In the recent article by Tamai et al. (Current Biology 14, pp. R104-R105), there is a typographical error for the units of light intensity in the second paragraph. The actual intensity of white light used in these experiments should read 500 microWatts/cm 2 (500 ␮Watts/cm 2), not 500 milliWatts/cm 2 (500 mWatts/cm 2).

We tend to perceive and emphasize the transition from Late Antiquity Early Middle Ages, especially in North Africa, through ruptures changes. This collection of papers highlights, alongside major changes transformations that affected entire Mediterranean region, longer-term processes developments Africa between AD 500 1000. In this time frame, region is shaped by Vandal, Byzantine Arab conquest...

0 7 4 0 7 4 5 9 / 0 1 / $ 1 0 . 0 0 © 2 0 0 1 I E E E problem; this impediment became known as the 500-Language Problem. In 1998, we realized that we had discovered a breakthrough in solving the 500LP— so we had something to offer regarding the Y2K problem. We immediately informed all the relevant Y2K solution providers and people concerned with the Y2K awareness campaign. In answer to our emai...