Why not walk faster? Limitations to walking speed imposed by inverted pendulum mechanics by Dr J. R. Usherwood
A simple model of the mechanics of walking provides an account for why bipeds (humans and birds) can't walk faster. The problem of 'take-off' when gravity cannot provide the centripetal acceleration required to keep the body arcing around the foot is greatest at beginning and end of stance; this is when the body is moving fastest, and the component of gravity along the leg is lowest. Thus, bipeds cannot walk at high speeds with long steps. Shorter steps permit faster walking without take-off, but then driving the swing leg fast enough becomes an issue.
Contact: Dr J. R. Usherwood, Structure and Motion Lab., The Royal Veterinary College, VBS, NORTH MYMMS, AL9 7TA, United Kingdom
Epidemiological implications of the contact network structure for cattle farms and the 20-80 rule by Professor MEJ Woolhouse and Dr DJ Shaw
Moving cattle between farm holdings has the potential to spread infectious diseases. Using data from DEFRA's Cattle Tracing System for 55 Scottish farms we worked out how many farms they sent cattle to and received cattle from during 2002; that is, how well 'connected' each farm was. On average, each holding was connected with 24 other holdings, but there was a lot of variation: most farms were connected with only a few others, but a few were connected with over 100. This variation is important: just 20% of farms contribute over 80% of the potential to spread infectious diseases by cattle movements.
Contact: Dr Professor Woolhouse, Centre for Infectious Diseases, University of Edinburgh, East
Contact: Tim Watson