But the study did find that habitual smokers of more than one substance had greater risk of lung cancer than those smoking just tobacco alone. We didn't do this study to fuel the controversy concerning the benefits or detriments of marijuana or crack cocaine. It was motivated because there's an increasing use of marijuana and crack cocaine and we wanted to see the effects of these substances on the lung. And also because we now understand some of the molecular steps that lead to lung cancer. For Science Today, I'm Larissa Branin.
Muscle atrophy refers to the shrinkage of muscle fiber from lack of forceful exertion.
Dr. Kenneth Baldwin of the University of California, Irvine worked with NASA to come up with an exercise routine to prevent this from occurring in astronauts traveling through space. Since muscle atrophy parallels the aging process, Baldwin says their findings can also be applied to the general public - especially those over forty. For Science Today, I'm Larissa Branin. On any given sidewalk, you're more than likely to encounter cracks in the pavement. These cracks develop when fluids in the cement mix with silica in the concrete, forming what's called an alkali- silica gel.