Bacterial pathogens can live on surfaces for days. What if frequently touched surfaces such as doorknobs could instantly kill them off?
Purdue University engineers have created a laser treatment method that could potentially turn any metal surface into a rapid bacteria killer -- just by giving the metal's surface a different texture.
In a study published in the journal Advanced Materials Interfaces, the researchers demonstrated that this technique allows the surface of copper to immediately kill off superbugs such as MRSA.
"Copper has been used as an antimicrobial material for centuries. But it typically takes hours for native copper surfaces to kill off bacteria," said Rahim Rahimi, a Purdue assistant professor of materials engineering.
"We developed a one-step laser-texturing technique that effectively enhances the bacteria-killing properties of copper's surface."
The technique is not yet tailored to killing viruses such as the one responsible for the COVID-19 pandemic, which are much smaller than bacteria.
Since publishing this work, however, Rahimi's team has begun testing this technology on the surfaces of other metals and polymers that are used to reduce risks of bacterial growth and biofilm formation on devices such as orthopedic implants or wearable patches for chronic wounds.
Giving implants an antimicrobial surface would prevent the spread of infection and antibiotic resistance, Rahimi said, because there wouldn't be a need for antibiotics to kill off bacteria from an implant's surface.
The technique might apply to metallic alloys that also are known to have antimicrobial properties.
Metals such as copper normally have a really smooth surface, which makes it difficult for the metal to kill bacteria by contact.
The technique developed by Rahimi's team uses a laser to create nanoscale patterns on the metal's surface. The patterns produce a rugged texture that increases surface area, allowing more opportunity for bacteria to hit the surface and rupture on the spot.
Researchers in the past have used various nanomaterial coatings to enhance the antimicrobial properties of metal surfaces, but these coatings are prone to leach off and can be toxic to the environment.
"We've created a robust process that selectively generates micron and nanoscale patterns directly onto the targeted surface without altering the bulk of the copper material," said Rahimi, whose lab develops innovative materials and biomedical devices to address health care challenges.
The laser-texturing has a dual effect: The technique not only improves direct contact, but also makes a surface more hydrophilic. For orthopedic implants, such a surface allows bone cells to more strongly attach, improving how well the implant integrates with bone. Rahimi's team observed this effect with fibroblast cells.
Read more at Science Daily
Apr 10, 2020
Black rhinos eavesdrop on the alarm calls of hitchhiking oxpeckers to avoid humans
In Swahili, red-billed oxpeckers are called Askari wa kifaru, or "the rhino's guard." Now, a paper appearing April 9 in the journal Current Biology suggests that this indigenous name rings true: red-billed oxpeckers may act as a first line of defense against poachers by behaving like sentinels, sounding an alarm to potential danger. By tracking wild black rhinos, researchers found that those carrying oxpeckers were far better at sensing and avoiding humans than those without the hitchhiking bird.
While conservation efforts have rebounded the critically endangered black rhino's numbers, poaching remains a major threat. "Although black rhinos have large, rapier-like horns and a thick hide, they are as blind as a bat. If the conditions are right, a hunter could walk within five meters of one, as long as they are downwind," says Roan Plotz (@RoanPlotz), a lecturer and behavioral ecologist at Victoria University, Australia., who co-authored the paper with ecological scientist Wayne Linklater (@PolitEcol) of California State University -- Sacramento. Oxpeckers, which are known to feed on the ticks and lesions found on the rhino's body, may make up for the rhino's poor eyesight by calling out if they detect an approaching human.
To study the role that oxpeckers might play, Plotz and his team recorded the number of oxpeckers on two groups of the rhinos they encountered. Rhinos tagged with radio transmitters -- which allowed researchers to track them while evading detection from oxpeckers -- carried the bird on their backs more than half the time. The untagged black rhinos they found, on the other hand, carried no oxpeckers most of the time -- suggesting that other untagged rhinos that carried the birds might have avoided encountering the researchers altogether. "Using the differences we observed between oxpeckers on the tagged versus untagged rhinos, we estimated that between 40% and 50% of all possible black rhino encounters were thwarted by the presence of oxpeckers," says Plotz.
Even when the researchers were able to locate the tagged rhinos, the oxpeckers' alarm calls still appeared to play a role in predator defense. The field team ran a "human approach" experiment, where one researcher would walk towards the rhino from crosswind while a colleague recorded the rhino's behavior. The field team recorded the number of oxpecker carried, the rhinos' behavior upon approach, and the distance of the researcher when either the rhinos became vigilant or, if undetected, it became unsafe to get any closer.
"Our experiment found that rhinos without oxpeckers detected a human approaching only 23% of the time. Due to the bird's alarm call, those with oxpeckers detected the approaching human in 100% of our trials and at an average distance of 61 meters -- nearly four times further than when rhinos were alone. In fact, the more oxpeckers the rhino carried, the greater the distance at which a human was detected," he says. He adds that these improved detection and distance estimates may even be conservative, because they don't take into account the untagged rhinos carrying oxpeckers that the team could not detect.
When a rhino perceived the oxpecker alarm call, it nearly always re-oriented itself to face downwind -- their sensory blind spot. "Rhinos cannot smell predators from downwind, making it their most vulnerable position. This is particularly true from humans, who primarily hunt game from that direction," says Plotz.
Taken together, these results suggest that oxpeckers are effective companions that enable black rhinos to evade encounters with people and facilitate effective anti-predator strategies once found. Some scientists even hypothesize that oxpeckers evolved this adaptive behaviour as a way to protect their source of food: the rhinos.
"Rhinos have been hunted by humans for tens of thousands of years, but the species was driven to the brink of extinction over the last 150 years. One hypothesis is that oxpeckers have evolved this cooperative relationship with rhinos relatively recently to protect their food source from human overkill," says Plotz.
Despite this closely tied relationship, oxpecker populations have significantly declined, even becoming locally extinct in some areas. As a result, most wild black rhino populations now live without oxpeckers in their environment. But based on the findings in this study, reintroducing the bird back into rhino populations may bolster conservation efforts. "While we do not know that reintroducing the birds would significantly reduce hunting impacts, we do know oxpeckers would help rhinos evade detection, which on its own is a great benefit," says Plotz.
Read more at Science Daily
While conservation efforts have rebounded the critically endangered black rhino's numbers, poaching remains a major threat. "Although black rhinos have large, rapier-like horns and a thick hide, they are as blind as a bat. If the conditions are right, a hunter could walk within five meters of one, as long as they are downwind," says Roan Plotz (@RoanPlotz), a lecturer and behavioral ecologist at Victoria University, Australia., who co-authored the paper with ecological scientist Wayne Linklater (@PolitEcol) of California State University -- Sacramento. Oxpeckers, which are known to feed on the ticks and lesions found on the rhino's body, may make up for the rhino's poor eyesight by calling out if they detect an approaching human.
To study the role that oxpeckers might play, Plotz and his team recorded the number of oxpeckers on two groups of the rhinos they encountered. Rhinos tagged with radio transmitters -- which allowed researchers to track them while evading detection from oxpeckers -- carried the bird on their backs more than half the time. The untagged black rhinos they found, on the other hand, carried no oxpeckers most of the time -- suggesting that other untagged rhinos that carried the birds might have avoided encountering the researchers altogether. "Using the differences we observed between oxpeckers on the tagged versus untagged rhinos, we estimated that between 40% and 50% of all possible black rhino encounters were thwarted by the presence of oxpeckers," says Plotz.
Even when the researchers were able to locate the tagged rhinos, the oxpeckers' alarm calls still appeared to play a role in predator defense. The field team ran a "human approach" experiment, where one researcher would walk towards the rhino from crosswind while a colleague recorded the rhino's behavior. The field team recorded the number of oxpecker carried, the rhinos' behavior upon approach, and the distance of the researcher when either the rhinos became vigilant or, if undetected, it became unsafe to get any closer.
"Our experiment found that rhinos without oxpeckers detected a human approaching only 23% of the time. Due to the bird's alarm call, those with oxpeckers detected the approaching human in 100% of our trials and at an average distance of 61 meters -- nearly four times further than when rhinos were alone. In fact, the more oxpeckers the rhino carried, the greater the distance at which a human was detected," he says. He adds that these improved detection and distance estimates may even be conservative, because they don't take into account the untagged rhinos carrying oxpeckers that the team could not detect.
When a rhino perceived the oxpecker alarm call, it nearly always re-oriented itself to face downwind -- their sensory blind spot. "Rhinos cannot smell predators from downwind, making it their most vulnerable position. This is particularly true from humans, who primarily hunt game from that direction," says Plotz.
Taken together, these results suggest that oxpeckers are effective companions that enable black rhinos to evade encounters with people and facilitate effective anti-predator strategies once found. Some scientists even hypothesize that oxpeckers evolved this adaptive behaviour as a way to protect their source of food: the rhinos.
"Rhinos have been hunted by humans for tens of thousands of years, but the species was driven to the brink of extinction over the last 150 years. One hypothesis is that oxpeckers have evolved this cooperative relationship with rhinos relatively recently to protect their food source from human overkill," says Plotz.
Despite this closely tied relationship, oxpecker populations have significantly declined, even becoming locally extinct in some areas. As a result, most wild black rhino populations now live without oxpeckers in their environment. But based on the findings in this study, reintroducing the bird back into rhino populations may bolster conservation efforts. "While we do not know that reintroducing the birds would significantly reduce hunting impacts, we do know oxpeckers would help rhinos evade detection, which on its own is a great benefit," says Plotz.
Read more at Science Daily
In a first, NASA measures wind speed on a brown dwarf
For the first time, scientists have directly measured wind speed on a brown dwarf, an object larger than Jupiter (the largest planet in our solar system) but not quite massive enough to become a star. To achieve the finding, they used a new method that could also be applied to learn about the atmospheres of gas-dominated planets outside our solar system.
Described in a paper in the journal Science, the work combines observations by a group of radio telescopes with data from NASA's recently retired infrared observatory, the Spitzer Space Telescope, managed by the agency's Jet Propulsion Laboratory in Southern California.
Officially named 2MASS J10475385+2124234, the target of the new study was a brown dwarf located 32 light-years from Earth -- a stone's throw away, cosmically speaking. The researchers detected winds moving around the planet at 1,425 mph (2,293 kph). For comparison, Neptune's atmosphere features the fastest winds in the solar system, which whip through at more than 1,200 mph (about 2,000 kph).
Measuring wind speed on Earth means clocking the motion of our gaseous atmosphere relative to the planet's solid surface. But brown dwarfs are composed almost entirely of gas, so "wind" refers to something slightly different. The upper layers of a brown dwarf are where portions of the gas can move independently. At a certain depth, the pressure becomes so intense that the gas behaves like a single, solid ball that is considered the object's interior. As the interior rotates, it pulls the upper layers -- the atmosphere -along so that the two are almost in synch.
In their study, the researchers measured the slight difference in speed of the brown dwarf's atmosphere relative to its interior. With an atmospheric temperature of over 1,100 degrees Fahrenheit (600 degrees Celsius), this particular brown dwarf radiates a substantial amount of infrared light. Coupled with its close proximity to Earth, this characteristic made it possible for Spitzer to detect features in the brown dwarf's atmosphere as they rotate in and out of view. The team used those features to clock the atmospheric rotation speed.
To determine the speed of the interior, they focused on the brown dwarf's magnetic field. A relatively recent discovery found that the interiors of brown dwarfs generate strong magnetic fields. As the brown dwarf rotates, the magnetic field accelerates charged particles that in turn produce radio waves, which the researchers detected with the radio telescopes in the Karl G. Jansky Very Large Array in New Mexico.
Planetary Atmospheres
The new study is the first to demonstrate this comparative method for measuring wind speed on a brown dwarf. To gauge its accuracy, the group tested the technique using infrared and radio observations of Jupiter, which is also composed mostly of gas and has a physical structure similar to a small brown dwarf. The team compared the rotation rates of Jupiter's atmosphere and interior using data that was similar to what they were able to collect for the much more distant brown dwarf. They then confirmed their calculation for Jupiter's wind speed using more detailed data collected by probes that have studied Jupiter up close, thus demonstrating that their approach for the brown dwarf worked.
Scientists have previously used Spitzer to infer the presence of winds on exoplanets and brown dwarfs based on variations in the brightness of their atmospheres in infrared light. And data from the High Accuracy Radial velocity Planet Searcher (HARPS) -- an instrument on the European Southern Observatory's La Silla telescope in Chile -- has been used to make a direct measurement of wind speeds on a distant planet.
But the new paper represents the first time scientists have directly compared the atmospheric speed with the speed of a brown dwarf's interior. The method employed could be applied to other brown dwarfs or to large planets if the conditions are right, according to the authors.
"We think this technique could be really valuable to providing insight into the dynamics of exoplanet atmospheres," said lead author Katelyn Allers, an associate professor of physics and astronomy at Bucknell University in Lewisburg, Pennsylvania. "What's really exciting is being able to learn about how the chemistry, the atmospheric dynamics and the environment around an object are interconnected, and the prospect of getting a really comprehensive view into these worlds."
Read more at Science Daily
Described in a paper in the journal Science, the work combines observations by a group of radio telescopes with data from NASA's recently retired infrared observatory, the Spitzer Space Telescope, managed by the agency's Jet Propulsion Laboratory in Southern California.
Officially named 2MASS J10475385+2124234, the target of the new study was a brown dwarf located 32 light-years from Earth -- a stone's throw away, cosmically speaking. The researchers detected winds moving around the planet at 1,425 mph (2,293 kph). For comparison, Neptune's atmosphere features the fastest winds in the solar system, which whip through at more than 1,200 mph (about 2,000 kph).
Measuring wind speed on Earth means clocking the motion of our gaseous atmosphere relative to the planet's solid surface. But brown dwarfs are composed almost entirely of gas, so "wind" refers to something slightly different. The upper layers of a brown dwarf are where portions of the gas can move independently. At a certain depth, the pressure becomes so intense that the gas behaves like a single, solid ball that is considered the object's interior. As the interior rotates, it pulls the upper layers -- the atmosphere -along so that the two are almost in synch.
In their study, the researchers measured the slight difference in speed of the brown dwarf's atmosphere relative to its interior. With an atmospheric temperature of over 1,100 degrees Fahrenheit (600 degrees Celsius), this particular brown dwarf radiates a substantial amount of infrared light. Coupled with its close proximity to Earth, this characteristic made it possible for Spitzer to detect features in the brown dwarf's atmosphere as they rotate in and out of view. The team used those features to clock the atmospheric rotation speed.
To determine the speed of the interior, they focused on the brown dwarf's magnetic field. A relatively recent discovery found that the interiors of brown dwarfs generate strong magnetic fields. As the brown dwarf rotates, the magnetic field accelerates charged particles that in turn produce radio waves, which the researchers detected with the radio telescopes in the Karl G. Jansky Very Large Array in New Mexico.
Planetary Atmospheres
The new study is the first to demonstrate this comparative method for measuring wind speed on a brown dwarf. To gauge its accuracy, the group tested the technique using infrared and radio observations of Jupiter, which is also composed mostly of gas and has a physical structure similar to a small brown dwarf. The team compared the rotation rates of Jupiter's atmosphere and interior using data that was similar to what they were able to collect for the much more distant brown dwarf. They then confirmed their calculation for Jupiter's wind speed using more detailed data collected by probes that have studied Jupiter up close, thus demonstrating that their approach for the brown dwarf worked.
Scientists have previously used Spitzer to infer the presence of winds on exoplanets and brown dwarfs based on variations in the brightness of their atmospheres in infrared light. And data from the High Accuracy Radial velocity Planet Searcher (HARPS) -- an instrument on the European Southern Observatory's La Silla telescope in Chile -- has been used to make a direct measurement of wind speeds on a distant planet.
But the new paper represents the first time scientists have directly compared the atmospheric speed with the speed of a brown dwarf's interior. The method employed could be applied to other brown dwarfs or to large planets if the conditions are right, according to the authors.
"We think this technique could be really valuable to providing insight into the dynamics of exoplanet atmospheres," said lead author Katelyn Allers, an associate professor of physics and astronomy at Bucknell University in Lewisburg, Pennsylvania. "What's really exciting is being able to learn about how the chemistry, the atmospheric dynamics and the environment around an object are interconnected, and the prospect of getting a really comprehensive view into these worlds."
Read more at Science Daily
Doubts about basic assumption for the universe
No matter where we look, the same rules apply everywhere in space: countless calculations of astrophysics are based on this basic principle. A recent study by the Universities of Bonn and Harvard, however, has thrown this principle into question. Should the measured values be confirmed, this would toss many assumptions about the properties of the universe overboard. The results are published in the journal Astronomy & Astrophysics, but are already available online.
Since the big bang, the universe has swollen like a freshly formed raisin roll put in a warm place to rise. Until recently, it was thought that this increase in size was occurring evenly in all directions, as with a good yeast dough. Astrophysicists call this "isotropy." Many calculations on the fundamental properties of the universe are based on this assumption. It is possible that they are all wrong -- or at least, inaccurate -- thanks to compelling observations and analyses of the scientists from the Universities of Bonn and Harvard.
For they have put the isotropy hypothesis to the test for the first time with a new method that allows more reliable statements than before. With an unexpected result: According to this method, some areas in space expand faster than they should, while others expand more slowly than expected. "In any case, this conclusion is suggested by our measurements," states Konstantinos Migkas, from the Argelander Institute for Astronomy at the University of Bonn.
Migkas and his colleagues have developed a new, efficient isotropy test in their study. It is based on the observation of so-called galaxy clusters -- in a sense, the raisins in the yeast bun. The clusters emit X-ray radiation that can be collected on Earth (in this case, this was done by the satellite-based telescopes Chandra and XMM-Newton). The temperature of the galaxy clusters can be calculated based on certain characteristics of the radiation. Also, their brightness can be measured. The hotter they are, the brighter they glow.
In an isotropic universe, a simple rule applies. The further away a celestial object is from us, the faster it moves away from us. From its speed, we can therefore deduce its distance from us, regardless of the direction in which the object lies. At least that's what we thought until now. "In reality, however, our brightness measurements seem to disagree with the above distance calculation," Migkas emphasizes.
This is because the amount of light that reaches the earth decreases with increasing distance. So, anyone who knows the original luminosity of a celestial body and its distance knows how bright it should shine in the telescope image. And it is precisely at this point that scientists have come across discrepancies that are difficult to reconcile with the isotropy hypothesis: that some galaxy clusters are much fainter than expected. Their distance from Earth is probably much greater than calculated from their speed. And for some others, however, the opposite is the case.
"There are only three possible explanations for this," states Migkas, who is doing his doctorate in the research group of Prof. Dr. Thomas Reiprich at the Argelander Institute. "Firstly, it is possible that the X-ray radiation, whose intensity we have measured, is attenuated on its way from the galaxy clusters to Earth. This could be due to as yet undiscovered gas or dust clouds inside or outside the Milky Way. In preliminary tests, however, we find this discrepancy between measurement and theory not only in X-rays but also at other wavelengths. It is extremely unlikely that any kind of matter nebula absorbs completely different types of radiation in the same way. But we won't know for sure for several months."
A second possibility are so-called "bulk flows." These are groups of neighboring galaxy clusters that move continuously in a certain direction -- for example, due to some structures in space that generate strong gravitational forces. These would therefore attract the galaxy clusters to themselves and thus change their speed (and thus also their derived distance). "This effect would also mean that many calculations on the properties of the local universe would be imprecise and would have to be repeated," explains Migkas.
The third possibility is the most serious: What if the universe is not isotropic at all? What if -- metaphorically speaking -- the yeast in the galactic raisin roll is so unevenly distributed that it quickly bulges in some places while it hardly grows at all in other regions? Such an anisotropy could, for example, result from the properties of the mysterious "dark energy," which acts as an additional driving force for the expansion of the universe. However, a theory is still missing that would make the behavior of the Dark Energy consistent with the observations. "If we succeed in developing such a theory, it could greatly accelerate the search for the exact nature of this form of energy," Migkas is certain.
Read more at Science Daily
Since the big bang, the universe has swollen like a freshly formed raisin roll put in a warm place to rise. Until recently, it was thought that this increase in size was occurring evenly in all directions, as with a good yeast dough. Astrophysicists call this "isotropy." Many calculations on the fundamental properties of the universe are based on this assumption. It is possible that they are all wrong -- or at least, inaccurate -- thanks to compelling observations and analyses of the scientists from the Universities of Bonn and Harvard.
For they have put the isotropy hypothesis to the test for the first time with a new method that allows more reliable statements than before. With an unexpected result: According to this method, some areas in space expand faster than they should, while others expand more slowly than expected. "In any case, this conclusion is suggested by our measurements," states Konstantinos Migkas, from the Argelander Institute for Astronomy at the University of Bonn.
Migkas and his colleagues have developed a new, efficient isotropy test in their study. It is based on the observation of so-called galaxy clusters -- in a sense, the raisins in the yeast bun. The clusters emit X-ray radiation that can be collected on Earth (in this case, this was done by the satellite-based telescopes Chandra and XMM-Newton). The temperature of the galaxy clusters can be calculated based on certain characteristics of the radiation. Also, their brightness can be measured. The hotter they are, the brighter they glow.
In an isotropic universe, a simple rule applies. The further away a celestial object is from us, the faster it moves away from us. From its speed, we can therefore deduce its distance from us, regardless of the direction in which the object lies. At least that's what we thought until now. "In reality, however, our brightness measurements seem to disagree with the above distance calculation," Migkas emphasizes.
This is because the amount of light that reaches the earth decreases with increasing distance. So, anyone who knows the original luminosity of a celestial body and its distance knows how bright it should shine in the telescope image. And it is precisely at this point that scientists have come across discrepancies that are difficult to reconcile with the isotropy hypothesis: that some galaxy clusters are much fainter than expected. Their distance from Earth is probably much greater than calculated from their speed. And for some others, however, the opposite is the case.
"There are only three possible explanations for this," states Migkas, who is doing his doctorate in the research group of Prof. Dr. Thomas Reiprich at the Argelander Institute. "Firstly, it is possible that the X-ray radiation, whose intensity we have measured, is attenuated on its way from the galaxy clusters to Earth. This could be due to as yet undiscovered gas or dust clouds inside or outside the Milky Way. In preliminary tests, however, we find this discrepancy between measurement and theory not only in X-rays but also at other wavelengths. It is extremely unlikely that any kind of matter nebula absorbs completely different types of radiation in the same way. But we won't know for sure for several months."
A second possibility are so-called "bulk flows." These are groups of neighboring galaxy clusters that move continuously in a certain direction -- for example, due to some structures in space that generate strong gravitational forces. These would therefore attract the galaxy clusters to themselves and thus change their speed (and thus also their derived distance). "This effect would also mean that many calculations on the properties of the local universe would be imprecise and would have to be repeated," explains Migkas.
The third possibility is the most serious: What if the universe is not isotropic at all? What if -- metaphorically speaking -- the yeast in the galactic raisin roll is so unevenly distributed that it quickly bulges in some places while it hardly grows at all in other regions? Such an anisotropy could, for example, result from the properties of the mysterious "dark energy," which acts as an additional driving force for the expansion of the universe. However, a theory is still missing that would make the behavior of the Dark Energy consistent with the observations. "If we succeed in developing such a theory, it could greatly accelerate the search for the exact nature of this form of energy," Migkas is certain.
Read more at Science Daily
Ancient teeth from Peru hint now-extinct monkeys crossed Atlantic from Africa
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| Marmoset. Ucayalipithecus perdita would have been very small, similar in size to a modern-day marmoset. |
The teeth are from a newly discovered species belonging to an extinct family of African primates known as parapithecids. Fossils discovered at the same site in Peru had earlier offered the first proof that South American monkeys evolved from African primates.
The monkeys are believed to have made the more than 900-mile trip on floating rafts of vegetation that broke off from coastlines, possibly during a storm.
"This is a completely unique discovery," said Erik Seiffert, the study's lead author and Professor of Clinical Integrative Anatomical Sciences at Keck School of Medicine of USC. "It shows that in addition to the New World monkeys and a group of rodents known as caviomorphs -- there is this third lineage of mammals that somehow made this very improbable transatlantic journey to get from Africa to South America."
Researchers have named the extinct monkey Ucayalipithecus perdita. The name comes from Ucayali, the area of the Peruvian Amazon where the teeth were found, pithikos, the Greek word for monkey and perdita, the Latin word for lost.
Ucayalipithecus perdita would have been very small, similar in size to a modern-day marmoset.
Dating the migration
Researchers believe the site in Ucayali where the teeth were found is from a geological epoch known as the Oligocene, which extended from about 34 million to 23 million years ago.
Based on the age of the site and the closeness of Ucayalipithecus to its fossil relatives from Egypt, researchers estimate the migration might have occurred around 34 million years ago.
"We're suggesting that this group might have made it over to South America right around what we call the Eocene-Oligocene Boundary, a time period between two geological epochs, when the Antarctic ice sheet started to build up and the sea level fell," said Seiffert. "That might have played a role in making it a bit easier for these primates to actually get across the Atlantic Ocean."
An improbable discovery
Two of the Ucayalipithecus perdita teeth were identified by Argentinean co-authors of the study in 2015 showing that New World monkeys had African forebears. When Seiffert was asked to help describe these specimens in 2016, he noticed the similarity of the two broken upper molars to an extinct 32 million-year-old parapithecid monkey species from Egypt he had studied previously.
An expedition to the Peruvian fossil site in 2016 led to the discovery of two more teeth belonging to this new species. The resemblance of these additional lower teeth to those of the Egyptian monkey teeth confirmed to Seiffert that Ucayalipithecus was descended from African ancestors.
"The thing that strikes me about this study more than any other I've been involved in is just how improbable all of it is," said Seiffert. "The fact that it's this remote site in the middle of nowhere, that the chances of finding these pieces is extremely small, to the fact that we're revealing this very improbable journey that was made by these early monkeys, it's all quite remarkable."
About this study
In addition to Seiffert, the study's other authors are Marcelo Tejedor and Nelson Novo from the Instituto Patagónico de Geología y Paleontología (CCT CONICET -- CENPAT); John G. Fleagle from the Department of Anatomical Sciences, Renaissance School of Medicine, Stony Brook University; Fanny Cornejo and Dorien de Vries from the Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University; Mariano Bond from CONICET, División Paleontología Vertebrados, Museo de Ciencias Naturales de La Plata and Kenneth E. Campbell Jr. from the Department of Vertebrate Zoology, Natural History Museum of Los Angeles County.
Read more at Science Daily
Apr 9, 2020
Origins of Earth's magnetic field remain a mystery
Microscopic minerals excavated from an ancient outcrop of Jack Hills, in Western Australia, have been the subject of intense geological study, as they seem to bear traces of the Earth's magnetic field reaching as far back as 4.2 billion years ago. That's almost 1 billion years earlier than when the magnetic field was previously thought to originate, and nearly back to the time when the planet itself was formed.
But as intriguing as this origin story may be, an MIT-led team has now found evidence to the contrary. In a paper published in Science Advances, the team examined the same type of crystals, called zircons, excavated from the same outcrop, and have concluded that zircons they collected are unreliable as recorders of ancient magnetic fields.
In other words, the jury is still out on whether the Earth's magnetic field existed earlier than 3.5 billion years ago.
"There is no robust evidence of a magnetic field prior to 3.5 billion years ago, and even if there was a field, it will be very difficult to find evidence for it in Jack Hills zircons," says Caue Borlina, a graduate student in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS). "It's an important result in the sense that we know what not to look for anymore."
Borlina is the paper's first author, which also includes EAPS Professor Benjamin Weiss, Principal Research Scientist Eduardo Lima, and Research Scientist Jahandar Ramezan of MIT, along with others from Cambridge University, Harvard University, the University of California at Los Angeles, the University of Alabama, and Princeton University.
A field, stirred up
Earth's magnetic field is thought to play an important role in making the planet habitable. Not only does a magnetic field set the direction of our compass needles, it also acts as a shield of sorts, deflecting away solar wind that might otherwise eat away at the atmosphere.
Scientists know that today the Earth's magnetic field is powered by the solidification of the planet's liquid iron core. The cooling and crystallization of the core stirs up the surrounding liquid iron, creating powerful electric currents that generate a magnetic field stretching far out into space. This magnetic field is known as the geodynamo.
Multiple lines of evidence have shown that the Earth's magnetic field existed at least 3.5 billion years ago. However, the planet's core is thought to have started solidifying just 1 billion years ago, meaning that the magnetic field must have been driven by some other mechanism prior to 1 billion years ago. Pinning down exactly when the magnetic field formed could help scientists figure out what generated it to begin with.
Borlina says the origin of Earth's magnetic field could also illuminate the early conditions in which Earth's first life forms took hold.
"In the Earth's first billion years, between 4.4 billion and 3.5 billion years, that's when life was emerging," Borlina says. "Whether you have a magnetic field at that time has different implications for the environment in which life emerged on Earth. That's the motivation for our work."
"Can't trust zircon"
Scientists have traditionally used minerals in ancient rocks to determine the orientation and intensity of Earth's magnetic field back through time. As rocks form and cool, the electrons within individual grains can shift in the direction of the surrounding magnetic field. Once the rock cools past a certain temperature, known as the Curie temperature, the orientations of the electrons are set in stone, so to speak. Scientists can determine their age and use standard magnetometers to measure their orientation, to estimate the strength and orientation of the Earth's magnetic field at a given point in time.
Since 2001, Weiss and his group have been studying the magnetization of the Jack Hills rocks and zircon grains, with the challenging goal of establishing whether they contain ancient records of the Earth's magnetic field.
"The Jack Hills zircons are some of the most weakly magnetic objects studied in the history of paleomagnetism," Weiss says. "Furthermore, these zircons include the oldest known Earth materials, meaning that there are many geological events that could have reset their magnetic records."
In 2015, a separate research group that had also started studying the Jack Hills zircons argued that they found evidence of magnetic material in zircons that they dated to be 4.2 billion years old -- the first evidence that Earth's magnetic field may have existed prior to 3.5 billion years ago.
But Borlina notes that the team did not confirm whether the magnetic material they detected actually formed during or after the zircon crystal formed 4.2 billion years ago -- a goal that he and his team took on for their new paper.
Borlina, Weiss, and their colleagues had collected rocks from the same Jack Hills outcrop, and from those samples, extracted 3,754 zircon grains, each around 150 micrometers long -- about the width of a human hair. Using standard dating techniques, they determined the age of each zircon grain, which ranged from 1 billion to 4.2 billion years old.
Around 250 crystals were older than 3.5 billion years. The team isolated and imaged those samples, looking for signs of cracks or secondary materials, such as minerals that may have been deposited on or within the crystal after it had fully formed, and searched for evidence that they were significantly heated over the last few billion years since they formed. Of these 250, they identified just three zircons that were relatively free of such impurities and therefore could contain suitable magnetic records.
The team then carried out detailed experiments on these three zircons to determine what kinds of magnetic materials they might contain. They eventually determined that a magnetic mineral called magnetite was present in two of the three zircons. Using a high-resolution quantum diamond magnetometer, the team looked at cross-sections of each of the two zircons to map the location of the magnetite in each crystal.
They discovered magnetite lying along cracks or damaged zones within the zircons. Such cracks, Borlina says, are pathways that allow water and other elements inside the rock. Such cracks could have let in secondary magnetite that settled into the crystal much later than when the zircon originally formed. Either way, Borlina says the evidence is clear: These zircons cannot be used as a reliable recorder for Earth's magnetic field.
"This is evidence we can't trust these zircon measurements for the record of the Earth's magnetic field," Borlina says. "We've shown that, before 3.5 billion years ago, we still have no idea when Earth's magnetic field started."
Read more at Science Daily
But as intriguing as this origin story may be, an MIT-led team has now found evidence to the contrary. In a paper published in Science Advances, the team examined the same type of crystals, called zircons, excavated from the same outcrop, and have concluded that zircons they collected are unreliable as recorders of ancient magnetic fields.
In other words, the jury is still out on whether the Earth's magnetic field existed earlier than 3.5 billion years ago.
"There is no robust evidence of a magnetic field prior to 3.5 billion years ago, and even if there was a field, it will be very difficult to find evidence for it in Jack Hills zircons," says Caue Borlina, a graduate student in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS). "It's an important result in the sense that we know what not to look for anymore."
Borlina is the paper's first author, which also includes EAPS Professor Benjamin Weiss, Principal Research Scientist Eduardo Lima, and Research Scientist Jahandar Ramezan of MIT, along with others from Cambridge University, Harvard University, the University of California at Los Angeles, the University of Alabama, and Princeton University.
A field, stirred up
Earth's magnetic field is thought to play an important role in making the planet habitable. Not only does a magnetic field set the direction of our compass needles, it also acts as a shield of sorts, deflecting away solar wind that might otherwise eat away at the atmosphere.
Scientists know that today the Earth's magnetic field is powered by the solidification of the planet's liquid iron core. The cooling and crystallization of the core stirs up the surrounding liquid iron, creating powerful electric currents that generate a magnetic field stretching far out into space. This magnetic field is known as the geodynamo.
Multiple lines of evidence have shown that the Earth's magnetic field existed at least 3.5 billion years ago. However, the planet's core is thought to have started solidifying just 1 billion years ago, meaning that the magnetic field must have been driven by some other mechanism prior to 1 billion years ago. Pinning down exactly when the magnetic field formed could help scientists figure out what generated it to begin with.
Borlina says the origin of Earth's magnetic field could also illuminate the early conditions in which Earth's first life forms took hold.
"In the Earth's first billion years, between 4.4 billion and 3.5 billion years, that's when life was emerging," Borlina says. "Whether you have a magnetic field at that time has different implications for the environment in which life emerged on Earth. That's the motivation for our work."
"Can't trust zircon"
Scientists have traditionally used minerals in ancient rocks to determine the orientation and intensity of Earth's magnetic field back through time. As rocks form and cool, the electrons within individual grains can shift in the direction of the surrounding magnetic field. Once the rock cools past a certain temperature, known as the Curie temperature, the orientations of the electrons are set in stone, so to speak. Scientists can determine their age and use standard magnetometers to measure their orientation, to estimate the strength and orientation of the Earth's magnetic field at a given point in time.
Since 2001, Weiss and his group have been studying the magnetization of the Jack Hills rocks and zircon grains, with the challenging goal of establishing whether they contain ancient records of the Earth's magnetic field.
"The Jack Hills zircons are some of the most weakly magnetic objects studied in the history of paleomagnetism," Weiss says. "Furthermore, these zircons include the oldest known Earth materials, meaning that there are many geological events that could have reset their magnetic records."
In 2015, a separate research group that had also started studying the Jack Hills zircons argued that they found evidence of magnetic material in zircons that they dated to be 4.2 billion years old -- the first evidence that Earth's magnetic field may have existed prior to 3.5 billion years ago.
But Borlina notes that the team did not confirm whether the magnetic material they detected actually formed during or after the zircon crystal formed 4.2 billion years ago -- a goal that he and his team took on for their new paper.
Borlina, Weiss, and their colleagues had collected rocks from the same Jack Hills outcrop, and from those samples, extracted 3,754 zircon grains, each around 150 micrometers long -- about the width of a human hair. Using standard dating techniques, they determined the age of each zircon grain, which ranged from 1 billion to 4.2 billion years old.
Around 250 crystals were older than 3.5 billion years. The team isolated and imaged those samples, looking for signs of cracks or secondary materials, such as minerals that may have been deposited on or within the crystal after it had fully formed, and searched for evidence that they were significantly heated over the last few billion years since they formed. Of these 250, they identified just three zircons that were relatively free of such impurities and therefore could contain suitable magnetic records.
The team then carried out detailed experiments on these three zircons to determine what kinds of magnetic materials they might contain. They eventually determined that a magnetic mineral called magnetite was present in two of the three zircons. Using a high-resolution quantum diamond magnetometer, the team looked at cross-sections of each of the two zircons to map the location of the magnetite in each crystal.
They discovered magnetite lying along cracks or damaged zones within the zircons. Such cracks, Borlina says, are pathways that allow water and other elements inside the rock. Such cracks could have let in secondary magnetite that settled into the crystal much later than when the zircon originally formed. Either way, Borlina says the evidence is clear: These zircons cannot be used as a reliable recorder for Earth's magnetic field.
"This is evidence we can't trust these zircon measurements for the record of the Earth's magnetic field," Borlina says. "We've shown that, before 3.5 billion years ago, we still have no idea when Earth's magnetic field started."
Read more at Science Daily
Long-living tropical trees play outsized role in carbon storage
A group of trees that grow fast, live long lives and reproduce slowly account for the bulk of the biomass -- and carbon storage -- in some tropical rainforests, a team of scientists says in a paper published this week in the journal Science. The finding that these trees, called long-lived pioneers, play a much larger role in carbon storage than previously thought may have implications in efforts to preserve forests as a strategy to fight climate change.
"People have been arguing about whether these long-lived pioneers contribute much to carbon storage over the long term," said Caroline Farrior, an assistant professor of integrative biology at The University of Texas at Austin and a primary investigator on the study. "We were surprised to find that they do."
It is unclear the extent to which tropical rainforests can help soak up excess carbon dioxide in the atmosphere produced by burning fossil fuels. Nonetheless, the new study provides insights about the role of different species of trees in carbon storage.
Using more than 30 years' worth of data collected from a tropical rainforest in Panama, the team has uncovered some key traits of trees that, when integrated into computer models related to climate change, will improve the models' accuracy. With the team's improved model, the scientists plan to begin answering questions about what drives forest composition over time and what factors affect carbon storage.
Most existing Earth system models used to forecast global climate decades from now, including those used by the Intergovernmental Panel on Climate Change, represent the trees in a forest as all basically the same.
"This analysis shows that that is not good enough for tropical forests and provides a way forward," Farrior said. "We show that the variation in tropical forest species's growth, survival and reproduction is important for predicting forest carbon storage."
The project was led by Nadja Rüger, research fellow at the German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig.
In addition to the finding about long-lived pioneers, the team found the composition of a tropical forest over time depends on how each tree species balances two different sets of trade-offs: growth versus survival (for example, one type of tree might grow fast but die young) and stature versus reproduction (another might grow tall but reproduce leisurely). Plotting every species as a point on a graph based on where they fall along these two different axes allowed the scientists to have a more sophisticated and accurate model than prior ones, which usually focused exclusively on the first of these two trade-offs or parametrized the groups by different means.
"To really appreciate that there is this second trade-off between stature and reproduction, and that it's important in old-growth forests, is a big deal biologically," Farrior said.
The team also discovered that the nearly 300 unique tree species that live on Barro Colorado Island, which sits in the middle of the Panama Canal, can be represented in their computer model by just five functional groups and still produce accurate forecasts of tree composition and forest biomass over time.
It's not possible to directly verify the forecasts of a forest model in future decades. So the researchers did the next best thing: They seeded their model with forest composition data collected at their site in Panama during the 1980s and then ran the model forward to show that it accurately represents the changes that occurred from then until now. This is called "hindcasting."
Next, they plan to explore how a warming world might benefit trees with certain traits over others, shifting forest composition and the potential of forests to store carbon.
Read more at Science Daily
"People have been arguing about whether these long-lived pioneers contribute much to carbon storage over the long term," said Caroline Farrior, an assistant professor of integrative biology at The University of Texas at Austin and a primary investigator on the study. "We were surprised to find that they do."
It is unclear the extent to which tropical rainforests can help soak up excess carbon dioxide in the atmosphere produced by burning fossil fuels. Nonetheless, the new study provides insights about the role of different species of trees in carbon storage.
Using more than 30 years' worth of data collected from a tropical rainforest in Panama, the team has uncovered some key traits of trees that, when integrated into computer models related to climate change, will improve the models' accuracy. With the team's improved model, the scientists plan to begin answering questions about what drives forest composition over time and what factors affect carbon storage.
Most existing Earth system models used to forecast global climate decades from now, including those used by the Intergovernmental Panel on Climate Change, represent the trees in a forest as all basically the same.
"This analysis shows that that is not good enough for tropical forests and provides a way forward," Farrior said. "We show that the variation in tropical forest species's growth, survival and reproduction is important for predicting forest carbon storage."
The project was led by Nadja Rüger, research fellow at the German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig.
In addition to the finding about long-lived pioneers, the team found the composition of a tropical forest over time depends on how each tree species balances two different sets of trade-offs: growth versus survival (for example, one type of tree might grow fast but die young) and stature versus reproduction (another might grow tall but reproduce leisurely). Plotting every species as a point on a graph based on where they fall along these two different axes allowed the scientists to have a more sophisticated and accurate model than prior ones, which usually focused exclusively on the first of these two trade-offs or parametrized the groups by different means.
"To really appreciate that there is this second trade-off between stature and reproduction, and that it's important in old-growth forests, is a big deal biologically," Farrior said.
The team also discovered that the nearly 300 unique tree species that live on Barro Colorado Island, which sits in the middle of the Panama Canal, can be represented in their computer model by just five functional groups and still produce accurate forecasts of tree composition and forest biomass over time.
It's not possible to directly verify the forecasts of a forest model in future decades. So the researchers did the next best thing: They seeded their model with forest composition data collected at their site in Panama during the 1980s and then ran the model forward to show that it accurately represents the changes that occurred from then until now. This is called "hindcasting."
Next, they plan to explore how a warming world might benefit trees with certain traits over others, shifting forest composition and the potential of forests to store carbon.
Read more at Science Daily
Looking for dark matter
Dark matter, which cannot be physically observed with ordinary instruments, is thought to account for well over half the matter in the Universe, but its properties are still mysterious. One commonly held theory states that it exists as 'clumps' of extremely light particles. When the earth passes through such a clump, the fundamental properties of matter are altered in ways that can be detected if instruments are sensitive enough. Physicists Rees McNally and Tanya Zelevinsky from Columbia University, New York, USA, have now published a paper in EPJ D proposing two new methods of looking for such perturbations and, thus, dark matter. This paper is part of a special issue of the journal on quantum technologies for gravitational physics.
Until now, searches for dark matter clumps have relied on the fact that tiny changes in the values of fundamental constants will alter the 'tick rate' of atomic clocks, some of which may be precise enough to pick up this difference. McNally and Zelevinsky's work adds methods that involve measuring a small extra 'push' or acceleration on normal matter caused by the clump, using, firstly, gravity sensors and, secondly, gravitational wave detectors. Gravity sensors are already spread around the world in the IGETS network, which is used for geological research; and scientists at the LIGO observatories in the United States are already looking for gravitational waves. Thus, McNally and Zelevinsky can mine the data from these ongoing experiments for evidence of dark matter.
McNally explains that this work was inspired by two things: the benefits of re-purposing existing experiments, and science fiction. "I enjoy novels like A Fire Upon the Deep [by Vernor Vinge] and The Three-Body Problem [by Liu Cixin] that explore what might happen if fundamental constants change, and it's fun to explore such things in the real world." As for practical applications of this work, however, he advised taking things one step at a time. "First we need to find out what Dark Matter is, then maybe we can find out how to use it."
From Science Daily
Until now, searches for dark matter clumps have relied on the fact that tiny changes in the values of fundamental constants will alter the 'tick rate' of atomic clocks, some of which may be precise enough to pick up this difference. McNally and Zelevinsky's work adds methods that involve measuring a small extra 'push' or acceleration on normal matter caused by the clump, using, firstly, gravity sensors and, secondly, gravitational wave detectors. Gravity sensors are already spread around the world in the IGETS network, which is used for geological research; and scientists at the LIGO observatories in the United States are already looking for gravitational waves. Thus, McNally and Zelevinsky can mine the data from these ongoing experiments for evidence of dark matter.
McNally explains that this work was inspired by two things: the benefits of re-purposing existing experiments, and science fiction. "I enjoy novels like A Fire Upon the Deep [by Vernor Vinge] and The Three-Body Problem [by Liu Cixin] that explore what might happen if fundamental constants change, and it's fun to explore such things in the real world." As for practical applications of this work, however, he advised taking things one step at a time. "First we need to find out what Dark Matter is, then maybe we can find out how to use it."
From Science Daily
Archaeologists on a 5,000-year-old egg hunt
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| Ostrich with eggs |
Long before Fabergé, ornate ostrich eggs were highly prized by the elites of Mediterranean civilisations during the Bronze and Iron Ages, but to date little has been known about the complex supply chain behind these luxury goods.
Examining ostrich eggs from the British Museum's collection, the team, led by Bristol's Dr Tamar Hodos, were able to reveal secrets about their origin and how and where they were made. Using state-of-the-art scanning electron microscopy, Dr Caroline Cartwright, Senior Scientist at the British Museum was able to investigate the eggs' chemical makeup to pinpoint their origins and study minute marks that reveal how they were made.
In the study, published today in the journal Antiquity, the researchers describe for the first time the surprisingly complex system behind ostrich egg production. This includes evidence about where the ostrich eggs were sourced, if the ostriches were captive or wild, and how the manufacture methods can be related to techniques and materials used by artisans in specific areas.
"The entire system of decorated ostrich egg production was much more complicated than we had imagined! We also found evidence to suggest the ancient world was much more interconnected than previously thought," said Dr Hodos, Reader in Mediterranean Archaeology in Bristol's School of Arts.
"Mediterranean ostriches were indigenous to the eastern Mediterranean and North Africa. Using a variety of isotopic indicators, we were able to distinguish eggs laid in different climatic zones (cooler, wetter and hotter, drier). What was most surprising to us was that eggs from both zones were found at sites in the other zone, suggestive of more extensive trade routes."
Dr Hodos and colleagues believe eggs were taken from wild birds' nests despite evidence of ostriches being kept in captivity during this period. This was no ordinary egg-hunt -- ostriches can be extremely dangerous so there was a tremendous risk involved in taking eggs from wild birds.
"We also found eggs require time to dry before the shell can be carved and therefore require safe storage. This has economic implications, since storage necessitates a long-term investment and this, combined with the risk involved, would add to an egg's luxury value," said Dr Hodos.
The study is part of an ongoing research project into ancient luxury goods, Globalising Luxuries.
Dr Hodos explains: "We are assessing not only how ancient luxuries were produced but also how they were used by different peoples. These questions are incredibly important for our own society today, in which the same object may have different social or symbolic meanings for different groups. Such knowledge and understanding helps foster tolerance and mutual respect in a multi-cultural society. If we can understand these mechanisms in the past, for which we have long-term outcomes in terms of social development, we can use this knowledge to better inform our own society in a number of ways."
Read more at Science Daily
Synchrotron X-ray sheds light on some of the world's oldest dinosaur eggs
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| Dinosaur egg concept |
University of the Witwatersrand scientists publish 3D reconstructions of the ~2cm-long skulls of some of the world's oldest dinosaur embryos in an article in Scientific Reports. The embryos, found in 1976 in Golden Gate Highlands National Park (Free State Province, South Africa) belong to South Africa's iconic dinosaur Massospondylus carinatus, a 5-meter long herbivore that nested in the Free State region 200 million years ago.
The scientific usefulness of the embryos was previously limited by their extremely fragile nature and tiny size. In 2015, scientists Kimi Chapelle and Jonah Choiniere, from the University of Witwatersrand, brought them to the European Synchrotron (ESRF) in Grenoble, France for scanning. At the ESRF, an 844 metre-ring of electrons travelling at the speed of light emits high-powered X-ray beams that can be used to non-destructively scan matter, including fossils. The embryos were scanned at an unprecedented level of detail -- at the resolution of an individual bone cell. With these data in hand, and after nearly 3 years of data processing at Wits' laboratory, the team was able to reconstruct a 3D model of the baby dinosaur skull. "No lab CT scanner in the world can generate these kinds of data," said Vincent Fernandez, one of the co-authors and scientist at the Natural History Museum in London (UK). "Only with a huge facility like the ESRF can we unlock the hidden potential of our most exciting fossils. This research is a great example of a global collaboration between Europe and the South African National Research Foundation," he adds.
Up until now, it was believed that the embryos in those eggs had died just before hatching. However, during the study, lead author Chapelle noticed similarities with the developing embryos of living dinosaur relatives (crocodiles, chickens, turtles, and lizards). By comparing which bones of the skull were present at different stages of their embryonic development, Chapelle and co-authors can now show that the Massospondylus embryos were actually much younger than previously thought and were only at 60% through their incubation period.
The team also found that each embryo had two types of teeth preserved in its developing jaws. One set was made up of very simple triangular teeth that would have been resorbed or shed before hatching, just like geckos and crocodiles today. The second set were very similar to those of adults, and would be the ones that the embryos hatched with. "I was really surprised to find that these embryos not only had teeth, but had two types of teeth. The teeth are so tiny; they range from 0.4 to 0.7mm wide. That's smaller than the tip of a toothpick!," explains Chapelle.
The conclusion of this research is that dinosaurs developed in the egg just like their reptilian relatives, whose embryonic developmental pattern hasn't changed in 200 million years. "It's incredible that in more than 250 million years of reptile evolution, the way the skull develops in the egg remains more or less the same. Goes to show -- you don't mess with a good thing!," concludes Jonah Choiniere, professor at the University of Witwatersrand and also co-author of the study.
Read more at Science Daily
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