A new set of high speed matrix addressing schemes for ferroelectric liquid crystal displays

A new set of matrix addressing schemes for ferroelectric liquid crystal displays is reported. The schemes use the minimum in the response time-voltage characteristic found in certain mixtures and deliver improved operating speed and contrast ratio compared with previously reported schemes operating in this mode.     

The magnetizability of excited-state hydrogen: temperature-independent paramagnetism in the B1Σ+u state

Components, of the magnetizability tensor for the B¹Σ⁺_u and a ³Σ⁺_g states ot the hydrogen molecule have been calculated for fixed bond lengths near equilibrium. Explicitly correlated “generalised James-Coolidge” type wavefunctions were used. It is found thilt in the B 1Σ⁺_u state the molecular magnetizability is a positive quantity.     

Framework Effects on Activation and Functionalisation of Methane in Zinc-Exchanged Zeolites

The first selective oxidation of methane to methanol is reported herein for zinc-exchanged MOR (Zn/MOR). Under identical conditions, Zn/FER and Zn/ZSM-5 both form zinc formate and methanol. Selective methane activation to form [Zn-CH₃]⁺ species was confirmed by ¹³C MAS NMR spectroscopy for all three frameworks. The percentage of active zinc sites, measured through quantitative NMR spectroscopy studies, varied with the zeolite framework and was found to be ZSM-5 (5.7 %), MOR (1.2 %) and FER (0.5 %). For Zn/MOR, two signals were observed in the ¹³C MAS NMR spectrum, resulting from two distinct [Zn-CH₃]⁺ species present in the 12 MR and 8 MR side pockets, as supported by additional NMR experiments. The observed products of oxidation of the [Zn-CH₃]⁺ species are shown to depend on the zeolite framework type and the oxidative conditions used. These results lay the foundation for developing structure–function correlations for methane conversion over zinc-exchanged zeolites.     

A note on the magnetic susceptibility of hydrogen and its isotopomers

A wavefunction used in an earlier calculation of the nuclear shielding of the hydrogen molecule has been tested by comparing the calculated magnetic susceptibility against that of Kolos and Wolniewicz. Good agreement is obtained. The procedure of Herman and Short for averaging over the nuclear motion has also been tested by comparing the predicted susceptibilities of H₂, Hd and D₂ with those obtained from averages of the Rydberg-Klein-Rees potential curves by Jain and Sahni. Again, good agreement is found.For the first time calculated values have been obtained for the susceptibilities of the isoropomers of hydrogen which contain tritium. It is predicted that accurate susceptibility measurements should not only be able to distinguish between all the various isotopomers but should also detect the temperature dependence of the susceptibility of any one isotopomer.     

PRELIMINARY COMMUNICATIONS A novel alignment technique for ferroelectric smectics

Until now a major problem in achieving practical ferroelectric displays has been the lack of a suitable technique for producing uniform alignment over large areas. This preliminary communication reports a novel alignment technique which utilizes mixtures with extended cholesteric pitches and has been found to give excellent alignment of ferroelectric smectics using the standard surface treatments employed in the nematic display industry.     

Medium effects on the fluorine chemical shifts of non-polar molecules in liquids

The gas-to-infinite dilution fluorine chemical shifts of CF₄, SiF₄, SF₆, C₆F₆, p-fluorotoluene and p-difluorobenzene have been measured for a series of non-polar solvents. Downfield displacements ranging from 3–16 p.p.m. have been observed. Comparisons with proton solvent shifts make it evident that the London dispersion forces are the principal agent in causing the shifts. However, unlike proton resonance where the local diamagnetic shielding is mostly affected, it is probably through the local paramagnetic shielding that solvents alter fluorine chemical shifts.