AbstractImplementation of a novel experimental approach using a bright source of narrowband x-ray emission has enabled the production of a photoionized argon plasma of relevance to astrophysical modelling codes such as Cloudy. We present results showing that the photoionization parameter ζ = 4πF/ne generated using the VULCAN laser was ≈ 50 erg cm s−1, higher than those obtained previously with more powerful facilities. Comparison of our argon emission-line spectra in the 4.15 - 4.25 Å range at varying initial gas pressures with predictions from the Cloudy code and a simple time-dependent code are also presented. Finally we briefly discuss how this proof-of-principle experiment may be scaled to larger facilities such as ORION to produce the closest laboratory analogue to a photoionized plasma.
Kinneyia are a class of microbially mediated sedimentary fossils. Characterized by clearly defined ripple structures, Kinneyia are generally found in areas that were formally littoral habitats and covered by microbial mats. To date, there has been no conclusive explanation of the processes involved in the formation of these fossils. Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin–Helmholtz-type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time. Theoretical predictions show that the ripple instability has a wavelength proportional to the thickness of the film. Experiments carried out using viscoelastic films confirm this prediction. The ripple pattern that forms has a wavelength roughly three times the thickness of the film. This behaviour is independent of the viscosity of the film and the flow conditions. Laboratory-analogue Kinneyia were formed via the sedimentation of glass beads, which preferentially deposit in the troughs of the ripples. Well-ordered patterns form, with both honeycomb-like and parallel ridges being observed, depending on the flow speed. These patterns correspond well with those found in Kinneyia, with similar morphologies, wavelengths and amplitudes being observed.
During surface-underground combined mining, the method to control the ground air leakage is adopted by the capping layer using the fragmented rocks and the discarded tailings. In order to study the air leakage characteristic with the capping, the porosity of the rock particles of seven sizes and the air leakage characteristics of the capping were studied and the relationship between the air leakage coefficient and amount of air leakage with the capping height were found basing on the laboratory analogue simulation tests. It can provide the theoretical basis for determining the capping height of iron mine.
Within the context of a balanced factorial design, white college students (40 males, 40 females) individually viewed a videotape of a black or white, male or female, financially needy “cohort” performing an alphanumeric substitution task, and were instructed to award money for performance, which was identical in all conditions. Female Ss awarded more money than male Ss, but males were given as much money as females, and blacks were given as much as whites. Results were compared to field studies of the relation of race and sex to helping behavior.
Acute effects of low and high dose alcohol on smoking lapse behavior in a laboratory analogue task