Thursday, September 9, 2010


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A team of astronomers has used a massive galaxy cluster as a cosmic magnifying lens to study the nature of dark energy for the first time. When combined with existing techniques, their results significantly improve current measurements of the mass and energy content of the universe. The findings appeared in the August 20 issue of the journal Science.

Astronomers employ a number of methods to study the geometry of the universe, which tells us something about the nature of dark energy—a mysterious force discovered in 1998 that speeds up the expansion of the universe, but about which little else is known. Uncovering the nature of dark energy, which makes up about 72 percent of all the mass and energy in the universe and will ultimately determine its fate, is one of the holy grails of modern-day cosmology.

Now an international team including Yale University cosmologist Priyamvada Natarajan has used gravitational lensing to learn more about this elusive force. Using data taken by the Hubble Space Telescope as well as ground-based telescopes, the team analyzed images of 34 extremely distant galaxies situated behind Abell 1689, one of the biggest and most massive known galaxy clusters in the universe.

Through the gravitational “lens” of Abell 1689, astronomers were able to detect the faint, distant background galaxies—whose light was bent and projected by the cluster’s massive gravitational pull—in a similar way that the lens of a magnifying lens distorts an object’s image.

The way in which the images were distorted gave the astronomers clues as to the geometry of the space that lies between the Earth, the cluster and the distant galaxies. “The content, geometry and fate of the universe are linked, so if you can constrain two of those things, you learn something about the third,” Natarajan said.

Using theoretical models of the distribution of both ordinary and dark matter in space, Natarajan and the team were able to narrow the range of current estimates about dark energy’s effect on the universe, denoted by the value w, by 30 percent. The team combined their new technique with other methods, including using supernovae, X-ray galaxy clusters and data from the Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft, to constrain the value for w.

The result confirms previous findings that the nature of dark energy likely corresponds to a flat universe. In this scenario, the expansion of the universe will continue to accelerate and the universe will expand forever.

(Photo: NASA, ESA, Eric Jullo/JPL, Priyamvada Natarajan/Yale, Jean-Paul Kneib/Université de Provence)

Yale University


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Just as cilia lining the lungs help keep passages clear by moving particles along the tips of the tiny hair-structures, man-made miniscule bristles known as nano-brushes can help reduce friction along surfaces at the molecular level, among other things.

In their latest series of experiments, Duke University engineers have developed a novel approach to synthesize these nano-brushes, which could improve their versatility in the future. These polymer brushes are currently being used in biologic sensors and microscopic devices, such as microcantilevers, and they will play an important role in the future drive to miniaturization, the researchers said.

Nano-brushes are typically made of polymer molecules grown on flat surfaces with strands of the molecules growing up and out from a surface, much like hairs on a brush. Polymers are large man-made molecules ubiquitous in the manufacture of everyday products.

Like microscopic orchard keepers, the Duke scientists have grafted bundles of polymer “limbs” on flat surfaces known as substrates, already covered with brush bristles. In their approach, two dissimilar brushes can be joined and patterned on the micro-scale. Because the “limbs” can be made out of a different substance than the substrate, the scientists believe these nano-structures are able to significantly modify the properties of a given surface.

To make such a nano-brush, scientists add a chemical known as an initiator to the flat surface, which spurs the growth of the strands.

“One of the common ways of growing brushes is much like a dot matrix printer, with an initiator being the ink ‘printed’ onto an inorganic substrate, such as a silicon wafer or a gold surface, which then causes the brush bristles to grow in specified patterns,” said Stefan Zauscher, Alfred M. Hunt Faculty Scholar and associate professor of mechanical engineering and materials science at Duke’s Pratt School of Engineering.

“In our patterning approach we are now also able to initiate polymer brush growth on existing brush substrates and thus obtain patterned block copolymer brushes, just like grafts, on polymeric substrates,” Zauscher said. “The ability to create more intricate brush structures provides the potential for using them in biomedical applications as sensors for the detection of proteins or glucose.”

The results of his team’s experiments were published online in the journal Small. The research is supported by the National Science Foundation.

Zauscher said this new approach could be readily expanded to many other types of polymers, and to make either single or double layers of brushes. These nano-brushes, he said, would have many potential uses, and would open up the possibilities for building more complicated polymer architectures, which are much in demand for current and future technologies.

In recent research, published earlier in the journal Advanced Materials, Zauscher showed that stimulus-responsive nano-brushes resemble and act like sea anemones, which have a multitude of arms reaching up from an attached base. In the same fashion as these sea animals, nano-brushes can be used to capture and release micro-particles as they move across a surface.

“These microstructures have a potential use in microfluidic systems -- such as labs-on-a-chip -- to capture and release particles at predefined locations, much like the sea anemones capture their prey and guide it to their mouths,” Zauscher said.

Other Duke members of the team are Tao Chen and Debby Chang.

(Photo: Stefan Zauscher, Pratt School of Engineering)

Duke University


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Timescales of early Solar System processes rely on precise, accurate and consistent ages obtained with radiometric dating. However, recent advances in instrumentation now allow scientists to make more precise measurements, some of which are revealing inconsistencies in the ages of samples. Seeking better constraints on the age of the Solar System, Arizona State University researchers Audrey Bouvier and Meenakshi Wadhwa analyzed meteorite Northwest Africa (NWA) 2364 and found that the age of the Solar System predates previous estimates by up to 1.9 million years.

By using a dating technique known as lead-lead dating, Bouvier and Wadhwa were able to calculate the age of a calcium-aluminum-rich inclusion (CAI) contained within the Northwest Africa 2364 chondritic meteorite. These CAIs are thought to be the first solids to condense from the cooling protoplanetary disk during the birth of the Solar System.

The study’s findings, published online on August 22 in Nature Geoscience, fix the age of the Solar System at 4.5682 billion years old, between 0.3 and 1.9 million years older than previous estimates. This relatively small revision to the currently accepted age of about 4.56 billion years is significant since some of the most important events that shaped the Solar System occurred within the first ~10 million years of its formation.

“This relatively small age adjustment means that there was as much as twice the amount of iron-60, a certain short-lived isotope of iron, in the early Solar System than previously determined. This higher initial abundance of this isotope in the Solar System can only be explained by supernova injection,” said Bouvier, a faculty research associate in the School of Earth and Space Exploration (SESE) in ASU’s College of Liberal Arts and Sciences. “This supernova event, and possibly others, could have triggered the formation of the Solar System. By studying meteorites and their isotopic characteristics, we bring new clues about the stellar environment of our Sun at birth.”

According to Meenakshi Wadhwa, professor in SESE and director of the Center for Meteorite Studies, “This work also helps to resolve some long-standing inconsistencies in early Solar System time scales as obtained by different high-resolution chronometers. However, there is certainly room for future studies. In particular, it will be important to conduct high precision chronologic investigations of CAIs from other pristine meteorites. We also need to understand the reasons for why the CAIs measured previously from two other chondritic meteorites, Allende and Efremovka, have yielded younger ages.”

One significant aspect of this study is that it is the first published lead-lead isotopic investigation that takes into account the possible variation of the uranium isotope composition. Earlier work conducted in Wadhwa’s laboratory by ASU graduate student Gregory Brennecka, in collaboration with SESE professor Ariel Anbar, has shown that the uranium isotope composition of CAIs, long assumed to be constant, can in fact be highly variable and this has important implications for the calculation of the precise lead-lead ages of these objects.

Using the relationship demonstrated by Brennecka and colleagues between the uranium isotope composition and other geochemical indicators in CAIs, Bouvier and Wadhwa inferred a uranium isotope composition for the CAI for which they reported the lead-lead age. Future work at ASU will focus on development of analytical techniques for the direct measurement of the precise uranium isotope composition of CAIs for which lead-lead isotopic investigations are being conducted.

“Our work can help researchers better understand the sequence of events that took place within the first few million years of the Solar system formation, such as the accretion and melting of planetary bodies,” Bouvier said. ”All these processes happened extremely rapidly, and only by reaching such a precision on isotopic measurements and chronology can we find out about these processes of planetary formation.”

(Photo: Audrey Bouvier)

Arizona State University


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More than two and a half billion years ago, Earth differed greatly from our modern environment, specifically in respect to the composition of gases in the atmosphere and the nature of the life forms inhabiting its surface. While today’s atmosphere consists of about 21 percent oxygen, the ancient atmosphere contained almost no oxygen. Life was limited to unicellular organisms. The complex eukaryotic life we are familiar with – animals, including humans – was not possible in an environment devoid of oxygen.

The life-supporting atmosphere Earth's inhabitants currently enjoy did not develop overnight. On the most basic level, biological activity in the ocean has shaped the oxygen concentrations in the atmosphere over the last few billion years. In a paper published today by Nature Geoscience online, Arizona State University researchers Brian Kendall and Ariel Anbar, together with colleagues at other institutions, show that "oxygen oases" in the surface ocean were sites of significant oxygen production long before the breathing gas began to accumulate in the atmosphere.

By the close of this period, Earth witnessed the emergence of microbes known as cyanobacteria. These organisms captured sunlight to produce energy. In the process, they altered Earth’s atmosphere through the production of oxygen – a waste product to them, but essential to later life. This oxygen entered into the seawater, and from there some of it escaped into the atmosphere.

“Our research shows that oxygen accumulation on Earth first began to occur in surface ocean regions near the continents where the nutrient supply would have been the highest,” explains Kendall, a postdoctoral research associate at the School of Earth and Space Exploration in ASU’s College of Liberal Arts and Sciences. “The evidence suggests that oxygen production in the oceans was vigorous in some locations at least 100 million years before it accumulated in the atmosphere. Photosynthetic production of oxygen by cyanobacteria is the simplest explanation.”

The idea of “oxygen oases,” or regions of initial oxygen accumulation in the surface ocean, was hypothesized decades ago. However, it is only in the past few years that compelling geochemical evidence has been presented for the presence of dissolved oxygen in the surface ocean 2.5 billion years ago, prior to the first major accumulation of oxygen in the atmosphere (known as the Great Oxidation Event).

Kendall’s work is the latest in a series of recent studies by a collaborative team of researchers from ASU; University of California, Riverside; and University of Maryland that point to the early rise of oxygen in the oceans. Together with colleagues from University of Washington and University of Alberta, this team first presented evidence for the presence of dissolved oxygen in these oceans in a series of four Science papers over the past few years. These papers focused on a geologic formation called the Mt. McRae Shale from Western Australia. One of these papers, led by the ASU team, presented geochemical profiles that showed an abundance of two redox-sensitive elements – rhenium (Re) and molybdenum (Mo) – implying that small amounts of oxygen mobilized these metals from the crust on land or in the ocean, and transport them through an oxic surface ocean to deeper anoxic waters where the metals were hidden into organic-rich sediments. Kendall participated in this research while a postdoctoral student at the University of Alberta.

Kendall’s goal in the new project was to look for evidence of dissolved oxygen in another location. He wanted to see if the geochemical evidence from the Mt. McRae Shale in Western Australia would be found in similarly-aged rocks from South Africa. Those rocks were obtained in a project supported by the Agouron Institute. Kendall’s research was supported by grants from NASA and the National Science Foundation.

What Kendall discovered was a unique relationship of high rhenium and low molybdenum enrichments in the samples from South Africa, pointing to the presence of dissolved oxygen on the seafloor itself.

“In South Africa, samples from the continental slope beneath the shallower platform were thought to be deposited at water depths too deep for photosynthesis," Kendall said. "So it was a big surprise that we found evidence of dissolved oxygen on the seafloor at these depths. This discovery suggests that oxygen was produced at the surface in large enough quantities that some oxygen survived as it was mixed to greater depths. That implies a significantly larger amount of oxygen production and accumulation in ‘oxygen oases’ than was previously realized.”

A key contribution to this study came from Christopher Reinhard and Timothy Lyons, collaborators at the University of California, Riverside, and Simon Poulton at Newcastle University, who found that the chemistry of iron (Fe) in the same shales is also consistent with the presence of dissolved oxygen.

“It was especially satisfying to see two different geochemical methods – rhenium and molybdenum abundances and Fe chemistry – independently tell the same story,” Kendall noted.

Evidence that the atmosphere contained at most minute amounts of oxygen came from measurements of the relative abundances of sulfur (S) isotopes. These measurements were performed by Alan Kaufman, a collaborator at the University of Maryland.

“Research like Brian’s on the co-evolution of Earth’s atmosphere, oceans and biosphere is not only important for unraveling key events in Earth history, it also has broad relevance to our search for life on other planets,” said Ariel Anbar, professor and director of the Astrobiology Program at ASU and Kendall’s postdoctoral mentor. “One of the ways we will look for life on planets orbiting other stars is to look for oxygen in their atmospheres. So we want to know how the rise of oxygen relates to the emergence of photosynthesis.”

On a more practical level, Anbar observes that the research also connects to emerging concerns about our own planet.

“Recent research in the modern oceans reveals that the amount of oxygen is decreasing in some places,” he said. “Some suspect this decrease is tied to global warming. One of the ways we might figure that out is to reconstruct ocean oxygen content on the slopes of the seafloor in recent history. So the same techniques that Brian is advancing and applying to billion-year-old rocks might be used to understand how humans are changing the environment today.”

(Photo: Susanne Neuer/Amy Hansen)

Arizona State University


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Scientists at the University of Oregon have determined the fine-scale genetic structure of the first animal to show an evolutionary response to rapid climate change.

They used a high-throughput sequencing technique called Restriction-site Associated DNA (RAD) tagging to make the discovery.

Their results, which focus on the pitcher plant mosquito, Wyeomyia smithii, are published in the journal Proceedings of the National Academy of Sciences (PNAS).

RAD tagging is an effective and straightforward way of barcoding sections of genomic material, much as grocery items are coded at the local supermarket, say the scientists.

"This project demonstrates the power of genomics technologies, which can provide new knowledge about the vast array of Earth's species," says Sam Scheiner, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which funded the research.

"Although this small mosquito has become the poster child for genetic response to climate change," says William Bradshaw, one of the paper's co-authors, "its evolution during post-glacial invasion of North America has been a question."

Using the RAD-Tag approach, the scientists have demonstrated that post-glacial populations of Wyeomyia smithii originated from a southern Appalachian Mountain refugium after recession of the Laurentide Ice Sheet some 22,000 to 19,000 years ago.

Range expansion into the previously glaciated north proceeded in a sequential, ordered wave rather than by a "hit-or-miss" hopscotch process, the biologists found.

With this detailed information, they will be able to determine the genetic mechanism underlying photoperiod response to rapid climate change--responsible for the correct timing of dormancy, migration, development and reproduction in temperate organisms.

The knowledge will act as a template for research on blood-feeding in mosquito vectors of dengue, encephalitis and malaria.

The mosquito in question lives within the water-filled leaves of the purple pitcher plant, Sarracenia purpurea, also known as the side-saddle flower, whose range includes the eastern seaboard of the U.S., the Great Lakes and southeastern Canada.

Sarracenia purpurea is the most common and widely distributed pitcher plant, and is the only member of the genus that inhabits cold temperate climates. Where the purple pitcher plant is found, so, too, is Wyeomyia smithii.

Before the time of Darwin, biologists sought links between apparently related groups of plants and animals with an eye toward understanding the world around us.

Relatedness was first described primarily as similarity in morphological characteristics: broad groupings of organisms were classified into orders, families and genera, much like one describes resemblance among one's extended family.

Early classification of organisms became more refined as developmental, physiological and behavioral observations were incorporated into these broad categories.

With the revelation of gene-based relationships, the search for an increasingly detailed understanding of genetic patterns became a driving force throughout all biological disciplines.

New technologies heralded new advances. "We have now arrived at an era in which genetically similar groups can be clustered quickly and at very low cost to effect a near-endless number of applications," says William Cresko, also a co-author of the PNAS paper.

Researchers can accurately describe genome-wide variation to shed light on evolution at the population level, to predict patterns of invasion of species during rapid climate change, and to correlate gene-based illnesses with susceptible human populations on a local or worldwide scale.

"The RAD-Tag protocol has increased the resolution of genetic relatedness among populations by 100-fold over previous molecular approaches," says Bradshaw.

"Along with the ability to illustrate the fine-scale phylogeographic patterns in species with few or no prior genomic resources," he says, "this technique will have applications in fields from ecology and evolution to human behavior and medicine."

(Photo: William Bradshaw and Christina Holzapfel)

National Science Foundation


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Oyster reefs are on the decline, with over-harvesting and pollution reducing some stocks as much as 98 percent over the last two centuries.

With a growing awareness of oysters' critical roles filtering water, preventing erosion, guarding coasts from storm damage, and providing habitat for other organisms, researchers have been investigating how oyster reefs form in order to better understand the organisms and offer potential guidance to oyster re-introduction projects.

At the same time, researchers have been studying marine animals' various adhesives, uncovering fundamental properties that could yield new innovations from replacements for medical sutures to surface coatings that keep waterborne craft from picking up marine hitchhikers.

Now, researchers from Purdue University and the University of South Carolina have shown that oysters produce a unique adhesive material for affixing themselves to each other, a cement that differs from the glues used by other marine organisms.

The researchers will publish their results in the Sept. 15, 2010, issue of the Journal of the American Chemical Society. (The article is available online now.)

"We wanted to learn how oysters attach themselves to surfaces, and each other, when building reef structures," said Purdue University chemist Jonathan Wilker, one of the lead researchers on the study. "Such knowledge can help us develop biomedical materials including wet setting surgical adhesives. These insights may also help us prevent marine bioadhesion for keeping ship hulls clean, thereby reducing drag, fuel consumption, and carbon emissions."

Wilker and his colleagues studied the common Eastern oyster, Crassostrea virginica, which the researchers collected from the Baruch Marine Field Laboratory on the South Carolina coast.

By comparing the oyster shells (inside and out) with the material connecting oyster to oyster, the researchers were able to determine the chemical composition of the cementing material.

"Our results indicate that there is a chemically distinct adhesive material holding the oysters together," said Wilker. "The cement contains significantly more protein than the shell. We also observed both iron and highly oxidized, cross-linked proteins, which may play a role in curing the material."

Cross-linked proteins are an emerging theme in the study of marine biological materials, central to the glues of mussels, barnacles, and now, oysters. However, the oysters use far less protein in their adhesive when compared to the analogous materials from mussels and barnacles.

Beyond this relatively minor protein component, the oyster adhesive appears to be unique, composed largely of chalky calcium carbonate. Oysters seem to prefer an adhesive that is more like a hard, inorganic cement versus the softer, organic glues of other organisms.

This research was supported by the National Science Foundation through the Chemistry of Life Processes program under grant CHE-0952928 and the Office of Naval Research through their Biofouling Control Coatings research program.

"This is exactly the kind of interdisciplinary, cutting-edge research that we strive to support, particularly by looking at research that lies outside the traditional sub-disciplines in the field," said Dan Rabinovich, the program officer in the NSF Division of Chemistry who supports Wilker's grant. "This is in agreement with the Division's realigned programs, which no longer bear the traditional 'organic', 'inorganic', 'physical' or 'analytical' descriptors in their names."

The researchers next hope to determine the interplay between the cement's organic and inorganic components. Then, the chemists will use what they learn to create new classes of synthetic materials as well as adhesion-preventing surfaces.

"By understanding how various marine organisms attach themselves to surfaces, it may be possible to rationally design coatings to inhibit this process without the use of toxic components," said Linda Chrisey, a program officer in the Naval Biosciences and Biocentric Technology program who helps fund the research. "This is one of the goals of the Office of Naval Research's Biofouling-Control Coatings research program."

(Photo: Jonathan Wilker, Purdue University)

National Science Foundation


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What makes something funny? Philosophers have been tossing that question around since Plato. Now two psychological scientists think they've come up with the formula: humor comes from a violation or threat to the way the world ought to be that is, at the same time, benign.

Most older theories of humor all come up short in one way or another, says A. Peter McGraw, of the University of Colorado-Boulder, who coauthored the study with Caleb Warren. Freud thought humor came from a release of tension; another theory holds that humor comes from a sense of superiority, and still another from incongruity. The researchers, however, point out that all of these could happen if you accidentally killed your spouse—but that wouldn't be funny. They thought that instead, a situation might be funny only if it also seems benign.

To test their hypothesis, the researchers presented various situations to volunteers they rewarded with candy bars. In one experiment, the volunteers read pairs of situations—for example, one where Jimmy Dean hired a rabbi as spokesman for their new line of pork products, and one where Jimmy Dean hired a farmer as spokesman for their new line of pork products. The situation with a moral violation—having a rabbi promote pork—was both more likely to be seen as wrong and more likely to make the reader laugh.

The other part of the study tested whether benign appraisals of a moral violation made it funnier. For one experiment, participants read a scenario in which either a church or a credit union raffles off an SUV to attract new members. The participants were disgusted when the church attracted members with a raffle, but not the credit union. But whether they were amused by the church depended in part on whether they went to church themselves; non-churchgoers were more likely to think that was funny. The researchers think this is because the non-churchgoers are "not particularly committed to the sanctity of churches," says McGraw—so for them, the moral violation seems benign. Another experiment confirmed that people who have more psychological distance from a moral violation are more likely to be amused. The research is published in Psychological Science, a journal of the Association for Psychological Science.

"We laugh when Moe hits Larry because we know that Larry's not really being hurt," says McGraw, referring to humorous slapstick. "It's a violation of social norms. You don't hit people, especially a friend. But it's okay because it's not real." He points out a recent example, an internet video of a chain-smoking Indonesian toddler. "When I was first told about that, I laughed, because it seems unreal—what parent would let their kids smoke cigarettes? The fact that the situation seemed unbelievable made it benign. Then when I saw the video of this kid smoking, it was no longer possible to laugh about it."

McGraw thinks the theory works for other kinds of humor, like puns, which break a linguistic convention or rule but are still okay because they adhere to another rule, so the sentence still makes sense. It also explains why dramas and action movies play better outside of their home countries than comedies do. "It's hard to find a comedy that's funny cross-culturally because the ways that violations can be benign differ from culture to culture. The comedy that is funny cross-culturally tends to involve a lot of physical humor. The violations are clear no matter who you are," he says.

Psychological Science


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Scientists may have discovered in Australia the oldest fossils of animal bodies. These findings push back the clock on the scientific world's thinking regarding when animal life appeared on Earth. The results suggest that primitive sponge-like creatures lived in ocean reefs about 650 million years ago.

The shelly fossils, found beneath a 635 million-year-old glacial deposit in South Australia, represent the earliest evidence of animal body forms in the current fossil record, predating other evidence by at least 70 million years.

"These scientists have found that animals may have appeared on Earth 90 million years earlier than previously known," said H. Richard Lane of the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"This is comparable to resetting modern times to begin during the late Cretaceous."

Previously, the oldest known fossils of hard-bodied animals were from two reef-dwelling organisms that lived around 550 million years ago.

There are also controversial fossils of soft-bodied animals that date to the latter part of the Ediacaran period between 577 and 542 million years ago.

Princeton University geoscientists Adam Maloof and Catherine Rose happened upon the new fossils while working on a project focused on the severe ice age that marked the end of the Cryogenian period 635 million years ago.

Their findings, published in the August 17 issue of the journal Nature Geoscience, provide the first direct evidence that animal life existed before--and probably survived--the severe "snowball Earth" event known as the Marinoan glaciation that left much of the globe covered in ice at the end of the Cryogenian.

"We were accustomed to finding rocks with embedded mud chips, and at first this is what we thought we were seeing," Maloof said.

"But then we noticed these repeated shapes that we were finding everywhere--wishbones, rings, perforated slabs and anvils. We realized we had stumbled upon some sort of organism, and we decided to analyze the fossils.

"No one was expecting that we would find animals that lived before the ice age, and since animals probably did not evolve twice, we are suddenly confronted with the question of how a relative of these reef-dwelling animals survived the ‘snowball Earth.'"

Analyzing the fossils turned out to be easier said than done, as the composition and location of the fossils made it such that they could not be removed from the surrounding rock using conventional techniques, nor could they be imaged using X-ray scanning techniques.

X-rays are only able to distinguish between materials with different densities, which is why they can be used to image bones that are inside the human body or buried within a rock.

But the most ancient skeletal fossils are made not of bone, but of calcite--the same material that makes up the rock matrix in which they are embedded.

Therefore X-rays could not be used to "illuminate" the newly discovered fossils and the researchers had to develop and refine another method.

Maloof, Rose and their collaborators teamed up with professionals at Situ Studio, a Brooklyn-based design and digital fabrication studio, to create three-dimensional digital models of two individual fossils that were embedded in the surrounding rock.

As part of the process, team members shaved off 50 microns of sample at a time--about half the width of a human hair--and photographed the polished rock surface each time. The team ground and imaged nearly 500 slices of the rock.

Using specialized software techniques developed specifically for this project, the researchers then "stacked" the outlines on top of one another to create a complete three-dimensional model of the creature.

The technique is similar to the way CAT scan technology combines a series of two-dimensional X-rays to create a three-dimensional image of the inside of the body.

The technique that was developed served to automate the process--turning a prohibitively time-consuming task into an efficient and effective method for fossil reconstruction.

"For Situ Studio, the most exciting aspect of this collaboration is that we were able to successfully employ knowledge developed within an architectural practice to help solve problems in an entirely different field--applying design tools to spatial problems on a completely different scale," said Bradley Samuels, a founding partner of Situ Studio.

"It became an exercise in marrying disparate bodies of knowledge to address pressing questions in the geosciences."

When they began the digital reconstruction process, the shape of some of the two-dimensional slices made the researchers suspect they might be dealing with the previously discovered Namacalathus, a goblet-shaped creature featuring a long body stalk topped with a hollow ball.

But their model revealed irregularly shaped, centimeter-scale animals with a network of internal canals. The creatures looked nothing like Namacalathus.

After considering a variety of alternatives, the scientists decided that the fossil organisms most closely resembled sponges--simple filter-feeding animals that extract food from water as it flows through specialized body channels.

Previously, the oldest known undisputed fossilized sponges were around 520 million years old, dating to the Cambrian Period.

In future research, Maloof and his collaborators intend to refine the three-dimensional digital reconstruction technique to automate and increase the speed of the process.

This could have a significant impact on paleontology, Maloof said, enabling the analysis of myriad early fossils that are currently inaccessible to the tools of modern science.

In addition to Maloof and Rose, Princeton researchers on the team included geoscientist Frederik Simons; former postdoctoral fellow Claire Calmet; Nan Yao, the director of the Imaging and Analysis Center in the Princeton Institute for the Science and Technology of Materials (PRISM); and PRISM senior research specialist Gerald Poirier.

The team also included Douglas Erwin of the Smithsonian Institution and Samuels, Robert Beach, Basar Girit, Wesley Rozen, Sigfus Briedfjord and Aleksey Lukyanov of Situ Studio.

(Photo: Adam Maloof)

National Science Foundation


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A new analysis of the unusually long solar cycle that ended in 2008 suggests that one reason for the long cycle could be a stretching of the sun's conveyor belt, a current of plasma that circulates between the sun's equator and its poles.

The sun goes through cycles lasting approximately 11 years that include phases with increased magnetic activity, more sunspots, and more solar flares, and phases with less activity.

The level of activity on the sun can affect navigation and communications systems on Earth.

The results of this study should help scientists better understand the factors controlling the timing of solar cycles and could lead to better predictions.

The study was conducted by Mausumi Dikpati, Peter Gilman, and Giuliana de Toma, all scientists in the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and by Roger Ulrich at the University of California, Los Angeles.

The results appeared on July 30 in the journal Geophysical Research Letters. The study was funded by the National Science Foundation (NSF), NCAR's sponsor, and by NASA.

"Understanding and predicting the solar cycle allows us to better prepare for coming space weather effects and, equally importantly, enables us to make more accurate decadal predictions of global climate change," says Richard Behnke of NSF's Division of Atmospheric and Geospace Sciences.

The occurrence of solar cycles has been reconstructed going back in time about 300 years.

Puzzlingly, solar cycle 23, the one that ended in 2008, lasted longer than previous cycles, with a prolonged phase of low activity that scientists had difficulty explaining.

The new analysis suggests that one reason for the long cycle could be changes in the sun's conveyor belt.

Just as Earth's global ocean circulation transports water and heat around the planet, the sun has a conveyor belt in which plasma flows along the surface toward the poles, sinks, and returns toward the equator, transporting magnetic flux along the way.

In their paper, Dikpati, Gilman, and de Toma use simulations to model how the solar plasma conveyor belt affects the solar cycle.

The authors find that the longer conveyor belt and slower return flow could have caused the longer duration of cycle 23.

The team's computer model, known as the Predictive Flux-transport Dynamo Model, simulates the evolution of magnetic fields in the outer third of the sun's interior (the solar convection zone).

It provides a physical basis for projecting the nature of upcoming solar cycles from the properties of previous cycles, as opposed to statistical models that emphasize correlations between cycles.

In 2004, the model successfully predicted that cycle 23 would last longer than usual.

"The key for explaining the long duration of cycle 23 with our dynamo model is the observation of an unusually long conveyor belt during this cycle," Dikpati says. "Conveyor belt theory indicates that shorter belts, such as observed in cycle 22, should be more common in the sun."

Recent measurements gathered and analyzed by Ulrich and colleagues show that in solar cycle 23, the poleward flow extended all the way to the poles, while in previous solar solar cycles the flow turned back toward the equator at about 60 degrees latitude.
As a result of mass conservation, the return flow was slower in cycle 23 than in previous cycles.

According to Dikpati, the duration of a solar cycle is probably determined by the strength of the sun's meridional flow.

The combination of this flow and the lifting and twisting of magnetic fields near the bottom of the convection zone generates the observed symmetry of the sun's global field with respect to the solar equator.

"This study highlights the importance of monitoring and improving measurement of the sun's meridional circulation," Ulrich says. "In order to improve predictions of the solar cycle, we need a strong effort to understand large-scale patterns of solar plasma motion."

(Photo: NCAR)

National Science Foundation




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