Martin Ames Harrison

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We have developed a three-channel ambulatory esophageal pressure monitor and tested it with a series of 24-h studies. The monitor is a battery-operated, microprocessor-based device that measures pressures from three transducers positioned in the esophagus, stores the data in its memory, and transfers the data to an IBM PC computer system at the end of the(More)
Quadratic Convexity and Sums of Squares Martin Ames Harrison The length of a sum of squares σ in a ring R is the smallest natural k such that σ can be realized as a sum of k squares in R. For a set S ⊆ R, the pythagoras number of S, denoted by P(S), is the maximum value of length over all σ ∈ S. This dissertation is motivated by the following simple(More)
In a retrospective study problem orientated physiotherapy records were examined on 156 consecutive stroke patients admitted to medical wards and referred to the physiotherapy department. The purpose of the study was to identify from the problem lists those problems physiotherapists are dealing with in stroke care. There were 1338 problems recorded, and(More)
The Helton-Nie Conjecture (HNC) is the proposition that every convex semialgebraic set is a spectrahedral shadow. Here we prove that HNC is equivalent to another proposition related to quadratically constrained quadratic programming. Namely, that the convex hull of the rank-one elements of any spectrahedron is a spectrahedral shadow. In the case of compact(More)