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The basic science underlying the process of bone healing has been a topic of intense research activity over the past 50 years. Increasing understanding of events on a molecular level has allowed a greater understanding of factors that might contribute to failure of these mechanisms. From this it has been possible to introduce new treatment methods as adjuncts to traditional methods, both for fresh fractures and for established non-unions. Knowledge of these topics is essential to the day to day practice of the majority of orthopaedic consultants and as such is a favourite topic of examiners in both basic surgical and specialist orthopaedic examinations. The first half of this article summarizes current understanding of the biology of bone healing, highlighting recent advances. The second part is an overview of the aetiology and management of non-union.

The authors have previously proposed a simplified method for the design of external beam±column joints. This paper extends that work to joints in which one of the beams is eccentric to the column. Such connections occur in practice owing to architectural and geometrical constraints. Results are presented for tests on ten specimens in which one of the two beams framing into the column was eccentric to the column. The authors are unaware of any previous tests on such specimens. The tests were designed to investigate the effects of eccentricity and reinforcement detailing on connection strength, cracking and deformation. The tests showed that such connections can be used in practice providing that the torsional capacity of the joint is not exceeded. An analytical model is developed for predicting the strength of such connections and preliminary design recommendations are made. The work is also relevant to the case of joints where the beam is wider than the column. internal; e, external; T, torsion; V, shear due to P e P c load on concentric beam P c0 maximum possible value of P c when P e 0 P e load on eccentric beam P e0 maximum possible value of P e when P c 0 T torsion T 0 maximum possible torsional strength of concentric beam T beam tensile force in beam reinforcement T clo tensile force in closing stirrup T col resultant force in leg 1 (see Fig. 2(b)) of column stirrups at top and bottom of joint t i thickness of wall i t max maximum permissible thickness of wall i U external perimeter of cross-section V c joint shear strength without stirrups V col shear force in column V i T shear force induced in wall i by torsion V j joint shear force V j0 uniaxial joint shear strength V jc joint shear force due to P c at joint shear failure V je joint shear force due to P e at joint shear failure Notation

A prototype supervisory control system for a remotely operated vehicle (ROV) is described and several key elements demonstrated in simulation and in-water tests.This system is specifically designed to fill the needs of JASON, a new ROV under development that will perform scientific tasks on the seafloor to depths of 6000 m. JASON will operate from the ARGO towed imaging platform, which is currently operational.Supervisory control is a paradigm for combined human and computer control. Several key elements of the supervisory control system are presented. These include the closed-loop positioning system based on a high-resolution acoustic navigation system, a monitoring capability for assessing performance and detecting undesirable changes, and an interface that allows the human operator and the computer system to specify the desired vehicle trajectory jointly.

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