Gray

The gray (symbolized Gy) is the standard unit of absorbed ionizing-radiation dose, equivalent to one joule per kilogram (1 J · kg-1). Reduced to base units in the International System of Units (SI), 1 Gy is equivalent to one meter squared per second squared (1 m2 · s-2).
In general, ionizing-radiation dose is the amount of X-ray, gamma-ray, or high-speed-particle energy absorbed per unit mass. The gray supersedes the rad, an older unit of radiation dose. In some documents the rad is still used; the gray is 100 times larger. To convert rads to grays, multiply by 0.01. To convert grays to rads, multiply by 100.

Also see gray per second, sievert, International System of Units

Stack
In programming, a stack is a data area or buffer used for storing requests that need to be handled. The IBM Dictionary of Computing says that a stack is always a push-down list, meaning that as new requests come in, they push down the old ones. Another way of looking at a push-down list - or stack - is that the program always takes its next item to handle from the top of the stack. (This is unlike other arrangements such as "FIFO" or "first-in first-out.")

Hope this helps, although I´m not so sure about the translation.