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Star light, star bright. Astronomy graduate student Michal Kolpak (GRS'03) is calculating the brightness of stars. Combined with a count of stars that are forming in a particular region of the Galaxy, the brightness measure allows Kolpak to calculate a luminosity distribution function, a valuable tool for investigating how stars form.

If the distance to a star is unknown, it is difficult to determine how bright it really is. Even on Earth, when someone is walking toward you with a flashlight, the light appears to get brighter, although the intrinsic light the flashlight emits remains the same. The key is accurately calculating the distance to the star -- no trivial matter.

Because the Galaxy rotates in a more or less systematic way, astronomers use the Doppler shift -- the change in the wavelength of light emanating from a star, caused by its motion -- to calculate the speed of the star. Using a model of how the Galaxy rotates, the star's velocity can then be used to calculate its distance from Earth. Unfortunately, the calculation produces two possible distances, one near and one far -- a problem known as kinematic distance ambiguity.

Kolpak and his colleagues at the GRS Institute for Astrophysical Research realized that the solution to this dilemma lies in the fact that light from sources far away travels through the galactic center. This region of fast-moving gas absorbs some of the light, producing an absorption feature that has been highly Doppler-shifted. Knowing this, the astronomers can determine the correct distance, separate the effects of distance and intrinsic brightness, and build an accurate luminosity function for a particular star-forming region. Kolpak's research, described in poster form, earned him the CAS Dean's Award at Science Day 2001.


Heartsick? Hearts fail for any number of reasons, including blocked arteries, faulty valves, and electrical malfunctions. But the most common cause for older people is a gradual malfunction of the muscle tissue that keeps the heart pumping efficiently. Typically, the muscular walls of the left ventricle -- the lower chamber of the heart, responsible for pumping blood through the body -- can thicken and become less elastic with age and result in cardiac failure. This limits the amount of blood that can fill the heart, causing it to work harder and producing fatigue, shortness of breath, angina, and ultimately, death.

Ph.D. candidate Timothy Whitehead (SAR '01) and colleagues at the Cardiovascular Biology Laboratory of Sargent College's department of health sciences, are seeking to understand the cellular mechanisms that underlie this process. It is known that the enlargement of the heart's walls is associated with protein accumulation in the spaces between muscle fibers. These proteins are from the extracellular matrix (ECM), which is the structural scaffolding of heart tissue.

Whitehead and his associates demonstrated similar dramatic age-associated changes in the mechanical properties of the fibrous tissue, or fibroblast, the most abundant nonmuscle cell type in the heart. They found that cardiac fibroblasts in the hearts of older rats create stronger bonds with the ECM proteins collagen and fibronectin than they do in younger animals. They also discovered that cell surface receptors, proteins that form links with the ECM proteins, are renewed less often in older cardiac fibroblasts. The researchers hypothesize that a better understanding of these changes in fibroblast mechanics in the aging heart will provide vital clues to devising new therapies to keep hearts pumping efficiently at any age. Whitehead's research, presented in poster form at Science Day 2001, earned the Sargent College Dean's Award.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit http://www.bu.edu/research.

       

15 May 2003
Boston University
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