Jan 22, 2017

Why the lights don't dim when we blink

New study finds that blinking steadies our gaze.
Every few seconds, our eyelids automatically shutter and our eyeballs roll back in their sockets. So why doesn't blinking plunge us into intermittent darkness and light? New research led by the University of California, Berkeley, shows that the brain works extra hard to stabilize our vision despite our fluttering eyes.

Scientists at UC Berkeley, Nanyang Technological University in Singapore, Université Paris Descartes and Dartmouth College have found that blinking does more than lubricate dry eyes and protect them from irritants. In a study published in today's online edition of the journal Current Biology, they found that when we blink, our brain repositions our eyeballs so we can stay focused on what we're viewing.

When our eyeballs roll back in their sockets during a blink, they don't always return to the same spot when we reopen our eyes. This misalignment prompts the brain to activate the eye muscles to realign our vision, said study lead author Gerrit Maus, an assistant professor of psychology at Nanyang Technological University in Singapore. He launched the study as a postdoctoral fellow in UC Berkeley's Whitney Laboratory for Perception and Action.

"Our eye muscles are quite sluggish and imprecise, so the brain needs to constantly adapt its motor signals to make sure our eyes are pointing where they're supposed to," Maus said. "Our findings suggest that the brain gauges the difference in what we see before and after a blink, and commands the eye muscles to make the needed corrections."

From a big-picture perspective, if we didn't possess this powerful oculomotor mechanism, particularly when blinking, our surroundings would appear shadowy, erratic and jittery, researchers said.

"We perceive coherence and not transient blindness because the brain connects the dots for us," said study co-author David Whitney, a psychology professor at UC Berkeley.

"Our brains do a lot of prediction to compensate for how we move around in the world," said co-author Patrick Cavanagh, a professor of psychological and brain sciences at Dartmouth College. "It's like a steadicam of the mind."

A dozen healthy young adults participated in what Maus jokingly called "the most boring experiment ever." Study participants sat in a dark room for long periods staring at a dot on a screen while infrared cameras tracked their eye movements and eye blinks in real time.

Every time they blinked, the dot was moved one centimeter to the right. While participants failed to notice the subtle shift, the brain's oculomotor system registered the movement and learned to reposition the line of vision squarely on the dot.

After 30 or so blink-synchronized dot movements, participants' eyes adjusted during each blink and shifted automatically to the spot where they predicted the dot to be.

Read more at Science Daily

Ultrafast Camera Captures 'Sonic Booms' of Light for First Time

Just as aircraft flying at supersonic speeds create cone-shaped sonic booms, pulses of light can leave behind cone-shaped wakes of light. Now, a superfast camera has captured the first-ever video of these events.

The new technology used to make this discovery could one day allow scientists to help watch neurons fire and image live activity in the brain, researchers say.

When an object moves through air, it propels the air in front of it away, creating pressure waves that move at the speed of sound in all directions. If the object is moving at speeds equal to or greater than sound, it outruns those pressure waves. As a result, the pressure waves from these speeding objects pile up on top of each other to create shock waves known as sonic booms, which are akin to claps of thunder.

Sonic booms are confined to conical regions known as "Mach cones" that extend primarily to the rear of supersonic objects. Similar events include the V-shaped bow waves that a boat can generate when traveling faster than the waves it pushes out of its way move across the water.

Previous research suggested that light can generate conical wakes similar to sonic booms. Now, for the first time, scientists have imaged these elusive "photonic Mach cones."

Light travels at a speed of about 186,000 miles per second (300,000 kilometers per second) when moving through vacuum. According to Einstein's theory of relativity, nothing can travel faster than the speed of light in a vacuum. However, light can travel more slowly than its top speed — for instance, light moves through glass at speeds of about 60 percent of its maximum. Indeed, prior experiments have slowed light down more than a million-fold.

The fact that light can travel faster in one material than in another helped scientists to generate photonic Mach cones. First,study lead author Jinyang Liang, an optical engineer at Washington University in St. Louis, and his colleagues designed a narrow tunnel filled with dry ice fog. This tunnel was sandwiched between plates made of a mixture of silicone rubber and aluminum oxide powder.

Then, the researchers fired pulses of green laser light — each lasting only 7 picoseconds (trillionths of a second) — down the tunnel. These pulses could scatter off the specks of dry ice within the tunnel, generating light waves that could enter the surrounding plates.

The green light that the scientists used traveled faster inside the tunnel than it did in the plates. As such, as a laser pulse moved down the tunnel, it left a cone of slower-moving overlapping light waves behind it within the plates.

To capture video of these elusive light-scattering events, the researchers developed a "streak camera" that could capture images at speeds of 100 billion frames per second in a single exposure. This new camera captured three different views of the phenomenon: one that acquired a direct image of the scene, and two that recorded temporal information of the events so that the scientists could reconstruct what happened frame by frame.

Essentially, they "put different bar codes on each individual image, so that even if during the data acquisition they are all mixed together, we can sort them out," Liang said in an interview.

There are other imaging systems that can capture ultrafast events, but these systems usually need to record hundreds or thousands of exposures of such phenomena before they can see them. In contrast, the new system can record ultrafast events with just a single exposure.

Read more at Discovery News

Jan 21, 2017

Ants find their way even when going backwards

Cataglyphis velox ant.
An international team including researchers at the university of Edinburgh and Antoine Wystrach of the Research Centre on Animal Cognition (CNRS/Université Toulouse III -- Paul Sabatier) has shown that ants can get their bearings whatever the orientation of their body. Their brains may be smaller than the head of a pin, but ants are excellent navigators that use celestial and terrestrial cues to memorize their paths. To do so, they use several regions of the brain simultaneously, proving once again that the brain of insects is more complex than thought. The researchers' findings were published in Current Biology on January 19, 2017.

Until now, ethological research suggested that ants memorized the scenery perceived along their route as it is projected on their multifaceted retinas -- thus using a body-centered, or egocentric, frame of reference. By this hypothesis, to recognize memorized surroundings and follow a path formerly traveled, ants would need to orient their bodies in the same way each time. But they sometimes need to walk backwards as well, and this doesn't prevent them from finding their way back to their nest. Could it be that ants can recognize a route when facing the opposite direction? Are they able to create a visual model of their environment that is independent of their body orientation?

To answer these questions, the researchers studied Cataglyphis velox, an Andalusian desert ant known for its solo navigation ability. First they let the insects familiarize themselves with a route that included a 90° turn. After a day of training, ants that received a cookie crumb light enough to carry while walking forward handled the turn without the slightest difficulty. However, those given large cookie crumbs had to move backward, and unlike the others, they maintained their bearing instead of turning.

They also exhibited unexpected behavior: After walking backward a bit, they would occasionally drop their crumb, turn around, observe the scenery while pointing their bodies in the right direction, return to the crumb, and resume towing it backward -- but this time in the correct direction. For these ants, body alignment thus seems necessary for recognition of scenery perceived by their retinas, but they are then able to memorize the new bearing and follow it backward. This behavior also shows that they can recall the existence of the dropped cookie crumb, and its location, in order to return to it after updating their bearing. These observations imply that at least 3 kinds of memory are working in unison: the visual memory of the route, the memory of the new direction to follow, and the memory of the crumb to retrieve.

Through another experiment using a mirror to reflect the sun1, the team demonstrated that the ants used celestial cues to maintain their bearing while walking backwards. Furthermore, ants were able to move in straight paths, whether walking forward, backward, or sideways. Once a bearing is memorized, they stay on it no matter how their bodies are oriented. Together these observations suggest that ants register direction using an external -- or allocentric -- frame of reference.

Read more at Science Daily

Study of round worm that returns to life after freezing

Antarctic nematode worms photographed under the microscope.
The first molecular study of an organism able to survive intracellular freezing (freezing within its cells) is published this week by British Antarctic Survey (BAS), in collaboration with researchers from the University of Otago, New Zealand. The paper represents a milestone in scientists' understanding of an extraordinary adaptation.

The tiny Antarctic nematode, more commonly known as a round worm, (Panagrolaimus sp. DAW1) was cultured from a coastal Antarctic penguin rookery at McMurdo Sound, and is the best-documented organism able to survive the disruptions brought about by total freezing. The nematode is also able to undergo a form of freeze avoidance by eliminating all of its water content, called cryoprotective dehydration. However, it is the ability to survive intracellular freezing which makes this organism really stand out.

Exploring gene expression patterns, the researchers were able to show how molecularly active the nematodes are while in a frozen state, highlighting certain key genes enabling them to endure such an extreme physical state.

This is the first study of its kind, shedding light on a possibly rare adaptation, which could lead to new applications.

From Science Daily

Astronomers Prepare to Search for Alien Life at Nearby 'Habitable' Exoplanet

As we continue the hunt for habitable worlds beyond our solar system, we're finding more and more candidates closer to home. There's even a small rocky exoplanet within the so-called "habitable zone" at Proxima Centauri, the dinky red dwarf star right next door. But there's more, and astronomers are beginning to identify which of these strange new worlds we could soon get a good look at with the next generation of advanced telescopes on Earth and in space.

One tantalizing potentially habitable exoplanet orbits the star Wolf 1061, only 14 light-years away — a distance that is practically on our galactic doorstep. Known to host three exoplanets, the Wolf 1061 system is interesting as it could be a target for NASA's James Webb Space Telescope (JWST) that is scheduled to launch in 2018. Sitting at the sun-Earth L2 point — an island of gravitational calm nearly one million miles away in Earth's shadow — the infrared JWST could be used to detect atmospheric components in worlds that could, hypothetically, support life. Other exoplanet-hunting projects are being launched, such as the Transiting Exoplanet Survey Satellite (TESS), the CHaracterising ExOPlanet Satellite (CHEOPS), and the PLAnetary Transits and Oscillations of stars (PLATO) mission, that will greatly benefit from this advanced research to characterize the habitable potential of distant worlds.

Nestled in the habitable zones of stars, exoplanets (like the one in Wolf 1061) are thought to be neither too hot or too cold for liquid water to persist on their surfaces. On Earth, where there's liquid water, there's life, and if there's water on these worlds, there could be life there too. That's the basic logic, but there are many other factors at play that determine whether a planet can indeed support life. So if we can properly characterize exoplanetary atmospheres, we might, some day, be able to detect the chemicals that may reveal information about any "biomarkers" that may be present — chemicals that reveal the presence of biological processes. As Wolf 1061 hosts a small rocky exoplanet (called Wolf 1061c) within its habitable zone, it is one of the closest exoplanetary locations where we could uncover this biological evidence.

"The Wolf 1061 system is important because it is so close and that gives other opportunities to do follow-up studies to see if it does indeed have life," said Stephen Kane, an astronomer at San Francisco State University and lead author of new research to be published in the Astrophysical Journal.

Working with researchers at Tennessee State University and in Geneva, Switzerland, Kane's team took precise measurements of the Wolf 1061 system to calculate the extent of its habitable zone, stellar activity and planetary orbits. Interestingly, Wolf 1061c has a chaotic orbit that is heavily influenced by the gravity of the other planets in the system, causing it to lurch sometimes closer to the star and at other times further away. It also occupies the inside edge of the star's habitable zone, which poses a quandary for its true habitable potential.

Venus, for example, lies within the inside edge of the sun's habitable zone, yet Venus is anything but "habitable" — despite being approximately Earth-sized. The toxic and thick Venusian atmosphere is the consequence of a runaway greenhouse effect where too much energy has been trapped by the atmosphere, causing it to heat up to lead-boiling temperatures. Though it may have once been a more temperate world, any water that once existed on its surface has been broken down into its component hydrogen and oxygen atoms. The only regions of Venus that are remotely "Earth-like" are high up in Venus' atmosphere — leading to speculative ideas that floating lifeforms may be present, or that humans may one day inhabit Venus in "cloud cities" that float high above the crushing lower atmospheric pressures.

Read more at Discovery News

Jan 20, 2017

Too much sitting, too little exercise may accelerate biological aging

As a cell ages, its telomeres naturally shorten and fray, but health and lifestyle factors, such as obesity and smoking, may accelerate that process. Shortened telomeres are associated with cardiovascular disease, diabetes and major cancers.
Researchers at University of California San Diego School of Medicine report that elderly women who sit for more than 10 hours a day with low physical activity have cells that are biologically older by eight years compared to women who are less sedentary.

The study, publishing online January 18 in the American Journal of Epidemiology, found elderly women with less than 40 minutes of moderate-to-vigorous physical activity per day and who remain sedentary for more than 10 hours per day have shorter telomeres -- tiny caps found on the ends of DNA strands, like the plastic tips of shoelaces, that protect chromosomes from deterioration and progressively shorten with age.

As a cell ages, its telomeres naturally shorten and fray, but health and lifestyle factors, such as obesity and smoking, may accelerate that process. Shortened telomeres are associated with cardiovascular disease, diabetes and major cancers.

"Our study found cells age faster with a sedentary lifestyle. Chronological age doesn't always match biological age," said Aladdin Shadyab, PhD, lead author of the study with the Department of Family Medicine and Public Health at UC San Diego School of Medicine.

Shadyab and his research team believe they are the first to objectively measure how the combination of sedentary time and exercise can impact the aging biomarker.

Nearly 1,500 women, ages 64 to 95, participated in the study. The women are part of the larger Women's Health Initiative (WHI), a national, longitudinal study investigating the determinants of chronic diseases in postmenopausal women. The participants completed questionnaires and wore an accelerometer on their right hip for seven consecutive days during waking and sleeping hours to track their movements.

"We found that women who sat longer did not have shorter telomere length if they exercised for at least 30 minutes a day, the national recommended guideline," said Shadyab. "Discussions about the benefits of exercise should start when we are young, and physical activity should continue to be part of our daily lives as we get older, even at 80 years old."

Read more at Science Daily

The Brains of Women and Men Are More Alike Than You May Think

We all know the cliches: Men are from Mars, women are from Venus. Women are quicker to cry. Men don't show their emotions.

But research that looked at differences in the brain — specifically in the brain's emotion center — suggests that may all be bunk.

"That belief that there's a male-type brain and female-type brain is just not true," said Lise Eliot, an associate professor of neuroscience at the Chicago Medical School of Rosalind Franklin University of Medicine and Science. "It's not true for the amygdala. It is turning out to be not true for the hippocampus, for the corpus callosum, for left-right dominance. There's just not an attribute of the brain that reliably marks it as male or female."

Eliot, whose 2009 book "Pink Brain, Blue Brain" explained how gender stereotypes are reinforced on young brains, led recent research that analyzed 6,726 MRIs taken from 58 separate studies. Her team scrutinized the brain scans of men and women, and measured the volume of the amygdala in each subject. Previous research using animal models and MRIs had suggested that the amygdala may be larger in males than in females.

The amygdala (of which there are two in the brain) is known as the center for emotion, social behavior, aggression and sexual drive. If men's amygdalae are, in fact, larger, it could be evidence of one way that men and women are wired differently.

The researchers did find that amygdala volumes were in fact about 10 percent larger in male brains. But, Eliot says that corresponds to men's larger body size, including the 10-12 percent overall larger volume of men's brains.

"The difference in amygdala volume is just in proportion to their size difference — it's 10-12 percent larger, which makes sense because men are 10 to 12 percent larger than women," Eliot said. "But if you control for individual head size, there's no difference."

The Franklin University team's finding, which was published in the journal NeuroImage, is the latest in a series of studies that have looked for differences in male and female brains — and found none.

Eliot's team found in a 2015 study that there is no discernible difference in the size of men's and women's hippocampus. The hippocampus plays a key role in the consolidation of learning from short-term memory to long-term memory and in spatial navigation.

A 1997 study from the University of Alberta analyzed scans from 49 studies published since 1980 and found no significant sex difference in the size or shape of the brain's corpus callosum. This bundle of nerves is the part of the mind that allows communication between the two hemispheres of the brain.

Then there is the common belief that people are either "right-brained" or "left-brained," and that women tend to be more right-brained and associated with creativity rather than the calculating, analytical characteristics commonly linked with the left brain. That notion, too, has been challenged.

A 2014 University of Utah Health Sciences study asserted that there is no evidence within brain imaging that indicates some people are right-brained or left-brained.

"It's absolutely true that some brain functions occur in one or the other side of the brain. Language tends to be on the left, attention more on the right," Jeff Anderson, the study's lead author, said at the time. "But people don't tend to have a stronger left- or right-sided brain network. It seems to be determined more connection by connection."

One of the most comprehensive surveys looked at several areas of the brain and analyzed the volume of gray matter and white matter in the brains of more than 1,400 individuals. The researchers from Tel Aviv University in Israel concluded in the 2015 research that all of our brains seem to share a patchwork of forms that crossed gender lines.

Finally, one might wonder if hormones are at play in the brain, leading men and women to think differently.

Again, Eliot says, the research just doesn't show it.

"The studies that have tried to find effects of estrogen and testosterone on thinking skills or emotional skills have been very sketchy," she remarked. "About the only thing we know for sure is that testosterone increases sex drive in both sexes. Other than that, estrogen and testosterone, it's the same thing — they appear to have no effect on any cognitive skills."

Read more at Discovery News

Seals Use Their Whiskers to Detect the Breathing of Hidden Prey

The whiskers on a harbor seal are more than just a touch of added cuteness - they're hunting tools that help it detect the smallest perturbations of water made by its favorite food hiding on the seafloor.

That's what researchers from the University of Rostock (UR) found when they tested the animals for the ability, in research just published in the Journal of Experimental Biology.

The prey at the root of the experiment, flatfish, a favorite food of harbor seals, are camouflage experts that can hide in plain sight or burrow under the sand on the seafloor. Trouble is (for the fish), the seals find them anyway, even when the fish are sitting stock still.

Scientists were already aware that seals will track prey - even over long distances - by honing in on the currents fish make when they swim. But, according to the researchers, the new study answered a question that had bedeviled marine scientists: How do the seals find stationary, hiding fish?

For the study, the researchers used a special training tank, with a platform through which air currents – calibrated to simulate a flounder "breathing" - were pumped.

Then, trained seals from UR's marine science center were given eye masks and tested for their ability to locate the fake-flounder (in real life masters of hiding in plain sight) breathing. The seals did just that. With or without the blindfolds, the scientists found, they were able to locate the currents and move their snouts over the openings from which the currents were created – just as they would be able to locate the breathing of flounder camouflaged on the seafloor.

This seal has learned to wear an eye mask and headphones for behavioral studies.
When their whiskers were covered, though, as New Scientist noted, the seals weren't able to locate the currents.

It's all thanks to the whiskers. Study co-author Wolf Hanke has spent a fair amount of research time on them, discovering, in 2011 that seals can use them to "see" shapes echoed in water ripples, as Live Science reported.

Now, a new ability can be ascribed to them.

"Seals feel these water movements with their beard hair, even when the seal moves forward at velocities of one meter per second, and when further wind and wave currents are present," the scientists explained in a press release.

Read more at Discovery News

Massive Burial Ground Unearthed at Medieval Monastery in Sudan

Four cemeteries, from which at least 123 individuals have been excavated so far, have been unearthed near the remains of a medieval Christian monastery in Sudan. A few of the burials contained individuals buried in unusual ways.

The cemeteries and remains, which have been excavated over the past two years, are located at a monastery called al-Ghazali near the Nile River. The people who were buried there lived about 1,000 years ago, during a time when a series of Christian kingdoms flourished in the area, according to Robert Stark, a doctoral student at McMaster University in Hamilton, Ontario, who presented the findings this month in Toronto at the joint annual meeting of the Archaeological Institute of America and the Society for Classical Studies.

The discoveries include well-preserved burial shrouds that in a few instances still cover the skulls of the deceased, Stark said. The archaeologists also found tombstones with engravings of prayers that were written in Greek or Coptic (an Egyptian language that uses the Greek alphabet). In one cemetery, some people were buried in mysterious ways: For example, two individuals were found with post-mortem cut marks incised in their bones.

Stark is part of an archaeological expedition of the Polish Centre of Mediterranean Archaeology, at the University of Warsaw, which is excavating al-Ghazali.

Massive burial ground

An archaeologist named Peter Shinnie first excavated the cemeteries at al-Ghazali in the 1950s, Stark said. While Shinnie believed al-Ghazali held more than 1,000 burials, he uncovered just a few during the course of his fieldwork. The Polish Centre of Mediterranean Archaeology is the first organization to conduct large-scale excavations at al-Ghazali's cemeteries, he added.

An overhead view of cemetery two, which is located beside the Christian monastery, at al-Ghazali in Sudan.
One of the cemeteries consists almost entirely of adult males and was probably used by the monks from the monastery, Stark said. Two cemeteries contain a wider mix of individuals and appear to have been used by people who lived in nearby settlements. The fourth cemetery was discovered recently by archaeologists and contains only 15 burials — and some of those have features that are unusual.

In all four of the cemeteries the remains of stone structures were found on the surface, above the burials, Stark said, adding that some of these structures have the remains of tombstones.

The writing on the tombstones tended to follow a particular format. "To make it simple. The writing on tombstones can be divided into two parts," Artur Obluski, the director of the excavations at al-Ghazali, told Live Science in an email.

The first part consisted of prayers, which included "a prayer for the soul of the deceased, a prayer to the Providence of God, the God himself often described as merciful," Obluski said. These prayers ask "that the soul will be taken care of and can rest on the bosom of Abraham, Isaac and Jacob or in the world of the Living."

The second part of the tombstone engravings "contains some individual information of the deceased: his name, age at the time of death, sometimes titles he bore during his life time — so-called cursus honorum — and professions he performed," said Obluski.

Read more at Discovery News

Jan 19, 2017

Lost Dark Age Kingdom Uncovered in Scotland

Archaeologists may have finally found the lost kingdom of Rheged, the most elusive of all the sixth century kingdoms of Dark Age Britain.

The mysterious kingdom was pre-eminent in northern Britain in the sixth century, but faded into obscurity after it was deliberately destroyed in the beginning of the following century.

Historians had speculated that the kingdom was headquartered in Cumbria, a county in north west England, but no evidence of it was ever found. Then digs carried in 2012 at Trusty's Hill, which overlooks the Fleet valley in Galloway in south-west Scotland, revealed clues of the presence of a royal stronghold.

"Our excavation revealed all the hallmarks of an early medieval royal site," Ronan Toolis at GUARD Archaeology in Glasgow, told Seeker.

The discovery is detailed in a new book, "The Lost Dark Age Kingdom of Rheged," which is being released Saturday.

Toolis and co-author Christopher Bowles found that in the decades around 600 A.D. the summit of the hill was fortified with a timber-laced stone rampart. They also recovered remains of supplementary defenses and enclosures along the lower-lying slopes, revealing that Trusty's Hill was fortified.

"This is a type of fort that has been recognized in Scotland as a form of high status secular settlement of the early medieval period," Toolis said. "The evidence makes a compelling case for Galloway being the core of the kingdom of Rheged."

Anglo-saxon style bronze jewellery. Originally gilded and silvered and made of leaded brass, it was probably brought to the site as loot.
Little is known about Rheged. Fragments of early medieval historical records and medieval poetry indicate the kingdom was particularly powerful under the warrior king Urien, whose prowess was celebrated by his court-bard Taliesin.

Toolis and Bowles discovered that anyone approaching the summit of the hill passed through a symbolic entrance way defined by Pictish carvings on one side and a large rock-cut basin on the other. The Picts were a tribal group of people who lived in what is today eastern and northern Scotland during the Late Iron Age and Early Medieval periods.

"It was a rite of passage where early medieval kings were perhaps anointed and ceremonies performed," Toolis said.

He noted the entrance way bears a close resemblance to one found some 180 miles north at Dunadd hillfort, the royal center for the kings of Dalriada in what is now Argyll and Bute. There, an entrance way with Pictish carving and a rock-cut basin was also found.

The king's hall may have stood at the highest part of Trusty's Hill on the west side. On the slightly lower area on the eastern side, the archaeologists found a workshop that produced metalwork of gold, silver, bronze and iron.

The team also unearthed e-ware, a type of pottery imported from continental Europe, which indicates the royal household was part of a trade network that linked western Britain with Ireland and continental Europe.

Other activities at Rheged included the spinning of wool, preparation of leather and feasting.

A laser scan image of the carved Pictish symbols.
"The household's wealth relied on their control of farming, animal husbandry and the management of local natural resources — minerals and timber — from an estate probably spanning the wider landscape of the Fleet valley and estuary," Christopher Bowles, Scottish borders council archaeologist, said.

"Control was maintained by bonding the people of this land and the districts beyond to the royal household, by gifts, promises of protection and the bounties of raiding and warfare," he added.

Analysis of the Pictish stone carvings revealed the symbols cannot be deciphered.

"The literal meaning of the symbols at Trusty's Hill will probably never be known. There is no Pictish Rosetta Stone," Toolis said.

Read more at Discovery News