TY - JOUR AB - To enhance the understanding of airflow characteristics in the human respiratory system, the expiratory airflow in a human respiratory tract model was simulated using large eddy simulation and dynamic mesh under different expiration conditions aligned with clinically measured data. The airflow unsteadiness was quantitatively assessed using power spectral density (PSD) and spectral entropy (SE). The following findings were obtained: (1) The airflow is highly turbulent in the mouth-pharynx region during expiration, with its dynamic characteristics being influenced by both the transient expiration flow pattern at mouth piece and the glottis motion. (2) PSD analysis reveals that the expiratory airflow is very unsteady, exhibiting a broad-band attenuation spectrum in the pharynx-trachea region. When only transient expiration or glottis motion is considered, the PSD spectrum changes slightly. When both are ignored, however, the change is significant, with the peak frequency reduced to 10% of the real expiration condition. (3) SE analysis indicates that the airflow transitions into turbulence in the trachea, and there may be multiple transitions in the region of soft palate. The transient expiration or glottis motion alone increases turbulence intensity by 2%-15%, while ignoring both reduces turbulence intensity by 10%-20%. This study implies that turbulence characteristics can be significantly different under different expiratory conditions, and therefore it is necessary to determine the expiratory flow characteristics using clinically measured expiratory data. AU - Jing, H.* AU - Ge, H.* AU - Tang, H.* AU - Farnoud, A. AU - Saidul Islam, M.* AU - Wang, L.* AU - Wang, C.* AU - Cui, X.* C1 - 69026 C2 - 53811 CY - 125 London Wall, London, England TI - Assessing airflow unsteadiness in the human respiratory tract under different expiration conditions. JO - J. Biomech. VL - 162 PB - Elsevier Sci Ltd PY - 2023 SN - 0021-9290 ER - TY - JOUR AB - Aim was to develop an in vivo technique which allows determination of femoro-tibial and of femoro-patellar 3D-kinematics in TKA simultaneously. The knees of 20 healthy volunteers and of eight patients with TKA (PCR, rotating platform) were investigated. Kinematics analysis was performed in an open MR-system at different flexion angles with external loads being applied. The TKA components were identified using a 3D-fitting technique, which allows an automated 3D-3D-registration of the TKA. Femoro-patellar and femoro-tibial 3D-kinematics were analyzed by image postprocessing. The validity of the postprocessing technique demonstrated a coefficient of determination of 0.98 for translation and of 0.97 for rotation. The reproducibility yielded a coefficient of variation (CV%) for patella kinematics between 0.17% (patello-femoral angle) and 6.8% (patella tilt). The femoro-tibial displacement also showed a high reproducibility with CV% of 4.0% for translation and of 7.1% for rotation. While in the healthy knees the typical screw-home mechanism was observed, a paradoxical anterior translation of the femur relative to the tibia combined with an external rotation occurred after TKA. Fifty percent of the TKA's experienced a condylar lift-off of >1mm predominately on the medial side. Regarding patellar kinematics significant changes were found in both planes in TKA with an increased patella height in the sagittal plane and patella tilt and shift in the transversal plane. The results demonstrate that the presented 3D MR-open based method is highly reproducible and valid for image acquisition and postprocessing and provides-for the first time-in vivo data of 3D-kinematics of the tibio-femoral and simultaneously of the patello-femoral joint during knee flexion. AU - von Eisenhart-Rothe, R.* AU - Vogl, T.* AU - Englmeier, K.-H. AU - Graichen, H.* C1 - 2449 C2 - 24753 SP - 3079-3088 TI - A new in vivo technique for determination of femoro-tibial and femoro-patellar 3D kinematics in total knee arthroplasty. JO - J. Biomech. VL - 40 IS - 14 PB - Elsevier PY - 2007 SN - 0021-9290 ER - TY - JOUR AU - Graichen, H.* AU - Hinterwimmer, S.* AU - von Eisenhart-Rothe, R.* AU - Vogl, T. AU - Englmeier, K.-H. AU - Eckstein, F.* C1 - 3993 C2 - 22885 SP - 755-760 TI - Effect of abducting and adducting muscle activity on glenohumeral translation, scapular kinematics and subacromial space width in vivo. JO - J. Biomech. VL - 38 PY - 2005 SN - 0021-9290 ER - TY - JOUR AU - Hinterwimmer, S.* AU - Gotthardt, M.* AU - Eisenhart-Rothe, R. von* AU - Sauerland, S.* AU - Siebert, M. AU - Vogl, T.* AU - Eckstein, F.* AU - Graichen, H.* C1 - 4321 C2 - 23165 SP - 2095-2101 TI - In vivo contact areas of the knee in patients with patellar subluxation. JO - J. Biomech. VL - 38 PY - 2005 SN - 0021-9290 ER - TY - JOUR AU - von Eisenhart-Rothe, R.* AU - Siebert, M. AU - Bringmann, C. AU - Vogl, T.* AU - Englmeier, K.-H. AU - Graichen, H.* C1 - 4113 C2 - 21921 SP - 927-934 TI - A new in vivo technique for determination of 3D kinematics and contact areas of the patello-femoral and tibio-femoral joint. JO - J. Biomech. VL - 37 PY - 2004 SN - 0021-9290 ER - TY - JOUR AU - Eckstein, F.* AU - Lemberger, B.* AU - Stammberger, T. AU - Englmeier, K.-H. AU - Reiser, M.* C1 - 21526 C2 - 19647 SP - 819-825 TI - Patellar cartilage deformation in vivo after static versus dynamic loading. JO - J. Biomech. VL - 33 PY - 2000 SN - 0021-9290 ER - TY - JOUR AU - Graichen, H.* AU - Stammberger, T. AU - Bonel, H.* AU - Englmeier, K.-H. AU - Reiser, M.* AU - Eckstein, F.* C1 - 21675 C2 - 19849 SP - 609-613 TI - Glenohumeral translation during active and passive elevation of the shoulder - a 3D open-MRI study. JO - J. Biomech. VL - 33 PY - 2000 SN - 0021-9290 ER - TY - JOUR AU - Herberhold, C.* AU - Faber, S.* AU - Stammberger, T. AU - Steinlechner, M.* AU - Putz, R.* AU - Englmeier, K.-H. AU - Reiser, M.* AU - Eckstein, F.* C1 - 21514 C2 - 19635 SP - 1287-1295 TI - In situ measurement of articular cartilage deformation in intact femoropatellar joints under static loading. JO - J. Biomech. VL - 32 PY - 1999 SN - 0021-9290 ER -