Research demonstrates that police reduce crime. We study this question by using a natural experiment in which a private university increased the number of police patrols within an arbitrarily defined geographic boundary. Capitalizing on the discontinuity in patrols at the boundary, we estimate that the extra police decreased crime in adjacent city blocks by 43–73%. Our results are consistent wi...

in sustainable agriculture, using of resistant plants is one of the best methods for integrated pest management. resistance of 140 rice promising lines against striped stem borer was evaluated in two planting date in the field under natural infections in sari agricultural science and natural resources university during 2008-2009. this study carried out as a factorial experiment in randomized co...

Overhead transmission lines are influenced by different factors which are mostly electrical and mechanical. These factors can cause problems for lines, distortions in network and outage of line. In designing transmission lines mechanical properties are evaluated after selecting a suitable conductor and clearance with regard to electrical properties. In lines designing, an important mechanical p...

A pseudo-complement of a quadrilateral D of order n, n, > 3, is a non-trivial (n+l)- regular linear space with n - 3n + 3 points and n + n - 3 lines. We prove that if n > 18 and D has at least one line of size n - 1, or if n > 25 , then the set of lines of D consists of three lines of size n -1, 6(n - 2) lines of size n - 2, and n - 5n + 6 lines of size n - 3. Furthermore, if n > 21 and D...

three iranian native strains and three japanese commercial lines of the silkworm bombyx mori were analyzed using amplified fragment length polymorphism (aflp) markers. a set of ten psti/taqi primer combinations amplified a total of 322 bands out of which 251 (%78) were polymorphic. estimates of nei’s gene diversity for all loci in individual strains and commercial lines indicated a higher degre...

Overhead transmission lines are influenced by different factors which are mostly electrical and mechanical. These factors can cause problems for lines, distortions in network and outage of line. In designing transmission lines mechanical properties are evaluated after selecting a suitable conductor and clearance with regard to electrical properties. In lines designing, an important mechanical p...