Stem cells may help in treating deafness New method produces sound-sensitive neurons

Human embryonic stem cells can be directed to form sound-detecting nerve cells in the inner ears of deaf gerbils.
Deafness often results from the loss of specialized nerve cells — called hair cells and spiral ganglion neurons — in the cochlea, the part of the inner ear that converts vibrations into nerve signals the brain understands as sounds. Until now, no one has been able to replace both types of nerve cells.
Researchers at the University of Sheffield in England devised a way to make human embryonic stem cells follow the same steps that sound-detecting nerves take during normal development. When transplanted into the cochleas of deaf adult gerbils, the human cells partially restored the animals’ hearing, the researchers report online September 12 in Nature.
Such cells may one day be used in combination with cochlear implants to treat deafness in people.

Postcards from Mars show rover's key science targets

NASA on Monday showed off the first high-resolution, color portrait images taken by the Mars rover Curiosity, detailing a mound of layered rock where scientists plan to focus their search for the chemical ingredients of life on the Red Planet.

The stunning images reveal distinct tiers near the base of the 3-mile- (5-km-)tall mountain that rises from the floor of the vast, ancient impact basin known as Gale Crater, where Curiosity landed on August 6 to begin its two-year mission.
Scientists estimate it will be a year before the six-wheeled, nuclear-powered rover, about the size of a small car, physically reaches the layers of interest at the foot of the mountain, 6.2 miles away from the landing site.
From earlier orbital imagery, the layers appear to contain clays and other hydrated minerals that form in the presence of water.
While previous missions to Mars have uncovered strong evidence for vast amounts of water flowing over its surface in the past, Curiosity was dispatched to hunt for organic materials and other chemistry considered necessary for microbial life to evolve.
The $2.5 billion Curiosity project, NASA's first astrobiology mission since the 1970s-era Viking probes to Mars, is the first to bring all the tools of a state-of-the-art geochemistry laboratory to the surface of a distant planet.
But the latest images from Curiosity, taken at a distance from its primary target of exploration, already have given scientists a new view of the formation's structure.
The layers above where scientists expect to find hydrated minerals show sharp tilts, offering a strong hint of dramatic changes in Gale Crater, located in the planet's southern hemisphere near its equator.
SLANTED LAYERS EXPOSED
Mount Sharp, the name given to the towering formation at the center of the crater, is believed to be the remains of sediment that once completely filled the 96-mile- (154-km-) wide basin.
"This is a spectacular feature that we're seeing very early," project scientist John Grotzinger, with the California Institute of Technology, told reporters on Monday. "We can sense that there is a big change on Mount Sharp."
The higher layers are steeply slanted relative to the layers of underlying rock, the reverse of similar features found in Earth's Grand Canyon.
"The layers are tilted in the Grand Canyon due to plate tectonics, so it's typical to see older layers be more deformed and more rotated than the ones above them," Grotzinger said. "In this case, you have flat-line layers on Mars overlaid by tilted layers. The science team, of course, is deliberating over what this means."
He added: "This thing just kind of jumped out at us as being something very different from what we ever expected."
Absent plate tectonics, the most likely explanation for the angled layers has to do with the physical manner in which they were built up, such as being deposited by wind or by water.
"On Earth, there's a whole host of mechanisms that can generate inclined strata," Grotzinger said. "Probably we're going to have to drive up there to see what those strata are made of."
Also Monday, NASA said it used the rover to broadcast a message of congratulations to the Curiosity team from NASA chief Charles Bolden, a demonstration of the high bandwidth available through a pair of U.S. science satellites orbiting Mars.
"This is the first time that we've had a human voice transmitted back from another planet" beyond the moon, said Chad Edwards, chief telecommunications engineer for NASA's Mars missions at the Jet Propulsion Laboratory in Pasadena, California.
"We aren't quite yet at the point where we actually have a human present on the surface of Mars ... it is a small step," Edwards said.

NASA's Mars rover ready to "drive, drive, drive"

The Mars rover Curiosity was due to wrap up an exhaustive, weeks-long instrument check on Thursday, clearing the way for its first lengthy drive to determine whether the Red Planet has ever been hospitable to life, NASA officials said.

The six-wheeled, nuclear-powered rover landed five weeks ago inside a giant impact basin called Gale Crater, near the Martian equator, to conduct NASA's first astrobiology mission since the 1970s-era Viking probes.
For its final equipment check, Curiosity will maneuver its robot arm so its close-up camera touches the tray where processed rock and soil samples will be analyzed.
The rover, equipped with an array of the most elaborate laboratory instruments ever sent to a distant world, also has a bit of sightseeing on its agenda. Scientists want to obtain video footage of the Martian moon Phobos passing by the sun.
Starting Friday evening, the plan is to "drive, drive, drive" until scientists find a suitable rock for the rover's first robotic "hands-on" analysis, mission manager Jennifer Trosper told reporters during a conference call on Wednesday.
It will stop when scientists find suitable soil to scoop up and run through Curiosity's onboard chemistry lab.
All the while, the rover will be heading toward a site scientists have labeled "Glenelg," where three different types of rock intersect. Glenelg, which lies about 1,312 feet away from Curiosity's current position, was named by mission geologists after a rock formation in northern Canada.
The overall purpose of the $2.5 billion Mars Science Lab mission is to search for places where microbial organisms could have evolved and been preserved. In addition to ferreting out the chemical and geologic footprints of water, Curiosity will hunt for organic compounds and other ingredients believed to be necessary for life.
Curiosity, which is designed to last two years, will venture about 4.3 miles from its landing site to climb a 3-mile-high mound of layered rock rising from the floor of Gale Crater. Dubbed Mount Sharp, it is believed to be the remains of sediment that once filled the 96-mile wide (154-meter) basin.
The rover has racked up 358 feet on its odometer during test drives. Before setting out for Mount Sharp, scientists expect to drive Curiosity about 131 feet a day during its planned trek to Glenelg, with several stops for science observations.

World's Most Stable Laser: Important for Even Better Optical Atomic Clocks

New silicon resonator keeps the frequency of a laser more stable than ever before -- Important for even better optical atomic clocks.

A laser with a frequency stability so far unequalled: This is the result of a research cooperation of the Physikalisch-Technische Bundesanstalt (PTB) within the scope of the Excellence Cluster QUEST (Centre for Quantum Engineering and Space-Time Research) with colleagues from the American NIST (National Institute of Standards and Technology)/JILA. Their development, about which they report in the scientific journal "Nature Photonics," is important for optical spectroscopy with highest resolution, e.g. of ultra-cold atoms. But, above all, an even more stable interrogation laser is now available for use in optical atomic clocks.
Optical atomic clocks require laser sources that radiate light with an extremely constant frequency. Commercial laser systems are not suited for this purpose without additional measures. However, this can be achieved by stabilizing them, for example, with the aid of optical resonators. These are composed of two highly reflecting mirrors which are kept at a fixed distance by means of a spacer. The decisive aspect is the following: In analogy to an organ pipe, the resonator length determines the frequency with which light can begin to oscillate in the resonator. Consequently, a resonator with a high length stability is required for a stable laser, i.e. the distance between the mirrors must be kept as constant as possible.
Modern resonator-stabilized laser systems have meanwhile been technically developed to such an extent that their stability is only limited by the thermal noise of the resonators. Similar to the Brownian motion of molecules, the atoms in the resonator are constantly moving and are, thus, limiting its length stability. Up to now, resonators have been made of glass, whose disordered and "soft" material structure shows particularly strong movements. For the new resonator, the research group has used single-crystal silicon, a particularly "stiff" and thus low-noise material. Cooled down to a temperature of 124 K (-149 degrees Celsius), silicon is characterized by an extremely small thermal expansion, and the remaining thermal noise is additionally reduced. To operate the resonator at this temperature, the researchers had to design, first of all, a suitable low-vibration cryostat. The result is something to be proud of: Comparison measurements with two glass resonators allowed the scientists to demonstrate a frequency stability so far unequalled of 1 · 10^-16 for the laser stabilized to the silicon resonator.
This allows them to remove an important obstacle in the development of even better optical atomic clocks, because the stability of the lasers used is a critical point. The "pendulum," i.e. the swinging system of such a clock, is a narrow optical absorption line in an atom or ion, whose transition frequency is read out by a laser. The linewidth of these transitions typically amounts to a few millihertz, a value which could not be reached by glass resonators due to their limited length stability.
But this is now possible. The laser to which the silicon resonator is stabilized reaches a linewidth of less than 40 mHz and can, thus, contribute to moving into a new dimension in the development of optical atomic clocks. This work could also benefit optical precision spectroscopy, another focal point of research of the Excellence Cluster QUEST.
"For the future, there is still room to improve the optical mirrors whose thermal noise limits the achievable stability," explains PTB physicist Christian Hagemann. Therefore, the researchers will in future go down to even lower temperatures and use novel highly reflecting structures to improve the frequency stability by another order of magnitude.