Flow birefringence in gaseous mixtures

In an earlier paper, an alignment of the rotational angular momenta of gas molecules produced by a gradient in the stream velocity has been shown to cause a measurable birefringence in the gas. The present paper reports an extension of these measurements to mixtures, specifically N₂ and HD with He, Ne and Ar. The concentration dependence found in these experiments can be well interpreted in terms of a kinetic theory, based on the Waldmann-Snider equation, employing data obtained from other experiments, such as the Senftleben-Beenakker effect and depolarized Rayleigh scattering.     

On finite-difference approximations and entropy conditions for shocks

Weak solutions of hyperbolic conservation laws are not uniquely determined by their initial values; an entropy condition is needed to pick out the physically relevant solution. The question arises whether finite-difference approximations converge to this particular solution. It is shown in this paper that tin the case of a single conservation law, monotone schemes, when convergent, always converge to the physically relevant solution. Numerical examples show that this is not always the case with non-monotone schemes, such as the Lax-Wendroff scheme.     

Demonstration of a mode-conversion cavity add-drop filter

We experimentally demonstrate a new type of add-drop filter incorporating an asymmetric Y-branch waveguide coupler and a shifted-grating mode-conversion cavity. The device relies on mode separation in the asymmetric Y-branch and wavelength-selective mode conversion upon reflection from the shifted-grating cavity. Add-drop functionality is demonstrated in a three-port integrated silicon-on-insulator device.     

Two-particle rapidity correlations in 205 GeV/c pp interactions

Using data obtained from an exposure of the 30-inch bubble chamber at NAL, inclusive and semi-inclusive two-particle rapidity correlations are analyzed for charged-charged, ??, ++, and ± particles. For the inclusive sample, positive correlations are observed in the central region. In the semi-inclusive case, the four-and six-prong events exhibit strong positive correlations near 90° CM. Selection of four-prong events with a large rapidity gap shows that the strong correlation seems to be associated with diffractive-type events.     

The martingales of an independent increment process

A simple proof is given of the representation of martingales adapted to the sigma fields of a process with stationary, independent increments.