Soft Matter Offers New Ways To Study How Ordered Materials Arrange Themselves

A fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials.

The doughnut-shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers. Droplets in this toroidal shape made of a liquid crystal – the same type of material used in laptop displays – may have properties very different from those of spherical droplets made from the same material.

A toroidal droplet made of a nematic liquid crystal material is shown inside a polymeric material. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by the surrounding springy material made of polymers.

Credit: Georgia Tech Photo: Gary Meek

While researchers at the Georgia Institute of Technology don't have a specific application for the doughnut-shaped droplets yet, they believe the novel structures offer opportunities to study many interesting problems, from looking at the properties of ordered materials within these confined spaces to studying how geometry affects how cells behave.

"Our experiments provide a fresh approach to the way that people have been looking at these kinds of problems, which is mainly theoretical. We are doing experiments with toroids whose geometry can be precisely controlled in the lab," said Alberto Fernandez-Nieves, an assistant professor in the Georgia Tech School of Physics. "This work opens up a new way to experimentally look at problems that nobody has been able to study before. The properties of toroidal surfaces are very different, from a general point of view, from those of spherical surfaces."

Development of these "stable nematic droplets with handles" was described May 20 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS). The research has been sponsored by the National Science Foundation (NSF), and also involves researchers at the Lorentz Institute for Theoretical Physics at Leiden University in The Netherlands and at York University in the United Kingdom.

Droplets normally form spherical shapes to minimize the surface area required to contain a given volume of liquid. Though they appear to be simple, when an ordered material like a crystal or a liquid crystal lives on the surface of a sphere, it provides interesting challenges to mathematicians and theoretical physicists.

A physicist who focuses on soft condensed matter, Fernandez-Nieves had long been interested in the theoretical aspects of curved surfaces. Working with graduate research assistant Ekapop Pairam and postdoctoral fellow Jayalakshmi Vallamkondu, he wanted to extend the theoretical studies into the experimental world for a system of toroidal shapes. 

Georgia Tech assistant professor Alberto Fernandez-Nieves examines the experimental setup used to create toroidal droplets of nematic liquid crystal materials. The injection needle is shown above the cuvette containing the polymeric material, which rests on the rotation stage.

Credit: Georgia Tech Photo: Gary Meek

But could doughnut-shaped droplets be made in the lab?

The partial answer came from churros Fernandez-Nieves ate as a child growing up in Spain. These "Spanish doughnuts" – actually spirals – are made by injecting dough into hot oil while the dough is spun and fried.

In the lab at a much smaller size scale, the researchers found they could use a similar process with two immiscible liquids such as glycerine or water and oil, a needle and a magnetically-controlled rotating stage. A droplet of glycerine is injected into the rotating stage containing the oil. In certain conditions, a jet forms at the needle, which closes up into a torus because of the imposed rotation.

"You can control the two relevant curvatures of the torus," explained Fernandez-Nieves. "You can control how large it is because you can move the needle with respect to the rotation axis. You can also infuse more volume to make the torus thicker."

If the stage is then turned off, however, the drop of glycerine quickly loses its doughnut shape as surface tension forces it to become a traditional spherical droplet. To maintain the toroidal shape, Fernandez-Nieves and his collaborators replace the surrounding oil with a springy polymeric material; the springy character of this material provides a force that can overcome surface tension forces.

"When you are making the toroid, the forces on the needle are large enough that the surrounding material behaves as a fluid," he explained. "Once you stop, the elasticity of the outside fluid overcomes surface tension and that freezes the structure in place."

The researchers have been using the doughnut shapes to study how liquid crystal materials, which are well known for their applications in laptop displays, organize inside the torus. These materials have degrees of order beyond those of simple liquids such as water. For these materials, the toroidal shape provides a new set of study opportunities from both theoretical and experimental perspectives.

"This changes how you think about a liquid inside a container," said Fernandez-Nieves. "The materials will still adopt the shape of the container, but its energy will be different depending on the shape. The materials feel distortions and will try to minimize them. In a given shape, the molecules in these materials will rearrange themselves to minimize these distortions."

Among the surprises is that the nematic droplets created with toroidal shapes become chiral, that is, they adopt a certain twisting direction and break their mirror symmetry.

"In our case, the materials we are using are not chiral under normal circumstances," he noted. "This was a surprise to us, and it has to do with how we are confining the molecules." 

Georgia Tech graduate research assistant Ekapop Pairam examines the experimental setup used to create toroidal droplets of nematic liquid crystal materials. The injection needle is shown above the cuvette containing the polymeric material, which rests on the rotation stage.

Credit: Georgia Tech Photo: Gary Meek

Beyond looking at the dynamics of creating the droplets and how ordered materials behave when the torus transforms into a sphere, Fernandez-Nieves and colleagues are also exploring potential biological applications, applying electrical fields to the droplets, and sharing the unique structures with scientists at other institutions.

"This is the first time that stable nematic droplets have been generated with handles, and we have exploited that to look at the nematic organization inside those spaces," said Fernandez-Nieves. "Our experiments open up a versatile new approach for generating handled droplets made of an ordered material that can self-assemble into interesting and unexpected structures when confined to these non-spherical spaces. Now that theoreticians realize we can generate and study these systems, there may be much more development in this area."

Contacts and sources:
John Toon
Georgia Institute of Technology

In addition to those already mentioned, the paper's authors included V. Koning, B.C. van Zuiden and V. Vitelli from Leiden University, M.A. Bates from the University of York in the United Kingdom, and P.W. Ellis from Georgia Tech.

The research described here has been sponsored by the National Science Foundation under CAREER award DMR-0847304. The findings and conclusions are those of the authors and do not necessarily represent the official views of the National Science Foundation.

Citation: E. Pairam, et al., "Stable nematic droplets with handles," (Proceedings of the National Academy of Sciences, 2013)

Early-Life Traffic-Related Air Pollution Exposure Linked To Hyperactivity

Early-life exposure to traffic-related air pollution was significantly associated with higher hyperactivity scores at age 7, according to new research from the University of Cincinnati (UC) and Cincinnati Children's Hospital Medical Center.

The research is detailed in a study being published Tuesday, May 21, inEnvironmental Health Perspectives, a peer-reviewed open access journal published by the National Institute of Environmental Health Sciences, an institute within the National Institutes of Health (NIH).

The research was conducted by faculty members from the UC College of Medicine's Department of Environmental Health in collaboration with Cincinnati Children's. Nicholas Newman, DO, director of the Pediatric Environmental Health and Lead Clinic at Cincinnati Children's, was the study's first author.

"There is increasing concern about the potential effects of traffic-related air pollution on the developing brain," Newman says. "This impact is not fully understood due to limited epidemiological studies.

"To our knowledge, this is the largest prospective cohort with the longest follow-up investigating early life exposure to traffic-related air pollution and neurobehavioral outcomes at school age." Scientists believe that early life exposures to a variety of toxic substances are important in the development of problems later in life.

Newman and his colleagues collected data on traffic-related air pollution (TRAP) from the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), a long-term epidemiological study examining the effects of traffic particulates on childhood respiratory health and allergy development. Funded by the National Institute of Environmental Health Sciences, CCAAPS is led by Grace LeMasters, PhD, of the environmental health department. Study participants—newborns in the Cincinnati metropolitan area from 2001 through 2003—were chosen based on family history and their residence being either near or far from a major highway or bus route.

Children were followed from infancy to age 7, when parents completed the Behavioral Assessment System for Children, 2nd Edition (BASC-2), assessing attention deficit hyperactivity disorder (ADHD) and related symptoms including attention problems, aggression, conduct problems and atypical behavior. Of the 762 children initially enrolled in the study, 576 were included in the final analysis at 7 years of age.

Results showed that children who were exposed to the highest third amount of TRAP during the first year of life were more likely to have hyperactivity scores in the "at risk" range when they were 7 years old. The "at risk" range for hyperactivity in children means that they need to be monitored carefully because they are at risk for developing clinically important symptoms.

"Several biological mechanisms could explain the association between hyperactive behaviors and traffic-related air pollution," Newman says, including narrowed blood vessels in the body and toxicity in the brain's frontal cortex.

Newman notes that the higher air pollution exposure was associated with a significant increase in hyperactivity only among those children whose mothers had greater than a high school education. Mothers with higher education may expect higher achievement, he says, affecting the parental report of behavioral concerns.

"The observed association between traffic-related air pollution and hyperactivity may have far-reaching implications for public health," Newman says, noting that studies have shown that approximately 11 percent of the U.S. population lives within 100 meters of a four-lane highway and that 40 percent of children attend school within 400 meters of a major highway.

"Traffic-related air pollution is one of many factors associated with changes in neurodevelopment, but it is one that is potentially preventable."

LeMasters, Patrick Ryan, PhD, Linda Levin, PhD, David Bernstein, MD, Gurjit Khurana Hershey, MD, PhD, James Lockey, PhD, Manuel Villareal, MD, Tiina Reponen, PhD, Sergey Grinshpun, PhD, Heidi Sucharew, PhD, and Kim Dietrich, PhD, were co-authors of the study.

Funding was provided by NIEHS and the National Institute for Occupational Safety and Health (NIOSH).


Contacts and sources:
Keith Herrell
University of Cincinnati Academic Health Center

Making Gold Green: New Non-Toxic Method For Mining Gold

Scientists launch ‘nano gold rush’ by replacing cyanide with cornstarch.
Northwestern University scientists have struck gold in the laboratory. They have discovered an inexpensive and environmentally benign method that uses simple cornstarch -- instead of cyanide -- to isolate gold from raw materials in a selective manner.

This green method extracts gold from crude sources and leaves behind other metals that are often found mixed together with the crude gold. The new process also can be used to extract gold from consumer electronic waste.

A modern day gold rush! A new method developed at Northwestern bypasses the use of toxic cyanide for gold purification by using an eco-friendly sugar (cyclodextrin) derived from starch. 

Illustration by Aleksandr Bosoy.

Current methods for gold recovery involve the use of highly poisonous cyanides, often leading to contamination of the environment. Nearly all gold-mining companies use this toxic gold leaching process to sequester the precious metal.

“The elimination of cyanide from the gold industry is of the utmost importance environmentally,” said Sir Fraser Stoddart, the Board of Trustees Professor of Chemistry in the Weinberg College of Arts and Sciences. “We have replaced nasty reagents with a cheap, biologically friendly material derived from starch.”

Sir Fraser’s team discovered the process by accident, using simple test tube chemistry. A series of rigorous follow-up investigations provided evidence for the competitive strength of the new procedure.

The findings are published today (May 14) in the online journalNature Communications.

Zhichang Liu, a postdoctoral fellow in Stoddart’s lab and first author of the paper, took two test tubes containing aqueous solutions -- one of the starch-derived alpha-cyclodextrin, the other of a dissolved gold (Au) salt (called aurate) -- and mixed them together in a beaker at room temperature.

Liu was trying to make an extended, three-dimensional cubic structure, which could be used to store gases and small molecules. Unexpectedly, he obtained needles, which formed rapidly upon mixing the two solutions.

“Initially, I was disappointed when my experiment didn’t produce cubes, but when I saw the needles, I got excited,” Liu said. “I wanted to learn more about the composition of these needles.”

“Nature decided otherwise,” said Stoddart, a senior author of the paper. “The needles, composed of straw-like bundles of supramolecular wires, emerged from the mixed solutions in less than a minute.”

After discovering the needles, Liu screened six different complexes -- cyclodextrins composed of rings of six (alpha), seven (beta) and eight (gamma) glucose units, each combined with aqueous solutions of potassium tetrabromoaurate (KAuBr4) or potassium tetrachloroaurate (KAuCl4).

He found that it was alpha-cyclodextrin, a cyclic starch fragment composed of six glucose units, that isolates gold best of all.

“Alpha-cyclodextrin is the gold medal winner,” Stoddart said. “Zhichang stumbled on a piece of magic for isolating gold from anything in a green way.”

Alkali metal salt waste from this new method is relatively environmentally benign, Stoddart said, while waste from conventional methods includes toxic cyanide salts and gases. The Northwestern procedure is also more efficient than current commercial processes.

The supramolecular nanowires, each 1.3 nanometers in diameter, assemble spontaneously in a straw-like manner. In each wire, the gold ion is held together in the middle of four bromine atoms, while the potassium ion is surrounded by six water molecules; these ions are sandwiched in an alternating fashion by alpha-cyclodextrin rings. Around 4,000 wires are bundled parallel to each other and form individual needles that are visible under an electron microscope.

“There is a lot of chemistry packed into these nanowires,” Stoddart said. “The elegance of the composition of single nanowires was revealed by atomic force microscopy, which throws light on the stacking of the individual donut-shaped alpha-cyclodextrin rings.”

The atomic detail of the single supramolecular wires and their relative disposition within the needles was uncovered by single crystal X-ray crystallography.

The research -- a prime example of serendipity at work, brought to fruition by contemporary fundamental science -- is poised to find technological application. This basic science has been forged by the team into a practical labscale process for the isolation of gold from scrap alloys.

The Defense Threat Reduction Agency and the National Science Foundation supported the research.

Contacts and sources: 

Megan Fellman

Northwestern University 

The paper is titled “Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin.” In addition to Stoddart and Liu, the other authors of the paper are Marco Frasconi, Juying Lei, Zachary J. Brown, Zhixue Zhu, Dennis Cao, Julien Iehl, Guoliang Liu, Albert C. Fahrenbach, Omar K. Farha, Joseph T. Hupp and Chad A. Mirkin, all from Northwestern, and Youssry Y. Botros of Intel Labs.

Salt Levels Dangerously High In Processed Food and Fast Food Industries

The dangerously high salt levels in processed food and fast food remain essentially unchanged, despite numerous calls from public and private health agencies for the food industry to voluntarily reduce sodium levels, reports a new Northwestern Medicine study conducted with the Center for Science in the Public Interest.

Credit: Wikipedia

The study, published May 13 in JAMA Internal Medicine, assessed the sodium content in selected processed foods and in fast-food restaurants in 2005, 2008 and 2011. The main finding was that the sodium content of food is as high as ever.

“The voluntary approach has failed,“ said Stephen Havas, M.D., corresponding author of the paper and a research professor of preventive medicine at Northwestern University Feinberg School of Medicine. “The study demonstrates that the food industry has been dragging its feet and making very few changes. This issue will not go away unless the government steps in to protect the public. The amount of sodium in our food supply needs to be regulated.”

Excess sodium prematurely kills as many as 150,000 people in the U.S. each year. About 90 percent of the U.S. population develops high blood pressure and high salt in the diet is a major cause. High blood pressure increases the risk of developing heart attacks and strokes, often resulting in death or disability.

“High salt content in food benefits the food industry,” Havas said. “High salt masks the flavor of ingredients that are often not the best quality and also stimulates people to drink more soda and alcohol, which the industry profits from.”

A typical American consumes an average of almost two teaspoons a day of salt, vastly higher than the recommended amount of three-fifths of a teaspoon or no more than 1,500 milligrams, as recommended by the American Heart Association. About 80 percent of our daily sodium consumption comes from eating processed or restaurant foods. Very little comes from salt we add to food.

“The only way for most people to meet the current sodium recommendation is to cook from scratch and not use salt,” Havas said. “But that’s not realistic for most people.”

The FDA needs to begin regulating food processors and the restaurant industry -- as has been recommended by the Institute of Medicine and others –- as soon as possible, Havas said.

Havas noted that our taste buds rapidly adapt to less salt. “If it’s reduced by 20 percent a year, no one would know the difference,” he said.

The study found that between 2005 and 2011, the sodium content in 402 processed foods declined by approximately 3.5 percent, while the sodium content in 78 fast-food restaurant products increased by 2.6 percent. Although some products showed decreases of at least 30 percent, a greater number of products showed increases of at least 30 percent. The predominant finding was the absence of any appreciable or statistically significant changes in sodium content during six years.

Contacts and sources: 

Marla Paul

Northwestern University

Cosmic Impact Wiped Out Woolly Mammoths: New Evidence For Global Destruction From Outer Space 12,800 Year Ago, Tons Of Spherules Found On 4 Continents

Herds of woolly mammoths once shook the earth beneath their feet, sending humans scurrying across the landscape of prehistoric Ohio. But then something much larger shook the Earth itself, and at that point these mega mammals’ days were numbered.

Something – global-scale combustion caused by a comet scraping our planet’s atmosphere or a meteorite slamming into its surface – scorched the air, melted bedrock and altered the course of Earth’s history. Exactly what it was is unclear, but this event jump-started what Kenneth Tankersley, an assistant professor of anthropology and geology at the University of Cincinnati, calls the last gasp of the last ice age.

The University of Cincinnati’s Ken Tankersley used excavations at Sheriden Cave in Wyandot Ohio in his research on the Younger Dryas.

Credit: University of Cincinnati

“Imagine living in a time when you look outside and there are elephants walking around in Cincinnati,” Tankersley says. “But by the time you’re at the end of your years, there are no more elephants. It happens within your lifetime.”

Tankersley explains what he and a team of international researchers found may have caused this catastrophic event in Earth’s history in their research, “Evidence for Deposition of 10 Million Tonnes of Impact Spherules Across Four Continents 12,800 Years Ago,” which was published in the Proceedings of the National Academy of Sciences. The prestigious journal was established in 1914 and publishes innovative research reports from a broad range of scientific disciplines. Tankersley’s research also was included in the History Channel series “The Universe: When Space Changed History” and will be featured in an upcoming film for The Weather Channel.

This research might indicate that it wasn’t the cosmic collision that extinguished the mammoths and other species, Tankersley says, but the drastic change to their environment.

“The climate changed rapidly and profoundly. And coinciding with this very rapid global climate change was mass extinctions.”

PUTTING A FINGER ON THE END OF THE ICE AGE

Tankersley is an archaeological geologist. He uses geological techniques, in the field and laboratory, to solve archaeological questions. He’s found a treasure trove of answers to some of those questions in Sheriden Cave in Wyandot County, Ohio. It’s in that spot, 100 feet below the surface, where Tankersley has been studying geological layers that date to the Younger Dryas time period, about 13,000 years ago.

The Younger Dryas Boundary strewnfield shown (red) with YDB sites as red dots and those by eight independent groups as blue dots. Also shown is the largest known impact strewnfield, the Australasian (purple).

Credit: University of Cincinnati

About 12,000 years before the Younger Dryas, the Earth was at the Last Glacial Maximum – the peak of the Ice Age. Millennia passed, and the climate began to warm. Then something happened that caused temperatures to suddenly reverse course, bringing about a century’s worth of near-glacial climate that marked the start of the geologically brief Younger Dryas.

There are only about 20 archaeological sites in the world that date to this time period and only 12 in the United States – including Sheriden Cave.

“There aren’t many places on the planet where you can actually put your finger on the end of the last ice age, and Sheriden Cave is one of those rare places where you can do that,” Tankersley says.

ROCK-SOLID EVIDENCE OF COSMIC CALAMITY

In studying this layer, Tankersley found ample evidence to support the theory that something came close enough to Earth to melt rock and produce other interesting geological phenomena. Foremost among the findings were carbon spherules. These tiny bits of carbon are formed when substances are burned at very high temperatures. The spherules exhibit characteristics that indicate their origin, whether that’s from burning coal, lightning strikes, forest fires or something more extreme. Tankersley says the ones in his study could only have been formed from the combustion of rock.

An environmental scanning electron microscope image of a carbon spherule from Sheriden Cave.

Credit: University of Cincinnati

The spherules also were found at 17 other sites across four continents – an estimated 10 million metric tons’ worth – further supporting the idea that whatever changed Earth did so on a massive scale. It’s unlikely that a wildfire or thunderstorm would leave a geological calling card that immense – covering about 50 million square kilometers.

“We know something came close enough to Earth and it was hot enough that it melted rock – that’s what these carbon spherules are. In order to create this type of evidence that we see around the world, it was big,” Tankersley says, contrasting the effects of an event so massive with the 1883 volcanic explosion on Krakatoa in Indonesia. “When Krakatoa blew its stack, Cincinnati had no summer. Imagine winter all year-round. That’s just one little volcano blowing its top.”

Other important findings include:

Micrometeorites: smaller pieces of meteorites or particles of cosmic dust that have made contact with the Earth’s surface.

Nanodiamonds: microscopic diamonds formed when a carbon source is subjected to an extreme impact, often found in meteorite craters.

Lonsdaleite: a rare type of diamond, also called a hexagonal diamond, only found in non-terrestrial areas such as meteorite craters.

THREE CHOICES AT THE CROSSROADS OF OBLIVION

Tankersley says while the cosmic strike had an immediate and deadly effect, the long-term side effects were far more devastating – similar to Krakatoa’s aftermath but many times worse – making it unique in modern human history.

An image of the X-ray diffraction pattern of lonsdaleite, or hexagonal diamond, from Sheriden Cave.

Credit: University of Cincinnati

In the cataclysm’s wake, toxic gas poisoned the air and clouded the sky, causing temperatures to plummet. The roiling climate challenged the existence of plant and animal populations, and it produced what Tankersley has classified as “winners” and “losers” of the Younger Dryas. He says inhabitants of this time period had three choices: relocate to another environment where they could make a similar living; downsize or adjust their way of living to fit the current surroundings; or swiftly go extinct. “Winners” chose one of the first two options while “losers,” such as the wooly mammoth, took the last.

“Whatever this was, it did not cause the extinctions,” Tankersley says. “Rather, this likely caused climate change. And climate change forced this scenario: You can move, downsize or you can go extinct.”

Humans at the time were just as resourceful and intelligent as we are today. If you transported a teenager from 13,000 years ago into the 21st century and gave her jeans, a T-shirt and a Facebook account, she’d blend right in on any college campus. Back in the Younger Dryas, with mammoth off the dinner table, humans were forced to adapt – which they did to great success.

WEATHER REPORT: CLOUDY WITH A CHANCE OF EXTINCTION

That lesson in survivability is one that Tankersley applies to humankind today.

“Whether we want to admit it or not, we’re living right now in a period of very rapid and profound global climate change. We’re also living in a time of mass extinction,” Tankersley says. “So I would argue that a lot of the lessons for surviving climate change are actually in the past.”

He says it’s important to consider a sustainable livelihood. Humans of the Younger Dryas were hunter-gatherers. When catastrophe struck, these humans found news ways and new places to hunt game and gather wild plants. Evidence found in Sheriden Cave shows that most of the plants and animals living there also endured. Of the 70 species known to have lived there before the Younger Dryas, 68 were found there afterward. The two that didn’t make it were the giant beaver and the flat-headed peccary, a sharp-toothed pig the size of a black bear.

Tankersley also cautions that the possibility of another massive cosmic event should not be ignored. Like earthquakes, tsunamis and volcanoes, these types of natural disasters do happen, and as history has shown, it can be to devastating effect.

“One additional catastrophic change that we often fail to think about – and it’s beyond our control – is something from outer space,” Tankersley says. “It’s a reminder of how fragile we are. Imagine an explosion that happened today that went across four continents. The human species would go on. But it would be different. It would be a game changer.”

BREAKING BARRIERS AND WORKING TOGETHER TOWARD REAL CHANGE

Tankersley is a member of UC’s Quaternary and Anthropocene Research Group (QARG), an interdisciplinary conglomeration of researchers dedicated to undergraduate, graduate and professional education, experience-based learning and research in Quaternary science and study of the Anthropocene. He’s proud to be working with his students on projects that, when he was in their shoes, were considered science fiction.

Collaborative efforts such as QARG help break down long-held barriers between disciplines and further position UC as one of the nation’s top public research universities.

“What’s exciting about UC and why our university is producing so much, is we have scientists who are working together and it’s this area of overlap that is so interesting,” Tankersley says. “There’s a real synergy about innovative, transformative, transdisciplinary science and education here. These are the things that really make people take notice. It causes real change in our world.”

Additional contributors to Tankersley’s research paper were James H. Wittke and Ted E. Bunch, Northern Arizona University; James C. Weaver, Harvard University; Douglas J. Kennett, Pennsylvania State University; Andrew M.T. Moore, Rochester Institute of Technology; Gordon C. Hillman, University College London; Albert C. Goodyear, University of South Carolina, Columbia; Christopher R. Moore, University of South Carolina, New Ellenton; Randolph I. Daniel Jr., East Carolina University; Jack H. Ray and Neal Lopinot, Missouri State University; David Ferraro, Viejo California Associated; Isabel Israde-Alcántara, Universidad Michoacana de San Nicólas de Hidalgo; James L. Bischoff, U.S. Geological Survey; Paul S. DeCarli, SRI International; Robert E. Hermes, Los Alamos National Laboratory; Han Kloosterman, Exploration Geologist; Zsolt Revay, Technische Universität München; George A. Howard, Restoration Systems; David R. Kimbel, Kimstar Research; Gunther Kletetschka and Ladislav Nabelek, Czech Academy of Science of the Czech Republic; Carl Lipo and Sachiko Sakai, California State University; Allen West, GeoScience Consulting; James P. Kennett, University of California, Santa Barbara; and Richard B. Firestone, Lawrence Berkeley National Laboratory.

Funding for this study was partially provided by the Court Family Foundation, UC’s Charles Phelps Taft Research Center, the University of Cincinnati Research Council, the U.S. Department of Energy and the U.S. National Science Foundation.


Contacts and sources:
Tom Robinette
University of Cincinnati

'Whodunnit' Of Irish Potato Famine Solved

It is the first time scientists have decoded the genome of a plant pathogen and its plant host from dried herbarium samples. This opens up a new area of research to understand how pathogens evolve and how human activity impacts the spread of plant disease.

Phytophthora infestans changed the course of history. Even today, the Irish population has still not recovered to pre-famine levels. "We have finally discovered the identity of the exact strain that caused all this havoc", says Hernán Burbano from the Max Planck Institute for Developmental Biology.

This is a potato specimen from the Kew Garden herbarium, collected in 1847, during the height of the Irish famine. The legend reads "Botrytis infestans", because it was not known yet thatPhytophthora does not belong to the mildew causing Botrytis fungi.

Credit: Marco Thines/Senckenberg Gesellschaft für Naturforschung

For research to be published in eLife, a team of molecular biologists from Europe and the US reconstructed the spread of the potato blight pathogen from dried plants. Although these were 170 to 120 years old, they were found to have many intact pieces of DNA.

"Herbaria represent a rich and untapped source from which we can learn a tremendous amount about the historical distribution of plants and their pests - and also about the history of the people who grew these plants," according to Kentaro Yoshida from The Sainsbury Laboratory in Norwich.

The researchers examined the historical spread of the fungus-like oomycete Phytophthora infestans, known as the Irish potato famine pathogen. A strain called US-1 was long thought to have been the cause of the fatal outbreak. The current study concludes that a strain new to science was responsible. While more closely related to the US-1 strain than to other modern strains, it is unique. "Both strains seem to have separated from each other only years before the first major outbreak in Europe," says Burbano.

The researchers compared the historic samples with modern strains from Europe, Africa and the Americas as well as two closely related Phytophthora species. The scientists were able to estimate with confidence when the various Phytophthora strains diverged from each other during evolutionary time. The HERB-1 strain ofPhytophthora infestans likely emerged in the early 1800s and continued its global conquest throughout the 19th century. Only in the twentieth century, after new potato varieties were introduced, was HERB-1 replaced by another Phytophthora infestans strain, US-1.

The scientists found several connections with historic events. The first contact between Europeans and Americans in Mexico in the sixteenth century coincides with a remarkable increase in the genetic diversity of Phytophthora. The social upheaval during that time may have led to a spread of the pathogen from its center of origin in Toluca Valley, Mexico. This in turn would have accelerated its evolution.

The international team came to these conclusions after deciphering the entire genomes of 11 historical samples of Phytophthora infestans from potato leaves collected over more than 50 years. These came from Ireland, the UK, Europe and North America and had been preserved in the herbaria of the Botanical State Collection Munich and the Kew Gardens in London.

"Both herbaria placed a great deal of confidence in our abilities and were very generous in providing the dried plants," said Marco Thines from the Senckenberg Museum and Goethe University in Frankfurt, one of the co-authors of this study. "The degree of DNA preservation in the herbarium samples really surprised us," adds Johannes Krause from the University of Tübingen, another co-author. Because of the remarkable DNA quality and quantity in the herbarium samples, the research team could evaluate the entire genome of Phytophthora infestans and its host, the potato, within just a few weeks.

Crop breeding methods may impact on the evolution of pathogens. This study directly documents the effect of plant breeding on the genetic makeup of a pathogen.

"Perhaps this strain became extinct when the first resistant potato varieties were bred at the beginning of the twentieth century," speculates Yoshida. "What is for certain is that these findings will greatly help us to understand the dynamics of emerging pathogens. This type of work paves the way for the discovery of many more treasures of knowledge hidden in herbaria."


Contacts and sources:
Dr. Detlef Weigel
Max-Planck-Gesellschaft

Citation:  Kentaro Yoshida et al.  Herbarium metagenomics reveals the rise and fall of the Phytophthora lineage that triggered the Irish potato famine eLife, in press, doi 10.7554/elife.00731
 

Slow Earthquakes: It's All In The Rock Mechanics

A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake.

Earthquakes that last minutes rather than seconds are a relatively recent discovery, according to an international team of seismologists. Researchers have been aware of these slow earthquakes, only for the past five to 10 years because of new tools and new observations, but these tools may explain the triggering of some normal earthquakes and could help in earthquake prediction.

"New technology has shown us that faults do not just fail in a sudden earthquake or by stable creep," said Demian M. Saffer, professor of geoscience, Penn State. "We now know that earthquakes with anomalous low frequencies -- slow earthquakes -- and slow slip events that take weeks to occur exist."

Slow slip events

Credit: Wikipedia

These new observations have put a big wrinkle into our thinking about how faults work, according to the researchers who also include Chris Marone, professor of geosciences, Penn State; Matt J. Ikari, recent Ph.D. recipient, and Achim J. Kopf, former Penn State postdoctural fellow, both now at the University of Bremen, Germany. So far, no one has explained the processes that cause slow earthquakes.

The researchers thought that the behavior had to be related to the type of rock in the fault, believing that clay minerals are important in this slip behavior to see how the rocks reacted. Ikari performed laboratory experiments using natural samples from drilling done offshore of Japan in a place where slow earthquakes occur. The samples came from the Integrated Ocean Drilling Program, an international collaborative. The researchers reported their results recently in Nature Geoscience.

These samples are made up of ocean sediment that is mostly clay with a little quartz.

"Usually, when you shear clay-rich fault rocks in the laboratory in the way rocks are sheared in a fault, as the speed increases, the rocks become stronger and self arrests the movement," said Saffer. "Matt noticed another behavior. Initially the rocks reacted as expected, but these clays got weaker as they slid further. They initially became slightly stronger as the slip rate increased, but then, over the long run, they became weaker."

The laboratory experiments that produced the largest effect closely matched the velocity at which slow earthquakes occur in nature. The researchers also found that water content in the clays influenced how the shear occurred.

"From the physics of earthquake nucleation based on the laboratory experiments we would predict the size of the patch of fault that breaks at tens of meters," said Saffer. "The consistent result for the rates of slip and the velocity of slip in the lab are interesting. Lots of things point in the direction for this to be the solution."

Common Cross Section of a Subduction Zone

Credit: Wikipedia

The researchers worry about slow earthquakes because there is evidence that swarms of low frequency events can trigger large earthquake events. In Japan, a combination of broadband seismometers and global positioning system devices can monitor slow earthquakes.

For the Japanese and others in earthquake prone areas, a few days of foreknowledge of a potential earthquake hazard could be valuable and save lives.

For slow slip events, collecting natural samples for laboratory experiments is more difficult because the faults where these take place are very deep. Only off the north shore of New Zealand is there a fault that can be sampled. Saffer is currently working to arrange a drilling expedition to that fault.

The National Science Foundation and the Deutsche Forschungsgemeinschaft supported this work.


Contacts and sources:
A'ndrea Elyse Messer
Penn State

Kinks And Curves At The Nanoscale

New research shows 'perfect twin boundaries' are not so perfect


One of the basic principles of nanotechnology is that when you make things extremely small—one nanometer is about five atoms wide, 100,000 times smaller than the diameter of a human hair—they are going to become more perfect.

Since 2004, materials scientists and nanotechnologists have been excited about a special of arrangement of atoms called a "coherent twin boundary" that can add strength and other advantages to metals like gold and copper. The CTB's are often described as "perfect," appearing like a one-atom-thick perfectly-flat plane in models and images. New research at the University of Vermont and Lawrence Livermore National Laboratory shows that these boundaries are not so perfect after all. Even more surprising, the newly discovered kinks and defects appear to be the cause of the CTB's strength.This image shows a simulation of atoms in a coherent twin boundary (shown in red) in copper. The newly discovered "kink" defects appear as green step-like structures and folds in the red areas. The red twin boundaries extend between columns of green atoms which represent grain boundaries within the copper.

Credit: Frederic Sansoz, University of Vermont

"Perfect in the sense that their arrangement of atoms in the real world will become more like an idealized model," says University of Vermont engineer Frederic Sansoz, "with smaller crystals—in for example, gold or copper—it's easier to have fewer defects in them."

And eliminating the defects at the interface separating two crystals, or grains, has been shown by nanotechnology experts to be a powerful strategy for making materials stronger, more easily molded, and less electrically resistant—or a host of other qualities sought by designers and manufacturers.

Since 2004, when a seminal paper came out in Science, materials scientists have been excited about one special of arrangement of atoms in metals and other materials called a "coherent twin boundary" or CTB.

Based on theory and experiment, these coherent twin boundaries are often described as "perfect," appearing like a perfectly flat, one-atom-thick plane in computer models and electron microscope images.

Over the last decade, a body of literature has shown these coherent twin boundaries—found at the nanoscale within the crystalline structure of common metals like gold, silver and copper—are highly effective at making materials much stronger while maintaining their ability to undergo permanent change in shape without breaking and still allowing easy transmission of electrons—an important fact for computer manufacturing and other electronics applications.

But new research now shows that coherent twin boundaries are not so perfect after all.

A team of scientists, including Sansoz, a professor in UVM's College of Engineering and Mathematical Sciences, and colleagues from the Lawrence Livermore National Laboratory and elsewhere, write in the May 19 edition of Nature Materials that coherent twin boundaries found in copper "are inherently defective."

Frederic Sansoz, a professor of engineering at the University of Vermont, works at the intersection of nanotechnology and materials science. His work makes extensive use of state-of-the-art atomistic simulation techniques, as well as of atomic force microscopy-based experiments for the discovery of new properties -- like a newly discovered set of defects in coherent twin boundaries.

Credit: Joshua Brown, University of Vermont, 2013

With a high-resolution electron microscope, using a more powerful technique than has ever been used to examine these boundaries, they found tiny kink-like steps and curvatures in what had previously been observed as perfect.

Even more surprising, these kinks and other defects appear to be the cause of the coherent twin boundary's strength and other desirable qualities.

"Everything we have learned on these materials in the past 10 years will have to be revisited with this new information," Sansoz says

The experiment, led by Morris Wang at the Lawrence Livermore Lab, applied a newly developed mapping technique to study the crystal orientation of CTBs in so-called nanotwinned copper and "boom—it revealed these defects," says Sansoz.

This real-world discovery conformed to earlier intriguing theoretical findings that Sansoz had been making with "atomistic simulations" on a computer. The lab results sent Sansoz back to his computer models where he introduced the newly discovered "kink" defects into his calculations. Using UVM's Vermont Advanced Computing Center, he theoretically confirmed that the kink defects observed by the Livermore team lead to "rather rich deformation processes at the atomic scale," he says, that do not exist with perfect twin boundaries.

With the computer model, "we found a series of completely new mechanisms," he says, for explaining why coherent twin boundaries simultaneously add strength and yet also allow stretching (what scientists call "tensile ductility")— properties that are usually mutually exclusive in conventional materials.

"We had no idea such defects existed," says Sansoz. "So much for the perfect twin boundary. We now call them defective twin boundaries."

For several decades, scientists have looked for ways to shrink the size of individual crystalline grains within metals and other materials. Like a series of dykes or walls within the larger structure, the boundaries between grains can slow internal slip and help resist failure. Generally, the more of these boundaries—the stronger the material.

Originally, scientists believed that coherent twin boundaries in materials were much more reliable and stable than conventional grain boundaries, which are incoherently full of defects. But the new research shows they could both contain similar types of defects despite very different boundary energies.

"Understanding these defective structures is the first step to take full use of these CTBs for strengthening and maintaining the ductility and electrical conductivity of many materials," Morris Wang said. "To understand the behavior and mechanisms of these defects will help our engineering design of these materials for high-strength applications."

For Sansoz, this discovery underlines a deep principle, "There are all manner of defects in nature," he says, "with nanotech, you are trying to control the way they are formed and dispersed in matter, and to understand their impact on properties. The point of this paper is that some defects make a material stronger."


Contacts and sources:
Joshua Brown
University of Vermont

Friday CME Arrives, No Geomagnetic Storm

A combined view of the coronal mass ejection, or CME, that occurred on May 17, 2013, at 5:36 EDT. The center yellow image was captured by NASA's Solar Dynamics Observatory and shows the sun as seen in UV light, in the 171 Angstrom wavelength. The SDO image is superimposed on top of an image from the Solar and Heliospheric Observatory showing the CME propagating into space.

Credit: NASA/SDO/Goddard, ESA&NASA SOHO

On 5:24 a.m. EDT on May 17, 2013, the sun erupted with an Earth-directed coronal mass ejection or CME, a solar phenomenon that can send billions of tons of solar particles into space that can reach Earth one to three days later and affect electronic systems in satellites and on the ground. Experimental NASA research models, based on observations from NASA’s Solar Terrestrial Relations Observatory, show that the CME left the sun at speeds of around 745 miles per second. The solar material in CMEs cannot pass through the atmosphere to affect humans on Earth.

Not to be confused with a solar flare, a CME can cause a space weather phenomenon called a geomagnetic storm, which occurs when they connect with the outside of the Earth's magnetic envelope, the magnetosphere, for an extended period of time.

The CME may also pass by Spitzer and its mission operators have been notified. If warranted, operators can put spacecraft into safe mode to protect the instruments from the solar material.

NOAA's Space Weather Prediction Center (http://swpc.noaa.gov) is the U.S. government's official source for space weather forecasts, alerts, watches and warnings.

The almost exclusively northward embedded magnetic field in the CME has resulted in no Geomagnetic Storm conditions at this writing. Things could change quickly if the field goes southward.

This video is a combination of two satellite views, showing both the sun and its atmosphere, the corona. The center image shows the sun in UV light, as captured by the Solar Dynamics Observatory, or SDO. The red and larger blue areas show the sun's corona as recorded by two instruments aboard the Solar and Heliospheric Observatory, or SOHO. The CME cloud appears and expands into space from the center left. The white dot on the far left is the planet Mars.  

Credit: NASA/SDO/Goddard, ESA& NASA SOHO


Contacts and sources:
Susan Hendrix
NASA/Goddard Space Flight Center

Cassini Shapes First Global Topographic Map of Titan

Scientists have created the first global topographic map of Saturn's moon Titan, giving researchers a valuable tool for learning more about one of the most Earth-like and interesting worlds in the solar system. The map was just published as part of a paper in the journal Icarus.

These polar maps show the first global, topographic mapping of Saturn’s moon Titan, using data from NASA's Cassini mission. To create these maps, scientists employed a mathematical process called splining, which uses smooth curved surfaces to “join” the areas between grids of existing topography profiles obtained by Cassini's radar instrument. The topography maps at bottom focus on the polar regions (north at left, south at right) in stereographic projection. The top maps show the 2-D radar data in gold and black, with topography data color-coded by elevation. The bottom images are from the new topography map, with contour lines added at 656 feet (200 meters) apart in elevation.   Visible are deep basins at 72 degrees south latitude and 20 degrees east longitude, and a wider basin at 68 degrees south latitude and 105 degrees east longitude.

Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann

Titan is Saturn's largest moon - with a radius of about 1,600 miles (2,574 kilometers), it's bigger than planet Mercury - and is the second–largest moon in the solar system. Scientists care about Titan because it's the only moon in the solar system known to have clouds, surface liquids and a mysterious, thick atmosphere. The cold atmosphere is mostly nitrogen, like Earth's, but the organic compound methane on Titan acts the way water vapor does on Earth, forming clouds and falling as rain and carving the surface with rivers. Organic chemicals, derived from methane, are present in Titan's atmosphere, lakes and rivers and may offer clues about the origins of life.

"Titan has so much interesting activity - like flowing liquids and moving sand dunes - but to understand these processes it's useful to know how the terrain slopes," said Ralph Lorenz, a member of the Cassini radar team based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., who led the map-design team. "It's especially helpful to those studying hydrology and modeling Titan's climate and weather, who need to know whether there is high ground or low ground driving their models."

Using data from NASA's Cassini spacecraft, scientists have created the first global topographic map of Saturn’s moon Titan, giving researchers a 3-D tool for learning more about one of the most Earthlike and interesting worlds in the solar system. 

Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann 

Titan's thick haze scatters light in ways that make it very hard for remote cameras to "see" landscape shapes and shadows, the usual approach to measuring topography on planetary bodies. Virtually all the data we have on Titan comes from NASA's Saturn-orbiting Cassini spacecraft, which has flown past the moon nearly 100 times over the past decade. On many of those flybys, Cassini has used a radar imager, which can peer through the haze, and the radar data can be used to estimate the surface height.

"With this new topographic map, one of the most fascinating and dynamic worlds in our solar system now pops out in 3-D," said Steve Wall, the deputy team lead of Cassini's radar team, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "On Earth, rivers, volcanoes and even weather are closely related to heights of surfaces - we're now eager to see what we can learn from them on Titan."

There are challenges, however. "Cassini isn't orbiting Titan," Lorenz said. "We have only imaged about half of Titan's surface, and multiple 'looks' or special observations are needed to estimate the surface heights. If you divided Titan into 1-degree by 1-degree [latitude and longitude] squares, only 11 percent of those squares have topography data in them."

To create the first global, topographic map of Saturn’s moon Titan, scientists analyzed data from NASA's Cassini spacecraft and a mathematical process called splining. This method effectively uses smooth curved surfaces to “join” the areas between grids of existing topography profiles obtained by Cassini's radar instrument. In the upper panel of this graphic, gold colors show where radar images have been obtained over almost half of Titan’s surface. Within the gold areas, narrow strips of rainbow colors show where height data have been obtained. Those data are laid over a blue-toned, near-global map of infrared color from the Cassini visual and infrared mapping spectrometer instrument. The lower panel shows the new topography map, with contour lines added at 656 feet (200 meters) apart in elevation. South polar depressions and four mountains are notably prominent; a dark region at 50 to 65 degrees south latitude and 0 to 60 degrees east longitude coincides with a major depression.  The radar and VIMS data were obtained from 2004 to 2011.

Lorenz's team used a mathematical process called splining - effectively using smooth, curved surfaces to "join" the areas between grids of existing data. "You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess," he said. "If you pick a point, and all the nearby points are high altitude, you'd need a special reason for thinking that point would be lower. We're mathematically papering over the gaps in our coverage."

The estimations fit with current knowledge of the moon - that its polar regions are "lower" than areas around the equator, for example - but connecting those points allows scientists to add new layers to their studies of Titan's surface, especially those modeling how and where Titan's rivers flow, and the seasonal distribution of its methane rainfall. "The movement of sands and the flow of liquids are influenced by slopes, and mountains can trigger cloud formation and therefore rainfall. This global product now gives modelers a convenient description of this key factor in Titan's dynamic climate system," Lorenz said.

The most recent data used to compile the map is from 2012; Lorenz says it could be worth revising when the Cassini mission ends in 2017, when more data will have accumulated, filling some of the gaps in present coverage. "We felt we couldn't wait and should release an interim product," he says. "The community has been hoping to get this for a while. I think it will stimulate a lot of interesting work."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

Contacts and sources:
Jia-Rui Cook
Jet Propulsion Laboratory

Blond Monkey Has Incredible Human Looking Face: Lesula, A New Species of Cercopithecus Monkey Endemic to the Democratic Republic of Congo

The scientific discovery of Cercopithecus lomamiensis was made in June 2007 when field teams saw a captive juvenile female of an unknown species at the residence of the primary school director in the town of Opala (S 0.50721°, E 24.22713°). The school director identified the animal as a “lesula” a vernacular name we had not recorded before, and said that it is well known by local hunters. He reported that he acquired the infant about two months earlier from a family member who had killed its mother in the forest near Yawende, south of Opala and west of the Lomami River (S 0.99772°, E 24.29810°). We took photographs of the animal and made arrangements for its care. We observed and photographed this animal regularly over the next 18 months.
New species of Cercopithecus Monkey discovered in  the Democratic Republic of Congo


Subsequent searches in Opala and in the Yawende area turned up other male and female captive juvenile lesula; all were photographed and some monitored for several months afterwards. The researchers first observation of the species in the wild was in the Obenge area (S 1.38461°, E 25.03749°) in December 2007 where the species is well known by local hunters.
Juvenile Lesula monkeys

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Captive Cercopithecus lomamiensis.

Citation: Cercopithecus lomamiensis J.Hart, Detwiler, Gilbert, Burrell, Fuller, Emetshu, T.Hart, Vosper, Sargis, and Tosi, sp. nov. urn:lsid:zoobank.org:act:8BA96F42-16A5-4​6B6-A194-B3DB0B2711B7.

World's Smallest Droplets

Physicists may have created the smallest drops of liquid ever made in the lab.

That possibility has been raised by the results of a recent experiment conducted by Vanderbilt physicist Julia Velkovska and her colleagues at the Large Hadron Collider, the world’s largest and most powerful particle collider located at the European Laboratory for Nuclear and Particle Physics (CERN) in Switzerland. Evidence of the minuscule droplets was extracted from the results of colliding protons with lead ions at velocities approaching the speed of light.

Credit: Istock

According to the scientists’ calculations, these short-lived droplets are the size of three to five protons. To provide a sense of scale, that is about one-100,000th the size of a hydrogen atom or one-100,000,000th the size of a virus.

“With this discovery, we seem to be seeing the very origin of collective behavior,” said Velkovska, professor of physics at Vanderbilt who serves as a co-convener of the heavy ion program of the CMS detector, the LHC instrument that made the unexpected discovery. “Regardless of the material that we are using, collisions have to be violent enough to produce about 50 sub-atomic particles before we begin to see collective, flow-like behavior.”

These tiny droplets “flow” in a manner similar to the behavior of the quark-gluon plasma, a state of matter that is a mixture of the sub-atomic particles that makes up protons and neutrons and only exists at extreme temperatures and densities. Cosmologists propose that the entire universe once consisted of this strongly interacting elixir for fractions of a second after the Big Bang when conditions were dramatically hotter and denser than they are today. Now that the universe has spent billions of years expanding and cooling, the only way scientists can reproduce this primordial plasma is to bang atomic nuclei together with tremendous energy.

A three-dimensional view of a p-Pb collision that produced collective flow behavior. The green lines are the trajectories of the sub-atomic particles produced by the collision reconstructed by the CMS tracking system. The red and blue bars represent the energy measured by the instrument's two sets of calorimeters.

 CMS Collaboration

The new observations are contained in a paper submitted by the CMS collaboration to the journal Physics Letters B and posted on the arXiv preprint server. In addition, Vanderbilt doctoral student Shengquan Tuo recently presented the new results at a workshop held in the European Centre for Theoretical Studies in Nuclear Physics and Related Areas in Trento, Italy.

Scientists have been trying to recreate the quark-gluon plasma since the early 2000s by colliding gold nuclei using the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This exotic state of matter is created when nuclei collide and dump a fraction of their energy into the space between them. When enough energy is released, it causes some of the quarks and gluons in the colliding particles to melt together to form the plasma. The RHIC scientists had expected the plasma to behave like a gas, but were surprised to discover that it acts like a liquid instead.

When the LHC started up, the scientists moved to the more powerful machine where they basically duplicated the results they got at RHIC by colliding lead nuclei.

In what was supposed to be a control run to check the validity of their lead-lead results, the scientists scheduled the collider to smash protons and lead nuclei together. They didn’t expect to see any evidence of the plasma. Because the protons are so much lighter than lead nuclei (they have only one-208th the mass), it was generally agreed that proton-lead collisions couldn’t release enough energy to produce the rare state of matter.

“The proton-lead collisions are something like shooting a bullet through an apple while lead-lead collisions are more like smashing two apples together: A lot more energy is released in the latter,” said Velkovska.

Shengquan Tuo, right, Julia Velkovska and graduate student Dillon Roach in Vanderbilt's CMS Center, a room set up with telecommunications equipment that allows them to monitor of the detector's performance and directly download data.

  Courtesy of Physics Department / Vanderbilt

Last September, the LHC did a brief test run to make sure it was adjusted properly to handle proton-lead collisions. When the results of the run were analyzed, team members were surprised to see evidence of collective behavior in five percent of the collisions—those that were the most violent. In these cases, it appeared that when the “bullet” passed through “apple” it released enough energy to melt some of the particles surrounding the bullet hole. They appeared to be forming liquid droplets about one tenth the size of those produced by the lead-lead or gold-gold collisions.

However, the initial analysis was limited to tracking the motion of pairs of particles. The researchers knew that this analysis could be influenced by another well-known phenomenon, the production of particle jets. So, when the scheduled proton-lead run took place in January and February, they searched the data for evidence of groups of four particles that exhibit collective motion. After analyzing several billion events, they found hundreds of cases where the collisions produced more than 300 particles flowing together.

According to Tuo, only two models were advanced to explain their observations at the workshop. Of the two, the plasma droplet model seems to fit the observations best. In fact, he reported that the new data is forcing the authors of the competing model – color glass condensate, which attributes the particle correlations to the internal gluon structure of the protons themselves – to incorporate hydrodynamic effects, meaning that it is also describing the phenomenon as liquid droplets.

U.S. members of the CMS collaboration are supported primarily by the U.S. Department of Energy and National Science Foundation.


Contacts and sources:
David Salisbury
Vanderbilt University

New Discovery Of Ancient Diet Shatters Conventional Ideas Of How Agriculture Emerged

Use of new analysis techniques provides food for thought about how people lived 5,000 years ago


Archaeologists have made a discovery in southern subtropical China which could revolutionise thinking about how ancient humans lived in the region.

They have uncovered evidence for the first time that people living in Xincun 5,000 years ago may have practised agriculture –before the arrival of domesticated rice in the region.

This is Dr Mingqi Li sampling one of the pebble tools for ancient starch using an ultrasonic bath, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences in Beijing.

Credit: Dr. Huw Barton

Current archaeological thinking is that it was the advent of rice cultivation along the Lower Yangtze River that marked the beginning of agriculture in southern China. Poor organic preservation in the study region, as in many others, means that traditional archaeobotany techniques are not possible.

Now, thanks to a new method of analysis on ancient grinding stones, the archaeologists have uncovered evidence that agriculture could predate the advent of rice in the region.

The research was the result of a two-year collaboration between Dr Huw Barton, from the School of Archaeology and Ancient History at the University of Leicester, and Dr Xiaoyan Yang, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, in Beijing.

Funded by a Royal Society UK-China NSFC International Joint Project, and other grants held by Yang in China, the research is published in PLOS ONE.

This shows the Xincun site under excavation, a) Neolithic living surface under cleaning.

Credit: Dr Jun Wei

Dr Barton, Senior Lecturer in Bioarchaeology at the University of Leicester, described the find as 'hitting the jackpot': "Our discovery is totally unexpected and very exciting.

"We have used a relatively new method known as ancient starch analysis to analyse ancient human diet. This technique can tell us things about human diet in the past that no other method can.

"From a sample of grinding stones we extracted very small quantities of adhering sediment trapped in pits and cracks on the tool surface. From this material, preserved starch granules were extracted with our Chinese colleagues in the starch laboratory in Beijing. These samples were analysed in China and also here at Leicester in the Starch and Residue Laboratory, School of Archaeology and Ancient History.

"Our research shows us that there was something much more interesting going on in the subtropical south of China 5,000 years ago than we had first thought. The survival of organic material is really dependent on the particular chemical properties of the soil, so you never know what you will get until you sample. At Xincun we really hit the jackpot. Starch was well-preserved and there was plenty of it. While some of the starch granules we found were species we might expect to find on grinding and pounding stones, ie. some seeds and tuberous plants such as freshwater chestnuts, lotus root and the fern root, the addition of starch from palms was totally unexpected and very exciting."

This is a map of the study region in southern China (A), Xincun site indicated by red triangle (B), and details of the Xincun site including excavation areas marked by red grids, stippling shows location of coastal sand dunes (C).

Credit: Xiaoyan Yang

Several types of tropical palms store prodigious quantities of starch. This starch can be literally bashed and washed out of the trunk pith, dried as flour, and of course eaten. It is non-toxic, not particularly tasty, but it is reliable and can be processed all year round. Many communities in the tropics today, particularly in Borneo and Indonesia, but also in eastern India, still rely on flour derived from palms.

Dr Barton said: "The presence of at least two, possibly three species of starch producing palms, bananas, and various roots, raises the intriguing possibility that these plants may have been planted nearby the settlement.

"Today groups that rely on palms growing in the wild are highly mobile, moving from one palm stand to another as they exhaust the clump. Sedentary groups that utilise palms for their starch today, plant suckers nearby the village, thus maintaining continuous supply. If they were planted at Xincun, this implies that 'agriculture' did not arrive here with the arrival of domesticated rice, as archaeologists currently think, but that an indigenous system of plant cultivation may have been in place by the mid Holocene.

"The adoption of domesticated rice was slow and gradual in this region; it was not a rapid transformation as in other places. Our findings may indicate why this was the case. People may have been busy with other types of cultivation, ignoring rice, which may have been in the landscape, but as a minor plant for a long time before it too became a food staple.

"Future work will focus on grinding stones from nearby sites to see if this pattern is repeated along the coast."
Contacts and sources:
Dr. Huw Barton
University of Leicester

Stacking 2-D Materials Produces Surprising Results

New experiments reveal previously unseen effects, could lead to new kinds of electronics and optical devices.

Graphene has dazzled scientists, ever since its discovery more than a decade ago, with its unequalled electronic properties, its strength and its light weight. But one long-sought goal has proved elusive: how to engineer into graphene a property called a band gap, which would be necessary to use the material to make transistors and other electronic devices.

Now, new findings by researchers at MIT are a major step toward making graphene with this coveted property. The work could also lead to revisions in some theoretical predictions in graphene physics.

From left: Prof. Ray Ashoori, postdocs Andrea Young and Ben Hunt, graduate student Javier Sanchez-Yamagishi, and Prof. Pablo Jarillo-Herrero.

Photo: Jarillo-Herrero and Ashoori groups

The new technique involves placing a sheet of graphene — a carbon-based material whose structure is just one atom thick — on top of hexagonal boron nitride, another one-atom-thick material with similar properties. The resulting material shares graphene’s amazing ability to conduct electrons, while adding the band gap necessary to form transistors and other semiconductor devices.

The work is described in a paper in the journal Science co-authored by Pablo Jarillo-Herrero, the Mitsui Career Development Assistant Professor of Physics at MIT, Professor of Physics Ray Ashoori, and 10 others.

“By combining two materials,” Jarillo-Herrero says, “we created a hybrid material that has different properties than either of the two.”

Graphene is an extremely good conductor of electrons, while boron nitride is a good insulator, blocking the passage of electrons. “We made a high-quality semiconductor by putting them together,” Jarillo-Herrero explains. Semiconductors, which can switch between conducting and insulating states, are the basis for all modern electronics.

To make the hybrid material work, the researchers had to align, with near perfection, the atomic lattices of the two materials, which both consist of a series of hexagons. The size of the hexagons (known as the lattice constant) in the two materials is almost the same, but not quite: Those in boron nitride are 1.8 percent larger. So while it is possible to line the hexagons up almost perfectly in one place, over a larger area the pattern goes in and out of register.

At this point, the researchers say they must rely on chance to get the angular alignment for the desired electronic properties in the resulting stack. However, the alignment turns out to be correct about one time out of 15, they say.

“The qualities of the boron nitride bleed over into the graphene,” Ashoori says. But what’s most “spectacular,” he adds, is that the properties of the resulting semiconductor can be “tuned” by just slightly rotating one sheet relative to the other, allowing for a spectrum of materials with varied electronic characteristics.

Others have made graphene into a semiconductor by etching the sheets into narrow ribbons, Ashoori says, but such an approach substantially degrades graphene’s electrical properties. By contrast, the new method appears to produce no such degradation.

The band gap created so far in the material is smaller than that needed for practical electronic devices; finding ways of increasing it will require further work, the researchers say.

“If … a large band gap could be engineered, it could have applications in all of digital electronics,” Jarillo-Herrero says. But even at its present level, he adds, this approach could be applied to some optoelectronic applications, such as photodetectors.

The results “surprised us pleasantly,” Ashoori says, and will require some explanation by theorists. Because of the difference in lattice constants of the two materials, the researchers had predicted that the hybrid’s properties would vary from place to place. Instead, they found a constant, and unexpectedly large, band gap across the whole surface.

In addition, Jarillo-Herrero says, the magnitude of the change in electrical properties produced by putting the two materials together “is much larger than theory predicts.”

The MIT team also observed an interesting new physical phenomenon. When exposed to a magnetic field, the material exhibits fractal properties — known as a Hofstadter butterfly energy spectrum — that were described decades ago by theorists, but thought impossible in the real world. There is intense research in this area; two other research groups also report on these Hofstadter butterfly effects this week in the journal Nature.

The research included postdocs Ben Hunt and Andrea Young and graduate student Javier Sanchez-Yamagishi, as well as six other researchers from the University of Arizona, the National Institute for Materials Science in Tsukuba, Japan, and Tohoku University in Japan. The work was funded by the U.S. Department of Energy, the Gordon and Betty Moore Foundation and the National Science Foundation.
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Contacts and sources:
Sarah McDonnell
Massachusetts Institute of Technology
Written by: David L. Chandler, MIT News Office

How Should Geophysics Contribute To Disaster Planning?

Identifying natural hazards is only a part of what the field should do, analysis suggests, and effective disaster risk reduction strategies integrate many different experts on community level

Earthquakes, tsunamis, and other natural disasters often showcase the worst in human suffering – especially when those disasters strike populations who live in rapidly growing communities in the developing world with poorly enforced or non-existent building codes.'

Taken at Ao Nang, Krabi Province, Thailand, during the 2004 Indian Ocean earthquake and tsunami in Thailand

Credit: Wikipedia

This week in Cancun, a researcher from Yale-National University of Singapore (NUS) College in Singapore is presenting a comparison between large-scale earthquakes and tsunamis in different parts of the world, illustrating how nearly identical natural disasters can play out very differently depending on where they strike.

The aim of the talk at the 2013 Meeting of the Americas, which is sponsored by the American Geophysical Union (AGU), is to focus on the specific role geoscientists can play in disaster risk reduction and how their work should fit in with the roles played by other experts for any given community.

"To reduce the losses from these disasters, a diverse group of researchers, engineers, and policy makers need to come together to benefit from each other's expertise," said Brian McAdoo, professor of science at Yale-NUS College. "Geophysicists play a crucial role in natural hazard identification and determining the key questions of, how often does a geophysical hazard affect a given area and how big will it be when it hits?" McAdoo said. "We need to be aware of how this information is incorporated into the disaster planning architecture."

San Francisco, Haiti, and New Zealand

In his talk, McAdoo will present case studies that he and his colleague Vivienne Bryner compiled comparing death counts and economic fallout following geophysical events of similar magnitude in areas with different levels of economic development.

What their analysis shows is that deaths tend to be higher in poor countries exposed to severe natural disasters because of existing socioeconomic, environmental, and structural vulnerabilities. At the same time, economic losses tend to be higher in developed nations, but developing countries may be less able to absorb those economic losses that do occur.

As an example, he points to the earthquakes that hit Haiti, San Francisco, and Christchurch and Canterbury, New Zealand, in 2010, 1989 and 2010-2011. While the quakes were nearly identical in magnitude, the consequences of these natural disasters were remarkably different.

Some 185 people died in the 2011 Canterbury earthquake, which was preceded by the larger Christchurch quake in 2010 in which nobody died. Both quakes and their aftershocks cost New Zealand about $6.5 billion, which was approximately 10-20 percent of its gross domestic product (GDP). The 1989 San Francisco earthquake killed 63 people, and it cost $5.6 billion (the equivalent of about $10 billion in 2010 dollars). The U.S. economy is so large, however, that it only caused a one-tenth of one percent drop in U.S. GDP. The 2011 earthquake in Haiti, on the other hand, killed some 200,000 people and resulted in economic losses approaching an estimated $8 billion, which is more than 80 percent of Haiti's GDP.

To address such disparities, McAdoo advocates what is known as Disaster Risk Reduction (DRR) decision making – a framework for finding solutions to best prepare for natural disasters, lessen their impact, and sensibly engage in post-disaster reconstruction. For such planning to work, he said, it must be broad-based.

"We won't ever be able to prevent disasters," he said. "The only way we will effectively minimize the effects of hazards is to collaborate across academic disciplines, businesses, governments, NGOs, and perhaps most critically the exposed community."

"Planning for any sort of natural disaster takes insight into what may be expected, which necessarily includes the important perspective of scientists," added Philip ("Bo") Hammer, Associate Vice President for Physics Resources at the American Institute of Physics (AIP) and co-organizer of the session in which McAdoo is speaking. "One reason why we organized this session in the first place was to encourage the sharing of such perspectives within the context of how geophysicists can build local capacity, not only for dealing with acute issues such as disasters, but also longer term challenges like building capacity for economic growth."

The talk, "Building Capacity for Disaster Risk Reduction," will be presented by Brian G. McAdoo and Vivienne Bryner on Friday, May 17, 2013, at the 2013 Meeting of the Americas in Cancún, Mexico. McAdoo is affiliated with Yale-NUS College in Singapore, and Bryner is at University of Otago in Dunedin, New Zealand.



Contacts and sources:
Jason Socrates Bardi
American Institute of Physics

Nanotechnology Could Help Fight Diabetes

Injectable nanogel can monitor blood-sugar levels and secrete insulin when needed.CAMBRIDGE, Mass. — Injectable nanoparticles developed at MIT may someday eliminate the need for patients with Type 1 diabetes to constantly monitor their blood-sugar levels and inject themselves with insulin.

The nanoparticles were designed to sense glucose levels in the body and respond by secreting the appropriate amount of insulin, thereby replacing the function of pancreatic islet cells, which are destroyed in patients with Type 1 diabetes. Ultimately, this type of system could ensure that blood-sugar levels remain balanced and improve patients’ quality of life, according to the researchers.

“Insulin really works, but the problem is people don’t always get the right amount of it. With this system of extended release, the amount of drug secreted is proportional to the needs of the body,” says Daniel Anderson, an associate professor of chemical engineering and member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science.

Anderson is the senior author of a paper describing the new system in a recent issue of the journal ACS Nano. Lead author of the paper is Zhen Gu, a former postdoc in Anderson’s lab. The research team also includes Robert Langer, the David H. Koch Institute Professor at MIT, and researchers from the Department of Anesthesiology at Boston Children’s Hospital.

Mimicking the pancreas

Currently, people with Type 1 diabetes typically prick their fingers several times a day to draw blood for testing their blood-sugar levels. When levels are high, these patients inject themselves with insulin, which breaks down the excess sugar.

In recent years, many researchers have sought to develop insulin-delivery systems that could act as an “artificial pancreas,” automatically detecting glucose levels and secreting insulin. One approach uses hydrogels to measure and react to glucose levels, but those gels are slow to respond or lack mechanical strength, allowing insulin to leak out.

The MIT team set out to create a sturdy, biocompatible system that would respond more quickly to changes in glucose levels and would be easy to administer.

Their system consists of an injectable gel-like structure with a texture similar to toothpaste, says Gu, who is now an assistant professor of biomedical engineering and molecular pharmaceutics at the University of North Carolina at Chapel Hill and North Carolina State University. The gel contains a mixture of oppositely charged nanoparticles that attract each other, keeping the gel intact and preventing the particles from drifting away once inside the body.

Using a modified polysaccharide known as dextran, the researchers designed the gel to be sensitive to acidity. Each nanoparticle contains spheres of dextran loaded with an enzyme that converts glucose into gluconic acid. Glucose can diffuse freely through the gel, so when sugar levels are high, the enzyme produces large quantities of gluconic acid, making the local environment slightly more acidic.

That acidic environment causes the dextran spheres to disintegrate, releasing insulin. Insulin then performs its normal function, converting the glucose in the bloodstream into glycogen, which is absorbed into the liver for storage.

Long-term control

In tests with mice that have Type 1 diabetes, the researchers found that a single injection of the gel maintained normal blood-sugar levels for an average of 10 days. Because the particles are mostly composed of polysaccharides, they are biocompatible and eventually degrade in the body.

The researchers are now trying to modify the particles so they can respond to changes in glucose levels faster, at the speed of pancreas islet cells. “Islet cells are very smart. They can release insulin very quickly once they sense high sugar levels,” Gu says.

Before testing the particles in humans, the researchers plan to further develop the system’s delivery properties and to work on optimizing the dosage that would be needed for use in humans.

The research was funded by the Leona M. and Harry B. Helmsley Charitable Trust and the Tayebati Family Foundation.


Contacts and sources:
Sarah McDonnell
Massachusetts Institute of Technology

Written by: Anne Trafton, MIT News Office

70's-Era Physics Prediction Finally Confirmed

New CCNY professor part of team confirming Hofstadter Butterfly in graphene

City College of New York Assistant Professor of Physics Cory Dean, who recently arrived from Columbia University where he was a post-doctoral researcher, and research teams from Columbia and three other institutions have definitively proven the existence of an effect known as Hofstadter’s Butterfly.

The phenomenon, a complex pattern of the energy states of electrons that resembles a butterfly, has appeared in physics textbooks as a theoretical concept of quantum mechanics for nearly 40 years. However, it had never been directly observed until now. Confirming its existence may open the door for researchers to uncover completely unknown electrical properties of materials.

Artist's illustration of a butterfly as if departing from a moire pattern in graphene formed on top of a sheet of boron nitride. 

Credit: James Hedberg

“We are now standing at the edge of an entirely new frontier in terms of exploring properties of a system that have never before been realized,” said Professor Dean, who developed the material that allowed the observation. "The ability to generate this effect could possibly be exploited to design new electronic and optoelectronic devices."

The international group, which also included the University of Central Florida, the National High Magnetic Field Laboratory, and Japan’s Tohoku University and National Institute for Materials Science, published its findings in the journal Nature; they appeared in an advance online publicationMay 15. Separate groups at the University of Manchester (UK) and Massachusetts Institute of Technology simultaneously reported similar results.

Douglas Hofstadter, a physicist and Pulitzer Prize-winning author, first predicted the existence of the butterfly in 1976, when he imagined what would happen to electrons subjected to two forces simultaneously: a magnetic field and the periodic electric field.

The energy spectrum, or pattern of energy levels, that these dueling forces create is said to be “fractal,” that is, infinitely smaller versions of the pattern appear within the main one. This effect is common in classical physics, but rare in the quantum world.

“When you plot the spectrum, it takes on the form of a butterfly. Zoom in on the spectrum and you see the butterfly again, zoom in and see butterfly again,” said Professor Dean. The light and dark sections of the pattern, respectively, correspond to light “gaps” in energy level that electrons cannot cross and dark areas where they can move freely.

“The existence of gaps changes the way electrons move through a material. Copper for example, has no gaps, whereas an insulator, like glass, has very large gaps,” explained Professor Dean. “The relationship between energy and how dense the electrons are in a material – energy density – determines all electrical properties. That’s why copper conducts, glass or ceramic doesn’t, and other materials weakly conduct, like semiconductors.”

“What you see in a Hofstadter spectrum is a very complicated structure of gaps arranged in a fractal pattern,” he continued, which suggests as yet unknown electrical properties.

The team produced the effect by sandwiching together flat sheets of graphene – a single-atom-thickness of carbon – and another material, called boron nitride, and twisting them against each other to create what is called a superlattice. “Graphene has hexagonal chicken wire structure and boron nitride does too,” he said. “It is as if you take screen door material and put one sheet on top of other. As you rotate it you see a periodic pattern appear. You get an interference effect – a ‘moiré’ pattern.” In the case of the chicken-wire structure of graphene and boron nitride, the pattern forms a fractal butterfly of energy states.

“This is a very good example of fundamental discovery that opens doors that we don’t even know about yet. Why go to a distant planet?” Professor Dean wondered, about the implications of the work. “We go there to discover what’s out there. We don’t yet know what this new world will result in and what will emerge out of this.”


Contacts and sources:
Jessa Netting
City College of New York

Citation: C. R. Dean, Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices, Nature, May 15, 2013 doi:10.1038/nature12186