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But for others , hair pulling is so automatic or habitual that they may do it unconsciously — they do n't realize that they're doing it . In technical terms , he obtained an upper bound for the sizes of a complex 's homology groups in terms of a poset property called width . The model developed by Tang and his coworkers is just one of many current efforts aimed at helping retailers cope with a highly competitive and volatile marketplace . It was n't until 1994 , however , that anyone actually stepped into a laboratory and succeeded in solving a computational problem in a test tube . " Unless we act , we will saddle our children and grandchildren with tens of trillions of dollars of unfunded obligations , " Bush said . To account for the relative sizes of the orbits of the six planets , he constructed an ingenious nesting of the polyhedra , choosing the order that gave the best agreement with the known proportions of planetary orbits .