Tuesday, October 20, 2009

ENERGY SAVINGS IN BLACK AND WHITE

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Anyone who has ever stepped barefoot onto blacktop pavement on a hot sunny day knows the phenomenon very well: Black surfaces absorb the sun's heat very efficiently, producing a toe-scorching surface. In the wintertime, that can be a good thing: A dark roof heats up in the sun and helps reduce your heating bill. But in summertime, it's definitely a bad thing: Your house gets even hotter, and your air conditioning has to work harder. In most places, the summertime penalty is greater than the wintertime gain, it turns out, so that's why many people, including U.S. Secretary of Energy Steven Chu, strongly advocate switching to white roofs.

It's no small matter. In fact, Chu says that turning all the world's roofs white would eliminate as much greenhouse gas emissions in 20 years as the whole world produces in a year. But some critics point out that in northern cities, the gain in summer could be outweighed by the loss in winter. The ideal situation, then, would be to get the advantage of white roofs when it's hot and black roofs when it's cold.

Now, there may be a way to have both. A team of recent MIT graduates has developed roof tiles that change color based on the temperature. The tiles become white when it's hot, allowing them to reflect away most of the sun's heat. When it's cold they turn black and absorb heat just when it's needed.

The team's lab measurements show that in their white state, the tiles reflect about 80 percent of the sunlight falling on them, while when black they reflect only about 30 percent. That means in their white state, they could save as much as 20 percent of present cooling costs, according to recent studies. Savings from the black state in winter have yet to be quantified.

The team, which the students call Thermeleon (rhymes with chameleon, because of its color-changing property), was one of the competitors in this year's Making and Designing Materials Engineering Contest (MADMEC), a competition for teams of MIT students (or 2009 graduates). Now in its third year, the contest this year was specifically devoted to projects aimed at improving energy efficiency through innovative uses of materials. The final showdown was held Wednesday night, and the Thermeleon team took first place, earning $5,000 in the process.

Nick Orf PhD ’09, a member of the Thermeleon team, explains that he and his teammates originally tried to develop a color-shifting roof tile using a system of mixed fluids, one dark and one light, whose density would change with temperature: the dark substance would float to the top when it was cold, and white would float when it was hot. But the system proved too complicated, and instead they hit on a simpler, less expensive method.

Now, they use a common commercial polymer (in one version, one that is commonly used in hair gels) in a water solution. That solution is encapsulated — between layers of glass and plastic in their original prototype, and between flexible plastic layers in their latest version — with a dark layer at the back.

When the temperature is below a certain level (which they can choose by varying the exact formulation), the polymer stays dissolved, and the black backing shows through, absorbing the sun's heat. But when the temperature climbs, the polymer condenses to form tiny droplets, whose small sizes scatter light and thus produce a white surface, reflecting the sun's heat.

They are now working on an even simpler version in which the polymer solution would be micro-encapsulated and the tiny capsules carried in a clear paint material that could be brushed or sprayed onto any existing surface. The tiny capsules would still have the color-changing property, but the surface could easily be applied over an existing black roof, much more inexpensively than installing new roofing material.

Although they have not yet made specific plans for forming a business to commercialize their concept, Orf says the team members are determined to pursue the project and develop it into a marketable product.

Because the materials are common and inexpensive, team members think the tiles could be manufactured at a price comparable to that of conventional roofing materials — although that won't be known for sure until they determine the exact materials and construction of their final version.

The biggest remaining question is over durability, and answering it will require spending some time to do accelerated testing by running the material through repeated hot-cold cycles.

Hashem Akbari, leader of the Heat Island Group at Lawrence Berkeley National Laboratory in California, is a long-time advocate of white roofs as an energy-saving measure. He says that some other groups, including a team at the University of Athens, have done research on the use of color-changing materials for roofs, but that in those tests, "the cost and durability has been a serious issue."

The Thermeleon team hopes to address those concerns. "It's got to stand up to very harsh conditions," Orf says. "Those sorts of tests would have to be done before we'll know if we have a viable product."

(Photo: Patrick Gillooly)

Massachusetts Institute of Technology

SECURING THE WEB

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More and more, malicious hackers are exploiting web site security holes to attack their victims' computers. Programmers try to identify those holes in advance and plug them with code that performs security checks; but if they find a hundred holes and miss one, their programs are still insecure. At next week's ACM Symposium on Operating Systems Principles, however, MIT researchers will present a new system called Resin, which automatically calls up security checks whenever they're required, even in unforeseen circumstances.

Typically, web programmers will associate security checks with particular application functions. If you belonged to a social-networking site, for instance, you might be able to e-mail your friends, or post remarks on their pages, or comment on their own posts, or tag their pictures, and so on. Each of these operations executes its own chunk of code, and the developer will usually attach a security check to each chunk, to ensure that the user is authorized to invoke it. (These types of security checks operate in the background: they don't require you, for instance, to reenter your user name and password.) Many web applications also "sanitize" data posted by their subscribers: if a friend posts something to your social-network page, the application probably won't show you the post without inspecting it for malicious code.

"We've looked at a lot of these web applications, and there's literally hundreds of places where these checks happen," says Nickolai Zeldovich, an assistant professor in MIT's Computer Science and Artificial Intelligence Lab. Indeed, Zeldovich and his colleagues identified one popular web application that sanitized data in more than 1,400 places (but still had about 60 security holes).

They also, however, identified a feature that web application security checks usually had in common: "Namely," Zeldovich says, "it's that the same data is being handled in all these hundreds of places."

So Zeldovich, grad students Alexander Yip and Xi Wang, and Professor Frans Kaashoek developed a system that associates security checks with particular chunks of data rather than with particular chunks of code. Any attempt to access the data, by any imaginable route, invokes the check.

The researchers modified 12 existing applications written in the popular web programming languages Python and PHP so that they used the Resin system. In experiments, the modified applications repelled attacks that exploited known security holes. But the researchers also developed their own attacks, which Resin thwarted as well.

For programmers, the new system should be easy to adopt. They're already writing code for security checks and sanitization anyway; now, they'd have to write it only once, instead of pasting it into their programs in hundreds of different places.

But the MIT system relies on additional software that tracks data as they flow through an application, to make sure that security rules remain associated with the information wherever it's being stored and however it's being used. And the data tracker presents the biggest obstacle to commercial adoption.

Web applications need to run on any type of computer, regardless of the operating system or web browser being used, so web languages like Python and PHP require an extra layer of software called a "runtime" to translate code into the language spoken by a given machine. Generally, the organizations that develop new programming languages also maintain the runtimes, which undergo sequential releases, just like any commercial program. The MIT system's data tracker would have to be incorporated into several different languages' runtimes, which could be a hard sell.

"At least in PHP, the focus tends to be on performance," says Eddie Kohler, an assistant professor of computer science at UCLA. Resin, Kohler says, "shows that you can do it without too much of a performance loss," but "it's not zero; it's not a performance gain." Kohler points out, however, that Resin could gain traction with the runtime gatekeepers if it first proves itself in some particular, real-world instances. "A place like, maybe Facebook, say, that runs other people's code on their servers already has an environment where they're much more worried about people stealing data out of their servers than they are necessarily about getting the last two percent of performance," Kohler says. "I expect that as it gets deployed, it would get deployed by individual companies first."

(Photo: Christine Daniloff)


PRINCETON PALEOMAGNETISTS PUT CONTROVERSY TO REST

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Princeton University scientists have shown that, in ancient times, the Earth's magnetic field was structured like the two-pole model of today, suggesting that the methods geoscientists use to reconstruct the geography of early land masses on the globe are accurate. The findings may lead to a better understanding of historical continental movement, which relates to changes in climate.

By taking a closer look at the 1.1 billion-year-old volcanic rocks on the north shore of Lake Superior, the researchers have found that Earth's ancient magnetic field was a geocentric axial dipole -- essentially a large bar magnet centered in the core and aligned with the Earth's spin axis.

Some earlier studies of these rocks had led other teams to conclude that the magnetic field of the ancient Earth had a far more complex structure -- some proposing the influence of four or even eight poles -- implying that present models of the supercontinents that relied on paleomagnetic data and an axial dipole assumption were wrong.

The report, which will appear in the October issue of Nature Geoscience, says that previous efforts to interpret the ancient geomagnetic field in rocks from North America were confused by the rapid migration of the continent toward the equator in the distant past.

The researchers "neatly lay to rest the long-standing controversy over the nature of Earth's magnetic field 1.1 billion years ago," writes geoscientist Joseph Meert of the University of Florida in an essay that accompanies the report.

"In this paper, we show that Earth's magnetic field has been more stable in the past than originally believed," said Adam Maloof, an assistant professor of geosciences at Princeton and one of the paper's authors.

The Earth's magnetic field wraps around the globe, shielding life from harmful cosmic rays. It is emanated by the Earth's iron core and is shaped by a multitude of factors, including the spinning of the Earth and circulatory motion influenced by the Earth's rotation and temperature differences between the inner core's outer layers and the lower mantle.

The researchers obtained magnetic measurements from a thick stack of lava flows in the Lake Superior region. The lavas erupted when geologic forces attempted to tear apart central North America forming the Keweenawan Rift. The researchers used the tiny magnetic minerals within the volcanic rocks to record the orientation of the geomagnetic field at the time the rocks erupted onto the Earth's surface. By knowing how those grains pointed to the magnetic field of that time, the scientists could deduce the latitude where they were located when the lava flows erupted and cooled. The grains pointed to where "paleo-north" was for each rock.

Studying layers of the basaltic lava flows, they used the information to track how the Earth's magnetic poles have "flipped" over the eons, with the North Magnetic Pole becoming the South Magnetic Pole and vice versa. The team studied three of these reversals that occurred over a few million years.

The scientists plan to use the data to better understand how continents moved in the distant past, massing to form supercontinents. "We needed to be able to have a working model of how the geomagnetic field behaved in the past if we are going to talk about where plates have moved, how fast they've moved and how ancient supercontinents were configured," said Nicholas Swanson-Hysell, a graduate student at Princeton and the first author on the paper.

Knowing the proper location of continents is key to understanding the climate of any era, Maloof said, because the shape and location of continents affect ocean currents, global average temperatures and wind patterns. And by understanding in detail what Earth's climate was like in ancient times, he noted, scientists can better comprehend the climate of today and make more accurate projections for the future.

According to scientific reconstructions, a supercontinent known as Rodinia existed between 1 billion and 800 million years ago. The extreme cooling of the global climate about 700 million years ago and the rapid evolution of primitive life during subsequent periods are often thought to have been triggered by the breaking up of Rodinia.

Rodinia predated a more recently created supercontinent called Pangaea, which came together about 300 million years ago. Scientists have pieced Rodinia together by comparing rocks with similar geological features that are now widely dispersed.

Knowing that they have confirmed the structure of the Earth's magnetic field at that time gives Maloof and Swanson-Hysell the confidence to learn more about the supercontinent and that epoch.

"For the past 30 years, scientists have feared that the geometry of Earth's field was complex and varied," Maloof said. "Such a complex field made it very hard for people to reconstruct the ancient geography of the planet because they could not rely on a predictable field. We show that these fears were unfounded -- at least for 1.1 billion years ago -- and that the evidence for a complex ancient field was an artifact of the way rocks had been sampled."

(Photo: Catherine Rose)

Princeton University

INSIDE THE FIRST BIRD, SURPRISING SIGNS OF A DINOSAUR

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The raptor-like Archaeopteryx has long been viewed as the archetypal first bird, but new research reveals that it was actually a lot less "bird-like" than scientists had believed.

In fact, the landmark study led by paleobiologist Gregory M. Erickson of The Florida State University has upended the iconic first-known-bird image of Archaeopteryx (from the Greek for "ancient wing"), which lived 150 million years ago during the Late Jurassic period in what is now Germany. Instead, the animal has been recast as more of a feathered dinosaur -- bird on the outside, dinosaur on the inside.

That's because new, microscopic images of the ancient cells and blood vessels inside the bones of the winged, feathered, claw-handed creature show unexpectedly slow growth and maturation that took years, similar to that found in dinosaurs, from which birds evolved. In contrast, living birds grow rapidly and mature in a matter of weeks.

Also groundbreaking is the finding that the rapid bone growth common to all living birds but surprisingly absent from the Archaeopteryx was not necessary for avian dinosaur flight.

The study is published in the Oct. 9, 2009, issue of the journal PLoS One. In addition to Erickson, an associate professor in Florida State's Department of Biological Science and a research associate at the American Museum of Natural History, co-authors include Florida State University biologist Brian D. Inouye and other U.S. scientists, as well as researchers from Germany and China.

"Living birds mature very quickly," Erickson said. "That's why we rarely see baby birds among flocks of invariably identical-size pigeons. Slow-growing animals such as Archaeopteryx would look foreign to contemporary bird-watchers."

Erickson said evidence already confirms that birds are, in fact, dinosaurs. "But just how dinosaur-like -- or even bird-like -- was the first bird?" he asked. "Almost nothing had been known of Archaeopteryx biology. There has been debate as to how well it flew, if at all. Some have suggested that early bird physiology may have been very different from living birds, but no one had tested fossils that were close to the base of bird ancestry."

Fossilized remains of Archaeopteryx were found in Germany in 1860, one year after Charles Darwin's "Origin of Species" was published. With its combination of bird-like features, including feathers and a wishbone, and reptilian ones -- teeth, three-fingered hands, a long bony tail -- the skeleton made evolutionary theory more credible. The 1860s evolutionist Thomas Henry Huxley saw the Archaeopteryx as a perfect transition between birds and reptiles. Erickson calls it "the poster child for evolution."

"For our study, which required tremendous collaboration, we set out to determine how Archaeopteryx grew and compare its growth to living birds, closely related non-avian dinosaurs, and other early birds that came after it," Erickson said. "I went to Munich with my colleague Mark Norell from the American Museum of Natural History, and we met with Oliver Rauhut, curator of the Bavarian State Collection for Palaeontology and Geology, which houses a small juvenile Archaeopteryx that is one of 10 specimens discovered to date. From that specimen, we extracted tiny bone chips and then examined them microscopically."

Surprisingly, the bones of the juvenile Archaeopteryx were not the highly vascularized, fast-growing type, as in other avian dinosaurs. Instead, Erickson found lizard-like, dense, nearly avascular bone.

"It led us to ask, 'Did Archaeopteryx grow in a unique way?'" he said.

To explain the strange bone type, the researchers also examined different-size species of dinosaurs that were close relatives of Archaeopteryx, including Deinonychosaurs, the raptors of "Jurassic Park" fame. They then looked to colleagues in China for specimens of two of the earliest birds: Jeholornis prima, a long-tailed creature, and the short-tailed Sapeornis chaochengensi, which had three fingers and teeth.

"In the smallest dinosaur specimens, and in an early bird, we found the same bone type as in the juvenile Archaopteryx specimen," Erickson said.

Next, the research team plugged bone formation rates into the sizes of the Archaeopteryx femora (thigh bones) to predict its rate of growth.

"We learned that the adult would have been raven-sized and taken about 970 days to mature," Erickson said. "Some same-size birds today can do likewise in eight or nine weeks. In contrast, maximal growth rates for Archaeopteryx resemble dinosaur rates, which are three times slower than living birds and four times faster than living reptiles.

"From these findings, we see that the physiological and metabolic transition into true birds occurred millions of years after Archaeopteryx," he said. "But, perhaps equally important, we've shown that avians were able to fly even with dinosaur physiology."

Inouye added, "Our data on dinosaur growth rates and survivorship are bringing modern physiology and population biology to a field that has historically focused more on finding and naming fossil species."

(Photo: Mick Ellison/© 2009 Mick Ellison & AMNH)

Florida State University

LAST TIME CARBON DIOXIDE LEVELS WERE THIS HIGH: 15 MILLION YEARS AGO, SCIENTISTS REPORT

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You would have to go back at least 15 million years to find carbon dioxide levels on Earth as high as they are today, a UCLA scientist and colleagues report Oct. 8 in the online edition of the journal Science.

"The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland," said the paper's lead author, Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.

"Carbon dioxide is a potent greenhouse gas, and geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout Earth's history," she said.

By analyzing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of Earth's atmosphere going back as far as 800,000 years, and they have developed a good understanding of how carbon dioxide levels have varied in the atmosphere since that time. But there has been little agreement before this study on how to reconstruct carbon dioxide levels prior to 800,000 years ago.

Tripati, before joining UCLA's faculty, was part of a research team at England's University of Cambridge that developed a new technique to assess carbon dioxide levels in the much more distant past — by studying the ratio of the chemical element boron to calcium in the shells of ancient single-celled marine algae. Tripati has now used this method to determine the amount of carbon dioxide in Earth's atmosphere as far back as 20 million years ago.

"We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years — the record of atmospheric C02 based on measurements of carbon dioxide in gas bubbles in ice," Tripati said. "This suggests that the technique we are using is valid.

"We then applied this technique to study the history of carbon dioxide from 800,000 years ago to 20 million years ago," she said. "We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years.

"A slightly shocking finding," Tripati said, "is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different."

Levels of carbon dioxide have varied only between 180 and 300 parts per million over the last 800,000 years — until recent decades, said Tripati, who is also a member of UCLA's Institute of Geophysics and Planetary Physics. It has been known that modern-day levels of carbon dioxide are unprecedented over the last 800,000 years, but the finding that modern levels have not been reached in the last 15 million years is new.

Prior to the Industrial Revolution of the late 19th and early 20th centuries, the carbon dioxide level was about 280 parts per million, Tripati said. That figure had changed very little over the previous 1,000 years. But since the Industrial Revolution, the carbon dioxide level has been rising and is likely to soar unless action is taken to reverse the trend, Tripati said.

"During the Middle Miocene (the time period approximately 14 to 20 million years ago), carbon dioxide levels were sustained at about 400 parts per million, which is about where we are today," Tripati said. "Globally, temperatures were 5 to 10 degrees Fahrenheit warmer, a huge amount."

Tripati's new chemical technique has an average uncertainty rate of only 14 parts per million.

"We can now have confidence in making statements about how carbon dioxide has varied throughout history," Tripati said.

In the last 20 million years, key features of the climate record include the sudden appearance of ice on Antarctica about 14 million years ago and a rise in sea level of approximately 75 to 120 feet.

"We have shown that this dramatic rise in sea level is associated with an increase in carbon dioxide levels of about 100 parts per million, a huge change," Tripati said. "This record is the first evidence that carbon dioxide may be linked with environmental changes, such as changes in the terrestrial ecosystem, distribution of ice, sea level and monsoon intensity."

Today, the Arctic Ocean is covered with frozen ice all year long, an ice cap that has been there for about 14 million years.

"Prior to that, there was no permanent sea ice cap in the Arctic," Tripati said.

Some projections show carbon dioxide levels rising as high as 600 or even 900 parts per million in the next century if no action is taken to reduce carbon dioxide, Tripati said. Such levels may have been reached on Earth 50 million years ago or earlier, said Tripati, who is working to push her data back much farther than 20 million years and to study the last 20 million years in detail.

More than 50 million years ago, there were no ice sheets on Earth, and there were expanded deserts in the subtropics, Tripati noted. The planet was radically different.

Co-authors on the Science paper are Christopher Roberts, a Ph.D. student in the department of Earth sciences at the University of Cambridge, and Robert Eagle, a postdoctoral scholar in the division of geological and planetary sciences at the California Institute of Technology.

The research was funded by UCLA's Division of Physical Sciences and the United Kingdom's National Environmental Research Council.

Tripati's research focuses on the development and application of chemical tools to study climate change throughout history. She studies the evolution of climate and seawater chemistry through time.

"I'm interested in understanding how the carbon cycle and climate have been coupled, and why they have been coupled, over a range of time-scales, from hundreds of years to tens of millions of years," Tripati said.

(Photo: Aradhna Tripati)

EARLY HOMINID FIRST WALKED ON TWO LEGS IN THE WOODS

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Among the many surprises associated with the discovery of the oldest known, nearly complete skeleton of a hominid is the finding that this species took its first steps toward bipedalism not on the open, grassy savanna, as generations of scientists – going back to Charles Darwin – hypothesized, but in a wooded landscape.

“This species was not a savanna species like Darwin proposed,” said University of Illinois anthropology professor Stanley Ambrose, a co-author of two of 11 studies published this week in Science on the hominid, Ardipithecus ramidus. This creature, believed to be an early ancestor of the human lineage, lived in Ethiopia some 4.4 million years ago.

One of the crucial pieces of evidence to show that Darwin didn’t get it right, Ambrose said, was the analysis of carbon isotopes in the soil and in the teeth of Ardipithecus and other animals that lived at roughly the same time and in the same location.

The mass of carbon atoms in the atmosphere varies, and during photosynthesis, trees and tropical grasses absorb different proportions of carbon-12, the most common carbon isotope, and carbon-13, which is rare. These isotopes pass into the soil and into the bodies of animals that eat the plants, making it possible to accurately reconstruct the proportions of grass to trees on the landscape and in the diets of the animals that lived there.

The fossil-bearing layer, in the Afar Rift region of northeastern Ethiopia, spans a broad arc about 9 kilometers long. Sandwiched between two layers of volcanic ash that both date to about the same age, it provides a well-focused snapshot of an ancient African ecosystem.

The carbon isotope ratios of the soils indicated that in the time of Ardipithecus the landscape varied from woodland in the western part of the study zone to wooded grassland in the east. None of the Ardipithecus specimens were found in the grassy eastern part of the arc.

“Fossils of many species are common all the way across the landscape,” Ambrose said. “But this species is missing in action from the east side of the distribution.”

Isotopic analysis of teeth found on the site gave a more complete picture of the habitat of the animals that lived and died there, Ambrose said.

“The distribution of plant carbon isotope ratios conveniently separates out grasslands from forests,” he said. “And it also separates out grazing animals, like zebras, from browsing animals that eat the leaves off of trees, like giraffes.”

The distribution of the fossil browsers and grazers echoed that of the habitat, he said.

“On the west we find lots of Ardipithecus fossils and they’re associated with a lot of woodland and forest animals,” he said. “And then there’s a break; Ardipithecus and most of the monkeys that live in trees disappear, and grass-eating animals become more abundant.”

The carbon isotope ratios of the Ardipithecus teeth also tell the story of a woodland creature, he said.

“The diet of the Ardipithecus is much more on the woodland and forest side,” he said. “It’s got a little bit more of the grassland ecosystem carbon in its diet than that of a chimpanzee but much less than its fully bipedal savanna-dwelling descendents, the australopithecines.”

This evidence, along with the anatomical studies indicating that Ardipithecus could walk upright but also grasped tree limbs with its feet, suggests that this early hominid took its first steps on two legs in the forest long before it ventured very far into the open grassland, Ambrose said.

“Multiple lines of evidence now suggest that they were beginning to leave the trees before they left the forest,” he said.

(Photo: L. Brian Stauffer)

University of Illinois

NEW ALUMINUM-WATER ROCKET PROPELLANT PROMISING FOR FUTURE SPACE MISSIONS

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Researchers are developing a new type of rocket propellant made of a frozen mixture of water and "nanoscale aluminum" powder that is more environmentally friendly than conventional propellants and could be manufactured on the moon, Mars and other water-bearing bodies.

The aluminum-ice, or ALICE, propellant might be used to launch rockets into orbit and for long-distance space missions and also to generate hydrogen for fuel cells, said Steven Son, an associate professor of mechanical engineering at Purdue University.

Purdue is working with NASA, the Air Force Office of Scientific Research and Pennsylvania State University to develop ALICE, which was used earlier this year to launch a 9-foot-tall rocket. The vehicle reached an altitude of 1,300 feet over Purdue's Scholer farms, about 10 miles from campus.

"It's a proof of concept," Son said. "It could be improved and turned into a practical propellant. Theoretically, it also could be manufactured in distant places like the moon or Mars instead of being transported at high cost."

Findings from spacecraft indicate the presence of water on Mars and the moon, and water also may exist on asteroids, other moons and bodies in space, said Son, who also has a courtesy appointment as an associate professor of aeronautics and astronautics.
The tiny size of the aluminum particles, which have a diameter of about 80 nanometers, or billionths of a meter, is key to the propellant's performance. The nanoparticles combust more rapidly than larger particles and enable better control over the reaction and the rocket's thrust, said Timothée Pourpoint, a research assistant professor in the School of Aeronautics and Astronautics.

"It is considered a green propellant, producing essentially hydrogen gas and aluminum oxide," Pourpoint said. "In contrast, each space shuttle flight consumes about 773 tons of the oxidizer ammonium perchlorate in the solid booster rockets. About 230 tons of hydrochloric acid immediately appears in the exhaust from such flights."

ALICE provides thrust through a chemical reaction between water and aluminum. As the aluminum ignites, water molecules provide oxygen and hydrogen to fuel the combustion until all of the powder is burned.

"ALICE might one day replace some liquid or solid propellants, and, when perfected, might have a higher performance than conventional propellants," Pourpoint said. "It's also extremely safe while frozen because it is difficult to accidentally ignite."

The research is helping to train a new generation of engineers to work in academia, industry, for NASA and the military, Son said. More than a dozen undergraduate and graduate students have worked on the project.

"It's unusual for students to get this kind of advanced and thorough training - to go from a basic-science concept all the way to a flying vehicle that is ground tested and launched," he said. "This is the whole spectrum."

Research findings were detailed in technical papers presented this summer during a conference of the American Institute of Aeronautics and Astronautics. The papers will be published next year in the conference proceedings.

Leading work at Penn State are mechanical engineering professor Richard Yetter and assistant professor Grant Risha.

The Purdue portion of the research is based at the university's Maurice J. Zucrow Laboratories, where researchers created a special test cell and control room to test the rocket. The rocket's launching site was located on a facility maintained by Purdue's School of Veterinary Medicine.

"Having a launching site near campus greatly facilitated this project," Pourpoint said.

Other researchers previously have used aluminum particles in propellants, but those propellants usually also contained larger, micron-size particles, whereas the new fuel contained pure nanoparticles.

Manufacturers over the past decade have learned how to make higher-quality nano-aluminum particles than was possible in the past. The fuel needs to be frozen for two reasons: It must be solid to remain intact while subjected to the forces of the launch and also to ensure that it does not slowly react before it is used.

Initially a paste, the fuel is packed into a cylindrical mold with a metal rod running through the center. After it's frozen, the rod is removed, leaving a cavity running the length of the solid fuel cylinder. A small rocket engine above the fuel is ignited, sending hot gasses into the center hole, causing the ALICE fuel to ignite uniformly.

"This is essentially the same basic procedure used in the space shuttle's two solid-fuel rocket boosters," Son said. "An electric match ignites a small motor, which then ignites a bigger motor."

Future work will focus on perfecting the fuel and also may explore the possibility of creating a gelled fuel using the nanoparticles. Such a gel would behave like a liquid fuel, making it possible to vary the rate at which the fuel is pumped into the combustion chamber to throttle the motor up and down and increase the vehicle's distance.

A gelled fuel also could be mixed with materials containing larger amounts of hydrogen and then used to run hydrogen fuel cells in addition to rocket motors, Son said.

(Photo: Purdue University/Andrew Hancock)

Purdue University

TURNING ALGAE INTO ENERGY

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As part of a project to create alternative sources of energy, researchers at Sandia National Laboratories are cultivating green algae that holds promise as a new supply of biofuel.

“People have been growing algae for centuries for food supplements for use by man and animals,” said Cecelia Williams, project lead. “It now has the potential to supply our energy needs too.”

Beginning in the 1950s, the Department of Energy recognized algae as a potential feedstock for energy and biofuels and funded the Aquatic Species Program between 1978 and 1996 with $25 million to investigate the production of biofuel from microalgae. DOE terminated the program in the mid-1990s due to low petroleum prices and other priorities. It has only been in the last few years that DOE has once again become interested in algae as a potential source of fuel.

Recently Williams and other Sandia researchers have grown green algae in a 12-by-30-foot greenhouse using a simulated dairy effluent, the nutrient-rich liquid remaining after bacterial digestion of dairy manure. The solids from the digestion of dairy manure can potentially be used to develop fertilizer and feed and the liquid serves as a nutrient source for algae. The algae are typically cultured for several days, followed by harvesting and dewatering, after which the algal oil is extracted. The algae produce lipids, the most useful being neutral oil made up largely of triacyglycerides (TAG) that can be converted to biofuels.

Williams said that growing algae for biofuels eliminates many problems associated with traditional biofuels.

“The current generation of biofuels [starch- and sugar-based ethanol and oil crop-based biodiesel] rely on the use of commodity crops and therefore compete for use of food crops, primarily corn,” she said. “Also, they are very farm-intensive and use a lot of good farming land, fuel and fertilizer inputs and fresh water.”

Algae ponds, on the other hand, can be put on marginal land and grown with non-fresh brackish water produced from energy mineral extraction (petroleum, natural gas, coal-bed methane), or nutrient-loaded wastewater from municipal and agricultural sources. The Southwest has the potential for being a leader in manufacturing this new type of biofuel because “it has lots of barren land that can’t be used for anything else, lots of sunlight and a lot of marginal water,” Sandia researcher Brian Dwyer said.

Sandia scientist Ron Pate noted that Sandia is bringing into play its scientific and engineering expertise to grow and process specific types of algae for biofuels and other useful coproducts. Sandia’s work in this area ties into broader biofuels efforts supported by DOE’s Office of Biomass Program (OBP) that focus on addressing challenges to commercially viable algal biofuels production. This includes participation in the development of the National Algal Biofuels Technology Roadmap Report, which is still in preparation and partnering with others on proposals to establish consortia for algal biofuels and for advanced fungible biofuels with potential funding from OBP. The Algal Biofuels Consortium specifically proposes a broad-based collaboration with Sandia and other national labs, industry and university partners that would pursue research and development of algal biofuels as an affordable, scaleable and sustainable solution that can contribute significantly to meeting the nation’s transportation fuel needs.

Williams anticipates that the Sandia research will have the potential to provide new jobs and economic development to New Mexico, the seventh largest dairy-producing state in the nation. The state’s dairy industry employs more than 5,000 people and has an annual impact of nearly $2.7 billion.

The 340,000 dairy cows in New Mexico produce large quantities of manure and nutrient-rich effluent water that represent a significant waste management problem and regulatory expense to the state’s dairy industry. These and other agri-industrial waste streams represent a valuable and underused feedstock for recycling of energy, biofuels, reusable water and other coproducts. The DOE Algal Biofuels Technology Roadmap currently in draft suggests the use of non-fresh water sources, including agricultural effluent, for algal biomass production. Besides providing a source of non-fresh water and the recycling of needed nutrients, the use of these waste streams in an integrated biorefinery will help to alleviate disposal regulatory requirements on dairies and other confined animal feeding operations in New Mexico and the broader United States.

(Photo: Randy Montoya)

Sandia National Laboratories

CLIMATE CHANGE TRIGGERED DWARFISM IN SOIL-DWELLING CREATURES OF THE PAST

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Ancient soil-inhabiting creatures decreased in body size by nearly half in response to a period of boosted carbon dioxide levels and higher temperatures, scientists have discovered.

The researchers' findings are published in the October 5, 2009, early online edition of the journal Proceedings of the National Academy of Sciences (PNAS).

Jon Smith, a scientist at the Kansas Geological Survey, and Stephen Hasiotis, a geologist at the University of Kansas, have demonstrated that soil-inhabiting creatures contracted in size by 30-46 percent during the Paleocene-Eocene Thermal Maximum (PETM).
The PETM was a short interval 55 million years ago marked by a spike in the atmosphere's carbon dioxide levels and global temperatures, conditions being repeated on Earth now.

The study is the first to establish that soil biota experienced a loss in size similar to mammals, which were reduced in size by as much as 50 percent during the PETM.

"The discovery that up to 50 percent of the body size reduction during the PETM was not just restricted to mammals, but also affected soil-dwelling organisms, has broad implications that may be very significant to understanding modern climate change and its impending effect on life," said H. Richard Lane. Lane is a program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research by Hasiotis and colleague Mary Kraus at the University of Colorado.

"In our initial hypothesis, we thought that there would be no response to climate change, that the animals would be protected because they're underground," said Hasiotis.

"We also proposed that there would be minimal and protracted change or some sort of a delayed response. Instead, we find that they did experience the same kind of change as vertebrates living during the same period."

The soil-dwelling organisms examined by Smith and Hasiotis are ancient relatives of modern ants, cicadas, dung beetles, earthworms and crayfish.

To establish their findings, the researchers examined trace fossils, or the burrows, nests, tracks, trails and borings of organisms preserved within the Willwood Formation, a thick sequence of mudstones and sandstones in Wyoming's Bighorn Basin.

They found that diameters of burrows and other traces were smaller during the PETM, suggesting that the soil-inhabiting organisms that had created the traces were correspondingly lesser in size.

The scientists say that their results foreshadow biological outcomes that may result due to the planet's current jump in carbon dioxide concentration and temperatures.

They suggest that museum collections of insects compiled over the last few hundred years should be studied to determine whether body sizes of modern insects are indeed getting smaller.

"The PETM is seen as a good analog for modern climate change because it's occurring at roughly the same speed and magnitude," said Smith.

"The take-home lesson is that there can be cascading effects that ripple through an ecosystem when you change just one aspect. Modern climate change can have many effects that aren't going to be as immediately visible as sea-level change.

"We could be changing soil conditions over vast portions of the world and affecting the soil organisms themselves--and that will impact our own agriculture."

The researchers attribute dwarfism in soil-dwelling creatures to faster rates of development in individuals, along with decreasing life spans.

"The soil biota evolved for certain soil temperatures and conditions--and for this geologically brief period of time, those conditions were changed," Hasiotis said. "They probably were adapting to those warmer conditions by having a smaller body size."

During their time in the Bighorn Basin, a typical day in the field for the researchers involved digging shoulder-width trenches that were a meter or so deep and several meters tall, then searching the soil for specific geometric shapes indicating ancient nests, cocoons and burrows.

"For each individual trace fossil, we'd measure the diameter," said Smith. "We'd compare like trace fossils from rocks that occurred before the PETM event, within the event, and after the event. Then we'd look for changes in those diameters through time."
"We were surprised to find that they were in fact smaller through the PETM."

(Photo: Steve Hasiotis and Jon Smith)

National Science Foundation

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