A class of algorithms named for this shape are generally IRC unsafe, with the exception of a “seedless infrared safe” algorithm. The inequality “parallel velocity over perpendicular velocity is less than the square root of the ratio of maximum to minimum magnetic field, minus one” defines one of these shapes that describes particles in a plasma that are “lost” by a magnetic (-5[1])mirror. (15[1])The indices of (-5[1])refraction of the core and cladding (-5[1])define one of these shapes that determines which photons are accepted by an optical fiber. (15[1])Particle (*) jets are generally assumed to have this shape. (10[2])The spacelike and timelike (10[1])parts of a Minkowski (10[3])diagram are divided (-5[1])by one of these shapes (-5[1])defined (-5[1])by the possible paths of a light ray. (10[2])For 10 points, (10[2])what shapes can be cut by a plane to produce ellipses, (10[2])hyperbolas, and other “sections?” (10[3])■END■ (10[1])