Two novel evolutionary formulations of the graph coloring problem

We introduce two novel evolutionary formulations of the problem of coloring the nodes of a graph. The first formulation is based on the relationship that exists between a graph's chromatic number and its acyclic orientations. It views such orientations as individuals and evolves them with the aid of evolutionary operators that are very heavily based on the structure of the graph and its acyclic orientations. The second formulation, unlike the first one, does not tackle one graph at a time, but rather aims at evolving a `program' to color all graphs belonging to a class whose members all have the same number of nodes and other common attributes. The heuristics that result from these formulations have been tested on some of the Second DIMACS Implementation Challenge benchmark graphs, and have been found to be competitive when compared to the several other heuristics that have also been tested on those graphs.Comment: To appear in Journal of Combinatorial Optimizatio

Efeito do expurgo com fosfina (Gastoxin) sobre a qualidade fisiológica de sementes de milho e sorgo.

O fosfato de aluminio (Gastoxin) vem sendo cada vez mais utilizado no controle de pragas de graos armazenados no Brasil. no entanto, ainda nao e conhecida a acao deste inseticida fumigante sobre a qualidade fisiologica de sementes. Com este objetivo, foi realizado um experimento com sementes de milho (Zea mays L.) e sorgo (Sorghum bicolor (L.) Moench). Utilizaram-se duas cultivares de milho (BR 105 e Maia XVII) e tres de sorgo (BR 005, BR 500 e BR 505) que sofreram de um a tres expurgos em duas dosagens (dosagen recomendada pelo fabricante - 5 comprimidos de Gastoxin por m3 e dobro desta dosagem). Os resultados mostraram que as cultivares de milho e sorgo possuiam caracteristicas distintas quanto a qualidade fisiologica, com sementes apresentando alto, medio e baixo vigor. O uso de inseticidas fumigante, AlPH3 (Gastoxin), ate o dobro da dosagem recomendada e ate tres expurgos, nao causou variações significativas no poder germinativo e nos tres testes de vigor aplicados as sementes destas especies. Baseado neste resultados, o Gastoxin pode ser utilizado no expurgo de sementes de milho e de sorgo, observadas as condicoes em que o experimento foi conduzido

On the effective action of the vacuum photon splitting in Lorentz-violating QED

We consider one-loop radiative corrections from Lorentz- and CPT- violating extended QED to address the specific problem of finding explicitly an effective action describing amplitude of photon triple splitting. We show that it is not possible to find a nonzero photon triple splitting effective action, at least by using the derivative expansion method (at zero external momenta), up to leading order in the Lorentz- and CPT- violating parameter.Comment: 4 pages, version to appear in EP