Author Archives: Eugenie Samuel Reich

US experiment to vote on dark matter

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A US experiment is poised to resolve confusion over whether dark matter has already been detected. The Large Underground Xenon Experiment (LUX) at Sanford Underground Laboratory in Lead, South Dakota — announced on 15 October that it will release its first results on 30 October.

LUX began taking data earlier this year, promising to rival or even surpass limits on dark-matter detection set by a competitor, XENON-100, which is located at Gran Sasso National Laboratory near L’Aquila, Italy. In 2011, XENON-100 ruled out many heavier and more strongly interacting dark matter particles, but its result is in tension with tantalizing data hinting at the existence of light dark-matter particles from two other US experiments, the Cryogenic Dark Matter Search (CDMS), and the CoGeNT experiment, both at Soudan Underground Laboratory in Minnesota. With more than 350 kilograms of liquid xenon held underground to snare dark-matter particles as they pass through the Earth, LUX might become the deciding vote. “I’m cautiously optimistic this could be the final word on the situation,” says dark-matter theorist Dan Hooper of Fermi National Accelerator Laboratory in Batavia, Illinois.

Of course the final word on whether CDMS and CoGeNT’s dark-matter particles are real is far from the final word on whether dark matter is detectable on Earth; more weakly interacting particles could still be out there, and plans exist to scale up both XENON-100 and LUX to try to find them.

Corrected October 24 to reflect that the CDMS is co-located with CoGeNT at Soudan Underground Laboratory.

Swedes claim confirmation of element 115

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Swedish researchers have reported strong evidence for the formation of element 115, some 9 years after Russian researchers first claimed to detect a nucleus with 115 protons.

A team led by nuclear physicist Dirk Rudolph of Lund University in Sweden formed element 115 by smashing isotopes of calcium into a film of americium at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The scientists monitored the emissions of alpha particles and X-rays to try to fingerprint decay products.

“I am quite satisfied with the success of the experiment as such; it was not easy to get it scheduled in the first place, but then it went technically and scientifically very well, even on short notice,” says Rudolph.

Their findings are accepted for publication in Physical Review Letters. They build on results obtained at the Flerov Laboratory for Nuclear reactions in Dubna, Russia, in 2004, which suggested that a nucleus containing 115 protons had fleetingly formed. In 2011, the International Union of Pure and Applied Chemistry, which names new elements, deemed that result too tentative to be a claim of discovery, although Dubna was recognized for co-discovering elements 114 and 116.

Now, Rudolph and his colleagues say they have identified more than 30 chains of nuclear decay products that may have originated with the formation of element 115. The element is now tentatively called ununpentium, but the The International Union of Pure and Applied Chemistry (IUPAC) has yet to recognize or name it. Rudolph says in a 28 August web posting that his team expects that IUPAC may seek yet more statistically significant evidence before ruling on the new element’s existence.

Further studies of the decay products should provide new glimpses into the world of extremely heavy nuclei, some of which deviate from the naively spherical picture of the nucleus and take on other shapes, including oblate, prolate, and most recently, pear-shaped.

Update 30 August: this blog post originally stated that publication in Physical Review Letters was scheduled for 27 August. Publication has since been delayed.

US panel calls for ambitious X-ray laser

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{credit}LBNL{/credit}

The United States should build a powerful new X-ray laser that could make movies of electrons moving in materials and chemical reactions, a US government advisory panel recommended today.

In so doing, the Basic Energy Sciences Advisory Committee (BESAC), which advises the US Department of Energy’s Office of Science and met today in Bethesda, Maryland, offered no ringing endorsement of any of four proposals for future X-ray sources that had actually been presented to it. Instead, the committee set out a more ambitious vision, which panel members suggested could be realized if proponents of the various camps joined forces.

“You want to make a revolutionary machine that really stands out,” says William Barletta, an accelerator physicist at the Massachusetts Institute of Technology in Cambridge, who served on the BESAC subpanel that studied the issue. The desired machine, Barletta says, would be a ‘free electron laser’, a machine that uses magnets to wiggle an electron beam so that it emits X-rays that are coherent, or in phase with one another. The new laser’s specifications, the panel suggested, should include a fast X-ray pulse repetition rate and a large X-ray photon energy range.

The idea of a free electron laser with a high pulse repetition rate resonates strongly with a proposal from Lawrence Berkeley National Laboratory in California to build a free electron laser that uses an electron beam accelerated by superconducting magnets. That proposal, called the Next Generation Light Source (NGLS) (pictured) has already been approved in principle by the Energy Department but has received scrutiny from appropriators in the US Congress.

However, the panel’s preferred energy range is larger than what was proposed for the NGLS, instead falling within the range of another proposal, from Stanford Linear Accelerator Center, in Menlo Park, California, to upgrade the Linear Coherent Light Source (LCLS), a free electron laser that is already operating there.

Berkeley Lab director Paul Alivisatos  says that the NGLS has been through a number of descopings, aimed at bringing construction estimates below the level of US$1 billion, and that more ambitious proposals do exist to go up to near the panel’s desired level of 5 kiloelectronvolts, but at higher cost. “It’s possible to do that and we think it’s a straightforward extension of our proposal,” he says. Barletta says that the panel felt that both the NGLS and the proposed upgrade to the LCLS had demerits and strengths, and that the two labs needed to work together on a unification of their ideas.

The panel also heard from proponents of ‘ultimate storage rings’, which are similar to the X-ray synchrotrons that already exist at several US National labs but able to emit coherent X-rays, and from proponents of an Energy Recovery Linac, a linear accelerator that, like a synchrotron, would save energy by recycling its beam.

Barletta says that the key insight from studying the proposal for an ultimate storage ring is that the Energy Department should carefully review plans to upgrade existing synchrotrons to ensure that the money would not be better spent building a new ultimate storage ring instead. Several other countries are building synchrotrons more advanced than those in the United States today, including Sweden, Brazil and Japan.

 

IceCube neutrinos came from outer space

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{credit}IceCube collaboration{/credit}

Two ultra-high-energy neutrinos captured by the IceCube experiment probably came from outside the Galaxy, according to an analysis posted by the collaboration today.

“We’re pretty excited about it. They’re the highest energy neutrinos that have ever been seen,” says Thomas Gaisser, an IceCube member at the University of Delaware in Newark. IceCube consists of 86 strings of detectors sunk in a cubic kilometre of ice near the South Pole.

The two neutrinos, which were announced in 2012 but had not at that time been analysed, had energies of more than a petaelectronvolt (PeV), which makes them 100 million times more energetic than the neutrinos emitted by supernovae that have reached Earth. One possibility is that they are produced in the atmosphere through the interactions of high-energy cosmic rays there, but given their high energy, that is unlikely, the collaboration finds. If they are instead astrophysical in origin, then they are probably produced by the same sources that make ultra-high-energy cosmic rays, the origin of which is one of the longest-running mysteries in astrophysics. Two possibilities are the gamma-ray bursts emitted from collapsing stars, or active galactic nuclei, the jets emanating from massive black holes at galactic centres, but it’s unknown which.  The collaboration puts the possibility of the particles having an astrophysical origin at a statistical confidence level of 2.8 sigma, falling just short of the 3 sigma needed to constitute hard evidence in physicists’ terminology.

IceCube’s detectors (see image) pick up the light emitted when neutrinos and other particles pass through.  The two recently analysed neutrinos were plucked from events collected between 2010 and 2012 after the collaboration filtered out lower-energy data. The team is now re-running the analysis with a lower threshold to see whether they can uncover more events from the same sources and reveal their origin.

For years, astronomers and physicists have collected the flighty neutrino particles emitted in the Sun and from supernovae. But being able to observe distant sources from outside the Galaxy would take the field to a new level, and would be a sign that IceCube is now working like a telescope, says Gaisser. “It opens up a new way of looking at the cosmos,” he says.

Investigation clears US interior-department staff of misconduct

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Klamath River

The Klamath River runs through Oregon and northern California. {credit}Pam Rentz on Flickr under Creative Commons{/credit}

In the first of its reports on alleged scientific misconduct to be released since the 2011 introduction of a new scientific integrity policy, the US Department of the Interior (DOI) has rejected allegations brought by Paul Houser, a scientific-integrity official and hydrologist who claimed in 2012 that he was fired for trying to do his job calling out bad science.

After his dismissal, Houser, now at George Mason University in Fairfax, Virginia, reached a settlement with the DOI in December 2012. But the DOI and Houser continue to disagree on whether the work he questioned during his time there contained examples of scientific misconduct.

Now the report, which was released by the DOI as part of a new scientific-integrity website launched on 15 March, agrees with Houser that a press release and scientific summary document prepared by DOI staff in 2011 downplayed the level of uncertainty around scientific studies suggesting that the proposed removal of four dams on the Klamath River in Northern California would be good for the environment. But it finds that the misrepresentations were not deliberate and did not rise to the level of scientific misconduct. “The issues he raises do not appear to constitute intentional distortion or omission of scientific facts, falsification of science, or compromise of scientific integrity,” the report states. Still, its executive summary warns the department that “false precision” is not desirable, and notes that panel members struggled with a lack of clarity over how the newly introduced integrity policy should be interpreted.

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Dark-matter search from the space station continues to tease

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Nobel prize winner Samuel Ting  (pictured) likes to keep people guessing. Nowhere was this more true than at his press conference this morning at the American Association for the Advancement of Science (AAAS) meeting in Boston, Massachusetts. The AAAS had suggested that Ting would be ready to present the first dark matter results from his brainchild, the US$1.5 billion Alpha Magnetic Spectrometer (AMS), basically a giant magnet and antimatter detector fixed to the outside of the International Space Station. Ting was prefaced by a line-up of physicist colleagues who described themselves as “very excited”. But Ting ended up only disappointing them and around 100 reporters who had gathered for the press conference. Ting said that he wasn’t ready to make an announcement yet. “In two to three weeks, we should be ready,” he said.

Ting did say that he is on the verge of releasing a paper showing how the ratio of positrons (the antimatter counterpart of electrons) to electrons passing through the space station’s near-Earth orbit varies with energy. That ratio is a key parameter in the search for dark matter, which is thought to make up 85% of the matter in the Universe. Some theories predict that dark-matter particles will annihilate in space, producing an excess of positrons that particle detectors can capture. At least two space missions, the Payload for Antimatter Exploration and Light-nuclei Astrophysics (PAMELA) and the Fermi space telescope, have already seen hints of such an antimatter excess,  but they have not captured a killer signature. Ting hopes that his more sensitive spectrometer can nail the signal, which would show up as an abrupt bump in the excess at a particular energy. Alternative astrophysical sources, such as pulsars, could also produce an excess, but couldn’t as easily produce a sharp bump.

Ting says that he has used some 8 million particle events to map the excess across an energy spectrum from 0.5 gigaelectronvolts to 350 gigaelectronvolts, and that he plans to report it in a paper to be sent to a high-energy physics journal in a couple of weeks. He does not yet have sufficient data to report the entire energy range that the AMS is sensitive to — up to 1 tera-electronvolt — in a statistically meaningful way. Ting had reporters hanging on his every word as he appeared at one point to hint that spectrum might drop off at some energy in a way that could be consistent with a theory of dark matter. But then he added in response to direct questions that he might also have no signal.

“It’s a let-down,”says Fermilab physicist and dark-matter expert Dan Hooper, who had tuned in online to follow the press conference live from Batavia, Illinois. The AMS will undoubtedly contribute our knowledge of the positron excesses seen by Fermi and PAMELA, he says, but today was not the day.

Neal Weiner, a theoretical physicist at New York University in New York who was present in the audience, says that even if Ting does announce a potential dark-matter signal, it will need to be interpreted with care. A very abrupt bump of the type that would point unambiguously to dark matter should already have shown up in existing data, he says. Probably, then, even if Ting’s events do show a positron excess, physicists will continue to debate whether that is produced by some more ordinary astrophysical source, or dark matter.

Ion collider flagged for closure

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Nuclear physicist Robert Tribble (right) looked markedly depressed as he presented his panel’s conclusions ranking three US nuclear science facilities against each other at a meeting in North Bethesda, Maryland, yesterday and today. The loser, as projected by Nature last August, is RHIC, the Relativistic Heavy Ion Collider at Brookhaven National Laboratory (BNL) in Upton, New York, where experiments creating trillion-degree subatomic soups of quarks and gluons may have to be shut down under the worst budget scenario.

“I am very concerned that if we have to close a major facility our field is going to continue a spiral down,” says Tribble, of Texas A&M University in College Station. “It’s a very, very difficult situation.”

For the past 8 months, the US nuclear science advisory committee (NSAC) has been tasked with choosing between three leading US facilities under two flat-funding scenarios (one rising with inflation, the other flat in real terms but effectively falling). Both are well below the levels assumed by a plan mapped out by another panel chaired by Tribble in 2007, recommending all three facilities be supported (see chart, below, after the jump). The latest panel struggled with the projected loss of nuclear science jobs and discoveries that losing any of the three facilities would bring. Its report, which is expected to be released at the end of this week, stops short of recommending RHIC’s early closure, Tribble says. Still, that is the report’s effective message as it ranks the ion collider below a planned upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson National Laboratory in Newport News, Virginia, and the construction of the Michigan State University’s Facility for Rare Isotope Beams (FRIB), in East Lansing, both of which are already well under way. Tribble says that RHIC is the most complex and expensive of the three facilities to operate. Continue reading →

Moon mapping mission ends with controlled crash

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{credit}NASA/ARC/MIT{/credit}

Twin spacecraft that mapped the gravity field of the Moon with unprecedented precision have succumbed to the very force they were made to measure.

Ebb and Flow, the two probes that make up NASA’s GRAIL, the Gravity Recovery and Interior Laboratory, crashed one after the other into the Moon at 5:28 p.m. Eastern Standard Time on 17 December — an end that mission planners always had in mind — after a mind-blowingly successful flight that has included producing the first ultra-high-resolution picture of the Moon’s gravitational field (right).

The probes, which flew in tandem exchanging radio signals in lunar orbits that were minutely but measurably perturbed by variations in the Moon’s density, were conceived of by Maria Zuber, a planetary scientist at the Massachusetts Institute of Technology in Cambridge. Their scientific findings so far include the result that the Moon’s crust is thinner than thought during the Apollo era, and that some impact craters thought to exist from lower-resolution maps are not there. The GRAIL researchers still needs to carry out the more detailed data analysis needed to map out the Moon’s more mysterious  core.

Pharma lab loses valuable gold stash

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Here’s a lesson for those who don’t keep careful track of their lab supplies. A medical lab at Pfizer’s Research and Development Center in Chesterfield, Missouri, has allegedly lost up to US$700,000 worth of gold dust bought last year, the St Louis Post–Dispatch reports. According to the newspaper, a keen-eyed Pfizer auditor was unable to account for some or all of the stash while conducting an inventory; police aren’t sure whether the missing amount was lost, stolen or used in experiments without a record being kept.

Pfizer hasn’t commented on why it purchased the gold, but some researchers at its Chesterfield centre have co-authored studies researching the possibility of  gold-particle-mediated vaccines. In such experiments, DNA capable of prompting an immune response might be adsorbed onto a microscopic gold particle, which is then blown through the skin using compressed gas — an approach that would trigger a reaction using less DNA than an injection. One Pfizer paper from 2010 describes protocols for experiments aimed at developing that particular concept that used several hundred micrograms of gold powder per sample (pictured, from Analytical and Bioanalytical Chemistry 398, 527–539). Although dozens of samples were tested, the amount of gold used was substantially less than the 10-plus kilograms police say are missing.

Nutrition researcher censured over serial misconduct

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At first glance, many of the western blots in the data of nutrition researcher Eric J. Smart, censured yesterday by the US government’s Office of Research Integrity over a 10 year career of misconduct, look innocuous.

But zooming in on two blots from one figure in a 2002 paper (pictured at right) from the Journal of Biological Chemstry, volume 277, pages 4925-31, reveals tell-tale noise patterns that may well betray the images’ common origin.

It is just one of 45 figures that the ORI says was fabricated by Smart in 10 papers,  7 grant applications, 1 submitted manuscript and 4 grant progress reports he prepared while on the faculty at the University of Kentucky(UKY) in Lexington. The office has recommended the papers be corrected or retracted.

Smart, who resigned from his position last May, is a nutritionist who studied cardiovascular disease, inflammation, and cholesterol. Some of his papers on membrane proteins have been cited hundreds of times. His violations included reporting data on knockout mice that did not exist in his laboratory as well as 33 instances of manipulating and duplicating western blots — a technique for identifying proteins.

Smart has agreed to exclude himself from raising grants from the National Institutes of Health for seven years as a result of the censure.

That is a relatively long exclusion compared to most ORI cases, which involve censures of three years or sometimes five. Indeed the longevity of Smart’s fakery seems comparable to that of Eric Poehlman, a researcher on aging at the University of Vermont in Burlington who was prosecuted for grant fraud in 2005 after faking data over eight years.

But as the US government made clear at the time, Poehlman’s fraud involved as many as 17 grant applications, and he also exacerbated his situation by destroying evidence and influencing witnesses. Smart resigned from UKY quietly in May, as a commenter on this Retraction Watch post about him points out.

Smart was not available for comment at time of publication.