Effects of image scale and system time delay on simulator sickness within head-coupled virtual environments.

Novel patterns of visual-vestibular intersensory stimulation often result in symptoms of simulator sickness, raising health and safety concerns regarding virtual environment exposure. Two experiments investigated the effect of conflicting visual-vestibular cues on subjective reports of simulator sickness during and after a 50-min exposure to a head-coupled virtual interface. Virtual image scale factors (0.5. 1.0, 2.0 magnification, generated by varying geometric field of view angle) were investigated in Experiment 1, and additional system time delays (125, 250 ms) were investigated in Experiment 2. Simulator sickness metrics included spoken self-reports during exposure and simulator sickness questionnaires (pre-exposure, immediate postexposure, and 20 min postexposure). Head yaw angular position data were also recorded. Reports of simulator sickness symptoms were significantly greater in the minification (0.5) and magnification (2.0) image scale factor conditions than in the neutral condition (1.0). Simulator sickness did not vary with changes in time delay, however. Furthermore, a comparison across experiments suggests no appreciable increase in simulator sickness with increasing time delays above the nominal value (48 ms). Head angular position data exhibited certain systematic variations across conditions. Actual or potential applications of this research include virtual environment training, simulation, and entertainment systems.

The use of an independent visual background to reduce simulator side-effects.

BACKGROUND: Simulator sickness (SS) is a major problem which potentially limits interface applications that feature simulated motion. While display imperfections play a role, a large part of SS is motion sickness (MS). Sensory rearrangement theory holds that MS is related to conflicting motion cues; in the case of simulators, mainly a conflict between inertial cues (usually indicating no self-motion) and visual stimuli from the display (indicating self-motion). It is suggested that MS does not arise from conflicting motion cues per se, but rather from conflicting rest frames selected from those motion cues. There is strong evidence that the visual rest frame is heavily influenced by the visual background. Providing an independent visual background (IVB) consistent with the inertial rest frame may reduce SS, even when the simulator's content-of-interest (CI) is not consistent with the inertial rest frame. METHODS: In two experiments, a circular vection stimulus was shown for 3-4.5 min in a head-mounted display, comparing see-through (i.e., IVB) to occluded (i.e., no IVB) modes. Measures included a standard SS questionnaire and a pre-exposure ataxia measure. Experiment 2 added a visual task which forced attention into the CI and a post-exposure ataxia measure. In both experiments, subjects rated the CI as significantly more visible than the IVB. RESULTS: A large effect was found for the reduction of SS and ataxia in the first experiment, and for pre-exposure ataxia in the second. CONCLUSIONS: Future research will further test the IVB idea and examine applications to high-end simulators.

Analysis of nickel refinery dusts.

After characterization of bulk samples by inductively coupled plasma emission spectroscopic (ICP-ES) quantitative analysis and X-ray powder diffraction studies, single particle techniques using quantitative image analysis, scanning electron microscopy--energy dispersive analysis by X-ray, and finally laser beam ionization mass spectrometry analysis (LIMA) for surface analysis have been applied to historical nickel refinery dust samples from the nickel refining plant at Clydach in Wales. There were two historical samples of processed material from 1920 and 1929. These samples had a remarkably small particle size range, mean 3 microns and range, 0.75-24 microns. The most significant difference in elemental composition was the presence of 10% arsenic in the 1920 sample compared with 1% in the 1929 sample. The X-ray spectra revealed the presence of NiO in both. However, surprisingly, CuO was identified only in the 1929 sample. Of particular interest was the presence of a component, in the 1920 sample only, identified as the mineral orcelite, a copper-iron-nickel-arsenide-sulphide mineral, predominantly, Ni5-XAs2. Using the LIMA technique, it was found that in both samples, arsenic and arsenic derivative peaks are prominent, indicating the surface availability of arsenic compounds.

Variation among individual White-Leghorn hens in the concentration of minerals in the albumen and yolk content of their eggs.

1. The mineral composition of the albumen and yolk was determined in several eggs from each of a number of individual hens from the same White-Leghorn strain. X-ray fluorescent spectrometry was used to undertake two independent series of analyses. A total of 8 minerals (calcium, chlorine, iron, magnesium, phosphorus, potassium, sodium, sulphur) were included in the analyses of the yolk and the same minerals, but excluding iron (which is present in only small amounts), in the albumen. 2. There was considerable variation between individuals in the mineral concentration in their eggs (coefficients of variation ranged between 3.8% for sodium to 19.9% for calcium in the albumen, and between 4.3% for phosphorus to 11.8% for iron in the yolk). 3. At the same time, the moderately high repeatability of mineral concentration (t = 0.4-0.6) in successive eggs from the same hen for several of the minerals analysed is indicative of some positive control by the hen of the mineral composition of her eggs. 4. There was a highly significant correlation (P < or = 0.001) between the mean concentration of potassium in the albumen and the hatchability of the eggs, supporting the claim that a deficiency of potassium in the egg could be the basis of some failures in hatchability. 5. The study also revealed variation among individual birds in the concentration of iron in the yolk which was negatively correlated (P < or = 0.01) with hatchability. No clear basis could be suggested for this variation among individual birds.

Draft guidelines on mutagenicity testing of new drugs issued by the CPMP. A four test screen.

In 1977 the Committee on Proprietory Medicinal Products (CPMP) decided that in order to further the harmonisation of data requirement required for marketing authorization an expert working party should be set up to draw up safety guidelines. Amongst other guidelines produced for the CPMP has been one on mutagenicity which has been issued as a consultative document. This paper outlines the philosophy underlying the working party's recommendations that a "four-test screen" comprising of a bacterial test, an in vitro test to determine chromosome breakage in mammalian cells, a test to demonstrate gene damage in vitro in mammalian cells, and finally a mammalian in vivo test to demonstrate chromosomal damage in proliferating tissue (bone marrow). It is not suggested that other tests are less suitable or that evidence from other tests would not be acceptable as alternatives to part of the package. However in these circumstances the use of the alternative may need to be justified. No single test can at the present time be accepted as a sufficient screen to investigate all possible mechanisms by which genetic damage can be produced. The four-test system greatly improves the probability of demonstrating any mutagenic hazard.