Average Kinematics Research Articles

In vivo weight-bearing kinematics with medial rotation knee arthroplasty

Knee arthroplasties are designed to accommodate flexion, axial rotation and anteroposterior (AP) translation. Axial rotation during extension varies, with some rotating platform devices allowing unrestricted rotation while some conforming fixed-bearing designs almost none. The purpose of this study was to examine in vivo kinematics of a fixed-bearing medial rotation-type arthroplasty (MRK) during weight-bearing activities. Fifteen knees with a medial pivot TKA design were studied during step and pivot activities using lateral fluoroscopy and model-image registration. Average knee kinematics during the step activity showed little AP translation or rotation from 0°–100° flexion. During the pivot activity, the mean tibial internal rotation in individual knees was 7° (3°–19°). Mean condylar translations for individual knees were 3 mm medially and 5 mm laterally. The medial pivot prosthesis design provides anteroposterior stability during demanding activities, and exhibits a medial pivot motion pattern when subjected to twisting.

Influence of Lunate Type on Scaphoid Kinematics

To assess the influence of lunate type on scaphoid kinematics. One hundred normal wrists had fluoroscopic assessment of the wrist in maximal radial, neutral, and ulnar deviation. The shortest distance in a neutral position between the capitate and triquetrum, C-T distance, determined lunate type. A type I lunate had a C-T distance of < or =2 mm, a type II lunate > or =4 mm, and an intermediate group lay between these values. Scaphoid flexion and translation in radial and ulna deviation was measured. There were 18 subjects with a type I lunate, 19 with an intermediate lunate, and 63 with a type II lunate. There was no statistically significant difference between lunate type, subject age, or hand dominance. There was a statistically significant higher proportion of women with a type I lunate. Subjects with a type II lunate had a statistically greater amount of flexion during radioulnar deviation as determined by CR index (0.79 vs 0.91) and scaphoid flexion index (0.21 vs 0.09). Subjects with a type II lunate had statistically less translation during radioulnar deviation as determined by translation ratio (0.22 vs 0.31) and scaphoid inclination index (0.18 vs 0.23). The average scaphoid kinematic index in subjects with a type II lunate was 1.24, intermediate 0.86, and type I 0.42. A scaphoid kinematic index of greater than 1 indicates the scaphoid has more flexion during radioulnar deviation than translation. Wrists with a type I lunate show statistically greater scaphoid translation with radial deviation. Wrists with a type II lunate show statistically greater scaphoid flexion with radial deviation. Intermediate lunates have intermediate scaphoid mechanics. This allows the surgeon to determine the likely wrist scaphoid mechanics based on the lunate type determined from a single posterior-anterior x-ray.

Flight control in the hawkmothManduca sexta: the inverse problem of hovering

The inverse problem of hovering flight, that is, the range of wing movements appropriate for sustained flight at a fixed position and orientation, was examined by developing a simulation of the hawkmoth Manduca sexta. Inverse problems arise when one is seeking the parameters that are required to achieve a specified model outcome. In contrast, forward problems explore the outcomes given a specified set of input parameters. The simulation was coupled to a microgenetic algorithm that found specific sequences of wing and body motions, encoded by ten independent kinematic parameters, capable of generating the fixed body position and orientation characteristic of hovering flight. Additionally, we explored the consequences of restricting the number of free kinematic parameters and used this information to assess the importance to flight control of individual parameters and various combinations of them. Output from the simulated moth was compared to kinematic recordings of hovering flight in real hawkmoths; the real and simulated moths performed similarly with respect to their range of variation in position and orientation. The simulated moth also used average wingbeat kinematics (amplitude, stroke plane orientation, etc) similar to those of the real moths. However, many different subsets of the available kinematic were sufficient for hovering flight and available kinematic data from real moths does not include sufficient detail to assess which, if any, of these was consistent with the real moth. This general result, the multiplicity of possible hovering kinematics, shows that the means by which Manduca sexta actually maintains position and orientation may have considerable freedom and therefore may be influenced by many other factors beyond the physical and aerodynamic requirements of hovering flight.

Repeatability of a model for measuring multi-segment foot kinematics in children

This study used a previously tested foot model and adapted it for use with children. A number of variations on this adapted model were implemented and tested for repeatability and accuracy on 15 healthy children on three occasions. These included redefinition of the long axes of the tibia and forefoot, assessment of the flexibility of the forefoot and evaluation of the variability of the wand marker on the heel for both static and dynamic trials. It was found that variations on the model produced only minimal changes in repeatability, the only significant change being elimination of the wand marker on the heel in the static trial, which reduced between-day variability of hindfoot motion in the transverse plane. However, some differences were evident in the mean values for all variations. Based on these results, the most accurate and appropriate version of the model is proposed, and average kinematic curves are presented based on the measurements from 14 healthy children.

Objective And Subjective Clinical Measures Of Function In Patients With Knee Osteoarthritis

Clinicians commonly use the WOMAC Index as a non-invasive subjective measure of the degree of pain, stiffness, and function for patients who suffer from knee osteoarthritis (OA). Researchers commonly use distance walked in 6 min as an objective functional measure of OA. The relationship between the WOMAC index and 6 min walk distance to gait mechanics in patients with knee OA has not been investigated, however. PURPOSE To determine differences between gait patterns as represented by angle-angle plots of the lower extremities when objective (distance walked in 6 min) and subjective (WOMAC score) measures are used to group patients suffering from knee OA. METHODS Fifty-two males and females (mean age =70.65 yrs  −+9.94 yrs) completed the WOMAC Inventory and were measured for total distance walked in 6 min. Twenty-two reflective markers and six digital cameras, each operating at 60 Hz, were used to capture 3-D kinematic variables as the participants walked on an elevated walkway at their freely chosen speed. Total score on the WOMAC (pain + stiffness + function) and distance walked in 6 min were used to rank order the 52 participants and divide them into three groups. Normalized joint kinematics for the hip, knee, and ankle for each participant in the three WOMAC (high, middle, low) and distance (short, medium, long) groups were averaged. Angle-angle plots of the average joint kinematics (hip-knee, knee-ankle, hip-ankle) for each of the three groups for the two measures of grouping (subjective = WOMAC self-reported scores and objective = distance walked in 6 min) were generated using Excel. RESULTS A Pearson Product Moment of the two measures (WOMAC and distance) revealed a correlation of −.44 and R2 of .20. Spatial-temporal values revealed similar timing when participants were grouped using WOMAC scores (stance = 61.8, 60.7, 61.25% of gait cycle for high, medium, and low, respectively) but different values when grouped using distance walked in 6 min (stance = 63.76, 60.96, 59.2% for short, medium, and long, respectively). Visual inspection of the angle-angle plots revealed similar shapes for the curves when grouped using WOMAC scores, but different degrees of joint flexion and extension. However, when participants were grouped using distance covered in 6 min, different patterns and degrees of joint flexion and extension were revealed. CONCLUSION Using an objective measure such as distance covered in 6 min is a better discriminator of levels of function (i.e., gait) in patients who suffer from knee OA than using a self-reported measure of function, pain, and stiffness such as the WOMAC Index. Supported by NIH grants 5P60AG10484-07 and M01RR0021.

Kinematics and dynamics of the Mesozoic orogeny and late-orogenic extensional collapse in the Sino-Mongolian border areas

The Sino-Mongolian border areas underwent two important tectonic events during Mesozoic time after late Paleozoic orogeny: a late Triassic to earlier Jurassic contractional event that resulted in a large-scale south-vergent thrust during the orogeny and a late Jurassic-earlier Cretaceous extensional event in a north-south direction that formed a metamorphic core complex. The kinematic and dynamic analyses show that the thrust sheet moved southwards with a kinematic vorticity number of ca. −0.10 and sub-horizontal maximum compressive stress axis that belongs to a contraction-thickening shear. The upper plate of the late-orogenic detachment relatively moved in a 165° direction. The average kinematic vorticity in its earlier stage was 0.74 that belongs to simple shear dominated shearing and related to the maximum compressive stress axes dipping at ~66°, while the later average kinematic vorticity was ~0.55 that belongs to pure shear dominated shearing with sub-vertical maximum compressive stress axes. This suggests that the thrusting led to the crust thickened and the lower plate rocks that were originally located in the upper crust depressed through a brittle-ductile transition zone into the lower crust and became warmer. The heated rocks trended to uplift since their increasing volume and decreasing density while the loading of the upper-plate rocks increased due to the structural thickening. Under the combined effect of the loading and the thermal-uplifting, the ductile shear zone in between increased in its component of vertical pure shear. Once its pure-shear component ex-ceeded its simple-shear one the ductile shear zone became an extension-thinned shear zone. This progressive transitional process reflects internal and essential temporal and spatial rela-tionships: the extensional factor nucleated during the crust thickening by thrusting and increase of the extensional factor finally led to late-orogenic collapse.

Tactile feedback contributes to consistency of finger movements during typing.

Touch typing movements are typically too brief to use on-line feedback. Yet, previous studies have shown that blocking tactile feedback of the fingertip of typists leads to an increase in typing errors. To determine the contribution of tactile information to rapid fine motor skills, we analyzed kinematics of the right index finger during typing with and without tactile feedback. Twelve expert touch typists copy-typed sentences on a computer keyboard without vision of their hands or the computer screen. Following control trials, their right index fingertip was anesthetized, and sentences were typed again. The movements of the finger were recorded with an instrumented glove and electromagnetic position sensor. During anesthesia, typing errors of that finger increased sevenfold. While the inter-keypress timing and average kinematics were unaffected, there was an increase in variability of all measures. Regression analysis showed that endpoint variability was largely accounted for by start location variability. The results suggest that tactile cues provide information about the start location of the finger, which is necessary to perform typing movements accurately.

Eddy Acceleration of the Mean Flow in the Atmosphere

An attempt has been made to analyze the zonally averaged zonal momentum budget of a GCM in light of its average kinematics. The analysis is based on an advection–diffusion operator in the meridional plane with transport characteristics as close as possible to the average advective transport of the model. The transport velocity of this advection–diffusion operator has been used to isolate the zonal acceleration due to meridional circulations including Stokes drift phenomena. The eddy effect relative to this framework is shown to be strong when the diffusivity is strong and vice versa. It is suggested that this is largely due to wave drags of growing waves. The mechanism by which this drag is created is studied by means of a modification of the circulation theorem. The observed eddy accelerations are compatible with estimates based on this theorem.

Upper extremity augmentation of lower extremity kinetics during countermovement vertical jumps

Twenty-five volleyball players (14 males, 11 females) were videotaped (60Hz) performing countermovement vertical jumps with and without an arm swing. Ground reaction force and video-based coordinate data were collected simultaneously. The resultant joint force and torque at the hip, knee, ankle and shoulder for two trials per subject per condition were computed and normalized. Average kinematic, resultant joint force and torque data were compared using repeated-measures analysis of variance. Larger values were recorded for the vertical velocity of the centre of mass at take-off in the jumps with (mean 2.75, s=0.3m.s-1) versus without (mean 2.44, s= 0.23m.s-1) an arm swing. The jumps with no arm swing produced larger torques at the hip during the first third of the propulsive phase (from zero to maximum vertical velocity of the centre of mass). During the final two-thirds of the propulsive phase, the arm swing augmented hip extensor torques by slowing the rate of trunk extension and placing the hip extensor muscles in slower concentric conditions that favoured the generation of larger forces and resultant joint torques. During the first two-thirds ofthe propulsive phase, knee extensor torque increased by 28% in the jumps with an arm swing, but maintained a relatively constant magnitude in the jumps with no arm swing.

On the registration of time and the patterning of speech movements.

In order to study speech coordination we frequently average kinematic and other physiological signals. The averages are assumed to be more representative of the underlying patterns of production than individual records. In this note we outline different approaches to averaging and present a new nonlinear normalization technique that offers better information than ensemble averaging, linear normalization, or feature alignment methods. We suggest that this technique provides a clear estimation of pattern shape while preserving information on the variation over time.

Predicting the Flexural Postcracking Performance of Steel Fiber Reinforced Concrete from the Pullout of Single Fibers

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Kinetic stability properties of relativistic nonneutral electron flow for low-frequency extraordinary-mode perturbations

The kinetic stability properties of relativistic nonneutral electron flow in planar diode geometry are examined for extraordinary-mode perturbations about the self-consistent Vlasov equilibrium . Here, the cathode is located at x = 0; the anode is located at x = d the outer edge of the electron layer is located at is the equilibrium flow velocity in the x-direction; n^b is the electron density at the cathode (x = 0); and is the axial magnetic field, with const. in the vacuum region (xb &lt; x ≤ d). The extraordinary-mode eigenvalue equation, derived in a companion paper for low-frequency, long-wavelength perturbations, is solved exactly. This leads to a formal dispersion relation, which can be used to determine the complex eigenfrequency ω over a wide range of system parameters and wavenumber k in the y-direction. The formal dispersion relation is further simplified for and , assuming low-frequency perturbations about a tenuous electron layer with and . Here, , and , where denotes the average equilibrium orbit, and [γ(x) − 1]mc2 is the average kinematic energy of an electron fluid element. The resulting approximate dispersion relation is solved numerically over a wide range of system parameters to determine the detailed dependence of stability properties on electromagnetic effects, layer thickness, and electron energy, as measured by , and γb − 1, respectively. Here, γb = γ(xb) denotes the electron energy at the outer edge of the electron layer. As a general remark, it is found that increasing the electron energy (γb − 1), increasing the strength of electromagnetic effects , and/or decreasing the layer thickness (xb/d) all have a stabilizing influence.

Nonlinear surge response of a tension leg platform to random wave forces

The response of a Tension Leg Platform (TLP) to wave-induced forces depends upon different factors which are considered in the analysis. It is not possible to include all factors in one single analysis. As a result the relative importance of the factors needs to be evaluated by parametric studies. In the present paper, effects of some factors on the surge response of a TLP to random wave forces are investigated. The factors include (i) the variable submergence effects such as variation in added mass and tension fluctuation in the tethers, (ii) variation in tension in the tethers produced by vertical wave forces, and (iii) method for calculating hydrodynamic forces. The effect of variable submergence on the water particle kinematics is included by both Chakrabarti's 1 and Hogben's 2 approaches. Hydrodynamic forces on the large-diameter members of the superstructure are obtained by means of a modified Morison equation by using (a) average water-particle kinematics across the diameter of the members, (b) water-particle kinematics calculated at the centre of the cross section, and (c) water-particle kinematics the same as (b) above, but with the inertia coefficient modified to take into account any diffraction effect. The nonlinear equation of motion describing the surge motion of the TLP is solved in the time domain by using an iterative step-by-step integration procedure.

Migration of enzymes on lidear polymers

We present a simple model based on the kinetics of DNA-dependent ATPases where the probability for enzyme migration on the linear activating polymer depends on the rate equations at the steady state. It is shown how the chemical velocity of the reaction is correlated to the average kinematic velocity along the polymer. The implications of this result are discussed.

Target residue recoil properties in the interaction of 8.0 GeVNe20withTa181

The thick target, thick catcher technique has been applied to determine the average kinematic properties of a number of target-fragmentation products formed in the reaction of 8.0 GeV (400 MeV/A) $^{20}\mathrm{Ne}$ with $^{181}\mathrm{Ta}$. The forward momentum transferred to the target as a function of product mass is larger than that for the reaction of 25 GeV $^{12}\mathrm{C}$ or relativistic protons with heavy targets, suggesting that limiting fragmentation has not been achieved in the interaction of 8 GeV $^{20}\mathrm{Ne}$ projectiles with a $^{181}\mathrm{Ta}$ target.NUCLEAR REACTIONS $^{181}\mathrm{Ta}$($^{20}\mathrm{Ne}$, spallation), $E=8.0$ GeV; measured target residue recoil properties; relativistic heavy ion reactions; thick target, thick catcher technique; Ge(Li) spectroscopy.

Rainfall Fields in Israel and Jordan and the Effect of Cloud Seeding on Them

Spatial correlation functions of daily rainfall were derived separately for various parts of the study area and for unseeded and seeded days. The structure of respective rainfall fields was studied by means of the relationship between the geometry of iso-correlation contours of daily rainfall and the average geometry and/or kinematics of cloud systems that produce the rainfall. Results were obtained on 1) the prevalent direction of storm movement over the study area and 2) the change in size of rainfall areas under varying conditions. Evidence is presented of an average increase of about 10 km in the dimensions of rainfall areas on seeded days. It is suggested that expanded rainfall areas have a twofold effect on the augmentation of the total yield of individual storms: 1) an increase of point rainfall resulting from prolonged exposure to moving cloud systems, and 2) an increase in the area thus affected. Consequently, the increase in water yield of a storm over the entire area covered by it, may not be fully represented by point measurements. In the regional context, a contraction of storm areas was found in the transition to the arid zone. It is suggested that the size of rainfall areas is one of the fundamental factors controlling regional variations of rainfall as well as variations resulting from cloud seeding.

The Low-Level Jet as Related to Nocturnal Thunderstorms over Midwest United States

Abstract The significance of the low-level jet in the development of nocturnal thunderstorms over the Midwest through the production of regions of convergence was investigated for an area centered at Omaha, Nebraska. A composite jet axis representing all non-frontal days during the summer months of 1955, 1956 and 1957 was found to coincide with the line of maximum frequency of thunderstorm occurrence. Correlation between average kinematic vertical velocities and per cent thunderstorm occurrence over the area centered at Omaha supports the view that the occurrence of summer nocturnal thunderstorms is closely related to the production of regions of convergence associated with the low-level jet.