  The onset of structural arrest and glass formation in a concentrated
suspension of silica nanoparticles in a water-lutidine binary mixture near its
consolute point is studied by exploiting the near-critical fluid degrees of
freedom to control the strength of an attraction between particles and
multispeckle x-ray photon correlation spectroscopy to determine the particles'
collective dynamics. This model system undergoes a glass transition both on
cooling and on heating, and the intermediate liquid realizes unusual
logarithmic relaxations. How vitrification occurs for the two different glass
transitions is characterized in detail and comparisons are drawn to recent
theoretical predictions for glass formation in systems with attractive
interactions.
