Volume 4, Issue 29 July 2007
The Telescope at the South Pole
Assembling the South Pole Telescope, December 2006. Antarctica's arid atmosphere provides the best viewing conditions available on earth. Credit: William Holzapfel
This past December, while children across the nation were concentrating on the North Pole, UC Berkeley Professor of Physics Bill Holzapfel was focused in the opposite direction. On Christmas Day, Holzapfel and his colleagues were mobilizing to assemble an ambitious new instrument at the coldest astronomy observing station in the world: the South Pole Telescope.
Holzapfel recalls the holiday as his most hectic to date. "Everyone opened their presents at home, came in, and started packing up the equipment." Their luggage ranged from long undies to supersensitive photon detectors and a cryogenic receiver the size of a Volkswagen bug.
By operating this gear at 90° south, Holzapfel and an international team of scientists from eight other institutions hope to gain insight into the recipe for the universe itself.
That recipe has three primary ingredients. The most familiar is regular matter, the kind that makes up plants and animals, planets and stars. But scientists have also deduced the existence of two more shadowy elements: dark matter, which has mass but cannot be seen; and dark energy, which is forcing the universe apart at an ever-increasing pace. The South Pole Telescope will help determine the relative proportions and properties of these ingredients.
Professor Holzapfel and colleagues were responsible for designing and building the detector system on the South Pole Telescope. Here, Holzapfel and his team are attaching the receiver to a large cryostat. The cryostat cools a secondary mirror that focuses light from the 10 meter reflector onto the detectors. Credit: William Holzapfel
To decode this cosmic formula, scientists are studying the radiation that flooded the universe after the Big Bang. These photons are known as the cosmic microwave background, or CMB. They have sailed through the cosmos since virtually the beginning of time. Today, they form a remarkably uniform backdrop throughout space. But every once in a great while, a few CMB photons will pile headlong into an aggregation of galaxies called a galaxy cluster. Among the most gargantuan structures in the universe, the mass of a single cluster may rival that of a million-billion of Suns.
Within that cluster, about one in a hundred CMB photons will slam into a superheated electron. The collision transfers energy to the low-energy CMB photon, boosting it to a higher frequency.
When the South Pole Telescope observes low-energy photons from that direction, the effect is like looking at x-rays that have been absorbed by bones: the background dims, leaving a hole in the CMB .
"If we can see these holes in the CMB, it tells us where the clusters of galaxies are," Holzapfel says. "We can use the CMB as a backlight to illuminate the universe."
The larger the photon hole, the more massive the galaxy cluster behind it. The South Pole Telescope will allow scientists to assemble a catalog of massive the galaxy clusters. Even the oldest and farthest clusters can be counted because, unlike the light from stars, CMB hole visibility is the same for clusters near and far.
The relative proportions of matter, dark matter, and dark energy "radically affects the formation of structure in the universe. And the thing that's most sensitive is the galaxy clusters," Holzapfel says.
The team will compare the results of their galaxy cluster survey with computer simulations of the evolving universe. The new data will help identify the abundances and properties of the ingredients that could have produced the universe we see today. In particular, they hope to shed new light on the yet mysterious dark energy that appears to dominate the dynamics of the universe.
The massive metal eye of the completed South Pole Telescope stares out over hundreds of miles of snow and ice. The receiver Holzapfel's team developed is installed at the end of the boxy scaffolding bolted to the dish. The dish can be rotated so that the receiver cabin "mates" with the control cabin below, allowing scientists to work on the equipment without being exposed to Antarctica's harsh winter weather. Credit: William Holzapfel
Holzapfel and his Berkeley colleagues designed and built the digital eyes that allow the South Pole Telescope to see the CMB. The heart of the system consists of a shiny silicon wafer roughly size of a Frisbee. On it are etched 960 bolometers, supersensitive heat detectors capable of finding dim spots where the CMB is a few millionths of a degree colder.
The telescope was built in Antarctica because it has some of the driest skies on the planet. Water vapor in the atmosphere obscures CMB radiation. "If you were to take the atmosphere above Berkeley on a good day, and squeeze it dry, you would get a layer of liquid water that's at least 1 cm deep. At the South Pole, in the dead of winter, you'll get 50 times less," Holzapfel says. The total darkness of the six month austral winter also minimizes the daily weather cycle , providing long stretches of dry, clear skies.
Upon landing at the bottom of the world, Holzapfel and colleagues got right to work installing, testing, and troubleshooting every piece of equipment they had brought with them. It turned out they hadn't a moment to waste. "We got on the sky, were able to observe a planet...and the next day they told us we had to leave," Holzapfel says. Temperatures were growing too cold to fly, forcing temporary visitors to leave or risk spending the winter in Antarctica. "We had all of an hour and a half to pack up our stuff and get on the plane," he says.
Now in the hands of two overwintering scientists, the telescope is online and making observations. The South Pole Telescope should produce preliminary results over the next few months and complete the planned cluster survey over the next several years. If all goes well, says Holzapfel, "we'll gain new insights into what's arguably the most interesting question in physics today."
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Keeping the Body On Schedule
Lance Kriegsfeld studies how the body's master clock coordinates systems ranging from hair growth to food digestion. photo courtesy of Lance Kriegsfeld
Hours before you wake, an inner alarm clock primes your body for a day on the go. From deep within your brain, it triggers the release of hormones that tell your cells to mobilize sugars, your blood pressure and temperature to rise, and your gut to make the enzymes that will break down breakfast. The rise and fall of these and other hormones throughout the day keep the body's systems working in harmony.
"Hormones are controlled on a daily or circadian schedule and this timed secretion has important implications for health and functioning," says UC Berkeley Professor of Psychology and Neuroscience Lance Kriegsfeld. "No matter what you look at, whether daily rhythms in cognitive function or testosterone, every system is controlled in a very precise manner with a peak at a certain time of day and a trough at another."
Anyone who has experienced the fatigue and insomnia of jet lag knows that messing around with the internal clock is bad news for the body. These troubles are magnified among the estimated 20 million Americans who work irregular or evening shifts. For example, female shiftworkers have a higher incidence of breast cancer, have more difficulty becoming pregnant and maintaining pregnancies.
Kriegsfeld is interested in how the brain's clock affects hormone cycles in the body. Kriegsfeld's current research determines how the body clock controls ovulation. His findings not only could help more women conceive but may also help make jet lag a thing of the past.
The suprachiasmatic nucleus (SCN) is the timekeeper that coordinates many bodily functions. It is located deep within the hypothalamus in rodents as well. image: Lance Kriegsfeld
In many creatures, the body clock controls ovulation with an iron fist. Hamsters, for example, "ovulate every 96 hours on the dot," says Kriegsfeld. Among humans, the circadian clock plays a more muted role. Work schedules and stressful family situations can dim its effects. "Yet even in humans, it's playing a role," says Kriegsfeld. "Stewardesses and other female shift workers with irregular schedules and sleep habits typically do not have normal menstrual cycles, indicating that there's circadian participation."
Ovulation occurs when a portion of the brain called the hypothalamus releases a substance called gonadotropin-releasing hormone, or GnRH. GnRH, in turn, triggers the pituitary gland to turn on a hormone that fosters egg production.
As eggs mature in the ovary, they release ever larger doses of the hormone estrogen. Throughout most of the reproductive cycle, estrogen tells the brain to keep GnRH production at a trickle. But at a critical level, estrogen suddenly switches roles: it goes from suppressing GnRH production to somehow turning it on again.
But after years of study, scientists still cannot explain this phenomenon. "To date, a cellular mechanism by which this switch occurs has not been found," Kriegsfeld says.
In 2004, scientists led by Kazuyoshi Tsutsui of Hiroshima University, Japan, announced they had isolated a hormone that was the antidote to GnRH in Japanese quail. For this reason, they called the molecule gonadotropin inhibitory hormone, or GnIH.
The brain clock, or SCN, controls the timing of ovulation. At the start of the cycle, SCN neurons trigger the release of the hormone GnRH. GnRH triggers the pituitary to manufacture other hormones (LH/FSH) that stimulate the ovaries to ripen an egg. Estrogen released by the maturing egg keeps the cycle on hold until ovulation. image: Lance Kriegsfeld
Kriegsfeld speculated that GnIH might be the missing link in the ovulatory process. He teamed up with Tsutsui and George Bentley, a professor of integrative biology at UC Berkeley, to tackle this question. By labeling GnIH neurons with a fluorescent tag, Kriegsfeld and colleagues were able to trace the hormone's origins and path of travel within the brains of rodents. They found that GnIH is made in neurons of the hypothalamus, and that these same neurons communicate directly with cells that manufacture GnRH. These studies suggested that GnIH might act as the brakes on the reproductive system until the time of ovulation.
Together, these findings suggest that estrogen from a developing egg encourages production of GnIH. GnIH then suppresses the manufacture of GnRH. Only when estrogen levels peak, indicating the egg is ripe, does GnIH fade, Kriegsfeld's current research suggests. Its disappearance allows GnRH production to resume and start the cycle all over again.
"Now we have a system that seems to be the missing link in the chain of events controlling ovulation," Kriegsfeld says. Kriegsfeld's present research investigates how the circadian clock might lift the brakes of GnIH to allow ovulation to occur.
More recently, Kriegsfeld, in collaboration with Gregory Demas, a professor of biology at Indiana University, has begun to examine yet another player in the system, a protein called kisspeptin. Kisspeptin acts like gasoline on the fire of the brain's reproductive system, accelerating the production of GnRH. They are now studying whether kisspeptin also plays a role in initiating ovulation.
"If we could get a handle on how hormone secretion is controlled over time, we could optimize body functioning for people with normal work schedules. We could also ameliorate the symptoms of jet lag for people who are forced to fly frequently or work odd hours," Kriegsfeld says. "Since hormones are in a position to talk rapidly to so many cells throughout the brain and body, they could be utilized as a mechanism for resynchronizing our physiology."
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Semiclassical Chemistry
The world as we know it is a soup of chemicals. Air has a complex recipe of oxygen, nitrogen, smog, and a dozen other substances; the oceans, their briny broth of salts and minerals and water. Even our own cells are seething cauldrons of ions and proteins and DNA.
These chemicals bump and mingle, swapping atoms and electrons to transmute themselves into new substances. These, in turn, react with still other molecules in an endless chain of chemical reactions. Light and heat are needed to spark some reactions; others occur in an instant, releasing small spurts of energy along the way.
Theoretical chemist William Miller has won the prestigious 2007 Welch Award in Chemistry for his work developing reaction kinetics theory. photo courtesy of William Miller
UC Berkeley Professor of Chemistry William Miller has developed the theory to help understand these molecular transformations molecule by molecule. As a theoretical chemist, he uses mathematics to work out the principles that control reaction kinetics.
"Chemical reaction rates have always been recognized as a central problem of chemistry. But for many years, it was considered a very messy problem, because chemists didn't have the tools to get in and look at reaction rates at the molecular level," Miller says.
These days, modeling the fate of thousands of atoms and molecules within a given system is a multimillion-dollar business. Such molecular dynamics simulations are used in drug design, biological reaction simulations, atmospheric models—virtually any area where chemical reactions occur in complex mixtures of molecules. Understanding what happens at the molecular level as these reactions proceed is critical to a wide range of chemical problems.
For example, Miller is currently working with colleagues in the Combustion Research Program at the Lawrence Berkeley National Laboratory to better understand how gasoline burns. "It's really a problem in chemical reaction dynamics. All sorts of reactions are going on," Miller says. "One can minimize pollutants, and control emissions by understanding how they're generated. If you can make these reactions just one percent more efficient, that's billions of dollars in savings."
At present, most molecular dynamics modeling programs use plain old Newtonian mechanics—the kind they teach in high school—to calculate the paths of thousands of atomic nuclei as they ricochet off some atoms and combine with others. But this can miss some important effects, Miller says.
"You can go a long way simply with classical mechanics, as in many molecular dynamics simulations for protein motion, folding and drug design. But it fails in some situations," Miller says.
The tricky thing about molecular dynamics is the properties of the molecules themselves. If they were as tiny as quarks and neutrinos, the complex equations of quantum mechanics would be required to predict their movements. If they were as heavy as golf balls or baseballs, the approximations of classical Newtonian mechanics would be sufficient. Atoms and molecules, however, fall somewhere in-between.
Miller realized that with certain mathematical approximations to quantum mechanics, he could combine the best of both worlds. His semiclassical theory makes it possible to calculate the motions of atomic nuclei using classical mechanics equations, but then add quantum effects to it. "The approach is basically doing classical mechanics calculations with a wrinkle thrown in. It makes the calculations harder, but not so much harder," Miller says. "It has all of classical mechanics in it, plus an approximate treatment of the quantum effects. So it doesn't miss anything qualitatively," Miller says.
Miller has now adapted a branch of his semiclassical theory called the 'initial value representation' to make molecular dynamics modeling even easier for large molecular systems. "We calculate the nuclear motions on the computer in the same way, using classical mechanics, but use them as input to our semiclassical theory," he says. "It's emerging as a very practical way to implement semiclassical theory for these large molecular systems."
Already several theoretical groups are using the simplest version of these equations. "My goal is to convince this body of people who do classical simulations to convert," Miller says.
One body he doesn't need to convince is other chemists. In May, it was announced that Miller will receive the 2007 Welch Award in Chemistry. He shares the $300,000 prize with fellow theoretical chemist Noel Hush of the University of Sydney. Miller and Hush, among the first chemists to specialize in theory, are the first in their field to win the award. Today, theoreticians make up ten to fifteen percent of the chemistry faculty at most major universities. "It's a recognition that theoretical chemistry is increasingly making significant contributions to the field," Miller says.
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