A weighty matter. Scientists believe that the amount of matter in the universe determines whether it will continue to expand as it has over the past 15 billion years, or whether the outward expansion will gradually slow down and begin to reverse direction. The fate of the universe depends in part on the amount of baryonic, or normal matter, that was created at the time of the Big Bang.
Over the past 20 years, a mere nanosecond in astronomical time, Tom Bania, a CAS astronomy professor, and colleagues at the University of Virginia and the National Radio Astronomy Observatory have developed painstaking techniques to precisely determine the abundance of the rare light element helium-3 in the Milky Way Galaxy. Their observations have allowed them to infer how much baryonic matter was present in the nascent universe just moments after the Big Bang -- a finding of only about 4 percent of the amount sufficient to reverse expansion. Their work also confirms the results of previous studies based on different analyses.
The scientists used the National Science Foundation’s 140-foot Radio Telescope in Green Bank, W.Va., to examine areas of helium-3 production -- to measure the helium-3 abundance in evolved solar-type stars, known as planetary nebulae, and in HII regions, zones where stars are currently forming. They found that contrary to current models, only a small number of planetary nebulae produce helium-3, and no evidence of helium-3 enrichment in HII regions.
“Since stellar processes appear to have little or no impact on the amount of helium-3, we were able to deduce two very important things,” says Bania. “First, since current theory predicts stellar production of helium-3, we need to rethink our understanding of the internal workings of stars like our sun. Second, since helium-3 has not been created or destroyed in our galaxy in any appreciable amounts, then what we detected is most likely equal to the abundance of primordial helium-3 created by the Big Bang.”
All of which leaves the questions of expansion or contraction of the universe and the gravitational pull that holds galaxies together squarely in the hands of astronomers investigating the other form of matter -- dark matter.
This work appeared in the January 3 issue of the Journal Nature.
Mechanical failure. Emphysema, a progressive and debilitating disease of the lungs, affects 1.8 million Americans. Associated with smoking and other pollutants as well as with advancing age, the disease attacks lung tissue, destroying the air sacs (alveoli) where oxygen is exchanged for carbon dioxide. Aveolar walls become thin and fragile, lungs lose elasticity, and those afflicted experience shortness of breath and an inability to exhale.
Scientists know that an imbalance of protease and antiprotease, enzymes that control the breakdown of proteins in the body, plays a major role in the destruction of the structural components of lung tissue. Bela Suki, an ENG associate professor of biomedical engineering, and colleagues at Brigham and Women’s Hospital and Harvard Medical School have completed a study that demonstrates that mechanical forces are also critical in the progression of the disease.
Normally resilient, lungs are stretched more than 15,000 times daily -- in breathing, yawning, sighing, and coughing. The researchers found that lungs weakened by emphysema are structurally unsound and more prone to mechanical failure when exposed to even the normal stresses and strains of life. Using an animal model, they developed sophisticated techniques to measure the stress-strain properties of sections of lung tissue and used immunofluorescent labeling to produce images of the elastin and collagen networks that provide support and elasticity in lung tissue. They found thickened elastin and collagen fibers in the damaged tissue that evidenced more distortion when stretched than normal tissue. The threshold for mechanical failure of collagen was also significantly reduced in these tissues.
The authors conclude that in lungs damaged by emphysema, even normal breathing creates cyclic mechanical forces sufficient to cause fatigue failure in the collagen fibers and results in the cascading deterioration of lung function characteristic of the disease.
These findings have significant implications for treatment and rehabilitation of those with the disease. Lung volume reduction surgery, for example, has proved of only temporary benefit, possibly because increased stress on the remaining tissue accelerates loss of function. Similarly, regular exercise, while having well-documented benefits, may also contribute to long-term progression of the disease by increasing stress on the lungs.
The work of Suki and colleagues was reported in a recent issue of the American Journal of Respiratory and Critical Care Medicine.
Briefs" is written by Joan Schwartz in the Office of the Provost. To read
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