The Berkeley Science Review: Articles

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Squealing Brakes
Did you know that when your car screeches to a stop, it doesn't mean your brakes are malfunctioning? The noise occurs because the brakes are slowing the car, but its exact origin is an elusive phenomenon that engineers have been studying for years. Your mechanic can address the noise by either slapping on a polymer to dampen it out or machining your brake rotor to reduce friction, but as soon as the temperature or humidity changes, that squeal could come back. Recently, UC Berkeley researchers, led by mechanical engineering professor Oliver O'Reilly in collaboration with mathematics professor Maciej Zworski, used a mathematical method called pseudospectral analysis to explain the brake system's extreme sensitivity to environmental parameters. The researchers showed that brake squeal becomes more or less likely in response to minute environmental changes, such as various amounts of "dissipation," or damping. Their analysis, published in the November 2007 issue of the Journal of Sound and Vibration, demonstrates why a little bit of damping can sometimes exacerbate the problem, and how variable conditions make it so hard to keep brakes quiet.
—Orapim Tulyathan

Behind Anemone Lines
What does it mean to be an animal? Daniel Rokhsar's lab in the Department of Molecular and Cell Biology is tackling this question using tools from computer science and biology. In an article published in the July 6, 2007 issue of the journal Science, the Rokhsar lab and an international group of colleagues sequenced the genome of one of their favorite "simple" animals, the starlet sea anemone Nematostella vectensis. At the start of the study, the researchers anticipated that the anemone, which has no organs and a nerve net instead of a brain, would have little in common with humans. So they were surprised to discover that "we actually have a lot in common with these simple, sac-shaped creatures," says Mansi Srivastava, a graduate student in the lab. "The fact that such simple animals have so much complexity in their genome raises a lot of questions." In fact, humans share many genes with the anemone that we do not share with closer cousins like the fruit fly, suggesting that complexity evolved much earlier in animal evolution than previously thought. Furthermore, an astonishing twenty percent of anemone genes code for sophisticated processes such as neural and muscular functions. Srivastava is now working to understand the functions of some of these genes in the hopes of shedding even more light on early animal evolution.
—Sharmistha Majumdar

Heavenly Halos
The frighteningly familiar flash of a lightning strike is caused by an electrical discharge between the atmosphere and the ground. Yet only in the past twenty years have scientists become aware of Transient Luminous Events (TLEs), otherworldly releases of energy in the upper atmosphere that accompany lightning strikes on the ground. TLEs can be hundreds of miles in diameter and have been given whimsical names such as "elves" and "sprites." Researchers Harald Frey and Stephen Mende of the UC Berkeley Space Sciences Laboratory recently probed the nature of the most elusive class of TLEs, called "halos." These diffuse, disk-shaped flashes were once thought to occur exclusively before the jagged red-orange slash of a sprite. However, Frey and Mende discovered that many halos occur in the absence of sprites, following open-water lightning strikes that carry a negative charge to the earth. This is a surprising result, as most other TLEs follow lightning of the opposite polarity, and the vast majority of lightning strikes occur on land. The authors postulate that most such halos were missed by previous studies because they are fairly small (about 40 miles) and last for only half a millisecond.
—Greg Alushin

Vole Love
From group hugs to backrub circles, college students have always been enthusiastic about showing friendly affection. But could these activities actually be fulfilling a deep-seated biological urge? Annaliese Beery, a neuroscience graduate student in Irving Zucker's lab, is exploring the origin of social behavior at a molecular level. Using meadow voles, a rodent species in which the females go from being solitary in the summer to super-cuddly in the shorter days of winter, Beery is exploring how hormones like estrogen can directly affect the voles' sociability. Estrogen levels in female meadow voles are known to change with the seasons, increasing during the summer and decreasing during the winter. However, Beery has explored this correlation even further. By taking female voles accustomed to a short day and treating them with estrogen, she showed that artificially high levels of estrogen can turn social voles into antisocial ones. In contrast, female voles exposed to long days are always antisocial, irrespective of their estrogen levels. Though these experiments indicate that estrogen is not the only chemical regulator of sociability, they do provide a striking example of the link between environmental factors, brain chemistry, and behavior.
—Jesse Dill

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