BOSTON — Scientists are releasing gases and fluorescent particles into Boston’s subway tunnels on Friday to study how toxic chemicals and lethal biological agents could spread through the nation’s oldest subway system in a terrorist attack.

It’s part of a weeklong study commissioned by the U.S. Department of Homeland Security to figure out ways to quickly minimize the impact of an airborne assault on the nation’s 15 subway systems and protect the nation’s infrastructure. U.S. subway systems include 810 miles of track in tunnels and accounted for about 3.45 billion trips taken last year, according to the American Public Transportation Association.

The scientists are monitoring concentration of the gases — which are invisible to the naked eye and nontoxic — and particles as they move throughout the system and then up into the streets above, pushed by turbulence created by trains thundering through the tunnels. Researchers use electronic devices to take air samples at more than 20 Massachusetts Bay Transportation Authority stations and in subway cars.

Test results will be used to craft ways to quickly detect an attack so authorities can shut down subways to limit the spread of contaminants.

Federal officials say similar tests were conducted in 2008 in the Washington, D.C., area, serving as an excellent contrast to the Boston study. The Massachusetts subway system, which opened its first tunnels in 1897, is poorly ventilated, while Washington’s is relatively modern and well-ventilated, DHS officials said. Read more at www.google.com

NASA researchers have created an online resource that dramatically changed how the agency fosters collaborative research. In this new innovative method capitalizing strengths of the Internet, scientists can share information about systems health and data mining while aiming to help improve aviation safety in ways never before possible. The web site is called Dashlink. DASH stands for Discovery in Aeronautics Systems Health. The name hints at the identity of the particular group of scientists who created this online gathering place in 2008. The site has more than 410 registered users. “The primary goal of Dashlink is to disseminate information on the latest data mining and systems health algorithms, data and research,” said Ashok Srivastava, principal investigator for NASA’s Integrated Vehicle Health Management Project at the agency’s Ames Research Center in California.

Dashlink allows researchers, whether inside or outside NASA, who are working on a particular software application to share the applications they have written, test each other’s work, and openly discuss the results. “It’s totally different from how other projects are run,” Srivastava said, noting that the usual form of communication among scientists is published papers, which can take months to distribute and offer no immediate interaction with the author. Interaction is important because a staple of scientific research is the ability of one group of scientists to duplicate the work of another group and achieve the same results. In the data mining field, duplicating results can be difficult and infrequent.

Dashlink is available to anyone with an interest in integrated vehicle health management software and sensor applications. Those outside NASA can join if a NASA civil servant sponsors the registration. That is what Suratna Budalakoti did when he joined the site in September 2008. Read more at www.nasa.gov