A bordered Chekanov-Eliashberg algebra

Given a front projection of a Legendrian knot $K$ in $\mathbb{R}^{3}$ which has been cut into several pieces along vertical lines, we assign a differential graded algebra to each piece and prove a van Kampen theorem describing the Chekanov-Eliashberg invariant of $K$ as a pushout of these algebras. We then use this theorem to construct maps between the invariants of Legendrian knots related by certain tangle replacements, and to describe the linearized contact homology of Legendrian Whitehead doubles. Other consequences include a Mayer-Vietoris sequence for linearized contact homology and a van Kampen theorem for the characteristic algebra of a Legendrian knot.Comment: Revised version, 38 pages, to appear in Journal of Topolog

Pions in Large-NN Quantum Chromodynamics

An effective field theory of quarks, gluons, and pions, with the number $N$ of colors treated as large, is proposed as a basis for calculations of hadronic phenomena at moderate energies. The qualitative consequences of the large $N$ limit are similar though not identical to those in pure quantum chromodynamics, but because constituent quark masses appear in the effective Lagrangian, the `t Hooft coupling in the effective theory need not be strong at moderate energies. To leading order in $1/N$ the effective theory is renormalizable, with only a finite number of terms in the Lagrangian.Comment: Version to be published in Phys. Rev. Letters. Two figures added, text and abstract revised and shortened. Clearer statement of aims of work. 9 page

Rats: an ecologically-based approach for managing a global problem

Many people have problems with pest rodents. Rats eat our crops, contaminate our stored food, damage our buildings and possessions and spread dangerous diseases to people and livestock. Compared to insect pests, controlling rats and mice can seem difficult. Experience has shown, however, that armed with the right knowledge and tools it is possible to sustainably reduce pest rodent populations in a cost-beneficial way. In recent years, applied research on ecologically-based rodent management (EBRM) has taken place in many countries throughout Asia and Africa, involving a number of research and extension institutions working together in collaboration with farming communities to develop effective, sustainable and cost-beneficial rodent management strategies. This article draws on the knowledge generated from these research and extension experiences, focusing on work carried out in the villages of Jakunipara, Sowara, Sahapur and Anandapur, all of them in Comilla, Bangladesh. We worked in partnership with the NGO Association for Integrated Development, Comilla, and with scientists from the Bangladesh Rice Research Institute, Australia’s CSIRO and the U.K.’s Natural Resources Institute