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Red blood cell mechanics and blood flow in narrow capillaries
‘40
Abstracts
TEMPOR AL AND KINEMATIC
CHARACrERISTICS
OF SKILLED
TRACKING
MOVEMENTS
G. L. SCHEIRMANand P. J. CHEETHAM (Department
of Biomechanics and Computer Services, United States Olympic Committee, 1750 East Boulder Street, Colorado Springs, CO 80909, U.S.A)
Present theory proposes that a motor program for a specific motion contains phasing information, but this pattern as a unit may be accelerated or decelerated to meet specific temporal movement constraints. The purpose of the present study was to measure the kinematic and temporal tracking modifications elicited by highly skilled Running Game Target Shooters and evaluate the possibility of motor program phasing. Three national class Running Game Target Shooters were tested undercompetitiveconditions. Horizontal and vertical positions of the muzzle were determined with a SELSPOT Motion Analysis System. Within the tracking time interval, aggregate component displacements and mean velocities were computed. The data indicated there were no temporal or kinematic tracking differences between directional conditions. However, between speed conditions, all subjects tracked the slower target at half the velocity for a proportionately longer duration and a further distance. These results suggest that the subjects learned to specify their movement patterns and duplicate them under directional changes, but the phasing of the motor programs may not be identical for both target speeds.
STRUCTURAL
MODELING
D. S. SCHNURand J. L. LEWIS (Harrington
AND DESIGN
OF KNEE ORTHOSES
Arthritis Research Center, Phoenix, AZ 85006, U.S.A.)
Three structural models of a knee orthosis were developed and analyzed to serve as aids for design: a twodimensional plane strain finite element model, a complete three-dimensional finite element model, and a simplified analytical model. After validating the models, some design features were examined. Several conclusions about orthosis design were derived from the model results. Four point fixation is more effective than three point. The ratio of the tissue to sidebar stiffness is an important design parameter for loading in the medial-lateral plane. For an orthosis with rigid sidebars, the suspension should be stiff, and the suspension points should be separated as much as possible with the proximal suspension point close to the knee. The sidebars and cuffs may not need to be very rigid to provide bending stability, but the effects on torsional stability are unknown. Experimental or clinical verification of the model results is needed.
RED BLOOD CELL MECHANICS AND BLOOD FLOW IN NARROW CAPILLARIES T. W. SECOMBand J. F. GROSS (Department of Physiology, University of Arizona, Tucson, AZ 85724, U.S.A.)
A series of theoretical models is reported for the motion of red blood cells in narrow capillaries, assuming axisymmetric geometry and using lubrication theory to describe the plasma flow around the cells. The simplest model assumes isotropic tension in the cell membrane, and is applicable at moderate to high flow rates (above about 1 mm s-i). To model flow at lower velocities, two further models are presented incorporating, successively, the effects of shear and bending elasticity in the membrane. Cell shapes are computed for flow in 6~ diameter vessels, and predictions of apparent viscosity over a wide range of flow rates are compared with published experimental values.
Supported
by
NIH Grant HL 17421.
POROELASTIC STRUCTURAL MODELS FOR HUMAN SPINAL MOTION SEGMENTS B. R. SIMON, J. S.-S. WV, J. H. EVANSand L. E. KAzARtAN.(Aerospaceand Mechanical Engineering, University of Arizona, Tucson, AZ; Strathclyde University, Glasgow, Scotland, U.K., and AFAMRL/BBD, WPAFB, Dayton, OH, USA) The mechanical response of a spinal motion segment plays a key role in the biomechanical behavior of the spine. A finite element model can provide quantitative data regarding deformations, strains and stresses, provided suitable constitutive laws are available to describe the properties of the materials in the spinal motion segment.
Abstracts
TEMPOR AL AND KINEMATIC
CHARACrERISTICS
OF SKILLED
TRACKING
MOVEMENTS
G. L. SCHEIRMANand P. J. CHEETHAM (Department
of Biomechanics and Computer Services, United States Olympic Committee, 1750 East Boulder Street, Colorado Springs, CO 80909, U.S.A)
Present theory proposes that a motor program for a specific motion contains phasing information, but this pattern as a unit may be accelerated or decelerated to meet specific temporal movement constraints. The purpose of the present study was to measure the kinematic and temporal tracking modifications elicited by highly skilled Running Game Target Shooters and evaluate the possibility of motor program phasing. Three national class Running Game Target Shooters were tested undercompetitiveconditions. Horizontal and vertical positions of the muzzle were determined with a SELSPOT Motion Analysis System. Within the tracking time interval, aggregate component displacements and mean velocities were computed. The data indicated there were no temporal or kinematic tracking differences between directional conditions. However, between speed conditions, all subjects tracked the slower target at half the velocity for a proportionately longer duration and a further distance. These results suggest that the subjects learned to specify their movement patterns and duplicate them under directional changes, but the phasing of the motor programs may not be identical for both target speeds.
STRUCTURAL
MODELING
D. S. SCHNURand J. L. LEWIS (Harrington
AND DESIGN
OF KNEE ORTHOSES
Arthritis Research Center, Phoenix, AZ 85006, U.S.A.)
Three structural models of a knee orthosis were developed and analyzed to serve as aids for design: a twodimensional plane strain finite element model, a complete three-dimensional finite element model, and a simplified analytical model. After validating the models, some design features were examined. Several conclusions about orthosis design were derived from the model results. Four point fixation is more effective than three point. The ratio of the tissue to sidebar stiffness is an important design parameter for loading in the medial-lateral plane. For an orthosis with rigid sidebars, the suspension should be stiff, and the suspension points should be separated as much as possible with the proximal suspension point close to the knee. The sidebars and cuffs may not need to be very rigid to provide bending stability, but the effects on torsional stability are unknown. Experimental or clinical verification of the model results is needed.
RED BLOOD CELL MECHANICS AND BLOOD FLOW IN NARROW CAPILLARIES T. W. SECOMBand J. F. GROSS (Department of Physiology, University of Arizona, Tucson, AZ 85724, U.S.A.)
A series of theoretical models is reported for the motion of red blood cells in narrow capillaries, assuming axisymmetric geometry and using lubrication theory to describe the plasma flow around the cells. The simplest model assumes isotropic tension in the cell membrane, and is applicable at moderate to high flow rates (above about 1 mm s-i). To model flow at lower velocities, two further models are presented incorporating, successively, the effects of shear and bending elasticity in the membrane. Cell shapes are computed for flow in 6~ diameter vessels, and predictions of apparent viscosity over a wide range of flow rates are compared with published experimental values.
Supported
by
NIH Grant HL 17421.
POROELASTIC STRUCTURAL MODELS FOR HUMAN SPINAL MOTION SEGMENTS B. R. SIMON, J. S.-S. WV, J. H. EVANSand L. E. KAzARtAN.(Aerospaceand Mechanical Engineering, University of Arizona, Tucson, AZ; Strathclyde University, Glasgow, Scotland, U.K., and AFAMRL/BBD, WPAFB, Dayton, OH, USA) The mechanical response of a spinal motion segment plays a key role in the biomechanical behavior of the spine. A finite element model can provide quantitative data regarding deformations, strains and stresses, provided suitable constitutive laws are available to describe the properties of the materials in the spinal motion segment.