Shocking case of indigestion in supermassive black hole

Left: Image of the Whirlpool galaxy and NGC 5195. Credit: Jon Christensen. Right: False colour image of NGC 5195 created by combining the VLA 20 cm radio image (red), the Chandra X-ray image (green), and the Hubble Space telescope H-alpha image (blue). The image shows the X-ray and H-alpha arcs, as well as the radio outflows from the supermassive black hole at the centre of NGC 5195. Right inset: e-MERLIN maps of the nuclear region of NGC 5195 at 1.4 GHz (left) and 5 GHz (right). The images display a partially resolved source with possible parsec-scale outflows.

A multi-wavelength study of a pair of colliding galaxies has revealed the cause of a supermassive black hole's case of 'indigestion'. Results will be presented by Dr Hayden Rampadarath at the National Astronomy Meeting at the University of Hull.

Once every couple of hundred million years, the small galaxy NGC 5195 falls into the outer arms of its larger companion, NGC 5194, also known as the Whirlpool galaxy. Both galaxies are locked in a gravitational dance that will result -- billions of years in the future -- in the formation of a single galaxy.

As NGC 5195 plunges into the Whirlpool, matter streams onto the supermassive black hole at NGC 5195's centre and forms an accretion disc. The disc grows to a point where the supermassive black hole can no longer accrete or 'digest' efficiently and matter is blasted out into the surrounding interstellar medium. Last year, NASA's Chandra X-Ray observatory spotted arcs of X-ray emission that appeared to result from this 'force-feeding'.

Now, new high-resolution images of the core of NGC 5195, taken with the e-MERLIN radio array, and archive images of the surrounding area from the Very Large Array (VLA), Chandra and the Hubble Space Telescope, reveal in detail how these blasts occur and spread. The study was led by astronomers at the University of Manchester's Jodrell Bank Centre for Astrophysics.

The supermassive black hole at the centre of NGC 5195 has a mass equivalent to 19 million Suns. When the accretion process breaks down, immense forces and pressures create a shock wave that pushes matter out into the interstellar medium. Electrons, accelerated close to the speed of light, interact with the magnetic field of the interstellar medium and emit energy at radio wavelengths. The shock wave then inflates and heats up the interstellar medium, which emits in the X-ray, and strips the electrons from surrounding neutral hydrogen atoms to make ionised hydrogen gas. This inflated bubble creates the arcs detected by Chandra and Hubble.

Rampadarath explains: "Comparing the VLA images at radio wavelengths to Chandra's X-ray observations and the hydrogen-emission detected by Hubble, shows that features are not only connected, but that the radio outflows are in fact the progenitors of the structures seen by Chandra and Hubble. This is an event of galactic proportions that we can see right across the electromagnetic spectrum."

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Dinosaurs' loss was frogs' gain: The upside of a mass extinction

The frog Hyla sanchiangensis from eastern China is a descendant of one of three lineages (Hyloidea) that made it through Earth's last mass extinction 66 million years ago to flourish worldwide today. It's ancestors diversified out of South America.

Most of the frogs alive today owe a big thank you to the asteroid or comet that delivered the coup de grace to the dinosaurs.

A new study by Chinese and American biologists shows that if the calamity had not wiped the planet clean of most terrestrial life 66 million years ago, 88 percent of today's frog species wouldn't be here. Nearly nine out of 10 species of frog today have descended from just three lineages that survived the mass extinction.

The results, to be published this week in the journal Proceedings of the National Academy of Sciences, are a surprise, because previous studies of frog evolution pinpointed the blossoming of the main frog lineages today to about 35 million years earlier, in the middle of the Mesozoic era.

The new analysis of 95 genes from frogs within 44 of 55 living families shows that these three lineages started to take off precisely at the boundary between the Cretaceous and Paleogene periods -- the K-Pg boundary, formerly called the KT boundary -- when the last mass extinction occurred, and not 100 million years ago.

According to herpetologist and co-author David Wake, a University of California, Berkeley professor of the graduate school and a curator of the Museum of Vertebrate Zoology, new frog species likely radiated rapidly throughout the world because so many environmental niches were available after the animals occupying them disappeared.

"We think the world was quite impoverished as a result of the KT event, and when the vegetation came back, angiosperms dominated. That's when trees evolved to their full flowering," Wake said. "Frogs started becoming arboreal. It was the arboreality that led to the great radiation in South America in particular."

Trees are an ideal habitat for frogs not only because they allow them to escape from terrestrial predators, but also because their fallen leaves provide protection while the frogs are on the ground, breeding habitat and plenty of food, such as insects. Trees and other flowering plants took off in the late Cretaceous, and were ready for exploitation by frogs after they recovered from the extinction.

Another adaptation that became popular was direct development, that is, producing young without a tadpole stage, which is standard for about half of all frog species today.

"The majority of the frogs that thrive now are thriving because of direct development of eggs in terrestrial situations," he said. "It is a combination of direct development and use of arboreal habitat that accounts for a great deal of the radiation."

Previous genetic analyses of frog evolution focused on mitochondrial DNA and how long the molecular clock had been ticking for mitochrondrial genes. However, analysis of molecular evolution in mitochondrial DNA often produces dates for lineage divergence that are too old. In the case of frogs, such analysis pinpointed the radiation of most living frogs at about 100 million years ago, which was a puzzle, since Earth's environment was stable at that time. A changing environment typically drives evolution.

The new analysis, based on data assembled primarily by graduate student Yan-Jie Feng at Sun Yat-Sen University in Guangzhou, China, focused on the sequences of 95 genes located on chromosomes in the nucleus and how they changed over time. He and his colleagues gathered genetic data from 156 frog species and combined this with earlier information about two genes from 145 different frogs, for a total of 301 distinct frog species from all 55 families of frogs. The data were calibrated using 20 dates derived from fossils and Earth historical events.

The team, which includes scientists from the Florida Museum of Natural History at the University of Florida and the University of Texas, Austin, concluded that perhaps 10 groups of frogs survived the extinction, but only three of them (Hyloidea, Microhylidae, and Natatanura) flourished and diversified to claim habitats and niches around the world.

Nothing other than luck distinguishes the survivors, Wake said. Remnants of the other surviving lineages are scattered in isolated spots around the world, but are just as diverse today in their habitats and breeding strategies as the 88 percent.

Two of the three surviving lineages that subsequently radiated widely came out of Africa, which remained intact as the continents shifted around over the ensuing eons, with the breakup of Pangea and then Gondwana to form the continents we see today. The African rift zone and mountain building in West Africa generated new habitats for the evolving frogs, Wake noted. The third, Hyloidea, radiated throughout what became South America.

Today's frogs, comprising more than 6,700 known species, as well as many other animal and plant species are under severe stress around the world because of habitat destruction, human population explosion and climate change, possibly heralding a new period of mass extinction. The new study provides one clear message for future generations.

Read more at Science Daily

Through fossil leaves, a step towards Jurassic Park

Ginkgo fossil.

For the first time, researchers have succeeded in establishing the relationships between 200-million-year-old plants based on chemical fingerprints. Using infrared spectroscopy and statistical analysis of organic molecules in fossil leaves, they are opening up new perspectives on the dinosaur era.

The unique results stem from a collaboration between researchers at Lund University, the Swedish Museum of Natural History in Stockholm, and Vilnius University.

"We have solved many questions regarding these extinct plants' relationships. These are questions that science has long been seeking answers to," says Vivi Vajda, a professor at the Department of Geology at Lund University and active at the Swedish Museum of Natural History.

The researchers have collected fossil leaves from rocks in Sweden, Australia, New Zealand and Greenland. Using molecular spectroscopy and chemical analysis, the fossil leaves were then compared with the chemical signatures from molecules in plant leaves picked at the Botanical Garden in Lund.

The use of genetic DNA analysis in modern research to determine relationships is not possible on fossil plants. The oldest DNA fragments ever found are scarcely one million-years-old. Therefore, the scientists searched for organic molecules to see what these could reveal about the plants' evolution and relationships.

The molecules were found in the waxy membrane, which covers the leaves and these showed to differ between various species. The membrane has been preserved in the fossil leaves, some of which are 200 million-years-old.

Using infrared spectroscopy, the researchers carried out analyses in several stages. Firstly, they examined leaves from living plants that have relatives preserved in the fossil archive. The analysis showed that the biomolecular signatures were similar among plant groups, much in the same way as shown by modern genetic DNA analysis.

When the method was shown to work on modern plants, the researchers went on to analyse their extinct fossil relatives. Among others, they examined fossil leaves from conifers and several species of Ginkgo. The only living species of Ginkgo alive today is Ginkgo biloba, but this genus was far more diverse during the Jurassic.

"The results from the fossil leaves far exceeded our expectations, not only were they full of organic molecules, they also grouped according to well-established botanical relationships, based on DNA analysis of living plants i.e. Ginkgoes in one group, conifers in another," says Vivi Vajda.

Finally, when the researchers had shown that the method gave consistent results, they analysed fossils of enigmatic extinct plants that have no living relatives to compare them with Among others, they examined Bennettites and Nilssonia, plants that were common in the area that is now Sweden during the Triassic and Jurassic around 250-150 million years ago. The analysis showed that Bennettites and Nilssonia are closely related. On the other hand, they are not closely related to cycads, which many researchers had thought until now.

Per Uvdal, Professor of Chemical Physics at Lund University and one of the researchers who conducted the study, considers that the overall results are astounding.

"The great thing about the biomolecules in the leaves' waxy membranes is that they are so much more stable than DNA. As they reflect, in an indirect way, a plants DNA they can preserve information about the DNA. Therefore, the biomolecules can tell us how one plant is related in evolutionary terms to other plants," he says.

Read more at Science Daily

An Enormous Crocodile with T. rex Teeth Was a Top Jurassic Predator

An artistic depiction of Razanandrongobe sakalavae scavenging on a sauropod carcass during the Middle Jurassic epoch in Madagascar. Unlike extant crocodilians, this terrestrial predator had a deep skull and walked on erect limbs.

The Jurassic period is often called the Age of the Ruling Reptiles, and for good reason. In the seas, aquatic reptiles such as the dolphin-like Stenopterygius were plentiful. In the air, flying reptiles known as pterosaurs searched for prey. On land, huge dinosaurs like Stegosaurus and meat-hungry Ceratosaurus had a commanding presence.

An important new addition to the list of ruling reptiles is Razanandrongobe sakalavae, or Razana for short. This gigantic crocodile, described in the journal PeerJ, was at the top of the Middle Jurassic food chain 164­–167 million years ago, and provides evidence that some crocodiles could take on even the fiercest dinosaur predators.

First known from a few teeth found a decade ago, Razana is now better understood due to recent analysis of additional cranial remains.

“We began with a couple of isolated teeth and ended up bringing back to life a one-ton terrifying bone crusher,” lead author Cristiano Dal Sasso of the Natural History Museum of Milan said.

He and colleagues Giovanni Pasini, Guillaume Fleury, and Simone Maganuco pieced together Razana based on fossils that include deep, massive jaw bones topped with large serrated teeth. The teeth were similar in size and shape to those of Tyrannosaurus rex, which is estimated to have exerted one of the largest bite forces among all terrestrial animals. At some 40 feet in length, T. rex was also an extremely large carnivore in its Late Cretaceous environment.

Paleontologists Cristiano Dal Sasso (left) and Simone Maganuco (right) standing next to the jaws of “Razana” at the Natural History Museum of Milan.

Razana, which lived close to 100 million years before T. rex, was 23 feet long. But it weighed an estimated 2,205 pounds and had erect legs, as opposed to the very low-to-the-ground limbs of modern alligators, crocodiles, and their relatives.

Its teeth and other remains suggest that Razana fed on hard tissues, such as bones and tendons. As a result, the researchers believe it could successfully bite into almost any animal — alive or dead.

“Razana was probably an opportunistic animal, just like hyenas and lions,” Dal Sasso said, adding that it was “not a very fast runner, but it was an ambush predator and a scavenger” that “could probably swim, just for crossing the nearby rivers, but it was built to walk on dry land.”

Its turf was a site now called the Mahajanga Basin of northwest Madagascar. Locals call the area the Sakalava region, so Razana’s full name means “giant lizard ancestor from the Sakalava region.”

Comparison between the estimated body size of the giant notosuchian crocodyliform Razanandrongobe sakalavae (nicknamed “Razana”) and a human.

The authors mention that this area is known for its “peculiar” collection of fossils representing everything from large marine reptiles called plesiosaurs to towering plant-eating dinosaurs known as sauropods.

“Madagascar was already separating from Africa, but was still connected to India, Australia and Antarctica,” Maganuco said.

Now an island nation, Madagascar remains known for its unique plant and animal life, often found nowhere else on Earth. Rare lemurs, for example, are native to Madagascar, which is also home to exotic orchids. Even crocodiles still thrive in Madagascar, with one infamous population of Nile crocodiles dwelling in caves.

Razana is long gone, but it holds a noteworthy place on the crocodile family tree. The scientists believe Razana was the largest and oldest “notosuchian,” predating other known forms of these animals by 42 million years. The term refers to certain early crocodilians and their extinct relatives. Previously, notosuchians were thought to appear in the Cretaceous, but Razana extends their dominance to the Jurassic.

While today’s crocodilians somewhat resemble Razana, much has changed due to evolution over millions of years.

“Modern crocs are well adapted to a semiaquatic lifestyle,” Maganuco said. “Their flattened skull with raised eyes is made for hunting in water.”

Paleo-artistic restoration of the head of Razanandrongobe sakalavae.

He continued that these animals today are incredible survivors, from an evolutionary standpoint. Their forerunners, such as Razana, were likely in direct competition with some of the most legendary predatory dinosaurs of all time. Some of these sturdy reptiles even managed to survive the end-Cretaceous extinction event that wiped out all dinosaurs, except for certain birds.

“The last fully terrestrial crocs lived up to the Middle Miocene about 15 million years ago, ruling the earth together with Cenozoic mammals and terror birds,” Maganuco said.

Terror birds, which could grow up to 12 feet tall, were flightless birds with ultra-sharp hooked beaks. Like Razana, they rose to the top of their food chain.

Read more at Discovery News

Controlling a single brain chemical may help expand window for learning language and music

This image shows (from left) Noah Roy, Ph.D., a postdoctoral research associate in Dr. Zakharenko's lab, and first author Jay Blundon, Ph.D., an associate scientist in Dr. Zakharenko's lab.

Learning language or music is usually a breeze for children, but as even young adults know, that capacity declines dramatically with age. St. Jude Children's Research Hospital scientists have evidence from mice that restricting a key chemical messenger in the brain helps extend efficient auditory learning much later in life.

Researchers showed that limiting the supply or the function of the neuromodulator adenosine in a brain structure called the auditory thalamus preserved the ability of adult mice to learn from passive exposure to sound much as young children learn from the soundscape of their world. The study appears June 30 in the journal Science.

"By disrupting adenosine signaling in the auditory thalamus, we have extended the window for auditory learning for the longest period yet reported, well into adulthood and far beyond the usual critical period in mice," said corresponding author Stanislav Zakharenko, M.D., Ph.D., a member of the St. Jude Department of Developmental Neurobiology. "These results offer a promising strategy to extend the same window in humans to acquire language or musical ability by restoring plasticity in critical regions of the brain, possibly by developing drugs that selectively block adenosine activity."

The auditory thalamus is the brain's relay station where sound is collected and sent to the auditory cortex for processing. The auditory thalamus and cortex rely on the neurotransmitter glutamate to communicate. Adenosine was known to reduce glutamate levels by inhibiting this neurotransmitter's release. This study also linked adenosine inhibition to reduced brain plasticity and the end of efficient auditory learning.

Researchers used a variety of methods to demonstrate that reducing adenosine or blocking the A1 adenosine receptor that is essential to the chemical messenger's function changed how adult mice responded to sound.

Much as young children pick up language simply by hearing it spoken, researchers showed that when adenosine was reduced or the A1 receptor blocked in the auditory thalamus, adult mice passively exposed to a tone responded to the same tone stronger when it was played weeks or months later. These adult mice also gained an ability to distinguish between very close tones (or tones with similar frequencies). Mice usually lack this "perfect pitch" ability.

Researchers also showed that the experimental mice retained the improved tone discrimination for weeks.

"Taken together, the results demonstrated that the window for effective auditory learning re-opened in the mice and that they retained the information," Zakharenko said.

Among the strategies researchers used to inhibit adenosine activity was the experimental compound FR194921, which selectively blocks the A1 receptor. If paired with sound exposure, the compound rejuvenated auditory learning in adult mice. "That suggests it might be possible to extend the window in humans by targeting the A1 receptor for drug development," Zakharenko said.

Read more at Science Daily

Jupiter: Atmosphere and aurora in unprecedented detail

Image of Jupiter taken on May 18, 2017, one day before the Juno spacecraft's sixth close approach to Jupiter, taken with a filter centered at 8.8 microns that is sensitive to Jupiter's tropospheric temperatures and the thickness of a cloud near the condensation level of ammonia gas. The Great Red Spot appears distinctively at the lower center of the planet as a cold region with a thick cloud layer. It is surrounded by a warm and relatively clear periphery. To its northwest is a turbulent and chaotic region of gas with bands of alternative warm, dry and cold, moist gas. Many other features are also present. This image shows the detailed atmospheric structure of the Great Red Spot and its surroundings that the Juno mission will encounter on its seventh closest approach to Jupiter on July 11, 2017. The instrument used to take these images is Subaru Telescope's facility instrument COoled Mid-Infrared Camera / Spectrometer (COMICS).

Subaru Telescope images reveal weather in Jupiter's atmosphere in the mid-infrared. High-resolution thermal imaging of Jupiter by the COoled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the Subaru Telescope on Maunakea is providing information that extends and enhances the information that the Juno mission is gathering in its unprecedented mission to probe that planet's interior and deep atmospheric structure together with details of the magnetosphere and its auroral interactions with the planet. "The Subaru observations of Jupiter so far this year have been timed to coordinate with the greatest benefit to Juno mission," said Glenn Orton, PI for the portion of the Keck Telescope exchange time with the Subaru Telescope and coordinator for Earth-based observations supporting the Juno project at JPL.

"During our May 2017 observations that provided real-time support for Juno's sixth perijove, we obtained images and spectra of the Great Red Spot and its surroundings. Our observations showed that the Great Red Spot, the largest known vortex in the solar system, had a cold and cloudy interior increasing toward its center, with a periphery that was warmer and clearer. This implied that winds were upwelling more vigorously toward its center and subsiding on the periphery. A region to its northwest was unusually turbulent and chaotic, with bands that were cold and cloudy, alternating with bands that were warm and clear bands. This region is where air heading east toward the Great Red Spot flows around it to the north, where it encounters a stream of air flowing over it from the east," adds Orton. "This information will allow us to determine the three-dimensional structure of winds that are otherwise only tracked in two dimensions using cloud features in reflected sunlight." "A wide variety of filters installed in COMICS is advantageous in sensing Jupiter's temperatures in its upper troposphere and in its stratosphere," noted co-investigator and Subaru Telescope staff astronomer Takuya Fujiyoshi.

Juno has now made five close-up passes of Jupiter's atmosphere, the first of which was on August 27, 2016 and the latest (the sixth) on May 19 of 2017. Each of these close passes has provided Juno's science team with unexpected surprises, and the Juno science return has benefited from a coordinated campaign of Earth-based support. This campaign includes observations from spacecraft near or orbiting the Earth, covering X-ray through visible wavelengths and ground-based observatories covering near-infrared through radio wavelengths.

Another set of supporting observations that were simultaneous with the Subaru observations were made by the Gemini North telescope's NIRI instrument, which imaged Jupiter in the near-infrared, measuring reflected sunlight from cloud and haze particle in Jupiter's upper troposphere and lower stratosphere -- levels generally higher in Jupiter's atmosphere than most of the Subaru measurements, providing complementary information. "Wide coverage of wavelength available from the telescopes on Maunakea is thus advantageous for the study," Fujiyoshi says.

Read more at Science Daily

Under pressure: Extreme atmosphere stripping may limit exoplanets' habitability

This is an artist's impression of HD189733b, showing the planet's atmosphere being stripped by the radiation from its parent star.

New models of massive stellar eruptions hint at an extra layer of complexity when considering whether an exoplanet may be habitable or not. Models developed for our own Sun have now been applied to cool stars favoured by exoplanet hunters, in research presented by Dr Christina Kay, of the NASA Goddard Flight Center, on Monday 3rd July at the National Astronomy Meeting at the University of Hull.

Coronal mass ejections (CMEs) are huge explosions of plasma and magnetic field that routinely erupt from the Sun and other stars. They are a fundamental factor in so called "space weather," and are already known to potentially disrupt satellites and other electronic equipment on Earth. However, scientists have shown that the effects of space weather may also have a significant impact on the potential habitability of planets around cool, low mass stars -- a popular target in the search for Earth-like exoplanets.

Traditionally an exoplanet is considered "habitable" if its orbit corresponds to a temperature where liquid water can exist. Low mass stars are cooler, and therefore should have habitable zones much closer in to the star than in our own solar system, but their CMEs should be much stronger due to their enhanced magnetic fields.

When a CME impacts a planet, it compresses the planet's magnetosphere, a protective magnetic bubble shielding the planet. Extreme CMEs can exert enough pressure to shrink a magnetosphere so much that it exposes a planet's atmosphere, which can then be swept away from the planet. This could in turn leave the planetary surface and any potential developing lifeforms exposed to harmful X-rays from the nearby host star.

The team built on recent work done at Boston University, taking information about CMEs in our own solar system and applying it to a cool star system.

"We figured that the CMEs would be more powerful and more frequent than solar CMEs, but what was unexpected was where the CMEs ended up" said Christina Kay, who led the research during her PhD work.

The team modelled the trajectory of theoretical CMEs from the cool star V374 Pegasi and found that the strong magnetic fields of the star push most CMEs down to the Astrophysical Current Sheet (ACS), the surface corresponding to the minimum magnetic field strength at each distance, where they remain trapped.

"While these cool stars may be the most abundant, and seem to offer the best prospects for finding life elsewhere, we find that they can be a lot more dangerous to live around due to their CMEs" said Marc Kornbleuth, a graduate student involved in the project.

The results suggest that an exoplanet would need a magnetic field ten to several thousand times that of Earth's to shield their atmosphere from the cool star's CMEs. As many as five impacts a day could occur for planets near the ACS, but the rate decreases to one every other day for planets with an inclined orbit.

Read more at Science Daily

'Perfect storm' led to 2016 Great Barrier Reef bleaching

Aerial view of the Great Barrier Reef.

Researchers from James Cook University and the Université catholique de Louvain, Louvain-la-Neuve, Belgium say unprecedented oceanographic conditions in 2016 produced the perfect storm of factors that lead to a mass coral bleaching.

JCU's Professor Eric Wolanski said even in very warm years with a summer el Nino event, such as 1998, there was no massive coral bleaching in the Torres Strait and only small to moderate bleaching in the northern Great Barrier Reef.

"So, the extensive coral bleaching in these areas during the summer of 2016 was an unwelcome surprise," he said.

A 2016 aerial survey of the northern Great Barrier Reef lead by Professor Terry Hughes from JCU's Center of Excellence for Coral Reef Studies showed that 90 per cent of reefs in some of these areas were severely bleached.

Professor Wolanski said satellite data showed the 2016 El Nino heating started in the Gulf of Carpentaria, with patches of water reaching an exceptionally high 34oC.

The water then flowed east onto the Torres Strait reefs and south to the Great Barrier Reef. The 'residence time' of the very warm water in the Torres Strait and the Northern Great Barrier Reef was exceptionally long, which increased the thermal stress on the coral.

All of these factors enabled local solar heating to proceed unrestricted.

"Examining surface currents suggests that the North Queensland Coastal Current in the Coral Sea, which would normally flush and cool the Northern Great Barrier Reef, actually did the opposite. It reversed course and brought very warm water to the Northern Great Barrier Reef."

Professor Wolanski said these processes together made it the perfect thermal storm.

He said the study employed oceanography models used extensively to study water flow in the region, which were then calibrated with real oceanographic data.

Professor Wolanski said the study was subjective to the extent that there was a lack of oceanographic field data in the Great Barrier Reef itself for the 2016 el Nino event. By contrast, the amount of oceanographic field data in the Torres Strait and the northern Coral Sea was very good.

Read more at Science Daily

Social status of listener alters our voice

Men and women might speak with higher-pitched voices towards high status people because a low-pitched voice sounds dominant, particularly in men, while a high-pitched voice sounds relatively submissive.

People tend to change the pitch of their voice depending on who they are talking to, and how dominant they feel, a study by the University of Stirling has found.

The psychology research, published in PLOS ONE, put participants through a simulated job interview task and discovered that individuals' vocal characteristics -- particularly pitch -- are altered in response to people of different social status.

Regardless of self-perceived social status, people tend to talk to high status individuals using a higher pitch.

Dr Viktoria Mileva, a Postdoctoral Researcher at the University of Stirling, said: "A deep, masculine voice sounds dominant, especially in men, while the opposite is true of a higher pitched voice. So, if someone perceives their interviewer to be more dominant than them, they raise their pitch. This may be a signal of submissiveness, to show the listener that you are not a threat, and to avoid possible confrontations.

"These changes in our speech may be conscious or unconscious but voice characteristics appear to be an important way to communicate social status. We found both men and women alter their pitch in response to people they think are dominant and prestigious."

The researchers also found that participants who think they are dominant -- who use methods like manipulation, coercion, and intimidation to acquire social status -- are less likely to vary their pitch and will speak in a lower tone when talking to someone of a high social status.

Individuals who rate themselves as high in prestige -- they believe people look up to them and value their opinions, thereby granting them social status -- do not change how loud they are speaking, no matter who they are speaking to. This may signal that they are more calm and in control of a situation.

The participants responded to introductory, personal, and interpersonal interview questions. They lowered the pitch of their voice most in response to the more complex, interpersonal questions, for example when explaining a conflict situation to an employer.

Dr Mileva added: "Signals and perceptions of human social status have an effect on virtually every human interaction, ranging from morphological characteristics -- such as face shape -- to body posture, specific language use, facial expressions and voices.

"Understanding what these signals are, and what their effects are, will help us comprehend an essential part of human behaviour."

Read more at Science Daily

Study reveals mysterious equality with which grains pack it in

A huge range of materials are classified as granular – including sand, gravel, snow, nuts, coal, rice, barley, coffee and cereals. Globally, they are the second-most processed type of material in industry, after water.

At the moment they come together, the individual grains in materials like sand and snow appear to have exactly the same probability of combining into any one of their many billions of possible arrangements, researchers have shown.

The finding, by an international team of academics at the University of Cambridge, UK, and Brandeis University in the US, appears to confirm a decades-old mathematical theory which has never been proven, but provides the basis for better understanding granular materials -- one of the most industrially significant classes of material on the planet.

A granular material is anything that comprises solid particles that can be seen individually with the naked eye. Examples include sand, gravel, snow, coal, coffee, and rice.

If correct, the theory demonstrated in the new study points to a fact of remarkable -- and rather mysterious -- mathematical symmetry. It means, for example, that every single possible arrangement of the grains of sand within a sand dune is exactly as probable as any another.

The study was led by Stefano Martiniani, who is based at New York University but undertook the research while completing his PhD at St John's College, University of Cambridge.

"Granular materials are so widely-used that understanding their physics is very important," Martiniani said. "This theory gives us a very simple and elegant way to describe their behaviour. Clearly, something very special is happening in their physics at the moment when grains pack together in this way."

The conjecture that Martiniani tested was first proposed in 1989 by the Cambridge physicist Sir Sam F. Edwards, in an effort to better understand the physical properties of granular materials.

Globally, these are the second-most processed type of material in industry (after water) and staples of sectors such as energy, food and pharmaceuticals. In the natural world, vast granular assemblies, such as sand dunes, interact directly with wind, water and vegetation. Yet the physical laws that determine how they behave in different conditions are still poorly understood. Sand, for example, behaves like a solid when jammed together, but flows like a liquid when loose.

Understanding more about the mechanics of granular materials is of huge practical importance. When they jam during industrial processing, for example, it can cause significant disruption and damage. Equally, the potential for granular materials to "unjam" can be disastrous, such as when soil or snow suddenly loosens, causing a landslide or avalanche.

At the heart of Edwards' proposal was a simple hypothesis: If one does not explicitly add a bias when preparing a jammed packing of granular materials -- for example by pouring sand into a container -- then any possible arrangement of the grains within a certain volume will occur with the same probability.

This is the analogue of the assumption that is at the heart of equilibrium statistical mechanics -- that all states with the same energy occur with equal probability. As a result the Edwards hypothesis offered a way for researchers to develop a statistical mechanics framework for granular materials, which has been an area of intense activity in the last couple of decades.

But the hypothesis was impossible to test -- not least because above a handful of grains, the number of possible arrangements becomes unfathomably huge. Edwards himself died in 2015, with his theory still the subject of heated scientific debate.

Now, Martiniani and colleagues have been able to put his conjecture to a direct test, and to their surprise they found that it broadly holds true. Provided that the grains are at the point where they have just jammed together (or are just about to separate), all possible configurations are indeed equally likely.

Helpfully, this critical point -- known as the jamming transition -- is also the point of practical significance for many of the granular materials used in industry. Although Martiniani modelled a system comprising soft spheres, a bit like sponge tennis balls, many granular materials are hard grains that cannot be compressed further once in a packed state.

"Apart from being a very beautiful theory, this study gives us the confidence that Edwards' framework was correct," Martiniani said. "That means that we can use it as a lens through which to look at a whole range of related problems."

Aside from informing existing processes that involve granular materials, there is a wider significance to better understanding their mechanics. In physics, a "system" is anything that involves discrete particles operating as part of a wider network. Although bigger in scale, the way in which icebergs function as part of an ice floe, or the way that individual vehicles move within a flow of traffic (and indeed sometimes jam), can be studied using a similar theoretical basis.

Martiniani's study was undertaken during his PhD under the supervision of Professor Daan Frenkel. It built on earlier research in which he developed new methods for calculating the probability of granular systems packing into different configurations, despite the vast numbers involved. In work published last year, for example, he and colleagues used computer modelling to work out how many ways a system containing 128 tennis balls could potentially be arranged. The answer turned out to be ten unquadragintilliard -- a number so huge that it vastly exceeds the total number of particles in the universe.

In the new study, the researchers employed a sampling technique which attempts to compute the probability of different arrangements of grains without actually looking at the frequency with which these arrangements occur. Rather than taking an average from random samples, the method involves calculating the limits of the possibility of specific arrangements, and then calculates the overall probability from this.

The team applied this to a computer model of 64 soft spheres -- an imaginary system which could therefore be "over-compressed" after reaching the jamming transition point. In an over-compressed state, the different arrangements were found to have different probabilities of occurrence. But as the system decompressed to the point of the jamming transition, at which the grains were effectively just touching, the researchers found that all probabilities became equal -- exactly as Edwards predicted.

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