Given a projective plane Σ and a polarity θ of Σ, the corresponding polarity graph is the graph whose vertices are the points of Σ, and two distinct points p1 and p2 are adjacent if p1 is incident to p θ 2 in Σ. A well-known example of a polarity graph is the Erdős-Rényi orthogonal polarity graph ERq, which appears frequently in a variety of extremal problems. Eigenvalue methods provide an uppe...

To study lipid interference in steroid radioimmunoassays in which dextran-coated charcoal is used as the separating agent, we tested triolein and phosphatidylcholine as model hydrophobic and amphipathic lipids, respectively. Addition of either caused distortion of the standard curve to an extent that was inversely related to the polarity of the steroid molecule. Both lipids form a dispersion th...