Thursday, 28 October 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Physicists Vote to Run Tevatron for 3 More Years

Posted: 27 Oct 2010 02:40 PM PDT

A group of high-energy particle physicists decided this week to recommend extending the life of the Tevatron, the second-most-powerful particle collider in the world, for 3 years.

The panel's recommendation goes to the Department of Energy, then Congress and ultimately to the White House. The funding decision could determine whether the United States or Europe wins the race to find the theoretical Higgs boson. It all comes down to $105 million, a tiny amount relative to the billions spent building the massive particle colliders competing for the find.

The Tevatron at Fermilab in Batavia, Illinois, is potentially powerful enough to confirm or deny the existence of the Higgs boson, which would help explain the origin of mass in the universe. But the machine needs more time, and its scheduled September 2011 shutdown would almost certainly allow Europe's new, more powerful Large Hadron Collider to get there first.

The LHC, run by CERN in Geneva, will have more than enough energy to find the Higgs, says Robert Roser, an experimental physicist at Fermilab. But mechanical breakdowns set the project's start date back for more than a year, to September 2008, and prompted CERN to ramp the LHC up far more slowly, and to just half its top energy, before a 16-month shutdown to fix faulty magnets planned for December 2011. This leaves a window open for the Tevatron to catch the Higgs first, if it isn't shuttered first.


The 15 members of the U.S. particle-physics community who gathered in Washington, D.C., this week voted 14 to 1 in favor of giving the Tevatron 3 more years. The machine costs around $50 million per year to run. Fermilab has agreed to come up with $15 million annually, which will be diverted from other scientific projects.

"Now it's up those people [at the DOE] to work together to figure out how to get $35 million per year out of the budget," Roser said. "With a $4.7 billion total [DOE] Office of Science budget, I'm hoping it won't be that hard. But we'll see."

Ultimately, the decision is up to the Barack Obama administration, whose budget is due out in February 2011. If approved, the 3.9-mile-long circular collider will be allowed to gather data and sift for signs of the Higgs through 2014.

"Finding the Higgs is kind of like a casino. The more chances you have at pulling the slot machine, the more chances you have of winning the jackpot," Roser said. "Data buys us probability, and that will increase our odds of coming up with a significant result."

If the scientists' extension request fails, the LHC can pick up where the Tevatron left off in 2013 with seven times the particle-colliding power, which is more than enough to squeeze the Higgs out of hiding, if it exists. But this could take several more years than it would to find it with the Tevatron, which is running better than it ever has, despite being well beyond its designed life expectancy.

"Right now we have a track record of success. Only in the last year has the Tevatron been in the Higgs game, where we're able to make statements about the Higgs particle," Roser said. "It would be a shame to be in that regime and just turn it off."

Ultimately, finding the Higgs would be the best supporting evidence yet for the Standard Model of Physics — the guidebook to the particles and forces at work in the universe.

"We're trying to understand how mass fits into the Standard Model, and it's perhaps the single most important question facing our field right now," Roser said. "We need to use every tool available to solve it."

Images: Fermilab/Fred Ulrich 1) The Tevatron with Wilson Hall in the background. 2) The Collider Detector at Fermilab, one of the Tevatron's two detectors.

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Monkey Fossils Suggest Primates Came Out of Asia, Not Africa

Posted: 27 Oct 2010 12:22 PM PDT

The discovery of four ancient, lemur-like creatures in what is now Libya suggests the human family tree's taproot is in the Middle East, not Africa.

The conventional narrative of primate development places the origins of anthropoids — monkeys and apes, including humans — in Africa. Some paleontologists, however, think Asia is the more likely cradle for that ur-primate, or what Christopher Beard has called the "Dawn Monkey."

Beard, a paleontologist at the Carnegie Museum of Natural History, is among the co-authors of the paper describing the new primates, published October 28 in Nature. The four species' fossils, representing three distinct taxonomic families, are 40 million years old. Nothing similar was known to have lived in Africa at that time.

The diversity and timing of the new anthropoids raises two scenarios. Anthropoids might simply have emerged in Africa much earlier than thought, and gone undiscovered by modern paleontologists. Or they could have crossed over from Asia, where evidence suggests that anthropoids lived 55 million years ago, flourishing and diversifying in the wide-open ecological niches of an anthropoid-free Africa.


That humans may trace their evolutionary lineage to creatures like the newly-discovered anthropoids, which likely weighed between four ounces and one pound and could sit in the palm of your hand, is an intriguing possibility. But other paleontologists warn that more investigation is required.

"These discoveries are exciting and very informative," said Stony Brook University paleoanthropologist William Jungers, who was not involved in the study. But "more than anything else, these discoveries indicate that we still have a lot to learn."

Image: Mark A. Klingler/Carnegie Museum of Natural History.

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Citation: "Late middle Eocene epoch of Libya yields earliest known radiation of African anthropoids." By Jean-Jacques Jaeger, K. Christopher Beard, Yaowalak Chaimanee, Mustafa Salem, Mouloud Benammi, Osama Hlal, Pauline Coster, Awad A. Bilal, Philippe Duringer, Mathieu Schuster, Xavier Valentin, Bernard Marandat, Laurent Marivaux, Eddy Metais, Omar Hammuda & Michel Brunet. Nature, Vol. 467 No. 1095, October 28, 2010.

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Record-Breaking Neutron Star is a Clue to Exotic Physics

Posted: 27 Oct 2010 11:45 AM PDT

A quick-spinning stellar corpse is the most massive of its kind ever seen. The dead star's extra bulk could rule out several theories about what these dense stellar objects are made of, and provide a celestial lab to explore exotic matter.

"For people who work in this field, it's huge," said neutron star astronomer M. Coleman Miller of the University of Maryland, who was not involved in the new study. "It's a big new addition to our information about a state of matter that we cannot explore in labs."

Weighing in at twice the mass of the sun, the new heavyweight champ — a pulsar dubbed J1614-2230 — is 20 percent more massive than any previously measured star of its class.

Pulsars are a special type of neutron star, the dense remains of ordinary stars that exploded as supernovas, that sweep the sky with a lighthouse-like beam of radio waves as they spin. As these radio beams swish past Earth, the stars appear to "pulse" at extremely regular intervals.

Neutron stars, true to their name, are formed almost entirely of neutrons, which can pack tightly into the densest form of matter known to exist without forcing the star to collapse into a black hole. But some theories suggest neutron stars could squish down even further by converting their neutrons to exotic types of matter. If neutron stars were packed with heavy, strange particles like hyperons or kaons, the stars would collapse under their own weight at much lower masses.

"If you're able to establish that there really is an object out there with high mass," Miller said, "it takes a lot of the predictions you would make with the exotic forms of matter and different particles, and says 'I'm sorry, you're wrong. Try again.'"


To take the extra-heavy pulsar's measurements, astronomers relied on a relativistic trick of the light.

Pulsars are usually among the most accurate clocks in the universe, blinking regularly tens to thousands of times per second. But J1614-2230 has a companion star, a white dwarf. When the radio pulses brush past the white dwarf, they slow down as if they were swimming through molasses, and take a longer time to get to Earth.

This effect, called the Shapiro delay, is due to Einstein's general relativistic prediction that clocks run slower in a gravitational field, at least as seen from far away. The more massive the white dwarf is, the slower the pulses get.

Astronomer Paul Demorest of the National Radio Astronomy Observatory and colleagues used the Green Bank Telescope in West Virginia to watch how the times between pulses changed at different points in the pulsar's orbit around the white dwarf over the course of 8.7 days. A new instrument called GUPPI (Green Bank Ultimate Pulsar Processing Instrument) provided more precise measurements of the pulse delay than previous attempts could muster.

The astronomers used the mass of the white dwarf plus data on the pulsar's orbit to find the pulsar's mass: A whopping 1.97 times the mass of the sun. The next most-massive neutron star was 1.67 times the mass of the sun, and most neutron stars cluster around 1.25 to 1.44 times the mass of the sun. The results are reported in the Oct. 28 Nature.

"The pulsar mass is quite a bit higher for this system than any that have been previously measured," Demorest said. "That changes our thinking about what is the maximum possible mass a neutron star can have."

Because the team used the Shapiro delay, the measurement is more reliable than previous attempts to measure neutron star mass, Miller added.

"The Shapiro delay depends only on the mass, full stop, no other effects," he said. "It's much easier to interpret than others that have previously suggested higher masses."

The bulky star rules out all but a few models for the composition of neutron stars. Rather than containing exotic particles, the stellar corpses are probably made of plain neutrons and protons.

But that's hardly a disappointment to Miller. "It's cool," he said. "It represents a state of matter and a state of physics that we cannot reproduce on Earth. By these distant and safe observations, we're able to learn things about fundamental physical law that we could not learn otherwise."

One pressing theoretical question remains: How did the pulsar get so big? Is it slowly devouring its companion? Or was it just born this big?

"Either would be a valid explanation," Demorest said. "We just don't know which is correct yet."

Image: Bill Saxton/NRAO/AUI/NSF

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Assassin Bug Eats Spiders After Feigning Capture

Posted: 27 Oct 2010 08:37 AM PDT

By Duncan Geere, Wired UK

A species of assassin bug has been found which creeps onto spiders' webs and pretends to be prey, then devours the spider when it comes to investigate.

The creature, known to entomologists as Stenolemus bituberus, and actually in the spider family itself too, is the subject of a paper just published in Proceedings of the Royal Society B by Annie Wignall from Macquarie University in Sydney, Australia. Wignall describes the exact process of "aggressive mimicry" by which the assassin bug stalks its target.

Most predators conceal themselves in order to capture prey, but the assassin bug takes the opposite approach — overtly advertising its presence in a way that entices its dinner to investigate. Web-building spiders use vibrations in their web to detect when it's caught something, so they can go over, bind it in more web, and eat it.

The assassin bug slowly approaches the spider on its web, using its forelegs to pluck the silk threads in a manner that simulates the vibrations of a fly struggling after being caught. Wignall studied the behavior of the bugs, and found that the response of the spider to the predator was the same as its response to when a vinegar fly or aphid was caught in the web.


Once the spider is close enough, the assassin bug lashes out, and eats the poor unsuspecting arachnid. Most of the time, anyway — Wignall also observed a few occasions of spiders counter-attacking the bugs and killing and eating them instead.

Wignall points out that the assassin bug doesn't identically replicate the vibrations caused by prey — there are several higher-amplitude vibrations that prey generate which aren't simulated by the bug. But the spider doesn't seem to be able to generally differentiate between the two.

The work could have implications for the physics of how vibrations propagate through three-dimensional webs.

Images: 1) Flickr/jeffsmallwood. 2) An assassin bug. Flickr/dhobern


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Neuron Recordings Capture Brain Focus on Josh Brolin

Posted: 26 Oct 2010 11:08 AM PDT

By measuring the activity of single neurons, researchers have recorded what happens when people narrow their focus on subjects like Josh Brolin or Marilyn Monroe.

The neuroscientists weren't interested in the actors, however, but rather the dynamics of attention.

"Say you're walking down the street, and there are cars, buildings, trees, people, all competing for your attention. Some stand out more than others, and you don't control that. It just happens. How does this happen in your brain?" said computational neuroscientist Moran Cerf of the California Institute of Technology.

For an experiment published October 28 in Nature, Cerf's team enlisted the help of epileptics whose brains had been temporarily wired to computer monitors, allowing doctors to see where seizure patterns began in anticipation of corrective surgery. Invasive deep-brain procedures aren't allowed for the sake of basic, non-medical research, but since the epileptics' brains are already wired, Cerf's team was able to conduct a unique experiment.

In earlier research, they'd correlated firings of individual neurons in the medial temporal lobes — the brain's processing centers — with individual people (namely, Halle Berry.) In this study, they linked neurons to easily recognizable people like Monroe, Brolin, Venus Williams and Michael Jackson.


Cerf's team simultaneously displayed pairs of their pictures on a computer monitor, then asked test subjects to concentrate on one person. As their minds focused, the images flickered back and forth, finally settling on the target image. As this happened, their mental activity was recorded in real-time.

The researchers weren't particularly interested in specific neurons, or even specific brain regions: Each wired neuron was representative of five million more, spread across the brain. Instead, he was looking for patterns of focus.

"The most exciting thing is that patients sometimes fail in the task. Someone sees a picture of Marilyn Monroe and Josh Brolin, and his task is to focus on Brolin. But, somehow, the image of Marilyn Monroe catches his attention more. The image moves away from Brolin. It's 90 percent Marilyn. And then, when he's about to fail, he manages to summon Josh Brolin in his mind," Cerf said.

"There's competition between two senses, between vision and imagery. The eyes bring one image, his mind's eye brings another, and those fight. We can see how one wins over the other. This is a remarkable moment, because it happens every day in our life, and we never saw it first-hand."

Cerf expected focus would result from an increase in target-focused activity, so with people asked to focus on Josh Brolin, the Brolin-linked parts of the brain would fire more. Instead, he found the Marilyn Monroe-linked regions fired less. Brains narrowed focus not by enhancing their targets, but by diminishing distraction.

As for how that selective diminishing was performed, Cerf couldn't tell. He likened the experiment to seeing flows of water at a river's end, without knowing what dam operators were doing upstream. Whatever was responsible for guiding focus wasn't wired with the electrodes in the patients, nor will it be.

"Upstream? I wish," said Cerf. "If I could, I'd put electrodes all the way from the vision area, and look at information flow from the moment you get photons hitting the retina to the point where they become concepts. But there isn't reason" to put those electrons in patients.

In future studies, Cerf hopes to measure associations more completely and see what other parts of the mind are triggered by thinking of larger concepts.

"There's a cloud of associations that surround each concept. We don't know how they're formed, or how far they go. The idea now is to try to find one concept, start moving away from it, and see where the borders are," he said.

Video: After the researchers map neurons to images in study participants' brains, on-screen images change depending on their mental focus./Moran Cerf.

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Citation: "On-line, voluntary control of human temporal lobe neurons." By Moran Cerf, Nikhil Thiruvengadam, Florian Mormann, Alexander Kraskov, Rodrigo Quian Quiroga, Christof Koch & Itzhak Fried. Nature, Volume 467 Number 7319, October 28, 2010.

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