Humans are not the only ones who have beliefs; animals do too, although it is more difficult to prove them than with humans. Dr. Tobias Starzak and Professor Albert Newen from the Institute of Philosophy II at Ruhr-Universität Bochum have proposed four criteria to understand and empirically investigate animal beliefs in the journal Mind and Language. The article was published online on 16 June 2020.
Flexible use of information about the world
The first criterion for the existence of beliefs worked out by the philosophers is that an animal must have information about the world. However, this must not simply lead to an automatic reaction, like a frog instinctively snapping at a passing insect.
Instead, the animal must be able to use the information to behave in a flexible manner. "This is the case when one and the same piece of information can be combined with different motivations to produce different behaviours," explains Albert Newen. "For example, if the animal can use the information that there is food available at that moment for the purpose of eating or hiding the food."
Information can be relinked
The third criterion says that the information is internally structured in a belief; accordingly, individual aspects of that information can be processed separately. This has emerged, for example, in experiments with rats that can learn that a certain kind of food can be found at a certain time in a certain place. Their knowledge has a what-when-where structure.
Fourthly, animals with beliefs must be able to recombine the information components in novel ways. This reassembled belief should then lead to flexible behaviour. Rats can do this too, as the US researcher Jonathan Crystal demonstrated in experiments in an eight-armed labyrinth. The animals learned that if they received normal food in arm three of the maze in the morning, chocolate could be found in arm seven at noon.
Crows and scrub jays meet all criteria
The authors from Bochum also cite crows and scrub jays as examples of animals with beliefs. British researcher Nicola Clayton carried out conclusive experiments with scrub jays. When the birds are hungry, they initially tend to eat the food. When they are not hungry, they systematically hide the leftovers. In the process, they encode which food -- worm or peanut -- they have hidden where and when. If they are hungry in the following hours, they first look for the worms they prefer. After the period of time has elapsed that takes worms to become inedible, they head for the peanut hiding places instead.
"What best explains this change in behaviour is the birds' belief about the worms being spoiled and their beliefs about the location of other food items," says Tobias Starzak. The animals also react flexibly in other situations, for example if they notice that they are being watched by rivals while hiding; if this is the case, they hide the food again later.
Read more at Science Daily
Jun 18, 2020
Viruses can steal our genetic code to create new human-virus genes
Like a scene out of "Invasion of the Body Snatchers," a virus infects a host and converts it into a factory for making more copies of itself. Now researchers have shown that a large group of viruses, including the influenza viruses and other serious pathogens, steal genetic signals from their hosts to expand their own genomes.
This finding is presented in a study published online today and in print June 25 in Cell. The cross-disciplinary collaborative study was led by researchers at the Global Health and Emerging Pathogens Institute at Icahn School of Medicine at Mount Sinai in New York, and at the MRC-University of Glasgow Centre for Virus Research in the UK.
The cross-disciplinary team of virologists looked at a large group of viruses known as segmented negative-strand RNA viruses (sNSVs), which include widespread and serious pathogens of humans, domesticated animals and plants, including the influenza viruses and Lassa virus (the cause of Lassa fever). They showed that, by stealing genetic signals from their hosts, viruses can produce a wealth of previously undetected proteins. The researchers labeled them as UFO (Upstream Frankenstein Open reading frame) proteins, as they are encoded by stitching together the host and viral sequences. There was no knowledge of the existence of these kinds of proteins prior to this study.
These UFO proteins can alter the course of viral infection and could be exploited for vaccine purposes.
"The capacity of a pathogen to overcome host barriers and establish infection is based on the expression of pathogen-derived proteins," said Ivan Marazzi, PhD, Associate Professor of Microbiology at Icahn School of Medicine and corresponding author on the study. "To understand how a pathogen antagonizes the host and establishes infection, we need to have a clear understanding of what proteins a pathogen encodes, how they function, and the manner in which they contribute to virulence."
Viruses cannot build their own proteins, so they need to feed suitable instructions to the machinery that builds proteins in their host's cells. Viruses are known to do this through a process called "cap-snatching," in which they cut the end from one of the cell's own protein-encoding messages (a messenger RNA, or mRNA) and then extend that sequence with a copy of one of their own genes. This gives a hybrid message to be read.
"For decades we thought that by the time the body encounters the signal to start translating that message into protein (a 'start codon') it is reading a message provided to it solely by the virus. Our work shows that the host sequence is not silent," said Dr. Marazzi.
The researchers show that, because they make hybrids of host mRNAs with their own genes, viruses (sNSVs) can produce messages with extra, host-derived start codons, a process they called "start snatching." This makes it possible to translate previously unsuspected proteins from the hybrid host-virus sequences. They further show that these novel genes are expressed by influenza viruses and potentially a vast number of other viruses. The product of these hybrid genes can be visible to the immune system, and they can modulate virulence. Further studies are needed to understand this new class of proteins and what the implications are of their pervasive expression by many of the RNA viruses that cause epidemics and pandemics.
Ed Hutchinson, PhD, corresponding author and a research fellow at MRC-University of Glasgow Centre for Virus Research, said, "Viruses take over their host at the molecular level, and this work identifies a new way in which some viruses can wring every last bit of potential out of the molecular machinery they are exploiting. While the work done here focusses on influenza viruses, it implies that a huge number of viral species can make previously unsuspected genes."
Researchers say the next part of their work is to understand the distinct roles the unsuspected genes play. "Now we know they exist, we can study them and use the knowledge to help disease eradication," said Dr. Marazzi. "A large global effort is required to stop viral epidemics and pandemics, and these new insights may lead to identifying novel ways to stop infection."
Read more at Science Daily
This finding is presented in a study published online today and in print June 25 in Cell. The cross-disciplinary collaborative study was led by researchers at the Global Health and Emerging Pathogens Institute at Icahn School of Medicine at Mount Sinai in New York, and at the MRC-University of Glasgow Centre for Virus Research in the UK.
The cross-disciplinary team of virologists looked at a large group of viruses known as segmented negative-strand RNA viruses (sNSVs), which include widespread and serious pathogens of humans, domesticated animals and plants, including the influenza viruses and Lassa virus (the cause of Lassa fever). They showed that, by stealing genetic signals from their hosts, viruses can produce a wealth of previously undetected proteins. The researchers labeled them as UFO (Upstream Frankenstein Open reading frame) proteins, as they are encoded by stitching together the host and viral sequences. There was no knowledge of the existence of these kinds of proteins prior to this study.
These UFO proteins can alter the course of viral infection and could be exploited for vaccine purposes.
"The capacity of a pathogen to overcome host barriers and establish infection is based on the expression of pathogen-derived proteins," said Ivan Marazzi, PhD, Associate Professor of Microbiology at Icahn School of Medicine and corresponding author on the study. "To understand how a pathogen antagonizes the host and establishes infection, we need to have a clear understanding of what proteins a pathogen encodes, how they function, and the manner in which they contribute to virulence."
Viruses cannot build their own proteins, so they need to feed suitable instructions to the machinery that builds proteins in their host's cells. Viruses are known to do this through a process called "cap-snatching," in which they cut the end from one of the cell's own protein-encoding messages (a messenger RNA, or mRNA) and then extend that sequence with a copy of one of their own genes. This gives a hybrid message to be read.
"For decades we thought that by the time the body encounters the signal to start translating that message into protein (a 'start codon') it is reading a message provided to it solely by the virus. Our work shows that the host sequence is not silent," said Dr. Marazzi.
The researchers show that, because they make hybrids of host mRNAs with their own genes, viruses (sNSVs) can produce messages with extra, host-derived start codons, a process they called "start snatching." This makes it possible to translate previously unsuspected proteins from the hybrid host-virus sequences. They further show that these novel genes are expressed by influenza viruses and potentially a vast number of other viruses. The product of these hybrid genes can be visible to the immune system, and they can modulate virulence. Further studies are needed to understand this new class of proteins and what the implications are of their pervasive expression by many of the RNA viruses that cause epidemics and pandemics.
Ed Hutchinson, PhD, corresponding author and a research fellow at MRC-University of Glasgow Centre for Virus Research, said, "Viruses take over their host at the molecular level, and this work identifies a new way in which some viruses can wring every last bit of potential out of the molecular machinery they are exploiting. While the work done here focusses on influenza viruses, it implies that a huge number of viral species can make previously unsuspected genes."
Researchers say the next part of their work is to understand the distinct roles the unsuspected genes play. "Now we know they exist, we can study them and use the knowledge to help disease eradication," said Dr. Marazzi. "A large global effort is required to stop viral epidemics and pandemics, and these new insights may lead to identifying novel ways to stop infection."
Read more at Science Daily
Origins of the beloved guinea pig
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| Guinea pigs |
Just published in the international science journal, Scientific Reports, the researchers use ancient DNA from archaeological guinea pig remains which reveals the transition from the animals being used as a wild food source 10,000 years ago to their domestication and later role as beloved pets and medical animal models.
It builds on previous research over many years by Professor of Biological Anthropology, Lisa Matisoo-Smith, tracing the DNA from plants and animals that Pacific settlers carried in their canoes and using that as a proxy for identifying human population origins and tracking their movement around the Pacific.
As part of her Otago Master's thesis research in Professor Matisoo-Smith's lab, Edana Lord, now at Stockholm University, Sweden and Dr Catherine Collins from Otago's Department of Anatomy and other international researchers, set about finding out where the guinea pigs that were introduced to the islands of the Caribbean came from.
Professor Matisoo-Smith explains it is generally accepted that modern guinea pigs were domesticated in the Andes region of what is now Peru. As an important food item that was also included in religious ceremonies, they were transported and traded around South America.
Sometime around AD500, guinea pigs were taken out to the islands of the Caribbean, through at least one of several established trade networks. The researchers expected that the guinea pigs found in the Caribbean would came from Colombia, one of the closer locations in South America to the Caribbean.
Using ancient DNA of guinea pigs remains excavated from several sites in the Caribbean, Peru, Colombia, Bolivia, Europe and North America, they found the guinea pigs on the islands did not originate in Colombia, but most likely originated in Peru.
What was a bigger surprise to the team was that the guinea pig remains found in the Colombian Highlands appeared to be from a totally different species. This suggests that guinea pig domestication likely took place independently in both Peru and Colombia.
The genetic information, along with archaeological contexts, also shows how the guinea pigs had different roles through time.
"They were and still are important food item in many parts of South America and cultures that derived from South America -- people took them live to introduce to new islands where they were not native or they traded them for other goods," Professor Matisoo-Smith explains.
"The guinea pig was brought to Europe in the late 1500s or early 1600s by the Spanish and to North America in the early 1800s as part of the exotic pet trade. In the 18th century guinea pigs began to be used by medical researchers as laboratory animals because they have many biological similarities to humans, thus the origin of the phrase 'being a guinea pig' in research.
"All guinea pigs today -- pets, those that are sold for meat in South America and Puerto Rico, and those used in medical research -- are derived from the Peruvian domesticated guinea pigs."
Why the guinea pig was viewed as a pet in some cultures and a food source in others can likely be attributed to long-established cultural notions of what is acceptable as food.
Professor Matisoo-Smith says the research demonstrates that the history of guinea pigs is more complex than previously known and has implications for other studies regarding mammal domestication, translocation and distribution.
"Identifying the origins of the guinea pig remains from the Caribbean helps us to understand how the human trade networks in the region moved in the past 1000 years or so.
Read more at Science Daily
Tomato's hidden mutations revealed in study of 100 varieties
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| Tomato varieties |
Today, scientists are teasing out how these physical changes show up at the level of genes -- work that could guide modern efforts to tweak the tomato, says Howard Hughes Medical Institute Investigator Zachary Lippman.
He and colleagues have now identified long-concealed hidden mutations within the genomes of 100 types of tomato, including an orange-berried wild plant from the Galapagos Islands and varieties typically processed into ketchup and sauce.
Their analysis, described June 17, 2020, in the journal Cell, is the most comprehensive assessment of such mutations -- which alter long sections of DNA -- for any plant. The research could lead to the creation of new tomato varieties and the improvement of existing ones, Lippman says. A handful of the mutations his team identified alter key characteristics, like flavor and weight, the researchers showed.
Previous studies have long shown that these mutations exist in plant genomes, says Lippman, a plant geneticist at Cold Spring Harbor Laboratory. "But until now, we didn't have an efficient way to find them and study their impact," he says.
A window into the genome
Mutations, or changes, in the four types of DNA letters carried within an organism's cells can alter its physical characteristics. Scientists studying plants have generally focused on a small, tractable kind of mutation, in which one DNA letter is swapped for another.
The mutations Lippman's team studied are much bigger -- they modify DNA's structure by copying, deleting, inserting, or moving long sections of DNA elsewhere in the genome. These mutations, also called structural variations, occur throughout the living world. Studies in humans, for example, have linked these variations to disorders such as schizophrenia and autism.
Scientists can identify mutations by reading out the letters of DNA using a technique known as genetic sequencing. Limitations in this technology, however, have made it difficult to decode long sections of DNA, Lippman says. So researchers haven't been able to capture a complete picture of structural mutations in the genome.
Even so, plant geneticists have suspected that these mutations contribute significantly to plants' traits, says Michael Purugganan, who studies rice and date palms at New York University and was not involved in the new study. "That's why this paper is so exciting," he says. Lippman's team not only found these mutations in tomato and its wild relatives, but also determined how they function within the plants, he says.
A guide for future tomatoes
The new study, a collaboration with Michael Schatz at Johns Hopkins University and others, identified more than 200,000 structural mutations in tomatoes using a technique called long-read sequencing. Lippman likens it to looking through a panoramic window at large sections of the genome. By comparison, more conventional sequencing offered only a peephole, he says.
The majority of the mutations they found do not change genes that encode traits. But what's clear, Lippman says, is that many of these mutations alter mechanisms controlling genes' activity. One such gene, for instance, controls tomato fruit size. By modifying DNA structure -- in this case, the number of copies of the gene -- Lippman's team was able to alter fruit production. Plants lacking the gene never made fruit, while plants with three copies of the gene made fruit about 30 percent larger than those with just a single copy.
Lippman's team also demonstrated how DNA structure can influence traits in an example he calls "remarkably complex." They showed that four structural mutations together were needed for breeding a major harvesting trait into modern tomatoes.
These sorts of insights could help explain trait diversity in other crops and enable breeders to improve varieties, Lippman says. For instance, perhaps adding an extra copy of the size gene to tiny ground cherries, a close relative of the tomato, could increase their appeal by making them larger, he says.
Read more at Science Daily
Jun 17, 2020
Antarctic sea ice loss explained in new study
Scientists have discovered that the summer sea ice in the Weddell Sea sector of Antarctica has decreased by one million square kilometres -- an area twice the size of Spain -- in the last five years, with implications for the marine ecosystem. The findings are published this month (June 2020) in the journal Geophysical Research Letters.
Sea ice surrounding Antarctica provides an important habitat for many species including penguins and seals, which rely on it to access food and to breed.
An international team of researchers studied satellite records of sea ice extent and weather analyses starting in the late 1970s to understand why summer sea ice in the Weddell Sea area of Antarctica has reduced by a third over the last five years. They found that ice loss occurred due to a series of severe storms in the Antarctic summer of 2016/17, along with the re-appearance of an area of open water in the middle of the 'pack ice' (known as a polynya), which had not occurred since the mid-1970s.
Lead author Professor John Turner, a climate scientist at British Antarctic Survey, says:
"Antarctic sea ice continues to surprise us. In contrast to the Arctic, sea ice around the Antarctic had been increasing in extent since the 1970s, but then rapidly decreased to record low levels, with the greatest decline in the Weddell Sea. In summer, this area now has a third less sea ice, which will have implications for ocean circulation and the marine wildlife of the region that depend on it for their survival."
The ocean around Antarctica freezes and doubles the size of the continent in the austral winter, with the sea ice extent reaching over 18 million square kilometres by late September. Through the spring and summer, the sea ice almost completely melts in most parts of the Antarctic, with only the Weddell Sea retaining a significant amount of sea ice.
There are few storms around the Antarctic in the austral summer, but in December 2016, a number of intense and unseasonal storms developed in the Weddell Sea and drew warm air towards the Antarctic, melting a large amount of sea ice. The ice-free ocean absorbed energy from the Sun and then created a warm ocean temperature anomaly that still persists today.
The winter of 2016 also saw the development of a polynya in the Weddell Sea, a large area of open water within the sea ice, which also contributed to the overall decline in sea ice extent. This polynya was created by the strong winds associated with the storms and unprecedented warm ocean conditions.
This recent rapid sea ice loss is affecting both the Weddell Sea ecosystem and the wider Antarctic wildlife/plants and animals. Many species, ranging from tiny ice algae and shrimp-like crustaceans called krill to seabirds, seals and whales, are highly adapted to the presence of sea ice. If the drastic changes observed continue, they will have repercussions throughout the food chain, from affecting nutrients to the reduction of essential habitat for breeding and feeding for vast numbers of animals, such as ice seals and some species of penguins.
Author and ecologist Professor Eugene Murphy from British Antarctic Survey says:
"The dramatic decline in sea ice observed in the Weddell Sea is likely to have significant impacts on the way the entire marine ecosystem functions. Understanding these wider consequences is of paramount importance, especially if the decline in ice extent continues."
Read more at Science Daily
Sea ice surrounding Antarctica provides an important habitat for many species including penguins and seals, which rely on it to access food and to breed.
An international team of researchers studied satellite records of sea ice extent and weather analyses starting in the late 1970s to understand why summer sea ice in the Weddell Sea area of Antarctica has reduced by a third over the last five years. They found that ice loss occurred due to a series of severe storms in the Antarctic summer of 2016/17, along with the re-appearance of an area of open water in the middle of the 'pack ice' (known as a polynya), which had not occurred since the mid-1970s.
Lead author Professor John Turner, a climate scientist at British Antarctic Survey, says:
"Antarctic sea ice continues to surprise us. In contrast to the Arctic, sea ice around the Antarctic had been increasing in extent since the 1970s, but then rapidly decreased to record low levels, with the greatest decline in the Weddell Sea. In summer, this area now has a third less sea ice, which will have implications for ocean circulation and the marine wildlife of the region that depend on it for their survival."
The ocean around Antarctica freezes and doubles the size of the continent in the austral winter, with the sea ice extent reaching over 18 million square kilometres by late September. Through the spring and summer, the sea ice almost completely melts in most parts of the Antarctic, with only the Weddell Sea retaining a significant amount of sea ice.
There are few storms around the Antarctic in the austral summer, but in December 2016, a number of intense and unseasonal storms developed in the Weddell Sea and drew warm air towards the Antarctic, melting a large amount of sea ice. The ice-free ocean absorbed energy from the Sun and then created a warm ocean temperature anomaly that still persists today.
The winter of 2016 also saw the development of a polynya in the Weddell Sea, a large area of open water within the sea ice, which also contributed to the overall decline in sea ice extent. This polynya was created by the strong winds associated with the storms and unprecedented warm ocean conditions.
This recent rapid sea ice loss is affecting both the Weddell Sea ecosystem and the wider Antarctic wildlife/plants and animals. Many species, ranging from tiny ice algae and shrimp-like crustaceans called krill to seabirds, seals and whales, are highly adapted to the presence of sea ice. If the drastic changes observed continue, they will have repercussions throughout the food chain, from affecting nutrients to the reduction of essential habitat for breeding and feeding for vast numbers of animals, such as ice seals and some species of penguins.
Author and ecologist Professor Eugene Murphy from British Antarctic Survey says:
"The dramatic decline in sea ice observed in the Weddell Sea is likely to have significant impacts on the way the entire marine ecosystem functions. Understanding these wider consequences is of paramount importance, especially if the decline in ice extent continues."
Read more at Science Daily
Insight into the black hole at the center of our galaxy
Like most galaxies, the Milky Way hosts a supermassive black hole at its center. Called Sagittarius A*, the object has captured astronomers' curiosity for decades. And now there is an effort to image it directly.
Catching a good photo of the celestial beast will require a better understanding of what's going on around it, which has proved challenging due to the vastly different scales involved. "That's the biggest thing we had to overcome," said Sean Ressler, a postdoctoral researcher at UC Santa Barbara's Kavli Institute for Theoretical Physics (KITP), who just published a paper in the Astrophysical Journal Letters, investigating the magnetic properties of the accretion disk surrounding Sagittarius A*.
In the study, Ressler, fellow KITP postdoc Chris White and their colleagues, Eliot Quataert of UC Berkeley and James Stone at the Institute for Advanced Study, sought to determine whether the black hole's magnetic field, which is generated by in-falling matter, can build up to the point where it briefly chokes off this flow, a condition scientists call magnetically arrested. Answering this would require simulating the system all the way out to the closest orbiting stars.
The system in question spans seven orders of magnitude. The black hole's event horizon, or envelope of no return, reaches around 4 to 8 million miles from its center. Meanwhile, the stars orbit around 20 trillion miles away, or about as far as the sun's nearest neighboring star.
"So you have to track the matter falling in from this very large scale all the way down to this very small scale," said Ressler. "And doing that in a single simulation is incredibly challenging, to the point that it's impossible." The smallest events proceed on timescales of seconds while the largest phenomena play out over thousands of years.
This paper connects small scale simulations, which are mostly theory-based, with large-scale simulations that can be constrained by actual observations. To achieve this, Ressler divided the task between models at three overlapping scales.
The first simulation relied on data from Sagittarius A*'s surrounding stars. Fortunately, the black hole's activity is dominated by just 30 or so Wolf-Rayet stars, which blow off tremendous amounts of material. "The mass loss from just one of the stars is larger than the total amount of stuff falling into the black hole during the same time," Ressler said. The stars spend only around 100,000 years in this dynamic phase before transitioning into a more stable stage of life.
Using observational data, Ressler simulated the orbits of these stars over the course of about a thousand years. He then used the results as the starting point for a simulation of medium-range distances, which evolve over shorter time scales. He repeated this for a simulation down to the very edge of the event horizon, where activity takes place in matters of seconds. Rather than stitching together hard overlaps, this approach allowed Ressler to fade the results of the three simulations into one another.
"These are really the first models of the accretion at the smallest scales in [Sagittarius] A* that take into account the reality of the supply of matter coming from orbiting stars," said coauthor White.
And the technique worked splendidly. "It went beyond my expectations," Ressler remarked.
The results indicated that Sagittarius A* can become magnetically arrested. This came as a surprise to the team, since the Milky Way has a relatively quiet galactic center. Usually, magnetically arrested black holes have high-energy jets shooting particles away at relativistic speeds. But so far scientists have seen little evidence for jets around Sagittarius A*.
"The other ingredient that helps create jets is a rapidly spinning black hole," said White, "so this may be telling us something about the spin of Sagittarius A*."
Unfortunately, black hole spin is difficult to determine. Ressler modeled Sagittarius A* as a stationary object. "We don't know anything about the spin," he said. "There's a possibility that it's actually just not spinning."
Ressler and White next plan to model a spinning back hole, which is much more challenging. It immediately introduces a host of new variables, including spin rate, direction and tilt relative to the accretion disc. They will use data from the European Southern Observatory's GRAVITY interferometer to guide these decisions.
The team used the simulations to create images that can be compared to actual observations of the black hole. Scientists at the Event Horizon Telescope collaboration -- which made headlines in April 2019 with the first direct image of a black hole -- have already reached out requesting the simulation data in order to supplement their effort to photograph Sagittarius A*.
The Event Horizon Telescope effectively takes a time average of its observations, which results in a blurry image. This was less of an issue when the observatory had their sights on Messier 87*, because it is around 1,000 times larger than Sagittarius A*, so it changes around 1,000 times more slowly.
"It's like taking a picture of a sloth versus taking a picture of a hummingbird," Ressler explained. Their current and future results should help the consortium interpret their data on our own galactic center.
Read more at Science Daily
Catching a good photo of the celestial beast will require a better understanding of what's going on around it, which has proved challenging due to the vastly different scales involved. "That's the biggest thing we had to overcome," said Sean Ressler, a postdoctoral researcher at UC Santa Barbara's Kavli Institute for Theoretical Physics (KITP), who just published a paper in the Astrophysical Journal Letters, investigating the magnetic properties of the accretion disk surrounding Sagittarius A*.
In the study, Ressler, fellow KITP postdoc Chris White and their colleagues, Eliot Quataert of UC Berkeley and James Stone at the Institute for Advanced Study, sought to determine whether the black hole's magnetic field, which is generated by in-falling matter, can build up to the point where it briefly chokes off this flow, a condition scientists call magnetically arrested. Answering this would require simulating the system all the way out to the closest orbiting stars.
The system in question spans seven orders of magnitude. The black hole's event horizon, or envelope of no return, reaches around 4 to 8 million miles from its center. Meanwhile, the stars orbit around 20 trillion miles away, or about as far as the sun's nearest neighboring star.
"So you have to track the matter falling in from this very large scale all the way down to this very small scale," said Ressler. "And doing that in a single simulation is incredibly challenging, to the point that it's impossible." The smallest events proceed on timescales of seconds while the largest phenomena play out over thousands of years.
This paper connects small scale simulations, which are mostly theory-based, with large-scale simulations that can be constrained by actual observations. To achieve this, Ressler divided the task between models at three overlapping scales.
The first simulation relied on data from Sagittarius A*'s surrounding stars. Fortunately, the black hole's activity is dominated by just 30 or so Wolf-Rayet stars, which blow off tremendous amounts of material. "The mass loss from just one of the stars is larger than the total amount of stuff falling into the black hole during the same time," Ressler said. The stars spend only around 100,000 years in this dynamic phase before transitioning into a more stable stage of life.
Using observational data, Ressler simulated the orbits of these stars over the course of about a thousand years. He then used the results as the starting point for a simulation of medium-range distances, which evolve over shorter time scales. He repeated this for a simulation down to the very edge of the event horizon, where activity takes place in matters of seconds. Rather than stitching together hard overlaps, this approach allowed Ressler to fade the results of the three simulations into one another.
"These are really the first models of the accretion at the smallest scales in [Sagittarius] A* that take into account the reality of the supply of matter coming from orbiting stars," said coauthor White.
And the technique worked splendidly. "It went beyond my expectations," Ressler remarked.
The results indicated that Sagittarius A* can become magnetically arrested. This came as a surprise to the team, since the Milky Way has a relatively quiet galactic center. Usually, magnetically arrested black holes have high-energy jets shooting particles away at relativistic speeds. But so far scientists have seen little evidence for jets around Sagittarius A*.
"The other ingredient that helps create jets is a rapidly spinning black hole," said White, "so this may be telling us something about the spin of Sagittarius A*."
Unfortunately, black hole spin is difficult to determine. Ressler modeled Sagittarius A* as a stationary object. "We don't know anything about the spin," he said. "There's a possibility that it's actually just not spinning."
Ressler and White next plan to model a spinning back hole, which is much more challenging. It immediately introduces a host of new variables, including spin rate, direction and tilt relative to the accretion disc. They will use data from the European Southern Observatory's GRAVITY interferometer to guide these decisions.
The team used the simulations to create images that can be compared to actual observations of the black hole. Scientists at the Event Horizon Telescope collaboration -- which made headlines in April 2019 with the first direct image of a black hole -- have already reached out requesting the simulation data in order to supplement their effort to photograph Sagittarius A*.
The Event Horizon Telescope effectively takes a time average of its observations, which results in a blurry image. This was less of an issue when the observatory had their sights on Messier 87*, because it is around 1,000 times larger than Sagittarius A*, so it changes around 1,000 times more slowly.
"It's like taking a picture of a sloth versus taking a picture of a hummingbird," Ressler explained. Their current and future results should help the consortium interpret their data on our own galactic center.
Read more at Science Daily
Study in Philadelphia links growth in tree canopy to decrease in human mortality
The first city-wide health impact assessment of the estimated effects of a tree canopy initiative on premature mortality in Philadelphia suggests that increased tree canopy could prevent between 271 and 400 premature deaths per year. The study by Michelle Kondo, a Philadelphia-based research social scientist with the U.S. Department of Agriculture Forest Service, and her partners suggest that increased tree canopy or green space could decrease morbidity and mortality for urban populations -- particularly in areas with lower socioeconomic status where existing tree canopies tend to be the lowest.
The study, "Health impact assessment of Philadelphia's 2025 tree canopy cover goals," examined the potential impact of Greenworks Philadelphia, a plan to increase tree canopy to 30 percent across the city by 2025, on human mortality. The analysis is one of the first to estimate the number of preventable deaths based on physical activity, air pollution, noise, heat, and exposure to greenspaces using a tool developed by public health researchers in Spain and Switzerland called the Greenspace-Health Impact Assessment
Kondo and her partners estimated the annual number of preventable deaths associated with projected changes in tree canopy cover in Philadelphia between 2014 and 2025 under three scenarios of increased urban green space. They found that increasing urban tree canopy to the Greenworks Philadelphia goal of 30 percent in all neighborhoods could prevent 400 deaths annually, but lesser increases in tree canopy still resulted in reduced mortality. A 5 percentage point increase in tree canopy only in areas without trees could result in an annual reduction of 302 deaths citywide, researchers found, and a 10 percentage point increase in tree canopy cover across the city was associated with an estimated reduction of 376 deaths
"This study supports the idea that increasing tree canopy and urban greening efforts are worthwhile, even at modest levels, as health-promoting and cost-saving measures," Kondo said.
Current tree canopy in Philadelphia ranges from 2 percent to 88 percent, with an average 20 percent urban tree canopy coverage based on 2014 data.
"In recent weeks, as residents of many cities experienced quarantine conditions, we experienced a heightened need for public green space," Kondo said. "While the COVID-19 pandemic has meant that we need to pay attention to our proximity to other people and take precautions to limit our contact, time outside in parks and forests has been critical to maintaining our mental and physical health."
Research partners included scientists from Universitat Pompeu Fabra, National Socio-Environmental Synthesis Center, Colorado State University, and Drexel University.
From Science Daily
The study, "Health impact assessment of Philadelphia's 2025 tree canopy cover goals," examined the potential impact of Greenworks Philadelphia, a plan to increase tree canopy to 30 percent across the city by 2025, on human mortality. The analysis is one of the first to estimate the number of preventable deaths based on physical activity, air pollution, noise, heat, and exposure to greenspaces using a tool developed by public health researchers in Spain and Switzerland called the Greenspace-Health Impact Assessment
Kondo and her partners estimated the annual number of preventable deaths associated with projected changes in tree canopy cover in Philadelphia between 2014 and 2025 under three scenarios of increased urban green space. They found that increasing urban tree canopy to the Greenworks Philadelphia goal of 30 percent in all neighborhoods could prevent 400 deaths annually, but lesser increases in tree canopy still resulted in reduced mortality. A 5 percentage point increase in tree canopy only in areas without trees could result in an annual reduction of 302 deaths citywide, researchers found, and a 10 percentage point increase in tree canopy cover across the city was associated with an estimated reduction of 376 deaths
"This study supports the idea that increasing tree canopy and urban greening efforts are worthwhile, even at modest levels, as health-promoting and cost-saving measures," Kondo said.
Current tree canopy in Philadelphia ranges from 2 percent to 88 percent, with an average 20 percent urban tree canopy coverage based on 2014 data.
"In recent weeks, as residents of many cities experienced quarantine conditions, we experienced a heightened need for public green space," Kondo said. "While the COVID-19 pandemic has meant that we need to pay attention to our proximity to other people and take precautions to limit our contact, time outside in parks and forests has been critical to maintaining our mental and physical health."
Research partners included scientists from Universitat Pompeu Fabra, National Socio-Environmental Synthesis Center, Colorado State University, and Drexel University.
From Science Daily
Hunting in savanna-like landscapes may have poured jet fuel on brain evolution
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| African savanna |
Northwestern University researchers recently discovered that complex landscapes -- dotted with trees, bushes, boulders and knolls -- might have helped land-dwelling animals evolve higher intelligence than their aquatic ancestors.
Compared to the vast emptiness of open water, land is rife with obstacles and occlusions. By providing prey with spaces to hide and predators with cover for sneak attacks, the habitats possible on land may have helped give rise to planning strategies -- rather than those based on habit -- for many of those animals.
But the researchers found that planning did not give our ancestors the upper hand in all landscapes. The researchers' simulations show there is a Goldilocks level of barriers -- not too few and not too many -- to a predator's perception, in which the advantage of planning really shines. In simple landscapes like open ground or packed landscapes like dense jungle, there was no advantage.
"All animals -- on land or in water -- had the same amount of time to evolve, so why do land animals have most of the smarts?" asked Northwestern's Malcolm MacIver, who led the study. "Our work shows that it's not just about what's in the head but also about what's in the environment."
And, no, dolphins and whales do not fall into the category of less intelligent sea creatures. Both are land mammals that recently (evolutionarily speaking) returned to water.
The paper will be published June 16 in the journal Nature Communications.
It is the latest in a series of studies conducted by MacIver that advance a theory of how land animals evolved the ability to plan. In a follow-up study now underway with Dan Dombeck, a professor of neurobiology at Northwestern, MacIver will put the predictions generated by this computational study to the test through experiments with small animals in a robotic reconfigurable environment.
MacIver is a professor of biomedical and mechanical engineering in Northwestern's McCormick School of Engineering and a professor of neurobiology in the Weinberg College of Arts and Sciences. Ugurcan Mugan, a Ph.D. candidate in MacIver's laboratory, is the paper's first author.
Simulating survival
In previous work, MacIver showed that when animals started invading land 385 million years ago, they gained the ability to see around a hundred times farther than they could in water. MacIver hypothesized that being a predator or a prey in the context of being able to see so much farther might require more brain power than hunting through empty, open water. However, the supercomputer simulations for the new study (35 years of calculations on a single PC) revealed that although seeing farther is necessary to advantage planning, it's not sufficient. Instead, only a combination of long-range vision and landscapes with a mix of open areas and more densely vegetated zones resulted in a clear win for planning.
"We speculated that moving onto land poured jet fuel on the evolution of the brain as it may have advantaged the hardest cognitive operation there is: Envisioning the future," MacIver said. "It could explain why we can go out for seafood, but seafood can't go out for us."
To test this hypothesis, MacIver and his team developed computational simulations to test the survival rates of prey being actively hunted by a predator under two different decision-making strategies: Habit-based (automatic, such as entering a password that you have memorized) and plan-based (imagining several scenarios and selecting the best one). The team created a simple, open world without visual barriers to simulate an aquatic world. Then, they added objects of varying densities to simulate land.
Survival of the smartest
"When defining complex cognition, we made a distinction between habit-based action and planning," MacIver said. "The important thing about habit is that it is inflexible and outcome independent. That's why you keep entering your old password for a while after changing it. In planning, you have to imagine different futures and choose the best potential outcome."
In the simple aquatic and terrestrial environments examined in the study, survival rate was low both for prey that used habit-based actions and those that had the capability to plan. The same was true of highly packed environments, such as coral reefs and dense rainforests.
"In those simple open or highly packed environments, there is no benefit to planning," MacIver said. "In the open aquatic environments, you just need to run in the opposite direction and hope for the best. While in the highly packed environments, there are only a few paths to take, and you are not able to strategize because you can't see far. In these environments, we found that planning does not improve your chances of survival."
The Goldilocks landscape
When patches of vegetation and topography are interspersed with wide open areas similar to a savanna, however, simulations showed that planning results in a huge survival payoff compared to habit-based movements. Because planning increases the chance of survival, evolution would have selected for the brain circuitry that allowed animals to imagine future scenarios, evaluate them and then enact one.
"With patchy landscapes, there is an interplay of transparent and opaque regions of space and long-range vision, which means that your movement can hide or reveal your presence to an adversary," MacIver said. "Terra firma becomes a chess board. With every movement, you have a chance to unfurl a strategy.
"Interestingly," he noted, "when we split off from life in the trees with chimpanzees nearly seven million years ago and quickly quadrupled in brain size, paleoecology studies point to our having invaded patchy landscapes, similar to those our study highlights, as giving the biggest payoff for strategic thinking."
Read more at Science Daily
Jun 16, 2020
As many as six billion Earth-like planets in our galaxy, according to new estimates
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| Exoplanet illustration |
To be considered Earth-like, a planet must be rocky, roughly Earth-sized and orbiting Sun-like (G-type) stars. It also has to orbit in the habitable zones of its star -- the range of distances from a star in which a rocky planet could host liquid water, and potentially life, on its surface.
"My calculations place an upper limit of 0.18 Earth-like planets per G-type star," says UBC researcher Michelle Kunimoto, co-author of the new study in The Astronomical Journal. "Estimating how common different kinds of planets are around different stars can provide important constraints on planet formation and evolution theories, and help optimize future missions dedicated to finding exoplanets."
According to UBC astronomer Jaymie Matthews: "Our Milky Way has as many as 400 billion stars, with seven per cent of them being G-type. That means less than six billion stars may have Earth-like planets in our Galaxy."
Previous estimates of the frequency of Earth-like planets range from roughly 0.02 potentially habitable planets per Sun-like star, to more than one per Sun-like star.
Typically, planets like Earth are more likely to be missed by a planet search than other types, as they are so small and orbit so far from their stars. That means that a planet catalogue represents only a small subset of the planets that are actually in orbit around the stars searched. Kunimoto used a technique known as 'forward modelling' to overcome these challenges.
"I started by simulating the full population of exoplanets around the stars Kepler searched," she explained. "I marked each planet as 'detected' or 'missed' depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalogue of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars."
Kunimoto's research also shed more light on one of the most outstanding questions in exoplanet science today: the 'radius gap' of planets. The radius gap demonstrates that it is uncommon for planets with orbital periods less than 100 days to have a size between 1.5 and two times that of Earth. She found that the radius gap exists over a much narrower range of orbital periods than previously thought. Her observational results can provide constraints on planet evolution models that explain the radius gap's characteristics.
Read more at Science Daily
Discovery of oldest bow and arrow technology in Eurasia
The island of Sri Lanka in the Indian Ocean, just south of the Indian subcontinent, is home to the earliest fossils of our species, Homo sapiens, in South Asia. It also preserves clear evidence for human occupation and the use of tropical rainforest environments outside of Africa from ~48,000 to 3,000 years ago -- refuting the idea that these supposedly resource-poor environments acted as barriers for migrating Pleistocene humans. The question as to exactly how humans obtained rainforest resources -- including fast-moving food sources like monkeys and squirrels -- remains unresolved.
In this new study, published in Science Advances, an international team of researchers from the Max Planck Institute for the Science of Human History (MPI-SHH) in Germany, Griffith University in Australia and the Department of Archaeology, Government of Sri Lanka, present evidence for the earliest use of bow-and-arrow technologies by humans anywhere outside of Africa. At ~48,000 years old, these tools are earlier than the first similar technology found in Europe. Clear evidence for use on the preserved bone arrowheads shows that they were likely used for hunting difficult-to-catch rainforest prey. Not only that, but the scientists show that other bone tools may have been used for making nets or clothing in tropical settings, dramatically altering traditional assumptions about how certain human innovations were linked with specific environmental requirements.
Hunting in the open and sheltering from the cold?
European cultural products in the form of cave art, amazingly detailed bone carvings, bone tool technologies, and tailored clothing have been frequently held up as the pinnacle of Late Pleistocene human cultural development. There, symbolic and technological innovations have been seen as key survival mechanisms equipping expanding populations to face cold northern climates. Meanwhile, discoveries of older bow-and-arrow technology and artistic or symbolic behaviors in open grassland or coastal settings in Africa have framed 'savannah' and marine environments, respectively, as key drivers behind early hunting and cultural experiments by Pleistocene humans in their evolutionary homeland.
As co-author of the new study, Patrick Roberts of the MPI-SHH argues that "this traditional focus has meant that other parts of Africa, Asia, Australasia, and the Americas have often been side-lined in discussions of the origins of material culture, such as novel projectile hunting methods or cultural innovations associated with our species." Nevertheless, the last twenty years have highlighted how Pleistocene humans occupied and adapted to a variety of extreme environments as they migrated beyond Africa, including deserts, high-altitude settings and tropical rainforests such as those of Sri Lanka.
A tropical home
The new study saw scientists turn to the beautifully preserved material culture from the cave of Fa-Hien Lena, deep in the heart of Sri Lanka's Wet Zone forests. As co-author Oshan Wedage, PhD at MPI-SHH, states, "Fa-Hien Lena has emerged as one of South Asia's most important archaeological sites since the 1980s, preserving remains of our species, their tools, and their prey in a tropical context." Some of the main finds from the site include remarkable single and doubled pointed bone tools that scientists had suspected were used in the exploitation of tropical resources. Direct proof had been lacking, however, in the absence of detailed high-powered microscopic analysis.
Michelle Langley of Griffith University, the lead author of the new study, is an expert in the study of microscopic traces of tool use and the creation of symbolic material culture in Pleistocene contexts. Applying cutting edge methods to the Fa-Hien Lena material confirmed the researchers' hypothesis. As Langley states, "the fractures on the points indicate damage through high-powered impact -- something usually seen in the use of bow-and-arrow hunting of animals. This evidence is earlier than similar findings in Southeast Asia 32,000 years ago and is currently the earliest clear evidence for bow-and-arrow use beyond the African continent."
The evidence for early human innovation did not stop there. Applying the same microscopic approach to other bone tools, the team identified implements which seem to have been associated with freshwater fishing in nearby tropical streams, as well as the working of fiber to make nets or clothing. "We also found clear evidence for the production of colored beads from mineral ochre and the refined making of shell beads traded from the coast, at a similar age to other 'social signaling' materials found in Eurasia and Southeast Asia, roughly 45,000 years ago," says Michelle Langley. Together, this reveals a complex, early human social network in the tropics of South Asia.
A flexible toolkit for new hunting grounds
The new study highlights that archaeologists can no longer link specific technological, symbolic, or cultural developments in Pleistocene humans to a single region or environment. "The Sri Lankan evidence shows that the invention of bows-and-arrows, clothing, and symbolic signaling occurred multiple times and in multiple different places, including within the tropical rainforests of Asia," says co-author Michael Petraglia of the MPI-SHH. In addition to insulation in cold environments, clothes may have also helped against tropical mosquitoes, "and instead of just hunting large grassland mammals," adds zooarchaeologist Noel Amano, another MPI-SHH co-author, "bows and arrows helped humans procure small, tree-dwelling primates and rodents."
Read more at Science Daily
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