Mammograms cut cancer toll
SARAH-JANE O'CONNOR looks back at some of the main findings from scientists around the world during the past week.
1. Breast cancer screening reduces mortality risk
Screening women for breast cancer reduces the risk of death from the disease, a study based in Norway has found.
A mammography project was gradually introduced in Norway between 1995 and 2005. The researchers found a 28 per cent decrease in the risk of dying from breast cancer for those women invited to be screened. The reduction in risk was 37 per cent for those women who actually participated in screening. However, some experts have warned that screening carries other costs, including the potential to be treated for conditions that might never have been life- threatening.
2. Fishing spiders
Every continent except Antarctica has spiders that eat fish, researchers from Switzerland and Australia have found after collating international data.
Fish-eating arachnids are semi-aquatic and live at the fringes of shallow rivers, lakes and other freshwater bodies. Their prey range in length from two to six centimetres and are among the most common fish in their geographic areas.
3. Killer icebergs
Drifting icebergs scour shallow seabeds and kill off many of the species that make those seabeds home. As the climate has warmed over the past two decades and sea ice has melted, icebergs are more often free to drift throughout the year - not just in summer.
Researchers from the British Antarctic Survey reported this week that the climate-linked increase in iceberg movement has meant areas that once hosted rich communities of species now mostly support just a single species. By looking at survey data from 1997 onwards, the scientists found that although no species had disappeared entirely, by last year almost all the observations consisted of just one species.
4. Fast-evolving bacteria
The bacteria that cause ulcers in humans dodge our immune system by rapidly evolving during the early stages of infection. Microbiologists in the United States and Australia teamed up to examine the genetic sequence of Helicobacter pylori, the bacterium that causes stomach ulcers, just before infection and several times after. They found rates of mutation were up to 50 times faster during the first stage of infection, when the immune response is highest, than later in the infection.
5. Deep water in the Earth
Researchers from the United States have found evidence for what could be Earth's largest store of water. They found deep pockets of magma some 650 kilometres beneath North America, which suggested water was present.
Scientists have long speculated that water is trapped in a "transition zone" between the lower and upper mantles, but this is the first direct evidence that there may be water in the area.
If just one per cent of the mantle in the transition zone was water, that would be nearly three times the amount of water in Earth's oceans, the researchers said.