We present the refinement of the crystal structure of charge-ordered LuFe2O4, based on single-crystal x-ray diffraction data. The arrangement of the different Fe-valence states, determined with bond-valence-sum analysis, corresponds to a stacking of charged Fe bilayers, in contrast with the polar bilayers previously suggested. This arrangement is supported by an analysis of x-ray magnetic circular dichroism spectra, which also evidences a strong charge-spin coupling. The nonpolar bilayers are inconsistent with charge order based ferroelectricity.

Abstract-This paper introduces a new text input device called the chording glove. The keys of a chord keyboard are mounted on the fingers of a glove. A chord can be made by pressing the fingers against any surface. Shift buttons placed on the index finger enable the glove to enter the full ASCII character set. The chording glove is designed as a text input device for wearable computers and virtual environments. An experiment was conducted to assess the performance of the glove. After an average of 80 min of a tutorial, ten subjects reached a continuous text input speed of 8:9 6 6 6 1:4 words/min, and after 10 1-hr sessions, they achieved 16:8 6 6 6 2:5 words/min.

Two one-dimensional (1D) single-crystalline gallium nitride (GaN) nanostructures with periodic zigzag (type I) and diameter-modulated (type II) shapes have been synthesized by passing through ammonia over a mixture of gallium and gallium oxide (Ga2O3) powders held at elevated temperature. The process was catalyzed by the dispersion of thio-capped Au nanoparticles on the substrate onto which GaN nanostructures were condensed. The transformation between these two nanostructure morphologies was also observed. A possible growth model for the zigzag-shaped nanostructures is proposed, in which the formation of the zigzag nanostructures results from the construction of two different nanoscale unit cells. This work provides an avenue to a group of 1D nanostructures with a zigzag shape. The possibility to form 1D nanostructures yet to be discovered by changing the stacking direction of the (0001) plane will facilitate the fabrication of nanoscale functional devices as well as our understanding of the growth behavior of nanoscale crystallites.

The synchrotron radiation (SR) induced, vacuum ultraviolet (vacuum UV) photodegradation of polystyrene was studied by fluorescence spectroscopy. Two broad, structureless transitions were observed in the dispersed fluorescence spectrum of polystyrene when wavelengths shorter than 2200 Á were used to excite the polymer films: the first was centered at 3200 Á, and the second was centered at 5300 Á. The fluorescence excitation spectrum of each emission band has been recorded from 450 to 3000 Á and is compared to the optical absorption spectrum of polystyrene from 1050 to 3000 Á. The 3200-Á band is due to an excimer to ground state transition. The 5300-Á band is due to fluorescence from a conjugated backbone structure which forms when the polystyrene films are exposed to vacuum UV radiation. Changes were observed in both the fluorescence and fluorescence excitation spectra following exposure to 1200-Á or broad-band SR. Based on the data, a qualitative model is used to account for the degradation and energy transfer within the polystyrene films.

The Biofeedback Pointer is a graphic input device controlled by wrist motion. Moving the wrist causes the pointer to move in that direction. The pointer detects the electromyograms of four of the muscles used to move the wrist. These are interpreted by a neural network which is trained for each user. The network takes about half a minute to train. The Biofeedback Pointer was found to perform 14% as well as the mouse in simple pointing tasks, which is about half of the lowest performance of a common graphic input device. Using a more sophisticated neural network or better training may improve the device to a more comparable level.