Abstract. The properties of multi-peaked "fitness landscapes" have attracted attention in a wide variety of fields, including evolutionary biology. However, relatively little attention has been paid to the properties of the landscapes themselves. Herein, we suggest a framework for the mathematical treatment of such landscapes, including an explicit mathematical model. A central role in this discussion is played by the autocorrelation of fitnesses obtained from a random walk on the landscape. Our ideas about average autocorrelations allow us to formulate a condition (satisfied by a wide class of landscapes we call AR(1) landscapes) under which the average autocorrelation approximates a decaying exponential. We then show how our mathematical model can be used to estimate both the globally optimal fitnesses of AR(1) landscapes and their local structure. We illustrate some aspects of our method with computer experiments based on a single family of landscapes (Kauffman's "N-k model"), that is shown to be a generic AR(I) landscape. We close by discussing how these ideas might be useful in the "tuning" of combinatorial optimization algorithms, and in modelling in the experimental sciences.

Phased-array coils distribute the high signal-to-noise ratio (SNR) performance of their small component surface coils over the larger area covered by the entire array. The inhomogeneous sensitivity profiles of the component surface coils result in images with very high signal near the phased-array and decreased signal far from the array. This paper presents a postprocessing algorithm for correcting these coil-related intensity variations. The algorithm's performance was evaluated by correcting images of volunteers acquired with several different receive-only phased-array surface coils.

No abstract

High inspired oxygen fraction during anesthesia is associated with CSF hyperintensity in the basilar cisterns and the cerebral sulcal subarachnoid space on FLAIR imaging in children and young adults. Physicians should be aware of this finding to avoid misinterpreting this artifact as an abnormality.

No abstract

Sonography of the lambdoid sutures shows excellent preliminary promise as a screening test of lambdoid sutural patency.

No abstract

No abstract