APS: Dark matter clues
The Fermi space telescope has reported seeing an excess of high-energy electrons that could hint at dark-matter annihilation in the universe. Full story is available here.
Nature Newsblog
Nature Newsblog
May 05, 2009
APS 2009: Back to DC
I'm set to head to the airport in a bit, and so this is sayonara. As usual, I didn't get to half the sessions that I wanted to, but that's part of the appeal. Just to keep us on our toes, it looks like APS is having its next April meeting in February. But it will be in Washington, DC, my home, so I'll be happy to offer insider tours. I'm a journalist, so my rates are cheap!
May 03, 2009
APS 2009: Pierre Auger backs off claims for cosmic ray source
The mysterious origin of ultra-high energy cosmic rays is, it seems, still a mystery. Two years ago, scientists at the Pierre Auger Observatory in Argentina thought they had it solved. They published a paper in Science, based on two dozen particles, that there was a correlation with the location of Active Galactic Nuclei -- supermassive black holes that accelerate jets of material at near-light speed throughout the universe. At the time of the announcment, there was some doubt: The Hi-Res project, which scans the northern sky like Auger does the south, found no such correlation.
And now, today, Stefan Westerhoff, an Auger scientist from the University of Wisconsin at Madison, said that, based on new particle detections -- they have more than 50 now -- the correlation no longer holds. "The signal strength is certainly considerably weaker now," he told his audience. "This is certainly a disappointment."
But the correlation isn't so weak that they can give up. The 70% correlation between the cosmic rays and the AGN at the time of the Science publication has now dropped to about 40% -- considerably less, but not enough to support the null hypothesis. What could cause some particles to come from AGN, but not others? Westerhoff says it might have something to do with their composition. Maybe the protons come from the AGN, whereas higher mass cosmic rays, say iron nuclei, do not.
Westerhoff says this will be sorted out as they track more particles -- which can only come with more time and bigger detectors. If Pierre Auger is the size of Rhode Island, the proposed Pierre Auger North, not too far from Denver, would be the size of Massachusetts -- and Westerhoff showed a slide how they can get the necessary statistics in a decade or two. No offense to the lovely state of Colorado, but I say keep the cow pasture free of Cerenkov detectors, and give folks like JEM-EUSO a chance to stick their 2.5-meter camera on the space station.
Image: Pierre Auger
APS 2009: Earth-observing astronomy
In my previous post, I talked about how not all astronomers use photons. Well, neither do all astronomers look up from Earth or Earth orbit. A new telescope aims to look down at the Earth -- precisely so that it can see the sky.
JEM-EUSO proposes fixing a downward looking camera on the space station. It would stare at Earth -- primarily the oceans -- and watch for ultra high energy cosmic rays (charged particles, typically protons) as they hit. It would work very much like the Pierre Auger Observatory in Argentina, which detects fluorescent showers of secondary particles caused by the cosmic rays colliding with atmospheric particles, followed by a final flash as the particles hit detectors on the Earth. Auger astronomers have detected the most energetic things in the universe, and asserted with bare bones statistics that they probably emanate from the supermassive black holes at the centers of galaxies. But some want better proof than that given by a few dozen high energy cosmic rays, and, for that, they need more hits.
Looking down from the space station, JEM-EUSO could monitor an area between 50 to 250 times as large as Pierre Auger. The 5-year mission goal would be to detect at least 1,000 particles with greater than 7x10e19 eV energies. Particles like that would be probes of energy regimes 10 million times bigger than those explored by the LHC. Maybe JEM-EUSO could even detect a few particles with 10e21 eV energies. Because then we could use my favorite prefix in the world, and talk about the Zev scale: Zettaelectronvolt particle physics. Yoshiyuki Takahashi, of University of Alabama Huntsville, and Mark Christl, of Marshall Space Flight Center gave a talk on JEM-EUSO on Saturday. They say it would take 20 years for Pierre Auger and its successor, Pierre Auger North (proposed for nearby southeastern Colorado), to do what JEM-EUSO could do.
The total cost? $220 million -- and that includes the rocket ride that it needs. ESA and NASA were once enthusiastic. But then, with the space shuttle retirement, NASA couldn't find a ride for EUSO. ESA also liked it but its transport vehicle, the ATV, can't deal quite handle it. Thankfully, JAXA, the Japanese space agency, seems to like the idea. And it may have a rocket, the new H-IIB, to fly it up -- if test flights later this year prove successful.
Takahashi says JAXA will make a final decision on JEM-EUSO in September, and it could launch sometime in 2013. It would be nice to get a real astrophysical experiment on the space station. Nobel prize winner Sam Ting seems to have found a way to get his $1.5 billion AMS up to the station on the shuttle's last flight. Why can't these guys fly a novel experiment that costs a fraction as much?
Image: JEM-EUSO
APS 2009: The muon shadow of the Moon
Astronomers typically use photons of some sort to figure out what's happening up there. Sure, some astronomers look for cosmic rays (which are not rays but in fact charged particles like protons), and eventually, gravitational waves are going to be important. But light is the way 99% of astronomy has been done. Now, a new window on the heavens is about to open -- and the window goes through the center of the Earth.
The $271 million IceCube project, stuck in the Antarctic ice, would be the largest observatory to use neutrinos -- chargeless, high-energy and nearly massless elementary particles. IceCube is a cubic kilometer array consisting of strings of detectors dropped down into ice cores made with hot-water drills. The detectors see the secondary effect of neutrinos colliding with atoms of ice. Neutrinos are terrific for astronomers because, lacking a charge, they aren't bent by galactic magnetic fields. They may provide some of the only evidence of what happens in the center of supernovae. But they are incredibly elusive -- they only rarely interact with matter. Thus the need for a cubic kilometre telescope.
On Saturday, Laura Gladstone of the University of Wisconsin showed that, based on data with only half of the telescope's 86 strings installed, IceCube was working pretty well: It could see the Moon's shadow. Common neutrinos particles called muons rain down on Antarctica -- some 9 million a lunar month land on IceCube. A much smaller signal was observed when the Moon passed overhead and absorbed some of those muons.
But what Gladstone and her colleagues really want to do is look for the neutrinos that, speeding through the Earth, come up and hit IceCube from underneath. That way, the Earth would blot out most of the common, lower energy muons that fill the galaxy, and instead filter for the zippy high-energy neutrinos that could be coming from pulsars and supernovae, maybe even extragalactic sources. Michael Baker, in the previous talk, said he didn't quite have the statistics yet to show any point sources in his through-the-Earth looking glass. They'll have to wait a little longer; IceCube is expected to have all 86 strings installed by 2011.
Image: NSF
May 02, 2009
APS 2009: Fermi seeing dark matter's signal?
Peter Michelson, head of the Large Area Telescope team on Fermi, the gamma ray telescope formerly known as GLAST, gave the opening talk this morning. He went through all the amazing things that it has found in its first 8 months: gamma-ray only pulsars, milli-second pulsars, and active galactic nuclei. But he saved the news for last: Fermi, like two other experiments PAMELA and ATIC, is seeing way too many electrons and positrons all around us -- which could be an indirect signal from the annihilation or decay of dark matter, the stuff that makes up up to a quarter of the mass of the universe, but has yet to be detected directly as a particle.
Last year, the PAMELA and ATIC teams showed rises in positrons and electrons -- far more than are expected to be in the diffuse galactic background. Now, Fermi, shows not just a rise, but a bump --- centered around 300 or 400 gigaelectronvolts. That bump could mark the center of mass for a dark matter particle, such as a WIMP (Weakly Interacting Massive Particle). The results of the different experiments are not exactly the same (Fermi counts the total electrons and positrons, whereas PAMELA can distinguish between the two), but they seem to be compatible. Michelson isn't ready to rule out a conventional source just yet -- the extra particles could be generated from nearby pulsars, and then whipped into a diffuse background by galactic magnetic fields -- but he says that there is a good chance that they could be observing new physics. "Exciting stuff," he says. Symmetry Breaking has their take on the discovery here. More news to come -- after I learn some more myself.
[Editor's update: that full story is now available here.]
APS 2009: Denver
Well here we are in Denver, at the American Physical Society April meeting, which this year just so happens to be in May. Denver, the mile-high city, should be in springtime bloom, all alpine sunshine and wildflowers. But it is colder than a Bose-Einstein condensate. Oh well -- there's so much good stuff going on in the basement of the Sheraton here that I probably won't be leaving the hotel. There are 1,025 preregistered attendees -- about the same as last year, says Don Wise of APS. But the number of abstracts are down slightly: 1,089, compared to 1,194 from last year.
March 20, 2009
APS: So long.
Well things are winding up, and I’m exhausted. It’s been a fascinating meeting, and I hope that you’ve enjoyed our blog! See you around, like a doughnut.
APS: Quantum cryptography is just plain cool
The meeting is wrapping up, and I’m getting ready to pack up here in Pittsburgh, but not before getting myself to a talk by Andrew Hammond a vice president at MagiQ Technologies. MagiQ is in the business of quantum key distribution, a process that uses quantum entanglement to ensure the secrecy of encrypted data.
This was all very academic when I wrote about it just a few years ago, but what was evident in Hammond’s talk is just how practical it’s becoming. According to Hammond, MagiQ’s system is now capable of refreshing a secure key at a rate of once a second. Considering that involves entangling two photons, sending one of them along a piece of optical fibre, and reading them both out when it arrives, that’s pretty darn impressive. And Hammond says there technology is constantly improving: they’re even working towards developing a PCI card that could fit inside a desktop computer.
The economic downturn has been bad for business, he admitted (banks thought to be among MagiQ’s relatively short list of highly confidential clients). But, he says, that parts of the federal government are now deploying their systems on a large scale. Assuming the economic downturn doesn’t turn into a meltdown, it sounds like quantum cryptography is here to stay.
APS: What to get the physicist with everything?
As I was zipping back and forth between sessions, I kept passing the APS’s legislative booth, a row of computers where physicists could sit down to write their members of congress. In past years, the letters have pleaded for better funding for the physical sciences, which rarely receive big spending boosts.
But this year things are different. Stimulus is the buzzword and the Treasury’s purse is wide open. For example, the US Department of Energy‘s office of science is receiving a 20% increase to it‘s US$4 billion dollar budget, and that‘s before the additional money contained in the US$787 stimulus package. Obama’s 2010 budget, unveiled earlier this month, is also promising substantial increases.
I asked Brian Mosley (right), a legislative assistant for the APS, what they could possibly want after such a bumper year. “Nothing’s guaranteed,” Mosley says nervously. The stimulus money is “a one shot thing,” and as the 2010 budget winds its way through congress, “there will be a lot of competing interests.” Physicists will need to make the case that what’s good for them is good for the economy.
They’ve done a pretty decent job of getting there voice heard this week: Mosley tells me that 1434 of the 7500 physicists at the meeting have written their legislators. Given that probably around half or more of the people here aren’t US citizens, that’s an impressive turnout.
March 19, 2009
APS: When is a solid not a solid? When it's a supersolid.
posted on behalf of Ed Gerstner
One of the advantages of being just one editor in an editorial team is that when something comes along that you just don't get, you can always try to pass responsibility for handling submissions on that topic to someone else. For me, supersolids was one of those things. They're fluids, superfluids in fact, but they have characteristics of a solid. What?!? Try as I might, I couldn't get my head around it.
But when I picked up a buzz about new evidence of supersolidity in an entirely new system, I figured it was time to push through this particular mental block.
The new results come from Dan Stamper-Kurn at UC Berkeley, who works on Bose-Einstein condensates (BEC) of ultracold gases. The atoms in a Bose-Einstein condensate don't exist at well defined positions like the atoms in a solid crystal. Each and every atom in a BEC spreads itself over the entire volume of the condensate, which can be tens of micrometres wide and hundreds of micrometres long. In the profoundest sense, a BEC has no atomic structure — not even the amorphous structure of the atoms that jostle about in a conventional liquid. This is one of the things that puts the 'super' in a superfluid.
And yet when Stamper-Kurn's group look at variations in the magnetic polarization of a trapped ultracold quantum gas of rubidium atoms (by shining light through it), they see sees a handful of microscopic blobs that order themselves around each other like the beginnings of a crystal (see the figure 2 of their preprint). It's not a typical crystal of course, the blobs are not atoms or groups of atoms forming in localized clusters in the gas — the density of the gas remains smooth and homogeneous. But its magnetic behaviour makes it look like a crystal. And crystalization is the signature of a solid.
And it's as simple as that. A supersolid is a thing that has the properties of both a superfluid — in this case a quantum gas that has no material structure — and a solid — in this case crystalline order amongst its magnetic domains.
What does this all mean? I'll tell you. I don't know. But finally I can see what it looks like.
image: arXiv:0901.3800v1
APS UPDATE: iron pnictides iron-based superconductors. WTF?!
So I woke up this morning to find an e-mail from David Singh that makes iron pnictides compounds even more interesting. Apparently, last year, Hsu et al. replaced arsenic with selenium and found that their new compound could superconduct at 8K. Now Singh tells me that other groups are reporting temperatures of up to 37K at high pressures for some FeSe compounds (there's plenty more on arXiv, so don't take that link as a conclusive lit search). Se compounds are chalcogenides, so he thinks they can’t rightly be called iron pnictides anymore.
Iron-based superconductors is a little bland. Anybody got a better name?
March 18, 2009
APS: Iron pnictides. WTF?
Pretty much anything with iron pnictides in the title is guaranteed to draw a crowd at this year’s meeting. I snapped this picture at a random session this morning, but others have been so rammed that it’s been hard to get in the door. Iron pnictides are the hottest new superconductor, so it’s not surprising that they’re getting a lot of attention. But I’ve been to a few of these talks, and I’m going to be frank--if you’re not an expert it’s very hard to follow. And I know what you’re thinking (particularly if you’re one of my editors): This guy’s a senior reporter with Nature and you’re telling me he can’t understand this stuff?
Well before you get on my case, it turns out I’m in good company. At a reception last night I sat down with David Singh, a theorist at Oak Ridge National Laboratory, and he told me that nobody really understands the pnictides. We’ve published a few papers recently suggesting that, unlike the cuprates (the other main class of high-temperature superconductors) pnictides seem to facilitate electron flow in three dimensions. But there’s still a lot of questions about what induces this superconductivity. “It’s new, it’s different and people don’t understand it,” Singh says.
So WTF? What’s all the excitement at this meeting about? Well Singh tells me that there’s a couple of things worth noting. First, people are synthesizing better quality pnictide samples. In particular, they’ve got single crystal samples that are of very high purity and thus yield better data. The second thing that’s happening is that groups are synthesizing a bunch of different compounds and checking them out. I sat in on a talk by Hai-Hu Wen of the National Laboratory for Superconductivity in Beijing, where he discussed the latest results for pnictide compounds that use iridium, rhodium and cobalt to name a few.
These compounds all superconduct in a similar range of temperatures, so there’s no big breakthrough as yet. But Singh says that they’ll help us to better understand what’s going on, and you never know, there could be a surprise. The main point, he says, is that after decades of working on just the cuprates, the community now has another high-temperature model to work with. “Nature has given us two different routes to high-Tc,” he says.
APS: Nanotubes as filters
I just got out of a pretty cool talk about filtering water with carbon nanotubes. Apparently because the walls of the tubes are so smooth, water molecules can flow super fast through them. On top of that, the rims of the tubes are charged and can therefore reject unwanted ions.
Olgica Bakajin of Lawrence Livermore National Laboratory had some impressive results on display. She fashioned crude filters by growing carbon nanotubes on a silicon surface. She embedded the tubes in silicon nitride and shaved down the compound until a few of the tubes' tops were open. As the image on the right reveals, it’s not the prettiest technique (only those tubes in yellow are actually open). But it works! Her filter allows lots of water through and rejects ions at rates compatible with commercial products.
The immediate application would be for water softening, a process by which ions are removed from water in order to prevent crusty build-up (as an American living in the UK I can attest that there’s plenty of room for improvement on that front). The good thing about the tubes is that they would be higher-throughput and thus more energy efficient than commercial products. And Bakajin tells me that if they can get the diameter a little smaller, they might even be able to desalinate seawater...
credit: Y. Wang/LLNL
APS: No limits imaging
Not many of the rules of physics are actually set in stone, but the diffraction limit is one of them. In imaging terms, the limit determines the smallest discernable feature you can make out through a microscope. It’s etched on this memorial to the 19th century German physicist Ernst Abbe, located in Jena (right).
But as the Bible proves, rules set in stone are made for breaking, and yesterday we heard from two clever physicists who’d beaten the diffraction limit. W.E. Moerner of Stanford University in California looked at fluorescing proteins in cells with a very dim light. Each cell gave off a little pinprick which could then be pinpointed using computer software, and in this way, Moerner could perform in situ imaging of individual proteins. Stefan Hell of the Max Planck Institute for Biophysical Chemistry in Gottingen had another scheme: He used two superimposed beams of light to make sure that only the protein directly under his microscope lit up. Both of these methods were able to image molecules just nanometers in size.
Of course, they’re not the only ones--there are plenty of non-optical systems that can resolve nanometer scale features (scanning-tunneling microscopes for example). But the advantage of these systems is that they can provide in situ images of biological molecules. It’s all sexy enough that our sister pub, Nature Methods, named these and related techniques as its method of the year. Check out their cool video to learn more:
Image: S. Hell
March 17, 2009
APS: Black holes in the lab
It’s not really the sort of thing that you’d expect to find at a meeting which is mainly about materials, but I heard an interesting talk about recreating black hole jets in the laboratory today. For those unfamiliar with what I‘m talking about, swirling material around the top of a black hole often gets ejected in a long narrow stream. The process is complex and guided largely by the behavior of the hot, ionized gas in the jet, known as plasma.
Paul Bellan of Caltech in Pasadena, California wanted to get a better idea of how it all worked, so he built his own (right). Bellan’s black hole isn’t a hole at all: it’s two circular metal plates, one inside the other. By putting an enormous voltage difference across the plates, he can ionize gas above their surface and, albeit briefly, recreate the giant jets of black holes. He’s used his experiments to model how magnetic fields create giant jets. His conclusion? “It’s kind of like squeezing a toothpaste tube.”
Credit: P. Bellan
APS: Wet and wild physics
As I mentioned earlier, you can find just about anything at the March meeting. And yesterday I found out why the tops of your feet get soaked if you’re walking across even a thin layer of water (in say, a wet parking lot). Jake Fontana of Kent State University has studied the problem in detail, using a high speed camera. With each step, a plume of water is flung from the underside of the shoe to the top of the foot. By Fontana’s calculations about 250 cubic millimeters land on your shoe with each step.
It may not sound like much, but over the course of a kilometer, that means your shoe gets half-a-liter of water dumped on it. Some studies just beg the question why? So I asked. “It’s just something that bugged us,” replied Fontana.
credit: J. Fontana
APS: The batteries of tomorrow today
Every session that’s got something to do with either solar cells or batteries is jammed packed, and it’s not hard to imagine why: The US Department of Energy (DOE) is going to be throwing a lot of money at renewable energy in the weeks and months to come.
At a press conference yesterday, we got a little update on various battery technologies that could have a big impact in the not-too-distant future. First up was Mohit Singh of SEEO, Inc. and his former supervisor Nitash Balsara of the University of California at Berkeley. SEEO is working on replacing the liquid electrolyte that is used to transport lithium ions in many batteries with more rigid polymers. These dry batteries would have some important advantages over what’s in your laptop. First is safety, the rigid polymers are less volatile than their liquid brethren, and so they are less likely to overheat and catch fire. Additionally, they would not degrade over time, meaning that your computer battery could keep its charge over years of use. Finally, they would allow batteries to operate at higher voltages, and thus higher charges.
The second speaker was Hiroyuki Nishide, of Waseda University in Tokyo. He updated us on advances in a plastic battery that could store charge in organic molecules. This can be used to create lightweight flexible batteries that could store energy in more imaginative ways than our current generation of batteries (The plastic shell of your laptop, for example, could work as the battery). Additionally, these batteries, like the one we reported on last week, are also able to charge and discharge in seconds.
Like a lot of recent advances in batteries, neither of these technologies are quite ready for prime time. Singh’s cells still require ultra long charging times to fill up with juice, and Nishide’s polymers don’t have the energy density needed to be used commercially. But they’re yet another sign that the battery business is booming.
March 16, 2009
APS Physics in Senegal: There isn’t much…
As anyone who spends a day at an APS conference can tell you, physics is a global affair. I’ve heard talks by Koreans, Japanese, Germans, Australians and Americans today (among others). But one region which is consistently underrepresented at the APS is Africa.
I dropped in on a session about physics in Africa and heard a case study: Senegal. Ndeye Arame Boye-Faye, a physicist at the University Cheikh Anta Diop, Dakar laid out the stats for physics in the country, and it became immediately clear that the problem (as is so often is the case) comes down to money. Senegal’s GDP is a meager US$13.9 billion, and of that just .05% (around US$7 million) goes to research. The nation’s main grants system, known as Fonds d’Impulsion de la Recherché Scientifique et Technique (FIRST), doles out US$700,000 in grants each year. That’s right, $700,000 for the entire country--there are single labs in the West that can suck up a grant that size.
Boye-Faye was quite low-key about it all: “You can see that it’s not a very big budget,” she said modestly. She hopes that the country can get a little help from France and other developed nations to boost its research efforts.
April 15, 2008
APS April 2008: Fermilab could rule out one type of Higgs
With all the excitement about the imminent turning on of the LHC, people are forgetting that the Tevatron at Fermilab will be nipping at the LHC's heels for a while. Brian Winer, of Ohio State University, gave an update on the Tevatron and explained how the scientists there are using every trick they can think of to wring more sensitivity out of the machine, such as using artificial neural networks to combine information from two different detection experiments. Also, the Tevatron has been running long enough now, at high enough luminosities, that they are getting enough collisions to make interesting statistics.
As early as this summer, Winer expects that Fermilab will be able to to statistically rule out the existence of a 160 GeV Higgs boson, one of the theoretically likely masses for the so-called “God particle.” (Barring a positive detection, of course.) It will be a lot harder for them to detect a lower-mass Higgs boson before the LHC starts pumping out data. But who knows?
As a tantalizing treat, Winer put up a picture, a couple years old, of a detection of a particle that had the perfect characteristics of the Higgs. Only problem was, the particle was four times as likely to be noise.
Now, if they could only get four or five more detections in the same spot, then they'd be in business.
Winer repeated the exhortation of a colleague: “We're one good idea away from finding this thing.”
APS April 2008: Textbooks getting worse
I came across an interesting little poster the other day. John Stewart, a physics professor at the University of Arkansas at Fayetteville, decided to look at lexical trends in physics textbooks. He used a method developed by the late, great Don Hayes, a sociologist at Cornell University, who looked at trends in all sorts of texts -- from school books to SATs -- to explain both the dumbing down of America and the jargoning up of science and technology.
Stewart examined trends between two physics texts, Halliday and Resnick 3rd edition, published in 1988, and Halliday, Resnick and Walker, 7th edition, from 2004. The lexical difficulty -- a measure of the book's readability -- increased by almost a grade level. The newer edition was prettier -- the amount of blank space in the book doubled -- but the addition of another author may have made the textbook worse, something along the lines of too many cooks in the kitchen. Stewart's conclusion? "The old Halliday and Resnick was a better object to read," he says. "It's very noticeable."
Now I haven't seen the 7th edition, but I do remember Halliday and Resnick 3rd edition -- it was the physics textbook I used in college. And it was plenty tough to read. I didn't realize I had it so good.
April 14, 2008
APS April 2008: The Answer to Life, the Universe, and Everything
At APS, there are the invited talks, and then there are the talks that might affectionately be known as the “crackpot” talks. Any member of APS, regardless of their background or affiliation, can submit an abstract and give a 10 minute talk. Nothing is rejected.
So about once a day, there's a session with a coded title like “Unconventional ideas in XXXX.” That's where the weird ones go. Sunday morning, Sunil Thakur, with an affiliation of “Individual Research”, was scheduled to give a talk on the “Nature of Reality.” In the abstract, Thakur promised to explain that “how the reality is revealed does not depend only on the properties of the reality itself but also depends on the properties of the medium through which the object is manifested.”
It looks like last year, Thakur submitted an abstract on black holes, where he claimed that temperature affects the speed of light. But today he didn't show up, and the session ended early. Everyone filed out of the room, maybe a touch disappointed.
“I wanted to learn the nature of reality,” muttered one young physicist, not without sarcasm. “Now I have to find something else to do.”
April 13, 2008
APS April 2008: Lobbying on the go
Many physicists are still smarting from the blows they took after Congress slashed various high-energy physics programs in the fiscal year 2008 budget. In the main conference area on Saturday morning, five computers sat beckoning. They weren't for quick email checks, but for physicists to sign and send form letters to their representatives in Congress. The form letter calls for a total of $510 million in emergency supplemental appropriations: $180 million for the NSF, $30 million for the NIST Core program, and $300 million for the DOE Office of Science.
Many Washington insiders think chances of this happening are quite slim, but APS officials are still pushing hard.
They collected 1,753 signatures at the March meeting in New Orleans, and in the first morning in St. Louis, they had garnered 142. Don Engel, a science policy fellow at APS in Washington, DC, was giving out stickers that read "I support science funding" to everyone that signed the form letter. "You want a sticker?" Engel asked his latest petitioner. "Then we know not to bother you again."
April 12, 2008
APS April 2008: Back in St. Louis
This is a bit of a homecoming for me; it has been almost exactly a year since I left the St. Louis Post-Dispatch. And so I was feeling fairly nostalgic as I walked the streets of downtown on this blustery Friday evening. My mood wasn't brightened at all by the utter desolation of downtown. With the Cardinals out of town, the streets were deserted, save for an empty beer can rattling in the wind. Attention physicists! Get out of downtown! The charm of St. Louis is hidden within its neighborhoods and side streets. Hop in a cab and say "Lafayette Square" or "Central West End" -- the cabbie will drop in the right place, and you won't be disappointed. I also hear that Schlafly, the local brewmeister (in addition to the local brewmeister, Anheuser-Busch), has a "Repeal of Prohibition" festival going on Saturday afternoon, if anyone is already looking to play hooky. I'm willing to trade more St. Louis tips for story tips -- email me at e.hand@nature.com. Looking forward to the conference!
March 14, 2008
APS 2008: Thanks for all the crawfish
The meeting is winding to a close, and it's just about time for me to high-tail it to the airport. Thank goodness, too. It seems like every day here in New Orleans is at least 10 percent warmer than the last.
This conference let me catch up on some of the hottest fields, but new developments can happen so fast. I wonder if listening to the latest results at next year's conference will feel like it did this year -- getting blasted with a firehose full of new information. I guess I'll just have to find out. Hope to see you in Pittsburg.
APS 2008: Everything is connected
All you theoretical superconductor folks certainly seem to be good collaborators. I don't know about polite, but network analysis seems to indicate you have a pretty tight community.
With roughly 17,000 authors listed in 7,000 March meeting talks, it’s hard to imagine finding any order to it all. But science is a collaborative pursuit, and Jake Hofman thinks network analysis could say something about the various physics communities hidden in that massive list.
Hofman, a graduate student at Columbia University, downloaded the list when the abstracts came online a few months ago. He used the data to create a network, linking physicists who were listed as co-authors on a talk.
Many presenters were only connected with a handful of other physicists. But there was also a group of 6755 physicists (the largest connected component, for network nerds) who were all linked to each other in one way or another – think six degrees of Kevin Bacon. Hofman then ran an community-identifying algorithm he's working on to look for clusters of physicists that seem particularly closely linked.
To the right you’ll see the visualization he ended up with. It’s a little tricky to interpret (and also quite preliminary), but the basic idea is that each of the 6755 physicists is shown in order on both the x- and y- axis. Blue points indicate co-authors, and white points show no affiliation. Large clumps of blue show communities, most of which seem to correspond to particular subfields.
Hofman just started analyzing the data, but he’s already highlighted some particularly collaborative communities. The visualization also shows that there are multiple communities that focus on the same thing. There are, for instance, at least two fairly large graphene communities. Rivalry!
For the nitty gritty details on Hofman’s approach, check out his paper in the arxiv.
APS 2008: A high-pressure pitch
Darkening a lecture room after a full day of sessions seems like a dangerous prospect. But Wednesday's Town Hall meeting on ultra-high pressures was actually pretty lively.
The basic idea? Squeeze hard on any element, ratchet up the temperature, and you end up with some unexpected new phases. At high enough pressures and temperatures, ordinary, transparent water becomes opaque. Push even further, and it becomes transparent. Dive down into Jupiter's atmosphere, and the pressures quickly become so high that even hydrogen becomes metallic.
This relatively small field of physics is expected to get bigger as the National Ignition Facility comes online, which might happen as early as next year. So the talks came with a request -- a call to arms for fellow physicists who might contribute.
"If as a result of this talk I infuriate you because I have overlooked some result or some phenomenon, then I have succeeded," said Raymond Jeanloz of the University of California, Berkeley, adding that his goal is to engage as many people to think about the subject as possible. But aside from the sheer excitement of mapping new phases of matter, what's the draw?
March 13, 2008
APS 2008: Eating dolphin
Graphene has been one of the hot topics at APS this year, consistently overflowing rooms. The atom-thick carbon sheets show lots of strange new physics, as well as the potential for exciting new technology.
But graphene guru Andre Geim isn't so keen on talking about the applications. At a packed lecture today, he prefaced a slide on what you can do with graphene disks with a parable.
On a trip to Florida, Geim said he was mesmerized by the graceful jumping of dolphins. It was all quite lovely until a little boy ruined the mood, shouting "Mom, can we eat that?"
In other words, asking about the utility of elegant basic research can be a bit of a downer. Despite his distaste, Geim proceeded to discuss how transparent, conductive graphene films might be useful in LCD and solar cell technology.
Then he got in a not-so-subtle dig. "In terms of applications, I didn't expect them to come so soon. But maybe they're not as exaggerated as other topics at this conference." There was hearty (maybe knowing?) laughter all around.
APS 2008: A viral pace
Although the conference has now passed its middle point, I've met few physicists who've shown any visible signs of exhaustion. Perhaps it's the chummy receptions each evening, or maybe everyone has just gotten used to the overwhelming flood that is 120 sessions a day. Some folks I've spoken with admit they've been spending more than a little time outdoors, enjoying sunny days that top 22 C.
Still, the conference must go on, and interesting work keeps popping up. Following a press conference this afternoon, I caught up with Bodgen Dragnea who has been studying a crystal system composed of virus capsids and gold. Dragnea, a chemist at Indiana University Bloomington, studies virus proteins that self-assemble to form capsid shells. Ordinarily these shells protect a virus' key RNA or DNA, but last year Dragnea's lab reported they had created a system of virus shells with gold nanoparticles inside. Because these 'virus-like particles' are so uniform, they also self-assemble, forming a uniform lattice.
Since his last publication, Dragnea's lab has begun using Raman scattering to measure slight changes in the distance between gold cores on the lattice. Capsid shells may swell, compress, or denature entirely depending on the chemical properties of their environment. Those changes in the virus shell would then show up in measurements of the lattice. Dragnea says he should eventually be able to identify particular conditions that make for especially stable shells. "Then the next question is if there is a place in the cell that has that same environment," he says.
March 12, 2008
APS 2008: Crumpled balls
Some physics experiments are just patently fun -- the science seems to sneak in by stealth, changing the way you view ordinary objects. Take crumpled balls, for example. An unassuming object with an extraordinarily complex shape. The path to get from an almost two-dimensional sheet to a three-dimensional object involves many energetic choices – whether it’s more efficient to fold in one direction or stretch in another. Understanding how crumpling happens has the potential to illuminate a lot of interesting physics about how folding happens in nature.
On Monday, Dominique Cambou presented the first results of a ostensibly simple project: mapping the 3D structure of a crumpled ball of aluminum foil. Cambou, a graduate student in Narayanan Menon's lab, systematically crumples balls and then subjects them to x-rays to image their internal structure.
March 10, 2008
APS 2008: To Congress, with love
This afternoon, I was blithely walking to a session when I found myself trapped between three very avid volunteers for the American Physical Society. All conference-goers caught in the cross-hairs were urged to sit down at a computer terminal to sign a letter calling for additional physics funding. It was an impressive example of technology meets advocacy. Fill out your contact information, click a few buttons, sign your name on a digital pad, and bang – letters to your local congresspersons are set to go.
Advocacy is a tradition at the March Meeting, but this year the stakes seem a bit higher. By the end of the day, it looked like every third physicist boasted an "I support science funding" sticker on their badge. The volunteers told me that sticker affords safe passage, the only way to avoid their cajoling the rest of the meeting.
APS 2008: Mississippi dynamics
Posted on behalf of Rachel Courtland:
Greetings from New Orleans, which is likely jazzed to host the American Physical Society March Meeting, dedicated to all things solid state and condensed matter. Some conference-goers arrived over the weekend, enjoying sunny weather and steam-calliope music along the riverbank. But the weather turned cloudy this morning, driving everyone in to 40 early-morning sessions dedicated to everything from the latest results on graphene properties to the dynamics of shaking cat paws.
Conference organizers are waiting for registration to finish before declaring this physics conference 2008's largest (it's met with some rivals in recent years). But the program, which tops out at 665 pages, no longer has room to display short abstracts for each talk, an indicator there's lots of great physics to be discussed.
After a quick cup of press room coffee, I'm off for round two of sessions. Stay tuned for more as the conference gets into a groove.
April 18, 2007
APS: goodbye from Jacksonville
Well that's all from me from this year's April meeting as I pack my bags to leave Jacksonville. You can read more physics stories reported from the meeting, however, such as this online story by David Harris about the results from the Xenon10 dark matter experiment at the Gran Sasso laboratory in Italy.
More stories will appear in Nature on Thursday, be sure to check back then.
April 17, 2007
Dark matter looks to be particularly wimpy
Experiment shows weakly-interacting particles must be very weak indeed.
The tiny, wimpy particles that might make up the Universe's dark matter must be even wimpier than some theories suggest.
APS: Fast cars, hot women
Not what you normally expect at a physics conference. But now I’ve got your attention, we can talk NASCAR physics.
Diandra Leslie-Pelecky, a University of Nebraska physicist and NASCAR fan, gave a public lecture at the APS on Monday night, and did a good job mixing science and speed.
Why NASCAR? Well, as she puts it: “in what other sports do engineers have their own weekly TV shows?”
Leslie-Pelecky got interested in the science behind NASCAR when she saw replays of a high-speed car crash that appeared to have no cause – no collision, no engine failure, no tire blowout. In figuring out how NASCAR drivers maintain 190 mph speeds around 31-degree banked tracks she spent time 'embedded' with a racing team. Her behind-the-scenes investigation revealed that the best drivers know a lot of physics and that a crash can happen simply because of aerodynamics (bad turbulence or drafting) when the cars get close enough.
She also explained the science behind NASCAR’s “car of tomorrow”, which has been 7 years in development and making its debut this season. To prevent teams building a different car for every track NASCAR decided to develop one design for everyone to use. But the car of tomorrow does have two aerodynamic features that the teams can tweak – a rear wing and a front splitter. Developed using computational fluid dynamics the car’s aerodynamic features are designed to improve driver safety and to make it easier for the cars to pass each other, so making the race more exciting.
Not convinced? You can join the 35 million NASCAR fans who watch the races on TV and judge for yourselves.
April 16, 2007
APS: Cool waves
This morning David Spergel of Princeton University ran through the many achievements of the Wilkinson Microwave Anisotropy Probe for the assembled physicists in Jacksonville. This probe measures temperature fluctuations of the cosmic microwave background – the oldest light in the universe. Since its launch in 2001 it has confirmed six predictions of the inflation model of big bang cosmology, including the fact that the universe is flat.
The next big quarry for the team is detecting gravitational waves in the WMAP data. They still have another two years of data from their five-year dataset to analyse before the mission ends in September 2009. Spergel is confident they will provide an upper limit on gravitational waves, even if they don’t discover them directly. After that we can expect the Planck mission, which will have three times the resolution and ten times the sensitivity of WMAP, to pick up the challenge.
APS: Save us from ourselves
Amory Lovins, leading energy conservation expert, appears somewhat less worried about conserving trees. He thrusts papers and books at everyone he meets. Ask a question at a press briefing and he chucks you a paper (fortunately he’s a good throw). So what’s the message behind the missiles?
It’s certainly hard not to be impressed by the facts and figures that Lovins has amassed. The Rocky Mountain Institute he founded in Snowmass, Colorado has documented in detail the inefficiencies of the energy sector, from waste heat at power plants to poorly designed consumer electronics that waste energy even when switched off. The engineering solutions RMI proposes for each energy challenge are equally impressive, from smart home insulation to ultralight cars made from carbon fibre composites.
But some of the RMI solutions make you wonder, why doesn’t everyone already do that? For me that's the hardest question to answer. Figuring out why humans make bad decisions, and continue to make bad decisions, in the face of sometimes overwhelming evidence, may be as big a part of the energy challenge as finding the right technology.
As far as I can tell we’re just not very good at making decisions about lifecycle costs (energy savings from compact fluorescent light bulbs, say) versus the sticker price (cheaper incandescent bulbs). And technologies that need to be ‘pushed’ on the market, rather than being ‘pulled’ by what people want, are understandably less attractive to businesses. Perhaps there are marketing experts and social scientists out there with answers to those questions.
April 14, 2007
APS: Prime-time physics
In a plenary talk this morning on his latest measurement of the electron's magnetic moment, Gerald Gabrielse of Harvard entertained the packed audiorium with a discussion of what he called 'perhaps the most obscure paper I've ever written'.
He showed a slide with the title of his PRL paper at the top: Stochastic Phase Switching of a Parametrically Driven Electron in a Penning Trap. And below it a clip from a February 2007 interview between Jim Carrey and talkshow host Conan O'Brien.
In a moment straight out of a parallel universe, Carrey tells Conan O' how much he likes reading about quantum physics before repeating verbatim the title of the Harvard paper. The contortionist star and the host both go on to discuss the physics of electrons in a Penning trap to much audience applause.
Before it was removed from YouTube the clip was viewed more than 90,000 times, try wrapping your head around that! You can still view the clip here: http://www.nbc.com/Late_Night_with_Conan_O'Brien/video/index.shtml#mea=64956
APS: Hello from Jacksonville, Florida
I've been here less than 24 hours and what I've discovered so far (some of this without leaving the hotel lobby) is that Jacksonville is home to bitter Granny Smith apples, very sweet iced tea and the extremely lazy St John river. This river is the longest North running river in the United States and as you arrive at Jacksonville airport you can see it snaking its way lazily across the mud flats. For the next few days at least there will be pasty faced physicists jostling with tanned Floridians along its riverbanks.
Consider me your blogging companion for this April meeting of the American Physical Society. It's my first time at this meeting - I've been to the larger March meeting many times, but this year I'm looking forward to getting stuck into the small and large-scale topics that are the focus of the April gathering - from nuclear and particle physics all the way up to astrophysics and cosmology. I'm expecting lots of explosions.
Sarah Tomlin
April 13, 2007
American Physical Society, April 2007
Join Sarah Tomlin at the APS April meeting in Florida. She'll be sending reports to our newsblog from 15-17 April.
March 08, 2007
APS March 07: So long, and thanks for all the fish
Alright blog readers, I'm off. I'll see you all next year!
APS March 07: Getting Political
The APS’s congressional relations people were out in force, trying to get physicists to write letters to their congress people,and implore them for cash. As a rule, the physics community is pretty good at making their funding voices heard. But condensed matter researchers appear apathetic: as of yesterday afternoon, just 900 of the roughly 7,300 people who showed up bothered to sign letters.
One thing that was clear in a session last night (in which I participated) is that physicists will need to speak much more loudly to the new congress if they want their voices heard over competing interest like Iraq, health care and education.
But, at this meeting at least, that didn't seem to grab people's attention. Maybe it’s the lack of big machines, or the fact that the field itself isn’t very cohesive. Whatever the reason, Mike Lubell, APS’s head of public affairs, says he hopes to boost participation next year.
March 07, 2007
APS March 07: Physicists as tippers
Last night, after the sessions were over, I found myself in a bar with two locals who work at a prominent Denver-area restaurant.
I asked them who, of the Denver conference circuit, were the best tippers. Surprisingly, they said that attendees of the annual sex business convention were most generous. Bible conferences tended to be the worst, possibly because they didn’t drink much.
Physicists, they told me, lie in the vast middle ground between the God-squad and the pornographers. But they do distinguish themselves in one way: they leave very precise tips. For example, they would leave a tip of $7.23, exactly 17% of a $42.50 bill.
The servers wanted me to ask all of you to start rounding, preferably up.
March 06, 2007
APS March 07: Vaccination—one lymph node at a time
Michael Deem of Rice University has an interesting vaccination strategy for HIV: vaccinate different parts of the body against different strains of the virus.
Deem claims that current vaccination plans have a weakness. If you vaccinate for one particular strain of HIV, the immune system will produce too many T-cells for that strain, while ignoring other dangerous variants. By injecting different vaccines into different lymph nodes (where T-cells get made), his mathematical calculations show that you could produce a more balanced immune response.
Of course, that’s all a little abstract since there isn’t an HIV vaccine yet. But the same strategy could work for different strains of Dengue Fever (there are apparently four). Deem says that he will soon test his ideas on animal subjects.
APS March 07: Nukes, what are they good for?
At a session at the meeting this morning, a group of government officials and nuclear weapons experts discussed the state of US strategic forces.
Everyone in the room seemed to sense that the US didn’t know quite what to do with the 10,000 nukes in its stockpile. US Strategic Command no longer considers the weapons its primary priority, according to Lt. General Robert Kehler. “We go days at a time without being involved in the nuclear weapons business,” he says.
The White House and other politicians seem similarly detached. Eminent physicist and arms control expert Sidney Drell summed it up pretty well: “We need an answer to the question—what are nuclear weapons for?"
Breath test for diabetes
Non-invasive test can pick up the whiff of disease.
Physicists have developed a simple breath test that may be capable of detecting Type I diabetes.
Read the story here.
March 05, 2007
APS March 07: Water on Mars? Maybe not...
At our first press conference today, we learned how a mysterious set of formations on Mars known as “razorbacks” may be made by static cling, rather than water. Razorbacks are spikes in the Martian soil, about a millimetre wide and a centimetre high. Scientists had theorized that water flowing through fractures on the surface might have created these dainty peaks.
Not so fast, says Troy Shinbrot of Rutgers University. By sliding tiny glass beads down a table, Shinbrot created similar structures here on earth. The terrestrial razorbacks were built up by the static cling of the beads rubbing together. Shinbrot believes that a similar process could be at work on Mars, especially since the dry atmosphere would facilitate static build-up.
This isn’t the first water on Mars theory Shinbrot has debunked. In 2004 he showed that the low gravity of Mars could cause dust to flow like water, creating gullies similar to those made by streams here on Earth.
APS Meeting, March 2007
Can't make it to the American Physical Society meeting in Denver this week, or having trouble hitting all the sessions? Keep up with all the news and get behind the scenes with Geoff Brumfiel's diary reports, here from Monday 5 March.
March 21, 2006
APS: standing room only
One of the challenges at any large conference is being in the right room at the right time - and then hoping that you can find a seat near the back in case the talk is not all it could be. It also helps if the speakers turn up - flu, problems with connecting flights and "a meeting in Washington" were three of the excuses on offer in Baltimore.
And one of the challenges for the organizers of any large conference is putting the right talk in the right room. Occasionally a speaker will find themselves speaking to a handful of people in a large hall, while, somewhere along the corridor, a 100 people might be trying to squeeze into a room with 64 chairs. A senior APS figure was overheard to speculate in Baltimore that the reason that some sessions were oversubscribed was because they were highlighted on the Nature site!
Posted on behalf of: Peter Rodgers, Nature Nanotechnology
March 17, 2006
APS: meet the Georgers
A few days ago, someone from the European Central Bank emailed Dirk Brockmann to ask for advice on how contaminated Euro notes might influence the spread of bird flu. Brockmann, who recounted this story in his invited talk today, explained that they’d made a common mistake in misunderstanding his work.
Back in January, Nature published an article by Brockmann and his colleagues that looked at how dollar bills travel across the United States. The paper is here. The idea was to study the dollar bills' movements as a proxy for how people travel. A model based on the dollar bills’ diffusion pattern could then be used in epidemiology, to help predict how diseases spread. But he was not, he emphasised, suggesting that bank notes themselves spread disease.
There’s another interesting aspect to this story, too.
The data for the study came from Where’s George?! - a website that collects sightings of marked dollar bills from enthusiasts across the United States. If you register, you get a small rubber stamp that says “Track me at www.wheresgeorge.com”. You mark your bills, throw them back into circulation (ie, spend them) and then watch to see where they turn up. People that really get into this call themselves “Georgers” and meet up around the country.
A few turned up at today’s session, to hear Brockmann speak. Before I took my spare dollar bills back to Britain, I went to talk to them…
APS: trip to Congress
I was trying to decide which session to attend when John Wei, a physicist from the University of Toronto, shanghaied me onto a bus headed for DC.
I found myself among eminent scientists on a mission. We were going to Congress and our aim was to convince US politicians that physics deserves more financial support.
How? Well, when we arrived at the venue, people were busy setting up fun physics demonstrations, from levitating magnets to balls that look like rubber but go thud instead of bouncing. Other displays used liquid nitrogen to cool superconductors, freeze flowers or shrink balloons. (A lot of work must have gone into organising this event. You don’t just drive up to the loading bay at Congress with tanks of liquid nitrogen!)
It was my first visit to the Capitol and I was looking forward to meeting some politicians. But I had trouble finding any. I went up to two men in uniform, who turned out to be physicists from the Naval Academy. Two others in suits were astronomers from the Naval Observatory.
Later, someone pointed out some House representatives, busy playing with the exhibits at the National Institute of Standards and Technology stand. They were laughing and enjoying themselves! Then we were treated to speeches from only two PhD physicists in Congress, Vernon Ehlers and Rush Holt.
They said that more scientists should be involved in politics. They’re right. We need to stand up for science education. One trip to Congress is probably not enough, but it’s a good start.
[Posted on behalf of May Chiao, Nature Physics ]
March 16, 2006
APS: the physicists sang along
Yesterday I mentioned that I was going to a physics sing-along. I was one of about 50 people who turned up. Some loiterers in the lobby of the hotel where it was happening tried to warn me off. “It’s like a lecture at the conference,” they said. “They’re using an overhead projector.”
I went anyway. And although I didn’t expect to be saying this, I enjoyed it. I even sang. There were two musicians; one with a guitar, the other a bongo; a singer and a laptop to provide backing music.
So, altogether now, to the tune of Loch Lomond…
“Oh, you be the B field, and I’ll be the E field,
Let’s dance through the cosmos, my lover!
With the ether set aside, you and I can freely glide,
Supported on the wings of each other.”
The next verses weren’t quite so lovely, but I thought that this opening was sublime. It begins a poetic love song, sung by an electric (E) field to a magnetic (B) field, which pays tribute to their partnership in an electromagnetic wave. The rest of the words and a recording of The Love Song of the Electric Field are here.
The lyrics are by Walter Smith, an associate professor in physics at Haverford College in Pennsylvania, and the coordinator of last night’s event. He runs a website that collects physics songs. Apparently, it was common in the early 1900s for physicists at the Cavendish Laboratory at the University of Cambridge to sing songs, which they had penned themselves, after dinner. More here.
For more funny lyrics from last night's karaoke session, relating to fraud and Nature, keep reading...
APS: a physics sing-along
What could be more relaxing after a day of brain-stretching physics than a bit of singing? Tonight we are to be treated to what the event’s website claims will be the first ever physics "sing-along / listen-a-long".
This evening’s entertainment has been heavily advertised around the conference. The posters read: “Come sing along to physics lyrics set to familiar tunes.” Then, rather worryingly, they reassured: “No singing ability required!”
I’m heading out to add my tuneless warble to the geek chorus. More tomorrow…
APS: science and politics
“Physicists forced to alter data?” asked the flyers handed out by the Union of Concerned Scientists (UCS) to delegates today.
There is deep concern among scientists in the US that, under the current Bush administration, political appointees have interfered with the reporting of scientific findings. The issue has made it into the news more than once over recent months – when climate scientist James Hansen said he was stifled by NASA’s press office, for example, and after Nobel laureate David Baltimore spoke out at the American Association for the Advancement of Science meeting in St Louis.
I visited the UCS stall in the exhibition hall to find out what response they’d got from the physicists here.
Michael Halpern, from the Scientific Integrity Program of the UCS, said that at some meetings people come up to the UCS table and look both ways before recounting some experience of their own. This time, he said, they’d heard fewer personal tales.
“We weren’t necessarily here to uncover tales of manipulation of science,” he says. Many of the delegates at this meeting work in fields that are unlikely to be politically sensitive.
Halpern said the goal of the UCS in being at the APS is to raise awareness. “Our view is that the scientific community needs to be engaged in a persistent and active way,” he said.
March 14, 2006
APS: helium's special effects
This morning I sat in a room that was full of confusion. The small group of physicists gathered for the session on “supersolids” was thoroughly perplexed.
Two years ago, researchers from Penn State University reported the first evidence for a supersolid – a strange new form of matter which is a solid but which, through quantum effects, can flow like a liquid.
Today we learnt that other groups have now repeated the result, but their experiments have also raised new questions.
APS: Kitty litter and uranium isotopes
So you think quantum mechanics is hard? Try being a border patrol agent in today’s post-9/11 world. The US has some 360,000 vehicles, 5,100 trucks, 2,600 aircraft and 600 vessels entering at their legal checkpoints – every single day. The Department of Homeland Security wants to install some 2,400 radiation monitors at their border crossings to spot clandestine nuclear material, and they still have some way to go. But even now the system is overloaded with false alarms.
This biggest problem: innocuous kitty litter. Apparently the clay in cat litter gives off enough radiation to set off a gamma detector. And its emission signature is very close to that of highly-enriched uranium. The current high-purity germanium (HPG) detectors can’t tell the difference.
Barry Zink and colleagues at NIST in Boulder, Colorado, along with their Los Alamos collaborators, have developed a gamma-ray detector that has ten times better resolution than existing HPG detectors. It uses a transition-edge thermometer to record the temperature difference between a superconducting bilayer, and a tiny island of tin that absorbs incoming gamma rays. The sensitivity comes from cooling the sensor down to 100 millikelvin above absolute zero. Zink admits that 100 mK is a ‘somewhat challenging’ temperature to achieve, but says that cryogenic technology has vastly improved in the past decade.
How robust is it? In order to test their detector out on a range of nuclear materials Zink and co-workers drove their prototype 400 miles in a minivan to the National Nuclear Security Agency division at Los Alamos. The sensor survived the trip okay, and successfully detected one of the usual suspects for nuclear weapons: the plutonium-239 isotope.
Right now the biggest sensor array NIST has made has 16 sensors, but they plan to build a 100-sensor array. Although it will never be big enough for general screening of, say, entire vessels, the detector can help to analyse and verify nuclear stockpiles, and to screen suspicious material flagged by other techniques.
And it may help prevent some of those costly kitty-litter false alarms.
APS: how to post comments
PS. If you want to comment on one of the posts on this page, either click on the entry's title or the red "Permalink" label at the end. This will bring up a page with a comment box.
APS: the beauty of Pi
Over the last few days, I’ve had to hop between hotels. The process has left me confused about my constantly-changing room number. But I'm not the only one struggling to keep track.
After a session here at the APS, I met a similarly bewildered scientist. He was flitting between some of the many parallel sessions in the convention centre, and couldn't remember which room he was meant to be in next. Then he cried, “ah, but of course, it was room 314. I won’t forget that, it’s Pi.”
Pi, of course, is the ratio of a circles’ circumference to its diameter (and it begins 3.14159 26535 8979). Such are the advantages of being into mathematics… Unfortunately, I haven't been able to think of any fundamental constants that start 409.
March 13, 2006
APS: some scary stats
The session on Nuclear Proliferation and Nuclear Terrorism this morning could have been renamed the session on scary numbers. Invited speakers Joseph Cirincione of the Carnegie Endowment for International Peace, Steve Fetter of the University of Maryland, Brent Park of LANL and Mike Carter of the Department of Homeland Security, did a good job at raising the audience’s personal ‘threat levels’ to Code Red.
APS: Some powerful materials
Press conference number two was all about using materials to generate, or save, electricity.
Sarah Kurtz of the National Renewable Energy Laboratory gave a briefing on high-efficiency solar cells, which are now almost as efficient as conventional coal and natural gas power plants.
Mercouri Kanatzidis of Michigan State University talked about thermoelectric materials which can take waste heat, such as the heat generated by a car’s engine, and convert it directly to energy.
And Fred Schubert of Renssaler Polytechnic University said a few words on the next generation of light emitting diodes (LEDs), which will niftily reproduce the spectrum of natural sunlight using just a fraction of the power consumed by your average light bulb.
Of course, none of these technologies are quite ready for prime-time. Kurtz’s cells are a bit too expensive, Kanatzids’ thermoelectrics a bit too inefficient, and Schubert’s LEDs a little too early in development to really be useful. But taken together they offered a taste of how future materials could help the coming power crunch.
APS: Will your next computer be made of ribbons?
The first of two press conferences today was on graphene--the high-tech name that physicists have given to honeycomb sheets of carbon that can be found in low-tech pencil lead.
If you manage to isolate a one-atom-thick layer of graphene, you can do some pretty neat stuff with it according to Walter De Heer of Georgia Tech University. Thin graphene ribbons behave in ways similar to conventional semiconductors. At the same time, electrons in a graphene ribbon have odd quantum properties that could be used in future components, he says.
Furthermore, graphene structures can be grown on a chip in a way that’s similar to conventional electronics with “no fusing and no musing,” as De Heer puts it.
So why isn’t graphene already on your motherboard? It turns out that it’s hard to connect it to more conventional materials. De Heer is optimistic, however, that the problem can be overcome. Intel seems to buy it; they’re helping to fund his research.
APS: Bloggers at the meeting
Alan Aspuru-Guzick , a post-doc from Berkeley, and Mark Dewing, of the National Center for Supercomputing Applications, are two people with blogs that we know are attending the APS meeting (because they have posted information about their own talks: 1 and 2). There must be more of you - let us know if you are blogging the conference.
APS: Superconducting eyes on the sky
This morning’s session on superconducting devices and applications kicked off with two intriguing talks about how to use superconductors as cameras for ground-based and space-based telescopes.
The first one, by Matthew Bell of the University at Buffalo, talked about using niobium nitride nanowires to detect photons. The idea is pretty simple: when photons hit the wire, they heat it up—disrupting the superconducting material and creating a measurable resistance. The second talk by Shwetank Kumar of Caltech talked about using a slightly more complicated setup of thin-film niobium resinators that also use the heat from photons to alter superconductoring behavior.
Kumar says that these devices could lead to a new generation of very sensitive astronomical cameras, but both talks showed that the devil is in the details. In the case of the wires, the theory doesn’t agree well with the data collected by Bell and his collaborators. Kumar says that unexplained noise on his group's devices are an ongoing problem. Still, he says that they are already good enough for some ground-based telescopes.
APS: in search of gossip
Hello,
I’m Jenny Hogan and, like Geoff, I'll be reporting from the APS. The conference began this morning with a queue for coffee from the Starbucks stand that was longer than the line for registration. We’ll need the caffeine: there are going to be around 6,500 talks over the next five days, on physics ranging from from energy policy to optical clocks.
I’ll be roaming the corridors seeking out the latest research trends, the quirkiest results and the juiciest gossip. Some of it I’ll post here. If you’re at the meeting, why don’t you comment with your stories? Physicists are a rowdy lot. They must be up to something.
Jenny
APS: Why do you come to March?
Hi everyone, my name is Geoff Brumfiel, and I’m one of Nature’s physics reporters based out of Washington, DC. I’m about to hop on a train to Baltimore, but I thought I’d kick off our blog by asking you a little about what makes the March meeting tick.
I must admit that I’ve always been a little flummoxed by it. Even though (or maybe because) it’s the APS’s largest annual gathering, I think myself and other science journalists have a tough time figuring out how to cover it. The April meeting has a few big toys (satellites, accelerators, etc.) that one can report on, but there’s so much at the March meeting that it’s hard to know where to focus.
So why do you come to the March meeting? What are this year’s really interesting bits? Do you wish it got more general media coverage? And if so, how would you suggest outsiders approach it?
OK, better catch that train!
Geoff
March 08, 2006
American Physical Society meeting
Nature will have several reporters and editors at the APS meeting from 13-17 March. Check back here from Monday to read their diary reports from the meeting, and to contribute to the chat.
Search
