebastian Wiesmaier, Kai-Uwe Hess, Bettina Scheu, Yan Lavallée, Donald B Dingwell
Sintering-or coalescence-of viscous droplets is an essential process in many natural and industrial scenarios. Current physical models of the dynamics of sintering are limited by the lack of an explicit account of the evolution of microstructural geometry. Here, we use high-speed time-resolved x-ray tomography to image the evolving geometry of a sintering system of viscous droplets, and use lattice Boltzmann simulations of creeping fluid flow through the reconstructed pore space to determine its permeability...
September 2017: Physical Review. E
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