Natural selection favors cheaters

Acmispon strigosus is an annual herb that is native to California.

Mutualisms, which are interactions between members of different species that benefit both parties, are found everywhere -- from exchanges between pollinators and the plants they pollinate, to symbiotic interactions between us and our beneficial microbes.

Natural selection -- the process whereby organisms better adapted to their environment tend to survive and produce more offspring -- predicts, however, that mutualisms should fall apart. Individuals that gain from the cooperation of others but do not reciprocate (so-called cheaters) should arise and destabilize mutualisms. Yet to date, surprisingly little evidence of such cheating or destabilization exists.

A team of biologists at the University of California, Riverside, has now found strong evidence of this cheating. Focusing on the interaction between nitrogen-fixing bacteria, or rhizobia, and their legume hosts spanning about 530 miles of California habitat, the researchers found that natural selection in their study populations favors cheating rhizobia.

The study, appearing in Ecology Letters, is the first to uncover cheater strains in natural populations and show how natural selection favors them.

The researchers used a previously published database to quantify the landscape abundance of different rhizobial strains. They focused on naturally occurring populations of rhizobia in the genus Bradyrhizobium and the native annual plants, Acmispon strigosus, that these bacteria inhabit. Within these datasets they found that the fewer benefits the rhizobia provide to their host plants, the more common the rhizobia are.

"Our data show that natural selection favors cheating rhizobia, and support predictions that rhizobia can often subvert plant defenses and evolve to exploit hosts," said Joel Sachs, a professor of biology in the Department of Evolution, Ecology & Organismal Biology, who led the research team.

Sachs explained that beneficial bacteria are increasingly appreciated to be key for human health as well as the productivity of crops and livestock. Little is understood, however, about how much these bacterial services vary in natural systems and the forces that modulate them.

"In crop plants, in particular, agronomists have attempted -- and failed -- for several decades to design crop biofertilizers based on beneficial bacteria," he said. "Similar challenges have been faced in applying bacteria in other host systems -- probiotics, for example, which rarely affect host microbes. Our dataset suggests a potential flaw in these approaches; the bacteria, with their own evolutionary interests, can destabilize these interactions."

In their paper, the researchers show how benefits of bacterial symbionts vary over space and time, and how rapidly these systems can evolve.

"We often view the services of bacteria as fixed, but this is not at all true," Sachs said. "Just as each human varies a great deal in almost any trait we can measure, bacterial populations are even more highly variable. Understanding this variation and its drivers will be key to usefully harnessing these bacteria for our own purposes."

Already, his team is actively working to better understand how beneficial bacteria can be applied to improve plant growth. Preliminary data show that it is crucial to carefully select among bacterial variants to avoid using harmful strains.

"Simply applying beneficial bacteria to a crop is often not going to be sufficient since exploitative strains are expected to be lurking within these populations," Sachs said.

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Weird, wild gravity of asteroid Bennu

The asteroid Bennu as seen by the OSIRIS-REx spacecraft. The flying saucer-like shape of Bennu is generated, in part, by its spin.

Research led by the University of Colorado Boulder is revealing the Alice in Wonderland-like physics that govern gravity near the surface of the asteroid Bennu.

The new findings are part of a suite of papers published today by the team behind NASA's Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission. And they come just three months after OSIRIS-REx first encountered Bennu on Dec. 3, 2018.

Since then, the spacecraft has completed a few dozen laps around the asteroid, which is about as tall as the Empire State Building, circling Bennu from a distance of about a mile. And those early circuits are giving scientists a whole new look at this mysterious rock, said CU Boulder's Daniel Scheeres, who leads the mission's radio science team.

In research appearing in Nature Astronomy, for example, his team reports the mass of that asteroid: a respectable 73 billion kilograms.

But Scheeres and his colleagues are also working to develop a map of the asteroid's gravitational pull. Their findings suggest that Bennu exists in a delicate balance between two competing forces, the result of the asteroid's wild spin. Bennu completes a full revolution about once every four hours.

And, Scheeres said, those forces could play an important role in the asteroid's long-term evolution -- and potential demise.

"When you spin this guy up, you create a competition between the gravity that's holding you down and the centrifugal acceleration, which is trying to throw you off," said Scheeres, distinguished professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences who leads the mission's radio science team.

To study those forces, Scheeres and his colleagues use OSIRIS-REx's navigational instruments to measure the minute tug that the asteroid exerts on the spacecraft.

And they dug up more than they expected. Based on the group's calculations, the region around Bennu's equator is trapped within a gravitational feature called a rotational Roche lobe -- something that scientists had not yet clearly observed on an asteroid.

In practice, that feature gets weird. If you were standing inside the boundaries of Bennu's Roche lobe and slipped on a banana peel, for example, not much would happen -- you'd be captured by the lobe and fall back to the surface.

"But if you were outside of the Roche lobe and slipped on a banana peel, you would roll toward the equator," Scheeres said. "And you could gain enough energy so that you'd roll off the equator and maybe up into orbit and then out into space."

It sounds like the sort of environment that Lewis Carroll could appreciate. But it also matters for the lifespan of Bennu, he added.

That's because radiation from the sun is causing Bennu to spin faster and faster over time. And as the asteroid's whirling builds up speed, its Roche lobe might also be shrinking, along with the forces that are holding Bennu together.

"As that Roche lobe narrows further and further around the equator, it becomes easier and easier for this asteroid to lose material," Scheeres said. "So far, that material has been trapped by gravity, but at some point, if the asteroid keeps spinning faster, then you fall off the cliff."

In other words, Bennu could be in the process of spinning itself into oblivion.

Understanding those physics matters for advance OSIRIS-REx's scientific mission, too, said Jay McMahon, an assistant professor in aerospace engineering and a co-author of the new study.

He explained that in 2020, mission scientists will nudge OSIRIS-REx to within a few feet of Bennu, using the spacecraft's retractable arm to collect a sample of material from the surface. And to do that safely, they will need to know the rock's physics inside and out.

"You need to know the gravitational field for spacecraft operations, really to enable all the other science," McMahon said.

"When you're going to a new world, you have some idea of what it might look like," Scheeres said. "Then you actually go there, and you can start comparing what you thought it might look like versus reality."

The University of Arizona leads science operations for OSIRIS-REx, which was built by the Colorado-based Lockheed Martin Space. NASA's Goddard Space Flight Center in Maryland manages the overall mission.

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Researchers create hydrogen fuel from seawater

A prototype device used solar energy to create hydrogen fuel from seawater.

Stanford researchers have devised a way to generate hydrogen fuel using solar power, electrodes and saltwater from San Francisco Bay.

The findings, published March 18 in Proceedings of the National Academy of Sciences, demonstrate a new way of separating hydrogen and oxygen gas from seawater via electricity. Existing water-splitting methods rely on highly purified water, which is a precious resource and costly to produce.

Theoretically, to power cities and cars, "you need so much hydrogen it is not conceivable to use purified water," said Hongjie Dai, J.G. Jackson and C.J. Wood professor in chemistry at Stanford and co-senior author on the paper. "We barely have enough water for our current needs in California."

Hydrogen is an appealing option for fuel because it doesn't emit carbon dioxide, Dai said. Burning hydrogen produces only water and should ease worsening climate change problems.

Dai said his lab showed proof-of-concept with a demo, but the researchers will leave it up to manufacturers to scale and mass produce the design.

Tackling corrosion

As a concept, splitting water into hydrogen and oxygen with electricity -- called electrolysis -- is a simple and old idea: a power source connects to two electrodes placed in water. When power turns on, hydrogen gas bubbles out of the negative end -- called the cathode -- and breathable oxygen emerges at the positive end -- the anode.

But negatively charged chloride in seawater salt can corrode the positive end, limiting the system's lifespan. Dai and his team wanted to find a way to stop those seawater components from breaking down the submerged anodes.

The researchers discovered that if they coated the anode with layers that were rich in negative charges, the layers repelled chloride and slowed down the decay of the underlying metal.

They layered nickel-iron hydroxide on top of nickel sulfide, which covers a nickel foam core. The nickel foam acts as a conductor -- transporting electricity from the power source -- and the nickel-iron hydroxide sparks the electrolysis, separating water into oxygen and hydrogen. During electrolysis, the nickel sulfide evolves into a negatively charged layer that protects the anode. Just as the negative ends of two magnets push against one another, the negatively charged layer repels chloride and prevents it from reaching the core metal.

Without the negatively charged coating, the anode only works for around 12 hours in seawater, according to Michael Kenney, a graduate student in the Dai lab and co-lead author on the paper. "The whole electrode falls apart into a crumble," Kenney said. "But with this layer, it is able to go more than a thousand hours."

Previous studies attempting to split seawater for hydrogen fuel had run low amounts of electric current, because corrosion occurs at higher currents. But Dai, Kenney and their colleagues were able to conduct up to 10 times more electricity through their multi-layer device, which helps it generate hydrogen from seawater at a faster rate.

"I think we set a record on the current to split seawater," Dai said.

The team members conducted most of their tests in controlled laboratory conditions, where they could regulate the amount of electricity entering the system. But they also designed a solar-powered demonstration machine that produced hydrogen and oxygen gas from seawater collected from San Francisco Bay.

And without the risk of corrosion from salts, the device matched current technologies that use purified water. "The impressive thing about this study was that we were able to operate at electrical currents that are the same as what is used in industry today," Kenney said.

Surprisingly simple

Looking back, Dai and Kenney can see the simplicity of their design. "If we had a crystal ball three years ago, it would have been done in a month," Dai said. But now that the basic recipe is figured out for electrolysis with seawater, the new method will open doors for increasing the availability of hydrogen fuel powered by solar or wind energy.

In the future, the technology could be used for purposes beyond generating energy. Since the process also produces breathable oxygen, divers or submarines could bring devices into the ocean and generate oxygen down below without having to surface for air.

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Scientists hunt down the brain circuit responsible for alcohol cravings

Confocal analysis at 63x magnification, followed by the three-dimensional reconstruction of neuronal cell bodies and branches. The image shows an example of eYFP and CRF in the same neuron. This rendered isosurface analysis demonstrated the colocalization of CRF immunoreactivity within CeA neurons that also expressed Cre-dependent eYFP and validates the crh-Cre rat as a tool to gain more direct access to CRF neurons to study their functional neuroanatomy.

Scientists at Scripps Research have found that they can reverse the desire to drink in alcohol-dependent rats -- with the flip of a switch. The researchers were able to use lasers to temporarily inactivate a specific neuronal population, reversing alcohol-seeking behavior and even reducing the physical symptoms of withdrawal.

"This discovery is exciting -- it means we have another piece of the puzzle to explain the neural mechanism driving alcohol consumption," says Olivier George, PhD, an associate professor at Scripps Research and senior author of the new study, published March 18, 2019 in the journal Nature Communications.

Although the laser treatment is far from ready for human use, George believes identifying these neurons opens the door to developing drug therapies or even gene therapies for alcohol addiction.

"We need compounds that are specific to this neuronal circuitry," George says.

According to the National Institute on Alcohol Abuse and Alcoholism, more than 15.1 million adults in the United States suffer from alcohol use disorder. Previous work at Scripps Research has shown that transitioning from casual drinking to dependent drinking occurs alongside fundamental changes in how the brain sends signals. These signals drive the intense cravings that make it so difficult for many people to scale back their alcohol consumption.

George and his colleagues have been hunting for the brain cells that driving drinking in an alcohol-addicted rat model. In 2016, they reported that they had found a possible source: a neuronal "ensemble," or group of connected cells in a brain region called the central nucleus of the amygdala (CeA). This finding marked major progress in mapping the brain, but the researchers needed to characterize the identity of the neurons in this ensemble.

For the new study, they tested the role of a subset of neurons in the ensemble, called corticotropin-releasing factor (CRF) neurons. The George laboratory had found that these CRF neurons make up 80 percent of the ensemble. Were these neurons the masterminds driving alcohol cravings?

The researchers studied these neurons using optogenetics, a technique that involves the use of light to control cells in living tissue. Rats used in this study were surgically implanted with optic fibers aimed to shine light on the CRF neurons -- to inactivate them at the flip of a switch.

First, the scientists established a baseline for how much the rats would drink before they got addicted to alcohol. The rats drank little this point -- the equivalent of a glass of wine or one beer for a human. The scientists then spent several months increasing consumption in these rats to establish alcohol dependence.

The researchers then withdrew the alcohol, prompting withdrawal symptoms in the rats. When they offered alcohol again, the rats drank more than ever. The CeA neuronal ensemble was active, telling the rats to drink more.

Then the scientists flipped on the lasers to inactivate the CRF neurons -- and the results were dramatic. The rats immediately returned to their pre-dependent drinking levels. The intense motivation to drink had gone away. Inactivating these neurons also reduced the physical symptoms of withdrawal, such as abnormal gait and shaking.

"In this multidisciplinary study, we were able to characterize, target and manipulate a critical subset of neurons responsible for excessive drinking." says Giordano de Guglielmo, PhD, first author of the study and staff scientist at Scripps Research. "This was a team effort, and while we used challenging techniques, working with experts in the field and with the right tools, made everything easier and enjoyable."

The effect was even reversible. Turn off the lasers, and the rats returned to their dependent behavior.

From a basic science standpoint, this breakthrough is huge: It reveals wiring in the brain that drives a specific, destructive behavior. George says the next step in translating this work to humans is to find a way to selectively inhibit only these specific CRF neurons, perhaps using a novel or repurposed compound identified using high-throughput screening of large libraries of compounds.

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Trembling aspen leaves could save future Mars rovers

The traditional harvester on the left, and the new harvester on the right.

Researchers at the University of Warwick have been inspired by the unique movement of trembling aspen leaves, to devise an energy harvesting mechanism that could power weather sensors in hostile environments and could even be a back-up energy supply that could save and extend the life of future Mars rovers.

University of Warwick third year engineering undergraduates have in recent years been set the task of the examining the puzzle of why Aspen leaves quiver in the presence of a slightest breeze. University of Warwick Engineering researchers Sam Tucker Harvey, Dr Igor A. Khovanov, and Dr Petr Denissenko were inspired to look more closely at this task they were annually setting for their students and to take the phenomenon one step further.

They decided to investigate whether the underlying mechanisms that produce the low wind speed quiver in Aspen leaves could efficiently and effectively generate electrical power, simply by exploiting the wind generated mechanical movement of a device modelled on the leaf. They have today 18th March 2019 published the answer to that question as a paper entitled "A Galloping Energy Harvester with Flow Attachment" in Applied Physics Letters and the answer is a resounding yes.

University of Warwick PhD engineering researcher Sam Tucker Harvey, the lead author on the paper, said:

"What's most appealing about this mechanism is that it provides a mechanical means of generating power without the use of bearings, which can cease to work in environments with extreme cold, heat, dust or sand. While the amount of potential power that could be generated is small, it would be more than enough to power autonomous electrical devices, such as those in wireless sensor networks. These networks could be utilised for applications such as providing automated weather sensing in remote and extreme environments."

Dr Petr Denissenko further noted that one future application could be as a backup power supply for future Mars landers and rovers.

"The performance of the Mars rover Opportunity far exceeded its designers' wildest dreams but even its hard working solar panels were probably eventually overcome by a planetary-scale dust storm. If we could equip future rovers with a backup mechanical energy harvester based on this technology, it may further the lives of the next generation of Mars rovers and landers."

The key to Aspen leaves' low wind but large amplitude quiver isn't just the shape the leaf but more importantly relates to the effectively flat shape of the stem.

The University of Warwick researchers used mathematical modelling to come up with a mechanical equivalent of the leaf. They then used a low speed wind tunnel to test a device with a cantilever beam like the flat stem of the Aspen leaf, and a curved blade tip with a circular arc cross section acting like the main leaf.

The blade was then oriented perpendicular to the flow direction, which allows the harvester to produce self-sustained oscillations at uncharacteristically low wind speeds like the aspen leaf. The tests showed that the air flow becomes attached to the rear face of the blade when the blade's velocity becomes high enough, hence acting more similarly to an aerofoil rather than to the bluff bodies which have typically been studied in the context of wind energy harvesting.

In nature, the propensity of a leaf to quiver is also enhanced by the thin stem's tendency to twist in the wind in two different directions. However, the researchers modelling and testing found that they did not need to replicate the additional complexity of a further degree of movement in their mechanical model. Simply replicating the basic properties of the flat stem in as a cantilever beam and curved blade tip with a circular arc cross section acting like the main leaf was enough to create sufficient mechanical movement to harvest power.

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Alligator study reveals insight into dinosaur hearing

American Alligators make neural maps of sound the same way birds do.

To determine where a sound is coming from, animal brains analyze the minute difference in time it takes a sound to reach each ear -- a cue known as interaural time difference. What happens to the cue once the signals get to the brain depends on what kind of animal is doing the hearing.

Scientists have known that birds are exceptionally good at creating neural maps to chart the location of sounds, and that the strategy differs in mammals. Little was known, however, about how alligators process interaural time difference.

A new study of American alligators found that the reptiles form neural maps of sound in the same way birds do. The research by Catherine Carr, a Distinguished University Professor of Biology at the University of Maryland, and her colleague Lutz Kettler from the Technische Universität München, was published in the Journal of Neuroscience on March 18, 2019.

Most research into how animals analyze interaural time difference has focused on physical features such as skull size and shape, but Carr and Kettler believed it was important to look at evolutionary relationships.

Birds have very small head sizes compared with alligators, but the two groups share a common ancestor -- the archosaur -- which predates dinosaurs. Archosaurs began to emerge around 246 million years ago and split into two lineages; one that led to alligators and one that led to dinosaurs. Although most dinosaurs died out during the mass extinction event 66 million years ago, some survived to evolve into modern birds.

Carr and Kettler's findings indicate that the hearing strategy birds and alligators share may have less to do with head size and more to do with common ancestry.

"Our research strongly suggests that this particular hearing strategy first evolved in their common ancestor," Carr said. "The other option, that they independently evolved the same complex strategy, seems very unlikely."

To study how alligators identify where sound comes from, the researchers anesthetized 40 American Alligators and fitted them with earphones. They played tones for the sleepy reptiles and measured the response of a structure in their brain stems called the nucleus laminaris. This structure is the seat of auditory signal processing. Their results showed that alligators create neural maps very similar to those previously measured in barn owls and chickens. The same maps have not been recorded in the equivalent structure in mammal brains.

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Rukwa Rift Basin Project names new Cretaceous mammal from East African Rift System

Side view of the lower jaw of Galulatherium jenkinsi, the most complete mammal yet know from the Cretaceous Period of the African continent, and named this week by researchers from Ohio University.

Ohio University researchers announced a new species of mammal from the Age of Dinosaurs, representing the most complete mammal from the Cretaceous Period of continental Africa, and providing tantalizing insights into the past diversity of mammals on the planet.

The National Science Foundation-funded OHIO team, in collaboration with international colleagues, identified and named the new mammal in an article published today in Acta Paleontologica Polonica. This nearly complete lower jaw represents the first named mammal species from the Late Cretaceous Period (100-66 million years ago) of the entire African continent. The squirrel-sized animal was probably related to a group of southern hemisphere mammals known as gondwanatherians, yet a bizarre combination of features (including evergrowing and enamel-less peg-like teeth) make it challenging to easily place within any group of mammals yet known, living or extinct.

The new mammal is named Galulatherium jenkinsi, a name based on the Galula rock unit (itself derived from one of the local villages in the field area) and therium, Latin for beast, with the species name "jenkinsi" honoring the late Farish Jenkins, distinguished professor of anatomy and organismic biology at Harvard University and a strong supporter of the Rukwa Rift Basin Project early in its development.

The type and only specimen of Galulatherium was discovered in 2002, when Rukwa Rift Basin Project researchers found a bone fragment eroding from Cretaceous-age red sandstones in the Rukwa Rift Basin in southwestern Tanzania. After painstakingly removing the rock from the delicate specimen, the team announced the discovery of a new mammal in 2003, yet they conservatively refrained from establishing a name for the enigmatic new species until additional details of its anatomy could be revealed. In the intervening years, improvements in high-resolution x-ray computed tomography enabled the team to document detailed anatomy of the specimen and to establish Galulatherium as a species new to science.

"The analysis of Galulatherium has been a collaborative process, engaging with a group of experts to tackle the unique morphology of this specimen," noted Dr. Patrick O'Connor, professor of anatomy at Ohio University and lead author of the paper. "Additional information gleaned from density-based microCT analyses, particularly the presence of ever-growing, enamel-less teeth, has allowed us to compare Galulatherium with other Mesozoic and early Cenozoic mammals, as well as with modern groups like sloths, in order to establish the best anatomical and functional analogs for this unique type of dentition."

Gonwanatherian mammals are best known from Cretaceous and early Cenozoic rock units in Madagascar and Argentina, with other specimens known from India and Antarctica. Members of the research team have worked across the globe in search of early mammals.

"The fact that this is the first discovery of an identifiable mammal fossil in the Late Cretaceous of all of mainland Africa is incredibly exhilarating on so many levels," added co-author David Krause, curator of paleontology at the Denver Museum of Nature and Science. "The needle is very small and the haystack is very big. And we know that there are so many more needles to find there."

The perplexing story of Galulatherium and identifying its closest relatives is just the starting point. Getting ANY insight into what mammals lived on the continent during this time is groundbreaking, but it seems that Galulatherium is not a predecessor of any of the mammals that live on Africa today. So what happened to it and its kin? Were they wiped out at the end of the Cretaceous? When did the ancestors of Africa's extant mammalian lineages arrive on the continent? Or were they living alongside Galulatherium and just have not yet been found?

"All great questions that will only be answered with the discovery of additional fossils, underscoring the need for exploratory research in places like the Rukwa Rift Basin and elsewhere on the continent," added O'Connor.

The study included experts from several institutions to pore over the tiny jaw. Yet the specimen preserved a truly unique combination of anatomical features, making it difficult to place in the existing framework of mammalian evolution, and ultimately raising more questions than it answers.

"What began with the description of a compact specimen became a broader quest to understand how this jaw fits into the complex puzzle of mammalian evolution," said Dr. Nancy Stevens, Ohio University professor and co-author on the paper.

Galulatherium is not the only animal discovered by the research team in the Rukwa Rift Basin. Other Cretaceous-age finds include bizarre relatives of early crocodiles and three distinct species of long-necked herbivorous sauropod dinosaurs. Finds from younger rocks in the region contain the oldest evidence of the split between monkeys and apes. Taken together, these findings from the East African Rift reveal a crucial glimpse into ancient ecosystems of Africa and encourage additional field exploration on the continent.

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Earliest known Mariner's Astrolabe research

Guinness World Records have independently certified an astrolabe excavated from the wreck site of a Portuguese Armada Ship that was part of Vasco da Gama's second voyage to India in 1502-1503 as the oldest in the world, and have separately certified a ship's bell (dated 1498) recovered from the same wreck site also as the oldest in the world.

Guinness World Records have independently certified an astrolabe excavated from the wreck site of a Portuguese Armada Ship that was part of Vasco da Gama's second voyage to India in 1502-1503 as the oldest in the world, and have separately certified a ship's bell (dated 1498) recovered from the same wreck site also as the oldest in the world.

The scientific process of verifying the disc as an astrolabe by laser imaging is described in a paper published today by Mearns and Jason Warnett and Mark Williams of WMG at the University of Warwick in the International Journal of Nautical Archaeology.

The Sodré astrolabe has made it into the Guinness Book of world records is believed to have been made between 1496 and 1501 and is unique in comparison to all other mariner's astrolabes.

Mariner's Astrolabes were used for navigating at sea by early explorers, most notably the Portuguese and Spanish.

They are considered to be the rarest and most prized of artefacts to be found on ancient shipwrecks and only 104 examples are known to exist in the world.

They were first used at sea on a Portuguese voyage down the west coast of Africa in 1481. Thereafter, astrolabes were relied on for navigation during the most important explorations of the late 15th century, including those led by Bartolomeu Dias, Christopher Columbus and Vasco da Gama.

It is the only solid disk type astrolabe with a verifiable provenance and the only specimen decorated with a national symbol: the royal coat of arms of Portugal.

As the earliest verifiable mariner's astrolabe it fills a chronological gap in the development of these iconic instruments and is believed to be a transitional instrument between the classic planispheric astrolabe and the open-wheel type astrolabe that came into use sometime before 1517.

The thin 175 mm diameter disk weighing 344 grams was analysed by a team from WMG who travelled to Muscat, Oman in November 2016 to collect laser scans of a selection of the most important artefacts recovered from the wreck site.

Using a portable 7-axis Nikon laser scanner, capable of collecting over 50,000 points per second at an accuracy of 60 microns, a 3D virtual model of the artefact was created.

Analysis of the results revealed a series of 18 scale marks spaced at uniform intervals along the limb of the disk.

Further analysis by WMG engineers showed that the spacing of the scale marks was equivalent to 5-degree intervals. This was critical evidence that allowed independent experts at Texas A&M University to include the disk in their global inventory as the earliest known mariner's astrolabe discovered to date.

Prof Mark Williams from WMG, University of Warwick comments:

"Using this 3D scanning technology has enabled us to confirm the identity of the earliest known astrolabe, from this historians and scientists can determine more about history and how ships navigated.

Technology like this betters our understanding of how the disc would have worked back in the 15th century. Using technology normally applied within engineering projects to help shed insight into such a valuable artefact was a real privilege"

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When is best time to get flu shot? Analysis compares scenarios

When flu season peaks after mid-winter, tens of thousands of influenza cases and hundreds of deaths can likely be avoided if older adults wait until October to get their flu immunization, a University of Pittsburgh School of Medicine analysis reveals in the April issue of the American Journal of Preventive Medicine.

The protection offered by the flu vaccine wanes as the season progresses, a previous study has shown, which indicates that waiting until closer to the start of flu season ensures greater immunity. However, if flu season arrives early or if delayed vaccination prompts more than one in 20 people who would otherwise be vaccinated to skip their flu shot, then the gains are negated, according to the new study, which is online now.

"There's controversy in the public health community over whether influenza vaccination should happen as soon as the vaccine becomes available in August, or if it's better to wait until later in the fall," said lead author Kenneth J. Smith, M.D., M.S., professor of medicine and clinical and translational science in Pitt's Division of General Internal Medicine. "What we've found is that it's a balancing act, but if a clinician believes a patient will return for vaccination in the fall, then our analysis shows that it is best if they advise that patient to wait."

Smith and his co-authors ran computer models to compare a "compressed" vaccination period that begins in October to the status quo, which typically begins in August, for people aged 65 or older. They focused on older adults because waning vaccine effectiveness is more of a threat to the elderly whose immune systems don't typically mount as strong of a defense to infections as younger people. Older adults also have higher early vaccination rates than younger adults.

Using data from the 2013-2014 and 2014-2015 flu seasons, the researchers forecast the number of cases, hospitalizations and deaths for compressed and status quo vaccination scenarios if the flu season had peaked in December, February or April -- early, normal or late, respectively. "Peak" refers to the period when the greatest number of people are sick that season.

In the projections for the normal and late flu seasons, compressed vaccination saved as many as 258 lives and prevented up to 22,062 cases of flu, compared to status quo vaccination timing.

But if flu season peaked early, as it does in about one of every four seasons, the model projected that dozens to hundreds of older adults would die because they wouldn't have been vaccinated in time.

In addition, the team found that if more than 5.5 percent of older adults who defer vaccination ultimately don't get the flu shot, then compressed vaccination will be a failure and will prevent fewer influenza cases than status quo vaccination.

Smith says these findings can help clinicians determine when to offer their patients flu immunizations -- if the patients have multiple appointments each year and will be in the office in the fall or if they are in a senior community where flu immunization is offered through a scheduled clinic, then waiting is likely advisable. But if a patient comes in only for an annual check-up and is unlikely to seek out the flu vaccine in the fall, or if offering vaccinations during a compressed window will put overwhelming strain on the clinic, then getting vaccinated when convenient -- even if that's in August -- is best.

Read more at Science Daily

World's oldest semen still viable

'Sir Freddie,' one of the original semen donors, in 1969.

Semen stored since 1968 in a laboratory in Sydney has been defrosted and successfully used to impregnate 34 Merino ewes, with the resulting live birth rate as high sperm frozen for just 12 months.

"This demonstrates the clear viability of long-term frozen storage of semen. The results show that fertility is maintained despite 50 years of frozen storage in liquid nitrogen," said Associate Professor Simon de Graaf from the Sydney Institute of Agriculture and School of Life and Environmental Sciences at the University of Sydney.

"The lambs appear to display the body wrinkle that was common in Merinos in the middle of last century, a feature originally selected to maximise skin surface area and wool yields. That style of Merino has since largely fallen from favour as the folds led to difficulties in shearing and increased risk of fly strike," Associate Professor de Graaf said.

His colleague on this project, Dr Jessica Rickard, said: "We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring."

Associate Professor de Graaf said that it was the reproductive biology and genetic aspects of these as-yet unpublished findings that were of most interest to him.

"We can now look at the genetic progress made by the wool industry over past 50 years of selective breeding. In that time, we've been trying to make better, more productive sheep," he said. "This gives us a resource to benchmark and compare."

Dr Rickard is a post-doctoral McCaughey Research Fellow in the Sydney Institute of Agriculture. She is continuing the strong animal reproduction research tradition in veterinary and biological sciences at the University of Sydney through her work in the Animal Reproduction Group.

Dr Rickard did the original work to determine if the stored semen was viable for artificial insemination. This involved thawing the semen, which is stored as small pellets in large vats of liquid nitrogen at -196 degrees. She and her colleagues then undertook in vitro tests on the sperm quality to determine the motility, velocity, viability and DNA integrity of the 50-year-old sperm.

"What is amazing about this result is we found no difference between sperm frozen for 50 years and sperm frozen for a year," Dr Rickard said.

Out of 56 ewes inseminated, 34 were successfully impregnated. This compares to recently frozen semen from 19 sires used to inseminate 1048 ewes, of which 618 were successfully impregnated. This gives a pregnancy rate of 61 percent for the 50-year-old semen against 59 percent for recently frozen sperm, a statistically equivalent rate.

The original semen samples were donated in the 1960s from sires owned by the Walker family. Those samples, frozen in 1968 by Dr Steven Salamon, came from four rams, including 'Sir Freddie' born in 1963, owned by the Walkers on their then property at Ledgworth.

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