Friday, 17 December 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Missing Black Holes Cause Trouble for String Theory

Posted: 17 Dec 2010 09:52 AM PST

By John Timmer, Ars Technica

The results continue to pour out of the LHC's first production run. This week, the folks behind the CMS detector have announced the submission of a paper to Physics Letters that describes a test of some forms of string theory. If this form of the theory were right, the LHC should have been able to produce small black holes that would instantly decay (and not, as some had feared, devour the Earth). But a look at the data obtained by CMS shows that a signature of the black holes' decay is notably absent.

String theory is an attempt to deal with the fact that the two major theories in physics, quantum mechanics and relativity, are fundamentally incompatible. It manages to merge the two by positing a set of extra dimensions beyond the usual four. We don't see these because they're tightly wrapped within a tiny radius that is inapproachable at normal energies.

In one form of string theory — the paper calls it the ADD model because Arkani-Hamed, Dimopoulos, and Dvali proposed it — this unification has consequences for gravity. Normally, gravity is very weak relative to the other forces, such that it could only become unified with the rest of them at energies many orders of magnitude higher than the LHC could reach. But, in the ADD model, gravity only looks weak because portions of it are caught up in the remaining dimensions. This drops the energies down to something right in the heart of the LHC's capabilities.


If everything went as the model proposes, particles that collided at energies above this cutoff could close to within a distance that's smaller than the space occupied by the additional dimensions. Once that happens, they'd feel the full force of gravity, and immediately merge to form a tiny black hole. So tiny, in fact, that it would instantly decay via Hawking radiation. This decay would be visible as jets of particles; physicists I've seen asked about these have more or less said "you couldn't miss it."

What you could do, however, is mistake something else for a black hole. Interactions governed by quantum chromodynamics will also produce jets at a certain frequency, so the black hole events would have to stand out above this background. So that's what the new analysis looks for. The authors model what the jets from both string and quantum theories should look like in order to allow them to pull out and save jet events. (This actually involved the same modeling software used by the people who evaluated the TSA's scanners.)

They then use an area of the LHC's energy spectrum that's too low to produce black holes to figure out the level of background jet production via quantum chromodynamics. Next, they extend the analysis into the energy range where black holes should appear, and see whether any signal stands out above this background. It doesn't. "We can exclude the production of black holes with minimum mass of 3.5-4.5eV for values of the multidimensional Planck scale up to 3.5TeV at 95 percent CL," the authors conclude.

The results are also useful for studies beyond string theory. Mini black holes aren't the only hypothetical items predicted to decay into jets, so the lack of a signal that's much above background puts some very severe constraints on the physics there, too.

One other nice thing here is that the energies involved are completely out of reach of the Tevatron. So, even if the older collider beats the new machine to the punch on the Higgs, we're clearly getting some useful physics out of the LHC.

Contrary to some reports, this result doesn't mean the death of string theory, only the particular flavor that predicted black holes at these energies. Eliminating some models is a critical process of narrowing down what's possible, but most theoretical constructs have a range of possible models, and string theory is no different. In fact, it's entirely possible that the ADD model was generated simply because physicists were looking for something they could possibly test in the LHC.

Images: CMS Collaboration/CERN. 1) The Large Hadron Collider's Compact Muon Solenoid (CMS) detector. 2) A collision event as expected from Standard Model processes. Such events are a background to the search for microscopic black holes. Credit: CMS Collaboration/CERN

Source: Ars Technica

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Opportunity Rover Finds Fresh Crater on Mars

Posted: 17 Dec 2010 09:21 AM PST

SAN FRANCISCO — The Mars rover Opportunity has just rolled up to a fresh new crater that could hold clues to when and why Mars dried up.

This image was downloaded from Opportunity at 10 am Pacific time on Dec. 15 and presented in a press conference at the American Geophysical Union meeting Dec. 16. Opportunity sits on the western rim of a 300-foot-wide crater called Santa Maria, which the rover team thinks has some of the freshest Martian dirt Opportunity has ever studied.

"We've never seen a crater this fresh, this big," said planetary scientist Ray Arvidson of Washington University in St. Louis, the Mars rovers' deputy principal investigator.

The rover was guided from above by NASA's sharp-eyed Mars Reconnaissance Orbiter (MRO), which carries an instrument that can detect what the rocks and soils 150 miles below are made of.

"It lets us make a spectral fingerprint to identify different minerals on the planet," said planetary scientist Janice Bishop of NASA's Ames Research Center and the SETI Institute.


Mars is dry now, but clues such as the presence of clay-like minerals that can form only in the presence of water suggest that the surface was once much wetter. The surface is also laced with materials called hydrated sulfates, which formed in a more acidic and dryer environment. Mars scientists think the region was once dotted with muddy lakes that dried out billions of years ago.

But since it dried up, dust and wind has coated the Martian surface with a thin layer of "desert varnish." These same processes, which chemically alter the soil's composition, happen on Earth as well, Arvidson said.

"If you fly across the southwest and it looks brown, that's all desert varnish," he said. "It obscures the true mineralogy of the bedrock."

Impact craters dig up the soil and give planetary geologists a glimpse of the bedrock below. And Santa Maria is one of the newest, freshest craters the rovers have encountered, just a few million years old.

"This is the first time where we may be able to see rocks that haven't been weathered or coated in the Mars environment," Arvidson said.

One patch on the southeastern rim has planetary scientists particularly excited. MRO's orbiting spectral studio detected signs of monohydrated sulfates in the 65-square-foot region, which could represent a transition between the wet and dry periods on Mars.

Opportunity will arrive there in January, just in time for the sun to pass between Earth and Mars and make sending commands to the rover difficult. The rover will take advantage of the communication blackout by spending a solid two weeks studying the strange patch, Arvidson said.

The next stop for Opportunity is the 14-mile-wide Endeavor crater, about 3.7 miles away. Since landing on Mars in January 2004, Opportunity has covered about 16 miles, even though it was only designed to last for 90 days.

"This vehicle is so far out of warranty, and works so supremely well," Arvidson said.

Opportunity is showing signs of age, though, said rover project manager John Callas. The rover's right front wheel started sticking about one Martian year (23 Earth months) ago. To more evenly distribute the wear and tear on the wheel gears, the team has been driving the rover backwards ever since.

Opportunity's twin rover, Spirit, had similar trouble shortly before its front right wheel failed for good. Spirit got stuck in a sand trap in 2009, and hasn't been heard from since March of this year. The rover team is still listening for Spirit to wake up, but they're anxious to avoid letting Opportunity fall into a similar trap.

Images: 1) View of Santa Maria's western edge from Opportunity's navigation cameras. 2) Santa Maria from orbit. NASA/JPL/Cornell/University of Arizona

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DIY Biotech Hacker Space Opens in NYC

Posted: 16 Dec 2010 02:25 PM PST

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NEW YORK — On the top floor of an old bank converted into an artist collective, just past prop design for Bjork's next music video, the do-it-yourself biotechnology revolution has begun.

A cadre of science entrepreneurs recently opened Genspace, the world's first government-compliant community biotech laboratory. The bedroom-sized facility was two years in the making and, for a $100-per-month membership, anyone can use the space for whatever experiments they dream up.

"If you work in a university lab, you have to do what your adviser tells you to do," said Genspace co-founder Dan Gruskhkin, a freelance journalist and self-described science enthusiast. "Here, you work under mentors and can do things you're interested in immediately."


The small space is made of found parts. A sliding patio door, Plexiglas panels and old wire screens enclose the lab, and stainless steel restaurant tables serve as lab benches.

The lab's glassware, micropipettes, centrifuges, electrophoresis machines, incubators, microscopes and other scientific equipment were donated. Genspace president and co-founder Ellen Jorgensen, a biomedical researcher at New York Medical College, used to work for Vector Research Ltd. and got the company to donate the gear after they shut down a facility.

The lab may be cobbled together, but biosafety officers approved it as compliant with the Center for Disease Control's biosafety level 1 regulations. That's a big difference between Genspace and D.I.Y. labs crammed into closets and garages across the country, says Jorgensen, and a big advantage.

"Most biological experiments are not one-offs. They're continuous processes that last more than one day," Jorgensen said. Before Genspace's lab was built, she, Grushkin and two other founders set up labs in their living rooms using plastic tarps. After each experiment, however, they had to be torn down, decontaminated and thrown away.

"Now we have a secure lab space where we can do quality, professional-level science," Jorgensen said.

Out of concerns for bioterrorism and illegal drug production, the FBI and New York Police Department were initially alarmed by the idea of a public biotech lab in they city. But Grushkin says a lot of sit-down meetings with the agencies have convinced them.

"The FBI now uses pictures of our space to show people what a [methamphetamine] drug lab doesn't look like," Grushkin said. One of their FBI contacts even showed up at the space's grand opening last week to congratulate Grushkin.

Genspace's seven current lab members already have projects underway, including a biofuel algae experiment and a bacteria-powered arsenic detection kit. Grushkin plans to create transgenic, multi-colored microganisms that will "race" across a growth plate, primarily for fun but also for educational purposes. Jorgensen wants to use the new space to support personal genetic testing.

"I like the idea of a community lab where somebody can go to test themselves for a gene that may predispose them to a disease," Jorgensen said. "I think people have a right to get their DNA without involving a doctor."

Grushkin says another purpose of Genspace, now under review for non-profit status, is to help inner city schools bolster their science curricula.

"We're working with students from Hofstra University on Long Island to get their twelve-dollar digital microscope into classrooms," Grushkin said. The microscope can blow objects up to 170x magnification and stream a video feed to the Web. Similar devices typically cost hundreds of dollars, Grushkin says.

Genspace also has programs designed to bring science to the public. Literally, in some cases.

"One thing we did was extract DNA from strawberries in a public park," Grushkin said. "You should have heard some of the things people said, like, 'Ew, DNA is gross!'"

Such educational stunts provide a premium opportunity to start life-changing conversations about science, Jorgensen says, and empower people with knowledge.

Genspace opened their doors on Dec. 10, and was in attendance. Peek inside of the D.I.Y. lab here.

Images: A biofuel algae experiment. Credit: Dave Mosher/

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Cultural Evolution Could Be Studied in Google Books Database

Posted: 16 Dec 2010 02:11 PM PST

Google's massive trove of scanned books could be useful for researchers studying the evolution of culture.

In a paper published December 16 in Science, researchers turned part of that vast textual corpus into a 500 billion-word database in which the frequency of words can be measured over time and space.

Their initial subjects of analysis, including cultural trajectories of popular modern thinkers and the conjugation of irregular verbs, hint at what might be done.

"There are many more questions, that we could never think of, that this data makes possible," said Harvard University evolutionary dynamicist Jean-Michel Baptiste. "What we present in the paper is our first explorations of what becomes possible when you have this dataset."

The new research is part of an emerging approach to applying rigorous statistical analyses, traditionally known from the study of biological evolution, to cultural evolution.


Unlike biological evolution, however, which can be studied through the fossil record and in genomic comparisons, cultural evolution has proved difficult to study.

Researchers have used archaeological documentation of Polynesian canoe shapes and records painstakingly assembled by comparative linguists, but rich and rigorously compiled datasets are rare.

One potential source is Google, which has scanned some 15 million books, or roughly 12 percent of every book ever published. Michel-Baptiste and his colleagues turned one-third of these, selected for legibility and fully documented origins, into a massive word database.

Patterns that can be queried from its cloud are not necessarily answers unto themselves, they say, but a way of illuminating subjects of further investigation.

"It's not just an answer machine. It's a question machine," said study co-author Erez Lieberman-Aiden, a computational biologist at Harvard University. "Think of this as a hypothesis-generating machine."

In the new study, the researchers restricted their queries to single words and names, as more sophisticated querying raised the potential of copyright violation. (Google and book publishers are currently negotiating terms of access to copyright material, putting scientific accessibility and legal restrictions at odds.)

Even with these limitations, they were able to show how verbs with irregular endings — dwelt instead of dwelled, burnt instead of burned — have been regularized in different fashion in the United States and United Kingdom.

They also traced the prominence of 20th century thinkers — at least numerically, Freud overtook Darwin shortly after World War II — and quantified the public effects of censorship on intellectuals in China and Nazi Germany.

Another analysis found that modern fame both accrues and fades faster now than a century ago, giving quantitative form to an intuitively held sentiment. That example is particularly instructive, as the database identified a trend, but the implied social dynamics need to be studied through non-quantitative approaches.

Cultural evolution researchers greeted the database with qualified enthusiasm.

"There's a shortage of datasets. This might add another important database. But how valuable it's going to be is going to require a lot of thought about various biases in how the data is gathered," said Stanford University biologist Paul Ehrlich, whose investigations of Polynesian canoe design were among the first of the new cultural evolution studies.

Ehrlich cited the frequency of obscenity or the treatment of women as two off-the-cuff examples of topics for which a database of published books may not be a simple indicator of cultural trends.

"How the books reflect society is a major issue that depends a lot on what particular research you're interested in," he said.

Mark Pagel, a University of Reading evolutionary biologist who has studied the evolution of language, called the database "thrilling."

But like Ehrlich, he said the usefulness of the database would only become evident with time, and will require more sophisticated use.

To describe the database's potential for studying cultural evolution, the study authors coined the term "culturomics," a term that resonates with the modern field of genomics.

"There was great promise to genomics, and enormous hype surrounding the completion of the Human Genome Project. It was a few years before people realized that having a list of genes wasn't very useful at all. We now appreciate that it's not genes that matter, but how genes are expressed in bodies," said Pagel.

"I'm not saying the data isn't useful. It's just that the database is not going to cough up simple answers," he said.

The database is freely available for online queries and complete download.

Images: 1) Textual frequencies of influential western thinkers during the 20th century./Science. 2) Contrasting evolution of "burned" and "burnt" in the United States and United Kingdom./Science. 3) Culinary trends./Science.

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Citation: "Quantitative Analysis of Culture Using Millions of Digitized Books." By Jean-Baptiste Michel, Yuan Kui Shen, Aviva Presser Aiden, Adrian Veres, Matthew K. Gray, The Google Books Team, Joseph P. Pickett, Dale Hoiberg, Dan Clancy, Peter Norvig, Jon Orwant, Steven Pinker, Martin A. Nowak, Erez Lieberman Aiden. Science, Vol. 330 Issue 6011, December 17, 2010.

Rare Brain Disorder Prevents All Fear

Posted: 16 Dec 2010 11:35 AM PST

A middle-aged woman known as SM blithely reaches for poisonous snakes, giggles in haunted houses and once, upon escaping the clutches of a knife-wielding man, didn't run but calmly walked away. A rare kind of brain damage precludes her from experiencing fear of any sort, finds a study published online December 16 in Current Biology.

SM has an unusual genetic disorder called Urbach-Wiethe disease. In late childhood, this disease destroyed both sides of her amygdala, which is composed of two structures the shape and size of almonds, one on each side of the brain. Because of this brain damage, the woman knows no fear, the researchers found.

Experiments have strongly implicated the amygdala in fear processing. Many of these were conducted on animals with amygdala damage. "But one thing we've never known for sure, because they're animals, is whether they can consciously feel fear," says study coauthor Justin Feinstein of the University of Iowa in Iowa City. "So we said, 'Let's take a human patient who has this same sort of damage, and for the first time, actually figure out how they're feeling.'"


Feinstein and his colleagues sifted through SM's past, looking for instances when she should have been scared. SM said she never felt fear, even when threatened with a knife or a gun. The researchers gave SM an electronic diary that she carried for three months to record her emotional state. Fear didn't make an appearance in the list of emotions. On a battery of questionnaires, SM wrote that she wasn't afraid of public speaking, death, her heart beating too fast or being judged negatively in a social setting.

Next, the researchers did their best to scare SM. They showed her clips from The Blair Witch Project, The Shining and Silence of the Lambs: She was interested, but not afraid. The Waverly Hills Sanatorium Haunted House in Kentucky didn't faze her. Instead of screaming, she laughed and poked one of the monsters in the head. The team took her to an exotic pet store with poisonous snakes and spiders. SM claimed to dislike the animals, but when she saw them she was overcome with curiosity, repeatedly asking to touch the snakes.

"What that suggests to us is that perhaps the amygdala is acting at a very instinctual, unconscious level," says Feinstein. "Without this area, instead of just losing your interest in things, you do the very thing that's opposite. She tends to approach the very things she should be avoiding."

Although the new study is based on a single patient, it is "a particularly clear example" of how the amygdala is important for fear, says neuroscientist Hans Markowitsch of the University of Bielefeld in Germany. "The woman indeed had almost no fear in quite divergent situations."

Markowitsch cautions that a study on a single person can't be extended to apply to other people, since many other factors influence how the brain and emotions work.

What's more, pinning a complex emotional state to a single brain structure isn't straightforward. "When you have to name a structure relevant for fear in the brain, everyone comes up with the amygdala," Markowitsch says. "But one could argue that the amygdala cannot act on its own — it's dependent on connections, on circuits, on other brain regions."

The study's authors can't dismiss other brain regions' roles in experiencing fear. Yet SM's complete inability to experience the emotion — in a wide variety of forms — highlights the amygdala's pivotal role in feeling afraid.

Image: Wikipedia/was a bee

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