Today's Globe: prematurity factors, flu spread, pet-store suit, Edward Lorenz

Researchers are reporting that they have developed a new way to help doctors and parents make some of the most agonizing decisions in medicine, about how much treatment to give tiny, extremely premature infants.

Scientists have pinpointed the path that flu takes as it sweeps the globe every year - starting with the birth of strains in Asia and ending when the virus burns out in South America.

A Whitman woman whose husband died after receiving a transplanted liver infected with a rodent virus is suing PetSmart Inc., contending the chain should have warned customers that hamsters can carry the virus.

Edward Lorenz (left), an MIT meteorologist whose meticulous attempt to predict the weather through an early computer unraveled into a spectacular failure that he turned into the chaos theory, died at his home in Cambridge yesterday. He was 90. At a meeting of scientists in 1972, he gave a talk with a title that captured the essence of his ideas: "Predictability: Does the Flap of a Butterfly's Wings in Brazil Set Off a Tornado in Texas?" The phrase "butterfly effect" has become part of the lexicon of both pop science and pop culture.