Cultivating S-P-E-L-L-E-R-S

P R O B L E M S

To be considered for publication, solutions should be received by September 1, 2011. 1866. Proposed by Sadi Abu-Saymeh and Mowaffaq Hajja, Mathematics Department, Yarmouk University, Irbid, Jordan. Let ABC be a triangle, and L and M points on AB and AC, respectively, such that AL = AM. Let P be the intersection of BM and CL. Prove that PB = PC if and only if AB = AC. 1867. Proposed by Ángel Pla...

P R O F I L E S

4 @bullet S C I E N C E & P R a C T I C E P E R S P E C T I V E S — a P R I L 2 0 0 7

Modern imaging techniques enable researchers to observe drug actions and consequences as they occur and persist in the brains of abusing and addicted individuals. This article presents the five most commonly used techniques, explains how each produces images, and describes how researchers interpret them. The authors give examples of key findings illustrating how each technique has extended and ...

S E A R C H P O R T I D I A P D a l l e M o l l e I n s t i t u t e

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We exhibit explicit, combinatorially defined graphs satisfying the kth extension axiom: Given any set of k distinct vertices and any partition of it into two pieces, there exists another vertex adjacent to all of the vertices in the first piece and to none in the second. Quisani:1 I’ve been reading about zero-one laws, and many of the results involve extension axioms. In the simple case of grap...