Acoustic surface wave generation over rigid cylinder arrays on a rigid plane.

Propagation of an airborne acoustic pulse from a point source above an array of regularly spaced rigid cylinders on a rigid plane has been investigated using a two-dimensional multiple scattering theory. Time domain simulations show a main arrival and a separate delayed "tail." Fourier analysis of the tail shows that, for a sufficiently sparse array of cylinders, it is composed of a series of spectral peaks resulting from constructive interference consistent with Bragg diffraction theory and amplitudes depending on the spacing and size of the cylinders.

Cross- and auto-correlation in early vision.

Neurons that respond selectively to the orientation of visual stimuli were discovered in V1 more than 50 years ago, but it is still not fully understood how or why this is brought about. We report experiments planned to show whether human observers use cross-correlation or auto-correlation to detect oriented streaks in arrays of randomly positioned dots, expecting that this would help us to understand what David Marr called the 'computational goal' of V1. The streaks were generated by two different methods: either by sinusoidal spatial modulation of the local mean dot density, or by introducing coherent pairs of dots to create moiré patterns, as Leon Glass did.

Precipitated egg white as a sealant for iatrogenic preterm premature rupture of the membranes.

Objective: The objective of the study was to investigate whether precipitated egg white could be used as a sealant for iatrogenic injury to fetal membranes.

Study Design: Membranes were collected, washed, and affixed to the bottom of glass cylinders filled with second-trimester amniotic fluid. An iatrogenic defect with an 8-gauge needle was created in the test column, and precipitated egg white was added.