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166. In Vivo Measurement of Localized Tibiofemoral Cartilage Strains in Response to Dynamic Activity.

Author

Sutter, E. Grant, Utturkar, Gangadhar M., Garrett, William E., Widmyer, Margaret R., Spritzer, Charles E., and DeFrate, Louis E.

Subjects
*KNEE physiology, *FEMUR physiology, *TIBIA physiology, *ARTICULAR cartilage, *BIOPHYSICS, *EXERCISE physiology, *MAGNETIC resonance imaging, *RESEARCH methodology, *MUSCLE strength testing, *PROBABILITY theory, *RESEARCH funding, *PHYSIOLOGICAL stress, *T-test (Statistics), *STATISTICAL significance, *BODY movement, *DICOM (Computer network protocol), *DESCRIPTIVE statistics, *PHYSIOLOGY
Abstract

Background: Altered local mechanical loading may disrupt normal cartilage homeostasis and play a role in the progression ofosteoarthritis. Currently, there are limited data quantifying local cartilage strains in response to dynamic activity in normal orinjured knees.Purpose/Hypothesis: To directly measure local tibiofemoral cartilage strains in response to a dynamic hopping activity in normalhealthy knees. We hypothesized that local regions of cartilage will exhibit significant compressive strains in response to hopping,while overall compartmental averages may not.Study Design: Controlled laboratory study.Methods: Both knees of 8 healthy subjects underwent magnetic resonance imaging before and immediately after a dynamic hoppingactivity. Images were segmented and then used to create 3-dimensional surface models of bone and cartilage. These preandpostactivity models were then registered using an iterative closest point technique to enable site-specific measurements ofcartilage strain (defined as the normalized change in cartilage thickness before and after activity) on the femur and tibia.Results: Significant strains were observed in both the medial and lateral tibial cartilage, with each compartment averaginga decrease of 5%. However, these strains varied with location within each compartment, reaching a maximum compressive strainof 8% on the medial plateau and 7% on the lateral plateau. No significant averaged compartmental strains were observed in themedial or lateral femoral cartilage. However, local regions of the medial and lateral femoral cartilage experienced significant compressivestrains, reaching maximums of 6% and 3%, respectively.Conclusion: Local regions of both the femur and tibia experienced significant cartilage strains as a result of dynamic activity. Anunderstanding of changes in cartilage strain distributions may help to elucidate the biomechanical factors contributing to cartilagedegeneration after joint injury.Clinical Relevance: Site-specific measurements of in vivo cartilage strains are important because altered loading is believed tobe a factor contributing to the development and progression of osteoarthritis. Specifically, this methodology and data could beused to evaluate the effects of soft tissue injuries (such as ligament or meniscus tears) on cartilage strains in response to dynamicactivities of daily living. [ABSTRACT FROM AUTHOR]

Published
2015
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173. Rapport d'activité 1989. Mission CTFT

Author

Bouillet, Jean-Pierre, Bouvet, Jean-Marc, Lefevre, M., and Sutter, E.

Subjects
Sylviculture, Plante ligneuse, Bouturage, Inventaire forestier, Amélioration des plantes, Fertilisation, Arboretum, K10 - Production forestière, Régime sylvicole, A50 - Recherche agronomique, Choix des espèces, Croissance, Arbre forestier
Published
1990

197. Kinetics of Water Oxidation at TiO2Nanotube Arrays at Different pH Domains Investigated by Electrochemical and Light-Modulated Impedance Spectroscopy

Author

Cachet, H. and Sutter, E. M. M.

Abstract

The electronic properties of a TiO2-nanotube (NT) array used as a photoelectrode for water oxidation at neutral and basic pH were characterized by combining complementary measurement techniques: transient photocurrents, stationary photocurrent–voltage curves, photo-electrochemical impedance spectroscopy (PEIS), and intensity-modulated photocurrent spectroscopy (IMPS). Transient measurements point out the slow chemical modification of the TiO2surface when going from dark to light, essentially around neutral pH. After this transient period, a new stationary state of the TiO2surface is established, allowing small amplitude perturbation techniques (PEIS and IMPS) to be applied to obtain information on transfer and recombination kinetics and on surface states contribution. The relevant information was obtained via theoretical models for the PEIS and IMPS responses, involving physical parameters with values extracted by nonlinear least-squares fitting. The main conclusions taken from our experiments include the following: (i) Under ultraviolet light illumination, the surface chemistry of TiO2was found relatively stable at basic pH but strongly modified (hydroxylation) at neutral pH. (ii) Hole transfer to solution species takes place preferentially via the valence band. (iii) Recombination is mainly a surface process. (iv) Rate constants for charge transfer and recombination were determined as a function of the applied potential in agreement with the stationary photocurrent–voltage curve.

Published
2015
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