90 research outputs found
Learning to push and learning to move: the adaptive control of contact forces
No full textTo be successful at manipulating objects one needs to apply simultaneously well controlled movements and contact forces. We present a computational theory of how the brain may successfully generate a vast spectrum of interactive behaviors by combining two independent processes. One process is competent to control movements in free space and the other is competent to control contact forces against rigid constraints. Free space and rigid constraints are singularities at the boundaries of a continuum of mechanical impedance. Within this continuum, forces and motions occur in “compatible pairs” connected by the equations of Newtonian dynamics. The force applied to an object determines its motion. Conversely, inverse dynamics determine a unique force trajectory from a movement trajectory. In this perspective, we describe motor learning as a process leading to the discovery of compatible force/motion pairs. The learned compatible pairs constitute a local representation of the environment's mechanics. Experiments on force field adaptation have already provided us with evidence that the brain is able to predict and compensate the forces encountered when one is attempting to generate a motion. Here, we tested the theory in the dual case, i.e., when one attempts at applying a desired contact force against a simulated rigid surface. If the surface becomes unexpectedly compliant, the contact point moves as a function of the applied force and this causes the applied force to deviate from its desired value. We found that, through repeated attempts at generating the desired contact force, subjects discovered the unique compatible hand motion. When, after learning, the rigid contact was unexpectedly restored, subjects displayed after effects of learning, consistent with the concurrent operation of a motion control system and a force control system. Together, theory and experiment support a new and broader view of modularity in the coordinated control of forces and motions
Correspondence to Committee on An Appeal for Human Rights From Harvey Pressman, April 2, 1960
No full textCorrespondence from Harvey Pressman of the Emergency Public Integration Committee to Committee on An Appeal for Human Rights. The letter details EPIC activities and membership and is a call to action for May 17 student demonstration. 1 page
Correspondence to Committee on An Appeal for Human Rights From Harvey Pressman, April 29, 1960
No full textCorrespondence from Harvey Pressman of Emergency Public Integration Committee to Committee on An Appeal for Human Rights. The letter lists schools participating in racial equality demonstrations, asking Committee on Appeal or Human Rights to add to it. 4 pages
Still points
No full textStill Points is a collection of remarkable and evocative still photographs taken by award-winning nonfiction filmmaker and author Robert Gardner during his anthropological and filming expeditions around the world. Thousands of his original photographic transparencies and negatives from the Kalahari Desert, New Guinea, Colombia, India, Ethiopia, Niger, and other remote locations are now housed in the Photographic Archives of Harvard's Peabody Museum of Archaeology and Ethnology. This elegantly produced volume presents a curated selection of more than 70 color and black-and-white images made by Gardner between the 1950s and the 1980s. Edited by Adele Pressman, Gardner's wife and literary executor, and with a foreword by Eliot Weinberger, Still Points both honors an important and influential artist and reveals new dimensions in his wor
Functional reorganization of upper-body movement after spinal cord injury
No full textSurvivors of spinal cord injury need to reorganize their residual body movements for interacting with assistive devices and performing activities that used to be easy and natural. To investigate movement reorganization, we asked subjects with high-level spinal cord injury (SCI) and unimpaired subjects to control a cursor on a screen by performing upper-body motions. While this task would be normally accomplished by operating a computer mouse, here shoulder motions were mapped into the cursor position. Both the control and the SCI subjects were rapidly able to reorganize their movements and to successfully control the cursor. The majority of the subjects in both groups were successful in reducing the movements that were not effective at producing cursor motions. This is inconsistent with the hypothesis that the control system is merely concerned with the accurate acquisition of the targets and is unconcerned with motions that are not relevant to this goal. In contrast, our findings suggest that subjects can learn to reorganize coordination so as to increase the correspondence between the subspace of their upper-body motions with the plane in which the controlled cursor moves. This is effectively equivalent to constructing an inverse internal model of the map from body motions to cursor motions, established by the experiment. These results are relevant to the development of interfaces for assistive devices that optimize the use of residual voluntary control and enhance the learning process in disabled users, searching for an easily learnable map between their body motor space and control space of the device
Climate-sensitive urban space: Concepts and Tools for Humanizing Cities
No full textUrbanismArchitectur
News ... of the Humane Society of the United States 16(4)
No full textHSUS releases Tuffy from tank HSUS gives new award to Born Free author Society opens office for Midwest region Chincoteague Ponies suffer abuse at annual roundup, auction HSUS, U.S. clash on seal killing Pressman investigations cause nationwide analysis of zoos HSUS joins poison suit Country treats unwanted dogs as garbage Conference Speakers: Working with environmentalists, Understand vets Legislation Roundup Help free this roadside bea
News ... of the Humane Society of the United States 16(4)
No full textHSUS releases Tuffy from tank HSUS gives new award to Born Free author Society opens office for Midwest region Chincoteague Ponies suffer abuse at annual roundup, auction HSUS, U.S. clash on seal killing Pressman investigations cause nationwide analysis of zoos HSUS joins poison suit Country treats unwanted dogs as garbage Conference Speakers: Working with environmentalists, Understand vets Legislation Roundup Help free this roadside bea
The Gender Poverty Gap in Developed Countries: Causes and Cures
No full textThis paper compares poverty rates for female-headed families and for other families in a number of developed countries. The author concludes that there are many different reasons female-headed families suffer relatively greater poverty in some countries but not in other countries. One implication of this analysis is that it is less important what gets done to help female-headed families, and more important that some policy be implemented to benefit female-headed families
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