What does "from concentrate" mean?

The words "from concentrate" often appear on juice labels. If a juice is made from concentrate, then the water in the originally squeezed juice is extracted to allow for easier and cheaper shipping. Once the more concentrated juice reaches its destination, water is then added to create the drink that appears in grocery stores. The nutritional value is the same whether a drink is from concentrate or not, but many find that juices "not from concentrate" carry a more authentic, preferable taste.

How do auto-dimming car mirrors work?

Auto-dimming mirrors take advantage of modern electrochromic technology. Electrochromic materials are those that change color when an electrical charge is supplied. Each mirror has electrochromic gel between two pieces of glass and is equipped with sensors that detect the intensity of glare from trailing cars' headlights. Based on the level of glare, an electrical charge is released from a battery source, causing the gel to darken and the glass to be effectively tinted. The darkening of the gel is commensurate with the intensity of glare detected, thus allowing the driver to see well through the rearview mirror.

Why is there no E grade in the grading scale?

The numerical grading system dates back to 1792 when William Farish, a tutor at University of Cambridge, developed the system to combat the seeming bias in oral examination grades. His system, as well as a number of other grading methods (e.g. ESNU, I/Y, I/II/III/IV/V, etc.), became a primary focus of educational systems throughout the nineteenth century; various grading systems became the subject of experimentation, and a refined system did not appear until the twentieth century when enrollment in school soared.

The letter-based system used today in many primary, secondary, and post-secondary schools was first used at Mount Holyoke College in 1897, with the exception that it used an E rather than F. Despite Mount Holyoke having the first complete A-E system, Harvard allegedly handed out a B grade in 1883. The letter-based grading scale at Mount Holyoke worked by assigning each letter a numerical range (e.g. A being 90-100), with E representing failure. Eventually, as the A-E grading scale became more popular, the E was dropped and replaced by an F because the letter F more logically denotes failure. The other letters in the system, A, B, C, and D, represent the four possible passing grades.