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[naturenews] from [nature.com]

[naturenews]
Published online 28 January 2010 | Nature | doi:10.1038/news.2010.40
News
Light extinguishes dark-matter claims
Starlight accounts for anomalous electron signals.
Eric Hand

{{An excess of high-energy electrons detected by the HESS telescope array and other instruments may not be due to dark matter after all.}
HESS collaboration}

By invoking the effects of starlight, theorists have created a model of the behaviour of galactic electrons, casting doubt on a signal that some had hoped pointed to a detection of dark matter.

Within the past two years, several experiments — in space, on the ground, and in a balloon — have reported detecting more high-energy electrons than were expected to be whirling around the galaxy. Many theorists attributed the surplus electrons as either the effect of a nearby pulsars, or, more provocatively, dark matter — the elusive stuff thought to make up as much as 85% of the matter in the Universe (see 'Dark matter intrigue deepens').

A paper in the 10 February issue of the Astrophysical Journalue¹ says that both explanations are wrong. The high-energy electrons can be produced naturally when the starlight they pass through is accounted for more correctly, says one of the paper's authors — Vahé Petrosian, a theorist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University in California. "We have to put dark matter on the shelf," he says.

Scattering effect

Galactic electrons are thought to originate in the explosion of supernovae, and conventional models predict that they lose energy as they pass through the Milky Way's magnetic field. The annihilation of proposed dark-matter particles would also create electrons, and some theorists had interpreted the recent experimental detections of surplus high-energy electrons as evidence for this process.

{{“I would say there's no compelling reason to invoke exotic explanations.”}
Werner Hofmann
High Energy Stereoscopic System}

But starlight also scatters the electrons. Petrosian says that starlight suppresses the energy of most electrons in a way that makes it seem as if there is an excess of certain high-energy electrons. The Stanford group's models show an excess that is similar to that reported by NASA's Fermi Gamma-ray Space Telescope; the High Energy Stereoscopic System (HESS), a ground-based detector in Namibia; and the Advanced Thin Ionization Calorimeter (ATIC), a balloon-borne detector that flew over Antarctica.

HESS spokesperson Werner Hofmann says that the Stanford group's models are "quite possible" and would make it very difficult to make a strong case for dark matter in the high-energy electron signal. "I would say there's no compelling reason to invoke exotic explanations," says Hofmann, an astrophysicist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany.

Need for ideas

More challenging for the group was explaining a signal arising from an Italian satellite, PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics), which measures the ratio of electrons to positrons, their antimatter partners. A rising fraction of high-energy positrons has also been interpreted as a possible dark-matter signal. (See 'Physicists await dark-matter confirmation')

But by tweaking parameters in their model, the Stanford group can also mimic the PAMELA results. Like the electrons, the positrons are also thought to originate near supernovae — although through secondary collisions of protons. By increasing the density of gas and the number of photons near these supernovae — both possible scenarios given that supernovae occur in gas-rich star-forming regions near lots of stars — the model predicts high-energy positrons similar to those reported by PAMELA. "It's a new possibility to consider and a new way to get 100 GeV [gigaelectronvolt] positrons to our Solar System," says Dan Hooper, a dark-matter theorist at Fermi National Accelerator Laboratory in Batavia, Illinois. "We need all the ideas we can get."

Using the high-energy electrons as a proxy for dark matter is just one of many approaches in the hunt. The Large Hadron Collider at CERN, the European particle-physics laboratory near Geneva, Switzerland, may create dark matter as it smashes high-energy protons together. And experiments underground use quiet environments to watch for the rare recoils of atomic nuclei that dark-matter particles ought to cause occasionally. In December, an underground detection group reported that it had seen two events that may have been dark-matter collisions — enough to get attention, but not yet enough to claim a definitive detection (see 'Two direct hits in dark matter hunt').

References
1. Stawarz, Ł., Petrosian, V. & Blandford, R. D. Astrophys. J. 710, 236-247 (2010); advance online publication doi:10.1088/0004-637X/710/1/236 | Article | OpenURL


[naturenews]
Published online 28 January 2010 | Nature | doi:10.1038/news.2010.43
News
Britain grants patent for iPS cells
The first issued outside Japan for reprogrammable stem cells credits different Japanese inventors.
Sabin Russell

A Californian biomedical company, iPierian, has been granted the first patent issued outside Japan for the genetic reprogramming technology used to create induced pluripotent stem (iPS) cells.

{{Induced pluripotent stem cells have the ability to develop into any cell type in the body.}
James Thomson, University of Wisconsin-Madison}

The 12 January decision, by the UK Intellectual Property Office, does not involve the work of Kyoto University's Shinya Yamanaka, whom many consider to have invented the technology behind iPS cells. Instead it credits the invention to a competing group of Japanese researchers, led by Kazuhiro Sakurada, who worked in Kobe for an affiliate of Bayer Schering Pharma. iPierian, based in South San Francisco, acquired rights to the patent claims in 2008.

Like embryonic stem cells, iPS cells can develop into any cell type in the body, but they avoid the ethical controversies involved in using embryos. Although various international research groups have filed more than 75 patent claims involving iPS cells, the only patents awarded until now have been issued by Japan for Yamanaka's work.

Crucially, iPierian contends that Bayer had filed its key claims for the use of iPS technology in human cells months ahead of any rivals, including Yamanaka.

Akemi Nakamura, a spokesperson for Kyoto University, disagrees. "We believe we have an advantage over his claim, as the Yamanaka claim was filed prior to the Sakurada claim," Nakamura wrote in an e-mail.

First to file

Yamanaka filed his initial claim regarding iPS technology in December 2006. That application, granted in December 2008 by the Japan Patent Office, covered methods for generating both mouse and human iPS cells using four genes introduced by viral vectors. Sakurada's claim was filed in Japan in June 2007, but specifically excluded the use of c-Myc, an oncogene that research teams have been eager to eliminate from the roster of players needed to trigger reprogramming. Sakurada has yet to be issued a patent in Japan.

The relationship between Yamanaka, Sakurada and iPierian is complicated. Yamanaka was involved in the early founding of iPierian, which initially set up shop inside the Gladstone Institutes, an affiliate of the University of California, San Francisco (UCSF), where Yamanaka works in a satellite laboratory once a month. Yamanaka has no direct stake in iPierian, but his Kyoto research laboratory collaborates with the company on efforts to refine methods of reprogramming cells — such as replacing the viral vectors used to ferry the genes that trigger the process that creates stem cells.

Sakurada briefly held the post of chief scientific officer of iZumi Bio, the company that became iPierian after it merged with Pierian — a start-up created by Harvard stem-cell researchers George Daley, Douglas Melton and Lee Rubin. Sakurada is no longer employed at iPierian, according to company spokeswoman Danielle Bertrand.

Pioneering spirit

Yamanaka could not be reached for comment about the British patent office decision. However, during a visit to the Gladstone Institutes in December, he spoke of his wish that intellectual property disputes would not slow down progress in the nascent field. "This kind of technology should not be confined to any region or country," he said.

Ken Taymor, executive director of the Berkeley Center for Law, Business and the Economy in California, says that patents are pertinent only in the countries where they are issued. The UK patent may have little impact on iPS patents pending in the United States. But he acknowledged that the British decision signals that at least one major patent office is taking the Sakurada claims seriously. "These are initial steps in defining the intellectual property landscape for this important technology," he says.

The stakes in intellectual property disputes about fundamental technologies are potentially enormous. Yamanaka is reminded of it every time he visits the Gladstone laboratory. Beyond his office window stands UCSF's Genentech Hall, built in part with $50 million wrested in an out-of-court settlement from the biotech giant, which was sued by the university for infringing its patents for human growth hormone, one of Genentech's first drugs.