Thursday, December 16, 2010

ASTRONOMERS USE MOON IN EFFORT TO CORRAL ELUSIVE COSMIC PARTICLES

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Seeking to detect mysterious, ultra-high-energy neutrinos from distant regions of space, a team of astronomers used the Moon as part of an innovative telescope system for the search. Their work gave new insight on the possible origin of the elusive subatomic particles and points the way to opening a new view of the Universe in the future.

The team used special-purpose electronic equipment brought to the National Science Foundation's Very Large Array (VLA) radio telescope, and took advantage of new, more-sensitive radio receivers installed as part of the Expanded VLA (EVLA) project. Prior to their observations, they tested their system by flying a small, specialized transmitter over the VLA in a helium balloon.

In 200 hours of observations, Ted Jaeger of the University of Iowa and the Naval Research Laboratory, and Robert Mutel and Kenneth Gayley of the University of Iowa did not detect any of the ultra-high-energy neutrinos they sought. This lack of detection placed a new limit on the amount of such particles arriving from space, and cast doubt on some theoretical models for how those neutrinos are produced.

Neutrinos are fast-moving subatomic particles with no electrical charge that readily pass unimpeded through ordinary matter. Though plentiful in the Universe, they are notoriously difficult to detect. Experiments to detect neutrinos from the Sun and supernova explosions have used large volumes of material such as water or chlorine to capture the rare interactions of the particles with ordinary matter.

The ultra-high-energy neutrinos the astronomers sought are postulated to be produced by the energetic, black-hole-powered cores of distant galaxies; massive stellar explosions; annihilation of dark matter; cosmic-ray particles interacting with photons of the Cosmic Microwave Background; tears in the fabric of space-time; and collisions of the ultra-high-energy neutrinos with lower-energy neutrinos left over from the Big Bang.

Radio telescopes can't detect neutrinos, but the scientists pointed sets of VLA antennas around the edge of the Moon in hopes of seeing brief bursts of radio waves emitted when the neutrinos they sought passed through the Moon and interacted with lunar material. Such interactions, they calculated, should send the radio bursts toward Earth. This technique was first used in 1995 and has been used several times since then, with no detections recorded. The latest VLA observations have been the most sensitive yet done.

"Our observations have set a new upper limit -- the lowest yet -- for the amount of the type of neutrinos we sought," Mutel said. "This limit eliminates some models that proposed bursts of these neutrinos coming from the halo of the Milky Way Galaxy," he added. To test other models, the scientists said, will require observations with more sensitivity.

"Some of the techniques we developed for these observations can be adapted to the next generation of radio telescopes and assist in more-sensitive searches later," Mutel said. "When we develop the ability to detect these particles, we will open a new window for observing the Universe and advancing our understanding of basic astrophysics," he said.

(Photo: Ted Jaeger, University of Iowa, NRAO/AUI/NSF)

The National Radio Astronomy Observatory

RAINFOREST COLLAPSE DROVE REPTILE EVOLUTION

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Global warming devastated tropical rainforests, 300 million years ago. Now scientists report the unexpected discovery that this event triggered an evolutionary burst amongst reptiles – and inadvertently paved the way for the rise of dinosaurs, a hundred million years later.

This event happened during the Carboniferous Period. At that time, Europe and North America lay on the equator and were covered by steamy tropical rainforests. But when the Earth’s climate became hotter and drier, rainforests collapsed, triggering reptile evolution.

Dr Howard Falcon-Lang of Royal Holloway, University of London, UK explained: “Climate change caused rainforests to fragment into small ‘islands’ of forest. This isolated populations of reptiles and each community evolved in separate directions, leading to an increase in diversity.”

Professor Mike Benton of the University of Bristol, UK added: “This is a classic ecological response to habitat fragmentation. You see the same process happening today whenever a group of animals becomes isolated from its parent population. It’s been studied on traffic islands between major road systems or, as Charles Darwin famously observed in the Galapagos, on oceanic islands.”

Ms Sarda Sahney, also of the University of Bristol, UK said: “It is fascinating that even in the face of devastating ecosystem-collapse, animals may continue to diversify through the creation of endemic populations.” However, she warned that: “Life may not be so lucky again in the future, should the Amazon rainforest collapse.”

To reach their conclusions, the scientists studied the fossil record of reptiles before and after rainforest collapse. They showed that reptiles became more diverse and even changed their diet as they struggled to adapt to rapidly changing climate and environment.

(Photo: Spencer Lucas, New Mexico Museum of Natural History)

University of Bristol

WHERE ARE ALL THE FLOWERS FROM?

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Amborella trichopoda, the world’s most ancient flowering plant, bloomed at the University’s Botanic Garden this autumn. The Garden’s Director, Professor Simon Hiscock, believes this unusual specimen may hold the key to unravelling Darwin’s ‘abominable mystery’ – the evolutionary origin of flowering plants.

The first flowering plants, or angiosperms, suddenly appeared over 130 million years ago, an event that perplexed Charles Darwin and remains a puzzle even now. Today the closest living relative of these flowers, Amborella trichopoda, is confined in the wild to the remote south Pacific island of New Caledonia. In 1999, new DNA evidence revealed that this strange specimen, with its tiny male or female flowers on separate plants, was the most primitive angiosperm alive, rather than the showier Magnolias as previously thought.

Since this revelation, many attempts have been made to collect and grow Amborella seeds. Most of these have failed, however, and because the unimpressive flowers have no commercial appeal the horticulture industry has shown no interest in them. Bristol's is the only Botanic Garden in the UK, and one of just a handful of gardens worldwide, where Amborella has been successfully grown, from seeds collected by Professor Hiscock during a trip to New Caledonia in 2007 with botanists from the University of Lyon, France.

One of the reasons that Amborella is so fascinating is that, unlike most angiosperms, the male and female reproductive organs occur on different plants. More than 95% of angiosperms are co-sexual, with both male and female reproductive organs in the same flower. This optimises reproductive efficiency and can allow self-fertilisation in the absence of pollinators. The flowers on co-sexual plants comprise both stamens, the male reproductive organs that produce pollen, and pistils, the female reproductive parts made up of one or more seed-bearing carpels. By contrast, male Amborella flowers comprise only stamens, while the females consist of a cluster of carpels, even though the fossil record suggests that Amborella’s ancestors were originally co-sexual.

One of Professor Hiscock’s collaborators at the University of Lyon, Dr Charlie Scutt, has demonstrated that certain genes involved in carpel development in Arabidopsis thaliana – a more recently evolved angiosperm widely used as a model organism in plant biology – play a similar role in Amborella flower development. Scutt and others have also shown that during the evolution of the flower these genes were co-opted from leaf development into carpel development, which must have been a critical step in the evolution of the angiosperm flower and its unique female reproductive structure, the carpel.

Using a similar approach, Professor Hiscock intends to use Amborella in his own research on reproduction in flowering plants to determine whether genes found in Amborella pollen and pistil are similar to those identified in Arabidopsis. This will provide important new insights into the evolution of the pollen-pistil interaction – a reproductive mechanism unique to angiosperms.

(Photo: Dave Pratt)

University of Bristol

THE OLDEST SALT MINE KNOWN TO DATE LOCATED IN AZERBAIJAN

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CNRS archeologists have recently provided proof that the Duzdagi salt deposits, situated in the Araxes Valley in Azerbaijan, were already being exploited from the second half of the 5th millennium BC. It is therefore the most ancient exploitation of rock salt attested to date. And, to the researchers' surprise, intensive salt production was carried out in this mine at least as early as 3500 BC. This work, conducted in collaboration with the Azerbaijan National Academy of Sciences and published on 1st December 2010 in the journal TÜBA-AR, should help to elucidate how the first complex civilizations, which emerged between 4500 BC and 3500 BC in the Caucasus, were organized.

The economic and symbolic importance of salt in ancient and medieval times is well known. Recent discoveries have shown that salt most probably played a predominant role in protohistoric societies, in other words those that preceded the appearance of writing. How is salt obtained? The two most widely used techniques are based on the extraction of rock salt, in other words a sedimentary deposit containing a high concentration of edible salt, and the collection of sun-dried salt in salt marshes, for example. Knowledge of the techniques used in former times to exploit raw materials such as salt, obsidian or copper enables archeologists to deduce essential information on the needs and the level of complexity of ancient societies. In the Caucasus, the first traces of intensive exploitation of rock salt appeared at the very moment when these protohistoric societies were undergoing profound economic and technological changes, particularly with regard to the development, for the first time, of copper metallurgy.

In order to understand these interactions, CNRS researcher Catherine Marro and her team have been exploring the Araxes basin (Turkey, Iran, Azerbaijan) for the last ten years or so. The archeologists have been focusing particularly on the Duzdagi salt mine situated in Azerbaijan, more specifically beside the old medieval Silk Road linking Tabriz (in the north west of Iran) with Constantinople. Until now, the oldest traces of exploitation of this deposit, which is still in activity, went back to the 2nd millennium BC. This dating was based on the fortuitous discovery in the 1970s of an ancient collapsed gallery that contained the remains of four workers buried with their tools.

In 2008, a French-Azerbaijani team directed by Marro and her colleague Veli Baxsaliyev began a systematic exploration of the Duzdagi mine. The team then made an inventory of a large number of remnants (tools, ceramics, etc.), the oldest of which date back to 4500 BC. It is the first time that artifacts from this period have been discovered in such large numbers in a salt mine. The researchers have thus been able to demonstrate that exploitation of this salt mine has been going on for a very long time, extending back at least to the second half of the 5th millennium BC: Duzdagi is therefore the oldest exploitation of rock salt known to date.

Another remarkable fact is that the abundance of artifacts dating from the early Bronze Age suggests that the Duzdagi mine was intensively exploited from as early as the 4th millennium BC. Hundreds of stone picks and hammers have in fact been found near the entrances of collapsed tunnels. The frequent presence nearby of ceramic pottery fragments specific to the culture known as “Kuro-Araxes” has made it possible to date these archeological artifacts. Their spatial and chronological distribution was analyzed by a geographic information system, combining satellite photos (Spot 5), aerial photos taken from a kite and the plotting of artifacts by DGPS, a sort of enhanced global positioning system. Such intensive extraction suggests that the salt from Duzdagi was not limited to local use by small self-sufficient communities. It was undoubtedly distributed, within a still unknown economic framework, to more far-off destinations. Furthermore, it appears that the extracted salt was not accessible to all of the communities in the Araxes Valley. Its exploitation from the 5th millennium BC seems to have been the prerogative of certain prominent groups.

This work raises a lot of questions. Who and what was the salt intended for in the 5th and 4th millennia BC. How were the communities that exploited these deposits organized? What were the political and economic links between the different regional sites (villages, workshops and mines), etc.? To find part of the answers, the archeologists hope to excavate the collapsed tunnels of this deposit, which covers more than 6 km2, in the near future.

(Photo: © Séverine Sanz / CNRS)

CNRS

STARS IN THE MILKY WAY MOVE IN MYSTERIOUS WAYS

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Rather than moving in circles around the center of the Milky Way, all the stars in our Galaxy are travelling along different paths, moving away from the Galactic center. This has just been evidenced by Arnaud Siebert and Benoit Famaey, astronomers at the Strasbourg Astronomical Observatory (CNRS/Université de Strasbourg), and by their colleagues in other countries. This strange behavior may be due to perturbation caused by the central bar and spiral arms of our Galaxy, forcing stars to leave their normal circular course and take an outward path.

Most galaxies, including our own Milky Way, are spiral-shaped and stars are distributed in a thin disk rotating around the galactic center, with areas divided into spiral arms or elliptical regions such as the central bar. Due to gravity, the spiral arms move through the disk in the form of density waves. For over twenty years, scientists believed that the potential impact of these density waves on stellar velocities in the Milky Way was insignificant in comparison with the circular motion of the stars in the galactic disk. This belief has now been blatantly proved wrong by an international team including several researchers from the Strasbourg Astronomical Observatory: near the Earth, stars move towards the exterior of the Galaxy at an average speed of around 10 kilometers per second, which is considerably faster than previously thought.

To reach this conclusion, the team systematically analyzed the velocities of over two hundred thousand stars located within a radius of a little over six thousand light years around the Sun. Using data from the major star survey RAVE (RAdial Velocity Experiment) collected since 2003 by the Australian Astronomical Observatory's Schmidt telescope, they were able to measure for the first time the radial velocities of hundreds of thousands of stars and determine whether they were moving towards or away from us.

The researchers were thus able to ascertain that the average speed of stars towards the exterior of the Galaxy increases with their distance from the Sun in the direction of the Galactic center, reaching 10 kilometers per second at a distance of 6 000 light years from us (in other words, 19 000 light years from the Galactic center). This result was completely unexpected and all the more surprising as it appeared to mainly affect old stars, several billion years old. Until now, it was thought that the spiral arms mostly affected the dynamics of young stars (only a few tens-of-million-years old). However, theoretical study of the combined effect of the spiral arms and the central bar, both within and outside the plane of the Galaxy, could explain the strange distortions of stellar motion observed by the astronomers in the RAVE team. Watch this space!

(Photo: © Gal Matijevic, Ljubljana University)

CNRS

PROJECT PIONEERS SILICON-GERMANIUM FOR SPACE ELECTRONICS

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A five-year project led by the Georgia Institute of Technology has developed a novel approach to space electronics that could change how space vehicles and instruments are designed. The new capabilities are based on silicon-germanium (SiGe) technology, which can produce electronics that are highly resistant to both wide temperature variations and space radiation.

Titled "SiGe Integrated Electronics for Extreme Environments," the $12 million, 63-month project was funded by the National Aeronautics and Space Administration (NASA). In addition to Georgia Tech, the 11-member team included academic researchers from the University of Arkansas, Auburn University, University of Maryland, University of Tennessee and Vanderbilt University. Also involved in the project were BAE Systems, Boeing Co., IBM Corp., Lynguent Inc. and NASA's Jet Propulsion Laboratory.

"The team's overall task was to develop an end-to-end solution for NASA -- a tested infrastructure that includes everything needed to design and build extreme-environment electronics for space missions," said John Cressler, who is a Ken Byers Professor in Georgia Tech's School of Electrical and Computer Engineering. Cressler served as principal investigator and overall team leader for the project.

A paper on the project findings will appear in December in IEEE Transactions on Device and Materials Reliability, 2010. During the past five years, work done under the project has resulted in some 125 peer-reviewed publications.

SiGe alloys combine silicon, the most common microchip material, with germanium at nanoscale dimensions. The result is a robust material that offers important gains in toughness, speed and flexibility.

That robustness is crucial to silicon-germanium's ability to function in space without bulky radiation shields or large, power-hungry temperature control devices. Compared to conventional approaches, SiGe electronics can provide major reductions in weight, size, complexity, power and cost, as well as increased reliability and adaptability.

"Our team used a mature silicon-germanium technology -- IBM's 0.5 micron SiGe technology -- that was not intended to withstand deep-space conditions," Cressler said. "Without changing the composition of the underlying silicon-germanium transistors, we leveraged SiGe's natural merits to develop new circuit designs -- as well as new approaches to packaging the final circuits -- to produce an electronic system that could reliably withstand the extreme conditions of space."

At the end of the project, the researchers supplied NASA with a suite of modeling tools, circuit designs, packaging technologies and system/subsystem designs, along with guidelines for qualifying those parts for use in space. In addition, the team furnished NASA with a functional prototype -- called a silicon-germanium remote electronics unit (REU) 16-channel general purpose sensor interface. The device was fabricated using silicon-germanium microchips and has been tested successfully in simulated space environments.

Andrew S. Keys, center chief technologist at the Marshall Space Flight Center and NASA program manager, said the now-completed project has moved the task of understanding and modeling silicon-germanium technology to a point where NASA engineers can start using it on actual vehicle designs.

"The silicon-germanium extreme environments team was very successful in doing what it set out to do," Keys said. "They advanced the state-of-the-art in analog silicon-germanium technology for space use -- a crucial step in developing a new paradigm leading to lighter weight and more capable space vehicle designs."

Keys explained that, at best, most electronics conform to military specifications, meaning they function across a temperature range of minus-55 degrees Celsius to plus-125 degrees Celsius. But electronics in deep space are typically exposed to far greater temperature ranges, as well as to damaging radiation. The Moon's surface cycles between plus-120 Celsius during the lunar day to minus-180 Celsius at night.

The silicon-germanium electronics developed by the extreme environments team has been shown to function reliably throughout that entire plus-120 to minus-180 Celsius range. It is also highly resistant or immune to various types of radiation.

The conventional approach to protecting space electronics, developed in the 1960s, involves bulky metal boxes that shield devices from radiation and temperature extremes, Keys explained. Designers must place most electronics in a protected, temperature controlled central location and then connect them via long and heavy cables to sensors or other external devices.

By eliminating the need for most shielding and special cables, silicon-germanium technology helps reduce the single biggest problem in space launches -- weight. Moreover, robust SiGe circuits can be placed wherever designers want, which helps eliminate data errors caused by impedance variations in lengthy wiring schemes.

"For instance, the Mars Exploration Rovers, which are no bigger than a golf cart, use several kilometers of cable that lead into a warm box," Keys said. "If we can move most of those electronics out to where the sensors are on the robot's extremities, that will reduce cabling, weight, complexity and energy use significantly."

NASA currently rates the new SiGe electronics at a technology readiness level of six, which means the circuits have been integrated into a subsystem and tested in a relevant environment. The next step, level seven, involves integrating the SiGe circuits into a vehicle for space flight testing. At level eight, a new technology is mature enough to be integrated into a full mission vehicle, and at level nine the technology is used by missions on a regular basis.

Successful collaboration was an important part of the silicon-germanium team's effectiveness, Keys said. He remarked that he had "never seen such a diverse team work together so well."

Professor Alan Mantooth, who led a large University of Arkansas contingent involved in modeling and circuit-design tasks, agreed. He called the project "the most successful collaboration that I've been a part of."

Mantooth termed the extreme-electronics project highly useful in the education mission of the participating universities. He noted that a total of 82 students from six universities worked on the project over five years.

Richard W. Berger, a BAE Systems senior systems architect who collaborated on the project, also praised the student contributions.

'"To be working both in analog and digital, miniaturizing, and developing extreme-temperature and radiation tolerance all at the same time -- that's not what you'd call the average student design project," Berger said.

BAE Systems' contribution to the project included providing the basic architecture for the remote electronics unit (REU) sensor interface prototype developed by the team. That architecture came from a previous electronics generation: the now cancelled Lockheed Martin X-33 Spaceplane initially designed in the 1990s.

In the original X-33 design, Berger explained, each sensor interface used an assortment of sizeable analog parts for the front end signal receiving section. That section was supported by a digital microprocessor, memory chips and an optical bus interface -- all housed in a protective five-pound box.

The extreme environments team transformed the bulky X-33 design into a miniaturized sensor interface, utilizing silicon germanium. The resulting SiGe device weighs about 200 grams and requires no temperature or radiation shielding. Large numbers of these robust, lightweight REU units could be mounted on spacecraft or data-gathering devices close to sensors, reducing size, weight, power and reliability issues.

Berger said that BAE Systems is interested in manufacturing a sensor interface device based on the extreme environment team's discoveries.

Other space-oriented companies are also pursuing the new silicon-germanium technology, Cressler said. NASA, he explained, wants the intellectual-property barriers to the technology to be low so that it can be used widely.

"The idea is to make this infrastructure available to all interested parties," he said. "That way it could be used for any electronics assembly -- an instrument, a spacecraft, an orbital platform, lunar-surface applications, Titan missions – wherever it can be helpful. In fact, the process of defining such an NASA mission-insertion roadmap is currently in progress."

Georgia Tech

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