PubMed · 16335140
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S B Roberts, C C Ward, A M Nahum. 1969. Head trauma--a parametric dynamic study.. https://doi.org/10.1016/0021-9290(69)90016-5
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Motion perception is impaired in many neuropathological conditions, including schizophrenia. Motion perception also declines in the course of normal aging. In this study, we ask whether aging is an additive factor in the motion-discrimination deficits of schizophrenia patients. We examined motion perception in schizophrenia patients (n=44) and non-psychiatric controls (n=40) whose ages ranged from 18 to 55. The tasks included velocity discrimination and contrast detection. Thresholds for each of the two tasks were determined for each subject using psychophysical methods. Schizophrenia patients showed significantly increased thresholds (degraded performance) for velocity discrimination compared with the controls. Degraded performance in patients was not related to age. In controls, however, velocity discrimination thresholds were significantly increased beginning by age 45. Performance on a contrast-detection task, which does not require precise discrimination of motion signals, was not significantly affected by age in either group. Aging, even in its early stages, degrades motion discrimination in normal adults. Aging, however, does not adversely affect motion-discrimination deficits in schizophrenia patients through age 55. A similar motion-discrimination deficit in schizophrenia patients and aging normal adults suggests that the mechanisms underlying motion processing in schizophrenia and normal aging may be associated.
The purpose of this study was to examine the validity of published regression equations designed to predict energy expenditure (EE) from accelerometers (Actigraph, Actical, and AMP-331) compared to indirect calorimetry, over a wide range of activities. Forty-eight participants (age: 35 +/- 11.4 years) performed various activities that ranged from sedentary behaviors (lying, sitting) to vigorous exercise. The activities were split into three routines of six activities, and each participant performed at least one routine. The participants wore three devices (Actigraph, Actical, and AMP-331) and simultaneously, EE was measured with a portable metabolic system. For the Actigraph, 15 previously published equations were used to estimate EE from the accelerometer counts. For the Actical, two published equations were used to estimate EE from the accelerometer counts. For the AMP-331 we used the manufacturer's equation to estimate EE. The Actigraph and Actical regressions tended to overestimate walking and sedentary activities and underestimate most other activities. The AMP-331 gave a close estimate of EE during walking, but overestimated sedentary/light activities and underestimated all other activities. The only equation not significantly different from actual time spent in both light and moderate physical activity was the Actigraph Freedson kcal equation. All equations significantly underestimated time spent in vigorous physical activity (P < 0.05). In conclusion, no single regression equation works well across a wide range of activities for the prediction of EE or time spent in light, moderate, and vigorous physical activity.
The advanced mechanical testing of microelectromechanical systems (MEMS) is necessary to provide feedback of measurements that can help the designer optimize MEMS structures and improve the reliability and stability of MEMS. We describe a digital image correlation (DIC) method for dynamic characterization of MEMS using an optical microscope with a high-speed complementary metaloxide semiconductor-based camera. The mechanical performance of a series of microgyroscopes is tested. The DIC method is employed to measure the microgyroscope in-plane displacement with subpixel accuracy. Use of the DIC method is less restrictive on the surface quality of the specimen and simplifies the measurement system. On the basis of a series of temporal digital images grabbed by a high-speed camera, the stability characteristic of the microgyroscopes is analyzed. In addition, the quality factors of the microgyroscopes are determined and agree well with other experimental methods.