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作者： Wheeler, D.L. Haynie, J.L. Berrey, H. Scarborough, M. Enneking, W. Department of Mechanical Engineering Biomedical Engineering Program Colorado State University Fort Collins CO 80523 United States

Allograft bone is the primary source of graft material for large skeletal defects. No study has determined the physical characteristics of such grafts after various periods of time in vivo for incorporation and remodeling. The purpose of this pilot study was to obtain allograft tissue and biomechanically evaluate the tissue to assess allograft bone material properties. The mechanical properties of the retrieved allograft tissue were compared to allograft bone prior to transplantation. Histological analysis of the retrieved allograft tissue is currently underway to correlate degree of incorporation, allograft porosity, and microfracture density with allograft material properties. After allograft retrieval, radiographs were used to plan sectioning for histological and biomechanical analyses. Rectangular sections of uniform dimensions (50 × 3 × 3 mm) were mapped and machined from the bulk specimens. The samples were loaded in bending in the medial to lateral direction using a 4-point bending fixture to obtain flexural elastic modulus and breaking strength. Preconditioning was applied to each specimen by cycling through 5 submaximal loading cycles (maximum deflection = 1% specimen length). After preconditioning, the specimens were loaded to failure at a rate of 1 mm/min. Retrieved specimens consisted of 1 tibia, 2 femurs, and 2 humeri ranging from 2 to 13 years in vivo. Two control tibia specimens were also tested. Assuming that material properties of cortical bone are consistent regardless of skeletal site, the preliminary data indicates that allograft modulus and strength decline with time in vivo. Testing and analysis of more specimens continue in order to corroborate these initial results.

关键词： biomedical equipment

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How simplifying assumptions affect the computation of three-dimensional knee loads in cycling

How simplifying assumptions affect the computation of three-...

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2001 ASME International mechanical engineering Congress and Exposition

作者： Gregersen, Colin S. Hull, M.L. Biomedical Engineering Program University of California Davis CA United States Department of Mechanical Engineering University of California Davis CA 95616 United States

The effect of simplifying assumptions on the computation of three dimensional knee loads in cycling was discussed. An inverse dynamics approach was used to calculate the knee loads. It was found that the analysis of c... 详细信息

关键词： Joints (anatomy)

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Multiscale finite element modeling of the trabeculated embryonic heart: Numerical evaluation of the constitutive relations for the trabeculated myocardium

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Computer Methods in Biomechanics and biomedical engineering 2001年第3期4卷 231-248页

作者： Xie, Wenjie Perucchio, Renato Department of Mechanical Engineering and Program of Biomedical Engineering University of Rochester Rochester NY 14627 United States

A numerical homogenization procedure for deriving the constitutive relations of the trabeculated embryonic myocardium is presented. This procedure is based on voxel modeling, nonlinear Finite Element analysis, and nonlinear data regression. Voxel reconstructions derived from digitized serial sections are used to construct local Finite Element meshes (called Representative Volume Elements) of the trabeculated myocardial wall. The orientation of the myofibrils is approximated by the geometrical skeleton of the voxel model. A 3-D nonlinear Finite Element research code, designed for modeling incompressible hyperelastic materials and capable of representing muscle activation and volumetric growth, is used to compute the mechanical response of the RVE. Bi-axial stretching experiments designed to generate tri-axial stress states are performed to compute the averaged stress-strain relations under passive and active conditions. New Strain Energy Density functions - both passive and active - are proposed for the RVE. A multi-dimensional Levenberg-Marquardt nonlinear regression is performed on the stress-strain data to yield the unknown parameters in the SED functions. The reliability and predictability of the computed functions is verified through additional tri-axial testing. © 2001 OPA (Overseas Publishers Association) N.V.

关键词： Finite element method

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Teaching in the Factory: Connecting Industry to engineering Education

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Industry and Higher Education 2001年第5期15卷 353-359页

作者： Teng, S. Gary Schreiner, Steven Nelson, J. Byron Engineering Management Graduate Program The University of North Carolina at Charlotte 9201 University City Blvd Charlotte 28223 NC United States Biomedical Engineering Program Western New England College 1215 Wilbraham Road SpringŽeld 01119 MA United States Department of Industrial and Manufacturing Engineering Western New England College United States

The ‘Teaching in the Factory’ approach goes beyond a simple engineering ‘co-op’ experience, bringing together academic rigour and real-world experiences and generating a winning situation for all constituents. This approach provides teams of engineering students with the opportunity to work on projects in a real factory environment, gives students a solid technical education, and exposes them to significant engineering challenges in a factory/business setting. It also benefits companies by bringing fresh engineering minds to solve problems, obtaining faculty expertise in systematic problem solving and project management, and acquiring help to complete important projects. © 2001, © 2001 SAGE Publications.

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Heat generation in bone cutting-implications for thermal necrosis

Heat generation in bone cutting-implications for thermal nec...

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2001 ASME International mechanical engineering Congress and Exposition

作者： Millon, Debra Chenet Hitt, Darren L. LaPointe, Stephan J. Biomedical Engineering Program University of Vermont Burlington VT United States Department of Mechanical Engineering University of Vermont Burlington VT United States Podiatry Institute Tucker GA United States Department of Surgery University of Vermont Burlington VT United States

A simulated osteotomy performed on a cadaver first metatarsal bone to delineate the heat generation and resulting temperature field was discussed. The experiment was accomplished by making in situ measurements of the time-varying temperature field in the bone during the cutting procedure. The temperature measurements were performed using K-type thermocouples with a sheath diameter, d = 0.8128mm, and accuracy of ± 0.2°C. It was observed that during a simulated osteonomy the temperature elevations regularly exceeded the threshold level in the bone at which thermal necrosis had occurred significantly.

关键词： biomedical engineering

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High-speed photographic evaluation of retropulsion momentum induced by a laser calculi lithotriptor

High-speed photographic evaluation of retropulsion momentum ...

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2001 ASME International mechanical engineering Congress and Exposition

作者： Lee, Ho Kim, Jeehyun Choi, Bernard Teichman, Joel M.H. Welch, A.J. Department of Mechanical Engineering University of Texas at Austin Austin TX United States Department of Electrical Engineering University of Texas at Austin Austin TX United States Biomedical Engineering Program University of Texas at Austin Austin TX United States Division of Urology University of Texas Health Science Center San Antonio TX United States

The retropulsive momentum induced by a laser calculi lithotriptor was evaluated by high-speed photography. Calculus phantoms made from plaster of paris were placed in a clear glass tube that served as in vitro model of the ureter. Movement of the calculus was monitored by a high-speed camera which had provided pictures in every 300μsecond. It was found that the recoil momentum proportionally increased with increasing laser energy and larger fiber diameter resulted in higher momentum.

关键词： Laser tissue interaction

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Transient characteristics of thermal contact conductance between isotropic rough surfaces of metals

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Heat Transfer - Asian Research 2001年第4期30卷 341-356页

作者： Kimura, Teruo Takeuchi, Masanori Nagai, Niroh Yoshida, Tetsuya Graduate Program of Advanced Fibro-Science Kyoto Institute of Technology Japan Department of Mechanical Engineering Fukui University Japan

Transient measurements of thermal contact conductance are made on the interface between isotropic rough surfaces of metals in air. We present an analytical solution for temperature distribution of the one-dimensional symmetric system with the condition of time-dependent temperatures at two points in each body, and thereby interface temperature drops and heat fluxes can be obtained without the condition of heat-flux continuity at the interface. Contacting surfaces of rod samples (Naval brass, JIS-SK5 carbon tool steel, and JIS-SUS 304 stainless steel) of 25-mm diameter are uniformly polished using an emery 320 paper. Transient characteristics of both temperatures and heat fluxes at the interface are experimentally determined using the analytical solution. It is revealed through the transient experiment that the thermal contact conductances are not constant at the early stage, but rapidly increase from zero and that the discontinuity of interface heat-flux is observed by about 20 percent for all metal pairs. For the contact between dissimilar metals, the dependence of thermal contact conductance on the direction of heat flow is not distinguishable. © 2001 Scripta Technica, Heat Trans Asian Res, 30(4): 341-356, 2001.

关键词： Heat conduction

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Left ventricular geometry immediately following defibrillation-strength shocks

Left ventricular geometry immediately following defibrillati...

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Computers in Cardiology (CinC)

作者： V. Ramanathan B. Hoffmeister A. de Jongh Joint Graduate Program in Biomedical Engineering University of Tennessee Health Science Center USA Department of Physics Rhodes College Memphis USA

A previous 2D ultrasound study (R.A. Malkin et al., 2001) suggested that there is relaxation of the myocardium after defibrillation. However, that 2D study could not measure activity occurring within the first 33 ms following the shock. Thus, the objective of our study is to determine the left ventricular (LV) geometry during this period. Biphasic defibrillation shocks were delivered to seven dogs. 1D short-axis ultrasound images of the LV cavity were acquired, the boundary of the anterior and posterior endocardial walls was extracted and the distance between them computed from 32 ms before to 32 ms after the shock. The normalized mean pre- and post-shock slopes were 0.2 /spl plusmn/ 2.2 and 3.3 /spl plusmn/ 7.9 %/10 ms, respectively. The post-shock LV diameter slope is positive in the first 32 ms following both successful and unsuccessful defibrillation shocks (p<0.05). Therefore, our results confirm that the bulk of the myocardium is relaxing immediately after a defibrillation shock.

关键词： Geometry Electric shock Defibrillation Ultrasonic imaging Pulse measurements Myocardium Ultrasonic variables measurement biomedical measurements Dogs Sampling methods

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Tissue-engineered skin using aggregates of normal human skin fibroblasts and biodegradable material

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Journal of Artificial Organs 2001年第4期4卷 353-356页

作者： Furukawa, Katsuko S. Ushida, Takashi Sakai, Yasuyuki Kunii, Kaiko Suzuki, Motoyuki Tanaka, Juuzo Tateishi, Tetsuya Biomedical Engineering Laboratory (Tateishi and Ushida Laboratory) Department of Mechanical Engineering Graduate School of Engineering University of Tokyo Tokyo 113-8656 713 8th Building 7-3-1 Hongo Bunkyo-ku Japan 3-Dimensional Cell and Tissue Engineering Group National Institute for Interdisciplinary Research Agency of Industrial Science and Technology Ministry of International Trade and Industry Tsukuba Japan Institute of Industrial Science University of Tokyo Tokyo Japan National Institute for Research in Inorganic Materials University of Tokyo Tsukuba Japan

Higher-density inoculation of fibroblasts into a three-dimensional scaffold should accelerate wound healing after skin implantation. This study attempted to develop tissue-engineered skin with a higher density of fibroblasts. We first attempted to fabricate three-dimensional high cell-density aggregates (spheroids) of normal human fibroblasts for application to tissue-engineered skin. Our method consisted of rotational shaking with nontreated dishes, decreasing fibroblast-material interactions, and augmenting cell-cell interaction. To prompt aggregate formation, the medium was supplemented with insulin, dexamethasone, ascorbic acid, and basic fibroblast growth factors that potentiate secretion of extracellular matrices. Under such improved conditions, fibroblasts were able to form spheroidal aggregates within 24 to 36h of rotational culture. Although the formed aggregates were irregular in shape and were composed of only several cells after 12h, they became almost spheroidal after 24h. The aggregates grew even more round after 36h, and their surfaces became smooth. After 36h of rotational culture, the fibroblast aggregates were collected and reinoculated onto a biodegradable mesh composed of polyglycolic acid coated with collagen. The aggregates were trapped in the material and became attached after 24h. Finally, because transforming growth factor-β₃ (TGF-β₃) is known to accelerate wound healing, we conducted a semiquantitative analysis of TGF-β₃ mRNA in both the fibroblast monolayers (two-dimensional culture) and the aggregates (three-dimensional culture). Analysis of TGF-β₃ mRNA expression showed that mRNA expression was greater in the fibroblasts of aggregates than in a monolayer. Therefore, our newly developed dermal graft is expected to accelerate wound healing faster than conventional grafts.

关键词： Biodegradable polymer Normal human skin fibroblast Tissue-engineered skin

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Effect of robot-assisted and unassisted exercise on functional reaching in chronic hemiparesis

Effect of robot-assisted and unassisted exercise on function...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： L.E. Kahn M.L. Zygman W.Z. Rymer D.J. Reinkensmeyer Department of Biomedical Engineering Northwestern University Evanston IL USA Sensory Motor Performance Program Rehabilitation Institute of Chicago Chicago IL USA Department of Mechanical and AeroSpace Engineering University of California Irvine Irvine CA USA

A common therapeutic approach for the rehabilitation of patients with hemiparesis involves repetitive voluntary movements with manual assistance from a therapist ("active-assist therapy"). We used a novel robotic device to deliver a controlled form of active-assist therapy in chronic stroke patients (N=7). To examine the utility of direct mechanical assistance in rehabilitation of voluntary arm movements, a matched group of subjects with chronic hemiparesis (N=7) performed the same repetitive exercises without the aid of the robotic device. Each group performed 24 therapy sessions over 8 weeks. We found that both groups demonstrated significant improvements in straightness of voluntary reaching movements, with limited improvements in range. Only the group that received robotic therapy significantly improved the smoothness of reaching. Improvements in both groups transferred to an unpracticed reaching movement and the timed performance of functional tasks. There were no significant differences in the magnitude of improvements between the two groups. These results suggest that it is the action of repetitively attempting to move, rather than the mechanical assistance provided by the robot, that stimulates arm movement recovery. However, imposing a smooth trajectory during practice of the reaching movements may help subjects learn how to produce smoother movements. In addition, practicing robot-assisted or unassisted reaching movements apparently improves control processes that generalize to other functional movements.

关键词： Robot kinematics Rehabilitation robotics Medical treatment Extremities Couplings Protocols biomedical engineering Aerospace engineering Process control Injuries

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