Movement and Orientation

The ways in which fish use space in nature are described, distinguishing between movements within a home range, dispersal and directed migration, as are the mechanisms that determine how fish use space. The external stimuli to which fish respond, how they use these cues to find their way around and the role of hormones in migration are also covered. An account is then given of how movement and orientation change with age, the evidence for inherited differences in these aspects of behaviour and environmental effects on development of space use patterns. The benefits that accrue to fish from moving in particular ways are described, as are adverse consequences of such movements, in the form of energetic costs and exposure to predators and pathogens. The ways in which benefits and costs are balanced against each other are discussed, with special reference to diurnal vertical migration. Although cultured fish usually inhabit confined spaces, their natural patterns of orientation and movement can cause a number of problems in aquaculture and some of these are described. Such problems are amenable to biological solutions and these are considered in the final section of this chapter, which also looks at the potential for using what is known about how fish move about to improve the effectiveness of general husbandry practices.

Is perception of upper body orientation based on the inertia tensor? Normogravity versus microgravity conditions

During lateral leg raising, a synergistic inclination of the supporting leg and trunk in the opposite direction to the leg movement is performed in order to preserve equilibrium. As first hypothesized by Pagano and Turvey (J Exp Psychol Hum Percept Perform, 1995, 21:1070-1087), the perception of limb orientation could be based on the orientation of the limb's inertia tensor. The purpose of this study was thus to explore whether the final upper body orientation (trunk inclination relative to vertical) depends on changes in the trunk inertia tensor. We imposed a loading condition, with total mass of 4 kg added to the subject's trunk in either a symmetrical or asymmetrical configuration. This changed the orientation of the trunk inertia tensor while keeping the total trunk mass constant. In order to separate any effects of the inertia tensor from the effects of gravitational torque, the experiment was carried out in normo- and microgravity. The results indicated that in normogravity the same final upper body orientation was maintained irrespective of the loading condition. In microgravity, regardless of loading conditions the same (but different from the normogravity) orientation of the upper body was achieved through different joint organizations: two joints (the hip and ankle joints of the supporting leg) in the asymmetrical loading condition, and one (hip) in the symmetrical loading condition. In order to determine whether the different orientations of the inertia tensor were perceived during the movement, the interjoint coordination was quantified by performing a principal components analysis (PCA) on the supporting and moving hips and on the supporting ankle joints. It was expected that different loading conditions would modify the principal component of the PCA. In normogravity, asymmetrical loading decreased the coupling between joints, while in microgravity a strong coupling was preserved whatever the loading condition. It was concluded that the trunk inertia tensor did not play a role during the lateral leg raising task because in spite of the absence of gravitational torque the final upper body orientation and the interjoint coupling were not influenced.

The Influence of Child Protection Orientation on Child Welfare Practice

This article reports the findings of the second part of a two-part research project examining the potential for social workers to make changes in their work with families and children. While social workers in the United Kingdom have been encouraged to shift from a child protection to a child welfare orientation in their practice, such changes have been hampered by professional and organisational concern to manage risk. The research explores the influence of a child protection orientation on practice in child welfare cases. The findings, from two file analyses and interviews with twenty-six social workers, indicate that such an influence is indeed apparent. This is evidenced in two ways; firstly patterns of practice in child welfare cases are similar to those in child protection cases. Secondly, while the majority of social workers express an attitudinal desire to move towards a child welfare orientation, they still prioritise the management of risk in their practice. It is argued that social workers need permission from their employing organisations to make changes in their practice. This, in turn, requires such organisations to state clear goals in line with a child welfare orientation and develop holistic strategies to achieve these.

Effects of tip structure on the generation of metal clusters by an STM tip: a way to control the orientation of nanocrystallites?

The role of the crystalline orientation of the STM tip in the generation of metal clusters is studied by atom dynamics simulations. When a (111) facet is facing the surface, the process is accompanied by a perturbation of the surface stronger than that observed for more open tip structures. This implies a technological application: the possibility of orienting a nanocrystallite deposited on a tip according to the changes observed in the force on the tip.