As far as the tile roofs, they last a long time. It isn't the tile that is the issue, it's the felt (or paper) underneath that gets replaced. Mine is 25 years old, has not been replaced yet. Some neighbors have had theirs redone, but many have not as yet. 04-06-2011, 12:00 AM.
Particle Accelerators Could Be Used to Produce Energy (and Plutonium) Particle accelerators, which are not renowned for their real-world applications, could in fact be used to produce energy, according to a 34-year-old research paper that resurfaced this week.
Aerosol particle counters are used to determine the air quality by counting and sizing the number of particles in the air. This information is useful in determining the amount of particles inside a building or in the ambient air. It also is useful in understanding the cleanliness level in a controlled environment. high intensity light source is used to illuminate the particle as it passes through the detection chamber. The particle passes through the light source (typically a laser or halogen light) and if light scattering is used, then the redirected light is detected by a photo detector.