Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women

Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent

Impact of end effector technology on telemanipulation performance

Generic requirements for end effector design are briefly summarized as derived from generic functional and operational requirements. Included is a brief summary of terms and definitions related to end effector technology. The second part contains a brief overview of end effector technology work as JPL during the past ten years, with emphasis on the evolution of new mechanical, sensing and control capabilities of end effectors. The third and major part is devoted to the description of current end effector technology. The ongoing work addresses mechanical, sensing and control details with emphasis on mechanical ruggedness, increased resolution in sensing, and close electronic and control integration with overall telemanipulator control system

Differential electrophysiological response during rest, self-referential, and non-self-referential tasks in human posteromedial cortex

The electrophysiological basis for higher brain activity during rest and internally directed cognition within the human default mode network (DMN) remains largely unknown. Here we use intracranial recordings in the human posteromedial cortex (PMC), a core node within the DMN, during conditions of cued rest, autobiographical judgments, and arithmetic processing. We found a heterogeneous profile of PMC responses in functional, spatial, and temporal domains. Although the majority of PMC sites showed increased broad gamma band activity (30-180 Hz) during rest, some PMC sites, proximal to the retrosplenial cortex, responded selectively to autobiographical stimuli. However, no site responded to both conditions, even though they were located within the boundaries of the DMN identified with resting-state functional imaging and similarly deactivated during arithmetic processing. These findings, which provide electrophysiological evidence for heterogeneity within the core of the DMN, will have important implications for neuroimaging studies of the DMN

X-56A Structural Dynamics Ground Testing Overview and Lessons Learned

The X-56A Multi-Utility Technology Testbed (MUTT) is a subscale, fixed-wing aircraft designed for high-risk aeroelastic flight demonstration and research. Structural dynamics ground testing for model validation was especially important for this vehicle because the structural model was directly used in the development of a flight control system with active flutter suppression capabilities. Structural dynamics ground tests of the X-56A MUTT with coupled rigid-body and structural modes provided a unique set of challenges. An overview of the ground vibration test (GVT) and moment of inertia (MOI) test setup and execution is presented. The series of GVTs included the wing by itself attached to a strongback and complete vehicle at two mass conditions: empty and full fuel. Two boundary conditions for the complete-vehicle test were studied: on landing gear and suspended free-free. Pitch MOI tests were performed using a compound pendulum method and repeated with two different pendulum lengths for independent verification. The original soft-support test configuration for the GVT used multiple bungees, resulting in unforeseen coupling interactions between the soft-support bungees and the vehicle structural modes. To resolve this problem, the soft-support test setup underwent multiple iterations. The various GVT configurations and boundary-condition modifications are highlighted and explained. Lessons learned are captured for future consideration when performing structural dynamics testing with similar vehicles

Investigating the effect of ball impact location on the overhead motion in tennis during game play

Tennis is a competitive sport played by millions of people worldwide. The characteristics of the game of tennis produce stress on the musculoskeletal system, especially in the upper extremity. Upper extremity injuries often occur when the arm is highly accelerated, as happens in tennis. These high accelerations require large forces to be applied to the wrist, elbow and shoulder. Upon ball impact, a large amount of force is transferred to the ball from the tennis racket. However, depend- ing on the impact location, large reaction forces can also be produced in the body. These large reaction forces must pass through the kinematic chain from the hand to the wrist, elbow and shoulder joints and into the torso. As a result, wrist, elbow and shoulder joint injuries are common. Motion capture has been used to study the biomechanics of the overhead motion in tennis; yet, this method measures pre- and post-impact dynamics not the actual instant at which the interaction between the ball and the racket occurs. Therefore, to make a more accurate representation, the impact itself needs to be studied. Investigating the impact itself will provide more insight into what is happening at the exact moment of the collision and how the kinematic chain is aected. A commercial racket was purchased and customized by substituting the orig- inal handle by a one inch diameter acetyl rod, and adding unidirectional and triaxial strain gauges to it. A custom electrical circuit was designed and built to measure the strain in the racket handle during ball impact. Two participants used the instrumented racket to each hit a total of 20 regular serves divided into 4 dierent sets. Participants were photographed during the serve using a high speed camera at 120 frames per second. These photographs were used to identify the ball impact location of each serve. Strain waveforms collected using a custom electrical circuit were ana- lyzed to determine the peak ball impact force, the wrist reaction forces, and torques from the bending moments developed in the racket handle during impact. Results showed that the instrumented tennis racket was able to evaluate the eect of ball impact location of the overhead motion in tennis during game play. The instrumented racket was able to measure ball forces, wrist reaction forces (equal in magnitude to ball forces but opposite in direction as a result of not taking into ac- count the transfer of linear and angular momentums) and torques generated by the bending moments at the hand during ball impact. This device or an improved version may be useful to get a better understanding of the forces and moments created with dierent types of movements during tennis play. It would be especially useful when employed in collaboration with a motion cap- ture system. A more complete understanding of tennis biomechanics can be gained by including racket impact forces and bending moments with motion capture to quantify the eect that ball impact location has on the transfer of forces to the joints passing through the kinematic chain

Life editing: Third-party perspectives on lifelog content

Lifelog collections digitally capture and preserve personal experiences and can be mined to reveal insights and understandings of individual significance. These rich data sources also offer opportunities for learning and discovery by motivated third parties. We employ a custom-designed storytelling application in constructing meaningful lifelog summaries from third-party perspectives. This storytelling initiative was implemented as a core component in a university media-editing course. We present promising results from a preliminary study conducted to evaluate the utility and potential of our approach in creatively interpreting a unique experiential dataset

High-Mast Light Poles Anchor Nut Loosening In Alaska - An Investigation Using Field Monitoring and Finite-Element Analysis

INE/AUTC 14.0