Mechanical Engineering Commons^™

Muscle Synergies Improve Estimation Of Knee Contact Forces During Walking, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

This study investigates whether use of subject-specific muscle synergies can improve optimization predictions of muscle excitation patterns and knee contact forces during walking. Muscle synergies describe how a small number of neural commands generated by the nervous system can be linearly combined to produce the broad range of muscle electromyographic (EMG) signals measured experimentally. By quantifying the interdependence of individual EMG signals, muscle synergies provide dimensionality reduction for the neural control redundancy problem. Our hypothesis was that use of subjectspecific muscle synergies to limit muscle excitation patterns would improve prediction of muscle EMG patterns at the hip, knee, and ankle …

Muscle Synergy Constraints Improve Prediction Of Knee Contact Force During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

Knowledge of patient-specific muscle and joint contact forces during activities of daily living could improve the treatment of movement-related disorders (e.g., osteoarthritis, stroke, cerebral palsy, Parkinson’s disease). Unfortunately, it is currently impossible to measure these quantities directly under common clinical conditions, and calculation of these quantities using computer models is limited by the redundant nature of human neural control (i.e., more muscles than theoretically necessary to actuate the available degrees of freedom in the skeleton). Walking is a particularly important task to understand, since loss of mobility is associated with increased morbidity and decreased quality of life. Though numerous musculoskeletal …

Evaluation Of Different Optimal Control Problem Formulations For Solving The Muscle Redundancy Problem, Friedl De Groote, Allison Kinney, Anil Rao, Benjamin Fregly

Allison Kinney

This study evaluates several possible optimal control problem formulations for solving the muscle redundancy problem with the goal of identifying the most efficient and robust formulation. One novel formulation involves the introduction of additional controls that equal the time derivative of the states, resulting in very simple dynamic equations. The nonlinear equations describing muscle dynamics are then imposed as algebraic constraints in their implicit form, simplifying their evaluation. By comparing different problem formulations for computing muscle controls that can reproduce inverse dynamic joint torques during gait, we demonstrate the efficiency and robustness of the proposed novel formulation.

Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd

Allison Kinney

This study investigates whether use of muscle excitation controls constructed from subjectspecific muscle synergy information can improve optimization prediction of knee contact forces and muscle excitations during walking. Muscle synergies quantify how a large number of experimental muscle electromyographic (EMG) signals can be reconstructed by linearly mixing a much smaller number of neural commands generated by the nervous system. Our hypothesis was that controlling all muscle excitations with a small set of experimentally calculated neural commands would improve prediction of knee contact forces and leg muscle excitations compared to using independently controlled muscle excitations.

Comparison Of Material Properties And Microstructure Of Specimens Built Using The 3d Systems Vanguard Hs And Vanguard Hiq+Hs Sls Systems, T.J. Silverman, Allison Kinney, W. Yong, J.H. Koo

Allison Kinney

The HiQ upgrade to the 3D Systems Vanguard selective laser sintering (SLS) machine incorporates a revised thermal calibration system and new control software. The paper compares the tensile modulus, tensile strength, elongation at break, flexural modulus, Izod impact resistance and microstructure of two batteries of standard specimens built from recycled Duraform PA (Nylon 12). The first set is built on a Vanguard HS system and the second on the same system with the HiQ upgrade installed. The upgrade reduces user intervention, decreases total build time and improves surface finish. However, using the default processing parameters, tensile, flexure and impact properties …

Three-Dimensional Confocal Microscopy Indentation Method For Hydrogel Elasticity Measurement, Donghee Lee, Md Mahmudur Rahman, You Zhou, Sangjin Ryu

Md Mahmudur Rahman

No abstract provided.

Force And Slip Detection With Direct-Write Compliant Tactile Sensors Using Multi-Walled Carbon Nanotube/Polymer Composites, Morteza Vatani, Erik Engeberg, Jae-Won Choi

Dr. Jae-Won Choi

A mechanically compliant tactile sensor has been developed through direct-write (DW) deposition of a flexible conductive nanocomposite embedded between flexible polyurethane materials. Dispersion of multi-walled carbon nanotubes (MWCNTs) in a flexible and photocurable monomer introduced electrical and piezoresistive properties to the polymer which was used for the flexible conductive nanocomposite. Dispensing experiments were performed using the developed DW system to precisely create and embed the sensor elements between polyurethane substrates. From the experimental results, several flexible sensors including highly stretchable sensor elements (wires) were fabricated. Experiments were also performed to show that the sensor could detect applied forces at distinct …

Continuous Size-Based Separation Of Microparticles In A Microchannel With Symmetric Sharp Corner Structures, Liang-Liang Fan, Xu-Kun He, Yu Hun, Li Du, Liang Zhao, Jiang Zhe

Dr. Jiang Zhe

A new microchannel with a series of symmetric sharp corner structures is reported for passive size-dependent particle separation. Micro particles of different sizes can be completely separated based on the combination of the inertial lift force and the centrifugal force induced by the sharp corner structures in the microchannel. At appropriate flow rate and Reynolds number, the centrifugal force effect on large particles, induced by the sharp corner structures, is stronger than that on small particles; hence after passing a series of symmetric sharp corner structures, large particles are focused to the center of the microchannel, while small particles are …

Deformation-Induced Martensite And Nanotwins By Cryogenic Laser Shock Peening Of Aisi 304 Stainless Steel And The Effects On Mechanical Properties, Chang Ye, Sergey Suslov, Dong Lin, Gary Cheng

Dr. Chang Ye

Laser shock peening (LSP) of stainless steel 304 was carried out at room and cryogenic temperature (liquid nitrogen temperature). It was found that the deformation-induced martensite was generated by LSP only when the laser-generated plasma pressure is sufficiently high. Compared to room temperature laser shock peening (RT-LSP), cryogenic laser shock peening (CLSP) generates a higher volume fraction of martensite at the same laser intensity. This is due to the increase in the density of potential embryos (deformation bands) for martensite nucleation by deformation at cryogenic temperature. In addition, CLSP generates a high density of deformation twins and stacking faults. After …

Novel Materials For The Direct Removal Of Water And Ions From The Body For Patients With Dialysis Needs, Lisa Furby, Ravinder Gupta, Ajay Mahajan, Jarlen Don, Tsuchin Chu, Bakul Dave, Bradley Schwartz

Dr. Ajay Mahajan

This paper describes a novel material for the direct removal of water and ions from the body of patients with End Stage Renal Disease (ESRD). The work is part of a larger project that is envisioned to be a new type of dialysis process that could replace or enhance existing dialysis methods. The main idea is to implant a unit either and/or outside the body of the patients with renal failure so that they do not have to go through the painstaking and exhausting hemodialysis or peritoneal dialysis processes existing today. The proposed work in its final embodiment will eliminate …

Construction And Validation Of A Complaint Model Of The Cerebrospinal Fluid System With Fluid Filled Syrinx, Bryn Martin, Wojciech Kalata, John Oshinski, Francis Loth, Thomas Royston

Dr. Bryn Martin

No abstract provided.

Pathological Biomechanics Of Cerebrospinal Fluid Pressure In Syringomyelia: Fluid Structure Interaction Of An In Vitro Coaxial Elastic Tube System, Bryn Martin, Richard Labuda, Thomas Royston, John Oshinski, Bermans Iskandar, Francis Loth

Dr. Bryn Martin

Full explanation for the formation and pathogenesis of syringomyelia (SM), a neurological pathology characterized by the formation of a cystic cavity (syrinx) in the center of the spinal cord (SC), has not yet been given. The SM pathology forms a coaxial elastic tube system with the inner tube formed by the spinal cord having a syrinx and the outer tube formed by the spinal column (dura and vertebrae).

The Influence Of Coughing On Cerebrospinal Fluid Pressure In An In Vitro Syringomyelia Model With Spinal Canal Stenosis, Bryn Martin, Francis Loth

Dr. Bryn Martin

Five in vitro models were constructed which were representative of various pathologies of the spinal canal (SC) associated with syringomyelia (SM). The models were subjected to a cough type flow impulse while monitoring the pressure environment in the syrinx and subarachnoid space (SAS) regions of the model. The results indicated that conditions can arise during a cough which would provide pressure forces to encourage cerebrospinal fluid (CSF) movement into the syrinx cavity.

A Multimode Sonic And Ultrasonic Diagnostic Imaging System With Application To Peripheral Vascular Characterization, Todd Spohnholtz, Thomas Royston, Yigit Yazicioglu, Bryn Martin, Francis Loth

Dr. Bryn Martin

No abstract provided.

Characterization Of The Discrepancies Between Four-Dimensional Phase-Contrast Magnetic Resonance Imaging And In-Silico Simulations Of Cerebrospinal Fluid Dynamics, Soroush Heidari, Alexander Bunck, Francis Loth, R. Tubbs, Theresia Yiallourou, Jan Kroeger, Walter Heindel, Bryn Martin

Dr. Bryn Martin

The purpose of the present study was to compare subject-specific magnetic resonance imaging (MRI)-based computational fluid dynamics (CFD) simulations with time-resolved three-directional (3D) velocity-encoded phase-contrast MRI (4D PCMRI) measurements of the cerebrospinal fluid (CSF) velocity field in the cervical spinal subarachnoid space (SSS). Three-dimensional models of the cervical SSS were constructed based on MRI image segmentation and anatomical measurements for a healthy subject and patient with Chiari I malformation. CFD was used to simulate the CSF motion and compared to the 4D PCMRI measurements. Four-dimensional PCMRI measurements had much greater CSF velocities compared to CFD simulations (1.4 to 5.6× greater). …

Quantitative Comparison Of 4d Mri Flow Measurements To 3d Computational Fluid Dynamics Simulation Of Cerebrospinal Fluid Movement In The Spinal Subarachnoid Space, Theresia Yiallourou, Leonie Asboth, J. Kroeger, David Maintz, A. Bunck, Nikolaos Stergiopulos, Bryn Martin

Dr. Bryn Martin

Computational fluid dynamic (CFD) simulations have provided detailed information about the complex flow and pressure field within the cerebrospinal fluid (CSF) system. The solutions of these simulations are sensitive to boundary conditions and thus need validation with in vivo measurements. However, validation of CFD flow results and MRI CSF flow measurements have been limited to through-plane pcMR measurements.

Impact Of Aortic Grafts On Hemodynamics: A 1d Computational Assessment, O. Vardoulis, E. Coppens, Bryn Martin, P. Reymond, N. Stergiopulos

Dr. Bryn Martin

Vascular prostheses currently used in aortic replacement surgery do not have the same mechanical properties as human arteries. In vivo studies have revealed that aortic grafts augment heart load and alter blood pressure and flow waveforms. A one-dimensional model of the arterial tree was developed in order to analyze the different mechanisms by which grafts placed in the ascending aorta (proximal) and descending aorta (distal) affect hemodynamics. Graft compliance and properties were based on in vitro tests

A Coupled Simulation Of Spinal Cord Blood Flow And Cerebrospinal Fluid Motion In The Spinal Subarachnoid Space Based On In Vivo Measurements, Bryn Martin, Philippe Reymond, Olivier Baledent, Jan Novy, Nikos Stergiopulos

Dr. Bryn Martin

A preliminary coupled 1-D model of the systemic arterial tree and cerebrospinal fluid (CSF) system was constructed. The systemic tree model includes arteries greater than 2 mm in diameter and a simplified spinal cord vasculature. Coupling of the arterial tree and CSF system is accomplished by a transfer function based on in vivo cerebral blood flow (CBF) and CSF pulsation measurements in 17 young healthy adults.

Spinal Subarachnoid Space Pressure Measurements In An In Vitro Spinal Stenosis Model: Implications On Syringomyelia Theories, Bryn Martin, Richard Labuda, Thomas Royston, John Oshinski, Bermans Iskandar, Francis Loth

Dr. Bryn Martin

Full explanation for the pathogenesis of syringomyelia (SM), a neuropathology characterized by the formation of a cystic cavity (syrinx) in the spinal cord (SC), has not yet been provided. It has been hypothesized that abnormal cerebrospinal fluid (CSF) pressure, caused by subarachnoid space (SAS) flow blockage (stenosis), is an underlying cause of syrinx formation and subsequent pain in the patient.

Coupled Vibration Of A Fluid‐Filled And Submerged Vascular Tube With Internal Transitional/ Turbulent Flow Due To A Constriction, Yigit Yazicioglu, Thomas Royston, Todd Spohnholtz, Bryn Martin, Francis Loth

Dr. Bryn Martin

No abstract provided.

Mr Measurement Of Cerebrospinal Fluid Velocity Wave Speed In The Spinal Canal, Wojciech Kalata, Bryn Martin, John Oshinski, Michael Jerosch-Herold

Dr. Bryn Martin

Noninvasive measurement of the speed with which the cere-brospinal fluid (CSF) velocity wave travels through the spinal canal is of interest as a potential indicator of CSF system pressure and compliance, both of which may play a role in the development of craniospinal diseases. However, measurement of CSF velocity wave speed (VWS) has eluded researchers primarily due to either a lack of access to CSF velocity measurements or poor temporal resolution.

Syringomyelia Hydrodynamics: An In Vitro Study Based On In Vivo Measurements, Bryn Martin, Wojciech Kalata, Francis Loth, Thomas Royston, John Oshinski

Dr. Bryn Martin

A simplified in vitro model of the spinal canal, based on in vivo magnetic resonance imaging, was used to examine the hydrodynamics of the human spinal cord and subarachnoid space with syringomyelia. In vivo magnetic resonance imaging (MRI) measurements of subarachnoid (SAS) geometry and cerebrospinal fluid velocity were acquired in a patient with syringomyelia and used to aid in the in vitro model design and experiment. The in vitro model contained a fluid-filled coaxial elastic tube to represent a syrinx.

Acoustic Radiation From A Fluid-Filled, Subsurface Vascular Tube With Internal Turbulent Flow Due To A Constriction, Yigit Yazicioglu, Thomas Royston, Todd Spohnholtz, Bryn Martin, Francis Loth, Hisham Bassiouny

Dr. Bryn Martin

The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interaction with the tube wall and surrounding

Towards Non-Invasive Assessment Of The Elastic Properties Of The Spinal Aqueduct, Bryn Martin, Thomas Royston, John Oshinski, Francis Loth

Dr. Bryn Martin

Analytical models are developed for cerebrospinal fluid (CSF) pressure wave propagation speed based on viscoelastic properties and geometry of the subarachnoid space (SAS). The models were compared to experimental tests on various compliant coaxial tube phantom models of the spinal SAS having different thicknesses and mechanical properties, with the ultimate goal of developing a noninvasive in vivo technique for determining the elastic properties of the spinal aqueduct.

Assessment Of Aortic Graft Impact On Hemodynamics, Orestis Vardoulis, Bryn Martin, Philippe Reymond, Nikos Stergiopulos

Dr. Bryn Martin

In vivo studies have revealed that aortic grafts augment heart load and alter blood pressure and flow waveforms [1]. A one-dimensional model of the arterial tree was developed in order to analyze the different mechanisms by which proximal and distal aortic grafts affect hemodynamics. Graft compliance and properties were based on in vitro tests. Predicted pressures at the aortic root were compared for the control, proximal and distal graft case.

Magnetic Resonance 4d Flow Analysis Of Cerebrospinal Fluid Dynamics In Chiari I Malformation With And Without Syringomyelia, Alexander Bunck, Jan Kroger, Alena Juettner, Angela Brentrup, Barbara Fiedler, Gerard Crelier, Bryn Martin, Walter Heindel, David Maintz, Wolfram Scwindt, Thomas Niederstadt

Dr. Bryn Martin

Objective

To analyse cerebrospinal fluid (CSF) hydrodynamics in patients with Chiari type I malformation (CM) with and without syringomyelia using 4D magnetic resonance (MR) phase contrast (PC) flow imaging.

Hydrodynamics Of Cerebrospinal Fluid In Spinal Canal With Chiari Malformation And Syringomyelia, Wojciech Kalata, Bryn Martin, Josh Oshinski, Francis Loth

Dr. Bryn Martin

No abstract provided.

The Effect Of Continuous Positive Airway Pressure On Total Cerebral Blood Flow In Healthy Awake Volunteers, Theresia Yiallourou, Celine Odier, Raphael Heinzer, Lorenz Hirt, Bryn Martin, Nikolaos Stergiopulos

Dr. Bryn Martin

Continuous positive airway pressure (CPAP) is the gold standard treatment for obstructive sleep apnea. However, the physiologic impact of CPAP on cerebral blood flow (CBF) is not well established. Ultrasound can be used to estimate CBF, but there is no widespread accepted protocol. We studied the physiologic influence of CPAP on CBF using a method integrating arterial diameter and flow velocity (FV) measurements obtained for each vessel supplying blood to the brain.

Ventricle Equilibrium Position In Healthy And Normal Pressure Hydrocephalus Brains Using An Analytical Model, K. Shahim, J. Drezet, Bryn Martin, S. Momjian

Dr. Bryn Martin

The driving force that causes enlargement of the ventricles remains unclear in case of normal pressure hydrocephalus (NPH). Both healthy and NPH brain conditions are characterized by a low transparenchymal pressure drop, typically 1 mm Hg. The present paper proposes an analytical model for normal and NPH brains using Darcy’s and Biot’s equations and simplifying the brain geometry to a hollow sphere with an internal and external radius. Self-consistent solutions for the large deformation problem that is associated with large ventricle dilation are presented and the notion of equilibrium or stable ventricle position is highlighted for both healthy and NPH …

A Coupled Hydrodynamic Model Of The Cardiovascular And Cerebrospinal Fluid System, Bryn Martin, Philippe Reymond, Jan Reymond, Jan Novy, Olivier Baledent, Nikolaos Stergiopulos

Dr. Bryn Martin

Coupling of the cardiovascular and cerebrospinal fluid (CSF) system is considered to be important to understand the pathophysiology of cerebrovascular and craniospinal disease and intrathecal drug delivery. A coupled cardiovascular and CSF system model was designed to examine the relation of spinal cord (SC) blood flow (SCBF) and CSF pulsations along the spinal subarachnoid space (SSS). A one-dimensional (1-D) cardiovascular tree model was constructed including a simplified SC arterial network. Connection between the cardiovascular and CSF system was accomplished by a transfer function based on in vivo measurements of CSF and cerebral blood flow. A 1-D tube model of the …