Emission of photon echoes in a strongly scattering medium.

We observe the two- and three-pulse photon echo emission from a scattering powder, obtained by grinding a Pr3+:Y2SiO5 rare earth doped single crystal. We show that the collective emission is coherently constructed over several grains. A well defined atomic coherence can therefore be created between randomly placed particles.

A vascular permeability factor in lymphocyte culture supernants from patients with nephrotic syndrome. II. Pharmacological and physicochemical properties.

Pharmacological properties of the "Skin Reactive Factor" demonstrated in nephrotic patients are similar to guinea-pig Skin Reactive Factor. This biological activity is not antagonized by anti-histaminic and anti-serotonin drugs. It is inhibited by meclofenamate and pyridinolcanbamate.