Tuesday, December 21, 2010

BLACKER THAN BLACK

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Black is black, right? Not so, according to a team of NASA engineers now developing a blacker-than pitch material that will help scientists gather hard-to-obtain scientific measurements or observe currently unseen astronomical objects, like Earth-sized planets in orbit around other stars.

The nanotech-based material now being developed by a team of 10 technologists at the NASA Goddard Space Flight Center in Greenbelt, Md., is a thin coating of multi-walled carbon nanotubes — tiny hollow tubes made of pure carbon about 10,000 times thinner than a strand of human hair. Nanotubes have a multitude of potential uses, particularly in electronics and advanced materials due to their unique electrical properties and extraordinary strength. But in this application, NASA is interested in using the technology to help suppress errant light that has a funny way of ricocheting off instrument components and contaminating measurements.

"This is a technology that offers a lot of payback," said engineer Leroy Sparr, who is assessing its effectiveness on the Ocean Radiometer for Carbon Assessment (ORCA), a next-generation instrument that is designed to measure marine photosynthesis. "It's about 10 times better than black paint" typically used by NASA instrument designers to suppress stray light, he said.

The technology works because of its super-absorption abilities. The nanotubes themselves are packed vertically much like a shag rug. The tiny gaps between the tubes absorb 99.5 percent of the light that hits them. In other words, very few photons are reflected off the carbon-nanotube coating, which means that stray light cannot reflect off surfaces and interfere with the light that scientists actually want to measure. The human eye sees the material as black because only a small fraction of light reflects off the material.

The team began working on the technology in 2007. Unbeknownst to the group, the New York-based Rensselaer Polytechnic Institute also had initiated a similar effort and announced in 2008 that its researchers had developed the darkest carbon nanotube-based material ever made — more than three times darker than the previous record. "Our material isn't quite as dark as theirs," said John Hagopian, the principal investigator leading the development team. "But what we're developing is 10 times blacker than current NASA paints that suppress system stray light. Furthermore, it will be robust for space applications," he said.

That is an important distinction, said Carl Stahle, assistant chief of technology for Goddard's Instrument Systems and Technology Division. Not all technology can be used in space because of the harsh environmental conditions encountered there. "That's the real strength of this effort," Stahle said. "The group is finding ways to apply new technology and fly it on our instruments."

The breakthrough was the discovery of a highly adhesive underlayer material upon which to grow the carbon nanotubes, which are just a few tens of nanometers in diameter. To grow carbon nanotubes, materials scientists typically apply a catalyst layer of iron to an underlayer on the silicon substrate. They then heat the material in an oven to about 750° C (1,382° F). While heating, the material is bathed in carbon-containing feedstock gas.

Stephanie Getty, the materials scientist on Hagopian's team, varied the underlayer as well as the thickness of the catalyst materials to create carbon nanotubes that not only absorb light, but also remain fixed to the material upon which they are grown. As a result, they are more durable and less likely to scratch off. The team also has grown durable nanotube coatings on titanium, a better structural material for space use. The team now is fine-tuning production techniques to assure consistent quality and light-suppression capabilities, Hagopian said.

Should the team prove the material's suitability in space, the material would provide real benefits to instrument developers, Hagopian added.

Currently, instrument developers apply black paint to baffles and other components to reduce stray light. Because reflectance tests have shown the coating to be more effective than paint, instrument developers could grow the carbon nanotubes on the components themselves, thereby simplifying instrument designs because fewer baffles would be required. To accommodate larger components, the team now is installing a six-inch furnace to grow nanotubes on components measuring up to five inches in diameter. And under a NASA R&D award, the team also is developing a separate technique to create sheets of nanotubes that could be applied to larger, non-conforming surfaces.

In addition to simplifying instrument design, the technology would allow scientists to gather hard-to-obtain measurements because of limitations in existing light-suppression techniques or to gather information about objects in high-contrast areas, including planets in orbit around other stars, Hagopian said.

The ORCA team, which is fabricating and aligning an instrument prototype, is the first to actually apply and test the technology. The instrument is the front-runner for the proposed Aerosol/Cloud/Ecosystems (ACE) mission and requires robust light-suppression technologies because more than 90 percent of the light gathered by the instrument comes from the atmosphere. Therefore, the team is looking for a technique to suppress the light so that it doesn't contaminate the faint signal the team needs to retrieve.

"It's been an issue with all the (ocean sensors) we've flown so far," said ORCA Principal Investigator Chuck McClain.

Working with the ORCA team, Hagopian's group grew the coating on a slit, the conduit through which all light will pass on ORCA. "Having an efficient absorber is critical and the nanotubes could provide the solution," McClain said. "Right now, it looks promising," Sparr added. "If I can support them and they can continue advancing the technology so that it can be applied to other spacecraft components, it could be a very important development for NASA."

(Photo: Chris Gunn/NASA)

Goddard Space Flight Center

RICE PHYSICISTS DISCOVER ULTRASENSITIVE MICROWAVE DETECTOR

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Physicists from Rice University and Princeton University have discovered how to use one of the information technology industry's mainstay materials -- gallium arsenide semiconductors -- as an ultrasensitive microwave detector that could be suitable for next-generation computers. The discovery comes at a time when computer chip engineers are racing both to add nanophotonic devices directly to microchips and to boost processor speeds beyond 10 gigahertz (GHz).

"Tunable photon-detection technology in the microwave range is not well-developed," said Rice physicist Rui-Rui Du, the study's lead author. "Single-photon detectors based on superconductors in the 10-GHz to 100-GHz range are available, but their resonance frequency has been difficult to tune. Our findings suggest that tunable single-photon detection may be within reach with ultrapure gallium arsenide."

The study, which is available online and due to appear in print this week in Physical Review Letters, is the latest result from a long-term collaboration between Du and Princeton University physicist Loren Pfeiffer, whose group produces the world's purest samples of gallium arsenide. For the new study, Rice graduate student Yanhua Dai cooled one of Pfeiffer's ultrapure samples to below 4 degrees Kelvin -- the temperature of liquid helium. She then bombarded the sample with microwaves while applying a weak magnetic field -- approximately the same strength as that of a refrigerator magnet. Du and Dai were surprised to find that microwaves of a specific wavelength resonated strongly with the cooled sample. They also found they could use the magnet to tune this resonance to specific microwave frequencies.

Du said previous experiments have typically measured weak resonance effects from microwaves. "A signal level of 1 percent is a common measurement. In our case, the change was a thousand times that much."

While the team does not yet understand the mechanism that leads to such a sensitive reaction, they are eagerly pursuing follow-up research to try to prove they can use the effect for single-photon measurements.

A photon is the smallest possible unit of light or electromagnetic radiation. By incorporating devices that create, transmit and measure digital information via photons, rather than with electrons, makers of computer chips hope to produce computers that are both faster and more powerful.

"The clock speed of a new computer right now is about 2 GHz," Du said. "For the next generation, the industry is shooting for around 100 GHz, which is a microwave device. The phenomenon we've observed is in this region, so we hope it may be useful for them."

Rice University

FACING A DIFFICULT CONDITION

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Imagine you’re a school-aged child and this is your reality: You go to school and nobody looks familiar; your classmates are essentially a sea of faces, none of which is recognizable from the day before. A girl walks over to chat and she seems to know a lot about you, but you can’t place the face—and she seems equally perplexed, if not a bit agitated.

Then, at a family gathering, you find out that the strange faces in your house are actually cousins, although you wouldn’t know them from your classmates, whom you wouldn’t know from anyone else on the street.

The condition is known as prosopagnosia, or “face blindness,” and according to U professor Al Yonas, it may affect 1 to 2 percent of the population. The problem is, very few people are aware of it, which makes proper diagnosis problematic. Yonas is hoping to change that reality.

Prosopagnosia is essentially the inability to recognize a face that you’ve seen before and should be able to recall. You can read emotions in a face, but identifying the person is next to impossible without cues like a unique hairstyle or distinctive jewelry. It’s much different, Yonas notes, from being unable to remember somebody’s name, which afflicts all of us from time to time.

There are two types of face blindness—one the result of some sort of brain injury and the other developmental or congenital. Until recently, most of the research has focused on face blindness in adults. Notables with face blindness include primatologist Jane Goodall, artist Chuck Close, and neuroscientist and author Oliver Sacks, who wrote the book The Man Who Mistook His Wife for a Hat, which deals in part with face blindness.

Since 2008, Yonas’s lab in the Institute of Child Development has focused on identifying the condition in children (see video). Yonas and his research assistants have developed a number of tests for face blindness and have collected data from about 200 control subjects—children of various ages who don’t have the condition.

The goal is to make more people aware that face blindness exists, as Yonas suspects many children are misdiagnosed with other cognitive disabilities.

“A lot of people don’t know they have this condition,” he says. “They go through their life with the disability and they don’t know anything is wrong.”

That can lead to uncomfortable and unrewarding social interactions, and it’s not uncommon for sufferers to become withdrawn.

“Children with developmental prosopagnosia really are facing a gigantic obstacle,” says Sherryse Corrow, a doctoral student who works in Yonas’s lab. “You don’t know your father from a different man, your mother from a different woman. So everyone is essentially a stranger.

“For a child this poses a substantial social problem, but also a substantial safety issue. You don’t know which members of your community are safe to you and which ones aren’t.” She adds that in school settings students become stressed “because how do you make friends if everyone is a stranger and you can't distinguish your friends from other classmates?”

Down the road, Yonas hopes that early diagnosis can lead to more effective treatments for the condition. At the very least, it could lead to children recognizing there’s a reason for their difficulties, as happened when people learned more about dyslexia.
“We’re hoping parents will be aware of the problem and contact us if they think their child may have this disability,” he says.

(Photo: Patrick O'Leary and Megan Drabandt)

The University of Minnesota

BLUE WHALE-SIZED MOUTHFULS MAKE FORAGING SUPER EFFICIENT

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Diving blue whales can dive for anything up to 15 minutes. However, Bob Shadwick from the University of British Columbia, Canada, explains that blue whales may be able to dive for longer, because of the colossal oxygen supplies they could carry in their blood and muscles, so why don't they?

'The theory was that what they are doing under water must use a lot of energy,' says Shadwick. Explaining that the whales feed by lunging repeatedly through deep shoals of krill, engulfing their own body weight in water before filtering out the nutritious crustaceans, Shadwick says, 'It was thought that the huge drag effect when they feed and reaccelerate this gigantic body must be the cost'. However, measuring the energetics of blue whale lunges at depth seemed almost impossible until Shadwick and his student Jeremy Goldbogen got chatting to John Hildebrand, John Calambokidis, Erin Oleson and Greg Schorr who were skilfully attaching hydrophones, pressure sensors and two-axis accelerometers to the elusive animals. Shadwick and Goldbogen realised that they could use Calambokidis's measurements to calculate the energetic cost of blue whale lunges. They publish their discovery that blue whales swallow almost 2,000,000kJ (almost 480,000kcalories) in a mouthful of krill, and take in 90 times as much energy as they burn during a single dive in The Journal of Experimental Biology at http://jeb.biologists.org.

Analysing the behaviour of each whale, Goldbogen saw that dives lasted between 3.1 and 15.2 minutes and a whale could lunge as many as 6 times during a single dive. Having found previously that he could correlate the acoustic noise of the water swishing past the hydrophone with the speed at which a whale was moving, Goldbogen calculated the blue whales' speeds as they lunged repeatedly during each dive. Next the team had to calculate the forces exerted on the whales as they accelerated their colossal mouthful of water. Noticing that the whales' mouths inflated almost like a parachute as they engulfed the krill, Goldbogen tracked down parachute aerodynamics expert Jean Potvin to help them build a mathematical model to calculate the forces acting on the whales as they lunged. With Potvin on the team, they were able to calculate that the whales used between 3226 kJ of energy during each lunge. But how did this compare with the amount of energy that the whales could extract from each gigantic mouthful of krill?

Goldbogen estimated the volume of the whales' mouths by searching the whaling literature for morphological data and teamed up with paleontologist Nick Pyenson to measure the size of blue whale jaw bones in several natural history museums. He also obtained krill density values from the literature – which are probably on the low side. Then he calculated the volume of water and amount of krill that a whale could engulf and found that the whales could consume anything from 34,776kJ up to an unprecedented 1,912,680kJ from a single mouthful of krill, providing as much as 240 times as much energy as the animals used in a single lunge. And when the team calculated the amount of energy that a whale could take on board during a dive, they found that each foraging dive could provide 90 times as much energy as they used.

Shadwick admits that he was initially surprised that the whales' foraging dives were so efficient. 'We went over the numbers a lot,' he remembers, but then he and Goldbogen realised that the whales' immense efficiency makes sense. 'The key to this is the size factor because they can engulf such a large volume with so much food in it that it really pays off,' says Shadwick.

The Company of Biologists Ltd

CARBON-RICH PLANET: A GIRL'S BEST FRIEND?

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A peculiar gas-giant planet orbiting a sun-like star 1200 light-years away is the first carbon-rich world ever observed.

The implications are big for planetary chemistry, because without much oxygen, common rocks throughout the planet would be made of pure carbon, in forms such as diamonds or graphite.

"On most planets, oxygen is abundant. It makes rocks such as quartz and gases such as carbon dioxide," said University of Central Florida professor Joseph Harrington, one of the study's lead researchers. "With more carbon than oxygen, you would get rocks of pure carbon, such as diamond or graphite, and lots of methane gas."

"This planet tells us that there are many other strange worlds out there, beyond even the imaginations of the people doing the science," added Nikku Madhusudhan of the Massachusetts Institute of Technology. He is the lead author of the study, which appears in the Dec. 9 issue of the journal Nature.

Harrington and his team at UCF led the Spitzer observations and data analysis. The UCF team used NASA's Spitzer Space Telescope to measure the light of the planet, WASP-12b, as it passed behind its star, a so-called secondary eclipse.

Madhusudhan performed the chemical analysis of data from NASA's Spitzer Space Telescope. By using UCF's data and other published results at different infrared wavelengths, he compared the infrared behavior of common gases to determine the composition of the planet's atmosphere. Researchers were surprised to find methane, a trace gas on Earth, because it typically does not exist in the searing-hot temperatures found on this planet.

Carbon is a key building block of life, but could life exist if there is too much carbon? NASA's recent announcement of a bacterium that thrives in a poisonous arsenic environment is yet another example of life's incredible adaptability.

"I wouldn't discount any cool planet as a possible haven for life, no matter what its chemistry," Harrington said.

WASP-12b isn't cool enough for life. It is so close to its star that its "year" is just 26 hours, and its daytime temperatures of about 4700 degrees Fahrenheit make it the second-hottest planet ever measured. It is also the second-largest known planet, as it is more than 80 percent wider than Jupiter.

The planet was discovered last year by a UK consortium, the Wide Angle Search for Planets. Some of the Spitzer data used by the UCF team were contributed by WASP team member Peter Wheatley of the University of Warwick.

(Photo: NASA/JPL-Caltech)

University of Central Florida

REPRODUCTIVE SCIENTISTS CREATE MICE FROM 2 FATHERS

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Using stem cell technology, reproductive scientists in Texas, led by Dr. Richard R. Berhringer at the M.D. Anderson Cancer Center, have produced male and female mice from two fathers.

The study was posted (Wednesday, December 8) at the online site of the journal Biology of Reproduction.

The achievement of two-father offspring in a species of mammal could be a step toward preserving endangered species, improving livestock breeds, and advancing human assisted reproductive technology (ART). It also opens the provocative possibility of same-sex couples having their own genetic children, the researchers note.

In the work reported today, the Behringer team manipulated fibroblasts from a male (XY) mouse fetus to produce an induced pluripotent stem (iPS) cell line. About one percent of iPS cell colonies grown from this XY cell line spontaneously lost the Y chromosome, resulting in XO cells. The XO iPS cells were injected into blastocysts from donor female mice. The treated blastocysts were transplanted into surrogate mothers, which gave birth to female XO/XX chimeras having one X chromosome from the original male mouse fibroblast.

The female chimeras, carrying oocytes derived from the XO cells, were mated with normal male mice. Some of the offspring were male and female mice that had genetic contributions from two fathers.

According to the authors, "Our study exploits iPS cell technologies to combine the alleles from two males to generate male and female progeny, i.e. a new form of mammalian reproduction."

The technique described in this study could be applied to agriculturally important animal species to combine desirable genetic traits from two males without having to outcross to females with diverse traits.

"It is also possible that one male could produce both oocytes and sperm for self-fertilization to generate male and female progeny," the scientists point out. Such a technique could be valuable for preserving species when no females remain.

In the future, it may also be possible to generate human oocytes from male iPS cells in vitro. Used in conjunction with in vitro fertilization, this would eliminate the need for female XO/XX chimeras, although a surrogate mother would still be needed to carry the two-father pregnancy to term.

Using a variation of the iPS technique, the researchers say "it may also be possible to generate sperm from a female donor and produce viable male and female progeny with two mothers."

The authors also caution that the "generation of human iPS cells still requires significant refinements prior to their use for therapeutic purposes."

Society for the Study of Reproduction

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