Most meteorites that have landed on Earth are fragments of planetesimals, the very earliest protoplanetary bodies in the solar system. Scientists have thought that these primordial bodies either completely melted early in their history or remained as piles of unmelted rubble.
But a family of meteorites has befuddled researchers since its discovery in the 1960s. The diverse fragments, found all over the world, seem to have broken off from the same primordial body, and yet the makeup of these meteorites indicates that their parent must have been a puzzling chimera that was both melted and unmelted.
Now researchers at MIT and elsewhere have determined that the parent body of these rare meteorites was indeed a multilayered, differentiated object that likely had a liquid metallic core. This core was substantial enough to generate a magnetic field that may have been as strong as Earth's magnetic field is today.
Their results, published in the journal Science Advances, suggest that the diversity of the earliest objects in the solar system may have been more complex than scientists had assumed.
"This is one example of a planetesimal that must have had melted and unmelted layers. It encourages searches for more evidence of composite planetary structures," says lead author Clara Maurel, a graduate student in MIT's Department of Earth, Atmospheric, and Planetary Sciences (EAPS). "Understanding the full spectrum of structures, from nonmelted to fully melted, is key to deciphering how planetesimals formed in the early solar system."
Maurel's co-authors include EAPS professor Benjamin Weiss, along with collaborators at Oxford University, Cambridge University, the University of Chicago, Lawrence Berkeley National Laboratory, and the Southwest Research Institute.
Oddball irons
The solar system formed around 4.5 billion years ago as a swirl of super-hot gas and dust. As this disk gradually cooled, bits of matter collided and merged to form progressively larger bodies, such as planetesimals.
The majority of meteorites that have fallen to Earth have compositions that suggest they came from such early planetesimals that were either of two types: melted, and unmelted. Both types of objects, scientists believe, would have formed relatively quickly, in less than a few million years, early in the solar system's evolution.
If a planetesimal formed in the first 1.5 million years of the solar system, short-lived radiogenic elements could have melted the body entirely due to the heat released by their decay. Unmelted planetesimals could have formed later, when their material had lower quantities of radiogenic elements, insufficient for melting.
There has been little evidence in the meteorite record of intermediate objects with both melted and unmelted compositions, except for a rare family of meteorites called IIE irons.
"These IIE irons are oddball meteorites," Weiss says. "They show both evidence of being from primordial objects that never melted, and also evidence for coming from a body that's completely or at least substantially melted. We haven't known where to put them, and that's what made us zero in on them."
Magnetic pockets
Scientists have previously found that both melted and unmelted IIE meteorites originated from the same ancient planetesimal, which likely had a solid crust overlying a liquid mantle, like Earth. Maurel and her colleagues wondered whether the planetesimal also may have harbored a metallic, melted core.
"Did this object melt enough that material sank to the center and formed a metallic core like that of the Earth?" Maurel says. "That was the missing piece to the story of these meteorites."
The team reasoned that if the planetesimal did host a metallic core, it could very well have generated a magnetic field, similar to the way Earth's churning liquid core produces a magnetic field. Such an ancient field could have caused minerals in the planetesimal to point in the direction of the field, like a needle in a compass. Certain minerals could have kept this alignment over billions of years.
Maurel and her colleagues wondered whether they might find such minerals in samples of IIE meteorites that had crashed to Earth. They obtained two meteorites, which they analyzed for a type of iron-nickel mineral known for its exceptional magnetism-recording properties.
The team analyzed the samples using the Lawrence Berkeley National Laboratory's Advanced Light Source, which produces X-rays that interact with mineral grains at the nanometer scale, in a way that can reveal the minerals' magnetic direction.
Sure enough, the electrons within a number of grains were aligned in a similar direction -- evidence that the parent body generated a magnetic field, possibly up to several tens of microtesla, which is about the strength of Earth's magnetic field. After ruling out less plausible sources, the team concluded that the magnetic field was most likely produced by a liquid metallic core. To generate such a field, they estimate the core must have been at least several tens of kilometers wide.
Such complex planetesimals with mixed composition (both melted, in the form of a liquid core and mantle, and unmelted in the form of a solid crust), Maurel says, would likely have taken over several million years to form -- a formation period that is longer than what scientists had assumed until recently.
But where within the parent body did the meteorites come from? If the magnetic field was generated by the parent body's core, this would mean that the fragments that ultimately fell to Earth could not have come from the core itself. That's because a liquid core only generates a magnetic field while still churning and hot. Any minerals that would have recorded the ancient field must have done so outside the core, before the core itself completely cooled.
Working with collaborators at the University of Chicago, the team ran high-velocity simulations of various formation scenarios for these meteorites. They showed that it was possible for a body with a liquid core to collide with another object, and for that impact to dislodge material from the core. That material would then migrate to pockets close to the surface where the meteorites originated.
"As the body cools, the meteorites in these pockets will imprint this magnetic field in their minerals. At some point, the magnetic field will decay, but the imprint will remain," Maurel says. "Later on, this body is going to undergo a lot of other collisions until the ultimate collisions that will place these meteorites on Earth's trajectory."
Was such a complex planetesimal an outlier in the early solar system, or one of many such differentiated objects? The answer, Weiss says, may lie in the asteroid belt, a region populated with primordial remnants.
Read more at Science Daily
Jul 25, 2020
MRI scans of the brains of 130 mammals, including humans, indicate equal connectivity
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| Illustration of neurons |
"We discovered that brain connectivity -- namely the efficiency of information transfer through the neural network -- does not depend on either the size or structure of any specific brain," says Prof. Assaf. "In other words, the brains of all mammals, from tiny mice through humans to large bulls and dolphins, exhibit equal connectivity, and information travels with the same efficiency within them. We also found that the brain preserves this balance via a special compensation mechanism: when connectivity between the hemispheres is high, connectivity within each hemisphere is relatively low, and vice versa."
Participants included researchers from the Kimron Veterinary Institute in Beit Dagan, the School of Computer Science at TAU and the Technion's Faculty of Medicine. The paper was published in Nature Neuroscience on June 8.
"Brain connectivity is a central feature, critical to the functioning of the brain," Prof. Assaf explains. "Many scientists have assumed that connectivity in the human brain is significantly higher compared to other animals, as a possible explanation for the superior functioning of the 'human animal.'" On the other hand, according to Prof. Yovel, "We know that key features are conserved throughout the evolutionary process. Thus, for example, all mammals have four limbs. In this project we wished to explore the possibility that brain connectivity may be a key feature of this kind -- maintained in all mammals regardless of their size or brain structure. To this end we used advanced research tools."
The project began with advanced diffusion MRI scans of the brains of about 130 mammals, each representing a different species. (All of the brains were removed from dead animals, and no animals were euthanized for the purposes of this study.) The brains, obtained from the Kimron Veterinary Institute, represented a very wide range of mammals -- from tiny bats weighing 10 grams to dolphins whose weight can reach hundreds of kilograms. Since the brains of about 100 of these mammals had never been MRI-scanned before, the project generated a novel and globally unique database. The brains of 32 living humans were also scanned in the same way. The unique technology, which detects the white matter in the brain, enabled the researchers to reconstruct the neural network: the neurons and their axons (nerve fibers) through which information is transferred, and the synapses (junctions) where they meet.
The next challenge was comparing the scans of different types of animals, whose brains vary greatly in size and/or structure. For this purpose the researchers employed tools from Network Theory, a branch of mathematics that enabled them to create and apply a uniform gauge of brain conductivity: the number of synopses a message must cross to get from one location to another in the neural network.
"A mammal's brain consists of two hemispheres connected to each other by a set of neural fibers (axons) that transfer information," Prof. Assaf explains. "For every brain we scanned, we measured four connectivity gages: connectivity in each hemisphere (intrahemispheric connections), connectivity between the two hemispheres (interhemispheric), and overall connectivity. We discovered that overall brain connectivity remains the same for all mammals, large or small, including humans. In other words, information travels from one location to another through the same number of synapses. It must be said, however, that different brains use different strategies to preserve this equal measure of overall connectivity: some exhibit strong interhemispheric connectivity and weaker connectivity within the hemispheres, while others display the opposite."
Prof. Yovel describes another interesting discovery. "We found that variations in connectivity compensation characterize not only different species but also different individuals within the same species," he says. "In other words, the brains of some rats, bats, or humans exhibit higher interhemispheric connectivity at the expense of connectivity within the hemispheres, and the other way around -- compared to others of the same species. It would be fascinating to hypothesize how different types of brain connectivity may affect various cognitive functions or human capabilities such as sports, music or math. Such questions will be addressed in our future research."
Read more at Science Daily
Jul 24, 2020
How COVID-19 causes smell loss
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| Coronavirus illustration |
Now, an international team of researchers led by neuroscientists at Harvard Medical School has identified the olfactory cell types most vulnerable to infection by SARS-CoV-2, the virus that causes COVID-19.
Surprisingly, sensory neurons that detect and transmit the sense of smell to the brain are not among the vulnerable cell types.
Reporting in Science Advances on July 24, the research team found that olfactory sensory neurons do not express the gene that encodes the ACE2 receptor protein, which SARS-CoV-2 uses to enter human cells. Instead, ACE2 is expressed in cells that provide metabolic and structural support to olfactory sensory neurons, as well as certain populations of stem cells and blood vessel cells.
The findings suggest that infection of nonneuronal cell types may be responsible for anosmia in COVID-19 patients and help inform efforts to better understand the progression of the disease.
"Our findings indicate that the novel coronavirus changes the sense of smell in patients not by directly infecting neurons but by affecting the function of supporting cells," said senior study author Sandeep Robert Datta, associate professor of neurobiology in the Blavatnik Institute at HMS.
This implies that in most cases, SARS-CoV-2 infection is unlikely to permanently damage olfactory neural circuits and lead to persistent anosmia, Datta added, a condition that is associated with a variety of mental and social health issues, particularly depression and anxiety.
"I think it's good news, because once the infection clears, olfactory neurons don't appear to need to be replaced or rebuilt from scratch," he said. "But we need more data and a better understanding of the underlying mechanisms to confirm this conclusion."
A majority of COVID-19 patients experience some level of anosmia, most often temporary, according to emerging data. Analyses of electronic health records indicate that COVID-19 patients are 27 times more likely to have smell loss but are only around 2.2 to 2.6 times more likely to have fever, cough or respiratory difficulty, compared to patients without COVID-19.
Some studies have hinted that anosmia in COVID-19 differs from anosmia caused by other viral infections, including by other coronaviruses.
For example, COVID-19 patients typically recover their sense of smell over the course of weeks -- much faster than the months it can take to recover from anosmia caused by a subset of viral infections known to directly damage olfactory sensory neurons. In addition, many viruses cause temporary loss of smell by triggering upper respiratory issues such as stuffy nose. Some COVID-19 patients, however, experience anosmia without any nasal obstruction.
Pinpointing vulnerability
In the current study, Datta and colleagues set out to better understand how sense of smell is altered in COVID-19 patients by pinpointing cell types most vulnerable to SARS-CoV-2 infection.
They began by analyzing existing single-cell sequencing datasets that in total catalogued the genes expressed by hundreds of thousands of individual cells in the upper nasal cavities of humans, mice and nonhuman primates.
The team focused on the gene ACE2, widely found in cells of the human respiratory tract, which encodes the main receptor protein that SARS-CoV-2 targets to gain entry into human cells. They also looked at another gene, TMPRSS2, which encodes an enzyme thought to be important for SARS-CoV-2 entry into the cell.
The analyses revealed that both ACE2 and TMPRSS2 are expressed by cells in the olfactory epithelium -- a specialized tissue in the roof of the nasal cavity responsible for odor detection that houses olfactory sensory neurons and a variety of supporting cells.
Neither gene, however, was expressed by olfactory sensory neurons. By contrast, these neurons did express genes associated with the ability of other coronaviruses to enter cells.
The researchers found that two specific cell types in the olfactory epithelium expressed ACE2 at similar levels to what has been observed in cells of the lower respiratory tract, the most common targets of SARS-CoV-2, suggesting a vulnerability to infection.
These included sustentacular cells, which wrap around sensory neurons and are thought to provide structural and metabolic support, and basal cells, which act as stem cells that regenerate the olfactory epithelium after damage. The presence of proteins encoded by both genes in these cells was confirmed by immunostaining.
In additional experiments, the researchers found that olfactory epithelium stem cells expressed ACE2 protein at higher levels after artificially induced damage, compared with resting stem cells. This may suggest additional SARS-CoV-2 vulnerability, but it remains unclear whether or how this is important to the clinical course of anosmia in patients with COVID-19, the authors said.
Datta and colleagues also analyzed gene expression in nearly 50,000 individual cells in the mouse olfactory bulb, the structure in the forebrain that receives signals from olfactory sensory neurons and is responsible for initial odor processing.
Neurons in the olfactory bulb did not express ACE2. The gene and associated protein were present only in blood vessel cells, particularly pericytes, which are involved in blood pressure regulation, blood-brain barrier maintenance and inflammatory responses. No cell types in the olfactory bulb expressed the TMPRSS2 gene.
Smell loss clue
Together, these data suggest that COVID-19-related anosmia may arise from a temporary loss of function of supporting cells in the olfactory epithelium, which indirectly causes changes to olfactory sensory neurons, the authors said.
"We don't fully understand what those changes are yet, however," Datta said. "Sustentacular cells have largely been ignored, and it looks like we need to pay attention to them, similar to how we have a growing appreciation of the critical role that glial cells play in the brain."
The findings also offer intriguing clues into COVID-19-associated neurological issues. The observations are consistent with hypotheses that SARS-CoV-2 does not directly infect neurons but may instead interfere with brain function by affecting vascular cells in the nervous system, the authors said. This requires further investigation to verify, they added.
The study results now help accelerate efforts to better understand smell loss in patients with COVID-19, which could in turn lead to treatments for anosmia and the development of improved smell-based diagnostics for the disease.
"Anosmia seems like a curious phenomenon, but it can be devastating for the small fraction of people in whom it's persistent," Datta said. "It can have serious psychological consequences and could be a major public health problem if we have a growing population with permanent loss of smell."
The team also hope the data can help pave inroads for questions on disease progression such as whether the nose acts as a reservoir for SARS-CoV-2. Such efforts will require studies in facilities that allow experiments with live coronavirus and analyses of human autopsy data, the authors said, which are still difficult to come by. However, the collaborative spirit of pandemic-era scientific research calls for optimism.
"We initiated this work because my lab had a couple of datasets ready to analyze when the pandemic hit, and we published an initial preprint," Datta said. "What happened after that was amazing, researchers across the globe offered to share and merge their data with us in a kind of impromptu global consortium. This was a real collaborative achievement."
Read more at Science Daily
COVID-19 lockdown caused 50 percent global reduction in human-linked Earth vibrations
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| Seismograph |
This quiet period, likely caused by the total global effect of social distancing measures, closure of services and industry, and drops in tourism and travel, is the longest and most pronounced quiet period of seismic noise in recorded history.
The new research, led by the Royal Observatory of Belgium and five other institutions around the world including Imperial College London, showed that the dampening of 'seismic noise' caused by humans was more pronounced in more densely populated areas.
The relative quietness allowed researchers to listen in to previously concealed earthquake signals, and could help us differentiate between human and natural seismic noise more clearly than ever before.
Co-author Dr Stephen Hicks, from Imperial's Department of Earth Science and Engineering, said: "This quiet period is likely the longest and largest dampening of human-caused seismic noise since we started monitoring the Earth in detail using vast monitoring networks of seismometers.
"Our study uniquely highlights just how much human activities impact the solid Earth, and could let us see more clearly than ever what differentiates human and natural noise."
The paper is published today in Science.
Anthropause
Measured by instruments called seismometers, seismic noise is caused by vibrations within the Earth, which travel like waves. The waves can be triggered by earthquakes, volcanoes, and bombs -- but also by daily human activity like travel and industry.
Although 2020 has not seen a reduction in earthquakes, the drop in human-caused seismic noise is unprecedented. The strongest drops were found in urban areas, but the study also found signatures of the lockdown on sensors buried hundreds of metres underground and in more remote areas.
Human-generated noise usually dampens during quiet periods like over the Christmas/New Year period and Chinese New Year, and during weekends and overnight. However, the drop in vibrations caused by COVID-19 lockdown measures eclipse even those seen during these periods.
Some researchers are dubbing this drop in anthropogenic (human-caused) noise and pollution the 'anthropause'.
Dr Hicks said: "This is the first global study of the impact of the coronavirus anthropause on the solid Earth beneath our feet."
To gather the data, researchers looked at seismic data from a global network of 268 seismic stations in 117 countries and found significant noise reductions compared to before any lockdown at 185 of those stations. Beginning in China in late January 2020, and followed by Europe and the rest of the world in March to April 2020, researchers tracked the 'wave' of quietening between March and May as worldwide lockdown measures took hold.
The largest drops in vibrations were seen in the most densely populated areas, like Singapore and New York City, but drops were also seen in remote areas like Germany's Black Forest and Rundu in Namibia. Citizen-owned seismometers, which tend to measure more localised noise, noted large drops around universities and schools around Cornwall, UK and Boston, USA -- a drop in noise 20 per cent larger than seen during school holidays. Countries like Barbados, where lockdown coincided with the tourist season, saw a 50 per cent decrease in noise. This coincided with flight data that suggested tourists returned home in the weeks before official lockdown.
Listening in
Over the past few decades, seismic noise has gradually increased as economies and populations have grown.
The drastic changes to daily life caused by the pandemic have provided a unique opportunity to study their environmental impacts, such as reductions in emissions and pollution in the atmosphere. The changes have also given us the opportunity to listen in to the Earth's natural vibrations without the distortions of human input.
The study reports the first evidence that previously concealed earthquake signals, especially during daytime, appeared much clearer on seismometers in urban areas during lockdown.
The researchers say the lockdown quietening could also help them differentiate between human-caused noise and natural signals that might warn of upcoming natural disasters.
Lead author Dr Thomas Lecocq from the Royal Observatory of Belgium said: "With increasing urbanisation and growing global populations, more people will be living in geologically hazardous areas. It will therefore become more important than ever to differentiate between natural and human-caused noise so that we can 'listen in' and better monitor the ground movements beneath our feet. This study could help to kick-start this new field of study."
The study's authors hope that their work will spawn further research on the seismic lockdown, as well as finding previously hidden signals from earthquakes and volcanoes.
Read more at Science Daily
Vikings had smallpox and may have helped spread the world's deadliest virus
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| Viking ship |
Smallpox spread from person to person via infectious droplets, killed around a third of sufferers and left another third permanently scarred or blind. Around 300 million people died from it in the 20th century alone before it was officially eradicated in 1980 through a global vaccination effort -- the first human disease to be wiped out.
Now an international team of scientists have sequenced the genomes of newly discovered strains of the virus after it was extracted from the teeth of Viking skeletons from sites across northern Europe. The findings have been published in Science today (July 23, 2020).
Professor Eske Willerslev, of St John's College, University of Cambridge, and director of The Lundbeck Foundation GeoGenetics Centre, University of Copenhagen, led the study.
He said: "We discovered new strains of smallpox in the teeth of Viking skeletons and found their genetic structure is different to the modern smallpox virus eradicated in the 20th century. We already knew Vikings were moving around Europe and beyond, and we now know they had smallpox. People travelling around the world quickly spread Covid-19 and it is likely Vikings spread smallpox. Just back then, they travelled by ship rather than by plane.
"The 1400-year-old genetic information extracted from these skeletons is hugely significant because it teaches us about the evolutionary history of the variola virus that caused smallpox."
Smallpox was eradicated throughout most of Europe and the United States by the beginning of the 20th century but remained endemic throughout Africa, Asia, and South America. The World Health Organisation launched an eradication programme in 1967 that included contact tracing and mass communication campaigns -- all public health techniques that countries have been using to control today's coronavirus pandemic. But it was the global roll out of a vaccine that ultimately enabled scientists to stop smallpox in its tracks.
Historians believe smallpox may have existed since 10,000 BC but until now there was no scientific proof that the virus was present before the 17th century. It is not known how it first infected humans but, like Covid-19, it is believed to have come from animals.
Professor Martin Sikora, one of the senior authors leading the study, from the Centre for GeoGenetics, University of Copenhagen, said: "The timeline of the emergence of smallpox has always been unclear but by sequencing the earliest-known strain of the killer virus, we have proved for the first time that smallpox existed during the Viking Age.
"While we don't know for sure if these strains of smallpox were fatal and caused the death of the Vikings we sampled, they certainly died with smallpox in their bloodstream for us to be able to detect it up to 1400 years later. It is also highly probable there were epidemics earlier than our findings that scientists have yet to discover DNA evidence of."
The team of researchers found smallpox -- caused by the variola virus -- in 11 Viking-era burial sites in Denmark, Norway, Russia, and the UK. They also found it in multiple human remains from Öland, an island off the east coast of Sweden with a long history of trade. The team were able to reconstruct near-complete variola virus genomes for four of the samples.
Dr Lasse Vinner, one of the first authors and a virologist from The Lundbeck Foundation GeoGenetics Centre, said: "Understanding the genetic structure of this virus will potentially help virologists understand the evolution of this and other viruses and add to the bank of knowledge that helps scientists fight emerging viral diseases.
"The early version of smallpox was genetically closer in the pox family tree to animal poxviruses such as camelpox and taterapox, from gerbils. It does not exactly resemble modern smallpox which show that virus evolved. We don't know how the disease manifested itself in the Viking Age -- it may have been different from those of the virulent modern strain which killed and disfigured hundreds of millions."
Dr Terry Jones, one of the senior authors leading the study, a computational biologist based at the Institute of Virology at Charité -- Universitätsmedizin Berlin and the Centre for Pathogen Evolution at the University of Cambridge, said: "There are many mysteries around poxviruses. To find smallpox so genetically different in Vikings is truly remarkable. No one expected that these smallpox strains existed. It has long been believed that smallpox was in Western and Southern Europe regularly by 600 AD, around the beginning of our samples.
"We have proved that smallpox was also widespread in Northern Europe. Returning crusaders or other later events have been thought to have first brought smallpox to Europe, but such theories cannot be correct. While written accounts of disease are often ambiguous, our findings push the date of the confirmed existence of smallpox back by a thousand years."
Dr Barbara Mühlemann, one of the first authors and a computational biologist, took part in the research during her PhD at the Centre for Pathogen Evolution at the University of Cambridge, and is now also based at the Institute of Virology at Charité, said: "The ancient strains of smallpox have a very different pattern of active and inactive genes compared to the modern virus. There are multiple ways viruses may diverge and mutate into milder or more dangerous strains. This is a significant insight into the steps the variola virus took in the course of its evolution."
Dr Jones added: "Knowledge from the past can protect us in the present. When an animal or plant goes extinct, it isn't coming back. But mutations can re-occur or revert and viruses can mutate or spill over from the animal reservoir so there will always be another zoonosis."
Zoonosis refers to an infectious disease outbreak caused by a pathogen jumping from a non-human animal to a human.
The research is part of a long-term project sequencing 5000 ancient human genomes and their associated pathogens made possible thanks to a scientific collaboration between The Lundbeck Foundation, The Wellcome Trust, The Nordic Foundation, and Illumina Inc.
Read more at Science Daily
Neanderthals may have had a lower threshold for pain
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| Depiction of early humans, photo concept |
As several Neanderthal genomes of high quality are now available researchers can identify genetic changes that were present in many or all Neanderthals, investigate their physiological effects and look into their consequences when they occur in people today. Looking into one gene that carries such changes, Hugo Zeberg, Svante Pääbo and colleagues found that some people, especially from central and south America but also in Europe, have inherited a Neanderthal variant of a gene that encodes an ion channel that initiates the sensation of pain.
By using data from a huge population study in the UK, the authors show that people in the UK who carry the Neanderthal variant of the ion channel experience more pain. "The biggest factor for how much pain people report is their age. But carrying the Neanderthal variant of the ion channel makes you experience more pain similar to if you were eight years older," says lead author Hugo Zeberg, a researcher at the Max Planck Institute for Evolutionary Anthropology and Karolinska Institutet. "The Neanderthal variant of the ion channel carries three amino acid differences to the common, 'modern' variant," explains Zeberg. "While single amino acid substitutions do not affect the function of the ion channel, the full Neanderthal variant carrying three amino acid substitutions leads to heightened pain sensitivity in present-day people."
On a molecular level, the Neanderthal ion channel is more easily activated which may explain why people who inherited it have a lowered pain threshold. "Whether Neanderthals experienced more pain is difficult to say because pain is also modulated both in the spinal cord and in the brain," says Pääbo. "But this work shows that their threshold for initiating pain impulses was lower than in most present-day humans."
From Science Daily
Jul 23, 2020
Flood data from 500 years: Rivers and climate change in Europe
Overflowing rivers can cause enormous problems: Worldwide, the annual damage caused by river floods is estimated at over 100 billion dollars -- and it continues to rise. To date it has been unclear whether Europe is currently in a flood-rich period from a long-term perspective.
Austrian flood expert Prof. Günter Blöschl from TU Wien (Vienna) has led a large international study involving a total of 34 research groups that provides clear evidence that the past three decades were among the most flood-rich periods in Europe during the past 500 years, and that this period differs from others in terms of its extent, air temperatures and flood seasonality. Compared to the past, floods tend to be larger in many places, the timing has shifted and the relationship between flood occurrence and air temperatures has reversed. In the past, floods tended to occur more frequently in cold phases, while today, global warming is one of the main drivers of their increase. The results of the study have now been published in "Nature" magazine.
Historical data from half a millennium
"From our previous research, we already knew how climate change has affected Europe's floods in the past 50 years," says Alberto Viglione from the Politecnico di Torino, one of the key authors of the publication. "For forecasts of the next decades, however, it is also important to understand whether this is a completely new situation or whether this is just a repetition of something that has already occurred. So far, the available data had not been sufficient to ascertain whether this is the case or not. We have examined this question in great detail and can now say with confidence: Yes, flooding characteristics in recent decades are unlike those of the previous centuries."
For the study, tens of thousands of historical documents containing contemporary flood reports from the period 1500 to 2016 were analysed. The TU Wien team has worked with historians from all over Europe. "The particular challenge of this study consisted in making the very different texts of the different centuries and different cultural regions comparable," explains Andrea Kiss from the Vienna University of Technology, researcher and historian herself, and one of the key authors of the publication. "We managed to achieve this comparability by putting all the texts in their respective historical contexts with painstaking attention to detail."
Formerly cold, now warm: River floods now function differently
The data analysis identified nine flood-rich periods and associated regions. Among the most notable periods were 1560-1580 (western and central Europe), 1760-1800 (most of Europe), 1840-1870 (western and southern Europe) and 1990-2016 (western and central Europe). Comparisons with air temperature reconstructions showed that these historical flood periods were substantially cooler than intervening phases.
"This finding seems to contradict the observation that, in some areas such as in the northwest of Europe, the recent warmer climate is aligned with larger floods," says Günter Blöschl. "Our study shows for the first time that the underlying mechanisms have changed: While, in the past, floods have occurred more frequently under colder conditions, the opposite is the case now. The hydrological conditions of the present are very different from those in the past."
The timing of the floods within the year has also changed. Previously, 41% of Central European floods occurred in the summer, compared to 55% today. These shifts are related to changes in precipitation, evaporation and snowmelt and are an important indicator for distinguishing the role of climate change from that of other controls such as deforestation and river management.
These findings have been made possible by a new data base compiled by the study authors that includes the exact dating of almost all flood events reported by written sources. So far, one had to often rely on other, less precise sources of information, such as lake sediments. It is the first study worldwide to evaluate historical flood periods for an entire continent in such detail.
Read more at Science Daily
Austrian flood expert Prof. Günter Blöschl from TU Wien (Vienna) has led a large international study involving a total of 34 research groups that provides clear evidence that the past three decades were among the most flood-rich periods in Europe during the past 500 years, and that this period differs from others in terms of its extent, air temperatures and flood seasonality. Compared to the past, floods tend to be larger in many places, the timing has shifted and the relationship between flood occurrence and air temperatures has reversed. In the past, floods tended to occur more frequently in cold phases, while today, global warming is one of the main drivers of their increase. The results of the study have now been published in "Nature" magazine.
Historical data from half a millennium
"From our previous research, we already knew how climate change has affected Europe's floods in the past 50 years," says Alberto Viglione from the Politecnico di Torino, one of the key authors of the publication. "For forecasts of the next decades, however, it is also important to understand whether this is a completely new situation or whether this is just a repetition of something that has already occurred. So far, the available data had not been sufficient to ascertain whether this is the case or not. We have examined this question in great detail and can now say with confidence: Yes, flooding characteristics in recent decades are unlike those of the previous centuries."
For the study, tens of thousands of historical documents containing contemporary flood reports from the period 1500 to 2016 were analysed. The TU Wien team has worked with historians from all over Europe. "The particular challenge of this study consisted in making the very different texts of the different centuries and different cultural regions comparable," explains Andrea Kiss from the Vienna University of Technology, researcher and historian herself, and one of the key authors of the publication. "We managed to achieve this comparability by putting all the texts in their respective historical contexts with painstaking attention to detail."
Formerly cold, now warm: River floods now function differently
The data analysis identified nine flood-rich periods and associated regions. Among the most notable periods were 1560-1580 (western and central Europe), 1760-1800 (most of Europe), 1840-1870 (western and southern Europe) and 1990-2016 (western and central Europe). Comparisons with air temperature reconstructions showed that these historical flood periods were substantially cooler than intervening phases.
"This finding seems to contradict the observation that, in some areas such as in the northwest of Europe, the recent warmer climate is aligned with larger floods," says Günter Blöschl. "Our study shows for the first time that the underlying mechanisms have changed: While, in the past, floods have occurred more frequently under colder conditions, the opposite is the case now. The hydrological conditions of the present are very different from those in the past."
The timing of the floods within the year has also changed. Previously, 41% of Central European floods occurred in the summer, compared to 55% today. These shifts are related to changes in precipitation, evaporation and snowmelt and are an important indicator for distinguishing the role of climate change from that of other controls such as deforestation and river management.
These findings have been made possible by a new data base compiled by the study authors that includes the exact dating of almost all flood events reported by written sources. So far, one had to often rely on other, less precise sources of information, such as lake sediments. It is the first study worldwide to evaluate historical flood periods for an entire continent in such detail.
Read more at Science Daily
Genomic basis of bat superpowers revealed: Like how they survive deadly viruses
The genetic material that codes for bat adaptations and superpowers -- such as the ability to fly, to use sound to move effortlessly in complete darkness, to tolerate and survive potentially deadly viruses, and to resist aging and cancer -- has been revealed and published in Nature. Liliana M. Dávalos, a Stony Brook University evolutionary biologist and co-author, worked as part of the executive committee of the global consortium of scientists, Bat1K, to sequence the genome of six widely divergent living bat species.
Although other bat genomes have been published before, the Bat1K genomes are 10 times more complete than any bat genome published to date.
One aspect of the paper findings shows evolution through gene expansion and loss in a family of genes, APOBEC3, which is known to play an important role in immunity to viruses in other mammals. The details in the paper that explain this evolution set the groundwork for investigating how these genetic changes, found in bats but not in other mammals, could help prevent the worst outcomes of viral diseases in other mammals, including humans.
"More and more, we find gene duplications and losses as important processes in the evolution of new features and functions across the Tree of Life. But, determining when genes have duplicated is difficult if the genome is incomplete, and it is even harder to figure out if genes have been lost. At extremely high quality, the new bat genomes leave no doubts about changes in important gene families that could not be discovered otherwise with lower-quality genomes," said Dávalos, a Professor in Department of Ecology and Evolution in the College of Arts and Sciences at Stony Brook University.
To generate the bat genomes, the team used the newest technologies of the DRESDEN-concept Genome Center, a shared technology resource in Dresden, Germany to sequence the bat's DNA, and generated new methods to assemble these pieces into the correct order and to identify the genes present. While previous efforts had identified genes with the potential to influence the unique biology of bats, uncovering how gene duplications contributed to this unique biology was complicated by incomplete genomes.
The team compared these bat genomes against 42 other mammals to address the unresolved question of where bats are located within the mammalian tree of life. Using novel phylogenetic methods and comprehensive molecular data sets, the team found the strongest support for bats being most closely related to a group called Fereuungulata that consists of carnivorans (which includes dogs, cats and seals, among other species), pangolins, whales and ungulates (hooved mammals).
To uncover genomic changes that contribute to the unique adaptations found in bats, the team systematically searched for gene differences between bats and other mammals, identifying regions of the genome that have evolved differently in bats and the loss and gain of genes that may drive bats' unique traits.
"It is thanks to a series of sophisticated statistical analyses that we have started to uncover the genetics behind bats' 'superpowers,' including their strong apparent abilities to tolerate and overcome RNA viruses," said Dávalos.
The researchers found evidence the exquisite genomes revealed "fossilized viruses," evidence of surviving past viral infections, and showed that bat genomes contained a higher diversity of these viral remnants than other species providing a genomic record of ancient historical interaction with viral infections. The genomes also revealed the signatures of many other genetic elements besides ancient viral insertions, including 'jumping genes' or transposable elements.
Read more at Science Daily
Although other bat genomes have been published before, the Bat1K genomes are 10 times more complete than any bat genome published to date.
One aspect of the paper findings shows evolution through gene expansion and loss in a family of genes, APOBEC3, which is known to play an important role in immunity to viruses in other mammals. The details in the paper that explain this evolution set the groundwork for investigating how these genetic changes, found in bats but not in other mammals, could help prevent the worst outcomes of viral diseases in other mammals, including humans.
"More and more, we find gene duplications and losses as important processes in the evolution of new features and functions across the Tree of Life. But, determining when genes have duplicated is difficult if the genome is incomplete, and it is even harder to figure out if genes have been lost. At extremely high quality, the new bat genomes leave no doubts about changes in important gene families that could not be discovered otherwise with lower-quality genomes," said Dávalos, a Professor in Department of Ecology and Evolution in the College of Arts and Sciences at Stony Brook University.
To generate the bat genomes, the team used the newest technologies of the DRESDEN-concept Genome Center, a shared technology resource in Dresden, Germany to sequence the bat's DNA, and generated new methods to assemble these pieces into the correct order and to identify the genes present. While previous efforts had identified genes with the potential to influence the unique biology of bats, uncovering how gene duplications contributed to this unique biology was complicated by incomplete genomes.
The team compared these bat genomes against 42 other mammals to address the unresolved question of where bats are located within the mammalian tree of life. Using novel phylogenetic methods and comprehensive molecular data sets, the team found the strongest support for bats being most closely related to a group called Fereuungulata that consists of carnivorans (which includes dogs, cats and seals, among other species), pangolins, whales and ungulates (hooved mammals).
To uncover genomic changes that contribute to the unique adaptations found in bats, the team systematically searched for gene differences between bats and other mammals, identifying regions of the genome that have evolved differently in bats and the loss and gain of genes that may drive bats' unique traits.
"It is thanks to a series of sophisticated statistical analyses that we have started to uncover the genetics behind bats' 'superpowers,' including their strong apparent abilities to tolerate and overcome RNA viruses," said Dávalos.
The researchers found evidence the exquisite genomes revealed "fossilized viruses," evidence of surviving past viral infections, and showed that bat genomes contained a higher diversity of these viral remnants than other species providing a genomic record of ancient historical interaction with viral infections. The genomes also revealed the signatures of many other genetic elements besides ancient viral insertions, including 'jumping genes' or transposable elements.
Read more at Science Daily
First ever image of a multi-planet system around a sun-like star captured by ESO telescope
The European Southern Observatory's Very Large Telescope (ESO's VLT) has taken the first ever image of a young, Sun-like star accompanied by two giant exoplanets. Images of systems with multiple exoplanets are extremely rare, and -- until now -- astronomers had never directly observed more than one planet orbiting a star similar to the Sun. The observations can help astronomers understand how planets formed and evolved around our own Sun.
Just a few weeks ago, ESO revealed a planetary system being born in a new, stunning VLT image. Now, the same telescope, using the same instrument, has taken the first direct image of a planetary system around a star like our Sun, located about 300 light-years away and known as TYC 8998-760-1.
"This discovery is a snapshot of an environment that is very similar to our Solar System, but at a much earlier stage of its evolution," says Alexander Bohn, a PhD student at Leiden University in the Netherlands, who led the new research published today in the Astrophysical Journal Letters.
"Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged," says co-author Matthew Kenworthy, Associate Professor at Leiden University, adding that "direct observations are important in the search for environments that can support life." The direct imaging of two or more exoplanets around the same star is even more rare; only two such systems have been directly observed so far, both around stars markedly different from our Sun. The new ESO's VLT image is the first direct image of more than one exoplanet around a Sun-like star. ESO's VLT was also the first telescope to directly image an exoplanet, back in 2004, when it captured a speck of light around a brown dwarf, a type of 'failed' star.
"Our team has now been able to take the first image of two gas giant companions that are orbiting a young, solar analogue," says Maddalena Reggiani, a postdoctoral researcher from KU Leuven, Belgium, who also participated in the study. The two planets can be seen in the new image as two bright points of light distant from their parent star, which is located in the upper left of the frame (click on the image to view the full frame). By taking different images at different times, the team were able to distinguish these planets from the background stars.
The two gas giants orbit their host star at distances of 160 and about 320 times the Earth-Sun distance. This places these planets much further away from their star than Jupiter or Saturn, also two gas giants, are from the Sun; they lie at only 5 and 10 times the Earth-Sun distance, respectively. The team also found the two exoplanets are much heavier than the ones in our Solar System, the inner planet having 14 times Jupiter's mass and the outer one six times.
Bohn's team imaged this system during their search for young, giant planets around stars like our Sun but far younger. The star TYC 8998-760-1 is just 17 million years old and located in the Southern constellation of Musca (The Fly). Bohn describes it as a "very young version of our own Sun."
These images were possible thanks to the high performance of the SPHERE instrument on ESO's VLT in the Chilean Atacama desert. SPHERE blocks the bright light from the star using a device called coronagraph, allowing the much fainter planets to be seen. While older planets, such as those in our Solar System, are too cool to be found with this technique, young planets are hotter, and so glow brighter in infrared light. By taking several images over the past year, as well as using older data going back to 2017, the research team have confirmed that the two planets are part of the star's system.
Read more at Science Daily
Just a few weeks ago, ESO revealed a planetary system being born in a new, stunning VLT image. Now, the same telescope, using the same instrument, has taken the first direct image of a planetary system around a star like our Sun, located about 300 light-years away and known as TYC 8998-760-1.
"This discovery is a snapshot of an environment that is very similar to our Solar System, but at a much earlier stage of its evolution," says Alexander Bohn, a PhD student at Leiden University in the Netherlands, who led the new research published today in the Astrophysical Journal Letters.
"Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged," says co-author Matthew Kenworthy, Associate Professor at Leiden University, adding that "direct observations are important in the search for environments that can support life." The direct imaging of two or more exoplanets around the same star is even more rare; only two such systems have been directly observed so far, both around stars markedly different from our Sun. The new ESO's VLT image is the first direct image of more than one exoplanet around a Sun-like star. ESO's VLT was also the first telescope to directly image an exoplanet, back in 2004, when it captured a speck of light around a brown dwarf, a type of 'failed' star.
"Our team has now been able to take the first image of two gas giant companions that are orbiting a young, solar analogue," says Maddalena Reggiani, a postdoctoral researcher from KU Leuven, Belgium, who also participated in the study. The two planets can be seen in the new image as two bright points of light distant from their parent star, which is located in the upper left of the frame (click on the image to view the full frame). By taking different images at different times, the team were able to distinguish these planets from the background stars.
The two gas giants orbit their host star at distances of 160 and about 320 times the Earth-Sun distance. This places these planets much further away from their star than Jupiter or Saturn, also two gas giants, are from the Sun; they lie at only 5 and 10 times the Earth-Sun distance, respectively. The team also found the two exoplanets are much heavier than the ones in our Solar System, the inner planet having 14 times Jupiter's mass and the outer one six times.
Bohn's team imaged this system during their search for young, giant planets around stars like our Sun but far younger. The star TYC 8998-760-1 is just 17 million years old and located in the Southern constellation of Musca (The Fly). Bohn describes it as a "very young version of our own Sun."
These images were possible thanks to the high performance of the SPHERE instrument on ESO's VLT in the Chilean Atacama desert. SPHERE blocks the bright light from the star using a device called coronagraph, allowing the much fainter planets to be seen. While older planets, such as those in our Solar System, are too cool to be found with this technique, young planets are hotter, and so glow brighter in infrared light. By taking several images over the past year, as well as using older data going back to 2017, the research team have confirmed that the two planets are part of the star's system.
Read more at Science Daily
New role for white blood cells in the developing brain
Whether white blood cells can be found in the brain has been controversial, and their role there a complete mystery. In a study published in Cell, an international team of scientists led by Professor Adrian Liston (Babraham Institute, UK & VIB-KU Leuven, Belgium) describe a population of specialised brain-resident immune cells discovered in the mouse and human brain, and show that the presence of white blood cells is essential for normal brain development in mice.
Like a highly fortified headquarters, our brain enjoys special protection from what is circulating in the rest of our body through the blood-brain barrier. This highly selective border makes sure that passage from the blood to the brain is tightly regulated.
The blood-brain barrier also separates the brain from our body's immune system, which is why it has its own resident immune cells, called microglia, which trigger inflammation and tissue repair. Microglia arrive in the brain during embryonic development, and later on, the population becomes self-renewing.
Yet, white blood cells -- which are part of our immune system -- have been found to play a role in different brain diseases, including multiple sclerosis, Alzheimer's and Parkinson's disease or stroke. Whether or not white blood cells can be found in healthy brains as well, and what they might be doing there, has been subject of intense debate. An interdisciplinary team of scientists led by Prof. Adrian Liston (Babraham Institute and VIB-KU Leuven) set out to find the answers.
White blood cells in the brain
"A misconception about white blood cells comes from their name," explains Dr Oliver Burton (Babraham Institute). "These 'immune cells' are not just present in the blood. They are constantly circulating around our body and enter all of our organs, including -- as it turns out -- the brain. We are only just starting to discover what white blood cells do when they leave the blood. This research indicates that they act as a go-between, transferring information from the rest of the body to the brain environment"
The team quantified and characterised a small but distinct population of brain-resident T helper cells present in mouse and human brain tissue. T cells are a specific type of white blood cells specialized for scanning cell surfaces for evidence of infection and triggering an appropriate immune response. New technologies allowed the researchers to study the cells in great detail, including the processes by which circulating T cells entered the brain and began to develop the features of brain-resident T cells.
Dr Carlos Roca (Babraham Institute): "Science is becoming increasingly multidisciplinary. Here, we didn't just bring in expertise from immunology, neuroscience and microbiology, but also from computer science and applied mathematics. New approaches for data analysis allow us to reach a much deeper level of understanding of the biology of the white blood cells we found in the brain."
An evolutionary role
When T helper cells are absent from the brain, the scientists found that the resident immune cells -- microglia -- in the mouse brain remained suspended between a fetal and adult developmental state. Observationally, mice lacking brain T cells showed multiple changes in their behavior. The analysis points to an important role for brain-resident T cells in brain development. If T cells participate in normal brain development in mice, could the same be true in humans?
"In mice, the wave of entry of immune cells at birth triggers a switch in brain development," says Liston. "Humans have a much longer gestation than mice though, and we don't know about the timing of immune cell entry into the brain. Does this occur before birth? Is it delayed until after birth? Did a change in timing of entry contribute to the evolution of enhanced cognitive capacity in humans?"
The findings open up a whole new range of questions about how the brain and our immune system interact. "It has been really exciting to work on this project. We are learning so much about how our immune system can alter our brain, and how our brain modifies our immune system. The two are far more interconnected than we previously thought," says Dr Emanuela Pasciuto (VIB-KU Leuven).
The study also brings in a connection with the gut microbiome, says Liston: "There are now multiple links between the bacteria in our gut and different neurological conditions, but without any convincing explanations for what connects them. We show that white blood cells are modified by gut bacteria, and then take that information with them into the brain. This could be the route by which our gut microbiome influences the brain."
Read more at Science Daily
Like a highly fortified headquarters, our brain enjoys special protection from what is circulating in the rest of our body through the blood-brain barrier. This highly selective border makes sure that passage from the blood to the brain is tightly regulated.
The blood-brain barrier also separates the brain from our body's immune system, which is why it has its own resident immune cells, called microglia, which trigger inflammation and tissue repair. Microglia arrive in the brain during embryonic development, and later on, the population becomes self-renewing.
Yet, white blood cells -- which are part of our immune system -- have been found to play a role in different brain diseases, including multiple sclerosis, Alzheimer's and Parkinson's disease or stroke. Whether or not white blood cells can be found in healthy brains as well, and what they might be doing there, has been subject of intense debate. An interdisciplinary team of scientists led by Prof. Adrian Liston (Babraham Institute and VIB-KU Leuven) set out to find the answers.
White blood cells in the brain
"A misconception about white blood cells comes from their name," explains Dr Oliver Burton (Babraham Institute). "These 'immune cells' are not just present in the blood. They are constantly circulating around our body and enter all of our organs, including -- as it turns out -- the brain. We are only just starting to discover what white blood cells do when they leave the blood. This research indicates that they act as a go-between, transferring information from the rest of the body to the brain environment"
The team quantified and characterised a small but distinct population of brain-resident T helper cells present in mouse and human brain tissue. T cells are a specific type of white blood cells specialized for scanning cell surfaces for evidence of infection and triggering an appropriate immune response. New technologies allowed the researchers to study the cells in great detail, including the processes by which circulating T cells entered the brain and began to develop the features of brain-resident T cells.
Dr Carlos Roca (Babraham Institute): "Science is becoming increasingly multidisciplinary. Here, we didn't just bring in expertise from immunology, neuroscience and microbiology, but also from computer science and applied mathematics. New approaches for data analysis allow us to reach a much deeper level of understanding of the biology of the white blood cells we found in the brain."
An evolutionary role
When T helper cells are absent from the brain, the scientists found that the resident immune cells -- microglia -- in the mouse brain remained suspended between a fetal and adult developmental state. Observationally, mice lacking brain T cells showed multiple changes in their behavior. The analysis points to an important role for brain-resident T cells in brain development. If T cells participate in normal brain development in mice, could the same be true in humans?
"In mice, the wave of entry of immune cells at birth triggers a switch in brain development," says Liston. "Humans have a much longer gestation than mice though, and we don't know about the timing of immune cell entry into the brain. Does this occur before birth? Is it delayed until after birth? Did a change in timing of entry contribute to the evolution of enhanced cognitive capacity in humans?"
The findings open up a whole new range of questions about how the brain and our immune system interact. "It has been really exciting to work on this project. We are learning so much about how our immune system can alter our brain, and how our brain modifies our immune system. The two are far more interconnected than we previously thought," says Dr Emanuela Pasciuto (VIB-KU Leuven).
The study also brings in a connection with the gut microbiome, says Liston: "There are now multiple links between the bacteria in our gut and different neurological conditions, but without any convincing explanations for what connects them. We show that white blood cells are modified by gut bacteria, and then take that information with them into the brain. This could be the route by which our gut microbiome influences the brain."
Read more at Science Daily
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