Mapping project completed, helping to save world’s reefs

 

Ailinginae Atoll - Ailinginae Atoll in the Marshall Islands.
Photo credit: Greg Asner

All of the world’s shallow coral reefs have been digitally mapped, thanks to a three-year project combining two million satellite images, enormous amounts of field data and University of Queensland-developed mapping techniques.

The Allen Coral Atlas project has officially launched its high-resolution maps of the world’s reefs which, together with the Atlas’s coral monitoring tool launched in May, will revolutionize reef management.

The project is an international research collaboration led by Arizona State University in partnership with UQ, Planet Ltd, National Geographic and Vulcan Inc.

UQ’s Remote Sensing Research Centre researcher Dr Chris Roelfsema said the digital atlas is a comprehensive and continually updated tool, perfect for scientists, policy makers and planners.

“To manage environmental assets like the world’s reefs, you need to know what’s happening at any given time,” Dr Roelfsema said.

“The Allen Coral Atlas provides maps that accurately describe the composition and extent of our reefs globally, and at a level of detail not seen before.

“These maps are connecting people with the data they need to save our reefs – it’s momentous.”

The Allen Coral Atlas, now available online, has been a global effort with UQ scientists playing the leading role in gathering verification data, developing and implementing the mapping approach for the world’s coral reefs.

“The verification and mapping approaches we’ve developed are based on 20 years of experience UQ has in combining reef knowledge, field data and earth observation processes to map and monitor coral reefs,” Dr Roelfsema said.

“This work combined 450 field data sets from global collaborators with machine learning and automated contextual-editing approaches, which helps us achieve the highest spatial and thematic resolution of coral reefs anyone has ever seen.”

The data is needed now more than ever, with models predicting 70 to 90 per cent of coral reefs will be lost by 2050, because of warming, polluted and acidic oceans.

Professor Greg Asner, Director of Arizona State University's Center for Global Discovery and Conservation Science and Managing Director of the Atlas project, said he was thrilled to announce the platform.

“It is a gratifying milestone after years of dedicated non-stop teamwork to bring this global map to fruition,” Dr Asner said.

“But the true value of the work will come when coral conservationists are able to better protect coral reefs based on the high-resolution maps and monitoring system.

“We must double down and use this tool as we work to save coral reefs from the impacts of our climate crisis and other threats.”

The Allen Coral Atlas is named for the late Microsoft co-founder Paul G. Allen, and founder of Vulcan Inc.

Source/Credit: University of Queensland

en091021_01

Silicon, Subatomic Particles and Possible ‘Fifth Force’

 

As neutrons pass through a crystal, they create two different standing waves – one along atomic planes and one between them. The interaction of these waves affects the path of the neutron, revealing aspects of the crystal structure.  Credit: NIST

Using a groundbreaking new technique at the National Institute of Standards and Technology (NIST), an international collaboration led by NIST researchers has revealed previously unrecognized properties of technologically crucial silicon crystals and uncovered new information about an important subatomic particle and a long-theorized fifth force of nature.

By aiming subatomic particles known as neutrons at silicon crystals and monitoring the outcome with exquisite sensitivity, the NIST scientists were able to obtain three extraordinary results: the first measurement of a key neutron property in 20 years using a unique method; the highest-precision measurements of the effects of heat-related vibrations in a silicon crystal; and limits on the strength of a possible “fifth force” beyond standard physics theories.

The researchers report their findings in the journal Science.

In a regular crystal such as silicon, there are many parallel sheets of atoms, each of which forms a plane. Probing different planes with neutrons reveals different aspects of the crystal.  Credit: NIST

To obtain information about crystalline materials at the atomic scale, scientists typically aim a beam of
particles (such as X-rays, electrons or neutrons) at the crystal and detect the beam’s angles, intensities and patterns as it passes through or ricochets off planes in the crystal’s lattice-like atomic geometry.

That information is critically important for characterizing the electronic, mechanical and magnetic properties of microchip components and various novel nanomaterials for next-generation applications including quantum computing. A great deal is known already, but continued progress requires increasingly detailed knowledge.

“A vastly improved understanding of the crystal structure of silicon, the ‘universal’ substrate or foundation material on which everything is built, will be crucial in understanding the nature of components operating near the point at which the accuracy of measurements is limited by quantum effects,” said NIST senior project scientist Michael Huber.

Neutrons, Atoms and Angles

Like all quantum objects, neutrons have both point-like particle and wave properties. As a neutron travels through the crystal, it forms standing waves (like a plucked guitar string) both in between and on top of rows or sheets of atoms called Bragg planes. When waves from each of the two routes combine, or “interfere” in the parlance of physics, they create faint patterns called pendellösung oscillations that provide insights into the forces that neutrons experience inside the crystal.

“Imagine two identical guitars,” said Huber. “Pluck them the same way, and as the strings vibrate, drive one down a road with speed bumps — that is, along the planes of atoms in the lattice — and drive the other down a road of the same length without the speed bumps — analogous to moving between the lattice planes. Comparing the sounds from both guitars tells us something about the speed bumps: how big they are, how smooth, and do they have interesting shapes?”

The latest work, which was conducted at the NIST Center for Neutron Research (NCNR) in Gaithersburg, Maryland, in collaboration with researchers from Japan, the U.S. and Canada, resulted in a fourfold improvement in precision measurement of the silicon crystal structure.

Not-Quite-Neutral Neutrons

Each neutron in an atomic nucleus is made up of three elementary particles called quarks. The three quarks’ electrical charge sum to zero, making it electrically neutral. But the distribution of those charges is such that positive charges are more likely to be found in the center of the neutron, and negative charges toward the outside.  Credit: NIST

In one striking result, the scientists measured the electrical “charge radius” of the neutron in a new way with an uncertainty in the radius value competitive with the most-precise prior results using other methods. Neutrons are electrically neutral, as their name suggests. But they are composite objects made up of three elementary charged particles called quarks with different electrical properties that are not exactly uniformly distributed.

As a result, predominantly negative charge from one kind of quark tends to be located toward the outer part of the neutron, whereas net positive charge is located toward the center. The distance between those two concentrations is the “charge radius.” That dimension, important to fundamental physics, has been measured by similar types of experiments whose results differ significantly. The new pendellösung data is unaffected by the factors thought to lead to these discrepancies.

Measuring the pendellösung oscillations in an electrically charged environment provides a unique way to gauge the charge radius. “When the neutron is in the crystal, it is well within the atomic electric cloud,” said NIST’s Benjamin Heacock, the first author on the Science paper.

“In there, because the distances between charges are so small, the interatomic electric fields are enormous, on the order of a hundred million volts per centimeter. Because of that very, very large field, our technique is sensitive to the fact that the neutron behaves like a spherical composite particle with a slightly positive core and a slightly negative surrounding shell.”

Vibrations and Uncertainty

A valuable alternative to neutrons is X-ray scattering. But its accuracy has been limited by atomic motion caused by heat. Thermal vibration causes the distances between crystal planes to keep changing, and thus changes the interference patterns being measured.

The scientists employed neutron pendellösung oscillation measurements to test the values predicted by X-ray scattering models and found that some significantly underestimate the magnitude of the vibration.

The results provide valuable complementary information for both x-ray and neutron scattering. “Neutrons interact almost entirely with the protons and neutrons at the centers, or nuclei, of the atoms,” Huber said, “and x-rays reveal how the electrons are arranged between the nuclei. This complementary knowledge deepens our understanding.

“One reason our measurements are so sensitive is that neutrons penetrate much deeper into the crystal than x-rays – a centimeter or more – and thus measures a much larger assembly of nuclei. We have found evidence that the nuclei and electrons may not vibrate rigidly, as is commonly assumed. That shifts our understanding on the how silicon atoms interact with one another inside a crystal lattice.”

Force Five

The Standard Model is the current, widely accepted theory of how particles and forces interact at the smallest scales. But it’s an incomplete explanation of how nature works, and scientists suspect there is more to the universe than the theory describes.

The Standard Model describes three fundamental forces in nature: electromagnetic, strong and weak. Each force operates through the action of “carrier particles.” For example, the photon is the force carrier for the electromagnetic force. But the Standard Model has yet to incorporate gravity in its description of nature. Furthermore, some experiments and theories suggest the possible presence of a fifth force.

“Generally, if there’s a force carrier, the length scale over which it acts is inversely proportional to its mass,” meaning it can only influence other particles over a limited range, Heacock said. But the photon, which has no mass, can act over an unlimited range. “So, if we can bracket the range over which it might act, we can limit its strength.” The scientists’ results improve constraints on the strength of a potential fifth force by tenfold over a length scale between 0.02 nanometers (nm, billionths of a meter) and 10 nm, giving fifth-force hunters a narrowed range over which to look.

The researchers are already planning more expansive pendellösung measurements using both silicon and germanium. They expect a possible factor of five reduction in their measurement uncertainties, which could produce the most precise measurement of the neutron charge radius to date and further constrain — or discover — a fifth force. They also plan to perform a cryogenic version of the experiment, which would lend insight into how the crystal atoms behave in their so-called “quantum ground state,” which accounts for the fact that quantum objects are never perfectly still, even at temperatures approaching absolute zero.

Source/Credit: National Institute of Standards and Technology

tn091021_01

How land birds cross the open ocean

 

Terrestrial birds are capable of flying for hundreds of kilometers over the open sea. Nourani et al. show that the autumn migration trajectories of some of these birds correspond with uplift over the sea surface. Suitable uplift means less drag, making sea-crossing less energetically demanding. Moreover, strong uplift can allow the birds to soar.
© Elham Nourani / Max Planck Institute of Animal Behavior

Migrating birds choose routes with the best wind and uplift conditions, helping them to fly nonstop for hundreds of kilometers over the sea

Researchers at the Max Planck Institute of Animal Behavior and University of Konstanz in Germany have identified how large land birds fly nonstop for hundreds of kilometers over the open ocean—without taking a break for food or rest. Using GPS tracking technology, the team monitored the global migration of five species of large land birds that complete long sea crossings. They found that all birds exploited wind and uplift to reduce energy costs during flight—even adjusting their migratory routes to benefit from the best atmospheric conditions. This is the most wide-ranging study of sea-crossing behavior yet and reveals the important role of the atmosphere in facilitating migration over the open sea for many terrestrial birds.

Flying over the open sea can be dangerous for land birds. Unlike seabirds, land birds are not able to rest or feed on water, and so sea crossings must be conducted as nonstop flights. For centuries, bird-watchers assumed that large land birds only managed short sea crossings of less than 100 kilometers and completely avoided flying over the open ocean.

However, recent advances in GPS tracking technology have overturned that assumption. Data obtained by attaching small tracking devices on wild birds has shown that many land birds fly for hundreds or even thousands of kilometers over the open seas and oceans as a regular part of their migration.

But scientists are still unraveling how land birds are able to accomplish this. Flapping is an energetically costly activity, and trying to sustain nonstop flapping flight for hundreds of kilometers would not be possible for large, heavy land birds. Some studies have suggested that birds sustain such journeys using tailwind, a horizontal wind blowing in the bird’s direction of flight, which helps them save energy. Most recently, a study revealed that a single species—the osprey—used rising air thermals known as “uplift” to soar over the open sea.

Now, the new study has examined sea-crossing behavior of 65 birds across five species to gain the most wide-ranging insight yet into how land birds survive long flights over the open sea. The researchers analyzed 112 sea-crossing tracks, collected over nine years, with global atmospheric information to pinpoint the criteria that the birds use for selecting their migration routes over the open sea. A large international collaboration of scientists shared their tracking data to make this study possible.

The findings not only confirm the role of tailwind in facilitating sea-crossing behavior, but also reveal the widespread use of uplift for saving energy during these nonstop flights. Suitable uplift means less drag, making sea crossing less energetically demanding.

“Until recently, uplift was assumed to be weak or absent over the sea surface. We show that is not the case,” says first author Elham Nourani, a DAAD PRIME postdoctoral fellow at the Department of Biology at the University of Konstanz, who did the work when she was at the Max Planck Institute of Animal Behavior.

Terrestrial birds are capable of flying for hundreds of kilometers over the open sea. Nourani et al. show that the autumn migration trajectories of

some of these birds correspond with uplift over the sea surface. Suitable uplift means less drag, making sea-crossing less energetically demanding. Moreover, strong uplift can allow the birds to soar.

“Instead, we find that migratory birds adjust their flight routes to benefit from the best wind and uplift conditions when they fly over the sea. This helps them sustain flight for hundreds of kilometers,” says Nourani.

The oriental honey buzzard, for example, flies 700 kilometers over the East China Sea during its annual migration from Japan to southeast Asia. The roughly 18-hour nonstop sea crossing is conducted in autumn when the air movement conditions are optimal. “By making use of uplift, these birds can soar up to one kilometer above the sea surface,” says Nourani.

The study also raises the question of how migration will be affected by a changing climate. “Our findings show that many land birds are dependent on atmospheric support to complete their migrations over the open sea, indicating their vulnerability to any changes to the Earth’s atmospheric circulation patterns,” says Nourani. “Collaborative studies like this are important to unravel general patterns about how migratory birds depend on the weather patterns. This enables future studies to make robust predictions about how these birds will be impacted by climate change.”

Source/Credit: Max-Planck-Gesellschaft

scn090921_04

The development of non-opioid painkillers to treat chronic pain

 

An image of the cryogenic electron microscopy structure of the human adenosine
A1 receptor (colored blue) bound to its signaling protein
(colored pink, green, and purple), adenosine (purple spheres)
and a proof-of-concept non-opioid analgesic (colored as orange spheres).

Monash University researchers have made a breakthrough discovery that could pave the way for the development of novel non-opioid painkillers (analgesics) to safely and effectively treat neuropathic pain.

The research was published today in the prestigious journal Nature.

Neuropathic pain is a type of chronic pain that can occur if your nervous system is damaged or not working correctly, and can be caused by injury, virus infection or cancer treatment, or be a symptom or complication of conditions such as multiple sclerosis and diabetes.

The new study, led by world-renowned drug researchers from the Monash Institute of Pharmaceutical Sciences (MIPS) and the Monash Biomedicine Discovery Institute (BDI), has demonstrated a new mode of targeting the adenosine A1 receptor protein, which has long been recognized as a promising therapeutic target for non-opioid painkillers to treat neuropathic pain but for which the development of painkillers had failed due to a lack of sufficient on-target selectivity, as well as undesirable adverse effects.

In the study, Monash researchers used electrophysiology and preclinical pain models to demonstrate that a particular class of molecule, called a ‘positive allosteric modulator’ (PAM), can provide much more selective targeting of the A1 receptor by binding to a different region of the protein than traditional, previously investigated, activators.

Another breakthrough in the study was facilitated by the application of cryo electron microscopy (cryoEM) to solve the high-resolution structure of the A1 receptor bound to both its natural activator, adenosine, and an analgesic PAM, thus providing the first atomic level snapshot of where these drugs bind.

Chronic pain remains a widespread global health burden, with lack of current therapeutic options leading to an over-reliance on opioid painkillers, which provide limited relief in patients with chronic (particularly neuropathic) pain, while exhibiting severe adverse effects, such as respiratory depression and addiction.

The new Monash discovery provides the opportunity for researchers to develop non-opioid drugs that lack such side effects.

Co-corresponding author of the study and Dean of the Faculty of Pharmacy and Pharmaceutical Sciences (home to MIPS), Professor Arthur Christopoulos said: “The world is in the grip of a global opioid crisis and there is an urgent need for non-opioid drugs that are both safe and effective.”

Associate Professor Wendy Imlach, who is the head of the Pain Mechanisms lab at Monash BDI and a co-corresponding author of the work, stated: “This study has helped us to better understand mechanisms underpinning allosteric drug actions. One of the exciting things we found is that not only were the PAMs able to decrease neuropathic pain with minimal unwanted effects, but they actually increase their level of effectiveness as the pain signals in the spinal cord get stronger – thus highlighting the potential for allosteric medicines that are uniquely sensitive to disease context”.

Professor Christopoulos added: “This multidisciplinary study now provides a valuable launchpad for the next stage in our drug discovery pipeline, which will leverage structure-based insights for the design of novel non-opioid allosteric drugs to successfully treat chronic pain.”

This work was performed in collaboration with researchers from the Universities of Sydney, Kansas and Tokyo, Uppsala University, and the ARC Centre for cryo-Electron Microscopy of Membrane Proteins. It was supported by the National Health and Medical Research Council of Australia, the Australian Research Council, the Australian Heart Foundation, the American Heart Association and the National Institutes of Health, and the Swedish Research Council.

Source/Credit: Monash University

scn090921_02

Mystery of icy plumes that may foretell deadly supercell storms

 

An Above Anvil Cirrus Plume emanates from the top of a storm.
(Image credit: NASA)

The most devastating tornadoes are often preceded by a cloudy plume of ice and water vapor billowing above a severe thunderstorm. New research reveals the mechanism for these plumes could be tied to “hydraulic jumps” – a phenomenon Leonardo Da Vinci observed more than 500 years ago.

When a cloudy plume of ice and water vapor billows up above the top of a severe thunderstorm, there’s a good chance a violent tornado, high winds or hailstones bigger than golf balls will soon pelt the Earth below.

A new Stanford University-led study, published Sept. 10 in Science, reveals the physical mechanism for these plumes, which form above most of the world’s most damaging tornadoes.

Previous research has shown they’re easy to spot in satellite imagery, often 30 minutes or more before severe weather reaches the ground. “The question is, why is this plume associated with the worst conditions, and how does it exist in the first place? That’s the gap that we are starting to fill,” said atmospheric scientist Morgan O’Neill, lead author of the new study.

The research comes just over a week after supercell thunderstorms and tornadoes spun up among the remnants of Hurricane Ida as they barreled into the U.S. Northeast, compounding devastation wrought across the region by record-breaking rainfall and flash floods.

Understanding how and why plumes take shape above powerful thunderstorms could help forecasters recognize similar impending dangers and issue more accurate warnings without relying on Doppler radar systems, which can be knocked out by wind and hail – and have blind spots even on good days. In many parts of the world, Doppler radar coverage is nonexistent.

“If there’s going to be a terrible hurricane, we can see it from space. We can’t see tornadoes because they’re hidden below thunderstorm tops. We need to understand the tops better,” said O’Neill, who is an assistant professor of Earth system science at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

Supercell storms and exploding turbulence

The thunderstorms that spawn most tornadoes are known as supercells, a rare breed of storm with a rotating updraft that can hurtle skyward at speeds faster than 150 miles an hour, with enough power to punch through the usual lid on Earth’s troposphere, the lowest layer of our atmosphere.

In weaker thunderstorms, rising currents of moist air tend to flatten and spread out upon reaching this lid, called the tropopause, forming an anvil-shaped cloud. A supercell thunderstorm’s intense updraft presses the tropopause upward into the next layer of the atmosphere, creating what scientists call an overshooting top. “It’s like a fountain pushing up against the next layer of our atmosphere,” O’Neill said.

As winds in the upper atmosphere race over and around the protruding storm top, they sometimes kick up streams of water vapor and ice, which shoot into the stratosphere to form the tell-tale plume, technically called an Above-Anvil Cirrus Plume, or AACP.

The rising air of the overshooting top soon speeds back toward the troposphere, like a ball that accelerates downward after cresting aloft. At the same time, air is flowing over the dome in the stratosphere and then racing down the sheltered side.

Using computer simulations of idealized supercell thunderstorms, O’Neill and colleagues discovered that this excites a downslope windstorm at the tropopause, where wind speeds exceed 240 miles per hour. “Dry air descending from the stratosphere and moist air rising from the troposphere join in this very narrow, crazy-fast jet. The jet becomes unstable and the whole thing mixes and explodes in turbulence,” O’Neill said. “These speeds at the storm top have never been observed or hypothesized before.”

Hydraulic jump

Scientists have long recognized that overshooting storm tops of moist air rising into the upper atmosphere can act like solid obstacles that block or redirect airflow. And it’s been proposed that waves of moist air flowing over these tops can break and loft water into the stratosphere. But no research to date has explained how all the pieces fit together.

The new modeling suggests the explosion of turbulence in the atmosphere that accompanies plumed storms unfolds through a phenomenon called a hydraulic jump. The same mechanism is at play when rushing winds tumble over mountains and generate turbulence on the downslope side, or when water speeding smoothly down a dam’s spillway abruptly bursts into froth upon joining slower-moving water below.

Leonardo DaVinci observed the phenomenon in flowing water as early as the 1500s, and ancient Romans may have sought to limit hydraulic jumps in aqueduct designs. But until now atmospheric scientists have only seen the dynamic induced by solid topography. The new modeling suggests a hydraulic jump can also be triggered by fluid obstacles in the atmosphere made almost entirely of air and which are changing shape every second, miles above the Earth’s surface.

The simulations suggest the onset of the jump coincides with a surprisingly rapid injection of water vapor into the stratosphere, upwards of 7000 kilograms per second. That’s two to four times higher than previous estimates. Once it reaches the overworld, water may stay there for days or weeks, potentially influencing the amount and quality of sunlight that reaches Earth via destruction of ozone in the stratosphere and warming the planet’s surface. “In our simulations that exhibit plumes, water reaches deep into the stratosphere, where it possibly could have more of a long-term climate impact,” said co-author Leigh Orf, an atmospheric scientist at the University of Wisconsin-Madison.

According to O’Neill, high-altitude NASA research aircraft have only recently gained the ability to observe the three-dimensional winds at the tops of thunderstorms, and have not yet observed AACP production at close range. “We have the technology now to go verify our modeling results to see if they’re realistic,” O’Neill said. “That’s really a sweet spot in science.”

This research was supported by the National Science Foundation and the NASA Precipitation Measurement Mission and Ground Validation program.

Source/Credit: Stanford University/Josie Garthwaite

en090921_04

Ancient sea ice core sheds light on modern climate change

 

A 170 m record of marine sediment cores extracted from Adélie Land in Antarctica by the Integrated Ocean Drilling Program is yielding new insights into the complicated relationship between sea ice and climate change.

In a new study published in Nature Geoscience, researchers at the University of Birmingham, have collaborated in an international project to identify how fluctuations in sea ice levels have interconnected with both algae blooms and weather events linked to El Nino over the past 12,000 years.

They found that Antarctic winds strongly affect the break-out and melting of sea ice, which in turn affects the levels of algae which can grow rapidly in surface waters when sea ice is reduced. Changes in the levels of algae growth in the waters surrounding the Antarctic are important enough to affect the global carbon cycle.

The researchers used techniques such as CT scan (computed tomography) imaging and analysis of microfossils and organic biomarkers, to examine the relationship between sea ice and large algae growth “bloom” events at annual timescales. The findings, produced in partnership with research institutes in New Zealand, Japan, France, Spain and the USA, span the entire Holocene period and have yielded a highly detailed picture of these relationships that can help predict future sea ice, climate and biological interactions.

The researchers found that algal bloom events occurred nearly every year before 4,500 years ago. However, a baseline shift to less frequent algal blooms and the type of algal production after 4.5 thousand years ago, saw bloom events responding to the El Nino Southern Oscillation (ENSO) and other climate cycles as sea-ice levels rapidly increased. Recent work by many of the same team links the expansion of sea ice at this time to glacial retreat and the development of the Ross Ice Shelf, which acts to cool Antarctic surface waters to create a “sea-ice factory”.

Dr James Bendle, of the University of Birmingham’s School of Geography, Earth and Environmental Science, is a co-author on the paper. He said: “While there’s a clear relationship between temperatures rising in the Arctic over recent decades and sea ice melting, the picture is more complex in the Antarctic. That’s because some areas of the Antarctic are warming, but in some areas sea ice has been increasing. Since sea ice reflects incoming sunlight, not only is the warming effect slowed down, but algae are unable to photosynthesize as easily. Climate models currently struggle to predict observed changes in sea ice for the Antarctic, and our findings will help climate researchers build more robust and detailed models.”

He added: “The relationship we have observed with these changing conditions and the ENSO wind fields is particularly significant. We know that El Nino amplifies the effects of climate change in some regions, so any insights linking this with Antarctic Sea ice is fascinating and has implications for how future long-term loss of sea ice may affect food webs in Antarctic waters, as well as carbon cycling processes within this globally important region.”


Dr Katelyn Johnson, of GNS Science, in New Zealand, is the lead author on the paper. She said: “While sea ice that persists from year to year can prevent these large algal blooms from occurring, sea ice that breaks out and melts creates a favorable environment for these algae to grow. These large algae ‘bloom events’ occur around the continent, form the base of the food webs and act as a carbon sink”.

“Unlike the Arctic where rising temperatures have led to reduced sea ice, the relationship in the Antarctic is less clear, as is the subsequent impact on primary productivity. Our new record provides a longer-term view of how sea ice and climate models like ENSO impact the frequency of these bloom events, allowing climate modelers to build more robust models.”

Source/Credit: University of Birmingham

en090921_03

Moth wingtips an ‘acoustic decoy’ to thwart bat attack

 

The Atlas moth (Attacus atlas) has a strong anti-bat acoustic decoy at the tip of its forewings. Composite image with photograph on right half and acoustic tomography on the left. Color indicates echo strength on a dB scale and red indicates highest echo amplitude. Note the red highly reflecting stripe created by the rippled part of the wingtip.
Image Credit: Dr Thomas Neil and Professor Marc Holderied

Wingtips of certain species of silkmoth are structured to reflect sound and throw off attackers, according to a new study.

Researchers at the University of Bristol have discovered that the tips of some saturniid moth forewings are curiously rippled and folded. They found that these unique structures strongly reflect sound, meaning that a bat hunting using echolocation is more likely to attack the wingtip region of the moth over the body, potentially saving the moth’s life.

Photograph of the Chinese tussar moth (Antheraea pernyi).
This silkmoth has a strong wingtip decoy based on ripples. 
Image Credit: Dr Thomas Neil

They also discovered that the ripples and folds of the forewing tips have evolved to act as hemispheric and corner retroreflectors respectively, meaning that they reflect sound strongly back to its point of origin. Coupled together, the folds and ripples of these wingtips cover a huge range of incident sounds angles, meaning that over the entire wingbeat cycle of a flying moth and most possible positions of an attacking bat, the wingtip would consistently produce the strongest echoes. The acoustic protection of wingtips is even stronger than that of common hindwing decoys.

Professor Marc Holderied of Bristol’s School of Biological Sciences explained: “We have demonstrated that the folded and rippled wingtips on the forewings of some silkmoths act as acoustic decoys.

“Structurally, the wingtips act as acoustic retroreflectors, reflecting sound back to its source from numerous angles, meaning a bat would be more likely to strike the wingtip over the more vulnerable body of the moth.”

The findings, published today in Current Biology, are the latest revelation in the bat-moth acoustic arms race - the battle between bats which hunt moths using echolocation, and the subsequent evolution of different defensive strategies amongst moths to increase their chances of survival.

Photograph of the Chinese tussar moth (Antheraea pernyi).
This silkmoth has a strong wingtip decoy
based on ripples. Image Credit: Dr Thomas Neil

Towed acoustic decoys are a well-established defense amongst some silkmoths. These species have evolved elongated hindwings which terminate in a coiled and twisted end. The morphology of these elongated hindwings means that they generate very strong echoes, so much so that they will often divert a bat’s acoustic gaze towards them, away from the exposed body of the moth, causing the bat to strike the expendable tail of the moth or miss the moth all together.

Lead author Dr Thomas Neil said: “There are many silkmoths that do not have these elongated hindwings, and we were interested in how they might protect themselves from bats. Through our research we discovered that there are many silkmoths that have rippled and folded structures not on the tips of their elongated hindwings but on the tips of their forewings. These resembled the twisted hindwing structures seen in other moths and so we wanted to know if they might also serve as an acoustic decoy to thwart a bat’s attack.

“To test this theory, we used innovative acoustic tomography analysis. We recorded echoes from moths from over 10,000 angles, to compare whether the echoes coming from the wingtips of these moths were stronger than the echoes from the body. If the echoes coming from the rippled and folded wingtips were stronger than that of the body, this would indicate that they were indeed acoustic decoys.

“Conclusive support for the idea that the forewing reflector is an acoustic decoy comes from our finding that acoustic forewing decoys always evolved as an alternative to acoustic hindwing decoys, with there being no species known to possess both.”

Now the researchers will try and collect behavioral data to corroborate their findings in the lab. They plan to monitor bats and moths with varying levels of folded wing morphologies to see how much of a survival advantage it really gives them.

Prof Holderied added:“The results of this study introduce another exciting aspect to the story of the bat-moths acoustic arms race. We have identified a novel form of acoustic defense amongst silkmoths which may give them an advantage over hunting bats. Wider implications might include improved man-made anti radar and sonar decoy architectures.”

Source/Credit: University of Bristol

scn090921_01

ESO captures best images yet of peculiar “dog-bone” asteroid

 

These eleven images are of the asteroid Kleopatra, viewed at different angles as it rotates. The images were taken at different times between 2017 and 2019 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s VLT.   Kleopatra orbits the Sun in the Asteroid Belt between Mars and Jupiter. Astronomers have called it a “dog-bone asteroid” ever since radar observations around 20 years ago revealed it has two lobes connected by a thick “neck”. 
Credit / Source: ESO/Vernazza, Marchis et al./MISTRAL algorithm (ONERA/CNRS)

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), a team of astronomers have obtained the sharpest and most detailed images yet of the asteroid Kleopatra. The observations have allowed the team to constrain the 3D shape and mass of this peculiar asteroid, which resembles a dog bone, to a higher accuracy than ever before. Their research provides clues as to how this asteroid and the two moons that orbit it formed.

“Kleopatra is truly a unique body in our Solar System,” says Franck Marchis, an astronomer at the SETI Institute in Mountain View, USA and at the Laboratoire d'Astrophysique de Marseille, France, who led a study on the asteroid — which has moons and an unusual shape — published today in Astronomy & Astrophysics. “Science makes a lot of progress thanks to the study of weird outliers. I think Kleopatra is one of those and understanding this complex, multiple asteroid system can help us learn more about our Solar System.”

Kleopatra orbits the Sun in the Asteroid Belt between Mars and Jupiter. Astronomers have called it a “dog-bone asteroid” ever since radar observations around 20 years ago revealed it has two lobes connected by a thick “neck”. In 2008, Marchis and his colleagues discovered that Kleopatra is orbited by two moons, named AlexHelios and CleoSelene, after the Egyptian queen’s children.

To find out more about Kleopatra, Marchis and his team used snapshots of the asteroid taken at different times between 2017 and 2019 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO’s VLT. As the asteroid was rotating, they were able to view it from different angles and to create the most accurate 3D models of its shape to date. They constrained the asteroid’s dog-bone shape and its volume, finding one of the lobes to be larger than the other, and determined the length of the asteroid to be about 270 kilometers or about half the length of the English Channel.

This image provides a size comparison of the asteroid Kleopatra with northern Italy.   The top half of the image shows a computer model of Kleopatra, a “dog-bone” shaped asteroid which orbits the Sun in the Asteroid Belt between Mars and Jupiter. End to end, Kleopatra is 270 kilometers long.   The bottom half of the image gives an aerial view of northern Italy, with the footprint Kleopatra would have if it were hovering above it.   
Credit / Sou: ESO/M. Kornmesser/Marchis et al.

In a second study, also published in Astronomy & Astrophysics and led by Miroslav Brož of Charles University in Prague, Czech Republic, the team reported how they used the SPHERE observations to find the correct orbits of Kleopatra’s two moons. Previous studies had estimated the orbits, but the new observations with ESO’s VLT showed that the moons were not where the older data predicted them to be.

“This had to be resolved,” says Brož. “Because if the moons’ orbits were wrong, everything was wrong, including the mass of Kleopatra.” Thanks to the new observations and sophisticated modelling, the team managed to precisely describe how Kleopatra’s gravity influences the moons’ movements and to determine the complex orbits of AlexHelios and CleoSelene. This allowed them to calculate the asteroid’s mass, finding it to be 35% lower than previous estimates.

Combining the new estimates for volume and mass, astronomers were able to calculate a new value for the density of the asteroid, which, at less than half the density of iron, turned out to be lower than previously thought. The low density of Kleopatra, which is believed to have a metallic composition, suggests that it has a porous structure and could be little more than a “pile of rubble”. This means it likely formed when material reaccumulated following a giant impact.

Kleopatra’s rubble-pile structure and the way it rotates also give indications as to how its two moons could have formed. The asteroid rotates almost at a critical speed, the speed above which it would start to fall apart, and even small impacts may lift pebbles off its surface. Marchis and his team believe that those pebbles could subsequently have formed AlexHelios and CleoSelene, meaning that Kleopatra has truly birthed its own moons.

The new images of Kleopatra and the insights they provide are only possible thanks to one of the advanced adaptive optics systems in use on ESO’s VLT, which is located in the Atacama Desert in Chile. Adaptive optics help to correct for distortions caused by the Earth’s atmosphere which cause objects to appear blurred — the same effect that causes stars viewed from Earth to twinkle. Thanks to such corrections, SPHERE was able to image Kleopatra — located 200 million kilometers away from Earth at its closest — even though its apparent size on the sky is equivalent to that of a golf ball about 40 kilometers away.

ESO’s upcoming Extremely Large Telescope (ELT), with its advanced adaptive optics systems, will be ideal for imaging distant asteroids such as Kleopatra. “I can’t wait to point the ELT at Kleopatra, to see if there are more moons and refine their orbits to detect small changes,” adds Marchis.

Source/Credit: ESO

sn090921_01
Released
09-09-21 12:00UTC

Biomarker predicts cognitive decline in Alzheimer’s disease

top-down view of a tau PET and MRI from a participant in the Northwestern study.
Warmer colors (red) indicate high Alzheimer's disease tau pathology.
(Image orientation: left is left, right is right).

 A biomarker in the brain predicts future cognitive decline in patients with the language form of Alzheimer’s disease 

Northwestern Medicine scientists discovered the buildup of tau protein in the brain predicts the amount of future cognitive decline over one year in individuals with AD. The study measured used a newer type of positron emission tomography (PET) imaging that shows the location of toxic tau protein in the brain. 

“Our new research shows tau PET imaging biomarkers can predict future decline in individuals with primary progressive aphasia due to AD,” said senior study author Emily Rogalski, associate director of Northwestern’s Mesulam Center for Cognitive Neurology and Alzheimer’s Disease. “These tau-based biomarkers may help predict the pace of progression of the disease and be important for early detection. They may eventually help us treat AD before we see symptoms.”

The higher the level of the bad form of tau in the brain, the worse a person’s cognitive performance, the study showed. The more tau protein a person had in a specific region of their brain, the more likely they were to have worse cognition a year later. The study also found the higher the level of tau, the more atrophy was occurring across the brain. 

The study was published Sept. 8 in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.

Early diagnosis of AD is important because the Food & Drug Administration recently approved Biogen’s Aduhelm (aducanumab) to treat patients in the disease’s mild stages, and other drugs are in the development pipeline. 

“The presence and level of these biomarkers might give us a picture of how aggressive the disease is going to be, providing important markers necessary for precision-medicine interventions,” said lead author Adam Martersteck. He conducted the research as a neuroscience graduate student at Northwestern University Feinberg School of Medicine and now is a postdoctoral fellow at the University of California Berkeley.

The study was among the first to show the amount of tau pathology in the brain predicts subsequent cognitive decline over time.

The individuals in the study had Progressive Primary Aphasia (PPA), which is often caused by an early-onset form of AD. In PPA, the parts of the brain that control language and speech degenerate.

“It’s important to show that AD in primary progressive aphasia is similar to the more common late-onset AD that causes memory problems, so that participants with PPA can be included in clinical trials and offered all the same opportunities,” Martersteck said.

The finding about predictive decline from tau pathology is also applicable to more common forms of AD in which memory loss is the primary symptom. One theory is that toxic forms of AD accumulate and then trigger events resulting in brain cell degeneration. This research supports this theory. 

Participants from around the country were seen locally or flown to Chicago for MRI, tau PET imaging and cognitive testing at Northwestern’s Mesulam Center for Cognitive Neurology and Alzheimer's Disease. The 19 participants all had been diagnosed with PPA. 

As a growing proportion of Americans age, the prevalence of AD is expected to rise. An estimated 50 million people worldwide and 6 million in the U.S. have AD, with those numbers expected to triple in the next 30 years.

In the study, scientists measured toxic tau at baseline and tested participants on their ability to name objects. Participants returned a year later and were tested again on their ability to name objects. The more tau they had in the left anterior temporal lobe on PET imaging, the more likely they were to have worse cognition and a decline in their naming. 

“The next steps for the research are to determine if these measurements are reliable at the individual level to guide prognosis and intervention targets,” Rogalski said. “We know some individuals with PPA progress more rapidly than others, but factors driving fast versus slow progression have been difficult to ascertain. Reliable biomarkers are one key to solving this conundrum.” 

Other Northwestern study authors are Jaiashre Sridhar, Christina Coventry, Sandra Weintraub and Dr. Marsel Mesulam.

Source/Credit: Northwestern University

scn090921_02

Coral cryopreservation for breeding key to survival

 

Fragment of endangered Caribbean elkhorn coral grown from cryopreserved sperm.
(Photo credit: Chris Page)

Flash-frozen sperm collected from corals in Florida and Puerto Rico was used to fertilize coral eggs from hundreds of miles away in Curaçao. The juvenile corals raised from this trans-Caribbean coupling demonstrate the reproductive compatibility of coral colonies that would otherwise be too far apart to produce offspring in the wild and they represent the largest wildlife population ever raised from cryopreserved material.

A paper describing this study, by an international team of researchers, including Mary Hagedorn at the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST), was published in the Proceedings of the National Academy of Sciences.

The technique could be used as a conservation tool by introducing genetic variation into endangered corals and potentially accelerating their adaptation to climate change.

“Most corals only attempt sexual reproduction once a year and the eggs and sperm are only viable for a short time period,” said Hagedorn, a research biologist at the Smithsonian Conservation Biology Institute and UH Mānoa’s Hawaiʻi Institute of Marine Biology. She is the lead author of this study, and has developed the technique to cryopreserve coral sperm in her laboratory at UH. “Cryopreservation allows us to breed corals with parentage from hundreds of miles apart.”

Assisted gene flow

“Corals are a vital foundation species for reef ecosystems,” said Iliana Baums, professor of biology at Penn State and one of the leaders of the research team. “Reefs provide habitat for astonishing species diversity, protect shorelines and are economically important for fisheries, but they are suffering in many places due to warming ocean waters. Without intervention, we will continue to lose corals to climate change with potentially disastrous consequences.”

Genetic diversity is the fuel for species adaptation. One of the main sources of genetic diversity is sexual reproduction—new combinations of genes are created when a sperm fertilizes an egg. However, sexual reproduction by Caribbean corals in the wild is now vanishingly rare. Worse yet, because corals are sessile creatures (fixed in one place), they have a limited ability to gain new genetic diversity through gene flow, the evolutionary force that increases genetic diversity when distant populations come together, each bringing with them their own unique versions of genes.

“To increase genetic diversity in corals, we can use ‘assisted gene flow’ by bringing corals together that are physically distant in the wild, but this is logistically incredibly difficult,” said Baums.

Cryopreservation

Most corals reproduce by broadcasting bundles of eggs and sperm into the sea water in a spectacular spawning event timed with the full moon. The researchers collected these bundles from corals in Florida and Puerto Rico, separated the eggs and sperm, and then quickly froze the sperm cells using a liquid nitrogen cryopreservation technique.

“Because these corals only produce eggs and sperm once per year, frozen sperm collected in Florida and Puerto Rico needed to be cryopreserved in advance and stored for over a year until it could be used for a spawning event in Curaçao,” said Baums.

Some of the sperm were kept frozen at the USDA National Animal Germplasm Program’s gene bank for up to 10 years. The frozen sperm was transported to Curaçao where it was thawed and used to fertilize fresh eggs collected locally. The fertilized eggs developed into larvae that were then transported to Mote Marine Laboratory and The Florida Aquarium in Florida, where they were allowed to develop into adults.

Source/Credit: University of Hawaiʻi

en090921_02