Nov 17, 2017

Lava or not, exoplanet 55 Cancri e likely to have atmosphere

The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist's concept, likely has an atmosphere thicker than Earth's but with ingredients that could be similar to those of Earth's atmosphere.
Twice as big as Earth, the super-Earth 55 Cancri e was thought to have lava flows on its surface. The planet is so close to its star, the same side of the planet always faces the star, such that the planet has permanent day and night sides. Based on a 2016 study using data from NASA's Spitzer Space Telescope, scientists speculated that lava would flow freely in lakes on the starlit side and become hardened on the face of perpetual darkness. The lava on the dayside would reflect radiation from the star, contributing to the overall observed temperature of the planet.

Now, a deeper analysis of the same Spitzer data finds this planet likely has an atmosphere whose ingredients could be similar to those of Earth's atmosphere, but thicker. Lava lakes directly exposed to space without an atmosphere would create local hot spots of high temperatures, so they are not the best explanation for the Spitzer observations, scientists said.

"If there is lava on this planet, it would need to cover the entire surface," said Renyu Hu, astronomer at NASA's Jet Propulsion Laboratory, Pasadena, California, and co-author of a study published in The Astronomical Journal. "But the lava would be hidden from our view by the thick atmosphere."

Using an improved model of how energy would flow throughout the planet and radiate back into space, researchers find that the night side of the planet is not as cool as previously thought. The "cold" side is still quite toasty by Earthly standards, with an average of 2,400 to 2,600 degrees Fahrenheit (1,300 to 1,400 Celsius), and the hot side averages 4,200 degrees Fahrenheit (2,300 Celsius). The difference between the hot and cold sides would need to be more extreme if there were no atmosphere.

"Scientists have been debating whether this planet has an atmosphere like Earth and Venus, or just a rocky core and no atmosphere, like Mercury. The case for an atmosphere is now stronger than ever," Hu said.

Researchers say the atmosphere of this mysterious planet could contain nitrogen, water and even oxygen -- molecules found in our atmosphere, too -- but with much higher temperatures throughout. The density of the planet is also similar to Earth, suggesting that it, too, is rocky. The intense heat from the host star would be far too great to support life, however, and could not maintain liquid water.

Hu developed a method of studying exoplanet atmospheres and surfaces, and had previously only applied it to sizzling, giant gaseous planets called hot Jupiters. Isabel Angelo, first author of the study and a senior at the University of California, Berkeley, worked on the study as part of her internship at JPL and adapted Hu's model to 55 Cancri e.

In a seminar, she heard about 55 Cancri e as a potentially carbon-rich planet, so high in temperature and pressure that its interior could contain a large amount of diamond.

"It's an exoplanet whose nature is pretty contested, which I thought was exciting," Angelo said.

Spitzer observed 55 Cancri e between June 15 and July 15, 2013, using a camera specially designed for viewing infrared light, which is invisible to human eyes. Infrared light is an indicator of heat energy. By comparing changes in brightness Spitzer observed to the energy flow models, researchers realized an atmosphere with volatile materials could best explain the temperatures.

There are many open questions about 55 Cancri e, especially: Why has the atmosphere not been stripped away from the planet, given the perilous radiation environment of the star?

"Understanding this planet will help us address larger questions about the evolution of rocky planets," Hu said.

Read more at Science Daily

On the origins of star stuff: Shedding new light on origin of anti-matter

The HAWC Observatory sits at an elevation of 13,500 feet, flanking the Sierra Negra volcano inside Pico de Orizaba National Park in the Mexican state of Puebla. Its more than 300 water tanks can detect cascades of particles initiated by high-energy packets of light called gamma rays.
A mountaintop observatory about four hours east of Mexico City, built and operated by an international team of scientists, has captured the first wide-angle view of gamma rays emanating from two rapidly spinning stars. The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory offers perspective on the very high energy light streaming from our stellar neighbors and casts serious doubt on one possible origin for a mysterious excess of anti-matter particles near Earth.

In 2008, a space-borne detector measured an unexpectedly high number of positrons -- the anti-matter cousins of electrons -- in orbit. Ever since, scientists have debated the cause of the anomaly, split over two competing theories of its origin. Some suggested a simple explanation: The extra particles might be coming from nearby collapsed stars called pulsars, which spin around several times a second and throw off electrons, positrons and other matter with violent force. Others speculated that the extra positrons have an exotic origin, perhaps coming from as-yet undetected processes involving dark matter -- the invisible but pervasive substance seen so far only through its gravitational pull.

"This new measurement is tantalizing because it strongly disfavors the idea that these extra positrons are coming to Earth from two nearby pulsars, at least when you assume a relatively simple model for their propagation," says Jordan Goodman, professor of physics at the University of Maryland and the lead investigator and US spokesperson for the HAWC collaboration. "Our measurement doesn't decide the question in favor of dark matter, but any new theory that attempts to explain the excess using pulsars will need to match the new data."

Using this new data from the HAWC observatory, researchers made the first detailed measurements of two pulsars previously identified as possible sources of the excess. By catching and counting particles of light streaming from these nearby stellar engines, the HAWC collaboration showed that the two pulsars are unlikely to be the origin of the positron excess. Despite being the right age and the right distance from Earth, the pulsars are surrounded by an extended murky cloud from which positrons can't escape in great numbers, according to results published this week in Science.

Petra Huentemeyer, associate professor physics at Michigan Technological University and founding member of the HAWC collaboration, started working with her former PhD student, Hao Zhou, on the related analysis of HAWC data while he was a postdoc at Michigan Tech in 2016.

"Our analysis does not support previous claims that the two nearby pulsars are responsible for the excess of positrons detected by two space-born telescopes, the Italian-lead PAMELA project and the AMS-02 detector of NASA," she says.

Some researchers posit that the positrons are produced in dark matter interactions.

"There are all kinds of efforts all over the globe to detect dark matter directly," she says. "Dark matter is difficult to detect. Dark matter is elusive. We don't see it. The reason we think it exists is because if you take what we know about gravitation and then look at the velocity of stars traveling around the center of disk galaxies, they are not traveling at the speeds we expect from visible matter. There must be dark, non-light emitting mass somewhere that causes this from what we understand about gravitation."

While the results in the Science paper do not affirm the detection of dark matter, they do confirm that positron excess is not explained by a pulsar nebula throwing off the particles.

Looking for Answers

The HAWC Observatory sits at an elevation of 13,500 feet, flanking the Sierra Negra volcano inside Pico de Orizaba National Park in the Mexican state of Puebla. More than 300 massive water tanks sit waiting at the site for cascades of particles initiated by high-energy packets of light called gamma rays -- many of which have more than a million times the energy of a dental X-ray.

When these gamma rays smash into the upper atmosphere, they blast apart atoms in the air, producing a shower of particles that moves at nearly the speed of light toward the ground. When this shower reaches HAWC's tanks, it produces coordinated flashes of blue light in the water, allowing researchers to reconstruct the energy and cosmic origin of the gamma ray that kicked off the cascade.

This measurement wouldn't have been possible without HAWC's wide view. It continuously scans about one-third of the sky overhead, which provided researchers with a broad view of the space around the pulsars.

"Thanks to its wide field of view, HAWC provides unique measurements on the very-high-energy gamma-ray profiles caused by the particle diffusion around nearby pulsars, which allows us to determine how fast the particles diffuse more directly than previous measurements," says Hao Zhou, now a scientist at the Los Alamos National Laboratory in New Mexico and Michigan Tech alumnus.

Zhou, one of the paper's corresponding authors, is responsible for developing the particle diffusion model and calculating the gamma-ray emission morphology around the two pulsars in HAWC data. He fit this model to the data to constrain the physical parameter about these sources, which describes how fast a particle diffuses away from its source.

As with an ordinary camera, collecting lots of light allows HAWC to build sharp images of individual gamma-ray sources. The highest energy gamma rays originate in the graveyards of big stars, such as the spinning pulsar remnants of supernovae. But that light doesn't come from the stars themselves. Instead, it's created when the spinning pulsar accelerates particles to extremely high energies, causing them to smash into lower-energy photons left over from the early universe.

The size of this stellar debris field, measured by the patch of sky that glows bright in gamma rays, tells researchers how quickly matter moves relative to a local astrophysical engine -- in this case, the nearby pulsars. This, in turn, enables researchers to estimate how quickly positrons are moving and how many positrons could have reached Earth from a given source. Using the most complete catalog of HAWC data to date, scientists have determined that the nearby pulsar Geminga and its unnamed sister are not sources of the positron excess. Even though the two pulsars are old enough and close enough to account for the excess, matter isn't drifting away from the pulsars fast enough to have reached the Earth.

Read more at Science Daily

Experimental Patch Could Ease Allergic Reactions to Peanuts

Having a food allergy requires more than a change in diet. For many people with a moderate to severe allergy, it requires a change in lifestyle.

In the United States, one of the most common food allergies is peanuts, an ingredient found in everything from lunch sandwiches to chili. In 2014, two percent of children in the United States under the age of 18 had a peanut allergy. It is the most common cause of anaphylaxis, a reaction in which a person experiences itchiness, swelling of the throat, plummeting blood pressure, fainting, or vomiting. When severe reactions are not treated with an emergency injection of epinephrine, the effect can sometimes be fatal.

While there is no cure for a peanut allergy, scientists are working on various treatments that can at least reduce the severity of reactions to the nut. Immunotherapy, where the patient is exposed to very small amounts of peanut protein over time, has garnered the attention of the science community in the past decade. While many of these studies have focused on oral doses of peanut protein — taken in a pill, for example — a new clinical trial shows that one solution may be skin deep.

The study, published in the Journal of the American Medical Association, on more than 200 peanut-allergic patients. Hugh Sampson of the Icahn School of Medicine at Mount Sinai School in New York led the research. Sampson is also the part-time, chief scientific officer at DBV Technologies, which makes the Viaskin Peanut patch and funded the study.

For the study, 221 participants between the ages of 6 and 55 years old were divided into four groups. One group received a placebo patch, which contained no peanut protein. The second, third, and fourth groups wore peanut patches containing either 50, 100, or 250 micrograms of peanut protein. The patients wore the patch on the back of their arm or their back every day for a year. In the end, 97 percent of the study participants — 207 patients — completed the full year.

The patch resembles a small round Band-Aid. When the patch is applied, the body’s natural water loss helps the peanut protein absorb the peanut protein inside, which is then absorbed into the skin and picked up by Langerhans cells. These cells then transport the protein to regional lymph nodes, where they educate regulatory T cells that might lessen an allergic response.

Sampson noted that the amount of peanut protein used in the study was very small when compared to the amounts used in other trials for oral immunotherapies. One oral immunotherapy, for example, gave patients up to two grams of peanut protein.

To be classified as a “responder” to the patch treatment, patients had to be able to tolerate 1,000 milligrams of the peanut protein at the end of the year, or 10 times more peanut protein than the amount that initially triggered their reactions at the beginning of the study.

After a year, a significant number of responders in the group wore the patch with 250 micrograms of peanut protein when compared to those wearing the placebo patch. There was no significant difference between those wearing the patches with 50 or 100 micrograms and the placebo group.

While Sampson said the results were in line with what his team was expecting, he added that there were some interesting findings when looking at the different age groups.

Children, or those 6 to 11 years old, had a better response to the patch when compared to the adolescent and adult groups. The result could be because of where the patch was placed — the patch was placed on the backs of the children while others wore the patch on the back of their arms — or the number of Langerhans cells exposed to the patch.

“We know that the Langerhans cells that pick up the protein tend to congregate around the hair follicle,” said Sampson. “Basically, you get so many hair follicles, and when you get older they spread out. So, it could be that using the same sized patch on an adult verses a child could mean that you’re not exposing as many Langerhans cells in an adult as you would a child.”

Read more at Seeker

Passenger Pigeon DNA Shows How Large, Stable Populations Can Quickly Go Extinct

A male passenger pigeon, estimated to sell for 8,000-12,000 GBP, is displayed at Summers Place Auctions on November 19, 2015 in Billingshurst, England.
The passenger pigeon was once the most abundant bird in North America, numbering between 3–5 billion. John Muir and many other naturalists were fascinated by these large, intelligent birds that often would passager, according to the French, or pass by, while migrating.

Muir devoted five full pages to passenger pigeons in his autobiography, mentioning that "the air was literally filled with pigeons" and the "continued buzz of wings" lulled him to sleep.

Over the course of Muir's lifetime, however, passenger pigeons died by the millions. In 1914 — the year of his own death — only one was left. Martha, as she was called, died on September 1 of that year at the Cincinnati Zoo, marking the species's extinction.

What lives on is a cautionary tale, according to a new genetic study on the birds published in the journal Science. Their DNA provides evidence that even large, stable populations can be at risk of extinction if rapid environmental change occurs.

"When passenger pigeon populations were large, there was natural selection for advantageous genes and against deleterious genes — both forms were highly efficient," senior author Beth Shapiro of the University of California, Santa Cruz told Seeker. "However, selection always works within a particular environment."

"In this case," she continued, "that environment was living in huge flocks. When the flocks became suddenly tiny — thanks to human hunting — these adaptations to life in large populations were suddenly of no use to the birds."

Female and male passenger pigeons from the collections of the Royal Ontario Museum
Shapiro, lead author Gemma Murray, and their international team were granted access to collections of passenger pigeons in museums. To cause minimal damage, the researchers extracted DNA from toe pads or bone samples of 84 of the birds.

The researchers then extracted DNA from four band-tailed pigeons. The band-tailed pigeon — a sociable bird with a mellow coo — is common in forests of the Pacific Coast and Southwest and is the closest living relative of the passenger pigeon.

A comparison of the two species' nuclear genomes revealed that the once-large population of passenger pigeons allowed for faster adaptive evolution than what is seen in band-tailed pigeons. High-diversity regions of passenger pigeon underwent stronger and faster genetic selection to remove harmful mutations and to maintain advantageous genes.

In short, passenger pigeons were almost perfectly adapted to their habitat and way of life.

The researchers were surprised to see that passenger pigeon populations were large even throughout the last ice age.

“This meant that these birds must have had both a very broad diet and a tremendous capacity to adapt to the enormous ecological changes that occurred as climate warmed into the present day," Shapiro said.

The apparent idyllic life of the passenger pigeon took a drastic turn for the worse when humans — first Native Americans, then Europeans — arrived in the Americas.

Because the meaty birds were close-knit and existed in large flocks, hunters could easily kill many at a time with little effort. By the 19th century, pigeon hunting intensified with growing demand for what was then considered to be cheap and good eats.

Passenger pigeons that survived the blood bath were reduced to living in small, isolated populations.

"Perhaps it was harder for them to find food, find a mate, and to do what it meant to be a passenger pigeon," Shapiro said. "If the decline had been slower, it is possible that passenger pigeons would have gradually adapted to their new ecological state."

Humans did not just hunt the birds. They also destroyed their habitat.

“The deforestation that was going on in the 19th century,” said Murray, “would have also had an impact, since passenger pigeons lived in forests and woodlands and ate nuts from trees."

With little time to adapt to the sudden changes, passenger pigeons went into a gradual decline from about 1800 to 1870, followed by a rapid decline between 1870 and 1890. The last confirmed passenger pigeon in the wild was thought to have been shot in 1901.

Band-tailed pigeons
Passenger pigeons and band-tailed pigeons co-existed, but did not interbreed, Shapiro said. She explained that the Rocky Mountains, which seem to be a barrier for band-tailed pigeons today, kept the two species apart.

Band-tailed pigeons may have survived, Murray said, because they form much smaller flocks and are less of a social species than passenger pigeons. “These features might make band-tailed pigeons more resilient than passenger pigeons to extinction, since they might allow them to live more successfully in smaller and more isolated populations," she said.

Read more at Seeker

Nov 16, 2017

Floating droplets: How droplets can 'levitate' on liquid surfaces

Visualization of vortices in a drop of silicone oil sitting on a warm bath. The temperature difference generates a recirculating flow that is visualized by shining a green laser light on fluorescent particles that are added as passive tracers within the drop.
A drop or two of cold cream in hot coffee can go a long way toward improving one's morning. But what if the two liquids didn't mix?

MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below. If the droplet is very cold, and the bath sufficiently hot, then the droplet should "levitate" on the bath's surface, as a result of the flows induced by the temperature difference.

The team's results, published today in the Journal of Fluid Mechanics, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.

The results may help researchers understand how biological or chemical substances are spread by rain or other sprays in nature. They could also serve as a guide for droplet-based designs, such as in microfluidic chips, in which droplets carrying various reagents can be designed to mix only in certain locations in a chip, at certain temperatures. With this new understanding, researchers could also engineer droplets to act as mechanical ball bearings in zero-gravity environments.

"Based on our new theory, engineers can determine what is the initial critical temperature difference they need to maintain two drops separately, and what is the maximum weight that a bearing constructed from these levitating drops would be able to sustain," says Michela Geri, a graduate student in MIT's Department of Mechanical Engineering and the study's lead author. "If you have a fundamental understanding, you can start designing things the way you want them to work."

Geri's co-authors are Bavand Keshavarz, a lecturer in mechanical engineering, John Bush, professor of applied mathematics in MIT's Department of Mathematics, and Gareth McKinley, the School of Engineering Professor of Teaching Innovation.

An uplifting experiment

The team's results grew out of a question that Bush posed in his graduate course 18.357 (Interfacial Phenomena): Why should a temperature difference play a role in a droplet's coalescence, or mixing?

Geri, who was taking the course at the time, took on the challenge, first by carrying out a series of experiments in McKinley's lab.

She built a small box, about the size of an espresso cup, with acrylic walls and a metal floor, which she placed on a hot/cold plate. She filled the cube with a bath of silicone oil, and just above the surface of the bath she set a syringe through which she pumped droplets of silicone oil of the same viscosity. In each series of experiments, she set the temperature of the hot/cold plate, and measured the temperatures of the oil pumped through the syringe and at the surface of the bath.

Geri used a high-speed camera to record each droplet, at 2,000 frames per second, from the time it was released from the syringe to the time at which it mixed thoroughly with the bath. She performed this experiment using silicone oils with a range of viscosities, from water-like to 500 times thicker.

She found that droplets appeared to levitate on a bath's surface as the temperature gradient between the two fluids increased. She was able to levitate a droplet, delaying its coalescence, by as long as 10 seconds, by maintaining a temperature difference of up to 30 degrees Celsius, or 86 degrees Fahrenheit, comparable to the difference between a drop of cold milk on a bath of hot black coffee.

Geri plotted the data and observed that the droplet's residence time on the bath's surface seemed to depend on the initial temperature difference between the two fluids, raised to the power of two-thirds. She also noticed that there exists a critical temperature difference at which a droplet of a given viscosity will not mix but instead levitate on a liquid surface.

"We saw this relationship clearly in the lab and then tried to develop a theory in hopes of rationalizing that dependence," Geri says.

A cushion's character

The team first looked to characterize the layer of air separating the droplet from the bath. The researchers hypothesized that a temperature difference between the two fluids may influence this air cushion, which may in turn act to keep a droplet afloat.

To investigate this idea mathematically, the researchers performed a calculation, referred to in fluid mechanics as a lubrication analysis, in which they appropriately simplified the complex equations describing fluid motion, to describe the flow of air between the droplet and the bath.

Through these equations, they found that temperature differences between the fluid drop and the fluid bath create convection, or circulating currents in the intervening layer of air. The greater the temperature difference, the stronger the air currents, and the greater the pressure that pushes against the droplet's weight, preventing it from sinking and making contact with the bath.

"We found the force coming from the droplet's weight and the force coming from the recirculation of the air layer will balance at a point, and to get that balance, you need a minimum, or critical temperature difference, in order for the droplet to levitate," Geri says.

Inside a single drop

Next, the team looked for a mathematical explanation for why they observed the 2:3 relationship between the amount of time a droplet levitates on a liquid surface and the initial temperature difference between the two fluids.

"For that, we had to think about how the temperature of the drop changes over time and approaches the temperature of the bath," Geri says.

"With a temperature difference, you generate a flow inside the drop, drawing up heat from the bath, which circulates around until the droplet temperature is the same as the bath and you don't levitate anymore," Bush adds. "We were able to describe that process mathematically."

To do so, the researchers adapted another set of equations, which describe the mixing of two fluids. They used the equations to model a warm parcel of liquid within the droplet that has been warmed by the bath below. They were able to characterize how that parcel of liquid mixed with the colder portions of the droplet, warming the entire droplet over time.

Through this modeling, they could observe how the temperature difference between fluids decreased over time, to the point at which a droplet stopped levitating and ultimately mixed with the rest of the bath.

"If you study that process mathematically, you can show the way in which temperature is changing in the droplet over time is exactly with this power law of 2/3 that we observed in our experiments," Geri says.

Bush says that their results can be used to characterize the spread of certain chemical and biological agents that are transferred through raindrops and sprays.

Read more at Science Daily

New treasures from Tutankhamun’s tomb

Embossed gold application with motif of animal combat of Levantine origin.
As part of a German-Egyptian project, archaeologists from Tübingen for the first time examine embossed gold applications from the sensational find of 1922. The motifs indicate surprising links between the Levant and the Egypt of the pharaohs.

Researchers from Tübingen working on a German-Egyptian project have examined embossed gold applications from the treasure of the tomb of the pharaoh Tutankhamun for the first time. The objects come from the famed find made by English archaeologist Howard Carter in 1922. Until now, they had been held in storage at the Egyptian Museum Cairo. They can be seen at a special exhibition at the museum which began on Wednesday. Conservators and archaeologists of the Institute of Ancient Near Eastern Studies (IANES, Professor Peter Pfälzner), the German Archaeological Institute, Cairo, (DAI, Professor Stephan Seidlmayer), and the Römisch-Germanischen Zentralmuseums Mainz (RGZM, Professor Falko Daim), as well as the Egyptian Museum have spent four years (2013-2017) analysing the find.

Through painstaking hours in the lab, the partners restored the objects at the Egyptian Museum. They also made drawings of the items and did comprehensive research on them. A team of conservators, Egyptologists and specialists in Near Eastern archaeology found the embossed gold applications in the same crate they were placed in by Howard Carter's team immediately after their discovery. At the time, the artefacts were photographed and packed, unrestored, and were never again removed until this project.

During years of detail work, conservators Christian Eckmann and Katja Broschat of the Römisch-Germanischen Zentralmuseum Mainz reassembled the fragments to produce 100 nearly complete embossed gold applications. They suspect the items are decorative fittings for bow cases, quivers and bridles. IANES archaeologists from Tübingen examined the images on the embossed gold applications and categorized them from an art-historical perspective. In her dissertation, doctoral candidate Julia Bertsch succeeded in distinguishing the Egyptian motifs on the embossed gold applications from those that could be ascribed to an "international," Middle Eastern canon of motifs.

Among these are images of fighting animals and goats at the tree of life that are foreign to Egyptian art and must have come to Egypt from the Levant. "Presumably these motifs, which were once developed in Mesopotamia, made their way to the Mediterranean region and Egypt via Syria," explains Peter Pfälzner. "This again shows the great role that ancient Syria played in the dissemination of culture during the Bronze Age."

Interestingly, he adds, similar embossed gold applications with thematically comparable images were found in a tomb in the Syrian Royal city of Qatna. There, the team of archaeologists from Tübingen led by Pfälzner, discovered a pristine king's grave in 2002. It dates back to the time of around 1340 B.C., so it is just a bit older than Tutankhamun's tomb in Egypt. The archaeologist says, "This remarkable aspect provided the impetus for our project on the Egyptian finds." Now," says Pfälzner, "we need to solve the riddle of how the foreign motifs on the embossed gold applications came to be adopted in Egypt." The professor says that here, chemical analyses have been illuminating. "The results showed that the embossed gold applications with Egyptian motifs and the others with foreign motifs were made of gold of differing compositions," he says. "That does not necessarily mean the pieces were imported. It may be that various local workshops were responsible for producing objects in various styles -- and that one used Near Eastern models."

Read more at Science Daily

Archaeology: Medieval treasure unearthed at the Abbey of Cluny

(1) Knotted tanned hide bundle before extraction of contents; (2) & (4) gold dinars; (3) signet ring with intaglio; (5) contents of knotted tanned hide bundle.
In mid-September, a large treasure was unearthed during a dig at the Abbey of Cluny, in the French department of Saône-et-Loire: 2,200 silver deniers and oboles, 21 Islamic gold dinars, a signet ring,1 and other objects made of gold. Never before has such a large cache of silver deniers been discovered. Nor have gold coins from Arab lands, silver deniers, and a signet ring ever been found hoarded together within a single, enclosed complex.

Anne Baud, an academic at the Université Lumière Lyon 2, and Anne Flammin, a CNRS engineer -- both from the Laboratoire Archéologie et Archéométrie (CNRS / Université Lumière Lyon 2 / Claude Bernard Lyon 1 University) -- led the archaeological investigation, in collaboration with a team of 9 students from the Université Lumière Lyon 2 and researchers from the Maison de l'Orient et de la Méditerranée Jean Pouilloux (CNRS / Université Lumière Lyon 2).

The excavation campaign, authorized by the Bourgogne-Franche-Comté Regional Department of Cultural Affairs (DRAC), began in mid-September and ended in late October. It is part of a vast research program focused on the Abbey of Cluny. Students in the Master of Archaeology and Archaeological Science program at the Université Lumière Lyon 2 have been participating in archaeological digs at the Abbey of Cluny since 2015. This experience in the field complements their academic training and gives them an insight into professional archaeology.

At the site, the team led by Anne Baud et Anne Flammin, including the students from the Université Lumière Lyon 2, discovered a treasure consisting of

§ more than 2,200 silver deniers and oboles -- mostly minted by the Abbey of Cluny and probably dating to the first half of the 12th century -- in a cloth bag, traces of which remain on some of the coins

§ a tanned hide bundle, found among the silver coins, fastened with a knot, and enclosing

o 21 Islamic gold dinars struck between 1121 and 1131 in Spain and Morocco, under the reign of Ali ibn Yusuf (1106-1143), who belonged to the Berber Almoravid dynasty.

o a gold signet ring with a red intaglio depicting the bust of a god and an inscription possibly dating the ring back to the first half of the 12th century

o a folded sheet of gold foil weighing 24 g and stored in a case

o a small circular object made of gold

Vincent Borrel, a PhD student at the Archaeology and Philology of East and West (CNRS / ENS) research unit -- AOROC for short -- is currently studying the treasure in more detail to identify and date the various pieces with greater precision.

A precious find . . .

This is an exceptional find for a monastic setting and especially that of Cluny, which was one of the largest abbeys of Western Europe during the Middle Ages. The treasure was buried in fill where it seems to have stayed for 850 years.

It includes items of remarkable value: 21 gold dinars and a signet ring, a very expensive piece of jewelry that few could own during the Middle Ages. At that time, Western currency was mostly dominated by the silver denier. Gold coins were reserved for rare transactions. The 2,200 or so silver deniers, struck at Cluny or nearby, would have been for everyday purchases. This is the largest stash of such coins ever found.

The fact that Arab currency, silver deniers, and a signet ring were enclosed together makes this discovery all the more interesting.

. . . opening new avenues of research into the history of the Abbey of Cluny

This discovery will breathe new life into research delving into the past of the abbey, a historic site open to the public and managed by the Centre des Monuments Nationaux (CMN). It also raises new questions worth answering:

ð Who owned the treasure? Was it a monk, a church dignitary, or a rich layman?

ð What can the coins teach us? Where were the silver deniers of Cluny struck? Where did they circulate? How did Islamic dinars minted in Spain and Morocco end up at Cluny?

Read more at Science Daily

Pluto's hydrocarbon haze keeps dwarf planet colder than expected

Pluto's haze layer is blue in this image taken by the New Horizons Ralph/Multispectral Visible Imaging Camera and computer generated to replicate true color. Haze is produced by sunlight-initiated chemical reactions of nitrogen and methane, leading to small particles that grow and settle toward the surface.
The gas composition of a planet's atmosphere generally determines how much heat gets trapped in the atmosphere. For the dwarf planet Pluto, however, the predicted temperature based on the composition of its atmosphere was much higher than actual measurements taken by NASA's New Horizons spacecraft in 2015.

A new study published November 16 in Nature proposes a novel cooling mechanism controlled by haze particles to account for Pluto's frigid atmosphere.

"It's been a mystery since we first got the temperature data from New Horizons," said first author Xi Zhang, assistant professor of Earth and planetary sciences at UC Santa Cruz. "Pluto is the first planetary body we know of where the atmospheric energy budget is dominated by solid-phase haze particles instead of by gases."

The cooling mechanism involves the absorption of heat by the haze particles, which then emit infrared radiation, cooling the atmosphere by radiating energy into space. The result is an atmospheric temperature of about 70 Kelvin (minus 203 degrees Celsius, or minus 333 degrees Fahrenheit), instead of the predicted 100 Kelvin (minus 173 Celsius, or minus 280 degrees Fahrenheit).

According to Zhang, the excess infrared radiation from haze particles in Pluto's atmosphere should be detectable by the James Webb Space Telescope, allowing confirmation of his team's hypothesis after the telescope's planned launch in 2019.

Extensive layers of atmospheric haze can be seen in images of Pluto taken by New Horizons. The haze results from chemical reactions in the upper atmosphere, where ultraviolet radiation from the sun ionizes nitrogen and methane, which react to form tiny hydrocarbon particles tens of nanometers in diameter. As these tiny particles sink down through the atmosphere, they stick together to form aggregates that grow larger as they descend, eventually settling onto the surface.

"We believe these hydrocarbon particles are related to the reddish and brownish stuff seen in images of Pluto's surface," Zhang said.

The researchers are interested in studying the effects of haze particles on the atmospheric energy balance of other planetary bodies, such as Neptune's moon Triton and Saturn's moon Titan. Their findings may also be relevant to investigations of exoplanets with hazy atmospheres.

Read more at Science Daily

Archaeological Treasures in Iraq Unearthed Just Before Deadly 7.3 Earthquake

Neo-Assyrian cylinder seal and imprint on right, height 1.5 inches. It depicts two winged genies on a sacred tree.
Iraq is the birthplace of numerous historic firsts. It is where the sailboat, wheel, and seed plow were invented. Lying within the Fertile Crescent, it is where cereal agriculture and commercial record keeping began. Even the concept of zero and 360-degree circles were formulated in what is now Iraq.

Iraq and nearby Iran’s history are therefore of great interest to archaeologists, who often must face both manmade and natural challenges when working in the region. Earthquakes, such as the 7.3 magnitude on that struck Iran and Iraq on November 12, threaten not only people, but also invaluable archaeological artifacts that are important to the collective history of humankind.

A recent six-week excavation in the province fortuitously ended before the earthquake struck. The work focused on the 7.4-acre site Gird-î Qalrakh on the Shahrizor Plain, and unearthed evidence for an ancient, centuries-old textile industry in a region now famed for its colorful Iraqi-Kurdish carpets and related woven goods.

The discoveries almost didn't happen.

Project leader Dirk Wicke of the Institute of Archaeology at Goethe University and his team were wrapping up their excavation, when student Lanah Haddad noticed a wall from a mysterious room within the trench where she was digging. Wicke asked her to keep removing dirt. As she did, several clay weights became visible, along with the charred remains of a large ancient loom.

“Lanah worked hard with the support of 1–2 students, and I decided to leave her trench alone and open for 2 more days — which was really worth it,” Wicke told Seeker.

Backfilling of trenches following excavation
His curiosity grew over other clay objects in the trench, due to their slightly off color and texture. Similar moments have happened to him before, he said, explaining that when he sees such clues, he will try to turn the clay objects over, in order to identify possible lines, dots, and curves, which form a pattern or shape.

“Once carefully dry-cleaned in the dig house, you start to twist the find beneath strong light from all sides in order to identify the images,” he said. “In this case, they were beautiful Sasanian griffins and horses.”

Griffins — mythical creatures with the head and wings of an eagle and the body of a lion — are perhaps best known to people today from the popular Harry Potter films.

Although the lighting was poor in the tiny, cramped dig house where he and his team were based during the excavation, they were able to photograph the griffin. His team determined that the object and others found with it were probably seals from rolls of fabric.

Seal impression of griffin, c. 2cm
About 16 and a half feet below the layer where the loom and seals were discovered, the researchers found an elaborate cylinder seal dating to a much earlier time, the 9th-7th century BC Assyrian period. Assyria refers to a major Mesopotamian kingdom that, at its peak, stretched from Cyprus and the East Mediterranean to Iran, and from what is now Armenia and Azerbaijan in the Caucasus, to the Arabian Peninsula, Egypt, and eastern Libya.

The scientists were able to take a clear photo of the Assyrian cylinder seal.

"The seal was used as in modern administrative procedures — to function like a signature and authorize a treaty, letter, or other official document,” Wicke said. “One has to bear in mind, that the Assyrian documents were written in cuneiform script on wet, clay tablets, which later dried or got baked to last."

The cylinder seal depicts two winged genies with a purifying "cone" and a bucket of purifying liquid that was most likely water. The genies, he said, "flank a sacred tree expressing purification," which is "a standard topic in neo-Assyrian art."

"It is difficult to pinpoint an exact meaning to it, but this image was very often depicted in the royal palaces and appears to act as a beneficiary motif used to magically protect the king and inhabitants of the palace or palaces," he said.

On the back of this seal, opposite the tree, is a spade associated with the Babylonian god Marduk. This suggests that the seal was made and used when there were strong connections between Assyria and Babylonia, which was another ancient empire at the time.

Also dating to the 9th-7th century BC is a terraced, stone wall. The archaeologists believe it was part of a watchtower.

Wicke said that the land at the site was, and still is, "very fertile," making it an attractive location for settlement. Additionally, springs upstream of the site provide a near-continuous supply of fresh water, even during the hot and arid summer months.

It is little wonder then that people thrived on the Shahrizor plain during the much later era of the loom, which to an untrained eye looks a bit like a skeleton stretched out in a grave. The pieces instead are what is left of the large standing device that featured vertical hanging threads, which were pulled vertically straight by the clay loom weights. The threads were then woven horizontally.

"This is one of the oldest arrangements of a loom," Wicke said.

Excavated corner of room with remnants of the loom between the wall (top) and a bench of six mud bricks. The round loom weights made from clay are visible, as are slabs of mud once forming some kind of shelving.
Wicke suspected that for many centuries prior to around 4 AD it was home to a small farming community, but now they are rethinking its significance.

"It looks as if the site was taking part in a larger, overarching network of the textile trade, but this, of course, needs further examination," he said. "Why it was burnt, I really can't say."

The loom and seals came as a surprise to the researchers, who are studying the region's ceramic history that currently "still lacks a coherent pattern chronology," Wicke said. This work has been funded since 2015 by the local antiquities cervice, the Thyssen Foundation, and the Enki e.V. Association located at Goethe.

Read more at Seeker

Nov 15, 2017

Why hot water freezes faster than cold water

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A team of researchers from Universidad Carlos III de Madrid, the Universidad de Extremadura and the Universidad de Sevilla have defined a theoretical framework that could explain the Mpemba effect, a counterintuitive physical phenomenon revealed when hot water freezes faster than cold water.

The researchers, who have recently published the findings in Physical Review Letters, have confirmed how this phenomenon occurs in granular fluids, that is, those composed of particles that are very small and interact among those that lose part of their kinetic energy. Thanks to this theoretical characterization, "we can simulate on a computer and make analytical calculations to know how and when the Mpemba effect will occur," said Antonio Lasanta. Lasanta is from the UC3M Gregorio Millán Barbany University Institute for Modeling and Simulation on Fluid Dynamics, Nanoscience and Industrial Mathematics. "In fact," he said, "we find not only that the hottest can cool faster but also the opposite effect: the coldest can heat faster, which would be called the inverse Mpemba effect."

The fact that preheated liquids freeze faster than those that are already cold was observed for the first time by Aristotle in the 4th century AD. Francis Bacon, the father of scientific empiricism, and René Descartes, the French philosopher, were also interested in the phenomenon, which became a theory when, in 1960, a Tanzanian student named Erasto Mpemba explained to his teacher in a class that the hottest mixture of ice cream froze faster than the cold one. This anecdote inspired a technical document about the subject, and the effect began to be analyzed in educational and science magazines. However, its causes and effects have hardly been studied until now.

"It is an effect that, historically, has not been addressed in a rigorous manner but merely as an anomaly and a didactic curiosity," said Antonio Prados, one of the researchers from the Universidad de Sevilla Department of Theoretical Physics. "From our perspective, it was important to study it in a system with the minimum ingredients to be able to control and understand its behavior," he said. This has enabled them to understand what scenarios it is easier to occur in, which is one of the main contributions of this scientific study. "Thanks to this, we have identified some of the ingredients so that the effect occurs in some physical systems that we can describe well theoretically," stated researcher Francisco Vega Reyes and Andrés Santos, from the Universidad de Extremadura Instituto de Computación Científica Avanzada (Institute of Advanced Scientific Computation).

"The scenario that the effect will most easily occur in is when the velocities of the particles before heating or cooling have a specific disposition -- for example, with a high dispersion around the mean value," he said. This way, the evolution of the temperature of the fluid can be significantly affected if the state of the particles is prepared before the cooling.

Read more at Science Daily