Introduction | Bibliography

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:zebra stripes (p1) A stable agar consisting of alternating bands of live and dead cells. Known spacefillers and many gray ships create patches of this agar. It is also the medium through which with the grain and against the grain negative spaceships travel. Many simple stabilizations of the boundaries of finite regions of this agar are known, as shown below.

    ..OO.......................
    ..O........................
    ....O..O..O..O..O..O..O....
    ...OOOOOOOOOOOOOOOOOOOO....
    ..O........................
    ...OOOOOOOOOOOOOOOOOO......
    .....................O.....
    .OOOOOOOOOOOOOOOOOOOO......
    O..........................
    .OOOOOOOOOOOOOOOOOOOOOO....
    .......................O.OO
    .OOOOOOOOOOOOOOOOOOOO..O.OO
    O....................O.O...
    .OOOOOOOOOOOOOOOOOOOO..O...
    .......................OO..
    ...OOOOOOOOOOOOOOOOOO......
    ..O..................O.....
    ...OOOOOOOOOOOOOOOOOO......
    ...........................
    .....OO..OO.O.OOOO.OO......
    .....OO..O.OO.O..O.OO......

:Z-hexomino The following hexomino. The Z-hexomino features in the pentoad, and also in Achim's p144.

    OO.
    .O.
    .O.
    .OO

:zone of influence The set of cells on which a chosen cell or pattern can potentially exert an influence in a given number of generations N. If N is not specified it is generally taken to be one, in which case the zone of influence simply coincides with the Moore neighbourhood of the cell or pattern.

The set for N generations consists of all the cells to which at least N paths of length N can be traced from the cell(s) in question. Contrast this with the range-N Moore neighbourhood, which consists of all cells to which at least one path of length n can be traced.

:Z-pentomino Conway's name for the following pentomino, which rapidly dies.

    OO.
    .O.
    .OO

:zweiback (p30) An oscillator in which two HW volcanoes hassle a loaf. This was found by Mark Niemiec in February 1995. A smaller version using Scot Ellison's reduced HW volcano is shown below.

    ..........O..............................
    ........OOOOO.................O..........
    .......O.....O..............OOOOO........
    .......O..OO.O.............O.....O.......
    ...O.OOO.O.O.OO............O.OO..O.......
    ...OO....O................OO.O.O.OOO.O...
    ......OO.OO....................O....OO...
    .OOOOO.O.O..O.................OO.OO......
    O......O...O.O..............O..O.O.OOOOO.
    OO..OOOOO.OO.O.............O.O...O......O
    ............OO.............O.OO.OOOOO..OO
    .....OO....OOO.............OO............
    .....OO....OOO.....OO......OOO....OO.....
    ............OO....O..O.....OOO....OO.....
    OO..OOOOO.OO.O.....O.O.....OO............
    O......O...O.O......O......O.OO.OOOOO..OO
    .OOOOO.O.O..O..............O.O...O......O
    ......OO.OO.................O..O.O.OOOOO.
    ...OO....O....................OO.OO......
    ...O.OOO.O.O.OO................O....OO...
    .......O..OO.O............OO.O.O.OOO.O...
    .......O.....O.............O.OO..O.......
    ........OOOOO..............O.....O.......
    ..........O.................OOOOO........
    ..............................O..........

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