The material contains cobalt atoms arranged in long chains and each atom acts like a tiny bar magnet that can point either ‘up’ or ‘down’.

When a magnetic field is applied at right angles to the aligned spin directions, the spins can ‘quantum tunnel’ between the ‘up’ and ‘down’ orientations. At a precise value of the applied field these fluctuations ‘melt’ the ferromagnetic order of the material resulting in a ‘quantum critical’ state.

‘You might expect to see random fluctuations of the spins at this critical point but what we uncovered was a remarkable structure in the resonances of the magnetic spins indicating a perfectly harmonious state,’ said Radu Coldea from Oxford University’s Department of Physics who led the team.

As the critical state was approached the researchers observed that the chain of atoms behaved like a ‘magnetic guitar string’.

Radu added: ‘The tension comes from the interaction between spins causing them to magnetically resonate. We found a series of resonant modes. Close to the critical field the two lowest resonant frequencies approached closely the golden ratio 1.618…, a characteristic signature of the predicted E8 symmetry.’

He is convinced that this is no coincidence and it reflects a subtle form of order present in the quantum system.

The resonant states seen experimentally in cobalt niobate may be our first glimpse of complex symmetries that can occur in the quantum world. “The results suggest that similar ‘hidden’ symmetries may also govern the physics of other materials near quantum critical points where electrons organize themselves according to quantum rules for strong interactions,’ Radu told us.

The research was supported by EPSRC and Radu aims to use a new EPSRC grant to explore the physics of materials near quantum criticality.

The team included Dr Radu Coldea, Dr Elisa Wheeler and Dr D Prabhakaran from Oxford University’s Department of Physics, as well as researchers from Helmholtz Zentrum Berlin, ISIS Rutherford Laboratory, and Bristol University.

The findings mean scientists now know of 10 genetic variants associated with chronic lymphocytic leukemia (CLL), scientists at Europe’s Institute of Cancer Research who conducted the study said.

The four new genetic factors are all common in European populations and each factor contributes to an increase in the risk of the disease.

CLL is the most common type of leukemia in adults, accounting for around 30 to 40 percent of all forms of leukemia in Western countries. Most of those diagnosed are over the age of 55, and while the incidence of CLL is broadly equal in black and white populations, the disease is rare among Asians.

Richard Houlston, who led the study, said it confirmed the inherited risk of CLL, and showed it was not due to a single gene due to the cumulative effect of many genetic changes.

Each person may carry any number, from a few of the identified risk factors to all of them, he said in research published in the journal Nature Genetics. And the more genetic factors carried, the higher their risk of developing CLL.
“People who have more than 13 risk factors are seven times more likely than the general population to develop CLL,” Houlston added in a statement about the study.

The risk factors were identified using a genetic analysis technique that scientists have used previously to find risk genes in breast, prostate, testes, brain and colon cancer and childhood leukemia.

The researchers scanned the genes of 2,503 CLL patients and compared them to 5,789 healthy people, looking for differences in DNA between the two groups.

In previous studies, Houlston’s team found that genetic factors could make people more susceptible to CLL, identifying six genetic factors more common among sufferers.

The four new factors add to those findings and the study also found that 87 percent of people with CLL would have at least one of these genetic risks.

David Grant, scientific director of the Leukemia Research charity which funded the study, said it confirmed some long-held suspicions that this form of leukemia may run in families.

“This research is providing the genetic evidence that an increased risk of developing CLL can be inherited,” he said in a statement.

“However it is clearly a complex picture and we need to study more families before we can be certain of the particular genetic traits that are most important.”

The footprints — many individual impressions, as well as some arranged in sets called trackways — are preserved in 395-million-year-old rocks in the Holy Cross Mountains, in the southeastern part of the country, paleontologist Per E. Ahlberg and colleagues report in the Jan. 7 Nature. That age substantially predates the time frame that paleontologists have pinned as the sea-to-land transition.

Evidence suggests that the carbonate rocks were laid down as sediments in the intertidal areas of a tropical shoreline, possibly in a lagoon, says Ahlberg, of Uppsala University in Sweden.

The presence of footprints in rocks of this age is surprising: The tracks date to 18 million years before body fossils of tetrapods show up in the geological record. And the footprints are about 10 million years older than body fossils of creatures such as Tiktaalik and Panderichthys (SN: 6/17/06, p. 379), believed to represent the transition from lobe-finned fish to creatures fully adapted to life on land.

Ahlberg and his colleagues contend that the findings “force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition.” While previous studies have suggested that the first tetrapods hauled up on lakeshores or in freshwater deltas, these trackways hint that the water-to-land transition could have happened in a shallow marine setting.

In some areas of the quarry, the fossilized footprints are so common that they fall on top of and partially obliterate one another, forming what Ahlberg and his colleagues call a “densely trampled surface.” Small craters peppering the surface were made by falling raindrops — a sign that the ancient sediments were exposed to the air at least part of the day, the researchers contend.

The arrangement of footprints in one trackway — including stride length and relative spacing, as well as the absence of an impression from a sagging tail — suggest a tetrapod between 40 and 50 centimeters long left the tracks. Individual footprints in this set didn’t have sharply defined edges, possibly because the creature traipsed through squishy sediment in shallow water, the researchers note.

Other footprints at the site, however, were made by a larger, similar creature and include signs of toes. The largest of those prints is about 15 centimeters wide and was probably made by a tetrapod about 2.5 meters long, the team estimates.

Because the rocks don’t contain any body fossils, it’s difficult to interpret what type of organism made the tracks, says Jennifer A. Clack, a paleontologist at the University of Cambridge in England. “If the isolated footprints are what they seem to be, the creature was relatively enormous,” she notes. And, she adds, “if fossils of the creature that made these tracks are ever found, they could well upset the apple cart of what people thought about tetrapod evolution.”

Constantly changing water levels make intertidal areas a dynamic environment, Clack says. In such a setting — where substantial quantities of food might have been stranded in shallow water when tides rolled out — evolution would have favored adaptable creatures, she contends.

The newly described footprints and trackways “are a very exciting find,” says Anthony J. Martin, a paleontologist at Emory University in Atlanta. “The combination of trampled surfaces, multiple trackways with tetrapodal gait patterns [and] distinct individual tracks with distinct digit impressions … makes a very persuasive argument that these structures are tetrapod trace fossils.”

Other scientists, however, aren’t convinced that tetrapods left the fossilized footprints.

“These are interesting trace fossils,” says Ted Daeschler, a paleontologist at the Academy of Natural Sciences in Philadelphia. However, he notes, trace fossils are notoriously difficult to interpret with confidence. Also, he adds, the arrangement of individual footprints in these trackways reflects a style of walking not seen again in the fossil record until 50 million years later. (No trackways that can be attributed to Tiktaalik or Panderichthys have been discovered.) “All together, the new evidence isn’t strong enough to make me discard the current, well-supported ideas about the timing of tetrapod evolution,” he says.

Many of the newly described footprints are indistinct and possibly not even made by tetrapods, but finding anything from that far back in time is still exciting, comments Robert L. Carroll, a paleontologist at the McGill University’s Redpath Museum in Montreal. The indistinct tracks could be impressions made in soft sediments by lobe-finned fish, he notes. And the footprints may have been made by members of a yet-to-be-discovered group of four-limbed creatures that went extinct and didn’t lead to today’s tetrapods.