Fireworks in the early universe

ScienceDaily (Sep. 19, 2012) — Galaxies in the early universe grew fast by rapidly making new stars. Such prodigious star formation episodes, characterized by the intense radiation of the newborn stars, were often accompanied by fireworks in the form of energy bursts caused by the massive central black hole accretion in these galaxies.

This discovery by a group of astronomers led by Peter Barthel of the Kapteyn Institute of the University of Groningen in the Netherlands is published September 19 in the Astrophysical Journal Letters.

Our Milky Way galaxy forms stars at a slow, steady pace: on average one new star a year is born. Since the Milky Way contains about a hundred billion stars, the actual changes are very slight. The Milky Way is an extremely quiet galaxy; its central black hole is inactive, with only weak energy outbursts due to the occasional capture of a passing star or gas cloud.

Bright, exotic radiation

This is in marked contrast to the 'active' galaxies of which there are various types and which were abundant in the early universe. Quasars and radio galaxies are prime examples: owing to their bright, exotic radiation, these objects can be observed as far as the edge of the observable universe. The light of the normal stars in their galaxies is extremely faint at such distances, but active galaxies can be easily detected through their luminous radio, ultraviolet or X-ray radiation, which results from steady accretion onto their massive central black holes.

Peculiar exotic objects

Until recently these distant active galaxies were only interesting in their own right as peculiar exotic objects. Little was known about the composition of their galaxies, or their relationship to the normal galaxy population. However, in 2009 ESA's Herschel space telescope was launched. Herschel is considerably larger than NASA's Hubble, and operates at far-infrared wavelengths. This enables Herschel to detect heat radiation generated by the processes involved in the formation of stars and planets at a small scale, and of complete galaxies at a large scale.

Initial inspection

Peter Barthel has been involved with Herschel since 1997 and heads an observational programme targeting distant quasars and radio galaxies. His team used the Herschel cameras to observe seventy of these objects. Initial inspection of the observations has revealed that many emit bright far-infrared radiation.

The Astrophysical Journal Letter 'Extreme host galaxy growth in powerful early-epoch radio galaxies', by Peter Barthel and co-authors Martin Haas (Bochum University, GER), Christian Leipski (Max-Planck Institute for Astronomy, Heidelberg, GER) and Belinda Wilkes (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), describes their project and the detailed analysis of the first three distant radio galaxies.

Simultaneous grow

The fact that these three objects, as well as many others from the observational sample, emit strong far-infrared radiation indicates that vigorous star formation is taking place in their galaxies, creating hundreds of stars per year during one or more episodes lasting millions of years. The bright radio emission implies strong, simultaneous black hole accretion. This means that while the black holes in the centres of the galaxies are growing (as a consequence of the accretion), the host galaxies are also growing rapidly.

The Herschel observations thereby provide an explanation for the observation that more massive galaxies have more massive black holes. Astronomers have observed this scaling relationship since the 1990s: the fireworks in the early universe could well be responsible for this relationship.

Barthel: 'It is becoming clear that active galaxies are not only among the largest, most distant, most powerful and most spectacular objects in the universe, but also among the most important objects; many if not all massive normal galaxies must also have gone through similar phases of simultaneous black hole-driven activity and star formation.'

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The above story is reprinted from materials provided by University of Groningen.

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Journal Reference:

1. Peter Barthel, Martin Haas, Christian Leipski, Belinda Wilkes. EXTREME HOST GALAXY GROWTH IN POWERFUL EARLY-EPOCH RADIO GALAXIES. The Astrophysical Journal, 2012; 757 (2): L26 DOI: 10.1088/2041-8205/757/2/L26

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19 Sep, 2012

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Evolutionary history of lizards and snakes reconstructed using massive molecular dataset

ScienceDaily (Sep. 18, 2012) — A new study, published online in Biology Letters on Sept. 19, has utilized a massive molecular dataset to reconstruct the evolutionary history of lizards and snakes. The results reveal a surprising finding about the evolution of snakes: that most snakes we see living on the surface today arose from ancestors that lived underground.

The article, entitled "Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species," describes research led by John J. Wiens, an Associate Professor in the Department of Ecology and Evolution at Stony Brook University. The study was based on 44 genes and 161 species of lizards and snakes, one of the largest genetic datasets assembled for reptiles.

The results show that almost all groups of snakes arose from within a bizarre group of burrowing blind snakes called scolecophidians. This finding implies that snakes ancestrally lived underground, and that the thousands of snake species living today on the surface evolved from these subterranean ancestors.

The authors suggest that there are still traces of this subterranean ancestry in the anatomy of surface-dwelling snakes. "For example, no matter where they live, snakes have an elongate body and a relatively short tail, and outside of snakes, this body shape is only found in lizards that live underground," said Professor Wiens. "Snakes have kept this same basic body shape as they have evolved to invade nearly every habitat on the planet -- from rainforest canopies to deserts and even the oceans."

Co-authors of the study include Carl R. Hutter, Daniel G. Mulcahy, Brice P. Noonan, Ted M. Townsend, Jack W. Sites Jr., and Tod W. Reeder. The work was performed at Stony Brook University, Brigham Young University, and San Diego State University.

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The above story is reprinted from materials provided by Stony Brook University.

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Journal Reference:

1. J. J. Wiens, C. R. Hutter, D. G. Mulcahy, B. P. Noonan, T. M. Townsend, J. W. Sites, T. W. Reeder. Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species. Biology Letters, 2012; DOI: 10.1098/rsbl.2012.0703

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19 Sep, 2012

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Crews uncover massive Roman mosaic in southern Turkey

ScienceDaily (Sep. 18, 2012) — A University of Nebraska-Lincoln archaeological team has uncovered a massive Roman mosaic in southern Turkey -- a meticulously crafted, 1,600-square-foot work of decorative handiwork built during the region's imperial zenith.

It's believed to be the largest mosaic of its type in the region and demonstrates the reach and cultural influence of the Roman Empire in the area in the third and fourth centuries A.D., said Michael Hoff, Hixson-Lied professor of art history at UNL and the director of the excavation.

"Its large size signals, in no small part, that the outward signs of the empire were very strong in this far-flung area," Hoff said. "We were surprised to have found a mosaic of such size and of such caliber in this region -- it's an area that had usually been off the radar screens of most ancient historians and archeologists, and suddenly this mosaic comes into view and causes us to change our focus about what we think (the region) was like in antiquity."

Since 2005, Hoff's team has been excavating the remains of the ancient city of Antiochia ad Cragum on the southern Turkish coast. Antiochus of Commagene, a client-king of Rome, founded the city in the middle of the first century.

"This region is not well understood in terms of history and archaeology," Hoff said. "It's not a place in which archaeologists have spent a lot of time, so everything we find adds more evidence to our understanding of this area of the Roman Empire.

"We're beginning to understand now that it was more Romanized, more in line with the rest of the Roman world than was suspected before. (The nature of the mosaic) hammers home how Roman this city truly is."

Antiochia ad Cragum had many of the trappings expected of a Roman provincial city -- temples, baths, markets and colonnaded streets, said Hoff. The city thrived during the empire from an economy focused on agricultural products, especially wine and lumber.

Excavation has focused on a third-century imperial temple, and also a street lined with shops. In July, the team began to explore the mosaic, which was part of a Roman bath. The decoration consists of large squares, each filled with different colored geometric designs and ornamentation.

"This would have been a very formal associated pavement attached to the bath," Hoff said. "This is a gorgeous mosaic, and its size is unprecedented" -- so large, in fact, that work crews have uncovered only an estimated 40 percent of its total area.

Hoff said it appears the mosaic served as a forecourt for the adjacent large bath, and that at least on one side, evidence shows there was a roof covering the geometric squares that would have been supported by piers. Those piers' remains are preserved, he said.

Meanwhile, the middle of the mosaic was outfitted with a marble-lined, 25-foot-long pool, which would have been uncovered and open to the sun. The other half of the mosaic adjacent to the bath is expected to contain similar decoration, Hoff said. Crews expect to unearth the entire work next summer.

Team members first noticed the mosaic in 2001 when a large archaeological survey project that included Hoff noticed a local farmer had plowed up pieces of a mosaic in a field next to a still-standing bath structure. The find was brought to the attention of the archeological museum in Alanya, which two years later made a minor investigation that revealed a small portion of the mosaic.

Last year, the museum invited Hoff to clear the mosaic and to preserve it for tourists and scholars. Hoff's 60-person team also included Birol Can, assistant professor of archaeology at Atatürk University in Ezrurum, Turkey, a sister university to the University of Nebraska; students from UNL; other students from Turkey and the United States; and workers from a nearby village. About 35 students participated in the project as part of a summer field school Hoff runs.

Phalin Strong, a sophomore art major from Lincoln, said the work was difficult but satisfying.

"It is strange to realize that you are the first person to see this for centuries -- a feeling that also made me think about impermanence and what importance my actions have on humanity and history," Strong said.

Ben Kreimer, a senior journalism major, agreed: "(Working on) the mosaic was great because the more soil you removed, the more mosaic there was," he said. "Visually, it was also stunning, especially once it got cleaned off. It wasn't very deep under the surface of the soil, either, so … we had to be careful not to swing the handpick too hard so as not to damage the priceless mosaic that lay just inches beneath us."

Hoff said the significance of this summer's discovery has him eager to return to the site and see what the rest of the excavation uncovers.

"As an archaeologist, I am always excited to make new discoveries. The fact that this discovery is so large and also not completely uncovered makes it doubly exciting," he said. "I am already looking forward to next year, though I just returned from Turkey."

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The above story is reprinted from materials provided by University of Nebraska-Lincoln. The original article was written by Kathe Andersen and Steve Smith.

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18 Sep, 2012

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Mathematicians show how shallow water may help explain tsunami power

ScienceDaily (Sep. 18, 2012) — While wave watching is a favorite pastime of beachgoers, few notice what is happening in the shallowest water. A closer look by two University of Colorado Boulder applied mathematicians has led to the discovery of interacting X- and Y-shaped ocean waves that may help explain why some tsunamis are able to wreak so much havoc.

Professor Mark Ablowitz and doctoral student Douglas Baldwin repeatedly observed such wave interactions in ankle-deep water at both Nuevo Vallarta, Mexico, and Venice Beach, Calif., in the Pacific Ocean -- interactions that were thought to be very rare but which actually happen every day near low tide. There they saw single, straight waves interacting with each other to form X- and Y-shaped waves as well as more complex wave structures, all predicted by mathematical equations, said Ablowitz.

When most ocean waves collide, the "interaction height" is the sum of the incoming wave heights, said Baldwin. "But the wave heights that we saw from such interactions were much taller, indicating that they are what we call nonlinear," he said.

Satellite observations of the 2011 tsunami generated by the devastating earthquake that struck Japan indicate there was an X-shaped wave created by the merger of two large waves. "This significantly increased the destructive power of the event," said Ablowitz. "If the interaction had happened at a much greater distance from shore, the devastation could have been even worse as the amplitude could have been even larger. Not every tsunami is strengthened by interacting waves, but when they do intersect there can be a powerful multiplier because of the nonlinearity."

Ablowitz first observed the nonlinear wave action in 2009 while visiting Nuevo Vallarta just north of Puerto Vallarta with his family. He took hundreds of photographs and videos of the peculiar waves over the next several years.

"Unlike most new physics, you can see these interactions without expensive equipment or years of training," said Ablowitz. "A person just needs to go to a flat beach, preferably near a jetty, within a few hours of low tide and know what to look for."

A paper on the subject by Ablowitz and Baldwin was published this month in the journal Physical Review E.

Baldwin, who is studying under Ablowitz, wanted to go the extra mile to verify that the wave interactions observed by his professor were not unique to one beach. In this case he drove more than 1,000 miles to the Los Angeles area "on a whim" to search for the types of waves Ablowitz had observed in Mexico. He hit the jackpot at Venice Beach.

"I don't think there is anything more enjoyable in science than discovering something by chance, predicting something you haven't seen, and then actually seeing what you predicted," said Baldwin.

To see photos and videos of the wave interactions visit http://www.douglasbaldwin.com/nl-waves.htmland http://www.markablowitz.com/line-solitons.

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Journal Reference:

1. Mark Ablowitz, Douglas Baldwin. Nonlinear shallow ocean-wave soliton interactions on flat beaches. Physical Review E, 2012; 86 (3) DOI: 10.1103/PhysRevE.86.036305

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19 Sep, 2012

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Jesus's wife? Scholar announces existence of a new early Christian gospel from Egypt

ScienceDaily (Sep. 18, 2012) — Four words on a previously unknown papyrus fragment provide the first evidence that some early Christians believed Jesus had been married, Harvard Professor Karen King told the 10th International Congress of Coptic Studies today.

King, the Hollis Professor of Divinity at Harvard Divinity School, announced the existence of the ancient text at the Congress's meeting, held every four years and hosted this year by the Vatican's Institutum Patristicum Augustinianum in Rome. The four words that appear on the fragment translate to, "Jesus said to them, my wife." The words, written in Coptic, a language of ancient Egyptian Christians, are on a papyrus fragment of about one and a half inches by three inches.

"Christian tradition has long held that Jesus was not married, even though no reliable historical evidence exists to support that claim," King said. "This new gospel doesn't prove that Jesus was married, but it tells us that the whole question only came up as part of vociferous debates about sexuality and marriage. From the very beginning, Christians disagreed about whether it was better not to marry, but it was over a century after Jesus's death before they began appealing to Jesus's marital status to support their positions."

Roger Bagnall, director of the Institute for the Study of the Ancient World in New York, believes the fragment to be authentic based on examination of the papyrus and the handwriting, and Ariel Shisha-Halevy, a Coptic expert at Hebrew University in Jerusalem, considers it likely to be authentic on the basis of language and grammar, King said. Final judgment on the fragment, King said, depends on further examination by colleagues and further testing, especially of the chemical composition of the ink.

One side of the fragment contains eight incomplete lines of handwriting, while the other side is badly damaged and the ink so faded that only three words and a few individual letters are still visible, even with infrared photography and computer photo enhancement. Despite its tiny size and poor condition, King said, the fragment provides tantalizing glimpses into issues about family, discipleship, and marriage that concerned ancient Christians.

King and colleague AnneMarie Luijendijk, an associate professor of religion at Princeton University, believe that the fragment is part of a newly discovered gospel. Their analysis of the fragment is scheduled for publication in the January 2013 issue of Harvard Theological Review, a peer-reviewed journal.

King has posted a draft of the paper, an extensive question-and-answer on the fragment and its meaning, and images of it, on a page on the Divinity School website.

The brownish-yellow, tattered fragment belongs to an anonymous private collector who contacted King to help translate and analyze it. The collector provided King with a letter from the early 1980s indicating that Professor Gerhard Fecht from the faculty of Egyptology at the Free University in Berlin believed it to be evidence for a possible marriage of Jesus.

King said that when the owner first contacted her about the papyrus, in 2010, "I didn't believe it was authentic and told him I wasn't interested." But the owner was persistent, so in December 2011, King invited him to bring it to her at Harvard. After examining it, in March 2012 King carried the fragment to New York and, together with Luijendijk, took it to Bagnall to be authenticated. When Bagnall's examination of the handwriting, ways that the ink had penetrated and interacted with the papyrus, and other factors, confirmed its likely authenticity, work on the analysis and interpretation of the fragment began in earnest, King said.

Little is known about the discovery of the fragment, but it is believed to have come from Egypt because it is written in Coptic, the form of the Egyptian language used by Christians there during the Roman imperial period. Luijendijk suggested that "a fragment this damaged probably came from an ancient garbage heap like all of the earliest scraps of the New Testament." Since there is writing on both sides of the fragment, it clearly belongs to an ancient book, or codex, not a scroll, she said.

The gospel of which the fragment is but a small part, which King and Luijendijk have named the Gospel of Jesus's Wife for reference purposes, was probably originally written in Greek, the two professors said, and only later translated into Coptic for use among congregations of Coptic-speaking Christians. King dated the time it was written to the second half of the second century because it shows close connections to other newly discovered gospels written at that time, especially the Gospel of Thomas, the Gospel of Mary, and the Gospel of Philip.

Like those gospels, it was probably ascribed to one or more of Jesus's closest followers, but the actual author would have remained unknown even if more of it had survived. As it stands, the remaining piece is too small to tell us anything more about who may have composed, read, or circulated the new gospel, King said.

The main topic of the dialogue between Jesus and his disciples is one that deeply concerned early Christians, who were asked to put loyalty to Jesus before their natal families, as the New Testament gospels show. Christians were talking about themselves as a family, with God the father, his son Jesus, and members as brothers and sisters. Twice in the tiny fragment, Jesus speaks of his mother and once of his wife -- one of whom is identified as "Mary." The disciples discuss whether Mary is worthy, and Jesus states that "she can be my disciple." Although less clear, it may be that by portraying Jesus as married, the Gospel of Jesus's Wife conveys a positive theological message about marriage and sexuality, perhaps similar to the Gospel of Philip's view that pure marriage can be an image of divine unity and creativity.

From the very beginning, Christians disagreed about whether they should marry or be celibate. But, King notes, it was not until around 200 that there is the earliest extant claim that Jesus did not marry, recorded by Clement of Alexandria. He wrote of Christians who claimed that marriage is fornication instituted by the devil, and says people should emulate Jesus in not marrying, King said. A decade or two later, she said, Tertullian of Carthage in North Africa declared that Jesus was "entirely unmarried," and Christians should aim for a similar condition. Yet Tertullian did not condemn sexual relations altogether, allowing for one marriage, although he denounced not only divorce, but even remarriage for widows and widowers as overindulgence. Nearly a century earlier, the New Testament letter of 1 Timothy had warned that people who forbid marriage are following the "doctrines of demons," although it didn't claim Jesus was married to support that point.

In the end, the view that dominated would claim celibacy as the highest form of Christian sexual virtue, while conceding marriage for the sake of reproduction alone. The Gospel of Jesus's Wife, if it was originally written in the late second century, suggests that the whole question of Jesus's marital status only came up over a century after Jesus died as part of vociferous debates about sexuality and marriage, King said. King noted that contemporary debates over celibate clergy, the roles of women, sexuality, and marriage demonstrate that the issues are far from resolved.

"The discovery of this new gospel," King said, "offers an occasion to rethink what we thought we knew by asking what role claims about Jesus's marital status played historically in early Christian controversies over marriage, celibacy, and family. Christian tradition preserved only those voices that claimed Jesus never married. The Gospel of Jesus's Wife now shows that some Christians thought otherwise."

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The above story is reprinted from materials provided by Harvard Divinity School. The original article was written by B. D. Colen, Harvard News Office.

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19 Sep, 2012

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How life arose on Earth: Researchers brew up organics on ice

ScienceDaily (Sep. 18, 2012) — Would you like icy organics with that? Maybe not in your coffee, but researchers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., are creating concoctions of organics, or carbon-bearing molecules, on ice in the lab, then zapping them with lasers. Their goal: to better understand how life arose on Earth.

In a new study published in the Astrophysical Journal Letters, the research team provides the first direct look at the organic chemistry that takes place on icy particles in the frigid reaches of our solar system, and in the even chillier places between stars. Scientists think that the basic ingredients of life, including water and organics, began their journey to Earth on these lonesome ice particles. The ice and organics would have found their way into comets and asteroids, which then fell to Earth, delivering "prebiotic" ingredients that could have jump-started life.

The various steps needed to go from icy organics to slime molds are not clear, but the new findings help explain how the process works. The lab experiments show that organic material can begin the processing it needs to become prebiotic -- while still frozen in ice.

"The very basic steps needed for the evolution of life may have started in the coldest regions of our universe," said Murthy Gudipati, lead author of the new study at JPL. "We were surprised to see organic chemistry brewing up on ice, at these very cold temperatures in our lab."

The organics looked at in the study are called polycyclic aromatic hydrocarbons, or PAHs for short. These carbon-rich molecules can be found on Earth as combustion products: for example, in barbecue pits, candle soot and even streaming out of the tail pipe of your car. They have also been spotted throughout space in comets, asteroids and more distant objects. NASA's Spitzer Space Telescope has detected PAHs in the swirling planet-forming disks around stars, in the spaces between stars and in remote galaxies.

Murthy and his colleague Rui Yang of JPL used their lab setup to mimic the environment of icy PAH molecules in the quiet cold of space, at temperatures as low as 5 Kelvin (minus 450 degrees Fahrenheit, or minus 268 degrees Celsius). First, they bombarded the particles with ultraviolet radiation similar to that from stars. Then, to determine the products of the chemical reaction, they used a type of laser system known as MALDI (for Matrix Assisted Laser Desorption and Ionization), which involves zapping the ice with both infrared and ultraviolet lasers.

The results revealed that the PAHs had transformed: they had incorporated hydrogen atoms into their structure and lost their circular, aromatic bonds, becoming more complex organics. According to Gudipati, this is the type of change that would need to occur if the material were to eventually become amino acids and nucleotides -- bits and pieces of protein and DNA, respectively.

"PAHs are strong, stubborn molecules, so we were surprised to see them undergoing these chemical changes at such freezing-cold temperatures," said Gudipati.

Another bonus for the research is that it might explain the mystery of why PAHs have not yet been identified on ice grains in space. While the hardy organics are pervasive in the cosmos as gases and hot dust, researchers have remained puzzled that their signatures do not show up on ice. The new findings show that PAHs, once they stick to the ice surface, are chemically transformed into other complex organics, explaining why they might not be seen.

While the new results teach us that life's journey could have already begun in the very cold regions of the universe, another question remains: Did it arise elsewhere beyond our sun, too? Researchers don't know, but studies like this one help the ongoing search for life beyond Earth.

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Journal Reference:

1. Murthy S. Gudipati, Rui Yang. In-Situ Probing of Radiation-Induced Processing of Organics in Astrophysical Ice Analogs—novel Laser Desorption Laser Ionization Time-Of-Flight Mass Spectroscopic Studies. The Astrophysical Journal, 2012; 756 (1): L24 DOI: 10.1088/2041-8205/756/1/L24

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19 Sep, 2012

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Quasars: Mileposts marking the universe's expansion

ScienceDaily (Sep. 18, 2012) — Scientists can't travel deep space the way Columbus sailed and charted the New World or Lewis and Clark mapped the west. But, researchers at Case Western Reserve University and two partnering institutions have found a possible way to map the spread and structure of the universe, guided by the light of quasars.

The technique, combined with the expected discovery of millions more far-away quasars over the next decade, could yield an unprecedented look back to a time shortly after the Big Bang, when the universe was a fraction the size it is today.

Researchers found the key while analyzing the visible light from a small group of quasars.

Patterns of light variation over time were consistent from one quasar to another when corrected for the quasar's redshift. This redshift occurs because an expanding universe carries the quasars away from us, thus making the light from them appear redder (hence the term), and also making the time variations appear to occur more slowly.

Turning this around, by measuring the rate at which a quasar's light appears to vary and comparing this rate to the standard rate at which quasars sampled actually vary, the researchers were able to infer the redshift of the quasar.

Knowing the quasar redshift enables the scientists to calculate the relative size of the universe when the light was emitted, compared to today.

"It appears we may have a useful tool for mapping out the expansion history of the universe," said Glenn Starkman, a physics professor at Case Western Reserve and an author of the study, published this summer in Physical Review Letters.

"If we could measure the redshifts of millions of quasars, we could use them to map the structures in the universe out to a large redshift."

The larger the redshift, the farther and older the light source.

The group plans to seek larger samples of quasars, to confirm the patterns are consistent and can be used to calculate their redshifts everywhere across the universe.

The work was led by De-Chang Dai, who earned his PhD working with Starkman and was most recently a member of the Astrophysics, Cosmology and Gravity Centre, University of Cape Town. The other authors include Amanda Weltman, PhD, a senior cosmology lecturer at the Centre, and brothers Branislav Stojkovic, a doctoral student in computer science and engineering, and Dejan Stojkovic, a physics professor at the State University of New York at Buffalo. Dejan Stojkovic also earned his PhD with Starkman and was later a visiting assistant professor at Case Western Reserve.

The scientists graphed the amount of light from 14 quasars recorded by the Massive Compact Halo Objects project, which sought evidence of dark matter in and around the Milky Way. Light from each quasar was measured repeatedly over hundreds of days.

Graphing revealed phases during which the amount of light would either increase or decrease in a linear fashion over an extended period of time.

Although other properties varied, the rate at which the measurable light changed was nearly identical among all 14 quasars, once scientists corrected for the effects of the universe's expansion.

"It's as if there was a dimmer switch on them with someone turning it to the left then the right," Starkman said. "The overall trend was surprisingly consistent."

This consistency of patterns enabled the scientists to accurately calculate the cosmological redshift of one quasar from another.

The researchers tested this capability in two ways.

They fit segments of the light curves, that is, the measured light over time, to straight lines. The slopes of the lines were consistent and appeared to be directly related to the quasars' redshifts.

By comparing corresponding slopes of 13 quasars with a known redshift value to the slopes of one other quasar, the researchers could calculate the redshift of the lone quasar within two percentage points.

In a second approach, the researchers took large sections of the light curves of two quasars and concentrated on the segments that matched most closely. By varying the ratio of the redshifts of the two quasars to try to get the best possible match of the two light curves, they were able to determine the ratio of the quasars' redshifts to within 1.5 percentage points.

Astronomers have used the bright light of supernovae with redshifts up to about 1.7 to measure the accelerating expansion of the universe. A star with a redshift of 1.7 would have been emitting that light when the universe was 2.7 times smaller than today.

Quasars are older and farther away and have been measured with redshifts of up to 7.1, which means they emitted the light we are seeing when the universe was as small as one-eighth the size it is today.

If this method of determining quasar redshifts proves applicable to higher redshift quasars, scientists could have millions of markers to trace the growth and evolution of structure and the expansion of the universe out to large distances and early times.

"This could help us learn about how gravity has assembled structure in the universe." Starkman said. "And, the rate of structure growth can help us determine whether dark energy or modified laws of gravity drive the accelerated expansion of the universe."

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The above story is reprinted from materials provided by Case Western Reserve University, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. De-Chang Dai, Glenn Starkman, Branislav Stojkovic, Dejan Stojkovic, Amanda Weltman. Using Quasars as Standard Clocks for Measuring Cosmological Redshift. Physical Review Letters, 2012; 108 (23) DOI: 10.1103/PhysRevLett.108.231302

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18 Sep, 2012

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Comet may have exploded over Canada 12,900 years ago after all

ScienceDaily (Sep. 18, 2012) — Did a massive comet explode over Canada 12,900 years ago, wiping out both beast and man in North America and propelling Earth back into an ice age?

That's a question that has been hotly debated by scientists since 2007, with the University of South Carolina's Topper archaeological site right in the middle of the comet impact controversy. However, a new study published Sept.17 in the Proceedings of the National Academy of Sciences (PNAS) provides further evidence that it may not be such a far-fetched notion.

USC archaeologist Albert Goodyear is a co-author on the study that upholds a 2007 PNAS study by Richard Firestone, a staff scientist at the Department of Energy's Lawrence Berkeley National Laboratory.

Firestone found concentrations of spherules (micro-sized balls) of metals and nano-sized diamonds in a layer of sediment dating 12,900 years ago at 10 of 12 archaeological sites that his team examined. The mix of particles is thought to be the result of an extraterrestrial object, such as a comet or meteorite, exploding in Earth's atmosphere. Among the sites examined was USC's Topper, one of the most pristine U.S. sites for research on Clovis, one of the earliest ancient peoples.

"This independent study is yet another example of how the Topper site with its various interdisciplinary studies has connected ancient human archaeology with significant studies of the Pleistocene," said Goodyear, who began excavating Clovis artifacts in 1984 at the Topper site in Allendale, S.C. "It's both exciting and gratifying."

Younger-Dryas is what scientists refer to as the period of extreme cooling that began around 12,900 years ago and lasted 1,300 years. While that brief ice age has been well-documented -- occurring during a period of progressive solar warming after the last ice age -- the reasons for it have long remained unclear. The extreme rapid cooling that took place can be likened to the 2004 sci-fi blockbuster movie "The Day After Tomorrow."

Firestone's team presented a provocative theory: that a major impact event -- perhaps a comet -- was the catalyst. His copious sampling and detailed analysis of sediments at a layer in the Earth dated to 12,900 years ago, also called the Younger-Dryas Boundary (YDB), provided evidence of micro-particles, such as iron, silica, iridium and nano-diamonds. The particles are believed to be consistent with a massive impact that could have killed off the Clovis people and the large North American animals of the day. Thirty-six species, including the mastodon, mammoth and saber-toothed tiger, went extinct.

The scientific community is rarely quick to accept new theories. Firestone's theory and support for it dominated the annual meeting of the American Geophysical Union and other gatherings of Paleoindian archaeologists in 2007 and 2008.

However, a 2009 study led by University of Wyoming researcher Todd Surovell failed to replicate Firestone's findings at seven Clovis sites, slowing interest and research progress to a glacial pace.

This new PNAS study refutes Surovell's findings with its lack of reported evidence.

"Surovell's work was in vain because he didn't replicate the protocol. We missed it too at first. It seems easy, but unless you follow the protocol rigorously, you will fail to detect these spherules. There are so many factors that can disrupt the process. Where Surovell found no spherules, we found hundreds to thousands," said Malcolm LeCompte, a research associate professor at Elizabeth City State University and lead author of the newly released PNAS article.

LeCompte began his independent study in 2008 using and further refining Firestone's sampling and sorting methods at two sites common to the three studies: Blackwater Draw in New Mexico and Topper. He also took samples at Paw Paw Cove in Maryland, a site common to Surovell's study.

At each site he found the same microscopic spherules, which are the diameter of a human hair and distinct in appearance. He describes their look as tiny black ball bearings with a marred surface pattern that resulted from being crystalized in a molten state and then rapidly cooled. His investigation also confirmed that the spherules were not of cosmic origin but were formed from earth materials due to an extreme impact.

LeCompte said it was Topper and Goodyear's collaboration, however, that yielded the most exciting results.

"What we had at Topper and nowhere else were pieces of manufacturing debris from stone tool making by the Clovis people. Topper was an active and ancient quarry at the time," LeCompte said. "Al Goodyear was instrumental in our approach to getting samples at Topper."

Goodyear showed LeCompte where the Clovis level was in order to accurately guide his sampling of sediments for the Younger Dryas Boundary layer. He advised him to sample around Clovis artifacts and then to carefully lift them to test the sediment directly underneath.

"If debris was raining down from the atmosphere, the artifacts should have acted as a shield preventing spherules from accumulating in the layer underneath. It turns out it really worked!" Goodyear said. "There were up to 30 times more spherules at and just above the Clovis surface than beneath the artifacts."

LeCompte said the finding is "critical and what makes the paper and study so exciting. The other sites didn't have artifacts because they weren't tool-making quarries like Topper."

While the comet hypothesis and its possible impact on Clovis people isn't resolved, Goodyear said this independent study clarifies why the Surovell team couldn't replicate the Firestone findings and lends greater credibility to the claim that a major impact event happened at the Younger Dryas Boundary 12,900 years ago.

"The so-called extra-terrestrial impact hypothesis adds to the mystery of what happened at the YDB with its sudden and unexplained reversion to an ice age climate, the rapid and seemingly simultaneous loss of many Pleistocene animals, such as mammoths and mastodons, as well as the demise of what archaeologists call the Clovis culture," Goodyear said. "There's always more to learn about the past, and Topper continues to function as a portal to these fascinating mysteries."

Goodyear joined USC's College of Arts and Sciences and its South Carolina Institute for Archaeology and Anthropology in 1974 to pursue prehistoric archaeology.

The Topper story

Al Goodyear, who conducts research through the University of South Carolina's S.C. Institute of Anthropology and Archaeology, began excavating Clovis artifacts along the Savannah River in Allendale County in 1984. It quickly became one of the most documented and well-known Clovis sites in the United States. In 1998, with the hope of finding evidence of a pre-Clovis culture earlier than the accepted 13,100 years, Goodyear began focused excavations on a site called Topper, located on the property of the Clariant Corp.

His efforts paid off. Goodyear unearthed small tools such as scrapers and blades made of the local chert that he believed to be tools of an ice age culture back some 16,000 years or more. His findings, as well as similar ones yielded at other pre-Clovis sites in North America, sparked great change and debate in the scientific community.

Goodyear reasoned that if Clovis and later peoples used the chert quarry along the Savannah River, the quarry could have been used by even earlier cultures.

Acting on a hunch in 2004, Goodyear dug even deeper into the Pleistocene terrace and found more artifacts of a pre-Clovis type buried in a layer of sediment stained with charcoal deposits. Radiocarbon dates of the burnt plant remains yielded ages of 50,000 years, which suggested man was in South Carolina long before the last ice age.

Goodyear's findings not only captured international media attention, but it has put the archaeology field in flux, opening scientific minds to the possibility of an even earlier pre-Clovis occupation of the Americas.

Since 2004, Goodyear has continued his Clovis and pre-Clovis excavations at Topper. With support of Clariant Corp. and SCANA, plus numerous individual donors, an expansive shelter and viewing deck now sit above the dig site to allow Goodyear and his team of graduate students and public volunteers to dig free from the heat and rain and to protect what may be the most significant early-man dig in America.

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The above story is reprinted from materials provided by University of South Carolina, via Newswise.

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Journal Reference:

1. M. A. LeCompte, A. C. Goodyear, M. N. Demitroff, D. Batchelor, E. K. Vogel, C. Mooney, B. N. Rock, A. W. Seidel. PNAS Plus: Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1208603109

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18 Sep, 2012

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Source: http://feeds.sciencedaily.com/~r/sciencedaily/top_news/top_science/~3/OMnV1g-flnI/120918111320.htm
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Higher levels of BPA in children and teens significantly associated with obesity

ScienceDaily (Sep. 18, 2012) — Researchers at NYU School of Medicine have revealed a significant association between obesity and children and adolescents with higher concentrations of urinary bisphenol A (BPA), a synthetic chemical recently banned by the U.S. Food and Drug Administration (FDA) from sippy cups and baby bottles. Still, the chemical continues to be used in aluminum cans, such as those containing soda.

The study appears in the September 19 issue of JAMA (Journal of the American Medical Association), dedicated to the theme of obesity.

"This is the first association of an environmental chemical in childhood obesity in a large, nationally representative sample," said lead investigator Leonardo Trasande, MD, MPP, associate professor of pediatrics and environmental medicine. "Our findings further demonstrate the need for a broader paradigm in the way we think about the obesity epidemic. Unhealthy diet and lack of physical activity certainly contribute to increased fat mass, but the story clearly doesn't end there."

BPA, a low-grade estrogen, was until recently found in plastic bottles labeled with the number 7 recycling symbol, and is still used as an internal coating for aluminum cans. Manufacturers say it provides an antiseptic function, but studies have shown the chemical disrupts multiple mechanisms of human metabolism that may increase body mass. BPA exposure has also been associated with cardiovascular disease, breast cancer, prostate cancer, neurological disorders, diabetes and infertility.

"In the U.S. population, exposure [to BPA] is nearly ubiquitous, with 92.6 percent of persons 6 years or older identified in the 2003-2004 National Health and Nutrition Examination Survey (NHANES) as having detectable BPA levels in their urine. A comprehensive, cross-sectional study of dust, indoor and outdoor air, and solid and liquid food in preschool-aged children suggested that dietary sources constitute 99 percent of BPA exposure," the investigators wrote.

Using a sample of nearly 3,000 children and adolescents, ages 6 through 19 years, randomly selected for measurement of urinary BPA concentration in the 2003-2008 NHANES, Dr. Trasande and his co-authors, Jan Blustein, MD, PhD, and Teresa Attina, MD, PhD, MPH, examined associations between urinary BPA concentrations and body mass.

After controlling for race/ethnicity, age, caregiver education, poverty to income ratio, sex, serum cotinine level, caloric intake, television watching, and urinary creatinine level, the researchers found children with the highest levels of urinary BPA had 2.6 times higher odds of being obese than those with the lowest measures of urinary BPA. Among the participants with the highest levels, 22.3 percent were obese compared with 10.3 percent of the participants with the lowest levels.

Further analyses showed this association to be statistically significant in only one racial subpopulation, white children and adolescents. The researchers also found that obesity was not associated with exposure to other environmental phenols commonly used in other consumer products, such as sunscreens and soaps.

"Most people agree the majority of BPA exposure in the United States comes from aluminum cans," Dr. Trasande said. "This data adds to already existing concerns about BPA and further supports the call to limit exposure of BPA in this country, especially in children. Removing it from aluminum cans is probably one of the best ways we can limit exposure. There are alternatives that manufacturers can use to line aluminum cans."

The researchers wrote in their study that advocates and policy makers have long been concerned about BPA exposure. "We note the recent FDA ban of BPA in baby bottles and sippy cups, yet our findings raise questions about exposure to BPA in consumer products used by older children. Last year, the FDA declined to ban BPA in aluminum cans and other food packaging, announcing 'reasonable steps to reduce human exposure to BPA in the human food supply' and noting that it will continue to consider evidence on the safety of the chemical. Carefully conducted longitudinal studies that assess the associations identified here will yield evidence many years in the future."

# # #

EDITOR'S NOTE: (JAMA. 2012;308[11]:1113-1121. Available pre-embargo to the media at http://media.jamanetwork.com)

About NYU School of Medicine:
NYU School of Medicine is one of the nation's preeminent academic institutions dedicated to achieving world class medical educational excellence. For 170 years, NYU School of Medicine has trained thousands of physicians and scientists who have helped to shape the course of medical history and enrich the lives of countless people. An integral part of NYU Langone Medical Center, the School of Medicine at its core is committed to improving the human condition through medical education, scientific research and direct patient care. The School also maintains academic affiliations with area hospitals, including Bellevue Hospital, one of the nation's finest municipal hospitals where its students, residents and faculty provide the clinical and emergency care to New York City's diverse population, which enhances the scope and quality of their medical education and training. Additional information about the NYU School of Medicine is available at http://school.med.nyu.edu/.

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Journal Reference:

1. Trasande L, Attina TM, Blustein J. Association Between Urinary Bisphenol A Concentration and Obesity Prevalence in Children and Adolescents. JAMA, 2012; 308 (11): 1113-1121 DOI: 10.1001/2012.jama.11461

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18 Sep, 2012

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How birds master courtship songs: Zebra finches shed light on brain circuits and learning

ScienceDaily (Sep. 17, 2012) — By studying how birds master songs used in courtship, scientists at Duke University have found that regions of the brain involved in planning and controlling complex vocal sequences may also be necessary for memorizing sounds that serve as models for vocal imitation.

In a paper appearing in the September 2012 issue of the journal Nature Neuroscience, researchers at Duke and Harvard universities observed the imitative vocal learning habits of male zebra finches to pinpoint which circuits in the birds' brains are necessary for learning their songs.

Knowing which brain circuits are involved in learning by imitation could have broader implications for diagnosing and treating human developmental disorders, the researchers said. The finding shows that the same circuitry used for vocal control also participates in auditory learning, raising the possibility that vocal circuits in our own brain also help encode auditory experience important to speech and language learning.

"Birds learn their songs early in life by listening to and memorizing the song of their parent or other adult bird tutor, in a process similar to how humans learn to speak," said Todd Roberts, Ph.D., the study's first author and postdoctoral associate in neurobiology at Duke University. "They shape their vocalizations to match or copy the tutor's song."

A young male zebra finch, Roberts said, learns his song in two phases -- memorization and practice. He said the pupil can rapidly memorize the song of an adult tutor, but may need to practice singing as many as 100,000 times in a 45-day period in order to accurately imitate the tutor's song.

During the study, voice recognition software was paired with optogenetics, a technology that combines genetics and optics to control the electrical activity of nerve cells, or neurons. Using these tools, the researchers were able to scramble brain signals coordinating small sets of neurons in the young bird's brain for a few hundred milliseconds while he was listening to his teacher, enabling them to test which brain regions were important during the learning process.

The study's results show that a song pre-motor region in the pupil's brain plays two different roles. Not only does it control the execution of learned vocal sequences, it also helps encode information when the pupil is listening to his tutor, Roberts said.

"We learn some of our most interesting behaviors, including language, speech and music, by listening to an appropriate model and then emulating this model through intensive practice," said senior author Richard Mooney, Ph.D., professor of neurobiology and member of the Duke Institute for Brain Sciences. "A traditional view is that this two-step sequence -- listening followed by motor rehearsal -- first involves activation by the model of brain regions important to auditory processing. This is followed days, weeks or even months later by activation of brain regions important to motor control."

"Here we found that a brain region that is essential to the motor control of song also has an essential role in helping in auditory learning of the tutor song," Mooney said. "This finding raises the possibility that the premotor circuits important to planning and controlling speech in our own brains also play an important role in auditory learning of speech sounds during early infancy." This brain region, known as Broca's area, is located in the frontal lobe of the left hemisphere.

The research has implications for the role of premotor circuits in the brain and suggests that these areas are important targets to consider when assessing developmental disorders that affect speech, language and other imitative behaviors in humans, Roberts said.

In addition to Roberts and Mooney, study authors include Sharon M. H. Gobes of Harvard University and Wellesley College; Malavika Murugan of Duke; and Bence P. Ölveczky of Harvard.

The research was supported by grants from the National Science Foundation and the National Institutes of Health (R01 DC02524) to Richard Mooney; and grants from NIH (R01 NS066408) and the Klingenstein, Sloan and McKnight Foundations to Bence P. Ölveczky; and a Rubicon fellowship from the Netherlands Organization for Scientific Research to Sharon M.H. Gobes.

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The above story is reprinted from materials provided by Duke University Medical Center, via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Todd F Roberts, Sharon M H Gobes, Malavika Murugan, Bence P Ölveczky, Richard Mooney. Motor circuits are required to encode a sensory model for imitative learning. Nature Neuroscience, 2012; DOI: 10.1038/nn.3206

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

18 Sep, 2012

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Source: http://feeds.sciencedaily.com/~r/sciencedaily/top_news/top_science/~3/IIk0D0jpgi0/120917173101.htm
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