Wave directional spreading from point field measurements.

Ocean waves have multidirectional components. Most wave measurements are taken at a single point, and so fail to capture information about the relative directions of the wave components directly. Conventional means of directional estimation require a minimum of three concurrent time series of measurements at different spatial locations in order to derive information on local directional wave spreading. Here, the relationship between wave nonlinearity and directionality is utilized to estimate local spreading without the need for multiple concurrent measurements, following Adcock & Taylor (Adcock & Taylor 2009 Proc. R. Soc. A465, 3361-3381. (doi:10.1098/rspa.2009.0031)), with the assumption that directional spreading is frequency independent. The method is applied to measurements recorded at the North Alwyn platform in the northern North Sea, and the results compared against estimates of wave spreading by conventional measurement methods and hindcast data. Records containing freak waves were excluded. It is found that the method provides accurate estimates of wave spreading over a range of conditions experienced at North Alwyn, despite the noisy chaotic signals that characterize such ocean wave data. The results provide further confirmation that Adcock and Taylor's method is applicable to metocean data and has considerable future promise as a technique to recover estimates of wave spreading from single point wave measurement devices.

Time for an ecosystem approach to public health? Lessons from two infectious disease outbreaks in Canada.

Ecosystem approaches recognize the complexity of many contemporary public health challenges and offer an alternative for dealing with problems that have proven intractable and unresponsive to conventional public health strategies. Infectious disease outbreaks are among the most dramatic aspects of systems failure, and the Canadian cases of SARS (Severe Acute Respiratory Syndrome) in Toronto, and the E. coli outbreak in Walkerton, serve as useful illustrative examples. This paper examines some of the limitations of current public health approaches, the fundamental tenets of an alternative, transdisciplinary ecosystem approach, and changes necessary for implementation, including those in philosophical approach, communications and education, and, finally, institutions and governance.

Application of stereolithography to subperiosteal implant manufacture.

Subperiosteal implants are an accepted and proven technique with a good long-term outcome. Although a technique of computed tomography to computer-assisted machining became available to drop the number of surgeries to one for ascertainment of bone topography, the problem of accurate bone modeling remains an issue. The advent of stereolithography as a new tool for modeling anatomy for subperiosteal implants and the advances in computed tomography offer a higher degree of build accuracy and repeatability than available before.