At a child care center, 18-month-old Hannah is clinging to her mother and crying as they enter. Her mother pulls Hannah’s hands from her arm, saying, “Don’t be such a crybaby and go play.” In a pediatrician’s waiting room, two-year-old Carlos climbs dangerously high on the furniture. He throws a toy at his mother when she calls his name. His mother laughs nervously and says quietly, “I don’t kn...

In 1769, Euler, by generalising Fermat's Last Theorem, conjectured that "it is impossible to exhibit three fourth powers whose sum is a fourth power", "four fifth powers whose sum is a fifth power, and similarly for higher powers". The first counterexample to the conjecture, was found in 1966 after a systematic computer search: 275 +845 + 1105 + 1335 = 1445. More recently, Euler's conjecture wa...

The k-th power H of a graph H is obtained from H by adding new edges between every two distinct vertices having distance at most k in H . Lau [Bipartite roots of graphs, ACM Transactions on Algorithms 2 (2006) 178–208] conjectured that recognizing k-th powers of some graph is NP-complete for all fixed k ≥ 2 and recognizing k-th powers of a bipartite graph is NP-complete for all fixed k ≥ 3. We ...

PURPOSE To determine whether rotational stability is improved with the longer Staar toric intraocular lens (IOL). SETTING A private practice, Los Altos, California, USA. METHODS Staar Surgical manufactures toric plate-haptic IOLs under +24.0 diopters (D) in 2 lengths. Fifty consecutive eyes requiring toric IOL spherical powers less than +24.0 D received the longer toric IOL (TL; 11.2 mm) us...