Answer to Question 1
The ring particles of Uranus do not last forever as they collide with each other and are exposed to radiation. The rings may be resupplied with fresh particles occasionally as impacts on icy moons scatter icy debris.
Collisions among the large particles in the ring produce small dust grains. Friction with
Uranus's tenuous upper atmosphere plus sunlight pressure act to slow the dust grains
and make them fall into the planet. The Uranian rings actually contain very little dust.
Answer to Question 2
Uranus rotates on an axis that is tipped 97.8 degrees from the perpendicular to its orbit, so its seasons are extreme. When one of its poles is pointed toward the Sun (a solstice), one would see the Sun above celestial pole, and it would never rise or set. As it orbits the Sun, the planet maintains the direction of its axis in space, and thus moves from pole to pole. At the time of an equinox on Uranus, the Sun would be on the celestial equator and would rise and set with each rotation of the planet. Since it takes 87 years for Uranus to orbit the Sun, each season would last approximately 20+ years.
Germ plasm and primordial germ cells (PGC) during gastrulation.
Heme consists of a complex organic ring structure, protoporphyrin
Size comparison of Earth and Uranus
The F Ring and One of Its Shepherds
Beta-lactam antibiotics: The beta-lactam ring is common to many different classes of antibiotics.
Size of Particles