Film supertwisted nematic liquid crystal displays (F-STN-LCDs) with a single birefringent plastic film can be used for monochromatic black-and-white (B/W) LCDs, but their contrast ratio is inferior to that of Double layered (D-)STN-LCDs. By measuring the wavelength dependence of the ellipticity and azimuth in STN-LCDs, the F-STN cell conditions which increase the contrast ratio are obtained. The incident linearly polarized light needs to pass through the STN-LCDs without changing the state of its polarized light in all wavelength regions. Accordingly an optical compensating layer which has the same wavelength dependence for the ellipticity and azimuth as the driving STN cell, must be positioned between the polarizer and the driving STN cell. By laminating two birefringent films with different optical axes, the optical activity caused by the liquid crystal's twist structure is canceled, and the contrast ratio of the F-STN-LCDs increases from 10:1 to 20:1.

No abstract

We calculate resummed perturbative predictions for gaps-between-jets processes and compare to HERA data. Our calculation of this non-global observable needs to include the effects of primary gluon emission (global logarithms) and secondary gluon emission (non-global logarithms) to be correct at the leading logarithm (LL) level. We include primary emission by calculating anomalous dimension matrices for the geometry of the specific event definitions and estimate the effect of non-global logarithms in the large N c limit. The resulting predictions for energy flow observables are consistent with experimental data.

We report on pump-probe measurements of vibrational decay times for the H − (X, Y) and Z local modes of CaF 2 :Lu 3+ C 4v H − centres using the Dutch free-electron laser. For excitation of the (X, Y) mode, a 10 K lifetime of 43 picoseconds is measured and is attributable to three-phonon anharmonic relaxation, which accounts well for the temperature dependence of the decay rate. The 10 K lifetime of the higher-energy Z mode results from a combination of one-phonon decay to the (X, Y) modes and three-phonon decay to the ground state. A simple rate equation model gives a good account of the observed transient.

No abstract