Elastic and length-force characteristics of the gastrocnemius of the hopping mouse (Notomys alexis) and the rat (Rattus norvegicus)

The aim of this study was to compare the contractile and series elastic properties of terrestrial mammals that use bipedal versus quadrupedal gaits. The gastrocnemius muscle of the hopping mouse (body mass 30.2 +/- 2.4 g, mean +/- S.D.) and the rat (313 +/- 10.7 g) were compared with data from the literature for the wallaby and the kangaroo rat to distinguish scaling effects and locomotion-related effects on muscle properties. Contractile length-force properties and series elastic stiffness were measured in situ during maximal tetanic contractions. The rat had a larger muscle-fibre-to-tendon-length ratio. The rat and hopping mouse showed similar normalised length-force characteristics of the gastrocnemius. Normalised stiffness in the hopping mouse was higher. The hopping mouse showed a higher capacity to store elastic energy per unit of contractile work capacity, as well as per unit of body mass. Accounting for body size differences, the rat had a smaller relative muscle mass and thus smaller work capacity than the three hopping animals considered. This is an agreement with a quadrupedal versus bipedal locomotion style. The differences in contractile and elastic properties of the gastrocnemius of the rat and hopping mouse seem to be closely related to locomotion patterns. Small animals seem to be able to utilise the storage and release of elastic energy to a far lesser extent than larger animals. However, even in animals as small as hopping mice, the storage and utilisation of elastic energy during locomotion is of functional significance and probably depends on locomotor behaviour

Two remarks to noiseless coding

An inequality concerning Kullback's I-divergence is applied to obtain a necessary condition for the possibility of encoding symbols of the alphabet of a discrete memoryless source of entropy H by sequences of symbols of another alphabet of size D in such a way that the average code length be close to the optimum H/log D. The same idea is applied to the problem of maximizing entropy per second for unequal symbol lenghts, too

Effects of changing travel patterns on travel satisfaction: A focus on recently relocated residents

Previous studies indicate that travel satisfaction is affected by elements such as travel mode choice and trip duration. However, how people’s satisfaction levels with travel adapt after changing their travel behaviour has not yet been analysed thoroughly. In this study we analyse travel satisfaction of 1650 respondents who recently relocated to selected neighbourhoods in the city of Ghent (Belgium), and therefore changed their daily travel patterns (i.e., commute and leisure trips). Based on a two-step approach, i.e., a factor analysis followed by a cluster analysis, respondents are segmented into four clusters based on their changes in travel behaviour after they moved. Results indicate that especially clusters with respondents that decreased travel distance and duration, and increased the use of car alternatives have high levels of travel satisfaction, for both commute trips and leisure trips. Respondents from these clusters also indicated the highest levels of travel satisfaction improvements. This study provides additional motivation for policy makers and urban planners to convince more people to relocate to urban areas, or for densification and land use mixing of existing neighbourhoods, as this will not only result in more sustainable travel patterns, but also in more satisfying travel patterns