"Minis" Have Mega Impact in the Brain

Embargoed: Not for Release Until 11:00 a.m. PDT Thursday, 24 June, 2004

PASADENA, Calif. — The brain is a maddeningly complex organ for scientists to understand. No assumption can remain unchallenged, no given taken as a given.

Take "minis" for example. That is, miniature excitatory synaptic events. The location where neurons communicate with each other is the synapse, the tiny gap between the ends of nerve fibers. That's where one nerve cell signals another by secreting special chemicals called neurotransmitters, which jump the gap. The synapse, and its ability to strengthen and wane, is thought to be at the heart of learning and memory. Minis, mere single, tiny packets of neurotransmitters, were always thought to have no biological significance, nothing more than "noise," or background chatter that played no role in the formation of a memory. Minis, it was thought, could be safely ignored.

Maybe not, says Mike Sutton, a postdoctoral scholar in the lab of Erin Schuman, an associate professor of biology at the California Institute of Technology, and an associate investigator for the Howard Hughes Medical Institute. Sutton, Schuman, and colleagues Nicholas Wall and Girish Aakalu report that on the contrary, minis may play an important role in regulating protein synthesis in the brain. Further, their work suggests the brain is a much more sensitive organ than originally perceived, sensitive to the tiniest of chemical signals. Their report appears in the June 25th issue of the journal Science.

Originally, Sutton et. al. weren't looking at minis at all, but at protein synthesis, the process through which cells assemble amino acids into proteins according to the genetic information contained within that cell's DNA. Proteins are the body's workhorses, and are required for the structure, function, and regulation of cells, tissues, and organs. Every protein has a unique function.

A neuron is composed of treelike branches that extend from the cell body. Numerous branches called dendrites contain numerous synapses that receive signals, while another single branch called an axon passes the signal on to another cell.

The original rationale behind the experiment was to examine how changes in synaptic activity regulate protein synthesis in a dendrite, says Sutton. His first experiment was a starting point to ask what happens when we first remove all types of activity from a cell, so he could then add it back later incrementally and observe how this affected protein synthesis in dendrites. "So we were going on the assumption that the spontaneous glutamate release--the minis--would have no impact, but we wanted to formally rule this out," he says.

Using several different drugs, Sutton first blocked any so-called action potentials, an electrical signal in the sending cell that causes the release of the neurotransmitter glutamate. Normally, a cell receives hundreds of signals each second. When action potentials are blocked, it receives only minis that arrive at about one signal each second. Next he blocked both the action potential and the release of any minis. "To our surprise, the presence or absence of minis had a very large impact on protein synthesis in dendrites," he says. It turned out that the minis inhibit protein synthesis, which increased when the minis were blocked. Further, says Sutton, "it appears the changes in synaptic activity that are needed to alter protein synthesis in dendrites are extremely small--a single package of glutamate is sufficient."

Sutton notes that it is widely accepted that synaptic transmission involves the release of glutamate packets. That is, an individual packet (called a vesicle) represents the elemental unit of synaptic communication. "This is known as the 'quantal' nature of synaptic transmission," he says, "and each packet is referred to as a quantum. The study demonstrates, then, the surprising point that protein synthesis in dendrites is extremely sensitive to changes in synaptic activity even when those changes represent a single neurotransmitter quantum.

"Because it's so sensitive," says Sutton, "there is the possibility that minis provide information about the characteristics of a given synapse (for example, is the signal big or small?), and that the postsynaptic or receiving cell might use this information to change the composition of that synapse. And it does this by changing the complement of proteins that are locally synthesized."

The ability to rapidly make more or fewer proteins at a synaptic site allows for quick changes in synaptic strength. Ultimately, he says, this ability may underlie long-term memory storage.

"It's amazing to us that these signals, long regarded by many as synaptic 'noise,' have such a dramatic impact on protein synthesis," says Schuman. "We're excited by the possibility that minis can change the local synaptic landscape. Figuring out the nature of the intracellular 'sensor' for these tiny events is now the big question."

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Unexpected Changes in Earth's Climate Observed on the Dark Side of the Moon

PASADENA, Calif.—Scientists who monitor Earth's reflectance by measuring the moon's "earthshine" have observed unexpectedly large climate fluctuations during the past two decades. By combining eight years of earthshine data with nearly twenty years of partially overlapping satellite cloud data, they have found a gradual decline in Earth's reflectance that became sharper in the last part of the 1990s, perhaps associated with the accelerated global warming in recent years. Surprisingly, the declining reflectance reversed completely in the past three years. Such changes, which are not understood, seem to be a natural variability of Earth's clouds.

The May 28, 2004, issue of the journal Science examines the phenomenon in an article, "Changes in Earth's Reflectance Over the Past Two Decades," written by Enric Palle, Philip R. Goode, Pilar Montañes Rodríguez, and Steven E. Koonin. Goode is distinguished professor of physics at the New Jersey Institute of Technology (NJIT), Palle and Montañes Rodríguez are postdoctoral associates at that institution, and Koonin is professor of theoretical physics at the California Institute of Technology. The observations were conducted at the Big Bear Solar Observatory (BBSO) in California, which NJIT has operated since 1997 with Goode as its director. The National Aeronautics Space Administration funded these observations.

The team has revived and modernized an old method of determining Earth's reflectance, or albedo, by observing earthshine, sunlight reflected by the Earth that can be seen as a ghostly glow of the moon's "dark side"—or the portion of the lunar disk not lit by the sun. As Koonin realized some 14 years ago, such observations can be a powerful tool for long-term climate monitoring. "The cloudier the Earth, the brighter the earthshine, and changing cloud cover is an important element of changing climate," he said.

Precision earthshine observations to determine global reflectivity have been under way at BBSO since 1994, with regular observations commencing in late 1997.

"Using a phenomenon first explained by Leonardo DaVinci, we can precisely measure global climate change and find a surprising story of clouds. Our method has the advantage of being very precise because the bright lunar crescent serves as a standard against which to monitor earthshine, and light reflected by large portions of Earth can be observed simultaneously," said Goode. "It is also inexpensive, requiring only a small telescope and a relatively simple electronic detector."

By using a combination of earthshine observations and satellite data on cloud cover, the earthshine team has determined the following:

= Earth's average albedo is not constant from one year to the next; it also changes over decadal timescales. The computer models currently used to study the climate system do not show such large decadal-scale variability of the albedo.

= The annual average albedo declined very gradually from 1985 to 1995, and then declined sharply in 1995 and 1996. These observed declines are broadly consistent with previously known satellite measures of cloud amount.

= The low albedo during 1997-2001 increased solar heating of the globe at a rate more than twice that expected from a doubling of atmospheric carbon dioxide. This "dimming" of Earth, as it would be seen from space, is perhaps connected with the recent accelerated increase in mean global surface temperatures.

= 2001-2003 saw a reversal of the albedo to pre-1995 values; this "brightening" of the Earth is most likely attributable to the effect of increased cloud cover and thickness.

These large variations, which are comparable to those in the earth's infrared (heat) radiation observed in the tropics by satellites, comprise a large influence on Earth's radiation budget.

"Our results are only part of the story, since the Earth's surface temperature is determined by a balance between sunlight that warms the planet and heat radiated back into space, which cools the planet," said Palle. "This depends upon many factors in addition to albedo, such as the amount of greenhouse gases (water vapor, carbon dioxide, methane) present in the atmosphere. But these new data emphasize that clouds must be properly accounted for and illustrate that we still lack the detailed understanding of our climate system necessary to model future changes with confidence." Goode says the earthshine observations will continue for the next decade. "These will be important for monitoring ongoing changes in Earth's climate system. It will also be essential to correlate our results with satellite data as they become available, particularly for the most recent years, to form a consistent description of the changing albedo. Earthshine observations through an 11-year solar cycle will also be important to assessing hypothesized influences of solar activity on climate."

Montañes Rodríguez says that to carry out future observations, the team is working to establish a global network of observing stations. "These would allow continuous monitoring of the albedo during much of each lunar month and would also compensate for local weather conditions that sometimes prevent observations from a given site." BBSO observations are currently being supplemented with others from the Crimea in the Ukraine, and there will soon be observations from Yunnan in China, as well. A further improvement will be to fully automate the current manual observations. A prototype robotic telescope is being constructed and the team is seeking funds to construct, calibrate, and deploy a network of eight around the globe.

"Even as the scientific community acknowledges the likelihood of human impacts on climate, it must better document and understand climate changes," said Koonin. "Our ongoing earthshine measurements will be an important part of that process."

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The Brain Can Make Errors in Reassembling the Color and Motion of Objects

PASADENA, Calif.—You're driving along in your car and catch a glimpse of a green SUV out of the corner of your eye. A few seconds later, you glance over, and to your surprise discover that the SUV is actually brown.

You may assume this is just your memory playing tricks on you, but new research from psychophysicists at the California Institute of Technology and the Helmholtz Institute in the Netherlands suggests that initial perceptions themselves can contain misassigned colors. This can happen in certain cases where the brain uses what it sees in the center of vision and then rearranges the colors in peripheral vision to match.

In an article appearing in this week's journal Nature, Caltech graduate student Daw-An Wu, Caltech professor of biology Shinsuke Shimojo, and Ryota Kanai of the Helmholtz Institute report that the color of an object can be misassigned even as observers are intently watching an ongoing event because of the way the brain combines the perceptions of motion and color. Because different parts of the brain are responsible for dealing with motion and color perception, mistakes in "binding" can occur, where the motion from one object is combined with the color of another object.

This is demonstrated when observers gaze steadily at a computer screen on which red and green dots are in upward and downward motion. In the center area of the screen, all the red dots are moving upward while all the green dots are moving downward.

Unknown to the observers, however, the researchers are able to control the motion of the red and green dots at the periphery of the screen. In other words, the red and green dots are moving in a certain direction in the center area of the screen, but their motion is partially or even wholly reversed on each side.

The observers show a significant tendency to mistake the motion of the red and green dots at the periphery. Even when the motion was completely reversed on the sides, the observers would see the same motion all across the screen.

According to Wu, the lead author of the paper, the design of the experiment exploits the fact that different parts of the brain are responsible for processing different visual features, such as motion and color. Further, the experiment shows that the brain can be tricked into binding the information back together incorrectly.

"This illusion confirms the existence of the binding problem the brain faces in integrating basic visual features of objects, " says Wu. "Here, the information is reintegrated incorrectly because the information in the center, where our vision is strongest, vetoes contradicting (but correct) information in the periphery."

The title of the article is "Steady-State Misbinding of Color and Motion."

 

 

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Physicists Successful in Trapping Ultracold Neutrons at Los Alamos National Laboratory

PASADENA, Calif.—Free neutrons are usually pretty speedy customers, buzzing along at a significant fraction of the speed of light. But physicists have created a new process to slow neutrons down to about 15 miles per hour—the pace of a world-class mile runner—which could lead to breakthroughs in understanding the physical universe at its most fundamental level.

According to Brad Filippone, a physics professor at the California Institute of Technology, he and a group of colleagues from Caltech and several other institutions recently succeeded in collecting record-breaking numbers of ultracold neutrons at the Los Alamos Neutron Science Center. The new technique resulted in about 140 neutrons per cubic centimeter, and the number could be five times higher with additional tweaking of the apparatus.

"Our principal interest is in making precision measurements of fundamental neutron properties," says Filippone, explaining that a neutron has a half-life of only 15 minutes. In other words, if a thousand neutrons are trapped, five hundred will have broken down after 15 minutes into a proton, electron, and antineutrino.

Neutrons normally exist in nature in a much more stable state within the nuclei of atoms, joining the positively charged protons to make up most of the atom's mass. Neutrons become quite unstable if they are stripped from the nucleus, but the very fact that they decay so quickly can make them useful for various experiments.

The traditional way physicists obtained free neutrons was by trying to slow them down as they emerged from a nuclear reactor, making them bounce around in material to get rid of energy. This procedure worked fine for slowing down neutrons to a few feet per second, but that's still pretty fast. The new technique at Los Alamos National Laboratory involves a second stage of slowdown that is impractical near a nuclear reactor, but which works well at a nuclear accelerator where the event producing the neutrons is abrupt rather than ongoing. The process begins with smashing protons from the accelerator into a solid material like tungsten, which results in neutrons being knocked out of their nuclei.

The neutrons are then slowed down as they bounce around in a nearby plastic material, and then some of them are slowed much further if they happen to enter a birthday-cake-sized block of solid deuterium (or "heavy hydrogen") that has been cooled down to a temperature a few degrees above absolute zero.

When the neutrons enter the crystal latticework of the deuterium block, they can lose virtually all their energy, and emerge from the block at speeds so slow they can no longer zip right through the walls of the apparatus. The trapped ultracold neutrons bounce along the nickel walls of the apparatus and eventually emerge, where they can be collected for use in a separate experiment. According to Filippone, the extremely slow speeds of the neutrons are important in studying their decays at a minute level of detail. The fundamental theory of particle physics known as the Standard Model predicts a specific pattern in the neutron's decay, but if the ultracold neutron experiments were to reveal slightly different behavior, then physicists would have evidence of a new type of physics, such as supersymmetry. Future experiments could also exploit an inherent quantum limit of the ultracold neutrons to bounce no lower than about 15 microns on a flat surface—or about a fifth the width of a human hair. With a cleverly designed experiment, Filippone says, this limit could lead to better knowledge of gravitational interactions at very small distances. The next step for the experimenters is to return to Los Alamos in October. Then, they will use the ultracold neutrons to study the neutrons themselves. The research was supported by about $1 million funding from Caltech and the National Science Foundation.

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Researchers demonstrate existenceof earthquake supershear phenomenon

PASADENA, Calif.--As if folks living in earthquake country didn't already have enough to worry about, scientists have now identified another rupture phenomenon that can occur during certain types of large earthquakes. The only question now is whether the phenomenon is good, bad, or neutral in terms of human impact.

Reporting in the March 19 issue of the journal Science, California Institute of Technology geophysics graduate student Kaiwen Xia, aeronautics and mechanical engineering professor Ares Rosakis, and geophysics professor Hiroo Kanamori have demonstrated for the first time that a very fast, spontaneously generated rupture known as "supershear" can take place on large strike-slip faults like the San Andreas. They base their claims on a laboratory experiment designed to simulate a fault rupture.

While calculations dating back to the 1970s have predicted that such supershear rupture phenomena may occur in earthquakes, seismologists only recently began assuming that supershear was real. The Caltech experiment is the first time that spontaneous supershear rupture has been conclusively identified in a controlled laboratory environment, demonstrating that super-shear fault rupture is a very real possibility rather than a mere theoretical construct.

In the lab, the researchers forced two plates of a special polymer material together under pressure and then initiated an "earthquake" by inserting a tiny wire into the interface, which is turned into an expanding plasma by the sudden discharge of an electrical pulse. By means of high-speed photography and laser light, the researchers photographed the rupture and the stress waves as they propagated through the material.

The data shows that, under the right conditions, the rupture propagates much faster than the shear speed in the plates, producing a shock-wave pattern, something like the Mach cone of a jet fighter breaking the sound barrier.

The split-second photography also shows that such ruptures may travel at about twice the rate that a rupture normally propagates along an earthquake fault. However, the ruptures do not reach supershear speeds until they have propagated a certain distance from the point where they originated. Based on the experiments, a theoretical model was developed by the researchers to predict the length of travel before the transition to supershear.

In the case of a strike-slip fault like the San Andreas, the lab results indicate that the rupture needs to rip along for about 100 kilometers and the magnitude must be about 7.5 or so before the rupture becomes supershear. Large earthquakes along the San Andreas tend to be at least this large if not larger, typically involving rupture lengths of about 300 to 400 kilometers.

"Judging from the experimental result, it would not be surprising if supershear rupture propagation occurs for large earthquakes on the San Andreas fault," said Kanamori.

Similar high-speed ruptures propagating along bimaterial interfaces in engineering composite materials have been experimentally observed in the past (by Rosakis and his group, reporting in an August 1999 issue of Science). These ruptures took place under impact loading; only in the current experiment have they been initiated in an earthquake-like set-up.

According to Rosakis, an expert in crack propagation, the new results show promise in using engineering techniques to better understand the physics of earthquakes and its human impact.

According to Kanamori, the human impact of the finding is still debatable. The most damaging effect of a strike-slip earthquake is believed to be caused by a pulse-like motion normal to the fault caused by the combined effect of the rupture and shear wave. The supershear rupture suppresses this pulse, which is good, but the persistent shock-wave (Mach wave) emitted by the supershear rupture enhances the fault-parallel component of motion (the ground motion that runs in the same direction that the plates slip) and could amplify the destructive power of ground motion, which is bad.

The outstanding question about supershear at this point is which of these two effects dominates. "This is still being debated," says Kanamori. "We're not committed to one view or the other." Only further laboratory-level experimentation can answer this question conclusively.

Several seismologists believe that supershear was exhibited in some large earthquakes, including those that occurred in Tibet in 2001 and in Alaska in 2002. Both earthquakes were located in a remote region and had little, if any, human impact, but analysis of the evidence shows that the fault rupture propagated much faster than would normally be expected, thus implying supershear.

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Robert Tindol
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Most distant object in solar system discovered; could be part of never-before-seen Oort cloud

PASADENA, Calif.--A planetoid more than eight billion miles from Earth has been discovered by researchers led by a scientist at the California Institute of Technology. The new planetoid is more than three times the distance of Pluto, making it by far the most distant body known to orbit the sun.

The planetoid is well beyond the recently discovered Kuiper belt and is likely the first detection of the long-hypothesized Oort cloud. With a size approximately three-quarters that of Pluto, it is very likely the largest object found in the solar system since the discovery of Pluto in 1930.

At this extreme distance from the sun, very little sunlight reaches the planetoid and the temperature never rises above a frigid 400 degrees below zero Farenheit, making it the coldest known location in the solar system. According to Mike Brown, Caltech associate professor of planetary astronomy and leader of the research team, "the sun appears so small from that distance that you could completely block it out with the head of a pin."

As cold as it is now, the planetoid is usually even colder. It approaches the sun this closely only briefly during the 10,500 years it takes to revolve around the sun. At its most distant, it is 84 billion miles from the sun (900 times Earth's distance from the sun), and the temperature plummets to just 20 degrees above absolute zero.

The discoverers---Brown and his colleagues Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University--have proposed that the frigid planetoid be named "Sedna," after the Inuit goddess who created the sea creatures of the Arctic. Sedna is thought to live in an icy cave at the bottom of the ocean--an appropriate spot for the namesake of the coldest body known in the solar system.

The researchers found the planetoid on the night of November 14, 2003, using the 48-inch Samuel Oschin Telescope at Caltech's Palomar Observatory east of San Diego. Within days, the new planetoid was being observed on telescopes in Chile, Spain, Arizona, and Hawaii; and soon after, NASA's new Spitzer Space Telescope was trained on the distant object.

The Spitzer images indicate that the planetoid is no more than 1,700 kilometers in diameter, making it smaller than Pluto. But Brown, using a combination of all of the data, estimates that the size is likely about halfway between that of Pluto and that of Quaoar, the planetoid discovered by the same team in 2002 that was previously the largest known body beyond Pluto.

The extremely elliptical orbit of Sedna is unlike anything previously seen by astronomers, but it resembles in key ways the orbits of objects in a cloud surrounding the sun predicted 54 years ago by Dutch astronomer Jan Oort to explain the existence of certain comets. This hypothetical "Oort cloud" extends halfway to the nearest star and is the repository of small icy bodies that occasionally get pulled in toward the sun and become the comets seen from Earth.

However, Sedna is much closer than expected for the Oort cloud. The Oort cloud has been predicted to begin at a distance 10 times greater even than that of Sedna. Brown believes that this "inner Oort cloud" where Sedna resides was formed by the gravitational pull of a rogue star that came close to the sun early in the history of the solar system. Brown explains that "the star would have been close enough to be brighter than the full moon and it would have been visible in the daytime sky for 20,000 years." Worse, it would have dislodged comets further out in the Oort cloud, leading to an intense comet shower, which would have wiped out any life on Earth that existed at the time.

There is still more to be learned about this newest known member of the solar system. Rabinowitz says that he has indirect evidence that there may be a moon following the planetoid on its distant travels--a possibility that is best checked with the Hubble Space Telescope--and he notes that Sedna is redder than anything known in the solar system with the exception of Mars, but no one can say why. Trujillo admits, "We still don't understand what is on the surface of this body. It is nothing like what we would have predicted or what we can currently explain."

But the astronomers are not yet worried. They can continue their studies as Sedna gets closer and brighter for the next 72 years before it begins its 10,500-year trip out to the far reaches of the solar system and back again. Brown notes, "The last time Sedna was this close to the sun, Earth was just coming out of the last the last ice age; the next time it comes back, the world might again be a completely different place."

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Robert Tindol
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Researchers discover fundamental scaling rule that differentiates primate and carnivore brains

PASADENA, Calif.--Everybody from the Tarzan fan to the evolutionary biologist knows that our human brain is more like a chimpanzee's than a dog's. But is our brain also more like a tiny lemur's than a lion's?

In one previously unsuspected way, the answer is yes, according to neuroscientists at the California Institute of Technology. In the current issue of the Proceedings of the National Academy of Sciences (PNAS), graduate student Eliot Bush and his professor, John Allman, report their discovery of a basic difference between the brains of all primates, from lemurs to humans, and all the flesh-eating carnivores, such as lions and tigers and bears.

The difference lies in the way the percentage of frontal cortex mass increases as the species gets larger. The frontal cortex is the portion of brain just behind the forehead that has long been associated with reasoning and other "executive" functions. In carnivores, the frontal cortex becomes proportionately larger as the entire cortex of the individual species increases in size--in other words, a lion that has a cortex twice the size of another carnivore's also has a frontal cortex twice the size.

By contrast, primates like humans and apes tend to have a frontal cortex that gets disproportionately larger as the overall cortex increases in size. This phenomenon is known as "hyperscaling," according to Bush, the lead author of the journal article.

What this says about the human relationship to the tiny lemurs of Madagascar is that the two species likely share a developmental or structural quirk, along with all the other primates, that is absent in all the carnivores, Bush explains. "The fact that humans have a large frontal cortex doesn't necessarily mean that they are special; relatively large frontal lobes have developed independently in aye-ayes among the lemurs and spider monkeys among the New World monkeys."

Bush and Allman reached their conclusions by taking the substantial histological data from the comparative brain collection at the University of Wisconsin at Madison. The collection, accumulated over many years by neuroscientist Wally Welker, comprises painstaking data taken from well over 100 species.

Bush and Allman's innovation was taking the University of Wisconsin data and running it through special software that allowed for volume estimations of the various structures of the brain in each species. Their results compared 43 mammals (including 25 primates and 15 carnivores), which allowed them to make very accurate estimations of the hyperscaling (or the lack thereof) in the frontal cortex.

The results show that in primates the ratio of frontal cortex to the rest of the cortex is about three times higher in a large primate than in a small one. Carnivores don't have this kind of systematic variation.

The hyperscaling mechanism is genetic, and was presumably present when the primates first evolved. "Furthermore, it is probably peculiar to primates," says Allman, who is Hixon Professor of Neurobiology at Caltech.

The next step will be to look at the developmental differences between the two orders of mammals by looking at gene expression differences. Much of this data is already available through the intense efforts in recent years to acquire the complete genomes of various species. The human genome, for example, is already complete, and the chimp genome is nearly so.

"We're interested in looking for genes involved in frontal cortex development. Changes in these may help explain how primates came to be different from other mammals," Bush says.

At present, the researchers have no idea what the difference is at the molecular level, but with further study they should be able to make this determination, Allman says. "It's doable."

The article is titled "The scaling of frontal cortex in primates and carnivores." For a copy of the article, contact Jill Locantore, PNAS communications specialist, at 202-334-1310, or e-mail her at jlocantore@nas.edu.

The PNAS Web site is at http://www.pnas.org.

For more information on Bush and Allman's research, go to the Web site http://allmanlab.caltech.edu/people/bush/3d-histol/3d-brain-recon.html

 

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Robert Tindol
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Planetary scientists find planetoid in Kuiper Belt; could be biggest yet discovered

PASADENA, Calif.—Planetary scientists at the California Institute of Technology and Yale University on Tuesday night discovered a new planetoid in the outer fringes of the solar system.

The planetoid, currently known only as 2004 DW, could be even larger than Quaoar--the current record holder in the area known as the Kuiper Belt--and is some 4.4 billion miles from Earth.

According to the discoverers, Caltech associate professor of planetary astronomy Mike Brown and his colleagues Chad Trujillo (now at the Gemini North observatory in Hawaii), and David Rabinowitz of Yale University, the planetoid was found as part of the same search program that discovered Quaoar in late 2002. The astronomers use the 48-inch Samuel Oschin Telescope at Palomar Observatory and the recently installed QUEST CCD camera built by a consortium including Yale and the University of Indiana, to systematically study different regions of the sky each night.

Unlike Quaoar, the new planetoid hasn't yet been pinpointed on old photographic plates or other images. Because its orbit is therefore not well understood yet, it cannot be given an official name.

"So far we only have a one-day orbit," said Brown, explaining that the data covers only a tiny fraction of the orbit the object follows in its more than 300-year trip around the sun. "From that we know only how far away it is and how its orbit is tilted relative to the planets."

The tilt that Brown has measured is an astonishingly large 20 degrees, larger even than that of Pluto, which has an orbital inclination of 17 degrees and is an anomaly among the otherwise planar planets.

The size of 2004 DW is not yet certain; Brown estimates a size of about 1,400 kilometers, based on a comparison of the planetoid's luminosity with that of Quaoar. Because the distance of the object can already be calculated, its luminosity should be a good indicator of its size relative to Quaoar, provided the two objects have the same albedo, or reflectivity.

Quaoar is known to have an albedo of about 10 percent, which is slightly higher than the reflectivity of our own moon. Thus, if the new object is similar, the 1,400-kilometer estimate should hold. If its albedo is lower, then it could actually be somewhat larger; or if higher, smaller.

According to Brown, scientists know little about the albedos of objects this large this far away, so the true size is quite uncertain. Researchers could best make size measurements with the Hubble Space Telescope or the newer Spitzer Space Telescope. The continued discovery of massive planetoids on the outer fringe of the solar system is further evidence that objects even farther and even larger are lurking out there. "It's now only a matter of time before something is going to be discovered out there that will change our entire view of the outer solar system," Brown says.

The team is working hard to uncover new information about the planetoid, which they will release as it becomes available, Brown adds. Other telescopes will also be used to better characterize the planetoid's features.

Further information is at the following Web site: http://www.gps.caltech.edu/~chad/2004dw

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Robert Tindol
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Researchers Using Hubble and Keck Telescopes Find Farthest Known Galaxy in the Universe

PASADENA, California--The farthest known object in the universe may have been discovered by a team of astrophysicists using the Keck and Hubble telescopes. The object, a galaxy behind the Abell 2218 cluster, may be so far from Earth that its light would have left when the universe was just 750 million years old.

The discovery demonstrates again that the technique known as gravitational lensing is a powerful tool for better understanding the origin of the universe. Via further applications of this remarkable technique, astrophysicists may be able to better understand the mystery of how the so-called "Dark Ages" came to an end.

According to California Institute of Technology astronomer Jean-Paul Kneib, who is the lead author reporting the discovery in a forthcoming article in the Astrophysical Journal, the galaxy is most likely the first detected close to a redshift of 7.0, meaning that it is rushing away from Earth at an extremely high speed due to the expansion of the universe. The distance is so great that the galaxy's ultraviolet light has been stretched to the point of being observed at infrared wavelengths.

The team first detected the new galaxy in a long exposure of the Abell 2218 cluster taken with the Hubble Space Telescope's Advanced Camera for Surveys. Analysis of a sequence of Hubble images indicate a redshift of at least 6.6, but additional work with the Keck Observatory's 10-meter telescopes suggests that the astronomers have found an object whose redshift is close to 7.0.

Redshift is a measure of the factor by which the wavelength of light is stretched by the expansion of the universe. The greater the shift, the more distant the object and the earlier it is being seen in cosmic history.

"As we were searching for distant galaxies magnified by Abell 2218, we detected a pair of strikingly similar images whose arrangement and color indicated a very distant object," said Kneib. "The existence of two images of the same object indicated that the phenomenon of gravitational lensing was at work."

The key to the new discovery is the effect the Abell 2218 cluster's gigantic mass has on light passing by it. As a consequence of Einstein's theory of relativity, light is bent and can be focused in a predictable way due to the warpage of space-time near massive objects. In this case the phenomenon actually magnifies and produces multiple images of the same source. The new source in Abell 2218 is magnified by a factor of 25.

The role of gravitational lensing as a useful phenomenon in cosmology was first pointed out by the Caltech astronomer Fritz Zwicky in 1937, who even suggested it could be used to discover distant galaxies that would otherwise be too faint to be seen.

"The galaxy we have discovered is extremely faint, and verifying its distance has been an extraordinarily challenging adventure," Kneib added. "Without the magnification of 25 afforded by the foreground cluster, this early object could simply not have been identified or studied in any detail with presently available telescopes. Indeed, even with aid of the cosmic lens, our study has only been possible by pushing our current observatories to the limits of their capabilities."

Using the unique combination of the high resolution of Hubble and the magnification of the cosmic lens, the researchers estimate that the galaxy is small--perhaps measuring only 2,000 light-years across—but forming stars at an extremely high rate.

An intriguing property of the new galaxy is the apparent lack of the typically bright hydrogen emission seen in many distant objects. Also, its intense ultraviolet signal is much stronger than that seen in later star-forming galaxies, suggesting that the galaxy may be composed primarily of massive stars.

"The unusual properties of this distant source are very tantalizing because, if verified by further study, they could represent those expected for young stellar systems that ended the dark ages," said Richard Ellis, Steele Family Professor of Astronomy, and a coauthor of the article.

The term "Dark Ages" was coined by the British astronomer Sir Martin Rees to signify the period in cosmic history when hydrogen atoms first formed but stars had not yet had the opportunity to condense and ignite. Nobody is quite clear how long this phase lasted, and the detailed study of the cosmic sources that brought this period to an end is a major goal of modern cosmology.

The team plans to continue the search for additional extremely distant galaxies by looking through other cosmic lenses in the sky.

"Estimating the abundance and characteristic properties of sources at early times is particularly important in understanding how the Dark Ages came to an end," said Mike Santos, a former Caltech graduate student involved in the discovery and now a postdoctoral researcher at the Institute of Astronomy in Cambridge, England. "We are eager to learn more by finding further examples, although it will no doubt be challenging."

The Caltech team reporting on the discovery consists of Kneib, Ellis, Santos, and Johan Richard. Kneib and Richard are also affiliated with the Observatoire Midi-Pyrenees of Toulouse, France. Santos is also at the Institute of Astronomy, in Cambridge.

The research was funded in part by NASA.

The W. M. Keck Observatory is managed by the California Association for Research in Astronomy, a scientific partnership between the California Institute of Technology, the University of California, and NASA. For more information, visit the observatory online at www.keckobservatory.org.

Writer: 
RT

Zombie Behaviors Are Part of Everyday Life, According to Neurobiologists

PASADENA, Ca.--When you're close to that woman you love this Valentine's Day, her fragrance may cause you to say to yourself, "Hmmm, Chanel No. 5," especially if you're the suave, sophisticated kind. Or if you're more of a missing link, you may even say to yourself, "Me want woman." In either case, you're exhibiting a zombie behavior, according to the two scientists who pioneered the scientific study of consciousness.

Longtime collaborators Christof Koch and Francis Crick (of DNA helix fame) think that "zombie agents"--that is, routine behaviors that we perform constantly without even thinking--are so much a central facet of human consciousness that they deserve serious scientific attention. In a new book titled The Quest for Consciousness: A Neurobiological Approach, Koch writes that interest in the subject of zombies has nothing to do with fiction, much less the supernatural. Crick, who for the last 13 years has collaborated with Koch on the study of consciousness, wrote the foreword of the book.

The existence of zombie agents highlights the fact that much of what goes on in our heads escapes awareness. Only a subset of brain activity gives rise to conscious sensations, to conscious feelings. "What is the difference between neuronal activity associated with consciousness and activity that bypasses the conscious mind?" asks Koch, a professor at the California Institute of Technology and head of the Computation and Neural Systems program.

Zombie agents include everything from keeping the body balanced, to unconsciously estimating the steepness of a hill we are about to climb, to driving a car, riding a bike, and performing other routine yet complex actions. We humans couldn't function without zombie agents, whose key advantage is that reaction times are kept to a minimum. For example, if a pencil is rolling off the table, we are quite able to grab it in midair, and we do so by executing an extremely complicated set of mental operations. And zombie agents might also be involved, by way of smell, in how we choose our sexual partners.

"Zombie agents control your eyes, hands, feet, and posture, and rapidly transduce sensory input into stereotypical motor output," writes Koch. "They might even trigger aggressive or sexual behavior when getting a whiff of the right stuff.

"All, however, bypass consciousness," Koch adds. "This is the zombie in you."

Zombie actions are but one of a number of topics that Koch and Crick have investigated since they started working together on the question of the brain basis of consciousness. Much of the book concerns perceptual experiments in normal people, patients, monkeys, and mice, that address the neuronal underpinnings of thoughts and actions.

As Crick points out in his foreword, consciousness is the major unsolved problem in biology. The Quest for Consciousness describes Koch and Crick's framework for coming to grips with the ancient mind-body problem. At the heart of their framework is discovering and characterizing the neuronal correlates of consciousness, the subtle, flickering patterns of brain activity that underlie each and every conscious experience.

The Quest for Consciousness: A Neurobiological Approach will be available in bookstores on February 27. For more information, see www.questforconsciousness.com. For review copies, contact Ben Roberts at Roberts & Company Publishers at (303) 221-3325, or send an e-mail to bwr@roberts-publishers.com.

Writer: 
Robert Tindol
Writer: 

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