Denys Fisher sale in Schofields department store in Leeds in 1965. A year later, Fisher licensed Spirograph to Kenner Products in the United States. In 1967 Spirograph was chosen as the UK Toy of the Year. Denys Fisher Toys, which also produced other toys and board games, was sold to Palitoy in 1970 and it was subsequently bought by Hasbro. Through the 1980s & 1990s Fisher continued to work with Hasbro in developing new toys and refining Spirograph. Denys Fisher Toys produced the following toys and games: Denys Fisher Denys Fisher (11 May 1918 – 17 September 2002) was an English engineer
Cone of curves Cone of curves In mathematics, the cone of curves (sometimes the Kleiman-Mori cone) of an algebraic variety formula_1 is a combinatorial invariant of much importance to the birational geometry of formula_1. Let formula_1 be a proper variety. By definition, a (real) "1-cycle" on formula_1 is a formal linear combination formula_5 of irreducible, reduced and proper curves formula_6, with coefficients formula_7. "Numerical equivalence" of 1-cycles is defined by intersections: two 1-cycles formula_8 and formula_9 are numerically equivalent if formula_10 for every Cartier divisor formula_11 on formula_1. Denote the real vector space of 1-cycles modulo numerical equivalence by formula_13. We define the